Math Blog

Sellfy free account to be discontinued

Just received some news from Sellfy:

Hi there,

We have important news about your Sellfy account and your store https://sellfy.com/mathtuition88

You have been on our transaction fee only plan (Legacy plan) since you signed up for Sellfy. We are truly thankful for being with us all this time!

Due to considerable technical adjustments in our platform and supporting services, we are forced to discontinue the Legacy plan on February 1st, 2020 and switch into supporting subscription-based plans only https://sellfy.com/pricing/. We no longer offer Legacy plan for new users since March, 2016.


Most likely, we won’t be continuing with Sellfy after February 1st, 2020.

Hence, this is the last 1-2 months to purchases math notes/material from our online store: https://sellfy.com/mathtuition88 if you are interested. Thank you for the support!

2 types of chi-squared test

Most people have heard of chi-squared test, but not many know that there are (at least) two types of chi-squared tests.

The two most common chi-squared tests are:

  • 1-way classification: Goodness-of-fit test
  • 2-way classification: Contingency test

The goodness-of-fit chi-squared test is to test proportions, or to be precise, to test if an an observed distribution fits an expected distribution.

The contingency test (the more classical type of chi-squared test) is to test the independence or relatedness of two random variables.

The best website I found regarding how to practically code (in R) for the two chi-squared tests is: https://web.stanford.edu/class/psych252/cheatsheets/chisquare.html

I created a PDF copy of the above site, in case it becomes unavailable in the future:

Chi-squared Stanford PDF

Best Videos on each type of Chi-squared test

Goodness of fit Chi-squared test video by Khan Academy:

Contingency table chi-square test:

Ohm Energy Referral Competition (2 Dec 2019 – 2 Feb 2020)

Just to share this Ohm Energy Referral Competition. If you are not a Ohm electricity user, sign up using the promo code OHMREF25CC5A now to begin the competition!

Also read my blog article explaining why Ohm is the best electricity supplier in Singapore: Ohm $20 Promo Code: OHMREF25CC5A.


We would like to thank you again for giving us the highest rating in the Energy Market Authority’s Customer Satisfy Survey. To show our appreciation, we will be rolling out 3 concurrent competitions from 2nd December 2019 with attractive cash prizes up for grabs.

Your Personal Referral code is: OHMREF25CC5A

Do access our Customer Portal Login to verify your referral code.

1. All-in Referral Competition (“All-in”) – All referral registered from the start of the Open Electricity Market soft launch on 1 April 2018 through 2nd February 2020 will be counted towards the prizes.

2. Fresh Referral Competition (“Fresh”) – All referrals registered between 2nd December 2019 through 2nd February 2020 will be counted towards the prizes.

At the end of the competition, the Top 10 referrers from each category, All-in and Fresh, will win cash prizes from Ohm according to the table below.

“Fresh Competition” Cash Prize “All-in Competition” Cash Prize
Top Referrer S$1000 S$1000
2nd Place S$500 S$500
3rd Place S$300 S$300
4th – 5th Place S$200 S$200
6th – 10th Place S$100 S$100

3. Periodic winners – We will also select a winner for six interval periods. The counter will reset every period and we will pick the customer with most referrals registered in that period. In the event of a tie, the award will be divided equally amongst the winners:

Period 1: 02 Dec 2019 to 15 Dec 2019 – S$40 cash prize

Period 2: 16 Dec 2019 to 29 Dec 2019 – S$50 cash prize

Period 3: 30 Dec 2019 to 12 Jan 2020 – S$60 cash prize

Period 4: 13 Jan 2020 to 19 Jan 2020 – S$80 cash prize

Period 5: 20 Jan 2020 to 26 Jan 2020 – S$90 cash prize

Period 6: 27 Jan 2020 to 02 Feb 2020 – S$100 cash prize

For all 3 competitions, eligible referrals must be keyed into the promotion code field at the point of registration as we are unable to retrospectively change or input referral codes. A referral is only eligible if we can detect that it has been applied in our systems and the customer’s transfer is confirmed by SP Services. Any manual credit to an account will not be counted as a referral.

Do visit our existing Referral Programme Terms and Conditions at Refer Us to A Friend and Ohm Referral Competition Terms and Conditions here for more details.

We wish you the best of luck and a great festive season!

Warm Regards,
Team Ohm

Fixed Ohm vs Ohm Discount

Many people have decided to switch to Ohm electricity, but are still confused which plan to take. The two best plans are Fixed Ohm and Ohm Discount.

Personally, I think Ohm Discount is the better one, with this blog post detailing my calculations: Ohm $20 Promo Code: OHMREF25CC5A.


*Ohm Promo Code: OHMREF25CC5A

After extensive research, I find that Ohm is one of the best alternative electricity suppliers. Choose either Fixed Ohm or Discount Ohm depending on your likings. I chose Discount Ohm as I have a feeling that the tariffs may drop. Fixed Ohm is also very good, and in fact better if tariffs rise.


The blog MoneySmart have also made their calculations and concluded that at this point in time, Discount Ohm is superior to Fixed Ohm.

Ohm Energy’s discount of 25% off is the best in the market, compared to other retailers who are offering only 22% or 23%. Yup, this means your bill will always be 25% less than whatever SP charges, which sounds awesome.

Right now, the tariff is 25.07¢ for Oct to Dec 2019, which actually makes the Ohm Discount plans cheaper than their fixed price plans, quite the anomaly in the electricity market.

Source: https://blog.moneysmart.sg/budgeting/ohm-energy-review/


Simply Ohm vs Market Ohm review

Other than Ohm Discount and Fixed Ohm, there are actually two other plans Simply Ohm and Market Ohm. Without going into too much details, we may just say that these two plans are not nearly as good as Ohm Discount or Fixed Ohm. You may read the MoneySmart article above for more details, basically they are more expensive in most cases for the average consumer.

Conclusion: Ohm Discount is Clear Winner, followed by Fixed Ohm

For the average consumer, it is safe to say that Ohm Discount is the plan you should go for. Both my blog article on Ohm, and MoneySmart comes to this exact same conclusion.

Fixed Ohm may be actually better in the event that tariffs start to rise significantly, but in the near future that does not seem to be happening (based on the trends). Simply Ohm and Market Ohm are very specialized plans targeted at very special cases, currently they are no match for Ohm Discount nor Fixed Ohm.

Do sign up for Ohm now using the promo code below!

*Ohm Promo Code: OHMREF25CC5A

Melafix Review and Research

Melafix is quite a popular medication in the aquarium hobby, by the company API. Chances are most people have at least heard about it. However, there is remarkably little information on this medication online, and whatever information is scattered and not centralized.


API MELAFIX Fish remedy For Bacterial Infection in Freshwater Aquarium 16-Ounce Bottle

What is Melafix and what is Melafix’s ingredient?

The active ingredient in Melafix is Melaleuca oil at 1.0% concentration. We can easily then see how Melafix got its name. Melaleuca oil comes from the a tree in the Melaleuca genus, which includes the popular “tea tree” from which “tea tree oil” is derived. Note that there is a technicality where “contrary to popular opinion it is not made from the common Tea treeMelaleuca alternifolia, but from Melaleuca leucadendra, also known as the Cajeput Tree” (Wikipedia).

Melafix Research

There seems to be not much research done on Melafix. One of the few research papers is the following:

The use of Melafix on goldfish and clownfish appears to be safe as no adverse effects were noted during the experimental period. The results also showed that Melafix has no effect on the water-quality parameters tested. In vitro efficacy studies were conducted by determining the minimum inhibitory concentration and minimum bactericidal concentration of Melafix on various pathogens. The study revealed that Melafix had no significant bactericidal or inhibitory effect on any of the pathogens tested. This observation suggests that anecdotal benefits of Melafix are not owing to antibacterial activity.

Source: https://www.sciencedirect.com/science/article/abs/pii/S1557506315000269

The above paper seems to show negative results (no antibacterial activity of Melafix), but at least there is no harmful effects on the fish nor water parameters. The effect of Melafix may not be due to the antibacterial activity per se, but possibly the healing and regenerative aspects of it, or boosting the fish’s immune system and regrowth of tissue.

A paper showing positive effects of Melafix is the following:

In particular, a combination treatment of Melafix® and Pimafix® was highly effective at reducing in vitro survival of parasites from 15 to 2 h and eradicating 95% of gyrodactylids in vivo. The unexpected high efficacy of this combination treatment is likely explained by the high content of terpenes and phenol propanoids in the cajuput and West Indian bay oils, as well as the anti-helminthic properties of the emulsifier Crovol PK 70. Hence, Melafix® and Pimafix® effectively reduce gyrodactylid burdens on fish, increasing the chances of efficient disease control in ornamental fish.

Source: https://www.int-res.com/articles/dao2015/115/d115p129.pdf

Yet another paper is not on Melafix, but on its active constituent Cajeput oil:

Main antibacterially active agents obtained from plants-Cajeput essential oil–1,8 cineol, linalool, alpha-terpineol and terpinen-4-ol, for example from Melalleuce leucadendron (Myrtaceae) as well as essential oil from Ocimum gratissimum (Labiatae) were combined in tests in vitro with selected antibiotics. Above mentioned plant products were found to be effective medicaments for local application in modern medical practice. Combinations with antibiotics potentiated their therapeutical action. On the basis of tests in vitro the synergistic action of these two kinds of medicaments, i.e., preparations traditionally used for a few last decades–antibiotics–might be well applied for therapeutical needs.

Source: https://europepmc.org/abstract/med/1293213

Hence, the above link supports the view that Cajeput oil (active ingredient of Melafix) does have antibacterial properties!

Anecdotal Evidence of Melafix

Judging by Amazon reviews (https://amzn.to/34G4Ubr), many people do claim that Melafix works in curing their fish of fin rot, popeye, and various other ailments.

The biggest advantages of Melafix are as follows:

  • Does not kill beneficial filter bacteria
  • Does not stain water (colorless)
  • Shrimp safe
  • Snail safe
  • Plant safe
  • All natural

The most “powerful” medication is of course fish antibiotics, but that is the last resort as there are many side effects of antibiotics, including possible wiping out all filter bacteria, and development of resistant bacteria.

An example of fish antibiotics is API General Cure, which is a very powerful fish medication that can treat very serious diseases such as “hole in the head”.


API GENERAL CURE Freshwater and Saltwater Fish Powder Medication 10-Count Box

Melafix Reviews

The below is an amazing case of recovery from popeye (eye dangling out) treated by Melafix.

It was absolutely the worst case of Popeye I have ever see with the eye protruding almost 3/8 of an inch and hanging down.. It was so nasty looking that the wife & kids wouldn’t go near the tank as the sight made them feel sick.. I was nearly to the point of putting it down as I figured it would surely get worse and if there was some type of infection involved, I didn’t want to contaminate the tank.

I decided to treat the tank with a product made by API called Melafix. This is an antibacterial made from the extract of Tea Trees. I only used 1/2 the recommended dose as to not create any major impact to the rest of my tank and system.

Long story short, within 2 days of the treatment I thought I noticed a change and saw the fish actually eat. I treated the tank again after 3 days and the eye definitely improved.. After the second treatment I just watch with amazement as the fish made a complete recovery within two week with no sign what so ever the initial problem.

Source: https://www.reef2reef.com/threads/severe-pop-eye.261687/

Ohm $20 Promo Code: OHMREF25CC5A

mathtuition88's avatarMathtuition88

*Ohm Promo Code: OHMREF25CC5A

After extensive research, I find that Ohm is one of the best alternative electricity suppliers. Choose either Fixed Ohm or Discount Ohm depending on your likings. I chose Discount Ohm as I have a feeling that the tariffs may drop. Fixed Ohm is also very good, and in fact better if tariffs rise.

Benefits of Ohm:

  1. Their discount off tariff rate is currently the best at 22% (Update: discount is now 25%)!
  2. Very smooth transition as they are partners with SP group. For instance, there is no need for any paper work nor additional payment of deposit.
  3. Very nicely done website. Signing up is immediate, just fill in some personal details online and you will get the Welcome Email in less than 15 minutes.
  4. Ohm absorbs the transmission loss. (Basically electrical energy is lost as heat while travelling through the cable, Ohm absorbs this and charges consumer…

View original post 238 more words

Ohm Electricity Review

I have been using Ohm as my electricity supplier since 01 Nov 2018. So far everything has been going 100% super smoothly. Cheaper electricity bills, and integrated billing system with SP services. Ohm has been processing everything efficiently in the background.

Their website design is super sleek and modern. Very easy to use.

*Ohm Promo Code: OHMREF25CC5A

Highly recommend everyone to go with Ohm as their electricity provider. Just spend 10 minutes of your time to switch now, the potential savings in the long run can add up to hundreds if not thousands of dollars. Good thing is everything is online, there is no need to go down to any location nor any physical paper work. It is also applicable to citizens, foreigners, PR, basically anyone who lives in Singapore.

If you have an extensive network of friends/relatives, their referral network is also amazing for you. You will get $20 off your electricity bill (and your friend too), with no upper limit and no expiry date. Imagine, if you have 500 loyal facebook friends who sign up through you, you will get $10k off your electricity bill, which may be enough to last your entire lifetime in most cases.

See my detailed review and also promo code here: Ohm $20 Promo Code: OHMREF25CC5A

*Ohm Promo Code: OHMREF25CC5A

After extensive research, I find that Ohm is one of the best alternative electricity suppliers. Choose either Fixed Ohm or Discount Ohm depending on your likings. I chose Discount Ohm as I have a feeling that the tariffs may drop. Fixed Ohm is also very good, and in fact better if tariffs rise.

Aquarium Salt dosage for Planted Tanks

As a general rule of thumb start with 1 tablespoon per 5-7 gallons of aquarium water. This is a safe dose for all fish and plants including salt sensitive corydoras.

Source: https://www.ibcbettas.org/aquarium-salt-the-healthy-preventative-v-2-0/

In terms of milliliters, it is approximately:

15 ml of salt for a 20 liter tank (5 US gallon tank)

5 ml of salt for a 7 liter tank (2 US gallon tank)

There are various arguments whether cooking salt can be used in place of aquarium salt. Personally, I use normal cooking salt (non-iodized) and so far it works fine (no fish nor shrimp nor snails have died).


Update: We have created a YouTube video on Aquarium Salt (Dosage, Benefits and Tips!)

Example of a 5 Gallon tank:

Example of a 2 Gallon tank:

Oven Power Trip

Bosch Oven Power Trip

Apparently, it is quite common in Singapore (and other tropical countries like Malaysia, Indonesia) that the electric oven cause a power trip (or short circuit) due to the high humidity. Basically, the heating element tends to attract moisture, and if the moisture accumulates too much it will cause a power trip. Since the humidity in the tropics is very high, the chances of this happening is also quite high.

There are two kinds of oven power trips:

  1. Oven power trips after a certain time (e.g. 5 minutes) from turning it on
  2. Oven causes power trip immediately upon switching on power

Clearly, Case 2 is more serious than Case 1. There is a simple solution for Case 1 Oven Power Trips that you may try: first switch on the oven to low temperature (50 degrees Celsius) to dry out the moisture. Only after reaching that temperature, then slowly turn up the temperature. This may solve your problem to stop the oven power trips.

For Case 2 Oven Power Trips, it is more serious, most likely you will need to call a professional to replace the heating element. For my case, I called the Bosch service repair on Friday, and they were able to come on Monday to repair the oven. It took less than half an hour, and it was free since my oven was still within the two year warranty period.

How to Prevent Future Oven Power Trips

To prevent future power trips or short circuits from occurring in the future, the ideal case is to use the oven more frequently (in all modes!). By “in all modes” I mean that you should use all of the modes, including the upper heater, lower heating element, and/or fans. This was emphasized by the Bosch repair man. (Previously I was only using one single mode, the “fan” mode.)

At the very least, one should still use the oven at least once a month (even if it is empty inside), to dry out the moisture, for a period of 10 to 30 minutes (recommended by many online sources as well as the Bosch repair man).

 


Bosch HBL5451UC 500 30″ Stainless Steel Electric Single Wall Oven – Convection

Popular packages in R and Python for Data Science

Most of the time, users of R and Python will rely on packages and libraries as far as possible, in order to avoid “reinventing the wheel”. Packages that are established are also often superior and preferred, due to lower chance of errors and bugs.

We list down the most popular and useful packages in R and Python for data science, statistics, and machine learning.

Packages in R

  • arules
  • arulesViz
  • car
  • caret
  • cluster
  • corrplot
  • ggplot2
  • lattice
  • perturb
  • psych
  • readr
  • recommenderlab
  • reshape2
  • ROCR
  • rpart
  • rpart.plot
  • tidyverse

Python Packages

  • factor_analyzer
  • math
  • matplotlib
  • numpy
  • pandas
  • scipy
  • seaborn
  • sklearn
  • statsmodels

Recall & Precision vs Sensitivity & Specificity

Other than accuracy rate, there are various metrics for machine learning to measure how “accurate” the model is.

Some popular ones for binary classification are sensitivity (true positive rate) and specificity (true negative rate).

In computer science, recall and precision are also common metrics.

It can be quite confusing to remember offhand what each metric means, and how they are related.

To summarize, the following are equivalent (for binary classification):

sensitivity = recall of positive class

specificity = recall of negative class

Sample source: https://onlinelibrary.wiley.com/doi/pdf/10.1002/cmdc.201700180

Other than the above metrics mentioned, there are also many other metrics, such as F1 score, etc.

LaTeX Table Style Guidelines

Drawing LaTeX tables is well known to be quite troublesome. Fortunately, there are some excellent tools online to generate LaTeX code for tables, e.g. Convert Excel to LaTeX.

Even after that, there are some stylistic dilemmas, for instance how many borders to include in the table?

I found this powerpoint slide that summarizes very nicely what to do (and what not to do) to create a nice LaTeX table. Source: https://inf.ethz.ch/personal/markusp/teaching/guides/guide-tables.pdf

Most Important Guidelines for Making Tables with LaTeX

  • Avoid vertical lines
  • Avoid “boxing up” cells, usually 3 horizontal lines are enough: above, below, and after heading (see examples in the guide above)
  • Avoid double horizontal lines
  • Enough space between rows
  • If in doubt, align left

The above 5 guidelines were invaluable and cleared up my doubts on how to make a nice table using LaTeX.

Express vs Normal Academic for borderline PSLE score

Just to share this old post on the dilemma of choosing Express vs Normal Academic (for borderline PSLE scores). Both choices have pros and cons and hence must be pondered carefully.

mathtuition88's avatarMathtuition88

For students scoring in the borderline of around 190- 200 PSLE score, there is a dilemma of going to Express stream in a neighborhood school, or Normal Academic N(A) in a more established school. Note that even good schools like Anderson, ACS (Barker) do have N(A) streams.

Here are some advices from people who have experience:

Source: Hardwarezone

First opinion says that N(A) in a good school is better:

“NA in good school

i myself is living example

in the end my parent chose express at neighborhood school

in the end that school is a s**** school. i cannot keep up with studies.

by secondary 2 i drop to NA

then stuck with the lousy neighborhood school and my whole life got ruin until now

if i can go back time i sure chose NA at good school”

This post (from Hardwarezone) made a good argument of why express stream…

View original post 606 more words

Ways To Turn Writing Inspiration Into Money

A good writer is gifted with imagination and the ability to capture the imagination of readers. A lot of these writers begin writing as a hobby. However, some have found a way of converting this hobby into an economic activity that brings revenue. You may take up freelance writing job or engage in other activities that will pay for the effort and skill you already possess.

Image

Writers have multiple options when looking for places to apply their skills. The options will depend on personal interests, available time, and the willingness to venture into a particular field, among other factors. Here are the options available to talented writers who wish to make a few dollars from their skills. 

Blogger

Open a blog where you share regular content with followers and readers. A lot of blogging platforms have emerged online that writers can use to launch their careers. A writer may also choose social media as a starting point for his or her blogging career. 

A blogger needs to identify the perfect niche for his or her blog. It should come out of interest so that your articles are insightful to read. Choose a unique style that your readers can identify with and always look forward to reading your articles. 

Writer

Individuals, businesses, and entrepreneurs are looking for the skilled persons who can tell their stories in writing. It means that a writer will never lose the opportunity to make money. You must possess the best skills that will enable you to meet your client’s expectations. 

Choose a niche and master the content needs for the area. For instance, a product reviewer will know what potential customers are looking for in a review. A content writer also understands the rules for producing the best description of merchandise. Your prowess in a given area will determine the number of clients who come looking for your services. Expert writers earn handsome returns. 

Editor

Editing is a skill that few have mastered. It requires a professional who understands the rules of writing and has a third eye to spot subtle mistakes. Editing eliminates errors that would distort communication leading to misreporting or misinformation. Experienced writers can take up editing roles and enjoy excellent returns. 

Ghostwriter 

Some individuals and institutions lack the time or skill to write but would desire to produce scripts and books. Ghostwriters are paid to complete the task but not take credit for the work. You have to master writing skills in a specific area like blogging, books, and such other genres. 

Trainer 

A lot of people desire to improve their writing skills. They are looking for mentors and trainers who can help them sharpen their writing skills. Since you understand writing and have specialized in a particular area, you can teach other persons looking for guidance or assist them in improving their skills. 

The amount of money earned from writing prowess depends on your area of choice and the ability to monetize the platforms you use. The money can be earned online or offline. Adapt to the latest writing tricks to improve your chances of making more money. 

 

Singaporean van Gogh – Mr Sim Kah Lim

Sim Kah Lim 2019 Update
Found 2 more excellent updated videos on Mr Sim Kah Lim, the artist.

mathtuition88's avatarMathtuition88

This is an amazing story of an amazing artist. His passion for painting is so great, according to his therapist he wants to paint 24/7 without eating or sleeping. I find his paintings of Singapore River very good.

“Bumboats on Old Singapore River”

“Singapore River of a Previous Era”

SINGAPORE: For nearly 35 years, Mr Sim Kah Lim’s world has been the walls of his ward at the Institute of Mental Health (IMH).

Outside, changes have swept the landscape, old buildings falling and new ones rising – skylines and shorelines of a 21st-century nation transformed.

But in his mind’s eye – and in his bold-stroked acrylic and watercolour paintings – Mr Sim’s homeland is one where bumboats still crowd the Singapore River, ferrying goods and passengers; and where Chinatown’s open-air markets thrive and its five-foot ways are bustling with locals, not tourists.

They are pictures, frozen in time and memory, from…

View original post 90 more words

Narrow Leaf Java Fern vs Normal Java Fern

It is well known that the Java Fern has different “varieties” — such as “trident”, “Windelov”, “Narrow Leaf” and “Needle Leaf”.

I kept normal Java Fern, as well as “Narrow Leaf” Java Fern in Singapore, at a temperature of around 29 to 30 degrees Celsius (85-86 Fahrenheit).

I found that the Normal Java Fern does well (nice green color, and grows baby plantlets), but the “Narrow Leaf” Java Fern does not do well (becomes browner and even blacker by the day).

I checked online and at least four other people have experienced this:

I think cooler temperatures might be the answer. My narrow leaf in syd are lush green and pearling like mad in temps of 25 celsius. In KL, 28-29 celsius, they grow a little, turn brown sometimes and are a bit of a hassle to keep. My normal java fern does well in any temps/conditions, just the narrow leaf, more demanding. Has anyone grew nice long narrow leaf in warm temps? Those in LFS have them in air conditioned rooms.

Source: http://www.aquaticquotient.com/forum/showthread.php/21779-Narrow-leaf-Java-Fern


Narrow Leaf Java Fern does better in cooler temperatures (around 25 degrees Celsius)

Other anecdotal evidence that Narrow Leaf Java Fern may do better in cooler waters:

Wes,

I’ve had a lot of success with Java Ferns and Narrow Leaf Java Ferns (NLJF) in my tank.

My tank is high-light (288Watts for 80gallon) and has lots of CO2 (3bps). I dose it with TMG almost every week. I tie the JF on driftwood and also bury them in my substrate, either way it grows well. Kwek Leong did share with me that growing them in substrate will produce longer leaves for NLJF and that holds true in my tank. I place them very new my water outlet as I read somewhere that the JF thrives in that environment. Also, I have a chiller that keeps my water temp at around 24.5-25.0C.

Hope this helps!

Cheers,

Roger

Another post:

I knew of a tank that grow Narrow Leaf Java Fern very well and the conditions are like what Roger has too. Under these conditions, they grow very rapidly and the leafs are jade green and very clean (no spots at all).

Yet another post:

I used to have prolific growth of Narrow Leaf Java Ferns in my tank. I don’t think CO2 injection is necessary but the ferns probably do better under low light and cold water.

Source: http://www.aquaticquotient.com/forum/showthread.php/49107-Best-conditions-for-Java-Fern

Methylene Blue and Narrow Leaf Java Fern

Something else interesting that I found out is that methylene blue seems to affect narrow leaf Java Fern negatively, but not normal Java Fern. Basically, the Methylene blue seems to stain the narrow leaf Java Fern, and lead to its demise. I tried this out inadvertently while dosing my fish tanks with methylene blue to cure ich.

The Narrow Leaf Java Fern is on the right of my fish tank in the video below (it was still in an ok state at that time):


I think the conclusion is that Narrow Leaf Java Fern is a slightly more demanding plant when it comes to temperature (does not do well above 27-28 Celsius). Due to global warming, many countries in the tropics are now stuck with 30 degrees Celsius temperature almost all year round, hence the normal Java Fern may be a better choice.

It also sort of makes sense in terms of plant biology. Usually plants with “thin” leaves tend to be those that live in colder/cooler weather such as pine trees. While plants with big wide leaves are those that live in hot tropical weather (such as banana tree). Using this “logic”, I would suppose that needle leaf Java Fern also does better in cooler waters.

How to Balance College and Work and Find Some Spare Time

No one said it would be easy, but if you’re looking for ways on how to balance college and work, use these tips to improve time management.

A recent survey revealed that the majority of students work while attending college. Learning how to balance college and work on a full-time basis is your key to achieving success with less student loan debt.

According to this survey, 24.4% of students claimed they were fully responsible for funding their education. If your dream depends on you getting a degree, please know that your goal is still within reach.

Attending school and working full-time isn’t easy, but any effort you invest in this endeavor will pay off big time. You, too, deserve to feel the pride of graduating with a degree.

Here are some tips on how to balance work and college full-time.

How to Balance College and Work: Time Management

Knowing how to balance work and college means mastering time management. Developing time management skills involves planning and budgeting your time well. When you have 2 schedules to juggle, you must keep track of both to succeed.

Make sure you either write down your work hours or mark them on your phone’s calendar. Use a college schedule maker to create a visual reminder of your class schedule.

Print several copies of this schedule, including a copy to carry with you and another copy to hang up in your workspace.

Designated Workspace Hours

Anyone who’s aware of how to balance school and work in college has a designated space where they complete their work. This space is organized, clean, and stocked with supplies. It’s also free of distractions, so getting work done is more doable there.

A designated workspace like this helps you be more productive. Once you get into the habit of doing schoolwork there, your brain starts associating that space with getting homework done. Then simply entering this workspace will kick your brain right into “homework mode.”

Carve out time that you’ll commit to spending in your workplace. During this time, you’ll study and complete homework. School is just as important as work, so you need to devote time to it.

This way, you won’t have to rush and can work on this next tip.

Sleep Schedule and “Me” Time

Make sure you maintain a regular sleep schedule. Also, try to enjoy some “me” time whenever you get the chance. Your schedule is already packed, so there’s no need to cram more stuff into your day.

Sure, caffeine will help you stay awake. But no amount of caffeine will energize you as much as a good night’s sleep can.

Work on your assignments as soon as possible instead of procrastinating. Getting work done on time reduces your need to rush or pull an all-nighter.

You Are a Success in Progress

The CDC recommends that you get at least 7 hours of sleep per 24-hour period. You can’t truly know how to balance college and work if you’re not getting enough sleep.

If you do pull an all-nighter, make sure you get sleep as soon as possible. An erratic sleep schedule will eventually hurt your work/academic performance.

Give yourself some credit⁠ and check out our resume and networking tips. It’ll improve your chances of landing a better job.

Bend It Like Beckham: How to Become a Pro Soccer Player

How to Become a Pro Soccer Player

Ever wanted to bend it like Beckham? Turns out, you can with the right training and dedication. Read on to learn how to become a pro soccer player.

Sure, a lot of people dream about becoming a professional athlete. But, most of them don’t have what it takes to go pro and wind up giving up on their dreams.

Becoming a pro soccer player requires a little bit more than a love for the game; it takes a lot of hard work, patience, and determination.

If you think you have what it takes to make it in the big league, but aren’t sure where to begin, we’re here to help you chart your course.

Here’s everything you need to know about how to become a professional soccer player.

Be Ready to Dedicate Yourself

If you’re serious about becoming a professional soccer player, you’re going to need to be ready to give your life over to your sport.

In the years leading up to and during your pro career, you’re going to need to eat, sleep, and breathe soccer. Your body is now your most important tool, and you’ll need to do everything you can to hone it and mold it into a soccer-playing machine.

You’ll need to put together a strict training regimen, and spend a few hours every day practicing.

Outside of training, you’ll need to change your eating and sleeping habits to make sure you’re taking proper care of your body. That means giving up late nights and junk food.

If you think you can handle molding your life around your sport, you can begin to pursue your professional career.

Join a Club or a Team

You can’t walk up to a recruiter and insist you can play at a professional level. You’re going to have to prove it. And, the best way to show off your soccer skills is by joining a local team or a club.

Playing minor league or college level soccer is one of the best ways to get noticed on the field. That said, playing university sports can pose the additional challenge of balancing classes on top of your practice time.

If you make your university’s team, you’ll want to sit down with a college schedule maker to plan your classes and study time around your soccer career.

Joining a team will also help you work on your communication and teamwork. These skills are essential when playing a professional level sport.

On top of that, a team will have the resources available to help you get in touch with club owners and recruiters.

Train On and Off the Field

If you want a chance at going pro, you’re going to need to train outside of team practices.

Work with your coach or professional trainer to construct a good crosstraining program. You’ll also want to go over the best activities you can do to help your body recover on your rest days.

Sticking to a rigorous training program can be tough. But, all your hard work will be worth it the first time you don your pro uniform.

Build Your Network

Finally, like with most careers, it’s not always about what you can do, it’s about who you know.

Go to networking events, talk to your coaches about your goals, and prepare a highlight reel to send out to various clubs and recruiters.

Building a network is one of the best ways to bring your pro soccer dreams to life.

Becoming a Pro Soccer Player

If you want to become a pro soccer player, the most important thing you can do is maintain belief in yourself and your goals.

Reaching the professional level can take years. And during that time you’re probably going to face a lot of rejection. But, if you never doubt yourself and keep working toward your goal, you’ll eventually reach it.

Are you looking for more advice on how to take your game to the next level? We’ve got you covered.

Check out the rest of our blog for more helpful articles today!

Fish at Yale-NUS Eco pond

Some very interesting fish (South American cichlids?) at the Yale-NUS Eco-pond. It is quite an unknown place, located deep inside U-Town. Not many people know of its existence. Do check it out if you pass by NUS.

At around the 1:45 mark in the video, you can see some juvenile cichlids eating algae growing on the rock.

Some photos of the Yale-NUS Ecopond:

The pond is behind this large circular fountain.

 

There is also this rare tree (supposedly the only one in Singapore) right behind the pond, called “Margaritaria indica”. I think only expert botanists can tell what is so special about this tree. To laymen (like me), it looks like any ordinary tree.

How to make work-life balance work (TED talk)

Quotes from the talk:

  • “People are working long hard hours at jobs they hate, to earn money to buy things they don’t need, to impress people they don’t like”

A book by the same speaker:


Fat, Forty, and Fired: One Man’s Frank, Funny, and Inspiring Account of Losing His Job and Finding His Life

Amazing method to unblock stuffy nose

Added another great way to unblock nose. This is a new method called Nasal Septum Mobilization invented by Dr Alan Mandell.

mathtuition88's avatarMathtuition88

Out of all the methods I checked on YouTube, this method seems to be the most effective in terms of instantly unblocking your nose.

Basically pinch your nose and sway, until you are almost out of breath, then breath in through your nose. I find it very effective.

This method is very good also: Nasal Septum Mobilization invented by Dr Alan Mandell. It is quite a novel method, so far I have only seen it on his YouTube channel and not anywhere else. I think it may work for people with Deviated Septum as a natural remedy. Basically, the way it works is by moving the septum so as to create a “motion” to unblock the nose.

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LaTeX Horizontal Flowchart (Workflow)

Source: https://tex.stackexchange.com/questions/368482/one-horizontal-line-flow-chart?rq=1

Just found an excellent source on how to draw a simple (slightly fanciful) horizontal flowchart using LaTeX (TikZ).

The output is very neat:

The code is reproduced here (in case the original source gets deleted):

\documentclass[tikz, margin=3mm]{standalone}
\usetikzlibrary{arrows.meta,
                chains,
                positioning,
                shapes.geometric
                }
% for fancy looks of data storages
\begin{document}
    \begin{tikzpicture}[
    node distance = 5mm and 7mm,
      start chain = going right,
 disc/.style = {shape=cylinder, draw, shape aspect=0.3,
                shape border rotate=90,
                text width=17mm, align=center, font=\linespread{0.8}\selectfont},
  mdl/.style = {shape=ellipse, aspect=2.2, draw},
  alg/.style = {draw, align=center, font=\linespread{0.8}\selectfont}
                    ]
    \begin{scope}[every node/.append style={on chain, join=by -Stealth}]
\node (n1) [disc] {Training\\ data};
\node (n2) [alg]  {Learning\\ algorithm};
\node (n3) [mdl]  {Model};
\node (n4) [disc] {Test\\ data};
\node (n3) [mdl]  {Accuracy};
    \end{scope}
\node[below=of n2]  {Step 1: Training};
\node[below=of n4]  {Step 2: Tresting};
    \end{tikzpicture}
\end{document}

Multiline Flow Chart

For flowcharts that exceed one line (and hence require a line break), the following Tikz code is very helpful! (Source: https://tex.stackexchange.com/questions/149602/drawing-flow-diagram-in-latex-using-tikz)

\documentclass[border=10pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{arrows,positioning,shapes.geometric}
\begin{document}
    \begin{tikzpicture}[>=latex']
        \tikzset{block/.style= {draw, rectangle, align=center,minimum width=2cm,minimum height=1cm},
        rblock/.style={draw, shape=rectangle,rounded corners=1.5em,align=center,minimum width=2cm,minimum height=1cm},
        input/.style={ % requires library shapes.geometric
        draw,
        trapezium,
        trapezium left angle=60,
        trapezium right angle=120,
        minimum width=2cm,
        align=center,
        minimum height=1cm
    },
        }
        \node [rblock]  (start) {Start};
        \node [block, right =2cm of start] (acquire) {Acquire Image};
        \node [block, right =2cm of acquire] (rgb2gray) {RGB to Gray};
        \node [block, right =2cm of rgb2gray] (otsu) {Localized OTSU \\ Thresholding};
        \node [block, below right =2cm and -0.5cm of start] (gchannel) {Subtract the \\ Green Channel};
        \node [block, right =2cm of gchannel] (closing) {Morphological \\ Closing};
        \node [block, right =2cm of closing] (NN) {Sign Detection \\ Using NN};
        \node [input, right =2cm of NN] (limit) {Speed \\ Limit};
        \node [coordinate, below right =1cm and 1cm of otsu] (right) {};  %% Coordinate on right and middle
        \node [coordinate,above left =1cm and 1cm of gchannel] (left) {};  %% Coordinate on left and middle

%% paths
        \path[draw,->] (start) edge (acquire)
                    (acquire) edge (rgb2gray)
                    (rgb2gray) edge (otsu)
                    (otsu.east) -| (right) -- (left) |- (gchannel)
                    (gchannel) edge (closing)
                    (closing) edge (NN)
                    (NN) edge (limit)
                    ;
    \end{tikzpicture}
\end{document}

Output:

Amazing method to unblock stuffy nose

Out of all the methods I checked on YouTube, this method seems to be the most effective in terms of instantly unblocking your nose.

Basically pinch your nose and sway, until you are almost out of breath, then breath in through your nose. I find it very effective.

This method is very good also: Nasal Septum Mobilization invented by Dr Alan Mandell. It is quite a novel method, so far I have only seen it on his YouTube channel and not anywhere else. I think it may work for people with Deviated Septum as a natural remedy. Basically, the way it works is by moving the septum so as to create a “motion” to unblock the nose.

Cai Yun Zhui Yue Piano Sheet Music (PDF)

This is a classical piano tune that is masterfully transcribed (by arranger Wang Jianzhong 王建中). In English, it is also called “Colourful Clouds Chasing the Moon”. In Chinese, it is called 彩云追月.

The transcription is really very nice, the harmony and the melody of the original tune is preserved and even enhanced. Few piano scores for Chinese music can achieve this effect.

The sheet music (or piano score) is originally from http://www.everyonepiano.com, we simply convert to PDF for the convenience of those who are seeking it:

PDF Sheet Music Score for Cai Yun Zhui Yue: Cai Yun Zhui Yue PDF

I checked that this version is the same as the one performed by Li Yundi:

Taiwan Aquarium Fish Tour

There are many blogs focusing on Taiwan tourism, this blog focuses on the aspect of fish you can see/eat in Taiwan.

Koi at Chiang Kai-Shek Memorial Hall

If you visit the Chiang Kai-Shek memorial hall in Taipei, do check out the pond just nearby. There are many koi in the pond, and also a vending machine with fish food for sale (around NT$10 for a tube of fish food). There are various colors of koi, ranging from dull gray to colorful red, white or gold colors.

Marimo Moss Ball Exhibition at National Taiwan Museum

The National Taiwan Museum is not as famous as the other museum, National Palace Museum (aka Gu Gong), but nonetheless it holds some interesting specimens related to Taiwan. When I went there, there was a small Marimo Moss ball exhibition. The Marimo Moss ball were of exceptional high quality (better than any moss ball I saw in Singapore). They were dark green, dense, and almost perfectly spherical.

Water Lettuce Bowl with Guppy

Very healthy looking Water Lettuce specimens in a large porcelain bowl. The leaves were almost perfect, with no holes. There is also a female guppy (camouflaged in the second picture), together with guppy fry living in the bowl. This was seen on Shifen Old Street towards the waterfall.

Koi Pond en route to Shifen Waterfall

On the way to the famous waterfall at Shifen, there is yet another Koi pond with the option to purchase fish food (this time at NT$20). Interestingly, I did spot fishes in the river adjoining the waterfall, but it is quite hard to photograph them due to their color (dull black) and the distance. I wonder what happens if they fall down the waterfall.

Aquarium Shops in Taipei

The most famous aquarium street in Taipei is the one at Section 5, Minquan East Road. Unfortunately, it is not very accessible via train. Despite sounding similar, the Minquan West Road Metro station is very far from Minquan East Road.

I went to a nearby aquarium in Shilin district instead. To my surprise, there was an alligator snapping turtle in the aquarium (together with various interesting species of aquatic tortoises). Just beside the aquarium was a local Taiwanese restaurant popular with locals, with free flow rice and ice-cream. In the restaurant, there are a few live fish and crabs for eating, and there was a moray eel inside!

One thing to note is that Cod Fish (Snow Fish or Xue Yu) is quite cheap in Taiwan, in the restaurant one slab of Cod Fish the size of my hand is just NT$180 or SGD$8. In Singapore, the price is at least double or triple that.

pip install keeps installing old/outdated packages

This article is suitable for solving the following few problems:

  1. module ‘sklearn.tree’ has no attribute ‘plot_tree’
  2. pip install (on Spyder, Anaconda Prompt, etc.) does not install the latest package.

The leading reason for “module ‘sklearn.tree’ has no attribute ‘plot_tree” is because the sklearn package is outdated.

Sometimes “pip install scikit-learn” simply does not update the sklearn package to the latest version. Type “print(sklearn.__version__)” to get the version of sklearn on your machine, it should be at least 0.21.

The solution is to force pip to install the latest package:

pip install --no-cache-dir --upgrade <package>

In this case, we would replace <package>  by “scikit-learn”.


Sometimes, pip install does not work in the Spyder IPython console, it displays an error to the effect that you should install “outside the IPython console”. This is not normal (i.e. it should not happen), but as a quick fix you can try “pip install” in Anaconda Prompt instead. It is likely that something wrong went on during the installation of Anaconda, Python, and the long-term solution is to reinstall Anaconda.

caret package in R: known issue when converting factor variables

In the R language, often you have to convert variables to “factor” or “categorical”. There is a known issue in the ‘caret’ library that may cause errors when you do that in a certain way.

The correct way to convert variables to ‘factor’ is:

trainset$Churn = as.factor(trainset$Churn)

In particular, “the train() function in caret does not handle factor variables well” when you convert to factors using other methods.
(See https://rpubs.com/SulmanKhan/444033)

Basically, if you use other ways to convert to ‘factor’, the code may still run, but there may be some ‘weird’ issues that leads to inaccurate predictions (for instance if you are doing logistic regression, decision trees, etc.)

Saving Rasbora from Dropsy

Recently, my mosquito rasbora (Boraras merah) was acting weirdly by hiding in a corner and sleeping more than usual.

Upon closer examination, I found “specks” on it. At first I thought it was velvet. However, this was an old tank and there has not been any introduced fish for more than 2 months. Then I realized it was probably dropsy and the specks were actually pineconing of the scales, which looks like specks of dust because of the smallness of the scales (this mosquito rasbora is one of the smallest fish in the freshwater aquarium, measuring less than 2 cm when fully grown). In conclusion, I think dropsy in tiny fish can probably look like velvet.

I think the reason is that the dwarf hairgrass (and Japanese hairgrass) planted in the sand substrate has failed to grow, and in fact has started to die and rot, releasing ammonia, nitrites and/or nitrates into the water. I do have a Seachem Ammonia Alert badge that did not show any readings.

Hence, I suspect it is probably nitrates. I added Methylene blue (full dose) after 50% water change, and then continued 50% water change on the second day, topping up the Methylene blue (half dose). On the third day, another 50% water change. (For all days during the water change, I removed the rotting hairgrass as well as any pond snails pests that I find, and wiped off algae).

After the third day, the mosquito rasbora began to behave normally again, swimming around and schooling together with the lambchop rasbora. I hope it will survive.

The lambchop rasbora seem unaffected and seem more hardy than the mosquito rasbora. I think the mosquito rasbora may be more sensitive to water parameters.

Mosquito Rasbora in (diluted) Methylene Blue water.

Philips Stainless Steel Pressure Cooker

The keyword here is “stainless steel”, because if you look at many pressure cookers, the inner pot is made of aluminum alloy. The bad thing about aluminum is that it is linked to Alzheimer’s disease. For instance, this medical paper states that “Immediate steps should be taken to lessen human exposure to Al (aluminum), which may be the single most aggravating and avoidable factor related to AD (Alzheimer’s disease).”

Philips makes one of the best brands of pressure cookers, including the famous HD2137 model which is sold in Singapore. It can be bought almost anywhere, including the Philips Qoo10 official store:

[S$147.00](▼64%)[PHILIPS]PHILIPS HD2137/62 Viva Collection All-in-One Cooker | HD2139/62 Pressure Cooker

WWW.QOO10.SG

The default Philips pressure cooker, however, comes with aluminum inner pot, no matter which model. Fortunately, there is a solution, which is to buy the Stainless Steel Inner Pot from the official Philips website.

Highly recommended to upgrade to this stainless steel inner pot.

The stainless steel inner pot is suitable for the following models: HD2137, HD2237, HD2178, HD2145. It is quite pricey at $59 (Singapore dollars), but I think it is worth it considering that it should last for a lifetime or at least a long time.

Interestingly, Philips sells these pressure cooker models mainly to Asian market. I don’t find them in the American Amazon.com website. Perhaps the American diet (steak, burgers, fries) don’t really require the pressure cooker? I am not sure.


Do check out some of the amazing recipes possible using the Philips Pressure Cooker with Stainless Steel Inner pot:

How to save sklearn tree plot as file (Vector Graphics)

The Scikit-Learn (sklearn) Python package has a nice function sklearn.tree.plot_tree to plot (decision) trees. The documentation is found here.

However, the default plot just by using the command

tree.plot_tree(clf)

could be low resolution if you try to save it from a IDE like Spyder.

The solution is to first import matplotlib.pyplot:

import matplotlib.pyplot as plt

Then, the following code will allow you to save the sklearn tree as .eps (or you could change the format accordingly):

plt.figure()
tree.plot_tree(clf,filled=True)  
plt.savefig('tree.eps',format='eps',bbox_inches = "tight")

To elaborate, clf is your Decision Tree classifier (to be defined before plotting the tree):

# Example from https://scikit-learn.org/stable/modules/generated/sklearn.tree.plot_tree.html
clf = tree.DecisionTreeClassifier(random_state=0)
clf = clf.fit(iris.data, iris.target)

The outcome is a Vector Graphics format (.eps) tree that will retain its full resolution when zoomed in. The bbox_inches=”tight” command prevents truncating of the image. Without that command, sometimes the sklearn tree will just be cropped off and be incomplete.

In the northern darkness there is a fish and his name is K’un.

Just realized that there is some parallel between the Chinese Giant Fish Kun (鲲) and the Jewish Giant Fish Leviathan.

Similarly, Chinese Giant Bird Peng (鹏) = Jewish Giant Bird Ziz.

In the northern darkness there is a fish and his name is K’un. The K’un is so huge I don’t know how many thousand li he measures. He changes and becomes a bird whose name is P’eng. The back of the P’eng measures I don’t know how many thousand li across and, when he rises up and flies off, his wings are like clouds all over the sky. When the sea begins to move, this bird sets off for the southern darkness, which is the Lake of Heaven.

Source: https://en.wikipedia.org/wiki/Peng_(mythology)

As Leviathan is the king of fishes, so the Ziz is appointed to rule over the birds. His name comes from the variety of tastes his flesh has; it tastes like this, zeh, and like that, zeh. The Ziz is as monstrous of size as Leviathan himself. His ankles rest on the earth, and his head reaches to the very sky.

Source: https://en.wikipedia.org/wiki/Ziz

Clockwise from left: Behemoth (on earth), Ziz (in sky), and Leviathan (under sea). From Wikipedia.
Cool picture of Giant Fish Kun from Baidu.

6 Things All Mathematicians Do

It can be hard when your child is struggling academically. When kids feel defeated they tend to push against the homework they’ve been assigned and before you know it everyone is upset and they keep falling further and further behind. And then comes the famous phrase “I’m never going to need to know this, anyway!” 

And sure, that may be true. But that doesn’t necessarily mean it isn’t worth learning. With the help of math tutors in Chicago or your area, you can get your child back on track and help them to not only find success in school but apply the skills they’ve learned to other areas of their life. 

Everyone is a mathematician! Seriously! Take a look at this list of things that mathematicians (you) do and consider how it will benefit your child in their life to learn all that math has to offer. The benefits of learning math certainly outweigh the fact they might not like it right now. 

1. Math Makes You A Problem Solver

Math is all about the analytical mindset and being experienced in math allows us to think critically and to reason. It seems weird to think about how a train leaving a station problem can truly affect our mindset, but when you learn to solve math problems you will exercise the same skills you will need to solve other problems. 

Problem-solving is all about taking the knowns and unknowns and implementing a process to make the best possible choice. Math exercises the brain and allows you to apply mathematical strategies to everyday life. Getting kids excited to be problem solvers isn’t hard, they come by it naturally. Help them engage them in math and they will succeed!

2. Cooking and Baking? All Math!

Think about the process of making pancakes on Saturday morning. There’s so much math going on that maybe you don’t even recognize. You have to measure ingredients and figure out how many pancakes each person is going to get. Maybe you need to double your recipe? It’s likely you don’t sit down to think about how to change the quantities of ingredients. 

The fractions and math needed in cooking and baking are just one real-world application of math skills and it’s also a great way to engage your child in the learning process. Having a reluctant learner learn fractions by baking cookies is a great option with a sweet reward. 

3. Math Helps Your Career

Sure, the adult world seems far away for your nine-year-old but the skills she is learning today will inevitably aid her career path. Math is used in almost every career somehow. Obviously mathematicians and scientists and doctors rely on math frequently. Whether or not you plan to utilize higher-level math on a regular basis you have to admit everyone uses math sometimes.

Imagine you’re driving on a road trip. Figuring out gas, mileage, and speed is all math and that’s stripping it down to the basics. Math is everywhere, even without you realizing it. Fostering math education is important for your child’s future. 

4. Money Is Math.

When you explain it to a child that way, they may suddenly get a lot more eager to figure out the math they’re struggling with. Even automated cash registers require some knowledge of basic arithmetic. Consider opening a savings account in your child’s name to spark their interest beyond what the tooth fairy is bringing. 

Even if your child is absolutely certain she will never use math, it’s worth mentioning she will eventually have to get a job and get paid. Understanding her take-home pay versus taxes and exemptions is a crucial part of financial planning and responsibility. In these basic terms, everyone uses math.

People who know math are less likely to go into debt because they are able to understand their account balances and can budget them correctly. Nobody likes overdraft fees but if you’re not mathematically conscious they’re far more likely to occur. When you teach a child the basics they will be able to be far more self-sufficient in the future.

5. No Matter Where You Go, Math is the Same!

One of the most interesting things about math is that it’s universal. All over the world, all  children learn the same math. Mathematical rules don’t change because you’re in another country — 1 + 1 = 2 no matter where you are. 

Understanding this concept early broadens your worldview and can inspire children to learn. Math can actually be a joyful concept when you add some perspective to a child’s education. It is often reassuring to children that there are others in the same situation as they are.

6. Technology Relies on Math

You know that smartphone your teenager just has to have? It runs because of math. Math is essential to learning new technologies. In today’s world technology is changing as we speak. Children today need to learn math so that they can keep up and helped create the next latest technological advancement. 

If you believe that children are our future you should also believe that math skills are an integral part of that future. So when your teenager gets frustrated that his app keeps crashing, explain that he could use his math skills to create an app of his own. 

Conclusion: 

It’s never too late to increase your brain’s capacity for learning math. It may take a little more work but you can always inspire your children to continue on their math education. When it seems like an uphill battle, it’s a great idea to bring in some outside help from a tutor. 

A solid mathematical education is essential for children no matter what their passions and ambitions are. Everyone uses math! It’s just a matter of finding the right way to get your child excited about it as well. Sure, Algebra may seem complicated but if they can conquer that they are on their way to being able to conquer anything at all.

Domain Authority 30

Previously, Page Rank was the more appropriate ranking system for how well a page or domain ranks on Google. However, Google has since temporarily (or permanently?) discontinued Page Rank.

Hence, now the closest measure to Page Rank is Domain Authority, by the company Moz.

Currently, Mathtuition88 has Domain Authority 30. Domain Authority is on a logarithmic scale, meaning that it is harder to increase from 80 to 90 than from 30 to 40.

According to the Moz forum, the Head Data Scientist said that a formula to convert to linear scale from the logarithm scale is:

If you just want an estimate, take the log (base 10). You’ll get a value from zero to two that will be roughly linear, and then you can scale it up to whatever range you need.

To be specific, a formula to convert Moz scale to “normal non-logarithmic scale” out of 100 is:

New Score = log(DA) * 50

Using this formula, the score for Mathtuition88 is log(30)*50 = 73.9.

Actually, I am a little skeptical about the above formula and how accurate it is. For instance, I think that one should take exponential (to the correct base) instead of log again for the “non-logarithmic” scale?

For instance,

log(40)* 50 = 80.1

log(80)*50 = 95.2

log(90)*50 = 97.7

Hence, to increase from DA 30 to DA 40 corresponds to an increase in “New Score” of 6.2. To increase from DA 80 to DA 90 corresponds to an increase in “New Score” of 2.5. This does not tally with the idea of “it is harder to increase from 80 to 90 than from 30 to 40”.

Another quote from Moz:

Dr. Matt Peters, Moz’s head of Data Science:

“PA and DA are the output from a machine learning model that we then rescale to values between 1-100.  The raw output from the model is dimensionless and doesn’t have any interesting meaning.  The rescaling is linear, but the inputs to the model are rescaled logarithmically before being used in the model.  We use the natural log (base e) but the base is pretty arbitrary since one can transform from one base to another by changing coefficients, and the coefficients themselves are set in a regression.  The key point is that since the inputs have a log applied to them it is much harder to increase DA from say 70 to 80 then it is from 30 to 40.”

Based on this, another formula to convert Moz’s Domain Authority to a Non-logarithmic score could be:

New Score = [e^(DA)/e^100)] * (100)?

The problem with the above formula is that it gives very low scores close to 0.

Mathtuition88’s Domain Authority:

MOZDomain Authority30

Recommended Air Purifier for Haze

Recently the Haze in Singapore is getting worse. One can literally smell the burning smell in the air.

A recommended cheap and good air purifier for home usage is the Xiaomi Air purifier. Xiaomi is well-known for producing high-tech goods at affordable prices. For instance, their weighing scale and fitness band (Mi Band) is top-notch for their price range.

[S$169.00](▼30%)[Local Warranty] XIAOMI Air Purifier Gen 3 // 2S // Pro (Ship by 25th Sep)

WWW.QOO10.SG

Where to park your car, according to math

Chinoiseries2014's avatarMath Online Tom Circle

This “Simple Car Parking” is the Decision Making Strategy demonstrated in our daily life, even in the micro-cell biological level in nature.

In the current USA-China Trade War, China Xi is taking the Prudent (中庸) approach of a partial 80% deal, while Trump is too Optimistic (or gung-ho) , insisting to accept either a “Full 100%” deal or None. Math tells you the smartest man’s approach is China Xi “Prudent” strategy.

Opportunity Score:

Meek : 1/5 score = ‘Kiasu’ (怕输 )

Prudent : 3/5 score = (中庸 )

Optimist : 5/5 or 0/5 score = (Gung-Ho)

Differential Equation:

https://m.phys.org/news/2019-09-car-math.html

In 三国演义 Three Kingdoms, the smartest military strategist Zhuge Liang (诸葛亮) was attacking the biggest northern enemy Wei (魏). He chose the Prudent (‘P’) route longer distance but less ambushes, rejected his General 魏延 ‘s Optimistic (‘O ‘) approach of taking the risky “子午谷” mountainous but shortest route.

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Chen Jingrun–Do You Really Know About the Giant (1)

tomhanforum's avatarQuantum Han's Forum

This time, let’s talk about math; exactly speaking, a mathematician.

My favorite things in this world are math and physics. Today, I cannot wait to share with you some stories of Chen Jingrun, considered by many to be one of the greatest Chinese mathematicians.

th

What makes me a little outraged is that most people, including many Chinese people, who have heard of his name, think of him as a nerd who knows nothing except math. Why do people think like that? I have been wondering about this and learning about his stories, and I still cannot discover the cause. Perhaps because of the distortion of some of his stories during the Cultural Revolution? Probably most people cannot understand why a person can be so passionate, enduring, persistent, patient, frugal, and kind. Probably they cannot understand what motivated him to dedicate his whole lifetime to only one conundrum-The Goldbach Conjecture, one…

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Chen Jingrun–Do You Really Know About the Giant? (2)

tomhanforum's avatarQuantum Han's Forum

“Each work of Mr. Chen Jingrun seems as if it is scaling the tallest mountains of the Himalayas. It is perilous [work], but if successful, will certainly affect the world.” (André Weil, Wolf Prize in Mathematics Laureate, 1979)

It is said that numerous ambitious youths have been inspired, spurred by Chen’s virtues and respectable spirits. Somebody said that to some extent, besides proving the “1+2” case of the Goldbach Conjecture, another contribution Dr. Chen made to mankind is that his stories invigorated countless young people striving for their futures and pushed a whole generation of mathematicians and scientists forward.

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Dr. Chen was born into a poor family, into an era when warfare has turned China into Les Miserables. His mother did not have breast milk and borrowed rice soup from their neighbors to feed the young Chen Jingrun so that he would not starve to death. He had to shoulder…

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Singapore Haze & Subgroup of Smallest Prime Index

mathtuition88's avatarMathtuition88

Recently, the Singapore Haze is getting quite bad, crossing the 200 PSI Mark on several occasions. Do consider purchasing a Air Purifier, or some N95 Masks, as the haze problem is probably staying for at least a month. Personally, I use Nasal Irrigation (Neilmed Sinus Rinse), which has tremendously helped my nose during this haze period. It can help clear out dust and mucus trapped in the nose.

[S$89.90][Clean Air]2015 Air Purifier Singapore brand and 1 year warranty with HEPA Activated Carbon UV-C germicidal killer lamp silent operation and high efficiency etc

WWW.QOO10.SG

[S$19.90]Haze Prevention~ Nasal Rinse™- Flush out mucous~germs~bacteria~and dirt internally. Clear blocked nose and very soothing.

WWW.QOO10.SG

Previously, we proved that any subgroup of index 2 is normal. It turns out that there is a generalisation of this theorem. Let $latex p$ be the smallest prime divisor of a group $latex G$. Then, any subgroup $latex Hleq…

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Group of order 56 is not simple + Affordable Air Purifier

mathtuition88's avatarMathtuition88

Haze strikes Singapore again, this time it is quite serious as the PSI is often above 300. For those seeking an affordable air purifier, do consider this air purifier which is one of the few that costs below $100. It is definitely reusable next year as the haze problem is not going to be solved in the near future.

[S$89.90][Clean Air]2015 Air Purifier Singapore brand and 1 year warranty with HEPA Activated Carbon UV-C germicidal killer lamp silent operation and high efficiency etc

WWW.QOO10.SG

Let G be a group of order 56. Show that G is not simple.

Proof:

We will use Sylow’s Theorem to show that either the 2-Sylow subgroup or 7-Sylow subgroup is normal.

$latex |G|=2^3cdot 7$

By Sylow’s Theorem $latex n_2mid 7, n_2equiv 1pmod 2$. Thus $latex n_2=1,7$.

Also, $latex n_7mid 8, n_7equiv 1pmod 7$. Therefore $latex n_7=1, 8$.

If $latex n_2=1$ or $latex n_7=1$, we are done…

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Haze affects Wifi Speed?

Recently, Singapore is plagued by the haze, arising from forest fires in Indonesia. This is a common occurrence that happens yearly.

Simultaneously, I noticed a drop in Wifi speed both at home and at work.

Is this a coincidence? Or could the haze particles be actually blocking/absorbing Wifi signals so that the Wifi is slowed down?

What do you think? Probably the same effect occurs for smog or fog.

It is well-known and established that rain affects Wifi. Hence, perhaps it is not too far-fetched to postulate that the haze affects Wifi too?

Advanced Excel Date Editing and Formatting

Suppose you have an Excel file with dates in the format DD/MM/YYYY.

So you have entries like 02/03/1999 (2 March 1999). Suppose you want to change it to 2/3/1999, i.e. remove leading zeroes from one digit days and months.

It sounds easy, but it is actually quite tricky to do it in Excel without knowledge of the correct method. The normal methods of date formatting will simply not work.

After some searching, I found and tested that the following method is probably the fastest and easiest way to do it:

Select the date column and then click Data > Text to Columns Next, Next, then select Date ‘MDY’

then you should be able to do this using a number format of m/dd/yyyy or m/d/yyyy if you don’t want a leading zero in the days as well

Source: StackOverflow

How to Score Good Marks in Class 11 Mathematics?

Mathematics is a high scoring subject in class 11 among all the subjects.  Mathematics plays an essential role for all the students to get admission in the best engineering colleges. Even though the students have prepared the problem many times, sometimes they are not confident enough while writing the examinations. Here, the list of topics and concepts in class 11 mathematics such as finding the sides of a triangle using  Pythagoras theorem in trigonometry, limits and derivatives, probability and so on are provided.

Sets – Students are suggested to practice as many questions as possible. Learn the definitions properly and draw the Venn diagram if required to score good marks.

Relations and Functions – Domain and range are the essential concepts in this chapter. Learn all the graphs of the functions given in the section “some functions and their graphs.”

Trigonometric Functions – Learn all the trigonometry formulas. This chapter contributes to prominent importance among all the sections. Also, learn the trigonometric ratios of standard angles, and trigonometric identities with its proof.

Principle of Mathematical Induction – Most of the students find this chapter exciting; you need to analyse the question from the section. One problem will come from this chapter.

Complex Numbers and Quadratic Equations – This chapter is one of the easiest chapters in class 11 mathematics as it requires only less time to prepare for the exam. Inevitably the questions are asked from the concepts such as polar representation and quadratic equations with complex roots.

Binomial Theorem – Go through the questions from “General and Middle Term of a Binomial Expansions”. The calculation errors are likely to happen in this chapter.

Permutation and Combination – Learn the definition of permutation concepts when all the objects are distinct or not distinct, and determine the combination of the given problem.

Linear Inequalities – This part needs more practice to work with the system of linear inequalities in one variable and two variables.

Sequences and Series – Since all the topics in this chapter are almost related to each other. You cannot skip any exercise. Master all the formulas in this chapter to score more.

Straight Lines – Read all the straight lines formulas. Use proper labelling, figures in the problem that should be clean and neat.

Conic Sections – Practice all the concept in this chapter. Go through the concepts such as a parabola, hyperbola, circles, and an ellipse.

Introduction to Three-Dimensional Geometry – Determine how to find the distance between two points in the 3D space and also study the section formula.

Limits and Derivatives – The essential concepts in this chapter are product rule and quotient rule. Find the derivative of a function and determine how to apply the limits of a polynomial, trigonometric and rational functions. Use trigonometry table to find the corresponding value for the trigonometric derivative function.

Mathematical Reasoning – This chapter does not require computations. Get the description of the statement and examine its validity.

Statistics – Read the formulas like mean, variance, standard deviation, and coefficient of variation of a continuous frequency distribution.

Probability – Go through all the topics in this chapter. Understand the contrast between “with replacement” and “without replacement.”

Subscribe to BYJU’S YouTube channel to discover various concepts in class 11 mathematics.

https://www.youtube.com/watch?v=z8deq-zdaIg

Calculate Cronbach Alpha using Python

R has the package “psych” which allows one to calculate the Cronbach’s alpha very easily just by one line:

psych::alpha(your_data, column_list)

For Python, the situation is more tricky since there does not seem to exist any package for calculating Cronbach’s alpha. Fortunately, the formula is not very complicated and it can be calculated in a few lines.

An existing code can be found on StackOverflow, but it has some small “bugs”. The corrected version is:

def CronbachAlpha(itemscores):
    itemscores = np.asarray(itemscores)
    itemvars = itemscores.var(axis=0, ddof=1)
    tscores = itemscores.sum(axis=1)
    nitems = itemscores.shape[1]

    return (nitems / (nitems-1)) * (1 - (itemvars.sum() / tscores.var(ddof=1)))

The input “itemscores” can be your Pandas DataFrame or any numpy array. (Note that this method requires you to “import numpy as np”).