How to build your own knowledge system?

Ye, the official account kitten of WeChat, focuses on learning methodology.

I have made a lot of efforts in the process of changing from a real academic scum to a fake academic bully, and I also shared some experiences in the second part of this series. Among them, "building knowledge system" is a very important link. At that time, small examples of "building knowledge tree" and "deducing formula" were given, but many students reflected that these were far from practical operation. So meow wrote a separate article on this part.

When I set out to build my own knowledge system, those specialized courses based on the two basic disciplines of mathematics and physics seemed to come alive, take off the boring coat and become smart. Just like a tree taking root and sprouting, it shows great vitality. With the deepening of my study and the enrichment of my knowledge, the branches and leaves of this big tree are more and more lush, and every knowledge point is inseparable-until now, I can still recall those professional knowledge when I use it.

This is Miao's fourth article on learning strategies.

The first article talks about how to cultivate good study habits and get positive feedback in time. Is there a refreshing learning method? -Zhihu; The second article is about how to overcome difficulties and efficiently complete learning tasks that you don't like and find difficult but can't do. How to finish the work/study tasks you don't like efficiently? -Zhihu. The third article is about how to improve learning ability. -Zhihu

Last time, how to improve learning ability? On the Zhihu, we divided learning into two types-knowledge-centered learning and self-centered learning. Knowledge-centered learning aims at passing exams or scientific research, and mainly emphasizes the understanding, memory, induction and problem solving of knowledge. Self-centered learning mainly emphasizes solving your own problems and improving your ability.

Similarly, we also divide "knowledge system" into two types-knowledge system centered on theoretical knowledge and knowledge system centered on application. As the name implies, establishing a knowledge system and mastering professional knowledge first corresponds to "knowledge-centered" learning. Constructing this type of knowledge system can help you understand and digest what you have learned in textbooks and classes, improve your theoretical level and get good grades in exams. The second knowledge system is established to solve problems. Corresponding to "self-centered learning", it can teach you how to actively obtain information and turn it into knowledge, how to "gather sand into a tower", how to learn to think without being brainwashed by WeChat chicken soup, how to critically accept new ideas, and how to become a better person.

The biggest difference between "theoretical knowledge" and "applied knowledge" in textbooks is that the former is a system in itself, but it seems to be chaotic just because the process of receiving this information is intermittent; The latter itself is some fragments, and the process of receiving this information is one-sided, so the fragments look more messy. For the former, what we need to do is "understanding-induction-memory", and when new knowledge points enter the system, we should "absorb and receive"; For the latter, we need "recombination-addition-recombination".

The "knowledge system" in this paper refers to the "theoretical knowledge-centered" knowledge system, and the suggestions and specific strategies given are also around how to better master professional courses (science and engineering) and how to achieve higher results. The next time (the sixth in the learning series), Miao will give the construction method of the second knowledge system.

The structure of the article is as follows:

Second, how to establish a knowledge system.

1) two tools

1. Mind map

Mind mapping is divergent thinking represented by charts. Divergent thinking process is also a process in which the brain thinks and produces ideas.

Mind mapping mainly has the following three characteristics:

(1) The central image is used to capture the main content-for example, if you plan a book with a mind map, you may put a picture of the book in the center.

(2) The branches are scattered in all directions from this picture. First, divide them into big themes and attach them to the central picture, and then this theme is also shown in the form of branches and attached to the branches at the next level.

(3) Branches consist of key images or keywords printed on one line.

Note that a very important element of mind mapping is "keywords", not "phrases" or "sentences". Mind mapping is suitable for reading notes of the whole book or textbook, but not for taking notes in class-if you can't find this keyword accurately from a sentence said by the teacher, you'd better take notes by Cornell note-taking method or traditional note-taking method. Moreover, the most important thing in classroom learning is to "keep up with the teacher's thinking", and the "divergent thinking" advocated by mind map is almost useless here.

The application scope of mind mapping is review or self-study, not classroom learning.

The following are the steps given by Tony Bozan in the textbook mind map:

(1) Browse and flip through the whole book or article quickly, and get a preliminary impression of the organization of its content.

(2) Prepare the time plan, and study and determine the content and quantity of materials that must be involved during this period.

(3) Draw a mind map for what is already known in this field, so as to establish the "catch hook" of associative thinking.

(4) Use a small mind map to establish the goals and objectives to be achieved in this learning stage, complete a different mind map, and answer all the questions that must be answered in the next learning stage.

(5) Look at the whole book or this article below, look at the table of contents, main titles, results, conclusions, abstracts, main schematic diagrams or pictures, and other important contents that attract your attention. This process will give you a central diagram and main branches (or basic classification concepts) of a new mind map drawn for the whole book or this article.

(6) Now turn to the preview stage and see if there are any materials that have not been included in the overview, especially the beginning and end of each paragraph, section and chapter, because these places often concentrate the most important information and then add it to the mind map.

(7) The next step is internal investigation. At this time, you can solve most of the learning problems, but you will still skip some major problem areas. When you are familiar with other parts of a book or article, you will find it easy to understand the meaning of each paragraph, and you will soon be able to complete the mind map.

(8) Finally, the review stage. You can go back to some difficult parts you skipped before and look back at the whole book or article to answer the remaining questions or fill in the blanks. At this time, you can complete your mind map notes.

It's a bit like a jigsaw puzzle, where small pieces are put together and then assembled.

It should be more intuitive to see examples ~

Hey ~ Do you remember what I just said? Mind mapping is suitable for a person to use when reading or reviewing. So, how do you take notes when listening to lectures or lectures? Let's take a look at Connor's notes!

2. Cornell note-taking method

There are many articles recommending this, so I won't go into details here. Below we can build our own knowledge system.

2) Specific steps to establish knowledge system

In order to make it easier for everyone to understand, I will demonstrate it directly with my own teaching materials, which will look more intuitive. Today, I use power electronics technology to raise a chestnut ~ ~ It doesn't matter if students who don't learn electricity can't understand the specific content, because this method only needs you to observe with your eyes to know how to operate it.

1. Determine what to add to the system.

If you don't know how to start with a textbook, look at its table of contents first.

This is the catalogue of power electronic technology:

We have learned the basics of digital electronics and analog electronics before. What is the connection or difference between the "high-power diode" and "high-power transistor" mentioned in the first chapter of the catalogue and the "diode" and "transistor" we learned in those two basic courses? Intuition tells you that there must be a connection between the two, right? ? If there is no connection, how can the names be so similar? But it will never be exactly the same, otherwise the word "high power" can be omitted.

Look at the summary of the first chapter after reading the catalogue:

Well, it seems that these devices are divided into several categories. I don't need to remember them now, just remember them. I want to listen carefully when the teacher talks about classification.

Let's go on to look at the contents behind the table of contents. The title of chapter 3 is AC-DC transformation, chapter 4 is DC-DC transformation, chapter 5 is DC-AC transformation, and chapter 6 is AC-AC transformation. Do you see it? Just like the arrangement and combination between two variables A and B, we know that a textbook usually writes some basic contents in the first few chapters as a foreshadowing (such as introducing high-power components); The middle chapter is usually the focus of the exam and the main theoretical basis of the subject; The last chapters are about the new development and application of new technologies in industry.

After reading the catalogue, we know that the focus of the book is the four chapters in the middle, and the focus should be placed here when studying, and from the topic, these four transformation methods are definitely related. What are the specific connections? When we study that part, we should pay special attention to finding the similarities and differences between them.

These important and interrelated knowledge is the basis of building a knowledge system.

Building blocks

To master the knowledge of science and engineering skillfully, we must create some conceptual chunks-this is the process of combining scattered pieces of information through meaning.

The first step of 1. chunking is to pay attention to the information that needs chunking.

2. Understand the second step of chunking activities. To package a basic concept into chunks, we must first understand this basic concept.

3. The third step of chunking is to obtain background information. You will see not only how to chunk, but also when and where to use them. Connection can increase the bandwidth of neural network, and make the neural line connected to the chunk not only stable, but also become a stop on many trajectory paths.

Sounds a little abstract. I use specific knowledge points to explain:

Knock on the blackboard! ! ! The following is very important! ! !

The knowledge points I want to build chunks are selected from Chapter 3 "AC-DC Transformation". We first learned a knowledge point called "single-phase half-wave controllable rectifier circuit", which is probably like this:

Two days later, we learned another knowledge point, called "three-phase and half-wave controllable rectifier circuit", which is about this:

Two days later, we learned the third knowledge point, which is called "three-phase bridge full-control rectifier circuit". It looks like this:

Did you find the connection between them?

The "three-phase half-wave controllable rectifier circuit" consists of three "single half-wave controllable rectifier circuits" * * * cathodes connected in parallel; "Three-phase bridge full-control rectifier circuit" is composed of a group of * * * cathodes and a group of * * * anodes-two "three-phase half-wave controllable rectifier circuits" connected in series.

Here are three related knowledge points.

In order to let yourself remember this great discovery, draw it into a small mind map:

Pay attention. Try to use "words" instead of "sentences" in the process of drawing mind maps, so the names are simplified above.

At this time, we only need to remember the most basic graphics of single-phase half-wave rectifier circuit, and then remember the relationship between them, so we can remember three circuit diagrams at once.

But just knowing this is not enough. We need to remember the waveform shapes under different trigger angles, know the calculation formulas of physical quantities such as DC average voltage, and add other knowledge points to make this microscopic network look richer:

For example, the resistive load of single-phase half-wave controllable rectifier circuit needs to master the average value of current on thyristor and free-wheeling diode in the special case of adding free-wheeling diode; For the three-phase half-wave controllable rectifier circuit, it is necessary to know the DC average voltage under two different conditions: the trigger angle is greater than or less than 30; For the three-phase bridge full-control rectifier circuit, it is necessary to remember the DC average voltage under two different conditions: the trigger angle is greater than or less than 60. ...

Let's add these to the mind map:

By comparison, it can be found that when the trigger angle is small, the formulas of three-phase half-wave circuit and three-phase bridge circuit are the same, but the values are different, so the comparative memory is available:

In order to ensure that we have a deep and stable memory of these knowledge points, we should find out how these formulas come from. At this time, we will go back to textbooks and read a lot of words-those are the principles we dislike the least, but they can help us understand the formula.

Take the DC average voltage Ud of three-phase half-wave circuit as an example. Ask yourself in the process of reading, where did this formula come from? The textbook gives the derivation process:

Let's look at the first formula first.

Why do you want to calculate the load current and load voltage at DC terminal? Because the purpose of "AC -DC" rectifier circuit is to convert alternating current into direct current, voltage and current are the basic physical quantities to describe electricity, and they are also intuitive standards to measure the conversion effect of this circuit.

How did each value in the formula come from? Why do you want to calculate like this? We can take a concrete look: let's talk about the formula itself first, because the output is DC, so the calculation is "average"; If the output is AC, the effective value is calculated. The meaning of integration is to calculate the accumulated value in a period, and then divide it by the length of the period to calculate the average value. See what these values mean:

Why is the previous factor 1/(2/3)? Because there are always three-phase voltages (2) in one cycle.

Why does the lower integral limit start from /6? Why does the upper limit of integral start from 5/6? This should start with the waveform diagram of three-phase half-wave controllable rectifier circuit:

The numbers 1, 2 and 3 in the figure are the three-phase voltage waveforms of A, B, C, B and C, and the point where any two phases intersect is called the natural commutation point, which I marked with a red circle in the figure. In the range of 0 to 180, it can be seen that the abscissa of the first point is 30, and that of the second point is 150. At this time, the trigger pulse is only applied when the natural commutation point is reached. If, after that, within 30, the trigger angle is large, how much will the phase shift back, so the above integral formula is obtained.

When it is greater than 30, the waveform changes greatly -DC is no longer continuous. When the voltage of one phase is less than 0, the thyristor is turned off and can't be turned on until the next trigger pulse comes. At this time, the output DC voltage and current are 0. The upper and lower integral limits of the corresponding formula have also changed.

Now, we have built a complete module about "single-phase half-wave controllable rectifier circuit-three-phase half-wave controllable rectifier circuit-three-phase bridge fully controlled rectifier circuit", which covers all the important knowledge points in this part by combining keywords and graphics. Next time you just need to look at the mind map, you can quickly recall this knowledge from your brain.

Please note that the most important thing in "building blocks by yourself" is "building blocks by yourself". If I throw the mind map directly to you, you won't think of the meaning of those formulas, and you will soon forget them by rote. And what if the content of the exam is "drawing the output voltage waveform when the trigger angle is 15"? If you understand, it must be easy to draw.

What I just demonstrated is a complete building block process. All the chunks are interwoven and arranged into a network, and the * * * isomorphism forms a complete knowledge system. For example, the knowledge system of power electronics technology:

Try to integrate the contents of Cornell notes (classroom knowledge) and the knowledge in textbooks into the same mind map ~

Review in time

Interval repetition helps to transfer information from working memory to long-term memory.

It is very important to recall what you have learned! What is not digested in class should be recalled in time after self-study and understanding. When you take a shower and before you fall asleep in bed at night, try to remember what you learned that day. Letting your brain extract key concepts instead of passively acquiring knowledge through repeated reading will make you use your study time more intensively and efficiently. The harder you try to recall the learning material, the deeper it will be embedded in your memory. Don't throw it away for too long to practice remembering, so you should consolidate the concept from the beginning every time. Especially for the first time, it is also quite challenging knowledge. When learning any new skills or new subjects, you need to practice a lot in different backgrounds.

You should review Cornell's notes as often as possible. Keep the good habit of reviewing notes for a long time, instead of cramming for the exam. This will greatly improve your memory and understanding.

After each chapter, review your mind map. Try it, if you open a new mind map and start drawing from memory. After the completion, compare the difference between the mind map and the new map you established in the learning process, and find out what knowledge points are missing and confused.

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Third, summary.

This article is written in detail to make it easier for everyone to understand the operation. Here is a brief summary:

If we compare each knowledge point to a gravel, knowledge without system is scattered, while knowledge with system can gather sand into a tower.

There are two kinds of "knowledge system"-knowledge system centered on theoretical knowledge and knowledge system centered on application. The former itself is a system, and the latter itself is some fragments. The applicable boundary of this paper is the first knowledge system.

This paper provides a note-taking tool-Connor's note-taking method and a thinking tool-mind map. The combination of the two is helpful for us to complete the establishment of knowledge system.

Knowledge system is integrated through lexical chunks. To build a knowledge system, we must first learn what to "integrate" and then build chunks. Knowledge points constitute chunks, and chunks constitute knowledge systems. Tell a super-detailed example to teach you to complete the whole knowledge network from scratch.

Some pictures in it look very troublesome. I've been writing for a day ... meowing ...

Welcome to pay attention to WeChat official account: Katie Qian Qian