This is a Problem-Solution Paragraph

The Invisible Danger

Nowadays strong EMF (Electro-magnetic Field) radiation is considered as pollution. The strong radiation threatens human health. The principle behind this is simple. Our body is made of molecules which are sensitive to EMF. When EMF radiation pass through human, molecules inside the body will receive thermal energy. If the radiation is strong enough, molecules will be heat up. For example, if a person put his hands on large transmitting antenna, the hands will be burned. That’s one of the most important reasons that large antenna must be built far away from living area.

In China, now a specific kind of EMF radiation which has become the main polluting source is cell phone radiation. It affects human health, because cell phone will be usually put close to human brain when it is used. The cell phone radiation has a direct impact in the brain. Now in China, the business circle of cell phone is very short. A new model of cell phone can mostly last one year in the market. And the safety standard of EMF radiation is not strictly controlled. As a result, cell phone radiation has become an invisible danger in China.

Solving this problem is not a one side job. Firstly, government must set strictly laws to regulate those cell phone producers. Secondly, lower power cell phone technologies should be used to reduce the EMF radiation strength. Thirdly, we need to use cell phone less in our daily life.

This is a Cause-Effect Paragraph

Nowadays strong EMF (Electro-magnetic Field) radiation is considered as pollution. The strong radiation threatens human health. The principle behind this is simple. Our body is made of molecules which are sensitive to EMF. When EMF radiation pass through human, molecules inside the body will receive thermal energy. If the radiation is strong enough, molecules will be heat up. For example, if a person put his hands on large transmitting antenna, the hands will be burned. That’s one of the most important reasons that large antenna must be built far away from living area.

In China, now a specific kind of EMF radiation which has become the main polluting source is cell phone radiation. It affects human health, because cell phone will be usually put close to human brain when it is used. The cell phone radiation has a direct impact in the brain. Now in China, the business circle of cell phone is very short. A new model of cell phone can mostly last one year in the market. And the safety standard of EMF radiation is not strictly controlled. As a result, cell phone radiation has become an invisible danger in China.

This is a comparison and contrast paragraph.

As the development of modern technologies, more and more semi-conductor based high tech products are being used in our daily life. Usually, the semi-conductor industry was called “Clean Industry”, because the products must be made in a professional clean house. However, most of these products are thrown after their life circle. Toxins in these trashes are normally lead, mercury, chromium, arsenide, and indium. As chemistry research showed, these elements are considered to be unhealthy for human. A Certain amount of these elements will cause serious diseases. This is the dark secret of the “Clean Industry”.

However, those metal elements will be great potential resource, if they can be recycle properly. Developing courtiers and developed countries made different approaches. In the Pearl River Delta of Southern China, cheap labors from country side are paid to open and sort the parts of different products like TVs, monitors, and keyboards. They burn cables to get copper. Air is polluted by burning plastic shield of the cables. They put the circuit boards and chips in acid to get gold. Then they will dump the acid into a nearby river. Soil and water are polluted by metal toxins. While in a country like Japan, they have better ways to recycle the trash. All these trash will be sent to some special factories. At those places, the trash will be taken care of specialized workers. They will use mechanical tools and chemical acid to get useful metal by following strict procedure. For example, the used Acid are not allow to be damped into rivers directly.

It is sad that my small toy is broken. And I don't know where I can buy a new one here.

I remembered forty people, including me started judo in NYP judo club in year 2004. But now only three people out of these forty still do judo. I don’t where the rest of them have gone. I still remembered the first competition we NYP Judo players fought tighter. But past is passed. I met one of my previous judo friend a few days ago. He got a job, a girlfriend and a lot of fats. He was very surprised that I still train Judo. In four years time, forty has become three. Things don’t change over night. But things do change over years. In Economics, it refers to short term effect and long term effect.

Sometimes I feel it is really hard to write an essay. I feel it is much easier for me to write a lab report. However, one of my friend said writing an essay is a easy job, it is just bullshitting.

I don't know. Maybe he is right.

I don’t know what my life is. I know I have faith from when I was a small child. My faith is I want to be better. I always want a better score, a better performance in competition to prove that I am stronger than others. After comparing with others, I always feel I am not good enough. I don’t know where I am heading to.

Free Topic

In engineering a lot of good ideas are actually common senses. It is important for engineering to use these senses instead of being slaves of formulas, especial for electrical circuit design.

First common sense is to minimize the heat loss power. Although engineer can choose any resistance value to get a required voltage gain, but reduce the heat lost is the first thing has to be considered. High heat loss cause the rising of resistance value, which may affect the voltage gain.

Second common sense is to choose big resistance value and small capacitance value. Choosing big resistance value can reduce the current flow, which reduce the risk of circuit breakdown. Choosing small capacitance can the size of capacitors inside the circuit, which save the space of packing.

Third common sense is to choose some parts in the circuits to have dominating value. The advantage is when engineers need to make a adjustment, they only need to adjust the parts which are dominating. And they can save some time.