assignment代写：malloc lab

下面为大家整理一篇优秀的assignment代写范文- malloc lab，供大家参考学习。在本实验中，您将为 C++编写一个通用动态存储分配器；也就是你自己的malloc，free，realloc和calloc函数版本。

Introduction

In this lab you will be writing a general purpose dynamic storage allocator for C programs; that is, your own version of the malloc, free, realloc, and calloc functions. You are encouraged to explore the design space creatively and implement an allocator that is correct, efficient, and fast.

Required Functions and Support Routines

Your dynamic storage allocator will implement the following functions, declared in mm.h and defined in mm.c:

bool mm_init(void);

void *malloc(size_t size);

void free(void *ptr);

void *realloc(void *ptr, size_t size);

void *calloc(size_t nmemb, size_t size);

bool mm_checkheap(int);

We provide you three versions of memory allocators:

mm.c: A placeholder that compiles correctly, but does not run.

mm-naive.c: A functional implementation that runs fast but gets very poor utilization, because it never reuses any blocks of memory.

mm-baseline.c: A fully-functional implicit-list allocator. We recommend that you use this code as your starting point.

Your allocator must run correctly on a 64-bit machine. It must support a full 64-bit address space, even though current implementations of x86-64 machines support only a 48-bit address space. The driver mdriver-emulate will evaluate your program’s correctness using benchmark traces that require the use of a full 64-bit address space.

Your submitted mm.c must implement the following functions:

mm_init: Performs any necessary initializations, such as allocating the initial heap area. The return value should be falseif there was a problem in performing the initialization, true otherwise. You must reinitialize all of your data structures in this function, because the drivers call your mm_init function every time they begin a new trace to reset to an empty heap.

malloc: The malloc routine returns a pointer to an allocated block payload of at least size bytes. The entire allocated block should lie within the heap region and should not overlap with any other allocated block.

Your malloc implementation must always return 16-byte aligned pointers.

free: The free routine frees the block pointed to by ptr. It returns nothing. This routine is only guaranteed to work when the passed pointer was returned by an earlier call to malloc, calloc, or realloc and has not yet been freed. free(NULL) has no effect.

realloc: The realloc routine returns a pointer to an allocated region of at least size bytes with the following constraints:

if ptr is NULL, the call is equivalent to malloc(size);

if size is equal to zero, the call is equivalent to free(ptr) and should return NULL;

if ptr is not NULL, it must have been returned by an earlier call to malloc or realloc and not yet have been freed. The call to realloc takes an existing block of memory, pointed to by ptr — the old block. Upon return, the contents of the new block should be the same as those of the old block, up to the minimum of the old and new sizes. Everything else is uninitialized. Achieving this involves either copying the old bytes to a newly allocated region or reusing the existing region.

For example, if the old block is 16 bytes and the new block is 24 bytes, then the first 16 bytes of the new block are identical to the first 16 bytes of the old block and the last 8 bytes are uninitialized. Similarly, if the old block is 16 bytes and the new block is 8 bytes, then the contents of the new block are identical to the first 8 bytes of the old block.

The function returns a pointer to the resulting region. The return value might be the same as the old block—perhaps there is free space after the old block, or size is smaller than the old block size—or it might be different. If the call to realloc does not fail and the returned address is different than the address passed in, the old block has been freed and should not be used, freed, or passed to realloc again.

Hint: Your realloc implementation will have only minimal impact on measured throughput or utilization. A correct, simple implementation will suffice.

calloc: Allocates memory for an array of nmemb elements of size bytes each and returns a pointer to the allocated memory. The memory is set to zero before returning.

Hint: Your calloc will not be graded on throughput or performance. A correct, simple implementation will suffice.

mm_checkheap: The mm_checkheap function (the heap consistency checker, or simply heap checker) scans the heap and checks it for possible errors (e.g., by making sure the headers and footers of each block are identical). Your heap checker should run silently until it detects some error in the heap. Then, and only then, should it print a message and return false. If it finds no errors, it should return true. It is very important that your heap checker run silently; otherwise, it will produce too much output to be useful on the large traces.

A quality heap checker is essential for debugging your malloc implementation. Many malloc bugs are too subtle to debug using conventional gdb techniques. The only effective technique for some of these bugs is to use a heap consistency checker. When you encounter a bug, you can isolate it with repeated calls to the consistency checker until you find the operation that corrupted your heap. Because of the importance of the consistency checker, it will be graded. If you ask members of the course staff for help, the first thing we will do is ask to see your checkheap function, so please write this function before coming to see us!

The mm_checkheap function takes a single integer argument that you can use any way you want. One very useful technique is to use this argument to pass in the line number of the call site:

mm_checkheap(__LINE__);

If mm_checkheap detects a problem with the heap, it can print the line number where mm_checkheap was called, which allows you to call mm_checkheap at numerous places in your code while you are debugging.

The semantics for malloc, realloc, calloc, and free match those of the corresponding libc routines. Type man mallocto the shell for complete documentation.

Support Routines

The memlib.c package simulates the memory system for your dynamic memory allocator. You can invoke the following functions in memlib.c:

void *mem_sbrk(intptr_t incr): Expands the heap by incr bytes, where incr is a non-negative integer, and returns a generic pointer to the first byte of the newly allocated heap area. The semantics are identical to the Unix sbrk function, except that mem_sbrk will fail for negative arguments. (Data type intptr_t is defined to be a signed integer large enough to hold a pointer. On our machines it is 64-bits long.)

void *mem_heap_lo(void): Returns a generic pointer to the first byte in the heap.

void *mem_heap_hi(void): Returns a generic pointer to the last byte in the heap.

size_t mem_heapsize(void): Returns the current size of the heap in bytes.

You are also allowed to use the following libc library functions: memcpy, memset, printf, fprintf, and sprintf. Other than these functions and the support routines, your mm.c code may not call any externally-defined function.

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英文论文“Critically Evaluate”的写作技巧

Critically Evaluate，就是批判性的评价，在英文论文写作中非常常见，也经常被当作论文的关键词。当然，由于中国留学生很少进行过批判性的训练，所以对英文论文中的Critically Evaluate写作还是有很大困难的。下面就给大家分享一下关于Critically Evaluate的写作技巧。

Critical一词通常都有负面的内涵和暗示，比如critique、criticise都有批评的意思。但在英文论文写作中，critically并非局限于负面含义，而是提倡作者将自己的观点，结合相关证据，有条理逻辑地展现出。

当在写作中遇到“critically evaluate”或者“critically review”时，一定记住，除了辩证的分析，描述性段落也是必不可少。

描述性写作--四个“W”

虽然是描述性，但上述的四个W也是必不可少，给读者直观的解释，帮助理解中心问题。

一篇好文章从来都不会只停留在描述性的表象，一定会深究根本。这也就是辩证型写作的特点，在于analysis和evaluation。辩证型写作要求作者分析how，why，what if，so what和what next questions。 如果描述型问题只需要几句话概括，那么辩证型问题则需要长篇大论。

辩证性

如何写好辩证型文章

首先要仔细阅读所有辩证分析的食材。通常情况下，同学们认为在杂志期刊发表的文章一定是“大家”所著，没有任何瑕疵。其实不然，作者在写研究的时候也是有选择性的决定研究的过程方法，而后辈的任务则是评估前辈的作品，取其精华去其糟粕。用不同的视角来审核前辈所得出结论背后的论点论据是否充足，知识点之间是否有联系和逻辑。

对于前辈的作品，方法论和讨论过程是最容易评估的章节。

方法论

根据研究背景，作者通常要选择适当的方法做研究，问卷调查、采访、观察采访等，调查的方法多种多样。最常见的辩证性分析方法论的问题是：取样范围是否足够大？所得出的结论是否只适用于取样地区而非普遍现象？

例如，研究调查中选取了在巴基斯坦偏远地区的250个本科学生，而作者试图用这个数据运用于在伦敦学习的学生。读者就可以指出，前者根本不能当作支撑后者的有效材料，因为巴基斯坦的学生条件和伦敦学习的学生条件大不相同。这就是辩证思考分析的过程。

讨论过程

Discussion章节用于作者直抒己见，并且以小见大。

例如上方案例，250个巴基斯坦的本科生中，225个人认为英语是就业的重中之重，因此作者的结论是学生们如果将来想有好工作，一定要学好英语。作为读者，首先我们意识到250个采访对象对于伦敦甚至全球并没有代表性，再者巴基斯坦的就业前景和伦敦的职业市场也大不相同，因此英语语言可能就不是伦敦本科生所考虑的因素。以偏概全，不可取之。

Critical的作用是鼓励读者挑战前辈的作品，没有任何作品是完美无瑕的，也没有任何理论是坚不可摧的，希望大家能拥有鹰一般的眼睛和智慧，善于问问题，并勤于解决问题。

看完这篇文章之后，相信大家再遇到“critically evaluate”或者“critically review”时也能轻松解决了吧！

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paper代写-The Current and Future of Small Aircraft

下面为大家整理一篇优秀的paper代写范文- The Current and Future of Small Aircraft，供大家参考学习，这篇论文讨论了小型飞机的发展。Uber的出现颠覆了出租车行业，并试图用自动驾驶汽车取代传统汽车。现在，Uber的目标已经不可思议地变成了在2020年将共享飞行器送上天空。其实关于飞行器，大家在电影上已经看过太多了，其中可行性最高的就是飞行汽车了。而飞行汽车要解决的最大难度，还是飞行安全的问题。

Development and Prospect of Small Aircraft

Uber subverted the taxi industry and tried to replace the traditional car with Self-driving Cars. Now, Uber's goal has already incredibly turned into send shared flight vehicles to the sky in 2020. (Howard Musoff 2015) Uber is not the only company dedicated to the small aircrafts. But is this practical? Or is it another marketing hype? For many people, the concept of a small aircraft which people can call it a flying car is a synonym for the future. Just like the silver conjoined in a science fiction in or the drug-like food, these dreams have not yet achieved. So how will the flying car?

The Appearance of a Flying Car

When I was young, I was curious about the sky. In ancient China mythology, there is a story of the moon-there is a very beautiful goddess, living on the moon, whose name is Change. In fact, in China, most gods live in the sky. This shows that people are very yearning for the sky. The emergence of the flying car can greatly improve people's travel efficiency, and solve the problem of traffic congestion at the same time. So what about the appearance of a flying car? In the classic concept, the flying car is: to fly the car.

In the novel world, Ian Fleming (author of the 007 series of novels) is a fan of the flying car, and around this conceptcreated his novel "flying universal car" in 1963. In the 1964, James Bond novel and the subsequent Bond film "Golden Shifu", he also incorporates the concept of a flying car. (Zput. Inc 2010) These concepts are based on this: the car usually like ordinary vehicles on the road, but when needed, you can fly it up.

Science fiction writers and directors are often directly erased the need for future transport driving on the ground. "Car" has become a small aircraft, just like the flying car of Anakin Skywalker in the "Star Wars: clone attack" . (David H. Titterton, John L 2005)

Recently, the common types of flying vehicles, from single-seat vehicles, multi-purpose helicopter unmanned aerial vehicles, light aircraft to the small water spacecraft are all designed in the form of "car". (Savage P.G 2006) Almost any manned small aircraft can be called flying cars. But obviously they are just small aircraft.

It is not difficult to find that the main features of the current flight are: light and flexible. In my opinion, the future development trend of the flying car, will continue this direction. Researchers should continuously focus on reducing the weight of materials, improving the technical level, and improving the design of the flight. (John E 2001) Only in this way can people make our flight dream come true at an early date.

The Security of Modern Small Aircraft

In fact, security is more important than appearance. Since the plane appeared and developed into a civilian transport, there have been many air crash. Some people even do not want to travel by plane. Therefore, in order to improve the use of the flying car, people should improve its safety performance at first. In this respect, the technician has done a lot of effort.

Any passenger who might take a flight would like to know, "What is the safety factor for this stuff?"The current answer is likely to be "less secure" as well as all early technologies. Relevant companies are actively working to make their aircraft "safe enough" to persuade regulators and governments to believe that these vehicles will not hurt life.But there are also incredible security challenges. One of the most severe tests is dealing with problems when there happens a serious safety accident. (Jordan J.W. 1969)For ordinary cars, people usually can brake our cars through the brake, so that the vehicle gradually stopped. But a flying car may fall from the air, which will not only kill its passengers, but also may be associated with passers-by's life.

China Billion Airways plans to install a parachute on its flight in the Dubai market. The "UAV Taxi" service delivers one passenger from one of Dubai's skyscrapers to another.

However, if the parachute is open, we do not know whether UAVs have a way to control the landing site and do not know the safety of the way of landing.

In today's aviation industry, many aircraft are automatic. Compared to driving, driving the aircraft is obviously much more difficult. On the other hand, flying car aims to reduce the human error in one flight. The future faying cars are likely to be self-driving, so no more needs for human pilots. But the existing aviation equipment and the flying cars are also different. The reason why people think that air travel safety, largely because the aircraft has a complete maintenance process. The probability of accidents is small. However, commercial vehicles are unlikely to have such a rigorous approach.

Figure 4 "Lily" all electric aircraft

Instead, the flying car is much simpler than the modern jet, and the latest flying care demonstration is showing that. Just like the "lily" all-electric aircraft, the use of a large number of small motors greatly reduces the complexity of maintenance. It also provides built-in redundancy for a single engine failure.

By simplifying the design of the flight, and improving the safety of materials and systems at the same time, the safety of the flight has been guaranteed. This creates conditions for our further use of the flying car.

The Speed of Small Aircraft

As a student, I need to go to school. Time is very important for office workers and students. There is a requirement for the speed of the flying car. The main purpose of designing flying cars is to solve the problem of traffic congestion. So, what is the speed of the current flying cars on the market? Can it meet the basic requirements of personal travel?

Is it not a good thing to avoid traffic jams in big cities? Indeed so.

For example, in the case of a normal traffic, it takes 23 minutes to drive from the office in Brisbane to the airport. If you take off from the roof of the office, the whole journey takes only 8 minutes.

Both the speed and distance are all optimized. On the one hand, the average speed of the airplane can reach 100 kilometers per hour; on the other hand, because of the line flight, the whole distance is only 13 kilometers.

This is a good example of a flying car display. Of course, it is also possible that the government and the supervisory authority require the flight fly on a preset line, so the distance is not a complete straight line. These pre-set routes are carefully planned to avoid densely populated areas to minimize risk.

After investigation, people can easily find that it can greatly shorten the distance of the journey. For human society, it can be a good protection of the environment. At the same time, due to the emergence of the flying cars, people can largely avoid traffic jams, reduce travel accidents. Through the above points, the design of the flying cars greatly facilitated people’s travel from the distance and speed.

The Feasibility of the Flight

However, the current realization of flying cars still have many obstacles. In my mind, the future traffic system should be three-dimensional. People will have an air travel path. But that also brings a series of problems. For example, the security risks in the air, the higher requirements of the public transport system, as well as people's travel habits, etc.. These points all put forward a very high demand for flying cars.

Many things about the flying car may be difficult, but some problems may become easier.

When people can start three-dimensional travels, the ground will have more space for ordinary cars.

When hundreds of meters above the ground space is used, the possibilities of a traffic congestion will be much less. People no longer need to spend a lot of money on the construction and maintenance of road infrastructure.

For unmanned aerial vehicles, traveling in the air will make traffic control easier.

I believe that through the continuous efforts of technical staff and government departments, people can overcome these problems successfully one day.

The Price of Small Aircraft

As a student, I can deeply feel that the cost of public transport is also a very important issue. In fact, both the design of flying cars, or the design of public transport systems, need to invest a lot of efforts. How much is the current flying cars? What can people do to reduce costs?

In fact, it is too early to talk about the economy of the pilots. Given the huge regulatory hurdles, the cost of security to overcome and the lack of special infrastructure to support the flight, it is difficult to estimate the cost of flying trips.

In the market of sharing cars, such as Uber, many companies are suffering from huge losses. It is reported that the fare paid by each superior passenger is less than half the actual cost of the journey. Uber hopes to improve the status quo by unmanned cars. Since the flying car is very likely to be unmanned, this may become a profit point.

Figure 7< https://en.wikipedia.org/wiki/Uber_(company) >

In order to save half of the travel time, how much will consumers willing to pay for ? In the history of Concorde aircraft, there is at least one well-known example that raises the same questions and has security problems at the same time. Unfortunately, Concorde supersonic airliners have withdrawn from the stage of history.(Gilmore J.P. 2010)

Although the price of the current flying car is still very high. But with the popularity of this technology, I believe that the price of the flying car will be reduced to formal level one day.

How long can it be achieved?

There are still a lot of things to do before the popularity of the flying cars. With the rapid development of UAV, such technology has walked through a long way. (Robin B 2013) But the technology of the aircraft itself is only a small part of a very complex system. As the increasing number of cars leading to more serious traffic jams, there are two ways to solve the problem. One type is using a fixed wing on the car which lift just as a propeller-driven aircraft. One other is using the highly revolving ducted fan to generate a thrust upwards to counterpart the gravity. But they all have weak points. The first cannot takeoff vertically. It needs a long runway to takeoff and cannot be used to solve the traffic jams problem.( Jang G 2000) The other kind is poorly performed in aerodynamic efficiency and endurance.

As the ground self-driving cars, if it can come true, the flying car may be the first to appear in some areas. Imagine that, for the senior management of the enterprise, this is a more economical but still high-end choice, just like Dubai's motion.(Yeon Fu Jiang 1992)For the rest of us, before we had the opportunity to board the flying car, perhaps we had already worn silver tuxedo and had a vegetarian meal in pills.

Modern science and technology constantly changing people's lives, the flying car is just a start. As a student, we have to bear our own responsibility, and strive to learn scientific and cultural knowledge. Because the future of mankind is in our own hands. Also, only through continuous discussion and learning, can human beings continue to progress. In fact, the future of transport will go onto develop and change, which highly demands the governments and researchers’ great efforts. To that day, the world will become smaller and smaller, the link between people will be more closely. In many science fiction movies, we can see the various ideas of the future of mankind. Some guesses are very bold but fancy. In the film "Independence Day", in order to resist alien attacks, people of different countries united. Human beings develop laser guns, jet aircraft as new weapons. Like the current international space station where the scientists from different countries work and learn together, people will communicate and cooperate in all aspects in the following days. The same fantastic guess can also be seen in the movie "Prometheus". In the distant 22th century, people overcome the limitations of life, they extend their life by deep sleep and do interstellar exploration. At the same time, artificial intelligence is highly developed. There even appear bionic people, biochemical people, who can help people carry out scientific research, and even daily life. In the movie, the robot David even developed a personal thinking which seems very dangerous. Although, some guesses are very bold and difficult to achieve, but actually it provides a clear direction for people to explore the unknown world with the rapid development of science and technology. Optimistically, now all countries are beginning to realize the importance of cooperation and innovation, and vigorously develop science and technology. I believe that in the continuous efforts of scientists, the future of human life will be greatly changed. Until that day, robots, flying cars, etc., will greatly improve people's quality of life.

Now Uber company has been developing unmanned vehicles, to explore the application of artificial intelligence in traffic. In my opinion, the future of the human world, will be greatly changed due to artificial intelligence. Robots can help people reduce traffic accidents and deal with family trivia. Flying cars help people improve their travel efficiency, to achieve the full use of space. Artificial intelligence brings many possibilities to the future of mankind. In terms of resource exploration, it will become possible for us to explore distant galaxies. However, all the good ideas, need to step by step to practice. In the study of the flying cars, people need to start from the safety and usability, constantly improve the performance of the flying cars. Even people can finally produce individual style of flying cars. What will happen in the future? Are you full of expectation?

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Paper代写：Explain North Korea's determination to develop nuclear weapons

本篇paper代写- Explain North Korea's determination to develop nuclear weapons讨论了朝鲜半岛的核武器问题。朝鲜半岛的核武器问题是一个历史性问题，最早可以追溯到1957年，因为当时美国政府部署了战术性核武器。因此，朝鲜也决定发展核武器，另一方面，朝鲜政府也需要利用核武器的发展来维持长期稳定的统治。但朝鲜发展核武器，也威胁着其他国家的安全。本篇paper代写由51due代写平台整理，供大家参考阅读。

Introduction

The nuclear problem in Korean Peninsula is a historical problem that can step back to 1957 when the U.S. Government deployed tactical nuclear weapons. The determination of North Korea to develop nuclear weapons, as a result, is a historical problem in not only Korean Peninsula area but also the among China, the U.S.,Japan and Russia. The essay will be divided into three parts to explain the two times of Nuclear power in North Korea and the rolls of these six counties play during the two conjunctures.

The first Nuclear Issue in North Korea

To explain the root of the study of the Nuclear Issue, the essay needs discuss the history traced back to post-war disposal of the Korean War. This war from the legal point of view, has not yet officially ended.

On July 27, 1953, with the highest commander of the Korean People's Army and the commander of the Chinese People's Volunteers as the party, with the commander-in-chief of the United Nations as the other party, both sides signed the "Korean Armistice Agreement" and the "temporary supplement on the armistice agreement protocol". But it is only a paper armistice agreement, rather than a peace treaty. That is, the relevant countries although in the truce, but still in a state of war. This can be regarded as one of the important causes of the stability of the Korean Peninsula for a long time.

North Korea has natural advantage of nuclear weapons development, that is its rich uranium mine. Take the two mines near Pyongyang, for example, are middle-size uranium mines. The two uranium mines are in the protection of the army that can't be overran only if there is a general war in North Korea.

In 1956, the government of North Korea cooperated with the former Soviet Union that concluded a plan called Nuclear Energy Research Cooperation Plan, and the country sent dozens of scientists each year to "Dubna Nuclear Research Center" in Moscow for studying nuclear knowledge. In the meantime, the government also cooperated with Eastern European countries for technology exchanges. In 1920, North Korea established a nuclear energy research institute to build reactors in Yongbyon area which is 90 kilometer north of Pyongyang. The institute was for nuclear energy research and development.

North Korea joined the International Atomic Energy Agency in 1974 and subsequently joined the Treaty on the Non-Proliferation of Nuclear Weapons in 1985. At the beginning of the 1980s, the country began its construction of a second reactor in Yongbyon. The 50-megawatt research reactor began operating in 1987 with the capability to produce about 700 kilograms of plutonium per year, which means it has potential to produce one or two nuclear weapons each year.

In 1991, the North Korea offered to denuclearize the Korean Peninsula, because South Korea was also ready to develop nuclear weapons as well as the United States in South Korea deployed tactical nuclear weapons. On December 31, 1991, the DPRK signed the Agreement on the Denuclearization of the Peninsula. In January 1992, the "safeguards agreement" was signed, and the DPRK accepted the IAEA's oversight and accepted its verification for 6 times from May 1992 to February 1993.

In the Untied States, on June 16, 1994, the U.S. Senate passed a resolution urging Clinton to take action to prepare the U.S. Military for "deterrence and repelling the Korean attack if necessary". However after the assessment, the U.S recognized that military action against DPRK would lead to North Korea's attack on the South Korea, which will result in a large number of innocent civilian’s casualties in both countries. During the time when the US was discussing about the military programs, the former US president Carter went to Pyongyang to visit and meet with Kim Zecheng, the leader of North Korea that time. The visiting brought back the information that North Korea was willing to negotiate with the United States. After that, the Clinton administration changed its attitude and chose the path of negotiations.

Since June 1993, North Korea and the US government had held three high-level talks in New York. The two sides signed the Framework Agreement on Solving the North Korean Nuclear Issue. The main contents include: North Korea agreed to abandon the construction process in the two graphite reactor. As compensation, the United States would organize and lead an international consortium to provide North Korea two $ 4 billion worth of light water reactors with capability of 1000 megawatts each as early as possible. In order to solve the energy problem in the reactor replacement process, the US would provide 500,000 tons of heavy oil to North Korea per year. This is the end of the first North Korean Issue.

The Second Nuclear Issue of North Korea

The second nuclear issue of North Korea began in 2003. However, before 2003, some evidence shows that the nuclear issue might be totally solved. At the end of the Clinton administration, there seemed to be some possibility that the relationship between DPRK and the US would become normal. On October 9, 2000 the first vice chairman of the National Defense Commission of North Korea visited the United States as Special Envoy of Kim Jong il. On 23 October, US Secretary of State Madeleine Albright held a two-day historic visit to North Korea and met with Kim Jong il. During this visit, Albright conveyed President. Clinton's vision of improving the relationship between the two countries. At the same time they discussed about North Korea's nuclear issue as well as the removal of the list from the "fear list". They also talked about the possibility of arranging Clinton's visit to the DPRK. But because of the president cycle in the US that time, the Clinton administration did not have the time and the energy to achieve the visit, which might be a good chance to solve the nuclear issue from the root.

In the State of the Union address in January 2002, President George W. Bush listed North Korea as an "axis of evil". In October 2002, the US intelligence agency claimed to have found North Korea's secret nuclear program and had evidence of North Korea's technology and equipment procurement in the international market. The evidence of North Korea's secret nuclear deal with Pakistan was exposed. The news was admitted by the Vice-Minister of North Korea.

This incident caused the United States and North Korea shocked. It seems that North Korea. While claiming to abandon the development of nuclear weapons. But also secretly research the development of uranium as raw material of nuclear weapons. From the US point of view, North Korea had renounced the agreement so they announced the end of bilateral negotiations. However in the North Korea's view, the US did not fulfill all the commitments in the framework agreement. The rupture of this relationship directly triggered the second nuclear issue.

In December 2002, under the auspices of the US, the Spanish Navy intercepted the North Korean cargo ship with a "Scud" missile in the Yemeni off the coast. In the same year on November 14, the US-led Korean Peninsula Energy Development Organization (KEDO) decided to stop sending oil to North Korea. North Korea believes that the US suspension of oil supply is a breach of contract, so on December 12, the country announced that it will restart under the "US-DPRK Framework Agreement" frozen nuclear program. On 10 January 2003, North Korea declared its formal withdrawal from the Treaty on the Non-Proliferation of Nuclear Weapons.

From 2003 to 2007, six counties including North Korea, the US, Russia, China, South Korea and Japan held 6 times of the six-party talks on the nuclear issue of Korean Peninsula. Although the talks signed statements including "September 19 joint statement" in 2005, Joint Statement issued on Tuesday 13 February 2007, North Korea still had 5 times nuclear test since 2006. The first test was on October 9 2006 and the 5th was on September 9, 2016.

Analysis

The main reason that North Korea keeps developing nuclear weapon, according to the two issues discussed above, is the threaten from other countries as well as the bargain chip in diplomacy. The government need use the development of nuclear weapon to maintain the rule of long-term stability, and to incite the great nationalist sentiment and patriotic need of the country. According to the history of nuclear issue and the six-party talks, the nuclear weapon development increased the bargain chip for economic and food aid to the United Nations countries dominated by the US and China.

For the other countries in the six-party talk they all have interest in the issue that cause the balance of this issue keeps unsolved. For the United State. If the North Korea nuclear weapon issue eases, the US will lose its situation in South Korea, and then the country will withdraw from East Asia. In the meantime, the other purpose in North Korea's strategy is China. The US needs to build all forces in Northeast Asia against North Korea.

For Japan, the country began to move forward a normal state after WWII since 1990s. The North Korea Nuclear issue is a good excuse for Japan. Since 2002, the DPRK missile Taupuhole series launch several times into the Sea of Japan as well as its exclusive economic zone. By these missile threat, the Japanese strengthened its domestic public opinion, modified the constitution, expanded the army and turned the SDF to self-defense forces to complete its normalization.

For South Korea, during war times, South Korea has no choice but to rely more on the US, in the interests of the US.

For Russia, Russia is located in the north of North Korea. The Korean Peninsula is Russia's stumbling block in the south. The Russia does not want to see a complete Korean Peninsula on the Mediterranean in Asia.

For China, the nuclear weapon might threaten the peace in north of China. Hence, during the six-party talk, China kept its opinion to stick to the denuclearization of the Korean Peninsula.

For the future discussion, there might be three different possibility for the nuclear weapon issue in North Korea.

The first situation is that the "sanctions-teat-and then sanctions-re-teat" cycle will be continued. North Korea is relatively closed and strong independence in some way. North Korea under the sanctions will not give up nuclear development. In fact, the country is subject to sanctions after the start of nuclear tests, as all five nuclear test are after the sanctions occurring. Hence, it is not difficult to judge that this situation will drag the North Korea nuclear issue. The escalation of the sanctions and the Korean nuclear test stimulate the cycle of repeated till the North Korean nuclear technology reaches the so called "critical point". The reason is that the determination of nuclear development is very firm for North Korea. Over the past 60 years as mentioned above, the DPRK has been trapped in external security pressure, repeatedly involved in peace talks failed to obtain security. Coupled with thee years occurred in other countries like Iraq and Syria. These all caused and strengthened its choice to hold nuclear weapons for self-protection.

The second situation is the collapse of the DPRK regime, which can't happen in short time. In recent years, North Korea's domestic agriculture and economic recovered while the people's live hood situation has improved compared to the most difficult period. Kim Jong un took over North Korea's top leaders after the basic stability of the situation. Although the DPRK's domestic policy and performance to the outside world is resentment, the hope of resolving the nuclear issue in the short-term collapse of the regime is difficult to achieve.

The third situation is the resumption of dialogue and serious negotiations, so that the nuclear issue will be alleviated or even resolved. This is also a hard method. Because over the past years, the US and North Korea has been extremely mutual distrust. The retrogression of the six-party talks has weakened the confidence of all parties.

Conclusion

From the historical point of view, the determination to develop nuclear weapons of North Korea began just after the war after 1953. With the influence from international politic environment and threaten of its neighbor countries as well as the US, North Korea developed its own nuclear weapon to keep its security. On the contrary, the nuclear issue of DPRK is a threaten to its neighbor countries and the US's interest, hence, the nuclear weapon is also an ideal bargain chip for North Korea to gain international aid and other aid in economics and energy.

Reference

Ying, FU. "The Korean Nuclear Issue: Past, Present, and Future A Chinese Perspective." n.d. Brokings. 9 June 2017.

"U.S.-DPRK Agreed Framework," U.S. Department of States, 15 February 2001.

"President Bush Address the Nation" Washington Post, 20 September 2001.

Condoleezza Rice. "Diplomacy is Working on North Korea."The Wall Street Journal. 26 June 2008.

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Essay代写：Smoking is harmful to health

下面为大家整理一篇优秀的essay代写范文- Smoking is harmful to health，供大家参考学习，这篇论文讨论了吸烟的危害。总所周知，吸烟的危害非常大。首先，你的牙齿会变黄，然后皮肤也会变得非常干燥。最严重的是，吸烟对肺的伤害非常大，会有肺癌和肺气肿的风险。吸烟的危害是如此之大，所以人们必须要正视这个问题，努力去戒烟。

In China, smokers told their kids：“Smoking is a matter of wasting life doing something that you don't enjoy”. It is a really good sentence, but smokers are just still smoking after they say this famous sentence. Everyone knows that smoke is bad for their health, but let me point out some important ideas that you don’t know. After this, I think you will really quit smoking. In this article, it is to discuss why smoke is bad for you.

First, smoking is bad for your teeth. The main reason for saying so is that smoking can turn your teeth yellow. When you smoke, you not only breath the smoke into your lung, but also into your lungs. Tobacco tar is brown, and that’s why it can make your teeth turn yellow. If you just start smoking, you definitely don’t want smoke cigarettes which have too much tobacco tar, because in your mind you think it is not good for your health and it is too strong for you. But if you are an old smoker, you really want a cigarette which has a large amount of tobacco tar inside of it, because the gentle one can’t satisfy you. If you just keep smoking, I bet your teeth will turn yellow. In addition, smoking is bad for your teeth as your tooth will decay easily. It is because that after smoking, the tobacco tar will linger on your teeth, and your tartar can’t get off easily.

Second, smoking is bad for your skin. I think not too many people know the influence of cigarettes on your skin, but it really does. It can makes your skin get dry. During the smoke, smoke that you breath out of your lungs will stop on face. Thus, your face’s blood circulation will turn slow. That’s why your skin will be dry easily.

Another fact explaining why it is bad for your skin is that smoke causes wrinkles. When your face’s blood circulation turned slow, your skin won’t be shiny and greasy.

At last, smoking is bad for your lungs which is known by everyone. First, smoking increase risk of lung cancer, as tobacco poison can dissolves in water or food easily, which make it destroy your DNA and result in gene mutation and chromosome modification. The second reason why smoking is bad for your lung is emphysema. First, it is necessary to know what is emphysema. “Chronic bronchitis and emphysema are familiar types of COPD.” This means a disabling disease of lungs. You will find itreally hard to breath when you get this problem.

Based on these three facts, you really should stop smoking, When you want smoke, try to think about how bad cigarette is.

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