Scientific Computing: Computational Chemistry

Theoretical Chemistry refers to using mathematical methods to express chemistry problems. And computational chemistry “is a branch of chemistry that uses computer simulation to assist in solving chemical problems. It uses methods of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids.” (Wiki) Computational chemistry does not pursue perfection or flawlessness because only a few chemical systems can be accurately calculated. However, almost all types of chemical problems can be and has been used approximation algorithms to express.

Theoretically, we can utilize fairly accurate theoretical method to calculate any molecules. Many computing software have contain these precise methods. But the amount calculating of these methods will increase exponentially or with the increasing number of electrons. Thus, they can only be applied to small molecules. For larger systems, it often adopts other larger degree approximation methods to find a balance between the accuracy results and the amount of computing.

Computational chemistry mainly uses existing computer programs and methods to study specific chemical problems. The development of algorithms and computer programs is completed by theoretical chemists and theoretical physicists. When studying properties of atomic and molecular, chemical reaction pathways, and other issues, it often focuses on solving two problems:

1. Using computer programs with quantum chemistry equations to calculate the properties of material such as energy, dipole moment, vibration frequencies and so on.  It can explain some specific chemical problems.

2. Using a computer program to do molecular dynamics simulations. This tries to compound predicted starting conditions of experiments, study chemical reaction mechanism, and explain the reaction phenomena, etc.

Reference:

http://en.wikipedia.org/wiki/Computational_chemistry

Scientific Computing: Computational Science

“Computational science (also scientific computing or scientific computation) is concerned with constructing mathematical models and quantitative analysis techniques and using computers to analyze and solve scientific problems.” (Wiki) Natural scientific laws are commonly expressed by various types of mathematical equations. The purpose of scientific computing is to find numerical solutions of these equations. This kind of calculation involves a huge amount of computations. Simple calculation tools cannot achieve this goal. Before the appearance of computers, scientific researches and engineering designs mainly rely on the data from experiments or tests and computing is only used for assistance. Because of the rapid development of computers, more and more complex calculations become possible. Utilizing the computer for scientific computing has brought huge economic benefits as well as made scientific technology itself fundamental change—the traditional scientific technology only includes two components: theory and experiment. Computing has become the third component that as important as the other components after using computers.

Computing process includes three stages: the establishment of mathematical model, the establishment of solving computational methods, and computer implement.

To establish a mathematical model is establish a series of quantitative relations for investigative objects based on the related theories, namely a set of mathematical formulas or equations. Reasonable to simplify complex models is an important measure to avoid the excessive computing. Mathematical models generally contain continuous variables, such as differential equations, integral equations. They cannot be directly processed on a digital computer. To this end, the first thing to do is discrete the problem, namely change the problem into a finite number of unknowns discrete form, such as finite algebraic equations. Then look for solving methods. Computer implement has a series of steps, which includes programming, commissioning, operation, and analyzing results. Development of software technology provides suitable programming languages and other software tools for scientific computing that greatly improve efficiency and reliability.

Reference:

http://en.wikipedia.org/wiki/Computational_science

Computer Graphics

Computer graphics “are graphics created using computers and the representation of image data by a computer specifically with help from specialized graphic hardware and software.” (Wiki) Computer Graphics have been nearly 40 years of development and got into a more mature phase. Its main application domain includes computer-aided design and processing, animation, military simulation, medical image processing, and visualization of meteorology, geology, electromagnetic, and financial and economics.

Due to the successful use of computer graphics in these areas, especially in the rapid development of the animation industry, has brought considerable economic benefits. Animation industry is the priori develop green industry in every countries, which has high-tech, high investment, and high output characteristics. According to statistics, as of March 2009, the 3D animation “Shrek 2”, was produced by DreamWorks with $150 million production budget, received around 920 million worldwide box offices. On the other hand, due to the promotion of these areas of application, the development of computer graphics has to face new opportunities and challenges.

In our daily lives, the popularity of digital cameras and home video camera is growing very fast. Digital image and video data processing has become a hot issue in computer research. The technology of computer graphics will be utilized within these image processing and visions. It can directly generate stylized pictures and animation sequences based on video and image data as well as achieve image-based three-dimensional models. Therefore, it can bring limitless imagination and construct a lot of visual effects.

References:

http://en.wikipedia.org/wiki/Computer_graphics

http://www.boxofficemojo.com/movies/?id=shrek2.htm

Computer Security

In general, a secure system will use some special secure features to control access of information. Only properly authorized people or the processes carry out in the name of these people can read, write, create, and delete information. With the development of computer hardware, the amount of programs and data are stored in the computer is become larger. How to protect the data in the computer from being lost, which should be the first consideration problem for any computer application department. Computer hardware and software production manufacturers are also trying to study and continue to solve this problem.

The main causes of losing data on a computer are: virus attack, theft, computer electromagnetic radiation, computer storage hardware damage and so on.
So far, there has found near million computer viruses. Vicious virus can crash the whole computer software system and destroy data completely. There are hundreds of such viruses. A computer virus is a small hidden program that attaches to computer software. It is similar with other working computer programs, but it will disrupt the normal function programs and data files. To prevent virus attacks, it mainly strengthen the administration, never open extraneous software, and text the system regularly. Also, we can insert the anti-virus card or use clear software to clear the virus that has been found on computers.
Thefts refers to people access computer systems in legal identity and extract data from a computer without permission to modify, transfer, copy and so on. One way to prevent is add software system security mechanisms so that thieves cannot enter the system with legal identity. For example, add recognition of legitimate users or password to stipulate different privileges for the users. So, it cannot freely access the data areas that should not be accessible. Second, encrypt the data. Even if the thieves get into the system,  they cannot read the data without the key. Keys can be soft code or hard code, but it requires being replaced at any time. Encrypted data has security in transmission. Third, setup operation log in computer. It automatically records reading, writing, or modifying important data. This log is a black box that only a handful of privileged people can open. It can be used to detect the theft.