Types Of Data Compression Computer Science Essay

Types Of Data Compression Computer Science Essay Data compression has come of age in the last 20 years. Both the quantity and the quality of the body of literature in this field provide ample proof of this. There are many known methods for data compression. They are based on different ideas, are suitable for different types of data, and produce different results, but they are all based on the same principle, namely they compress data by removing redundancies from the original data in the source file. This report discusses the different types of data compression, the advantages of data compression and the procedures of data compression. 2.0 DATA COMPRESSION Data compression is important in this age because of the amount of data that is transferred within a certain network. It makes the transfer of data relatively easy [1]. This section explains and compares lossy and lossless compression techniques. 2.1 LOSSLESS DATA COMPRESSION Lossless data compression makes use of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. This can be contrasted to lossy data compression, which does not allow the exact original data to be reconstructed from the compressed data. Lossless data compression is used in many applications [2]. Lossless compression is used when it is vital that the original and the decompressed data be identical, or when no assumption can be made on whether certain deviation is uncritical. Most lossless compression programs implements two kinds of algorithms: one which generates a statistical model for the input data, and another which maps the input data to bit strings using this model in such a way that probable (e.g. frequently encountered) data will produce shorter output than improbable data. Often, only the former algorithm is named, while the second is implied (through common use, standardization etc.) or unspecified [3]. 2.2 LOSSY DATA COMPRESSION A lossy data compression technique is one where compressing data and its decompression retrieves data that may will be different from the original, but is close enough to be useful in some way. There are two basic lossy compression schemes: First is lossy transform codecs, where samples of picture or sound are taken, chopped into small segments, transformed into a new basis space, and quantized. The resulting quantized values are then entropy coded [4]. Second is lossy predictive codecs, where previous and/or subsequent decoded data is used to predict the current sound sample or image frame. In some systems the two methods are used, with transform codecs being used to compress the error signals generated by the predictive stage. The advantage of lossy methods over lossless methods is that in some cases a lossy method can produce a much smaller compressed file than any known lossless method, while still meeting the requirements of the application [4]. Lossless compression schemes are reversible in-order for the original data can be reconstructed, while lossy schemes accept some loss of data in order to achieve higher compression. In practice, lossy data compression will also come to a point where compressing again does not work, although an extremely lossy algorithm, which for example always removes the last byte of a file, will always compress a file up to the point where it is empty [5]. 2.3 LOSSLESS vs. LOSSY DATA COMPRESSION Lossless and lossy data compressions are two methods which are use to compressed data. Each technique has its individual used. A compression between the two techniques can be summarised as follow [4-5]: Lossless technique keeps the source as it is during compression while a change of the original source is expected in lossy technique but very close to the origin. Lossless technique is reversible process which means that the original data can be reconstructed. However, the lossy technique is irreversible due to the lost of some data during extraction. Lossless technique produces larger compressed file compared with lossy technique. Lossy technique is mostly used for images and sound. 3.0 DATA COMPRESSION TECHNIQUES Data compression is known as storing data in a way which requires fewer spaces than the typical. Generally, it is saving of space by the reduction in data size [6]. This section explains Huffman coding and Lempel-Ziv-Welch (LZW) compression techniques. 3.1 HUFFMAN CODING Huffman coding is an entropy encoding method used for lossless data compression. The term means the use of a variable-length code table for encoding a source symbol (such as a character in a file) where the variable-length code table has been derived in a particular way based on the estimated probability of occurrence for each possible value of the source symbol. It was developed by David A. Huffman while he was a Ph.D. student at MIT, and published in the 1952 paper A Method for the Construction of Minimum-Redundancy Codes [4]. Huffman coding implements a special method for choosing the representation for each symbol, resulting in a prefix code (sometimes called prefix-free codes, that is, the bit string representing some particular symbol is never a prefix of the bit string representing any other symbol) that expresses the most common source symbols using shorter strings of bits than are used for less common source symbols [5]. The technique works by creating a binary tree of nodes. These can be stored in a regular array, the size of which depends on the number of symbols, n. A node can be either a leaf node or an internal node. Initially, all nodes are leaf nodes, which contain the symbol itself, the weight (frequency of appearance) of the symbol and optionally, a link to a parent node which makes it easy to read the code (in reverse) starting from a leaf node. Internal nodes contain symbol weight, links to two child nodes and the optional link to a parent node. The process practically starts with the leaf nodes containing the probabilities of the symbol they represent, and then a new node whose children are the 2 nodes with smallest probability is created, such that the new nodes probability is equal to the sum of the childrens probability. With the 2 nodes combined into one node (thus not considering them anymore), and with the new node being now considered, the procedure is repeated until only one node remains, the Huffman tree [4]. The simplest construction algorithm is one where a priority queues where the node with lowest probability is given highest priority [5]: 1. Create a leaf node for each symbol and add it to the priority queue. 2. While there is more than one node in the queue: Remove the two nodes of highest priority (lowest probability) from the queue. Create a new internal node with these two nodes as children and with probability equal to the sum of the two nodes probabilities. Add the new node to the queue. 3. The remaining node is the root node and the tree is complete [7]. Figure (1). 3.2 LEMPEL-ZIV-WELCH (LVW) COMPRESSION Lempel-Ziv-Welch (LZW) is a data compression algorithm created by Abraham Lempel, Jacob Ziv, and Terry Welch. It was published by Welch in 1984 as a development of the LZ78 algorithm published by Lempel and Ziv in 1978. The algorithm is designed to be fast to implement but is not usually optimal because it performs only limited analysis of the data. LZW can also be called a  substitutional  or  dictionary-based encoding algorithm. The algorithm normally builds a  data dictionary  (also called a  translation table  or  string table) of data occurring in an uncompressed data stream. Patterns of data (substrings) are identified in the data stream and are matched to entries in the dictionary. If the substring is not present in the dictionary, a code phrase is created based on the data content of the substring, and it is stored in the dictionary. The phrase is then written to the compressed output stream [8]. When a reoccurrence of a substring is found in the data, the phrase of the substring already stored in the dictionary is written to the output. Because the phrase value has a physical size that is smaller than the substring it represents, data compression is achieved. Decoding LZW data is the reverse of encoding. The decompressor reads the code from the stream and adds the code to the data dictionary if it is not already there. The code is then translated into the string it represents and is written to the uncompressed output stream [8]. LZW goes beyond most dictionary-based compressors because it is not necessary to keep the dictionary to decode the LZW data stream. This can save quite a bit of space when storing the LZW-encoded data [9]. TIFF, among other file formats, applies the same method for graphic files. In TIFF, the pixel data is packed into bytes before being presented to LZW, so an LZW source byte might be a pixel value, part of a pixel value, or several pixel values, depending on the images bit depth and number of colour channels. GIF requires each LZW input symbol to be a pixel value. Because GIF allows 1- to 8-bit deep images, there are between 2 and 256 LZW input symbols in GIF, and the LZW dictionary is initialized accordingly. It is not important how the pixels might have been packed into storage; LZW will deal with them as a sequence of symbols [9]. The TIFF approach does not work very well for odd-size pixels, because packing the pixels into bytes creates byte sequences that do not match the original pixel sequences, and any patterns in the pixels are obscured. If pixel boundaries and byte boundaries agree (e.g., two 4-bit pixels per byte, or one 16-bit pixel every two bytes), then TIFFs method works well [10]. The GIF approach works better for odd-size bit depths, but it is difficult to extend it to more than eight bits per pixel because the LZW dictionary must become very large to achieve useful compression on large input alphabets. If variable-width codes were implemented, the encoder and decoder must be careful to change the width at the same points in the encoded data, or they will disagree about where the boundaries between individual codes fall in the stream [11]. 4.0 CONCLUSION In conclusion, because of the fact that one cant hope to compress everything, all compression algorithms must assume that there is some bias on the input messages so that some inputs are more likely than others, i.e. that there will always be some unbalanced probability distribution over the possible messages. Most compression algorithms base this bias on the structure of the messages i.e., an assumption that repeated characters are more likely than random characters, or that large white patches occur in typical images. Compression is therefore all about probability.

Health Care Policy Making in the Federal System Essay

Patient Protection and Affordable Health Care Act Open policymaking in the United States is molded on a basic level by American federalism. Federalism in the United States is defined as â€Å"a governmental system whereby power and authority are shared by national and state governments, with ultimate authority derived from the people†Ã‚  (Levin-Waldman, 2012). The interaction between the levels makes a muddled approach process. Government policymakers and bureaucrats at diverse levels of the elected framework – national, state and local – regularly have truly distinctive interests and points of view on how specific policies ought to be developed and implemented. In regards to health care policy, the national government has accepted essential obligation, with states playing a significant but auxiliary role. For national and state policymakers, there are three key objectives in healthcare policy: control services expenses of health care, improve the quality of health care, and allow for all citizens to have access to health care. The challenge is to beat the long-standing status of the U.S. as a nation with high medical costs paired with deficient coverage for a number of its citizens. On March 23, 2010, after a multitude of debates and votes, Congress approved and President Obama signed into law the Patient Protection and Affordable Health Care Act (obamacarefacts.com). This is the most comprehensive health care law passed at the national level, and possibly the most controversial too. This enactment is giving a real test of American federalism. Each state is required to create an exchange in which people can look for a competitive plan. This online exchange will offer individual people, families, and small businesses a venue in which to review suitable and affordable plans. In the event that a state does not make an exchange, the national government will do so. There are many debates surrounding this new law as many feel it will do more harm than good. Under the law, tens of millions of uninsured will get access to competitive, quality, health insurance. In order to help cover the many millions who require monetary assistance, there are new taxes, generally felt by the upper income levels. These taxes are in the form of mandates; either as an individual mandate or an employer mandate. These mandates require individuals to obtain coverage, get an exemption, or pay a fee. However, it is estimated that over half of those uninsured prior to this new law, will be able to obtain free or low cost coverage thru their State’s exchange. Similarly, employers with an equivalent of 50 full time employees must provide health insurance coverage to their employees or they will have to pay a fine. This has prompted some businesses to cut employee hours to avoid meeting the criteria, although small businesses can qualify for up to 50% of their employees premium costs. (healthcarereform.procon.org) While the law allows young adults to remain on their parents plans until the age of 26, there is concern that the premiums these young adults could be paying on their own would help offset the rise in premiums due to the sick. In order for the premiums to remain low, there needs to be a significantly large healthy pool of insured. Their premiums will offset the expenses the insurance company will have to pay for the claims of those that are sick. If healthy young adults remain on their parent’s plans longer, it decreases the cushion the insurance company has to cover such claims. Since you cannot be dropped from your plan when you become sick, insurance companies must cover the sick and this causes premiums to rise. (healthcarereformprocon.org) Many question whether or not the government can enforce such a law. The U.S. Constitution makes no reference to health care policy or services as rights. To play a role in such, the national government must turn to less particular parts of the Constitution, for example, the  obligation to â€Å"promote the general welfare,† provide â€Å"equal protection under the laws,† or â€Å"regulate commerce among the states.† State constitutions by and large make no particular reference to health awareness as a commitment of state government or right of residents. Likewise with the national government, state power around there rests principally on more general protected provisions to promote the benefit of everyone. The law was presented to the Supreme Court and upheld by a vote of 5 to 4. â€Å"The Affordable Care Act’s requirement that certain individuals pay a financial  penalty for not obtaining health insurance may reasonably be characterized as a tax,† Chief Justice Roberts wrote in the majority opinion. â€Å"Because the Constitution permits such a tax, it is not our role to forbid it, or to pass upon its wisdom or fairness.† (nytimes.com). Conclusion Policymaking in our federal system is laden with challenges. In health care, policymakers and other government authorities at all three levels of government assume vital and interconnected parts. Policymaking in our federal system has served the United States well for a long time, yet it remains a real test. It is uncommon that one level of government can bring an approach through to its fulfillment. Rather, most arrangements incorporate an imperative intergovernmental element. The unpredictability of intergovernmental policymaking and the numerous purposes of potential restriction in an elected framework put a premium on practicing successful initiative and making intergovernmental connections. To push ahead in the 21st Century, national, state and local policymakers will require a full set of administration and interpersonal abilities to unite all parties in the federalism process of policy making. References Levin-Waldman, O. M. (2012). American government. San Diego, CA: Bridgepoint Education, Inc. Liptak, A. (2012, June 28). Supreme Court Upholds Health Care Law, 5-4, in Victory for Obama. The New York Times. Retrieved from www.nytimes.com Is the Patient Protection and Affordable Care Act (Obamacare) Good for America? (2010, September). Retrieved from http://healthcarereform.procon.org The Pros and Cons of Obamacare. (n.d.). Retrieved from http://obamacarefacts.com

A Startling Fact about Global Issues Topics for Essays Uncovered

A Startling Fact about Global Issues Topics for Essays Uncovered Knowing the most usual IELTS essay topics permits you to revolve around the most significant vocabulary. You also need to realise that IELTS is a worldwide exam and once the writers of the exam are making the questions, their principal concern is writing questions that may be understood by nearly everybody in the world. Students often discover that the majority of their work on those essays is done before they even begin writing. If you're going to succeed in the IELTS test you should be using and exposing yourself to English everyday. For instance, in college, you might be requested to compose a paper from the opposing viewpoint. There is an abundance of research papers on the internet that you can see to acquire a notion of the range of work you will need to produce. Reading a research paper on the internet can also offer you a good of how passionate and intrigued you will need to be about a topic to generate a lengthy research paper on. Since you may see, there are lots of global issues, which can allow it to be overwhelming for a student to settle on a topic to write their research paper about. As stated above, one of the methods where the examiner judges your vocabulary is the way many topic certain words you use. A persuasive essay is one where the writer is attempting to demonstrate the reader a different approach to examine a specific subject. Don't be concerned about the originality. It's a tough and intricate question for commentators to reply. Also, a couple mistakes need to be made for the progress to occur, and everything must be questioned for the answers to appear. No matter your reasons are, it's great if you're passionate about the matter of climate change because it will be simpler to conduct research and persuade the reader to adopt your perspective. Go over both points of view and provide your opinion. New Step by Step Roadmap for Global Issues Topics for Essays The use of the ocean is an important part in climate regulation, yet ocean acidification isn't looked at as a huge deal once it comes to global warming. In addition, the impacts could be felt locally but the issue is a worldwide issue and can't be addressed easily. A gain in the worldwide population greatly affects many aspects of routine life for everybody in the world. It's increasingly harder to clean up existing environmental disasters and halt additional degradation of important al l-natural resources. Eliminating child labour is among the biggest challenges that the entire world is facing. It is possible to discover your fix in an international city. You need to focus on these very first, particularly if you don't have a lot of time before the test. There are lots of problems, even on your own campus, which need to be resolved. You will have the ability to find tons of sources to cite. There are a couple of main things you want to be aware of before you even begin picking social issues essay topics. There are two primary means by which you can use the most frequent IELTS essay topics to your benefit. Topic You ought to be attentive when selecting a topic for a worldwide problems paper. You don't need to acquire super technical with legal argumentative essays, but remember to do your homework on what the recent laws about your preferred topic actually say. Everyone on earth has an opinion on these types of everyday topics and you want to recognize that the examiners aren't trying to find the best' ideas, they are simply on the lookout for relevant ideas. The social issues research papers may appear easy to write in comparison with different topics, but still it demands an extremely creative strategy, a massive quantity of curiosity and capacity to think beyond the box and search info in unconventional sources. There are lots of trouble in the world that impact all of us and selecting a topic on this subject can be difficult but when you find one it is not hard to locate the facts relating to this issue. Odds are, all you have to do is relax and locate a topic you're passionate about and, naturally, one that's debatable. There are a few important things which you want to understand as a way to write up an outstanding essay. This is a somewhat broad category, so there are a whole lot of topics to pick from and even more that you could create all on your own. Here we're planting the four issues and on the lookout for possible solutions.

Thomas Aquinas Work to Prove the Existence of God Essays

Being a devout Christian, Thomas Aquinas naturally believed in God, but he wanted to prove Gods existence to those who could not accept things on faith alone. As a result he made five proofs, which he claims, prove the existence of God. With each proof there is always a beginning, a starting point, Aquinas claims it must be God that is the beginning of each. The first proof does not do complete justice to Aquinas’s claim that God exist, while the fifth proof could be used alone to prove Gods existence. One of Aquinas’s proofs is based on the idea of a first mover and another is based on the idea that intelligence is necessary to direct non-intelligent objects. St. Thomas Aquinas first argument tries to prove that there must be a†¦show more content†¦We also see that non-intelligent things cannot move toward their end unless directed by an intelligent being. As an example, St. Thomas Aquinas uses an arrow. An arrow will not achieve its purpose (that of reaching its mark) unless directed to do so by an archer. Obviously, humans are the intelligent beings that direct the small objects of our world, but there must be a greater intelligence that directs the larger bodies of the universe, such as the stars and the planets, since we obviously have no control over them. This higher intelligence is what we call God. These two arguments approach the problem of proving Gods existence in two completely different ways. One goes the route of saying there must be something that started everything, and the other says there must be something that controls the things that are here, even if it did not create them. Both of these arguments seem, at first, to be good and valid in their separate approaches. However, the first does have one major flaw. St. Thomas Aquinas says that the line of movers cannot go on to infinity, which common sense would tell you to be true. He thus establishes the arbitrary endpoint of God. The problem is that this argument could always be tested to be false by asking the question, What Moved God? St. Thomas Aquinas would probably answer that nothing moved God because God has always existed. I personally believe this to be true, but, to prove his first argument, St. ThomasShow MoreRelatedSt. Thomas Aquinas Essay823 Words   |  4 PagesSt. Thomas Aquinas, was a Dominican monk, wh o generally one of the greatest Scholastic writers of all times. He used ancient philosophy to prove religious propositions. One of the ancient philosophers that St. Thomas Aquinas used to prove religious facts was Aristotle. One of the greatest works that Aristotle did was to prove that god really exists. St. Thomas Aquinas used the forms that Aristotle and Plato used to prove the same philosophical question, does god really exist? St. Thomas AquinasRead MoreThomas Aquinas vs. Descarates Essays673 Words   |  3 PagesTHOMAS AQUINA’S V. 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