the atmosphere‚ surrounds our planet. It provides us with the air we breathe‚ and it protects us from the full blast of the sun’s radiation. Way up in the part of the atmosphere‚ called the stratosphere‚ a layer of gas filters out most of the sun’s damaging ultraviolet rays. This layer of gas is called ozone and is located about five miles to 25 miles above the surface of the Earth. (Bright‚ 1991). Only about one-millionth of our atmosphere is made up of ozone. But it has a tremendously important
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Data Link Layer INTRODUCTION: Now a day’s communication is vital for the entire world‚ nothing happens without communication. The cell radio communication and wireless computer networks of GSM (Global System Mobile)‚ CDMA (Code Division Multiple Access) type are worldwide communication systems. All these communication systems are based on the reference model OSI-RM (Open System Interconnection-Reference Model) Description of OSI-RM System: OSI-RM is an International Standard ISO that defines
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Outline the most serious threats posed to the physical environment and vulnerable populations by soil degradation Soil degradation is the decrease in the quality and quantity of soil caused by agriculture and industrial purposes. Types of soil degradation are water and wind erosion‚ physical degradation and chemical degradation. Some of these are human causes and some are physical causes. Overgrazing‚ deforestation‚ overpopulation‚ fertilizer and pesticide use and conflict are some examples of
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1. Crust: The Earth’s surface is composed mostly of water‚ basalt and granite. Oceans cover about 70% of Earth’s surface. The Earth’s thin‚ rocky crust is composed of silicon‚ aluminum‚ calcium‚ sodium and potassium. The crust is divided into continental plates which drift slowly (only a few centimeters each year) atop the less rigid mantle. The crust is thinner under the oceans; this is where new crust is formed. Continental crust is about 25-90 km thick. 2. Mantle: Under the crust is the rocky
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Abstract Secure Socket Layer (SSL) and Transport Layer Security (TLS) is the protocol above TCP‚ which can protect user’s privacy when they sending data from a client side to a web server‚ this is an important protocol due to the expansion of Internet. In fact‚ it is a long way to make the SSL/TLS protocol perfectly. However there are still shortcomings and problems during the development of SSL/TLS‚ and we cannot deny that there maybe some other potential security hole in the latest version
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TECHNOLOGY AND NIGERIA’S NATIONAL SECURITY: CHALLENGES AND PROSPECTS INTRODUCTION 1. Human existence has been characterized with attempts by man to apply technology to control his environment with a view to improving his material existence. This has resulted in epoch making developments such as the discovery of gun powder and the invention of industrial machines both of which have had significant impact on the development of the society.[i] These technological innovations also had significant
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There are many different layers within the Earth. The core is at center of the Earth. The Earth’s core takes up sixteen percent of Earth’s volume‚ containing thirty-three percent of its Mass ..Pressure rises steadily inside the earth because of the weight of overlying rock. Therefore ‚the Pressure at the outer boundary of the core reaches 1.37 million atmospheres‚ 3.7 million Atmospheres. The core is made mostly of iron and nickel and possibly smaller amounts of lighter elements including sulfur
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inputs processing • What is the system required to do? • Functional requirements: what the system is expected to do • Non-functional requirements: how well the system will provide the functionalities • Usability requirements: good match between the system and the users outputs Use cases • Specify the behaviour of the system from the user point of view • Some ways to do them: – Text: use case descritions – UML: sequence diagrams – UML: collaboration diagrams data Marcelo Santos
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Table of Contents Part 1: General review of data link layer 2 a) Explain the working principles of the data link layer. 2 b) Is controlled access better than contention for media access control? Discuss. 2 c) Why is error detection important in this layer? What is being measured? 3 d) Identify three significant noises that can cause errors in data communication digital circuits. Briefly explain. 3 Part 2: General review of error correction 4 a) Why is cyclical redundancy
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The ozone layer is a layer in Earth’s atmosphere which absorbs most of the Sun’s UV radiation. It contains relatively high concentrations of ozone (O3)‚ although it is still very small with regard to ordinary oxygen‚ and is less than ten parts per million‚ the average ozone concentration in Earth’s atmosphere being only about 0.6 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere from approximately 20 to 30 kilometres (12 to 19 mi) above Earth‚ though the
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