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Tuesday, 30 October 2012


The network layer of the internet is called internet protocol (IP). Internet protocol version 4 (IPv4) was implemented in the year 1984. The three important aspects of internet protocol are addressing, fragmentation, reassembly and routing. The four important addresses are hardware addresses (layer 2 MAC), network addresses (layer 3 IP), domain based addresses (email) and universal reference locator (URL). 48-bit addresses are used in ethernet and token ring. A 12-bit DLCI connection identifier is employed in frame relay. Telephone numbers are used in SMDS. CIDR is classless interdomain routing where address space is used efficiently by reserving the number of addresses needed for a subnet. DHCP is dynamic host configuration protocol and is used where only a few of the subscribers are logging in at a time. Domain Name System (DNS) is a distributed directory service which is used for the translation between IP addresses and names. DNS is also used for the control of internet e-mail delivery.

Sunday, 21 October 2012

Transmission line distortion and loading

The main two varieties of distortion in transmission line are frequency distortion and phase distortion ( or delay distortion). Both frequency distortion and phase distortion are not due to any non-linearity of the system and hence they are linear distortions. The correction for frequency distortion in a transmission line is possible by using a two-port network, called equalizer. This network is mounted at the receiving end which is designed to have transmission loss complementary to that of the particular transmission line used at least over the bandwidth of interest. Measurement of phase distortion is carried out in terms of delay distortion coefficient.  Delay distortion coefficient which is also known as differential delay is the difference between the maximum and minimum group delays for frequencies within a specified band. Four methods that can be adopted for a distortion less line are reducing R, increasing G, reducing C and increasing L. Increasing the inductance (L) of the line is called loading. There are two types of loading mechanisms- continuous loading and lumped loading. In continuous loading, inductance of the line is increased uniformly along the length of the line. In lumped loading, inductance coils are wound on torroidal magnetic dust cores which are connected periodically and in series with the transmission line.

Tuesday, 16 October 2012

Global hydrologic system

Hydrological cycle is a system which comprise of components like precipitation, infiltration, runoff and evaporation. A hydrological system can be defined as a structure in space, bounded by a defined boundary that accepts rain water and or other inputs, operates on them internally, and produces them as outputs. The global hydrological system consists of three parts. They are atmospheric water system, surface water system and sub-surface water system. Precipitation, interception, transpiration and evaporation take place in atmospheric water system. Overland flow, surface run-off, sub-surface outflow, groundwater outflow and runoff to the streams and the oceans Take place in the surface water system.  Infiltration, groundwater recharge, sub-surface flow and groundwater flow take place in sub-surface water system.

Saturday, 6 October 2012

Principles of energy conservation

Recycling of waste is an important component here. We can make use of this in paper industry and aluminium can manufacturing industry where used product has an intrinsic value. In Japan, more than half of its waste materials are recycled. Modernization of technology can also be used for energy conservation. Developed countries are using modern technologies and are able to reduce the energy consumption during production. Waste heat utilization is a significant way of energy conservation, especially in glass industry. Flue gases produced from the furnace of a glass industry can be used for the generation of electric power by proper mechanism. The exhaust from backpressure turbine during electric power generation can be used for crop drying and similar applications. If there is any condensed water vapors, we can use it for heating fish farm, poultry farm, pig farm etc. Optimum use of proper types of energy and fuel can save energy considerably. Cogeneration where electricity and heat are generated in a single installation is an excellent tool for energy conservation. Manpower skill is an important component in energy conservation. Proper training has to be given to improve their skill and attitude. Proper training helps them to carry out proper operation and maintenance.