Electrical and Electronics

An adequate blood supply is required for the normal functioning of all organs in the body. However this flow can be impeded due to several reasons, thrombus or clot being a major one. Detection of such clots is done with the help of an imaging technique called “DOPPLER ULTRASONOGRAPHY” by transmitting an ultrasound pulse and calculating the frequency of the received signal. If there is no clot the reception is always a homogenous signal, whereas if a certain part being sonographed has a clot the received signal shows a variance in frequency which depends upon the distance from the receiver. Hence blood clot detection in ultrasonography is based on obtaining the frequency variance and applying adaptive thresholding. In this work we propose a ZOOM FFT based technique followed by automated adaptive thresholding to detect the clot. Data files are synthesized by simulation in MATLAB. Also the entire system is developed in a Matlab environment for the system to be both simple and cost-effective. Experimental results show that the accuracy of the system is very high even under noisy conditions.

A wireless sensor network (WSN) consists of spatially distributed autonomous sensors to monitor physicalor environmental conditions, such as temperature, sound, pressure, PIR etc. and to cooperatively pass their data through the network to a main location. The development of wireless sensor networks was motivated by military applications such as battlefield surveillance; today such networks are used in many industrial and consumer applications, such as industrial process monitoring and control, machine health monitoring, and so on. The WSN is built of "nodes" from a few to several hundreds or even thousands, where each node is connected to one (or sometimes several) sensors. Each such sensor network node has typically several parts: a radio transceiver with an internal antenna or connection to an external antenna, a microcontroller, an electronic circuit for interfacing with the sensors and an energy source, usually a battery or an embedded form of energy harvesting. A sensor node might vary in size from that of a shoebox down to the size of a grain of dust, although functioning "motes" of genuine microscopic dimensions have yet to be created. The cost of sensor nodes is similarly variable, ranging from a few to hundreds of dollars, depending on the complexity of the individual sensor nodes. Size and cost constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational speed and communications bandwidth. The topology of the WSNs can vary from a simple star network to an advanced multi-hop wireless mesh network. The propagation technique between the hops of the network can be routing or flooding.

Wireless Sensor Network has a growing demand worldwide. This network plays a vital role in creating reliable and scalable system making human life easier and faster. WSN is a sensitive network which is effective and efficient. In this paper we have implemented WSN for keeping regular updates on a health of a machine and its control. For wireless communication purpose Zigbee protocol is deployed. Required algorithms have been developed allowing evaluation of additional parameters using data from measurements held.

IEEE 802.16 family of standards (also known as WiMAX) is a broadband wireless access technology that is designed to offer high-speed connectivity. Broadband access to Internet is currently dominated by wired technologies like DSL and cable. WiMAX technology provides wireless alternative to broadband access and need to support various Internet traffics and applications. In this paper focus is to simulate and transfer of different traffics with different error correction techniques implemented in MAC layer and provides the comparative analysis of the throughput and end-to-end delay characteristics. Channel error rate is varied to observe the performance differences. Simulation results show that the error control techniques at MAC layer provides substantial improvements in end-to-end throughput and delay characteristics at lower error rates. Hybrid ARQ mechanism outperformed all other error control schemes even at significantly high error rates.

In this paper, we have presented a wide range phase locked loop (PLL) based frequency synthesizer using a voltage tuning variable length ring oscillator (RO). The frequency of the used ring oscillator can be changed dynamically from one frequency to another frequency by changing the length of the oscillator electronically. An analog frequency tuning mechanism is also introduced here to make it suitable for applications in PLL based systems. The proposed PLL based frequency synthesizer can successfully synthesize different harmonics (Nf_r ) of the reference signal (f_r ) within the lock range of the oscillator. The experimental results from a prototype hardware electronic circuit are presented here to support the validity of the proposed architecture of the RO and the frequency synthesizer.

Voltage instability is the major concern of power system stability. It is caused due to the deficit of reactive power in the system. Improving the systems voltage by increasing the reactive power handling capacity of the system by using Static VAR Compensator, during a large disturbance is the area of study. The simulations are carried out for IEEE 14 bus system by using MATLAB/PSAT software. The result shows the effectiveness of SVC to improve the voltages when connected to a system.

This paper presents the solution to the problem of grid voltage instability during occurrence of fault, on a system connected with wind turbine - driven doubly-fed induction generator (DFIG) which supplies alternating current (AC) power to the utility grid. Here, two pulse width modulated voltage source converters are connected back to back between the rotor terminals and utility grid via common direct current (DC) link. The grid side converter controls the power flow between the DC bus and the AC side. It allows the system to be operated in sub-synchronous and super synchronous mode of operation. The rotor excitation is provided by the machine side converter. The model makes use of d-q rotor reference frame using dynamic vector approach for machine model. The controller was implemented by the orientation of the generator stator flux vector along a synchronous reference axis. In this way, constant voltage and frequency was obtained and the generator would supply the active and reactive power demanded for the voltage correction by the load, while the wind turbine will be responsible for achieving power balance in the system. The system is modelled and simulated in the Matlab Simulink environment in such a way that it can be suited for modelling of all types of induction generator configurations. The results of the simulations show that DFIG wind turbines improved the voltage stability of the system through its ability to control reactive power and decouple control of active and reactive power by independently controlling the rotor excitation current especially during fault.

The low voltage profile of the Nigeria grid results in poor voltage regulation in the network. The objective of this paper is to improve the voltage profile of the network using Static Var Compensator. The condition of the network was obtained through load flow technique. After performing load flow analysis, it was observed that some buses were violated that is, they were operating below the standard limit of 0.95 - 1.05 PU (313.5kV - 346.5kV). The Static Var Compensator is an important FACTS device which contains majorly a combined combination of the capacitor, inductor and the thyristor. The installation of SVC helped to improve the voltage profile of the affected buses to 1PU.

This paper deals with series connection of stator windings and with decoupled dynamic control, it has been introduced recently. The two-motor drive system is supplied from a single five-phase voltage source inverter (VSI) and the machines are controlled using vector control scheme. In literature this drive configuration utilizes current control in the stationary reference frame so current fed machine models are employed and the current regulated PWM multi-phase inverter replicates the current references. If current control is to be implemented in the rotating reference frame, a PWM method for the five-phase VSI is needed to generate required reference voltages. This paper proposes voltage modulation scheme to generate five-phase inverter output signals using a simple approach, in such a way that independent and decoupled control of two five-phase series-connected machines is achieved with minimum interaction between the two machines. The proposed method offers significant advantages over the existing space vector PWM. The suggested method generates output voltages that contain two fundamentals at operating frequencies required by the two machines with reduced computational burden on digital signal processor (DSP). The concept is verified by simulation and experimental approach.

The experiment carried out on voltage and current measurement on TTL logic gates, by the students of electrical and information engineering in the final year of their studies, in the department’s laboratory, which help to understand the voltage and current characteristics of TTL gates and how also how to measure the voltage and current values of TTL gates. This experiment basically shows how voltage and current of TTL gate can be measured. KL- 22001 Basic Electrical/Electronic Circuit lab and KL-26001 Combinational Logic Circuit experiment module are the major equipment used to perform the experiment .These were used because it is much more self-explanatory and easier to work with compared other models. It was discovered that Due to its higher resistance value the LS series, TTL gates have lower input current than the standard series TTL gates. Their output currents are about equal.