An observation has been carried out at different incidence angle by X-band scatter meter to retrieve the surface roughness when moisture was kept constant. Polarization ratio approach has been proposed to retrieve the surface roughness at constant moisture. A co-polarized (Horizontal-Horizontal; HH and Vertical-Vertical; VV) ratio (p=HH/VV) ratio based model is proposed to retrieve the bare surface roughness. The regression analyses have been carried out to pre-decide the suitable incidence angle to observe the surface roughness (0.5 to 4.18 cm) at X-band. It was found that the suitable incidence is 35 and least square optimization (LSE) method has been applied to retrieve the surface roughness when moisture is kept constant. The retrieved values of rms heights are in good agreement (root mean square error, RMSE-1.22) with observed values of rms heights. The significance of the results has been tested by F-ratio test and it was found quite significant. This type of results are helpful to use the microwave techniques to assess the surface roughness by the air-borne or space borne sensor and propose the suitable angle of incidence to observe the surface roughness at X-band.

Matrix converter induction motor drive system operated with a direct torque control (DTC) shows a sluggish response during startup and under changes of torque command. Fuzzy logic is used in conjunction with direct torque control to minimize these problems. A fuzzy logic controller chooses the switching states based on a set of fuzzy state variables. Flux position, error in flux magnitude and error in torque are used as fuzzy state variables. Fuzzy rules are determined by observing the vector diagram of flux and currents. The operation of the direct torque controller becomes difficult at low speeds due to the effect of change in stator resistance on the flux measurements. To improve the system performance at low speeds a fuzzy resistance estimator is proposed to eliminate the error due to the change in stator resistance. At constant flux and torque commands any change in stator resistance of the induction machines causes an error in stator current. This error is utilized by the fuzzy resistance estimator to correct the stator resistance used by the controller to match the machine resistance. Both fuzzy controller and fuzzy resistance estimator are implemented using DSP TMS320C6711 for a 3 hp induction motor drive system. Results demonstrate enhanced performance.

An ad hoc network is a mobile wireless network that has no fixed access point or centralized infrastructure. Each node in the network also function as a mobile router of data packets for other nodes. However, due to node mobility, link failures in such networks are very frequent and render certain standard protocols inefficient resulting in wastage of power and loss in throughput. We propose two solutions based on two different approaches to alleviate the problems caused by link failures. The first solution, the Network-Link scheme, deals with preventing ‘false’ link failures and failures and in avoiding actual link failures. The scheme involves predicting a failure in advance by monitoring the power levels of all nodes in communication. On the other hand, the Transport-Link scheme deals with the inability of Transmission Control Protocol (TCP) to distinguish between link failures and congestion. TCP, as such, assumes that a packet loss is due to network congestion and invokes congestion control measures. However, in ad hoc networks, packet loss is most often due to link failures, and the congestion control methods invoked only reduce the throughput. Our second solution informs TCP of a link failure thus allowing it to treat such cases differently. In both cases, we observed an improvement in throughput and power utilization efficiency when compared to standard cases: the Network-Link scheme resulted in an average throughput increase of 1.74 times and the Transport-Network scheme, an average Increase of 1.71 times. Both schemes also resulted in a reduction in the percentage of Network layer control packets transmitted, thereby improving power utilization.

This paper introduces and analyses a class of non-liner congestion control algorithms called polynomial congestion control algorithms. These algorithms generalize the AIMD algorithms used for the TCP connections. These algorithms provide additive increase using a polynomial of the inverse of the current window size and provide multiplicative decrease using the polynomial of the current window size. They are further parameterized by a and B. There are infinite numbers of TCP-compatible polynomial algorithms by assuming polynomial of different order. This paper analyses the performance of two models of these generalized algorithms for mobile Ad hoc TCP networks. TCP compatibility of these algorithms are evaluated using the simulation of the implementations of the proposed two models. Simulations are done using ns2, a discrete event simulator. One such model is also proved to be TCP-compatible. The results of simulation are compared with that of TCP and TCP/Reno.

Confocal microscopy is a special technique in the field microscopy with wide applications in the areas of surface micro structuring of mental and non-mental surfaces, finger print observations in forensic science, 3d volume rendering of biological specimen etc. The main feature of confocal microscope is higher lateral as well as higher axial resolution. The higher axial resolution of confocal microscope gives rise to optical slicing capability. In the present paper the line-spread function (LSF) is evaluated with the help of edge spread function (ESF) obtained through point scanning of an edge object in reflection mode confocal microscopic setup. The spread of the LSF is also evaluated from the edge image obtained through a conventional transmission mode microscope fitted with a video camera. The comparison of LSF spread yields an estimation of improvement in lateral resolution in a confocal microscopic setup.

In this paper electromagnetic (EM) fields and radiated power from a small loop type antenna in a conductive (lossy) medium in VLF and LF ranges are studied theoretically. The derived field equations can also be used for free space, by applying proper simplification to the expression for the propagation constant. The equations are valid for the values of the ratio of antenna radius to nearest field point distance equal to or less than 0.1 and the radius of the antenna to be equal to or less than 2/IYI Is the magnitude of the propagation constant in a conductive medium. Validation of the derived equations is shown by use of Maxwell’s equations and by comparison of the simplified expressions for free space by another method.

In this paper, optical transmission system at 10Gb/s using NRZ source has been simulated with commercial package OptSlm. The bit Error Rate (BER) for optical transmission system using a variety of available fibers near reference loss wavelength of 1550 nm in the presence of chromatic dispersion and fiber nonlinearties has been estimated up to 300 kms. Results have been obtained by considering the impact of second and third order dispersion terms. It has been investigated that the highest repeater less distance without dispersion compensation for DS Anomalous fiber is 246 kms at BER 10-10.

The popularity of portable computing devices coupled with the recent development in computing, has not only rendered the mobile and wireless networks important but the design of flexible, efficient and portable routing algorithms for highly mobile and hoc networks a very difficult task. The existing routing protocols suffer for many drawbacks such as existence of non-overlapping zones leading to network partitions due to inefficient use of battery power, network wide flooding, processing overheads etc. In his paper, a protocol called “Power Efficient Self-Adjusting Routing protocol (PESAR)� has been designed.

This paper proposes a neural- network current-regulated switching strategy for a matrix converter induction motor drive system. In this paper, the design and implementation of the induction motor system has been investigated. This paper has provided a systematic and analytic approach for designing a high performance matrix converter induction motor drive system. All the control algorithms, which include switching strategy, current regulation, are executed by a digital signal processor TMS320C6711. By using this new switching strategy, current harmonics of the system are effectively reduced. Several experimental results are shown to validate the theoretical analysis.