Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 8 of 8

Full-Text Articles in Engineering

Propagation And Scattering Of Collimated Beam Wave In Vegetation Using Scalar Transport Theory, Michael Yu-Chi Wu May 2001

Propagation And Scattering Of Collimated Beam Wave In Vegetation Using Scalar Transport Theory, Michael Yu-Chi Wu

Theses

The scalar time-dependent equation of radiative transfer is used to develop a theory of pulse beamwave propagation and scattering in a medium character ized by many random discrete scatterers which scatter energy strongly in the forward scattering direction. Applications include the scattering of highly collimated millimeter waves in vegetation and optical beams in the atmosphere. The specific problem analyzed is that of a periodic sequence of Gaussian shaped pulses normally incident from free space onto the planar boundary surface of a random medium half-space, such as a forest, that possesses a power scatter (phase) function consisting of a strong, narrow …


Optical Properties Of Photonic Crystals, Anand G. Shenoy May 2001

Optical Properties Of Photonic Crystals, Anand G. Shenoy

Theses

The ability to confine light in three dimensions has important implications for quantum optics and quantum-optical devices. Photonic crystals, the optical analog of electronic crystals, provide us a means of achieving this goal. This analogy has motivated a whole new series of experimental and theoretical searches for elusive photonic band-gap structures. Combinations of metallic and dielectric materials can be used to obtain the required three-dimensional (3D) periodic variation in the dielectric constant. This could pave the way for photonic crystal structures that have widespread applications.

The working of 3D photonic crystals into the wavelength regimes where most optoelectronic devices operate, …


Highway Advisory Radio In The State Of New Jersey, Thomas Mark Nemeth Jan 2001

Highway Advisory Radio In The State Of New Jersey, Thomas Mark Nemeth

Theses

Highway Advisory Radio (HAR) is a broadcasting system used by transportation agencies to disseminate vital real-time traffic information to motorists. Each transmitter is restricted by the rules and regulations of the Federal Communications Commission (FCC) to an average broadcast radius of three to five miles. Most commonly these transmitters are located at major highway intersections, such that motorists may take alternate routes in case of congestion or emergencies.

All operational HAR transmitters in New Jersey were identified and their coverage zones were quantitatively characterized in terms of the signal to noise ratio at the receiver. These experimental results were then …


An Efficient Expression Of The Timestamp And Period In Packet-And Cell-Based Schedulers, Dong Wei Jan 2001

An Efficient Expression Of The Timestamp And Period In Packet-And Cell-Based Schedulers, Dong Wei

Theses

Scheduling algorithms are implemented in hardware in high-speed switches to provide Quality-of-Service guarantees in both cell-based and packet-based networks. Being able to guarantee end-to-delay and fairness, timestamp-based fair queuing algorithms, which include SCFQ, WFQ, WF2Q and WF2Q+, have received much attention in the past few years. In timestamp-based fair queuing algorithms, the size of timestamp and period determines the supportable rates in terms of the range and accuracy. Furthermore, it also determines the scheduler's memory in terms of offchip bandwidth and storage space. An efficient expression can reduce the size of the timestamp and period without compromising the accuracy. In …


A Study And Some Experimental Work Of Digital Image And Video Watermarking, Tsui-Feng Liu Jan 2001

A Study And Some Experimental Work Of Digital Image And Video Watermarking, Tsui-Feng Liu

Theses

The rapid growth of digitized media and the emergence of digital networks have created a pressing need for copyright protection and anonymous communications schemes. Digital watermarking (or data hiding in a more general term) is a kind of steganography technique by adding information into a digital data stream. Several most important watermarking schemes applied to multilevel and binary still images and digital videos were studied. They include schemes based on DCT (Discrete Cosine Transform), DWT (Discrete Wavelet Transform), and fractal transforms. The question whether these invisible watermarking techniques can resolve the issue of rightful ownership of intellectual properties was discussed. …


Dynamic Performance Of Isolated Power Converters, David Badia Jan 2001

Dynamic Performance Of Isolated Power Converters, David Badia

Theses

Isolated power converters are primarily used in applications where electrical galvanic isolation is required for safety purposes. They are also used in applications, which require various output voltages level. They have been studied from many different aspects, but in this thesis the fundamental circuits of the flyback, the forward and the half-bridge converters are studied and compared extensively, with regard to their dynamic performance.

This analysis will lead us to a better understanding of their behaviour, that is a crucial point in the selection of each topology for a particular application. Moreover, the dynamic response of each converter is different; …


Uniform Random Number Generation Using Pseudorandom Binary Sequences, Susan Rea Jan 2001

Uniform Random Number Generation Using Pseudorandom Binary Sequences, Susan Rea

Theses

Random numbers have conventionally been used in a range of applications such as numerical analysis, lotteries and computer simulation and as cryptographic keys. The algorithms used for the production of random numbers are termed pseudorandom, as the numbers produced are not truly random as they emanate from a deterministic periodic source that is they are predictable if a subset of the sequence is known. However, for most applications these pseudorandom number sources are entirely suitable.

For cryptographic key sources, however, the random number sequences must be statistically good and difficult to predict. Linear feedback shift registers are presented in this …


Analysis And Synthesis Of Primary Side Cycle By Cycle Control Of Isolated Flyback Converters, Radoslaw Nalepa Jan 2001

Analysis And Synthesis Of Primary Side Cycle By Cycle Control Of Isolated Flyback Converters, Radoslaw Nalepa

Theses

This work presents the analysis and design of an isolated flyback converter, without feedback from the load side. The converter is controlled from the primary side using the switch voltage and innovative control circuit topologies.

A detail study of the flyback circuit is undertaken including all known parasitics. Besides the standard parasitics, for example the capacitor resistive effect, other more subtle effects are included in the model development such as inter coil couplingj source capacitance etc. Development of these models has provided information about circuit simplifications without losing accuracy of the model. As a consequence of this model development, it …