Showing papers by "University of Central Florida published in 1997"

Nonlinear Partial Differential Equations for Scientists and Engineers

Abstract: Preface to the Third Edition.- Preface.- Linear Partial Differential Equations.- Nonlinear Model Equations and Variational Principles.- First-Order, Quasi-Linear Equations and Method of Characteristics.- First-Order Nonlinear Equations and Their Applications.- Conservation Laws and Shock Waves.- Kinematic Waves and Real-World Nonlinear Problems.- Nonlinear Dispersive Waves and Whitham's Equations.- Nonlinear Diffusion-Reaction Phenomena.- Solitons and the Inverse Scattering Transform.- The Nonlinear Schroedinger Equation and Solitary Waves.- Nonlinear Klein--Gordon and Sine-Gordon Equations.- Asymptotic Methods and Nonlinear Evolution Equations.- Tables of Integral Transforms.- Answers and Hints to Selected Exercises.- Bibliography.- Index.

Skyscraper broadcasting: a new broadcasting scheme for metropolitan video-on-demand systems

Abstract: We investigate a novel multicast technique, called Skyscraper Broadcasting (SB), for video-on-demand applications. We discuss the data fragmentation technique, the broadcasting strategy, and the client design. We also show the correctness of our technique, and derive mathematical equations to analyze its storage requirement. To assess its performance, we compare it to the latest designs known as Pyramid Broadcasting (PB) and Permutation-Based Pyramid Broadcasting (PPB). Our study indicates that PB offers excellent access latency. However, it requires very large storage space and disk bandwidth at the receiving end. PPB is able to address these problems. However, this is accomplished at the expense of a larger access latency and more complex synchronization. With SB, we are able to achieve the low latency of PB while using only 20% of the buffer space required by PPB.

Using stated preference data for studying the effect of advanced traffic information on drivers' route choice

Abstract: This paper presents a statistical analysis of commuters' route choice including the effect of traffic information. The paper utilizes data collected from two stated preference survey techniques. Two route choice models were estimated. The first model used five hypothetical binary choice sets collected in a computer-aided telephone interview. The objective of the model was to determine how travel time variation affects route choice, and the potential interplay among travel time variation, traffic information acquisition and route choice. The second model used data collected in a mail survey from three binary route choice stated preference scenarios customized according to each respondent's actual commute route and travel time. The objective of the model was to investigate the potential effect of advanced traveler information systems on route choice. The correlation among error components in repeated measurement data was addressed in this paper with individual-specific random error components in a binary logit model with normal mixing distribution. The results underscored the significance of traffic information and the potential effect of advanced traveler information systems (ATIS) on route choice.

Quality-of-life changes in patients with thyroid cancer after withdrawal of thyroid hormone therapy.

Abstract: Quality of life (QOL) is an important consideration as patients survive longer with cancer and is an area of increasing interest in patients with thyroid cancer who undergo long-term cancer surveillance. However, there are few disease-specific QOL tools available to evaluate QOL in patients with thyroid cancer. The purposes of this longitudinal, repeated-measures study were to: (1) test a new instrument, the QOL-Thyroid Scale, during thyroid hormone withdrawal; and (2) to evaluate the impact of thyroid hormone withdrawal on patients' perceived changes in quality of life. The sample included 34 subjects (mean age 40 years) undergoing thyroid hormone withdrawal in preparation for scanning procedures. Subjects completed three instruments (demographic data tool, the QOL-Thyroid, and the FACT-G) at four specific time points in relationship to scanning. The results demonstrated that the QOL-Thyroid tool is a reliable and valid measure of QOL. Cronbach's alpha coefficient of r = .78 between QOL-Thyroid and FACT-G indicated good concurrent validity. Second, the impact of thyroid hormone withdrawal on QOL showed significant changes in physical, psychological, and social well-being across the four testing points. The greatest changes occurred between peak hormone withdrawal and thyroxine (T4) therapy. While it is generally known that patients suffer troublesome physical symptoms relating to thyroid hormone withdrawal, the negative psychological, family, and work sequelae are less apparent. In conclusion, the QOL-Thyroid is a reliable and valid measure for use in evaluating patients undergoing scanning procedures and may be used to identify and target teaching and support for high-risk areas in patients lives that are negatively affected by hormone withdrawal.

The nonlinear optical properties of AlGaAs at the half band gap

Abstract: We report experimental values for the nonlinear optical coefficients of AlGaAs, in the half-band-gap spectral region. The dispersion of the nonlinear refractive-index coefficient, n/sub 2/, is measured for both TE- and TM-polarized light. We observe n/sub 2/(TE)>n/sub 2/(TM) and a ratio of cross-phase modulation to self-phase modulation (TE) of /spl sim/0.95, as predicted from band structure calculations. The spectral dependence of the two- and three-photon absorption coefficients are also measured. Finally, the implications for all-optical switching and spatial soliton propagation are discussed.

Estimating Magnitude and Duration of Incident Delays

Abstract: Traffic congestion is a major operational problem on urban freeways In the case of recurring congestion, travelers can plan their trips according to the expected occurrence and severity of recurring congestion However, nonrecurring congestion cannot be managed without real-time prediction Evaluating the efficiency of intelligent transportation systems (ITS) technologies in reducing incident effects requires developing models that can accurately predict incident duration along with the magnitude of nonrecurring congestion This paper provides two statistical models for estimating incident delay and a model for predicting incident duration The incident delay models showed that up to 85% of variation in incident delay can be explained by incident duration, number of lanes affected, number of vehicles involved, and traffic demand before the incident The incident duration prediction model showed that 81% of variation in incident duration can be predicted by number of lanes affected, number of vehicles involved, truck involvement, time of day, police response time, and weather condition These findings have implications for on-line applications within the context of advanced traveler information systems (ATIS)

Postcranial evidence of cold adaptation in European Neandertals

Abstract: The low brachial and crural indices of the European Neandertals have long been considered indicative of cold adaptation. Recent work has documented lower limb/trunk ratios and deeper chests (anterior-posterior diameter) in European Neandertals than among their successors. The present study uses variables reflective of limb length, body mass and trunk height, and compares European Neandertals to 15 globally diverse recent human samples (1 “Eskimo,” 3 North African, 4 sub-Saharan African and 7 European). Bivariate plots, as well as principal components analysis plots of log shape-transformed data, indicate that European Neandertals had an overall body shape that falls at the extreme end of modern higher latitude groups' range of variation. Cluster analysis (minimum spanning tree on a principal coordinates plot) indicates that the Neandertals are closest in body shape to modern “Eskimos,” but even in this dendrogram, they are joined to the “Eskimo” via a long branch. In fact, it appears that European Neandertals were “hyperpolar” in body shape, likely due to two factors: 1) the extremely cold temperatures of glacial Europe and 2) less effective cultural buffering against cold stress. Am J Phys Anthropol 104:245–258, 1997. © 1997 Wiley-Liss, Inc.

Automatic feature detection and age classification of human faces in digital images

Abstract: The invention includes a four step process for automatically finding facial images of a human face in an electronically digitized image (for example, taken by a video-camera), and classifying the age of the person (associated with the face) into an age category. For example three age categories: a baby(up to approximately age 3), a junior person(above age 3 to approximately age forty), and a senior adult (over forty years old). Categories can be further subdivided whereas every three years could be a further age category. Step 1 of the process is to find facial features of the digital image encompassing the chin, sides of the face, virtual top of the head, eyes, mouth and nose of the image. Step 2 is to compute the facial feature ratios of the facial features ratios of the facial features found in Step 1. Step 3 is to compute a wrinkle analysis of the image. Step 4 is to combine the previous two steps to categorize age of the facial image. The invention can locate and detect facial images for age classification from digital camera images and computerized generated images. The invention can be practiced in areas such as population statistic gathering for patrons at entertainment/amusement parks, television viewer ratings. Furthermore, the invention has utility in automated security/surveillance systems, demographic studies, safety monitoring systems, computer human-interface operations and automated photography. The latter to allow for point and shoot focus on specific individuals as a function of their age classification.

Three dimensional optical imaging colposcopy

Abstract: An optical coherence tomography(OCT) and spectral interferometry imaging probe for the automatic screening and diagnosis of cervical and skin cancer in vivo. The probe eliminates the old techniques of having to perform Pap smears followed by a biopsy, known as colposcopy. The novel probe is cylindrical in shape and has a disposable outer plastic shield. Inside the probe is a motor driven rotatable casing having a planar optical fiber bundle array therein. The fiber bundle array has plastic light coupling lenslet arrays on both ends. The exposed end of the probe has one lenslet array disc that couples light between the probe and an interior of the cervix area being examined. Both the casing and the bundle array rotate relative to the outer probe walls. Inside the casing is a rotatable motor driven scanning mirror which couples passes light from an incoming second fiber bundle array to the lenslet array on the inside end of the rotatable casing fiber bundle array. The incoming second fiber bundle array is attached to a detector located external and remote to the probe. The detector has a tunable light source and a spectrometer for providing 3-D images of the interior of the cervix. The proposed technique of simultaneous OCT imaging and spectral interferometry and analysis has potential use in either multi-layer optical disk read out using low coherence tomography and spectral interferometry. Alternatively, by employing spectral interferometry, the measured optical spectrum also provides a unique mapping of the recorded bits into the observed spectral modulation. The unique feature is that by simultaneously employing both spectral interferometry and low coherence tomography, the resultant data transfer rate is increased, but the combination also allows for error rate analysis.

Acceleration of the EM Algorithm by using Quasi‐Newton Methods

Abstract: The EM algorithm is a popular method for maximum likelihood estimation. Its simplicity in many applications and desirable convergence properties make it very attractive. Its sometimes slow convergence, however, has prompted researchers to propose methods to accelerate it. We review these methods, classifying them into three groups: pure, hybrid and EM-type accelerators. We propose a new pure and a new hybrid accelerator both based on quasi-Newton methods and numerically compare these and two other quasi-Newton accelerators. For this we use examples in each of three areas: Poisson mixtures, the estimation of covariance from incomplete data and multivariate normal mixtures. In these comparisons, the new hybrid accelerator was fastest on most of the examples and often dramatically so. In some cases it accelerated the EM algorithm by factors of over 100. The new pure accelerator is very simple to implement and competed well with the other accelerators. It accelerated the EM algorithm in some cases by factors of over 50. To obtain standard errors, we propose to approximate the inverse of the observed information matrix by using auxiliary output from the new hybrid accelerator. A numerical evaluation of these approximations indicates that they may be useful at least for exploratory purposes.

The Effect of the Environment on Export Performance among Telecommunications New Ventures

Abstract: The importance of exports for achieving business growth and superior financial performance is widely recognized in the literature. Consequently, researchers have sought to identify the variables th...

A generalized model for passively Q-switched lasers including excited state absorption in the saturable absorber

Abstract: A generalized model of a passively Q-switched laser is presented. It enables performance optimization including cases in which the saturable absorber exhibits both ground and excited state absorption (ESA) at the laser wavelength. The model accounts for the properties of the lasing material, the saturable absorber, and the resonator. The procedure for using this model to determine resonator and Q-switch parameters which optimize the laser's performance is described and the model is applied to reported systems to demonstrate its use.

Chaining: a generalized batching technique for video-on-demand systems

Abstract: Although the bandwidth of the storage I/O typically dictates the performance of a conventional DBMS, network-I/O bandwidth limitation is the main operating constraint of most multimedia database systems. In spite of the fact that the throughput of a public network (e.g. ATM) can be huge, the network-I/O bottleneck limits the number of client stations a media server can support simultaneously. A possible solution to this problem is to batch requests for the same video and multicast the data to these requesters to save the network I/O bandwidth. A disadvantage of this scheme is that it unfairly forces requests arriving early in a batch to wait for the latecomers. As a result, the reneging rate can be high in a system which employs this technique. To reduce the long access latency, we examine in this paper a new batching mechanism called chaining. This approach allows the server to serve a "chain" of client stations using a single data stream. The idea is to pipeline the data stream through the chain of stations. Requests arriving early in a chain (virtual batch), therefore, do not have to experience long delays as in conventional batching. Our simulation results based on an ATM networking environment indicate that very significant performance improvement over batching can be obtained.

Synthesis and electron field emission of nanocrystalline diamond thin films grown from N2/CH4 microwave plasmas

Abstract: Nanocrystalline diamond films have been synthesized by microwave plasma enhanced chemical vapor deposition using N2/CH4 as the reactant gas without additional H2. The nanocrystalline diamond phase has been identified by x-ray diffraction and transmission electron microscopy analyses. High resolution secondary ion mass spectroscopy has been employed to measure incorporated nitrogen concentrations up to 8×1020 atoms/cm3. Electron field emission measurements give an onset field as low as 3.2 V/μm. The effect of the incorporated nitrogen on the field emission characteristics of the nanocrystalline films is discussed.

Performance of radial-basis function networks for direction of arrival estimation with antenna arrays

Abstract: The problem of direction of arrival (DOA) estimation of mobile users using linear antenna arrays is addressed. To reduce the computational complexity of superresolution algorithms, e.g. multiple signal classification (MUSIC), the DOA problem is approached as a mapping which can be modeled using a suitable artificial neural network trained with input output pairs. This paper discusses the application of a three-layer radial-basis function neural network (RBFNN), which can learn multiple source-direction findings of a six-element array. The network weights are modified using the normalized cumulative delta rule. The performance of this network is compared to that of the MUSIC algorithm for both uncorrelated and correlated signals. It is also shown that the RBFNN substantially reduced the CPU time for the DOA estimation computations.

Focused Ion Beam Milling and Micromanipulation Lift-Out for Site Specific Cross-Section Tem Specimen Preparation

Abstract: A site specific technique for cross-section transmission electron microscopy specimen preparation of difficult materials is presented. Focused ion beams are used to slice an electron transparent sliver of the specimen from a specific area of interest. Micromanipulation lift-out procedures are then used to transport the electron transparent specimen to a carbon coated copper grid for subsequent TEM analysis. The experimental procedures are described in detail and an example of the lift-out technique is presented.

Quality of life in women with ovarian cancer

Abstract: Despite growing interest in quality of life (QOL) as an important variable in nursing and health care, little research focuses on QOL in women with ovarian cancer (OVCA). The purpose of this study was to examine QOL in OVCA survivors. The convenience sample consisted of 152 women in all disease stages. Quantitative data were collected using the QOL-Cancer Survivors tool and a demographic sheet. Qualitative data were collected by asking participants to write their definitions and experiences of QOL since their diagnosis. Reliability and validity of all data and findings were established. Findings reveal that QOL is moderately high for this group of cancer survivors, despite some specific negative facets of the illness and treatment experience. Qualitative analysis elaborates the four domains of Ferrell's QOL model: physical, psychological, social, and spiritual well-being. Qualitative data also reflect the complexity of the cancer experience.

Learning effect in multinational diffusion of consumer durables: An exploratory investigation

Abstract: Literature reflects that a product/technological innovation introduced later in a country results in faster diffusion as the consumers in the lag market have an opportunity to learn about the new product from the consumers in the lead market. A systematic understanding of the learning that takes place between consumers in two countries—a pair of lead and lag countries—can provide insights for a firm’s international market entry decisions. To provide a richer understanding of the underlying structure and patterns that govern this process, propositions linking factors (country characteristics, product/innovation characteristics, and time lag) to the learning process are drawn. Subsequently, these propositions are tested through an empirical investigation of the diffusion patterns of four consumer innovations in multiple European countries. The findings help provide some preliminary guidelines for manufacturers regarding selection of foreign markets and the timing and order-of-entry decisions.

Quality of Life Among Long-Term Cancer Survivors

Abstract: Thanks to advances in cancer diagnosis and treatment, there are now more than 10 million cancer survivors in the United States. Successful treatment of cancer has resulted in increased demands on survivors and has had diverse effects on the quality of life (QOL) of patients and their families. A model of QOL encompassing dimensions of physical, psychological, social, and spiritual well-being has been applied to illustrate the multidimensional needs of cancer survivors and the necessity of comprehensive care extending over the long term. Data from a recent survey of members of the National Coalition of Cancer Survivorship (NCCS) is presented, along with a summary of issues compiled by the NCCS that merit future attention. [ONCOLOGY 11(4):565-571, 1997]

Public Support for Correctional Treatment: The Continuing Appeal of the Rehabilitative Ideal:

Abstract: For three decades, American correctional policy has focused on “getting tough” with offenders, and recent innovations continue this trend. It is unclear, however, that the public desires such a singularly punitive approach to crime. This study reports results from a statewide, contemporary assessment of citizens' attitudes toward rehabilitation. The results indicate that the public still believes that rehabilitation should be an integral part of correctional policy. Furthermore, support for a treatment approach is fairly consistent across demographic groups and across different types of questions used to tap citizens' views. The policy implications of these findings are discussed.

Dilation characteristics of confined concrete

Abstract: SUMMARY Confinement of concrete enhances its strength and ductility by restraining lateral dilation. The accuracy of a confinement model depends on how well it captures the dilation tendency of concrete. In recent years, external confinement of concrete by fibre composites has become increasingly popular for civil infrastructure applications. This includes fibre-wrapping of existing columns or encasement of concrete in a fibre reinforced plastics (FRP) shell. A total of 54-concrete-filled FRP tubes were tested in uniaxial compression under displacement control mode. Full instrumentation of the specimens has allowed the variation of tangent Poisson’s ratio for concrete to be captured. The dilation trend of confined concrete is shown to be a function of jacket stiffness. In steel-encased members, once steel yields, confining pressure becomes constant and the jacket renders itself ineffective in containing the dilation of concrete. On the other hand, for linear-elastic materials such as fibre composites, a strain reversal occurs that results in containment of dilation. A method for predicting the dilation is developed that can be easily adopted in any active confinement model. Moreover, a new confinement model for FRP-encased concrete is discussed. # 1997 by John Wiley & Sons, Ltd.

Optimization of optical limiting devices based on excited-state absorption.

Abstract: Limiting devices protect sensitive optical elements from laser-induced damage (LID). Passive devices use focusing optics to concentrate the light through a nonlinear optical (NLO) element (or elements) to reduce the limiting threshold. Unfortunately, these NLO elements may themselves undergo LID for high inputs, restricting the useful dynamic range (DR). Recently, efforts at optimizing this DR have focused on distributing the NLO material along the propagation path z of a focused beam, resulting in different portions of the device (in z) exhibiting NLO response at different inputs. For example, nonlinear absorbers closer to the lens, i.e., upstream, protect device elements downstream near the focal plane. This results in an undesirable increase in the threshold, although the lowest threshold is always obtained with the final element at focus. Thus there is a compromise between DR and threshold. This compromise is determined by the material. We concentrate on reverse saturable absorber (RSA) materials (molecules exhibiting larger excited-state than ground-state absorption). We look at both tandem devices and devices in which the concentration of the NLO material is allowed to spatially vary in z. These latter devices require solid-state hosts. The damage threshold of currently available solid-state hosts is too low to allow known RSA materials to reach their maximum absorption, which occurs when all molecules are in their excited state. This is demonstrated by approximate analytical methods as well as by a full numerical solution of the nonlinear wave propagation equation over extremely large distances in z (up to 103Z0, where Z0 is the Rayleigh range of the focused beam). The numerical calculations, based on a one-dimensional fast Fourier transform, indicate that proper inclusion of diffraction reduces the effectiveness of reverse saturable absorption for limiting, sometimes by more than a factor of 10. Liquid-based devices have higher damage thresholds (damage occurs to the cuvette wall) and, thus, larger nonlinear absorption. However, RSA material in liquid hosts may suffer from larger thermal lensing.

Multiwavelength 10-GHz picosecond pulse generation from a single-stripe semiconductor diode laser

Abstract: A single-stripe GaAs-AlGaAs semiconductor optical amplifier (SOA) has been used to generate four tunable wavelength-division multiplexed (WDM) channels simultaneously, each transmitting 12-ps pulses at 2.5 GHz, for an aggregate pulse rate of 10 GHz. Wavelength tuning over 18 nm has been demonstrated with channel spacing ranging from 0.8 to 2.1 nm. A potential spectral correlation across the multiwavelength spectrum has been studied in both experiment and simulation methods. These results show the potential for utilizing single stripe laser diodes as multiwavelength sources in WDM-TDM network.

Spatial Modulational Instability and Multisolitonlike Generation in a Quadratically Nonlinear Optical Medium

Abstract: A novel type of spatial modulational instability induced by the dynamical interaction of two strongly coupled fundamental and harmonic fields in a second-order nonlinear optical material is demonstrated experimentally. This phenomenon is explained theoretically on the basis of a one-dimensional Floquet theory. At high intensities, the formation of a 1D solitary wave lattice is superseded by the onset of 2D modulational instabilities.

Capillary discharge extreme ultraviolet lamp source for EUV microlithography and other related applications

Abstract: Capillary discharge extreme ultraviolet lamp sources for EUV microlithography and other applications. The invention covers operating conditions for a pulsed capillary discharge lamp for EUVL and other applications such as resist exposure tools, microscopy, interferometry, metrology, biology and pathology. Techniques and processes are described to mitigate against capillary bore erosion, pressure pulse generation, and debris formation in capillary discharge-powered lamps operating in the EUV. Additional materials are described for constructing capillary discharge devices fore EUVL and related applications. Further, lamp designs and configurations are described for lamps using gasses and metal vapors as the radiating species.

Optimization of Chemical Bath Deposited Cadmium Sulfide Thin Films

Abstract: We report the optimization of CdS thin film grown by chemical bath deposition where homogenous reactions are minimized. The optimum parameters have enabled us to maximize the thickness of the deposited film in a single dip and to grow thicker films by periodically replenishing the concentration of reactants while the substrate remains continuously dipped in the reaction bath. Characterization results reveal the deposited CdS films exhibit improved optical and electrical properties.