The wireless revolution has taken the telecommunication industry by storm. The convenience provided by wireless in the day to day activities is the driving force behind it's popularity. With the increasing demand for such systems, research in multiple access techniques has received much interest. CDMA has been proposed as a next generation multiple access technique for cellular systems. The performance capabilities of a CDMA system are gauged by a variety of methods including analytical studies and simulations. Simulation studies are the most reliable and popular performance measurement techniques. This thesis studies the application of Importance Sampling to the simulation of the IS-95 CDMA standard. Importance Sampling techniques help to achieve the simulation results by sending fewer bits and thus reduce the simulation time by a significant factor. Different versions of Importance Sampling techniques have been discussed and applied to the system. The results of Importance Sampling have been compared with the original results for the Bit Error Rate and Frame Error Rate to prove the validity and the effectiveness of Importance Sampling Techniques. / Master of Science

Tattooing is an ancient art. Tattoos have been used to worship gods, to show tribal membership, and to display wealth. However, in modern Western culture tattooing has been a devalued practice reserved for the those on the fringe of society. In the last twenty-five years, however, more mainstream people, including college students, have begun to get tattoos. Despite the increased acceptance of tattoos, a person aspiring to become a professional who gets a tattoo is putting her/his personal life and career at risk. This study examines the process by which college students become tattooed. Two models put forth by Sanders will be used to facilitate this examination. The findings reveal that college students come to be tattooed in a different manner than do others. College students are more risk averse. They choose small, easily concealed, non-violent tattoos. Their designs have themes such of nature, fraternity/sorority membership, and animal appreciation. These differences have led the author to term this form of tattoos, "College Tattoos." In future research, the first objective should be to gain an estimate of the population of tattooed college students. Next, research should examine the psychological profiles of tattooed college students to see how they might vary from those in the mainstream of college. This will allow researchers to see if College Tattoos are a form of psychopathology or if they are simply an alternate mode of self-expression. / Master of Science

This research compared the effectiveness of three methods of instruction for two domains of learning. A text-based instructional system (control condition) was compared to a standard computer-based multimedia system (experimental treatment 2) and to a computer-based multimedia system that simulated a mock industrial setting (experimental treatment 3). Each condition was measured for its effectiveness in teaching verbal information skills (memorization) and intellectual (problem-solving) skills. The research design used was a three-by-two, mixed factors design with Method of Instruction as the between-subjects variable and Domain of Learning as the within-subjects variable. It was hypothesized that the multimedia treatment conditions would result in greater original learning among subjects than the control condition. It was further hypothesized that there would be an interaction between Method of Instruction and Domain of Learning, and also that the multimedia simulation condition would result in greater original learning among subjects than the standard multimedia condition. Thirty subjects of similar knowledge, skills, and abilities were selected to participate in the study. An experimental post-test was administered to subjects to measure their degree of original learning. The scores were recorded and an Analysis of Variance (ANOVA) was performed. This analysis showed a significant difference in the effectiveness of Method of Instruction on subjects’ original learning, but no significant effects were found with the main effect of Domain of Learning or the interaction of Method of Instruction with Domain of Learning. A Newman-Keuls post-hoc test was performed to determine the locus of the main effect of Method of Instruction. This test showed that only the standard multimedia system (experimental treatment 2) resulted in significantly better original learning than the control condition. The effect of the multimedia simulation system (experimental treatment 3) was not shown to be statistically significant. / Master of Science

A habitat suitability index (HSI) model for white-tailed deer (Odocoileus virginianus) was tested to determine the relationship between habitat quality predicted by the model and habitat quality suggested by the condition of 1.5 year-old bucks on Quantico Marine Corps Base, Virginia. Additionally, new models were developed that predict the response of habitat variables important to a variety of species to succession and management. Habitat quality predicted by the white-tailed deer HSI model for 11 different deer management units was not strongly correlated with body weight (Spearman's r = -0.40, f = 0.221, n = 11), beam diameter (rs = 0.06, f = 0.851, n = 11), beam length (rs = 0.37, f = 0.265, n = 11), and number of points (rs = -0.24, f = 0.473, n = 11). The area within each management unit with HSI > 0.5 was weakly correlated (rs = 0.48, P = 0.13) with beam diameter and beam length. We attempted to model the response of vegetation to succession and management. The strength of the relationship between habitat changes and stand age (succession) varied depending on the variable and cover type being modeled. R2adj values were highest on average for habitat parameters associated with overstory trees, including basal area, dbh, density, and height. R2adj values were low (R2a~ < 0.5) and regressions nonsignificant (f > 0.10) for models associated with shrubs and herbaceous vegetation. In general, the response of habitat parameters was most predictable in loblolly-shortleaf pine plantations that were hand planted and not subject to the same variation associated with naturally regenerated stands. / Master of Science

The goal of this study is to provide a model for maritime accidents which focuses on human factor related safety concerns and permits the economic evaluation of countermeasures. In order to halt the trend of maritime accidents it is necessary to identify the human related factors that are associated with them and address a method of analysis to isolate these factors and evaluate their economic impact. The United States Coast Guard (USCG) investigates and records data on accidents for vessels in U.S. waters and U.S. flag vessels all over the world. Other organizations which collect accident data are Lloyds of London, the P&I Club and some marine insurance companies. In order to understand the magnitude of human factor related accidents the USCG casualty database CASMAIN, which provides consistently gathered data for a period of more than ten years from (1981 to 1991), is analyzed. This database contains close to 66,133 records on 42,367 accidents. Accident analysis in the past was restricted to statistical reporting of the nature of casualty and its primary causes. Analysis rarely add ressed such issues as contributing causes and the variety of human factors causes and still further those contributing factors which led to failure of the human being from performing at an that more than 80% of the accidents were a result, whether direct or indirect, of human error. Such issues as workload, fatigue and stress in the transportation arena are being considered only now and other factors such as the effects of circadian rhythms and alertness switches are still in the realm of research. To better understand the human factors causes and their rationale a functional model of critical tasks and resources to carry them out is outlined. The human factors causes of accidents are also detrimental to the personnel resources required for a safe ship operation. If the risks posed by these factors can be assessed we would be in a better position to ensure that the tasks are performed properly and thus realize a safer and more efficient maritime system. Past historical accident data from the USCG CASMAI N database was then developed and organized to provide numerical estimates of human error frequencies for use in the proposed model. The resulting model would permit assessing costs and alternatives and result in a methodology of better addressing marine transportation safety with an emphasis on its prime creator, user and benefiter:-The Human. / Master of Science

A novel method of fabricating low reflectance mirrors has been developed based on the photosensitivity of hydrogen-loaded, germanium-doped optical fibers. Using a side-writing technique, point-wise refractive index changes have been induced in the core of Ge-doped optical fibers via ultraviolet light from a high power excimer laser. These refractive index changes cause Fresnel reflections at the boundary of the higher photoinduced index change and the lower index in the unexposed core. The boundary of the two refractive indices may be considered a low reflectance mirror. Several techniques have been explored to characterize the Fresnel reflectors including optical time domain reflectometry (OTDR) and spectral analysis. In-line, optical fiber Fresnel reflectors have applications as internal mirrors in intrinsic Fabry-Perot interferometric (IFPI) sensors and OTDR distributed strain sensors. Photoinduced IFPI sensors have performed well as temperature sensors, strain sensors, and vibration sensors. Improved manufacturing techniques are also discussed for future developments. The photoinduced IFPI sensor is inexpensive to manufacture and involves little skill, in contrast to the labor-intensive fabrication techniques of conventional IFPI sensors. The IFPI sensor has commercial applications in embedded structures, high temperature environments, and situations with large EMI conditions. / Master of Science

Corn pollen and glass beads were used as surrogates of natural fine particulate organic matter (FPOM). These particles were released into ten streams in three different physiographic regions, Appalachian Mountains, Rocky Mountains, and Central Plains, within the United States. Mean travel distance for corn pollen was 121 m and that for glass beads 40 m. Rates of deposition through the water column for both particles were 0.484 mm/sec and 0.643 mm/sec, respectively. This empirically derived deposition velocity was only a fraction of the still water fall velocity. Hydraulic parameters indicate that flow conditions at the stream bed prevent establishment of a laminar sublayer. As a result, corn pollen and glass beads should be entrained and moved as bed- or suspended load. Gradient was the single best stream characteristic to explain variation in retention rates for both corn pollen and glass beads. Based on deposition velocities, estimates of benthic FPOM turnover times ranged from 20 hours to 8.3 days, rate of FPOM downstream movement was 1-24 m/d, and carbon turnover length was 1-24 km. / Master of Science

This paper is an evaluation of the efficiency of the Government National Mortgage Association (GNMA) mortgage-backed securities market. GNMA securities represent a $702 billion market. Despite this size, the securities do not trade on an organized exchange. Trading on an organized exchange implies that a maximum amount of available information is incorporated into prices. Consequently, can the GNMA market be efficient? An efficient market, as posited by Eugene Fama and others, is one where all of the information available in a market is incorporated in the prices in that market. There are various levels of efficiency ranging from the use of all publicly available information to the use of that information plus information not generally available (i.e. proprietary and "insider" information".) This paper considers the more general case of information available in period t not being used in that period but rather being incorporated in the prices of period t+n. The analysis uses monte carlo simulation to generate paths of discount rates based on the yield curve for U.S. Treasury securities. These periodic rates along with a common spread are used to discount the estimated cash flows on the GNMA securities. The common spread is termed the Option Adjusted Spread ("OAS") and is postulated to incorporate all of the market information over and above that is used in setting prices (and their corollary, yields) in the Treasury market. The test of market efficiency is whether or not the prices in period t are correlated with the OAS of a subsequent period. / Master of Arts

The majority of deaths and injuries in compartment fires result from inhalation of the toxic gas, carbon monoxide (CO), especially in locations remote from the burning compartment. This causes the transport and oxidation of CO in burning buildings to become an important topic. Studies have been conducted to determine the toxic environments produced inside, and in locations remote from, a burning compartment; however, no studies have investigated the composition of the exhaust gases during transport to remote locations. The goal of this study was to investigate fire exhaust gas transport through a hallway to determine the important parameters affecting the efficiency of sustained external burning in oxidizing toxic gases, including the hydrodynamic effects of different hallway configurations. Underventilated compartment fire experiments were performed with a compartment exhausting along the axis of a hallway. The design of the compartment allowed direct measurement of the global equivalence ratio which was used as a main correlating parameter. Characteristic global equivalence ratios and an ignition index concept were investigated to determine when sustained external burning would occur. Gas sampling was performed downstream of the hallway to determine the overall efficiency of sustained external burning, and in the hallway to provide detailed data on the processes occurring in the hallway. The oxidation of the exhaust gases traveling through the hallway was determined to vary among different species, and also to be very sensitive to the hydrodynamic mixing between the rich exhaust plume and the cooler ambient air in the hallway. In general, the overall oxidation of hydrocarbons was much more complete than for CO or soot. The gas temperatures in the hallway and fuel vaporization rate were also determined to affect oxidation in the hallway. Variations in the hallway inlet and exit soffits affected the hydrodynamic structure of the exhaust plume and oxidation efficiencies, with the inlet soffit exhibiting the strongest effect. / Master of Science

Today's highly competitive marketplaces require production systems that are flexible and responsive to changing demands. To remain competitive, companies need close coordination and exchange of computer interpretable information between product design and the manufacturing system. Computer-Aided Process Planning (CAPP) is an essential key for achieving closer links among design and manufacturing activities. The purpose of process planning is to generate feasible sequences for producing a part in a given production facility. To generate process plans automatically (true generative CAPP), design information along with production facility information needs to be appropriately represented. Most CAPP systems assume feasible designs as input and lack the capability to evaluate designs for manufacturability with respect to the production facility. The objective of this research is to develop a true generative CAPP system that is an integral part of a design for manufacturability (DFM) application for machined components. It involves determining appropriate representation schemes of machined components and production facility resources. The created CAPP Module, developed using C++, consists of five process dependent modules for automatic process plan generation and evaluation: (1) Process selection, (2) Machine/Tool Selection, (3) Setup/Fixture Planning, (4) Operation Sequence Planning, and (5) Process Plan Evaluation. Process plan generation is performed by the first four modules. Evaluation of process plans is performed by the Process Plan Evaluation Module. Criteria such as cost, resource utilization, and production requirement, are used to generate the most appropriate process plan and to select additional process plans as needed. / Master of Science