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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
401

Poster: Investigating Doppler Effects on Vehicle-to-Vehicle Communication: An Experimental Study

Jordan, Dwayne, Kyte, Nicholas, Murray, Scott, Ahmed, Md Salman, Hoque, Mohammad A., Khattak, Asad 16 October 2017 (has links)
Doppler effects on vehicular communication have been theoretically modeled by many researchers. However, very limited experimental studies have been conducted to investigate the impact of Doppler shift on the vehicle-to-vehicle (V2V) communication range and reliability with high speed mobility. The current work-in-progress research aims to quantify the impact of Doppler effects on V2V communication reliability, range, and reachability using singlehop Dedicated Short Range communications (DSRC) between two opposite traffic. We conducted our experiments by mounting the after-market DSRC on-board units on the dashboard of two vehicles that cross each other from opposite directions with constant relative speeds on a real interstate freeway. Our preliminary results indicate that the communication time and range drop to approximately 70% and 40% after the two vehicles cross and start moving away from each other with the average relative speeds of 110 and 140 mph, respectively. Similarly, the packet delivery ratio is also drastically reduced after the vehicles start moving away from each other. Apparently, these results indicate that there might be a strong effect of Doppler phenomena on the transmission range, packet delivery rate and the duration of the communication.
402

A new approach to the adult respiratory distress syndrome : biological modelling and early identification of ventilation : perfusion inequalities in the management of patients at risk

Cloete, Anacreon 20 July 2017 (has links)
No description available.
403

Student to Teacher Racial/Ethnic Ratios as Contributors to Regional Achievement Gaps, 1999-2008

Hays, James M. 12 1900 (has links)
With the advent of No Child Left Behind legislation in 2002 and its mandates for annual yearly progress for all students, many districts and schools in Texas have had difficulty elevating African American and Hispanic students’ scores. The current study examined these students’ achievement on the annual Texas high-stakes measure as a function of a numerical construct that aligns the race/ethnicity of students when the teacher race is White. Earlier studies have shown that racial/ethnic compatibility between students and teachers improves student achievement in the primary grades. The study, which was set in 10 north Texas school districts and 30 high schools, middle schools, and elementary schools, examined African American and Hispanic students’ achievement on the Texas state assessments in reading and mathematics over a 10-year period. District performance data came from 4,664,192 African American, Hispanic, and White students and 222, 834 White teachers. Campus level data encompassed 188,839 10th graders, 93,573 eighth graders, and 40,083 fourth graders, and 20,471 White teachers. Analysis revealed that, as the ratios of African American and Hispanic students to White teachers increased, the percentages of these two student groups passing the Texas assessments decreased. These patterns differed for White students whose passing percentages increased as these students’ numbers increased relative to White teachers in all settings except in elementary schools. These preliminary findings suggested that racial alignment at the high school and middle school levels might elevate African American and Hispanic achievement. Implications may lead to shifting focus on teacher quality and class size as the primary determinants of student achievement. Findings need validation with further study using larger data sets and sequential grade levels. If validated through further studies involving larger samples, contiguous grade levels, and more sophisticated statistical analysis, this study’s findings may have implications for teacher education curriculum, recruitment of minority teacher candidates, workforce retention, and state policy on class size limits.
404

Altering Positive/Negative Interaction Ratios in Relationships of Mothers and Young Children: A Preliminary Investigation

Armstrong, Andrew B. 01 May 2010 (has links)
Based on classic marital research of John Gottman, a popular notion exists that interpersonal relationships thrive when the number of positive interactions outweighs negative interactions by a ratio of five to one. Though many have given similar advice for parents and caregivers, Gottman's findings and methodology may not generalize to relationships of parents and young children. Were similar ratio findings to be validated for parent-child relationships, explicit ratio advice may be incorporated as a component of clinical practice (e.g., behavioral parent training). To begin investigating potential clinical implications, a project was conducted that examined mothers' ability to achieve prescribed ratios following brief instruction. Baseline ratio levels for a small sample of nonclinical mother-child dyads were approximately one positive for every one negative. When instructed to attain a 5 to 1 ratio, all participants improved their ratios; half the sample achieved the target ratio. Mothers in the study altered their ratios primarily by boosting the number of positives they used with their children.
405

The Use of Progressive-Ratio Schedules to Assess Negative Reinforcers

Knighton, Ryan 01 May 2012 (has links)
We used a combined multi-element, ABCBC reversal design to examine whether qualities of various negative reinforcers can be assessed under progressive-ratio schedules. Two adults with disabilities participated in this study. We assessed five sounds three times using progressive-ratio schedules to obtain mean break points for each stimulus and ranked negative reinforcers according to their mean break points. We called the stimulus with the highest mean break point the high-quality escape (HQE) stimulus and the stimulus with the lowest break point the low-quality escape (LQE) stimulus and examined responding according to different schedules of reinforcement for each stimulus: FR2, FR4, and FR8 for Jenny and FR1 and FR11 for April. We identified preferred and nonpreferred sounds for both participants.We observed differential responding for both participants between preferred and nonpreferred sounds. We observed differential responding between HQE and LQE stimuli for April but not for Jenny; a larger range in break points was observed for April. These results demonstrate a method to identify preferred and nonpreferred sounds and provide support for the possibility of using progressive-ratio schedules to rank negative reinforcers of various qualities.
406

Effect of Casein/Fat Ratio on Milk Fat Recovery in Cheddar Cheese

Yiadom-Farkye, Nana A. 01 May 1984 (has links)
Cheddar cheese was made by the traditional 4.5-h method from three experimental lots of milk, each standardized to casein/fat ratios of approximately 0.64, 0.67 and 0.70. The effect of casein/fat ratio on milk fat recovery was determined. The effects of milk composition on curd firmness at cutting, cheese composition and resulting yield of cheese were evaluated. Correlations between milk constituents and various cheese components were obtained. Milk fat recovery was unaffected by casein/fat ratios within the limits of 0.64 and 0.71. Average milk fat recovery was 91.58 ± 1.73%. Cheese yield was a function of milk protein, milk fat and cheese moisture; and a modified Van Slyke equation predicted cheese yield better than the original equation within the limits of casein/fat ratio studied. Strong negative correlations were observed between casein/fat ratio and cheese fat and cheese fat in the dry matter whereas positive correlations were observed between casein/fat ratio and cheese protein. At constant protein levels curd firmness increased directly with the amount of fat in cheese milk.
407

A Method for Quantifying the Effects of Apomorphine Upon the Gnawing Syndrome of the Rat

Robinson, Paul 01 May 1967 (has links)
Various methods were tried in an attempt to obtain a technique for quantifying the gnawing effects of apomorphine on rats. A technique using a restraining tube was developed. Under a 2 milligram per kilogram intraperitoneal injection of apomorphine, four female Long Evans hooded rats were placed on continuous and fixed reinforcement schedules using a gnawable pine block. Subjects would learn to turn their heads away from the gnawable object in order to obtain 15 seconds of gnawing time. The rate of response increased from less than one response in 5 minutes to over 3 responses per minute in 10 one-half hour conditioning sessions. Rates of response stabilized during the last 5 experimental sessions and fixed ratio schedules of up to 5:1 were obtained in five additional 1 '1/ 2 hour sessions.
408

The Highest Local Density of Reinforcement Controls Overall Post-Reinforcement Pause Duration on Ratio Schedules

Bonem, Elliott J. 01 May 1988 (has links)
A series of experiments were conducted with pigeons to investigate the variables responsible for differential postreinforcement pause (PRP) durations found on ratio schedules. In Experiment I, behavior on fixed-ratio (FR) and variable-ratio (VR) schedules were compared to behavior evoked by two interpolated schedules. The addition of a single FR 1 component to the FR 50 baseline schedule reduced the overall PRP to a duration comparable to that found on the VR 50 schedule. The addition of both an FR 1 and an FR 215 component to an FR 50 baseline reduced PRP and IRT durations below those on a VR 50 schedule. Experiments II and III were designed to isolate the conditions under which the smallest ratio component exerts predominant control over PRP duration. The results of Experiment II demonstrated that a local increase in reinforcement density was a necessary, but not sufficient condition for reducing median PRP duration. That is, exposure to a response-independnt increase in reinforcement density attenuated, but did not eliminate the reduction in median PRP duration associated with the interpolated FR 1 component. The results of Experiment III demonstrated that neither random session location of the FR 1 component nor unsignaled presentation of the FR 1 component were necessary conditions for reducing the duration of the PRP. That is, a brief, response-dependent increase in reinforcement density was a sufficient condition for reducing PRP duration given a subject free from historical exposure to response-independent reinforcement. It was concluded that the difference in PRP duration produced by two, comparably-sized, fixed- and variable-ratio schedules is a function of the size of the smallest ratio component present in the reinforcement schedule. More generally, the highest local density of reinforcement controls the overall duration of the PRP on a response-dependent, ratio schedule.
409

Numerical Analysis and Spanwise Shape Optimization for Finite Wings of Arbitrary Aspect Ratio

Hodson, Joshua D. 01 August 2019 (has links)
This work focuses on the development of efficient methods for wing shape optimization for morphing wing technologies. Existing wing shape optimization processes typically rely on computational fluid dynamics tools for aerodynamic analysis, but the computational cost of these tools makes optimization of all but the most basic problems intractable. In this work, we present a set of tools that can be used to efficiently explore the design spaces of morphing wings without reducing the fidelity of the results significantly. Specifically, this work discusses automatic differentiation of an aerodynamic analysis tool based on lifting line theory, a light-weight gradient-based optimization framework that provides a parallel function evaluation capability not found in similar frameworks, and a modification to the lifting line equations that makes the analysis method and optimization process suitable to wings of arbitrary aspect ratio. The toolset discussed is applied to several wing shape optimization problems. Additionally, a method for visualizing the design space of a morphing wing using this toolset is presented. As a result of this work, a light-weight wing shape optimization method is available for analysis of morphing wing designs that reduces the computational cost by several orders of magnitude over traditional methods without significantly reducing the accuracy of the results.
410

Joint modeling of bivariate time to event data with semi-competing risk

Liao, Ran 08 September 2016 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Survival analysis often encounters the situations of correlated multiple events including the same type of event observed from siblings or multiple events experienced by the same individual. In this dissertation, we focus on the joint modeling of bivariate time to event data with the estimation of the association parameters and also in the situation of a semi-competing risk. This dissertation contains three related topics on bivariate time to event mod els. The first topic is on estimating the cross ratio which is an association parameter between bivariate survival functions. One advantage of using cross-ratio as a depen dence measure is that it has an attractive hazard ratio interpretation by comparing two groups of interest. We compare the parametric, a two-stage semiparametric and a nonparametric approaches in simulation studies to evaluate the estimation perfor mance among the three estimation approaches. The second part is on semiparametric models of univariate time to event with a semi-competing risk. The third part is on semiparametric models of bivariate time to event with semi-competing risks. A frailty-based model framework was used to accommodate potential correlations among the multiple event times. We propose two estimation approaches. The first approach is a two stage semiparametric method where cumulative baseline hazards were estimated by nonparametric methods first and used in the likelihood function. The second approach is a penalized partial likelihood approach. Simulation studies were conducted to compare the estimation accuracy between the proposed approaches. Data from an elderly cohort were used to examine factors associated with times to multiple diseases and considering death as a semi-competing risk.

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