This research presents more realistic models for left-turn and through volume capacity by taking into account the probabilistic nature of the left-turn bay blockages and spillbacks at a signalized intersection under the leading phasing scheme with a short left-turn bay. Generally, the left-turn bay spillback situation has been overlooked in the leading left-turn signal because much attention has been given to the more common problem of left-turn blockage under the leading left signal. The left-turn spillback situation, however, might happen because the ratio of left-turning vehicle tends to be relatively high in the traffic after the occurrence of left-turn bay blockage. That is, left-turn bay blockage, spillback situations, left-turn capacity, and through capacity are closely connected with one another. Hence, this research estimates more precisely the capacity for through and left-turn movement by considering the left-turn bay blockage and spillback situations associated with left-turn bay under leading left-turn signal operations. In order to find general agreement between the results from this proposed model and a real-world situation, the developed capacity model is validated with the results from CORSIM simulations of a real-world signalized intersection. The binomial distribution is applied as the arrival distribution for through movement considering the characteristics of expected arrivals under heavy flow conditions. Finally, since left-turn bay blockage and spillback situation seem to have adverse impacts on each other, this research investigates if there are any dependent relationships between left-turn bay blockage and spillback. Here, this study confirmed that close relationships between left-turn bay blockage and spillback situations obviously exists.

No description available.

Zugl.: Vallendar, WHU - Otto Beisheim School of Management, Diss., 2009

No description available.

Advancements in the power electronics systems have been directly related to the availability of improved power semiconductor devices. The device performance greatly determines the efficiency, reliability, volume, and cost of the power electronics system. This dissertation is dedicated to develop an advanced high power semiconductor device, the emitter turn-off (ETO) thyristor, which is targeted to improve the limitations of the present high power devices. Major improvements in electrical and mechanical designs of the ETO for high power and high frequency operation are proposed which result in improved snubberless turn-off capability, low conduction loss, and low gate drive power consumption of the new generation ETO. A revolutionary self-power generation method of the ETO is proposed. Different from the conventional high power devices which require the external power input for their gate drivers, ETO achieves complete optically controlled turn-on and turn-off and all the internal power required is self-generated. This advancement will have a major impact to high power converter designs. A novel integrated method to eliminate the dead-time requirement is proposed for ETO. This method not only improves the output waveform quality but also increases the reliability and reduces the cost of the high power PWM voltage source converters. With this unique function, the upper and the lower ETO's within a converter phase leg can receive the ideal complementary (without dead-time) PWM signals and solve shoot-through problems. Method to measure the ETO current and transfer the current information to a PWM signal is proposed. Based on the ETO's built-in current sensor, the over-current protection function of the ETO is designed as well. The experimental results show that the built-in current sensor has a very high precision, and the over-current protection function can effectively protect the ETO during the short circuit faults. In order to improve ETO's turn-off capability, a comprehensive investigation of the turn-off failure mechanism of the ETO was performed. A series of simulations and experiments are carried out to study the ETO turn-off operation. The detail turn-off failure mechanisms are presented. The conditions to cause the ETO failure are addressed. The approaches to improve the ETO's turn-off capability are discussed. / Ph. D.

Collagen is one of the most important and abundant proteins in mammals. It consists of three left-handed PPII helixes coiled along a common axis to form a very compact right-handed super helix. The primary structure is shown to be (Gly-Xaa-Yaa)n repeats with high content of prolyl residues at both Xaa and Yaa positions. <i>Cis-trans</i> isomerization of the prolyl amide bonds is one of the rate-limiting steps during collagen triple helix folding. The conformationally locked alkene isosteres Fmoc-Gly-Ψ[(E)CH=C]-Pro-Hyp(tBu)-OH and Fmoc-Pro-Ψ[(E)CH=C]-Pro-OH were designed and synthesized. The synthesis of the Gly-Pro isostere had no stereo-control, and the two diastereomers of the tripeptide isostere Fmoc-Gly-Ψ[(E)CH=C]-Pro-Hyp(tBu)-OBn were separated by normal phase HPLC. Although the stereoselectivity of the asymmetric reduction was not good for the Pro-Pro isostere, the resulting diastereomers was separable by flash chromatography, and the absolute stereochemistry of the two diastereomers was determined by Mosher's method. The Gly-Pro alkenyl peptides, and their control peptide Ac-(Gly-Pro-Hyp)8-Gly-Gly-Tyr-NH2 were synthesized and purified. All three peptides showed a maximum around 225 nm and a minimum close to 200 nm in the CD spectra, which indicated the formation of PPII helixes. The Tm value of the control peptide was determined to be 50.0 °C. The peptide with Gly-Ψ[(E)CH=C]-L-Pro-Hyp as the guest triplet formed a stable triple helix with a Tm value of 28.3 °C. The peptide with Gly-Ψ[(E)CH=C]-D-Pro-Hyp as the guest triplet showed a linear decrease in the ellipticity with increasing temperature, which indicated that no triple helix was formed. The Pro-Pro alkenyl peptide and its control peptide H-(Pro-Pro-Gly)₁₀-OH were synthesized and purified. The T_m value of control peptide was determined to be 31.6 °C by extrapolation to 0 M TMAO in PBS buffer, which was very close to the measured value of 31.5 °C. The Pro-Pro alkenyl peptide began to show a maximum around 225 nm in the CD spectra when the concentration of TMAO was higher than 2.5 M. After extrapolation to 0 M TMAO, the T_m value was determined to be –22.0 °C. These results indicate that the backbone inter-chain hydrogen bond is one of the major forces in stabilizing the collagen triple helix, while <i>cis-trans</i> isomerization has limited contribution. The intrinsic properties of the amide bond may have huge influence on the stability of the collagen triple helix. The helix-turn-helix motif is an important tertiary structure in DNA-binding proteins. Stepwise modifications of the Antennapedia HTH peptide (27-55) were performed to improve the helicity and stability. The peptide with more side-chain ion-pairs was over 4 times more helical than the native Antp peptide, while the Ala-based peptide was over 9 times more helical than the native peptide. A 12-membered ring, Fmoc-protected HTH-turn mimic was designed and synthesized, and was ready for solid phase peptide synthesis. The solubility of the cyclic peptide was very poor, and the purification of the final product was very difficult. The solubility problem might also affect solid phase peptide synthesis in the future. / Ph. D.

Zugl.: Siegen, Universiẗat, Diss., 2007.

Zugleich: Diss. Siegen. / Literaturverz.

Thesis (MScEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Capacity waste happens when right-turn vehicles have right-of-way during a separate right-turn phase and lanes (e.g., through lanes) of the same approach of the intersection cannot discharge vehicles during that green phase. Right-turn traffic consumes the capacity which otherwise could be provided to through traffic movements at an at-grade signalized intersection. Therefore, it is widely considered that it would lower intersection capacity and increase total delay (Lin, Machemehl, Lee & Herman, 1984). The pre-signal strategy proposed in this research is specifically designed to improve this problem. The following aspects of this strategy were studied in this research, - Capacity benefits of this strategy, - Relationships between the capacity and the length of sorting area (the area between the two signals), - Signal timing of both main signal and pre-signal, - Clearance time of the sorting area, - Main signal phasing options - Signal coordination between the main signal and the pre-signal, - Utilization of the sorting area, and - Pre-signal strategy performance in a simulated environment. The results of this study showed that right-turn movement benefits significantly from this pre-signal strategy. For example, right-turn capacity can be doubled if a presignal is installed on one through lane of an approach with one right-turn lane. It was also found, the maximum approach capacity benefit is not affected significantly by the length of the sorting area for a given green period. The optimal green time and the available pre-signal green time for right-turn movement were also derived in this research. Different main signal phasing options were studied and compared. Phasing options which fit the proposed pre-signal strategy were found. Recommended values for right-turn green time of both signals were given based on different lengths of sorting area. The case study, which compared the performance of some critical movements at the intersection with and without the proposed pre-signal system, confirms the results concluded in this study. A potential problem with this strategy when applied at a real intersection is that it may confuse drivers. Drivers need to be educated and will need time to get familiar with this signal control method. / AFRIKAANSE OPSOMMING: Beskermde regsdraaifases vir verkeer by gelykvlak seinbeheerde kruisings gebruik die kapasiteit wat benut kon word deur deurbewegings. Dit verlaag interseksie kapasiteit en totale oponthoud verhoog. Die voorseinstrategie wat in die navorsing studie voorgestel word is spesifiek ontwikkel om die probleem op te los of te verminder. Die volgende aspekte van die strategie is ondersoek in die navorsingsstudie: - Kapasiteitsvoordele van die strategie. - Die verhouding tussen die kapasiteit en die lengte van die sorteringsarea (die area tussen die twee seine). - Seintydstoedeling van beide die hoofseinfase en die voorseinfase. - Ontruimingstyd van die stoorarea. - Hoofseinfaseopsies. - Seinkoordenasie tussen die hoofsein en die voorsein. - Benutting van die sorterings area, en - Voorseinstrategieprestasie in ‘n gesimuleerde omgewing. Die resultate bewys dat die regsdraaibeweging grootliks bevoordeel word nadat die voorseinstrategie ingestel is. Byvoorbeeld, regsdraaikapasiteit kan verdubbel word as ‘n voorseinfase ingestel word op een van die deurlane tesame met ‘n enkele regsdraailaan. Daar is ook gevind dat die kapasiteit nie grootliks beinvloed word deur die lengte van die stoorgebied nie. Die optimale groentyd en die beskikbare voorsein groen tyd vir die regsdraaibeweging is ook afgelei in die navorsing. Verskillende hoofseinfaseopsies is bestudeer en vergelyk. Faseringsopsies vir die voorgestelde voorseinstrategie is gevind. Voorgestelde waardes vir regsdraaigroentyd van voorseine en hoofseine is bereken om kapasiteit te verbeter, gebasseer op verskillende lengtes van die stoorarea. Die gevallestudie wat die prestasie op ‘n aanloop met en sonder die voogestelde voorseinstrategie vergelyk, bewys resultate wat ooreenstem met die bevindinge in die studie. Die verwagte probleem met die voorseinstrategie, wanneer dit ingestel word by ‘n werklike interseksie, is verwarring van die bestuurders. Bestuurders sal opgevoed moet word en sal tyd nodig hê om gewoond te raak aan die voorseinmetode.

The objective of this study was to provide an estimate of the protected dual left turn saturation flow rates in the Tucson area. The data were collected from dual left turn lanes at six intersections. The headway times were measured in order to calculate the saturation flow rates at each of the study sites. Observations were made at four intersections with left turn protected and at two intersections with permitted plus protected left turns. Saturation flow was measured from the third to the last vehicle in the queue. Observations were made during the time of expected peak traffic flow. A stop watch was used to measure the time intervals to the nearest tenth of a second. The saturation flow rates were then calculated and varied from 1621 to 2017 Vehicles Per Hour of Green Per Lane (VPHGL) for the inside lane to 1737 to 1802 VPHGL in the outside lane.