Three programmed rapid-start control schemes for the electronic ballasts with a half-bridge series-resonant inverter are proposed to improve the starting performance of the rapid-start fluorescent lamps. Included are: (1) programmed rapid-start control scheme with an ac switch, (2) programmed rapid-start control scheme with inductively coupled filament-heating circuit, and (3) programmed frequency control scheme with a series-resonant energy-tank. The first control scheme is simply to add a solid-state ac switch onto the series-resonant electronic ballast to provide programmed rapid-start for the rapid-start fluorescent lamp. The ac switch is turned on to have a zero voltage across the lamp to eliminate the glow current during the preheating interval. By adjusting the operation frequency and the duty-ratio, the electronic ballast produces first an adequate resonant current for preheating the cathode filaments, then a sufficiently high lamp voltage for ignition, and finally a stable lamp arc of the required lamp power. The second control scheme is accomplished by adding two auxiliary windings on the inductor of the power-factor-correction (PFC) circuit for the filament-heating circuits. During the preheating period, the PFC circuit is activated to provide the filament heating while the inverter remains idle to keep the lamp voltage at zero and hence to eliminate the glow current. After the filaments have been heated to the appropriate temperature, the inverter is initiated to ignite the lamp and then operate it at the required power. The third control scheme is realized by programming the operation frequency of the electronic ballast with an additional series-resonant energy-tank on the load resonant network. During the preheating interval, the electronic ballast is programmed to operate at the resonance frequency of the series-resonant energy-tank to reduce the lamp voltage and hence to eliminate the glow discharge. With carefully designed circuit parameters, the electronic ballast is able to provide an adequate current for preheating. After the emission temperature has been reached, the operation frequency is adjusted to generate a high lamp voltage for ignition, and then is located at the steady-state frequency driving the lamp with the desired power and filament current. In this dissertation, the mode operations of the proposed ballast circuits are analyzed in accordance with the conducting conditions of the power switches. The equivalent resistance model of fluorescent lamp is implemented to calculate the performances of the ballast-lamp circuit at steady-state. The design equations are derived and the computer analyses are performed with the fundamental approximation on the equivalent circuit models of fluorescent lamps. In addition, in order to accurately predict the operating characteristic of the preheating circuit, a mathematical model is developed to interpret the variations of the filament resistance during preheating. Finally, the laboratory electronic ballasts with the proposed control schemes are built and tested. Satisfactory performances are obtained from the experimental results.

Many people instinctively agree that entrepreneurial experience is a valuable property more useful in identifying new opportunities. In fact, many entrepreneurs who had started an enterprise thought that they identified a new opportunity but failed in new enterprise. This let us consider a question ¡§How entrepreneurial experience effects opportunity identification¡H¡¨ Past researches have discussed more about ¡§prior knowledge¡¨, but not deeply discussed about the content of entrepreneurial experience. It is hard to express the unique value of entrepreneurial experience and to explain the logic of the relation between entrepreneurial experience and opportunity identification. This research further describes and defines the content of entrepreneurial experience on the basis of ¡§prior knowledge¡¨ discussed by past researches, and explains the relation between entrepreneurial experience and opportunity identification. Analyzing literature, this research generalizes a conclusion that entrepreneurial experience includes ¡§start-up experience¡¨, ¡§management experience¡¨ and ¡§industry-specific experience¡¨. ¡§Start-up experience¡¨ is the most unique and is also the key point of this research. Through discussion with entrepreneur, the content of ¡§start-up experience¡¨ includes ¡§sustained opportunity identification¡¨, ¡§establishment of networks of stakeholders¡¨ and ¡§establishment of honor¡¨. The goals of these activities are reacting to the environmental impact of high uncertainty, variance and time pressure in start-up period. Finally, according to the result of case study, this research finds ¡§sustained opportunity identification¡¨ and ¡§establishment of networks of stakeholders¡¨ could be useful or harmful to opportunity identification in different conditions. ¡§Establishment of honor¡¨ is absolutely useful to opportunity identification. So it can be understood that entrepreneurial experience could give opportunity identification a positive or negative effect.

A new starting profile, instead of ANSI C82.11, is defined to illustrate the starting transient of rapid-start fluorescent lamps driven by high-frequency electronic ballasts. By scrutinizing the lamp voltage and current waveforms, the starting transient can be classified into preheating, glow, and glow-to-arc stages. By the new definition, the starting characteristics of all ballast-lamp circuits can be well interpreted. To investigate the starting performance, a test system is set up. Experimental results show that the time required for glow and glow-to-arc stage is significantly affected by the starting voltage, the filament preheating and the environment temperature. On the basis of the in-depth analysis on the investigated results, the starting characteristics of rapid-start fluorescent lamps are well understood, providing useful information for designing the starting scenario for the ballast.

This research proposes a new signal operation strategy aimed at efficient utilization of green time by cutting down on the start up and response loss times. The idea is to have a "pre-signal" on each main approach a few hundred feet upstream of the intersection in addition to the main intersection signal, which is coordinated with the pre-signal. The offset between the main and pre-signal ensures that the majority of start up losses does not occur at the main signal. The benefits of the system under various traffic conditions were evaluated based on analysis of the queue discharge process and Corridor Simulation (CORSIM) study. The proposed measure should reduce the travel time and total control delay for the signalized network. To attain the objective the following two studies were undertaken: 1. Development of a queue discharge model to investigate the expected benefits of the system. 2. Simulation of the system: In the second part of the research, the proposed strategy was tested using CORSIM to evaluate its performance vis-à-vis the baseline case. The queue discharge model (QDM) was found to be linear in nature in contrast to prior expectations. The model was used to quantify the benefits obtained from the pre-signal system. The result of this analysis indicated that the proposed strategy would yield significant travel time savings and reductions in total control delay. In addition to the QDM analysis, CORSIM simulations were used to code various hypothetical scenarios to test the concept under various constraints and limitations. As per expectations, it was found that the system was beneficial for high demand levels and longer offsets. The upper limit on offsets was determined by visual observation of platoon dispersion and therefore the maximum offset distance was restricted to 450 feet. For scenarios where split phasing was used, the break even point in terms of demand level was found to be 2500 vph on a three lane approach, whereas that for a lag-lag type of phasing strategy was found to be 1800 vph, also on a three lane approach.

This thesis investigates the impact of preheating and glow current on the life-time of rapid-start fluorescent lamps during the starting transient period. A set of electronic ballast circuit is designed to adjust the starting transient preheating current, open-circuit voltage, and preheating time, so that the preheating conditions and the intended amount of glow current can be scheduled. In the experiments, the tested lamps are frequently switched on and off for 35 seconds and 25 seconds, respectively, to accelerate the life-cycle test. Experimental results show that the effect of the glow current on the life-cycle is trivial. Insignificant difference is found between the test lamps with different glow currents when the preheating conditions are the same. On the other hand, the preheating degree is found to be the main factor that affects the lamp life-time. The tested lamps which are adequately preheated last for more than 100000 test cycles. On the other hand, the tested lamps with insufficient preheating are premature with black ends or even damaged only after the several thousands cycles.

No description available.

Thesis (M.S.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references (leaves 93-98). Also available on the World Wide Web.

Thesis (Ph. D.) in Psychology--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 96-116).

Background Exploring the literature stream of the knowledge perspective as well as that of start-ups andincubation, and subsequently bringing the two together. Aim To construct propositions regarding the process of developing managerial capability in incubatedstart-ups. Methodology The study entails 3 start-ups that provide a high technology product. The development ofmanagerial capability was explored through a comparative case study in which founders, businesscoaches and externally recruited employees where interviewed. Findings The process of managerial capability development in incubated start-ups can be deconstructedinto two processes, knowledge acquisition and knowledge integration, where each process presentdistinct attributes in different stages of development of the start-up. This managerial capabilityformation is an incremental process that drives growth.

No description available.