Direct Energy Transfer for High Efficiency Photovoltaic Energy Systems Part I: Concepts and Hypothesis

This two-part paper presents a comprehensive comparative study on parallel power processing (PPP) and standard schemes in dc/dc converters for photovoltaic (PV) energy systems. It is demonstrated how PPP can improve direct energy transfer (DET), which results in PV systems operating at higher voltage and efficiency. Discussions of the concepts, hypotheses and computer simulations are presented in Part I. Part II provides the experimental results, which confirm the validity of the analysis and simulations.     

Extensions of the Discrete-Average Models for Converter Power Stages

An improved power converter model is developed by combining the average and discrete modeling techniques. The parameter determination of the proposed discrete-average model is shown to be dependent on the type of duty cycle control law and the nature of the error processor used in the feedback loop. Furthermore, the paper pinpoints deficiencies of the conventional loop gain measurement technique which is widely used in industries.     

Reduced lymphocyte activation in space: role of cell-substratum interactions.

We investigated the effect of substratum adhesiveness on stimulated lymphocyte blastogenesis by reducing and blocking cell adhesion with poly (2-hydroxyethyl methacrylate) (poly-HEMA) in a simple on-ground system. Cells grown on medium-thick and thick poly-HEMA films were rounded in shape and displayed no signs of spreading. By contrast, on tissue culture plastic and very thin poly-HEMA films, they showed clear signs of spreading. The mitogenic response of lymphocytes grown on thick poly-HEMA films was reduced by up to 68% of the control (tissue culture plastic). Interferon-gamma production was near zero when the cells were grown on the least adhesive substratum. On uncoated plastic, activated lymphocytes subjected to high gravity (20g) exhibited an increased proliferation rate (40%) compared with 1g. By contrast, on poly-HEMA, high gravity did not improve lymphocyte responsiveness. These results show that activated lymphocytes need to anchor and spread prior to achieving an optimal proliferation response. We conclude that decreased lymphocyte adhesion could contribute to the depressed in vitro lymphocyte responsiveness found in the microgravity conditions of space flight.     

Adaptive Input Filter Compensation for Switching Regulators

An input filter is frequently employed between a switching regulator and its power source. However, its presence often results in degradation of dynamic performances and stability. The detrimental interaction is between an input filter and a switching regulator and is a function of the input filter parameters and also of the supply voltage. An earlier paper presented an analysis and design procedure aimed at developing a feed-forward loop to cancel this undesirable interaction. The feed-forward design is extended here to encompass a scheme that automatically accounts for changes in the supply voltage; the result is an adaptive compensation that tracks the input voltage variations. Experimental results are presented that confirm the adaptive nature of the design.     

Photochemical initiation of gaseous detonations

Direct initiation of detonations in gaseous mixtures of C₂H₂-O₂, H₂-O₂ and H₂-Cl₂ in the pressure range of 10–150 torr using flash photolysis was studied. Similar to blast initiation using a concentrated powerful energy source, it was found that for photochemical initiation, there exists a certain threshold of flash intensity and energy for each mixture at any given initial pressure and composition below which a deflagration is formed. At the critical threshold, however, a fully developed detonation is rapidly formed in the immediate vicinity of the window of incident UV radiation. However, at super critical flash energies, the amplitude of the detonation formed decreases and combustion of the entire irradiated volume approaches a constant volume explosion. It was found that photo-chemical initiation requires both a certain minimum peak value of the free radical concentration generated by the photo-dissociation as well as an appropriate gradient of this free radical distribution. The minimum peak radical concentration permits rapid reaction rates for the generation of strong pressure waves, while the gradient is necessary for the amplification of the shock waves to a detonation. If the gradient is absent and the free radicals are uniformly distributed in the mixture, then the entire volume simply explodes as in a constant volume process. The present study reveals that the mechanism of photochemical initiation is one of proper temporal synchronization of the chemical energy release to the shock wave as it propagates through the mixture. In analogy to the LASER, the term SWACER is introduced to represent this mechanism of Shock Wave Amplication by Coherent Energy Release. There are strong indications that this SWACER mechanism is universal and plays the main role in the formation of detonations whenever a powerful concentrated external source is not used to generate a strong shock wave in the explosive.     

ISO 9000 认证所带来的利益及质量管理之发展(英文)

本文总结了９项有关ＩＳＯ９０００认证的研究,主要论述了这套国际标准为实施者所带来之利益。这９项研究分别在英国、新西兰、澳大利亚、中国香港特区、美国、巴西、加拿大、法国、德国、日本、韩国、瑞典和荷兰等地进行。研究发现,ＩＳＯ９０００的主要优点有：令运作方式系统化、减少损耗、增加效率和减少顾客投诉。取得ＩＳＯ９０００认证的公司,大多采取较严格的方法去控制分供方。不少取得证书的公司还表示,他们会进一步采用其他的质量管理方法,例如全面优质管理,ＩＳＯ９０００,ＩＳＯ１４０００和优质奖的规格。     

Strapdown INS error model for multiposition alignment

The relationship between quaternion errors and tilt angles from true navigation frame to analytic platform frame is newly derived for strapdown inertial navigation system (SDINS). Using the relationship it is shown that the quaternion error model for attitude and velocity is equivalent to the conventional perturbation error model. Based upon the equivalency, the quaternion errors during a multiposition alignment are determined and analyzed. Furthermore, it is shown that the heading rotation of 180 deg achieves the minimal quaternion error for 2-position ground alignment     

Improved Switching Converter Model Using Discrete and Averaging Techniques

The nonlinear modeling and analysis of dc-dc converters has been done by averaging and discrete-sampling techniques. The averaging technique is simple, but inaccurate, as the modulation frequencies approach the theoretical limit of one-half the switching frequency. The discrete technique is accurate even at high frequencies, but is very complex and cumbersome. An improved model is developed by combining the aforementioned techniques. This new model is easy to implement in circuit and state variable forms and is accurate to the theoretical limit.     

Space policy for late comer countries: A case study of South Korea

Korea’s space development program was created almost 40 years behind those of the advanced countries but it has nevertheless made remarkable progress. Korean space development has been focused on technology catch-up, where commercialization and growth of industrial competitiveness are important rationales. However, the program has several problems, including: lack of a space equipment manufacturing industry, total system companies in the space manufacturing industry and communication between industry and researchers, and much concentration of projects and initiatives in the Korean Aerospace Research Institute (KARI). This study analyzes the problem by comparing space agencies and programs in Korea and other countries, particularly Japan and the USA. It is shown that the role of a national laboratory is critical in space industry development and argued that KARI should make greater efforts to promote the Korean space industry by encouraging technology transfer, sharing equipment and communication between companies. For successful space development, the main organization – usually the national research institute – should change its role from a research-only laboratory to manager and supporter of space development and industry. Such a move would invigorate Korea’s space industry and allow it to catch up with countries with a similar environment.     

Control of approach and landing phase for reentry vehicle using fuzzy logic

The reentry vehicle is affected by various disturbances such as a wind gust, atmospheric condition or aerodynamic problems in the approach and landing phase. Therefore it is necessary to design a robust control scheme. This paper presents a control scheme using Mamdani fuzzy PD controller. In this paper, the reference trajectories are generated using geometric parameters for disturbed circumstances with 4 cases: nominal, headwind and tailwind, drag increased case. Then, a Mamdani fuzzy PD controller was designed in this study. Twenty-five rules were applied in the knowledge-based system. The max–min method for a fuzzy inference system and the center-of-mass method in defuzzification were used. Finally, guidance and control simulations are performed for verification of proposed controller using generated reference trajectories. In addition, the Monte Carlo simulation is performed considering various disturbances. The results show that proposed Mamdani fuzzy PD controller has reliability and robustness for control of reentry vehicle with wind disturbance in the approach and landing phases.