三门峡水利枢纽汛期排沙平水发电冲淤特性分析

1994～1999年三门峡水利枢纽进行汛期发电试验.洪水期降低水位敞泄排沙,恢复库容;平水期控制水位发电,入库泥沙经垂水段分选,出库泥沙数量与粒径减小.壅水段淤积物大致以锥体形态分布在北村以下,选择适当时机或利用洪水降低水位排沙3～4天,可全部清理出库.北村以上河道在前期大幅冲刷的基础上,溯源中刷继续发展,向上延伸至黄淤33断面附近.6年汛期发电试验,古夺以下库段冲淤基本平衡,潼-古段因受水沙变化的影响,累计淤积0.16亿m3.     

The Top Management Team,Reflexivity, Knowledge Sharing and New Product Performance: A Study of the Irish Software Industry

In the present study, we develop a model to predict new product performance incorporating the literature on top management team (TMT) composition, trustworthiness, knowledge sharing and task reflexivity in organizations. We hypothesize that diversity and trustworthiness in the TMT should influence knowledge sharing and reflexivity and reflexivity and knowledge sharing would be positively associated with new product performance. We test the model using data collected from 39 indigenous software firms in Ireland. Results indicate that age diversity was positively related to knowledge sharing ability while educational level, tenure and functional diversity of the TMT did not have any direct effect on reflexivity or knowledge sharing ability or motivation. However, educational level of TMT, tenure and age diversity had indirect effects on reflexivity and knowledge sharing through the intervening variable of TMT trustworthiness. Further, knowledge sharing and task reflexivity had direct effects on market new product performance. Implications for research and practice are discussed.     

Simulating the Thermal Behavior of Buildings Using Artificial Neural Networks-Based Coarse-Grain Modeling

This paper reports on the development of a new approach for simulating the thermal behavior of buildings that overcome the limitations of conventional heat-transfer simulation methods such as the finite difference method and the finite element method. The proposed technique uses a coarse-grain approach to model development whereby each element represents a complete building component such as a wall, internal space, or floor. The thermal behavior of each coarse-grain element is captured using empirical modeling techniques such as artificial neural networks (ANNs). The main advantages of the approach compared to conventional simulation methods are (1) simplified model construction for the end-user; (2) simplified model reconfiguration; (3) significantly faster simulation runs (orders of magnitude faster for two- and three-dimensional models); and (4) potentially more accurate results. The paper demonstrates the viability of the approach through a number of experiments with a model of a composite wall. The approach is shown to be able to sustain highly accurate long-term simulation runs, if the coarse-grain modeling elements are implemented as ANNs. In contrast, an implementation of the coarse-grain elements using a linear model is shown to function inaccurately and erratically. The paper concludes with an identification of on-going work and future areas for development of the technique.     

Advanced space solar cells

This paper will present a brief overview of the status of research and development of advanced space solar cells from a variety of materials. Most of the investigations at present are focused on binary, ternary and quaternary III–V semiconducting compounds such as InP, GaInAs and GaInP₂. Growth techniques used for producing laboratory cells include liquid-phase epitaxy (LPE), organometallic vapor phase epitaxy (OMVPE), molecular beam epitaxy (MBE) or any of a number of variations of these techniques, such as atomic layer epitaxy (ALE), etc. Gallium arsenide is at present the only commercially available III–V compound solar cell. Compound III–V multiple bandgap cells are now under development in a jointly sponsored NASA/Air Force manufacturing technology demonstration program. In general, the decision to use a particular cell technology in space is determined by several factors, emphasis on any particular one depending on the mission environment: some are related to the properties of the photovoltaic material itself, such as efficiency and resistance to radiation damage, and some are related to details of the cell structure and associated materials, such as survivability under repeated thermal cycling and resistance to atomic oxygen erosion. The impact of these requirements on cell material selection and structural design is briefly discussed. This paper was produced under the auspices of the US Government and is therefore not subject to copyright in the USA     

METHODOLOGY CHOICE,COMPLEXITY TEXTURE,SELF-REFLECTION

Substantial efforts have been dedicated toward the development of systems methodologies for “problem solving,” with various research groups concentrating on particular approaches. Recently, however, there have been moves toward reconciling these varying approaches within one overall framework, thus cutting out “isolationism” and inevitable ensuing sniping. This paper provides an overview of three attempts to promote such openness and conciliation (in terms of theory, methodology, and ideology), draws them together, and then demonstrates the practical importance of a critical approach through a series of contrasting applications and by reflecting on ideas from the three approaches.     

Influence of the dislocation density on the performance ofheteroepitaxial indium phosphide solar cells

The authors point out that heteroepitaxial indium phosphide solar cells developed to date have low efficiency due to misfit dislocations. Dislocations act as recombination centers and strongly influence the solar cell performance. Calculations have been made to study the dependence of heteroepitaxial InP solar cell efficiency on dislocation density. The effects of surface recombination velocity and cell emitter thickness are also considered. Calculated results are compared with the available experimental results on representative InP solar cells. It is shown that heteroepitaxial InP cells with over 20% AM0 efficiency could be fabricated if dislocation density can be reduced to <10⁵ cm^-2 and the surface recombination velocity reduced to <10⁵ cm/s     

关于我国防洪问题的几点思考：从德,法,荷三国防洪减灾看我国防洪工作

德国、法国、荷兰三国经济发达,其防洪减灾工作取得了显著成就,在防洪策略、工程措施和非工程措施建设等方面有许多经验值得我们借鉴。结合我国防洪工作的实际,有必要从认识、投入、高新技术的应用、洪水风险等方面进行进一步的探讨。     

EDFA-based DWDM lightwave transmission systems with end-to-end power and SNR equalization

An approximate analysis is presented which can be used to predict the performance of power and signal-to-noise ratio (SNR) equalization schemes when applied to dense wavelength-division multiplexing (DWDM) lightwave systems employing erbium-doped fiber amplifier (EDFA) cascades. Expressions are provided which relate the maximum number of amplifiers, EDFA gain imbalance, bit rate (R/sub b/), transmitter power, receiver dynamic range and number of channels. The relative advantages of these two equalization strategies are quantified by comparing the maximum number of amplifiers allowed by each scheme. It is shown that, while SNR equalization represents, on balance, the more desirable equalization strategy for future EDFA-based DWDM lightwave transmission systems, under certain conditions power equalization may be a better choice. When employing an APD receiver, for instance, power equalization can support 1.9 times more amplifiers than SNR equalization. However, when employing the more conventional preamplified PIN/FET receiver, SNR equalization can support 1.7 times more amplifiers than power equalization.     

Genre, rhetorical interpretation, and the open case: teaching theanalytical report

Analytical reports, being one of the most difficult genres to teach in a technical writing course, are best taught through the “open case” method. Open cases take advantage of the fact that students are already situated in a workplace environment, the college campus. Engineering students can use the genre to impose order on this chaotic environment, conducting various forms of research on engineering-related campus issues. A process for developing open case assignments is provided     

Japanese encephalitis on Saipan: a survey of suspected mosquito vectors

An outbreak of Japanese encephalitis (JE) occurred on Saipan, Commonwealth of Northern Mariana Islands, in October 1990. Adult and larval mosquitoes were collected during September-October 1991 to retrospectively determine the probable mosquito vector(s). Virus was not isolated from 119 mosquito pools composed of 7,250 adult specimens as follows: Aedes vexans nocturnis (14%), Culex tritaeniorhynchus (39%), Cx. sitiens group (11%), Culex (Culex) species (35%), and < 1% each of Ae. albopictus, Ae. oakleyi, Aedes saipanensis, Cx. annulirostris marianae, and Cx. fuscanus. Three additional species were collected only as larvae: Anopheles indefinitus, Ae. neopandani, and Cx. quinquefasciatus. Among the vectors of JE incriminated in other areas, Cx. tritaeniorhynchus was the predominant species in our collections and the principal species feeding on swine. This is the first published record of the occurrence of this species on Saipan. Culex tritaeniorhynchus is abundant and widely distributed on the southern half of Saipan where human JE cases occurred in 1990, and where swine seroconversions were detected. Although the identity of the mosquito vector(s) responsible for the 1990 outbreak cannot be established with certainty, our results suggest that Cx. tritaeniorhychus was probably involved.