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排序方式: 共有295条查询结果,搜索用时 31 毫秒
281.
存域网(SAN)在数字图书馆中信息安全的应用研究 总被引:2,自引:0,他引:2
数字图书馆是图书馆信息化建设的必然趋势 ,通过采用存域网 (SAN ,StorageAreaNetwork)技术 ,可以保证图书馆数据信息的可靠与安全 ,笔者分析了根据不同的需求 ,采用不同的SAN拓扑结构 ,为图书馆信息网络建设提供了多种可靠的解决方案 相似文献
282.
Donald L. Chery Calvin G. Clyde Roger E. Smith 《Journal of the American Water Resources Association》1979,15(4):1126-1145
ABSTRACT: Mathematical models for predicting watershed surface flow responses are available, most of which are elaborate nonlinear numerical surface and channel flow models linked with infiltration models. Such models may be used to make predictions for ungaged areas, assuming an acceptable fitting of the model to the topography and roughness of the real system. For some application purposes, these models are impractical because of their complexity and expensive computer solutions. A procedure is developed that uses a complex model of an ungaged area to derive a simpler parametric nonlinear system model for repetitious simulation with input sequences. The predicted flow outputs are obtained with the simpler model at significant savings of money and time. The procedures for constructing a complex kinematic model of a 40 acre (161,880 m2) reference watershed and deriving the simpler system model are outlined. The results of predictions from both models are compared with a selected set of measured events, all having essentially the same initial conditions. Peak discharges ranged from 3 to 118 ft3/sec (0.085 to 3.34 m3/sec), which includes the largest event of record. The inherent limitations of lumped systems models are demonstrated, including the bias caused by their inability to model infiltration losses after rainfall ceases. Computer costs and times for the models were compared. The derived simple model has a cost advantage when repeated use of a model is required. Such an applications hydrologic model has an engineering tradeoff of reduced accuracy, and lumping bias, but is more economical for certain design purposes. 相似文献
283.
D. I. Cary A. B. Crane D. J. Hernderson 《Journal of the American Water Resources Association》1978,14(1):109-118
Abstract: The diffuculty in understanding the listings of many available hydrologic models programmed in FORTRAN is a serious limitation to their verification and use. By expending more effort in creating clearly written computer programs, more information can be transferred to those interested in modeling hydrologic process. The use of simulation languages to produce more understandable program listings and increase the flow of informationg is recommended. An example is presented in which surface water runoff from storms on small rural watershedds is modeled. 相似文献
284.
论述介绍了微机监测控制系统用于污水处理,提出了系统硬件组成结构和软件模块,讨论了影响参数测量精度的主要因素及对应措施。 相似文献
285.
介绍了建筑防火设计的现状及发展趋势,特别提到计算机模拟技术在建筑工程防火性能化设计中的重要性,并且应用CFD系列防火软件中的FDS软件对室内火灾的特征进行了模拟与描述,体现了计算机模拟技术在建筑防火设计中应用的优越性与实效性。 相似文献
286.
287.
The ever-increasing amount of electronic scrap and the steadily-decreasing contents of the precious metals used in electronics, as well as the ever-growing environmental awareness, challenges such conventional precious-metal-oriented recycling techniques as pyrometallurgy. Separation and beneficiation of various materials encountered in electronic scrap might provide a correct solution ahead. In this context, mechanical separation-oriented characterization of electronic scrap was conducted in an attempt to evaluate the amenability of mechanical separation processes. Liberation degrees of various metals from the non-metals, which are crucial for mechanical separation, were analyzed by means of a grain counting approach. It is found that the metallic particles below 2 mm achieve almost complete liberation. Particle shapes were also quantified through an image processing system. The results obtained show that the shapes of the particles, as a result of shredding, turn out to be heterogeneous, thereby complicating mechanical separation processes. In addition, separability of various materials was ascertained by a sink–float analysis. It has been shown that density-based separation techniques shall be viable in separating metals from plastics, light plastics (ABS, PS and PVC, etc.) from glass fiber reinforced resins and aluminum from heavy metals. Specifically, a high quality copper concentrate can be expected by density-based separation techniques. Moreover, FT-IR spectra of plastics pieces from the light fractions after the sink–float testing show that PC scrap primarily contains ABS, PS and PVC plastics with the density range of +1.0–1.5 g/cm3, whereas PCB scrap mainly contains glass fiber reinforced epoxy resins plastics with the density range of +1.5–2.0 g/cm3. 相似文献
288.
289.
Ashraf A. Shikdar Mahmoud A. Al-Kindi 《International journal of occupational safety and ergonomics》2013,19(2):215-223
The objective of this research was to study and identify ergonomic deficiencies in computer workstation design in typical offices. Physical measurements and a questionnaire were used to study 40 workstations. Major ergonomic deficiencies were found in physical design and layout of the workstations, employee postures, work practices, and training. The consequences in terms of user health and other problems were significant. Forty-five percent of the employees used nonadjustable chairs, 48% of computers faced windows, 90% of the employees used computers more than 4 hrs/day, 45% of the employees adopted bent and unsupported back postures, and 20% used office tables for computers. Major problems reported were eyestrain (58%), shoulder pain (45%), back pain (43%), arm pain (35%), wrist pain (30%), and neck pain (30%). These results indicated serious ergonomic deficiencies in office computer workstation design, layout, and usage. Strategies to reduce or eliminate ergonomic deficiencies in computer workstation design were suggested. 相似文献
290.
Kerstin Norman Håkan Alm Ewa Wigaeus Tornqvist Allan Toomingas 《International journal of occupational safety and ergonomics》2013,19(1):53-68
Background. The purpose was to study the test-retest reliability and internal consistency of questions in aquestionnaire concerning working conditions and health and the inter-rater reliability of observations andmeasurements according to an ergonomic checklist. Method. Fifty-seven operators participated in a retestquestionnaire and 58 operators participated in an inter-observer test. Results. The questions had fair to good or higher reliability in 142 of the total of 312. Twenty-seven of the total of 44 variables in the ergonomicchecklist were classified as having fair to good or higher reliability. Conclusions. About half of the questionshad fair to good or higher reliability and can be recommended for further analyses. The majority of variablesin the ergonomic checklist were classified as having fair to good or higher reliability. Low reliability does notnecessarily indicate that the reliability of the test, per se, is low but may signify that the conditions measuredvary over time or that the answers are aggregated in one part of the scale. 相似文献