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Y. KONDO C. SAKAE M. KUBOTA H. KITAHARA K. YANAGIHARA 《Fatigue & Fracture of Engineering Materials & Structures》2006,29(3):191-199
The fatigue limit diagram provides the critical condition of non‐failure against fatigue under constant amplitude loading. The fatigue limit diagram is usually considered to give the allowable stress if every stress component is kept within the fatigue limit diagram. In the case of variable amplitude fretting fatigue, however, this study showed that fatigue failure could occur even when all stresses were within the fatigue limit diagram. An example of such a condition is a repeated two‐step loading such as when the first step stress is R=?1 and the second step stress has a high mean value. The reason why such a phenomenon occurs was investigated. A non‐propagating crack was formed by the first step stress even when well below the fatigue limit. The resultant non‐propagating crack functioned as a pre‐crack for the second step stress with a high mean value. Consequently, fatigue failure occurred even when every stress was within the fatigue limit diagram of constant amplitude loading. The fatigue limit diagram obtained in constant amplitude fatigue test does not necessarily guarantee safety in the case of variable amplitude loading in fretting fatigue. 相似文献
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Atsushi KUWABARA Shin-ichi KURODA Hitoshi KUBOTA 《等离子体科学和技术》2007,9(2):181-189
The polymer treatment with a low-temperature plasma jet generated on the atmospheric pressure surface discharge (SD) plasma is performed. The change of the surface property over time, in comparison with low pressure oxygen (O2) plasma treatment, is examined. As one compares the treatment by atmospheric pressure plasma to that by the low pressure O2 plasma of PS (polystyrene) the treatment effects were almost in complete agreement. However, when the atmospheric pressure plasma was used for PP(polypropylene), it produced remarkable hydrophilic effects. 相似文献
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This paper deals with fuzzy scheduling and path planning problems by genetic algorithms. We have proposed a self-organizing manufacturing system (SOMS) that is composed of a number of autonomous modules. Each module decides output through interaction with other modules, but the module does not share complete information concerning other modules in the SOMS. Therefore, we require structured intelligence as a whole system. In this paper, we consider a manufacturing line composed of machining centres and conveyor units. The manufacturing procedure can be divided into a sequence of three modules: (a) tool locating module, (b) scheduling module, and (c) path planning module. The tool locating problems have been already solved. In this paper, we first solve the scheduling problem as global preplanning. Here we assume that the processing time is not constant, because some delay may occur in the machining centres. We therefore apply fuzzy theory to represent incomplete information abou t the machining time. We solve the fuzzy scheduling problem with a genetic algorithm. After global preplanning, the path planning module transports materials and products. Next, the scheduling module acquires the actual processing time of each machining centre. Based on the processing time, the schedule module generates a fuzzy number for the processing time. We discuss the effectiveness of the proposed method through the computer simulation results. 相似文献
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化学储热利用可逆化学变化中的吸、放热进行储能和释能,较之显/潜热储热,其能量密度呈数量级上升且可长期稳定储存热能。本文以低品位能源利用为前提,将化学储热分为化学吸附储热与化学反应储热两大类,对目前广泛研究、前景较大的化学储热材料进行了相应原理、特点、现存问题及其应用发展趋势的分析讨论与总结;经过对不同纯材料的分析对比,发现水合盐可以作为一类较理想的化学储热材料,但也存在易潮解等缺点,而复合材料的形成可为弥补各种纯材料的弊端提供了有效的解决路径;与此同时,目前仍缺乏可在反应器中良好运行的化学储热材料。最后对化学储热,尤其是储热材料的选择方面指出未来需要解决的问题及其进一步的研究方向。 相似文献
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XIAO Ye-xiang HAN Feng-qin ZHOU Jing-lin KUBOTA Takashi 《水动力学研究与进展(B辑)》2007,19(3):356-364
Different from the reaction turbines, the hydraulic performance of Pelton turbine is dynamic due to the unsteady flow in the rotating buckets in time and space. The dynamic energy efficiency of bucket ηEB and power efficiency of bucket ηPB within a short period can be predicted from the dynamic flow pattern of the free-surface sheet flow in the rotating bucket, whereas the dynamic discharge efficiency of bucket ηQB is defined as the resident discharge in the bucket at the respective moment. Under the operation of higher unit speed nDH than the optimum one, the power efficiency of bucket is deteriorated by the jet interference with the rear surface of bucket ?Prear at the first stage of the dynamic performance, as well as the loss power due to the spilt flow from the cutout of bucket at the later stage of performance. Based on the dynamic performance prediction presented, the future possibility of the quantitative investigation for the negative scale effect of Pelton turbines was discussed. 相似文献
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Y. KONDO C. SAKAE M. KUBOTA T. KUDOU 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(8):675-682
Fatigue tests on material containing small defects were performed under a wide range of mean stress for three grades of steels with different hardness. The ΔKth of small defects had a peculiar dependency on material hardness and mean stress, which was quite different from those of long cracks or plain specimens. The crack closure of short cracks was measured. It was shown that the formation of the crack closure was affected by the material hardness and mean stress. This behaviour of crack closure resulted in characteristic fatigue limit properties of materials containing small defects. 相似文献