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ABSTRACTThis paper presents an empirical assessment of four state-of-the-art risk-averse approaches to deal with the capacitated lot-sizing problem under stochastic demand. We analyse two mean-risk models based on the semideviation and on the conditional value-at-risk risk measures, and alternate first and second-order stochastic dominance approaches. The extensive computational experiments based on different instances characteristics and on a case-study suggest that CVaR exhibits a good trade-off between risk and performance, followed by the semideviation and first-order stochastic dominance approach. For all approaches, enforcing risk-aversion helps to reduce the cost-standard deviation substantially, which is usually accomplished via increasing production rates. Overall, we can say that very risk-averse decision-makers would be willing to pay an increased price to have a much less risky solution given by CVaR . In less risk-averse settings, though, semideviation and first-order stochastic dominance can be appealing alternatives to provide significantly more stable production planning costs with a marginal increase of the expected costs. 相似文献
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介绍了安装在液压试验机上的一种集冲裁、切口作用于一体的复合冲裁模的设计,解决了没有压力机的情况下冲裁件的加工问题。 相似文献
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冷成型模具低温锌系磷化 总被引:4,自引:1,他引:3
研制出适用于冷成型模具高硬度表面的低温锌系磷化工艺。其中磷化液含Zn(H2 PO4 ) 2 ·2H2 O 6 0g/L ,Zn(NO3) 2 ·6H2 O 90g/L ,NaNO2 1.5g/L ,稀土促进剂 0~ 1.0g/L ,游离酸度 4~ 6点 ,总酸度 70~ 75点。该磷化液在 4 0℃下 ,处理 30~ 4 0min后可获得厚约 10 μm的磷化膜。性能测试表明 ,其减摩、润滑性能良好 ,摩擦系数约降 0 .1,与未处理试样相比磨损量下降 96 % ,附着力 1级。 相似文献
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Li2O在保护渣中的作用 总被引:7,自引:0,他引:7
采用在不同玻璃性的两种基渣中加入Li2O为研究Li2O对保护渣粘度,熔化温度及玻璃性能的影响,并对Li2O改善保护渣玻璃性的机理进行了探讨,提出了寻找高速连铸保护渣中Li2O的代用物的一种方法。 相似文献
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Second-law-based thermodynamic analysis of two-stage and mechanical-subcooling refrigeration cycles 总被引:1,自引:0,他引:1
Thermodynamic analysis of HFC-134a vapor-compression refrigeration cycles is investigated by both the first and second laws of thermodynamics. Second-law analysis is carried out for both two-stage and mechanical-subcooling refrigeration cycles. The analysis is performed on each of the system components to determine their individual contribution to the overall system irreversible losses. It is found that most of the losses are due to a low compressor efficiency. Irreversibilities of expansion valves and condenser are also significant. In addition, it is shown that the optimum inter-stage pressure for two-stage and mechanical-subcooling refrigeration systems is very close to the saturation pressure corresponding to the arithmetic mean of the refrigerant condensation and evaporation temperatures. These results are compared with the existing practice in the industry. Furthermore, theoretical results of a two-stage refrigeration system performance are also compared with experimental values for a CFC-22 system. 相似文献
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Yoshiyuki Uno Akira Okada Kensuke Uemura Purwadi Raharjo Toshihiko Furukawa Kosaku Karato 《Precision Engineering》2005,29(4):171-455
A new finishing process for metal molds by large-area electron beam (EB) irradiation is proposed in this study. In the large-area EB irradiation equipment used here, an EB with high-energy density is irradiated without focusing the beam, and so the EB with a maximum diameter of 60 mm can be used for melting or evaporating metal surface instantly. Experimental results show that the surface roughness decreases from 6 μmRz to less than 1 μmRz in just a few minutes under proper machining conditions. The corrosion resistance of metal mold surface also could be greatly improved by large-area EB irradiation. Furthermore, the surface roughness of tilting surface close to 90° could be well improved. Therefore, large-area EB irradiation method has a possibility to become a high-efficiency finishing process for metal molds. 相似文献