An Optimization Model for Aircraft Service Logistics

Scheduling is one of the most difficult issues in t he planning and operations of the aircraft services industry. In this paper, t he various scheduling problems in ground support operation of an aircraft mainte nance service company are addressed. The authors developed a set of vehicle rout ings to cover each schedule flights; the objectives pursued are the maximization of vehicle and manpower utilization and minimization of operation time. To obta in the goals, an integer-programming model with geneti...     

ON MANAGERIAL DECISION PROBLEM OF THE AUCTION SITES

This paper studies one managerial decision problem of the auction sites： how to combine penalties with commissions？ It is shown that when there exists secondary auction market, the auction whose penalty is a linear function of the seller＇s commission will be more efficient than the auction with only commissions but no penalties. It has also been proven that using this strategy can maximize the expected revenue for the seller, the auction site and their total expected revenues.     

网络机房的维护策略

网络机房的维护是一项繁琐的工作 ,要做到事半功倍 ,应把握住这项工作的关键。可以在机房维护中采取两方面的策略 :一是做好应对机房故障的准备 ,二是做好日常安全防范     

Structure prediction for the down state of a potassium channel voltage sensor

Voltage-gated potassium (Kv) channels, essential for regulating potassium uptake and cell volume in plants and electrical excitability in animals, switch between conducting and non-conducting states as a result of conformational changes in the four voltage-sensing domains (VSDs) that surround the channel pore. This process, known as gating, is initiated by a cluster of positively charged residues on the fourth transmembrane segment (S4) of each VSD, which drives the VSD into a 'down state' at negative voltages and an 'up state' at more positive voltages. The crystal structure of Kv1.2 probably corresponds to the up state, but the local environment of S4 in the down state and its motion in voltage gating remains unresolved. Here we employed several conditional lethal/second-site suppressor yeast screens to determine the transmembrane packing of the VSD in the down state. This screen relies on the ability of KAT1, a eukaryotic Kv channel, to conduct potassium when its VSDs are in the down state, thereby rescuing potassium-transport-deficient yeast. Starting with KAT1 channels bearing conditional lethal mutations, we identified second-site suppressor mutations throughout the VSD that recover yeast growth. We then constructed a down state model of the channel using six pairs of interacting residues as structural constraints and verified this model by engineering suppressor mutations on the basis of spatial considerations. A comparison of this down state model with the up state Kv1.2 structure suggests that the VSDs undergo large rearrangements during gating, whereas the S4 segment remains positioned between the central pore and the remainder of the VSD in both states.     

Wet spinning of PVA composite fibers with a large fraction of multi-walled carbon nanotubes

PVA composites fibers with a large fraction of multi-walled carbon nanotubes modified by both covalent and non-covalent functionalization were produced by a wet-spinning process.Model XQ-1 tensile tester,thermogravimetric analysis,scanning electron microscopy,differential scanning calorimetry,and wide-angle X-ray diffraction were used to characterize the properties of PVA/MWNT composite fibers.The TGA results suggested that MWNTs content in composite fibers were ranged from 5.3 wt%to 27.6 wt%.The mechanical properties of PVA/MWNT composite fibers were obviously superior to pure PVA fiber.The Young's modulus of composite fibers enhanced with increasing the content of MWNTs,and it rised gradually from 6.7 GPa for the pure PVA fiber to 12.8 GPa for the composite fibers with 27.6 wt%MWNTs.Meanwhile,the tensile strength increased gradually from 0.39 GPa for the pure PVA fiber to 0.74 GPa for the composite fibers with 14.4 wt%MWNTs.Nevertheless,the tensile strength of the composite fibers decreased as the MWNTs content up to 27.6 wt%.SEM results indicated that the MWNTs homogeneously dispersed in the composite fibers,however some agglomerates also existed when the content of MWNTs reached27.6 wt%.DSC results proved strong interfacial interaction between MWNTs and PVA chain,which benefited composite fibers in the efficient stress-transfer.WXAD characterization showed that the orientation of PVA molecules declined from 94.1%to 90.9%with the increasing of MWNTs content.The good dispersibility of MWNTs throughout PVA matrix and efficient stress-transfer between MWNTs and PVA matrix may contributed to significant enhancement in the mechanical properties.     

最优价格与回收努力激励的闭环供应链协调

根据最优激励理论,探讨了制造商采用激励契约实现闭环供应链协调的可行性.其中制造商对零售商采用最优销售价格激励契约,对回收商采用最优回收努力激励契约.研究结果发现,最优销售价格激励契约可以实现闭环供应链生产销售部分的协调.最优回收努力激励契约可以协调闭环供应链的逆向回收部分,并分别分析了影响最优销售价格激励契约与最优回收努力激励契约的因素,最后用算例分析验证了结果的正确性.     

废润滑油无酸再生技术研究及应用进展

概述了以加氢精制法、分子蒸馏法、膜处理法、微波热解法为代表的废润滑油无酸再生技术的原理;结合具体的应用,评述了相关的废润滑油无酸再生技术的成效及存在的问题,并指出了废润滑油无酸再生技术的发展方向。     

预加轴力对基坑交叉工程稳定性影响

针对长春卫星广场节点范围内快速路结构工程与既有车站主体结构交叉的问题,综合现场实测和无预加轴力不对称开挖的模拟分析,对原有的基坑开挖方案进行了模拟和优化。结果表明：当采用无预加轴力不对称开挖方案时,基坑桩体水平位移呈现出朝向基坑且上大下小的变形特征,其中由于土体开挖引起荷载变化造成的最大变形量占总变形量的75％以上;采用增加200 kN 预加轴力的优化方案后,基坑桩体水平位移呈中间大两端小的变形特征,桩体的最大水平位移减小了10．84 mm,比原方案减小52．1％,与无预加轴力模拟的结果相比,西侧最大变形增大了0．31 mm,东侧最大变形减小了0．82 mm;方案优化后,两侧基坑变形趋于平衡并关于主体对称,减小了结构的剪力;桩体最大水平变形的位置下移至桩顶以下9 m 处,有效约束了桩体上部的变形。     

Forecasting China’s Foreign Trade Volume with a Kernel-Based Hybrid Econometric-Ai Ensemble Learning Approach

Due to the complexity of economic system and the interactive effects between all kinds of economic variables and foreign trade, it is not easy to predict foreign trade volume. However, the difficulty in predicting foreign trade volume is usually attributed to the limitation of many conventional forecasting models. To improve the prediction performance, the study proposes a novel kernel-based ensemble learning approach hybridizing econometric models and artificial intelligence （AI） models to predict China＇s foreign trade volume. In the proposed approach, an important econometric model, the co-integration-based error correction vector auto-regression （EC-VAR） model is first used to capture the impacts of all kinds of economic variables on Chinese foreign trade from a multivariate linear analysis perspective. Then an artificial neural network （ANN） based EC-VAR model is used to capture the nonlinear effects of economic variables on foreign trade from the nonlinear viewpoint. Subsequently, for incorporating the effects of irregular events on foreign trade, the text mining and expert＇s judgmental adjustments are also integrated into the nonlinear ANN-based EC-VAR model. Finally, all kinds of economic variables, the outputs of linear and nonlinear EC-VAR models and judgmental adjustment model are used as input variables of a typical kernel-based support vector regression （SVR） for ensemble prediction purpose. For illustration, the proposed kernel-based ensemble learning methodology hybridizing econometric techniques and AI methods is applied to China＇s foreign trade volume prediction problem. Experimental results reveal that the hybrid econometric-AI ensemble learning approach can significantly improve the prediction performance over other linear and nonlinear models listed in this study.     

从实验废液中回收提纯碘

本介绍了利用氧化还原反应，采用升华、萃取法回收实验废液中的碘的工艺。该工艺操作简便，成本低廉，所得产物纯度高，回收率高。