Impulse controls and uncertainty in economics: Method and application

We develop a stochastic optimal control framework to address an important class of economic problems where there are discontinuities and a decision maker is able to undertake impulse controls in response to unexpected disturbances. Our contribution is two fold: (1) to develop a linear programming algorithm that produces a consistent approximation of the maximum value and optimal policy functions in the context of stochastic impulse controls; and (2) to illustrate the economic benefits of impulse controls optimized, using our framework, and calibrated to the population dynamics of a marine fishery. We contend that the framework has wide applicability and offers the possibility of higher economic pay-off for a wide-range of policy problems in the presence of discontinuities and adverse shocks.     

鄂尔多斯盆地胡尖山地区长61致密砂岩储层成岩特征与孔隙度定量恢复

在对大量岩心和薄片分析的基础上,运用扫描电镜、阴极发光、高压压汞等实验手段,系统分析了鄂尔多斯盆地胡尖山地区长6₁储层的成岩作用特征及其对储层物性的影响,并进一步对孔隙演化进行了定量恢复。结果表明：胡尖山地区长6₁储层整体处于中成岩阶段A期,主要经历了压实—压溶、胶结、溶蚀等成岩作用,且不同成岩作用对储层的孔隙发育造成了不同程度的影响。压实作用破坏了大量原生粒间孔,是导致研究区储层致密最主要的因素,孔隙度平均减少了18.41%,孔隙空间损失率达56.62%;胶结作用次之,在堵塞了孔隙空间的同时也一定程度地增强了颗粒的抗压实强度,孔隙度平均降低了10.38%,孔隙空间损失率达19.78%;溶蚀作用使碎屑颗粒及填隙物等不稳定组分溶解而产生大量的次生孔隙,从而改善了储层物性,增加的孔隙度平均为2.26%。根据成岩作用对物性的影响,结合测井响应特征,将该区长6₁致密砂岩储层划分出绿泥石膜剩余粒间孔相、剩余粒间孔相、长石溶蚀相、黏土矿物胶结相、碳酸盐胶结相及压实相等6种成岩相带,绿泥石膜剩余粒间孔相是研究区最有利的油气储集相带,剩余粒间孔相次之。     

电解液浓度对AT61、AP65镁合金阳极电化学性能的影响

采用X射线衍射仪、扫描电镜、能谱测试仪、电化学测试仪和电池测试仪等检测技术,分析了轧制退火态AT61(Mg-6%Al-1%Sn)和AP65(Mg-6%Al-5%Pb)镁合金阳极的成分,研究了质量分数分别为3.5%和7.0%NaCl电解液对这两种镁合金阳极电化学性能的影响。结果表明:经430 ℃×16 h均匀化热处理后,轧制退火态AT61和AP65镁合金中Mg₁₇Al₁₂相扩散于基体中;相对3.5%NaCl电解液,两种镁合金阳极在7.0%NaCl电解液中放电性能得到很大提升,同时镁合金-空气电池的放电稳定性得到增强。     

Effect of Al5Ti1B master alloy on microstructures and properties of AZ61 alloys

AZ61 alloys with different levels of Al5Ti1B master alloy additions were prepared by conventional casting method.The effects of Al5Ti1B contents and holding time on microstructures and microhardness of AZ61 alloys were studied by XRD,OM and microhardness testing techniques.The results show that when the addition level of Al5Ti1B master alloy is less than 0.5%(mass fraction),the average grain size of the alloys decreases with the increase of Al5Ti1B content at the same holding time.But the grain size increases somewhat with further addition of Al5Ti1B.The average grain size of the alloys decreases with the increase of the holding time as it is less than 30 min at the same addition level of Al5Ti1B.It is considered that TiB2 particles can serve as the heterogeneous nucleation sites ofα-Mg during solidification,and heterogeneous nucleation is the main reason for the grain refinement of AZ61 alloys.The microhardness of the refined AZ61 alloys with 1.0%Al5Ti1B addition is increased by about 8%.     

新SIMA制备坯料触变挤压AZ61镁合金零件的组织与性能(英文)

新应变诱导熔化激活法被用来制备高质量的AZ61镁合金半固态坯料。利用光学显微镜和拉伸实验,研究触变挤压成形零件的微观组织与力学性能。结果表明:当施加的压力为784MPa,保压时间为90s,模具温度为450℃时,半固态坯料能够完全充填模具型腔。与半固态等温处理方法相比,新SIMA法制备的半固态坯料触变挤压成形零件的抗拉强度和伸长率分别为300.5MPa和22%;并且成形零件的微观组织晶粒细小、组织均匀。随着等温处理温度的升高和保温时间的延长,成形零件的抗拉强度和伸长率先增加后降低。当挤压道次从1增加至4时,成形零件的抗拉强度和伸长率明显增加。     

挤压态HAl61-4-3-1合金高温本构模型构建及其加工图

采用Gleeble-3500热模拟实验机在变形温度为600～800℃和应变速率为0.01～10 s-1时对HA161-4-3-1铝黄铜合金进行等温热压缩实验,对实验所获得真实应力-应变曲线进行摩擦修正,并以修正后的应力应变数据构建了考虑应变补偿的Arrhenius本构模型.其次,根据修正的应力应变数据构建了应变为0.3...     

基于感应加热的镁合金带内筋筒形件热强旋旋前温度场研究

对于镁合金带内筋筒形件的热强旋成形,旋前管坯的温度场分布对成形过程中的材料流动及旋压件的成形质量具有重要影响.基于多物理场耦合软件COMSOL,建立了ZK61镁合金带内筋筒形件热强旋旋前管坯电磁感应加热模型,模拟分析了不同感应加热参数条件下管坯温度场的分布情况,并通过实验验证了模型的可靠性.研究结果表明:相比电流强度,...     

Synthesis and Characterization of Mesoporous Alumina as a Catalyst Support for Hydrodechlorination of 1,2-Dichloropropane: Effect of Catalyst Preparation Method

A mesoporous alumina was synthesized by a posthydrolysis method. The prepared mesoporous alumina was found to have randomly ordered pores, and retained relatively high surface area with narrow pore size distribution centered at ca. 4nm. Nickel precursors were then supported on the mesoporous alumina by an impregnation (Ni-IMP) and vapor deposition (Ni-VD) method. Several characterizations were carried out in order to investigate physical and chemical properties of mesoporous alumina and supported Ni catalysts. TPR, XPS, and UV-DRS measurements revealed that the Ni-IMP catalyst retained much more amounts of surface nickel aluminate-like species than the Ni-VD sample. TPD experiments also showed that nickel aluminate species affected the adsorption amounts of reactant (1,2-dichloropropane). In the hydrodechlorination of 1,2-dichloropropane (DCPA), DCPA conversion over the Ni-VD catalyst was about two times higher than that over the Ni-IMP catalyst at 300 °C. It is probably due to the fact that the Ni-VD catalyst, which had low contents of nickel aluminate species compared to the Ni-IMP catalyst, exhibited higher degree of reduction than the Ni-IMP catalyst at pretreatment conditions. The difference in DCPA conversion between two catalysts was closely related to the degree of reduction of nickel species and the amounts of adsorption of DCPA onto the catalyst as well.     

W61-800各色有机硅耐高温涂料研究

以改性有机硅树脂为成膜物,添加如云母粉、石英粉、石棉粉等填料及低熔点耐高温玻璃粉和陶瓷粉、耐高温颜料、助剂及溶剂制备出一种具有良好耐热性和耐蚀性、在约800℃下可长期使用的耐高温防腐蚀涂料。