Mixed halide complexes of lead. A comparison with theoretical predictions

Experimentally and theoretically derived formation constants of mixed lead halide complexes are compared at 25.0°C and one molar ionic strength. The formation constant of PbBrCl, ₁₁=79±10, is somewhat larger than the theoretical results, ₁₁=55, predicted using the formation constants of PbBr₂ and PbCl₂. The molar absorptivity of PbBrCl was observed to be intermediate in character between the molar absorptivities of PbBr₂ and PbCl₂. Determinations of the formation constants of PbBr₂Cl^– and PbBrCl₂ ^– are in reasonable agreement with the predictions based on the formation constants of PbBr₃ ^– and PbCl₃ ^–. Mixed ligand species dominated the complexation scheme of Pb(II) in our test media.     

基于可控提前期和服务水平约束的(Q,r)库存问题

本文研究了存在顾客流失情况下，基于可控提前期和服务水平约束的连续盘点（Q，r）库存管理同题。当市场需求分布未知时采用MiniMax方法建立年总成本函数表达式，修正以往研究中对安全系数取值范围错误判断，推导出合理的安全系数取值范围，并给出最优解的计算方法。     

Impact of information sharing and lead time on bullwhip effect and on-hand inventory

This work analyzes a two echelon (warehouse–retailer) serial supply chain to study the impact of information sharing (IS) and lead time on bullwhip effect and on-hand inventory. The customer demand at the retailer is assumed to be an autoregressive (AR(1)) process. Both the echelons use a minimum mean squared error (MMSE) model for forecasting lead time demand (LTD), and follow an adaptive base-stock inventory policy to determine their respective order quantities. For the cases of without IS and inter as well as intra echelon IS, expressions for the bullwhip effect and on-hand inventory for the warehouse are obtained, considering deterministic lead-time. The results are compared with the previous research work and an easy analysis of the various bullwhip effect expressions under different scenarios, is done to understand the impact of IS on the bullwhip effect phenomenon. It is shown that some part of bullwhip effect will always remain even after sharing both inter as well as intra echelon information. Further, with the help of a numerical example it is shown that the lead time reduction is more beneficial in comparison to the sharing of information in terms of reduction in the bullwhip effect phenomenon.     

Optimal policy for a two-facility inventory problem with storage constraints and two freight modes

This paper considers a two-facility supply chain for a single product in which facility 1 orders the product from facility 2 and facility 2 orders the product from a supplier in each period. The orders placed by each facility are delivered in two possible nonnegative integer numbers of periods. The difference between them is one period. Random demands in each period arise only at facility 1. There are physical storage constraints at both facilities in each period. The objective of the supply chain is to find an ordering policy that minimizes the expected cost over a finite horizon and the discounted stationary expected cost over an infinite horizon. We characterize the structure of the minimum expected cost and the optimal ordering policy for both the finite and the discounted stationary infinite horizon problems.     

12种蔬菜作物对铅,铜,镉抗性的研究

通过对12种常见蔬菜作物幼苗在Hoagland营养液中进行水培处理,对其在3种重金属(Pb2 ,Cu2 ,Cd2 )胁迫下的抗性进行了比较研究.结果表明:在12.00 mg/L Pb2 胁迫下,抗性最强的为苋菜,抗性最弱的为大白菜或小白菜;在0.50 mg/L Cu2 胁迫下,抗性最强的为空心菜,抗性最弱的为小白菜;在1.00 mg/L Cd2 胁迫下,抗性最强的为空心菜,抗性最弱的为大白菜.     

Improved solution for inventory model with defective goods

This paper is a consequence for a paper of Lin et al. [S.W. Lin, Y.W. Wou, P. Julian, Note on minimax distribution free procedure for integrated inventory model with defective goods and stochastic lead time demand, Appl. Math. Model. 35 (2011) 2087–2093]. We simplified their complicated solution procedure and then presented a revision to patch their negligence for the boundary minimums. Numerical examples are provided to demonstrate our findings.     

基于MCMC的随机库存系统中提前期需求分布的计算

在需求和提前期均是随机的库存系统中,提前期需求的分布是由提前期分布与需求分布复合而成的,这个复合分布的计算通常是困难的。本文采用基于Gibbs抽样的马尔科夫链蒙特卡洛(MCMC,Markov chain Monte Carlo)方法,抽取条件分布样本作为提前期需求分布的样本,通过样本来计算提前期需求分布密度、服务水平和损失函数。这种方法避免了直接求解复杂积分计算上的困难,也克服了近似分布拟合偏差过大的问题,有效地解决了随机需求与随机提前期的复杂库存系统中提前期需求确定问题。理论与数值分析结果表明:与现有方法相比较,基于MCMC的方法具有计算简便、拟合精度高、通用性好等特点。     

Two-storage inventory model with lot-size dependent fuzzy lead-time under possibility constraints via genetic algorithm

Multi-item inventory models with stock dependent demand and two storage facilities are developed in a fuzzy environment where processing time of each unit is fuzzy and the processing time of a lot is correlated with its size. These are order-quantity reorder-point models with back-ordering if required. Here possibility and crisp constraints on investment and capacity of the small storehouse respectively are considered. The models are formulated as fuzzy chance constrained programming problem and is solved via generalized reduced gradient (GRG) technique when crisp equivalent of the constraints are available. A genetic algorithm (GA) is developed based on fuzzy simulation and entropy where region of search space gradually decreases to a small neighborhood of the optima and it is used to solve the models whenever the equivalent crisp form of the constraint is not available. The models are illustrated with some numerical examples and some sensitivity analyses have been done. For some particular cases results observed via GRG and GA are compared.     

The impact of stochastic lead time reduction on inventory cost under order crossover

We use exponential lead times to demonstrate that reducing mean lead time has a secondary reduction of the variance due to order crossover. The net effect is that of reducing the inventory cost, and if the reduction in inventory cost overrides the investment in lead time reduction, then the lead time reduction strategy would be tenable.We define lead time reduction as the process of decreasing lead time at an increased cost. To date, decreasing lead times has been confined to deterministic instances. We examine the case where lead times are exponential, for when lead times are stochastic, deliveries are subject to order crossover, so that we must consider effective lead times rather than the actual lead times. The result is that the variance of these lead times is less than the variance of the original replenishment lead times.Here we present a two-stage procedure for reducing the mean and variance for exponentially distributed lead times. We assume that the lead time is made of one or several components and is the time between when the need of a replenishment order is determined to the time of receipt.     

含铅空位的PbWO4晶体光学性质及其偏振特性的研究

利用完全势缀加平面波局域密度泛函近似，计算了含铅空位的PbWO₄（PWO）晶 体的电 子结构，模拟计算了复数折射率、介电函数及吸收光谱的偏振特性. 比较含铅空位的PWO晶 体与完整的PWO晶体的吸收光谱及其偏振特性，得到与铅空位相关的吸收光谱及其偏振特性 ，计算结果与实验结果基本相符. 计算得到的含铅空位的PWO晶体的光学偏振特性反映了PWO 晶体的结构对称性. 计算结果表明PWO晶体中350，420，550和680 nm的吸收带的出现与PWO 晶体中铅空位的存在直接相关. 关键词： 4晶体')" href="#">PbWO₄晶体 电子结构 光学性质 铅空位