微波消解氢化物发生-原子荧光光谱法测定食品接触材料高密度聚乙烯中痕量锑

应用微波消解氢化物发生-原子荧光光谱(HG-AFS)法测定了食品接触材料高密度聚乙烯中痕量锑,采用盐酸作为反应介质,并对最佳分析条件进行了探讨。结果表明,该方法的检出限为0.3μg/L,线性范围为1.0～10.0μg/L,添加水平为0.25、1.0和2.0mg/kg时,加标回收率为80.4%～106.5%,相对标准偏差小于6.9%。该方法操作简便,精密度和准确度好,检出限低,具有实际应用价值。     

An effective mathematical formulation for the unidirectional cluster-based quay crane scheduling problem

The quay crane scheduling problem plays an important role in the paradigm of port container terminal management, due to the fact that it closely relates to vessel berthing time. In this paper, we focus on the study of a special strategy for the cluster-based quay crane scheduling problem that forces quay cranes to move unidirectionally during the scheduling. The scheduling problem arising when this strategy is applied is called the unidirectional quay crane scheduling problem in the literature. Different from other researches attempting to construct more sophisticated searching algorithms, in this paper, we seek for a more compact mathematical formulation of the unidirectional cluster-based quay crane scheduling problem that can be easily solved by a standard optimization solver. To assess the performance of the proposed model, commonly accepted benchmark suites are used and the results indicate that the proposed model outperforms the state-of-the-art algorithms designed for the unidirectional cluster-based quay crane scheduling problem.     

Water-soluble octahedral polyammonium nanocapsules: synthesis and encapsulation studies

The syntheses of two water-soluble octahedral polyammonium nanocapsules 5e and 5f are described. Nanocapsule 5e was prepared via the TFA-catalyzed condensation reaction of six MOM-protected 4-hydroxybutyl-footed tetraformyl cavitands 3c with 12 ethylene diamines, followed by reduction and acidic hydrolysis of the intermediate octahedral polyimino nanocapsule. Nanocapsule 5f was prepared from 5e via the oxidation of the 4-hydroxybutyl feet to 3-carboxypropyl feet. Both nanocapsules are soluble in water below pH 5. 5f is also water-soluble above pH 7. In acidic aqueous solution, nanocapsule 5e encapsulates small negatively charged, partially hydrophobic guests, such as p-toluenesulfonic acid, N-BOC-aspartic acid, or 4-methylumbelliferyl phosphate. The single site microscopic binding constants for the latter guests are 150±30, 510±50, 1550±150 M⁻¹, respectively and were determined from ¹H NMR titrations and DOSY experiments by assuming a 6:1 binding model with six identical, independent binding sites per nanocapsule (statistical binding). 5e doesn't bind small neutral hydrophobic molecules in aqueous solution. However, both nanocapsules bind to nucleotides, such as ATP, dAMP, dGMP or TTP. NMR experiments support that nucleotides are not encapsulated, but bind to the outside of the nanocapsules.     

Capacity allocation problem with random demands for the rail container carrier

In this paper, we consider the formulation and heuristic algorithm for the capacity allocation problem with random demands in the rail container transportation. The problem is formulated as the stochastic integer programming model taking into account matches in supply and demand of rail container transportation. A heuristic algorithm for the stochastic integer programming model is proposed. The solution to the model is found by maximizing the expected total profit over the possible control decisions under the uncertainty of demands. Finally, we give numerical experiments to demonstrate the efficiency of the heuristic algorithm.     

The sample average approximation method for empty container repositioning with uncertainties

One of the challenges faced by liner operators today is to effectively operate empty containers in order to meet demand and to reduce inefficiency in an uncertain environment. To incorporate uncertainties in the operations model, we formulate a two-stage stochastic programming model with random demand, supply, ship weight capacity, and ship space capacity. The objective of this model is to minimize the expected operational cost for Empty Container Repositioning (ECR). To solve the stochastic programs with a prohibitively large number of scenarios, the Sample Average Approximation (SAA) method is applied to approximate the expected cost function. To solve the SAA problem, we consider applying the scenario aggregation by combining the approximate solution of the individual scenario problem. Two heuristic algorithms based on the progressive hedging strategy are applied to solve the SAA problem. Numerical experiments are provided to show the good performance of the scenario-based method for the ECR problem with uncertainties.     

考虑AGV作业行为的自动化集装箱码头水平运输优化

针对自动化集装箱码头水平作业的AGV调度问题(AGVSP),在解决整体作业优化的同时,考虑AGV作业行为对作业效率及能耗的影响,建立以AGV作业效率以及能源消耗作为双目标的双层规划模型。该模型考虑了独立装卸与同步装卸两种模式下的AGV水平运输的特点。在此基础上,设计了对应的双层遗传算法进行求解。并通过数值实验,对模型在考虑行为与不考虑行为,独立作业与同步装卸作业模式下的作业效果进行验证比较。结果表明:本模型在不影响作业效率的前提下,可有效降低AGV的作业能耗。     

A priori policy evaluation and cyclic-order-based simulated annealing for the multi-compartment vehicle routing problem with stochastic demands

We develop methods to estimate and exactly calculate the expected cost of a priori policies for the multi-compartment vehicle routing problem with stochastic demands, an extension of the classical vehicle routing problem where customer demands are uncertain and products must be transported in separate partitions. We incorporate our estimation procedure into a cyclic-order-based simulated annealing algorithm, significantly improving the best-known solution values for a set of benchmark problems. We also extend the updating procedure for a cyclic order’s candidate route set to duration-constrained a priori policies.     

直接接触药品包装材料和容器中的重金属检测方法概述

介绍了直接接触药品的包装材料和容器的分类及重金属的来源,对重金属的检测方法进行了综述,主要包括比色法、紫外–可见分光光度法、原子吸收光谱法、原子荧光光谱法以及电感耦合等离子体光谱法,展望了重金属检测技术的发展方向。     

Acyclic cucurbituril congener binds to local anaesthetics

The recognition properties of acyclic cucurbit[n]uril (CB[n]) congener 1 towards seven local anaesthetic drugs (2–8) are reported. Job plots constructed from ¹H NMR experiments confirm the 1:1 host:guest nature of these complexes, whereas the changes in chemical shift observed upon complex formation (Δδ values) provide information about the geometry of the host–guest complexes. For complexes between host 1 and guests 2–5 and 8, a single geometry was preferred, whereas for guests 6 and 7 a mixture of two diastereomeric complexes was indicated. The K _a values for complexes between 1 and 2–8 fall in the range of 10³–10⁸ M^? 1 as determined by UV–vis and ¹H NMR competition experiments. The results further establish that acyclic CB[n]-type receptor 1 is preorganised into the C-shape required for binding and that its aromatic o-xylylene walls endow it with a potency towards aromatic ammonium ions. The K _a values reported in this paper constitute a blind data-set used in the SAMPL3 challenge aimed at testing computational methods relevant to protein√ligand systems. The work thus highlights the great potential of CB[n] receptors as model systems to promote synergy between the supramolecular and computational chemistry communities.     

Free and forced oscillations of a frictionless liquid in a long rectangular tank with structural obstructions at the free liquid surface

Summary If a free liquid surface is partly covered with a solid wall, the natural frequencies and the response of the liquid in the container may be drastically changed. The fundamental natural frequency of a frictionless and incompressible liquid in an infinitely long rectangular container is determined for increasing structural coverage of the free surface. With increasing coverage of the surface by a rigid structural member, the natural frequencies increase drastically and reduce the sloshing motion. The response to translational excitation is evaluated also numerically. The procedure may be applied to arbitrary coverages of a three-dimensional rectangular container, and may also be used as a test case for purely numerical procedures such as the finite element method. Received 13 July 1999; accepted for publication 26 October 1999