要掌握物理量定义的方法

建立物理量的目的是通过该量来表征物质或物体的状态或性质，并通过探求各量之间所表征的全部内容，集中地包含在它的定义式中．因此，掌握物理量定义的方法，对物理教学具有重要意义．     

Validating vehicle routing zone construction using Monte Carlo simulation

The primary purpose of this paper is to validate a clustering procedure used to construct contiguous vehicle routing zones (VRZs) in metropolitan regions. Given a set of customers with random demand for pickups and deliveries over the day, the goal of the design problem is to cluster the customers into zones that can be serviced by a single vehicle. Monte Carlo simulation is used to determine the feasibility of the zones with respect to package count and tour time. For each replication, a separate probabilistic traveling salesman problem (TSP) is solved for each zone. For the case where deliveries must precede pickups, a heuristic approach to the TSP is developed and evaluated, also using Monte Carlo simulation. In the testing, performance is measured by overall travel costs and the probability of constraint violations. Gaps in tour length, tour time and tour cost are the measure used when comparing exact and heuristic TSP solutions.     

双周期平行四边形排列裂纹反平面问题的有限元分析

提出了双周期平行四边形排列裂纹反平面问题的有限元方法,通过对单位胞元引入周期边界条件,在裂纹尖端采用奇异单元,解决了有限元分析这类问题的效率和精度问题.利用Ansys软件计算,在各种有解析解对照的情形下,应力强度因子的相对误差都在0.2%以内.与现有通常限于对称阵列的双周期裂纹的研究相比,本文发展的方法适用于一般的非对称平行四边形裂纹阵列.算例揭示了行向裂纹间的相互干涉放大应力强度因子,而叠向裂纹间的作用相互屏蔽.对于平行四边形阵列的情形,这两种相反的干涉效应使应力强度因子与裂纹错动参数间呈现非单调依赖关系.     

Reactions governed by a binomial redistribution process—The ehrenfest urn problem

A distributive process of the binomial type in a one-dimensional discrete space with an absorbing barrier is studied. A simple expression for the particle number Σ(t) is derived. The analysis is based on recursion relationships and sum rules for the underlying eigenvectors, the Krawtchouk polynomials. The first passage time is determined, and the validity of the passage time approximation to Σ(t) tested. The continuous limit, corresponding to the diffusion and reaction of a harmonically bound particle, is briefly described.     

Determination of Ibandronate and its Degradation Products by Ion-Pair RP LC with Evaporative Light-Scattering Detection

A simple method has been developed for analysis of ibandronate and related substances by ion-pair reversed-phase high-performance liquid chromatography (RPIC) with evaporative light-scattering detection (ELSD). After optimization of the chromatographic conditions satisfactory separation of the compounds was achieved on an Intersil C₈ column with an isocratic mobile phase—8:4:88 (v/v) acetonitrile–methanol–12 mM ammonium acetate buffer containing 35 mM n-amylamine (pH 7.0). The mobile phase flow rate was 1.0 mL min^?1. The calibration plot was linear in the range 352 to 1760 µg mL^?1 for ibandronate. The precision and reproducibility were 0.3% and 0.5%, respectively. The average recovery of ibandronate was 100.4% and RSD was 0.6%. The method was validated and shown to be precise, accurate, and specific for assay of ibandronate in bulk material and dosage forms. The proposed liquid chromatographic method can be satisfactorily used for quality control of ibandronate.     

Staffing call centers under arrival-rate uncertainty with Bayesian updates

We consider the problem of staffing service centers with quality-of-service constraints. We focus on the case where the arrival rates are uncertain. We introduce formulations that handle staffing decisions made over two decision periods, minimizing the staffing costs over the stages while satisfying a service quality constraint on the second stage operation. A Bayesian update is used to obtain the second-stage arrival-rate distribution based on the first stage prior arrival-rate distribution and the observations in the first stage.     

Activity-Structure Study on the Peptide Fraction of AG2: a Potent In Vitro Transfection Agent

Applied Biochemistry and Biotechnology - Gemini-based amphiphiles are candidates for biomedical applications. In fact, most of the gemini compounds described in the literature have been prepared to...     

UPLC–MS/MS determination of flavokawain B,a novel anti‐tumor chemotherapeutic agent in rat plasma and its application to a pharmacokinetic study in rats

A sensitive, selective and rapid ultra‐performance liquid chromatography/tandem mass spectrometry method was developed and validated for the quantification of flavokawain B in rat plasma using myrislignan as an internal standard. Sample preparation was accomplished through a protein precipitation extraction process. Chromatographic resolution of flavokawain B and the IS was achieved on an Agilent XDB‐C₁₈ column (2.1 × 100 mm, 1.8 μm) using a gradient mobile phase comprising 0.1% formic acid in water and acetonitrile delivered at a flow rate of 0.5 mL/min. Flavokawain B and the IS eluted at 3.27 and 1.96 min, respectively. The total chromatographic run time was 6.0 min. A linear response function was constructed in the concentration range 0.524–1048 ng/mL. Method validation was performed as per the US Food and Drug Administration guidelines and the results met the acceptance criteria. Intra‐ and inter‐day accuracy and precision were in the ranges of ?14.3–13.2 and 3.4–11.8%, respectively. Flavokawain B was demonstrated to be stable under various stability conditions. This method has been applied to a pharmacokinetic study in rats.     

A robust power spectrum split cancellation-based spectrum sensing method for cognitive radio systems

Spectrum sensing is an essential component to realize the cognitive radio, and the requirement for real-time spectrum sensing in the case of lacking prior information, fading channel, and noise uncertainty, indeed poses a major challenge to the classical spectrum sensing algorithms. Based on the stochastic properties of scalar transformation of power spectral density（PSD）, a novel spectrum sensing algorithm, referred to as the power spectral density split cancellation method（PSC）, is proposed in this paper. The PSC makes use of a scalar value as a test statistic, which is the ratio of each subband power to the full band power. Besides, by exploiting the asymptotic normality and independence of Fourier transform,the distribution of the ratio and the mathematical expressions for the probabilities of false alarm and detection in different channel models are derived. Further, the exact closed-form expression of decision threshold is calculated in accordance with Neyman–Pearson criterion. Analytical and simulation results show that the PSC is invulnerable to noise uncertainty,and can achive excellent detection performance without prior knowledge in additive white Gaussian noise and flat slow fading channels. In addition, the PSC benefits from a low computational cost, which can be completed in microseconds.     

三苄基锡(Ⅳ)喹诺酮酸酯配合物的合成与表征

合成了三苄基锡（Ⅳ）吡哌酸酯、三苄基锡（Ⅳ）氟哌酸酯两种配合物,通过元素分析,IR,UV和^1 H NMR对其结构进行了表征,结果表明,锡原子可能是五配位的,羧基是以双齿形式与锡原子配位,环羰基氧没有参与配位。