An open-systems approach to calculating time-dependent spectra

Abstract

A new method to calculate the spectrum using cascaded open systems and a master equation is presented. The method uses two-state analyser atoms which are coupled to the system of interest, whose spectrum of radiation is read from the excitation of these analyser atoms. The ordinary definitions of a spectrum uses two-time averages and Fourier transforms. The present method uses only one-time averages. The method can be used to calculate time-dependent as well as stationary spectra.     

供应链环境下的供应商管理库存模型研究

基于文献[8]提出的供应商管理的订货和派送库存模型存在的参数设计过于复杂、储存成本计算有欠商榷的缺点,重新确定储存成本,并删除了对库存没有实质影响的部分参数,提出了既考虑顾客需要,又考虑供应商运输成本规模经济的固定周期检查派送和存货补足库存模型,给出了该模型的全局最优解计算,最后给出算例分析,并同经济定货模型进行比较。     

A rule-based multi-criteria approach to inventory classification

The traditional inventory classification method classifies stock keeping units (SKUs) to three classes based on their annual dollar usage, while in real world problems, other criteria are important as well. In this paper, considering multi-criteria situations, a simple, effective and practical rule-based method is designed and implemented in a real world case, using MATLAB software. The most important characteristic of the proposed method is taking into account the inherent ambiguities that exist in the reasoning process of the system of classification. The methodology and the method proposed here may be easily implemented by inventory managers. The results obtained from the case study in this paper are compared with the analytic hierarchy process (AHP) method. Finally concluding remarks and suggestions for future work are provided.     

时滞微分方程特征值的近似求解方法

通过将时滞微分方程变换为积分方程后并进行离散,得到相应的差分方程,从理论上建立了差分方程的系统矩阵的特征值与原线性时滞微分系统的特征值之间的关系,从而得到了一种求解时滞微分方程特征值的新方法。作为算例,计算了时滞的Logistic方程的前10阶特征值。误差分析表明,提出的近似方法不但简单,并且有很高的精度。     

An improved compounding method for calculating stress-intensity factors

The compounding methods for calculating stress-intensity factors for complex geometrical configurations are reexamined. It is shown that techniques which were developed specifically for problems involving localized loads, e.g. a pin-loaded hole with a crack at its edge, can also be used when the loading is remote from the crack. When these techniques are used for cracks at unloaded holes, and for cracks in stiffened sheets, the compounding equations are as simple as those derived previously. However, fewer additional calculations are now needed and numerical tests show that there is no loss of accuracy. These advantages make the new procedures preferable to those used in the earlier compounding method.     

On the estimation of on-hand stocks for base-stock policies and lost sales systems and its impact on service measures

This paper focuses on computing on-hand stock levels at the beginning of a replenishment cycle for a lost sales inventory system with periodic reviews and discrete demand. A base-stock policy is used for replenishments. The literature provides an Exact method which requires a huge computational effort, and two closed-form approximate methods that arise from the backordering case, the Non-stockout and the Bijvank & Johansen. In this paper we propose three new and closed-form approaches that explicitly consider the lost sales assumptions: the Adjusted Non-stockout, the Polar Opposite and the 1-Step methods. Existing and proposed methods are evaluated in terms of their accuracy when computing the cycle service level and the fill rate. In this sense, results show that the Bijvank & Johansen and 1-Step methods provide similar performance but present different behaviours in terms of under or over estimating service measures that have different implications on the design of stock policies.     

A systems approach to accident causation in mining: An application of the HFACS method

This project aimed to provide a greater understanding of the systemic factors involved in mining accidents, and to examine those organisational and supervisory failures that are predictive of sub-standard performance at operator level. A sample of 263 significant mining incidents in Australia across 2007–2008 were analysed using the Human Factors Analysis and Classification System (HFACS). Two human factors specialists independently undertook the analysis. Incidents occurred more frequently in operations concerning the use of surface mobile equipment (38%) and working at heights (21%), however injury was more frequently associated with electrical operations and vehicles and machinery. Several HFACS categories appeared frequently: skill-based errors (64%) and violations (57%), issues with the physical environment (56%), and organisational processes (65%). Focussing on the overall system, several factors were found to predict the presence of failures in other parts of the system, including planned inappropriate operations and team resource management; inadequate supervision and team resource management; and organisational climate and inadequate supervision. It is recommended that these associations deserve greater attention in future attempts to develop accident countermeasures, although other significant associations should not be ignored. In accordance with findings from previous HFACS-based analyses of aviation and medical incidents, efforts to reduce the frequency of unsafe acts or operations should be directed to a few critical HFACS categories at the higher levels: organisational climate, planned inadequate operations, and inadequate supervision. While remedial strategies are proposed it is important that future efforts evaluate the utility of the measures proposed in studies of system safety.     

An engineering method of calculating a jet in a fluidized bed

An engineering method is described for calculating a gas jet in a fluidized bed on the basis of a solution for the kinematics of the jet.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 6, pp. 1002–1011, December, 1970.     

An analytical approach for calculating vacuum properties of outgassing tubing systems

A method has been investigated to calculate vacuum properties, such as flow conductance and pressure drop, for complex tubing systems, taking into account the outgassing of the tube walls. The procedure is based on the determination of the pressure drop, Δp_i, of each tube element, starting at the chamber with a given mass flow rate, q_b1. The flow conductance, G, of the system follows from the overall pressure drop, ΔpΣⁿ_i Δp_i as $\text{G\&z.dbnd;q}{}_{\mathrm{b1}}\text{/Δp}$. The results are applied to analysing a vacuum system of the First Spacelab Payload.     

核心台套加卫星台套订货方式在上海通用汽车的应用

介绍常见的进口件订货方式和改进的方式-模块式订货,推出根据上海通用汽车的实际情况提出的核心台套加卫星台套采购方案,即分别订购各车型共用件和各车型配置独特件,通过订货方式改进以调和市场需求的剧烈波动和进口供应链的长订货提前期之间的矛盾。     

A constrained EPSAC approach to inventory control for a benchmark supply chain system

The design of an appropriate inventory control policy for a supply chain (SC) plays an essential role in tempering inventory instability and bullwhip effect. Several constraints are commonly encountered in actual operations so managers are required to take these physical restrictions into account when designing the inventory control policy. Model predictive control (MPC) appears as a promising solution to this issue, due to its capability of finding optimal control actions for a constrained SC system. Therefore, the inventory control problem for a benchmark SC is solved using the extended prediction self-adaptive control approach to MPC. To extend methodologies in our previous work, the control framework relies on generic process model and incorporates the physical constraints arising from practical operations to form the general constrained optimisation problems. The managers can choose from decentralised and centralised control structures according to specific informational and organisational factors of their SCs. The proposed control schemes in this study may be appropriate for industrial practice because the designed policy can bring a reduction of over 30% in operating cost and a significant increase of customer satisfaction level compared with that of the conventional policy.     

一种计算航船对近海海洋环境噪声贡献的算法

为了研究浅海中低频段的海洋环境噪声,文章构建了一种计算航船对近海海洋环境噪声贡献的算法,利用某海域航船信息,结合实际水文参数,对该海域的航运噪声进行了仿真计算。航船信息通过访问船舶自动识别系统数据库获取。主要关注50~400 Hz的中低频段,将仿真计算结果和实验数据进行对比,验证了算法的可靠性,并进行了误差分析。利用该算法可获取接收点处航船噪声的水平方向分布特点,并可初步定量分析航船噪声对海洋环境噪声的贡献。     

An application of cost-effective fuzzy inventory controller to counteract demand fluctuation caused by bullwhip effect

This paper develops a fuzzy inventory model to counteract the demand fluctuation in supply demand networks, which combines fuzzy logic controller with (s,?S) policy based on economic order quantity (EOQ) model. Following a literature review and a discussion of counteractions to the bullwhip effect and the obstruction of general counteraction in supply demand networks, a multi-echelon fuzzy inventory model in supply demand networks is proposed. A simulation model with one- and two-echelon supply demand network is built and tested for (s, S) policy based on the classical EOQ model and the proposed fuzzy inventory model. Based on the simulation, results of the relevance performance are presented and discussed, which show that the proposed multi-echelon fuzzy inventory model provides not only a cost-effective management of inventory (e.g. lower inventory levels and cost) in market uncertainty, but also another effective alternative for counteracting demand fluctuation. In particular, the proposed multi-echelon fuzzy inventory model shows benefit in counteracting demand fluctuation in multi-echelon supply demand networks. Finally, some conclusions and suggestions for further research works are presented.     

An engineering approach to safety assessment for non-J-controlled crack growth

The -integral has been proposed as a new fracture parameter for non-J-controlled crack growth in previous studies. In this paper, the -integral is investigated to assess the safety of structures with defects. The estimation formula for the -integral is presented to calculate the crack driving force by referring to the engineering estimation expression of the J-integral. The material resistance curves J_R−Δa and , of A533B material, are obtained by tests and nonlinear finite element analyses. The -integral failure criterion for non-J-controlled crack growth is assumed in the paper according to the crack driving force and the material resistance curves. The method of admissible stress curve, i.e. the stress-crack length curve, is developed to simplify the conventional engineering assessment procedure by following the failure criterion for non-J-controlled crack growth. A new engineering safety assessment approach is proposed to assess the ductile fracture instability of flawed structures for non-J-controlled crack growth by the method of an admissible stress curve. Two examples for the compact tension configuration and the cylinder with a surface crack under internal pressure are examined by using the new engineering assessment approach. The new engineering safety assessment approach obviously simplifies the conventional engineering assessment procedure. By comparing with the tests, the results from these two examples show that this new engineering safety assessment approach for non-J-controlled crack growth gives a reliable prediction for the ultimate load capacity of flawed structures.     

An integrated approach to evaluate policies for controlling traffic law violations

Modeling dynamics of the driver behavior is a complex problem. In this paper a system approach is introduced to model and to analyze the driver behavior related to traffic law violations in the Emirate of Abu Dhabi. This paper demonstrates how the theoretical relationships between different factors can be expressed formally, and how the resulting model can assist in evaluating potential benefits of various policies to control the traffic law violations Using system approach, an integrated dynamic simulation model is developed, and model is tested to simulate the driver behavior for violating traffic laws during 2002-2007 in the Emirate of Abu Dhabi. The dynamic simulation model attempts to address the questions: (1) “what” interventions should be implemented to reduce and eventually control traffic violations which will lead to improving road safety and (2) “how” to justify those interventions will be effective or ineffective to control the violations in different transportation conditions. The simulation results reveal promising capability of applying system approach in the policy evaluation studies.     

An approximate method for calculating transfer coefficients for partially ionized gas mixtures

A universal method, economical in the number of calculations required, is proposed for calculating transfer coefficients for partially ionized gas mixtures with an unlimited number of components. Its use is illustrated with the example of calculating heat transfer in a flow of low-temperature plasma.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 34, No. 3, pp. 444–451, March, 1978.     

Effective investment to reduce lost-sales rate in a periodic review inventory model

In 1973 Montgomery et al. proposed an (R, T) type of a periodic review inventory model in which the lost-sales rate caused by stockout is given. The purpose of this article is to investigate in this heuristic periodic review inventory model with partial lost-sales to effectively increase investment and to reduce the lost-sales rate. We discuss two models: complete (normal distribution) and partial (distribution free) information about the protection interval (i.e., review period plus lead time) demand distribution. For each model, two commonly used investment cost functional forms, logarithmic and power, are employed for lost-sales rate reduction. That is, for these two investment cost functions, we first assume that the protection interval demand follows a normal distribution, and then we assume that only first and second moments of the probability distribution of protected interval demand are known. Two algorithms are developed to find the optimal investment decision, and six numerical examples are given to illustrate the results.     

An analytical method for calculating stiffness of two-dimensional tri-axial braided composites

This paper presents a new analytical method for calculation of the stiffness of two-dimensional tri-axial braided composites. A unit cell has been introduced as a representative cell of a braided composite and its components. The braided composite is considered as consisting of three layers. The first two layers represent braided tows and the third layer is the axial tow. Then, using rule of mixtures, mechanical properties of each layer are calculated. Next, using analytical relations, the undulation of representative layers of braided tows is calculated. Finally, using a volume averaging method, the total stiffness of the braided composite is calculated. The results are compared with those obtained from experimental methods and the effect of braided tows crimp on the stiffness of braided composites is examined.