On the Methods of Beam Direction and Misorientation Angle/Axis Determination by Systematic Tilt

1.Intl.oductionTheelectronbeamdirectionBisanimportantparameterfortransmissionelectronmicroscopy.Es-peciallyBisoneofthebasicinputdatarequiredforthecomputedelectronmicrographsanddefectiden-tificationinthecaseofthecrystalsexhibitingstrongelasticanisotropyl1].Inrecentyears,thecoincidencesitelattice(CSL)representationhasbecomethebasisofthemodelsdescribinggrainboundarygeome-try,whichareoftenassociatedwithlowenergiesf2].InCSLmodel,apairofmisorientationaxisandangle(I/6)isusedtodescribetheorientati…     

Three-dimensional finite element analysis for through-wall crack in thick plate

A superposition method, in which analytical and finite element solutions are combined through the variational principle, is presented for determining the three-dimensional stress intensity factors of the through-wall crack. Cumbersome volume integral due to the singular terms at the crack tip is carried on by applying the least squares methods to the results obtained by the Legendre-Gauss quadrature. Several numerical calculations are made based on the present method, showing that the three-dimensional effects cannot be neglected especially for the cases of larger Poisson's raito. The comparison of the present method with the other finite element methods proposed for determining the three-dimensional stress intensity factors indicates that the former has the obvious superiority to the latters in respect to the numbers of elements and nodal points necessary to obtain reasonable results.     

Simulation of a non-Gaussian stochastic process based on a combined distribution of the UHPM and the GBD

To simulate non-Gaussian stochastic processes based on the first four moments, various simulation methods are presented, in which the determination of the transformation model and the calculation of the correlation coefficients between non-Gaussian stochastic processes and Gaussian stochastic processes are the critical procedures in these simulation methods. However, some existing simulation methods are limited to specific ranges. Furthermore, their practical applications are affected negatively due to the expensive cost of determining the transformation model and the correlation coefficients between non-Gaussian and Gaussian stochastic processes. Therefore, an accurate and efficient simulation method of a non-Gaussian stochastic process with a broader range is proposed in this article. Since the simulation of non-Gaussian processes and the Nataf transformation of non-Gaussian variables have some similar characteristics, a new combined distribution is proposed based on the unified Hermite polynomial model (UHPM) and the generalized beta distribution (GBD). Then, the combined distribution is employed in the simulation of non-Gaussian stochastic processes, in which the transformation model is deduced by the combined distribution. The correlation coefficient transformation function (CCTF) between the Gaussian and non-Gaussian stochastic processes can be evaluated through the interpolation method. Furthermore, numerical examples are presented to show the accuracy and effectiveness of the proposed simulation method for non-Gaussian stochastic processes.     

Analytical method of combining global longitudinal loads for ocean-going ships

Based on three kinds of still-water load models, i.e. the Ferry Borges–Castanheta, Poisson and alternating renewal models, three methods of determining characteristic values of still-water loads for ocean-going ships have been established and evaluated. These models of still-water loads have been applied to establish models for combining still-water and wave loads, by which consistent combined characteristic values are predicted numerically. Based on the point-crossing method, an analytical formula for the combined characteristic value of still-water and wave loads for ocean-going ships is derived by adopting Poisson load models, the exponential peak distribution of wave loads and the minimum of Turkstra’s combination solutions. The numerical analyses show that the analytical formula developed has the same accuracy as the numerical methods.     

道路工程成本控制浅谈

本文从道路工程成本控制的角度,结合参与的道路工程项目施工与管理经验,分析了目前道路施工成本控制中的影响因素和存在的主要问题,提出了道路工程成本控制方法和改进措施,以期降低施工成本,提高经济效益。     

An Input/Output Control System For The Dynamic Job Shop

A combined input/output control system is presented for periodically determining the set of jobs to be released (input variables) and the capacities of processing centers (output variables) in the dynamic job shop, so that a composite cost function is minimized. An interactive heuristic optimizing algorithm incorporating a 0-1 linear mixed integer program is formulated. The resulting control system is compared by simulation with an alternate system for which only input is subject to control. Significant improvements are obtained for most performance measures evaluated.     

Unified measurements in determining traces of dissolved metals by optical spectroscopy

Basic methods are given for determining traces of dissolved heavy metals at concentrations in the range 10⁻⁹–10⁻⁴%. Spectroscopic methods can be combined: atomic absorption, atomic emission, and atomic fluorescence. Unified measurements in this area are considered together with apparatus for the purpose. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 60–63, March, 2000.     

空气源热泵除霜控制方法研究现状及展望

空气源热泵在除霜过程中"误除霜"故障时有发生,"有霜不除"会导致机组制热能力和性能下降,"无霜除霜"会导致系统供热量损失,因此空气源热泵在除霜时最佳除霜起止点的判定尤为重要.除霜控制是通过选择恰当的除霜切入点和结束点,使除霜周期内空气源热泵系统稳定性好、节能以及能保证室内的热舒适.本文通过总结国内外学者对除霜控制方法的...     

Modelling crack growth by level sets in the extended finite element method

An algorithm which couples the level set method (LSM) with the extended finite element method (X‐FEM) to model crack growth is described. The level set method is used to represent the crack location, including the location of crack tips. The extended finite element method is used to compute the stress and displacement fields necessary for determining the rate of crack growth. This combined method requires no remeshing as the crack progresses, making the algorithm very efficient. The combination of these methods has a tremendous potential for a wide range of applications. Numerical examples are presented to demonstrate the accuracy of the combined methods. Copyright © 2001 John Wiley & Sons, Ltd.     

粘弹性材料的微振子模型研究

针对利用粘弹性材料进行结构主被动控制的需要,建立了一套确定微子模型各参数的方法,并且与标准流变模型,分数导数模型以及试验结果进行比较,算例表明确定微振子模型各参数的方法有效,同时也表明微振子模型不但能准确描述粘弹性材料的本构关系,而且能与有限元方法相融合,建立二阶线性系统,能很方便地利用线性系统控制理论进行控制设计。     

The house of quality in a design process

The product development process is subject to randomness of duration of design activities and a path followed through the network of activities. In this paper, the qualitative relationships between various attributes of the design process and the corresponding design process variables are captured using the house of quality and then transformed into quantitative relationships. The impact of the process control variables on the design process attributes is discussed. The problem of determining optimal values of the design process variables to maximize the combined quality index of the critical design activities is modelled as a geometric programming problem.     

Integrating load-based order release and priority dispatching

Workload control (WLC) is a well-established production control concept for job shops that put primary emphasis on load-based order release. Recent advances in load-based order release research have led to an improved delivery performance at reduced shop floor workloads. But although order release is the primary focus of WLC research, it must be coupled with priority dispatching on the shop floor if order progress is to be regulated. Prior simulation research suggests that load-based order release methods should only be coupled with simple dispatching rules because other, more powerful rules can conflict with the functioning of the release method. Yet, recent empirical research suggests that powerful priority dispatching rules – such as due date-oriented dispatching rules – are in fact needed for a high level of delivery performance to be obtained in practice. This paper focuses on overcoming the conflict between order release and dispatching, so load-based order release can be combined with due date-oriented dispatching. Preliminary analysis reveals that part of the conflict is because existing due date-oriented dispatching rules overcompensate for schedule deviations that occur when orders are either released earlier or later than planned. Two alternative new dispatching rules based on an improved method of determining operation due dates are then developed to better account for schedule deviations and overcome the conflict with load-based order release. Further improvements in delivery performance are obtained, while the large workload reductions achieved by recently developed load-based order release methods are retained.     

Minimum cost tolerancing under uncertain cost estimates

This paper presents Cost Tolerance Sensitivity Analysis (CTSA), a new method of determining which features are critical and non-critical early in the design phase when cost information is uncertain. The method utilizes minimum cost tolerancing methods combined with designed experiments to determine which features are sensitive or insensitive to uncertainties in the cost-tolerance curve estimates. The paper also discusses novel aspects that must be considered in estimating cost tolerance curves in the early design phases. The method is demonstrated on the case study of a windmill transmission. The results show that the method could successfully identify critical and non-critical dimensions, both cost and tolerances must be considered simultaneously, and examination of near optimal solutions improves the results.     

模拟破片杀伤战斗部空爆冲击波与高速破片群联合作用的等效试验方法

破片杀伤战斗部空爆冲击波与高速破片群联合毁伤作用下目标结构的毁伤特性、防护效能等是当前防护领域的热点和难点,但目前的试验研究手段和方法存在不足,为此,提出采用等效缩比战斗部(其原理为炸药爆炸驱动预制破片分散)来模拟破片杀伤战斗部,可作为进行空爆冲击波与高速破片群对防护结构的联合毁伤作用的实验方法。在确定防御目标战斗部、防御目标弹丸和几何缩尺比的基础上,根据爆炸力学相关经验公式,提出了求解等效缩比战斗部的装药和预制破片的相关参数的等效计算方法。该等效试验方法考虑了多破片侵彻的增强效应以及与爆炸冲击波的联合毁伤增强效应,且等效计算方法参数较少、简单实用。     

Disappearing and reappearing polymorphs—an anathema to crystal engineering?

“Crystal engineering” implies control over the design and preparation of desired crystal structures. That control can be compromised by the existence or appearance of polymorphs for the compound in question. Regaining control requires an understanding of the conditions for obtaining each of the crystalline forms of the material. Chemical microscopy can be useful in determining those conditions. The historic importance of thermomicroscopic methods is reviewed and a number of examples of translating thermomicroscopic observations into single crystals suitable for X-ray study are presented.     

Modelling peroxide crosslinking in polyolefins

This article describes a framework for correct interpretation of cure behaviour. It concludes that several published methods for determining crosslinking kinetics do not accurately represent performance seen with a number of polyolefin elastomers. Commonly used methods of curemeter interpretation were found to be severely flawed because of the combined effects of non-linear evolution of elastically active chains, trapped entanglements and slowly relaxing chain structures. The results indicate that one should not assume proportionality between curemeter torque and crosslink density, especially at low- to mid-range crosslink densities. Such an assumption will lead to a significant overestimation of crosslink density.     

Relative-humidity profiling in the troposphere with a Raman lidar

We describe a Raman-lidar-based approach to acquiring profiles of the relative humidity of air. For this purpose we combined in one instrument the Raman-lidar techniques that are used for the profiling of water vapor and temperature. This approach enabled us to acquire, for the first time to our knowledge, vertical profiles of relative humidity through the entire troposphere exclusively from Raman-lidar data. The methods applied to determining the water-vapor mixing ratio, temperature, and relative humidity and the corresponding uncertainties caused by systematic errors and signal noise are presented. The lidar-derived profiles are compared with profiles measured with radiosondes. Radiosonde observations are also used to calibrate the Raman lidar. Close agreement of the profiles of relative humidity measured with lidar and those measured with radiosonde demonstrates the potential of this novel approach.     

T4 DNA连接酶酶活力测定方法

工具酶的酶活力检测是工具酶产品质量控制的关键,研究和建立工具酶酶活力的测定方法是工具酶产品标准化制定的重点和难点。该文采用改进的粘性末端单位测定T4 DNA连接酶酶活力。经验证,方法重复性好,稳定性佳,为建立T4 DNA连接酶质量检测标准奠定了基础。     

Inventory management practices and their implications on perceived planning performance

This paper focuses on the use of material planning methods to control material flow to inventories of purchased items. The first sub-objective is to evaluate the perceived planning performance of material planning methods used to control material flows in different inventory types in manufacturing and distribution companies. The second sub-objective is to evaluate the difference in perceived planning performance depending on the way planning parameters are determined and the methods used. Five material planning methods are studied: the re-order point method, the fixed order interval method, run-out time planning, Kanban and MRP. Our analysis is based on survey data from 153 manufacturing and 53 distribution companies. Findings conclude that the use of material planning methods differs depending on where along the material flow they are applied, whether the inventory is located in manufacturing or in distribution operations and between companies of various sizes. The modes of applying a material planning method affect its perceived performance. In particular, the way of determining and the review frequency of safety stocks and lead times have great importance for the planning performance of MRP methods, while the determination and review of order points, review frequencies and run-out times were important for re-order point methods.     

Method of Determining the Coefficient of Visual Extinction of Materials with Variable Optical Density

The present article describes methods of determining the coefficient of visual extinction that are fundamental in the technology of digital processing of video information along with methods of determining the transmission spectrum in the visible region of optically semitransparent materials. The article is also concerned wtih the case of materials subjected to the action of high-energy optical radiation. The investigations demonstrated that the proposed designs would be useful in estimating the optical properties of materials in aids for the protection of eyes.