Hybrid LES — Review and assessment

In the late eighties and up to the beginning of nineties computation of turbulent flows is mostly dominated by RANS (Reynolds Averaged Navier-Stokes Simulation) type modelling. During the last few years URANS (Unsteady RANS) and LES (Large Eddy Simulation) type of approaches have been attempted with some success. Yet, there have been many difficulties when LES is applied to practical engineering problems and to high Reynolds number flows as energy dissipating eddies become really small and mesh resolution required for a reasonably resolved LES approaches that of DNS (Direct Numerical Simulation). An alternative solution suggested was to combine RANS and LES, which in general referred to as Hybrid LES. There have been many proposals for combining RANS and LES in different ways. In this article, some of the issues involved in performing hybrid LES reported in the recent literature is briefly reviewed.     

锌基合金模具的应用及探讨

本文分析了锌基合金模具制造及使用过程中容易出现热裂、翘曲、收缩的问题，并提出了解决这些问题的措施。     

可编程序控制器PLC的抗干扰措施

对可编程序控制器系统常见的一些干扰现象进行分析，对不同的干扰采用了相应的防护措施。     

Flow Control Through the Use of Topography

In this work, optimal shaft shapes for flow in the annular space between a rotating shaft with axially-periodic radius and a fixed coaxial outer circular cylinder, are investigated. Axisymmetric steady flows in this geometry are determined by solving the full Navier-Stokes equations in the actual domain. A measure of the flow field, a weighted convex combination of the volume averaged square of the L₂-norm of the velocity and vorticity vectors, is employed. It has been demonstrated that boundary shape can be used to influence the characteristics of the flow field, such as its velocity component distribution, kinetic energy, or even vorticity. This ability to influence flow fields through boundary shape may be employed to improve microfluidic mixing or, possibly, to minimize shear in biological applications.     

Extracting Electron Densities in N-Type GaAs From Raman Spectra: Theory

In this paper, we present the theory for calculating Raman line shapes as functions of the Fermi energy and finite temperatures in zinc blende, n-type GaAs for donor densities between 10¹⁶ cm⁻³ and 10¹⁹ cm⁻³. Compared to other theories, this theory is unique in two respects: 1) the many-body effects are treated self-consistently and 2) the theory is valid at room temperature for arbitrary values of the ratio R = (Q²/α), where Q is the magnitude of the normalized wave vector and α is the normalized frequency used in the Raman measurements. These calculations solve the charge neutrality equation self-consistently for a two-band model of GaAs at 300 K that includes the effects of high carrier concentrations and dopant densities on the perturbed densities of states used to calculate the Fermi energy as a function of temperature. The results are then applied to obtain the carrier concentrations from Fermi energies in the context of line shapes in Raman spectra due to the coupling between longitudinal optical phonons and plasmons. Raman measurements have been proposed as a non-destructive method for wafer acceptance tests of carrier density in semiconductor epilayers. The interpretation of Raman spectra to determine the majority electron density in n-type semiconductors requires an interdisciplinary effort involving experiments, theory, and computer-based simulations and visualizations of the theoretical calculations.     

陕西南部路基病害分布特征及主要控制因素探讨

在统计分析的基础上,归纳总结了陕西南部各类路基病害的分布特征,并从自然因素和人为因素两个方面分析了各类路基病害发生的主要控制因素。     

CSP连铸机大型液压缸的故障分析与改进

论述引进德国SMS连铸机大包托臂液压缸存在的寿命短问题，分析设计制造缺陷．通过增大缸头密封支持面、(φ600)内圆孔倒角、再增加一道软支撑环、缸头导向部分开润滑槽、改进球杆的润滑流道、柱塞杆整体淬火等措施，消除了原来的问题．同时分析了此项改进的技术经济效果．     

Data mining of resilience indicators

In recent years, the Asia-Pacific region has experienced several financial setbacks, including speculative attacks in 1998 and the SARS outbreak in 2003. Financial stresses of this nature are unanticipated, and not all of the dangers can be predicted by the examination of market information and macroeconomic indicators. The Early Warning System (EWS) that has been adopted by the International Monetary Fund may not be able to predict future financial crises for all possible scenarios, because shocks come in many different forms. To supplement the EWS, this paper proposes a data mining framework to measure the resilience of an economy. The resilience framework does not predict a crisis, but rather assesses the current state of health of an economy and its ability to withstand a financial shock should one occur. The framework is based on a feedback system consisting of two stages. The first stage assigns a resilience score to each economy based on a fuzzy logic scoring scheme that is built on the ambiguous reasoning of experts. The second stage uses the classification tree approach to estimate thresholds for each economic indicator, and examines the quality of the fuzzy score. The result from the second stage is then passed back to the first stage as feedback. The final result is obtained when the feedback system reaches its equilibrium state. The proposed resilience framework is applied to the external-sector and the public-sector economies of several countries to illustrate its applicability.     

分子筛吸附器自动再生系统在DCS中实现

介绍了空分装置的分子筛吸附器再生系统的自动控制原理，选用集散控制(DCS)系统实现控制过程，解决了原仪表控制系统的设计、操作和运行上存在问题。新系统更合理、更安全可靠、操作更方便、直观，同时提高了净化工艺的自动化水平。     

耀江大厦顶层屋面热泵的振动治理

本文通过耀江大厦27层屋面上六台热泵振动治理前后的振动和噪声测试数据的对比，简要阐述了安装在屋面上热泵的振动影响的程度和范围、产生振动影响和固体噪声传递的原因，并介绍了热泵双层隔振的方法和隔振效果。