Facebook数据中心热环境仿真及室内空气品质分析

Facebook在美国俄勒冈州的数据中心采用的是空气侧全新风自然冷却方案。本文针对其建筑结构与冷却方案结合且无管道的特点,采用计算流体力学仿真手段进行物理建模和热环境模拟。结果表明,当室外新风进风温度为10℃时,可以实现全新风自然冷却。机房3 kW机柜区域垂直温度场分布均匀性很好,21 kW三联柜区域垂直温度场分布较为均匀,机柜冷却指数RCI_(HI)和RCI_(LO)分别为99.76%和100%。并指出,新风自然冷却还要考虑空气品质的要求,固体颗粒物的洁净度等级须达到ISO中8.5级,有害气体对铜或银2种金属的腐蚀程度须达到G1级别,新风自然冷却方案的实施要做好方案经济性和运维管理。     

Estimating quality costs in an automotive stamping plant through the use of simulation

The pressures of modern manufacturing require that the quality-cost benefits are determined when evaluating new procedures or alternative operating policies. Traditionally, cost reports and other quality metrics have been used for this purpose. However, the interactions between the main quality cost drivers cannot be understood at the superficial level and the effect that a new process or an alternative operating policy may have on quality costs is difficult to determine. An alternative to the traditional costing methods is simulation. The current work uses simulation to evaluate quality costs in an automotive stamping plant where the quality control is determined by operator inspection of their own work. Self-inspection quality control provides instantaneous feedback of quality problems, allowing for quick rectification. However, the difficult nature of surface finish inspection of automotive panels can create inspection and control errors. A simulation model was developed to investigate the cost effects of inspection and control errors and it was found that inspection error had a significant effect in increasing total quality cost, with the magnitude of this increase dependent on the level of control. Further, the simulation found that the lowest cost quality control policy was that which allowed a number of defective panels to accumulate before resetting the press-line.     

Estimating the root mean square of a wave front and its uncertainty

The root mean square (rms) of the surface departure or wave-front deformation is an important value to extract from an optical test. The rms may be a tolerance that an optical fabricator is trying to meet, or it may be a parameter used by an optical designer to evaluate optical performance. Because the calculation of a rms involves a squaring operation, the rms of the measured data map is higher on average than the rms of the true surface or wave-front deformation, even if the noise is zero on average. The bias becomes significant as the scale of the noise becomes comparable to the true surface or wave-front deformation, as can be the case in the testing of ultraprecision optics. We describe and demonstrate a simple data analysis method to arrive at an unbiased estimate of the rms and a means to determine the measurement uncertainty.     

Emission rate estimation through data assimilation of gamma dose measurements in a Lagrangian atmospheric dispersion model

This paper presents an efficient algorithm for estimating the unknown emission rate of radionuclides in the atmosphere following a nuclear accident. The algorithm is based on assimilation of gamma dose rate measured data in a Lagrangian atmospheric dispersion model. Such models are used in the framework of nuclear emergency response systems (ERSs). It is shown that the algorithm is applicable in both deterministic and stochastic modes of operation of the dispersion model. The method is evaluated by computational simulations of a 3-d field experiment on atmospheric dispersion of ?1Ar emitted routinely from a research reactor. Available measurements of fluence rate (photons flux) in air are assimilated in the Lagrangian dispersion model DIPCOT and the ?1Ar emission rate is estimated. The statistical analysis shows that the model-calculated emission rates agree well with the real ones. In addition the model-predicted fluence rates at the locations of the sensors, which were not used in the data assimilation procedure are in better agreement with the measurements. The first evaluation results of the method presented in this study show that the method performs satisfactorily and therefore it is applicable in nuclear ERSs provided that more comprehensive validation studies will be performed.     

低温送风空调系统的房间内气流组织数值模拟

采用三维紊流k-ε模型，应用Fluent6．1计算室内空调的气固传热问题，并对室内空调的气流组织形式，主要是对流速场、温度场进行数值模拟计算，为空调室内的气流组织形式的优化设计及舒适性提供研究依据。     

Estimating hydrodynamical drag of a seagoing vessel by data of remote trajectory measurements

A method for determining the hydrodynamical drag of a seagoing vessel using the data of a coastal two-coordinate surveillance radar is described and verified. The results of large-scale numerical simulation are presented.     

Improving the quality of water and air by standards

正The Ministry of Ecology and Environment recently released 15 new national standards on environmental protection in response to the needs of social and economic development and eco-environmental regulation.     

非理想聚焦引起的激光粒度仪系统误差的数值模拟

因机械因素产生的非理想聚焦对激光粒度测量精度会产生影响,对此建立了相应的散射光强数学模型。模型的数值积分模拟表明,散焦降低了系统的分辨率,并且对于大颗粒的测量有着显著影响,使得测量结果中大颗粒数量减少,粒度分布向小粒径方向展宽。系统误差可以通过计算积分式光能分布系数矩阵校正。     

Analysis of fatigue failure on the keyway of the reduction gear input shaft connecting a diesel engine caused by torsional vibration

The vibratory torque of a diesel engine caused by the reciprocating motion of the mass and gas pressure force of a cylinder is one of the main causes of the failure of the driving shaft of the diesel engine and the connecting shaft to the reduction gear. Because high cycle torsional fatigue can occur in the reduction gear shaft connecting the engine under vibratory torsional stress, the US Navy restricts it under the MIL G 17859D(SH) standard and suggests a procedure for evaluating the safety of the shaft for the reduction gear. In this study, the structural safety of the reduction gear input shaft in which fatigue failure occurs in typical naval vessels is investigated in accordance with the VDI 3822 RCA (root cause analysis) procedure based on the MIL G 17859D(SH) standard. When evaluating the safety factor in accordance with the MIL G 17859D(SH) standard, the alternating bending moment from the lateral vibration and the stress concentration factor under static load are considered. In addition, an improved design is suggested by CAE to satisfy the safety factor suggested by the MIL G 17859D(SH) standard.     

In search of representativeness: evolving the environmental data quality model.

Environmental regulatory policy states a goal of "sound science." The practice of good science is founded on the systematic identification and management of uncertainties; i.e., knowledge gaps that compromise our ability to make accurate predictions. Predicting the consequences of decisions about risk and risk reduction at contaminated sites requires an accurate model of the nature and extent of site contamination, which in turn requires measuring contaminant concentrations in complex environmental matrices. Perfecting analytical tests to perform those measurements has consumed tremendous regulatory attention for the past 20-30 years. Yet, despite great improvements in environmental analytical capability, complaints about inadequate data quality still abound. This paper argues that the first generation data quality model that equated environmental data quality with analytical quality was a useful starting point, but it is insufficient because it is blind to the repercussions of multifaceted issues collectively termed "representativeness." To achieve policy goals of "sound science" in environmental restoration projects, the environmental data quality model must be updated to recognize and manage the uncertainties involved in generating representative data from heterogeneous environmental matrices.     

Experimental investigations of air conditioning solutions in high power density data centers using a scaled physical model

The widespread use of data centers, the dramatical increase of the data center power density and the need for improving cooling system efficiency to maintain reliable operation temperature and save cooling energy make the study of data center thermal management an urgent issue. In the current paper, three different configurations for thermal management solution of high power density data centers are investigated, compared and evaluated. A scaled physical model data center has been designed and constructed for the sake of the study using the theory of scale modeling of air flow experiments. The results showed that (i) by using aisle partition and aisle containment the rack inlet temperature can be reduced by 3–13% and 13–15.5% for aisle partition and aisle containment configurations, respectively; (ii) the intake air temperature reduction increases with increasing power density; and (iii) using aisle partitions and aisle containment with raised floor improves the data center cooling performance.     

Estimating the quality of measuring devices on the basis of a small number of tests

An approach based on the use ofa priori and experimental data on the distribution law of an observed random variable is proposed. The approach takes into account the contribution of thea priori and experimental data to information about the true distribution of the random variable. It is intended for estimating the numerical characteristics and parameters of the distribution of the observed indicators so as to demonstrate the operational requirements imposed on the performance indicators of measuring devices on the basis of a small number of tests. Translated from Izmeritel'naya Tekhnika, No. 1, pp. 25–28, January, 1997.     

Radiation impact caused by activation of air from the future GSI accelerator facility fair

The Gesellschaft für Schwerionenforschung in Darmstadt is planning a new accelerator Facility for Antiproton and Ion Research (FAIR). Two future experimental areas are regarded to be the most decisive points concerning the activation of air. One is the area for the production of antiprotons. A second crucial experimental area is the so-called Super Fragment Separator. The production of radioactive isotopes in air is calculated using the residual nuclei option of the Monte Carlo program FLUKA. The results are compared with the data for the activation of air given by Sullivan and in IAEA report 283. The resulting effective dose is calculated using a program package from the German Federal Office for Radiation Protection, the Bundesamt für Stranlenschutz. The results demonstrate that a direct emission of the total radioactivity produced into the air will probably conflict with the limits of the German Radiation Protection Ordinance. Special measures have to be planned in order to reduce the amount of radioactivity released into the air.     

Simple model for the input impedance of a wire monopole radiator with a dielectric coat

Closed-form formulae are derived for the input impedance of a wire monopole radiator coated with dielectric and fed through a metal plate. Contrary to the previous models, they can be written in the equation block of a radio frequency circuits simulator. They allow for much faster simulations because they involve little numerical work. The simulation results compare well with the experimental data.     

A decrease in the effective cross section of a cooling stream caused by hot air penetration into the blowout channel

The phenomenon of penetration of a hot air stream into a channel of finite depth by which a cooling stream is injected was revealed and studied by numerical methods. The penetrating stream decreases the effective cross section of the cooling stream, increases the velocity of this stream, and reduces the near-wall gas screen cooling efficacy.     

The impact of Internet transmission on the uncertainty in the electric power quality estimation by means of a distributed measurement system

There is increasing evidence, in literature, that the estimation of the electric power quality requires the simultaneous measurement of several quantities and indices in all lines connected to the same point of common coupling. The increase in the performance that the measuring systems based on digital signal processing techniques has undergone during recent years and the capability of the digital systems of interconnecting and exchanging data are making these systems more and more appealing and cost-effective for power quality applications. Moreover, the availability of a world-wide, low-cost, and public-domain interconnection system, the Internet, is pushing the evolution of the remote measurement systems, where the measurement results provided by in-field measurement systems are collected and stored by a central unit, toward the distributed measurement systems, where different systems, located in different places, share the same data in order to perform a measurement. It is known that the major drawback of these systems is the lack of synchronization of the shared data, due to the variable and unpredictable throughput of the net, which may affect the uncertainty of the result of the measurement in a quite significant way. This paper analyzes a distributed measurement system for electric power quality measurements and shows how the possible detrimental effects of data transmission over an Internet connection can be reduced by means of a suitable use of averaging techniques, thus avoiding a strict and expensive synchronization between the different units of the distributed measurement system. Finally, an estimate of the effects of the possible transmission delays on the measurement uncertainty is given.     

一种质粒DNA标准物质的定值数据统计及不确定度评定

为研制一种质粒DNA标准物质,应用紫外分光光度法(UV)和高分辨电感耦合等离子体质谱法(HR-ICPMS)对质粒DNA标准物质候选物的浓度进行测定,统计定值结果,并对测量的不确定度进行评定。最终,质粒DNA标准物质的浓度表示为(75.1±2.1)ng/μL(k=2)。