基于新存取原理的无计数损失“ADC-缓存”系统

本系统以新的数据存取方式——“DMA+N”取代古典的多道分析器(MCA)存取方式——“DMA+1”。N是计数换失修正权重因子。计数换失修正方法是基于虚拟脉冲发生器原理,修正工作用硬件实现,不需占用机器时间,从而优越于软件修正,可工作于高计数率。

中子能谱测量中的本底测定及计数损失分析

分析了中子能谱测量中的本底测定技术,实验测量了DT源中子能谱、源本底中子能谱和样品本底中子能谱,在不同线性门设置、主放大器成形时间常数下测量了线性门信号输入输出比,通过选择在分辨谱谷底附近不同位置的单道阈值,测量了由DT源中子产生的反冲质子谱,测量了不同能量范围的中子、伽玛分辨二维谱,对BC501A液体闪烁体探测器信号计数损失的相关因素进行了分析,提出了几种减少计数损失的方法,结果可供中子能谱测量相关实验研究参考。

基于Geant4模拟^(37)Ar活度测量计数损失的修正方法

目的 采用内充气正比计数器开展放射性惰性气体^(37)Ar活度绝对测量时,需要对计数器阈值以下的计数损失进行修正。方法 利用Geant4蒙特卡罗模拟软件,构建正比计数器模型并获得^(37)Ar能量沉积谱,模拟分析计数损失产生原因及修正方法。结果 模拟计数器工作压强60 kPa下对光子探测效率,结果仅为38.7%,漏计数损失主要来源于光子逃逸产生的壁效应,可通过增大工作气体压强的方式减小,并通过外推的方式予以修正。模拟压强100 kPa下,壁效应影响为4.4%,与实验偏差在0.6%以内。结论 可利用Geant4确定计数器阈值以下漏计数修正因子,从而实现正比计数器法对^(37)Ar活度的准确测量。

γ探测死时间与计数修正因子的关系

为在γ放射性活度很大的测量中使测量系统得到更好的准确度，本文使用干扰源研究 HPGe探测器得到了测量系统死时间与计数损失的关系。在γ能量为0.3～1.3 M eV 时进行实验，使用10^4～10^5 Bq量级的放射源，修正能峰的计数率一般保持在几十s－1，证明在误差范围（3％）内，计数损失随死时间变化的关系与射线能量和计数强度无关，任意强度的任意核素均可使用这一修正公式进行计数损失修正。

核计数实时修正器

本文介绍一种具有死时间计数损失实时修正能力的新型双插宽NIM插件——核计数实时修正器的电路原理、实验结果和主要技术指标。

Calculations of Energy-Loss Function for 26 Materials

We present a fitting calculation of energy-loss function for 26 bulk materials, including 18 pure elements （Ag, A1, Au, C, Co, Cs, Cu, Er, Fe, Ge, Mg, Mo, Nb, Ni, Pd, Pt, Si, Te） and 8 compounds （AgCl, Al2O3, AlAs, CdS, SiO2, ZnS, ZnSe, ZnTe） for application to surface electron spectroscopy analysis. The experimental energy-loss function, which is derived from measured optical data, is fitted into a finite sum of formula based on the Drude-Lindhard dielectric model. By checking the oscillator strength-sum and perfect- screening-sum rules, we have validated the high accuracy of the fitting results. Further-more, based on the fitted parameters, the simulated reflection electron energy-loss spec- troscopy （REELS） spectrum shows a good agreement with experiment. The calculated fitting parameters of energy loss function are stored in an open and online database at http：//micro.ustc.edu.cn/ELF/ELF.html.

Influence of A Hyperons ^1S0 Superfluidity on the Direct Urca Processes with Hyperons

In the framework of the relativistic mean field theory （RMFT）, the relativistic energy losses of the direct Urea processes with hyperons （Y-DURCA ） for reactions A → p ＋ e ＋ υe and ≡^-→ A＋e＋υe are studied in neutron stars. We calculate the energy gap of A hyperons and investigate the effects of the ^1S0 superfluidity （SF） of A hyperons on the Y-DURCA processes. The calculated results are in line with the recent experimental data △ BAA ～ 1.01 ±0.20-0.11^＋0.18 MeV. The results indicate that the ^1S0 SF of A hyperons exists in most density ranges of happening the two reactions. The theoretical cooling curves are in agreement with observation data.

Application of fuzzy theory on earthquake damage rate estimation of buildings

Variations between earthquakes result in many factors that influence post-earthquake building damage(e.g.,ground motion parameters,building structure,site information,and quality of construction).Consequently,it is necessary to develop an appropriate building damage-rate estimation model.The building damage survey data were recorded and constructed into files by the Architecture and Building Research Institute(ABRI),Taiwan for the 1999 Chi-Chi earthquake in the Nantou region as a basis for developing a building damage rate estimation model by applying fuzzy theory to express the fragility curves of buildings as a membership function.Empirical verification was performed using post-earthquake building damage data in the Taichung city that suffered relatively severe damage.Results indicate that fuzzy theory can be applied to predict building damage rates and that the estimated results are similar to actual disaster figures.Prediction of disaster damage using building damage rates can provide a reference for immediate disaster response during earthquakes and for regular disaster prevention and rescue planning.

Flow Loss in Screens： A Fresh Look at Old Correlation

Pressure losses in flow components are generally characterized either by pressure loss coefficients or by discharge coefficients. The pressure drop for incompressible flow across a screen of fractional free area a is often calculated from widely used correlation provided in Perry＇s Handbook. This correlation was developed based on experimental work which have covered a wide range of fractional free area （a = 0.14 to 0.79）. The present work aims at validation for a flow in plain square mesh screen with a particular fractional free area （porosity, a） of 0.25 using CFD （Computational Fluid Dynamics） approach. The simulations are carried out for wide range of screen Reynolds number （Re = 0.1 to 105） covering both laminar and turbulent flow regimes. Initial simulations are carried out for incompressible fluid （water） and further extended to compressible fluid （air）. Discharge coefficients obtained from the simulations are compared with experimental values. Effect of compressibility on discharge coefficients is described.

Analysis on Transmission Heat Loss in Hot Water System of Residential Building

Based on the data of China Statistical Yearbooks, the current situation and development trend of the energy consumption of residential hot-water was discussed in this paper. Two hundred and sixty eight apartments were surveyed on the installation and operation situations of residential water heaters in five cities. Based on survey data, the proportion of pipeline heat loss was calculated in the energy consumption of a shower/bath. The influence factors of heat loss in residential hot-water pipeline network were discussed, and the measures were suggested for reducing the transport heat loss. The statistics and analysis conclusion have directive significance to reducing the transport heat loss.

Investigation of Non-Axisymmetric Endwall Contouring in a Compressor Cascade

The current paper presents experimental and computational results to assess the effectiveness of non-axisymmetric endwall contouring in a compressor linear cascade. The endwaU was designed by an endwall design optimi- zation platform at 0° incidence （design condition）. The optimization method is based on a genetic algorithm. The design objective was to minimize the total pressure losses. The experiments were carried out in a compressor cascade at a low-speed test facility with a Mach number of 0.15. Four nominal inlet flow angles were chosen to test the performance of non-axisymmetric Contoured Endwall （CEW）. A five-hole pressure probe with a head diameter of 2 mm was used to traverse the downstream flow fields of the flat-endwall （FEW） and CEW cascades. Both the measured and predicted results indicated that the implementation of CEW results in smaller comer stall, and reduction of total pressure losses. The CEW gets 15.6% total pressure loss coefficient reduction at design condition, and 22.6% at off-design condition （＋7° incidence）. And the mechanism of the improvement of CEW based on both measured and calculated results is that the adverse pressure gradient （APG） has been reduced through the groove configuration near the leading edge （LE） of the suction surface （SS）.

QUADRATIC ADMISSIBLE ESTIMATE OF COVARIANCE IN PSEUDO-ELLIPTICAL CONTOURED DISTRIBUTION

This article mainly discusses the admissibility of quadratic estimate of covariance in pseudoelliptical distribution. Under the quadratic loss function, the necessary and sufficient conditions that a quadratic estimator is an admissible estimator of covariance in the class of quadratic estimators are obtained. A complete class of the quadratic estimator class is also given.

IMPROVED ANOVAE OF THE COVARIANCE MATRIX IN GENERAL LINEAR MIXED MODELS

In this paper, the problem of estimating the covariance matrix in general linear mixed models is considered. A new class of estimators is proposed. It is shown that this new estimator dominates the analysis of variance estimate under two squared loss functions. Finally, some simulation results to compare the performance of the proposed estimator with that of the analysis of variance estimate are reported. The simulation results indicate that this new estimator provides a substantial improvement in risk under most situations.

MINIMAX INVARIANT ESTIMATOR OF CONTINUOUS DISTRIBUTION FUNCTION UNDER LINEX LOSS

In this paper we consider the problem of estimation of a continuous distribution function under the LINEX loss function. The best invariant estimator is obtained and proved to be minimax for any sample size n ≥ 1.

Empirical Model for the Quantitative Prediction of Losses of Radial Fans based on CFD Calculations

In a classical layout process of a fan the quantity of losses is estimated as a sum and expressed in the overall efficiency rote However the characteristic of the pressure rise, the losses and the efficiency rate beside the design point is not known. Against this background a numerical model was developed to calculate quantitative values of occurring losses at radial fan impellers at an early stage in the design process. It allows to estimate the pressure rise and efficiency rate of a given fan geometry at and beside the design point. The physics of losses are described in literature, but obtaining quantitative values is still a challenge. As common in hydraulic theory the losses are calculated with analytic formulas supported by coefficients and efficiency rates, which have to be determined empirically. This paper shows the method how to determine the coefficients for a given radial fan. Therefore a representative radial fan with backward curved blades was designed in reference to classical design guidelines. Performance measuring was done conform to ISO 5801. The flow was calculated at 8 different operation points using CFD methods. The RANS equations are solved by using the SST-k-omega turbulence model. The flow do- main consists of one blade section including inlet channel and outflow chamber. Spatial discretization is done by a block-structured mesh of approx. 1.8 million cells. Performance data show a very good agreement between measurement and calculation.

Exploring the intention of Using Aspirated Cascade to Replace Tandem Cascades

In the present paper,computational fluid dynamics(CFD) simulations were executed to exploring the intent of using aspirated cascade to replace tandem cascades.Firstly,the ONERA tandem cascades were investigated,and the performance of the cascades at the design point were listed,such as diffusion factor,total pressure loss coefficient,deviation angle etc.For replacing the ONERA tandem cascades,a new cascade was designed with the codes BLADEGEN developed by the authors.The quasi 3-D calculations were carried out using the collection of programs for cascade analysis and design,MISES.The cascade was analyzed and designed by using this code.And the cascade was simulated and analyzed by commercial CFD software.It is found there is an obvious separation on the suction side.Based on the 3D CFD simulation results of the cascade without aspiration,an aspirated cascade was designed by introducing a slot on the suction side.The performance of the aspirated cascade was investigated and compared with the tandem cascades,indicated that under the same inlet condition,the total pressure loss of the single row aspirated cascade was less than that of the tandem cascades,and the outlet static pressure is higher than that of the tandem cascades.Meanwhile,the different suction slot location,suction width and suction mass flow are studied for the aspirated cascade.

Effect of Winglet Geometry Arrangement and Incidence on Tip Clearance Control in a Compressor Cascade

An experimental study is conducted to investigate the influences of blade tip winglet on the flow field of a compressor cascade. The tests are performed in a low speed linear cascade with stationary endwall, with three blade tip configurations, including the baseline tip, the suction-side winglet tip and the pressure-side winglet tip. The fiowfield downstream of the cascade is measured using five-hole probe, from which the three-dimensional velocity field, vorticity field and pressure field are obtained. Static pressure measurements are made on the endwall above the blade row using pressure taps embedded in the plywood endwall. All measurements are made at both design and off-design conditions for tip clearance level of about 2 percent of the blade chord. The results revealed the incidence variation significantly affects the secondary flow and the associated loss field downstream of the cascade, where the tip leakage vortex and passage vortex exist as the major contributors on the field. The winglet geometry arrangements can change the trajectory of the tip leakage vortex. The suction-side winglet tip blade provides a lower overall total pressure loss coefficient when compared to the baseline tip blade and pressure-side winglet tip blade at all incidence angles.