泥砂介质注浆渗流通道形成力学机理分析

为研究在泥砂介质中的注浆渗流通道形成机理,设计了注浆实验系统;并由实验结果可知化学浆液在泥沙介质中渗流的主要形式为柱形渗流和面形渗流两种;在格里菲斯判据的基础上,推导了浆液形成渗流通道所需要的最小注浆压力p min;在渗流力学的基础上分析了浆液在介质中渗流的的压力损失,得知浆液在渗流通道不同位置处的注浆压力p1;当p1p min时,浆液将劈裂被注介质形成新的渗流通道;当p1p min时,浆液将停止劈裂被注介质,该通道封闭。     

Estimating a general function of a quadratic function

Let be an observation from a spherically symmetric distribution with unknown location parameter . For a general non-negative function c, we consider the problem of estimating c(||x − θ||²) under the usual quadratic loss. For p ≥ 5, we give sufficient conditions for improving on the unbiased estimator γ₀ of c(||x − θ||²) by competing estimators γ _s = γ₀ + s correcting γ₀ with a suitable function s. The main condition relies on a partial differential inequality of the form k Δs + s ² ≤ 0 for a certain constant k ≠ 0. Our approach unifies, in particular, the two problems of quadratic loss estimation and confidence statement estimation and allows to derive new results for these two specific cases. Note that we formally establish our domination results (that is, with no recourse to simulation).      

热重分析法测定矿产品中的吸附水及烧失减量

采用热重分析法(TGA)测量矿产品中的吸附水及烧失减量,验证了方法的准确性及精密度。对多种矿产品样品采用TGA法和常规马弗炉加热法进行测量,对比结果表明,这两种方法没有显著性差异。TGA法具有方便快捷、准确可靠等优点,是矿产品吸附水及烧失减量检验的首选。     

利用混合FE-SEA方法的前围隔声性能优化设计*

为了提升某重型商用车前围的隔声性能,建立了用于分析前围传递损失的有限元-统计能量分析(FE-SEA)模型。针对前围结构复杂的特点,依据FE-SEA模型建模原则,提出了通过在表面创建声腔来确保能量在模型中的正确传递路径。将仿真结果与测试值对比,二者误差小于1.6 dB(A),验证了FE-SEA方法的准确性。用吸声材料与隔声材料复合设计前围声学包,采用正交试验法对前围声学包进行优化设计并对各个试验方案进行仿真计算。对仿真结果进行极差分析与方差分析,选出了在传递损失、重量和厚度三方面达到最佳平衡的声学包:毛毡(10 mm)+EPDM隔声垫(2 mm)。结果表明,优化后的前围传递损失在测试频率315 Hz～2000 Hz范围内最小提升了3.8 dB(A),最大提升了7 dB(A),前围的隔声性能得到较大的提升。     

On attenuation of free and forced waves in an infinitely long visco-elastic layer of a constant thickness

The conventional concepts of a loss factor and a complex-valued elastic module are used to study wave attenuation in a visco-elastic layer. The hierarchy of reduced order models is employed to assess attenuation levels of free and forced waves in various situations. First, the free waves are considered. In the low frequency limit, the attenuation of these waves is found to be in the excellent agreement with the existing knowledge. At high frequencies, predictions of the reduced order models fully agree with the solutions of exact Rayleigh–Lamb problem. Alternative excitation cases are considered for the forcing problem and a measure of the attenuation level is proposed and validated. The differences between two regimes, the low frequency one, when a waveguide supports only one propagating wave, and the high frequency one, when several waves are supported, are demonstrated and explained.     

移动通信电波路径损耗的测试

对具体地面电波传播的信号进行测试。经比较,验证了在地面LOS范围的双斜率及室内对数距离路径损耗模式,并提出针对2．4GHz频段的拟合参数取值,对无线组网有参考价值。     

Bayesian Copulae Distributions, with Application to Operational Risk Management

The aim of this paper is to introduce a new methodology for operational risk management, based on Bayesian copulae. One of the main problems related to operational risk management is understanding the complex dependence structure of the associated variables. In order to model this structure in a flexible way, we construct a method based on copulae. This allows us to split the joint multivariate probability distribution of a random vector of losses into individual components characterized by univariate marginals. Thus, copula functions embody all the information about the correlation between variables and provide a useful technique for modelling the dependency of a high number of marginals. Another important problem in operational risk modelling is the lack of loss data. This suggests the use of Bayesian models, computed via simulation methods and, in particular, Markov chain Monte Carlo. We propose a new methodology for modelling operational risk and for estimating the required capital. This methodology combines the use of copulae and Bayesian models.      

光伏并网电站损耗探讨

为了减少大型兆瓦级光伏并网电站中的损耗,本文归纳了大型光伏并网电站中主要几个方面的损耗,并对每种损耗分析原因,提出切实可行的改进方法。     

大学生廉洁教育的思考与对策

大学生廉洁教育,是高校学生思想政治工作的一个重要课题,同时也是时代赋予当今高校的一个严肃的政治任务。大学生是未来社会的中坚力量,开展大学生廉洁教育具有重要意义。本文从理解和把握大学生廉洁教育的意义出发,对廉洁教育的现状,原因和解决对策等方面进行探讨。     

Birefringence,dispersion and loss properties for PCFs with rectangular air-holes

In this paper, the solid-core fiber designs constructed by omitting one air-hole at the center of square-lattice silica photonic crystals with rectangular shaped air-holes have been investigated theoretically and their characteristics have been compared with those of square ones. Using commercial simulation software, birefringence, dispersion, numerical aperture and confinement loss of the fundamental modes are analyzed.