磨料射流及高分子减阻改善射流性能的实验研究

本文设计了磨料射流系统及喷嘴结构,实验研究了磨料射流切割与破碎物料的性能,确定了磨料喷嘴出口的最佳长度,对清水和磨料溶液进行了射流冲击性能比较试验;并进一步在磨料射流中加入高分子聚合物添加剂,实验证明,高分子减阻剂同样对磨料射流性能有改善.     

Feature selection and machine learning with mass spectrometry data for distinguishing cancer and non-cancer samples

This is a comparative study of various clustering and classification algorithms as applied to differentiate cancer and non-cancer protein samples using mass spectrometry data. Our study demonstrates the usefulness of a feature selection step prior to applying a machine learning tool. A natural and common choice of a feature selection tool is the collection of marginal p-values obtained from t-tests for testing the intensity differences at each m/z ratio in the cancer versus non-cancer samples. We study the effect of selecting a cutoff in terms of the overall Type 1 error rate control on the performance of the clustering and classification algorithms using the significant features. For the classification problem, we also considered m/z selection using the importance measures computed by the Random Forest algorithm of Breiman. Using a data set of proteomic analysis of serum from ovarian cancer patients and serum from cancer-free individuals in the Food and Drug Administration and National Cancer Institute Clinical Proteomics Database, we undertake a comparative study of the net effect of the machine learning algorithm–feature selection tool–cutoff criteria combination on the performance as measured by an appropriate error rate measure.     

Bayesian Inference in Dynamic Disequilibrium Models: An Application to the Polish Credit Market

We propose a Bayesian approach for inference in a dynamic disequilibrium model. To circumvent the difficulties raised by the Maddala and Nelson (1974) specification in the dynamic case, we analyze a dynamic extended version of the disequilibrium model of Ginsburgh et al. (1980). We develop a Gibbs sampler based on the simulation of the missing observations. The feasibility of the approach is illustrated by an empirical analysis of the Polish credit market, for which we conduct a specification search using the posterior deviance criterion of Spiegelhalter et al. (2002).     

In-Sample or Out-of-Sample Tests of Predictability: Which One Should We Use?

It is widely known that significant in-sample evidence of predictability does not guarantee significant out-of-sample predictability. This is often interpreted as an indication that in-sample evidence is likely to be spurious and should be discounted. In this paper, we question this interpretation. Our analysis shows that neither data mining nor dynamic misspecification of the model under the null nor unmodelled structural change under the null are plausible explanations of the observed tendency of in-sample tests to reject the no-predictability null more often than out-of-sample tests. We provide an alternative explanation based on the higher power of in-sample tests of predictability in many situations. We conclude that results of in-sample tests of predictability will typically be more credible than results of out-of-sample tests.     

Testing for Circular Reflective Symmetry about a Known Median Axis

Circular data arise in many contexts, a particularly rich source being animal orientation experiments. Often, in the analysis of such data, a fundamental question of scientific interest is whether the underlying distribution is reflectively symmetric about some specific axis. In this paper, the situation in which the axis of interest is known to be a median axis is considered and a simple, asymptotically distribution- free test for circular reflective symmetry against skew alternatives is developed. The results from a simulation study lead to a testing strategy incorporating the new test and the circular analogue of the modified runs test of Modarres & Gastwirth (1996). The application of the testing strategy is illustrated using circular data arising from two animal orientation experiments.     

铂族金属及钴、镍高效液相色谱分离分析

本文报道以新试剂2—(6—甲基-2苯并噻唑偶氮)-5—二乙氨基酚作柱前衍生试剂,以甲醇/水=82/18(v/v),含20mmol/L pH5.0醋酸盐缓冲溶液,12mmol/L水扬酸,5mmol/L TBA·Br作流动相.柱温35℃,流速1.0mL/min,检测波长575nm,反相高效液相色谱定量分离和测定了Os(Ⅳ)、Rh(Ⅲ)、Ru(Ⅲ)、Pd(Ⅱ)、Pt(Ⅱ)、Co(Ⅱ)和Ni(Ⅱ)等7个元素.当S/N=3时,各金属离子的检出限分别为(ng):2.79,0.31,8.20,1.14,9.45,0.27,0.040.方法应用于合成样的分析,标准回收率在95.0—104.0%之间.     

Production efficiency in Indian agriculture: An assessment of the post green revolution years

In this paper we use the nonparametric method of Data Envelopment Analysis (DEA) to obtain Pareto-Koopmans measures of technical efficiency of individual states over the years 1970–71 through 2000–01 in a multi-output, multi-input model of agricultural production. We disaggregate overall efficiency into two distinct components representing output and input efficiencies and identify the contribution of individual outputs and inputs to the measured level of overall efficiency. Because introduction of modern inputs has been a major component of the process of modernization of Indian agriculture, we examine to what extent different states succeeded in utilizing the modern inputs compared to the traditional inputs. Variations in the DEA efficiency scores across states and over years is explained in terms of differences in various institutional and demographic factors in a second stage regression analysis.     

低沸点工质水平蒸发换热强化管评述

本文分析总结了许多低沸点工质水平蒸发换热强化管的实验和理论研究成果,得到如下结论:在通常情况下,螺旋微翅片管的强化换热为最佳,其强化效果好、压力损失小;较优的翅片形状为锯齿形或翅顶为平形、翅槽为圆形;较佳的结构几何尺寸范围为:螺旋角β为10～25°、翅高h为0.15～0.20 mm、翅片数n为60～70.据此,作者提出了进一步深化研究的设想.     

美国社区学院的办学特色及对我们的启示

发展高等职业教育对社会发展和经济建设具有重要意义和作用。文章介绍了美国社区学院的办学特色 ,从而为我国高等职业技术教育的办学提供借鉴     

李白与盛唐山水诗——《蜀道难》再解读

以《蜀道难》为代表的李白山水诗的主旨是表现崇高,并由此与主要表现优美的王、孟诗相区别,形成盛唐山水诗中的两种不同艺术范型。《蜀道难》是在以边塞诗和王、孟山水诗为代表的盛唐两种主导审美类型下产生的一个特殊变体。它所代表的崇高审美经验与另一种‘销魂’审美经验,同样指向一种个体与社会环境的不可调和的矛盾,指向社会生活和人生的否定方面。