稀土氨基酸在混合溶剂中的配位常数测定及热力学常数计算

用ｐＨ法测定了镧和天门冬氨酸在水—二甲基亚砜、钕和甘氨酸在水—二氧六环混合溶剂中的配位常数．测定精度为±０．０１ｐＨ单位．通过加入一定量硝酸钾溶液维持溶液的离子强度（０．１０ｍｏｌ／Ｌ）．测定时采用氮气氛保护并保持温度变化不超过±０．２Ｋ．利用配位常数计算了这些配合物在混合溶液中的△Ｇ°、△Ｈ°和△Ｓ°．     

改性天然丝光沸石结构与性能的研究

本文对天然丝光沸石依次进行盐酸脱铝,铵离子交换,510℃焙烧,再铵离子交换,815℃焙烧,二次盐酸脱铝,稀土离子交换等一系列处理。用热分析,X—射线衍射和红外光谱等方法讨论了上述处理对催化剂的结构和性能的影响。经上述处理的天然丝光沸石可适用于催化裂化反应。为天然丝光沸石代替合成丝光沸石作裂化催化剂提供了依据。     

Large deviations of multiclass M/G/1 queues

Consider a multiclass M/G/1 queue where queued customers are served in their order of arrival at a rate which depends on the customer class. We model this system using a chain with states represented by a tree. Since the service time distribution depends on the customer class, the stationary distribution is not of product form so there is no simple expression for the stationary distribution. Nevertheless, we can find a harmonic function on this chain which provides information about the asymptotics of this stationary distribution. The associated h‐transformation produces a change of measure that increases the arrival rate of customers and decreases the departure rate thus making large deviations common. The Canadian Journal of Statistics 37: 327–346; 2009 © 2009 Statistical Society of Canada     

Designing sampling plans to capture rare objects

This article focuses on two‐phase sampling designs for a population with unknown number of rare objects. The first phase is used to estimate the number of rare or potentially rare objects in a population, and the second phase to design sampling plans to capture a certain number or a certain proportion of such type of objects. A hypergeometric‐binomial model is applied to infer the number of rare or potentially rare objects and Monte Carlo simulation based approaches are developed to calculate needed sample sizes. Simulations and real data applications are discussed. The Canadian Journal of Statistics 37: 417–434; 2009 © 2009 Statistical Society of Canada     

Surveying migrant households: a comparison of census-based, snowball and intercept point surveys

Summary.  Few representative surveys of households of migrants exist, limiting our ability to study the effects of international migration on sending families. We report the results of an experiment that was designed to compare the performance of three alternative survey methods in collecting data from Japanese–Brazilian families, many of whom send migrants to Japan. The three surveys that were conducted were households selected randomly from a door-to-door listing using the Brazilian census to select census blocks, a snowball survey using Nikkei community groups to select the seeds and an intercept point survey that was collected at Nikkei community gatherings, ethnic grocery stores, sports clubs and other locations where family members of migrants are likely to congregate. We analyse how closely well-designed snowball and intercept point surveys can approach the much more expensive census-based method in terms of giving information on the characteristics of migrants, the level of remittances received and the incidence and determinants of return migration.     

F-tests with a rare pathology

ANOVA is routinely used to compare pathologies. Nevertheless, in many situations, the sample dimensions may not be known when planning the study. This is specially relevant when one of the pathologies is rare. Thus, the sample size for that pathology or for all pathologies must be considered as random. Sample selection for the non-rare pathologies may be carried out to increase the balance of the model. This leads to F-tests with random non-centrality parameters and random degrees of freedom for the errors. The distribution of such tests statistics is obtained.     

衢州珍稀濒危植物资源及保护对策

衢州是浙江省珍稀濒危植物最丰富的地区之一,共有珍稀濒危植物22种,隶属12科19属,其中1级保护植物3种,2级保护植物19种。本文主要分析这些珍稀濒危植物的区系组成和生物学特性,提出珍稀濒危植物的保护对策。     

稀土发光材料的特点及应用介绍

本文概述了稀土发光材料近几年的研究进展,重点介绍稀土发光材料的特点、合成方法和应用,以及我国稀土发光材料生产现状和未来发展前景展望。     

郑和下西洋反思

通过对十五世纪中、西方远航船队的比较 ,昭示世人郑和船队的伟大。通过对郑和下西洋目的的辨析 ,阐明了明成祖朱棣和明宣宗朱瞻基派遣郑和下西洋的真实意图 ,追求“天下共主”的虚名和“贸采琛异”的耗费 ,给明朝社会经济带来了沉重打击。这是“埋葬”伟大郑和船队的根本原因