Virtual Reality Learning System for Digital Terrain Model Surveying Practice

This research builds a virtual reality learning system for the digital terrain model surveying practice based on the triangular irregular network (TIN). The proposed system offers students an interactive, individual, three-dimensional, measurable, immediate feedback learning process. The system operating procedure is divided into five operations: (1) selecting topographical control points; (2) TIN editing; (3) evaluating errors; (4) analyzing errors; and (5) demonstrating performance. Students are able to carry out selecting the topographical control points and editing TIN under the virtual reality environment as if they implemented these surveying operations in the field. In addition, the magnitude and distribution of elevation errors can be recognized immediately after these operations are completed. Therefore, students have immediate feedback. After using the system in real practice courses, significant effects were found between the experimental set and contrast set.     

Factors Affecting the Use of Precast Concrete Systems in the United States

The use of precast concrete systems offers several advantages such as speedy erection, higher quality, lower project cost, better sustainability, and enhanced occupational health and safety. In spite of these advantages, the share of precast concrete systems in the U.S. building construction market is very low. The factors behind this low market share are discussed in several studies. This study aims to identify the current factors that affect the use of precast concrete systems, compare them with the ones that prevailed in 1995, and figure out what has changed through the last 11?years in the American precast concrete industry. The findings of an extensive survey indicate that most of the dominating barriers to the extensive use of precast concrete systems in 1995 are either eliminated or drastically reduced, while some of them still prevail. Practitioners should be well informed about the factors that affect the use of precast concrete systems if these systems are to be used more extensively.     

食品污染物监测及其健康影响评价的研究简介

为保障食品安全，“食品污染物监测及其健康影响评价的研究”被列入国家科技部“十五”攻关课题。主要研究内容为食品污染物分析质量控制研究；污染物(包括金属污染物，农药残留)监测技术研究；建立有害物质暴露危险性评估技术；生物学标志物研究。研究完成后，建立了我国与国际接轨的污染物监测网框架，提出了我国食品污染物监测分析质量控制评价原则，提高了我国污染物监测水平。绘制了我国食品污染物基本状况表。我国食品中重金属污染主要是铅污染，各年龄段铅的摄入量偏高，特别是儿童已经达到PTWI的105．6％～109．7％。说明我国食品中铅的含量偏高，应该修订国家标准。镉污染主要在鱼类，全国平均值超过国家标准，其中河南省淡水鱼的镉平均值是国家标准的近3倍，其他食品镉的污染不严重。砷、汞在食品中的污染不严重。成功地以总膳食研究为手段进行膳食暴露评估。在国际上首先建立了反映人体微量氯丙醇暴露的8—氯乳酸的痕量检测技术，并作为理想的接触标志物用于人体氯丙醇的暴露评价；初步建立了以监测母乳中二噁英负荷水平作为接触标志物和生殖内分泌指标作为效应标志物的体系；应用人胚肾LH／CG受体重组细胞株生物发光法测定血清中的BCG。研制出监测网研制数据上报系统计算机软件。该研究对保障食品安全提供了方法和科学依据。     

Research scene

This opinion survey about the future of international construction concerns several time horizons, but only the five-year horizon is discussed in this paper. The analysis focuses on construction market attractiveness - a measure obtained by combining opinions about the rate of growth, profitability and openness to foreign competition - and construction industry competitiveness with respect to both services and materials. The results of the survey rank attractiveness of construction markets by country and city. The analysis of competitiveness of construction services and materials largely points to the same countries and indicates some important medium-term trends in the international construction market.

Cette étude d'opinions sur l'avenir de la construction internationale s'intéresse à plusieurs horizons mais seul l'horizon à 5 ans est examiné dans ce document. Cette analyse se concentre sur l'attractivité du marché de la construction - que l'on mesure en combinant les opinions sur le taux de croissance, la rentabilité et l'ouverture à la concurrence internationale et sur la compétitivité de cette industrie en termes de services et de matériaux. Les résultats de l'étude classent l'attractivité des marchés de la construction par pays et par ville. L'analyse de la compétitivité des services et des matériaux de construction met nettement en eéidence les mêmes pays et indique certaines tendances à moyen terme qui se dessinent sur le marché de la construction internationale.     

Automated analysis and exploration of image databases: Results,progress, and challenges

In areas as diverse as earth remote sensing, astronomy, and medical imaging, image acquisition technology has undergone tremendous improvements in recent years. The vast amounts of scientific data are potential treasure-troves for scientific investigation and analysis. Unfortunately, advances in our ability to deal with this volume of data in an effective manner have not paralleled the hardware gains. While special-purpose tools for particular applications exist, there is a dearth of useful general-purpose software tools and algorithms which can assist a scientist in exploring large scientific image databases. This paper presents our recent progress in developing interactive semi-automated image database exploration tools based on pattern recognition and machine learning technology. We first present a completed and successful application that illustrates the basic approach: the SKICAT system used for the reduction and analysis of a 3 terabyte astronomical data set. SKICAT integrates techniques from image processing, data classification, and database management. It represents a system in which machine learning played a powerful and enabling role, and solved a difficult, scientifically significant problem. We then proceed to discuss the general problem of automated image database exploration, the particular aspects of image databases which distinguish them from other databases, and how this impacts the application of off-the-shelf learning algorithms to problems of this nature. A second large image database is used to ground this discussion: Magellan's images of the surface of the planet Venus. The paper concludes with a discussion of current and future challenges.     

成都居民膳食中天然放射性核素水平及所致内照射剂量的研究

为了解成都市城乡居民膳食中天然放射性核素摄入水平以及所致内照射剂量,应用总膳食研究方法,测定了１２ 种混合食物试样中天然放射性核素铀、钍、镭、钾含量。结果：４ 种放射性核素的比活度大小依次为４０ Ｋ＞ ２２６ Ｒａ ＞ ２３８ Ｕ＞ ２３２ Ｔｈ 。贡献率城乡均以４０ Ｋ 最大。所致的全身剂量当量城乡分别为每年１１７ ．２ μ Ｓｖ 和１７３ ．２ μ Ｓｖ ,平均为１４５ ．２ μ Ｓｖ ,高于我省人均内照射剂量当量１０８ ．６ μ Ｓｖ ,但仍属于天然辐射水平。