带有中心值的百分数的公差的表示

<正>对于量值的公差,当上、下公差相同时,无歧义的表示方式,可以使用带有公差的中心值,例如:100 k Pa±5k Pa或(100±5)k Pa,50.2 mm±0.2 mm或(50.2±0.2)mm。但对于带有中心值的百分数的公差,唯一正确的表示形式是"(n±m)%",例如"(80±5)%",任何时候都不得写作80±5%,也不应写作80%±5%。前者已不是百分数的公差,后者则会产生歧义,有可能误将"±5%"理解成"80%     

带有中心值的百分数的公差的表示

对于量值的公差,当上、下公差相同时,无歧义的表示方式,可以使用带有公差的中心值,例如：100kPa＋5kPa或（100±5）kPa,50．2mm±0．2mm或（50．2±0．2）mm。     

带有中心值的百分数的公差的表示

<正>对于量值的公差,当上、下公差相同时,无歧义的表示方式,可以使用带有公差的中心值,例如:100 kPa±5kPa或(100±5)kPa,50.2 mm±0.2 mm或(50.2±0.2)mm。但对于带有中心值的百分数的公差,唯一正确的表示形式是"(n±m)%",例如"(80±5)%",任何时候都不得写作80±5%,也不应写作80%±5%。前者已不是百分数的公差,后者则会产生歧义,有可能误将"±5%"理解成"80%     

氰化亚金钾的生产工艺的研究

氰化亚金钾是在高新电子材料表面处理上具有重要用途的一种产品,本文研究的利用碱还原-KCN络合法获得的产品质量良好、工艺简单、金回收率高、成本合算。     

带有中心值的百分数的公差的表示

正对于量值的公差,当上、下公差相同时,无歧义的表示方式,可以使用带有公差的中心值,例如:100 k Pa±5k Pa或(100±5)k Pa,50.2 mm±0.2 mm或(50.2±0.2)mm。但对于带有中心值的百分数的公差,唯一正确的表示形     

带有中心值的百分数的公差的表示

<正>对于量值的公差,当上、下公差相同时,无歧义的表示方式,可以使用带有公差的中心值,例如:100 k Pa±5k Pa或(100±5)k Pa,50.2 mm±0.2 mm或(50.2±0.2)mm。但对于带有中心值的百分数的公差,唯一正确的表示形式是"(n±m)%",例如"(80±5)%",任何时候都不得写作80±5%,也不应写作80%±5%。前者已不是百分数的公差,后者则会产生歧义,有可能误将"±5%"理解成"80%     

带有中心值的百分数的公差的表示

对于量值的公差,当上、下公差相同时,无歧义的表示方式,可以使用带有公差的中心值,例如：100kPa±L5kPa或（10±＋5）kPa,50．2mm±0．2mm或（50．2±0．2）mm。但对于带有中心值的百分数的公差,唯一正确的表示形式是“（n±m）％”,例如“（80±5）％”,任何时候都不得写作80±5％,     

带有中心值的百分数的公差的表示

<正>对于量值的公差,当上、下公差相同时,无歧义的表示方式,可以使用带有公差的中心值,例如:100 k Pa±5k Pa或(100±5)k Pa,50.2 mm±0.2 mm或(50.2±0.2)mm。但对于带有中心值的百分数的公差,唯一正确的表示形     

带有中心值的百分数的公差的表示

<正>对于量值的公差,当上、下公差相同时,无歧义的表示方式,可以使用带有公差的中心值,例如:100 kPa±5kPa或(100±5)kPa,50.2 mm±0.2 mm或(50.2±0.2)mm。但对于带有中心值的百分数的公差,唯一正确的表示形式是"(n±m)%",例如"(80±5)%",任何时候都不得写作80±5%,也不应写作80%±5%。前者已不是百     

带有中心值的百分数的公差的表示

<正>对于量值的公差,当上、下公差相同时,无歧义的表示方式,可以使用带有公差的中心值,例如:100 kPa±5kPa或(100±5)kPa,50.2 mm±0.2 mm或(50.2±0.2)mm。但对于带有中心值的百分数的公差,唯一正确的表示形式是"(n±m)%",例如"(80±5)%",任何时候都不得写作80±5%,也不应写作80%±5%。前者已不是百分数的公差,后者则会产生歧义,有可能误将"±5%"理解成"80%     

区域尺度城市增长时空动态模型及其在京津唐都市圈应用

Dynamic urban expansion simulation at regional scale is one of the important re-search methodologies in Land Use/Cover Change (LUCC) and global environmental change influenced by urbanization. However, previous studies indicate that the single urban expan-sion simulation for future scenarios at local scale cannot meet the requirements for charac-terizing and interpreting the interactive mechanisms of regional urbanization and global en-vironmental change. This study constructed a regional Dynamic Urban Expansion Model (Reg-DUEM) suitable for different scenarios by integrating the Artificial Neural Network (ANN)and Cellular Automaton (CA) model. Firstly we analyzed the temporal and spatial character-istics of urban expansion and acquired a prior knowledge rules using land use/cover change datasets of Beijing-Tianjin-Tangshan metropolitan area. The future urban expansion under different scenarios is then simulated based on a baseline model, economic models, policy models and the structural adjustment model. The results indicate that Reg-DUEM has good reliability for a non-linear expansion simulation at regional scale influenced by macro-policies.The simulating results show that future urban expansion patterns from different scenarios of the metropolitan area have the tremendous spatio-temporal differences. Future urban ex-pansion will shift quickly from Beijing metropolis to the periphery of Tianjin and Tangshan city along coastal belt.     

北京城市空间发展和土地利用—伦敦经验启示

Beijing is facing a huge challenge to manage the growth of its built-up area whilst also retaining both productive arable land and land for conservation purposes in order to simultaneously realize the three aims of economic development, protecting arable land and generating environmental improvements. Meanwhile, London, as a world city with more than 200 years of industrialization and urbanization, has accumulated rich theoretical and practical experiences for land use planning in a major urban area, such as the creation of Garden Cities, a designated Green Belt and New Towns. This paper firstly analyzes the main characteristics of the spatial distribution of the built-up area, arable land and conservation land in Beijing. Then, some of the key aspects of urban fringe planning in the London region are examined. Lastly, several implications from the experience of London are provided with respect to land-use planning for Beijing, concentrating on a re-appraisal of land-use functions around Beijing, measures to improve the green belt, the development of small towns to house rural-urban migrants and urban overspill, and effective implementation of land-use planning.     

Urban neighborhoods and mental health: Psychological contributions to understanding toxicity, resilience, and interventions.

The psychological consequences of living in urban neighborhoods are described by using examples related to 3 models of neighborhood characteristics. These models highlight the impact of physical, structural, and social characteristics on various types of mental health outcomes. In addition, the characteristics of individuals and neighborhoods that encourage resilience to negative outcomes are discussed. Finally, examples of how psychology can contribute to neighborhood interventions that ameliorate or prevent residents' distress and improve neighborhood conditions are described. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discovering how urban poverty and violence affect health: Development and validation of a neighborhood stress index.

Health problems of the urban poor have been attributed to psychosocial effects of environmental stress. Testing such models requires an ability to measure neighborhood characteristics that make life stressful. The City Stress Inventory (CSI) uses self-report to assess perceived neighborhood disorder and exposure to violence. Data from an interracial sample of urban adolescents show the CSI to be internally consistent, stable, and correlated with census indices of social disadvantage. Validity for stress research is indicated by correlations with trait depression, anger, hostility, self-esteem, and mood changes during a debate with an unfamiliar peer. The CSI can be completed by persons with an 8th-grade education. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

结构-土-结构体系动力特性的模型实验

为研究邻近结构对土-结构体系动力特性的影响,基于弹性相似律,制作了框架结构在刚性基础（RF）、单一结构土-结构相互作用（SSI）和结构-土-结构相互作用（SSSI）的缩尺模型.采用脉冲激励方法识别出三个模型的频率、模态和阻尼比,并与原型有限元计算结果相比较.实验和数值计算结果表明：相应于SSI体系的模态,SSSI体系的模态成对出现,两阶模态的频率接近而相位相反,且SSI体系相应模态的频率位于这两阶频率之间;由于相邻结构的影响,SSSI体系基础的竖向位移和倾覆转角进一步加强.     

Transgenic insertional mutagenesis. Applications to inner-ear genetics

STUDY OBJECTIVE: Despite significant declines since the late 1960s, coronary mortality remains the leading cause of death for African Americans. African Americans in the US South suffer higher rates of cardiovascular disease than African Americans in other regions; yet the mortality experiences of rural-dwelling African Americans, most of whom live in the South, have not been described in detail. This study examined urban-rural differentials in coronary mortality trends among African Americans for the period 1968-86. SETTING: The United States South, comprising 16 states and the District of Columbia. STUDY POPULATION: African American men and women aged 35-74 years. DESIGN: Analysis of urban-rural differentials in temporal trends in coronary mortality for a 19 year study period. All counties in the US South were grouped into five categories: greater metropolitan, lesser metropolitan, adjacent to metropolitan, semirural, and isolated rural. Annual age adjusted mortality rates were calculated for each urban status group. In 1968, observed excesses in coronary mortality were 29% for men and 45% for women, compared with isolated rural areas. Metropolitan areas experienced greater declines in mortality than rural areas, so by 1986 the urban-rural differentials in coronary mortality were 3% for men and 11% for women. CONCLUSIONS: Harsh living conditions in rural areas of the South precluded important coronary risk factors and contributed to lower mortality rates compared with urban areas during the 1960s. The dramatic transformation from an agriculturally based economy to manufacturing and services employment over the course of the study period contributed to improved living conditions which promoted coronary mortality declines in all areas of the South; however, the most favourable economic and mortality trends occurred in metropolitan areas.     

Urban mortality--race or place?

Several concomitant trends have occurred in American society in the 20th century. First, life expectancy has improved overall, and the gap between blacks and whites has narrowed. Second, as the nature of the economy has changed from rural agrarian to urban postindustrial, there have been fundamental changes in population residential patterns, with most Americans now living in metropolitan areas. Within metropolitan areas, blacks have become concentrated in poor inner cities as whites have moved to the more affluent suburbs. Black mortality rates are higher in big cities than elsewhere, and appear to be directly related to the proportion of blacks in those cities. Black-white mortality ratios, however, are lower in cities of medium size than in either very large or small cities. At the national level age-adjusted mortality ratios between blacks and whites are associated with different causes of death; but only limited cause-specific mortality data are available for large cities. Understanding and ameliorating social conditions that lead to elevated black mortality in U.S. cities will require more information at the municipal level than is currently available.     

Effects of marital status on the risk of mortality in poor and non-poor neighborhoods

PURPOSE: The purpose of this paper is to consider whether the mortality risks associated with marital status are conditioned by the socioeconomic quality of neighborhoods. METHODS: The analysis is based on the first National Health and Nutrition Examination Survey 1971-1974 (NHANES I), and the 1987 NHANES I Epidemiologic Followup Survey (NHEFS). Cox proportional hazards regressions were used to assess whether the effect of marital status on the risk of all-cause and cause-specific mortality is altered by local area poverty. Analyses are stratified by age, sex, and urbanicity. RESULTS: The interaction between neighborhood poverty and marital status is suggested for non-elderly men, particularly for cancer mortality and for men in urban areas. Interaction effects are evident among older women residing in urban areas. CONCLUSIONS: The absence of a spouse elevates the risk of mortality but this risk is moderately higher in impoverished neighborhoods, notably in urbanized areas, for non-elderly men and elderly women. Future studies with larger samples of non-married persons where marital status changes are incorporated are needed to improve our understanding of the joint mortality effects of local area poverty and marital status.     

Children of human immunodeficiency virus-infected members of the Army Reserve components

OBJECTIVES: Little is known about the numbers of children who will be left without one or both parents because of human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome. This report evaluates childbearing patterns among U.S. Army reserve component members, a group largely made up of men with limited contact with the military. METHODS: HIV status was determined from routinely collected data, with demographic information obtained from personnel records. Number of children was estimated from number of dependents reported. No information was available on the infection status of children or spouses of members. RESULTS: There were 1,884 HIV-positive members, with an estimated total of 843 children. Childbearing patterns varied across several demographic characteristics. Among 14 metropolitan statistical areas, the proportion reporting any children and the number of children of infected members per 100,000 varied substantially. CONCLUSIONS: This report documents the numbers of children of HIV-positive adults in this population and provides evidence that certain metropolitan areas will be disproportionately affected.     

厦门岛城市空间扩张特征及其影响因素

Most of the world's cities are concentrated in coastal areas. As a special geo-graphical component of the coastal system, island urban spatial expansion is the outcome of interactions between city development and the physical environment. This paper takes Xia-men Island, located in Southeastern China, as an example to analyze island urban spatial expansion and its determinants by combining an analysis of the literature on urban devel-opment policies, urban overall plans, population growth and industrial development, with geographical information analysis using historical maps and remote sensing photographs.Firstly, we reviewed the history of the Xiamen City development during the last 100 years,which can be divided into four periods:the embryonic modern city and early development from 1908 to 1949; administrative boundary expansion and infrastructure development from 1950 to 1979; special economic zone construction and rapid urbanization from 1980 to 2003;and Bay City construction since 2003. The dynamic changes to the coastline, island shape,built-up area, transportation, administrative division, and major land use type conversion which occurred during approximately the past 100 years were analyzed and the characteris-tics of the island urban spatial expansion were concluded:early expansion from a central point, followed by expansion along a section of coastline, and expansion from the coastline inland. Secondly, we discussed the potential determinants of island urban spatial expansion including administrative division adjustment, urban master planning revision, industrial de-velopment, topographical factors, coastal area reclamation, transportation expansion, and population growth. Finally, the effects of each potential determinant on island urban spatial expansion were concluded. Island urban spatial expansion is the result of a synthesis of natural and socio-economic factors which are not independent but interacting. Built-up area expansion is the major driver of island land cover and land use changes. By this paper, we hope to provide a scientific reference contributing to the rational understanding of island and coastal sustainable urbanization in China, and the world beyond.