Interfamily economic exchange: A function of culture or economics?

This study explores differences in inter-household exchange of goods and services in Anglo- and Mexican-American families controlling for income level and for ethnicity. The extent of such exchange, its perceived importance to the family's quality of life, satisfaction with the exchange, and the relation of persons in the exchange process are examined. Significant differences are found more often between higher income Anglo- and Mexican-Americans than between low-income families, both in the family providing goods and services for others and in the receipt of them. Higher income Mexican-American families are more likely than their Anglo- counterparts to exchange with relatives. Ethnic effects are more prevalent in higher income households than in low-income households. Economic effects are more predominant than ethnic effects.This study contributes to interregional Agricultural Experiment Station Research Project NC-128, Quality of Life as Influenced by Area of Residence. Cooperating states: Arizona, California, Colorado, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, Nevada, Ohio, Texas.Flora L. Williams' current research interests include income adequacy, financial problems, and indicators of change in economic well-being. She is an Associate Professor, Consumer Sciences and Retailing, Purdue University, West Lafayette, IN 47907.     

Origins and destinies: Immigration to the United States since World War II

Contemporary immigration to the United States and the formation of new ethnic groups are the complex and unintended social consequences of the expansion of the nation to its post-World War II position of global hegemony. Immigrant communities in the United States today are related to a history of American military, political, economic, and cultural involvement and intervention in the sending countries, especially in Asia and the Caribbean Basin, and to the linkages that are formed in the process that open a variety of legal and illegal migration pathways. The 19.8 million foreign-born persons counted in the 1990 U.S. census formed the largest immigrant population in the world, though in relative terms, only 7.9% of the U.S. population was foreign-born, a lower proportion than earlier in this century. Today's immigrants are extraordinarily diverse, a reflection of polar-opposite types of migrations embedded in very different historical and structural contexts. Also, unlike the expanding economy that absorbed earlier flows from Europe, since the 1970s new immigrants have entered an hourglass economy with reduced opportunities for social mobility, particularly among the less educated, and new waves of refugees have entered a welfare state with expanded opportunities for public assistance. This paper seeks to make sense of the new diversity. A typology of contemporary immigrants is presented, and their patterns of settlement, their distinctive social and economic characteristics compared to major native-born racial-ethnic groups, and their different modes of incorporation in—and consequences for—American society are considered.     

高校在我国科技经济与国际接轨过程中的作用

我国经济的高速发展,有力地推动着我国科技、经济与世界经济的联系,促使我国对外贸易的扩大和海外来华投资额的迅速增加。要实现我国经济工作以增加效益为中心,保持国民经济持续、快速、健康发展的目标,必须注重科技进步的作用．高等学校在促进我国科技进步以及经济与国际接轨过程中,具备技术、软件优势;智力、人才优势;超前意识的时空利用优势和学科交叉的综合优势,可以充分发挥时空差的有效利用、注入科技进步以提高产品素质的作用,做好我国产品参与国际竞争的导向工作。     

Sampling from spatial databases

This paper deals with techniques for obtaining random point samples from spatial databases. We seek random points from a continuous domain (usually ²) which satisfy a spatial predicate that is represented in the database as a collection of polygons. Several applications of spatial sampling (e.g. environmental monitoring, agronomy, forestry, etc) are described. Sampling problems are characterized in terms of two key parameters: coverage (selectivity), and expected stabbing number (overlap). We discuss two fundamental approaches to sampling with spatial predicates, depending on whether we sample first or evaluate the predicate first. The approaches are described in the context of both quadtrees and R-trees, detailing the sample first, acceptance/rejection tree, and partial area tree algorithms. A sequential algorithm, the one-pass spatial reservoir algorithm is also described. The relative performance of the various sampling algorithms is compared and choice of preferred algorithms is suggested. We conclude with a short discussion of possible extensions.     

1997早稻长秧龄旱育“壮杆足穗”栽培技术

本文对早稻长秧龄旱育“壮杆足穗”栽培技术进行了概括和论证：“壮苗”是壮杆足穗的基础;“足穗”是决定高产的第一因素;“壮杆”是高产的重要保证：“增粒壮籽”是壮秆足穗的最终的目标。     

小麦新品种“绵阳26”主要性状与产量的关系

对45个试验点的资料分析,多抗、丰产、优质、广适小麦新品种绵阳26的主要性状有效穗x1、穗粒数x2和千粒x3、单穗重x4与产量y的回归方程为：y＝－614．8425＋9.8683x1＋7.3223x2＋10．5315x3＋22．5748x4。经偏回归和偏相关分析,产量构成因素中,千粒重、有效穗对绵阳26产量的贡献和影响最大（b'3＝1．7435,b'1＝1．5372,R3y.＝0．7983,R1y＝0．6991）。在现有产量的基础上稳定千粒重,主攻穗数和穗粒数,是发挥绵阳26高产潜力的决定因素。     

一类四阶非线性常微分方程的两点边值问题解的存在性与唯一性

本文利用Hammerstein型积分算子和上下解方法,研究了一类四阶非线性常微分方程的两点边值问题     

受控核聚变的一种新途径──低能注入式磁盖势阱约束法受控核聚变

提出了磁盖势阱（ＭＬＰＷ）一种静电装置,该装置是在球形静电势阱的外围加上磁盖而构成的,可用于受控核聚变．通过建立磁盖势阱中带电粒子的运动方程并取单粒子谐振子近似以及运用自洽场的统计方法,球形聚变炉内大量带电粒子的集体行为被计算机所研究和模拟．由于使用了电场与磁场的联合约束,与单独的磁约束或惯性约束受控核聚变相比,所需达到的技术指标将有所改善,工程技术上的难度也会有所降低     

昆嵛山野生经济植物及开发利用

报道了昆嵛山野生经济植物６８１种及变种,隶属１０１科,５５２属．根据其经济用途分为七大类,并提出了开发利用意见．     

双核铜(Ⅱ)与N,N,N′,N′-四〔2-(2-吡啶基)乙基〕(o,m,p)苯二甲酰胺配合物的合成与表征

通过酰氯与胺的作用合成了配体Ｎ,Ｎ,Ｎ′,Ｎ′－四〔２－（２－吡啶基）乙基〕（ｏ,ｍ,ｐ）苯二甲酰胺．该配体和铜（Ⅱ）配合,合成了三种新配合物,并以红外光谱、电子光谱、摩尔电导率、元素分析及核磁共振谱进行了表征．