美国土壤侵蚀过程及其预报模型研究进展

土壤侵蚀过程的研究将为基于物理过程的侵蚀预报模型研发提供重要的理论基础。介绍了美国土壤侵蚀过程研究进展 ,叙述了土壤侵蚀过程研究对研发水蚀预报模型 (WEPP)的重要贡献 ,阐述了近期侵蚀过程研究对WEPP模型中侵蚀过程概念模型的挑战 ,希望对中国侵蚀过程及其预报模型的研究有借鉴作用。     

基于粒子滤波算法的汽车状态估计技术

将粒子滤波（particle filter, PF）算法应用到汽车的状态估计之中,建立了包含定常统计特性噪声和非线性轮胎的汽车动力学模型,根据汽车非线性状态转移函数完成对粒子的预测,基于当前时刻的量测值实现对预测粒子权重的评估,最后通过重采样完成对汽车关键状态量估计。将PF估计器与常见的EKF、UKF估计器进行了比较分析,基于ADAMS/Car的虚拟试验和实车试验验证了PF在汽车状态估计中的可行性。     

The effect of high temperature interruptions during inductive period on the extent of flowering and on metabolic responses in olives (Olea europaea L.)

The effect of the duration of high temperature interruption and the timing of its occurrence during inductive period on the extent of inhibition of inflorescence production in ‘Arbequina’ olive trees was investigated. Trees kept under inductive conditions in different growth chambers were subjected to high daytime temperature (26 ± 1 °C) interruptions for 3, 6, and 12 days. There was no significant difference in the extent of flowering between trees given an uninterrupted induction period and the trees where inductive period was interrupted with high daytime temperatures for three days. Inflorescence production was significantly reduced by both 6 and 12 days high temperature interruptions. Number of flowers per inflorescence was significantly reduced only with 12 days high temperature interruption. Since there was no significant difference between the extent of inhibition of inflorescence by 6 and 12 days high temperature interruption, therefore, 6 days high temperature interruption was used in subsequent experiments to study the effect of timing of interruption. A six day interruption of high temperature produced significant reduction (more than 83%) in inflorescence production irrespective of the time of interruption (i.e., 40 or 50 days after the start of induction) or number of interruptions. None of these treatments had any significant effect on the number of flowers per inflorescence. Higher levels of free arginine were found in trees that had greatest number of inflorescences produced under inductive conditions without any high temperature interruption.     

Interactions of an introduced shrub and introduced earthworms in an Illinois urban woodland: Impact on leaf litter decomposition

This study examined an ‘invasional meltdown’, where the invasion of a Midwestern woodland by an exotic shrub (Rhamnus cathartica L.P. Mill) and the invasion by Eurasian earthworms facilitated one another. Using a litterbag approach, we examined mass loss of four substrates (R. cathartica, Acer saccharum, Quercus rubra, and Quercus alba) along a gradient of Eurasian earthworm density and biomass throughout a 40.5 ha oak woodland in Glencoe, Illinois. Earthworm densities and biomass were greatest in patches where R. cathartica prevailed, and populations were lowest in an upland forest subcommunity within the woodland. At each of three points along this earthworm gradient, we placed replicated litterbags constructed either to permit or to deny access to the litter by earthworms. The treatments were, therefore, plot treatments (low, medium and high earthworm density and biomass) and litterbag treatments (earthworm access and earthworm excluded). We found that earthworms promoted a very rapid loss of litter from R. cathartica bags. Within 3 months greater than 90% of this litter was lost from the litterbags. Earthworm impacts on other substrates followed the sequence A. saccharum>Q. alba=Q. rubra. Effects of both litterbag and plot treatments were found within 3 months for A. saccharum but Quercus species were affected only after a year. We propose that the impact of earthworms on litter breakdown creates conditions that promote and sustain invasion by R. cathartica. Previous work has demonstrated that R. cathartica may alter soil properties in a way that promotes and sustains invasion by earthworms. These findings have implications for the restoration management of these systems, since the legacy of R. cathartica on soil properties and earthworm populations may persist even after the plant has been physically removed.     

中美高校“马克思主义基本原理”课程教学的比较研究

通过对中美两国"马克思主义基本原理"课程的教学内容、教学方法、考核方式等方面的比较,从注重学习原著、开展讨论式教学、改革考核方式等三方面对中国高校"马克思主义基本原理"的课程教学改革提出了可行性建议。     

中美园艺学科硕士研究生课程设置比较研究

课程设置是实现研究生培养目标的基础,是提升研究生教育水平的关键。基于实例收集和对比分析的方法,以中美两国办学历史悠久、实力相对雄厚且招收园艺学硕士研究生的20所院校为研究标的,比较了两国20所院校的园艺学硕士研究生的课程设置异同,分析了两国园艺学硕士研究生的教育现状与发展趋势,在此基础上提出国内园艺学科硕士研究生的课程设置应加大专题课与讨论课的建议。     

从篮球文化视角下洞悉历届奥运会美国篮球成绩

通过文献资料、逻辑分析等研究方法,得出,美国男篮参加了17届奥运会的男子篮球比赛,获得14 次金牌、1次银牌和2次铜牌;美国女篮参加了9届奥运会篮球比赛,取得7金1银1铜;美国篮球文化具有鲜 明的“民族性”特点;美国篮球层层衔接的竞赛训练体系是美国篮球取得辉煌成绩的基石。     

简述美国家庭农场

美国的农业主要由家庭农场来经营,经历了150多年的发展历程,目前美国共有农场219.6万多个,其中,家庭农场214.3万个;非家庭农场（主要是合伙农场、公司农场）5.34万个.美国家庭农场的经营管理一般由其家庭成员负责.经营者的文化、科学素质较高,据我多次访问调查,至少半数以上的经营者具有大学学历.在家庭农场的经营下,美国农业得以持续发展,成为全球粮、农生产和出口大国,其成绩很大,在国际社会上受到应有的尊重和赞誉.目前农村两极分化的现象十分严重.     

Contribution of Health Attributes,Research Investment,and Innovation to Developments in the Blueberry Industry

Abstract

This paper examines how the United States and Canadian highbush and lowbush blueberry industries have changed over the last two decades. Production increases have been driven by a combination of changing consumer preferences for healthy foods and the development of new cultivars that have opened new production regions, expanded fresh market opportunities, and created new food products. Canada has found it advantageous and economical to invest its research effort in the development of the lowbush blueberry, exploiting its health protective properties. The Unites States has concentrated its research effort on highbush cultivars to lengthen the harvest window and promote diversification opportunities in the Southern United States. Highbush production expansion in the Pacific Northwest has relied very little on new cultivar development and improvements in yield but more on increases in cultivated area.     

河北联合大学校园植物多样性调查

为了解河北联合大学校园植物的多样性,通过实地考察法,对其植物物种的种类、数量等进行系统调查。结果表明：河北联合大学校园植物资源较为丰富,共有植物138种,隶属于57科114属。其中菊科、蔷薇科物种较多,多年生木本植物应用频率较高,但绿化结构简单。