试析水泵的节能性与安全性

在水处理中,水泵是极其重要的机器设备,它的正常和高效运行对整个水处理过程起着决定性的作用。但由于一般的污水处理中,水泵都处于高压高腐蚀性等环境,因此,它的安全使用技术是非常重要的。此外,水泵属于一种高能耗设备,在使用过程中的节能问题又是一个关键。本文就将重点探讨水泵在水处理中应该注意的节能性和安全性这两方面的技术问题。     

浅谈新技术在冷却塔系统中的运用

工业生产或冷却工艺过程中产生的废热,一般要用冷却水来导走。冷却塔的作用是将挟带废热的冷却水在塔内与空气进行热交换,使废热传输给空气并散人大气。结合实际,重点介绍了新技术在冷却塔系统中的运用。     

Finite element modelling and experimental study of oblique soccer ball bounce

In this study, we develop a finite element model to examine the oblique soccer ball bounce. A careful simulation of the interaction between the ball membrane and air pressure in the ball makes the model more realistic than analytical models, and helps us to conduct an accurate study on the effect of different parameters on a bouncing ball. This finite element model includes a surface-based fluid cavity to model the mechanical response between the ball carcass and the internal air of the ball. An experimental set-up was devised to study the bounce of the ball in game-relevant impact conditions. Ball speed, angle, and spin were measured before and after the bounce, as well as ball deformation and the forces during the impact. The finite element model has been validated with three different sets of data, and the results demonstrate that the finite element model reported here is a valuable tool for the study of ball bounce. After validation of the model, the effect of the friction coefficient on soccer ball bounce was studied numerically. Simulation results show that increasing the friction coefficient may result in reversal of the horizontal impact force.     

Differential item functioning analysis of the 2003-04 NHANES physical activity questionnaire

Using differential item functioning (DIF) analyses, this study examined whether there were any DF items in the National Health and Nutrition Examination Survey (NHANES) physical activity (PA) questionnaire. A subset of adult data from the 2003-04 NHANES study (n = 3,083) was used. PA items related to respondents' occupational, transportation, domestic, leisure-time, strength-related, and sedentary activities were analyzed for DIF using Mantel-Haenszel, SIBTEST, and analysis of variance procedures. Some items were identified as DF items, with the majority of those items favoring advantaged social groups. For example, items about domestic activity and moderate-intensity leisure-time activity were DF items favoring non-Hispanic Whites, and persons with higher levels of education (e.g., some college or more) or income (e.g, annual family income [AFI] > $34,999). The vigorous activity item was a DIF item favoring younger adults (ages 20-59 years) and persons with higher levels of education or income. Occupational PA presented DF favoring Hispanics and persons with lower levels of education (e.g., high school or less), and the transportation-related PA item presented DF favoring persons with lower incomes (e.g., AFI $34,999). These findings highlight the importance of conducting DF analysis in PA survey construction and emphasize the need to introduce DIF concepts and methods to PA researchers.     

Fundamental movement skill performance of preschool children in relation to family context

Evidence suggests the development of fundamental movement skill (FMS) is a key factor in promoting long-term physical activity. Low levels of activity among preschool children and the relationship between physical activity and the development of fundamental movement skills underline the need to determine the factors associated with children's development of such skills. As parents play an important role in the socialization process, the aim of this study was to examine correlates of family and neighbourhood characteristics as well as parental behaviour and beliefs on FMS performance in 4- to 6-year-old preschool children. Relationships between preschool children's FMS performance and family contextual variables were examined within a sample of 846 preschool children. Results identified positive associations of FMS performance with parental education, father's physical activity, transport to school by bicycle, and the high value placed by parents high on sport-specific aspects of children's physical activity. Variables negatively associated with preschool children's FMS performance included father-child interaction in TV-viewing and reading books, the high importance placed by parents on winning and performance in children's physical activity. Furthermore, the ambiguity of associations between FMS performance and parental beliefs underlined its complexity.     

全球公共物品

面对新冠疫情的爆发,中国没有太多考虑经济问题,选择采取严格防控措施.这与西方世界流行的做法形成鲜明对比,即我们都接受某种程度的"灵活"封闭,主要目的是挽救老年人的生命.然而中国人却在创纪录的短时间内扩大了医院的容量,并带回了居住在国外的中国公民,这几乎都不在大多数西方国家的考虑之列.     

美国非本土博士与本土博士的工作角色与薪酬比较———对美国1999—2008年博士学位获得者的调查

对那些参与了美国国家科学基金会博士学位获得者调查（SDR）的非美国本土的博士学位获得者完成学业后的工资、工资增长和就业单位等方面进行了调查,调查结果显示,非美国本土的劳动者在1999年的平均年薪比美国本土的同行低,但是10年后的2008年,非美国本土的劳动者的工资超过了那些美国本土的同行.分析还发现,非美国本土与美国本土的博士10年间工资增长存在差异.差异可能是由于学科专业和市场需求等因素导致的.     

高校图书馆读者服务工作的创新

文章分析了高校图书馆读者服务过程中存在的问题及面临的挑战,提出加强对读者导读工作,提高读者工作的服务水平,开展网络信息服务与咨询服务,各高校图书馆之间实现资源共享等一系列创新图书馆读者服务工作的举措。     

贝多芬的吻

我16岁时,由于与音乐教师发生分歧,处于某种危机之中。后来,一个著名的钢琴家艾米尔·冯·萨尔——李斯特最后一个活着的弟子,来到布达佩斯,要求我为他弹奏。他专心地听我弹了巴赫的C大调《Toccata》,并要求听更多的曲子。我全身心投入弹奏贝多芬的《Pathetique》奏鸣曲和舒曼的作品《Papillons》之中。最后,艾米尔·冯·萨尔起身,在我的前额上吻了一下。＂我的孩子,＂他说,＂在像你这么大时,我成了李斯特的学生。     

给伊丽莎白一支红玫瑰

伊丽莎白捧着一束雏菊走到院子里。 “美丽的鲜花献给……给……噢,我看我永远都说不好了!”她叫着,把雏菊扔到地上。