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排序方式: 共有266条查询结果,搜索用时 31 毫秒
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This paper reports a technique for temperature-induced merging of droplets in a microchannel. The multiphase system consists of water droplet and oil as the dispersed phase and the carrying continuous phase. A resistive heater provides heating in a rectangular merging chamber. The temperature of the chamber is controlled by the voltage applied to the heater. The merging process of two neighboring droplets was investigated with different applied voltage, flow rate ratio between water and oil and total flowrate. Merging is found to be effective at high flow rate ratio, high temperature, and low total flowrate. The presented technique could be used for merging and mixing in droplet-based lab-on-a-chip platforms. 相似文献
73.
除了美观上的效果,垂直绿化缓解热岛效应,减少水土流失,防尘减噪,节能环保,延长建筑寿命等作用也被越来越多的人意识到,有关垂直绿化各方面定性的研究也不断得到开展.以南京的三种墙面绿化形式—攀援式墙面绿化、铺贴式墙面绿化和组合移动式墙面绿化作为研究对象,通过测定垂直绿化的降温、减噪和心理效应探讨垂直绿化对建筑环境的综合影响. 相似文献
74.
Hopper CA Munoz KD Gruber MB Nguyen KP 《Research quarterly for exercise and sport》2005,76(2):130-139
This study examined the efficacy of a school-based exercise and nutrition program with a parent component. Third-grade children (N = 238) from six elementary schools participated in the study, with three schools randomly assigned to a program group and the other three schools to a control group. The program group received a health-related fitness school-based program and a home program that required parents and children to complete activities and earn points for nutrition and exercise activities. The control group received their traditional physical education and nutrition education program. Univariate analysis of variance on pre- and posttest scores were completed on the following variables: height, weight, body mass index, skinfold, blood cholesterol, mile run, exercise and nutrition knowledge, calories, protein, carbohydrates, total fat, saturated fat, dietary cholesterol, fiber, sodium, percentage of calories from carbohydrates, and percentage of calories from fat. At pretest, the treatment and control groups did not significantly differ on the measures using schools as the unit of analysis. Girls scored significantly higher than boys on skinfold and pretest knowledge. At posttest, the treatment group scored significantly higher than the control group on exercise and nutrition knowledge and significantly lower than the control group on total fat intake, using schools as the unit of analysis. There was no improvement in physiological measures, including blood cholesterol. The study demonstrated that schools can adjust curriculum to meet some health needs of students and achieve modest changes in exercise and nutrition knowledge and diet. The family component of the program provided a practical approach to improving physical activity and nutrition behaviors for elementary school teachers who teach many participants in a crowded curriculum. 相似文献
75.
Mougin F Bourdin H Simon-Rigaud ML Nguyen NU Kantelip JP Davenne D 《Journal of sports sciences》2001,19(2):89-97
The aim of this study was to determine the hormonal responses, which are dependent on the sleep wake cycle, to strenuous physical exercise. Exercise was performed after different nocturnal regimens: (i) a baseline night preceded by a habituation night; (ii) two nights of partial sleep deprivation caused by a delayed bedtime or by an early awakening; and (iii) two nights of sleep after administration of either a hypnotic compound (10 mg zolpidem) or a placebo. Eight well-trained male endurance athletes with a maximal oxygen uptake of 63.5 +/- 3.8 ml x kg(-1) x min(-1) (mean value +/- s(x)) were selected on the basis of their sleeping habits and their physical training. Polygraphic recordings of EEG showed that both nights with partial sleep loss led to a decrease (P< 0.01) in stage 2 and rapid eye movement sleep. A delayed bedtime also led to a decrease (P < 0.05) in stage 1 sleep. Zolpidem had no effect on the different stages of sleep. During the afternoon after an experimental night, exercise was performed on a cycle ergometer. After a 10-min warm-up, the participants performed 30 min steady-state cycling at 75% VO(2-max) followed by a progressively increased workload until exhaustion. The recovery period lasted 30 min. Plasma growth hormone, prolactin, cortisol, catecholamine and lactate concentrations were measured at rest, during exercise and after recovery. The concentration of plasma growth hormone and catecholamine were not affected by partial sleep deprivation, whereas that of plasma prolactin was higher (P < 0.05) during the trial after an early awakening. Plasma cortisol was lower (P < 0.05) during recovery after both sleep deprivation conditions. Blood lactate was higher (P < 0.05) during submaximal exercise performed after both a delayed bedtime and an early awakening. Zolpidem-induced sleep did not affect the hormonal and metabolic responses to subsequent exercise. Our results demonstrate only minor alterations in the hormonal responses to exercise after partial sleep deprivation. 相似文献
76.
This paper reports the improvement of rectification effects in diffuser∕nozzle structures with viscoelastic fluids. Since rectification in a diffuser∕nozzle structure with Newtonian fluids is caused by inertial effects, micropumps based on this concept require a relatively high Reynolds numbers and high pumping frequencies. In applications with relatively low Reynolds numbers, anisotropic behavior can be achieved with viscoelastic effects. In our investigations, a solution of dilute polyethylene oxide was used as the viscoelastic fluid. A microfluidic device was fabricated in silicon using deep reactive ion etching. The microfluidic device consists of access ports for pressure measurement, and a series of ten diffuser∕nozzle structures. Measurements were carried out for diffuser∕nozzle structures with opening angles ranging from 15° to 60°. Flow visualization, pressure drop and diodicity of de-ionized water and the viscoelastic fluid were compared and discussed. The improvement of diodicity promises a simple pumping concept at low Reynolds numbers for lab-on-a-chip applications. 相似文献
77.
Thi Tuyet Tran 《Journal of Education & Work》2018,31(1):59-71
Literature suggests that educational attainment is one of the significant factors affecting youth transition to work. The process of capital accumulation through education is suggested as the key marker of social inclusion and exclusion. This paper compares the educational attainment among youth in Vietnam with their status in employment. It uses the data from the school-to-work transition survey of the International Labour Office with 2722 youth participants aged 15–29 in different geographical areas in Vietnam. The findings indicate that Vietnamese youth have to face many challenges when negotiating their transition to work, especially when the educational attainment of the majority youth is low. A wide gap between education and learners’ needs and interests, the economic burden many young people had to bear and the low level of development of the economy with a large proportion of the informal sector are the main reasons for youth in Vietnam to leave school early and to accept low quality work to earn their living. These problems need to be solved to help youth in Vietnam approach better jobs in the market. 相似文献
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