Energy harvesting with a slotted-cymbal transducer     

Jiang-bo Yuan  Xiao-biao Shan  Tao Xie  Wei-shan Chen 《浙江大学学报(A卷英文版)》2009,10(8):1187-1190

A cymbal transducer is made up of a piezoceramic disk sandwiched between two dome-shaped metal endcaps. High circumferential stresses caused by flexural motion of the metal endcaps can induce the loss of mechanical input energy. Finite element analysis shows that the radial slots fabricated in metal endcaps can release the circumferential stresses, and reduce the loss of mechanical input energy that could be converted into electrical energy. In this letter, the performance of a slotted-cymbal transducer in energy harvesting was tested. The results show that the output voltage and power of the cymbal are improved. A maximum output power of around 16 mW could be harvested from a cymbal with 18 cone radial slots across a 500 kΩ resistive load, which is approximately 0.6 times more than that of the original cymbal transducer.  相似文献   

Use of probabilistic and deterministic measures to identify unfavorable earthquake records     

Abbas Moustafa  Izuru Takewaki 《浙江大学学报(A卷英文版)》2009,10(5):619-634

This study introduces measures to identify resonant （concentration of energy in a single or a few frequencies） or unfavorable earthquake ground motions. Probabilistic measures based on the entropy rate and the geometric properties of the power spectral density function （PSDF） of the ground acceleration are developed first. Subsequently, deterministic measures for the frequency content of the ground acceleration are also developed. These measures are then used for identifying resonance and criticality in stochastic earthquake models and 110 acceleration records measured at rock, stiff, medium and soft soil sites. The unfavorable earthquake record for a given structure is defined as the record having a narrow frequency content and dominant frequency close to the structure fundamental natural frequency. Accordingly, the measures developed in this study may provide a basis for selecting records that are capable of producing the highest structural response. Numerical verifications are provided on damage caused to structures by identified resonant records.  相似文献   

税收优惠的节能减排效应——基于省级面板数据的实证分析   总被引：1，自引：0，他引：1  

郭存芝  孙康 《资源科学》2013,35(2):261-267

本文借助国家税务总局提供的减免税调查数据,在使用因子分析等方法测算节能减排效率的基础上,建立面板数据模型,在考虑经济发展水平、工业产业结构、R&D投入强度、出口依存度等节能减排的其他主要影响因素的同时,通过实证检验税收减免率与节能效率、减排效率、节能减排效率之间的关系,分析我国现行税收优惠政策的节能减排效应,包括总体分析、分地区分析两个方面.实证结果显示,无论是从全国总体看,还是分地区看,税收减免率与节能效率、减排效率、节能减排效率之间基本上都呈现出了正相关关系,但税收优惠对节能效率、减排效率、节能减排效率的提高的促进效应,只在90％的置信度下显著,或者不显著,没有达到在95％或99％的置信度下显著.这说明税收优惠可以在促进节能减排中发挥作用,但作用有限.究其原因,可能与税收优惠具有激励作用而不具有约束作用有关,要充分发挥税收在促进节能减排中的重要作用,需要激励性税收政策和约束性税收政策的有效结合.  相似文献   

基于能级模型的我国金属矿产资源评价     

刘金平  赵月 《资源科学》2013,35(5):977-982

针对我国金属矿产资源的开采利用量大、浪费严重和我国金属矿产资源评价模型研究匮乏等问题,本文首次提出金属矿产资源能级的概念——金属矿产资源为国民经济和社会发展提供商品或服务的能量大小.建立了基于金属矿产资源质量M、数量Q、重要程度I和技术条件T等4个指标的定量评价模型,对各指标进行细化、归一化并划分等级.以金属铁、铝、金、铜、钼、钨、锡为例的分析表明,其能级分别为1.748、1.015、1.65、1.353、2.419、2.953、2.025,能级模型可对我国所有的金属矿产资源进行能级测算和划分,从而针对不同能级的金属矿产资源采取不同的开采、管理措施,实现我国金属矿产资源的有效管理.  相似文献   

低碳发展方案编制指南(第三部分)——制定低碳发展规划     

周南  Lynn  Price  Stephanie  Ohshita  Nina  Zheng  胡敏 《科学与管理》2013,(6):62-69

本节介绍制定低碳发展计划常用的核心步骤。本指南侧重城市层面;同样的步骤也适用于企业、市、省和国家等层级。中国自"十一五规划"起,对改善国内能源强度定出目标,包括各经济部门的节能目标。2009年12月中国政府公布了其碳强度目标,重点放在单位GDP用能引发的二氧化碳排放量。为实现该强度目标以及"循环经济"等经济性目标,制定低碳发展规划尤其必要。  相似文献   

Changes in energy availability across the season in Division I female soccer players     

Jennifer L. Reed  Mary Jane De Souza 《Journal of sports sciences》2013,31(3):314-324

Abstract

Low energy availability [(energy intake – exercise expenditure)/kg lean body mass], a component of the Female Athlete Triad, has been associated with menstrual disturbances and low bone mass. No studies have examined the energy availability of athletes across a season. The purpose of this study was to assess the prevalence of, and what contributes to, low energy availability in Division I female soccer players across a season. Nineteen participants aged 18–21 years (mean [Vdot]O_2max: 57.0 ± 1.0 mL · kg^?1 · min^?1) were studied during the pre, mid, and post season. Mean energy availability was overall lowest at mid season, and lower at mid than post season (35.2 ± 3.7 vs. 44.5 ± 3.7 kcal · kg^?1 lean body mass, P = 0.009). Low energy availability (<30 kcal · kg^?1 lean body mass) was observed in 5/19 (26.3%), 5/15 (33.3%), and 2/17 (11.8%) of participants during the pre, mid, and post season. Dietary energy intake was lower mid (P = 0.008) and post season (P = 0.022) than it was pre season (pre: 2794 ± 233 kcal · day^?1; mid: 2208 ± 156 kcal · day^?1; post: 2161 ± 143 kcal · day^?1). Exercise energy expenditure decreased significantly (P ≤ 0.001) over time (pre: 819 ± 57 kcal · day^?1; mid: 642 ± 26 kcal · day^?1; post: 159 ± 28 kcal · day^?1). Low energy availability was due to lower dietary energy intake at lunch during pre season (P = 0.014) and during lunch and dinner during mid season (P ≤ 0.030). Energy availability was inversely related to body dissatisfaction (r = ?0.62, P = 0.017) and drive for thinness (r = ?0.55, P = 0.041) during mid season. Although most Division I female soccer players are not at risk for low energy availability, a concerning proportion exhibited low energy availability at pre or mid season. Further studies are needed to explore strategies to prevent and monitor low energy availability in these athletes.  相似文献   

Energy turnover during 24 hours and 6 days of adventure racing     

Jonas K. Enqvist  Patrik H. Johansson  Thibault Brink-Elfegoun  Linda Bakkman  Björn T. Ekblom 《Journal of sports sciences》2013,31(9):947-955

Abstract

Energy turnover was assessed in two conditions of mixed ultra-endurance exercise. In Study 1, energy expenditure and intake were measured in nine males in a laboratory over 24 h. In Study 2, energy expenditure was assessed in six males during an 800-km Adventure race (mean race time 152.5 h). Individual correlations between heart rate and oxygen uptake ([Vdot]O₂) were established during pre-tests when kayaking, cycling, and running. During exercise, energy expenditure was estimated from continuous heart rate recordings. Heart rate and [Vdot]O₂ were measured regularly during fixed cycling work rates to correct energy expenditure for drift in oxygen pulse. Mean energy expenditure was 18,050 ± 2,390 kcal (750 ± 100 kcal · h^?1) and 80,000 ± 18,000 kcal (500 ± 100 kcal · h^?1) in Study 1 and Study 2 respectively, which is higher than previously reported. Energy intake in Study 1 was 8,450 ± 1,160 kcal, resulting in an energy deficit of 9,590 ± 770 kcal. Body mass decreased in Study 1 (?2.3 ± 0.8 kg) but was unchanged in Study 2. Fat mass decreased in Study 2 (?2.3 ± 1.5 kg). In Study 1, muscle glycogen content decreased by only 60%. Adventure racing requires a high energy expenditure, with large inter-individual variation. A large energy deficit is caused by inadequate energy intake, possibly due to suppressed appetite and gastrointestinal problems. The oxygen pulse, comparing start to 12 h of exercise and beyond, increased by 10% and 5% in Study 1 and Study 2 respectively. Hence, estimations of energy expenditure from heart rate recordings should be corrected according to this drift.  相似文献   

Parallel assessment of nutrition and activity in athletes: Validation against doubly labelled water, 24-h urea excretion,and indirect calorimetry     

Karsten Koehler  Hans Braun  Markus De Marées  Gerhard Fusch  Christoph Fusch  Joachim Mester 《Journal of sports sciences》2013,31(13):1435-1449

Abstract

The assessment of nutrition and activity in athletes requires accurate and precise methods. The aim of this study was to validate a protocol for parallel assessment of diet and exercise against doubly labelled water, 24-h urea excretion, and respiratory gas exchange. The participants were 14 male triathletes under normal training conditions. Energy intake and doubly labelled water were weakly associated with each other (r = 0.69, standard error of estimate [SEE] = 304 kcal · day^?1). Protein intake was strongly correlated with 24-h urea (r = 0.89) but showed considerable individual variation (SEE = 0.34 g · kg^?1 · day^?1). Total energy expenditure based on recorded activities was highly correlated with doubly labelled water (r = 0.95, SEE = 195 kcal · day^?1) but was proportionally biased. During running and cycling, estimated exercise energy expenditure was highly correlated with gas exchange (running: r = 0.89, SEE = 1.6 kcal · min^?1; cycling: r = 0.95, SEE = 1.4 kcal · min^?1). High exercise energy expenditure was slightly underestimated during running. For nutrition data, variations appear too large for precise measurements in individual athletes, which is a common problem of dietary assessment methods. Despite the high correlations of total energy expenditure and exercise energy expenditure with reference methods, a correction for systematic errors is necessary for the valid estimation of energetic requirements in individual athletes.  相似文献   

Energy substrate metabolism during dual work rate exercise: Effects of order     

David Egan  Tony Head 《Journal of sports sciences》2013,31(11):889-894

Changes in workload are evident during many physical activities. The aim of this study was to assess total substrate metabolism when the temporal placement of a period of higher-intensity work (75% VO 2max ) was varied within a low-intensity exercise session (50% VO 2max ). One experimental trial (higher intensity first) comprised 5 min low-intensity work, followed by 15 min high-intensity work, followed by 40 min low-intensity work. The other trial (low intensity first) comprised 40 min low-intensity work, followed by 15 min high-intensity work, followed by 5 min low-intensity work. The trials were designed to achieve an identical total energy expenditure. Energy expenditure, fat and carbohydrate utilization were estimated by expired gas analysis and compared between conditions. Mean total energy expenditure during the higher-intensity phase was 1076 kJ and 1128 kJ in the high-intensity first and low-intensity first trials respectively (t 6 = -3.76, P = 0.0047). Mean total energy expenditure for the whole trial was 3356 kJ and 3452 kJ in the high-intensity first and low-intensity first trials respectively (t 6 = -3.48, P = 0.0065). Mean whole-trial fat utilization was 1753 kJ and 1857 kJ in the high-intensity first and low-intensity first trials respectively (t 6 = -0.76, P = 0.24). Our findings suggest that changing the temporal placement of higher-intensity work within a low-intensity exercise session has a significant effect on total energy expenditure but not on the rate of fat oxidation.  相似文献   

我国新能源和可再生能源CDM项目发展问题与对策研究     

杨锦琦 《科技广场》2013,(8):126-134

本文根据我国清洁机制发展网发布的信息,对我国新能源和可再生能源CDM项目的开发、项目分布等情况进行了归类统计,并且分析了项目发展中存在的问题及未来发展潜力,提出项目发展的对策。  相似文献