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131.
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
132.
丁见民 《福建师范大学学报(哲学社会科学版)》2009,(4)
"红种人权力"运动作为美国印第安人历史上的重大事件之一,并非仅具有象征性作用,而是产生了重大影响,推动印第安人族裔意识的勃兴.这主要表现在三个方面:一是推动印第安人在1960-1970年代广泛开展泛印第安人抗议运动;二是全国性土著组织如雨后春笋般纷纷建立;三是激发了印第安人个体的族裔认同感和民族自豪感.所有这些又进一步促使土著民族自治运动以星火燎原之势在全国范围内迅速展开. 相似文献
133.
王华 《包头职业技术学院学报》2012,(2):53-54,63
分析历年来包头供电局近年在预防输电线路外力破坏过程中存在的输电线路遭受外力破坏的几种类型及原因,总结防范输电线路的相关经验,提出有效防治的措施。 相似文献
134.
Vassilios Gourgoulis Nickos Aggelousis Giorgos Mavromatis Athanasios Garas 《Journal of sports sciences》2013,31(8):643-652
We investigated the linear kinematics and the change in energy of the barbell and the angular kinematics of the trunk and leg during the snatch technique of 12 elite male Greek weightlifters under competitive conditions after the new weight classification. Two S-VHS cameras operating at 60 Hz were used to record the lifts. The spatial coordinates of selected points were calculated using the direct linear transformation procedure; after digital filtering of the raw data, the angular displacements and angular velocities were calculated for the hip, knee and ankle joints. The following variables were also calculated for the barbell: vertical and horizontal displacement, vertical linear velocity and acceleration, external mechanical work and power output. The results revealed that all weightlifters flexed their knees during the transition phase, independently of their weight category. This indicates that the athletes use the elastic energy produced during the stretch–shortening cycle to enhance their performance. In nine athletes, we found that the barbell trajectory did not cross a vertical reference line that passed through the initial position of the barbell. The vertical linear velocity of the barbell was increased continuously from the beginning of the movement until the second maximum extension of the knee joint, with no notable dip being observed. Regarding the change in energy of the barbell, we found that the mechanical work for the vertical displacement of the barbell in the first pull was significantly greater than the mechanical work in the second pull. In contrast, the estimated average mechanical power output of the athletes during the vertical displacement of the barbell was significantly greater in the second pull than in the first pull. We conclude that the major elements of the snatch technique of elite Greek weightlifters have not been aff ected by the new weight classification. 相似文献
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为提高设备检修效率,减少检修成本,提高检修质量,对当前本单位机械动力设备检修存在的问题,从设备检修管理、安全效益角度出发,做一个系统的反思,并探究设备检修管理的理念及方式方法,采取多种措施切实提高检修管理水平和检修质量。 相似文献
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This paper contributes to sport, sociology and the body literature by exploring the ‘exposure and effect’ of culture, in particular bodily practices placed on three adolescent swimmers immersed in the Australian swimming culture using an ethnographic framework. The research reported is particularly notable as it addresses two distinct time points in the swimmers’ lives. The first section explores the adolescent experiences of three female swimmers within the cultural context of Australian swimming by articulating some of the specific body practices and ‘memes’ (ideas, symbols and practices) that they were exposed to and/or engaged within relation to the body. The second section of this paper focuses on the same three swimmers in the ‘present day’, some 10–30 years after being immersed in the Australian swimming culture as adolescents. It excavates their body practices and the relationships they now have with their body, and thus pursues the sustained impact of the body practices and ‘memes’ they were exposed to as adolescents. Analysis employs concepts drawn mainly from Foucault, particularly his thesis in regard to ‘disciplinary power’, ‘regulation’ ‘classification’ and ‘surveillance’. At a club (amateur) and National level, Australian swimming is revealed as an institution, a site and culture where particular techniques of power have become concentrated and have been brought to bear on individuals in systematic ways, with sometimes damaging effects arising for athletes’ long-term health and well-being, particularly if the individuals concerned continue to engage with cultural practices in regard to the body post-career. 相似文献