地效飞行器动力增升系统安装位置的实验研究

本文通过模型实验研究了动力增升系统的安装位置对典型地效飞行器静态推力恢复和静态升力的影响,进而研究了改变动力增升系统的安装位置后,飞行器起飞距离、起飞速度和升力系数的变化,并探讨了主翼端板对上述实验结果的影响。实验结果证明,设计合理的动力增升系统能够在保持地效飞行器纵向稳定性的同时能有效改善起飞性能。     

数字化电源功率因数校正器的设计

本文以单相功率因数校正器（PFC）为对象讨论了如何设计数字电源,重要的是讨论了单相PFC的小信号模型,在这个基础上阐明了电源双环控制的组成,详细讨论了设计控制器的方法,完善了从小信号建模等理论直到完成整个数字化电源控制的过程,并对具体的工程技术问题给出了具体的分析手段和可操作的解决方法。     

“李森科”事件再思考

随着前苏联国内部分档案材料的解密和最新研究,＂李森科＂事件的来龙去脉变得越来越清晰。从表面上看,整个事件的发生是由于国家权力的滥用所致,实质上这一事件的产生除了由于李森科本人趁机利用当时的国内政治形势和意识形态状况达到个人目的外,科学家自身立场的摇摆不定和前苏联国内科技管理的纷乱,是李森科事件发生和兴起的根本原因。     

Temporal specificity of training: intra-day effects on biochemical responses and Olympic-Weightlifting performances

The aim of this study was to investigate the performance of an Olympic-Weightlifting session training at three times of the day on the performance related to biochemical responses. Nine weightlifters (21 ± 0.5 years) performed, in randomised order, on three Olympic-Weightlifting training (snatch, clean and jerk) sessions (08:00 a.m., 02:00 p. m., 06:00 p. m.). Blood samples were collected: before, 3 min and 48 h after each training session. Haematological parameters and markers of muscle injury were assessed. Resting oral temperature and rating of perceived exertion (RPE) were also assessed during each session. ANOVA showed that the performance was better (P < 0.001) at 02:00 p. m. with a less RPE (P < 0.01) compared to the morning and the evening sessions while there was higher (P < 0.05) oral temperature at 06:00 p. m. versus 08:00 a.m. and 02:00 p. m. Muscle damage changed immediately (without significant effect after 48 h) after the training sessions with lower values ??in the evening compared to the morning. In conclusion, the afternoon training is more effective than morning or evening sessions for weightlifters. Therefore, coaches and weightlifters should be advised to schedule their training session in the afternoon hour.     

公司重整管理人的法律地位与权责研究——从公司控制权的角度展开

公司重整时期对公司事务的控制权从董事会向重整管理人转移,明确重整管理人的法律地位和权责对正确适用相关法律规则具有积极意义。由于重整制度价值目标的多元性,管理人不是对债权人会议负责的机构,也不是债权人的利益代表,而应当是一个中立的机构。在债务人自行管理和管理人管理的不同情形下,重整管理人具有不同的角色和职权,但总体上管理人都应承担起信息披露义务、中立义务、忠实义务和勤勉义务,对违反义务者可参照董事责任进行追究。     

FTU技术在公路建设供电电网中的应用分析

在对公路建设用电供电电网负荷变化情况调查的基础上,基于柔性输电理论,分析在供电电网中适时采用FTU技术,提高供电质量和供电可靠性的必要性及可行性,提出解决公路建设用电的具体实施方案,为公路建设供电改造提出决策依据.     

Effect of gear ratio on peak power and time to peak power in BMX cyclists

The aim of this study was to ascertain if gear ratio selection would have an effect on peak power and time to peak power production in elite Bicycle Motocross (BMX) cyclists. Eight male elite BMX riders volunteered for the study. Each rider performed three, 10-s maximal sprints on an Olympic standard indoor BMX track. The riders’ bicycles were fitted with a portable SRM power meter. Each rider performed the three sprints using gear ratios of 41/16, 43/16 and 45/16 tooth. The results from the 41/16 and 45/16 gear ratios were compared to the current standard 43/16 gear ratio. Statistically, significant differences were found between the gear ratios for peak power (F(2,14)?=?6.448; p?=?.010) and peak torque (F(2,14)?=?4.777; p?=?.026), but no significant difference was found for time to peak power (F(2,14)?=?0.200; p?=?.821). When comparing gear ratios, the results showed a 45/16 gear ratio elicited the highest peak power,1658?±?221?W, compared to 1436?±?129?W and 1380?±?56?W, for the 43/16 and 41/16 ratios, respectively. The time to peak power showed a 41/16 tooth gear ratio attained peak power in ?0.01?s and a 45/16 in 0.22?s compared to the 43/16. The findings of this study suggest that gear ratio choice has a significant effect on peak power production, though time to peak power output is not significantly affected. Therefore, selecting a higher gear ratio results in riders attaining higher power outputs without reducing their start time.     

Assessment of leg muscles mechanical capacities: Which jump,loading, and variable type provide the most reliable outcomes?

This study aimed to explore the strength of the force–velocity (F–V) relationship of lower limb muscles and the reliability of its parameters (maximum force [F₀], slope [a], maximum velocity [V₀], and maximum power [P₀]). Twenty-three men were tested in two different jump types (squat and countermovement jump: SJ and CMJ), performed under two different loading conditions (free weight and Smith machine: Free and Smith) with 0, 17, 30, 45, 60, and 75?kg loads. The maximum and averaged values of F and V were obtained for the F–V relationship modelling. All F–V relationships were strong and linear independently whether observed from the averaged across the participants (r?≥?0.98) or individual data (r?=?0.94–0.98), while their parameters were generally highly reliable (F₀ [CV: 4.85%, ICC: 0.87], V₀ [CV: 6.10%, ICC: 0.82], a [CV: 10.5%, ICC: 0.81], and P₀ [CV: 3.5%, ICC: 0.93]). Both the strength of the F–V relationships and the reliability of their parameters were significantly higher for (1) the CMJ over the SJ, (2) the Free over the Smith loading type, and (3) the maximum over the averaged F and V variables. In conclusion, although the F–V relationships obtained from all the jumps tested were linear and generally highly reliable, the less appropriate choice for testing the F–V relationship could be through the averaged F and V data obtained from the SJ performed either in a Free weight or in a Smith machine. Insubstantial differences exist among the other combinations tested.     

Sports’ disciplinary legacy and the challenge of ‘coaching differently’

Be empowering. Be athlete-centered. Be autonomy supportive. These are three related topics currently being promoted by sport psychologists and sport pedagogists in an effort to recognize athletes’ unique qualities and developmental differences and make coaching more holistic and coaches more considerate. This has led us to ask, how likely are such initiatives to lead to coaches putting their athletes at the center of the coaching process given that coaches’ practices have largely been formed through relations of power that subordinate and objectify athletes’ bodies through the regular application of a range of disciplinary techniques and instruments [e.g. Barker-Ruchti, N., &; Tinning, R. (2010). Foucault in leotards: Corporeal discipline in women's artistic gymnastics. Sociology of Sport Journal, 27, 229–250; Heikkala, J. (1993). Discipline and excel: Techniques of the self and body and the logic of competing. Sociology of Sport Journal, 10, 397–412; Gearity, B., &; Mills, J. P. (2012). Discipline and punish in the weight room. Sports Coaching Review, 1, 124–134]? In other words, to try to develop athlete-centered coaches capable of coaching in ways that will empower their athletes without also problematizing the discursive formation of coaches’ practices concerns us [Denison, J., &; Mills, J. P. (2014). Planning for distance running: Coaching with Foucault. Sports Coaching Review, 3, 1–16]. Put differently: how can athlete empowerment initiatives be anything more than rhetoric within a disciplinary framework that normalizes maximum coach control? It is this question that we intend to explore in this paper. More specifically, as Foucauldians, we will argue that coaching with greater consideration for athletes’ unique qualities and developmental differences needs to entail coaching in a less disciplinary way and with an awareness and appreciation of the many unseen effects that disciplinary power can have on coaches’ practices and athletes’ bodies.     

Optimal sampling frequency in recording of resistance training exercises

The purpose of this study was to analyse the raw lifting speed collected during four different resistance training exercises to assess the optimal sampling frequency. Eight physically active participants performed sets of Squat Jumps, Countermovement Jumps, Squats and Bench Presses at a maximal lifting speed. A linear encoder was used to measure the instantaneous speed at a 200 Hz sampling rate. Subsequently, the power spectrum of the signal was computed by evaluating its Discrete Fourier Transform. The sampling frequency needed to reconstruct the signals with an error of less than 0.1% was f_99.9 = 11.615 ± 2.680 Hz for the exercise exhibiting the largest bandwidth, with the absolute highest individual value being 17.467 Hz. There was no difference between sets in any of the exercises. Using the closest integer sampling frequency value (25 Hz) yielded a reconstruction of the signal up to 99.975 ± 0.025% of its total in the worst case. In conclusion, a sampling rate of 25 Hz or above is more than adequate to record raw speed data and compute power during resistance training exercises, even under the most extreme circumstances during explosive exercises. Higher sampling frequencies provide no increase in the recording precision and may instead have adverse effects on the overall data quality.