Bar velocities capable of optimising the muscle power in strength-power exercises

This study aimed at testing whether there are mean propulsive velocities (MPVs) capable of maximising the mean propulsive power (MPP) during the execution of bench press (BP), bench throw (BT), half squat (HS) and jump squat (JS). Additionally, we assessed the differences in MPP/MPV between ballistic and traditional exercises. Seventeen male rugby sevens players performed MPP tests in BP, BT, HS and JS and maximum isometric force (MIF) tests in HS and BP. The JS presented higher MPP (977.4 ± 156.2 W) than the HS (897.9 ± 157.7 W) (P < 0.05); the BP (743.4 ± 100.1 W) presented higher MPP than the BT (697.8 ± 70.4 W) (P < 0.05). Ballistic exercises presented higher optimum MPV (JS = 1.02 ± 0.07 m·s^?1; BT = 1.67 ± 0.15 m·s^?1) than traditional exercises (HS = 0.93 ± 0.08 m·s^?1; BP = 1.40 ± 0.13 m·s^?1) (P < 0.05). The optimum MPP in the JS, BT, HS and BP occurred at 28.2 ± 5.79, 23.3 ± 4.24, 32.4 ± 9.46 and 27.7 ± 5.33% of the MIF, respectively. The coefficient of variation (CV) of MPV at optimum MPP ranged from 7.4% to 9.7%, while the CV of %MIF ranged from 18.2% to 29.2%. The MPV is a more precise indicator of the optimum loads than the percentages of MIF due to its low inter-subject variability as expressed by CV. Therefore, MPV can be used to determine the optimum power load in the four investigated exercises.     

动态称重技术问题的分析与研究

根据目前动态称重技术现状以及经济发展对动态称重的要求,通过深入分析车辆的动力荷载、称重系统的动力学模型以及新的计量方法的探讨,提出了一种基于称重系统参数估值的动态称重计量方法。仿真结果表明该方法可以充分利用称重系统的动态信息求得称重数据的稳态值。     

通过语音强化训练提高听力理解的实验研究

听力是英语学习的重点和难点。听力课堂不仅要解决"听什么",更要解决"怎么听"的问题。通过分析传统的"听录音—检查练习—听录音"模式的不足,提出有针对性的"听录音—语音训练—听录音"模式,通过实验研究尝试解决新生听音障碍,提高听力的有效方法。     

Experimental study of lightweight aggregate concrete under multiaxial stresses

Lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) and plate specimens (100 mm×100 mm×50 mm) were tested under biaxial compression-compression (CC) and compression-tension (CT) load combinations. For comparison, normal concrete plate specimens (100 mm×100 mm×50 mm) were tested under the same load combinations. Based on the test results, a two-level strength criterion of lightweight aggregate concrete in both octahedral stress coordinate and principal stress coordinate was suggested. The lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) were then tested under triaxial compression-compression-compression (CCC) load combination with corresponding tests on normal concrete cube specimens (100 mm×100 mm×100 mm). The effect of intermediate principal stress on triaxial compressive strength is further examined. A "plastic flow plateau" area was apparent in principal compressive stress-strain relationships of lightweight aggregate concrete but not in normal concrete. A quadratic formula was suggested for the expression of strength criterion under triaxial compression.     

冗余系统切换输出扰动问题的研究——ControlLogix冗余系统应用解决方案

冗余系统切换时发生输出扰动,对控制现场危害很大,引起的原因可能是网络硬件组态,也可能是程序运行结果,文章主要列举了冗余切换输出扰动的引起原因及解决方案.     

Performance of biotrickling filters for hydrogen sulfide removal under starvation and shock loads conditions

In the industrial operation of biotrickling filters for hydrogen sulfide (H₂S) removal, shock loads or starvation was common due to process variations or equipment malfunctions. In this study, effects of starvation and shock loads on the performance of biotrickling filters for H₂S removal were investigated. Four experiments were conducted to evaluate the changes of biomass and viable bacteria numbers in the biotrickling filters during a 24-d starvation. Compared to biomass, viable bacteria numbers decreased significantly during the starvation, especially when airflow was maintained in the absence of spray liquid. During the subsequent re-acclimation, all the bioreactors could resume high removal efficiencies within 4 d regardless of the previous starvation conditions. The results show that the re-acclimation time, in the case of biotrickling filters for H₂S removal, is mainly controlled by viable H₂S oxidizing bacteria numbers. On the other hand, the biotrickling filters can protect against shock loads in inlet fluctuating H₂S concentration after resuming normal operation. When the biotrickling filters were supplied with H₂S at an input of lower than 1700 mg/m³, their removal efficiencies were nearly 98% regardless of previous H₂S input. Project supported by the Foundation for Society Development of Jilin Province (No. 20080412-1), the Education Research Foundation for Science and Technology Development of Jilin Province, and the Foundation for Doctor Research in Northeast Dianli University of Jilin Province (No. BSJXM-200710), China     

落地式高耸三面广告牌面板风压系数取值探讨

为准确计算正三角形广告牌面板上的风荷载,对比了《户外广告设施钢结构技术规程》（CECS148：2003）和《建筑结构荷载规范》（GB50009-2012）中关于三面广告牌面板风载体型系数的取值和计算方法,并与正三角形三面广告牌的仿真分析结果进行比较,发现在不同的风向角下《户外广告设施钢结构技术规程》（CECS148：2003）规定的风载体型系数最小,而仿真分析得到的风荷载压力系数最大。为保证结构的安全,基于仿真分析的结果,给出了三面广告牌风载体型系数建议值;同时考虑到风荷载的非平稳性和随机性,引入风荷载的偏心距系数,为落地式三面广告牌的设计提供参考。     

基于车辙发展分析的高速公路沥青路面养护措施的费用-效益研究(英文)

为了调查江苏省各种路面养护措施的费用-效益,对路面管理系统的养护历史资料、交通轴载信息、路面性能的数据进行观察和分析.与增长模型、线性模型、对数模型和指数模型相比,立方模型具有更高的回归精度,能够捕捉路面性能衰退曲线,因此采用立方模型来模拟路面车辙的发展.计算效益费用比来定量评价路面养护措施的费用-效益.研究结果表明,在中、低交通条件下,热拌沥青薄层罩面和微表处比其他养护措施的费用-效益更大;在重、特重交通高速公路上,热再生和厚热沥青罩面具有更长的使用寿命和更大的费用-效益.     

血清肌酸激酶的运动训练负荷监控作用研究述评

综述了近年来有关肌酸激酶在运动训练过程中变化情况的研究.肌酸激酶（CK）是运动训练过程中变化比较敏感的指标之一,无论是大强度还是低强度的训练,都会使血清中肌酸激酶的活性产生不同程度的增高.在运动训练实践和运动生理生化研究中,血清肌酸激酶是评定训练负荷最敏感的指标之一,可以用来进行训练负荷的监控.     

谈高运动负荷状态下短跑训练中恢复的效用与影响

随着现代短跑竞技运动水平的不断提高,比赛的激烈对抗和赛事的日益频繁,对运动员连续承受大负荷比赛与训练提出了越来越高的要求,大强度训练已成为当代高水平短跑运动员的重要体能训练特点。训练负荷的安排是以强度作为训练负荷的灵魂,但值得注意的是,训练负荷的增大须在完善恢复措施的保障下进行,恢复是高质量训练的保证也是训练的延续。因此如何科学地把握短跑的训练过程,以实现训练效益的最大化,就必然成为训练研究的重要任务之一。