中学数学建模与最值问题     

蒋自国 《阿坝师范高等专科学校学报》2003,(3):106-108

讨论了如何求解中学数学中的最值问题,将中学数学中的最值问题分成若干个子类进行讨论,如利用一元单峰函数的性质、函数的值域、方程、不等式等。  相似文献   

非晶丝材料磁阻抗特性测量系统研制     

王立锦  周毛毛  龚占双  丁毅寿  李希胜  于广华 《实验技术与管理》2011,(11)

将幅频/相频分析专用集成电路芯片AD8302用于非晶丝磁阻抗特性的测量中,结合磁场自动扫描技术、计算机自动数据采集技术设计制作了磁阻抗特性测试系统,实现了非晶丝磁阻抗特性的自动化测量。该系统集样品信号驱动调理、数据采样、数据处理、参数计算等功能于一体,测试范围宽、精度高、用户界面友好。数据采集控制软件还能在计算机屏幕、打印机上绘出被测样品的磁阻抗特性曲线,并生成标准数据文件供ORIGIN等数据处理软件调用。对实际非晶丝样品进行了测试分析,效果良好。  相似文献   

Performing under pressure: Exploring the psychological state underlying clutch performance in sport     

Christian Swann  Lee Crust  Patricia Jackman  Stewart A. Vella  Mark S. Allen  Richard Keegan 《Journal of sports sciences》2017,35(23):2272-2280

Clutch performance is improved performance under pressure. However, little research has examined the psychological state experienced by athletes in these situations. Therefore, this study qualitatively examined the subjective experience underlying clutch performance across a range of sports (e.g., team, individual) and standards (Olympic to recreational athletes). Sixteen athletes (M_age = 27.08 years; SD = 6.48) took part in in-depth, semi-structured interviews primarily after an exceptional performance (M = 4.38 days later; SD = 3.14). Data were analysed inductively and thematically. Clutch states involved 12 characteristics, including heightened and deliberate concentration, intense effort, and heightened awareness, which distinguished the experience of clutch from other optimal psychological states such as flow. Other characteristics, such as perceptions of control, were also reported and supported previous experimental research on clutch. These findings present in-depth qualitative insights into the psychological state underlying clutch performance, and are discussed in relation to the existing literature on optimal psychological states in sport.  相似文献   

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

Lee P. Rylands  Simon J. Roberts  Howard T. Hurst 《European Journal of Sport Science》2017,17(2):127-131

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.  相似文献   

浅析女子蹼泳短距离技术蹼频与蹼幅之关系     

成章  彭学军 《湖北体育科技》2011,30(4):479-481

通过对第3届全国体育大会蹼泳比赛女子50m、100m蹼泳前8名运动员比赛技术数据进行分析,对现状与理论最佳值的比较,了解当今世界女子蹼泳项目优秀运动员速度、蹼频、蹼幅的变化特征。结果表明：竞技蹼泳的速度,关键取决于蹼频与蹼幅两个因素,蹼频和蹼幅可有效评价蹼泳技术能力,并能应用到各种训练中,从而提高蹼泳成绩。  相似文献   

青少年击剑运动员膝关节屈伸肌群等速肌力测试分析     

宣磊  江海魁 《安徽体育科技》2011,(5):50-53

运用文献资料法、实验法、数据统计法,对安徽省击剑队青少年运动员下肢膝关节屈伸肌群等速肌力进行分析研究,客观评价青少年与成年击剑运动员在下肢膝关节屈伸肌群力量特征方面存在的差异,同时为青少年击剑专项力量训练提供理论依据和针对性建议。  相似文献   

攀岩运动员正反握法下肘关节等速肌力及峰力矩角度研究     

杨建伟  马楚虹  尤廷明  钱永东  戴燕 《军事体育进修学院学报》2011,30(4):102-105

采用德国Isomed2000等速肌力测试系统,通过对优秀攀岩运动员左右肘关节正反两握法下的等速向心肌力及峰力矩角度的测试与分析,探讨肘关节屈伸肌群在攀岩竞技能力发展中的作用,为科学安排专项训练及预防运动损伤提供一定的理论依据。其测试结果表明：优秀攀岩运动员肘关节屈伸峰力矩（PT）随测试速度的增大而减小,峰力矩屈伸比值随...  相似文献   

光磁共振实验中干扰峰的分析及利用   总被引：1，自引：0，他引：1  

董素梅  彭跃华 《湖南科技学院学报》2008,29(4):31-33

本文分析了在光磁共振实验中用扫场法测量铷原子的因子时所产生干扰峰的形成原因,并且巧妙地利用干扰峰来计算地磁场的水平分量.  相似文献   

长春市大学女生体成分与骨密度的调查研究   总被引：1，自引：0，他引：1  

刘娜 《吉林体育学院学报》2010,26(3):81-82

研究长春市大学女生的身体成分和骨量水平,探讨骨密度的影响因素。方法：应用双能X线骨密度测定仪和体成分分析仪对长春市251名大学女生的体成分、腰椎、股骨颈和Ward’S区的骨密度进行测定。结果：相关分析显示总体重、BMI、瘦体重及体脂百分比均与骨密度呈显著正相关,相关性大小排序为：总体重〉BMI〉体脂百分比〉瘦体重;经常运动女生的腰椎、股骨颈及Ward’S区骨密度与较少运动者有显著性差异。结论：总体重可能影响女性骨骼健康;体育运动可促进形成较高的峰值骨密度,预防骨质疏松。  相似文献   

单电源宽带放大器的设计与实现     

淮文军  张进峰 《苏州市职业大学学报》2010,21(4):22-25

提出了一种采用单电源的高增益、宽带放大器.采用多个放大器阻容耦合的方式,有效改善了放大器的低频特性,提高了放大增益范围.以TI公司的低噪声电压反馈型运放OPA820ID作为首级运放电路,利用电流型运放THS3091作为末级放大电路,TPS61087DRC的DC-DC变换器作为末级运放电路供电,利用低功耗的MSP430单片机进行输出电压有效值和最大值的测量,并在LCD上实时显示.经过测试,在20 kHz～15 MHz频段上信号增益稳定、噪声小.  相似文献