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排序方式: 共有432条查询结果,搜索用时 15 毫秒
1.
为了开展液压元件溢流阀实验课教学,设计并搭建了可视化溢流阀振动测试实验平台。该实验平台不仅可以直观反映溢流阀工作中阀芯的运动变化过程,并且实时输出阀芯运动变化曲线。研究液压阀的失稳机理和颤振行为,同时对阀体关键部位采用透明设计,可以方便在线观察阀芯的振动过程。加装合适传感器便于研究不同结构、不同参数对溢流阀振动影响,为研究溢流阀工作失稳机理和阀颤振行为提供参考。 相似文献
2.
Residual categories are those which cannot be formally represented within a given classification system. We examine the forms
that residuality takes within our information systems today, and explore some silences which form around those inhabiting
particular residual categories. We argue that there is significant ethical and political work to be done in exploring residuality. 相似文献
3.
Gamma Glutamyl Transferase (γ-GT) is a microsomal enzyme. Its activity in serum is assayed in alcoholics with liver abscess
and alcoholics without liver abscess after screening by ultrasonography. The enzyme activity in serum is increased by 334%
in the patients with liver abscess compared to normal control subjects (p<0.0001), and 172% when compared to patients with
chronic alcoholism without liver abscess (p<0.0001). The enzyme activity was increased by 59.3% in the serum of patients without
liver abscess compared to the normal control subjects (p<0.001). Measurement of γ-GT in serum appears to be a sensitive index
in the diagnosis of alcoholics with liver abscess. 相似文献
4.
李根强 《科学学与科学技术管理》2016,(12):125-135
亲组织非伦理行为(unethical pro-organizational behavior,UPB)对企业声誉和社会利益造成严重危害,设法防止UPB的发生显得尤为迫切。基于组织认同理论和调节焦点理论,通过对489名企业员工进行问卷调查,研究伦理型领导对员工亲组织非伦理行为的影响机制,包括这一机制中组织认同的中介作用和特质调节焦点的调节作用,以制定相应的防范策略。结果发现:伦理型领导与UPB呈倒U型关系;组织认同在伦理型领导和UPB的关系间起中介作用;特质调节焦点调节了伦理型领导与UPB之间的倒U型关系。 相似文献
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Ana Cristina de David Felipe Pivetta Carpes Darren Stefanyshyn 《Journal of sports sciences》2015,33(4):391-397
Joint moments can be used as an indicator of joint loading and have potential application for sports performance and injury prevention. The effects of changing walking and running speeds on joint moments for the different planes of motion still are debatable. Here, we compared knee and ankle moments during walking and running at different speeds. Data were collected from 11 recreational male runners to determine knee and ankle joint moments during different conditions. Conditions include walking at a comfortable speed (self-selected pacing), fast walking (fastest speed possible), slow running (speed corresponding to 30% slower than running) and running (at 4 m · s?1 ± 10%). A different joint moment pattern was observed between walking and running. We observed a general increase in joint load for sagittal and frontal planes as speed increased, while the effects of speed were not clear in the transverse plane moments. Although differences tend to be more pronounced when gait changed from walking to running, the peak moments, in general, increased when speed increased from comfortable walking to fast walking and from slow running to running mainly in the sagittal and frontal planes. Knee flexion moment was higher in walking than in running due to larger knee extension. Results suggest caution when recommending walking over running in an attempt to reduce knee joint loading. The different effects of speed increments during walking and running should be considered with regard to the prevention of injuries and for rehabilitation purposes. 相似文献
8.
Kelly A. Mackintosh Nicola D. Ridgers Melitta A. McNarry 《Journal of sports sciences》2019,37(13):1506-1511
Physical activity (PA) is a key element in Cystic Fibrosis (CF) treatment strategies, yet little is known as to whether activity compensation occurs. This study examined whether PA and/or sedentary time on one day were temporally associated with time spent in these intensities the following day in youth with CF. Time spent sedentary and in different PA intensities were objectively-measured for seven consecutive days in 50 youth (22 boys; 12.0 ± 2.7 years); 25 with mild-to-moderate CF and 25 age- and sex-matched controls. Multilevel analyses (day and child) were conducted using generalised linear latent and mixed models. On any given day, every additional 10 minutes spent in sedentary time or moderate-to-vigorous physical activity (MVPA) were associated with 1.9 (95%CI: ?3.6 to ?1.2) and 12.4 (95%CI: ?22.1 to ?2.9) minutes less sedentary time the following day, respectively. These temporal associations were also observed when split by group (3.1 vs. 1.9 minutes for healthy and CF, respectively). These findings indicate that youth do not compensate their PA, irrespective of disease status, between days, but may compensate their sedentary time between days. Experimental studies are warranted to fully elucidate whether compensatory responses to PA and sedentary time occur, which is fundamental for informing PA promotion strategies. 相似文献
9.
杨小芳 《河北体育学院学报》2016,30(3):81-85
采用三维高速摄像技术和运动生物力学原理,对后旋踢技术身体重心移动、动作所用时间、踝关节角度、膝关节角度和髋关节角度的运动学特征进行比较分析,得出结论:踢击腿在离地瞬间身体重心要快速向回旋方向移动;踢击腿膝关节最大程度弯曲,以缩短动作时间、加快踢击速度;踢击腿髋关节只有最大程度地弯曲,弯曲的膝关节才能快速展开;踢击腿的髋关节最大程度弯曲再打开时,踝关节能快速鞭打;支撑腿弯曲后在踢击腿踢出的瞬间,髋关节开始伸展,将对打击高度产生影响;踢击腿膝关节和髋关节最大程度弯曲时能增加击打力度. 相似文献
10.
摘要:目的:以神经元和神经胶质细胞相关神经生物学变化为切入点,探讨有氧运动对慢性应激大鼠脑海马区神经可塑性的影响。方法:以SD大鼠为研究对象,按照体重均衡分为对照组(CON)、慢性应激模型组(MOD)、氟西汀组(FLU)、低强度运动组(LIR)和中等强度运动组(MIR)。给予大鼠4周慢性应激,并分别伴随氟西汀给药、低强度或者中等强度的运动干预。4周后,通过开场实验、蔗糖饮水实验、新奇抑制摄食实验以及新物体识别实验检测运动对慢性应激大鼠抑郁样行为、焦虑样行为以及认知障碍的影响;同时,利用酶联免疫法和蛋白免疫印迹法,检测运动对慢性应激大鼠血清皮质酮、海马内前炎因子IL1-β,以及蛋白GFAP、S100β、BDNF、p-ERK、p-CREB表达的影响,探讨运动抗抑郁的行为学效应和作用机制。结果:1)低强度和中等强度运动能够显著增加慢性应激大鼠的开场活动、缩短新奇抑制摄食潜伏期,同时提高慢性应激大鼠新物体的识别指数;2)运动有效逆转了慢性应激大鼠血清皮质酮的异常升高,同时降低海马内前炎性因子IL1-β的分泌;3)运动可显著星形胶质细胞的标志性功能蛋白GFAP和S100β的表达水平,增强慢性应激大鼠的BDNF/ERK/CREB信号转导通路中重要蛋白BDNF、p-ERK、p-CREB的表达。结论:运动可以通过提高慢性应激大鼠脑海马区神经可塑性来达到抗抑郁的目的。可能与以下因素有关:1)运动调节血清皮质酮的异常升高,降低海马内前炎性因子的释放,同时,提高与神经胶质细胞相关蛋白GFAP和S100β活性,从而起到神经元保护的作用;2)运动可以通过激活CREB,BDNF以及ERK等重要信号蛋白的表达,提高神经营养作用,促进神经元的生长,增加神经可塑性和神经发生来发挥抗抑郁作用。 相似文献