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排序方式: 共有173条查询结果,搜索用时 296 毫秒
81.
孙济洲 《天津大学学报(英文版)》2002,8(3):178-182
对利用网络资源解决复杂且耗时的计算问题做了尝试 .选择典型的粒子跟踪整体光照计算问题作为研究对象 ,提出一种改进的且充分发掘其内在相关特性的密度估计算法 .在以太网连接的多台微机上 ,以PVM (并行虚拟机 )机制实现了该算法的并行计算 .通过对各项运算性能指标的测试与分析 ,结果显示可获得良好的加速比 ,并且PVM在分布式网络并行计算上将有很好的应用前景 相似文献
82.
Li Niu Joshua Brown Lindsay Till Hoyt Anthony Salandy Anne Nucci-Sack Viswanathan Shankar Robert D. Burk Nicolas F. Schlecht Angela Diaz 《Child development》2021,92(4):1421-1438
This study examines associations between childhood maltreatment and developmental trajectories of sexual risk behaviors (SRBs) in a sample of 882 sexually active adolescent girls, predominantly Hispanic or Black, assessed every 6 months between 13 and 23 years. Latent profile analyses revealed four distinct maltreatment profiles: Low Maltreatment (76%), Moderate Emotional Neglect Only (15%), Severe Physical/Emotional Abuse (3%), and Severe Sexual Abuse (6%). Multilevel growth analyses showed the Moderate Emotional Neglect Only and Severe Sexual Abuse profiles exhibited more SRBs starting in late adolescence, and the Severe Sexual Abuse profile also exhibited a faster increase than the Low Maltreatment profile. Understanding heterogeneity within maltreated populations may have important implications for healthy sexual development. 相似文献
83.
Jean Slawinski Nicolas Houel Alice Bonnefoy-Mazure Kevin Lissajoux Valery Bocquet Nicolas Termoz 《Journal of sports sciences》2017,35(9):858-865
The aim of this study was to compare the kinetic and kinematic parameters of standing and crouch sprint starts. Parallel starts (PS), false starts (FS), jump starts (JS) and crouch starts (3PS) were compared. Eighteen participants performed each start on a force plate and six infrared cameras captured the three-dimensional coordinates of 36 retro-reflective markers. Performance during a five-metre sprint (T5m) was analysed. Duration of the start phase (Tstart), mean values of horizontal and total ground reaction forces (GRFs) (Fx_mean and Ftot_mean), ratio of force (RF), maximal power (Pmax) and kinetic energy (KE) of each limb were calculated. Significant differences were found for T5m, Tstart, KE, Pmax, Fx_mean, Ftot_mean and RF for the crouch start compared to the other starts (P ≤ 0.05). Significant correlations were found between T5m and Tstart (r = 0.59; P ≤ 0.001), and T5m and Pmax, Fx_mean and RF (?0.73 ≤ r ≤ ?0.61; P ≤ 0.001). To conclude, the crouch start resulted in the best performance because Tstart was shorter, producing greater Pmax, Fx_mean with a more forward orientation of the resultant force. Greater KE of the trunk in each start condition demonstrated the role of the trunk in generating forward translation of the centre of mass (CM). 相似文献
84.
Mark A. Williams Julian D. Ward Paul Ward Nicolas J. Smeeton 《Research quarterly for exercise and sport》2013,84(3):428-433
Abstract Initial performance, final performance, and the amount of learning in 50 trials of the rho test motor performance task were obtained on 120 boys and girls, aged 10 and 14. Initial and final performance showed significant age, sex, and age w/i sex differences. The amount of learning showed no differences. 相似文献
85.
Digital piracy, although negatively altering the recorded music market, has a positive impact on other segments of the music market, such as live music or ancillary goods, because it generates a positive externality benefiting those activities. Through a 2-player strategic game between a record company and an artist, this study shows that a renegotiation of music contracts could allow the internalizing of this positive externality, while being welfare-improving for both record companies and artists. This study also shows, however, that pervasive piracy is not desirable for an artist. 相似文献
86.
87.
The main aim of this study was to examine mediating effects in the relationships between cohesion, collective efficacy and performance in professional basketball teams. A secondary aim was to examine the correlates of collective efficacy in a professional sport. A total of 154 French and foreign professional players completed French or English versions of questionnaires about cohesion and collective efficacy. Two composite measures of individual performance were used (pre- and post-performance). Individual-level analyses were performed. Regression analyses supported two mediating relationships with collective efficacy as a mediator of the pre-performance - Group integration-task relationship, and Group integration-task as a mediator of the pre-performance - collective efficacy relationship. Statistical analyses indicated that neither Group integration-task nor collective efficacy was a better mediator in the relationship between pre-performance and the other group variables. Results also revealed positive relationships between three dimensions of cohesion (i.e. Individual attractions to the group-task, Group integration-task, Group integration-social) and collective efficacy. These findings suggest that in professional basketball teams, staff members should look after athletes who perform at a lower or below their usual level because their performances might lead them into a downward cohesion - collective efficacy spiral. Staff members should also develop a high quality of group functioning, both on and off the basketball court, given its relationship with collective efficacy. 相似文献
88.
This experiment was designed to investigate whether and how decreasing the amount of attentional focus invested in postural control could affect bipedal postural control. Twelve participants were asked to stand upright as immobile as possible on a force platform in one control condition and one cognitive condition. In the latter condition, they performed a short-term digit-span memory task. Decreased center-of-gravity displacements and decreased center-of-foot-pressure displacements minus center-of-gravity displacements were observed in the cognitive condition relative to the control condition. These results suggest that shifting the attentional focus away from postural control by executing a concurrent attention-demanding task could increase postural performance and postural efficiency. 相似文献
89.
90.