超超临界机组机炉协调系统的min-max模糊模型预测跟踪控制

为了提高非线性超超临界火电机组的控制性能,提出了一种改进的min-max模糊模型预测跟踪控制.首先,建立了 T-S模糊模型来近似非线性机炉协调系统的动态特性.然后,基于包含状态变量和输出变量的扩展模糊模型,在保证闭环系统稳定性和输入在给定约束的同时,推导了 min-max模糊模型预测跟踪控制用于输出调节.为了获得更大的...     

Association of daily sitting time and leisure-time physical activity with body fat among U.S. adults

Background:Prolonged sitting and reduced physical activity lead to low energy expenditures.However,little is known about the joint impact of daily sitting time and physical activity on body fat distribution.We investigated the independent and joint associations of daily sitting time and physical activity with body fat among adults.Methods:This was a cross-sectional analysis of U.S.nationally representative data from the National Health and Nutrition Examination Survey2011-2018 among adults aged ...     

Epidemiology of insertional and midportion Achilles tendinopathy in runners:A prospective cohort study

Background:Achilles tendinopathy(AT) is a common problem among runners.There is only limited evidence for risk factors for AT,and most studies have not defined the AT subcategories.No study has compared the incidence and risk factors between insertional AT and midportion AT,though they are considered distinct.This study aimed to assess incidence and risk factors of AT based on data from a large prospective cohort.The secondary aim was to explore differences in risk factors between insertional an...     

五位拳坛巨星的拳击哲学

拳击是一项很特别的运动。一方面,任何人都可以学习拳击。另一方面,只有极少数的人才能达到卓越的水平。立志要成为冠军的人,为了寻求技术上的提高,会日复一日在训练馆里挥汗如雨,同一个动作重复成千上万次,直到达到完美。从这个角度上来说,拳击能够帮你探测身体和意志上的极限。纵观拳击的历史,有许多已经到达巅峰的传奇人物。     

我在马来西亚看到的羽毛球

这里是马来西亚紫色联盟最著名的俱乐部——八打灵羽毛球娱乐部,日本队首次拿到汤姆斯杯的功臣田児贤一退役后,也加盟到这里,做教练兼球员。我也不知道他吃了什么,居然胖成这样,人很nice,只是他一口马来口音的英语让我有点儿猝不及防。俱乐部楼道墙上挂起来的比赛服见证了俱乐部的发展,如果说都认识,这一定是暴露年龄的行为了。     

商品个性标志的定义及其在美国流行文化中的角色

在过去的一个多世纪,商品的个性标志一直是美国人钟爱的广告工具。各种各样被广告商作为传播体系的＂会说话的动物＂和＂会跳舞的产品＂已悄无声息地蔓延在美国的流行文化中。1982年,有人在做调查后发现,凡是商品特征明显的广告,在改变品牌偏好的能力上要比同行业其他品牌强。这一点表明社会正在接收商品个性标志这样的讯息。然而,尽管商品个性标志的运用在广告商和消费者中大受欢迎,却几乎被完全遗忘在广告和流行文化研究的角落。本文将从相关文学的角度解析什么是商品个性标志,以及其如何运用在现代广告业中,并与消费者进行交流。     

Evaluating effects of atmospheric CO2 on stability of global climate: a cell-to-cell mapping approach

Atmospheric carbon dioxide concentration [CO2], incoming solar radiation and sea ice coverage are among the most important factors that control the global climate. By applying the simple cell-to-cell mapping technique to a simplified atmosphere-ocean-sea ice feedback climate model, effects of these factors on the stability of the climatic system are studied. The current climatic system is found to be stable but highly nonlinear. The resiliency of stability increases with [CO2] to a summit when [CO2] reaches 290 μL/L which is comparable to the pre-industrial level, suggesting carbon dioxide is essential to the stability of the global climate. With [CO2] rising further, the global climate stability decreases, the mean ocean temperature goes up and the sea ice coverage shrinks in the polar region. When the incoming solar radiation is intensified, the ice coverage gradually diminishes, but the mean ocean temperature remains relatively constant. Overall, our analysis suggests that at the current levels of three external factors the stability of global climate is highly resilient. However, there exists a possibility of extreme states of climate, such as a snow-ball earth and an ice-free earth.     

美国世界一流大学经费支出研究及启示

本文运用固定效应模型,分析近十年美国公立世界一流大学的经费支出数据。研究发现:美国一流公立大学中教学科研经费是主要支出;经费总支出与一流大学的排名没有显著相关性,但部分经费支出对大学排名有显著影响。对于无医院服务支出的高校,公共服务支出与大学排名显著正相关;对于有医院服务支出的高校,辅助经营支出的增加有助于大学排名的提升,公共服务支出的影响却相反。因此,提高经费使用效率比增加总额更为重要。我国“双一流”建设高校应该革新经费支出配置理念,建立科学有效的经费配置体系,增大学校各类服务支出。     

Maximizing recovery time between knock-out races improves sprint cross-country skiing performance

Background:In a sprint cross-country(XC)ski competition,the difference in recovery times separating the first and the second semi-final(SF)heats from the final(F)may affect performance.The aim of the current study was to compare the effects of longer vs.shorter recovery periods prescribed between the 3 knock-out races of a simulated sprint XC ski competition involving a prologue(P),quarter-final(QF),SF,and F.Methods:Eleven well-trained XC ski athletes completed 2 simulated sprint XC ski competitions on a treadmill involving 4×883-m roller-ski bouts at a 4°incline using the gear 3 ski-skating sub-technique.The first 3 bouts were completed at a fixed speed(PFIX,QFFIX,and SFFIX)corresponding to~96%of each individual’s previously determined maximal effort.The final bout was performed as a self-paced sprint time trial(FSTT).Test conditions differed by the time durations prescribed between the QFFIX,SFFIX,and FSTT,which simulated real-world XC ski competition conditions using maximum(MAX-REC)or minimum(MIN-REC)recovery periods.Results:The FSTT was completed 5.4±5.5 s faster(p=0.009)during MAX-REC(179.2±18.1 s)compared to MIN-REC(184.6±20.0 s),and this was linked to a significantly higher power output(p=0.010)and total metabolic rate(p=0.009).The pre FSTT blood lactate(BLa)concentration was significantly lower during MAX-REC compared to MIN-REC(2.5±0.8 mmol/L vs.3.6±1.6 mmol/L,respectively;p=0.027),and the pre-to-post FSTT increase in BLa was greater(8.8±2.1 mmol/L vs.7.1±2.3 mmol/L,respectively;p=0.024).No other differences for MAX-REC vs.MIN-REC reached significance(p>0.05).Conclusion:Performance in a group of well-trained XC skiers is negatively affected when recovery times between sprint heats are minimized which,in competition conditions,would occur when selecting the last QF heat.This result is combined with a higher pre-race BLa concentration and a reduced rise in BLa concentration under shorter recovery conditions.These findings may help inform decision making when XC skiers are faced with selecting a QF heat within a sprint competition.     

游戏陪练:并不那么灰色的"另类玩家"职业生活

游戏陪练陪玩是近些年来伴随着电子竞技的兴起,而快速发展起来的一个电竞周边产业.游戏陪练的运作方式,一般是消费玩家通过线上或者线下,缴纳一定的费用(通常采用按时计价方式),获得与相关陪练人员一同玩游戏的机会.