城市道路交通信号实时优化控制模型     

牛华伟  兰奇逊 《四川教育学院学报》2010,26(7):107-109

针对单点信号交叉口的交通情况,构造了一种产生交通流序列的方法,同时提出一种使车辆延误最小的单路口多相位信号实时配时模型。对所产生的交通流,制定了简单的实时信号配时方案。最后对结论进行了一定的分析和总结。  相似文献   

Suburban legend: School cutoff dates and the timing of births     

Stacy Dickert-Conlin  Todd Elder 《Economics of Education Review》2010

Many states require children to reach age 5 by a specified date in the calendar year in order to begin kindergarten. We use birth certificate records from 1999 to 2004 to assess whether parents systematically time childbirth before these eligibility cutoff dates to capture the option value of sending their child to school at a relatively young age, thereby avoiding a year of child care costs. Testing for discontinuities in the distribution of births around cutoff dates, we find no evidence that the option value influences the timing of birth. Similarly, we find no systematic discontinuities in average mothers’ characteristics or babies’ health outcomes around cutoff dates. Timing in the neighborhood of eligibility cutoffs occurs only when the cutoffs coincide with weekends or holidays, which may have implications for recent research that assumes birth dates in the neighborhood of cutoffs are essentially randomly assigned.  相似文献   

运动训练时间信息的分类与调控   总被引：1，自引：0，他引：1  

李波 《西安体育学院学报》2005,22(2):81-85,90

以时间学理论为基础, 将运动训练时间学作为一个系统进行研究, 对运动训练时间信息的概念、特性进行了分析, 并根据运动训练实际进行了细致的分类。同时探讨了运动训练时间系统调控的原理、调控的主要内容及相关的概念、具体分类及规律, 并对调控的具体方法、方式进行了较为系统地研究。  相似文献   

碳交易机制下造林碳汇项目投资时机与投资期权价值分析   总被引：1，自引：0，他引：1  

曹先磊 《资源科学》2020,42(5):825-839

碳交易试点机制可为造林碳汇项目投资提供额外资金支持。但是,在该机制下造林碳汇项目的顺利开展仍面临着较大的经济政策不确定性。充分考虑上述特征,从投资者视角揭示造林碳汇项目投资时机临界阈值和投资的期权价值,可为造林碳汇项目投资者的最优决策和政府推动造林碳汇项目投资的政策制定提供更全面的参考。为此,基于实物期权最优投资时机选择理论,利用Faustmann-Hartman模型测度造林碳汇项目价值,运用动态规划法求解造林碳汇项目在项目前期规划备案阶段和项目建设阶段最优投资时机临界阈值和投资期权价值的解析表达式,并以湿地松为例,对造林碳汇项目最优投资时机临界阈值及投资期权价值进行了实证与模拟分析。研究发现：①湿地松造林碳汇项目在项目前期规划备案阶段和项目建设阶段的投资期权价值分别为0.12万和0.59万元/hm²,最优投资时机临界阈值分别为79.23和57.33元/t,理性的投资者只有在大于临界阈值时,才会从事立即投资,否则选择延迟投资。②碳价格波动率、碳汇交易成本、劳动力价格变量对湿地松造林碳汇项目投资时机临界阈值和投资期权价值有显著的影响;上述因素提高增加了项目投资的期权价值和最优投资时机临界阈值,但最优投资时机临界阈值提高却延迟了最优投资的时机;③木材价格上涨、项目备案成功率提高将使最优投资时机临界阈值下降,即上述因素提高可缩短投资者延迟投资的时机。基于此,为促进造林碳汇项目投资、发挥林业在应对和适应气候变化中的作用,政府应进一步完善碳价格波动调控政策和项目备案管理政策,并采取综合措施降低碳汇交易成本。此外,考虑到林业投资所具有的长期性、公益性等典型特征及中国劳动力价格不断上涨的趋势,未来相关部门还需建立和实施林业碳汇补贴制度。  相似文献   

大学艺术类专业课程“定题定时法”教学策略见解     

黄辉 《南昌教育学院学报》2014,(5):56-59

如何搞好大学艺术类专业课程教学是艺术专业人才培养过程中常探讨的课题。文章在分析大学艺术类专业课程教学特点的基础上,结合多年的教学经验,提高"定题定时法"教学策略,对比常见的一些教学方法,阐明了"定题定时法"教学策略的优势和实施办法。  相似文献   

一种基于时间隐蔽信道的WSN认证算法     

何磊  郭晓军  张春玉 《实验技术与管理》2014,31(9)

为解决无线传感器网络(WSN)内节点与网关及网关与终端之间的数据安全传输问题,针对WSN节点受到严格时空资源限制的特点,提出了一种在WSN节点之间、节点与网关之间利用时间隐蔽通信来进行身份认证的算法,被认证方可通过调整发送的数据包间隔特征来携带认证信息,认证方则从接收的数据包间隔特征中提取认证信息以进行验证。仿真结果表明,在阈值选取适当的情况下,基于时间隐蔽通信的认证算法能在WSN环境下稳定地工作,获得正确可靠的编解码结果,可以以较低的时空开销保证WSN节点之间、节点与网关之间数据传输的安全性。  相似文献   

网络搜索关键词时序变化特征研究*--以H7 N9禽流感关键词实验为例     

卢洪涛  李纲 《情报杂志》2014,(11)

利用网络搜索关键词的搜索量变化来分析和预测相关事物发展趋势是一种逐渐被广泛关注的研究领域。提出网络搜索关键词时序变化特征包括领先、同步和滞后三种特征。通过采集搜索网站关键词的搜索量数据,针对分析预测对象进行时差相关分析,可以识别出相关关键词时序变化特征。通过H7 N9禽流感关键词时序变化特征识别实验,说明该方法的可行性。  相似文献   

少儿羽毛球兴趣初级班有球练习方法的应用研究     

郭立三 《搏击·武术科学》2014,(5):119-120

少儿羽毛球兴趣初级班最大的特点就是兴趣,而专业传统的初级教学是进行大量、反复无球技术动作练习,枯燥的练习大大削减了少儿学习羽毛球的兴趣,如何既要维持少儿学习羽毛球的热情,又能规范地掌握羽毛球技术,文章从少儿的心理特点出发,通过长期的教学实践研究,总结出少儿羽毛球兴趣初级班不同方式的有球练习。  相似文献   

Labor market conditions and college graduation: Evidence from Brazil     

《Economics of Education Review》2023

College students graduating in a recession have been shown to face large and persistent negative effects on their earnings, health, and other outcomes. This paper investigates whether students delay graduation to avoid these effects. Using data on the universe of students in higher education in Brazil and leveraging variation in labor market conditions across time, space, and chosen majors, the paper finds that students in public institutions delay graduation to avoid entering depressed labor markets. A typical recession causes the on-time graduation rate to fall by 6.5% in public universities and there is no effect on private institutions. The induced delaying increases average graduation by 0.11 semesters, consistent with 1 out of 18 students delaying graduation by one year in public universities. The delaying effect is larger for students with higher scores, in higher-earnings majors, and from more advantaged backgrounds. This has important implications for the distributional impact of recessions.  相似文献   

Self-controlled amount and pacing of practice facilitate learning of a sequential timing task     

Christopher A. Aiken  Phillip G. Post  Michael C. Hout  Jeffrey T. Fairbrother 《Journal of sports sciences》2020,38(4):405-415

ABSTRACT

Allowing learners to control the number of practice trials has been shown to facilitate motor learning (Lessa & Chiviacowsky, 2015; Post et al., 2011; 2014). However, it is uncertain the extent to which prior findings were influenced by the combined effects of allowing participants to control both the pacing- and amount-of-practice. The present study examined the independent effects of self-controlled amount- and pacing-of-practice on learning a sequential timing task. Participants were assigned to a self-controlled-amount-of-practice (SCA), self-controlled-pacing-of-practice (SCP), yoked-amount-of-practice (YKA), or a yoked-pacing-of-practice (YKP) group. Participants completed acquisition, immediate retention/transfer and delayed retention/transfer. During acquisition, SCA controlled the number of acquisition blocks completed with a fixed inter-trial interval while SCP controlled the inter-trial interval with a fixed number of blocks. Yoked groups were matched to a self-control counterpart so the amount (YKA) and pacing (YKP) were equivalent. Self-control groups demonstrated lower absolute constant error during immediate-retention and lower absolute constant error and variable error during delayed retention (p < .05). For intrinsic motivation, SCA scored significantly higher than SCP for the subscale Interest/Enjoyment (p < .05). Findings indicated that self-control, regardless of type, facilitated motor learning. Further work is needed to continue to examine the relationship between controlling the amount and pacing of practice on skill acquisition.  相似文献