基于Proteus的555级联电路的仿真及频率计算

分析了救护车报警电路和555定时器的工作原理,用Proteus组合555芯片、电阻、电容对救护车报警电路进行了仿真,并将其仿真波形在同一屏幕上呈现出来,计算了其频率,计算结果与仿真结果一致.     

Reaction Time and Anticipation Time: Effects of Development

Abstract

The developmental nature of reaction time (RT) and anticipation timing (AT) performance, as well as the relationship between them, was investigated using 15 male and 15 female subjects at each of five age levels—7, 9, 11, 13, and 20 yrs. Each subject was given 40 trials for both RT and AT performance with task order counterbalanced. Results indicated that as age increased RT decreased, with males having more rapid RT than females. The two younger age groups differed from the three older groups on AT performance. RT was significantly correlated with AT (|CE| measure) for the 7, 9, and 11 yr old males but not in any other age by gender condition. Apparently neither young males nor young females have a good motor plan in memory to control AT performance. However, the more rapid RT (and thus better response initiation) of the males allows better AT performance at the younger ages. Beginning about 10–11 yrs of age, better motor plans are developed in children's memory system, leading to less reliance on rapid RT for good AT performance, and thus the correlation between RT and AT performance is not present.     

Responses to Speed Changes in Coincidence-Anticipation Judgments after Extended Practice

Abstract

Coincidence-anticipation performance has been found to vary with changes in the speed of the task's stimulus. This may be due to bias effects. The present study was designed to investigate the existence of directional error, its persistence after extended practice, and its occurrence upon transfer to new contextual stimuli. Two groups of 20 women athletes each were tested for 270 trials over 3 days on a Bassin anticipation task. One group judged stimulus speeds of 2, 3, and 4 mph and the other group speeds of 2, 4, and 6 mph. Both groups improved during training, but tended to respond late, less accurately, and more variably to the slowest speed. Following a 30-trial warmup on Day 4, the second group transferred to the same speeds given the first group. Following transfer, the Transfer Group demonstrated increased directional bias to the slowest stimulus speed despite having seen this speed throughout training. By the second block of trials following transfer, however, they were performing at an error level similar to that of the Control Group. The present findings are in agreement with those concerning psychophysical judgments, and suggest that skill acquisition may be subject to bias effects if the task involves judgments of varying speeds.     

Effects of Series Elasticity on the Human Knee Extension Torque-Angle Relationship in Vivo

Abstract

This paper examines whether self-controlled feedback schedules enhance learning, because they are more tailored to the performers' needs than externally controlled feedback schedules. Participants practiced a sequential timing task. One group of learners (self-control) was provided with feedback whenever they requested it, whereas another group (yoked) had no influence on the feedback schedule. The self-control group showed learning benefits on a delayed transfer test. Questionnaire results revealed that self-control learners asked for feedback primarily after good trials andyoked learners preferred to receive feedback after good trials. Analyses demonstrated that errors were lower on feedback than no-feedback trials for the self-control group but not for the yoked group. Thus, self-control participants appeared to use a strategy for requesting feedback. This might explain learning advantages of self-controlled practice.     

基于USB2.0和FPGA的高速数据采集卡

介绍一种采用USB2.0接口与PC机进行数据传输的高速数据采集卡的设计。采集卡由可变增益放大器对采样信号进行预处理,使用异步并行的A/D转换技术实现40 Msps的数据采集,由FPGA实现时序控制和数据高速FIFO,由内嵌MCU的USB控制器实现USB2.0接口功能。文章给出了硬件的基本结构和软件固件设计的基本方法,并对用FPGA设计FIFO作了重点阐述,同时对使用异步并行A/D转换与使用采样率为40 Msps的ADC器件的采样数据在FIFO内的数据传输进行了时序仿真,分析了仿真结果。     

城市道路交通信号实时优化控制模型

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。     

Suburban legend: School cutoff dates and the timing of births

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.     

运动训练时间信息的分类与调控

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。     

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

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。     

大学艺术类专业课程“定题定时法”教学策略见解

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。