定时器的PLC程序设计

本文旨在实现接通延时定时器、断开延时定时器、多谐震荡器的时序图及PLC程序设计。     

基于AVR单片机的监测抢跑智能短跑计时系统

本文主要介绍了利用ATmega128单片机设计智能短跑计时器的硬件设计和软件设计,详细介绍了计时器系统的监测设备的硬件设计和利用中断、中断扩展以及定时器等软件技术实现计时器的功能,以及智能短跑计时器的使用方法和注意事项。     

基于Multisim的555定时器与运放构成的矩形波发生器比较分析

为了详细分析目前比较常用的555定时器和运放构成的矩形波发生器,填补其他文章仅单单分析一种电路的空白,利用Multisim强大的仿真分析功能,结合理论计算,对这两种方波发生器进行输出电压特性、占空比调节、输出频率、电源电压范围等方面的比较分析,希望给制作矩形波发生器的读者提供一定的参考价值。     

定时器与计数器浅析

工业控制中,经常要用到定时器/计数器,本文分析了三种定时/计数器各自的优缺点,重点浅析了可编程定时/计数器8253。     

Timing versus Buy and Hold: A Model for Determining Predictive Accuracy Required for Superior Performance

In this application, we develop a model to simulate the decisions of a trader whose subjective distribution of returns may be correlated with realized stock returns. Using empirically estimated parameters from stocks in the CRSP database, we obtain performance data on a number of measures, including mean returns, volatility, the Sharpe measure, and the probability of a correct trading decision. The model suggests that daily trading of a portfolio of 20 volatile stocks gives a Sharpe measure better than that of buying and holding the S&P 500 when timing accuracy is 53% or better.     

555IC应用的一个新思路

从555IC的基本逻辑功能和基本特性出发,论述了把555IC定时器用作门电路的理论依据和电路接线方案,分析了该门的电压传输特性、输出特性、负载能力等。该门具有一般门不可比拟的特色和突出特点:电路简单,使用灵活方便;该门电路的负载能力比普通门提高了几十倍甚至上百倍,解决了普通门阈值电压不便调节以及输出电平转换难的问题。     

单片机控制的8通道计时器的设计

设计制作了一种基于单片机AT89C51为控制核心的大量程高精度8通道计时器。使用Protel DXP 2004软件仿真设计。开始、结束信号经整形处理后进入单片机进行比较、计算、储存、显示、打印等处理。采用7位LED数码管显示。显示精度为999.999秒,并可直接连接微型打印机直接打印所需数据。     

双积分A/D转换技术

双积分是一种常用的转换技术,具有精度高,抗干扰能力强等优点。本文介绍了双积分A/D转换技术的原理,及其用51单片机和通用分立器件构成的双积分A/D转换器。     

Comparison Between First‐timers and Repeaters for Relationship Marketing Implications

This research note examines how different relationships affect visitors' tourism experiences at agritourism encounters, recognizing the differences between repeaters and first‐timers from a relationship marketing perspective. Results from a survey of 431 visitors to farms in Texas found that most of relationships with service providers, other customers and companions were important but differently related to satisfaction. By examining the differences and similarities between first‐timers and repeaters, this study suggests that visitors' relationships not only with service providers but also with other customers and companions should be embraced into the components of relationship marketing models in tourism. Copyright © 2011 John Wiley & Sons, Ltd.     

浅谈555定时器的原理与应用

555定时器是一种模拟和数字功能相结合的中规模集成器件,外形为双列直插8脚结构,体积小,价格低,使用方便。只要在外部配上适当的阻容元件,就可以构成史密特触发器、单稳态触发器及自激多谐振荡器等脉冲信号产生与变换电路。它经常作为定时器广泛应用于仪器仪表、家用电器、电子测量及自动控制等方面。