一种新的双单片机互连方案的研究

提出一种通过对实时时钟电路的分时损伤实现通信的双单片机系统的结构,给出了公共总线结构和通信协议,该方案可以扩展为多单片机系统。     

塑料石英钟机芯注塑模的设计与制造工艺

介绍了塑料石英钟机芯的产品结构设计要点、高精度的模具设计要点以及机芯模具型腔加工特殊的加工工艺流程。     

时钟驱动的原理和实现

介绍了基于MC146818RTC和Intel8254PIT的一种通用时钟驱动的实现方法,给出了硬件和软件方面的实现流程。     

Join operations in temporal databases

Joins are arguably the most important relational operators. Poor implementations are tantamount to computing the Cartesian product of the input relations. In a temporal database, the problem is more acute for two reasons. First, conventional techniques are designed for the evaluation of joins with equality predicates rather than the inequality predicates prevalent in valid-time queries. Second, the presence of temporally varying data dramatically increases the size of a database. These factors indicate that specialized techniques are needed to efficiently evaluate temporal joins.We address this need for efficient join evaluation in temporal databases. Our purpose is twofold. We first survey all previously proposed temporal join operators. While many temporal join operators have been defined in previous work, this work has been done largely in isolation from competing proposals, with little, if any, comparison of the various operators. We then address evaluation algorithms, comparing the applicability of various algorithms to the temporal join operators and describing a performance study involving algorithms for one important operator, the temporal equijoin. Our focus, with respect to implementation, is on non-index-based join algorithms. Such algorithms do not rely on auxiliary access paths but may exploit sort orderings to achieve efficiency.Received: 17 October 2002, Accepted: 26 July 2003, Published online: 28 October 2003Edited by: T. Sellis     

特殊分频电路设计

在数字系统中各个模块所需的时钟频率往往不相同,通常采用分频的方法由系统时钟得到所需频率。计数器作为一种典型分频电路有容易实现、波形均匀等优点,其遵循二分频原理也就要求在应用中系统时钟必须是输出频率整数倍为前提。详细介绍了2种特殊的分频电路积分分频电路和半整数分频电路,这2种电路分别基于分数分频和小数分频的原理,突破了计数器电路的局限性,具有较高的应用价值。     

基于EWB的数字钟设计与实现

Electronics Workbench(EWB)EDA软件是目前各种电路仿真软件中最理想的一种软件,该软件具有完整的混合模拟与数字信号模拟的功能。介绍了一种基于EWB软件设计电子钟的方法,系统由石英晶体振荡器、分频器、计数器、译码电路、LED显示电路、校时电路、整点报时电路组成。     

摄像头阅卷系统图像预处理算法研究

本文讨论了摄像头自动阅卷系统中的图像预处理算法，对答题卡图像预处理过程中的图像灰度化、二值化、光学畸变校正和图像偏斜纠正等关键步骤进行了描述。在灰度化过程中采用彩色模型转换的方法获得灰度图，在二值化过程中采用由用户指定阈值的方法，在畸变变换中采用二元多项式法，在偏斜纠正中使用Hough变换检测倾斜角度。     

An integrated 0.35 μm CMOS optical receiver with clock and data recovery circuit

This paper presents an integrated optical receiver that operates at 1 Gb/s in a standard 0.35 μm digital CMOS technology. The receiver consists of an integrated CMOS photodetector, a transimpedance amplifier (TIA) followed by a post-amplification stage and a dual-loop clock and data recovery (CDR) circuit. At a wavelength of 860 nm, the circuit requires an average light input power of −19.7 dBm to obtain a bit-error rate (BER) of 10⁻¹². The complete receiver consumes a total power of approximately 155 mW from a 3.3-V supply. The core circuit area is 0.85×1.32 mm².     

一种基于PLL的CBR业务时钟恢复方案

信元在 ATM 网内传输时,由于网内缓存的存在,造成了信元延时变化。信元延时变化对基于锁相环(PLL)的恒定比特率业务时钟的恢复有很大影响,即时钟的抖动和漂移比较明显。从而使这种基于 PLL 的CBR 业务时钟恢复方案在某些场合不能应用。本文提出了一种基于 PLL 的时钟恢复新方案,该方案可以明显地降低由于信元延时变化而造成的 CBR 业务时钟的抖动和漂移,同时不增加缓存的容量。     

The Gts1 protein stabilizes the autonomous oscillator in yeast

Continuous cultures of Saccharomyces cerevisiae show a robust autonomous temperature compensated oscillation in many metabolic functions. Respiratory activity, a convenient output to measure, oscillates with a period of 40 min. Deletion of GTS1, whose protein product has homology to the circadian per protein, has been implicated in temporal events within yeast, causes a reduction in periodicity to 18 min (wild-type period 40-60 min). The dilution rate was steadily increased from 0.04/h to 0.085/h and the oscillation stabilized after four to six dilutions. However, Gts1p's involvement in the maintenance and generation of metabolic synchrony, and in the central oscillating loop, appear to be minimal, as the mutant oscillation was robust and autonomous. Deletion of GTS1 did cause decreased temperature compensation of the period of the oscillation from Q(10) = 1.07 for the wild-type to Q(10) = 1.6 for the mutant. Also the degree of nutrient compensation observed for the wild-type was not observed in the GTS1-null mutant strain. It is postulated that Gts1p is involved in the mechanism that communicates external conditions, such as temperature, to the central oscillating loop.