基于授时GPS的高精度频率源设计与实现

介绍了一种基于授时GPS实现的频率源，它利用GPS具有长期稳定度好、跟踪保持特性强的优点作为参考，结合具有短期稳定特性好的OCXO，构成数字锁相（DPLL），以锁定后的DPLL输出频率作为直接数字频率合成器（DDS）的参考，最终输出任意的、长期稳定度好、精度高的时钟基准和频率参考。     

基于FPGA全新锁相倍频系统的设计

给出了DPLL的基本概念,阐述了DPLL的缺点,并结合最新的模拟锁相和数字锁相技术,提出了一种基于FPGA的全新锁相倍频系统的设计方法,简单地介绍了设计的思路、原理及其算法,并对该方案的性能进行了分析,给出了仿真波形。     

卫星USB测控副载波同步算法研究

吉林一号卫星测控采用USB测控体制,遥控接收采用FFT+DPLL1+DPLL2的架构,FFT主要实现对载波的粗捕,DPLL1在FFT的基础上实现对载波相位的精跟踪,DPLL2实现副载波的跟踪。对遥控副载波跟踪所用到的数字PLL技术进行了研究,首先给出了载波多普勒折算到副载波上的方法,然后对模拟PLL数字化进行了详细的论述,并设计了遥控副载波同步用的PLL2,对其稳定性、快捕带及快捕时间、捕获带和捕获时间、同步速率等进行了分析和仿真。结果表明,该方法具有捕获时间短、跟踪精度高、稳定性好等特点,易于数字化实现,已成功在吉林一号系列卫星中得到应用。     

基于SystemC的SAT求解器设计

该文描述了可满足性问题(SAT)求解器的设计及性能。首先,基于DPLL算法设计了一个单核SAT求解器的SystemC模型。校准这个模型,使之与工作站级计算机的软件性能相匹配,结果发现通过不连续内存访问数可以准确地估计运行时间。接着,设计了一个多核SAT求解器模型,使之能共享学习短句。通过广泛地仿真,演示了这个方法的并行效率。针对DPLL算法并行化水平低时的性能退化问题,进行了算法改进,结果得到了明显的改善。     

数字锁相环的原理及应用

<正> 一、前言锁相环电路(PLL),以往大多采用模拟技术制成。近年来,随着数字技术的发展,出现了数字化锁相环(DPLL)。我们将以SN54/74LS297电路为例,介绍DPLL的原理及应用。SW54/74LS297采用低功耗肖特基工艺制成。其主要特点如下: ·PLL完全数字化; ·可以设定频带宽度及中心频率; ·不用VCO,可以减轻温度、电源电压对整个环路的影响; ·利用串级方式,可更容易形成高次环路。     

C2E:一个高性能的EPCCL编译器

提出一个新的基于DPLL的编译算法KCDP,从而成功地将EPCCL理论和SAT求解联系起来,使得目前很多应用在基于DPLL的SAT求解器中先进的技术都能被引入到EPCCL理论的编译中以提高编译效率;提出规约规则,并基于该规则,提出能在多项式时间内终止的REDUCE算法对EPCCL理论进行规约;结合KCDP和REDUCE算法,实现了编译器C2E,并在随机问题和国际通用的测试用例上测试了C2E的编译效率和编译质量,实验结果表明,无论从编译效率还是编译质量来说,C2E都是一个高性能的EPCCL编译器.     

基于FPGA的数字锁相环设计

介绍了一种应用VHDL语言设计数字锁相环的设计方法,阐明其基本工作原理和设计思想,给出了系统主要模块的设计过程和仿真结果;用可编程逻辑器件FPGA予以实现。该方案提高了DPLL的快速锁定性能,同时保证了锁定精度。     

正则(3,4)-CNF公式的社区结构

通过构造适当的极小不可满足公式以实现在多项式时间内将3-CNF公式归约转换为一个正则(3,4)-CNF公式,转换后的公式与原公式具有相同的可满足性,同时公式的结构也发生相应的变化。图的社区结构反映了图的模块特性,文中将CNF公式转化为相应的图,研究公式图的模块特性与公式某些性质之间的关系。将归约前后的两类公式转换为相应的图并研究其模块特性,发现转换后得到的正则(3,4)-CNF公式具有较高的模块度。此外,在使用DPLL(Davis Putnam Logemann Loveland)算法求解CNF公式的过程中,发生冲突时利用冲突驱动子句学习策略,得到一个学习子句并将其添加到原公式中,使得原公式的模块度降低。研究发现:将DPLL算法与冲突驱动子句学习策略结合应用到正则(3,4)-CNF公式时,其学习子句所包含的绝大部分变元位于不同的社区中。     

基于TSDPLL的时钟漂移补偿算法容错研究*

提出集成TSDPLL对系统节点本地时钟计时频率漂移进行有效补偿的时钟同步方法,大大提高了应用网络时间同步技术（如NTP、PTP等）的同步精度。为确保TSDPLL能在网络出现拥塞的情况下仍然正常工作,通过分析收敛函数基本特征,提出基于收敛函数的容错方案。仿真实验结果表明,该方案算法简单、容错效果明显,是基于DPLL时钟漂移补偿算法不可或缺的关键组成部分。     

带文字改名策略的DPLL算法

限制在不可满足公式的不可满足性的证明,给出了一个改进的DPLL算法—RSMLS。新的算法带有一条对称规则(文字改名规则)和三条简化规则((1,*)-消解、子公式、重复规则)。作为一个应用实例,将RSMLS算法应用于鸽巢公式P_(n-1)~n的不可满足性证明。证明了:关于RSMLS算法,公式P_(n-1)~n有一棵反驳证明树至多带有O(n~3)个结点。     

Computer experience, learning style, and hypermedia navigation

This study focused on the extent to which prior computer-related experiences predicted linear and nonlinear navigation when using a hypermedia learning environment. Those with more years’ experience at working with computers and those with more authoring experience took more linear steps, whereas those with more data base experience and those with more hypermedia experience took fewer linear steps. Those with more years experience at working with computers, those with more programming experience, and those with more authoring experience had a lower percentage of nonlinear steps than those with more experience in those three areas. Those with more word-processing experience, more spreadsheet experience, and more hypermedia experience had a higher percentage of nonlinear steps than those with less experience in those three areas. Also, those with more hypermedia experience took less time than those with less hypermedia experience. A major implication of the study is that we can predict the extent to which a hypermedia user may engage in a hypermedia environment in a nonlinear way by knowing his or her experience in a variety of computer-related uses.     

Control 5.0: From Newton to Merton in Popper's Cyber-Social-Physical Spaces

The future of control in cyberspace of parallel worlds is discussed. It argues for the coming age of Control 5.0, the control technology for the new IT capable of dealing with artificial worlds with VR, AR, AI and robotics. The discipline of automation needs a new interpretation of its core knowledge and skill set of modeling, analysis, and control for cyber-socialphysical systems, and a paradigm shift from Newtonian Systems with Newton's Laws or Big Laws with Small Data to Mertonian Systems with Merton's Laws or Small Laws with Big Data.      

Worm wheel mechanism with passive rollers

In this study, we developed new worm wheel mechanisms with passive rollers as their teeth and confirmed useful functions of these worm wheels with passive rollers to transmit power from worm gears with higher energy efficiency than ordinary worm wheels. By using passive rollers as their teeth, the developed worm wheels could realize high-power transmission efficiency with rolling frictional resistance instead of sliding frictional resistance. A worm wheel with conical passive rollers and one with disk-shaped passive rollers was fabricated as prototypes and examined in experiments. Smooth back-drivability of the worm wheels with passive rollers, which is difficult to realize with conventional worm wheels, was also demonstrated in the experiments. These serial experiments revealed that the developed worm wheel mechanism with passive rollers can replace conventional worm wheels with the same number of teeth and module in ordinary power transmission mechanisms with worm gearing and realize higher energy efficiency and smooth back-drivability. These features can be very useful to realize safe and soft actuators for automation systems in a human environment.     

PHP在Web数据库的应用研究

信息社会的到来,使昝ＷＥＢ技术与数据库技术紧密结合起来。该文着重对ＰＨＰ在ＷＥＢ数据库中的开发技术作了分析,并与其它ＷＥＢ数据库开发技术进行了比较,提出取Ｌｉｎｕｘ为系统平台,利用ＰＨＰ与ＭｙＳＱＬ构建民ＷＥＢ数据库系统的方案民,并对其前景作了展望。     

A review on queueing network models with finite capacity queues for software architectures performance prediction

A review is carried out on how queueing network models with blocking have been applied so far into the performance evaluation and prediction of Software Architectures (SA). Queueing network models with finite capacity queues and blocking have recently been introduced and applied as more realistic models of systems with finite capacity resources and population constraints. Queueing network models have been often adopted as models for the evaluation of software performance. Starting from our own experience, we observe the need of a more accurate definition of the performance models of SA to capture some features of the communication systems. We consider queueing networks with finite capacity and blocking after service (BAS) to represent some synchronization constraints that cannot be easily modeled with queueing network models with infinite capacity queues. We investigate the use of queueing networks with blocking as performance models of SA with concurrent components and synchronous communication. Queueing theoretic analysis is used to solve the queueing network model and study the synchronous communication and performance of concurrent software components. Our experience is supported by other approaches that also propose the use of queueing networks with blocking. Directions for future research work in the field are included.     

The impact of communication technologies on life and relationship satisfaction

Previous studies have shown a relationship between the use of communications technology and well-being, particularly mediated through its effect on personal relationships. However, there is some debate over whether this effect is positive or negative. The present study explored this issue further, examining whether the effect varies depending on the type of communications technology, and the nature of the personal relationship. An online survey was conducted with 3421 participants in three countries (Australia, UK and US). It examined the use of ten communication methods, overall satisfaction with life and satisfaction with four different kinds of relationships (close and extended family, and close and distant friends).Results indicate that richer communication methods, which include non-verbal cues, were positively associated with both overall satisfaction with life and satisfaction with relationships. These methods included face-to-face communication, and phone and video calls. Conversely, more restricted methods, such as text messaging and instant messaging, were negatively associated with both variables. Social networking was negatively associated with overall satisfaction, but not with satisfaction with relationships. The strength of the association between a communications method and satisfaction with a relationship varied depending on the type of relationship, but whether it was positive or negative did not change.     

An interactive tool to promote musical creativity in people with dementia

Dementia is a growing problem that affects the lives of those diagnosed and caregivers, with symptoms having an effect on memory, communication, the ability to learn new skills and problems with behaviour, such as aggression, agitation and depression. Participation in activities can improve quality of life for people with dementia, reducing behavioural problems and aiding relaxation. Research has established that people with dementia can be both artistically and musically creative, and have an appreciation of music even in the latter stages of the disease. The symptoms of the disease, however, mean that supporting music making activities with this group of people is challenging. This paper describes a prototype system designed to enable people with dementia to create music, using a touch screen interface to control a system which utilises chords to create pleasant-sounding music regardless of any prior musical knowledge. Results of usability studies suggest the system is easy to use, and that pleasant-sounding music can be created with it. Participants, including people with dementia, appeared actively engaged during use of the system, many reporting they enjoyed the experience. Future testing will establish the degree to which people with dementia could be musically creative using such a system.     

The role of Persian-language word exercise games in improving spelling of students with dyslexia: Word exercise games in improving spelling

Children with dyslexia have reduced sensitivity to phonological sounds and words, and this deficiency in lexical processing causes many problems for them. Word exercise games based on phonological awareness have emphasized the mistakes of students with dyslexia, attempting to help children avoid these mistakes. This study was conducted to investigate the effect of Persian-language word exercise games on the spelling of students with dyslexia. The design of the present study was quasi-experimental, with a pretest and posttest of an experimental group and a control group. Participants were 30 students with dyslexia from second grade to fifth grade in elementary schools in Bojnord, who completed the spelling test as a pretest and posttest. The experimental group played eleven 40-min sessions of word exercise games. The results showed that the word exercise programme improved the spelling of the children with dyslexia. This suggests that basing training on the phonological mistakes of students with dyslexia and using the word exercise games can improve their spelling.     

DOGeye: Controlling your home with eye interaction

Nowadays home automation, with its increased availability, reliability and with its ever reducing costs is gaining momentum and is starting to become a viable solution for enabling people with disabilities to autonomously interact with their homes and to better communicate with other people. However, especially for people with severe mobility impairments, there is still a lack of tools and interfaces for effective control and interaction with home automation systems, and general-purpose solutions are seldom applicable due to the complexity, asynchronicity, time dependent behavior, and safety concerns typical of the home environment. This paper focuses on user-environment interfaces based on the eye tracking technology, which often is the only viable interaction modality for users as such. We propose an eye-based interface tackling the specific requirements of smart environments, already outlined in a public Recommendation issued by the COGAIN European Network of Excellence. The proposed interface has been implemented as a software prototype based on the ETU universal driver, thus being potentially able to run on a variety of eye trackers, and it is compatible with a wide set of smart home technologies, handled by the Domotic OSGi Gateway. A first interface evaluation, with user testing sessions, has been carried and results show that the interface is quite effective and usable without discomfort by people with almost regular eye movement control.     

Integrated text entry from power wheelchairs

Power wheelchair joysticks have be used to control a mouse cursor on desktop computers, but they offer no integrated text entry solution, confining users to point-and-click or point-and-dwell with on-screen keyboards. On-screen keyboards reduce useful screen real-estate, exacerbating the need for frequent window management, and impose a secondary focus of attention. By contrast, we present two integrated gestural text entry methods designed for use from power wheelchairs: one for use with joysticks and the other for use with touchpads. Both techniques are adaptations of EdgeWrite, originally a stylus-based unistroke method designed for people with tremor. In a preliminary text entry study of 7 power wheelchair users, we found that EdgeWrite with a touchpad was faster than the on-screen keyboard WiViK with a joystick, and EdgeWrite with a joystick was only slightly slower. These results warranted a multi-session comparison of text entry with EdgeWrite and WiViK using joysticks and touchpads, in which we found touchpads faster than joysticks, and EdgeWrite faster than WiViK with both devices after initial learning periods.