555定时器及其应用

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。本文介绍555定时器以及由555定时器的应用。     

LED手电筒的高效调光电路设计与实现

为了提高LED手电筒的工作效率,文章提出了基于PWM调光策略的高效调光电路,采用555定时器构建了PWM信号发生单元,设计了调光电路,进行了理论分析和测试验证。实验结果表明,本调光电路结构简单,工作可靠,实现了手电筒亮度的无级调光,手电筒的亮度变换均匀柔和,调光范围宽,精度高,使用方便,成本低廉,克服了市场上现有的手电筒采用电阻与LED串联调光导致照明效率低下的缺点。     

彩虹常“红”的秘诀

紧抓党建工作不动摇、依靠职工办企业、坚持“小产品大市场”，是采访中刘荣富说得最多的三句话。事实上，这也是彩虹集团发展为全球最大电热毯生产企业的“制胜法宝”     

彩虹四十年：传“出圈” 创“出彩”

<正>2023年,成都彩虹电器集团股份有限公司迎来了四十岁的高光时刻。有人说,成都彩虹是一个象征。因改革开放而生,因改革开放而兴,是诠释中国改革开放的生动注脚。有人说,成都彩虹是一个传奇。四十年,走出了一条从濒临破产到兴旺发达的逆袭之路,成为全球电热毯制造知名企业,中国股市“电热毯第一股”。     

浅析微波加热器温度自动控制系统硬件设计

微波加热具有加热迅速、高效及安全等优点，目前已成为实验室加热的首选方式，具有温度自动控制功能的微波加热器设计与开发有着广阔的应用前景，可以满足生物医学工程领域，实验室科研等有关恒温加热要求。本文设计了一种基于STC89C52单片机控制的微波加热器温度自动控制系统，主要阐述构成该系统的硬件组成。     

单片机定时器的应用与误差纠正

本文通过对MCS-51单片机定时器的原理及使用过程中的几个关键问题进行了讨论,给出定时器的使用方法与误差补偿方法。     

应用热塑性弹性体材料生产一次成型三角带的研制

<正>热塑性弹性体(TPE)是近年来研究较多的一种新型共混聚合物弹性体。这种用三元乙丙橡胶(EPDM)和聚丙烯(PP)共混,同时进行一定的动态硫化作用制成的FPE具有良好的物理性能及耐候性、耐热老化性、耐化学腐蚀性、耐臭氧化性,它的最大特点是,传统的硫化橡胶重新加热到原来成型温度,不能使之软化或热塑性流动,而TPE加热到原来成型温度可以再次软化并具有热塑性,其废品和边角料可以重新成型加工和多次反复利用,是一种很好的环保型新材料。     

夏淮: 无组织、无纪律的女人

“一个吸烟的女人可能属于三种情况:一是艺术家,二是风尘女子,三是女强人。”当夏淮在她宽敞明亮的办公室里点燃一支555牌香烟,开始我们的专访时,我不禁想起了台湾女作家吴淡如的这句话。夏淮是上海开麦拉影视传播文化公司的合伙人。就像那些非科班出身的经理人一样,夏淮并没有讲很多 MBA 的道理,她讲了3个小故事。第一个故事     

告别‘95年——兼看96年股市

<正> 送走了春天又是秋天,送走了今年又是明年。一天又一天,月月年年,我们的心不变,我们的股市却变化万千。 ‘95:风雨兼程的一年 弹指一挥,‘95的股市已落下帷幕。回顾这一年,上证指数从637点起步,最高曾达5月22日的926点,最低为2月7日的524点;年末报收555点;落差为402点     

明贬暗褒,广告做巧

国外有家报纸刊登过这样一则广告 :“狮牌保险柜最大的缺点是密码上锁 ,必须用密码开锁。否则要用焊枪切开 ,这是唯一的办法。记密码有困难的人 ,请不要使用狮牌保险柜 ,免得麻烦”。乍一看 ,这好像在暴露自己产品的缺点 ,但仔细一想 ,反而觉得这“缺点”正是其优点。狮牌保险柜非密码莫开的“最大缺点” ,不正反衬出“保险”功能非同寻常这一“最大的优点”吗 ?想买保险柜的人 ,看了这独具一格的广告 ,谁不动心呢 ?英国名牌车“罗伊斯·伊尔斯”的广告也与其有异曲同工之妙 :“车速在６０公里时 ,罗伊斯·伊尔斯车内唯一的噪音是电子钟走动…     

Introduction to Special Section on Sensitivity Analysis and Summary of NCSU/USDA Workshop on Sensitivity Analysis

This guest editorial is a summary of the NCSU/USDA Workshop on Sensitivity Analysis held June 11–12, 2001 at North Carolina State University and sponsored by the U.S. Department of Agriculture's Office of Risk Assessment and Cost Benefit Analysis. The objective of the workshop was to learn across disciplines in identifying, evaluating, and recommending sensitivity analysis methods and practices for application to food‐safety process risk models. The workshop included presentations regarding the Hazard Assessment and Critical Control Points (HACCP) framework used in food‐safety risk assessment, a survey of sensitivity analysis methods, invited white papers on sensitivity analysis, and invited case studies regarding risk assessment of microbial pathogens in food. Based on the sharing of interdisciplinary information represented by the presentations, the workshop participants, divided into breakout sessions, responded to three trigger questions: What are the key criteria for sensitivity analysis methods applied to food‐safety risk assessment? What sensitivity analysis methods are most promising for application to food safety and risk assessment? and What are the key needs for implementation and demonstration of such methods? The workshop produced agreement regarding key criteria for sensitivity analysis methods and the need to use two or more methods to try to obtain robust insights. Recommendations were made regarding a guideline document to assist practitioners in selecting, applying, interpreting, and reporting the results of sensitivity analysis.     

Distinguishing traumatic, vicarious and routine operational stressor exposure and attendant adverse consequences in a sample of police officers

Problems in studying occupational stress within the police service are identified and the paucity of work on operational duties as potential stressors are discussed. The present study reports the results of a factor analysis of operational stressors (N = 601 serving British police officers) that revealed three factors: exposure to death and disaster; violence and injury; sexual crime. These were demonstrated to be reliable scales and were included in logistic regression models together with a range of demographic and psychological variables. Models were applied to men and women separately, which showed there to be different predictors of the likelihood of suffering distress (measured by the General Health Questionnaire, GHQ) in terms of the officer's gender and operational role. Overall the model for women officers was better at predicting psychological distress than that for men. These findings are related to aspects of the police occupational culture. Further discussion is offered that conceptualizes police operational stressors as traumatic, routine and vicarious. Finally, some implications are drawn for the provision of stress intervention in the light of this differentiation.     

Power,authority and legitimacy

Management, human resources, organization, control, leadership, etc., all seem to be just so many euphemisms for power, and this suggests a discourse of management and organization that calls things by their proper name. This paper on the contrary stresses the need to resolve the concept of ‘power’ itself into more differentiated notions, and proposes that clarification may be derived from distinctions once explicit in the vocabulary of Classical antiquity, but lost in modern European languages. It argues that nothing but confusion in thinking about organizations, management and legitimation can result from the failure to recognize that the phenomena this vocabulary identifies and distinguishes are irreducibly different.     

Criteria for selecting a production control philosophy

Logistic objectives constitute a compromise between having short leadtimes and a low volume of work in progress on the one hand and a high resource loading and due date obligation on the other. Miscellaneous production planning approaches offered today provide different combinations of logistic objectives for satisfying a manufacturing strategy. To combine the strength of the various approaches into a unified system, a new approach based on a dynamic and distributed production planning methodology is proposed. To customize the approach, various analyses and specifications have to be made and for that reason some important characteristics and criteria for analysing production control philosophies will be given.     

Employees' perceptions of organizational restructuring: the role of social support

Organizational change and restructuring is often perceived as leading to increased occupational stress, impacting negatively on the psychological well-being of employees. This pragmatic study investigates the role of social support and dispositional affect as moderators of role stress post-restructuring for employees in a public utility company. A total of 176 employees, including 37 managers, 60 graded staff and 78 industrial staff completed a self-report questionnaire, approximately 1 year postrestructuring, retrospectively assessing role conflict, ambiguity, overload and positive and negative feedback pre- and post-restructuring. Results suggested that overall role stress increased for managers/ senior officers and graded staff, but not for industrial staff. Social support was linked with lower role stress, more positive feedback and less negative feedback at post-restructuring. For certain role stressors this impact was moderated by dispositional affect, but the effect was not consistent across occupational groups. Positive affect enhanced the effect of manager support in reducing role conflict for graded staff, and the effect of co-worker support in increasing positive feedback and reducing negative feedback for industrial staff. Findings suggest that managers should pay particular attention to support and feedback for employees during periods of chronic occupational stress following organizational restructuring.     

The Danish psychosocial work environment and symptoms of stress: the main, mediating and moderating role of sense of coherence

The aim of this cross-sectional study was to explore the main, mediating and moderating role of sense of coherence (SOC) on stress symptoms and on the association between perceived psychosocial work environment and stress symptoms. The sample includes 2053 Danish employees from 52 workplaces. Hierarchical regression models were applied for each measure of stress. The results strongly supported the presence of a main effect for SOC. People with high levels of SOC experienced fewer stress symptoms. A mediating effect of SOC was also supported. Thus, SOC in part explained the association between work environment and stress symptoms. In addition, some support for a moderating effect of SOC was found, suggesting that people with higher SOC coped more efficiently with work environmental strain that people with lower SOC. Taken together the regression models explained 11-32% of the variance in stress symptoms. The results suggest that measures of individual factors such as SOC should be included in analyses of the effects of work environmental factors on stress and well-being.     

Control at work: a generalized resource factor for the prevention of musculoskeletal symptoms?

During the last two decades two potent groups of predictors for work-related musculoskeletal problems have been identified: physical work load and poor psychosocial working conditions. However, little is known about their combined effects. In this study the buffering effect of control at work with respect to the negative effects of psychological demands and physical work load on musculoskeletal problems is examined. All study variables were sampled from 431 people working in geriatric nursing homes in Germany by means of questionnaires. Main effects and interactions were tested with multiple regression analysis. The results showed that control buffered the effects of high psychological demands, but not of high physical work load; the buffering effect of control was observed only when physical work load was low. The combined effects of demands and physical work load were over-additive. Thus, the power of different predictors for musculoskeletal symptoms depended on the level of other predictors. This suggests that the efficiency of certain strategies for the prevention of musculoskeletal problems is likely to depend on the level of risk factors, with different strategies being appropriate for different levels of risk.     

The social construction of the meaning of acute stressors: a qualitative study of the personal accounts of police officers using a stress counselling service

The police profession is one in which acute stressors are encountered more frequently than in other occupations. Using the personal accounts of 35 police officers attending an in-house stress counselling clinic, the aim of the present study was to provide a qualitative examination of how the institutional context of policing influenced the ways in which acute stressors signified to individual police officers experiencing felt distress. Using the framework of Rational Emotive Behaviour Therapy as an analytical tool, it is argued that beliefs contributing to the experience of felt distress are related to the way in which policing as both an identity and an activity is constructed through the police organizational culture. Not only do these constructions influence the ways in which officers perceive themselves and their environments, but they also operate at the collective level to 'normalize' some emotional responses and to 'pathologize' others which, it is argued, could impact upon the outcomes of interventions such as stress counselling.     

The moderating role of social support in Karasek's job strain model

This paper examines whether social support is a boundary-determining criterion in the job strain model of Karasek (1979). The particular focus is the extent to which different sources of social support, work overload and task control influence job satisfaction, depersonalization and supervisor assessments of work performance. Hypotheses are tested using prospective survey data from 80 clerical staff in a university setting. Results revealed 3-way interactions among levels of support (supervisor, co-worker, non-work), perceived task control and work overload on levels of work performance and employee adjustment (self-report). After controlling for levels of negative affect in all analyses, there was evidence that high levels of supervisor support mitigated against the negative effects of high strain jobs on levels of job satisfaction and reduced reported levels of depersonalization. Moreover, high levels of non-work support and co-worker support also mitigated against the negative effects of high strain jobs on levels of work performance. The results are discussed in terms of the importance of social support networks both at, and beyond, the work context.     

Job insecurity, coping resources and personality dispositions in occupational strain

This paper presents research on the relationships between the work-related stressor of perceived job insecurity and various indicators of occupational strain, taking into account employees' personality dispositions (trait negative and positive affectivity) and coping resources. Respondents were 222 Australian public servants surveyed during organizational restructuring that involved downsizing and threat to job certainty. The research was formulated within an adaptation of Osipow, Doty, and Spokane's (1985) framework of stress-strain-coping that included the possible direct as well as moderating effects of personality dispositions in reporting occupational strain (Parkes, 1990). Findings from hierarchical regression analyses indicate consistent significant independent effects of personality dispositions, coping resources and perceived job insecurity on various indicators of strain. There was also support for the moderating roles of negative affectivity and self-care in the relation between perceived job insecurity and physical strain. Implications for the role of dispositional factors, especially negative affectivity, and the utility of various coping resources in accounting for occupational strain in times of threatened job security are discussed.