Scheduling tool changes and special jobs on a single machine to minimize makespan

This paper considers a variation of the classical single machine scheduling problem with tool changes. In the variation, two sets of jobs, namely special jobs and normal jobs, are considered. By special jobs, we mean that each special job must be processed within the first prefixed time units of a tool life. To solve the scheduling problem with small size and moderate size, we propose two mathematical programming models. To solve the scheduling problem with large size, we propose three sets of algorithms and focus on the performance of six algorithms based on the studies of a new bin packing problem. Worst-case analysis is conducted. Numerical experiment shows that each of the six algorithms can solve instances with up to 5000 jobs in about 0.5 s with an average relative error less than 4%.     

W18Cr4V刀具带磁切削的试验研究

通过W18Cr4V刀具带磁切削试验研究,探讨了高速钢刀具带磁切削的基本规律及机理,得出结论:带磁切削能有效降低切削力、提高刀具耐用度、提高生产率、降低成本,同时能明显地提高加工质量.     

Optimization models for the tool change scheduling problem

Traditional machine scheduling literature generally assumes that a machine is available at all times. Yet this assumption may not be accurate in real manufacturing systems. In many cases, a machine's tool must be changed after it has continuously worked for a period of time. This paper deals with a single machine scheduling problem subject to tool wear, given the allowed maximum continuous working time of the machine is _TL$T_{\mathrm{L}}$ (tool life) and the tool change time is _TC$T_{\mathrm{C}}$. Job processing and tool changes are scheduled simultaneously. In this paper, we examine this problem to minimize the total tardiness of jobs. Two mixed binary integer programming models are developed to optimally solve this problem. Computational experiments are performed to evaluate the models’ efficiency.     

Poverty and Pediatric Palliative Care: What Can We Do?

It has been recognized that families of children with life-limiting health conditions struggle with significant financial demands, yet may not have awareness of resources available to them. Additionally, health care providers may not be aware of the socioeconomic needs of families they care for. This article describes a mixed-methods study examining the content validity and utility for health care providers of a poverty screening tool and companion resource guide for the pediatric palliative care population. The study found high relevance and validity of the tool. Significant barriers to implementing the screening tool in clinical practice were described by participants, including: concerns regarding time required, roles and responsibilities, and discomfort in asking about income. Implications for practice and suggestions for improving the tool are discussed. Screening and attention to the social determinants of health lie within the scope of practice of all health care providers. Social workers can play a leadership role in this work.     

西方世界推崇马克思的原因探究

西方推崇马克思的原因,需要从马克思主义学说的基本内容与当代世界社会发展的实际关系层面来理解。一是由于马克思主义产生的社会条件还存在,当代发达资本主义较之其初期虽然有了很大的变化,但其剥削、压迫劳动者的本质并没有变,所以劳动者总是把马克思、马克思主义作为自己追求解放的旗帜。二是马克思提供的认识和改造世界的理性工具——即唯物辩证法,对人类具有永恒的价值。西方社会也普遍在利用这一理性工具解决自己的问题,推动社会不断进步。三是马克思根据自己的价值目标,通过分析当时的社会现实,把握社会发展规律,而对社会发展趋势做出的推测和根据这些推测做出的一系列对策安排——包括对社会主义基本制度的设计,这些东西中有很多被后来的社会发展的实践所一一证实,这也是西方知识界推崇马克思的原因。有些人在根本不了解马克思主义的情况下,也不对社会主义出现的挫折和问题作具体分析,就盲目地排斥马克思主义,这是极不严肃的态度。今天,我们应坚持以马克思主义为指导,正确地处理好马克思主义与本国文化传统的关系,广泛吸取人类创造的全部文明,大胆创新,努力构建与我们国家的现代化建设相适应的有中国特色的社会主义新文化。     

论工具理性对人的全面发展的制约

人的全面发展是人类一直追寻的理想,它引导人们超越现实,不断走向未来的价值目标。在不同的历史时代,人的全面发展所面对的问题是不相同的,在现代社会我们所面临的最大问题是工具理性的超强控制力,它对人的全面发展所带来的制约具体表现在:人的感性发展受到扭曲;人的个性发展受到压抑;从本源的意义上把人视为物欲性的存在。     

正确估价两汉农业生产水平

研究汉代乡村社会，对农业生产水平的认识是一个重要前提。我们既要注意代表当时农业水平成就的内容，如铁犁、牛耕等等，也要注意两汉时代农业水平的另一侧面，如水耨火耕、蹠来而耕等等，也就是说，必须真正深入到当时的乡村社会，去把握其实际生产水平与生产状况。     

Reducing the number of setups for CNC punch presses

Large computer numerical control (CNC) punch presses are widely used for punching holes in heavy gage sheet metals. The turret of such presses has limited tool capacity, and any tool changes require dismantling the turret. Dismantling and reloading the turret generally takes several hours and is the dominant element of the total flow time for a batch of sheet metals. Reducing the turret setup time requires judicious grouping of the required tool set. We formulated an integer program to obtain the minimum number of setups. However, since the problem is nondeterministic polynomial-time hard (NP-hard), we offer three heuristics to solve the problem. We compare solutions obtained from the three heuristics with their respective optimal solutions using three simulated data sets and an industrial data set.     

‘Management Standards’ work-related stress in the UK: practical development

Research commissioned for the UK's Health & Safety Executive (HSE) supports the view that a preventative, risk-assessment based approach would be more effective than case-based methods in achieving a nationwide reduction in work-related stress. The background to this approach is described and discussed in a companion paper in this issue (Mackay, Cousins, Kelly, Lee, & McCaig, ). The present paper describes the development of HSE's new stress Management Standards—which offer organizations continuous improvement through a three-phase stress preventative process—and the development of a supporting ‘Indicator Tool’ (a two-phase questionnaire to assess employee perceptions of working conditions). The Management Standards comprise a series of ‘states to be achieved’, which are statements of good practice in six key stressor areas: demands, control, support, relationships, role and organizational change. For each stressor area there is also a ‘platform statement’ that outlines the main aims to be achieved by the organization. This statement may include a target percentage of employees finding that the organization meets the standard: this matter will be settled after the standards have been assessed in a public consultation campaign. To use the new process, an organization's state can first be assessed using the Indicator Tool; liaising with workers in focus groups enables a further exploration of issues raised; finally, there may be formulation of interventions and subsequent review. It is not intended that the standards will be legally enforceable. HSE's aim is that they and the associated methodology will enable organizations to effectively tackle work-related stress, and subsequently reduce both its incidence and prevalence.     

Psychosocial risk assessment in organizations: Concurrent validity of the brief version of the Management Standards Indicator Tool

The Management Standards Indicator Tool (MSIT) is a 35-item self-report measure of the psychosocial work environment designed to assist organizations with psychosocial risk assessment. It is also used in work environment research. Edwards and Webster presented a 25-item version of the MSIT based on the deletion of items having a factor loading of < .65. Stress theory and research suggest that psychosocial hazard exposures may result in harm to the health of workers. Thus, using data collected from three UK organizations (N = 20,406) we compared the concurrent validity of the brief and full versions of the MSIT by exploring the strength of association between each version of the instrument and a measure of psychological wellbeing (GHQ-12 and Maslach Burnout Inventory). Analyses revealed that the brief instrument offered similar but not always equal validity to that of the full version. The results indicate that use of the brief instrument, which would be less disruptive for employees, would not elevate the risk of false negative or false positive findings in risk assessment.