calender, machine that has wide application in the finishing of textile fabrics, the production of vinyl plastic sheeting, rubber sheeting, coated fabrics, and the manufacture of paper.

The mechanized plain calender was in common use in the mid-18th century after having been introduced into England from Flanders in the 17th century. A special type called the friction calender was patented in 1805 by William Smith, and the schreiner calender was developed about 1895. Calenders for embossing and moiréing are other types in use.

Calenders are made in many different forms and employ from 2 to 12 heavy rollers, usually mounted vertically in a series on a strong frame. The essentials of the machine are the pressure and temperature applied when the material being processed passes under or between the rollers. The number, arrangement, and type of rollers are the chief factors that determine how the calender functions. In the finishing of broad-woven fabrics, calendering produces results similar to ironing clothes. The pressure applied closes the threads, removes creases from the cloth, flattens it to the required thickness, and imparts a smoothness and lustre, or tither special effects, to the cloth.

In the plastics industry calendering is a method for producing vinyl film or sheeting. Resin and other ingredients are blended and formed into a hot plastic mass and passed through the hot rollers of the calender. The plastic emerges as a flat film or sheet whose thickness is determined and made uniform by the gap set on the gauging rollers of the calender. Similar applications are employed in the production of coated fabrics or rubber sheeting.

This article was most recently revised and updated by Amy Tikkanen.
Related Topics:
soft skills
discipline

time management, self-management with an explicit focus on time in deciding what to do; on how much time to allocate to activities; on how activities can be done more efficiently; and on when the time is right for particular activities. The term time management became familiar in the 1950s and 1960s as referring to a tool to help managers make better use of available time. The tool was based on practical experience, in the form of dos and don’ts. The term appears to indicate that time is managed, but actually it is activities that are managed over time. Much of the advice on time management concerns the standardization and routinization of activities to increase efficiency. The time gained with this increased efficiency can be used for other activities, deliberately chosen as worthwhile, rather than activities that serve only as means to achieve less worthwhile goals, so-called time wasters. In other words, time is gained for activities that deserve it, and full concentration can be devoted to these activities for a longer period of time.

Similar to self-management, time management is focused on solving problems. Examples of common problems are: feeling overwhelmed by the workload; planning too optimistically; being unable to deal with distractions; deadline pressure; and procrastination. The core of time management is to prevent these problems by preparation and planning. Many scheduling techniques can be used that aim at obtaining an overview of tasks, subtasks, and actions and methods to remember them—for example, making a to-do list, organizing it according to priority based on importance (relevant to effectiveness) and urgency (relevant to timeliness), and scheduling tasks to months, weeks, and days.

In addition, time management may be seen as a way to stay on track in dynamic conditions. As such, it is more than planning, and it involves a cycle of goal setting, planning, keeping track of progress (monitoring), and the evaluation of goal achievement.

Despite the worldwide popularity of time management training, the research on time management has been relatively scarce. That is, although several studies have been conducted about study behaviour among students and, to a lesser extent, among individuals in a work setting, there are only a few study results to substantiate the claims of time management to increased efficiency and better performance.

Therese Hoff Macan proposed a model of time management in which time management behaviours such as goal setting and organizing result in perceived control of time, which leads to outcomes such as increased performance and less tension. Research that investigated this model established the relationship between perceived control of time and tension several times. However, the relationship between certain types of behaviour and control of time, and between control of time and performance, resulted in inconsistent research outcomes.

Apart from this model, the approach to time management has been largely atheoretical, focused on personal skills, without consideration of why the problems arise and why they are so common. Not much is known about the work context, which may play an important role in the pressures on and the enhancement of the use of time. A more comprehensive theoretical framework of time management than presented so far would have to involve task content and social influences as well. Relevant issues, for example, are as follows: Does a person have the autonomy to self-manage activities over time, to delegate activities, or to say no to certain requests? How heavy is the person’s workload?

Some authors proposed that time management may be seen as an individual difference variable, and there are several indications that some people are better planners and more attentive to time than others. Examples of these individual differences are time urgency (the degree to which a person is hurried and focused on time); polychronicity (the preference to handle several activities simultaneously); and time use efficiency.

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