• Journal of Korea Society of Industrial Information Systems
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• v.29 no.1
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• pp.63-76
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• 2024

In this study, we analyzed queue length and sojourn time of discrete-time BMAP/G/1 queues under the workload control. Group customers (packets) with correlations arrive at the system following a discrete-time Markovian arrival process. The server starts busy period when the total service time of the arrived customers exceeds a predetermined workload threshold D and serves customers until the system is empty. From the analysis of workload and waiting time, distributions of queue length at the departure epoch and arbitrary time epoch and system sojourn time are derived. We also derived the mean value as a performance measure. Through numerical examples, we confirmed that we can obtain results represented by complex forms of equations, and we verified the validity of the theoretical values by comparing them with simulation results. From the results, we can obtain key performance measures of complex systems that operate similarly in various industrial fields and to analyze various optimization problems.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.10 no.4
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• pp.295-303
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• 2016

Rehabilitation of upper limb motor function of hemiplegic patient must maintain interest and demand a device for a quantitative evaluation of rehabilitation training. In this paper, we developed the device that is composed of arm cradle, handle, and balance ball for rehabilitation exercise. We have performed experiment for validity as to whether to use the rehabilitation device when tilting the upper extremity training device developed to measure changes in the EMG signal to the main upper limb muscles for 7 healthy volunteers. We have analyzed muscle activation signals on agonist and antagonist as a reference in the muscle contraction and relaxation in the upper limb extension and flexion when the balance-handle device is tilted to front-rear and left-right. The experimental results showed that a tendency of muscle activation of biceps, triceps, and deltoid used in upper limb motor function of hemiplegic patients from extension and flexion evaluation items of Fugl-Meyer Assessment(FMA). These results may be helpful for rehabilitation training for upper limb motor function of hemiplegic patients by utilizing a developed unit.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.6
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• pp.1235-1241
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• 2012

In this paper, each driving motor for leg joints on a robot is controlled by estimating the direction of the legs measuring each joint angle and attitude angle of robot. We used quadruped working robot named TITAN-VIII in order to carry out this experimental study. 4 load cells are installed under the bottom of 4 legs to measure the pressed force on each leg while it's walking. The walking experiments of the robot were performed in 8 different conditions combined with duty factor, the length of a stride, the trajectory height of the foot and walking period of robot. The validity of attitude control for quadruped walking robot is evaluated by comparing the pressed force on a leg and the power consumption of joint driving motor. As a result, it was confirmed that the slip-condition of which the foot leave the ground late at the beginning of new period of the robot during walking process, which means the attitude control of the robot during walking process wasn't perfect only by measuring joint and attitude angle for estimating the direction of the foot.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.381-387
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• 2002

In this work, the dynamic characteristics of an oil-lubricated, short SFD with a central feeding groove are derived based on a theoretical analysis considering the effect of a groove. The validity of the analysis is investigated experimentally using an Active Magnetic Bearing (AMB) system as an exciter. For the theoretical solution, the fluid film forces of a grooved SFD are analytically derived so that the dynamic coefficients of a SFD are expressed in terms of its design parameters. For the experimental validation of the analysis, a test rig using AMB as an exciter is proposed to identify the dynamic characteristics of a short SFD with a central groove. As an exciter, the AMB represents a mechatronic device to levitate and position the test journal without any mechanical contact, to generate relative motions of the journal inside the tested SFD and to measure the generated displacements during experiments with fairly high accuracy. Using this test rig, experiments are extensively conducted with different clearance, which is one of the most important design parameters, in order to investigate its effect on the dynamic characteristics and the performance of SFDs. Damping and inertia coefficients of the SFD that are experimentally identified are compared with the analytical results to demonstrate the effectiveness of the analysis. It is also shown that AMB is an ideal device for tests of SFDs.

• Journal of Advanced Navigation Technology
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• v.25 no.6
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• pp.456-465
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• 2021

For predictive aviation safety management, the establishment of safety performance indicators to measure and manage the safety performance of service providers must be preceded. In particular, leading indicators are significant in that they play an important role in identifying and managing the causes of accident/incident in advance. However, the current safety performance indicators of the domestic aviation industry have limitations in that they focus on lagging indicators based on events that have already occurred. Therefore, the purpose of this study is to construct Korean leading indicators for preventive safety management. In addition, we verify the validity and importance of the indicators based on review of the experts and AHP analysis. This study is meaningful in that it can support the proactive safety management of the domestic aviation industry through the development of leading safety indicators, which have been relatively lacking in research.

• Journal of Korean Academy of Nursing
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• v.48 no.1
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• pp.38-49
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• 2018

Purpose: This study aimed to develop an instrument to assess the quality of childbirth care from the perspective of a mother after delivery. Methods: The instrument was developed from a literature review, interviews, and item validation. Thirty-eight items were compiled for the instrument. The data for validity and reliability testing were collected using a questionnaire survey conducted on 270 women who had undergone normal vaginal delivery in Korea and analyzed with descriptive statistics, exploratory factor analysis, and reliability coefficients. Results: The exploratory factor analysis reduced the number of items in the instrument to 28 items that were factored into four subscales: family-centered care, personal care, emotional empowerment, and information provision. With respect to convergence validation, there was positive correlation between this instrument and birth satisfaction scale (r=.34, p<.001). The internal consistency reliability was acceptable (Cronbach's alpha =.96). Conclusion: This instrument could be used as a measure of the quality of nursing care for women who have a normal vaginal delivery.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.926-936
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• 2000

Actual and strict definition of the shift quality for the powertrain system equipped an automatic transmission must be understood through the acceleration change of the vehicle body, which the driver directly feels as a shift shock. For this reason, it is necessary to concurrently analyze the characteristics of the powertrain system and the vehicle body. This paper presents the mathematical model of the vehicle body, which is based on the equivalent lumped system, to append to the developed model of the powertrain system. The concept of tire slip is also introduced for the experimental relationship between tire/road and driving force. Using the developed dynamic simulation programs, shift transients characteristics are analyzed. Theoretical results are compared with experimental ones from real car tests in equal conditions in order to prove the validity of presented model. In these tests, the system to measure the vehicle acceleration is used with various speeds and engine throttle sensors. It is expected that the presented modeling techniques can provide good predictions of the vehicle driving comfortability.

• Journal of the Korean Society for Library and Information Science
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• v.4
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• pp.43-71
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• 1975

Operations research has developed rapidly since its origins in World War II. Practitioners of O. R. have contributed to almost every aspect of government and business. More recently, a number of operations researchers have turned their attention to library and information systems, and the author believes that significant research has resulted. It is the purpose of this essay to introduce the library audience to some of these accomplishments, to present some of the author's hypotheses on the subject of library management to which he belives O. R. has great potential, and to suggest some future research directions. Some problem areas in librianship where O. R. may play a part have been discussed and are summarized below. (1) Library location. It is usually necessary to make balance between accessibility and cost In location problems. Many mathematical methods are available for identifying the optimal locations once the balance between these two criteria has been decided. The major difficulties lie in relating cost to size and in taking future change into account when discriminating possible solutions. (2) Planning new facilities. Standard approaches to using mathematical models for simple investment decisions are well established. If the problem is one of choosing the most economical way of achieving a certain objective, one may compare th althenatives by using one of the discounted cash flow techniques. In other situations it may be necessary to use of cost-benefit approach. (3) Allocating library resources. In order to allocate the resources to best advantage the librarian needs to know how the effectiveness of the services he offers depends on the way he puts his resources. The O. R. approach to the problems is to construct a model representing effectiveness as a mathematical function of levels of different inputs(e.g., numbers of people in different jobs, acquisitions of different types, physical resources). (4) Long term planning. Resource allocation problems are generally concerned with up to one and a half years ahead. The longer term certainly offers both greater freedom of action and greater uncertainty. Thus it is difficult to generalize about long term planning problems. In other fields, however, O. R. has made a significant contribution to long range planning and it is likely to have one to make in librarianship as well. (5) Public relations. It is generally accepted that actual and potential users are too ignorant both of the range of library services provided and of how to make use of them. How should services be brought to the attention of potential users? The answer seems to lie in obtaining empirical evidence by controlled experiments in which a group of libraries participated. (6) Acquisition policy. In comparing alternative policies for acquisition of materials one needs to know the implications of each service which depends on the stock. Second is the relative importance to be ascribed to each service for each class of user. By reducing the level of the first, formal models will allow the librarian to concentrate his attention upon the value judgements which will be necessary for the second. (7) Loan policy. The approach to choosing between loan policies is much the same as the previous approach. (8) Manpower planning. For large library systems one should consider constructing models which will permit the skills necessary in the future with predictions of the skills that will be available, so as to allow informed decisions. (9) Management information system for libraries. A great deal of data can be available in libraries as a by-product of all recording activities. It is particularly tempting when procedures are computerized to make summary statistics available as a management information system. The values of information to particular decisions that may have to be taken future is best assessed in terms of a model of the relevant problem. (10) Management gaming. One of the most common uses of a management game is as a means of developing staff's to take decisions. The value of such exercises depends upon the validity of the computerized model. If the model were sufficiently simple to take the form of a mathematical equation, decision-makers would probably able to learn adequately from a graph. More complex situations require simulation models. (11) Diagnostics tools. Libraries are sufficiently complex systems that it would be useful to have available simple means of telling whether performance could be regarded as satisfactory which, if it could not, would also provide pointers to what was wrong. (12) Data banks. It would appear to be worth considering establishing a bank for certain types of data. It certain items on questionnaires were to take a standard form, a greater pool of data would de available for various analysis. (13) Effectiveness measures. The meaning of a library performance measure is not readily interpreted. Each measure must itself be assessed in relation to the corresponding measures for earlier periods of time and a standard measure that may be a corresponding measure in another library, the 'norm', the 'best practice', or user expectations.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2006.11a
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• pp.264-267
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• 2006

Timely completion and a satisfied owner are the prime objectives of a construction project. The success to achieve these objectives of a project is fully depend on the working approaches (attitude) of a contractor company. Attitude is very difficult to be measured directly; therefore it must be inferred from assumed relationship with observable indicators. Commonly, behavior shown by a person or organization represents its attitude about things or persons or issues. The aim of this paper is to develop a framework for measuring attitude of contractors in an ongoing construction project. In this paper a set of key attitude indicators (KAIs) measured both objectively and subjectively have been developed through a field survey. The validity of the proposed KAIs is also tested by four case studies. The results of the study show that the KAIs stated in the paper can reasonably measure the attitude of contractors and can be helpful for the owners and project managers to control their projects effectively. This study also provides significant insights into developing a general and comprehensive base for further study.

• Korean Journal of Construction Engineering and Management
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• v.16 no.3
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• pp.78-90
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• 2015

Due to a significant decrease in the number of construction projects in the domestic market of Korea, overseas expansion of the Korean construction companies has been accelerated in recent years. However, the practice of bidding at a low price and lacking information about foreign new markets caused many companies to fail in their entries to these markets. As a measure to prevent such failures, this study has developed a framework which first defines the key research items that must be identified beforehand and then classifies them into a structured way so that the construction companies can actually use this framework to be better prepared for their forays into the new markets. The framework was actually applied for a construction project in Morocco, and its usefulness was proven by the user's successful participation into the project, nevertheless the application and result was limited. Although perhaps this framework should be applied to many more construction projects for its validity to be verified and for its structure to be better standardized, the framework still has its value due to the following two reasons: first, it has systemized the research items that had been only conceptually defined but had never been organized, and second it can be utilized as a investigation tool at the marketing stage.