• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1304-1316
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• 2018

An adaptive sliding-mode observer for speed estimation in sensorless vector controlled induction machine drives is proposed in this paper to balance the dilemma between the requirement of fast reaching transient and the chattering phenomenon reduction on the sliding-mode surface. It is well known that the sliding-mode observer (SMO) suffers from the chattering phenomenon. However, the reduction of the chattering phenomenon will lead to a slow transient process. In order to balance this dilemma, an adaptive exponential reaching law is introduced into SMO by optimizing the reaching way to the sliding-mode surface. The adaptive exponential reaching law is based on the options of an exponential term that adapts to the variations of the sliding-mode surface and system states. Moreover, the proposed sliding-mode observer considering adaptive exponential reaching law, which is called adaptive sliding-mode observer (ASMO), is capable for reducing the chattering phenomenon and decreasing the reaching time simultaneously. The stability analysis for ASMO is achieved based on Lyapunov stability theory. Simulation and experimental results both demonstrate the correctness and the effectiveness of the proposed method.

• Journal of Information Technology Services
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• v.20 no.3
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• pp.1-12
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• 2021

Reactor Coolant Pump (RCP) is core part of nuclear power plant to provide the forced circulation of reactor coolant for the removal of core heat. Properly monitoring vibration of RCP is a key activity of a successful predictive maintenance and can lead to a decrease in failure, optimization of machine performance, and a reduction of repair and maintenance costs. Here, we developed real-time RCP Vibration Analysis System (VAS) that web based platform using NoSQL DB (Mongo DB) to handle vibration data of RCP. In this paper, we explain how to implement digital signal process of vibration data from time domain to frequency domain using Fast Fourier transform and how to design NoSQL DB structure, how to implement web service using Java spring framework, JavaScript, High-Chart. We have implement various plot according to standard of the American Society of Mechanical Engineers (ASME) and it can show on web browser based on HTML 5. This data analysis platform shows a upgraded method to real-time analyze vibration data and easily uses without specialist. Furthermore to get better precision we have plan apply to additional machine learning technology.

• Journal of the Semiconductor & Display Technology
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• v.22 no.1
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• pp.124-128
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• 2023

Semiconductor engineers have long sought to enhance the energy efficiency of mobile semiconductors by reducing their voltage. During the final stages of the semiconductor manufacturing process, the screening and evaluation of voltage is crucial. However, determining the optimal test start voltage presents a significant challenge as it can increase testing time. In the semiconductor manufacturing process, a wealth of test element group information is collected. If this information can be controlled to predict the test voltage, it could lead to a reduction in testing time and increase the probability of identifying the optimal voltage. To achieve this, this paper is exploring machine learning techniques, such as linear regression and ensemble models, that can leverage large amounts of information for voltage prediction. The outcomes of these machine learning methods not only demonstrate high consistency but can also be used for feature engineering to enhance accuracy in future processes.

• Structural Engineering and Mechanics
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• v.31 no.1
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• pp.57-74
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• 2009

Power signals resulting from spindle and feed motor, present a rich content of physical information, the appropriate analysis of which can lead to the clear identification of the nature of the tool wear. The partial least-squares regression (PLSR) method has been established as the tool wear analysis method for this purpose. Firstly, the results of the application of widely used techniques are given and their limitations of prior methods are delineated. Secondly, the application of PLSR is proposed. The singular value theory is used to noise reduction. According to grey relational degree analysis, sample variable is filtered as part sample variable and all sample variables as independent variables for modelling, and the tool wear is taken as dependent variable, thus PLSR model is built up through adapting to several experimental data of tool wear in different milling process. Finally, the prediction value of tool wear is compare with actual value, in order to test whether the model of the tool wear can adopt to new measuring data on the independent variable. In the new different cutting process, milling tool wear was predicted by the methods of PLSR and MLR (Multivariate Linear Regression) as well as BPNN (BP Neural Network) at the same time. Experimental results show that the methods can meet the needs of the engineering and PLSR is more suitable for monitoring tool wear.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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• pp.673-682
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• 2007

Recently the trend of automobile industry is that IQS evaluation index against a sensitivity quality is increasing. To reduce rattle noise due to speaker sound at low frequencies, it is required the advanced technology analysis process of body structure. This paper optimized the design parameters of package tray panel according to the theoretical background about robust design and suggested the design guideline for resonance avoidance and the reduction of vibrational sensitivity considering the excitation frequency of woofer speaker. And this paper described the design process of a door module panel through the sensitivity analysis in case of the door speaker excitation. Finally, the analysis of the quality deviation using mother car is suggested to guarantee the stable characteristics of vehicle vibration in the early stage of vehicle development. These improvements can lead to shortening the time needed to develop better vehicles.

• Korean Journal of Community Nutrition
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• v.5 no.4
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• pp.615-623
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• 2000

Under the assumption that people go through stages in making dietary behavior change, this study was attempted to apply the stages of a change model for fat intake by examining the associations of social psychological variables with stages of change in dietary fat reduction. Derived from social psychological theories, 10 social psychological variables on motivational beliefs(6), social influence(3) and self-efficacy(1) related specifically to selecting every day diets low in fat were constructed. Fat and energy intakes were assessed by a short form semi-quantitative food frequency questionnaire. The associations of stages of change with motivational beliefs, social influence, and self-efficacy variables and energy and fat intakes were assessed in 333 female adults from large cities in Korea. Dietary stage groups differed significantly on most of the social psychological variables in ways predicted by theory. Motivational factors that lead to a psychological state of readiness to take action were important in the early stages of the dietary change process. Social influences were more important in the stages as people decide to take action. Self efficacy and motivational beliefs, particularly, reduction of perceived barriers were important in maintaining fat reduction behavior. The results of our study indicate differences in stages of change in fat reduction behavior in terms of nutrient intakes and social psychological correlates and suggests that adding a time dimension to social psychological models increases our understanding of dietary change, which assist us in designing nutrition education interventions that are more appropriately targeted by stage of change. (Korean J Community Nutrition 5(4) 615∼623, 2000)

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.2
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• pp.11-16
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• 2015

A lot of factor effects on the enterprise's innovation and business performance, for instance CEO and members intention etc.. Niehoff et al. says, The success factors of innovation enterprise's management lead to members of vision, innovation, innovation activities and support for an aggressive attitude of the enterprise members. However, today's products consumers wanted diverse and complex needs. CEO and members of the enterprise has been the diversity effort. The increase cost savings as well as in the profit improve factors that enterprise's participated a education and training, Subgroup activities, process quality, eliminate waste, improve yields, lead time reduction, process capability increasing, ets. This paper is a report of an empirical survey performed to 277 small and medium-sized enterprise in the korea. Cronbach's alpha coefficient is employed to analyze the reliability of the data. The effect analysis of each group is performed by the SEM(structural equation model). We use the SPSS' Amos program to analyze the equation modeling and test the hypotheses of the model.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.130-137
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• 2018

In long freight trains, there is a brake time delay in the neighboring freight cars that causes damage and fractures of couplers, especially the knuckle of them. If there is a problem for couplers in the cars, this could cause a derailment and lead to damage of human life and property damage. In this study, maximum forces on the couplers are studied when a long freight car brakes, with brake delay time and coupler gap. We have made a dynamic model of 50 freight cars and couplers, applying contact between couplers and a characteristic curve for expressing force and displacement of buffers with SIMPACK, a multi-body dynamics program. We use EN 14531-2 from the British Standards Institution, a standard of freight car brakes for the verification of the dynamic model. We also use a simplified method to analyze the dynamic model of 50 freight cars. With changing coupler gap and brake delay time, we do comparative analysis with AAR M-201 from the Association of American Railroads, a standard of AAR couplers. From this result, we find that the standard on fatigue limit is satisfied, such that the brake delay time is within 0.06 second if the coupler gap of the AAR coupler is within 20 millimeters.

• Korean Journal of Bronchoesophagology
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• v.6 no.2
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• pp.177-180
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• 2000

Backgrounds： Patients with respiratory failure may require prolonged mechanical ventilation. The purpose of this study was to determine the optimal time for tracheostomy and complications of tracheostomy. Methods : All medical records of 27 patients who underwent tracheostomy in department of thoracic & cardiovascular surgery at Yondong Severance hospital between January 1, 1990 and December 31, 1998, were reviewed. Variables analyzed include underlying disease, primary indication of tracheostomy, interval from 1st intubation to tracheostomy, duration from tracheostomy to weaning ventilator, duration of decannulation, and complication. There were 18 men and 9 women. Mean age at the time of the tracheostomy was 54 years (rage, 11 to 64 yeras). Results : Underlying diseases included lung cancer in 14 patients (51.9%), trauma in 8 patients (29.6%), and TE fistula in 2 patients. The indication for tracheostomy were as follows: prolonged mechanical ventilation in 13 patients, purpose of bronchial toilet in 9 patients, and tracheal stenosis in 5 patients. The mean interval between the first intubation and tracheostomy was 8.1 days. The mean duration from tracheostomy to weaning ventilator was 10.1 days. Conclusions : Timing of tracheostomy Is very important. Tracheostomy may benefit patients because it can accelerate the process of weaning and thus lead to a reduction in the duration of ventilation, length of hospitalization, and cost.

• International journal of advanced smart convergence
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• v.5 no.4
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• pp.48-53
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• 2016

In this paper, all elements used in integrated infrastructure for job competency assessments of NCS (National Competency Standards) will be merged into assessment system using multiple devices(ASMD). NCS is a systematic approach on required abilities (knowledge, technical expertise, attitude) to process the tasks in the fields by industry. Competiveness of ASMD design is that no limitation of time and space using personal devices like PC, laptop, smartphone, and tablet, while seeing screen, hearing, touching, speaking, and writing. Question type can be limitless to express the situation. To lead technologies and market for domestic and oversea assessment system, supporting on multiple devices with connectivity that will eliminate limitation of time and space is the key feature for design competitiveness. Design of integrated assessment system proposed in this paper can be applied to NCS, fundamental competency evaluation, online test, job aptitude test, and foreign language test which involve listening, reading, writing, and speaking. Compared with existing evaluation method, reduction of investment and operating cost will be greater. Along with development of ICT technologies, the next generation of integrated assessment system will be quickly changed to ASMD, which already involves connected service between internet and smart devices.