• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.2
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• pp.117-122
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• 2014

A novel method to reduce the vibration of drum type washing machine is proposed. Recently, as the capacity of the drum-type washing machine gets expanded and its washing performance is improved, its market share is increasing in the whole world. But, the capacity of washing machine is limited because of door size and built-in washing machine size. The vibration of washing machine is caused by unbalanced cloths in high spining drum, and the displacement of tub is maximized at transient range about 3 Hz(180 rpm). Previous researches were concerned about steady-state vibration in spinning. In this study, concerned about transient vibration and the displacement of tub is decreased by using gyroscope system. Mutibody dynamic model of washing machine include gyroscope is designed and the vibration of tub have been reduced by 44.7 % over original.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.63-72
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• 2011

In recent years, hot-stamped components are more increasingly used in the automotive industry in order to reduce weight and to improve the strength of vehicles. In hot stamping process, blank is hot formed and press hardened in a tool. However, in hot stamping without cooling channel, temperature of the tool increases gradually in mass production thus cannot meet the critical cooling rate to obtain high strength over 1500MPa. Warpage occurs in the hot stamped component due to non-uniform stress state caused by unbalanced cooling. Therefore, tools should be uniformly as well as rapidly cooled down by the coolant which flows through cooling channel. In this paper, optimal design method of cooling channel to obtain uniform and high strength of the component is proposed. Optimized cooling channel is applied to the hot press V-bending process. As a result of measuring strength, hardness and microstructure of the hot formed parts, it is known that the design methodology of cooling channel is effective to the hot stamping process.

• Journal of Korean Society on Water Environment
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• v.29 no.3
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• pp.400-408
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• 2013

Total phosphorus was set as a target indicator to prevent eutrophication and algae growth, etc., in three major rivers (Nakdong River, Geum River and Yeongsang/Seomjin River) for the second phase (2011 ~ 2015) in total maximum daily loads (TMDLs) system. However, total phosphorus management was restrictively introduced, i.e., upstream of the Lake Daechung, in the Geum River watershed. Total phosphorus concentration and trophic levels in downstream of the Lake Daechung (include Mangyeong and Dongjin rivers) were increased more than upstream. Therefore, it is necessary to expand total phosphorus management in all watersheds of the Geum River. If total phosphorus was managed in all area of the Geum River watershed, it is possible to decrease total phosphorus concentration and trophic levels, and solve the unbalanced water quality between up and downstream of the Lake Daechung.

• Proceedings of the Korea Contents Association Conference
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• 2006.05a
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• pp.423-426
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• 2006

The present situation where the hearing handicapped can never get any information from IT related devices in his place of work and house, the development of the wireless device for communicating with the hearing handicapped can be regarded as the very important research which can solve the problem of the new obstacle in unbalanced information. In this paper, we propose the multipurpose wireless communication device using information and communication technology, for coping with quickly a state of emergency and assisting the normal life of the hearing handicapped.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.5
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• pp.448-455
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• 2015

A model predictive control (MPC) method without individual PWM has been recently researched to simplify and improve the control flexibility of a multilevel inverter. However, the input power of each H-bridge cell and the switching frequency of switching devices are unbalanced because of the use of a restricted switching state in the MPC method. This paper proposes a control method for balancing the switching patterns and cell power supplied from each isolated dc source of a cascaded H-bridge inverter. The supplied dc power from isolated dc sources of each H-bridge cells is balanced with the proposed cell balancing method. In addition, the switching frequency of each switching device of the CHB inverter becomes equal. A simulation and experimental results are presented with nine-level and five-level three-phase CHB inverter to validate the proposed balancing method.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.3
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• pp.199-206
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• 2010

Matrix converter is an energy conversion device of controlled power semiconductor switches that directly connects the three-phase source to the three-phase load. With no dc-link components for energy storage in the matrix converter the input current depends directly upon the load currents and the switch state of the converter. Therefore the unbalanced and distorted input voltages can result in unwanted output harmonic currents. This paper presents a current compensator based on neural network to improving output current quality for matrix converter under abnormal input voltage conditions. The effectiveness and feasibility of the proposed technique has been proven through numerical simulations and experimental tests.

• Journal of the Korean Society of Food Culture
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• v.8 no.2
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• pp.103-116
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• 1993

The purpose of this study was to assess the nutrition education and training needs as a basis for program planning for day care children. Nutrition achievement test developed by American National Dairy Council and Iowa state University was modified and used for measuring the level of basic knowledge of food and nutrition for day care children. The results of this study can be summarized as follows 1. Over 70% of mothers indicated their children had a certain degree of food behavior and feeding problems in terms of unbalanced food habit, irregular meal period. 2. Mean score for the nutrition achievement test for day care children was 9.3. 3. The nutrition achievement test score for children with high socio-economic status was significantly higher than those of children with middle and lower group. 4. Inspection of the difficulty difference indices showed that over the 50% of the children had more items that were easier in the content of physiological facts than in the food handling and social psychological aspects of foods.

• Journal of the Korea Institute of Building Construction
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• v.13 no.4
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• pp.360-371
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• 2013

Fast delivery of construction projects provides more value to project owners. Batch production, which is production not in single pieces, but in batches, is a common approach in repetitive construction projects such as multi-unit residential building construction projects. In batch production, the use of a small batch size allows the early start of subsequent activities, and thus can lead to early completion of projects. In addition to batch size, balance between productivities in construction activities can affect project duration. However, the impact of the balance between productivities with regard to their order on project duration has not been studied. The main goal of this study is to test a hypothesis, which is that the order of construction activities' unbalanced productivities affects the amount of time reduction that can be achieved by using a small batch size. A computer-based simulation model was developed, and five different cases were simulated to test the hypothesis. The conclusion of the simulation result is that the order of productivities does not affect the time reduction achieved by using a small batch size. It is expected that the findings of this study can help general contractors make decisions in terms of batch size.

• Journal of Power Electronics
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• v.11 no.3
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• pp.369-374
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• 2011

Usually, a LPF (low pass filter) is used in the feedback loop of a SRF (synchronous reference frame) - PLL (phase locked loop) system because the measured grid voltage contains harmonic distortions and sensor noises. In this paper, it is shown that the cut-off frequency of the LPF should be designed to suppress the harmonic ripples contained in the measured voltage. Also, a new design method for the loop gain of the PI-type controller in the SRF-PLL is proposed with consideration of the dynamics of the LPF. As a result, a better transient response can be obtained with the proposed design method. The LPF frequency and the PI controller gain are designed in coordination according to the steady state and dynamic performance requirements. Furthermore, in the proposed method, the controller gain and the LPF cut-off frequency are changed from their normal value to a transient value when a voltage disturbance is detected. This paper shows the feasibility and usefulness of the proposed methods through the computer simulations and experimental results.

• Journal of the Korean Society of Food Culture
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• v.11 no.1
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• pp.13-21
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• 1996

To find out the reference data of the school food service system, I serveyed four primary schools in Seoul, Korea and Nara, Japan respectively. The school children and their parents of whom arbitrary selected two classes among each primary school, were taken the questionaire about the present school food service system and their favorate food. The results were as follows; 1) 74.8% of Korean and Japanese children, and 92.5% of their parents were in favor of school food service. 2) Korean childrin wanted more amount of food and less salty taste. 3) Korean and Japanese children and their parents believed that the school food service system correct children's unbalanced diet. 4) Korean children wished more kinds of foods, western-styled cooking and that the food would be served in warm state. 5) Korean parents wanted that school food service system should be natural and better quality food material, and teacher should educate good eating habit. 6) Korean school children prefer yogurt, cuttle-fish, chicken, bean-curd, tomato, orange, dried laver, sweet potato, pine-mushroom in each food group. In conclusion, school food service system should be enough to meet children's good nutrition status, and the menu would be selected with consideration of children's preference and Korean traditional diet habit. Good table manner and eating all kinds of foods should be targht by school food service system as well as preparing good quality of food.