• The Journal of the Acoustical Society of Korea
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• v.43 no.2
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• pp.162-167
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• 2024

Low frequency noise emitted by wind turbines is one of the most noise complaints. In this study, the reliability of the models was examined by comparing the measured sound pressure levels with the predicted levels based on Denish model and commercial programs of the SounPLAN and the ENPro based on ISO 9613. As a result of applying it to representative 3 MW wind turbines, on lnad, the measured and the predicted values differed within a maximum of 5 dB in the frequency range of 12.5 Hz to 80 Hz. It may be due to the change in the acoustic power levels because the wind turbines have been in operation for more than 7 years. However, considering that the Boundary Element Method (BEM) predicted value, which is known to be the most accurate in the low frequency band, the predicted values are well matched within 2.5 dB, the models of this study are expected to be used as deviation within 3 dB.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.34-37
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• 2003

The frequency of power system will change when the load-generation equilibrium is disturbed. Insufficiency of generation from the imbalance between load and generation decreases the power system frequency. In case of the severe emergency, the under frequency load shedding scheme is applied for the power system defense plan. In this paper, we analyzed the dynamic characteristics of under frequency load shedding using new Transient Security Assessment Tool ; TSAT. We applied the actual UFLS scheme to these studies and considered the possible contingency.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.5
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• pp.520-526
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• 2009

Efficient stowage plan is required for handling large number of containers in a container terminal. Before a ship enters port, most of container terminals prepare a stowage plan based on information received from the shipping company. If this information does not have the accurate information of containers in the vessel, the stowage plan might be often changed or sometimes it becomes useless. In order to avoid this problem, we apply RFID system in the container ship and we propose a framework for communication between ships and terminals using RFID and Web Services technology.

• Plant Journal
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• v.9 no.1
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• pp.43-49
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• 2013

In this study, the natural frequency of the actual operating vertical pump in the P combined cycle power plant is measured and the cause of high vibration is determined by using fluid-structure coupled vibration theory. Choosing the vibration reduction plan suited for field conditions and using the numerical analysis verify effectiveness of the plan. The plan is applied to the actual pump and the empirical experiments are conducted.

• The Journal of Korea Robotics Society
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• v.1 no.2
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• pp.107-116
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• 2006

We propose a planning algorithm to automatically generate a robust behavior plan (RBP) with which mobile robots can achieve their task goal from any initial states under dynamically changing environments. For this, task description space (TDS) is formulated, where a redundant task configuration space and simulation model of physical space are employed. Successful task episodes are collected, where $A^*$ algorithm is employed. Interesting TDS state vectors are extracted, where occurrence frequency is used. Clusters of TDS state vectors are found by using state transition tuples and features of state transition tuples. From these operations, characteristics of successfully performed tasks by a simulator are abstracted and generalized. Then, a robust behavior plan is constructed as an ordered tree structure, where nodes of the tree are represented by attentive TDS state vector of each cluster. The validity of our method is tested by real robot's experimentation for a box-pushing-into-a-goal task.

• Structural Engineering and Mechanics
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• v.33 no.3
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• pp.339-355
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• 2009

The sealed, tuned liquid column gas damper (TLCGD) with gas-spring effect extends the frequency range of application up to about 5 Hz and efficiently increases the modal structural damping. In this paper the influence of several TLCGDs to reduce coupled translational and rotational vibrations of plan-asymmetric buildings under wind or seismic loads is investigated. The locations of the modal centers of velocity of rigidly assumed floors are crucial to select the design and the optimal position of the liquid absorbers. TLCGD's dynamics can be derived in detail using the extended non-stationary Bernoulli's equation for moving reference systems. Modal tuning of the TLCGD renders the optimal parameters by means of a geometrical transformation and in analogy to the classical tuned mass damper (TMD). Subsequently, fine-tuning is conveniently performed in the state space domain. Numerical simulations illustrate a significant reduction of the vibrations of plan-asymmetric buildings by the proposed TLCGDs.

• Korean Journal of Human Ecology
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• v.20 no.3
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• pp.713-729
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• 2011

The purpose of this study is to suggest an activation plan for community centers. The community centers, categorized into 3 types by the number of visitors, were comparatively analyzed by their programs, operation, and visitors' opinion. 6 community centers in Heungduk-gu, Cheongju-city, their 6 operators, and their 220 visitors were the sample. This study surveyed community centers on the spot about their space characteristics and programs, interviewed operators, and asked questionnaires to visitors. The data of the 3 categorized centers were analyzed by frequency, average, and percentage. The following is the result: 1) The number of visitors was dependent on the type of residence and age of the residents. The activated community centers were found in residence type apartment blocks, and with an age group in its 40s. 2) The space satisfaction was dependent on the year of construction; it was higher with newer buildings and wider sizes. 3) All the centers were affirmative on the communication of the participants of programs. In conclusion, the activation plan of the community center has to comprise a renovation of old buildings, public promotion, and the development of programs taking into consideration the age group of the residents.

• Journal of Construction Engineering and Project Management
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• v.4 no.3
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• pp.1-12
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• 2014

Construction management has been suffering from many problems, which need to be solved or better understood. Most of construction projects have not achieved efficiency as expected. In this context, waste was also considered as a problem of efficiency decrease, and poor production planning was considered as a cause for waste. This study was conducted on the basis of waste concepts and production planning processes based on the philosophies of Lean Construction. A survey to find out the relationship between them was carried out through questionnaire, which was answered by experienced people in construction projects. The results have shown that frequency of wastes occurrence is quite high, and production planning processes are superficially performed in construction phase. There is a significant negative relationship between production planning and waste occurrence (r = -0.262). Weekly Work Plan (WWP) is the most dominant plan for waste control with seventeen in total of nineteen waste factors, and phase plan is the most dominant plan for two remaining waste factors. A case study was adopted to validate the relationship between production planning and waste occurrence. The results showed that the better the project was planned, the fewer the waste would occur on construction sites.

• Journal of The Korean Society of Integrative Medicine
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• v.2 no.1
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• pp.77-89
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• 2014

Purpose : The objective of this study was to investigate the basis for effective introduction of home visiting physical therapy to provide basic information. Thus in our study, we investigated awareness, necessity and operation plan of home visiting physical therapy for patients and guardian. Method : We conducted a survey 172 and guardian. The questionnaire consisted of items for general characteristics, awareness, necessity and operation plan. Data was collected from 2013 november 1 to november 30. Based on the collected data of self-administered questionnaires, we analyzed for frequency of each questionnaire about awareness, necessity and operation plan of home visiting physical therapy. Result : The awareness for home visiting physical therapy. The necessity for home visiting physical therapy indicated a high result. The result for operation plan indicated a national program. Conclusion : Improving on people's awareness is needed, because the awareness about home visiting physical therapy was low but the need was high. In addition, government institutional arrangements will be needed for advanced medical services as soon as possible.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.265-271
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• 2003

This study is for the stable optical source in order to get the precision measurement, which contributes to help the laser frequency and the output to be settled. The laser optical frequency is changed by the length of resonance cavity. The length variation of the laser resonance amplitude is affected by the thermal expansion of that system. So, we try not only to adjust the temperature of the laser tube using the heater for fine length of resonance cavity, but also to maintain the fixed temperature of the resonance cavity for outputting the safe laser optical frequency. Therefore, we must take materials with the thermal expansion of the supporting system, which is closer to it of the laser resonance cavity. Using the materials, we can promote to stabilize the temperature of it. In advance, we also plan to get the settlement of the laser frequency and the output in the long km, optimizing and stabilizing the system.