• Journal of Power System Engineering
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• v.3 no.3
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• pp.60-69
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• 1999

The noise and vibration sources of rotary compressor for room air-conditioner are pressure pulsation of compression process, cavity resonance of inner space, structural radiation noise of shell and impact noise of discharge valve. Among them, pressure pulsation is very important noise and vibration source. Because it transferred various kinds of noise and vibration like as mentioned above. In this reason, muffler and resonator are used in order to absorb and remove these noises. But an analytical prediction using acoustic analysis does not coincident with the experimental result. The difference between analysis and actual state is due to the assumption of analysis. This paper covered with new concept of muffler design based on the turbulence kinetic energy of flow by using CFD. From this analysis, it is possible to decide the best position of discharge port of muffler. Therefore $2{\sim}3dB$ noise reduction effect is acquired in rotary compressor of 5000 BTU grade. Also new approach of resonator design is suggested. From this study, the characteristics of resonator and surge hole (a kind of resonator without pipe length) are identified. The former is useful for pure tone noise (narrow frequency band), and the latter is effective for broad frequency band. This paper shows that it is very available to use 3 dimensional analysis of resonator in order to predict more exact tuning frequency. The result is proved by a lot of experiments. From combination of fluid analysis and acoustic analysis, up stream position is effective location of resonator concerning turbulence motion of fluid.

• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.289-298
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• 2000

In order to minimize the impact of water hammer In a pipeline, a determination of optimum position of hydraulic structures with best operation of pressure relief valve was explored at the Seobyun pumping station. Method of characteristics is used to simulate a surge impact originating from abrupt stop of pumping operation in a pipeline. Genetic algorithm shows a powerful capability in searching a global solution, especially for a nonlinear problem The application results suggests that the maximum positive pressure can be relaxed by decreasing the opening time of pressure relief valve, meanwhile the maximum negative pressure can be relaxed by increasing the opening time of pressure relief valve. This study shows that the integration of a genetic algorithm with a transient analysis technique such as method of characteristic can improve the design of hydraulic structure in a pipe network.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.25-34
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• 2017

Since the 30-year-old facility is expected to surge from 10.5% to 23.9% in 10 years, the new evaluation system is needed to establish efficient maintenance system for securing the safety and extending the life span of existing facilities. In this study, Delphi and AHP(Analytic Hierarchy Process) was conducted to provide a systematic new evaluation system for the NATM tunnel, which is the most frequently constructed structure of the existing tunnel. Since the existing assessment systems are limited in scope of evlauatuon criteria, the survey was conducted in conjunction with closed questionnaires on existing items and open questionnaires for eliciting new items. In results, suitable evaluation factors were derived for the NATM tunnel through the validation of the survey results. Also after calculating weighted value of the derived assessment item using AHP technique, a new evaluation system is proposed to meet the characteristics of the NATM tunnel, so that they can be used as reference materials for revising and supplementing detatiled guidelines in the future.

• The KSFM Journal of Fluid Machinery
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• v.13 no.1
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• pp.9-16
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• 2010

In the power generation industry, various efforts are needed to cope with tightening regulation on carbon dioxide emission. Integrated gasification combined cycle (IGCC) is a relatively environmentally friendly power generation method using coal. Moreover, pre-combustion $CO_2$ capture is possible in the IGCC system. Therefore, much effort is being made to develop advanced IGCC systems. However, removal of $CO_2$ prior to the gas turbine may affect the system performance and operation because the fuel flow, which is supplied to the gas turbine, is reduced in comparison with normal IGCC plants. This study predicts, through a parametric analysis, system performances of both an IGCC plant using normal syngas and a plant with $CO_2$ capture. Performance characteristics are compared and influence of $CO_2$ capture is discussed. By removing $CO_2$ from the syngas, the heating value of the fuel increases, and thus the required fuel flow to the gas turbine is reduced. The resulting reduction in turbine flow lowers the compressor pressure ratio, which alleviates the compressor surge problem. The performance of the bottoming cycle is not influenced much.

• Journal of Navigation and Port Research
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• v.42 no.2
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• pp.127-136
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• 2018

The motion response of floating structures is of significant concern in marine engineering. Floating structures can be disturbed by waves, winds, and currents that create undesirable motions of the vessel, therefore causing challenges to its operation. For a floating structure, mooring lines are provided in order to maintain its position; these should also produce a restoring force when the vessel is displaced. Therefore, it is important to investigate the tension of mooring lines and the motion responses of a twin barge when moored to guarantee the safety of the barge during its operation. It is essential to precisely identify the characteristics of the motion responses of a moored barge under different loading conditions. In this study, the motion responses of a moored twin barge were measured in regular waves of seven different wave directions. The experiment was performed with regular waves with different wavelengths and wave directions in order to estimate the twin-barge motions and the tension of the mooring line. In addition, the motion components of roll, pitch, and heave are completely free. In contrast, the surge, sway, and yaw components are fixed. In the succeeding step, a time-domain analysis is carried out in order to obtain the responses of the structure when moored. As a result, the Response Amplitude Operator (RAO) motion value was estimated for different wave directions. The results of the experiment show that the motion components of the twin barge have a significant effect on the tension of the mooring lines.

• Journal of Environmental Science International
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• v.19 no.10
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• pp.1187-1201
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• 2010

The formation and development conditions of the cloud streets over the yellow sea by the Cold Surge of Siberian Anticyclone Expansion which produce the heavy snowfall events over the southwestern coast, Honam District of the Korean peninsula, has been investigated through analyses of the three dimensional snow cloud structures by using the CAPPI, RHI, VAD and VVP data of X-band Radar at Muan Weather Observatory and S-band Radar at Jindo Weather Station. The data to be used are obtained from January 04, 2003, when heavy snow storm hits on Gwangju and Honam District. The PPI Radar images show that the cloud bands distribute in perpendicular to the expansion direction of the high pressure and that the radius of cloud cells is about 5~8 km with 20~30 dBz and distance between each cell is about 10 km. And but the vertical Radar images show that the cloud street is a small scale convective type cloud within height of about 3 km where a stable layer exists. From the VVP images, the time period of the high pressure expansion, the moving direction and development stages of the system are delineated. Finally, the vertical distribution of wind direction is fairly constants, while the wind speed sheer increases with altitude to 3 km.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.2
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• pp.78-85
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• 2007

The malfunction accidents such as kept within elevator, sudden rise, sudden stop, error of level indication which can bring about uneasiness of elevator passenger and be related with life accident are occurring. However, as there is not field recurrence for this portion and they are accidents that occur and then disappear, it is actually difficult to confirm the reason of accident. Therefore, we made an experiment for tolerance in three models which is being built recently according to EN12016(2004) standard and analyzed the movement characteristics of elevator to study the reason which can bring about confine and malfunction. Furthermore after supplementing measures for malfunction, Finally this paper will be used as reference to suggest methods for malfunction of elevator facility and the analysis for mutual relation between Power Quality and malfunction and fault of elevator.

• Journal of the Korea Society for Simulation
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• v.26 no.3
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• pp.47-54
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• 2017

This paper analyzed the motion characteristics of two ships according to the ship's dimension using Ship Handling Simulator. When the panamax container ship passes the smaller ship, peak point and patterns of interaction forces for the moored ship are noticeable. Accordingly, special attention should be paid to the movements of moored ship because surge force and yaw moment changes in the opposite direction before and after condition of ship's beam. However, when the container ship passes the larger moored ship in reverse, peak point stood out on the passing ship at the beginning of ship-to-ship interaction and attraction force on the passing ship occurred steadily during 1L(length overall of passing ship) interval at a point of beam. In addition, as the lateral distance between the hull of two ships decreases less than 2B(breadth of passing ship), interaction forces on the passing ship at the beginning are sharply increase.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.4
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• pp.599-604
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• 2021

In the information age, internet was developed from the wired access to the wireless Internet access. When a surge in demand for wireless Internet access, efficiency and performance of 2.4 and 5GHz band which leads to saturation of the communication was significantly fall. In this paper, we studied the design and fabrication of slot patch antenna to be used in wireless communication systems operating at around 10GHz band. To obtain optimal antenna parameters such as patch size, inter patch space, sL, sW, feed L, feed w, slot patch antenna was simulated by HFSS(High Frequency Structure Simulator). From these parameters, slot and patch antenna is fabricated using FR-4 substrate of dielectric constant 4.4. The characteristics of fabricated antenna were analyzed by network analyzer. The fabricated slot patch antenna showed a center frequency as 10.23GHz, the minimum return loss as -32dB, and -10dB bandwidth as 420MHz respectively.

• Journal of Family Relations
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• v.23 no.2
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• pp.67-87
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• 2018

Objectives: The purpose of this study is to critically review the recent discourse on single-person households (SPH) that appeared in Korean newspapers. Specifically, we analyzed articles in five major daily newspapers, which are representative of the media in Korean society, and examined the types of titles, subjects, and contents of articles in which SPH were mentioned. Method: For this purpose, 538 articles on SPH or "living alone" that appeared in the five major Korean newspapers during 2011-2017 were analyzed using content analysis methods. Results: Our analysis revealed eight major topics(living arrangement and household characteristics; financial instruments; food, clothing, and housing culture; policy; welfare; relationships; safety; values and attitudes). The results show that there is a surge of articles portraying neutral images of SPH in Korean newspapers, thereby emphasizing the recent growth in the number of SPH and the information relating to this population group. Although negative images of SPH continue to exist in the discourse, in recent times we found these attitudes to have become less prevalent compared to neutral images or even positive discourse. We also found that the discourse on these topics and arguments can be divided into four themes-the diversity of SPHs, the solo economy for single households, safety issues, and social relationships. Conclusions: Theoretical and policy implications on family studies relating to SPH are discussed.