• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.231-234
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• 2003

This paper presents a novel high frequency transformer linked full-bridge type soft-switching phase-shift PWM control scheme DC-DC power converter, which can be used as power conditioner fur small-scale fuel cell power generation system. Using full-bridge soft-switching DC-DC converter topology makes possible to use low voltage high performance MOSFETs to achieve high efficiency of the power conditioner. A tapped inductor filter is implemented in the proposed soft-switching converter topology to achieve soft-switching PWM constant high frequency operation for a wide load variation range. to minimize circulating and idling currents without using additional resonant circuit and auxiliary power switching devices. The practical effectiveness of the proposed soft-switching DC-DC converter is verified in laboratory level experiment with 1 kW 100kHz breadboard setup using power MOSFETs. Actual efficiency of 94-96$\%$ is obtained for the wide load range

• Journal of Korean Society of Steel Construction
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• v.13 no.6
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• pp.715-723
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• 2001

This paper represents the behavior of CFT column to H-beam full-scale connection with external T-stiffener. 6 specimens whose T-stiffeners which are compounded of vertical element and horizontal element were made under the parameter of the strength ratio of each elements(vertical element and horizontal element in T-stiffener) to the beam full plastic moment. The analysis-parameters demonstrated in the base of the data that we get in experiment are strength stiffness, and plastic rotational capacity. All of specimen showed stable hysteretic behavior, and the horizontal element is more critical than vertical element in strength and stiffness. The mean beam plastic rotation of all specimen except the TS-2 specimen is 2.97% rad.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.42-46
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• 2005

In spite of fast growing of prediction codes, there is still not negligible uncertainty in their results. This uncertainty affects on the turbine structural design and power production prediction. With the growing size of wind turbine, reducing this uncertainty is becoming one of critical issues for high performance and efficient wind turbine design. In this respect, there are international efforts to evaluate and tune prediction codes of wind turbine. As the reference data for this purpose, field test data is not appropriate because of its uncontrollable wind characteristics and its inherent uncertainty. Wind tunnel can provide controllable wind. For this reason, NREL has done the full scale test of the 10m turbine at NASA-Ames. With this reference data, a blind comparison has been done with participation of 18 organizations with 19 modeling tools. The results were not favorable. In Europe, a similar project is going on. Nine organizations from five countries are participating in the MEXICO project to do full scale wind tunnel tests and calculation with prediction codes. In this study. these two projects were reviewed in respect of wind tunnel test and its contribution. As a conclusion, it is suggested that scale model wind tunnel tests can be a complementary tool to calculation codes which were evaluated worse than expected.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.519-526
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• 2006

In this study, the major operating factors in SND(simultaneous nitrification and denitrification) using bioreactor packed with submerged cilia media and granular sulfur such as variation of nitrification rate, organic matter removal efficiency and denitrification efficiency in different DO concentration were mainly evaluated. Synthetic wastewater and actual sewage were used as influent wastewater. Experiment with synthetic wastewater as influent wastewater was divided into three phases with the adjustment of DO concentration. As the results, nitrification efficiency and T-N removal efficiency in the Phase 3(DO 1.0~2.0 mg/L) were 99% and 52.3%, which is significantly greater than those in other two phases. Also, loading rate and denitrification efficiency of SCPGS(Submerged Cilia media Packed with Granular Sulfur) were calculated as $0.44kg\;NO_3^--N/m^3-day$ and 50%, respectively. On the other hand, nitrification rate was decreased from 99% to 64% according to the DO concentration with the variation from 3.0~3.5 mg/L(phase1) to 0.4~0.6mg/L(phase2). Although the nitrification rate was decreased in 64% according to the variation of the DO concentration, T-N removal rate was rapidly increased to 49% by increasing of the denitrification efficiency. Experiment with actual sewage as influent wastewater was carried out to evaluate efficiency of SCPGS in real operation condition of full-scale sewage water treatment plant. At the time, T-N removal rate in this experiment and full-scale wastewater treatment plants were given by 43% and 20%, respectively. The above results indicate that SCPGS can be used as an advanced treatment process for economical efficiency considered.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.1
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• pp.58-63
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• 2009

Dissolved air flotation (DAF) process is generally considered more effective than sedimentation process in raw water containing algae, humus materials, and low density particles. This study presents the treatment efficiencies by the coagulation and flocculation conditions at a drinking water treatment plant using a laboratory tester and the full scale DAF pump system. The full scale DAF pump system (F-DAF) in this study had a capacity of 5,000 $m^3$/d and a hydraulic surface loading of 10 m/hr. F-DAF in D drinking water treatment plant was continuously operated to determine the operational performance and pretreatment (mixing and coagulation) conditions. Results in the laboratory experiment showed that the optimum coagulant (PSO-M) doses required to 2.7~4.5 mL/$m^3$/NTU with raw water turbidity from 13.8 NTU to 56.3 NTU. F-DAF in the optimum coagulant dosage could be operated in effluent turbidity of 1 NTU or below for a month.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2600-2608
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• 2011

The dynamic stability of railway vehicle has been one of the important issues in railway safety. The dynamic simulator has been used in the study about the dynamic stability of railway vehicle and wheel/rail interface. Especially, a small scale simulator has been widely used in the fundamental study in the laboratory instead of full scale roller rig which is not cost effective and inconvenient to achieve diverse design parameters. But the technique for the design of the small scale simulator for the fundamental study about the dynamic characteristics of the wheel-rail system and the bogie system has not been well developed in Korea. Therefore, the research about the development of the small scale simulator and the bogie has been conducted. As this paper, To predict the dynamic behavior of railway vehicle, we studied running stability test of 1/5 scaled bogie that similarity laws is applied using small scale derailment simulator. For the operation of the small scale derailment simulator, it is required to investigate the performance and characteristics of the system. This could be achieved by a comparative study between an analysis and an experiment. This paper presented the analytical model which could be used for verifying of the test results and understanding of the physical behavior of the dynamic system comprising the small scale bogie and the simulator.

• Wind and Structures
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• v.19 no.6
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• pp.649-663
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• 2014

The present paper discusses the characteristics of unsteady aerodynamic forces on long-span curved roofs. A forced vibration test is carried out in a wind tunnel to investigate the effects of wind speed, vibration amplitude, reduced frequency of vibration and rise/span ratio of the roof on the unsteady aerodynamic forces. Because the range of parameters tested in the wind tunnel experiment is limited, a CFD simulation is also made for evaluating the characteristics of unsteady aerodynamic forces on the vibrating roof over a wider range of parameters. Special attention is paid to the effect of reduced frequency of vibration. Based on the results of the wind tunnel experiment and CFD simulation, the influence of the unsteady aerodynamic forces on the dynamic response of a full-scale long-span curved roof is investigated on the basis of the spectral analysis.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.57-64
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• 2021

Maneuvering motions of a ship in calm water are studied through the concept of MMG model. Governing forces are defined by the use of available empirical formulae that require only main ship particulars as input variables. In order to validate the calculation tool, a full-scale sea experiment was carried out in Osaka Bay using a 17-m twin-screw passenger ferry. Test execution and data measurement were performed through the utilization of an autopilot control unit and satellite compass. The result of a straight running test confirms the acceptable accuracy in addressing the surge motion problem. Reasonable agreement between simulation and experiment is also confirmed for 5°/5° and 10°/10° zig-zag tests despite the strong environmental disturbance. The current model can generally represent the subject ship maneuvering motions and is promising for the application to other ship hulls.

• International Journal of Highway Engineering
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• v.17 no.6
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• pp.105-115
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• 2015

PURPOSES : This study aimed to evaluate the appropriateness of safety with the standard for threshold zone luminance as specified in the Recommendation for Lighting of Traffic Tunnel, which has been widely adopted worldwide. METHODS : A driving test of the subject in a full-scale road tunnel was conducted. The adaptation luminance and threshold zone luminance, which should be known for the driver to perceive an object within stopping sight distance, were obtained. These values were compared with the adaptation luminance and threshold zone luminance obtained by the existing reduced model test and tunnel lighting standard that has served as a guideline for the current threshold zone luminance standard. RESULTS : According to this study, threshold zone luminance should be increased to at least 1.8 times the value proposed in the existing studies and to twice the domestic tunnel lighting standard (KS C 3703: 2014). CONCLUSIONS : The threshold zone luminance proposed in this study differs largely from that obtained from indoor tests and from the current tunnel lighting standard used worldwide; this difference may be attributed to the fact that the indoor tests did not incorporate driving workload, non-uniformity of luminance distribution in terms of sight, and factors that reduce the visibility of the driver, such as the light reflected into the driver's eyes. Hence, it is necessary to further review the factors that reduce the visibility of drivers approaching tunnels in order to determine the rational tunnel threshold zone luminance.

• Structural Engineering and Mechanics
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• v.50 no.1
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• pp.89-103
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• 2014

According to experimental studies made so far, design formula of shear characteristics suggested by ISO 22762 and JEAG 4614, representative design code for Lead Rubber Bearing(LRB) shows dependence caused by changes in compressive stress. Especially, in the case of atypical special structure, such as a nuclear power structure, placement of seismic isolation bearing is more limited compared to that of existing structures and design compressive stress is various in sizes. As a result, there is a difference between design factor and real behavior with regards to shear characteristics of base isolation device, depending on compressive stress. In this study, a full-scale low hardness device of LRB, representative base isolation device was manufactured, analyzed, and then evaluated through an experiment on shear characteristics related to various compressive stresses. With design compressive stress of the full-scale LRB (13MPa) being a basis, changes in shear characteristics were analyzed for compressive stress of 5 MPa, 10 MPa, 13 MPa, 15 MPa, and 20 MPa based on characteristics test specified by ISO 22762:2010 and based on the test result, a regression analysis was made to offer an empirical formula. With application of proposed design formula which reflected the existing design formula and empirical formula, trend of horizontal characteristics was analyzed.