• Structural Engineering and Mechanics
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• v.16 no.1
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• pp.101-114
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• 2003

A base isolation system is proposed for earthquake protection of structures. The system incorporates spherical supports for the base, a specially designed spring-cam system to keep the base rigidly supported under normal condition and to allow it to move for the duration of the earthquake under the constraint of a spring with optimized non-linear characteristics. A single-story model is constructed to investigate the feasibility of the concept. Numerical simulations of the system as well as experimental results show that 95% reduction of the transmitted force to the structure can be achieved. To demonstrate the effectiveness of this isolation mechanism, the maximum dynamic bending stress developed at predetermined critical points within the frame of the structure is measured. Significant reduction of the dynamic stresses is obtained.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.460-461
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• 2006

Computer Loads can be found in all of modern society. The switching mode power supplies used in personal computers are major sources of harmonic currents. Harmonic currents can cause lots of harmonic problems such as disruption in computer performance. A series resonant filter is very effective in harmonic reduction for personal computer loads. Voltage sags are short duration reductions in rms voltage. The main causes of voltage sags are faults, motor starting, and transformer energizing. Personal computers are another example of devices sensitive to voltage sags. A serious voltage sag at the terminals way lead mis-operation of the equipment. This paper presents an in depth analysis to evaluate the effect of harmonics reduction based on the IEC 61000-3-2 and the effect of voltage sag using ITI curve by applying a series resonant filter for personal computer loads.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.225-230
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• 2003

The major purpose of this study is to find the optimized split injection quantities and dwell angles for PM reduction without increasing NOx. The tests were performed on a Common-Rail DI Diesel Engine to obtain optimum injection timing and duration. In this study, total injection quantities were divided into the ratio of 25-75%, 50-50% and 75-25%. NOx and PM were measured on the condition of the same bsfc by increasing dwell angles. It was found that the split injection reduced NOx with dwell angle increase. For 50_50, 75_25% split injection cases, PM was reduced with 10 to 12(CAD) dwell angles. For 25_75% split injection 33% PM reduction was achieved with 8 to 12(CAD) dwell angles.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2008.04a
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• pp.251-255
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• 2008

Nowadays the scale of domestic construction becomes large, sophisticated and specialized. It has led to a growing need for the high quality, cost reduction, safety and reduction of work duration. Therefore the importance of construction materials management is emphasized to perform the project successfully. It becomes an current issue about method of construction material management according to the flow of construction progress in the construction field. Therefore, various researches using RFID for efficiency of construction material are being studied. We analyzed the case study using RFID, drew the problems through the investigation of status about the management of material in the field, and then suggested the method of material management using in the apartment building construction field.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.839-842
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• 2010

In this paper, we propose a residual echo and noise reduction scheme for hands-free telephony applications. The proposed algorithm uses a noise robust modified AP algorithm which estimate well echo path in noisy and whitens residual echo signal using linear prediction at non double-talk duration. It is confirmed that the proposed algorithm shows better performance from acoustic interference cancellation (AIC) viewpoint.

• Computers and Concrete
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• v.34 no.1
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• pp.49-61
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• 2024

The present study concerns a removal of chloride ions and structural behaviour of concrete beam at electrochemical chloride extraction (ECE). The electrochemical properties included 1000 mA/m2 current density for 2, 4 and 8 weeks. It was found that an increase in the duration of ECE resulted in an increase in the extraction rate of chlorides, in the range of 35-85%, irrespective of chloride contamination. In structural behaviour, the strength and maximum bending moment of specimen was always lowered by ECE. Moreover, the flexural rigidity and bending stiffness were reduced by the loss of effective cross-section area in the linear elastic range. Simultaneously, the inertia moment was substantially subjected to 70% loss of the cross-section by the tensile strain at the condition of the failure. However, a lower rate of the inertia moment reduction was achieved by ECE, implying the higher resistance to the cracking, but the higher risk of deformation.

• Journal of Korean Foot and Ankle Society
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• v.1 no.2
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• pp.112-118
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• 1997

Tarsometatarsal fracture-dislocation is uncommon but severe lesion. Since this lesion is sometimes difficult to recognize by roentgenography, it is easily overlooked. Three patients were treated with open reduction and internal fixation with 3.5 mm cannulated screw and K-wire, two had treatment with open reduction and internal fixation with 3.5 mm cannulated screw only and two had treatment with dosed reduction and short leg cast only between January 1994 and May 1996. The duration of follow-up ranged from twelve to twenty-nine months after the diagnosis. Results were assessed by a subjective questiormaire, physical examination, and radiographic analysis. Multiple fixation techniques for maintaining the reduction of tarsometatarsl joint have been introduced. We recent]y used the 3.5 mm cannulated screw for internal fixation of the tarso-first and second metatarsal fracture-dislocation. We think cannulated screw fixation has several advantages; 1. The cannulated screw fixation is more rigid than the K-wire fixation. 2. There is an decreased risk of screw breakage with early weight bearing. 3. It is possible to compress the involved joints, if necessary. There were no disability in all patients. One patient who was treated with delayed open reduction and internal fixation with 3.5 mm cannulated screw and K-wire had a radiographic mild degenerative arthritis. And one patient who was treated with dosed reduction and short leg cast had a mild metatarsus adductus. But. these two patients were symptom free. There was no correlation between the severity of the diastasis and the patient s functional result.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.350-353
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• 2009

In the present study, the effect of initial microstructure, cold reduction ratio, and annealing temperature on the spherodization rate of SK85 high carbon steel sheet was investigated. High carbon steel sheet fabricated by POSCO was soaked at $800^{\circ}C$ for 2 hr in a box furnace and then treated at $570^{\circ}C$ for 5 min in a salt bath furnace followed by water quenching to obtain a fine pearlite structure. Cold rolling was conducted on the sheets of fine pearlite by reduction ratios of 20, 30, and 40% and heat treatment for spheroidization was carried out at 600 and $720^{\circ}C$ for the various time intervals from 0.1 to 32 hrs. Area fraction of spheroidized cementite was measured with an image analyzer as a function of cold reduction ratios and duration times.

• Journal of Soil and Groundwater Environment
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• v.21 no.6
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• pp.14-21
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• 2016

This study evaluated the applicability of stabilization of arsenic (As)-contaminated soil with iron (Fe) oxides at the former Janghang smelter site. Three Fe oxides (magnetite, goethite, and hematite) were tested as stabilizing agents to one soil sample collected from the study site. Amendment of 5% of magnetite, goethite, or hematite for one week showed the 64, 58, and 36% of reduction of the SBRC (Solubility/Bioavailability Research Consortium)-extractable (bioaccessible) As, respectively. Duration of stabilization more than one week did not show an additional reduction in SBRC-extractable As. Amendment of 5% of magnetite, which showed the highest As stabilization efficiency, was applied to 24 soil samples collected from the same site for one week, and 72% of reduction in the bioaccessible As was observed. The potential carcinogenic human health risk at the study site caused by As was $1.7{\times}10^{-5}$, which could be reduced to $8.1{\times}10^{-6}$ by the amendment of 5% magnetite for one week.

• Journal of Environmental Science International
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• v.26 no.12
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• pp.1389-1397
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• 2017

In this study, we calculated the fixed-type Areal Reduction Factor (ARF) of the Hancheon River basin in Jeju Island, and compared the calculated ARF and the ARF of the four major river basins suggested by the Ministry of Land, Infrastructure and Transport. As a result, the maximum fluctuation ratios of ARF for the four major river basins calculated using area, frequency, and initial duration time were significant: 7.61% for the Hangang River basin; 12.69% for the Nakdonggang River basin; 8.09% for the Kumgang River basin; and 17.98% for the Yeongsangang River basin. In addition, the differences between the maximum and minimum value of ARF for the Hancheon River basin based on 48 hours was 2.13%, and it was smaller than the one for the four major river basins: 8.92% for the Hangang River basin; 11.41% for the Nakdonggang River basin; 8.87% for the Kumgang River basin; and 17.17% for the Yeongsangang River basin. The Yeongsangang River basin had the highest difference.