• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.33-44
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• 1999

An energy balance procedure is developed to incorporate the effects of earthquake duration which involves the effect of cyclic loading and the corresponding cumulative plastic deformation. Particular emphasis is given to the flexural failure of non-seismically designed columns of reinforced concrete frames. For this, conceptual strength deterioration models for columns, governed by concrete, anchorage failure and longitudinal steel fracture due to low-cycle fatigue, are proposed. It is evident that the energy-based method has good agreement with the experimental data and is able to predict the failure mode.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.65-80
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• 2014

This study conducted Trapdoor tests with actual tunnel shape, investigated the mechanical behavior of ground and loosening load on tunnels, and evaluated the mechanism of progressive failure by numerical simulation. The loosening load sharply decreased initially, but it generally increased and reached the stabilized level exhibiting the arching effect, and loose sand showed relatively higher values than those of dense sand. The shear band started from the tunnel shoulder with $63^{\circ}$ (loose sand) to $69^{\circ}$ (dense sand), and gently curved inward to the ground surface. The widths of shear band formation above the tunnel showed a range from 1.8b to 1.9b (b=Tunnel width), which are similar to those values calculated from existing formular. The vertical height of this shear band for deep tunnel was turned out to be a bit lower than that from existing studies (3.0*Tunnel Height).

• Journal of Trauma and Injury
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• v.29 no.1
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• pp.22-27
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• 2016

Purpose: The optimal method of fixation of symphysis pubis (SP) diastasis in pelvic ring injuries is still controversial. In this study, we investigated the radiological and the clinical results of a precontoured 4.5-mm symphysis pubis (SP) plate with tension band wiring (TBW) after an anterior pelvic injury in pelvic fractures. Methods: We treated 25 patients with traumatic SP diastasis by open reduction and internal fixation with plates and wires. We used a four-hole 4.5-mm precontoured SP plate with a tension band wiring. Results: Patients with a SP with TBW fixation achieved excellent or good results at final follow-up. Post-operative complications included two (8%) patients with metal work movement. The mean symphyseal width was smaller in 4.5 mm SP plate with TBW during 1-year follow up period. Conclusion: A precontoured symphysis pubis plate (4.5 mm) with figure-of-eight fashion tension band wiring shows favorable radiological results, excellent or good clinical outcome, and a lower complication (hardware failure and revision surgery).

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.133-136
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• 1987

This paper presents a new algorithm of optimal measurement system by using band matrix characteristic respectively for state estimation. A performance index of measurement system is established to reflect relation among measurement sets, probability of measurement failure and cost of individual meter installation. Selection ranking in the candidates of measurement sets is composed to guarantee the observability for any any single meter outage. Performance index sensitivity is introduced and recursive formula which based on the matrix inversion lemma used for selection. The proposed algorithm is composed of successive addition algorithm, successive elimination algorithm and combinatorial algorithm. The band matrix characteristic could save in memory requirements and calculate the performance index faster than earlier.

• Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.6-11
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• 2009

It is anticipated that quality assurance for the Ka band Communication Payload System(COPS) development program of the communication, Ocean & Meteorological Satellite(COMS) may be a core technical factor to be concerned in order to avoid any failure, and to assure its final performance during the mission lifetime in space. Those can be managed and verified and assessed by performing the Quality Assurance (QA) and risk management which helps to prevent and to reduce the critical fails. This paper introduces the Product Assurance (PA) system and procedures for controlling and monitoring sub-contractors which were participated in Ka band Communication Payload System (COPS) development. Also this paper shows Quality Assurance (QA) procedures and detailed their processes for assured the product performed by local companies from site survey for selecting companies to delivery of their equipment.

• Journal of Aerospace System Engineering
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• v.2 no.1
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• pp.22-27
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• 2008

It is anticipated that quality assurance for the Ka band Communication Payload System(COPS) development program of the Communication, Ocean & Meteorological Satellite(COMS) may be a core technical factor to be concerned in order to avoid any failure, and to assure its performance during the mission lifetime in space. Those can be managed and verified and assessed by performing the Quality Assurance (QA) and risk management which helps to prevent and reduce the critical fails. This paper introduces the Product Assurance (PA) system and procedures for Ka band Communication Payload System which was established and performed during the Qualification Model (QM) manufacturing phase. In this paper, we present detailed process for the products manufactured by local companies according to PA procedures operated through whole phases from design to test of equipment. Also this paper shows Quality Assurance (QA) procedures and detailed their processes for assured the product quality manufactured by local companies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.41-49
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• 2014

In order to investigation splitting bond strength of the deformed longitudinal reinforcing bars in the R C members strengthened laterally with the external steel-band, a total 9 sets of test re-bars with and without active confining force given by the external steel-band are pulled monotonically until failure. Test results indicate that the bond strength becomes higher with the increase in number of steel-band sets and their initial stress magnitude. This is due to the active confining force given by the steel-band, and passive confining forces given by the steel-band and transverse reinforcements, in which the passive confinement effect varies depending on the magnitude of active confining force. An equation to estimate the splitting bond strengths for the R C members strengthened laterally with the external steel-band is developed based on the several experimental results of the present study.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.1
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• pp.40-46
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• 2010

DC link electrolytic capacitors are widely used in various PWM power converter system, such as adjustable speed driver(ASD) or DC/DC converter. Electrolytic capacitors, which is the most of the time affected by aging effect, plays a very important role for the power electronics system quality and reliability. This objective of this paper is to propose a improvement method to detect the rise of equivalent series resistor(ESR) in order to realize the online failure prediction of electrolytic capacitor for DC link of PWM power converter. The ESR detection scheme is based on the determination of the electrolytic capacitor AC losses calculated from voltage/current measurement using AC coupling. Therefore, the preposed online failure prediction method has the merits of easy ESR computation and circuit simplicity compare with BPF method. Simulation results show the veridity of the proposed on-line ESR estimation method.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.199-204
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• 1998

To analysis the failure character of Low-Heat concrete which is used to prevent the thermal crack caused by hydration heat, static loading test was performed by this test method, "Determination of the Fracture Energy of Motar and Concrete by Means of Three-Point Band Tests on Notched Beam" (suggested by RILEM 50-FMC Committe). This study compared and analysised the fracture energy of Mode I (opening mode), the most general pattern in the view of water-cemente ratio(W/C), compressive strength and age of Ordinary Portland Concrete and Low-Heat Concrete under the same mixture. The test results show that the case of Ordinary Portland Concrete and Low-Heat Concrete, low Water-Cemente ratio(W/C) cause the increase of fracture energy, and high failure-strength decrease failure-deflection, and the fracture energy of Low-Heat Concrete is similar to Ordinary Portland Concrete as the age increase. increase.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.118-121
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• 2002

Polyvinylidene di-fluoride (PVDF) film sensor appeared to be practically useful for the structural health monitoring of composite materials and structures. PVDF film sensors were either attached to or embedded in the graphite/epoxy composite (CFRP) samples to detect the fatigue damage at the bondline of single-lap joints or the tensile failure of unidirectional laminates. PVDF sensors were sensitive enough to detect and determine the crack front in linear location since composites usually produce very energetic acoustic emission (AE). PVDF sensors are extremely cost-effective, as flexible as other plastic films, in low profile as thin as a few tens of microns, and have relatively wide-band response, all of which characteristics are readily utilized for the structural health monitoring of composite structures. Signals due to fatigue damage showed a characteristics of mode II (shear) type failure whereas those from fiber breakage at DEN notches showed that of mode I (tensile) type fracture.