• 대한기계학회논문집
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• 제19권8호
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• pp.1927-1939
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• 1995

An experimental investigation is conducted to find out the large scale coherent structures in the intermediate wake past a rotating cylinder with a single tripping wire attached. Relation between the vortex shedding frequency and the spin rate of rotating cylinder and the effects of the tripping wire on the flow characteristics were studied by using spectral analysis and conditional phase average technique, respectively. It is found that the vortex shedding frequency is bound to a certain range and varies regularly as spin rate increases. The coherent structures are compared with those of the plain rotating cylinder in the case of spin rate of 1.0. Distance between the upper and lower center of vortices increase and the vortex shedding time is delayed, the velocity fluctuation energy decreases near the center line of vortices and it spreads out to the outer region. The Reynolds shear stress increases highly in the upper region and the turbulent wake width expands with strong entrainment process.

• Steel and Composite Structures
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• 제28권2호
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• pp.139-147
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• 2018

Moment frames have considerable ductility against cyclic lateral loads and displacements; however, sometimes this feature causes the relative displacement to exceed the permissible limits. This issue can bring unfavorable hysteretic behavior on the frame due to the reduction in the stiffness and resistance against lateral loads. Most of common bracing systems usually control lateral displacements through increasing stiffness while result in decreasing the capacity for energy absorption. This has direct effect on hysteresis curves of moment frames. Therefore, a system that is capable of both having the capacity of energy absorption as well as controlling the displacements without a considerable increase in the stiffness is quite important. This paper investigates retrofitting of a single-storey steel moment frame using a delayed wire-rope bracing system equipped with the ductile middle steel plate. The steel plate is considered at the middle intersection of wire ropes, where it causes cables to be continuously in tension. This integrated system has the advantage of reducing considerable stiffness of the frame compared to cross bracing systems as a result of which it could also preserve the frame's energy absorption capacity. In this paper, FEM models of a delayed wire-rope bracing system equipped by steel plates with different geometries have been studied, validated, and compared with other researchers' laboratory test results.

• 한국기계가공학회지
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• 제21권5호
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• pp.1-8
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• 2022

Fused deposition modeling (FDM), based on stacking a continuous filament of polymer or composite materials, is well matured and is thus widely used in additive manufacturing technology. To advance FDM-based 3D printing technology, the mechanical properties of additively manufactured composite materials must be improved. In this study, we proposed a novel FDM 3D printing process using metal wire-polymer composites, enabling enhanced mechanical properties. In addition, we developed a new type FDM filament of copper wire wrapped in nylon material for stable 3D printing without thermal damage during the printing process. After FDM printing of the copper wire-nylon composite filament, we conducted a tensile test to investigate the mechanical behavior of the printed composite materials. The experimental results confirmed that the tensile strength of the 3D-printed metal wire-polymer composites was higher than that of the conventional single polymer material. Thus, we expect that the FDM printing process developed in this study may be promising for high-load-bearing applications.

• 대한두개안면성형외과학회지
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• 제16권3호
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• pp.119-124
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• 2015

Background: The Kirschner wire (K-wire) technique allows stable fixation of bone fragments without periosteal dissection, which often lead to bone segment scattering and loss. The authors used the K-wire fixation to simplify the treatment of laborious comminuted zygomatic bone fracture and report outcomes following the operation. Methods: A single-institution retrospective review was performed for all patients with comminuted zygomatic bone fractures between January 2010 and December 2013. In each patient, the zygoma was reduced and fixed with K-wire, which was drilled from the cheek bone and into the contralateral nasal cavity. For severely displaced fractures, the zygomaticofrontal suture was first fixated with a microplate and the K-wire was used to increase the stability of fixation. Each wire was removed approximately 4 weeks after surgery. Surgical outcomes were evaluated for malar eminence, cheek symmetry, K-wire site scar, and complications (based on a 4-point scale from 0 to 3, where 0 point is 'poor' and 3 points is 'excellent'). Results: The review identified 25 patients meeting inclusion criteria (21 men and 4 women). The mean age was 52 years (range, 15-73 years). The mean follow up duration was 6.2 months. The mean operation time was 21 minutes for K-wire alone (n=7) and 52 minutes for K-wire and plate fixation (n=18). Patients who had received K-wire only fixation had severe underlying diseases or accompanying injuries. The mean postoperative evaluation scores were 2.8 for malar contour and 2.7 for K-wire site scars. The mean patient satisfaction was 2.7. There was one case of inflammation due to the K-wire. Conclusion: The use of K-wire technique was associated with high patient satisfaction in our review. K-wire fixation technique is useful in patient who require reduction of zygomatic bone fractures in a short operating time.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1046-1048
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• 2002

The increase of triplen harmonics in three-phase four-wire systems leads to overloaded neutral conductor, common-mode noise problems, derating of transformers, and so on. Various compensator has been designed to prevent the problems associated with the triplen harmonics. But these can not protect distribution system effectively because the triplen harmonic source is distributed extensively and distribution system type is diverse. This paper explain the operation and installation of single phase active power filter to eliminate triplen harmonics and then it is verified by simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 학술대회 논문집 전문대학교육위원
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• pp.147-153
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• 2006

Voltage unbalance will be generated by the load unbalance operation such as combination operation of single & three phase load and current unbalance will be more severe by the deteriorated voltage quality. Under the these unbalance conditions, all power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. it may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration. This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system by the unbalance and harmonic components. It was able to confirm that the number of torque pulsation decreased and torque ripple values increased by the harmonics that reduction was difficult by five harmonics filters at additional driving time of single-phase non-linear load.

• Journal of Power Electronics
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• 제8권1호
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• pp.81-90
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• 2008

This paper presents an investigation of a voltage and frequency controller for an isolated asynchronous generator (IAG) driven. by a wind turbine and supplying 3-phase 4-wire loads to the isolated areas where a grid is not accessible. The control strategy is based on the indirect current control of the VSC (voltage source converter) using the frequency PI controller. The proposed controller consists of three single-phase IGBT (Insulated Gate Bipolar Junction Transistor) based VSC, which are connected to each phase of the IAG through three single phase transformers and a battery at their DC link. The controller has the capability of controlling reactive and active powers to regulate the magnitude and frequency of the generated voltage, harmonic elimination, load balancing and neutral current compensation. The proposed isolated system is modeled and simulated in MATLAB using Simulink and PSB (Power System Block-set) toolboxes to verify the performance of the controller.

• 한국분말재료학회지
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• 제18권6호
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• pp.526-531
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• 2011

Fecralloy is the promising materials for high temperature exhaust filtering system due to the excellent its oxidation resistance property. In this research, Fecralloy nanoparticles coated Fecralloy thin foil was prepared by a single nozzle electrospray system in order to increase surface area of Fecralloy foil. Fecralloy nanoparticles were fabricated by electrical wire explosion method in ethanol using Fecralloy wires as a source material. Electrospray modes with applied D.C voltages to Fecralloy colloidal solution were investigated to make a stable cone-jet mode. Coated layers with and without additional heat treatment were observed by FE-SEM (field emission-scanning electron microscope) and tape test for evaluating their adhesion to substrate were performed as well.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2001년도 학술발표회 발표논문집
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• pp.271-274
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• 2001

Experiments on the yield strength of pipe connectors made of metal wire, joint pins, pole pipes, multi span insertion joints, and T-clamp joints used in pipe houses were conducted. The strength of connections of a pipe connector made of metal wire was adequate but it had a big difference according to loading direction. The collapse load of pipes connected with a joint pin was lower than that of single pipes. Also experimental results showed that pole pipes for use in a part of frame buried under the ground were safe, and the strength of multi span insertion joints should be increased. The resistant moment of T-clamp was about 13.7% of a single pipe.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.295-299
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• 1996

In order to investigate the relation between the microstructure and the V-I characteristics of HTSC wire, single and 19 filamentary silver-sheathed Bi2223 tapes were fabricated using the powder-in-tube method. Higher J$\_$c/ at 77.3 K(0 T) and 4.2 K(in magnetic field) can be achieved for the 19 filamentary Bi tape, comparing the single filamentary tape. However, the I$\_$c/ distribution of 19 filamentary Bi2223 tape was found to be wider by analyzing the curve obtained from 2nd differential of V-I data. This was considered to be resulted from worse uniformity of oxide filament due to severe cold working.