• Journal of the Korean Institute of Gas
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• v.21 no.2
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• pp.26-31
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• 2017

The purpose of this paper is to study for turbocharger system in a vehicle of diesel engine. The first example, it certified the fact that a car engine is not to accelerate by clogged the exhaust tube as the turbine was damaged because of turbine wheel broken. The a vehicle with turbocharger must to stop engine operation after maintaining the appropriate idle revolution as it can be the sticking phenomenon if the operator immediately stop the engine being high revolution. The second example, it knew the phenomenon of acceleration faulty that the rod of VGT actuator that operating the turbocharger adhered with the bracket of VGT. The third example, it confirmed the power insufficiency phenomenon when driving by of alternator resistor and fan intercooler fan relay connector mistaken assembly. Therefore, the operator have to scrutinize manage no the failure of turbocharger system.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.484-492
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• 2013

With the industrial acceleration in a lot of countries of the world, the demand for anti-corrosion and anti-abrasion material increases continuously. Particularly, stainless steel with the fine surface and excellent corrosion resistance is widely used in various industrial fields including ship, offshore structures tidal power plant, and etc. In marine environment, however, it is easy to generate by the corrosion damage by $Cl^-$ ion and cavitation damage due to high rotation speed on stainless steel. Therefore, in this research, the cavitation erosion-corrosion test (Hybrid test) was performed for 304 stainless steel specimen used in the high flow rate seawater environment. And the cavitation damage behavior in the corrosive environment was analyzed overall. The high hardness was shown due to the formation of compressive residual stress by the water cavitation peening effect in cavitation condition. However, high current density in the potentiodynamic polarization experiment presented with the breakdown of the passive film caused by physical impact. Therefore, both electrochemical characteristics and mechanical properties must be taken into account to improve the cavitation resistance in seawater.

• Elastomers and Composites
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• v.42 no.3
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• pp.151-158
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• 2007

MWNTs have been widely investigated due to unique properties of such as good electrical conductivity and thermal stability in polymer composites industries. This paper established the procedure to fabricate PMMA/MWNT composites by a modular intermeshing co-rotating twin screw extruder with L/D ratio of 42. The electrical properties of PMMA/MWNT composites with different content of MWNT have been investigated. A sheet resistance percolation was observed at 4 wt% of MWNT for the melt processed composites. Sheet resistance of PMMA/MWNT composite film containing 4 wt% of MWNT was nearby $10^4{\Omega}/sq$ and this shows the possibility of potential application to EMI (Electronic Magnetic Interference) shielding materials. The characteristics of composites were analyzed by TGA, DSC, and SEM. In addition, MFI (Melt Flow Index) has been measured to analyze the rheological property.

• Elastomers and Composites
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• v.44 no.3
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• pp.232-243
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• 2009

The specialized and diversified synthetic and compounding technologies are used to meet the requirements for the advanced high performance tire tread materials with better balance of fuel economy(rolling resistance), safety(wet traction) and wear resistance. These techniques involve the methodology for the improvement of chemical and physical interaction between filler and the rubber matrix using coupling agents as well as a variety of chemically-modified solution SBRs. The research trends about the high performance functional SBRs and coupling agents which can interact with the surface of fillers and their working mechanism were investigated in the conventional carbon black-filled rubber and silica-filled SBR systems developed recently as "green tire".

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.205-205
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• 2010

투명 전극(transparent conducting oxide, TCO)은 높은 전기전도도 및 낮은 비저항 ($10^{-4}{\sim}10^{-3}\;{\Omega}cm$)과 가시광영역에서의 우수한 광투과도(> 80%) 특성을 가지며, 주로 디스플레이, 태양전지, 가스 센서 소자 등에 쓰인다. 투명전극으로 쓰이는 대표적인 물질로서는 ITO, ZnO, $SnO_2$ 등이 있으며, ITO는 전기적 특성이 우수하여 널리 사용되고 있으나 가격이 비싸고 화학적으로 불안정하고, ZnO는 ITO에 비해 가격이 저렴하지만 고온에서 불안정한 특성을 가지고 있다. 반면, $SnO_2$는 ITO와 ZnO에 비해 전기적 특성은 떨어지지만, 우수한 열적, 화학적 안정성 및 높은 내마모성을 가지고 제조단가가 저렴하여 TCO 재료로 많은 연구가 진행되고 있다. TCO 박막을 증착시키는 방법으로 CVD, ion plating, sputtering, spray pyrolysis 등이 있으며, 이 중 sputtering 방법은 균일한 입자로 균질의 박막을 입힐 수 있고 우수한 재현성과 낮은 온도에서도 증착이 가능하여 박막 제조 방법으로 널리 이용되고 있다. 본 연구에서는 $SnO_2$ 박막을 실리콘 (100) 및 글라스 (Eagle 2000) 기판 위에 RF magnetron sputtering 방법을 사용하여 제작하였다. 박막 증착을 위해 99.99%의 2 인치 un-doped $SnO_2$ 타겟을 사용하였고, 기판은 20 rpm 으로 회전시켜 균일한 박막이 형성될 수 있도록 하였으며, 초기 진공도는 $1{\times}10^{-6}\;Torr$가 되도록 하였다. 증착 변수로 기판-타겟간 거리, RF 파워, $O_2/(Ar+O_2)$ 비, 공정압력, 기판 온도 등을 각각 변화 시키며 $SnO_2$ 박막을 증착하였다. 증착된 박막의 구조적 및 광학적 특성을 분석하기위해 FE-SEM, AFM, XRD, UV/VIS spectrophotometer, Photoluminescence 등을 사용하였다.

• Journal of the Korean Institute of Gas
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• v.15 no.3
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• pp.47-52
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• 2011

The purpose of this paper analyzes and studies to seek the failure examples of electronic control actuators for engine in liquified petroleum gas vehicle. The first, it was verified phenomenon for intial starting damage and no-acceleration of engine because of occasionally fuel feeding interception by clogged of emergency cutting solenoid valve filter. The second, the contact resistance produced in the connecting part of engine control relay because of no fully surface contacting by processes and assembly badness. It was displayed phenomenon of re-starting badness. The actuator that idle speed control system was sticked inside because of intake-air decreasing by carbon deposit. As a result, it was verified the phenomenon of disharmony that repeated up and down the engine revolution.

• Journal of the Korean Society of Physical Medicine
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• v.13 no.4
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• pp.113-121
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• 2018

PURPOSE: This study was conducted to identify a more effective intervention in sling and resistance exercise for chronic low back pain patients. METHODS: Seventy (70) subjects were randomly divided into the sling group (SG) and resistance exercise group (REG). Muscular activity of the internal oblique (IO), external oblique (EO), rectus abdominis (RA), and pelvic rotation angle during active straight leg raise (ASLR), a pressure pain threshold (PPT) and a visual analog scale (VAS) were measured. Sling and resistance exercises were conducted for 12 weeks. Intermediate measurements were taken after 8 weeks and final measurements were taken after 12 weeks. RESULTS: Both groups showed significantly decreased RA muscle activity and significantly increased IO muscle activity (p<.05). Additionally, EO muscle activity was significantly decreased in the REG, but significantly increased in the SG (p<.05), while the pelvic rotation angle and VAS were significantly decreased in the SG (p<.05). The pressure pain threshold was significantly increased in both groups (p<.05). CONCLUSION: Based on the results of this study, a 12-week intervention seems to be effective at improving back pain in both groups. However, a lower VAS was seen in the sling group after 8 weeks of intervention. Therefore, it is recommended that the sling be applied first when establishing a chronic back pain treatment program to shorten the treatment period and reduce the pain period.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.115-123
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• 2008

In the present study, a three dimensional hydrodynamic characteristics around the fully submerged dual breakwaters with a sand beach has been investigated numerically using a 3-D numerical scheme, which can determine the eddy viscosity with LES turbulence model and is able to consider wave-structure-seabed interaction in 3-dimensional wave field (LES-WASS-3D), recently developed by Hur and Lee (2007). Based on the numerical experiments, strong vortices can be generated fore and aft edges of the structures, and propagate lee sides. Thus relatively large circulation flows are occurred around submerged breakwaters. The 3-D flow hydrodynamic characteristics have been examined by mean flows and mean vortices for various x-y, x-z sections and y-z layers. Wave height distribution and wave set-up around and over submerged breakwaters, and breaking point migration toward shore side is discussed in detail.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6A
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• pp.651-659
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• 2009

This study dealt with the behavior of pile-abutment joints in integral abutment bridges. Two types of pile-abutment joints were proposed to strengthen its rigid action. One was fabricated with transverse rebars which penetrated the H-pile in the abutment. The other was composed of stud shear connectors on the flanges of the H-pile. Three half scaled pile-abutment joint specimens were fabricated and loading tests were performed to evaluate the behavior of proposed joints. The results showed that the initial stiffness in elastic region of all specimens was sufficient to be applied for the integral abutment bridges. However, the performances of the proposed joints were shown to be more effective in rigid action compared to the joints types suggested by the Integral Bridge Design Guideline. The results from stiffness, strength, rotation and crack propagation tests supported this matter.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.293-303
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• 2012

Recently, as construction technology improved, concrete structures not only became larger, taller and longer but were able to perform various functions. However, if extreme loads such as impact, blast, and fire are applied to those structures, it would cause severe property damages and human casualties. Especially, the structural responses from extreme loading are totally different than that from quasi-static loading, because large pressure is applied to structures from mass acceleration effect of impact and blast loads. Therefore, the strain rate effect and damage levels should be considered when concrete structure is designed. In this study, the low velocity impact loading test of steel fiber reinforced concrete (SFRC) slabs including 0%~1.5% (by volume) of steel fibers, and strengthened with two types of FRP sheets was performed to develop an impact resistant structural member. From the test results, the maximum impact load, dissipated energy and the number of drop to failure increased, whereas the maximum displacement and support rotation were reduced by strengthening SFRC slab with FRP sheets in tensile zone. The test results showed that the impact resistance of concrete slab can be substantially improved by externally strengthening using FRP sheets. This result can be used in designing of primary facilities exposed to such extreme loads. The dynamic responses of SFRC slab strengthened with FRP sheets under low velocity impact load were also analyzed using LS-DYNA, a finite element analysis program with an explicit time integration scheme. The comparison of test and analytical results showed that they were within 5% of error with respect to maximum displacements.