• 한국음향학회지
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• 제32권4호
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• pp.301-307
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• 2013

수중무기체계에 있어 소나 탐지 성능은 생존성 향상을 위한 중요한 인자이다. 소나의 음향수신 성능을 파악하기 위해서 탄성이론을 이용하여 소나 다층구조의 음향 성능을 해석하였다. 단순구조물에 대하여 탄성이론을 적용하여 얻은 본 해석 결과를 상용해석프로그램인 ANSYS와 비교하였고, 만족할만한 결과를 얻었다. 검증된 탄성이론을 이용하여 소나 다층구조의 층별 두께 변화에 따른 음압 및 반향음 감소 해석을 수행하였다. 무반향(anechoic)층의 두께가 증가할수록 주파수에 따른 음압이 고르게 분포하고 반향음 감소량이 약간 증가하는 것을 확인하였다. 비결합(decoupling)층과 스틸(steel)층의 경우 두께에 따른 음압의 변화는 거의 없으나 두꺼워질수록 반향음이 약간 감소하는 결과를 나타내었다. 탄소강화플라스틱(Carbon Reinforced Platic, CRP)층의 두께 변화는 음압과 반향음 감소량에 영향이 없는 것을 확인하였다. 따라서 소나 다층구조의 음향성능을 높이기 위해서는 무반향층을 두껍게 하고, 비결합층, 스틸층과 탄소강화플라스틱층은 최소화하는 것이 바람직할 것으로 예상된다.

• Physical Therapy Rehabilitation Science
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• 제2권2호
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• pp.75-80
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• 2013

Objective: The purpose of this study was to examine the effect of cold applied the night before or in the morning on pain and symptoms of plantar fasciitis. Design: Experimental study. Methods: Thirty subjects with plantar fasciitis were recruited for this study. Subjects with plantar fasciitis either had no intervention, cold applied (20 minutes) at night before bed, or 20 minutes in the morning upon wakening. Plantar fascia tenderness and pain were evaluated. There were ten subjects in each group. Measures included visual analog scale, plantar facial thickness via high resolution ultrasound, algometer measure, and range of motion of the ankle and foot. There were 3 groups of 10 subjects, control (no intervention), cold the night before bed, and cold in the morning before rising. Results: The greatest relief of symptoms was cold used at bedtime the night before the measurements. Cold used in the morning was not as effective as cold used in the evening before bed. Cold use reduced the thickness of the plantar fascia and irritation. There was a 13% reduction in plantar fascia thickness with cold the night before (p<0.05), a 44% reduction in pain and an 86 % increase in the force that could be applied to the bottom of the foot without pain (p<0.05). Conclusions: Cold applied for 20 minutes prior bedtime is effective for reduced symptomology caused by plantar fascia inflammation.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.807-812
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• 2008

The various attempts is made to solve the energy and environment problems. In addition, people interested in their life quality want the more eco-friendly living space. So we suggested that the earth-sheltered house could be one of the eco-friendly and low energy consuming houses to meet the social interest. And we also made data for design of the earth-sheltered house to be applicable to climate of Korea. In this study, a simulation was performed to estimate a boundary temperature according to earth sheltering thickness at the earth-sheltered part(exterior wall) in the case of earth sheltering on the plane ground not using a sloped site. And we analyzed the reduction of a thermal load by using this boundary temperature. We also compared a case of earth sheltering at the vertical wall with a case of earth sheltering at the roof to know the thermal reduction effect of a case of earth sheltering at the vertical wall.

• Transactions on Electrical and Electronic Materials
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• 제7권4호
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• pp.163-166
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• 2006

The dishing and the erosion were evaluated on the tungsten CMP process with conventional and new developed slurry. The tungsten thin film was polished by orbital polishing equipment. Commercial pattern wafer was used for the evaluation. Both slurries were pre tested on the oxide region on the wafer surface and the removal rate was not different very much. At the pattern density examination, the erosion performance was increased at all processing condition due to the reduction of thickness loss in new slurry. However, the dishing thickness was not remarkably changed at high pattern density despite of the improvement at low pattern density. At the large pad area, the reduction of dishing thickness was clearly found at new tungsten slurry.

• Coupled systems mechanics
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• 제2권3호
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• pp.289-302
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• 2013

The piled raft is a geotechnical construction, consisting of the three elements-piles, raft and the soil, that is applied for the foundation of a tall buildings in an increasing number. The piled rafts nowadays are preferred as the foundation to reduce the overall and differential settlements; and also, provides an economical foundation option for circumstances where the performance of the raft alone does not satisfy the design requirements. The finite element analysis of the piled raft foundation is presented in this paper. The numerical procedure is programmed into finite element based software SAFE in order to conduct the parametric study wherein soil modulus and raft thickness is varied for constant pile diameter. The problems of piled raft for three different load patterns as considered in the available literature (Sawant et al. 2012) are analyzed here using SAFE. The results obtained for load pattern-I using SAFE are compared with those obtained by Sawant et al. (2012). The fair agreement is observed in the results which demonstrate the accuracy of the procedure employed in the present investigation. Further, substantial reduction in maximum deflections and moments are found in piled raft as compared to that in raft. The reduction in deflections is observed with increase in raft thickness and soil modulus. The decrease in maximum moments with increase in soil modulus is seen in raft whereas increase in maximum moments is seen in piled raft. The raft thickness and soil modulus affects the response of the type of the foundation considered in the present investigation.

• 한국표면공학회지
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• 제49권3호
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• pp.316-321
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• 2016

To study emission characteristics for dual-emission tandem organic light emitting display (OLED), we fabricated blue fluorescent OLED according to thickness variation of $MoO_x$ as charge generation layer and Al as cathode. The bottom emission characteristics of OLED with $MoO_x$ 2, 3, 5 nm thickness showed threshold voltage of 9, 7, 9 V, maximum current emission efficiency of 19.32, 23.18, 15.44 cd/A and luminance of $1,000cd/m^2$ at applied voltage of 17.6, 13.2, 16.5 V, respectively. The top emission characteristics of OLED with $MoO_x$ 2, 3, 5 nm thickness indicated threshold voltage of 13, 10, 13 V, maximum current emission efficiency of 0.17, 0.23, 0.16 cd/A and luminance of $50cd/m^2$ at applied voltage of 22.6, 16.5, 20.1 V, respectively. In case of thicker or thinner than $MoO_x$ of 3 nm, the emission characteristics were decreased because of mismatching of electron and hole in emission layer. The bottom emission characteristics of OLED with Al 15, 20, 25 nm thickness showed threshold voltage of 8, 8, 7 V, maximum current emission efficiency of 18.42, 22.98, 23.18 cd/A and luminance of $1000cd/m^2$ at applied voltage of 16.2, 13.9, 13.2 V, respectively. The reduction of threshold voltage and increase of maximum current emission efficiency are caused by the increase of current injection according to increase of Al cathode thickness. The top emission characteristics of OLED with Al 15, 20, 25 nm thickness indicated threshold voltage of 7, 7, 8 V, maximum emission luminance of 371, 211, $170cd/m^2$, respectively. The top emission OLED of Al cathode with 15 nm thickness showed maximum luminance and it decreased at thickness of 20 nm. These phenomena are caused by the decrease of intensity of emitted light by reduction of optical transmittance according to increase of Al cathode thickness.

• 한국소음진동공학회논문집
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• 제24권8호
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• pp.643-650
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• 2014

Gear transmission system is widely applied in engineering. As the problem of contact fatigue, wear, lubrication failure etc, the condition of gear teeth contacts will be worse. The vibration and sound signals in the gear system will be affected by the some failures like scuffing, abrasive wear and spalling due to the deterioration of gear teeth surface. By studying the estimation of specific film thickness, measurement of reduction in tooth thickness, visual examination of wear mechanisms on the gear teeth and their effects on the statistical parameters of vibration and sound signals, the research obtained the satisfactory results on accessing the surface fatigue wear in a spur gear system. The paper utilizes the relationship between statistical parameters obtained from sound signals and Stribeck curve to confirm the hypothesis of dependency of surface fatigue wear, specific film thickness.

• Structural Engineering and Mechanics
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• 제62권5호
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• pp.587-593
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• 2017

The objective of this analytical study is to calculate the elasto-plastic stresses of Functionally Graded (FG) hyperbolic disc subjected to uniform temperature. The material properties (elastic modulus, thermal expansion coefficient and yield strength) and the geometry (thickness) of the disc are assumed to vary radially with a power law function, but Poisson's ratio does not vary. FG disc material is assumed to be non-work hardening. Radial and tangential stresses are obtained for various thickness profile, temperature and material properties. The results indicate that thickness profile and volume fractions of constituent materials play very important role on the thermal stresses of the FG hyperbolic discs. It is seen that thermal stresses in a disc with variable thickness are lower than those with constant thickness at the same temperature. As a result of this, variations in the thickness profile increase the operation temperature. Moreover, thickness variation in the discs provides a significant weight reduction. A disc with lower rigidity at the inner surface according to the outer surface should be selected to obtain almost homogenous stress distribution and to increase resistance to temperature. So, discs, which have more rigid region at the outer surface, are more useful in terms of resistance to temperature.

• Elastomers and Composites
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• 제56권3호
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• pp.164-171
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• 2021

Due to the problem of environmental pollution by plastics, it is necessary to decrease their consumption. In the case of PET bottles, it is essential to reduce the thickness of the bottle for the reduction of plastic used. For manufacturing PET bottles with reduced thickness, it is a prerequisite to design a preform with reduced thickness and study its molding capability. In this study, the injection molding capability was investigated after reducing the body thickness of the preform to 15% and 20%, respectively, for the two preform models currently in use. Injection molding analysis was performed on the existing models and on the models for reduced weight, under the molding conditions of the existing models. Using the computed results, temperature distribution, pressure distribution, deformation and clamping force were compared. Based on the analysis, the injection conditions of the preform model with less thickness were discussed.

• Advances in Energy Research
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• 제2권2호
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• pp.73-84
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• 2014

Fuel cells of proton exchange membrane type (PEMFC) working with hydrogen in the anode and ambient air in the cathode ('air breathing') have been prepared and characterized. The cells have been studied with variable thickness of the cathode catalyst layer ($L_{CL}$), maintaining constant the platinum and ionomer loads. Polarization curves and electrochemical active area measurements have been carried out. The polarization curves are analyzed in terms of a model for a flooded passive air breathing cathode. The analysis shows that $L_{CL}$ affects to electrochemical kinetics and mass transport processes inside the electrode, as reflected by two parameters of the polarization curves: the Tafel slope and the internal resistance. The observed decrease in Tafel slope with decreasing $L_{CL}$ shows improvements in the oxygen reduction kinetics which we attribute to changes in the catalyst layer structure. A decrease in the internal resistance with $L_{CL}$ is attributed to lower protonic resistance of thinner catalyst layers, although the observed decrease is lower than expected probably because the electronic conduction starts to be hindered by more hydrophilic character and thicker ionomer film.