• 센서학회지
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• 제7권6호
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• pp.446-451
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• 1998

전도성 고분자는 전기적 에너지를 기계적 에너지로 직접 전환할 수 있는 물질로서 액츄에이터 물질로 사용될 수 있다. 본 논문에서는 다양한 합성조건에서 합성한 폴리피롤의 두께를 측정하고 여러 두께의 고분자 필름의 기계적 벤딩을 측정하고 해석하였다. 기계적 벤딩의 측정을 위해 bridge 형태의 시편으로 bending beam method를 사용하였다. 폴리피롤의 두께는 합성시간에 선형적으로 비례하며 전류밀도에도 비교적 큰 전류밀도를 제외하고는 선형적으로 증가하였다. 가장 큰 변위는 $5.4{\mu}A/mm^2$, 120분에서 합성된 $18.35{\mu}m$ 두께의 필름이 0.1Hz의 주파수에서 나타났다.

• Asian Pacific Journal of Cancer Prevention
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• 제17권11호
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• pp.4981-4984
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• 2016

Background: Adnexal torsion results in ischemia of structures distal to twisted pedicle and acute onset of pain is responsible for about 3% of all gynecologic emergencies. Ovarian torsion classically occurs in a pathological enlarged ovary, as with cancer, but diagnosis remains a challenge. Objective: Our purpose was to evaluate clinical risk factors predictive of torsion with gangrenous adnexa. Material and methods: A retrospective descriptive study and chart review of surgically proven ovarian torsion/adnexal torsion cases at the Obstetrics and Gynecology Department of Prapokklao Hospital, Chanthaburi, Thailand between January 2011 and December 2015 was conducted. Result: Seventy-eight cases were identified. Mean age at presentation was 35.5 years. The average maximum diameter of the ovarian tumors was 10.8 cm. The percentage of gangrenous ovarian cysts in this study was 46.2 (36/78). The precision to determine the pathological site by patient, physician and ultrasonography was 8.5, 24.2 and 83.3 percent, respectively with statistically significant variation. Conclusion: Ovarian/adnexal torsion remains a challenge condition especially in young nulliparous women. Sophisticated investigation does not guarantee ovary preservation. Combining clinical acumen, appropriate tests and detailed consideration may be the best practice at the present time.

• 한국안전학회지
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• 제33권5호
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• pp.1-8
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• 2018

A fuel cell is an energy conversion device that converts a chemical energy directly into an electrical energy and has higher energy efficiency than an internal combustion engine, but solid oxide fuel cell (SOFC) consisting of brittle ceramic material remains as a major issue regarding the mechanical properties as the crack formation and propagation. In this study, the stress distribution and crack behavior around the crack tip were evaluated, due to investigated the effects of the surface crack at the operating condition of high temperature. As a result, the difference of the generated stress was insignificant at operating conditions of high temperature according to the surface crack length changes. This is because, the high stiffness interconnect has a closed structure to suppress cell deformation about thermal expansion. The stress intensity factor ratio $K_{II}/K_I$ increased as the crack depth increased, at that time the effect of $K_{II}$ is larger than that of $K_I$. Also the maximum stress intensity factor increased as the crack depth increased, but the location of crack was generated at the electrolyte/anode interface, not at the crack tip.

• E2M - 전기 전자와 첨단 소재
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• 제7권2호
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• pp.145-151
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• 1994

The multi-dielectric layer SiOz/Si3N4/SiO2(ONO) is used to scale down the memory device. In this paper, the change of composition in ONO layer due to the process condition and the conduction mechanism are observed. The composition of the oxide film grown through the oxidation of nitride film is analyzed using auger electron spectroscopy(AES). AES results show that oxygen concentration increases at the interface between oxide and nitride layers as the thickness -of the top oxide layer increases. Results of I-V measurement show that the insulating properties improve as the thickness of the top oxide layer increases. But when the thickness of the nitride layer decreases below 63.angs, insulating peoperties of film 28.angs. of top oxide and film 35.angs. turn over showing that insulating property of film 28.angs. of top oxide is better than that of film 35.angs. of top oxide. This phenomenon of turn over is thought as the result of generation of surface state due to oxygen flow into nitride during oxidation process. As the thickness of the top oxide and nitride increases, the electrical breakdown field increases, but when the thickness of top oxide reaches 35.angs, the same phenomenon of turn over occurs. Optimum film thickness for scaled multi-layer dielectric of memory device SONOS is estimated to be 63.angs. of nitride layer and 28.angs. of top oxide layer. In this case, maximum electrical breakdown field and leakage current are 18.5[MV/cm] and $8{\times}{10^-12}$[A], respectively.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1589-1597
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• 1997

The high-velocity impact forging process with eccentric loading condition is analyzed using the explicit time integration finite element method. In order to consider the strain hardening, strain rate hardening and thermal softening effects, which are frequently observed in high-velocity deformation phenomena, the Johnson-Cook constitutive model is applied to model the workpiece. It is assumed that the material response of the dies is elastic in the study. As a result of the eccentric loading simulation, it is found that the increase of the eccentric ratio and the allowable tilting angle cause the decrease of the maximum forging load and the blow efficiency, and it is also found that the forging load and the blow efficiency generated in the high-velocity impact forging process with three-dimensional geometry can be obtained efficiently.

• 설비공학논문집
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• 제2권2호
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• pp.119-126
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• 1990

In this study, the overall heat transfer coefficients are calculated on fluidized bed double pipe heat exchanger and single phase double pipe heat exchanger at the same condition. The effect of the particle size, its material, fluidizing velocity and static bed height on overall heat transfer coefficient has been investigated. The main conclusions obtained from the experiment are as follows. 1. The overall heat transfer coefficient of the fluidized bed heat exchanger is higher than that of single phase forced convective heat exchanger (maximum 2.3 times) 2. The value of the overall heat transfer coefficient increase with an increase in static bed height and decrease with an increase in particle size. 3. For the same particle size, the particle of low density can obtain higher overall heat transfer coefficient than that of high density.

• 대한가정학회지
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• 제37권12호
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• pp.59-67
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• 1999

This study analyzed firefighter's actual wearing condition of turnout gear The results are as fellows: 1. When a firefighter is employed, Korea applies only the minimum of firefighters stature and weight but America applies both the minimum and the maximum. The choice of size is highly related with stature more than chest circumference. 2. The satisfaction degree of thermal barrier is very low, 3%. They used rubber gloves rather than heatproof gloves. This is more serious in small country like 'up', 'myun' than in cities. For laundering, they used sprinkling method with firefighting hose. Firefigthers hoped that their clothes could be classified tv the seasons and fire places. 3. frefighter had high unsatisfaction with the movement of hands and leges in the aspect of movement adjustability, air permeability, weight, body temperature regulation, and breathing in the hygenic aspect, fire resistance, thermal resistance property, water proof, chemical reactivity and electrical conductivity. Thev were also unsatisfied with water proof boots and gloves. They were generally satisfied with helmets but firefighters over 90kg of weight were rather unsatisfied. 4. The satisfaction degree for physical fitness was very low and the items with which they were not satisfied depend on physical features. 5. To develop turnout gear, they wanted changes in design, material and size. Reflection tape need to be replaced with high quality products and they wanted the use of velcro and zipper in fastening system.

• 대한기계학회논문집A
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• 제30권12호
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• pp.1618-1625
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• 2006

During the last two decades, several guidelines have been developed and used for assessing the integrity of a defective steam generator (SG) tube that is generally caused by stress corrosion cracking or wall-thinning phenomenon. However, as some of SG tubes are also failed due to fretting and so on, alternative failure estimation schemes are required for relevant defects. In this paper, parametric three-dimensional finite element (FE) analyses are carried out under internal pressure condition to simulate the failure behavior of SG tubes with different defect configurations; elliptical wear, tapered and flat wear type defects. Maximum pressures based on material strengths are obtained from more than a hundred FE results to predict the failure of SG tube. After investigating the effect of key parameters such as defect depth, defect length and wrap angle, simplified failure estimation equations are proposed in relation to the equivalent stress at the deepest point in wear region. Comparison of failure pressures predicted by the proposed estimation scheme with corresponding burst test data showed a good agreement.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.453-458
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• 2008

Under driving condition, A vehicle experiences various kinds of loads, which brings on the buckling and fracture of suspension systems. Lower control arm (LCA), which consists of 2 bush joints and 1 ball joint connection, is the one of the most important parts in the suspension system. The bush joints absorb the impact load and reduce the vibration from the road. When analyzing the LCA behavior, it is important to understand the material properties and boundary conditions of bushing systems correctly, because of the nonlinearity characteristics of the rubber. In this paper, in order to predict the large scale deformation of the LCA more precisely, three factors are newly suggested, that is, coupling of bush stiffness between translation and rotation, bush extraction force and maximum rotation angle of ball joint. LCA stiffness is estimated by CAE and component test. Analysis and test results are almost same and the validity of considering three factors in LCA analysis is verified.

• 한국재료학회지
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• 제15권6호
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• pp.419-425
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• 2005

In this paper, we describe the luminescent properties of the phosphors synthesized via sol-gel technique. When the phosphor prepared by sol-gel technique, reaction factors, such as pH condition, $R_w$ and drying temperature affected the luminescent intensity, particle size and morphology of final product. Therefore, we attempt to control these reaction factors in order to improve the luminescent efficiency of phosphors. As a result of our study, when the acid catalyst (HCl) was used, emission intensity was higher than the case of base catalyst $(NH_4OH)$. The product prepared at $R_w=60$ indicated the maximum intensity. As the increase of the $R_w$ value, the particle was agglomerated and emission intensity was decreased. Finally, optimum drying temperature of gel was found to be$ 180^{\circ}C$.