• Structural Engineering and Mechanics
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• 제90권6호
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• pp.601-610
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• 2024

Free vibration of layered conical shell frusta of thickness filled with fluid is investigated. The shell is made up of isotropic or specially orthotropic materials. Three types of thickness variations are considered, namely linear, exponential and sinusoidal along the radial direction of the conical shell structure. The equations of motion of the conical shell frusta are formulated using Love's first approximation theory along with the fluid interaction. Velocity potential and Bernoulli's equations have been applied for the expression of the pressure of the fluid. The fluid is assumed to be incompressible, inviscid and quiescent. The governing equations are modified by applying the separable form to the displacement functions and then it is obtained a system of coupled differential equations in terms of displacement functions. The displacement functions are approximated by cubic and quintics splines along with the boundary conditions to get generalized eigenvalue problem. The generalized eigenvalue problem is solved numerically for frequency parameters and then associated eigenvectors are calculated which are spline coefficients. The vibration of the shells with the effect of fluid is analyzed for finding the frequency parameters against the cone angle, length ratio, relative layer thickness, number of layers, stacking sequence, boundary conditions, linear, exponential and sinusoidal thickness variations and then results are presented in terms of tables and graphs.

• Corrosion Science and Technology
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• 제23권3호
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• pp.235-245
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• 2024

DLC coatings have been widely applied in industrial fields that require high corrosion resistance due to their excellent mechanical characteristics and chemical stability. In this research, effects of DLC coating thickness and defects on corrosion resistance were investigated for application of metallic bipolar plates in polymer membrane electrolyte fuel cells (PEMFCs). Results revealed that a DLC coating thickness of 0.7 ㎛ could lead to a defect size reduction of about 75.9% compared to that of 0.3 ㎛.As a result of potentiodynamic polarization experiments, the current density under a potential of 0.6 V was measured to be less than 1 ㎂/cm²,which was an excellent value. Inparticular, the delamination ratio and the decrease rate of maximum pitting depth were up to 84.8% and 63.3%, respectively, with an increase in the DLC coating thickness. These results demonstrate that DLC coating thickness and defects are factors that can affect corrosion resistance of DLC coating and its substrate.

• Clinics in Shoulder and Elbow
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• 제10권1호
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• pp.42-49
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• 2007

목적: 회전근 개 전층 파열의 봉합술 후 회전근 개의 두께를 자기 공명 영상에서 측정하여 파열이 없는 젊은 층 및 장노년층 대조군과 비교하고 술 전 파열의 정도와의 상관 관계를 알아보고자 하였다. 대상 및 방법: 본원에서 시행한 회전근 개 전층 파열에 대한 봉합술 시행 후 자기 공명 영상을 시행하였던 19예의 환자($45{\sim}77$세, 평균 63.3세)를 제 1군, 파열이 없는 환자들 중 제 1군과 비슷한 장,노년기 환자 23예를 제 2군($46{\sim}69$세, 평균 57.9세), 30세 이하의 청년기 환자 22예를 제 3군($18{\sim}30$세, 평균 23.3세)으로 하여 각 군의 회전근 개의 두께를 비교하였다. 제 1군에서 파열의 길이는 자기 공명 관절 조영술 사위 관상면 영상에서, 넓이는 사위 시 상면에서 측정하여 그 중 큰 값을 파열의 크기로 하였고, 회전근 개의 두께는 관절와 후외연으로부터 전방 15 mm 지점의 사위 관상면에서 측정하였다. 또한, 제 1군의 파열의 크기와 술 후 회전근 개의 두께와의 상관 관계를 알아보았다. 결과: 제 1군의 술 후 회전근 개의 평균 두께는 3.0 mm였고, 술 전 파열의 크기와 회전근 개의 두께는 반비례하였으며(P<0.001), 제 2군, 제 3군의 회전근 개의 두께는 각각 3.9 mm, 5.0 mm로 세 군의 두께가 통계적으로 유의한 차이를 보였다(P<0.05). 결론: 회전근 개의 두께는 연령이 많을수록 작았고 전층 파열 봉합술 후 두께는 술 전 파열의 크기와 반비례하였으며 정상군에 비해 작았다.

• 한국산업융합학회 논문집
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• 제23권5호
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• pp.843-852
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• 2020

Among the many packaging materials used in cushion packaging, there is a lack of optimum design for packaging trays and cushion pads used in pear packaging for export and domestic distribution. It causes over-packaging due to excessive material input, and can be solved by applying various parameters needed to optimize the design of the packaging tray and cushion pad considering the packaging material and the number of pears in the box. In the case of a cushion pad for pears, the economic efficiency of material and thickness should be considered. Therefore, it is possible to design a packaging tray and cushion pad depending on eco-friendly packaging materials (PLA, PET) used by applying appropriate design parameters. The static characteristics of the materials used for the packaging of pears were analyzed using FEA (finite element analysis) simulation technique to derive the optimal design parameters. In this study, we analyzed the contact stress and deformation of PET, PLA tray (0.1, 0.5 1.0, 1.5 and 2 mm) and PET foam (2.0, 3 .0 and 4.0 mm) with pears to derive appropriate cushion packaging design factors. The contact stress between the pear and PET foam pad placed on PLA, PET trays were simulated by FEA considering the bioyield strength (192.54±28 kPa) of the pears and safety factor (5) of packaging design, which is the criterion of damage to the pears. For the combination of PET tray and PET foam buffer pad, the thickness of the PET foam is at least 3 mm, the thickness of the PET foam is at least 1.0 mm, the thickness of the foam is at least 2 mm, and if the thickness of the PET tray is at least 1.5 mm, the thickness of the foam is at least 1 mm, suitable for the packaging design. In addition, for the combination of PLA tray and PET foam pad, the thickness of the PET foam was not less than 2 mm if the thickness of the PLA tray was 0.5 mm, and 1 mm or more if the thickness of the PLA tray was not less than 1.0 mm, the thickness of the PET foam was suitable for the packaging design.

• Journal of Animal Science and Technology
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• 제51권3호
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• pp.255-262
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• 2009

본 시험은 초음파 진단장치를 이용한 한우 번식우의 산차 및 지역별 산육특성에 관한 연구에 대하여 알아보고자 실시하였다. 강원도 6개시 군 한우 번식우 1,386두를 공시하여 초음파 진단장치(HS-2000, Japan)를 이용하여 배최장근단면적(LMAU; Longissimus Muscle Area Ultrasound), 등지방두께(BFTU; Back Fat Thickness Ultrasound), 근내지방도(MSU; Marbling Score Ultrasound), 둔근지방두께(P8 FTU; P8 Fat Thickness Ultrasound)를 측정하였다. 성적 조사 및 자료의 조정 후 각 한우의 출생년도-계절, 지역 및 산차별 산육특성을 비교 분석한 결과는 다음과 같다. 산차별 산육특성을 비교했을 때 산차가 증가할수록 산육 형질은 6산까지 증가하다가 7산차 이후에는 감소하는 경향을 나타냈다. 또한, 지역별 산육특성을 비교하면 모든 지역에서 고도의 유의적(p<0.01)인 차이를 보였으며 화천지역의 암소에서 배최장근단면적과 근내지방도가 가장 높은 수치를 나타냈으며, 양구지역의 경우 등지방두께, 둔근지방두께가 가장 낮은 수치를 보였다. 출생년도와 계절에 따른 산육형질에서는 2000년 가을철 태생의 개체의 배최장근단면적과 근내지방도, 2005년과 2006년 가을철 태생에서 각각 등지방두께 및 둔근지방두께가 우수한 것으로 분석되었다. 산육특성관련 형질간의 상관관계에서는 상호간 상관이 어느 정도 높은 것으로 나타났으며, 등지방두께와 둔근지방두께의 상관계수가 가장 높았고, 반대로 배최장근단면적과 둔근지방두께의 상관계수가 가장 낮았다. 이상의 결과를 종합하여 볼 때, 6산차까지의 산육형질이 우수한 것으로 분석되었고, 지역 차이에 따른 산육형질의 특징이 나타났으며, 등지방두께와 둔근지방두께의 상관관계가 가장 높은 것으로 분석되어, 본 시험결과는 앞으로 한우 번식우 개량 및 사양관리에 적절하게 이용할 수 있을 것으로 판단된다.

• 한국산학기술학회논문지
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• 제20권11호
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• pp.458-468
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• 2019

본 연구는 12주간 웨이트트레이닝에 의한 체지방 감소가 개인적인 특성과 피부두겹의 변화 등에 어떠한 영향을 미치고 있는지를 분석하여 보다 효과적인 웨이트트레이닝 전략을 제안한 연구이다. 분석결과 첫째 개인특성이 피부두겹의 변화에 유의한 영향을 미치지 않았으나 체지방 변화에는 높은 수준의 영향을 미치는 것으로 나타났다. 둘째, 피부두겹의 변화는 체지방 변화에 통계적으로 유의한 영향을 주었다. 셋째, 웨이트트레이닝에 의한 피부두겹의 변화는 남성이 여성에 비해 상대적으로 높은 변화수준을 보였다. 체지방 변화에 있어서도 남성이 여성에 비해 높은 변화를 보이는 것으로 나타났다. 본 결과를 종합하면 12주간의 웨이트트레이닝을 통해 나타난 피부두겹과 체지방의 변화는 개인특성에 의해 수준의 차이가 존재하고 있으며, 피부두겹의 변화는 체지방 변화에 높은 수준의 영향을 미치고 있음을 확인할 수 있다. 이는 본 연구의 웨이트트레이닝 프로그램은 획일적인 방법과 양으로 같은 성과를 나타내려는 노력보다는 개인특성에 맞는 웨이트트레이닝의 시간, 양, 수준을 고려한 규칙적인 웨이트트레이닝 프로그램을 실시한다면 현대인의 비만 문제를 해결하고, 건강관련 체력을 향상시키는데 보다 긍정적인 영향을 미칠 것으로 생각된다.

• 한국안광학회지
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• 제9권2호
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• pp.281-290
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• 2004

근시안에서 각막 중심부와 주변부의 두께를 측정하여 굴절이상 도에 따른 중심부와 주변부 두께의 상관관계와 각막두께의 변화상에 대하여 알아보고자 하였다. 20세에서 49세까지의 99명 198안을 대상으로 Orbscan Topography System(Orbtex, Inc, USA)을 사용하여 중심부 두께와 좌 우안 중심부를 기준으로 상 하, 이 비측 각 2mm 지점에서 주변부 두께를 측정하여 성별, 연령별, 좌 우안별 그리고 굴절이상도에 따라 분석하였다. 전체 대상자의 각막 중심부 두께는 $530.12{\pm}43.41{\mu}m$때, 주변부 두께는 상측 $591.91{\pm}36.88{\mu}m$, 하측 $561.04{\pm}41.82{\mu}m$, 비측 $584.23{\pm}41.97{\mu}m$, 이측 $567.35{\pm}43.25{\mu}m$로 측정되어 중심부와 주변부 각막두께의 차이는 유의한 차이를 보였다. 그러나 굴절이상도, 연령, 성별 그리고 좌 우안에 따른 각막두께는 통계적으로 유의한 차이는 없었다.

• The Korean Journal of Physiology
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• 제2권1호
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• pp.31-38
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• 1968

Total body fat measurement by means of skinfold thickness was performed in 94 secondary school boys. Hydrostatic weighing was made on the same subject and corrected for residual volume in lung. Skinfold thicknesses at four sites, namely, back, waist, arm and abdomen, were compared with total body fat calculated from the equation given by Keys and Brozek and regression equation were computated. In 48 middle school boys aged between 13 and 16 years and 46 high school boys aged between 16 and 19 years, skinfold thicknesses increased at all 4 sites as age increased. The body density, however, showed different pattern. In middle school ages, body density showed little variation. Density in 13-14 years was 1.0608, in 14-15 years 1.0578 and in 15-16 years 1.0546. In high school ages density in-creased abruptly to 1.0703 (16 yr.), 1.0730 (17 yr.) and 1.0740 (18 yr.). Subsequently 15 years was a boundary for density change and total body fat change. In middle school boys as a group of 48 the observed values were: density: 1.0562, total body fat: 15.9%, mean skinfold thickness at four sites: 6.02 mm. The coefficient of correlation between mean skinfold thickness and density were r=-0.759 and r=0.781 with %fat. The regression equations were : Body $density=-0.00527{\times}Mean$ skinfold thickness (mm)+1.0879, %Fat=$1.933{\times}Mean$ skinfold thickness (mm)+4.26 In high school boys the values were: density: 1.0723, body fat: 10.4%, and mean skinfold thickness: 7.89 mm. Coefficients of correlation between mean skinfold thickness and density were r=-0.868 and r=0.855 with % fat. Thus, Body density=$-0.00365{\times}Mean$ skinfold thickness (mm)+1.1008, and %Fat=$1.326{\times}Mean$ skinfold thickness (mm)-0.064, were obtained. Although skinfold thicknesses at 4 sites showed a continuous increase in absolute value as age increased, relative growth of skinfold at specific site differed. On arm the growth of skinfold showed a decrease and on waist it showed an increase as compared to the mean thickness.

• 대한치과보철학회지
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• 제44권5호
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• pp.503-513
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• 2006

Statement of the problem: The cold-cured resins used in fabrication of the provisional crown and fixed partial dentures could cause pulpal damage by heat generated during exothermic polymerization reactions. Purpose: In this in vitro study investigates the how external conditions such as material of the matrix, thickness of the matrix and thickness of dentin affect the temperature of the tooth during polymerization reaction of the cold-cured resins. Material and methods : To measure the temperature of the resin, metal die was maintained to the temperature of $37^{\circ}C$ with water bath to simulate the temperature of thetooth and thermocouple was placed in the center of the metal die. Acrylic pipe was cut in height of 1, 2, 3, 6, 10 mm and placed on the metal die and mixed resin was pored in the acrylic pipe As the resin polymerized temperature was recorded with the thermometer. Temperature of the resin using matrix was recorded by using the individual tray relieved in different thickness 2, 5, 7, 10 mm. The material of the matrix was irreversible hydrocolloid impression material, vinyl polysilloxane impression material and vacuum-formed template Temperature rise of the resin using different thickness of tooth section was record ed by placing tooth section on the metal die and placing resin over the tooth section. Results : Conclusion : 1. Temperature rise increased as the thickness of the resin increased but there was no significant differences over 3 mm thickness of the resin. 2. The lowest temperature rise was showed in irreversible hydrocolloid impression material and vinyl polysilloxane impression material vacuum-formed template as in orders. 3, Temperature rise of the resin decreased regardless of the thickness of the matrix when vinyl polysilloxane impression material was used as the matrix. 4 When irreversible hydrocolloid impression material was used as matrix, the temperature rise of the resin decreased as the thickness of the matrix increased and there was no temperature rise when thickness of the matrix reached 10 mm, 5. The temperature rise of the resin did not decreased when Polypropylene vacuum-formed template was used as the matrix. 6, The temperature of the resin increased as the thickness of the dentin decreased.

• Journal of Periodontal and Implant Science
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• 제37권1호
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• pp.103-113
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• 2007

The purpose of this study was to measure the thickness of masticatory mucosa in the hard palate as a donor site for mucogingival surgery by using computerized tomography(CT), Thickness measurements were performed in 84 adult patients who took CT on maxilla for implant surgery and 24 standard measurement points were defined in the hard palate according to the gingival margin and mid palatal suture. Radiographic measurements were utilized after calibration for standardization. Data were analyzed to determine the differences in mucosal thickness by gender, age, tooth positions and depth of palatal vault. The results of this study were as follows: 1. Mean thickness of palatal masticatory mucosa was $3.93{\pm}0.6mm$ and females had significantly thinner mean masticatory mucosa($3.76{\pm}0.56mm$) than males($4.04{\pm}0.6mm$)(p<0.05). 2. The thickness of palatal masticatory mucosa increased by aging. 3. Depending on position, masticatory mucosa thickness increased from canine to premeolar, but decreased at the first molar, and increased again in the second molar region(p<0.0001). 4. No significant difference in mean thickness of palatal masticatory mucosa were indentified between low palatal vault group and high palatal vault group(p>0.05). The results suggest that canine and premolar area appears to be the most appropriate donor site for soft tissue grafting procedure. The measurement of the thickness of palatal masticatory mucosa by using computerized tomography can offer useful information clinically but further studies in as-sessing the validity and reliability of the method using computerized tomography is needed.