• 한국기계가공학회지
• /
• 제16권2호
• /
• pp.102-107
• /
• 2017

This study focuses on the effect of the elasticity modulus of jig material on blade edge shape in the grinding process of a sapphire medical knife. The ELID grinding process was applied as the edge-grinding method for sapphire material. Carbon steel and copper have been selected as the hard and soft jig materials, respectively. The blade edge created by ELID grinding was measured by a surface roughness tester and optical microscope. The shape of the ground edge and surface roughness were compared using the measurement results. As a result, it was found that chipping in the blade edge of the sapphire knife occurred more than in the case of jig material with a high-elasticity modulus because of the high normal force in the grinding process. Moreover, the maximum height surface roughness, $R_{max}$,of the ground surface was higher in the case of the jig material with a high-elasticity modulus due to the difference in elasticelongation. It was considered to lead to chipping from the notch effect.

• Advances in materials Research
• /
• 제5권4호
• /
• pp.245-261
• /
• 2016

Thermo-mechanical buckling problem of functionally graded (FG) nanoplates supported by Pasternak elastic foundation subjected to linearly/non-linearly varying loadings is analyzed via the nonlocal elasticity theory. Two opposite edges of the nanoplate are subjected to the linear and nonlinear varying normal stresses. Elastic properties of nanoplate change in spatial coordinate based on a power-law form. Eringen's nonlocal elasticity theory is exploited to describe the size dependency of nanoplate. The equations of motion for an embedded FG nanoplate are derived by using Hamilton principle and Eringen's nonlocal elasticity theory. Navier's method is presented to explore the influences of elastic foundation parameters, various thermal environments, small scale parameter, material composition and the plate geometrical parameters on buckling characteristics of the FG nanoplate. According to the numerical results, it is revealed that the proposed modeling can provide accurate results of the FG nanoplates as compared some cases in the literature. Numerical examples show that the buckling characteristics of the FG nanoplate are related to the material composition, temperature distribution, elastic foundation parameters, nonlocality effects and the different loading conditions.

• 대한인간공학회지
• /
• 제31권3호
• /
• pp.455-461
• /
• 2012

The aim of this study was to investigate the appropriate elasticity of the textile material used for making women's girdle. Background: The elastic textiles have been used for making girdle. The hard type girdle gave high pressure on the body to make slim look. However, excessively high garment pressure caused negative effect to human bodies. This study studied the material giving proper garment pressure in girdle. Method: In this study five experimental girdles were made fabrics with various elasticities. The change of garment pressures and body girths were measured after subjects wearing the experimental girdles. The garment pressure was measured at 10 points. Body girths measured at abdomen, hip, and thigh. Results: The garment pressure of the commercial girdle was high at side of waistband, side femur and back gluteal fold. The experimental girdles made with high elasticity material definitely lowered garment pressure at those points. After wearing experimental girdle their abdomen and hip girths measurements were decreased. But, thigh girth was not reduced. Conclusion: The girdle made with excellent elasticity materials reduced garment pressure significantly and it made body slim as much as the commercial girdle except the thighs. Application: This study provides guideline for the developing girdle that applying optimum range of garment pressure with body slim effect.

• 노동경제논집
• /
• 제36권1호
• /
• pp.1-44
• /
• 2013

이 논문은 한국 노동시장의 수요구조에 관한 기존 연구들을 서베이한 것이다. 한국 노동수요의 특징을 보면 노동과 자본 간에 대체재 관계가 성립하며, 노동을 사무직과 생산직으로 세분해도 대체관계는 변함없다. 대체탄력성의 크기는 0과 1 사이에 있다. 고용과 근로시간은 대체/보완 관계가 명확하지 않다. 법정 근로시간 단축은 실 근로시간을 단축시켰으나 고용은 늘지 않았다. 노동수요 탄력성은 단기에 0.5 미만으로 작다. 기술변화는 1980년대 중반 이후 노동절약적으로 변하였고 1990년대 중반 이후 숙련편향적 성격으로 숙련노동 수요를 늘렸다.

• 대한치과교정학회지
• /
• 제50권6호
• /
• pp.391-400
• /
• 2020

Objective: Increased gingival elasticity has been implicated as the cause of relapse following orthodontic rotational tooth movement and approaches to reduce relapse are limited. This study aimed to investigate the effects of sulforaphane (SFN), an inhibitor of osteoclastogenesis, on gene expression in gingival fibroblasts and relapse after rotational tooth movement in beagle dogs. Methods: The lower lateral incisors of five beagle dogs were rotated. SFN or dimethylsulfoxide (DMSO) were injected into the supra-alveolar gingiva of the experimental and control group, respectively, and the effect of SFN on relapse tendency was evaluated. Changes in mRNA expression of extracellular matrix components associated with gingival elasticity in beagles were investigated by real-time polymerase chain reaction. Morphology and arrangement of collagen fibers were observed on Masson's trichrome staining of buccal gingival tissues of experimental and control teeth. Results: SFN reduced the amount and percentage of relapse of orthodontic rotation. It also decreased the gene expression of lysyl oxidase and increased the gene expression of matrix metalloproteinase (MMP) 1 and MMP 12, compared with DMSO control subjects. Histologically, collagen fiber bundles were arranged irregularly and were not well connected in the SFN-treated group, whereas the fibers extended in parallel and perpendicular directions toward the gingiva and alveolar bone in a more regular and well-ordered arrangement in the DMSO-treated group. Conclusions: Our findings demonstrated that SFN treatment may be a promising pharmacologic approach to prevent orthodontic rotational relapse caused by increased gingival elasticity of rotated teeth in beagle dogs.

• Structural Engineering and Mechanics
• /
• 제7권2호
• /
• pp.181-202
• /
• 1999

Dynamic response of axisymmetric arbitrary laminated composite cylindrical shell of finite length, using three-dimensional elasticity equations are studied. The shell is simply supported at both ends. The highly coupled partial differential equations are reduced to ordinary differential equations (ODE) with variable coefficients by means of trigonometric function expansion in axial direction. For cylindrical shell under dynamic load, the resulting differential equations are solved by Galerkin finite element method, In this solution, the continuity conditions between any two layer is satisfied. It is found that the difference between elasticity solution (ES) and higher order shear deformation theory (HSD) become higher for a symmetric laminations than their unsymmetric counterpart. That is due to the effect of bending-streching coupling. It is also found that due to the discontinuity of inplane stresses at the interface of the laminate, the slope of transverse normal and shear stresses aren't continuous across the interface. For free vibration analysis, through dividing each layer into thin laminas, the variable coefficients in ODE become constants and the resulting equations can be solved exactly. It is shown that the natural frequency of symmetric angle-ply are generally higher than their antisymmetric counterpart. Also the results are in good agreement with similar results found in literatures.

• Geomechanics and Engineering
• /
• 제12권5호
• /
• pp.739-752
• /
• 2017

This study was intended to evaluate the improved strength of the ground by applying the bio grouting method to a loose sandy ground. The injection material was prepared in the form of cement-like powder, with the bio injection material produced by microbial reactions. The grouting test was conducted under the conditions similar to the field where the bio injection material can be applied. In addition, the injection materials (cement and sodium silicate No. 3) used for Labile Waterglass (LW) method and the conventional grouting methodwere prepared through a two-solution one-step process. The injection into the specimens was done at a pressure of 150 kPa and then, with a bender element, their moduliof elasticity were measured on the 7th, 14th, 21st and 28th curingdays to analyze their strengths according to the duration of curing. It was confirmed that in all injection materials the moduli of elasticity increased over time. In particular, when 30% of the bio injection material was added to 100% cement, the modulus of elasticity tended to increase by about 15%. This confirmed that the applicability became higher when the bio injection material was used in place of the conventional sodium silicate.

• 한국통신학회논문지
• /
• 제34권8C호
• /
• pp.801-805
• /
• 2009

컴퓨터 네트워크의 지속적인 보급과 멀티미디어에 대한 수요의 급증은 화상 회의 등의 새로운 수요에 대응 할 수 있는 초고속 근거리 통신망의 중요성을 부각시키고 있다. 이러한 초고속 근거리 통신망의 구현을 위해서는 연결된 컴퓨터들 간의 데이터 전송이 지연 없이 실시간으로 수행될 수 있도록 동기화시키는 것이 매우 중요하다. 네트워크상의 모든 컴퓨터들이 거의 같은 주기의 클럭을 사용할 경우, 데이터 정체를 최대한 줄일 수 있는 장점이 있는 반면, 송신단으로부터의 데이터를 수신단에서 받아들일 때 비동기 데이터 샘플링에 의한 준안정성 문제가 발생할 수 있기 때문에 그에 대한 해결을 위한 신축 버퍼가 필요하며, 본 논문에서는 고속 동작용 신축버퍼의 구현에 대해 논의한다.

• 산업진흥연구
• /
• 제5권4호
• /
• pp.63-72
• /
• 2020

본 연구는 기혼여성의 생활스트레스와 생활만족도에 자아탄력성과 대처방식의 매개효과를 알아보는데 목적을 두고 있다. 본 연구를 위해 서울특별시와 인천광역시, 경기도에 거주하는 30~60대 기혼여성 200명을 대상으로 2020년 1월 2일~15일 설문조사를 진행하였고, 상관관계, 요인분석, 회귀분석을 실시하였고, 매개효과를 알아보기 위해 Sobel test을 통해 분석하였다. 연구결과 기혼여성의 생활스트레스는 여러 원인 중에서도 경제문제, 자녀관계, 고부갈등이 주요 원인인 것으로 파악되었고, 생활만족도와의 관련성 분석을 통해 생활스트레스와 생활만족도가 관련성이 있으며, 생활만족도 저하에 영향을 미치는 것을 확인할 수 있었다. 또한, 기혼여성의 생활스트레스와 생활만족도의 영향관계에서 자아탄력성과 대처방식은 부분 매개효과가 있는 것으로 검증되었다. 이로써 자아탄력성과 대처방식을 향상할 경우 기혼여성의 생활스트레스를 완화하여 생활만족도를 높이는 방안이 될 수 있을 것으로 보인다.

• 한국건설순환자원학회논문집
• /
• 제3권3호
• /
• pp.206-211
• /
• 2015

최근에 활발히 연구되어지고 있는 UHPC의 경우, 강섬유 혼입량에 의해서 인장강도가 절대적으로 영향을 받는 이유로 본 논문에서는 압축강도, 강섬유량 등을 변수로 하여 압축강도, 탄성계수 및 인장강도 등을 실험적으로 구한 후, 그 결과를 분석하였다. 실험결과에 의하면, 압축강도와 탄성계수 및 인장강도는 비례관계로 상당한 상관성을 가지는 것으로 나타났으며, 섬유혼입률에 따른 압축강도와 인장강도의 관계 역시는 비례관계의 상관성을 가지는 것으로 나타났다. 탄성계수의 경우, 실험결과와 현행 국내 설계기준 식의 차이는 그다지 크지 않은 것으로 나타나, 기존의 설계기준 식을 준용하여도 UHPC 탄성계수 평가에는 큰 문제가 없을 것으로 예상된다. 한편 인장강도의 경우, 현행 설계기준에서 제시되지 않은 이유로 비선형 회귀분석을 실시하여 섬유혼입률을 고려한 인장강도 식을 제안하였으며, 제안된 식은 좋은 상관성을 보이는 것으로 나타났다.