• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1747-1755
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• 2008

Design of the reinforced roadbed thickness is concerned with safe operation of trains at specified levels of speed, axle load and tonnage. There are two methods for evaluating it. One is using an experimental equation and the other is using elastic theory with considering axle load, material properties of subsoils and allowable elastic settlement. Multi-layered theory is used to determine reinforced roadbed thickness by RTRI. Although their reinforced roadbed thickness is designed with an objective of achieving a minimum standard 2.5mm of settlement on the subgrade surface, it is hardly applied to real design. Li(1994) has suggested the experimental model which design approach is to limit plastic strain and deformations for the design period. It is worth due to adopting soil equivalent number of repeated load application. Moreover, it has been a more advanced method than existing design methods because including resilient modulus of subsoil beneath track, soil deviator stress caused by train axle loads and MGT. In this paper, it is analyzed under domestic track conditions to estimate the reinforced roadbed thickness with different soil types.

• 한국항해항만학회지
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• 제26권1호
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• pp.43-49
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• 2002

본 연구에서는 비감쇠 자유진동을 하는 점용접된 사각평판의 고유진동수를 수치해석을 통하여 살펴보고, 실험을 통하여 결과를 검증하였다 설계변수로는 점용접에 미치는 여러 설계변수 중에서 점용접이 차지하는 면적을 사각평판의 면적으로 나눈 면적비와 점용접점 사이의 거리를 평판의 한 변의 길이로 나눈 거리비로 무차원화하여 사용하였으며, 목적함수로는 점용접으로 인한 두께효과를 진동수에 대한 처짐의 비로써 나타낸 등가두께로써 무차원화하여 정의하였다. 수치해석에는 범용유한요소해석 프로그램인 ANSYS 5.6을 사용하였고, 실험에는 B&K Data analyzer를 통하여 주파수분석을 수행하였다. 연구의 결과 다음과 같은 결론을 얻었다. 1. 점용접의 면적비가 단지 4.52%인데 비해 점 용접으로 인한 두께효과는 55%로써 매우 크게 나타났다. 2. 거리비에 따른 두께효과는 거리비가 0.4일 때 가장 크게 나타났다.

• 한국방사선학회논문지
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• 제17권6호
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• pp.1001-1007
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• 2023

방사선영상검사에서 발생하는 피폭선량에 대한 선량제한이 없으므로 방사선방호를 위한 정당화와 최적화가 반드시 필요하다. 조직등가물질 볼루스를 이용하여 방사선영상검사로 인한 피폭선량을 저감하면서 동시에 영상화질을 유지할 수 있는 범위를 확인하였다. 손 후전방향 프로젝션을 기준으로 50 kVp, 5 mAs, SID 100 cm, 8×10 inch 조건으로 볼루스를 0, 3, 5, 8, 10 mm 적용하여 손 부위 입사선량과 영상의 SNR을 확인하였다. 볼루스의 두께별 손 부위 입사선량(μGy)은 각각 125.41±0.288, 106.85±0.255, 104.97±0.221, 91.68±0.299, 90.94±0.106으로 나타나 볼루스의 사용여부와 그 두께에 따라 유의한 피폭선량 감소를 보였다. 영상의 SNR은 볼루스 각 두께에서 13.997, 13.906, 12.240, 12.538, 12.548로 나타나 큰 차이를 보이지 않았다. 방사선영상검사의 종류와 검사 부위에 따라 적절한 두께와 크기의 볼루스를 사용한다면 영상화질의 저하없이 유의한 피폭선량 저감효과를 볼 수 있음을 확인하였다.

• 대한기계학회논문집A
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• 제35권11호
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• pp.1415-1422
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• 2011

운송기계구조물의 제작에 사용되는 판재 알루미늄 합금재료는 일정한 피로응력조건하에서 두께에 따라 균열진전속도의 차이를 보인다. 이러한 두께효과는 판재 알루미늄합금의 주요한 피로파괴특성 중 하나이다. 본 연구에서는 일정한 피로응력조건하에서 실시한 후판 및 박판 Al 2024-T3 합금재료의 피로 시험을 통하여 두께효과를 파악하고, 이를 형상인자인 두께비, $R_t$ 및 하중인자인 두께별 등가유효응력확대비, $U_{i}^{equ}$에 의한 상호관계식, $U_{i}^{equ}=f(R_t)$로 나타내었다. 그리고 두께효과에 의한 후판 대비 박판시험편의 균열진전 지연거동을 ${\Delta}K$ 환산법을 사용하여 정량적으로 분석하였다. 두께효과의 경향을 정량으로 나타내기 위해 두께감소율(DoT)과 응력확대계수범위, ${\Delta}K$의 감소율(DoS) 등의 값을 구하여 이들 상호관계를 규명하였다.

• 치과방사선
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• 제29권1호
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• pp.33-42
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• 1999

Geometrically standardized dental radiographs were taken. We prepared Digital Cu-Equivalent Image Analyzing System for quantitative assessment of mandible bone. Images of radiographs were digitized by means of Quick scanner and personal Mcquintosh computer. NIH image as software was used for analyzing images. A stepwedge composed of 10 steps of 0.1mm copper foil in thickness was used for reference material. This study evaluated the effects of step numbers of copper wedge adopted for calculating equation. kVp and exposure time on the coefficient of determination(r²)of the equation for conversion to Cu-equivalent image and the coefficient of variation and Cu-Eq value(mm) measured at each copper step and alveolar bone of the mandible. The results were as follows: 1. The coefficients of determination(r²) of 10 conversion equations ranged from 0.9996 to 0.9973(mean=0.9988) under 70kVp and 0.16 sec. exposure. The equation showed the highest r was Y=4.75614612-0.06300524x +0.00032367x² -0.00000060x³. 2. The value of r² became lower when the equation was calculated from the copper stepwedge including 1.0mm step. In case of including 0mm step for calculation. the value of r showed variability. 3. The coefficient of variation showed 0.11, 0.20 respectively at each copper step of 0.2, 0.1mm in thickness. Those of the other steps to 0.9 mm ranged from 0.06 to 0.09 in mean value. 4. The mean Cu-Eq value of alveolar bone was 0.14±0.02mm under optimal exposure. The values were lower than the mean under the exposures over 0.20sec. in 60kVp and over 0.16sec. in 70kVp. 5. Under the exposure condition of 60kVp 0.16sec.. the coefficient of variation showed 0.03. 0.05 respectively at each copper-step of 0.3, 0.2mm in thickness. The value of r² showed over 0.9991 from both 9 and 10 steps of copper. The Cu-Eq value and the coefficient of variation was 0.14±0.01mm and 0.07 at alveolar bone respectively. In summary. A clinical application of this system seemed to be useful for assessment of quantitative assessment of alveolar provided high coefficient of determination is obtained by the modified adoption of copper step numbers and the low coefficient of variation for the range of Cu-Equivalent value of alveolar bone from optimal kVp and exposure time for each x-ray machine.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1998년도 학술발표대회 논문집 제17권 2호
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• pp.129-132
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• 1998

A bond graph modeling approach which is equivalent to a finite element method is formulated in the case of the piezoelectric thickness vibrator. This formulation suggests a new definition of the generalized displacements for a continuous system as well as the piezoelectric thickness vibrator. The newly defined coordinates are illustrated to be easily interpreted physically and easily used in analysis of the system performance. The bond graph model offers the primary advantage of physical realizability and has a greater physical accuracy because of the use of multiport energic elements. While results are presented is general in scope and can be applied to arbitrary physical systems.

• 치과방사선
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• 제22권2호
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• pp.273-282
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• 1992

The purpose of this study was to propose the utility which was evaluated the digital image processing and clinical application of the videodensitomery. The experiments were performed with IBM-PC/16bit-AT compatible, video camera(CCdtr55, Sony Co., Japan), an color monitor(MultiSync 3D, NEC, Japan) providing the resolution of 512×480 and 64 levels of gray. Sylvia Image Capture Board for the ADC(analog to digital converter) was used, composed of digitized image from digital signal and the radiographic density was measured by 256 level of gray. The periapical radiograph(Ektaspeed EP-21, Kodak Co., U. S. A) which was radiographed dried human mandible by exposure condition of 70 kVp and 48 impulses, was used for primary X-ray detector. And them evaluated for digitzed image by low and high pass filtering, correlations between aluminum equivalent values and the thickness of aluminum step wedge, aluminum equivalent values of sound enamel, dentin, and alveolar bone, the range of diffuse density for gray level ranging from 0 to 255. The obtained results were as follows: 1. The edge between aluminum steps of digitized image were somewhat blurred by low pass filtering, but edge enhancement could be resulted by high pass filtering. Expecially, edge enhancement between distal root of lower left 2nd molar and alveolar lamina dura was observed. 2. The correlation between aluminum equivalent values and the thickness of aluminum step wedge was intimated, yielding the coefficient of correlation r=0.9997(p<0.00l), the regression line was described by Y=0.9699X+0.456, and coefficient of variation amounting to 1.5%. 3. The aluminum equivalent values of sound enamel, dentin, and alvolar bone were 15.41㎜, 12.48㎜, 10.35㎜, respectively. 4. The range of diffuse density for gray level ranging from 0 to 255 was wider enough than that of photodenstiometer to be within the range of 1-4.9.

• 한국전자파학회논문지
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• 제26권3호
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• pp.311-316
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• 2015

본 논문에서는 저항성 sheet를 이용한 광대역 박형 흡수체 설계법을 제안한다. 제안된 흡수체의 등가회로는 직렬 RLC 공진회로와 종단이 단락된 전송선으로 이루어진다. 이 등가회로를 바탕으로 임의의 설계주파수에서 흡수체가 ${\lambda}/4$보다 얇은 두께를 가지면서도, 광대역 흡수율 특성을 가지는 세가지 조건을 정리하였다. 수치해석을 통해 이를 동시에 만족하는 R, L, C 소자 값을 구했다. 구한 등가 R, L, C값은 특정한 chip 저항이나 표면저항을 가지는 십자 모양의 구조로써 구현이 가능하다. 이러한 설계법을 설계 중심주파수 3 GHz에서 적용해서 두께가 18.75 mm(전기적 길이 $67.5^{\circ}$)이고, 90 % 흡수율 기준으로 116 % 대역폭을 갖는 광대역 흡수체를 설계하였다.

• 한국정밀공학회지
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• 제19권2호
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• pp.79-86
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• 2002

In end milling process the undeformed chip thickness and the cutting force components vary periodically with phase change of the tool. In this study, up end milling process is transformed to the equivalent oblique cutting. The varying undeformed chip thickness and the cutting force components in end milling process are replaced with the equivalent average ones. Then it can be possible to analyze the chip-tool friction and shear process in the shear plane of the end milling process by the equivalent oblique cutting system. According to this analysis, when cutting Inconel 718, 61, 64 and 55% of the total energy is consumed in the shear process with the helix angle 30$^{\circ}$, 40$^{\circ}$ and 50$^{\circ}$ respectively, and the balance is consumed in the friction process. With the helix angle of 40$^{\circ}$ the specific cutting energy consumed is smaller than with the helix angle 30$^{\circ}$ and 50$^{\circ}$.

• Journal of Microbiology and Biotechnology
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• 제7권4호
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• pp.267-271
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• 1997

We developed a dermal equivalent (DE) which was engineered using human dermal fibroblasts and a matrix of collagen gel. The in vitro construction of the DE was accomplished by casting a porcine collagen type I solution plus concentrated medium with isolated and cultured fibroblasts. These constructs were attached to culture dishes or left floating in culture medium. Contraction of attached gels results in decreased gel thickness without a change in gel diameter, and contraction of floating gels results in decreased gel thickness and diameter. After contraction, there was no increase in cell number in floating gels, but cells in attached gels began to increase after about 4 days of the lag phase in cell growth curve. At this lag phase, addition of fibroblast growth factor (FGF) at a concentration of $0.1{\mu}$/ml promoted cell proliferation in the attached collagen gels, but no effect in floating gels. These results indicate that the method of contraction had an influence on the extracellular matrix (ECM) organization, and this influenced not only cell growth but also fibroblast responsiveness to FGF. This suggests that attached collagen gel is more suitable as a dermal equivalent than the floating gel. And the final contracted area of attached gel is much larger than that of the floating gel since floating gel is contracted in all directions but attached gel is contracted only vertically.