신라대학교 주변 백양산의 동물상

노치권(외 6명) 신라대학교 자연과학연구소 2012 自然科學論文集 Vol.22 No.-

To study fauna of Silla University located in Mt. Baek-yang, we conducted six surveys from 29 May 2011 to 28 April 2012. We found five phyla 41 orders 197 species of animals inhabiting in this area: four phyla 27 orders 163 species of invertebrates and in vertebrates one order six species of fishes, three orders nine species of amphibians and reptiles, six orders 14 species of aves, and four orders five species of mammals. Of these species, some Korean endemic species were included: a fish of Rhodeus uyekii in a pond near main gate of this university, a frog of Rana coreana in a creek near a dormitory, and a rabbit of Lepus coreanus and a water deer of Hydropotes inermis in a grass region near a main stadium. A kind of hawk, Falco tinnunculus as a natural monument (animal) of no. 323-8, was observed on a building of medical and life science. A blue frog of Hyla japonica as a variation was found near a spring resort. Therefore, this area is considered an ecologically important area having a high animal diversity.

압축하중을 받는 원형디스크의 등경 및 등색프린지의 이론 및 실험적 분포

백태현,김환 국립7개대학공동논문집간행위원회 2004 공업기술연구 Vol.4 No.-

Photoelastic fringes of a circular disk under diametrical compression are simulated to calculate the phase maps of isoclinics and isochroamtics. Theoretical distributions of isoclinics and isochrmatics along a specified lines are calculated. Also, experimental fringes of a stress-frozen disk were measured by 8-step fringe shift method. The magnitudes of isoclinics and isochromatics obtained from fringe phase shift method with 8-step are compared with those calculated by theory and manual measurements. Close agreement among the results can be observed.

광중합형 수복용 복합레진의 인장강도에 미치는 thermal cycling과 시효 처리의 영향

백상현,채민수,이주형,김태조,배태성 대한치과기재학회 1998 대한치과재료학회지 Vol.25 No.1

The improvement in the mechanical properties of restorative composites has contributed to their increased use in recent years. In spite of their growing popularity, composites still have low resistance to fracture and wear in oral environments. This study was performed to examine whether the tensile strengths of light-cured restorative composites were affected by thermal cycling and aging in water. Five commerically available light-activated composites(Heliomolar : HM, Aelitefil : AF, Amelogen : AG, Clearfil AP-X : CF, Z100 : ZH) were used. Rectangular tension test specimens were fabricated in a teflon mold giving 5 mm in gauge length and 2mm in thickness. All samples were divided into 3 groups. Group 1 was stored in a desiccator for 10 days. Group 2 was immersed in a 37℃ distilled water for 10 days. Group 3 was subjected to 10,000 thermal cycles between 5℃ and 55℃, and the immersion time in each bath was 15 seconds per cycle. Tensile testing was carried out at a crosshead speed of 0.5 mm/min and fracture surfaces were observed with scanning electron microscope. The results obtained were summarized as follows; 1. The strength data fit to single-mode Weibull distribution(r²> 0.86) and Weibull parameters decreased after thermal cycling test. 2. The highest characteristics strength was observed in the CF group but the highest Weibull modulus was obtained in the AF group after thermal cycling test. 3. The highest tensile strength value of 83.92 MPa was obtained in the CF group and the lowest value of 13.91 MPa was obtained in the AG group. Tensile strengths showed no significant difference between HM and AG groups but other groups showed the significant differences in each group(p<0.05). 4. According to the microscopic observation of the fracture surfaces, fractures of large fillers were observed in the hybrid composites of the AF and CF groups.

광중합형 수복용 복합레진의 강도에 미치는 Thermal Cycling의 영향

백상현,채민수,배태성 대한치과기재학회 1996 대한치과재료학회지 Vol.23 No.1

This study was performed to investigate the effects of thermal cycling on the strength of light cured restorative composite resins. Five commerically available light-activated composite resins(Photo Clearfil A : CA. Lite-Fil A : LF, Clearfil Photo Posterior : CP, Prisma AP.H. : PA, Z100 : ZH) were used. The specimens of 12mm in diameter and 0.7mm in thickness were made, and a thermal cycling test of 1000 cycles at 15 seconds dwell time each in 5℃ and 55℃ baths was performed. In order to investigate the deterioration of composite resins in the thermal cycling test, the bi-axial flexure strengths were measured, and the surface after thermal cycling test were examined by SEM. The results obtained were summarized as follows; 1. Biaxial flexure strength significantly decreased due to the thermal cycling(P<0.01). 2. Biaxial flexure strengths showed the maximum value of 125.65MPa for ZH group and the minimum value of 64.86MPa for ZA group, after thermal cycling test, Biaxial fleure strengths of ZH and CP group were higher then those of PA, CF, and CA groups after thermal cycling test(p<0.05). 3. Fracture surfaces showed that the composite resin failure developed along the matrix and the filler/resin interface region, and the cracks propagated in the conical shape from the maximum tensile stress zone.

VCR用 DD캡스턴 모터의 特性 改善을 위한 設計製作 硏究

白壽鉉,任泰彬 東國大學校 1991 東國論叢 Vol.30 No.-

The DD capstan motor for VCR must be designed fast and adaptively as a small, light and slim type and have the high accuracy of control characteristic because the life cycle of its applying machinery has become shorter and it requires high accuracy of control characteristic. In this study, the design theory of the electric and magnetic parts for DD captan motor for VCR is systematized. Also the design theory and manufacturing method of MR sensor device as a speed detector is presented to enhance the accuracy of speed control, and the flux density of permanent magnet is made uniformly so as to magnetize the super multi-poles and as that result the FG with a high output and high accuracy can be designed and manufactured, which has 0.2% maximum fluctuation of the frequency and -60 dB minimum ratio of S/N. Applying these results to the design of DD capstan motor for VCR, the excellency of this can be proved.

강봉의 냉간 인발시 발생하는 잔류응력 성분에 관한 유한요소 해석

백태현,최희진 국립7개대학공동논문집간행위원회 2005 공업기술연구 Vol.5 No.-

Prediction the behaviour of steel during a deformation process under service conditions is one of the main challenges in cold forming, The design of optimized forging schedules, by means of conventional trial and error methods, has become increasingly heavy in terms of time and cost in a competitive environment. During the last few years, numerical simulations have become a very efficient tool to arrive these goals. In this paper, finite element analysis was used to analyze the distribution of residual stress components in a rod with respect die angle and/or area reduction in cold drawing process. Cold drawing brought sunken-in deformation at the bottom land of the rod that was in accord with the result obtained from the analysis using ABAQUS. The results obtained from finite element analysis were in close agreement with the determined high-accuracy measurements.

광탄성프린지 위상이동법을 이용한 에지균열판의 응력 해석

백태현,김명수,조성호 한국비파괴검사학회 2000 한국비파괴검사학회지 Vol.20 No.3

광탄성법은 투명한 물체에 힘을 가하면 복굴절 현상이 나타나며, 편광기에 의해 등색 및 등경프린지가 나타난다. 등색프린지를 이용하여 주응력차이 또는 평면상 전단응력을 계산할 수 있으며, 등경프린지에 의해 주응력 방향을 결정할 수 있다. 재래식 광탄성법에서는 특정한 위치에서 프린지를 개별적으로 측정해야 되는 불편한 점이 있어, 디지털 영상처리에 의해 광탄성 프린지로부터 전체적인 응력장을 해석할 수 있도록 프린지이동에 의한 위상이동법이 개발되었다. 프린지 위상이동법은 원형편광기에서 검광자를 0˚, 45˚, 90˚ 및 135˚회전시켜 프린지가 이동된 4개의 영상을 얻고, 이들로부터 위상차리로 나타나는 프린지분포를 측정한다. 본 연구에서는 프린지 위상이동법에 관한 광학적인 이론을 이용하여 압축하중을 받는 원형디스크의 프린지분포를 위상이동법으로 측정한 후 이론 값과 비교하였다. 또한, 인장하중을 받는 에지균열판의 응력분포 해석에 프린지 위상이동법을 적용하였다. 실험결과, 프린지 위상이동법으로 측정한 결과는 유한요소 해석 결과와 잘 일치하였다. 광탄성에서 위상이동법은 등경선과 평행하거나 직교하는 선상에서 응력분포를 용이하게 측정할 수 있으나, 일반적인 프린지 해석시 프린지 위상이동법을 적용하면 오차가 포함될 수 있다. The method of photoelasticity allows one to obtain principal stress differences and principal stress directions in a photoelastic model. In the classical approach, the photoelastic parameters are measured manually point by point. The previous methods require much time and skill in the identification and measurement of photoelastic data. Fringe phase shifting method has been recently developed and widely used to measure and analyze fringe data in photo-mechanics. This paper presents the test results of photoelastic fringe phase shifting technique for the stress analysis of a circular disk under compression and an edge-cracked plate subjectes to tensile load. The technique used here requires four phase stepped photoelastic images obtained from a circular polariscope by rotating the analyzer at 0˚, 45˚, 90˚ and 135˚. Experimental results are compared with those of FEM. Good agreement between the results can be observed. However, some error may be included if the technique is used to general direction which is not parallel to isoclinic fringe.

커패시터 放電 임펄스 着磁機의 컴퓨터 모델링 및 着磁요크의 磁界解析

白壽鉉,任泰彬,金必洙 東國大學校 1992 東國論叢 Vol.31 No.-

In a capacitor-discharge impulse magnetizer, a magnet is magnetized by the discharging current of capacitors. The conventional design of the magnetizer has been based on many year's experience. The behaviour of flux in the magnetizer should be calculated in order to produce the desired magnets. The analysis of the flux distribution in quite difficult. This is because both the magnetizing current and the applied voltage to the magnetizer are unknown. This paper describes the development of a computer model for a circuit of capacitor-discharge impulse magnetizer using SPICE. Also, the detailed distribution of the flux density in two applied type magnet magnetized by the impulse magnetizer be analyed.

光彈性技法을 利用한 應力强度係數 測定

白泰鉉 群山大學校自然科學硏究所 1990 自然科學硏究 Vol.5 No.-

Coefficients of power series type Williams equations, together with the exact origin of the crack, were calculated from data sets on the fringe sharpened isochromatic loops in the vicinity of the crack tip. Results of calculated values were evaluated by comparing experimental data points with the regenerated theoretical fringe loops. Accuracy evaluation indicated that the first four terms of Williams equations are sufficient to describe the stress field in the vicinity of the crack tip for both Mode I and Mixed Mode cases.

광탄성 프린지 위상이동법을 적용한 디스크의 등경 및 등색프린지 분리법에 관한 시뮬레이션

백태현,김명수,조성호 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.2

광탄성법은 전체적인 응력장 해석을 위하여 가장 많이 사용되는 방법중의 하나이다. 광탄성법에서 주응력의 차이와 방향은 등색선과 등경선으로 나타난다. 재래식 방법으로는 주응력 방향은 평면 편광기의 편광자와 검광자를 동시에 회전시켜 수작업으로 측정하며, 이를 타디보간법이라 한다. 이러한 방법은 전체적인 응력장 해석시 매우 번거로우며 많은 시간이 걸린다. 재래식 광탄성법에서는 광탄성 프린지로부터 등경선을 분리시킬 수 없다. 본 연구에서는 광탄성이론을 Jones행렬로 나타내고 4단계와 8단계의 위상이동법에 대해서 기술하였다. 컴퓨터시뮬레이션을 통하여 압축하중을 받는 원형디스크의 광탄성 프린지로부터 등경선과 등색선을 분리시킬 수 있는 시험을 하였다. 디스크의 프린지는 응력-광 법칙에 의하여 생성하였다. 8단계 위상이동법으로 얻은 등경선과 등색선의 크기를 이론으로 계산한 값과 비교하였다. 컴퓨터 시뮬레이션으로부터 광탄성 프린지로부터 등경선과 등색선을 분리시킬 수 있는 가능성ㅇ르 예시하였다. Photoelasticity is one of the most widely used methods for whole field stress analysis. In photoelasticity, the difference and the directions of the principal stresses are given isochromatic and isoclinic fringe patterns. Conventionally, principal stress directions are measured by rotating the polarizer and analyzer of a plane polariscope at the same time. This is known to be the Tardy compensation method. This measurement can be very tedious and time consuming in whold field analysis. It is not possible to separate isoclincs from photoelastic fringes by conventional photoelastic technique. In this study, photoelastic theory is represented by Jones matrices and 4-steps and 8-steps phase shifting methods are described. A feasibility study using computer simulation is done to separate isoclincs and isochomatics from photoelastic fringes of a circular disk under diametrical compression. Fringe patterns of the disk are generated using stress optic law. The magnitudes of isoclincs and isochromatics obtained from 8-step phase shifting method are compared with those of theories. From computer simulation, it is verified to separate isoclincs and isochmatics from photoelastic fringes.