• 구강회복응용과학지
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• 제32권1호
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• pp.47-59
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• 2016

목적: 하악 제1대구치 상실 시 인접 및 대합 치아들의 경사 및 정출 정도에 따른 교합력의 변화를 스트레인게이지를 이용하여 측정 및 비교하는 것이다. 연구 재료 및 방법: 인접 및 대합 치아들의 경사 및 정출이 심화되는 정도를 점진적으로 네 개의 다이에 표현 후, CAD/CAM 제작 맞춤형 다이 시스템을 통하여 주모형에 부착 및 교체 가능하도록 하였다. 치아에 스트레인게이지를 부착 후, 만능물성시험기로 저작력을 가하면서 상하악 치아의 교합력을 측정하였다. 통계처리는 독립표본 t검증과 일원배치 분산분석을 시행하였다(${\alpha}=.05$). 결과: 대구치 상실 후 치아이동에 따른 교합력의 양상은, 네 단계의 모형에 대한 교합력의 차이가 통계적으로 유의하였고, 감소 추세였다. 음식물 저작 시 인접 치아들의 이동에 따라 상악 제1, 2소구치, 하악 제2대구치에서 점차 교합력이 감소되었다. 음식물의 경도가 감소함에 따라 치아의 교합력이 점차적으로 감소하였다. 육포 저작 시 하악 제2대구치의 교합력이 가장 높게 측정되었다(P < 0.05). 결론: 하악 제1대구치가 상실되고 치아 이동이 일어나기 전에는 저작 시 치아가 상실되지 않았을 때에 비해 인접 및 대합 치아들의 교합력이 높은 반면, 치아 이동이 진행됨에 따라 교합력은 정량적으로 감소하였다.

• Transactions on Electrical and Electronic Materials
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• 제3권2호
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• pp.32-37
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• 2002

This paper gives the basic mechanical properties of indium-tin-oxide (ITO) films on polymer substrates which are exposed to externally and thermally induced bending force. By using modified Storney formula including triple layer structure and bulge test measuring the conductive changes of patterned ITO islands as a function of bending curvature, the mechanical stability of ITO films on polymer substrates was intensively investigated. The numerical analyses and experimental results show thermally and externally induced mechanical stresses in the films are responsible for the difference of thermal expansion between the ITO film and the substrate, and leer substrate material and its thickness, respectively. Therefore, a gradually ramped heating process and an organic buffer layer were employed to improve the mechanical stability, and then, the effects of the buffer layer were also quantified in terms of conductivity-strain variations. As a result, it is uncovered that a buffer layer is also a critical factor determining the magnitude of mechanical stress and the layer with the Young's modulus lower than a specific value can contribute to relieving the mechanical stress of the films.

• 대한기계학회논문집A
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• 제30권3호
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• pp.269-278
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• 2006

This paper proposes slip line fields for bending of unequally notched specimens in plane strain that have a sharp crack in one side and a sharp V-notch in the other side. Depending on the back angle, two slip line fields are proposed, from which the limit moment and crack tip stress fields are obtained as a function of the back angle. Excellent agreement between slip line field solutions with those from detailed finite element limit analysis based on non-hardening plasticity provides confidence in the proposed slip line fields. One interesting point is that, for the unequally notched specimen, the difference between the crack tip triaxial stress for tension and that for bending increases significantly with increasing the back angle. This suggests that such a specimen could be potentially useful to investigate the crack tip constraint effect on fracture toughness of materials. In this respect, the possibility of designing a new toughness testing specimen with varying crack tip constraint is discussed.

• Computers and Concrete
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• 제23권5호
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• pp.321-327
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• 2019

Experimental isotherm compressive tests show that concrete behaviour is dependent on temperature. The aim of such tests is to reproduce how concrete will behave under environmental changes within a moderate range of temperature. In this paper, a novel constitutive elastic damage behaviour law is proposed based on a free energy with an apparent damage depending on temperature. The proposed constitutive behaviour leads to classical theory of thermo-elasticity at small strains. Fixed elastic mechanical characteristics and fixed evolution law of damage independent of temperature and the material volume element size are considered. This approach is applied to compressive tests. The model predicts compressive strength and secant modulus of elasticity decrease as temperature increases. A power scaling law is assumed for specific entropy as function of the specimen size which leads to a volume size effect on the stress-strain compressive behaviour. The proposed model reproduces theoretical and experimental results from literature for tempertaures ranging between $20^{\circ}C$ and $70^{\circ}C$. The effect of the difference in the coefficient of thermal expansion between the mortar and coarse aggregates is also considered which gives a better agreement with FIB recommendations. It is shown that this effect is of a second order in the considered moderate range of temperature.

• 생명과학회지
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• 제19권7호
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• pp.917-922
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• 2009

SD계 흰쥐를 사용하여 motor activity 실험에서 동물들의 자발적인 운동성을 측정한 결과, 주어진 시간 내 움직인 시간과 움직인 거리에는 n-3 지방산이 적절히 함유된 식이군 (Adq group)과 DHA가 첨가된 식이군(Adq+DHA group)간에 유의적 차이를 관찰할 수가 없었다. 학습효과 실험에서 n-3 지방산이 적절히 함유된 식이군 (Adq group)의 경우 목적 플랫트폼까지 걸리는 시간이 DHA 첨가 식이군(Adq+DHA group)에 비하여 다소 길었으나 유의적 차이는 관찰할 수가 없었다. 수영 속도(swimming speed)에서 DHA 첨가 식이군(Adq+DHA group)의 경우, n-3 지방산이 적절히 함유된 식이군 (Adq group)에 비해 유의적으로 빨랐으나 수영 풀에서 움직인 거리 (swimming distance)에는 두 식이군 간의 유의적 차이가 없었다. 두 식이군의 흰쥐들이 수영한 시간(swimming time)과 쉬고 있는 시간(resting time)의 경우, 쉬는 시간에는 유의적 차이가 없었으나 수영 시간 또한 n-3 지방산이 적절이 함유된 식이(Adq group)로 사육된 쥐가 DHA가 첨가된 식이로 사육된 쥐(Adq+DHA group)보다 수영한 시간이 길었으나 여기서도 유의적 차이는 없었다. 기억력 테스트에서 n-3 지방산이 적절히 함유된 식이군(Adq group) 및 DHA가 첨가된 식이군(Adq+DHA group) 모두는 목적 플랫트폼이 있었던 A 지역에 대한 기억이 우수하여 다른 지역들인 B, C, D를 지나가는 횟수보다 유의적으로 많았음을 관찰하였다(p<0.05). 이상의 결과로부터 임신에서부터 성인이 될 때까지 n-3 지방산이 적절히 함유된 식이로 사육된 쥐와 비교할 때 DHA가 첨가된 식이로 사육된 흰쥐가 Morris water maze를 이용한 공간기억력 실험에서 다소 우수한 기억 학습효과를 나타내었으나 유의적 차이는 없었음을 관찰 할 수가 있었다.

• Toxicological Research
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• 제26권3호
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• pp.171-175
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• 2010

The human genome contains approximately 13 orphan cytochrome P450 (P450, CYP) genes, of which the apparent function or substrate has not been identified. However, they seem to possess their own biological relevance in some tissues or developmental stages. Here, we characterized the heterologously expressed CYP2W1, an orphan P450 enzyme. The recombinant CYP2W1 protein containing a $6{\times}$(His)-tag at Nterminus has been expressed in Escherichia coli and purified. Expression level of CYP2W1 holoenzyme was around 500 nmol P450 holoenzyme per liter culture medium. The reduced CO difference spectrum of CYP2W1 showed a maximum absorption at 449 nm. CYP2W1 indicated the significant induction to bioactivate Trp-P-1, MeIQ, and IQ in E. coli DJ701 tester strain. However, the bioactivation of B[$\alpha$]P, and NNK by CYP2W1 was relatively low. The model structure of CYP2W1 suggested the characteristic P450 folds with the lengths and orientations of the individual secondary elements. The F-G loop is situated on the distal side of heme to accommodate the flexibility of active site of CYP2W1. These studies can provide useful information for the finding of its biological roles and structure-function relationships of an orphan CYP2W1 enzyme.

• Journal of Nutrition and Health
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• 제29권9호
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• pp.934-942
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• 1996

This study was performed to investigate the influence of dietary fibers on the serum lipid level and bowel function in aged rats. Fiber sources of experimental diets were made from mugwort(M), butterbur(B), apple(A), sea mustard(S) by drying and milling. Each of fiber sources was mixed into the diet at the level of 5, 15% of diet. Sprague-Dawley strain, 13 month old male rats were divided into 9 groups by randomized complete block design : C, M5, B5, A5, S5, M15, B15, A15, S15. The animals were fed ad libitum each of experimental diets for 4 weeks. Control group showed lower food intake compare to the other groups. There were no significant difference between 5% groups and 15% groups in food intake. Fecal weight, dry fecal weight and fecal water content of control group were significantly lower than those of experimental groups, and fecal water content was increased by increasing level of dietary fibber. Apple group showed the lowest values, sea mustard group showed the highest. The shorter transit time was observed in the group of higher intake of dietary fiber. At the same level of dietary fiber, transit time of sea mustard group was shorter than the other groups. With increasing age, serum triglycerides, total cholesterol were increased and HDL-cholesterol was decreased. Fiber fed groups showed lower serum TG, TC and higher HDL-c level compare to the control group. Absorption rates of calcium, magnesium and phosphorus was tend to be lower in the group fed dietary fiber sources than control group. Mucosa weight and maltase activity in the small intestine were decreased by increasing age. As intake of dietary fiber increaed, mucosa weight in the small intestine was not different but maltase activity was decreased.

• 구강회복응용과학지
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• 제22권4호
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• pp.329-340
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• 2006

Statement of problem: Damping of the peak force transmitted to implants has been reported by in vitro studies using impact forces on resin-veneered superstructures. Theoretical assumptions suggest that use of acrylic resin for the occlusal surfaces of a prosthesis would protect the connection between implant and bone. Therefore, the relationship between prosthesis materials and the force transmitted through the implant system also needs to be investigated under conditions that resemble the intraoral mechanical environment. Purpose: The purpose of this study was to analyze the fracture strength and modes of temporary prosthesis when a flange or occlusally extended structure were connected on the top of the abutment. Material and method: Modified abutments of winged and bulk design were made by casting the desired wax pattern which is made on the UCLA type plastic cylinder. Temporary crowns were made using templates on the modified abutments, and its fracture toughness and strain were compared to the traditional temporary prosthesis. To evaluate the effect of aging, 5.000 times of thermocycling were performed, and their result was compared to the 24hours specimen result. Results: The following conclusions were drawn from this study: 1. In the fracture toughness test, temporary crown's fracture line located next to the screw hole while modified designs with metal support showed fracture line on the metal and its propagation along the metal-resin interface. 2. Wing and bulk structure didn't show significant difference in the fracture toughness (p>0.05), but wing structure showed stress concentration on the screw hole area compared to bulk structure which showed even stress distribution. 3. In the fracture toughness test after thermocycling, wing and bulk structure showed increased or similar results in metal supported area while off-metal area and temporary crown showed decreased results. 4. In the strain measurement after thermocycling, its value increased in the temporary and bulk structure. However, wing structure showed decreased value in the loading point while increased value in the screw hole area. Conclusion: Wing type design showed compatible result to the bulk type that its application with composite resin prosthesis to the implant dentistry is considered promising.

• Journal of Nutrition and Health
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• 제20권6호
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• pp.432-441
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• 1987

흰쥐에서의 알콜섭취와 식이지방랴잉 성장과 간기능 및 혈액의 생화학적 특성에 미치는 영향을 조사하기 위하여 160g 내외의 Sprague-Dawley 종 숫쥐 48마리를 4군, 즉 고지방비알콜군, 고지방 알콜군, 저지방비알콜군, 저지방알콜군으로 나누어 3주간 6주간 사육하였다. 저지방과 고지방식이는 총 Calorie의 12%와 30%지방 Calorie로 하였고 알콜은 급수용 물에 1-% ethanol로 하였고 알콜은 급수용 물에 10% ethanol을 섞어 공급하였다. 만성적인 알콜섭취에서는 알콜 자체와 영양결핍이 상호작용하여 여러가지 생화학적 임상학적 변화를 초래하게 되므로, 본 연구에서는 식이에 lipotropic agents인 choline과 nethionine을 포함한 모든 필수영영소들을 충분히 제공한 상태에서 알콜과 식이지방의 효과를 측정하고자 하였다. 총 Calorie는 고지방알콜 군에서 21.86% 저지방알콜군에서는 23.61%에 해당 하여 moderate drinking에 해당하였다. 성장에 미치는 영향은 저지방알콜군이 유의하게 저조한 성장을 보였으며 낮은 식이효율을 나타냈다. 혈장내 triglyceride농도는 알콜섭취군에서 증가하였고 섭췻기간이 길수록 그 차이는 커진 반면에 식이지방 함량에 따른 차이는 보이지 않았다. 총 cholesterol과 Hdl-cholesterol농도는 군간의 차이를 보이지 않았으며 vitamin $B_1$상태를 나타내는 trighyceride 활성과 TPP effrct도 군가의 차이가 없었다. 간기능을 간접적으로 시사하는 혈청 GPT활성과 간 mitochondria의 respiration rate도 알콜섭취와 지방함량에 따른 차이를 보여주지 않았다.

• Smart Structures and Systems
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• 제25권5호
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• pp.605-617
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• 2020

The existence of damages in structures causes changes in the physical properties by reducing the modal parameters. In this paper, we develop a two-stages approach based on normalized Modal Strain Energy Damage Indicator (nMSEDI) for quick applications to predict the location of damage. A two-dimensional IsoGeometric Analysis (2D-IGA), Machine Learning Algorithm (MLA) and optimization techniques are combined to create a new tool. In the first stage, we introduce a modified damage identification technique based on frequencies using nMSEDI to locate the potential of damaged elements. In the second stage, after eliminating the healthy elements, the damage index values from nMSEDI are considered as input in the damage quantification algorithm. The hybrid of Teaching-Learning-Based Optimization (TLBO) with Artificial Neural Network (ANN) and Particle Swarm Optimization (PSO) are used along with nMSEDI. The objective of TLBO is to estimate the parameters of PSO-ANN to find a good training based on actual damage and estimated damage. The IGA model is updated using experimental results based on stiffness and mass matrix using the difference between calculated and measured frequencies as objective function. The feasibility and efficiency of nMSEDI-PSO-ANN after finding the best parameters by TLBO are demonstrated through the comparison with nMSEDI-IGA for different scenarios. The result of the analyses indicates that the proposed approach can be used to determine correctly the severity of damage in beam structures.