• 한국정밀공학회지
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• 제22권7호
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• pp.164-169
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• 2005

The micro-gripper system is one of the systems that should be improved in the respect of performance for practical usage. In the previous works, the important issues are considered and presented using axiomatic design approach. In this paper, the functional requirements and design parameters are evaluated in order to improve the performance and efficiency of the system. The evaluation is a very difficult task since many variables are related to the outcomes. To provide a basis for correct design decisions, axiomatic design principles have been advanced. Since the framework of axiomatic design makes design issues easier to understand when they are analyzed, we used those as an evaluation tool. The object of the system is to handle micro-size parts. Main device is a micro-gripper using two bender-typed and one stack-typed PZTs as actuators. And it has three tips made of tungsten wires fur holding function. Also the system must satisfy other functional requirements for appropriate handling performance. The results of this study show design improvements of micro-gripper system such as structural change of gripper, additional element, and integration of physical parts. Axiomatic design guides presented suitable design parameters corresponding to functional requirements and made the design elements improve through diagrams of whole system.

• 한국전산구조공학회논문집
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• 제17권2호
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• pp.141-150
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• 2004

최근의 철근콘크리트 교량의 부식과 노후화에 대한 관심이 많다. 콘크리트 안의 부식되어진 철근은 교량구조의 안전뿐만 아니라 철근콘크리트 부재의 휨강도에도 영향을 준다. 기존의 성능평가를 고려한 철근콘크리트속의 부식율 및 휨강도 특성 경제성 분석은 명확하지 많았다. 본 연구의 목적은 철근의 부식감소에 따라서 철근콘크리트 교량의 저항강도기능과 생애주기비용을 연구하고자 한다 따라서 현재의 부식 및 휨강도 산출공식을 제시하고 부식된 철근 콘크리트 교량의 잔여수명을 정확히 평가하고자 한다.

• 한국위성정보통신학회논문지
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• 제11권4호
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• pp.21-26
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• 2016

PPS 소자가 삽입된 N형 실리콘 제어 정류기(NSCR_PPS) 소자에서 채널차단영역의 이온주입 변화가 정전기 보호 성능에 미치는 영향을 연구하였다. 종래의 NSCR 표준소자는 on 저항, 스냅백 홀딩 전압 및 열적 브레이크다운 전압이 너무 낮아 마이크로칩의 정전기보호소자로 적용이 어려웠다. 그러나 본 연구에서 제안하는 채널 차단 영역의 이온주입 조건을 변화시켜 각각 변형설계된 소자에서는 채널 차단 이온주입이 정전기 보호성능의 향상에 영향을 주는 중요한 파라미터였으며, CPS_PDr+HNF 구조의 변형소자는 정전기보호소자의 설계창을 만족시키는 향상된 정전기보호성능을 나타내어 고전압 동작용 마이크로 칩의 정전기보호 소자로 적용 가능함을 확인하였다.

• 한국산학기술학회논문지
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• 제16권9호
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• pp.6254-6259
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• 2015

광시스템상에는 외부로부터의 잡음과 시스템 자체의 잡음이 항상 존재하는데, 이러한 잡음은 광시스템의 성능을 저하시키는 요인으로 작용하게 되어 결국에는 시스템의 에러확율을 변화시키게 된다. 이에 본 논문에서는 광시스템의 특성변수인 m 값을 도입하여 다양한 m값의 변화에 따라 광시스템의 에러확률을 ${\kappa}$-자승법을 이용하여 계산하였다. 계산 결과 m값에 따라 광시스템의 에러확률이 변화함을 확인하였고, 광시스템의 표준에럭확률인 $10^{-9}$을 유지하는 경우 m값을 400정도로 유지하면 됨을 확인하였다. 이는 m값이 큰 경우는 광시스템이 저출력임을 의미하므로 보다 작은 출력의 광원을 사용해도 광시스템의 에러확율을 유지하는데 문제가 없음을 알 수 있었다. 이는 일반적인 경우 저출력의 광원을 사용하는 경우 광시스템의 수신단에서 신호를 증폭하는 전치증폭기를 사용하지 않아도 됨을 의미하므로 보다 효율적이며 저렴하게 광시스템을 구현할 수 있음을 의미한다.

• Structural Engineering and Mechanics
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• 제83권3호
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• pp.293-304
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• 2022

In this work, a novel reliability approach for combined high and low cycle fatigue (CCF) estimation is developed by combining active learning strategy with least squares support vector machines (LS-SVM) (named as ALS-SVM) surrogate model to address the multi-resources uncertainties, including working loads, material properties and model itself. Initially, a new active learner function combining LS-SVM approach with Monte Carlo simulation (MCS) is presented to improve computational efficiency with fewer calls to the performance function. To consider the uncertainty of surrogate model at candidate sample points, the learning function employs k-fold cross validation method and introduces the predicted variance to sequentially select sampling. Following that, low cycle fatigue (LCF) loads and high cycle fatigue (HCF) loads are firstly estimated based on the training samples extracted from finite element (FE) simulations, and their simulated responses together with the sample points of model parameters in Coffin-Manson formula are selected as the MC samples to establish ALS-SVM model. In this analysis, the MC samples are substituted to predict the CCF reliability of turbine blades by using the built ALS-SVM model. Through the comparison of the two approaches, it is indicated that the reliability model by linear cumulative damage rule provides a non-conservative result compared with that by the proposed one. In addition, the results demonstrate that ALS-SVM is an effective analysis method holding high computational efficiency with small training samples to gain accurate fatigue reliability.

• 한국위성정보통신학회논문지
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• 제10권4호
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• pp.6-11
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• 2015

PPS 소자가 삽입된 N형 실리콘 제어 정류기(NSCR_PPS)소자에서 게이트와 $N^+$ 확산층 간격(Gate to Primary $N^+$ diffusion Space; GPNS)의 변화가 정전기 보호 성능에 미치는 영향을 연구하였다. FPW 구조와 CPS 이온주입을 행하지 않은 구조를 갖는 종래의 NSCR 표준소자는 on 저항, 스냅백 홀딩 전압 및 열적 브레이크다운 전압이 너무 낮아 정전기 보호소자의 필요조건을 만족시키지 못해 마이크로칩의 정전기보호소자로 적용이 어려웠다. 그러나 본 연구에서 제안하는 PPW 구조와 CPS 이온주입을 동시에 적용하여 변형설계된 소자에서는 GPNS의 변화가 정전기 보호성능의 향상에 영향을 주는 중요한 파라미터였으며, 정전기보호소자의 설계창을 만족시키는 향상된 정전기보호성능을 나타내어 고전압 동작용 마이크로 칩의 정전기보호 소자로 적용 가능함을 확인하였다.

• 펄프종이기술
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• 제29권1호
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• pp.73-83
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• 1997

Most of the materials used in various industrial fields and also in our daily life are multi-component materials or composite materials, and it is well known that there are many cases where adhesion between the constituents within the bonded systems plays an important role. There are various types of performance evaluation tests for the bonded materials, among which tests for evaluating the bond performance under various conditions may be regarded as the most interesting ones for those engaged in work related to adhesion. I have studied on the mechanism of adhesion form the rheological standpoint with my colleagues, including some students from Korea, and I am very happy to be able to have a talk on some of our research works. In Japan, the so-called "adhesives" are usually classified into two categories;adhesives and pressure sensitive adhesives (PSA). Adhesives are the materials which solidify after bonding and are after used as the structural adhesives because the adhesive strength is comparatively strong. On the other hand, the pressure sensitive adhesives never solidify and are used as PSA tapes, labels or decals. About the adhesives, we have examined the dependence of adhesive strength(shear, tensile, peel) upon both temperature and rate of deformation, and found out some empirical rules which are applicable to most of the adhesive systems. We have also developed a simplified theory of adhesion, which is deseribed in terms of mechanical equivalent mode1 and a few failure criteria. Although some of the common rules can be accounted for according to this theory, it must be pointed out that a fracture mechanical approach ms inevitable especially in the region where the meehanical relaxation time of the adhesive is extremely large [W. W. Lim and H. Mizumachi]. About the pressure sensitive adhesives, we have studied on the PSA performance (peel, tack, holding power) as a function of both the viscoelastic properties and surface chemical properties of the materials, and found out some rules, and again we have developed a theory which deseribes the mechanism. And in addition, we have studied on the miscibility between linear polymers and oligomers, because PSA is generally manufactured by blending gums and tackifier resins. Many phase diagrams have been found and some of them have been analyzed on thermodynamic basis, and it became evident that the miscibility is a very important factor in PSA [H. J. Kin and H. Mizumachi]. In this presentation, I want to emphasize the fact that the adhesion performance is closely related to the structure/property of the adhesives.adhesives.

• Animal Bioscience
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• 제35권3호
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• pp.484-493
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• 2022

Objective: This study was conducted to evaluate the effects of the supplementation of diets of broiler chickens with hot-melt extruded CuSO₄ (HME-Cu) on their growth performance, nutrient digestibility, gut microbiota, small intestinal morphology, meat quality, and copper (Cu) bioavailability. Methods: A total of 225 broilers (Ross 308), one-day old and initial weight 39.14 g, were weighed and distributed between 15 cages (15 birds per cage) in a completely randomized experimental design with 3 treatments (diets) and 5 replicates per treatment. Cages were allotted to three treatments including control (without supplemental Cu), IN-Cu (16 mg/kg of CuSO₄), and HME-Cu (16 mg/kg of HME processed CuSO₄). Results: The HME-Cu treatment tended to increase the overall body weight gain (p<0.10). The apparent digestibility of Cu was increased by supplementation of HME-Cu at phase 2 (p<0.05). The Escherichia coli count in cecum tended to decrease with the supplementation with Cu (p<0.10). In addition, the HME-Cu treatment had a higher pH of breast meat than the control and IN-Cu treatments (p<0.05). Significant increases in the cooking loss, water-holding capacity, and lightness in the breast were observed in the HME-Cu treatment compared to the control (p<0.05). The Cu content of excreta increased with the Cu supplementation (p<0.05). The concentration of excreta Cu in broilers was decreased in the HME-Cu compared to the IN-Cu in phase 2 (p<0.05). The Cu concentration in the liver was increased with the HME-Cu supplementation, compared with the control diets (p<0.05). Conclusion: This study showed that HME-Cu supplementation at the requirement level (16 mg/kg diets) in broiler diets did not affect the growth performance and the physiological function of Cu in broilers. However, supplementation of Cu in HME form improved the meat quality and the bioavailability of Cu.

• 한국도로학회논문집
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• 제17권1호
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• pp.129-142
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• 2015

PURPOSES : The purpose of this study is to suggest a basis for setting appropriate safety goals specifically related to the threshold zone luminance in a vehicular traffic tunnel. METHODS : In the test, drivers were divided into two groups. One group consisted of all drivers (average drivers) group with an age ratio of drivers holding domestic driver's license and driver group by age to produce threshold zone luminance in the tunnel. The threshold zone luminance produced as a result was used to analyze how it affects the safety level of each driver group and provide a basis for setting an appropriate safety criterion that can be used to determine threshold zone luminance. We used test equipment, test conditions, and ananalysis of threshold zone luminance identical to that reported by ChoandJung(2014) but the values of adaptation luminance in our analys is were expanded to range from100 to $10,000cd/m^2$. RESULTS : Adaptation luminance and threshold zone luminance are found to be related by a quadratic function. The threshold zone luminance needed by older drivers to ensure a certain safety level is significantly higher than that for drivers of other age brackets when adaptation luminance increases. 56% of older drivers are at an increased risk of an accident at the same luminance for which the safety level of average drivers is 75%. The safety level that can be achieved for older drivers increases to above 60% when threshold zone luminance level is set with the goal of attaining a safety level of more than 85% for average drivers. The safety level that can be attained for average drivers is above 90% when the threshold zone luminance is high enough to ensure over 75% in the safety level of older drivers. Results of this study are applicable to highways and others whose designed speed is 100 km/h. CONCLUSIONS : Threshold zone luminance determined on the basis of drivers having average visual ability is of limited value as a performance standard for ensuring the safety of older drivers. Hence, safety level for older drivers should be considered separately from safety levels for drivers with an average ability to avoid risk. Upward adjustment of older drivers' safety level in the process of determining appropriate threshold zone luminance in a vehicular traffic tunnel may bring both tangible and intangible benefit as a result of reducing accidents. However, there is an associated dollar cost arising from installing and operating lights. As a result, the economic impact of these trade-offs should also be considered.

• 한국과학교육학회지
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• 제34권1호
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• pp.33-42
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• 2014

교사의 과학관 학습 실행은 개인적 요소와 상황맥락적 요소들 간의 복잡한 상호작용을 바탕으로 이루어진다. 이에 CHAT를 분석 도구로 사용한 사례연구를 통해 두 교사의 과학관 학습 실행을 분석하였다. 연구 결과, 두 교사 모두 활동체계에서 주체 요소와 규칙, 공동체, 분업 요소들 간의 모순에 의해 과학관 학습 실행에 어려움을 겪는 것으로 나타났다. 두 교사는 유사한 모순에 의한 어려움을 겪었으나 과학관 학습 실행의 주체인 교사의 과학관 학습에 대한 인식이나 경험, 과학관 학습 실행에 대한 열정과 동기수준에 따라 갈등에 대한 내면화와 외면화의 양상에는 차이가 있었다. 이는 현장에서 과학관 학습의 활성화를 위해서는 교사가 과학관 학습 실행에 대한 정서적, 사회적 지원을 받을 수 있는 활동체계를 조성하기 위한 노력이 필요함을 시사한다. 한편, 도구요소인 과학관 학습에 대한 연수가 교사의 과학관 학습 실행을 중재하는 데 많은 한계가 있는 것으로 나타났다. 따라서 과학관 학습 관련 연수에서는 학습한 교수전략을 실제로 적용해볼 수 있는 기회와 그에 대한 적절한 피드백을 제공하고, 교사들이 활동체계의 요소들을 과학관 학습 실행에 유리하게 확장하는 것을 도울 필요가 있을 것이다.