• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.217-217
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• 2003

W-Cu 합금은 우수한 전기적, 열적 특성으로 인하여 열소산재료(Heat sink)로 많이 응용되고 있다. 첨단 전자부품 이외에도 핵융합로의 Diverter가 그 예로서, 내부는 고강도와 고융점의 특성을 요구하는 반면, 외부는 높은 열전도성을 필요로 한다. 그래서 동일한 조성의 일반적인 W-Cu 합금보다 W과 Cu의 조성이 점차적으로 변화하는 경사기능재료(Functionally Graded Materials)가 냉각효율이 클 것으로 기대된다. 현재, W-Cu FGM에 대한 많은 연구가 진행되고 있지만, 그 조성이 연속적으로 변화하는 W-Cu FGM에 대한 연구는 전무한 실정이다 본 연구에서는 방전플라즈마 소결장치(Spark Plasma Sintering System)와 용침고정을 이용하여 연속적인 조성변화를 갖는 W-Cu FGM을 제조하고 그 특성에 관해 분석하고자 하였다. 소결체가 밀도 변화를 갖게 되도록 제작한 특수 경사기능 몰드에 W분말을 장입한 후, 15㎬의 압력하에서 SPS를 이용하여 W소결체를 제조하였다. 제조된 W소결체는 수평관상로에서 수소분위기 하에 Cu 용침을 실시하여 W-Cu FGM을 제조하였다 SEM을 이용한 각 위치별 조직관찰과 Image Analyzer를 이용한 W과 Cu의 면적비, 그리고 비커스경도계에 의한 경도 측정을 실시하였다. 또 열기계적 분석기를 이용하여 측정된 선팽창률로부터 열팽창계수를 구하였다. 80$0^{\circ}C$에서 ？칭하는 반복적인 싸이클을 통해 열충격시험을 실시하였고, Laser flash method로 열확산계수를 측정하였다.

• Korean Journal of Optics and Photonics
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• v.23 no.2
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• pp.77-86
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• 2012

The connection between the continuousness of Rabi oscillation and the discontinuity of quantum jumps has long remained one of the conceptual difficulties since the discovery of the quantum physical paradigm. In this study, however, we demonstrate that the behavior of the atom-field composite system gradually changes from the continuous Rabi interaction to the discontinuous quantum jumps as the atom-field coupling strength is reduced. The reduction occurs through enlarging the quantization volume of the mode so that the mode approaches one of the infinitely many modes of the thermal background.

• The Journal of the Acoustical Society of Korea
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• v.18 no.8
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• pp.9-16
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• 1999

Generally, a speaker structures utterances very clearly by grouping words into phrases. This facilitates the listener's recovery of the meaning of the utterance and the speaker's intention. To this purpose, a speaker uses, among other things, prosodic information such as intonation pause, duration, intensity, etc. The research described here is concerned with the relationship between the strength of prosodic boundaries in spoken utterances as perceived by untrained listeners(Perceptual boundary strength, PBS)-In this paper, the preceptual boundary strength is used as the same meaning of the prosodic boundary strength-and prosodic information. We made a rule determinating the prosodic boundaries and verified the usefulness of the prosodic phrase as a recognition unit. Experiments results showed that the performance of speech recognition(SR) is improved in aspect of recognition rate and time compared with that using sentences as recognition unit. In the future we will suggest the methods that estimate more appropriate boundaries and study more various methods of prosody assisted SR.

• The KIPS Transactions:PartB
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• v.10B no.6
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• pp.639-646
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• 2003

This paper proposes a neural network model for extracting optical illusions produced by a sequence of discontinuous dot stimuli. The proposed model is based on visual cell's characters founded by visual information processing path. This study approaches on the basis of physiological observation of the perceptual phenomena that some simple ways of discrete dots are perceived as a continuous virtual contour rather than as separate dots. This paper presents the implementation of the optical illusions from discrete dot stimuli that are composed of virtual polygons from 6 to 10 dots. This experimental data are similar to those of Smith & Vos's physiological experiments. The proposed model shows that it can extract continuous illusion contours from discrete dot stimuli successfully.

• Magazine of the Korea Concrete Institute
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• v.9 no.4
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• pp.187-196
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• 1997

시멘트를 기초로하는 복합재료의 파괴거동은 주균열이 진행하기 이전에 파괴진행영역이라고 하는 미세균열대가 콘크리트 내부에 형성고기 때문에 선형파괴역하게 입각하여 해석하게 되면 실험치와 상당한 차이를 나타낸다. 이러한 문제점을 해결하기 위해 가상균열모델이나 균열띠 모델, 두 파라메터 파괴모델 등 비선형해석에 따른 여러 파괴역학모델들이 제안되었으나 이들 모델들은 2차원 해석에 근거를 두고 있기 때문에 구조체의 두께 방향으로 동일한 균열이 형성되며, 특히 콘크리트 실험에서 관찰되는 비연속적 균열발생에 대해서 설며이 어려웠다. 이에 본 연구는 콘크리트를하나의 다종복합체로 가정하고 연립변형모드 및 진행파괴모드 방향으로 구성재료를 배열한 상태에서 가상균열 이론에 근거한 비선형해석방법으로 모델링하였다. 진행파괴모드로 구성재료를 배열하면 강성이 높은 구성재료를 통과하여 균열이 진행될 때 균열선단으로부터 분포된 응력이 상층의 허용인장강도를 초과하게 되어 균열이 발생되며 이러한 균열은점진적인 균열진행과는 달리 비연속 동시 발생 균열ㄹ로 나타났다. 본 연구는 진행파괴모드에서의 파괴 해석 방법과연립변형모드에서의 해석 방법을 제시하였으며, 해석결과를 실험결과와 비교함으로써 검증하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.2
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• pp.41-53
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• 1994

In this paper, rotating-bending fatigue tests of the SiC-whisker- reinforced 6061-T6 aluminum alloy and 6061-T6 alumiunm alloy made by power metallurgy were carried out to investigate the fatigue characteristics of plain and notched specimens at room temperature. The fatigue mechnisms in both materials were clarified through successive surface observations using the plastic replica method. In the case of the SiC-whisker-reinforced composites, there are whisker rich and poor zones and the fatigue crack is nucleated from the end of whiskers near the boundary. On the other hand, in the case of the 6061-T6 aluminum alloy, the fatigue crack is nucleated from defects and propagates by shear. Moreover, the results were discussed based on linear notch mechanics.

• Proceedings of the Korea Society for Simulation Conference
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• 1998.10a
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• pp.187-191
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• 1998

DEVS(Discrete Event system Specification)형식론은 계층적이고 모듈화 된 형식으로 시스템을 설계함으로써 신뢰성 있는 모델링이 가능하도록 이론적으로 잘 정립된 시뮬레이션 방법론이다. 시뮬레이션의 진행과정 및 결과를 표현하기 위한 애니메이션 개발 환경에 있어서도 DEVS 모델의 구조를 반영하여 계층적 애니메이션 환경을 구현 할 수 있다. 계층적 애니메이션은 시뮬레이션 관찰자가 시스템의 특정 레벨에 맞추어 애니메이션 진행 상황을 볼 수 있도록 한다. 이는 일반적으로 시뮬레이션 애니메이션이 갖는 장점인 시스템 이해 및 모델의 신뢰성 검증의 향상 뿐 아니라, 다양한 관점에서 시스템의 변화를 확인 할 수 있다는데 그 필요성이 요구된다. 본 논문에서는 계층적인 애니메이션과 그래픽 표현이 가능하도록 하기위해 DEVS 모델의 구조를 반영한 계층성을 갖는 애니메이터(시뮬레이션과 애니메이션의 연결 프로세서)를 설계하였다. 이러한 애니메이터는 모델과 같은 구조로 각 모델에 필요한 애니메이션 객체들을 유지·관리함으로써 계층적 애니메이션을 가능하게 하며, 시뮬레이션의 이산적인 시각 경과와 애니메이션의 연속적인 시간 경과와 애니메이션의 연속적인 시간 경과 사이에 동기화를 용이하게 한다.

• Korean Journal of Comparative Education
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• v.28 no.2
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• pp.77-95
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• 2018

This study introduces the Classroom Assessment Scoring System (CLASS) and explores the characteristics of CLASS for observing classroom. The CLASS is a standardized observation instrument that was largely developed for use in the USA. The CLASS attempts to provide a conceptual framework for categorizing classroom interactions and consists of three broad domains of quality (emotional supports, classroom organization, instructional supports). We simulated this method to the elementary school classes. The professional-teacher makes the best use of student's initiation behaviors, and the novice teacher focused on the leading the contents of subject. The novice teacher tyr to make more positive climate and to present more frequent feedback to students than professional teacher's classroom. The professional teacher would like to reveal the student's opinions, questions and subtle emotional state. The CLASS can be used to collect data on a wide range of specific aspects of the teaching and learning process at any given time.

• Korean Journal of Animal Reproduction
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• v.25 no.2
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• pp.147-153
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• 2001

This study was performed to elucidate the effects of lead poisoning on the reproductive organ of rats. After consecutive oral administrations of lead acetate, the weights of testis, the numbers and motilities of sperms and histological changes of organs were compared between control and experimental groups. 1. Testis weights of 1,000, 2,000 or 4,000 ppm/kg of lead acetate-administrated rats decreased compared with control group in dose-dependent manner. 2. The sperm numbers of 1,000, 2,000 or 4,000 ppm/kg of lead acetate-administrated rats were lowered significantly in dose dependent manners than those of control groups. 3. The sperm motilities of 1,000, 2,000 or 4,000 ppm/kg of lead acetate-administrated rats decreased in dose-dependent manners compared with those of control groups. 4. The weights of livers and kidneys of 1,000, 2,000 or 4,000 ppm/kg of lead acetate-administrated rats decreased or increased. The weights of livers increased and the kidney weights decreased and changes were dose-independent manner. 5. Necrosis of hepatocytes around the central veins, infiltrations of neutrophils, accumulations of bile and infiltrations of fine granules-harboring macrophages in psychymal and interstitial tissues were found out in the livers of copper sulfate-administrated rats. The Bowman's capsule, tubular epithelium and includes in nucleus of kidneys were filled with hyaline materials and hematophilic centers appeared in several lymph nodes.

• Journal of Veterinary Clinics
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• v.20 no.1
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• pp.12-21
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• 2003

In this study, we evaluated effects of three anastomotic techniques of small intestine on adhesions in the dog. Twenty six healthy mixed dogs were randomly assigned to three groups. Group I(n = 8) was sutured with a simple continuous suture, group II(n = 7) was sutured with a simple interrupted approximating suture and group III(n = 11) was sutured with a single layer continuous Connell suture. On completion of any intestinal anastomosis, a pedicle of greater omentum was wrapped around the suture line in all experimental dogs. One percent sodium carboxymeth-ylcellulose (5ml/kg) was administrated into the abdomen by feeding tube prior to closing the last part of peritoneum in all dogs. Postoperative adhesions were evaluated at 14th day after operation. The adhesions consisted primarily in two dogs in group I, three dogs in group II and group III. There were adhesions between intestinal serosal surfaces in eight dogs in all groups, but there were no intestinal serosa-visceral peritoneum adhesion and intestinal serosa-mesentery adhesion. Mean adhesion scores were less than score 2 in all groups. Between anastomotic site and omental graft, there were 13.13$\pm$4.97 mm (mean$\pm$S.D.) adhesion formation in group I and 17.29$\pm$4.68 mm in group II and 14.64$\pm$3.80mm in group III. A simple continuous suture resulted in the least adhesion formation and a simple interrupted approximating suture resulted in the greatest adhesion formation among the groups. However, there were no significant differences among three suture techniques in the severity of adhesions. Intestinal intussusception only encountered in one dog during the 14 days, the dog operated and survived. Daily monitoring of temperature, activity, appetite, defecation and micturition were done. All of those vital signs were within normal values and there were no obvious differences among the groups. In conclusion, even though there were no significant differences among three groups, a simple continous suture pattern is recommended to prevent adhesions when operating intestinal anastomosis in dogs.