Cu-Al-Ni-Ti-Mn 합금의 변태특성 및 기계적 성질에 미치는 가공열처리의 영향

강조원,장우양,양권승,이영수,곽사호,김춘동,백승남 한국열처리공학회 1999 熱處理工學會誌 Vol.12 No.2

The distribution of the second phase, the change of transformation temperature and mechanical properties with thermomechanical treatment conditions were investigated by metallography, calorimetry, EDS, tensile test and fractography in a Cu-Al-Ni-Ti-Mn alloy. The cast structure revealed Ti-rich precipitates(X_L phase) between dendrite arms, which have been identified as (Cu,Ni)₂TiAl intermetallic compounds. By homogenizing above 900℃, the X_L phase was melted in the matrix, while the X_s phase was precipitated in matrix and the volume fraction of it was increased. When hot-rolled specimen was betatized below 750℃, recrystallization could not be observed. However, the specimen betatized above 800℃ was recrystallized and the grain size was about 50㎛, while X_s phase was precipitated in matrix. With raising betatizing temperature, M_s and A_s temperatures were fallen and transformation hysteresis became larger. The strain of the specimen betatized at 800℃ was 8.2% as maximum value. The maximum shape recovery rate could be obtained in the specimen betatized at 800℃ but it was decreased due to the presence of X_s phase with increasing betatizing temperature.

LPG 탱크로리 수송중 위험성 평가에 관한 연구

이재준,김윤화,엄성인,고재욱,백종배,윤성렬 한국산업안전학회 1997 한국안전학회지 Vol.12 No.4

Demand of LPG and LNG will increase continuously due to high calories, clearness, and convenience for usage. These gases are used widely for power plants, industrial plants, and domestic fuel. But accidents related with gas are increasing in proportion to increment of gas usage. Especially, LPG has high ignitability due to weak dispersion to air and accumulation at low place because LPG is heavier than air. There are many hazards during transportation as well as production, storage, and usage of LPG. Commonly, tank lorry is used for inland transportation of LPG. If tank lorry were to raise leakage incidents and then LPG released during transporting, the accidents cause serious effects on the environment as well as human damage of surrounding area. In this study, therefore, hazards which cause LPG of tank lorry to leak during transportation were identified and risk of LPG transportation was assessed quantitatively. Also, the result of this study might be a useful measure for predicting damage and preparing safe transportation strategies of LPG tank lorry.

독성물질 사용 저장시설에 대한 개인적 위험성 산정에 관한 연구

김성빈,김윤화,이철,엄성인,고재욱,백종배 한국산업안전학회 1997 한국안전학회지 Vol.12 No.1

These days leakage incidents of toxic materials cause serious effects on the nearby residents as well as the workers around the accidents accompanying massive material losses and human damages through widening influencial areas. The risk measure through adequate quantitative analysis as well as the qualitative analysis of the leakage incidents of toxic materials becomes an urgent issue. The damage, of the leakage incident on the surrounding area of the dangerous toxic material facilities was calculated quantitatively by adopting several models in this research. First, the calculations of the leakage velocity from the factories were performed by using source model for the assessment of the influential area, and the damages on the nearly residents were calculated by using the dispersion model and the effect model. The probability of the incidents was computed based on $quot;The manual for classification and priorization of major incidents$quot; published by IAEA(International Atomic Energy Agency). Above calculated damage area and incident probability were further adopted in this study to induce the individual and societal risk, quantitatively. The calculated data of the real incident of the toxic material leakage showed reasonable agreements to the actual damage of the incidents, which showed a validity of this study. The result of this study might be a helpful measure for predicting damages and preparing safety systems for similar kinds of incidents.

슬래그중 고체철의 산화거동에 관한 속도론적 고찰

백종문,이홍기,고정호,민동준 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.12

The kinetic experiments have been made on iron oxidation in slag by oxidizing gases at 1387∼1500℃. The effect of temperature, FeO content and oxygen potential of gas on the reaction rate have been examined. The iron oxidizing rate is considerably increased with increasing temperature and FeO content in slag. It was also found that the rate controlling step of reaction have been depended on the temperature, FeO content in slag and (P_(co₂)/P_(co) as an oxygen potential at gas/slag interface. The dependence of the overall reaction rate constant on temperature and initial FeO content in slag at 1450℃ could be expressed as follows; log k_(overall) = -0.36-10,820/T[㏖/㎠·sec·atm] k_(overall) = 1.04×10^(-7)(wt%FeO)^(0.75)[㏖/㎠·sec·atm] In condition of high oxygen potential such as high FeO content and (P_(co₂)/P_(co)), the chemical reaction at interface between slag and gas might play a important role as a rate controlling step of overall reaction, which is controlled by the dissociation of CO₂ at slag/gas interface. But in case of low (P_(co₂)/P_(co)), mass transfer and chemical reaction at interface between slag and iron become important as a rate controlling step. The reaction mechanism of iron oxidization in slag by gas have been discussed in terms of rate constant for elementary reactions.

최근의 금형 표면기술 현황

김성완,이구현,남기석,권식철,백운승 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.2

몽골의 식물 유전자원 연구현황

임무상,바이에르숙,백형진,이석영,이동진 한국국제농업개발학회 1997 韓國國際農業開發學會誌 Vol.9 No.4

몽골에서는 1920년대부터 러시아와 공동으로 식물 유전자원을 탐색, 수집하였으며 이들을 재료로 1950년대부터는 품종을 육성하였다. 다칸의 식물학 및 농업연구소는 1979년에 설립되어 10년 장기계획을 토대로 식물유전자원 연구를 실시하였는바, 다양한 농업생태 지역을 바탕으로 육종모본이 될 작물들을 수집하였다. 현재 다칸의 식물 및 농업연구소에는 밀 8,448점, 보리 4,423점, 귀리 1,672점 등 총 21,132점이 상온에 보존되어 있고 그중에 1,200점은 연구소 자체, 국제기관 또는 국제협력에 의해 수집된 재래종이다. 1991년에는 5개년 계획으로 식물유전자원의 수집, 도입, 안전보존, 평가, 교환, 정보화 및 이용 등에 대하여 진행되고 있다. 이들 자원에 대한 연구는 다칸의 식물학 및 농업연구소를 중심으로 Choibalsan의 동부지역 농업연구소, Hovd의 알타이지역 농업연구소, Ulaangom의 서부지역 농업시험장, 울란바타르의 가축사양연구소 등과 협력적으로 운영되고 있다. 유전자원에 대한 국가적인 전략은 작물의 생산성 향상, 환경내성 품종 육성을 위한 야생근연종 등 다양한 자원의 확보와 현지내의 보존 및 장,단기보존 방법의 개발, 전문가양성 및 외국과의 공동연구를 통한 종자 및 정보의 교환에 역점을 두고 있다. In Mongolia, collection and exploration of traditional crop genetic resources was initiated in 1920s with the assistance of Russian researchers and first local varieties have been developed through breeding programmes. from 1950s With the establishment of Plant Genetic Resources(PGR) Section at Plant Science and Agricultural Research Institute(PSARI) in 1979, comprehensive preservation, exploration and collection of PGR was started on a regular basis and First 10 Year Programme for PGR exploration was launched. The programme involved collection, introduction and exploration of crop genetic resources in different agro-ecological zones to develope initial materials for breeding, enrich crop species with new varieties and identify suitable agroecological zones for crop production. In 1991, a new Five Year National Programme for PGR was started. This programme involved the collection, introduction, preservation, evaluation, exchange, documentation and utilization of PGR. All of the agricultural research institutes of Mongolian National Agricultural University(MNAU) are participating in this programme. In 1992, the National Board of PGRNBPGR) was established to address the urgent need for the coordination of the activities in the managment of PGR in Mongolia.

경계요소법에 의한 아크균열의 응력확대계수 해석

백열선,이장규,우창기 한국산업안전학회 1999 한국안전학회지 Vol.14 No.4

In this paper, A circular arc crackered plate in biaxially stretched sheets was investigated in the boundary element method. The applications of fracture mechanics have traditionally concentrated on crack problems under an mode I, straight crack. However, many service failures occur from growth of cracks subjected to mixed mode Loadings. A rectangular plate with arc crack or slanted central crack, under biaxial tensile loading, was treated analytically and also solved numerically. The Results from BEM applying different loading conditions, crack length (a/W), arc angle(α) are presented and discussed The stress intensity factors are evaluated by the techniques of the J-integral. The decomposition method, used to decouple the stress intensity factors in mixed mode problems, is implemented by a considering a small circular contour path around each crack tip. The BIE method was successfully applied to a circular arc crackerd plate problem, also slanted centre cracked plate under mixed mode.

Penstemon penlandii 의 발아촉진방법

이석영,최원열,백형진,윤문섭,줄리라프만 한국국제농업개발학회 1999 韓國國際農業開發學會誌 Vol.11 No.2

Penstemon penlandii는 미국의 록키산맥에서 소집단으로 발견되나 자연상태에서는 발아가 불량하여 멸종위기에 처해있어 이 식물의 보존을 위한 발아방법을 구명하기 위하여 본 시험을 수행한 결과는 다음과 같다. 1. P. penlandii종자는 thermogradient에서 발아시킨 결과 10-30, 15-25, 20-30, 25, 25-30 그리고 15-30℃ 등의 변온조건에서 발아가 증진되었으며 높은 온도 조건에서는 미생물 오염에 의해 발아 및 유묘생장이 장해를 받았다. 2. 30psi에서 10-20초 동안 종피에 자극을 주었을 때 발아율 및 발아속도지수가 높았으나 일부 종자는 휴면타파가 이루어지지 않았다. 3. 종피에 물리적자극을 준 종자를 1mM의 GA3에 24시간 동안 침지하면서 15ccs-1속도로 aeration 시킨 후 blotter에 치상하였을 때 발아가 가장 촉진되었다. This study was undertaken to determine the germination requirements of Penstemon penlandii. The highest germination occurred using the scarified seeds (either hand or mechanical) on the thermogradient plate at 10-30, 15-25, 20-30, 25, 25-30 and 15-30℃. Individual germinators were used to verify thermogradient plate results, and speed of germination analysis suggested that 15-30℃ was the optimum temperature for rapid germination of P. penlandii after mechanical scarification. Laboratory germinations at 15-30℃ of mechanically scarified seeds (20-30 psi and 10-80 seconds) were correlated with seedling emergence in the greenhouse. Scarification rates of 30psi for 10-20 seconds produced highest rates of germination and emergence in laboratory and greenhouse tests. The germination procedure of submerging seeds in aerated 1mM GA3 for 24hours, placing seed on water moistened blotters at 15-25℃, and hand scarifying ungerminated seeds after 14days and allowing them to germinate for an additional week gave comparable germination percentage to hand scarification, mechanical scarification, and tetrazolium viability. Based on these data the recommended germination method for this species would be to submerge seeds in aerated (15ccs-1)1mM GA3 for 24h, place seeds on water moistened blotters, make the first counts at 14d and hand scarify the remaining dormant seed with final counts at 21d, or scarify seed by hand or with a mechanical scarifier before germination on blotters moistened with 1mM GA3, and counted after 7, 14, and 21 days.

An Exploration of the Relationship Between Motivation and Boredom Attribution in Korean University Students’ EFL Learning

Baek,Soondo(Soondo Baek) 이화여자대학교 교과교육연구소 2024 교과교육학연구 Vol.28 No.4

The present study explored the relationship between motivation and boredom attribution in learning English as a foreign language in Korea. Participants were university students majoring in the English language and literature. Ninety-one participants responded to a questionnaire probing their motivation and perceived boredom precursors in English learning. Motivation and perceived boredom precursors were operationalized by three motivational factors (integrative/intrinsic, instrumental-social status, instrumental-desired career) and two boredom precursors (being over-challenged, lack of meaning). Bivariate correlation analysis showed that lower integrative/intrinsic motivation and instrumental-desired career motivation were associated with greater boredom attribution to both types of precursors whereas the instrumental-social status motivation was not significantly related to any type of boredom attribution. Stepwise multiple regression analyses further suggested that the instrumental-desired career motivation acts more like the integrative/intrinsic motivation than the instrumental-social status motivation especially in relation to boredom arising from lack of meaning. The findings suggested a complicated pattern of links between motivation and boredom, offering theoretical and pedagogical implications for how to better address boredom in EFL learning.

통화(通貨)·생산(生産)·물가(物價)의 비선형인과관계(非線型因果關係) 검정(檢定)

백웅기,Baek, Ehung-gi 한국개발연구원 1991 韓國 開發 硏究 Vol.13 No.4

본고(本稿)는 둘 혹은 여러 변수(變數)가 서로 비선형적(非線型的) 인과관계(因果關係)의 특정한 구조를 가질 때 주어진 관측치(觀測値)로부터 인과관계(因果關係)에 관한 올바른 추론(推論)을 유도하기 위한 새로운 이론인 Baek-Brock의 방법(方法)을 소개하고 이것을 통화(通貨), 생산(生産) 및 물가(物價)의 세 변수(變數)에 적용하여 기존의 인과성(因果性) 검정(檢定)과 어떻게 다른 결과를 얻는지 살펴본다. Baek-Brock의 방법(方法)은 일반적으로 두 변수(變數) 사이의 인과관계(因果關係)를 검정(檢定)하는 데 사용될 수 있으나 변수간(變數間)에 내재하는 실제 인과관계(因果關係)가 선형(線型)인 경우 Granger 검정법(檢定法) 등 기존의 방법(方法)이 높은 검정력(檢定力)을 보이므로 여기서는 주로 비선형인과성(非線型因果性) 검정(檢定)에 초점을 맞춘다. 본(本) 검정법(檢定法)은 인과성(因果性) 여부를 조건부확률에 기초하여 정의한 후 개별확률을 상관적분(相關積分) (correlation integral)을 사용하여 추정(推定)토록 하였다. 이 방법(方法)은 변수간(變數間)의 인과관계(因果關係)가 비선형적(非線型的)일 때 유효하다는 장점을 지니나 인과성(因果性)이 없다는 귀무가설하(歸無假說下)에서 표본수에 따른 검정통계량(檢定統計量)의 점근분포(漸近分布), 그릇된 귀무가설(歸無假說)에 대한 최대의 기각력(棄却力)을 창출하는 척도모수(尺度母數)(scale parameter) 등에 관한 이론적 배경이 미흡하다는 단점이 있다. 본고(本稿)에서는 이를 Monte Carlo 시뮬레이션을 실시하여 보완하였다. 통화(通貨), 생산(生産) 및 물가간(物價間)에는 Granger 검정법(檢定法)을 실시했을 경우 통화(通貨)와 생산(生産)만이 서로 인과성(因果性)이 있을 뿐 물가(物價)와 다른 변수간(變數間)의 인과성(因果性) 증거는 희박하였다. 한편 Baek-Brock의 검정법(檢定法)은 이미 벡터자기회귀모형(自己回歸模型)(VAR)을 통해 밝혀진 선형관계(線型關係) 외에 물가(物價)가 생산(生産) 및 통화(通貨)에 미치는 비선형인과성(非線型因果性)에 관한 추가적 정보를 제공해 주고 있으며 구체적으로 그러한 인과관계(因果關係)가 몇 기(期) 후부터 나타나는지 밝혀 준다. 그러나 이를 이용한 구체적인 모형화(模型化)는 추후의 논문을 통해 밝히기로 한다. The purpose of this paper is primarily to introduce a nonparametric statistical tool developed by Baek and Brock to detect a unidirectional causal ordering between two economic variables and apply it to interesting macroeconomic relationships among money, production and prices. It can be applied to any other causal structure, for instance, defense spending and economic performance, stock market index and market interest rates etc. A key building block of the test for nonlinear Granger causality used in this paper is the correlation. The main emphasis is put on nonlinear causal structure rather than a linear one because the conventional F-test provides high power against the linear causal relationship. Based on asymptotic normality of our test statistic, the nonlinear causality test is finally derived. Size of the test is reported for some parameters. When it is applied to a money, production and prices model, some evidences of nonlinear causality are found by the corrected size of the test. For instance, nonlinear causal relationships between production and prices are demonstrated in both directions, however, these results were ignored by the conventional F-test. A similar results between money and prices are obtained at high lag variables.