鋼 熔着金屬의 熱變形脆化에 關한 硏究

鄭世喜,金台永,林載奎,鄭熙敦,朴昌彦 全北大學校 1984 論文集 Vol.26 No.-

The susceptibility of weld metal(AWS, F76-EH14) on hot straining embrittlement has been examined. The sharp notch was machined on the weld metal of 1st bead and on coarse-grained HAZ transformed by next pass. After machining the notch, these specimens were bended at 250℃ to receive the hot straining embrittlement and they were done COD fracture toughness test by the three point bending, and then the change of plastic zone at notch tip was evaluated by microhardness test. The obtained results are summarized as follows. 1. Fracture toughness of weld metal was greater than that of base metal. 2. Fracture toughness of the coarse-grained HAZ was similar to that of weld metal. 3. Hardness of weld metal reheated by next pass was lower than that of weld metal owing to the effect of heat treatment. 4. Plastic deformation of the coarse-grained HAZ was less than that of weld metal.

알루미늄-크롬 용융도금강판의 미세조직과 집합조직에 미치는 크롬의 영향

임병문,홍승현,정재인,최장현,정원섭 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.10

Microstructure and texture changes of aluminized coatings on steel sheets having Cr ranging from 0.0% to 1.0% in the coated layer were investigated. The surface morphology of the Al-Cr coated steel is not influenced by the increase of Cr contents in the coated layer. While the coated layer of aluminized steel consisted of two phases of Al and Al_(5)Fe₂, the aluminized coating layer containing Cr was composed of three phases of Al, Al_(13)Cr₂, and Al_(13)Fe₄+Al_(5)Fe₂. The surface layer was Al, the middle layer was Al_(13)Cr₂, and the interfacial layer between the coating and the steel substrate was Al_(13)Fe₄and Al_(5)Fe₂. The texture of the aluminized coating without Cr was characterized as a {001} fiber texture which major orientation was {001}<110>. As the Cr content in the aluminized layer was increased to 1.0%, the texture of the aluminized coating was not changed but the intensity of the {001} fiber texture was increased. The major orientation in the {001} fiber texture was changed from the rotated cube orientation of the aluminized coating with 0.1%Cr to the cube orientation of the aluminized coating with 1.0%Cr.

염수분무 환경에서 알루미늄-크롬 용융도금강판의 부식생성물이 내식성에 미치는 영향

임병문,홍승현,정재인,최장현,정원섭 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.10

The effect of corrosion products of hot-dip Al-Cr steel sheet on the corrosion resistance were investigated. The results of XRD and XPS measurements showed that there was not found a hydroxide type corrosion product on the surface of aluminized steel after salt spray test(SST) but there was found some cracks in the surface layer which accelerates corrosion during SST. In Al-Cr coated steel case, the main phase of the corrosion products after salt spray test was found to be Al(OH)₃. The polalization curves of aluminized steel after SST shows that there was no passivation layer. For the Al coated layer, a porosity in the Al-oxide film on the surface layer leads to preferential corrosion. After the Al coated layer was completely removed, the Al_(5)Fe₂layer was selectively corroded and then, the steel substrate was exposed to the electrolyte. However, the polalization curves of Al-Cr coated steel after SST shows that the passivation layer was formed, which could increase the corrosion resistance of Al-Cr coated steel. In case of the Al-Cr coated layer, the densely covered hydroxide layer of Al(OH)₃and the intermetallic compound layer of Al_(13)Cr₂became a barrier against further corrosion after the Al layer was removed. In this case, corrosion was not proceeded even through the same current density. The densely covered hydroxide of Al(OH)₃and the intermetallic compound layer of Al_(13)Cr₂were considered to be one of the reasons of high corrosion resistance for Al-Cr coating.

초등학교 자연과에서의 야외 수업 실태와 개선 방안 및 지도 방략

정완호,권치순,김재영,임채성 한국교원대학교 과학교육연구소 1996 청람과학교육연구논총 Vol.6 No.1

When we consider the developmental level of children, minds-on/hands-on experiences have very important value for effective science learning. As a basis for the development of outdoor-inquiry materials, we surveyed the status of outdoor activities in the elementary school science, then analyzed the data. Data were obtained from fifty-one teachers of nineteen elementary schools. Most of them (about 80%) recognized the necessity of outdoor instruction. However, they were using the outdoor activities 1.7 times at average per school year in practice. Most of these activities were practiced within school or nearby areas including parks. The major reasons for these poor use of outdoor activities presented by respondents were the cognitive characteristics of children and the excessive amount of science content to be covered. Also, these outdoor activeities were focused only to the observations in natural environment and cognitive aspects. Several factors, such as the lack of time, appropriate outdoor sites and instructional materials, and the insufficient experiences on the outdoor activities of teacher oneself, were acknowledged. These results have implications for the development of instructional materials for both of children and teachers. In this study, we suggested the effective instructional methods at outdoor environment in relation to the characteristics of children, topics, and sites.

축냉재 포접화합물의 열물성에 관한 실험적 연구(Ⅲ) : 충전량 변화 Variations of Charging Conditions

임재경,고광옥,김진흥,정낙규,하옥남 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.1

The objective of this paper is to investigate the thermal properties of TMA-clathrate compound in order to applicate cold storage system to residential air-conditioning. Especially, the test tube experiments are performed by comparing and analyzing the concentration of TMA-clathrate compound, the temperature of heat source, and the phase change temperature, specific heat and subcooling characteristics on the point of the variation of charge capacity. The results are summarized as follows; 1) When the temperature of heat source is -15℃, the stability of the thermal properties is appeared high in the whole experiments 2) The effect of subcooling suppression is improved around 0.6℃ when the temperature of heat source is -15℃, while the teemperature of subcooling is about 2.2℃ when the temperature of heat source is -10℃. Especially, it did not almost present any subcooling in the 26wt% of the 5g and the 25wt%, 30wt% of the 10g. Thus, we concluded that TMA-clathrate compound has thermal properties as the cold storage medium for residential air-conditioning.

ARCS 학습동기화 모형을 적용한 영어 학습 웹 코스웨어의 설계 및 구현

임유택,정재열 신라대학교 교육과학연구소 2001 교육과학연구 Vol.- No.6

In the information age, computer has taken roots as indispensable education material. Thanks to the development of the Web and Internet, a lot of web- coursewares for computer have developed and used in the learning areas. As most web-coursewares, however, neglect the mode and the form needed as education materials, they don't attract the learner's attention. In spite of the computer's wide effect, it is ironic that only very few students use computers as a tutor. so, this study is to develop web-based courseware for English learning and improve the motivational attributes, with a systematic approach called the ARCS model of Keller.

畵夜間 溫度差(DIF)處理에 의한 고추 '녹광' 플러그苗의 生長反應

임기병,오중열,정재동 慶北大學校農業科學技術硏究所 1996 慶北大農學誌 Vol.14 No.-

고추 '녹광' 품종의 플러그 육묘시 주야간 온도차 처리에 따른 생육조사 결과 초장은 주간온도와 DIF에 의해 영향을 받으며 절간장도 초장과 비슷한 경향이었다. 엽전개속도는 주로 일 평균 온도에 의해 좌우되었다. 엽장, 엽폭은 일 평균 온도가 증가함에 따라 증가 하는 것으로 나타났으며 생체중은 주야간 온도가 15℃처리구에서 가장 낮았고 일평균 온도가 증가함에 따라 증가하는 경향이었다. 생체중과는 반대로 엽록소함량은 일평균 온도가 15℃처리구에서 가장 높게 나타났으며 전체적으로는 야간온도가 증가할수록 엽록소함량이 저하되었다. 줄기직경은 DT/NT=15/15처리구에서 가장 낮았고 다른 처리구는 비슷한 경향이었다. T/R율은 DT/NT=30/15℃(+15DIF)처리구에서 가장 높게 나타나 지상부가 지하부에 비해 과번무됨을 알수 있었다. 따라서 녹광 고추의 플러그 육묘시 충실한 묘를 생산하기 위해서는 주간온도가 22.5℃, 야간온도는 15-22.5℃범위의 0DIF또는 약한 +DIF조건에서 육묘하는 것이 강건한 묘생산에 유리할 것으로 판단된다. Capsicum annuum 'Nokkwang' plug seedlings were treated with 9 different day and night temperatures to investigate on growth and differentiation in controlled environment conditions. The plant height was the most affected by day temperature and DIF and stem length was the similler results as plant height. However, Leaf unfolding rate and leaf length and width increased as average daily temperature increased. and especially fresh weight was worst at ADT was 15℃ and increased as ADT increased. In contrast with fresh weight, chlorophyll content calculated highest when ADT was 15℃, and decreased as NT increased respectively. The stem lengths were not significantly different among treatments with exception of DT/NT=15/15℃ which significantly decreased. The ultimate +DIF condition, DT/NT=30/15℃, caused high T/R ratio due to abundant top growth. It is concluded that DT is 22.5℃, caused high T/R ratio due to abundant top growth. It is concluded that DT is 22.5℃, and NT is ranged from 15℃ to 22.5℃ to be produced short, healthy plug seedlings in Capsicumannuum 'Nokkwang'.

Cr-Mo鋼 鎔接熱影響部의 鏞接後熱處理에 關한 硏究

林載奎,鄭世喜 全北大學校 1985 論文集 Vol.27 No.-

Post weld heat treatment(PWHT) of weldment of the low alloy steel, in general, is carried out not only to remove residual stress and hydrogen existing in weldment but to improve fracture toughness of weld HAZ. There occur some problems when PWHT is practiced. They are toughness drecrement and stress relief cracking(SRC), which especially exist in the coarse-grained region of weld HAZ taken the effect of tempering treatment because PWHT is conducted at high temperature more than 600℃. Therefore, in this study, the effect of heating rate during PWHT on fracture toughness under the various kinds of stresses simulated residual stress in weld HAZ of Cr-Mo steel were evaluated by crack opening displacement(COD) test and microhardness test. The experimental results are as follows; 1. Fracture toughness of weld HAZ was improved by PWHT, but it decreased as heat treated under the stress. 2. Fracture toughness of weld HAZ was dependant upon heating rate during PWHT. In case of no stress, it was decreased with increment of heating rate, but it was improved with increment of heating rate in case of stress. 3. The difference of transition temperature, (ΔT_tr)_(σ=0), was linearly changed to hardness ratio, Hv/(Hv)_(σ=0), due to the varity of heating rate. And fracture toughness was increased with decrement of hardness ratio at the heating rate of 600℃/hr and 220℃/hr, but it was the reverse at 60℃/hr.

급성하벽심근경색에서 전흉부유도 ST절 하강의 의의

정병천,배호상,곽동훈,김영태,배용학,황종현,임현주,류재근,조용근,채성철,전재은,박의현 慶北大學校 醫科大學 1997 慶北醫大誌 Vol.38 No.2

목적 : 급성하벽심근경색증 환자에서 심전도상 흔히 동반되는 전흉부유도 ST절 하강의 의의를 알아보았다. 방법 : 심근경색후 24시간에서 48시간에 얻은 심전도를 기준으로 52명의 급성하벽심근경색증 환자를 전흉부유도에서 ST절의 하강이 있는 군과 없는 군으로 나누었으며 심도자, 관상동맥조영술, 심초음파도 및 방사성 핵종을 이용한 좌심구혈율 측정 등을 시행하였다. 결과 : 1) 좌심실확장기말압은 전흉부유도에서 ST절의 하강이 있는 경우에서 16.9±5.33mmHg로 없는 경우의 11.0±4.02mmHg보다 유의하게 높았다(p<0.05). 그러나 운동량 및 좌심구혈을은 흥부 유도상 ST절의 하강이 있는 경우 7.6±3.0 METs 및 53.9±9.1%로 없는 경우의 9.1±2.7 METs 및 54.6±9.5%보다 낮았으나 통계적 유의성은 없었다(p=0.180, p=0.823). 2) 관상동맥조영술상 전흉부 ST절의 하강이 동반된 군에서는 유의한 좌전하행지나 좌회선지의 협착이 있는 경우가 60.9% 및 57.9%로 ST절의 하강이 없는 군에서의 34.5% 및 7.7%와 비교해 좌관상동맥에 협착이 동반된 경우가 많았다(p=0.050, p=0.001). 3) 관상동맥조영술상 세 혈관질환의 빈도는 흉부유도상 ST절의 하강을 보인 23예에서 10예로 ST절 하강이 없었던 29예중 2예에 비하여 유의하게 많았고(P=0.007), 단 혈관질환의 빈도는 ST절의 하강을 보인 군에서 23예중 5예로 ST절 하강이 없었던 29예중 17예에 비하여 유의하게 적었다(P=0.002). 두 혈관질환의 경우에는 각각 8예와 10예로 양군간에 유의한 차이가 없었다. 4) 흉부유도상 ST절 하강의 빈도는 단 혈관질환 22예 중 5예에서, 두 혈관질환 18예중 8예, 세 혈관질환 12예 중 10예에서 관찰되어 협착이 있는 관상동맥의 수가 많을수록 ST절의 하강이 나타나는 빈도가 많음을 보였다(p=0.00308). 그러나 흉부유도상 나타난 ST절의 하강을 모두 합하여 구한 ST절 하강의 합은 협착이 있는 관상동맥의 수와 통계적인 유의성이 없었다. 5) 심초음파도상 좌심실 하벽의 벽운동은 ST절 하강을 보인 군에서는 akinesia가 83.3%, hypokinesia가 11.1%, 정상 벽운동이 5.6%로, ST절 하강이 없었던 군에서의 dyskinesia가 3.6%, akinesia가 39.3%, hypokinesia가 25.0%, 정상 벽운동이 32.1%와 비교하여 ST절의 하강이 있는 군에서 유의하게 벽운동의 장애가 빈번함을 보였다(p=0.03891). 그러나 좌심실전벽, 측벽 및 중격부위에서는 유의한 벽운동의 차이가 없었다. 결론 : 급성하벽심근경색증 환자의 전흉부유도에서 ST절의 하강이 동반되는 경우 다혈관 질환의 가능성이 높으며 좌심실확장기말압이 상승되었고 운동능력은 감소되어 있었다. 또한 심초음파도상 좌심실하벽의 벽운동장애도 심하였다. 따라서 전흉부 ST절의 하강을 동반한 급성하벽심근경색증 환자는 전흉부유도에 ST절 하강이 없는 경우보다 예후가 불량할 것으로 생각되며, 보다 적극적인 치료가 필요할 것으로 생각된다. The purpose of this study was to determine the significance of precordial ST segment depression appearing during acute inferior myocardial infarction and to assess the correlation of that with angiographic finding. 52 patients were allocated into two groups based on the existence of precordial ST segment depression : 23 patients with ST segment depression and 29 patients without ST segment depression. The extent of coronary artery disease as well as the prevalence of significant stenosis (≥70%) in left anterior descending artery were more frequent in patients showing precordial ST segment depression than in patients not showing them (p=0.050) and the result were similar in cases of left circumplex artery (p=0.001). On echocrdiographic examination of left ventricular (LV) wall motion, it showed more severely decreased inferior LV wall motion in patients showing precordial ST segment depression than in patients not showing them (p=0.03891) even though the other segment of LV wall motion didn't show the statistical difference between both groups. The other cardiac parameters such as LVEDP, exercise amount (METs) and ejection fraction were tend to showing bad profile in patients with precordial ST segment depression. From the above results, we could deduce that patients with precordial ST segment depression have relatively large infarction or concomitant left coronary artery disease, so they need more caution and intensive theraphy.

수중운동 프로그램이 뇌성마비아의 체력에 미치는 영향

정재권,임석주 한국특수교육문제연구소 2002 특수교육저널 : 이론과 실천 Vol.3 No.3

본 연구는 수중운동 프로그램이 뇌성마비아들의 체력에 미치는 영향을 살펴보고자 뇌성마비학생 5명에게 12주 동안 수중운동 프로그램윤 적용하여 뇌성마비학생들의 근력,근 지구력,유연성,민첩성,평형성 등의 변인들을 측정 분석한 결과 근력인 악력,근 지구력인 윗몸 일으키기,민첩성인 왕복달리기,유연성인 체전굴,평형성인 한발로 서기에 긍정적인 변화가 있었다. 이상과 같은 연구 결과를 동하여 볼 때 수중운동은 체력 요인에 긍정적인 영향을 미쳐 체력 향상 및 건강증진에 많은 도움이 될 것으로 사료된다. The purpose of this study were to evaluate the effect of aquatic exercise on body composition, pulmonary function and physical fitness. The subjects for this study were five spasticity cerebral palsy(18 - 20 years). The aquatic exercise program consisted of 11 item, and performed for 30-40mins in a bout, 3 times a week at the intensity of HRmax(40-65%) for 12 weeks. And the change of body weight, %fat, fat mass, vital capacity, hand grip, sit-ups, trunk flexion, closed eyes foot balance and shuttle-run have been measured in baseline, post 4, 8 and 12 weeks respectively. The following results were obtained from this study. Hand grip(2-4kg), sit-ups(5-8 bouts), trunk flexion (1 -4cm) and closed eyes foot balance(O.25-2.43sec) were increased after individually aquatic exercise for 12 weeks respectively. And, shuttle-run(O.37 - 0.9secl was decreased after aquatic exercise. These results suggest that aqustic exercise for 12 weeks affects on body composition, pulmonary function and physical fitness to the spasticity cerebral palsy. On the other hand, long term regular aquatic exercise programs are applicable to the spasticity cerebral palsy with abnormal movement in safety through the re-composition of exercise intensity and mode.