초음파 공명 분광법(RUS)을 이용한 SiC 입자강화 Al 기지복합재료의 탄성계수 해석

홍순형,주영상,정용무,정현규 韓國非破壞檢査學會 1999 한국비파괴검사학회지 Vol.19 No.3

SiC 입자강화 2124Al 금속복합재료의 강화재 부피분율에 따른 탄성 stiffness를 초음파 공명 스펙트로스코피(resonant ultrasound spectroscopy: RUS) 방법을 이용하여 측정하였다. RUS 방법은 한 개의 소형 시편으로 9개의 독립변수를 가진 사방정계(orthorhombic) 탄성계수를 간단한 실험으로 측정가능함을 보여주었다. SiC 강화재 부피분율 변화에 따른 탄성계수를 측정하였는데 이 경우 초기 추정 탄성계수를 구하기 위해서 부피분율에 따른 미세조직 사진으로부터 강화재의 형상(aspect ratio)과 방향을 고려한 유효 aspect ratio 개념을 도입하였고, Mori-Tanaka 이론식에 의한 계산결과를 이용하였다. 이로부터 계산된 공진주파수와 RUS의 측정 공진주파수 사이를 최소화함으로 정확한 탄성계수를 측정하였다. 측정된 stiffnesses로부터 공학적 탄성계수인 Young's modulus를 계산하였으며, 계산된 Young's modulus와 압출방향으로 인장시험한 Young's modulus를 비교분석하였다. SiC 입자의 부피분율이 증가함에 따라 탄성계수가 증가함을 나타내었고, 탄성 stiffness의 거동은 강화재가 많이 첨가될수록 횡등방성(transversely isotropic) 이 강하게 나타났으며 이것은 압출공정에 의해 강화재 입자의 방향성 재배열에 기인한다. 한편 일정크기 시편에 있어서 기본 공진주파수가 강화재 부피분율에 따라 고주파수 영역으로 이동하는 현상이 관찰되었으며, 이로 부터 비파괴적으로 강화재 부피분율을 예측할 수 있는 가능성을 제시하였다. The dynamic elastic properties of metal matrix composites were investigated by resonant ultrasound spectroscopy(RUS). The composites used in this study consisted of 2124 aluminum alloy reinforced with different concentrations of SiC particles. RUS can determine the nine independent elastic stiffness(C )for the orthorhombic symmetry on a small specimen simultaneously. The elastic constants were determined as a function of the volume fraction. A concept of effective aspect ratio, which combine the aspect ratio and the orientation of reinforcement, was used to calculate the initial moduli from Mori-Tanaka theory for the input of RUS minimization code. Young's moduli can be obtained from the measured stiffnesses. The results show that the elastic stiffness increases with increment of the particle content. The behavior of elastic stiffness indicates that the particle redistribution induced by the extrusion process enlarges the transversely isotropic symmetry as the fraction of reinforced particles increase. This relationship could be used for determination of the volume fractions of reinforcement as a potential tool of nondestructive material characterization.

영일만에 출현하는 부유성 난과 자치어의 종조성 및 계절변화

한경호,홍지선,김영섭,전경암,김영숙,홍병규,황동식 한국어류학회 2003 韓國魚類學會誌 Vol.15 No.2

경상북도 영일만 연안에서 2001년 2월, 5월, 8월 및 11월에 계절별로 채집된 부유성 난과 자치어의 종조성 및 계절변화를 연구하였다. 채집된 부유성 난은 총 9개 분류군으로, 멸치가 출현량의 63.4%로 가장 우점하였고, 다음 까나리는 23.7%를 차지하였으며, 나머지는 7개 분류군이 12.9%를 차지하였다. 자치어는 총 7목 28과 37개의 분류군이 출현하였는데, 그 중 32개 분류군은 종 수준까지, 3개 분류군은 속 수준까지, 2개 분류군은 과 수준까지 동정하였다. 2월에는 2목 7과 12종, 5월에는 3목 5과 7종, 8월에는 6목 18과 21종, 11월에는 6목 14과 16종이 출현하였다. 주요 출현종으로서는 까나리가 자치어 출현량의 22.7%를 차지하여 가장 우점하였으며, 다음은 멸치가 16.7%, 동갈양태속 어류가 14.1%를 차지하였고, 노래미와 쥐노래미가 각각 5.7%와 5.5를 차지하였다. The ichthyoplanktons in coastal waters of Yongil Bay were sampled during four different months (February, May, August and November 2001) to study their distribution. The collected fish eggs were identified as belonging to nine species. The most dominant species Engraulis japonicus accounted for 63.4% of the total fish eggs, followed by Ammodytes personatus (23.7%) and Sardinops melanostictus (9.2%). The collected larvae and juveniles were identified into 37 taxa (28 families, 7 orders). Of these, 32 were identified to species, three were identified to genus and two were identified to family level. The dominant species Ammodytes personatus accounted for 22.7% of the total larvae and juveniles, followed by Engraulis japonicus (16.7%), and Repomucenus sp. (14.1%). These three taxa constituted 53.5% of the total collected larvae and juveniles.

고분자형 자외선 안정제를 함유한 SBR과 NR의 UV 노화 거동에 관한 연구

남경태 ( Kyoung Tae Nam ),홍창국 ( Chang Kook Hong ),채규호 ( Kyu Ho Chae ),강신영 ( Shin Young Kaang ) 한국고무학회 2006 엘라스토머 및 콤포지트 Vol.41 No.3

본 연구에서는 고분자형 자외선 안정제 DGEBA-HALS의 광분해 억제 효과를 평가하기 위해 SBR과 NR 고무를 사용하여 광안정제 첨가에 따른 UV 조사 영향을 고찰하였다. 이를 위해 광안정제를 첨가하지 않은 배합고무, 사용화된 광안정제인 Cyabsorb UV-3529를 첨가한 배합고무, 그리고 고분자형 DGEBA-HALS를 첨가한 배합고무의 영율, 인장장고, blow-off 변형, 가교밀도 측정을 통한 시편의 물리적 특성변화 등을 관찰하였다. UV 조사 후 모든 시편에서 영율이 증가하였으며 인장강도는 광안정제를 첨가한 시편이 첨가하지 않은 시편보다 우수했다. 특히 NR의 경우 DGEBA-HALS 첨가 시 인장강도가 향상되었다. Blow-off 변형 실험결과도 영율 실험 결과와 비슷하였다. UV-vis transmissinon spectra를 통한 SBR 배합고무의 투과도를 조사한 결과 광안정제를 첨가함으로써 약 4%의 향상된 투과도를 보였다. Cyabsorb UV-3529와 DGEBA-HALS의 첨가는 비슷한 경향의 투과도를 나타내었다. SEM을 통해 시편의 표면을 관찰한 결과 광안정제를 첨가함으로써 UV 조사에 의한 균열의 크기가 작아짐을 알 수 있었고, 특히 DGEBA-HALS는 상용화된 Cyabsorb UV-3529 보다 더 좋은 광분해 안정효과를 갖는 것을 확인할 수 있었다. The retardation effects of a new polymeric UV stabilizer, DGEBA-HALS, on the UV degradation of SBR and NR were investigated in this study. The UV degradation behaviors of three different rubber compounds, without any photostabilizer and with commercial Cyabsorb UV-3529 and DGEBA-HALS, were compared. Also, the physical characteristics such as Young`s modulus, tensile strength, blow-off deformation and crosslink density were examined. The Young`s modulus was increased by UV irradiation for all samples, and the tensile strength, after UV irradiation, of the compound with UV stabilizer was better than that of the compound without stabilizer. Especially, the tensile strength of UV irradiated NR was improved by adding DGEBA-HALS. The results of blow-off deformation were in accord with those of Young`s modulus. The degree of transmission of SBR compounds obtained from UV-vis transmission spectra was improved about 4% by adding the UV stabilizer. Commercial Cyabsorb UV-3529 and DGEBA-HALS showed similar trends of transmission. The SEM photographs of SBR surface showed that the size of cracks created by UV irradiation became smaller by adding UV stabilizer. In particular, it is observed that the stabilization effect of DGEBA-HALS was better than that of commercial Cyabsorb UV-3529.

고령자 남녀와 20대 남녀에 있어서 다양한 등속수축중 최대 모멘트의 비교

金智源(Ji-Won Kim),金相佑(Sang-Woo Kim),文基旭(Ki-Wook Moon),嚴光文(Gwang-Moon Eom),李泳揆(Young-Gyu Lee),南貞淑(Jung-Sook Nam),朴寬龍(Kwan-Yong Park),金耀翰(Yo-Han Kim),洪廷和(Jeong-Hwa Hong),朴炳奎(Bung-Kyu Park) 대한전기학회 2008 전기학회논문지 Vol.57 No.10

In this paper, we investigated the maximum ankle joint plantarflexion moment (MPM) of young and elderly subjects during various modes of isokinetic contractions with special interest in the elderly females who were reported to have higher fall rate than the elderly males. Subjects include the young subjects (14 males: 22.7±2.5yrs, 13 females: 20.5±1.3yrs) and the elderly subjects (17 males: 65.8±10.5yrs, 26 females: 71.4±5.2yrs). The MPM was normalized by each subject's body weight. The MPM of elderly females was the weakest among the groups, particularly, at the eccentric contractions. The male-to-female ratio of MPM was greater in the elderly than in the young and the young-to-elderly ratio of MPM was greater in female than in male, both during the eccentric contractions. The result suggests that the decreased muscle force per body weight, especially at the eccentric contraction, may be one reason for the more frequent fall of the elderly female than the elderly male.

리눅스 클러스터 서버 상에서 RTSP 기반의 VOD 스트리밍 시스템의 설계 및 구현

홍기호,김영진,최황규 江原大學校 産業技術硏究所 2001 産業技術硏究 Vol.21 No.A

Linux cluster Server makes a high performance PC cluster system, and provides scalablity and availability as compared with an expensive single server. In this paper, we design and implement a VOD streaming service system to serve video and audio streaming services on the Linux cluster serve. Our Streaming server supports the MS Window Media Format based on the RTSP streaming protocol.

Floristic characteristics of vascular plants and first distributional report of Pseudostellaria baekdusanensis M. Kim in Yongneup wetland protected area

Young-Chul Kim,Hyun-Hee Chae,Sang-Heock Oh,Seung-Ho Choi2,Moon-Pyo Hong3,Gi-Heum Nam,Jae-Yoon Choi,Hyun-Sook Choi,Kyu-Song Lee 한국환경생태학회 2015 한국환경생태학회지 Vol.29 No.2

Yongneup wetland protected area, the only high moor in Korea, is a core area to conserve biodiversity. Even though the Yongneup wetland protected area is relatively small, various plant species are distributed in the Yongneup wetland protected area because it includes various habitats showing different environmental gradients. Vascular plants distributed in the Yongneup wetland protected area were identified as a total of 376 taxa that is composed of 73 families, 217 genera, 322 species, 3 subspecies, 44 varieties and 7 forms. For endangered plants designated by the Ministry of Environment, 5 species including Trientalis europaea var. arctica, Lilium dauricum, Halenia corniculata, Lychnis wilfordii and Menyanthes trifoliata were found and 34 taxa were confirmed to be distributed only in the mountainous wetland habitats. Regarding naturalized plants, a total of 11 taxa were distributed, but most of them were distributed in the areas where artificial interference has occurred. And in areas inside the wetlands that are relatively well preserved, 2 species of Bidens frondosa and Erigeron annuus were observed. In this study, the occurrence and distribution of Pseudostellaria baekdusanensis M. Kim, which was recently found in Mt. Baekdu and reported as a new species, were identified in the Yongneup wetland protected area. A wetland is a very vulnerable area to drastic environmental changes and damages to its ecosystem could cause the extinction of rare plant species which are distributed only in the wetlands. Therefore, it is mandatory that current status of the Yongneup wetland protected area is evaluated and actions to prevent rapid environmental changes are taken. Fourteen separate investigations were conducted in 2013 and another four in 2014, to evaluate current status of the Yongneup wetland protected area. These investigations have provided us the basic information for future actions of conservation and restoration.

도시 거주 노인 수면 습관 및 불면증상의 요인 : 인구학적,질병 및 정신증상의 관련성

홍진표,안준호,윤영국,박종익,이소영,함봉진,김장규,한오수,조맹제 대한신경정신의학회 2000 신경정신의학 Vol.39 No.6

연구목적 : 본 연구는 국내 노인의 습관을 조사하고 불면 증상과 연관 있는 인구학적, 질병학적 요인을 알고자 했다. 방 법 : 1997년 12월부터 1998년 1월까지 약 1개월에 걸쳐 2단계 층화집락표본추출의 역학조사법을 통해 선정된 3개 4개동 거주의 만 65세 이상 노인을 대상으로 수행되었다. 대상자 중 723명에서 등답을 받았으며 응답률은 73.8였다. 대학생인 설문조사요원들을 훈련시킨 뒤, 이들로 하여금 대상지역의 노인거주가정을 방문하여 개개 노인을 대상으로 반구조화된 면담으로 수면습관 및 불면증상 설문을 실시하였으며 그 외 한국어판 노인정신장애평가척도, 삶의 질 척도를 이용한 설문조사와 과거 질병력을 청취조사하게 하였다. 결 과 : 국내 노인들은 평균 오후 10시 16분에 자리에 누워 오전 5시22분에 일어나서 총 7시간 6분의 수면시간을 보였다. 노인의 11.7%가 거의 매일 밤 불면증을 14.8%가 간헐적 불면증을 호소하였다. 남자에서는 연령이 증가할수록 침상에 누워있는 시간이 증가하고, 또, 입면시까지 소요되는 시간과 수면 중의 각성회수가 증가되었으나 여성에서는 명확하지 않았다. 단변수 분석에서 요통, 중풍 병력의 환자에서 불면증상이 심했다. 다변량분석 결과 불면 증상과 관련 깊은 요인으로 남자에게서는 고령과 우울증상이 여자에게서는 남자의 위험요인에다 신체통증과 피부병력이 추가로 관련이 있었다. 결 론 : 지역 거주 노인에서 불면 증상은 매우 흔한 증상이며 우울증상과 명확한 상관관계를 보이고 있었다. 불면증을 극복하기 위해 불면증 위험요인의 인과관계에 대한 추후 연구가 필요하다. Objectives : The purpose of this study is to analyze sleep habit and investigate the association between insomnia and demographic, health and psycho-behavioral symptomatology in Korean urban elderly Method : A total of 723 community residents aged 65 years or older were surveyed by two stage, random cluster sampling method. The response rate was 76.2%. Interviewers performed door to door visits and administered a questionnaire about sleep, past medical history, and several scales as the Psychogeriatric Assessment Scale(PAS), the short form Quality of Life Scale (SF-36) and etc. Results : The mean scores are as follows : retiring time was ten-sixteen p.m., wake-up time was five twenty two a.m., duration of sleep was seven hours and six minutes. Among the elderly, 11.6% and 14.8% of the subjects reported chronic and intermittent difficulty in sleeping, respectively. The patients with back pain and history of stroke complained of more insomnia symptoms in univariate analysis. In ANCOVA analysis, insomnia symptoms were associated with an old age, depressive symptoms in male. Bodily pain and history of dermatologic disease were additional risk factors in female. Conclusions : The data suggest insomnia is one of most common health problems among elderly Koreans living in the community. Strong positive relationship between depressive symptoms and insomnia were found. Further research is needed to explore the causal relationship between insomnia and risk factors.

Pt-Co 합금박막형 측온저항체 온도센서의 제작과 그 특성

홍석우,최영규,정귀상 경북대학교 센서기술연구소 1998 센서技術學術大會論文集 Vol.9 No.1

We made Pt-Co alloy resistance patterns on the Al_(2)O_(3) substrates by lift-off method and investigated the physical and electrical characteristics of these films under various conditions (the input power, working vacuum, annealing temperature, thickness of thin films) and also after annealing these films. The TCR value of Pt-Co alloy thin films was measured with various thickness of thin films and annealing conditions. The optimum TCR value is gained under conditions 3000Å of thin films thickness and 1000°C of annealing temperature. These results indicate that Pt-Co alloy thin films have potentiality for the high resolution RTD temperature sensors.

양계산물의 수입자유화가 국가경제에 미치는 영향

홍성규,어영준,서대석 건국대학교 1995 學術誌 Vol.39 No.1

This study is aimed to identify effects of import liberalization of chicken products not only on agriculture but also on national economy overall. The extending influences on production and income are generally measured using input-output analysis tool. But the reaction induced by import liberalization of chicken products would not be considered in the open static input-output-model, far example multiplicator effects between income and consumption. In order to overcome the defect of the open static input-output-model, the open static Leontief-model is extended to the income-consumption relation in measuring the extended effects of the import liberalization of chicken products. This study is undertaken using the results of KREI(Jan. 1994) which concluded that the direct losses in agriculture from 1995 to 2001 could be 113 billion won at the constant price of 1990. It was calculated that the indirect production losses of the other related industries could be 165 billion won, and 246 billion won in the view of income-consumption relation. It was also predicted that the indirect income losses of the other related industries would be 89 billion won, and 126 billion won in the view of income-consumption relation. As a result import liberalization of chicken products could possibly bring about larger losses to the other industries than to agriculture. Especially, in the "Other flood preparations" sector, the indirectly largest loses could predict to be occured.

천추 갈색종양(Brown tumor)으로 발현된 부갑상선 기능항진증 1예

홍우정,구본정,이재민,한상우,이효진,나소영,노흥규,김영건,송민호 충남대학교 의학연구소 2003 충남의대잡지 Vol.30 No.2

부갑상선 기능항진증에 의한 골병변으로 갈색종양이 있다. 갈색종양은 주로 장골을 침범하고 척추골에서의 발생은 매우 드물다. 국내의 보고에서 갈색종양의 장골 침범은 있었으나, 척추골에서의 발생은 보고된바 없다 .저자들은 부갑상선 기능항진증으로 인하여 척추골의 천추에 발생된 갈색종양 1예를 경험하였기에 문헌고찰과 함께 보고하는 바이다. The bony involvement in primary hyperparathyroidism present as browm tumor or osteitis fibrosa cystica and lead to pathologic fracture. Brown tumor commonly involve long bone such as femur, tibia, fibula, humerus, and radius. Brown tumor of axial skeleton is a rare entity. Previously reported case that involve axial skeleton still not present. We report a 47-year-old male patient that he has a hyperparathyroidism presenting as brown tumor involving sacrum.