적층압축에 의한 접합재의 경계면 성장거동에 대한 수치 시뮬레이션

정태훈,류제구,後藤學 서울産業大學校 1997 논문집 Vol.45 No.1

Under plane strain compression, of two blocks with sawtoothed interface, the sawtooth growth occurred. We presumed in the previous paper that such growth was caused by the shear-band formation starting from the tip of sawtooth and its degree depended on the material properties of the block. In this paper, Compression in the case where similar blocks are twinned and also compression in the case where dissimilar blocks are twinned variously are carried out in the condition of lubricated interface. Further, in the latter, compression where the interface is degreased is also performed. The degree of growth is experimentally investigated. Moreover, numerical simulations are carried out by the elastic-plastic FEM for the case of the dissimilar blocks with the initial sawtooth angle of 60℃ . In the experiment, the harder material yields larger growth than the softer one, and the growth in the case of initial sawtooth angle 60℃ is greater than that of 90℃ . Larger ratio of total height to sawtooth height gives larger growth in comparison with the previous experimental result. In the case where the dissimilar blocks are twinned, larger difference between material properties leads smaller growth, and the degreased interface leads smaller growth than that in the lubricated one. Furthermore, by the simulation of compression where dissimilar blocks are twinned, it is confirmed that the tendency of the general deformation pattern is very similar to the experiment.

정상 성인에서 갈근(Radix puerariae)의 장기투여가 혈중 알콜 농도에 미치는 영향

박제민,김지훈,김명정,김성곤,정영인 大韓神經精神醫學會 1996 신경정신의학 Vol.35 No.6

알콜 의존에서 알콜 소비량을 감소시키고 음주 재발을 방지하는데 효과가 있다는 약물들이 몇 가지 있으며 갈근이 알콜 의존증의 치료에 효과가 있다는 자료들이 있다. 저자들은 정상 성인을 대상으로 알콜을 섭취하게 한 후 갈근 투여 전, 후의 혈중 알콜 농도를 비교함으로써 갈근이 알콜 대사를 방해하여 혈중 알콜 농도를 상승시키는지를 검증하고자 하였다. 알콜을 비롯한 약물 남용이나 의존증이 있거나 기타 정신 질환이 없고 주요 신체질환이 없는 20∼29세 남자 의과 대학생들을 대상으로 하였다. 대상자는 모두 25% 알콜을 3ml/kg(100%알콜 0.75ml/kg)을 마시게 한 후 투여 전, 투여 후 10, 30, 60, 90, 그리고 120분에 혈중 알콜 농도를 측정하게 한 다음 14일간 갈근 하루 6g을 투여한 후 첫날과 같은 방법으로 알콜을 복용하게 한 후 알콜 혈중 농도를 측정하여 약물 투여 전, 후의 알콜 혈중 농도를 비교한 결과 갈근 투여 후에 음주시 30, 60, 90, 그리고 120분에 혈중 알콜 농도가 유의하게 상승하였다. In alcohol dependence, some drugs reduce alcohol consumption and prevent the recurrence of alcohol drinking. There were some evidences that Radix puerariae was effective in the treatment of alcohol dependence. We studied the effect of Radix puerariae on blood alcohol concentration in healthy adults. The subjects were medical students, who did not have major physical disorders, drug abuse or dependence including alcohol, and other psychiatric disorders. After drinking 25% alcohol 3ml/kg, all subjects were measured for blood alcohol concentration at 0, 10, 20, 30, 45, 60, 120 minutes by Alco-sensor Ⅳ. Next day, all subjects were made to take Radix puerariae 6g/day(3g bid) for 14 days. And then blood alcohol concentration were measured by the same method. The results were significant increase in blood alcohol concentration at 30, 60, 90 and 120 minutes.

經濟危機의 歷史的 比較 : 韓國經濟에의 示唆 Implications for Korean Economy

朴濟勳 서울大學校經濟硏究所 1998 經濟論集 Vol.37 No.2

우리나라를 비롯한 아시아 경제위기가 이들 경제의 구조조정을 촉진시켜 경제체질개선을 위한 호기가 되어 재도약의 발판으로 작용할지 또는 세계대공학의 전조가 될런지는 여러 요인의 작용에 따라 달라질 것이다. 그러나 그 중 가장 중요한 현실적 변수는 미국경제의 앞날이다. 미국경제에 대한 평가는 미국내에서는 아직은 낙관론이 우세한 것으로 보인다. 그러나 유럽 등에서는 비관론도 적지 않다. 사회주의권의 붕괴의 교훈은 자본주의시장경제체제의 무오류성을 증명하는 것은 아니라고 할 때 비관론에도 대비해야 한다. 그러나 극단적 비관론은 무대책을 낳을 수 있다. 미국경제의 최근의 경쟁력 회복은 80년대 이후 꾸준히 추진해 온 구조조정 노력이 결실을 맺고 있는 것으로 해석해야 한다는 주장도 일리가 있다. 한 가지 확실한 것은 미증유의 경제위기를 겪고 있는 우리로서는 여러 이론ㆍ사상에 입각한 다양한 시각과 견해에 귀기울이면서 모든 경우에 대비하는 냉정한 현실인식 하에 세계의 역사적 경험과 우리의 현실ㆍ조건을 고려한 새로운 발전패러다임의 정립 노력을 서둘러야 할 때라는 사실이다.

서해산 돌가자미 Kareius bicoloratus의 초기발생시 수온과 염분의 영향

전제천,김치홍,정의영,이창훈,김병균 한국어류학회 2002 韓國魚類學會誌 Vol.14 No.3

본 연구는 돌 가자미(Kareius bicoloratus)의 난발생에 미치는 수온과 염분의 영향을 알아보지 위하여 수행되었다. 5단계의 수온 조건 (7, 10, 13, 16 및 19℃) 및 5단계의 염분 조건(25, 30, 35, 40psu 및 현장해수 염분 : 33.6psu)에서 수정란을 발생시켜 발생 속도와 부화율 측정하였다. 수정란의 발생속도는 수온이 높을수록 빨랐으며, 수온(T: ℃)과 각 발생 단계별 소요시간(h:hour) 사이의 관계를 직선 함수에 회귀시켰을 때 각 발생단계별 관계식은 다음과 같다. 8세포기 : 1/h = 0.01441T - 0.02728(r^(2) = 0.998) 낭배기 : 1/h = 0.00269T - 0.00319(r^(2) = 0.997) 안포형성기 : 1/h = 0.00171T - 0.00053(r^(2) = 0.998) 심장형성기 : 1/h = 0.00121T - 0.00018(r^(2) = 0.995) 부화기 : 1/h = 0.00101T - 0.00266)(r^(2) = 0.998) 이상의 관계식으로부터 추정된 돌 가자미의 난 발생이 개시되는 생물학적 영도는 1.3℃이었다. 8세포기, 낭배기, 안포형성기. 심장형성기 및 부화기까지의 적산수온은 각각 72.9, 356.7, 525.8, 735.2 및 1156.7℃로 계산되었다. 수온은 부화율에 큰 영향을 미치는 것으로 나타났다(p<0.001). 부화율이 수온이 증가할수록 감소하였으며, 7℃일 때 부화율이 62.0%로 가장 높았다. 수온이 16℃ 이상일 때 기형어의 출현율이 증가하였다(p<0.05). 염분 또는 부화율에 큰 영향을 미치고 있었다(p<0.001). 염분에 따른 부화율은 자연해수의 염분인 33.6psu에서 54.1%로 가장 높았고, 이보다 낮거나 높은 경우에는 부화율이 감소하였다. 특히, 염분이 30psu 미만으로 감소할 경우 기형어의 출현율 증가하였다(p<0.04). 돌 가자미의 난 발생 및 정상적인 부화를 위한 조건은 산란시기의 수온과 염분에 가까울수로고 좋은 것으로 판단된다. This study was conducted to determine the influences of water temperature and salinity on the embryonic development of the stone flounder, Kareius bicoloratus as a part of research on the artificial seedling production of the fish. Embryos were incubated under five different temperatures (7, 10, 13, 16 and 19℃) and five different salinities (25, 30, 35, 40 psu and the ambient salinity: 33.6 psu) until they hatched. The required times for embryonic development decreased with increase of water temperature. The relationships between the water temperature (T: ℃) and required times (h: hour) for the embryo to attain each develop-mental stage were obtained by linear regressions as follows; 8-cell stage : l/h = 0.01441T-0.02728 (r² = 0.998) 50%-epiboly stage : Uh = 0.00269T-0.00319 (r² = 0.997) Optic vesicle formation stage : l/h = 0.00171T-0.00053 (r² = 0.998) Heart formation stage : l/h = 0.00121T-0.00018 (r² = 0.995) Hatching stage : l/h = 0.00101T-0.00266 (r²= 0.998) From these equations, the biological minimum temperature for embryonic development of K. bicoloratus was estimated to be 1.3℃. Cumulative water temperatures to reach 8-cell stage, 50%-epiboly stage, optic vesicle formation stage, hearth formation stage, and hatching stage were 72.9, 356.7, 525.8, 735.2, and 1,156.7℃, respectively. Water temperature affected significantly the hatching rate (p< 0.001). The hatching rate decreased with increase of water temperature. The highest hatching rate was 62.0% at 7℃. When the water temperature was higher than 16℃, the proportion of abnormal larvae increased (p < 0.05). Salinity also affected significantly the hatching rate (p< 0.001). The highest hatching rate was 54.1% at the salinity (33.6 psu) of ambient seawater. When the salinity was lower than 30 psu, the proportion of abnormal larvae increased ip < 0.05).

전산유체 기법을 이용한 DAF 부상조에서의 수리 특성 고찰

김성훈,유제선,김영미,박희경 대한상하수도학회 2002 상하수도학회지 Vol.16 No.4

Dissolved air flotation is a solid-liquid separation process that uses fine rising bubbles to remove particles in water. DAF is found most effective in treating algae and lower density flocs that are hard to remove in sedimentation process. Some researcher reports the results of an experimental study which examined the flow within the flotation zone of a DAF tank (ONeill at al., 1997). I would be concluded that, in general, the flow within flotation zone is robust and that differences in the performance of individual DAF tanks must be the result of processes occurring within the contact zones of these tank, not as the result of flotation processes. In this research, the authors thought that the efficiency of the DAF process is strongly related to bubble size. It means bubble rising velocity at the air injection nozzle is most important factor of DAF process. However, bubble movement in DAF tank is somewhat complicate, so it is hard to make up conceptual model through simple mass balance as other researchers did (Leppinen at. al., 2000). For the modeling of turbulent 2-phase flow in the tank, the standard k-ε model was used in CFD code because it is widely accepted and the coefficients for the model are well established. This model uses the eddy-viscosity hypothesis for the turbulence. As the result of this study, the authors concluded that bubble size and its rising velocity is very important factor of DAF process and the recycle ratio must be also consider for the flotation zone parameter. Also, For the improved model, relation between turbulent intensity and bubble-particle attachment must be studied.

헬름홀츠 코일을 이용한 강자성체의 와전류검사

성제중,서동만,신용훈,엄태건,서동섭 한국비파괴검사학회 2003 학술대회 논문집 Vol.- No.1

Ferromagnetic material like the steel tubes can easily distort eddy current testing signal due to increased magnetic permeability for defects. Because magnetic field of the test probe is affected in an inconsistent way when the material under the testing has permeability. This permeability effect can be reduced by magnetic saturation. In this paper eddy current testing system was developed to detect flaws on the steel tubes. Magnetic saturation probe with helmholtz coil was designed for saturation and inspection of the steel tubes. When using the designed test probe, the relationship between flaw signals and noises was obviously discriminated. Additionally, a high pass filter was included in the eddy current board to minimize noises due to DC magnetic field.

전산유체 기법을 이용한 용존공기부상법에서의 접촉도 조건변화에 따른 충돌효율평가

김성훈,유제선,박희경 대한상하수도학회 2004 상하수도학회지 Vol.18 No.2

Dissolved air flotation (DAF) is a solid-liquid separation process that uses fine rising bubbles to remove particles in water. Most of particle-bubble collision occurs in the DAF contact zone. This initial contact considered by the researchers to play a important role for DAF performance. It is hard to make up conceptual model through simple mass balance for estimating collision efficiency in the contact zone because coupled behavior of the solid-liquid-gas phase in DAF system is 90 complicate. In this study, 2-phase(gas-liquid) flow equations for the conservation of mass, momentum and turbulence quantities were solved using an Eulerian-Eulerian approach based on the assumption that very small particle is applied in the DAF system. For the modeling of turbulent 2-phase flow in the reactor, the standard k-ε mode Ⅰ(liquid phase) and zero-equation(gas phase) were used in CFD code because it is widely accepted and the coefficients for the model are well established. Particle-bubble collision efficiency was calculated using predicted turbulent energy dissipation rate and gas volume fraction. As the result of this study, the authors concluded that bubble size and recycle ratio play important role for flow pattern change in the reactor. Predicted collision efficiency using CFD showed good agreement with measured removal efficiency in the contact zone. Also, simulation results indicated that collision efficiency at 15% recycle ratio is higher than that of 10% and showed increasing tendency of the collision efficiency according to the decrease of the bubble size.

운동전략이 기립자세의 기능적 전방 팔뻗기에 미치는 영향

박제상,권오윤,최흥식,김택훈 한국전문물리치료학회 2000 한국전문물리치료학회지 Vol.7 No.1

The purpose of this study is to determine whether movement strategies affect functional forward reach distance in a standing position. Forty-seven healthy subjects were selected for this study: 23 men and 24 women, with an average age of 22.3. Functional forward reach distances were measured as hip strategy and squat strategy(included knee and ankle movement strategy) in a standing position, respectively. The mean values of functional forward reach distance in hip strategy, squat strategy were 33.57㎝, 29.48㎝, respectively. There was significantly difference in functional forward reach distance between hip strategy and squat strategy(p<.001). There was no difference of functional forward reach distance between male and female in hip strategy, but there was significant difference in other strategy(p<.05). These results suggest that movement strategies should be considered during functional forward reach test in standing. Further study is required to determine whether movement strategies affect functional reach distance in elderly and disabled groups.

Dissolved Air Flotation(DAF) 접촉조의 수리동력학적 조건이 입자의 제거에 미치는 영향

유제선,김성훈,신은허,박희경 대한상하수도학회 2003 상하수도학회지 Vol.17 No.1

Hydrodynamic conditions for optimum solids capture within the contact zone, which are governed by the geometry and flow, are not yet well understood. In this research, dimensionless parameters which represent hydrodynamic conditions in the contact zone were derived, using the Buckingham π theorem. Those parameters are Reynolds No. (Re), Froude No. (Fr), Weber No. (We), Local Weber No., and Bubble Capacity No. (Bc). The particle removal rate was investigated by changing each value of the dimensionless parameters. The experimental results indicate that particle removal rate, when gravity dominates and the flow is semi-turbulent (Fr < 0.3, Re < 8000), is higher than when inertia dominates and flow is turbulent. For the We, higher removal rates were obtained in the range of the We < 40. Relative to the Local We, smaller bubbles which are influenced more by surface tension than inertia, demonstrated a higher particle removal rate than larger bubbles. For the Bc, the optimal range is from 0.3 to 0.5. We suggest that these dimensionless parameters can be used to diagnose the performance of and to design a DAF reactor.

인조 합성 테니스 바닥재의 지면 반력 분석

조승제,정미라,서국웅,박승범,윤양진,이훈식,강영택 釜山大學校 附設 體育科學硏究所 1998 體育科學硏究所 論文集 Vol.14 No.-

Some authors suggest that certain types of surfaces are the origin of such injuries. A few years after the first medical concerns about surfaces were voiced, publications of biomechanical measurements apperared, describing accleration, force, and impact measurement on different types of surfaces. In many sport activities, surfaces can be under very high dynamic load. This was the reason for the development of various methods for impact simulation, like the development of various methods for impact simulation, like the artificial athlete. Furthermore, it is important to collect information about the hardness of new and already existing surfaces in sport arenas. The idea on which this measuring system is based Is as follows: The stiffness of the material can be computed from the kinematics measurd at touch down of a rigid body onto a material sample. The results show the following The result for the artifical surfaces(Synpave ace) is surprising. It is known that these surfaces are much harder than synpave rebound classic, synpave spring. This finding suggests that it may be possible that the subjective impression is used as one criterion in the selection of landing(or style) strategies. The number of subjects in this experiment is too small to make statistically significant conclusions. It is shown analytically that when an object a deformable surface, the acceleration it experiences is inversely propotional to its mass. In future, it need to stress that the interaction between shoe and surface is important, and this aspect has now become well accepted. Considering biomechanical aspect in player's injury, it request Korean Standards for synthetic playing surfaces in sport like ASTM(America Society for Testing & Materials) standards of America, DIN 18035 standards of Germany, BSI standards of U.K.