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황재석,서재국,이효재,남정환,Hwang, Jae-Seok,Suh, Jae-Guk,Lee, Hyo-Jae,Nam, Jeong-Hwan,Rpwlands, R.E. 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.10
SPATE(Stress Pattern Analysis by Thermal Emission) can be effectively used to analyze the stress distribution of the orthotropic structure under the repeated load by non-contact. In this research, the measuring conception and method of stress intensity factor of orthotropic material using SPATE are suggested. The relationships between the maximum values of SPATE signal and $1/\sqrt{X'}$ (or $1/\sqrt{y'}$) are theoretically established in the vicinity of crack tip of the orthotropic material. It is certified through SPATE experiment that their linear quality is very excellent.
황재석,서재국,이효재,남정환,최영철,Hwang, Jae-Seok,Seo, Jae-Guk,Lee, Hyo-Jae,Nam, Jeong-Hwan,Rowlangs, R.E.,Choe, Yeong-Cheol 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.3
SPATE(Stress Pattern Analysis by Thermal Emission) can be effectively used to analyze the stress distributions of isotropic structure under the repeated load by non-contact. In this research, the measuring method and the measuring concept of stress intensity factor of isotropic material by SPATE are suggested. The validity of the method and the concept was certified through SPATE experiment.
등방성/직교이방성 이종재료의 진전 계면균열에 대한 동적 광탄성 실험 하이브리드 법 개발
황재석,신동철,김태규,Hwang, Jae-Seok,Sin, Dong-Cheol,Kim, Tae-Gyu 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.7
When the interfacial crack of isotropic/orthotropic bi-materials is propagated with constant velocity along the interface, stress and displacement components are derived in this research. The dynamic photoelastic experimental hybrid method for the bimaterial is introduced. It is assured that stress components and dynamic photoelastic hybrid developed in this research are valid. Separating method of stress components is introduced from only dynamic photoelastic fringe patterns. Crack propagating velocity of interfacial crack is 69∼71% of Rayleigh wave velocity of epoxy resin. The near-field stress components of bonded interface of bimaterial are similar with those of pure isotopic material and two dissimilar isotropic bimaterials under static or dynamic loading, but very near-field stress components of bonded interface of bimaterial are different from those.
식도운동질환과 위식도역류질환에서 산청소능 비교 - 저진폭수축파 비특이성 식도운동질환을 중심으로
황재석(Jae Seok Hwang),강영우(Young Woo Kang) 대한소화기학회 1995 대한소화기학회지 Vol.27 No.5
N/A Background/Aims: The aim of this study was to evaluate acid clearance in esophageal disease, a common cause of noncardiac chest pain, and to evaluate the correlation between the swa]lowing number for acid clearance and the amplitude of contractions. Methods: The study population was divided into four groups. Group 1(n=8) was controls with no complaints of any gastrointestinal symptoms. Group II(n=9) was gastroesophagea1 reflux disease. Group III(n=6) was nutcracker esophagus. Group IV(n=7) was nonspecific esophageal motility disorder with low amp]itude contractions. We performed standard acid clearance test and compared it with the amplitude of esophageal contractions. Results: In Group I, the swal]owing number was 6.12+ 0.58(mean+ SE); in Group II, 15.33 3.96; and in Group lll and IV, 9.83 + 2.70 and 20.42 ' 4.43 respectively. The number of swallowing was significantly increased in Group IV than in the other groups(P=0.05) and showed the reversed correlation with amplitude(r=-0.81, p=0.026). Conclusions: Group IV had significantly delayed esophageal acid clearance and also showed the reversed correlation with amplitude. (Korean J Gastroenterol 1995;27: 493-498)
비심장성 흉통환자에서 Edrophonium 유발검사후 식도 수축파변화의 의의
황재석(Jae Seok Hwang),강영우(Young Woo Kang) 대한내과학회 1995 대한내과학회지 Vol.49 No.3
Objectives: Although Edrophonium chloride is a widely used provocative test to assess noncardiac chest pain, the change in esophageal contractions and its clinical implication leave much to be criticized. This study was performed to examine the changes in esophageal contractions and its significance after Edrophonium provocative test. Methods: Forty two patients complaining of noncardiac chest pain and thirteen control subjects were selected from Keimyung University Dongsan Hospital between September 1988 and May 1993, and were categorized into three groups. The first group comprises of 13 normal adults as control. The second group consists of 25 patients with nor- mal esophageal manometry but complained of chest pain. The third group comprises of 17 patients with nutcracker esophagus. After Edrophonium provocative test, the amplitude and duration of esophageal contractions were measured and compared among groups. Results: Age and sex distribution were not significantly different among three groups. In patients with nutcracker esophagus, not only the difference of amplitude (p=0.0016) and duration of esophageal contractions(p=0.001) but also the percent change of duration(p=0.008), between basal state and after Edrophonium showed significant increase. Furthermore, ANCOVA analysis in which the basal value was taken into consideration, also showed significant increase in duration of esophageal contractions in patients with nutcreacker esophagus. The calculated regression coefficient from this analysis can be used as another tool for diagnosing nutcracker esophagus. Conclusion: Among the patients complaining of noncardiac chest pain the duration of esophsgeal contractiona in patients with nutcracker esophagus, increased significantly after Edrophonium pro- vocative test. Although this can he used as another tool for diagnosing nutcracker esophagus, further clinical studies are needed.
황재석(Jae-Seok Hwang),김주환(Ju-Hwan Kim),김종우(Jong-Woo Kim) 한국암반공학회 2018 터널과지하공간 Vol.28 No.2
단층대에 위치한 근접병설터널에 대하여 단층의 폭과 경사, 단층암의 물성을 달리한 수치해석과 모형실험을 통해 단층이 터널 안정성에 미치는 영향을 알아보았다. 병설터널 사이에 존재하는 필라의 강도/응력비를 구할 때는 필라 중앙부의 응력, 필라 전체의 평균응력, 필라 좌우단부의 응력을 각각 적용하였는데, 이중 마지막 방법은 단층대의 유무에 관계없이 터널 안정성의 보수적 평가에 적합하였고 터널 굴착시점을 실시간적으로 반영하였다. 필라 좌우단부의 응력을 적용하여 구한 강도/응력비는 단층의 폭과 경사가 커질수록, 단층암의 물성이 연약할수록 감소하는 경향을 보였다. 축소모형실험에서 단층을 포함한 모형은 불포함 모형에 비해 균열개시압력이 작았고, 단층의 폭이 큰 모형일수록 터널 안정성은 낮게 나타났다. 단층은 터널의 파괴거동에도 큰 영향을 미쳤는데, 단층이 없는 모형에서는 필라의 좌우하단부와 양쪽터널 측벽부에서 수평방향의 균열이 발생하였지만, 단층을 포함한 모형에서는 필라부 단층대에서 경사진 균열이 발생하였다. The effect of fault on the stability of the closely-spaced twin tunnels located in fault zones was investigated by numerical analyses and scaled model tests on condition of varying widths, inclinations and material properties of fault. When obtaining the strength/stress ratios of pillar between twin tunnels, three different stresses were used which were measured at the middle point of pillar, calculated to whole average along the pillar section and measured at the left/right edges of pillar. Among them, the method by use of the left/right edges turned out to be the most conservative stability estimation regardless of the presence of fault and reflected the excavating procedures of tunnel in real time. It was also found that the strength/stress ratios of pillar were decreased as the widths and inclinations of fault were increased and as the material properties of fault were decreased on condition using the stresses measured at the left/right edges of pillar. As a result of scaled model tests, it was found that the model with fault showed less crack initiating pressure than the model without fault. As the width of fault was larger, tunnel stability was decreased. The fault had also a great influence on the failure behavior of tunnels, such as the model without fault showed failure cracks generated horizontally at the left/right edges of pillar and at the sidewalls of twin tunnels, whereas the model with fault showed failure cracks directionally generated at the center of pillar located in the fault zone.