• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.13-18
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• 2009

Flight vehicles such as wheel wells and bomb bays have many cavities. The flow around a cavity is characterized as an unsteady flow because of the formation and dissipation of vortices brought about by the interaction between the free stream shear layer and the internal flow of the cavity. The resonance phenomena can damage the structures around the cavity and negatively affect the aerodynamic performance and stability of the vehicle. In this study, a numerical analysis was performed for the cavity flows using the unsteady compressible three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equation with Wilcox's turbulence model. The Message Passing Interface (MPI) parallelized code was used for the calculations by PC-cluster. The cavity has aspect ratios (L/D) of 2.5 ~ 7.5 with width ratios (W/D) of 2 ~ 4. The Mach and Reynolds numbers are 0.4 ~ 0.6 and $1.6{\times}106$, respectively. The occurrence of oscillation is observed in the "shear layer and transient mode" with a feedback mechanism. Based on the Sound Pressure Level (SPL) analysis of the pressure variation at the cavity trailing edge, the dominant frequencies are analyzed and compared with the results of Rossiter's formula. The dominant frequencies are very similar to the result of Rossiter's formula and other experimental data in the low aspect ratio cavity (L/D = ~ 4.5). In the large aspect ratio cavity, however, there are other low dominant frequencies due to the leading edge shear layer with the dominant frequencies of the feedback mechanism. The characteristics of the acoustic wave propagation are analyzed using the Correlation of Pressure Distribution (CPD).

• 대한기계학회논문집A
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• 제21권8호
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• pp.1195-1208
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• 1997

Bellows is a component in piping systems which absorbs mechanical deformation with flexibility. Its geometry is an axial symmetric shell which consists of two toroidal shells and one annular plate or conical shell. In order to analyze bellows, this study presents the finite element analysis using a conical frustum shell element. A finite element analysis is developed to analyze various bellows. The validity of the developed program is verified by the experimental results for axial and lateral stiffness. The formula for calculating the natural frequency of bellows is made by the simple beam theory. The formula for fatigue life is also derived by experiments. The shape optimal design problem is formulated using multiple objective optimization. The multiple objective functions are transformed to a scalar function by weighting factors. The stiffness, strength and specified stiffness are considered as the multiple objective function. The formulation has inequality constraints imposed on the fatigue limit, the natural frequencies, and the manufacturing conditions. Geometric parameters of bellows are the design variables. The recursive quadratic programming algorithm is selected to solve the problem. The results are compared to existing bellows, and the characteristics of bellows is investigated through optimal design process. The optimized shape of bellows is expected to give quite a good guideline to practical design.

• 한국강구조학회 논문집
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• 제19권6호
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• pp.725-735
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• 2007

이 연구에서는 두께가 얇은 강판을 가진 철골-콘크리트 합성기둥에서 강판의 국부 좌굴 강도 및 국부 좌굴 후 강도에 대한 해석적인 연구를 수행하였다. 콘크리트 충전에 의하여 합성기둥에서 판의 국부 좌굴 성능이 향상되는 것을 경계 조건을 조정하여 해석에 반영하였고, 탄성 좌굴 해석을 통해 한계 폭-두께비를 제안하였다. 또한 초기 처짐 및 잔류 응력을 해석에 반영하여, 다양한 폭-두께비에 해당하는 평판의 비선형 유한 요소 해석을 통해 초기 국부 좌굴 강도 및 좌굴 후 강도를 산정하였다. 이러한 비선형 해석 결과를 이용하여 판의 유효 폭을 산정하였고, 유효 폭을 이용한 철골-콘크리트 합성기둥의 최대 압축 내력식을 제안하였다. 제안식에 의한 계산된 값과 기존의 실험결과를 비교함으로서 제안식의 타당성을 검증하였다.

• 한국해안·해양공학회논문집
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• 제23권1호
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• pp.109-117
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• 2011

국내 경사식 방파제의 대표적인 피복재인 Tetrapod는 대부분 경험식을 사용하여 중량을 산정한다. 경험식은 수리 실험의 결과를 곡선맞춤(curve-fitting)하여 제안되기 때문에 실험 오차에 따른 불확실성이 내포되어 있다. 이런 불확실성을 최소화하기 위해 인경신경망과 M5' model tree를 사용하여 피복재 안정수를 예측하였다. 각 모형의 불확실성의 정도는 예측된 안정수와 수리실험의 안정수 사이의 일치지수(index of agreement)를 사용하여 평가하였다. 일치지수가 가장 큰 인공신경망은 우수한 예측 능력을 가지고 있지만 일반 설계자들이 쉽게 사용할 수 없는 큰 단점이 있다. 반면에 M5' model tree는 인공신경망보다는 예측 능력이 조금 떨어지지만 기존의 경험식보다는 예측능력이 우수하고 또한 일반 설계자들이 쉽게 사용할 수 있는 공식의 형태로 주어지는 장점이 있다.

• 대한한의학방제학회지
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• 제6권1호
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• pp.199-214
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• 1998

This study was performed to prove the antithrombotic effects of DoHongYeum fluid by way of experimental methods. The thrombosis was induced by injection of collagen the mixture (0.1ml/10g, 2mg/kg B.W)plus serotonin (5mg/kg B.W) into the caudal vein of rat, 2 hours after liquid extract of DoHongYeum was oral administration. The effect of the fluid of DoHongYeum was rxamined by the number of RBC and platelets, bleeding time, blood clotting time, death rate, platelet aggregation, plasmacoagulation factor activity, exvivo and fibrinolytic activity of englobulin fracture in the rats. The results were summerized as followings. 1. The number of RBC and platelets was significantly increased in DoHomeYeum group incomparison with the control group. 2. Bleeding time was significantly shortened in DHY group in comparison with the controlgroup. 3. Blood clotting time was significantly prolonged in DHY group in comparison with the control group. 4. The death rate of mouse was inhibited in DHY group in comparison with the control group. 5. The platelet aggregation was inhibited in DHY group in comparison with the control group. 6. The prothrombin time and activated partial thromboplastin time on the test of plasmacoagulation factor activity was prolonged but was not valuable in DHY group. 7. Fibrinogen lyses time of rat was reduced and lyses area was increased in DHY group incomparison with the control group. 8. Fibrinogen lyses time of rat in vitro assay was reduced in DHY group. From the above results, it was thought that the DoHongYeum could be applied effectively in the thrombosis.

• 대한한의학방제학회지
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• 제10권1호
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• pp.81-92
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• 2002

This study was performed to observe the effect of hyulbuchukeo-tang and its component groups on recovery of hepatoxicity in alloxan treated rats. The experimental group was divided into 3 groups: hyulbuchukeo-tang(HCT) and its components groups, sayeok-san(H-sa) and dohong-samul-tang (H-do). The results were obtained as follows: 1. The level of Glucose was considerably reduced by HCT, H-sa, H-do with high significancy. 2. In the change of GOT activity, HCT and H-do were decreased with high significancy, H-do was decreased with some significancy. 3. In the change of GPT activity, HCT was decreased with high significancy, H-sa and H-do were decreased with some significancy. 4. In the change of ${\gamma}-GPT$ activity, HCT was decreased with high significancy, H-do was decreased with some significancy. 5. In the change of ALP activity. only HCT was decreased with some significancy. 6. In the change of LDH activity, HCT was decreased with high significancy, H-sa and H-do were decreased with some significancy. 7. In the change of bilirubin contents. only HCT was decreased with some significancy. As result, hyulbuchukeo-tang(HCT) has significant effects on recovery of hepatoxicity, and its components groups. sayeok-san(H-sa) and dohong-samul-tang(H-do) have some effects. It suggests that sayeok-san(H-sa) and dohong-samul-tang(H-do) have more effects on recovery of hepatoxicity in case of the combination of the two (that is hyulbuchukeo-tang) than in case of the separation.

• 대한한의학방제학회지
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• 제10권1호
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• pp.73-80
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• 2002

We have examined the purgative effect of three Jechun-jun formulas in sprague dawley(SD) rat. Three jechun-jun formulas were Jechun-jun(Sample I ) and augmented Jechun-jun(Sample II) and augmented Jechun-jun add rhubarb(sample III ). We examined the amount and the humidity of feces in rat. The experimental animals were devided into four groups. as control group and three Jechun-jun (sample I, II, III). We administerd the water extract of sample I, II, III to rat per oral for 8days long. After every 24hours measured the amount of wet feces from rats in metabolic cage. Humidity rate of feces from rat was at first measure wet feces for 24hours (W) and measure dried feces (W1) and then we consider W-W1 as humidity. High humidity rate means constipation changes into moistening stool. The amount of wet feces and humidity rate of feces in rats were increased in sample I, II, III. Sample I has highest humidity rate of feces. so showed strong moistening effect. Sample II has mild effect in treating constipation. sample III has most amount of wet feces. in conclusion Jechun-jun has an effect of moistening stool. and augmented Jechun-jun add rhubarb has strong purgative effect.

• 대한한의학방제학회지
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• 제6권1호
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• pp.157-173
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• 1998

The following study looked at the effects of Hyangsayukgunjatang and Hyangsayukgunjatang-ga-kyenegum, moryobun on gastric ulcers in rats. In the 1st experiment, ulcers were induced by method of shay's pylorus-ligated in rats. Subjects were administered 2 kinds of medicine, Hyangsayukgunjatang and Hyangsayukgunjatang-ga-kyenegum, moryobun, which were taken orally. The quantity of gastric juice secretion, total acidity of gastric juice, HCI secretion and serumgastrin content were measured and tissues of gastric mucosa epithelium were observed. 1. The quantity of gastric juice secretion in Hyangsayukgunjatang-treated and Hyangsayukgunjatang-ga-kyenegum, moryobun-treated groups showed significant decrease incomparision with the control group. 2. In relation to total acidity of gastric juice, only Hyangsayukgunjatang -treated groupshowed significant decrease in comparison with the control group. 3. HCI secretion of Hyangsayukgunjatang-treated and Hyangsayukgunjatang-ga-kyenegum, moryobun-treated groups showed significant decrease in comparision with the control group. 4. Content of serum gastrin, which were present in Hyangsayukgunjatang -treated and Hyangsayukgunjatang-ga-kyenegum, moryobun- treated groups showed significant decrease in comparision with the control group. 5. The degree of ulcer occurrence & parietal cell numbers and chief cell numbers of Hyangsayukgunjatang-treated and Hyangsayukgunjatang-ga-kyenegum, moryobun-treatedgroups, which were observed by macrographic & histologic method showed signicant decreasein comparison with the control group. Hyangsayukguniatang-treated group prooved to be increasingly effective. From above the experiment results it can be concluded that Hyangsayukgunjatang will be more clinical effective on curing gastric ulcers induced by method of Shay's pylorus-ligated rather than that of Hyangsayukgunjatang-ga-kyenegum, moryobun.

• 대한한의학방제학회지
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• 제23권1호
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• pp.91-99
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• 2015

Objectives : Herba on lipid levels in serum and lipid accumulation in liver tissue in high fat diet-induced hyperlipidemic mice. Methods : Experimental groups were subdivided into four; Normal diet group (Nor), Hyperlipidemic mice (Con), Lysimachiae Herba water extract administered mice (LWE), Lysimachiae Herba methanol extract administered mice (LME). Thereafter the changes in body weight, total cholesterol, LDL-cholesterol, HDL-cholesterol, triglyceride, AST, ALT, fasting blood glucose in serum were measured. In addition histopathological changes in liver tissue was also observed. Results : Body weight, AST and ALT were not affected by the administration of water or methanol extracts of Lysimachiae Herba. However, methanol extracts of Lysimachiae Herba down regulated the total cholesterol and triglyceride in high fat diet - induced hyperlipidemic mice. Conclusions : In this study, results of total cholesterol and triglyceride showed significant effect in LME compared with LWE, but other results didn’t. Therefore, it is necessary to have more study of Lysimachiae Herba to apply hyperlipidemia.

• 대한한의학회지
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• 제26권2호
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• pp.13-24
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• 2005

Objectives & methods; In order to evaluate the in vivo synergic effect of Mawhangyounpye-tang, a traditional poly-herbal formula used in the treatment of respiratory diseases in Korea, with the quinolone antibiotic ciprofloxacin (CPFX), the viable bacterial number and histopathological changes were monitored after experimental respiratory infection with Streptococcus Pneumoniae ATCC 6303. Results: 1. In CPFX groups, the viable bacterial numbers were significantly decreased compared to that of the control group, and were even more dramatically decreased in concomitant group treated with Mawhangyounpye-tang. 2. In the control group, severe infiltration of inflammatory cells, hemorrhage and hypertrophy of alveolar linings were demonstrated at microscopic levels. However, these abnormal histopathological changes were significantly decreased compared. to that of the control group in CPFX groups, and were even more dramatically decreased in concomitant groups treated with Mawhangyounpye-tang. 3. In CPFX groups, the LSA (Iuminal surface of alveoli $\%$) were significantly increased compared to that of the control group, and more dramatically in concomitant groups treated with Mawhangyounpye-tang. Conclusions: According to these results, it is considered that the in vivo antibacterial activity of CPFX against Streptococcus Pneumoniae ATCC 6303 infection of respiratory tract was dramatically increased by concomitant use of Mawhangyounpye-tang.