• 대한기계학회논문집B
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• 제27권5호
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• pp.668-676
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• 2003

The effect of nozzle height on heat transfer of a hot steel plate cooled by an impinging liquid jet is not well understood. Previous studies have been based on the dimensionless parameter z/d. To test the validity of this dimensionless parameter and to investigate gravitational effects on the jet, stagnation velocity of an impinging liquid jet were measured and the cooling experiments of a hot steel plate were conducted for z/d from 6.7 to 75, and an inverse heat conduction method is applied for the quantitative comparison. Also, the critical instability point of a liquid jet was examined over a range of flow rates. The experimental velocity data for the liquid jet were well correlated with the dimensionless number 1/F $r_{z}$$^2$based on distance. It was thought that the z/d parameter was not valid for heat transfer to an impinging liquid jet under gravitational forces. In the cooling experiments, heat transfer was independent of z when 1/F $r_{z}$$^2$< 0.187(z/d = 6.7). However, it was found that the heat transfer quantity for 1/F $r_{z}$$^2$=0.523(z/d = 70) is larger 11% than that in the region for 1/F $r_{z}$$^2$=0.187. The discrepancy between these results and previous research is likely due to the instability of liquid jet.uid jet.

• 대한기계학회논문집B
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• 제26권5호
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• pp.629-639
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• 2002

In-vitro flow characteristics downstream of a polyurethane artificial heart valve and a Bjork-Shiley Monostrut mechanical valve have been comparatively investigated in pulsatile flow using particle image velocimetry (PIV). With a triggering system and a time-delayed circuit the velocity distributions on the two perpendicular measurement planes downstream of the valves are evaluated at any given instant in conjunction with the opening behaviors of valve leaflets during a cardiac cycle. The regions of stasis and high shear stress can be found simultaneously by examining the entire view of the instantaneous velocity and Reynolds shear stress fields. It is known that high shear stress regions exist at the interface between strong axial jet flows along the wall and vortical flows in the central area distal to the valves. In addition. there are large stagnation or recirculation regions in the vicinity of the valve leaflet, where thrombus formation can be induced by accumulation of blood elements damaged in the high shear stress zones. A correlation between the unsteady flow patterns downstream of the valve and the corresponding opening postures of the polyurethane valve membrane gives useful data necessary for improved design of the frame structure and leaflet geometry of the polyurethane valve.

• Korea-Australia Rheology Journal
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• 제16권4호
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• pp.183-191
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• 2004

High Deborah or Weissenberg number problems in viscoelastic flow modeling have been known formidably difficult even in the inertialess limit. There exists almost no result that shows satisfactory accuracy and proper mesh convergence at the same time. However recently, quite a breakthrough seems to have been made in this field of computational rheology. So called matrix-logarithm (here we name it tensor-logarithm) formulation of the viscoelastic constitutive equations originally written in terms of the conformation tensor has been suggested by Fattal and Kupferman (2004) and its finite element implementation has been first presented by Hulsen (2004). Both the works have reported almost unbounded convergence limit in solving two benchmark problems. This new formulation incorporates proper polynomial interpolations of the log­arithm for the variables that exhibit steep exponential dependence near stagnation points, and it also strictly preserves the positive definiteness of the conformation tensor. In this study, we present an alternative pro­cedure for deriving the tensor-logarithmic representation of the differential constitutive equations and pro­vide a numerical example with the Leonov model in 4:1 planar contraction flows. Dramatic improvement of the computational algorithm with stable convergence has been demonstrated and it seems that there exists appropriate mesh convergence even though this conclusion requires further study. It is thought that this new formalism will work only for a few differential constitutive equations proven globally stable. Thus the math­ematical stability criteria perhaps play an important role on the choice and development of the suitable con­stitutive equations. In this respect, the Leonov viscoelastic model is quite feasible and becomes more essential since it has been proven globally stable and it offers the simplest form in the tensor-logarithmic formulation.

• 한국추진공학회지
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• 제16권1호
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• pp.36-44
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• 2012

친환경 추진제인 고농도 과산화수소와 케로신을 추진제로 사용하는 다중 분사기 액체 로켓 엔진을 설계하였다. 엔진의 설계 요구 조건을 결정한 후 엔진의 주요 형상 치수를 이론적인 배경을 통하여 결정하였다. 다중 분사기는 6개의 분사기를 장착하였으며, 상용 해석 툴을 이용하여 과산화수소 매니폴드 내의 유동 해석을 수행하여 매니폴드 내에서 균일한 유량분포 및 냉각성능 확보를 위해 유동 정체 구간과 재순환 영역을 최소화하였다. 매니폴드 유동장 해석 결과를 바탕으로 유동이 최적화 되는 다중 분사기를 제작하였으며, 수류 실험을 통하여 추진제의 유량, 분무각 및 분무 성능을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제24권2호
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• pp.197-204
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• 2003

The intracluster ion-molecule reactions of $Ti^+(H_2O)_n,\;Ti^+(CH_3OCH_3)_n,\;and\;Ti^+(CH_3OD)_n$ complexes produced by the mixing of the laser-vaporized plasma and the pulsed supersonic beam were studied using a reflectron time-of-flight mass spectrometer. The reactions of $Ti^+$ with water clusters were dominated by the dehydrogenation reaction, which produces $TiO^+(H_2O)_n$ clusters. The mass spectra resulting from the reactions of $Ti^+\;with\;CH_3OCH_3$ clusters exhibit a major sequence of $Ti^+(OCH_3)_m(CH_3OCH_3)_n$ cluster ions, which is attributed to the insertion of $Ti^+$ ion into C-O bond of $CH_3OCH_3$ followed by $CH_3$ elimination. The prevalence of $Ti^+(OCH_3)_m(CH_3OD)_n$ ions in the reaction of $Ti^+\;with\;CH_3OD$ clusters suggests that D elimination via O-D bond insertion is the preferred decomposition pathway. In addition, the results indicate that consecutive insertion reactions by the $Ti^+$ ion occur for up to three precursor molecules. Thus, examination of $Ti^+$ insertion into three different molecules establishes the reactivity order: O-H > C-O > C-H. The experiments additionally show that the chemical reactivity of heterocluster ions is greatly influenced by cluster size and argon stagnation pressure. The reaction energetics and formation mechanisms of the observed heterocluster ions are also discussed.

• 대한한방부인과학회지
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• 제28권2호
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• pp.40-54
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• 2015

Objectives : In the theory of Korean medicine, Citri Reticulatae Viride Pericarpium (CRVP) can soothe the liver to break qi stagnation, eliminate mass and relieve dyspepsia. This study was carried out to investigate the effects of CRVP on the apoptotic cell death in breast cancer cells. Methods : In the present experiment, the effects of CRVP on proliferation rates, type of cell death, cell cycle distribution, and intracellular oxidative stress were investigated using MDA-MB-231 cells in vitro. In addition, the effects on expression levels of caspase 3, caspase 9, Bax and Bcl-2 were also investigated. Results : Treatment with CRVP decreased proliferation rates in a dose dependent manner. ID50 (50% inhibitory dosage) was 175.4 μg/ml. In the CRVP treated group, cell volumes showed smaller than non-treated normal. In addition, CRVP increased percentage of apoptotic and sub G1 arrested cells respectively. 200 μg/ml of CRVP treatment increased intracellular ROS level significantly. Finaly the expression level of caspase 3 and Bax/Bcl-2 ratio were elevated by treatment with CRVP respectively. Conclusions : These results suggest that CRVP can trigger intrinsic apoptotic pathway in MDA-MB-231 cells.

• 한방안이비인후피부과학회지
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• 제29권4호
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• pp.114-130
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• 2016

Objectives : This study is performed to investigate the therapy on tinnitus through the literature of Eastern and Western medicine. Methods : This study review the definition, etiology, classification, internal and external methods of treatment of tinnitus based on 50 articles of Eastern medicine, 16 articles of Western medicine about the treatment of tinnitus. Results : The results were as follows. 1. In Eastern medicine, the cause and mechanism of disease of tinnitus arose from the state of qi-blood deficiency, internal dampness-heat and depression stagnation. In Western medicine, there are mainly caused by damage to the auditory system the lower induced changes in the upper. 2. In Eastern medicine, differentiation of syndromes classifies clinical aspects, and cause and mechanism of disease. In Western medicine, it divides into an generating region, clinical and associated symptoms aspects. 3. In Eastern medicine, internal method of treatments of tinnitus are divided into four treatments. In Western medicine, internal methods of tinnitus are vasodilators, blood-flow improvers, Metabolism improvers etc. 4. In Eastern medicine, external method of treatments of tinnitus are paste preparation method, powder preparation method, pill preparation method, acupuncture & moxibustion method. In Western medicine, external method of treatments of Tinnitus are divided into injection, other surgical therapies and adjuvant therapy. Conclusions : Until now, there is no perfect, effective single treatment. We think that Eastern medicine approach and treatment can be helpful to overcome the limitations of tinnitus cure.

• 한방안이비인후피부과학회지
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• 제29권4호
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• pp.1-13
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• 2016

Objectives : The purpose of this study is to compare hair and alopecia of Korean Medicine with those of western medicine. Methods : We studied relationships between hair and essense(精), qi(氣), blood(血), five vicera(五臟) and meridians(經絡) through literature review about hair and alopecia. We compared Korean medicine with western medicine on physiology of hair and treatment of alopecia based on the study. Results & Conclusion : 1. Congenital essense(先天之精) is related with genetic factor and acquired essence(後天之精) is connected with nutritional factor. Defending function of Defense qi(衛氣) is related with immune reaction and qi stagnation(氣鬱) is associated with stress reaction. Atrophy of vascular tissues observed in alopecia scalp means deep relationship between blood(血) and alopecia, further deficiency of blood can cause telogen effluvium. 2. Kidney qi(腎氣) is related with inhibiting combination of Androgen receptor and Dihydrotestosterone(DHT) or activating hair growth factior. Pi(脾) is connected with alopecia seborrheica caused by damp-heat(濕熱) and alopecia areata caused by excessive prudence(思慮過度). Heart(心) is associated with atrophy in vascular tissue of scalp and liver(肝) is connected with metabolism. 3. Armpit hair and pubic hair as secondary sex characteristics are realated with Yangming Meridian(陽明經) and beard and hair at crown part where Type II $5{\alpha}$-reductase is activated much are associated with Taiyang Meridian(太陽經). 4. Juglandis Semen pharmacopuncture and Ganoderma lucidum pharmacopucture have better effects on inhibit $5{\alpha}$-reductase than Finasteride. Minoxidil and PRP are similar with promoting blood flow and removing stasis(活血祛瘀). Seven-star needling(七星針) is similar with microneedling. 5. Alopecia can be caused by due to lack of circulation Views we need solution to improve circulation coincide in opinion with Korean Medicine and Western medicine.

• 대한한방내과학회지
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• 제21권1호
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• pp.162-168
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• 2000

Irritable Bowel Syndrome(IBS) is the most common disease in the western male, and it is founded in $70{\sim}80%$ patient who has Gastrointestinal trouble. It is characterized by the formation of disorders of Gastrointestinal tract, for example, constipation, diarrhea, abdominal pain& discomfort, stool urgency, and so on. The etiology of IBS is uncertain, but the majority of patients has emotional problems. The aims of this study are to investigate and summarize the current trends of treatment for IBS so as to suggest the effective and available way to treat this disease. In Oriental Medicine, the IBS is recognized as Stagnation of the Iiver-qi(肝氣鬱結), Incoordination between the liver and the stomach(肝胃不和). So the point of treatment of IBS is Invigorating the spleen and relieving the depression of Iiver-qi(疏肝健脾), Regulating the function of the liver and the flow of qi(調肝理氣), Regulating the stomach and lowering the adverse flow(和胃降逆), and the treatment can be approached in several ways through herb drugs, acupuncture. Some of the herb drugs have substances which promote gastric and small intestinal emptying. Acupuncture and moxibustion therapies stimulate the meridian points of LR(足厥陰肝經), ST(足陽明胃經), LI(手陽明腸經), SI(手太陽小腸經) and is reported to be effective for releafing syndromes. Anal therapy, attachment of herb drug to umbilicus are annunced as the effective treatments. So, this study of the approach and application of these treatments on IBS would be necessary.

• 대한한방내과학회지
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• 제34권2호
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• pp.122-133
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• 2013

Objectives : Burning mouth syndrome (BMS) is characterized by chronic pain or a burning sensation in the mouth. There is limited evidence available to provide clear guidelines for treating BMS patients and a variety of different treatments have been used. This study was designed to investigate the Effects of Korean medicine therapies on oral pain in patients with BMS. Methods : We surveyed 30 BMS patients who newly visited the Oral Diseases Clinic in the Kyung Hee University Korean Medicine Hospital from February 2012 to March 2013. When the patients visited the clinic for the first time, they were evaluated on sociodemographic characteristics, BMS questionnaire, severity of pain using visual analogue scale (VAS) and pressure pain threshold (PPT) of the acupuncture point CV17. After 3 weeks of Korean medicine therapies (acupuncture, electroacupuncture, pharmacopuncture and herbal medicine), they were re-evaluated with the VAS and the PPT. Results : After 3 weeks of Korean medicine therapies, 30 patients' oral pain improved and the PPT score on CV17 rose, which means decrease of qi-stagnation score. Conclusions : Korean medicine therapies were effective on oral pain in patients with BMS. To confirm the additional curative effect and evaluate the efficacy of each treatment, well-designed randomized controlled trials will be needed in the future.