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Oscillation dynamics of colloidal particles caused by surfactant in an evaporating droplet
서해원,Narian Jung,Chun Sang Yoo 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2
Surfactant-induced Marangoni flows can alter the typical outward capillary flows in a drying droplet. Previous studies show that intricate time-dependent periodic motions of colloidal particles, such as Marangoni eddies and back-and-forth oscillatory motions, can be developed due to the coupled dynamics of surfactant and evaporation. Here, the temporal motions are investigated using a coarse-grained lattice model. We show that during the evaporation, aggregation and depletion zones of colloidal particles emerge close to the contact line when the capillary and Marangoni flows are comparable in the opposite directions. It is found that the type of periodic motions is determined by the initial surfactant concentration. When the strength of the Marangoni flows is sufficiently large at the early stage of evaporation swirling motions rather than oscillatory motions are developed. The periodic motions of particles persist until the surfactant concentration on the surface is saturated. Also, the onset and terminate times of the motions decrease with the initial surfactant concentration.
徐海源 서울大學校 保建大學院 1968 公衆保健雜誌 Vol.5 No.2
A survey on the status of deaths(5∼19 years of age) in Seoul City was carried out during two months from March to May, 1968. All deaths occurred among the population 5∼19 years of age during 1967 were surveyed by 5 trained and qualified persons and the results were analysed. As the result of this study the following conclusions were obtained. 1. Regarding the number of deaths, male showed more higher rate(1.2 per 1,000 pop.) than female (0.9 per 1,000 pop.). 2. The highest age specific death rate was 1.8 per 1.000 population in the groups of 18 & 19 years of age and the death rate among the group 5∼19 years of age was 1.0 per 1,000 population. 3. In regard to reasons for death the highest number of deaths were occurred by accident (34.0%), which were followed by infectious & parasitic disease and the lowest was cancer & other tumors with 1.7%. 4. The death by drowning showed the highest rate (28.3%) among all deaths due to accident. 5. It was observed that the accidental deaths were more occurred in male than female and more common in summer season. 6. Deaths by tuberculosis occupied 46.0% of all infectious & parasitic diseases. 7. In relation to the location of the lesions, it was found that the highest rate(43.8%) was seen with pulmonary TB which was followed by 32.2% with TB meningitis, and the lowest rate was 1.7% with kidney TB, bone & joint TB and miliary TB respectively. 8. Among the deaths by tuberculosis, the more cases were occurred in the groups with relatively older and younger ages.
양극성 전기응고기구(LigasureTM)를 이용한 치핵절제술:반개방성 치핵절제술과 비교
서해원 대한대장항문학회 2003 Annals of Coloproctolgy Vol.19 No.5
Purpose: LigasureTM is a feedback-controlled bipolar diathermy originally devised to seal vessels and developed to weld tissue bundles. The tissue fusion mechanism consists of melting collagen and elastin, and the tissue welding property of LigasureTM can be used in a hemorrhoidectomy. To confirm the efficacy of LigasureTM in hemorrhoidectomies, I compared it with the conventional semi-open method. Methods: One hundred patients with grade III or IV hemorrhoids were randomly assigned to the LigasureTM (n=50) or the conventional semi-open (n=50) hemorrhoidectomy group. The operation time, the postoperative analgesic requirement, the hospital stay, the time to return to normal life, and complications were prospectively recorded and analyzed. Results: There was no difference in sex and age between the two groups. The operation time was markedly shorter in the LigasureTM group than semi-open group (10.8±4.0 versus 23.7±5.2 min; P<0.001). Although the hospital stay was not statistically different, the time to return to the normal life was shorter in the LigasureTM group (9.5±3.8 versus 12.7±4.0 days; P<0.05). The requirement for postoperative analgesics within 48 hours (nalbuphine, 5mg) was not significantly different. In each group, an urinary retention was noted and treated with urinary catheterization. In LigasureTM group, an anal stenosis was developed and was successfully treated with advancement flap surgery. In each group a secondary bleeding and a skin tag were noted. There was no wound infection or incontinence. Conclusions: LigasureTM hemorrhoidectomy reduces the operation time and the time to return to the normal life. If anal stenosis is to be prevented, careful attention is required to preserve the anal skin and mucosa. LigasureTM is simple to use and is useful in the treatment of patients with grade III or IV hemorrhoids.
서해원,서이수,권순석 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.-
The theoretical study addresses the nature of motions and heat transfer in confined rectangular enclosure heated from below and colled on the top simultaneously subject to themal wall conditions that the side walls are insulated or cooled alternately. Also the flow dynamics and the characteristics of convective performance are argued in the numerical scheme by using Grashof no. and Reynolds no. as variable parameters according to the moving conditions in which the natural convections are discussed for fixed condition and the forced and mixed convection also discussed for moving wall at constant speed. It is envisaged that follows below The circulation velocity caused by the buoyant effects exhibits the tendency toward increasing at low Reynolds no., especially this trend is obvious near Re=100. As Re no. is increased, the vortexflow produced at the corners in the low part is inclined to develop thus reduce heat transfer, especially this phenomenon turns to be clear by the advancement of multi-cell at Gr=10^5 and Re=400∼500. The vortex also occurs in the corner under the natural convection, however the effects of the eddy on the heat transfer seems to be more insignificant than in the forced and mixed case. It is also shown that the point at which heat transports best tends to shift from right to left as Re no. is increased, and the reduction of heat transfer neighbouring the wall side is remarkable inproportion to Grashof number.
결막이완증 환자에서 백내장 수술 중 통증 경감을 위한 결막 보호막의 효과
서해원,최석규,이도형,김진형,Hae Won Seo,Suk Kyue Choi,Do Hyung Lee,Jin Hyoung Kim 대한안과학회 2013 대한안과학회지 Vol.54 No.1
Purpose: To evaluate the effect of conjunctival shield on pain alleviation during cataract surgery in conjunctivochalasis patients for conjunctiva drawn into speculum suction holes during cataract surgery. Methods: Forty patients with conjunctivochalasis undergoing cataract surgery using un aspirating speculum were evaluated in the present study. A thin piece of surgical wipe (conjunctival shield) was inserted between the lid and bulbar conjunctiva to shield the conjunctiva from the suction hole and thereby prevent it from being sucked into the hole. Additionally, patients were asked to rank pain following speculum placement both before and after conjunctiva shield insertion by visual analogue scale. Results: The pain scores were 2.50 ± 0.78 points before conjunctival shield insertion, and 1.25 ± 0.66 points after conjunctival shield insertion, which was a significant decrease (p = 0.01). In addition, the results showed a 70% reduction in pain following shield insertion. Conclusions: Conjunctivochalasis causes pain during cataract surgery when using an aspirating speculum. The conjunctival shield insertion is a safe and simple method for pain-free cataract surgery in conjunctivochalasis patients.
타카야수동맥염 환자에서 발생한 포도막염 및 각막염 1예
서해원,김진형,이도형,이종현,Hae Won Seo,Jin Hyoung Kim,Do Hyung Lee,Jong Hyun Lee 대한안과학회 2012 대한안과학회지 Vol.53 No.10
Purpose: To report a rare case of simultaneous uveitis and keratitis in Takayasu’s arteritis. Case summary: A 22-year-old woman presented with complaints of redness and decrease in vision in both eyes. The patient was diagnosed a decade earlier as having Takayasu’s arteritis. No other systemic or ophthalmic abnormalities were found. She complained of ophthalmic symptom aggravation during an upper respiratory infections and before menstruation. Bilateral corneal edema, conjunctival injection, and anterior uveitis were observed on slit-lamp examination. Concurrent treatments were started in consultation with an internist. Steroid eye drop and steroid systemic administration relieved the ocular pain and symptoms. Conclusions: When a patient presents with recurrent red eyes and visual disturbances with Takayasu’s ateritis, simultaneous uveitis and keratitis due to Takayasu’s arteritis should be considered as a possible diagnosis. J Korean Ophthalmol Soc 2012;53(10):1528-1531