• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.649-652
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• 2011

A series of hybrid rocket combustion experiments were carried out with PMMA/GOx changing diameter and length of the disk installed at pre-chamber. The disk can generate vortex shedding flow and change flow conditions prior to entering the fuel grain which could also alter the combustion characteristics and pressure oscillations. Isolated dimple-like surface roughness patterns distributed all over the fuel surface, which can be thought of as a realization of the inherent flow instability. It is very likely that the formation of cell structures is originated from the modification of boundary layer characteristics of an entering oxidizer flow caused by a blowing effect mainly taking place near the wall. This coincided with our LES results. It would be a meaningful basis to understand combustion instability of hybrid rocket motor.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.4
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• pp.345-356
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• 2004

Open-cut method has been widely used to construct underground structures, but it causes several problems such as traffic congestion and public resentment resulting from severe construction noise and ground settlement. In many cases, it is very difficult to build underground structures safely due to the unknown locations of buried facilities such as water pipes, drainage pipes, gas pipes and high-pressure cable conduits etc. Also in open-cut method, moving buried facilities causes additional cost and extension of construction period. Therefore, this paper is to present a case study in which Tubular Roof construction Method (T.R.c.M.), a newly developed construction method for underground structures using slab steel pipes and PC wall trench, is applied for the construction of a subway tunnel in Seoul. As a result, it is found that T.R.c.M. is a construction method by which tunnels can be constructed safely without any effect on the surrounding environment and traffic flow due to the minimized construction vibration and noise.

• Journal of Advanced Navigation Technology
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• v.21 no.1
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• pp.126-131
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• 2017

This paper designs a smart safety measurement system with Bluetooth beacon sensor nodes that can provide risk detection and evacuation/countermeasure services. The Bluetooth beacon sensor nodes is easily able to be attached to old building wall or construction or civil structure with potential danger. The proposed smart safety measurement system transmits various sensor data such as acceleration, gyroscope, geomagnetic, pressure, altitude, temperature, humidity at the spot where Bluetooth beacon sensor nodes are installed, and we can use them for risk perception, prediction, and warning services. To verify the effectiveness of the proposed system, we performed filed tests which showed that measured displacement values of precast retaining walls were within the permitted displacement value of 38.5 mm.

• Journal of Korean Neurosurgical Society
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• v.30 no.3
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• pp.371-375
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• 2001

Intracranial hemorrhage due to preeclampsia in the postpartum woman is rarely documented. Generally, the incidence of stroke is increased during pregnancy and early postpartum. Preeclampsia is considered a main cause of both nonhemorrhagic and hemorrhagic stroke. We present a 32-year-old woman who had intracranial hemorrhage at 5 days postpartum. At admission, her consciousness was semicomatose with elevated blood pressure. Computerized tomography revealed intracranial hemorrhage on right frontal lobe. Additional angiography did not reveal abnormal vascular lesion. Emergency craniectomy with hematoma removal was done. However, the patient showed no recovery and died 2 weeks later. We conclude that postpartum care of preeclampsia is important to prevent intraparenchymal hemorrhage. Relative high risk of stroke during the postpartum period suggests a causal roles for the large decrease in blood volume or the rapid changes in hormonal status that follow a live birth or stillbirth, perhaps by means of hemodynamics, coagulative, or vessel wall changes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.3
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• pp.167-175
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• 2009

In this study, condensation heat transfer coefficients(HTCs) of R22, R123, R134a and R245fa are measured on both 26fpi low fin and Turbo-C tubes. All data are taken at the vapor temperature of $39^{\circ}C$ with a wall subcooling of $3{\sim}8^{\circ}C$. Test results show that HTCs of the newly developed low vapor pressure alternative refrigerant, R245fa, are $7.8{\sim}9.2%$ and $10.3{\sim}18.6%$ higher than those of R123 for 26fpi low fin tube and Turbo-C tube respectively. For all refrigerants tested, HTCs of Turbo-C enhanced tube are higher than those of 26fpi low fin tube. For the low fin tube, Beatty and Katz's prediction equation yielded 20% deviation for all fluids. The heat transfer enhancement ratio of R245fa on the Turbo-C tube is $5.9{\sim}6.4$ while that of R123 is $5.7{\sim}5.9$. From the view point of environmental safety and condensation heat transfer, R245fa is a long term candidate to replace R123 currently used in centrifugal chillers.

• Korean Journal of Veterinary Service
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• v.40 no.1
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• pp.67-70
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• 2017

A 4 months old, intact male Shih-tzu was referred to the Veterinary Medical Teaching Hospital of Chungnam National University for evaluation of the cause of cardiac murmur and syncope. Thoracic radiography revealed right-sided cardiomegaly. Echocardiography showed marked hypertrophy of right ventricular free wall and obstruction of right ventricular outflow tract, indicating double chambered right ventricle (DCRV). The dog was medicated with atenolol and sildenafil for DCRV, however, clinical signs did not control by medication. Balloon dilation for DCRV was performed to ameliorate patient's clinical signs. The peak systolic pressure gradient across the obstruction region was decreased and clinical signs was improved by balloon dilation procedure. This is the first case report of balloon dilation for the treatment of canine DCRV in South Korea.

• Journal of Chest Surgery
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• v.23 no.6
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• pp.1057-1066
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• 1990

The possible relationship between pulmonary vascular pathologic changes and an increased pulmonary blood flow and pulmonary blood pressure has been the subject of investigation for many years. In an attempts to study the effects of increased pulmonary blood flow. long-term observations have been made in neonatal goats in which the total pulmonary vascular bed was restricted by means of ligation of left pulmonary artery, thereby diverting the total right ventricular output through the right lung. The left pulmonary artery and patent ductus arteriosus were ligated in 6 neonatal goats of under 3 weeks of age, and the goats were put to death at interval between 1 and 7 months of age. Pulmonary arterial development in both right and left lungs was studied by applying quantitative morphometric techniques, and compared with control group of goats between 1 and 6 months of age. The axial pulmonary artery and its branches were larger in the right lung than in the control group in all animals, and they were abnormally small in the left lung. In the right lung, arteries smaller than 50\ulcornerm showed abnormal increase in `% wall thickness’ in postoperative 2,3,5 and 6th months[p<0.05]. The proportion of non-muscular arteries was over 50% at postoperative 1st month in both right and left lungs, but an increase in proportion of partially muscular and wholly muscular arteries occurred thereafter. The ratio of alveoli/arteries was lower than normal in the right lung of postoperative 1st month[p<0.05], but was elevated thereafter. The failure to perfuse one pulmonary artery in neonatal goats changed growth and development of both lungs.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.34-40
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• 2006

For a cooling performance research of the combustor operated in a extreme environment of a high temperature and high pressure, we accomplished a cooling performance analysis. Generally a heat transfer characteristic in cooling passage is known well experimentally and theoretically, however heat flux in the combustion chamber isn't. In this study, fluid flow combined with heat transfer and thermal structural analysis is accomplished about a combustor nozzle. We tried to analyze the cooling performance with a heat transfer characteristic of a gas and coolant side in the view point of quantity on the mass flow rate to be supplied to the cooling channel. And finally, evaluation on the thermal and structural safety of nozzle wall material was accomplished.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.963-971
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• 2008

Unsaturated soil mechanics has been often used to find out a cause of failure (tensile failure) of retaining walls and hill slopes containing sandy soils. Checking shear strength is a popular method by considering suction stress developed form pore water menisci among the grains and saturated pockets of pore water under negative pressure. Linear Mohr-Coulomb failure criterion is generally adopted as a failure criterion. However, depending on relative density, stress history, and the magnitude of stress, the failure behavior of sand may not follow linear M-C frictional behavior. For stress in the large compressive ranges, say from tens to hundreds of kPa, the linear M-C criterion is an adequate representation for the shear strength behavior of sand. However, less than tens of kPa, the M-C criterion often can not be accurately represented. Depending on failure criterion, the uniaxial tensile strength is different over 100% relative error. For sand behavior under small compression regimes, therefore, such as under low or zero gravity, or under undergoing tensile failure in the crest area of hill slopes or behind retaining walls, it is important to consider the non-linear behavior.

• Tuberculosis and Respiratory Diseases
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• v.65 no.3
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• pp.222-224
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• 2008

Spontaneous pneumomediastinum is defined as a clinical syndrome that's characterized by the presence of air in the mediastinal space, which is not due to an old previous injury or surgery. The condition is caused by a sustained increase in the intraalveolar and intrabronchial pressure with extravasated air dissecting along the perivascular spaces of the mediastinum. This is an uncommon complication of sports activity. The most common symptom is chest pain. This diagnosis should be considered for younger people who present with pleuritic chest pain or dyspnea and a characteristic crackling feel (known as subcutaneous crepitation) when touching of the skin covering the chest wall or neck, and they look otherwise well with normal vital signs. Usually no treatment is required, but the mediastinal air will be absorbed faster if the patient inspires high concentrations of oxygen. We present here a case of spontaneous pneumomediastinum that occurred during a Taekwondo match, along with a review of the relevant literature.