• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.2
• /
• pp.24-30
• /
• 2016

An experimental study for the characteristics of the thrust-vectoring of a sonic jet utilizing the coanda flap installed at a rectangular nozzle exit is performed. Two side plates are installed at both sides of the flap to decrease the three dimensional effects of the jet on the flap surface. Schlieren flow visualizations and quantitative measurements of the deflection angle of thrusting vector show that the side plates are able to delay the separation of the jet at the downstream of the flap surface. Substantial increase in the deflection angle of the jet as high as $72^{\circ}$ and small thrust loss as low as 7% are obtained by the present thrust-vectoring technique using the side plates.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1070_1071
• /
• 2009

Recently, small hydropower attracts attention because of its clean, renewable and abundant energy resources to develop. Therefore, a cross-flow hydraulic turbine is proposed for small hydropower development in this study. The turbine‘s simple structure and high possibility of applying to the sites of relatively low effective head and large flow rate can be advantages for the introduction of the small hydropower development. The purpose of this study is not only to investigate the effects of air layer in the turbine chamber on the performance and internal flow of the cross-flow turbine, but also to suggest a newly developed air supply method. CFD analysis for the performance and internal flow of the turbine is conducted by an unsteady state calculation using a two-phase flow model in order to embody the air layer effect on the turbine performance effectively. The result shows that air layer effect on the performance of the turbine is considerable. The air layer located in the turbine runner passage plays the role of preventing a shock loss in the runner axis and suppressing a recirculation flow in the runner. The location of air suction hole on the chamber wall is very important factor for the performance improvement. Moreover, the ratio between air from suction pipe and water from turbine inlet is also significant factor of the turbine performance.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
• /
• 2008.10a
• /
• pp.153-161
• /
• 2008

Agriculture and forest are basis for livelihood in Nepal while both sectors constitute around 40 percent of the national product and over two-thirds of the economically active population is dependent on agriculture. However, radical changes in land use, depletion in crops production and food availability are major threats due to loss of soil fertilityand severe environmental degradation. In this study, we used time series data from 1986/87 to 2005/06 about food crop production and population published by Government of Nepal, Ministry of Agriculture and Cooperatives and Central Bureau of Statistics. Descriptive statistics and ArcGIS were used to assess and map the food security status of Nepalese Terai based on the local food demand and supply system. Food supply to demand ratio(FSDR) was the main idea of assessment. Our results showed that out of 20 districts, only 8 districts were categorised under secured food districts whereas 5 districts were still under food unsecured situation. The analysis further revealed that 7 districts had faced food deficit more than 8-16 times during the last 20 year periods. Data further showed that there was surplus food supply relative to the requirements dictated by FSDR. However, the average FSDR was less than 1.2(less than 20% surplus) exploring fact that most of the districts were not producing sufficient food to cope up the food shock and after 1995 it was relatively stagnant. Our prediction reveals that food supply in Terai even in the future would remain at almost the same level as now, and there will not more than 16-17% surplus by 2021 considering medium vibrant population growth. The findings thus, indicate that Terai may not be a food secure region in the future, even though the region is considered as a food storage house of Nepal. In addition, this paper suggests ways to make future comprehensive case studies more widely comparable in Terai, Nepal.

• Journal of Life Science
• /
• v.24 no.9
• /
• pp.1019-1024
• /
• 2014

Skeletal muscle atrophy can be defined as a decrease in or a disease of the muscle tissue, or as a disorder of the nerves that control the muscle, through injury or lack of use. This condition is associated with reactive oxygen species (ROS), resulting in various muscular disorders. Exposure to ROS induces muscle atrophy through several biological factors, such as SOD1 and HSP70. We found that cymbidium root extract reduced the $H_2O_2$-induced viability loss in C2C12 myoblasts and inhibited apoptosis. In addition, we showed that the cymbidium root extract increased the expression of HSP70 and decreased the expression of SOD1 in the $H_2O_2$-induced C2C12 myoblasts. These results suggest that cymbidium root extract might have therapeutic value in reducing ROS-induced muscle atrophy.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.22 no.5
• /
• pp.66-72
• /
• 2018

A numerical study was conducted to investigate the performance characteristics of a STED with various pressure ratios (PRs) and cone shapes. Due to momentum loss, the pressure in vacuum chamber increased with cone angle for a PR of 75. Also, the STED is started between PRs of 36 and 37 in the case of a cone angle of $15^{\circ}$ and a blockage ratio (BR) of 15%. The results for various PRs and cone shapes are presented, and the optimal cone shape is found to have a cone angle of between $5{\sim}20^{\circ}$ and a BR of between 15~40%.

• Journal of Biosystems Engineering
• /
• v.30 no.3 s.110
• /
• pp.147-154
• /
• 2005

The improved hitch device, which connecting the trailer to power tiller, was developed. This device, composed with spring and rubber, could reduce the vibration and shock levels during driven on off-road. The vertical vibration accelerations for the improved hitch device were measured at 6 positions, i.e. engine, hitch, seat, and three points in trailer (front, middle, and rear) for not driving but at low engine speed of 500 rpm, and compared with the existing hitch device. The results of this study could be summarized as follows; The average vibration acceleration up to 120 Hz was $0.4m/s^2$ at engine part, but it was 0.08 and $0.05m/s^2$ at trailer for existing and improved hitch device, respectively. About $38\%$ of average acceleration level could be absorbed for the improved hitch device compared with existing hitch device. The average vibration acceleration up to 40 Hz was reduced to 0.12 and $0.06m/s^2$ at trailer for existing and improved hitch device respectively, showing the reduction effect of $50\%$. The maximum acceleration occurred at up to 20 Hz of low frequency was much higher than total acceleration occurred at up to 120 Hz, which means that much loss or damage could be occurred during transporting of agricultural products on off-road. The portions of average acceleration occurred at up to 20 Hz of low frequency were $27\%\;and\;21\%$ for the existing and improved hitch device, respectively.

• The Journal of the Korea Contents Association
• /
• v.8 no.10
• /
• pp.259-267
• /
• 2008

This research will examine the probabilities of future global resource crisis and what significance and effect will come upon our economy through the rise of the cost of resources. From now on, the lack of the supply of global resources will dull the world economic growth. Not only that, but the direction of each country's economic development will be decided by the appropriate measure to the resource crisis. If we are to sustain this inefficient industrial structure, as a country with high dependancy on foreign resources, Korea might face macroeconomic shock and the loss of industrial competitiveness. Therefore, we must increase the efficiency of the resource usage in the manufacturing industry such as the chemical and steel industry, and now is a period when we must add high value to our products. Henceforth, the structural constraints of supply will be the root cause of resource crisis. Thus, we must lead the subject of the economic agencies, such as companies and consumers, so that they will be able to adapt to a new paradigm called the fundamental lack of resources, rather than temporal crisis management. The Korean economy must adjust the environment for industry transformation to be achieved.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.29 no.12
• /
• pp.654-662
• /
• 2017

When emergency core cooling system (ECCS) is operated during loss of coolant accident (LOCA) in a pressurized water reactor (PWR), pressurized thermal shock (PTS) phenomenon can occur as cooling water is injected into a cold leg, mixed with hot primary coolant, and then entrained into a reactor vessel. Insufficient flow mixing may cause temperature stratification and steam condensation. In addition, flow vibration may cause thermal stresses in surrounding structures. This will reduce the life of the reactor vessel. Due to the importance of PTS phenomenon, in this study, calculation was performed for Test 1 among six types of OECD/NEA ROSA tests with ANSYS CFX R.17. Predicted results were then compared to measured data. Additionally, because temperature difference between the hot coolant at the inlet of the cold leg and the cold cooling water at the inlet of the ECCS injection line is 200 K or more, buoyancy force due to density difference might have significant effect on thermal-hydraulic characteristics of flow. Therefore, in this study, the necessity to include buoyancy force term in governing equations for accurate prediction of single phase thermal stratification in both cold legs and downcomer by ECCS injection was numerically studied.

• The Journal of Korean Physical Therapy
• /
• v.26 no.6
• /
• pp.418-424
• /
• 2014

Purpose: This study was performed to investigate the effect of joint mobilization on pain relief and cartilage repair in an induced osteoarthritis rat model by analyzing the expression of heat shock protein 70 in articular cartilage. Methods: MIA was injected into SD rats to induce osteoarthritis. These rats were divided into 4 groups: control group (n=30), no further treatment after the MIA injection ; experimental group I(n=30), performed swimming exercise after the MIA injection experimental group II (n=30), underwent joint mobilization after the MIA injection and experimental group III (n=30), performed swimming exercise and underwent joint mobilization after the MIA injection. For the histologic and pathophysiologic evaluation, safranin-O staining and for the immunohistochemical evaluation, the expression of HSP 70 in articular cartilage was analyzed 1, 7, 14, and 21 days after the MIA injection. Results: The inflammatory response and loss of tissue declined in experimental groups I and II over time, whereas the greatest decreases were noted in experimental group III. In the articular cartilage, low expression of HSP 70 was observed in every group on day 1, whereas HSP 70 expression was elevated on days 7 and 14 in experimental groups II and III. After 21 days, experimental group II displayed the strongest positive reaction, whereas HSP 70 was higher in experimental group III at this time point compared to that after 14 days. Conclusion: Our results showed that swimming exercise and joint mobilization had positive effects on pain relief and histologic and functional recovery in an induced osteoarthritis rat model.

• The Journal of Internal Korean Medicine
• /
• v.44 no.5
• /
• pp.1050-1061
• /
• 2023

This study reported the case of a patient with quadriparesis due to cerebral aneurysm rupture, subarachnoid hemorrhage, and intraventricular hemorrhage (IVH) treated with Korean medicine. The patient was treated with acupuncture, herbal medicine (mainly Tonggyuhwalhyeol-tang-gagam), Western medicine, moxibustion, cupping, and rehabilitative therapy for 75 days, and improved after administration. After treatment, the Manual Muscle Test grade improved from 4/4-/3+/3 to 4+/4+/4+/4+, the Korean version of the modified Barthel Index score improved from 9 to 100, the National Institute of Health's Stroke Scale score improved from 2 to 0, the Global Deterioration Scale score improved from 3 to 2, and the Korean version of the Mini-Mental State Examination score improved from 22 to 30. During administration, the patient did not show seizures, shock, or loss of consciousness, and the vital signs were stable in the normal range. We followed up the brain computed tomography findings for 2 times and found that there was no definite evidence of intracranial hemorrhage or IVH or re-rupture or rebleeding after Korean medicine treatment. This study suggests that Korean medicine treatment with blood-invigorating and stasis-removing herbs could be a safe and effective intervention option for improving quadriparesis due to cerebral aneurysm rupture and subarachnoid hemorrhage.