• Journal of Korean Neurosurgical Society
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• v.46 no.5
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• pp.451-458
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• 2009

Objective : The purpose of this study was to analyze risk factors that are associated with intracranial lesion, and to propose criteria for classification of mild head injury (MHI), and appropriate treatment guidelines. Methods : The study was based on 898 patients who were admitted to our hospital with Glasgow Coma Scale (GCS) score of 13 to 15 between 2003 and 2007. The patients' initial computerized tomography (CT) findings were reviewed and clinical findings that were associated with intracranial lesions were analyzed. Results : GCS score, loss of consciousness (LOC), age and skull fracture were identified as independent risk factors for intracranial lesions. Based on the data ana lysed in this study, MHI patients were divided into four subgroups : very low risk MHI patients are those with a GCS score of 15 and without a history of LOC or headache; low risk MHI patients have a GCS score of 15 and with LOC and/or headache; medium risk MHI patients are those with a GCS score of 15 and with a skull fracture, neurological deficits or with one or more of the risk factors; high risk MHI patients are those with a GCS score of 15 with abnormal CT findings and GCS score of 14 and 13. Conclusion : A more detailed classification of MHI based on brain CT scan findings and clinical risk factors can potentially improve patient diagnosis. In light of our findings, high risk MHI patients should be admitted and treated in same manner as those with moderate head injury.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.237-243
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• 1996

Current low head and small scale hydroturbines have limitations in the minimum required head and flow rate for efficient operation. This study attempts to develop a new concept hydroturbine which is expected to run efficiently even in very low head and small flow rate, so that the limitations on the conventional small scale hydropower could be alleviated and competition with other alternative energy sources in the economic respect could be attained. A small scale catapillar track- hydroturbine was fabricated and the performance test was carried out in a water tunnel over the head range of H = 0.8 m ~ 1.26 m. The peak turbine efficiency was 41.3% at the speed ratio of 0.6, and the turbine loss was mostly due to the friction at the chain drive used for power transmission from the runner to the shafts. This type of turbine is expected to become competitive when some improvement in the power transmission mechanism is made.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.3
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• pp.129-135
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• 2016

There are many visual enhancement devices for people with low vision. However, almost conventional devices have been simple magnifying and high cost. The symptoms of people with low vision are very variety. It needs to control of image magnifying, brightness, and contrast to improve the visuality. We developed a portable microdisplay driver and device for visual enhancement. This device based on our suggested four methods such as image magnifying, specific color control, BLU brightness control, and visual axis control using a prism. The basic clinical experiments of the proposed Head Mounted Visual Enhancement Device (HMVED) have been performed. The results show beneficiary effects compared with conventional devices, and improve the life quality on people with low vision on account of low weight, low cost, and easy portability.

• Korean Journal of Head & Neck Oncology
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• v.18 no.1
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• pp.46-49
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• 2002

Background: Free flaps have become a very important role in the ablative head and neck surgery with functional preservation of defect sites. The forearm free flap has many advantage of lack of bulk, ease of dissection, vascularity, and malleability. Patients and Methods: A review of 51 radial forearm free flaps performed between may 1990 and feburary 2001 at the Korea University was undertaken to determine outcome. Patient age ranged 27 to 72 years (mean 56). There were 44 men and 7 women. The most prevalent neoplasm was squamous cell carcinoma. Results: The tans verse cervical artery and the external jugular vein were the most frequent receipient sites for microvascular anastomosis. Total flap loss occurred in 2 cases (4%) and other complications were seen in 42%. Fifteen patients received preoperative irradiation and the complication was higher than non-irradiation patients, but statistically not significant. Conclusion: The radial forearm free flap offers a variety of reconstructive options for head and neck. Its low flap loss and complication rates offer the best choice for reconstruction of defect of head and neck malignancy.

• Journal of KSNVE
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• v.9 no.4
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• pp.643-651
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• 1999

A brief description of the current technology (contact-start-stop) employed in most of today's hard disk drive is presented. The dynamics and head/disk interactions during a start/stop process are very complicated and no one has been able to accurately model the interactions. Thus, the head/disk interface that meets the start/stop durability and stiction requirements are always developed statistically. In arriving at a solution. many sets of statistical tests are run by varying several parameters. such as, the carbon overcoat thickness. lubricant thickness. disk surface roughness, etc. Consequently, the cost associated III developing an interface could be significant since the outcome is difficult to predict. An alternative method known as Load/Unload technology alters the problem set. such that. the start/stop performance can be designed in a predictable manner. Although this techno¬logy offers superior performance and significantly reduces statistical testing time, it also has some potential problems. However. contrary to the CSS technology. most of the problems can be solved by design and not by trial and error. One critical problem is that of head/disk contacts during the loading and unloading processes. These contact can cause disk and slider damage because the contacts are likely to occur at high disk speeds resulting in large friction forces. Use of glass substrate disks also may present problems if not managed correctly. Due to the low thermal conductivity of glass substrates. any head/disk contacts may result in erasure due to frictional heating of the head/disk interface. In spite of these and other potential problems. the advantage with L/UL system is that these events can be understood. analyzed. and solved in a deterministic manner.

• Korean Journal of Head & Neck Oncology
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• v.32 no.2
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• pp.35-39
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• 2016

Castleman's disease (CD) is an uncommon lymphoproliferative disorder. The disease entity is classified into 2 clinical subtypes, unicentric and multicentric type. Prevalence of lymphoid malignancy in multicentric CD (MCD) is very low. In this case, we report a case of 77 years old woman who developed high fever and swelling in both side of her neck. Neck lymph node biopsy revealed plasma cell hyperplasia. Patient's symptom was subsided after treatment with Dexamethasone. Three months later, multiple lymph node enlargement was developed in abdomen and neck area again. Repeated neck lymph node biopsy confirmed diffuse large B cell lymphoma. The patient started chemotherapy.

• The KSFM Journal of Fluid Machinery
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• v.17 no.5
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• pp.67-71
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• 2014

Recently, the cross flow turbine attracts more and more attention for its good performance over a large operating regime at off design point. This study adopts a very low head cross flow turbine that has barely been studied before, and investigates the effect of air layer on the performance of the cross flow turbine. As open duct is applied in this study and free surface model is used between the air layer and water, an engineering definition of efficiency, instead of traditional definition of efficiency, is used. As torque at the runner fluctuates up and down at a reasonable limit, statistical method is used. Pressure and water volume fraction contours are shown to present the characteristics of air-water flow. With constant air suction in the runner chamber, the water level gradually drops below the runner and efficiency of the turbine can be raised by 10 percent. All considered, the effect of air layer on the performance of turbine is considerable.

• The KSFM Journal of Fluid Machinery
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• v.18 no.1
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• pp.11-19
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• 2015

Recently, the cross flow turbines attract more attention for their good performance over a large operating regime at off design point. This study employs a very low head cross flow turbine, which has open inlet duct and has barely been studied before, to investigate the performance of the cross flow turbine with air suction from the rear part of the runner. Unlike conventional cross flow turbines, a draft tube is attached to the outlet of runner to improve the turbine performance. Water level and pressure in the draft tube are monitored to investigate the influence of air suction. Torque at local blade passage of three parts of runner is examined in detail under the conditions of different air suction. Consequently, it is found that with proper air suction in the runner chamber, the water level in the draft tube gradually drops to Stage 2 of the runner and the efficiency of the turbine can be raised by 10%. Overall, the effect of air-layer on the performance of the turbine is considerable.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.190-198
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• 2010

This study was conducted to examine the effects of dams on benthic macroinvertebrate communities in Korean streams and rivers. Four low-head dams and three large dams were studied throughout South Korea. Sampling was taken at immediately upper (impoundment), lower (riffle area), and control (riffle area) sites from the dams during 2004-2007. The upper sites, of which substrate heterogeneity and velocity were relatively low, showed a lower degree of species richness, density, and diversity indices, which is very different from the lower and control sites. Heavily polluted streams showed a lesser degree of community differences between the upper and lower sites. In the large dams, the upper and lower sites showed very low values of species diversity indices and very high values of dominance indices compared to the control sites. In the low-head dams, however, the difference of degree of the values was relatively smaller. Compositions of the functional feeding groups and the habitat orientation groups were relatively simpler at the upper sites than at the lower sites and the degree of difference was greater in the large dams. Species richness and community indices of benthic macroinvertebrates were more significantly affected by habitat characteristics than water quality at the upper sites; however, those were more significantly related with water quality at the lower sites. In conclusion, large and low-head dams could simplify stream habitats particularly at the upper sites (impoundment), and they negatively affected on the benthic macroinvertebrate communities inhabited the habitats. The impact was larger in the large dams than in the low-head dams.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.2
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• pp.284-290
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• 2006

For the case of high head and critical low flow rate range of micro hydropower resources, it requires very low specific speed turbines which are lower than conventional impulse turbine's specific speed. In order to satisfy the request for very low specific speed turbine with high efficiency, a new positive displacement turbine is developed. The performance characteristics of the new turbine is tested and compared with a conventional impulse turbine, which is used for automatic water faucet system. The purpose of present study is to develop an high performance turbine that can be used to extract micro hydropower potential of a water supply system. The test results show that the positive displacement turbine is much more efficient than the conventional turbine and it can sustain high efficiency under the wide range of operating conditions. The pressure pulsations at the inlet and outlet of the positive displacement turbine can be considerably minimized by using simple pressure damper.