• Journal of Internet Computing and Services
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• v.12 no.4
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• pp.1-14
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• 2011

This paper analyzes the fairness and efficiency of channel sharing when heterogeneous wireless networks that have different transmission power and/or coverage coexist with the contention-based channel access protocol. First, we show that the existing CSMA (carrier sensing multiple access) protocol, that is a prevailing contention-based mechanism, results in significant unfairness of channel access because of (1) the asymmetric capability of carrier sensing and (2) the blindness of binary exponential backoff and link adaptation mechanisms to the interference-driven transmission failures. Next, we derive the feasible region of carrier sensing thresholds that assures spatial reuse and fair channel sharing simultaneously. Moreover, we establish an analytical model for per-system throughput and investigate the effect of contention window size and transmission rate on the fairness and efficiency of channel sharing. Finally, we compare the performance of several approaches for fair channel sharing via simulations under various network configurations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1918-1920
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• 2005

The color and structure of urban constructions is a factor of urban landscape and shows their characteristics. Hence the modern buildings with their materials and external appearance makes up the urban image. But still yet, it was not easy to evaluate the value of visual landscape of buildings with objective measuring method. Most of all, it depends on the subjective estimation of a few talented or high educated experts with a sense of beauty. In relation to this kind of problems, it was tried here in this study to analyse the human response of brain wave pattern (EEG) with use of SD method, while the tested persons watched the urban landscape constructed in a visual reality. The tested persons were 10 adult males and females with no color blindness and intact cognitive function. Light source with color filter was used for color environment in chamber room. The signal of EEG is analysed digitally and grouped into the $\alpha$ and $\beta$ waves. The result showed that relative power of $\alpha$ wave ratio increased in natural landscape scenary clearly. From these results it was possible to evaluate the human response, which was affected by urban color and structure stimulation and it might be useful as an indicator of visual cognition amenity toward the design of urban construction environment.

• The Journal of Internal Korean Medicine
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• v.28 no.4
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• pp.733-740
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• 2007

Objective : This study investigated the relationship between warning signs and Sasang constitution (SC) in acute stroke patients. Methods : From October in 2005 to March in 2007, 629 acute stroke patients were studied. Patients were hospitalized within 14 days after the onset ofstroke at one of 3 oriental medical hospitals in Seoul and Kyong-gi province. We assessed the type of SC of acute stroke patients by Questionnaire for Sasang Constitution Classification II (QSCC II). We investigated warning signs (motor weakness, blindness, dysarthria, sensory disturbance, finger dullness, facial & eyelid spasm, neck stiffness), general characteristics, etc. Results : This study showed a higher proportion of Tae-eum & So-eum experience upper extremity sensory disturbance but So-yangexperience lower extremity sensory disturbance. Smoker So-eumexperience 1st & 2nd finger dullness more than non-smoker So-eum. So-eum women experience motor weakness more than So-eum men. Conclusion : Besides these results, we could observe almost no relationship between warning signs and Sasang constitution (SC) in acute stroke patients. More data from prospective cohort studies will help people better understand the relationship between warning signs and Sasang constitution (SC) in acute stroke patients.

• The Journal of the Korea Contents Association
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• v.13 no.12
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• pp.276-290
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• 2013

PURPOSE: This study compared the elderly falls and the intrinsic fall risk factors according to gender. METHODS: This descriptive cross-sectional study was a secondary analysis of the data collected for medical checkups for the Transitional Periods of Life supported from the National Health Insurance. The subjects examined were 255,505 people aged 66 years in Korea between January and December, 2008. RESULTS: The elderly people aged 66 when in the transitional periods of life experienced 10.6% of their first falls. The first falls of women (12.4%) was greater than that of men (8.5%) in the elderly. The risk factors for falls included dysuria with an odds ratio of 6.2 to 6.6, depression with an odds ratio of 1.5 to 1.8, gait disturbance with an odds ratio of 1.3 to 1.5, and blindness with an odds ratio of 1.3 to 1.4 in both elderly women and men. CONCLUSIONS: Effective fall prevention should focus on dysuria because it is a more important predictor of falls, even though many intrinsic fall risk factors can affect falls in elderly people.

• Journal of the Korean Society of Safety
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• v.32 no.3
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• pp.74-82
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• 2017

This study was conducted to test the impacts of distractions caused by smartphones on pedestrians whilst walking alongside or across vehicular traffic in a high-density urban zone in South Korea. Through this study, we propose objective evidence for a link between the risk of traffic accidents and distractions from smartphones for pedestrians because of less likely notice activities surrounding road along their walking. This means that smartphones usage may cause inattentional blindness even during a simple activity that should require few cognitive resources. We conducted an experiment comparing pedestrian behavioral patterns of walking with smartphone distractions (such as listening to music with earphones or sending text messages) and normal walking without any distractions. In the experiment, participants walked along a pedestrian path prescribed by researchers and were observed at 8 points which were as follows: two observation points through which participants were instructed to listen to music whilst walking, two points where participants were instructed to send text messages, and four points through which participants were instructed not to use a smartphone at all. According to pedestrian behavior analysis, there is a trend for attention to be distributed amongst whatever other activities pedestrians are doing whilst walking. Therefore, this study proposes that pedestrians walking with such distractions are at a higher risk of traffic accidents compared to those who walk without such distractions. Thus, we advise for the South Korean government to consider ways to traffic policy that will enhance traffic safety for pedestrians.

• Journal of Korean Neurosurgical Society
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• v.48 no.3
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• pp.213-218
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• 2010

Objective : Pituitary apoplexy (PA) is described as a clinical syndrome characterized by sudden headache, vomiting, visual impairment, and meningismus caused by rapid enlargement of a pituitary adenoma, We retrospectively analyzed the clinical presentation and surgical outcome in PA presenting with cranial neuropathy. Methods : Twelve cases (33%) of PA were retrospectively reviewed among 359 patients diagnosed with pituitary adenoma, The study included 6 males and 6 females, Mean age of patients was 49,0 years, with a range of 16 to 74 years, Follow-up duration ranged from 3 to 20 months, with an average of 12 months, All patients were submitted to surgery, using the transsphenoidal approach (TSA). Results : Symptoms included abrupt headache (11/12), decreased visual acuity (12/12), visual field defect (11/12), and cranial nerve palsy of the third (5/12) and sixth (2/12) Mean height of the mass was 29.0 mm (range 15-46) Duration between the ictus and operation ranged from 1 to 15 days (mean 7.0) The symptom duration before operation and the recovery period of cranial neuropathy correlated significantly (p = 0.0286) TSA resulted in improvement of decreased visual acuity in 91.6%, visual field defect in 54.5%, and cranial neuropathy in 100% at 3 months after surgery. Conclusion : PA is a rare event, complicating 3.3% in our series, Even in blindness following pituitary apoplexy cases, improvement of cranial neuropathy is possible if adequate management is initiated in time, Surgical decompression must be considered as soon as possible in cases with severe visual impairment or cranial neuropathy.

• Journal of Environmental Science International
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• v.15 no.4
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• pp.305-310
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• 2006

The color and structure of urban constructions is a factor of urban landscape and shows their characteristics. Hence the modern buildings deal with their materials and external appearance as an important factor, making up the urban image. But it was nearby impossible to evaluate the value of visual landscape with objective measuring method. Most of all, it depends on the subjective estimation of a few talented or high educated experts with a sense of beauty. Such kinds of estimation can in some cases include arbitrary interpretations. In relation to this kind of problems, it is tried here in this study to analyse the human response of brain wave pattern (EEG) with use of SD method, while the tested persons watch the urban landscape scenery constructed in a visual reality. The tested persons were 20 adult male and female with no color blindness and intact cognitive function. Light source with color filter was used for color environment in a dark soundproof chamber. The signal of EEG is analysed digitally and grouped into the ${\alpha}$ and ${\beta}$ waves. The result showed that relative power of ${\alpha}$ wave ratio increased in the natural landscape scenery with blue and green color. From these results it was possible to evaluate the human response, which is affected by urban and natural color and structure stimulation and it might be useful as an indicator of visual cognition amenity toward the design of urban construction environment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.5
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• pp.283-288
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• 2016

A non-lethal weapon is a device that can subdue targets without causing death or mortal wounds. A high-intensity flash generator can negate electro-optical sensors and cause temporal flash blindness with a high intensity of light. In this study, we derive the design parameters of an explosive-driven high-intensity flash generator that uses the interaction of plasma caused by the detonation of explosives with surrounding inert gas. To determine the design parameters of the flash generator, we analyze test results measured using optical sensors. The experimental results show that the light intensity of xenon gas is about four times higher than that of air. In addition, the intensity increases with the weight of the explosive, and the inert gas cross-sectional area encountered a shock wave in the airframe. The light intensity caused by a double-initiation generator is about two times higher than that of the single-initiation generator.

• The Korean Journal of Food And Nutrition
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• v.29 no.4
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• pp.506-512
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• 2016

Bitter melon (Momordica charantia) is used in traditional herbal medicine in many Asian countries for the treatment of several diseases such as diabetes, eczema, night blindness, psoriasis, and rheumatism. Especially, most reports concerning the biological activities of bitter melon have focused on its effects on diabetes and hyperglycemia. Also, bitter melon is regarded as a longevity food, suggesting that it has several beneficial effects on anti-aging and the maintenance of a healthy state. Thus, we investigated whether bitter melon could increase the capacity of exercise in this study. Interestingly, bitter melon fruit extract activated AMP-activated protein kinase (AMPK), which is important for regulating glucose homeostasis, mitochondrial content and exercise capacity. In addition, bitter melon extract increased the expression of enzymes involved in fatty acid oxidation such as mitochondrial uncoupling protein 3 (UCP3), carnitine palmitoyl transferase 1b (CPT1b), and pyruvate dehydrogenase lipoamide kinase isozyme 4 (PDK4). Moreover, exercise tolerance was much more enhanced in bitter melon treated animals compared to the non-treated control group. These results suggest that bitter melon is a promising candidate for the development of functional foods beneficial for physical strength and the enhancement of exercise capacity.

• Journal of the Korea Society of Computer and Information
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• v.25 no.11
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• pp.59-65
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• 2020

Lately the VR (Virtual Reality) game genre is becoming increasingly more popular and it has been cementing its place in the market as its own independent game genre. The key advantage of VR is that it lowers the barrier between player and the virtual world, thus creating an immersive experience. The suggested method develops a game that allows the player to experience what it is like to be visually impaired using the unique characteristics of VR. A distinctive feature of this game is that the character is provided only a limited range of sight, which is created using silhouette outlines. This restrictive visual field is then grafted onto VR and the player can indirectly experience blindness in a highly immersive manner. The silhouette outline along with the particle system is created using Oculus Rift, a headset highly used in VR game development, and Unity 3D game engine. We will also explain in detail regarding the removal of borders between the objects.