• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.12
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• pp.10-21
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• 2015

Cellular Network assisted device-to-device (D2D) communication has been growing to reduce the overload of eNodeB and mitigate the frequency shortage. However, by sharing the uplink frequency resource with the cellular network, the interference between cellular and D2D is increased. In this paper, we propose the advanced receiver based on soft decision to reduce the interference between cellular and D2D. The proposed receiver can suppress and cancel the interference by calculating the unbiased estimation value of interference signal using minimum mean square error (MMSE) or interference rejection combing (IRC) receiver. The interference signal is updated using soft information expressed by log-likelihood ratio (LLR). We perform a system level simulation based on the 20-MHz bandwidth of the 3GPP LTE-A system. Simulation results show that the proposed receiver can improve SINR, throughput and spectral efficiency compared to conventional receivers.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.13-18
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• 2016

In Long Term Evolution-Advanced (LTE-A), small cell enhancement(SCE) has been developed as a cost-effective way of supporting exponentially increasing demand of wireless data services and satisfying the user quality of service(QoS). However, there are many problems such as the transmission rate and transmission quality degradation due to the dense and irregular distribution of a large number of small cells. In this paper, we propose a clustering based interference management scheme in dense small cell network. We divide the small cells into different clusters according to the reference signal received power(RSRP) from user equipment(UE). Within a cluster, an almost blank subframe(ABS) is implemented to mitigate interference between the small cells. In addition, we apply the power control to reduce the interference between the clusters. Simulation results show that proposed scheme can improve Signal to Interference plus Noise Ratio(SINR), throughput, and spectral efficiency of small cell users. Eventually, proposed scheme can improve overall cell performance.

• Journal of the Korean Geographical Society
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• v.49 no.6
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• pp.935-948
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• 2014

As chronic diseases have become more prevalent and problematic, effective cares for major chronic diseases have been a locus of the healthcare policy. In this regard, this study examines how region-specific characteristics affect the prevalence of hypertension in South Korea. To analyze, we combined a unique multi-year data set including key indicators of health conditions and health behaviors at the 237 small administrative districts. The data are collected from the Annual Community Health Survey between 2009 and 2011 by Korea Centers for Disease Control and Prevention and other government organizations. For the purpose of investigating regional variations, we estimated using Geographically Weighted Regression (GWR) and decision tree model. Our finding first suggests that using the multi-year data is more legitimate than using the single-year data for the geographical analysis of chronic diseases, because the significant annual differences are observed in most variables. We also find that the prevalence of hypertension is more likely to be positively associated with the prevalence of diabetes and obesity but to be negatively associated with population density. More importantly, noticeable geographical variations in these factors are observed according to the results from the GWR. In line with this result, additional findings from the decision tree model suggest that primary influential factors that affect the hypertension prevalence are indeed heterogeneous across regional groups. Taken as a whole, accounting for geographical variations of health conditions, health behaviors and other socioeconomic factors is very important when the regionally customized healthcare policy is implemented to mitigate the hypertension prevalence. In short, our study sheds light on possible ways to manage the chronic diseases for policy makers in the local government.

• Journal of the Korean Geotechnical Society
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• v.29 no.1
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• pp.23-27
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• 2013

The risks of debris flows caused by climate change have increased significantly around the world. Recently, landslide disaster prevention technology is more focused on the failure and post-failure dynamics to mitigate the hazards in flow-prone area. In particular, we should define the soil strength and flow characteristics to estimate the debris flow mobility in the mountainous regions in Korea. To do so, we selected known ancient landslides area: Inje, Pohang and Sangju debris flows. Firstly we measured physical and mechanical properties: liquidity index and undrained shear strength by fall cone penetrometer. From the test results, we found that there is a possible relationship between liquidity index and undrained shear strength, $C_{ur}=(1.2/I_L)^{3.3}$, in the selected areas, even though they were different in geological compositions. Assuming that the yield stress is equal to the undrained shear strength at the initiation of sliding, we examined the flow characteristics of weathered soils in Korea. When liquidity index is given as 1, 1.5 and 3.0, the debris flow motion of weathered soils is compared with that of mud-rich sediments, which are known as low-activity clays. At $I_L=1$, it seems that debris flow could reach approximately 250m after 5 minutes. As liquidity index increased from 1 to 3, the debris flow propagation of weathered soils is twice than that of low-activity clays. It may be due to the fact that soil masses mixed with the ambient water and then highly fragmented during flow, thereby leading to the high mobility. The results may help to predict the debris flow propagation and to develop disaster prevention technology at similar geological settings, especially for the weathered soils, in Korea.

• Journal of the Korean Institute of Gas
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• v.23 no.6
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• pp.1-7
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• 2019

Most oil refineries and chemical plants have flare systems designed to mitigate pressure rises in process facilities in case of emergencies that require the release of large amounts of gas due to sudden process shutdowns such as power outages. However, the rise of the flame of the flare system causes civil complaints from residents around the factory due to visible pollution, and economic loss occurs in the company, which requires constant management. In this study, two items were diagnosed and analyzed in order to derive the optimal operation method of flare system. First, to detect the cause of the rise in flame height, the acoustic leak detector was used to check gas leaks in safety valves and pressure control valves. Second, to identify the cause of flame instability, the pulsation phenomenon was diagnosed through the CFD simulation and modeling experiments of the sealing drum. By confirming the leak at 4.3% of the safety valve and 10% of the pressure control valve, the cause of abnormal sparking was derived. The information presented in this study can be easily applied to any company that has a flare system, and is expected to prevent complaints and product loss.

• Journal of the Korean Geographical Society
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• v.40 no.6 s.111
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• pp.730-747
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• 2005

This study examines relationships between climatic factors and spatial-temporal patterns and recent changes of tropical night phenomenon(TN) occurring through nighttime stages in South Korea. Frequencies of daily TN at different times of night are extracted from long term(1973-2004) 6 hourly nighttime(9PM and 3AM) temperature and daily minimum temperature data at 61 weather stations. Temporally, the occurrences of TN are more pronounced in the evening(9PM) and during the Changma Break period(late July - early August). Spatially, the TNs in the evening frequently occur in the urbanized inland cities at low latitudes due to urban heat islands, whereas the TNs in the middle of night(3AM) or at dawn frequently appeared along the coastal areas within 30km from ocean due to the thermal inertia of ocean. By contrast, the evening(dawn) TN is not seen in the highlands whose elevation is greater than 800m(300m) along the Taebaek and Sobaek mountain ridges due to temperature lapse rates with height Correlation and multivariate regression analyses reveal that the impacts of human or physical climatic factors, such as latitude, elevation, proximity to ocean, and population density, are diverse on the frequencies of TN according to nighttime stages. Recent temporal changes of the late Changma period and intensified urbanization during the 1990s have increased the occurances of TN in urban areas. Therefore, strategies to mitigate the increasing urban TN should be prepared in the near future.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.13
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• pp.5117-5121
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• 2014

Endocrine-disrupting chemicals (EDCs) have been reported to interfere with estrogen signaling. Exposure to these chemicals decreases the immune response and causes a wide range of diseases in animals and humans. Recently, many studies showed that licorice (Glycyrrhiza glabra) root extract (LRE) commonly called "gamcho" in Korea exhibits antioxidative, chemoprotective, and detoxifying properties. This study aimed to investigate the mechanism of action of LRE and to determine if and how LRE can alleviate the toxicity of EDCs. LRE was prepared by vacuum evaporation and freeze-drying after homogenization of licorice root powder that was soaked in 80% ethanol for 72 h. We used 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as an EDC, which is known to induce tumors or cancers; MCF-7 breast cancer cells were used as a tumorigenic model. These were treated with TCDD and various concentrations of LRE (0, 50, 100, 200, $400{\mu}g/mL$) for 24, 48, and 72 h. As a result, TCDD stimulated MCF-7 cell proliferation, but LRE significantly inhibited TCDD-induced MCF-7 cell proliferation in a dose- and time-dependent manner. Expression of TCDD toxicity-related genes, i.e., aryl hydrocarbon receptor (AhR), AhR nuclear translocator, and cytochrome P450 1A1, were subsequently down-regulated by LRE in a dose-dependent manner. Analysis of cell cycle distribution after treatment of MCF-7 cells with TCDD and various concentrations of LRE showed that LRE inhibited the proliferation of MCF-7 cells via G2/M phase arrest. Reverse transcription-polymerase chain reaction and Western blot analyses also revealed that LRE dose-dependently increased the expression of the tumor suppressor genes p53 and p27 and down-regulated the expression of cell cycle-related genes. These data suggest that LRE can mitigate the tumorigenic effects of TCDD in breast cancer cells by suppression of AhR expression and cell cycle arrest. Thus, LRE can be used as a potential toxicity-alleviating agent against EDC-mediated disease.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.4
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• pp.454-459
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• 2016

Pre- or post-harvest processing is required to mitigate the risk of norovirus infection mediated by shellfish or seafood. We investigated the environmental resistance of human norovirus (HuNoV) under various conditions of temperature, salinity, and pH in seawater. Male-specific coliphage (MSC) was as the reference virus for all tests. At 4℃, HuNoV GII4 spiked into seawater was continually detected by RT-PCR for 35 days, regardless of salinity or pH level. It maintained nearly stable concentrations, meaning HuNoV can sustain a viral population in seawater long enough to be accumulated by shellfish and other filter feeders during winter. MSC was also stable at 4℃ although viral infectivity dropped sharply after 28 days. The effects of salinity and pH on MSC were indistinct. At 25℃ the detectable period of HuNoV GII4 by RT-PCR in seawater decreased to about one-third or half of the period at 4℃. High salinity (32 psu) and alkaline pH (8.5) were also unfavorable for sustaining HuNoV abundance at 25℃ in seawater. The resistance patterns of MSC to high temperature, high salinity, and alkaline pH were more dramatic and viral infectivity decreased over time, almost in direct proportion to experimental days. MSC was undetectable after 12 days under all salinities and pH levels at 25℃.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.264-274
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• 2018

This study constructed a prediction model based on covariance structure to identify the causal relationship between job stress, fatigue, burnout, and job satisfaction on turnover intention in nurses working in general hospitals. The study subjects were 648 nurses at a general hospital in D city. Data collection was surveyed by using self-administered questionnaires structured during the period from November 1, 2016 to December 31, 2016. As a result, the level of turnover intention was significantly higher in the group showing higher job stress, fatigue, and burnout and significantly higher in the group showing lower job satisfaction. The turnover intention of subjects showed a significant positive correlation with job stress, fatigue, and burnout but showed a negative correlation with job satisfaction. As a result of covariance structure analysis, job stress had greater influence on turnover intention than fatigue, burnout, and job satisfaction. Higher job stress, fatigue, and burnout and lower job satisfaction were associated with increased turnover intention. The results of this study show that the turnover intention of general hospital nurses is significantly related to job stress, fatigue, burnout, and job satisfaction. In particular, job stress had a greater effect on turnover than fatigue, burnout, and job satisfaction. Therefore, in order to lower the turnover intention of general hospital nurses, it is necessary to seek ways to mitigate job stress.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.806-816
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• 2017

This study aims to offer effective policies for managing local temperatures and reducing the heat island effect by identifying elements that affect local temperatures. The three elements of natural environment, land use, and land coverage were first selected, and then control factors were applied, including season, weather, and measurement units for wind speed. In order to analyze these factors' relations to summer temperatures, an integrated model was developed, and an analysis was conducted of the urban heat island reduction effect of elements impacting local temperatures. The analysis used nationwide weather system (AWS) data from July and August 2007 and 2011-2016, land coverage data provided by the Ministry of Environment, and land use area data from local governments after rearranging them based upon their falling within a 500-meter radius ($0.79km^2$) of AWS measuring points. The study results show that the natural environment, land use, and land coverage all have a relation to changes in local temperatures. Natural elements have the greatest impact, and land use has the lowest. The results could provide basic data for establishing more effective policies to mitigate the heat island effect and strategies for enhancing the sustainability of cities.