• The Korean Journal of Applied Statistics
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• v.30 no.3
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• pp.453-462
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• 2017

Double propensity score adjustment is an analytic solution to address bias due to incomplete matching. However, it is difficult to estimate the standard error of the estimated treatment effect when using double propensity score adjustment. In this study, we propose two bootstrap methods to estimate the standard error. The first is a simple bootstrap method that involves drawing bootstrap samples from the matched sample using the propensity score as well as estimating the standard error from the bootstrapped samples. The second is a complex bootstrap method that draws bootstrap samples first from the original sample and then applies the propensity score matching to each bootstrapped sample. We examined the performances of the two methods using simulations under various scenarios. The estimates of standard error using the complex bootstrap were closer to the empirical standard error than those using the simple bootstrap. The simple bootstrap methods tended to underestimate. In addition, the coverage rates of a 95% confidence interval using the complex bootstrap were closer to the advertised rate of 0.95. We applied the two methods to a real data example and found also that the estimate of the standard error using the simple bootstrap was smaller than that using the complex bootstrap.

• Weed & Turfgrass Science
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• v.6 no.4
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• pp.306-312
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• 2017

This study was carried out to develop new hybrid zoysiagrass cultivar 'Seah' (The application no. for cultivar protection : 2014-22). Native zoysiagrasses were collected from south-west seaside of Korea from 2010 to 2011. Artificial crossing was conducted to develop F1 hybrid between Z2011 (Z. sinica) and NM1 (Z. matrella) at plastic house in 2011. Among the progenies, 'Seah' showed fine leaf texture and high shoot density from the space planting plots at field. 'Seah' showed genetically light green color, with fine leaf with 1.8mm and height to the lowest leaf blade was 1.94 cm. Ground coverage rate was slower than medium leaf zoysiagrass (Jung-gi), but plant height of 7.1 cm was the lowest among the compared zoysiagrasses and height to lowest leaf of 1.94 cm was lower than most zoysiagrass, which may allow low mowing height.

• Journal of Korean Academy of Nursing
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• v.24 no.4
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• pp.568-583
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• 1994

In the changing social and economic conditions, reorientation of the health care system is a process of rearranging health care resources keeping in mind the appropriativeness, relevancy, and efficacy of health care programs. Also it has been recognized recently that the CHP program is in need of review for the same reasons, that is to say, the ease in which health care facilities are available, the high rate of coverage with insurance and the development of an effective transportation system. Therefore there is a social inclination to think that there are no remote areas and to question the roles of public health facilities, health centers, health sub centers and CHP posts. This paper was done to review problems and to propose new directions for the CHP system. The findings of this study are as follows ; 1) It is necessary that primary health care should be simplified into three parts, medical treatment, preventive care services and the organization of administration and logistics. Also each department should be supplemented with the appropriate professional personnel in order to develop a task oriented system. The reorientation of the CHP system should be managed in keeping with that of other public health care systems. Therefore it is necessary to look at the CHP system problems as one aspect of the reorientation process of public health care systems, and to work to find new ways to address these problems. 2) The location of the CHP post should be decided by the needs of the community in both the medical and preventive areas. If the people have a minimum need, the location of the CHP post should be altered and the existing roles of the CHP should be modified to allow for flexibility according to the community needs. 3) Use of the problem solving method in regular team meetings will prove to be as efficient as continuing education programs in improving job competancy. 4) The supervision of CHP's activities should be made by the same type professional personnel, that is, senior CHPs or charge nurses in the public health center at the county level. 5) The operational expensies of CHP post should be supported by the administrative department of the public health center and should create working conditions that will allow the CHP to concentrate on community health service programs. 6) The organizations for community participation, working committees, community health workers and a number of the local assembly, should be activated to provide for participation in finding solutions to health related problems in the com-munity.

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.385-398
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• 2002

To accommodate the increasing number of mobile terminals in the limited radio spectrum, wireless systems have been designed as micro/picocellular architectures for a higher capacity. This reduced coverage area of a cell has caused a higher rate of hand-off events, and the hand-off technology for efficient process becomes a necessity to provide a stable service. Population-based Bandwidth Reservation(PBR) Scheme is proposed to provide prioritized handling for hand-off calls by dynamically adjusting the amount of reserved bandwidth of a cell according to the amount of cellular traffic in its neighboring cells. We analyze the performance of the PBR scheme according to the changes of a fractional parameter, f, which is the ratio of request reservation to the total amount of bandwidth units required for hand-off calls that will occur for the next period. The vague of this parameter, f should be determined based on QoS(Quality of Service) requirement. To meet the requirement the value of Parameter(f) must be able to be adjusted dynamically according to the changing traffic conditions. The best value of f can be determined by a function of the average speed of mobile stations, average call duration, cell size, and so on. This paper considers the average call duration and the cell size according to the speed of mobile stations. Although some difference exists as per speed, in the range of 0.4 $\leq$ f $\leq$ 0.6, Blocking Probability, Dropping Probability and Utilization show the best values.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.29-39
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• 2009

The need for radio spectrum is recently considered as a huge hurdle towards the rapid development of wireless networks. Large parts of the spectrum are allocated to licensed radio services in proprietary way. However, enormous success of the wireless services and technologies in the unlicensed bands has brought new ideas and innovations. In recent years cognitive radio has gained much attention for solving the spectrum scarcity problem. It changes the way spectrum is regulated so that more efficient spectrum utilization is possible. Multi-hop relay technology on the other hand has intensively been studied in the area of ad hoc and peer-to-peer networks. But in cellular network, only recently the integration of multi-hop capability is considered to enhance the performance significantly. Multi-hop relaying can extend the coverage of the cell to provide high data rate service to a greater distance and in the shadowed regions. Very few papers still exist that combine these methods to maximize the spectrum utilization. Thus we propose a network architecture combining these two technologies in a way to maximize the system throughput. We present the throughput capacity equations for the proposed system model considering various system parameters like utilization factor by the primary users and primary users' transmission radius and through extensive numerical simulations we analyze the significance of work.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.6-13
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• 2006

In this paper, we studied vehicle to vehicle (VTV) communication system using DSRC of 5.8 GHz bands. Nowadays, in the road traffic system is going intelligent and advancing, communication between driving vehicle is very important technology for ITS. We can contrive smoothness and safety traffic flowing by exchanging information about velocity, location, braking and driving condition of nearby vehicles. Therefore, we developed and verified the system which required for the communication among vehicles using DSRC technology of 5.8 GHz band hasa 1 Mbps data rate in the high mobility condition. For this, we developed DSRC modem, data link layer and logic link layer to make it possible that communication between vehicles of perfectly operation, and developed application service program for VTV communication. We performed to communication test in the general road and ascent road. In case of the general mad, obtained VTV communication results are more than number of 17 with in 300 m LOS coverage, and total communication time are $2.34{\sim]18.7$ msec that considered maximum 8-transaction. We blow that obtained results can be used VTV communication or the in areas form the feasibility road test as a function or various conditions. In the future, this system is very useful of advanced safety vehicle (ASV) and super smart vehicle system (SSVS) and so on.

• Asian Journal of Turfgrass Science
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• v.25 no.2
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• pp.147-152
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• 2011

This study was conducted to evaluate the growth characteristics of creeping bentgrass cultivars for fairway of golf course at Yeoju area in Korea. At germination and coverage rate of creeping bentgrass, 'Shark' and 'CY-2' were excellent, 'L-93', 'Alpha', 'T-1 was in order', respectively. Visual qualities of 'Shark' and 'CY-2' also were excellent. Especially, 'Shark', 'T-1', and 'CY-2' showed excellent visual quality in summer days, the critical times for the bentgrass fairway quality. 'Shark', 'CY-2' and 'T-1' were excellent in Chlorophyll contents throughout the evaluation period. Chlorophyll content of 'T-1' was maintained very high in summer. 'CY-2' and 'Shark' showed the best root growth at the beginning of the study and contained longer and hairy roots. Which might make these two cultivars' water absorption easier than other's. NDVI (normalized difference vegetation index)of 'Shark', 'L-93' and 'CY-2' was excellent, respectively. 'T-1' showed the highest density and 'Shark', 'CY-2', 'Alpha', 'L-93' was followed by. The density of 'T-1' was rather increased in summer season, while those of other cultivars were decreased. Three diseases such as anthracnose, brown patch, and dollar spot, were appeared during the evaluation period. 'T-1' and 'L-93' were very sensitive to anthracnose which occurred at the beginning days of the study. The most susceptible cultivars to brown patch were 'Alpha' and 'L-93'. 'T-1' was the least resistant to dollar spot which occurred at the same time with brown patch.

• Korean Journal of Ecology and Environment
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• v.53 no.2
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• pp.208-219
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• 2020

Forest thinning brought the large variation to forest ecosystem including environment and animal. Our study was result of long-term monitoring for ground-dwelling arthropod communities after thinning in forest ecosystem. In this study, we conducted field study on plantation forest in Chuncheon, Korea in 2018, and compared with previous study data (2006 and 2008). We found that the effect of thinning was still existent 10 years later from thinning with difference of habitat environment(depth of ground organic matter, coverage rate of ground vegetation and canopy). And ground-dwelling arthropod communities showed changes of abundance and taxa at the study area and thinning conditions. Ground-dwelling arthropod communities in 2018 were dominant in the order of Diptera, Hymenoptera, Coleoptera (Insecta), Araneae (Arachnida) and Collembola (Collembola). Among the conditions of thinning, Araneae (Arachnida), Coleoptera and Hymenoptera (Insecta) showed amount of abundance in heavy thinning. And Collembola (Collembola) and Diptera (Insecta) were most common in area of light thinning. In 2018 ground-dwelling arthropod communities, abundance of Diptera and Coleoptera (Insecta) and Isopoda (Crustacea) were decreased although Hemiptera and Orthoptera (Insecta) were increased than 2008 arthropod communities. Arthropod communities in 2018 were more similar with those in 2008 (after thinning) than with those in 2006 (before thinning).

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.2 no.2 s.3
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• pp.43-54
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• 2003

As the demand for ubiquitous mobile wireless Internet grows, vehicles are receiving a lot of attention as new networking platforms. The demand for 4G all-IP networks encourages vehicle networks to be connected using IPv6. By means of network mobility (NEMO) support, we can connect sensors, controllers, local ,servers as well as passengers' devices of a vehicle to the Internet through a mobile router. The mobile router provides the connectivity to the Internet and mobility transparency for the rest of the mobile nodes of an in-vehicle nv6 network. So, it is .important for the mobile router to assure reliable connection and a sufficient data rate for the group of nodes behind it. To provide reliability, this paper proposes an adaptive multihoming architecture of multiple mobile routers. Proposed architecture makes use of different mobility characteristics of different vehicles. Simulation results with different configurations show that the proposed architecture increases session preservation thus increases reliability and reduces packet loss. We also show that the proposed architecture is adaptive to heterogeneous access environment which provide different access coverage areas and data rates. The result shows that our architecture achieves sufficient data rates as well as session preservation.

• The Journal of Korean Medicine
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• v.17 no.2 s.32
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• pp.34-47
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• 1996

We have seen a sharp increase in the utilization rate of medical services since the launch of Nation Health Insurance system in 1989. However, the market share of oriental medicine in the Korean health sector has been gradually diminished mainly due to low insurance coverage and high price. Especially high price as an entry barrier to oriental medical services has played a major role in decreasing market share. This paper investigated the effects of price discount on the financial condition and market share of oriental medical institutions. Microeconomic theory and multiple regression analysis were used as a methodology in testing the alternative hypothesis: price discount of enveloped herb drug will result in increases in both the revenue and market share of oriental medical institutions. Data was collected from the statistical yearbook and sample survey. The price elasticity of demand for enveloped herb drug was estimated at 5.8 during 1987-1995 period, which means that a 1% decrease in price will bring about a 5.8% increase in the utilization of oriental medical services. The empirical result shows that a drastic price discount for the enveloped herb drug will eventually improve the financial status of the oriental medical institutions and enlarge the market share of oriental medicine in the Korean health care sector.