• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.4
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• pp.726-747
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• 2013

In order to support a large number of mobile stations (MSs) with statistical multiplexing in cellular networks, a random access scheme is widely used for uplink (UL) bandwidth request (BR). In the design of a random access based BR scheme, there are two important requirements: short connection delay and diverse Quality of Services (QoSs) support. Such requirements are crucial for IMT-Advanced systems like IEEE 802.16m to provide various types of fourth generation (4G) data services. IEEE 802.16m provides advanced UL BR schemes for non-real time polling service (nrtPS) and best-effort (BE) service to meet the requirements of short connection time and multiple QoS level support. In order to provide short connection time and multiple QoS support, three-step and differentiated BR procedures are adopted. In this paper, a novel modelling of IEEE 802.16m contention based BR scheme is proposed that uses a 2-dimensional discrete time Markov chain. Both the short access delay three-step BR procedures and normal five-step BR procedure are considered in the model. Our proposed model also incorporates the IEEE 802.16m differentiated BR procedure. With the proposed model, we extensively evaluate the performance of IEEE 802.16m BR for two different service classes by changing QoS parameters, such as backoff window size and BR timer. Computer simulations are performed to corroborate the accuracy of the proposed model for various operation scenarios. With the proposed model, accurate QoS parameter values can be derived for the IEEE 802.16m contention-based BR scheme.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1128-1135
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• 2011

The purpose of this study was to identify the effects of field athletes' self-management on their psychological happiness. The subjects of the study were 184 athletes (male=82, female=102) who participated in the 91th National Athletes Meeting. All statistical analyses and description methods were computed by SPSS window 18.0. The discriminant analysis was used to find effects of self-management on their psychological happiness, ANOVA and Multiple regression. The results of this study were as followings: Frist, there was not significant difference to The Relationship between social-demographical variables and self-management, their psychological happiness. Second, self-management had a significant effect on psychological happiness. Based on the results, Field athletes's self-management has a positive effect on their psychological happiness.

• Korean Management Science Review
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• v.32 no.4
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• pp.109-133
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• 2015

This paper considers the allocation and engagement scheduling of air defense missiles by using MIP (mixed integer programming). Specifically, it focuses on developing a realistic MIP model for a real battle situation where multiple enemy missiles are headed toward valuable defended assets and there exist multiple air defense missiles to counteract the threats. In addition to the conventional objective such as the minimization of surviving target value, the maximization of total intercept altitude is introduced as a new objective. The intercept altitude of incoming missiles is important in order to minimize damages from debris of the intercepted missiles and moreover it can be critical if the enemy warhead contains an atomic or chemical bomb. The concept of so called the time window is used to model the engagement situation and a continuous time is assumed for flying times of the both missiles. Lastly, the model is extended to simulate the situation where the guidance radar, which guides a defense missile to its target, has the maximum guidance capacity. The initial mathematical model developed contains several non-linear constraints and a non-linear objective function. Hence, the linearization of those terms is performed before it is solved by a commercially available software. Then to thoroughly examine the MIP model, the model is empirically evaluated with several test problems. Specifically, the models with different objective functions are compared and several battle scenarios are generated to evaluate performance of the models including the extended one. The results indicate that the new model consistently presents better and more realistic results than the compared models.

• Journal of Advanced Navigation Technology
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• v.21 no.1
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• pp.119-125
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• 2017

In this paper, we propose a method that merges and splits players in the MeanShift tracking framework. The MeanShift tracking moves the center of tracking window to the maximum probability location given the target probability distribution. This tracking method has been widely used for real-time tracking problems because of its fast processing speed. However, it hardly handles occlusions in multiple object tracking systems. Occlusions can be usually solved by applying data association methods. In this paper, we propose a method that can be applied before data association methods. The proposed method automatically merges and splits the overlapped players by adjusting the each player's tracking map. We have compared the tracking performance of the MeanSfhit tracking algorithm and the proposed method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.7
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• pp.783-788
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• 2016

An LTE enhancement for licensed-assisted access (LAA) to unlicensed spectrum has been studied recently and the first version of its design has been released in early 2016. As both 2.4 and 5GHz ISM bands have multiple channels and Wi-Fi devices already support multi-channel operation, LTE LAA has also been designed such that an eNB can access multiple channels at the same time. In this paper, we review several design variants of listen before talk (LBT) procedure for multi-channel transmission in downlink and perform simulation to investigate coexistence of Wi-Fi and LAA as well as the performance of both.

• KIEAE Journal
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• v.15 no.4
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• pp.91-104
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• 2015

Recently, various researches for the improvement of Han-ok performance carried out. But, most of them are tend to come from the viewpoint of suppliers rather than that of Han-ok habitants. It means that environmental elements which real habitants feel are not reflected in the design of initial Han-ok design. Therefore, it is necessary that many researchers should analyze the degree of dwelling satisfaction derived from real life. Purpose: The purpose of this study is to find the avaliable factors that need to be considered in the process of initial Han-ok design and construction through the analysis on the living performance satisfaction ratio of modern New Han-ok's habitants. Method: To achieve this goal, surveys were carried out in 83 Han-oks which actual habitants were living, located in 14 happy villages Jeonnam province. Following are survey items about residential environmental conditions; kinds of wall material, gap(connection joint between wall and wood columns) reinforcement or not, kinds of window, kinds of facilities around windows, kinds of heating source, heating types(single, multiple), financial burdens, selective heating or not and so on. Result: The results of this study may be used to improve the living performance satisfaction ratio of new Han-ok habitants and as a basis for the specifying the desired thermal comfort environment of dwelling.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.1
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• pp.52-58
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• 2006

Single-electron transistor (SET)-based logic cells and SET/FET hybrid integrated circuits have been fabricated on SOI chips. The input-output voltage transfer characteristic of the SET-based complementary logic cell shows an inverting behavior where the output voltage gain is estimated to be about 1.2 at 4.2K. The SET/FET output driver, consisting of one SET and three FETs, yields a high voltage gain of 13 and power amplification with a wide-range output window for driving next circuit. Finally, the SET/FET literal gate for a multi-valued logic cell, comprising of an SET, an FET and a constant-current load, displays a periodic voltage output of high/low level multiple switching with a swing as high as 200mV. The multiple switching functionality of all the fabricated logic circuits could be enhanced by utilizing a side gate incorporated to each SET component to enable the phase control of Coulomb oscillations, which is one of the unique characteristics of the SET-based logic circuits.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.388-394
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• 2008

In this paper, MAC(Medium Access Control) algorithm for the IEEE 802.11 DCF(Distributed Coordination Function) improving the performance is proposed and analyzed by simulation. The MAC of IEEE 802.11 WLAN to control data transmission uses two control methods called DCF and PCF(Point Coordination function). The DCF controls the transmission based on CSMA/CA(Carrier Sense Multiple Access With Collision Avoidance). The DCF shows excellent performance relatively in situation that competition station is less but has a problem that performance is fallen from throughput and delay viewpoint in situation that competition station is increased. This paper proposes an enhanced DCF algorithm that increases the CW to maximal CW after collision and decreases the CW smoothly after successful transmission in order to reduce the collision probability by utilizing the current status information of WLAN. To prove efficiency of proposed algorithm, a lots of simulations are conducted and analyzed.

• The Journal of Korean Academic Society of Nursing Education
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• v.17 no.1
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• pp.80-89
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• 2011

Purpose: The purpose of this study was to discover the effect of emotional intelligence on organizational performance in clinical nurses regarding anger expression, job satisfaction, job commitment, and turnover intention. Methods: Data were collected by self-administered questionnaires from 162 clinical nurses in three university hospitals in 2008, and analyzed by the SPSS 14.0 Window program, using descriptive statistics, pearson correlation, and stepwise multiple regression. Results: Emotional intelligence showed a statistically significant association with each of anger expression-in, anger expression-control, job satisfaction, job commitment, turnover intention, and organizational performance. The multiple regression analysis also showed that organizational performance was statistically significant with job satisfaction, job commitment, and emotional intelligence respectively. 38.0% of the variation of organizational performance was explained by these variables. Conclusion: Emotional intelligence significantly affected organizational performance together with job satisfaction and job commitment. From this result, it could be concluded that nursing interventions for emotional intelligence have a positive effect on improving organizational performance. Further studies are needed to develop nursing intervention programs for emotional intelligence and test its effects on organizational performance.