• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4287-4306
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• 2016

Network resilience provides an effective way to overcome the problem of network failure and is crucial to Internet protocol (IP) network management. As one of the main challenges in network resilience, recovering from link failure is important to maintain the constancy of packets being transmitted. However, existing failure recovery approaches do not handle the traffic engineering problem (e.g., tuning the routing-protocol parameters to optimize the rerouting traffic flow), which may cause serious congestions. Moreover, as the lack of QoS (quality of service) restrictions may lead to invalid rerouting traffic, the QoS requirements (e.g., bandwidth and delay) should also be taken into account when recovering the failed links. In this paper, we first develop a probabilistically correlated failure model that can accurately reflect the correlation between link failures, with which we can choose reliable backup paths (BPs). Then we construct a mathematical model for the failure recovery problem, which takes maximum rerouting traffic as the optimizing objective and the QoS requirements as the constraints. Moreover, we propose a heuristic algorithm for link failure recovery, which adopts the improved k shortest path algorithm to splice the single BP and supplies more protection resources for the links with higher priority. We also prove the correctness of the proposed algorithm. Moreover, the time and space complexity are also analyzed. Simulation results under NS2 show that the proposed algorithm improves the link failure recovery rate and increases the QoS satisfaction rate significantly.

• Journal of Korean Society of Transportation
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• v.21 no.6
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• pp.89-99
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• 2003

Considering a path represented by a sequence of link numbers in a network, the vine is differentiated from the loop in a sense that any link number can be appeared in the path only once, while more than once in the loop. The vine provides a proper idea how to account for complicated travel patterns such as U-turn and P-turn witnessed nearby intersections in urban roads. This paper proposes a new algorithm in which the vine travel pattern can be considered for finding K number of sequential paths. The main idea of this paper is achieved by replacing the node label of the existing Yen's algorithm by the link label technique. The case studies show that the algorithm properly represent the vine travel patterns in searching K number of paths. A noticeable result is that the algorithm may be a promising alternative for ITS deployment by enabling to provide reasonable route information including perceived traveler costs.

• Korea Journal of Hospital Management
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• v.21 no.2
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• pp.50-62
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• 2016

The study was conducted to compare organizational innovation depending on the leadership type of middle managers in general hospital. Moreover, the study was also to prove whether employees'readiness causes any differences to the link between leadership and organizational innovation. The result is based on 769 sheets of survey paper answered by administrations and nurses working at general hospitals or the same level of hospitals located in the metropolitan area. The methods of analysis used are as follows: reliability analysis, frequency analysis, t-test, ANOVA, multiple regression analysis, and hierarchical regression analysis. Main results of the study can be summarized as below. First, by analyzing the influence of task-behavior leadership on organizational innovation, R squre on knowledge management which is organizational innovation factor was 12.5%, R squre on creativity was 9.1%, and R squre on innovation behavior was 10.3%. Regression model appeared to be statistically significant as well. Both task-behavior and relationship-behavior leadership have influence on organizational innovation and it is learned that relationship-behavior leadership has a bigger influence on all the organizational innovation factors. Second, moderating effect of the employee's readiness is examined in terms of the link between leadership and organizational innovation. As a result, the member's readiness had positive influence when it comes to the link between leadership and organizational innovation. Also, after verifying moderating effect of readiness (ability/willingness), this study shows that ability readiness has positive influence on the link between task-behavior(or relationship-behavior) leadership and creativity, and innovation behavior while willingness readiness positively influences the link between task-behavior(or relationship-behavior) leadership and creativity & innovation behavior. To summarize results of the study, this study shows that the members who possess high readiness also have high organizational innovation, which promises their positive role in a group.

• Proceedings of the Korean Institute of Interior Design Conference
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• 2005.10a
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• pp.191-192
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• 2005

This project is to establish an annex clinic center under 5 floors with gross floor area of 3,000 Pyeong behind existing Chosun university Hospital main building with 600 beds. The goal of the design is connecting the new clinic center with the existing main building and completing a combined hospital that has synergy effects. Given the old condition of the hospital and characteristics of the ground, I tried to embody the image of Medical Pulse, which is very alive with strong pulse, and suggest vision of 21st century hospital. First, one main entrance as a combined hospital. For optimum access and functions, I used the entrance of existing building as the only main entrance of new combined hospital, rearrange the road in front of the main building and improve traffic system, and upgrade the image and function of combined main entrance by planning new atrium united robby that makes link to the main building easier. Second, section planning considering the optimum functions and convenience. I established 4 floors linking functionally with the existing building, minimized vertical traffic line, and enhanced convenience through barrier free environment, which is a horizontal traffic line without barriers, crucial to hospital. Third, combined zoning generating synergy effects. I linked sterilizing room with logistics center by operating room and service bridge, and arranged central treatment department horizontally, Also, by horizontally arranging cancer center and department of nuclear medicine close with PET and cyclotron center, I established identity of specialized departments.

• Journal of Communications and Networks
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• v.12 no.5
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• pp.499-509
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• 2010

A plethora of transmission control protocol (TCP) congestion control algorithms have been devoted to achieving the ultimate goal of high link utilization and fair bandwidth sharing in high bandwidth-delay product (HBDP) networks. We present a new insight into the TCP congestion control problem; in particular an end-to-end delay-based approach for an HBDP network. Our main focus is to design an end-to-end mechanism that can achieve the goal without the assistance of any network feedback. Without a router's aid in notifying the network load factor of a bottleneck link, we utilize goodput and throughput values in order to estimate the load factor. The obtained load factor affects the congestion window adjustment. The new protocol, which is called TCP-goodput and throughput (GT), adopts the carefully designed inversely-proportional increase multiplicative decrease window control policy. Our protocol is stable and efficient regardless of the link capacity, the number of flows, and the round-trip delay. Simulation results show that TCP-GT achieves high utilization, good fairness, small standing queue size, and no packet loss in an HBDP environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.6
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• pp.1323-1333
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• 1997

In this paper, we propose an efficient architecture for a high-speed cell concentrator/distributor(HCCD) in an ATM(Asynchronous Transfer Mode) switch and by analyzeing the simulation results evaluate the performance of the proposed architecuture. The proposed HCCD distributes cells from a switch link to local processors, or concentrates cells from local processor s to a switch link. This design is to guarntee a high throughput for the IPC (inter-processor communication) link in a distributed ATM switching system. The HCCD is designed in a moudlar architecture to provide the extensibility and the flexibility. The main characteristics of the HCCD are 1) Adaption of a local CPU in HCCD for improving flexibility of the system, 2) A cell-baced statistical multiplexing function for efficient multiplexing, 3) A cell distribution function based on VPI(Virtual Path Identifier), 4) A bypassing capability for IPC between processor attached to the same HCCD, 5) A multicasting capability for point-to-multipoint communication, 6) A VPI table updating function for the efficient management of links, 7) A self-testing function for detecting system fault.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.13-19
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• 2011

The purpose of this study is to analyze the characteristics of traffic accidents and to develop the models by day and night-time in the case of the arterial link sections. In pursuing the above, this study uses the 224 accident data occurred at the 24 arterial link sections in Cheongju. The main results analyzed are as follows. First, it was analyzed that the number of accidents during day was more than night, but the accidents rate during night was higher than day. Second, four models which were all statistically significant were developed. Finally, the differences between the day and night models were comparatively analyzed using independent variables.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.5
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• pp.888-908
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• 2011

The increasing demand from passengers in vehicles to improve safety, traffic efficiency, and comfort has lead to the growing interest of Wi-Fi based vehicle-to-infrastructure (V2I) communications. Although the V2I system provides fast and cost-effective Internet connectivity to vehicles via roadside Wi-Fi access points (APs), it suffers from frequent handoffs due to the high mobility of vehicles and the limited coverage of Wi-Fi APs. Recently, the Mobile AP (MAP) platform has emerged as a promising solution that overcomes the problem in the V2I systems. The main advantage is that MAPs may yield longer service duration to the nearby vehicles that have similar mobility patterns, yet they provide smaller link capacities than the roadside APs. In this paper, we present a new association control technique that harnesses available connection duration as well as achievable link bandwidth in high-speed vehicular network environments. We also analyze the tradeoff between two association metrics, namely, available connection duration and achievable link bandwidth. Extensive simulation studies based on real traces demonstrate that our scheme significantly outperforms the previous methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3393-3412
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• 2017

As a main challenge in network virtualization, virtual network embedding problem is increasingly important and heuristic algorithms are of great interest. Aiming at the problems of poor correlation in node embedding and link embedding, long distance between adjacent virtual nodes and imbalance resource consumption of network components during embedding, we herein propose a two-stage virtual network embedding algorithm NA-PVNM. In node embedding stage, resource requirement and breadth first search algorithm are introduced to sort virtual nodes, and a node fitness function is developed to find the best substrate node. In link embedding stage, a path fitness function is developed to find the best path in which available bandwidth, CPU and path length are considered. Simulation results showed that the proposed algorithm could shorten link embedding distance, increase the acceptance ratio and revenue to cost ratio compared to previously reported algorithms. We also analyzed the impact of position constraint and substrate network attribute on algorithm performance, as well as the utilization of the substrate network resources during embedding via simulation. The results showed that, under the constraint of substrate resource distribution and virtual network requests, the critical factor of improving success ratio is to reduce resource consumption during embedding.

• Journal of the Korean Society of Safety
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• v.27 no.3
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• pp.141-146
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• 2012

This study deals with the accident model using panel data which are composed of time series data of 2005 through 2007 and cross sectional data of link sections in Cheongju. Panel data are repeatedly collected over time from the same sample. The purpose of the study is to develop the traffic accident model using the above panel data. In pursuing the above, this study gives particular attentions to deriving the optimal models among various models including TSCSREG (Time Series Cross Section Regression). The main results are as follows. First, 8 panel data models which explained the various effects of accidents were developed. Second, $R^2$ values of fixed effect models were analyzed to be higher than those of random effect models. Finally, such the variables as the sum of the number of crosswalk on intersections and sum of the number of intersections were analyzed to be positive to the accidents.