• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.3
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• pp.322-331
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• 2013

Wireless Mesh Networks(WMNs) is generally composed of radio nodes in the mesh topology. WMNs consists of mesh client, mesh router and gateway connected to a wired network. Each client and router relay messages to the gateway for communication. WMNs is widely used recently in many areas can provide extended coverage based on multi-hop communication and ubiquitous communication at any time and any location. However the competition and collision between each node to transmit data is inevitable when the same channel is used for transmission. The transmission opportunities and the throughput of nodes located far from gateway decrease more if the communication channel is accessed based on competitive CSMA/CA scheme using DCF(Distributed Coordination Function) provided by IEEE 802.11 MAC. In this paper, we improve the performance of the TCP fairness and throughput of the nodes with more than 2 hops by applying various algorithms for controlling contention window values. Also, we evaluate the performance using ns-2 simulator, According to the results, proposed scheme can enhance the fairness characteristic of each node irrespective of data to the gateway.

• The KIPS Transactions:PartB
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• v.17B no.5
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• pp.389-398
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• 2010

The Vehicle Routing and Scheduling Problem with Time Windows(VRSPTW) is to establish a delivery route of minimum cost satisfying the time constraints and capacity demands of many customers. The VRSPTW takes a long time to generate a solution because this is a NP-hard problem. To generate the nearest optimal solution within a reasonable time, we propose the heuristic by using an ACO(Ant Colony Optimization) with multi-cost functions. The multi-cost functions can generate a feasible initial-route by applying various weight values, such as distance, demand, angle and time window, to the cost factors when each ant evaluates the cost to move to the next customer node. Our experimental results show that our heuristic can generate the nearest optimal solution more efficiently than Solomon I1 heuristic or Hybrid heuristic applied by the opportunity time.

• Journal of Korean Neurosurgical Society
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• v.42 no.3
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• pp.168-172
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• 2007

Objective : Hirabayashi's open-door laminoplasty is a good procedure to use to treat patients with myelopathy of the cervical spine; however, the authors have experienced problems in maintaining an open-window in cervical spines after the surgery. The authors developed a modified method of the expanded open-door laminoplasty and compared the radiological and clinical results with those of the classical method. Methods : In the modified method, wiring fixation with lateral mass screws on the contra lateral-side instead of fixing the paraspinal muscle or facet joint, as in the classical methods, was used in the open window of the cervical spine. Fifteen patients with cervical myelopathy were treated using the classical method and 12 patients were treated using the modified method. Preoperative and postoperative clinical conditions were assessed according to the Japanese Orthopedic Association (JOA) score. The radiological results were compared with the preoperative and postoperative computed tomography (CT) findings. Results : In both methods, the clinical results revealed a significant improvement in neurological function (p<0.001). Image analysis revealed that the cervical canals were continuously expanded in patients treated using the modified methods. However, authors have observed restenosis during the follow-up periods in 4 patients treated using the original method. Progression to deformity and spinal instability were not observed in any of the patients in the radiological results. Conclusion : Although analysis with a larger population and a longer follow-up period needs to be undertaken, our modified open-door laminoplasty has shown an advantage in better maintaining an open window in comparison with the Hirabayashi's open-door laminoplasty.

• Journal of Intelligence and Information Systems
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• v.15 no.3
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• pp.137-150
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• 2009

This paper proposes the hybrid heuristic method to apply the opportunity time to solve the vehicle routing and scheduling problem with time constraints(VRSPTW). The opportunity time indicates the idle time which remains after the vehicle performs the unloading service required by each customer's node. In this proposed heuristic, we add the constraints to VRSPTW model for the opportunity time. We also obtain the initial solution by applying the cost evaluation function to the insertion strategy considering the opportunity time. In addition, we improve the former result by applying the opportunity time to the tabu search strategy by swapping the customer's node. Finally, we suggest the construction strategies of initial routing which can efficiently acquire the nearest optimal solution from various types of data in terms of geographical condition, scheduling horizon and vehicle capacity. Our experiment show that our heuristic can get the nearest optimal solution more efficiently than the Solomon's I1 heuristic.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.3
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• pp.285-292
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• 2011

The purpose of thise study was to measure the thickness of the sinus lateral wall using computed tomography (CT), and to find the most suitable vertical position for lateral window opening prior to sinus elevation. Thirty patients requiring sinus elevation had CT images taken with Philips Brilliance iCT. The thickness of the sinus lateral wall was measured according to its vertical position against the sinus inferior border, and its mean was calculated through three repeated measurements. When measured 2 mm above the sinus inferior border (SIB+2), the thickness of the sinus lateral wall was observed to be more than 2 mm. When measured 3 mm above the sinus inferior border (SIB +3), the sinus lateral wall was less than 2 mm in thickness. It is recommended that the lateral wall window be made 3 mm above the sinus inferior border when performing sinus elevation using the lateral approach.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.7
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• pp.543-552
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• 2013

For the safety messages in IEEE 802.11p/WAVE vehicles network environment, strict periodic beacon broadcasting requires status advertisement to assist the driver for safety. In crowded networks where beacon message are broadcasted at a high number of frequencies by many vehicles, which used for beacon sending, will be congested by the wireless medium due to the contention-window based IEEE 802.11p MAC. To resolve the congestion, we consider a MAC scheme based on slotted p-persistent CSMA as a simple non-cooperative Bayesian game which involves payoffs reflecting the attempt probability. Then, we derive Bayesian Nash Equilibrium (BNE) in a closed form. Using the BNE, we propose new congestion control algorithm to improve the performance of the beacon rate under saturation condition in IEEE 802.11p/WAVE vehicular networks. This algorithm explicitly computes packet delivery probability as a function of contention window (CW) size and number of vehicles. The proposed algorithm is validated against numerical simulation results to demonstrate its stability.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.3
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• pp.285-289
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• 2004

Recently, due to the high development of the internet, needs for multimedia streams such as digital audio and video is increasing much more. In case of transmitting multimedia streams using the User Datagram Protocol (UDP), it may cause starvation of TCP traffic on the same transmission path, thus resulting in congestion collapse and enormous delay because UDP does not perform TCP-like congestion control. Because of this problem, diverse researches are being conducted on new transmission schemes and protocols intended to efficiently reduce the transmission delay of real-time multimedia streams and perform congestion control. The TCP-friendly congestion control schemes can be classified into the window-based congestion control, which uses the general congestion window management function, and the rate-based congestion control, which dynamically adjusts transmission rate by using TCP modeling equations and the like. In this paper, we suggest the square-root congestion avoidance algorithm with the hybrid TCP-friendly congestion control scheme which the window-based and rate-based congestion controls are dealt with in a combined way. We apply the proposed algorithm to the existing TEAR. We simulate the performance of the proposed TEAR by using NS, and the result shows that it gives better improvement in the stability needed for providing congestion control than the existing TEAR.

• Journal of Digital Contents Society
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• v.9 no.1
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• pp.61-67
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• 2008

In this paper, MAC algorithm for the IEEE 802.11 DCF 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(Distributed Coordination Function) and PCF(Point Coordination Function). The DCF controls the transmission based on CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance), that decides a random backoff time with the range of CW(Contention Window) for each station. Normally, each station increase the CW to double after collision, and reduces the CW to the minimum after successful transmission. 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.

• Journal of the Korea Convergence Society
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• v.10 no.12
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• pp.109-115
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• 2019

This study was conducted to identify the relationship among the cognitive function of the elderly with dementia in the nursing home and the oral health condition and pathogenic microorganisms in the mouth. Data was collected for a month in February 2019 for 30 people through a non-probable sampling method due to the special nature of dementia elderly people aged 70 years or older, living in nursing homes in Daegu. Technical statistics, ANOVA, and Pearson's correlation coefficient were analyzed using the SPSS window ver. 21.0 program. According to the study, the lower the rating of long - term care classification in nursing homes, the more the number of high-risk oral pathogens, and the more the number of existing permanent teeth, the more the number of microbes in the mouth. However, there was no significant difference in cognitive function. Therefore, it is suggested that oral health care, an elderly dementia people in nursing homes, should have different management methods depending on the oral environment, and also professional managers should be able to manage oral health condition for actual care.

• Journal of the Korea Society of Computer and Information
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• v.18 no.3
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• pp.119-126
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• 2013

In this paper, we propose and describe the system to visualize the story of contents such as movies and novels. Character-net is applied as story model in order to visualize story. However, it is the form to be accumulated for total movie story, though it can depict the relationship between characters. We have developed the system that analyzes and shows the variation of Character-net and characters' tendency in order to represent story variation depending on movie progression. This system is composed by two windows that can play and analyze sequential Character-nets by time, and can analyze time variant graph of characters' degree centrality. First window has a function that supports to find important story points like the scenes that main characters appear or meet firstly. Second window supports a function that track each character's tendency or a variation of his tendency through analyzing in-degree graph and out-degree. This paper describes the proposed system and discusses additional requirements.