• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1616-1640
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• 2006

In this paper, we deal with a network optimization problem arising from the deployment of Ethernet-based BcN access network. BcN convergence services require that access networks satisfy QoS measures. BcN services have two types of traffics: stream traffic and elastic traffic. Stream traffic uses blocking probability as a QoS measure, while elastic traffic uses delay factor as a QoS measure. Incorporating the QoS requirements, we formulate the problem as a nonlinear mixed-integer programming model. The proposed model seeks to find a minimum cost dimensioning solution, while satisfying the QoS requirement. We propose tabu search heuristic algorithms for solving the problem, and simulate tabu result. We demonstrate the computational efficacy of the proposed algorithm by solving a network design problem.

• Journal of Digital Contents Society
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• v.8 no.1
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• pp.69-76
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• 2007

The blocking of malicious traffic in groupware network system is used to prevent the spread and distribution of malicious traffic. The method protecting from malicious traffic in groupware system is designed to handle the malicious traffic of various routes with the internal course of groupware, which leads to lighten the load of security and traffic. It was impossible to block this kind of traffic at the traditional structure. When the protection of the proposed groupware system is performed, there appears to be a great change for the rate of a load factor at the CPU of Backbone Switch which is connected to the internal gateway. The load factor of CPU, which was increased with the traffic, is now remarkably reduced after the internal gateway is set up. This is to show that a lot of malicious traffic pass through the internal network and that network environment is faced to the menace of many malicious traffics. This paper is to show the efficiency of protection of internal gateway proposed in this study, for the rate of CPU of Backbone Switch was about 17% a day, but was dropped up to the 4% after the malicious traffic was removed.

• Journal of the Korean Institute of Landscape Architecture
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• v.39 no.5
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• pp.12-20
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• 2011

Parks and green spaces have various functions for improving urban physical and social environments. Urban parks and green space planning have been applied in this study for the purpose of enhancing the urban environment. The most popular method for urban parks and green space planning is incrementing the quantity of parks and green spaces. However, it may not be possible to designate new parks and green spaces in a large city because of the difficulty of obtaining land. This study explores how urban parks and green space planning produces better quality urban environments without having to designate new parks and green spaces. The study evaluates existing parks and green spaces according to the satisfaction of the users. This evaluation could be a useful tool for those planning urban parks and green space systems. The study was performed in Tama Newtown, Japan, within two districts with two distinct characteristics of park systems: concentration and equality arrangement forms. For comparison, on-site questionnaires were used, with 319 residents in the area responding to the study. The data was collected and analyzed, using t-test, factor analysis, and multiple regression methods. The study found there was no difference in satisfaction factors be tween the two districts. However, differences were found within each of the districts, depending on parks and green space components. For example, the quality of green space was the most important factor for the district with a planned concentration arrangement form of parks and green spaces, but, separation of the pedestrian and vehicular systems was the most important factor in the district with a planned equality arrangement form of park system. Factors affecting the satisfaction of parks and green spaces that were common between the two sites were: accessibility, quality of park, quality of green space, and separation of pedestrian and vehicular traffics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.11
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• pp.979-985
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• 2012

The design of an efficient scheduler is a key design factor in IEEE 802.16m systems, in order to support services with various QoS smoothly. Although conventional studies of schedules have been suggested, those had problems that are not able to satisfy the delay condition and make the through-put declined, because they only focused on a specific action scenario rather than reflecting practical action scenarios which have real-time and non-real-time traffics variously. In this paper, an efficient uplink scheduling algorithm is proposed for IEEE 802.16m system by introducing the concepts of Virtual Time(VT) and Virtual Finish Time(VFT) based priority determination, and separate buffers for each QoS class in the mobile terminal. Simulation results showed that the proposed scheme had satisfied the delay requirement of real-time services even with improved throughput performance compared to conventional methods.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.11
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• pp.1-12
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• 2005

In wireless personal area networks(PANs), the successful design of channel time allocation algorithm is a key factor in guaranteeing the various quality of service(QoS) requirements for the stringent real-time constraints of multimedia services. In this paper we propose a dynamic channel time allocation algerian for providing delay guarantees to multimedia traffics such as MPEG streams in the IEEE 802.15.3 high-rate WPANs. The dynamic algorithm exploits the characteristics of MPEG stream, wherein the devices (DEVs) send their channel time requests only at the end of superframe boundaries. The algerian uses mini packets for feedback control in order to deliver dynamic parameters for channel time requests from the DEVs to the piconet coordinator (PNC). In this scheme, the duration of channel time allocated to a DEV during a superframe is changed dynamically depending on the MPEG frame type, traffic load and delay bound of the frame, etc. Performance of the proposed scheme is investigated by simulation. Our results show that compared to traditional scheme, the proposed scheme is very effective and has high performance while guaranteeing the delay bound.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.6
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• pp.695-701
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• 2014

Blackhole attacks having a unauthorized change of routing data will cause critical effects for transmission performance. The transmission performance will be improved to the a certain level by using or having IDS(Intrusion Detection System)/IPS(Intrusion Prevention System) as countermeasures to blackhole attacks. In this papar, the effects of IDS to ene-to-end performance of packet aggregation transmission are analyzed on MANET(Mobile Ad-hoc Network) with IDS under blackhole attacks. MANET simulator based on NS-2 is used to analyze performance parameters as MOS, connection ratio, delay and packet loss rate as standard performance parameters, an another performance factor which is suggested in this paper. VoIP(Voice over Internet Protocol) traffics, one of voice services, is used for performance analysis. A suggestion for IDS implementation on MANET with packet aggregations under blackhole is shown as one of results.

• The Korean Journal of Malacology
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• v.30 no.4
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• pp.421-428
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• 2014

Total 20 surface sediments were collected in Anjung bay to investigate the physicochemical environment and heavy metal contents. The physicochemical investigation ranged from 6.41% to 11.68% (average $9.52{\pm}1.28%$) for ignition loss (IL), from 17.99 mg/g to 43.84 mg/g (average $27.53{\pm}6.39mg/g$) for chemical oxygen demand (COD), and from 0.05 mg/g to 0.61 mg/g (average $0.17{\pm}0.14mg/g$) for acid volatile sulfide (AVS) with significant correlation between water content (W/C) and COD. A contour of spatial distribution indicated higher organic pollution at the bottom of ascidian, Stylea clava, cultural waters. Most of metals contents was not exceeded the NOAA's effect range-low (ERL). Estimated enrichment factor (EF) ranging 0.96-1.12 indicated that the sediment environment of the studied waters was relatively pristine from heavy metal pollution in spite of increased vessel traffics, so far.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.4
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• pp.188-200
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• 2002

The WRR scheduling algorithm is widely used in ATM networks due to its simplicity and the low cost of hardware implementation. It guarantees minimum cell rate according to the weight of each queue. The fairness is a important factor for ABR service. That is, scheduling algorithm allocates network resources fairly to each VC. However, WRR algorithm shows worse performance on bursty traffic. Because it schedules input traffics according to predetermined weight, it can not satisfies fairness criteria, MCR plus equal share and Maximum of MCR or Max-Min share, defined by ATM Forum TM 4.1 specification. The Nabeshima et al algorithm is not adapt to network status rapidly because it is not compensate the weights of unused bandwidth to VCs and assign the unused bandwidth to VCs by RR method. In this paper, we propose a scheduling algorithm for satisfying the two fairness criteria, MCR plus equal share and Maximum of MCR or Max-Min share, among the six criteria defined by ATM Forum TM 4.1 specification. The WRR, Nabeshima et al, and the proposed scheduling algorithms are compared with respect to fairness and convergence time throughout experimental simulation. According to the simulation results, the proposed algorithm shows higher fairness and more rapid convergence than other algorithms.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.10
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• pp.1-9
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• 2001

The MAC (Medium Access Control) protocol is needed for the OLT(Optical Line Termination) to allocate bandwidth to ONUs(Optical Network Units) and ONTs(Optical Network Terminations) dynamically in the ATM PON(Passive Optical Network). With the protocol, the OLT gathers ONUs' informations and provides grants efficiently to each ONU. Two important functions of the MAC protocol is the grant request procedure and the grant distribution algrithm. The latter has the greatest arithmetic portion in the TC(Transmission Convergence) module, occupies a relatively large portion of the overall chip area, has often been the limiting factor in terms of speed, and should be designed to guarantee the quality of service for various traffics. In this paper, we implement the MAC with the FPGA which can allocate grants dynamically according to the queue length information and the number of active ONUs and distribute grants uniformly to minimize the cell delay variation for each ONU. The structure of the MAC scheduler for the dynamic bandwidth assignment has a programmable look-up table. Also, it has a simple structure, the less chip area, and the lower delay time.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.4 no.2
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• pp.157-167
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• 1994

This study was conducted to analyze the relationship between the types of fiber and its content and the levels of airborne fiber concentrations at eight parking lots where sprayed insulation material was found on the walls and ceilings. Also this study was designed to find the relationship between the levels of airborne fiber concentrations and such variables as air current, humidity, total exhaust volume, surface condition of insulation material and building age. The results obtained were as follows : 1. No significant correlation was found between the levels of airborne tiber concentration and the building age, air current, humidity, total exhaust volume, space and the number of traffics. 2. A significant correlation was found between the levels of airborne fiber concentration and the MMMF content of the insulation material(r=0.7594). However, no significant correlation was found between the levels of airborne fiber concentration and total fiber content of insulation material. 3. The differences of the airborne fiber concentrations among Cateogory 1, 2 and 3 classified by the degrees of surface insulation material maintenance were very significant. 4. Two bulk samples contained 30% crodicolite and 1% anthophylite. The MMMFs, in all parking lots, included mineral wool, cellulose fiber, trace cellulose fiber, trace tiber glass and vermiculite. 5. The mean value and the range of airborne fiber concentrations at 8 parking lots were $0.0239{\pm}0.0095f/cc$ and 0.0054-0.0447 f/cc, respectively. The fiber concentrations of 35 out of 38 samples(92%) were over 0.01 f/cc which is the Environment Administration's recommended asbestos level for the underground space. This study suggests that most of building insulation materials used in Korea, contain MMMF and sometimes asbestos. Currently, MMMF pollution levels may exceed the Environment Administration's recommended level for underground space. It has been found that airborne fiber concentrations increased significantly with MMMF content and with the maintenance condition of surface material. Therefore, it is recommended that a proper management technique should be developed and immediately implemented since the conditions of surface material will be gradually deteriorated due to building age and usage. Since health hazards of the MMMF, similar to those of asbestos, are being gradually acknowledged, a proper management technique which is applicable to control total airborne fiber concentrations, both asbestos and MMMF, be developed and an acceptable indoor air standard be promulgated as early as possible.