• Restorative Dentistry and Endodontics
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• v.27 no.2
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• pp.158-174
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• 2002

The aim of this study was to investigate the effect of light irradiation modes on polymerization shrinkage, degree of cure and microleakage of a composite resin. VIP$^{TM}$ (Bisco Dental Products, Schaumburg, IL, USA) and Optilux 501$^{TM}$ (Demetron/Kerr, Danbury, CT, USA) were used for curing Filtek$^{TM}$ Z-250 (3M Dental Products, St. Paul., MN, USA) composite resin using following irradiation modes: VIP$^{TM}$ (Bisco) 200mW/$\textrm{cm}^2$ (V2), 400mW/$\textrm{cm}^2$ (V4), 600mW/$\textrm{cm}^2$ (V6), Pulse-delay (200 mW/$\textrm{cm}^2$ 3 seconds, 5 minutes wait, 600mW/$\textrm{cm}^2$ 30seconds, VPD) and Optilux 501$^{TM}$ (Demetron/Kerr) C-mode (OC), R-mode (OR). Linear polymerization shrinkage of the composite specimens were measured using Linometer (R&B, Daejeon, Korea) for 90 seconds for V2, V4, V6, OC, OR groups and for up to 363 seconds for VPD group (n=10, each). Degree of conversion was measured using FTIR spectrometer (IFS 120 HR, Bruker Karlsruhe, Germany) at the bottom surface of 2 mm thick composite specimens V2, Y4, V6, OC groups were measured separately at five irradiation times (5, 10, 20, 40, 60 seconds) and OR, VPD groups were measured in the above mentioned irradiation modes (n=5 each). Microhardness was measured using Digital microhardness tester (FM7, Future-Tech Co., Tokyo, Japan) at the top and bottom surfaces of 2mm thick composite specimens after exposure to the same irradiation modes as the test of degree of conversion(n=3, each). For the microleakage test, class V cavities were prepared on the distal surface of the ninety extracted human third molars. The cavities were restored with one of the following irradiation modes : V2/60 seconds, V4/40 seconds, V6/30 seconds, VPD , OC and OR. Microleakage was assessed by dye penetration along enamel and dentin margins of cavities. Mean polymerization shrinkage, mean degree of conversion and mean microhardness values for all groups at each time were analyzed using one-way ANOVA and Duncan's multiple range test, and using chi-square test far microleakage values. The results were as follows : . Polymerization shrinkage was increased with higher light intensity in groups using VIP$^{TM}$ (Bisco) : the highest with 600mW/$\textrm{cm}^2$, followed by Pulse-delay, 400mW/$\textrm{cm}^2$ and 200mW/$\textrm{cm}^2$ groups, The degree of polymerization shrinkage was higher with Continuous mode than with Ramp mode in groups using Optilux 501$^{TM}$ (Demetron/Kerr). . Degree of conversion and microhardness values were higher with higher light intensity. The final degree of conversion was in the range of 44.7 to 54.98% and the final microhardness value in the range of 34.10 to 56.30. . Microleakage was greater in dentin margin than in enamel margin. Higher light intensity showed more microleakage in dentin margin in groups using VIP$^{TM}$ (Bisco). The microleakage was the lowest with Continuous mode in enamel margin and with Ramp mode in dentin margin when Optilux 501$^{TM}$ (Demetron/Kerr) was used.

• 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 Korea Multimedia Society
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• v.12 no.9
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• pp.1273-1287
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• 2009

PEGASIS, a chain-based protocol, forms chains from sensor nodes so that each node transmits and receives from a neighbor. In this way, only one node (known as a HEAD) is selected from that chain to transmit to the sink. Although PEGASIS is able to balance the workload among all of the nodes by selecting the HEAD node in turn, a considerable amount of energy may be wasted when nodes which are far away from sink node act as the HEAD. In this study, DERP (Distance-based Energy-efficient Routing Protocol) is proposed to address this problem. DERP is a chain-based protocol that improves the greedy-algorithm in PEGASIS by taking into account the distance from the HEAD to the sink node. The main idea of DERP is to adopt a pre-HEAD (P-HD) to distribute the energy load evenly among sensor nodes. In addition, to scale DERP to a large network, it can be extended to a multi-hop clustering protocol by selecting a "relay node" according to the distance between the P-HD and SINK. Analysis and simulation studies of DERP show that it consumes up to 80% less energy, and has less of a transmission delay compared to PEGASIS.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.1
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• pp.436-444
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• 2011

As practical use degree of multicasting increase, security for multicast is recognized as an important issue. Previous research in the area of secure multicast has mainly focused on group key management. The most important thing about the security of multicast is that only authorized members of this group will be able to access the data. The member of access to multicast communication is to use cryptography with a common shared session encryption key. We propose decentralized group key management based on agent for dynamic multicast with large groups and frequent joins or leaves in this paper. Whole group divide to several subgroup using agent technology and each agent manage members of each subgroup. Also, when rekeying updates that using one-way hash function can prevent the key exposure, and reduce the key distribution delay.

• Journal of Arbitration Studies
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• v.21 no.1
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• pp.33-56
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• 2011

Korea Supreme Court has cancelled four cases of thirty-nine Arbitral awards made by Korean Commercial Arbitration Board since Korea arbitration act was enacted in 1966. Three cases of them were cancelled by the reason of the arbitrator's disqualification in relation to impartiality or independence and the other to arbitration agreement enable to select the lawsuit or arbitration. When a person is approached in connection with his possible appointment as an arbitrator or has already been appointed as such, he shall without delay disclose all circumstances likely to give rise to justifiable doubts as to his impartiality or independence according to the one of the article 13 of Korean Arbitration Act. Upon being notified of the appointment as an arbitrator, each arbitrator shall immediately disclose in writing to the Secretariat any circumstances which might cause reasonable doubt about impartiality or independence. An arbitration agreement shall be made clearly and in writing not to appeal to the court or to be brought in the court. However most of the korean construction contracts have the arbitration agreement clause enable to appeal to the court or the arbitration on government official's advice. Many of these disputes are resolved by litigation after the precedent(Law case number : 2003da318) set by the Supreme Court on August 22, 2003 between the Korea(government) and the Korea Railroad or abandoned its attempt to arbitration. But each year, about four hundreds of arbitration business transactions were resolved arbitration, the voluntary submission of a dispute to an impartial person or persons for final and binding determination. Arbitration has proven to be an effective way to resolve these disputes privately, promptly, and economically.

• Journal of Communications and Networks
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• v.7 no.3
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• pp.313-324
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• 2005

The success of the IEEE 802.11 standard has prompted research into efficiency of the different medium access methods and their support for different traffic types. A modified version of the point coordination function (PCF) called modified PCF has been introduced as a way to improve the efficiency over the standard method. It has been shown through a simulation study and a mathematical analysis that channel utilization can be much improved compared to the standard, in case there is no so-called hidden station problem. However, under the hidden station problem, the efficiency of the modified PCF would obviously decrease. In this paper, some enhancements of the modified PCF are introduced. Firstly, we propose a retransmission process to allow frames involved in collisions to be retransmitted. Then, we propose a collision resolution mechanism to reduce the frame collision probability due to the hidden station problem. In addition, we propose a priority scheme to support prioritization for different traffic types such as interactive voice and video, and real-time data traffic in the modified PCF. To prevent the starvation of one low priority traffic, minimum transmission period is also guaranteed to each traffic type via an admission control algorithm. We study the performance of the modified PCF under the hidden station problem and the performance of the modified PCF with priority scheme through simulations. To illustrate the efficiency of the priority scheme, we therefore compare its simulation results with those of some standardized protocols: The distributed coordination function (DCF), the enhanced distributed channel access (EDCA), the PCF, and our previously proposed protocol: The modified PCF without priority scheme. The simulation results show that the increment of delay in the network due to the hidden station problem can be reduced using the proposed collision resolution mechanism. In addition, in a given scenario the modified PCF with priority scheme can provide better quality of service (QoS) support to different traffic types and also support a higher number of data stations than the previous proposals.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.135-142
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• 2010

Wireless mesh network, which is an access network technology, adopts ubiquitous features of ad-hoc network that includes capabilities of self-configuration and self-management. This paper proposes a scheme which enables nodes along route in wireless mesh network to authenticate data and verify data integrity. The scheme distinguishes infra-node, which is a network device used to form mesh network, and user node in ad-hoc network, which operates functions as a sender, receiver or relayer, to deploy different authentication scheme. That is, hop-based authentication scheme along route forming wireless backbone differs from authentication scheme for user nodes in route over MANET. The proposed scheme is less complex than previously proposed schemes from the repects of security setup procedures and managements. In addition, the scheme is able to reduce transmission delay from a source to a destination owing to fast authentication over wireless backbone.

• Physical Therapy Korea
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• v.2 no.2
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• pp.9-23
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• 1995

The objective of this study was to identify the effects of weight-transfer training on the weight bearing distribution and gait patterns of hemiplegic patients through visual and auditory feedback using a limb load monitor. The subjects of this study were 18 hemiplegic patients who had been hospitalized or were visited out-patient department of the Rehabilitation Hospital, College of Medicine, Yonsei University, from January 5, 1995 through March 15, 1995. Pre-and post-training changes in gait patterns were measured using ink foot prints as well as by recording weight bearing distribution using a limb load monitor. The data were analyzed by the repeated measure one-way ANOVA and paired t-test. The finding were as follows: 1. Prior to the training, 18 subjects bore more weight on the sound leg(61.6 %) than on the affected leg(38.4 %). 2. Posterior to the training, the average percentage of weight bearing on the affected leg increased significantly from 38.4 % prior to training; to 46.0 % immediately after training; 45.7 % after a 30 second delay; and 45.3 % after a 60 second 3. The difference in gait patterns between pre- and post- training was statistically significant, with an increase in gait velocity to 3.65 cm/sec post-training; an increase in stride length to 5.37 cm on the affected side; 4.77 cm on the sound side; and a narrowing of the base of support to 1.19 cm. In conclusion, hemiplegic weight-transfer training using visual and auditory feedback with a limb load monitor was found to be enhancing symmetrical standing posture, and simultaneously improve gait patterns.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.5
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• pp.105-111
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• 2008

Mobility support for mobile networks will be important to minimize the packet overhead, to optimize routing, to reduce handoff latency, and to reduce the volume of handoff signals. Mobile IPv6 (MIPv6) and Hierarchical MIPv6 (HMIPv6) are one of mobility management protocols (MMPs) that provides network layer mobility over all access technologies. However, the communication quality of these candidates is severely degraded during handoffs. As another way to improve the handoff performance of a mobile network by conventional MMPs such as MIPv6 and HMIPv6, we propose a Low Latency Handoff Scheme (LLHS) combining Fast MIPv6 (FMIPv6) with HMIPv6 extension with buffering function, in which Mobility Anchor Points (MAPs) buffer packets destined to the Mobile Routers (MRs) or MNs within a mobile network during handoffs. The simulation results show that the proposed scheme reduces transmission delay and packet loss in UDP communication.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.5
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• pp.737-748
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• 1995

In this paper, we studyed the variables in the design of multichip memory modules with 4M$\times$1bit DRAM chips to construct high capacity and high speed memory modules. The configuration of the module was 8 bit, 16 bit, and 32 bit DRAM modules with employing 0.6 W, 70 nsec 4M$\times$1 bit DRAM chips. We optimized routing area and wiring density by performing the routing experiment with the variables of the chip allocation, module I/O terminal, the number of wiring, and the number of mounting side of the chips. The multichip module was designed to be able to accept MCM-L techiques and low cost PCB materials. The module routing experiment showed that it was an efficient way to align chip I/O terminals and module I/O terminals in parallel when mounting bare chips, and in perpendicular when mounting packaged chips, to set module I/O terminals in two sides, to use double sided substrates, and to allocate chips in a row. The efficient number of wiring layer was 4 layers when designing single sided bare chip mounting modules and 6 layers when constructing double sided bare chip mounting modules whereas the number of wiring layer was 3 layers when using single sided packaged chip mounting substrates and 5 layers when constructing double sided packaged chip mounting substrates. The most efficient configuration was to mount bare chips on doubled substrates and also to increase the number of mounting chips. The fabrication of memory multichip module showed that the modules with bare chips can be reduced to a half in volume and one third in weight comparing to the module with packaged chips. The signal propagation delay time on module substrate was reduced to 0.5-1 nsec.