• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1654-1662
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• 2006

An ad hoc network is multi-hop network composed of radio links. and the transmission quality of a radio link is more unstable than that of a wired circuit. Packet loss thus occurs frequently in an ad hoc network, and the consequent connection failure results in a severe deterioration of TCP performance. TCP performance also deteriorates because of the collision of data packets and ACK packets in the radio channel. In this paper we study to improve the performance of the Mobile Ad-hoc network by using Delayed ACK algorithm with our proposed ODA(Ordering-Delayed ACK) method. The proposed ODA algorithm increases the number of the data packets orderly at the receiver side which is going to be applied for the Mobile Ad-hoc network. We accomplished a computer simulation using NS-2. From the simulation results, we find the proposed ODA algorithm obviously enlarge the channel capacity and improve the network performance at the situation of multi-hop of ad-hoc network than the existing Delayed ACK algorithm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.5
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• pp.113-118
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• 2015

Mobile wireless networks have received a lot of attention as a future wireless network due to its rapid deployment without communication infrastructure. In these networks communication path between two arbitrary nodes break down because some links in the path are beyond transmission range($r_0$) due to the mobility of the nodes. The set of total path break down time(${\bigcup}T_i$), which is the union of path break down time of every node pair, can be a good measure of the connectivity of the dynamic mobile wireless network. In this paper we show that the distribution of the total path break down time can be approximated as a exponential probability density function and confirms it through experimental data. Statistical knowledge of break down time enables quantitative prediction of delay, packet loss between two nodes, thus provides confidence in the simulation results of mobile wireless networks.

• Genomics & Informatics
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• v.11 no.3
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• pp.129-134
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• 2013

Orthostatic hypotension (OH) is defined by a 20-mm Hg difference of systolic blood pressure (dtSBP) and/or a 10-mm Hg difference of diastolic blood pressure (dtDBP) between supine and standing, and OH is associated with a failure of the cardiovascular reflex to maintain blood pressure on standing from a supine position. To understand the underlying genetic factors for OH traits (OH, dtSBP, and dtDBP), genome-wide association studies (GWASs) using 333,651 single nucleotide polymorphisms (SNPs) were conducted separately for two population-based cohorts, Ansung (n = 3,173) and Ansan (n = 3,255). We identified 8 SNPs (5 SNPs for dtSBP and 3 SNPs for dtDBP) that were repeatedly associated in both the Ansung and Ansan cohorts and had p-values of < $1{\times}10^{-5}$ in the meta-analysis. Unfortunately, the SNPs of the OH case control GWAS did not pass our p-value criteria. Four of 8 SNPs were located in the intergenic region of chromosome 2, and the nearest gene (CTNNA2) was located at 1 Mb of distance. CTNNA2 is a linker between cadherin adhesion receptors and the actin cytoskeleton and is essential for stabilizing dendritic spines in rodent hippocampal neurons. Although there is no report about the function in blood pressure regulation, hippocampal neurons interact primarily with the autonomic nervous system and might be related to OH. The remaining SNPs, rs7098785 of dtSBP trait and rs6892553, rs16887217, and rs4959677 of dtDBP trait were located in the PIK3AP1 intron, ACTBL2-3' flanking, STAR intron, and intergenic region, respectively, but there was no clear functional link to blood pressure regulation.

• Journal of Communications and Networks
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• v.7 no.3
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• pp.325-336
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• 2005

Mobile ad hoc networks (MANET) are composed of moving wireless hosts which, within range of each other, form wireless networks. For communication to occur between hosts that are not within each other's range, routes involving intermediate nodes must be established; however, since the hosts may be in motion, a host that was part of a route may move away from its upstream and downstream partners, thus breaking the route. In this paper, we propose anticipated route maintenance (ARM) protocol with two extensions to route discovery based routing scheme: Extend the route when nodes on a link move apart from each other and they have common neighbor that can be 'inserted' in the path, and shrink route when a node discovers that one of its neighbor which is not the next hop is also on the same route several hops later on. By utilizing only local geographic information (now a part of some route finding algorithms), a host can anticipate its neighbor's departure and, if other hosts are available, choose a host to bridge the gap, keeping the path connected. We present a distributed algorithm that anticipates route failure and performs preventative route maintenance using location information to increase a route lifespan. The benefits are that this reduces the need to find new routes (which is very expensive) and prevents interruptions in service. As the density of nodes increases, the chance to successfully utilize our route maintenance approach increases, and so does the savings. We have compared the performance of two protocols, pure dynamic source routing (DSR) protocol and DSR with ARM. The simulation results show how ARM improves the functionality of DSR by preventing the links in the route from breaking. Packets delivery ratio could be increased using ARM and achieved approximately $\100%$ improvement. The simulations clarify also how ARM shows a noticeable improvement in dropped packets and links stability over DSR, even though there is more traffic and channel overhead in ARM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.4
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• pp.334-342
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• 2014

Military communications for future warfare have limited resources but highly requirements. MANET has a lot of advantages for future military network due to easily deploying without infrastructure and supporting dynamic topology in restricted environments. But, one of the biggest issues for MANET is difficulty of transmitting data due to link failure in dynamic topology. Content Centric Networking is a future Internet paradigm which solves various IP network problem. In this paper, we propose a future military communication routing scheme using CCN in military tactical MANET. Simulation results show our scheme gets lower control message overhead and faster data downloads as number of node increases and mobile speed increases than other two schemes.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.7 no.2
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• pp.9-17
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• 2012

This paper integrates elements from the theory of agency, the entrepreneurship education, the start-up policies. Entrepreneurship education is demanded to enhance success of business candidate for business establishment and to increase start-up survival. Three researches are made by this study. First of all, Educational performance is measured and it explains why linked policies is needed. To explain linked performance, this paper introduces several hypothesis. These are about a rate of start-up failure caused by agency problem and a rate of education effect decreasing agency problem. Secondly, operation performance of it can be increased by linking among policies and should be for the original goals of start-up policies. Finally, several ideas including start-up certification is proposed. Start-up certification has role of contact point of different entrepreneurship policies. As a result, level of satisfaction of policies will increase and specially of education program by linked effects.

• BMB Reports
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• v.41 no.10
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• pp.716-721
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• 2008

To explore the effects of deregulated expression of the EBNA1 binding protein 2 (EBP2) on cell growth, we generated human HEK293 stable clones constitutively expressing an EBP2-EGFP fusion protein. We found both RNA and protein levels of cyclin E1, a dominant oncoprotein, were elevated in the EBP2- EGFP stable clones. These findings were confirmed by flow cytometry bivariate analysis of cyclin expression versus DNA content. Moreover, the increase in p21 expression and the specific phosphorylation at Ser1981 of ATM and Ser15 of p53 were also observed in these stable clones, and these observations may explain the failure to observe an increase in Cdk2 kinase activity. In addition, after one year of passage culture, the EBP2-EGFP stable clones tended to lose 4 to 5 chromosomes per cell when compared to that of control cells. All of these findings provide a possible link between deregulated expression of EBP2 and tumor development.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.4
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• pp.352-362
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• 2008

In the mobile ad hoc network, network nodes are continuously capable of movement, but have battery limitations and these characteristics of MANET cause network link failure. Therefore, when performing ubiquitous services with the application of MANET, a technique is required to improve the packet transmission rates as to enable continuous packet transmission while flexibly adapting to topology changes caused by the mobility of nodes. In this paper, we are proposing PAOMDV(Possibility based AOMDV) and OLSR-ME(OLSR with Modified Energy Efficiency) which are mixed-type protocols to solve the problem for design a more efficient protocol. Especially by classifying mobile ad hoc networks as clusters, OLSR-ME protocol is implemented on communication within the clusters, while PAOMDV is used in protocols between clusters. In addition, a selection algorithm for forwarding nodes that responding packet relays in the case of increased hops was proposed for designing a more efficient protocol than existing protocols. We verified the performance of the proposed protocols through a comparative experiment with AODV, AOMDV, ZRP, and the existing protocols. We confirmed the results of the experiment revealed that the proposed protocol had the best packet transmission rate, the shortest delay between nodes, and showed better results in routing overhead.

• Health Policy and Management
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• v.24 no.3
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• pp.205-218
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• 2014

Background: Most studies on the national health insurance benefit expansion policy have focused on policy tools or decision-making process. Hence there was not enough understanding on how policies are actually implemented within the specific policy context in Korea which has a national mandatory health insurance system with a dominant proportion of private providers. The main objectives of this study is to understand the implementation process of the benefit coverage expansion policy. Unlike other implementation studies, we tried to examine both the process of implementation and decision making and how they interact with each other. Methods: Interviews were conducted with the ex-members of the Health Insurance Policy Review Committee. Medical doctors who implement the policy at the 'street-level' were also interviewed. To figure out major variables and the degree of their influences, the data were analyzed with Winter's Policy Implementation Model which integrates the decision making and implementation phases. Results: As predicted by the Winter model, problems in the decision making phase, such as conflicts among the members of committee, lack of applicable causal theories application of highly symbolic activities, and limited attention of citizen to the issue are key variables that cause the 'implementation failure.' In the implementation phase, hospitals' own financial interests and practitioners' dependence on the hospitals' guidance were barriers to meeting the policy goals of providing a better coverage for patients. Patients, the target group, tend to prefer physicians who prescribe more treatment and medicine. To note, 'fixers' who can link and fill the gap between the decision-makers and implementers were not present. Conclusion: For achieving the policy goal of providing a better and more coverage to patients, the critical roles of medical providers as street-level implementers should be noted. Also decision making process of benefit package expansion policy should incorporate its influence on the implementation phase.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.653-661
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• 2012

High-availability seamless redundancy (HSR) is a redundancy protocol for Ethernet networks that provides two frame copies for each frame sent. Each copy will pass through separate physical paths, pursuing zero fault recovery time. This means that even in the case of a node or a link failure, there is no stoppage of network operations whatsoever. HSR is a potential candidate for the communications of a smart grid, but its main drawback is the unnecessary traffic created due to the duplicated copies of each sent frame, which are generated and circulated inside the network. This downside will degrade network performance and might cause network congestion or even stoppage. In this paper, we present two approaches to solve the above-mentioned problem. The first approach is called quick removing (QR), and is suited to ring or connected ring topologies. The idea is to remove the duplicated frame copies from the network when all the nodes have received one copy of the sent frame and begin to receive the second copy. Therefore, the forwarding of those frame copies until they reach the source node, as occurs in standard HSR, is not needed in QR. Our example shows a traffic reduction of 37.5%compared to the standard HSR protocol. The second approach is called the virtual ring (VRing), which divides any closed-loop HSR network into several VRings. Each VRing will circulate the traffic of a corresponding group of nodes within it. Therefore, the traffic in that group will not affect any of the other network links or nodes, which results in an enhancement of traffic performance. For our sample network, the VRing approach shows a network traffic reduction in the range of 67.7 to 48.4%in a healthy network case and 89.7 to 44.8%in a faulty network case, compared to standard HSR.