• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.10
• /
• pp.29-39
• /
• 2008

Greedy routing which is easy to apply to geographic wireless sensor networks is frequently used. Greedy routing works well in dense networks whereas in sparse networks it may fail. When greedy routing fails, it needs a recovery algorithm to get out of the communication void. However, additional recovery algorithm causes problems that increase both the amount of packet transmission and energy consumption. Communication void is a condition where all neighbor nodes are further away from the destination than the node currently holding a packet and it therefore cannot forward a packet using greedy forwarding. Therefore we propose a VODUA(Virtually Ordered Distance Upgrade Algorithm) as a novel idea to improve and solve the problem of void. In VODUA, nodes exchange routing graphs that indicate information of connection among the nodes and if there exist a stuck node that cannot forward packets, it is terminated using Distance Cost(DC). In this study, we indicate that packets reach successfully their destination while avoiding void through upgrading of DC. We designed the VODUA algorithm to find valid routes through faster delivery and less energy consumption without requirement for an additional recovery algorithm. Moreover, by using VODUA, a network can be adapted rapidly to node's failure or topological change. This is because the algorithm utilizes information of single hop instead of topological information of entire network. Simulation results show that VODUA can deliver packets from source node to destination with shorter time and less hops than other pre-existing algorithms like GPSR and DUA.

• Journal of KIISE:Information Networking
• /
• v.35 no.6
• /
• pp.521-528
• /
• 2008

Such conventional maritime communication technologies as radio have short some comings in their transmission quality. It can be overcome by wireless channels provided by satellites such as INMARSAT, which nevertheless suffer from the high costs. In this paper, we propose a novel technology resolving the above problems, featuring in the establishment of maritime communication networks with multi-hop structures. The inter vessel and ship-to- shore networks previously modeled after MANET are remodeled by SANET (Ship Ad Hoc Networks) in the present work. Fan-shaped Search Zone Routing (FSR) protocol also is presented, which utilizes not only static geographical information including the locations of ports and the navigations of courses but also the unique characteristics of ships in terms of mobile nodes. The FSR finds the fan-shaped search zone on which the shortest path is located. The performance of LAR protocol is compared with that of FSR in several ways. First, FSR does not make use of a type of control packets as beaconing data, resulting in a full utilization of the bandwidth of the wireless channels. Second, the delivery rate by the FSR is 100% for the fan-shaped search zone includes at least one route between source and destination nodes on its border line, where as that of LAR has been turned out to be 64%. Third, the optimality of routes searched by the FSR is on a 97% level. Of all, the FSR shows a better performance than LAR by about 50%.

• Journal of Korean Society of Transportation
• /
• v.22 no.2 s.73
• /
• pp.145-154
• /
• 2004

The growing demand for customer-responsive, made-to-order manufacturing is stimulating the need for improved dynamic decision-making processes in commercial fleet operations. Moreover, the rapid growth of electronic commerce through the internet is also requiring advanced and precise real-time operation of vehicle fleets. Accompanying these demand side developments/pressures, the growing availability of technologies such as AVL(Automatic Vehicle Location) systems and continuous two-way communication devices is driving developments on the supply side. These technologies enable the dispatcher to identify the current location of trucks and to communicate with drivers in real time affording the carrier fleet dispatcher the opportunity to dynamically respond to changes in demand, driver and vehicle availability, as well as traffic network conditions. This research investigates key aspects of real time dynamic routing and scheduling problems in fleet operation particularly in a truckload pickup-and-delivery problem under various settings, in which information of stochastic demands is revealed on a continuous basis, i.e., as the scheduled routes are executed. The most promising solution strategies for dealing with this real-time problem are analyzed and integrated. Furthermore, this research develops. analyzes, and implements hybrid algorithms for solving them, which combine fast local heuristic approach with an optimization-based approach. In addition, various partitioning algorithms being able to deal with large fleet of vehicles are developed based on 'divided & conquer' technique. Simulation experiments are developed and conducted to evaluate the performance of these algorithms.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.1
• /
• pp.146-170
• /
• 2017

Joint channel assignment and routing is a well-known problem in multi-radio wireless mesh networks for which optimal configurations is required to optimize the overall throughput and fairness. However, other objectives need to be considered in order to provide a high quality service to network users when it deployed with high traffic dynamic. In this paper, we propose a re-configuration optimization model that optimizes the network throughput in addition to reducing the disruption to the mesh clients' traffic due to the re-configuration process. In this multi-objective optimization model, four objective functions are proposed to be minimized namely maximum link-channel utilization, network average contention, channel re-assignment cost, and re-routing cost. The latter two objectives focus on reducing the re-configuration overhead. This is to reduce the amount of disrupted traffic due to the channel switching and path re-routing resulted from applying the new configuration. In order to adapt to traffic dynamics in the network which might be caused by many factors i.e. users' mobility, a centralized heuristic re-configuration algorithm called State-Aware Joint Routing and Channel Assignment (SA-JRCA) is proposed in this research based on our re-configuration model. The proposed algorithm re-assigns channels to radios and re-configures flows' routes with aim of achieving a tradeoff between maximizing the network throughput and minimizing the re-configuration overhead. The ns-2 simulator is used as simulation tool and various metrics are evaluated. These metrics include channel-link utilization, channel re-assignment cost, re-routing cost, throughput, and delay. Simulation results show the good performance of SA-JRCA in term of packet delivery ratio, aggregated throughput and re-configuration overhead. It also shows higher stability to the traffic variation in comparison with other compared algorithms which suffer from performance degradation when high traffic dynamics is applied.

• Journal of the Korea Society of Computer and Information
• /
• v.15 no.12
• /
• pp.75-84
• /
• 2010

As broadcasting in Mobile Ad hoc NETwork (MANET) is the process that a node sends a packet to all other nodes in the network. it is used for routing protocols such as Ad hoc On demand Distance Vector (AODV) to disseminate control information for establishing the routes. In this paper, we propose Probabilistic Broadcasting mechanism based on Distance Ratio between sender and receive node in MANETs. The proposed approach is based on the combination of probability and distance based approach. A mobile node receiving broadcast packets determines the probability of rebroadcasting considering distance ratio from sender. The distance ratio of a node is calculated by the distance from sender and the length of radio field strength. As a node with high distance ratio is located far away from sender, rebroadcast probability is set to high value. On contrary, the low rebroadcast probability is set for a node with low distance ratio which is close to sender. So it reduces packets transmission caused by the early die-out of rebroadcast packets. Compared with the simple flooding and fixed probabilistic flooding by simulation, our approach shows better performances results. Proposed algorithm can reduce the rebroadcast packet delivery more than 30% without scanting reachability, where as it shows up to 96% reachability compared with flooding.

• Archives of design research
• /
• v.18 no.3 s.61
• /
• pp.95-104
• /
• 2005

Although the volume and complexity of available information have increased, our ability to process such volume of complex information has not been met with corresponding development. Information designers have been given the responsibility to address such unbalanced progress by developing effective visual systems to deliver and communicate such information to the masses in a manner that is quick and easy to process and understand. This study originated in recognition of these issues. This study seeks to find a solution to these issues in rhetorics in order to proliferate visual communications in recognition of the increasing importance of information and visual communication. Rhetorics, a field of study with a long history of analyzing the delivery of communication, provides numerous possibilities for the re-establishment of importance placed on visual information communication. Included in this study are (i) a thorough analysis of the principals of expression and logic offered by rhetorics, as applicable to information design (ii) a proposal to the solution to the above-mentioned issues encompassing the rhetoric process and methods of expression of information design and (iii) the practical application of these design principals to social activities. In order to provide an example of the practical use of the rhetoric methodology Presented in this study, we applied the rhetoric methodology to the 'Information Design for Public Transportation of Seoul.' and developed a new map and a guidebook. The raw data necessary for the foregoing were obtained through the analysis of the information designs that are currently in use in connection with mass transportation in Seoul and the survey evaluation conducted among Seoul residents. We modulated the infrastructure of Seoul by using 48 TAZs, computed the routes that are most likely to be used, and proposed the predictable information analysis process. The design proposed on this study encompasses color coding and use of combined information, and application of style and sequential information analysis process.

• The KIPS Transactions:PartD
• /
• v.12D no.3 s.99
• /
• pp.417-428
• /
• 2005

Today, IT organizations perform projects with vision related to marketing and financial profit. The objective of realizing the vision is to improve the project performing ability in terms of QCD. Organizations have made a lot of efforts to achieve this objective through process improvement. Large companies such as IBM, Ford, and GE have made over $80\%$ of success through business process re-engineering using information technology instead of business improvement effect by computers. It is important to collect, analyze and manage the data on performed projects to achieve the objective, but quantitative measurement is difficult as software is invisible and the effect and efficiency caused by process change are not visibly identified. Therefore, it is not easy to extract the strategy of improvement. This paper measures and analyzes the project performance, focusing on organizations' external effectiveness and internal efficiency (Qualify, Delivery, Cycle time, and Waste). Based on the measured project performance scores, an OT (Opportunity Tree) model was designed for optimizing the project performance. The process of design is as follows. First, meta data are derived from projects and analyzed by quantitative GQM(Goal-Question-Metric) questionnaire. Then, the project performance model is designed with the data obtained from the quantitative GQM questionnaire and organization's performance score for each area is calculated. The value is revised by integrating the measured scores by area vision weights from all stakeholders (CEO, middle-class managers, developer, investor, and custom). Through this, routes for improvement are presented and an optimized improvement method is suggested. Existing methods to improve software process have been highly effective in division of processes' but somewhat unsatisfactory in structural function to develop and systemically manage strategies by applying the processes to Projects. The proposed OT model provides a solution to this problem. The OT model is useful to provide an optimal improvement method in line with organization's goals and can reduce risks which may occur in the course of improving process if it is applied with proposed methods. In addition, satisfaction about the improvement strategy can be improved by obtaining input about vision weight from all stakeholders through the qualitative questionnaire and by reflecting it to the calculation. The OT is also useful to optimize the expansion of market and financial performance by controlling the ability of Quality, Delivery, Cycle time, and Waste.

• Korean Journal of Health Education and Promotion
• /
• v.16 no.2
• /
• pp.137-155
• /
• 1999

The purpose of this study was to assess the effect of sex education on knowledge and attitude related to sex. The subjects were taken from by 199 students in 3 classes from 1st grade in H girl's junior high school as the study group, and 2 classes from 1st grade in S girl's junior high school as control group. During the survey period(September 21, 1998 to September 30, 1998), 6 times in terms of one-hour class for sex education were taught to the study group. A pre-test was executed on September 19, 1998 and the post-test on September 30. The findings were as follows. 1. According to the research, 20.1％ of the subjects have experienced sex education from parents and 89.9％ from teacher. They have mostly obtained the sex-related information from teachers(59.8％), following movie, radio, TV, or video tape(40.7％), friends(35.2％), reading materials such as books, cartoons, news papers and magazines(31.7％), parents(15.6％), siblings(7.0％), PC(1.5％) and telephone service(1.5％). 2. 27.1％ of the subjects reported that they had sex-related worry concerning from friendship with the opposite sex, following physiological phenomenon(31.5％), sex violence(11.1％), physical characteristics(7.4％), VD and contraception(5.6％), sexual impulse(5.6％), pregnancy and delivery(5.5％), and sexual behaviour(3.7％). The research showed that the adolescents usually solved their problems through the consultation with theifriends(44.4％). However, 16.7％ of the subjects were turned out not to request any solution. The other minor routes to settle their problems were written materials such as books, magazines(13.0％), parents(13.0％), movie, radio, TV, or video tape(5.5％), acquainted female elders(3.7％) and teachers(3.7％). 3. The most interesting part regarding sex was the friendship with the opposite sex(61.8％), following adolescent's emotion(55.8％), physiological differences between two genders(52.8％), AIDS(48.7％), VD(46.7％), pregnancy(45.2％), contraception(45.2％), abortion(41.7％), intercourse(41.7％), masturbation(41.2％), sex violence(41.2％) and genital structure and secondary sexual characteristics(28.6％). 4. In regard to characteristics of the subjects influencing sex-related knowledge, the higher educational career of mother, living with at least either parent and the experience of sex education by teachers were statistically significant factors(p〈0.05). 5. In regard to characteristics of the subjects influencing attitudes toward sex, the experience of sex education by parents or teachers was a statistically significant factor(p〈0.05). 6. The analysis of knowledge score comparing results before and after sex education showed that control group's score decreased from 12.5 to 12.44 while the study group's score increased from 12.33 to 21.31, which was statistically significant(p〈0.001). 7. The analysis of the attitude scores before and after sex education showed that the control group's score slightly increased from 55.57 to 56.36, while the study group's score increased from 54.79 to 61.95, which was statistically significant(p〈0.001). 8. The level of sex-related concerns of the study group after sex education marked both the increase in some items and the decrease in others. 9. Most instructive session among the sex education was the third “to be a good friend to the opposite sex”(27.0％).