• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.3
• /
• pp.1087-1094
• /
• 2013

This study aims at enhancing the objective estimation of social cost of air quality due to mobile emission. More specifically, it examines the difference between the daily oriented and hourly oriented estimation results of social air quality cost and draws implications from the comparative analysis. The result indicates that the social cost of air quality differs up to approximately 24 times depending on the analysis time period. Moneywise, the difference between daily and hourly assignments amounts to the average of 653.5 billion won whereas only 1% of error occurred in the estimation result based on peak and nonpeak based hourly assignment. This study reaffirms the need for time-based travel demand management for emission reduction, and confirms the feasibility of emission estimation by travel demand forecasting method over the conventional method employed by the CAPSS.

• The KIPS Transactions:PartC
• /
• v.11C no.7 s.96
• /
• pp.905-916
• /
• 2004

Self-organizing hierarchical ad hoc network (SOHAN) is a new ad-hoc network architecture designed to improve the scalability properties of conventional 'flat' ad hoc networks. This network architecture consists of three tiers of ad-hoc nodes, i.e.. access points, forwarding nodes and mobile nodes. This paper presents a topology discovery and routing protocol for the self-organization of SOHAN. We propose a cross-layer path metric based on link quality and MAC delay which plays a key role in producing an optimal cluster-based hierarchical topology with high throughput capacity. The topology discovery protocol provides the basis for routing which takes place in layer 2.5 using MAC addresses. The routing protocol is based on AODV with appropriate modifications to take advantage of the hierarchical topology and interact with the discovery protocol. Simulation results are presented which show the improved performance as well as scalability properties of SOHAN in terms of through-put capacity, end-to-end delay, packet delivery ratio and control overhead.

• Journal of Internet Computing and Services
• /
• v.10 no.4
• /
• pp.189-198
• /
• 2009

Unstructured peer-to-peer systems are most commonly used in today's internet. But file placement is random in these systems and no correlation exists between peers and their contents. There is no guarantee that flooding queries will find the desired data. In this paper, we propose to cluster nodes in unstructured P2P systems using the agglomerative hierarchical clustering algorithm to improve the search method. We compared the delay time of clustering the nodes between our proposed algorithm and the k-means clustering algorithm. We also simulated the delay time of locating data in a network topology and recorded the overhead of the system using our proposed algorithm, k-means clustering, and without clustering. Simulation results show that the delay time of our proposed algorithm is shorter compared to other methods and resource overhead is also reduced.

• Journal of the Korea Convergence Society
• /
• v.5 no.3
• /
• pp.23-27
• /
• 2014

In recent times, there is an increasing interest in wireless charge of smartphones and devices, and many companies are developing wireless charges. The range of application of wireless charge would be expanded to almost all electronics, including not only mobile devices, but also notebook computers and vacuum cleaners. On-line electric vehicles are to be launched in the market this year in a massive scale. As such wireless charge-related markets are inexhaustible. Wireless charge is included in the world's top 10 promising technologies, and its rapid growth is expected to have annual growth by more than 100%. However, there's a need to establish a safe environment, by analyzing security threats to technical limitations and harmfulness to human body, and arrange institutional compliments. The development of communication method for a variety of wireless charging are delivering comfortable and safe information. This paper aims to examine the factors to threaten electric vehicle, which are usually intruded through network system and analyzes security threats to and security requirements for magnetic resonance mode-based wireless charge in mobile devices, and suggests security requirements.

• Korean Journal of Occupational Health Nursing
• /
• v.30 no.3
• /
• pp.120-131
• /
• 2021

Purpose: This study aimed to compare the effects of an 8 week, self-managed, app-based and poster-based stretching program on musculoskeletal symptoms, flexibility, stretching frequency, self-efficacy, social support, and musculoskeletal disorder knowledge in small manufacturing business workers. Methods: This was a cluster randomized, two-group pretest-posttest design. Workers were assigned to either an app-based (n=20) or a poster-based (n=25) stretching intervention. Both groups received an educational class. The app group also received mobile phone text messages and an app with stretching videos, stretching alarms, stretching records, and information on musculoskeletal disorders. The poster group received workplace stretching posters. Data were collected from April to September 2018 and analyzed with the 𝑥² test, paired t-test, and independent t-test. Results: There was only a significant difference in social support. Significant increase in flexibility and musculoskeletal symptoms were noted for both groups, but social support and musculoskeletal disorder knowledge were significantly changed only in the poster group. More than half of the workers practiced stretching at least 3 times a week. Conclusion: The 8 week, self-managed, workplace stretching program was effective to increase flexibility and stretching frequency to at least 3 times a week. However, effective interventions for musculoskeletal symptoms could not be identified.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.4
• /
• pp.95-103
• /
• 2009

In this paper, a generation method of transmit and receive beamforming vectors based on base station cooperation is proposed which maximizes the user SINR in mobile cellular multi-user MIMO systems. There are two main sources of interference which deteriorate the performance of the system, i.e. the inter-user interference caused by the usage of the same radio resource for multiple users in the system, and the inter-cluster interference from neighboring base stations which are not participating in cooperative transmission. The proposed scheme cancels out the inter-user interference by using the block diagonalization(BD) method, and mitigate the inter-cluster interference by using optimal transmit and receive beamforming vectors based on optimal combining(OC) with the statistic information of inter-cluster interference. We perform computer simulations to verify the performance of the proposed scheme, and compare the result to the conventional performance obtained from utilizing the receiver side information only or utilizing the information from neither sides. The performance evaluations are conducted not only over the independent MIMO channels, but over correlated MIMO channels to demonstrate the robustness of the proposed scheme over the channels with correlation among antennas.

• Journal of KIISE:Computing Practices and Letters
• /
• v.14 no.1
• /
• pp.22-30
• /
• 2008

Warehouse has many changes for the stocks by entering and taking. Management about the stocks is important. To manage, sensor network based on RFID is deployed in warehouse. Sensor network uses fluster based on energy and hierarchical routing. Supporting mobility between clusters makes guarantee connectivity for mobile nodes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.2B
• /
• pp.120-129
• /
• 2012

Wireless mesh network (WMN) has recently emerged as a promising technology for tactical operation. If a platoon is organized with MPs, this system is suitable for tactical coverage is given for battle field where there is a shortage of wired infrastructure. However, MPs of typical WMN are generally fixed. This condition does not apply to diverse tactical scenarios. In this paper, it is considered that MPs have group mobility for flexible tactical networks. We propose cluster based multi-channel MAC scheme for mobilie WMN with single antenna condition. We have reduced the collision problems and message storming problems occur by mobility, so the reliability of WMN has been improved. Consequently, reliable communication is guaranteed by our framework in mobile WMN.

• Journal of Environmental Health Sciences
• /
• v.38 no.5
• /
• pp.369-379
• /
• 2012

Objectives: Spatial analysis is useful for understanding complicated causal relationships. This paper focuses trends and appling methods for spatial analysis associated with environmental asbestos exposure. Methods: Literature review and reflection of experience of authors were conducted to know academic background of spatial analysis, appling methods on epidemiology and asbestos exposure. Results: Spatial analysis based on spatial autocorrelation provides a variety of methods through which to conduct mapping, cluster analysis, diffusion, interpolation, and identification. Cause of disease occurrence can be investigated through spatial analysis. Appropriate methods can be applied according to contagiousness and continuity. Spatial analysis for asbestos exposure source is needed to study asbestos related diseases. Although a great amount of research has used spatial analysis to study exposure assessment and distribution of disease occurrence, these studies tend to focus on the construction of a thematic map without different forms of analysis. Recently, spatial analysis has been advanced by merging with web tools, mobile computing, statistical packages, social network analysis, and big data. Conclusions: Because the trend in spatial analysis has evolved from simple marking into a variety of forms of analyses, environmental researchers including asbestos exposure study are required to be aware of recent trends.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.11 no.3
• /
• pp.69-77
• /
• 2015

MANET is composed of only the mobile nodes have a limited transmission range. The dynamic topology by the frequent movement of nodes makes routing difficult and is also cause exposed to security vulnerabilities. In this paper, we propose the security routing technique consisted of mechanism of two steps in order to respond effectively to attack by the modification of the routing information and transmit secure data. The hierarchical structure is used and the authentication node that issues the key of the nodes within each cluster is elected in this proposed method. The authentication node manages key issues and issued information for encrypting the routing information from the source node. The reliability value for each node is managed to routing trust table in order to secure data transmission. In the first step, the route discovery is performed using this after the routing information is encrypted using the key issued by the authentication node. In the second step, the average reliability value of the node in the found path is calculated. And the safety of the data transmission is improved after the average reliability value selects the highest path. The improved performance of the proposed method in this paper was confirmed through comparative experiments with CBSR and SEER. It was confirmed a better performance in the transmission delay, the amount of the control packet, and the packet transmission success ratio.