• Journal of the Korean Society of Industry Convergence
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• v.2 no.2
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• pp.173-180
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• 1999

When Automobile runs high velocity, it causes sleepy velocity profile then that generates lift force and drag force. Lift force reduce tire friction force. Drag force increase consumed power. For improve automobile performance, reduction of Lift force and Drag force was seriously considered. It measured experimently using wind tunnel, numerically using numerical analysis. Finite difference method is using difference equation and simplifed mesh. This method require less calculation time and computer power than other method.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.4 s.346
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• pp.1-12
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• 2006

In this paper we propose an efficient mobile multimedia communication protocol, mobile terminal software platform and mobile VoIP application for IP-based convergence networks. The Proposed mobile multimedia communication protocol is called as ST-MRSVP (Split tunnel based Mobile Resource reServation Protocol) which integrates split tunnel based Mobile IP and RSVP in order to support hish speed mobility. Since mobile terminal platform supports QoS (Qualify of Service) with keeping seamless mobility, mobile QoS supporting modules are developed and interworked together by means of shared memory mechanism. Testbed is composed of a core-network embedding the proposed protocols and wireless LAN-based access networks. We verify functionality and performance of the proposed techniques by using various mobility test over the testbed. As a result, the proposed architecture can reduce the handover delay time with QoS support under 30% comparing with the standard mechanisms and support voice quality as good as CDMA phone.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.229-240
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• 2012

The development of multimedia applications followed by development of high-speed networks has improved the performance of mobile devices with high transfer speed broadband. Mobile internet access has made possible seamless indoor and outdoor mobile multicast services. Multicasting services are used to support efficient group communications. However, mobile multicasting services have two constraints: tunnel convergence and handover latency. Many protocols and handover methods have been proposed to address these problems. The inter-LMA optimized handover model for multicasting services has previously been proposed for PMIPv6-based networks. The proposed model removes the tunnel convergence issue and reduces router processing costs. It also makes possible the performance of fast handover operations with adaptive transmission mechanisms. In addition, the proposed scheme exhibits low packet delivery costs and handover latency in comparison with existing schemes, and ensures fast handover when moving the inter-LMA domain

• Journal of Internet Computing and Services
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• v.9 no.2
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• pp.35-42
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• 2008

Mobile IP is a solution to support mobile nodes, however, it does not handle NEtwork MObility (NEMO). The NEMO Basic Support (NBS) protocol ensures session continuity for all the nodes in the mobile network. Since the protocol is based on Mobile IP, it inherits the same fundamental problem such as tunnel convergence, when supporting the multicast for NEMO. In this paper, we propose the multicast route optimization scheme for NEMO environment. We assume that the Mobile Router (MR) has a multicast function and the Nested Mobile Router Information (NeMRI) table. The NeMRI is used to record o list of the CoAs of all the MRs located below it. And it covers whether MRs desire multicast services. Any Route Optimization (RO) scheme can be employed here for pinball routing. Therefore, we achieve optimal routes for multicasting based on the given architecture. We also propose cost analytic models to evaluate the performance of our scheme. We observe significantly better multicast cost in NEMO compared with other techniques such as Bi-directional Tunneling, Remote Subscription, and Mobile Multicast based on the NBS protocol.

• Journal of Convergence for Information Technology
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• v.10 no.7
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• pp.147-152
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• 2020

The research is carried out to analyze the cost-effectiveness of blasting patterns with regard to the diameters and design of blasting holes. Blasting patterns for single diameter array, and mixed diameter array were comparatively analyzed with regard to drilling and charging time, and materials required. The number of blasting holes required for single array pattern and mixed array pattern were 138 and 93 holes, respectively. From the drilling time analysis, reduction in time and its efficiency of mixed pattern were 139 minutes and 25%, respectively, in comparison with single pattern. Charging time reduction and its efficiency of mixed blasting pattern were evaluated as 22.5 minutes per worker and 33%, respectively, compare to single blasting pattern. The explosive quantities of G1 and G2 required for single array patterns were 270 and 30, while those were 222 and 20 for mixed array patterns for tunnelling 4m. And single pattern required 45 more detonators than the mixed pattern. The evaluation of material required can also be positive parameter for cost reduction of tunnel construction.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.99-108
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• 2005

One of the most important and difficult tasks in designing underground structure is the estimation of engineering properties of the ground. The main purpose of this study is to propose a new back-analysis technique in tunnelling to estimate geotechnical parameters around a tunnel. In this study, the Extended Bayesian Method, which appropriately combines objective information with subjective one, is adopted to optimize engineering parameters. By using only relative convergence data measured during tunnelling as input values in back-analysis, inevitable errors in absolute convergence estimation are excluded and 3-dimensional numerical analysis is applied to consider a trend of relative convergence occurrence. Finally, 3-dimensional back-analysis technique using relative convergence is proposed and evaluated using a hypothetical site.

• Smart Structures and Systems
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• v.25 no.4
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• pp.487-499
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• 2020

This paper proposes a novel approach to model updating for a large-scale cable-stayed bridge based on ambient vibration tests coupled with a hybrid metaheuristic search algorithm. Vibration measurements are carried out under excitation sources of passing vehicles and wind. Based on the measured structural dynamic characteristics, a finite element (FE) model is updated. For long-span bridges, ambient vibration test (AVT) is the most effective vibration testing technique because ambient excitation is freely available, whereas a forced vibration test (FVT) requires considerable efforts to install actuators such as shakers to produce measurable responses. Particle swarm optimization (PSO) is a famous metaheuristic algorithm applied successfully in numerous fields over the last decades. However, PSO has big drawbacks that may decrease its efficiency in tackling the optimization problems. A possible drawback of PSO is premature convergence leading to low convergence level, particularly in complicated multi-peak search issues. On the other hand, PSO not only depends crucially on the quality of initial populations, but also it is impossible to improve the quality of new generations. If the positions of initial particles are far from the global best, it may be difficult to seek the best solution. To overcome the drawbacks of PSO, we propose a hybrid algorithm combining GA with an improved PSO (HGAIPSO). Two striking characteristics of HGAIPSO are briefly described as follows: (1) because of possessing crossover and mutation operators, GA is applied to generate the initial elite populations and (2) those populations are then employed to seek the best solution based on the global search capacity of IPSO that can tackle the problem of premature convergence of PSO. The results show that HGAIPSO not only identifies uncertain parameters of the considered bridge accurately, but also outperforms than PSO, improved PSO (IPSO), and a combination of GA and PSO (HGAPSO) in terms of convergence level and accuracy.

• Journal of information and communication convergence engineering
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• v.14 no.2
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• pp.115-121
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• 2016

Currently there is a lack of literature on SPICE-level models of double-gate (DG) tunnel field-effect transistors (TFETs). A DG TFET compact model is presented in this work that is used to develop a SPICE model for DG TFETs implemented with Verilog-A language. The compact modeling approach presented in this work integrates several issues in previously published compact models including ambiguity about the use of tunneling parameters A_k and B_k, and the use of a universal equation for calculating the surface potential of DG TFETs in all regimes of operation to deliver a general SPICE modeling procedure for DG TFETs. The SPICE model of DG TFET captures the drain current-gate voltage (I_ds-V_gs) characteristics of DG TFET reasonably well and offers a definite computational advantage over TCAD. The general SPICE modeling procedure presented here could be used to develop SPICE models for any combination of structural parameters of DG TFETs.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.5
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• pp.89-95
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• 2023

The underground utility tunnel is an urban infrastructure that accommodates and manages important facilities such as water and sewage, electricity, and communication in the city, and is a national facility that needs to be protected from disasters such as fire, earthquake, and flooding. In establishing a disaster safety life cycle management system such as prediction, prevention, preparedness, response, and recovery, a disaster safety management platform for underground utility tunnel is being developed by utilizing digital twin technology in which advanced ICT technology and data are converged. In this paper, the maturity model for the disaster safety digital twin was reviewed, and the datasets necessary for implementing the digital twin at each stage were defined.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.2 s.40
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• pp.67-75
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• 2007

There are a number of risks in constructing tunnel-structures. Therefore, the precise and rapid observation about inside deformation of the tunnel is required to prevent these risks from occurring and to secure safety. But currently, the real situation is that the crown settlement, cavity deformation and ground surface settlement rely upon the universal mensuration which uses total station or various kinds of measuring instruments. Recently, according to improvement and progress of measuring technology, three-dimensional laser scanning is used as the method to provide data for maintaining structures. It solves the reliability problem of measuring method for the transformational volume of existing structures, provides data that enables to judge visually by three-dimensioning the shape change of structures and makes it possible to deliberate speedy countermeasure. And it can also be efficiently used in the structure maintenance and field measurement.