• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.9
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• pp.741-749
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• 2012

Ad Hoc Self-Organizing TDMA (ASO-TDMA) has been proposed as a specification to support the multi-hop data communication service for ships over VHF band. It allows for organizing a multi-hop ad-hoc network in a distributed manner by sharing the radio resources among the ships navigating along the route. In this paper, Markov chain analysis is given to provide the average throughput performance for ASO-TDMA protocol Furthermore, the analytical results are verified with computer simulation, which shows that there exists the optimal transmission rate to maximize the average throughput as the subframe size and the number of ships are varying in each hop region.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.3
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• pp.29-35
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• 1997

The megastructure combined with the modular concept is an effcient structural system adequate for ultra-tail buildings for the future. An ingeneous structural control system can be developed by separating the internal subframe in one or many modules from the external megaframe, thus taking advantage of the effect of tuned mass dampers without adding any aditional mass. This so called mega-subcontrol system is generally modeled by a 20DF system for parametric study and for finding optimal values of the parameters. In this study the equation of motion for the system is obtained frist and the preconditions for the simplified modeling are investigated. Finally the optimal value for the subsreucture strffness is fomputed with given mass and damping ratios and transfer functions for responses are abtained for white noise ground exitation to verify the effectiveness of the mega-subcontrol system.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.3
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• pp.55-58
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• 2008

Hydroforming is a forming technology in which a steel tube is set in a die and formed to fit a specified shape by applying hydraulic pressure from inside the tube while also applying force in the tube axial direction (axial feed). In present study, the entire design process chain for an automotive cross-member was simulated and developed using hydroforming technology on high-strength steel. The part design stage required a feasibility study. The process was designed using computer-aided design techniques to confirm the actual hydroformability of the part in detail. The possibility of using hydroformable cross-member parts was examined using cross-sectional analyses, which were essential to ensure the formability of the tube material for each forming step, including pre-bending and hydroforming. The die design stage included all the components of a prototyping tool. Press interference was investigated in terms of geometry and thinning.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.240-246
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• 2013

In heterogeneous networks, the almost blank subframes (ABS) for inter-cell interference coordination (ICIC), which can be protected from the CCI due to unutilized subframes (i.e., ABS) is proposed. However, the analytical model for ABS-based systems has not been fully studied yet. In this paper, we derive a new analytical model to evaluate the performance of ABS-based systems. In an analytic model, we assume that each carrier in multicarrier systems, such as in OFDMA, is subject to large-scale fading, which is independent of other carriers. As a performance measure, we present the cumulative distribution function (CDF) for the effective SINR. We show the accuracy of the analytical model via simulation results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.122-125
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• 2006

The Substructure Synthesis means the technology to predict the dynamic properties of an assembly from the properties of its components, or to predict the effect of a modification on a structure. The FRF Based Substructuring method is a kind of the Substructure Synthesis and very useful to predict the efficiency of the product in the early stage of development. Especially, the Hybrid FBS method is very useful to predict the vehicle NVH characteristics after modifying some components of the vehicle. Target components can be established on the basis of test models and FE models of the prototype constructed in the early stage of development. In this study, the Hybrid FBS method was applied to vehicle subframe and car-body in order to reduce vehicle interior noise induced by engine exciting force.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.108-113
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• 2005

The damageability and repairability of similar platform type vehicles could be very concerned with design optimization. In all the vehicles crash tested, small size passenger vehicles were weakness in aspect of damageability and repairability. The most critical area appears to be repair cost considering that parts cost is the largest portion of total repair cost segments. Besides repair cost, attaching method of front sidemember and subframe are placed special importance for impact energy absorption and damageability and repairability. So in order to improve damageability and repairability of vehicle structure and body component of the monocoque type passenger vehicles, the end of front side member and front back beam should be designed with optimum level and to supply the end of front side member as a partial condition approx 300mm. The effectiveness of design concept on the 40% offset frontal impact characteristics of the passenger vehicle structure is investigated and summarized.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.10
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• pp.907-914
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• 2010

While rubber components are extensively used in automobile vehicle, there are still a lot of difficulties in designing the rubber components applied in complex shapes and preloaded states because of the complicated material properties. In this paper, an efficient experimental method is suggested, which estimates the dynamic stiffness of a rubber component using rubber material test and static stiffness of the bush. And it is verified by comparing with FEM predictions and experimental results. This method is capable of predicting the dynamic stiffness of a rubber bush under various load conditions from minimized test data. Also it estimates dynamic characteristics of a rubber component using rubber material test and FEM calculation.

• Steel and Composite Structures
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• v.25 no.2
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• pp.245-255
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• 2017

The performance of an Industrialised Building System (IBS) consists of prefabricated reinforced concrete components, is greatly affected by the behaviour of the connection between beam and columns. The structural characteristics parameters of a beam-to-column connection like rotational stiffness, strength and ductility can be explained by load-rotation relationship of a full scale H-subframe under gravitational load. Furthermore, the connection's degree of rigidity directly influences the behaviour of the whole frame. In this research, rotational behaviour of a patented innovative beam-to-column connection with unique benefits like easy installation, no wet work, no welding work at assembly site, using a hybrid behaviour of steel and concrete, easy replacement ability, and compatibility with architecture was investigated. The proposed IBS beam-to-column connection includes precast concrete components with embedded steel end connectors. Two full-scale H-subframes constructed with a new IBS and conventional cast in-situ reinforced concrete system beam-to-column connections were tested under incremental static loading. In this paper, load-rotation relationship and ratio of the rigidity of IBS beam-to-column connection are studied and compared with conventional monolithic reinforced concrete connection. It is concluded that this new IBS beam-to-column connection benefits from more rotational ductility than the conventional reinforced concrete connection. Furthermore, the semi-rigid IBS connection rigidity ratio is about 44% of a full rigid connection.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.519-525
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• 2010

The finite element (FE) method is generally used to model and simulate the physical behavior of large structures, such as passenger vehicles or aircraft. However, FE analysis involves a very large computation time and cost for developing the analysis model. Therefore, the vibration characteristics of large structural systems are often analyzed using the component mode synthesis (CMS) method, which is one of the substructure synthesis methods. In this study, the vibration characteristics of passenger vehicles are analyzed by using the substructure synthesis method. A passenger vehicle model, which includes a vehicle body, suspension systems, and a sub-frame, is presented. The physical components of the vehicle system are modeled as equivalent substructures using the Craig-Bampton method of CMS. The vibration characteristics, such as the natural frequencies and mode shapes and frequency response, of the vehicle system are determined. The effects of variations in some design parameters on the vibration characteristics of the full vehicle model are also investigated.

• The Journal of the Acoustical Society of Korea
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• v.24 no.7
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• pp.395-401
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• 2005

In this paper, the high-band codec for bandwidth scalable wideband speech codec is proposed. The wideband input speech signal is separated into low-band signal and high-band signal, and the low-band signal is encoded by the standard narrow-band speech codec and the high-band signal is encoded by the proposed codec. In the high-band codec. the signal is transformed into frequency domain by MLT on a subframe basis, and MLT coefficients are splitted into magnitude and sign for quantization. The magnitudes of MLT coefficients are arranged into several time-frequency bands and each band is quantized in 2D-DCT domain, where the low-band information is utilized for better performance. The sign of MLT coefficient is quantized based on a priority selection process with the weighting measurement. The objective and subjective performance of wideband speech codec including the proposed high-band codec is measured, and it is confirmed that the proposed codec has better performance than 32kbps G.722.1.