• Earthquakes and Structures
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• v.18 no.1
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• pp.45-56
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• 2020

The application of critical excitation method with displacement-based objective function for multi degree of freedom (MDOF) systems is investigated. To this end, a new critical excitation method is developed to find the critical input motion of a MDOF system as a synthetic accelerogram. The upper bound of earthquake input energy per unit mass is considered as a new constraint for the problem, and its advantages are discussed. Considering this constraint, the critical excitation method is then used to generate synthetic accelerograms for MDOF models corresponding to three shear buildings of 10, 16, and 22 stories. In order to demonstrate the reliability of generated accelerograms to estimate dynamic response of the structures, three target ground motions with considerable level of energy contents are selected to represent "real critical excitation" of each model, and the method is used to re-generate these ground motions. Afterwards, linear dynamic analyses are conducted using these accelerograms along with the generated critical excitations, to investigate the key parameters of response including maximum displacement, maximum interstory drift, and maximum absolute acceleration of stories. The results show that the generated critical excitations can make an acceptable estimate of the structural behavior compared to the target ground motions. Therefore, the method can be reliably implemented to generate critical excitation of the structure when real one is not available.

• Journal of Broadcast Engineering
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• v.1 no.1
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• pp.1-6
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• 1996

Digital DBS service using Korea Sat starts at Korea Telecom's Yong-in transmission site. Total 6 transmitting stations are needed. At each transmitting station, 4 TV programs are compressed and multiplexed using MPEG-2, modulated into IF, RF signals, then finally transmitted through antenna. At DBS transponder, received signal is down converted, amplified and re-transmitted to earth. At receiver, signal is received by 45cm dish antenna, then wanted program is selected, demultiplexed and decoded. Transmission performance of BER lOE-ll is implemented by using FEe coding and QPSK modulation. For pay TV management, conditional access system, smart card and modem are used.

• International Journal of Quality Innovation
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• v.6 no.2
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• pp.59-89
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• 2005

Manufacturing Resources Planning (MRPII) is one kind of manufacturing information system that can help manufacturing companies gain competitive advantages. It is estimated that more than one hundred MRPII systems are available in the market, many of them are mature enough to solve most operational issues in accordance with users' requirements. More often than not, many of these systems provide more functions than a company expects. Manufacturing companies worldwide have attempted to implement these MRPII systems, however, many companies experienced failure (Turbide, 1996) due to managerial rather than technical issues. The authors propose an approach utilising a roadmap to integrate BPR and the MRPII implementation in order to overcome this difficulty. A detail road map is developed to guide this implementation, which is designed using a hierarchical analysis technique known as Integrated DEFinition Method (IDEF). IDEF is a systematic manufacturing management and integration-modeling tool. The proposed approach is implemented and illustrated using a reference company and the results indicated that 66% reduction in errors for maintaining the bills of materials system; 99% reduction in time to carry out material requirement planning; and 70% reduction in time previously taken for non-productive discussions.

• Korea-Australia Rheology Journal
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• v.18 no.4
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• pp.171-181
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• 2006

We present a short review for authors' previous work on direct numerical simulations for inertialess hard particle suspensions formulated either with a Newtonian fluid or with viscoelastic polymeric fluids to understand the microstructural evolution and the bulk material behavior. We employ two well-defined bi-periodic domain concepts such that a single cell problem with a small number of particles may represent a large number of repeated structures: one is the sliding bi-periodic frame for simple shear flow and the other is the extensional bi-periodic frame for planar elongational flow. For implicit treatment of hydrodynamic interaction between particle and fluid, we use the finite-element/fictitious-domain method similar to the distributed Lagrangian multiplier (DLM) method together with the rigid ring description. The bi-periodic boundary conditions can be effectively incorportated as constraint equations and implemented by Lagrangian multipliers. The bulk stress can be evaluated by simple boundary integrals of stresslets on the particle boundary in such formulations. Some 2-D example results are presented to show effects of the solid fraction and the particle configuration on the shear and elongational viscosity along with the micro-structural evolution for both particles and fluid. Effects of the fluid elasticity has been also presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1170-1176
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• 2006

This study aims to investigate numerically the static and dynamic stiffness characteristics of porous air bearing and to estimate appropriate permeability values of porous medium. In particular, a new roughness model is proposed and implemented into the commercial CFD code (FLUENT Ver.6.2). The predicted results are extensively compared with experimental data for static cases. The roughness model is also validated through comparison with the results from open literature. For the dynamic cases, the deforming and re-meshing technique is used for describing fluid-solid interactions. It is found that the predictions for static stiffness are in good agreement with experimental data and the dynamic stiffness appears to be relatively smaller than the static stiffness. In addition, moving and dynamic analysis of air bearing seems to be possible to provide qualitative predictions even if there are somewhat discrepancies quantitatively, compared to experimental data.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.8
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• pp.1368-1387
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• 2011

In recent years, ubiquitous and pervasive scenarios have emerged as a complex ecosystem where differentiated software/hardware components interoperate wirelessly and seamlessly. The goal is to enable users to continuously access services and contents, and to always get the best out of their current environment and available resources. In such dynamic and flexible scenarios, the need emerges for flexible and general solutions for continuous runtime self-reconfiguration and self-optimization of ubiquitous support software systems. This paper proposes a fully reconfigurable middleware approach that aims at reconfiguring complex software systems made up of heterogeneous off-the-shelf components from both functional and non-functional perspectives. Our middleware can also extend already existing and non-reconfigurable middleware/applications in an easy and flexible way, with no need to re-design them. The proposed design principles have been practically applied to the implementation of a runtime self-reconfigurable middleware called Off-The-Shelf Ready To Go (OTS-RTG), implemented on top of iPOJO. The reported experimental results both exhibit a limited overhead and show the wide applicability of the proposed solution to many application scenarios, including complex, industrial, Enterprise Service Bus-based ones.

• Phonetics and Speech Sciences
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• v.1 no.1
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• pp.63-67
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• 2009

In this paper, in order to protect music copyrights, we propose a music identification system which is scalable to the number of pieces of registered music and robust to signal-level variations of registered music. For its implementation, we define the new concepts of 'music word' and 'music phoneme' as recognition units to construct 'music acoustic models'. Then, with these concepts, we apply the HMM-based framework used in continuous speech recognition to identify the music. Each music file is transformed to a sequence of 39-dimensional vectors. This sequence of vectors is represented as ordered states with Gaussian mixtures. These ordered states are trained using Baum-Welch re-estimation method. Music files with a suspicious copyright are also transformed to a sequence of vectors. Then, the most probable music file is identified using Viterbi algorithm through the music identification network. We implemented a music identification system for 1,000 MP3 music files and tested this system with variations in terms of MP3 bit rate and music speed rate. Our proposed music identification system demonstrates robust performance to signal variations. In addition, scalability of this system is independent of the number of registered music files, since our system is based on HMM method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.2
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• pp.193-204
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• 1999

Performance of a variable-speed, roller-type vane compressor was evaluated at low evaporating temperature. First, an experimental investigation was conducted to examine the performance variation as functions of both outdoor temperature and rotating speed. For this purpose, a typical heat pump was implemented as a test apparatus to measure mass flow rate and power input. Secondly, computational investigations corresponding to the heat pump test conditions were performed to predict compressor performance using ORNL Map-Based compressor model. Results obtained from the heat-pump experiments showed that both mass flow rate and power consumption were sensitively dependent on both evaporating temperature and compressor speed as was predicted from the computational results. From the comparisons of both experimental and computational results, it was well recognized that the ORNL model was subjected to larger error in the accuracy of prediction as outdoor temperature decreased. When the outdoor temperature was above $-5^{\cire}C$, errors of predicted values corresponding to both mass flow rate and power consumption were estimated as $\pm$10% and $\pm$ 15%, respectively. Finally, it is suggested that the ORNL model needs to be re-evaluated if compressor map data tested below $-5^{\cire}C$(in evaporating temperature) are available.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1451-1459
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• 2004

In this paper, a low-power 32-point IMDCT structure is proposed for MP3. Through re-odering of IMDCT matrices, we propose the systolic structure operating with 16, 8, 4, 2, and 1 cycle, respectively. To reduce power consumption, multiplication of each sub blocks are implemented by add and shift operation with CSD(Canrmic sigled digit) form coefficients. To reduce, furthermore, the number of adders, we utilize the common sub-expression sharing techniques. With these techniques, the relative power consumption of the proposed structure is reduced by 58.4% comparison to the conventional structure using only 2's complement form coefficient. Validity of the proposed structure is proved through Verilog-HDL coding.

• Journal of Electrical Engineering and information Science
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• v.2 no.5
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• pp.9-16
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• 1997

This paper describes the design of a multistandard video encoder. The proposed encoder accepts conventional NTSC/PAL video signals, It also processes he PAL-plus video signal which is now popular in Europe. The encoder consists of five major building functions which are letter-box converter, color space converter, digital filters, color modulator and timing generator. In order to support multistandard video signals, a programmable systolic architecture is adopted in designing various digital filters. Interpolation digital filters are also used to enhance signal-to-noise ratio of encoded video signals. The input to the encoder can be either YCbCr signal or RGB signal. The outputs re luminance(Y), chrominance(C), and composite video baseband(Y+C) signals. The architecture of the encoder is defined by using Matlab program and is modelled by using Veriflog-HDL language. The overall operation is verified by using various video signals, such as color bar patterns, ramp signals, and so on. The encoder contains 42K gates and is implemented by using 0.6um CMOS process.