• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.186-192
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• 2011

In this paper, we propose a new procedure for improvement of the linear predictive coding. To reduce the error power incurred by the coding, we interchanged the order of the two procedures of windowing on the signal and linear prediction. This scheme corresponds to LPC extraction with windowed autocorrelation. The proposed method requires more calculational time because it necessitates matrix inversion on more parameters than the conventional technique where an efficient Levinson-Durbin recursive procedure is applicable with smaller parameters. Experimental test over various speech phonemes showed, however, that our procedure yields about 5 % less power distortion compared to the conventional technique. Consequently, the proposed method in this paper is thought to be preferable to the conventional technique as far as the fidelity is concerned. In a separate study of speaker-dependent speech recognition test for 50 isolated words pronounced by 40 people, our approach yielded better performance too.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.7
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• pp.666-676
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• 1992

In this paper, algorithm and testable circuit to find all PSF(Pattern Sensitive Fault ) occured in RAM were proposed. Conventional test circuit and algorithm took much time in testing because consecutive test for RAM cells or f-dimensional memory struciure was not employed. In this paper, methodology for parallel RAM-testing was proposed by compensating additional circuit for test to conventional RAM circuit. Additional circuits are parallel comparator, error detector, group selector circuit and a modified decoder used for parallel testing. And also, the constructive method of Eulerian path to obtain efficient test pattern was performed. Consequently, If algorithm proposed in this paper Is used, the same operations as 32sxwor4 lines will be needed to test b x w=n matrix RAM. Circuit simulation was performerd, and 10 bits x :If words testable RAM was designed.

• Journal of the Korean Data and Information Science Society
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• v.28 no.1
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• pp.11-20
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• 2017

In this paper, we introduced linear spatial time series (space-time autoregressive and moving average model) and nonlinear spatial time series (space-time bilinear model). Also we estimated the parameters by Kalman Filter method and made comparative studies of power of forecast in the final model. We proposed several weight matrices such as equal proportion allocation, reciprocal proportion between distances, and proportion of population sizes. For applications, we collected Mumps data at Korea Center for Disease Control and Prevention from January 2001 until August 2008. We compared three approaches of weight matrices using the Mumps data. Finally, we also decided the most effective model based on sum of square forecast error.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.3
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• pp.9-15
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• 2013

Recent works on ad hoc network study have shown that achievable throughput can be made to scale linearly with the number of receive antennas even if the transmitter has only a single antenna. In this paper, we propose a non-parametric linear minimum mean square error (MMSE) receiver for achieving further gain in performance when the channel state information at receiver (CSIR) of interferers is imperfect. The key feature to make our approach effective is to exploit the autocorrelation of the received signal. In fact, by incorporating the desired channel information on top of the observations including interference and noise only, the proposed method achieves large fraction of the optimal MMSE transmission capacity without transmission rate loss. From the SINR analysis as well as transmission capacity simulations in realistic ad hoc network system, we show that the proposed non-parametric linear MMSE receiver brings substantial performance gain over existing multiple receive antenna algorithms.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.7
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• pp.57-65
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• 2002

In this paper, a 2.5V 10-bit 300MSPS CMOS D/A Converter is described. The architecture of the D/A Converter is based on a current steering 8+2 segmented type, which reduces non-linearity error and other secondary effects. In order to achieve a high performance D/A Converter, a novel current cell with a low spurious deglitchnig circuit and a novel inverse thermomeer decoder are proposed. To verify the performance, it is integrated with $0.25{\mu}m$ CMOS 1-poly 5-metal technology. The effective chip area is $1.56mm^2$ and power consumption is about 84mW at 2.5V power supply. The simulation and experimental results show that the glitch energy is 0.9pVsec at fs=100MHz, 15pVsec at fs=300MHz in worst case, respectively. Further, both of INL and DNL are within ${\pm}$1.5LSB, and the SFDR is about 45dB when sampling, frequency, is 300MHz and output frequency is 1MHz.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.10
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• pp.3079-3094
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• 1996

Recently, the high-precision vibration attenuation technology becomes the essence fo the seccessful development of high-integrated and ultra-precision industries, and is expected to continue playing a key role in the enhancement of manufacturing technology. Vibration isolation system using an air-spring is widely employed owing to its excellent isolation characteristics in a wide frequency range. It has, however, some drawbacks such as low-stiffness and low-damping features and can be easily excited by exogenous disturbances, and then vibration of table is remained for a long time. Consequently, the need for active vibration control for an air-spring vibration isolation system becomes inevitable. Furthermore, for an air-spring isolation table to be successfully employed in a variety of manufacturing sites, it should have a guaranteed robust performance not only to exogenous disturbances but also to uncertainties due to various equipments which might be put on the table. In this study, an active vibration suppression control system using H.inf. theory is designed and experiments are performed to verify its robust performance. An air-spring vibration isolation table with voice-coil-motors as its actuators is designed and built. The table is modeled as 3 degree-of-freedom system. An active control system is designed based on $H_\infty$control theory using frequency-shaped weighting functions. Analysis on its performance and frequency responce properties are done through numerical simulations. Robust characteristics of$H_\infty$ control on disturbances and model uncertainties are experimentally verified through (i) the transient response to the impact excitation of the table, (ii) the steady-state response to the harmonic excitation, and (iii) the response to the mass change of the table itself. An LQG controller is also designed and its performance is compared with the $H_\infty$ controller.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.499-504
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• 2001

A validation of a 3D CFD model for predicting local subcooling of moderator in the vicinity of calandria tubes in a CANDU reactor is performed. The small scale moderator experiments performed at Sheridan Park Experimental Laboratory(SPEL) in Ontario, Canada[1] is used for the validation. Also a comparison is made between previous CFD analyses based on 2DMOTH and PHOENICS, and the current model analysis for the same SPEL experiment. For the current model, a set of grid structures for the same geometry as the experimental test section is generated and the momentum, heat and continuity equations are solved by CFX-4.3, a CFD code developed by AEA technology. The matrix of calandria tubes is simplified by the porous media approach. The standard $k-\varepsilon$ turbulence model associated with logarithmic wall treatment and SIMPLEC algorithm on the body fitted grid are used and buoyancy effects are accounted for by the Boussinesq approximation. For the test conditions simulated in this study, the flow pattern identified is a buoyancy-dominated flow, which is generated by the interaction between the dominant buoyancy force by heating and inertial momentum forces by the inlet jets. As a result, the current CFD moderator analysis model predicts the moderator temperature reasonably, and the maximum error against the experimental data is kept at less than $2.0^{\circ}C$ over the whole domain. The simulated velocity field matches with the visualization of SPEL experiments quite well.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.143-147
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• 2017

In this study, a driving load measuring method has developed without utilizing WFT. To measure the driving load, we developed a three-axis load cell with a strain gage. A method to verify the performance of load cells was developed. A system to measure the input load was proposed, and it was verified by evaluation. The measurement error of the impact road surface was found to be less than 20％. However, except under impact road surface conditions, the proposed system can be applied for actual vehicle input load measurement. The influence of tire evaluation tests were carried out through the handling verification evaluation. The input load measurement methods proposed in the present study make performance verification possible without using WFT.

• Advances in concrete construction
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• v.10 no.5
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• pp.381-391
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• 2020

This study aimed to develop reference materials (RMs) for mortar that can simulate the initial flow characteristics with constant quality over a long period. Through the previous research on the development of RMs for cement paste, the combination of limestone, glycerol, and water was used as the basic matrix for developing RMs for mortar in this study. In addition, glass beads of three particle sizes (0.5, 1.0, and 2.0 mm) and ISO standard sand were selected as tentative candidates to derive fine aggregate substitutes. The mixture of glass beads could simulate the initial flow characteristics of mortar, but under the same mixing ratio, replicates showed an unstable tendency to indicate inconsistent values due to the generation of electrostatic properties between materials and equipment. On the other hand, the mixture using ISO standard Sand not only simulates the constant flow characteristics for a long period of time, but also shows stable results with little error in replicates. Therefore, limestone, glycerol, ISO standard sand, and water were finally determined as components that met the required properties of RMs for mortar. The effect of each component on the flow characteristics of RMs was analyzed. It was found that glycerol increased the cohesion between the particles of standard sand, resulting in a constant increase both in the plastic viscosity and yield stress. Both limestone and standard sand had a dominant effect on the yield stress. The relationships between various mortar mixing ratios and the corresponding mixing ratios of RMs were established. In addition, the results of the verification experiment showed that the rheological properties of the RMs obtained through the relationships correlated with various water/cement ratios and the fine aggregate volume fractions of mortar obtained with same manner. In other words, the RMs for mortar developed in this study can be used as standard samples because they can simulate the initial flow characteristics of mortar of various mixing ratios for a long period without any chemical changes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.63-69
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• 2017

In next generation satellite broadcasting system, requirement of high throughput efficiency has been increasing continuously. To increase throughput efficiency and improve bit error performance simultaneously, FTN method and LDPC codes are employed in new sattelite standard, DVB-S3 system. This paper considered three kinds of methods for increase throughput efficiency. Firstly, as conventional one, high coding rate parity matrix in LDPC encoder is considered. Secondly, punctured coding scheme which delete the coded symbols according to appropriate rules is considered. Lastly, FTN method which transmit fater than Nyquist rate is considered. Among of three kinds of methods, FTN method is most efficient in aspect to performance while maintain same throughput efficiency.