• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.285-288
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• 2005

In this paper, we propose a two step Binary Exponential search algorithm for rapid acquisition time of UWB(Ultra Wide Band) signal on UWB communication systems. Previous proposed timing acquisition algorithm is searching whole frame that consist of the number of n Bins to terminate search, however this paper proposed two step Binary Exponential search algorithm can achieve remarkable reduction of UWB signal acquisition time as limiting search group. Proposed search algorithm is consisting of search group establishment step and Bit Reversing of search group establishment step.

• Journal of the Korean Statistical Society
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• v.34 no.3
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• pp.219-233
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• 2005

The 3-way balanced multi-level rotation design has been discussed (Park Kim and Kim, 2003), where the 3-way balancing is done on interview time, in monthly sample and rotation group and recall time. A greater advantage of 3-way balanced design is accomplished by an estimator. To obtain the advantage, we generalized previous generalized composite estimator (GCE). We call this as l-step GCE. The variance of the l-step GCE's of various characteristics of interest are presented. Also, we provide the coefficients which minimize the variance of the l-step GCE. Minimizing a weighted sum of variances of all concerned estimators of interest, we drive one set of the compromise coefficient of l-step GCE's to preserve additivity of estimates.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2142-2148
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• 2015

This paper proposes novel real-time footstep planning and following methods for the navigation of humanoid robots. A footstep command is defined by a walking direction and step lengths for footstep planning. The walking direction is determined by a uni-vector field navigation method, and the allowable yawing range caused by hardware limitation is considered. The lateral step length is determined to avoid collisions between the two legs while walking. The sagittal step length is modified by a binary search algorithm when collision occurs between the robot body and obstacles in a narrow space. If the robot body still collides with obstacles despite the modification of the sagittal step length, the lateral step length is shifted at the next footstep. For footstep following, a walking pattern generator based on a 3-D linear inverted pendulum model is utilized, which can generate modifiable walking patterns using the zero-moment point variation scheme. Therefore, it enables a humanoid robot to follow the footstep command planned for each footstep. The effectiveness of the proposed method is verified through simulation and experiment.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.3
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• pp.43-50
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• 2014

In this paper, we deal with a single machine scheduling problems integrating with step deterioration effect and a rate-modifying activity (RMA). The scheduling problem assumes that the machine may have a single RMA and each job has the processing time of a job with deterioration is a step function of the gap between recent RMA and starting time of the job and a deteriorating date that is individual to all jobs. Based on the two scheduling phenomena, we simultaneously determine the schedule of step deteriorating jobs and the position of the RMA to minimize the makespan. To solve the problem, we propose a hybrid typed genetic algorithm compared with conventional GAs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.10 s.253
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• pp.1320-1327
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• 2006

Parallel procedure and performance of two-step Eulerian code have not been reported sufficiently yet even though it was developed and utilized widely in the impact simulation. In this study, parallel strategy of two-step Eulerian code was proposed and described in detail. The performance was evaluated in the self-made linux cluster computer. Compared with commercial code, a relatively good performance is achieved. Through the performance evaluation of each computation stage, remap is turned out to be the most time consuming part among the other part such as FE processing, communication, time marching etc.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.2B
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• pp.125-136
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• 2002

It is very important to acquire the synchronization in a intercell asynchronous WCDMA system, and it is carried out through the three-step cell search process. The cell search can operate in a stepwise parallel manner, where each step works in pipelined operation, to reduce the cell search time. In case that the execution time is set to be the same in each step, excessive accumulations will be caused in both step 1 and step 3, because step 2 should take at least one frame for its processing. In general, the effect of post-detection integration becomes saturated as the number of the accumulations increases. Therefore, the stepwise parallel scheme does not give much enhancement. In this paper, the performance of the stepwise parallel processing for cell search in WCDMA system is analyzed over Rayleigh fading channels. Through the analysis, the effect of cell search parameters such as the number of accumulations in each step and the power ratio allocated among channels is investigated. In addition, the performance of the stepwise parallel cell search is improved by adjusting the execution time appropriately for each step and is compared with that of the conventional stepwise serial processing.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.5
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• pp.27-32
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• 2021

This paper evaluates the equalization performance of FC-MMA adaptive equalization algorithm by the fixed step size that is used for the minimization of the intersymbol interference which occurs in the time dispersive communication channel. The FC-MMA has a fast convergence speed in order to adapts the new environment more rapidly in case of the time varying charateristics and the abnormal situation like as outage of the communication channel. But the algorithms operates in adative method, convegence speed is depend on fixed step size for adaptation. For this situation, its performance was evaluated by changing the step size value, the residual isi and maximum distortion and MSE performance index which means the convergence characteristics are widely adapted in the adaptive equalizer, SER were applied. As a result of computer simulation, the large step size can improves the convergence speed for reaching the steady state, but has a poor performance compared to small step size in residual values after steady state. The research result shows that the FC-MMA algorithm is applied the large step size for rapidly reaching the steady state in initial time, then adjust the small step size after reaching the steady state for reducing the residual values for equalization.

• The Korean Journal of Applied Statistics
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• v.34 no.2
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• pp.239-254
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• 2021

This paper studies time series analysis with estimation and forecasting for Korean COVID-19 confirmed cases, based on the approach of a heterogeneous autoregressive (HAR) model with two-piece t (TP-T) distributed errors. We consider HAR-TP-T time series models and suggest a step-by-step method to estimate HAR coefficients as well as TP-T distribution parameters. In our proposed step-by-step estimation, the ordinary least squares method is utilized to estimate the HAR coefficients while the maximum likelihood estimation (MLE) method is adopted to estimate the TP-T error parameters. A simulation study on the step-by-step method is conducted and it shows a good performance. For the empirical analysis on the Korean COVID-19 confirmed cases, estimates in the HAR-TP-T models of order p = 2, 3, 4 are computed along with a couple of selected lags, which include the optimal lags chosen by minimizing the mean squares errors of the models. The estimation results by our proposed method and the solely MLE are compared with some criteria rules. Our proposed step-by-step method outperforms the MLE in two aspects: mean squares error of the HAR model and mean squares difference between the TP-T residuals and their densities. Moreover, forecasting for the Korean COVID-19 confirmed cases is discussed with the optimally selected HAR-TP-T model. Mean absolute percentage error of one-step ahead out-of-sample forecasts is evaluated as 0.0953% in the proposed model. We conclude that our proposed HAR-TP-T time series model with optimally selected lags and its step-by-step estimation provide an accurate forecasting performance for the Korean COVID-19 confirmed cases.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.506-511
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• 2001

This paper presents how redevelopment of the boundary layer in a backward-facing step flow is affected by boundary conditions imposed on velocity at the inlet, top and exit of the flow. A two-dimensional, laminar, incompressible flow over a backward-facing step with an open top boundary has been computed by using numerical methods of second-order time and spatial accuracy and a fractional-step method that guarantees a divergence-free velocity field at all time. The inlet velocity profile above the step is of Blasius type. Along the top boundary, shear-tree and Dirichlet conditions on the streamwise velocity were considered and at the exit fully-developed and convective boundary conditions were examined. (The vertical velocity at all boundaries were assumed to be zero explicitly or implicitly.) From the computed flow fields, the reattachment on the bottom side of shear layer separated from the tip of the step and succeeding redevelopment of the boundary layer were investigated.

• Phonetics and Speech Sciences
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• v.13 no.4
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• pp.47-53
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• 2021

Autoregressive Text-to-Speech (TTS) models suffer from inference instability and slow inference speed. Inference instability occurs when a poorly predicted sample at time step t affects all the subsequent predictions. Slow inference speed arises from a model structure that forces the predicted samples from time steps 1 to t-1 to predict the sample at time step t. In this study, an end-to-end non-autoregressive fast text-to-speech model is suggested as a solution to these problems. The results of this study show that this model's Mean Opinion Score (MOS) is close to that of Tacotron 2 - WaveNet, while this model's inference speed and stability are higher than those of Tacotron 2 - WaveNet. Further, this study aims to offer insight into the improvement of non-autoregressive models.