• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.227-233
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• 2002

A vehicle longitudinal control strategy with guaranteed string stability for vehicle stop-and-go(SG) cruise control is presented in this paper. The SG cruise control systems should be designed such that string stability can be guaranteed in addition to that every vehicle in a string of SG cruise control vehicles must track any bounded acceleration and velocity profile of its preceding vehicle with a bounded spacing and velocity error. An optimal vehicle following control law based on the information of the 1311owing distance (clearance) and its velocity relative to the vehicle ahead (relative velocity) has been used and string stability analysis has been done based on the control law and constant time gap spacing policy, A validated multi-vehicle simulation package has been shown that the string stability analysis using the approximate model of the vehicle servo-loop which includes vehicle powertrain and brake control system dynamics is valid in the design of the SG cruise control law with guaranteed string stability.

• The Transactions of the Korea Information Processing Society
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• v.5 no.10
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• pp.2591-2599
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• 1998

In this paper, we proose a method of recognizing unknown words and correcting spelling errors(including spacing erors) to increase the performance of Korean information processing systems. Unknown words are recognized through comparative analysis of two or more morphologically similar eojeols(spacing units in Korean) including the same unknown word candidates. And spacing errors and spelling errors are corrected by using lexicatlized rules shich are automatically extracted from very large raw corpus. The extractionof the lexicalized rules is based on morphological and contextual similarities between error eojeols and their corection eojeols which are confirmed to be used in the corpus. The experimental result shows that our system can recognize unknown words in an accuracy of 98.9%, and can correct spacing errors and spelling errors in accuracies of 98.1% and 97.1%, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.4
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• pp.335-341
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• 2015

In this study, we analyzed a two-dimensional Stokes flow through a microchannel containing projections with constant spacing attached to each wall. The projections on the top and bottom walls were semi-circular in shape, with in-phase locations. By considering the periodicity and symmetry of the flow, the eigenfunction expansion and least squared error method were applied to determine the stream function and pressure distribution. For some typical radius and spacing values, the streamline patterns and pressure distributions in the flow field are shown, and the shear stress distributions on the boundary walls are plotted. In addition, the average pressure gradients in the microchannel are also calculated and shown with the radius and spacing of the projections. In particular, the results for the case of extremely small gaps between the projections on the top and bottom walls are in good agreement with the lubrication results.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.8
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• pp.72-78
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• 2009

We developed a line standards measurement system using an optical microscope and measured two kinds of line standards. It consists of three main parts: an optical microscope module including a CCD camera, a stage system with a linear encoder, and a measurement program for a microscopic image processing. The magnification of microscope part was calibrated using one-dimensional gratings and the angular motion of stage was measured to estimate the Abbe error. The threshold level in line width measurement was determined by comparing with certified values of a line width reference specimen, and its validity was proved through the measurement of another line width specimen. The expanded uncertainty (k=2) was about 100 nm in the measurements of $1{\mu}m{\sim}10{\mu}m$ line width. In the comparison results of line spacing measurement, two kinds of values were coincide within the expanded uncertainty, which were obtained by the one-dimensional measuring machine in KRISS and the line standards measurement system. The expanded uncertainty (k=2) in the line spacing measurement was estimated as $\sqrt{(0.098{\mu}m)^2+(1.8{\times}10^{-4}{\times}L)^2}$. Therefore, it will be applied effectively to the calibration of line standards, such as line width and line spacing, with the expanded uncertainty of several hundreds nanometer.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.129-130
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• 2007

Self servo track writing(SSTW)은 servo track writer(STW)를 이용하지 않고 hard disk drive의 내부 VCM을 이용하여 servo track을 기록하는 방식이다. SSTW는 이전 servo track을 상대적인 reference로 하여 기록하게 되므로 초기에 발생된 error와 외부의 disturbance의 영향으로 error는 급속하게 증가된다. 이것을 radial error propagation 이라 한다. 본 논문에서는 radial error propagation을 억제하기 위한 correction signal을 설계하고 servo writing 과정에서 발생하는 disturbance의 영향을 제거하기 위하여 disturbance observer(DOB)를 add-on type으로 구성하여 tracking 제어기를 설계하였다. 또한 DOB를 적용한 경우와 유사한 gain margin, phase margin과 sensitivity function을 갖는 제어기를 설계하여 그 성능을 비교하였다. 제안된 방식은 radial error propagation을 억제 하였을 뿐만 아니라 disturbance의 최소화하여 쓰여진 track의 DC track spacing과 AC track Squeeze가 개선된 것을 모의실험을 통하여 검증하였다.

• Journal of the Korea Convergence Society
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• v.12 no.12
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• pp.65-74
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• 2021

Recently, studies on Korean spelling correction have been actively conducted based on machine translation and automatic noise generation. These methods generate noise and use as train and data set. This has limitation in that it is difficult to accurately measure performance because it is unlikely that noise other than the noise used for learning is included in the test set In addition, there is no practical error type standard, so the type of error used in each study is different, making qualitative analysis difficult. This paper proposes new 'error type classification' for deep learning-based Korean spelling correction research, and error analysis perform on existing commercialized Korean spelling correctors (System A, B, C). As a result of analysis, it was found the three correction systems did not perform well in correcting other error types presented in this paper other than spacing, and hardly recognized errors in word order or tense.

• Journal of the Korean School Mathematics Society
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• v.16 no.4
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• pp.797-820
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• 2013

This study intended on analyzing the error patterns of mathematic problem posing sentences by the 100 elementary pre-teachers and discussing about the solutions. The results showed that the problem posing sentences have five error patterns: phonological error patterns, word error patterns, sentence error patterns, meaning error patterns, and notation error patterns. Divided into fourteen specific error patterns, they are as in the following. 1) Phonological error patterns are consisted of the 'ㄹ' addition error pattern and the abbreviated word error pattern. 2) Words error patterns are divided with the inappropriate usage of word error pattern and the inadequate abbreviation error pattern, which are formulized four subgroups such as the case maker, ending of the word, inappropriate usage of word, and inadequate abbreviation of article or word error pattern in detail. 3) Sentence error patterns are assumed four kinds of forms: the reference, ellipsis of sentence component, word order, and incomplete sentence error pattern. 4) Meaning error patterns are composed the logical contradiction and the ambiguous meaning. 5) Notation error patterns are formed four patterns as the spacing, punctuation, orthography of Hangul, and spelling rules of foreign words in Korean. Furthermore, the solutions for these error patterns were discussed: First, it has to be perceived the differences between spoken and written language. Second, it has to be rejected the spoken expressions in written contexts. Third, it should be focused on the learning of the basic sentence patterns during the class. Forth, it is suggested that the word meaning should have the logical development perception based on what it means. Finally, it is proposed that the system of spelling of Korean has to be learned. In addition to these suggestions, a new understanding is necessary regarding writing education for college students.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.3100-3102
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• 2000

In this paper, we propose to a robust frequency offset estimation method of OFDM signals. A carrier frequency offset may be decomposed into an integer multiple of the subcarrier spacing and a residual frequency offset. Fractional part of frequency offset is obtained by using the maximum likelihood estimation(MLE) method. And we use the correlation of the samples at the output of the discrete Fourier transform(DFT) to estimate integer part of frequency offset. The result shows that the estimation frequency offset is almost linear to frequency offset. We propose to an improved estimation error variance of the carrier frequency offset estimation. The proposed estimator has better performance than the conventional ones in terms of error variance and tracking range.

• Journal of Korean Institute of Industrial Engineers
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• v.38 no.2
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• pp.80-88
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• 2012

This paper focuses on small touch key size and spacing that affect the usability of the smart phones. The experiments examined thirty-six different touch key designs, combinations of four touch key sizes (width (mm) ${\times}$height (mm); $4{\times}4$, $4{\times}7$, $7{\times}4$, and $7{\times}7$), and nine spacings (horizontal (mm)${\times}$vertical (mm); $0{\times}0$, $0{\times}1$, $0{\times}3$, $1{\times}0$, $1{\times}1$, $1{\times}3$, $3{\times}0$, $3{\times}1$, and $3{\times}3$). Forty participants volunteered in the experiment. The completion time, error rate, identification discomfort, and control discomfort were measured. The results revealed that the touch key sizes of $7{\times}7$ and $7{\times}4$ provide the best performance in terms of the error rate measure, while the touch key size of $7{\times}7$ provides the best results for other measures. In addition, touch key spacings of $1{\times}1$, $1{\times}3$ and $3{\times}1$ are regarded as the best for all the measures. The results of this study suggest a practical approach for the small touch key design for the smart phones.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.6
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• pp.438-444
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• 2019

In this paper, we proposed a 16-element array antenna design to improve signal detection performances. The array antenna characteristics, such as mutual coupling, pattern deviation, and half power beamwidth of the active element, were examined to obtain an optimal spacing between individual elements. The single element of the array antenna consists of an indirect feed using L-shaped feed and shorted radiating patch to achieve a broadband operation. Root mean square(RMS) errors based on the incident angle of the signal were calculated to verify the signal detection performance of the proposed antenna. The results demonstrate that the proposed array antenna with optimal spacing is suitable for detecting interference signals with low RMS error.