• Korean Journal of Materials Research
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• v.25 no.6
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• pp.279-287
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• 2015

In order to prepare anode materials for high power lithium ion secondary batteries, carbon composites were fabricated with a mixture of petroleum pitch and coke (PC) and a mixture of petroleum pitch, coke, and natural graphite (PC-NG). Although natural graphite has a good reversible capacity, it has disadvaantages of a sharp decrease in capacity during high rate charging and potential plateaus. This may cause difficulties in perceiving the capacity variations as a function of electrical potential. The coke anodes have advantages without potential plateaus and a high rate capability, but they have a low reversible capacity. With PC anode composites, the petroleum pitch/cokes mixture at 1:4 with heat treatment at $1000^{\circ}C$ (PC14-1000C) showed relatively high electrochemical properties. With PC-NG anode composites, the proper graphite contents were determined at 10~30 wt.%. The composites with a given content of natural graphite and remaining content of various petroleum pitch/cokes mixtures at 1:4~4:1 mass ratios were heated at $800{\sim}1200^{\circ}C$. By increasing the content of petroleum pitch, reversible capacity increased, but a high rate capability decreased. For a given composition of carbonaceous composite, the discharge rate capability improved but the reversible capacity decreased with an increase in heat treatment temperature. The carbonaceous composites fabricated with a mixture of 30 wt.% natural graphite and 70 wt.% petroleum pitch/cokes mixture at 1:4 mass ratio and heat treated at $1000^{\circ}C$ showed relatively high electrochemical properties, of which the reversible capacity, initial efficiency, discharge rate capability (retention of discharge capacity in 10 C/0.2 C), and charge capacity at 5 C were 330 mAh/g, 79 %, 80 %, and 60 mAh/g, respectively.

• The KSFM Journal of Fluid Machinery
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• v.18 no.6
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• pp.71-75
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• 2015

The flow and noise characteristics of the regenerative blower are evaluated experimentally. To decrease the noise of regenerative blower at a high frequency, we arrange the impeller vanes unevenly by special formula. The uneven pitch formular consists of the combination of trigonometric function. The magnitude of degree between each vanes and the control parameters of trigonometric functions are main design parameters for the uneven pitch. The flow characteristics of even and uneven impellers are tested by the fan tester and compared each results. The efficiency of a blower is calculated by the axial power using a dynamo system. The noise property of designed impeller is measured in an anechoic room. In this study, we certify that the uneven pitch impeller is effective in the noise reduction at a high frequency.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.1
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• pp.1-9
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• 2013

This paper presents a new control algorithm for dynamic control of a unicycle robot. The unicycle robot motion consists of a pitch that is controlled by an in-wheel motor and a roll that is controlled by a reaction wheel pendulum. The unicycle robot doesn't have any actuator for a yaw axis control, which makes the derivation of the dynamics relatively simple. The Euler-Lagrange equation is applied to derive the dynamic equations of the unicycle robot to implement the dynamic speed control of the unicycle robot. To achieve the real time speed control of the unicycle robot, the sliding mode control and LQ regulator are utilized to guarantee the stability while maintaining the desired speed tracking performance. In the roll controller, the sigmoid-function based sliding mode controller has been adopted to minimize the chattering by the switching function. The LQR controller has been implemented for the pitch control to drive the unicycle robot to follow the desired velocity trajectory in real time using the state variables of pitch angle, angular velocity, angle and angular velocity of the wheel. The control performance of the two control systems form a single dynamic model has been demonstrated by the real experiments.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.2
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• pp.81-87
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• 2016

This paper presents a new approach to control of stable motion of single wheel driving robot system of a pitch that is controlled by an in-wheel motor and a roll that is controlled by a reaction wheel. This robot doesn'thave any actuator for a yaw axis control, which makes the derivation of the dynamics relatively simple. The Lagrange equations was applied to derive the dynamic equations of the one wheel driving robot to implement the dynamic speed control of the mobile robot. To achieve the real time speed control of the unicycle robot, the sliding mode control and optical regulator are utilized to prove the reliability while maintaining the desired speed tracking performance. In the roll controller, the sigmoid-function based robust controller has been adopted to reduce the vibration by the situation function. The optimal controller has been implemented for the pitch control to drive the unicycle robot to follow the desired velocity trajectory in real time using the state variables of pitch angle, angular velocity, angle and angular velocity of the driving wheel. The control performance of the control systems from a single dynamic model has been illustrated by the real experiments.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.503-505
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• 1992

This paper describes the optimization of design variables of SLIM using finite element method and SUMT(Sequential Unconstrained Minimization Technique). Thrust is taken as an objective function in order to maximize thrust under constant current drive, and seven independent design variables and nine constraints are chosen. As a result, $\tau$/g(pole pitch/airgap) and $\tau$/$d_{AL}$(pole pitch/aluminum depth) of good criteria in SLIM design are determined.

• Phonetics and Speech Sciences
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• v.5 no.1
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• pp.91-98
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• 2013

This paper investigated Korean prosody as it relates to graded internal structure in an identification function. Within Korean prosody, variants regarded as dialectal variations can appear as different prosodic scales, which contain the range of within-category variations. The current experiment was intended to show how the prosodic scale corresponding to the range of within-category differences relates to f0 contours for speakers of two Korean dialects, North Kyungsang and South Cholla. In an identification task, participants responded by selecting an item from two answer choices. The probability of choosing the correct response from the two choices was computed by a logistic regression analysis using intercepts and slopes. That is, the correct response between two choices was used to show a linear line with an s-shape presentation. In this paper, to investigate the graded internal structure of labeling, 25%, 50%, and 75% of predicted probability were assessed. Listeners from North Kyungsang showed progressive variations, whereas listeners from South Cholla revealed random patterns in the internal structure of the identification function. In this paper, the results were plotted using scatterplot graphs, applying the range of within-category variation and predicted probability obtained from the logistic regression analyses. The scatterplot graphs showed the different degree of the responses for f0 scales (i.e., variations within categories). The results demonstrate that the gradient structures of native pitch accent users become more progressive in response to f0 scales.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.43-51
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• 2009

In the flight of air vehicles, accurate air data information is required to control them effectively. Especially, helicopters are often put in drastic motion involved with high angle of attacks in order to perform difficult missions. Among various sensors, the multi function probe (MFP) has been used in the present study mainly owing to its advantages in structural simplicity and capability of providing various information such as static and total pressure, speed, and pitch and yaw angles. In this study, a five-hole multi-function probe (FHMFP) is developed and its calibration is conducted using multiple regressions. In this work a calibration study on the FHMFP, an air data sensor for helicopters, is reported. It is shown that the pitch and yaw angles' accuracy of calibration is ${\pm}0.91^{\circ}$ at a cone angle of $0^{\circ}{\sim}30^{\circ}$ and ${\pm}2.0^{\circ}$ at $30^{\circ}{\sim}43^{\circ}$, respectively, which is summarized in table 3.

• Speech Sciences
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• v.9 no.4
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• pp.215-234
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• 2002

This study is designed for two purposes. The first one is to compare the realization and perception of English contrastive focus between Korean learners of English and native speakers of English. The second purpose is to study the phonological and phonetical features of contrastive focus by examining the results of production and perception experiments. English native speakers' results show that the English contrastive accents are generally accompanied by higher peak heights. The findings agree with the results of Bartels & Kingston (1994). Unlike native speakers of English, Korean speakers seem to be poor at relating the phonetical features of contrastive focus to their actual speech. Korean speakers' results are especially unsuccessful when the contrast is not distinctly grasped through syntactic structure, or when the function words are contrasted. Furthermore, Korean speakers' utterances tend to have pitch accents on every content word, whether the word is contrasted or not.

• The Journal of the Acoustical Society of Korea
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• v.10 no.4
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• pp.12-18
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• 1991

Detecting the fundamental frequency(Fo) of the speech signal is a problem in many speech applications. A problem of the pitch detection method in the frequency domain is occurred by the first formant and the background noise. Thus, in this paper, we proposed a pitch detection algorithm in the frequency domain that reduces the effects of the first formant and the background noise by the spectral AMDF function. Several computer simulation results showed that the proposed algorithm was very effective for fundamental frequency detection.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.193-199
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• 2000

The effects of Reynolds number on the non-nulling calibration of a cone-type five-hole probe in low-speed flows have been investigated at the Reynolds numbers of $2.04{\times}10^3,\;4.09{\times}10^3$, and $6.13{\times}10^3$. The calibration is conducted at the pitch and yaw angles in ranges between -35 degrees and 35 degrees with an angle interval of 5 degrees. The result shows that each calibration coefficient, in general, is a function of the pitch and yaw angles, so that the pre-existing calibration data in a nulling mode are not enough in accounting for the full non-nulling calibration characteristics. Due to the interference of the probe stem, the calibration coefficients have more Reynolds number sensitivity at positive pitch angles than at negative ones.