• Journal of the Korean Society for Precision Engineering
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• v.28 no.2
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• pp.168-175
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• 2011

Contouring accuracy of CNC machine tools is very important for high-speed and high-precision machining. In particular, large contour error may occur during corner tracking. In order to reduce the corner contouring error, acceleration and deceleration control or tool-path planning methods have been suggested. However, they do not directly control the corner contouring error. In the meantime, network servo systems are widely used because of their easiness of building and cost effectiveness. Communication latency between the master controller and servo drives, however, may deteriorate contouring accuracy especially during corner tracking. This paper proposes a control strategy that can accurately calculate and directly control the corner contouring error. A prediction control is combined with the above control to cope with communication latency. The proposed control method is evaluated through computer simulation and experiments. The results show its validity and usefulness.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1132-1138
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• 2009

Brake friction materials in railway applications are one of critical elements for acceleration and/or deceleration of vehicle, stop at designated position, and stability of vehicle operation. In this investigation, a comprehensive overview on international standards on brake friction materials, including UIC, JI, and AAR, was conducted to understand the current standards creation trend and collect the related information on brake friction materials with different applications. Moreover, the detailed conditions such as testing conditions and environment, testing items, and materials, were carefully reviewed and compared by each standard. The preliminary results will be used for the creation of Korean railway standards (KRS) on brake shoe materials.

• Journal of Astronomy and Space Sciences
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• v.24 no.3
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• pp.219-226
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• 2007

Among the interplanetary shock (IP shock)s observed by ACE spacecraft at 1AU during 1997 to 2000, we have selected 31 IP shocks which had triggered the interplanetary type II radio bursts detected by the WIND spacecraft while those shocks were leaving the Sun. We compared the observed IP shock propagation speeds and the IP shock transit speeds estimated by time difference between the interplanetary type II radio burst detection and the IP shock observation. Then, we found that the mean acceleration of the IP shocks between the Sun and the Earth is about $-1.02m/sec^2$, which means the deceleration contrary to the positive acceleration predicted by Parker solar wind model. It is also verified that the acceleration of the IP shock does not show any linear correlation with the shock propagation speed and the Mach number of the IP shock.

• International Journal of Automotive Technology
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• v.7 no.4
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• pp.385-390
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• 2006

A fast response $CO_2$ analyzer has been developed to study transient characteristics on an SI engine. The analyzer has the delay time of 4.5 ms and time constant of 2.8 ms, which is fast enough to measure $CO_2$ concentration on a transient condition. Wide range of A/F(Air/Fuel) ratio can be estimated using the analyzer with an additional switch type oxygen sensor. The results of measurement of $CO_2$ concentration and A/F ratio on a transient condition including rapid acceleration/deceleration and EGR(Ehxaust Gas Recirculation) on/off are presented and compared with a commercial exhaust gas analyzer and UEGO(Universial Exhaust Gas Oxyzen) sensor.

• KSTLE International Journal
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• v.2 no.2
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• pp.127-132
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• 2001

The steady state performance of the counterrotating floating ring journal bearings is analyzed with isothermal finite bearing theory. The effect of counterrotating speed of the sleeve on the performance of the bearing is investigated. It is shown that counterrotating floating ring journal bearings can have considerable load capacity at the same counterrotating speeds, while conventional circular journal bearings with one fluid film cannot. Investigating the relationship between the frictional torques exerted on the ring due to the inner and outer films and the rotational speed of the ring, the stability of the equilibrium state is identified and the operating characteristics of the counterrotating floating ring journal bearing according to the method of acceleration or deceleration of the rotational speeds of the journal and sleeve are clarified. It is theoretically confirmed that floating ring journal bearings can be used in counterrotating journal-bearing system and become good substitutes for rolling bearings in counterrotating systems.

• Journal of the Korean Society of Safety
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• v.28 no.2
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• pp.6-13
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• 2013

This study focuses on finding ECO driving patterns which consider driving safety of the ATO system train and reliability and which optimize efficiency of the driving energy consumption. Research results derived by performing simulation of those 5 models show that the emergency braking which affects safety of passenger and the machinery is minimized, and safe driving speed is maintained by the prohibition of drastic acceleration/deceleration, coasting and constant-speed driving. Therefore if this result is applied to the urban railway train by amending or making ATO program to save energy usage that improve environmental quality, its effects as ECO driving pattern is huge.

• Tribology and Lubricants
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• v.7 no.1
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• pp.28-34
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• 1991

The performance of the counterrotating floating ring journal bearing is analysed with isothermal finite bearing theory. The effect of counterrotating speed of the sleeve on the performance of the bearing is investigated. It is shown that counterrotating floating ring journal bearings properly designed can have considerable load capacity at the same counterrotating speed, while conventional circular journal bearing with one fluid film cannot. Investigating the relationship between the frictional torques on the ring due to the inner and outer films and the rotational speed of the ring, the stability of the equilibrium state is identified and the operating characteristics of the counterrotating floating ring journal bearing according to the method of acceleration or deceleration of the rotational speeds of the journal and sleeve are clarified. It is theoretically confirmed that floating ring journal bearings can be used in counterrotating journal-bearing system and become good substitutes for rolling bearings in counterrotating systems.

• Proceedings of the KOSOMBE Conference
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• v.1991 no.11
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• pp.79-82
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• 1991

Digital FHR monitoring system based on the personal computer combined wi th the digital signal processing (DSP) board was implemented. The DSP board acquires and digitally processes ultrasound fetal Doppler signal for digital rectification, envelope detection, autocorrealtion function calculation and its peak position detection. The personal computer interfaced with the DSP board is in charge of graphic display, hardcopy, data taransmission and on-line analysis of fetal heart rate change including on-line warning system, base-line estmation, acceleration, deceleration and variability. The advantages of PC-DSP based system can be summarized as follows: 1) Minimum hardware realization. 2) Increased flexibility. 3) Total care system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.584-589
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• 1994

A time-varying nonlinear mathematical model was derived to consider the effect of change in roll radius on tension varation during winding and unwinding. A variable-gain PID controller was designed for tension control at start and stop in a multi-span continuous process system. The controller gains are updated at every control loop as roll radii continuously change. Computer simulation was carried out by using the mathematical model and the controller developed for a typical operating condition including acceleration and deceleration. When the variable-gain PID controller was used, the tension control performance was improved compared with that of existing control method during start-up and stop.

• Journal of Biomedical Engineering Research
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• v.12 no.3
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• pp.209-214
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• 1991

Digital fetal monitoring system based on the personal computer combined with the digital signal processing (DSP) board was implemented. The DSP board acquires and digitally processes ultra- sound fetal Doppler signal for digital signal conditioning, rectification, low -pass filtering, autocorrealtion function calculation and its peak detection. The personal computer interfaced with the DSP board is in charge of graphic display, hardcopy, data transmission and on -line analysis of fetal heart rate change including on - line warning system, base -line estmation, acceleration, deceleration and variability. It is one of the most suitable situation to apply the DSP chip for siganl conditioning, digital filtering of ultrasound fetal Dopier signal and fetal heart rate estimation using autocorrelation technique .