• Proceedings of the IEEK Conference
• /
• 2001.06e
• /
• pp.177-180
• /
• 2001

A saw-tooth waveform generator with current-controllable frequency is described. The generator utilizes operational transconductance amplifiers as switching element. It features simple and wide sweep capability. The circuit built with commercially avaliable components exhibits good linearity of current to frequency and relatively low temperature sensitivity.

• Geomechanics and Engineering
• /
• v.31 no.6
• /
• pp. 583-597
• /
• 2022

Frost heave can cause uneven ground uplift that may damage geo-infrastructure. To assist damage-prevention strategies, standard frost heave testing methods and frost susceptibility criteria have been established and used in various countries. ASTM International standard testing method is potentially the most useful standard, as abundant experimental data have been acquired through its use. ASTM International provides detailed recommendations, but the method is expensive and laborious because of the complex testing procedure requiring a freezing chamber. A simple frost heave testing method using a temperature-controllable cell has been proposed to overcome these difficulties, but it has not yet been established whether a temperature-controllable cell can adequately replace the ASTM International recommended apparatus. This paper reviews the applicability of the ASTM International testing method using the temperature-controllable cell. Freezing tests are compared using various soil mixtures with and without delivering blow to depress the freezing point (as recommended by ASTM International), and it is established that delivering blow does not affect heave rate, which is the key parameter in successful characterization of frost susceptibility. As the freezing temperature decreases, the duration of supercooling of pore water shortens or is eliminated; i.e., thermal shock with a sufficiently low freezing temperature can minimize or possibly eliminate supercooling.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.163-163
• /
• 2009

Viewing angle controllable liquid crystal display (LCD) associated with fringe-field switching (FFS) mode with high image quality is proposed. In the device, one pixel is composed of main and sub pixels, in which adjacent sub pixel is patterned with pixel electrodes direction orthogonal to the adjacent one. In this way, light leakage can be generated in the all viewing angle directions except the normal direction, realizing view angle controllable LCD in both horizontal and vertical directions.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.1836-1840
• /
• 2003

This paper, we propose a new phase-locked loop (PLL) system with the controllable output phase, independent from the output frequency, and lock-up time. This PLL system has a dual control loop is described, the inner loop greatly improved VCO characteristic such as faster speed response as well as higher operation bandwidth, to minimize the effect of the VCO noise and the power supply variation and also get better linearity of VCO output. The main loop is the heart of this PLL which greatly improved the output frequency instability due to the external high frequency noise coupling to the input reference frequency also the main loop can control the output phase, independent from the output frequency, and reduce the lock-up time of the step frequency response. The experimental results confirm the validity of the proposed strategy.

• Journal of Aerospace System Engineering
• /
• v.6 no.4
• /
• pp.24-28
• /
• 2012

In this paper, 2-D experiment and steady-state computational fluid analysis were conducted for measuring the hear transfer coefficient of pintle type controllable thruster in high pressure and temperature. In case of 2-D experiment, transient liquid crystal technique was used for measuring heat transfer coefficient for the 2-D pintle model. The experimental result was used to validate the CFD result. The CFD results well predicted the heat transfer coefficient on the pintle surface except the nozzle downstream region, where the results by CFD was higher than experimental results. The CFD results were also compared with the result by Bartz equation and the it was shown that the Bartz equation overestimated the heat transfer coefficient on the nozzle throat as much as 80%.

• Journal of Korean Society for Quality Management
• /
• v.28 no.1
• /
• pp.41-56
• /
• 2000

Recently, the regulations from the government and concerns of the people give rise to the interest in noise from a passengers car In this paper, Taguchi method is adopted to reduce the noise from the intake system of a cu. Based on the current design of the intake system, the factors such as the length and radius of each component of the intake system, which are thought to be effective for the system are arranged using L$_{18}$ table of orthogonal array Moreover, the non-controllable factors are included for the analysis. Thus, the relation between control factors and non-controllable factors are analyzed with constraints..

• Journal of Energy Engineering
• /
• v.15 no.1 s.45
• /
• pp.67-73
• /
• 2006

A calculation method on performance impact of the controllable operations parameter such as GT inlet filter ${\Delta}P$, compressor efficiency, and condenser pressure was devised to achieve best performance of combined cycle power plant with the on-line performance monitoring system. This method calculates the performance impact on the deviation between 'Expected' values and 'Actual' values. Controllable parameter targets are determined based on achievable performance given existing equipments and control conditions.

• Journal of Power Electronics
• /
• v.18 no.4
• /
• pp.1140-1153
• /
• 2018

The harmonic impedance characteristic of a traction power supply system (TPSS) is necessary for taking actions to suppress the high-order harmonic resonances caused by AC electric locomotives. This paper proposes a controllable harmonic generating method (CHGM) for measuring the TPSS harmonic impedance by injecting harmonic disturbances of different frequencies and amplitudes into the TPSS. This method applies phase shifted pulse-width modulation (PSPWM) and ensures that the undesired sideband harmonics can be negligible while the desired harmonic is both controllable and adjustable. Multiple harmonics can be emitted at the same time. The implementation of the method is also presented. Simulations are carried out to validate the performance of the proposed method. Finally, experimental results on a 5 H-bridge converters platform verified the effectiveness and feasibility of the proposed method.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.13 no.4
• /
• pp.1-8
• /
• 2004

Various controllable parameters of an experiment have influence on grinding process. In order to get good products with a high quality, these parameters should be considered whether each parameter has relations to the quality. This paper describes the use of the design of experiments to minimize geometric error in surface grinding. Controllable parameters for the design of experiments were selected as spindle speed, table speed, depth of cut and grain size. From the experimental results, a degree of influence between these parameters and the geometric error was evaluated. An optimal set of grinding conditions was obtained by means of analysis of variance(ANOVA).

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.8 no.1
• /
• pp.57-63
• /
• 2009

Magneto-Rheological(MR) fluid composes of a base fluid and ferromagnetic particles less than tens of micrometer size dispersed in the fluid. It is called as a smart material because its rheological properties are changable by a magnetic field. Its important applications are active devices such as controllable dampers and controllable clutches. The merit of those products is that their functional characteristics are controllable such that they enable active control strategies. This paper proposes an idea for machine tool applications of the MR fluid clutch as a safety device for power transmission. FEM has been used for magnetic field analyses and the results are compared with some former experiments. Some design syntheses of the MR clutches are suggested and hopefully considered that it may be an effective safety device for power transmission of machine tools.