• Journal of the Korea Society of Computer and Information
• /
• v.20 no.8
• /
• pp.61-67
• /
• 2015

The existing methods for control between smart devices in near used Bluetooth, WiFi-Direct, or socket communication using Wi-Fi. However, those have a problem that can not use when operating system of each smart devices is different or when socket server is not working. In this paper, we proposed a new near control technology using High frequencies in audible frequency between smart devices to supplement the problem of existing methods. High frequencies use micro-phone and speaker of smart device and are a control signals that is combined high frequencies within 18kHz ~ 22kHz among audible frequency range. The proposed technology using High frequencies do not need any extra communication modules or socket servers and can use the most smart devices without operating system of devices. To evaluate the performance of the proposed technology, we developed a music play and music control application applied the proposed technology and tested a control experiment using the developed applications. The control success rate was 97% and recognition rate of surrounding people about using high frequencies was under 5%. Therefore, the proposed technology will be the useful technology to control between smart devices in near.

• Journal of Positioning, Navigation, and Timing
• /
• v.9 no.4
• /
• pp.357-366
• /
• 2020

This paper addressed a relative navigation method for autonomous rendezvous and docking of cube-satellites using single frequency Differential GPS (DGPS) under the intermittent communication between satellites. Since the ionospheric error of GPS measurement is variable depending on the visible satellites, a few meters error of relative navigation is occurred in the Low-Earth Orbit (LEO) environment. Therefore, it is essential to remove the ionospheric error to perform relative navigation. Besides, an intermittent communication period for receiving GPS measurements of the target satellite is limited for getting information every sampling time. To solve this problem, a method combining range domain DGPS and orbit propagation is proposed in this paper. The proposed method improves the performance of DGPS by using Hatch filter and solves an intermittent communication problem by estimating the relative position and velocity using Hill-Clohessy-Wiltshire Equation. Through the simulation, it is verified that the suggested algorithm provides the relative position error within RMS 0.5 m and the relative velocity error within RMS 3 cm/s. Furthermore, it has the advantage that it is suitable for real-time implementation using single-frequency GPS measurements and is computationally efficient.

• Journal of the Korean Home Economics Association
• /
• v.39 no.5
• /
• pp.15-26
• /
• 2001

The purpose of this study is to examine specific consumer problems in internet commerce and analyze them in the age of information. The way of sorting consumer problems in internet commerce from this study. For this empirical analysis, the data was collected 319 consumers by internet on-line survey from Feb. 13 to Feb. 20, 2000. The methods for study was frequency, percentage, mean, correlation, multiple regression using SAS PC program. The major findings of this study were as follows: 1. The level of consumer problem experiences in internet commerce was examined. The problems of privacy was the most problem and the problem of price was the second. Then delivery, advertisement, information was next, and the problem of quality, and A/S, change, cancel was the next consumer problem. 2. Among factors influence on experience consumer problem in internet commerce, the amount of usable money, information search were significant.

• Journal of Digital Convergence
• /
• v.19 no.12
• /
• pp.641-648
• /
• 2021

This study examined the effects of irrational beliefs, impulsivity and happiness on problem gambling of Korean and Australian college students. Data were collected from 581 college students of Korea, and 100 college students of Cairns of Australia. As a result, The overall mean of the CPGI was significantly different between Koreans and Australians (t=-29.828**). As for classification of gamblers by sub-type of CPGI, the number of problem gamblers in Australians was 7.0% compared to 5.3% for Koreans, showing a significant difference. In Multiple regression analyses, irrational beliefs, happiness, and the frequency of gambling significantly predicted problem gambling of Koreans (R2 = 0.175 F = 23.441, p < .001). On the other hands, irrational beliefs and the frequency of gambling significantly predicted problem gambling of Australians(R2 = 0.368, F = 10.844, p < .001). Through this study, it was found that the factors affecting the problem gamblers of Korean and Australian are different. It is required to continue further education on gambling among young adults of Korea and Australia.

• Journal of the Korean Society for Precision Engineering
• /
• v.31 no.8
• /
• pp.697-703
• /
• 2014

This paper is study of solving vibration problem occurred in moving hand of wafer transfer robot in semiconductor manufacturing line. Long settling time for decreasing vibration makes low production rate, and moreover the excessive vibration of hand sometimes breaks the wafer in a cassette. The ways of reducing the moving speed and changing the type of motion profile did not help for lessening vibration. Therefore, we analyzed the mechanical property of the hand such as natural frequency, and frequency component of the motion profile currently used in the manufacturing line. In several conditions of motion profile, we found the best condition of which the frequency component in near of natural frequency of the hand is minimal and this induced small vibration in moving hand. The results were verified theoretically and experimentally using frequency analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1993.10a
• /
• pp.299-304
• /
• 1993

A 1/4 car model(2 DOF system) is employed to evaluate the performance included a quadratic cost functional in frequency domain. The design procedure of feedback control to optimize the performance index results in a modified Linear-Quadratic-Gaussian problem and cultivates a quite simple control algorithm. Computer simulation result is shown that the LQG method using frequency shaped performance index is outstanding in ride comfort and its response converges to the steady state very rapidly in comparison with the known passive suspension, classical design methods LQR/ and LQG.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1991.04a
• /
• pp.105-110
• /
• 1991

The conventional high-frequency testing method is difficult to detect flaw in concrete because the high frequency stress wave is strongly attenuated due to the large grain size and heterogeneous structure. For restoration of this problem, we develop the stu요 of flaw detection in large concrete block containing various artificial flaws by low frequency spectrum anlysis of impact-echo waveforms. This impact-echo testing method is possible to determine the flaw size, shape and location in large concrete block even if required some attention in case of containing reinforcing steel bar.

• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.45-48
• /
• 2000

By the use of he DSP and microprocessor controller many high power converter such as especially inverter and motor drive system may be enhanced resulting in the improved robustness of EMI the ability to communicate the operating conditions and the ease of adjusting the control parameters. However the digital controller using DSP or microprocessor has not been applied in the high frequency switching power supplies especially in full bridge dc/dc converters. this paper presents a promising solution to the dc bias control problem of high frequency transformer in high power full bridge converter.

• Journal of the Korean Society for Precision Engineering
• /
• v.6 no.3
• /
• pp.100-108
• /
• 1989

The frequency equation and numerical process of natural frequencies for several boundary conditions of L-type folded plate given to the different thickness and lenth are derived by using Rayleigh-Ritz method in this study. Those natural frequencies are attaind by choosing the proper eigenfunction for boundary conditions of x-direction and y-direfction beams, by considering the convergence of numerical results.

• Proceedings of the KIPE Conference
• /
• 1998.07a
• /
• pp.221-224
• /
• 1998

A PWM inverter with an induction motor often has a problem with a high-frequency leakage current that flows through the distributed electrostatic capacitance from the motor windings to ground. This paper presents an equivalent circuit for high-frequency leakage currents in PWM inverter feeding an induction motor, which forms an LCR series resonant circuit.