• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.213-216
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• 2011

The feasibility study must be conducted for construction of complex for generation of electric power such as items to get permission and grid connection etc. including wind resource to construct a complex for wind power generation. Since wind power can be used by converting only around 20~40% of energy coming in that kinetic energy of wind passes through blades and driving device into electric energy, when constructing a complex, the survey of wind resource takes up the most important part. Data logger used to measure this wind energy are expressed by calculating generally electromotive that is created from a sensor, variable-type, pulse-type signal to be proper for the actual value, and most data loggers have a type without considering geographical features. Besides, in the case of Met mast that is installed to survey the wind resource, since it is installed lower than the hub height of a wind power generator due to permission matters and the economic factors, the height of wind speed by utilizing Deacon equation is compensated to revise this. In this study, a device measuring wind speed was made by using algorithm that is possible to compensate the height of wind speed according to regional features and by applying Deacon equation, and the function of data storage through SD card or RS232 communication was added as well. Besides it's possible to check data more easily with a type of graph by using LCD touch screen for the convenience of users.

• Corrosion Science and Technology
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• v.11 no.3
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• pp.96-102
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• 2012

Outer diameter stress corrosion cracking (ODSCC) has occurred for Alloy 600 (Ni 75 wt%, Cr 15 wt%, Fe 10 wt%) as a heat exchanger tube of the steam generator (SG) in nuclear power plants (NPP) during long term operation. Among many causes for SCC, lead (Pb) is known to be one of the most deleterious species in the secondary system. In the present work, the oxide formed on Alloy 600 was characterized as a function of the PbO content in 0.1 M NaOH at $315^{\circ}C$ by using an electrochemical impedance spectroscopy (EIS), a transmission electron microscopy (TEM), equipped with an energy dispersive x-ray spectroscopy (EDS). The oxide property was analyzed in view of SCC susceptibility.

• Korean Journal of Optics and Photonics
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• v.22 no.2
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• pp.83-89
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• 2011

In order to improve the calculation speed of an integrating-sphere simulator based on a ray-tracing method, parallel processing with OpenMP directive was implemented into the simulator and the randomness of Monte Carlo method was guaranteed by utilizing a parallel random number generator. It was confirmed that simulation results obtained with more than $10^7$ rays showed good agreement with theoretical results within the error range of 0.5%, and that the calculation speed improved as the number of threads increased. Finally, the spatial response distribution functions of a real integrating sphere were simulated and compared with previous results.

• The Journal of the Acoustical Society of Korea
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• v.39 no.5
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• pp.435-440
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• 2020

Single-beam acoustic tweezers that are capable of manipulating micron-size particles in a non-contact manner have been used in many biological and biomedical applications. Current single-beam acoustic tweezer systems developed for in vitro experiments consist of a function generator and a power amplifier, thus the system is bulky and expensive. This configuration would not be suitable for in vivo and clinical applications. Thus, in this paper, we present a portable single-beam acoustic tweezer system and its performances of trapping and manipulating micron-size objects. The developed system consists of an Field Programmable Gate Array (FPGA) chip and two pulsers, and parameters such as center frequency and pulse duration were controlled by a Personal Computer (PC) via a USB (Universal Serial Bus) interface in real-time. It was shown that the system was capable of generating the transmitting pulse up to 20 MHz, and producing sufficient intensity to trap microparticles and cells. The performance of the system was evaluated by trapping and manipulating 40 ㎛ and 90 ㎛ in diameter polystyrene particles.

• Journal of the Korean Operations Research and Management Science Society
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• v.20 no.2
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• pp.159-178
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• 1995

Supervisory control is an approach based on formal language. it is used to model and control discrete event systems in which each discrete event process is represented as an automation. A supervisor is a generator that switches control patterns in such a way that a given discrete evenet process behaves in obedience to various constraints. A flexible manufacturing cell (FMC) is one of discrete evenet systems. Functions necessary for the operation of an FMC are characterized by operational components and informational compoments. The operational components can be modeled using the finite state machines and the informational components can be modeled using the abstract formalism which describes supporting operations of the cell controller. In this paper, we addressed function required for FMC control specification, software engineering aspects on FMC control based on supervisory control, a concept of event queue for resolving synchronization problem, and complexity reduction. Based on the mathematical model of an FMC. we synthesized the controller by integrating a supervisor for FMC with control specification that specifies event-driven operation of the cell controller. The proposed control scheme is stable mathematically so that the system always behaves on a controlled way even under the existence of uncontrollable events. Furthermore, using an event queue concept, we can solve a synchronization problem caused by the violation of instantaneity assumption of supervisory control theory in real life situation. And also, we can propotype a control software rapidly due to the modularity of the proposed control scheme.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.4
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• pp.73-78
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• 2018

In this paper, we consider a system where multiple sources are encrypted in separated nodes and sent through their respective public communication channels into a joint sink node. We are interested at the problem on protecting the security of an already existing system such above, which is found out to have correlated encryption keys. In particular, we focus on finding a solution without introducing additional secret keys and with minimal modification to minimize the cost and the risk of bringing down an already running system. We propose a solution under a security model where an eavesdropper obtains all ciphertexts, i.e., encrypted sources, by accessing available public communication channels. Our main technique is to use encoders of universal function to encode the ciphertexts before sending them to public communication channels.

• The Journal of Korean Association of Computer Education
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• v.10 no.6
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• pp.69-77
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• 2007

In this paper we implement main functions of electronic measuring devices, which are essential to design electric/electronic virtual laboratories on the Web. The implemented virtual electronic measuring devices such as virtual analog multimeter(VAM), virtual function generator(VFG), virtual oscilloscope(VOSC) enable the learners to perform the virtual experiments on the Web by simple mouse clicks. In order to show their validity virtual experiments for understanding how to use them are designed. The virtual experiments for measuring resistance(OHM), AC/DC Voltage(ACV/DCV) and DC Current(DCA) by the VAM are illustrated. In addition, the learners can change the frequency of the signal generated from the VFG and measure by the VOSC several types of the signals generated from the VFG such as triangular, pulse, sinusoidal waveforms. The VOSC can measure voltage and current through two channels of it and provide the learners with additional functions such as zooming, trigger, cursor, summing of waveforms. Since the virtual electronic measuring devices have been implemented as forms of Java classes, various types of applications are available according to the structures of virtual laboratories.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.3
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• pp.55-62
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• 2000

This paper presents an analysis of the chaotic behavior in the discrete-time voltage mode chaotic generator fabricated using 0.8${\mu}{\textrm}{m}$ single poly CMOS technology. An approximated empirical equation is extracted from the measurement data of a nonlinear function block. Then the bifurcation diagram is simulated according to input variables and Lyapunov exponent λ which represent a dependence on an initial value is calculated. We show the interrelations among time waveforms, state transition, and power spectra for the state condition of chaotic circuit, such as equilibrium, periodic, and chaotic state. And results of experiments in the chaotic circuit with the $\pm$2.5V power supply and sampling clock frequency of 10KHz are shown and compared with the simulated results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.98-105
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• 2007

In this paper, we propose a timing detector using suboptimal maximum likelihood method. The proposed method has an simple reference signal generator. Additionally, timing detector's gain of the proposed method is the same to Early-Late gate and ML method. We reveal that tracking range of time tracker is narrow because of using data-decision, that is, tracking range is ${\pm}0.06ns$ for the 4-order Gaussian monocycle with 0.7ns pulse width. Therefore we can find that searcher must have very accurate acquisition procedure. When estimating a performance of time tracker, we consider a jitter in transmitter and receiver's pulse generation process as well as background noise. By using computer simulation, we propose mean/variance of timing detector and tracking process. Also we consider a mobility in tracking process, i.e., timing error modeled ramp function. In order to propose a performance of time tracker, we consider only one correlation demodulator.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.3
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• pp.501-507
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• 2015

The online banking service handles a banking business over the internet, it is necessary to ensure that all financial transactions are processed securely. So, there are various authentication technique for e-banking service : a certificate, a personal identification number(PIN), a security card and a one-time password(OTP). Especially, the security card is most important means including secret information. If the secret information of card is leaked, it means not only loss of security but also easy to attack because security card is a difficult method to get. In this paper, we propose that a multi-channel security card saves an secret information in distributed channel. Proposed multi-channel security card reduces vulnerability of the exposed and has a function to prevent phishing attacks through decreasing the amount of information displayed and generating secret number randomly.