• Journal of the Korean Society for Marine Environment & Energy
• /
• v.12 no.4
• /
• pp.273-278
• /
• 2009

Overtopping Wave Energy Convertor (OWEC) is an offshore wave energy convertor for collecting the overtopping waves and converting the water pressure head into electric power through the hydro turbines installed in the vertical duct which is fixed in the sea bed. The numerical wave tank based on the commercial computational fluid dynamics code Fluent is established for the corresponding analysis. Several incident wave conditions and shape parameters of the overtopping device are calculated. The straight line type and parabolic type of the sloping arm are compared in the optimal designing investigation of the overtopping characteristics and discharge for OWEC device. The numerical results demonstrate that the parabolic sloping arm is available for wave running up and the overtopping discharge increasing.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.28 no.5
• /
• pp.1089-1098
• /
• 2018

As the development of quantum computers becomes visible, the researches on post-quantum cryptography to alternate the present cryptography system have actively pursued. To substitute RSA and Elliptic Curve Cryptosystem, post-quantum cryptography must also consider side channel resistance in implementation. In this paper, we propose a side channel analysis on NTRU, based on the implementation made public in the NIST standardization. Unlike the previous analysis which exploits a thousands of traces, the proposed attack can recover the private key using a single power consumption trace. Our attack not only reduces the complexity of the attack but also gives more possibility to analyze a practical public key cryptosystem. Furthermore, we suggested the countermeasure against our attacks. Our countermeasure is much more efficient than existing implementation.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.5
• /
• pp.14-21
• /
• 2020

In order to provide confidential services between two communicating parties, block data encryption using a symmetric secret key is applied. A power analysis attack on a cryptosystem is a side channel-analysis method that can extract a secret key by measuring the power consumption traces of the crypto device. In this paper, we propose an attack model that can recover the secret key using a power analysis attack based on a deep learning convolutional neural network (CNN) algorithm. Considering that the CNN algorithm is suitable for image analysis, we particularly adopt the recurrence plot (RP) signal processing method, which transforms the one-dimensional power trace into two-dimensional data. As a result of executing the proposed CNN attack model on an XMEGA128 experimental board that implemented the AES-128 encryption algorithm, we recovered the secret key with 22.23% accuracy using raw power consumption traces, and obtained 97.93% accuracy using power traces on which we applied the RP processing method.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.46 no.2
• /
• pp.22-27
• /
• 2009

In this paper, an automatic functional inspection system EVT (Emulated Vision Tester) for LCD drive module PCB has been proposed and implemented. Typical automatic inspection system such as probing methods and vision-based systems are widely known and used, however, there exist undetectable defects due to critical timing factors which they may miss to catch from LCD equipments. Especially typical vision-based systems have inconsistency on acquisition of images so that distinction between gray scales can be difficult which results in low level of performance and reliability on the inspection results. The proposed EVT system is pure hardware solution. It directly compares pattern signals from a pattern generator to output signals from LCD drive module. It also inspects variety of analog signals such as voltage, resistance, wave forms and so forth. The EVT system not only shows high performance in terms of reliability and processing speed but reduces costs on inspection and maintenance. Also, full automation of entire production line can be realized when EVT is applied in in-line inspection processes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.13 no.1
• /
• pp.94-101
• /
• 1999

In this paper the problems associated with the switching surge of PWM inverter devices were analysed. As the application of ASD for efficient speed control of AC rmtors is increased, so is the rrntor and ASD-related failure increased. In the industrial rmtor awlications, the introduction of PWM drives can sometmes cause insulation breakdown between the phase windings due to high transient voltage peak. The motor cable length combined with the high switching frequency becomes more sensitive issue for proper drive operation. Effects of the cable length and high switching frequency influence both on rmtor and inverter. When the insulation level of rmtor winding is low, the failure probability caused by high peak voltage and fast voltage rise times(dv/dt) is high. Voltage refloctions are simulated far rmtor capacities, ASD and rise times and are presented graphically. The filtering techniques are discussed to reduce the rmtor terminal overvoltage and dv/dt in inverter fed AC rrntor drive systems. We confirmed that the lower motar capacity and rmtar insulation level, the shorter switching time and cable length and the higrer the probability of insulation breakdown .kdown .

• Korea Science and Art Forum
• /
• v.20
• /
• pp.421-428
• /
• 2015

Electronic/hybrid car and electroplating rectifier should have switching devices such as SCR, MOSFET, IGBT. And those switching devices should be operated by gate driver. In this paper, we propose high power gate driver that contains H-Bridge using 4 BJTs. H-Bridge and transformer generate isolate power. And gate control signal is transferred to isolated one by photo coupler and operate real switching device. We designed H-Bridge and 555-Timer by PSpice simulation and manufactured real product. Finally we succeed to operate 27V 50,000A electroplating rectifier using proposed gate driver.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.10
• /
• pp.681-687
• /
• 2016

It is essential for micro jet injectors in the biomedical sector to operate under high pressure. High pressure injection, however, is accompanied by high volumes. On/Off valves that can be operated at high speeds have been used to address this problem. In this research, piezoelectric actuators which have a response frequency of the order of hundreds of kilohertz were used as the On/Off valve and experiments were applied. Researchers developed a controller to precisely manipulate the piezoelectric valve with various waveforms. They also fabricated five types of nozzles to consider the effect of nozzle type on injection. This allowed researchers to manipulate and confirm factors that can affect the injection volume and force. Results of this experiment have shown how to decrease the injection volume and increase the injection force. and it is predicted that the optimized injection volume and force value can be determined depending on the skin type.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.7 no.3
• /
• pp.262-271
• /
• 2002

In PWM inverters used in traction motor drive systems, the switching frequency is restricted by their large power capacity and thus the electromagnetic acoustic noise is generated. To reduce such an audible noise, the new MRSF-PWM(Modified Random Switching Frequency PWM) method is proposed. In the Proposed MRSF-PWM method, both triangular wave and sawtooth wave are used together as carrier waves for harmonic diffusion and reference wave is generated by injecting 3rd harmonic into the stone wave to expand the linear control region of output voltages. To verify the validity of the proposed MRSF-PWM method, computer simulations are carried out. And the results show that the MRSF-PWM method is more excellent than other RPWM methods in the aspects of both linearity and harmonic diffusion md more effective than SPWM(Sinusoidal PWM) method for the reduction of an audible noise.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.2 no.3
• /
• pp.44-50
• /
• 1997

This paper describes an indirect sensing method for the rotor flux position of interior permanent magnet (IPM) brushless DC motors. The phase inductances of an IPM motor vary appreciably according to the rotor position. The waveform characteristics of the terminal voltage of IPM brushless DC motors is analysed and a simple and practical method for indirect sensing of the rotor position is proposed. A compact and economical sensorless drive is implemented and tested using a 87c196mc 16-bit one-chip microprocessor. The experimental results show the validity of the proposed method. The drive is applied to drive a compressor of air-conditioner and works well from 1,200 to 6,600 [rpm].

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.14 no.3
• /
• pp.15-21
• /
• 2000

This paper presents the modeling method of $3\Phi$ phase-controlled rectifier for the DC motor drive in MATLAB/SIMULINK environment. This method has no need to extend the system mathematically and thus it's easy to integrate the various systems. The whole model consists of $3\Phi$ phase-controlled rectifier block, DC motor block and speed/current controller block. The simulation results show that the model outputs are almost similar to those of the real system and therefore that the presented method is suitable for the research of the closed-loop controlled power electronic systems.