• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.1
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• pp.83-90
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• 2014

In this paper, we address the problem of designing and implementing an oil pump control system driven by a brushless DC (BLDC) motor. The proposed oil pump plays the role of providing fuel to the engine clutch and transmission of hybrid vehicles. Main consideration is given to enhancing response feature and accuracy of the oil pump by simplifying the controller that is driven by a BLDC motor under PWM voltage control, which is a standard control method for BLDC motors. The proposed control scheme also helps to increase efficiency and reliability of the oil pump system. To validate the performance of the proposed system, we conduct experiments on BLDC motor speed control and oil pump operations.

• Journal of the Korea Society of Computer and Information
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• v.6 no.1
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• pp.45-50
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• 2001

Congestion may take place in the ATM network because of high-speed cell transmission features, and cell delay and loss also can be caused by unexpected traffic variation. Thus. traffic control mechanisms are needed. One of them to decrease congestion is the cell shaping. This paper proposes a hybrid type cell shaper composed of a Leaky Bucket with token pool, EWMA with time window, and a spacing control buffer. The simulator BONeS with the ON/OFF traffic source model evaluates the performance of the proposed cell shaping method. Simulation results show that the cell shaping concerning the respective source traffics is adapted to and then controlled on the mean bit rate.

• Journal of Ocean Engineering and Technology
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• v.23 no.3
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• pp.35-39
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• 2009

The main objective of this study was to investigate fiber reinforced composite materials (FRCM) with electromagnetic shielding characteristics using aluminum (Al) film and copper (Cu) meshes. This study investigated the electromagnetic interference (EMI) shielding effectiveness (SE) of fiber reinforced composites filled with Al film, Cu meshes, and nano carbon black as hybrid conductive fillers to provide the electromagnetic shielding property of the fiber reinforced composites. The coaxial transmission line method of ASTM D 4935-89 was used to measure the EMI shielding effectiveness of composites in the frequency range of 300 MHz to 1.5 GHz. The variations of SE of FRCM with Al film, fine Cu, and general Cu meshes are described. The results indicate that the FRCM having Al film exhibited up to 75 dB of SE at 1.5 GHz.

• Polymer(Korea)
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• v.26 no.3
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• pp.381-388
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• 2002

The properties of polyurethane (PU) nanocomposites with organoclay have been compared in terms of their thermo-mechanical properties, morphology, and gas permeability. Hexadecylamine-montmorillonite ($C_{16}$-MMT) was used as an organoclay to make PU hybrid films. The properties were investigated as a function of organoclay content (1-4 wt%) in the PU matrix. Transmission electron microscopy (TEM) photographs showed that most clay layers were dispersed homogeneously into the matrix polymer in nano-scale, although some particles of clay were agglomerated. We also found that the addition of only a small amount of organoclay was enough to improve the thermal stabilities and mechanical properties of PU hybrid films while gas permeability was reduced. Even at low organoclay content (<5 wt%), the PU nanocomposite showed much better thermo-mechanical properties, and lower gas permeability than pure PU.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3C
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• pp.228-236
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• 2006

A Multicarrier code division multiple access(MC-CDMA) is a scheme that combines multicarrier modulation with CDMA. It offers robustness to frequency selective fading effect and can support higher rate data transmission with higher spectral efficiency. The objective of this article is proposed and analyzed a new asynchronous MC-CDMA system with various kinds of data rates which employs a multiple access interference (MAI) canceller. The proposed multirate MC-CDMA system can be accomplished by changing the number of Parallel branch(P) according to their data rate and hybrid interference canceller(HIC) are used for MAI cancellation. We compare the performance of proposed system in terms of average bit error rate(BER) with that of a single rate MC-CDMA system. The results show the large improvement in performance that can be attained by the cancellation scheme under multipath environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11B
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• pp.1413-1421
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• 2011

A next generation military communication system called Tactical Information Communication Network(TICN) is designed to advance into large capacity, high speed, and long distance wireless relay transmission. To support mobility in battlefield, the application of Ad-hoc networking technology to its wireless communication is being considered. In Ad-hoc network, the key management technique is very important to ensure the confidentiality, integrity, and authentication. In this paper, we propose a new hybrid key management scheme considering the hierarchical characteristics of the tactical ad-hoc such as TICN. For upper layer with sufficient energy and computation capability, we apply PKI based key management scheme. For lower layer with restricted resources, we propose a new key management scheme using the location-based authentication to ensure the energy efficiency.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2367-2369
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• 2004

It is well known that an indirect methanol based fuel cell system imposes a performance limitation on the fuel cell electric vehicle (FCEV) due to the reformer lag. An optional battery system can be used together with fuel cell to improve this performance limitation and it is called a fuel cell hybrid electric vehicle (FCHEV) this paper first describes the configuration of FCHEV with explanation of the energy flow between subsystems. Mathematical modeling of each subsystem such as a fuel cell system, a battery system, a driving motor with the transmission are formulated and coded using Matlab/simulink software. It is illustrated by simulation results that fuel cell modeling yields appropriate stack voltage in order to get the required current quantity with varying hydrogen flow.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.42-54
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• 2016

A hybrid color and grayscale images encryption scheme based on the quaternion Hartley transform (QHT), the two-dimensional (2D) logistic map, the double random phase encoding (DRPE) in gyrator transform (GT) domain and the three-step phase-shifting interferometry (PSI) is presented. First, we propose a new color image processing tool termed as the quaternion Hartley transform, and we develop an efficient method to calculate the QHT of a quaternion matrix. In the presented encryption scheme, the original color and grayscale images are represented by quaternion algebra and processed holistically in a vector manner using QHT. To enhance the security level, a 2D logistic map-based scrambling technique is designed to permute the complex amplitude, which is formed by the components of the QHT-transformed original images. Subsequently, the scrambled data is encoded by the GT-based DRPE system. For the convenience of storage and transmission, the resulting encrypted signal is recorded as the real-valued interferograms using three-step PSI. The parameters of the scrambling method, the GT orders and the two random phase masks form the keys for decryption of the secret images. Simulation results demonstrate that the proposed scheme has high security level and certain robustness against data loss, noise disturbance and some attacks such as chosen plaintext attack.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.338-342
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• 2008

Hybrid Electric Vehicle(HEV) is driven by an internal-combustion engine and an electric motor. It is a combination of an internal-combustion engine and several electrical equipments which use a high voltage battery, an electric motors, an inverter and others. But there is not any separate detailed enforcement regulations for high voltage electric appliances in the existing vehicle-related safety standards. So, test standards suggestion as well as test technique development need to be done for ensuring electrical safety, for an electric motor, a high voltage battery, a(n) inverter/converter and an electric power transmission units and other equipments to ensure the safety of high voltage electric appliances which is the HEV key electrical component. In this paper, We are to provide helpful data to support test technique development and test standard establishment for HEV design and electrical safety security by the following methods; by measuring the voltage, the electric current, and the frequency of HEV, by analyzing electrical characteristics of high voltage electric appliances, and by analyzing temperature characteristics of the electrical current among the analyzed electrical characteristics by thermal imagining cameras.

• Particle and aerosol research
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• v.8 no.2
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• pp.83-88
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• 2012

The electrical wire explosion process in liquid media is promising for nano-sized metal and/or alloy particles. The hybrid Pt/Fe-Cr-Al and Pt/Ni-Cr-Fe nanoparticles for exhaust emission control system are synthesized by electrical wire explosion process in liquid media. The alloy powders have spherical shape and nanometer size. According to the wire component, while Pt/Fe-Cr-Al nanoparticles are shown the well dispersed Pt on the Fe-Cr-Al core particle, Pt/Ni-Cr-Fe nanoparticles are shown the partially separated Pt on the Ni-Cr-Fe core particle. Morphologies and component of two kinds of hybrid nano catalyst particles were characterized by transmission electron microscope and energy dispersive X-ray spectroscopy analysis.