• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.135-136
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• 2006

A precise linear motion stage supported by magnetically preloaded air bearings is introduced where preloading magnetic actuators are combined with permanent magnets and coils to adjust air bearing clearance by controlling magnetic force actively. Each of the magnetic actuators has a permanent magnet generating nominal magnetic flux for required preload and a coil to perturb the magnetic force resulting adjustment of air-bearing clearance. The characteristics of porous aerostatic bearing are analyzed by numerical analysis, and analytic magnetic circuit model is driven for magnetic actuator to calculate nominal preload and variation of force due to current. A 1-axis linear stage motorized with a coreless linear motor and a linear encoder is built for verifying this design concept. With the active magnetic preloading actuators controlled with DSP board and PWM power amplifiers, the active on-line adjusting tests about the vertical, pitching and rolling motion were performed, and the result shows very good linearity.

• Journal of Internet Computing and Services
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• v.3 no.3
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• pp.19-29
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• 2002

Recently, cyber evaluation systems on the Web-based remote education do not consider the personalized characteristic and propensity of individual students. Especially, in setting of the questions far examination, the traditional simple and general methods for all students group have been used for evaluation. This paper proposes on efficient cyber evaluation system using user profile. First, questions are filtered by using user profile for the personalized characteristic and propensity of individual students, This personalized characteristic and propensity have been disregarded in traditional evaluation systems. And then, filtered questions are set for examination, Therefore, efficiency of the evaluation system is enhanced and students make good results from their study. When user profile is adapted, the setting method of question for examination have combined category-based method with keyword-based method. This make students get the interest and pleasure for questions.

• Journal of Korea Society of Industrial Information Systems
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• v.6 no.1
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• pp.82-89
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• 2001

This paper presents recognition of unconstrained handwritten numeral strings using decision value generator, which is combined with both isolated digit identifier and recognizer designed with structural characteristics of digits. Numerical string recognition system is composed of three modules, which are pre-segmentation, segmentation and recognition. Pre-segmentation module classifies a numeral string into sub-images, which are isolated digit, touched digits or broken digit, using confidence value of decision value generator. Segmentation module segments touched digits using reliability value of decision value generator that will separate the leftmost digit from touched string of digits. Segmentation-based and segmentation-free methods have used for classification and segmentation, respectively. To evaluate proposed method, experiments have carried out with handwritten numeral strings of NIST SD19 and higher recognition performance than previous works has obtained with 96.7%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5513-5529
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• 2016

Doppler Effect is a prominent obstacle in vehicular networks, which dramatically increase the Bit-Error-Rate (BER). This problem is accompanied with the presence of the Orthogonal Frequency Division Multiplexing (OFDM) systems in which the Doppler shift interrupts the subcarriers orthogonality. Additionally, Inter-Symbol Interference (ISI) and high Peak-to-Average Power Ratio (PAPR) are likely to occur which corrupt the received signal. In this paper, the single-carrier combined with the frequency domain equalizer (SC-FDE) is utilized as an alternative to the OFDM over the IEEE 802.11p uplink vehicular channels. The Minimum Mean Squared Error (MMSE) and Zero-Forcing (ZF) are employed in order to study the impact of these equalization techniques along with the SC-FDE on the propagation medium. In addition, we aim to enhance the BER, improve the transmitted signal quality and achieve ISI and PAPR mitigation. The proposed schemes are investigated and we found that the MMSE outperforms the ZF equalization under different Doppler shift effects and modulations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.7
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• pp.3116-3133
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• 2020

Based on the teleportation by quantum walk, a quantum secret sharing scheme with credible authentication is proposed. Using the Hash function and quantum local operation, combined with the two-step quantum walks circuit on the line, the identity authentication and the teleportation of the secret information in distribution phase are realized. Participants collaborate honestly to recover secret information based on particle measurement results, preventing untrusted agents and external attacks from obtaining useful information. Due to the application of quantum walk, the sender does not need to prepare the necessary entangled state in advance, simply encodes the information to be sent in the coin state, and applies the conditional shift operator between the coin space and the position space to produce the entangled state necessary for quantum teleportation. Security analysis shows that the protocol can effectively resist intercept/resend attacks, entanglement attacks, participant attacks, and impersonation attacks. In addition, the quantum walk circuit used has been implemented in many different physical systems and experiments, so this quantum secret sharing scheme may be achievable in the future.

• The Korean Journal of Food & Health Convergence
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• v.5 no.6
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• pp.17-21
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• 2019

This article addresses issues related to environmental pollution.Particular attention is paid to the prevention of environmental pollution by livestock waste, which prompted the creation of closed ecological and biotechnical systems as environmentally closed production structures that can fit into the equilibrium system of the environment with minimal damage to it. An energy-saving and environmental protection technology for the processing and disposal of livestock waste with a maximum coefficient of energy transfer to livestock products has been developed, which consists in a combined treatment of waste in three stages, by transferring waste from one technological module to another, which makes it possible to completely utilize mineral substances in waste. The focus is on vermicultivation, microalgae cultivation and anaerobic fermentation in a bioenergy plant. To increase the productivity of growing microalgae, the authors proposed a deep type cultivator with submerged movable light sources.The technological parameters of the bioenergy installation for waste treatment are determined. An energy-saving and environmental-friendly technology has been developed for processing The main contribution of the study is the development of energy-saving and environmental technology for the processing and disposal of livestock waste with a maximum coefficient of energy transfer to livestock products.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.4
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• pp.19-26
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• 2011

Relay-assisted multiple input multiple output (MIMO) technique has become a promising candidate for next generation broadband wireless communications. In this paper, we propose maximum ratio combining (MRC) minimum mean-square-error (MMSE) equalization for single carrier-frequency domain equalizer (SC-FDE) in amplify-and-forward (AF) relaying networks. The performance of SC-FDE system can be improved considerably by achieving both the diversity gain and the MMSE equalization gain when the signals from source-destination (S->D) and source-relay-destination (S->R->D) are combined and equalized by means of the MMSE criteria. We find the weighting coefficients of MRC combining and the tap coefficients of MMSE equalizer for SC-FDE in AF relaying networks. Simulation results show that the proposed relay-based system considerably outperforms the conventional SC-FDE system.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.2
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• pp.15-22
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• 2014

This paper proposes a CUDA simulation framework for non-x86 computing platforms based on QEMU and GPGPU-sim. Previous simulators for heterogeneous computing platforms did not support for non-x86 CPU models or CUDA computing platform. In this work, we combined the QEMU and the GPGPU-Sim to support the non-x86 CPU models and the CUDA platform, respectively. This approach provides a simulation framework for CUDA computing on non-x86 CPU models.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.2
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• pp.102-108
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• 2002

This paper describes the overvoltage analysis and reduction methods of insulation joint boxes in underground transmission power cables when direct lightning surge strikes to overhead transmission line. An actual 154kV combined transmission line with underground Power cables was modelled in ATPDraw for simulation. Simulations were performed to analyze the overvoltage between insulation joint boxes, sheath-to-ground voltage according to the distance between cable conductors, cable lengths, burying types, CCPU connection types. The most effective method to reduce the induced overvoltage of Insulation joint boxes was proposed. It is evaluated that the proposed reduction method riven from the detailed simulations can be effectively applied to the actual underground power cable systems.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.11
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• pp.563-571
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• 2003

In this paper, the control algorithm and control method for a combined system of shunt passive filter and series active filter in 3-phase 4-wire system are discussed. Moreover, the three-phase four-wire system is widely employed in distributing electric energy to several office building and manufacturing plants. In such systems, the third harmonic and its 3th harmonics are termed as triple and zero sequence components that do not cancel each other in the system neutral. Consequently, the triple harmonics add together creating a primary source of excessive neutral current. Regarding this concern, this paper presents a new control algorithm for a series hybrid active system, whereas the control approach it adopts may directly influence its compensation characteristics. Hence, the advantage of this control algorithm is direct extraction of compensation voltage reference and the required rating of the series active filter is much smaller than that of a conventional shunt active filter. Some experiments were executed and experimental results from a prototype active power filter confirm the suitability of the proposed approach.