• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.6
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• pp.2317-2337
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• 2015

Cryptography provides an effective solution to secure the communication over public networks. The communication over public networks that includes electronic commerce, business and military services, necessitates the requirement of simple and robust encryption techniques. In this paper, a novel image encryption method which employs calligraphy based hybrid scan and random number is presented. The original image is scrambled by pixel position permutation with calligraphy based diagonal and novel calligraphy based scan patterns. The cipher image is obtained by XORing the scrambled image with random numbers. The suggested method resists statistical, differential, entropy, and noise attacks which have been demonstrated with a set of standard images.

• Computers and Concrete
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• v.21 no.5
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• pp.505-511
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• 2018

This paper investigates the potential of a hybrid model which combines the least squares support vector machine (LSSVM) and an improved particle swarm optimization (IMPSO) techniques for prediction of concrete compressive strength. A modified PSO algorithm is employed in determining the optimal values of LSSVM parameters to improve the forecasting accuracy. Experimental data on concrete compressive strength in the literature were used to validate and evaluate the performance of the proposed IMPSO-LSSVM model. Further, predictions from five models (the IMPSO-LSSVM, PSO-LSSVM, genetic algorithm (GA) based LSSVM, back propagation (BP) neural network, and a statistical model) were compared with the experimental data. The results show that the proposed IMPSO-LSSVM model is a feasible and efficient tool for predicting the concrete compressive strength with high accuracy.

• Journal of the military operations research society of Korea
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• v.24 no.2
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• pp.57-74
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• 1998

This paper is aimed to propose an testing and evaluation strategy and plan in Military Information Systems, especially focusing on development an“New-generation Wargame Model”. Through this research, we concluded that the effective and efficient testing/evaluation strategy/plan can aid the productivity, maintainability, availability, etc., of the Militray Information Systems. Highlights of the proposed testing and evaluation strategy and plan for Military Information Systems are as follows. First, in the unit and module integration testing phase, hybrid of black-box and white-box testing techniques are available for Military Information Systems and progressive approach for module integration phase should be considered because of the complexity. Second, in the system testing phase, integrated module should be tested with respect to the function and performance that should be satisfied with the user requirements, specifications, risk analysis, etc., Third, in the acceptance testing phase, reliability, interoperability, maintainability, availability, integrity, etc., must be considered in the actual or mini-operational environments for testing efficiently and effectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1754-1757
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• 2001

In this paper, a R-band hybrid amplifier with the coplanar waveguide(CPW) and the photonic bandgap(PBG) structure is designed and fabricated. The PBG and the CPW techniques are simultaneously employed in amplifier to improve the power added efficiency(PAE) and the IMD(Intermodulation Distortion) in R-band. In this paper, the PBG structures are optimized to obtain matching network. The output impedance of amplifier and the input impedance of PBG are matched to minimize the return loss. The PAE and the IMD were improved 15% and 4.5dB compared with the conventional amplifier, respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.166-171
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• 2013

In this study, low noise designs of a Savonius wind turbines are numerically investigated. From a previous study, it was found that the high harmonic components whose fundamental frequency is higher than the BPF were found to be dominant in noise spectrum of a Savonius wind turbine. On a basis of this observation, S-shaped blade tip is proposed as a low design factors that decrease wind turbine noise by inducing phase differences in vortex shedding. The conventional Savonius and S-shaped turbines are investigated using Hybrid CAA method where flow field around the turbine are computed using CFD techniques and the radiated noise are predicted by applying acoustic analogy to the computed flow data. Noise reductions by these design factors are confirmed by comparing the predicted noise levels from these turbines.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.78-83
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• 2003

General algorithm is developed for the prediction of internal flow-induced noise. This algorithm is based on the integral formula derived by using the General Green Function, Lighthills acoustic analogy and Curls extension of Lighthills. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve are compared with actual measurements. This illustrative computation shows that the current method permits generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.725-730
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• 2012

In this paper, flow noise characteristics of Savonius-type vertical-axis wind turbines are numerically investigated using hybrid CAA techniques. High frequency harmonics as well as BPF components are identified in the predicted noise spectra from a Savonius wind turbine. As the BPF components belong to infrasound, the higher harmonic components affects human response dominantly. Further analysis is performed to investigate the reason causing the higher frequency harmonic noise by changing operational conditions of a Savonius wind turbine. Based on this result, it is revealed that the frequency of higher harmonic components is determined by the radius of blades and angular velocity of Savonius wind turbine.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.6
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• pp.743-757
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• 2006

Volatile organic compound (VOC) has been well-known to Korea since the end of 1990's however, it has not been well documented until now. In this study, present ambient VOC levels, VOC emission sources, and VOC control technologies were reviewed and discussed. In addition, VOC management strategies to cut down ozone concentrations were suggested based on the present VOC database. For anthropogenic VOC reduction, VOC emitted from painting processes and automobiles should be controlled in the first place in large cities such as Seoul, Daegu, and Incheon. For natural VOC management, low emission trees need to be planted in those cities. It is also very significant to keep updating present and future VOC emission inventories for efficient VOC control strategies. As a conclusion, more systematic VOC control road-map based on BACT (best available control technology) needs to be made up. and more economical and efficient VOC control techniques have to be developed under strong national support in order to lower toxic VOC and photochemical oxidant levels.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2005.11a
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• pp.110-112
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• 2005

• Journal of Magnetics
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• v.21 no.1
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• pp.83-93
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• 2016

Due to their performances and inherent benefits, especially in medium-voltage and high-power applications, multilevel inverters have received an increasing attention in real world industrial applications. The present paper deals with a review of the main multilevel inverter topologies as well their most common derived and hybrid structures quoted in previous research works. It also encompasses an investigation on voltage harmonic elimination and THD estimation. For that reason, the paper summarizes the most relevant modulation techniques used so far to enhance the output voltage quality. Theoretical formulas evoked in the literature, for calculating the output voltage THD upper and lower bounds are reported and verified by adequate simulations.