• Textile Coloration and Finishing
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• v.23 no.2
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• pp.146-153
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• 2011

Silver nano-particles have been synthesized by liquid phase reduction method and alcohol reduction process. Silver nano-particles of the size 30 ~ 40 nm were formed successfully by alcohol reduction process. The formation, structure, morphology and size of silver nano-particles have been studied using FE-SEM, TEM, XRD, UV-visible spectroscopy. In particular high dispersion stability of the synthesized silver nano-particles could be obtained by PVP binding. Antibacterial activity of Ag/PET master batch sample made from its nano-silver particles showed excellent antibacterial activity against S. aureus and E. coli.

• Journal of the Korea Society of Computer and Information
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• v.8 no.1
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• pp.7-12
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• 2003

Because some systems limit the supported maximal degree, the degree reduction of NURBS is necessary in Parametric curves and surfaces of the different geometric modeling systems. Therefore an approximate degree reduction method of NURBS curves was introduced in this research. Also the existing Eck's B$\'{e}$zier degree reduction method and knot removal algorithm were used to reduce data in the degree reduction process. Finally we found that this method was stable, efficient for implementations, and easy to use algorithms.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.4
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• pp.242-246
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• 2005

Silver nanoparticles were synthesized by liquid phase reduction method from aqueous silver nitrate solution and borohybride as a reduction agent. The morphology, particle size and shape were influenced by the reaction conditions such as the concentration of $AgNO_3$, a reduction agent and addition of surfactant. The particle size decreased with decreasing the concentration of silver nitrate and using a borohydride. The obtained Ag particles showed the spherical shape with the range of 10-20 nm.

• The Pure and Applied Mathematics
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• v.31 no.1
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• pp.57-81
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• 2024

We introduce a new degree reduction method for homogeneous symmetric polynomials on binary variables that generalizes the conventional degree reduction methods on monomials introduced by Freedman and Ishikawa. We also design an degree reduction algorithm for general polynomials on binary variables, simulated on the graph coloring problem for random graphs, and compared the results with the conventional methods. The simulated results show that our new method produces reduced quadratic polynomials that contains less variables than the reduced quadratic polynomials produced by the conventional methods.

• Carbon letters
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• v.24
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• pp.1-9
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• 2017

We studied the basic properties and fabrication of reduced graphene oxide (rGO) prepared using eco-friendly reduction agents in the graphene solution process. Hydrazine is generally used to reduce graphene oxide (GO), which results in polluting emissions as well as fixed nitrogen functional groups on different defects in the graphene sheets. To replace hydrazine, we developed eco-friendly reduction agents with similar or better reducing properties, and selected of them for further analysis. In this study, GO layers were produced from graphite flakes using a modified Hummer's method, and rGO layers were reduced using hydrazine hydrate, L-ascorbic acid, and gluconic acid. We measured the particle sizes and the dispersion stabilities in the rGO dispersed solvents for the three agents and analyzed the structural, electrical, and optical properties of the rGO films. The results showed that the degree of reduction was in the order L-ascorbic acid ${\geq}$ hydrazine > glucose. GO reduced using L-ascorbic acid had a sheet resistance of $121k{\Omega}/sq$, while that reduced using gluconic acid showed worse electrical properties than the other two reduction agents. Therefore, L-ascorbic acid is the most suitable eco-friendly reduction agent that can be substituted for hydrazine.

• Structural Monitoring and Maintenance
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• v.5 no.3
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• pp.417-428
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• 2018

In this paper, various model reduction methods were assessed using a shear frame, plane and space truss structures. Each of the structures is one-dimensional, two-dimensional and three-dimensional, respectively. Three scenarios of poor, better, and the best were considered for each of the structures in which 25%, 40%, and 60% of the total degrees of freedom (DOFs) were measured in each of them, respectively. Natural frequencies of the full and reduced order structures were compared in each of the numerical examples to assess the performance of model reduction methods. Generally, it was found that system equivalent reduction expansion process (SEREP) provides full accuracy in the model reduction in all of the numerical examples and scenarios. Iterated improved reduced system (IIRS) was the second-best, providing acceptable results and lower error in higher modes in comparison to the improved reduced system (IRS) method. Although the Guyan's method has very low levels of accuracy. Structures were classified with the excitation frequency. High-frequency structures compared to low-frequency structures have been poor performance in the model reduction methods (Guyan, IRS, and IIRS).

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.7
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• pp.421-428
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• 2003

After the cable is installed, many geometric factors, such as bowing types of the cable and the length difference of the cable between each minor section will cause the impedance unbalance between cables. The impedance unbalance will increase or decrease the sheath circulating currents, which are critical to human safety and sustaining the capabilities of electric power. Accordingly, in this paper, a new method is also proposed to reduce the sheath circulating currents and an reduction equipment according to the theory of the new method is developed. The reduction equipment is tested when the cable is on service. The test results show that it can reduce the sheath circulating currents by up to 97.8［%］. This confirms the validation of the new method and the reduction equipment, and assures the safe operation of the transmission cables. In order to illustrate the safe operation of the cable with new current reduction equipment at transient state due to lightning and single line-to-ground fault, extensive simulations have been made. Then the protection scheme of sheath circulating currents reduction equipment is proposed by adopting the new device of RDP(Reduction Device Protector).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.756-762
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• 2012

A method of the low-frequency noise reduction in an enclosure by using an array of Helmholtz resonator is presented. An integral form of equation, which represents the acoustical coupling between the internal sound field and the resonator array, is formulated so that the boundary element method can be applied to solve the coupling problem. It is shown that the resonator array on the surface of the enclosure can be regarded as impedance patches on the boundary element. Experiments on a simple enclosure acoustically coupled with an array of resonators are conducted to verify the method. The predicted noise reduction by the boundary element method shows good agreement with the measured one. The effects of the resistance of resonators as well as the number of resonators on the noise reduction are demonstrated. As a practical example, the presented method is applied to the payload fairing of a space launcher with resonator arrays. It is demonstrated that the resistance of resonators affects significantly the required number of resonators to achieve a desired noise reduction.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.2
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• pp.29-37
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• 1996

High speed engines with high power are increasingly on demands and almost engines employ crankshafts Such problems as bending and torsional vibrations become the point at issue in crankshaft analysis and design. In this study to overcome the diffiiculty with the large amount of computation in finite element vibration analysis of a crankshaft, a reduction method based on influence coefficient and lumped parameter is presented. which reduces the computation amount effectively and can be used in vibrational analysis and design of any types of crankshafts Crank journal and pinparts are meodelled as elements with 6degrees of freedom per node. Crank web part is modelled using equivalent mass and stiffness matices . based up on lumped parameter and influence coefficient respectively to reduce total degrees of freedom considerablely. To confirm the scheme of the study the results are compared with the known data and they are coincident. Also a simple crankshaft is designed and manufactured for experiments. The calculated results using reduction method and the experimental results agree well The scheme of this study can be utilized in evaluation results agree well. The calculated result are compared with the known data and they are coincident. Also a simple crankshaft is designed and manufactured for experiments. The calculated results using reduction method and the experimental results agree well. The scheme of this study can be utilized in evaluation and development of high speed engine.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.439-443
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• 2019

To improve the noise characteristics, software-based noise reduction algorithms are widely used in cadmium zinc telluride (CZT) pixelated semiconductor gamma camera system. The purpose of this study was to develop an improved median filtering algorithm using a thresholding method for noise reduction in a CZT pixelated semiconductor gamma camera system. The gamma camera system simulated is a CZT pixelated semiconductor detector with a pixel-matched parallel-hole collimator and the spatial resolution phatnom was designed with the Geant4 Application for Tomography Emission (GATE). In addition, a noise reduction algorithm with a median filter using an improved thresholding method is developed and we applied our proposed algorithm to an acquired spatial resolution phantom image. According to the results, the proposed median filter improved the noise characteristics compared to a conventional median filter. In particular, the average for normalized noise power spectrum, contrast to noise ratio, and coefficient of variation results using the proposed median filter were 10, 1.11, and 1.19 times better than results using conventional median filter, respectively. In conclusion, our results show that the proposed median filter using improved the thresholding method results in high imaging performance when applied in a CZT semiconductor gamma camera system.