• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.964-969
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• 2002

The flexural vibration of laminated composite beams with passive constrained layer damping has been investigated to design structure with maximum possible damping capacity. The equations of motion are derived for flexural vibrations of symmetrical, multi-layer laminated beams. The damping ratio and modal damping of the first bending mode are calculated by means of Iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.2
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• pp.135-147
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• 2015

With the miniaturization and digitalization of electronics industry, demand for Multi-Layer Ceramic Capacitor(MLCC) has increased steadily because of its various applications such as DC Blocking, Decoupling and Filtering etc. The modeling techniques of MLCC has been studied for a long time but most of these modeling method can only be applied after measurement and this has some losses of material, time in both production stage and measurement stage. This paper proposes the modeling method which can predict the frequency characteristics of MLCC from structure data and material data in design stage. The impedance of N-Layer Capacitor can be expressed in differential mathematical form based on coupled transmission line equations. By using this formula, we can predict the impedance of MLCC. As a result, proposed modeling is correspond with simulation, and it takes much less time to obtain the result than the simulation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.11
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• pp.859-864
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• 2011

An operation temperature of $Pb(Zr,Ti)O_3$ based piezoelectric ultrasonic flowmeter was generally restricted to below 200$^{\circ}C$ due to a low depoling temperature of its ceramic material. Thus, a new designed piezoelectric ultrasonic flowmeter was fabricated in order to protect from the extremely hot fluid. Its structure is optimized by a finite element method to effectively stop heat flowing along a waveguide. Various materials such as Cu, Al, SUS were examined as a multi-plate radiation shield to enhance the performance of piezoelectric ultrasonic flowmeter. The SUS was evaluated as the most effective material to enhance the performance of piezoelectric ultrasonic flowmeter. As the number of plates of the radiation shield increased, the temperature at piezoelectric transducer away from the hot fluid was constantly decreased with a ratio of 3.12$^{\circ}C$ per the plate number.

• Analytical Science and Technology
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• v.30 no.1
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• pp.1-9
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• 2017

Starch is a mixture of amylose (AMY) and amylopectin (AMP) which are different in physical properties such as molar mass (M), rms radius ($R_g$) and hydrodynamic diameter ($d_H$). The rheological and functional properties of starch are influenced by various factors including the molecular size, molar mass distribution (MD) and the concentration ratio of AMY and AMP. It is also important to analyze proteinaceous material in starch as they affect the flavor and texture of food to which starch is added. In this study, asymmetrical flow field-flow fractionation (AF4) was employed for separation and quantitation of AMY and AMP in starches (Amaranth, potato, taros and quinoa). AF4 was coupled with a multi-angle light scattering (MALS) and a refractive index (RI) detector for determination of the absolute M, MD and molecular structure. It was found that AMP has the M and $R_g$ ranging $3.7{\times}10^7{\sim}6.5{\times}10^8g/mol$ and 84 ~ 250 nm, respectively. Also the existence of branch was confirmed in higher M. In addition, proteinaceous material in starch was analyzed by AF4 coupled with a fluorescence detector (FS) after fluorescence-labeling. AF4-FS with fluorescence-labelling showed a potential for investigation on existence of proteinaceous material and the interaction between proteinaceous material and polysaccharide in starch.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.10
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• pp.656-664
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• 2017

This paper presents the design and fabrication of a high power piezoelectric ultrasonic surgery unit for multi-purpose dental implantation. A conventional piezoelectric ultrasonic surgery units consists of a transducer and a tip. However, the drawback of this simple structure is that the output performance of the transducer considerably changes with the change of the tips. An ultrasonic surgery unit that has an additional booster between the transducer and the tip can solve this problem to some extent; for this, an optimal structural design for the transducer is required. We used the Bolted Langevin Transducer (BLT) as the basic transducer; it consists of piezoelectric ceramics and a metal body. It's structure was optimized using mathematical methods to determine the length and radius of the tail and head masses. Additionally, the booster was also subjected to the same methods. Using these mathematical methods, optimal results in terms of the resonance frequency (24.96 kHz), displacement ($14.27{\mu}m$), and pressure (2.8 MPa), could be obtained. The validity of this proposed surgery unit was confirmed experimentally, exhibiting a cutting force of around 7% higher than that of a conventional surgery unit.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.1
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• pp.47-52
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• 2018

In this study, a collimator composed of multi-dielectric structures is designed using the phase field design method, a kind of topology optimization methods. It is also purposed to improve the mechanical-structural performance of a collimator by replacing previously used air regions with another dielectric material. Polypropylene and paraffin are selected as the dielectric materials for the design process taking manufacturability into account. The design objective is formulated by integrating the intensity of the electromagnetic field in the pre-determined target area to realize the collimating performance. The model for accurate numerical analysis was derived from the final result obtained from the design process through the simple cut-off method and it shows the improved performance of 105% compared with the free space wave propagation. For the designed model, the possibility of reverse transformation, the mechanical durability evaluation under the compression load, and the electromagnetic performance in the X-band range were also evaluated.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.433.1-433.1
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• 2014

The research of graphene, a monolayer of carbon atoms with honeycomb lattice structure, has explosively increased after appeared in 2004. As a result, its high transmittance, mobility, thermal conductivity, and outstanding mechanical and chemical stability have been proved. Especially, many researches were executed about the field of transparent electrode highlighting material of substituting the indium tin oxide (ITO). In addition, qualitative and quantitative improvements have been achieved due to many synthesis methods were discovered. Among them, mostly used method is chemical vapour deposition of graphene grown on copper or nickel. The transmittance, mobility, sheet resistance, and other many properties are completely changed according to these two types of synthesis method of graphene. In this research, considering the difference of characteristics as the synthesis method of graphene, what types of graphene should be used and how to use it were studied. The stacked graphene harvested on copper and multi-layer graphene harvested on nickel were compared and analyzed, as a result, the transmittance of 90% and the sheet resistance of $70{\Omega}{\square}$ was showed even though stacked graphene layers were 4 layers. The reason that could bring these results is lowered sheet resistance due to stacked monolayer graphenes. Moreover, light output power of the three stacked graphene spreading layer shows the highest value, but light-emitting diode with multi-layer graphene died out from 12mA due to also its high sheet resistance. Therefore, we need to clarify about what types of graphene and how to use the graphene in use.

• Journal of Surface Science and Engineering
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• v.47 no.4
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• pp.192-197
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• 2014

Red-emitting nitride phosphors recently attracted considerable attention because of their high thermal stability and high color rendering index properties. For excellent phosphor of white light-emitting-diode, ternary nitride phosphor of $Sr/SmSi_5N_8:Eu^{2+}$ with different $Eu^{2+}$ ion concentration were synthesized by solid state reaction method. In this work, red-emitting nitride $Sr/SmSi_5N_8:Eu^{2+}$ phosphor was successfully synthesized by using multi-step high frequency induction heat treatment. The effects of molar ratio of component and experimental conditions on luminescence property of prepared phosphors have been investigated. The structure and luminescence properties of prepared $Sr/SmSi_5N_8:Eu^{2+}$ phosphors were investigated by XRD and photoluminescence spectroscopy. The excitation spectra of $Sr/SmSi_5N_8:Eu^{2+}$ phosphors indicated broad excitation wavelength range of 300 - 550 nm, namely from UV to visible area with distinct enhanced emission peaks. With an increase of $Eu^{2+}$ ion concentration, the peak position of emission in spectra was red-shifted from 613 to 671 nm. After via multi-step heat treatment, prepared phosphor showed excellent luminescence properties, such as high emission intensity and low thermal quenching, better than commercial phosphor of $Y_3Al_5O_{12}:Ce^{3+}$. Using $Eu_2O_3$ as a raw material for $Eu^{2+}$ dopant with nitrogen gas flowing instead of using commercial EuN chemical for $Sr/SmSi_5N_8:Eu^{2+}$ synthesis is one of characteristic of this work.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.543-547
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• 2005

Organic electroluminescence devices were made from 1,4-bis-(9-anthrylvinyl)benzene (AVB) and 1,4-bis-(9-aminoanthryl)benzene (AAB) anthracene derivatives. Device structure was ITO/AVB/PANI(EB)/Al (multi-layer device) and ITO/AAB:DCM/Al(single-layer device). In these devices, AVB, polyaniline(emeraldine base) (PANI(EB)) and AAB were used as the emitting material. 4-(dicyanomethylene)-2-methyl-6-p-(dimethylamino)styryl-4H -pyran(DCM) was used as red fluorescent dopant. We studied change of fluorescence wavelength with concentration of DCM doped in AAB. The ionization potential (IP) and optical band gap (Eg) were measured by cyclic voltammetry and UV-visible spectrum. We compared with difference of emitting wavelength between photoluminescence and electroluminescence spectrum. In case of the multi-layer device, PANI and AVB EL spectra have similar wave pattern to each PL spectrum and when PAM and AVB were used at the same time, and multi-layer device showed that a balanced recombination and radiation kom PANI and AVB. In case of the single-layer device, with the increase of DCM concentration, the blue emission decreases and red emission increases. This indicates that DCM was excited by the energy transfer from AAB to DCM or the direct recombination at the dopant sites due to carrier trapping, or both. The device with $1.0wt\%$ DCM concentration gave white light.

• Journal of Korean Association for Spatial Structures
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• v.5 no.3 s.17
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• pp.83-89
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• 2005

This paper provides the results of the investigation on the optimum topology of simply supported deep beam structures with multi-point load cases. In this study, the strain energy to be minimized is considered as the objective function and the initial volume of structures is used as the constraint function. The resizing algorithm based on the optimality criteria is adopted to update the hole size existing inside the material. In this study, the sensitivities of topology optimization parameters to the optimum topology of the deep bean structures is investigated and also the effect of filtering process on the optimum topology is thoroughly tested. From numerical tests, the optimum topology of the deep beam is closely related with the optimization parameters used in the iteration and the filtering process play important role in order to find the optimum topology of the deep beam.