• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.613-624
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• 2000

In this study, new design method of prosthetic foot was suggested which can evaluate the performance of prosthetic foot by implementing amputee's gait simulation using the finite element analysis. The basic shape of ESPF(Energy Storing Prosthetic Foot) was designed which is suitable for the below-knee amputee considering mechanical properties and kinematic properties. And, the performance evaluations were performed using the Taguchi method with orthogonal array L25. As a result, average main effect of factors for the ESPF's performance were calculated and then optimum condition of given shape was selected. Essential particulars for the performance evaluation from the simulation result were the quantity of external work needed in stance phase, the quantity of transferred energy from the ESPF through the knee, and the vertical displacement of knee at toe-off. Reasonable optimum condition was obtained from the using performance index. From this study, it was found that it is necessary for the design of ESPF to consider the geometrical data related to the magnitude of load on elastic material.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.695-699
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• 2009

We studied the transfer of oxygen vacancy and proton in Y-doped BaZr$O_3$ (BYZ) using density functional theory (DFT). An oxygen vacancy was generated in the $2{\times}2{\times}2$ BYZ superstructure by replacing two Zr atoms with two Y atoms to satisfy the charge neutrality condition. The O vacancy transfer between the first and second nearest O atom sites from a Y atom showed the lowest activation energy barrier of 0.42 eV, compared to the other transfers between first and first, and second and second in the superstructure. Two protons were inserted in the structure by adding a proton and hydroxyl that were supplied by the dissociation of a water molecule. The two protons bonded to the first and second nearest O atoms were energetically the most favorable. The activation energy barrier for a proton transfer in the structure was 0.51 eV, when either proton transferred to its neighbor O atom. This value was well matched with the experimentally determined one.

• The KIPS Transactions:PartC
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• v.17C no.1
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• pp.81-88
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• 2010

Sensors in sensor networks are operated by their embedded batteries and they can not work any more if the batteries run out. The data collected by sensors should be transferred to a sink node through the efficient routes. Many energy efficient routing algorithms were proposed. However, the previous algorithms consume more energy since they did not consider the transmission range and direction. In this paper we propose an algorithm TDRP(Transmission range and Direction Routing Protocol) that considers the transmission range and direction for the efficient data transmission. Since TDRP does not produce clusters or grids but four quadrants and send data to the nodes in one quadrant in the direction of the sink node, it has less network overhead. Furthermore since the proposed algorithm sends data to the smaller number of nodes compared to the previous algorithms, the energy efficiency is better than other algorithms in communication node fields that are located in packet transmit directions.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.222-222
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• 2011

Titanium dioxide (TiO2) has a number of applications in optics and electronics due to its superior properties, such as physical and chemical stability, high refractive index, good transmission in vis and NIR regions, and high dielectric constant. Atomic layer deposition (ALD), also called atomic layer epitaxy, can be regarded as a special modification of the chemical vapor deposition method. ALD is a pulsed method in which the reactant vapors are alternately supplied onto the substrate. During each pulse, the precursors chemisorb or react with the surface groups. When the process conditions are suitably chosen, the film growth proceeds by alternate saturative surface reactions and is thus self-limiting. This makes it possible to cover even complex shaped objects with a uniform film. It is also possible to control the film thickness accurately simply by controlling the number of pulsing cycles repeated. We have investigated the ALD of TiO2 at 100$^{\circ}C$ using precursors titanium tetra-isopropoxide (TTIP) and H2O on -O, -OH terminated Si surface by in situ X-ray photoemission spectroscopy. ALD reactions with TTIP were performed on the H2O-dosed Si substrate at 100$^{\circ}C$, where one cycle was completed. The number of ALD cycles was increased by repeated deposition of H2O and TTIP at 100$^{\circ}C$. After precursor exposure, the samples were transferred under vacuum from the reaction chamber to the UHV chamber at room temperature for in situ XPS analysis. The XPS instrument included a hemispherical analyzer (ALPHA 110) and a monochromatic X-ray source generated by exciting Al K${\alpha}$ radiation (h${\nu}$=1486.6 eV).

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.286-291
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• 2008

Insulation of refrigerator with gasket material near door becomes the technical point at the aspect of heat loss and energy efficiency. Heat loss of refrigerator through the gasket is nearly 30%. In this paper, quantitative evaluation method of heat loss through gasket in established suggest the method for the improvement of heat loss. To analyze the heat transfer, we have used the common software Fluent that is used to CFD. Because of using the convection coefficient of heat transfer, we have solved only the equation of energy for heat transfer. As a result, we have known that heat loss flows through the heat flux vector and that the heat gathered out of the outside iron plate is transferred inner part through the gasket and ABS, etc. Through the result of the numerical simulation that use sub-gasket, we have known that we are able to reduce the heat loss about $20{\sim}40%$. when we applied that sub-gasket on a real refrigerator, the power consumption had reduced about 4.76%. In addition, when we applied a more improved sub-gasket on a real refrigerator and measured the power of the refrigerator the power consumption does reduce about 3% and we will try to apply the improved sub-gasket on a new models of refrigerator.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.251-259
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• 1999

A computer simulation was conducted for heat and momentum transfer in a roller kiln. Time-averaged Navier-Stokes equation conjugated with energy balance equation was numerically solved to predict the temperature distribution and fluid flow field in the roller kiln. A computer simulation was performed for a roller kiln for three cases. Firstly, when there are no ceramic materials in the roller kiln, the effect of natural convection was studied on the temperature distribution and fluid flow field. From the result, it was observed that air takes the heat of wall away from the roller kiln by natural convection and the heat was not transferred effectively. Secondly, with ceramic materials temperature difference of ceramic material from the borrom to the top of a ceramic material was about 255K in 5th zone and this is because the heat is transferred from the surface of a ceramic material to flowing air with relatively low temperature. Finally, we considered effect of radiation heat transfer. Temperature difference of ceramic material in 5th zone was about 300 K, due to radiation heat transfer on the ceramic material surfaces.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.22-28
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• 2013

Robotic GMA (Gas Metal Arc) welding process is one of widely acceptable metal joining process. The heat and mass inputs are coupled and transferred by the weld arc to the molten weld pool and by the molten metal that is being transferred to the weld pool. The amount and distribution of the input energy are basically controlled by the obvious and careful choices of welding process parameters in order to accomplish the optimal bead geometry and the desired quality of the weldment. To make effective use of automated and robotic GMA welding, it is imperative to predict online faults for bead geometry and welding quality with respect to welding parameters, applicable to all welding positions and covering a wide range of material thickness. MD (Mahalanobis Distance) technique was employed for investigating and modeling the GMA welding process and significance test techniques were applied for the interpretation of the experimental data. To successfully accomplish this objective, two sets of experiment were performed with different welding parameters; the welded samples from SM 490A steel flats. First, a set of weldments without any faults were generated in a number of repeated sessions in order to be used as references. The experimental results of current and voltage waveforms were used to predict the magnitude of bead geometry and welding quality, and to establish the relationships between weld process parameters and online welding faults. Statistical models developed from experimental results which can be used to quantify the welding quality with respect to process parameters in order to achieve the desired bead geometry based on weld quality criteria.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.105-106
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• 2013

Surface plasmon resonance (SPR) is classified into the propagating surface plasmon (PSP) excited on flat metal surfaces and the local surface plasmon (LSP) excited by metalnanoparticles. It is known that fluorescence signals are enhanced by these two SPR-fields.On the other hand, fluorescence is quenched by the energy transfer to metal (FRET). Bothphenomena are controlled by the distance between dyes and metals, and the degree offluorescence enhancement is determined by the correlation. In this study, we determined thecondition to achieve the maximum fluorescence enhancement by adjusting the distance of ametal nanoparticle 2D sheet and a quantum dots 2D sheet by the use of $SiO_2$ spacer layers. The 2D sheets consisting of myristate-capped Ag nanoparticles (AgMy nanosheets) wereprepared at the air-water interface and transferred onto hydrophobized gold thin films basedon the Langmuir-Schaefer (LS) method [1]. The $SiO_2$ sputtered films with different thickness (0~100 nm) were deposited on the AgMy nanosheet as an insulator. TOPO-cappedCdSe/CdZnS/ZnS quantum dots (QDs, ${\lambda}Ex=638nm$) [2] were also transferred onto the $SiO_2$ films by the LS method. The layered structure is schematically shown in Fig. 1. The result of fluorescence measurement is shown in Fig. 2. Without the $SiO_2$ layer, the fluorescence intensity of the layered QD film was lower than that of the original QDs layer, i.e., the quenching by FRET was predominant. When the $SiO_2$ thickness was increased, the fluorescence intensity of the layered QD film was higher than that of the original QDs layer, i.e., the SPR enhancement was predominant. The fluorescence intensity was maximal at the $SiO_2$ thickness of 20 nm, particularly when the LSPR absorption wavelength (${\lambda}=480nm$) was utilized for the excitation. This plasmonic nanosheet can be integrated intogreen or bio-devices as the creation point ofenhanced LSPR field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.37-42
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• 2012

LIFT (laser-induced forward transfer) is an advanced laser processing method used for selectively transferring micron-sized objects. In our study, this process was applied in order to deposit solder balls in microsystem packaging processes for electronics. Locally melted solder paste could be transferred to a rigid substrate using laser pulses. A thin glass plate with a solder cream layer was used as a donor film, and an IR laser pulse (wavelength = 1070 nm) was used to transfer a micron-sized solder ball to the receptor. Mass balance and energy balance were applied to analyze the shape and temperature profiles of the solder paste drops. The transferred solder bumps had measured diameters of 30-40 ${\mu}m$ and thicknesses of 50 ${\mu}m$ in our experiment. The limits and applications of this method are also presented.

• Korean Journal of Materials Research
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• v.19 no.4
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• pp.224-227
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• 2009

Nanofabrication is an essential process throughout industry. Technologies that produce general nanofabrication, such as e-beam lithography, dip-pen lithography, DUV lithography, immersion lithography, and laser interference lithography, have drawbacks including complicated processes, low throughput, and high costs, whereas nano-transfer printing (nTP) is inexpensive, simple, and can produce patterns on non-plane substrates and multilayer structures. In general nTP, the coherency of gold-deposited stamps is strengthened by using SAM treatment on substrates, so the gold patterns are transferred from stamps to substrates. However, it is hard to apply to transfer other metallic materials, and the existing nTP process requires a complicated surface treatment. Therefore, it is necessary to simplify the nTP technology to obtain an easy and simple method for fabricating metal patterns. In this paper, asnTP process with poly vinyl alcohol (PVA) mold was proposed without any chemical treatment. At first, a PVA mold was duplicated from the master mold. Then, a Mo layer, with a thickness of 20 nm, was deposited on the PVA mold. The Mo deposited PVA mold was put on the Si wafer substrate, and nTP process progressed. After the nTP process, the PVA mold was removed using DI water, and transferred Mo nano patterns were characterized by a Scanning electron micrograph (SEM) and Energy Dispersive spectroscopy (EDS).