• Journal of Powder Materials
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• 제27권1호
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• pp.25-30
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• 2020

Recently, the amount of heat generated in devices has been increasing due to the miniaturization and high performance of electronic devices. Cu-graphite composites are emerging as a heat sink material, but its capability is limited due to the weak interface bonding between the two materials. To overcome these problems, Cu nanoparticles were deposited on a graphite flake surface by electroless plating to increase the interfacial bonds between Cu and graphite, and then composite materials were consolidated by spark plasma sintering. The Cu content was varied from 20 wt.% to 60 wt.% to investigate the effect of the graphite fraction and microstructure on thermal conductivity of the Cu-graphite composites. The highest thermal conductivity of 692 W m^-1K^-1 was achieved for the composite with 40 wt.% Cu. The measured coefficients of thermal expansion of the composites ranged from 5.36 × 10^-6 to 3.06 × 10^-6K^-1. We anticipate that the Cu-graphite composites have remarkable potential for heat dissipation applications in energy storage and electronics owing to their high thermal conductivity and low thermal expansion coefficient.

• Proceedings of the Materials Research Society of Korea Conference
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.42.2-42.2
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• 2011

$TiO_2$ films were modified by adding a glass frit as a light scattering particle and applied to an anode electrode in dye-sensitized solar cells (DSSCs) to enhance the adhesion between $TiO_2$ and fluorine doped transparent oxide (FTO). Low melting point glass frits at contents of (3 to 7wt%) were added to the nano crystalline $TiO_2$ films. The light scattering properties, photovoltaic properties and microstructures of the photo electrodes were examined to determine the role of the low glass transition temperature ($T_g$) glass frit. Electrochemical impedance spectroscopy, Brunauer-Emmett-Teller method and scratch test were conducted to support the results. The DSSC with the $TiO_2$ film containing 3wt% low Tg glass frit showed optimal performance (5.1%, energy conversion efficiency) compared to the $TiO_2$-based one. The photocurrent density slightly decreased by adding 3wt% of the frit due to its large size and non conductivity. However, the decrease of current density followed by the decrease of electron transfer due to the large frit in $TiO_2$ electrode was compensated by the scattering effect, high surface area and reduced the electron transfer impedance at the electrolyte-dye-$TiO_2$ interface. The stability of the photo electrodes was improved by the frit, which chemically promoted the sintering of $TiO_2$ at relatively low temperature ($450^{\circ}C$).

• Journal of the Korean Magnetics Society
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• 제4권3호
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• pp.239-243
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• 1994

$NiFe/TbCo/Si_3N_4$ thin films were fabricated, which can be employed as dualOongitudinal and transverse) biased magnetoresistive elements utilizing surface magnetic exchange at the interface of NiFe/TbCo films. When Tb area percent was 36 % and substrate bias was not applied, magnetic exchange fields of 100~180 Oe were obtained. The thicknesses of NiFe, TbCo and $Si_3N_4$(Protective layer) were $470\;{\AA},\;2400\;{\AA}\;and\;600\;{\AA}$, respectively. Magnetoresistance ratio of 1.45 % was obtained using NiFe films fabricated with 1000 W power and 2.5 mTorr of Ar pressure. The MR ratio of microstructured elements was reduced to 1.31 % and the MR response curves were shown not to saturate due to demagnetizing fields of the elements. When elements were fabricated with $36^{\circ}$ of misalignment with respect to the exchange field direction using films having 150 Oe exchange field, MR response curve was shifted by 85 Oe, and the operating point of the device shifted to the linear region of the response. Also, the Barkhausen noise was eiminated due to longitudinal bias field originating from the exchange field.

• Journal of the Institute of Electronics Engineers of Korea CI
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• 제49권4호
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• pp.71-81
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• 2012

In order to support simple authoring an application of augmented reality for diverse users, the process for the object registration comprised of tracking and recognizing the object should be accomplished intuitively and simple. Although many 3D reconstruction methods to be applied to the object registration have been developed, the methods have not beyond the experimental level yet. In this paper, we proposed a novel marker-based tangible interfaces for various users to manipulate the object with intuitive and simple approaches during an authoring applications fo augmented reality. The proposed method make use of marker as intuitive interface to obtain 3D geometric information of 3D reconstruction. 3D geometric information of an object surface is acquired by touching the object directly with the proposed tangible interfaces. The tangible interfaces not only support 3D reconstruction for graphical modeling but also offer features information which is used for augmented reality. Finally, we verify efficiency of the proposed method with demonstration of an augmented reality application using the proposed method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 1992년도 추계학술대회 논문집
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• pp.123-127
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• 1992

When MOS devices is exposed to radiation, radiation effects of P-type MOS capacitor can cause modulation and/or degradation in devices characteristics and its operating life. The oxide layer is grown in $O_2$+T.C.E. and its thickness ranges from 40 to 80 nm. Irradiations on MOS capacitor were performed by Cobalt-60 gamma ray source and total dose ranges from $10^4$ to $10^8$ rads. The radiation effect on electrical conduction characteristics(I-V) in MOS capacitor was measured as a function of gate oxide thickness and total dose. From the experimental result, I-V characteristics is found to be influenced strongly by total dose in irradiated p-type MOS capacitors. The ohmic current is dependant on of total dose in irradiated P-type MOS capacitors. This results are explained using surface states at interface radiation-induced traps.

• Journal of Welding and Joining
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• 제26권2호
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• pp.55-61
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• 2008

Various research to reduce weight of a car is achieving. This research is tendencious to manufacture solid piston rod of shock absorber as hollow piston rod using friction welding. This study deals with the friction welding of SM45C to SM45C-Pipe that is used in car shock absorber, The friction time was variable conditions under the conditions of spindle revolution of 2,000rpm, friction pressure of 55MPa, upset pressure of 75MPa, and upset time of 2.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied of friction weld, and so the results were as follows. 1. In tensile strength, the hole processing is better than non-hole processing. 2. When the friction time was 1.5seconds under the conditions, the maximum tensile strength of the friction weld happened to be 869MPa, which is 103% of SM45C's tensile strength and 91% of SM45C's Pipe. 3. When the friction time was 2.0seconds under the conditions, the maximum bending strength of the friction weld happened to be 1599MPa, which is 80% of SM45C's bending strength and 118% of SM45C's Pipe.

• Korean Journal of Materials Research
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• 제9권9호
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• pp.865-871
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• 1999

Effect of sintering condition in mechanical properties of ZrSiO\ulcorner shell molds was investigated. Number of microcrack in primary layer of the mold was maximized after preheating at $1000^{\circ}C$ for 1.5 hours. Yield strength and specific surface area of the mold were inversely proportion to sintering temperature and time. After hot deformation test at $1500^{\circ}C$ for 4 hours, molds were deformed opposite to the loading direction and backup layers were cracked along the interface between stucco and zircon slurry. Reverse deformation of the molds during hot deformation test was considered to be resulted from the difference of thermal expansion coefficient between alumina stucco and zircon slurry in primary coat, and size difference between zircon stucco and zircon slurry in backup coat.

• Korean Journal of Agricultural and Forest Meteorology
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• 제22권3호
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• pp.128-134
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• 2020

The daily gridded meteorological information and climatology with high resolution (30m and 270m) was produced from 94 Automated Surface Observing System (ASOS) of Korea Meteorological Administration (KMA) for the past 50 years (1971-current) by different downscaling methods. In addition, the difference between daily meteorological data and the mean state of past 30 years (1981-2010) was calculated for the analysis of climate change. These datasets with GeoTiff format are available from the web interface (https://agecoclim. agmet.kr). The performance of the data is evaluated using 172 Automatic Weather S tation (AWS ) of Rural Development of Administration (RDA). The data have biases lower than 2.0, and root mean square errors (RMSE) lower than 3.8. This data may help to better understand the regional climatic change and its impact on agroecosystem in S outh Korea.

• Aerospace Engineering and Technology
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• 제3권1호
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• pp.126-133
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• 2004

Photogrammetry, as its name implies, is a 3-dimensional coordinate measuring technique that uses photographs as the fundamental medium for metrology. In the last few years the accuracy of photogrammetry has increased dramatically thanks to the rapid advance of digital camera manufacturing technique. This paper discusses photogrammetric measurement of the interface surface of MSC(Multi-Spectral Camera), which is a main payload of KOMPSAT-2. Total 24 paper targets on the objective surfaces and two scale bars calibrated with high accuracy were used for measurement, and multiple images were taken from 11 different camera angles by using a spacecraft rotation dolly. As a result of analysis, 3D coordinates of each targeted point were obtained and the flatness value based on the selected reference plane was calculated and compared with the pre-determined requirement. The technique acquired by this study is expected to be used for the 3D precise measurement of ultra-light weight and inflatable space structures such as a satellite antenna and a solar array.

• Journal of the Korean Electrochemical Society
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• 제8권1호
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• pp.1-5
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• 2005

Electric double layer capacitors(EDLCS) based on the charge stored at the interface between a hi팀 surface area carbon electrode and an organic electrolyte solution are widely used as a maintenance-free power source for IC memories and microcomputers. The achievement of the excellent performance of the capacitor requires an electrolyte solution which provides high conductivities over a wide temperature range and good electrochemical stabilities to allow the capacitor to be operated at high voltage. The electrochemical capacitor using a carbon material as electrodes and using an organic electrolyte with $1M-LiPF_6$ in PC-GBL-DEC(volume ratio 1:1:2) has specific capacitance of 64F/g.