• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.1
• /
• pp.211-218
• /
• 2014

In this paper the magnetic field properties of the soft magnetic alloys (Fe-Si-Cr and Fe-Ni-Cr) are studied in advance for the development of electro-magnetic shielding films, which could be used in the IT Devices (NFC, mobile phone, computer, etc.).As a result each of the selected soft magnetic alloy melts of the corresponding compositions is water-dispersed into the disk-shaped grains, which are soaked in polymer resin, and of which two types of thin film of thickness 0.1mm and 1mm are made by passing through the heating calendar roller. And the magnetic permeability and the shielding effectiveness of the polymer films containing the soft magnetic alloy grains are measured over the whole frequency bands from the low frequency to 10GHz. Before the experiments of the soft magnetic alloy, a special equation is proposed to estimate the permeability of the alloy, and the equation is verified with the pre-published data by MATLAB, and from which the most optimal compositions can be decided. And the SE(Shielding Effectiveness) of the polymer films containing the soft magnetic alloy grains is simulated by the HFSS.

• Journal of the Microelectronics and Packaging Society
• /
• v.22 no.4
• /
• pp.83-89
• /
• 2015

In this paper, we propose a fabrication technique for enhanced electrical properties of piezoelectric thick films with excellent patterning property using sol-infiltration and a direct-patterning process. To achieve the needs of high-density and direct-patterning at a low sintering temperature (< $850^{\circ}C$), a photosensitive lead zirconate titanate (PZT) solution was infiltrated into a screen-printed thick film. The direct-patterned PZT films were clearly formed on a locally screen-printed thick film, using a photomask and UV light. Because UV light is scattered in the screen-printed thick film of a porous powder-based structure, there are needs to optimize the photosensitive PZT sol infiltration process for obtaining the enhanced properties of PZT thick film. By optimizing the concentration of the photosensitive PZT sol, UV irradiation time, and solvent developing time, the hybrid films prepared with 0.35 M of PZT sol, 4 min of UV irradiation and 15 sec solvent developing time, showed a very dense with a large grain size at a low sintering temperature of $800^{\circ}C$. It also illustrated enhanced electrical properties (remnant polarization, $P_r$, and coercive field, $E_c$). The $P_r$ value was over four times higher than those of the screen-printed films. These films integrated on silicon wafer substrate could give a potential of applications in micro-sensors and -actuators.

• Journal of the Korean Wood Science and Technology
• /
• v.36 no.6
• /
• pp.1-12
• /
• 2008

A series of the studies on the applied physical properties of domestic species have been conducted last three years. Liriodendron tulipifera, Betula costata, Paulownia coreana were examined on sorption property, thermal property, electric property, acoustic property. Because the same apparatus and experimental procedures were used for all species, their results can be easily comparable. The experiments for sorption property were conducted with 80 mesh wood powder and resulted in their EMC's and sorption isotherms. The thermal conductivity and diffusivity, and electric resistance and volumetric electric resistivity were measured with a thermal-wire device and a high electric resistance meter. The differences of the thermal and electric properties between quarter-and flat-sawn specimens were observed, which was partially attributed to their anatomical differences. An acoustic measurement system was used to evaluate dynamic MOE and internal friction. This paper provides the useful fundamental data for designing a wood structure, correcting a portable resistance-type moisture meter, and acoustic properties of wood.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2002.05a
• /
• pp.23-28
• /
• 2002

This paper describes the machining characteristics of the $MoSi_2$ based composites by electric discharge drilling with various tubular electrodes, besides, Hardness characteristics and microstructures of $Nb/MoSi_2$ laminate composites were evaluated from the variation of fabricating conditions such as preparation temperature, applied pressure and pressure holding time. $MoSi_2$ -based composites has been developed in new materials for jet engine of supersonic-speed airplanes and gas turbine for high- temperature generator. Achieving this objective may require new hard materials with high strength and high temperature-resistance. However, With the exception of grinding, traditional machining methods are not applicable to these new materials. Electric discharge machining (EDM) is a thermal process that utilizes a spark discharge to melt a conductive material, the tool electrode being almost non-unloaded, because there is no direct contact between the tool electrode and the workpiece. By combining a nonconducting ceramics with more conducting ceramic it was possible to raise the electrical conductivity. From experimental results, it was found that the lamination from Nb sheet and $MoSi_2$ powder was an excellent strategy to improve hardness characteristics of monolithic $MoSi_2$. However, interfacial reaction products like (Nb, Mo)$SiO_2$ and $Nb_2Si_3$ formed at the interface of $Nb/MoSi_2$ and increased with fabricating temperature. $MoSi_2$ composites which a hole drilling was not possible by the conventional machining process, enhanced the capacity of ED-drilling by adding $NbSi_2$ relative to that of SiC or $ZrO_2$ reinforcements.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.25 no.8
• /
• pp.664-669
• /
• 2012

Nano-structured one-dimensional $Na_2Ti_6O_{13}$ particles were synthesized by a molten salt process. Effects of processing parameters on the microstructure and band gap energy of the $Na_2Ti_6O_{13}$ powder were studied in this paper. For the synthesis of the $Na_2Ti_6O_{13}$ particles, two different raw materials of tubular shaped Na-titanate (Na-TiNT) and spherical shaped $TiO_2$ were utilized. Synthesizing with the raw material of Na-TiNT, around 70nm thick 1D-$Na_2Ti_6O_{13}$ with the bandgap energy of 3.5 eV was obtained at $810^{\circ}C$. Below $810^{\circ}C$ or without the presence of NaCl, 1D-$Na_2Ti_6O_{13}$ was in a relatively short in length and agglomerated state. With the processing temperature increased, the thickness of the 1D-$Na_2Ti_6O_{13}$ was also observed to be increased. On the other hand, when $TiO_2$ was employed as a raw material, the mixed amount of $Na_2CO_3$ played an important role in transforming the morphology and phase of the raw material, affecting the bandgap energy of the synthesized product. Specific surface area of the synthesized 1D-$Na_2Ti_6O_{13}$ was significantly affected by the raw and mixed materials as well as processing temperature. When Na-TiNT was processed at $810^{\circ}C$ with NaCl, the specific surface area of the 1D-$Na_2Ti_6O_{13}$ showed the best value of 30.63 $m^2/g$.

• Journal of Korean Society of Environmental Engineers
• /
• v.31 no.4
• /
• pp.256-262
• /
• 2009

The use of hydrodynamic separator is becoming increasingly popular for suspended solids reduction in urban storm runoff. This study is a laboratory investigation of the use of Vortex Screen to reduce the solids concentration of synthesized storm runoff. The synthesized storm runoff was made with water and addition of particles; manhole sediment, road sediment, fly ash, and ployvinyl chloride powder. Vortex Screen was made of acryl resin with 250 mm of diameter and height of 700 mm. To determine the removal efficiency for various influent concentrations of suspended solids (SS) and chemical oxygen demand (COD), tests were performed with different operational conditions. The samples were taken simultaneously at the influent storage tank and effluent tank, and measured SS and COD concentrations. The ranges of surface loading rate were 110 to 1,550 $m^3/m^2$/day, and influent SS concentrations were varied from 141 to 1,986 mg/L. This paper was intended to evaluate the effect of inlet baffle and the ratio of underflow to overflow ($Q_U/Q_O$) on particle separation efficiency for various particle size using Vortex Screen. It was found that when increase of $Q_U/Q_O$ from 10% to 20%, SS removal efficiency was increased about 6%. The range of SS and COD removal efficiencies of road sediment particle size 125<$d_p$<300 ${\mu}m$ were 68.0~81.0%, 53.1~71.9%, respectively. Results showed that SS removal efficiency with inlet baffle improved by about 10~20% compared without inlet baffle.

• Journal of the Microelectronics and Packaging Society
• /
• v.20 no.2
• /
• pp.39-46
• /
• 2013

In this paper, organic solar cells(OSCs) based on bulk-heterojunction structures were fabricated by spin coating method using polymer P3HT and fullerene PCBM as a photoactive layer. The fabricated OSCs had a simple glass/ITO/PEDOT:PSS/P3HT:PCBM/Al structures. The photoactive layer of mixed P3HT:PCBM was formed with 1:1 weight ratio. The hole transport layer(HTL) was used conducting polymer PEDOT:PSS concentration with gold nanoparticles. The annealing temperature and concentration of nanoparticles in HTL were verified to improve the OSC characterization. The percentage of gold nanoparticles in HTL were 0.5 wt% and 1.0 wt%, and the surface morphology, electrical properties and absorption intensities were investigated. The devices were 0.5 wt%, and the highest 3.1% of the powder conversion efficiency(PCE), 10.2 $mA/cm^2$ of the maximum short circuit current density($J_{SC}$), 0.535V of the open circuit voltage($V_{OC}$) and 55.8% of the fill factor(F.F) could be obtained when the nanoparticle concertration was 0.5 wt%. The annealing temperature of HTL was $110^{\circ}C$, $130^{\circ}C$, $150^{\circ}C$ in vacuum oven and measured the absorption intensities, surface morphology, crystallinity and electrical properties were investigated. The best property was obtained in HTL annealed at $130^{\circ}C$ for gold nanoparticles of 0.5 wt%, showing that $J_{SC}$, $V_{OC}$, F.F and PCE were about 12.0 $mA/cm^2$, 0.525V, 64.2% and 4.0%, respectively.

• Journal of the Korea Concrete Institute
• /
• v.16 no.1 s.79
• /
• pp.1-9
• /
• 2004

This paper represents the permeability of chloride ions and the corrosion performance in the concrete blended with granulate blast furnace slag exposed to chloride environment. An ordinary cement (type I ) and sulfate resisting cement(type V) were used for the experiment. The two cements were combined with $0\%$, $25 \%$, $40\%$, and $55\%$ of the granulated blast furnace slag. The accelerated permeability tests of chloride ions were performed in accordance with ASTM C1202, and the accelerated corrosion tests of steel were carried out by using the method of immersion/drying cycles. After water curing 28 days, 56 days and 91 days, these tests were conducted until 30 cycles. In every cycle, test specimens were wetted in $3\%$ NaCl solution for three days and dried again in $60^{\circ}C$ air for four days. As an experimental results, the diffusion coefficient of chloride ions of the ordinary cement Concrete Combined granulated blast furnace slag was much lower than that of non granulated blast furnace slag concrete. Moreover, the diffusion coefficient of chloride ions of sulfate resisting cement concrete was higher than that of ordinary cement concrete. On the basis of the results of accelerated corrosion tests, corrosion resistance of the concrete mixed with granulated blast furnace slag shows good to corrosion resistance, however, the concrete with sulfate resisting cement shows bad to corrosion resistance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1993.05a
• /
• pp.79-84
• /
• 1993

This paper describes the development of lithium rechargeable cell. $LiCoO_2$ is recently recognized as a suitable cathode active material of a high voltage, high energy lithium rechargeable batteries because $Li^+$ ion can be electrochemically deintercalated/intercalated from/to $Li_xCoO_2$. The transition metal oxide of $LiCoO_2$ was investigated for using as a cathode active material of 4V class Li rechargeable cell. $LiCoO_2$ cathode was prepared by using a active material of 85 wt%, graphite powder of 12 wt% as a conductor and poly-vinylidene fluoride of 3 wt% as a binder. The electrochemical and charge/discharge properties of $LiCoO_2$ were investigated by cyclic voltammetry and galvanostatic charge/discharge. The open circuit voltage of prepared $LiCoO_2$ electrode exhibited approximately. potential range between 3.32V and 3.42V. During the galvanostatic charge/discharge, $LiCoO_2/Li$ cell showed stable cycling behavior at scan rate of 1mV/sec and potential range between 3.6V and 4.2V. Also its coulombic efficiency as function of cycling was 81%~102%. In this study the $LiCoO_2/Li$ cell showed the available discharge capacity of 90.1 mAh/g at current density of $1mA/cm^2$ and cell discharge voltage range between 3.6V~4.2V.

• Korean journal of applied entomology
• /
• v.9 no.2
• /
• pp.85-90
• /
• 1970

This study was conducted to find out the evidence of a sex attraction in the fall webworm moths, Hyphantria cunea D., in the fold conditions. The study dealt with the sex attraction between the sexes, selection of effective trap type, effect of moth age on the sex attractiveness, sex attractiveness after copulation, and the time of the sex attraction in the day, The trap was baited with a living moth in the cylindrical screened case 4cm. in long and 2.7cm in diameter. The traps were attached on the tree in a horizontal position at the height of about 3m. on the ground. A sex pheromone was evident in the female moth which attracted the male to the lure, and the modified sticky trap was most effective in this experiment. The trap consisted of a cylindrical powder milk can 11.5cm. in long and 10cm. in diameter with the entry hole 4.8cm, in diameter at both ends of the can, and the inside of can was lined with paper coated with acri-soil(sodium poliacrilate) to catch them. Males were mostly attracted to females during their first 2 days of life, and its attractiveness decreased with moth age, No males were attracted to females more than five days old, and no females lived for more than six days. After copulation, sexual attractiveness was decreased swiftly, Sexual attractiveness was found to be greatest between 4 and 6 A.M. Living females can be used as effective baits for luring the males to the fold trapt.