• The Korean Journal of Physiology and Pharmacology
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• v.2 no.6
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• pp.677-685
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• 1998

To investigate the effects of neonatal stress on behavior and neurochemistry, rats were exposed to the footshock stress on postnatal day (PND) 14 or PNDs 14 and 21. Rats were exposed to uncontrollable electric shocks delivered to the floor with a constant current (0.8 mA) for 5 sec period. Daily sessions consisted of 60 trials on a random time schedule with an average of 55 sec. The first exposure to footshocks on PND 14 decreased body weight gain for 1 day. However, the second exposure to footshocks on PND 21 did not affect body weight gain. Exploratory activity was measured by exposing a rat to a novel environment 24 h after experience of footshocks. Similar to the body weight changes, a decreased activity was noted after the first exposure to footshocks, while no changed activity was noted after the second exposure to footshocks. However, the Bmax value of $5-HT_{2A/2C}$ receptors in the cortex decreased by the second exposure to footshocks, but not by the first exposure to footshocks. Moreover, an autoradiographic study revealed that the density of $[^3H]dexamethasone$ binding in hippocampus decreased in rats exposed to footshocks 4 times during PND $14{\sim}20.$ These results suggest that the uncontrollable footshock stress changes 5-hydroxytryptamine and glucocorticoid receptor systems acutely and that the repeated exposure to the same stress may not elicit behavioral alterations by the compensatory activity of young brain although changes in some neurochemistry exist.

• Journal of Pharmaceutical Investigation
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• v.23 no.3
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• pp.41-50
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• 1993

The iontophoretic delivery across rat skin of quaternary ammonium salts (isopropamide: ISP, pyridostigmine: PS), which are positively charged over a wide pH range, was measured ill vitro. The study showed that: (a) iontophoresis significantly enhanced delivery of ISP and PS compared to respective passive transport; (b) delivery of ISP and PS was directly proportional to the applied continuous direct current density over the range of $0-0.69\;mA/cm^2;$ (c) delivery of ISP and PS was also proportional to the drug concentration in the donor compartment over the range of $0-2{\time}l0^{-2}M:$ (d) sodium ion in the donor compartment inhibited the drug transport possibly due to decreasing the electric transference number of the drug; (e) delivery of ISP and PS increased as the pH of the donor solution increased over the pH range 2-7 suggesting permselective nature of the epidermis, and inhibition of the transference number of the drugs by hydronium ion; (f) some organic anions such as taurodeoxycholate, salicylate and benzoate which form lipophilic ion-pair complexes with ISP inhibited the delivery of ISP. The degree of inhibition by the organic anions was linearly proportional to the extraction coefficient $(K_e)$ of ISP from the partition system with each counteranion between phosphate buffer (pH 7.4) and n-octanol. For PS, however, taurodeoxycholate, but not salicylate and benzoate inhibited the iontophoretic delivery. It suggests that not only sodium ion and hydronium ion but also the counteranions which form lipophilic ion-pairs with quaternary ammonium drugs are not favorable components in formulating the donor solution of the drugs to achieve an effective iontophoretic delivery.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.109-114
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• 2013

Power MOSFET (metal-oxide semiconductor field-effect transistor) are widely used in power electronics applications, such as BLDC (Brushless Direct Current) motor and power module, etc. For the conventional power MOSFET device structure, there exists a tradeoff relationship between specific on-state resistance and breakdown voltage. In order to overcome the tradeoff relationship, a non-uniform super-junction (SJ) trench MOSFET (TMOSFET) structure for an optimal design is proposed in this paper. It is required that the specific on-resistance of non-uniform SJ TMOSFET is less than that of uniform SJ TMOSFET under the same breakdown voltage. The idea with a linearly graded doping profile is proposed to achieve a much better electric field distribution in the drift region. The structure modelling of a unit cell, the characteristic analyses for doping density, and potential distribution are simulated by using of the SILVACO TCAD 2D device simulator, Atlas. As a result, the non-uniform SJ TMOSFET shows the better performance than the uniform SJ TMOSFET in the specific on-resistance at the class of 100V.

• Solar Energy
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• v.17 no.1
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• pp.59-66
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• 1997

The solar cell electrical output parameters such as the open circuit voltage($V_{oc}$) and short circuit current density($V_{sc}$) are intrinsic characteristics depending on junction depth, doping concentration, metal contacts barriers and cell structure. As a role of thumb for solar cell design, the metal contact barriers for phosphorus doped emitter should have lower work function in order to provide lower series resistance. The fabrication of PESC(passivated emitter solar cell) structure usually involves the use of titanium as a metal contact barrier. Chromium, which work function is similar to titanium but conductance is higher than titanium is being investigated as the new metal contact barrier. Although titanium has lower work function difference than chromium, the electric performances of chromium as contact barrier are higher than titanium. This better performance is attributed to the lower resistivity from chromium. This paper, therefore, compares the attributes of metal barrier contacts using titanium and chromium.

• Journal of Welding and Joining
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• v.32 no.5
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• pp.32-43
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• 2014

Welding and joining technology has become a core field. Therefore it is more widely applied to nonferrous metals, inorganic and polymeric materials. That is because the high performance, high function and diversification trend of materials used as industrial technology develops. In the laser welding process, STS 304 and SCP1-S were used as the base materials, the output density was fixed $7MW/cm^2$, the protective gas was argon(Ar) and the transfer rate was fixed 5 mm/sec. and it was progressed while the magnetic field is gradually increasing by 100 mT ranging 0 to 400 mT. The tensile test showed in average about 6 % tensile strength improvement in the case of the laser welding process using the magnetic fields. In the shielded metal arc welding process using SPHC only or the combination of SPHC+STS304 as base materials. The electric current was set at 80 Amperes and the protective gas used argon(Ar) the same as the laser welding process and the strength of magnetic fields. In the shielded metal arc welding process using the magnetic fields, the tensile tests showed about 5 % tensile strength improvement in the case of using SPHC only, 3 % tensile strength improvement in the case of using the combination of SPHC+ STS304. In comparing the results of numerical analysis to the results of experimental tests, it was revealed that the temperature, thermal stress distribution and the behavior of molten pool were similar to those of real tests. Consequently, it may be considered that the numerical assumption and the analytical model used in this study were reasonable.

• Journal of Energy Engineering
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• v.21 no.2
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• pp.194-201
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• 2012

In this research, a sewage sludge solubilization study using electrolysis was performed as a pre-treatment for anaerobic digestion efficiency improvement. SCOD potency increased as the treatment time and electric current density increased with sludge electrolysis treatment while SCOD, TN, and TP especially showed the highest increase of 7.4 times, 1.9 times, and 1.3 times respectively at the 60 minute point of treatment. Solubilization was high at the strong acidic and alkaline status for the sewage sludge electrolysis treatment results along early stage pH, and especially, a high solubilization percentage of 32.9% was seen at pH 12. The above result shows that there was an increase of organic matter able to be used by microorganisms from sludge floc and the destruction of EPS structure due to direct and indirect oxidation following electrolysis.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.171-171
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• 2009

The electrodes are usually made of a porous mixture of carbon-supported platinum and ionomers. $SnO_2$ particles provide as supports that have been used for DMFCs, and it have high catalytic activities toward methanol oxidation. The main advantage of $SnO_2$ supported electrodes is that it has strong chemical interactions with metallic components. The high activity to a synergistic bifunctional mechanism in which Pt provides the adsorption sites for CO, while oxygen adsorbs dissociative on $SnO_2$. The reaction between the adsorbed species occurs at the Pt/$SnO_2$ boundary. The morphological observations were characterized by FESEM and transmission electron microscopy (TEM). $SnO_2$ particles crystallinity was analyzed by the X-ray diffraction (XRD). The surface bonded state of the $SnO_2$ particles and electrode materials were observed by the X-ray photoelectron spectroscopy (XPS). The electric properties of the Pt/$SnO_2$ catalyst for methanol oxidation have been investigated by the cyclic voltametry (CV) in 0.1M $H_2SO_4$ and 0.1M MeOH aqueous solution. The peak current density of methanol oxidation was increased as the $SnO_2$ content in the anode catalysts increased. Pt/$SnO_2$ catalysts improve the removal of CO ads species formed on the platinum surface during methanol electro-oxidation.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.287-287
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• 2011

ITRS(international technology roadmap for semiconductors)에 따르면 MOS (metal-oxide-semiconductor)의 CD(critical dimension)가 45 nm node이하로 줄어들면서 poly-Si/SiO2를 대체할 수 있는 poly-Si/metal gate/high-k dielectric이 대두되고 있다. 일반적으로 metal gate를 식각시 정확한 CD를 형성시키기 위해서 plasma를 이용한 RIE(reactive ion etching)를 사용하고 있지만 PIDs(plasma induced damages)의 하나인 PICD(plasma induced charging damage)의 발생이 문제가 되고 있다. PICD의 원인으로 plasma의 non-uniform으로 locally imbalanced한 ion과 electron이 PICC(plasma induced charging current)를 gate oxide에 발생시켜 gate oxide의 interface에 trap을 형성시키므로 그 결과 소자 특성 저하가 보고되고 있다. 그러므로 본 연구에서는 이에 차세대 MOS의 metal gate의 식각공정에 HDP(high density plasma)의 ICP(inductively coupled plasma) source를 이용한 중성빔 시스템을 사용하여 PICD를 줄일 수 있는 새로운 식각 공정에 대한 연구를 하였다. 식각공정조건으로 gas는 HBr 12 sccm (80%)와 Cl2 3 sccm (20%)와 power는 300 w를 사용하였고 200 eV의 에너지로 식각공정시 TEM(transmission electron microscopy)으로 TiN의 anisotropic한 형상을 볼 수 있었고 100 eV 이하의 에너지로 식각공정시 하부층인 HfO2와 높은 etch selectivity로 etch stop을 시킬 수 있었다. 실제 공정을 MOS의 metal gate에 적용시켜 metal gate/high-k dielectric CMOSFETs의 NCSU(North Carolina State University) CVC model로 effective electric field electron mobility를 구한 결과 electorn mobility의 증가를 볼 수 있었고 또한 mos parameter인 transconductance (Gm)의 증가를 볼 수 있었다. 그 원인으로 CP(Charge pumping) 1MHz로 gate oxide의 inteface의 분석 결과 이러한 결과가 gate oxide의 interface trap양의 감소로 개선으로 기인함을 확인할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.334-334
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• 2012

Transparent oxide semiconductors have recently attracted much attention as channel layer materials due to advantageous electrical and optical characteristics such as high mobility, high stability, and good transparency. In addition, transparent oxide semiconductor can be fabricated at low temperature with a low production cost and it permits highly uniform devices such as large area displays. A variety of thin film transistors (TFTs) have been studied including ZnO, InZnO, and InGaZnO as the channel layer. Recently, there are many studies for substitution of Ga in InGaZnO TFTs due to their problem, such as stability of devices. In this work, new quaternary compound materials, tantalum-indium-tin oxide (TaInSnO) thin films were fabricated by using co-sputtering and used for the active channel layer in thin film transistors (TFTs). We deposited TaInSnO films in a mixed gas (O2+Ar) atmosphere by co-sputtering from Ta and ITO targets, respectively. The electric characteristics of TaInSnO TFTs and thin films were investigated according to the RF power applied to the $Ta_2O_5$ target. The addition of Ta elements could suppress the formation of oxygen vacancies because of the stronger oxidation tendency of Ta relative to that of In or Sn. Therefore the free carrier density decreased with increasing RF power of $Ta_2O_5$ in TaInSnO thin film. The optimized characteristics of TaInSnO TFT showed an on/off current ratio of $1.4{\times}108$, a threshold voltage of 2.91 V, a field-effect mobility of 2.37 cm2/Vs, and a subthreshold swing of 0.48 V/dec.

• Journal of Sensor Science and Technology
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• v.9 no.1
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• pp.83-89
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• 2000

BST thin films were deposited on the ITO coated glass for using TFELD insulating layer by rf magnetron sputtering method. $O_2/(Ar+O_2)$ mixing ratio was 10%, substrate temperature was changed from R.T. to $500^{\circ}C$, and working pressure was changed from 5 mTorr to 30 mTorr. BST thin films deposited with various conditions were investigated electrical, optical, structural properties, and stoichiometry. The result of investigation was achieved good fabrication condition that substrate temperature of $400^{\circ}C$, and working pressure of 30 mTorr. Relative dielectric constant of 254 at 1 kHz, leakage current density was below $3.3{\times}10^{-7\;}A/cm^2$ at 5\;MV/cm applied electric field, and transmittance was over 82% at visible range.