• Journal of the Microelectronics and Packaging Society
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• v.26 no.2
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• pp.31-43
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• 2019

In this study, polymer elastic bumps were fabricated for the flexible electronic package flip chip bonding and the viscoelastic and viscoplastic behavior of the polymer elastic bumps according to the temperature and load were analyzed using FEM and experiments. The polymer elastic bump is easy to deform by the bonding load, and it is confirmed that the bump height flatness problem is easily compensated and the stress concentration on thin chip is reduced remarkably. We also develop a spiral cap type and spoke cap type polymer elastic bump of $200{\mu}m$ diameter to complement Au metal cap crack phenomenon caused by excessive deformation of polymer elastic bump. The proposed polymer elastic bumps could reduce stress of metal wiring during bump deformation compared to metal cap bump, which is completely covered with metal wiring because the metal wiring on these bumps is partially patterned and easily deformable pattern. The spoke cap bump shows the lowest stress concentration in the metal wiring while maintaining the low contact resistance because the contact area between bump and pad was wider than that of the spiral cap bump.

• Journal of IKEEE
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• v.23 no.1
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• pp.193-199
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• 2019

In this study, we have proposed a floating metal guard ring structure based on TCAD simulation in order to enhance the breakdown voltage characteristics of gallium oxide ($Ga_2O_3$) vertical high voltage switching Schottky barrier diode. Unlike conventional guard ring structures, the floating metal guard rings do not require an ion implantation process. The locally enhanced high electric field at the anode corner was successfully suppressed by the metal guard rings, resulting in breakdown voltage enhancement. The number of guard rings and their width and spacing were varied for structural optimization during which the current-voltage characteristics and internal electric field and potential distributions were carefully investigated. For an n-type drift layer with a doping concentration of $5{\times}10^{16}cm^{-3}$ and a thickness of $5{\mu}m$, the optimum guard ring structure had 5 guard rings with an individual ring width of $1.5{\mu}m$ and a spacing of $0.2{\mu}m$ between rings. The breakdown voltage was increased from 940 V to 2000 V without degradation of on-resistance by employing the optimum guard ring structure. The proposed floating metal guard ring structure can improve the device performance without requiring an additional fabrication step.

• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.138-143
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• 2011

To investigate the electromagnetic interference shielding efficiency (EMI SE) property based on heat treatment effects of carbon fibers in various temperatures, the polyacrilonitrle-based carbon fibers were prepared by electrospinning method and treated at 1073, 1323, 1873 and 2573 K. The surface morphology of carbon fibers was investigated by using FE-SEM and the carbon crystallization was studied by Raman spectroscopy based on effects of reaction temperatures. The electrical conductivity was obtained by measuring the surface resistance with four probe method on carbon crystallization. The permittivity, permeability and EMI SE were investigated by using S-parameter in the range of 800~4500 MHz. In case of carbon fibers treated at 2573 K, the improved carbon crystallization was confirmed by Raman spectrum and the enhanced electrical conductivity showing 54.7 S/cm was also observed. The permittivity was dramatically improved by factor of 4 based on effect of high reaction temperature. Eventually, the highly improved EMI SE value was obtained showing around 41.7 dB.

• Membrane Journal
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• v.31 no.6
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• pp.443-455
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• 2021

In this study, polyphenylene sulfide (PPS) was used as a support and a separator was manufactured using polysulfone and inorganic additives to manufacture a separator with low membrane resistance for application of an alkali water electrolysis system, and then the effect on the thickness and porosity of the support was analyzed. The PPS felt used as a support was compressed with variables of temperature (100℃, 150℃, 200℃) and pressure (1 ton, 2 tons, 3 tons, 5 tons) to adjust the thickness. A porous separator could be manufactured by preparing a slurry with polysulfone using BaTiO₃ and ZrO₂ which have high hydrophilicity and excellent alkali resistance as inorganic particles and casting the slurry on a compressed PPS felt. Changes in morphology of the separator according to compression conditions were confirmed through an electron scanning microscope (SEM). After that, the porosity was calculated, and the thickness and porosity tended to decrease as the compression conditions increased. Various characteristics were evaluated to confirm whether it could be used as a separator for water electrolysis. As a result of measuring the mechanical strength, it was confirmed that the tensile strength gradually increased as the compression conditions (temperature and pressure) increased. Finally, it was confirmed that the porous separator manufactured through the alkali resistance test has excellent alkali resistance, and through the IV test, it was confirmed that the membranes compressed at 100℃ and 150℃ had a lower voltage and improved performance than the existing uncompressed membrane.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.4
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• pp.85-89
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• 2021

AlGaN-based UV-C light-emitting diodes (LEDs) were applied for p-type activation by electrochemical potentiostatic activation (EPA). The p-type activation efficiency was increased by removing hydrogen atoms through EPA treatment using a neutral Mg-H complex that causes high resistance and low conductivity. A neutral Mg-H complex is decomposed into Mg^- and H⁺ depending on the key parameters of solution, voltage, and time. The improved hole carrier concentration was confirmed by secondary ion mass spectroscopy (SIMS) analysis. This mechanism eventually improved the internal quantum efficiency (IQE), the light extraction efficiency, the leakage current value in the reverse current region, and junction temperature, resulting in better UV-C LED lifetime. For systematic analysis, SIMS, Etamax IQE system, integrating sphere, and current-voltage measurement system were used, and the results were compared with the existing N₂-annealing method.

• Journal of Bio-Environment Control
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• v.23 no.4
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• pp.329-336
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• 2014

As an abiotic stress, chilling stress is one of the major factors limiting plant growth and increasing susceptibility to pathogens. Therefore, enhancing stress tolerance in plants is an important strategy for their survival under unfavorable environmental conditions. The objective of this study was to determine the effects of the exogenous application of salicylic acid (SA) or nitric oxide (NO) on chilling tolerance in pepper seedlings. Pepper (Capsicum annuum L. 'kidaemanbal') seedlings were grown under normal growing conditions ($20/25^{\circ}C$, 15 hours photoperiod, $145{\pm}5{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, fluorescence lamps) for 23 days after transplanting. The solution (3 mL) of 1 mM SA and 0.3 mM NO with surfactant triton 0.1% were sprayed two times a week, respectively. Right after the completion of chemical application, seedlings were subjected to chilling condition at $4^{\circ}C$ for 6 hours under dark condition and then the seedlings were recovered at the normal growing conditions for 2 days. In order to assess plant tolerance against chilling stress, growth characteristics, chlorophyll fluorescence (Fv/Fm), and membrane permeability were determined after chilling stress imposition. Total phenolic concentration and antioxidant capacity were measured during the whole experimental period. Disease incidence for pepper bacterial spot and wilt was also analyzed. Pepper seedlings treated with SA or NO were maintained similar dry mass ratio, while the value in control increased caused by chilling stress suggesting relatively more water loss in control plants. Electrolyte leakage of pepper seedlings treated with SA or NO was lower than that of control 2 days after chilling treatment. Fv/Fm rapidly decreased after chilling stress in control while the value of SA or NO was maintained about 0.8. SA increased higher total phenolic concentration and antioxidant capacity than NO and control during chemical treatment. In addition, increase in total phenolic concentration was observed after chilling stress in control and NO treatment. SA had an effect on the reduction of bacterial wilt in pepper seedlings. The results from this study revealed that pre-treatment with SA or NO using foliar spray was effective in chilling tolerance and the reduction of disease incidence in pepper seedlings.

• Journal of Life Science
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• v.19 no.9
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• pp.1226-1231
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• 2009

Enzyme substitution with recombinant phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) is currently being explored for treatment of phenylketonuria (PKU), an autosomal recessive genetic disorder with mutations of the gene encoding phenylalanine-4-hydroxylase (EC 1.14.16.1). However, oral administration of PAL is limited because of proteolytic digestion in the gastrointestinal tract. The aim of this study was to determine the biochemical properties of PAL and delinate the susceptibility of wild-type PAL to pancreatic proteolysis by exploring several mutants, and to develop therapeutic drugs with PAL for PKU. The specific activity of PAL was assayed and its optimal pH, temperature stability, and intestinal protease susceptibility were investigated. Its $V_{max}$ values for phenylalanine and tyrosine were 1.77 and $0.47{\mu}mol$/ min/mg protein, respectively, and its $K_m$ values were $4.77{\times}10^{-4}$ and $4.37{\times}10^{-4}\;M$, respectively. PAL showed an optimal pH at 8.5, corresponding to the average pH range of the small intestine. It showed no loss of activity at $-80^{\circ}C$ for 5 months and possessed 93.4% of its activity under $4^{\circ}C$ for 4 wks. PAL was susceptible to chymotrypsin digestion and, to a lesser extent, to trypsin, elastase, carboxypeptidase A, and B. The trypsin and chymotrypsin cleaving sites were mutated to investigate protection from pancreatic digestion and the specific activities of these mutants were evaluated. The six mutants displayed low specific activities compared to the wild-type, suggesting that the primary trypsin and chymotrypsin cleaving sites may be essential for catalytic reaction. The PAL mutants could therefore be applied as a pretreatment modality without susceptibility to proteolytic attack, however, additional modification for enhancing enzymatic activity is needed to reduce the Phe levels effectively.

• The Korean Journal of Pesticide Science
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• v.9 no.1
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• pp.26-34
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• 2005

3D-QSAR studies for the fungicidal activities against resistance phytophthora blight (RPC; 95CC7303) and sensitive phytophthora blight (Phytopthora capsici) (SPC; 95CC7105) by a series of new 2-alkoxyphenyl-3-phenylthioisoindoline-1-one derivatives (A & B) were studieded using comparative molecular similarity indices analyses (CoMSIA) methodology. From the based on the results, the two CoMSIA models, R5 and S1: as the best models were derivated. The statistical results of the models showed the best predictability and fitness for the fungicidal activities based on the cross- validated value ($q^2=0.714{\sim}0.823$) and non cross-validated, value ($r^2_{ncv.}=0.918{\sim}0.954$), respectively. The model R5 for fungicidal activity of RPC generated from the field fit alignment and combination of electrostatic field, H-bond acceptor field and LUMO molecular orbital field. The model S1 (or S5) for fungicidal activity of SPC generated from the atom based fit alignment and combination of steric field and HOMO molecular orbital field. The models also shows that inclusion of H-bond acceptor field (A) improved the statistical significance of the models. From the based graphical analyses of CoMSIA contribution maps, it was revealed that the novel selective character for fungicidal activities between the two fungi by modify of X-sub-stituent on the N-phenyl group and R-substituent on the S-phenyl group will be able to achivement.

• Journal of Korean Society of Forest Science
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• v.38 no.1
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• pp.27-32
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• 1978

The diurnal pattern of leaf water potential in cuttings by Dye Method was as follows: 1. Diurnal pattern of leaf water potential (${\psi}_l$) in Viburnum Awabuki K. Koch and Daphne odora Thunb. was shown the pattern of the curves without mutual relation with soil classes when soil water potential (${\psi}_s$) was 0 bar. When ${\psi}_s$ was above -0.01 bar, the cuttings in the loamy sand (L.S.) was shown by the maximum values than that in sandy clay (S.C.) by about -1 bar gap (Fig. 1). 2. The diurnal changes of ${\psi}_l$ was shown the most high from two to eight O'clock in the morning, the maximum value was -3 bars when ${\psi}_s$ was above -0.01 to -0.02 bar, and was -4 bars below -0.03 bar. The diurnal the lowest values of ${\psi}_l$ showed -20 to -22 bars from one to two O'clock in the afternoon. In the fifteenth day after cutting V.A., the staying time in the diurnal maximum values of ${\psi}_l$ is about half in comparison with it in the fifth day. The curves of recovery of water stress (Fig. 1), the former reached to the diurnal maximum values -1 to -2 bars lately every hours comparing with it of the latter. The general diurnal pattern of ${\psi}_l$ was most clearly related to change with air temperature and the relative humitidy. 3. Comparing the treatment block by IAA 50 ppm with controlled block in fifteenth day after V.A. cuttings, in case of treatment reached to maximum values -2 to -3 bars lately as shown Fig. 2., and also staying times was only half in comparison with controlled block. 4. The cuttings 4 leafs was much rootings than 2 leafs in V.A. (Table. 1), and the former reached maximum value -2 to -3 bars lately every hours comparing with the latter. 5. In case of Buxus microphylla var. Koreana as shown Fig. 3., comparing the pattern curves of in the cuttings 8 leafs with 4 leafs, the former reached to maximum values -2 to -3 bars lately in comparison with the latter, but reffering to the amount of rooting (Table. 2), the former is less than the latter.

• Korean journal of applied entomology
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• v.46 no.3
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• pp.343-348
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• 2007

To assess the environmental risks of transgenic chili pepper with PepEST gene on non-target organisms before it exposes to the agro-ecosystem environments, we conducted the three sets of green peach aphids (Myzus persicas S.) life table experiment under laboratory conditions (Temp. $25^{\circ}C$, R.H. 50-70%, Photoperiod L16 : D8) in series during 2005-2006. We measured the net reproductive rate ($R_0)^*$, the intrinsic rate of increase ($r_m$), the mean generation time ($T_c$), $fecundity^*$, life span, and reproduction period between non-transgenic chili peppers and transgenic chili peppers, respectively. The life span of green peach aphids from three sets was 31, 27, 25 days, and the period of life span was similar to the general average length of green peach aphids, 25-29 days. Although the first reproduction of transgenic pepper was similar to the non transgenic pepper (P>0.05), the fecundity and the net reproductive rate ($R_o$) by using Jackknife method of transgenic pepper were lower than those of non transgenic pepper (P<0.05). Conclusively, we observed the adverse effect from our results but we should execute further experiments to confirm the results at the fields with the similar way.