• Journal of Microbiology and Biotechnology
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• v.8 no.2
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• pp.158-164
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• 1998

Crystal structural analyses of the API-TLCK complex revealed that the ${\epsilon}$-amino group (NZ) of the lysyl part of TLCK forms hydrogen bonds with OD1 of $Asp^225$ which is a substrate specificity determinant of API, OG of $Ser^214$, O of $Ser^214$, OG1 of $Thr^189$, and O of $Thr^189$ l89/. The ${\beta}$-carboxyl oxygen of $Asp^225$ forms hydrogen bonds with the NE1 of $Trp^182$. From these observations, it is thought that besides $Asp^225$, $Thr^189$, $Ser^214$, and $Trp^182$ may also contribute to the steric specificity for lysine and high proteolytic activity of API. The side-chain hydroxyl groups of $Thr^189$ and $Ser^214$ were removed to elucidate the role of these hydrogen bonds in the $S_1$-pocket. The $k_{cat}$/$K_m$ of T189V, S214A, and T189V.S214A were decreased to 1/4, 1/3, and 1/46, respectively, of the value for native API. The decreased activities were mainly due to the increase of $K_m$. The CD and fluoroscence spectra of the three mutants were similar to those of wild-type API. With regards to the kinetic parameters ($K_i\;and\;k_2$) of mutants for the reaction involving TLCK and DFP, $k_2$decreased by increase of $K_1$ only. These results suggest that the decreased catalytic activity of these mutants is caused by the partial loss of the hydrogen bond network in the $S_1$-pocket. On the other hand, the similarity of enzymatic properties between W182F and the native enzyme suggests that the hydrogen bond between OD2 of $Asp^225$ and NE1 of $Trp^182$ is not directly related to the reaction of $Asp^225$ with the substrate.

• The Korean Journal of Malacology
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• v.27 no.4
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• pp.291-297
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• 2011

In an attempt to improve the substrate condition for Manila clam (Ruditapes philippinarum) culture, crushed oyster (Crassostrea gigas) shells were spread on the muddy tidal flat of Namseong-ri, Podu-myeon, Goheung-gun, Jeollannam-do in April 2008. To test the suitability of the crushed oyster shell added substrate, seed clams were transplanted from Taehwa river estuary in Ulsan city in June 2008. Over 23 months of sampling, the mean grain size and the sorting in the experimental site containing the crushed oyster shell were significantly higher than the control site. The ignition loss, water content, chemical oxygen demand (COD) and acid-volatile sulfide (AVS) level were also significantly higher in the crushed oyste shell added substratum. Survival of the clams transplanted to the crushed oyster shell added substratum was significantly higher and all the clams transplanted to the normal muddy substratum died in August 2009, 13 months after the transplantation. At the end of the experiment in April 2010, the transplanted clams reached 36.10 mm in shell length and 8.92 g in total weight with survival of 43.5%. Our study suggested than crushed oyster shell added in the mud dominant substratum greatly improved living condition and survivability of clams.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.549-556
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• 2003

Various researches on the application of polymer dispersions to the cement mortar and concrete have been practised in many countries like America, Japan and Germany and so on because of high performance and good modification effect of these. In this study, SBR, Polymer dispersion that widely used in situ is employed that the self-flowability may be induced in the cemen mortar. In order to comprehend and investigate the modification of cement mortar with self-flowability by SBR and properties and fracture mode of adhesive strength in tension of that, experimental parameter was set as SBR solid-Cement ratio(S/C) and Cement:Fine aggregate(C:F) and the experiments such as Unit weight, Flow, Consistency change, Crack resistance and Segregation that inform on the general properties have been done. In addition of that, Adhesion in tension is measured with a view to comprehending the properties and fracture mode in tensile load. Consistency change of cement mortar modified by SBR did grow better as the ratio of SBR solid-Cement increased and was much superior to that of resin based flooring such as polyurethane and epoxy which recorded the loss of consistency in 90min. after mixing. Adhesive strength in tension increased with continuity in the curing age and showed the maximum in case of C:F=1:1 and S/C=20%. As the increase of curing age, the fracture mainly happened in the concrete substrate and the interface between the specimen and concrete substrate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.9
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• pp.931-935
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• 2012

In this study, we fabricate and investigate low-temperature solid oxide fuel cells with a ceramic substrate/porous metal/ceramic/porous metal structure. To realize low-temperature operation in solid oxide fuel cells, the membrane should be fabricated to have a thickness of the order of a few hundreds nanometers to minimize IR loss. Yttrium-doped barium zirconate (BYZ), a proton conductor, was used as the electrolyte. We deposited a 350-nm-thick Pt (anode) layer on a porous substrate by sputter deposition. We also deposited a 1-${\mu}m$-thick BYZ layer on the Pt anode using pulsed laser deposition (PLD). Finally, we deposited a 200-nm-thick Pt (cathode) layer on the BYZ electrolyte by sputter deposition. The open circuit voltage (OCV) is 0.806 V, and the maximum power density is 11.9 mW/$cm^2$ at $350^{\circ}C$. Even though a fully dense electrolyte is deposited via PLD, a cross-sectional transmission electron microscopy (TEM) image reveals many voids and defects.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.1
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• pp.8-18
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• 2000

We presented a BGA(Ball Grid Array) package for RF circuit modules and extracted its electrical parameters. As the frequency of RF system devices increases, the effect of its electrical parasitics in the wireless communication system requires new structure of RF circuit modules because of its needs to be considered of electrical performance for minimization and module mobility. RF circuit modules with BGA packages can provide some advantages such as minimization, shorter circuit routing, and noise improvement by reducing electrical noise affected to analog and digital mixed circuits, etc. We constructed a BGA package of ITS(Intelligent Transportation System) RF module and measured electrical parameters with a TDR(Time Domain Reflectometry) equipment and compared its electrical parasitic parameters with PCB RF circuits. With a BGA substrate of 3${\times}$3 input and output terminals, we have found that self capacitance of BGA solder ball is 68.6fF, and self inductance 146pH, whose values were reduced to 34% and 47% of the value of QFP package structure. S11 parameter measurement with a HP4396B Network Analyzer showed the resonance frequency of 1.55GHz and the loss of 0.26dB. Routing length of the substrate was reduced to 39.8mm. Thus, we may improve electrical performance when we use BGA package structures in the design of RF circuit modules.

• Journal of Microbiology and Biotechnology
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• v.24 no.1
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• pp.26-35
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• 2014

Saccharothrix algeriensis NRRL B-24137 produces naturally different dithiolopyrrolone derivatives. The enzymatic activity of pyrrothine N-acyltransferase was determined to be responsible for the transfer of an acyl group from acyl-CoA to pyrrothine core. This activity was also reported to be responsible for the diversity of the dithiolopyrrolone derivatives. Based on this fact, nine dithiolopyrrolone derivatives were produced in vitro via the crude extract of Sa. algeriensis. Three of them have never been obtained before by natural fermentation: acetoacetyl-pyrrothine, hydroxybutyryl-pyrrothine, and dimethyl thiolutin (holomycin). Two acyltransferase activities, acetyltransferase and benzoyltransferase catalyzing the incorporation of linear and cyclic acyl groups to the pyrrothine core, respectively, were biochemically characterized in this crude extract. The first one is responsible for formation of acetyl-pyrrothine and the second for benzoyl-pyrrothine. Both enzymes were sensitive to temperature changes: For example, the loss of acetyltransferase and benzoyltransferase activity was 53% and 80% respectively after pre-incubation of crude extract for 60 min at $20^{\circ}C$. The two enzymes were more active in neutral and basal media (pH 7-10) than in the acidic one (pH 3-6). The optimum temperature and pH of acetyltransferase were $40^{\circ}C$ and 7, with a $K_m$ value of $7.9{\mu}M$ and a $V_{max}$ of $0.63{\mu}M/min$ when acetyl-CoA was used as limited substrate. Benzoyltransferase had a temperature and a pH optimum at $55^{\circ}C$and 9, a $K_m$ value of $14.7{\mu}M$, and a $V_{max}$ of $0.67{\mu}M/min$ when benzoyl-CoA was used as limited substrate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.839-843
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• 2011

ZnO nanostructures were developed on a Si (100) substrate from powder mixture of ZnO and 5 mol% Pd (ZP-5) as reactants by ${\times}$ sccm oxygen pressures(x= 0, 10, 20, 40). DTA (differential thermal analysis) result shows the Pd(5 mol%)+ZnO mixtured powder(PZ-5) is easily evaporated than pure ZnO powder. The PZ-5 mixtured powder was characterized by DTA to determine the thermal decomposition which was found to be at $800^{\circ}C$, $1,100^{\circ}C$. Weight loss(%) and ICP (inductively coupled plasma) analysis reveal that Zn vaporization is decreased by increased oxygen pressures from the PZ-5 at $1,100^{\circ}C$ for 30 mins. Needle-like ZnO nanostructures array developed from 10 sccm oxygen pressure, was well aligned vertically on the Si substrate at $1,100^{\circ}C$ for 30 mins. The lengths of the Needle-like ZnO nanostructures is about 2 ${\mu}m$ with diameters of about 65 nm. The developed ZnO nanostructures exhibited growth direction along [001] with defect-free high crystallinity. It is considered that Zn vaporization is responsible for the growth of Needle-like ZnO nanostructures by controlling the oxygen pressures. The photoluminescence spectra of ZnO nanostructures exhibited stronger 376.7 nm NBE (near band-edge emission) peak and 529.3 nm DLE (deep level energy) peak.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.331-337
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• 2003

This paper represents 50 ㎓ narrow band pass filters for fiber optical communication fabricated by dual ion beam sputtering method. We have analyzed the characteristics of the TA$_2$ $O_{5}$ and $SiO_2$ single layers in order to optimize the process conditions for the 50 ㎓ narrow band pass filters, and controlled the film thickness uniformity to less than 0.1 nm deviation by dual peak spike filter pre-deposition. We designed and fabricated 50 ㎓ narrow band pass filters that consist of 216 layers including 4 cavities based on quarter wave optical thickness. Class substrates with high thermal expansion coefficients were used to reduce the film stress. Anti-reflection coating at the rear side of the substrate was also needed to reduce the optical thickness errors of the Optical Monitoring System caused by multiple beam interference between the front side and the rear side of substrate. The optical characteristics of this 50 ㎓ narrow band pass filters are insertion loss of 0.40 ㏈, pass band ripple of 0.20 ㏈, and pass bandwidth at -0.5 ㏈ of 0.20 nm. and isolation bandwidth at -25 ㏈ of 0.6 nm, which satisfy specifications of dense WDM system in fiber optical communications.tions.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1015-1022
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• 2023

In this paper, we propose DLP(Dual Linear Polarization) antenna with aperture coupled feeding structure for private network. The proposed antenna has general aperture coupled structure and design two port between top and bottom layer to obtain the enhanced isolation. Also, The size of each substrate(top and bottom layer) is 34.0 mm(W)×34.0 mm(L), which is designed on the FR-4 substrate which thickness (h) is 1.0 mm, and the dielectric constant is 4.4. Also, the size of patch antenna is 12.70 mm(W2)×14.60 mm(L3), and it is located on the top layer. The size of feeding line is 24.0 mm(W2)×1.6 mm(L3), and is located at the bottom layer Also, rectangular slot is located on the ground plane between top layer and bottom layer. From the fabrication and measurement results, bandwidths of 300 MHz (4.52 to 4.82 GHz) for feeding port 1, and 170 MHz (4.65 to 4.82 GHz) for feeding port 2 are obtained on the basis of -10 dB return loss and transmission coefficient S21 is got under the -30 dB. Also, cross polarization isolation between each feeding port obtained

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.4
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• pp.323-332
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• 2009

In this paper, we introduce a modified short-circuited stub bandpass filter suitable for ultra-wideband(UWB) applications utilizing low temperature co-fired ceramic(LTCC) technology. By modifying the conventional short-circuited stub bandpass filter structure with stubs and connecting lines of lower characteristic impedances, the number of stubs has been reduced from 5 to 2 on a high dielectric constant substrate($\varepsilon_r$ = 40). A wireless local area network (WLAN) stopband in the frequency range of 5.15 to 5.825 GHz has been inserted into the filter characteristic using three short-circuited coupled lines. The filter has been measured with an insertion loss less than 1.0 dB and return loss better than 10 dB in the pass bands. A bandwidth ratio of 109.49 % has been achieved. Measurement results agree well with simulation results. The dimensions of the filter are $4{\times}8{\times}0.57\;mm^3$.