• Journal of Photoscience
• /
• v.4 no.1
• /
• pp.1-5
• /
• 1997

A hitherto unknown diphenylbutadiene analog viz. 1-(p-N,N-dimethylaminophenyl)-4-phenyl-2-methyl-1E,3E-butadiene (10) has been prepared and its absorption, excitation, and fluorescent emission properties in different media including various organic solvents and aqueous bovine serum albumin (BSA) have been studied. For comparision, these properties have also been investigated for the parent diphenylbutadiene (2). Diene 10 exhibits solvent polarity/polarizability-sensitive fluorescence properties ($\lambda$$_{max}$, $\Phi$$_f$, $\tau$$_f$, K$_f$, f). It also binds to the hydrophobic domains of aqueous bovine serum albumin (BSA) with a binding constant of 3.89 x 10$^4$ M$^{-1}$. The relative fluorescence quantum yield of 10 increases, while, the fluorescence lifetime decreases with increasing concentration of-BSA. The results highlight the polar character of the singlet excited state of diphenylpolyenes and the utility of 10 as fluorescence probe for studying microenvironments of organized assemblies and biological supramolecular structures.

• Journal of the Korean Magnetic Resonance Society
• /
• v.6 no.2
• /
• pp.103-112
• /
• 2002

The photoproduced cation radical of N-methylphenothiazine $(PC_1)$ doped into phenyltriehtoxysilane (PhiTEOS), vinyltriethoxysilane (VTEOS) and methyltriethoxysilane (METOS) was studied with electron spin resonance (ESR) and electron nuclear double resonance (ENDOR). The photoinduced charge separation efficiency was determined by integration of ESR spectra which correspond to the amount of photoproduced cation radical in the matrices. This was correlatively studied with the polarity and pore size of the gel matrices. The relative polarity of the matrices was determined by measuring ${\lambda}_{max}$ values of $PC_1$ in the different matrices. The relative pore size among the matrices was determined by measuring relative proton matrix ENDOR line widths of the photoproduced cation of $PC_1$. The decay kinetic constants of the cation radical of $PC_1$ in the different matrices with relatively studied with fitting the biexponential decay curves after exposure at the ambient condition. This is correlatively interpreted with the polarity and pore size of the matrices.

• The KSFM Journal of Fluid Machinery
• /
• v.11 no.1
• /
• pp.9-17
• /
• 2008

A numerical study for three-dimensional laminar flow in the entrance region of helical tubes connected with straight ones is carried out to investigate the effects of Reynolds number, pitch and curvature ratio on the oscillation periods of the flow. The fully elliptic governing equations were solved by means of a finite volume method. The fully developed laminar flow boundary condition was applied at the straight tube inlet. This results cover a curvature ratio range of 1/10${\sim}$1/320, a pitch range of 0.0${\sim}$3.2, and a Reynolds number range of 62.5${\sim}$2000. A comparison is made with previous experimental correlations and numerical data. The developments of velocity, local and average friction factors are discussed. The average friction factors are oscillatory in the entrance region of helical pipes. It has been found that the angle required for the flow to be similarly developed is most affected by the curvature ratio. The pitch and Reynolds number do not have any significant effect on the angle. The characteristic angle ${\phi}_c(={\phi}/sqrt{\delta})$, or the characteristic length to diameter ratio $s_c(=l\sqrt{\delta} cos(atan{\lambda})/d)$, can be useful to represent the development of flow in helical tubes. As the pitch increases and as the curvature ratio and Reynolds number decrease, the amplitude and the number of flow oscillations along the main streamwise direction decrease.

• Economic and Environmental Geology
• /
• v.47 no.4
• /
• pp.441-453
• /
• 2014

Thermal and physical properties were measured on 206 Jurassic granite samples obtained from three boreholes in the central part of Korea. Thermal conductivity(${\lambda}$), thermal diffusivity(${\alpha}$), and specific heat(Cp) were measured in a laboratory; the average values are ${\lambda}$=2.813 W/mK, ${\alpha}=1.296mm^2/sec$, and Cp=0.816 J/gK, respectively. In addition, porosity(${\phi}$), and dry and saturated density(${\rho}$) were measured in the laboratory; the average values are ${\phi}$=0.01, ${\rho}(dry)=2.662g/cm^3$ and ${\rho}(saturated)=2.67g/cm^3$, respectively. Thermal diffusivity of 10 granite samples were measured with increasing temperature from $25^{\circ}C$ to $200^{\circ}C$. In this study, we found that thermal diffusivity at $200^{\circ}C$ is about 30% lower than thermal diffusivity at $25^{\circ}C$. In correlation analysis, thermal conductivity increases with increasing thermal diffusivity. However, thermal conductivity does not show good correlation with porosity and density. Consequently, we know that thermal conductivity of granite would be more influenced by mineral composition than by porosity. We also derived ${\rho}=-2.393{\times}{\phi}+2.705$ from density and porosity data. XRD and XRF analysis were performed to investigate effects of mineral and chemical composition on thermal conductivity. From those results, we found that thermal conductivity increases with increasing quartz and $SiO_2$, and decreases with increasing albite and $Al_2O_3$. Regression analysis using those mineral and chemical composition were carried out ; we found $K=0.0294V_{Quartz}+1.93$ for quartz, $K=0.237W_{SiO_2}-14.09$ for $SiO_2$, and $K=0.053W_{SiO_2}-0.476W_{Al_2O_3}+6.52$ for $SiO_2$ and $Al_2O_3$. Specific gravities were measured on 10 granite samples in the laboratory. The measured specific gravity depends on chemical compositions of granite. Therefore, specific gravity can be estimated by the felsic-mafic index(F) that is calculated from chemical composition. The estimated specific gravity ranges from 2.643 to 2.658. The average relative error between measured and estimated specific gravities is 0.677%.

• Journal of the Korean Society of Visualization
• /
• v.7 no.2
• /
• pp.64-71
• /
• 2010

The flow and noise characteristics of wake behind wind-turbine blades have been investigated experimentally using a two-frame particle image velocimetry (PIV) technique. Experiments were carried out in a POSTECH subsonic large wind-tunnel ($1.8^W{\times}1.5^H{\times}4.3^L\;m^3$) with KBP-750D (3-blade type) wind-turbine model at a freestream velocity of $U_o\;=\;15\;m/s$ and a tip speed ratio $\lambda\;=\;6.14$ (2933 rpm). The wind-turbine blades are connected to an AC servo motor, brake, encoder and torque meter to control the rotational speed and to extract a synchronization signal for PIV measurements. The wake flow was measured at four azimuth angles ($\phi\;=\;0^{\circ}$, $30^{\circ}$, $60^{\circ}$ and $90^{\circ}$) of the wind-turbine blade. The dominant flow structure of the wake is large-scale tip vortices. The turbulent statistics such as turbulent intensity are weakened as the flow goes downstream due to turbulent dissipation. The dominant peak frequency of the noise signal is identical to the rotation frequency of blades. The noise seems to be mainly induced by the tip vortices.

• Journal of the Korean Magnetics Society
• /
• v.5 no.5
• /
• pp.659-662
• /
• 1995

Co-ferrite ($CoO-Fe_{2}O_{3}$) thin films have been prepared by two ways of low temperature solid reaction including oxidation process, being based on $Co-layer/{\alpha}-Fe_{2}O_{3}$ films and $Co-layer/Fe_{3}O_{4}$ films. Magnetic properties of both Co-ferrite films have been measured and compared. The samples from $Co-layer/Fe_{3}O_{4}$ films have a large coercive force in the direction perpendicular and have a great poler kerr rotation angle at wavelength 700 nm than ones from $Co-layer/{\alpha}-Fe_{2}O_{3}$ films. The typical magnetic properties are as follows; saturation magnetization $4{\pi}Ms$, 2.9 kG; remnant magnetization $4{\pi}Mr$, 2.0 kG; coercive force Hc, 4.0 kOe; kerr rotation angle ${\PHI}k$, 0.39 deg($\lambda\;=\;700\;nm$); and initial magnetization energy E, $3.3\;{\times}\;10^6\;erg/\textrm{m}^3$, respectively.

• Korean Journal of Ichthyology
• /
• v.19 no.2
• /
• pp.83-87
• /
• 2007

Edwardsiella tarda, a gram (-) pathogen causing edwardsiellosis in farmed fish, was transformed via electroporation with a plasmid expression vector driving the PhiX174 E-lysis gene under the transcriptional control by lambda PR regulatory sequence. The persistent maintenance of the plasmid vector in recombinant E. tarda was found in numerous subculture procedures over up to 6 months without any adverse effect on the original copy number of plasmids. Comparative examination based on semi-quantitative RT-PCR analysis on transcriptional efficiency of E-lysis gene between recombinant E. coli and E. tarda indicated that promoter strength and induction capacity of bacterial ghosts would be retarded in E. tarda as compared to the E. coli. However, the completeness of induction for bacterial ghosts in E. tarda was the same with E. coli, in which at least 99.99% of induction rate was possible and further the viability of recombinant bacteria was completely eliminated by a post-induction procedure including washing and freeze drying lyophilization.

• Korean Journal of Materials Research
• /
• v.15 no.6
• /
• pp.361-369
• /
• 2005

InP(100) crystal surface was irradiated by ion beams with low energy $(180\~225\;eV)$ and high flux $(\~10^{15}/cm^2/s)$, Self-organization process induced by ion beam was investigated by examining nano structures formed during ion beam sputtering. As an ion source, an electrostatic closed electron Hall drift thruster with a broad beam size was used. While the incident angle $(\theta)$, ion flux (J), and ion fluence $(\phi)$ were changed and InP crystal was rotated, cone-like, ripple, and anistropic nanostrucuture formed on the surface were analyzed by an atomic force microscope. The wavelength of the ripple is about 40 nm smaller than ever reported values and depends on the ion flux as $\lambda{\propto}J^{-1/2}$, which is coincident with the B-H model. As the incident angle is varied, the root mean square of the surface roughness slightly increases up to the critical angle but suddenly decreases due to the decrease of sputtering yield. By the rotation of the sample, the formation of nano dots with the size of $95\~260\;nm$ is clearly observed.