• Bulletin of the Korean Chemical Society
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• v.28 no.8
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• pp.1358-1362
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• 2007

The structures, energetics and transfer integrals of the acene tetramers up to pentacene are investigated with the ab initio molecular orbital method at the level of second-order Møller-Plesset perturbation theory (MP2). Calculated geometries for the herringbone-style structures found in the crystal structure were characterized as local minima, however the geometrical discrepancy between crystal and MP2 theoretical structure is reasonably small. The binding energy of pentacene tetramer was calculated up to 40 kcal/mol (MP2/6-31G(d)) and about 90 kcal/mol (MP2/aug-cc-pVDZ), and the latter seems to be too much overestimated. The tendency of the hole transfer integrals computed with ab initio MP2/3-21G(d) geometry is well agreement with those estimated with crystal structure with some discrepancy, and the gradual increment of the transfer integrals at the crystal geometry is attributed to mainly packing structure rather than the intrinsic property of acene such as a size of acene.

• Korean Journal of Optics and Photonics
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• v.17 no.6
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• pp.500-506
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• 2006

An optical fiber displacement sensor has the advantages of relatively simplicity, cheap, small probe size and immunity against environmental perturbation. The working principle of the sensor is based on the intensity modulation that is detection light intensity reflecting from the surface being measured. This paper presents the mathematical model of displacement measurement mechanism of this sensor type. The theoretical and experimental data are compared to verify the model in describing the realistic approach to sensor design. Finally, the analysis results show that displacement response characteristics such as sensitivity, measuring range are easily modified by principal design parameters such as magnitude of optical Power, diameter of optical fiber core and distance between transmitting fiber and receiving fiber.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.727-739
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• 2002

Based on a generalized variational principle for magneto-thermo-elasticity, a theoretical model is proposed to describe the coupled magneto-thermo-elastic interaction in soft ferromagnetic plates. Using the linearized theory of magneto-elasticity and perturbation technique, we analyze the magneto-elastic and magneto-thermo-elastic instability of simply supported ferromagnetic plates subjected to thermal and magnetic fields. A nonlinear finite element procedure is developed next to simulate the magneto-thermo-elastic behavior of a finite-size ferromagnetic plates. The effects of thermal and magnetic fields on the magneto-thermo-elastic bending and buckling is investigated in some detail.

• Structural Engineering and Mechanics
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• v.71 no.6
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• pp.669-682
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• 2019

We in this article study nonlinear thermal buckling of bi-directional functionally graded beams in the theoretical frameworks of nonlocal strain graded theory. To begin with, it is assumed that the effective material properties of beams vary continuously in both the thickness and width directions. Then, we utilize a higher-order shear deformation theory that includes a physical neutral surface to derive the size-dependent governing equations combining with the Hamilton's principle and the von $K{\acute{a}}rm{\acute{a}}n$ geometric nonlinearity. It should be pointed out that the established model, containing a nonlocal parameter and a strain gradient length scale parameter, can availably account for both the influence of nonlocal elastic stress field and the influence of strain gradient stress field. Subsequently, via using a easier group of initial asymptotic solutions, the corresponding analytical solution of thermal buckling of beams is obtained with the help of perturbation method. Finally, a parametric study is carried out in detail after validating the present analysis, especially for the effects of a nonlocal parameter, a strain gradient length scale parameter and the ratio of the two on the critical thermal buckling temperature of beams.

• Journal of Microbiology and Biotechnology
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• v.22 no.6
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• pp.754-762
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• 2012

Colbricon Superiore and Inferiore are two small adjacent high-mountain lakes located in the Paneveggio Natural Park (Italy) that offer the rare opportunity to study two iso-ecologic water environments differing only by area and volume in a ratio of 2:1 and 3:1, respectively. We took advantage of this setting to investigate phytoplankton dynamics, compare variability and productivity differences between the two basins, and assess size-dependent issues. The phytoplankton group of the Dinophyceae was chosen as the indicator organisms of ecological perturbation owing to their high sensitivity to environmental variations, as well as their acknowledged nature of versatile proxy to report global climatic changes. The study was conducted for over 10 years with fortnightly samplings. Results indicated that (a) the Dinophyceae communities in the smaller lake were significantly more resistant to changes exerted by the fluctuation of lakewater transparency and pH; and (b) the smaller lake sustained a consistently higher production with an average Dinophyceae density 1.73 fold higher than that of the larger lake. The coefficients of variation show that the chemical parameters in the smaller lake display higher time-related fluctuation while being spatially homogeneous and that such conditions correlate with a higher stability of the Dinophyceae assemblage. The use of this setting is also proposed as a model to test relationships between ecosystem production and physical stability.

• Journal of Integrative Natural Science
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• v.15 no.3
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• pp.99-110
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• 2022

Solar photovoltaic (PV) system shows a non-linear current (I) -voltage (V) characteristics, which depends on the surrounding environment factors, such as irradiance, temperature, and the wind. Solar PV system, with current (I) - voltage (V) and power (P) - Voltage (V) characteristics, specifies a unique operating point at where the possible maximum power point (MPP) is delivered. At the MPP, the PV array operates at maximum power efficiency. In order to continuously harvest maximum power at any point of time from solar PV modules, a good MPPT algorithms need to be employed. Currently, due to its simplicity and easy implementation, Perturb and Observe (P&O) algorithms are the most commonly used MPPT control method in the PV systems but it has a drawback at suddenly varying environment situations, due to constant step size. In this paper, to overcome the difficulties of the fast changing environment and suddenly changing the power of PV array due to constant step size in the P&O algorithm, least mean Square (LMS) methods is proposed together with P&O MPPT algorithm which is superior to traditional P&O MPPT. PV output power is predicted using LMS method to improve the tracking speed and deduce the possibility of misjudgment of increasing and decreasing the PV output. Simulation results shows that the proposed MPPT technique can track the MPP accurately as well as its dynamic response is very fast in response to the change of environmental parameters in comparison with the conventional P&O MPPT algorithm, and improves system performance.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.2
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• pp.95-101
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• 2016

In this paper, miniaturized ${\lambda}/4$ folded microstrip antennas is presented for parking monitoring base station system. The proposed antenna reduced a width of the radiating element for miniaturizing a size and we changed an aperture such as folded shape for reducing a length of the antenna by the pertubation effect by reducing a width of the antenna. Finally, the ${\lambda}/2$ length of the folded microstrip antenna to ${\lambda}/4$ folded microstrip antenna was miniaturized by reducing the length. The proposed antenna was designed to receive 425 MHz of center frequency that can be used without permission. Dimensions are $134mm{\times}143.85mm{\times}20.1mm$($0.19{\lambda}{\times}0.2{\lambda}{\times}0.028{\lambda}$, ${\lambda}$ is wavelength at 425 MHz) that are compared with basic microstrip patch antenna miniaturized 97.2%. Also, Measured -10 dB bandwidth was 2.44 MHz(0.57%). On the other hand, measured radiation patterns was 1.82 dBi at E-plane $15^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.5 s.96
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• pp.501-510
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• 2005

In this paper, the miniaturized linear and circular polarization microstrip antennas are designed and fabricated at the resonant frequency of 1.575 GHz. To miniaturize the microstrip patch antenna(MPA), the 'L' type plates are attached under the rectangular microstrip patch. In case of the linear polarization, the size of the microstrip antenna attached the 14 plates is reduced to $67.9\%(47mm{\times}47mm)$ compared with general $MPA(83mm{\times}83mm)$. The return loss and -10 dB bandwidth are -34.4 dB and 49 $MHz(3.1\%)$. And the radiation pattern is broad through the size reduction of the patch. Also in case of the circular polarization, the size of the microstrip antenna with 13 plates is reduced to $54.6\%(53mm{\times}54mm)$ compared with the general $MPA(76mm{\times}83mm)$. The axial ratio is 1.37dB at 1.575 GHz, the 2 dB axial ratio bandwidth is 14 $MHz(0.8\%)$. As that result, we could confirm that 3-dimensional structure with attached 'L' shaped plate is proper form for the miniaturization of linear and circular polarization microstrip antenna.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.467-473
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• 2012

Coenzyme Q10 (CoQ10) is a natural lipid cofactor with antioxidant and anti-aging properties as cosmetic and food ingredients, involved in cellular energy metabolism. Here, nano-emulsions with CoQ10 were fabricated with lecithin, ethanol, oil, and sorbitan monostearate (Arlacel 60), as major components. Phase inversion emulsion method with ultrasonicator was utilized in producing CoQ10 solution, and stabilization effects from lecithin and ethanol and other diverse perturbation factors were evaluated over time. Physical properties of the emulsion were characterized such as its size, surface charges by zeta-potential, and the overall structures. Optimal concentrations of CoQ10 and Arlacel 60 were 0.8% and 3%, respectively, for producing the smallest sizes of nanoemersions in a 100 nm diameter with best morphology. No notable changes in the size were observed over 7 days from Ostwald ripening, when the concentration of Arlacel 60 was higher than 2%. Even after 270 days at room temperature, the size of nanoemulsions maintained as 115 nm in diameter, revealing only a 10% increase with high degrees of long termed stability and substantiality. In addition, changes in the surface potential occurred possible due to the flocculation effect on the nanoparticles.

• KSBB Journal
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• v.26 no.3
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• pp.199-205
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• 2011

Using tetrameric ${\beta}$-galactosidase as a model protein, anchoring motives were screened in Bacillus subtilis spore display system. Eleven spore coat proteins were selected considering their expression levels and the location in the spore coat layer. After chromosomal single-copy homologous integration in the amyE site of Bacillus subtilis chromosome, cotE and cotG were chosen as possible spore surface anchoring motives with their higher whole cell ${\beta}$-galactosidase activity. PAGE and Wester blot of extracted fraction of outer layer of purified spore, which express CotE-LacZ or CotG-LacZ fusion verified the existence of exact size of fusion protein and its location in outer coat layer of purified spore. ${\beta}$-galactosidase activity of spore with CotE-LacZ or CotG-LacZ fusion reached its highest value around 16~20 h of culture time in terms of whole cell and purified spore. After intensive spore purification with lysozyme treatment and renografin treatment, spore of BJH135, which expresses CotE-LacZ, retained only 1~2% of its whole cell ${\beta}$-galactosidase activity. Whereas spore of BJH136, which has cotG-lacZ cassette in the chromosome, retained 10~15% of its whole cell ${\beta}$-galactosidase activity, proving minor perturbation of CotG-LacZ, when incorporated in the spore coat layer of Bacillus subtilis compared to CotE-LacZ. Usage of Bacillus subtilis WB700, of which 7 proteases are knocked-out and thereby resulting in 99.7% decrease in protease activity of the host, did not prevent the proteolytic degradation of spore surface expressed CotG-LacZ fusion protein.