• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.201-208
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• 2017

Recently, the installation of photovoltaic(PV) systems has been increasing due to the worldwide interest in eco-friendly and abundant solar energy. On the other hand, a PV system has approximately 25% power loss while the energy generated from solar cells is transformed to the power coupling point through a power conversion system (DC/AC). If the output voltage of a string in the PV system is lower than the operating range of the inverter when a part of module in the string has a shadow due to weather conditions, the string is not synchronized and the whole efficiency of output power in a PV system may be reduced significantly. Therefore, to overcome this problem, this paper proposes a novel control method to compensate for the lower voltage by introducing a DC/DC voltage regulator for each string in a PV system, which adopts a concept for MPPT (Maximum Power Point Tracking) control function using the P&O algorithm and adopts constant voltage control method used in an existing inverter. This paper also implements a 2kW DC/DC voltage regulator based on the proposed algorithm and performs a variety of scenario-based experiments. From the simulation result, it was confirmed that the operation efficiency in the proposed method is improved compared to the existing method.

• Experimental and Molecular Medicine
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• v.50 no.11
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• pp.3.1-3.11
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• 2018

This study aimed to verify the effects of estrogen on the onset and development of adolescent idiopathic scoliosis and the mechanisms associated with these effects by constructing a pubescent bipedal rat model. Experiments were conducted to investigate whether scoliosis progression was prevented by a Triptorelin treatment. One hundred twenty bipedal rats were divided into female, OVX (ovariectomy), OVX + E2, Triptorelin, sham, and male groups. According to a spinal radiographic analysis, the scoliosis rates and curve severity of the female and OVX + E2 groups were higher than those in the OVX, Triptorelin, and male groups. The measurements obtained from the sagittal plane of thoracic vertebrae CT confirmed a relatively slower growth of the anterior elements and a faster growth of the posterior elements between T11 and T13 in the female and OVX + E2 groups than in the OVX and Triptorelin groups. Histomorphometry and immunohistochemistry revealed a significantly longer hypertrophic zone of the vertebral cartilage growth plates that expressed more type X collagen and less type II collagen in the OVX and Triptorelin groups than in the female and OVX + E2 groups. Ki67 immunostaining confirmed an increase in the proliferation of vertebral growth plate chondrocytes in the OVX group compared with the female and OVX + E2 groups. In conclusion, estrogen obviously increased the incidence of scoliosis and curve severity in pubescent bipedal rats. The underlying mechanism may be a loss of coupling of the endochondral ossification between the anterior and posterior columns. Triptorelin decreased the incidence of scoliosis and curve magnitudes in bipedal female rats.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.5
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• pp.301-313
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• 2021

Theoretical background for the meaning of various piezoelectric properties can be easily found in a number of textbooks and academic papers. In contrast, how they are actually measured and characterized are rarely described, though this information would be the most important especially to the researchers who just started working on the field. It follows that this report was intended to provide a practical guidance for measuring basic but essential properties of ferroelectric-based piezoelectric materials. The discussion begins with how to measurement dielectric properties such as dielectric permittivity and loss (dissipation factor), followed by piezoelectric properties such as piezoelectric constants, electromechanical coupling factor, and quality factor as well as ferroelectric features, i.e., electric field dependent polarization hysteresis. Though our discussion here is limited to the techniques that are already well-standardized, it is expected to make a seed to be developed into more challenging and creative ones.

• Geophysics and Geophysical Exploration
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• v.24 no.4
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• pp.180-193
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• 2021

The complex resistivity method is an exploration technique that can obtain various characteristic information of underground media by measuring resistivity and phase in the frequency domain, and its utilization has recently increased. In this paper, a three-dimensional inversion algorithm for the CR data was developed to increase the utilization of this method. The Poisson equation, which can be applied when the electromagnetic coupling effect is ignored, was applied to the modeling, and the inversion algorithm was developed by modifying the existing algorithm by adopting comlex variables. In order to increase the stability of the inversion, a technique was introduced to automatically adjust the Lagrangian multiplier according to the ratio of the error vector and the model update vector. Furthermore, to compensate for the loss of data due to noisy phase data, a two-step inversion method that conducts inversion iterations using only resistivity data in the beginning and both of resistivity and phase data in the second half was developed. As a result of the experiment for the synthetic data, stable inversion results were obtained, and the validity to real data was also confirmed by applying the developed 3D inversion algorithm to the analysis of field data acquired near a hydrothermal mine.

• The Journal of the Convergence on Culture Technology
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• v.9 no.1
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• pp.111-118
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• 2023

The purpose of this study is to study jewelry designs presented to general consumers who seek new products and diversity. We would like to present a modular jewelry design with a structure and combination method that is distinct from jewelry in a multimodal replacement method that allows various product modules sold in the past to be worn interchangeably. Problems are likely to occur when a number of existing rather small parts are manufactured in a complex combination method, and difficulties may follow when consumers replace decorative parts and lose them in the process of assembling small fixture parts. Therefore, in order to reduce these problems, we try to make it different from jewelry products made with a simple and simple design so that it can be easily replaced and worn without the need for other coupling parts, and produced using the latest 3D printer (Rapid Prototyping). In this study, based on the experience and know-how gained while engaging in field work, it was possible to make a real object and focused on minimizing problems during the production process, and through this, time and economic loss can be reduced. The purpose of the study is to produce improved jewelry products by expressing more sophisticated and differentiated shapes by using 3D programs (CAD).

• Journal of Korean Society of Environmental Engineers
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• v.35 no.4
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• pp.247-256
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• 2013

In this study, alginate beads containing birnessite (Bir-AB), a highly reactive oxidative catalyst for the transformation of phenolic compounds, was prepared and its 1-naphthol (1-NP) removal efficiency was investigated in a batch test. Based on scanning electron microscopy image, it can be inferred that the alginate gel cluster acts as a bridge which bind the birnessite particles together. Kinetic experiment with Bir-AB of different mixing ratios of birnessite to alginate (Bir : AG=0.25 : 1~1 : 1 w/w) indicate that pseudo-first order kinetic constants, $k(hr^{-1})$ for the 1-NP removals increased about 1.5 times when the birnessite mixing ratio was doubled. The removals of 1-NP was found to be dependent on solution pH and the pesudo-first order rate constants were increased from 0.331 $hr^{-1}$ at pH 10 to 0.661 $hr^{-1}$ at pH 4. The analysis of total organic carbon for the reaction solutions showed that a higher removal of dissolved organic carbon was achieved with Bir-AB as compared to birnessite. HPLC chromatographic analysis of the methanol extract after reaction of 1-NP with Bir-AB suggest that the reaction products could be removed through incorporation into the aliginate beads as a bound residue. Mn ions produced from the oxidative transformation of 1-NP by birnessite were also removed by sorption to Bir-AB. The Bir-AB was recovered quantitatively by simple filtration and was reused twice without significant loss of the initial reactivity.

• Korean Journal of Microbiology
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• v.52 no.1
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• pp.10-17
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• 2016

Enzyme immunoassay to analyze specific binding activity of antibody to antigen uses horseradish peroxidase (HRP) or alkaline phosphatase (AP). Chemical methods are usually used for coupling of these enzymes to antibody, which is complicated and random cross-linking process. As results, it causes decreases or loss of functional activity of either antibody or enzyme. In addition, most enzyme assays use secondary antibody to detect antigen binding activity of primary antibody. Enzymes coupled to secondary antibody provide a binding signal by substrate-based color development, suggesting secondary antibody is required in enzyme immunoassay. Additional incubation time for binding of secondary antibody should also be necessary. More importantly, non-specific binding activity caused by secondary antibody should also be eliminated. In this study, we cloned AP isolated from Escherichia coli (E. coli) chromosome by PCR and fused to) hAY4 single-chain variable domain fragment (ScFv) specific to death receptor (DR4) which is a receptor for tumor necrosis factor ${\alpha}$ related apoptosis induced ligand (TRAIL). hAY4 ScFv-AP expressed in E. coli showed 73.8 kDa as a monomer in SDS-PAGE. However, this fusion protein shown in size-exclusion chromatography (SEC) exhibited 147.6 kDa as a dimer confirming that natural dimerization of AP by non-covalent association induced ScFv-AP dimerization. In several immunoassay such as ELISA, Western blot and immunocytochemistry, it showed antigen binding activity by color development of substrates catalyzed by AP directly fused to primary hAY4 ScFv without secondary antibody. In summary, hAY4 ScFv-AP fusion protein was successfully purified as a soluble dimeric form in E. coli and showed antigen binding activity in several immunoassays without addition of secondary antibody which sometimes causes time-consuming, expensive and non-specific false binding.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.1 s.116
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• pp.62-75
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• 2007

This paper describes a shaped-beam antenna for increasing the antenna gain of a radiating element. The proposed antenna structure is composed of an exciting element and a multi-layered disk array structure(MDAS). The stack micro-strip patch elements were used as the exciter for effectively radiating the electromagnetic power to the MDAS over the broadband, and finite metallic disk array elements - which give the role of a director for shaping the antenna beam with the high gain - were finitely and periodically layered onto it. The efficient power coupling between the exciter and the MDAS should be carried out in such a way that the proposed antenna has a high gain characteristic. The design parameters of the exciter and the MDAS should be optimized together to meet the required specifications to meet the required specifications. In this study, a shaped-beam antenna with high gain was optimally designed under the operating conditions with a linear polarization and the frequency band of $9.6{\sim}10.4\;GHz$. Two methods constructed using thin dielectric film and dielectric foam materials respectively were also proposed in order to implement the MBAS of the antenna. In particular, through the computer simulation process, the electrical performance variations of the antenna with the MDAS realized by the thin dielectric film materials were shown according to the number of disk array elements in the stack layer. Two kinds of antenna breadboard with the MDAS realized with the thin dielectric film and dielectric foam materials were fabricated, but experimentation was conducted only on the antenna breadboard(Type 1) with the MDAS realized with the thin dielectric film materials according to the number of disk array elements in the stack layer in order to compare it with the electrical performance variations obtained during the simulation. The measured antenna gain performance was found to be in good agreement with the simulated one, and showed the periodicity of the antenna gain variations according to the stack layer number of the disk array elements. The electrical performance of the Type 1 antenna was measured at the center frequency of 10 GHz. As the disk away elements became the ten stacks, a maximum antenna gain of 15.65 dBi was obtained, and the measured return loss was not less than 11.4 dB within the operating band. Therefore, a 5 dB gain improvement of the Type 1 antenna can be obtained by the MDAS that is excited by the stack microstrip patch elements. As the disk array elements became the twelve stacks, the antenna gain of the Type 1 was measured to be 1.35 dB more than the antenna gain of the Type 2 by the outer dielectric ring effect, and the 3 dB beam widths measured from the two antenna breadboards were about $28^{\circ}$ and $36^{\circ}$ respectively.