• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.122-123
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• 2006

Tin oxide nanoparticles (n-SnO and $n-SnO_2$) were synthesized by the inert gas condensation (IGC) method under dynamic gas flow of oxygen and argon at various conditions. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) method were used to analysis the size, shape and crystal structure of the produced powders. The synthesized particles were mostly amorphous and their size increased with increasing the partial pressure of oxygen in the processing chamber. The particles also became broader in size when higher oxygen pressures were applied. Low temperature annealing at $320^{\circ}C$ in air resulted to crystallization of the amorphous n-SnO particles to $SnO_2$.

• Journal of Electrochemical Science and Technology
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• v.13 no.3
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• pp.347-353
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• 2022

Agarose hydrogel, a solid electrolyte, was investigated voltammetrically in terms of transport properties and natural convection effects using a ferrocenyl compound as a redox probe. To confirm the diffusion properties of solute on the agarose interface, the diffusion coefficients (D) of ferrocenemethanol in agarose hydrogel were determined by cyclic voltammetry (CV) according to the concentration of agarose hydrogel. While the value of D on the agarose interface is smaller than that in the bulk solution, the square root of the scan rate-dependent peak current reveals that the mass transport behavior of the solute on the agarose surface shows negligible convection or migration effects. In order to confirm the reduced natural convection on the gel interface, scan rate-dependent CV was performed in the solution phase and on the agarose surface, respectively. Slow scan voltammetry at the gel interface can determine a conventional and reproducible diffusion-controlled current down to a scan rate of 0.3 mV/s without any complicated equipment.

• Advances in nano research
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• v.14 no.2
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• pp.179-193
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• 2023

Physical activities enhance blood flow in the vessels, which may increase the quality of medicine delivery. The emergence of revolutionary technologies such as nanoscience, made it possible to treat the incurable illnesses such as cancer. This paper investigates the impact of sport and physical exercises on the quality and quantity of the drug-delivery based on the mathematical modeling of a nanomotor made by nanotubes carrying the nano-drug capsules. Accordingly, the mathematical equations of rotating nanomotor are generated by considering the both of higher-order beam model and nonlocal strain gradient model, as a comprehensive continuum theory. Next, through the generalized differential quadrature together with Newmark-beta methods, the differential relations are discretized and solved. Finally, the impact of varied parameters on the dynamical behavior of the nanomotor is examined in detail. The outcomes of this investigation can be useful to achieve an excellent design of nanomotors carrying nano-drugs.

• Journal of Electrochemical Science and Technology
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• v.15 no.1
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• pp.152-160
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• 2024

In this study, ZnCo₂O₄ nanoparticles were synthesized via the coprecipitation method using different annealing temperatures from 200℃ to 800℃. By varying the treatment temperature, the morphology changed from amorphous to tetragonal, and finally to polygonal particles. As temperature increased, the sizes of the nanoparticles also changed from 5 nm at 200℃ to approximately 500 nm at 800℃. The fabricated material was used to modify the working electrode of a screen-printed carbon electrode (SPE), which was subsequently used to survey the detection performance of the antibiotic, chloramphenicol (CAP). The electrochemical results revealed that the material exhibits a good response to CAP. Further, the sample that annealed at 600℃ displayed the best performance, with a linear range of 1-300 μM, and a limit of detection (LOD) of 0.15 μM. The sensor modified with ZnCo₂O₄ also exhibited the potential for utilitarian application when the recovery in a real sample was above 97%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.715-720
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• 2016

This paper proposes a PWM (Pulse Width Modulation) voltage mode DC-DC step-up converter for portable devices. The converter, which is operated with a 1 MHz switching frequency, is capable of reducing the mounting area of passive devices, such as inductor and capacitor, and is suitable for compact mobile products. This step-up converter consists of a power stage and a control block. The circuit elements of the power stage are an inductor, output capacitor, MOS transistors Meanwhile, control block consist of OPAMP (operational amplifier), BGR (band gap reference), soft-start, hysteresis comparator, and non-overlap driver and some protection circuits (OVP, TSD, UVLO). The hysteresis comparator and non-overlapping drivers reduce the output ripple and the effects of noise to improve safety. The proposed step-up converter was designed and verified in Magnachip/Hynix 0.18um 1-poly, 6-metal CMOS process technology. The output voltage was 5 V with a 3.3 V input voltage, output current of 100 mA, output ripple less than 1% of the output voltage, and a switching frequency of 1 MHz. These designed DC-DC step-up converters could be applied to the Personal Digital Assistants(PDA), cellular Phones, Laptop Computer, etc.

• Journal of Physiology & Pathology in Korean Medicine
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• v.23 no.2
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• pp.397-404
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• 2009

For standardization of LMK02 quality, Ginsenoside Rg3 of Red Ginseng and Decursin of Angelica gigas Nakai in the constituents of LMK02 were estimated as indicative components. From LMK02 water extract, has been used in vitro test for its beneficial effects on neuronal survival and neuroprotective functions, particularly in connection with APP-related dementias and Alzheimer's disease (AD). $A{\beta}$ oligomer derived from proteolytic processing of the ${\beta}$-amyloid precursor protein (APP), including the amyloid-${\beta}$ peptide ($A{\beta}$), play a critical role in the pathogenesis of Alzheimer's dementia. We determined that oligomer amyloid-${\beta}$ ($A{\beta}$) have a profound attenuation in the increase in rat hippocampus H19-7 cells from. Experimental evidence indicates that LMK02 protects against neuronal damage from cells, but its cellular and molecular mechanisms remain unknown. Using a hippocampus cell line on $A{\beta}$ oligomer-induced neuronal cytotoxicity, we demonstrated that LMK02 inhibits formation of $A{\beta}$ oligomer, which are the behavior, and possibly causative, feature of AD. In the Red Ginseng, the average amounts of Ginsenoside Rg3 were $47.04{\mu}g/g$ and $42.3{\mu}g/g$, 90 % of its weight were set as a standard value. And, in the Angelica gigas Nakai, the average amounts of Decursin were 2.71 mg/g and 2.44mg/g, 90 % of its weight were also set as a standard value. The attenuated $A{\beta}$ oligomer in the presence of LMK02 was observed in the conditioned medium of this $A{\beta}$ oligomer-induced cells under in vitro. In the cells, LMK02 significantly activated antiapoptosis and decreased the production of ROS. These results suggest that neuronal damage in AD might be due to two factors: a direct $A{\beta}$ oligomer toxicity and multiple cellular and molecular neuroprotective mechanisms, including attenuation of apoptosis and direct inhibition of $A{\beta}$ oligomer, underlie the neuroprotective effects of LMK02 treatment.

• Journal of the Korean Vacuum Society
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• v.19 no.6
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• pp.423-431
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• 2010

In order to teach the accumulated knowledge of nanoscience, nanoengineering and nanotechnology to graduate school students and young scientists with the sense of public engagement, Osaka University started from 2004 to prepare and offer various kinds of education and training programs such as trans-disciplinary graduate-school minor program, evening course refresher program, short-term international research training program, etc. It offers a series of lectures, partly broadcasted live to satellite classrooms. In addition, the students can join intensive hands-on training programs using modern facilities, allowing them to design, fabricate, measure, characterize and functionalize nanomaterials and nanodevices. In addition, there are four specially designed lectures and research training programs aimed for nanocommunication including social, legal and ethical relationship: "Nanotechnology Career-up Lectures", "Social Engagement on Nanotechnology", "Road Map Design on Nanotechnology", and "Project-Aimed Learning and Training Programs (PAL)". The outline of the whole programs is described together with the specialized programs for nanocommunication.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.21-26
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• 2016

This paper presents a step-down DC-DC buck converter with a CCM/DCM dual-mode function for the internal power stage of portable electronic device. The proposed converter that is operated with a high frequency of 1 MHz consists of a power stage and a control block. The power stage has a power MOS transistor, inductor, capacitor, and feedback resistors for the control loop. The control part has a pulse width modulation (PWM) block, error amplifier, ramp generator, and oscillator. In this paper, an external capacitor for compensation has been replaced with a multiplier equivalent CMOS circuit for area reduction of integrated circuits. In addition, the circuit includes protection block, such as over voltage protection (OVP), under voltage lock out (UVLO), and thermal shutdown (TSD) block. The proposed circuit was designed and verified using a $0.18{\mu}m$ CMOS process parameter by Cadence Spectra circuit design program. The SPICE simulation results showed a peak efficiency of 94.8 %, a ripple voltage of 3.29 mV ripple, and a 1.8 V output voltage with supply voltages ranging from 2.7 to 3.3 V.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.504-510
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• 2017

This paper presents an AC-DC power module design and evaluates its efficiency and reliability when used for electronics appliances. This power module consists of a PWM control IC, power MOSFETs, a transformer and several passive devices. The module was tested at an input voltage of 220V (RMS) (frequency 60 Hz). A test was conducted in order to evaluate the operation and power efficiency of the module, as well as the reliability of its protection functions, such as its over-current protection (OVP), overvoltage protection (OVP) and electromagnetic interference (EMI) properties. Especially, we evaluated the thermal shut-down protection (TSP) function in order to assure the operation of the module under high temperature conditions. The efficiency and reliability measurement results showed that at an output voltage of 5 V, the module had a ripple voltage of 200 mV, power efficiency of 73 % and maximum temperature of $80^{\circ}C$ and it had the ability to withstand a stimulus of high input voltage of 4.2 kV during 60 seconds.

• Korean Journal of Optics and Photonics
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• v.33 no.5
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• pp.218-229
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• 2022

We have investigated reliable inspection methods for finding the defects generated during the manufacturing process of lightweight, large-aperture satellite telescope mirrors using silicon carbide, and we have measured the basic physical properties of the mirrors. We applied the advanced ceramic material (ACM) method, a combined method using liquid-silicon penetration sintering and chemical vapor deposition for the carbon molded body, to manufacture four SiC mirrors of different sizes and shapes. We have provided the defect standards for the reflectors systematically by classifying the defects according to the size and shape of the mirrors, and have suggested effective nondestructive methods for mirror surface inspection and internal defect detection. In addition, we have analyzed the measurements of 14 physical parameters (including density, modulus of elasticity, specific heat, and heat-transfer coefficient) that are required to design the mirrors and to predict the mechanical and thermal stability of the final products. In particular, we have studied the detailed measurement methods and results for the elastic modulus, thermal expansion coefficient, and flexural strength to improve the reliability of mechanical property tests.