• Journal of Sensor Science and Technology
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• v.17 no.6
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• pp.406-413
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• 2008

We have been implemented simple statistical pattern recognition methods for harmful gases classification using gas sensors array fabricated by MEMS (Micro Electro Mechanical System) technology. The performance of pattern recognition method as a gas classifier is highly dependent on the choice of pre-processing techniques for sensor and sensors array signals and optimal classification algorithms among the various classification techniques. We carried out pre-processing for each sensor's signal as well as sensors array signals to extract features for each gas. We adapted simple statistical pattern recognition algorithms, which were PCA (Principal Component Analysis) for visualization of patterns clustering and MLR (Multi-Linear Regression) for real-time system implementation, to classify harmful gases. Experimental results of adapted pattern recognition methods with pre-processing techniques have been shown good clustering performance and expected easy implementation for real-time sensing system.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1123-1130
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• 2018

Voltage stabilization is an essential component of power quality in low voltage DC (LVDC) microgrid. The microgrid demands the interconnection of a number of small distributed power resources, including variable renewable generators. Therefore, the voltage can be maintained in a stable manner through the control of these distributed generators. In this study, we did research on the new advanced operating method for a photovoltaic (PV) simulator in order to achieve interconnection to a bipolar LVDC microgrid. The validity of this voltage stabilization method, using the distributed generators, is experimentally verified. The test LVDC microgrid is configured by connecting the developed PV simulator and DC load, DC line, and AC/DC rectifier for connecting the main AC grid. The new advanced control method is applied to the developed PV simulator for the bipolar LVDC grid in order to stabilize the gird voltage. Using simulation results, the stabilization of the grid voltage by PV simulator using the proposed control method is confirmed the through the simulation results in various operation scenarios.

• Biomolecules & Therapeutics
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• v.8 no.3
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• pp.269-275
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• 2000

Silibinin(silybin) is the active component of silymarin from Silybum marianum and has hepato-protective effect. It is water-insoluble and has low bioavailability. To improve its bioavailability, self-micro-emulsifying drug delivery system (SMEDDS) has been developed by Hanmi Pharmaceutical Company (Silyma $n^{R}$ 140 soft capsule). In this study, the pharmacokinetic profiles of Silyma $n^{R}$ were examined and compared it with a reference preparation, L Caps140 of B Pharmaceutical Company. This study was approved by Yonsei University Severance Hospital IRB(approval No. CR0004) and followed the bioequivalence test guideline of Korean FDA. Eighteen healthy adult volunteers were allocated based on 2$\times$2 Latin square cross-over design. They were given 2 capsules (each contains silymarin 140 mg (60 mg as silibinin)) of either drug at each period and crossed over after a week of drug-free washout period. Blood concentration of silibinin was measured by HPLC. The $C_{max}$ and AUC of the Silyma $n^{R}$ were 1542.0 $\pm$ 402.7 ng/ml and 3323.3 $\pm$ 824.7 ng.h/ml, respectively, and were significantly higher than those of reference preparation. The Tmax was 0.8 $\pm$ 0.3 h and significantly shorter than reference preparation. The $K_{e}$ and $T_{1}$2/ of both drugs were comparable. Percent differences in means against reference preparation were +88.3% for AUC, +222.6% for $C_{max}$, and -61.1% for $T_{max}$./.>././.>./.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.195-198
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• 2006

The technology of Solar Power conversion System is defined as a solar cell that changes the sol ar energy into the direct electric energy, power conversion and control technology that convert the dc power into ac power The solar cell module, power conversion, and a control part in component parts consisting a solar power conversion system have influence on its performance. The roles of power conversion and a control part supply the direct current generated by solar cell module for a load with high efficiency as conveniently as possible in this study, the power conversion systen that can generate solar power using DSC module was developed and its characteristics was experimented. The characteristics of the DSC power conversion system including MOSFET and DSP micro processor, high speed devices, was simulated using Psim. According to the results, converter and inverter was manufactured in detail and the performance characteristics were studied.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.112-118
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• 2021

In this study, an inspection method using a color image is proposed to conduct a real-time inspection of covalent organic framework (COF) films to detect defects, if any. The COF film consists of an upper pattern SR and a lower PI. The proposed system detects the defects of more than 20 ㎛ on the SR surface owing to the characteristics of the pattern, whereas on the PI surface, it detects defects of more than 4 ㎛ by utilizing a micro-optical system. In the existing system, it is difficult for the operator to conduct a full inspection through a high-performance microscope. The proposed inspection algorithm performs the inspection by separating each color component using the color contrast of the pattern on the SR side, and on the PI surface it inspects the bonding state of the mounted chip. As a result, it is possible to confirm the exact location of the defects through the SR and PI surface inspections in the implemented inspection.

• Current Optics and Photonics
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• v.2 no.6
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• pp.576-581
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• 2018

A new approach for identification of a microwave frequency using an integrated optical waveguide chip, combined with a phase modulator (PM) and two microring resonators (MRRs), is proposed, theoretically deduced, and verified. By wavelength tuning to set the PM under the condition of a double side band (DSB), the measurement range can be started from the dc component, and the measurement range and response slope can be adjusted by designing the radius and transmission coefficient of the MRR. Simulations reveal that the amplitude comparison function (ACF) has a monotonic relationship from dc to 32.5 GHz, with a response slope of 5.15 dB under conditions of DSB modulation, when the radius values, transmission coefficients, and the loss factors are designed respectively as $R_1=400{\mu}m$, $R_2=600{\mu}m$, $t_1=t_2=0.63$, and ${\gamma}_1={\gamma}_2=0.66$. Theoretical calculations and simulation results both indicate that this new approach has the potential to be used for measuring microwave frequencies, with the advantages of compact structure and superior reconfigurability.

• Coupled systems mechanics
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• v.10 no.1
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• pp.39-60
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• 2021

The present paper is concerned with the study of nonlinear ultrasonic waves in a magneto thermo (MT) elastic armchair single-walled carbon nanotube (ASWCNT) resting on polymer matrix. The analytical formulation is developed based on Eringen's nonlocal elasticity theory to account small scale effect. After developing the formal solution of the mathematical model consisting of partial differential equations, the frequency equations have been analyzed numerically by using the nonlinear foundations supported by Winkler-Pasternak model. The solution is obtained by ultrasonic wave dispersion relations. Parametric work is carried out to scrutinize the influence of the non local scaling, magneto-mechanical loadings, foundation parameters, various boundary condition and length on the dimensionless frequency of nanotube. It is noticed that the boundary conditions, nonlocal parameter, and tube geometrical parameters have significant effects on dimensionless frequency of nano tubes. The results presented in this study can provide mechanism for the study and design of the nano devices like component of nano oscillators, micro wave absorbing, nano-electron technology and nano-electro- magneto-mechanical systems (NEMMS) that make use of the wave propagation properties of armchair single-walled carbon nanotubes embedded on polymer matrix.

• Transactions of Materials Processing
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• v.31 no.4
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• pp.240-245
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• 2022

In this study, to achieve good electrical conductivity of a charging terminal component in electric vehicles, we investigated the microstructure evolution of pure-Cu subjected to metal injection molding by controlling the sintering variables, such as temperature and time. Thus, three samples were sintered at temperatures ranging from 1000 ℃ to 1050 ℃ near to the melting temperature of 1085 ℃ for 1 and 10 h after thermal evaporation of binder at 730 ℃. Both procedures were made using a unified furnace under Ar+H₂ gas with high purity. The structural observation displayed that the grain size as well as the compactness (a reciprocal of porosity) increased simultaneously as temperature and time increased. This gave rise to high thermal conductivity of 90% IACS together with high density, which was mainly attributed to decrease in fractions of grain boundaries and micro-pores working as effective scattering center for electron movement.

• Tribology and Lubricants
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• v.38 no.5
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• pp.222-226
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• 2022

Between diaphragms made of stainless steel (SUS), which is the main component of a hydrogen gas compressor, micro-slip occurs owing to repeated bending, resulting in scratches on the surface. The surface scratch of the compressor part is a problem with airtightness, which reduces the efficiency of the compressor; in severe cases, damage is a possibility. In this study, the changes in friction and wear characteristics due to the surface polishing of SUS and carbon-based solid lubricant films (graphene and CNT) were analyzed. Bare SUS, polished SUS, graphene film, and CNT film specimens were prepared. The surface roughness of the SUS was significantly reduced by surface polishing but increased by carbon-based solid lubricating films. In contrast, the friction coefficient maintained a similar value after surface polishing but was significantly reduced by the carbon-based solid lubricant films. In particular, the graphene film exhibited the lowest initial friction coefficient, while the CNT film exhibited the lowest overall average friction coefficient. Regarding the wear rate, polished SUS exhibited the lowest value, but the surface condition of the wear track showed that the carbon-based solid lubricating films were relatively less damaged. Although the wear rate measured was largely attributed to the solid lubricating film peeling off, the SUS surface under the film was considered protected.

• Progress in Superconductivity and Cryogenics
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• v.12 no.4
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• pp.41-45
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• 2010

Miniature Joule-Thomson refrigerators have been widely used for rapid cooling of infrared detectors, optoelectronic device, and integrated circuits of micro electronics. The typical J-T refrigerator consists of the recuperative heat exchanger with the double helical tube and fin configuration, J-T nozzle, a mandrel, Dewar and a compressed gas storage bottle. In this study, to predict the thermodynamic behaviors of the refrigerator with a compressed gas storage bottle during the cool-down time, numerical study of transient characteristics for a J-T refrigerator was developed. A simplified transient one.dimensional model of the momentum and energy equations was simultaneously solved to consider the thermal interactions of the each component of the refrigerator. To account for effects of the thermal mass of the solid, the heat capacities of the tube, fins, mandrel and Dewar are considered. The results show the charged gas pressure of the gas storage bottle has significant effects on the performance of the J-T refrigerator. At the elevated gas pressure of the gas storage bottle, the large capacity of the compressed gas storage does not need to get the fast cool-down performance of the J-T refrigerator in the cool-down stage.