• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.37-37
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• 2008

Hydrogenated nanocrystalline Si (nc-Si:H) thin films were prepared by plasma enhanced chemical vapor deposition (PECVD). The films were deposited with a radio frequency power of 100 W, while substrates were exposed to direct current (DC) biases in the range from 0 to -400 V. The effects of the DC bias on the formation of nanoscale Si crystallites in the films and on their optical characteristics were investigated. The size of the Si crystallites in the films ranges from ~ 1.9 to ~ 4.1 nm. The relative fraction of the crystallites in the films reached up ~ 56.5 % when the DC bias of -400 V was applied. Based on the variation in the structural, chemical, and optical features of the films with DC bias voltages, a model for the formation of nanostructures of the nc-Si:H films prepared by PECVD was suggested. This model can be utilized to understand the evolution in the size and relative fraction of the nanocrystallites as well as the amorphous matrix in the nc-Si:H films.

• Bulletin of the Korean Chemical Society
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• v.26 no.6
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• pp.939-942
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• 2005

For the detection of cyanobacterial toxin, an Enzyme-linked immunosorbent assay (ELISA) was integrated into a PDMS microchip. The conjugates of microcystin-LR (MCLR) and keyhole limpet hemocyanin (KLH) were adsorbed on the surface of polystyrene beads and these MCLR-KLH polystyrene beads were introduced into a microchamber. MCLR on the surface of polystyrene beads reacted with horseradish peroxides (HRP) conjugated anti-MCLR monoclonal antibody (mAb) which had a competitive reaction with MCLR in water sample. After the enzyme substrate 3,3,5,5-tetramethyl benzidine (TMB) was injected into the chamber and catalyzed by HRP, the color change was detected with a liquid-cord waveguide. This integration shortened the conventional ELISA analysis time from several hours to about 30 min with only 4.2 $\mu$L MCLR sample consuming which was useful for the environmental analysis. More over, troublesome operations required for ELISA could be replaced by simple operations. The microchip based detection system showed a good sensitivity of 0.05 $\mu$g/L and maintained good reliability through its quantitative range with low coefficients of variation (2.5-10.5%).

• Structural Engineering and Mechanics
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• v.21 no.6
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• pp.635-658
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• 2005

The possibility of detecting a crack in L-shaped pipes filled with fluid based on measurement of transverse natural frequencies is examined. The problem is solved by representing the crack by a massless rotational spring, simulating the out-of-plane transverse vibration only without solving the coupled torsional vibration and using the transfer matrix method for solution of the governing equation. The theoretical solutions are verified by experiments. The cracks considered are external, circumferentially oriented and have straight front. Pipes made of aluminium and mild steel are tested with water as internal fluid. Crack size to pipe thickness ratio ranging from 0.20 to 0.57 and fluid (gauge) pressure in the range of 0 to 10 atmospheres are examined. The rotational spring stiffness is obtained by an inverse vibration analysis and deflection method. The details of the two methods are given. The results by the two methods are presented graphically and show good agreement. Crack locations are also determined by the inverse analysis. The maximum absolute error in the location is 13.80%. Experimentally determined variation of rotational spring stiffness with ratio of crack size to thickness is utilized to predict the crack sizes. The maximum absolute errors in prediction of crack size are 17.24% and 16.90% for aluminium and mild steel pipes respectively.

• Journal of Power Electronics
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• v.12 no.5
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• pp.778-786
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• 2012

In this paper, a novel scheme for the condition monitoring of lithium polymer batteries is proposed, based on the sigma-point Kalman filter (SPKF) theory. For this, a runtime-based battery model is derived, from which the state-of-charge (SOC) and the capacity of the battery are accurately predicted. By considering the variation of the serial ohmic resistance ($R_o$) in this model, the estimation performance is improved. Furthermore, with the SPKF, the effects of the sensing noise and disturbance can be compensated and the estimation error due to linearization of the nonlinear battery model is decreased. The effectiveness of the proposed method is verified by Matlab/Simulink simulation and experimental results. The results have shown that in the range of a SOC that is higher than 40%, the estimation error is about 1.2% in the simulation and 1.5% in the experiment. In addition, the convergence time in the SPKF algorithm can be as fast as 300 s.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.225-227
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• 2009

The conventional fixed gain PI controller is very sensitive to step change of command speed, parameter variation and load disturbances. The precise speed control of interior permanent magnet synchronous motor(IPMSM) drive becomes a complex issue due to nonlinear coupling among its winding currents and the rotor speed as well as the nonlinear electromagnetic developed torque. Therefore, there exists a need to tune the PI controller parameters on-line to ensure optimum drive performance over a wide range of operating conditions. This paper is proposed artificial intelligent-PI(AIPI) controller of IPMSM drive using adaptive learning mechanism(ALM) and fuzzy neural network(FNN). The proposed controller is developed to ensure accurate speed control of IPMSM drive under system disturbances and estimation of speed using artificial neural network(ANN) controller. The PI controller parameters are optimized by ALM-FNN at all possible operating condition in a closed loop vector control scheme. The validity of the proposed controller is verified by results at different dynamic operating conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.3
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• pp.171-176
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• 2013

In this paper, we present a MEMS (micro-electro-mechanical system) implantable blood pressure sensor which has designed and fabricated with consideration of size, design flexibility, and wireless detection. Mechanical and electrical characterizations of the sensor were obtained by mathematical analysis and computer aided simulation. The sensor is composed of two coils and a air gap capacitor formed by separation of the coils. Therefore, the sensor produces its resonant frequency which is changed by external pressure variation. This frequency movement is detected by inductive coupling between the sensor and an external antenna coil. Theoretically analyzed resonant frequency of the sensor under 760 mmHg was calculated to 269.556 MHz. Fused silica was selected as sensor material with consideration of chemical and electrical reaction of human body to the material. $2mm{\times}5mm{\times}0.5mm$ pressure sensors fitted to radial artery were fabricated on the substrates by consecutive microfabrication processes: sputtering, etching, photolithography, direct bonding and laser welding. Resonant frequencies of the fabricated sensors were in the range of 269~284 MHz under 760 mmHg pressure.

• Korean Journal of Materials Research
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• v.16 no.12
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• pp.739-742
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• 2006

The ${\gamma}-Fe_2O_3$ nano particles in the size range of $5{\sim}30$ nm were prepared by a chemical coprecipitation method. The nano particles were coated with 2nd surfactants for obtaining the water-based. The size effect of ${\gamma}-Fe_2O_3$ nano particles for the ultraviolet protection was investigated. The variation of the UV-Vis transmittance spectra as a function of wavelength for a ${\gamma}-Fe_2O_3$ nano particles were showed red-shifted increase with the particle size. The protective effects of UVA onset at near 469, 494, 591 nm for a particle size of 8.7, 9.1 and 12 nm. It is shown that the ${\gamma}-Fe_2O_3$ nano particles was good materials for protect of UV.

• Mass Spectrometry Letters
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• v.4 no.3
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• pp.55-58
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• 2013

Dioscin is a biologically active steroidal saponin with anticancer and hepatoprotective effects. A rapid, selective, and sensitive liquid chromatographic method with electrospray ionization tandem mass spectrometry was developed for the quantification of dioscin in rat plasma. Dioscin was extracted from rat plasma using ethyl acetate at acidic pH. The analytes were separated on a Halo C18 column using gradient elution of acetonitrile and 0.1% formic acid and detected by tandem mass spectrometry in selected reaction monitoring mode. The standard curve was linear ($r^2$ = 0.998) over the concentration range of 1-100 ng/mL. The lower limit of quantification was 1.0 ng/mL using 50 ${\mu}L$ of plasma sample. The coefficient of variation and relative error for intra- and inter-assay at four QC levels were 1.3 to 8.0% and -5.4 to 10.0%, respectively. This method was applied successfully to the pharmacokinetic study of dioscin after oral administration of dioscin at a dose of 29.2 mg/kg in male Sprague-Dawley rats.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.146-151
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• 2012

The present article shows how the fracture strength of single crystal silicon chips, which are generally used as semiconductor devices, is influenced by loading rate variation during a 3-point bending test. It was found that the fracture strength of the silicon chips slightly increases up to 4% with increasing loading rate for loading rates lower than 20 mm/min. Meanwhile, the fracture strength of the chips hardly increases with increase of loading rate to levels higher than 40 mm/min. However, there was an abrupt transition in the fracture strength within a loading rate range of 20 mm/min to 40 mm/min. This work explains through microscopic examination of the fracture surface of all test chips that such a big transition is related to the deflection of crack propagation direction from the (011) [${\bar{1}}00$] system to the (111) [${\bar{2}}11$] system in a particular loading rate (i.e. from 20 mm/min to 40 mm/min).

• Health Policy and Management
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• v.2 no.1
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• pp.1-16
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• 1992

This study compares the physician payment of national fee schedule for Korean Medical Insurance with that of the United States based on Resource Based Relative Value Scales (RBRVS) which Hsiao developed in 1988 for the Medicare reimbursement. Through the comparison of two fees schedules, this study is purposed to evaluate the appropriateness of relative values which assigned to each physician services of Korean fee schedule. A total of 264 physician services are selected for the comparison. The ratio of Korean schedule to RBRVS is selected as an index of appropriateness. It the score of index shows large variation among services, the relative value of Korean fee schedule is inappropriate with U.S. RBRVS which was developed recently. The Ratios of Korean schedule to RBRVS are widly variated ; the range of those is 8.1 to 379.3. In subgroups which are regrouped to controll systematic differences between two national fee schedules, these ratios are also variated. Services which are relatively less compensated are management/evaluation services, while services which are relatively more compensated are invasive and imaging services. By the way, the service classification of Korean fee schedule is unclear, specially in management/evalutaion services. Therefore, Korean Medical Insurance fee schedule should be modified to be more balanced and rational.