• Journal of Biomedical Engineering Research
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• v.20 no.2
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• pp.205-212
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• 1999

When we want to observe and record a patient's EEG in an operating room, the operation of electrosurgical unit(ESU) causes undesirable artifacts with high frequency and high voltage. These artifacts make the amplifiers of the conventional EEG system saturated and prevent the system from measuring the EEG signal. This paper describes a high-performance bipolar EEG amplifier for a CSA (compressed spectral array ) system with reduced ESU artifacts. The designed EEG amplifier uses a balanced filter to reduce the ESU artifacts, and isolates the power supply and the signal source of the preamplifier from the ground to cut off the current from the ESU to the amplifier ground. To cancel the common mode noise in high frequency, a high CMRR(common mode rejection ratio) diffferential amplifier is used. Since the developed bipolar EEG amplifier shows high gain, low noise, high CMRR, high input impedance, and low thermal drift, it is possible to observe and record more clean EEG signals in spite of ESU operation. Therefore the amplifier may be applicable to a high-fidelity CSA system.

• Plant Journal
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• v.10 no.3
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• pp.45-51
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• 2014

This study performs several experiments on a newly developed temperature safety system that can be used for residential building heating systems, the heat source of which is derived from a conventional fuel cell. Prior to this, the hot water made from a fuel cell was not used in residential housing but just went to waste. The present safety system is installed in the current underfloor heating system. At first we used the CFD technique to develop a new heat exchanger. The fuel cell must satisfy the thermal conditions of the inlet temperature being $55^{\circ}C$ and the outlet temperature being $60^{\circ}C$. But variations in weather cause fluctuations in the heating water temperature. The experimental results show our new system capable of maintaining the temperature difference within a ${\pm}0.5^{\circ}C$ range. So we believe that our new PFMFC fuel cell stack array is a good candidate for being used in residential heating systems.

• Journal of the Optical Society of Korea
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• v.9 no.1
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• pp.16-21
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• 2005

Using a cantilever type nanoprobe having a 100㎚m aperture at the apex of the pyramidal tip of a near-field scanning optical microscope (NSOM), nanopatterning of polymer films are conducted. Two different types of polymer, namely a positive photoresist (DPR-i5500) and an azopolymer (Poly disperse orange-3), spincoated on a silicon wafer are used as the substrate. A He-Cd laser with a wavelength of 442㎚ is employed as the illumination source. The optical near-field produced at the tip of the nanoprobe induces a photochemical reaction on the irradiated region, leading to the fabrication of nanostructures below the diffraction limit of the laser light. By controlling the process parameters properly, nanopatterns as small as 100㎚ are produced on both the photoresist and azopolymer samples. The shape and size variations of the nanopatterns are examined with respect to the key process parameters such as laser beam power, irradiation time or scanning speed of the probe, operation modes of the NSOM (DC and AC modes), etc. The characteristic features during the fabrication of ordered structures such as dot or line arrays using NSOM lithography are investigated. Not only the direct writing of nano array structures on the polymer films but also the fabrication of NSOM-written patterns on the silicon substrate were investigated by introducing a passivation layer over the silicon surface. Possible application of thereby developed NSOM lithography technology to the fabrication of data storage is discussed.

• Korean Journal of Materials Research
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• v.27 no.1
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• pp.32-38
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• 2017

Insulating $TaN_x$ films were grown by plasma enhanced atomic layer deposition using butylimido tris dimethylamido tantalum and $N_2+H_2$ mixed gas as metalorganic source and reactance gas, respectively. Crossbar devices having a $Pt/TaN_x/Pt$ stack were fabricated and their electrical properties were examined. The crossbar devices exhibited temperature-dependent nonlinear I (current) - V (voltage) characteristics in the temperature range of 90-300 K. Various electrical conduction mechanisms were adopted to understand the governing electrical conduction mechanism in the device. Among them, the PooleFrenkel emission model, which uses a bulk-limited conduction mechanism, may successfully fit with the I - V characteristics of the devices with 5- and 18-nm-thick $TaN_x$ films. Values of ~0.4 eV of trap energy and ~20 of dielectric constant were extracted from the fitting. These results can be well explained by the amorphous micro-structure and point defects, such as oxygen substitution ($O_N$) and interstitial nitrogen ($N_i$) in the $TaN_x$ films, which were revealed by transmission electron microscopy and UV-Visible spectroscopy. The nonlinear conduction characteristics of $TaN_x$ film can make this film useful as a selector device for a crossbar array of a resistive switching random access memory or a synaptic device.

• Korean Journal of Medicinal Crop Science
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• v.23 no.5
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• pp.385-394
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• 2015

Background : Dibenzocyclooctadiene lignans are secondary metabolites present abundantly in the fruits belonging to the genus Schisandra. According to previous studies, Schisandra lignans exhibit anti-inflammatory, anti-cancer and anti-diabetic properties, as well as an inhibitory effect on platelet aggregation. Therefore, establishing the Korean "Omija" (Schisandra chinensis) as a lignan-rich source, in addition to identifying and quantifying the lignans, is extremely valuable. Methods and Results : Dibenzocyclooctadiene lignans were analyzed with liquid chromatography using diode array detection/mass spectrometry, from methanol extracts subsequently identified by a constructed chemical library of 50 lignans. A total of 27 components of lignan including gomisin S were identified, of which schisandrin, gomisin A, gomisin N, deoxyschisandrin, ${\gamma}$-schisandrin, and schisandrin C were identified as the major components in the Korean Omija, Schisandra chinensis. These compounds were divided into two groups, S-biphenyl and R-biphenyl based on the configurations of the stereoisomers structures with contents of 661.7 and 1350.1mg per 100 g dry weight, respectively. The total lignan content averaged 2011.4mg per 100 g dry weight, of which schisandrin and gomisin N comprised the majority (771.8 and 420.5mg per 100 g dry weight respectively). Conclusions : Lignans which are present in high quantities in the ripe fruit of Schisandra chinensis are important functional compounds that play a major role in the prevention and treatment of human diseases.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2002.11a
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• pp.59-62
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• 2002

Wavelength selection and prediction algorithm for determining hematocrit are investigated. A model based on the difference in optical density induced by the pulsation of heart beat is developed by taking approximation of Twersky's theory on the assumption that the variation of blood vessel size is small during arterial pulsing[1]. A device is constructed with a five-wavelength LED array as light source. The selected wavelengths are two isobestic points and three in compensation for tissue scattering. Data are collected from 549 out-patients who are randomly grouped as calibration and prediction sets. The range of percent hematocrit was 19.3∼51.8. The ratio of the variations of optical density between systole and diastole at two different wavelengths is used as a variable. We selected several such variables that show high reproducibility among all variables. Multiple linear regression analysis is made. The relative percent error is 8% and the standard deviation is 3.67 for the calibration set. The relative % error and standard deviation of the prediction set are 8.2% and 3.69 respectively. We successfully demonstrate the possibility of non-invasive hematocrit measurement, particularly, using the wavelengths below 1000nm.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.8
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• pp.45-53
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• 1999

Electromagnetic scattering by finite number of conducting strips loaded on a grounded dielectric is considered for the TM polarization case from the viewpoints of transmitting(receiving) leaky wave antenna and grating coupler. An integro-differential equation whose unknowns are the induced currents over the strips is derived and solved by use of the method of moments. In order to construct the non-uniform leaky wave structures with specific source(current) distributions over the strips, distances between two adjacent strips and strip width are simultaneously varied along the structure. From some results for the current distributions over the strips and surface wave powers, it is observed that the maximum coupling efficiencies of the appropriately constructed non-uniform leaky wave structures from the viewpoints of both a receiving leaky wave antenna and a grating coupler amount upto 95%, which are about 15% improvements compared with those(80%) of the uniform structures.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.330-332
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• 2009

Highly stable bottom gate thin film transistors(TFTs) with a zinc indium tin oxide(Zn-In-Sn-O:ZITO) channel layer have been fabricated by rf-magnetron co-sputtering using a indium tin oxide(ITO:90/10), a tin oxide and a zinc oxide targets. The ZITO TFT (W/L=$40{\mu}m/20{\mu}m$) has a mobility of 24.6 $cm^2$/V.s, a subthreshold swing of 0.12V/dec., a turn-on voltage of -0.4V and an on/off ratio of >$10^9$. When gate field of $1.8{\times}10^5$ V/cm was applied with source-drain current of $3{\mu}A$ at $60^{\circ}C$, the threshold voltage shift was ~0.18 V after 135 hours. We fabricated AM-OLED driven by highly stable bottom gate Zn-In-Sn-O TFT array.

• The Journal of the Acoustical Society of Korea
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• v.36 no.3
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• pp.218-227
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• 2017

In this paper, an algorithm to calculate both bearing and distance error for target detection and localization is proposed using the Cramer Rao lower bound to estimate the minium variance of their error in DOA (Direction Of Arrival) estimation. The performance of arrays in detection and localization depends on the accuracy of DOA, which is affected by a variation of SNR (Signal to Noise Ratio). The SNR is determined by sonar parameters such as a SL (Source Level), TL (Transmission Loss), NL (Noise Level), array shape and beam steering angle. For verification of the suggested method, a Monte Carlo simulation was performed to probabilistically calculate the bearing and distance error according to the SNR which varies with the relative position of the target in space and noise level.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.239.1-239.1
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• 2012

This paper presents the results of one of early sciences with Korean VLBI Network (KVN): a large fringe survey of compact radio sources at 43GHz. We established the catalog of correlated flux densities in three ranges of baseline projection lengths of 637 sources from a 43 GHz (Q-band) survey observed with the Korean VLBI Network. Of them, 623 sources have not been observed before at Q-band with VLBI. The goal of this work in the early science phase of the new VLBI array is twofold: to evaluate the performance of the new instrument that operates in a frequency range of 22--129 GHz and to build a list of objects that can be used as targets and as calibrators. We have observed the list of 799 target sources with declinations down to $-40{\circ}$. Among them, 724 were observed before with VLBI at 22 GHz and had correlated flux densities greater than 200 mJy. The overall detection rate is 78%. The detection limit, defined as the minimum flux density for a source to be detected with 90% probability in a single observation, was in a range of 115--180 mJy depending on declination. However, some sources as weak as 70 mJy have been detected. Of 623 detected sources, 33 objects are detected for the first time in VLBI mode. We determined their coordinates with the median formal uncertainty 20 mas. The results of this work set the basis for future efforts to build the complete flux-limited sample of extragalactic sources at frequencies 22 GHz and higher at 3/4 of the celestial sphere.