• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.8
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• pp.8-14
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• 1998

A new process is developed to improve the electrical characteristics of high .beta. and low saturation voltage power transistor for lamp solenoid driver application. To prevent punch-through breakdown, appropriate combination of base doping and base width is necessary in the range of operating voltage of the circuit. The optimum values of base doping and sheet resistance are $Q_{D}$= $1.5{\times}10^{14}$atoms/$\textrm{cm}^2$ and $R_{s}$= 350 $\Omega/\square$ base wodtj $W_{B}$= $2.5{\mu}m$respectively. Under this condition it is possible to control $\beta$ of the transistor to 1500, maintaining $VB_{CBO}$ =200V. To reduce scattered distribution of .beta. of the devices on the wafer, it is necessary to improve emittter predeposition process. As a result, scattered distribution of .beta. of the devices on the wafer was reduced to 1/6 by using the new process. To improve collector to emitter forward voltage drop, $V_{ECF}$ of damper diode, an additional silicon etching process is used, which resulted in improving the value of $V_{eCF}$ from 2.8 V to 1.8V. With the suggested process superior device performance and higher yield are achieved.

• Journal of electromagnetic engineering and science
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• v.18 no.3
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• pp.188-198
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• 2018

In this study, we propose an approach for the design and satisfy the requirements of the fabrication of a small, lightweight, reliable, and stable ultra-wideband receiver for millimeter-wave bands and the contents of the approach. In this paper, we designed and fabricated a stable receiver with having low noise figure, flat gain characteristics, and low noise characteristics, suitable for millimeter-wave bands. The method uses the chip-and-wire process for the assembly and operation of a bare MMIC device. In order to compensate for the mismatch between the components used in the receiver, an amplifier, mixer, multiplier, and filter suitable for wideband frequency characteristics were designed and applied to the receiver. To improve the low frequency and narrow bandwidth of existing products, mathematical modeling of the wideband receiver was performed and based on this spurious signals generated from complex local oscillation signals were designed so as not to affect the RF path. In the ultra-wideband receiver, the gain was between 22.2 dB and 28.5 dB at Band A (input frequency, 18-26 GHz) with a flatness of approximately 6.3 dB, while the gain was between 21.9 dB and 26.0 dB at Band B (input frequency, 26-40 GHz) with a flatness of approximately 4.1 dB. The measured value of the noise figure at Band A was 7.92 dB and the maximum value of noise figure, measured at Band B was 8.58 dB. The leakage signal of the local oscillator (LO) was -97.3 dBm and -90 dBm at the 33 GHz and 44 GHz path, respectively. Measurement was made at the 15 GHz IF output of band A (LO, 33 GHz) and the suppression characteristic obtained through the measurement was approximately 30 dBc.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.2
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• pp.106-113
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• 2009

Recently, due to many industrial accidents at construction sites, a variety of researches for structural health monitoring (SHM) of buildings are progressing. For real site application of SHM, one of the advanced technologies has blown as wireless sensor networks (WSN). In this paper, we proposed WIVA(WSN Monitoring framework based on 3D Visualization and Augmented Reality in Mobile Devices) system that applies 3D visualization and AR technology to mobile devices with camera based on WSN in order to expand the extent of information can observe. Moreover, we performed experiments to validate effectiveness in 3D and AR mode that utilize WSN data based on IEEE 802.15.4. In real implementation scenario, we demonstrated a fire occurrence test in 3-story building miniature.

• Corrosion Science and Technology
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• v.20 no.5
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• pp.289-294
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• 2021

In this study, after measuring polarization characteristics of 97.3 wt% Ag, Au-Coated 97.3 wt% Ag (ACA) and 100 wt% Au wires in 1 wt% H₂SO₄ and 1 wt% HCl electrolytes at 25 ℃, corrosion rate and corrosion characteristics were comparatively analyzed. Comparing corrosion potential (E_CORR) values in sulfuric acid solution, ACA wire had more than six times higher E_CORR value than Au wire. Thus, it seems possible to use a broad applied voltage range of bonding wire for semiconductor packaging which ACA wire could be substituted for the Au wire. However, since the E_CORR value of ACA wire was three times lower than that of the Au wire in a hydrochloric acid solution, it was judged that the use range of the applied voltage and current of the bonding wire should be considered. In hydrochloric acid solution, 97.3 wt% Ag wire showed the highest corrosion rate, while ACA and Au showed similar corrosion rates. Additionally, in the case of sulfuric acid solution, all three types showed lower corrosion rates than those under the hydrochloric acid solution environment. The corrosion rate was higher in the order of 97.3 wt% Ag > ACA > 100 wt% Au wires.

• Journal of Microbiology and Biotechnology
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• v.28 no.11
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• pp.1782-1790
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• 2018

Assessment of microorganism viability is useful in many industrial fields. A large number of methods associated with the use of fluorescent probes have been developed, including fluorimetry, fluorescence microscopy, and cytometry. In this study, a microvolume spectrofluorometer was used to measure the membrane potential variations of Escherichia coli. In order to estimate the sensitivity of the device, the membrane potential of E. coli was artificially disrupted using an ionophore agent: carbonyl cyanide 3-chlorophenylhydrazone. The membrane potential was evaluated using two ratiometric methods: a Rhodamine 123/4',6-diamidino-2-phenylindole combination and a JC-10 ratiometric probe. These methods were used to study the impact of freezing on E. coli, and were compared with the conventional enumeration method. The results showed that it was beneficial to use this compact, easy-to-use, and inexpensive spectrofluorometer to assess the viability of bacterial cells via their membrane potential.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.469-474
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• 2006

A $1{\times}16$ thermo-optic switch with small excess loss using multimode interference(MMI) couplers is designed, fabricated, and measured. This paper introduces the proposed $1{\times}16$ thermo-optic switch, and discusses the measurement results. The $1{\times}16$ thermo-optic switch is farmed as 4-stage which consists of 15 unit devices. The unit devices are the $2{\times}2$ thermo-optic switches with Mach-Zehnder interferometer(MZI) structure. The characteristics of the $1{\times}16$ thermo-optic switch depends strongly on each unit device. The unit deviceconsists of two 3-dB general interference MMI couplers and two single mode waveguide arms as a phase shifter. First of all, the 3-dB optical splitter and $2{\times}2$ MZI thermo-optic switch have been tested to confirm the characteristics of the unit devices of the $1{\times}16$ MZI thermo-optic switch. Using the measurement results of the unit devices, the $1{\times}16$ MZI thermo-optic switch can be produced with better characteristics. The resultant structure of the MMI coupler with the optical light source of wavelength of 1550nm for the $1{\times}16$ thermo-optic switch is that the width and the optimized length are $25{\mu}m\;and\;1580{\mu}m$, respectively. The smallest excess loss fur the unit device is -0.5dB and the average excess loss is -0.7dB.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.63.1-63.1
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• 2015

The next generation electronics need to not only be smaller but also be more flexible. To meet such demands, van der Waals (vdW) heterostructures using two dimensional (2D) atomic crystals such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs) have been attracted intensely. In particular, for high performance of vdW heterostructures device, ultraclean interface between stacked 2D atomic crystals should be guaranteed. In this talk, I will present fabrication and characterization of the vdW field effect transistors toward performance enhancement by employing TMDCs channel, h-BN insulating layer and graphene electrode. Furthermore, it will also be introduced the characterization and surface engineering of graphene for gas molecule sensor.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.8
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• pp.853-862
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• 2012

The present study develops a method for directly measuring the temperature field in the primary deformation zone with a high spatial resolution during 2-D orthogonal machining. This is enabled by the use of a high-speed, charge-coupled device (CCD) based, infra-red (IR) imaging system which allows characteristics of the temperature field such as the location and magnitude of the highest temperature and temperature gradient in the primary deformation zone to be identified. Based on these data, the relation between the machining temperature and the cutting conditions is investigated.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.398.2-398.2
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• 2002

A column switching HPLC assay was developed to allow the separation and quantitation of cetirizine in human plasma by ultraviolet (UV) detection. Plasma samples were prepared by liquid-liquid extraction. After drying, the residue was reconstituted in 20 mM phosphate buffer (pH 2.8) containing 15% acetonitrile. The samples were initially injected onto a clean-up Capcell Pak MF C18 column. (50 mm $\times$ 4.6 mm I.D.), and the chromatographic region containing the peaks of interest was followed in an analytical C18 microcolumn (250 mm$\times$1.5 mm I. D.) via column switching device. (omitted)

• Journal of the Korea Computer Graphics Society
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• v.27 no.2
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• pp.1-11
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• 2021

In a virtual environment, a 3D workspace and 3D interaction are possible, but most virtual reality applications use a 2D color picker. This paper implements a 3D color picker based on 3D color space in a virtual environment, and compares color selection performance with the existing 2D color picker. The 3D color picker is intuitive by using the 3D color space as it is, and it can position the 3D pointer at a specific point in the color space using a controller, which is a virtual reality device, so a user can select a color in one step. On the other hand, the 2D color picker has the advantage of being familiar with existing users who work with colors in a computer environment, but has a disadvantage that requires several steps of user interaction since it has to set color properties through 2D interfaces. Based on user experiments, we confirmed the usefulness of a 3D color picker in addition to a 2D color picker in a virtual environment, and it was possible to perform natural 3D work in a virtual environment using the 3D color picker.