• IEIE Transactions on Smart Processing and Computing
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• v.3 no.6
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• pp.416-424
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• 2014

This paper presents an 8-bit pipelined analog-to-digital converter. The supply voltage applied for comparators and other sub-blocks of the ADC were 0.7V and 0.5V, respectively. This low power ADC utilizes the capacitive charge pump technique combined with a source-follower and calibration to resolve the need for the opamp. The differential charge pump technique does not require any common mode feedback circuit. The entire structure of the ADC is based on fully dynamic circuits that enable the design of a very low power ADC. The ADC was designed to operate at 1MS/s in 90nm CMOS process, where simulated results using ADS2011 show the peak SNDR and SFDR of the ADC to be 47.8 dB (7.64 ENOB) and 59 dB respectively. The ADC consumes less than 1mW for all active dynamic and digital circuitries.

• Journal of Sensor Science and Technology
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• v.18 no.4
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• pp.307-310
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• 2009

This paper describes the formation of porous 3C-SiC by anodization. 3C-SiC thin films were deposited on p-type Si(100) substrates by APCVD using HMDS(Hexamethyildisilane: $Si_2(CH_3)_6$). UV-LED(380 nm) was used as a light source. The surface morphology was observed by SEM and the pore size was increased with increase of current density. Pore diameter of 70 $\sim$ 90 nm was achieved at 7.1 mA/cm$^2$ current density and 90 sec anodization time. FT-IR was conducted for chemical bonding of thin film and porous 3C-SiC. The Si-H bonding was observed in porous 3C-SiC around wavenumber 2100 cm$^{-1}$. PL shows the band gap enegry of thin film(2.5 eV) and porous 3C-SiC(2.7 eV).

• Polymer(Korea)
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• v.31 no.6
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• pp.461-468
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• 2007

In order to understand the structure of the existing aggregate in the nanocomposite, which has been prepared with polyester and trisilanolisobutyl polyhedral oligomeric silsesquioxane(TBPOSS), laser light scattering(LLS) and SEM-EDS were applied to its 1,1,1,3,3,3-hexafluoro-2-propanol solution and original sample, respectively. Although aggregate particles appeared as spherical shape of the average diameter of 120 nm in SEM image, they were not microgels but almost linear copolymer chains ($M_w=2.3{\times}10^6\;g/mol$) alternating 320 molecules of TBPOSS with polyester subchains. It has been microphase-separated from the matrix polyester due to the difference of chemical composition. As the matrix, polyester chain of $M_w=4.0{\times}10^4\;g/mol$ had averagely 2.5 molecules of TBPOSS per chain. It is also found that about 93% of total TBPOSS molecules existed in matrix phase and the residual 7% in spherically aggregated phase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.3
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• pp.292-296
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• 2022

(La_0.5Nd_0.2Sr_0.3)MnO₃ specimens were prepared by a solid-state reaction. In all specimens, X-ray diffraction patterns of an orthorhombic structure were shown. The fracture surfaces of (La_0.5Nd_0.2Sr_0.3)MnO₃ specimens showed a transgranular fracture pattern be possibly due to La ions (0.122 nm) as a perovskite A-site dopant substituting for Nd ions (0.115 nm) having a small ionic radius. The full-width at half maximum (FWHM) of the Mn 2p XPS spectra showed a value greater than that [8] of the single valence state, which is believed to be due to the overlapping of Mn²⁺, Mn³⁺, and Mn⁴⁺ ions. The dependence of Mn 2p spectra on the Mn³⁺/Mn⁴⁺ ratio according to sintering time was not observed. Electrical resistivity resulted in the minimum value of 100.7 Ω-cm for the specimen sintered for 9 hours. All specimens show a typical negative temperature coefficient of resistance (NTCR) characteristics. In the 9-hour sintered specimen, TCR, activation energy, and B25/65-value were -1.24%/℃, 0.19 eV, and 2,445 K, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.320-320
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• 2011

We describe fabrication of superhydrophobic surface on non-woven fabric (NWF) having nano-hairy structures and a hydrophobic surface coating. Oxygen plasma was irradiated on NWF for nano-texuring and a precursor of HMDSO (Hexamethydisiloxane) was introduced as a surface chemical modification for obtaining superhydrophobicity using 13.56 MHz radio frequency-Plasma Enhanced Chemical Vapor Deposition (rf-PECVD). O2 plasma treatment time was varied from 1 min to 60 min at a bias voltage of 400V, which fabricated pillar-like structures with diameter of 30 nm and height of 150 nm on NWF. Subsequently, hydrophobic coating using hexamethyldisiloxane vapor was deposited with 10 nm thickness on NWF substrate at a bias voltage of 400 V. We evaluate superhydrophobicity of the modified NWF with sessile drop using goniometer and high speed camera, in which aspect ratio of nanohairy structures, contact angle and contact angle hysteresis of the surfaces were measured. With the increase of aspect ratio, the wetting angle increased from $103^{\circ}$ to $163^{\circ}$, and the contact angle hysteresis decreased dramatically below $5^{\circ}$. In addition, we had conducted experiment for nucleation and condensation of water via E-SEM. During increasing vapor pressure inside E-SEM from 3.7 Torr to over 6 Torr which is beyond saturation point at $2^{\circ}C$, we observed condensation of water droplet on the superhydropobic NWF. While the condensation of water on oxygen plasma treated NWF (superhydrophilic) occurred easily and rapidly, superhydrophobic NWF which was fabricated by oxygen and HMDSO was hardly wet even under supersaturation condition. From the result of wetting experiment and water condensation via E-SEM, it is confirmed that superhydrophobic NWF shows the grate water repellent abilities.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.3
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• pp.191-196
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• 2016

In order to establish the basic data for the growth of fish in the aquaculture industry, the behavior analysis of rockfish (Sebastes inermis) depending on the temperature and LED lights was conducted. In this study, water temperatures were set from $3^{\circ}C$ to $30^{\circ}C$ were used. One red light (wave length: 622 nm; light power: 811 mW) and one green lights (wave length: 518 nm; light power: 648 mW) were used. Behavior of the rockfish was expressed as average moving distance (AMD) for 1 minutes and a rate of movement. The mean AMD depending on the temperature was 1.0 m and the mean rates of movement was 50%. The mean AMD were 1.5 m, 1.9 m and 0.7 m in the red LED light, green LED light and control condition respectively. The mean rates of movement were 54%, 65% and 45% in the red LED light, green LED light and control condition respectively.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.1
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• pp.120-125
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• 2010

For application of transparent bulletproof materials, the SLS(soda-lime-silicate) glass was heated by 2-step crystallization. The DTA curve for SLS glass revealed the nucleation and crystal growth temperature at about $575^{\circ}C$ and $675^{\circ}C$, respectively. The crystallized glass was heated at various conditions(temperature, time). As a result, the maximum nucleation and crystal growth rates were $3.8\times10^5/mm^3{\cdot}hr$ at $575^{\circ}C$ and 20.58nm/min at $680^{\circ}C$, respectively. The bending strength, fracture toughness and vickers hardness were 451.7MPa, $0.9388MPa{\cdot}m^{1/2}$, and $693.9H_v$ which were 201%, 31%, and 22% higher than parent glass, respectively. Surface image and transmittance of crystallized SLS glass were analyzed by optical microscopy and UV/VIS/NIR spectrophotometer. Transmittance of crystallized SLS glass at visible-range(200~800nm) was not changed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.3
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• pp.240-245
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• 2017

In order to study for the growth of fish in the aquaculture industry, the behavior analysis of rock bream (Oplegnathus fasciatus) depending on the temperature and LED lights was conducted. In this study, water temperatures from 10 to 30 degrees were used. One red light (wave length: 622 nm; light power: 811 mW) and one green light (wave length: 518 nm; light power: 648 mW) were used. Behavior of the rock bream was analyzed at an average moving distance for one minutes (AMD) and a rate of movement. The mean AMD were respectively 5.3 m, 7.3 m and 3.0 m in the red LED light, green LED light and control condition. The mean rates of movement were 77%, 88% and 61% respectively in the red LED light, green LED light and control condition. The mean AMD during 24 hours were 3.1 m, 3.1 m and 3.3 m respectively in the red LED light, green LED light and control condition.

• Journal of Electrochemical Science and Technology
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• v.14 no.1
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• pp.15-20
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• 2023

Ionic liquids are considered as a promising, alternative solvent for the electrochemical synthesis of metals because of their high thermal and chemical stability, relatively high ionic conductivity, and wide electrochemical window. In particular, their wide electrochemical window enables the electrodeposition of metals without any side reaction of electrolytes such as hydrogen evolution. The electrodeposition of silver is conducted in 1-n-butyl-3-methylimidazolium chloride ([C4mim]Cl) ionic liquid system with a silver source of AgCl. This study is the first attempt to electrodeposit silver nanoparticles without using co-solvents other than [C4mim]Cl. Pulse electrolysis is employed for the synthesis of silver nanoparticles by varying applied potentials from -3.0 V to -4.5 V (vs. Pt-quasi reference electrode) and pulse duration from 0.1 s to 0.7 s. Accordingly, the silver nanoparticles whose size ranges from 15 nm to ~100 nm are obtained. The successful preparation of silver nanoparticles is demonstrated regardless of the kinds of substrate including aluminum, stainless steel, and carbon paper in the pulse electrolysis. Finally, the antimicrobial property of electrodeposited silver nanoparticles is confirmed by an antimicrobial test using Staphylococcus aureus.

• Atmosphere
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• v.21 no.2
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• pp.131-142
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• 2011

Spectral solar irradiances were observed using a visible and UV Multi-Filter Rotating Shadowband Radiometer on the rooftop of the Science Building at Yonsei University, Seoul ($37.57^{\circ}N$, $126.98^{\circ}E$, 86 m) during one year period in 2006. 1-min measurements of global(total) and diffuse solar irradiances over the solar zenith angle (SZA) ranges from $20^{\circ}$ to $70^{\circ}$ were used to examine the effects of clouds and total optical depth (TOD) on enhancing four solar irradiance components (broadband 395-955 nm, UV channel 304.5 nm, visible channel 495.2 nm, and infrared channel 869.2 nm) together with the sky camera images for the assessment of cloud conditions at the time of each measurement. The obtained clear-sky irradiance measurements were used for empirical model of clear-sky irradiance with the cosine of the solar zenith angle (SZA) as an independent variable. These developed models produce continuous estimates of global and diffuse solar irradiances for clear sky. Then, the clear-sky irradiances are used to estimate the effects of clouds and TOD on the enhancement of surface solar irradiance as a difference between the measured and the estimated clear-sky values. It was found that the enhancements occur at TODs less than 1.0 (i.e. transmissivity greater than 37%) when solar disk was not obscured or obscured by optically thin clouds. Although the TOD is less than 1.0, the probability of the occurrence for the enhancements shows 50~65% depending on four different solar radiation components with the low UV irradiance. The cumulus types such as stratoculmus and altoculumus were found to produce localized enhancement of broadband global solar irradiance of up to 36.0% at TOD of 0.43 under overcast skies (cloud cover 90%) when direct solar beam was unobstructed through the broken clouds. However, those same type clouds were found to attenuate up to 80% of the incoming global solar irradiance at TOD of about 7.0. The maximum global UV enhancement was only 3.8% which is much lower than those of other three solar components because of the light scattering efficiency of cloud drops. It was shown that the most of the enhancements occurred under cloud cover from 40 to 90%. The broadband global enhancement greater than 20% occurred for SZAs ranging from 28 to $62^{\circ}$. The broadband diffuse irradiance has been increased up to 467.8% (TOD 0.34) by clouds. In the case of channel 869.0 nm, the maximum diffuse enhancement was 609.5%. Thus, it is required to measure irradiance for various cloud conditions in order to obtain climatological values, to trace the differences among cloud types, and to eventually estimate the influence on solar irradiance by cloud characteristics.