• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1035-1041
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• 2002

The adhesion characteristics of adsorbent during impregnation of Y-type and ZSM-5type zeolites into ceramic paper were analyzed, as the amount of silica sol in slurry for impregnation was varied. 31 wt% of zeolite particle, which is useful for VOC adsorption, was evenly dispersed and adhered on ceramic paper and original crystal structure of the zeolite remained unchanged even after binder application and heat treatment. Surface area of the impregnated ceramic paper was decreased compared with that of zeolite powder. And it was found to be attributed to the reduction of volume of mesopore while the volume of micropore under $20{\AA}$ was unchanged. Zeolite-impregnated honeycomb cylinder, whose diameter and length were 10 cm and 40 cm, respectively, was subjected to adsorption/desorption test with respect to toluene, MEK, cyclohexanone. All of the VOC's were removed by adsorption with efficiency higher than 97% and from the static adsorption test, $42 Nm^3/h$ of 300 ppmv-VOC-laden air was calculated be treated continuously, when the honeycomb was used in an adsorptive rotor system.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.4
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• pp.150-155
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• 2020

Alumina (Al₂O₃) is mainly used as a structural ceramic material and to have good mechanical properties requires a dense microstructure. In commercial fabrication, the liquid phase sintering process is adjusted to reduce the sintering temperature of alumina. In this study, the effect of added amounts of cobalt oxide as a coloring agent on the microstructure and mechanical properties was investigated in the CaO-SiO₂-MgO-system liquid phase sintering of 92 % alumina at various sintering temperatures. When 11 wt% Co₂O₃ was added, a rearrangement of alumina particles, which is the main densification step in liquid phase sintering, occurred from a sintering temperature of 1200℃. Solution re-precipitation and coalescence steps followed from 1300℃ with the grain growth of alumina particles. The addition of excess Co₂O₃ and sintering temperatures above 1400℃ resulted in a decrease in sintered density and Vickers hardness, because of the low viscosity of the liquid phase. In 92 % alumina with the addition of 11 wt% Co₂O₃, a sintered density and Vickers hardness of 3.86 g/㎤ and 12.32 GPa, respectively, were obtained at a sintering temperature of 1350℃.

• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.2
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• pp.145-151
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• 2014

The goal of this study was to describe dental consultation of pediatric inpatients to the department of pediatric dentistry at Yonsei University Severance Hospital. 391 dental consultations at Yonsei University Severance Hospital referred to pediatric dentistry in the year 2012 were included in this study. Consultations were categorized according to patients' gender, age, chief complaint, referred department and diagnosis. 288 patients (166 males and 122 females) with an average age of 5.9 were referred to the Department of Pediatric Dentistry. 129 cases (33.1%) from Department of Rehabilitation Medicine, 80 cases (20.5%) from Pediatric Hematology- Oncology, 51 cases (13.0%) from Pediatric Cardiology, and 44 cases (11.3%) from Pediatric Neurology. Chief complaints were ranked from oral examination (39.7%), dental caries (14.0%), pre-operative evaluation (12.8%) and others (33.5%); including oral pain, trauma, tooth mobility, orthodontic treatment, self-injury, fabrication of obturator and etc. Dental consultations should be encouraged as dental care and treatment could affect the control of systemic diseases of admitted patients. Pediatric inpatients have been referred to pediatric dentistry for not only comprehensive oral exam but also various chief complaints. The most frequent dental diagnosis made and treatment performed were dental caries and non-invasive/preventive care respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.1
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• pp.81-88
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• 2003

For driver's convenience, the ACC(Adaptive Cruise Control) requires a system which determines the direction of vehicles and controls the vehicle to keep the distance among the automobiles constant. This paper describes the microstrip array antennas designed to operate at 24 GHz, and used as a direction indicator of moving vehicles. 8${\times}$2 transmit array antenna with wide beamwidth, 8${\times}$4 receive center array antenna, and two 8${\times}$8 receive array antennas with narrow beamwidth were designed and fabricated. Measurement results for the arrays showed that the azimuthal beamwidth is 50$^{\circ}$and the gain is 16.7 dBi for the transmit array antenna. For the receive array antenna, the center, the left, and the right array antenna have beamwidths of 20$^{\circ}$, 13$^{\circ}$, 13$^{\circ}$respectively, and have gains of more than 20 dBi. The left and right array antenna have the beam tilt angle of ${\pm}$18$^{\circ}$. The measured radiation patterns showed a good agreement with the simulated patterns, and the designed array antennas are suitable fur detecting 3 directions of the vehicle within the scan angle area.

• KSBB Journal
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• v.23 no.3
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• pp.263-270
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• 2008

A poly-(dimethylsiloxane) (PDMS) surface modified by the successive deposition of the polyelectrolytes, poly-(allylamine hydrochloride) (PAH), poly-(diallyldimethylammoniumchloride) (PDAC), poly-(4-ammonium styrenesulfonic acid) (PSS), and poly-(acrylic acid) (PAA), was presented for the application of selective cell immobilization. It is formed via electrostatic attraction between adjacent layers of opposite charge. The modified PDMS surface was examined using static contact angle measurements and fourier transform infrared (FT-IR) spectrophotometer. The wettability of the PDMS surface could be easily controlled and functionalized to be biocompatible through regulation of layer numbers. The modified PDMS surface provides appropriate environment for adhesion to cells, which is essential technology for cell patterning with high yield and viability in the patterning process. This method is reproducible, convenient, and rapid. It could be applied to the fabrication of biological sensing, patterning, microelectronics devices, screening system, and study of cell-surface interaction.

• Archives of design research
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• v.13 no.4
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• pp.233-242
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• 2000

The traditional image of hydraulic excavator started to change in two ways since 1990. First, post-heavy equipment's visual image was new waves to traditional image of heavy, strong, and wild. They are the negative aspect that excavators have. Another movement of getting rid of its negative image can be found in late-heavy equipment, which was intended to adapt traditional and positive, but off negative images. In 1990s, the design trend is moving from warm/hard to warm/soft, and KOBELCO can be exceptional example that went even further, gone up to cool-soft image. KOBELCO specially aimed 'post- excavator image' strategy, which has been successful. Image of cabin as a human space changed little bit further than outside image. Each company tried to differentiate the design of cabin focusing on its safety. Following paragraphs show specific trend of image change in form, colour, texture, and the composition. Major visual image change in form tries to follow the image of cars and home appliances which are showing the movement from tough and hard image to soft one. Structural change on local image shows the movement from angular edge to edgeless and the movement of cabin's pillar C placed to back of the equipment with gentle inclination. All of these movements are the result of effort to improve traditional excavator's negative image, that top structure is assembled separately, to positive ones. Today's tendency about its color becomes important to apply two different colour styles. Each style has brightness and tone comparison. As an enormous power convey system, it was in common that its brightness comparison was useful because of the alarm of its damage possibility. However, as its colour control and its design have been emphasized gradually, the tone comparison takes a part in an important role, too. As an example, there is an occasion that these comparisons are compromised simultaneously. In the respect of its image creation, its texture treatments make the tendency of being the same as passenger cars. It is caused from its development of the manufacture techniques of from the fabrication method in small business to the press method in big firm. Further, it is also because of its improvement of painting & coating skills. It may prohibit the reflection effect from solar rays. In the point of view of its visual images, it is recognized the prominent tendency that its composition has been gradually decreased. Lots of windows and the frames tends dark-colour as a whole. It is more preferred to have one colour image, but except KOBELCO and HITACHI. As well, there is another high-tendency to improve its standard treatments, especially for its corner and texture treatments.

• Applied Chemistry for Engineering
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• v.24 no.2
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• pp.165-170
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• 2013

An external gelation method in place of an internal gelation method applied to the fabrication process of an intermediated compound of Uranium Oxy-Carbide (UCO) kernel spheres for Very High Temperature Reactor (VHTR) fuel preparation is under development in Korea. For the preliminary experiments of the UCO kernel sphere preparation using an external gelation method, the carbon black dispersion experiments were carried out using a simulated broth solution. From the selection experiments of various kinds of carbon black through dispersion experiments in a viscous metal salt solution, Cabot G carbon black was selected owing to its dispersion stability, and the homogeneous dispersing state of carbon black particles in our system. For the effective dispersion of nano-size aggregated carbon black particles in a high viscous liquid, the carbon black particles in a metal salt solution were first de-aggregated with ultrasonic force. The mixed solution was then dispersed secondly by the use of the extremely high-speed agitation with a mechanical mixer of 6000 rpm after feeding the Poly Vinyl Alcohol (PVA) in the solution. This results in the broth solution with good stability and homogeneity alongside no further changes in physical properties.

• Membrane Journal
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• v.28 no.1
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• pp.75-82
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• 2018

Forward osmosis (FO) desalination system has been highlighted to improve the energy efficiency and drive down the carbon footprint of current reverse osmosis (RO) desalination technology. To improve the trade-off between water flux and salt rejection of thin film composite (TFC) desalination membrane, thin film nanocomposite membranes (TFN), in which nanomaterials as a filler are embeded within a polymeric matrix, are being explored to tailor the separation performance and add new functionality to membranes for water purification applications. The objective of this article is to develop a graphene nanocomposite membrane with high performance of water selective permeability (high water flux, high salt rejection, and low reverse solute diffusion) as a next-generation FO desalination membrane. For advances in fabrication of graphene oxide (GO) membranes, layer-by-layer (LBL) technique was used to control the desirable structure, alignment, and chemical functionality that can lead to ultrahigh-permeability membranes due to highly selective transport of water molecules. In this study, the GO nanocomposite membrane fabricated by LBL dip coating method showed high water flux ($J_w/{\Delta}{\pi}=2.51LMH/bar$), water selectivity ($J_w/J_s=8.3L/g$), and salt rejection (99.5%) as well as high stability in aqueous solution and under FO operation condition.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.606-610
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• 2010

Films consisting of a silicon quantum dot superlattice were fabricated by alternating deposition of silicon rich silicon nitride and $Si_3N_4$ layers using an rf magnetron co-sputtering system. In order to use the silicon quantum dot super lattice structure for third generation multi junction solar cell applications, it is important to control the dot size. Moreover, silicon quantum dots have to be in a regularly spaced array in the dielectric matrix material for in order to allow for effective carrier transport. In this study, therefore, we fabricated silicon quantum dot superlattice films under various conditions and investigated crystallization behavior of the silicon quantum dot super lattice structure. Fourier transform infrared spectroscopy (FTIR) spectra showed an increased intensity of the $840\;cm^{-1}$ peak with increasing annealing temperature due to the increase in the number of Si-N bonds. A more conspicuous characteristic of this process is the increased intensity of the $1100\;cm^{-1}$ peak. This peak was attributed to annealing induced reordering in the films that led to increased Si-$N_4$ bonding. X-ray photoelectron spectroscopy (XPS) analysis showed that peak position was shifted to higher bonding energy as silicon 2p bonding energy changed. This transition is related to the formation of silicon quantum dots. Transmission electron microscopy (TEM) and electron spin resonance (ESR) analysis also confirmed the formation of silicon quantum dots. This study revealed that post annealing at $1100^{\circ}C$ for at least one hour is necessary to precipitate the silicon quantum dots in the $SiN_x$ matrix.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.586-591
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• 2010

Solar cells have been more intensely studied as part of the effort to find alternatives to fossil fuels as power sources. The progression of the first two generations of solar cells has seen a sacrifice of higher efficiency for more economic use of materials. The use of a single junction makes both these types of cells lose power in two major ways: by the non-absorption of incident light of energy below the band gap; and by the dissipation by heat loss of light energy in excess of the band gap. Therefore, multi junction solar cells have been proposed as a solution to this problem. However, the $1^{st}$ and $2^{nd}$ generation solar cells have efficiency limits because a photon makes just one electron-hole pair. Fabrication of all-silicon tandem cells using an Si quantum dot superlattice structure (QD SLS) is one possible suggestion. In this study, an $SiO_x$ matrix system was investigated and analyzed for potential use as an all-silicon multi-junction solar cell. Si quantum dots with a super lattice structure (Si QD SLS) were prepared by alternating deposition of Si rich oxide (SRO; $SiO_x$ (x = 0.8, 1.12)) and $SiO_2$ layers using RF magnetron co-sputtering and subsequent annealing at temperatures between 800 and $1,100^{\circ}C$ under nitrogen ambient. Annealing temperatures and times affected the formation of Si QDs in the SRO film. Fourier transform infrared spectroscopy (FTIR) spectra and x-ray photoelectron spectroscopy (XPS) revealed that nanocrystalline Si QDs started to precipitate after annealing at $1,100^{\circ}C$ for one hour. Transmission electron microscopy (TEM) images clearly showed SRO/$SiO_2$ SLS and Si QDs formation in each 4, 6, and 8 nm SRO layer after annealing at $1,100^{\circ}C$ for two hours. The systematic investigation of precipitation behavior of Si QDs in $SiO_2$ matrices is presented.