• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1183-1184
• /
• 2006

Core loss of soft magnetic powder cores have been focused on to achieve high efficiency of power supplies. In this study the effects of crystal grain size on core loss were investigated by changing heat treatment conditions. It was found that core loss is influenced by crystal grain size because eddy current loss decreased and hysteresis loss increased by making crystal grain size smaller, and it is also influenced by particle size.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2002.11a
• /
• pp.51-54
• /
• 2002

This study is intended to investigate an influence of the kinds and the maximum size of aggregate on the compressive strength of small size core specimen. According to the results, the compressive strength of standard specimen is large in order of basalt, granite and limestone aggregate, and shows increasing tendency as the maximum size of aggregate grows large. The compressive strength of concrete using basalt aggregate shows similar tendency to granite aggregate, and that of concrete using limestone aggregate decreases slightly, compared with granite aggregate. The reducing ratio of the compressive strength of 25mm core specimen is least when the maximum size of aggregate is 10mm. But the compressive strength of 50 and 100mm core specimen is almost not influenced by the maximum size of aggregate.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.7 no.4
• /
• pp.709-714
• /
• 2006

The propose of this study was to investigate the feasibility of using waste lime core to remove phosphorus from wastewater in continuous flow reaction. The phosphorus was found to be removed from municipal wastewater by hydroxyapatite crystallization and precipation. Waste lime core size 1, 2 showed phosphorus removal rate of about 90% during early 11 hrs of run time. In addition, breakpoint time was decreased by increased inflow rate regardless of waste lime core size.

• Journal of the Korean Society for Heat Treatment
• /
• v.16 no.4
• /
• pp.197-204
• /
• 2003

Honeycomb structure has been fabricated by brazing method using 0.1 wt%C and 1.0wt%C carbon steel core and STS304 stainless steel face sheet. Core shear strength ratio in W and L directions was 1:1.03 in 7 mm cell size, whereas 1:1.45 in 4 mm cell size. Flexural strength on face sheet was 166.4 MPa (0.1 wt%C, W direction), 171.1 MPa (0.1 wt%C, L direction), and 120.2 MPa (1.0 wt%C, W direction) in 7 mm cell size. And in 4mm cell size specimen, it was 169.2 MPa (0.1 wt%C, W direction), 224.2 MPa (0.1 wt%C, L direction). This means that flexural strength of 0.1 wt%C core material was higher than that of 1.0wt%C core material, which was contrary to expectation. SEM and EDS analysis represented that grain boundary diffusion had occurred in0.1 wt%C core, but no grain boundary diffusion in 1.0 wt%C core. And corrugated surface of 0.1 wt%C core was flat, whereas that of 1.0 wt%C core was not flat. As a result, contact area between two 1.0 wt%C cores was much less than that of 0.1 wt% cores, It is thought to be main reason for lower flexural strength of 1.0 wt%C core.

• Journal of the Semiconductor & Display Technology
• /
• v.20 no.3
• /
• pp.11-17
• /
• 2021

I performed a semi-analytical numerical analysis of the effects of core size and electric field intensity on the light emission wavelength of CdSe/ZnS quantum dots (QDs). The analysis used a quantum mechanical approach; I solved the Schrödinger equation describing the electron-hole pairs of QDs. The numerical solutions are described using a basis set composed of the eigenstates of the Schrödinger equation; they are thus equivalent to analytical solutions. This semi-analytical numerical method made it simple and reliable to evaluate the dependency of QD characteristics on the QD core size and electric field intensity. As the QD core diameter changed from 9.9 to 2.5 nm, the light emission wavelength of CdSe core-only QDs varied from 262.9 to 643.8 nm, and that of CdSe/ZnS core/shell QDs from 279.9 to 697.2 nm. On application of an electric field of 8 × 10⁵ V/cm, the emission wavelengths of green-emitting CdSe and CdSe/ZnS QDs increased by 7.7 and 3.8 nm, respectively. This semi-analytical numerical analysis will aid the choice of QD size and material, and promote the development of improved QD light-emitting devices.

• Bulletin of the Korean Chemical Society
• /
• v.23 no.6
• /
• pp.872-879
• /
• 2002

One of the improtant characteristics of core-shell type nanoparticles is the long-term storage and reuse as an aqueous injection solution when required. For this reason, reconstruction of lyophilized core-shell type nanoparticles is considered to be essential . BAB type triblock copolymers differ from AB type diblock copolymers, which contain the A block as a hydrophilic part and the B block as a hydrophobic part. by not being easily redistributed into phosphate-buffered saline (PBS, pH 7.4, 0.1 M). Therefore, lyophilized core-shell type nanoparticles of CEC triblock copolymer were reconstituted using a somication process with a bar-type sonicator in combination with a freezing-thawing process. Soncation for 30s only resuspended CEC nanoparticles in PBS; their particle size distribution showed a monomodal pattern with narrow size distribution. The bimodal size distribution pattern and the aggregates were reduced by further sonication for 120 s but these nanoparticles showed a wide size distribution. The initial burst of drug release was increased by reconstitution process. The reconstitution of CEC core-shell type nanoparticles by freezing-thawing resulted in trimodal distribution pattern and formed aggregates, although freezing-thawing process was easier than sonication . Drug release form CEC nanoparticles prepared by freezing-thawing was slower than from the original dialysis solution. Although core-shell typenanoparticles of CEC triblock copolymers were not easily performed. Cytotoxicity testing of core-shell type nanoparticles of CEC-2 triblock copolymers containing clonazepam (CNZ) was performed using L929 cells. Cytotoxicity of CNZ was decreased by incorporation into nanoparticles.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.611-614
• /
• 2005

This study concerns the strength of concrete cores drilled from existing structures. The test factors are core size, drilled position of core, concrete age and concrete strength. The test results are as follows; (1) Under the filled condition of curing, concrete strength for three years are larger than that of 28 days by $15\~20\%$ (2) According to the core size effect from diameter of 75mm to 150mm , the variation of core strength are by $8\~18\%$ (3) According to the wall height of 1m, the strength of lower point of wall is than larger that of the upper point by $5\~20\%$. (4) In Accessing the core strength of concrete as a basis, the effect of core size and drilling position should be considered.

• Transactions of the Korean hydrogen and new energy society
• /
• v.28 no.6
• /
• pp.663-668
• /
• 2017

SOFC anode fabricated core-shell using machano-fusion method using core with submicron size Ni, nano size YSZ for shell. Using prepared core-shell, depending on the thickness of the shell, we studied how the characteristics of sintering and SOFC cell change by sintering the anode. The Ni-YSZ core-shell has a Ni core of 0.5 to $1.2{\mu}m$ over 2 to 7 YSZ of 15 to 20 nm is, and as the high speed mixing time increases, the YSZ number increases and the shell thickness becomes uniform increased. When the fuel electrode is manufactured with core-shell, it has superior sintering property, has grain of uniform size compared with the one synthesized by general mixing, the falling path is short, the conductors (electrons and ions) connection is excellent, the electrical conductivity has become excellent. The thicker the shell, the lower the electrical conductivity. When the thickness of shell ranged from 46 to 139 nm and 61 to 81 nm, the performance was the highest and the ASR was the smallest.

• Korean Journal of Materials Research
• /
• v.22 no.6
• /
• pp.298-302
• /
• 2012

Fe/$SiO_2$ core-shell type composite nanoparticles have been synthesized using a reverse micelle process combined with metal alkoxide hydrolysis and condensation. Nano-sized $SiO_2$ composite particles with a core-shell structure were prepared by arrested precipitation of Fe clusters in reverse micelles, followed by hydrolysis and condensation of organometallic precursors in micro-emulsion matrices. Microstructural and chemical analyses of Fe/$SiO_2$ core-shell type composite nanoparticles were carried out by TEM and EDS. The size of the particles and the thickness of the coating could be controlled by manipulating the relative rates of the hydrolysis and condensation reaction of TEOS within the micro-emulsion. The water/surfactant molar ratio influenced the Fe particle distribution of the core-shell composite particles, and the distribution of Fe particles was broadened as R increased. The particle size of Fe increased linearly with increasing $FeNO_3$ solution concentration. The average size of the cluster was found to depend on the micelle size, the nature of the solvent, and the concentration of the reagent. The average size of synthesized Fe/$SiO_2$ core-shell type composite nanoparticles was in a range of 10-30 nm and Fe particles were 1.5-7 nm in size. The effects of synthesis parameters, such as the molar ratio of water to TEOS and the molar ratio of water to surfactant, are discussed.

• Journal of Adhesion and Interface
• /
• v.3 no.4
• /
• pp.27-36
• /
• 2002

The organic/organic core-shell composite polymer for nonwomen binder were synthesized by stage polymerization of methyl methacrylate and styrene with ammonium persulfate after preparing monomer pre-emulsion in the presence of anionic surfactant. We study the effect of initiator concentration, $0.79{\times}10^{-3}{\sim}3.16{\times}10^{-3}mol/L$ for core polymer, $2.0{\times}10^{-4}{\sim}8.0{\times}10^{-4}mol/L$ for shell polymer, sulfactant concentration, $1.45{\times}10^{-5}{\sim}4.15{\times}10^{-5}mol/L$ for core polymer, $0.73{\times}10^{-5}{\sim}2.91{\times}10^{-5}mol/L$ for shell polymer on core-shell structure of polymethyl methacrylate/polystyrene and polystyrene/polymethyl methacrylate. Emulsion stability was major test method, particle size and particle size distribution were measured using particle size analyzer and the morphology of the core-shell composite polymer was determined using transmission electron microscope, glass temperature was also measured using differential scanning calorimeter.