• Journal of Periodontal and Implant Science
• /
• 제28권1호
• /
• pp.87-102
• /
• 1998

The purpose of this stuffy was to assess and compare the osseous responses to implanted particles of porous synthetic HA (Interpore $200^{(R)}$, Interpore International, U.S.A.), resorbable natural bovine derived HA (Bio-$oss^{(R)}$, Gestlich Pharma, Switzerland) and calcium carbonate(Biocoral $450^{(R)}$, Inoteb, France) in bone defects. Four calvarial defects of 2.5mm diameter were created in earth of 16 Sprague-Dawley rats. The experimental materials were subsequently implanted hi three defects, leaving the fourth defect for control purpose. Four animals were earth sacrificed at 3 days, 1week, 2weeks and 4 weeks after surgery. The tissue response was evaluated under light microscope. Overall, histologic responses showed that all the particles were well tolerated and caused no aberrent tissue responses. There were difference in the amount of newly formed bone at the experimental sites and control site. There was more new bone formation associated with calcium carbonate site. In addition, the calcium carbonate site displayed multinucleated giant cells surrounding calcium carbonate particles after the 1st week, and osteoid tissue within the particle after the 2nd week. After 4 weeks, calcium carbonate particles were resorbed and replaced with new bone. The healing of the natural bovine derived HA site was similar to that of porous synthetic HA, except that new bone growth between the two particles have progressed more in the former site after the 2nd week. In the natural bovine derived HA site, the particle was surrounded by newly formed bone after the 4th week. After 4 weeks, the control site showed more mature bone than other sites. In conclusion, the grafted site were better in new bone formation than non-grafted sites. In particular the calcium Carbonate site showed the ability of osteoinduction and natural bovine denver HA showed osteoconduction in rat calvarial defects. This suggest that calcium carbonate and natural bovine derived HA could enhance the regenerative potential in periodontal defects.

• 펄프종이기술
• /
• 제41권1호
• /
• pp.24-29
• /
• 2009

The use of fluorescent whitening agents (FWAs) increases as the demand for the whiter and brighter printing papers increases. FWAs are used as internal and surface treatment chemicals. FWAs that are not used properly in the papermaking process, however, remain in the process water and may demage the paper quality and processes. In this study, a new idea to eliminate FWAs from the process water, consisted of the floc formation of FWAs with cationic chemicals, such as cationic polyelectrolytes and alum, and the removal of the floc by screening or sedimentation, was proposed. Flocculation of FWAs, that is the first step to remove FWAs from the process water, was investigated using turbidity and particle size measurement. Relationship between turbidity and particle size showed that the turbidity could reflect the particle size change of FWA flocs and was proper for the evaluation of flocculation phenomena. Poly-DADMAC was more efficient than PEI to induce the flocculation of FWAs. Alum was effective chemical for the flocculation and sedimentation of FWAs.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
• /
• pp.571-572
• /
• 2006

Tungsten CMP needs interconnect of semiconductor device ULSI chip and metal plug formation, CMP technology is essential indispensable method for local planarization. This Slurry development also for tungsten CMP is important, slurry of metal wiring material that is used present is depending real condition abroad. It is target that this research makes slurry of efficiency that overmatch slurry that is such than existing because focus and use colloidal silica by abrasive particle to internal production technology development. Compared selectivity of slurry that is developed with competitor slurry using 8" tungsten wafer and 8" oxide wafer in this experiment. And removal rate measures about density change of $H_2O_2$ and Fe particle. Also, corrosion potential and current density measure about Fe ion and Fe particle. As a result, selectivity find 83:1, and expressed similar removal rate and corrosion potential and current density value comparing with competitor slurry.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2006년도 춘계학술대회
• /
• pp.425-428
• /
• 2006

Natural gas hydrate has been a major problem for its plugging nature in the pipeline. With the demand of deep-water production, the importance of flow assurance technology, preventing hydrate, asphaltene and wax in the pipeline becomes bigger Kinetic models combined with the flow simulator are being developed to explain the nature of hydrate plug formation in the pipeline. To simulate the hydrate plug formation, each stage including the nucleation, growth and agglomeration should be considered. The hydrate nucleation is known to be stochastic and is believed hard to be predicted. Recent publications showed hydrate growth and agglomeration can be observed rigorously using a particle size analyzer. However properties of the hydrate should be investigated to model the growth and agglomeration. The attractive force between hydrate particles, supposed to be the capillary force, was revealed to be stochastic. Alternative way to model the hydrate agglomeration is to simulate by the discrete element method. Those parameters, particle size distribution, attractive force, and growth rate are embedded into the kinetic model which is combined Into the flow simulator. When compared with the flowloop experimental data, hydrate kinetic model combined into a flow simulator showed good results. With the early results, the hydrate kinetic model is promising but needs more efforts to improve it.

• 한국재료학회지
• /
• 제31권6호
• /
• pp.313-319
• /
• 2021

Understanding of effects of changes in the particle size of the matrix material on the mullite whisker growth during the production of porous mullite is crucial for better design of new porous ceramics materials in different applications. Commercially, raw materials such as Al₂O₃/SiO₂ and Al(OH)₃/SiO₂ are used as starting materials, while AlF₃ is added to fabricate porous mullite through reaction sintering process. When Al₂O₃ is used as a starting material, a porous microstructure can be identified, but a more developed needle shaped microstructure is identified in the specimen using Al(OH)₃, which has excellent reactivity. The specimen using Al₂O₃/SiO₂ composite powder does not undergo mulliteization even at 1,400 ℃, but the specimen using the Al(OH)₃/SiO₂ composite powder had already formed complete mullite whiskers from the particle size specimen milled for 3 h at 1,100 ℃. As a result, the change in sintering temperature does not significantly affect formation of microstructures. As the particle size of the matrix materials, Al₂O₃ and Al(OH)₃, decreases, the porosity tends to decrease. In the case of the Al(OH)₃/SiO₂ composite powder, the highest porosity obtained is 75 % when the particle size passes through a milling time of 3 h. The smaller the particle size of Al(OH)₃ is and the more the long/short ratio of the mullite whisker phase decreases, the higher the density becomes.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
• /
• pp.7-11
• /
• 2012

Plasma electrolytic oxidation of magnesium alloys is a well known technique to produce corrosion and wear resistant coatings. The addition of particles to the electrolyte provides a possibility to produce coatings with an increasing range of composition by in-situ incorporation of those particles into the coating. An extensive literature review has revealed that the mode of incorporation depends mainly on the melting point of the used particles and the energy provided by the discharges of the PEO process. The spectrum ranges from inert to partly reactive incorporation, but a complete reactive incorporation and a formation of a new single phase coating was not observed so far. Thus a new approach in PEO processing is introduced using specific particles as a kind of sintering additive, changing not only the composition but lowering the melting temperature and increase the liquid phase fraction during the discharges, resulting in a new amorphous coating.

• 천문학회보
• /
• 제39권2호
• /
• pp.42.1-42.1
• /
• 2014

Neutrino science has received a boost of attention quite recently in cosmology, since the outstanding discovery in particle physics over the last decade that neutrinos are massive: pinpointing the neutrino masses is one of the greatest challenges in science today, at the cross-road between particle-physics, astrophysics, and cosmology. Cosmology offers a unique 'laboratory' with the best sensitivity to the neutrino mass, as primordial massive neutrinos comprise a small portion of the dark matter and are known to significantly alter structure formation. I will first introduce a new suite of state-of-the-art hydrodynamical simulations with cold dark matter, baryons and massive neutrinos, specifically targeted for modeling the low-density regions of the intergalactic medium as probed by the Lyman-Alpha forest at high-redshift. I will then present and discuss how these simulations are used to constrain the parameters of the LCDM cosmological model in presence of massive neutrinos, in combination with BOSS data and other cosmological probes, leading to the strongest bound to date on the total neutrino mass.

• 대기
• /
• 제22권1호
• /
• pp.73-85
• /
• 2012

The collision efficiency data for collision between graupel or hail particles and cloud drops that take into account the differences of particle density are applied to the Takahashi cloud model. The original setting assumes that graupel or hail collision efficiency is the same as that of the cloud drops of the same volume. The Takahashi cloud model is run with the new collision efficiency data and the results are compared with those with the original. As an initial condition, a thermodynamic profile that can initiate strong convection is provided. Three different CCN concentration values and therefore three initial cloud drop spectra are prescribed that represent maritime (CCN concentration = 300 $cm^{-3}$), continental (1000 $cm^{-3}$) and extreme continental (5000 $cm^{-3}$) air masses to examine the aerosol effects on cloud and precipitation development. Increase of CCN concentration causes cloud drop sizes to decrease and cloud drop concentrations to increase. However, the concentration of ice particles decreases with the increase of CCN concentration because small drops are difficult to freeze. These general trends are well captured by both model runs (one with the new collision efficiency data and the other with the original) but there are significant differences: with the new data, the development of cloud and raindrop formation are delayed by (1) decrease of ice collision efficiency, (2) decrease of latent heat from riming process and (3) decrease of ice crystals generated by ice multiplication. These results indicate that the model run with the original collision efficiency data overestimates precipitation rates.

• 한국재료학회지
• /
• 제13권5호
• /
• pp.328-332
• /
• 2003

Characteristics of $TiO_2$nanoparticles controlled by precursor flow rate and reaction temperature in chemical vapor condensation process were interpreted in the view of decisive reaction factors, i.e. supersaturation ratio, concentration of vapor molecule, collision frequency and rate, and residence time, which directly affect the particle size and size distribution in CVC reactor. As results, the increases of precursor flow rate and reaction temperature induced the increase in the average sizes of $TiO_2$ nanoparticles in CVC reactor by acceleration of coagulation growth due to the increase of collision between $TiO_2$vapor molecules and particles. The effects of reaction factors on the characteristics of$TiO_2$nanoparticles were discussed with considering particle formation process in CVC reactor under given process parameters.

• 한국재료학회지
• /
• 제24권1호
• /
• pp.60-65
• /
• 2014

Fe-based amorphous coatings were fabricated on a soda-lime glass substrate by the vacuum kinetic spray method. The effect of the gas flow rate, which determines particle velocity, on the deposition behavior of the particle and microstructure of the resultant films was investigated. The as-fabricated microstructure of the film was studied by field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). Although the activation energy for transformation from the amorphous phase to crystalline phase was lowered by severe plastic deformation and particle fracturing under a high strain rate, the crystalline phases could not be found in the coating layer. Incompletely fractured and small fragments 100~300 nm in size, which are smaller than initial feedstock material, were found on the coating surface and inside of the coating. Also, some pores and voids occurred between particle-particle interfaces. In the case of brittle Fe-based amorphous alloy, particles fail in fragmentation fracture mode through initiation and propagation of the numerous small cracks rather than shear fracture mode under compressive stress. It could be deduced that amorphous alloy underwent particle fracturing in a vacuum kinetic spray process. Also, it is considered that surface energy caused by the formation of new surfaces and friction energy contributed to the bonding of fragments.