• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.1
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• pp.72-79
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• 1999

The binder plays important roles in determining the quality of pigment coating. In addition to its primary role of binding the pigment to the base paper, the binder performs several other important functions. The binder, also referred to as the adhesive, is the dominant in the aqueous phase of the formulation. Thus it plays a major role in determining viscosity, rheology, water release, and setting time for the coating. Latices based on styrene-butadiene dominate the market for synthetic paper coating binders. Consumption is high and is expected to increase further due to the present tendeyncy toward high-solids coating. The purpose of this study is understanding the impact of various parameters of latex(i.e. Tg, Particle size) affecting prontabilities and optical properties of the coated papers, as well as providing basic information on the use of amphoteric latex for improving print qualities of coated papers. Recently, amphoteric latices, Which are cationic at low pH's but turn anionic at high pH's have attracted interests of paper scientists and engineers. Therefore we investigated the effect of the Tg(glass transition temperature) and particle size of amphoteric latex on the coating qualities. We also studied the effect of mixing ratios (Amphoteric / Anionic)of latex on the coating qualities. Our results showed that Tg and particle size of amphoteric latex have to be controlled for optimizing coated paper qualities. The formulation consisting of 10 parts of amphoteric latex and 5 parts of anionic latex gave best results in ink receptivity, smoothness, air permeability, opacity and sheet gloss. If the results hold for the industrial paper coatings, the amount of expensive amphoteric latex can be reduced while achieving best available printing quality.

• Microbiology and Biotechnology Letters
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• v.18 no.4
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• pp.352-359
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• 1990

The synergistic effect of glucoamylase and a -amylase on the hydrolysis of raw corn starch in an agitated bead reaction system was studied by investigating the changes of sugar profiles, the granular structure, particle size distribution, and X-ray diffraction pattern of residual raw corn starch. The enzymatic hydrolysis of raw corn starch was greatly enhanced by synergistic effect of glucoamylase and $\alpha$ -amylase. Even though the sugar profiles were mainly determined by the mixing ratio of glucoamylase and $\alpha$-amylase; raw starch was mainly converted to glucose directly without accumulation of any significant amount of oligosaccharides. The cavity formation and fragmentation phenomena of raw corn starch granule subjected to enzyme reaction were analyzed by means of SEM and the particle size distribution. The X-ray diffraction pattern of raw starch was not changed at the initial stage of reaction but slightly changed at the late stage of hydrolysis, which may be caused by the preferential degradation of amorphous region by enzymatic reaction, not by the destruction of microcrystalline structure of raw corn starch.

• Journal of Pharmaceutical Investigation
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• v.39 no.5
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• pp.339-343
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• 2009

Recently, co-delivery of drug and gene has been attempted for higher therapeutic effects of anticancer agents. In this study, cationic liposomes were prepared using 1,2-dioleoyl-3-trimethylammoniopropane (DOTAP) as a cationic lipid to investigate the effect of drug loading on the physicochemical characteristics of cationic liposomes/DNA complexes. The complex formation between cationic liposomes and negatively charged plasmid DNA was confirmed and the protection from DNase was observed. Particle size of complexes was reduced not by drug loading, but by the increased ratio of cationic lipid to plasmid DNA. Meanwhile, zeta potential of complex was increased by the addition of cationic liposomes to complexes and the effect of drug loading on the zeta potential was not much higher than on particle size. Gel retardation of complexes was indicated when the complexation weight ratios of cationic lipid to plasmid DNA were higher than 24:1 for drug free complexes and 20:1 for drug loaded ones, respectively. Agarose gel retardation showed the similar complexation between plasmid DNA and drug free liposomes or drug loaded liposomes. Both complexes protected plasmid DNA from DNase independent of complexation temperature. From the results, drug loading may affect not the complex formation of cationic liposomes and plasmid DNA, but the particle size of complex.

• Particle and aerosol research
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• v.6 no.3
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• pp.123-129
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• 2010

As the indoor activity increases in recent years, the indoor air quality becomes more important. One of the major contaminants in office space is the copy machines and the laser based printers. These devices usually emit nano-particles and chemical species that may give some health effect. The amount of particles generated by the printers and copy machines depend on printer models, printing speed, toners, papers, humidity and so on. To evaluate the emission rate of nano-particles from Laser Printers, the mass concentration measurement method has been used (BAM, 2004). However, the mass concentration measurement method for nano-particles is tedious and time consuming. Therefore, for the development of a new nano-particle counting method, the nano-particle emission characteristics and size distributions are evaluated.

• Journal of the Korean Applied Science and Technology
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• v.21 no.1
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• pp.69-75
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• 2004

In this study, various model composite latexes were synthesized using n-butyl acrylate and methyl methacrylate as comonomers by seeded multi-staged emulsion polymerization. Monodispersed model composite latex particles with size of 190 nm and polydispersity index of 1.05, which have various morphology including random copolymer particle, soft-core/hard-shell particle, hard-core/soft shell particle, and gradient-type copolymer particle, homopolymers particles were prepared. The designed morphology of model composite particles were confirmed.

• Journal of Energy Engineering
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• v.6 no.1
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• pp.77-86
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• 1997

In this study, numerical computations were performed to scrutinize the effect of the size of coal particles on reactive flow fields and concentration distribution of product gases for five cases with four different particle sizes (40 $\mu\textrm{m}$, 60 $\mu\textrm{m}$, 100 $\mu\textrm{m}$, 120 $\mu\textrm{m}$, 140 $\mu\textrm{m}$) in an axisymmetric cylindrical coal gasifier in which Alaska Usibelli subbituminous coals were gasified. Predictions showed that coal particle size affected the concentration distribution of product gases. When coals of 100 $\mu\textrm{m}$ were gasified, the maximum average concentrations of major products, H$_2$and CO, were predicted at the exit of the gasifier. The average mole fractions of CO and H, were shown to be 0.62, and 0.16 (dry basis, inert free), respectively. The cold gas efficiency of 83% was also predicted for the same particle size of 100 $\mu\textrm{m}$.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.7
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• pp.523-529
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• 2011

This study has been performed to examine the influence of the size of particles on the stabilization in the aerobic stabilization equipment connected with MBT system. The biodegradable waste inside the reactor (60% of food waste, 25% of paper waste, 2% of wood waste and 5% of compost) has been charged in same composition. The degree of stabilization was compared and analyzed after charging with adjustment of particle size in 5 mm, 10 mm, 20 mm, 50 mm, 100 mm and state of no separation. The experiment revealed that highest temperature beyond $65^{\circ}C$ was shown in the particle size of less than 50 mm in change of temperature and the highest temperature was about $50^{\circ}C$ in reactor of 100 mm and no separation. The proportionality between generated quantity of $CO_2$ and particle size was not observed, even the highest in generated quantity was shown in over 100 mm. The weight changes based on wet and dry conditions in the reaction process showed the 30% and 46% of reduction in the smallest particle size of 5 mm and it showed the trend of the lower reduction rate at the bigger particle size. The water soluble $COD_{Cr}$ and TOC showed the reduction rate of 60% in reactor of particle size in 100 mm and no separation while the reduction rate comparing to the initial stage of reaction in the reactor of less than 50 mm was 80%. Such result derived the conclusion of acceleration in the decomposing stabilization of biodegradable material due to the decomposing rate of organic substance as the particle size of biodegradable waste gets smaller. It is concluded as necessary to react in adjustment under 50 mm of particle size as much as possible.

• Computers and Concrete
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• v.28 no.5
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• pp.521-532
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• 2021

Present paper focuses on the modeling of size effect on the compressive strength of normal concrete with the application of Discrete Element Method (DEM). Test specimens with different size and shape were cast and uniaxial compressive strength test was performed on each sample. Five different concrete mixes were used, all belonging to a different normal strength concrete class (C20/25, C30/37, C35/45, C45/55, and C50/60). The numerical simulations were carried out by using the PFC 5 software, which applies rigid spheres and contacts between them to model the material. DEM modeling of size effect could be advantageous because the development of micro-cracks in the material can be observed and the failure mode can be visualized. The series of experiments were repeated with the model after calibration. The relationship of the parallel bond strength of the contacts and the laboratory compressive strength test was analyzed by aiming to determine a relation between the compressive strength and the bond strength of different sized models. An equation was derived based on Bazant's size effect law to estimate the parallel bond strength of differently sized specimens. The parameters of the equation were optimized based on measurement data using nonlinear least-squares method with SSE (sum of squared errors) objective function. The laboratory test results showed a good agreement with the literature data (compressive strength is decreasing with the increase of the size of the specimen regardless of the shape). The derived estimation models showed strong correlation with the measurement data. The results indicated that the size effect is stronger on concretes with lower strength class due to the higher level of inhomogeneity of the material. It was observed that size effect is more significant on cube specimens than on cylinder samples, which can be caused by the side ratios of the specimens and the size of the purely compressed zone. A limit value for the minimum size of DE model for cubes and cylinder was determined, above which the size effect on compressive strength can be neglected within the investigated size range. The relationship of model size (particle number) and computational time was analyzed and a method to decrease the computational time (number of iterations) of material genesis is proposed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.275-282
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• 2014

Particle-reinforced metal matrix composites exhibit a strengthening effect due to the particle size-dependent length scale that arises from the strain gradient, and thus from the geometrically necessary dislocations between the particles and matrix that result from their CTE(Coefficient of Thermal Expansion) and elastic-plastic mismatches. In this study, the influence of the size-dependent length scale on the particle-matrix interface failure and ductile failure in the matrix was examined using finite-element punch zone modeling whereby an augmented strength was assigned around the particle. The failure behavior was observed by a parametric study, while varying the interface failure properties such as the interface strength and debonding energy with different particle sizes and volume fractions. It is shown that the two failure modes (interface failure and ductile failure in the matrix) interact with each other and are closely related to the particle size-dependent length scale; in other words, the composite with the smaller particles, which is surrounded by a denser dislocation than that with the larger particles, retards the initiation and growth of the interface and matrix failures, and also leads to a smaller amount of decrease in the flow stress during failure.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.1
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• pp.10-26
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• 2013

To understand the traffic emissions with high temporal and spatial resolutions on road, a mobile laboratory was developed. The objective of this study is to characterize on-road air pollution on Naebu express way surrounding the northern area of Seoul, Korea. We measured the number concentration of ultrafine particles larger than 5 nm and particle size distribution using a condensation particle counter and a fast mobility particle sizer, respectively on 3, 7, and 8 December 2009. The average ultrafine particle number concentration on the Naebu express way excluding tunnels was 126,000 particles/$cm^3$ and 4.2 times higher than that on internal road at Korea Institute of Science and Technology in Seoul, and more than twice higher than that measured on and at the arterial roads of Seoul in previous studies. The maximum ultrafine particle number concentration was observed at the tunnel sections. It was 232,000 particles/$cm^3$ and 1.8 times higher than average ultrafine particle number concentration for the other sections on Naebu express way. The ultrafine particle number concentration on the wider roads with higher traffic volume along the Han River was similar to that in the residential section, probably because of enhanced dilution effect in widely open environment. The size distribution of particles on the Naebu express way was highly fluctuated for a short duration. Ultrafine particles measured at the tunnel showed a bimodal size distribution with mode diameters of ~10 nm and ~50 nm. At the Han riverside section, ~10 nm particles appeared significantly compared with size distribution at the tunnel. This on-road measurement approach can be utilized to manage vehicle-related air pollution in urban area.