• Journal of Drive and Control
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• v.19 no.3
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• pp.16-22
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• 2022

Crushers are equipment that crush natural stones, to produce aggregates used at construction sites. As the crusher proceeds, the inner liner becomes worn, causing the size of the aggregate produced to gradually increase. The vision sensor-based aggregate analysis system analyzes the size and distribution of aggregates in production, in real time through image analysis. This study developed an algorithm that can segmentate aggregates in images in real time. using image preprocessing technology combining various filters and morphology techniques, and aggregate region characteristics such as convex hull and concave hull. We applied the developed algorithm to fine aggregate, intermediate aggregate, and thick aggregate images to verify their performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.46-53
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• 2003

Effects of electric force on the morphology and growth of aggregates were studied experimentally. Nano-sized NaCl particles were supplied to a flame to perform the unipolar charging state. This electric precursor did not modify a temperature profile of the flame. The morphology of aggregates was measured by TEM image processing technique and the light scattering technique. In the unipolar charged state, the fractal dimension of aggregates was smaller than that of' the electrically neutral state. This result was in good agreement with our previous numerical simulations.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.1
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• pp.36-43
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• 2016

The aim of this study was to evaluate the effect of blood contamination on the push-out bond strength and surface morphology of tricalcium silicate materials; Biodentine$^{(R)}$, Theracal$^{(R)}$ and mineral trioxide aggregate. The standardized lumens of root slices prepared from extracted single-root human teeth were filled with Biodentine$^{(R)}$, Theracal$^{(R)}$ and mineral trioxide aggregate by manufacturer's instruction. The specimens were randomly divided into 2 groups (n = 20) for each material and then incubated for 4 days at $37^{\circ}C$; control group (phosphate buffered saline solution) and experimental group (fetal bovine serum). The push-out bond strengths were then measured by a universal testing machine and the surface morphology of each experimental group was analyzed by scanning electron microscope. Biodentine$^{(R)}$ and Theracal$^{(R)}$ showed higher push-out bond strength compared with mineral trioxide aggregate after exposure to fetal bovine serum. A substantial change in the surface morphology of each material was observed after exposure to fetal bovine serum. In conclusion, the push-out bond strengths of Biodentine$^{(R)}$ and Theracal$^{(R)}$ were higher than mineral trioxide aggregate when exposed to blood contamination. Therefore, it is supposed that the use of Biodentine$^{(R)}$ and Theracal$^{(R)}$ is appropriate in the presence of blood.

• International Journal of Concrete Structures and Materials
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• v.4 no.2
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• pp.119-125
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• 2010

In this study, the effects of the fineness modulus of reactive aggregate on ASR expansion and ASR products have been investigated. The reactive aggregate used was metamorphic aggregate originated from Korea. ASR tests were conducted according to accelerated mortar bar test. The morphology and chemical composition of products formed in mortar bars, 5 years after the mortar bar test had been performed, were studied by scanning electron microscopy equipped with energy dispersive spectroscopy. Test results indicated that ASR expansion of mortar bars decrease in linear proportion to the fineness modulus of reactive aggregate. SEM images indicated that mortar bars showed reactive products formed in cement paste, within air voids and within cracks through particles except for the mortar bar with the fineness modulus of 3.25. The EDS analysis of the reactive products showed presence of silica, calcium and sodium, typical of ASR product composition.

• Journal of the korean academy of Pediatric Dentistry
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• v.51 no.2
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• pp.165-175
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• 2024

This study aimed to investigate the effects of blood contamination on the Vickers hardness and the surface morphology of premixed MTA and compare them with the effects on conventional MTA. The Vickers microhardness of Endocem MTA Premixed Regular (EP) and ProRoot MTA (PM) was assessed after immersion in fetal bovine serum (FBS) and saline. Stem cells from human exfoliated deciduous teeth (SHED) were seeded on MTA after immersion in FBS, saline, and deionized water (DW). Cell adhesion patterns and surface morphology were visualized via scanning electron microscopy (SEM). The surface microhardness of EP and PM in FBS was lower than in saline. However, short-term exposure of PM to FBS did not reduce the microhardness compared to saline. Angular crystals formed in water, while rounded crystals with more air voids appeared in FBS. Favorable SHED attachment occurred in all groups. Overall, the surface hardness of EP and PM decreased after FBS exposure, although PM was less influenced. We suggest minimizing the amount of bleeding when using MTA clinically; nevertheless, PM remains an option with more expected blood contamination than EP. In summary, exposure to FBS decreased mechanical performance but allowed cell adhesion for both MTAs, with PM being more resistant to these changes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.9
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• pp.1139-1150
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• 1999

The evolution of silica aggregate particles in coflow diffusion flames has been studied experimentally using light scattering and thermophoretic sampling techniques. The measurements of scattering cross section from $90^{\circ}$ light scattering have been utilized to calculate the aggregate number density and volume fraction using with combination of measuring the particle size and morphology through the localized sampling and a TEM image analysis. Aggregate or particle number densities and volume fractions were calculated using Rayleigh-Debye-Gans and Mie theory for fractal aggregates and spherical particles, respectively. Of particular interests are the effects of flame temperature on the evolution of silica aggregate particles. As the flow rate of $H_2$ increases, the primary particle diameters of silica aggregates have been first decreased, but, further increase of $H_2$ flow rate causes the diameter of primary particles to increase and for sufficiently larger flow rates, the fractal aggregates finally become spherical particles. The variation of primary particle size along the upward jet centerline and the effect of burner configuration have also been studied.

• Economic and Environmental Geology
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• v.55 no.6
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• pp.649-659
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• 2022

This study examined the granite, quartzite, phyllite, schist, and gneiss as aggregate resources among the original rock distributed in the Chungju-Goesan area. The granite distributed in the study area is mainly composed of Jurassic biotite granite, and the quartzite layer is from the Daehyangsan quartzite Formation distributed on the upper part of the Gyemyeongsan Formation and the Hyangsan-ri dolomitic limestone Formation. In addition, phyllite is pophyrytic phyllite-schist from the Hwanggangri Formation of the Okcheon group, schist is chlorite schist, from the Munjuri Formation of the Okcheon group, and gneiss is porphyroblastic gneiss which is the upper part of the Seochangri Formation. Aggregate quality evaluation factors of these rocks included fineness modulus, absorption, unit weight, absolute dry density, solid content, porosity, resistance to abrasion, and soundness. In the case of granite, it was found to be partially unsatisfactory in terms of unit weight, solid content, porosity, and resistance to abrasion. Gneiss was found to be out of the standard values in resistance to abrasion and schist in porosity and solid content. As for the overall quality of aggregate resources, it was analyzed that quartzite, gneiss, and phyllite showed excellent quality. Aggregate quality tests are performed simply for each rock, but the rock may vary depending on the morphology of the mineral. Therefore, when analyzing and utilizing the quality evaluation of aggregate resources, it will be possible to use them more efficiently if the rock-mineralological research is performed together.

• Macromolecular Research
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• v.14 no.5
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• pp.545-551
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• 2006

Aqueous dispersions of pristine and functionalized (COOH- and $NH_2$-) multi-walled, carbon nanotubes (MWNTs) were prepared by using three types of surf act ants: sodium dodecyl sulfate (SDS, anionic), PEO-PPO-PEO (Pluronic P84, non-ionic), and poly(styrene/$\alpha-methyl$ styrene/acrylic acid) random terpolymer, i.e., alkali-soluble resin (ASR). The aggregate size, $\zeta-potential$, and storage stability of the MWNT aqueous dispersions were investigated by using dynamic light scattering and the turbidity method at room temperature. The exfoliation of the MWNT aggregates was determined by a UV-visible spectrophotometer and the morphology of the surfactant-coated MWNTs was observed by transmission electron microscopy (TEM). In all cases, ASR showed better dispersion stability with the smallest aggregate size, compared with the other surfactants, because of its unique molecular structure, i.e., randomly incorporated carboxylic acid groups and planar phenyl groups that can be irreversibly and effectively adsorbed on the MWNT surface. A predominantly-exfoliated morphology of MWNTs was observed in the presence of ASR from the strong intensity of the UV-vis spectrum at 263 nm.

• Restorative Dentistry and Endodontics
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• v.42 no.3
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• pp.176-187
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• 2017

Objectives: This study aimed to evaluate the chemical and biological properties of fast-set white mineral trioxide aggregate (FS WMTA), which was WMTA combined with calcium chloride dihydrate ($CaCl_2{\cdot}2H_2O$), compared to that of WMTA. Materials and Methods: Surface morphology, elemental, and phase analysis were examined using scanning electron microscope (SEM), energy dispersive X-ray microanalysis (EDX), and X-ray diffraction (XRD), respectively. The cytotoxicity and cell attachment properties were evaluated on human periodontal ligament fibroblasts (HPLFs) using methyl-thiazoldiphenyltetrazolium (MTT) assay and under SEM after 24 and 72 hours, respectively. Results: Results showed that the addition of $CaCl_2{\cdot}2H_2O$ to WMTA affected the surface morphology and chemical composition. Although FS WMTA exhibited a non-cytotoxic profile, the cell viability values of this combination were lesser than WMTA, and the difference was significant in 7 out of 10 concentrations at the 2 time intervals (p < 0.05). HPLFs adhered over the surface of WMTA and at the interface, after 24 hours of incubation. After 72 hours, there were increased numbers of HPLFs with prominent cytoplasmic processes. Similar findings were observed with FS WMTA, but the cells were not as confluent as with WMTA. Conclusions: The addition of $CaCl_2{\cdot}2H_2O$ to WMTA affected its chemical properties. The favorable biological profile of FS WMTA towards HPLFs may have a potential impact on its clinical application for repair of perforation defects.

• Textile Coloration and Finishing
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• v.27 no.4
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• pp.229-244
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• 2015

The effects of synthesis conditions on characteristics of the calcium-azo complex pigment, C.I. Pigment Red 57:1, were studied. It was mainly considered that the industrially required synthesis conditions for lowering electrical conductivity of the pigment solution keeping pigment quality such as particle size and color characteristics. Three parameters were chosen as control factors during the synthesis. The first was the amount of hydrochloric acid added to transform sodium nitrite into nitrous acid. The second was the amount of calcium chloride added to insolubilize the synthesized azo dye. The final factor was pH control during the coupling reaction. The electrical conductivity and pigment aggregate particle size were dependent on the amount of hydrochloric acid and calcium chloride. Higher HCl concentration gave brighter yellowish-red color because of smaller particle aggregate size and narrower size distribution. Amount of charged ions in the synthesis process might affect the "lake" formation resulting different particle aggregate size and color shade.