• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.1
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• pp.42-48
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• 2001

Over two decades, many researchers have performed studies on strength size effects in composite laminates under tensile and flexural loads. It is well known that there is a tendency for the strength of fibre-reinforced composites to decrease with increasing specimen size. Under compressive load, however, little work has been done on the effect of specimen size to failure strength. This is due to the fact that compressive testing of composite is very difficult. In this paper, the effect of the test specimen size on the compressive strength of composites containing open hole was considered using T300/924C, $>[45/-45/0/90]_{3S}$. For sizing test specimens, the in-plane scaling method is used i.e., the change of two- dimensional specimen area in specimen width and gauge length. The results clearly show that there is a hole size effect in the finite width plates. In addition, the specimens which have the same a/W(hole diameter/specimen width) exhibit a tendency of size effect. In contrast, test results of the unnotched specimens did not show a clear strength size effect.

• Restorative Dentistry and Endodontics
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• v.46 no.4
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• pp.57.1-57.9
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• 2021

Objectives: This study aimed to compare and evaluate the porosity and pore size distribution of high-viscosity glass ionomer cements (HVGICs) and conventional glass ionomer cements (GICs) using micro-computed tomography (micro-CT). Materials and Methods: Forty cylindrical specimens (n = 10) were produced in standardized molds using HVGICs and conventional GICs (Ketac Molar Easymix, Vitro Molar, MaxxionR, and Riva Self-Cure). The specimens were prepared according to ISO 9917-1 standards, scanned in a high-energy micro-CT device, and reconstructed using specific parameters. After reconstruction, segmentation procedures, and image analysis, total porosity and pore size distribution were obtained for specimens in each group. After checking the normality of the data distribution, the Kruskal-Wallis test followed by the Student-Newman-Keuls test was used to detect differences in porosity among the experimental groups with a 5% significance level. Results: Ketac Molar Easymix showed statistically significantly lower total porosity (0.15%) than MaxxionR (0.62%), Riva (0.42%), and Vitro Molar (0.57%). The pore size in all experimental cements was within the small-size range (< 0.01 mm³), but Vitro Molar showed statistically significantly more pores/defects with a larger size (> 0.01 mm³). Conclusions: Major differences in porosity and pore size were identified among the evaluated GICs. Among these, the Ketac Molar Easymix HVGIC showed the lowest porosity and void size.

• The Korean Journal of Malacology
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• v.27 no.4
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• pp.345-351
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• 2011

Comparison of different morphological characteristics of bivalves is very useful for distinguishing species. Therefore, this study used a morphometric approach to document patterns of phenotypic change through the specimens of family Pinnidae inhabiting the bottom sediments at the coasts of An Thoi Archipelago (south-eastern Gulf of Thailand), in that way excluding intraspecific variations among different populations along a wide geographical range. It was revealed that individuals determined as Pinna trigonium separated from specimens of Pinna nigra and Atrina vexillum at high level, but P. nigra and A. vexillum were the single species A. vexillum, as it is assumed now. Also, it was found that both groups of P. trigonium individuals and A. vexillum specimens divided into tree subgroups unified the specimens with the similar morphometric parameters: small, medium and large within the populations, though there were no evident divisions into subgroups in the size distributions of the populations. In addition to the interspecific morphological variations, the species also showed significant intraspecific morphological variations even in the same population. Most probable reason for the appearance of the intraspecific morphological variations and division of all specimens into size-specific subgroups in the population is the fact that the growth of Pinnidae bivalves is not isometric.

• Journal of the Korean Ceramic Society
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• v.34 no.12
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• pp.1213-1220
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• 1997

Effect of particle size of alumina and amount of talc on tape casting and densification behaviors of alumina-talc system were investigated. The pseudoplastic behaviors of slurries increased with increase in amount of talc addition and decrease in alumina particle size. In case of using coarse alumina powder, densification of specimens were accelerated with increase of sintering temperature and amount of talc addition. On the contrary, fine alumina powder retarded of rearrangement of alumina particle during liquid phase sintering due to premature densification of alumina matrix region before formation of liquid phase and then densification of specimens were suppressed with increase of sintering temperature and amount of talc addition.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.164-169
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• 2018

In this study, the effect of the size of the specimen on the apparent resistivity was investigated at the laboratory level for electrical resistivity. The specimens were measured for apparent resistivity by fabricating specimens with different sides and heights. Experimental results show that the apparent resistivity increases as the side and height of the specimen become smaller. Also, it was confirmed that the influence of the size of the specimen on the electrical resistivity measurement was not linear.

• Journal of the Korean Ceramic Society
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• v.40 no.3
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• pp.273-278
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• 2003

The effects of content and particle size of sewage sludge slag on the sound absorption was investigated and the physical$.$mechanical properties of porous ceramics for sound absorbent material was studied. The physical$.$mechanical properties of specimens have depended on sintering temperature and slag content without particle size effect of slag. As water glass content increase and particle size of slag decrease at the same slag content, physical$.$mechanical properties of them have been improved. The bulk density and compressive strength of specimens with the batch composition of 77∼89 wt% of slag content and particles with 1∼3 mm, and sintered at 1,050$^{\circ}C$ for 2 h were 1.48∼1.71 and 86∼163 kgf/$\textrm{cm}^2$, respectively. The specimens with 1∼3 mm and <1 mm of particles size showed good sound absorption property at low frequency and high frequency region. With increasing thickness of specimens, sound absorption properties at low frequency region were increased.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.3
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• pp.61-67
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• 2001

The remaining life estimation for the aged component is very important because mechanical properties of the compo-nents are degraded with time of service exposure in high temperature etc. The destructive method is widely used for the estimation of material degradation, but it has a difficulty in preparing specimens from in-service industrial facilities. In order to evaluate the feasibility of ultrasonic evaluation method for properties of high temperature materials, 2.25Cr-1Mo steel specimens which were prepared by the isothermal aging heat treatment at 63$0^{\circ}C$ were evaluated by ultra-sonic measurements investigating the change of velocities and attenuation coefficient. In this results, attenuation coefficient was found to be sensitive to material degradation mainly attributed to the change of grain size and the precipitation of impurities in grain boundaries, but velocity was not for all specimens.

• 전기의세계
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• v.31 no.6
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• pp.437-444
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• 1982

Although several kinds of conduction mechanism of PTC thermistor have been reported, there were few satisfying results. In this paper, the reported conduction mechanism theories were scrutinized and analyzed by using the experimental results. PTC thermistors for this study were manufactured by adding Sb$\_$2/O$\_$3/, AI$\_$2/O$\_$3/, TiO$\_$2/, and SiO$\_$2/ to BaTiO$\_$3/, and by sintering it at different temperatures. In order to analyze the conduction mechanism, R-T characteristics and its frequency dependence of specimens were measured. And also, the structures of specimens were studied. Especially this paper emphasized the explanation of the resistivity characteristics as the grain growth state of PTC thermistor specimens with respect to soaking temperature. According to the results, the resistivity of PTC thermistor whose grain was formed by semiconducting, was independent to the grain size at room temperature. For small and uniform grain size, the slope of the resistivity near the Curie temperature and the resistivity above the Curie temperature became greater and PTCR effect was improved.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.162-163
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• 2015

A borosilicate glass was powdered to incorporation into the cement for the purpose of improving the neutron shielding performance of concrete. The particle size of the borosilicate glass powder was prepared by a similar to that of cement. 50×50×50mm size of cube specimens were measured a compressive strength. As a result, compressive strength of 10% borosilicate glass powder replaced specimens were improved than that of plain specimens.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.526-531
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• 2021

The diet composition of john dory Zeus faber, was investigated using 266 specimens collected in the coastal waters of the South Sea, Korea. The specimens ranged in total length (TL) from 12.5 to 43.2 cm. The Z. faber fed mainly on Pisces and less often on Macrura. We further analyzed the data by dividing the specimens into five classes (<15.0 cm, 15.0-20.0 cm, 20.0-25.0 cm, 25.0-30.0 cm, ≥30.0 cm). The Z. faber diet shifted with size class from predominantly consuming Macrura to Pisces. The proportion of Macrura consumed decreased with increasing body size, whereas the consumption of Pisces increased gradually.