• Structural Engineering and Mechanics
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• v.61 no.2
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• pp.275-282
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• 2017

The Fleck-Hutchinson theory on strain gradient plasticity (SGP), proposed in Adv. Appl Mech 33 (1997) 295, has recently been reformulated by adopting the strategy of decomposing the second order strain presented by Lam et al. in J Mech Pays Solids 51 (2003) 1477. The newly built SGP satisfies the non negativity of plastic dissipation, which is still an outstanding issue in other SGP theories. Furthermore, it explicitly shows how elastic strain gradients and corresponding elastic characteristic length scales come into play in general elastic-plastic loading histories. In this study, the relation between elastic length scales and plastic length scales is investigated by taking wire torsion as an example. It is concluded that the size effects arising when two sets of length scales are of the same order are essentially elastic instead of plastic.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.287-289
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• 2015

Meso-scale combustion is defined as combustion phenomena within limited characteristic length scales that are comparable with the laminar flame length scales. In the laminar flame theory, four representative length scales have been involved; i.e., a reaction layer thickness, a thermal layer thickness, a quenching distance, and a Markstein length. When the effects of these length scales on the flame characteristics are understood, the laminar flame theories can be clarified. Therefore, a study on the meso-scale combustion phenomena should not be thought as just a specific phenomena occurring in an exceptional combustion condition. Instead, all combustion phenomena within meso-scale spaces need to be explained by our knowledge. During this challenge, our understanding on laminar flame structures can be extended. Considering that most turbulent combustion phenomena in engineering application are still have local laminar flame structures, studies on laminar flame structures need to be re-visited especially in academic aspects.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.3
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• pp.324-330
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• 2023

We investigated the relative growth and squamation of larvae and juveniles of cultured Larimichthys polyactis. Analysis of the relative growth of larvae and juveniles showed that their preanal length, head length, eye diameter, body depth, and snout length increased with growth. There was no significant chage in the relative growth. The ratio of preanus length to standard length (SL) increased rapidly until SL was approximately 12 mm, and then increased gradually. Cycloid scales first appeared on the lateral line, progressed to the abdominal cavity at 15.13 mm SL, and expanded to the occipital region, base of pectoral fin, and ventral region of the eye at 17.82 mm SL. At 18.03 mm SL, scales formed on the cheek, and those at the base of pectoral fin and in the abdominal cavity were connected to each other. At 19.06 mm SL, major part of the head was covered by scales, except near the lower jaw. Cycloid scales on the lateral line changed to ctenoid scales at the range of 31.71-32.24 mm SL, and those on the nape changed at the range of 69.02-70.84 mm SL. Our results may help to establish conservation and management strategy for Larimichthys polyactis aquaculture.

• Wind and Structures
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• v.14 no.1
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• pp.15-34
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• 2011

Three wind-tunnel simulations of the atmospheric boundary layer (ABL) flow in suburban country exposure were generated for length scale factors 1:400, 1:250 and 1:220 to investigate scale effects in wind-tunnel simulations of the suburban ABL, to address recommended wind characteristics for suburban exposures reported in international standards, and to test redesigned experimental hardware. Investigated parameters are mean velocity, turbulence intensity, turbulent Reynolds shear stress, integral length scale of turbulence and power spectral density of velocity fluctuations. Experimental results indicate it is possible to reproduce suburban natural winds in the wind tunnel at different length scales without significant influence of the simulation length scale on airflow characteristics. However, in the wind tunnel it was not possible to reproduce two characteristic phenomena observed in full-scale: dependence of integral length scales on reference wind velocity and a linear increase in integral length scales with height. Furthermore, in international standards there is a considerable scatter of recommended values for suburban wind characteristics. In particular, recommended integral length scales in ESDU 85020 (1985) are significantly larger than in other international standards. Truncated vortex generators applied in this study proved to be successful in part-depth suburban ABL wind-tunnel simulation that yield a novel methodology in studies on wind effects on structures and air pollution dispersion.

• International Journal of Concrete Structures and Materials
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• v.18 no.1E
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• pp.23-28
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• 2006

In this study, the general theory of fractality is discussed to provide a fundamental understanding of fractal geometry applied to heterogeneous material surfaces like pavement surface and rock surface. It is well known that many physical phenomena and systems are chaotic, random and that the features of roughness are found at a wide spectrum of length scales from the length of the sample to the atomic scales. Studying the mechanics of these physical phenomena, it is absolutely necessary to characterize such multi scaled rough surfaces and to know the structural property of such surfaces at all length scales relevant to the phenomenon. This study emphasizes the role of fractal geometry to characterize the roughness of various surfaces. Pavement roughness and rock surface roughness were examined to correlate their roughness property to fractality.

• Journal of architectural history
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• v.17 no.4
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• pp.7-23
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• 2008

This study is examine the scales applied to buildings in the age of Unified Silla through construction sites excavated and its results are as follows; First, scales used in the age of Unified Silla were varied like Jucheok, Dangcheok and Hancheok, but it was generally accepted that Dangcheok was used in Yeongjocheok Since it was found that the scales applied to Dabotap at the Bulguksa temple and main building of the Gameunsa temple belonged to Goguryeo, Yeongjocheok scale used early in the age of Unified Silla was transitional and it was thought that Goguryeocheok and Dangcheok were used togethar. Second, according to actual rulers in Korea, china and Japan, the length of Dangcheok(ruler used in Chinese Tang era) mostly belonged to the extent of $29.25cm\;{\sim}\;30.5cm$(central value: 29,71cm). Third, plane features of main building of temple are assumed that it had five rooms in front compartment until the 7th century and then it was diversified to three, five and seven compartment. The size of compartment was same in the scale of front Eokan and Hyeopkan until late 7th century, but since then the dimension of Eokan tended to be wider than Hyeopkan. It was judged that the front Eokan used triple scales like 9, 12, 15, 18 cheok. Fourth, the length of residential structures was 17.5cheok${\sim}$36cheok and Bcheok was commonly used for front side of structure, The length of official structures was 8.4cheok${\sim}$36.3cheok which is similar to residential structures. However it has been confirmed that each of 9cheok, 12cheok, and 15cheok has been used for Eokan and Hyeopkan which gave presumption that triple scales was used for the measure.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.846-857
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• 1995

An experimental study is made of turbulent shear flows in a nearly two-dimensional 90.deg. curved duct by using the hot-wire anemometer. The Reynolds normal and shear stresses, triple velocity products, integral length scales, Taylor micro length scales and dissipation length scales are measured and analyzed. For a positive shear at the inlet, the afore-mentioned turbulence quantities are all suppressed. However, when the inlet shear flow is negative, they are augmented, i.e., the convex curvature suppresses the turbulence whereas the concave curvature augments it. It is found that the curvature effects are rather sensitive to the triple velocity products than the Reynolds stresses. The evolution of turbulence under the curvature with the different shear conditions is well described by the modified curvature parameter S' and the non-dimensional development time ${\tau}$.'

• Advances in materials Research
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• v.1 no.1
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• pp.13-29
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• 2012

In order to simultaneously enhance the strength and plasticity in nanostructured / ultrafine-grained alloys, a strategy of introducing multiple length scales into microstructure (or called bimodal composite microstructure) has been developed recently. This paper presents a brief overview of the alloy developement and the mechanical behavior of ultrafine-grained Ti-Fe-based alloys with different length-scale phases, i.e., micrometer-sized primary phases (dendrites or eutectic) embedded in an ultrafine-grained eutectic matrix. These ultrafine-grained titanium bimodal composites could be directly obtained through a simple single-step solidification process. The as-prepared composites exhibit superior mechanical properties, including high strength of 2000-2700 MPa, large plasticity up to 15-20% and high specific strength. Plastic deformation of the ultrafine-grained titanium bimodal composites occurs through a combination of dislocation-based slip in the nano-/ultrafine scale matrix and constraint multiple shear banding around the micrometer-sized primary phase. The microstructural charactersitcs associated to the mechanical behaivor have been detailed discussed.

• Parasites, Hosts and Diseases
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• v.51 no.3
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• pp.369-373
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• 2013

The present study was performed to trace the decisive evidence for mixed infection of 2 Myxobolus species, M. episquamalis and Myxobolus sp., in the gray mullet, Mugil cephalus, from Korean waters. Mullets with whitish cyst-like plasmodia on their scales were collected near a sewage plant in Yeosu, southern part of Korea, in 2009. The cysts were mainly located on scales and also found in the intestine. The spores from scales were oval in a frontal view, tapering anteriorly to a blunt apex, and measured $7.2{\mu}m$ (5.8-8.0) in length and $5.3{\mu}m$ (4.7-6.1) in width. Two polar capsules were pyriform and extended over the anterior half of the spore, measuring $3.5{\mu}m$ (2.3-4.8) in length and $2.0{\mu}m$ (1.5-2.2) in width. In contrast, the spores from the intestine were ellipsoidal, $10.4{\mu}m$ (9.0-11.9) in length and $8.4{\mu}m$ (7.3-10.1) in width. The polar capsules were pyriform but did not extend over the anterior half of the spore, $3.7{\mu}m$ (2.5-4.5) in length and $2.2{\mu}m$ (1.8-2.9) in width. The nucleotide sequences of the 18S rDNA gene of the 2 myxosporean spores from scales and intestine showed 88.1% identity to each other and 100% identity with M. episquamalis and 94.5% identity with M. spinacurvatura from mullet, respectively. By the above findings, it is first confirmed that mullets from the Korean water are infected with 2 myxosporean species, M. episquamalis and Myxobolus sp.

• Journal of the Korean Society of Combustion
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• v.14 no.3
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• pp.29-36
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• 2009

Simulation is performed to analyze the characteristics of turbulent spray combustion in a diesel engine condition. An extended Conditional Moment Closure (CMC) model is employed to resolve coupling between chemistry and turbulence. Relevant time and length scales and dimensionless numbers are estimated at the tip and the mid spray region during spray development and combustion. The liquid volume fractions are small enough to support validity of droplets assumed as point sources in two-phase flow. The mean scalar dissipation rates (SDR) are lower than the extinction limit to show flame stability throughout the combustion period. The Kolmogorov scales remain relatively constant, while the integral scales increase with decay of turbulence. The chemical time scale decreases abruptly to a small value as ignition occurs with subsequent heat release. The Da and Ka show opposite trends due to variation in the chemical time scale. More work is in progress to identify the spray combustion regimes.