• Korean Journal of Metals and Materials
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• v.50 no.12
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• pp.931-937
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• 2012

The microstructure of Cu-15 wt%Ag composites fabricated by equal channel angular pressing (ECAP) with intermediate heat treatment at $320^{\circ}C$ was investigated by transmission electron microscopy (TEM) observations. Ag precipitates with a thickness of 20-40 nm were observed in the eutectic region of the Cu-15 wt%Ag composite solution treated at $700^{\circ}C$ before ECAP. The Cu matrix and Ag precipitates had a cube on cube orientation relationship. ECAPed composites exhibited ultrafine-grained microstructures with the shape and distribution dependent on the processing routes. For route A in which the sample was pressed without rotation between each pass, the Cu and Ag grains were elongated along the shear direction and many micro-twins were observed in elongated Cu grains as well as in Ag filaments. The steps were observed on coherent twin boundaries in Cu grains. For route Bc in which the sample was rotated by 90 degrees after each pass, a subgrain structure with misorientation of 2-4 degree by fragmentation of the large Cu grains were observed. For route C in which the sample was rotated by 180 degrees after each pass, the microstructure was similar to that of the route A sample. However, the thickness of the elongated grains along the shear direction was wider than that of the route A sample and the twin density was lower than the route A sample. It was found that more microtwins were formed in ECAPed Cu-15 wt%Ag than in the drawn sample. Grain boundaries were observed in relatively thick and long Ag filaments in Cu-15 wt%Ag ECAPed by route C, indicating the multi-crystalline nature of Ag filaments.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.128-136
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• 2011

Equal channel angular pressing (ECAP) with intermediate heat treatment was employed to optimize the strength of Cu-15 wt.%Ag. Changes in microstructure, electrical properties and mechanical properties were studied as a function of pressing methods and heat treatment. ECAPed Cu-15wt.%Ag exhibited ultrafine-grained microstructures with the shape and distribution of Ag-rich lamellae dependent on the processing routes. For route A in which the sample was pressed without rotation between each pass, the initial dendrites of Ag-rich phase were elongated along the shear direction and developed into elongated filaments. For route C in which the sample was rotated by 180 degree after each pass, the morphology of initial dendrites of Ag-rich phase was not much modified and the networked structure remained even after 8 passes of ECAP. For route Bc in which the sample was rotated by 90 degree after each pass, the initial dendrites became finer by fragmentation with no pronounced change of the shape and distribution of Ag-rich lamellae. The strength of Cu-15wt.%Ag ECAPed using route Bc was found to be greater than those ECAPed using route A, suggesting that the substructural strengthening is more effective in strengthening than the interface strengthening.

• Geomechanics and Engineering
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• v.34 no.6
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• pp.649-664
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• 2023

Structural inertial interaction is a representative the effect of dynamic soil-foundation-structure interaction (SFSI), which leads to a relative displacement between soil and foundation, period lengthening, and damping increasing phenomena. However, for a system with a significantly heavy foundation, the dynamic inertia of the foundation influences and interacts with the structural seismic response. The structure-to-foundation mass ratio (MR) quantifies the distribution of mass between the structure and foundation for a structure on a shallow foundation. Although both systems exhibit the same vertical factor of safety (FS_v), the MR and corresponding seismic responses attributed to the structure and foundation masses may differ. This study explored the influence of MR on the permanent deformation and seismic response of soil-foundation-structure system considering SFSI via numerical simulations. Given that numerous dimensionless parameters of SFSI described its influence on the structural seismic response, the parameters, except for MR and FS_v, were fixed for the sensitivity analysis. The results demonstrated that the foundation inertia of heavier foundations induced more settlement due to sliding behavior of heavily-loaded systems. Moreover, the structural inertia of heavier structures evidently exhibited foundation rocking behavior, which results in a more elongated natural period of the structure for lightly-loaded systems.

• Korean Journal of Materials Research
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• v.19 no.11
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• pp.581-587
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• 2009

Fe powders with elongated and aggregated structure as heat pellet material for thermal battery applications were prepared by spray pyrolysis under various preparation conditions. The precursor powders with spherical shapes and hollow morphologies turned into Fe powders after reduction at a temperature of 615$^{\circ}C$ under 20% $H_2$/Ar gas. The powders had pure Fe crystal structures irrespective of the preparation conditions of the precursor powders in the spray pyrolysis. The morphologies and mean sizes of the Fe powders are affected by the preparation conditions of the precursor powders in the spray pyrolysis. Therefore, the ignition sensitivities and the burn rates of the heat pellets formed from the Fe powders prepared by spray pyrolysis are affected by the preparations of the precursor powders. The Fe powders prepared under the optimum preparation conditions have a BET surface area of 2.9 $m^2g^1$. The heat pellets prepared from the Fe powders with elongated and aggregated structure have a good ignition sensitivity of 1.1W and a high burn rate of 18 $cms^1$.

• Development and Reproduction
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• v.21 no.3
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• pp.327-333
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• 2017

Gonadotropins are heterodimers consisting an alpha chain ($Cg{\alpha}$) and a beta chain. Interestingly, presence of complicated $LH-{\beta}$ transcripts in rat testis was accidently found; testicular $LH-{\beta}$ transcripts were confined in seminiferous tubules to spermatids, and the translated products were localized in the elongated spermatids. We hypothesized that mouse testis has potential to produce the tissue specific $LH-{\beta}$ with similar structure to the rat testicular forms. To verify our hypothesis, we examined the adult mouse (ICR) testis using RT-PCR and immunohistochemistry. The PCR revealed the presence of the identical products in the reactions for three LH subunit types. The expected product sizes for mouse $Cg{\alpha}$ and $LH-{\beta}$ known as pituitary type were 224 bp and 503 bp, respectively. The testicular type $LH-{\beta}$ products were produced by a primer set based on the rat sequences, with unexpected size of 800 bp. Sequencing revealed that the proximal and distal parts (2-82 and 661- 773 bp, respectively) were homologous to rat testicular $LH-{\beta}$ cDNA, and middle part (83-660 bp) was a unique mouse-specific region. Both $Cg{\alpha}$ and $LH-{\beta}$ positive signals were in the round and elongated spermatids and mature sperms, and the $LH-{\beta}$ signals were more intense. In conclusion, our study demonstrated that the presence and localization of the LH subunits in mouse testis. Further studies will be needed to understand the precise structure and function of mouse testicular LH.

• Journal of Plant Biology
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• v.30 no.2
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• pp.79-94
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• 1987

This study was carried out to investigate the epidermal structure, the stomatal types, the ontogeny of stomara in various parts of each organ of K. blossfeldiana, K. kewensis, and K. tometosa belonging to Kalanchoe. The epidermal cells were polygonal or isodiametric ones in the leaves, and mostly rectangular, tetragonal, and elongated ones in the leaves, and mostly rectangular, tetragonal, and elongated ones in the other organs. The candelabrum-like, triradiate stellete trichomes in the aerial parts of all organs of K. tomentosa were found. The cuticular striations and square crystals of calcium oxalate in the epidermal cells of petals of K. blossfeldiana were observed. The great majority of the mature stomata in various parts of all the organs were commonly helicocytic types. This type was subdivided into three subtypes such as parahelicocytic, anomohelicocytic, and dianisocytic stomata on the basis of the division angle of the guard mother cells. Somethies, the anisocytic type was found in most organs. This type was subdivided into three subtyes such as paranisocytic, nomoanisocytic, and dianisocytic stomata in the same way as the helicocytic type. A new stomataltype with anisocytic stoma within a girdle of four subsidiary cells of tetracytic type in the leaf of K. kewensis was firstly observed in the vascular plants. This type was termed the coaniso-tetracytic type. The anomomeristic pattern in the mesogenous category of stomatal types was found in various organs of all the material plants. Developmental mode of stomata was constant in all the parts of each organ within the same plant. The stomata was observed to be a few similar stomatal types in various parts of each organ within the same plant. The ontogeny of all the types is eumesogenous or mesogenous type. The ontogenetic type of stomata was mostly helico-eumesogenous type in all the organs of all the material plants. The mature stoma varied from organ to in regard of the number and arrangement of subsidiary cells.

• Earthquakes and Structures
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• v.2 no.3
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• pp.257-277
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• 2011

An evaluation is presented of the response of a 3-storey R/C structure during the destructive Lefkada earthquake of 14/08/2003. Key aspects of the event include: (1) the unusually strong levels of ground motion (PGA = 0.48 g, $SA_{max}$ = 2.2 g) recorded approximately 10 km from fault, in downtown Lefkada; (2) the surprisingly low structural damage in the area; (3) the very soft soil conditions ($V_{s,max}$ = 150 m/s). Structural, geotechnical and seismological aspects of the earthquake are discussed. The study focuses on a 3-storey building, an elongated structure of rectangular plan supported on strip footings, that suffered severe column damage in the longitudinal direction, yet minor damage in the transverse one. Detailed spectral and time-history analyses highlight the interplay of soil, foundation and superstructure in modifying seismic demand in the two orthogonal directions of the building. It is shown that soil-structure interaction may affect inelastic seismic response and alter the dynamic behavior even for relatively flexible systems such as the structure at hand.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.259-266
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• 2009

An experimental study was conducted to investigate the effects of forcing amplitude on the flow structure near the nozzle exit of forced jet diffusion flames. The jet was excited up to the blowout occurrence by a considerable large amplitude with a periodic velocity fluctuation at the tube resonating frequency. In the attached flame regime, we disclosed the very interesting result newly that adding of a moderate forcing amplitude caused the jet flame to become longer in spite of being forced. Particular attention is focused on the turnabout mechanism of vortex roll-up around the elongated flame, which has not been reported previously, and on the inner coherent structure of the forced jet in the attached flame regime. From the velocity and flow visualization results, it was ascertained that the surrounding air due to the occurrence of negative velocity parts was suck into the fuel nozzle. To aid in understanding the rotating phenomenon of coherent structure, we present a schematic diagram of the turnabout mechanism of vortex roll-up. The mechanism of vortex turnabout phenomenon can be easily understood by considering the positive and negative velocity amplitudes about the instantaneous velocity of the forcing flow, as shown in this diagram.

• Journal of Microbiology and Biotechnology
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• v.9 no.1
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• pp.39-43
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• 1999

A flocculent aggregate produced by Lactococcus lactis subsp. lactis in broths containing Tween 80, including MRS broth, had a microscopic structure of intertwined thread-like filaments. The filamentous structure was not elongated bacterial cells, but consisted of an organic solvent-soluble portion and an insoluble solid. L. lactis subsp. lactis grown at $25^{\circ}C$ for 15 days in tryptic soy broth with 0.1% Tween 80 and 1.0% malt extract produced 13 mg/l of flocculent aggregate, which contained 0.84 g/g of organic solvent-soluble component. The organic solvent-soluble part was identified as 10-hydroxyoctadecanoic acid.

• Journal of Plant Biology
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• v.32 no.3
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• pp.163-172
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• 1989

Nerium indicum has adaxial colleters on each petiole, bract, bracteole, calyx and corolla. The colleters are finger-shaped sometimes lobed structures with tall heads on short stalks. The petiolar colleters are more abundant than those on the bract, bracteole, calyx and corolla but their structure is similar. Meristematic activity in a small group of protodermal and hypodermal cells at the base of the developing leaf gives rise to the colleter that further differentiates by frequent anticlinal and periclinal divisions. Many of the colleters are vascullarized, sometimes a layer of redially elongated cells is present beneath the epithelial cells. Senescence of a colleter begins when the leaves have either completed their growth or are still expanding. In senescent colleters, the central cell cytoplasm and nuclei are considerably reduced. Thin layer chromatography of the freshly harvested exudate of colleter shows the presence of rhamnose, glucose and arabinose sugars.