• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.22 no.6
• /
• pp.265-268
• /
• 2012

The growth of AlN single crystals of large size and good quality is of prime importance for UV LEDs and power devices applications. However, the crystals having the size of more than 1 inch and high quality have not been reported in the world. In the PVT growth of AlN, the crystal morphology of as grown were important because the preferred orientation of growth of it was evaluated for growth rate increase. In the present study, the AlN single crystals grown by PVT process were evaluated by the side of the growth morphology. Optical microscopic characterization was carried out to observe the shape of the crystals and the growth facets. Furthermore the growth habit of it were discussed by observation of the surface of AlN crystals.

• Journal of Plant Biology
• /
• v.31 no.1
• /
• pp.51-68
• /
• 1988

To clarity the species of genus Melandrium (Caryophyllaceae) in Korea, the taxonomic characters were described and interspecific relationships were discussed to the extemal morphology with light and scanning electron microscopy. The position and size of appendages on petal, the shape and venation pattern of leaf, and the external morphology of seed and pollen were approved as the good characters to classify genus Melandrium in Korea. As the result, genus Melandrium in Korea could be arranged as 6 species, 1 variety, 1 forma. M. umbellatum was exclusively distributed in north Korea, and its taxonomic treatment was reserved.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.120.2-120.2
• /
• 2015

We propose a novel direct writing technique with a femtosecond laser enabling selective modification of not only the morphology of conducting polymer thin films but also the orientation and alignment of the polymer crystal. Surface relief gratings resulting from photoexpansion on P3HT:PCBM and PEDOT:PSS thin films were fabricated by femtosecond laser direct writing. The photoexpansion was induced at laser fluence below the ablation threshold of the thin film. The morphology (size and shape) of photoexpansion could be quantitatively controlled by laser writing parameters such as focused beam size, writing speed, and laser fluence. GIWAX results showed that face-on P3HT crystals were largely increased in the photoexpansion in comparison with pristine region of the thin film. In addition, the face-on P3HTs in the photoexpansion were aligned with their orientation along the polarization of the laser. The micro-RAMAN spectra confirmed that neither chemical composition change nor the polymer chain breaking was observable after femtosecond laser irradiation. We believe that this laser direct writing technique opens a new door to the fabrication of more efficient OPVs via non-contact, toxic-free approach.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.2
• /
• pp.267-269
• /
• 1996

Morphology of two foreign species of tongue soles (Cynoglossidae), Cynogiossus browni and C. senekalensis, was observed based on specimens collected from Kunsan fish market from 1992 to 1994. These species are externally similar to Cynoglossus robustus from Korean coast. But these are quite distincitive from Cynogiossus robustus by interlinear scale rows, body size, other counts and proportional measurements of body. The Cynogfossus browni and C. senegalensis are only distributed in western coast of Africa and commercially imported to Korea through Pusan fish market.

• Journal of the Korean Ceramic Society
• /
• v.32 no.4
• /
• pp.462-470
• /
• 1995

The characteristics of spray-dried granules are important for dry pressing operation since they have great influences on die-filling, compaction ratio, and resulting green microstructure. An attempt was made to control granule morphology and the packing structure of fine Si3N4 particles in granules by adjusting suspension property. Mercury porosimetry was used to characterize the pore structures of both granules and green compacts. Finally, the effects of particle packing structure in granules and green microstructure on sintering behavior were investigated.

• ALGAE
• /
• v.19 no.2
• /
• pp.91-105
• /
• 2004

Ten taxa of the genus Spirogyra (Zygnemataceae, Chlorophyta) in Korea were examined for morphology and taxonomic category with field as well as cultured materials: S. africana (Fritsch) Czurda, S. decimina (Muller) Kutzing, S. distenta Transeau, S. dubia Kutzing, S. ellipsospora Transeau, S. ellipsospora var. crassoidea Transeau, S. gracilis (Hassall) Kutzing, S. submajuscula Kutzing, S. peipingensis Jao and S. variformis Transeau. Features of vegetative cell and female gametangium, shape of septum, chloroplast number, sexuality, size and shape of zygospore, and ornamentation of spore wall were major characteristics used for determination of the species. All of them were described for the first time in Korea.

• Journal of Electrochemical Science and Technology
• /
• v.14 no.2
• /
• pp.194-204
• /
• 2023

Models based on diffusion-limited aggregation (DLA) have been extensively used to explore the mechanisms of dendritic particle aggregation phenomena. The physical and chemical properties of systems in which DLA aggregates emerge are given in their fractal. In this paper, we present a comprehensive study of the growth of electrodeposited copper dendrites in flat plate electrochemical cells from a fractal perspective. The effects of growth time, applied voltage, copper ion concentration, and electrolyte acidity on the morphology and fractal dimension of deposited copper were examined. 'Phase diagram' set out the variety of electrodeposited copper fractal morphology analysed by metallographic microscopy. The box counting method confirms that the electrodeposited dendritic structures manifestly exhibit fractal character. It was found that with the increase of the voltage and copper ion concentration. The fractal copper size becomes larger and its morphology shifts towards a dendritic structure, with the fractal dimension fluctuating around 1.60-1.70. In addition, the morphology of the deposited copper is significantly affected by the acidity of the electrolyte. The increase in acidity from 0.01 to 1.00 mol/L intensifies the hydrogen precipitation side reactions and the overflow path of hydrogen bubbles affects the fractal growth of copper dendrites.

• Macromolecular Research
• /
• v.16 no.2
• /
• pp.85-102
• /
• 2008

The development of reliable synthetic routes to polymer nanomaterials with well-defined size and morphology is a critical research topic in contemporary materials science. The ability to generate nanometer-sized polymer materials can offer unprecedented, interesting insights into the physical and chemical properties of the corresponding materials. In addition, control over shape and geometry of polymer nanoparticles affords versatile polymer nanostructures, encompassing nanospheres, core-shell nanoparticles, hollow nanoparticles, nanorods/fibers, nanotubes, and nanoporous materials. This review summarizes a diverse range of synthetic methods (broadly, hard template synthesis, soft template synthesis, and template-free synthesis) for fabricating polymer nanomaterials. The basic concepts and significant issues with respect to the synthetic strategies and tools are briefly introduced, and the examples of some of the outstanding research are highlighted. Our aim is to present a comprehensive review of research activities that concentrate on fabrication of various kinds of polymer nanoparticles.

• Applied Microscopy
• /
• v.42 no.4
• /
• pp.194-199
• /
• 2012

The anatomy and morphology of seeds from 10 Hawaiian Portulaca taxa were examined to explore patterns of variation among the taxa, and to evaluate their phylogenetic relationships. Features of seeds were assessed employing microtechnique procedures, statistical analysis, and scanning electron microscopy (SEM). Anatomically, the orientation of embryo was consistent across taxa, and all seeds examined had central nutritive tissue and integuments comprising the peripheral embryo. Seeds were generally small, circular to ovoid in shape, and either smooth or rough-surfaced, with tubercules. Variation in seed size was noted, although minimal within small seeded group. The size of seeds ranged from 0.50~1.26 mm in length, and 0.55~1.34 mm in width, with similar weights. Seeds were distinguished by the sculpture and arrangement of the testa epidermis and the way in which their stellulate-tessellate cells uniquely fit together. Using a multiple range test (ANOVA), two groups were established by seed characteristics. The SEM also demonstrated morphological differences in testa sculpturing. The results obtained confirm the usefulness of seed characteristics in the identification of the species examined, and furthermore, allow for the separation of the Hawaiian Portulaca into two groups.

• Journal of Powder Materials
• /
• v.5 no.2
• /
• pp.111-121
• /
• 1998

Thick and dense deposit of higher than 97% of theoretical density was formed by induction plasma spraying. To investigate the effects of powder morphology on the density of deposit, two different kinds of Yttria-Stabilized-Zirconia powder, METCO202NS (atomized & agglomerated) and AMDRY146 (fused & crushed), were used and compared. After plasma treatment, porous METCO202NS powder was all the more densely deposited and its density was increased. In addition to the effect of powder morphology, the process parameters such as, sheath gas composition, probe position, particle size and spraying distance, and so on, were evaluated. The result of experiment with AMDRY146 powder, particle size and spraying distance affected highly on the density of the deposit. The optimum process condition for the deposition of -75 ${\mu}m$ of 20%-Yttria-Stabilized-Zirconia powder was 120/201/min of Ar/$H_2$ gas rate, 80 kW of plasma plate power, 8 cm of probe position and 150 Torr of spraying chamber pressure, at which its density showed 97.91% of theoretical density and its deposition rate was 20 mm/min. All the results were assessed by statistical approach what is called ANOVA.