• 한국초전도ㆍ저온공학회논문지
• /
• 제21권2호
• /
• pp.36-39
• /
• 2019

Effects of the spherically shaped Ge and the rod-like carbon-coated Ge on the superconducting properties of $MgB_2$ were investigated. Pure Ge and carbon-coated Ge nano-powders were synthesized under the different amount of $CH_4$ (0 to 5 kPa) by using DC thermal plasma method. When the $CH_4$ was added ~100 nm sized Ge with a spherical shape changed to rod-like morphology with a diameter of ~30-70 nm and a length of ~400-500 nm. Also it was confirmed that thin carbon layers of a few nanometers were formed along the rod length and the agglomerated carbons were found on the edges of rods. Pure spherical Ge and Ge/C rods were mixed and milled with Mg & B precursor to form the doped $MgB_2$ bulk samples by the solid-state reaction method. Almost no change of $T_c$ was noticed for the pure Ge-added $MgB_2$, whereas $T_c$ was found to decrease with the Ge/C-added $MgB_2$ samples. It was found that the pure spherical Ge showed to have a negative effect on the flux pinning of $MgB_2$. However, Ge/C rods can enhance the flux pinning property of $J_c$ due to the coated carbon on Ge rods.

• 한국환경과학회지
• /
• 제20권5호
• /
• pp.623-630
• /
• 2011

This study investigated the degradation of N, N-Dimethyl-4-nitrosoaniline (RNO, indicator of the generation of OH radical) by using dielectric barrier discharge (DBD) plasma. The DBD plasma reactor of this study consisted of a quartz dielectric tube, titanium discharge (inner) and ground (outer) electrode. The effect of shape (rod, spring and pipe) of ground electrode, diameter (9~30 mm) of ground electrode of spring shape and inside diameter (4~13 mm) of quartz tube, electrode diameter (1~4 mm), electrode materials (SUS, Ti, iron, Cu and W), height difference of discharge and ground electrode (1~15.5 cm) and gas flow rate (1~7 L/min) were evaluated. The experimental results showed that shape of ground electrode and materials of ground and discharge electrode were not influenced the RNO degradation. The thinner the diameter of discharge and ground electrode, the higher RNO degradation rate observed. The effect of height gap of discharge between ground electrode on RNO degradation was not high within the experimented value. Among the experimented parameters, inside diameter of quartz tube and gas flow rate were most important parameters which are influenced the decomposition of RNO. Optimum inside diameter of quartz tube and gas flow rate were 7 mm and 4 L/min, respectively.

• 한국정밀공학회지
• /
• 제17권12호
• /
• pp.145-150
• /
• 2000

Micro punching is one of general methods to fabricate simple holes such as permanent ink-jet printer nozzles. A thin punch, that is need for micro punching, usually has been obtained by mechanical machining. There are some method to obtain a thin punch from a cylindrical rod, e.g., microgrinding and WEDG (Wire Electro-Discharge Grinding). Inefficiently, only one punch can be obtained from these machining methods. In contrast with these methods, many punches can be fabricated simultaneously by electrochemical process. Electrochemical process has usually aimed to obtain very sharp probe for atomic force microscopy (AFM) or scanning tunneling microscopy (STM), and it has not been considered the whole shape of a probe in spite of good merits. In this paper, an ultrathin punch with a tapered shape and a cylindrical tip is newly fabricated by electrochemical process.

• Animal Systematics, Evolution and Diversity
• /
• 제31권3호
• /
• pp.182-190
• /
• 2015

Two heterotrichid ciliates, Climacostomum virens (Ehrenberg, 1838) Stein, 1859 from brackish water and freshwater, and Fabrea salina Henneguy, 1890 from a solar saltern, were collected in Korea. They are novelly investigated in Korea by means of live observation, protargol staining and nuclear small subunit (SSU) rRNA gene sequencing. Climacostomum virens is characterized by pouch-like body shape, body length of $200-370{\mu}m$ in vivo, conspicuous cytopharyngeal tube, macronuclei ribbon-like shape, and one to four in number, with or without symbiont algae in cytoplasm, 34-66 somatic kineties, 67-113 adoral zone of membranelles, 8-42 peristomial kineties, 24-37 apical membranelles. SSU rDNA sequence size is 1,591 bp and GC contents 48.52%. Fabrea salina is also characterized by scoop-like body shape with proboscis, body length of $190-240{\mu}m$ in vivo, one to two rod-shaped macronuclei, oval micronuclei, grayish green cortical granules, 104-186 somatic kineties, 4-8 preoral kineties, 7-19 peristomial kineties and fragmented paroral membrane. SSU rDNA sequence size is 1,598 bp and GC contents 47.50%.

• 한국패류학회지
• /
• 제24권1호
• /
• pp.1-10
• /
• 2008

Spermatogenesis and the reproductive cycle in male Spisula sachalinensis were investigated by cytological and histological observations. The morphology of the spermatozoon has a primitive type and is similar to those of other bivalves in that it contains a short midpiece with four mitochondria surrounding the centrioles. But spermatozoon of this species has not axial rod and satellite body in the midpiece. The morphologies of the sperm nucleus type and the acrosome shape of this species have a globe-shape type and modified cap-like shape, respectively. The spermatozoon is approximately $40-45{\mu}m$ in length including the sperm nucleus length (about $1.35{\mu}m$), acrosome length (about $1.50{\mu}m$) and tail flagellum. The axoneme of the sperm tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail shows a 9+2 structure. The spawning period of these species lasts from June to July, and the main spawning occurs in July when seawater temperatures are greater than $20^{\circ}C$. The male reproductive cycle of this species can be categorized into five successive stages: early active stage (October to January), late active stage (February to April), ripe stage (April to June), partially spawned stage (June and July), and spent/inactive stage (August to September).

• KSBB Journal
• /
• 제28권4호
• /
• pp.249-253
• /
• 2013

In this study, we analyzed the attachment amount and the surface properties, such as shape and attachment aspect of silver nanoparticles on the surface of salt and sucrose. In addition, we investigated the antimicrobial activity of silver nanoparticles by measuring total colony counts and total coliforms in sewage according to the time and the amount of silver nanoparticles. As a result, it is found that silver nanoparticles are attached on the surface of salt and sucrose from the SEM images and there is no microorganisms on the surface of salt and sucrose. Silver nanoparticles on salt were rod shape but silver nanoparticles on sucrose were round shape. Also, the content of silver was 0.735 mg/g on salt and 0.885 mg/g on sucrose. In all experiments, total colony counts and total coliforms sharply declined initially, and it decreased gradually as change the time. When injection amount of nano silver sucrose and salt increased, the width of decline was greater. The amount of total colony counts and total coliforms of nano silver salt was much lower and the disinfection efficiency was higher comparing with nano silver sucrose. That means the case of nano silver salt is much better at the antimicrobial activity.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.154-155
• /
• 2006

This study investigated a mechanism for controlling the shape of Cu nanocrystals fabricated using the polyol process, which considers the thermodynamic transition from a facetted surface to a rough surface and the growth mechanisms of nanocrystals with facetted or rough surfaces. The facetted surfaces were stable at relatively low temperatures due to the low entropy of perfectly facetted surfaces. Nanocrystals fabricated using a coordinative surfactant stabilized the facetted surface at a higher temperature than those fabricated using a non-coordinative surfactant. The growth rate of the surface under a given driving force was dependent on the surface structure, i.e., facetted or rough, and the growth of a facetted surface was a thermally activated process. Surface twins decreased the activation energy for growth of the facetted surface and resulted in rod- or wire-shaped nanocrystals

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
• /
• pp.116-117
• /
• 2006

I-D ZnO nanostructures were fabricated by thermal evaporation method on Si(100), GaN and $Al_2O_3$ substrates without a catalyst at the reaction temperature of $700^{\circ}C$. Only pure Zn powder was used as a source material and Ar was used as a carrier gas. The shape and growth direction of synthesized ZnO nanostructures is determined by the crystal structure and the lattice mismatch between ZnO and substrates. The ZnO nanostructure on Si substrate were inclined regardless of their substrate orientation. The origin of ZnO/Si interface is highly lattice-mismatched and the surface of the Si substrate inevitably has the $SiO_2$ layer. The ZnO nanostructure on the $Al_2O_3$ substrate was synthesized into the rod shape and grown into particular direction. For the GaN substrate, however, ZnO nanostructure with the honeycomb-like shape was vertically grown, owing to the similar lattice parameter with GaN substrate.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2023년도 가을학술발표대회논문집
• /
• pp.21-22
• /
• 2023

In order to manufacture high-quality free-form concrete panel (FCP), it is necessary to analyze the limitations of free-form silicone mold (FSM) and conduct technology development research. Currently, the FSM used in FCP manufacture is classified into a side silicon mold(SSM) and a lower silicon mold(LSM). In this study, the limitations of each silicon mold were analyzed and solutions were proposed. In the case of side silicon mold, there is a limit to cannot supporting the side pressure of concrete. Therefore, a mold stacking method was proposed, and at the same time, a process of correcting the movement value of the rod was proposed. In the case of the lower silicon mold, there is a limit to completely implementing the design shape. Therefore, a real-time scanning method and a process of displaying FCP shape coordinates were proposed. The results of this study are expected to be used as basic data for manufacturing high-quality FCP.

• 대한기계학회논문집A
• /
• 제34권8호
• /
• pp.1083-1089
• /
• 2010

형상기억합금은 지능형 재료와 구조물에 널리 쓰인다. 큰 힘과 변위를 발생시키는 것이 특징이며 작동기, 소음 및 진동감쇠, 동역학적 튜닝, 형상의 변형 제어 등의 다양한 분야에 응용될 수 있다. 본 논문에 서는 형상기억합금튜브와 초탄성 스프링으로 구성된 형상기억합금 비틀림 작동기를 제안하였고 각각의 거동 특성을 알아보았다. 열전달 해석을 통해 저항열과 히터의 열을 동시에 형상기억합금튜브에 가하면 작동기의 성능을 더 향상시킬 수 있음을 확인하였다. 접촉 해석으로는 실제 작동기의 거동을 시뮬레이션하였고 정상적으로 작동함을 알 수 있었다. 3 차원 형상기억합금의 거동을 표현하기 위해 비선형 구성방정식을 유한요소 법으로 풀고 ABAQUS 의 U-MAT 기능을 이용하여 비선형 해석을 수행하였다.