• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.93-94
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• 2006

A novel production method for porous metal components has been developed by applying powder space holder (PSH) method to metal powder injection molding (MIM) process. The PSH-MIM method has an industrial competitive advantage that is capable of net-shape manufacturing the micro-sized porous metal products with complicated shapes and controlled porosity and pore size. In this study, the small impeller with homogeneous micro-porous structure was manufactured by the PSH-MIM method. The effects of combinations in size and fraction of PMMA particle on dimensional tolerance and variation of sintered porous specimens were investigated. It was concluded that the PSH-MIM method could manufacture commercially microporous metal components with high dimensional accuracy.

• Journal of Species Research
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• 제9권2호
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• pp.122-130
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• 2020

Cavernocypris reddelli n. sp. is a new species of the genus Cavernocypris collected from spring waters of Texas, U.S.A.. This is the sixth species of the genus described so far. It can be distinguished from the other species of the genus by the shape and length of carapace, presence of robust marginal pore canals on right valve, number and length of setae on second antenna, shape of hemipenis, numbers of whorls on the Zenker organ, and differences in other parts of chaetotaxy. The new species was compared with other species and a new taxonomic key for the genus is presented for future studies.

• Archives of Metallurgy and Materials
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• 제65권4호
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• pp.1341-1344
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• 2020

In this study, a simple and effective way to fabricate highly porous scaffolds with controlled porosity and pore size is demonstrated. Ti-7Zr-6Sn-3Mo shape memory alloy fibers were prepared through a melt overflow process. The scaffolds with porosity of 65-85% and large pores of 100-700 ㎛ in size were fabricated by sintering the as-solidified fibers. Microstructures and transformation behaviors of the porous scaffolds were investigated by means of SEM, DSC and XRD. The scaffolds were composed of β phase at room temperature. Superelasticity with the superelastic recovery strain of 7.4% was achieved by β ↔ α" phase transformation. An effect of porosity on mechanical properties of porous scaffolds was investigated by using compressive test. As the porosity increased from 65% to 85%, elastic modulus and compressive strength decreased from 0.95 to 0.06 GPa and from 27 to 2 MPa, respectively.

• 한국전기전자재료학회논문지
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• 제23권8호
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• pp.581-586
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• 2010

The porous Si (PS) was annealed at various temperature in air, argon, and nitrogen atmosphere. Structural and optical properties of the annealed PS were investigated by scanning electron microscopy (SEM) and photoluminescence (PL). It is found that the shape of pore is changed from circle to channel as increasing annealing temperature which was annealed in air and argon atmosphere. In case of PS annealed in nitrogen atmosphere, the shape of pore is changed from channel to circle with increase annealing temperature from 600 to $800^{\circ}C$. The PL peak position is blue-shifted with increasing annealing temperature. As annealing temperature increases, the PL intensity of the PS annealed in argon is decreased but that of the PS annealed in nitrogen is increased. It might be due to the formation of Si-N bonds and it passivates the non-radiative centers which is Si dangling bonds on the surface of the PS.

• 한국재난정보학회 논문집
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• 제20권3호
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• pp.593-600
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• 2024

연구목적: 본 연구에서는 아크 용접 과정에서 발생하는 불티를 포집하기 위한 기초 연구를 수행하였다. 연구방법: 이를 위해서 불티를 흡입하기 위한 송풍기와 노즐 그리고 흡입부의 필터와 자석으로 구성된 목업 포집 장치를 제작하였다. 필터의 형상과 자력 특성에 따른 상관관계를 분석하기 위하여 용접기의 용량 1,800W, 용접 시간 70s인 조건에서 카본필터와 콜게이트 필터 각각의 기공률과 기공의 크기를 정량화하였으며, 자력 크기 2.6, 3.4, 4.05kgf인 경우 불티의 포집 효율을 산출하였다. 연구결과 및 결론: 그 결과 불티를 포집하기 위한 송풍기 흡입 용량, 자력의 크기, 기공률 그리고 기공 직경에 대한 경험식을 도출하였으며, 실험 결과가 ± 10% 이내에서 일치하는 것을 확인하였다. 본 연구 결과는 건설 현장에서 용접 작업에 따른 화재 확산 위험을 최소화할 수 있는 정량화된 포집기 설계 방안을 제시하는데 활용이 가능할 것으로 판단된다.

• Geomechanics and Engineering
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• 제5권5호
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• pp.419-445
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• 2013

This paper presents an experimental study on the influence of principal stress direction and magnitude of intermediate principal stress on the undrained stress-strain-strength behaviors of Bangkok Clay. The results of torsional shear hollow cylinder and advanced triaxial tests with various principal stress directions and magnitudes of intermediate principal stress on undisturbed Bangkok Clay specimens are presented. The analysis of testing results include: (i) stress-strain and pore pressure behaviors, (ii) stiffness characteristics, and (iii) strength characteristics. The results assert clear evidences of anisotropic characteristics of Bangkok Clay at pre-failure and failure conditions. The magnitude of intermediate principal stress for plane-strain condition is also investigated. Both failure surface and plastic potential in deviatoric plane of Bangkok Clay are demonstrated to be isotropic and of circular shape which implies an associated flow rule. It is also observed that the shape of failure surface in deviatoric plane changes its size, while retaining its circular shape, with the change in direction of major principal stress. Concerning the behavior of Bangkok Clay found from this study, the discussions on the effects of employed constitutive modeling approach on the resulting numerical analysis are made.

• 펄프종이기술
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• 제34권3호
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• pp.25-31
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• 2002

The purpose of this study was to analyze how the fiber properties and mixing ratio of softwood and hardwood pulp affect on roundness of printed image. Softwood pulp and hardwood pulp were refined to 400 and 600ml CSF by Valley beater and handsheets of 70 g/$m^2$ basis weight were made at different mixing ratios of hardwood and softwood pulp. The roundness, dot area, and shape of the printed dot were measured by Image Analyzer. The depths and shapes of the acridine orange penetration into paper were measured by CLSM. With higher mixing ratio of hardwood pulp, the paper showed higher air-permeability and better formation, especially at lower freeness. The roundness of the printed image became better and the dot size became smaller when the amount of hardwood pulp increased. Penetration depth of acridine orange by CLSM became greater and roundness increased to real circle when the amount of hardwood pulp increased. It was thought that higher mixing ratio of hardwood fibers resulted in efficient penetration by better formation with uniform micro-pore distribution and it increased roundness. It was thought that fiber properties and mixing ratio affected the structure of paper and the shape of the printed dot. This study showed that the measurement of depth of the liquid penetration into paper without destruction and contact was feasible. Moreover, this method showed that the shape of the liquid penetration was measurable.

• 한국주조공학회지
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• 제22권5호
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• pp.265-270
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• 2002

A novel jewelry master pattern manufacturing process which reduce manufacturing steps by employing a Duraform rapid prototyping mold and a low melting alloy has been suggested. The novel process follows the steps of 'jewelry 3D CAD design ${\rightarrow}$ Durafrom RP mold ${\rightarrow}$ low melting alloy master pattern' while the previous process follows more complicated steps of 'jewelry idea sketch ${\rightarrow}$ detailed drawing ${\rightarrow}$ wax carving ${\rightarrow}$ flask ${\rightarrow}$ silver master pattern.' An upper and a lower part of molds have been manufactured of Duraform powder, of which melting point is $190^{\circ}C$. A maser pattern was manufactured by pouring a low melting alloy of Pb-Sn-Bi-Cd, so called Woods Metal, of which melting point is $70^{\circ}C$, into the mold. The master pattern is a shape of a disk of 20mm diameter that contains various design factors. The variations of dimensions, surface roughness, surface pore ratio were measured by an optical microscope, a surface roughness profilometer, and a Rockwell hardness tester. The pattern made of were maeasured by an optical microscope, a surface roughness profilometer, and a Rockwell hardness tester. The pattern made of low melting alloy has sufficient surface hardness, and surface pore ratio to be used as the jewelry master pattern.

• 대한환경공학회지
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• 제22권5호
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• pp.927-938
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• 2000

박테리아를 토양과 같은 다공성 매질에 주입시키고 적절한 기질과 영양분을 공급시키면 박테리아는 매질의 표면에 부착하여 성장한다. 그 결과 바이오필름이 생성되어 공극의 크기가 감소하여 매질의 투수계수가 감소되며, 오염물질을 분해시키는 생물학적 오염분해 능력을 갖게 된다. 본 연구는 투수계수가 비교적 큰 모래와 화강풍화토에 박테리아를 접종, 배양한 후 토양의 투수계수의 변화를 측정하였으며, 배양된 바이오필름의 화학물질에 대한 저항성 및 온도변화에 대한 내구성 실험을 통해 대용 차수재로의 가능성을 평가하였다. 또한 bio-barrier의 유기물질 분해능 및 bio-barrier의 두께에 따른 미생물의 생장도를 column test를 통하여 측정하여 bio-barrier 내에서의 기질의 이동 및 생분해와 박테리아 농도의 분포 변화간의 관계를 제시하였다.

• 한국가축번식학회지
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• 제19권2호
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• pp.105-117
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• 1995

This study was carried out to investigate the histomorphological changes and the electrophoretic patterns of egg components, obtained from 100 of 1-year-old female catfish(Silurus asotus). Especially, the light microscopic and ultrastructural changes of ooplasm and follicular membranes of oocytes, were observed by light and transmission electron microscope. All data were collected from October in 1992 to May in 1993. The size of the nucleoli and number of the yolk granules increased as the oocyte grew. Yolk granules were deposited in the oocyte as fluid. Due to the presence of large early and late maturing oocytes, their ovaries were large, transparent, granular, and greenish in color. As the percentages of fish in LMO and RO stage increased from March to April, mean of GSI values(19.95%) increased. Follicle cells such as granulosa cell and thecal cell change a squamous into cuboid shape in LPO and EMO stage. Processes, microvilli, from the granulosa cells and from the oocyte grow and make contact with each other in the pore canals of the zona radiata during vitellogenesis, but are withdrawn as the zona radiate becomes more compact and devoid of pore canals during oocyte maturation. The electrophoretic pattern of major band in mature stage was much thicker(21k, 24k, 32k, 45k, 67∼110k, 170k dalton) than that in previtellogenic phase.