• Title/Summary/Keyword: twisted fibers

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Effect of Twisted Hollow Fiber Membranes in a Module: Computational Fluid Dynamics Simulations on the Pressure and Concentration Profile of the Module in the forward Osmosis (비틀린 중공사막이 모듈에 미치는 영향: 전산 유체역학 시뮬레이션을 통한 정삼투 모듈의 압력과 농도 분포)

  • Kim, Suhun;Lee, Chulmin;Kim, In S.
    • Membrane Journal
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    • v.30 no.1
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    • pp.66-77
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    • 2020
  • The current study focused on the effect of twisting hollow fibers (HFs) in a module during forward osmosis operation mode. Computational fluid dynamics simulation was employed for a straight HF module and twisted modules with five different angles to predict the mass transfer and observe the draw solution profile in terms of concentration and pressure. The simulation results showed that when the membranes were twisted, the concentration was distributed more evenly and the pressure at the module outlet increased gradually as the twisting angle increased. As pressure at the outlet increased, the fluid velocity inside the membrane decreased and the residence time of fluid increased, thereby facilitating mass exchange across the membrane. This is evidenced by a doubling of the ratio of water flux through the membrane in module flux when the HFs were twisted.

Structural Analysis and Characterization of PZT Fiber Fabricated by Electrospinning (Electrospinning법으로 제조된 PZT 섬유의 구조분석 및 특성평가)

  • Park, Chun Kil;Yun, Ji Sun;Jeong, Young Hun;Nam, Joong-Hee;Cho, Jeong Ho;Paik, Jong-Hoo;Jeong, Dae Young
    • Journal of the Korean Ceramic Society
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    • v.50 no.6
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    • pp.466-469
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    • 2013
  • Currently, piezoelectric ceramics are being applied in various fields, such as ultrasonic sensors, vibration devices, sound filters, and various energy conversion devices. Flexible piezoelectric ceramics are widely studied in an effort to mitigate the disadvantages of their brittle and inductile properties. Structural damage to piezoelectric fibers is much less than that to thin films when piezoelectric fibers are twisted or bent. Therefore, stretchable devices can be fabricated if piezoelectric fibers are obtained using an elongated substrate. In this study, sintering processes of PZT ($Pb(Zr_{0.53}Ti_{0.47})O_3$) fibers prepared by electrospinning were optimized through the TGA and XRD analyses. The crystal structure and microstructure of the piezoelectric fibers were investigated by XRD, FE-SEM and TEM.

Flexural toughness density of High Performance Fiber Reinforced Cementitious Composites (고인성 섬유보강 시멘트 복합재료의 휨인성 밀도)

  • Kim, Dong-Joo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2010.05a
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    • pp.401-402
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    • 2010
  • This research initially suggest flexural toughness density as a key parameter describing energy absorption capacity of High Performance Fiber Reinforced Cementitious Composites [HPFRCC] regardless of the size of specimen. Two types of high strength steel fibers, Hooked and Twisted fiber, were used in two types of flexural specimen ($100{\times}100{\times}350mm^3$ and $150{\times}150{\times}500mm^3$) to estimate and validate the flexural toughness density.

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Engineering Cellulose Fibers for High-Value Added Products for Pulp & Paper Industry

  • Ko, Young Chan;Park, Jong-Moon
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.47 no.6
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    • pp.22-40
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    • 2015
  • Cellulose fibers is one of the most abundant in nature. It has many distinctive features: abundant in nature, biodegradable, non-toxic, eco-friendly, sustainable, easy to fabricate, hydrophilic, and cost-effective. Cellulose fibers, known as pulp, is produced from cellulose-containing materials by the pulping process. As the raw material, wood has been most commonly used while recycled pulp has been also used to some degree. Thus, pulp usually refers to wood pulp. Generally, the pulp and paper industry is regarded as the commodity market where the cost should be much more important than the quality. It also belongs to a mature market where the growth is slow, or even in decline. Accordingly, technological development has been rather stagnant for the industry. Recently, however, the pulp and paper industry has faced very serious challenges. First, due to digital technology, there has been a steady decline in the need for pulp and paper products. The digital industry has continuously replaced printed products such as books, newspapers, and magazines. Second, there has been a trend initiated by developed countries to limit the use of wood as the raw material for the sake of environmental protection. This forces the industry to find a more efficient use of wood pulp as well as finding alternative, non-wood sources. Third, as an individual becomes wealthier and more conscious of health-care, the quality of a product becomes more important than the cost. Thus, a paradigm shift is needed from the cost-conscientious to the quality conscientious. The objective of this article is to review the technologies aimed at engineering cellulose fibers for producing high-value added paper products.

The Effect of Structural Factors on the Torsional Rigidity of Yarns

  • Park, Jung Whan
    • Fashion & Textile Research Journal
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    • v.2 no.5
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    • pp.437-442
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    • 2000
  • In this paper, in order to examine the torsional behaviour of twisted yarn closely, the torsional rigidity would be derived in terms of physical and mechanical characteristics of its constituent fibers and yarn structural parameters by energy-method. And the propriety of the theory will be discussed by comparing with experimental results. The torsional rigidity of yarn in both experimental and theoretical results decreases with surface helix angle increases. But the experimental values are more higher than those of the theoretical ones.

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Study on the Strength Retention of Technical Cord Yarn

  • Cho Dae-Hwan;Jeong Young-Jin
    • Fibers and Polymers
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    • v.7 no.3
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    • pp.305-309
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    • 2006
  • This research studies the factors which influence the tensile strength of tire cords. Five yam samples are made by changing the spinning conditions and viscosity to get various physical properties. Different twisting methods are introduced and the yams are twisted under different processing conditions for each twisting process. With the experimental results, various analyses are performed to find the important factors in retaining strength after the twisting process. SEM and optical microscopic photographs are taken along with some measurements to assist the analysis.

KNOTS IN S3 ADMITTING GRAPH MANIFOLD DEHN SURGERIES

  • Kang, Sungmo
    • Journal of the Korean Mathematical Society
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    • v.51 no.6
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    • pp.1221-1250
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    • 2014
  • In this paper, we construct infinite families of knots in $S^3$ which admit Dehn surgery producing a graph manifold which consists of two Seifert-fibered spaces over the disk with two exceptional fibers, glued together along their boundaries. In particular, we show that for any natural numbers a, b, c, and d with $a{\geq}3$ and $b,c,d{\geq}2$, there are knots in $S^3$ admitting a graph manifold Dehn surgery consisting of two Seifert-fibered spaces over the disk with two exceptional fibers of indexes a, b, and c, d, respectively.

Effect of treatment temperature on mechanical properties of silk textiles made with silk/polyurethane core-spun yarn

  • Bae, Yeon Su;Um, In Chul
    • International Journal of Industrial Entomology and Biomaterials
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    • v.33 no.2
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    • pp.108-112
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    • 2016
  • Silk has been used extensively in textile applications because of its good luster and feel. However, the low elongation and elastic recovery of silk has limited its use in a wider variety of textile applications. In this study, silk textile samples were made with a highly twisted silk/polyurethane core-spun yarn. They were immersed in water and dried at different temperatures, and the effect of treatment temperature on the mechanical properties of the silk textile was examined. It was found that the water temperature strongly affected the morphology and mechanical properties of the silk textile, whereas the drying temperature did not. As the water temperature was increased, the weft silk yarn became tangled and the interval between warp yarns decreased, resulting in shrinkage of the silk textile. When the silk textile was immersed in water at high temperature (i.e., $100^{\circ}C$), the elongation of the textile increased eight-fold as compared to an untreated silk textile. The maximum elastic recovery ratio of the silk textile was 96.7%.

Effect of Washing Conditions on Dimensional Change and Mechanical Properties in Polyester/Spandex Knit Fabric (세탁조건에 따른 폴리에스터/스판덱스 편성물의 형태안정성과 역학적 특성 변화)

  • Roh, Eui Kyung;Kim, Eunae
    • Fashion & Textile Research Journal
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    • v.20 no.1
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    • pp.93-100
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    • 2018
  • This study comparatively analyzed the changes in the dimensional stability and the mechanical properties of stretch knit fabrics associated with washings conditions in order to determine the most appropriate washing method. Polyester and spandex knit fabrics were washed 25 cycles with nine washing condition profiles that controled detergent, hardness. temperature and RPM. The knit fabrics with repeated washings were evaluated by dimensional stability and measured by the KES-FB system. Polyester and spandex fibers have good chemical resistance. However, the changes in the dimensional stability and the mechanical properties were observed in washed knit fabrics. After repeated washings, the knit fabrics washed in an alkali or neutral detergent had good dimensional stability compared with the knit fabric washed in functional detergent. The washed knit fabrics were extended, stiff, rough, and had a smaller volume. The changes were the result of the rearrange of polyester fibers which twisted around spandex core and chemical interactions involving the detergent and the physical and mechanical forces of washing. Especially, using an alkali detergent resulted in increased stiffness and roughness of the knit fabric. In conclusion, the washing in water with low hardness and a neutral detergent can minimize the changes in dimensional stability and mechanical properties of polyester and spandex knit fabric.

Photoisomerization and Photo-induced Optical Anisotropy of Polymethacrylate Containing Aminonitroazobenzene

  • Park, Dong-Hoon;Cho, Kang-Jin
    • Fibers and Polymers
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    • v.2 no.1
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    • pp.123-130
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    • 2001
  • Photoresponsive side chain copolymer and homopolymer containing an aminonitroazobenzene were synthesized for studying photoisomerization behavior and photo-induced anisotropy. Trans-to-cis photoisomerization was observed under the exposure of a circularly polarized visible light with UV-Vis absorption spectroscopy. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532nm. Polarized absorption spectroscopy was employed to investigate the anisotropy of the polymer film during irradiationg of the excitation light. Layers of two photosensitive polymers were used for aligning liquid crystal(LC) molecules instead of one of the rubbed polyimide layers in the conventional twisted nematic cell. For producing homogeneous alignment of a nematic LC molecule, a linearly polarized light was exposed to the films of two polymers. The stability of the LC alignment upon the linearly polarized light exposure was also studied.

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