• Title/Summary/Keyword: Tubes

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Effect of corrosion environment on the SCC of Al-brass tube for vessel (선박용 Al-황동세관의 SCC에 미치는 부식환경의 영향)

  • 임우조;정해규
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.39 no.4
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    • pp.291-297
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    • 2003
  • Al-brass is usually used as the tube material of vessel's heat exchanger for seawater cooling system because it has high thermal conductivity and good mechanical properties and high corrosion resistance due to cuprous oxide (Cu20) layer against seawater. However, Al-brass tubes of heat exchanger for vessel at the actual environment is reported that local corrosion such as stress corrosion cracking occurred by synergism effect between mechanical factor and corrosion environment In this paper, the effect of corrosion environment on the stress corrosion cracking of Al-brass in various NH4OH of 3.5% NaCl solution, under flow by constant displacement tester. Based on the test results, the behavior of polarization, stress corrosion crack propagation and dezincification phenomenon of Al-brass are investigated. The main results are as follows:(1) Increasing range of potential from open circuit potential to repassivation gets lower, as the contain rate of NH4OH gets higher. (2) As contain rate of NH4OH gets higher, SCC of Al-brass is become activation but the protection film(Cu20) of Al-brass is created in 3.5% NaCl solution. (3) According as content of NH4OH increases in 3.5% NaCl solution, the dezincifiction area is spread. It is concluded that dezincification occurred by localized preferential anodic dissolution at stress focusing region.

Biological performance evaluation of tubular subsurface cage system for sea cucumber, Apostichopus japonicus, grow-out by in-situ tests (해상 실험에 의한 침하식 해삼 양성 기구의 생물학적 성능 평가)

  • Oh, Moo-Hwan;Kwon, Inyeong;Kim, Taeho
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.50 no.2
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    • pp.202-213
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    • 2014
  • The sea cucumber, Apostichopus japonicus, is becoming an important aquaculture species in China, Japan and Korea. The purpose of this study is to evaluate the biological performance of a tubular type of subsurface cage for sea cucumber grow-out by in-situ tests. The cage structure was constructed of PP (polypropylene) frames and PP tubes (${\phi}130mm{\times}24pieces$). A set of tests were conducted at a depth of 15 m near Seosaeng, Ulsan, Korea for 295 days (23 July, 2012 to 13 May, 2013). A total of 155 sea cucumbers were used and fed a mixed diet containing mud, mineral, wheat, fish meal, etc (3% of their body weight). At the end of the experiments, sea cucumber showed a higher survival rate in feed shelter (77.14%) rather than no feed shelter (64.71%). The specific growth rate (SGR) of sea cucumbers in feed condition (0.04% $day^{-1}$) was higher than that of no feed culture animals (-0.49% $day^{-1}$) during total experimental periods. The result was able to find a no significance difference in survival rate but a significance difference in SGR under feed and no feed treatments.

Development of Pressure Monitoring System and Pressure Changes during Kimchi Fermentation (김치발효 중 가스압력 변화와 압력측정시스템의 개발)

  • Lee, Young-Jin;Chun, Jae-Kun
    • Korean Journal of Food Science and Technology
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    • v.22 no.6
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    • pp.686-689
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    • 1990
  • For the monitoring of kimchi fermentation states, pressure detecting sensor and monitoring device were designed and fabricated. The system was consisted of an air tight fermenting tube(31.5 ml), strain gauge type pressure sensor and signal processing device built with operational amplifier and A/D converter, and interfaced to personal computer. Chiness cabbage kimchi was fermented in the plastic container($150{\times}220{\times}160mm$) at $25^{\circ}C\;and\;30^{\circ}C$. The fermentation was monitored with fermenting tubes containing kimchi. The pressure based kimchi fermentation curve was constructed and showed a typical kimchi curing curve having 2 stepwise pressure increasing pattern.

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Condensation Heat Transfer Characteristics of Hydrocarbon Refrigerants in Horizontal Tubes of 7.73 mm and 5.80 mm (7.73 mm와 5.80 mm 수평관내 탄화수소 냉매의 응축 열전달 특성)

  • Son, Chang-Hyo
    • Journal of Hydrogen and New Energy
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    • v.19 no.4
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    • pp.331-339
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    • 2008
  • 본 논문은 내경 7.73 mm와 5.80mm의 수평관내 프레온계 냉매 R-22와 탄화수소계 냉매 R-290과 600a의 응축 열전달 계수의 실험적 결과를 나타내었다. 실험장치는 압축기, 응축기, 팽창밸브, 증발기 등으로 구성된다. 응축 실험은 질량유속 $35.5{\sim}210.4\;kg/m^2s$이고, 응축온도 40$^{\circ}C$인 조건에서 수행하였다. 주요 결과를 요약하면 다음과 같다. 탄화수소계 냉매 R-290과 R-600a의 평균 열전달 계수는 프레온계 냉매 R-22보다 높게 나타났으며, R-600a의 평균 열전달 계수가 모든 관경에 대해 가장 높게 나타났다. 실험결과와 종래의 상관식을 비교한 결과, 모든 관경과 냉매에 대해 Haraguchi 등의 상관식이 가장 좋은 일치를 보였다. 그 중에서 Cavallini-Zecchin의 상관식은 7.73 mm 관경의 실험데이터와, Dobson 등의 상관식은 내경 5.80 mm 관경의 데이터와 좋은 일치를 보였다.

Analysis of UreB Protein Synthesis from Transgenic Lily Pollen (형질전환 백합화분을 이용한 UreB단백질의 발현분석)

  • 박희성;박인혜
    • KSBB Journal
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    • v.17 no.6
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    • pp.577-581
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    • 2002
  • In an attempt to produce recombinant proteins using the pollen enriched in some plant species, a 1.7 kb DNA encoding urease subunit B (UreB) amplified by PCR from Helicobacter pylori urease gene cluster in pH808 plasmid was cloned to be expressed under CaMV35S promoter in lily (Lilium longiflorum) pollen tubes elongated in vitro. Lily pollen at early germinating stage was transformed with the ureB DNA using Agrobacterium via vacuum infiltration and, incubated for a full pollen tube growth 16 - 24 h in the dark in the presence of kanamycin. DNA integration and expression in the transgenic pollen were analyzed by the standard molecular techniques and the results suggest that the pollen in vitro may be employed as a protein factory in a disposable fashion.

Degree of conversion of resin composite cured by light through a translucent fiber posts

  • Urapepon, Somchai
    • The Journal of Advanced Prosthodontics
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    • v.6 no.3
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    • pp.194-199
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    • 2014
  • PURPOSE. This study evaluated the depth of cure of resin composite cured by light through a translucent fiber post. MATERIALS AND METHODS. The opaque plastic tubes in various lengths of 2, 4, 6, 8, 10, 12, 14 mm. were filled with resin composite in which two different translucent fiber posts were inserted into the center and photo-polymerized for 40 seconds. The degree of conversion of the cured composite at bottom surface were examined using Fourier transform infrared attenuated total reflection spectrometer (FTIR/ATR) at 0.1, 0.5 and 1.0 mm apart from the post surface. RESULTS. The degree of conversion of the 0.1 mm, 0.5 mm, 1.0 mm apart from the post surface was highest at the 2 mm level and continuously decreased when the distance from the light source was increased and drastically decreased when the depth from the top of the post was greater than 4-6 mm. For each level, the highest degree of conversion was at 0.1 mm from the post surface and decreased continuously when the distance apart from the post surface was increased. CONCLUSION. The quantity of light transmission depends on the type of post and the light transmission capability of the post, especially after 4-6 mm depth and the area further apart from the post surface, are insufficient for clinical light activation of resin composite.

Column Shortening Prediction of Concrete Filled Tubes using Monte Carlo Method (몬테카를로 기법을 이용한 CFT 기둥축소량의 예측)

  • Jang, Sung-Woo;Song, Hwa-Cheol;Sho, Kwang-Ho
    • Journal of Korean Association for Spatial Structures
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    • v.10 no.1
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    • pp.75-84
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    • 2010
  • According to the available study and experimental data about the long term behavior of CFT(Concrete Filled Tube) columns, the creep and of concrete in CFT columns are smaller than those of RC columns because of the confinement effect of outer steel columns. In this study, the uncertainties associated with assumed values for concrete properties such as strength, creep coefficients, and service load have been considered and analyzed for the prediction of time-dependent column shortening of CFT column. The CFT column shortening analysis using Monte Carlo method is proposed and an of a 37 story tall building with CFT columns is studied for illustration. According to the results obtained by the probability analysis with multi parameters, the effect of variation coefficient for 3 parameters is investigated considering confidence interval.

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An Isothermal Mganetohydrodynamic Code and Its Application to the Parker Instability

  • KIM JONGSOO;RYU DONGSU;JONES T. W.;HONG S. S.
    • Journal of The Korean Astronomical Society
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    • v.34 no.4
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    • pp.281-283
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    • 2001
  • As a companion to an adiabatic version developed by Ryu and his coworkers, we have built an isothermal magnetohydrodynamic code for astrophysical flows. It is suited for the dynamical simulations of flows where cooling timescale is much shorter than dynamical timescale, as well as for turbulence and dynamo simulations in which detailed energetics are unimportant. Since a simple isothermal equation of state substitutes the energy conservation equation, the numerical schemes for isothermal flows are simpler (no contact discontinuity) than those for adiabatic flows and the resulting code is faster. Tests for shock tubes and Alfven wave decay have shown that our isothermal code has not only a good shock capturing ability, but also numerical dissipation smaller than its adiabatic analogue. As a real astrophysical application of the code, we have simulated the nonlinear three-dimensional evolution of the Parker instability. A factor of two enhancement in vertical column density has been achieved at most, and the main structures formed are sheet-like and aligned with the mean field direction. We conclude that the Parker instability alone is not a viable formation mechanism of the giant molecular clouds.

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Polycrystalline Ceramic Fibers by Extrusion

  • Sagesser, Peter;Wegmann, Markus;Gut, Beat;Berroth, Karl;,
    • The Korean Journal of Ceramics
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    • v.4 no.4
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    • pp.382-386
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    • 1998
  • titanate and a silicon carbide/zirconium diboride particulate composite have each been blended with thermoplastic of aqueous binders and extruded. The green extrudates have diameters ranging between 50 and 150 ㎛ and polyethylene-base 150 ${\mu}m$ diameter fibers can be drawn down at elevated temperature to approximately 40 ${\mu}m$ diameter. Hollow fibers with 150${\mu}m$ outer and 90 ${\mu}m$ inner diameter can also be fabricated. Green fibers have been processed into chopped fiber felts for use as gas distributors/current collectors in an experimental solid oxide fuel cell (SOFC) and the first attempts at producing simple textile structures have been successful. The fibers, tubes and felts have been successfully debound and sintered and characterization of the sintered PSZ fibers, for example, has revealed a density in excess of 99% and tensile failure stresses up to 1.0 GPa for 78 ${\mu}m$ diameter fibers.

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The Effect of Processing Parameters on HTS Tube Characteristics

  • Jung, Sengho;Jang, Guneik;Ha, Dongwoo;Sung, Taehyun
    • Transactions on Electrical and Electronic Materials
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    • v.5 no.2
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    • pp.55-60
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    • 2004
  • High-temperature Superconductor(HTS) tubes were fabricated in terms of different chemical compositions and various SrSO$_4$additions by centrifugal forming method. For powder melting by induction the optimum range of melting temperatures and preheating temperature were 1050$^{\circ}C$, 1100$^{\circ}C$ and 550$^{\circ}C$ for 30 min, respectively. The mould rotating speed was 1000 rpm. A tube was annealed at 840$^{\circ}C$ for 72 hours in oxygen atmosphere. The plates like grains more than 20 $\mu\textrm{m}$ were well developed along the rotating direction of mould regardless of initial chemical compositions and the amounts of SrSO$_4$in Bi2212. The specimen with Bi2212 composition exhibited T$\_$c/ of 83 K, while the specimens fabricated with other compositions are lower than 60 K. The measured I$\_$c/ and J$\_$c/ at 77 K(B = 0 T) in Bi2212 with 7 % SrSO$_4$ composition were about 680 A and 380 A/$\textrm{cm}^2$.