• Title, Summary, Keyword: Surface Tension

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Fractography of Sound and Tension Woods of Quercus mongolica by Shear and Bending Stress (신갈나무 정상재와 인장이상재의 전단 및 휨 파면해석)

  • Kwon, Sung-Min;Kwon, Gu-Joong;Jang, Jae-Hyuk;Kim, Nam-Hun
    • Journal of the Korean Wood Science and Technology
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    • v.39 no.4
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    • pp.351-358
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    • 2011
  • This study has been carried out to understand the fracture characteristics of the tension wood of Quercus mongolica under the shear and bending stress. Macroscopically, the wood fluff in the shear surface appeared more frequently in tension wood than sound wood, and more coarse wood fluffs were observed in 30% than 10% moistured shear surface. In the fractured tension wood from bending stress, more thick and long wood fiber appeared than sound wood. The observation using scanning electron microscope indicated that both sound and tension wood samples from radial shear surface showed the intrawall dominated failure and the fracture surface of the ray parenchyma cell showed the transwall dominated failure. In tangential shear surface, wood fiber surface showed the intrawall failure and short and coarse wood fiber was observed in tension wood. Ray parenchyma cell of sound and tension wood samples showed the transwall failure. The surfaces of tension wood’s ray parenchyma cell were relatively clean. The fractured tension wood from bending stress showed unsharp and flat wood fiber compared with sound wood.

Surface Tension Change of Simulant Gel Propellant according to the Metal Particle Addition (금속입자 첨가에 따른 모사젤 추진제의 표면장력 변화)

  • Kim, Kyehwan;Kim, Sijin;Han, Seungjoo;Kim, Jinkon;Moon, Heejang
    • Journal of the Korean Society of Propulsion Engineers
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    • v.21 no.3
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    • pp.34-40
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    • 2017
  • In this study, the surface tension of simulant gel propellants was measured by Du $No{\ddot{u}}y$ ring method. The variation of the surface tension was investigated with respect to the amount of the gelling agent, and metal particle addition. Distilled water was used as the base fluid for the preparation of the simulant gel propellant where Carbopol 941 was used as a gelling agent and SUS304 spherical metal particles (mean diameter : 100 nm) as simulant energetic particles. As a result of measurements, surface tension increased with increasing gelling agent concentration while, in the presence of metal particle, different behavior of surface tension has been observed.

Molecular Dynamics Simulation of a Small Drop of Liquid Argon

  • Lee, Song Hi
    • Bulletin of the Korean Chemical Society
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    • v.33 no.11
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    • pp.3805-3809
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    • 2012
  • Results for molecular dynamics simulation method of small liquid drops of argon (N = 1200-14400 molecules) at 94.4 K through a Lennard-Jones intermolecular potential are presented in this paper as a preliminary study of drop systems. We have calculated the density profiles ${\rho}(r)$, and from which the liquid and gas densities ${\rho}_l$ and ${\rho}_g$, the position of the Gibbs' dividing surface $R_o$, the thickness of the interface d, and the radius of equimolar surface $R_e$ can be obtained. Next we have calculated the normal and transverse pressure tensor ${\rho}_N(r)$ and ${\rho}_T(r)$ using Irving-Kirkwood method, and from which the liquid and gas pressures ${\rho}_l$ and ${\rho}_g$, the surface tension ${\gamma}_s$, the surface of tension $R_s$, and Tolman's length ${\delta}$ can be obtained. The variation of these properties with N is applied for the validity of Laplace's equation for the pressure change and Tolman's equation for the effect of curvature on surface tension through two routes, thermodynamic and mechanical.

Surface Activity in Various Pulmonary Diseases (각종 폐질환에서의 Pulmonary Surfactant 에 대해서)

  • Lim, Buyng-Wha;Shin, Keun-Soo;Kim, Jin-Sik
    • The Korean Journal of Thoracic and Cardiovascular Surgery
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    • v.5 no.1
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    • pp.1-8
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    • 1972
  • On the study of surface activity in excized lung extracts of various pulmonary diseases, following facts were concluded. 1]The minimum surface tension measured in lung extracts of tuberculous tissue surrounding cavitary lesion was 26.3dyne/cm and its stability index was 0.53. 2]Macroscopically almost normal lung tissue at a distance of tuberculous lesion in same lobe revealed 21.3 dyne/cm of minimum surface tension in extracts and its stability index showed 0.66. This low surface activity may be due to the chronic pneumonitis microscopically. 3] In the atelectatic lung which had been collapsed by chronic empyema the extracts revealed much higher minimum surface tension in 27.3 dyne/cm and its stabillry index revealed the least value of 0.47 without correlation of duration of disease. This suggests that the longstanding collapsed lung may be soon collapsed even after mechanical full expansion because of lack of surfactant.

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Surface-Tension Effects on the Flow Caused by a Two-Dimensional Pulsating Source Moving with a Constant Speed beneath the Free Surface (전진하며 동요하는 2차원 특이점에 의하여 발생되는 자유표면파에 미치는 표면장력의 영향)

  • Hang-S.,Choi;Jae-S.,Choi
    • Bulletin of the Society of Naval Architects of Korea
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    • v.27 no.1
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    • pp.57-62
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    • 1990
  • This paper deals with the flow caused by a two-dimensional pulsating source, which moves with a constant horizontal speed beneath the free surface. The analysis is based on lincar potential theory including surface tension effects. In the case of subcritical reduced frequencies $\tau<1/4(\tau=U_{\omega}/g$, U=constant speed, $\omega$=circular frequency, g=gravitational acceleration), six wave components arc found. Two of them are largely affected by surface tension, which propagate ahead of the source in the direction of and opposite to the steady translation, respectively. The rest are almost identical with those found by Haskind(1954), i.e. for which the surface tension effect is negligible. For low oscillation frequencies, the resonant frequency still exists at $\tau$ only slightly greater than 1/4. For oscillation frequencies greater than $\nu(={\omega}^2/g)>20$, the surface tension effect is so significant that it disperses generated waves and consequently the singular phenomenon is removed. However, in addition to the gravity breaking, capillary breakings occur when the translation speed coincides with the minimum capillary celerity.

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Effect of surfactant addition on curtain coating color properties and curtain stability (계면활성제 첨가가 커튼 코팅용 도공액의 물성과 커튼 안정성에 미치는 영향)

  • Oh, Kyu-Deok;Kim, Chae-Hoon;Youn, Hye-Jung;Lee, Hak-Lae
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.43 no.5
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    • pp.49-54
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    • 2011
  • Curtain coating has been considered as the best coating technology because it is a coating technology that forms contour coating layer with better coverage. To increase the curtain stability surfactants are being used. In this study, the effect of a surfactant on the stability of curtain coating colors was examined by evaluating dynamic surface tension with a bubble surface tensiometer. Di-2-ethylhexyl sodium sulfosuccinate was used as a surfactant since it showed low dynamic surface tension at low surface age. And we evaluated the influence of surfactant on coating color properties including surface tension, viscosity and curtain stability. The surface tension of coating color was decreased when surfactant addition was increased up to 0.5 pph, but it was leveled off at 0.3 pph of surfactant addition. With the increase of surfactant addition rate, viscosity of coating color were increased. Micelles formed by surfactant contributed to the increase of the viscosity. Curtain stability was improved with the addition of surfactant until it reached up to 0.5 pph. Excessive addition of surfactant (> 0.5 pph) didn't improve curtain stability. This was attributed to Marangoni effect(self-healing) and decreasing of curtain thickness.

The Effect of Contaminants on Tracking Aging in Polymer Insulating Materials (고분자 절연재료의 트랙킹 열화에 미치는 오손액의 영향)

  • 조한구;박용관
    • Electrical & Electronic Materials
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    • v.10 no.8
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    • pp.770-777
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    • 1997
  • Some polymer materials including epoxy resin are being instead of porcelain for outdoor insulating materials such as insulators bushings cable terminators and surge arrester housing. And the largest problem to be overcomed is the tracking and erosion of the outdoor polymer material brought about by dry band arcing during prolonged exposure to contaminations. In this paper the effect of surface tension wettability flow rate of contaminants with varying surfactant content and frequency of applied voltage on the tracking breakdown of epoxy insulating materials were investigated. As the flow rate of contaminant is increased the surface resistivity is decreased and the leakage current is increased the time to tracking breakdown is decreased. It is found that time to tracking breakdown depends on the surface tension of contaminant that is difference of wettability. And as the frequency of applied voltage is increased time to tracking breakdown decreased.

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NUMERICAL SIMULATION OF FLOWS INDUCED BY WALL ADHESION (벽면흡착에 의해 야기되는 유동 수치해석)

  • Myong, H.K.
    • 한국전산유체공학회:학술대회논문집
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    • pp.2-5
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    • 2011
  • This paper presents a numerical study on multiphase flows induced by wall adhesion The CSF(Continuum Surface Force} model is used for the calculation of the surface tension force and implemented in an in-house solution code(PowerCFD). The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with volume capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing As an application of the present method, the effects of wall adhesion are numerically simulated with the CSF model for a shallow pool of water located at the bottom of a cylindrical tank. Two different cases are computed, one in which the water wets the wall and one in which the water does not wet the wall. It is found that the present method simulates efficiently and accurately surface tension-dominant multiphase flows induced by wall adhesion.

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A Study of the Surface Tension of Some Electrolytic Solutions (몇가지 電解質溶液의 表面張力에 관한 硏究)

  • Sakong, Yull;Hwang, Jung-Euy;Son, Moo-Yong
    • Journal of the Korean Chemical Society
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    • v.8 no.1
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    • pp.1-4
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    • 1964
  • Relative surface tensions of aqueous solutions of KCl, KI and NaI have been measured at 25$^{circ}C$(30$^{circ}C$ for KCl) over a concentration range of 0.0001 to 3M solution. It was observed that there was a minimum in the surface tension-concentration curve for the extremely dilute solutions. Appearance of the minimum has been reported for the other salt solutions so far reported. At moderate and high concentration, these three salts increase the surface tension of water almost linearly as concentration increased, and behaved as a typical "capillary inactive substance", whereas they acted as a capillary active substance in very dilute solutions. Since the Onsager-Samaras equation for the surface tension as a function did not agree with the experimental data, the following empirical equations for the whole concentration range used were obtained. ${\sigma}_r\;=\;1\;+\;0.00072{\sqrt{c}}\;-\;0.0011c\;+\;0.023c^2\; for\;KCl\;at\;30^{\circ}C$ ${\sigma}_r\;=\;1\;+\;0.0077{\sqrt{c}}\;-\;0.0015c\;+\;0.024c^2\;for\;KI\;at\;25^{\circ}C$ ${\sigma}_r\;=\;1\;+\;0.00011{\sqrt{c}}\;-\;0.0090c\;+\;0.077c^2\;for\;NaI\;at\;25^{\circ}C$

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Effects of the Rapier Weaving Tension Characteristics on the Surface Properties of PET Fabrics (래피어 직기 장력특성이 PET 직물의 표면특성에 미치는 영향)

  • Kim, Seung-Jin;Park, Kyung-Soon
    • Fashion & Textile Research Journal
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    • v.7 no.6
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    • pp.673-679
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    • 2005
  • This study surveys the fabric surface properties such as mean value of the coefficient of friction(MIU), mean deviation of the coefficient of friction(MMD) and mean deviation of surface roughness(SMD) due to warp and weft tension differences using KES-FB system. For this purpose, fabric is designed as 5 harness Satin weave using 150d/48f warp and 200d/384f weft polyester filaments, and is woven by Omega$^{(R)}$ rapier loom by Textec Co.Ltd and Vamatex-P1001ES$^{(R)}$ rapier loom by Vamatex Co.Ltd respectively. These grey fabrics are processed on the same dyeing and finishing processes. The fabric surface properties according to the weaving looms are analysed with warp and weft weaving tensions. And also surveyed the difference of fabric surface properties according to the fabric positions such as center and each edge of fabrics for the sensitive garment. Fabric thickness was also measured and discussed according to the fabric positions such as center and each of fabrics with two looms weaving tensons.