• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.199-199
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• 1999

상용의 PVC가 갖는 소수 특성을 개선하기 위해 산소, 아르곤, 수소 이온의 이온 보조 반응법을 이용하여 표면의 친수성을 증대시키고 이때 친수성 증가의 직접적 원인인 표면에너지 증가를 각각의 이온조사에 따라서 비교하였다. 이온 소스는 직경 5-cm의 cold hollow cathod ion gun을 이용하였으며 산소, 아르곤, 수소이온을 이온 조사량 5$\times$1014~1$\times$1017ions/cm2까지 변화시키고 산소의 유량을 0~8sccm까지 변화시키면서 표면 에너지 변화를 관찰하였다. 표면 에너지는 두 가지의 극성 용매인 물과 포름아마이드의 접촉각을 정적 접촉각 측정기를 이용하여 측정한 후에 이로부터 dispersion force와 polar force를 계산하여 얻었다. 계산된 결과를 보면 처리 전과후의 dispersion force의 변화는 거의 없으나 polar force는 크게 증가하였다. 이때 표면 에너지의 증가는 표면 형상의 변화와 극성을 띠는 친수성기의 증가로 여겨지며 각각의 경우에 대한 분석을 위해 AFM과 XPS 분석을 시행하여 각각의 이온에 따르는 표면 형상의 변화와 친수성기의 형성 및 상대적인 양을 비교하였다.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.169-175
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• 2008

A fine carbon fibers dispersion model is implemented to calculate the scattering range and ground level concentration of carbon fibers emitted at certain altitudes of atmospheric boundary layer. This carbon fibers dispersion model was composed by coupling a commonly used atmospheric dispersion model and an atmospheric boundary layer model. The atmospheric boundary layer model, applying the Monin-Obukov Similarity Rule obtained from measurement input data at ground level, was used to create the atmospheric boundary layer structure. In the atmospheric dispersion model, the Lagrangian Particle Model and the Markov Process were applied to calculate the trajectory of scattered carbon fibers relative to gravity and aerodynamic force, as well as carbon fibers specification.

• Journal of the Korean Society of Clothing and Textiles
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• v.15 no.4 s.40
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• pp.431-435
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• 1991

The dispersion and Poiar force components of the surface free energy of PET fibers untreated and treated with hydrophilic chemicals, such as nonionic-soil release polymer (SRP), anionic, nonionic and hydrophilic silicone, were determined using harmonic-mean and geometric-mean methods. Contact angles of water and methylene iodide on the fibers were determined from the adhesion tensions using tensiometric method. Fibers treated with hydrophilic chemicals have the increased polar force component and the decreased dispersion force component. The adhesion tensions of triolein for the hydrophilic treated fibers were smaller than that for untreated fiber.

• Journal of the Korean Chemical Society
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• v.23 no.4
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• pp.210-216
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• 1979

A simple method to calculate the interfacial tension between two immiscible molten polymers has been developed. The theory is based on the significant structure theory of liquids. The energy of adhesion is expressed as a geometric mean of the cohesion energies multiplied by correction factor $({\Phi}12)$, ${\Delta}E_{12}={\Phi}_{12}\sqrt{{\Delta}E_{11}{\Delta}E_{22^{\circ}}$. In the calculation of ${\Delta}E_{11}\;and\;{\Delta}E_{22}$, a quasilattice of polymer chains has been assumed. It is assured that, besides the dispersion force, the polar force interactions between polymer constituent groups should be considered in the calculation of the interfacial tensions.

• Applied Chemistry for Engineering
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• v.24 no.2
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• pp.165-170
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• 2013

An external gelation method in place of an internal gelation method applied to the fabrication process of an intermediated compound of Uranium Oxy-Carbide (UCO) kernel spheres for Very High Temperature Reactor (VHTR) fuel preparation is under development in Korea. For the preliminary experiments of the UCO kernel sphere preparation using an external gelation method, the carbon black dispersion experiments were carried out using a simulated broth solution. From the selection experiments of various kinds of carbon black through dispersion experiments in a viscous metal salt solution, Cabot G carbon black was selected owing to its dispersion stability, and the homogeneous dispersing state of carbon black particles in our system. For the effective dispersion of nano-size aggregated carbon black particles in a high viscous liquid, the carbon black particles in a metal salt solution were first de-aggregated with ultrasonic force. The mixed solution was then dispersed secondly by the use of the extremely high-speed agitation with a mechanical mixer of 6000 rpm after feeding the Poly Vinyl Alcohol (PVA) in the solution. This results in the broth solution with good stability and homogeneity alongside no further changes in physical properties.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.4
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• pp.570-577
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• 2002

Charged liquid particle's behavior in electric and flow field was simulated to define the effect of electric field on the contact area and its dispersion. For the simulation of flow and electric field finite volume method was applied. To find out the particle's moving path in that field lagrangian equation of motion was solved by Runge-Kutta methods. We assumed that the particle was charged 10% of Rayleigh limit while the particle passing through the electrode and the particle does not have an effect on the electric field. In case of 30[Kv] of voltage charging the particles injected from the central 60% of the nozzle injection area adhere to the grounded moving plate and no dispersion occurred. Increasing the charged voltage to 40[Kv], it brought about the same phenomena as that of 30[Kv] charging except the dispersion. Voltage increasing from 30[Kv] to 40 [Kv] caused higher Coulomb force acts on the particle and it made the particle dispersion.

• Wind and Structures
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• v.9 no.4
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• pp.315-330
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• 2006

Flow and scalar dispersion around Cheomseongdae are numerically investigated using a three-dimensional computational fluid dynamics (CFD) model with the renormalization group (RNG) $k-{\varepsilon}$ turbulence closure scheme. Cheomseongdae is an ancient astronomical observatory in Gyeongju, Korea, and is chosen as a model obstacle because of its unique shape, that is, a cylinder-shaped architectural structure with its radius varying with height. An interesting feature found is a mid-height saddle point behind Cheomseongdae. Different obstacle shapes and corresponding flow convergences help to explain the presence of the saddle point. The predicted size of recirculation zone formed behind Cheomseongdae increases with increasing ambient wind speed and decreases with increasing ambient turbulence intensity. The relative roles of inertial and eddy forces in producing cavity flow zones around an obstacle are conceptually presented. An increase in inertial force promotes flow separation. Consequently, cavity flow zones around the obstacle expand and flow reattachment occurs farther downwind. An increase in eddy force weakens flow separation by mixing momentum there. This results in the contraction of cavity flow zones and flow reattachment occurs less far downwind. An increase in ambient wind speed lowers predicted scalar concentration. An increase in ambient turbulence intensity lowers predicted maximum scalar concentration and acts to distribute scalars evenly.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1600-1602
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• 1996

We have investigated the anisotropic dispersion force effects for surfaces alignment of liquid crystals (LCs) on rubbed polystyrene (PS) surfaces by unidirection. In microphotographs an of the textures, we obtained the nematic (N) LCs are shown to align in both direction parallel and perpendicular to the rubbing for region up to medium rubbing, however to align in the direction perpendicular to the rubbing for strong rubbing region. We suggest that the anisotropic dispersion force is very important rather than macro-surface groove effect to uniform alignment of LCs. We also measured the temperature dependence of extrapolation length of 5CB on rubbed PS surfaces for strong rubbing. It is shown that the polar anchoring strength of 5CB is very weak on rubbed PS surface compared to the rubbed polyimide (PI) surface.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.994-1000
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• 2004

It is growing the application of the removal ground anchor with tension force for earth retaining constructions in the downtown. Nowadays, we can find the compression dispersion anchor on many site. But, it is occur some probelems in behabior of anchors because of impossible to tense p.c strand uniformly with existing equipment due to different length of p.c strand. So we tried to tense each p.c strand uniformly with auto back equipment in-situ test. This study compared and analyzed in-situ test results of an existing equipment with those of auto back equipment by appling elastic theory. As a result of the test, It has been proved that differences of tension force in the existing equipment increases with increasing the number of p.c strands. This can cause the ultimate failure of the concentrated p.c strand and the shear failure of ground. So it has been proved that auto back equipment is necessary.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1441-1444
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• 2013

Hetero-dimer anions of naphthalene (Np), anthracene (An), phenanthrene (Ph) and pyrene (Py) were investigated using the time-of-flight mass spectrometer (TOF-MS), anion photoelectron spectroscopy (PES) and theoretical calculation. There are two possible geometries with their electron affinity (EA) difference: parallel displaced (PD) and T-shaped. Dispersion force plays a key role in PD structure with the formation of a new anionic core while ${\pi}$-hydrogen interaction plays a key role in T-shaped structure with the monomer anionic core. The optimized structures and charge distributions can simply be explained by the relative difference of EA.