• 한국의류학회지
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• 제17권4호
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• pp.511-517
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• 1993

Changes of the surface and interface tension with temperature for washing liquids and alkanes were measured by FACE surface tensiometer. Using the extended Fowkes' equation, the dispersion and polar force components of the surface tension were estimated. The results were as follows : 1. The surface tensions of washing liquids and alkanes decreased almost linearly with the increase of temperature. 2. The interface tensions of 0.25% DBS/alkane increased slowly with the increase of temperature. In the case of nonionic surfactant solutions, however, the interface tensions with alkanes varied with the number of hydrophilic ethylene oxide(EO) groups. 3. Of the surface tension of water at $20^{\circ}C$, the dispersion force component was 25.3 dyn/cm and the polar force component was 47.8 dyn/cm. As the temperature increased, both the polar and dispersion force components decreased in a similar fashion. 4. The dispersion force component of surface tension of 0.25% DBS solution was 30.0 dyn/cm, and the polar force component was 2.2 dyn/cm at $20^{\circ}C$. The two components decreased with the increase of temperature. 5. As the temperature increased, the dispersion force component of surface tension decreased and the polar force component increased significantly for 0.25% NPPG-7.5EO solution. In the case of 025% NPPG-10EO, both the dispersion and polar force components decreased slowly, but the polar force component is expected to increase from $60^{\circ}C$. However, the polar force component of surface tension decreased with the increase of temperature for 025% NPPG-15EO solution, and at the temperature higher than $60^{\circ}C$ the surface tension is expected to be composed of only dispersion force component.

• Tribology and Lubricants
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• 제27권6호
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• pp.332-337
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• 2011

The object of this experimental study is to investigate influences of vibrator amplitude on clamping force in vibration for bolted joint. The experiment is that change the vibrator amplitude to check clamping force. also the friction coefficient calculated by equation to use an obtained in experiments. The main purpose of generation vibrations is decreasing the clamping force dispersion. also If vibration occurs while tightening the bolt is reduced coefficient of friction. In this paper, In experiments to measure the clamping force before vibrator's amplitude changing. Vibrator's amplitude changes to 5.5mm from 4.4mm. As a result, under various vibration condition, relationship of clamping force and Vibrator amplitude.

• 한국분말재료학회지
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• 제20권6호
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• pp.479-486
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• 2013

In the present work, physicochemical treatments were introduced for de-aggregation and stable dispersion of detonation nanodiamonds (DND) in polar solvents. The DNDs in water exhibited a particle size of 138 nm and high dispersion stability without particular treatment. However, the DNDs in ethanol were severely aggregated to several micrometers in size and showed poor dispersion stability with time. To break down aggregates of DNDs and enhance the dispersion stability of them in ethanol, mechanical force and chemical surfactant were introduced as functions of zirconia ball size, kind of surfactant and amount of surfactant added. From the analyses of average particle size and Turbiscan results, it was suggested that the size of DNDs in ethanol can be reduced by only mechanical force; however, the DNDs were re-aggregated due to high surface activity. The long-term dispersion stability can be achieved by applying mechanical force to break down the aggregates of DNDs and by preventing re-aggregation of them using proper surfactant.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1207-1212
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• 2004

A model for the phonon dispersion relationship for cubic zinc sulfide structure, for example SiC, is developed in terms of two unknown force constants. Born model that incorporates bond bending and bond stretching, is used for the force constants. The force constants are determined by fitting to experimental data. Using only the nearest-neighbor coupling results in $6{\times}6$ sized dynamic matrix. The eigenvalues of dynamics matrix for each wavenumber in 3-D ${\kappa}$ space correspond to frequencies, 3 for optical phonon and 3 for acoustic phonon, which is so-called dispersion relation (${\kappa}$-${\omega}$). The density of state is determined by counting the states for each frequency bin, and the properties such as specific heat and thermal conductivity can be obtained. The specific heat is estimated on this model and compared with experiment and other models, i.e. Debye model, Einstein model and combined Debye-Einstein model. In spite of the simple bond potential model, reasonable agreements are found.

• 한국전산유체공학회지
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• 제18권2호
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• pp.99-108
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• 2013

The standard drag force and virtual mass force, which exert to the primary flow direction, are generally considered in two-phase analysis computational codes. In this paper, the lift force, wall lubrication force, and turbulent dispersion force including turbulence models, which are essential for a computational multi-fluid dynamics model and play an important role in motion perpendicular to the primary flow direction, were introduced and verified with conceptual problems.

• 대한화장품학회지
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• 제38권4호
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• pp.271-276
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• 2012

본 연구에서는 파우더와 첨가제의 종류, 함량에 따른 저점도 가용화 제형에서의 파우더 분산성을 연구하였다. 파우더는 화학 구조상 부분적 극성이 존재하여 반발력이 존재하고, 물리적인 구조상 다공성 물질로 접촉 면적이 넓고 밀도가 낮은 PMMA 파우더가 뛰어난 분산성을 보였다. 파우더가 분산되어 있는 견본에 염을 첨가한 견본의 경우 염이 첨가되지 않은 견본에 비해 우수한 분산성을 보여주었다. 이때의 분산성은 염의 농도에 의존적인 성향을 보이며, 같은 농도에서 1가 이온으로 이루어진 NaCl, KCl에 비해 2가 이온으로 이루어진 $MgSO_4$에서 더 높은 분산능을 보였다. 이는 염이 이온화되어 파우더의 주변에 존재하여 파우더간의 반발력을 높여주기 때문에 응집 현상이 줄어들고 분산능을 증가시키는 것으로 해석할 수 있다. 마지막으로 MgSO4 염이 첨가되어 있는 견본에 EDTA를 첨가제로 첨가하면 그렇지 않은 견본에 비해 더욱 뛰어난 분산능을 보여 주었다. EDTA는 금속 양이온과 결합하여 그 작용을 막으므로, EDTA가 포함된 견본은 음이온에 의한 작용이 극대화되어 파우더간의 반발력이 더욱 커지게 된다. 이는 결국 파우더의 수분산성을 향상시키고 제형의 안정화에 도움을 줄 수 있다.

• 한국의류학회지
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• 제20권4호
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• pp.690-696
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• 1996

In order to study the affect of surfactants on the soil removal, the dispersion and polar force components of surface tension for surfactant solutions (such as LAS, AS, AOS, AES, AE) were calculated using extended Fowkes equation. The contact angles on paraffin and surface tension of surfactant solutions were measured. Cmcs of LAS, AS, AES and AE were below the concentration of 0.05%, but the cmc of AOS was between 0.05% and 0.1%. The surface tension of AE was lowest but the dispersion force component was greastest. Total surface tension of every mixed anionic surfactant was lower than that of single surfactants, and the dispersion force components were almost decreased. The addition of sodium carbonate to the sufactant solutions decreased the surface tension, and the surface tensions of surfactant solutions were lowered after washing.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.105-108
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• 1996

We have studied the anisotropic dispersion force effects for surfaces alignment of liquid crystals (LCs) on rubbed polystyrene (PS) surfaces by unidirection. In microphotographs 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 legion. 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 (Pl) surface.

• 동력기계공학회지
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• 제20권2호
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• pp.43-50
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• 2016

This research proposal is based on a novel non-contact technique of micro-sized bead injection process for fabrication of electronic paper display. This non-contact injection process is based on the principle of electrostatic force and uses micro-sized metal-coated beads dispersed in a solution. The dispersion retention times of three different solutions with viscosities of 10 cps, 100 cps, and 1000 cps were measured by optical equipment showing the retention times of 5 mins, 10 mins, and 30 mins respectively. The dispersion retention rate dropped as the time passed. The dispersion retention characteristic of 1000 cps solution was more stable as compared to those of 10 cps and 100 cps meaning that higher viscosity has better retention properties. The experimental results of bead injection at different viscosity levels of the solution were also measured and a stable injection result was achieved by using 1000 cps solution. This results show that stable injection is dependent on solution viscosity and dispersion.

• 폴리머
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• 제25권5호
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• pp.671-678
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• 2001

Sodium 또는 zinc로 중화된 poly(ethylene-co-methacrylic acid)의 아이오노머는 ethylene 사슬 부분들로만 이루어진 결정상, acid 그룹이 존재하는 amorphous 영역, 그리고 ionic aggregate의 세 가지 상으로 나누어진다. Soaking에 의하여 흡수된 nonionic dye 분자들은 결정상을 제외한 amorphous 부분이나 ionic aggregate 분근에 존재하는데, 주위 사슬의 극성에 따라 dispersion force (ethylene 사슬 부분), polar force (acid 부분), ionic dipole (ionic aggregate 부분)의 세 가지 다른 힘의 영향 아래 놓이게 된다. 극성이 적은 ethylene 사슬부분의 dispersion force 영향 아래에 존재하는 Nile Red의 UV/Vis 흡수피크는 500nm 부근에서, polar한 acid 그룹의 영향을 받는 dye 피크는 525 nm, 그리고 ionic aggregate의 영향에 의한 dye는 Na+-아이오노머의 경우 550 nm, divalent이어서 더 큰 ionic dipole을 가지는 $Zn^{2+}$-아이오노머의 경우 610nm에서 각각 피크가 나타났다.