• Journal of Adhesion and Interface
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• v.16 no.2
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• pp.55-62
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• 2015

It was investigated that the effect of surface modification and concentration of fumed silica on the adhesion properties and thermal stability of 2-EHA/AA pressure sensitive adhesive (PSAs) prepared by UV irradiation. The influence of repeating units of crosslinking agent on PSAs were also studied. From SEM analysis, PSAs synthesized with surface modified silica had finer dispersion of silica particles in polymer matrix due to the interfacial interaction. Results of the study showed that increase in tack and peel strength when under 0.3 wt% of silane treated silica were added in the reaction mixture. The addition of PEGDMA for crosslinking agent offers positive effect on adhesion properties in comparison with PSAs using EGDMA for crosslinker, which may be attributed to high mobility of ethylene oxide repeating units in PEGDMA. From the thermal degradation residue of PSAs, it was revealed that thermal stability was improved with silica addition due to the strong interfacial bonding between silane modified silica and polymer matrix, which may act as a thermal barriers into 2-EHA/AA PSAs.

• Elastomers and Composites
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• v.34 no.4
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• pp.360-365
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• 1999

In this study, the blends of acrylic quaternary polymer (PEBEV) which was co- polymerized from 2-ethylhexyl acrylate (2-EHA), n-butyl acrylate (BA) and ethyl acrylate (EA), vinyl acetate (VAc), and poly(vinyl chloride-co-vinyl propionate) (PVCVP) were prepared by solution blending. Pressure sensitive adhesive (PSA) properties of PEBEV/PVCVP blends were compared with those of PEBEV/poly(vinyl chloride-co-vinyl acetate) (PVCVAc) blends. Compatibility of PEBEV/PVCVP was better than that of PEBEV/PVCVAc. Tackiness of both blend systems were similar, but holding power began to decrease at 15wt% or higher PVCVAc contents in PEBEV/PVCVAc blends. On the other hands, holding power of PEBEV/PVCVP increased as the contents of PVCVP increased. Failure modes of the blends were adhesive failure except 5wt% of PVCVP was blended.

• Journal of Adhesion and Interface
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• v.9 no.1
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• pp.22-27
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• 2008

The effect of functional monomers on the acrylic pressure sensitive adhesive (PSA) property was measured. Design of experiments in order to optimal peel adhesion was applied and commercial program (MINITAB) was used. Analysis was used to mixture design (special cubic model) in response surface methodology. Optimal monomer compositions was construed by 2-EHA (0.8861), EA (0.0639), MAA (0.03) and AAm (0.02). The estimated regression equation was as follows : $$y=54.8816x_1+80.7067x_2-44.4700x_3-99.0288x_1x_2+60.7706x_1x_3-441.030x_2x_3+974.341x_1x_2x_3$$.

• Journal of Astronomy and Space Sciences
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• v.26 no.2
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• pp.211-220
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• 2009

As one of the GNSS error simulation case studies, we computed tropospheric signal delays based on three well-known models (Hopfield, Modified Hopfield and Saastamoinen) and a simple model. In the computation, default meteorological values were used. The result was compared with the GIPSY result, which we assumed as truth. The RMS of a simple model with Marini mapping function was the largest, 31.0 cm. For the other models, the average RMS is 5.2 cm. In addition, to quantify the influence of the accuracy of meteorological information on the signal delay, we did sensitivity analysis of pressure and temperature. As a result, all models used this study were not very sensitive to pressure variations. Also all models, except for the modified Hopfield model, were not sensitive to temperature variations.

• Journal of Adhesion and Interface
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• v.20 no.1
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• pp.15-22
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• 2019

In this study, polybutadiene based di-functional urethane acrylate oligomer (PB-UAO) were synthesized from polybutadiene diol and isophorone diisocyanate. And then, pressure sensitive adhesive films were prepared by mixing with synthesized oligomer, tri-functional acrylate monomer (Tris(2-acryloyloxyethyl) isocyanurate (TAOEIC) or Trimethylolpropane triacrylate (TMPTA) or Pentaerythritol triacrylate (PETA)), mono-functional acrylate monomer (Stearyl acrylate) and UV initiators. Effects of types and contents of trifunctional acrylate monomers on peel strength, tensile strength, elongation, thermal stability and water absorption property were studied. As the contents of tri-functional acrylate monomer increased, and as the molecular weight of tri-functional acrylate monomer decreased, peel strength, elongation and water absorption showed a tendency to decrease whereas tensile strength and thermal stability showed a tendency to increase.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.4
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• pp.337-348
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• 2003

The propagation mechanism of a detonation pressure with fully coupled charge is clarified and the blasting pressure propagated in rock mass is derived from the application of shock wave theory. The blasting pressure was a function of detonation velocity, isentropic exponent, explosive density, Hugoniot parameters, and rock density. Probabilistic distribution is obtained by using explosion tests on emulsion and rock property tests on granite in Seoul and then the probabilistic distribution of the blasting pressure is derived from the above mentioned properties. The probabilistic distributions of explosive properties and rock properties show a normal distribution so that the blasting pressure propagated in rock can be also regarded as a normal distribution. Parametric analysis was performed to pinpoint the most influential parameter that affects the blasting pressure and it was found that the detonation velocity is the most sensitive parameter. Moreover, uncertainty analysis was performed to figure out the effect of each parameter uncertainty on the uncertainty of blasting pressure. Its result showed that uncertainty of natural rock properties constitutes the main portion of blasting pressure uncertainty rather than that of explosive properties. In other words, since rock property uncertainty is much larger than detonation velocity uncertainty the blasting pressure uncertainty is more influenced by the former than by the latter even though the detonation velocity is found to be the most influencing parameter on the blasting pressure.

• Wind and Structures
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• v.16 no.1
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• pp.93-115
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• 2013

This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.7 no.2
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• pp.109-115
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• 2013

In this paper, we developed pressure mesuring system for powered wheelchair and tried to validate the usefulness of developed system by pressure measuring experiment with 3D motion analysis. This system consist of 64ch seat FSR(Force Sensitive Resistance) sensor unit, 30ch*2 armchair FSR sensor unit, analog and digital hardware board, 2ch rotary encoder unit and realtime signal processing & display S/W. And each data acquired from this system has sampling frequency of 12bit, 10Hz. Pressure measuring experiment for 10 persons who use wheelchair in real life was performed in the 3D vision analysis room. From the experiment, we obtained result that the center line of body inclined to outside direction during powered-wheelchair rotate any direction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.9-16
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• 2014

In recent years, the structural shock response to UNDEX (UNDerwater EXplosion) has been studied as much, or more, through numerical simulations than through testing for several reasons. Very high costs and sensitive environmental concerns have kept destructive underwater explosion testing to a minimum. Increase of simulation capabilities and sophisticated simulation tools has made numerical simulations more efficient analysis methods as well as more reliable testing aids. In this study, the main issue is the fluid-structure interaction. Here, appropriate relations between the acoustic pressure on the fluid surface and displacements on the structure surface are formed internally. The analysis was carried out using ABAQUS/Explicit and the results have been visualized in ABAQUS CAE. The shock loading history, acoustic pressure, stress of stand-off point, the velocity and strain energy time histories were presented.

• Archives of Plastic Surgery
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• v.41 no.6
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• pp.668-672
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• 2014

Background Negative-pressure wound therapy (NPWT) is believed to accelerate wound healing by altering wound microvascular blood flow. Although many studies using laser Doppler have found that NPWT increases perfusion, recent work using other modalities has demonstrated that perfusion is reduced. The purpose of this study was to investigate the influence of NPWT on tissue oxygenation of the foot, which is the most sensitive region of the body to ischemia. Methods Transcutaneous partial pressure of oxygen ($TcpO_2$) was used to determine perfusion beneath NPWT dressings of 10 healthy feet. The sensor was placed on the tarso-metatarsal area of the foot and the NPWT dressing was placed above the sensor. $TcpO_2$ was measured until it reached a steady plateau state. The readings obtained at the suction-on period were compared with the initial baseline (pre-suction) readings. Results $TcpO_2$ decreased significantly immediately after applying NPWT, but gradually increased over time until reaching a steady plateau state. The decrease in $TcpO_2$ from baseline to the steady state was 2.9 to 13.9 mm Hg (mean, $9.3{\pm}3.6$ mm Hg; $13.5{\pm}5.8%$; P<0.01). All feet reached a plateau within 20 to 65 minutes after suction was applied. Conclusions NPWT significantly decrease tissue oxygenation of the foot by 2.9 to 13.9 mm Hg. NPWT should be used with caution on feet that do not have adequate tissue oxygenation for wound healing.