• Title/Summary/Keyword: surface pressure measurement

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The Study of Plantar Foot Pressure Distribution during Obstacle Crossing with Different Height in Normal Young Adults (보행 시 장애물 높이에 따른 정상 성인의 족저압 분포 연구)

  • Han, Jin-Tae;Lee, Myung-Hee;Kim, Kyoung
    • Korean Journal of Applied Biomechanics
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    • v.18 no.2
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    • pp.1-9
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    • 2008
  • The purpose of this study was to investigate the effect of different obstacle heights on the plantar foot pressure during obstacle crossing. Sixteen healthy adults who had no musculoskeletal disorders were instructed to perform unobstructed level walking and to step over obstacles corto 10cm, 20cm, 30cm. Plantar foot forces and pressures were recorded by the Footmat system(Tekscan, Boston, USA) during level and obstacle walking with barefoot. Plantar foot surface was defined as seven regions for pressure measurement; two toe regions, three forefoot regions, one midfoot region, one heel region. One-way ANOVA was used to compare each region data of foot according to various heights. The results indicated that there are significant differences on peak pressure and maximal forces regarding each region at stance phase. As height of obstacle became high, the pathway of COP had a tendency to be short and abducted. Plantar pressure of foot could be changed by obstacle height and these findings demonstrated that obstacle with different height have an effect on structure and function of the foot.

The Effects of Coupling Agent and Crosslinking Agent in the Synthesis of Acrylic Pressure Sensitive Adhesive for Polarizer Film (편광필름용 아크릴 점착제의 합성에서 커플링제와 가교제의 효과)

  • Lim, Chang-Hyuk;Ryu, Hoon;Cho, Ur-Ryong
    • Polymer(Korea)
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    • v.33 no.4
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    • pp.319-325
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    • 2009
  • The solution polymerization was conducted to synthesize pressure sensitive adhesive for polarizer film using acrylic monomers. 2-Ethylhexylacrylate, butylacrylate, acrylic acid were used as acrylic monomers. The ratio was 2-ethylliexylacrylate:butylacrylate:acrylic acid=25:50:3.6 by reflecting $-40^{\circ}C$ of glass transition temperature in the pressure sensitive adhesive. When 1 wt% of coupling agent was added to the polymerized pressure sensitive adhesive, the light transmissivity was significantly increased. This result is due to the enhancement of adhesive power against liquid crystal cell by Si-O bond of coupling agents. Cross-linking agent was added by 0.5, 1.0, and 1.5 wt% with respect to the synthesized polymer. Initial tackiness decreased, while cohesion increased with increasing crosslinking agent. In the analysis of contact angle, the increase of crosslinking agents yielded the enhancement of surface energy, resulting in the decrease of contact angle. From the measurement of heat resistance, the acrylic pressure sensitive adhesive showed excellent heat resistance regardless of change in temperature and contents in crosslinking agent. In the observation of a cutting plane, the increased crosslinking agent represented a smoother and cleaner section. Comprehensively, the optimum additive amount of crosslinking agent was determined to be 1.0 wt% to monomer.

Numerical Study on Cavitation Flow and Noise in the Flow Around a Clark-Y Hydrofoil (Clark-Y 수중익형 주변 공동 현상에 의한 유동장과 소음 예측에 대한 수치적 연구)

  • Ku, Garam;Cheong, Cheolung;Kim, Sanghyeon;Ha, Cong-Tu;Park, Warn-Gyu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.2
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    • pp.87-94
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    • 2017
  • Because the cavitation flow driven by an underwater propeller corrodes the materials around it and generates a high level of noise, it has become an important topic in engineering research. In this study, computational fluid dynamics techniques are applied to simulate cavitation flow, and the noise in the flow is predicted by applying the acoustic analogy to the predicted flow. The predicted results are compared with measurement results and other predictions in terms of surface pressure distribution and the temporal variation in liquid volume fraction. The predicted results are found to be in good agreement with the measured results. The source of the noise attributed to the time rate of change in the liquid volume fraction around the hydrofoil is modeled as a monopole source, and the source of the noise due to unsteady pressure perturbations on the hydrofoil surface is modeled as a dipole source. Then the predicted noise results are analyzed in terms of directivity and SPL spectrum. The noise caused by unsteady pressure perturbations was dominant in the entire frequency range considered in the study.

Synthesis and Characterization of Interfacial Properties of Sorbitan Laurate Surfactant (Sorbitan Laurate 계면활성제 합성 및 계면 특성에 관한 연구)

  • Lee, Seul;Kim, ByeongJo;Lee, JongGi;Lim, JongChoo
    • Applied Chemistry for Engineering
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    • v.22 no.1
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    • pp.37-44
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    • 2011
  • The critical micelle concentration (CMC) of sorbitan laurate SP 20 surfactant in this paper was near $7.216{\times}10^{-4}mol/L$ and the surface tension at CMC was about 26.0 mN/m, which showed higher CMC and lower surface tension than those of octylphenol ethoxylate octylphenol ethoxylate (OPE) 10 surfactant. Dynamic surface tension measurement using a maximum bubble pressure tensiometer showed that the adsorption rate at the interface between air and surfactant solution was found to be slower with SP 20 surfactant, presumably due to a low mobility of SP 20 surfactant monomer. The contact angle of SP 20 surfactant solution was observed to decrease with an increase in surfactant concentration and showed a larger value than that of OPE 10 surfactant solution. Half-life time for foams generated with 1 wt% surfactant solution was also larger with SP 20 surfactant, which indicated higher foam stability with SP 20 surfactant. Dynamic behavior study reveals that the solubilization of n-decane oil was much lower with SP 20, which is in good agreement with experimental results of foam stability, contact angle and CMC. Dynamic interfacial tension measurement by a spinning drop tensiometer shows that interfacial tensions at equilibrium condition in both systems were almost the same but the time required to reach equilibrium was longer with SP 20.

Measurement of Plasma Parameters (Te and Ne) and Reactive Oxygen Species in Nonthermal Bioplasma Operating at Atmospheric Pressure

  • Choi, Eun Ha;Kim, Yong Hee;Kwon, Gi Chung;Choi, Jin Joo;Cho, Guang Sup;Uhm, Han Sup;Kim, Doyoung;Han, Yong Gyu;Suanpoot, Pradoong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.141-141
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    • 2013
  • We have generated the needle-typed nonthermal plasma jet by using an Ar gas flow at atmospheric pressure. Diagnostics of electron temperature anddensity is critical factors in optimization of the atmospheric plasma jet source in accordance with the gas flow rate. We have investigated the electron temperature and density of plasma jet by selecting the four metastable Ar emission lines based on the atmospheric collisional radiative model and radial profile characteristics of current density, respectively. The averaged electron temperature and electron density for this plasma jet are found to be ~1.6 eV and ~$3.2{\times}10^{12}cm^{-3}$, respectively, in this experiment. The densities of OH radical species inside the various bio-solutions are found to be higher by about 4~9 times than those on the surface when the argon bioplasma jet has been bombarded onto the bio-solution surface. The densities of the OH radicalspecies inside the DI water, DMEM, and PBS are measured to be about $4.3{\times}10^{16}cm^{-3}$, $2.2{\times}10^{16}cm^{-3}$, and $2.1{\times}10^{16}cm^{-3}$, respectively, at 2 mm downstream from the surface under optimized Ar gas flow 250 sccm.

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Measurement of Friction Angle of Sand from Horizontal Stress and Torque Acting on Vane (베인에 작용하는 수평응력과 토크를 이용한 모래의 마찰각 측정)

  • Park, Sung-Sik;Kim, Dong-Rak;Lee, Sae-Byeok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.38 no.1
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    • pp.63-71
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    • 2018
  • In this study, the torque and horizontal stress acting on vane were measured and then used to determine a friction angle of sand. A dry Nakdong River sand was prepared for loose and dense conditions in a cell and then pressurized with 25, 50, 75 or 100 kPa from the surface of sand. A vane (5cm in diameter and 10cm in height) was rotated and the torque and horizontal stress were measured at real time. A maximum torque was 3.5-9.5Nm for loose sand and 7.4-17.6Nm for dense sand, respectively. The maximum torque increased as an overburden pressure increased. The maximum torque obtained at 14-20 degrees of vane rotation, which was not influenced by the initial alignment of earth pressure and vane blade. An initial horizontal stress ratio was 0.33-0.35 on the average. The horizontal stress increased initially and then decreased due to particle disturbance. A friction angle was calculated from real time varying horizontal stress and torque, which decreased with increasing overburden pressure. The friction angle of loose sand from vane shear test was similar to that of direct shear test but that of dense sand was overestimated.

Development of Hard-wired Instrumentation and Control for the Neutral Beam Test Facility at KAERI

  • Jung Ki-Sok;Yoon Byung-Joo;Yoon Jae-Sung;Seo Min-Seok
    • Journal of Electrical Engineering and Technology
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    • v.1 no.3
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    • pp.359-365
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    • 2006
  • Since the start of the KSTAR (Korea Superconducting Tokamak Advanced Research) project, Instrumentation and Control (I&C) of the Neutral Beam Test Facility (NB-TF) has been striving to answer diverse requests arising from various facets during the project's development and construction phases. Hard-wired electrical circuits have been designed, tested, fabricated, and finally installed to the relevant parts of the system. In relation to the vacuum system I&C, controlling functions for the rotary pumps, a Roots pump, two turbomolecular pumps, and four cryosorption pumps have been constructed. I&C for the ion source operation are the temperature and flow rate signal monitoring, Langmuir probe signal measurements, gradient grid current measurements, and arc detector circuit. For the huge power system to be monitored or safely operated, many temperature measurement functions have also been implemented for the beam line components like the neutralizer, bending magnet, ion dump, and calorimeter. Nearly all of the control and probe signals between the NB test stand and the control room were made to be transmitted through the optical cables. Failures of coolant flow or beam line vacuum pressure were made to be safely blocked from influencing the system by an appropriate interlock circuit that will shut down the extraction voltage application to the system or prevent damages to the vacuum components. Preliminary estimation of the beam power through the calorimetric measurement shows that 87.9% of the total power of the 60kV/18A beam with 200 seconds duration is absorbed by the calorimeter surface. Most of these I&C results would be highly appropriate for the construction of the main NBI facility for the KSTAR national fusion research project.

Study on the measurement of activation temperature of Non-Evaporable Getter (비증발형 게터의 활성화 온도 측정방법에 관한 연구)

  • Lee D. J.;Kim K. B.;In S. R.;Lim J. Y,;Kim W. B.
    • Journal of the Korean Vacuum Society
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    • v.14 no.1
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    • pp.1-6
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    • 2005
  • Getters are invariably covered with thin layers of oxides even in air. For the getter to function properly it is necessary to activate them by heating in vacuum during which the oxide layer is removed exposing clean surface. The so-called activation temperature is an important parameter along with gas sorption capacity since it determines the maximum temperature of a device in which a getter can be installed. Nevertheless, no standard method to measure activation temperature has been documented yet. In this study, a relatively simple method to measure the activation temperature based on the ultimate pressure measurement was suggested. The activation temperature of TiZrV alloy measured by the method was between 100℃~200℃.

Development and Application of Micromodel for Visualization of Supercritical CO2 Migration in Pore-scale (공극 규모에서의 초임계상 이산화탄소 거동 가시화를 위한 마이크로모델의 개발과 적용)

  • Park, Bogyeong;Lee, Minhee;Wang, Sookyun
    • Journal of Soil and Groundwater Environment
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    • v.20 no.4
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    • pp.73-82
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    • 2015
  • Despite significant effects on macroscopic migration and distribution of CO2 injected during geological sequestration, only limited information is available on wettability in microscopic scCO2-brine-mineral systems due to difficulties in pore-scale observation. In this study, a micromodel had been developed to improve our understanding of how scCO2 flooding and residual characteristics of porewater are affected by the wettability in scCO2-water-glass bead systems. The micromodel (a transparent pore structure made of glass beads and glass plates) in a pressurized chamber provided the opportunity to visualize scCO2 spreading and porewater displacement. CO2 flooding followed by fingering migration and dewatering followed by formation of residual water were observed through an imaging system. Measurement of contact angles of residual porewater in micromodels were conducted to estimate wettability in a scCO2-water-glass bead system. The measurement revealed that the brine-3M NaCl solution-is a wetting fluid and the surface of glass beads is water-wet. It is also found that the contact angle at equilibrium decreases as the pressure decreases, whereas it increases as the salinity increases. Such changes in wettability may significantly affect the patterns of scCO2 migration and porewater residence during the process of CO2 injection into a saline aquifer at high pressures.

Measurement of EUV Emission and its Plasma Parameters Generated from the Coaxial Plasma Focus of Mather and Hypocycloidal Pinched Electrodes

  • Lee, Sung-Hee;Lee, Kyung-Ae;Hong, Young-June;Uhm, Han-Sup;Choi, Eun-Ha
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.08a
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    • pp.332-332
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    • 2011
  • The extreme ultraviolet (EUV) radiation, whose wavelength is from 120 nm down to 10 nm, and the energy from 10 eV up to 124 eV, is widely utilized such as in photoelectron spectroscopy, solar imaging, especially in lithography and soft x-ray microscopy. In this study, we have investigated the plasma diagnostics as well as the debris characteristics between the two types of dense plasma focusing devices with coaxial electrodes of Mather and hypocycloidal pinch (HCP), respectively. The EUV emission intensity, electron temperature and plasma density have been investigated in these cylindrical focused plasma along with the debris characteristics. An input voltage of 5 kV has been applied to the capacitor bank of 1.53 uF and the diode chamber has been filled with Ar gas at pressure ranged from 1 mTorr and 180 mTorr. The inner surface of the cathode was covered by polyacetal insulator. The central anode electrode has been made of tin. The wavelength of the EUV emission has been measured to be in the range of 6~16 nm by a photo-detector (AXUV-100 Zr/C, IRD). The visible emission has also been measured by the spectrometer with the wavelength range of 200~1,100 nm. The electron temperature and plasma density have been measured by the Boltzmann plot and Stark broadening methods, respectively, under the assumption of local thermodynamic equilibrium (LTE).

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