• Title/Summary/Keyword: Flat surface

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Effect of Uneven Surface Gait Training on Ankle Muscle Activation and Balance in Stroke Patients

  • Ji, Young-Ho;Lee, Jae-Kwang;Lee, Jong-Kyung
    • The Journal of Korean Physical Therapy
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    • v.34 no.4
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    • pp.161-167
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    • 2022
  • Purpose: The purpose of this study was to investigate the effects of regular training on the uneven surface that stroke patients encounter in their daily life on their ankle joint muscle activity and balance ability. They were divided into two groups: the gait training group on uneven surfaces and the gait training group on normal surfaces. Methods: In this study, 30 patients diagnosed with stroke and undergoing rehabilitation were selected. 15 people in the uneven surface gait training group and 15 people in the flat gait training group were selected. The muscle activation of the ankle muscles was measured when walking again on a even surface after walking on an uneven surface and on a flat ground. After each gait training, the limit of stability and Romberg test were performed to evaluate the balance ability. Results: As a result of the experimental results before and after walking by group, the tibialis anterior muscle activity of the paralyzed side was significantly decreased in the uneven surface walking group. As a result of measuring balance ability after training, the limit of stability in all directions was significantly increased in the uneven surface gait training group, and the area and length moved significantly decreased in the uneven surface gait training group in the Romberg test as well (p<0.05). Conclusion: After walking on uneven surface, it was confirmed that the muscle activity of the ankle joint decreased in normal flat walking, and thus the efficiency of muscle activity was increased. In addition, it was possible to confirm the improvement of the balance ability of the gait training on the uneven surface, and in conclusion, it could be confirmed that it had an effect on the improvement of the walking ability.

Experimental Study on Micro-Scale Surface Texturing for Friction Reduction (저마찰을 위한 Micro-Scale Surface Texturing의 실험적 연구)

  • 채영훈
    • Tribology and Lubricants
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    • v.20 no.5
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    • pp.266-271
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    • 2004
  • The aim of this paper is to investigate the effect of surface texturing on reduction friction and to understand the potential of friction reduction through micro-scale dimple to fabricate by photolithography on pin-on-disk test using flat-on-flat contact geometry. It was verify that the friction property with respect to the same pitch has been influence on the size of dimple under lubricated sliding contact. Also, we can recognize from Stribeck curve that the friction property has a connection with the size of dimple. It can explain a relationship between the friction coefficient and a dimensionless parameter for lubrication condition. The friction property has been an effect on the size of surface texture on reduction friction, not only because the density of dimple, but also because the ratio of diameter/pitch. This ratio of approximately 0.5 recommend under the tested friction condition. It suggested that the ratio of d/p is an important parameter for surface texture design.

A Study on the Formation and the Loss of the Protective Layer the Sliding Surface According to the Lubricating Conditions (미끄럼운동을 하는 면에 윤활 조건에 따라 발생하는 보호막의 형성과 파괴에 관한 연구)

  • 이영제
    • Tribology and Lubricants
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    • v.7 no.1
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    • pp.16-27
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    • 1991
  • The mechanism of failure of lubricated surfaces at high sliding speeds was investigated. Experiments were performed with the ball-on-flat and cylinder-on-flat geometries, using lubricants of four different chemical reactivities. Surface failure was found to not be predictable using the ratio, $\lambda$, of fluid film thickness to composite surface roughness except when chemically inert lubricants are used. Even then the influence of temperature rise on fluid film thickness does not adequately explain the low load carrying capacity of lubricants at high sliding speeds, which causes surface failure. The protective layers on sliding surfaces that form by chemical reaction with the lubricant were found to reduce the surface roughening and increase the load carrying capacity of surfaces to values of $\lambda$ as low as 0.03. Neither the surface roughening nor the formation of the protective layers have been incorporated into failure models for lubricated systems.

Treatment of Contact between Roll/Roll and Roll/Strip for Rolling Process Simulation (압연공정해석을 위한 판과 롤의 접촉 경계면 처리)

  • 김태효;황상무
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.05a
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    • pp.156-159
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    • 2003
  • Surface normal vector and surface velocity are very important parameters to simulate rolling processes precisely. In this study, Local displacement functions are constructed for each node on the contact surface and parameters are found by the least square fitting of displacement on the neighbor nodes. Deformation gradient tensor is calculated from the displacement function and surface normal vector and velocity also can be derived. Flat rolling simulation model is presented on the basis of the suggested contact scheme. Series of rolling process simulation are carried out and the results are compared with the experiments.

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A Study on the Spindle Run-out Effects on Cutter Mark and Surface Roughness (주축 런아웃이 절삭흔과 표면거칠기에 미치는 영향에 관한 연구)

  • Hwang, Young-Kug;Lee, Choon-Man
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.2
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    • pp.84-91
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    • 2007
  • The radial error motion of a machine tool cutter/spindle system is critical to the dimensional accuracy of the parts to be machined. This paper presents an investigation into spindle run-out effects on cutting mark and surface roughness. We experimented the effects of spindle run-out on surface roughness in flat-end milling by cutting AL 7075 workpiece in various cutting conditions. In order to analyze the effects of run-out on the surface roughness, the spindle's radial error motions was measured by mounting a sphere target onto the spindle as a reference. From the experimental results, it was found that spindle un-out makes a directive effects on surface roughness in flat-end milling.

Precision of Digital Photogrammetry for the Roughness Measurement of Rock Surfaces

  • Lee, Hyo-Sung;Ahn, Ki-Won;Park, Byung-Uk;Kim, Yong-Il
    • Korean Journal of Geomatics
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    • v.3 no.1
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    • pp.43-51
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    • 2003
  • This paper presents the benefits of using close-range digital photogrammetric techniques for measuring the roughness of rock surfaces, using digital stereo images obtained from a Rolleiflex 6006 metric camera. To precisely measure surface roughness, we researched on how to use the flat and curved reference surface obtained from geometrically corrected digital images of the rock surface by using the least squares method. To test the precision of the proposed technique, the surface roughness has been measured between the reference surface and sample areas of very smooth-surfaced rock. Then the results were compared with the measurements obtained from a laser sensor profilometer.

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Changes of Sedimentary Environments in the Southern Tidal Flat of Kanghwa Island (강화 남부 갯벌의 퇴적환경 변화)

  • Woo, Han-Jun;Je, Jong-Geel
    • Ocean and Polar Research
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    • v.24 no.4
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    • pp.331-343
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    • 2002
  • The southern tidal flat of Kanghwa Island with an area of approximately $90km^2$ is one of the biggest flats on the west coast of Korea. Surface sediments for sedimentary analyses were sampled at 83 stations in August 1997, September 1999 and August 2000. The very poorly-sorted mud sediments were predominant in the eastern part of the tidal flat, whereas the poorly-sorted sand-mud mixed sediments were dominant in the western part. The area of muddy sediment distribution diminished, but that of sandy mud sediment extended to southeastward tidal flat for three years. In the western part of tidal flat, deposition occurred during the period of spring to summer, whereas erosion occurred in winter. Sediment accumulation rates during three years indicated that the sediments deposited continuously in the eastern part of tidal flat, whereas eroded in the western part of tidal flat. Recently, construction of artificial structures such as new airport, island-connecting bridges and dikes near the tidal flat might change tidal current and river flow pattern. In order to reduce the ecological damage and to preserve tidal-flat environment, it is necessary to Investigate long-term impacts on sedimentary environment and ecology.

Controlled Formation of Surface Wrinkles and Folds on Poly (dimethylsiloxane) Substrates Using Plasma Modification Techniques

  • Nagashima, So;Hasebe, Terumitsu;Hotta, Atsushi;Suzuki, Tetsuya;Lee, Kwang-Ryeol;Moon, Myoung-Woon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.08a
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    • pp.223-223
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    • 2012
  • Surface engineering plays a significant role in fabricating highly functionalized materials applicable to industrial and biomedical fields. Surface wrinkles and folds formed by ion beam or plasma treatment are buckling-induced patterns and controlled formation of those patterns has recently gained considerable attention as a way of creating well-defined surface topographies for a wide range of applications. Surface wrinkles and folds can be observed when a stiff thin layer attached to a compliant substrate undergoes compression and plasma treatment is one of the techniques that can form stiff thin layers on compliant polymeric substrates, such as poly (dimethylsiloxane) (PDMS). Here, we report two effective methods using plasma modification techniques for controlling the formation of surface wrinkles and folds on flat or patterned PDMS substrates. First, we show a method of creating wrinkled diamond-like carbon (DLC) film on grooved PDMS substrates. Grooved PDMS substrates fabricated by a molding method using a grooved master prepared by photolithography and a dry etching process were treated with argon plasma and subsequently coated with DLC film, which resulted in the formation of wrinkled DLC film aligning perpendicular to the steps of the pre-patterned ridges. The wavelength and the amplitude of the wrinkled DLC film exhibited variation in the submicron- to micron-scale range according to the duration of argon plasma pre-treatment. Second, we present a method for controlled formation of folds on flat PDMS substrates treated with oxygen plasma under large compressive strains. Flat PDMS substrates were strained uniaxially and then treated with oxygen plasma, resulting in the formation of surface wrinkles at smaller strain levels, which evolved into surface folds at larger strain levels. Our results demonstrate that we can control the formation and evolution of surface folds simply by controlling the pre-strain applied to the substrates and/or the duration of oxygen plasma treatment.

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R-22 Condensation in Flat Aluminum Multi-Channel Tubes (알루미늄 다채널 평판관내 R-22 응축에 관한 연구)

  • Kim, Jung-Oh;Cho, Jin-Pyo;Kim, Nae-Hyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.2
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    • pp.241-250
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    • 2000
  • In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-22. Two internal geometries were tested ; one with smooth inner surface and the other with micro-fins. Data are presented for the followin~ range of variables ; vapor quality($0.1{\sim}0.9$), mass flux($200{\sim}600kg/m^2s$) and heat flux($5{\sim}15kW/m^2$). The micro-fin tube showed higher heat transfer coefficients compared with those of the smooth tube. The difference increased as the vapor quality increased. Surface tension force acting on the micro-fin surface at the high vapor quality is believed to be responsible. Different from the trends of the smooth tube, where the heat transfer coefficient increased as the mass flux increased, the heat transfer coefficient of the micro-fin tube was independent of the mass flux at high vapor quality, which implies that the surface tension effect on the fin overwhelms the vapor shear effect at the high vapor quality. Present data(except those at low mass flux and high quality) were well correlated by equivalent Reynolds number, Existing correlations overpredicted the present data at high mass flux.