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1
Jaszak, Przemysław. "Optimized design of a semimetal gasket operating in flange-bolted joints." Open Engineering 11, no. 1 (November 19, 2020): 56–66. http://dx.doi.org/10.1515/eng-2021-0004.
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AbstractThe paper presents a new design of semimetal gasket, which has been subjected to the optimization process. The main objective function was to achieve the maximum elastic recovery of the gasket at imposed functional and strength limitations. The objective function was described indirectly in the form of the required minimum angle of the gasket’s unload curve inclination, which was a measure of the average value of the elastic modulus at unloading. Strength limitations resulted from not exceeding the ultimate stress of the materials, while functional limitations imposed the achievement of proper contact pressure that ensures a given level of tightness class. The characteristic dimensions describing the cross-section of the gasket’s core were described by five descriptive parameters. As a result of the interrelationship of these parameters, 210 construction models were created that were subjected to compression simulations. This problem was solved using the Finite Element Method. The variant of the gasket fulfilling the imposed limitations and the required minimum objective function was tested experimentally.
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GOMBA, J. M., and G. M. HOMSY. "Regimes of thermocapillary migration of droplets under partial wetting conditions." Journal of Fluid Mechanics 647 (March 18, 2010): 125–42. http://dx.doi.org/10.1017/s0022112010000078.
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We study the thermocapillary migration of two-dimensional droplets of partially wetting liquids on a non-uniform heated substrate. An equation for the thickness profile of the droplet is derived by employing lubrication approximations. The model includes the effect of a non-zero contact angle introduced through a disjoining–conjoining pressure term. Instead of assuming a fixed shape for the droplet, as in previous works, here we allow the droplet to change its profile with time. We identify and describe three different regimes of behaviour. For small contact angles, the droplet spreads into a long film profile with a capillary ridge near the leading edge, a behaviour that resembles the experiments on Marangoni films reported by Ludviksson & Lightfoot (Am. Inst. Chem. Eng. J., vol. 17, 1971, pp. 1166). For large contact angles, the droplet moves as a single entity, weakly distorted from its static shape. This regime is the usual one reported in experiments on thermocapillary migration of droplets. We also show some intriguing morphologies that appear in the transition between these two regimes. The occurrence of these three regimes and their dependence on various parameters is analysed.
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Hwang, T. W., C. J. Evans, and S. Malkin. "High Speed Grinding of Silicon Nitride With Electroplated Diamond Wheels, Part 2: Wheel Topography and Grinding Mechanisms." Journal of Manufacturing Science and Engineering 122, no. 1 (June 1, 1999): 42–50. http://dx.doi.org/10.1115/1.538909.
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This is the second in a series of two papers concerned with high speed grinding of silicon nitride with electroplated diamond wheels. In the first article (ASME J. Manuf. Sci. Eng., 122, pp. 32–41), it was shown that grinding of silicon nitride is accompanied by dulling of the abrasive grains and a significant increase in the grinding forces and power. High wheel speed caused more wheel wear, which was attributed to a longer accumulated sliding length between the abrasive grains and the workpiece. This second paper is concerned with the progressive change in wheel topography during grinding and how it affects the grinding process. A statistical model is developed to characterize the wheel topography during grinding in terms of active cutting grains and wear flat area. According to this model, continued grinding is accompanied by an increase in both the number of active grains and the wear flat area on the wheel surface as the wheel wears down. The measured increase in grinding forces and power was found to be proportional to the wear flat area, which implies a constant average contact pressure and friction coefficient between the wear flats and the workpiece. Increasing the wheel speed from 85 to 149 m/s significantly reduced the contact pressure, which may be attributed to a reduction of the interference angle, but had almost no effect on the attritious wear rate of the diamond abrasive. Therefore, more rapid wear of the diamond wheel at higher wheel speeds due to a longer sliding length may be offset by reduced contact pressures and lower grinding forces. [S1087-1357(00)00401-9]
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Tyowua, Andrew Terhemen, and Stephen Gbaoron Yiase. "Contact Angle Hysteresis – Advantages and Disadvantages: A Critical Review." Reviews of Adhesion and Adhesives 8, no. 1 (March 1, 2020): 47–67. http://dx.doi.org/10.7569/raa.2020.097302.
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The existence of contact angle hysteresis – the difference between the values of the advancing and receding contact angles – is evident in nature (e.g. sticking of rain drops to car windscreens and window panes) and many industrial processes (e.g. surface coating, spraying, and dyeing of fabrics). This phenomenon is often viewed as a nuisance, but it is advantageous in many processes including dip and spin coating, spraying, and painting. With the early theoretical framework of Thomas Young, Robert Wenzel, and A. B. D. Cassie and S. Baxter, describing the wettability of solid surfaces and by extension contact angle, contact angle hysteresis has been deeply investigated. We review here the various ways of measuring contact angle and, consequently, contact angle hysteresis as well as related theoretical models. The successes and limitations of these models are highlighted. We conclude with the advantages and disadvantages of contact angle hysteresis whose presence in many processes is often considered as a nuisance, especially when "coffee stain" forms from the evaporation of a volatile liquid drop containing nonvolatile components.
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Koshevoi, Veniamin L., Anton O. Belorus, Matyushkin В. Matyushkin, Ilya M. Pleshanov, Pavel V. Seredin, Sergey A. Ivkov, and Alexander S. Lenshin. "ВНЕДРЕНИЕ СЕРЕБРА В МАТРИЦУ ПОРИСТОГО КРЕМНИЯ МЕТОДОМ ЭЛЕКТРО-ТЕРМОДИФФУЗИИ." Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases 21, no. 3 (September 26, 2019): 390–98. http://dx.doi.org/10.17308/kcmf.2019.21/1158.
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В работе были проведены исследования возможности внедрения серебра в пористый кремний методом электро-термодиффузии и установлено влияние процедуры осаждения на адсорбционные свойства поверхности пористой матрицы. Композиты пористого кремния с внедренными частицами металла относятся к многофункциональным материалам и перспективны для применения в современной оптоэлектронике, сенсорике и персонализированной медицине.
ИСТОЧНИК ФИНАНСИРОВАНИЯИсследование выполнено при поддержке РФФИ в рамках научного проекта 19-32-50038мол_нр «Исследование морфологических, физико-химических и оптических свойств матриц наоснове por-Si в зависимости от методов их формирования и функционализации».
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Kleps I., Miu M., Danila M., Simion M., Ignat T., Bragaru A., Dumitru L., Teodosiu G. Silver/porous silicon (PS) nanocomposite layers for biomedical applications. Proc. of “2006 International Semiconductor Conference”, 27-29 Sep., 2006, no. 9211112. https://doi.org/10.1109/SMICND.2006.283935
Ensafi A. A., Rezaloo F., Rezaei B. Electrochemical sensor based on porous silicon/silver nanocomposite for the determination of hydrogen peroxide. Sensors and Actuators B, 2016, v. 231, pp. 239–244. https://doi.org/10.1016/j.snb.2016.03.018
Jinjie Yin, Xiang Qi, Liwen Yang, Guolin Hao, Jun Li, Jianxin Zhong A hydrogen peroxide electrochemical sensor based on silver nanoparticles decorated silicon nanowire arrays. Electrochimica Acta, 2011, v. 56(11), pp. 3884–3889. https://doi.org/10.1016/j.electacta. 2011.02.033
Spivak Yu. M., Bespalova K. A., Belorus A. O., Panevin A. A., Somov P. A., Grigor’eva N. Yu., Chistyakova L. V., Zhuravskiy S. G., Moshnikov V. A. Sposob polucheniya i primer lekarstvennoy funktsionalizatsii poverkhnosti nanochastits poristogo kremniya [A method of obtaining and an example of drug functionalization of the surface of porous silicon nanoparticles]. Biotekhnosfera [Biotechnosphere], 2017 (3), pp. 69–75. (in Russ.)
Pastukhov A. I., Belorus A. O., Bukina Ya. V., Spivak Yu. M., Moshnikov V. A. Infl uence of technology conditions on the surface energy of porous silicon using the method of contact angle. Proc. of “2017 IEEE Conference of Russian Young Researchers in Electrical and Electronic Engineering (EIConRus)”, 1–3 Feb., 2017, pp. 1183-1185. https://doi.org/10.1109/eiconrus.2017.7910770
Matyushkin L. B. Tekhnologiya i oborudovanie dlya polucheniya kolloidnykh kvantovykh tochek CsPbX3 (X = Cl, Br, I), CdSe/ZnS, plazmonnykh nanochastits Ag/SiO2 i gibridnykh struktur na ikh osnove [Technology and equipment for obtaining CsPbX3 colloidal quantum dots (X = Cl, Br, I), CdSe/ZnS, Ag/SiO2 plasmonic nanoparticles and hybrid structures based on them. Cand. Sci. (Eng.) diss. St. Petersburg, 2018, 138 p. URL: https://elibrary.ru/item.asp?id=35115356 (in Russ.)
Permiakov N. V., Matyushkin L. B., Belorus A. O., Koshevoi V. L. Investigation of a program-controlled process of impregnation of porous semiconductors with silver nanoparticles to create an electrical contact. Proc. of “IEEE Conference of Russian Young Researchers in Electrical and Electronic Engineering (EIConRus)”, 2018, pp. 539–543. https://doi.org/10.1109/EICon- Rus.2018.8317154
Travkin P. G., Vorontsova N. V., Vysotsky S. A., Lenshin A. S., Spivak Yu. M., Moshnikov V. A. Issledovanie zakonomernostey formirovaniya struktury poristogo kremniya pri mnogostadiynykh rezhimakh elektrokhimicheskogo travleniya [Study of regularities of porous silicon structure formation with multistage modes of electrochemical etching]. Izvestiya SPBGETU LETI, 2011(4). pp. 3–9. (in Russ.)
Belorus A. O., Komlev A. A. Certifi cate of state registration of computer programs No. 2014613394. Measurement of contact angle (MofCA) 26 March 2014. (in Russ.)
Van Hoonacker A., Englebienne P. Revisiting silver nanoparticle chemical synthesis and stability by optical spectroscopy. Current Nanoscience, 2006, v. 2(4), pp. 359–371. https://doi.org/10.2174/157341306778699310
Girel K. V., Bondarenko A. V. Formirovanie nanostruktur serebra metodom immersionnogo osazhdeniya [Formation of silver nanostructures by immersion deposition method onto porous silicon and study of their optical properties]. Doklady BGUIR, 2014, v. 86(8), pp. 5–10. (in Russ.)
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Wang, Lei, Lei Chen, and Zhanxiong Li. "End-Blocked Silanization of Side-Chain Fluoroalkyl Oligoether and its Surface Properties." Australian Journal of Chemistry 71, no. 11 (2018): 855. http://dx.doi.org/10.1071/ch18126.
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In this study, three novel side-chain fluoroalkyl oligoethers with different molecular weights were synthesised via a ring-opening reaction of 2,2,3,3,4,4,5,5,5-nonafluoropentyloxirane. The fluorooligoethers were then silanized and characterised by FT-IR,1H, and 19F NMR spectroscopies. These silanlized fluorooligoethers were used to fabricate hydrophobic coatings on silicon substrates, which were pre-treated with O2 plasma, by the method of liquid phase deposition. The chemical compositions and structures of the film surfaces were analysed by X-ray photoelectron spectroscopy and the results showed that silanized fluorooligoethers formed self-assembled films on the silicon wafer. The surface wettability of the coatings was measured by water contact angles. It is noted that the annealing process can improve the hydrophobicity with the highest water contact angle being 115.2 ± 1° and hexadecane contact angle being 67.2 ± 1°. The surface morphologies and roughness of the self-assembled films were measured by atomic force microscopy (AFM), as a result, the surface was found to be rougher with the increment of the molecular weight of the fluorooligoethers.
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Ponomarev, B. B., and S. H. Nguyen. "Evaluation of Surface Roughness in Five-Axis Ball-End Milling." Proceedings of Higher Educational Institutions. Маchine Building, no. 05 (722) (May 2020): 21–31. http://dx.doi.org/10.18698/0536-1044-2020-5-21-31.
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Unlike three-axis machining, five-axis machining allows the end tool or workpiece to be oriented at any angle relative to the machine axis OZ. It can be achieved by changing the values of the tool tilt angle and lead angle relative to the surface normal in the contact zone of the tool surface and the workpiece, taking into account the direction of the table feed. The article presents experimental results of analyzing the influences of tool orientation on transverse roughness during ball end milling using 2-flute and 4-flute 8 mm diameter mills. The analysis the arithmetic mean deviation of the assessed profile at various values of tool tilt angle and lead angle showed that the position of the tool point with a zero cutting speed significantly affects the surface quality. The results of the evaluation of the tool orientation influence on the surface roughness enable the selection of optimal tool orientation angles when developing control programs for end milling of free-form surfaces on five-axis CNC milling machines.
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Cortes, Nelson, James Onate, João Abrantes, Linda Gagen, Elizabeth Dowling, and Bonnie Van Lunen. "Effects of Gender and Foot-Landing Techniques on Lower Extremity Kinematics during Drop-Jump Landings." Journal of Applied Biomechanics 23, no. 4 (November 2007): 289–99. http://dx.doi.org/10.1123/jab.23.4.289.
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The purpose of this study was to assess kinematic lower extremity motion patterns (hip flexion, knee flexion, knee valgus, and ankle dorsiflexion) during various foot-landing techniques (self-preferred, forefoot, and rear foot) between genders. 3-D kinematics were collected on 50 (25 male and 25 female) college-age recreational athletes selected from a sample of convenience. Separate repeated-measures ANOVAs were used to analyze each variable at three time instants (initial contact, peak vertical ground reaction force, and maximum knee flexion angle). There were no significant differences found between genders at the three instants for each variable. At initial contact, the forefoot technique (35.79° ± 11.78°) resulted in significantly (p= .001) less hip flexion than did the self-preferred (41.25° ± 12.89°) and rear foot (43.15° ± 11.77°) techniques. At peak vertical ground reaction force, the rear foot technique (26.77° ± 9.49°) presented significantly lower (p= .001) knee flexion angles as compared with forefoot (58.77° ± 20.00°) and self-preferred (54.21° ± 23.78°) techniques. A significant difference for knee valgus angles (p= .001) was also found between landing techniques at peak vertical ground reaction force. The self-preferred (4.12° ± 7.51°) and forefoot (4.97° ± 7.90°) techniques presented greater knee varus angles as compared with the rear foot technique (0.08° ± 6.52°). The rear foot technique created more ankle dorsiflexion and less knee flexion than did the other techniques. The lack of gender differences can mean that lower extremity injuries (e.g., ACL tears) may not be related solely to gender but may instead be associated with the landing technique used and, consequently, the way each individual absorbs jump-landing energy.
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Cai, Shaobiao, and Bharat Bhushan. "Meniscus and viscous forces during separation of hydrophilic and hydrophobic smooth/rough surfaces with symmetric and asymmetric contact angles." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, no. 1870 (January 11, 2008): 1627–47. http://dx.doi.org/10.1098/rsta.2007.2176.
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Adhesive or repulsive forces contributed by both meniscus and viscous forces can be significant and become one of the main reliability issues when the contacting surfaces are ultra smooth, and the normal load is small, as is common for micro/nano devices. In this study, both meniscus and viscous forces during separation for smooth and rough hydrophilic and hydrophobic surfaces are studied. The effects of separation distance, initial meniscus height, separation time, contact angle and roughness are presented. Meniscus force decreases with an increase of separation distance, whereas the viscous force has an opposite trend. Both forces decrease with an increase of initial meniscus height. An increase of separation time, initial meniscus height or a decrease of contact angle leads to an increase of critical meniscus area at which both forces are equivalent. An increase in contact angle leads to a decrease of attractive meniscus force but an increase of repulsive meniscus force (attractive or repulsive dependent on hydrophilic or hydrophobic surface, respectively). Contact angle has a limited effect on the viscous force. For asymmetric contact angles, the magnitude of the meniscus force and the critical meniscus area are in between the values for the two angles. An increase in the number of surface asperities (roughness) leads to an increase of meniscus force; however, its effect on viscous force is trivial. A slightly attractive force is observed for the hydrophobic surface during the end stage of separation though the magnitude is small. The study provides a fundamental understanding of the physics of the separation process and it can be useful for control of the forces in nanotechnology applications.
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Ferreira, Rodrigo, Gabriel Lopes de Castro Martinelli, Alessandro Roger Rodrigues, and Reginaldo Teixeira Coelho. "Tool Feed and Burr Size Influence on Wettability of Ti6Al4V Micro End-Milled." International Journal of Engineering Materials and Manufacture 6, no. 3 (July 15, 2021): 114–23. http://dx.doi.org/10.26776/ijemm.06.03.2021.02.
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Surface texturing, using micro-milling, has promising applications in the industry of medical implants, since it can assist cell adhesion and thus improve osseointegration. Ti6Al4V alloy is used as implant material due to its excellent biocompatibility and high mechanical strength. However, those mechanical properties reduce machinability creating some challenges for micro-milling. The way to initially assess cell adhesion is using surface wettability, usually conducted with water. At the present work, micro-channels were machined in Ti6Al4V by micro end-milling with 500 µm width per 50 µm depth with 1000 µm distant from each other. The effect of feed per tooth (fz) on wettability was analysed and some interesting relations with burrs formed on channel walls were obtained. Values of feed per tooth were 3, 6, 12 and 15 µm. Wettability results showed that slotted surface is more hydrophilic on channel direction, with contact angles around 30° to 43°. In contrast, on the perpendicular direction the surface tends to be hydrophobic with contact angles between 75° and 146°. In addition, contact angle increases (hydrophobic tendency) as feed per tooth increases (along with roughness), even on channel direction. The presence of burrs also tends to disturb wettability results. Therefore, surface wettability depends on channel direction, burr size and tool feed per tooth, as well.
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Miura, Kousei, Hideki Kadone, Masao Koda, Keita Nakayama, Hiroshi Kumagai, Katsuya Nagashima, Kentaro Mataki, et al. "Visualization of walking speed variation-induced synchronized dynamic changes in lower limb joint angles and activity of trunk and lower limb muscles with a newly developed gait analysis system." Journal of Orthopaedic Surgery 26, no. 3 (September 1, 2018): 230949901880668. http://dx.doi.org/10.1177/2309499018806688.
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Purpose: To evaluate a newly developed system for dynamic analysis of gait kinematics and muscle activity. Methods: We recruited 10 healthy men into this study. Analyses of three-dimensional motion and wireless surface electromyogram (EMG) were integrated to achieve synchronous measurement. The participants walked continuously for 10 min under two conditions: comfortable and quick pace. Outcome measures were joint angles of the lower limbs determined from reflective markers and myoelectric activity of trunk and lower limbs determined from EMG sensors, comparing comfortable and quick gait pace. Results: Lower limb joint angle was significantly greater at the quick pace (maximum flexion of the hip joint: 4.1°, maximum extension of hip joint: 2.3°, and maximum flexion of the knee joint while standing: 7.4°). The period of maximum flexion of the ankle joint during a walking cycle was 2.5% longer at a quick pace. EMG amplitudes of all trunk muscles significantly increased during the period of support by two legs (cervical paraspinal: 55.1%, latissimus dorsi: 31.3%, and erector spinae: 32.6%). EMG amplitudes of quadriceps, femoral biceps, and tibialis anterior increased significantly by 223%, 60.9%, and 67.4%, respectively, between the periods of heel contact and loading response. EMG amplitude of the gastrocnemius significantly increased by 102% during the heel-off period. Conclusion: Our gait analysis synchronizing three-dimensional motion and wireless surface EMG successfully visualized dynamic changes in lower limb joint angles and activity of trunk and lower limb muscles induced by various walking speeds.
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Ferguson, Sue A., Fadi A. Fathallah, Kevin P. Granata, Jung Y. Kim, and William S. Marras. "Coactivity Effects upon Carpal Tunnel Contact Forces." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 37, no. 10 (October 1993): 705–9. http://dx.doi.org/10.1177/154193129303701013.
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Contact force on the carpal tunnel structures due to flexor tendon forces have been identified as an important contributor to the compression of the median nerve. Therefore, a pilot study was conducted to assess the increase in carpal contact force due to the antagonistic coactivity of the finger extensor muscles. Surface EMG activities of the superficial finger flexor and extensor muscles of four subjects were measured during several isometric power grip exertions at seven different wrist angles. The results showed that a linear relation between EMG and muscle force holds under the prescribed isometric conditions. An EMG-assisted model was developed to predict tensile forces in an equivalent flexor tendon. For a given angle, the model predicts increased tensile force in the flexor tendon with increased extensor (antagonist) coactivity in response to isometric grip exertions. It was found that if one accounts for muscle coactivity, predicted force in the flexor tendons would be as much as 33% greater than force predicted by models which neglect coactivity. This increase would also be observed in carpal contact force since this force is linearly related to the flexor tendon force. Models that neglect coactivity severely underestimate flexor tendon forces and consequently contact forces in the carpal tunnel.
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Putz, J., Robert Hol/yst, and M. Schick. "Nonmonotonic behavior of a contact angle on approaching critical end points." Physical Review A 46, no. 6 (September 1, 1992): 3369–72. http://dx.doi.org/10.1103/physreva.46.3369.
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Narita, Hirohisa. "Cutting Features Between Surface Roughness in Feed Direction and Machining State of Radius End Mill Against Inclined Surfaces (In Case of Contour Machining and Five-Axis Machining with Constant Tilt Angle)." International Journal of Automation Technology 14, no. 1 (January 5, 2020): 46–51. http://dx.doi.org/10.20965/ijat.2020.p0046.
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Optimum experimental conditions, that realize good surface roughness in feed direction, for a radius end mill against some inclined surfaces is obtained by the Taguchi method. Some cutting features due to the unique shape of the radius end mill are revealed via the degree of influence of various factors, which are calculated by the Taguchi method, and the geometric relationship of some contact states of the tool. The experimental conditions include cutting type, spindle speed, feed rate, depth of immersion, inclination angle, and corner radius. The results revealed that the contact states are highly significant, and can be categorized into three types. Furthermore, bottom and corner edges must be contacted simultaneously in order to obtain good surface roughness.
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Putz, J., Robert Hołyst, and M. Schick. "Erratum: Nonmonotonic behavior of a contact angle on approaching critical end points." Physical Review E 48, no. 1 (July 1, 1993): 635. http://dx.doi.org/10.1103/physreve.48.635.
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Sun, Kang, Mingjie Liu, Hongliang Liu, Pengchao Zhang, Junbing Fan, Jingxin Meng, and Shutao Wang. "Semi-Egg-Like Heterogeneous Compartmentalization of Cells Controlled by Contact Angle Hysteresis." Advanced Functional Materials 25, no. 28 (June 12, 2015): 4506–11. http://dx.doi.org/10.1002/adfm.201501527.
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Weng, Rui, Chong Rui Wang, Lian Meng Zhang, and Shui Ping Wang. "Preparation and Properties Fluoralkylpolysiloxane Modified Polyurethane Films." Materials Science Forum 620-622 (April 2009): 741–44. http://dx.doi.org/10.4028/www.scientific.net/msf.620-622.741.
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Fluoralkylpolysiloxane modified Polyurethane (FSPU) films with high water contact angle (CA) were prepared. fluoralkylpolysiloxane was obtained using perfluoro octyl sulfuryl fluoride and terminal amino-silicone oil as reactants. Then, the isocyanate end capped PU prepolymer was synthesized by reacting isocyanate with a soft segment mixed by active amino-end-capping fluoralkylpolysiloxane and polyether glycol. The fluoralkylpolysiloxane modified PU films were obtained after the PU prepolymer was cured by 3,3 '- dichloro -4,4' – amino - diphenyl methane (MOCA). The results showed that the modified polyurethane with 10% (mass fraction) PFATPS had a good compatibility, low surface energy, surface water contact angle and surface oil contact angle was improved by 49° and 37° respectively, and heat resistance, water resistance was apparently improved.
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Hunt, Kenneth, Richard Fuld, Judas Kelley, Nicholas Anderson, and Todd Baldini. "The Role of Calcaneofibular Ligament (CFL) Injury in Ankle Instability." Foot & Ankle Orthopaedics 2, no. 3 (September 1, 2017): 2473011417S0002. http://dx.doi.org/10.1177/2473011417s000211.
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Category: Ankle Introduction/Purpose: Acute inversion ankle sprains are among the most common musculoskeletal injuries. Higher grade sprains, which include anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) injury, can be particularly problematic and often require surgical repair. The implications of CFL injury on ankle instability are unclear. We aim to evaluate the impact of CFL injury on ankle stability and subtalar joint biomechanics. We hypothesized that CFL injury will result in decreased stiffness and torque, and alteration of ankle contact mechanics compared to the uninjured ankle in a cadaveric model. Methods: Twenty matched cadaveric ankles dissected of skin and subcutaneous tissue were mounted to an Instron with 20° of ankle plantar flexion and 15° of internal rotation. Intact specimens were axially loaded to body weight, then underwent inversion stress along the anatomic axis of the ankle from 0 to 20° (simulating inversion injury) for three cycles. ATFL and CFL were sequentially sectioned, and inversion testing repeated for each condition. Stiffness and change in torque were recorded using an Instron, and pressure and contact area were recorded using a calibrated Tekscan sensor system. Inversion angle of the talus and calcaneus relative to the ankle mortise were recorded using a three-dimensional motion capture system. Paired t tests were performed for inter and intra-group comparisons. Results: Stiffness and torque did not significantly decrease after sectioning of the ATFL, but did decreased significantly after sectioning of CFL. Peak pressures in the tibiotalar joint decreased significantly following CFL release compared to both the uninjured ankle and ATFL-only release. Mean contact area significantly increased following CFL release compared to both the uninjured ankle and ATFL release. There was a concentration of force in the anteromedial ankle joint during weight-bearing inversion. However, the center-of-force shifts 1.22 mm posteromedial after CFL release relative to an intact ankle. Motion capture showed a significant and sequential increase in inversion angle of both the calcaneus and talus, after release of each ligament. There was significantly more inversion in the subtalar joint than the tibiotalar joint with weight-bearing inversion. Conclusion: There is significantly lower stiffness and torque with weight-bearing inversion of the ankle joint complex following injury to both ATFL and CFL, and sequentially greater inversion of the talus and calcaneus with progressive ligament injury. This corresponds to a significant shift in the center of force in the tibiotalar joint. CFL contributes considerably to lateral ankle stability, and sprains that include CFL injury result in substantial alteration of contact mechanics at the ankle and subtalar joints. Repair of CFL may be beneficial during lateral ligament reconstruction, potentially mitigating long-term consequences (e.g., articular damage) of a loose or incompetent CFL.
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Naik, Saurabh, Gabriel Malgaresi, Zhenjiang You, and Pavel Bedrikovetsky. "Well productivity enhancement by applying nanofluids for wettability alteration." APPEA Journal 58, no. 1 (2018): 121. http://dx.doi.org/10.1071/aj17149.
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Water blocking is a frequent cause for gas productivity decline in unconventional and conventional fields. It is a result of the capillary end effect near the wellbore vicinity. It creates significant formation damage and decreases gas well productivity. The alteration of the rock wettability by nanofluids is an effective way to reduce water blockage and enhance gas production. Presently, several types of surfactants and nanofluids are used in the industry for contact angle alteration. In this study, we developed an analytical model and analysed the sensitivity to several parameters. After the treatment, the porous medium in the well vicinity (or along the core) will have a stepwise constant contact angle profile. We derive analytical models for compressible steady-state two-phase linear and axi-symmetric flows, accounting for the piecewise-constant contact angle and contact-angle-dependent capillary pressure and relative permeability. The modelling reveals a complex interplay between the competing effects of compressibility, viscous and capillary forces, which influence the optimal contact angle for treatment. The optimal contact angle for treatment will depend on the initial wettability of the formation, the water cut and the capillary-viscous ratio.
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Abbasi, Sarwar Ali, Ping Fa Feng, Yuan Ma, X. C. Cai, Ding Wen Yu, and Zhi Jun Wu. "Finite Element Deformation Analysis of Long Thin Cantilever Shape Parts in High Speed Ball End Milling of Titanium Alloy Ti-6Al-4V with PCD Tools at Various Tool Inclination Angles." Key Engineering Materials 693 (May 2016): 1038–45. http://dx.doi.org/10.4028/www.scientific.net/kem.693.1038.
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In this study the influence of tool inclination angle on deformation of thin wall cantilever shape part has been analyzed using finite element numerical simulations. Polycrystalline diamond, PCD tool has been chosen as a tool material in this study because PCD tool has given better results in terms of surface roughness, tool life and productivity in end milling of titanium alloy Ti-6Al-4V. Firstly, in this study, the effect of tool inclination angle on tool contact geometry, cutting speed and cutting forces has been discussed. Then, finite element numerical simulations (FEM) have been carried out in AdvantEdge® for the prediction of cutting forces with PCD tool at four different tilt angles viz. 70°, 75°, 80° and 85° and the results have been compared to the coated carbide tool. Then the maximum magnitude of the forces which occurred in tangential direction (FY) were input in the Abaqus® software as a load acting on the thin long cantilever part and deformation results were analyzed. Results show that PCD tool due to its high hardness, strength and better wear resistance produce lower cutting forces at all angles studied and at an angle near the perpendicular to the surface being machined both tools have lower values of the deformation. The FEM simulation results match well with the theoretical study as theoretical analysis also shows that at angles nearer to perpendicular to the surface being machined, the tool will have lower effective cutting speed & forces and hence proved as the key to achieving better accuracies for long thin wall parts.
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Sauli, Zaliman, Vithyacharan Retnasamy, Aaron Koay Terr Yeow, Goh Siew Chui, K. Anwar, and Nooraihan Abdullah. "Surface Roughness and Wettability Correlation on Etched Platinum Using Reactive Ion Ecthing." Applied Mechanics and Materials 487 (January 2014): 263–66. http://dx.doi.org/10.4028/www.scientific.net/amm.487.263.
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As the world of semiconductor is moving towards smaller and high-end applications, the quality of the bonding adhesion for wire bonding is very critical. Although aluminium has been the metallization of choice in integrated circuits, it can be easily oxidized during high temperature and pressure. On the other hand, Platinum metallization layer has high thermal coefficient resistance and inert to oxygen. This paper reports the correlation between surface roughness and the wettability in the form of contact angle for Platinum deposited wafer etched using Inductively Couple Plasma-Reactive Ion Etching (ICP-RIE). Surface roughness was measured using AFM while contact angle was obtained via droplet test. The results clearly suggested that both surface roughness and wettabily, calculated by its contact angle value has the same trend. Surface roughness is directly proportional to the contact angle. This indicates that surface roughness have great influence on the surface wettability. Therefore, the adhesion for wire bonding process on platinum metallization which can be used in high end applications can be controlled by its surface roughness and wettability.
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Shiguematsu, Yukitoshi Minami, Przemyslaw Kryczka, Kenji Hashimoto, Hun-Ok Lim, and Atsuo Takanishi. "Heel-Contact Toe-Off Walking Pattern Generator Based on the Linear Inverted Pendulum." International Journal of Humanoid Robotics 13, no. 01 (March 2016): 1650002. http://dx.doi.org/10.1142/s021984361650002x.
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We propose a novel heel-contact toe-off walking pattern generator for a biped humanoid robot. It is divided in two stages: a simple model stage where a Linear Inverted Pendulum (LIP) based heel-contact toe-off walking model based on the so-called functional rockers of the foot (heel, ankle and forefoot rockers) is used to calculate step positions and timings, and the Center of Mass (CoM) trajectory taking step lengths as inputs, and a multibody dynamics model stage, where the final pattern to implement on the humanoid robot is obtained from the output of the first simple model stage. The final pattern comprises the Zero Moment Point (ZMP) reference, the joint angle references and the end effector references. The generated patterns were implemented on our robotic platform, WABIAN-2R to evaluate the generated walking patterns.
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Liu, X.-L., P. Yang, and P.-R. Yang. "Analysis of the lubricating mechanism for tilting rollers in rolling bearings." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 225, no. 11 (September 23, 2011): 1059–70. http://dx.doi.org/10.1177/1350650111413839.
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In practice, the tilting roller occurs widely in rolling bearings. In order to investigate the lubricating mechanism of tilting rollers in rolling bearings, a contact between a tilting cylindrical roller and an infinite plane is assumed in the present paper. Using the multi-grid method, a numerical solution has been obtained for the isothermal elastohydrodynamic lubrication of the contact. The film thickness and pressure with different tilt angles have been given. Results show that the property of the tilting roller’s lubrication is different from that of the parallel roller contact investigated in the past, and asymmetry is common both for the film thickness and the oil pressure under tilting conditions. Moreover, the larger the tilt angle, the smaller the minimum film thickness, and the more easily the local wear occurs in bearings. The effects of the maximum Hertzian pressure, velocity parameter, and length and end profile radius of the roller on the lubricating performance of the contact have been discussed. The conclusion can be made that better lubrication of tilting roller contact needs light load, high velocity parameter, short length, and larger end profile radius of the roller. Comparisons between the starved and fully flooded lubrication in the tilting roller contact have been given, and it has been found that starvation status can worsen the lubrication and reduce the life of roller bearings.
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Kuhta, P. C., and J. L. Smith. "Scratch responses in normal cats: hindlimb kinematics and muscle synergies." Journal of Neurophysiology 64, no. 6 (December 1, 1990): 1653–67. http://dx.doi.org/10.1152/jn.1990.64.6.1653.
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1. Scratch responses evoked by a tactile stimulus applied to the outer ear canal were characterized in nine adult cats. Chronic electromyographic (EMG) electrodes were surgically implanted in selected flexor and extensor muscles of the hip, knee, and ankle joints to determine patterns of muscle activity during scratching. In some trials EMG records were synchronized with kinematic data obtained by digitizing high-speed cine film, and in one cat, medial gastrocnemius (MG) tendon forces were recorded along with EMG. For analysis the response was divided into three components: the approach, cyclic, and return periods. Usually scratch responses were initiated with the cat in a sitting position, but in some trials the animal initiated the response from a standing or lying posture. 2. During the approach period the hindlimb ipsilateral to the stimulated ear was lifted diagonally toward the head by a combination of hip and ankle flexion with knee extension. Hindlimb motions during the approach period were associated with sustained EMG activity in hip-flexor, knee-extensor (occasionally), and ankle-flexor muscles. Initial hindlimb motions were typically preceded by head movements toward the hindpaw, and at the end of the approach period, the head was tilted downward with the stimulated pinna lower than the contralateral ear. During the return period movements were basically the reverse of the approach period, with the hindpaw returning to the ground and the head moving away from the hindlimb. 3. During the cyclic period the number of cycles per response varied widely from 1 to 60 cycles with an average of 13 cycles, and cycle frequency ranged from 4 to 8 cycles/s, with a mean of 5.6 cycles/s. During each cycle the paw trajectory followed a fairly circular path, and the cycle was defined by three phases: precontact, contact, and postcontact. On average the contact phase occupied approximately 50% of the cycle and was characterized by extensor muscle activity and extension at the hip, knee, and ankle joints. The hindpaw contacted the pinna or neck at the base of the pinna throughout the contact phase, and paw contact typically resulted in a rostral motion of the head as the hindlimb extended. 4. The postcontact phase constituted approximately 24% of scratch cycle and was usually initiated by the onset of knee flexion. Ankle and then hip flexion followed knee flexion, and flexor muscles were active during the postcontact phase as the paw was withdrawn from the head. The precontact phase constituted approximately 26% of scratch cycle and was initiated by knee joint extension and knee-extensor activity.(ABSTRACT TRUNCATED AT 400 WORDS)
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Schmatz, Joyce, Jop Klaver, Mingze Jiang, and Janos L. Urai. "Nanoscale Morphology of Brine/Oil/Mineral Contacts in Connected Pores of Carbonate Reservoirs: Insights on Wettability From Cryo-BIB-SEM." SPE Journal 22, no. 05 (February 6, 2017): 1374–84. http://dx.doi.org/10.2118/180049-pa.
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Summary We used broad-ion-beam slope cutting in combination with scanning electron microscopy undertaken under cryogenic conditions (Cryo-BIB-SEM) to study mineral/oil/brine contacts in reservoir carbonates. This direct-imaging method allows pore-scale investigation of in-situ fluids and their distributions down to the nanometer scale. In this study, we compare two types of carbonate reservoirs: a fine-grained Lixhe limestone (Belgium) and a coarse-grained limestone from the Maastricht area (The Netherlands). In both rock types, we first quantify the porosity with BIB-SEM and derive the spatially resolved pore connectivity of the rock from BIB-SEM on Wood's Metal (WM) injected subsamples. In the second step, subsamples were saturated with the oil analog n-hexadecane, and then flooded with NaCl brine and MgSO4 brine, respectively, to study the effect of the brine chemistry on the microscopic fluid distribution. Cryo-BIB-SEM in combination with high-resolution energy-dispersive-spectroscopy (EDS) imaging and automated image analysis on the saturated samples allowed for a quantification of the oil-droplet size, the lengths of carbonate/oil interfaces, and the 2D contact angle of carbonate with brine and oil. Our results show that these features (e.g., interface length, contact angles, effect of asperities) are present on the scale of a few tens of nanometers to a few micrometers, which is in agreement with numerous theoretical and experimental studies. Lixhe limestone showed relatively less carbonate/oil contacts despite a larger oil fraction in the MgSO4-brine-flooded sample compared with the sample flooded with NaCl brine, indicating a more-hydrophilic nature of the carbonate surface in this experiment. This feasibility study showed that the technique permits the testing of predictions on the morphology and dynamics of contact lines in relation to the mineral properties, which is not possible with other imaging methods, such as X-ray microcomputed tomography (µ-CT), because of limits in resolution.
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Mattes, Klaus, Stefanie Wolff, and Shahab Alizadeh. "Kinematic Stride Characteristics of Maximal Sprint Running of Elite Sprinters – Verification of the “Swing-Pull Technique”." Journal of Human Kinetics 77, no. 1 (January 30, 2021): 15–24. http://dx.doi.org/10.2478/hukin-2021-0008.
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Abstract Maximum sprinting speed constitutes an optimum relation between the stride length and the step rate in addition to an appropriate sprinting technique. The kinematics of the sprint step at maximum sprinting speed have already been examined in numerous studies, without reaching a consensus. The aim of this study was to analyze the relationship between maximum sprinting speed and the stride kinematics based on the “Swing-Pull Technique”. German elite sprinters (N = 26, body height = 182 ± 6 cm, leg length 93.8 ± 4.1 cm) were tested while performing a 30-meter flying sprint at maximum sprinting speed. The relationship between sprinting speed and kinematic variables was determined via Pearson correlation. Sprinting speed (10.1 – 11.3 m/s) correlated with stride length (r = 0.53), ground contact time (r = -0.53) and variables from the technique model: the knee angle at the end of the knee lift swing (r = 0.40), the maximum knee angle prior to backswing (r = 0.40), the hip extension angle velocity (r = 0.63), and vertical foot velocity (r = 0.77) during pre-support, the ankle angle at the take-on (r = -0.43), knee flexion (r = -0.54), and knee extension (r = -0.47) during support. The results indicate that greater stride length, smaller contact time, and the mentioned kinematic step characteristics are relevant for the production of maximum sprinting speed in athletes at an intermediate to advanced performance level. The association of sprinting speed and these features should primarily be taken into account in conditioning and technical training.
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Tittal, Ram K., Satish Kumar, and R. N. Ram. "Crystal structure of (Z)-2,3-dichloro-1,4-bis(4-methoxyphenyl)but-2-ene-1,4-dione." Acta Crystallographica Section E Structure Reports Online 70, no. 9 (August 23, 2014): o1049—o1050. http://dx.doi.org/10.1107/s1600536814018790.
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The title compound, C18H14Cl2O4, adopts aZconformation around the cental C=C bond. The two aromatic rings of the molecule are nearly perpendicular to each other, with a dihedral angle between of 86.22 (14)°. The methoxy substituents lie close to the plane of the attached benzene rings. The C(ar)—C(ar)—O—C(Me) torsion angles are −2.4 (7) and 7.5 (6)°. Weak C—H...O interactions link the molecules forming a three-dimensional network. The crystal packing also displays short [3.160 (3) Å] Cl...O halogen-bonding contacts between molecules related by the screw axis. The structure exhibits disorder of one carbonyl O atom with a refined occupancy ratio of 0.21 (6):0.79 (6).
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Kurpiers, Nicolas, Paul McAlpine, and Uwe G. Kersting. "A biomechanical field testing approach in snow sports: Case studies toward a detailed analysis of joint loading." Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology 234, no. 4 (June 16, 2020): 337–46. http://dx.doi.org/10.1177/1754337120918037.
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In this study, kinematic and kinetic measurements were combined to assess the effects of removing the stiff shaft from a ski boot. It was hypothesized that joint flexion at the ankle, knee and hip increase and reduce joint loading specifically at the knee. A previously developed force sensor was combined with a high-speed camera system for data collection of 6 degrees of freedom ground reaction forces and three-dimensional marker data in the field on a wave slope. The collected data were used as input to a musculoskeletal model for the estimation of joint kinematics and joint moments and contact forces in the ankle and knee. The force sensor, which was previously used for skiing, had experienced wear and tear and was thus prone to breakage. As a result, joint loading could only be analyzed for two skiers. These two skiers did not use the added range of ankle flexion to its full extent, but showed substantial reductions in joint moments and joint contact forces (e.g. knee compression force from 85 to 57 N/kg). Only one of the five experienced skiers tested was able to adopt the anticipated movement pattern by substantially increased maximum ankle joint flexion angle (from 10° to 37°) and knee joint flexion angle (from 93° to 105°) and the respective ranges of motion when skiing through a wave course. The study provides information on possible individual adaptations to ski boot modifications. The mechanical construction of the force sensor will need to be modified to withstand the high forces expected during freestyle skiing. The study also supports the future use of this measurement setup for comprehensive studies in snow sports, provided that a sufficient training period is given.
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Kingston, David C., and Stacey M. Acker. "Prediction of thigh-calf contact parameters from anthropometric regression." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 233, no. 4 (March 7, 2019): 414–23. http://dx.doi.org/10.1177/0954411919832037.
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High knee flexion postures are common in industry and cultural practices, but the mechanical effect of intersegmental force, particularly thigh-calf contact force, on knee joint compressive force is poorly understood. Although some studies have measured thigh-calf contact parameters occurring in a number of high flexion postures, joint contact modeling would benefit from efforts to predict thigh-calf contact force for use in computational models. Therefore, this study assessed the strength of correlations and linear multiple regression models on the following five high flexion thigh-calf contact parameters in a young, healthy population: the onset angle of thigh-calf contact, maximum flexion angle, total thigh-calf contact force, center of force, and contact area at maximum flexion. Regressions used anthropometric values (and in some cases, maximum flexion angle). Overall, maximum flexion angle and center of force location had the most significant correlates and strong linear fits with regressive models. Thigh-calf contact onset, total force magnitude, and contact area had only moderate to weak relationships. An exploratory attempt at regression using grouped movements into gross patterns (e.g. two types of squatting were grouped into a general squatting category) using maximum flexion angle and center of force location as dependent variables resulted in similar model fitting. These findings suggest that a causal relationship between select anthropometrics and lower limb range of motion may exist, but further exploration is necessary to determine clinically reliable predictive models.
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LIU, Z. Y., J. Y. WANG, Q. L. YAN, Y. KOU, and X. G. JIAN. "NOVEL HYDROPHILIC RESIN APPLIED IN HEAT-RESISTANT WATER-BORNE COATINGS." Surface Review and Letters 13, no. 06 (December 2006): 733–36. http://dx.doi.org/10.1142/s0218625x06008761.
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Poly(phthalazinone ether nitrile ketone)s (PPENK) was modified with NaOH in N,N-dimethyl acetamide (DMAc) in order to find a hydrophilic resin applied in heat-resistant water-borne coatings. The properties of hydrolyzates (HPPENK) in different hydrolysis time were characterized by FT-IR and 1H-NMR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle (water) as well as solubility measurements. The results indicated that, along with the prolonged hydrolysis time, nitrile groups conversion ratio and glass transition temperature (T g ) of hydrolyzates increase, whereas weight loss ratio of HPPENK decreases. As expected, the hydrophilicity of HPPENK was improved greatly, e.g., when CN conversion ratio was 93.82%, the water contact angles were found to decrease from 75.3° of PPENK to 54.4° of HPPENK. HPPENKc dispersion has no separation more than 20 days in terms of shelf-life.
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DE LAZZER, A., and D. LANGBEIN. "Liquid surface in regular N-pods." Journal of Fluid Mechanics 358 (March 10, 1998): 203–21. http://dx.doi.org/10.1017/s0022112097008173.
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The shape of liquid surfaces in regular N-pods in the absence of gravity is considered. A liquid volume in the vertex of a regular N-pod wets the adjacent faces if the sum of the liquid's contact angle γ with the faces and half the dihedral angle α between adjacent faces is smaller than π/2. A suggestion for why the surface shape in the wedge approaches its cylindrical shape at infinity exponentially is given. The range of this exponential decrease is related to the curvature of the meniscus and the angles α and γ: The decrement of the decrease generally shows a weak dependence on α+γ, predominantly depending on the liquid volume. Extremely close to the wetting limit, when α+γ approaches π/2, the decrement vanishes. The exponential meniscus shape leads to a similarity relation and allows small relative liquid volumes in polyhedrons to be split up into partial volumes ascribed to the corners and others ascribed to the wedges. The respective relations among volume, curvature, contact angle and corner geometry are obtained by numerical simulation and the limits of applicability are discussed. This greatly simplifies the calculation of liquid surfaces in the limit of small liquid volumes. The results obtained apply to liquid surfaces in a Space environment, e.g. to metallic melts in crucibles and to propellants and other technical fluids in tanks and reservoirs, as well as to liquid surfaces on Earth, e.g. to liquids trapped in polyhedral pores and to liquid foams, provided their characteristic length is sufficiently small compared to the capillary length.
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Callaghan, Christopher J., and John C. McKinley. "Assessing risk of damage to posterior ankle structures during total ankle arthroplasty." Bone & Joint Open 2, no. 7 (July 1, 2021): 503–8. http://dx.doi.org/10.1302/2633-1462.27.bjo-2021-0057.r1.
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Aims Arthroplasty has become increasingly popular to treat end-stage ankle arthritis. Iatrogenic posterior neurovascular and tendinous injury have been described from saw cuts. However, it is hypothesized that posterior ankle structures could be damaged by inserting tibial guide pins too deeply and be a potential cause of residual hindfoot pain. Methods The preparation steps for ankle arthroplasty were performed using the Infinity total ankle system in five right-sided cadaveric ankles. All tibial guide pins were intentionally inserted past the posterior tibial cortex for assessment. All posterior ankles were subsequently dissected, with the primary endpoint being the presence of direct contact between the structure and pin. Results All pin locations confer a risk of damaging posterior ankle structures, with all posterior ankle structures except the flexor hallucis longus tendon being contacted by at least one pin. Centrally-aligned transcortical pins were more likely to contact posteromedial neurovascular structures. Conclusion These findings support our hypothesis that tibial guide pins pose a considerable risk of contacting and potentially damaging posterior ankle structures during ankle arthroplasty. This study is the first of its kind to assess this risk in the Infinity total ankle system. Cite this article: Bone Jt Open 2021;2(7):503–508.
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Yuan, Song Mei, Si Liu, Lu Tao Yan, and Qing Chun Xiong. "Experimental Evaluation on the Effect of the Position of the Nozzle in End Milling under Minimum Quantity Lubrication Condition." Applied Mechanics and Materials 155-156 (February 2012): 42–46. http://dx.doi.org/10.4028/www.scientific.net/amm.155-156.42.
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Stricter environmental regulations are making the use of an ample amount of conventional coolant impossible because of its negative impact on the environment. Consequently, the use of minimum quantity lubrication (MQL) has been regarded as an promising alternative to conventional fluid coolant applications. Despite several studies, there have been a few investigations about the influence of the MQL nozzle position, such as distance from tool-workpiece contact zone, elevation angles, the included angle between jet direction and feed direction. The current study presents experimental investigations on influences of the above parameters on performance in end milling. Tool wear and surface roughness are experimentally studied to compare the effects of different positions. The results show that the setting location of the nozzle is an important factor regarding the effective application of MQL oil mist.
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Maruyama, Tsubasa, Mitsunori Tada, and Haruki Toda. "Riding Motion Capture System Using Inertial Measurement Units with Contact Constraints." International Journal of Automation Technology 13, no. 4 (July 5, 2019): 506–16. http://dx.doi.org/10.20965/ijat.2019.p0506.
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The measurement of human motion is an important aspect of ergonomic mobility design, in which the mobility product is evaluated based on human factors obtained by digital human (DH) technologies. The optical motion-capture (MoCap) system has been widely used for measuring human motion in laboratories. However, it is generally difficult to measure human motion using mobility products in real-world scenarios, e.g., riding a bicycle on an outdoor slope, owing to unstable lighting conditions and camera arrangements. On the other hand, the inertial-measurement-unit (IMU)-based MoCap system does not require any optical devices, providing the potential for measuring riding motion even in outdoor environments. However, in general, the estimated motion is not necessarily accurate as there are many errors due to the nature of the IMU itself, such as drift and calibration errors. Thus, it is infeasible to apply the IMU-based system to riding motion estimation. In this study, we develop a new riding MoCap system using IMUs. The proposed system estimates product and human riding motions by combining the IMU orientation with contact constraints between the product and DH, e.g., DH hands in contact with handles. The proposed system is demonstrated with a bicycle ergometer, including the handles, seat, backrest, and foot pedals, as in general mobility products. The proposed system is further validated by comparing the estimated joint angles and positions with those of the optical MoCap for three different subjects. The experiment reveals both the effectiveness and limitations of the proposed system. It is confirmed that the proposed system improves the joint position estimation accuracy compared with a system using only IMUs. The angle estimation accuracy is also improved for near joints. However, it is observed that the angle accuracy decreases for a few joints. This is explained by the fact that the proposed system modifies the orientations of all body segments to satisfy the contact constraints, even if the orientations of a few joints are correct. This further confirms that the elapsed time using the proposed system is sufficient for real-time application.
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SHUCHI, Ryo, Toshiki HIROGAKI, Eiichi AOYAMA, and Keiji OGAWA. "B6 Investigation of Finished Surface Machined by Ball Nose End-milling under Constant Contact Angle with a Five-axis Controlled Machining Center(Advanced machine tool)." Proceedings of International Conference on Leading Edge Manufacturing in 21st century : LEM21 2009.5 (2009): 83–88. http://dx.doi.org/10.1299/jsmelem.2009.5.83.
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Ponomarev, B. B., and Nguyen Sy Hien. "The Influence of Tool Orientation on Cutting Forces during End Milling." Proceedings of Higher Educational Institutions. Маchine Building, no. 3 (708) (March 12, 2019): 11–20. http://dx.doi.org/10.18698/0536-1044-2019-3-11-20.
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This article presents the results of single-factor modeling and analysis of the influence of tool orientation with regard to the tilt angle and lead angle, on cutting forces when finish milling by a ball end cutter. The program NX 10 is used to build boundaries and contact areas of the tool and the workpiece, and the SIMULIA ABAQUS software is used to create a three-dimensional finite element model and determine the cutting forces. Graphs that describe dependencies of the cutting forces on the tool rotation angle are obtained for different orientations of the tool axis relative to the surface normal. The computational results will allow transition to the two-factor analysis of the influence of tilt angle combinations on the cutting forces and the determination of the optimal tool orientation during five-axis milling with maximum productivity.
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Chuang, Tzu-Wen, and Feng-Huei Lin. "SURFACE CHARACTERIZATION AND HEMOCOMPATIBILITY OF HEPARINIZED 316L STAINLESS STEEL." Biomedical Engineering: Applications, Basis and Communications 20, no. 01 (February 2008): 1–8. http://dx.doi.org/10.4015/s1016237208000544.
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Poor compatibility between blood and metallic coronary artery stents is one reason for arterial restenosis. Immobilization of heparin on stent's surface is feasible for improving compatibility. We examined possible surface-coupling agents for anticoagulant agent immobilization. Hexamethylene diisocyanate (HMDI) was examined as surface-coupling agent to activate 316L stainless steel (e.g. stent material). Afterwards, we grafted PEG on the HMDI activated surface to provide heparin with higher conformational freedom and a more hydrophilic environment. The effectiveness of HMDI activated and PEG grafted surface was confirmed by FTIR, XPS, and water contact angle test. Heparin was then immobilized onto the activated 316L stainless steel. The heparin surface density was 9.5 μg/cm2. Sessile drop water contact angles showed that the heparingrafted surface is even more hydrophilic than the PEG grafted one. The function of grafted heparin was evaluated by antithrombrin III (ATIII) adsorption testing and SEM. The surface with heparin grafting shows better ATIII binding ability and hemocompatibility than the native one.
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Jo, S. H., Sun Keun Hwang, Hyoung Jin Choi, Beong Bok Hwang, and B. D. Ko. "Rigid-Plastic Finite Element Analysis Applied Frictional Contact Problem in the Composite Rod Extrusion Process." Materials Science Forum 475-479 (January 2005): 3239–42. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.3239.
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This paper presents the plastic deformation behavior of bimetal composite rods during the axisymmetric and steady-state extrusion process through a conical die. In this study, the finite element code, DEFORM commercial package, considering frictional contact problem was used to analyze the effects for the diameter ratio of the core to sleeve layer on the material flow. Different cases of initial composite material are simulated under different conditions of extrusion process, which includes the semi-die angle, reduction in area and end distance, from the end of sleeve to the end of core, with constant value of reduction area, die corner radius and die land. The main design parameters influencing on deformation pattern are diameter ratio of the composite components and semi-die angle. Simulation results indicate that there is an obvious difference of forming pattern with various diameter ration and semi-die angle. The predicted forming load, the end distance and outer radius of sleeve of the rods are also obtained from numerical results. The analysis in this paper is concentrated on the evaluation of the design parameters on the deformation pattern of composite rod.
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Tao, Gaoliang, Ziyue Li, Lisheng Liu, Yangyang Chen, and Kai Gu. "Effects of Contact Angle on the Hysteresis Effect of Soil-Water Characteristic Curves during Dry-Wet Cycles." Advances in Civil Engineering 2021 (April 11, 2021): 1–11. http://dx.doi.org/10.1155/2021/6683859.
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The hysteresis characteristics of soil-water characteristic curves (SWCCs) under dry-wet cycling conditions are very important for understanding unsaturated soil properties, so it is crucial to propose an accurate and efficient method for predicting the hysteretic behaviors of SWCCs. To this end, this paper investigates the hysteresis characteristics of SWCCs in the full suction range of seven kinds of Hunan red clay with different initial dry densities by combination of the pressure plate method, the paper filter method, and the saturated salt solution method. It is found that there are, respectively, strong and weak hysteresis zones in the drying and wetting SWCCs under dry-wet cycling conditions. By combining this feature and based on the drying curve, the soil volume and contact angle changes during the drying and wetting processes are employed to predict the hysteretic behaviors of SWCCs. To verify the validity of the prediction method, the predicted curves of the samples with different initial dry densities are compared with the measured curves. The results show that in the strong hysteresis zone, the hysteresis characteristics of the drying and wetting SWCCs are mainly resulted from the changes in the soil pore structure; in the weak hysteresis zone, the hysteresis characteristics are mainly influenced by the changes in the receding and advancing contact angles corresponding to the drying and wetting processes. The Young–Laplace theory is used to transform the changes of contact angle during the drying and wetting processes into the proportional relationship k of matric suction, and the corresponding wetting curve is obtained by smoothing the drying curve. It is found that the prediction effect in the high suction part (the strong hysteresis zone) is better than that in the weak hysteresis zone, which confirms that the hysteresis effect of SWCCs in the high suction part is influenced by the contact angle. Our proposed method can greatly reduce the test period and has a significant practical application value, which provides a new idea for the prediction of SWCCs under dry-wet cycling conditions.
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Buford, J. A., and J. L. Smith. "Adaptive control for backward quadrupedal walking. II. Hindlimb muscle synergies." Journal of Neurophysiology 64, no. 3 (September 1, 1990): 756–66. http://dx.doi.org/10.1152/jn.1990.64.3.756.
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1. To compare the basic hindlimb synergies for backward (BWD) and forward (FWD) walking, electromyograms (EMG) were recorded from selected flexor and extensor muscles of the hip, knee, and ankle joints from four cats trained to perform both forms of walking at a moderate walking speed (0.6 m/s). For each muscle, EMG measurements included burst duration, burst latencies referenced to the time of paw contact or paw off, and integrated burst amplitudes. To relate patterns of muscle activity to various phases of the step cycle, EMG records were synchronized with kinematic data obtained by digitizing high-speed cine film. 2. Hindlimb EMG data indicate that BWD walking in the cat was characterized by reciprocal flexor and extensor synergies similar to those for FWD walking, with flexors active during swing and extensors active during stance. Although the underlying synergies were similar, temporal parameters (burst latencies and durations) and amplitude levels for specific muscles were different for BWD and FWD walking. 3. For both directions, iliopsoas (IP) and semitendinosus (ST) were active as the hip and knee joints flexed at the onset of swing. For BWD walking, IP activity decreased early, and ST activity continued as the hip extended and the knee flexed. For FWD walking, in contrast, ST activity ceased early, and IP activity continued as the hip flexed and the knee extended. For both directions, tibialis anterior (TA) was active throughout swing as the ankle flexed and then extended. A second ST burst occurred at the end of swing for FWD walking as hip flexion and knee extension slowed for paw contact. 4. For both directions, knee extensor (vastus lateralis, VL) activity began at paw contact. Ankle extensor (lateral gastrocnemius, LG) activity began during midswing for BWD walking but just before paw contact for FWD walking. At the ankle joint, flexion during the E2 phase (yield) of stance was minimal or absent for BWD walking, and ankle extension during BWD stance was accompanied by a ramp increase in LG-EMG activity. At the knee joint, the yield was also small (or absent) for BWD walking, and increased VL-EMG amplitudes were associated with the increased range of knee extension for BWD stance. 5. Although the uniarticular hip extensor (anterior biceps femoris, ABF) was active during stance for both directions, the hip flexed during BWD stance and extended during FWD stance.(ABSTRACT TRUNCATED AT 400 WORDS)
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Gerbert, Go¨ran, and Francesco Sorge. "Full Sliding Adhesive-Like Contact of V-Belts." Journal of Mechanical Design 124, no. 4 (November 26, 2002): 706–12. http://dx.doi.org/10.1115/1.1514662.
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Analysis of power transmission in a belt drive consisting of, e.g., two pulleys might be treated as a boundary value problem. Tight side tension FT, slack side tension FS and the wrap angle α are the three natural boundary conditions. In the literature, theories are developed where seating and unseating as well as the power transmitting part of the contact are considered. The solutions presented so far don’t fulfill the boundary conditions properly, since a certain tension ratio FT/FS is associated with a certain contact angle and not an a priori specified one. It appears that a new type of full sliding solution must be introduced to handle the boundary condition problem. During part of the contact there is almost no tension variation in spite of the full sliding conditions. The designation adhesive-like solution is here introduced for that part. Conditions and character of the adhesive-like solution are outlined in the paper.
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Chen, Chien Yi, and Tsung Chia Chen. "Experimental and Numerical Analysis of Titanium Alloy Microtube Tube-End Nosing Forming." Materials Science Forum 920 (April 2018): 16–21. http://dx.doi.org/10.4028/www.scientific.net/msf.920.16.
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This study is mainly based on five sets of mold cone angle and friction coefficient of micro-tube tube end necking forming analysis, and the tool cone angle of 60° experimental verification is carried out to analyze the titanium alloy (Grade 1) micro-tube for different mold cone angle and the different friction coefficient caused by the difference between the shrinkage forming. In this paper, Prandtl-Reuss's plastic flow rule, combined with finite element deformation theory and updated Lagrangian formulation (ULF) concept, establish an incremental elasto-plastic finite element analysis program for simulating the miniature tube end necking. The forming process also uses the generalized rmin algorithm to deal with elasto-plastic state and contact problems. From the simulation data of necking process, deformation history, punch load and punch stroke, stress and strain distribution is obtained. The analysis results show that by increasing the mold cone angle and friction coefficient, the thickness tends to be thicker in the certain area.
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King, Mark, Harley Towler, Romanda Dillon, and Stuart McErlain-Naylor. "A Correlational Analysis of Shuttlecock Speed Kinematic Determinants in the Badminton Jump Smash." Applied Sciences 10, no. 4 (February 13, 2020): 1248. http://dx.doi.org/10.3390/app10041248.
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The forehand jump smash is an essential attacking stroke within a badminton player’s repertoire. A key determinate of the stroke’s effectiveness is post-impact shuttlecock speed, and therefore awareness of critical technique factors that impact upon speed is important to players/coaches. Three-dimensional kinematic data of player, racket and shuttlecock were recorded for 18 experienced players performing maximal effort forehand jump smashes. Joint angles and X-factor (transverse plane pelvis-thorax separation) were calculated at key instants: preparation, end of retraction, racket lowest point, turning point and shuttlecock contact. Peak shoulder, elbow, and wrist joint centre linear velocities, phase durations and jump height were also calculated. Correlational analyses were performed with post-impact shuttlecock speed, revealing significant correlations to peak wrist joint centre linear velocity (r = 0.767), acceleration phase duration (r = −0.543), shoulder internal/external rotation angle at shuttlecock contact (r = 0.508) and X-factor at the end of retraction (r = −0.484). Multiple linear regression analysis revealed 43.7% of the variance in shuttlecock speed could be explained by acceleration phase duration and X-factor at the end of retraction, where shorter acceleration phase durations and more negative X-factor at end of retraction caused greater shuttlecock speeds. These results suggest that motions of the proximal segments (shoulder and pelvis–thorax separation) are critical to developing greater distal linear velocities, which subsequently lead to greater post-impact shuttlecock speed.
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Chen, Xiao Xiao, and Jun Zhao. "Geometrical Modeling of Tool-Workpiece Contact Zone and Chip Formation in Finish Ball End Milling Process with Tool Inclination Angles." Key Engineering Materials 693 (May 2016): 788–94. http://dx.doi.org/10.4028/www.scientific.net/kem.693.788.
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The tool-workpiece contact zone is an important issue in the ball end milling process. This paper investigated the effects of tool inclination angles on the tool-workpiece contact zone, and variations of the cutting section area and perimeter with the increasing tilt and lead angles were also analyzed by geometrical modeling and measurement method for ball end milling process. The appropriate tool inclination angles, which could avoid the extrusion and friction between tool tip and the uncut materials, shorten the loading time on the cutting flute, and decrease the maximum cutting forces, could be preferentially selected according to the distribution characteristics of the tool-workpiece contact zone and the variations of the cutting section area and perimeter corresponding to various tool postures.
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Zhang, Tie, and Xiaohong Liang. "Disturbance Observer-Based Robot End Constant Contact Force-Tracking Control." Complexity 2019 (October 29, 2019): 1–20. http://dx.doi.org/10.1155/2019/5802453.
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A disturbance observer-based hybrid sliding mode impedance control method is proposed in this paper, which is able to achieve robot end constant contact force-tracking control without force/torque sensors. The method requires only the values of joint torque, joint angle, and joint angular velocity, which are converted by robot servo motor signals, to implement the control. The control scheme consists of two parts: one is a disturbance observer and the other is a hybrid sliding mode impedance controller. The disturbance observer, which takes robot internal signals mentioned above as the inputs to estimate the robot end contact force, is designed based on generalized momentum, thus improving the estimation accuracy. The hybrid sliding mode impedance controller, which uses the values estimated by the disturbance observer and the robot internal signals as the inputs to calculate the corresponding position adjustment, integrates both the impedance control and sliding mode control, thus improving the force-tracking performance and robustness. Experimental results show that the proposed disturbance observer-based hybrid sliding mode impedance control method possesses high control precision.
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Mo, Jingwen, Jingjie Sha, Dengke Li, Zhigang Li, and Yunfei Chen. "Fluid release pressure for nanochannels: the Young–Laplace equation using the effective contact angle." Nanoscale 11, no. 17 (2019): 8408–15. http://dx.doi.org/10.1039/c8nr08987f.
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Cocciaro, Bruno, Sandro Faetti, and Crescenzo Festa. "Experimental investigation of capillarity effects on surface gravity waves: non-wetting boundary conditions." Journal of Fluid Mechanics 246 (January 1993): 43–66. http://dx.doi.org/10.1017/s0022112093000035.
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Damping and eigenfrequencies of surface capillary—gravity waves greatly depend on the boundary conditions. To the best of our knowledge, so far no direct measurement has been made of the dynamic behaviour of the contact angle at the three-phase interface (fluid—vapour—solid walls) in the presence of surface oscillation. Therefore, theoretical models of surface gravity–capillary waves involve ad hoc phenomenological assumptions as far as the behavior of the contact angle is concerned. In this paper we report a systematic experimental investigation of the static and dynamic properties of surface waves in a cylindrical container where the free surface makes a static contact angle $\theta_{\rm c} = 62^{\circ}$ with the vertical walls. The actual boundary condition relating the contact angle to the velocity of the contact line is obtained using a new stroboscopic optical method. The experimental results are compared with the theoretical expressions to be found in the literature. Two different regimes are observed: (i) a low-amplitude regime, where the contact line always remains at rest and the contact angle oscillates during the oscillation of the free surface; (ii) a higher-amplitude regime, where the contact line slides on the vertical walls. The profile, the eigenfrequency and the damping rate of the first non-axisymmetric mode of the surface gravity waves are investigated. The eigenfrequency and damping rate in regime (i) are in satisfactory agreement with the predictions of the Graham-Eagle theory (1983) of pinned-end edge conditions. The eigenfrequency and damping rate in regime (ii) show a strongly nonlinear dependence on the oscillation amplitude of the free surface. All the experimental results concerning regime (ii) can be explained in terms of the Hocking (1987 a) and Miles (1967, 1991) models of capillary damping by introducing an ‘effective’ capillary coefficient $\lambda_{\rm eft}$. This coefficient is directly obtained for the first time in our experiment from dynamic measurements on the contact line. A satisfactory agreement is found to exist between theory and experiment.
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Mansouri, Reyhaneh, Fariba Bahrami, Reza Rajabi, Hooman Minoonejad, and Katarzyna Kaczmarczyk. "Investigating the landing kinetics factors and preparatory knee muscle activation in female handball players with and without dynamic knee valgus while performing single leg landing." Biomedical Human Kinetics 13, no. 1 (January 1, 2021): 155–62. http://dx.doi.org/10.2478/bhk-2021-0019.
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Abstract Study aim: to examine the differences in landing kinetics factors (LKF) to assess the whole body stability and preparatory muscle activation (PMA) in female handball players with and without dynamic knee valgus. Material and methods: Twenty-four professional female handball players (11 with (DKV) and 13 without (Control) dynamic knee valgus) were asked to perform three trials of a single-leg landing. LKF and surface EMG were recorded. Initial contact knee valgus angle (IC KVA), vertical ground reaction force (vGRF), confidence ellipse area of center of pressure (CEA), time to stability (TTS) and EMG from 100 ms prior to ground contact were used in the data analyses. Results: Multivariate analyzing of LKF showed significant differences between two groups (p = 0.001) while for PMA the result was not significant (p = 0.361). Conclusion: Altered landing mechanism considered as a predictor of non-contact knee injuries such as ACL rupture. Therefore according to current study it seems important to focus on reducing valgus angle in designing injury prevention program.
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Tichá, Petra, Maria Domonkos, Jan Trejbal, Pavel Demo, and Zdeněk Prošek. "Electrospun SiO2 Nanotextiles for Preservation of a Tangible Cultural Heritage." Key Engineering Materials 868 (October 2020): 86–91. http://dx.doi.org/10.4028/www.scientific.net/kem.868.86.
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The developing nanotechnology is getting infiltrated into a wide area of industries. A variety of nanotextiles can be produced from different materials (e.g. polymers, SiO2). Their applications are possible in many industrial branches as well as civil engineering. Silica-based nanotextiles can play a fundamental role in civil engineering. The potential utilization of nanotextiles in civil engineering is promising as surface protective layers. Wettability of SiO2 nanotextiles was studied on different thicknesses of samples and were tested under static conditions by determination of the water contact angle. Their water contact angle, which indicates the degree of wetting, was measured using an optical tensiometer.
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Martinelli, Nicoló, Silvia Baretta, Alberto Bianchi Castagnone Prati, Francesco Malerba, Carlo Corrado Bonifacini, and Fabio Galbusera. "Contact Stresses in a Fixed-Bearing Total Ankle Replacement." Foot & Ankle Orthopaedics 2, no. 3 (September 1, 2017): 2473011417S0002. http://dx.doi.org/10.1177/2473011417s000284.
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Category: Ankle, Ankle Arthritis, Basic Sciences/Biologics Introduction/Purpose: Third-generation ankle implants with good clinical results continued to increase the popularity of total ankle arthroplasty (TAA) to address end-stage ankle osteoarthritis preserving joint movement. Newer TAA used fixed-bearing designs, with a theoretical increase of contact stresses leading to a higher polyethylene wear. The purpose of this study was to investigate the contact stresses in the polyethylene component of a new third-generation TAA, with a fixed-bearing design, using 3D finite element analysis. Methods: A three-dimensional finite element model was developed based on the Zimmer Trabecular Metal Total Ankle (ZTMTA) and a finite element analysis was employed to evaluate the contact pressure, contact area and Von Mises stress in the polyethylene articular surface in the stance phase of the gait cycle. Results: The peak values were found at the anterior regions of the articulating surface, where reached 19.8 MPa at 40% of gait cycle. The average contact pressure during the stance phase of gait was 6.9 MPa. The maximum von Mises stress of 14.1 MPa in the anterior section was reached at 40% of the gait cycle. For the central section the maximum von Mises stress of 10.8 MPa was reached at 37% of the gait cycle, whereas for posterior section the maximum of 5.4 MPa was reached at the end of the stance phase (60% of the gait cycle). Conclusion: Although, the average von Mises stress was less than 10 MPa, high peak pressure values were recorded. Advanced models to quantitatively estimate the wear are needed to assess polyethylene and metal component survivorship.