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1
Jacobsson, H. "Disc brake judder considering instantaneous disc thickness and spatial friction variation". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 217, nr 5 (1.05.2003): 325–42. http://dx.doi.org/10.1243/095440703321645043.
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Brake judder is a braking-induced vibration. The character of judder is typical of forced vibrations passing through a critical speed. No specific friction characteristic is needed for judder to occur. In two previous models, i.e. a rotor-stator model and a whole vehicle model, the vibration during a brake application was simulated. The vibrations were assumed to be driven by a brake torque variation (BTV) during a wheel revolution. The BTV was assumed to be proportional to the brake pressure variation (BPV) which was measured. Moreover, the proportionality constant was assumed to be independent of the braking conditions. Verifying measurements were made on a street going vehicle with strong disc thickness variation (DTV) on one of its front wheels. The measured vibration variation during braking was predicted almost exactly by the models. However, the maximum measured vibration level could only be approximated. In the present paper a more accurate analysis of the measurements was found to improve strongly the agreement between predicted and measured vibrations. Hence, the deviation in slope between measured and experimentally generated curves was markedly reduced by replacing the overall mean values of brake pressure level, etc. by slowly varying time functions. The new extended model of the present paper takes into account that the BTV may be generated by variations in normal force (i.e. BPV) and other synchronous variations (called BXV), e.g. spatial friction variation and variation of the equivalent brake radius. The result indicates that BXV may be induced by high BPV levels. Even at judder vibrations primarily caused by heavy DTV (20 μm or more in the cold state), there may be considerable contributions to the vibration level from other synchronous disturbances, i.e. BXV. Further, it was found that the pad stiffness increases with the brake pressure. For such a pad stiffness characteristic, an increase of the DTV level (for whatever reason) by 50 per cent might result in more than a 100 per cent increase in the corresponding BPV and BTV levels. Hence, a progressive pad is more sensitive to increases of the DTV level than a linear pad would be.
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Jung, Sung Pil, Hyun Seok Song, Tae Won Park i Won Sun Chung. "Numerical Analysis of Thermoelastic Instability in Disc Brake System". Applied Mechanics and Materials 110-116 (październik 2011): 2780–85. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.2780.
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Thermal energy generated by the friction between the disc and pad is transferred to both components and causes thermal expansion of material of each component, and futher affects the friction contact condition. This is the main factor of the thermoelastic instability (TEI) of a disc brake. In this study, TEI is analyzed using the finite element analysis technique. Three dimensional thermo-mechanical analysis model of the disc brake system is created. An intermediate processor based on the staggered approach is used to exchange analysis results: temperature, friction contact power, nodal displacement and deformation. Disc thickness variation (DTV) and temperature distribution of the disc are calculated, and the tendency and meaning of the results are discussed.
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Febriani, Risky Ayu, Hong-Seok Park i Chang-Myung Lee. "A Rule-Based System for Quality Control in Brake Disc Production Lines". Applied Sciences 10, nr 18 (20.09.2020): 6565. http://dx.doi.org/10.3390/app10186565.
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Currently, challenges in quality improvement have driven various enterprises to create quality management systems in smart factories. The development of quality management systems enables quality control for reviewing product quality, identification, and eliminating product failures. However, process adjustment in quality control decisions may be hard to determine when failures are detected. To overcome this problem, an expert system (ES) that applies the failure mode and effects analysis (FMEA) method for developing quality control systems in brake disc production lines is considered. This quality control system concentrates on analyzing product defects that occur frequently in the production line and will lead to an improved performance of the braking system; the selected product defects are disc thickness variation (DTV), runout, and parallelism. This quality control system developed two modules, the designed FMEA (DFMEA) and component FMEA, which apply a rule-based algorithm for selecting actions. We propose the rules of configuration into the expert system code. The results indicate that the operator can carry out a quality control system with decision-making that can be supported by intelligent searching and reasoning in an expert system.
4
Kang, Jaeyoung, i Sungjin Choi. "Brake dynamometer model predicting brake torque variation due to disc thickness variation". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 221, nr 1 (styczeń 2007): 49–55. http://dx.doi.org/10.1243/09544070jauto91.
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Gupta, Vandana, i S. B. Singh. "Creep Modeling in a Composite Rotating Disc with Thickness Variation in Presence of Residual Stress". International Journal of Mathematics and Mathematical Sciences 2012 (2012): 1–14. http://dx.doi.org/10.1155/2012/924921.
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Steady-state creep response in a rotating disc made of Al-SiC (particle) composite having linearly varying thickness has been carried out using isotropic/anisotropic Hoffman yield criterion and results are compared with those using von Mises yield criterion/Hill's criterion ignoring difference in yield stresses. The steady-state creep behavior has been described by Sherby's creep law. The material parameters characterizing difference in yield stresses have been used from the available experimental results in literature. Stress and strain rate distributions developed due to rotation have been calculated. It is concluded that the stress and strain distributions got affected from the thermal residual stress in an isotropic/anisotropic rotating disc, although the effect of residual stress on creep behavior in an anisotropic rotating disc is observed to be lower than those observed in an isotropic disc. Thus, the presence of residual stress in composite rotating disc with varying thickness needs attention for designing a disc.
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Yang, Shang, Hui Qun Yuan i Yan Li. "Analysis on Mechanical Characteristics of Flexible Membranous Disc Coupling". Advanced Materials Research 655-657 (styczeń 2013): 506–10. http://dx.doi.org/10.4028/www.scientific.net/amr.655-657.506.
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Using the basic finite element theory, 3D finite element models of flexible membranous disc coupling with different disc thickness is built by ANSYS ，and then the dynamic characteristics are analyzed in working conditions. In particular, the analysis of static stress and harmonic response to the thickness of 0.85 model is done for getting the stress variation under a rated condition. The date calculated by dynamic characteristics and stress analysis can satisfy the design requirements. Those researches and analysis provide a theoretical consideration for complex vibration situation of flexible membranous disc coupling and for the improvement and optimization of coupling product.
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Du, Xinyu, Lichao Mai, Hamed Kazemi i Hossein Sadjadi. "Fault Detection and Isolation for Brake Rotor Thickness Variation". Annual Conference of the PHM Society 12, nr 1 (3.11.2020): 8. http://dx.doi.org/10.36001/phmconf.2020.v12i1.1130.
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Brake rotors are critical parts of the disc braking system for modern vehicles. One common failure for brake rotors is the thickness variation, which may result in unpleasant brake pulsation, vehicle vibration during braking, or eventually lead to the malfunction of the braking system. In order to improve customer satisfaction, vehicle serviceability and availability, it is necessary to develop an onboard fault detection and isolation solution. In our previous work, the vibration features of master cylinder pressure, vehicle longitudinal acceleration and wheel speed were identified as fault signatures. Based on these fault signatures, a vibration- based fault detection and isolation algorithm is developed in this work. The difference of frequency response between the braking period and the normal driving period (non-braking) is employed to improve the algorithm robustness. The experiment results demonstrate the proposed algorithm can robustly diagnose the thickness variation fault and isolate the fault to each vehicle corner.
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Venkatachalam, R., i S. Balasivanandha Prabu. "An Experimental Investigation on the Vibration Responses of a Mild Steel Sandwich Shaft Disc System". Advanced Materials Research 584 (październik 2012): 391–95. http://dx.doi.org/10.4028/www.scientific.net/amr.584.391.
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The main aim of this work is to identify the natural frequency of mild steel sandwich shaft disc system. An experimental evaluation is completed to evaluate the natural frequency and damping response of mild steel sandwich shaft disc system using Lab VIEW 8.5 software and National Instrument’s data acquisition (DAQ) system. The validation of the experimental results carried out using ANSYS 13.0, a finite element analysis software package. In addition, the effect of shaft thickness, disc thickness, shaft length variation, second, third, four and five systems also studied. The outcome of the results show that the increase in the parameter values have significant effect in the vibration responses of the mild steel sandwich shaft disc system which provide very much helpful information for the designers and researchers.
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Gupta, Vandana, i S. B. Singh. "Effect of anisotropy on creep behavior in a functionally graded material disc of variable thickness". International Journal of Computational Materials Science and Engineering 03, nr 03 (wrzesień 2014): 1450017. http://dx.doi.org/10.1142/s2047684114500171.
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In this paper, an effort has been made to study the effect of anisotropy on the steady state creep behavior in the functionally graded material disc with hyperbolic thickness made of Al - SiC (particle). The content of silicon carbide particles in the disc is assumed to decrease linearly from the inner to the outer radius of the disc. The creep behavior of the disc under stresses developing due to rotation at 15,000 rpm has been determined by Sherby's law. The creep parameters of the FGM disc vary along the radial distance due to varying composition and this variation has been estimated by regression fit of the available experimental data. The creep response of rotating disc is expressed by a threshold stress with value of stress exponent as 8. The study reveals that the anisotropy has a significant effect on the steady state creep response of rotating FGM disc. Thus, the care to introduce anisotropy should be taken for the safe design of the rotating FGM disc with hyperbolic thickness.
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Alexandrova, N. N., i P. M. M. Vila Real. "Elastic-plastic stress distributions and limit angular velocities in rotating hyperbolic annular discs". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 221, nr 2 (1.02.2007): 137–42. http://dx.doi.org/10.1243/0954406jmes325.
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Plastic analytical stress analysis of a rotating annular disc with its contours being free from the radial pressure and with specifically variable thickness is presented in terms of the Mises-yield criterion and its associated flow rule. The hyperbolic form of thickness variation is considered and optimized towards the maximum rotational speed and favourable stress combinations. Radial and circumferential stress distributions in the disc both in the intermediate elastic-plastic and in the limit plastic states are obtained. As a particular case, limit elastic angular velocity parameter is derived. The influences of rotational speed as well as the disc's thickness profile on the plastic solution and size of elastic-plastic zone are demonstrated and discussed. The results obtained may be used for the correct implementation of numerical codes and preliminary engineering design.
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Thumm, Armin, Mark Riddell, Bernadette Nanayakkara, Jonathan Harrington i Roger Meder. "Mapping Within-Stem Variation of Chemical Composition by near Infrared Hyperspectral Imaging". Journal of Near Infrared Spectroscopy 24, nr 6 (1.01.2016): 605–16. http://dx.doi.org/10.1255/jnirs.1206.
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A near infrared (NIR) imaging spectrograph was used to generate maps of chemical composition distribution on the surface of transverse wood discs taken from tree stems. The measured chemical components were lignin, galactose, glucose and mannose as well as cellulose and hemicelluloses, which were calculated from monomeric sugars. These components were determined using NIR-based chemistry models, which had been developed specifically for the imaging spectrograph. Explained test-set variation for key constituents ranged between 60% (galactan) and 78% (lignin). Day-to-day variability was 1–2% (standard deviation/range) depending on the chemical property. Various operational parameters such as room temperature, sample temperature, sample surface preparation and sample thickness were found to have a non-negligible, but manageable, influence on predicted results. The influence of room and sample temperatures could be reduced by incorporating temperature changes into the chemistry model. Extractives, transported to, and concentrated at, the disc surface during drying, needed to be physically removed from the surface to avoid an unpredictable influence on chemical results. Wood fibre angles at the disc surface needed to be aligned in a consistent manner to the camera. NIR information was found to derive from a sample depth of up to 10 mm. This distance was consequently chosen as the minimal sample thickness.
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Berg-Johansen, Britta, Misung Han, Aaron J. Fields, Ellen C. Liebenberg, Brandon J. Lim, Peder EZ Larson, Cigdem Gunduz-Demir, Galateia J. Kazakia, Roland Krug i Jeffrey C. Lotz. "Cartilage Endplate Thickness Variation Measured by Ultrashort Echo-Time MRI Is Associated With Adjacent Disc Degeneration". SPINE 43, nr 10 (maj 2018): E592—E600. http://dx.doi.org/10.1097/brs.0000000000002432.
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Ocansey, Stephen, Emmanuel Kwasi Abu, Andrew Owusu-Ansah, Shadrack Mensah, John Oduro-Boateng, Rene Abalo Kojo, Samuel Kyei i in. "Normative Values of Retinal Nerve Fibre Layer Thickness and Optic Nerve Head Parameters and Their Association with Visual Function in an African Population". Journal of Ophthalmology 2020 (11.02.2020): 1–14. http://dx.doi.org/10.1155/2020/7150673.
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Purpose. To determine normative values of retinal nerve fibre layer thickness (RNFL) and optic nerve head (ONH) parameters and their association with routine clinical tests such as refractive error (RE), stereoacuity (SA), and contrast sensitivity (CS) in an African population. Methods. In a cross-sectional observational study, 100 normal subjects aged 20 to 78 years were evaluated using the Cirrus HD-OCT 5000 and matched with 200 glaucoma patients. Results. Average (±SD) RNFL thickness for normal subjects was found to be 102.37 ± 7.45 (range, 82–119 microns) compared with 90.74 ± 14.50 found for glaucoma subjects. Females had higher average RNFL values (104.84 ± 6.90) compared with males (99.80 ± 7.18). Significant associations were calculated between quadrant RNFL thickness and SA, SE, and CS (all p<0.05). The mean cup to disc ratio (CDR) was 0.49 ± 0.12, and mean optic disc area (DA) was 2.08 mm2 ± 0.40. Smaller DA was recorded for participants aged 60+ years (1.86 ± 0.25), followed by 40–59 age group (2.01 ± 0.41) and then 20–39 age group (2.19 ± 0.41). Significant associations were calculated between SA and ONH parameters, except rim area (all p<0.01), and RE was significantly associated with DA and average CDR (all p<0.05). Conclusion. RNFL thickness in healthy black Ghanaian population was significantly higher than that reported in other races. The values and associations reported in this study can inform clinical decision on the normal variation in RNFL and optic disc parameters.
14
Okamura, Toshikazu. "Interactive Effects of Thermal Deformation and Wear on Lateral Runout and Thickness Variation of Brake Disc Rotors". SAE International Journal of Passenger Cars - Mechanical Systems 9, nr 3 (18.09.2016): 1214–26. http://dx.doi.org/10.4271/2016-01-1939.
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Wang, Qing, Xian Jun Zhou, Zhi Liang Liu i Hong Jie Bi. "Performance Analysis and Optimization of Flange Bolt Joint under the Influence of Inhomogeneous Temperature Field". Applied Mechanics and Materials 121-126 (październik 2011): 1656–62. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.1656.
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A three-dimensional mechanical model and a transcalent model of flange bolt joint were built, considering the nonlinearity of gasket and the contact problem, the effect of inhomogeneous temperature field and its variation to pressure of bolt and gasket was studied, and the joint parameters of two schemes were compared; based on the orthogonal text, two bolt system schemes, adding disc spring and adding sleeve, were experimentally studied. The investigation showed that the sealability of different parts of the gaskets is different, owing to the difference of each bolt in radial and axial displacement under the influence of inhomogeneous temperature field, and the fatigue of gasket and bolt is easily caused; the scheme of disc spring is better than sleeve, and the disc spring, whose thickness is 0.9mm, was selected to improve the mechanical performance of bolt system.
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Mousa, Mohammed Imran, Zulkurnain Abdul-Malek i Zainab Imran Mousa. "Leakage Current Based Thermal Modeling of Glass Disc Insulator Surface". Indonesian Journal of Electrical Engineering and Computer Science 6, nr 3 (1.06.2017): 504. http://dx.doi.org/10.11591/ijeecs.v6.i3.pp504-512.
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The stability of transmission lines relies on the health of the insulators, such as glass string insulators, which may occasionally flashover during an overvoltage. The likelihood of flashover increases notably when the glass insulator is wrapped by a wet contaminant layer. In this paper a study of the surface thermal profile of glass disc insulators insulation had been carried out for both clean and polluted surfaces. A finite-element simulation with time dependent model was carried out using COMSOL Multiphysics software. The variation of the insulator surface temperature with applied voltage as well as with pollution layer thickness is explained. The results illustrate the significant effect of pollution conductivity on heat propagate along the surface of the glass insulators with the increase higher voltages' magnitudes. Study of the aging level impact on a steady state thermal for glass insulation surface is also carried out.
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Deng, Zhi Yong, Feng Chong Lan, Wei Huang, Hui Guo i Pei Huan Chen. "The Research on Thermal-Mechanical Coupled Analysis and the Lightweight Design of Engine Exhaust Valve". Applied Mechanics and Materials 729 (styczeń 2015): 143–48. http://dx.doi.org/10.4028/www.scientific.net/amm.729.143.
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Four types of exhaust valve models are established, the lightweight on engine exhaust valve is designed. The results on thermal mechanical coupled analysis of four exhaust valve models show that: The maximum values of mises stress appear in contact surface between the valve cone and valve seat; Comparing the maximum mises stress, as wall thickness of the hollow valve increases, there are gradual decrease trends in the same positions of the valve cone, the locking groove, neck and end face of the valve disc. The research on the stress distribution of exhaust valves and the variation law between hollow valves′s strength and their wall thickness provide a good reference for improvement in the future.
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Guo, F., i P. L. Wong. "An Anomalous Elastohydrodynamic Lubrication Film: Inlet Dimple". Journal of Tribology 127, nr 2 (1.04.2005): 425–34. http://dx.doi.org/10.1115/1.1866165.
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This paper presents a deliberately designed elastohydrodynamical lubrication (EHL) experiment for the study of the individual effect of the limiting shear stress and wall slippage. Very slow entrainment speeds were employed to avoid influential shear heating and oils of high viscosities were chosen to ensure that the conjunction was under typical EHL. An anomalous EHL film, characterized by a dimple at the inlet region, was obtained. Literature revealed that this inlet dimple was reported in some numerical studies taking into consideration the limiting-shear-stress characteristics of the lubricant and wall slippage. It was found that even under the same kinematic conditions, different types of film shape would be generated by simple disc sliding and simple ball sliding. Simple disc sliding produces an inlet dimple with a comparatively thick inlet film thickness, which droops rapidly toward the outlet region. For simple ball sliding, there is also an inlet dimple but the central film thickness is rather uniform. However, by prerunning the conjunction at a zero entrainment velocity (at the same linear speeds but in opposite directions) before the sliding experiment, the slope of the central film of simple disc sliding becomes smaller. It is probably due to the modification of solid-liquid interface, i.e., the slippage level, by the highly pressurized and stressed prerunning conditions. With a prescribed prerunning, which can produce very similar films at simple disc sliding and simple ball sliding, variation of film thickness was studied and it was found that the inlet dimple film has obvious dependence on entrainment speeds, but was not sensitive to loads. The present experimental results can be considered as direct evidence for those numerical findings of the inlet dimple. Tentatively, an effective viscosity wedge is proposed to account for the formation of the inlet dimple.
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To, Naoki, Saulius Juodkazis i Yoshiaki Nishijima. "Detailed Experiment-Theory Comparison of Mid-Infrared Metasurface Perfect Absorbers". Micromachines 11, nr 4 (14.04.2020): 409. http://dx.doi.org/10.3390/mi11040409.
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Realisation of a perfect absorber A = 1 with transmittance and reflectance T = R = 0 by a thin metasurface is one of the hot topics in recent nanophotonics prompted by energy harvesting and sensor applications ( A + R + T = 1 is the energy conservation). Here we tested the optical properties of over 400 structures of metal–insulator–metal (MIM) metasurfaces for a range of variation in thickness of insulator, diameter of a disc and intra-disc distance both experimentally and numerically. Conditions of a near perfect absorption A > 95 % with simultaneously occurring anti-reflection property ( R < 5 % ) was experimentally determined. Differences between the bulk vs. nano-thin film properties at mid-IR of the used materials can be of interest for plasmonic multi-metal alloys and high entropy metals.
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Bueno-Gimeno, Inmaculada, Enrique España-Gregori, Andres Gene-Sampedro, Juan Carlos Ondategui-Parra i Carlos J. Zapata-Rodriguez. "Variations of OCT measurements corrected for the magnification effect according to axial length and refractive error in children". Journal of Innovative Optical Health Sciences 11, nr 01 (20.11.2017): 1850001. http://dx.doi.org/10.1142/s1793545818500013.
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Purpose: The aim of this paper was to examine the distribution of macular, retinal nerve fiber layer (RNFL) thickness and optic disc parameters of myopic and hyperopic eyes in comparison with emmetropic control eyes and to investigate their variation according to axial length (AL) and spherical equivalent (SE) in healthy children. Methods: This study included 293 pairs of eyes of 293 children (145 boys and 148 girls), ranging in age from 6 to 17 years. Subjects were divided according to SE in control (emmetropia, 99 children), myopia (100 children) and hyperopia (94 children) groups and according to axial AL in 68 short ([Formula: see text]22.00[Formula: see text]mm, 68), medium (from [Formula: see text]22.00[Formula: see text]mm to 25.00[Formula: see text]mm, 189) and long eyes ([Formula: see text]25.00[Formula: see text]mm, 36). Macular parameters, RNFL thickness and optic disc morphology were assessed by the CirrusTM HD-OCT. AL was measured using the IOL-Master system. Littmann’s formula was used for calculating the corrected AL-related ocular magnification. Results: Mean age ([Formula: see text][Formula: see text]SD) was 10.84[Formula: see text][Formula: see text][Formula: see text]3.05 years; mean ([Formula: see text][Formula: see text]SD) SE was [Formula: see text]0.14[Formula: see text][Formula: see text][Formula: see text]0.51 D (range from [Formula: see text]8.75 to [Formula: see text]8.25 D) and mean AL ([Formula: see text][Formula: see text]SD) was 23.12[Formula: see text][Formula: see text][Formula: see text]1.49. Average RNFL thickness, average macular thickness and macular volume decreased as AL and myopia increased. No correlations between AL/SE and optic disc parameters were found after correcting for magnification effect. Conclusions: AL and refractive error affect measurements of macular and RNFL thickness in healthy children. To make a correct interpretation of OCT measurements, ocular magnification effect should be taken into account by clinicians or OCT manufacturers.
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Das, Bimal, Surajit Kumar Paul, Akhilendra Singh, Kanwer Singh Arora i Mahadev Shome. "The effect of thickness variation and pre-strain on the cornering fatigue life prediction of a DP600 steel wheel disc". International Journal of Fatigue 139 (październik 2020): 105799. http://dx.doi.org/10.1016/j.ijfatigue.2020.105799.
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Wang, Luzhen, i Hailing Kong. "Failure Behavior of Thin Disc Sandstone under Coupled Bending-Seepage Condition". Geofluids 2020 (28.08.2020): 1–15. http://dx.doi.org/10.1155/2020/8830358.
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A floor aquifuge usually bends and fails when mining above a confined aquifer, which may lead to water inrush disaster. The floor aquifuge was simplified as a thin disc model in this paper, and a series of coupled bending-seepage tests of sandstone were carried out by a patent test system. The variation characteristics of load-displacement, load-time, and permeability-time were analyzed. The deflection and stress in the thin disc rock samples were deduced; the initiation and propagation of cracks were analyzed. The failure behavior of the thin disc rock samples was described. It shows the following: (1) The bending failure behavior relates to the stress distribution and crack evolution inside the thin disc. (2) The main cause of crack initiation is a tension-shear failure. (3) The 5 mm thickness thin discs form petal-shaped cracks, due to tensile stress, while petal-shaped cracks only appear at the cap block of the 10 mm discs, which are sheared into two pieces along the conical surface with an inclination about 45°. (4) Water inrush occurs after bending failure in the floor aquifuge, and it is an opportune moment to grout along the crack propagation trend lines to prevent the water inrush disasters.
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Kaur, Gurinder, i Nishi Gupta. "Systematic Review Based on the Study of Elastic-Plastic Transition Stresses". Journal of University of Shanghai for Science and Technology 23, nr 07 (22.07.2021): 1077–84. http://dx.doi.org/10.51201/jusst/21/07269.
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A systematic review based upon the study of elastic-plastic transition stresses. A worthwhile work about the analysis of elastic-plastic transition stresses in different rotating materials by varying different parameters is discussed. In the case of compressible material, the strain rates have a maximum value at the internal surface. It has been observed that radial stress has a higher value at the internal surface of the rotating disc made of incompressible material as compared to circumferential stress with thermal effect and this value of radial stress further increases. With the increase of angular speed, the value of radial stress further increases as compared to the case with no thermal effect. The magnitude of the stresses and pressure reduce with the variation of thickness needed for a fully plastic state. At the inner surface, the effect of heat increases stress for compressible material. The thickness and density parameters decrease the value of angular speed at the internal surface of the rotating disc of compressible material as well as incompressible materials. The radial and the hoop stress, both decrease with the increased value of temperature at the Elastic-Plastic stage, but with the reverse result obtained for a fully Plastic state.
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Azevedo Cubas, Gloria Beatriz de, Guilherme Brião Camacho, Flávio Fernando Demarco i Tatiana Pereira-Cenci. "The Effect of Luting Agents and Ceramic Thickness on the Color Variation of Different Ceramics against a Chromatic Background". European Journal of Dentistry 05, nr 03 (lipiec 2011): 245–52. http://dx.doi.org/10.1055/s-0039-1698888.
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ABSTRACTObjectives: The aim of this study was to assess the influence of various ceramic thicknesses and luting agents on color variation in five ceramic systems. Methods: Fifteen disc-shaped ceramic specimens (11 mm diameter; shade A3) were fabricated with each of the six veneering ceramics tested, with 1, 1.5, or 2 mm thickness (n=5). Resin composite discs (Z-250, shade C4) were used as bases to simulate a chromatic background. The cementation of the veneers was carried out with an opaque resin-based cement (Enforce, shade C4), a resin-based cement (Enforce, shade A3), or without cement (C4, control group). Color differences (ΔE*) were determined using a colorimeter. Three-way ANOVA was used to analyze the data, followed by a Tukey post-hoc test (α=.05). Results: The L*a*b* values of the ceramic systems were affected by both the luting agent and the ceramic thickness (P<.05). In general, there was no difference between the control group and the group using the resin-based cement. The use of an opaque luting agent resulted in an increase of the color coordinates a*, b*, L*, producing differences in ΔE* values for all ceramics tested, regardless of the thickness (P<.05). For the 2-mm thick veneers, higher values in the color parameters were obtained for all ceramics and were independent of the luting agent used. Conclusions: The association of 2-mm thickness with opaque cement presented the strongest masking ability of a dark colored background when compared to a non-opaque Lutinging agent and the other thicknesses tested. (Eur J Dent 2011;5:245-252)
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Prajapati, Deepak K., i Mayank Tiwari. "Use of Artificial Neural Network (ANN) to Determining Surface Parameters, Friction and Wear during Pin-on-Disc Tribotesting". Key Engineering Materials 739 (czerwiec 2017): 87–95. http://dx.doi.org/10.4028/www.scientific.net/kem.739.87.
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In tribological analysis of machine elements (such as gears, ball/roller bearings etc.), surface roughness plays very important role, ultimately it affects the friction coefficient, wear, rolling contact fatigue (micro pitting) and other failure mechanisms. Surface geometry and topography changes with time (number of cycles) during rolling/sliding motion of contacting surfaces. So, it is important to show the variation of surface topography parameter during wear process. This work presents the evolution of roughness parameters, wear and friction coefficient during pin-on-disc tribotesting under dry condition. The test is performed using pin on disc apparatus under room temperature condition. The pin (25mm long, 6mm diameter) is made of medium carbon steel (AISI 1038) whereas the disc (165mm diameter, 8mm thickness) is made of high carbon steel (SAE 52100). This works demonstrates the potential of Artificial Neural Network (ANN) for prediction of roughness parameters, friction coefficient and wear coefficient. Experimental results obtained from wear testing are compared with those obtained using artificial neural network (ANN) analysis. A very good agreement in results suggests that a well trained neural network is capable to predict the parameters in wear process.
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Uno, Y., H. Imai, K. Shinano, H.-H. Qiao, J. R. Dawson, S. L. Breen i J. F. Gómez. "Modelled 3D distribution of OH/IR stars in the Galactic disc". Monthly Notices of the Royal Astronomical Society 502, nr 2 (22.01.2021): 3012–20. http://dx.doi.org/10.1093/mnras/stab176.
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ABSTRACT We have modelled the 3D distribution of OH/IR stars in the Galactic plane, traced by 1612 MHz OH maser sources with classic double horned spectral profiles. We statistically analysed over 700 maser sources detected by the HI/OH/Recombination line survey of the Milky Way (THOR) and the Australia Telescope Compact Array interferometric follow-up observations of the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH). With a simple model constructed from a classical density distribution of stars and luminosity functions of OH maser sources in the Galaxy, we estimate the scale height, or the half thickness of the OH/IR star distribution along the Galactic disc to be 90–290 pc. The simple model also implies that there are ∼4000 OH/IR stars hosting 1612 MHz OH masers along the Galactic Plane. Therefore, next generation telescopes such as the Australian Square Kilometre Array Pathfinder (ASKAP) and SKA Phase 1 will detect about 80 per cent of such OH/IR stars in the Galaxy at a 10 mJy detection limit. Comparing the data of previously detected circumstellar 1612 MHz OH maser sources with those of THOR and SPLASH, the maser source lifetime is estimated to be ∼300 yr. This is likely a lower limit, since non-detections of masers in some cases could be affected by the flux variation of the maser source.
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Mandal, Sandip, i D. V. Khakhar. "Granular surface flow on an asymmetric conical heap". Journal of Fluid Mechanics 865 (18.02.2019): 41–59. http://dx.doi.org/10.1017/jfm.2019.26.
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We carry out an experimental study of the granular surface flow of nearly monodisperse glass beads on a conical heap formed on a rough circular disc by a narrow stream of the particles from a hopper, with the pouring point displaced from the centre of the disc. During the growth phase, an axisymmetric heap is formed, which grows either by periodic avalanches or by non-periodic avalanches that occur randomly over the azimuthal location of the heap, depending on the operating conditions and system properties. The dynamics of heap growth is characterized by the variation of the heap height, angle of repose and the angular velocity of the periodic avalanche with time, for different mass flow rates from the hopper. When the base of the heap reaches the edge of the disc closest to the pouring point, the heap stops growing and a steady surface flow of particles is developed on the heap surface, with particles flowing over the edge of the disc into a collection tray. The geometry is a unique example of a granular flow on an erodible bed without any bounding side walls. The corresponding steady state geometry of the asymmetric heap is characterized by means of surface contours and angles of repose. The streamwise and transverse surface velocities are measured using high-speed video photography and image analysis for different mass flow rates. The flowing layer thickness is measured by immersing a coated needle in the flow at different positions on the mid-line of the flow. The surface angle of the flowing layer is found to be significantly smaller than the angle of repose and to be independent of the mass flow rate. The velocity profiles at different streamwise positions for different mass flow rates are found to be geometrically similar and are well described by Gaussian functions. The flowing layer thickness is calculated from a model using the measured surface velocities. The predicted values match the measured values quite well.
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Jiang, Lan, Yanli Jiang, Liang Yu, Hongliang Yang, Zishen Li i Youdong Ding. "Thermo-Mechanical Coupling Analyses for Al Alloy Brake Discs with Al2O3-SiC(3D)/Al Alloy Composite Wear-Resisting Surface Layer for High-Speed Trains". Materials 12, nr 19 (27.09.2019): 3155. http://dx.doi.org/10.3390/ma12193155.
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In the present work, a theoretical model of three-dimensional (3D) transient temperature field for Al alloy brake discs with Al2O3-SiC(3D)/Al alloy wear-resisting surface layer was established. 3D transient thermo-stress coupling finite element (FE) and computational fluid dynamic (CFD) models of the brake discs was presented. The variation regularities of transient temperature and internal temperature gradient of the brake discs under different emergency braking conditions were obtained. The effects of initial braking velocity (IBV) and thickness of Al2O3-SiC(3D)/Al alloy composite wear-resisting layer on the maximum friction temperature evolution of the disc were discussed. The results indicated the lower temperature and thermal stress distributed uniformly on the wear-resisting surface, which was dominated by high conductivity and cooling ability of the Al alloy brake disc. The maximum friction temperature was not obviously affected by the thickness of the wear-resisting layer. The maximum friction temperature of the brake discs increased with the increase of the IBV, the maximum friction temperature and thermal stress of the brake discs is about 517 °C and 192 MPa at IBV = 97 m/s considering air cooling, respectively. The lower thermal stress and fewer thermal cracks are produced during the braking process, which relatively decrease the damage. The friction behavior of the tribo-couple predicted using FE method correlated well with the experimental results obtained by sub-scale testing.
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Nam, Ki Yup, Bum Jun Kim, Woo Hyuk Lee i Yong Seop Han. "Repeatability of Spectral Domain Optical Coherence Tomography Measurements of Bruch’s Membrane Opening-Minimum Rim Width in Epiretinal Membrane Patients with Peripapillary Involvement". Journal of Clinical Medicine 10, nr 11 (21.05.2021): 2240. http://dx.doi.org/10.3390/jcm10112240.
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The Bruch’s membrane opening-minimum rim width (BMO-MRW) is a recently introduced parameter of the neuroretinal rim. We analyzed the repeatability of spectral-domain optical coherence tomography (SD-OCT) measurements of BMO-MRW in epiretinal membrane (ERM) patients with peripapillary involvement, since the surface around the optic disc is distorted in such patients. BMO-MRW and retinal nerve fiber layer (RNFL) thickness measurements were performed using SD-OCT in prospectively enrolled ERM patients and age-matched healthy control individuals. After two consecutive measurements with a 5 min interval, repeatability was analyzed using the intraclass correlation coefficient (ICC), repeatability coefficient (RC), and coefficient of variation (CV). Fifty-two eyes of 52 ERM patients and 62 eyes of 62 healthy controls were included in the study. The ICCs of the mean BMO-MRW/RNFL thickness measurements were 0.999/0.985 in ERM eyes and 0.999/0.999 in normal eyes, respectively. The RC values of mean BMO-MRW/RNFL thickness measurements were 9.0/6.25 μm in ERM eyes and 4.61/0.92 μm in normal eyes, respectively. The CV values were 0.91% and 1.45% for BMO-MRW and RNFL thickness in ERM eyes, and 0.63% and 0.33% in normal eyes, respectively. In ERM eyes, the RC, CV of average BMO-MRW were 1.9 and 1.4 times greater than those of normal eyes, but 6.8 and 4.4 times greater for average RNFL thickness. BMO-MRW and RNFL thickness showed good repeatability in the diseased eyes with peripapillary involvement and healthy control eyes. Based on the ICC, RC, and CV values, the repeatability of BMO-MRW measurements in peripapillary membrane patients was better than that of RNFL thickness.
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Hakobyan, V. N., H. A. Amirjanyan i K. Ye Kazakov. "Axisymmetric Stressed State of Uniformly Layered Space with Periodic Systems of Internal Disc-Shaped Cracks and Inclusions". Herald of the Bauman Moscow State Technical University. Series Natural Sciences, nr 2 (89) (kwiecień 2020): 25–40. http://dx.doi.org/10.18698/1812-3368-2020-2-25-40.
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Using the Hankel integral transform, we construct discontinuous solutions for the problem of the axisymmetric stress state of a piecewise homogeneous, uniformly layered space, obtained by alternately connecting two heterogeneous layers of the same thickness. The space on the middle planes of the first heterogeneous layer contains a periodic system of circular disc-shaped parallel cracks, and on the middle planes of the second layer has a periodic system of circular disc-shaped parallel rigid inclusions. The determining system of equations is obtained in the form of a system of integral equations with kernels of the Weber --- Sonin type with respect to the crack extension and tangent contact stresses acting on the facial surfaces of rigid inclusions. With the help of rotation operators, the resulting determining system of equations is reduced to a system of integral equations of the second kind of Fredholm type. The equation solution is constructed by the method of mechanical quadratures. A numerical analysis was carried out and regularities were revealed in the variation of the intensity factors of rupture stresses, crack extension and contact stresses under the inclusions depending on the physical and mechanical and geometrical characteristics of the problem
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Strashnov, Stanislav, Sergei Alexandrov i Lihui Lang. "Description of Residual Stress and Strain Fields in FGM Hollow Disc Subject to External Pressure". Materials 12, nr 3 (31.01.2019): 440. http://dx.doi.org/10.3390/ma12030440.
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Elastic/plastic stress and strain fields are obtained in a functionally graded annular disc of constant thickness subject to external pressure, followed by unloading. The elastic modulus and tensile yield stress of the disc are assumed to vary along the radius whereas the Poisson’s ratio is kept constant. The flow theory of plasticity is employed. However, it is shown that the equations of the associated flow rule, which are originally written in terms of plastic strain rate, can be integrated with respect to the time giving the corresponding equations in terms of plastic strain. This feature of the solution significantly facilitates the solution. The general solution is given for arbitrary variations of the elastic modulus and tensile yield stress along the radial coordinate. However, it is assumed that plastic yielding is initiated at the inner radius of the disc and that no other plastic region appears in the course of deformation. The solution in the plastic region at loading reduces to two ordinary differential equations. These equations are solved one by one. Unloading is assumed to be purely elastic. This assumption should be verified a posteriori. An illustrative example demonstrates the effect of the variation of the elastic modulus and tensile yield stress along the radius on the distribution of stresses and strains at the end of loading and after unloading. In this case, it is assumed that the material properties vary according to power-law functions.
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Xu, Xinfu, i Hermann Winner. "Transfer behaviours and influences of high-order hot judder in passenger cars". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 232, nr 3 (7.05.2017): 400–417. http://dx.doi.org/10.1177/0954407017702995.
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Hot judder consists of brake-induced forced vibrations which are characterized by hot spots on the brake discs. It mainly influences the driving comfort as perceived by the driver as vibrations and low-frequency noises. This article concentrates on the transfer behaviours of high-order hot judder and its effects on the driver’s subjective perception. A novel testing method is applied in this investigation, simulating the high-order hot judder by using discs that are artificially modified to generate tenth-order disc thickness variations or tenth-order lateral run-out. A high quality is achieved with respect to identification of the transfer functions from the brake pressure variation and the brake torque variation to the essential driver interface quantities of hot judder. The threshold values of the brake pressure variation and the brake torque variation for perception of the high-order hot judder in a high-frequency range are obtained on the basis of a regression analysis between subjective evluaitons and objective evaluations of the hot-judder-induced vibrations and the selected critical sound pressure level inside a vehicle. Generally, a brake pressure variation of more than 10 bar or a brake torque variation of 100 Nm is required for perception of the high-order judder-induced vibrations, whereas a brake torque variation of 50 Nm can result in annoying noises. According to the transfer functions and the threshold values of the brake pressure variation and the brake torque variation, the drone noise is shown to be the main reason for potential customer complaints arising from high-order hot judder. The practical significance of high-order judder to the driver’s perception is suitably quantified for the first time. Also, with these results, the impacts of high-order hot judder can be assessed from the observed brake pressure variation and the observed brake torque variation, which are mainly measured using dynamometers.
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Wang, Gang, Xin Xin Ma, Guang Ze Tang, Yong Liu, Shi Yu He i De Zhuang Yang. "Tribological Behaviors at High Load of MoSX/Au Films in Vacuum". Advanced Materials Research 150-151 (październik 2010): 800–804. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.800.
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MoSx/Au films about 1μm in thickness were deposited on 9Cr18 steel substrate discs by magnetron sputtering method. The chemical composition and chemical states of the as-deposited films were determined by X-ray photoelectron spectroscopy (XPS). The effect of high loads (15~50N) on tribological behaviors of the MoSx/Au films in vacuum was studied by pin-disc wear tests. The pins were made of 2Cr13 steel. The morphologies of as-deposited films and wear track were observed by scanning electron microscopy (SEM). The results show the friction coefficient and the wear life of the films decrease with the increase of load at a sliding velocity of 1.6 m•s-1. The wear life of the films at 15N can reach 2000m. The friction process of the films can be divided into four stages based on typical variation of friction coefficient with sliding time in vacuum, e.g. running-in stage, steady stage, severe damage stage and thorough wear stage. In steady stage, the films peel in small pieces and the abrasion mechanism appears delamination wear. When the film was damaged thoroughly, the wear test carried out between 2Cr13 pin/9Cr18 disc. The adhesive wear becomes the dominant abrasion mechanism.
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Kim, Min-Su, Hyung-Bin Lim, Woo-Hyuk Lee, Yeo-Kyoung Won, Ki-Yup Nam i Jung-Yeul Kim. "Wide-Field Swept-Source OCT Analysis of Interocular Symmetry of Choroidal Thickness in Subjects with Uncomplicated Pachychoroid". Journal of Clinical Medicine 10, nr 18 (19.09.2021): 4253. http://dx.doi.org/10.3390/jcm10184253.
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Background: We aimed to study the bilateral choroidal thickness (CT) symmetry and difference in uncomplicated pachychoroid subjects using wide-field swept-source optical coherence tomography (SS-OCT). Methods: All subjects underwent a wide-field 16-mm one-line scan using SS-OCT. Bilateral CT was measured at, and compared among, the following 12 points: three points at 900-µm intervals from the nasal optic disc margin (nasal peripapillary area), one point at the subfovea, six points at 900-µm intervals from the fovea to the nasal and temporal areas (macular area), and two peripheral points 5400 and 8100 µm from the fovea (peripheral area). Results: There were no statistically significant differences in CT between the right and left eyes in any area (all p > 0.05); they all showed significant positive correlations (all p < 0.01). However, the correlation coefficients (ρ) were smaller for the nasal peripapillary and peripheral areas compared to the macular area. Conclusions: The CTs in each region were bilaterally symmetrical in subjects with uncomplicated pachychoroid. However, interocular difference in CT increased from the center to the periphery, indicating that the anatomical variation of the nasal peripapillary and peripheral choroid was greater than that of the macula.
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Poll, GWG, i D. Wang. "Fluid rheology, traction/creep relationships and friction in machine elements with rolling contacts". Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 226, nr 6 (25.01.2012): 481–500. http://dx.doi.org/10.1177/1350650111431790.
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The correct prediction of shear stresses in lubricants applied to concentrated rolling/sliding contacts has been an issue of intense debate for many years. Traction testers of various kinds such as two-disc roller rigs or ball on disc apparatus have been extensively used in order to obtain experimental data, as well as, more recently, molecular dynamics simulations. Several, partly competing, phenomenological models have been developed to describe the dependence of shear stresses on various parameters. Evidently, the importance lies in the need to predict and reduce friction, or, more accurately, resistance to motion of rolling element bearings in order to increase efficiency of machines and vehicles. Also, it plays a crucial role in design and performance of traction drives. As a prerequisite, experimental data for a wide variety of fluids were obtained from two-disc roller tests with a wide variation of contact pressures, rolling speeds and slide-to-roll ratios. Following earlier investigations, the amount of slip created by the elastic deformation of the discs was separated from the contribution of the fluids and their rheological properties. In accordance with experiments of Jacobson a threshold pressure in the fluid was identified which marks the onset of a nearly linear relationship between a limiting shear stress and pressure. However, this threshold does not appear to be constant but rather declining with decreasing hydrodynamic film thickness respective of rolling speed, while the slope changes to a lesser extent. When measurements were extended far into the mixed lubrication regime close to the limiting case of boundary lubrication, the shear stress/pressure relationship became quasi-Coulomb with a virtually zero threshold pressure. These results have successfully been used to predict the friction torque of angular contact ball bearings and the traction characteristics in toroidal drives.
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Oswald, Walter, Jan Lauk, Lutz Gödeke, Peter Ehrhard i Norbert Willenbacher. "Analysis of Paint Flow Pulsations during High-Speed Rotary Bell Atomization". Coatings 9, nr 10 (17.10.2019): 674. http://dx.doi.org/10.3390/coatings9100674.
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High-speed rotary bell atomization is the preeminent coating technique in the automotive industry. It is widely accepted that a narrow droplet size distribution and constant spray are necessary in order to guarantee uniform film thickness and high-quality appearance. This may be deteriorated by paint flow pulsations. So far, however, no studies exist regarding such fluctuations quantitatively for this type of atomizers. We fill this gap using image analysis of high-speed recordings close to the bell edge. We could show that the fundamental pulsation frequency increases linearly with rotational speed. A ratio of pulsation frequency and true rotational speed of about 3 was found, indicating that pulsations were initiated mainly by the three struts of the distributor disc. The coefficient of variation, i.e., the amplitude of fluctuation increased with decreasing liquid volume rate and rotational speed. Beyond that, we could show that the formation of droplets larger than 100 μm, which are assumed to cause paint defects, is promoted by the degree of fluctuation. These findings may stimulate development of bell cups showing less paint flow pulsations.
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Huang, Xiaomao, Shun Zhang, Chengming Luo, Wencheng Li i Yitao Liao. "Design and Experimentation of an Aerial Seeding System for Rapeseed Based on an Air-Assisted Centralized Metering Device and a Multi-Rotor Crop Protection UAV". Applied Sciences 10, nr 24 (10.12.2020): 8854. http://dx.doi.org/10.3390/app10248854.
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To improve the overall mechanization level of rapeseed production in China, especially in some hilly regions where ground machinery cannot enter the fields or can only enter with very low economic benefits, a special aerial seeding system for rapeseed based on a miniature air-assisted centralized metering device was designed and tested in this study. Unlike existing commercial aerial seeding systems, the proposed seed meter was a miniaturized version derived from the traditional air-feeding seed meter on ground planters. The new version contained a redesigned seed feeding component to overcome problems of serious air backflow to the seed box and difficult seed feeding after miniaturization. Three groups of experiments were designed and conducted to optimize the parameters of the seed meter and test its performance. Results from the orthogonal experiment showed that the seed feeding component performed best when the seed layer thickness was 45 mm, the rotational speed of the gear disc was 45 r/min, and the airflow pressure was 2450 Pa. Results from the static workbench test showed that the designed seeding system had a maximum average total sowing efficiency of 537.17 g/min, with the maximum values of the stability variation coefficient of total seeding rate (seven ports) and the consistency variation coefficient between each port was 2.37% and 4.89%, respectively. Field tests further proved that the designed aerial seeding system could work stably, uniformly, and efficiently, so that the agronomic requirements of rape crop planting could be well met.
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Sutcliffe, M. P. F. "Traction Measurements in Mixed Elastohydrodynamic Lubrication with a Controlled Circumferential Roughness". Proceedings of the Institution of Mechanical Engineers, Part C: Mechanical Engineering Science 205, nr 4 (lipiec 1991): 265–73. http://dx.doi.org/10.1243/pime_proc_1991_205_118_02.
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The transition between smooth elastohydrodynamics (EHL) and micro-EHL is investigated. Traction measurements in a disc machine with a controlled circumferential roughness are used to infer film thicknesses under the asperity tops. These are then compared with hydrodynamic theory. At the two extremes where there is little pressure rippling between the asperity tops and the adjoining valleys or where there is little pressure in the valleys the theoretical and experimentally inferred films are in reasonable agreement. In the transition region the experimentally deduced films are not reliable. Traction behaviour is estimated in the transition region by making some simple assumptions. The film thickness under the asperities is taken as that given by theory for no pressure in the valleys, and the valley pressure in the transition region is estimated by assuming a simple variation with speed. Theoretical traction curves are calculated by apportioning the load between the valleys and the asperity tops and agree well with measured curves, suggesting that this is a good picture of the contact. The traction behaviour was found to depend on sliding speed in a way typical of hydrodynamic lubrication even for estimated oil films as small as 8 nm.
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Junmahasathien, Taepin, Pattaraporn Panraksa, Paytaai Protiarn, Doosadee Hormdee, Rajda Noisombut, Nutthapong Kantrong i Pensak Jantrawut. "Preparation and Evaluation of Metronidazole-Loaded Pectin Films for Potentially Targeting a Microbial Infection Associated with Periodontal Disease". Polymers 10, nr 9 (13.09.2018): 1021. http://dx.doi.org/10.3390/polym10091021.
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The objective of this study was to develop the metronidazole loaded high and low methoxyl pectin films (HM-G-MZ and LM-G-MZ) for the treatment of periodontal disease. The films were prepared by pectin 3% w/v, glycerin 40% w/v, and metronidazole 5% w/v. The developed films were characterized by scanning electron microscope and evaluated for thickness, weight variation, and elasticity. The developed films showing optimal mechanical properties were selected to evaluate radial swelling properties, in vitro release of metronidazole and the antimicrobial activity against Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans by the disc diffusion method. The results demonstrated that LM-MZ and HM-G-MZ films were colorless and yellowish color, respectively, with the film thickness around 0.36–0.38 mm. Furthermore, both films exhibited good elasticity with low puncture strength (1.63 ± 0.37 and 0.84 ± 0.03 N/mm2, respectively) and also showed slight increase in radial swelling, so that they could be easily inserted and fitted into the periodontal pocket during a clinical use. However, HM-G-MZ showed a decrease in radial swelling after 1 h due to the film erosion. The in vitro release study of LM-G-MZ showed a burst release that was initially followed by a slow release rate profile, capable to maintain the therapeutic level in periodontal pocket for seven days, whereas HM-G-MZ showed an immediate release profile. The cumulative percentage of metronidazole release from HM-G-MZ was less than LM-G-MZ during the first 5 min as metronidazole was in a crystalline form inside HM-G-MZ film. For antimicrobial activity test, both films showed the inhibitory effect against P. gingivalis and A. actinomycetemcomitans, and there was no difference in the inhibition zone between LM-G-MZ and HM-G-MZ. The present study showed, for the first time, that low methoxyl pectin film containing glycerin and metronidazole could be potentially considered as a promising clinical tool for the drug delivery via intra-periodontal pocket to target an oral disease that is associated with polymicrobial infection.
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Arakere, N. K., i C. Nataraj. "Vibration of High-Speed Spur Gear Webs". Journal of Vibration and Acoustics 120, nr 3 (1.07.1998): 791–800. http://dx.doi.org/10.1115/1.2893899.
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High cycle fatigue loading of gear webs due to in-plane stresses, caused by forced excitation resulting from centrifugal loading and dynamic tooth loads, has been known to cause radial fatigue cracks. This is especially prevalent in high-speed gears used in aerospace applications, with small web thickness, for weight reduction. Radial cracks have also been observed to originate at the outer edge of lightening holes machined in gear webs for weight reduction. This paper presents an analytical treatment of the in-plane vibration of high-speed gear webs resulting from rotational effects and periodic excitation from dynamic tooth loading. Dynamic tooth loads result from the combined effect of inertia forces of gear wheels which are significant at high speeds, the periodic variation of gear mesh stiffness, and involute tooth profile errors. The gear web is modeled as a thin rotating disc and the governing differential equations of motion and the associated boundary conditions are derived from first principles. The equations are then nondimensionalized which leads to some essential nondimensional parameters. A comprehensive tooth stiffness model for spur gears is used that accounts for periodic variation of mesh stiffness. The dynamic tooth loads are obtained by solving the pertinent equations of motion, using a collocation method, that yields a closed-form expression for the periodic excitation, that is used as an input for the in-plane vibration problem. The in-plane vibration equations are solved by an approximate method of weighted residuals. It is found that the displacement fields and the resulting stresses can be significant under certain speeds and loading conditions. The interaction between the forcing frequencies due to gear teeth dynamics and the in-plane vibration natural frequencies can result in resonances that induce high fatigue stresses in the gear web. The in-plane stresses leading to high cycle fatigue loading, and frequency components of the resulting response are discussed in detail.
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Rusu, Marius, Kathrin Mörseburg, Øyvind Gregersen, Asuka Yamakawa i Sari Liukkonen. "Relation between fibre flexibility and cross-sectional properties". BioResources 6, nr 1 (10.01.2011): 641–55. http://dx.doi.org/10.15376/biores.6.1.641-655.
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The correlation between the fibre flexibility and cross-sectional area moment of inertia of thermomechanical pulp fibres was investigated. The main effects of refining were found to be internal fibrillation, external fibrillation, and fibre shortening. Internal fibrillation increases fibre flexibility and fibre collapsibility, improving fibre-to-fibre contact in a paper sheet. The raw materials used were pulps produced from six different Norway spruce logs and six different Scots pine logs, chosen in a manner that allowed variation of fibre wall thickness and fibril angle independently. Each wood sample was refined in four stages using a pressurized 12″ Sprout Waldron single disc refiner. Fibre flexibility was assessed by FiberMaster bendability measurements. Fibre bendability was measured on the +48 Bauer McNett fractions of the twelve 2nd, 3rd, and 4th stage thermomechanical pulps (TMP). The fibre cross-sectional samples were imaged using scanning electron microscopy (SEM). An image analysis method to calculate the area moment of inertia of each fibre using numerical integration was developed. Fiber bendability increased with specific energy consumption for both wood species (spruce and pine) from the 2nd refining stage to the fourth refining stage. Spruce had a higher rate of bendability increase than pine upon refining. It was expected that fibres with a low area moment of inertia would result in higher bendability, but no such correlation was found for either spruce or pine. Fibre bendability increased with internal fibrillation, as assessed from Simons staining. These results imply that local damage of the fibre wall such as delaminations, kinks, and compressions was the main effect in increasing the flexibility through refining of TMP.
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Kazemi, Hamed, Xinyu Du, Samba Drame, Regan Dixon i Hossein Sadjadi. "Prognostics Model to Predict Brake Rotor Thickness Variation". Annual Conference of the PHM Society 11, nr 1 (22.09.2019). http://dx.doi.org/10.36001/phmconf.2019.v11i1.796.
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Brake rotor thickness variation causes brake torque variation which can lead to brake judder and pulsation, steering wheel oscillations and chassis vibration. In this paper, we have proposed a prognostics methodology to predict the degradation level of brake rotor due to disc thickness variation. Leveraging the time and frequency domain analysis, this model creates health indicators to assess the health of the rotor and predict the rotor thickness variations of 36 micrometers or more. These health indicators that are calculated during braking events include: (i) envelope or variance of the brake master cylinder pressure (MCP); (ii) envelope or variance of the longitudinal acceleration (AX); (iii) the root mean square amplitude of the average order spectrum of the MCP at order one; and (iv) the root mean square amplitude of the average order spectrum of the AX at order one. This paper demonstrates that the above health indicators are significantly larger for a degraded brake rotor due to thickness variation compared to a healthy rotor.
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Magalhães, Tarquinio Mateus. "Effects of site and tree size on wood density and bark properties of Lebombo ironwood (Androstachys johnsonii Prain)". New Zealand Journal of Forestry Science 51 (14.04.2021). http://dx.doi.org/10.33494/nzjfs512021x32x.
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Background: Wood and bark are important renewable natural resources. Density is an important property that is used to describe wood and bark quality for a number of end uses. However, wood and bark density, bark proportion and dimensions vary with age and site, as well as among and within trees. The aim of this study was to investigate the effect of site, diameter class, and vertical position within the stem on the density of wood and bark, bark volume, bark dry-mass and thickness of Lebombo ironwood (Androstachys johnsonii Prain). Methods: The study was conducted on 93 Lemombo ironwood trees growing in Mozambique. Eight discs were sampled from each selected tree and diameter over and under bark was measured. Bark thickness, bark mass and bark density were determined along with the basic wood density of each disc. Results: The overall average whole-stem properties were estimated at: 786 kg m–3 wood density, 586 kg m–3 bark density, 19% bark volume, 19% bark dry-mass, and 9 mm bark thickness. Height level uniquely explained most of the variation in bark mass (97%), bark volume (95%) and wood density (86%). Diameter class explained most of the variation in bark density (51%) and bark thickness (51%). Site only explained a small proportion of the variation in all dependent variables. Conclusions: Overall, the patterns of variation of all wood and bark properties were highly dependent on tree diameter class and vertical position within the stem. Site differences were not a significant source of variation in the properties studied. Improved knowledge of the wood and bark properties of this species will aid its sustainable management and utilisation.
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Kurtul, Bengi Ece, Ayşe İdil Çakmak, Ahmet Elbeyli, Abdulkerim Karaaslan i Çiğdem El. "Association of childhood obesity with retinal microvasculature and corneal endothelial cell morphology". Journal of Pediatric Endocrinology and Metabolism, 10.12.2020. http://dx.doi.org/10.1515/jpem-2020-0483.
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AbstractObjectivesTo investigate the optical coherence tomography angiography (OCTA) and specular microscopy (SM) findings in obese children and compare them with healthy ones.Methodsthis prospective study, 50 eyes of 25 obese children [body mass index (BMI) ≥95th percentile], 36 eyes of 18 control age- and sex- matched healthy subjects (BMI <85th percentile) were included. Demographic features and ophthalmological examination including OCTA measurements as well as SM findings were assessed. Cellular morphology was observed by noncontact SM and results for corneal endothelial cell density (cells/mm2), coefficient of variation of cell size and percentage of hexagonal cells were obtained. The OCTA was performed with 6 × 6 mm sections for macula and 4.5 × 4.5 mm sections for optic disc in all eyes. Foveal retinal thickness (FRT), retinal nerve fiber layer (RNFL) thickness, vessel density in different sections of retina and optic nerve head were analyzed.ResultsAll SM parameters, RNFL thickness for average, and all quadrants and optic disc radial peripapillary capillary densities were similar between groups. However, FRT, flow area for choriocapillaris, superficial and deep foveal capillary densities were significantly higher in obese group when compared to controls (242.4 ± 18.2 µm vs. 232.1 ± 16.5 µm, p=0.024, 2.2 ± 0.1 mm2 vs, 2.2 ± 0.0 mm2, p=0.042, 22.4 ± 6.9% vs. 15.6 ± 5.5%, p=0.001, and 38.9 ± 7.5% vs. 31.1 ± 8.6 %, p=0.001, respectively).ConclusionsObese children seem to have higher values of FRT, flow area for choriocapillaris, superficial and deep foveal capillary densities. These results may have significant implications for understanding of how childhood obesity could affect retinal microvasculature.
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Jin, Xuyang, Jing Wang, Yiming Han, Nannan Sun i Jianrong Zhu. "Discrepancy in oil film distribution observed in ZEV reciprocating motion". Industrial Lubrication and Tribology ahead-of-print, ahead-of-print (25.09.2020). http://dx.doi.org/10.1108/ilt-01-2020-0021.
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Purpose This study aims to present the discrepancy in oil film distribution in reciprocating motion experimentally with zero entraining velocity (ZEV) on a conventional ball-disk test rig with oil lubrication. Design/methodology/approach Driven independently by two individual servomotors, a steel ball and a sapphire disc move at equal speed but in opposite directions in a triangle wave. The oil film images between the ball and the disc were recorded by a camera. After the experiments, the mid-section film thickness was evaluated by using a dichromatic interference intensity modulation approach. Findings The dimpled oil film in transient condition is shallower than that at steady state with the same load and velocities, and the transient dimple depth decreases with the decrease of time. The increase of the applied load offers a beneficial effect on lubrication. Boundary slippage happens in ZEV reciprocating motion. The slippage at the interface is related to the transient effect and applied load. Originality/value This study reveals the significant difference of the oil film variation in ZEV reciprocating motion, especially the complex boundary slippage at the interface of the oil and the sapphire disc. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0021
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Cardenas-Flechas, Leydi Julieta, Claudia Patricia Mejía-Villagran, Miryam Rincon-Joya i Jhon Jairo Olaya-Florez. "Synthesis of nanostructured (Ti-Zr-Si)N coatings deposited on Ti6Al4V alloy". Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales, 19.05.2021. http://dx.doi.org/10.18257/raccefyn.1198.
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d Zr targets. The synthesis of the coatings was carried out by varying the discharge power in the Ti5 well as a variation in the deposit temperature at room temperature 130° and 260°C. The coatings were characterized by means of X-ray diffraction (XRD), evidencing the formation of the phase that belongs to the solid solution (Zr, Ti)N, scanning electron microscopy (SEM), UV-Vis spectroscopy and hardness and pin-on-disc tests. The thickness was measured through interferometry with values between 662 and 481nm for the deposited coatings. According to the failure mechanism in the scratch test, the best results were obtained with a power of 170W and 260°C with a cohesive failure Lc1 = 2.1N and an adhesive failure Lc2 = 4.7N.
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Lyu, Hanyi, Qiuying Chen, Guangyi Hu, Ya Shi, Luyao Ye, Yao Yin, Ying Fan i in. "Characteristics of Fundal Changes in Fundus Tessellation in Young Adults". Frontiers in Medicine 8 (26.04.2021). http://dx.doi.org/10.3389/fmed.2021.616249.
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Purpose: To explore the characteristics and associated factors of fundus tessellation, especially the alternation of choroidal thickness among different degrees of tessellated fundus in young adults.Design: Cross-sectional, population-based study.Methods: A total of 796 students were included in the study and underwent comprehensive ophthalmic examinations, including anterior segment examinations and swept-source optical coherence tomography (OCT) measurements. The degree of tessellated fundus was assessed by fundus photographs applying an early treatment of diabetic retinopathy study grid to evaluate the location of fundus tessellation and then divided into five groups. The topographic variation and factors, tilted disc ratio, parapapillary atrophy (PPA), retinal thickness (ReT), choroidal thickness (ChT), and subfoveal scleral thickness (SST) related to tessellated fundus were analyzed.Results: Compared to normal fundus, tessellated fundus had a lower spherical equivalent (SE) (p < 0.0001), worse best-corrected visual acuity (BCVA)(p = 0.043), longer axial length (AL) (p < 0.0001), thinner retina (p < 0.0001), thinner (p < 0.0001) choroid, and thinner sclera in center fovea (p = 0.0035). Among all subfields of macular and peripapillary regions, center fovea and macula-papillary region showed the most significant decrease in choroidal thickness. The proportion of fundus tessellation significantly increased with lower body weight index (BMI) (p = 0.0067), longer AL (p < 0.0001), larger PPA(p = 0.0058), thinner choroid (p < 0.0001), and thinner sclera (p < 0.0001).Conclusions: Eyes showed more severe myopic morphological alternation with the increasement of proportion of fundus tessellation to the center fovea, including a significant decrease in both choroid and scleral thickness. Choroidal thinning may progress most rapidly in the macula-papillary region as fundus tessellation approaches to the center fovea.
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Lima, Israel Luiz de, Beatriz Ribeiro Zanon, Eduardo Luiz Longui i Sandra Monteiro Borges Florsheim. "VARIAÇÃO RADIAL DA DENSIDADE BÁSICA E DIMENSÕES CELULARES DE Croton floribundus". FLORESTA 40, nr 3 (1.10.2010). http://dx.doi.org/10.5380/rf.v40i3.18929.
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Croton floribundus(capixingui) é encontrado nos estados de Minas Gerais, São Paulo e Paraná. Face à necessidade de novos conhecimentos das propriedades desta madeira, em condições de laboratório, objetivou-se estudar a variação radial da densidade básica e as dimensões celulares desta espécie, oriunda de população natural. De cinco árvores, com DAP médio de 20,35 cm, coletou-se um disco de 7 cm de espessura na região do DAP. Estas árvores estavam localizadas no Parque Estadual da Cantareira, do Instituto Florestal do Estado de São Paulo. De cada disco foram retiradas amostras representando as posições próximo à medula, região intermediária e próximo à casca, para o estudo da variação radial, das seguintes variáveis: densidade básica; comprimento, diâmetro e frequência de vasos; altura, largura e freqüência de raios; comprimento, diâmetro, espessura da parede e lume das fibras. Os resultados indicaram que ocorreu uma tendência de aumento no diâmetro de vasos e uma diminuição na frequência de raios no sentido medula-casca, e para as demais variáveis não ocorreu a mesma tendência.Palavras-chave: Croton floribundus; células da madeira; variação radial. AbstractRadial variation of the basic density and cellular dimensions of Croton floribundus. Croton floribundus(capixingui) is found in the States of Minas Gerais, São Paulo and Paraná. In view of the necessity of new knowledge of the wood properties in laboratory conditions, this work aimed to study the radial variation of the basic density and cellular dimensions of this species. Discs from five trees with average DBH of 20,35 cm, with thickness of 7 cm, were collected at DBH height. The trees came from the Cantareira State Park, property of the Forestry Institute of Sao Paulo State. From each disc, samples were removed, representing the positions pith, intermediate and bark, to study the radial variation of the following variables: basic density; length, diameter, and vessels frequency; length, width, and rays frequency; wall length, diameter, and thickness; and lumen diameter. The results indicated that occurred an increase tendency in the vessels diameter and reduction in the ray frequency from the pith to the bark; the other variables did not show this trend.Keywords:Croton floribundus; wood cells; pith-bark variation.
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Modes, Karina Soares, Raquel Lúcia Ludwig, Magnos Alan Vivian i Joni Stolberg. "WOOD QUALITY OF Pinus patula Schltdl & Cham FOR THE PULP PRODUCTION". Revista Árvore 43, nr 2 (2019). http://dx.doi.org/10.1590/1806-90882019000200007.
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ABSTRACT The softwood pulp industry is based on the supply of Pinus taeda and P. elliottii woods, and competes for this raw material with other timber sectors. The study aimed to evaluate the wood quality of Pinus patula for pulp and paper production. Trees aged 14 years were obtained from a plantation located in Ponte Alta do Norte, State of Santa Catarina/Brazil. Discs were collected along the commercial height for determining the weighted basic density and its longitudinal variation in the trees, and the chemical composition. For the anatomical characterization, a disc was extracted from the base of each tree to determine the radial variation of tracheids morphological characteristics, and their quality indexes for the production of kraft pulp. The weighted basic density (365 kg.m-3) of the wood was low when compared with other species of the same genus. Regarding the tracheids morphology, a mean length of 2.37 mm; wall thickness of 5.49 µm; width of 40.32 µm and a lumen diameter of 29.09 µm were observed. The chemical composition of the species showed low contents of lignin (25.06%) and ashes (0.27%), compatible content of holocellulose (70.76%), and high content of extractives (6.24%) compared with conifers of traditional use. In general, P. patula species shows characteristics compatible with those traditionally used for the pulp and paper production, and it should be considered in more advanced studies with this species in this segment.
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Tagawa, Miho, Sotaro Ooto, Kenji Yamashiro, Hiroshi Tamura, Akio Oishi, Manabu Miyata, Masayuki Hata, Munemitsu Yoshikawa, Nagahisa Yoshimura i Akitaka Tsujikawa. "Characteristics of pachychoroid neovasculopathy". Scientific Reports 10, nr 1 (1.10.2020). http://dx.doi.org/10.1038/s41598-020-73303-w.
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Abstract Recently, several research groups have reported a newly recognized clinical entity of choroidal neovascularization, termed pachychoroid neovasculopathy. However, its characteristics have yet to be well described. The purpose of this study was to investigate the clinical and genetic characteristics of pachychoroid neovasculopathy regardless of treatment modality. This study included 99 eyes of 99 patients with treatment-naïve pachychoroid neovasculopathy. Mean initial best-corrected visual acuity (BCVA) was 0.20 ± 0.32 logMAR, and did not change (P = 0.725) during follow-up period (mean ± SD, 37.0 ± 17.6 months). Subretinal hemorrhage (SRH) (≥ 4 disc areas in size) occurred in 20 eyes (20.2%) during follow-up. Age, initial BCVA, central retinal thickness, SRH (≥ 4 disc areas in size) and treatment (aflibercept monotherapy) were significantly associated with the final BCVA (P = 0.024, < 0.001, 0.031, < 0.001, and 0.029, respectively). Multiple regression analysis showed initial BCVA and presence of SRH to be significant predictors of final BCVA (both P < 0.001). Polypoidal lesions were more common in the SRH group than in the non-SRH group (85.0% vs 48.1%, P = 0.004). There was no significant difference in the frequency of the risk allele in ARMS2 A69S, CFH I62V, CFH Y402H between these groups (P = 0.42, 0.77, and 0.85, respectively). SRH (29.1% vs 9.1%, P = 0.014) and choroidal vascular hyperpermiability (65.5% vs 43.2%, P = 0.027) were seen more frequently in the polypoidal lesion (+) group than in the polypoidal lesion (−) group. There was considerable variation in lesion size and visual function in patients with pachychoroid neovasculopathy, and initial BCVA and presence of SRH at the initial visit or during the follow-up period were significant predictors of final BCVA.