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Izawa, Yasuhide, e Chikako Shingyoji. "Mechanical induction of oscillatory movement in demembranated, immotile flagella of sea urchin sperm at very low ATP concentrations". Journal of Experimental Biology 223, n.º 20 (13 de agosto de 2020): jeb225797. http://dx.doi.org/10.1242/jeb.225797.
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ABSTRACTOscillation is a characteristic feature of eukaryotic flagellar movement. The mechanism involves the control of dynein-driven microtubule sliding under self-regulatory mechanical feedback within the axoneme. To define the essential factors determining the induction of oscillation, we developed a novel experiment by applying mechanical deformation of demembranated, immotile sea urchin sperm flagella at very low ATP concentrations, below the threshold of ATP required for spontaneous beating. Upon application of mechanical deformation at above 1.5 µmol l−1 ATP, a pair of bends could be induced and was accompanied by bend growth and propagation, followed by switching the bending direction. For an oscillatory, cyclical bending response to occur, the velocity of bend propagation towards the flagellar tip must be kept above certain levels. Continuous formation of new bends at the flagellar base was coupled with synchronized decay of the preceding paired bends. Induction of cyclical bends was initiated in a constant direction relative to the axis of the flagellar 9+2 structure, and resulted in the so-called principal bend. In addition, stoppage of the bending response occasionally occurred during development of a new principal bend, and in this situation, formation of a new reverse bend did not occur. This observation indicates that the reverse bend is always active, opposing the principal bend. The results show that mechanical strain of bending is a central component regulating the bend oscillation, and switching of the bend direction appears to be controlled, in part, by the velocity of wave propagation.
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Shingyoji, C., e K. Takahashi. "Cyclical bending movements induced locally by successive iontophoretic application of ATP to an elastase-treated flagellar axoneme". Journal of Cell Science 108, n.º 4 (1 de abril de 1995): 1359–69. http://dx.doi.org/10.1242/jcs.108.4.1359.
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To elucidate the mechanism of oscillatory bending in cilia and flagella, we studied the effect of protease digestion on the response of axonemes to localized application of ATP. When the axonemes were treated with elastase and then reactivated locally by ATP iontophoresis, a pair of local bends were formed due to localized unidirectional sliding in the vicinity of the ATP pipette. Upon repeated application of ATP, the direction of bending with respect to the sperm head axis changed cyclically from side to side over several cycles. The bends were planar and similar to those observed in axonemes that had not been treated with elastase. In trypsin-treated axonemes, in contrast, repetitive local reactivation did not induce such cyclical bending; instead, it induced a bend that grew only in one direction upon repeated application of ATP. Moreover, the bends were not planar. Electron microscopy of these protease-digested axonemes showed that both the interdoublet (nexin) links and the radial spokes were disrupted, but the effects of these proteases were different; trypsin disrupted 60–70% of these structures whereas elastase disrupted 20–30% of them. In both cases, spokes no. 3 and no. 8 (and no. 7) were more resistant to digestion than the others, although they tended to be more resistant to elastase than to trypsin. The importance of radial spokes and interdoublet links in the generation of cyclical bending and the determination of the bending plane is discussed.
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Contreras-González, Aldo-Francisco, Manuel Ferre, Miguel Ángel Sánchez-Urán, Francisco Javier Sáez-Sáez e Fernando Blaya Haro. "Efficient Upper Limb Position Estimation Based on Angular Displacement Sensors for Wearable Devices". Sensors 20, n.º 22 (12 de novembro de 2020): 6452. http://dx.doi.org/10.3390/s20226452.
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Motion tracking techniques have been extensively studied in recent years. However, capturing movements of the upper limbs is a challenging task. This document presents the estimation of arm orientation and elbow and wrist position using wearable flexible sensors (WFSs). A study was developed to obtain the highest range of motion (ROM) of the shoulder with as few sensors as possible, and a method for estimating arm length and a calibration procedure was proposed. Performance was verified by comparing measurement of the shoulder joint angles obtained from commercial two-axis soft angular displacement sensors (sADS) from Bend Labs and from the ground truth system (GTS) OptiTrack. The global root-mean-square error (RMSE) for the shoulder angle is 2.93 degrees and 37.5 mm for the position estimation of the wrist in cyclical movements; this measure of RMSE was improved to 13.6 mm by implementing a gesture classifier.
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Zhang, Baozhuo, e Marcus L. Young. "High-energy synchrotron X-ray diffraction measurements of simple bending of pseudoelastic NiTi shape memory alloy wires". Powder Diffraction 31, n.º 2 (23 de maio de 2016): 104–9. http://dx.doi.org/10.1017/s0885715616000154.
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Many technological applications of austenitic shape memory alloys (SMAs) involve cyclical mechanical loading and unloading in order to take advantage of pseudoelasticity. In this paper, we investigated the effect of mechanical bending of pseudoelastic NiTi SMA wires using high-energy synchrotron radiation X-ray diffraction (SR-XRD). Differential scanning calorimetry was performed to identify the phase transformation temperatures. Scanning electron microscopy images show that micro-cracks in compressive regions of the wire propagate with increasing bend angle, while tensile regions tend not to exhibit crack propagation. SR-XRD patterns were analyzed to study the phase transformation and investigate micromechanical properties. By observing the various diffraction peaks such as the austenite (200) and the martensite (${\bar 1}12$), (${\bar 1}03$), (${\bar 1}11$), and (101) planes, intensities and residual strain values exhibit strong anisotropy, depending upon whether the sample is in compression or tension during bending.
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Franklin, C. E., e I. A. Johnston. "Muscle power output during escape responses in an Antarctic fish". Journal of Experimental Biology 200, n.º 4 (1 de fevereiro de 1997): 703–12. http://dx.doi.org/10.1242/jeb.200.4.703.
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Escape responses (C-shaped fast-starts) were filmed at 500 frames s-1 in the Antarctic rock cod (Notothenia coriiceps) at 0 °C. The activation and strain patterns of the superficial fast myotomal muscle were measured simultaneously using electromyography and sonomicrometry respectively. In order to bend the body into the initial C-shape, the muscle fibres in the rostral myotomes (at 0.35L, where L is total length) shortened by up to 13 % of their resting length at a maximum velocity of 1.68 fibre lengths s-1. During the contralateral contraction, muscle fibres were stretched (by 5 % and 7 % at 0.35L and 0.65L, respectively) and were activated prior to the end of lengthening, before shortening by up to 12 % of resting fibre length (peak-to-peak strain). Representative strain records were digitised to create cyclical events corresponding to the C-bend and contralateral contraction. Isolated fibres were subjected to the abstracted strain cycles and stimulated at the same point and for the same duration as occurs in vivo. During the early phase of shortening, muscle shortening velocity (V) increased dramatically whilst the load was relatively constant and represented a substantial fraction of the maximum isometric stress. Pre-stretch of active muscle was associated with significant force enhancement. For the contralateral contraction, V exceeded that predicted by the steady-state force­velocity relationship for considerable periods during each tailbeat, contributing to relatively high maximum instantaneous power outputs of up to 290 W kg-1 wet muscle mass. In vitro experiments, involving adjusting strain, cycle duration and stimulation parameters, indicated that in vivo muscle fibres produce close to their maximum power. During escape responses, the maximum velocity and acceleration recorded from the centre of gravity of the fish were 0.71±0.03 m s-1 and 17.1±1.4 m s-2, respectively (mean ± s.e.m., N=7 fish). Muscle performance was sufficient to produce maximum velocities and accelerations that were within the lower end of the range reported for temperate-zone fish.
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Lizunov, Petro, e Valentyn Nedin. "THE PARAMETRIC OSCILLATIONS OF ROTATING ELASTIC RODS UNDER THE ACTION OF THE PERIODIC AXIAL FORCES". Management of Development of Complex Systems, n.º 44 (30 de novembro de 2020): 56–64. http://dx.doi.org/10.32347/2412-9933.2020.44.56-64.
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The paper presents the results of numerical investigation of the periodic axial forces’ influence on the transverse oscillations of long rotating rods. The gyroscopic inertia forces are taken to account and space oscillating process of rotating rods is considered with account of geometric nonlinearity. The study has been done with computer program with a graphical interface that is developed by authors. The process of numerical solution of the differential equations of oscillations of rotating rods using the method of numerical differentiation of rod’s bend forms by polynomial spline-functions and the Houbolt time integration method is described. A general block diagram of the algorithm is shown. This algorithm describes the process of repeated (cyclical) solving of the system of differential equations of oscillations for every point of mechanical system in order to find the new coordinates of the positions of these points in each next point of time t+∆t. The computer program in which the shown algorithm is realized allows to monitor for the behavior of moving computer model, which demonstrates the process of oscillatory motion in rotation. Moreover, the program draws the graphics of oscillations and changes of angular speeds and accelerations in different coordinate systems. Using this program, the dynamics of a range of objects which are modeled by long elastic rods have been studied. For investigated objects is shown that on various rotational speeds and beat frequencies the oscillatory motion of the rods occurs with different character of behavior. On certain speeds with different frequencies of axial load the oscillations have definite periodicity and occur with beats of amplitude which are the result of the periodic axial force action.
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Ritter, Scott M., James E. Barrick e M. Randall Skinner. "Conodont sequence biostratigraphy of the Hermosa Group (Pennsylvanian) at Honaker Trail, Paradox Basin, Utah". Journal of Paleontology 76, n.º 3 (maio de 2002): 495–517. http://dx.doi.org/10.1017/s0022336000037331.
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In cyclical Pennsylvanian strata, conodonts find their greatest stratigraphic utility as biotic signatures of physically defined stratigraphic entities (cycles, parasequences, high frequency sequences, etc.) rather then the primary means of stratigraphic subdivision (e.g., biostratigraphic interval zones). The practice of identifying depositional entities for purposes of regional correlation on the basis of their constituent conodont faunas is herein called conodont sequence biostratigraphy. In this paper, the concept is utilized to successfully correlate Pennsylvanian cycles of the Paradox basin with their Midcontinent counterparts.The Honaker Trail section is the most accessible and well-studied succession of carbonate shelf strata in the Paradox basin. Approximately 350 m of cyclically bedded limestone, sandstone, and shale comprising 53 fifth-order cycles are exposed along the cliffs of the deeply entrenched San Juan River. Maximum transgressive facies of 19 cycles yielded Idiognathodus-Neognathodus- and/or Streptognathodus-dominated conodont faunas. Those from the Chimney Rock, Gothic, LHT-5, UHT-3, UHT-5, UHT-8, unnamed limestone, and Shafer correspond to faunas from the Verdigris, Lower Fort Scott, Altamont (Lake Neosho), Lost Branch, Hertha (Mound City), Swope (Hushpuckney), Dennis (Stark), and South Bend cycles of the Midcontinent, respectively. By extrapolation, all minor cycles of the Marmaton, Pleasanton, and Bronson Groups (except for the Critzer) also appear to have counterparts at Honaker Trail.The position of the Desmoinesian–Missourian boundary in the Honaker Trail section can be approximated using conodonts in conjunction with fusulinids. The highest Desmoinesian conodont fauna, the Idiognathodus nodocarinatus fauna, occurs in cycle UHT-3 in the lower part of the Upper Honaker Trail sequence. The highest occurrence of Beedeina occurs in the same cycle. The lowest conodont fauna with the Missourian species I. eccentricus appears two cycles higher, in cycle UHT-5. Because in the Midcontinent region a small interval of strata separates the first appearance of I. eccentricus from the base of the Missourian, we place the base of the Missourian at the base of cycle UHT-4 (bed 105) at Honaker Trail. The appearance of Streptognathodus firmus and S. pawhuskaensis in the Shafer limestone indicates that the Missourian–Virgilian boundary lies slightly above or below this stratigraphic horizon.
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Lizunov, Petro, e Valentyn Nedin. "The gyroscopic forces influence on the oscillations of the rotating shafts". Strength of Materials and Theory of Structures, n.º 105 (30 de novembro de 2020): 223–31. http://dx.doi.org/10.32347/2410-2547.2020.105.223-231.
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The results of numerical investigation of shafts transverse oscillations with account of gyroscopic inertia forces are presented. It is shown what the action and how the gyroscopic forces influence on the transverse oscillations of the shafts during rotation. The study has been done with computer program with a graphical interface that is developed by authors. The process of numerical solution of the differential equations of oscillations of rotating rods using the method of numerical differentiation of rod's bend forms by polynomial spline-functions and the Houbolt time integration method is described. A general block diagram of the algorithm is shown. This algorithm describes the process of repeated (cyclical) solving the system of differential equations of oscillations for every point of mechanical system in order to find the new coordinates of positions of these points in each next point of time t+Dt. The computer program in which the shown algorithm is realized allows to monitor for the behavior of moving computer model, which demonstrates the process of oscillatory motion in rotation. Moreover, the program draws the graphics of oscillations and changes of angular speeds and accelerations in different coordinate systems. Defines the dynamic stability fields and draw the diagrams of found fields. Using this program, the dynamics of a range of objects which are modeled by long elastic rods have been studied. For some objects is shown that on special rotational speeds of shafts with different lengths, in the rotating with shaft coordinate system, the trajectories of center of the section have an ordered character in the form of n-pointed star in time interval from excitation to the start of established circular oscillation with amplitude that harmoniously changes in time. It is noted that such trajectories are fact of the action of gyroscopic inertia forces that arise in rotation.
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Abdalla, Hany F., Mohammad M. Megahed e Maher Y. A. Younan. "Determination of Shakedown Limit Load for a 90-Degree Pipe Bend Using a Simplified Technique". Journal of Pressure Vessel Technology 128, n.º 4 (9 de fevereiro de 2006): 618–24. http://dx.doi.org/10.1115/1.2349575.
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In this paper a simplified technique is presented to determine the shakedown limit load of a 90-degree pipe bend subjected to constant internal pressure and cyclic in-plane closing bending moment using the finite element method. The simplified technique determines the shakedown limit load without performing time consuming full elastic-plastic cyclic loading simulations or conventional iterative elastic techniques. Instead, the shakedown limit load is determined by performing two finite element analyses namely; an elastic analysis and an elastic-plastic analysis. By extracting the results of the two analyses, the shakedown limit load is determined through the calculation of the residual stresses developed in the pipe bend. In order to gain confidence in the simplified technique, the output shakedown limit moments are used to perform full elastic-plastic cyclic loading simulations to check for shakedown behavior of the pipe bend. The shakedown limit moments output by the simplified technique are used to generate the shakedown diagram of the pipe bend for a range of constant internal pressure magnitudes. The maximum moment carrying capacity (limit moment) the pipe bend can withstand and the elastic limit are also determined and imposed on the shakedown diagram of the pipe bend. In order to get acquainted with the simplified technique, it is applied beforehand to a bench mark shakedown problem namely, the Bree cylinder (Bree, J., 1967, J. Strain Anal., 3, pp. 226–238) problem. The Bree cylinder is subjected to constant internal pressure and cyclic high heat fluxes across its wall. The results of the simplified technique showed very good correlation with the analytically determined Bree diagram of the cylinder.
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Kim, Seung Mo, Eun Sook Shon, Yoon Hyun Ka, Yong Joon Kim, Jin Young Kim e Jae Dong Kim. "Reliability Characterization of Organic Solderability Preservatives (OSP) of IC Packages by Drop and Cyclic Bend Test". Key Engineering Materials 297-300 (novembro de 2005): 893–98. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.893.
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Cyclic bend test and drop test were carried out as a second level reliability test method in order to characterize the joint performance between electronic components and board. Two types of package substrates were used for the test. The one was NiAu plated, and the other one was organic solderability preservatives (OSP) finished. Drop test was done in accordance with JEDEC standard test method [1]. Drop impact and duration time was 1,500G and 0.5ms, respectively. Cyclic bend test was performed with Amkor internal specification because there is no international standard for the test. The Amkor internal specification was edited based on the IPC/JEDEC specification [2]. Board deflection and cyclic frequency was 3mm and 1Hz, respectively. NiAu substrate showed better mean life performance about by 30% in cyclic bend test. OSP substrate showed the same or better failure rate performance in drop test. Typical solder joint failures and intermetalic crack were found by failure analysis.
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Abdalla, Hany F., Mohammad M. Megahed e Maher Y. A. Younan. "Shakedown Limits of a 90-Degree Pipe Bend Using Small and Large Displacement Formulations". Journal of Pressure Vessel Technology 129, n.º 2 (17 de setembro de 2006): 287–95. http://dx.doi.org/10.1115/1.2716433.
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In this paper the shakedown limit load is determined for a long radius 90-deg pipe bend using two different techniques. The first technique is a simplified technique which utilizes small displacement formulation and elastic–perfectly plastic material model. The second technique is an iterative based technique which uses the same elastic–perfectly plastic material model, but incorporates large displacement effects accounting for geometric nonlinearity. Both techniques use the finite element method for analysis. The pipe bend is subjected to constant internal pressure magnitudes and cyclic bending moments. The cyclic bending loading includes three different loading patterns, namely, in-plane closing, in-plane opening, and out-of-plane bending. The simplified technique determines the shakedown limit load (moment) without the need to perform full cyclic loading simulations or conventional iterative elastic techniques. Instead, the shakedown limit moment is determined by performing two analyses, namely, an elastic analysis and an elastic–plastic analysis. By extracting the results of the two analyses, the shakedown limit moment is determined through the calculation of the residual stresses developed in the pipe bend. The iterative large displacement technique determines the shakedown limit moment in an iterative manner by performing a series of full elastic–plastic cyclic loading simulations. The shakedown limit moment output by the simplified technique (small displacement) is used by the iterative large displacement technique as an initial iterative value. The iterations proceed until an applied moment guarantees a structure developed residual stress, at load removal, equal to or slightly less than the material yield strength. The shakedown limit moments output by both techniques are used to generate shakedown diagrams of the pipe bend for a spectrum of constant internal pressure magnitudes for the three loading patterns stated earlier. The maximum moment carrying capacity (limit moment) the pipe bend can withstand and the elastic limit are also determined and imposed on the shakedown diagram of the pipe bend. Comparison between the shakedown diagrams generated by the two techniques, for the three loading patterns, is presented.
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Fellner, K., P. F. Fuchs, G. Pinter, T. Antretter e T. Krivec. "Method development for the cyclic characterization of thin copper layers for PCB applications". Circuit World 40, n.º 2 (29 de abril de 2014): 53–60. http://dx.doi.org/10.1108/cw-09-2013-0032.
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Purpose – The overall aim of this research work was the improvement of the failure behavior of printed circuit boards (PCBs). In order to describe the mechanical behavior of PCBs under cyclic thermal loads, thin copper layers were characterized. The mechanical properties of these copper layers were determined in cyclic four-point bend tests and in cyclic tensile-compression tests, as their behavior under changing tensile and compression loads needed to be evaluated. Design/methodology/approach – Specimens for the four-point bend tests were manufactured by bonding 18-μm-thick copper layers on both sides of 10-mm-thick silicone plates. The silicone was characterized in tensile, shear and blow-up tests to provide input data for a hyperelastic material model. Specimens for the cyclic tensile-compression tests were produced in a compression molding process. Four layers of glass fiber-reinforced epoxy resin (thickness 90 μm) and five layers of copper (thickness 60 μm) were applied. Findings – The results showed that, due to the hyperelastic material behavior of silicone, the four-point bend tests were applicable only for small strains, while the cyclic tensile-compression tests could successfully be applied to characterize thin copper foils in tensile and compression up to 1 percent strain. Originality/value – Thin copper layers (foils) could be characterized successfully under cyclic tensile and compression loads.
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Wu, Junjun, Lu Gem Gao, Wei Ren e Donald G. Truhlar. "Anharmonic kinetics of the cyclopentane reaction with hydroxyl radical". Chemical Science 11, n.º 9 (2020): 2511–23. http://dx.doi.org/10.1039/c9sc05632g.
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Pang, John H. L., e F. X. Che. "Isothermal Cyclic Bend Fatigue Test Method for Lead-Free Solder Joints". Journal of Electronic Packaging 129, n.º 4 (27 de agosto de 2007): 496–503. http://dx.doi.org/10.1115/1.2809442.
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Isothermal three-point and four-point cyclic bend fatigue test methods have been developed for Sn–Ag–Cu solder joints. Reported bend tests from the literature were conducted at room temperature (25°C) and there is lack of data for lead-free solder joints. In this study, very-thin quad flat no-lead (VQFN) assembly with Sn–Ag–Cu lead-free solder was tested under three-point and four-point cyclic bending loads at both room temperature (25°C) and high temperature (125°C). The correlation between three-point and four-point bend tests was developed. Two different board surface finishes of electroless Ni and immersion gold (ENIG) and organic solderability preservatives (OSP) were investigated. Bending fatigue resistance of VQFN with OSP finish is slightly better than ENIG finish case. The acceleration factor of failure at high temperature (125°C) is higher than that at room temperature (25°C). Finite element analysis modeling and simulation were performed for different test conditions to investigate the solder joint stress-strain behavior. Volume-averaged energy density was used as a fatigue damage parameter and energy-based bending fatigue models were developed for VQFN with Sn–Ag–Cu solder joint under cyclic bending load at both 25°C and 125°C.
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Muylaert, Toon, e Wim De Waele. "Design of a four-point bend test for ultra-low cycle fatigue of pipelines under inelastic bending". International Journal Sustainable Construction & Design 3, n.º 1 (6 de novembro de 2012): 70–79. http://dx.doi.org/10.21825/scad.v3i1.20558.
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This master thesis is situated in the research domain dealing with the ductile failure of pipelinesunder extreme loading conditions. It is part of an umbrella research aiming to develop innovativeexperimental and computational methodologies to simulate fracture of steel structural elements under ultralow cycle fatigue. The focus of this study is on steel pipeline applications. The objective of this thesis is todesign a large-scale four-point bend test setup to cyclically bend pipes. The feasibility of instrumentationwill be evaluated using small scale test specimens. In this paper some ideas, constraints and opportunitiesfor the design are considered, based on a literature review of several test setups for other applications. Thedesign parameters have been calculated to compose the design windows and an initial overview of thepossible instrumentation is given.
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Natesan, S., e M. Gilman. "YY1 facilitates the association of serum response factor with the c-fos serum response element." Molecular and Cellular Biology 15, n.º 11 (novembro de 1995): 5975–82. http://dx.doi.org/10.1128/mcb.15.11.5975.
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YY1 is a multifunctional transcription factor that acts as an activator or repressor in different contexts. YY1 binds to multiple sites in the mouse c-fos promoter, inducing at each site a sharp DNA bend. Binding of YY1 to a site situated between the cyclic AMP response element (CRE) and the TATA box bends the DNA in a way that interferes with the interaction of proteins bound at the CRE and TATA elements, resulting in repression of transcription. Here, we show that binding of YY1 to a different site in the c-fos promoter has a different result. Binding of YY1 to the c-fos serum response element (SRE) enhances the binding of serum response factor (SRF). This enhancement requires the binding of YY1 to SRE DNA. YY1 and SRF can cooccupy the SRE at least transiently. In the region of overlapping contact, YY1 contacts DNA in the major groove, while SRF contacts DNA in the minor groove. YY1 also enhances the association of SRF with the SRE in transfected insect cells. Thus, although YY1 induces similar structural changes in DNA at different binding sites, it can have distinct local effects on protein-DNA and protein-protein interactions. These data support a general role for YY1 in the building of highly organized promoter complexes.
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Rolovic, Radovan, e Steven M. Tipton. "Multiaxial Cyclic Ratcheting in Coiled Tubing—Part II: Experimental Program and Model Evaluation". Journal of Engineering Materials and Technology 122, n.º 2 (21 de setembro de 1999): 162–67. http://dx.doi.org/10.1115/1.482782.
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An experimental program was conducted to evaluate the plasticity model proposed in a separate paper (Part I). Constant pressure, cyclic bend-straighten tests were performed to identify material parameters required by the analytical model. Block pressure, bend-straighten tests were conducted to evaluate the proposed model. Experiments were performed on full-size coiled tubing samples using a specialized test machine. Two commonly used coiled tubing materials and four specimen sizes were subjected to load histories consisting of bending-straightening cycles with varying levels of internal pressure. It was observed that cyclic ratcheting rates can be reversed without reversing the mean stress, i.e., diametral growth of coiled tubing can be followed by diametral shrinkage even when the internal pressure is kept positive, depending on the loading history. This material behavior is explained in the context of the new theory. The correlation between the predictions and the test data is very good. [S0094-4289(00)00502-8]
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Huh, Yong Hak, Seong Jae Cho e Jiho Song. "Chraracteristics of Crack Growth of Alumina Ceramics Under Cyclic Loads". International Journal of Modern Physics B 17, n.º 08n09 (10 de abril de 2003): 1737–43. http://dx.doi.org/10.1142/s0217979203019599.
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Characteristics of crack growth under cyclic loading for alumina ceramics have been investigated. Three alumina ceramics with different grain size were fabricated by hot-pressing. Cyclic fatigue tests were carried out using four-point bend specimen. From examination of crack path and microstructural behavior from the tested specimens, grain bridging along the crack interface and intergranular fracture mode at the fracture surface were observed. The crack growth rate curve presented by using the cyclic parameter, [Formula: see text], could be divided into three regions. These regions were closely related to the fraction of intergranular fracture area. Crack closure influencing the cyclic parameter was evaluated as a function of stress ratio.
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Pazhanivel, K., N. Ramadoss, K. Poyyathappan, P. Anandan e G. B. Bhaskar. "Flexural Analysis on GFRP Composites Subjected to Cyclic Gradual Load and Cyclic Impact". Advanced Materials Research 685 (abril de 2013): 35–39. http://dx.doi.org/10.4028/www.scientific.net/amr.685.35.
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Glass fiber reinforced polymeric (GFRP) composite laminates have been prepared by hand layup method. According to ASTM standard, the test specimens have been prepared to carry out the flexural bending tests. The specimens have been subjected to both cyclic impact load and cyclic gradual load with various frequencies prior to the flexural bending analysis. Three point bend method has been adopted to find out the flexural strength and flexural modulus. Flexural strength and modulus have been calculated from the load deflection curve obtained from the tensometer for respective specimens. The flexural bending properties of GFRP composites subjected to cyclic gradual load and cyclic impact have been compared and found that the GFRP composite materials are effective for gradual cyclic load than the cyclic impact load.
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Shingyoji, C., I. R. Gibbons, A. Murakami e K. Takahashi. "Effect of imposed head vibration on the stability and waveform of flagellar beating in sea urchin spermatozoa". Journal of Experimental Biology 156, n.º 1 (1 de março de 1991): 63–80. http://dx.doi.org/10.1242/jeb.156.1.63.
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The heads of live spermatozoa of the sea urchin Hemicentrotus pulcherrimus were held by suction in the tip of a micropipette mounted on a piezoelectric device and vibrated either laterally or axially with respect to the head axis. Within certain ranges of frequency and amplitude, lateral vibration of the pipette brought about a stable rhythmic beating of the flagella in the plane of vibration, with the beat frequency synchronized to the frequency of vibration [Gibbons et al. (1987), Nature 325, 351–352]. The sperm flagella, with an average natural beat frequency of 48 Hz, showed stable beating synchronized to the pipette vibration over a range of 35–90 Hz when the amplitude of vibration was about 20 microns or greater. Vibration frequencies below this range caused instability of the beat plane, often associated with irregularities in beat frequency. Frequencies above about 90 Hz caused irregular asymmetrical flagellar beating with a marked decrease in amplitude of the propagated bends and a skewing of the flagellar axis towards one side; the flagella often stopped in a cane shape. In flagella that were beating stably under imposed vibration, the wavelength was reduced at higher frequencies and increased at lower frequencies. When the beat frequency was equal to or lower than the natural beat frequency, the apparent time-averaged sliding velocity of axonemal microtubules, obtained as twice the product of frequency and bend angle, decreased with beat frequency in both the proximal and distal regions of the flagella. However, at vibration frequencies above the natural beat frequency, the sliding velocity increased with frequency only in the proximal region of the flagellum and remained essentially unchanged in more distal regions. This apparent limit to the velocity of sliding in the distal region may represent an inherent limit in the intrinsic velocity of active sliding, while the faster sliding observed in the proximal region may be a result of passive sliding or elastic distortion of the microtubules induced by the additional energy supplied by the vibrating pipette. Axial vibration with frequencies either close to or twice the natural beat frequency induced cyclic changes in the waveform, compressing and expanding the bends in the proximal region, but did not affect bends in the distal region or alter the beat frequency.
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Liang, Ting, Gang Chen, Qi Zhang e Xu Chen. "Ratcheting Boundary Analysis of Straight and Elbow Piping". Advanced Materials Research 118-120 (junho de 2010): 131–35. http://dx.doi.org/10.4028/www.scientific.net/amr.118-120.131.
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The ratcheting strains of the straight and elbow piping under two kinds of loads—pressurized piping under symmetric cyclic bending and pulsating cyclic pressure were analyzed based on Chaboche constitutive model. The locations of the maximum ratcheting strain were determined. The ratcheting boundaries of the two piping structures under two kinds of loads were compared and calculated by the C-TDF method. For the pressurized piping under symmetric cyclic bending, the allowable bending load increases from E90S to E90L under the same pressure. In the higher cyclic pressure range, the allowable pressure have little difference under the same bending load which indicates that the bend moment have a bit effects on the ratcheting boundary in the higher cyclic pressure range.
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Ritter, J. E., J. P. Fahey e T. H. Service. "Cyclic Fatigue Behavior of Resinoid-Bonded Abrasives". Journal of Vibration and Acoustics 108, n.º 3 (1 de julho de 1986): 276–81. http://dx.doi.org/10.1115/1.3269339.
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The cyclic fatigue behavior of a resinoid-bonded abrasive was determined in ambient air (22°C and 50 percent relative humidity). The number of cycles to failure was dependent on the cyclic stress by a power functional relation, consistent with fracture mechanics concepts of fatigue crack growth. Additionally, it was found that the cyclic fatigue behavior did not depend on the cyclic stress waveform or the test sample geometry and loading (four-point bend bars and radically loaded nonreinforced and reinforced wheels). Based upon fracture mechanics concepts, a reliability analysis was developed for reinforced, resinoid-bonded abrasives in service, taking into account the variability in strength and the fatigue behavior exhibited by these materials.
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Hensman, James J., C. V. Cristodaro, Gareth Pierce e Keith Worden. "On the Reproducibility of Transducer Coupling for Acoustic Emission Testing". Advanced Materials Research 13-14 (fevereiro de 2006): 117–24. http://dx.doi.org/10.4028/www.scientific.net/amr.13-14.117.
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An acoustic emission test was simulated using a three point bend specimen and an artificial AE source. Waveform data was recorded as the sample was cyclically loaded in three point bending, and the cross correlation coefficient of the waveforms was used to measure the repeatability of the test. Results were twofold: the stress state of a specimen affects the ultrasonic propagation therein; and the coupling condition of a transducer may not remain constant during a test.
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Vossoughi, H., K. Soudki, R. N. White, A. R. Ingraffea e M. Sansalone. "Fatigue of Thick Steel Plates Bent to a Low R/t Ratio". Journal of Pressure Vessel Technology 111, n.º 3 (1 de agosto de 1989): 259–65. http://dx.doi.org/10.1115/1.3265673.
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The use of cold-bent plates, instead of welded corner joints, in the fabrication of pressure vessels can reduce production costs. The cold-bending operation is relatively easy, inexpensive, and requires minimum quality control. The attractiveness of using cold-bent plates as a potential substitute for plates with welded corner joints motivated the fatigue study described here. Fatigue test resutls are reported for nineteen 25-mm thick HY80 and HY100 steel plates, cold-bent to a nominal bend angle of 90 deg and an R/t (inner bend radius/thickness) of 1.5, and ten 25-mm thick HY80 welded corner joints. Testing was performed under zero-to-tension loading (stress ratio R = 0) at room temperature and at a frequency of 4 Hz on specimens that retained the actual cold-bending-induced residual stresses. These test results indicate that the cold-bent plates may be a good alternative to welded corner joints for cyclic loading histories.
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Maldonado, Mariângela Bueno Cordeiro, Francine Messias Ciríaco Henry, Teissiane Fernanda de Vasconcelos Ferreira, Barbara Piffero Mello, Mario Binelli e Claudia Maria Bertan Membrive. "Use of protein kinase C and phospholipase A2 inhibitors in bovine endometrial cells treated with estradiol and calcium ionophore". Brazilian Journal of Veterinary Research and Animal Science 58 (7 de maio de 2021): e174355. http://dx.doi.org/10.11606/issn.1678-4456.bjvras.2021.174355.
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The release of endometrial prostaglandin-F2α (PGF2α) in bovine females can be induced in vivo by estradiol (E2). However, its role in this mechanism has not been clarified. We hypothesized that E2 stimulates the activity and abundance of protein kinase C (PKC) and phospholipase A2 (PLA2). Our objective in this study was to analyze the effects of PKC and PLA2 inhibitors on PGF2α synthesis induced by E2 and calcium ionophore (CI) in bovine endometrial cells (BEND cells; Experiment 1). Additionally, we evaluated the abundance of PKC and PLA2 in endometrial explants of cows treated or not with E2 17 days after estrus (D17, D0 = estrus; Experiment 2). In Experiment 1, BEND cells were submitted to a PKC inhibitor (10 μM of C25H24N4O2; bisindolylmaleimide I, or BIS I), a PLA2 inhibitor (20 μM of arachydoniltrifluoromethane or AACOCF3), or none. The BEND cells were subsequently treated with E2 and CI, and PGF2α concentrations were measured in the culture medium through radioimmunoassay. For DIF-12 (PGF2α concentration 12 h after treatment subtracted from PGF2α concentration at hour 0), no PKC inhibitor effect was observed (P= 0.2709). However, DIF-12 was lower (P < 0.05) for groups treated with the PLA2 inhibitor and PLA2 inhibitor + CI + E2 groups than the control and CI + E2 groups. Thus, AACOCF3 was an efficient PLA2 inhibitor in the BEND cells culture system, and E2 did not stimulate the synthesis of PKC and PLA2. In Experiment 2, cyclic Nellore heifers received none (n = 5) or 3 mg (n = 6) of 17β-E2 on D17 and were slaughtered 2 h after administration. The abundance of PKC and PLA2 in the endometrial tissue was evaluated using Western blotting analysis. No E2 effect was observed on PKC (P = 0.08) and PLA2 (P = 0.56). We concluded that E2 did not stimulate the activity and abundance of PKC and PLA2.
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Seitl, Stanislav, Zbyněk Keršner, Vlastimil Bílek e Zdeněk Knésl. "Fatigue Parameters of Cement-Based Composites with Various Types of Fibres". Key Engineering Materials 417-418 (outubro de 2009): 129–32. http://dx.doi.org/10.4028/www.scientific.net/kem.417-418.129.
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The paper introduces the basic fracture mechanics parameters of advanced building material – cement-based composites with various types of fibres, prepared as high performance concrete/mortar developed by ZPSV, a.s. company for production of thin-walled panels/elements. To this end three-point bend specimens with starting notch were prepared and tested under static (load–deflection diagram, effective fracture toughness) and cyclic loading (fatigue parameter – Wöhler curve). The experimentally obtained results of cement-based composites are compared and the suitability of these types composites for its application are discussed.
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Loganathan, T. G., R. Krishna Murthy e Chandrasekaran Kesavan. "Effect of Cyclic Loading Frequency on Flexural Modulus of GFRP Laminates with Resin Rich Intermediate Layers". Applied Mechanics and Materials 787 (agosto de 2015): 543–47. http://dx.doi.org/10.4028/www.scientific.net/amm.787.543.
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The flexural modulus of composite laminates subjected to cyclic loads of varying cycle periods are experimentally investigated in this work. GFRP composite laminate specimen of configuration 0/R/0/0/0, 0/R/30/60/0, 0/R/90/90/0 and 0/R/45/-45/0 are prepared by hand lay-up technique with a uniquely processed resin-rich intermediate layer for the testing. Specimens are exposed to constant amplitude cyclic loading of frequencies 4.6 Hz and 8.6 Hz. A cantilever configuration of specimen with cyclic tip loading is considered to simulate the conditions of a leaf of a laminated automobile leaf spring. The flexural response of the laminate is measured using three point bend test as per ASTM D 790 and damping by hysteresis loop. The observed reduction in flexural modulusand the increase in damping factor after loading are compared with virgin. Minimised flexural modulus deviations between the loading frequencies are favoured by the cushioning of resin rich intermediate layer in the lay-up.
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Somers, Marnick, Saosometh Chhith, Wim De Waele e Reza Hojjati Talemi. "Fatigue fracture assessment of high strength steel using thermographic analysis". International Journal Sustainable Construction & Design 8, n.º 1 (30 de outubro de 2017): 8. http://dx.doi.org/10.21825/scad.v8i1.6812.
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Fatigue behaviour is most commonly evaluated in uni-axial cyclic stress tests using standardised dog-bone samples. When components are sharply bent into shape and subjected to cyclic loading, the fatigue damage will accumulate at the inside of the bend. This paper reports on an experimental investigation about the feasibility of infrared thermographic techniques to monitor fatigue damage initiation and accumulation. By monitoring spectral components of the thermal response, the fatigue limit, the onset of crack initiation and the ratio of initiation to propagation lifetime can all be determined. Also the effect of surface treatments on initiation properties is investigated. Most results are consistent with expected behaviour based on a previous study, indicating that thermographic techniques have a greater sensitivity and can be used to reduce the number of samples and time required for fatigue characterisation.
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Korotky, Anatoly, Edward Marchenko, Sergey Popov, Julianna Marchenko e Nikolai Dontsov. "Theoretical foundations of modeling the process of transport vehicles steel ropes structural defects formation". E3S Web of Conferences 175 (2020): 05018. http://dx.doi.org/10.1051/e3sconf/202017505018.
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The article presents materials on the study of mathematical modeling of splicing (binding) of steel rope used to transmit traction by friction. The developed mathematical model splicing (binding) describes the stress-strain state of strands (wires) from quasistatic loads, arising in the cyclic tension process and bending of steel rope on rope sheave, in which the resultant force in steel rope cross section is shifted relative to the central axis, causing it to bend and torsion. Using experimental data, it was found that the steel rope torsion and bending is caused by the linking technology in the nodes where strands are replaced. Experimentally established, that defects on the splicing (binding) site manifested as a result of cyclic tensile and bending loads on rope sheave, which is connected to limited mobility of the strands in nodes due to cross section symmetry violation.
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van Bogaert, P., e S. van Bogaert. "Mechanics of Bend-Over-Sheave (Shoeshine) Fatigue Testing of Cord-Rubber Laminates". Tire Science and Technology 39, n.º 3 (1 de setembro de 2011): 168–92. http://dx.doi.org/10.2346/1.3637742.
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Abstract The Bend-Over-Sheave test is used for screening reinforcement cords used in tires, especially on fatigue interply delamination as well as rubber-fabric and rubber-cord adhesion degradation. The typical cyclic load of tension-tension of the sidewalls or tension-compression of the belt can be achieved by the proper definition of two-ply laminates bent over a sheave. The objective of this paper is to define relevant fatigue test conditions that can predict the performance of new materials. A finite element model of the Bend-Over-Sheave test configuration is presented and shows that, for the test arrangements studied in this paper, flanged wheels should be used to prevent lateral buckling in the compressed cords. Besides, a simplified model enables us to determine the different factors that have significant effect on the strain levels in the cords. The material of the cords, the rubber hardness (“Shore”), and the sample manufacturing process are shown to have an influence on the specimen strain levels. The test conditions, i.e., the sheave radius, the traction force, and the contact angle between the sheave and the sample, also affect the behavior specimen strain levels. On the other hand, if the sample length is higher than a certain value, it is shown not to have a significant effect on the results.
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Masuda, Yuichi. "Bioactive 3D structures of naturally occurring peptides and their application in drug design". Bioscience, Biotechnology, and Biochemistry 85, n.º 1 (janeiro de 2021): 24–32. http://dx.doi.org/10.1093/bbb/zbaa008.
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Abstract Naturally occurring peptides form unique 3D structures, which are critical for their bioactivities. To gain useful insights into drug design, the relationship between the 3D structure and bioactivity of the peptides has been studied. Solid-state nuclear magnetic resonance (NMR) analysis of the 42-residue amyloid β-protein (Aβ42) suggested the presence of toxic conformers with a turn structure at positions 22 and 23 in the aggregates. Antibodies specific to this turn structure could be utilized for immunotherapy and early diagnosis of Alzheimer's disease. Solution NMR analysis of apratoxin A, a cyclic depsipeptide with potent cytotoxicity, proposed an accurate structural model with an important bend structure, which led to the development of highly active mimetics. X-ray crystal analysis of PF1171F, a cyclic hexapeptide with insecticidal activity, indicated the formation of 4 intramolecular hydrogen bonds, which play an important role in cell membrane permeability of PF1171F.
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Zang, Li Min, Jian Hui Qiu, Chao Yang e Sakai Eiichi. "Preparation and Characterization of Conducting Polymer Microspheres". Applied Mechanics and Materials 543-547 (março de 2014): 3874–77. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.3874.
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Functional floating bead (F-FB), prepared by anchoring the organic sulfonic acid on the surface of the blackberry-like structural FB, was used as both the inorganic substrate and the in situ dopant for the in situ chemical oxidative polymerization of pyrrole to obtain the polypyrrole/functional floating bead (PPy/F-FB) composites. The encapsulating morphologies were revealed with the scanning electron microscopy technique. The PPy/F-FB composites were characterized with Fourier transform infrared spectroscopy and thermogravimetric analysis. Based on the cyclic voltammetry of the composites, it was found that the composites performed typical electrochemical supercapacitor behavior.
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Pinheiro, Andre, Ana Oliveira, Francisco de Sousa, João Soares, Gilberto Saraiva, Alcineia Oliveira e Rossano Lang. "CeFe-Based Bead Nanocomposites as Catalysts for Oxidation of Ethylbenzene Reaction". Catalysts 8, n.º 11 (26 de outubro de 2018): 495. http://dx.doi.org/10.3390/catal8110495.
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Oxides with good catalytic performances and more selectivity to valuable chemicals attract numerous research interests for the oxidation of hydrocarbon fuels. Taking advantage of the nanocasting route, CeFe-based nanocomposites were prepared and characterized to achieve superior stability in the oxidation of cyclic compounds. Adding a third metal (Me = Ni2+, Mn2+/Mn3+ or Co2+/Co3+) to the CeFe-based oxide helped the formation of Ce3+/Ce4+, Fe2+/Fe3+ and active couples in the ternary nanocomposites. The solids having a spherical morphology and good textural properties enabled the formation of promising ternary oxide catalysts for the oxidation of ethylbenzene compared with those of binary and single monoxide nanocomposites. The close contact among the Ce3+/Ce4+ and Fe2+/Fe3+ pairs with Ni2+ species provided the formation of a highly stable CeFeNi catalyst with enhanced performance in the oxidation of cyclic compounds such as ethylbenzene, styrene and benzyl alcohol substrates.
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Qi, Yong, Ci Mian Zhu, Shu Sheng Zhong, Jia Lv e Zhi Gang Guo. "Comparative Study on the Pseudo Static Testing of Beam Transfer Structure of Frame-Supported Short-Leg Shearwall with and without Haunch". Advanced Materials Research 243-249 (maio de 2011): 188–92. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.188.
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In order to analyse seismic behaviors of the haunched beam-shaped transfer floor, carried out the pseudo static testing, which were subjected to vertical loads and horizontal cyclic loads, respectively on two specimens, including the framed short-leg shear wall haunched beam-shaped transfer plane framework and the same dimension unhaunched beam-shaped transfer frame. The test shows that: 1) Haunched beam-shaped transfer structure can apparently improve the shear-bearing-capacity of the abutment section and reduce the beam dimension effectively, and it is easier to implement the aseismatic design principles, including “strong column and weak beam, strong shearing and weak bend”; 2) if the design is reasonable, haunched beam-shaped transfer structure can get better seismic behavior.
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Bardakov, V. V., A. I. Sagaydak e S. V. Elizarov. "ACOUSTIC EMISSION BEHAVIOUR OF OVER-REINFORCED CONCRETE BEAMS". Kontrol'. Diagnostika, n.º 255 (2019): 4–12. http://dx.doi.org/10.14489/td.2019.09.pp.004-012.
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The paper presents the results of the conducted experimental studies on three-point bend testing of over-reinforced concrete beams with incremental cyclic load, up to destruction, using the acoustic emission method. In total 3 RC beams differ from each other in reinforcement type, concrete composition and ultimate load were tested. Special attention is paid to the investigation of the relationship between destructive processes occurring during the testing of reinforced concrete beams and the evolution of acoustic emission data registered during the test. The analysis described in the article makes it possible, on the basis of acoustic emission data, recorded during the tests, to distinguish the stages corresponding to the different technical state of over-reinforced concrete structures.
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Yurtcan, Ayşe Bayrakçeken. "Formic Acid and Methanol Oxidation for Pt/C Catalyst Depending on Rotating Speed, Scan Rate and Concentration". Brilliant Engineering 1, n.º 2 (17 de dezembro de 2019): 1–4. http://dx.doi.org/10.36937/ben.2020.002.001.
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The oxidation of small organic molecules on the catalyst under electrocatalytic conditions is important for the operation of liquid feed fuel cells. The basic reaction mechanisms toward the oxidation of methanol and formic acid continue to be a matter of debate under real operational conditions of electrochemical systems. The electrocatalytic activity of the commercial Pt/C catalyst was investigated in sulfuric acid/methanol and sulfuric acid/formic acid mixtures using electrochemical measurements. This work presents the variation of formic acid and methanol oxidation on the catalyst depending on hydrodynamic conditions using the rotating disk electrode. Cyclic voltammograms were obtained at different scan rates, rotating speeds and concentrations. As the rotating speed increases, the oxidation activity of formic acid and methanol decrease under voltammetric measurements. The peak currents of formic acid and methanol oxidation increased with the increase in the scan rate and concentration.
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Glaser, B., Nenad Gubeljak e Jožef Predan. "Calibration Function for Fatigue Crack Propagation". Key Engineering Materials 665 (setembro de 2015): 109–12. http://dx.doi.org/10.4028/www.scientific.net/kem.665.109.
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Components and structures exposed to elastic dynamic loading respond with different surface or bulk material changes which could be monitored on the through surface deformation measurements. The measurements could be performed with electronic devices used for on-line computerized measurement systems. Fatigue induced flaw growth was monitored on a 4-point specimen, loaded by cyclic dynamic bend forces. The flaw growth was monitored by strain gauges and analyzed to determine the shape, propagation and cross sections of the crack. To determine the stress intensity factor a numerical model was developed based on measured crack shapes, material properties and cyclic loading data of the actual tested specimen. The analyses results showed that derived calibration curve could be used to predict surface deformations as a result of crack propagation and growth. With the determination of surface deformation, one could follow the crack transition from surface crack to through thickness crack. The goal of this paper is to describe methodology and results based on experimental analysis during crack propagation and potential use of this technique for online monitoring purposes.
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Liu, Yunqiu, Anqi Fu, Binsong Jiang, Liyuan Yu e Xiaobing Wang. "Study on the Static and Dynamic Fracturing Properties of Marble after Being Damaged Dynamically". Advances in Civil Engineering 2020 (4 de setembro de 2020): 1–13. http://dx.doi.org/10.1155/2020/8886198.
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A split Hopkinson pressure bar (SHPB) system was first used to perform the cyclic impact loading tests on notched semicircular bend (NSCB) marble specimens. Then, static and dynamic three-point bending tests were conducted on these dynamically damaged specimens, respectively. In the cyclic impact loading tests, the dynamic elastic modulus decreases gradually as the impact number increases, but dynamic cumulative damage exhibits a growing trend. In the static and dynamic three-point bending tests, when dynamic cumulative damage is less than 0.345, the dynamic fracture toughness values are larger than the static fracture toughness values, but the experimental data exhibit the opposite results when dynamic cumulative damage ranges from 0.345 to 0.369. Through the quantitative analysis of fracture surface morphologies, the roughness and area of the fracture surfaces increase with an increasing dynamic cumulative damage. Under the same dynamic cumulative damage of the specimens, both the roughness and area of the surfaces fractured by static three-point bending are larger than those fractured by dynamic three-point bending.
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McQuaid, Conor, Andrea Halsey, Maëva Dubois, Ignacio Romero e David Male. "Comparison of polypeptides that bind the transferrin receptor for targeting gold nanocarriers". PLOS ONE 16, n.º 6 (4 de junho de 2021): e0252341. http://dx.doi.org/10.1371/journal.pone.0252341.
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The ability to target therapeutic agents to specific tissues is an important element in the development of new disease treatments. The transferrin receptor (TfR) is one potential target for drug delivery, as it expressed on many dividing cells and on brain endothelium, the key cellular component of the blood-brain barrier. The aim of this study was to compare a set of new and previously-described polypeptides for their ability to bind to brain endothelium, and investigate their potential for targeting therapeutic agents to the CNS. Six polypeptides were ranked for their rate of endocytosis by the human brain endothelial cell line hCMEC/D3 and the murine line bEnd.3. One linear polypeptide and two cyclic polypeptides showed high rates of uptake. These peptides were investigated to determine whether serum components, including transferrin itself affected uptake by the endothelium. One of the cyclic peptides was strongly inhibited by transferrin and the other cyclic peptide weakly inhibited. As proof of principle the linear peptide was attached to 2nm glucose coated gold-nanoparticles, and the rate of uptake of the nanoparticles measured in a hydrogel model of the blood-brain barrier. Attachment of the TfR-targeting polypeptide significantly increased the rates of endocytosis by brain endothelium and increased movement of nanoparticles across the cells.
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Farajian, Majid, Thomas Nitschke-Pagel e Klaus Dilger. "Stability and Relaxation of Welding Residual Stresses". Materials Science Forum 681 (março de 2011): 55–60. http://dx.doi.org/10.4028/www.scientific.net/msf.681.55.
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Residual stress relaxation of butt-welded small scale steel specimens under static and cyclic mechanical loading was investigated. The experiments were carried out on different types of steel with yield strengths between 300 and 1200MPa. The x-ray and neutron diffraction techniques were applied for the residual stresses analysis. The maximum values of initial residual stresses were measured at the weld bead centerline and were not as frequently assumed as high as the yield strength of the material. From fatigue point of view the internal stresses at the weld toe are of importance. It was observed that only a fraction of maximum residual stress accommodated in the weld bead centerline, is available at the weld toe. Under static tensile and compressive loading by increasing the load level the residual stress field relaxes continuously. The relaxation sets in with delay under compression since the tensile residual stresses should be first overcome. Under cyclic loading, once the first relaxation takes place further cyclic relaxation is either not considerable or continues moderately depending on loading conditions. In high cycle fatigue the residual stresses are stable until 2x106 cycles. In low cycle fatigue however the variation of the residual stresses continues until failure. This variation is partly related to crack initiation and propagation. The von Misses failure criterion with the local yield strength as material resistance against plastic deformation was able to describe the relaxation of surface welding residual stresses in low cycle fatigue.
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Fruehmann, R. K., W. Wang, Janice M. Dulieu-Barton e S. Quinn. "The Application of Thermoelastic Stress Analysis to Evaluate Debond Damage in Composite Sandwich Structures". Applied Mechanics and Materials 70 (agosto de 2011): 470–75. http://dx.doi.org/10.4028/www.scientific.net/amm.70.470.
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The work described in the paper investigates the stresses in the vicinity of a debond between the face sheet and core in a foam core / composite sandwich beam. Experiments were conducted in which the damaged side of the beam was loaded in compression in a four point bend test. Thermoelastic stress analysis (TSA) was used to obtain a measure of the stress field in the central part of the beam to evaluate its potential for damage detection and assessment. It is shown that TSA is capable of both identifying the damage and assessing its severity in terms of the remnant load carrying capacity of the beam. Fatigue tests were also performed, which showed that the cyclic load applied as a necessity for TSA did not cause the damage to grow, thereby demonstrating the potential of TSA as a non-destructive method for inspecting sandwich structures.
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Shah, Rahul S., Kuo-Chiang Wang e Mary Jane Kleinosky. "Prediction of the Low-Cycle Fatigue Life of HY-100 Undermatched Welds in Marine Structures". Journal of Ship Production 11, n.º 02 (1 de maio de 1995): 71–80. http://dx.doi.org/10.5957/jsp.1995.11.2.71.
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Finite-element and analytical models are used in this study to predict the low-cycle fatigue life of undermatched (lower yield strength) weldments of HY-100 steel. The objective was to determine the feasibility of replacing conventional overmatched welds in marine structures. Fatigue tests were performed on standard, smooth specimens, notched cylindrical specimens and a four-point-bend test on a full-scale butt beam specimen. Numerical analyses were conducted using finite elements, with a two-surface plasticity algorithm to simulate the cyclic behavior of the individual materials. The stress and strain concentrations at the notches were also evaluated using two analytical models: the Neuber and Glinka relations. The finite-element predictions compared well with experimental data and produced detailed predictions of the strain distributions, which were then used to assess the crack initiation life. Glinka's relation demonstrated superior predictive capabilities for local strains over Neuber's relation.
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Huang, Kuanchen, Zichen Ling e Qixin Zhou. "Urethane Diols through Non-Isocyanate Approach and Their Application in MF Coating". Journal of Composites Science 5, n.º 7 (20 de julho de 2021): 194. http://dx.doi.org/10.3390/jcs5070194.
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In this work, two urethane diols with different middle chain lengths were prepared by the non-isocyanate approach from 1,4-diaminobutane or 1,6-diaminohexane with ethylene cyclic carbonate at room temperature without the aid of a catalyst. Different weight percentages of hexa(methoxymethyl) melamine (HMMM) crosslinker was mixed with urethane diols then cured under elevated temperature to generate the melamine-formaldehyde (MF) coating films. Two different linear diols without urethane linkage were chosen to crosslink with HMMM as the control group. The mechanical properties of these MF coatings were investigated by tensile test, adhesion test, and conical mandrel bend test. It was found that coatings incorporated with urethane diols exhibited enhanced mechanical properties and flexibility. These properties were also influenced by the weight percentage of HMMM crosslinker. This study provided a facile non-isocyanate way to produce urethane diols and successfully applied them in MF coating.
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Liu, Jin, Liang Jian e Du Xiuli. "Experimental study on seismic behavior of full scale square concrete filled steel tubular stocky columns". E3S Web of Conferences 272 (2021): 02024. http://dx.doi.org/10.1051/e3sconf/202127202024.
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This study mainly presented a pseudo-static experiment on two full-scale square CFST short columns with the cross-sectional width of 600 mm under combined constant axial load and cyclic lateral load. The seismic performance of the two full-scale CFST columns were investigated. Meanwhile, the plastic hinge length of the specimens was discussed. The test results presented that the specimens suffered bend-shear failure. The local buckling of steel tube occurred at the end of the specimens and the core concrete crushed. The safety redundancy of lateral bearing capacity decreased in full-scale specimen. By the method of physical observation, the plastic hinge length Lp1 was determined mainly according to the range of the local buckling of steel tube. There had a great difference between the prediction of plastic hinge lengths by the existing calculation model and the plastic hinge lengths obtained by the test.
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Pereira, Juliete N., David Márcio Macêdo Dias, Natal Nerímio Regone, Marcos A. Fernandes, Sandra Nakamatsu, Sylma Carvalho Maestrelli e Neide Aparecida Mariano. "Effect of Corrosion of Stainless Steel Welded within Lithium Chloride". Materials Science Forum 869 (agosto de 2016): 470–73. http://dx.doi.org/10.4028/www.scientific.net/msf.869.470.
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The difficulties experienced in welding processes of martensitic stainless steel led to development of a new class of them, known as stainless mild martensitic steels. Also, due to the current high demand for energy and materials to oil extraction at great depths, scientists have being developing specific researches about mechanical resistance and corrosion of steels and how these properties are influenced by high temperature processes. This research studies the effect of welding process over the corrosion resistance of the 13Cr4Ni0.02C steel in a lithium chloride solution with a concentration of 120,000 PPM Cl-. The corrosion tests were conducted by cyclic potentiodynamic polarization in the base metal, weld bead and heat affected zone (HAZ) areas of the steel, in average temperatures of 23°C (as reference) and 3°C. The results revealed that the weld bead and heat affected zones of the 13Cr4Ni0.02C steel in a temperature of 3°C are less resistant to corrosion in this environment than the base metal in the same conditions.
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Chen, Sun Yi. "Model and Imitation of the Cycle Temperature Fields and Deformations of Coke Drum". Advanced Materials Research 197-198 (fevereiro de 2011): 1389–94. http://dx.doi.org/10.4028/www.scientific.net/amr.197-198.1389.
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When the operating process of delay coking is cyclically changing from 25°C to 500°C, it would usually induce the effect of heat treatment on the shell of coke drum. After a special model of the kinetic medium climbing along the inside-wall of the coke drum at a steady rate set up, the resulting two-dimensional kinetic temperature field of shell in radial and axial directions has been calculated and analyzed by FEM. The relation between the material physical property of the shell and its temperature has been considered. The results show that the radial temperature difference or the axial temperature difference caused by the cooling water is more than that caused by the hot oil. The maximum temperature difference between the inside-wall and the outside-wall is 40°C below the medium level, 30mm by the hot oil and 60 °C or 25 mm by the cooling water. The circumferential uneven temperature field, location and concave/convex or incline/bend of body have been surveyed and analyzed. The lat-circle deformation of transverse section has been discussed.
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Schmieder, Annett, Thorsten Heinze e Markus Michael. " Failure Analysis of High-Strength Fiber Ropes". Materials Science Forum 825-826 (julho de 2015): 891–98. http://dx.doi.org/10.4028/www.scientific.net/msf.825-826.891.
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Until the present days, in discontinuous conveyor systems, e.g. cranes and elevators, steel wire ropes and steel chains are the exclusively used tension members. Nevertheless, these tension members are exhibiting essential disadvantages, e.g. high dead weight, low bending flexure and high susceptibility to corrosion. For fulfilling the steadily increasing requirements especially in running ropes, alternative tension members have to be developed and approved concerning their series-production readiness by utilization of new technologies and new materials. High-strength fiber ropes are demonstrating promising mechanical properties, regarding tensile strength, vibration behavior and bending fatigue life. Still, the application of such high-strength fiber ropes is limited, due to unavailable systematic investigations and insufficient guidelines for dimensioning and processes for determination of discard criteria. With the help of new technologies and procedures, e.g. multi-zone cyclic bend-over-sheave (CBOS) test machinery and computer-assisted tomography, new knowledge concerning the wear behavior of fiber ropes is to be gained and new discard criteria are to be developed.
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Ali, Qaisar, Tom Schacher, Mohammad Ashraf, Bashir Alam, Akhtar Naeem, Naveed Ahmad e Muhammad Umar. "In-Plane Behavior of the Dhajji-Dewari Structural System (Wooden Braced Frame with Masonry Infill)". Earthquake Spectra 28, n.º 3 (agosto de 2012): 835–58. http://dx.doi.org/10.1193/1.4000051.
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This paper presents experimental and numerical investigations conducted on typical dhajji buildings found in the northern mountainous areas of Kashmir and surrounding regions to evaluate their in-plane lateral load response. The experimental work included an in-plane quasistatic cyclic test on three full-scale walls as well as monotonic tension and bend tests on main connections. The test results show that the dhajji-dewari system of buildings possesses tremendous resilience against lateral forces. The function of connections, especially the connections between the vertical posts and bottom plate, control the performance of the system. The test results also indicate that although masonry infill does not contribute to lateral load capacity, it significantly increases the energy dissipation capacity of system. The data accrued from the tests has been used in nonlinear static push-over analysis of the numerical models to develop simplified analytical tools for facilitating lateral load performance evaluation of dhajji structures.
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Fei, Kang, e Jinxin Xu. "Dynamic Behavior of Clay-Aggregate Mixtures". Advances in Materials Science and Engineering 2017 (2017): 1–10. http://dx.doi.org/10.1155/2017/2479507.
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Clay-aggregate mixtures are frequently used in engineering practice. To improve the understanding of the effects of coarse particles on the dynamic behavior of clay-aggregate mixtures, series of stress controlled cyclic triaxial tests were performed on clay specimens with various glass bead contents. The results show that the initial shear modulus of clay-aggregate mixtures increased with the increase of the coarse aggregate content and the confining stress. At the confining stress of 100, 200, and 400 kPa, the addition of 32% coarse particles caused an increase in the initial shear modulus of 117%, 110%, and 67%, respectively. Moreover, the normalized shear modulus decreased and damping ratio increased with the coarse aggregate content, and the influence of the confining stress on the strain-dependent dynamic properties was negligible. The specimen with a higher coarse aggregate content was observed to have larger cyclic shear strength and smaller excess pore water pressure, but the effects of the coarse aggregate content became less pronounced under large cyclic stresses.
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Okerstrom, S., W. Geng, D. Kramer e W. Gerberich. "Slip Band Analysis by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM)". Microscopy and Microanalysis 3, S2 (agosto de 1997): 1273–74. http://dx.doi.org/10.1017/s1431927600013258.
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Fatigue is a common cause of failure in components subjected to cyclic stresses. Repeated loads much smaller than the yield stress of the material can cause a fatigue failure. One such component subject to cyclic stresses is a titanium heart valve housing. The valve is subjected to a low level of stress with each heart beat as a disc pivots and closes against the housing. Interest in the initiation of fatigue in such components was an impetus to examine surface plasticity and accumulated damage which could lead to fatigue initiation. Grade 4 titanium used in heart valves and pure titanium have been studied.The three phases of fatigue are initiation of a crack, propagation, and catastrophic failure. Minimum defect size for crack propagation and failure are fairly well understood by scientists and engineers. However, the initiation portion of fatigue as a function of accumulated surface microplasticty is less well defined. SEM and AFM have been be used to evaluate microplasticity on the surface of titanium and correlate damage accumulation to the initiation of a crack.Fully reverse loaded four point bend testing was conducted on a an electropolished pure titanium sample 15 mm by 5 mm by 1 mm thick. The sample was oxidized at 300°C for one hour prior to fatigue testing. The sample was fatigued for 25,000 cycles using a ±45N load.