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1
Perny, G. "Oscillator strength of instantaneous diatomic sodium molecules." Zeitschrift f�r Physik D Atoms, Molecules and Clusters 21, no. 4 (1991): 293–94. http://dx.doi.org/10.1007/bf01438399.
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Nasser, Hussain Ali Bilal Ali Ahmed Ibn Sina Eman Sabeeh Hussein. "The Momentary Strength Exercisesand The Strength Distinguished By Speedwith Electrical Stimulation (Ems) And Its Effect On Some Biomechanical Variables And Achievement Of Hammer Throw." Multicutural Education 7, no. 4 (2021): 29. https://doi.org/10.5281/zenodo.4661597.
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<strong><em>Article History</em></strong> Received: January 04, 2021 <em>The effectiveness of throwing a hammer is one of the of games that require high-level technical performance and requires that the archers possess a correlation in Physical abilities such as types of strength rotational speed and compatibility as well as mastering the technical aspects according to the mechanical conditions that characterize this effectiveness, Through the experience of field researchers in the field of athletics, especially in throwing events, he noted that there is a low level of digital achievement and a large difference between the numbers recorded in this event for the youth category between the countries of the world and what is recorded for hammer archers in Iraq. The importance of research in preparing the momentary strength exercises and the strength distinguished by speed with electrical stimulation (EMS) and knowing their effect on some vital mechanical variables and the level of archers achievement of the category (youth) The research assumes that there are statistically significant differences between the pre and posttests of the research sample in values(Angular transmission speed, Hammer launch speed, The instantaneous strength of throwing for the full performance of the two legs , The instantaneous strength of throwing from a steadfast leg. The instantaneous push time of the arms at the moment of throwing , The instantaneous strength of the arms at the throwing, Completion distance for full performance). The implementation of the training curriculum took 12 weeks, at the rate of (3) training units per week, i.e. with a total of (36) training units during the research period. The researcher has concluded several conclusions, the most important of which were the effectiveness of exercises (instantaneous strength and strength distinguished by speed with electrical stimulation), which were used within the prepared training Approach In improving the values of the number of biomechanical variables at the moment of throwing, which had a significant impact on the Evolution of achievement.</em>
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Biscarini, Andrea. "Measurement of Power in Selectorized Strength-Training Equipment." Journal of Applied Biomechanics 28, no. 3 (2012): 229–41. http://dx.doi.org/10.1123/jab.28.3.229.
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The author derived the exact analytical expression of the instantaneous joint power in exercises with single-joint, variable-resistance, selectorized strength-training equipment, taking into account all the relevant geometric, kinematic, and dynamic variables of both the movable equipment elements (resistance input lever, cam–pulley system, weight stack) and of the user’s exercising limb. A numerical algorithm was also designed to express, in the presence of a cam, the rectilinear kinematic variables of the weight stack as a function of the rotational kinematic variables of the resistance input lever, and vice versa. Given that information, one can measure the value of the instantaneous and mean joint power exclusively by means of a linear encoder placed on the weight stack or, alternatively, only by the use of an angular encoder placed on the rotational axis of the resistance lever. The results highlight that, for knee extension exercises with leg extension equipment, the real values of both instantaneous and mean joint power may differ by more than 50% in comparison with the values obtained by taking into account only the mass and velocity of the weight stack. These differences are notable not only in explosive exercises, but also whenever considerable joint velocities/accelerations occur within the range of motion.
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Rakhmonov, Jovid, Kun Liu, Paul Rometsch, Nick Parson, and X. Grant Chen. "Improving the Mechanical Response of Al–Mg–Si 6082 Structural Alloys during High-Temperature Exposure through Dispersoid Strengthening." Materials 13, no. 22 (2020): 5295. http://dx.doi.org/10.3390/ma13225295.
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The feasibility and efficacy of improving the mechanical response of Al–Mg–Si 6082 structural alloys during high temperature exposure through the incorporation of a high number of α-dispersoids in the aluminum matrix were investigated. The mechanical response of the alloys was characterized based on the instantaneous high-temperature and residual room-temperature strengths during and after isothermal exposure at various temperatures and durations. When exposed to 200 °C, the yield strength (YS) of the alloys was largely governed by β” precipitates. At 300 °C, β” transformed into coarse β’, thereby leading to the degradation of the instantaneous and residual YSs of the alloys. The strength improvement by the fine and dense dispersoids became evident owing to their complementary strengthening effect. At higher exposure temperatures (350–450 °C), the further improvement of the mechanical response became much more pronounced for the alloy containing fine and dense dispersoids. Its instantaneous YS was improved by 150–180% relative to the base alloy free of dispersoids, and the residual YS was raised by 140% after being exposed to 400–450 °C for 2 h. The results demonstrate that introducing thermally stable dispersoids is a cost-effective and promising approach for improving the mechanical response of aluminum structures during high temperature exposure.
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Yan, Jianbing, Xiaoqiang Zhang, Kai Wang, Xuanmin Song, Shaofei Yue, and Jian Hou. "Experimental Study on Creep Characteristics and Long–Term Strength of Anthracite." Processes 11, no. 3 (2023): 947. http://dx.doi.org/10.3390/pr11030947.
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Coal pillars from old mines undergo creep, a type of time−dependent deformation. Research on underground engineering stability of coal mines has increasingly focused on long−term strength as an important mechanical index of the creep characteristics of coal pillars. This study performed conventional triaxial compression and triaxial creep tests of anthracite under different confining pressures. The creep law of anthracite and the long−term strength of anthracite was studied according to the test results. The test results demonstrated the following: (1) The conventional elastic modulus and peak strain of anthracite increased exponentially with the confining pressure. (2) Under low stress levels, anthracite exhibited only instantaneous deformation and attenuation creep. In contrast, anthracite exhibited instantaneous deformation, attenuation creep, and steady creep under high stress levels; accelerated creep occurred until failure when the stress reached a particular value. (3) By fitting the steady−state creep rate of anthracite under high stress levels, the functional relationship between axial stress and steady−state creep rate was established, and the threshold of the steady−state creep rate in high−stress−level areas was suggested as the optimum long−term strength of anthracite. (4) The ratio of the long−term strength to instantaneous strength under various confining pressure grades ranged from 70% to 91%.
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Wang, Yu, and Feng Liu. "Experimental Investigation on Mechanical Properties of Soft Rock under Instantaneous Triaxial Compression." Advanced Materials Research 594-597 (November 2012): 218–21. http://dx.doi.org/10.4028/www.scientific.net/amr.594-597.218.
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Using the RMT-150C rock mechanics test system, the instantaneous triaxial compression tests for muddy siltstone were carried out under different confining pressures, and the instantaneous mechanical properties of soft rock were obtained. The results show that the strength parameters of sample have a positive linear relation with the confining pressure, and the sensitivity of peak strength on the confining pressure is higher than that of residual strength. The elastic and deformation modulus of sample linearly increase with the confining pressure going up, and the elastic modulus is more sensitive to the confining pressure. The soft rock sample shows typical ductility failure characteristic, while the damage characteristic is mainly shear failure and the shear failure angle linearly decreases with the confining pressure going up.
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Larionov, Evgeny. "A long-term strength of constructive materials." MATEC Web of Conferences 251 (2018): 04068. http://dx.doi.org/10.1051/matecconf/201825104068.
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A long-term strength materials under an axially loading of constructive elements is considered and the estimates of this strength are reduced. The proposed approach is connected with the notion so-called energy of entirety [1]. It is notable that this value can be used instead of known Reiner’s invariant [2]. A material (concrete, steel, graph) is considered as a union of its links with statistical disturbed strengths [3]. This conception allows to modify Boltzmann’s principle superposition of fraction creep deformations [4] and in addition, implies the identity of non-linear stresses function for the instantaneous and retarding deformations. The degeneration of long-term strength because of vibrational influence take into account and the strengthening of the materials in the course of their formation is considered.
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Brovka, A. G., I. V. Dedyulya, and A. A. Murashko. "DEPENDENCE OF STRENGTH CHARACTERISTICS OF MUDSTONE-LIKE CLAYS FROM THE AMOUNT OF UNFROZEN WATER." Nature Management, no. 2 (December 28, 2021): 96–105. http://dx.doi.org/10.47612/2079-3928-2021-2-96-105.
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The article presents a methodology for studying of the strength properties of frozen soils using a modernized automated testing complex (AIC "ASIS") produced by NPP "Geotek" LLC (Penza, Russia) and determining the dependence of the amount of unfrozen water in the soil on the temperature using an adiabatic calorimeter. On the samples of mudstone-like clay, it was found that the conditionally instantaneous strength of frozen soils depends non-linearly on the temperature and salt presence in pore solution. The dependences of the conditional instantaneous strength of mudstone – like clay samples on the amount of unfrozen water in these samples are studied. It is established that the strength properties of clay soils at negative temperatures are mainly determined by the total amount of unfrozen water. The genesis of unfrozen water (temperature or the combined effect of temperature and salt concentration in the pore solution) does not matter.
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Dong, Jinyu, Tanyu Wang, and Yawen Zhao. "Experimental Study on Shear Creep Characteristics of Residual Soil with Different Stone Content." Applied Sciences 14, no. 15 (2024): 6829. http://dx.doi.org/10.3390/app14156829.
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The residual soil on a slope can slowly move downward under the influence of gravity, forming a creep landslide. These types of landslides are known for their extensive coverage, significant magnitude, and prolonged duration of hazard. A systematic study of the creep properties of creep landslide geotechnical bodies is essential for the analysis of the deformation process and long-term safety evaluation of landslides. This paper focuses on studying a creep landslide involving residual soil in western Henan Province. The creep characteristics of residual soil with different stone content are investigated through direct shear creep experiments. The findings reveal that stone content has a profound impact on the creep behavior of residual soil. As the stone content of the soil increased, the structure of the test soil changed significantly, resulting in a gradual decrease in its shear creep. The Burgers model can effectively fit the deceleration creep and steady-state creep stages of the residual soil. With the increase in stone content, the four parameters of the Burgers model show a significant increase, with the instantaneous elasticity coefficient G1 and the viscosity coefficient η1 experiencing more noticeable changes. The average long-term strength of specimens with different stone content is only 54% of their instantaneous strength. Additionally, as the stone content increases, the ratio of long-term strength to instantaneous strength also increases. Notably, the long-term strength of specimens with 10–30% stone content is significantly lower than that of specimens with 50–70% stone content.
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Ning, Haifeng, Hualin Zheng, and Xinman Yuan. "Establishment of instantaneous milling force prediction model for multi-directional CFRP laminate." Advances in Mechanical Engineering 13, no. 6 (2021): 168781402110277. http://dx.doi.org/10.1177/16878140211027706.
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Carbon fiber reinforced polymer (CFRP) is widely used in the aerospace field due to its light weight and high strength. The CFRP milling process is prone to damage such as burrs and tears. The cutting force is closely related to the damage of CFRP and tool wear. In this paper, a back propagation (BP) neural network model of cutting force and edge force coefficients was established. The model considers the effects of instantaneous uncut chip thickness, fiber cutting angle, spindle speed, and axial depth of cut. The unidirectional CFRP laminate instantaneous milling model considering the cutting edge force was further established. The instantaneous milling force prediction model was extended to multi-directional CFRP laminates. And the relationship between the damage mechanism of CFRP and the instantaneous milling force was analyzed. Experiments have proved that the instantaneous milling force prediction model built in this paper has high accuracy.
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Gryspeerdt, Edward, Johannes Quaas, Sylvaine Ferrachat, et al. "Constraining the instantaneous aerosol influence on cloud albedo." Proceedings of the National Academy of Sciences 114, no. 19 (2017): 4899–904. http://dx.doi.org/10.1073/pnas.1617765114.
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Much of the uncertainty in estimates of the anthropogenic forcing of climate change comes from uncertainties in the instantaneous effect of aerosols on cloud albedo, known as the Twomey effect or the radiative forcing from aerosol–cloud interactions (RFaci), a component of the total or effective radiative forcing. Because aerosols serving as cloud condensation nuclei can have a strong influence on the cloud droplet number concentration (Nd), previous studies have used the sensitivity of theNdto aerosol properties as a constraint on the strength of the RFaci. However, recent studies have suggested that relationships between aerosol and cloud properties in the present-day climate may not be suitable for determining the sensitivity of theNdto anthropogenic aerosol perturbations. Using an ensemble of global aerosol–climate models, this study demonstrates how joint histograms betweenNdand aerosol properties can account for many of the issues raised by previous studies. It shows that if the anthropogenic contribution to the aerosol is known, the RFaci can be diagnosed to within 20% of its actual value. The accuracy of different aerosol proxies for diagnosing the RFaci is investigated, confirming that using the aerosol optical depth significantly underestimates the strength of the aerosol–cloud interactions in satellite data.
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Mukai, Tohru, and Kohji Iida. "Instantaneous target strength measurement of live squid with synchronized video image." Journal of the Acoustical Society of America 109, no. 5 (2001): 2305. http://dx.doi.org/10.1121/1.4744093.
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Bai, Jian Yu, Senlin Tong, Zai He Yu, and Di Zheng. "Kinetics Analysis and Simulations on Load Fork Mechanism in Forward-Type Stacker." Applied Mechanics and Materials 37-38 (November 2010): 608–13. http://dx.doi.org/10.4028/www.scientific.net/amm.37-38.608.
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It is frequently reported by customers that the lower-left and lower-right wheels in the load fork mechanism of a kind of forward-type stacker designed based on static strength analysis are abraded faster than expected. In this paper, we studied by means of kinetics analysis and simulations the forces applied on parts of the fork mechanism. The simulation results show that the maximum values of instantaneous forces during operations are much higher than those derived based static force analysis, and thus explained the reason of the above-mentioned abnormal abrasion. The results also mean that static force analysis is not suitable for part strength design. Instead, one shall adopt kinetics analysis to explore the instantaneous forces in design.
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Cerik, Burak Can, and Joonmo Choung. "Progressive Collapse Analysis of Intact and Damaged Ships under Unsymmetrical Bending." Journal of Marine Science and Engineering 8, no. 12 (2020): 988. http://dx.doi.org/10.3390/jmse8120988.
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This study examined the hull girder strength of intact and damaged ships by adopting the incremental-iterative method for progressive collapse analysis, which was extended to the general case of the unsymmetrical bending of beams with an arbitrary cross-section. The sources of an unsymmetrical loading, including rotation of the loading plane and section asymmetry caused by structural damage, are described. A fast and robust procedure is presented to determine the translation and rotation of the instantaneous neutral axis at each curvature increment when applying Smith’s progressive collapse analysis method. A series of analyses were conducted on a double hull VLCC and a bulk carrier, considering various loading plane angles and damage conditions. The decrease in ultimate strength and the influences of rotation of the instantaneous neutral axis and ship heeling are discussed. The proposed method can be used for a rapid and rational assessment of the hull girder strength under adverse conditions.
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Bo, Li, Ge Wenqing, Zhao Yiqiang, and Chen Shanshi. "Shift Force Loading Rules Research for Automated Mechanical Transmission." Open Mechanical Engineering Journal 9, no. 1 (2015): 574–78. http://dx.doi.org/10.2174/1874155x01509010574.
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To improve the system reliability and reduce the shift shock of Automated Mechanical Transmission, shift force loading rules is researched on the basis of strength and stiffness analyzing of shift fork. The shift mechanism of A-5- speed manual transmission is used as an example to illustrate the simulation, co-relation and validation of the shift fork strength and stiffness. The three-dimensional model of the shift fork is built and the finite element analysis model based on ABAQUS is established. And then, the influence of strength and stiffness of shift fork on the shift force loading rules can be analyzed. The fork tends to deflect with the synchronizer sleeve during synchronization thus acting as a damper and storing energy, the maximum instantaneous force output by driving device under the strength requirement of shift fork is determined. The shift control strategy is corrected according to the stiffness analysis of shift fork. The results shown that, in order to meet the strength requirement of shift fork, the maximum instantaneous force for the 4 gear fork is 1185.5N. In the same time, the maximum deformation on fork legs is 0.617 mm. The research provides a sufficient theoretical basis for formulating the shift control strategy.
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Chen, Hui Guo, Ying Min Li, Wei Zhang, and Zhe Qian Wu. "The Parameter Study of Instantaneous Spectrum of Spatially Varying Ground Motion." Applied Mechanics and Materials 166-169 (May 2012): 2353–57. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.2353.
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In this paper ,the parameter study of the instantaneous spectrum model is transformed to that of strength envelope model and instantaneous frequency model, based on the real ground motion array data, the statistical analysis result of the parameter of multipoint ground motion at local sites indicate that the most parameters are associated with projection distance and soil layer thickness, and the regression model and the value selection of various parameters provided in this paper can also be used for the reference of artificial synthesis of multipoint ground motion.
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Fan, Qiu Yan, Cai Lin Liu, Ke Qing Yang, and Mei Qian Wang. "Test Study on Creep Character of Anchor Rod in Argillaceous Soft Rock." Advanced Materials Research 396-398 (November 2011): 565–70. http://dx.doi.org/10.4028/www.scientific.net/amr.396-398.565.
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The creep character of anchor rod in argillaceous soft rock is remarkable. The big undisturbed mudstone samples in Nanning Basin as a typical argillaceous soft rock is chosen to the research object in this paper. The laboratory simulated destructive tests and the creep tests of full grouted anchor rod have been down. Through the destructive tests of mudstone sample, the instantaneous adhesive strength between the anchor body and mudstone in Nanning Basin is 70kPa. By analyzing the creep curves of anchor rod, a conclusion is that there is a long-term adhesive strength of anchor rod in argillaceous soft rock. When the design adhesive strength of anchor rod is less than the long-term adhesive strength, eventually the anchor rod is stable during the process of long-term pull-out. When the design adhesive strength of anchor rod is greater than the value, the creep of anchor rod with the time will do not stop until the anchor rod failure. The greater difference value between the instantaneous and long-term adhesive strength, the faster the rate of creep, the faster the anchor rod failure. Finally, for the permanent support engineering design of anchor rod in argillaceous soft rock, the paper gives two principles, as follows: (1) the design of anchor rod in argillaceous soft rock must be determined according to the long-term adhesive strength. (2) by using variety of technical measures, the impact of various factors on the creep of anchor rod will be decreased.
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Matsuo, Tsuyoshi, Masayuki Nakada, and Kazuro Kageyama. "Prediction of fiber-directional flexural strength of carbon fiber-reinforced polypropylene based on time–temperature superposition principle." Journal of Composite Materials 52, no. 6 (2017): 793–805. http://dx.doi.org/10.1177/0021998317714638.
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This study verified that the time–temperature superposition principle for fiber-directional flexural strength can be applied to thermoplastic composites undergoing instantaneous fast phenomena such as impact failure and long-term phenomena such as creep failure, by constructing the time- and temperature-dependent master curve of relaxation modulus of thermoplastic resin. The master curve could be transformed to another master curve that predicts fiber-directional flexural strength of carbon fiber-reinforced thermoplastic composites based on the micro-buckling failure theory expressed mainly by the resin’s elastic modulus. The experimental results obtained from high-speed bending test, static bending test at various temperatures, and creep bending test demonstrated that kink band failure occurred on the compressive surface of the specimen at every test condition. This validation and verification related to thermoplastic composites made it possible to predict static and dynamic flexural strengths at arbitrary temperature and creep flexural strength.
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Jia, Jinbo, Yansen Wang, and Yangguang Leng. "Unloading Creep Characteristics of Frozen Clay Subjected to Long-Term High-Pressure K0 Consolidation before Freezing." Advances in Civil Engineering 2019 (September 18, 2019): 1–18. http://dx.doi.org/10.1155/2019/7192845.
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Artificial ground freezing has been widely applied in the construction of vertical shafts in deep and thick alluvia. As an important factor, the in situ creep behavior of deep, frozen soil affects the mechanical properties of frozen walls and the safety and stability of shaft linings. Acquiring creep characteristics and deep soil parameters by methods that ignore the engineering and geological situations is currently inadvisable. A series of triaxial unloading tests were conducted with frozen clay subjected to long-term high-pressure K0 consolidation before freezing to research the unloading creep characteristics, creep strength, and other parameters of the clay, and the results indicated the following: (1) The creep behaviors of frozen clay are affected by the consolidation time and consolidation stress. Long-term high-pressure K0 consolidation reduces the creep strain and creep rate of frozen clay. (2) The decrease in the ice and the unfrozen water contents of frozen clay caused by the prolongation of consolidation time result in an increase in the long-term strength and instantaneous strength. Consolidation time has an obvious effect on long-term strength and weakens the creep property of frozen clay. Consolidation stress significantly affects the instantaneous strength. (3) The deformation resistance capability of frozen clay is enhanced by compaction; thus, E1, η1, and η2 increase with prolonged consolidation, and the nonlinearity of the accelerated creep increases.
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Pesterev, A. A., S. S. Kostinskiy, and N. D. Narakidze. "Empirical substantiation of the advantage of using the modified method of symmetrical components to estimate the value of zero-sequence current in distribution grids." Вестник Северо-Кавказского федерального университета, no. 4 (103) (2024): 28–38. http://dx.doi.org/10.37493/2307-907x.2024.4.3.
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Introduction. The tendency of growth in the number and increase in the installed capacity of single-phase nonlinear electric consumers leads to the deterioration of power quality. One of the criteria for assessing the quality of electric power is the zero-sequence and reverse sequence asymmetry indices. And the zero-sequence asymmetry coefficient is conditioned by the zero-sequence current strength. Goal. To empirically substantiate the advantages of using the method based on the measurement of instantaneous values of current strength synchronously on three phases for one period to estimate the zero-sequence asymmetry coefficient, as compared to the method of symmetrical components, implemented using the turnaround operator, for a more accurate assessment of current strength asymmetry in distribution networks. Materials and methods. To achieve the set goal, an experimental stand of the power supply system was designed and assembled. The developed stand allowed to obtain a set of synchronously measured instantaneous values of current and voltage in each phase, as well as in the zero working conductor, when the magnitude, nature and non-sinusoidality of the load changes independently in each phase. In this case, the criterion for assessing the accuracy of calculation of the zero-sequence asymmetry coefficient was the value of current measured in the neutral working conductor. Results and discussion. The use of the basic method of symmetrical components to determine the zero sequence current in the case of amplitude-phase asymmetry under active-inductive non-sinusoidal load leads to an unacceptable error, the median value of which is 21.25%. In order to reduce this error it is recommended to use in these modes the method based on the measurement of instantaneous values of current synchronously on three phases for one period, in this case the median value of the error does not exceed 0.16 %. Conclusion. To reduce the zero-sequence current calculation errors, it is recommended to use a method based on the measurement of instantaneous current values synchronously on three phases for one period.
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Lesik, Dale F., and D. J. Laurie Kennedy. "Ultimate strength of fillet welded connections loaded in plane." Canadian Journal of Civil Engineering 17, no. 1 (1990): 55–67. http://dx.doi.org/10.1139/l90-008.
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Fillet welded connections are frequently loaded eccentrically in shear with the externally applied load in the same plane as the weld group. While some current design tables are based on ultimate strengths, methods of analysis that incorrectly mix inelastic and elastic approaches are still used. These methods give conservative and variable margins of safety. Design standards generally use a lower-bound approach basing strengths on the longitudinal value neglecting, conservatively, the increase in strength for other directions of loading. The factored resistance of fillet welds, as a function of the direction of loading, is established based on ultimate strength expressions developed herein and using geometric, material variations, and test-to-predicted ratios reported in the literature. Factored resistances of eccentrically loaded fillet weld groups are established. These are basesd on the method of instantaneous centres, ultimate strengths, and the load–deformation expressions developed herein that are functions of the angle of loading. Also, statistical data on geometry, material variations, and the comparison of predicted strengths with the full-scale test results of others are used. Tables of design coefficients giving factored resistances for various eccentrically loaded fillet welded connections are developed. The coefficients, on the average, are essentially the same as those in current design tables. Key words: connections, design tables, eccentric, fillet welds, limit states, ultimate strength.
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Alqahtani, Fahad K., and Idrees Zafar. "Evaluating the creep behaviour of plastic-processed aggregate-based concrete." Materials Science-Poland 43, no. 1 (2025): 51–66. https://doi.org/10.2478/msp-2024-0052.
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Abstract In this study, the mechanical and creep characteristics of concrete integrating the plastic-processed aggregates (PPAs) were evaluated. A constant water-to-cement ratio was used with PPAs that were incorporated at 25, 50, 75 and 100% to formulate the concrete mixes. The mixing of PPAs in concrete has resulted in a decrease in mainstream mechanical properties, including dry density, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity by 18.6, 27.8, 37.2, 26.4, and 63.6%, respectively, at 100% aggregate replacement. The instantaneous creep strain, ultimate shrinkage strain, and ultimate creep strain of the PPA concrete mixes were significantly higher than that of the reference concrete especially at total replacement of PPA in the concrete mix. The increase in instantaneous creep strain, ultimate shrinkage strain, and ultimate creep strain at 100% replacement was found to be 100, 119, and 69%, respectively. The increase in creep strains of the PPA concrete mixes can be attributed to the reduction in the mechanical properties of subsequent concrete. Even with the reduction in the mechanical and creep properties of PPA concrete, the use of plastic-based aggregates in non-structural concrete applications is encouraged.
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Rowe, Nick P., Lily Cheng Clavel, and Patricia Soffiatti. "Failure without Tears: Two-Step Attachment in a Climbing Cactus." Biomimetics 8, no. 2 (2023): 220. http://dx.doi.org/10.3390/biomimetics8020220.
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Climbing plants can be extremely adaptable to diverse habitats and capable of colonising perturbed, unstructured, and even moving environments. The timing of the attachment process, whether instantaneous (e.g., a pre-formed hook) or slow (growth process), crucially depends on the environmental context and the evolutionary history of the group concerned. We observed how spines and adhesive roots develop and tested their mechanical strength in the climbing cactus Selenicereus setaceus (Cactaceae) in its natural habitat. Spines are formed on the edges of the triangular cross-section of the climbing stem and originate in soft axillary buds (areoles). Roots are formed in the inner hard core of the stem (wood cylinder) and grow via tunnelling through soft tissue, emerging from the outer skin. We measured maximal spine strength and root strength via simple tensile tests using a field measuring Instron device. Spine and root strengths differ, and this has a biological significance for the support of the stem. Our measurements indicate that the measured mean strength of a single spine could theoretically support an average force of 2.8 N. This corresponds to an equivalent stem length of 2.62 m (mass of 285 g). The measured mean strength of root could theoretically support an average of 13.71 N. This corresponds to a stem length of 12.91 m (mass of 1398 g). We introduce the notion of two-step attachment in climbing plants. In this cactus, the first step deploys hooks that attach to a substrate; this process is instantaneous and is highly adapted for moving environments. The second step involves more solid root attachment to the substrate involving slower growth processes. We discuss how initial fast hook attachment can steady the plant on supports allowing for the slower root attachment. This is likely to be important in wind-prone and moving environmental conditions. We also explore how two-step anchoring mechanisms are of interest for technical applications, particularly for soft-bodied artefacts, which must safely deploy hard and stiff materials originating from a soft compliant body.
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Yu, Qiaojuan, Qizhi Zhu, Yunxing Lu, and Zhanyou Luo. "Experimental Investigation and Micromechanics-Based Analytical Modeling of Creep and Relaxation Behaviors of Beishan Granite." Applied Sciences 12, no. 23 (2022): 12083. http://dx.doi.org/10.3390/app122312083.
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This paper investigates experimentally and numerically the short- and long-term strength and deformation behaviors of Beishan granite at room temperature. Single-stage creep, relaxation, and conventional triaxial compression tests were performed on cylindrical rock samples. Its typical brittle response is captured and the dependence of peak strength on confining pressure and time-dependent response on deviatoric stress are revealed. For constitutive modeling, a unified micromechanics-based plasticity-damage model is formulated based on the Mori–Tanaka method and the subcritical cracking theory postulate, with the focus on simulating both instantaneous strain and time-dependent deformation process over a broad range of time scales. Its unification is achieved by representing the evolution of damage, which is strongly coupled with plastic deformation induced by frictional sliding along closed cracks, as an internal variable that can be decomposed into instantaneous and time-dependent parts. The performance of the model with analytical predictions is well validated using the experimental results on Beishan granite.
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Alberti, Tommaso, Paola De Michelis, Lucia Santarelli, Davide Faranda, Giuseppe Consolini, and Maria Federica Marcucci. "Tracking Geomagnetic Storms with Dynamical System Approach: Ground-Based Observations." Remote Sensing 15, no. 12 (2023): 3031. http://dx.doi.org/10.3390/rs15123031.
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Using a dynamical systems approach, we examine the persistence and predictability of geomagnetic perturbations across a range of different latitudes and levels of geomagnetic activity. We look at the horizontal components of the magnetic field measured on the ground between 13 and 24 March 2015, at approximately 40 observatories in the Northern Hemisphere. We introduced two dynamical indicators: the extremal index θ, which quantifies the persistence of the system in a particular state and the instantaneous dimension d, which measures the active number of degrees of freedom of the system. The analysis revealed that during disturbed periods, the instantaneous dimension of the horizontal strength of the magnetic field, which depends on latitude, increases, indicating that the geomagnetic response is externally driven. Furthermore, during quiet times, the instantaneous dimension values fluctuate around the state-space dimension, indicating a more stochastic and thus less predictable nature system.
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Harbig, P., I. Barat, P. Lund Nielsen, and E. M. Damsgaard. "Instantaneous detection of nonadherence: quality, strength, and weakness of an electronic prescription database." Pharmacoepidemiology and Drug Safety 21, no. 3 (2012): 323–28. http://dx.doi.org/10.1002/pds.2351.
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Zhou, Jianguo, Liyuan Ren, and Zhiliang Liu. "Instantaneous lift-off distance estimation in magnetic flux leakage testing of steel wire ropes." Journal of Physics: Conference Series 2184, no. 1 (2022): 012051. http://dx.doi.org/10.1088/1742-6596/2184/1/012051.
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Abstract Steel wire rope (SWR) defects plagued its application in many important fields, such as cranes, ports, etc. However, the accuracy of SWRs’ local flaws detection based on magnetic flux leakage (MFL) method is susceptible to the lift-off distance. This paper proposes an instantaneous lift-off distance estimation method to study the effect of lift-off distance on MFL detection for SWR. We firstly derive the relation between the lift-off distance and the MFL field strength based on the magnetic dipole model. After obtaining the time-frequency representation of the MFL signal by using multi-synchrosqueezing transform, we extract the instantaneous amplitude (IA) of the strand signal without other noise interference. Finally, the nonlinear least-squares method is used to fit the relation between the IAs of the strand signals and the lift-off distances to achieve the estimation of the instantaneous lift-off distance. A SWR with three local flaws is tested to validate the proposed method. This work provides instantaneous monitoring of lift-off distances, and it can be used in future noise suppressing methods development or quantitative analysis of local flaws.
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Villalobos Céspedes, Daniel. "INSTANTANEOUS PRODUCTION GROWTH IN A DYNAMIC ECONOMY." Economía y Sociedad 28, no. 64 (2023): 1–32. http://dx.doi.org/10.15359/eys.28-64.1.
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The purpose of this study is to measure the average and instantaneous rates of production growth and to provide new formulas for measuring the contribution to and share of resources in that growth. This is the key idea in a new method of attack as suggested by Cobb and Douglas—as of yet not solved by economic growth theory—to demonstrate that distribution processes are modeled on those of the production of value. We intend to validate the strength of the proposed model by systematizing and analyzing production, investment and employment data from a dynamic economy, i.e., the United States of America, provided by the Bureau of Economic Analysis (BEA) and the Federal Reserve (Fed) for the years 2012 to 2022, the results of which can be found in the Appendix. We conclude that greater convergence with equity between labor and capital contribution and share in production growth results when the elasticity of its composition is between ½ and 1. Outside of this range, we see divergence with inequity adverse to labor. Our model could improve the formulation and execution of macroeconomic policies (fiscal, monetary and trade) and promote greater convergence/equity in the contribution to and share of resources in production growth.
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Zhu, Chun Mei, You Zhi Wang, Bin Yan, and Hong Wei Gao. "Numerical Simulation on Real-Time Temperature Field and Strength Field of Bridge Mass Concrete." Applied Mechanics and Materials 99-100 (September 2011): 346–49. http://dx.doi.org/10.4028/www.scientific.net/amm.99-100.346.
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Access to the internal concrete temperature of the instantaneous temperature field and the strength of the field Real-time monitoring , Concrete temperature field and stress field of the numerical simulation analysis method was proposed . Intuitive accurate prediction that the temperature field and stress field provide a reliable basis on the distribution of temperature control schemes and the construction scheme formulated.
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Ojha, Maheswar, Uma Shankar, and Ranjana Ghosh. "Gas Hydrates, Subsurface Structures and Tectonic Features of the Tuaheni Landslide Complex in the Northern Hikurangi Margin, New Zealand, Revealed by Seismic Attribute Analysis." Journal of Marine Science and Engineering 11, no. 7 (2023): 1359. http://dx.doi.org/10.3390/jmse11071359.
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The Tuaheni Landslide Complex, located on the upper slope of the northern Hikurangi Margin in New Zealand, is a unique place to research on slow slip creep-like deformation and seabed failure, as well as their possible relationship with the presence of gas hydrates, cold seeps, and fluid migration. Based on the visual interpretation of seismic data, it is sometimes very difficult to identify various subsurface structures and tectonic features. We study certain seismic attributes, namely the reflection strength, instantaneous frequency, instantaneous phase, and the Hilbert transform, in the Tuaheni Landslide Complex and observe that these attributes play a very important role in identifying and interpreting various subsurface geological features and bed boundaries that are not clearly visible in the seismic sections. In general, these seismic attributes are studied to identify hydrocarbons such as oil and gas. However, in this present study these seismic attributes nicely illustrate the fluid migration pathways, the decollement of the sediment slide, the base of the debris flow, the base of the deformed sediment and gas migration, etc., along two perpendicular seismic profiles crossing the Site U1517 of IODP Expedition 372. The instantaneous phase and Hilbert transform attribute depict the bed boundaries and discontinuities, whereas the reflection strength and instantaneous frequency attributes characterize the various strata in terms of whether they are associated with fluid at their bases. The possible role of tectonic activity and seafloor slope failure due to gas hydrate dissociation and vice versa is clearly visible through fluid-filled weak zones in the seismic attribute volumes. Gas hydrates are dissociating and BSRs are abruptly pinching out towards the seafloor due to the movement of hot fluid and free gas, enhancing seafloor sliding and local tectonic activities together.
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Dong, Jinyu, Yawen Zhao, Handong Liu, et al. "Creep Characteristics of a Strongly Weathered Argillaceous Sandstone Sliding Zone and the Disaster Evolution Mechanism of the Huaipa Landslide, China." Applied Sciences 13, no. 15 (2023): 8579. http://dx.doi.org/10.3390/app13158579.
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The creep characteristics of sliding zones strongly influence slope deformation and long-term stability, as well as the occurrence of landslide catastrophes. In this paper, large-scale triaxial creep tests were performed on the strongly weathered argillaceous sandstone sliding zone of the Huaipa landslide in the Henan Province, China, to study its creep characteristics and long-term strength in natural and saturated states. Three-dimensional numerical simulations were conducted to analyze the deformation creep law and catastrophic evolution mechanism of the slope after excavation and rainfall. The results show that the sliding zone underwent appreciable creep deformation prior to failure, and that the progression of specimen damage with an increasing stress level followed decay creep → steady creep → accelerated creep. The stress level played a decisive role in the creep deformation, with higher stress levels resulting in higher instantaneous displacement, creep displacement, and longer times required to reach steady creep. The stress level also determined the specimen’s creep stage. When the stress level was low, the adjustment of the specimen’s internal structure was dominated by air space compression and particle movement, whereas particle fragmentation mostly occurred at high stress levels. The long-term rock strength was approximately 62–66% of the instantaneous strength, the internal friction angle decreased by approximately 8° relative to the instantaneous strength, and the cohesion decreased by approximately 30%. The slope foot unloaded and deformed owing to the excavation of a bauxite mine at its front edge, after which the slope deformed via creep. The landslide disaster occurred when the deformation was significantly accelerated and the slope started to slide as a whole once the sliding zone became water saturated owing to continuous rainfall. The simulation results indicate that the landslide can be divided into a front edge bulging zone, central sliding zone, and trailing edge tension zone, which provides valuable insight on the creep deformation evolution process and the disaster mechanism of the landslide under the action of front edge excavation and rainfall.
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Yang, B., C. T. Liu, T. G. Nieh, M. L. Morrison, P. K. Liaw, and R. A. Buchanan. "Localized heating and fracture criterion for bulk metallic glasses." Journal of Materials Research 21, no. 4 (2006): 915–22. http://dx.doi.org/10.1557/jmr.2006.0124.
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In this study, we demonstrated that the failure of bulk metallic glasses (BMGs) results from a sudden temperature rise within a shear band. Using a shear transformation zone model, we successfully calculated the temperature within a shear band and found it consistent with the observation from an in situ infrared thermographic system. The instantaneous temperature within a shear band at fracture agrees remarkably well with the glass transition temperature (Tg providing a new criterion to determine the strength of BMGs from their Tg. This agreement also discloses the fact that catastrophic failure of BMG is caused by the sudden drop in viscosity inside the shear band when the instantaneous temperature within a shear band approaches Tg.
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Zhou, W., and S. W. Jones. "Surface charge and calcium channel saturation in bullfrog sympathetic neurons." Journal of General Physiology 105, no. 4 (1995): 441–62. http://dx.doi.org/10.1085/jgp.105.4.441.
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Currents carried by Ba2+ through calcium channels were recorded in the whole-cell configuration in isolated frog sympathetic neurons. The effect of surface charge on the apparent saturation of the channel with Ba2+ was examined by varying [Ba2+]o and ionic strength. The current increased with [Ba2+]o, and the I-V relation and the activation curve shifted to more positive voltages. The shift of activation could be described by Gouy-Chapman theory, with a surface charge density of 1 e-/140 A2, calculated from the Grahame equation. Changes in ionic strength (replacing N-methyl-D-glucamine with sucrose) shifted the activation curve as expected for a surface charge density of 1 e-/85 A2, in reasonable agreement with the value from changing [Ba2+]o. The instantaneous I-V for fully activated channels also changed with ionic strength, which could be described either by a low surface charge density (less than 1 e-/1,500 A2), or by block by NMG with Kd approximately 300 mM (assuming no surface charge). We conclude that the channel permeation mechanism sees much less surface charge than the gating mechanism. The peak inward current saturated with an apparent Kd = 11.6 mM for Ba2+, while the instantaneous I-V saturated with an apparent Kd = 23.5 mM at 0 mV. This discrepancy can be explained by a lower surface charge near the pore, compared to the voltage sensor. After correction for a surface charge near the pore of 1 e-/1,500 A2, the instantaneous I-V saturated as a function of local [Ba2+]o, with Kd = 65 mM. These results suggest that the channel pore does bind Ba2+ in a saturable manner, but the current-[Ba2+]o relationship may be significantly affected by surface charge.
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CHRISTENSEN, K. T., and R. J. ADRIAN. "Statistical evidence of hairpin vortex packets in wall turbulence." Journal of Fluid Mechanics 431 (March 25, 2001): 433–43. http://dx.doi.org/10.1017/s0022112001003512.
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The structure of velocity in the outer region of turbulent channel flow (y+ [gsim ] 100) is examined statistically to determine the average flow field associated with spanwise vortical motions. Particle image velocimetry measurements of the streamwise and wall-normal velocity components are correlated with a vortex marker (swirling strength) in the streamwise–wall-normal plane, and linear stochastic estimation is used to estimate the conditional average of the two-dimensional velocity field associated with a swirling motion. The mean structure consists of a series of swirling motions located along a line inclined at 12°–13° from the wall. The pattern is consistent with the observations of outer-layer wall turbulence in which groups of hairpin vortices occur aligned in the streamwise direction. While the observational evidence for the aforementioned model was based upon both experimental and computational visualization of instantaneous structures, the present results show that, on average, the instantaneous structures occur with sufficient frequency, strength, and order to leave an imprint on the statistics of the flow as well. Results at Reτ = 547 and 1734 are presented.
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Koyankin, A. A., V. M. Mitasov, I. Ya Petuhova, and T. A. Tshay. "STRESS-STRAIN STATE OF PREFABRICATED MONOLITHIC BENDING ELEMENT AT GRADUAL INSTALLATION AND LOADING." Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture, no. 6 (December 29, 2019): 101–14. http://dx.doi.org/10.31675/1607-1859-2019-21-6-101-114.
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The stress-strain state of the prefabricated monolithic element depends on its gradual installation and loading. Regulatory documents of the Russian Federation indicate the need to calculate precast-monolithic structures for two stages of construction: before and after the specified monolithic concrete strength acquired. In this case, the stress-strain state that appeared in the prefabricated elements before the specified monolithic concrete strength should be considered. However, the construction and loading stages at issue and accumulation of stresses and strains are not disclosed in the regulatory documents. In addition, this problem is insufficiently studied. In this regard, the aim of this paper is to study the pre-loading effect of the prefabricated element on its stress-strain state and the load-bearing capacity. During the experiments, a pre-loaded prefabricated part is studied. The obtained results are compared with instantaneously loaded test samples. Other parameters of the experimental models are completely identical. In all, 5 samples are tested (step-by-step loading of 3 samples and instantaneous loading of 2 samples). It is shown that pre-loading of the preloaded prefabricated part significantly affects the stress-strain state of the whole structure and its total load-bearing capacity.
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INOUE, Takumi, Ren KADOWAKI, and Kenta MORI. "Nondestructive evaluation of seal strength of heat sealing using instantaneous frequency of ultrasonic pulse." Transactions of the JSME (in Japanese) 82, no. 843 (2016): 16–00327. http://dx.doi.org/10.1299/transjsme.16-00327.
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YANAGIHARA, Daiki, Takumi INOUE, Takahiro NAKANO, and Tatsuya ODA. "625 Estimation of Adhesive Strength on Heat Seal by Instantaneous Frequency of Ultrasonic Waves." Proceedings of the Dynamics & Design Conference 2012 (2012): _625–1_—_625–8_. http://dx.doi.org/10.1299/jsmedmc.2012._625-1_.
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Wang, Xingkai, Leibo Song, Caichu Xia, Guansheng Han, and Zheming Zhu. "Nonlinear Elasto-Visco-Plastic Creep Behavior and New Creep Damage Model of Dolomitic Limestone Subjected to Cyclic Incremental Loading and Unloading." Sustainability 13, no. 22 (2021): 12376. http://dx.doi.org/10.3390/su132212376.
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For many rock engineering projects, the stress of surrounding rocks is constantly increasing and decreasing during excavating progress and the long-term operation stage. Herein, the triaxial creep behavior of dolomitic limestone subjected to cyclic incremental loading and unloading was probed using an advanced rock mechanics testing system (i.e., MTS815.04). Then, the instantaneous elastic strain, instantaneous plastic strain, visco-elastic strain, and visco-plastic strain components were separated from the total strain curve, and evolutions of these different types of strain with deviatoric stress increment were analyzed. Furthermore, a damage variable considering the proportion of irrecoverable plastic strain to the total strain was introduced, and a new nonlinear multi-element creep model was established by connecting the newly proposed damage viscous body in series with the Hookean substance, St. Venant body, and Kelvin element. The parameters of this new model were analyzed. The findings are listed as follows: (1) When the deviatoric stress is not more than 75% of the compressive strength, only instantaneous deformation, transient creep, and steady-state creep deformation occur, rock deformation is mainly characterized by the instantaneous strain, whereas the irrecoverable instantaneous plastic strain accounts for 38.02–60.27% of the total instantaneous strain; (2) Greater deviatoric stress corresponds to more obvious creep deformation. The visco-elastic strain increases linearly with the increase of deviatoric stress, especially the irrecoverable visco-plastic strain increases exponentially with deviatoric stress increment, and finally leads to accelerated creep and delayed failure of the sample; (3) Based on the experimental data, the proposed nonlinear creep model is verified to describe the full creep stage perfectly, particularly the tertiary creep stage. These results could deepen our understanding of the elasto-visco-plastic deformation behavior of dolomitic limestone and have theoretical and practical significance for the safe excavation and long-term stability of underground rock engineering.
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Volkov, A., O. Matsko, and A. Mosalova. "Minimization of power and energy consumption of mechatronic drives in robotics and technological equipment." Journal of Physics: Conference Series 2131, no. 3 (2021): 032028. http://dx.doi.org/10.1088/1742-6596/2131/3/032028.
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Abstract The maximum instantaneous power consumption of robot drives determines the requirements for the energy supply system and the dimensions of the machine. For numerous machines, there are no technological restrictions on the types of applied motion laws and their numerical characteristics i.e. maximum speeds and accelerations. The type of the motion law and especially its parameters are traditionally determined according to the preferences of the design engineer without any justification, though some-times restrictions on maximum accelerations or speeds are considered. The restrictions on maximum accelerations are related to ensuring the strength and accuracy of the drive, and the restrictions on maximum speeds are related to the safety of personnel in the workplace. The motor power is selected according to the maximum value of the instantaneous power and thermal load, which depends on the duration of switching on. The article analyzes the ways of minimizing of this maximum (peak) of instantaneous power inside the cycle for different laws and different loads. The main parameter by which the maximum (peak) power is minimized for all types of laws is the acceleration and braking times. On the example of the most common motion laws, the dependence of instantaneous power and energy consumption on accelerating time and braking time for various types of loads are studied. In this article, the dependence of instantaneous power and energy consumption on accelerating time and braking time for various types of loads are studied on the example of the most common motion laws. The research results are intended to create a design technique for drives of modern equipment.
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Ren, Xiaopeng, Yajun Xin, Baoshan Jia, Kun Gao, Xuping Li, and Yu Wang. "Large Stress-Gradient Creep Tests and Model Establishment for Red Sandstone Treated at High Temperatures." Energies 15, no. 20 (2022): 7786. http://dx.doi.org/10.3390/en15207786.
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Red sandstone samples treated at high temperatures feature complex creep properties. Uniaxial compression tests and the incremental creep tests at different stress gradients were conducted on 10 red sandstone samples of the same specifications divided into five groups on an RLW-2000 triaxial servo rheometer in the laboratory. Relationships of the instantaneous strain and creep strain of red sandstone samples treated at high temperatures with the stress level were explored, and the creep properties and strength of the samples at different temperature gradients were investigated. In addition, the creep failure patterns and failure mechanism of the red sandstone samples were determined, and a creep constitutive model was established for the samples considering the effects of temperature. The conformity between test data and theoretical curves was discussed. Results show that as the stress increases, the instantaneous strain tends to decrease rapidly, slowly, then increase slowly; the creep strain tends to decrease, steadily increase, then increase substantially. At the same stress, as the stress gradient is doubled, the instantaneous strain decreases by 47.45%, and the creep strain decreases by 48.30%. For samples treated at 300~900 °C, the number of stress levels experienced gradually decreases; as the temperature increases, the creep failure strength of samples first increases, then decreases in an arcuate form, and the creep strain tends to decrease, increase, then increase rapidly. In the temperature range, the creep strain at the two stress gradients has a growing difference, with the maximum difference reaching 0.0134%; there is an inflection point at 300 °C in the creep failure strength of samples. At the same stress, the more the stress levels experienced, the lower the creep failure strength, and the temperature, creep failure strength, and creep strain can be characterized by a quadratic polynomial. At 300 °C, mineral particles in samples are sintered and cemented into chains, and there is a significant primary control plane, so the samples show oblique shear failure of a single primary control plane. At 600~900 °C, particles and blocks in samples begin to be sintered and flow, and the cemented chains are broken. Under the condition, the samples mainly show failure dominated by mixed and crossed primary and secondary control planes and crushing failure due to transverse compression. The established Burgers–Kelvin-Temperature (BKT) creep constitutive model is sensitive to changes in temperature; the theoretical curves are consistent with the test data.
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Romashko-Maistruk, Olena Vasylivna, and Vasyl Mykolayovych Romashko. "RESISTANCE OF COMPRESSED CONCRETE TO LONG-TERM LOADS." Collection of Scientific Works of the Ukrainian State University of Railway Transport, no. 206 (December 11, 2023): 112–20. http://dx.doi.org/10.18664/1994-7852.206.2023.296654.
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This article deals with the main regularities and features of compressed concrete deformation under the action of long-term loads. The main efforts are aimed at establishing an analytical dependence on determining the long-term strength level of compressed concrete. A critical analysis of the currently existing dependencies based on its calculation was carried out. These studies are based on the general provisions and hypotheses of the previously developed energy model of concrete and reinforced concrete deformation.The defining hypothesis of the specific potential energy invariance of the concrete ultimate deformation (destruction) and its independence from the loading mode of the concrete itself was used. The specific potential energy of compressed concrete deformation at the moment of its destruction under three loading modes is considered: instantaneous dynamic, standardized short-term and long-term. The level of compressed concrete long-term strength is related to the dynamic increase factor limit values (DIFu) under the instantaneous loading mode. In turn, the compressed concrete dynamic increase factor is functionally related to the generally recognized coefficient of compressed concrete standardized elastic-plastic properties under a short-term loading regime. In this way, the functional dependence of the level of compressed concrete long-term strength was obtained not only on its standardized elastic-plastic characteristics, but also on the rate of concrete deformation or on the rate of its loading. The evaluation of the proposed methodology for determining the level of compressed concrete long-term strength is reduced to a comparison of the relevant theoretical calculations results with the various researchers’ published experimental data.
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Meinhart, Carl D., Steve T. Wereley, and Juan G. Santiago. "A PIV Algorithm for Estimating Time-Averaged Velocity Fields." Journal of Fluids Engineering 122, no. 2 (2000): 285–89. http://dx.doi.org/10.1115/1.483256.
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A PIV algorithm is presented for estimating time-averaged or phase-averaged velocity fields. The algorithm can be applied to situations where signal strength is not sufficient for standard cross correlation techniques, such as a low number of particle images in an interrogation spot, or poor image quality. The algorithm can also be used to increase the spatial resolution of measurements by allowing smaller interrogation spots than those required for standard cross correlation techniques. The quality of the velocity measurements can be dramatically increased by averaging a series of instantaneous correlation functions, before determining the location of the signal peak, as opposed to the commonly used technique of estimating instantaneous velocity fields first and then averaging the velocity fields. The algorithm is applied to a 30μm×300μm microchannel flow. [S0098-2202(00)00602-7]
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Vasilikos, Ioannis, Graciosa Q. Teixeira, Andreas Seitz, et al. "Can UVA-light-activated riboflavin-induced collagen crosslinking be transferred from ophthalmology to spine surgery? A feasibility study on bovine intervertebral disc." PLOS ONE 16, no. 6 (2021): e0252672. http://dx.doi.org/10.1371/journal.pone.0252672.
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Background Collagen cross-links contribute to the mechanical resilience of the intervertebral disc (IVD). UVA-light-activated riboflavin-induced collagen crosslinking (UVA-CXL) is a well-established and effective ophthalmological intervention that increases the mechanical rigidity of the collagen-rich corneal matrix in Keratoconus. This study explores the feasibility, safety and efficacy of translating this intervention in reinforcing the IVD. Methods Annulus fibrosus (AF) cells were isolated from bovine IVDs and treated with different combinations of riboflavin (RF) concentrations (0.05–8 mM) and UVA light intensities (0.3–4 mW/cm2). Metabolic activity (resazurin assay), cell viability (TUNEL assay), and gene expression of apoptosis regulators C-FOS and PT5 were assessed immediately and 24 hours after treatment. Biomechanical effects of UVA-CXL on IVDs were measured by indentation analysis of changes in the instantaneous modulus and by peel-force delamination strength analysis of the AF prior and after treatment. Results Different intensities of UVA did not impair the metabolic activity of AF cells. However, RF affected metabolic activity (p < 0.001). PT53 expression was similar in all RF conditions tested while C-FOS expression decreased 24 hours after treatment. Twenty-four hours after treatment, no apoptotic cells were observed in any condition tested. Biomechanical characterizations showed a significant increase in the annular peel strength of the UVA-CXL group, when compared to controls of UVA and RF alone (p < 0.05). UVA-CXL treated IVDs showed up to 152% higher (p < 0.001) instantaneous modulus values compared to the untreated control. Conclusion This is the first study on UVA-CXL treatment of IVD. It induced significantly increased delamination strength and instantaneous modulus indentation values in intact IVD samples in a structure–function relationship. RF concentrations and UVA intensities utilized in ophthalmological clinical protocols were well tolerated by the AF cells. Our findings suggest that UVA-CXL may be a promising tool to reinforce the IVD matrix.
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Wu, Junhua, Zheshu Ma, and Yonghui Zhang. "A Time-Frequency Research for Ultrasonic Guided Wave Generated from the Debonding Based on a Novel Time-Frequency Analysis Technique." Shock and Vibration 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/5686984.
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Carbon fibre composites have a promising application in the future of the vehicle, because of their high strength and light weight. Debonding is a major defect of the carbon fibre composite. The time-frequency analysis is fundamental to identify the defect on ultrasonic nondestructive evaluation and testing. In order to obtain the instantaneous frequency and the peak time of modes of the ultrasonic guided wave, an algorithm based on the Smoothed Pseudo Wigner-Ville distribution and the peak-track algorithm is presented. In the algorithm, a masking step is proposed, which can guarantee that the peak-track algorithm can automatically exact the instantaneous frequency and the instantaneous amplitude of different modes on the Smoothed Pseudo Wigner-Ville distribution. An experiment for detecting the debonding for a type of carbon fibre composite is done. The presented algorithm is employed on the experimental signals. The processed result of experimental signals reveals that the defect can stimulate new modes, and there is a quantitative relationship between the defect size and the frequency of the new mode. The presented technique provides a valuable way to detect the presentence, calculate the size, and locate the position of the debonding defect.
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Liu, Xiao Wen, and Xiao Mu Geng. "Microcosmic Deform Incoordination and the Law of Limiting Strength Release during Shearing Failure of Concrete." Advanced Materials Research 152-153 (October 2010): 1188–91. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.1188.
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Concrete is a sort of inhomogeneous and discontinuous diverse mixture, it has very complicated interior structure and working mechanism[1,2]. But the research about concrete constitutive relation and strength theory was based on the condition of concrete continuity. The law for microcosmic deform during concrete destroy was little considered[3]. Mechanism of shearing failure was researched through concrete sample’s experiment to explored interior microcosmic disharmony and the law of limiting strength release in this paper. Shearing experiments of concrete show shearing displacements of various local district in shearing surface during shearing have apparent discrepancy from beginning to end. This discrepancy leads to destroy of shearing surface from one local to another local and brings course of shearing limiting strength release discontinuous, one-off and non-instantaneous.
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Wang, Chuang, Jinyu Dong, Shengwen Qi, Jiancang Zhao, Lei Xue, and Dengpo Fan. "Experimental study on the shear creep behavior of residual soil with varying rock content." PLOS ONE 20, no. 2 (2025): e0311156. https://doi.org/10.1371/journal.pone.0311156.
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Using residual soil from the Shanghecun landslide in the western Henan Province, shear creep tests of residual soil samples with different rock contents (RCs) were performed to explore the creep characteristics, creep rate, and long-term strength of the residual soil. The test results indicate that the residual soil samples with different RCs display typical creep characteristics. With increasing RC, both the instantaneous deformation and the total creep deformation of the residual soil gradually decrease. The shear strain of the residual soil increases gradually with increasing shear stress for the different RCs. With increasing time, the slope of the isochronous stress–strain curves of the residual soil samples with different RCs increases gradually. The Burgers model can simulate the rheological process of the residual soil samples with different RCs. The RC has a significant effect on the shear strength and the long-term strength of the residual soil. With increasing RC, the shear strength and the long-term strength of the residual soil gradually increase, with the long-term strength being approximately 39%–63% of the shear strength.
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Feng, Zeng Ming, Jun Long Li, and Guang Wu Liu. "Dynamic Analysis of Silent Chain Drive System for Hybrid Car." Advanced Materials Research 694-697 (May 2013): 84–89. http://dx.doi.org/10.4028/www.scientific.net/amr.694-697.84.
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Based on study of the power transmission system theory for hybrid car, a silent chain drive system which is used to transmit power between motor and gear box was designed. Using multi-body dynamic software RecurDyn, the dynamic behavior of the silent chain system was simulated, the chain tension, meshing impact load and instantaneous transmission ratio of the drive system under different velocity was analyzed. The results show that, at the whole speed range, the chain tension is always less than the chain rotation fatigue strength (including a safety factor of 1.3 times), its able to meet the working requirements, the instantaneous impact load when link plate meshing into sprocket relate to chain tension and sprocket rotation speed, the transmission error of silent chain system is within the allowable range and can meet the transmission requirement.
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Park, I. D., Seok Hwan Ahn, and Ki Woo Nam. "Solid Solution Strengthening Behavior of 25Cr-20Ni Austenite Stainless Steel." Key Engineering Materials 261-263 (April 2004): 1209–14. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.1209.
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The purpose of this paper is to investigate the effect of solid solution strengthening on the high temperature creep strength of STS310J1TB. To make clear the effect of solid solution strengthening, the stress abrupt change test was carried out to observe the instantaneous plastic strain and the stress relaxation test was carried out to investigate the ratio of solid solution strengthening to applied stress. The instantaneous plastic strain was observed in the stress abrupt change test of STS310S, while it was absent in STS310J1TB. This clearly indicates that the dislocations glide viscously in STS310J1TB, while they move in a free flight manner in STS310S. As a result of TEM observation, the dislocation structure of STS310J1TB is more uniform than that of STS310S. From the analysis of the stress relaxation curve, the effective stress to total applied stress was found to be about 16 %.
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Wang, Ting, Na Li, Beibei Kong, Xiaomei Ni, and Xiangbao Li. "Analysis of disc movement during the closing process of axial flow check valves." Journal of Physics: Conference Series 2720, no. 1 (2024): 012057. http://dx.doi.org/10.1088/1742-6596/2720/1/012057.
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Abstract In a long-distance pipeline system, when the pump is stopped, the axial flow check valve will suddenly close under the pressure difference force of the medium, and the instantaneous valve disc will collide and impact the valve seat at a certain speed, which will have a certain impact on the structural strength and service life of the check valve. This article uses explicit dynamics to simulate the movement process of the instantaneous valve disc when it is completely closed and analyzes the velocity of the valve disc after the collision. Based on the spring damping model theory, the velocity of the valve disc after collision is derived. After error analysis, the reliability of numerical simulation has been verified, which has a certain guiding significance for the practical application and design improvement of axial flow check valves.
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Yamaoka, Hitoshi, Kiyoshi Kadota, Hideki Yamai, Satoru S. Kano, and Junji Fujita. "Instantaneous measurement of magnetic field strength with combining beam probe and Doppler‐tuned laser spectroscopy." Review of Scientific Instruments 59, no. 1 (1988): 115–19. http://dx.doi.org/10.1063/1.1139997.
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