Journal articles on the topic 'Load variation pattern'
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1
Stevenson, R. "The Morphology of Machining Chips Formed During Low Speed Quasi-Orthogonal Machining of CA 360 Brass and a Model for Their Formation." Journal of Engineering for Industry 114, no. 4 (November 1, 1992): 404–11. http://dx.doi.org/10.1115/1.2900691.
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In a previous study of orthogonal machining of CA 360 brass, periodic load fluctuations were related to geometric features observed on the machining chip. In this study, the metallography of these machining chips was examined using both optical and scanning electron microscopy with the goal of better understanding the cutting mechanism and the origin of the load fluctuations. It was determined that the load variations were associated with periodic variations in chip thickness, implying a periodic variation in shear angle. It is difficult to detect such a variation in shear angle using an etch to identify deformation patterns, but shear angle variations could be inferred from the chip morphology and from the distortion of the lead particles in the machining chip. A simple model is presented which exhibits periodic shear angle variations if deformation is assumed to occur in a shear zone of finite thickness and if the material’s workhardening capacity is exhausted at strains comparable with those developed during machining. Computations incorporating the features of this model are shown to accurately reproduce the pattern of the experimental observations.
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Etzel, Joset A., Ya’el Courtney, Caitlin E. Carey, Maria Z. Gehred, Arpana Agrawal, and Todd S. Braver. "Pattern Similarity Analyses of FrontoParietal Task Coding: Individual Variation and Genetic Influences." Cerebral Cortex 30, no. 5 (February 21, 2020): 3167–83. http://dx.doi.org/10.1093/cercor/bhz301.
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Abstract Pattern similarity analyses are increasingly used to characterize coding properties of brain regions, but relatively few have focused on cognitive control processes in FrontoParietal regions. Here, we use the Human Connectome Project (HCP) N-back task functional magnetic resonance imaging (fMRI) dataset to examine individual differences and genetic influences on the coding of working memory load (0-back, 2-back) and perceptual category (Face, Place). Participants were grouped into 105 monozygotic twin, 78 dizygotic twin, 99 nontwin sibling, and 100 unrelated pairs. Activation pattern similarity was used to test the hypothesis that FrontoParietal regions would have higher similarity for same load conditions, while Visual regions would have higher similarity in same perceptual category conditions. Results confirmed this highly robust regional double dissociation in neural coding, which also predicted individual differences in behavioral performance. In pair-based analyses, anatomically selective genetic relatedness effects were observed: relatedness predicted greater activation pattern similarity in FrontoParietal only for load coding and in Visual only for perceptual coding. Further, in related pairs, the similarity of load coding in FrontoParietal regions was uniquely associated with behavioral performance. Together, these results highlight the power of task fMRI pattern similarity analyses for detecting key coding and heritability features of brain regions.
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Wenning, Angela, Brian J. Norris, Anca Doloc-Mihu, and Ronald L. Calabrese. "Variation in motor output and motor performance in a centrally generated motor pattern." Journal of Neurophysiology 112, no. 1 (July 1, 2014): 95–109. http://dx.doi.org/10.1152/jn.00856.2013.
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Central pattern generators (CPGs) produce motor patterns that ultimately drive motor outputs. We studied how functional motor performance is achieved, specifically, whether the variation seen in motor patterns is reflected in motor performance and whether fictive motor patterns differ from those in vivo. We used the leech heartbeat system in which a bilaterally symmetrical CPG coordinates segmental heart motor neurons and two segmented heart tubes into two mutually exclusive coordination modes: rear-to-front peristaltic on one side and nearly synchronous on the other, with regular side-to-side switches. We assessed individual variability of the motor pattern and the beat pattern in vivo. To quantify the beat pattern we imaged intact adults. To quantify the phase relations between motor neurons and heart constrictions we recorded extracellularly from two heart motor neurons and movement from the corresponding heart segments in minimally dissected leeches. Variation in the motor pattern was reflected in motor performance only in the peristaltic mode, where larger intersegmental phase differences in the motor neurons resulted in larger phase differences between heart constrictions. Fictive motor patterns differed from those in vivo only in the synchronous mode, where intersegmental phase differences in vivo had a larger front-to-rear bias and were more constrained. Additionally, load-influenced constriction timing might explain the amplification of the phase differences between heart segments in the peristaltic mode and the higher variability in motor output due to body shape assumed in this soft-bodied animal. The motor pattern determines the beat pattern, peristaltic or synchronous, but heart mechanics influence the phase relations achieved.
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Farooq, Samir A., Samuel J. Weisenthal, Melissa Trayhan, Robert J. White, Kristen Bush, Peter R. Mariuz, and Martin S. Zand. "Revealing HIV viral load patterns using unsupervised machine learning and cluster summarization." F1000Research 7 (July 27, 2018): 1144. http://dx.doi.org/10.12688/f1000research.15591.1.
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HIV RNA viral load (VL) is an important outcome variable in studies of HIV infected persons. There exists only a handful of methods which classify patients by VL patterns. Most methods place limits on the use of viral load measurements, are often specific to a particular study design, and do not account for complex, temporal variation. To address this issue, we propose a set of four unambiguous computable characteristics (features) of time-varying HIV viral load patterns, along with a novel centroid-based classification algorithm, which we use to classify a population of 1,576 HIV positive clinic patients into one of five different viral load patterns (clusters) often found in the literature: durably suppressed viral load (DSVL), sustained low viral load (SLVL), sustained high viral load (SHVL), high viral load suppression (HVLS), and rebounding viral load (RVL). The centroid algorithm summarizes these clusters in terms of their centroids and radii. We show that this allows new VL patterns to be assigned pattern membership based on the distance from the centroid relative to its radius, which we term radial normalization classification. This method has the benefit of providing an objective and quantitative method to assign VL pattern membership with a concise and interpretable model that aids clinical decision making. This method also facilitates meta-analyses by providing computably distinct HIV categories. Finally we propose that this novel centroid algorithm could also be useful in the areas of cluster comparison for outcomes research and data reduction in machine learning.
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Yorkina, Nadiia, Natalia Tarusova, Ava Umerova, Polina Telyuk, and Yevheniia Cherniak. "Spatial Organization of the Micromollusc Community under Recreational Load." Grassroots Journal of Natural Resources 4, no. 2 (May 30, 2021): 1–22. http://dx.doi.org/10.33002/nr2581.6853.040201.
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The recreational load is an important factor in transforming the living conditions of living organisms in the urban environment. This article examines the role of recreation as a driver of the changing habitat of soil micromolluscs in the park environment in an urban landscape. The hypothesis that recreational exposure changes the hierarchical organization of the spatial distribution of the micromollusc community was tested. An experimental polygon was located in Novooleksandrivskiy Park (Melitopol, Ukraine) and represented 7 transects with 18 test points in each. The set of soil properties explained 24.7% of the variation in the mollusc community. The distance from trees was able to explain 6.8% of mollusc community variation. The distance from recreational pathways was able to explain 12.2% of the variation in the mollusc community. The spatial eigenfunctions were able to explain 54.2% of mollusc community variation. The spatial patterns of variation in the structure of the assemblage of molluscs were found to be due to various causes. Thus, the broad-scale component was due to the distance from trees and the distance fro m the recreational pathways and was associated with the variability of soil penetration resistance, aggregate structure, electrical conductivity, soil moisture and density. The recreational load is the cause of this pattern formation. In turn, the medium-scale component reflected the influence of soil aggregate composition on the mollusс community and components independent of soil properties. The fine-scale component reflected the variability of the mollusc community, which was independent of soil properties.
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Lavagnino, M., J. Madison, M. R. Williams, and S. P. Arnoczky. "The equine forelimb suspensory ligament exhibits a heterogeneous strain pattern under tensile load." Veterinary and Comparative Orthopaedics and Traumatology 28, no. 05 (2015): 306–11. http://dx.doi.org/10.3415/vcot-15-01-0018.
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SummaryObjectives: To determine if regional variations in strain patterns occur within the suspensory ligament under tensile load. Local increases in strain may put certain regions of the suspensory ligament at risk and may explain the poor healing and high recurrence rates associated with suspensory branch injuries.Methods: The suspensory ligament and its bone attachments were isolated from each of 10 adult equine cadaveric forelimbs and radiodense reference beads were inserted throughout the length of the ligament. Specimens were attached to a custom fixture secured to a materials testing system. Radio-graphs were acquired at 50, 445, 1112, and 2224 N of applied tensile load. Changes in distances between the beads in each region of the suspensory ligament were measured and the regional strain was calculated. Significant differences were determined using a repeated-measures analysis of variance.Results: The suspensory ligament exhibited significant differences in regional strain (p <0.001). The distal branches of the suspensory ligament had significantly greater strains than the proximal (p = 0.025) and mid-body (p = 0.002) regions. The mid-body of the suspensory ligament also exhibited local strain variation, with the distal mid-body having significantly higher strains than the proximal mid-body (p = 0.038).Clinical significance: The equine suspensory ligament demonstrates a heterogeneous strain pattern during tensile loading, with the distal regions exhibiting significantly more strain than the proximal region. The nonhomogenous strain pattern could explain the regional difference in injury and re-injury rates.
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Yin, Shui Ping, and Min Yu. "Dynamic Visco-Elastic Properties of Polycarbonate (PC) under Static and Dynamic Load." Advanced Materials Research 146-147 (October 2010): 1090–93. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.1090.
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The purpose of this work was to investigate the effects of pre-load static load and dynamic load on the visco-elastic in polycarbonate. In the paper, static-dynamic sweep experiment of polycarbonate was performed on EPLEXOR 500N, which was manufactured by GABO of Germany. The variation laws of storage modulus, loss modulus and loss tangent as changing dynamic load in a large range were systematically analyzed and the spectral characteristics of dynamic-viscoelastic under static-dynamic loads were obtained. The experiment results on dynamic visco-elastic under the high load shows that the load effects on dynamic visco-elasticity of polycarbonate performing on the changing of the dynamic visco-elastic parameters, storage modulus become lager with the increasing of static load and decreasing with the increasing of dynamic load, while loss tangent decreases with the increasing of dynamic load and varies in a more complicated pattern as the increasing of static load.
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Liu, Lan Bin, Ai Juan Zou, and Yu Fei Ma. "A Method of Load Prediction in District-Heating System Based on Data Mining." Advanced Materials Research 918 (April 2014): 154–59. http://dx.doi.org/10.4028/www.scientific.net/amr.918.154.
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According to the internal mechanism of the formation of heat load, the formation of heat load consists of two parts, the systemic heat load, which is determined by the building envelope and outdoor environmental parameters and random load caused by the users randomness of events and solar radiation etc. Toward systemic heat load, this paper considered the influence of environmental parameters before the prediction time and used the method of stepwise trials and MSE to obtain the optimal solution. Toward random load, it is considered that the day of the same type have the same variation pattern. On this basis, this paper introduced a correction coefficient to obtain random load eventually. This paper selected DeST, the widely used energy simulation software in China, to analysis the case. The result shows that the prediction method is feasible and 50% of the predicted loads have the relative error of less than 5%.
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Daubenspeck, J. A., and E. S. Rhodes. "Effect of perception of mechanical loading on human respiratory pattern regulation." Journal of Applied Physiology 79, no. 1 (July 1, 1995): 83–93. http://dx.doi.org/10.1152/jappl.1995.79.1.83.
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We applied external flow resistive (R) and elastic (E) mechanical loads over the entire respiratory cycle to five normal subjects by using a pseudorandom loading protocol. Loads ranged in magnitude from imperceptible (R0/E0) through just perceptible (R1/E1) to large (R2/E2) and resulted in respiratory pattern responses that were due to reflex responses alone (R0/E0) or to a combination of reflex responses and behavioral reactions to the perception of impeded breathing (R1/E1 and R2/E2). Pattern regulation dynamics were estimated from the computed impulse responses of tidal volume and inspiratory and expiratory durations. We anticipated that emergence of behavioral contributions would be marked by increased variability in response strategies and by increased nonlinearity in the observed responses. Regarding the immediate pattern response to loading, there was a tendency for increased qualitative variation across subjects as the load size increased, but the within-subject variability (coefficient of variation) was unaffected. We found no evidence for increased nonlinearity as loads became perceptible. The emergence of behavioral control in some instances seemed to be marked by reduction of complexity of the impulse response to one dominated by the zeroth-order lag, leading to dynamically simpler responses compared to control.
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Hisham, Naja Aqilah, Sheikh Ahmad Zaki Shaikh Salim, Aya Hagishima, Fitri Yakub, and Hafizah Farhah Saipan Saipol. "Statistical analysis of air-conditioning and total load diversity in typical residential buildings." Bulletin of Electrical Engineering and Informatics 10, no. 1 (February 1, 2021): 1–9. http://dx.doi.org/10.11591/eei.v10i1.2299.
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Electricity consumption by air-conditioners in residential buildings significantly affects the electrical grid. The stability of the grid can be improved by a precise prediction of air-conditioning (AC) variations. Therefore, more information about the electricity usage patterns specifically on AC load is important. This paper aims to determine the consumption patterns of AC and total load through a field measurement of 20 dwellings located in Kuala Lumpur and Selangor. Next, correlation and clustering are employed to identify the relationship between outdoor temperature and AC electricity consumption. The results revealed 75% of the occupants use the AC almost every day for about five to six hours per day at the rates of 0.93 kWh/day during day time and 3.43 kWh/day during night time. The correlation coefficient between the total daily AC consumption and the mean daily outdoor temperature ranged from -0.1 to 0.48. The variation of electricity consumption with time shows that AC electricity consumption increases with the increase of usage time. Lastly, the clustering process of AC usage pattern based on outdoor temperature displayed the uncommon behaviour from dwellings whereby high AC electricity consumption was recorded at low outdoor temperature.
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Hilal, Iin Shabrina, Mochammad Afifuddin, and Muttaqin Hasan. "Simulation of Shear Capacity of Reinforced Concrete Column with Variation of Stirrups Using Finite Element Method Analysis." Key Engineering Materials 927 (July 29, 2022): 203–8. http://dx.doi.org/10.4028/p-3b98q9.
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Shear failure of column causes the column to have shear reinforcement that cannot withstand shear forces so that it loses of lateral strength quickly. This research aims to see the effect of the configuration with the addition of shear reinforcement in the direction and perpendicular to the direction of the shear force on the capacity of reinforced concrete columns that are loaded with axial and lateral loads. The test was carried out by providing a constant axial load (0.3 P0) followed by a shear load until the test object failed. The numerical analysis was carried out using software based on the finite element method, namely ATENA Version 5 and GID Version 13.0.1 developed by Cervenka Consulting. This study used reinforced concrete with three variables of shear reinforcement. It can be the normal columns without stirrup reinforcement (S0P2), the addition three (3) stirrups in the direction of the shear reinforcement (S4P2) and the addition of two (2) stirrups in the direction of the shear reinforcement and one (1) stirrups perpendicular to the shear reinforcement (S5P2). After the numerical analysis is carried out, the results are verifies using experimental testing. The numerical analysis and experimental results give the load and deflection relationship results that are almost close. Therefore, the difference in shear loads compared to the experiments results and numerical analysis on columns S0P2, S4P2, and S5P2 is 0.11%, 3.95% and 1.16%, respectively, with a deflection ratio of 4.72%, 37.80% and 9.44%. The pattern of column destruction in the numerical model resembles the destruction pattern of the experimental results, both of which indicate that the column has shear cracks.
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Chen, Hong Yi, and Fu Ma. "Different Force Conditions on Nonlinear Finite Element Analysis of Small Concrete Hollow Block Wall with Failure Modes of Influence." Advanced Materials Research 788 (September 2013): 602–5. http://dx.doi.org/10.4028/www.scientific.net/amr.788.602.
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This paper mainly studies small hollow concrete block wall sets a certain level of reinforcement, vertical bar, core column and high aspect ratio, vertical and horizontal load, changes in load point height wall by shear form and bending failure pattern changes and shear capacity and flexural capacity. Nonlinear analysis simulation using ANSYS finite element analysis software of the specimen, mainly analysis and predict the failure modes of the different loading conditions wall. Obtained by calculating the failure pattern of the specimen, the load-displacement curve, the various stages of the load-displacement values and calculated the relative deformation and ductility factor of the wall under various loading height. Comparative analysis of the load-displacement curve variation of the shear failure and bending failure form, draw the conclusion that bending failure energy consumption better performance.
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O'Connor, T. G., C. M. Mulqueeny, and P. S. Goodman. "Determinants of spatial variation in fire return period in a semiarid African savanna." International Journal of Wildland Fire 20, no. 4 (2011): 540. http://dx.doi.org/10.1071/wf08142.
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Fire pattern is predicted to vary across an African savanna in accordance with spatial variation in rainfall through its effects on fuel production, vegetation type (on account of differences in fuel load and in flammability), and distribution of herbivores (because of their effects on fuel load). These predictions were examined for the 23 651-ha Mkuzi Game Reserve, KwaZulu-Natal, based on a 37-year data set. Fire return period varied from no occurrence to a fire every 1.76 years. Approximately 75% of the reserve experienced a fire approximately every 5 years, 25% every 4.1–2.2 years and less than 1% every 2 years on average. Fire return period decreased in relation to an increase in mean annual rainfall. For terrestrial vegetation types, median fire return periods decreased with increasing herbaceous biomass, from forest that did not burn to grasslands that burnt every 2.64 years. Fire was absent from some permanent wetlands but seasonal wetlands burnt every 5.29 years. Grazer biomass above 0.5 animal units ha–1 had a limiting influence on the maximum fire frequency of fire-prone vegetation types. The primary determinant of long-term spatial fire patterns is thus fuel load as determined by mean rainfall, vegetation type, and the effects of grazing herbivores.
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Goronszy, Mervyn C., Nigel Slater, and Dennis Konicki. "The cyclic activated sludge system for resort area wastewater treatment." Water Science and Technology 32, no. 9-10 (November 1, 1995): 105–14. http://dx.doi.org/10.2166/wst.1995.0675.
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Significant load variation is imposed on wastewater treatment infrastructure at resort centres. The type of resort centre plays a large part in both hydraulic and organic loading dynamics. Climatic conditions may also be a determining factor on the loading pattern. Holiday patterns also have a large impact upon loading dynamics. Performance of the Portage/Catawba Cyclic Activated Sludge System, located on the shores of Lake Erie, is described relative to the loading dynamics of the Summer/Winter populations.
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Lim, Jae Kwang, Byung-Tae Choi, and Heung-Sik Tae. "Analysis of luminance variation with display load and display pattern in AC-plasma display panels." Displays 31, no. 1 (January 2010): 9–14. http://dx.doi.org/10.1016/j.displa.2009.09.003.
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Aritonang, Ririn Vionica, and Nurmaidah Nurmaidah. "Pengaruh Variasi Jarak Tulangan Sengkang Spiral Terhadap Kuat Lentur Balok Beton Bertulang." Jurnal PenSil 9, no. 3 (September 26, 2020): 188–95. http://dx.doi.org/10.21009/jpensil.v9i3.17080.
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This study aimed to determine the flexural strength of rectangular reinforced concrete beams by varying the concrete's spiral spacing. Test objects used dimensional beam 15 × 15 × 60 cm with a total of 20 samples, each variation made from 5 samples. The variation in spiral spacing without reinforcement was 2,5 cm, 5 cm, and 10 cm. The concrete quality plan used FC 30 MPa. Based on the analysis results noted that at a maximum flex load of 47.54 kN and a maximum bending moment of 3.579 kNm, the maximum bending load of 37.8 kN and a maximum bending moment of 2.849 kNm, and a maximum bending moment of 33.26 kN and A maximum of flexible paces of 2.508 kNm for every variation in the distance of the spiral. Based on the hypothesis test using a regression analysis method, the equation obtained was Y = 3,749 -13, 213X. The variation in the spiral spacing of reinforced concrete beams had no significant effect. The crack pattern that occurred on all test objects was generally a bending pattern and subjected to vertical cracks in the 1/3 portion of the beam's pull towards the press area.
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Soehardjono, Agoes, and Candra Aditya. "ANALYSIS OF THE EFFECT OF SLAB THICKNESS ON CRACK WIDTH IN RIGID PAVEMENT SLABS." EUREKA: Physics and Engineering, no. 2 (March 29, 2021): 42–51. http://dx.doi.org/10.21303/2461-4262.2021.001693.
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Cracks that occur in rigid pavements include longitudinal cracks, transverse cracks, and corner cracks. The relatively large crack width not only spoils the aesthetics of the concrete structural elements but can also lead to structural failure. This study aims to determine the crack width of a rigid pavement concrete slab located above the subgrade which is considered a beam on an elastic foundation, so that a minimum rigid pavement concrete slab thickness can be recommended. The specimen will be observed at various thicknesses to obtain the optimum thickness. The load used is a centralized monotonous load, which represents the load of the truck vehicle. The research limitation is using a test object in the form of a concrete plate measuring 2000x600 mm which is placed on the ground with CBR=6 %. The quality of reinforced concrete slabs is fc'=40 MPa and fy=440.31 MPa. The thickness of the concrete slab varies between 100 mm, 150 mm, and 200 mm. The slab placed on the ground is then given a central loading in the form of a centralized monotonic load. The loading range starts from a load of 2–180 kN with a load interval of 2 kN. The experimental results show that the rigid pavement slab has a bending failure so that the crack pattern that occurs begins with the first crack on the underside of the slab. The crack pattern in terms of slab thickness variation has a similar pattern. The initial crack width on the slab is 0.04 mm. The thicker the slab smaller the crack width at the same load. Based on the maximum allowable crack width=0.3 mm. For loads between (80–100) kN (Road Class I, II, and III), a minimum thickness of rigid pavement slabs (70–80) mm is recommended. For loads between (130–140) kN, the minimum thickness of the rigid pavement slab (105–115) mm is recommended
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Tang, Twen Poh, and David L. Macmillan. "The Effects of Sensory Manipulation upon Interlimb Coordination during Fast Walking in the Cockroach." Journal of Experimental Biology 125, no. 1 (September 1, 1986): 107–17. http://dx.doi.org/10.1242/jeb.125.1.107.
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1. A re-examination of fast stepping in free-walking cockroaches showed that there was considerable variation in the alternating tripod gait. 2. Small load increments applied to the whole animal significantly reduced this variability and concentrated the range and speed of movements used. 3. Animals suspended above oiled glass surfaces moved their legs in normal gait patterns indicating that mechanical coupling via the substrate was not a critical factor for normal high-speed coordination. 4. Increasing the viscosity of the oil produced the same reduction in variability found with load increment so the change cannot be due to increased mechanical coupling. 5. Increasing the viscosity of the oil under one leg alone resulted in concentration over the whole pattern so the result was not considered to be due to viscosity changes. 6. The changes seen in artificial loading situations were mimicked in natural loading situations such as walking up a slight incline. 7. The functional significance of the phenomenon for the stability of the rapidly moving animal is considered and the role of load afference in biasing central pattern generators to produce a continuous range of functional output is discussed.
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Anoliefo, EA, and O. Oparaku. "AN INVESTIGATION INTO THE APPLICABILITY OF NATURAL LOAD VARIATION SCHEME TO THE MEASUREMENT OF ENERGY YIELD OF PHOTOVOLTIC MODULE." Nigerian Journal of Technology 36, no. 3 (June 30, 2017): 858–66. http://dx.doi.org/10.4314/njt.v36i3.28.
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Currently, photvoltaic (PV) modules are characterized based on open circuit voltage, short circuit current as well as voltage and current at maximum power point under strictly specified laboratory conditions. Among manufacturers, regulators and experts, this approach appears reasonably adequate. Nevertheless, among end users and and low level technicians, it may be misleading. This is on account of the critical difference between the laboratory and in situ conditions. This often results to improper design which in turn is capable of accelerating a premature system failure. The present work explores the potentials of natural load variation scheme as a low cost option that is capable of estimating the actual yield of PV modules. Essentially, the scheme consists of a firmware controlling the switching of a number of resistors(loads) connected in parallel. By looping through the resistors in parallel, the firmware matches load impedance to the impedance of the module thus the module operates at its maximum power point. The research results indicate a similar response pattern for constant and variable loads. Nevertheless, the quantitative value of recorded voltage, current, power and energy tended to increase as the number of available resistors incresed. Though clear convergence was not achieved, natural load variation scheme more realistically captures the yield potentials of polycrystalline PV modules under low irradiance conditions. http://dx.doi.org/10.4314/njt.v36i3.28
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Fujihara, Masayaki, Edward Lapong, Tomoki Izumi, and Noriyuki Kobayashi. "Temporal Variation Analyses of Suspended Sediment Load in an Agricultural Catchment and its Land Use Implications." Journal of Engineering, Environment and Agriculture Research 1 (October 22, 2018): 1. http://dx.doi.org/10.34002/jeear.v1i0.13.
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The suspended sediment load of a small agricultural river was estimated using suspended sediment rating curves established using discharge-suspended sediment discharge correlation and stratified aggregate or seasonally clustered data; and the results were correlated to the land use of the watershed. The results showed that: (a) on regression, nonlinear least squares method in establishing rating curves produced significantly better and more efficient suspended sediment rating curves; (b) seasonally clustering the data produced better suspended sediment rating curves; (c) based on statistical and physical relations, suspended sediment load in the catchment followed a clear cyclical seasonal pattern; and (d) the land use and agricultural activities, other than rainfall, had a significant impact on the temporal distribution and variability of the suspended sediment load.
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Naduvinamani, Neminath Bhujappa, Siddangouda Apparao, and Ayyappa G. Hiremath. "Effect of Surface Roughness and Viscosity-Pressure Dependency on the Couple Stress Squeeze Film Characteristics of Parallel Circular Plates." Advances in Tribology 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/387413.
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Combined effects of surface roughness and viscosity-pressure dependency on the couple stress squeeze film characteristics of parallel circular plates are presented. On the basis of Christensen’s stochastic theory, two types of one-dimensional roughness structures, namely, the radial roughness and azimuthal roughness patterns, are considered and the stochastic modified Reynolds equation for these two types of roughness patterns is derived for Stokes couple stress fluid by taking into account variation of viscosity with pressure. The standard perturbation technique is employed to solve the averaged Reynolds equation and closed form expressions for the mean fluid film pressure, load carrying capacity, and squeeze film time are obtained. It is found that the effects of couple stresses and viscosity-pressure dependency are to increase the load carrying capacity, and squeeze film time for both types of roughness patterns. The effect of azimuthal (radial) roughness pattern is to increase (decrease) these squeeze film characteristics as compared to the corresponding smooth case.
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Jordan, Michael, John A. Chamberlain, and Rebecca B. Chamberlain. "Response of Nautilus to Variation in Ambient Pressure." Journal of Experimental Biology 137, no. 1 (July 1, 1988): 175–89. http://dx.doi.org/10.1242/jeb.137.1.175.
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Juvenile Nautilus, tested in a high-pressure animal maintenance apparatus, are sensitive to increases in ambient hydrostatic pressure as small as lx105Nm−2 (= 1 atm = 100kPa). They respond to such pressure increases in a characteristic ‘depth alarm’ behaviour pattern, which consists primarily of rapid upward swimming. These activity bursts may serve to restore them to their original depth. The animals apparently continue this behaviour until fatigued. Pressure decrease elicits no obvious response. The pressure-sensing mechanism may be located within the statocyst, or possibly in the posterior mantle or siphuncle. The operation of. the latter two mechanisms involves tensional strain induced by the hydrostatic load in the outermost septum and wall of the siphuncular tube.
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Kulish, T. "Spatial variation of soil temperature fields in a urban park." IOP Conference Series: Earth and Environmental Science 1049, no. 1 (June 1, 2022): 012056. http://dx.doi.org/10.1088/1755-1315/1049/1/012056.
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Abstract Soil temperature is the most important factor that regulates the rate of physical, chemical and biological processes in the soil. A peculiarity of the urban environment is the occurrence of “heat islands”. The increased temperature of urban environment significantly changes environmental conditions and contributes to the activation of phenomena that lead to the acceleration of global climate change. The aim of the work is to reveal the patterns of spatial variation of soil temperature in a city park at the different scale levels. Soil temperature was measured on a regular grid with different lags between measurement points. The measurement results were processed using geostatistical methods to quantify the spatial process at different scales. The results obtained allowed to quantify the patterns of spatial variability of temperature fields at different hierarchical levels. Scale-dependent effects of soil temperature variation were identified. The role of stand density, litter depth, and soil moisture on soil temperature variation was found. The results of the study are the basis for developing an optimal soil temperature measurement plan for environmental monitoring purposes. Suggestions were also made for the management of park stands in order to reduce the temperature load. The spatial variation in soil temperature demonstrates the occurrence of scale-dependent patterns. The spatial organization of temperature fields must be taken into account for optimal environmental monitoring and urban environmental management strategies. The soil temperature regime is characterised by a significant level of stability compared to air temperature. The soil temperature fields in an artificial park plantation are characterized by spatial patterns of a complex nature. The temperature field presents a spatial component that is invariant to time. It is most likely that the spatial variability of soil properties induced by natural factors and recreation are the cause of the generation of this pattern. Also in the soil temperature field there is a spatial pattern, which reflects the different sensitivity of the soil to the seasonal trend of temperature change. The generation of this pattern is due to the different insulating capacity of the forest litter in the park plantation. The results obtained point to the important role of leaf litter as a factor in the dynamics of the soil temperature regime. It is hypothesized that leaf litter in the park contributes to the enhancement of carbon sequestration during winter time.
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Stouffer, D. C., D. L. Butler, and D. Hosny. "The Relationship Between Crimp Pattern and Mechanical Response of Human Patellar Tendon-Bone Units." Journal of Biomechanical Engineering 107, no. 2 (May 1, 1985): 158–65. http://dx.doi.org/10.1115/1.3138536.
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The objectives of this study are twofold. First, to further develop the understanding of the relationship between the observed mechanical response and changes in the crimp pattern in human patellar tendon bone units. This is accomplished through the use of a specially constructed test frame and microscope system that permits observation and measurement of the crimp patterns as a function of load. Second, the results of the experimental study are used to develop a constitutive equation that includes spatial variation in the crimp pattern. The results of both the experimental and analytical study imply that local strain in the proximity of the attachment site is significantly larger than the strain in the central region of the tendon. The experimental and histological results are for specimens taken from four human bone-patellar tendon-bone units.
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Dorey, Alfred B., David W. Murray, and J. J. Roger Cheng. "Initial Imperfection Models for Segments of Line Pipe." Journal of Offshore Mechanics and Arctic Engineering 128, no. 4 (October 2, 2005): 322–29. http://dx.doi.org/10.1115/1.2199565.
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Initial imperfections have long been acknowledged as having an effect on the behavior of shell structures, affecting both the global and local behavior. Yet, despite their significance, initial imperfections are rarely included in analytical models for pipelines. This is usually because of the complicated nature of initial imperfections, the difficulty in measuring them, and the small amount of available literature that describes their geometry. Some recent investigations at the University of Alberta in Edmonton have focused on the effect of initial imperfections on the behavior of segments of line pipe. Imperfections measured across the inside surface of pipe test specimens were incorporated into a finite element model that was developed to predict the experimental behavior of the specimens tested under combined loads of internal pressure, axial load and bending moment. Test-to-predicted ratios for the load carrying capacity of the test specimens had a mean value of 1.035 with a coefficient of variation of 0.047. The improvements in the accuracy of the finite element analysis models that include the initial imperfection pattern indicate their importance in modeling the experimental behavior. Once the importance of initial imperfections was established, idealized patterns were developed to simplify numerical modeling. This paper presents the results of different patterns investigated for both plain and girth-welded segments of line pipe and provides recommended simplified assumed initial imperfection patterns.
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Graham, R. Scott, Eric K. Oberlander, John E. Stewart, and David J. Griffiths. "Validation and use of a finite element model of C-2 for determination of stress and fracture patterns of anterior odontoid loads." Journal of Neurosurgery: Spine 93, no. 1 (July 2000): 117–25. http://dx.doi.org/10.3171/spi.2000.93.1.0117.
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Object. The finite element (FE) method is a powerful tool for the analysis of stress patterns of anatomical structures. In this study a highly refined FE model of C-2 was created and validated. The model was then used to characterize stress patterns, predicted fracture patterns, and transitions between Type II and Type III odontoid fractures. Methods. An anatomically accurate three-dimensional model of C-2 was created from computerized tomography data obtained from the Visible Human Project. The C-2 model was broken down into an FE mesh consisting of 32,815 elements and 40,969 nodes. For validation, the FE model was constrained and loaded to simulate that used in previous biomechanical studies. The validated model was then loaded in an iterative fashion, varying the orientation of the load within the validated range. A matrix of stress plots was created for comparative analysis. Results of the validation testing closely correlated with those obtained in previous biomechanical testing. Pure extension loading produced a Type III stress pattern with maximum stress of 134 MPa. Loading at 45° produced a Type II stress distribution with a maximum stress of 123 MPa. These stresses are within 3% and 11%, respectively, of the reported yield stress of cortical bone (138 MPa). In the second portion of the study, systematic variation in the orientation of the load vector revealed that higher stresses were associated with increased lateral angulation and increasing upward inclination of the load vectors. A transition from a Type III to Type II pattern occurred with lateral orientations greater than 15° and with compressive loads of 45°. Conclusions. The validated C-2 FE model described in this study both qualitatively and quantitatively was able to simulate the behavior of the C-2 vertebra in biomechanical testing. In this study the authors demonstrate the utility of the FE method when used in conjunction with traditional biomechanical testing.
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Cortés, Camilo Andrés, Wim Deprez, Johan Driesen, and Jhon J. Pérez. "Determining electrical loss in electromagnetically-modelled induction motors using the finite element method." Ingeniería e Investigación 28, no. 3 (September 1, 2008): 64–74. http://dx.doi.org/10.15446/ing.investig.v28n3.15122.
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This paper shows the pattern of a 7.5 kW squirrel-cage induction motor’s electrical loss in balanced and unbalanced conditions, modelling the motor using the finite element method and comparing the results with experimental data obtained in the laboratory for the selected motor. Magnetic flux density variation was analysed at four places in the machine. The results so obtained showed that the undervoltage unbalanced condition was the most critical from the motor’s total loss point of view. Regarding variation of loss in parts of the motor, a constant iron loss pattern was found when the load was changed for each type of voltage supply and that the place where the loss had the largest rise was in the machine’s rotor.
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Hoover, Kara C., and J. Colette Berbesque. "Early Holocene morphological variation in hunter-gatherer hands and feet." PeerJ 6 (September 5, 2018): e5564. http://dx.doi.org/10.7717/peerj.5564.
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BackgroundThe Windover mortuary pond dates to the Early Archaic period (6,800–5,200 years ago) and constitutes one of the earliest archaeological sites with intact and well-preserved human remains in North America. Unlike many prehistoric egalitarian hunter-gatherers, the Windover people may not have practiced a sex-based division of labor; rather, they may have shared the load. We explore how mobility and subsistence, as reconstructed from archaeological data, influenced hand and foot bone morphology at Windover.MethodsWe took length and width measurements on four carpal bones, four tarsal bones, and load-bearing tarsal areas (calcaneus load arm, trochlea of the talus). We analyzed lateralization using side differences in raw length and width measurements. For other hypothesis testing, we used log transformed length-width ratios to mitigate the confounding effects of sexual dimorphism and trait size variation; we tested between-sex differences in weight-bearing (rear foot) and shock-absorbing (mid foot) tarsal bones and between-sex differences in carpal bones.ResultsWe identified no significant between-sex differences in rear and midfoot areas, suggesting similar biomechanical stresses. We identified no significant between-sex differences in carpal bones but the test was under-powered due to small sample sizes. Finally, despite widespread behavioral evidence on contemporary populations for human hand and foot lateralization, we found no evidence of either handedness or footedness.DiscussionThe lack evidence for footedness was expected due its minimal impact on walking gait but the lack of evidence for handedness was surprising given that ethnographic studies have shown strong handedness in hunter-gatherers during tool and goods manufacture. The reconstructed activity patterns suggested both sexes engaged in heavy load carrying and a shared division of labor. Our results support previous findings—both sexes had stronger weight-bearing bones. Male shock-absorbing bones exhibited a trend towards greater relative width (suggesting greater comparative biomechanical stress) than females which may reflect the typical pattern of male hunter-gatherers engaging in walking greater distances at higher speeds than females. While there were no significant between-sex differences in carpal bones (supporting a shared work load model), females exhibited greater variation in index values, which may reflect a greater variety of and specialization in tasks compared to males. Because carpals and tarsals are so well-preserved at archaeological sites, we had surmised they might be useful proxies for activity in the absence of well-preserved long bones. Tarsals provide a stronger signal of past activity and may be useful in the absence of, or in addition to, preferred bones. Carpals, however, may not be useful as the effect size of biomechanical stress (in this study at least) is low and would require larger samples than may be possible at archaeological sites.
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Majooni, Azam, Mona Masood, and Amir Akhavan. "An eye-tracking study on the effect of infographic structures on viewer’s comprehension and cognitive load." Information Visualization 17, no. 3 (April 3, 2017): 257–66. http://dx.doi.org/10.1177/1473871617701971.
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The basic premise of this research is investigating the effect of layout on the comprehension and cognitive load of the viewers in the information graphics. The term ‘Layout’ refers to the arrangement and organization of the visual and textual elements in a graphical design. The experiment conducted in this study is designed based on two stories and each one of these stories is presented with two different layouts. During the experiment, eye-tracking devices are applied to collect the gaze data including the eye movement data and pupil diameter fluctuation. In the research on the modification of the layouts, contents of each story are narrated using identical visual and textual elements. The analysis of eye-tracking data provides quantitative evidence concerning the change of layout in each story and its effect on the comprehension of participants and variation of their cognitive load. In conclusion, it can be claimed that the comprehension from the zigzag form of the layout was higher with a less imposed cognitive load.
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YANG, Y. B., M. C. CHENG, and K. C. CHANG. "FREQUENCY VARIATION IN VEHICLE–BRIDGE INTERACTION SYSTEMS." International Journal of Structural Stability and Dynamics 13, no. 02 (March 2013): 1350019. http://dx.doi.org/10.1142/s0219455413500193.
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The variation of the instantaneous frequencies of bridges under moving vehicles is a problem not well studied in the literature. A theoretical framework is presented for the problem, considering the variation in frequencies for both the bridge and moving vehicle. First, the equations of motion are written for the two sub-systems. By solving the eigenvalue problem, analytical solutions in closed-form are derived from the frequencies of the vehicle and bridge that are coupled with each other. Based on this, the variation pattern, range, and dominating factors involved are studied, along with the special cases of moving mass and moving load. The results reveal that, if a moving vehicle is to be used as a tool for measuring the bridge frequencies or for detecting the bridge damages, the frequency variation caused by moving vehicles should be taken into account. Such an effect will be crucial when the vehicle mass is not negligible compared with the bridge mass or when the resonance condition is approached.
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Lefeuvre, Pierre-Marie, Miriam Jackson, Gaute Lappegard, and Jon Ove Hagen. "Interannual variability of glacier basal pressure from a 20 year record." Annals of Glaciology 56, no. 70 (2015): 33–44. http://dx.doi.org/10.3189/2015aog70a019.
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AbstractBasal pressure has been recorded at the Svartisen Subglacial Laboratory, northern Norway, for 20 years, and is measured by load cells installed at the ice–rock interface under ~200m of glacier ice. Synchronous pressure variations between load cells are investigated as evidence of stress redistribution and hydrological bed connectivity. A running Pearson correlation is used to study the temporal variation in the response of several sensors. By studying the nature of this correlation as well as the correlation between sensor pairs, it is possible to investigate the evolution of the degree of synchronous response, and to some extent basal connectivity, at the glacier bed. Persistent seasonal variations associated with the melt season are observed throughout the measurement period, indicating dependence on surface hydrological forcing. Overlying this pattern, specific years with longer periods of positive and negative correlation of pressure between sensors are presented to show contrasting interannual variability in basal pressure. An anticorrelated connectivity is associated with a local increase in the rate of daily subglacial discharge, and is caused by load transfer or passive cavity opening. Stable weather appears to enhance connectivity of the sensors, which is attributed to the development of a persistent drainage system and stress redistribution.
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Wardlaw, Andrew, William Fourney, and Ulrich Leiste. "Target Loading from a Submerged Explosion." Shock and Vibration 17, no. 3 (2010): 317–28. http://dx.doi.org/10.1155/2010/978545.
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The pressure on a flat plate suspended over a submerged detonation is measured and simulated. Calculation and experiment are in relatively good agreement, although there is variation in experimental results and simulations are sensitive, near the centerline, to the computational details. This sensitivity is linked to the instability of the accelerating plume, typical of a Richtmyer-Meshkov instability. The plate loading features an initial force at plate center, followed by an expanding circular loading pattern. The initial load is due to plume impact, while the circular load arises from the impact of water transported up the edges of the explosion cavity.
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Kumakura, H., M. Sasaki, and D. Suzuki. "Low NOx Combustor for Automotive Ceramic Gas Turbine—Reliability Assurance." Journal of Engineering for Gas Turbines and Power 115, no. 3 (July 1, 1993): 547–53. http://dx.doi.org/10.1115/1.2906742.
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Two aspects of reliability assurance are discussed. First, this paper deals with the reliability design of emissions under transient conditions. The optimization was made from the simulation results of the relationship between the response of the variable combustor geometry to follow load changes and the resulting exhaust emission levels. The load variation pattern used in this investigation was that of the Japanese ten-mode regulation. Second, this paper describes the validity of the reliability design prepared for the ceramic liner of the combustor. A service life prediction was made for the liner on the basis of stress analysis results and fatigue parameters.
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Li, Qiaoyan, Guowei Ma, Ping Li, and Zhandong Su. "Dynamic characteristics of tailings dam with geotextile tubes under seismic load." REVIEWS ON ADVANCED MATERIALS SCIENCE 60, no. 1 (January 1, 2021): 599–614. http://dx.doi.org/10.1515/rams-2021-0046.
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Abstract Geotextile tubes are one of the emerging and promising technologies to build fine-grain tailings dams. In this study, shaking table model tests are conducted to evaluate the seismic performance as characterized by horizontal acceleration and displacement of the tailings dam subject to horizontal peak ground accelerations (HPGAs). The test results indicate that the tailings dam is sustainable, whereas the whole dam tends to slide forward. Test results reveal a W-pattern variation of acceleration amplification coefficient (A m) at the same elevation despite different HPGA, whereas A m on the geotextile tubes exhibits minimal changes with increasing HPGA. A m inside the dam is highly variable in terms of the elevation and the specific position. The maximum vertical displacement occurs at the top of the geotextile tubes as the side of the geotextile tubes tilting upward. The highest horizontal displacement is observed in the middle section of the geotextile tubes, resulting in an overall convex deformation pattern. Two reinforcement schemes are proposed accordingly including strengthening the drainage and installing the anti-slide piles. The dynamic behaviors of the tailings dam subject to earthquakes from this study can serve as guidance for seismic design and technology promotion.
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Dal Cin, Alessandra, Lorenzo Massaria, and Enzo Siviero. "Mechanical Performance of a Plate Made by RC and Repaired through SFRC Material." Advanced Materials Research 1119 (July 2015): 677–82. http://dx.doi.org/10.4028/www.scientific.net/amr.1119.677.
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The aim of this study is to evaluate the influence of SFRC repairs of different thicknesses on the mechanical performance of RC slabs, especially with respect to the crack pattern and level of cracking load. To understand the influence of SFRC, in terms of performance and variation of cracking load after repairing, a comparison with a reinforced concrete slab without fiber reinforcement was made. The study shows also the mechanical characterization of SFRC through conventional testing, to evaluate compressive strength, fracture energy, tensile strength and toughness. Concerning the application of SFRC on the concrete slab surface, the bond was improved by removing a small amount of superficial material. Finally, the experimental results on cracks distribution, displacements and level of cracking load are shown.
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Sharma, Desh Deepak, and S. N. Singh. "Aberration detection in electricity consumption using clustering technique." International Journal of Energy Sector Management 9, no. 4 (November 2, 2015): 451–70. http://dx.doi.org/10.1108/ijesm-11-2014-0001.
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Purpose – This paper aims to detect abnormal energy uses which relate to undetected consumption, thefts, measurement errors, etc. The detection of irregular power consumption, with variation in irregularities, helps the electric utilities in planning and making strategies to transfer reliable and efficient electricity from generators to the end-users. Abnormal peak load demand is a kind of aberration that needs to be detected. Design/methodology/approach – This paper proposes a Density-Based Micro Spatial Clustering of Applications with Noise (DBMSCAN) clustering algorithm, which is implemented for identification of ranked irregular electricity consumption and occurrence of peak and valley loads. In the proposed algorithm, two parameters, a and ß, are introduced, and, on tuning of these parameters, after setting of global parameters, a varied number of micro-clusters and ranked irregular consumptions, respectively, are obtained. An approach is incorporated with the introduction of a new term Irregularity Variance in the suggested algorithm to find variation in the irregular consumptions according to anomalous behaviors. Findings – No set of global parameters in DBSCAN is found in clustering of load pattern data of a practical system as the data. The proposed DBMSCAN approach finds clustering results and ranked irregular consumption such as different types of abnormal peak demands, sudden change in the demand, nearly zero demand, etc. with computational ease without any iterative control method. Originality/value – The DBMSCAN can be applied on any data set to find ranked outliers. It is an unsupervised approach of clustering technique to find the clustering results and ranked irregular consumptions while focusing on the analysis of and variations in anomalous behaviors in electricity consumption.
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Roberts, Jordan C., and Ralph V. Cartar. "Shape of wing wear fails to affect load lifting in common eastern bumble bees (Bombus impatiens) with experimental wing wear." Canadian Journal of Zoology 93, no. 7 (July 2015): 531–37. http://dx.doi.org/10.1139/cjz-2014-0317.
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Wing wear reflects the accumulation of irreversible damage to an insect’s wings over its lifetime and this damage should influence flight performance. In the case of bumble bees, flight seems robust to variation in wing-area asymmetry and air pressure, but not to loss of wing area. However, how the pattern of wing wear affects flight performance remains unstudied. In nature, wing wear typically occurs in a ragged and haphazard pattern along the wing’s trailing margin, a shape strikingly different from the straight cut applied in past studies. In this study, we test if shape of wing wear (implemented as four distinct treatments plus a control) affects maximum load-lifting capabilities and wingbeat frequency of worker common eastern bumble bees (Bombus impatiens Cresson, 1863). We found that shape of wing wear of 171 mg bees had no detectable effect on maximum load-lifting capability (detectable effect size = 18 mg) or on wingbeat frequency (detectable effect size = 15 Hz), but that loss of wing area reduced load-lifting capability and increased wingbeat frequency. The importance of wing area in explaining the load-lifting ability of bumble bees is reinforced in this study. But, paradoxically, shape of wing wear did not detectably affect lift generation, which is determined by unsteady aerodynamic forces in these lift-reliant insects.
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Rahim, Mohd Reyaz Ur, and Prem Kumar Bharti. "Buckling Analysis of Innovative Corrugated Column by using Response Surface Methodology." Acta Marisiensis. Seria Technologica 17, no. 2 (December 1, 2020): 8–17. http://dx.doi.org/10.2478/amset-2020-0013.
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AbstractTubular steel structures with slender compression cross-sections are prone to local buckling. In this paper the axial compression is investigation of the innovative fabricated structural steel column consisting of sinusoidal corrugated pattern. When it comes to the design of compressive individuals, buckling is a crucial layout provision. The paper describes the effect of variation in the sectional properties like mean diameter, thickness, amplitude, and frequency of corrugation on the buckling axial load. A quadratic model was developed to correlate the independent variables for maximum buckling load by using central composite design (CCD) method. Subsequently ANOVA, a statistical tool is used to analyse and compare the different combinations and finding the most influential factor on buckling load. Response surface methodology is adopted to review the interaction models between the different combinations.
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Ribeiro, Leandro, Maurício Roberto Tosti Narciso, Tatiane Hoshida Felipe, Karina Ramirez Starikoff, Gisele Oliveira de Souza, José Soares Ferreira Neto, Fernando Ferreira, et al. "Decay of Mycobacterium bovis in whole milk submitted to pasteurization parameters." Semina: Ciências Agrárias 37, no. 5Supl2 (November 9, 2016): 3727. http://dx.doi.org/10.5433/1679-0359.2016v37n5supl2p3727.
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Parameters for milk pasteurization were established a long time ago, considering the thermal resistance of Mycobacterium bovis, and the systematic adoption of this process has drastically reduced the incidence of human tuberculosis caused by this pathogen. However, more recently, molecular methods have allowed the identification of genetic variations in this bacterium that may lead to greater thermal resistance. The aim of this study was to investigate whether genetic variation leads to variation in the death pattern of this bacterium during the milk pasteurization process. Samples of UHT (ultra-high temperature)-treated whole milk were artificially contaminated with four different Mycobacterium bovis spoligotypes and were subjected to pasteurization by low-temperature long-time (LTLT) and high-temperature short-time (HTST) treatments. The M. bovis spoligotypes were quantified (Colony Forming Unit per milliliter of milk) before and during the thermal process. The decay of the pathogen was quantified by calculating the difference between the measurements at the beginning and at the end of the thermal treatment. The data demonstrated that the LTLT and HTST pasteurization processes considerably reduced the M. bovis load in the milk; however, the bacterium was not eliminated. There was no difference in the thermal resistance of the spoligotypes tested or in the efficiency of pasteurization processes (LTLT versus HTST). However, heating phase was more effective in reducing the M. bovis load than the target temperature maintenance phase.
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Dawood, Sarmad Dawood Salman, Ahmad Salahuddin Mohd Harithuddin, and Mohammad Yazdi Harmin. "Modal Analysis of Conceptual Microsatellite Design Employing Perforated Structural Components for Mass Reduction." Aerospace 9, no. 1 (January 4, 2022): 23. http://dx.doi.org/10.3390/aerospace9010023.
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Mass reduction is a primary design goal pursued in satellite structural design, since the launch cost is proportional to their total mass. The most common mass reduction method currently employed is to introduce honeycomb structures, with space qualified composite materials as facing materials, into the structural design, especially for satellites with larger masses. However, efficient implementation of these materials requires significant expertise in their design, analysis, and fabrication processes; moreover, the material procurement costs are high, therefore increasing the overall program costs. Thus, the current work proposes a low-cost alternative approach through the design and implementation of geometrically-shaped, parametrically-defined metal perforation patterns, fabricated by standard processes. These patterns included four geometric shapes (diamonds, hexagons, squares, and triangles) implemented onto several components of a structural design for a conceptual satellite, with a parametric design space defined by two scale factors and also two aspect ratio variations. The change in the structure’s fundamental natural frequency, as a result of implementing each pattern shape and parameter variation, was the selection criterion, due to its importance during the launcher selection process. The best pattern from among the four alternatives was then selected, after having validated the computational methodology through implementing experimental modal analysis on a scaled down physical model of a primary load-bearing component of the structural design. From the findings, a significant mass reduction percentage of 23.15%, utilizing the proposed perforation concept, was achieved in the final parametric design iteration relative to the baseline unperforated case while maintaining the same fundamental frequency. Dynamic loading analysis was also conducted, utilizing both the baseline unperforated and the finalized perforated designs, to check its capability to withstand realistic launch loads through applying quasi-static loads. The findings show that the final perforated design outperformed the baseline unperforated design with respect to the maximum displacements, maximum Von Mises stresses, and also the computed margin of safety. With these encouraging outcomes, the perforated design concept proved that it could provide an opportunity to develop low-cost satellite structural designs with reduced mass.
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Tang, Yuanyan, Yi Hui, and Ke Li. "LES study on variation of flow pattern around a 4:1 rectangular cylinder and corresponding wind load during VIV." Journal of Wind Engineering and Industrial Aerodynamics 228 (September 2022): 105121. http://dx.doi.org/10.1016/j.jweia.2022.105121.
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Frantziskonis, G. "Surface Effects in Brittle Materials and Internal Length Estimation." Applied Mechanics Reviews 45, no. 3S (March 1, 1992): S62—S70. http://dx.doi.org/10.1115/1.3121392.
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The concept of state of degradation is employed as a tool to study the effect of initial material (structure) inhomogeneity and the implications of surface (skin) effects on brittle material response. The initial heterogeneity pattern and its growth under external load is studied experimentally via ultrasonic scanning measurements on prismatic simulated rock samples subjected to mechanical load. Numerical solutions are compared with the experimental results. The skin effects are also studied experimentally through the spatial variation of dissipated energy within the samples tested. In addition, microstructure considerations highlight the skin effect and its implications. The material length for the simulated rock is estimated (for load levels up to peak load) through the experimental observations which yielded 1≃0.24 inches (0.61 cm). The analytical solution of a simple problem including microstructure considerations for the same material yielded 1≃0.21 inches (0.53 cm). This paper integrates and extends the recent work of the author and co-workers.
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Soogun, Adenike O., Ayesha B. M. Kharsany, Temesgen Zewotir, Delia North, Ebenezer Ogunsakin, and Perry Rakgoale. "Spatiotemporal Variation and Predictors of Unsuppressed Viral Load among HIV-Positive Men and Women in Rural and Peri-Urban KwaZulu-Natal, South Africa." Tropical Medicine and Infectious Disease 7, no. 9 (September 6, 2022): 232. http://dx.doi.org/10.3390/tropicalmed7090232.
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Unsuppressed HIV viral load is an important marker of sustained HIV transmission. We investigated the prevalence, predictors, and high-risk areas of unsuppressed HIV viral load among HIV-positive men and women. Unsuppressed HIV viral load was defined as viral load of ≥400 copies/mL. Data from the HIV Incidence District Surveillance System (HIPSS), a longitudinal study undertaken between June 2014 to June 2016 among men and women aged 15–49 years in rural and peri-urban KwaZulu-Natal, South Africa, were analysed. A Bayesian geoadditive regression model which includes a spatial effect for a small enumeration area was applied using an integrated nested Laplace approximation (INLA) function while accounting for unobserved factors, non-linear effects of selected continuous variables, and spatial autocorrelation. The prevalence of unsuppressed HIV viral load was 46.1% [95% CI: 44.3–47.8]. Predictors of unsuppressed HIV viral load were incomplete high school education, being away from home for more than a month, alcohol consumption, no prior knowledge of HIV status, not ever tested for HIV, not on antiretroviral therapy (ART), on tuberculosis (TB) medication, having two or more sexual partners in the last 12 months, and having a CD4 cell count of <350 cells/μL. A positive non-linear effect of age, household size, and the number of lifetime HIV tests was identified. The higher-risk pattern of unsuppressed HIV viral load occurred in the northwest and northeast of the study area. Identifying predictors of unsuppressed viral load in a localized geographic area and information from spatial risk maps are important for targeted prevention and treatment programs to reduce the transmission of HIV.
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Moon, Jihoon, Yongsung Kim, Minjae Son, and Eenjun Hwang. "Hybrid Short-Term Load Forecasting Scheme Using Random Forest and Multilayer Perceptron." Energies 11, no. 12 (November 25, 2018): 3283. http://dx.doi.org/10.3390/en11123283.
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A stable power supply is very important in the management of power infrastructure. One of the critical tasks in accomplishing this is to predict power consumption accurately, which usually requires considering diverse factors, including environmental, social, and spatial-temporal factors. Depending on the prediction scope, building type can also be an important factor since the same types of buildings show similar power consumption patterns. A university campus usually consists of several building types, including a laboratory, administrative office, lecture room, and dormitory. Depending on the temporal and external conditions, they tend to show a wide variation in the electrical load pattern. This paper proposes a hybrid short-term load forecast model for an educational building complex by using random forest and multilayer perceptron. To construct this model, we collect electrical load data of six years from a university campus and split them into training, validation, and test sets. For the training set, we classify the data using a decision tree with input parameters including date, day of the week, holiday, and academic year. In addition, we consider various configurations for random forest and multilayer perceptron and evaluate their prediction performance using the validation set to determine the optimal configuration. Then, we construct a hybrid short-term load forecast model by combining the two models and predict the daily electrical load for the test set. Through various experiments, we show that our hybrid forecast model performs better than other popular single forecast models.
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Gunasekaran, Vijay, Jeyaraj Pitchaimani, Lenin Babu Mailan Chinnapandi, and Ashish Kumar. "Analytical Solution for Sound Radiation Characteristics of Graphene Nanocomposites Plate: Effect of Porosity and Variable Edge Load." International Journal of Structural Stability and Dynamics 21, no. 06 (April 5, 2021): 2150087. http://dx.doi.org/10.1142/s0219455421500875.
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The effects of graded dispersion of graphene platelets and porosity on vibro-acoustics of nanocomposite plate exposed to variable edge loads are analytically investigated. Voigt and Halpin–Tsai micromechanics model is used to obtain effective properties of the porous graphene nanocomposites. The strain energy technique is implemented to estimate the buckling load ([Formula: see text]). By means of Reddy’s third-order shear deformation theorem and Rayleigh Integral, vibration and acoustic responses are obtained. After validating the present analysis with the published results, the nature of edge loads on buckling and vibro-acoustic response is significant. It is noted that an increase in the intensity of non-uniform in-plane loads leads to changes in free vibration modes and resonant amplitude of response. The weight percentage and grading pattern of graphene reinforcement cause the stiffness hardening effect, whereas porosity distribution and coefficients cause the stiffness softening effect on the nanocomposite plate. It is found that the plate with symmetric distribution of graphene platelets with more concentration at the surface and symmetric porosity variation with more porosity at the center radiates less sound power.
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Yuda, Hu, Li Zhe, Du Guojun, and Wang Yanan. "Magneto-Elastic Combination Resonance of Rotating Circular Plate with Varying Speed Under Alternating Load." International Journal of Structural Stability and Dynamics 18, no. 03 (February 27, 2018): 1850032. http://dx.doi.org/10.1142/s0219455418500323.
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Nonlinear magneto-elastic combined resonance of parametric and forced excitations is investigated for a rotating circular plate with a variable speed under alternating load. According to the magneto-elastic vibration equations of a conductive rotating thin circular plate, the axisymmetric vibration differential equations of the rotating circular plate under transverse magnetic field are obtained through the application of the Galerkin integral method. The method of multiple scales is applied to solve the differential equations of the circular plate under alternating magnetic field, and the resonance states of the system under combined parametric and forced excitations are obtained by analyzing secular terms. The respective amplitude–frequency response equations are also derived, as well as the necessary and sufficient conditions of the system to make it stable. A numerical method is adopted to acquire amplitude–frequency response curves, bifurcation diagrams of amplitude and the variation pattern of amplitude with magnetic induction intensity and radial force. The influence of parameter variation on stability of the system is also investigated. Based on the global bifurcation diagram of the system, the influence of the change of bifurcation parameters on the system dynamics is discussed.
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Krisnamurti, Agoes Soehardjono, Achfas Zacoeb, and Ari Wibowo. "Flexural performance of HPFRC plates using PPC and variation of steel fiber composition." MATEC Web of Conferences 195 (2018): 02003. http://dx.doi.org/10.1051/matecconf/201819502003.
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High-Performance Fiber-Reinforced Concrete (HPFRC) is widely used in infrastructure applications due to its mechanical properties such as fracture toughness, ductility, control of crack width, and plate thickness reduction compared to normal concrete. However, there are still doubts about the strategy to develop the concrete technology to meet the sustainability requirements in the construction process. This study aims to investigate the improvement of flexural performance on HPFRC plates that utilize Portland Pozzolana Cement (PPC) with various compositions of steel fiber. This research uses PPC, Lumajang sand, gravel from the Malang area, water, silica fume, superplasticizer, and steel fiber. Tests were performed on 1600 mm x 900 mm x 80 mm HPFRC plates. The average HPFRC compressive strength is 59.59 MPa. The splitting tensile strength is 3.54 MPa. Steel fibers vary from 0.2% to 1.0% of the HPFRC plate volume. The test was performed with the three-point bending method. Observations were made to the load capacity, deflection and the crack pattern of the HPFRC plates. The study shows that the optimum bending strength failure of the HPFRC plate is obtained when the steel fiber composition is about 0.8% with an external load value of 31.76 kN and a deflection of 14.99 mm.
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Li, Peng, Hui Zhang, Shengyuan Jiang, and Weiwei Zhang. "Analysis and Testing of Load Characteristics for Rotary-Percussive Drilling of Lunar Rock Simulant with a Lunar Regolith Coring Bit." Shock and Vibration 2017 (2017): 1–15. http://dx.doi.org/10.1155/2017/3012749.
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Based on an optimized lunar regolith coring bit (LRCB) configuration, the load characteristics of rotary-percussive drilling of lunar rock simulant in a laboratory environment are analyzed to determine the effects of the drilling parameters (the rotational velocity, the penetration rate, and the percussion frequency) on the drilling load. The process of rotary drilling into lunar rock using an LRCB is modeled as an interaction between an elemental blade and the rock. The rock’s fracture mechanism during different stages of the percussive mechanism is analyzed to create a load forecasting model for the cutting and percussive fracturing of rock using an elemental blade. Finally, a model of the load on the LRCB is obtained from the analytic equation for the bit’s cutting blade distribution; experimental verification of the rotary-impact load characteristics for lunar rock simulant with different parameters is performed. The results show that the penetrations per revolution (PPR) are the primary parameter influencing the drilling load. When the PPR are fixed, increasing the percussion frequency reduces the drilling load on the rock. Additionally, the variation pattern of the drilling load of the bit is in agreement with that predicted by the theoretical model. This provides a research basis for subsequent optimization of the drilling procedure and online recognition of the drilling process.
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Hechinger, Ryan F., Kate L. Sheehan, and Andrew V. Turner. "Metabolic theory of ecology successfully predicts distinct scaling of ectoparasite load on hosts." Proceedings of the Royal Society B: Biological Sciences 286, no. 1917 (December 18, 2019): 20191777. http://dx.doi.org/10.1098/rspb.2019.1777.
Full textAbstract:
The impacts of parasites on hosts and the role that parasites play in ecosystems must be underlain by the load of parasites in individual hosts. To help explain and predict parasite load across a broad range of species, quantitative theory has been developed based on fundamental relationships between organism size, temperature and metabolic rate. Here, we elaborate on an aspect of that ‘scaling theory for parasitism’, and test a previously unexplored prediction, using new data for total ectoparasite load from 263 wild birds of 42 species. We reveal that, despite the expected substantial variation in parasite load among individual hosts, (i) the theory successfully predicts the distinct increase of ectoparasite load with host body size, indicating the importance of geometric scaling constraints on access to host resources, (ii) ectoparasite load appears ultimately limited by access—not to host space—but to host energy, and (iii) there is a currency-dependent shift in taxonomic dominance of parasite load on larger birds. Hence, these results reveal a seemingly new macroecological pattern, underscore the utility of energy flux as a currency for parasitism and highlight the promise of using scaling theory to provide baseline expectations for parasite load for a diversity of host species.
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Худолій, О. М., О. В. Іващенко, and В. І. Бекетов. "Technological Approaches to Evaluating Training Effects of Power Load in Primary Schoolers." Teorìâ ta Metodika Fìzičnogo Vihovannâ, no. 1 (March 29, 2015): 16. http://dx.doi.org/10.17309/tmfv.2015.1.1121.
Full textAbstract:
Research objective. To experimentally ground the technological approaches to evaluating training effects of primary schoolers’ power loads.Materials and methods. To achieve the objectives outlined, the research used the following methods: analysis of scientific and methodological literature, pedagogical testing, modeling, pedagogical observation and experiment, methods of mathematical experiment planning (complete factorial experiment, 2k type), discriminant analysis. The participants in the study were 32 second grade boys.Research results. The training pattern affects the dynamics in the test results for the second grade boys. The test results can improve provided that the power load brings about significant changes after the training at each spot, after the training (immediate training effect), and twenty four hours after the power load (delayed training effect). The higher the dynamics is for the immediate and delayed training effects, the more significant are the improved power tests results observed after as few as three lessons.Conclusions. The discriminant function can be used to classify the training effects of the second grade boys’ power loads. The first canonical function explains the results variation by 85.0%, the second one — by 14.0%. This suggests that they are highly informative. The centroid coordinates for five groups allow to interpret the canonical functions according to the role differentiating the grades by the training effects of the primary schoolers’ power loads. The positive pole of the first function has the condition centroids at the beginning of the power loads, after three, six, nine and twelve lessons; the negative pole has the centroids of the training effects after the power loads, after the lesson, after 24 hours.Thus, the reaction to the power load has immediate, delayed and cumulative training effects.