Academic literature on the topic 'Negative Curvature Parameters'
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Journal articles on the topic "Negative Curvature Parameters"
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Wang, Liming, and Thomas J. McCarthy. "Capillary-bridge–derived particles with negative Gaussian curvature." Proceedings of the National Academy of Sciences 112, no. 9 (February 17, 2015): 2664–69. http://dx.doi.org/10.1073/pnas.1424383112.
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We report the preparation of millimeter-scale particles by thermal polymerization of liquid monomer capillary bridges to form catenoid-shaped particles that exhibit negative Gaussian curvature. The shape of the capillary bridges and resulting particles can be finely tuned using several addressable parameters: (i) the shape, size, and orientation of lithographic pinning features on the spanned surfaces; (ii) the distance between opposing support surfaces; and (iii) the lateral displacement (shear) of opposing features. The catenoid-shaped particles exhibit controllable optical properties as a result of their concave menisci, the shape of which can be easily manipulated. The particles self assemble in the presence of a condensing liquid (water) to form reversible neck-to-neck pairs and less reversible end-to-end aggregates. We argue that this approach could be scaled down to micrometer dimensions by fabricating an array of micrometer-scale particles. We also argue, with a discussion of dynamic wetting, that these particles will exhibit interesting anisotropic adhesive properties.
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Fomin, Yu D., N. V. Gribova, and V. N. Ryzhov. "Complex Phase Behavior of Systems with Negative Curvature Potentials." Defect and Diffusion Forum 277 (April 2008): 155–60. http://dx.doi.org/10.4028/www.scientific.net/ddf.277.155.
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The comprehensive computer simulation study of the phase diagram of the repulsive step potential system in three dimensions is represented. We show that the system with a simple purely repulsive isotropic potential demonstrates a number of unusual features. The maxima and minima on the melting curve are found for some regions of potential parameters. It is shown that the phase diagram in ρ-T plane includes two isostructural crystalline parts separated by the disordered phase which is amorphous at low enough temperatures. Phase diagram in the (P-T) plane shows that the transition to the amorphous state occurs approximately along the extrapolated spinodals. Structural FCC-BCC phase transition is found at high densities.
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Alagashev, G. K., A. D. Pryamikov, A. F. Kosolapov, A. N. Kolyadin, A. Yu Lukovkin, and A. S. Biriukov. "Impact of geometrical parameters on the optical properties of negative curvature hollow-core fibers." Laser Physics 25, no. 5 (April 8, 2015): 055101. http://dx.doi.org/10.1088/1054-660x/25/5/055101.
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Junesch, Juliane, Gustav Emilsson, Kunli Xiong, Shailabh Kumar, Takumi Sannomiya, Hudson Pace, Janos Vörös, Sang-Hyun Oh, Marta Bally, and Andreas B. Dahlin. "Location-specific nanoplasmonic sensing of biomolecular binding to lipid membranes with negative curvature." Nanoscale 7, no. 37 (2015): 15080–85. http://dx.doi.org/10.1039/c5nr04208a.
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Беляева, Ирина Николаевна, Игорь Константинович Кириченко, Олег Дмитриевич Пташный, Наталья Николаевна Чеканова, and Татьяна Александровна Ярхо. "NORMALIZATION OF CLASSICAL HAMILTONIAN SYSTEMS WITH TWO DEGREES OF FREEDOM." Physical and Chemical Aspects of the Study of Clusters, Nanostructures and Nanomaterials, no. 12() (December 15, 2020): 348–55. http://dx.doi.org/10.26456/pcascnn/2020.12.348.
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В работе исследовано семейство гамильтоновых систем с двумя степенями свободы. Расчетами сечений Пуанкаре показано, что при произвольных значениях параметров функции Гамильтона система является неинтегрируемой и в ней реализуется динамический хаос. Найдено, что для трех наборов параметров рассматриваемая система является интегрируемой, однако в одном интегрируемом случае при этих же значениях параметров на поверхности потенциальной энергии имеется область с отрицательной гауссовой кривизной, в то же время в двух других случаях интегрируемости при соответствующих значениях параметров областей с отрицательной гауссовой кривизной не имеется. Таким образом, наличие областей с отрицательной гауссовой кривизной на поверхности потенциальной энергии не достаточно для развития в системе глобального хаоса. Получена классическая нормальная форма для произвольных значений параметров. The family of the Hamiltonian systems with two degrees of freedom was investigated. The calculations of the Poincaré sections show that with arbitrary values of the parameters of the Hamilton function, the system is non-integrable and dynamic chaos is realized in it. For the three parameter sets, the system in question was found to be integrable, but shows that in one integrable case on the potential energy surface (PES) there are regions with the negative Gaussian curvature. It was found that in one integrable case for the same values of the parameters, the potential energy surface has a region with the negative Gaussian curvature. At the same time, in the other two cases, the domains with negative Gaussian curvature are not integrable for the corresponding values of the parameters. Thus, the presence of regions with negative Gaussian curvature on the potential energy surface is not enough for the development of the global chaos in the system. The classical normal form for arbitrary parameter values is obtained.
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Xu, Jin, Kui Yang, YiMing Shao, and GongYuan Lu. "An Experimental Study on Lateral Acceleration of Cars in Different Environments in Sichuan, Southwest China." Discrete Dynamics in Nature and Society 2015 (2015): 1–16. http://dx.doi.org/10.1155/2015/494130.
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In view of the tremendous improvements in the dynamic performance of automobiles and changes in the composition of drivers over the past several decades, it is valuable to examine the distribution of automobile’s lateral acceleration in new environments. The lateral accelerations, speeds, and trajectory curvatures of a passenger car on twelve highways with different design speeds and topographies were obtained. By synchronizing, matching, and counting, the distribution of the lateral acceleration was obtained, and the level of driving comfort was estimated. The10th,15th,50th,85th, and90thpercentile values of the lateral acceleration on three road types (six-lane road, four-lane road, and two-lane road) were found. Combined with scatter diagrams of the lateral acceleration over the curvature, the negative correlation between the lateral acceleration and the curvature was analyzed and interpreted. In addition, regression models of the lateral acceleration with the curvature for the three kinds of roads were established. Based on scatter diagrams of the lateral acceleration over the speed, regression models of the averageaydepending on the speed and the85thpercentileaydepending on the speed of passenger cars and buses were established. The research provides calculation parameters and a control basis for operating speed prediction, pavement material design, and maximum and minimum limit value determination for the superelevation ratios and curve radii.
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CHERN, DE-CHING, JAMES M. NESTER, and HWEI-JANG YO. "POSITIVE ENERGY TEST OF POINCARÉ GAUGE THEORY." International Journal of Modern Physics A 07, no. 09 (April 10, 1992): 1993–2003. http://dx.doi.org/10.1142/s0217751x92000879.
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The positive total energy test is applied to the Poincaré Gauge Theory of gravity. Both the asymptotically flat and asymptotically constant negative curvature case are considered. The test shows that in either case, the theory with generic values for the parameters is not viable.
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Huisman, A. E., and D. J. Brown. "Genetic parameters for bodyweight, wool, and disease resistance and reproduction traits in Merino sheep. 4. Genetic relationships between and within wool traits." Animal Production Science 49, no. 4 (2009): 289. http://dx.doi.org/10.1071/ea08173.
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The aim of this paper was to describe the genetic relationship among expressions at different ages of seven wool traits: greasy and clean fleece weights, fibre diameter, coefficient of variation of fibre diameter, staple length and strength, and mean fibre curvature. Genetic correlations among measurements at different ages for the same trait were moderate to high, and ranged from ~0.6 for both fleece weights to 0.9 and higher for mean fibre diameter and curvature. Generally, low to moderate genetic correlations (0.3–0.4) were estimated between fleece weights and fibre diameter, clean fleece weight and staple length, and fibre diameter and staple strength. Small positive genetic correlations (0.2) were estimated between greasy and clean fleece weight with fibre diameter coefficient of variation, and between fibre diameter and staple length. Mean fibre curvature had a negative genetic correlation (approximately –0.4) with most other wool traits, the exceptions were staple strength (~0.0) and coefficient of variation of fibre diameter (approximately –0.1). Fibre diameter, staple length and staple strength had negative genetic correlations with coefficient of variation of fibre diameter (–0.15, –0.10, and –0.61, respectively). The results indicate that for most wool traits only one measurement across ages is required to make accurate selection decisions. The relationships between traits are generally moderate to low suggesting that simultaneous genetic improvement is possible.
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Qiu, Dandan, Lei Luo, Songtao Wang, Bengt Ake Sunden, and Xinhong Zhang. "Analysis of heat transfer and fluid flow of a slot jet impinging on a confined concave surface with various curvature and small jet to target spacing." International Journal of Numerical Methods for Heat & Fluid Flow 29, no. 8 (August 5, 2019): 2885–910. http://dx.doi.org/10.1108/hff-07-2018-0354.
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Purpose This study aims to focus on the surface curvature, jet to target spacing and jet Reynolds number effects on the heat transfer and fluid flow characteristics of a slot jet impinging on a confined concave target surface at constant jet to target spacing. Design/methodology/approach Numerical simulations are used in this research. Jet to target spacing, H/B is varying from 1.0 to 2.2, B is the slot width. The jet Reynolds number, Rej, varies from 8,000 to 40,000, and the surface curvature, R2/B, varies from 4 to 20. Results of the target surface heat transfer, flow parameters and fluid flow in the concave channel are performed. Findings It is found that an obvious backflow occurs near the upper wall. Both the local and averaged Nusselt numbers considered in the defined region respond positively to the Rej. The surface curvature plays a positive role in increasing the averaged Nusselt number for smaller surface curvature (4-15) but affects little as the surface curvature is large enough (> 15). The thermal performance is larger for smaller surface curvature and changes little as the surface curvature is larger than 15. The jet to target spacing shows a negative effect in heat transfer enhancement and thermal performance. Originality/value The surface curvature effects are conducted by verifying the concave surface with constant jet size. The flow characteristics are first obtained for the confined impingement cases. Then confined and unconfined slot jet impingements are compared. An ineffective point for surface curvature effects on heat transfer and thermal performance is obtained.
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ITIN, YAKOV. "COFRAME TELEPARALLEL MODELS OF GRAVITY: EXACT SOLUTIONS." International Journal of Modern Physics D 10, no. 04 (August 2001): 547–73. http://dx.doi.org/10.1142/s0218271801001025.
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The superstring and superbrane theories include gravity as a necessary and fundamental part of a (future) unified field theory. Thus it is important to consider the alternative representations of general relativity as well as the alternative models of gravity.We study the coframe teleparallel theory of gravity with a most general quadratic Lagrangian. The coframe field on a differentiable manifold is a basic dynamical variable. A metric tensor as well as a metric compatible connection is generated by a coframe in a unique manner.The Lagrangian is a general linear combination of Weitzenböck's quadratic invariants with free dimensionless parameters ρ1, ρ2, ρ3. Every independent term of the Lagrangian is a global SO(1,3)-invariant 4-form. For a special choice of parameters which confirms with the local SO(1,3) invariance this theory gives an alternative description of Einsteinian gravity — teleparallel equivalent of GR.The field equations of the theory is studied by a "diagonal" coframe ansatz which is a subclass of a most general spherical-nsymmetric Einstein–Mayer ansatz. The restricted Lagrangian depends only on two free parameters ρ1, ρ3.We obtain a formula for scalar curvature of a pseudo-Riemannian manifold with a metric constructed from the static "diagonal" solution of the field equation. It is proved that the sign of the scalar curvature depends only on a relation between the parameters ρ1and ρ3. Thus by a specific choice of free parameters a manifold of positive or negative curvature can be obtained. The scalar curvature vanishes only for a subclass of models with ρ1=0. This subclass includes the teleparallel equivalent of GR.We obtain the explicit form of all spherically symmetric static solutions of the "diagonal" type to the field equations for an arbitrary choice of free parameters. We prove that the unique asymptotic-flat solution with Newtonian limit is the Schwarzschild solution that holds for a subclass of teleparallel models with ρ1=0. Thus the Yang–Mills-type term of the general quadratic coframe Lagrangian should be rejected.
Dissertations / Theses on the topic "Negative Curvature Parameters"
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Mohammed, Abdulhakeem Othman. "Slimness, Thinness and other Negative Curvature Parameters of Graphs." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1561995374485276.
Full textConference papers on the topic "Negative Curvature Parameters"
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Akand, Tawhida, Md Jahrul Islam, and Md Rejvi Kaysir. "Effect of capillary parameters on the performance of modified negative curvature hollow core fibers." In 2020 11th International Conference on Electrical and Computer Engineering (ICECE). IEEE, 2020. http://dx.doi.org/10.1109/icece51571.2020.9393049.
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Sethuraman, Eashwar, Dimitris E. Nikitopoulos, and Sumanta Acharya. "Heat/Mass Transfer in Rotating, Smooth, High Aspect-Ratio (4:1) Coolant Channels With Curved Walls in 90° and 45° Orientation." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50247.
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The paper presents an experimental study of heat/mass transfer coefficient in 4:1 aspect ratio smooth channels with non-uniform cross-sections. Curved leading and trailing walls are studied for two curvatures and for two different curvature configurations. One configuration has curved walls with curvature corresponding to the blade profile (positive curvature on both leading and trailing walls), and the other configuration has leading and trailing walls that curve inwards into the coolant passage (negative curvature on the leading surface and positive curvature on the trailing surface). The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. Only the radially outward flow is considered for the present study at a Reynolds number of 20,000, rotation numbers in the range 0–0.051 and for 90° and 45° orientations with respect to the direction of rotation. In addition to area averaged values, the span-wise mass transfer distributions of fully developed regions of the channel walls are presented in order to delineate the effects of rotation number, channel shape and orientation. The mass transfer data from the curved wall channels are compared to those from a smooth 4:1 rectangular duct with similar flow parameters. Pressure drop along each channel is also measured and put in perspective of the mass/heat transfer results for the 90° orientation, through the presentation of a performance factor.
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Sethuraman, Eashwar, Dimitris E. Nikitopoulos, and Sumanta Acharya. "Mass/Heat Transfer in Rotating, Smooth, High-Aspect Ratio (4:1) Coolant Channels With Curved Walls." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90052.
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The paper presents an experimental study of heat/mass transfer coefficient in 4:1 aspect ratio smooth channels with non-uniform cross-sections. Curved leading and trailing edges are studied, for two curvatures of 9.06 m−1 (0.23 in−1) and 15.11 m−1 (0.384 in−1) and for two different curvature configurations. One configuration has curved walls with curvature corresponding to the blade profile (positive curvature on both leading and trailing walls), and the other configuration has leading and trailing walls that curve inwards into the coolant passage (negative curvature on the leading surface and positive curvature on the trailing surface). A detailed study at Re = 10,000 with rotation numbers in the range of 0–0.07 is undertaken for the two different curvature configurations. All experiments are done for a 90° passage-orientation with respect to the plane of rotation. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. Only the radially outward flow is considered for the present study. The span-wise mass transfer distributions of fully developed regions of the channel walls are also presented. The mass transfer data from the curved wall channels is compared to those from a smooth 4:1 rectangular duct with similar flow parameters. The local mass transfer data is analyzed mainly for the fully developed region, and area-averaged results are presented to delineate the effect of the rotation number. Heat transfer enhancement especially in the leading wall is seen for the lower curvature channels, and there is a subsequent reduction in the higher curvature channel, when compared to the 4:1 rectangular smooth channel. This indicates that an optimal channel wall curvature exists for which heat transfer is the highest.
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Powledge, Aaron C., Darren J. Hartl, and Richard J. Malak. "Experimental Analysis of Self-Folding SMA-Based Sheet Design for Simulation Validation." In ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7546.
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The goal of this research is to experimentally characterize the capabilities of a concept for a self-folding reconfigurable sheet for use in origami-inspired engineering design and to use this characterization to validate simulations of physics-based models of the sheet. The sheet consists of an active, self-morphing laminate that contains two shape memory alloy (SMA) mesh layers and a passive compliant medium between these layers. The SMA layers are thermally actuated, allowing bending to occur in both positive and negative directions to create soft hill and valley folds. These folds are completely reversible, allowing the structure to fold and unfold without permanent deformation. Unlike past work on self-folding structures, these sheets can have folds along any line, be subsequently unfolded, and then be folded again in a new way. To explore the effect of changing design parameters on the performance metrics of the sheet, it is desirable to use Finite Element Analysis (FEA) simulations instead of relying on time consuming experiments. Such models have been created incorporating user material subroutines (UMATs) in an FEA solver such as Abaqus to capture material behavior, but these must now be validated against experimental data to establish how well they match experimental performance. The primary performance metric of the sheet was chosen to be the radius of curvature measured perpendicularly to the line of heating. Both experiment and simulation focus on the radius of curvature achieved by the sheet for a given set of design parameters and actuation path. The goal of validation is to achieve a desirable level of agreement and repeatability in these results. To measure the deformation and curvature in the sheet as it actuates, a 3D Digital Image Correlation (3D DIC) system is employed to track the movement of points along the surface of the sample as it is heated to a temperature above the transformation temperature of the SMA and allowed to fully actuate. These tools are utilized for a number of samples so that validation of the sheet encompasses multiple values for each of the primary design parameters.
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Chen, Da-Ming, Y. F. Xu, and W. D. Zhu. "Operational Modal Analysis and Damage Identification of Structures Undergoing Random Vibration Using a Continuously Scanning Laser Doppler Vibrometer System." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88058.
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A continuously scanning laser Doppler vibrometer (CSLDV) system is capable of efficient and spatially dense vibration measurements by sweeping its laser spot along a scan path assigned on a structure. This paper proposes a new operational modal analysis (OMA) method based on a data processing method for CSLDV measurements of a structure, called the lifting method, under white-noise excitation and applies a baseline-free method to identify structural damage using estimated mode shapes from the OMA method. The lifting method enables transformation of raw CSLDV measurements into measurements at individual virtual measurement points, as if the latter were made by use of an ordinary scanning laser Doppler vibrometer in a step-wise manner. It is shown that a correlation function with non-negative time delays between lifted CSLDV measurements of two virtual measurement points on a structure under white-noise excitation and its power spectrum contain modal parameters of the structure, i.e., natural frequencies, modal damping ratios and mode shapes. The modal parameters can be estimated by using a standard OMA algorithm. A major advantage of the proposed OMA method is that curvature mode shapes associated with mode shapes estimated by the method can reflect local anomaly caused by small-sized structural damage, while those estimated by other existing OMA methods that use CSLDV measurements cannot. Numerical and experimental investigations are conducted to study the OMA method and baseline-free structural damage identification method. In the experimental investigation, effects of the scan frequency of a CSLDV system on the two methods were studied. It is shown in both the numerical and experimental investigations that modal parameters can be accurately estimated by the OMA method and structural damage can be successfully identified in neighborhoods with consistently high values of curvature damage indices.
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Farhang, K., D. Y. Hua, P. Wang, and Y. Li. "An Assessment of Statistical Theory of Contact Between Macroscopically Conforming Rough Surfaces." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63309.
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Most engineering surfaces possess topographies that are anisotropic. Some of the anisotropic surfaces are unintended result of machining process and others are by design for the purpose of lubricant retention or other considerations. Such is the case in problems involving piston liner and mechanical seal performance wherein the conformal contact of two rough surfaces is considered. It becomes critical to component performance to predict average contact pressure and gap between rough surfaces. Two of the well-known asperity-based statistical theories along with a deterministic method, based on Multi Level Multi Summation (MLMS) technique, are used to study the contact of nominally flat rough surfaces. The asperity-based statistical theories are GW model (Greenwood and Williamson, [1]), and its extension proposed by Chang, Bogy and Etsion [2], CEB model, for treating elastic-plastic contact. The contact examined is a set of nominally flat rough surfaces with a smooth flat. This study attempts to address two questions. The first concerns the effectiveness of asperity-based statistical theories in predicting average contact stress of rough surfaces with various degrees of topographic anisotropy. The second question involves the use of directional curvatures to ascertain the appropriateness of plane curvatures when degree of anisotropy is significant. To this end random surfaces are generated for five degrees of anisotropy including correlation length ratios 1, corresponding to an isotropic surface, and 3, 9, 36 and 81, corresponding to an increasing degree of geometric anisotropy. A module of Surface Distress Analytical Toolset (SDAT), for treating dry contact using deterministic approach with MLMS technique, is utilized to compute the contact pressure for these surfaces. This analysis constitutes ten surfaces for each correlation ratio resulting in fifty simulations of SDAT. For each correlation ratio statistical averages and variations of the maximum and mean contact pressures are found. Using the generated random surfaces, GW and CEB models are furnished with the parameters that include the standard deviation of summit height distribution, area summit density and six curvatures associated with asperity summit. These involve four directional curvatures that include curvatures along the x, y, positive diagonal, negative diagonal, and two equivalent curvatures, one based on spherical tip using average of the four diagonal curvatures and the other based on ellipsoidal asperity summit (Fig 1). The study suggests that GW and CEB typically overestimate average contact pressure. The mean pressures predicted using the largest directional summit curvature agrees most favorably with those predicted by SDAT. Surprisingly, agreement is most favorable for highest geometrical anisotropy. Both statistical methods seem effective in predicting mean gap between surfaces for moderate to low nominal pressures.
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Conners, Briana M., Ehsan Rajabi-Jaghargh, and Rupak K. Banerjee. "Effect of the Anastomotic Angle on the Wall Shear Stress Profiles in the Arteriovenous Fistulae." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14405.
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A significant number of arteriovenous fistulae (AVFs) fail to mature to support hemodialysis. Hemodynamic parameters, mainly wall shear stress (WSS), are believed to play a crucial role in the maturation or failure of AVFs. Our goal is to study the effects of the AVF configuration on the WSS profile. Idealized AVFs with 90°, 60°, and 30° anastomotic angles were created based on our previous experimental data from an in-vivo swine model [1]. The hemodynamic parameters were then obtained using numerical techniques under steady state condition. The average WSS values for our models were within range of the swine model average WSS (= 174.9±64.6 dyne/cm 2). For all AVFs, WSS was higher along the bend. The highest WSS occurred on the outer wall (OW) of the 30° AVF (= 613 dyne/cm 2) compared to the 60° (= 407 dyne/cm 2) and 90° AVFs (= 329 dyne/cm 2). WSS on the inner wall (IW) of the bend was negative with the smallest magnitude in the 90° AVF (= −91 dyne/cm 2) compared to the 60° (= −172 dyne/cm 2) and 30° AVFs (= −169 dyne/cm 2). In addition, the maximum difference in WSS (ΔWSS: measure of axial WSS gradient) was less for the 90° AVF (= 158 dyne/cm 2) than the 60° (= 170 dyne/cm 2) and 30° AVFs (= 414 dyne/cm 2). A similar trend was found on the OW with ΔWSS of 161, 405, and 870 dyne/cm 2 for the 90°, 60°, 30° AVF, respectively. Moreover, AVFs with different angles can be categorized based on Dean number ( De) which showed an inverse correlation to WSS range. Thus, creating an AVF with a surgical configuration that results in a low De, representing a sharp bend with large radius of curvature, could result in a hemodynamic condition (high WSS and ΔWSS) that could have adverse effects on the fistula maturation.
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Eckstein, Eugene C., Vinay Bhal, JoDe M. Lavine, Baoshun Ma, Mark Leggas, and Jerome A. Goldstein. "Nested First-Passages of Tracer Particles in Flows of Blood and Control Suspensions: Symmetry and Lorentzian Transformations." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69549.
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Theory of molecular Taylor-Aris dispersion (TAD) is an accepted framework describing tracer dispersion in suspension flows and determining effective diffusion coefficients. Our group reported a pseudo-Lagrangian method to study dispersion in suspension flows at FEDSM-2000. Tracer motions were studied in a steadily moving inertial reference frame (SMIRF) aligned with the flow direction; increments of change of axial position of individual tracers were collected to demonstrate how the tracer moved as they, individually, interacted with similar collections of other bodies brought to and from the region. First, individual tracers with no apparent axial velocity component (NAAVC) were identified; they exhibited fixed positions in video recordings of images collected in the SMIRF. Then, time increments were measured for tracers to pass at least 5, but usually 10 pre-selected, nested distances in the up- or downstream direction laid out with respect to the zero-site in the SMIRF. Such data were richer than measurements of tracer spread over time because stations along each path were serial first-passages (FP) with probabilistic meaning. Dispersion of various types of suspension and two transformation rules for combining velocity components are discussed herein. Traditional low-speed continuum theory and particle dynamics use Galilean transforms. Yet, to recognize the limited speed in laws for channel flows, Lorentzian transformations may be appropriate. In a four-space, deterministic paths would begin at NAAVC sites and continue in time-like conical regions of four-space. Distances in this space are measured using Minkowski’s metric; at the NAAVC site and on the boundary of the space-time cone, this metric has the format of the Fürth, Ornstein, and Taylor (FOT) equation when only terms to order t2 are used. Data shown at FEDSM-2000 can be reinterpreted as “prospective paths” in time-like regions that were consolidated in normalized cumulative probability distributions to provide retrospective descriptions. The ad hoc sign alteration of the FOT equation to fit the data of FEDSM-2000 is now taken as a part of measuring lengths using a Minkowski metric, which signifies a hyperbolic geometry, for which an inherent scaling constant is a negative curvature. The space also has an intrinsic distance of ℓ = Sτ, obtained from fitting parameters (S, τ) for the FOT equation. Integrals of the area under the FOT curve have units of volume, which are considered as describing an average volume of dispersion on S3, the 3-sphere. Path motion through this volume was kinematic dispersion, S2τ, which was the form for effective diffusivity in continuum theory used in FEDSM-2000. Weiner and Wilmer describe transformations in four-spaces in terms of commutating rotations on orthogonal planes, a concept readily linked to symmetries in the hyperbolic space typical of Lorentzian transformations; they also describe a second order ODE like the FOT equation.
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Wu, Haoran, Xiaobin Lin, and Jie Zhang. "An Arrow-Shaped Honeycomb Pedestal With Negative Poisson Ratio and its Impact Resistance." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95745.
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Abstract The ship’s pedestal is the connection structure between the ship’s equipment and the hull, and is also the basis for the installation of the equipment. The pedestal bears both the static load generated by the weight of the equipment and the dynamic load generated during the operation of the equipment, and at the same time transmits the external load received by the hull to the equipment, and the load it bears is very complicated. If there is a problem with the pedestal in an impact environment, the accuracy of the system equipment will be affected, the system equipment will not work properly. Negative Poisson’s ration structures have a unique set of properties because of their tensile expansion, such as increased shear modulus, enhanced fracture toughness, better energy absorption and co-curvature. In recent years, the negative Poisson’s ration honeycomb structure has been applied to the pedestal of marine equipment, which demonstrates good vibration damping effect. However, the pedestal has two functions: vibration damping and impact resistance, there is not much research on the impact resistance of the pedestal. In this paper, an “arrow-shaped” honeycomb pedestal is taken as the research object. Firstly, the analytical expression of the Poisson’s ration of the honeycomb pedestal is derived theoretically and the influence of each parameter on the Poisson’s ration is analyzed. Secondly, the effect of Poisson’s ration on the impact resistance of the pedestal was analyzed by ensuring that the pedestal height was constant. It was found that with the reduction of Poisson’s ration, the impact resistance of the pedestal and the output impact environment of the pedestal panel were effectively optimized. Finally, by ensuring that the height of the pedestal is constant and the Poisson’s ration is the same, the influence of the number of honeycomb layers on the impact resistance of the pedestal is analyzed.
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Razavi, Seyed Reza, and Masoud Boroomand. "Optimal Design and Aerodynamic Study of Leaned Transonic Axial Flow Fan Rotors." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-39796.
Full textAbstract:
Multi-Objective Optimization Problems (MOP) are very usual and complicated subjects in Turbomachinery and there are several methodologies for optimizing these problems. Genetic Algorithm (GA) and Artificial Neural Network (ANN) are the most popular ones to solve MOP. In this study, optimization was done for leaned rotor blades to achieve maximum performance parameters including specifically stage pressure ratio, efficiency and operating range. By bending an existing transonic rotor which is well-known as NASA rotor-67 in tangential direction, effect of leaning on performance and aerodynamic parameters of transonic axial-flow compressor rotors was studied. To understand all effects of lean angle, an organized investigation including numerical simulation of basic rotor, implementation of curvatures on basic rotor, numerical simulation of leaned blades and optimization were applied. Various levels of lean angles were implemented to basic rotor and by employing a three dimensional compressible turbulent model, the operating parameters were achieved. Afterwards, the results were used as input data of optimization computer code. Finally, the ANN optimization method was used to achieve maximum stage pressure ratio, efficiency and safe operating range. it was found that the Optimized leaned blades according to their target function had positive or negative optimized angles and the optimized lean angles effectively increased the safe operating range about 12% and simultaneously increase the pressure ratio and efficiency by 4% and 5%, respectively.