Academic literature on the topic 'Angle pairing'
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Journal articles on the topic "Angle pairing"
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Wang, Wei, and Xinle Shang. "The effect of the angle dependence of d-wave pairing gap on the asymmetric fermion superfluids." Modern Physics Letters B 29, no. 05 (February 20, 2015): 1550011. http://dx.doi.org/10.1142/s0217984915500116.
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A general analysis for the d-wave pairing in two components fermion system. Two physical conditions which can induce mismatched Fermi surfaces are considered: (i) Fixed chemical potential asymmetry δμ and (ii) fixed fermion number asymmetry α. In case (i), the gapless quasiparticle excitation arises both in usual Bardeen–Cooper–Schrieffer (BCS) and Sarma state due to the angle-dependent pairing gap, and they should be distinguished by gap susceptibility κΔ rather than the constraint Δ < δμ. Meanwhile, the d-wave pairing can hold larger chemical potential asymmetry δμ than the s-wave pairing. In case (ii), we find the angle dependence of the d-wave pairing gap can enhance the superfluidity for large asymmetry at low temperature.
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Jinli, C., G. Hong, and S. Weimin. "Angle estimation using ESPRIT without pairing in MIMO radar." Electronics Letters 44, no. 24 (2008): 1422. http://dx.doi.org/10.1049/el:20089089.
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Bok, Jin Mo, Jong Ju Bae, Han-Yong Choi, Chandra M. Varma, Wentao Zhang, Junfeng He, Yuxiao Zhang, Li Yu, and X. J. Zhou. "Quantitative determination of pairing interactions for high-temperature superconductivity in cuprates." Science Advances 2, no. 3 (March 2016): e1501329. http://dx.doi.org/10.1126/sciadv.1501329.
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A profound problem in modern condensed matter physics is discovering and understanding the nature of fluctuations and their coupling to fermions in cuprates, which lead to high-temperature superconductivity and the invariably associated strange metal state. We report the quantitative determination of normal and pairing self-energies, made possible by laser-based angle-resolved photoemission measurements of unprecedented accuracy and stability. Through a precise inversion procedure, both the effective interactions in the attractive d-wave symmetry and the repulsive part in the full symmetry are determined. The latter is nearly angle-independent. Near Tc, both interactions are nearly independent of frequency and have almost the same magnitude over the complete energy range of up to about 0.4 eV, except for a low-energy feature at around 50 meV that is present only in the repulsive part, which has less than 10% of the total spectral weight. Well below Tc, they both change similarly, with superconductivity-induced features at low energies. Besides finding the pairing self-energy and the attractive interactions for the first time, these results expose the central paradox of the problem of high Tc: how the same frequency-independent fluctuations can dominantly scatter at angles ±π/2 in the attractive channel to give d-wave pairing and lead to angle-independent repulsive scattering. The experimental results are compared with available theoretical calculations based on antiferromagnetic fluctuations, the Hubbard model, and quantum-critical fluctuations of the loop-current order.
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Zhang, Lufeng, Tongyun Huang, Ying Liang, and Tianxing Ma. "Ground state superconducting pair correlations in twisted bilayer graphene." Modern Physics Letters B 34, no. 01 (December 18, 2019): 2050016. http://dx.doi.org/10.1142/s0217984920500165.
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Motivated by the recent novel electronic features extracted from the magic-angle graphene superlattices, we studied the ground state superconducting pairing correlations within the Hubbard model on a twisted bilayer honeycomb lattice. Using Constrained-Path Quantum Monte Carlo method, we found that the [Formula: see text] pairing correlation dominates over other pairing patterns among various electron fillings and interaction strengths, and the effective pairing interaction was enhanced as the on-site Coulomb interaction increased. We further examined the effect of the nearest neighbor interaction [Formula: see text], and the effective pairing interaction with [Formula: see text] pairing symmetry was also enhanced by either a repulsive or attractive interaction. Our intensive numerical results confirm the interaction driven superconductivity with a dominant [Formula: see text] pairing symmetry in twisted bilayer graphene.
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Xudong, Wang, Xiaofei Zhang, Jianfeng Li, and Jinchao Bai. "Improved ESPRIT Method for Joint Direction-of-Arrival and Frequency Estimation Using Multiple-Delay Output." International Journal of Antennas and Propagation 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/309269.
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An automatic pairing joint direction-of-arrival (DOA) and frequency estimation is presented to overcome the unsatisfactory performances of estimation of signal parameter via rotational invariance techniques- (ESPRIT-) like algorithm of Wang (2010), which requires an additional pairing. By using multiple-delay output of a uniform linear antenna arrays (ULA), the proposed algorithm can estimate joint angles and frequencies with an improved ESPRIT. Compared with Wang’s ESPRIT algorithm, the angle estimation performance of the proposed algorithm is greatly improved. The frequency estimation performance of the proposed algorithm is same with that of Wang’s ESPRIT algorithm. Furthermore, the proposed algorithm can obtain automatic pairing DOA and frequency parameters, and it has a comparative computational complexity in contrast to Wang’s ESPRIT algorithm. By the way, this proposed algorithm can also work well for nonuniform linear arrays. The useful behavior of this proposed algorithm is verified by simulations.
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Chen, Shihong, Qingchang Tao, Zhongtian Yang, Xudong Wang, Sijia Liu, and Wei Xu. "Joint Angle and Frequency Estimation in Linear Arrays Based on Covariance Reconstruction and ESPRIT." Mathematical Problems in Engineering 2021 (July 8, 2021): 1–15. http://dx.doi.org/10.1155/2021/5477848.
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Joint angle and frequency estimation, one of the key technologies in wireless communication and radar science, has been extensively studied by scholars. For linear arrays, this paper proposes a joint angle and frequency estimation method based on covariance reconstruction and the estimation of signal parameters via rotational invariance techniques (CR-ESPRIT). We first use the received conjugate signal to reconstruct a covariance matrix. Then, we use the least squares-ESPRIT (LS-ESPRIT) algorithm to estimate the desired frequencies. Finally, we estimate the angles according to the reconstructed matrix. The proposed method can estimate signal parameters via automatic pairing and without an additional parameter pairing process under the condition of a uniform or a nonuniform array. Moreover, this method has high estimation accuracy, excellent and stable anti-noise performance, and strong algorithmic robustness. Through a computer simulation analysis, we can confirm the reliability and validity of the proposed parameter estimation method. A comparison with other methods further proves the performance advantages of the developed method. The method in this paper can be easily applied to many signal processing contexts, such as electronic reconnaissance and wireless communication.
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POMORSKI, KRZYSZTOF. "PAIRING AS A COLLECTIVE MODE." International Journal of Modern Physics E 16, no. 02 (February 2007): 237–48. http://dx.doi.org/10.1142/s0218301307005685.
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The collective pairing hamiltonian is obtained in the framework of the generator coordinate method using the Gaussian overlap approximation. A slightly modified BCS wave function is used as a generator function. The pairing gap parameter Δ and the gauge transformation angle ϕ are chosen as generator coordinates. This model gives not only an approximate particle-number projection but also the form of the ground state collective wave function in the (Δ, ϕ) plane. It was found that the most probable Δ does not corresponds to the minimum (Δ eq ) of the energy function E BCS (Δ) but it is systematically shifted towards smaller values than Δ eq . This effect is due to the strong dependence of the mass parameters on the pairing gap. The influence of the dynamics in the pairing degrees of freedom on the fission life-times as well as the quadrupole collective excitations is examined.
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Choi, Han-Yong, and Jin Mo Bok. "How to pin down the pairing interaction for high Tc superconductivity in cuprates." International Journal of Modern Physics B 32, no. 17 (July 9, 2018): 1840026. http://dx.doi.org/10.1142/s021797921840026x.
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The normal and pairing self-energies are the microscopic quantities which reflect and characterize the underlying interaction in superconductors. The momentum and frequency dependence of the self-energies, therefore, provides the experimental criteria which can single out the long sought-after pairing interaction among many proposed ideas. This line of research to pin down the pairing interaction for the cuprate superconductors has been carried out with some success by analyzing the momentum distribution curves (MDCs) of laser angle-resolved photo-emission spectroscopy (ARPES) data. Some progress and results are presented and compared with theoretical calculations based on leading proposals. Comments are made on the proposed scenarios from the comparisons.
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Yan, Yanjun, Huihui Xu, Ning Zhang, Guangjie Han, and Mingliu Liu. "Dynamic Divide Grouping Non-Orthogonal Multiple Access in Terrestrial-Satellite Integrated Network." Sensors 21, no. 18 (September 16, 2021): 6199. http://dx.doi.org/10.3390/s21186199.
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Non-orthogonal multiple access (NOMA) has been extensively studied to improve the performance of the Terrestrial-Satellite Integrated Network (TSIN) on account of the shortage of frequency band resources. In this paper, the terrestrial network and satellite network synergistically provide complete coverage for ground users, and based on the architecture, we first formulate a constrained optimization problem to maximize the sum rate of the TSIN under the limited spectrum resources. As the terrestrial networks and the satellite network will cause interference to each other, we first investigate the capacity performance of the terrestrial networks and the satellite networks separately, in which the optimal power control factor expression is derived. Then, by constructing the relationship model between user elevation angle, beam angle and distance, we develop a dynamic group pairing schemes to ensure the effective pairing of NOMA users. Based on the user pairing, to obtain the optimal resource allocation, a joint optimization algorithm of power allocation, beam channel and base station channel resource is proposed. Finally, simulation results are provided to evaluate the user paring scheme as well as the total system performance, in comparison with the existing works.
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Brandstätter, G., H. W. Weber, T. Chattopadhyay, R. Cubitt, H. Fischer, M. Wylie, G. A. Emel'chenko, and A. Wiedenmann. "Neutron Diffraction by the Flux Line Lattice in YBa2Cu3O7−δ Single Crystals." Journal of Applied Crystallography 30, no. 5 (October 1, 1997): 571–74. http://dx.doi.org/10.1107/s0021889897001854.
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Small-angle neutron diffraction was used to image the mixed state in a large superconducting YBa2Cu3O7−δ single crystal. The flux line lattice was observed in fields up to 2 T at various temperatures from 2.4 to 80 K. The integrated intensity I of the (10) reflection was calculated as a function of temperature for three different fields (0.8, 1 and 2 T). From these I(T) curves, the magnetic penetration depth λ(T) was obtained on an absolute scale. This quantity is of particular interest, since it provides information on the nature of the pairing mechanism in the superconductor, i.e. the symmetry of the wavefunction of the electron pairs. The results are discussed in terms of BCS theory (s-wave pairing) and of d-wave pairing with and without impurity scattering.
Dissertations / Theses on the topic "Angle pairing"
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Xu, Yiming. "Angle-resolved Photoemission Studies on Hole Doped Iron Pnictides Ba1-xKxFe2As2." Thesis, Boston College, 2010. http://hdl.handle.net/2345/1417.
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Thesis advisor: Hong DingThesis advisor: Ziqiang Wang
The discovery of the high-Tc superconductivity in iron-arsenic materials in 2008 immediately became one of the hottest topics in the condensed matter physics. This dissertation presents a systematic study on the pairing symmetry and electronic structure on the hole doped materials of BaFe2As2 (so called “122”-system), by angle-resolved photoemission spectroscopy (ARPES). In the early ARPES studies on “122”-pnictides, we observed two hole-like Fermi surfaces (FSs) centered at the Brillouin zone (BZ) center, (Γ), and two electron-like FSs centered at the zone corner (M), which is (π, π) in the BZ or (π, 0) in the unfolded BZ. The size of these FS sheets can be changed by carrier doping, which causes change of the chemical potential. In the superconducting state, temperature (T) and momentum (k) dependence of ARPES measurements reveals the Fermi-surface-dependent nodeless superconducting gaps in this system and shows that an s-wave symmetry is the most natural interpretation for our findings in terms of the pairing order parameter. The ratio 2Δ/kBTc switches from weak to strong coupling on different FS sheets. Large superconducting gaps are observed with a strong coupling coefficient (2Δ/kBTc) on the near-nested FSs connected by the antiferromagnetic (AF) wave vector ((π, π) in the BZ or (π, 0) in the unfolded BZ). When Tc is suppressed in the heavily overdoped materials, the near-nesting condition vanishes, or more precisely, the (π, π) inter-FS scattering disappears due to the absence of either the hole-like or the electron-like FS at the Fermi energy (EF). We have also performed ARPES measurements on kz-dependence of the superconducting gap and band structure of the optimally hole doped sample Ba0.6K0.4Fe2As2. By varying the photon energy, we can tune kz continuously. While significant kz dispersion of the superconducting gaps is observed on the hole-like bands, much weaker kz dispersion of the superconducting gaps is observed on the electron-like bands. Remarkably, we find that a 3D gap function based on short-range pairing can fit the superconducting gaps on all the FS sheets. Moreover, an additional hole-like FS (referred as the α‘ FS) predicted by local density approximation (LDA) calculations is observed around the Z point. The disappearance of intensity of the α‘ band near EF at kz = π/2 suggests that the α‘ band could either sink below EF or be degenerate with the inner hole (α) band. The studies on the α‘ band in the superconducting state reveal a nearly isotropic superconducting gap on this FS sheet. Underdoped samples Ba0.75K0.25Fe2As2 are used to study how the AF fluctuations and superconductivity interplay in the underdoped regime that is closer to the AF phase. we observe that the superconducting gap of the underdoped pnictides scales linearly with Tc. A distinct pseudogap develops upon underdoping and coexists with the superconducting gap. Remarkably, this pseudogap occurs mainly on the FS sheets that are connected by the AF wave vector, where the superconducting pairing is stronger as well. This suggests that both the pseudogap and the superconducting gap are driven by the AF fluctuations, and the long-range AF ordering competes with the superconductivity. The observed dichotomic behaviour of the pseudogap and the SC gap on different FS sheets in the underdoped pnictides shares similarities with those observed in the underdoped copper oxide superconductors, providing a possible unifying picture for both families of high-temperature superconductors
Thesis (PhD) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
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Filik, Tansu. "Planar Array Structures For Two-dimensional Direction-of-arrival Estimation." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611841/index.pdf.
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In this thesis, two-dimensional (2-D) direction-of-arrival (DOA) estimation problem is considered. Usually, DOA estimation is considered in one dimension assuming a fixed elevation angle. While this assumption simplifies the problem, both the azimuth and elevation angles, namely, the 2-D DOA estimates are required in practical scenarios. In this thesis, planar array structures are considered for 2-D DOA estimation. In this context, V-shaped arrays are discussed and some of the important features of these arrays are outlined. A new method for the design of V-shaped arrays is presented for both isotropic and directional beam patterns. The design procedure is simple and can be applied for both uniform and nonuniform V-shaped sensor arrays. Closed form expressions are presented for the V-angle in order to obtain isotropic angle performance. While circular arrays have the isotropic characteristics, V-shaped arrays present certain advantages due to their large aperture for the same number of sensors and inter-sensor distance. The comparison of circular and V-shaped arrays is done by considering the azimuth and elevation Cramer-Rao Bounds (CRB). It is shown that V-shaped and circular arrays have similar characteristics for the sensor position errors while the uniform isotropic (UI) V-array performs better when there is mutual coupling and the sources are correlated.
In the literature, there are several techniques for 2-D DOA estimation. Usually, fast algorithms are desired for this purpose since a search in two dimensions is a costly process. These algorithms have a major problem, namely, the pairing of the azimuth-elevation couples for multiple sources. In this thesis, a new fast and effective technique for this purpose is proposed. In this technique, a virtual array output is generated such that when the ESPRIT algorithm is used, the eigenvalues of the rotational transformation matrix have the 2-D angle information in both magnitude and phase. This idea is applied in different scenarios and three methods are presented for these cases. In one case, given an arbitrary array structure, array interpolation is used to generate the appropriate virtual arrays. When the antenna mutual coupling is taken into account, a special type of array structure, such as circular, should be used in order to apply the array interpolation. In general, the array mutual coupling matrix (MCM) should have a symmetric Toeplitz form. It is shown that the 2-D DOA performance of the proposed method approaches to the CRB by using minimum number of antennas in case of mutual coupling. This method does not require the estimation of the mutual coupling coefficients. While this technique is effective, it has problems especially when the number of sources increases. In order to improve the performance, MCM is estimated in the third approach. This new approach performs better, but it cannot be used satisfactorily in case of multipath signals. In this thesis, the proposed idea for fast 2-D DOA estimation is further developed in order to solve the problem when mutual coupling and multipath signals jointly exist. In this case, real arrays with some auxiliary sensors are used to generate a structured mutual coupling matrix. It is shown that the problem can be effectively solved when the array structure has a special form. Specifically, parallel uniform linear arrays (PULA) are employed for this purpose. When auxiliary sensors are used, a symmetric banded Toeplitz MCM is obtained for the PULA. This allows the application of spatial smoothing and ESPRIT algorithm for 2-D DOA estimation. The proposed algorithm uses triplets and presents closed form paired 2-D DOA estimates in case of unknown mutual coupling and multipath signals. Several simulations are done and it is shown that the proposed array structure and the method effectively solve the problem.
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Chang, Yi-jen, and 張議仁. "Two-Dimensional DOA Estimation with a New Angles Pairing Method." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/01646403504201456211.
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碩士國立中央大學
通訊工程學系
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A novel method is presented in this paper for pair matching of elevation and azimuth angles in a two-dimensional direction-of-arrival estimation problem, employing the antenna configuration of two uniform linear arrays. The proposed method exploits maximum likelihood estimation to pair two individual DOA angles in a 3-D space from the received signals impinging on each ULA, and consequently, multiple sources' DOAs can be identified automatically. Simulation results show that the proposed method has better performance in case of small angular separation among multiple signal sources compared to the conventional methods.The proposed method also has less computational complexity and higher estimation accuracy than the previously published works.
Book chapters on the topic "Angle pairing"
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Wallnig, Thomas. "Enlightenment-Empire: A Difficult Pairing, Viewed from a Habsburg Angle." In L’Avenir des Lumières, 235–52. Hermann, 2019. http://dx.doi.org/10.3917/herm.andri.2019.01.0235.
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Green, Jeremy. "From Crisis to Stagnation." In The Political Economy of the Special Relationship, 251–70. Princeton University Press, 2020. http://dx.doi.org/10.23943/princeton/9780691197326.003.0009.
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This chapter describes some of the major themes of the postcrisis political economy of Anglo-America. Identifying the central policy pairing between fiscal austerity and monetary loosening, it draws upon accounts of the structural crisis of neoliberal capitalism, arguing that, despite the adoption of unorthodox monetary policy and the restoration of growth, economic recovery has failed to arrest the underlying structural crisis of Anglo-American political economies. In the postcrisis era, the reliance upon a strategy of ultralow interest rates and quantitative easing initiated by the US and the UK demonstrated the continued centrality of Anglo-American central bank leadership to the global economy. But the sluggish return to growth in the West, and the continued stagnation of living standards within the UK and the US specifically, have revealed the declining ability of neoliberal capitalism to deliver economic growth and distributional gains in amounts adequate to bolster democratic consent. The rise of antiestablishment politics in both states—and the fracturing of the longstanding eoliberal center ground of party politics—has led to new political and economic dynamics. Alongside these changes, the rebalancing of the City–Bank–Treasury nexus toward Chinese finance, the policies of Donald Trump, and Brexit are transforming the global economy.
Conference papers on the topic "Angle pairing"
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Zheng, Zhi Dong, Jian Yun Zhang, Peng Ma, and Chun Sheng Liu. "Angle Estimation with Automatic Pairing for Bistatic MIMO Radar." In 2009 2nd International Congress on Image and Signal Processing (CISP). IEEE, 2009. http://dx.doi.org/10.1109/cisp.2009.5304419.
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Wang, Jian, Zhenzhen Song, Honglian Zhao, Bing Liu, and DeFeng Chen. "Eye detection algorithm base on area-blocks pairing and multi-angle template matching." In 2009 Chinese Control and Decision Conference (CCDC 2009). IEEE, 2009. http://dx.doi.org/10.1109/ccdc.2009.5194866.
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Lu, Xiaolin, Yong Zhou, and Vincent W. S. Wong. "A Joint Angle and Distance based User Pairing Strategy for Millimeter Wave NOMA Networks." In 2020 IEEE Wireless Communications and Networking Conference (WCNC). IEEE, 2020. http://dx.doi.org/10.1109/wcnc45663.2020.9120456.
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Tomasi, Matilde, and Alessio Artoni. "Muscle Contracture Modeling and Optimal Control for Crouch Gait Prediction." In ASME 2020 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/detc2020-22528.
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Abstract Prediction of human movement, and especially of pathological gait, is nowadays an important and mostly unsolved research challenge. In this work, a recently developed computational framework based on optimal control was adopted and explored to assess its potential for predicting a pathological gait pattern, in particular the crouch gait typical of subjects affected by cerebral palsy. To this end, the generic musculoskeletal model on which this optimal control framework is based was made representative of such pathological case by modeling contracture of relevant muscle groups commonly associated with crouch gait, namely knee and hip flexors. All the conducted simulations succeeded in inducing the model into a crouch gait pattern, despite their diversity in cost functions. Moreover, the obtained joint angle trajectories correlated well with the experimental ones obtained from a CP child walking in crouch. These kinematic results suggest that optimal control techniques and proper tuning of musculotendon parameters are an important pairing for predictive simulations of human walking. On the other hand, the obtained results confirm that estimation of muscle activations is strongly dependent on the selected objective function and still requires deeper investigations.
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Garrido-Mendoza, Carlos A., K. P. Thiagarajan, Antonio Souto-Iglesias, Benjamin Bouscasse, and Andrea Colagrossi. "Numerical Investigation of the Flow Features Around Heave Plates Oscillating Close to a Free Surface or Seabed." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23818.
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Performance of heave plates used in offshore structures is strongly influenced by their added mass and damping, which are affected by proximity to a boundary. A previous paper by the authors presented numerical simulations of the flow around a circular solid disk oscillating at varying elevations from seabed [1]. The force calculated was used to evaluate the added mass and damping coefficients for the disk. The simulations suggest that as the structure moves closer to the seabed the added mass and damping coefficients (Ca and Cb) increases continuously. In order to understand the physics behind the added mass and damping trends, when a heave plate is moving near a seabed or closer to the free surface, the flow characteristics around the heave plate are examined numerically in this paper. Flow around oscillating disks is dominated by generation and development of phase-dependent vortical structures, characterized by the KC number and the distance from the seabed or free surface to the heave plate. Numerical calculations presented in this paper have comprised the qualitative analysis of the vortex shedding and the investigation of the links between such vortex shedding and, on one hand the damping coefficient, and on the other hand, pairing mechanisms such as the shedding angle.
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Schutt, Riley R., and C. H. K. Williamson. "Unsteady Sail Dynamics due to Bodyweight motions." In SNAME 22nd Chesapeake Sailing Yacht Symposium. SNAME, 2016. http://dx.doi.org/10.5957/csys-2016-005.
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In small sailboats, the bodyweight of the sailor is proportionately large enough to induce significant unsteady dynamics of the boat and sail. Sailors use a variety of techniques to create sail dynamics which can provide an increment in thrust, increasing the boatspeed. In this study, we experimentally investigate the unsteady aerodynamics associated with two such techniques, “upwind leech flicking" and “downwind S-turns". We employ a two-part approach. First, on-the-water experiments are carried out using a Laser class sailboat sailed by Olympic and world championship level sailors. Data collected from an on-board GPS, IMU, anemometer, and camera array is used to generate characteristic motions of the boat and sail relative to the apparent wind. Second, laboratory experiments using the characteristic motion of the sail are run in a computer-controlled 3 degree-of-freedom (X, Y, and θ) towing tank. We use water as the working fluid. Rather than directly experiment with three-dimensional sail shapes, we represent the primary effects of the sail dynamics using rapidly prototyped two-dimensional flexible sail geometries. Shapes are based on extruded draft stripes from the upper third of the sail. The laboratory experiments approximately match the key non-dimensional parameters of the on-the-water sailing conditions, including the reduced frequency and heave-to-chord ratio. Particle Image Velocimetry and force measurements are used to analyze the flow field and thrust generated by the model sail during the dynamic motions. On-the-water testing shows that the characteristic sail motion in leech flicking is a combination of periodic heave caused by the actions of the sailor and a passive twisting of the sail due to rig flexibility. The heaving sail motions are due to rotation (roll) of the rig around the longitudinal axis of the hull. This is at an angle to the apparent wind, resulting in heave that has components both perpendicular and parallel to the oncoming wind flow. This is distinct from classical aerodynamic studies with heave purely perpendicular to the incoming flow. In laboratory experiments, the characteristic flicking motion is applied to a NACA 0012 airfoil and a 2D sail, both angled at 15 deg to the flow. Lift increases and drag decreases, leading to an overall increase in resultant driving force of the boat. The beneficial effect of this dynamic motion becomes greater as the apparent wind angle increases. In the case of leech flicking, the experiments show that the formation of vortex pairs is fundamental to the augmented thrust due to heaving. The presence of S-turns, whereby the sailor changes the boats direction simultaneous with rolling the boat, generally in the downwind direction, is also associated with vortex formation and pairing, which will be described at the conference. During downwind S-turns, large amplitude heaving motions are paired with substantial rotations of the sail caused by both adjustments of the main sheet and changes in heading. Increased velocity made good downwind is measured from the on-the-water experiments, and is associated with an increase of thrust during characteristic dynamics of the airfoil or sail shape in the laboratory.
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Wu, Hailang, and Xiaofei Zhang. "DOD and DOA tracking algorithm for bistatic MIMO radar using PASTD without additional angles pairing." In 2012 IEEE Fifth International Conference on Advanced Computational Intelligence (ICACI). IEEE, 2012. http://dx.doi.org/10.1109/icaci.2012.6463350.
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Schuler, Julia, and Norbert Kockmann. "Investigation of Multiphase Interfaces in Small Channels Using Micro CT." In ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/icnmm2019-4203.
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Abstract For the process intensification in miniaturized equipment with multiphase systems the spatial extension and shape of the interface is crucial. However, examining interfaces on the submillimeter to the submicron range is challenging due to limited optical accessibility. Therefore, in this work, micro computed X-ray tomography was applied to visualize static multiphase interfaces in small channels. The present work also introduces an image processing procedure used for the reconstruction of the tomographic data. To demonstrate both, the information value of 3D tomographic data and its advantages compared to conventional 2D imaging techniques, the contact angle between different fluid pairings and the solid channel is determined. This work forms the foundation for the three dimensional examination of multiphase flows and mass transfer in micro and milli channels.
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Bari, Joseph M., Carl D. Crane, David B. Dooner, and Javier Roldan Mckinley. "The Design of a Single Degree of Freedom Open-Loop Spatial Mechanism That Incorporates Geared Connections." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12806.
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A means has been discovered to apply gear pairing to create a one degree of freedom open-loop spatial mechanism. A specially chosen geometry consisting of three pairs of parallel joint axes is constricted by five sets of gears, three of which are parallel planar, allows for a reconfigurable mechanism that is suited for repetitive tasks. Previous work has examined three-dimensional rigid body guidance in closed-loop geared mechanisms, but has not come to a solution for the open-loop case. Gear pairs are designed based upon a desired position and orientation path for the end effector. Numerical optimization is performed to obtain physically realizable gear profiles. Non-circular gear centrodes must be continuous and smooth as well as mono-directional, that is, gear ratios of a given pair may not switch signs. These constraints eliminate non-realizable or non-optimal gears in favor of simple, more easily produced profiles. Variable parameters include link lengths, joint offsets and twist angles. Numerical examples are presented.
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Bianchini, Alessandro, Francesco Balduzzi, John M. Rainbird, Joaquim Peiro, J. Michael R. Graham, Giovanni Ferrara, and Lorenzo Ferrari. "An Experimental and Numerical Assessment of Airfoil Polars for Use in Darrieus Wind Turbines: Part 1 — Flow Curvature Effects." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42284.
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A better comprehension of the aerodynamic behavior of rotating airfoils in Darrieus Vertical-axis wind turbines (VAWTs) is crucial both for the further development of these machines and for improvement of conventional design tools based on zero or one-dimensional models (e.g. BEM models). When smaller rotors are designed with high chord-to-radius (c/R) ratios so as not to limit the blade Reynolds number, the performance of turbine blades has been suggested to be heavily impacted by a virtual camber effect imparted on the blades by the curvilinear flow they experience. To assess the impact of this virtual camber effect on blade and turbine performance, a standard NACA0018 airfoil and a NACA0018 conformally transformed such that the airfoil’s chord line follows the arc of a circle, where the ratio of the airfoil’s chord to the circle’s radius is 0.25 were considered. For both airfoils, wind tunnel tests were carried out to assess their aerodynamic lift and drag coefficients for Reynolds numbers of interest for Darrieus VAWTs. Unsteady CFD calculations have been then carried out to obtain curvilinear flow performance data for the same airfoils mounted on a Darrieus rotor with a c/R of 0.25. The blade incidence and lift and drag forces were extracted from the CFD output using a novel incidence angle deduction technique. According to virtual camber theory, the transformed airfoil in this curvilinear flow should be equivalent to the NACA0018 in rectilinear flow, while the NACA0018 should be equivalent to the inverted transformed airfoil in rectilinear flow. Comparisons were made between these airfoil pairings using the CFD output and the rectilinear performance data obtained from the wind tunnel tests and XFoil output in the form of pressure distributions and lift and drag polars. Blade torque coefficients and turbine power coefficient are also presented for the CFD VAWT using both blade profiles.