JFKengine: A Jacobian and Forward Kinematics Generator
Fischer, K.N.
2003-02-13
During robot path planning and control the equations that describe the robot motions are determined and solved. Historically these expressions were derived analytically off-line. For robots that must adapt to their environment or perform a wide range of tasks, a way is needed to rapidly re-derive these expressions to take into account the robot kinematic changes, such as when a tool is added to the end-effector. The JFKengine software was developed to automatically produce the expressions representing the manipulator arm motion, including the manipulator arm Jacobian and the forward kinematic expressions. Its programming interface can be used in conjunction with robot simulation software or with robot control software. Thus, it helps to automate the process of configuration changes for serial robot manipulators. If the manipulator undergoes a geometric change, such as tool acquisition, then JFKengine can be invoked again from the control or simulation software, passing it parameters for the new arm configuration. This report describes the automated processes that are implemented by JFKengine to derive the kinematic equations and the programming interface by which it is invoked. Then it discusses the tree data structure that was chosen to store the expressions, followed by several examples of portions of expressions as represented in the tree. The C++ classes and their methods that implement the expression differentiation and evaluation operations are described. The algorithms used to construct the Jacobian and forward kinematic equations using these basic building blocks are then illustrated. The activity described in this report is part of a larger project entitled ''Multi-Optimization Criteria-Based Robot Behavioral Adaptability and Motion Planning'' that focuses on the development of a methodology for the generalized resolution of robot motion equations with time-varying configurations, constraints, and task objective criteria. A specific goal of this project is the implementation of this generalized methodology in a single general code that would be applicable to the motion planning of a wide class of systems and would automate many of the processes involved in developing and solving the motion planning and controls equations. This project is funded by the U.S. Department of Energy's Environmental Management Science Program (DOE-EMSP) as project EMSP no. 82794 and is transitioning to the DOE-Office of Biological and Environmental Research (OBER) as per FY-02.
NASA Technical Reports Server (NTRS)
Chen, Yu-Che; Walker, Ian D.; Cheatham, John B., Jr.
1992-01-01
We present a unified formulation for the inverse kinematics of redundant arms, based on a special formulation of the null space of the Jacobian. By extending (appropriately re-scaling) previously used null space parameterizations, we obtain, in a unified fashion, the manipulability measure, the null space projector, and particular solutions for the joint velocities. We obtain the minimum norm pseudo-inverse solution as a projection from any particular solution, and the method provides an intuitive visualization of the self-motion. The result is a computationally efficient, consistent approach to computing redundant robot inverse kinematics.
Unseren, M.A.; Reister, D.B.
1995-07-01
A method for kinematically modeling a constrained rigid body mechanical system and a method for controlling such a system termed input relegation control (IRC) were applied to resolve the kinematic redundancy of a serial link manipulator moving in an open chain configuration in. A set of equations was introduced to define a new vector variable parameterizing the redundant degrees of freedom (DOF) as a linear function of the joint velocities. The new set was combined with the classical kinematic velocity model of manipulator and solved to yield a well specified solution for the joint velocities as a function of the Cartesian velocities of the end effector and of the redundant DOF variable. In the previous work a technique was proposed for selecting the matrix relating the redundant DOF variable to the joint velocities which resulted in it rows being orthogonal to the rows of the Jacobian matrix. The implications for such a selection were not discussed in. In Part 1 of this report a basis for the joint space is suggested which provides considerable insight into why picking the aforementioned matrix to be orthogonal to the Jacobian is advantageous. A second objective of Part 1 is to compare the IRC method to the Extended Jacobian method of Baillieul and Martin and other related methods.
Challenges of Inversely Estimating Jacobian from Metabolomics Data
Sun, Xiaoliang; Länger, Bettina; Weckwerth, Wolfram
2015-01-01
Inferring dynamics of metabolic networks directly from metabolomics data provides a promising way to elucidate the underlying mechanisms of biological systems, as reported in our previous studies (Weckwerth, 2011; Sun and Weckwerth, 2012; Nägele et al., 2014) by a differential Jacobian approach. The Jacobian is solved from an overdetermined system of equations as JC?+?CJT?=??2D, called Lyapunov Equation in its generic form,1 where J is the Jacobian, C is the covariance matrix of metabolomics data, and D is the fluctuation matrix. Lyapunov Equation can be further simplified as the linear form Ax?=?b. Frequently, this linear equation system is ill-conditioned, i.e., a small variation in the right side b results in a big change in the solution x, thus making the solution unstable and error-prone. At the same time, inaccurate estimation of covariance matrix and uncertainties in the fluctuation matrix bring biases to the solution x. Here, we first reviewed common approaches to circumvent the ill-conditioned problems, including total least squares, Tikhonov regularization, and truncated singular value decomposition. Then, we benchmarked these methods on several in silico kinetic models with small to large perturbations on the covariance and fluctuation matrices. The results identified that the accuracy of the reverse Jacobian is mainly dependent on the condition number of A, the perturbation amplitude of C, and the stiffness of the kinetic models. Our research contributes a systematical comparison of methods to inversely solve Jacobian from metabolomics data. PMID:26636075
NASA Technical Reports Server (NTRS)
Hsia, T. C.; Lu, G. Z.; Han, W. H.
1987-01-01
In advanced robot control problems, on-line computation of inverse Jacobian solution is frequently required. Parallel processing architecture is an effective way to reduce computation time. A parallel processing architecture is developed for the inverse Jacobian (inverse differential kinematic equation) of the PUMA arm. The proposed pipeline/parallel algorithm can be inplemented on an IC chip using systolic linear arrays. This implementation requires 27 processing cells and 25 time units. Computation time is thus significantly reduced.
Real-time inverse kinematics techniques for anthropomorphic limbs.
Tolani, D; Goswami, A; Badler, N I
2000-09-01
In this paper we develop a set of inverse kinematics algorithms suitable for an anthropomorphic arm or leg. We use a combination of analytical and numerical methods to solve generalized inverse kinematics problems including position, orientation, and aiming constraints. Our combination of analytical and numerical methods results in faster and more reliable algorithms than conventional inverse Jacobian and optimization-based techniques. Additionally, unlike conventional numerical algorithms, our methods allow the user to interactively explore all possible solutions using an intuitive set of parameters that define the redundancy of the system. PMID:12143897
Robust inverse kinematics using damped least squares with dynamic weighting
NASA Technical Reports Server (NTRS)
Schinstock, D. E.; Faddis, T. N.; Greenway, R. B.
1994-01-01
This paper presents a general method for calculating the inverse kinematics with singularity and joint limit robustness for both redundant and non-redundant serial-link manipulators. Damped least squares inverse of the Jacobian is used with dynamic weighting matrices in approximating the solution. This reduces specific joint differential vectors. The algorithm gives an exact solution away from the singularities and joint limits, and an approximate solution at or near the singularities and/or joint limits. The procedure is here implemented for a six d.o.f. teleoperator and a well behaved slave manipulator resulted under teleoperational control.
Iterative inverse kinematics with manipulator configuration control
Grudic, G.Z.; Lawrence, P.D.
1993-08-01
A new method, termed the offset modification method (OM method), for solving the manipulator inverse kinematics problem is presented. The OM method works by modifying the link offset values of a manipulator until it is possible to derive closed-form inverse kinematics equations for the resulting manipulator (termed the model manipulator). This procedure allows one to derive a set of three nonlinear equations in three unknowns that, when numerically solved, give an inverse kinematics solution for the original manipulator. The OM method can be applied to manipulators with any number of degrees of freedom, as long as the manipulator satisfies a given set of conditions (Theorem 1). The OM method is tested on a 6-degree-of-freedom manipulator that has no known closed-form inverse kinematics equations. It is shown that the OM method is applicable to real-time manipulator control, can be used to guarantee convergence to a desired endpoint position and orientation (if it exists), and allows one to directly choose which inverse kinematics solution the algorithm will converge to (as specified in the model manipulator closed-form inverse kinematics equations). Applications of the method to other 6-DOF manipulator geometries and to redundant manipulators (i.e. greater than 6 DOF geometries) are discussed.
Inverse kinematic-based robot control
NASA Technical Reports Server (NTRS)
Wolovich, W. A.; Flueckiger, K. F.
1987-01-01
A fundamental problem which must be resolved in virtually all non-trivial robotic operations is the well-known inverse kinematic question. More specifically, most of the tasks which robots are called upon to perform are specified in Cartesian (x,y,z) space, such as simple tracking along one or more straight line paths or following a specified surfacer with compliant force sensors and/or visual feedback. In all cases, control is actually implemented through coordinated motion of the various links which comprise the manipulator; i.e., in link space. As a consequence, the control computer of every sophisticated anthropomorphic robot must contain provisions for solving the inverse kinematic problem which, in the case of simple, non-redundant position control, involves the determination of the first three link angles, theta sub 1, theta sub 2, and theta sub 3, which produce a desired wrist origin position P sub xw, P sub yw, and P sub zw at the end of link 3 relative to some fixed base frame. Researchers outline a new inverse kinematic solution and demonstrate its potential via some recent computer simulations. They also compare it to current inverse kinematic methods and outline some of the remaining problems which will be addressed in order to render it fully operational. Also discussed are a number of practical consequences of this technique beyond its obvious use in solving the inverse kinematic question.
A Simplified Scheme for Kinematic Source Inversion
NASA Astrophysics Data System (ADS)
Iglesias, A.; Castro-Artola, O.; Singh, S.; Hjorleifsdottir, V.; Legrand, D.
2013-05-01
It is well known that different kinematic source inversion schemes lead to non-unique solutions. For this reason, a simplified scheme, which yields the main characteristics of the rupture process, rather than the details, may be desirable. In this work we propose a modification of the frequency-domain inversion scheme of Cotton & Campillo (1995) to extract kinematic parameters using simplified geometries (ellipses). The forward problem is re-parameterized by including one or two ellipses in which the displacement is smoothly distributed. For the ellipses we invert for the position of the centers within the fault plane, the major and minor semi-axes, the maximum displacements, the angles of rotation and a parameter that controls the distribution of slip. A simulated annealing scheme is used to invert near-source displacements. We first test the method on synthetic displacement records corresponding to the Guerrero-Oaxaca earthquake (20/03/2012, Mw=7.5) by comparing the results obtained from the modified technique with the original method. In the next step, we use displacements obtained by double numerical integration of recorded accelerograms. We find that, in spite of the simple geometry, the modified method leads to a good fit between observed and synthetic displacements and recovers the main rupture characteristics.
Grid Approach for Kinematic Source Inversion
NASA Astrophysics Data System (ADS)
Fujii, Y.; Takenaka, H.
2003-12-01
In seismic tomography for local parameterization of the spatial functions to be reconstructed (e.g., seismic velocities) there are two basic approaches: one is the block (cell) approach and the other is the grid approach. In the block approach the medium under study is divided into many blocks (cells) and the seismic velocity in every block is taken as unknown parameter. In the grid approach grid nodes are adopted to model the earth structure and velocities at the nodes are taken as unknown parameters; the velocity at any point in the model is calculated by interpolation from those at the nodes surrounding the point. In the grid method the velocity is continuous everywhere, while in the block method artificial velocity discontinuities are introduced into the model between the blocks. In kinematic source inversion the above two approaches, the block approach and the grid approach, can also be considered. The multi-time window linear inversion (e.g., Hartzell and Heaton, 1983) belongs to the block approach, which is now a most popular method and has been widely applied to broadband seismic records including teleseismic and strong-ground motion records to estimate spatio-temporal slip distribution on seismic fault planes of middle to large earthquakes. In this method the fault plane is conventionally divided into many subfaults (cells) to express spatial variation, and each subfault is represented by a single or many point sources placed at constant intervals on the planar surface. Such conventional subfault discretization corresponds to the block approach of seismic tomography, and it is not continuous at the subfault boundaries. Since this conventional subfault discretization is used by most existing methods for kinematic source inversion applied to waveform data, they may all be categorized into the block approach. One exception is Ide and Takeo's (1997, JGR) method, which belongs to the grid method. In their method the spatio-temporal distribution of slip velocity is expanded with the linear b-spline basis functions in 2D space as well as in time. This discretization can give a slip distribution continuous everywhere. In the present study we propose an extension of this grid method. Main extension is that the effect of the rupture propagation is included even under the sub-grid level by using the presentation of slip velocity with an explicit rupture propagation term, which has recently been exploited by Takenaka et al. (2002) for extracting spatially continuous slip distribution from results of conventional source inversion. Furthermore our method can also treat slip direction change on the fault plane unlike Ide and Takeo's original method. In the presentation we demonstrate the feasibility of our method by using simulation data.
Forward and inverse kinematics of double universal joint robot wrists
NASA Technical Reports Server (NTRS)
Williams, Robert L., II
1991-01-01
A robot wrist consisting of two universal joints can eliminate the wrist singularity problem found on many individual robots. Forward and inverse position and velocity kinematics are presented for such a wrist having three degrees of freedom. Denavit-Hartenberg parameters are derived to find the transforms required for the kinematic equations. The Omni-Wrist, a commercial double universal joint robot wrist, is studied in detail. There are four levels of kinematic parameters identified for this wrist; three forward and three inverse maps are presented for both position and velocity. These equations relate the hand coordinate frame to the wrist base frame. They are sufficient for control of the wrist standing alone. When the wrist is attached to a manipulator arm; the offset between the two universal joints complicates the solution of the overall kinematics problem. All wrist coordinate frame origins are not coincident, which prevents decoupling of position and orientation for manipulator inverse kinematics.
Inverse kinematics problem in robotics using neural networks
NASA Technical Reports Server (NTRS)
Choi, Benjamin B.; Lawrence, Charles
1992-01-01
In this paper, Multilayer Feedforward Networks are applied to the robot inverse kinematic problem. The networks are trained with endeffector position and joint angles. After training, performance is measured by having the network generate joint angles for arbitrary endeffector trajectories. A 3-degree-of-freedom (DOF) spatial manipulator is used for the study. It is found that neural networks provide a simple and effective way to both model the manipulator inverse kinematics and circumvent the problems associated with algorithmic solution methods.
NASA Astrophysics Data System (ADS)
Akli, Isma; Achour, Noura
2008-06-01
This article presents a differential kinematic study for a car-like mobile system carrying a four degrees of freedom manipulator. The generalized coordinates and velocities of the mobile manipulator are required, when the position and the velocity of the end-effector are imposed in the cartesian space. Our approach consists of planning the motion of the mobile platform with make the onboard manipulator able to follow the cartesian trajectory. The resulted generalized coordinates are exploited to calculate the Forward Differential Kinematic Model. Since the mobile manipulator is redundant regarding to the task, we profit from the system characteristics to augment the jacobian matrix, while integrating additional constraints, to inverse the differential kinematic model.
Inverse Kinematic Analysis of Human Hand Thumb Model
NASA Astrophysics Data System (ADS)
Toth-Tascau, Mirela; Pater, Flavius; Stoia, Dan Ioan; Menyhardt, Karoly; Rosu, Serban; Rusu, Lucian; Vigaru, Cosmina
2011-09-01
This paper deals with a kinematic model of the thumb of the human hand. The proposed model has 3 degrees of freedom being able to model the movements of the thumb tip with respect to the wrist joint centre. The kinematic equations are derived based on Denavit-Hartenberg Convention and solved in both direct and inverse way. Inverse kinematic analysis of human hand thumb model reveals multiple and connected solutions which are characteristic to nonlinear systems when the number of equations is greater than number of unknowns and correspond to natural movements of the finger.
NASA Astrophysics Data System (ADS)
Kordy, M.; Wannamaker, P.; Maris, V.; Cherkaev, E.; Hill, G.
2016-01-01
We have developed an algorithm, which we call HexMT, for 3-D simulation and inversion of magnetotelluric (MT) responses using deformable hexahedral finite elements that permit incorporation of topography. Direct solvers parallelized on symmetric multiprocessor (SMP), single-chassis workstations with large RAM are used throughout, including the forward solution, parameter Jacobians and model parameter update. In Part I, the forward simulator and Jacobian calculations are presented. We use first-order edge elements to represent the secondary electric field (E), yielding accuracy O(h) for E and its curl (magnetic field). For very low frequencies or small material admittivities, the E-field requires divergence correction. With the help of Hodge decomposition, the correction may be applied in one step after the forward solution is calculated. This allows accurate E-field solutions in dielectric air. The system matrix factorization and source vector solutions are computed using the MKL PARDISO library, which shows good scalability through 24 processor cores. The factorized matrix is used to calculate the forward response as well as the Jacobians of electromagnetic (EM) field and MT responses using the reciprocity theorem. Comparison with other codes demonstrates accuracy of our forward calculations. We consider a popular conductive/resistive double brick structure, several synthetic topographic models and the natural topography of Mount Erebus in Antarctica. In particular, the ability of finite elements to represent smooth topographic slopes permits accurate simulation of refraction of EM waves normal to the slopes at high frequencies. Run-time tests of the parallelized algorithm indicate that for meshes as large as 176 Ă— 176 Ă— 70 elements, MT forward responses and Jacobians can be calculated in Ëś1.5 hr per frequency. Together with an efficient inversion parameter step described in Part II, MT inversion problems of 200-300 stations are computable with total run times of several days on such workstations.
An adaptive inverse kinematics algorithm for robot manipulators
NASA Technical Reports Server (NTRS)
Colbaugh, R.; Glass, K.; Seraji, H.
1990-01-01
An adaptive algorithm for solving the inverse kinematics problem for robot manipulators is presented. The algorithm is derived using model reference adaptive control (MRAC) theory and is computationally efficient for online applications. The scheme requires no a priori knowledge of the kinematics of the robot if Cartesian end-effector sensing is available, and it requires knowledge of only the forward kinematics if joint position sensing is used. Computer simulation results are given for the redundant seven-DOF robotics research arm, demonstrating that the proposed algorithm yields accurate joint angle trajectories for a given end-effector position/orientation trajectory.
Computational neural learning formalisms for manipulator inverse kinematics
NASA Technical Reports Server (NTRS)
Gulati, Sandeep; Barhen, Jacob; Iyengar, S. Sitharama
1989-01-01
An efficient, adaptive neural learning paradigm for addressing the inverse kinematics of redundant manipulators is presented. The proposed methodology exploits the infinite local stability of terminal attractors - a new class of mathematical constructs which provide unique information processing capabilities to artificial neural systems. For robotic applications, synaptic elements of such networks can rapidly acquire the kinematic invariances embedded within the presented samples. Subsequently, joint-space configurations, required to follow arbitrary end-effector trajectories, can readily be computed. In a significant departure from prior neuromorphic learning algorithms, this methodology provides mechanisms for incorporating an in-training skew to handle kinematics and environmental constraints.
Detecting System for Correlation Experiments in Inverse Kinematics
NASA Astrophysics Data System (ADS)
Artukh, A. G.; Gridnev, G. F.; Denikin, A. N.; Klygin, S. A.; Maidikov, V. Z.; Perov, S. V.; Semchenkov, A. G.; Semchenkova, O. V.; Sereda, Yu. M.; Teterev, Yu. G.; Zagrebaev, U. I.; Zamiatin, N. I.; Vorontsov, A. N.; Budzanowski, A.; Koscielniak, F.; Szmider, J.
2002-04-01
Stripping proton and exchange few nucleon experiments with radioactive nuclear beams (RNB) in inverse kinematics have been proposed as a spectroscopic tool to study the structure of bound and unbound states of exotic nuclei near and beyond the neutron drip-line for the element with magic shell Z = 8 (oxygen isotopes). Few nucleon transfer reactions with radioactive beams on targets of the lightest element (hydrogen isotopes) look most promising, because of relatively large cross-sections, simpler kinematics and easier spectroscopy. Comparatively large thicknesses of targets (several mg/cm2) are mainly used, because it is necessary to compensate for the weak intensity of the RNB. Configuration of the correlation experiment based on the three-particle kinematic coincidences is discussed.
Learning inverse kinematics: reduced sampling through decomposition into virtual robots.
de Angulo, Vicente Ruiz; Torras, Carme
2008-12-01
We propose a technique to speedup the learning of the inverse kinematics of a robot manipulator by decomposing it into two or more virtual robot arms. Unlike previous decomposition approaches, this one does not place any requirement on the robot architecture, and thus, it is completely general. Parametrized self-organizing maps are particularly adequate for this type of learning, and permit comparing results directly obtained and through the decomposition. Experimentation shows that time reductions of up to two orders of magnitude are easily attained. PMID:19022727
Hu, Xinyao; Soh, Gim Song
2014-01-01
This paper describes a preliminary study of using four inertial measurement units (IMUs) attached to the heel and pelvis to estimate the joint angles of normal subjects during walking. The IMU, consisting of a 3-D accelerometer and gyroscope, is used to estimate the planar displacement of the heel and pelvis and the angular change of heel in one gait cycle. We then model the gait as a planar 3R serial chain and solve its inverse kinematics by using such information. The results are validated by comparing the estimated joint angles of lower limbs (i.e. hip, knee and ankle angles) with an optical motion capture system. This study can benefit the future research on conducting complete lower limbs kinematics analysis with minimal and unobtrusive wearable sensors. PMID:25571585
Kinematic Waveform Inversion: Application in Southwest Iberia Seismicity
NASA Astrophysics Data System (ADS)
Domingues, A. L.; Custodio, S.; Cesca, S.
2011-12-01
The seismic activity that affects the Portuguese territory occurs mainly and more frequently offshore, in the south and southwest of Mainland Portugal. The study of the Portuguese seismicity is conditioned by the poor azimuthal coverage, due to the geographic location of Portugal, and by the large sedimentary basin west of the straight of Gibraltar (Cadiz Basin). In this work we focus on the study of regional seismicity in Portugal (mostly offshore earthquakes) using a recently developed package - the KIWI (Kinematic Waveform Inversion) tools. This new technique performs point and finite source inversions at regional distances. The KIWI routine is a multi-step approach composed of 3 steps, finding different source parameters at different steps. At first, we assume a point source approximation. We initially retrieve the focal mechanism of the earthquake (strike, dip, and rake), the seismic scalar moment M0 and the depth. This inversion step is performed in the spectral domain, by fitting amplitude spectra. In the second step, compressive and dilatation quadrants are retrieved, which is carried out in the time domain. Refined latitude and longitude for the centroid, as well as an earthquake origin time, are also given at this time. The final step of the inversion consists of a simplified finite-fault inversion. We assume the eikonal source model, and determine parameters such as the fault plane orientation (discrimination between fault and auxiliary plane), radius (rupture extension), nucleation point coordinates (indicative of directivity effects) and average rupture velocity of the earthquake. This inversion is performed in the frequency domain by fitting amplitude spectra in a wider frequency band (including higher frequencies). This multi-step approach has the advantage of using different inversion methods, seismic phases and range of frequencies to infer specific parameters. In this work we study 17 regional earthquakes occurred in Southwest Iberia between 2007 and 2009 with moderate magnitude (3.3 to 4.4). The small magnitude of these earthquakes prevents their study with the third step of the algorithm. The solutions obtained are evaluated by a quality criteria and compared with other moment tensor solutions. The quality factor is based on the number of stations and on the misfit between the recorded and the synthetic waveforms. Apart from this study another offshore event was analyzed. The earthquake occurred SW of St Vincent Cape on February 12, 2007 with Mw 5.9. In this study the KIWI tools were employed to infer both the point and finite source parameters of this earthquake. The results of the kinematic source inversion step indicate that the 2007 HAP earthquake ruptured a plane trending WNW-ESE, whereas previous studies suggest that the conjugate fault plane (ENE-WSW) is the true rupture plane. The proposed solution also indicates that the earthquake occurred within the SWIM fault-zone. However, the 46Â° dip is difficult to reconcile with the sub-vertical nature of the SWIM faults.
Coulomb excitation of radioactive nuclear beams in inverse kinematics
Zamfir, N.V. |||; Barton, C.J.; Brenner, D.S.; Casten, R.F. |; Gill, R.L.; Zilges, A. |
1996-12-31
Techniques for the measurement of B (E2:0{sub 1}{sup +} {r_arrow} 2{sub 1}{sup +}) values by Coulomb excitation of Radioactive Nuclear Beams in inverse kinematics are described. Using a thin, low Z target, the Coulomb excited beam nuclei will decay in flight downstream of the target. For long lifetimes (nanosecond range) these nuclei decay centimeters downstream of the target and for shorter lifetimes (picoseconds or less) they decay near the target. Corresponding to these two lifetime regimes two methods have been developed to measure {gamma} rays from the Coulomb excited nuclei: the lifetime method in which the lifetime of the excited state is deduced from the decay curve and the integral method in which the B(E2) value is extracted from the measured total Coulomb excitation cross section.
Advanced control schemes and kinematic analysis for a kinematically redundant 7 DOF manipulator
NASA Technical Reports Server (NTRS)
Nguyen, Charles C.; Zhou, Zhen-Lei
1990-01-01
The kinematic analysis and control of a kinematically redundant manipulator is addressed. The manipulator is the slave arm of a telerobot system recently built at Goddard Space Flight Center (GSFC) to serve as a testbed for investigating research issues in telerobotics. A forward kinematic transformation is developed in its most simplified form, suitable for real-time control applications, and the manipulator Jacobian is derived using the vector cross product method. Using the developed forward kinematic transformation and quaternion representation of orientation matrices, we perform computer simulation to evaluate the efficiency of the Jacobian in converting joint velocities into Cartesian velocities and to investigate the accuracy of Jacobian pseudo-inverse for various sampling times. The equivalence between Cartesian velocities and quaternion is also verified using computer simulation. Three control schemes are proposed and discussed for controlling the motion of the slave arm end-effector.
NASA Technical Reports Server (NTRS)
Kelmar, Laura; Khosla, Pradeep K.
1990-01-01
An algorithm is proposed for automatically generating both the forward and inverse kinematics of a serial-link N-degree-of-freedom reconfigurable manipulator (RM). Generation of the kinematic equations that govern a modular manipulator starts with geometric descriptions of the units, or modules, as well as their sequence in the manipulator. This geometric information is used to obtain the Denavit-Hartenberg (DH) parameters of an RM. The DH kinematic parameters are then used to obtain the forward kinematic transformation of the system. The problem of obtaining the inverse kinematics of RMs is addressed, and the idea of scaling an RM to automate the inverse kinematics and make the procedure as general as possible is proposed.
Kinematic Source Inversion Using Smoothly Curved Fault Model
NASA Astrophysics Data System (ADS)
Suzuki, W.; Aoi, S.; Sekiguchi, H.
2010-12-01
In source inversion analysis, an approximation of fault geometry by a single plane is sometimes insufficient for explaining the observed data and a multiple fault plane model is used instead. One example is the 2008 Northern Iwate earthquake in Japan (Mw 6.9), which occurred within the subducting Pacific plate deeper than 100 km (Suzuki et al., 2009; BSSA). Preliminary inversion analysis using a single planar fault model that strikes southward referring to the moment tensor solution could not reproduce the waveforms observed at some stations located in certain azimuth as favorably as at the other stations. Taking account of the fact that the source mechanism estimated from P-wave first motion has a different strike angle from the moment tensor solution by 44 degrees, the two-plane fault model composed of the southern-striking plane in the northern part and the southwestern-striking plane in the southern part was then constructed. This fault model improved the waveform fitting for above-mentioned stations and total misfit value. Another example is the 2009 Suruga Bay earthquake in Japan (Mw 6.4), which occurred within the subducting Philippine Sea plate around 20 km deep (Aoi et al, 2010; Nature Geoscience). The aftershock distribution precisely determined using the double-difference algorithm showed the complex geometry in which the dipping directions in the northern and southern portions of the aftershock area were significantly different. To follow the aftershock distribution, the fault model used for source inversion consisted of two nearly orthogonal planes; one in the southern source area was dipping to the southeast and the other in the northern area was dipping to the northeast. Although the two-plane fault models used in those studies well explained the observed data, there was a gap between the fault planes. More realistic fault model would continuously change the strike and dip angles, and/or it would not have gaps. To construct such a fault model, it is necessary to express the fault geometry as curved surface. In this study we develop an inversion method to derive a kinematic source rupture process using a curved fault model. The fault surface is mathematically presented by Non-Uniform Rational B-Spline (NURBS), which offers the flexible surface modeling. Multi-time-window linear waveform inversion scheme is implemented to the curved fault model. Points for calculating Green's function are generated at a shorter interval than subfaults for deriving slip history. This means that each subfault is also expressed by the curved surface, whereas the subfaults were based on the planar elements in most of previous studies that estimated source process on the curved fault. We apply the developed method to the 2008 Northern Iwate earthquake. Large slip areas are estimated at similar locations to the two-plane fault analysis. The synthetic waveforms agree with the observed ones comparably for both fault models. The total seismic moment is smaller for the curved fault than for the two-plane fault, which may indicate that inversion analysis using curved fault model could suppress artificial slip.
Inelastic Proton Scattering on 21Na in Inverse Kinematics
NASA Astrophysics Data System (ADS)
Austin, Roby
2009-10-01
R.A.E. Austin, R. Kanungo, S. Reeve, Saint Mary's University; D.G. Jenkins, C.Aa.Diget, A. Robinson, A.G. Tuff, O. Roberts, University of York, UK; P.J. Woods, T. Davinson, G. J. Lotay, University of Edinburgh; C.-Y. Wu, Lawrence Livermore National Laboratory; H. Al Falou, G.C. Ball, M. Djongolov, A. Garnsworthy, G. Hackman, J.N. Orce, C.J. Pearson, S. Triambak, S.J. Williams, TRIUMF; C. Andreiou, D.S. Cross, N. Galinski, R. Kshetri, Simon Fraser University; C. Sumithrarachchi, M.A. Schumaker, University of Guelph; M.P. Jones, S.V. Rigby, University of Liverpool; D. Cline, A. Hayes, University of Rochester; T.E. Drake, University of Toronto; We describe an experiment and associated technique [1] to measure resonances of interest in astrophysical reactions. At the TRIUMF ISAC-II radioactive beam accelerator facility in Canada, particles inelastically scattered in inverse kinematics are detected with Bambino, a Î´E-E silicon telescope spanning 15-40 degrees in the lab. We use the TIGRESS to detect gamma rays in coincidence with the charged particles to cleanly select inelastic scattering events. We measured resonances above the alpha threshold in ^22Mg of relevance to the rate of break-out from the hot-CNO cycle via the reaction ^ 18Ne(Î±,p)^21Na. [1] PJ Woods et al. Rex-ISOLDE proposal 424 Cern (2003).
Coulomb excitation of radioactive nuclear beams in inverse kinematics
NASA Astrophysics Data System (ADS)
Barton, Charles Joseph, III
2000-09-01
Techniques for the measurement of B (E2; 0+1-->2+1 ) values at Radioactive Nuclear Beam (RNB) facilities are developed and described. In low energy Coulomb excitation experiments of even-even nuclei in inverse kinematics only the 2+1 state is appreciably populated. The beam particles impinge upon a thin, low Z target and exit with a velocity of <=5% the velocity of light, c. If the lifetime of the excited state is ~1 ns, the decay curve can be measured as the Coulomb excited radioactive nuclei decay in flight downstream of the target as they pass in front of a linear array of NaI(Tl) detectors. For nuclei whose lifetimes are shorter, or whose yields are very small, a high efficiency through-well NaI(Tl) detector can be used to determine the B (E2; 0+1-->2+1 ) value by direct measurement of the Coulomb excitation cross section. Two additional techniques, measuring the decay curve through the detection of conversion electrons, and a macro-plunger (for distances of millimeters) for Doppler shift measurements using the Recoil Distance Method to measure lifetimes, have been investigated. The results of test experiments with stable beams are presented. The first radioactive nuclear beam experiment performed at the Holifield Radioactive Ion Beam Facility (HRIBF) is described. This experiment employed the Integral Method which incorporates the high efficiency through-well NaI(Tl) detector. Results from this first radioactive beam experiment are presented as well as the design improvements made to the apparatus. The value of measuring only a few nuclear observables is discussed in the context of the valence correlation scheme, NPN N.
Seeing the world topsy-turvy: The primary role of kinematics in biological motion inversion effects.
Fitzgerald, Sue-Anne; Brooks, Anna; van der Zwan, Rick; Blair, Duncan
2014-01-01
Physical inversion of whole or partial human body representations typically has catastrophic consequences on the observer's ability to perform visual processing tasks. Explanations usually focus on the effects of inversion on the visual system's ability to exploit configural or structural relationships, but more recently have also implicated motion or kinematic cue processing. Here, we systematically tested the role of both on perceptions of sex from upright and inverted point-light walkers. Our data suggest that inversion results in systematic degradations of the processing of kinematic cues. Specifically and intriguingly, they reveal sex-based kinematic differences: Kinematics characteristic of females generally are resistant to inversion effects, while those of males drive systematic sex misperceptions. Implications of the findings are discussed. PMID:25469217
Seeing the world topsy-turvy: The primary role of kinematics in biological motion inversion effects
Fitzgerald, Sue-Anne; Brooks, Anna; van der Zwan, Rick; Blair, Duncan
2014-01-01
Physical inversion of whole or partial human body representations typically has catastrophic consequences on the observer's ability to perform visual processing tasks. Explanations usually focus on the effects of inversion on the visual system's ability to exploit configural or structural relationships, but more recently have also implicated motion or kinematic cue processing. Here, we systematically tested the role of both on perceptions of sex from upright and inverted point-light walkers. Our data suggest that inversion results in systematic degradations of the processing of kinematic cues. Specifically and intriguingly, they reveal sex-based kinematic differences: Kinematics characteristic of females generally are resistant to inversion effects, while those of males drive systematic sex misperceptions. Implications of the findings are discussed. PMID:25469217
Spatial operator approach to under-actuated manipulator kinematics and dynamics
NASA Technical Reports Server (NTRS)
Jain, A.; Rodriguez, G.
1991-01-01
A study is made of the kinematics and dynamics of under-actuated manipulators. The presence of passive hinges causes the kinematics and dynamics of these manipulators to be considerably more complex when compared with fully actuated manipulators. Techniques from the spatial operator algebra are used to develop expressions for the generalized Jacobian, the mass matrix, and an efficient inverse dynamics computational algorithm.
Inverse kinematic solution for near-simple robots and its application to robot calibration
NASA Technical Reports Server (NTRS)
Hayati, Samad A.; Roston, Gerald P.
1986-01-01
This paper provides an inverse kinematic solution for a class of robot manipulators called near-simple manipulators. The kinematics of these manipulators differ from those of simple-robots by small parameter variations. Although most robots are by design simple, in practice, due to manufacturing tolerances, every robot is near-simple. The method in this paper gives an approximate inverse kinematics solution for real time applications based on the nominal solution for these robots. The validity of the results are tested both by a simulation study and by applying the algorithm to a PUMA robot.
Manipulator inverse kinematics control based on particle swarm optimization neural network
NASA Astrophysics Data System (ADS)
Wen, Xiulan; Sheng, Danghong; Guo, Jing
2008-10-01
The inverse kinematics control of a robotic manipulator requires solving non-linear equations having transcendental functions and involving time-consuming calculations. Particle Swarm Optimization (PSO), which is based on the behaviour of insect swarms and exploits the solution space by taking into account the experience of the single particle as well as that of the entire swarm, is similar to the genetic algorithm (GA) in that it performs a structured randomized search of an unknown parameter space by manipulating a population of parameter estimates to converge on a suitable solution. In this paper, PSO is firstly proposed to optimize feed-forward neural network for manipulator inverse kinematics. Compared with the results of the fast back propagation learning algorithm (FBP), conventional GA genetic algorithm based elitist reservation (EGA), improved GA (IGA) and immune evolutionary computation (IEC), the simulation results verify the particle swarm optimization neural network (PSONN) is effective for manipulator inverse kinematics control.
NASA Astrophysics Data System (ADS)
Dong, Gangqi; Zhu, Z. H.
2016-04-01
This paper proposed a new incremental inverse kinematics based vision servo approach for robotic manipulators to capture a non-cooperative target autonomously. The target's pose and motion are estimated by a vision system using integrated photogrammetry and EKF algorithm. Based on the estimated pose and motion of the target, the instantaneous desired position of the end-effector is predicted by inverse kinematics and the robotic manipulator is moved incrementally from its current configuration subject to the joint speed limits. This approach effectively eliminates the multiple solutions in the inverse kinematics and increases the robustness of the control algorithm. The proposed approach is validated by a hardware-in-the-loop simulation, where the pose and motion of the non-cooperative target is estimated by a real vision system. The simulation results demonstrate the effectiveness and robustness of the proposed estimation approach for the target and the incremental control strategy for the robotic manipulator.
Pain, S. D.; Bardayan, Daniel W; Blackmon, Jeff C; Chae, K. Y.; Chipps, K.; Cizewski, J. A.; Hatarik, Robert; Johnson, Micah; Jones, K. L.; Kapler, R.; Kozub, R. L.; Livesay, Jake; Matei, Catalin; Moazen, Brian; Nesaraja, Caroline D; O'Malley, Patrick; Smith, Michael Scott; Swan, T. P.; Thomas, J. S.; Wilson, Gemma L
2009-01-01
The development of high quality radioactive beams has made possible the measurement of transfer reactions in inverse kinematics on unstable nuclei. Measurement of (d,p) reactions on neutron-rich nuclei yield data on the evolution of nuclear structure away from stability, and are of astrophysical interest. Experimentally, (d,p) reactions on heavy (Z=50) fission fragments are complicated by the strongly inverse kinematics, and relatively low beam intensities. Consequently, ejectile detection with high resolution in position and energy, a high dynamic range and a high solid angular coverage is required. The Oak Ridge Rutgers University Barrel Array (ORRUBA) is a new silicon detector array optimized for the measurement of (d,p) reactions in inverse kinematics.
Thick-target yields of radioactive targets deduced from inverse kinematics
NASA Astrophysics Data System (ADS)
Aikawa, M.; Ebata, S.; Imai, S.
2015-06-01
The thick-target yield (TTY) is a macroscopic quantity reflected by nuclear reactions and matter properties of targets. In order to evaluate TTYs on radioactive targets, we suggest a conversion method from inverse kinematics corresponding to the reaction of radioactive beams on stable targets. The method to deduce the TTY is theoretically derived from inverse kinematics. We apply the method to the natCu(12C,X)24Na reaction to confirm availability. In addition, it is applied to the 137Cs + 12C reaction as an example of a radioactive system and discussed a conversion coefficient of a TTY measurement.
Foot inversion-eversion and knee kinematics during walking.
Lafortune, M A; Cavanagh, P R; Sommer, H J; Kalenak, A
1994-05-01
The purpose of this study was to monitor selected aspects of the three-dimensional kinematics of the knee during walking with regular shoes and with modified shoes that induced either pronation or supination of the foot. Steinmann traction pins were inserted into the right tibia and femur of five adult men who had apparently normal lower extremities. Target clusters mounted onto the pins were filmed by four cine cameras operating at 100 frames/sec. Two trials per subject were analyzed for each of the three experimental conditions: regular running shoes, running shoes with a 10 degree valgus wedge, and running shoes with a 10 degree varus wedge. The different types of footwear induced only minor kinematic changes at the knee during the stance phase of walking. The angular patterns of the tibiofemoral joint were modified by less than 1 degree, whereas the translatory patterns were altered by 2 mm. Immediately following foot-strike, the valgus-wedge shoes caused the tibia to rotate internally 4 degrees more than the varus-wedge shoes, but at the tibiofemoral joint no consistent differences in the pattern of internal-external rotation between normal and modified footwear were measureable. These findings suggest that, in the healthy lower extremity, increased internal and external tibial rotation is resolved at the hip joint, with changes at the tibiofemoral joint that barely are detectable with the techniques used in this study. PMID:8207595
NASA Astrophysics Data System (ADS)
Zielke, Olaf; McDougall, Damon; Mai, Martin; Babuska, Ivo
2014-05-01
Seismic, often augmented with geodetic data, are frequently used to invert for the spatio-temporal evolution of slip along a rupture plane. The resulting images of the slip evolution for a single event, inferred by different research teams, often vary distinctly, depending on the adopted inversion approach and rupture model parameterization. This observation raises the question, which of the provided kinematic source inversion solutions is most reliable and most robust, and — more generally — how accurate are fault parameterization and solution predictions? These issues are not included in "standard" source inversion approaches. Here, we present a statistical inversion approach to constrain kinematic rupture parameters from teleseismic body waves. The approach is based a) on a forward-modeling scheme that computes synthetic (body-)waves for a given kinematic rupture model, and b) on the QUESO (Quantification of Uncertainty for Estimation, Simulation, and Optimization) library that uses MCMC algorithms and Bayes theorem for sample selection. We present Bayesian inversions for rupture parameters in synthetic earthquakes (i.e. for which the exact rupture history is known) in an attempt to identify the cross-over at which further model discretization (spatial and temporal resolution of the parameter space) is no longer attributed to a decreasing misfit. Identification of this cross-over is of importance as it reveals the resolution power of the studied data set (i.e. teleseismic body waves), enabling one to constrain kinematic earthquake rupture histories of real earthquakes at a resolution that is supported by data. In addition, the Bayesian approach allows for mapping complete posterior probability density functions of the desired kinematic source parameters, thus enabling us to rigorously assess the uncertainties in earthquake source inversions.
Direct and Inverse Kinematics of a Novel Tip-Tilt-Piston Parallel Manipulator
NASA Technical Reports Server (NTRS)
Tahmasebi, Farhad
2004-01-01
Closed-form direct and inverse kinematics of a new three degree-of-freedom (DOF) parallel manipulator with inextensible limbs and base-mounted actuators are presented. The manipulator has higher resolution and precision than the existing three DOF mechanisms with extensible limbs. Since all of the manipulator actuators are base-mounted; higher payload capacity, smaller actuator sizes, and lower power dissipation can be obtained. The manipulator is suitable for alignment applications where only tip, tilt, and piston motions are significant. The direct kinematics of the manipulator is reduced to solving an eighth-degree polynomial in the square of tangent of half-angle between one of the limbs and the base plane. Hence, there are at most 16 assembly configurations for the manipulator. In addition, it is shown that the 16 solutions are eight pairs of reflected configurations with respect to the base plane. Numerical examples for the direct and inverse kinematics of the manipulator are also presented.
Real-time neuromorphic algorithms for inverse kinematics of redundant manipulators
NASA Technical Reports Server (NTRS)
Barhen, Jacob; Gulati, Sandeep; Zak, Michail
1989-01-01
The paper presents an efficient neuromorphic formulation to accurately solve the inverse kinematics problem for redundant manipulators. The approach involves a dynamical learning procedure based on a novel formalism in neural network theory: the concept of 'terminal' attractors. Topographically mapped terminal attractors are used to define a neural network whose synaptic elements can rapidly encapture the inverse kinematics transformations, and, subsequently generalize to compute joint-space coordinates required to achieve arbitrary end-effector configurations. Unlike prior neuromorphic implementations, this technique can also systematically exploit redundancy to optimize kinematic criteria, e.g., torque optimization. Simulations on 3-DOF and 7-DOF redundant manipulators, are used to validate the theoretical framework and illustrate its computational efficacy.
NASA Astrophysics Data System (ADS)
Farget, F.; Caamańo, M.; Ramos, D.; Rodr?guez-Tajes, C.; Schmidt, K.-H.; Audouin, L.; Benlliure, J.; Casarejos, E.; Clément, E.; Cortina, D.; Delaune, O.; Derkx, X.; Dijon, A.; Doré, D.; Fernández-Dom?nguez, B.; Gaudefroy, L.; Golabek, C.; Heinz, A.; Jurado, B.; Lemasson, A.; Paradela, C.; Roger, T.; Salsac, M. D.; Schmitt, C.
2015-12-01
Inverse kinematics is a new tool to study nuclear fission. Its main advantage is the possibility to measure with an unmatched resolution the atomic number of fission fragments, leading to new observables in the properties of fission-fragment distributions. In addition to the resolution improvement, the study of fission based on nuclear collisions in inverse kinematics beneficiates from a larger view with respect to the neutron-induced fission, as in a single experiment the number of fissioning systems and the excitation energy range are widden. With the use of spectrometers, mass and kinetic-energy distributions may now be investigated as a function of the proton and neutron number sharing. The production of fissioning nuclei in transfer reactions allows studying the isotopic yields of fission fragments as a function of the excitation energy. The higher excitation energy resulting in the fusion reaction leading to the compound nucleus 250Cf at an excitation energy of 45MeV is also presented. With the use of inverse kinematics, the charge polarisation of fragments at scission is now revealed with high precision, and it is shown that it cannot be neglected, even at higher excitation energies. In addition, the kinematical properties of the fragments inform on the deformation configuration at scission.
Neutron capture surrogate reaction on 75As in inverse kinematics using (d,p )
Peters, W. A.; Cizewski, J. A.; Hatarik, Robert; O'Malley, Patrick; Jones, K. L.; Schmitt, Kyle; Moazen, Brian; Chae, K. Y.; Pittman, S. T.; Kozub, R. L.; Vieira, D. J.; Jandel, M.; Wilhelmy, J. B.; Matei, Catalin; Escher, J.; Bardayan, Daniel W; Pain, Steven D; Smith, Michael Scott
2010-01-01
The 75As(d,p ) reaction in inverse kinematics as a surrogate for neutron capture was performed at Oak Ridge National Laboratory using a deuterated plastic target. The intensity of the 165 keV -ray from 76As in coincidence with ejected protons, from exciting 76As above the neutron separation energy populating a compound state, was measured. A tight geometry of four segmented germanium clover -ray detectors together with eight ORRUBA-type silicon-strip charged-particle detectors were used to optimize geometric acceptance. The preliminary analysis of the 75As experiment and the ecacy and future plans of the (d,p ) surrogate campaign in inverse kinematics are discussed.
Neutron Capture Surrogate Reaction on 75As in Inverse Kinematics Using (d,p(gamma))
Peters, W A; Cizewski, J A; Hatarik, R; O?Malley, P D; Jones, K L; Schmitt, K; Moazen, B H; Chae, K Y; Pittman, S T; Kozub, R L; Vieira, D; Jandel, M; Wilhelmy, J B; Matei, C; Escher, J; Bardayan, D W; Pain, S D; Smith, M S
2009-11-09
The {sup 75}As(d,p{gamma}) reaction in inverse kinematics as a surrogate for neutron capture was performed at Oak Ridge National Laboratory using a deuterated plastic target. The intensity of the 165 keV {gamma}-ray from {sup 76}As in coincidence with ejected protons, from exciting {sup 76}As above the neutron separation energy populating a compound state, was measured. A tight geometry of four segmented germanium clover {gamma}-ray detectors together with eight ORRUBA-type silicon-strip charged-particle detectors was used to optimize geometric acceptance. The preliminary analysis of the {sup 75}As experiment, and the efficacy and future plans of the (d,p{gamma}) surrogate campaign in inverse kinematics, are discussed.
Cortex Inspired Model for Inverse Kinematics Computation for a Humanoid Robotic Finger
Gentili, Rodolphe J.; Oh, Hyuk; Molina, Javier; Reggia, James A.; Contreras-Vidal, JosĂ© L.
2013-01-01
In order to approach human hand performance levels, artificial anthropomorphic hands/fingers have increasingly incorporated human biomechanical features. However, the performance of finger reaching movements to visual targets involving the complex kinematics of multi-jointed, anthropomorphic actuators is a difficult problem. This is because the relationship between sensory and motor coordinates is highly nonlinear, and also often includes mechanical coupling of the two last joints. Recently, we developed a cortical model that learns the inverse kinematics of a simulated anthropomorphic finger. Here, we expand this previous work by assessing if this cortical model is able to learn the inverse kinematics for an actual anthropomorphic humanoid finger having its two last joints coupled and controlled by pneumatic muscles. The findings revealed that single 3D reaching movements, as well as more complex patterns of motion of the humanoid finger, were accurately and robustly performed by this cortical model while producing kinematics comparable to those of humans. This work contributes to the development of a bioinspired controller providing adaptive, robust and flexible control of dexterous robotic and prosthetic hands. PMID:23366569
Cortex inspired model for inverse kinematics computation for a humanoid robotic finger.
Gentili, Rodolphe J; Oh, Hyuk; Molina, Javier; Reggia, James A; Contreras-Vidal, JosĂ© L
2012-01-01
In order to approach human hand performance levels, artificial anthropomorphic hands/fingers have increasingly incorporated human biomechanical features. However, the performance of finger reaching movements to visual targets involving the complex kinematics of multi-jointed, anthropomorphic actuators is a difficult problem. This is because the relationship between sensory and motor coordinates is highly nonlinear, and also often includes mechanical coupling of the two last joints. Recently, we developed a cortical model that learns the inverse kinematics of a simulated anthropomorphic finger. Here, we expand this previous work by assessing if this cortical model is able to learn the inverse kinematics for an actual anthropomorphic humanoid finger having its two last joints coupled and controlled by pneumatic muscles. The findings revealed that single 3D reaching movements, as well as more complex patterns of motion of the humanoid finger, were accurately and robustly performed by this cortical model while producing kinematics comparable to those of humans. This work contributes to the development of a bioinspired controller providing adaptive, robust and flexible control of dexterous robotic and prosthetic hands. PMID:23366569
NASA Astrophysics Data System (ADS)
Shimada, K.; Nagae, D.; Asahi, K.; Arai, T.; Takemura, M.; Inoue, T.; Takase, K.; Kagami, S.; Hatakeyama, N.; Kobayashi, Y.; Ueno, H.; Yoshimi, A.; Kameda, D.; Nagatomo, T.; Sugimoto, T.; Kubono, S.; Yamaguchi, H.; Wakabayashi, Y.; Amadio, G.; Hayakawa, T.; Murata, J.; Kawamura, H.
2007-06-01
The development of techniques to produce low-energy spin-polarized radioactive nucleon beams (RNBs) is reported. It employs the inverse-kinematics reactions of law energy heavy-ion beams for the RNB production with in-flight separator. Some plans of research are discussed that apply these well-focused, conveniently energetic spin-polarized RNB to nuclear structure physics and material science.
Shimada, K.; Nagae, D.; Asahi, K.; Arai, T.; Takemura, M.; Inoue, T.; Takase, K.; Kagami, S.; Hatakeyama, N.; Kobayashi, Y.; Ueno, H.; Yoshimi, A.; Kameda, D.; Nagatomo, T.; Sugimoto, T.; Kubono, S.; Yamaguchi, H.; Wakabayashi, Y.; Amadio, G.; Hayakawa, T.
2007-06-13
The development of techniques to produce low-energy spin-polarized radioactive nucleon beams (RNBs) is reported. It employs the inverse-kinematics reactions of law energy heavy-ion beams for the RNB production with in-flight separator. Some plans of research are discussed that apply these well-focused, conveniently energetic spin-polarized RNB to nuclear structure physics and material science.
Chen, Elvis C S; Ellis, Randy E
2006-01-01
A motion-based Inverse Kinematics Knee (IKK) model was developed for Total Knee Replacement (TKR) joints. By tracking a sequence of passive knee motion, the IKK model estimated ligament properties such as insertion locations. The formulation of the IKK model embedded a Forward Kinematics Knee (FKK) model in a numerical optimization algorithm known as the Unscented Kalman Filter. Simulation results performed on a semi-constrained TKR design suggested that ligament insertions could be accurately estimated in the medial-lateral (ML) and the proximal-distal (PD) directions, but less reliably in the anterior-posterior (AP) direction for the tibial component. However, the forward kinematics produced by both the true and estimated ligament properties were nearly identical, suggesting that the IKK model recovered a kinematically equivalent set of ligament properties. These results imply that it may not be necessary to use a patient-specific CT or MRI scan to locate ligaments, which considerably widens potential applications of kinematic-based total knee replacement. PMID:17354905
Investigating the reliability of kinematic source inversion with dynamic rupture models
NASA Astrophysics Data System (ADS)
Zhang, Y.; Song, S.; Dalguer, L. A.; Clinton, J. F.
2011-12-01
An essential element of understanding the earthquake source processes is obtaining a reliable source model via geophysical data inversion. However, the epistemic uncertainties in the kinematic source inversion produce a variety of source model estimates for any given event. Thus, as done in the Source Inversion Validation (SIV) project, it is important to validate our inversion methods with synthetic data by testing forward Green's function calculation and comparing various inversion methods. Spontaneous dynamic rupture modeling, which incorporates the conservation laws of continuum mechanics and the constitutive behavior of rocks under frictional sliding, is capable of producing physically self-consistent kinematic description of the fault and its associated seismic wave propagation resulting in ground motions on the surface. Here we develop accurate dynamic rupture simulation of a vertical strike slip fault. Our source model is composed of well-defined asperities (patches of large stress drop) and we assume that fault rupture is governed by the linear slip weakening friction model. The resulting near-source ground motions dominated by low frequency (up to 1Hz) are used for testing our inversion method. We performed various inversion tests and compared estimated solutions with true solutions obtained by the forward dynamic rupture modeling. Our preliminary results show that estimated model spaces could be significantly perturbed, depending on data and modeling schemes used in the inversion, not only in terms of spatial distribution of model parameters, but also in terms of their auto- and cross-correlation structure. The Bayesian approach in source inversion is becoming increasingly popular because of the recent common availability of high performance computing capabilities. We adopted the Bayesian approach in our source inversion test, so that we can more effectively analyze the uncertainty of estimated models and also implement physically guided regularization in the prior. In addition, the recent emergence of high-rate Global Navigation Satellite Systems (GNSS) data can considerably improve the observation capabilities for dynamic surface movements (sampling up to 100 Hz) during large earthquakes. GNSS receivers are used to accurately measure both dynamic and static ground displacements without saturation or sensitivity to tilt and with a sampling interval below 1 second and sub-centimeter accuracy across the frequency spectrum. We expect that we can resolve the issue of relative weighting often faced in multiple data inversion, i.e., joint inversion of both geodetic and seismic data, by inverting ground displacement data recorded by the high rate GNSS receivers.
Exclusive measurements of quasi-free proton scattering reactions in inverse and complete kinematics
NASA Astrophysics Data System (ADS)
Panin, V.; Taylor, J. T.; Paschalis, S.; Wamers, F.; Aksyutina, Y.; Alvarez-Pol, H.; Aumann, T.; Bertulani, C. A.; Boretzky, K.; Caesar, C.; Chartier, M.; Chulkov, L. V.; Cortina-Gil, D.; Enders, J.; Ershova, O.; Geissel, H.; GernhĂ¤user, R.; Heil, M.; Johansson, H. T.; Jonson, B.; KeliÄ‡-Heil, A.; Langer, C.; Le Bleis, T.; Lemmon, R.; Nilsson, T.; Petri, M.; Plag, R.; Reifarth, R.; Rossi, D.; Scheit, H.; Simon, H.; Weick, H.; Wimmer, C.
2016-02-01
Quasi-free scattering reactions of the type (p , 2 p) were measured for the first time exclusively in complete and inverse kinematics, using a 12C beam at an energy of âĽ 400Â MeV /u as a benchmark. This new technique has been developed to study the single-particle structure of exotic nuclei in experiments with radioactive-ion beams. The outgoing pair of protons and the fragments were measured simultaneously, enabling an unambiguous identification of the reaction channels and a redundant measurement of the kinematic observables. Both valence and deeply-bound nucleon orbits are probed, including those leading to unbound states of the daughter nucleus. Exclusive (p , 2 p) cross sections of 15.8(18) mb, 1.9(2) mb and 1.5(2) mb to the low-lying 0p-hole states overlapping with the ground state (3 /2-) and with the bound excited states of 11B at 2.125 MeV (1 /2-) and 5.02 MeV (3 /2-), respectively, were determined via Îł-ray spectroscopy. Particle-unstable deep-hole states, corresponding to proton removal from the 0s-orbital, were studied via the invariant-mass technique. Cross sections and momentum distributions were extracted and compared to theoretical calculations employing the eikonal formalism. The obtained results are in a good agreement with this theory and with direct-kinematics experiments. The dependence of the proton-proton scattering kinematics on the internal momentum of the struck proton and on its separation energy was investigated for the first time in inverse kinematics employing a large-acceptance measurement.
NASA Technical Reports Server (NTRS)
Podhorodeski, R. P.; Fenton, R. G.; Goldenberg, A. A.
1989-01-01
Using a method based upon resolving joint velocities using reciprocal screw quantities, compact analytical expressions are generated for the inverse solution of the joint rates of a seven revolute (spherical-revolute-spherical) manipulator. The method uses a sequential decomposition of screw coordinates to identify reciprocal screw quantities used in the resolution of a particular joint rate solution, and also to identify a Jacobian null-space basis used for the direct solution of optimal joint rates. The results of the screw decomposition are used to study special configurations of the manipulator, generating expressions for the inverse velocity solution for all non-singular configurations of the manipulator, and identifying singular configurations and their characteristics. Two functions are therefore served: a new general method for the solution of the inverse velocity problem is presented; and complete analytical expressions are derived for the resolution of the joint rates of a seven degree of freedom manipulator useful for telerobotic and industrial robotic application.
Study of the 6Li + p 3He + 4He reaction in inverse kinematics
NASA Astrophysics Data System (ADS)
Betsou, Ch.; Pakou, A.; Cappuzzello, F.; Acosta, L.; Agodi, C.; Aslanoglou, X.; Carbone, D.; Cavallaro, M.; Di Pietro, A.; Fernández-García, J. P.; Figuera, P.; Fisichella, M.; Foti, A.; Keeley, N.; Marquinez-Duran, G.; Martel, I.; Mazzocco, M.; Nicolis, N. G.; Pierroutsakou, D.; Rusek, K.; Sgouros, O.; Soukeras, V.; Stiliaris, E.; Strano, E.; Torresi, D.
2015-07-01
Angular distribution measurements were performed for the 6 Li + p 3 He + 4 He reaction in inverse kinematics at incident energies of 2.7, 3.3, 4.2 and 4.8MeV/ u . The detection of both recoils ( 3He and 4He over the laboratory angle range to allowed the determination of the angular distribution over a wide angular range in the center-of-mass frame ( to . The results clarify inconsistencies between existing data sets and are consistent with compound nucleus model calculations.
NASA Astrophysics Data System (ADS)
Castro-Artola, O.; Iglesias Mendoza, A.
2012-04-01
Aiming to obtain some information about the rupture process of intermediate to great earthquakes, many waveform inversion schemes have been proposed. Usual methods involve several subfaults on the fault plane to obtain a detailed image of the kinematic rupture process. On the other hand, it has been questioned the resolution over obtained paramters on the inversion process. In the literature contradictory results can be found for the same earthquake, using different schemes. For this reason, recently, simplified schemes of the rupture process have been proposed, while not providing details it can recover their main characteristics. In this work we propose a modification of the Cotton & Campillo (1995) inversion scheme, while unlike considering the problem as a "rupture process tomographic inversion", we invert the main characteristics assuming simplified geometries (ellipses). Based on the work quoted, the direct problem is reparameterized including one or two ellipses in which the maximum displacement is distributed. For the first ellipse, the position of the center within the fault plane, the major and minor semi-axis are inverted. For the second one we invert the position with respect to the first ellipse and the two semi-axis. To avoid the linearization of the problem, we use a simulated annealing scheme for inversion. When there is not enough evidence of the proper fault plane, we perform an inversion for the two nodal planes published to solve the ambiguity between the auxiliary plane and the fault plane that a point source inversion schemes involve. We tested our method for the well studied earthquake September 30th 1999 Oaxaca (Mw=7.5) (e.g. Hernandez et al., 2001) which is one of the intraslab earthquakes within the Northamerican Plate of moderate magnitude and well recorded. The scheme is evaluated as well with the data generated by the "Escenario 2011" framework for an hypothetical earthquake in Guerrero, Mexico. Results will give us the opportunity to evaluate their later routinary implementation to the earthquakes occurring within Mexico.
34P(7Li,7Be+?) reaction at 100A??MeV in inverse kinematics.
Zegers, R G T; Meharchand, R; Shimbara, Y; Austin, Sam M; Bazin, D; Brown, B A; Diget, C Aa; Gade, A; Guess, C J; Hausmann, M; Hitt, G W; Howard, M E; King, M; Miller, D; Noji, S; Signoracci, A; Starosta, K; Tur, C; Vaman, C; Voss, P; Weisshaar, D; Yurkon, J
2010-05-28
We report on the first successful extraction of a ?+ Gamow-Teller strength distribution from a radioactive isotope in an intermediate-energy charge-exchange experiment in inverse kinematics. The (7Li,7Be+?(429??keV)) reaction at 100A??MeV was used to measure Gamow-Teller transition strengths from 34P to states in 34Si. The results show that little mixing occurs between sd and pf shell configurations for the low-lying 0+ and 2+ states even though 34Si neighbors the island of inversion and low-lying 2?? intruder states exist. Shell-model calculations in the sdpf model space are consistent with these findings. PMID:20867091
Kinematically redundant robot manipulators
NASA Technical Reports Server (NTRS)
Baillieul, J.; Hollerbach, J.; Brockett, R.; Martin, D.; Percy, R.; Thomas, R.
1987-01-01
Research on control, design and programming of kinematically redundant robot manipulators (KRRM) is discussed. These are devices in which there are more joint space degrees of freedom than are required to achieve every position and orientation of the end-effector necessary for a given task in a given workspace. The technological developments described here deal with: kinematic programming techniques for automatically generating joint-space trajectories to execute prescribed tasks; control of redundant manipulators to optimize dynamic criteria (e.g., applications of forces and moments at the end-effector that optimally distribute the loading of actuators); and design of KRRMs to optimize functionality in congested work environments or to achieve other goals unattainable with non-redundant manipulators. Kinematic programming techniques are discussed, which show that some pseudo-inverse techniques that have been proposed for redundant manipulator control fail to achieve the goals of avoiding kinematic singularities and also generating closed joint-space paths corresponding to close paths of the end effector in the workspace. The extended Jacobian is proposed as an alternative to pseudo-inverse techniques.
Integrated Analytic and Linearized Inverse Kinematics for Precise Full Body Interactions
NASA Astrophysics Data System (ADS)
Boulic, Ronan; Raunhardt, Daniel
Despite the large success of games grounded on movement-based interactions the current state of full body motion capture technologies still prevents the exploitation of precise interactions with complex environments. This paper focuses on ensuring a precise spatial correspondence between the user and the avatar. We build upon our past effort in human postural control with a Prioritized Inverse Kinematics framework. One of its key advantage is to ease the dynamic combination of postural and collision avoidance constraints. However its reliance on a linearized approximation of the problem makes it vulnerable to the well-known full extension singularity of the limbs. In such context the tracking performance is reduced and/or less believable intermediate postural solutions are produced. We address this issue by introducing a new type of analytic constraint that smoothly integrates within the prioritized Inverse Kinematics framework. The paper first recalls the background of full body 3D interactions and the advantages and drawbacks of the linearized IK solution. Then the Flexion-EXTension constraint (FLEXT in short) is introduced for the partial position control of limb-like articulated structures. Comparative results illustrate the interest of this new type of integrated analytical and linearized IK control.
An inverse kinematics algorithm for a highly redundant variable-geometry-truss manipulator
NASA Technical Reports Server (NTRS)
Naccarato, Frank; Hughes, Peter
1989-01-01
A new class of robotic arm consists of a periodic sequence of truss substructures, each of which has several variable-length members. Such variable-geometry-truss manipulator (VGTMs) are inherently highly redundant and promise a significant increase in dexterity over conventional anthropomorphic manipulators. This dexterity may be exploited for both obstacle avoidance and controlled deployment in complex workspaces. The inverse kinematics problem for such unorthodox manipulators, however, becomes complex because of the large number of degrees of freedom, and conventional solutions to the inverse kinematics problem become inefficient because of the high degree of redundancy. A solution is presented to this problem based on a spline-like reference curve for the manipulator's shape. Such an approach has a number of advantages: (1) direct, intuitive manipulation of shape; (2) reduced calculation time; and (3) direct control over the effective degree of redundancy of the manipulator. Furthermore, although the algorithm was developed primarily for variable-geometry-truss manipulators, it is general enough for application to a number of manipulator designs.
Inversion kinematics at deep-seated gravity slope deformations revealed by trenching techniques
NASA Astrophysics Data System (ADS)
PasquarĂ© Mariotto, Federico; Tibaldi, Alessandro
2016-03-01
We compare data from three deep-seated gravitational slope deformations (DSGSDs) where palaeoseismological techniques were applied in artificial trenches. At all trenches, located in metamorphic rocks of the Italian Alps, there is evidence of extensional deformation given by normal movements along slip planes dipping downhill or uphill, and/or fissures, as expected in gravitational failure. However, we document and illustrate - with the aid of trenching - evidence of reverse movements. The reverse slips occurred mostly along the same planes along which normal slip occurred, and they produced drag folds in unconsolidated Holocene sediments as well as the superimposition of substrate rocks on Holocene sediments. The studied trenches indicate that reverse slip might occur not only at the toe portions of DSGSDs but also in their central-upper portions. When the age relationships between the two deformation kinematics can be determined, they clearly indicate that reverse slips postdate normal ones. Our data suggest that, during the development of long-lived DSGSDs, inversion kinematics may occur in different sectors of the unstable rock mass. The inversion is interpreted as due either to locking of the frontal blocks of a DSGSD or to the relative decrease in the rate of downward movement in the frontal blocks with respect to the rear blocks.
NASA Astrophysics Data System (ADS)
Castaldo, R.; Tizzani, P.; Lollino, P.; CalĂ˛, F.; Ardizzone, F.; Lanari, R.; Guzzetti, F.; Manunta, M.
2015-11-01
The aim of this paper is to propose a methodology to perform inverse numerical modelling of slow landslides that combines the potentialities of both numerical approaches and well-known remote-sensing satellite techniques. In particular, through an optimization procedure based on a genetic algorithm, we minimize, with respect to a proper penalty function, the difference between the modelled displacement field and differential synthetic aperture radar interferometry (DInSAR) deformation time series. The proposed methodology allows us to automatically search for the physical parameters that characterize the landslide behaviour. To validate the presented approach, we focus our analysis on the slow Ivancich landslide (Assisi, central Italy). The kinematical evolution of the unstable slope is investigated via long-term DInSAR analysis, by exploiting about 20 years of ERS-1/2 and ENVISAT satellite acquisitions. The landslide is driven by the presence of a shear band, whose behaviour is simulated through a two-dimensional time-dependent finite element model, in two different physical scenarios, i.e. Newtonian viscous flow and a deviatoric creep model. Comparison between the model results and DInSAR measurements reveals that the deviatoric creep model is more suitable to describe the kinematical evolution of the landslide. This finding is also confirmed by comparing the model results with the available independent inclinometer measurements. Our analysis emphasizes that integration of different data, within inverse numerical models, allows deep investigation of the kinematical behaviour of slow active landslides and discrimination of the driving forces that govern their deformation processes.
NASA Astrophysics Data System (ADS)
Xu, Wenfu; She, Yu; Xu, Yangsheng
2014-12-01
Redundant space manipulators, including Space Station Remote Manipulator System (SSRMS), Special Purpose Dexterous Manipulator (SPDM) and European Robotic Arm (ERA), have been playing important roles in the construction and maintenance of International Space Station (ISS). They all have 7 revolute joints arranged in similar configurations, and are referred to as SSRMS-type manipulators. When a joint is locked in an arbitrary position due to some failures, a 7R manipulator degrades to a 6R manipulator. Without a spherical wrist or three consecutive parallel joints, the inverse kinematics of the 6R manipulator is very complex. In this paper, we propose effective methods to resolve the inverse kinematics for different cases of any joint locked in an arbitrary position. Firstly, configuration characteristics of the SSRMS-type redundant manipulators are analyzed. Then, an existing of closed-form inverse kinematics is discussed for locking different joints. Secondly, D-H frames and corresponding D-H parameters of the new 6-DOF manipulator formed by locking a joint in an arbitrary position are re-constructed. A unified table is then created to describe the kinematics for all possible cases of single joint locking failure. Thirdly, completely analytical and semi-analytical methods are presented to solve the inverse kinematics equations, and the former is used for locking joint 1, 2, 6 or 7 while the latter for locking joint 3, 4 or 5. Finally, typical cases for single joint locking are studied. The results verify the proposed methods.
Optimization methods for hyper-redundant robots' inverse kinematics in biomedical applications
NASA Astrophysics Data System (ADS)
Espinoza, Mario SĂˇenz; Pereira, Ana I.; GonĂ§alves, JosĂ©
2012-09-01
The present work describes and compares several approaches applied to compute the inverse kinematics of a ten degrees of freedom hyper-redundant robot. The proposed approaches are based on an exhaustive method and several error-optimization algorithms. The algorithms' performance was evaluated based on two criteria: computational processing time and final actuator positioning error. The results obtained show that for a small number of modules (less or equal to four), the exhaustive method provides the best problem solution: acceptable computational processing time as well as minimum error. However, for larger number of modules, the error-optimization approach has far better performance regarding the error to processing time ratio. The mentioned hyper-redundant robot was projected to be used in biomedical applications.
Monte Carlo Sampling with Linear Inverse Kinematics for Simulation of Protein Flexible Regions.
Hayward, Steven; Kitao, Akio
2015-08-11
A Monte Carlo linear inverse-kinematics method for the simulation of protein chains with fixed ends is introduced. It includes backbone bond-angle bending and simultaneous loop and ring closure to allow full proline ring flexibility. An obstacle to linear null-space methods is the eventual drift of the end group. Maintenance of the end group at its initial position by occasional reset is performed in a way that is consistent with the overall methodology and minimally disruptive to the current conformation. The implementation permitted multiple rigid regions within the chain, enabling the simulation of domain movements where domains are rigid bodies connected by flexible interdomain regions. The method was tested on polyalanine, polyglycine, loop 6 of triosephosphate isomerase, and glutamine binding protein. Simulations of glutamine binding protein, where only 11 of the 226 residues at the interdomain bending regions were flexible, accurately reproduced the experimentally determined domain movement. PMID:26574470
Over-constrained rigid multibody systems: differential kinematics and fault tolerance
NASA Astrophysics Data System (ADS)
Yi, Yong; McInroy, John E.; Chen, Yixin
2002-07-01
Over-constrained parallel manipulators can be used for fault tolerance. This paper derives the differential kinematics and static force model for a general over-constrained rigid multibody system. The result shows that the redundant constraints result in constrained active joints and redundant internal force. By incorporating these constraints, general methods for overcoming stuck legs or even the complete loss of legs are derived. The Stewart platform special case is studied as an example, and the relationship between its forward Jacobian and its inverse Jacobian is also found.
NASA Astrophysics Data System (ADS)
Zhang, Youbing; Dalguer, Luis A.; Song, Seok Goo; Clinton, John; Giardini, Domenico
2015-01-01
The effect of network density and geometric distribution on kinematic non-linear source inversion is investigated by inverting synthetic ground motions from a buried strike-slip fault (Mw 6.5), that have been generated by dynamic spontaneous rupture modelling. For the inversion, we use a physics-based regularized Yoffe function as slip velocity function. We test three different cases of station network geometry: (i) single station, varying azimuth and epicentral distance; (ii) multistation circular configurations, that is stations at similar distances from the fault, and regularly spaced around the fault; (iii) irregular multistation configurations using different numbers of stations. Our results show: (1) single station tests suggest that it may be possible to obtain a relatively good source model even using a single station. The best source model using a single station is obtained with stations at which amplitude ratios between three components are not large. We infer that both azimuthal angle and source-to-station distance play an important role in the design of optimal seismic network for source inversion. (2) Multistation tests show that the quality of the inverted source systematically correlates neither with the number of stations, nor with waveform misfit. (3) Waveform misfit has a direct correlation with the number of stations, resulting in overfitting the observed data without any systematic improvement of the source. It suggests that the best source model is not necessarily derived from the model with minimum waveform misfit. (4) A seismic network with a small number of well-spaced stations around the fault may be sufficient to obtain acceptable source inversion.
Three-body model for the analysis of quasifree scattering reactions in inverse kinematics
NASA Astrophysics Data System (ADS)
Moro, A. M.
2015-10-01
A new method to calculate cross sections for (p ,p n ) and (p ,2 p ) reactions measured under inverse kinematics conditions is proposed. The method uses the prior form of the scattering transition amplitude and replaces the exact three-body wave function appearing in this expression with an expansion in terms of p -n or p -p states, covering the physically relevant excitation energies and partial waves. A procedure of discretization, similar to that used in continuum-discretized coupled-channels calculations, is applied to make this expansion finite and numerically tractable. The proposed formalism is nonrelativistic, but several relativistic kinematical corrections are applied to extend its applicability to energies of current interest. The underlying optical potentials for the entrance and exit channels are generated microscopically by folding an effective density-dependent G matrix with the density of the composite nucleus. Numerical calculations for 12C(p ,2 p ), 12C(p ,p n ), and 23O(p ,p n ) at 400 MeV/nucleon are presented to illustrate the method. The role of final-state interactions and Pauli principle between the outgoing nucleons is also discussed.
NASA Astrophysics Data System (ADS)
ozeren, M. S.; Klein, E. C.; Kreemer, C.
2013-12-01
Despite the advent of space geodesy, the question of strain rate inversion using geodetic data is still a matter of debate. Traditionally, Global Positioning System (GPS) inversion algorithms aim to obtain a best-fit with GPS velocities, while satisfying the kinematic compatibility conditions. Yet, the strain rates that come out of these inversions are non-unique for a variety of reasons. Perhaps, the most important source of non-uniqueness in the inversion is the way in which the variance-covariance operators are formulated. Even for the isotropic case, there are more than a few ways to approach these formulations (e.g., specifying a priori defined non-uniform distributions rather than single, uniform distributions). Here, we experiment with seismicity-based variance-covariance matrices using a grid system composed of quadrilateral cells. Specifically we imbed the seismicity of the Aegean region directly into the a priori variance-covariance matrices. We normalize the contributions of seismicity within individual cells and from neighboring cells by seismogenic volume. Because recorded seismicity predates emplacement of GPS stations, we use only that portion of the seismic catalog for which we have GPS observations. Unlike Kostrov relation-based inversions that directly link the strain rates to the moment tensor sums, we take the seismicity as a rate-process (assuming that the rates do not change significantly within the time scale we are looking at) and feed this into the variances without any directional information. We do not use the seismicity as a numerical measure of the total seismic deformation; we instead use it as a measure for the capacity of the upper crustal material to deform. This is analogous to simplified effective medium approaches employed in engineering. The earthquakes are spatially non-uniform and likely cause some inelastic deformation in addition to the elastic deformation within the cells used for our numerical calculations. Although these are kinematic inversions rather than dynamic ones, the variance-covariance matrices behave like viscosity tensors that control the deformability of the medium in an isotropic or anisotropic context (Beavan and Haines, 2001). In this work, we utilize more than 100,000 events from the seismic catalog of the European-Mediterranean Seismological Centre (http://www.emsc-csem.org) and more than 1400 GPS observations from the literature. Our experiments that employ seismicity constraints yield better velocity misfits than for cases where the only bias of the inversion came from the inhomogeneity of the cell sizes and a tolerance coefficient for the entire grid system. We present results for the Eastern Mediterranean where the GPS coverage and earthquake detection level threshold is spatially inhomogeneous. We therefore ran various cases with different spatial scales and for different seismogenic volumes and saw that this new approach for the variance formulations helps us to better represent the macro-scale behavior of the system. When we isolate western Turkey where the seismicity is widespread and continental extension occurs on very low-angle detachment faults rather than on a few major normal faults, the fit improves. Overall, the robustness of this new method is insensitive to the application of plate motion boundary conditions for the examples we show.
Recursive inverse kinematics for robot arms via Kalman filtering and Bryson-Frazier smoothing
NASA Technical Reports Server (NTRS)
Rodriguez, G.; Scheid, R. E., Jr.
1987-01-01
This paper applies linear filtering and smoothing theory to solve recursively the inverse kinematics problem for serial multilink manipulators. This problem is to find a set of joint angles that achieve a prescribed tip position and/or orientation. A widely applicable numerical search solution is presented. The approach finds the minimum of a generalized distance between the desired and the actual manipulator tip position and/or orientation. Both a first-order steepest-descent gradient search and a second-order Newton-Raphson search are developed. The optimal relaxation factor required for the steepest descent method is computed recursively using an outward/inward procedure similar to those used typically for recursive inverse dynamics calculations. The second-order search requires evaluation of a gradient and an approximate Hessian. A Gauss-Markov approach is used to approximate the Hessian matrix in terms of products of first-order derivatives. This matrix is inverted recursively using a two-stage process of inward Kalman filtering followed by outward smoothing. This two-stage process is analogous to that recently developed by the author to solve by means of spatial filtering and smoothing the forward dynamics problem for serial manipulators.
NASA Technical Reports Server (NTRS)
Fielding, Eric; Sladen, Anthony; Avouac, Jean-Philippe; Li, Zhenhong; Ryder, Isabelle; Burgmann, Roland
2008-01-01
The presentations explores kinematics of the Wenchaun-Beichuan earthquake using data from ALOS, Envisat, and teleseismic recordings. Topics include geomorphic mapping, ALOS PALSAR range offsets, ALOS PALSAR interferometry, Envisat IM interferometry, Envisat ScanSAR, Joint GPS-InSAR inversion, and joint GPS-teleseismic inversion (static and kinematic).
Algorithmic vs. finite difference Jacobians for infrared atmospheric radiative transfer
NASA Astrophysics Data System (ADS)
Schreier, Franz; Gimeno GarcĂa, SebastiĂˇn; Vasquez, Mayte; Xu, Jian
2015-10-01
Jacobians, i.e. partial derivatives of the radiance and transmission spectrum with respect to the atmospheric state parameters to be retrieved from remote sensing observations, are important for the iterative solution of the nonlinear inverse problem. Finite difference Jacobians are easy to implement, but computationally expensive and possibly of dubious quality; on the other hand, analytical Jacobians are accurate and efficient, but the implementation can be quite demanding. GARLIC, our "Generic Atmospheric Radiation Line-by-line Infrared Code", utilizes algorithmic differentiation (AD) techniques to implement derivatives w.r.t. atmospheric temperature and molecular concentrations. In this paper, we describe our approach for differentiation of the high resolution infrared and microwave spectra and provide an in-depth assessment of finite difference approximations using "exact" AD Jacobians as a reference. The results indicate that the "standard" two-point finite differences with 1 K and 1% perturbation for temperature and volume mixing ratio, respectively, can exhibit substantial errors, and central differences are significantly better. However, these deviations do not transfer into the truncated singular value decomposition solution of a least squares problem. Nevertheless, AD Jacobians are clearly recommended because of the superior speed and accuracy.
Unseren, M.A.
1993-04-01
The report discusses the orientation tracking control problem for a kinematically redundant, autonomous manipulator moving in a three dimensional workspace. The orientation error is derived using the normalized quaternion error method of Ickes, the Luh, Walker, and Paul error method, and a method suggested here utilizing the Rodrigues parameters, all of which are expressed in terms of normalized quaternions. The analytical time derivatives of the orientation errors are determined. The latter, along with the translational velocity error, form a dosed loop kinematic velocity model of the manipulator using normalized quaternion and translational position feedback. An analysis of the singularities associated with expressing the models in a form suitable for solving the inverse kinematics problem is given. Two redundancy resolution algorithms originally developed using an open loop kinematic velocity model of the manipulator are extended to properly take into account the orientation tracking control problem. This report furnishes the necessary mathematical framework required prior to experimental implementation of the orientation tracking control schemes on the seven axis CESARm research manipulator or on the seven-axis Robotics Research K1207i dexterous manipulator, the latter of which is to be delivered to the Oak Ridge National Laboratory in 1993.
NASA Astrophysics Data System (ADS)
Heimann, Sebastian; Sudhaus, Henriette; Wang, Rongjiang; Cesca, Simone; Dahm, Torsten
2014-05-01
The notorious discrepancies among finite fault slip inversion results have attracted much attention over the last years. In consequence, much effort has been put into methods to improve the robustness of such inversions and to quantify uncertainties on results. The techniques exploited include controlling the smoothness of the inferred slip distribution, reducing dimensionality of parameter-space, propagation of observational errors through Bayesian inference, Monte-Carlo modelling and bootstrapping. The difficulties in earthquake finite source parameter estimation arise from three distinct origins: (1) observational errors, (2) the (in)ability of the earthquake source model to represent nature, and (3) mismodelling of synthetic seismograms. While observational errors can often be formally included in the source parameter estimation process, the latter two are much harder to to handle. Appropriateness of the source model (2) is hard to achieve because more realistic models require more model parameters and quickly lead to underdetermined systems. Mismodelling of synthetic seismograms (3) has not been investigated much, probably because the technical effort to deal with it is usually high (because forward modelling may have to be repeated for many earth model variations). In this presentation, we will show that freely available precomputed Green's functions for ensembles of different earth models will make such investigations feasible for routine practice. We will illustrate this with a synthetic test case of a regional kinematic source parameter optimization. The presented work is closely related with the development of a new open source Python toolbox for the handling of precomputed Green's functions and for synthetic seismogram generation (http://emolch.github.io/pyrocko/gf). Ultimately, we would like to launch a community driven open access Green's function sharing platform and web services for synthetic seismogram and test scenario generation (http://kinherd.org/).
Kinematics of back-arc inversion of the Western Black Sea Basin
NASA Astrophysics Data System (ADS)
Munteanu, I.; Matenco, L.; Dinu, C.; Cloetingh, S.
2011-10-01
Back-arc basin evolution is driven by processes active at the main subduction zone typically assuming the transition from an extensional back-arc, during the retreat of a mature slab, to a contractional basin, during high-strain collisional processes. Such a transition is observed in the Black Sea, where the accurate quantification of shortening effects is hampered by the kinematically unclear geometries of Cenozoic inversion. By means of seismic profiles interpretation, quantified deformation features and associated syn-tectonic geometries on the Romanian offshore, this study demonstrates that uplifted areas, observed by exploration studies, form a coherent thick-skinned thrust system with N-ward vergence. Thrusting inverted an existing geometry made up by successive grabens that were inherited from the Cretaceous extensional evolution. The shortening started during late Eocene times and gradually affected all areas of the Western Black Sea Basin during Oligocene and Miocene times, deformation being coherently correlated across its western margin. The mechanism of this generalized inversion is the transmission of stresses during the collision recorded in the Pontides-Balkanides system. Syn-tectonic sedimentation in the Western Black Sea demonstrates that this process was continuous and took place through the onset of gradual shortening migrating northward. Although the total amount of shortening is roughly constant in an E-W direction, individual thrusts have variable offsets, deformation being transferred between structures located at distance across the strike of the system. The Black Sea example demonstrates that the vergence and offset of thrusts can change rapidly along the strike of such a compressional back-arc system. This generates apparently contrasting geometries that accommodate the same orogenic shortening.
Cerebellum-inspired neural network solution of the inverse kinematics problem.
Asadi-Eydivand, Mitra; Ebadzadeh, Mohammad Mehdi; Solati-Hashjin, Mehran; Darlot, Christian; Abu Osman, Noor Azuan
2015-12-01
The demand today for more complex robots that have manipulators with higher degrees of freedom is increasing because of technological advances. Obtaining the precise movement for a desired trajectory or a sequence of arm and positions requires the computation of the inverse kinematic (IK) function, which is a major problem in robotics. The solution of the IK problem leads robots to the precise position and orientation of their end-effector. We developed a bioinspired solution comparable with the cerebellar anatomy and function to solve the said problem. The proposed model is stable under all conditions merely by parameter determination, in contrast to recursive model-based solutions, which remain stable only under certain conditions. We modified the proposed model for the simple two-segmented arm to prove the feasibility of the model under a basic condition. A fuzzy neural network through its learning method was used to compute the parameters of the system. Simulation results show the practical feasibility and efficiency of the proposed model in robotics. The main advantage of the proposed model is its generalizability and potential use in any robot. PMID:26438095
Direct measurement of 38K(p , ?) 39Ca in inverse kinematics
NASA Astrophysics Data System (ADS)
Lotay, Gavin; Christian, Gregory; Burke, Devin; Chen, Alan; Connolly, Devin; Davids, Barry; Fallis, Jenniffer; Hager, Ulrike; Hutcheon, Dave; Mahl, Adam; Rojas, Alex; Ruiz, Chris; Sun, Xuan
2014-09-01
Sensitivity studies have identified 38K(p , ?) 39Ca as one of a handful of significant reactions in ONe novae, with the potential to change 38Ar, 39K, and 40Ca abundances in ONe ejecta by factors of ~18, ~17 and ~24, respectively. We have performed the first ever measurement of this reaction using the DRAGON recoil mass separator at TRIUMF. The experiment was performed in inverse kinematics using a beam of radioactive 38K. To date, this is the most massive projectile ever used in a radiative capture experiment. The astrophysical reaction rate is expected to be dominated by low- l resonances inside the Gamow window. Hence we have focused our efforts on the resonances at Ec.m. = 386, 515, and 689 keV. In this talk, I will present an overview of the experiment and data analysis and show preliminary resonance strengths (or upper limits) measured at each of the three energies. Finally, I will discuss the astrophysical implications of the measurements as they relate to ONe novae.
NASA Technical Reports Server (NTRS)
Williams, Robert L., III
1992-01-01
This paper presents three methods to solve the inverse position kinematics position problem of the double universal joint attached to a manipulator: (1) an analytical solution for two specific cases; (2) an approximate closed form solution based on ignoring the wrist offset; and (3) an iterative method which repeats closed form position and orientation calculations until the solution is achieved. Several manipulators are used to demonstrate the solution methods: cartesian, cylindrical, spherical, and an anthropomorphic articulated arm, based on the Flight Telerobotic Servicer (FTS) arm. A singularity analysis is presented for the double universal joint wrist attached to the above manipulator arms. While the double universal joint wrist standing alone is singularity-free in orientation, the singularity analysis indicates the presence of coupled position/orientation singularities of the spherical and articulated manipulators with the wrist. The cartesian and cylindrical manipulators with the double universal joint wrist were found to be singularity-free. The methods of this paper can be implemented in a real-time controller for manipulators with the double universal joint wrist. Such mechanically dextrous systems could be used in telerobotic and industrial applications, but further work is required to avoid the singularities.
Measurement of the ^134Te(d,p)^135Te Reaction in Inverse Kinematics
NASA Astrophysics Data System (ADS)
Pain, Steven
2007-10-01
The development of high quality radioactive beams, such as those at the HRIBF at ORNL, has made possible the performance of transfer reactions on unstable nuclei. Measurements of (d,p) reactions on n-rich fission fragments yield data on nuclear structure away from stability, and are of astrophysical interest due to the proximity to suggested r- process paths. The energies and spectroscopic information of single-particle states near to shell closures are of particular importance, since they provide both an important constraint on nuclear structure models and are directly relevant to direct neutron-capture cross sections. The single-neutron states in ^ 135Te, one neutron beyond the N=82 shell closure, are of particular interest, both for r-process nucleosynthesis and its relevance to an isotopic anomaly of Xe found in pre-solar meteoritic grains. The ^134Te(d,p)^135Te reaction has been measured in inverse kinematics at the HRIBF utilizing a beam of ^134Te at 643 MeV and a deuterated plastic target. Proton ejectiles were detected forward and backwards of ?lab = 90^o using an early implementation of the Oak Ridge Rutgers University Barrel Array (ORRUBA) in conjunction with SIDAR. Details of the experiment and the current stage of the data analysis will be presented.
NASA Astrophysics Data System (ADS)
von Schmid, M.; Bagchi, S.; Bönig, S.; Csatlós, M.; Dillmann, I.; Dimopoulou, C.; Egelhof, P.; Eremin, V.; Furuno, T.; Geissel, H.; Gernhäuser, R.; Harakeh, M. N.; Hartig, A.-L.; Ilieva, S.; Kalantar-Nayestanaki, N.; Kiselev, O.; Kollmus, H.; Kozhuharov, C.; Krasznahorkay, A.; Kröll, T.; Kuilman, M.; Litvinov, S.; Litvinov, Yu A.; Mahjour-Shafiei, M.; Mutterer, M.; Nagae, D.; Najafi, M. A.; Nociforo, C.; Nolden, F.; Popp, U.; Rigollet, C.; Roy, S.; Scheidenberger, C.; Steck, M.; Streicher, B.; Stuhl, L.; Thürauf, M.; Uesaka, T.; Weick, H.; Winfield, J. S.; Winters, D.; Woods, P. J.; Yamaguchi, T.; Yue, K.; Zamora, J. C.; Zenihiro, J.; for the EXL collaboration
2015-11-01
We have measured the nuclear-matter distribution of the doubly-magic N = Z nucleus 56Ni by investigating elastic proton scattering in inverse kinematics. The radioactive beam of 56Ni was injected and stored in the experimental storage ring (ESR, GSI) and interacted with an internal hydrogen gas-jet target. The high revolution frequency of the ions in the ring enabled a high luminosity, despite the low density of the target being used. This way, measurements at very low momentum transfers became possible. By measuring the energy and the scattering angle of the recoiling protons, we were able to separate the elastic reaction channel from inelastic scattering to the first excited {2}+ state of 56Ni and deduced the differential cross section of 56Ni {(p,p)}56 Ni. The data were analyzed within the framework of the Glauber multiple-scattering theory in order to extract the nuclear-matter radius and radial matter distribution of 56Ni. Parameterizing the matter distribution with the phenomenological Symmetrized Fermi distribution, a preliminary value of 3.5 fm for the rms matter radius was deduced. This experiment was part of an EXL (EXotic nuclei studied in Light-ion induced reactions at storage rings) campaign at GSI in 2012 and was the first successful investigation of nuclear reactions with a stored radioactive beam ever.
NASA Astrophysics Data System (ADS)
Bagchi, S.; Gibelin, J.; Harakeh, M. N.; Kalantar-Nayestanaki, N.; Achouri, N. L.; Akimune, H.; Bastin, B.; Boretzky, K.; Bouzomita, H.; Caamańo, M.; Cŕceres, L.; Damoy, S.; Delaunay, F.; Fernández-Domínguez, B.; Fujiwara, M.; Garg, U.; Grinyer, G. F.; Kamalou, O.; Khan, E.; Krasznahorkay, A.; Lhoutellier, G.; Libin, J. F.; Lukyanov, S.; Mazurek, K.; Najafi, M. A.; Pancin, J.; Penionzhkevich, Y.; Perrot, L.; Raabe, R.; Rigollet, C.; Roger, T.; Sambi, S.; Savajols, H.; Senoville, M.; Stodel, C.; Suen, L.; Thomas, J. C.; Vandebrouck, M.; Van de Walle, J.
2015-12-01
The Isoscalar Giant Monopole Resonance (ISGMR) and the Isoscalar Giant Dipole Resonance (ISGDR) compression modes have been studied in the doubly-magic unstable nucleus 56Ni. They were measured by inelastic ?-particle scattering in inverse kinematics at 50 MeV/u with the MAYA active target at the GANIL facility. The centroid of the ISGMR has been obtained at Ex = 19.1 ± 0.5 MeV. Evidence for the low-lying part of the ISGDR has been found at Ex = 17.4 ± 0.7 MeV. The strength distribution for the dipole mode shows similarity with the prediction from the Hartree-Fock (HF) based random-phase approximation (RPA) [1]. These measurements confirm inelastic ?-particle scattering as a suitable probe for exciting the ISGMR and the ISGDR modes in radioactive isotopes in inverse kinematics.
NASA Astrophysics Data System (ADS)
Hossen, M. Jakir; Cummins, Phil R.; Dettmer, Jan; Baba, Toshitaka
2015-09-01
This paper considers the importance of model parameterization, including dispersion, source kinematics, and source discretization, in tsunami source inversion. We implement single and multiple time window methods for dispersive and nondispersive wave propagation to estimate source models for the tsunami generated by the 2011 Tohoku-Oki earthquake. Our source model is described by sea surface displacement instead of fault slip, since sea surface displacement accounts for various tsunami generation mechanisms in addition to fault slip. The results show that tsunami source models can strongly depend on such model choices, particularly when high-quality, open-ocean tsunami waveform data are available. We carry out several synthetic inversion tests to validate the method and assess the impact of parameterization including dispersion and variable rupture velocity in data predictions on the inversion results. Although each of these effects has been considered separately in previous studies, we show that it is important to consider them together in order to obtain more meaningful inversion results. Our results suggest that the discretization of the source, the use of dispersive waves, and accounting for source kinematics are all important factors in tsunami source inversion of large events such as the Tohoku-Oki earthquake, particularly when an extensive set of high-quality tsunami waveform recordings are available. For the Tohoku event, a dispersive model with variable rupture velocity results in a profound improvement in waveform fits that justify the higher source complexity and provide a more realistic source model.
Pain, S. D.; Cizewski, J. A.; Hatarik, Robert; Jones, K. L.; Thomas, J. S.; Bardayan, Daniel W; Blackmon, Jeff C; Nesaraja, Caroline D; Smith, Michael Scott; Kozub, R. L.; Johnson, Micah
2007-01-01
The development of high quality radioactive beams, such as those at the HRIBF at Oak Ridge National Laboratory, has made possible the measurement of transfer reactions in inverse kinematics on unstable nuclei. Measurement of (d,p) reactions on neutron-rich nuclei yield data on the evolution of nuclear structure away from stability, and are of astrophysical interest due to the proximity of suggested nuclear burning paths in the astrophysical r-process in supernovae. Experimentally, (d,p) reactions on heavy (Z = 50) fission fragments are complicated by the strongly inverse kinematics, and the relatively low beam intensities. Consequently, ejectile detection with high resolution in position and energy, a high dynamic range and a high solid angular coverage is required. The Oak Ridge Rutgers University Barrel Array (ORRUBA) is a new silicon detector array currently under construction, optimized for the measurement of (d,p) reactions in inverse kinematics. It consists of two rings of silicon detectors, providing a high solid angular coverage for angles symmetrically forward and backward of 90 degrees. Resistive strip detectors are used to obtain high precision position and energy measurement of reaction ejectiles.
Astrophysical(?,?) reaction in inverse kinematics; Electron screening effect in the beta-decay
NASA Astrophysics Data System (ADS)
Uji?, P.; de Oliveira, F.; Lagoyannis, A.; Mertzimekis, T. J.; Harissopulos, S.; Demetriou, P.; Spyrou, A.; Stodel, C.; Saint-Laurent, M. G.; Kamalou, O.; Lefebvre-Schuhl, A.; Grevy, S.; Caceres, L.; Lewitowicz, M.; Amthor, M. A.; Perot, L.; Coc, A.; Tatischeff, V.; Kiener, J.; Sorlin, O.; Lepailleur, A.; Assié, M.; Bastin, B.; Achouri, L.; Borcea, R.; Borcea, C.; Stanoiu, M.; de France, G.; Clement, E.; Pautrat, A.; Buta, A.; Gaudefroy, L.; Meot, V.; Deloncle, I.
2012-02-01
The abundance calculations of the p-nuclei produced in explosive stellar sites rely on the Hauser-Feshbach (HF) theory with the alpha-article optical model potential (?-OMP) one of its major ingredients. To date, most of the (?, ?) cross sections measured show that HF calculations can be wrong by a factor of ten or more especially when phenomenological ?-OMP are employed. To investigate the relevant uncertainties entering the HF calculations and furthermore develop global microscopic ?-OMPs, systematic (?, ?) cross-section measurements are necessary. This led us to perform a feasibility study of (?, ?) measurements in inverse kinematics that will allow us to employ also radioactive beams in the future. Hence, the 4He(78Kr,?)82Sr reaction was studied using the LISE3 spectrometer to separate the 82Sr recoils from the primary 78Kr beam. Although an excellent rejection factor > 1010 was achieved, the position of the ions of interest was unexpectedly masked by a secondary beam of high intensity. Given these, new setup improvements are proposed to remove the pollutant ions. Recently, many experiments were conducted in order to study the influence of the environment (especially in a metallic material) on the decay probability of radioactive nuclei. Additionally, hydrogen-like fusion reactions were performed indicating a change in the cross-section due to the influence of the Coulomb field screening induced by quasi-free electrons in metals. This was explained by the Debye screening model which treats metallic electrons within Maxwell-Boltzmann statistics. We measured the decay rate of 19O in metallic, insulating and superconducting environments whereas the electrons in the superconductors should obey the Bose-Einstein statistics. The decay rate measurement was supported by a branching ratios measurement. We found that the effect on the decay rate, if any, is less than the 0.1%, far below the theoretical predictions.
Spectroscopy of beryllium-12 using the (lithium-7, beryllium-7) reaction in inverse kinematics
NASA Astrophysics Data System (ADS)
Meharchand, Rhiannon
The quenching of the N = 8 shell gap has been under investigation for more than 40 years, yet there remains significant controversy over the extent of mixing between 0ho and 2ho configurations in 12Be. Recent neutron knockout and transfer measurements have helped quantify 2ho contributions to the ground and excited 0+ states. The current study measures the 0ho component of the 0+ wavefunctions for the first time. The Gamow-Teller strength (B(GT)) of transitions from the ground state of 12B to the 0+ states in 12Be has been measured using the (7Li, 7Be) charge-exchange reaction in inverse kinematics. Since the ground state of 12B is dominated by 0ho configurations, Gamow-Teller (DeltaL=0, DeltaS=1) transitions to 0+ states in 12Be selectively probe the 0ho component of the wavefunction. The extracted B(GT) to the 0+ states in 12Be were compared with shell model calculations, performed using the code OXBASH and employing a modified WBP interaction in the spsdpf model space. To reproduce the observed B(GT) distribution, a 0hDelta admixture of 25.48+/-5.49% is required in the ground state of 12Be, and a 0hDelta admixture of 59.83+/-4.78% is required in the the 2.24 MeV 0+ state. These results are compared with the wavefunctions extracted from neutron knockout and transfer measurements, and the theoretical predictions of Fortune and Sherr, Barker, and Romero-Redondo et al.
Estimating periodic organ motions based on inverse kinematics using tetrahedron mesh registration
NASA Astrophysics Data System (ADS)
Kang, Nahyup; Kim, Ji-Yeon; Kim, Kyung Hwan; Lee, Hyong-Euk; Kim, James D. K.
2013-03-01
Minimally/Non-invasive surgery has become increasingly widespread because of its therapeutic benefits such as less pain, less scarring, and shorter hospital stay. However, it is very difficult to eliminate the target cancer cells selectively without damaging nearby normal tissues and vessels since the tumors inside organs cannot be visually tracked in realtime with the existing imaging devices while organs are deformed by respiration and surgical instruments. Note that realtime 2D US imaging is widely used for monitoring the minimally invasive surgery such as Radiofrequency ablation; however, it is difficult to detect target tumors except high-echogenic regions because of its noisy and limited field of view. To handle these difficulties, we present a novel framework for estimating organ motion and deformed shape during respiration from the available features of 2D US images, by means of inverse kinematics utilizing 3D CT volumes at the inhale and exhale phases. First, we generate surface meshes of the target organ and tumor as well as centerlines of vessels at the two extreme phases considering surface correspondence. Then, the corresponding tetrahedron meshes are generated by coupling the internal components for volumetric modeling. Finally, a deformed organ mesh at an arbitrary phase is generated from the 2D US feature points for estimating the organ deformation and tumor position. To show effectiveness of the proposed method, the CT scans from real patient has been tested for estimating the motion and deformation of the liver. The experimental result shows that the average errors are less than 3mm in terms of tumor position as well as the whole surface shape.
NASA Astrophysics Data System (ADS)
Rollins, Christopher; Barbot, Sylvain; Avouac, Jean-Philippe
2015-05-01
Due to its location on a transtensional section of the Pacific-North American plate boundary, the Salton Trough is a region featuring large strike-slip earthquakes within a regime of shallow asthenosphere, high heat flow, and complex faulting, and so postseismic deformation there may feature enhanced viscoelastic relaxation and afterslip that is particularly detectable at the surface. The 2010 El Mayor-Cucapah earthquake was the largest shock in the Salton Trough since 1892 and occurred close to the US-Mexico border, and so the postseismic deformation recorded by the continuous GPS network of southern California provides an opportunity to study the rheology of this region. Three-year postseismic transients extracted from GPS displacement time-series show four key features: (1) 1-2 cm of cumulative uplift in the Imperial Valley and 1 cm of subsidence in the Peninsular Ranges, (2) relatively large cumulative horizontal displacements 150 km from the rupture in the Peninsular Ranges, (3) rapidly decaying horizontal displacement rates in the first few months after the earthquake in the Imperial Valley, and (4) sustained horizontal velocities, following the rapid early motions, that were still visibly ongoing 3 years after the earthquake. Kinematic inversions show that the cumulative 3-year postseismic displacement field can be well fit by afterslip on and below the coseismic rupture, though these solutions require afterslip with a total moment equivalent to at least a earthquake and higher slip magnitudes than those predicted by coseismic stress changes. Forward modeling shows that stress-driven afterslip and viscoelastic relaxation in various configurations within the lithosphere can reproduce the early and later horizontal velocities in the Imperial Valley, while Newtonian viscoelastic relaxation in the asthenosphere can reproduce the uplift in the Imperial Valley and the subsidence and large westward displacements in the Peninsular Ranges. We present two forward models of dynamically coupled deformation mechanisms that fit the postseismic transient well: a model combining afterslip in the lower crust, Newtonian viscoelastic relaxation in a localized zone in the lower crust beneath areas of high heat flow and geothermal activity, and Newtonian viscoelastic relaxation in the asthenosphere; and a second model that replaces the afterslip in the first model with viscoelastic relaxation with a stress-dependent viscosity in the mantle. The rheology of this high-heat-flow, high-strain-rate region may incorporate elements of both these models and may well be more complex than either of them.
NASA Astrophysics Data System (ADS)
Kneller, Erik A.; Johnson, Christopher A.; Karner, Garry D.; Einhorn, Jesse; Queffelec, Thomas A.
2012-12-01
Published plate reconstructions commonly show significant differences in initial plate configuration and syn-extensional opening directions. The variability of published models is primarily due to the difficulty associated with restoring crustal stretching history. Here we present an inverse non-rigid kinematic method that inverts plate motion and present day crustal thickness to approximate the history of bulk lateral strain and crustal thinning associated with lithospheric stretching. The kinematic link between plate motion and bulk crustal thickness that is used with this method is based on insights obtained from geodynamic models. We implement this approach in open source kinematic modeling software and apply it to test new Early Mesozoic plate kinematic models of the Central Atlantic. This application shows that the patterns of stretching inferred from the syn-rift basins of the Newark Supergroup can be explained if (1) syn-rift Euler pole flow lines were parallel to the Grand Banks transform margin and (2) initial formation of the East Coast Margin Igneous Province was coincident with the formation of the Central Atlantic Magmatic Province. These syn-rift to breakup models of the Central Atlantic lead to better constrained models of early seafloor spreading that show full spreading velocities in the ultraslow regime and within the transition from ultraslow to slow spreading regimes.
Development of a kinematically focused neutron source with the p(7Li,n)7Be inverse reaction
NASA Astrophysics Data System (ADS)
Lebois, M.; Wilson, J. N.; HaliprĂ©, P.; Leniau, B.; Matea, I.; Oberstedt, A.; Oberstedt, S.; Verney, D.
2014-01-01
Directional beams of neutrons can be produced, if a nuclear reaction, which emits neutrons, is initiated in inverse kinematics with a heavy ion projectile bombarding a light target. In this paper we investigate the use of the p(7Li,n)7Be inverse reaction to produce kinematically focused, quasi-mono-energetic neutron beams with a view to develop such an unusual neutron source for fundamental and applied nuclear physics studies. An experiment was carried out to validate the concept and to test the viability of two types of hydrogen-rich solid targets: polypropylene and TiH2. Neutron time-of-flight/energy spectra at 3 m distance from the source have been measured at 7Li bombarding energies of 13.5, 15, 15.5, 16, and 17 MeV, and neutron backgrounds from parasitic reactions have been characterized. The neutron angular distribution in the laboratory has been measured at 15 MeV. A Monte-Carlo code based on two-body relativistic kinematics has been developed and validated by comparison with the experimental data. Code-based extrapolations have then been used to deduce neutron energy spectra and maximum neutron fluxes available for future irradiation of samples placed in the neutron beam at small distances. For neutrons produced with thin (4 ÎĽm) and thick (28 ÎĽm) polypropylene targets the maximum available fluxes are calculated to be 107n/s/sr and 7Ă—107 n/s/sr respectively. The development of a dedicated facility to produce kinematically focused neutrons is discussed.
Study of the {sup 56}Ni({sup 3}He,d){sup 57}Cu reaction in inverse kinematics.
Jiang, C. L.; Rehm, K. E.; Ackermann, D.; Ahmad, I.; Greene, J. P.; Harss, B.; Henderson, D.; Henning, W. F.; Janssens, R. V. F.; Nolen, J.; Pardo, R. C.; Reiter, P.; Schiffer, J. P.; Seweryniak, D.; Sonzogni, A.; Uusitalo, J.; Wiedenhoever, I.; Wuosmaa, A. H.; Brumwell, F.; McMichael, G.; Paul, M.; Segel, R. E.; Hebrew Univ.; Northwestern Univ.
2009-01-01
Measurements of (3He,d) reactions can provide information on the proton widths of states that play a role in astrophysically important (p,?) reactions. We report on the first study of the (3He,d) reaction in inverse kinematics with a 56Ni (T1/2=6.1 d) ion beam. The Q-value resolution of keV achieved in this experiment was sufficient to separate the transitions populating the ground state and the 1/2--5/2- doublet at Ex 1.1 MeV in 57Cu. Prospects for similar (3He,d) experiments with improved energy resolution are also discussed.
Geometry and kinematics of Late Cretaceous inversion structures in the Jiuquan Basin, western China
Wang, B.; Chen, H.; Yang, S.; Xiao, A.; Cheng, X.; Rupp, J.A.
2005-01-01
Late Cretaceous inversion structures, which are significant for oil and gas accumulation, are widely distributed throughout the Jiuquan Basin. These structures are primarily made up of inverted faults and fault-related folds. Most of the axial planes of folds are parallel to inverted faults trending north-east, indicating that the principal stress direction was north-west - south-east in the Late Cretaceous. The average inversion ratios of faults in the four sags that were investigated are 0.39, 0.29, 0.38, 0.32. The average inversion ratio in the Jiuquan Basin is 0.34 and the degree of inversion is moderate to strong. As moderate inversion is suitable for forming excellent hydrocarbon traps, there is considered to be significant potential in the basin for the presence of structural traps. ?? 2005 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Barki, Anum; Kendricks, Kimberly; Tuttle, Ronald F.; Bunker, David J.; Borel, Christoph C.
2013-05-01
This research highlights the results obtained from applying the method of inverse kinematics, using Groebner basis theory, to the human gait cycle to extract and identify lower extremity gait signatures. The increased threat from suicide bombers and the force protection issues of today have motivated a team at Air Force Institute of Technology (AFIT) to research pattern recognition in the human gait cycle. The purpose of this research is to identify gait signatures of human subjects and distinguish between subjects carrying a load to those subjects without a load. These signatures were investigated via a model of the lower extremities based on motion capture observations, in particular, foot placement and the joint angles for subjects affected by carrying extra load on the body. The human gait cycle was captured and analyzed using a developed toolkit consisting of an inverse kinematic motion model of the lower extremity and a graphical user interface. Hip, knee, and ankle angles were analyzed to identify gait angle variance and range of motion. Female subjects exhibited the most knee angle variance and produced a proportional correlation between knee flexion and load carriage.
Gibbs vector kinematics and inverse dynamics for decoupled spacecraft attitude maneuvers
NASA Technical Reports Server (NTRS)
Dwyer, T. A. W., III
1986-01-01
By use of Gibbs vectors as kinematic variables, multi-axial spacecraft equations of rotational motion are shown to be globally and rationally feedback-equivalent to a set of unconstrained and decoupled harmonic oscillators, driven by generalized acceleration commands. Advantages over alternative formulations with Euler angles and quaternions are pointed out.
NASA Astrophysics Data System (ADS)
Wang, Lejing; Zou, Rui; Weidert, Simon; Landes, Juergen; Euler, Ekkehard; Burschka, Darius; Navab, Nassir
2011-03-01
For trauma and orthopedic surgery, maneuvering a mobile C-arm X-ray device into a desired position in order to acquire the right picture is a routine task. The precision and ease of use of the C-arm positioning becomes even more important for more advanced imaging techniques as parallax-free X-ray image stitching, for example. Standard mobile C-arms have only five degrees of freedom (DOF), which definitely restricts their motions that have six DOF in 3D Cartesian space. We have proposed a method to model the kinematics of the mobile Carm and operating table as an integrated 6DOF C-arm X-ray imaging system.1 This enables mobile C-arms to be positioned relative to the patient's table with six DOF in 3D Cartesian space. Moving mobile C-arms to a desired position and orientation requires finding the necessary joint values, which is an inverse kinematics problem. In this paper, we present closed-form solutions, i.e. analytic expressions, obtained in an algebraic way for the inverse kinematics problem of the 6DOF C-arm model. In addition, we implement a 6DOF C-arm system for interactively radiation-free C-arm positioning based on a continuous guidance from C-arm pose estimation. For this we employ a visual marker pattern attached under the operating table and a mobile C-arm system augmented by a video camera and mirror construction. In our experiment, repositioning C-arm to a pre-defined pose in a phantom study demonstrates the practicality and accuracy of our developed 6DOF C-arm system.
NASA Astrophysics Data System (ADS)
LarrasoaĂ±A, Juan Cruz; ParĂ©S, Josep MarĂA.; MillĂˇN, HĂ©Ctor; Del Valle, JoaquĂN.; Pueyo, Emilio Luis
2003-12-01
The Pamplona Fault in the Pyrenees is a major transverse structure that has been classically interpreted as a strike-slip fault. However, lack of consensus concerning the sense of movement casts doubt on its actual kinematics and, as a consequence, its role in the Cenozoic evolution of the Pyrenees remains controversial. In order to assess its kinematics, we have conducted a paleomagnetic, structural, and stratigraphic study focused on the Mesozoic and Tertiary sedimentary rocks that outcrop around the southern segment of the fault. Restoration of balanced cross sections allows us to examine the present-day spatial relationship of the sedimentary sequences on both sides of the fault and to reconstruct the geometry of the extensional basins formed during Mesozoic rifting episodes in the Bay of Biscay and Pyrenean domains. Paleomagnetic results indicate that no significant tectonic rotations occurred around the fault during Tertiary inversion of the Pyrenees. The lack of tectonic rotations and revaluation of previous hypotheses argues against a strike-slip movement of the fault. We propose a new model in which the Pamplona Fault is treated as a large-scale "hanging wall drop" fault whose kinematics was determined by variations in the geometry and thickness of Mesozoic sequences on both sides of the fault. These variations influenced the geometry of the thrust sheet developed during Tertiary compression. We are unaware of any other transverse fault that has been interpreted in this fashion; thus the Pamplona Fault serves as a case study for the evolution of transverse faults involved in basin inversion processes.
NASA Astrophysics Data System (ADS)
Gallovic, Frantisek; Cirella, Antonella; Plicka, Vladimir; Piatanesi, Alessio
2013-04-01
On 14 June 2008, UTC 23:43, the border of Iwate and Miyagi prefectures was hit by an Mw7 reverse-fault type crustal earthquake. The event is known to have the largest ground acceleration observed to date (~4g), which was recorded at station IWTH25. We analyze observed strong motion data with the objective to image the event rupture process and the associated uncertainties. Two different slip inversion approaches are used, the difference between the two methods being only in the parameterization of the source model. To minimize mismodeling of the propagation effects we use crustal model obtained by full waveform inversion of aftershock records in the frequency range between 0.05-0.3 Hz. In the first method, based on linear formulation, the parameters are represented by samples of slip velocity functions along the (finely discretized) fault in a time window spanning the whole rupture duration. Such a source description is very general with no prior constraint on the nucleation point, rupture velocity, shape of the velocity function. Thus the inversion could resolve very general (unexpected) features of the rupture evolution, such as multiple rupturing, rupture-propagation reversals, etc. On the other hand, due to the relatively large number of model parameters, the inversion result is highly non-unique, with possibility of obtaining a biased solution. The second method is a non-linear global inversion technique, where each point on the fault can slip only once, following a prescribed functional form of the source time function. We invert simultaneously for peak slip velocity, slip angle, rise time and rupture time by allowing a given range of variability for each kinematic model parameter. For this reason, unlike to the linear inversion approach, the rupture process needs a smaller number of parameters to be retrieved, and is more constrained with a proper control on the allowed range of parameter values. In order to test the resolution and reliability of the retrieved models, we present a thorough analysis of the performance of the two inversion approaches. In fact, depending on the inversion strategy and the intrinsic 'non-uniqueness' of the inverse problem, the final slip maps and distribution of rupture onset times are generally different, sometimes even incompatible with each other. Great emphasis is devoted to the uncertainty estimate of both techniques. Thus we do not compare only the best fitting models, but their 'compatibility' in terms of the uncertainty limits.
A new approach to solve inverse kinematics of a planar flexible continuum robot
NASA Astrophysics Data System (ADS)
Amouri, Ammar; Mahfoudi, Chawki; Zaatri, Abdelouahab; Merabti, Halim
2014-10-01
Research on the modeling of continuum robots, focused on ways to constrain the geometrical models, while maintaining maximum specificities and mechanical properties of the robot. In this paper we propose a new numerical solution for solving the inverse geometric model of a planar flexible continuum robot, we assuming that each section is curved in an arc of a circle, while having the central axis of the inextensible structure. The inverse geometric model for one section is calculated geometrically, whereas the extreme points, of each section, used in calculating the inverse geometric model for multi-section is calculated numerically using a particle swarm optimization (PSO) method. Simulation examples of this method are carried to validate the proposed approach.
Kinematic Point Source Moment Tensor Inversion Using a Hierarchical Bayesian Approach
NASA Astrophysics Data System (ADS)
MustaÄ‡, Marija; TkalÄŤiÄ‡, Hrvoje
2014-05-01
The seismic moment tensor (MT) reveals details about source processes within the Earth that cause earthquakes. Although uncertainties in MT inversions are important for estimating solution robustness, they are rarely available. When earthquake location is simultaneously recovered with the MT, uncertainties in structural Green's functions also need to be included in the method. The problem becomes nonlinear and uncertainties in the source mechanism cannot be calculated in a simple manner. We have developed a method and software for a hierarchical Bayesian MT inversion to study moderate earthquakes and explosions generating waveform data at regional distances. The Bayesian inversion gives a posterior probability distribution of model parameters, based on prior knowledge about the MT and the model likelihood, determined by the data. MT uncertainties can then be estimated from the posterior probability distribution. The hierarchical Bayes approach enables us to recover the nature of the data noise and the weight of each waveform, treating them as unknowns in the inversion. Critically, data noise covariance matrix is implemented to account for measurement and theory errors. This knowledge, in turn, enables us to recover the solution within a reasonable range of uncertainty; in other words, it prevents us from "fitting the noise" that can lead to erroneous solutions and interpretation. Synthetic experiments were performed to test the codes, particularly the retrieval of non double-couple components of the MT. A suite of synthetic and observed focal mechanisms was used to create the synthetic data. Additionally, we add noise to synthetic data (as a fraction of data rms) to test its effect on the inversion. Experiments are performed using uncorrelated Gaussian white noise, as well as using correlated noise. Parameter space for the event mechanism is sampled exhaustively, while the code rapidly converges towards the input hypocenter location. Both the input mechanism and noise level were retrieved in the inversion. The codes are currently being applied on real data to test earthquakes in a variety of tectonic settings.
Kinematic earthquake source inversion and tsunami runup prediction with regional geophysical data
NASA Astrophysics Data System (ADS)
Melgar, D.; Bock, Y.
2015-05-01
Rapid near-source earthquake source modeling relying only on strong motion data is limited by instrumental offsets and magnitude saturation, adversely affecting subsequent tsunami prediction. Seismogeodetic displacement and velocity waveforms estimated from an optimal combination of high-rate GPS and strong motion data overcome these limitations. Supplementing land-based data with offshore wave measurements by seafloor pressure sensors and GPS-equipped buoys can further improve the image of the earthquake source and prediction of tsunami extent, inundation, and runup. We present a kinematic source model obtained from a retrospective real-time analysis of a heterogeneous data set for the 2011 Mw9.0 Tohoku-Oki, Japan, earthquake. Our model is consistent with conceptual models of subduction zones, exhibiting depth dependent behavior that is quantified through frequency domain analysis of slip rate functions. The stress drop distribution is found to be significantly more correlated with aftershock locations and mechanism types when off-shore data are included. The kinematic model parameters are then used as initial conditions in a fully nonlinear tsunami propagation analysis. Notably, we include the horizontal advection of steeply sloping bathymetric features. Comparison with post-event on-land survey measurements demonstrates that the tsunami's inundation and runup are predicted with considerable accuracy, only limited in scale by the resolution of available topography and bathymetry. We conclude that it is possible to produce credible and rapid, kinematic source models and tsunami predictions within minutes of earthquake onset time for near-source coastal regions most susceptible to loss of life and damage to critical infrastructure, regardless of earthquake magnitude.
NASA Astrophysics Data System (ADS)
Lucca, Ernestina; Festa, Gaetano; Emolo, Antonio
2010-05-01
We present a non linear technique to invert strong motion records with the aim of obtaining the final slip and the rupture velocity distributions on the fault plane. Kinematic inversion of strong motion data is an ill-conditioned inverse problem, with several solutions available also in the case of noise-free synthetic data (Blind test on earthquake source inversion,http://www.seismo.ethz.ch/staff/martin/BlindTest.html).On the other hand, complete dynamic inversion still looks impracticable, because of an unclear understanding of the physical mechanisms controlling the energy balance at the rupture tip and a strong correlation between the initial stress field and the parameters of the constitutive law. Hence a strong effort is demanded to increase the robustness of the inversion, looking at the details of the slip and rupture velocity parameterization, at the global exploration techniques, at the efficiency of the cost-function in selecting solutions, at the synthesis process in retrieving the stable features of the rupture. In this study, the forward problem, i.e. the ground motion simulation, is solved evaluating the representation integral in the frequency domain by allowing possible rake variation along the fault plane. The Green's tractions on the fault are computed using the discrete wave-number integration technique that provides the full wave-field in a 1D layered propagation medium. The representation integral is computed through a finite elements technique on a Delaunay triangulation of the fault plane. The rupture velocity is finally defined on a coarser regular grid and rupture times are computed by integration of the eikonal equation. For the inversion, the slip distribution is parameterized by 2D overlapping Gaussian functions, which can easily relate the spectrum of the possible solutions with the minimum resolvable wavelength, related to source-station distribution and data processing. The inverse problem is solved by a two-step procedure aimed at separating the computation of the rupture velocity from the evaluation of the slip distribution, the latter being a linear problem, when the rupture velocity is fixed. The non-linear step is solved by optimization of an L2 misfit function between synthetic and real seismograms, and solution is searched by the use of the Neighbourhood Algorithm. The conjugate gradient method is used to solve the linear step instead. The developed methodology has been applied to the M7.2, Iwate Nairiku Miyagi, Japan, earthquake that was recorded by the K-net and Kik-net accelerometric networks.
NASA Astrophysics Data System (ADS)
Sarantites, D. G.; Reviol, W.; Elson, J. M.; Kinnison, J. E.; Izzo, C. J.; Manfredi, J.; Liu, J.; Jung, H. S.; Goerres, J.
2015-08-01
A high-efficiency, forward-hemisphere detector system for light charged particles and low-Z heavy ions, as obtained in an accelerator experiment, is described. It consists of four 8×8 pixel multianode photomultiplier tubes with 2.2-mm thick CsI(Tl) and 12 -?m thick fast-plastic scintillation detectors. Its phoswich structure allows individual Z resolution for 1H, 4He, 7Li, 4He+4He, 9Be, 11B, 12C, and 14N ions, which are target-like fragments detected in strongly inverse kinematics. The device design has been optimized for use with a 4? ?-ray array, and the main applications are transfer reactions and Coulomb excitation. A high-angular resolution for the detection of the target-like fragments is achieved which permits angular distributions to be measured in the rest frame of the projectile-like fragment with a resolution of ~ 2 °.
Experimental study of the {sup 56}Ni({sup 3}He,d){sup 57}Cu reaction in inverse kinematics
Jiang, C. L.; Rehm, K. E.; Ackermann, D.; Ahmad, I.; Greene, J. P.; Harss, B.; Henderson, D.; Henning, W. F.; Janssens, R. V. F.; Nolen, J.; Pardo, R. C.; Reiter, P.; Schiffer, J. P.; Seweryniak, D.; Sonzogni, A.; Uusitalo, J.; Wiedenhoever, I.; Wuosmaa, A. H.; Brumwell, F.; McMichael, G.
2009-10-15
Measurements of ({sup 3}He,d) reactions can provide information on the proton widths of states that play a role in astrophysically important (p,{gamma}) reactions. We report on the first study of the ({sup 3}He,d) reaction in inverse kinematics with a {sup 56}Ni (T{sub 1/2}=6.1 d) ion beam. The Q-value resolution of {approx} keV achieved in this experiment was sufficient to separate the transitions populating the ground state and the 1/2{sup -}-5/2{sup -} doublet at E{sub x}{approx}1.1 MeV in {sup 57}Cu. Prospects for similar ({sup 3}He,d) experiments with improved energy resolution are also discussed.
NASA Astrophysics Data System (ADS)
Sanetullaev, Alisher
Transfer reactions have been the classic tool for studying the angular distributions, the excitation energies, and the spectroscopic factors of possible single-particles states. With the advent of radioactive beams, there has been a renewed effort to utilize these beams in transfer reactions in inverse kinematics. The exact shell structure of the unstable doubly magic nucleus 56Ni has attracted a lot of interest recently. To test if 56Ni has a closed f7/2 orbital, we have carried out the 56Ni(p,d)55Ni transfer reaction measurement with the radioactive 56Ni beam in inverse kinematics for the first time at the NSCL using the HiRA array and S800 spectrograph. The spectroscopic factor predicted by the independent particle model is 8, shell-model calculations give value of 6.8. We have extracted spectroscopic factors of the 56Ni(p,d)55Ni reaction, for the ground and two excited states of 55Ni. The neutron SF value of 7 for the 56Ni(p,d)55Ni ground state agrees with shell-model calculations supports the view that 56Ni is a closed shell nucleus. This result supports the use of 56Ni as a core in shell-model calculations. Another important goal was to study the structure of 55Ni by determining the spin and parities of excited states. We have assigned an â„“ value of 1 to first excited state of 55Ni for 2.089 MeV state of 55Ni. We have extracted a spectroscopic factor of 0.14 for this state. This serves as a second test of the shell model, and the results agree with the shell model calculations. We have confirmed the tentative â„“ = 0 assumption for 3.185 MeV state. A neutron spectroscopic factor of 1.2 was obtained for this state.
Spectroscopy of {sup 16}O Using {alpha}+{sup 12}C Resonant Scattering in Inverse Kinematics
Ashwood, N. I.; Freer, M.; Bloxham, T. R.; Curtis, N.; Haigh, P. J.; Price, D. L.; Achouri, N. L.; Catford, W. N.; Harlin, C. W.; Patterson, N. P.; Thomas, J. S.; Soic, N.
2009-08-26
A measurement of the {alpha}({sup 12}C,{alpha}){sup 12}C reaction has been performed using resonant scattering with a gas target. Beam energies of 46, 51, 56 and 63 MeV were used to populate resonances in the excitation energy range of 11.6 to 22.9 MeV in {sup 16}O. The angular distributions of the elastic scattering were measured at zero degrees using an array of segmented silicon strip detectors with a minimum range of 0 deg. to 30 deg. in the centre of mass. The spins of 8 resonances between 14.1 and 18.5 MeV were obtained, confirming spin assignments made using elastic scattering in normal kinematics. An R-matrix analysis of the data was performed which indicates that the present understanding of {sup 16}O in this region is good, but not complete.
Kinematics of an in-parallel actuated manipulator based on the Stewart platform mechanism
NASA Technical Reports Server (NTRS)
Williams, Robert L., II
1992-01-01
This paper presents kinematic equations and solutions for an in-parallel actuated robotic mechanism based on Stewart's platform. These equations are required for inverse position and resolved rate (inverse velocity) platform control. NASA LaRC has a Vehicle Emulator System (VES) platform designed by MIT which is based on Stewart's platform. The inverse position solution is straight-forward and computationally inexpensive. Given the desired position and orientation of the moving platform with respect to the base, the lengths of the prismatic leg actuators are calculated. The forward position solution is more complicated and theoretically has 16 solutions. The position and orientation of the moving platform with respect to the base is calculated given the leg actuator lengths. Two methods are pursued in this paper to solve this problem. The resolved rate (inverse velocity) solution is derived. Given the desired Cartesian velocity of the end-effector, the required leg actuator rates are calculated. The Newton-Raphson Jacobian matrix resulting from the second forward position kinematics solution is a modified inverse Jacobian matrix. Examples and simulations are given for the VES.
NASA Technical Reports Server (NTRS)
Williams, Robert L., II
1992-01-01
The forward position and velocity kinematics for the redundant eight-degree-of-freedom Advanced Research Manipulator 2 (ARM2) are presented. Inverse position and velocity kinematic solutions are also presented. The approach in this paper is to specify two of the unknowns and solve for the remaining six unknowns. Two unknowns can be specified with two restrictions. First, the elbow joint angle and rate cannot be specified because they are known from the end-effector position and velocity. Second, one unknown must be specified from the four-jointed wrist, and the second from joints that translate the wrist, elbow joint excluded. There are eight solutions to the inverse position problem. The inverse velocity solution is unique, assuming the Jacobian matrix is not singular. A discussion of singularities is based on specifying two joint rates and analyzing the reduced Jacobian matrix. When this matrix is singular, the generalized inverse may be used as an alternate solution. Computer simulations were developed to verify the equations. Examples demonstrate agreement between forward and inverse solutions.
Pin, F.G.; Belmans, P.F.R.; Culioli, J.C.; Carlson, D.D.; Tulloch, F.A.
1994-12-31
A new analytical method to resolve underspecified systems of algebraic equations is presented. The method is referred to as the Full Space Parameterization (FSP) method and utilizes easily- calculated projected solution vectors to generate the entire space of solutions of the underspecified system. Analytic parameterizations for both the space of solutions and the null space of the system reduce the determination of a task-requirement-based single solution to a m {minus} n dimensional problem, where m {minus} n is the degree of underspecification, or degree of redundancy, of the system. An analytical solution is presented to directly calculate the least-norm solution from the parameterized space and the results are compared to solutions of the standard pseudo-inverse algorithm which embodies the (least-norm) Moore-Penrose generalized inverse. Application of the new solution method to a variety of systems and task requirements are discussed and sample results using four-link planar manipulators with one or two degrees of redundancy and a seven degree-of-freedom manipulator with one or four degrees of redundancy are presented to illustrate the efficiency of the new FSP method and algorithm.
NASA Astrophysics Data System (ADS)
Serra, Eugenio Maria Toraldo; Emolo, Antonio; Orefice, Antonella; Zollo, Aldo
2013-08-01
We present an approach to infer the slip and rupture velocity distributions on the fault plane from the non-linear inversion of the apparent source time functions, obtained from the empirical Green's function deconvolution method. The main advantage of this technique is that it allows overcoming, in the forward modelling, the limitations related to the computation of the Green's function, as the choice of a correct and reliable earth propagation model. We perform a parameter resolution and uncertainty study, which is based on the analysis of the misfit function in the neighbourhood of the best-fitting model. In this paper, we present the results obtained by applying the technique to synthetic and real records from an Mw 4 event which occurred during the 2009 L'Aquila (central Italy) aftershock sequence. Results show a heterogeneous slip distribution, characterized by two main high slip patches located NW of the hypocentre and an average slip of 3.7 cm, corresponding to a seismic model of about 0.82 × 1015 Nm.
Study of the ^18Ne(?,p)^21Na Reaction in Inverse Kinematics
NASA Astrophysics Data System (ADS)
Sinha, S.; Greene, J.; Henderson, D.; Janssens, R. V. F.; Jiang, C. L.; Moore, E. F.; Mukherjee, G.; Pardo, R. C.; Pennington, T.; Rehm, K. E.; Chen, A.; Jisonna, L.; Segel, R. E.; Wuosmaa, A. H.; Artemov, S.
2003-10-01
There are three breakout reactions from the hot CNO cycle into the rp-process: ^18F(p,?)^19Ne, ^15O(?,?)^19Ne and ^18Ne(?,p)^21Na. The latter plays a role only at higher temperatures (T_9 1) which can occur on the surface of neutron stars during X-ray bursts. Two measurements of the cross sections have been performed previously using a ^4He target and a radioactive ^18Ne beam with cross sections differing by a factor of about 5. We have measured an excitation function for the inverse ^21Na(p,?)^18Ne reaction with a solid CH2 target and used the principle of detailed balance to obtain information about the astrophysical ^18Ne(?,p)^21Na reaction rate. The ^21Na beam was produced via the d(^20Ne,^21Na)n reaction using the in-flight facility at the ATLAS accelerator. ^21Na beams with variable energies in the range E_lab=4.3-5 MeV and intensities of 2x10^5 particles/s on target were obtained. The outgoing particles (^18Ne and ?) were detected in coincidence in an annular ionization chamber silicon-strip detector system with a detection efficiency of about 70%. Information about transitions to excited states populated in the ^18Ne(?,p)^21Na reaction were obtained through a measurement of inelastic scattering ^21Na(p,p')^21Na with the same setup. The influence of this reaction on the breakout from the hot CNO cycle into the rapid proton capture process will be discussed. This work was supported by the US Department of Energy, Nuclear Physics Division, under contract No. W-31-109-ENG-38.
Two measurements of the 22Na+p resonant scattering via thick-target inverse-kinematics method
NASA Astrophysics Data System (ADS)
Wang, Y. B.; Jin, S. J.; Jing, L.; Han, Z. Y.; Bai, X. X.; Guo, B.; Li, Y. J.; Li, Z. H.; Lian, G.; Su, J.; Sun, L. J.; Yan, S. Q.; Zeng, S.; Liu, W. P.; Yamaguchi, H.; Kubono, S.; Hu, J.; Kahl, D.; He, J. J.; Wang, J. S.; Tang, X. D.; Xu, S. W.; Ma, P.; Zhang, N. T.; Bai, Z.; Huang, M. R.; Jia, B. L.; Jin, S. L.; Ma, J. B.; Ma, S. B.; Ma, W. H.; Yang, Y. Y.; Zhang, L. Y.; Jung, H. S.; Moon, J. Y.; Lee, C. S.; Teranishi, T.; Wang, H. W.; Ishiyama, H.; Iwasa, N.; Komatsubara, T.; Brown, B. A.
2016-02-01
22Na is an important isotope for the study of extinct radioactivity, meanwhile its sufficiently long half life provides the possibility to observe live 22Na in nearby nova explosions. The 22Na(p,Îł) 23Mg is one of the key reactions that influence the 22Na abundance in nova ejecta. To study the proton resonant states in 23Mg relevant to the astrophysical 22Na(p,Îł) 23Mg reaction rates, two measurements have been carried out at the CRIB separator of University of Tokyo, and the RIBLL secondary beamline in Lanzhou, respectively. The 22Na secondary beam was produced via the 1H(22Ne, 22Na)n charge exchange reaction. Thick-target inverse-kinematics method is applied to obtain the excitation function of 22Na+p elastic scattering. Extended gas target and solid state polyethylene foil were used in the two measurements, respectively, to map the different excitation energy region of the compound nucleus 23Mg. Several new resonant levels are observed and their contribution to the 22Na(p,Îł) 23Mg reaction rate is evaluated.
Multi-GPU Jacobian Accelerated Computing for Soft Field Tomography
Borsic, A.; Attardo, E. A.; Halter, R. J.
2012-01-01
Image reconstruction in soft-field tomography is based on an inverse problem formulation, where a forward model is fitted to the data. In medical applications, where the anatomy presents complex shapes, it is common to use Finite Element Models to represent the volume of interest and to solve a partial differential equation that models the physics of the system. Over the last decade, there has been a shifting interest from 2D modeling to 3D modeling, as the underlying physics of most problems are three-dimensional. Though the increased computational power of modern computers allows working with much larger FEM models, the computational time required to reconstruct 3D images on a fine 3D FEM model can be significant, on the order of hours. For example, in Electrical Impedance Tomography applications using a dense 3D FEM mesh with half a million elements, a single reconstruction iteration takes approximately 15 to 20 minutes with optimized routines running on a modern multi-core PC. It is desirable to accelerate image reconstruction to enable researchers to more easily and rapidly explore data and reconstruction parameters. Further, providing high-speed reconstructions are essential for some promising clinical application of EIT. For 3D problems 70% of the computing time is spent building the Jacobian matrix, and 25% of the time in forward solving. In the present work, we focus on accelerating the Jacobian computation by using single and multiple GPUs. First, we discuss an optimized implementation on a modern multi-core PC architecture and show how computing time is bounded by the CPU-to-memory bandwidth; this factor limits the rate at which data can be fetched by the CPU. Gains associated with use of multiple CPU cores are minimal, since data operands cannot be fetched fast enough to saturate the processing power of even a single CPU core. GPUs have a much faster memory bandwidths compared to CPUs and better parallelism. We are able to obtain acceleration factors of 20 times on a single NVIDIA S1070 GPU, and of 50 times on 4 GPUs, bringing the Jacobian computing time for a fine 3D mesh from 12 minutes to 14 seconds. We regard this as an important step towards gaining interactive reconstruction times in 3D imaging, particularly when coupled in the future with acceleration of the forward problem. While we demonstrate results for Electrical Impedance Tomography, these results apply to any soft-field imaging modality where the Jacobian matrix is computed with the Adjoint Method. PMID:23010857
NASA Astrophysics Data System (ADS)
Roma, Maria; Pla, Oriol; ButillĂ©, Mireia; Roca, Eduard; Ferrer, Oriol
2015-04-01
The widespread extensional deformation that took place during Jurassic to Cretaceous times in the Western Europe and north-Atlantic realm resulted in the formation of several rift systems. Some of the basins associated to these rifts show broad syncline-shapes filled by thick sedimentary successions deposited overlying a hyperextended crust (i.e., Parentis, Cameros, OrganyĂ or Columbrets basins in Iberia). The development of these syncline basins has been associated to the slip of low-angle lithospheric-scale extensional faults with ramp/flat geometries. The shape and kinematics of such faults have been usually established using the architecture of syn-kinematic layers and assuming a complete coupling of the hangingwall rocks and a layer parallel flexural slip deformation mechanism. However almost all these basins include pre-kinematic Upper Triassic salt layers which undubtoufully acted as an effective detachment decoupling the structure of sub- and suprasalt units. The presence of this salt is denoted by the growth of salt structures as diapirs or salt walls at the edges of these basins where the overburden was thinner. During latest Cretaceous and Cenozoic these basins were partially inverted and often incorporated into thrust-and-fold belts as the Pyrenees . Contractional deformation resulted in the reactivation of major extensional faults and, above the salt, the squeezing of pre-existent salt structures. The pre-kinematic salt clearly acted again as as a major detachment decoupling the contractional deformation. Using an experimental approach (scaled sand-box models) the aim of our research is threefold: 1) to determine the geometrical features of the hangingwall above a convex upwards ramp of a low angle extensional fault with and without pre-kinematic salt, and consequently; 2) to decipher the role played by a pre-kinematic viscous layer, such as salt, in the development of these syncline basins; and 3) to characterize the contractional deformation that took place in them during a later contractional inversion. To achieve this goal an experimental program including seven different sand-box models has been carried out. The experimental results show that fault shape controls the geometry and the kinematic evolution of the ramp synclines formed on the hangingwall during extension and subsequent inversion. Regarding this, the experiments also demonstrate that the presence of a viscous layer changed significantly the kinematic of the basin developing two clearly different structural styles above and below the polymer. The kinematic of this basin during extension change dramatically when the silicone layer was depleted with the formation of primary welds. Since this moment model's kinematic becomes similar to the models without silicone. During the inversion, models show that low shortening produced the contractional reactivation of the major fault arched and uplifted the basin. In this scenario, if salt is rather continuous, took place an incipient reactivation of the silicone layer as a contractional detachment. By contrast, high shortening produces the total inversion of the detachment faults and the pop-up of the extensional basin. Finally, models are compared with different natural analogues from Iberia validating previous published interpretations or proposing new interpretations inferring the geometry of the major fault, specially if the presence of a salt interlayer in the deformed rocks is known or suspected.
Flux Jacobian Matrices For Equilibrium Real Gases
NASA Technical Reports Server (NTRS)
Vinokur, Marcel
1990-01-01
Improved formulation includes generalized Roe average and extension to three dimensions. Flux Jacobian matrices derived for use in numerical solutions of conservation-law differential equations of inviscid flows of ideal gases extended to real gases. Real-gas formulation of these matrices retains simplifying assumptions of thermodynamic and chemical equilibrium, but adds effects of vibrational excitation, dissociation, and ionization of gas molecules via general equation of state.
NASA Astrophysics Data System (ADS)
Sasano, M.; Yasuda, J.; Zegers, R. G. T.; Baba, H.; Chao, W.; Dozono, M.; Fukuda, N.; Inabe, N.; Isobe, T.; Jhang, G.; Kamaeda, D.; Kubo, T.; Kurata-Nishimura, M.; Milman, E.; Motobayashi, T.; Otsu, H.; Panin, V.; Powell, W.; Sakai, H.; Sako, M.; Sato, H.; Shimizu, Y.; Stuhl, L.; Suzuki, H.; Tangwancharoen, S.; Takeda, H.; Uesaka, T.; Yoneda, K.; Zenihiro, J.; Kobayashi, T.; Sumikama, T.; Tako, T.; Nakamura, T.; Kondo, Y.; Togano, Y.; Shikata, M.; Tsubota, J.; Yako, K.; Shimoura, K.; Ota, S.; Kawase, S.; Kubota, Y.; Takaki, M.; Michimasa, S.; Kisamori, K.; Lee, C. S.; Tokieda, H.; Kobayashi, M.; Koyama, S.; Kobayashi, N.; Wakasa, T.; Sakaguchi, S.; Krasznahorkay, A.; Murakami, T.; Nakatsuka, N.; Kaneko, M.; Matsuda, Y.; Mucher, D.; Reichert, S.; Bazin, D.; Lee, J. W.
2016-01-01
The charge-exchange (p,n) reaction at 220 MeV has been measured to extract the strength distribution of Gamow-Teller transitions from the doubly magic unstable nucleus 132Sn. A recently developed experimental technique of measuring the (p,n) reaction in inverse kinematics has been applied to the study of unstable nuclei in the mass region around AËś100 for the first time. We have combined the low-energy neutron detector WINDS and the SAMURAI spectrometer at the RIKEN radioactive isotope beam factory (RIBF). The particle identification plot for the reaction residues obtained by the spectrometer provides the clear separation of the CE reaction channel from other background events, enabling us to identify kinematic curves corresponding the (p, n) reaction. Further analysis to reconstruct the excitation energy spectrum is ongoing.
NASA Astrophysics Data System (ADS)
Melis, Nikolaos S.; Miliorizos, Marios N.; Oshoano Aipoh, Hilary
2013-04-01
The present work compliments the application of a methodology, in reviewing and investigating further the kinematic history of faults, based on striation analysis and stress inversion of earthquake focal mechanisms and combines them to refine tectonic modelling and hence improve further hazard assessment. Two areas are chosen for this application: the Bristol Channel, UK and the Ionian Zone, Greece. Striation analysis is carried out in two complementary fault terranes. The first along the northern margin of the Inner Bristol Channel, UK, offers a natural laboratory to study in detail the reactivation history of the inverted Bristol Channel basin; and, the second along the north western coastline of the Ionian Zone, Greece, presents an opportunity to illustrate the relationship between movement of a framework of faults within the external orogenic zone of the Hellenides and the stress deduced from focal mechanisms of earthquakes in the region. The UK example reveals phases of Mesozoic negative inversion of Late Palaeozoic basement frontal and oblique ramp thrust faults, followed by Caenozoic positive inversions of Mesozoic normal and strike slip faults. The Greek example shows an equally composite history of faulting; Tethyan basement strata contain normal faults that pass up sequence and across unconformities into Mesozoic and Caenozoic strata, with thrusts and positively inverted faults recording typical dextral transpression. The fault framework in older strata and the veneers of Recent strata above them display Neotectonic fault histories of sinistral transtension, in addition to the transpression. Since the Ionian Zone lies suitably in the external zone, deformation favours the reactivation of fault lineaments, rather than the genesis of pristine faults. Both examples are used to demonstrate this structural principle. Focal mechanisms of Greek earthquake data are used in stress inversion and the results are applied upon the inherited fault framework and are postulated to reactivate it. For example, structures are selected in the field from the tectonised strata of northern Corfu and from recent geological maps of north western Greece. These data are used in conjunction with the results of stress inversion of focal mechanisms, in order to anticipate and then test the gross senses of fault reactivation. Tests are investigated using structural field techniques and available international striation analysis software modules. The defined framework analysis is applied to both the data from ancient faults, in UK and the focal mechanisms of earthquakes, in Greece. Stress tensors are calculated and fault kinematic histories are evaluated. Hence, this application permits the effects of a modern stress regime to be deduced for a known fault framework, in order to complete and understand fully the kinematic history to the present day. As a corollary, the significant field techniques of tracing major fault lines across regional unconformities and measuring the sense of displacements across these stratigraphic boundaries permit kinematic histories to be defined more precisely in both terranes, than by using only structural techniques.
Suzuki, T.; Rainovski, G.; Koike, T.; Ahn, T.; Carpenter, M. P.; Costin, A.; Danchev, M.; Dewald, A.; Janssens, R. V. F.; Joshi, P.; Lister, C. J.; Moller, A.; Pietralla, N.; Shinozuka, T.; Timar, J.; Wadsworth, R.; Vaman, C.; Zhu, S.; Physics; Tohoku Univ.; Univ. of Sofia; State Univ. of New York; Univ. of Tennessee; Univ. zu Koln; Univ. of York; TU Darmstadt; ATOMKI, Hungary; Michigan State Univ.
2008-01-01
Lifetimes of chiral candidate structures in {sup 103,104}Rh were measured using the recoil distance Doppler-shift method. The Gammasphere detector array was used in conjunction with the Cologne plunger device. Excited states of {sup 103,104}Rh were populated by the {sup 11}B({sup 96}Zr,4n){sup 103}Rh and {sup 11}B({sup 96}Zr,3n){sup 104}Rh fusion-evaporation reactions in inverse kinematics. Three and five lifetimes of levels belonging to the proposed chiral doublet bands are measured in {sup 103}Rh and {sup 104}Rh, respectively. The previously observed even-odd spin dependence of the B(M1)/B(E2) values is caused by the variation in the B(E2) values, whereas the B(M1) values decrease as a function of spin.
NASA Astrophysics Data System (ADS)
Margerin, V.; Lotay, G.; Woods, P. J.; Aliotta, M.; Christian, G.; Davids, B.; Davinson, T.; Doherty, D. T.; Fallis, J.; Howell, D.; Kirsebom, O. S.; Mountford, D. J.; Rojas, A.; Ruiz, C.; Tostevin, J. A.
2015-08-01
In Wolf-Rayet and asymptotic giant branch (AGB) stars, the Alg26(p ,Îł )27Si reaction is expected to govern the destruction of the cosmic Îł -ray emitting nucleus 26Al. The rate of this reaction, however, is highly uncertain due to the unknown properties of key resonances in the temperature regime of hydrogen burning. We present a high-resolution inverse kinematic study of the Alg26(d ,p )27Al reaction as a method for constraining the strengths of key astrophysical resonances in the Alg26(p ,Îł )27Si reaction. In particular, the results indicate that the resonance at Er=127 keV in 27Si determines the entire Alg26(p ,Îł )27Si reaction rate over almost the complete temperature range of Wolf-Rayet stars and AGB stars.
NASA Astrophysics Data System (ADS)
Ersoy, Ediz
2011-10-01
The (p,y) process plays an important role in stellar nucleosynthesis and the long term evolution of stars. The (p,y) direct capture process is difficult to observe experimentally due to the low energies and small reaction cross-sections involved, however by comparison, the (d,n)^ proton transfer process has higher reaction cross-sections in addition to providing insight into the (p,y) process through observations involving neutron kinematics. The particular (d,n) reaction investigated using inverse kinematics was the ^17O(d,n)^18F reaction. Neutron detection for the ^17O(d,n)^18F reaction is to be done utilizing the LENDA (Low Energy Neutron Detector Array) detectors. Several calculations were conducted to observe specific excitation levels of astrophysical interest between 5 and 7MeV. These calculations included correlations of neutron and ^18F kinetic energies with their center of mass and scattering angles at different excitation energies. The calculations further included detector placement and coverage for the observation of neutrons and ^18F isotopes. The time-of-flight and angular resolutions of the LENDA detectors were also studied in the calculations.
Hacker, C.J.; Fries, G.A.; Pin, F.G.
1997-01-01
Few optimization methods exist for path planning of kinematically redundant manipulators. Among these, a universal method is lacking that takes advantage of a manipulator`s redundancy while satisfying possibly varying constraints and task requirements. Full Space Parameterization (FSP) is a new method that generates the entire solution space of underspecified systems of algebraic equations and then calculates the unique solution satisfying specific constraints and optimization criteria. The FSP method has been previously tested on several configurations of the redundant manipulator HERMIES-III. This report deals with the extension of the FSP driver, Inverse Kinematics On Redundant systems (IKOR), to include three-dimensional manipulation systems, possibly incorporating a mobile platform, with and without orientation control. The driver was also extended by integrating two optimized versions of the FSP solution generator as well as the ability to easily port to any manipulator. IKOR was first altered to include the ability to handle orientation control and to integrate an optimized solution generator. The resulting system was tested on a 4 degrees-of-redundancy manipulator arm and was found to successfully perform trajectories with least norm criteria while avoiding obstacles and joint limits. Next, the system was adapted and tested on a manipulator arm placed on a mobile platform yielding 7 degrees of redundancy. After successful testing on least norm trajectories while avoiding obstacles and joint limits, IKORv1.0 was developed. The system was successfully verified using comparisons with a current industry standard, the Moore Penrose Pseudo-Inverse. Finally, IKORv2.0 was created, which includes both the one shot and two step methods, manipulator portability, integration of a second optimized solution generator, and finally a more robust and usable code design.
NASA Astrophysics Data System (ADS)
Healy, D.; Kusznir, N.
2004-05-01
Recent discoveries of depth-dependent stretching and mantle exhumation at rifted continental margins require new models of margin formation. A two-dimensional coupled fluid mechanics/thermal kinematic model of sea-floor spreading initiation has been developed to predict the deformational and thermal evolution of rifted continental margins through time. The model can also include the effects of pre-breakup pure-shear stretching of continental lithosphere. Rifted margin lithosphere thinning and thermal evolution is dependent on ocean-ridge spreading rate (Vx), the mantle upwelling velocity beneath the ridge axis (Vz), and the pre-breakup lithosphere stretching factor (a). The model predicts the thinning of the upper crust, lower crust and lithospheric mantle of the continental margin, and the history of rifted margin subsidence, water depths and top basement heat-flow. We apply inverse methods to this new forward model of rifted margin formation to explore how successfully model input parameters may be extracted from observational data at rifted margins. The ability of the inverse method to find a unique solution has been established using synthetic data from forward modelling. Output parameters from the inversion are the horizontal and vertical velocities of sea-floor spreading, their variation with time, and the initial pre-breakup lithosphere stretching factor. Initial inversion tests used forward model predictions of the stretching of the upper crust, the whole crust and the whole lithosphere. These model predictions control the variation of crustal thickness and lithosphere temperature beneath the thinned continental margin and adjacent ocean, which in turn control margin subsidence and gravity anomaly. For application of the inversion procedure to observed data on rifted margins, the input data used are measured bathymetry, sediment thickness, gravity anomaly and upper crustal stretching. The forward problem is characterised by a non-linear relationship between parameters and data, and a significant computational burden. We adopt a non-linear minimisation approach implemented through parallel programming on a multi-node computing cluster. We present preliminary results from inversions of observed data measured on 2D profiles for Atlantic continental margins. This work forms part of the NERC Margins iSIMM project. iSIMM investigators are from Cambridge and Liverpool Universities, Schlumberger Cambridge Research and Badley Geoscience, supported by the NERC, the DTI, Agip UK, BP, Amerada Hess Ltd, Anadarko, Conoco, Philips, Shell, Statoil and WesternGeco.
Learning the inverse kinetics of an octopus-like manipulator in three-dimensional space.
Giorelli, M; Renda, F; Calisti, M; Arienti, A; Ferri, G; Laschi, C
2015-06-01
This work addresses the inverse kinematics problem of a bioinspired octopus-like manipulator moving in three-dimensional space. The bioinspired manipulator has a conical soft structure that confers the ability of twirling around objects as a real octopus arm does. Despite the simple design, the soft conical shape manipulator driven by cables is described by nonlinear differential equations, which are difficult to solve analytically. Since exact solutions of the equations are not available, the Jacobian matrix cannot be calculated analytically and the classical iterative methods cannot be used. To overcome the intrinsic problems of methods based on the Jacobian matrix, this paper proposes a neural network learning the inverse kinematics of a soft octopus-like manipulator driven by cables. After the learning phase, a feed-forward neural network is able to represent the relation between manipulator tip positions and forces applied to the cables. Experimental results show that a desired tip position can be achieved in a short time, since heavy computations are avoided, with a degree of accuracy of 8% relative average error with respect to the total arm length. PMID:25970238
Analytical Jacobian and its application to tilted-wave interferometry.
Fortmeier, Ines; Stavridis, Manuel; Wiegmann, Axel; Schulz, Michael; Osten, Wolfgang; Elster, Clemens
2014-09-01
Tilted-wave interferometry (TWI) is a novel optical measurement principle for the measurement of aspherical surfaces. For the reconstruction of the wavefront and the surface under test, respectively, perturbation methods are applied, which require the calculation of the Jacobian matrix. For the practical use of the instrument, a fast and exact calculation of the Jacobian matrices is crucial, since this strongly influences the calculation times of the TWI. By applying appropriate approaches in optical perturbation methods we are able to calculate the required Jacobian matrices analytically when the nominal optical path through the system is given. As a result, calculation times for the TWI can be considerably reduced. We finally illustrate the improved TWI procedure and apply methods of optimal design to determine optimal positions of the surface under test. For such applications the fast calculation of the Jacobian matrices is essential. PMID:25321510
Off-diagonal Jacobian support for Nodal BCs
Peterson, John W.; Andrs, David; Gaston, Derek R.; Permann, Cody J.; Slaughter, Andrew E.
2015-01-01
In this brief note, we describe the implementation of o-diagonal Jacobian computations for nodal boundary conditions in the Multiphysics Object Oriented Simulation Environment (MOOSE) [1] framework. There are presently a number of applications [2{5] based on the MOOSE framework that solve complicated physical systems of partial dierential equations whose boundary conditions are often highly nonlinear. Accurately computing the on- and o-diagonal Jacobian and preconditioner entries associated to these constraints is crucial for enabling ecient numerical solvers in these applications. Two key ingredients are required for properly specifying the Jacobian contributions of nonlinear nodal boundary conditions in MOOSE and nite element codes in general: 1. The ability to zero out entire Jacobian matrix rows after \
Kinematic analysis of 7 DOF anthropomorphic arms
NASA Technical Reports Server (NTRS)
Kreutz-Delgado, K.; Long, M.; Seraji, H.
1990-01-01
A kinematic analysis of anthropomorphic seven-degree-of-freedom serial link spatial manipulators with revolute joints is presented. To uniquely determine joint angles for a given end-effector position and orientation, the redundancy is parameterized by a scalar variable which corresponds to the angle between the arm plane and a reference plane. The forward kinematic mappings from joint-space to end-effector coordinates and arm angle and the augmented Jacobian matrix which gives end-effector and arm angle rates as functions of joint rates are given. Conditions under which the augmented Jacobian becomes singular are given and are shown to correspond to the arm being either at a kinematically singular configuration or at a nonsingular configuration for which the arm angle ceases to parameterize the redundancy.
Kinematic analysis of 7-DOF manipulators
NASA Technical Reports Server (NTRS)
Kreutz-Delgado, Kenneth; Long, Mark; Seraji, Homayoun
1992-01-01
This article presents a kinematic analysis of seven-degree-of-freedom serial link spatial manipulators with revolute joints. To uniquely determine the joint angles for a given end-effector position and orientation, the redundancy is parameterized by a scalar variable that defines the angle between the arm plane and a reference plane. The forward kinematic mappings from joint space to end-effector coordinates and arm angle and the augmented Jacobian matrix that gives end-effector and arm angle rates as functions of joint rates are presented. Conditions under which the augmented Jacobian becomes singular are also given and are shown to correspond to the arm being either at a kinematically singular configuration or at a nonsingular configuration for which the arm angle ceases to parameterize the redundancy.
Analysis of the Jacobian-free multiscale method (JFMM)
NASA Astrophysics Data System (ADS)
Rahul; De, Suvranu
2015-11-01
In this paper we perform in-depth analysis of Jacobian-free multiscale method (JFMM) in which explicit computation of the Jacobian matrix at the macroscale is circumvented using a Newton-Krylov process. Not having to explicitly compute and store the Jacobian matrix at each Newton step reduces storage requirements and computational costs compared to previous efforts based on homogenized material coefficients with Jacobian computation at every Newton step. We present an estimate of the optimal perturbation step-size that minimizes the finite difference approximation error associated with the Jacobian-vector product in the Jacobian-free approach. Two- and three-dimensional numerical examples demonstrate that while the rate of convergence of Newton iterations for the JFMM and the computational homogenization-based two-level finite element ({FE}2) multiscale method is comparable, the computational cost of JFMM varies linearly with increasing number of degrees of freedom ( n) at the macroscale, and not exponentially as in the {FE}2 method. The storage requirement for the method increases linearly with increasing n at the macroscale, whereas, it increases as approximately O(n^{8/5}) and O(n^{9/5}) for the {FE}2 method in two- and three-dimensions, respectively.
NASA Astrophysics Data System (ADS)
Kortyna, C. D.; DeCelles, P. G.; Carrapa, B.
2012-12-01
The Eastern Cordillera and Santa Barbara systems of northwest Argentina exhibit a transition in structural style between thick- and thin-skinned features. Traditionally, Andean foreland structural geometries are correlated with the orientation of the subducting Nazca Plate. However, deformation in northwest Argentina is controlled by inversion of inherited Cretaceous rift structures of the Salta rift. South of Salta, in the ranges surrounding the Calchaquí and Lerma Valleys (between ~25°-26°S and ~65°-66°W), the foreland thrust belt is characterized by steep west-verging, north-south trending reverse faults juxtaposing Precambrian-Cambrian basement rocks on Mesozoic-Cenozoic syn-to-post-rift and foreland basin deposits. Geologic mapping, structural data and stratigraphic relationships confirm that these reverse faults are primarily reactivated extensional faults of the Cretaceous Salta rift, a complex of extensional basins beneath the modern foreland basin. The rift geometry provides a major control on fold and fault geometries in the area. New detailed (1:24,000 scale) geologic mapping in the Amblayo, Tonco, and Calchaquí Valleys documents a transition in structural style in the Andean thrust belt that correlates with palinspastic geometries of the Salta rift basin. The southern region correlates with the Salta rift flanks whereas the northern region correlates with the rift interior. Reverse faulting in the southern region is characterized by multiple high angle splays (~40°-70°) with variable amounts of stratigraphic separation that, in places, shortcut high angle normal faults of the Salta rift. In the northern region, reverse faulting is less steep (~25°-50°) and is characterized by a singular fault plane that juxtaposes overturned fault propagation folds in the hanging wall and footwall. Overturned limbs are shallowly dipping at ~20°-30°. Fault planes are approximated by thick, m's-scale orange fault gouge and breccia. This study also describes a new synorogenic unit that constrains timing of rift inversion. Described in north Tonco Valley, this unit consists of localized poorly sorted granular-boulder conglomerates and breccias with a poorly sorted mud-to-coarse sand matrix. The breccia outcrops unconformably on underlying Miocene Angastaco Formation and is in faulted contact with overriding Salta Group. Clasts consist primarily of stromatolitic, oolitic, and micritic limestones with subordinate meta-sandstones and mudstones. The larger, angular clasts are almost uniformly limestone and interpreted to be sourced from the Yacoraite Formation that outcrops in the overlying hanging wall. This unit was deposited as synorogenic muddy debris flows to mud slurries derived locally from the Yacoraite Formation as it was exhumed during fault-propagation folding in the hanging wall of the main reverse fault that juxtaposes the Amblayo and Tonco Valleys. The unit was then overridden by the hanging wall strata as the main fault reached the surface. The youngest detrital U-Pb zircon age population combined with low-T-thermochronology will help constrain timing of deformation along this fault and in the region.
NASA Astrophysics Data System (ADS)
Diao, Faqi; Wang, Rongjiang; Aochi, Hideo; Walter, Thomas R.; Zhang, Yong; Zheng, Yong; Xiong, Xiong
2016-02-01
During the 20th century, a series of devastating earthquakes occurred along the North Anatolian Fault. These generally propagated westwards, such that the main fault segment beneath the Marmara Sea appears as a seismic gap. For the nearby megacity Istanbul, rapid seismic hazard assessment is currently of great importance. A key issue is how a strong earthquake in the Marmara Sea can be characterized reliably and rapidly using the seismic network currently operating in this region. In order to investigate this issue, several scenario earthquakes on the main Marmara fault are simulated through dynamic modelling based on a 3-D structure model. The synthetic datasets are then used to reconstruct the source processes of the causal events with a recently developed iterative deconvolution and stacking method based on simplified 1-D Earth structure models. The results indicate that, by using certain a priori information about the fault geometry and focal mechanism, the tempo-spatial slip patterns of the input scenarios can be well resolved. If reasonable uncertainties are considered for the a priori information, the key source parameters, such as moment magnitude, fault size and slip centroid, can still be estimated reliably, while the detailed tempo-spatial rupture pattern may reveal significant variations. To reduce the effect induced by employing the inaccurate event location and focal mechanism, a new approach for absolute source imaging is proposed and tested. We also investigate the performance of the new source imaging tool for near real-time source inversion under the current network configuration in the Marmara Sea region. The results obtained are meaningful particularly for developing the rapid earthquake response system for the megacity Istanbul.
NASA Astrophysics Data System (ADS)
Konca, A.; Galetzka, J.; Avouac, J.; Sieh, K.; Natawidjaja, D. H.; Fang, P.; Genrich, J.; Song, A.; Bock, Y.; Chlieh, M.; Ji, C.; Helmberger, D. V.
2007-12-01
On September 12, 2007, the Mw8.4 South Pagai earthquakes ruptured the subduction interface offshore southern Sumatra. The earthquake occurred within the area monitored by the Sumatra Geodetic Array (SuGAr). The cGPS stations on South Pagai Island show about 1.5 m of southwestward displacement, up to 0.6 m of uplift of the western coast of the island, and 0.1 m of subsidence of the eastern coast. Coastal stations near Bengkulu show about 70 cm southwest motion. We have obtained a finite-fault source model of the earthquake from the inversion of co-seismic displacements measured at 13 near-field cGPS stations from the SUGAR network together with the teleseismic waveforms measured at 35 stations. In addition, the model geometry was checked and adjusted by comparing observed and predicted long period surface waves and normal modes. The source is a northward unilateral rupture with two main asperities, a deeper one, extending relatively deep beneath Bengkulu coastal area and a shallower one beneath South Pagai. Co-seismic slip reached a maximum of about 5.5 meters under South Pagai. The earthquake was not very impulsive with rise times of the order 10 seconds and a rupture velocity of about 2 km/s. The rupture initiated at the southeastern edge of a patch of the subduction interface that had been shown to be strongly locked from geodetic and paleogeodetic interseismic measurements. The rupture propagated unilaterally to the north rupturing only a fraction of a strongly coupled fault patch. The previous large earthquake on that portion of the megathrust was a M8.6 event in 1833 which produced much larger co-seismic uplift. The 2007 event released only a small fraction of the deficit of moment that has accumulated since then due to interseismic locking of the subduction interface.
Piatanesi, A.; Cirella, A.; Spudich, P.; Cocco, M.
2007-01-01
We present a two-stage nonlinear technique to invert strong motions records and geodetic data to retrieve the rupture history of an earthquake on a finite fault. To account for the actual rupture complexity, the fault parameters are spatially variable peak slip velocity, slip direction, rupture time and risetime. The unknown parameters are given at the nodes of the subfaults, whereas the parameters within a subfault are allowed to vary through a bilinear interpolation of the nodal values. The forward modeling is performed with a discrete wave number technique, whose Green's functions include the complete response of the vertically varying Earth structure. During the first stage, an algorithm based on the heat-bath simulated annealing generates an ensemble of models that efficiently sample the good data-fitting regions of parameter space. In the second stage (appraisal), the algorithm performs a statistical analysis of the model ensemble and computes a weighted mean model and its standard deviation. This technique, rather than simply looking at the best model, extracts the most stable features of the earthquake rupture that are consistent with the data and gives an estimate of the variability of each model parameter. We present some synthetic tests to show the effectiveness of the method and its robustness to uncertainty of the adopted crustal model. Finally, we apply this inverse technique to the well recorded 2000 western Tottori, Japan, earthquake (Mw 6.6); we confirm that the rupture process is characterized by large slip (3-4 m) at very shallow depths but, differently from previous studies, we imaged a new slip patch (2-2.5 m) located deeper, between 14 and 18 km depth. Copyright 2007 by the American Geophysical Union.
Doornenbal, P.; Reiter, P.; Grawe, H.; Wollersheim, H. J.; Gerl, J.; Gorska, M.; Kojouharov, I.; Prokopowicz, W.; Schaffner, H.; Bednarczyk, P.; Caceres, L.; Cederkaell, J.; Ekstroem, A.; Jhingan, A.; Kumar, R.; Singh, R. P.
2008-09-15
The 2{sub 1}{sup +} states of {sup 114,116}Sn were excited in two consecutive experiments by means of Coulomb excitation in inverse kinematics on a {sup 58}Ni target. A precise determination of the reduced transition probability B(E2; 0{sub g.s.}{sup +}{yields}2{sub 1}{sup +}) of {sup 114}Sn relative to the well-known 2{sub 1}{sup +} excitation strength in {sup 116}Sn was achieved by comparing the relative projectile to target 2{sub 1}{sup +}{yields}0{sub g.s.}{sup +} decay intensities. The obtained B(E2{up_arrow}) value of 0.232(8) e{sup 2}b{sup 2} for {sup 114}Sn confirms the tendency of large B(E2{up_arrow}) values for the light tin isotopes below the midshell {sup 116}Sn that has been observed recently in various radioactive ion beam experiments. The result establishes most clearly the discrepancy between the current B(E2{up_arrow}) value predictions from large-scale shell-model calculations and the experimental deviation, which commences already for the stable {sup 114}Sn isotope.
NASA Astrophysics Data System (ADS)
Henry, Eric M.
The CHIMERA multi-detector array at LNS Catania has been used to study the inverse-kinematics reaction of 78Kr + 40Ca at a bombarding energy of 10 A MeV. The multi-detector is capable of detecting individual products of the collision essential for the reconstruction of the collision dynamics. This is the first time CHIMERA has been used at low-energy, which offered a unique challenge for the calibration and interpretation of experimental data. Initial interrogation of the calibrated data revealed a class of selected events characterized by two coincident heavy fragments (atomic number Z>3) that together account for the majority of the total mass of the colliding system. These events are consistent with the complete fusion and subsequent binary split (fission) of a composite nucleus. The observed fission fragments are characterized by a broad A, Z distribution and are centered about symmetric fission while exhibiting relative velocities significantly higher than given by Viola systematics. Additional analysis of the kinematic relationship between the fission fragments was performed. Of note, is that the center-of-mass angular distribution (dsigma/dtheta) of the fission fragments exhibits an unexpected anisotropy inconsistent with a compound-nucleus reaction. This anisotropy is indicative of a dynamic fusion/fission-like process. The observed angular distribution features a forward-backward anisotropy most prevalent for mass-asymmetric events. Furthermore, the more massive fragment of mass-asymmetric events appears to emerge preferentially in the forward direction, along the beam axis. Analysis of the angular distribution of alpha particles emitted from these fission fragments suggests the events are associated mostly with central collisions. The observations associated with this subset of events are similar to those reported for dynamic fragmentation of projectile-like fragments, but have not before been observed for a fusion/fission-like process. Comparisons to dynamic and statistical reaction model predictions are inconsistent with known phenomena, but suggest a peculiar dynamics-driven scenario. A plausible explanation of the experimental results is the existence of a phenomenon similar to a "fusion window", or a range of impact parameters in which complete fusion cannot be achieved. In this scenario, the system must absorb all the relative motion and convert it to vibrational energy or heat. As the energy increases the system may not be able to accommodate this conversion of energy without breaking apart.
Roberts, R.G.; Repperger, D.W.
1999-01-01
This article presents some results on the closed-form, singular-value decomposition of the orientational Jacobian for three- and four-degree-of-freedom wristlike mechanisms. These results are used to study the kinematics of a centrifuge simulator, and to determine the centrifuge`s limitations in achieving maximum angular velocities. Also, the issue of fault tolerance for a redundant wrist is addressed.
Force-free Jacobian equilibria for Vlasov-Maxwell plasmas
Abraham-Shrauner, B.
2013-10-15
New analytic force-free Vlasov-Maxwell equilibria for thin current sheets are presented. The magnetic flux densities are expressed in terms of Jacobian elliptic functions of one Cartesian spatial coordinate. The magnetic flux densities reduce to previously reported hyperbolic functions in one limit and sinusoidal functions in another limit of the modulus k. A much wider class of nonlinear force-free Vlasov-Maxwell equilibria open expanded possibilities for modeling of solar system, astrophysical and laboratory plasmas. Modified Maxwellian distribution functions are determined explicitly in terms of Jacobian elliptic functions. Conditions for double peaked distribution functions that could be unstable are developed.
Exploring Strange Nonchaotic Attractors through Jacobian Elliptic Functions
ERIC Educational Resources Information Center
Garcia-Hoz, A. Martinez; Chacon, R.
2011-01-01
We demonstrate the effectiveness of Jacobian elliptic functions (JEFs) for inquiring into the reshaping effect of quasiperiodic forces in nonlinear nonautonomous systems exhibiting strange nonchaotic attractors (SNAs). Specifically, we characterize analytically and numerically some reshaping-induced transitions starting from SNAs in the context of…
Exploring Strange Nonchaotic Attractors through Jacobian Elliptic Functions
ERIC Educational Resources Information Center
Garcia-Hoz, A. Martinez; Chacon, R.
2011-01-01
We demonstrate the effectiveness of Jacobian elliptic functions (JEFs) for inquiring into the reshaping effect of quasiperiodic forces in nonlinear nonautonomous systems exhibiting strange nonchaotic attractors (SNAs). Specifically, we characterize analytically and numerically some reshaping-induced transitions starting from SNAs in the context ofâ€¦
Multi-GPU Jacobian accelerated computing for soft-field tomography.
Borsic, A; Attardo, E A; Halter, R J
2012-10-01
Image reconstruction in soft-field tomography is based on an inverse problem formulation, where a forward model is fitted to the data. In medical applications, where the anatomy presents complex shapes, it is common to use finite element models (FEMs) to represent the volume of interest and solve a partial differential equation that models the physics of the system. Over the last decade, there has been a shifting interest from 2D modeling to 3D modeling, as the underlying physics of most problems are 3D. Although the increased computational power of modern computers allows working with much larger FEM models, the computational time required to reconstruct 3D images on a fine 3D FEM model can be significant, on the order of hours. For example, in electrical impedance tomography (EIT) applications using a dense 3D FEM mesh with half a million elements, a single reconstruction iteration takes approximately 15-20 min with optimized routines running on a modern multi-core PC. It is desirable to accelerate image reconstruction to enable researchers to more easily and rapidly explore data and reconstruction parameters. Furthermore, providing high-speed reconstructions is essential for some promising clinical application of EIT. For 3D problems, 70% of the computing time is spent building the Jacobian matrix, and 25% of the time in forward solving. In this work, we focus on accelerating the Jacobian computation by using single and multiple GPUs. First, we discuss an optimized implementation on a modern multi-core PC architecture and show how computing time is bounded by the CPU-to-memory bandwidth; this factor limits the rate at which data can be fetched by the CPU. Gains associated with the use of multiple CPU cores are minimal, since data operands cannot be fetched fast enough to saturate the processing power of even a single CPU core. GPUs have much faster memory bandwidths compared to CPUs and better parallelism. We are able to obtain acceleration factors of 20 times on a single NVIDIA S1070 GPU, and of 50 times on four GPUs, bringing the Jacobian computing time for a fine 3D mesh from 12 min to 14 s. We regard this as an important step toward gaining interactive reconstruction times in 3D imaging, particularly when coupled in the future with acceleration of the forward problem. While we demonstrate results for EIT, these results apply to any soft-field imaging modality where the Jacobian matrix is computed with the adjoint method. PMID:23010857
Yang, C L; Wei, H Y; Adler, A; Soleimani, M
2013-06-01
Electrical impedance tomography (EIT) is a fast and cost-effective technique to provide a tomographic conductivity image of a subject from boundary current-voltage data. This paper proposes a time and memory efficient method for solving a large scale 3D EIT inverse problem using a parallel conjugate gradient (CG) algorithm. The 3D EIT system with a large number of measurement data can produce a large size of Jacobian matrix; this could cause difficulties in computer storage and the inversion process. One of challenges in 3D EIT is to decrease the reconstruction time and memory usage, at the same time retaining the image quality. Firstly, a sparse matrix reduction technique is proposed using thresholding to set very small values of the Jacobian matrix to zero. By adjusting the Jacobian matrix into a sparse format, the element with zeros would be eliminated, which results in a saving of memory requirement. Secondly, a block-wise CG method for parallel reconstruction has been developed. The proposed method has been tested using simulated data as well as experimental test samples. Sparse Jacobian with a block-wise CG enables the large scale EIT problem to be solved efficiently. Image quality measures are presented to quantify the effect of sparse matrix reduction in reconstruction results. PMID:23719094
Analytical Jacobian Calculation in RT Model Including Polarization Effect
NASA Astrophysics Data System (ADS)
Okabayashi, Y.; Yoshida, Y.; Ota, Y.
2014-12-01
The greenhouse gas observing satellite "GOSAT" launched in January 2009 has been observing global distribution of CO2 and CH4. The TANSO-FTS mounted on GOSAT measures the two polarized components (called "P" and "S") of short wavelength infrared (SWIR) spectrum reflected from the earth's surface. In NIES, column-averaged dry air mole fraction of CO2 and CH4 (XCO2 and XCH4) are retrieved from SWIR spectra. However, the observed polarization information is not effectively utilized in the retrieval process due to the large computational cost of a vector RT model, instead the polarization synthesized spectra and a scalar RT model are used in the operational processing. An optical path length modification due to aerosol scattering is known as the major error source for XCO2 and XCH4 retrieval from SWIR spectra. Because the aerosol scattering changes polarization state of light, more accurate or additional aerosol information is expected by using the observed polarization spectra effectively in the retrieval process, which improves the retrieval accuracy of XCO2 and XCH4. In addition, for information content analysis, sensitivity analysis and error analysis, Jacobian matrix is important onto retrieval algorithm design before analyses for actual observed data. However, in the case of using RT model including polarization effect in retrieval process, the computational cost of Jacobian matrix calculations in maximum a posteriori retrieval is significantly large. Efficient calculation of analytical Jacobian is necessary. As a first step, we are implementing an analytical Jacobian calculation function to the vector RT model "Pstar". RT scheme of Pstar is based on hybrid method comprising the discrete ordinate and matrix operator methods. The reflection/transmission matrices and source vectors are obtained for each vertical layer through the discrete ordinate solution, and the vertically inhomogeneous system is constructed using the matrix operator method. Because the delta-M truncation method is used in the Pstar to reduce the computational cost, single scattering component correction called TMS method is implemented. Calculation of analytical Jacobian has to be constructed above the RT scheme. We will show the formulation and some results of the analytical Jacobian implementation at the presentation.
Generic robotic kinematic generator for virtual environment interfaces
NASA Astrophysics Data System (ADS)
Flueckiger, Lorenzo; Piguet, Laurent; Baur, Charles
1996-12-01
The expansion of robotic systems' performance, as well as the need for such machines to work in complex environments (hazardous, small, distant, etc.), involves the need for user interfaces which permit efficient teleoperation. Virtual Reality based interfaces provide the user with a new method for robot task planning and control: he or she can define tasks in a very intuitive way by interacting with a 3D computer generated representation of the world, which is continuously updated thanks to multiple sensors fusion and analysis. The Swiss Federal Institute of Technology has successfully tested different kinds of teleoperations. In the early 90s, a transatlantic teleoperation of a conventional robot manipulator with a vision feedback system to update the virtual world was achieved. This approach was then extended to perform teleoperation of several mobile robots (Khepera, Koala) as well as to control microrobots used for microsystems' assembly in the micrometer range. One of the problems encountered with such an approach is the necessity to program a specific kinematic algorithm for each kind of manipulator. To provide a more general solution, we started a project aiming at the design of a 'kinematic generator' (CINEGEN) for the simulation of generic serial and parallel mechanical chains. With CINEGEN, each manipulator is defined with an ascii file description and its attached graphics files; inserting a new manipulator simply requires a new description file, and none of the existing tools require modification. To have a real time behavior, we have chosen a numerical method based on the pseudo-Jacobian method to generate the inverse kinematics of the robot. The results obtained with an object-oriented implementation on a graphic workstation are presented in this paper.
Inversion strategies for visco-acoustic waveform inversion
NASA Astrophysics Data System (ADS)
Kamei, R.; Pratt, R. G.
2013-08-01
Visco-acoustic waveform inversion can potentially yield quantitative images of the distribution of both velocity and the attenuation parameters from seismic data. Intrinsic P-wave attenuation has been of particular interest, but has also proven challenging. Frequency-domain inversion allows attenuation and velocity relations to be easily incorporated, and allows a natural multiscale approach. The Laplace-Fourier approach extends this to allow the natural damping of waveforms to enhance early arrivals. Nevertheless, simultaneous inversion of velocity and attenuation leads to significant `cross-talk' between the resulting images, reflecting a lack of parameter resolution and indicating the need for pre-conditioning and regularization of the inverse problem. We analyse the cross-talk issue by partitioning the inversion parameters into two classes; the velocity parameter class, and the attenuation parameter class. Both parameters are defined at a reference frequency, and a dispersion relation is assumed that describes these parameters at any other frequency. We formulate the model gradients at a forward modelling frequency, and convert them to the reference frequency by employing the Jacobian of the coordinate change represented by the dispersion relation. We show that at a given modelling frequency, the FrĂ©chet derivatives corresponding to these two parameter classes differ only by a 90Â° phase shift, meaning that the magnitudes of resulting model updates will be unscaled, and will not reflect the expected magnitudes in realistic (Q-1 â‰Ş 1) media. Due to the lack of scaling, cross-talk will be enhanced by poor subsurface illumination, by errors in kinematics, and by data noise. To solve these issues, we introduce an attenuation scaling term (the inverse of a penalty term) that is used to pre-condition the gradient by controlling the magnitudes of the updates to the attenuation parameters. Initial results from a suite of synthetic cross-hole tests using a three-layer randomly heterogenous model with both intrinsic and extrinsic (scattering) attenuation demonstrate that cross-talk is a significant problem in attenuation inversion. Using the same model, we further show that cross-talk can be suppressed by varying the attenuation scaling term in our pre-conditioning operator. This strategy is effective for simultaneous inversion of velocity and attenuation, and for sequential inversion (a two-stage approach in which only the velocity models are recovered in the first stage). Further regularization using a smoothing term applied to the attenuation parameters is also effective in reducing cross-talk, which is often highly oscillatory. The sequential inversion approach restricts the search space for attenuation parameters, and appears to be important in retrieving a reliable attenuation model when strong time-damping is applied. In a final test with our synthetic model, we successfully carry out visco-acoustic inversions of noise-contaminated data.
Kinematic analysis of the ARID manipulator
NASA Technical Reports Server (NTRS)
Doty, Keith L
1992-01-01
The kinematic structure of the ARID manipulator lends itself to simple forward and inverse kinematics analysis. The purpose of this paper is to fully document and verify an existing analysis. The symbolic software package MATHEMATICA was used to produce and verify the equations presented here. In the analysis to follow, the standard Devenit-Hartenberg kinematic parameters of the ARID were employed.
Semistable modifications of families of curves and compactified Jacobians
NASA Astrophysics Data System (ADS)
Esteves, Eduardo; Pacini, Marco
2015-07-01
Given a family of nodal curves, a semistable modification of it is another family made up of curves obtained by inserting chains of rational curves of any given length at certain nodes of certain curves of the original family. We give comparison theorems between torsion-free, rank-1 sheaves in the former family and invertible sheaves in the latter. We apply them to show that there are functorial isomorphisms between the compactifications of relative Jacobians of families of nodal curves constructed through Caporaso's approach and those constructed through Pandharipande's approach.
Endomorphism rings of certain Jacobians in finite characteristic
NASA Astrophysics Data System (ADS)
Zarkhin, Yu G.
2002-08-01
We prove that, under certain additional assumptions, the endomorphism ring of the Jacobian of a curve y^\\ell=f(x) contains a maximal commutative subring isomorphic to the ring of algebraic integers of the \\ellth cyclotomic field. Here \\ell is an odd prime dividing the degree n of the polynomial f and different from the characteristic of the algebraically closed ground field; moreover, n\\geqslant 9. The additional assumptions stipulate that all coefficients of f lie in some subfield K over which its (the polynomial's) Galois group coincides with either the full symmetric group S_n or with the alternating group A_n.
Luanjing Guo; Hai Huang; Derek Gaston; Cody Permann; David Andrs; George Redden; Chuan Lu; Don Fox; Yoshiko Fujita
2013-03-01
Modeling large multicomponent reactive transport systems in porous media is particularly challenging when the governing partial differential algebraic equations (PDAEs) are highly nonlinear and tightly coupled due to complex nonlinear reactions and strong solution-media interactions. Here we present a preconditioned Jacobian-Free Newton-Krylov (JFNK) solution approach to solve the governing PDAEs in a fully coupled and fully implicit manner. A well-known advantage of the JFNK method is that it does not require explicitly computing and storing the Jacobian matrix during Newton nonlinear iterations. Our approach further enhances the JFNK method by utilizing physics-based, block preconditioning and a multigrid algorithm for efficient inversion of the preconditioner. This preconditioning strategy accounts for self- and optionally, cross-coupling between primary variables using diagonal and off-diagonal blocks of an approximate Jacobian, respectively. Numerical results are presented demonstrating the efficiency and massive scalability of the solution strategy for reactive transport problems involving strong solution-mineral interactions and fast kinetics. We found that the physics-based, block preconditioner significantly decreases the number of linear iterations, directly reducing computational cost; and the strongly scalable algebraic multigrid algorithm for approximate inversion of the preconditioner leads to excellent parallel scaling performance.
Margerin, V; Lotay, G; Woods, P J; Aliotta, M; Christian, G; Davids, B; Davinson, T; Doherty, D T; Fallis, J; Howell, D; Kirsebom, O S; Mountford, D J; Rojas, A; Ruiz, C; Tostevin, J A
2015-08-01
In Wolf-Rayet and asymptotic giant branch (AGB) stars, the (26g)Al(p,Îł)(27)Si reaction is expected to govern the destruction of the cosmic Îł-ray emitting nucleus (26)Al. The rate of this reaction, however, is highly uncertain due to the unknown properties of key resonances in the temperature regime of hydrogen burning. We present a high-resolution inverse kinematic study of the (26g)Al(d,p)(27)Al reaction as a method for constraining the strengths of key astrophysical resonances in the (26g)Al(p,Îł)(27)Si reaction. In particular, the results indicate that the resonance at E(r)=127â€‰â€‰keV in (27)Si determines the entire (26g)Al(p,Îł)(27)Si reaction rate over almost the complete temperature range of Wolf-Rayet stars and AGB stars. PMID:26296114
NASA Astrophysics Data System (ADS)
Yue, Han; Lay, Thorne; Li, Linyan; Yamazaki, Yoshiki; Cheung, Kwok Fai; Rivera, Luis; Hill, Emma M.; Sieh, Kerry; Kongko, Widjo; Muhari, Abdul
2015-03-01
Tsunami observations have particular importance for resolving shallow offshore slip in finite-fault rupture model inversions for large subduction zone earthquakes. However, validations of amplitude linearity and choice of subfault discretization of tsunami Green's functions are essential when inverting tsunami waveforms. We explore such validations using four tsunami recordings of the 25 October 2010 Mentawai Mw 7.8 tsunami earthquake, jointly inverted with teleseismic body waves and 1 Hz GPS (high-rate GPS) observations. The tsunami observations include near-field and far-field deep water recordings, as well as coastal and island tide gauge recordings. A nonlinear, dispersive modeling code, NEOWAVE, is used to construct tsunami Green's functions from seafloor excitation for the linear inversions, along with performing full-scale calculations of the tsunami for the inverted models. We explore linearity and finiteness effects with respect to slip magnitude, variable rake determination, and subfault dimensions. The linearity assumption is generally robust for the deep water recordings, and wave dispersion from seafloor excitation is important for accurate description of near-field Green's functions. Breakdown of linearity produces substantial misfits for short-wavelength signals in tide gauge recordings with large wave heights. Including the tsunami observations in joint inversions provides improved resolution of near-trench slip compared with inversions of only seismic and geodetic data. Two rupture models, with fine-grid (15 km) and coarse-grid (30 km) spacing, are inverted for the Mentawai event. Stronger regularization is required for the fine model representation. Both models indicate a shallow concentration of large slip near the trench with peak slip of ~15 m. Fully nonlinear forward modeling of tsunami waveforms confirms the validity of these two models for matching the tsunami recordings along with the other data.
Luanjing Guo; Chuan Lu; Hai Huang; Derek R. Gaston
2012-06-01
Systems of multicomponent reactive transport in porous media that are large, highly nonlinear, and tightly coupled due to complex nonlinear reactions and strong solution-media interactions are often described by a system of coupled nonlinear partial differential algebraic equations (PDAEs). A preconditioned Jacobian-Free Newton-Krylov (JFNK) solution approach is applied to solve the PDAEs in a fully coupled, fully implicit manner. The advantage of the JFNK method is that it avoids explicitly computing and storing the Jacobian matrix during Newton nonlinear iterations for computational efficiency considerations. This solution approach is also enhanced by physics-based blocking preconditioning and multigrid algorithm for efficient inversion of preconditioners. Based on the solution approach, we have developed a reactive transport simulator named RAT. Numerical results are presented to demonstrate the efficiency and massive scalability of the simulator for reactive transport problems involving strong solution-mineral interactions and fast kinetics. It has been applied to study the highly nonlinearly coupled reactive transport system of a promising in situ environmental remediation that involves urea hydrolysis and calcium carbonate precipitation.
Low-rank Quasi-Newton updates for Robust Jacobian lagging in Newton methods
Brown, J.; Brune, P.
2013-07-01
Newton-Krylov methods are standard tools for solving nonlinear problems. A common approach is to 'lag' the Jacobian when assembly or preconditioner setup is computationally expensive, in exchange for some degradation in the convergence rate and robustness. We show that this degradation may be partially mitigated by using the lagged Jacobian as an initial operator in a quasi-Newton method, which applies unassembled low-rank updates to the Jacobian until the next full reassembly. We demonstrate the effectiveness of this technique on problems in glaciology and elasticity. (authors)
Solving Nonlinear Solid Mechanics Problems with the Jacobian-Free Newton Krylov Method
J. D. Hales; S. R. Novascone; R. L. Williamson; D. R. Gaston; M. R. Tonks
2012-06-01
The solution of the equations governing solid mechanics is often obtained via Newton's method. This approach can be problematic if the determination, storage, or solution cost associated with the Jacobian is high. These challenges are magnified for multiphysics applications with many coupled variables. Jacobian-free Newton-Krylov (JFNK) methods avoid many of the difficulties associated with the Jacobian by using a finite difference approximation. BISON is a parallel, object-oriented, nonlinear solid mechanics and multiphysics application that leverages JFNK methods. We overview JFNK, outline the capabilities of BISON, and demonstrate the effectiveness of JFNK for solid mechanics and solid mechanics coupled to other PDEs using a series of demonstration problems.
Bonnet, Vincent; Mazzŕ, Claudia; Fraisse, Philippe; Cappozzo, Aurelio
2013-07-01
This study aimed at the real-time estimation of the lower-limb joint and torso kinematics during a squat exercise, performed in the sagittal plane, using a single inertial measurement unit placed on the lower back. The human body was modeled with a 3-DOF planar chain. The planar IMU orientation and vertical displacement were estimated using one angular velocity and two acceleration components and a weighted Fourier linear combiner. The ankle, knee, and hip joint angles were thereafter obtained through a novel inverse kinematic module based on the use of a Jacobian pseudoinverse matrix and null-space decoupling. The aforementioned algorithms were validated on a humanoid robot for which the mechanical model used and the measured joint angles virtually exhibited no inaccuracies. Joint angles were estimated with a maximal error of 1.5°. The performance of the proposed analytical and experimental methodology was also assessed by conducting an experiment on human volunteers and by comparing the relevant results with those obtained through the more conventional photogrammetric approach. The joint angles provided by the two methods displayed differences equal to 3±1°. These results, associated with the real-time capability of the method, open the door to future field applications in both rehabilitation and sport. PMID:23392337
NASA Astrophysics Data System (ADS)
Hoffmann, V.-E.; Dunkl, I.; von Eynatten, H.; Jähne, F.; Voigt, T.; Kley, J.
2009-04-01
During the Late Cretaceous to Early Tertiary some parts of the Central European Basin System (CEBS) were uplifted along NW-SE to WNW-ESE striking compressive fault systems. As a result Pre-Zechstein (Permian) basement is exposed at the southern border of the CEBS from Central Germany to the sudetes still further east (e.g. Harz Mountains, Thuringian Forest). Thrust-related basins like the Subhercynian Cretaceous Basin (SCB) in the foreland of the Harz Mountains accumulated up to 2500m of siliciclastic and chemical sediments in only 10 million years (Late Turonian to Lower Campanian, Voigt et al., 2006). By means of low-temperature thermochronology it is possible to characterise these basin inversion processes with respect to timing, pattern and rates of cooling and exhumation. Differed authors have already applied Apatite Fission Track analysis (AFT) in certain areas of the southern margin of CEBS. Thomson and Zeh (2000) published AFT apparent ages of 69 to 81 Ma for the Ruhla Crystalline Complex in the Thuringian Forest. Similar AFT-ages (73-84 Ma) of granitoids from the Harz Mountains were reported by Thomson et al. (1997). The late Carboniferous felsic volcanic rocks near Halle yield a much broader range of AFT apparent ages (75-108 Ma; Jacobs and Breitkreuz, 2003). Comparable AFT-ages (84-90 Ma) had been also observed for gabbros from the north-eastern part of the Mid German Crystalline High (Ventura et al. 2003). The present study tries to bridge some of the major gaps in the regional distribution of thermochronological data by analysing samples from central and southern parts of the CEBS. Overall almost 50 AFT-ages from Saxony-Anhalt, Lower Saxony, Thuringia, Hesse and North Rhine-Westphalia were measured. Emphasis is placed on the regions from the Harz Mountains to the Rhenish Uplands and the Thuringian Forest and its foreland. Furthermore, apatite (U-Th)/He thermochronology is used to better constrain the time-temperature history models. Apart from some mixed age information two different age groups can be recognized. A major group that is similar to the one reported above points to a short but intense pulse of exhumation and inversion in Coniacian to Campanian time. A younger, less significant age cluster yields information on a second phase of cooling and exhumation in the Paleocene-Eocene. The length distribution of AFT data leads to the assumption of rapid, partially multi-phase, exhumation events. In addition, the data of this study provides indications for thick Jurassic burial that likely reflect phases of Mesozoic extensional tectonics in at least parts of the CEBS. Jacobs, J., Breitkreuz, C. (2003): Zircon and apatite fission-track thermochronology of Late Carboniferous volcanic rocks of the NE German Basin. International Journal of Earth Sciences (Geologische Rundschau), 92, 165-172. Thomson, S., Brix, M., Carter, A. (1997): Late Cretaceous denudation of the Harz Massif assessed by apatite fission track analysis. In: G. Büchel and H. Lützner (Editors), Regionale Geologie von Mitteleuropa, 149. Hauptversammlung Deutsche Geologische Gesellschaft, Jena. Schriftenreihe der Deutschen Geologischen Gesellschaft, 3, 115. Thomson, S.N., Zeh, A. (2000): Fission-track thermochronology of the Ruhla Crystalline Complex:. New constraints on the post-Variscan thermal evolution of the NW Saxo-Bohemian Massif. Tectonophysics, 324, 17-35. Ventura, B., Lisker, F., Kopp, J. (2003): Apatite fission track data from the dill-core Züllsdorf 1/63: implications for the reconstruction of the post Variscan exhumation of the Mid German Crystalline High. Zeitschrift für Geologische Wissenschaften, 31, 251-261. Voigt, T., Wiese, F., von Eynatten, H., Franzke, H.-J. & Gaupp, R. (2006): Facies evolution of syntectonic Upper Cretaceous deposits in the Subhercynian Cretaceous Basin and adjoining areas (Germany). Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 157/2, 203-244.
Prejean, S.; Ellsworth, W.; Zoback, M.; Waldhauser, F.
2002-01-01
We have determined high-resolution hypocenters for 45,000+ earthquakes that occurred between 1980 and 2000 in the Long Valley caldera area using a double-difference earthquake location algorithm and routinely determined arrival times. The locations reveal numerous discrete fault planes in the southern caldera and adjacent Sierra Nevada block (SNB). Intracaldera faults include a series of east/west-striking right-lateral strike-slip faults beneath the caldera's south moat and a series of more northerly striking strike-slip/normal faults beneath the caldera's resurgent dome. Seismicity in the SNB south of the caldera is confined to a crustal block bounded on the west by an east-dipping oblique normal fault and on the east by the Hilton Creek fault. Two NE-striking left-lateral strike-slip faults are responsible for most seismicity within this block. To understand better the stresses driving seismicity, we performed stress inversions using focal mechanisms with 50 or more first motions. This analysis reveals that the least principal stress direction systematically rotates across the studied region, from NE to SW in the caldera's south moat to WNW-ESE in Round Valley, 25 km to the SE. Because WNW-ESE extension is characteristic of the western boundary of the Basin and Range province, caldera area stresses appear to be locally perturbed. This stress perturbation does not seem to result from magma chamber inflation but may be related to the significant (???20 km) left step in the locus of extension along the Sierra Nevada/Basin and Range province boundary. This implies that regional-scale tectonic processes are driving seismic deformation in the Long Valley caldera.
Shotput kinematics made simple
NASA Astrophysics Data System (ADS)
Faella, O.; De Luca, R.
2013-11-01
We show that some results in the kinematics of a point particle can be easily recalled by introducing simple definitions. In particular, in the parabolic motion of a particle thrown from a height h above the origin O at an angle ? from the horizontal direction, the optimum angle ?* for reaching the maximum distance Rmax on the ground, measured from the origin, can be found by calculating the inverse tangent of the ratio between the initial velocity V0 and the final velocity Vf. The value of Rmax is itself found to be easily expressed as V0Vf/g, g being the acceleration due to gravity.
Study of the Jacobian of an Extended Kalman Filter for soil analysis in SURFEXv5
NASA Astrophysics Data System (ADS)
Duerinckx, A.; Hamdi, R.; Mahfouf, J.-F.; Termonia, P.
2014-10-01
An externalised surface scheme like SURFEX allows computationally cheap offline runs. This is a major advantage for surface assimilation techniques such as the Extended Kalman Filter (EKF), where the offline runs allow a cheaper numerical estimation of the observation operator Jacobian. In the recent past an EKF has been developped within SURFEX for the initialisation of soil water content and soil temperature based on screen-level temperature and relative humidity observations. In this paper we make a comparison of the Jacobian calculated with offline SURFEX runs and with runs coupled to the atmospheric ALARO model. Comparisons are made with respect to spatial structure and average value of the Jacobian, gain values and increments. We determine the optimal perturbation size of the Jacobian for the offline and coupled approaches and compare the linearity of the Jacobian for these cases. Results show that the offline Jacobian approach gives similar results as the coupled approach and it allows for smaller perturbation sizes that better approximate this linearity assumption. We document a new case of non-linearities that can hamper this linearity assumption and cause spurious 2?t oscillations in small parts of the domain for the coupled as well as the offline runs. While these oscillations do not have a detrimental effect on the model run, they can introduce some noise in the Jacobian in the affected locations. The oscillations influence both the surface fluxes and the screen-level variables. The oscillations occur in the late afternoon in summer when a stable boundary layer starts to form near the surface. We propose a filter to remove the oscillations and show that this filter works accordingly.
Study of the Jacobian of an extended Kalman filter for soil analysis in SURFEXv5
NASA Astrophysics Data System (ADS)
Duerinckx, A.; Hamdi, R.; Mahfouf, J.-F.; Termonia, P.
2015-03-01
An externalised surface scheme like SURFEX allows computationally cheap offline runs. This is a major advantage for surface assimilation techniques such as the extended Kalman filter (EKF), where the offline runs allow a cheaper numerical estimation of the observation operator Jacobian. In the recent past an EKF has been developed within SURFEX for the initialisation of soil water content and soil temperature based on screen-level temperature and relative humidity observations. In this paper we make a comparison of the Jacobian calculated with offline SURFEX runs and with runs coupled to the atmospheric ALARO model. Comparisons are made with respect to spatial structure and average value of the Jacobian, gain values and increments. We determine the optimal perturbation size of the Jacobian for the offline and coupled approaches and compare the linearity of the Jacobian for these cases. Results show that the offline Jacobian approach gives similar results to the coupled approach and that it allows for smaller perturbation sizes that better approximate this linearity assumption. We document a new case of non-linearities that can hamper this linearity assumption and cause spurious 2? t oscillations in small parts of the domain for the coupled as well as offline runs. While these oscillations do not have a detrimental effect on the model run, they can introduce some noise in the Jacobian at the affected locations. The oscillations influence both the surface fluxes and the screen-level variables. The oscillations occur in the late afternoon in summer when a stable boundary layer starts to form near the surface. We propose a filter to remove the oscillations and show that this filter works accordingly.
Hicks, H.R.; Dory, R.A.; Holmes, J.A.
1983-01-01
We illustrate in some detail a 2D inverse-equilibrium solver that was constructed to analyze tokamak configurations and stellarators (the latter in the context of the average method). To ensure that the method is suitable not only to determine equilibria, but also to provide appropriately represented data for existing stability codes, it is important to be able to control the Jacobian, tilde J is identical to delta(R,Z)/delta(rho, theta). The form chosen is tilde J = J/sub 0/(rho)R/sup l/rho where rho is a flux surface label, and l is an integer. The initial implementation is for a fixed conducting-wall boundary, but the technique can be extended to a free-boundary model.
Kinematics and control of redundant robotic arm based on dielectric elastomer actuators
NASA Astrophysics Data System (ADS)
Branz, Francesco; Antonello, Andrea; Carron, Andrea; Carli, Ruggero; Francesconi, Alessandro
2015-04-01
Soft robotics is a promising field and its application to space mechanisms could represent a breakthrough in space technologies by enabling new operative scenarios (e.g. soft manipulators, capture systems). Dielectric Elastomers Actuators have been under deep study for a number of years and have shown several advantages that could be of key importance for space applications. Among such advantages the most notable are high conversion efficiency, distributed actuation, self-sensing capability, multi-degree-of-freedom design, light weight and low cost. The big potentialities of double cone actuators have been proven in terms of good performances (i.e. stroke and force/torque), ease of manufacturing and durability. In this work the kinematic, dynamic and control design of a two-joint redundant robotic arm is presented. Two double cone actuators are assembled in series to form a two-link design. Each joint has two degrees of freedom (one rotational and one translational) for a total of four. The arm is designed to move in a 2-D environment (i.e. the horizontal plane) with 4 DoF, consequently having two degrees of redundancy. The redundancy is exploited in order to minimize the joint loads. The kinematic design with redundant Jacobian inversion is presented. The selected control algorithm is described along with the results of a number of dynamic simulations that have been executed for performance verification. Finally, an experimental setup is presented based on a flexible structure that counteracts gravity during testing in order to better emulate future zero-gravity applications.
Using ADIFOR and ADIC to provide Jacobians for the SNES component of PETSc
Wu, Po-Ting; Bischof, C.H.; Hovland, P.D.
1997-11-01
The solution of large-scale nonlinear problems is important to many areas of computational science. The SNES component of PETSc provides a robust and flexible suite of numerical routines for the solving such problems. These routines generally utilize the Jacobian matrix. We present a strategy for using ADIFOR or ADIC to assist in the development of a subroutine for computing this matrix. We illustrate this strategy using one of the PETSc example programs and four different approaches to computing the Jacobian via automatic differentiation.
Kinematic functions for the 7 DOF robotics research arm
NASA Technical Reports Server (NTRS)
Kreutz, K.; Long, M.; Seraji, Homayoun
1989-01-01
The Robotics Research Model K-1207 manipulator is a redundant 7R serial link arm with offsets at all joints. To uniquely determine joint angles for a given end-effector configuration, the redundancy is parameterized by a scalar variable which corresponds to the angle between the manipulator elbow plane and the vertical plane. The forward kinematic mappings from joint-space to end-effector configuration and elbow angle, and the augmented Jacobian matrix which gives end-effector and elbow angle rates as a function of joint rates, are also derived.
Flux Jacobian matrices and generaled Roe average for an equilibrium real gas
NASA Technical Reports Server (NTRS)
Vinokur, Marcel
1988-01-01
Inviscid flux Jacobian matrices and their properties used in numerical solutions of conservation laws are extended to general, equilibrium gas laws. Exact and approximate generalizations of the Roe average are presented. Results are given for one-dimensional flow, and then extended to three-dimensional flow with time-varying grids.
Fully-implicit Jacobian-free Newton-Krylov Solvers for the nonhydrostatic Euler equations
NASA Astrophysics Data System (ADS)
Kelly, J. F.; Giraldo, F.; Carr, L.
2009-12-01
For most atmospheric flows, gravity and acoustic waves are the fastest waves in the system. These fast waves severely restrict the time-step in the explicit integration of the non-hydrostatic compressible Euler equations. To circumvent this problem, a fully-implicit time-integrator is proposed using the Jacobian-Free Newton Krylov (JFNK) framework. Since forming and storing the Jacobian matrix is computationally expensive, JFNK methods form the action of the Jacobian matrix on a vector. This matrix-vector computation naturally extends the semi-implicit element-based continuous Galerkin paradigm wherein a system of linear equation is solved at each time-step using a Krylov-subspace solver. The JFNK integrator is implemented for the nonhydrostatic, compressible Euler equations in non-conservative form using spectral elements and compared to pervious explicit and semi-implicit codes. Since the resulting Jacobian is poorly conditioned, a block Jacobi preconditioner is developed and implemented, resulting in a significant reduction in the number of Krylov iterations. Numerical results are reported for several test cases, including 1) a rising thermal bubble and 2) flow over hydrostatic and non-hydrostatic mountains.
Jacobian matrix algorithm for Lyapunov exponents of the discrete fractional maps
NASA Astrophysics Data System (ADS)
Wu, Guo-Cheng; Baleanu, Dumitru
2015-05-01
The Jacobian matrix algorithm is often used to calculate the Lyapunov exponents of the chaotic systems. This study extends the algorithm to discrete fractional cases. The tangent maps with memory effect are presented. The Lyapunov exponents of one and two dimensional fractional logistic maps are calculated. The positive ones are used to distinguish the chaotic areas of the maps.
Simulating avian wingbeat kinematics.
Parslew, Ben; Crowther, William J
2010-12-01
Inverse dynamics methods are used to simulate avian wingbeats in varying flight conditions. A geometrically scalable multi-segment bird model is constructed, and optimisation techniques are employed to determine segment motions that generate desired aerodynamic force coefficients with minimal mechanical power output. The results show that wingbeat kinematics vary gradually with changes in cruise speed, which is consistent with experimental data. Optimised solutions for cruising flight of the pigeon suggest that upstroke wing retraction is used as a method of saving energy. Analysis of the aerodynamic force coefficient variation in high and low speed cruise leads to the proposal that a suitable gait metric should include both thrust and lift generation during each half-stroke. PMID:20732684
Magnetotelluric inversion via reverse time migration algorithm of seismic data
Ha, Taeyoung . E-mail: tyha@math.snu.ac.kr; Shin, Changsoo . E-mail: css@model.snu.ac.kr
2007-07-01
We propose a new algorithm for two-dimensional magnetotelluric (MT) inversion. Our algorithm is an MT inversion based on the steepest descent method, borrowed from the backpropagation technique of seismic inversion or reverse time migration, introduced in the middle 1980s by Lailly and Tarantola. The steepest descent direction can be calculated efficiently by using the symmetry of numerical Green's function derived from a mixed finite element method proposed by Nedelec for Maxwell's equation, without calculating the Jacobian matrix explicitly. We construct three different objective functions by taking the logarithm of the complex apparent resistivity as introduced in the recent waveform inversion algorithm by Shin and Min. These objective functions can be naturally separated into amplitude inversion, phase inversion and simultaneous inversion. We demonstrate our algorithm by showing three inversion results for synthetic data.
Fault tolerant kinematic control of hyper-redundant manipulators
NASA Technical Reports Server (NTRS)
Bedrossian, Nazareth S.
1994-01-01
Hyper-redundant spatial manipulators possess fault-tolerant features because of their redundant structure. The kinematic control of these manipulators is investigated with special emphasis on fault-tolerant control. The manipulator tasks are viewed in the end-effector space while actuator commands are in joint-space, requiring an inverse kinematic algorithm to generate joint-angle commands from the end-effector ones. The rate-inverse kinematic control algorithm presented in this paper utilizes the pseudoinverse to accommodate for joint motor failures. An optimal scale factor for the robust inverse is derived.
A Constrained Multibody System Dynamics Avoiding Kinematic Singularities
NASA Astrophysics Data System (ADS)
Huang, Chih-Fang; Yan, Chang-Dau; Jeng, Shyr-Long; Cheing, Wei-Hua
In the analysis of constrained multibody systems, the constraint reaction forces are normally expressed in terms of the constraint equations and a vector of Lagrange multipliers. Because it fails to incorporate conservation of momentum, the Lagrange multiplier method is deficient when the constraint Jacobian matrix is singular. This paper presents an improved dynamic formulation for the constrained multibody system. In our formulation, the kinematic constraints are still formulated in terms of the joint constraint reaction forces and moments; however, the formulations are based on a second-order Taylor expansion so as to incorporate the rigid body velocities. Conservation of momentum is included explicitly in this method; hence the problems caused by kinematic singularities can be avoided. In addition, the dynamic formulation is general and applicable to most dynamic analyses. Finally the 3-leg Stewart platform is used for the example of analysis.
Modal kinematics for multisection continuum arms.
Godage, Isuru S; Medrano-Cerda, Gustavo A; Branson, David T; Guglielmino, Emanuele; Caldwell, Darwin G
2015-06-01
This paper presents a novel spatial kinematic model for multisection continuum arms based on mode shape functions (MSF). Modal methods have been used in many disciplines from finite element methods to structural analysis to approximate complex and nonlinear parametric variations with simple mathematical functions. Given certain constraints and required accuracy, this helps to simplify complex phenomena with numerically efficient implementations leading to fast computations. A successful application of the modal approximation techniques to develop a new modal kinematic model for general variable length multisection continuum arms is discussed. The proposed method solves the limitations associated with previous models and introduces a new approach for readily deriving exact, singularity-free and unique MSF's that simplifies the approach and avoids mode switching. The model is able to simulate spatial bending as well as straight arm motions (i.e., pure elongation/contraction), and introduces inverse position and orientation kinematics for multisection continuum arms. A kinematic decoupling feature, splitting position and orientation inverse kinematics is introduced. This type of decoupling has not been presented for these types of robotic arms before. The model also carefully accounts for physical constraints in the joint space to provide enhanced insight into practical mechanics and impose actuator mechanical limitations onto the kinematics thus generating fully realizable results. The proposed method is easily applicable to a broad spectrum of continuum arm designs. PMID:25969947
Multiscale modeling of polycrystalline materials with Jacobian-free multiscale method (JFMM)
NASA Astrophysics Data System (ADS)
Rahul; De, Suvranu
2015-04-01
The non-linear constitutive response of polycrystalline aggregate of single crystal grains is obtained using a micro-macro transition scheme, which is realized within a Jacobian-free multiscale method (JFMM). The Jacobian-free approach circumvents computation of the tangent matrix at the macroscale using a Newton-Krylov process. This has a major advantage in terms of storage requirements and computational cost over existing approaches based on homogenized material coefficients, which may require considerable effort to form the exact Jacobian at every Newton step. The rate-independent constitutive response of polycrystalline copper and rate-dependent stress-strain response of -RDX (cyclotrimethylene trinitramine) polycrystal is verified against the computational homogenization based two-level finite element multiscale method. Numerical examples demonstrate that while the rate of convergence of Newton iterations for the JFMM and method is comparable, the computational cost of JFMM is nearly constant as opposed to exponential increase for the latter with increasing number of degrees of freedom at the macroscale. The storage requirement for the JFMM increases linearly with increasing , whereas, it increases as approximately for the method.
Principal Component Geostatistical Approach for large-dimensional inverse problems
Kitanidis, P K; Lee, J
2014-01-01
The quasi-linear geostatistical approach is for weakly nonlinear underdetermined inverse problems, such as Hydraulic Tomography and Electrical Resistivity Tomography. It provides best estimates as well as measures for uncertainty quantification. However, for its textbook implementation, the approach involves iterations, to reach an optimum, and requires the determination of the Jacobian matrix, i.e., the derivative of the observation function with respect to the unknown. Although there are elegant methods for the determination of the Jacobian, the cost is high when the number of unknowns, m, and the number of observations, n, is high. It is also wasteful to compute the Jacobian for points away from the optimum. Irrespective of the issue of computing derivatives, the computational cost of implementing the method is generally of the order of m2n, though there are methods to reduce the computational cost. In this work, we present an implementation that utilizes a matrix free in terms of the Jacobian matrix Gauss-Newton method and improves the scalability of the geostatistical inverse problem. For each iteration, it is required to perform K runs of the forward problem, where K is not just much smaller than m but can be smaller that n. The computational and storage cost of implementation of the inverse procedure scales roughly linearly with m instead of m2 as in the textbook approach. For problems of very large m, this implementation constitutes a dramatic reduction in computational cost compared to the textbook approach. Results illustrate the validity of the approach and provide insight in the conditions under which this method perform best. PMID:25558113
Principal Component Geostatistical Approach for large-dimensional inverse problems
NASA Astrophysics Data System (ADS)
Kitanidis, P. K.; Lee, J.
2014-07-01
The quasi-linear geostatistical approach is for weakly nonlinear underdetermined inverse problems, such as Hydraulic Tomography and Electrical Resistivity Tomography. It provides best estimates as well as measures for uncertainty quantification. However, for its textbook implementation, the approach involves iterations, to reach an optimum, and requires the determination of the Jacobian matrix, i.e., the derivative of the observation function with respect to the unknown. Although there are elegant methods for the determination of the Jacobian, the cost is high when the number of unknowns, m, and the number of observations, n, is high. It is also wasteful to compute the Jacobian for points away from the optimum. Irrespective of the issue of computing derivatives, the computational cost of implementing the method is generally of the order of m2n, though there are methods to reduce the computational cost. In this work, we present an implementation that utilizes a matrix free in terms of the Jacobian matrix Gauss-Newton method and improves the scalability of the geostatistical inverse problem. For each iteration, it is required to perform K runs of the forward problem, where K is not just much smaller than m but can be smaller that n. The computational and storage cost of implementation of the inverse procedure scales roughly linearly with m instead of m2 as in the textbook approach. For problems of very large m, this implementation constitutes a dramatic reduction in computational cost compared to the textbook approach. Results illustrate the validity of the approach and provide insight in the conditions under which this method perform best.
Exact Jacobians in an implicit Newton method for two-phase flow in porous media
NASA Astrophysics Data System (ADS)
BĂĽsing, H.; Clauser, C.
2012-04-01
Geological storage of CO2 is one option for mitigating the effects of CO2 emissions on global warming. Since extensive on-site monitoring of the CO2 plume propagation is expensive, numerical simulations are an attractive alternative for gaining deeper insight in the dynamics of this system. We consider a model for two-phase flow in porous media for representing the injection stage of a CO2 sequestration scenario, when the plume propagation is dominated by advection. The porous medium filled by the two phases CO2 and brine is modelled as an initial-boundary-value problem consisting of two nonlinear, coupled partial differential equations, which are complemented by appropriate boundary and initial conditions. We present a new numerical approach to solve this fully coupled system using exact Jacobians. The method is based on the finite element, finite volume, box method [Huber & Helmig(2000)] for the space discretization and, since stability of the method is one of the main concerns, the fully implicit Euler method for the time discretization. A simple first order upwind method takes into account advective contributions. The resulting system of nonlinear algebraic equations is linearized by Newton's method. The required Jacobians can be obtained elegantly by automatic differentiation (AD) [Griewank & Walther(2008), Rall(1981)], a source code transformation giving exact derivatives of the discretized equations with respect to primary variables. The resulting system of linear equations is then solved by an iterative method (BiCGStab) with ILU0 preconditioning in every Newton step. We compare the forward AD differentiation mode to the standard finite difference method in terms of precision and performance. It turns out that AD performs favourable in both aspects. We also illustrate the advantages of exact Jacobians for two-phase flow in a sequestration scenario investigating the evolution of pressure and saturation.
Marchesseau, Stéphanie; Heimann, Tobias; Chatelin, Simon; Willinger, Rémy; Delingette, Hervé
2010-01-01
Simulating soft tissues in real time is a significant challenge since a compromise between biomechanical accuracy and computational efficiency must be found. In this paper, we propose a new discretization method, the Multiplicative Jacobian Energy Decomposition (MJED) which is an alternative to the classical Galerkin FEM (Finite Element Method) formulation. This method for discretizing non-linear hyperelastic materials on linear tetrahedral meshes leads to faster stiffness matrix assembly for a large variety of isotropic and anisotropic materials. We show that our new approach, implemented within an implicit time integration scheme, can lead to fast and realistic liver deformations including hyperelasticity, porosity and viscosity. PMID:20879236
Employment of Jacobian elliptic functions for solving problems in nonlinear dynamics of microtubules
NASA Astrophysics Data System (ADS)
Slobodan, Zekovi?; Annamalai, Muniyappan; Slobodan, Zdravkovi?; Louis, Kavitha
2014-02-01
We show how Jacobian elliptic functions (JEFs) can be used to solve ordinary differential equations (ODEs) describing the nonlinear dynamics of microtubules (MTs). We demonstrate that only one of the JEFs can be used while the remaining two do not represent the solutions of the crucial differential equation. We show that a kink-type soliton moves along MTs. Besides this solution, we also discuss a few more solutions that may or may not have physical meanings. Finally, we show what kind of ODE can be solved by using JEFs.
Acceleration of k-Eigenvalue / Criticality Calculations using the Jacobian-Free Newton-Krylov Method
Dana Knoll; HyeongKae Park; Chris Newman
2011-02-01
We present a new approach for the $k$--eigenvalue problem using a combination of classical power iteration and the Jacobian--free Newton--Krylov method (JFNK). The method poses the $k$--eigenvalue problem as a fully coupled nonlinear system, which is solved by JFNK with an effective block preconditioning consisting of the power iteration and algebraic multigrid. We demonstrate effectiveness and algorithmic scalability of the method on a 1-D, one group problem and two 2-D two group problems and provide comparison to other efforts using silmilar algorithmic approaches.
NASA Astrophysics Data System (ADS)
Hammond, G. E.; Valocchi, A. J.; Lichtner, P. C.
2005-04-01
Modern multicomponent geochemical transport models require the use of parallel computation for carrying out three-dimensional, field-scale simulations due to extreme memory and processing demands. However, to fully exploit the advanced computational power provided by today's supercomputers, innovative parallel algorithms are needed. We demonstrate the use of Jacobian-free Newton-Krylov (JFNK) within the Newton-Raphson method to reduce memory and processing requirements on high-performance computers. We also demonstrate the use of physics-based preconditioners, which are often necessary when using JFNK since no explicit Jacobian matrix is ever formed. We apply JFNK to simulate enhanced in situ bioremediation of a NAPL source zone, which entails highly coupled geochemical and biodegradation reactions. The algorithm's performance is evaluated and compared with conventional solvers and preconditioners. We found that JFNK provided substantial saving in memory (i.e. 30-60%) on problems utilizing up to 512 processors on LANL's ASCI Q. However, the performance based on wallclock time was less advantageous, coming out on par with conventional techniques. In addition, we illustrate deficiencies in physics-based preconditioner performance for biogeochemical transport problems with components that undergo significant sorption or form a local quasi-stationary state.
Recovery Discontinuous Galerkin Jacobian-Free Newton-Krylov Method for All-Speed Flows
HyeongKae Park; Robert Nourgaliev; Vincent Mousseau; Dana Knoll
2008-07-01
A novel numerical algorithm (rDG-JFNK) for all-speed fluid flows with heat conduction and viscosity is introduced. The rDG-JFNK combines the Discontinuous Galerkin spatial discretization with the implicit Runge-Kutta time integration under the Jacobian-free Newton-Krylov framework. We solve fully-compressible Navier-Stokes equations without operator-splitting of hyperbolic, diffusion and reaction terms, which enables fully-coupled high-order temporal discretization. The stability constraint is removed due to the L-stable Explicit, Singly Diagonal Implicit Runge-Kutta (ESDIRK) scheme. The governing equations are solved in the conservative form, which allows one to accurately compute shock dynamics, as well as low-speed flows. For spatial discretization, we develop a â€śrecoveryâ€ť family of DG, exhibiting nearly-spectral accuracy. To precondition the Krylov-based linear solver (GMRES), we developed an â€śOperator-Splitâ€ť-(OS) Physics Based Preconditioner (PBP), in which we transform/simplify the fully-coupled system to a sequence of segregated scalar problems, each can be solved efficiently with Multigrid method. Each scalar problem is designed to target/cluster eigenvalues of the Jacobian matrix associated with a specific physics.
Jacobian-free Newton-Krylov methods with GPU acceleration for computing nonlinear ship wave patterns
NASA Astrophysics Data System (ADS)
Pethiyagoda, Ravindra; McCue, Scott W.; Moroney, Timothy J.; Back, Julian M.
2014-07-01
The nonlinear problem of steady free-surface flow past a submerged source is considered as a case study for three-dimensional ship wave problems. Of particular interest is the distinctive wedge-shaped wave pattern that forms on the surface of the fluid. By reformulating the governing equations with a standard boundary-integral method, we derive a system of nonlinear algebraic equations that enforce a singular integro-differential equation at each midpoint on a two-dimensional mesh. Our contribution is to solve the system of equations with a Jacobian-free Newton-Krylov method together with a banded preconditioner that is carefully constructed with entries taken from the Jacobian of the linearised problem. Further, we are able to utilise graphics processing unit acceleration to significantly increase the grid refinement and decrease the run-time of our solutions in comparison to schemes that are presently employed in the literature. Our approach provides opportunities to explore the nonlinear features of three-dimensional ship wave patterns, such as the shape of steep waves close to their limiting configuration, in a manner that has been possible in the two-dimensional analogue for some time.
NASA Astrophysics Data System (ADS)
Aires, F.; Prigent, C.; Rossow, W. B.
2004-05-01
Used for regression fitting, neural network (NN) models can be used effectively to represent highly nonlinear, multivariate functions. In this situation, most emphasis has been on estimating the output errors, but almost no attention has been given to errors associated with the internal structure of the NN model. The complex relationships linking the inputs to the outputs inside the network are the essence of the model and assessing their physical meaning makes all the difference between a "black box" model with small output errors and a physically meaningful model that will provide insight on the problem and will have better generalization properties. Such dependency structures can, for example, be described by the NN Jacobians: they indicate the sensitivity of one output with respect to the inputs of the model. Estimating these Jacobians is essential for many other applications as well. We use a new method of uncertainty estimate developed in the work of [2004] to investigate the robustness of the quantities that characterize the NN structure. A regularization strategy based on principal component analysis is proposed to suppress the multicolinearities that are a major concern when analyzing the internal structure of such a model. The theory is applied to the remote sensing application already presented in the work of [2004] and [2004].
Regularity of mappings inverse to Sobolev mappings
Vodop'yanov, Sergei K
2012-10-31
For homeomorphisms {phi}:{Omega}{yields}{Omega}' on Euclidean domains in R{sup n}, n{>=}2, necessary and sufficient conditions ensuring that the inverse mapping belongs to a Sobolev class are investigated. The result obtained is used to describe a new two-index scale of homeomorphisms in some Sobolev class such that their inverses also form a two-index scale of mappings, in another Sobolev class. This scale involves quasiconformal mappings and also homeomorphisms in the Sobolev class W{sup 1}{sub n-1} such that rankD{phi}(x){<=}n-2 almost everywhere on the zero set of the Jacobian det D{phi}(x). Bibliography: 65 titles.
Real time markerless motion tracking using linked kinematic chains
Luck, Jason P. (Arvada, CO); Small, Daniel E. (Albuquerque, NM)
2007-08-14
A markerless method is described for tracking the motion of subjects in a three dimensional environment using a model based on linked kinematic chains. The invention is suitable for tracking robotic, animal or human subjects in real-time using a single computer with inexpensive video equipment, and does not require the use of markers or specialized clothing. A simple model of rigid linked segments is constructed of the subject and tracked using three dimensional volumetric data collected by a multiple camera video imaging system. A physics based method is then used to compute forces to align the model with subsequent volumetric data sets in real-time. The method is able to handle occlusion of segments and accommodates joint limits, velocity constraints, and collision constraints and provides for error recovery. The method further provides for elimination of singularities in Jacobian based calculations, which has been problematic in alternative methods.
Magnetotelluric Inversion in a 2D Anisotropic Environment
NASA Astrophysics Data System (ADS)
Mandolesi, E.; Jones, A. G.
2012-04-01
In recent years several authors have proposed algorithms to perform magnetotelluric (MT) inversion in a 3D environment. The development of high performance computer (hpc) machines allows the solution of these inverse problems in a reasonable time, nevertheless the solution of a 3D problem remains at the present extremely challenging. Moreover it is proofed that any magnitude of anisotropy possibly present in the subsurface conductivity can be modeled by a sufficient dense discretization of a 3D isotropic domain, keeping the recognition of intrinsically anisotropic bulks virtually impossible for a 3D code. These arguments convinced us to develop a 2D inverse code able in assessing anisotropy and running in an affordable time, testing several scenario for the same dataset in the same time in which a 3D inversion code produces its first model. In this work we report results from synthetic tests we performed. MT inverse problem is challenging because of several reasons. It is both highly non-linear, ill-conditioned and suffers of a severe non-uniqueness of the solution, therefore we developed an inversion algorithm based on the classic Levenberg-Marquardt (LM) strategy, minimizing the objective function (?-G-(m)-d)2 ?(m )= ? +?aLa +?sLs in which m is the model, G the forward operator, d the data vector, L* the regularization matrix and ?* the trade-off parameter for respectively anisotropy and structure. Usually LM method is used for medium size problems, mainly because it requires the explicit computation and storage of the Jacobian matrix J and the explicit knowledge of the product JTJ. To compute the Jacobian it has proofed that the electrical reciprocity theorem is a valuable tool, allowing to compute the full Jacobian with the evaluation of one forward problem per station in spite of one forward problem per parameter as usually done with the finite-difference method. Moreover the computation of the forward response can be easily performed in parallel, due the mutual independency of the different spectral components, storing the Jacobian in a distribute machine memory and solving at the same time the problem of the huge memory requirements used to store the product JTJ and speeding up the whole process. We performed tests on the simple synthetic model released with the code from Pek and Santos [2004]: an 84-100 cells grid, grouped in 3 up to 20 blocks sharing the same conductivities. Results proof the capacity of the algorithm in recovering the subsurface structure with good precision, reaching an RMS of the magnitude 10-5 for the 20 block case without the use of regularization. More tests will be presented and results highlighted.
Application of the least-squares inversion method: Fourier series versus waveform inversion
NASA Astrophysics Data System (ADS)
Min, Dong-Joo; Shin, Jungkyun; Shin, Changsoo
2015-11-01
We describe an implicit link between waveform inversion and Fourier series based on inversion methods such as gradient, Gauss-Newton, and full Newton methods. Fourier series have been widely used as a basic concept in studies on seismic data interpretation, and their coefficients are obtained in the classical Fourier analysis. We show that Fourier coefficients can also be obtained by inversion algorithms, and compare the method to seismic waveform inversion algorithms. In that case, Fourier coefficients correspond to model parameters (velocities, density or elastic constants), whereas cosine and sine functions correspond to components of the Jacobian matrix, that is, partial derivative wavefields in seismic inversion. In the classical Fourier analysis, optimal coefficients are determined by the sensitivity of a given function to sine and cosine functions. In the inversion method for Fourier series, Fourier coefficients are obtained by measuring the sensitivity of residuals between given functions and test functions (defined as the sum of weighted cosine and sine functions) to cosine and sine functions. The orthogonal property of cosine and sine functions makes the full or approximate Hessian matrix become a diagonal matrix in the inversion for Fourier series. In seismic waveform inversion, the Hessian matrix may or may not be a diagonal matrix, because partial derivative wavefields correlate with each other to some extent, making them semi-orthogonal. At the high-frequency limits, however, the Hessian matrix can be approximated by either a diagonal matrix or a diagonally-dominant matrix. Since we usually deal with relatively low frequencies in seismic waveform inversion, it is not diagonally dominant and thus it is prohibitively expensive to compute the full or approximate Hessian matrix. By interpreting Fourier series with the inversion algorithms, we note that the Fourier series can be computed at an iteration step using any inversion algorithms such as the gradient, full-Newton, and Gauss-Newton methods similar to waveform inversion.
The endomorphism rings of jacobians of cyclic covers of the projective line
NASA Astrophysics Data System (ADS)
Zarhin, Yuri G.
2004-03-01
Suppose that K is a field of characteristic zero, K_a is its algebraic closure, and that f(x) in K[x] is an irreducible polynomial of degree n ? 5, whose Galois group coincides either with the full symmetric group Sn or with the alternating group An. Let p be an odd prime, Z[zeta_p] the ring of integers in the pth cyclotomic field Q(zeta_p). Suppose that C is the smooth projective model of the affine curve y(p {=} f(x)) and J(C) is the jacobian of C. We prove that the ring End(J(C)) of K_a-endomorphisms of J(C) is canonically isomorphic to Z[zeta_p
Jacobian and stiffness analysis of a novel class of six-DOF parallel minimanipulators
Tashmasebi, F.; Tsai, Lung-Wen
1992-08-01
The Jacobian and stiffness matrices of two types of novel, six-DOF parallel minimanipulators are derived. A minimanipulator consists of three inextensible limbs, each of which is driven by a two-DOF driver. Bilinear stepper motors are used as drivers in the first type minimanipulator, whereas five-bar linkages are used as drivers in the second type minimanipulator. All of the minimanipulator actuators are base-mounted. Inextensible limbs (and five-bar linkage drivers in the second type minimanipulator) improve positional resolution and stiffness of the minimanipulators in certain directions. It is shown that, at the central configuration, the stiffness matrix of the first type minimanipulator can be diagonalized (decoupled). It is also shown that the first type minimanipulator can be designed to possess direct or torsional isotropic stiffness properties. Moreover, guidelines for designing the drivers of the second type minimanipulator are established. 20 refs.
Jacobian and stiffness analysis of a novel class of six-DOF parallel minimanipulators
Tashmasebi, F. . Goddard Space Flight Center); Tsai, Lung-Wen . Dept. of Mechanical Engineering)
1992-01-01
The Jacobian and stiffness matrices of two types of novel, six-DOF parallel minimanipulators are derived. A minimanipulator consists of three inextensible limbs, each of which is driven by a two-DOF driver. Bilinear stepper motors are used as drivers in the first type minimanipulator, whereas five-bar linkages are used as drivers in the second type minimanipulator. All of the minimanipulator actuators are base-mounted. Inextensible limbs (and five-bar linkage drivers in the second type minimanipulator) improve positional resolution and stiffness of the minimanipulators in certain directions. It is shown that, at the central configuration, the stiffness matrix of the first type minimanipulator can be diagonalized (decoupled). It is also shown that the first type minimanipulator can be designed to possess direct or torsional isotropic stiffness properties. Moreover, guidelines for designing the drivers of the second type minimanipulator are established. 20 refs.
Augmented kinematic feedback system
NASA Astrophysics Data System (ADS)
Andert, Ed P., Jr.; Archipley-Smith, Donna K.
1994-07-01
This paper discusses a real-time augmented kinematic feedback system which can be used as a diagnosis tool for individuals with motor disabilities. The system captures and analyzes movement via color targets attached to an individual and then feeds back information about movement kinematics. This target tracking approach has a high potential for achieving a real- time kinematic assessment capability. The approach recognizes distinct moving colored targets using video data. Multiple colored targets are attached to an individual at strategic locations and then target movement is tracked using a video data acquisition system. The ability to track and assess movement in real-time allows researchers and practitioners to better study and potentially treat various motor disabilities. Recent research has suggested that kinematic feedback can enhance motor recovery of disabled individuals. This approach addresses the need for a real-time measure of human movement and discusses using kinematic feedback to enhance disability recovery.
NASA Astrophysics Data System (ADS)
Reynolds, Daniel R.; Samtaney, Ravi; Tiedeman, Hilari C.
2012-01-01
Single-fluid resistive magnetohydrodynamics (MHD) is a fluid description of fusion plasmas which is often used to investigate macroscopic instabilities in tokamaks. In MHD modeling of tokamaks, it is often desirable to compute MHD phenomena to resistive time scales or a combination of resistive-Alfvén time scales, which can render explicit time stepping schemes computationally expensive. We present recent advancements in the development of preconditioners for fully nonlinearly implicit simulations of single-fluid resistive tokamak MHD. Our work focuses on simulations using a structured mesh mapped into a toroidal geometry with a shaped poloidal cross-section, and a finite-volume spatial discretization of the partial differential equation model. We discretize the temporal dimension using a fully implicit ? or the backwards differentiation formula method, and solve the resulting nonlinear algebraic system using a standard inexact Newton-Krylov approach, provided by the sundials library. The focus of this paper is on the construction and performance of various preconditioning approaches for accelerating the convergence of the iterative solver algorithms. Effective preconditioners require information about the Jacobian entries; however, analytical formulae for these Jacobian entries may be prohibitive to derive/implement without error. We therefore compute these entries using automatic differentiation with OpenAD. We then investigate a variety of preconditioning formulations inspired by standard solution approaches in modern MHD codes, in order to investigate their utility in a preconditioning context. We first describe the code modifications necessary for the use of the OpenAD tool and sundials solver library. We conclude with numerical results for each of our preconditioning approaches in the context of pellet-injection fueling of tokamak plasmas. Of these, our optimal approach results in a speedup of a factor of 3 compared with non-preconditioned implicit tests, with that performance gap rapidly widening with increasing mesh refinement.
Radiance and Jacobian Intercomparison of Radiative Transfer Models Applied to HIRS and AMSU Channels
NASA Technical Reports Server (NTRS)
Garand, L.; Turner, D. S.; Larocque, M.; Bates, J.; Boukabara, S.; Brunel, P.; Chevallier, F.; Deblonde, G.; Engelen, R.; Atlas, Robert (Technical Monitor)
2000-01-01
The goals of this study are the evaluation of current fast radiative transfer models (RTMs) and line-by-line (LBL) models. The intercomparison focuses on the modeling of 11 representative sounding channels routinely used at numerical weather prediction centers: seven HIRS (High-resolution Infrared Sounder) and four AMSU (Advanced Microwave Sounding Unit) channels. Interest in this topic was evidenced by the participation of 24 scientists from 16 institutions. An ensemble of 42 diverse atmospheres was used and results compiled for 19 infrared models and 10 microwave models, including several LBL RTMs. For the first time, not only radiances, but also Jacobians (of temperature, water vapor, and ozone) were compared to various LBL models for many channels. In the infrared, LBL models typically agree to within 0.05-0.15 K (standard deviation) in terms of top-of-the-atmosphere brightness temperature (BT). Individual differences up to 0.5 K still exist, systematic in some channels, and linked to the type of atmosphere in others. The best fast models emulate LBL BTs to within 0.25 K, but no model achieves this desirable level of success for all channels. The ozone modeling is particularly challenging. In the microwave, fast models generally do quite well against the LBL model to which they were tuned. However significant differences were noted among LBL models. Extending the intercomparison to the Jacobians proved very useful in detecting subtle and more obvious modeling errors. In addition, total and single gas optical depths were calculated, which provided additional insight on the nature of differences. Recommendations for future intercomparisons are suggested.
Radiance and Jacobian Intercomparison of Radiative Transfer Models Applied to HIRS and AMSU Channels
NASA Technical Reports Server (NTRS)
Garand, L.; Turner, D. S.; Larocque, M.; Bates, J.; Boukabara, S.; Brunel, P.; Chevallier, F.; Deblonde, G.; Engelen, R.; Hollingshead, M.; Goodman, H. Michael (Technical Monitor)
2000-01-01
The goals of this study are the evaluation of current fast radiative transfer models (RTMs) and line-by-line (LBL) models. The intercomparison focuses on the modeling of 11 representative sounding channels routinely used at numerical weather prediction centers: 7 HIRS (High-resolution Infrared Sounder) and 4 AMSU (Advanced Microwave Sounding Unit) channels. Interest in this topic was evidenced by the participation of 24 scientists from 16 institutions. An ensemble of 42 diverse atmospheres was used and results compiled for 19 infrared models and 10 microwave models, including several LBL RTMs. For the first time, not only radiances, but also Jacobians (of temperature, water vapor and ozone) were compared to various LBL models for many channels. In the infrared, LBL models typically agree to within 0.05-0.15 K (standard deviation) in terms of top-of-the-atmosphere brightness temperature (BT). Individual differences up to 0.5 K still exist, systematic in some channels, and linked to the type of atmosphere in others. The best fast models emulate LBL BTs to within 0.25 K, but no model achieves this desirable level of success for all channels. The ozone modeling is particularly challenging, In the microwave, fast models generally do quite well against the LBL model to which they were tuned. However significant differences were noted among LBL models, Extending the intercomparison to the Jacobians proved very useful in detecting subtle and more obvious modeling errors. In addition, total and single gas optical depths were calculated, which provided additional insight on the nature of differences. Recommendations for future intercomparisons are suggested.
Resolving spectral information from time domain induced polarization data through 2-D inversion
NASA Astrophysics Data System (ADS)
Fiandaca, Gianluca; Ramm, James; Binley, Andrew; Gazoty, Aurélie; Christiansen, Anders Vest; Auken, Esben
2013-02-01
Field-based time domain (TD) induced polarization (IP) surveys are usually modelled by taking into account only the integral chargeability, thus disregarding spectral content. Furthermore, the effect of the transmitted waveform is commonly neglected, biasing inversion results. Given these limitations of conventional approaches, a new 2-D inversion algorithm has been developed using the full voltage decay of the IP response, together with an accurate description of the transmitter waveform and receiver transfer function. This allows reconstruction of the spectral information contained in the TD decay series. The inversion algorithm is based around a 2-D complex conductivity kernel that is computed over a range of frequencies and converted to the TD through a fast Hankel transform. Two key points in the implementation ensure that computation times are minimized. First, the speed of the Jacobian computation, time transformed from frequency domain through the same transformation adopted for the forward response is optimized. Secondly, the reduction of the number of frequencies where the forward response and Jacobian are calculated: cubic splines are used to interpolate the responses to the frequency sampling necessary in the fast Hankel transform. These features, together with parallel computation, ensure inversion times comparable with those of direct current algorithms. The algorithm has been developed in a laterally constrained inversion scheme, and handles both smooth and layered inversions; the latter being helpful in sedimentary environments, where quasi-layered models often represent the actual geology more accurately than smooth minimum-structure models. In the layered inversion approach, a general method to derive the thickness derivative from the complex conductivity Jacobian is also proposed. One synthetic example of layered inversion and one field example of smooth inversion show the capability of the algorithm and illustrates a complete uncertainty analysis of the model parameters. With this new algorithm, in situ TD IP measurements give access to the spectral content of the polarization processes, opening up new applications in environmental and hydrogeophysical investigations.
Testing earthquake source inversion methodologies
Page, M.; Mai, P.M.; Schorlemmer, D.
2011-01-01
Source Inversion Validation Workshop; Palm Springs, California, 11-12 September 2010; Nowadays earthquake source inversions are routinely performed after large earthquakes and represent a key connection between recorded seismic and geodetic data and the complex rupture process at depth. The resulting earthquake source models quantify the spatiotemporal evolution of ruptures. They are also used to provide a rapid assessment of the severity of an earthquake and to estimate losses. However, because of uncertainties in the data, assumed fault geometry and velocity structure, and chosen rupture parameterization, it is not clear which features of these source models are robust. Improved understanding of the uncertainty and reliability of earthquake source inversions will allow the scientific community to use the robust features of kinematic inversions to more thoroughly investigate the complexity of the rupture process and to better constrain other earthquakerelated computations, such as ground motion simulations and static stress change calculations.
NASA Astrophysics Data System (ADS)
Sabaapour, Mohammad Reza; Zohoor, Hassan
Swashplate mechanism is the steering control mechanism used in most helicopters. It is a complex multi-loop closed kinematic chain which controls the angles of attack of the main rotor blades. In most new model helicopters, this mechanism is also equipped with the bell-hiller stabilizer bar (flybar), to improve the stability. This paper aimed at the kinematic analysis of one of the latest architectures of the swashplate mechanism, used for hingeless rotor with the flybar. Hence, the position analysis of each module and whole mechanism, based on parallel manipulators concept with more details involved than other works, was presented here. The kinematic model was further developed to obtain Jacobian matrices, velocity and acceleration analysis in detail. Finally, a particular example was conducted and compared with an ADAMS rigid body dynamic model, to verify the analytical model. In many simulated cases, the results matched.
Kinematic synthesis of bevel-gear-type robotic wrist mechanisms
NASA Astrophysics Data System (ADS)
Lin, Chen-Chou
Bevel-gear-type robotic wrist mechanisms are commonly used in industry. The reasons for their popularity are that they are compact, light-weight, and relatively inexpensive. However, there are singularities in their workspace, which substantially degrade their manipulative performance. The objective of this research is to develop an atlas of three-degree-of-freedom bevel-gear-type wrist mechanisms, and through dimensional synthesis to improve their kinematic performance. The dissertation contains two major parts: the first is structural analysis and synthesis, the other is kinematic analysis and dimensional synthesis. To synthesize the kinematic structures of bevel-gear-type wrist mechanisms, the kinematic structures are separated from their functional considerations. All kinematic structures which satisfy the mobility condition are enumerated in an unbiased, systematic manner. Then the bevel-gear-type wrist mechanisms are identified by applying the functional requirements. Structural analysis shows that a three-degree-of-freedom wrist mechanism usually consists of non-fractionated, two degree-of-freedom epicyclic gear train jointed with the base link. Therefore, the structural synthesis can be simplified into a problem of examining the atlas of non-fractionated, two-degree-of-freedom epicyclic gear trains. The resulting bevel-gear-type wrist mechanism has been categorized and evaluated. It is shown that three-degree-of-freedom, four-jointed wrist mechanisms are promising for further improving the kinematic performance. It is found that a spherical planetary gear train is necessarily imbedded in a three-degree-of-freedom, four-jointed wrist mechanism. Therefore, to study the workspace and singularity problems of three-degree-of-freedom four-jointed spherical wrist mechanisms, we have to study the trajectories of spherical planetary gear trains. The parametric equations of the trajectories and some useful geometric properties for the analysis and synthesis of workplace are derived. The workspace boundary equations can be derived via both geometric consideration and Jacobian analysis. The workspace is divided by inner and outer boundaries into regions of accessibility of zero, two, and four. The design criteria of full workspace and a maximum four-root region are established.
Tetrahedral Element Shape Optimization via the Jacobian Determinant and Condition Number
FREITAG,LORI A.; KNUPP,PATRICK
1999-09-27
We present a new shape measure for tetrahedral elements that is optimal in the sense that it gives the distance of a tetrahedron from the set of inverted elements. This measure is constructed from the condition number of the linear transformation between a unit equilateral tetrahedron and any tetrahedron with positive volume. We use this shape measure to formulate two optimization objective functions that are differentiated by their goal: the first seeks to improve the average quality of the tetrahedral mesh; the second aims to improve the worst-quality element in the mesh. Because the element condition number is not defined for tetrahedral with negative volume, these objective functions can be used only when the initial mesh is valid. Therefore, we formulate a third objective function using the determinant of the element Jacobian that is suitable for mesh untangling. We review the optimization techniques used with each objective function and present experimental results that demonstrate the effectiveness of the mesh improvement and untangling methods. We show that a combined optimization approach that uses both condition number objective functions obtains the best-quality meshes.
An optimal resolved rate law for kinematically redundant manipulators
NASA Technical Reports Server (NTRS)
Bourgeois, B. J.
1987-01-01
The resolved rate law for a manipulator provides the instantaneous joint rates required to satisfy a given instantaneous hand motion. When the joint space has more degrees of freedom than the task space, the manipulator is kinematically redundant and the kinematic rate equations are underdetermined. These equations can be locally optimized, but the resulting pseudo-inverse solution has been found to cause large joint rates in some cases. A weighting matrix in the locally optimized (pseudo-inverse) solution is dynamically adjusted to control the joint motion as desired. Joint reach limit avoidance is demonstrated in a kinematically redundant planar arm model. The treatment is applicable to redundant manipulators with any number of revolute joints and to non-planar manipulators.
Ulbrich, S; de Angulo, V R; Asfour, T; Torras, C; Dillmann, R
2012-08-01
The kinematics of a robot with many degrees of freedom is a very complex function. Learning this function for a large workspace with a good precision requires a huge number of training samples, i.e., robot movements. In this paper, we introduce the Kinematic Bézier Map (KB-Map), a parameterizable model without the generality of other systems but whose structure readily incorporates some of the geometric constraints of a kinematic function. In this way, the number of training samples required is drastically reduced. Moreover, the simplicity of the model reduces learning to solving a linear least squares problem. Systematic experiments have been carried out showing the excellent interpolation and extrapolation capabilities of KB-Maps and their relatively low sensitivity to noise. PMID:22481828
Three tooth kinematic coupling
Hale, Layton C. (Livermore, CA)
2000-01-01
A three tooth kinematic coupling based on having three theoretical line contacts formed by mating teeth rather than six theoretical point contacts. The geometry requires one coupling half to have curved teeth and the other coupling half to have flat teeth. Each coupling half has a relieved center portion which does not effect the kinematics, but in the limit as the face width approaches zero, three line contacts become six point contacts. As a result of having line contact, a three tooth coupling has greater load capacity and stiffness. The kinematic coupling has application for use in precision fixturing for tools or workpieces, and as a registration device for a work or tool changer or for optics in various products.
Kinematic control of robot with degenerate wrist
NASA Technical Reports Server (NTRS)
Barker, L. K.; Moore, M. C.
1984-01-01
Kinematic resolved rate equations allow an operator with visual feedback to dynamically control a robot hand. When the robot wrist is degenerate, the computed joint angle rates exceed operational limits, and unwanted hand movements can result. The generalized matrix inverse solution can also produce unwanted responses. A method is introduced to control the robot hand in the region of the degenerate robot wrist. The method uses a coordinated movement of the first and third joints of the robot wrist to locate the second wrist joint axis for movement of the robot hand in the commanded direction. The method does not entail infinite joint angle rates.
ERIC Educational Resources Information Center
Nelson, Jane Bray; Nelson, Jim
2009-01-01
Written by Jim and Jane Nelson, Teaching About Kinematics is the latest AAPT/PTRA resource book. Based on physics education research, the book provides teachers with the resources needed to introduce students to some of the fundamental building blocks of physics. It is a carefully thought-out, step-by-step laboratory-based introduction to the…
ERIC Educational Resources Information Center
Coleman, J. J.
1982-01-01
Describes mathematics of the nonliner relationships between a constant-speed, capstan-driven magnetic tape transport mechanism and a constant-angular-velocity take-up reel. The relationship, derived from the sum of a partial, serves in recognition of a finite tape. Thickness can serve as an example of rotational kinematics. (Author/SK)
Andersen, David R.; Bershady, Matthew A. E-mail: mab@astro.wisc.edu
2013-05-01
Using the integral field unit DensePak on the WIYN 3.5 m telescope we have obtained H{alpha} velocity fields of 39 nearly face-on disks at echelle resolutions. High-quality, uniform kinematic data and a new modeling technique enabled us to derive accurate and precise kinematic inclinations with mean i{sub kin} = 23 Degree-Sign for 90% of these galaxies. Modeling the kinematic data as single, inclined disks in circular rotation improves upon the traditional tilted-ring method. We measure kinematic inclinations with a precision in sin i of 25% at 20 Degree-Sign and 6% at 30 Degree-Sign . Kinematic inclinations are consistent with photometric and inverse Tully-Fisher inclinations when the sample is culled of galaxies with kinematic asymmetries, for which we give two specific prescriptions. Kinematic inclinations can therefore be used in statistical ''face-on'' Tully-Fisher studies. A weighted combination of multiple, independent inclination measurements yield the most precise and accurate inclination. Combining inverse Tully-Fisher inclinations with kinematic inclinations yields joint probability inclinations with a precision in sin i of 10% at 15 Degree-Sign and 5% at 30 Degree-Sign . This level of precision makes accurate mass decompositions of galaxies possible even at low inclination. We find scaling relations between rotation speed and disk-scale length identical to results from more inclined samples. We also observe the trend of more steeply rising rotation curves with increased rotation speed and light concentration. This trend appears to be uncorrelated with disk surface brightness.
Task-Directed Inverse Kinematics For Redundant Manipulators
NASA Technical Reports Server (NTRS)
Long, Mark K.
1994-01-01
Paper presents algorithms for use in controlling redundant robotic manipulators in such way as to exploit redundancy to satisfy task requirements beyond placement of end effectors at desired positions and orientations.
NASA Astrophysics Data System (ADS)
Sergienko, Olga
2013-04-01
Since Doug MacAyeal's pioneering studies of the ice-stream basal traction optimizations by control methods, inversions for unknown parameters (e.g., basal traction, accumulation patterns, etc) have become a hallmark of the present-day ice-sheet modeling. The common feature of such inversion exercises is a direct relationship between optimized parameters and observations used in the optimization procedure. For instance, in the standard optimization for basal traction by the control method, ice-stream surface velocities constitute the control data. The optimized basal traction parameters explicitly appear in the momentum equations for the ice-stream velocities (compared to the control data). The inversion for basal traction is carried out by minimization of the cost (or objective, misfit) function that includes the momentum equations facilitated by the Lagrange multipliers. Here, we build upon this idea, and demonstrate how to optimize for parameters indirectly related to observed data using a suite of nested constraints (like Russian dolls) with additional sets of Lagrange multipliers in the cost function. This method opens the opportunity to use data from a variety of sources and types (e.g., velocities, radar layers, surface elevation changes, etc.) in the same optimization process.
HyeongKae Park; Robert R. Nourgaliev; Richard C. Martineau; Dana A. Knoll
2008-09-01
We present high-order accurate spatiotemporal discretization of all-speed flow solvers using Jacobian-free Newton Krylov framework. One of the key developments in this work is the physics-based preconditioner for the all-speed flow, which makes use of traditional semi-implicit schemes. The physics-based preconditioner is developed in the primitive variable form, which allows a straightforward separation of physical phenomena. Numerical examples demonstrate that the developed preconditioner effectively reduces the number of the Krylov iterations, and the efficiency is independent of the Mach number and mesh sizes under a fixed CFL condition.
NASA Astrophysics Data System (ADS)
Zhu, Jia-Min; Lu, Zhi-Ming; Liu, Yu-Lu
2008-06-01
One of the advantages of the variational iteration method is the free choice of initial guess. In this paper we use the basic idea of the Jacobian-function method to construct a generalized trial function with some unknown parameters. The Jaulent Miodek equations are used to illustrate effectiveness and convenience of this method, some new explicit exact travelling wave solutions have been obtained, which include bell-type soliton solution, kink-type soliton solutions, solitary wave solutions, and doubly periodic wave solutions.
Inverse Problem of Capillary Filling
NASA Astrophysics Data System (ADS)
Elizalde, Emanuel; Urteaga, RaĂşl; Koropecki, Roberto R.; Berli, Claudio L. A.
2014-04-01
The inverse problem of capillary filling, as defined in this work, consists in determining the capillary radius profile from experimental data of the meniscus position l as a function of time t. This problem is central in diverse applications, such as the characterization of nanopore arrays or the design of passive transport in microfluidics; it is mathematically ill posed and has multiple solutions; i.e., capillaries with different geometries may produce the same imbibition kinematics. Here a suitable approach is proposed to solve this problem, which is based on measuring the imbibition kinematics in both tube directions. Capillary filling experiments to validate the calculation were made in a wide range of length scales: glass capillaries with a radius of around 150 ÎĽm and anodized alumina membranes with a pores radius of around 30 nm were used. The proposed method was successful in identifying the radius profile in both systems. Fundamental aspects also emerge in this study, notably the fact that the l(t)âťt1/2 kinematics (Lucas-Washburn relation) is not exclusive of uniform cross-sectional capillaries.
Inverse problem of capillary filling.
Elizalde, Emanuel; Urteaga, Raúl; Koropecki, Roberto R; Berli, Claudio L A
2014-04-01
The inverse problem of capillary filling, as defined in this work, consists in determining the capillary radius profile from experimental data of the meniscus position l as a function of time t. This problem is central in diverse applications, such as the characterization of nanopore arrays or the design of passive transport in microfluidics; it is mathematically ill posed and has multiple solutions; i.e., capillaries with different geometries may produce the same imbibition kinematics. Here a suitable approach is proposed to solve this problem, which is based on measuring the imbibition kinematics in both tube directions. Capillary filling experiments to validate the calculation were made in a wide range of length scales: glass capillaries with a radius of around 150???m and anodized alumina membranes with a pores radius of around 30??nm were used. The proposed method was successful in identifying the radius profile in both systems. Fundamental aspects also emerge in this study, notably the fact that the l(t)?t1/2 kinematics (Lucas-Washburn relation) is not exclusive of uniform cross-sectional capillaries. PMID:24745427
Inverse Dynamics for Action Recognition.
Mansur, Al; Makihara, Yasushi; Yagi, Yasushi
2013-08-01
Pose-based approaches for human action recognition are attractive owing to their accurate use of human motion information. Traditionally, such approaches used kinematic features for classification. However, in addition to having high dimensions and a small interclass variation, kinematic features do not consider the interaction of the environment on human motion. In this paper, we propose a method for action recognition using dynamic features, derived by applying inverse dynamics to a physics-based representation of the human body. The physics-based model is articulated and actuated with muscles and consists of joints with variable stiffness. Dynamic features under consideration include the torques from the knee and hip joints of both legs and, implicitly, gravity, ground reaction forces, and the pose of the remaining body parts. These features are more discriminative than kinematic features, resulting in a low-dimensional representation for human actions, which preserves much of the information of the original high-dimensional pose. This low-dimensional feature achieves good classification performance even with a relatively small training data set in a simple classification framework such as a hidden Markov model. The effectiveness of the proposed method is demonstrated through experiments on the Carnegie Mellon University motion capture data set and Osaka University Kinect action data set with various actions. PMID:26502432
Slickenside kinematic indicators
NASA Astrophysics Data System (ADS)
Doblas, Miguel
1998-09-01
A new classification of slickenside kinematic indicators is presented based on 61 criteria. These slickensides have been subdivided into eleven major groups: `V' or crescentic markings, steps, fractures, trains of inclined planar structures, trailed material, asymmetric elevations, deformed elements, mineralogical/crystallographic orientations, asymmetric plan-view features, asymmetric cavities, and asymmetric folds. This classification constitutes a useful tool for geologists interested in the determination of the shear sense in fault surfaces bearing slickensides. Examples of application of this classification to natural fault surfaces at different scales are presented.
Kinematics and galactic structure
Sandage, A.
1986-12-01
A radial velocity and photometric study of some 900 high proper motion stars in the solar neighborhood, recently completed at Mount Wilson, is combined with the earlier subdwarf literature to review the dependencies of kinematics on metallicity. The data confirm the conclusion that the oldest stars, with only a very few exceptions, are moving on highly eccentric orbits, and have higher W velocities than younger stars. The interpretation is again put forward for a collapse from a larger volume as the formation process of the Galaxy.
NASA Technical Reports Server (NTRS)
Nguyen, Charles C.; Pooran, Farhad J.
1989-01-01
This paper deals with a class of robot manipulators built based on the kinematic chain mechanism (CKCM). This class of CKCM manipulators consists of a fixed and a moving platform coupled together via a number of in-parallel actuators. A closed-form solution is derived for the inverse kinematic problem of a six-degre-of-freedom CKCM manipulator designed to study robotic applications in space. Iterative Newton-Raphson method is employed to solve the forward kinematic problem. Dynamics of the above manipulator is derived using the Lagrangian approach. Computer simulation of the dynamical equations shows that the actuating forces are strongly dependent on the mass and centroid of the robot links.
Speaker independent acoustic-to-articulatory inversion
NASA Astrophysics Data System (ADS)
Ji, An
Acoustic-to-articulatory inversion, the determination of articulatory parameters from acoustic signals, is a difficult but important problem for many speech processing applications, such as automatic speech recognition (ASR) and computer aided pronunciation training (CAPT). In recent years, several approaches have been successfully implemented for speaker dependent models with parallel acoustic and kinematic training data. However, in many practical applications inversion is needed for new speakers for whom no articulatory data is available. In order to address this problem, this dissertation introduces a novel speaker adaptation approach called Parallel Reference Speaker Weighting (PRSW), based on parallel acoustic and articulatory Hidden Markov Models (HMM). This approach uses a robust normalized articulatory space and palate referenced articulatory features combined with speaker-weighted adaptation to form an inversion mapping for new speakers that can accurately estimate articulatory trajectories. The proposed PRSW method is evaluated on the newly collected Marquette electromagnetic articulography -- Mandarin Accented English (EMA-MAE) corpus using 20 native English speakers. Cross-speaker inversion results show that given a good selection of reference speakers with consistent acoustic and articulatory patterns, the PRSW approach gives good speaker independent inversion performance even without kinematic training data.
NASA Astrophysics Data System (ADS)
Nuber, AndrĂ©; Manukyan, Edgar; Maurer, Hansruedi
2014-05-01
Conventional methods of interpreting seismic data rely on filtering and processing limited portions of the recorded wavefield. Typically, either reflections, refractions or surface waves are considered in isolation. Particularly in near-surface engineering and environmental investigations (depths less than, say 100 m), these wave types often overlap in time and are difficult to separate. Full waveform inversion is a technique that seeks to exploit and interpret the full information content of the seismic records without the need for separating events first; it yields models of the subsurface at sub-wavelength resolution. We use a finite element modelling code to solve the 2D elastic isotropic wave equation in the frequency domain. This code is part of a Gauss-Newton inversion scheme which we employ to invert for the P- and S-wave velocities as well as for density in the subsurface. For shallow surface data the use of an elastic forward solver is essential because surface waves often dominate the seismograms. This leads to high sensitivities (partial derivatives contained in the Jacobian matrix of the Gauss-Newton inversion scheme) and thus large model updates close to the surface. Reflections from deeper structures may also include useful information, but the large sensitivities of the surface waves often preclude this information from being fully exploited. We have developed two methods that balance the sensitivity distributions and thus may help resolve the deeper structures. The first method includes equilibrating the columns of the Jacobian matrix prior to every inversion step by multiplying them with individual scaling factors. This is expected to also balance the model updates throughout the entire subsurface model. It can be shown that this procedure is mathematically equivalent to balancing the regularization weights of the individual model parameters. A proper choice of the scaling factors required to balance the Jacobian matrix is critical. We decided to normalise the columns of the Jacobian based on their absolute column sum, but defining an upper threshold for the scaling factors. This avoids particularly small and therefore insignificant sensitivities being over-boosted, which would produce unstable results. The second method proposed includes adjusting the inversion cell size with depth. Multiple cells of the forward modelling grid are merged to form larger inversion cells (typical ratios between forward and inversion cells are in the order of 1:100). The irregular inversion grid is adapted to the expected resolution power of full waveform inversion. Besides stabilizing the inversion, this approach also reduces the number of model parameters to be recovered. Consequently, the computational costs and the memory consumption are reduced significantly. This is particularly critical when Gauss-Newton type inversion schemes are employed. Extensive tests with synthetic data demonstrated that both methods stabilise the inversion and improve the inversion results. The two methods have some redundancy, which can be seen when both are applied simultaneously, that is, when scaling of the Jacobian matrix is applied to an irregular inversion grid. The calculated scaling factors are quite balanced and span a much smaller range than in the case of a regular inversion grid.
Karimova, D.K.; Pavlovskaya, E.D.
1984-01-01
Proper motions determined by the authors are utilized to study the kinematics of 79 O-type stars at distance r< or =2.5 kpc. The sample is divided into two groups, having space-velocity dispersions tau/sub I/roughly-equal10 km/sec, sigma/sub II/roughly-equal35 km/sec. Solutions for the velocity-field parameters for group I yield a galactic angular rotation speed ..omega../sub 0/ = 24.9 km sec/sup -1/ kpc/sup -1/ at the sun (for R/sub 0/ = 10.0 kpc) and an Oort constant A = 12.2 km sec/sup -1/ kpc/sup -1/. Most of the O stars exhibit a small z-velocity directed away from the galactic plane. The velocity-ellipsoid parameters and box-orbit elements are calculated.
Kinematically Detected Halo Streams
NASA Astrophysics Data System (ADS)
Smith, Martin C.
Clues to the origins and evolution of our Galaxy can be found in the kinematics of stars around us. Remnants of accreted satellite galaxies produce over-densities in velocity-space, which can remain coherent for much longer than spatial over-densities. This chapter reviews a number of studies that have hunted for these accretion relics, both in the nearby solar-neighborhood and the more-distant stellar halo. Many observational surveys have driven this field forwards, from early work with the Hipparcos mission, to contemporary surveys like RAVE and SDSS. This active field continues to flourish, providing many new discoveries, and will be revolutionized as the Gaia mission delivers precise proper motions for a billion stars in our Galaxy.
NASA Astrophysics Data System (ADS)
Büsing, Henrik
2013-04-01
Two-phase flow in porous media occurs in various settings, such as the sequestration of CO2 in the subsurface, radioactive waste management, the flow of oil or gas in hydrocarbon reservoirs, or groundwater remediation. To model the sequestration of CO2, we consider a fully coupled formulation of the system of nonlinear, partial differential equations. For the solution of this system, we employ the Box method after Huber & Helmig (2000) for the space discretization and the fully implicit Euler method for the time discretization. After linearization with Newton's method, it remains to solve a linear system in every Newton step. We compare different iterative methods (BiCGStab, GMRES, AGMG, c.f., [Notay (2012)]) combined with different preconditioners (ILU0, ASM, Jacobi, and AMG as preconditioner) for the solution of these systems. The required Jacobians can be obtained elegantly with automatic differentiation (AD) [Griewank & Walther (2008)], a source code transformation providing exact derivatives. We compare the performance of the different iterative methods with their respective preconditioners for these linear systems. Furthermore, we analyze linear systems obtained by approximating the Jacobian with finite differences in terms of Newton steps per time step, steps of the iterative solvers and the overall solution time. Finally, we study the influence of heterogeneities in permeability and porosity on the performance of the iterative solvers and their robustness in this respect. References [Griewank & Walther(2008)] Griewank, A. & Walther, A., 2008. Evaluating Derivatives: Principles and Techniques of Algorithmic Differentiation, SIAM, Philadelphia, PA, 2nd edn. [Huber & Helmig(2000)] Huber, R. & Helmig, R., 2000. Node-centered finite volume discretizations for the numerical simulation of multiphase flow in heterogeneous porous media, Computational Geosciences, 4, 141-164. [Notay(2012)] Notay, Y., 2012. Aggregation-based algebraic multigrid for convection-diffusion equations, SIAM Journal on Scientific Computing, 34, A2288-A2316.
Kinematic analysis of generalized adaptive trusses
NASA Technical Reports Server (NTRS)
Tidwell, Paul H.; Reinholtz, Charles F.; Robertshaw, Harry H.; Horner, C. G.
1991-01-01
Adaptive trusses offer the greatest stiffness and strength for a given weight of any articulated structure or mechanism. Because of this, there are many potential extraterrestrial applications of these variable-geometry trusses, including serpentine manipulators, payload isolation, tracking, pointing and docking mechanisms, and gimbals. All of these applications will require the ability to precisely control the kinematic parameters of the mechanism, including position, velocity, and acceleration. This paper explores the fundamental nature of adaptive trusses by examining the basic truss elements or unit cells. A general method for analyzing forward and inverse motion of all the basic truss units is presented, followed by a more efficient formulation for the octahedral unit cell. Finally, general closed-form techniques are presented for finding velocity, acceleration, and all higher derivatives of truss motion.
Efficient Inversion of Mult-frequency and Multi-Source Electromagnetic Data
Gary D. Egbert
2007-03-22
The project covered by this report focused on development of efficient but robust non-linear inversion algorithms for electromagnetic induction data, in particular for data collected with multiple receivers, and multiple transmitters, a situation extremely common in eophysical EM subsurface imaging methods. A key observation is that for such multi-transmitter problems each step in commonly used linearized iterative limited memory search schemes such as conjugate gradients (CG) requires solution of forward and adjoint EM problems for each of the N frequencies or sources, essentially generating data sensitivities for an N dimensional data-subspace. These multiple sensitivities allow a good approximation to the full Jacobian of the data mapping to be built up in many fewer search steps than would be required by application of textbook optimization methods, which take no account of the multiplicity of forward problems that must be solved for each search step. We have applied this idea to a develop a hybrid inversion scheme that combines features of the iterative limited memory type methods with a Newton-type approach using a partial calculation of the Jacobian. Initial tests on 2D problems show that the new approach produces results essentially identical to a Newton type Occam minimum structure inversion, while running more rapidly than an iterative (fixed regularization parameter) CG style inversion. Memory requirements, while greater than for something like CG, are modest enough that even in 3D the scheme should allow 3D inverse problems to be solved on a common desktop PC, at least for modest (~ 100 sites, 15-20 frequencies) data sets. A secondary focus of the research has been development of a modular system for EM inversion, using an object oriented approach. This system has proven useful for more rapid prototyping of inversion algorithms, in particular allowing initial development and testing to be conducted with two-dimensional example problems, before approaching more computationally cumbersome three-dimensional problems.
NASA Technical Reports Server (NTRS)
Bryfogle, Mark D.; Nguyen, Charles C.; Antrazi, Sami S.; Chiou, Peter C.
1993-01-01
Design of a parallel force-reflecting hand controller that implements a friction- and inertia canceling control loop about the entire mechanism based on wrench sensing in the mechanism handgrip is discussed. Kinematics of the controller under consideration is analyzed and results are presented using a closed-form solution for the inverse kinematics and Newton-Raphson's method for the forward kinematics. Results indicate that the force control scheme based on a handgrip force sensor provides smaller steady-state errors than the scheme without a handigrip sensor.
Uncertainty Quantification of Kinematic Source Parameters using a Bayesian Approach
NASA Astrophysics Data System (ADS)
Razafindrakoto, H.; Mai, M.
2012-04-01
Ground-motion simulations for seismic hazard analysis and dynamic rupture modeling suffer not only from the non-uniqueness of kinematic source models but also from the unknown robustness of source-inversion solutions. Therefore, adequate uncertainty analysis of kinematic source model parameters is critical to better understand the main factors that lead to rupture model variability, and to explore the robustness of kinematic source model parameters. Thanks to large improvements in computational tools, Bayesian techniques have become feasible to estimate comprehensive model uncertainties by producing the probability density functions (PDF) of model parameters. In this study, we use a Bayesian technique to infer the ensemble of all possible source models that are consistent with seismological data and the available prior information. Two different procedures are followed. In the first one, we use a two-step procedure that initially explores the parameter space in search for the best fitting model (using a non-linear optimization algorithm) and then applies a Markov Chain Monte Carlo (MCMC) method for Bayesian inference on the kinematic rupture parameters. The second procedure is a one-step procedure that immediately applies MCMC by assuming Gaussian uncertainty for the seismological data. This second technique is computationally cheaper and explores the full parameter space, but does not provide a best-fitting "reference solution". Our study presents synthetic tests based on the "Source Inversion Validation" (SIV) exercise. We analyze the performance of those two approaches in terms of efficiency, and their ability to image the known kinematic rupture details. For the two-step procedure, we additionally perform jackknife tests to examine the robust and sensitive features of the best-fitting model. Our results indicate that the well-resolved part of the fault is conserved through all the delete-one jackknife tests, and that the posterior PDF follows a Gaussian like distribution only within the well-resolved regions of the fault.
Joint inversion of acoustic and resistivity data for the estimation of gas hydrate concentration
Lee, Myung W.
2002-01-01
Downhole log measurements, such as acoustic or electrical resistivity logs, are frequently used to estimate in situ gas hydrate concentrations in the pore space of sedimentary rocks. Usually the gas hydrate concentration is estimated separately based on each log measurement. However, measurements are related to each other through the gas hydrate concentration, so the gas hydrate concentrations can be estimated by jointly inverting available logs. Because the magnitude of slowness of acoustic and resistivity values differs by more than an order of magnitude, a least-squares method, weighted by the inverse of the observed values, is attempted. Estimating the resistivity of connate water and gas hydrate concentration simultaneously is problematic, because the resistivity of connate water is independent of acoustics. In order to overcome this problem, a coupling constant is introduced in the Jacobian matrix. In the use of different logs to estimate gas hydrate concentration, a joint inversion of different measurements is preferred to the averaging of each inversion result.
Detailed solution to a complex kinematics chain manipulator
March-Leuba, S.; Jansen, J.F.; Kress, R.L.; Babcock, S.M.
1992-12-31
This paper presents a relatively simple method based on planar geometry to analyze the inverse kinematics for closed kinematics chain (CKC) mechanisms. Although the general problem and method of approach are well defined, the study of the inverse kinematics of a closed-chain mechanism is a very complicated one. The current methodology allows closed-form solutions to be found, if a solution exists, for the displacements and velocities of all manipulator joints. Critical design parameters can be identified and optimized by using symbolic models. This paper will focus on planar closed-chain structures extended with a rotational base. However, with open and CKC mechanisms combined in different planes, the extension to the case is straightforward. Further, real-time algorithms are developed that can be handled by existing microprocessor technology. To clarify the methodology, the Soldier Robot Interface Project (SRIP) manipulator is analyzed, and a graphic simulation is presented as a verification of the results. This manipulator has 17 links, 24 one-degree-of-freedom (DOF) joints, and 7 CKC loops working in a plane and a rotational base, which determine its 3 DOFs. The SRIP manipulator allows a decoupled linear motion along the vertical or horizontal directions using only one of its linear actuators. The symbolic solution for the inverse kinematics allows optimization to be performed to further decouple the Cartesian motions by changing link lengths of the manipulator. The conclusion achieved by the optimization is that only two link lengths need to be changed to tune the manipulator for a perfect decoupling at each area of the workspace.
Detailed solution to a complex kinematics chain manipulator
March-Leuba, S; Jansen, J F; Kress, R L; Babcock, S M
1992-01-01
This paper presents a relatively simple method based on planar geometry to analyze the inverse kinematics for closed kinematics chain (CKC) mechanisms. Although the general problem and method of approach are well defined, the study of the inverse kinematics of a closed-chain mechanism is a very complicated one. The current methodology allows closed-form solutions to be found, if a solution exists, for the displacements and velocities of all manipulator joints. Critical design parameters can be identified and optimized by using symbolic models. This paper will focus on planar closed-chain structures extended with a rotational base. However, with open and CKC mechanisms combined in different planes, the extension to the case is straightforward. Further, real-time algorithms are developed that can be handled by existing microprocessor technology. To clarify the methodology, the Soldier Robot Interface Project (SRIP) manipulator is analyzed, and a graphic simulation is presented as a verification of the results. This manipulator has 17 links, 24 one-degree-of-freedom (DOF) joints, and 7 CKC loops working in a plane and a rotational base, which determine its 3 DOFs. The SRIP manipulator allows a decoupled linear motion along the vertical or horizontal directions using only one of its linear actuators. The symbolic solution for the inverse kinematics allows optimization to be performed to further decouple the Cartesian motions by changing link lengths of the manipulator. The conclusion achieved by the optimization is that only two link lengths need to be changed to tune the manipulator for a perfect decoupling at each area of the workspace.
Robust Inversion and Data Compression in Control Allocation
NASA Technical Reports Server (NTRS)
Hodel, A. Scottedward
2000-01-01
We present an off-line computational method for control allocation design. The control allocation function delta = F(z)tau = delta (sub 0) (z) mapping commanded body-frame torques to actuator commands is implicitly specified by trim condition delta (sub 0) (z) and by a robust pseudo-inverse problem double vertical line I - G(z) F(z) double vertical line less than epsilon (z) where G(z) is a system Jacobian evaluated at operating point z, z circumflex is an estimate of z, and epsilon (z) less than 1 is a specified error tolerance. The allocation function F(z) = sigma (sub i) psi (z) F (sub i) is computed using a heuristic technique for selecting wavelet basis functions psi and a constrained least-squares criterion for selecting the allocation matrices F (sub i). The method is applied to entry trajectory control allocation for a reusable launch vehicle (X-33).
NASA Astrophysics Data System (ADS)
Kordy, M.; Wannamaker, P.; Maris, V.; Cherkaev, E.; Hill, G.
2016-01-01
Following the creation described in Part I of a deformable edge finite-element simulator for 3-D magnetotelluric (MT) responses using direct solvers, in Part II we develop an algorithm named HexMT for 3-D regularized inversion of MT data including topography. Direct solvers parallelized on large-RAM, symmetric multiprocessor (SMP) workstations are used also for the Gauss-Newton model update. By exploiting the data-space approach, the computational cost of the model update becomes much less in both time and computer memory than the cost of the forward simulation. In order to regularize using the second norm of the gradient, we factor the matrix related to the regularization term and apply its inverse to the Jacobian, which is done using the MKL PARDISO library. For dense matrix multiplication and factorization related to the model update, we use the PLASMA library which shows very good scalability across processor cores. A synthetic test inversion using a simple hill model shows that including topography can be important; in this case depression of the electric field by the hill can cause false conductors at depth or mask the presence of resistive structure. With a simple model of two buried bricks, a uniform spatial weighting for the norm of model smoothing recovered more accurate locations for the tomographic images compared to weightings which were a function of parameter Jacobians. We implement joint inversion for static distortion matrices tested using the Dublin secret model 2, for which we are able to reduce nRMS to Ëś1.1 while avoiding oscillatory convergence. Finally we test the code on field data by inverting full impedance and tipper MT responses collected around Mount St Helens in the Cascade volcanic chain. Among several prominent structures, the north-south trending, eruption-controlling shear zone is clearly imaged in the inversion.
Kinematic precision of gear trains
NASA Technical Reports Server (NTRS)
Litvin, F. L.; Goldrich, R. N.; Coy, J. J.; Zaretsky, E. V.
1982-01-01
Kinematic precision is affected by errors which are the result of either intentional adjustments or accidental defects in manufacturing and assembly of gear trains. A method for the determination of kinematic precision of gear trains is described. The method is based on the exact kinematic relations for the contact point motions of the gear tooth surfaces under the influence of errors. An approximate method is also explained. Example applications of the general approximate methods are demonstrated for gear trains consisting of involute (spur and helical) gears, circular arc (Wildhaber-Novikov) gears, and spiral bevel gears. Gear noise measurements from a helicopter transmission are presented and discussed with relation to the kinematic precision theory.
Development of fully Bayesian multiple-time-window source inversion
NASA Astrophysics Data System (ADS)
Kubo, Hisahiko; Asano, Kimiyuki; Iwata, Tomotaka; Aoi, Shin
2016-03-01
In the estimation of spatiotemporal slip models, kinematic source inversions using Akaike's Bayesian Information Criterion (ABIC) and the multiple-time-window method have often been used. However, there are cases in which conventional ABIC-based source inversions do not work well in the determination of hyperparameters when a non-negative slip constraint is used. In order to overcome this problem, a new source inversion method was developed in this study. The new method introduces a fully Bayesian method into the kinematic multiple-time-window source inversion. The multiple-time-window method is one common way of parametrizing a source time function and is highly flexible in terms of the shape of the source time function. The probability distributions of model parameters and hyperparameters can be directly obtained by using the Markov chain Monte Carlo method. These probability distributions are useful for simply evaluating the uniqueness and reliability of the derived model, which is another advantage of a fully Bayesian method. This newly developed source inversion method was applied to the 2011 Ibaraki-oki, Japan, earthquake (Mw 7.9) to demonstrate its usefulness. It was demonstrated that the problem with using the conventional ABIC-based source inversion method for hyperparameter determination appeared in the spatiotemporal source inversion of this event and that the newly developed source inversion could overcome this problem.
Aero-optimum hovering kinematics.
Nabawy, Mostafa R A; Crowther, William J
2015-08-01
Hovering flight for flapping wing vehicles requires rapid and relatively complex reciprocating movement of a wing relative to a stationary surrounding fluid. This note develops a compact analytical aero-kinematic model that can be used for optimization of flapping wing kinematics against aerodynamic criteria of effectiveness (maximum lift) and efficiency (minimum power for a given amount of lift). It can also be used to make predictions of required flapping frequency for a given geometry and basic aerodynamic parameters. The kinematic treatment is based on a consolidation of an existing formulation that allows explicit derivation of flapping velocity for complex motions whereas the aerodynamic model is based on existing quasi-steady analysis. The combined aero-kinematic model provides novel explicit analytical expressions for both lift and power of a hovering wing in a compact form that enables exploration of a rich kinematic design space. Good agreement is found between model predictions of flapping frequency and observed results for a number of insects and optimal hovering kinematics identified using the model are consistent with results from studies using higher order computational models. For efficient flight, the flapping angle should vary using a triangular profile in time leading to a constant velocity flapping motion, whereas for maximum effectiveness the shape of variation should be sinusoidal. For both cases the wing pitching motion should be rectangular such that pitch change at stroke reversal is as rapid as possible. PMID:26248884
One-dimensional kinematics of particle stream flow with application to solar wind simulation
NASA Technical Reports Server (NTRS)
Olmsted, C.; Akasofu, S.-L.
1985-01-01
A simple kinematic method for determining the particle velocity distribution of a model solar wind for which the spatial distribution of particles is given as a function of particle travel time has been developed by Hakamada and Akasofu (1982). Here their method is formalized mathematically and an inverse procedure for determining the particle distribution from a given velocity distribution is derived. This inverse procedure is then applied to a simulated velocity distribution obtained from an MHD finite difference code.
Kinematics, controls, and path planning results for a redundant manipulator
NASA Technical Reports Server (NTRS)
Gretz, Bruce; Tilley, Scott W.
1989-01-01
The inverse kinematics solution, a modal position control algorithm, and path planning results for a 7 degree of freedom manipulator are presented. The redundant arm consists of two links with shoulder and elbow joints and a spherical wrist. The inverse kinematics problem for tip position is solved and the redundant joint is identified. It is also shown that a locus of tip positions exists in which there are kinematic limitations on self-motion. A computationally simple modal position control algorithm has been developed which guarantees a nearly constant closed-loop dynamic response throughout the workspace. If all closed-loop poles are assigned to the same location, the algorithm can be implemented with very little computation. To further reduce the required computation, the modal gains are updated only at discrete time intervals. Criteria are developed for the frequency of these updates. For commanding manipulator movements, a 5th-order spline which minimizes jerk provides a smooth tip-space path. Schemes for deriving a corresponding joint-space trajectory are discussed. Modifying the trajectory to avoid joint torque saturation when a tip payload is added is also considered. Simulation results are presented.
Kinematic analysis of a flexible six-DOF parallel mechanism.
Jing, Feng-Shui; Tan, Min; Hou, Zeng-Guang; Liang, Zi-Ze; Wang, Yun-Kuan; Gupta, Madan M; Nikiforuk, Peter N
2006-04-01
In this paper, a new type of six-degrees of freedom (DOF) flexible parallel mechanism (FPM) is presented. This type of parallel mechanism possesses several favorable properties: (1) its number of DOFs is independent of the number of serial chains which make up the mechanism; (2) it has no kinematical singularities; (3) it is designed to move on rails, and therefore its workspace is much larger than that of a conventional parallel manipulator; and (4) without changing the number of DOFs and the kinematics of the mechanisms, the number of the serial chains can be reconfigured according to the needs of the tasks. These properties make the mechanism very preferable in practice, especially for such tasks as joining huge ship blocks, in which the manipulated objects vary dramatically both in weights and dimensions. Furthermore, the mechanism can be used as either a fully actuated system or an underactuated system. In the fully actuated case, the mechanism has six DOF motion capabilities and manipulation capabilities. However, in the underactuated case, the mechanism still has six DOF motion capabilities, but it has only five DOF manipulation capabilities. In this paper, both the inverse and forward kinematics are studied and expressed in a closed form. The workspace and singularity analysis of the mechanism are also presented. An example is presented to illustrate how to calculate the kinematics of the mechanism in both fully-actuated and underactuated cases. Finally, an application of such a mechanism to manufacturing industry is introduced. PMID:16602597
A global approach for using kinematic redundancy to minimize base reactions of manipulators
NASA Technical Reports Server (NTRS)
Chung, C. L.; Desa, S.
1989-01-01
An important consideration in the use of manipulators in microgravity environments is the minimization of the base reactions, i.e. the magnitude of the force and the moment exerted by the manipulator on its base as it performs its tasks. One approach which was proposed and implemented is to use the redundant degree of freedom in a kinematically redundant manipulator to plan manipulator trajectories to minimize base reactions. A global approach was developed for minimizing the magnitude of the base reactions for kinematically redundant manipulators which integrates the Partitioned Jacobian method of redundancy resolution, a 4-3-4 joint-trajectory representation and the minimization of a cost function which is the time-integral of the magnitude of the base reactions. The global approach was also compared with a local approach developed earlier for the case of point-to-point motion of a three degree-of-freedom planar manipulator with one redundant degree-of-freedom. The results show that the global approach is more effective in reducing and smoothing the base force while the local approach is superior in reducing the base moment.
Error analysis and optimization of a 3-degree of freedom translational Parallel Kinematic Machine
NASA Astrophysics Data System (ADS)
Shankar Ganesh, S.; Koteswara Rao, A. B.
2014-06-01
In this paper, error modeling and analysis of a typical 3-degree of freedom translational Parallel Kinematic Machine is presented. This mechanism provides translational motion along the Cartesian X-, Y- and Z-axes. It consists of three limbs each having an arm and forearm with prismatic-revolute-revolute-revolute joints. The moving or tool platform maintains same orientation in the entire workspace due to its joint arrangement. From inverse kinematics, the joint angles for a given position of tool platform necessary for the error modeling and analysis are obtained. Error modeling is done based on the differentiation of the inverse kinematic equations. Variation of pose errors along X, Y and Z directions for a set of dimensions of the parallel kinematic machine is presented. A non-dimensional performance index, namely, global error transformation index is used to study the influence of dimensions and its corresponding global maximum pose error is reported. An attempt is made to find the optimal dimensions of the Parallel Kinematic Machine using Genetic Algorithms in MATLAB. The methodology presented and the results obtained are useful for predicting the performance capability of the Parallel Kinematic Machine under study.
Deformation field validation and inversion applied to adaptive radiation therapy
NASA Astrophysics Data System (ADS)
Vercauteren, Tom; De Gersem, Werner; Olteanu, Luiza A. M.; Madani, Indira; Duprez, Fréderic; Berwouts, Dieter; Speleers, Bruno; De Neve, Wilfried
2013-08-01
Development and implementation of chronological and anti-chronological adaptive dose accumulation strategies in adaptive intensity-modulated radiation therapy (IMRT) for head-and-neck cancer. An algorithm based on Newton iterations was implemented to efficiently compute inverse deformation fields (DFs). Four verification steps were performed to ensure a valid dose propagation: intra-cell folding detection finds zero or negative Jacobian determinants in the input DF; inter-cell folding detection is implemented on the resolution of the output DF; a region growing algorithm detects undefined values in the output DF; DF domains can be composed and displayed on the CT data. In 2011, one patient with nonmetastatic head and neck cancer selected from a three phase adaptive DPBN study was used to illustrate the algorithms implemented for adaptive chronological and anti-chronological dose accumulation. The patient received three 18F-FDG-PET/CTs prior to each treatment phase and one CT after finalizing treatment. Contour propagation and DF generation between two consecutive CTs was performed in Atlas-based autosegmentation (ABAS). Deformable image registration based dose accumulations were performed on CT1 and CT4. Dose propagation was done using combinations of DFs or their inversions. We have implemented a chronological and anti-chronological dose accumulation algorithm based on DF inversion. Algorithms were designed and implemented to detect cell folding.
Kinematics of a New High Precision Three Degree-of-Freedom Parallel Manipulator
NASA Technical Reports Server (NTRS)
Tahmasebi, Farhad
2005-01-01
Closed-form direct and inverse kinematics of a new three degree-of-freedom (DOF) parallel manipulator with inextensible limbs and base-mounted actuators are presented. The manipulator has higher resolution and precision than the existing three DOF mechanisms with extensible limbs. Since all of the manipulator actuators are base-mounted; higher payload capacity, smaller actuator sizes, and lower power dissipation can be obtained. The manipulator is suitable for alignment applications where only tip, tilt, and piston motions are significant. The direct kinematics of the manipulator is reduced to solving an eighth-degree polynomial in the square of tangent of half-angle between one of the limbs and the base plane. Hence, there are at most sixteen assembly configurations for the manipulator. In addition, it is shown that the sixteen solutions are eight pairs of reflected configurations with respect to the base plane. Numerical examples for the direct and inverse kinematics of the manipulator are also presented.
Functional kinematics of the wrist.
Rainbow, M J; Wolff, A L; Crisco, J J; Wolfe, S W
2016-01-01
The purpose of this article is to review past and present concepts concerning functional kinematics of the healthy and injured wrist. To provide a context for students of the wrist, we describe the progression of techniques for measuring carpal kinematics over the past century and discuss how this has influenced today's understanding of functional kinematics. Next, we provide an overview of recent developments and highlight the clinical relevance of these findings. We use these findings and recent evidence that supports the importance of coupled motion in early rehabilitation of radiocarpal injuries to develop the argument that coupled motion during functional activities is a clinically relevant outcome; therefore, clinicians should develop a framework for its dynamic assessment. This should enable a tailored and individualized approach to the treatment of carpal injuries. PMID:26568538
Emergent gravity requires kinematic nonlocality.
Marolf, Donald
2015-01-23
This Letter refines arguments forbidding nonlinear dynamical gravity from appearing in the low energy effective description of field theories with local kinematics, even for those with instantaneous long-range interactions. Specifically, we note that gravitational theories with universal coupling to energy-an intrinsically nonlinear phenomenon-are characterized by Hamiltonians that are pure boundary terms on shell. In order for this to be the low energy effective description of a field theory with local kinematics, all bulk dynamics must be frozen and, thus, irrelevant to the construction. The result applies to theories defined either on a lattice or in the continuum, and requires neither Lorentz invariance nor translation invariance. PMID:25658991
NASA Astrophysics Data System (ADS)
Repetto, P.; Rosado, M.; Gabbasov, R.; Fuentes-Carrera, I.
2010-06-01
In this work we present scanning Fabry-Perot H? observations of the isolated interacting galaxy pair NGC 5278/9 obtained with the PUMA Fabry-Perot interferometer. We derived velocity fields, various kinematic parameters and rotation curves for both galaxies. Our kinematical results together with the fact that dust lanes have been detected in both galaxies, as well as the analysis of surface brightness profiles along the minor axis, allowed us to determine that both components of the interacting pair are trailing spirals.
Knupp, P.M.
1999-03-26
Three-dimensional unstructured tetrahedral and hexahedral finite element mesh optimization is studied from a theoretical perspective and by computer experiments to determine what objective functions are most effective in attaining valid, high quality meshes. The approach uses matrices and matrix norms to extend the work in Part I to build suitable 3D objective functions. Because certain matrix norm identities which hold for 2 x 2 matrices do not hold for 3 x 3 matrices. significant differences arise between surface and volume mesh optimization objective functions. It is shown, for example, that the equivalence in two-dimensions of the Smoothness and Condition Number of the Jacobian matrix objective functions does not extend to three dimensions and further. that the equivalence of the Oddy and Condition Number of the Metric Tensor objective functions in two-dimensions also fails to extend to three-dimensions. Matrix norm identities are used to systematically construct dimensionally homogeneous groups of objective functions. The concept of an ideal minimizing matrix is introduced for both hexahedral and tetrahedral elements. Non-dimensional objective functions having barriers are emphasized as the most logical choice for mesh optimization. The performance of a number of objective functions in improving mesh quality was assessed on a suite of realistic test problems, focusing particularly on all-hexahedral ''whisker-weaved'' meshes. Performance is investigated on both structured and unstructured meshes and on both hexahedral and tetrahedral meshes. Although several objective functions are competitive, the condition number objective function is particularly attractive. The objective functions are closely related to mesh quality measures. To illustrate, it is shown that the condition number metric can be viewed as a new tetrahedral element quality measure.
NASA Astrophysics Data System (ADS)
Padhi, Amit
Seismic prestack waveform inversion is an ill posed, nonlinear inverse problem with nonunique solutions. Additionally the problem suffers from the existence of multiple local optima in the topography of the data misfit measure and high computational cost. These problems get aggravated as the number of model parameters to be estimated per layer or grid point increase. The number of parameters per layer or grid point depends on the assumptions necessary for modeling the seismic data. Hence it is necessary to investigate the physical processes affecting the observed data significantly in specific situations and then develop appropriate inversion methodologies. In this dissertation I apply a local inversion scheme based on nonlinear least squares (NLS) approach to invert one dimensional synthetic and one and two dimensional field seismic prestack waveform data in an area with sparse direct measurements to estimate sound speed in the oceanic water column. This is because seismic propagation is acoustic and isotropic in water and density does not change significantly. The two dimensional results are further compared to that obtained using a completely global approach. I also develop an adjoint state method based Jacobian computation for the NLS scheme to be applied to the problem of acoustic seismic inversion. Next, I investigate and propose an efficient method to monitor CO2 sequestrated reservoirs by combining multiphase flow simulation results with seismic modeling. Finding that such a monitoring scheme would require multicomponent seismic waveform data inversion under elastic anisotropic assumptions, I cast the inverse problem as a multiobjective optimization problem and solve it using a nondominated sorting genetic algorithm. Synthetic and real data tests show that while local inversion schemes work reasonably well for acoustic inversion, elastic anisotropic inversion requires a global approach utilizing multicomponent data. Hence monitoring CO2 sequestrated reservoirs efficiently using proxy stack of anisotropic layers requires the second approach. I also show that the NLS approach can be made efficient using the adjoint state method if the number of model parameters to be estimated is large enough. In the other case, computing the Jacobian using the traditional method and parallelization is preferable and can be implemented easily.
KINEMATIC ANALYSIS OF MODULAR, TRUSS-BASED MANIPULATOR UNITS
Salerno, R. J.
1994-06-01
Decontamination and Dismantling (D&D) activities within the U.S. Department of Energy (DOE) require a long reach manipulator with a large load capacity. Variable Geometry Trusses (VGTs) are a unique class of mechanical structures which allow the advantages of truss structures for large scale applications to be applied to large robotic manipulators. Individual VGT units may be assembled to create a modular, long-reach, truss-type manipulator. Each module of such a manipulator system is either a static truss section or one of several possible VGT geometries. While many potential applications exist for this technology, the present work is largely motivated by the need for generic robotic systems for remote manipulation. A manipulator system based on VGT modules provides several advantages. The reconfigurable nature of the manipulator system allows it to be adapted on site to unforeseen conditions. The kinematic redundancy of the manipulator enables it to work effectively even in a highly obstructed workspace. The parallel structure of the truss modules enables the manipulator to be withdrawn in the event of a structural failure. Finally, the open framework of the modules provides a clear, protected passageway for control and power cabling, waste conveyance, or other services required at the end effector. As is implied in a truss structure, all primary members of a VGT are ideally loaded in pure tension or compression. This results in an extremely stiff and strong manipulator system with minimal overall weight. Careful design of the joints of a VGT is very important to the overall stiffness and accuracy of the structure, as several links (as many as six) are joined together at each joint. The greatest disadvantage to this approach to manipulator design has traditionally been that the kinematics of VGT structures are complex and poorly understood. This report specifically addresses the kinematics of several possible geometries for the individual VGT units. Equations and solution techniques are developed for solving the "forward" or "direct" and "inverse" kinematic problems for these geometries. The" forward" kinematic problem is that of finding the position and orientation of the distal end of the VGT relative to the proximal end, given the specific displacements of the (linear) actuators. This problem is rarely solvable in closed form. However, powerful iterative algorithms capable of solution in real time on typical modern robot control hardware are presented. The "inverse" kinematic problem is that of finding the required actuator displacements given the position and orientation of the distal end of the VGT relative to the proximal end. For specific VGT geometries, closed-form solutions are presented. For the more general problem, iterative algorithms capable of solution in real time are again derived and presented.
Trajectory optimization for kinematically redundant arms
NASA Technical Reports Server (NTRS)
Carignan, Craig R.
1991-01-01
A review of local optimization methods for resolving joint configurations in underconstrained manipulation tasks is conducted. A new approach is developed for observing joint limits and avoiding obstacles during the trajectory planning. The methodology is used in a four-link arm example to avoid a workspace singularity and is compared with results using the extended Moore-Penrose technique. An alternative measure of arm 'manipulability' based directly on the rank of the Jacobian is also introduced.
Christensen, Gary E.; Song, Joo Hyun; Lu, Wei; Naqa, Issam El; Low, Daniel A.
2007-06-15
Breathing motion is one of the major limiting factors for reducing dose and irradiation of normal tissue for conventional conformal radiotherapy. This paper describes a relationship between tracking lung motion using spirometry data and image registration of consecutive CT image volumes collected from a multislice CT scanner over multiple breathing periods. Temporal CT sequences from 5 individuals were analyzed in this study. The couch was moved from 11 to 14 different positions to image the entire lung. At each couch position, 15 image volumes were collected over approximately 3 breathing periods. It is assumed that the expansion and contraction of lung tissue can be modeled as an elastic material. Furthermore, it is assumed that the deformation of the lung is small over one-fifth of a breathing period and therefore the motion of the lung can be adequately modeled using a small deformation linear elastic model. The small deformation inverse consistent linear elastic image registration algorithm is therefore well suited for this problem and was used to register consecutive image scans. The pointwise expansion and compression of lung tissue was measured by computing the Jacobian of the transformations used to register the images. The logarithm of the Jacobian was computed so that expansion and compression of the lung were scaled equally. The log-Jacobian was computed at each voxel in the volume to produce a map of the local expansion and compression of the lung during the breathing period. These log-Jacobian images demonstrate that the lung does not expand uniformly during the breathing period, but rather expands and contracts locally at different rates during inhalation and exhalation. The log-Jacobian numbers were averaged over a cross section of the lung to produce an estimate of the average expansion or compression from one time point to the next and compared to the air flow rate measured by spirometry. In four out of five individuals, the average log-Jacobian value and the air flow rate correlated well (R{sup 2}=0.858 on average for the entire lung). The correlation for the fifth individual was not as good (R{sup 2}=0.377 on average for the entire lung) and can be explained by the small variation in tidal volume for this individual. The correlation of the average log-Jacobian value and the air flow rate for images near the diaphragm correlated well in all five individuals (R{sup 2}=0.943 on average). These preliminary results indicate a strong correlation between the expansion/compression of the lung measured by image registration and the air flow rate measured by spirometry. Predicting the location, motion, and compression/expansion of the tumor and normal tissue using image registration and spirometry could have many important benefits for radiotherapy treatment. These benefits include reducing radiation dose to normal tissue, maximizing dose to the tumor, improving patient care, reducing treatment cost, and increasing patient throughput.
Barberis, Emanuela; /Northeastern U.
2006-05-01
A summary of the results on the measurement of the Top Quark mass and the study of the kinematics of the t{bar t} system at the Tevatron collider is presented here. Results from both the CDF and D0 collaborations are reported.
First order ball bearing kinematics
NASA Technical Reports Server (NTRS)
Kingbury, E.
1984-01-01
Two first order equations are given connecting geometry and internal motions in an angular contact ball bearing. Total speed, kinematic equivalence, basic speed ratio, and modal speed ratio are defined and discussed; charts are given for the speed ratios covering all bearings and all rotational modes. Instances where specific first order assumptions might fail are discussed, and the resulting effects on bearing performance reviewed.
Kinematic Parameters of Signed Verbs
ERIC Educational Resources Information Center
Malaia, Evie; Wilbur, Ronnie B.; Milkovic, Marina
2013-01-01
Purpose: Sign language users recruit physical properties of visual motion to convey linguistic information. Research on American Sign Language (ASL) indicates that signers systematically use kinematic features (e.g., velocity, deceleration) of dominant hand motion for distinguishing specific semantic properties of verb classes in production…
Kinematic Parameters of Signed Verbs
ERIC Educational Resources Information Center
Malaia, Evie; Wilbur, Ronnie B.; Milkovic, Marina
2013-01-01
Purpose: Sign language users recruit physical properties of visual motion to convey linguistic information. Research on American Sign Language (ASL) indicates that signers systematically use kinematic features (e.g., velocity, deceleration) of dominant hand motion for distinguishing specific semantic properties of verb classes in productionâ€¦
Kinematic support using elastic elements
NASA Technical Reports Server (NTRS)
Geirsson, Arni; Debra, Daniel B.
1988-01-01
The design of kinematic supports using elastic elements is reviewed. The two standard methods (cone, Vee and flat and three Vees) are presented and a design example involving a machine tool metrology bench is given. Design goals included thousandfold strain attenuation in the bench relative to the base when the base strains due to temperature variations and shifting loads. Space applications are also considered.
Kinematics and dynamics of robotic systems with multiple closed loops
NASA Astrophysics Data System (ADS)
Zhang, Chang-De
The kinematics and dynamics of robotic systems with multiple closed loops, such as Stewart platforms, walking machines, and hybrid manipulators, are studied. In the study of kinematics, focus is on the closed-form solutions of the forward position analysis of different parallel systems. A closed-form solution means that the solution is expressed as a polynomial in one variable. If the order of the polynomial is less than or equal to four, the solution has analytical closed-form. First, the conditions of obtaining analytical closed-form solutions are studied. For a Stewart platform, the condition is found to be that one rotational degree of freedom of the output link is decoupled from the other five. Based on this condition, a class of Stewart platforms which has analytical closed-form solution is formulated. Conditions of analytical closed-form solution for other parallel systems are also studied. Closed-form solutions of forward kinematics for walking machines and multi-fingered grippers are then studied. For a parallel system with three three-degree-of-freedom subchains, there are 84 possible ways to select six independent joints among nine joints. These 84 ways can be classified into three categories: Category 3:3:0, Category 3:2:1, and Category 2:2:2. It is shown that the first category has no solutions; the solutions of the second category have analytical closed-form; and the solutions of the last category are higher order polynomials. The study is then extended to a nearly general Stewart platform. The solution is a 20th order polynomial and the Stewart platform has a maximum of 40 possible configurations. Also, the study is extended to a new class of hybrid manipulators which consists of two serially connected parallel mechanisms. In the study of dynamics, a computationally efficient method for inverse dynamics of manipulators based on the virtual work principle is developed. Although this method is comparable with the recursive Newton-Euler method for serial manipulators, its advantage is more noteworthy when applied to parallel systems. An approach of inverse dynamics of a walking machine is also developed, which includes inverse dynamic modeling, foot force distribution, and joint force/torque allocation. inverse dynamic modeling of a quadruped with pantograph legs is derived. The inverse dynamics of this quadruped walking in different wave gaits is then studied.
Kinematics and trajectory generation for MIRADAS arms
NASA Astrophysics Data System (ADS)
Sabater, J.; GĂłmez, J. M.; Torra, J.; LĂłpez, M.; Raines, S. N.; Eikenberry, S. S.
2015-05-01
The Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS) is a NIR multi-object spectrograph for the Gran Telescopio Canarias (GTC). The instrument has a multiplexing system (MXS) that enables the simultaneous observation of twenty objects located within its field of view. These user selected targets are acquired by twenty deployable robotic probe arms with pickoff mirror optics operating at cryogenic temperatures. The MIRADAS probe arm is a close-loop mechanism designed with optics simplicity in mind, presenting good stability when it is operated upside down. Calculating optimum collision-free trajectories requires a good knowledge of the MIRADAS arm behavior based on its geometry and its mechanical constraints. This study introduces a geometric model for the two degree-of-freedom (DoF) mechanism, including solutions for the forward and inverse kinematics problem. The concepts of zone-of-avoidance (ZoA), workspace and envelope of MIRADAS arm are presented and studied. Finally, the paper proposes two different patrolling approaches that can be exploited when planning trajectories.
NASA Astrophysics Data System (ADS)
Jen, Fu-Hua
This work studies three related aspects of robotics: the set of possible kinematic representations of robot motion, the range of all possible robot positions, i.e., the workspace, and the designing of stable grasps with a multifingered end-effector. A survey of alternatives to the homogeneous transformation to represent robot coordinate translations and rotations is given. The advantages and disadvantages of each are discussed, and their computational complexities are compared, giving the number of arithmetic operations required by the different methods. In viewing rigid body motions, two aspects are considered: point transformations, which result in matrix-based transformations, and line transformations, which result in screw-based transformations. Algebraic expressions for the robot workspace are helpful in the design of robots. Here, a complete methodology is developed to obtain algebraic expressions to aid robot workspace construction, based on the analysis of Jacobian matrices. Reduction of the complexity of the workspace analysis is achieved by choice of the coordinate system used in the representation. It is shown that, in the worst case 2 x 2 submatrices of the Jacobian need to be checked, and with some specific kinematic structures, it is sufficient to examine only a set of scalar expressions. Examples of using algebraic expressions to generate workspace without mechanical limitations are given. The third part of this work represents the first application of Liapunov stability theory of differential equations to the problem of generating stable grasps of an object with a multifingered hand. The analysis of grasp stability where finger forces are maintained constant is considered, as well as certain modified force control laws that introduce damping. In the robotics community there is considerable research emphasis related to the use of force control methods rather than the usual position control, and this motivates the study. Stability theory for nonlinear differential equations is applied to establish the conditions on finger locations and grasp force directions that are associated with Liapunov stability, with asymptotic stability, and with instability of grasps. Relationships are given between these mathematical concepts and various desirable properties of grasp that have previously been used in defining various concepts of stable grasp. A geometrical representation of the stability condition is given which assists the synthesis of the grasp, and examples in two and three dimensions are given.
NASA Technical Reports Server (NTRS)
Nguyen, Charles C.; Pooran, Farhad J.
1989-01-01
This report presents results from the research grant entitled Active Control of Robot Manipulators, funded by the Goddard Space Flight Center, under Grant NAG5-780, for the period July 1, 1988 to January 1, 1989. An analysis is presented of a 6 degree-of-freedom robot end-effector built to study telerobotic assembly of NASA hardware in space. Since the end-effector is required to perform high precision motion in a limited workspace, closed-kinematic mechanisms are chosen for its design. A closed-form solution is obtained for the inverse kinematic problem and an iterative procedure employing Newton-Raphson method is proposed to solve the forward kinematic problem. A study of the end-effector workspace results in a general procedure for the workspace determination based on link constraints. Computer simulation results are presented.
Influence of kinematic analysis methods on detecting ankle and subtalar joint instability.
Choisne, Julie; Ringleb, Stacie I; Samaan, Michael A; Bawab, Sebastian Y; Naik, Dayanand; Anderson, Claude D
2012-01-01
Patients with subtalar joint instability may be misdiagnosed with ankle instability, which may lead to chronic instability at the subtalar joint. Therefore, it is important to understand the difference in kinematics after ligament sectioning and differentiate the changes in kinematics between ankle and subtalar instability. Three methods may be used to determine the joint kinematics; the Euler angles, the Joint Coordinate System (JCS) and the helical axis (HA). The purpose of this study was to investigate the influence of using either method to detect subtalar and ankle joints instability. 3D kinematics at the ankle and subtalar joint were analyzed on 8 cadaveric specimens while the foot was intact and after sequentially sectioning the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), the cervical ligament and the interosseous talocalcaneal ligament (ITCL). Comparison in kinematics calculated from sensor and anatomical landmarks was conducted as well as the influence of Euler angles and JCS rotation sequence (between ISB recommendation and previous research) on the subtalar joint. All data showed a significant increase in inversion when the ITCL was sectioned. There were differences in the data calculated using sensors coordinate systems vs. anatomic coordinate systems. Anatomic coordinate systems were recommended for these calculations. The Euler angle and JCS gave similar results. Differences in Euler angles and JCS sequence lead to the same conclusion in detecting instability at the ankle and subtalar joint. As expected, the HA detected instability in plantarflexion at the ankle joint and in inversion at the subtalar joint. PMID:22056198
Kinematic solution of spherical Stephenson-III six-bar mechanism
NASA Astrophysics Data System (ADS)
Liu, Yanfang; Yang, Suixian
2013-09-01
A closed-form solution can be obtained for kinematic analysis of spatial mechanisms by using analytical method. However, extra solutions would occur when solving the constraint equations of mechanism kinematics unless the constraint equations are established with a proper method and the solving approach is appropriate. In order to obtain a kinematic solution of the spherical Stephenson-III six-bar mechanism, spherical analytical theory is employed to construct the constraint equations. Firstly, the mechanism is divided into a four-bar loop and a two-bar unit. On the basis of the decomposition, vectors of the mechanism nodes are derived according to spherical analytical theory and the principle of coordinate transformation. Secondly, the structural constraint equations are constructed by applying cosine formula of spherical triangles to the top platform of the mechanism. Thirdly, the constraint equations are solved by using Bezout’s elimination method for forward analysis and Sylvester’s resultant elimination method for inverse kinematics respectively. By the aid of computer symbolic systems, Mathematica and Maple, symbolic closed-form solution of forward and inverse displacement analysis of spherical Stephenson-III six-bar mechanism are obtained. Finally, numerical examples of forward and inverse analysis are presented to illustrate the proposed approach. The results indicate that the constraint equations established with the proposed method are much simpler than those reported by previous literature, and can be readily eliminated and solved.
Exploring MaNGA's kinematic maps
NASA Astrophysics Data System (ADS)
Weijmans, Anne-Marie; MaNGA Team
2016-01-01
Different galaxy formation processes leave different imprints on the gas and stellar kinematic patterns for a galaxy. With MaNGA, we now have after one year of observations an unprecedented sample of 1400 nearby galaxies for which we can study gas and stellar kinematics in much detail, based on integral-field spectroscopy. We are measuring kinematic quantities such as LambdaR (angular momentum) and their (possible) correlations with other galaxy properties such as mass, morphology and environment. By quantifying the kinematic (sub)structures in velocity and dispersion maps, we will construct a kinematic galaxy classification that can be linked to their formation processes.
Kinematic and stability motion limits for a hexapod walking machine
NASA Astrophysics Data System (ADS)
Dunton, Elizabeth M.
1995-03-01
The major problem addressed by this research is to investigate and implement the basic concepts necessary to lay the groundwork for efficient forms of motion planning, motion control, and gait algorithms with respect to hexapod walking machines. Specifically, the approach taken was to develop and implement the concepts of a stability margin and a joint space motion margin on an object-oriented representation of the Aquarobot. The model was generated in Franz Common Lisp and simulated via Allegro Common Windows. A method by which distance computations can be calculated and applied to the center of mass and triangular support pattern of a walking machine to determine the stability margin is introduced. Inverse kinematics and joint limits are utilized to ascertain the joint space motion margin of the model. Response to impending instability and the effect when a joint hits or approaches a joint kinematic limit on the motion of the hexapod walking machine by stopping the model is also addressed. The results are as follows: the concepts of the joint space motion margin and the stability margin can be successfully implemented on a kinematic model and graphical simulation of a hexapod walking machine. These concepts contribute to future work in the area of more efficient free gait algorithms, specifically asynchronous gait algorithms.
Analysis of a closed-kinematic chain robot manipulator
NASA Technical Reports Server (NTRS)
Nguyen, Charles C.; Pooran, Farhad J.
1988-01-01
Presented are the research results from the research grant entitled: Active Control of Robot Manipulators, sponsored by the Goddard Space Flight Center (NASA) under grant number NAG-780. This report considers a class of robot manipulators based on the closed-kinematic chain mechanism (CKCM). This type of robot manipulators mainly consists of two platforms, one is stationary and the other moving, and they are coupled together through a number of in-parallel actuators. Using spatial geometry and homogeneous transformation, a closed-form solution is derived for the inverse kinematic problem of the six-degree-of-freedom manipulator, built to study robotic assembly in space. Iterative Newton Raphson method is employed to solve the forward kinematic problem. Finally, the equations of motion of the above manipulators are obtained by employing the Lagrangian method. Study of the manipulator dynamics is performed using computer simulation whose results show that the robot actuating forces are strongly dependent on the mass and centroid locations of the robot links.
Influence of biological kinematics on abstract concept processing.
Badets, Arnaud; Bidet-Ildei, Christel; Pesenti, Mauro
2015-01-01
During a random number generation task, human beings tend to produce more small numbers than large numbers. However, this small number bias is modulated when motor behaviour, such as a turn of the head, is performed during the random number generation task. This result fits with the finding that number representation is linked to laterally oriented actions, with small- and large-magnitude numbers generally linked to movement towards the left or the right side of space, respectively. To test whether this number-space association is specific to human motor behaviours or extends to any type of laterally oriented movements, we assessed whether the presentation of biological or nonbiological leftward or rightward movement affected a subsequent random number generation task. Biological and nonbiological movements were obtained by varying the kinematic parameters of the movements. Biological kinematics represented the tangential velocity actually observed in a human pointing movement; nonbiological kinematics represented equivalent movements but with an inverse tangential velocity along the path. The results show that only the observation of biological movements induces a space-number bias whereas observing nonbiological movements does not. This finding is the first evidence of a link between a biological marker and the semantic representation of a concept as abstract as number. PMID:25219421
Kinematic Fitting of Detached Vertices
Paul Mattione
2007-05-01
The eg3 experiment at the Jefferson Lab CLAS detector aims to determine the existence of the $\\Xi_{5}$ pentaquarks and investigate the excited $\\Xi$ states. Specifically, the exotic $\\Xi_{5}^{--}$ pentaquark will be sought by first reconstructing the $\\Xi^{-}$ particle through its weak decays, $\\Xi^{-}\\to\\pi^{-}\\Lambda$ and $\\Lambda\\to\\pi^{-}$. A kinematic fitting routine was developed to reconstruct the detached vertices of these decays, where confidence level cuts on the fits are used to remove background events. Prior to fitting these decays, the exclusive reaction $\\gamma D\\rightarrow pp\\pi^{-}$ was studied in order to correct the track measurements and covariance matrices of the charged particles. The $\\Lambda\\rightarrow p\\pi^{-}$ and $\\Xi^{-}\\to\\pi^{-}\\Lambda$ decays were then investigated to demonstrate that the kinematic fitting routine reconstructs the decaying particles and their detached vertices correctly.
Contact kinematics of biomimetic scales
NASA Astrophysics Data System (ADS)
Ghosh, Ranajay; Ebrahimi, Hamid; Vaziri, Ashkan
2014-12-01
Dermal scales, prevalent across biological groups, considerably boost survival by providing multifunctional advantages. Here, we investigate the nonlinear mechanical effects of biomimetic scale like attachments on the behavior of an elastic substrate brought about by the contact interaction of scales in pure bending using qualitative experiments, analytical models, and detailed finite element (FE) analysis. Our results reveal the existence of three distinct kinematic phases of operation spanning linear, nonlinear, and rigid behavior driven by kinematic interactions of scales. The response of the modified elastic beam strongly depends on the size and spatial overlap of rigid scales. The nonlinearity is perceptible even in relatively small strain regime and without invoking material level complexities of either the scales or the substrate.
Contact kinematics of biomimetic scales
Ghosh, Ranajay; Ebrahimi, Hamid; Vaziri, Ashkan
2014-12-08
Dermal scales, prevalent across biological groups, considerably boost survival by providing multifunctional advantages. Here, we investigate the nonlinear mechanical effects of biomimetic scale like attachments on the behavior of an elastic substrate brought about by the contact interaction of scales in pure bending using qualitative experiments, analytical models, and detailed finite element (FE) analysis. Our results reveal the existence of three distinct kinematic phases of operation spanning linear, nonlinear, and rigid behavior driven by kinematic interactions of scales. The response of the modified elastic beam strongly depends on the size and spatial overlap of rigid scales. The nonlinearity is perceptible even in relatively small strain regime and without invoking material level complexities of either the scales or the substrate.
Of cilium and flagellum kinematics
NASA Astrophysics Data System (ADS)
Bandyopadhyay, Promode R.; Hansen, Joshua C.
2009-11-01
The kinematics of propulsion of small animals such as paramecium and spermatozoa is considered. Larger scale models of the cilium and flagellum have been built and a four-motor apparatus has been constructed to reproduce their known periodic motions. The cilium model has transverse deformational ability in one plane only, while the flagellum model has such ability in two planes. When the flagellum model is given a push-pull in one diametral plane, instead of transverse deflection in one plane, it forms a coil. Berg & Anderson's postulation (Nature 245 1973) that a flagellum rotates, is recalled. The kinematics of cilia of paramecium, of the whipping motion of the spermatozoa flagella, and of the flapping motion (rolling and pitching) of the pectoral fins of much larger animals such penguins, have been reproduced in the same basic paramecium apparatus. The results suggest that each of the tiny individual paramecium propulsors have the intrinsic dormant kinematic and structural building blocks to optimize into higher Reynolds number propulsors. A synthetic hypothesis on how small might have become large is animated.
Thickness dependence of drag and kinematic viscosity in quasi-two-dimensional flows
NASA Astrophysics Data System (ADS)
Fontana, Paul W.; Titmus, Edward; Kirn, Adrian
2009-11-01
In many experimental and natural quasi-two-dimensional (Q-2D) flows the effects of internal viscosity and surface friction are significant but difficult to distinguish. We have made precise, independent measurements of both kinematic viscosity and coefficient of external drag as functions of film thickness in a Q-2D experiment using soap films in a circular Couette cell configuration, using a combination of vortex decay rates and steady-state shear lengths. Both the kinematic viscosity and the drag coefficient are found to depend inversely on film thickness, as expected theoretically. This result is enabling quantitative experimental study of stability thresholds in Q-2D basic flows.
MEERSCHAERT, MARK M.; STRAKA, PETER
2013-01-01
The inverse stable subordinator provides a probability model for time-fractional differential equations, and leads to explicit solution formulae. This paper reviews properties of the inverse stable subordinator, and applications to a variety of problems in mathematics and physics. Several different governing equations for the inverse stable subordinator have been proposed in the literature. This paper also shows how these equations can be reconciled. PMID:25045216
Kinematic Characterization of Left Ventricular Chamber Stiffness and Relaxation
NASA Astrophysics Data System (ADS)
Mossahebi, Sina
Heart failure is the most common cause of hospitalization today, and diastolic heart failure accounts for 40-50% of cases. Therefore, it is critical to identify diastolic dysfunction at a subclinical stage so that appropriate therapy can be administered before ventricular function is further, and perhaps irreversibly impaired. Basic concepts in physics such as kinematic modeling provide a unique method with which to characterize cardiovascular physiology, specifically diastolic function (DF). The advantage of an approach that is standard in physics, such as the kinematic modeling is its causal formulation that functions in contrast to correlative approaches traditionally utilized in the life sciences. Our research group has pioneered theoretical and experimental quantitative analysis of DF in humans, using both non-invasive (echocardiography, cardiac MRI) and invasive (simultaneous catheterization-echocardiography) methods. Our group developed and validated the Parametrized Diastolic Filling (PDF) formalism which is motivated by basic physiologic principles (LV is a mechanical suction pump at the mitral valve opening) that obey Newton's Laws. PDF formalism is a kinematic model of filling employing an equation of motion, the solution of which accurately predicts all E-wave contours in accordance with the rules of damped harmonic oscillatory motion. The equation's lumped parameters---ventricular stiffness, ventricular viscoelasticity/relaxation and ventricular load---are obtained by solving the 'inverse problem'. The parameters' physiologic significance and clinical utility have been repeatedly demonstrated in multiple clinical settings. In this work we apply our kinematic modeling approach to better understand how the heart works as it fills in order to advance the relationship between physiology and mathematical modeling. Through the use of this modeling, we thereby define and validate novel, causal indexes of diastolic function such as early rapid filling energy, diastatic stiffness, and relaxation and stiffness components of E-wave deceleration time.
NASA Astrophysics Data System (ADS)
Kordy, M. A.; Wannamaker, P. E.; Maris, V.; Cherkaev, E.; Hill, G. J.
2014-12-01
We have developed an algorithm for 3D simulation and inversion of magnetotelluric (MT) responses using deformable hexahedral finite elements that permits incorporation of topography. Direct solvers parallelized on symmetric multiprocessor (SMP), single-chassis workstations with large RAM are used for the forward solution, parameter jacobians, and model update. The forward simulator, jacobians calculations, as well as synthetic and real data inversion are presented. We use first-order edge elements to represent the secondary electric field (E), yielding accuracy O(h) for E and its curl (magnetic field). For very low frequency or small material admittivity, the E-field requires divergence correction. Using Hodge decomposition, correction may be applied after the forward solution is calculated. It allows accurate E-field solutions in dielectric air. The system matrix factorization is computed using the MUMPS library, which shows moderately good scalability through 12 processor cores but limited gains beyond that. The factored matrix is used to calculate the forward response as well as the jacobians of field and MT responses using the reciprocity theorem. Comparison with other codes demonstrates accuracy of our forward calculations. We consider a popular conductive/resistive double brick structure and several topographic models. In particular, the ability of finite elements to represent smooth topographic slopes permits accurate simulation of refraction of electromagnetic waves normal to the slopes at high frequencies. Run time tests indicate that for meshes as large as 150x150x60 elements, MT forward response and jacobians can be calculated in ~2.5 hours per frequency. For inversion, we implemented data space Gauss-Newton method, which offers reduction in memory requirement and a significant speedup of the parameter step versus model space approach. For dense matrix operations we use tiling approach of PLASMA library, which shows very good scalability. In synthetic inversions we examine the importance of including the topography in the inversion and we test different regularization schemes using weighted second norm of model gradient as well as inverting for a static distortion matrix following Miensopust/Avdeeva approach. We also apply our algorithm to invert MT data collected at Mt St Helens.
Inversion of high frequency surface waves with fundamental and higher modes
Xia, J.; Miller, R.D.; Park, C.B.; Tian, G.
2003-01-01
The phase velocity of Rayleigh-waves of a layered earth model is a function of frequency and four groups of earth parameters: compressional (P)-wave velocity, shear (S)-wave velocity, density, and thickness of layers. For the fundamental mode of Rayleigh waves, analysis of the Jacobian matrix for high frequencies (2-40 Hz) provides a measure of dispersion curve sensitivity to earth model parameters. S-wave velocities are the dominant influence of the four earth model parameters. This thesis is true for higher modes of high frequency Rayleigh waves as well. Our numerical modeling by analysis of the Jacobian matrix supports at least two quite exciting higher mode properties. First, for fundamental and higher mode Rayleigh wave data with the same wavelength, higher modes can "see" deeper than the fundamental mode. Second, higher mode data can increase the resolution of the inverted S-wave velocities. Real world examples show that the inversion process can be stabilized and resolution of the S-wave velocity model can be improved when simultaneously inverting the fundamental and higher mode data. ?? 2002 Elsevier Science B.V. All rights reserved.
Astroblemes and geomagnetic inversions
NASA Astrophysics Data System (ADS)
Kalinin, Yu. D.
1993-08-01
A comparison is made of the age distributions of astroblemes and magnetic inversions, and it is found that these distributions are well correlated. This provides another argument in support of a hypothesis whereby the geomagnetic inversions and geomagnetic polarity superchrons result from the impact of giant asteroids against the earth.
Dewpoint temperature inversions analyzed
NASA Technical Reports Server (NTRS)
Ashby, W. C.; Bogner, M. A.; Moses, H.
1969-01-01
Dewpoint temperature inversion, with regard to other simultaneous meteorological conditions, was examined to establish the influence of meteorological variables on the variation of dewpoint temperature with height. This report covers instrumentation and available data, all the climatological features of dewpoint inversions, and specific special cases.
Teaching about Inverse Functions
ERIC Educational Resources Information Center
Esty, Warren
2005-01-01
In their sections on inverses most precalculus texts emphasize an algorithm for finding f [superscript -1] given f. However, inspection of precalculus and calculus texts shows that students will never again use the algorithm, which suggests the textbook emphasis may be misplaced. Inverses appear primarily when equations need to be solved, which…
Jackiewicz, Jason
2009-09-16
With the rapid advances in sophisticated solar modeling and the abundance of high-quality solar pulsation data, efficient and robust inversion techniques are crucial for seismic studies. We present some aspects of an efficient Fourier Optimally Localized Averaging (OLA) inversion method with an example applied to time-distance helioseismology.
ERIC Educational Resources Information Center
Bedard, Catherine; Belin, Pascal
2004-01-01
Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consisted…
Kinematic correction for roller skewing
NASA Technical Reports Server (NTRS)
Savage, M.; Loewenthal, S. H.
1980-01-01
A theory of kinematic stabilization of rolling cylinders is developed for high-speed cylindrical roller bearings. This stabilization requires race and roller crowning to product changes in the rolling geometry as the roller shifts axially. These changes put a reverse skew in the rolling elements by changing the rolling taper. Twelve basic possible bearing modifications are identified in this paper. Four have single transverse convex curvature in the rollers while eight have rollers with compound transverse curvature composed of a central cylindrical band of constant radius surrounded by symmetric bands with both slope and transverse curvature.
Inverse strategies for characterization of material properties
NASA Astrophysics Data System (ADS)
Aguilo, Miguel Alejandro
The imaging of constitutive parameters is of interest in many science and engineering fields. Indeed, non-invasive and nondestructive techniques are used to characterize key properties of a system given its response due to an external excitation. Then, assuming a priori a given model of the system, the measured response and an inverse approach are used to identify material properties. This work was undertaken in the context of identification of spatially-varying elastic and viscoelastic parameters of solids using vibroacoustics based techniques. Two optimization approaches, nongradient and gradient-based optimization, were investigated in this work. Initially, nongradient-based algorithms were preferred over gradient-based algorithms because of there ability to find global minima irrespective of initial guesses. For instance, Gaussian radial basis functions were used to construct a finite-dimensional representation of the elastic moduli. Then, an inverse approach was used to approximate the spatiallyvarying elastic moduli through the system response induced by the radiation force of ultrasound. The inverse problem was cast as an optimization problem in which a least-square error functional that quantified the misfit between the experimental and finite element representation system response is minimized by searching over a space of admissible vectors that best describe the spatial distribution of the elastic moduli. Subsequently, gradient-based optimization was preferred over nongradient-based optimization as the number of design variables increased due to the increment in computational cost. Two inverse approaches, L2-adjoint and concept of error in constitutive equation, were investigated in the context of gradient-based optimization. First, the L2-adjoint inverse approach was used to characterize spatially-varying viscoelastic properties because of its advantage to efficiently calculate the gradient of the error functional with respect to the design variables by solving the corresponding adjoint equations. The inverse problem was cast as an optimization problem in which a least-square error functional that quantified the misfit between the experimental and the finite element representation system response is minimized by searching over a space of admissible functions that best describe the spatially-varying viscoelastic properties. Given that the least-square error functional is non-convex, an inverse approach based on the concept of error in constitutive equation was investigated. The convexity property of the error in constitutive equation functionals, shown extensively for elliptic boundary value problems, reduce the sensitivity of the inverse solution to parameter initialization. The inverse problem was cast as an optimization problem in which an error in constitutive equation functional that quantified the misfit between the kinematically and dynamically admissible stress fields is minimized by searching over a space of admissible functions that best describe the spatially-varying viscoelastic properties. Contrary to the L2-adjoint inverse approach, the gradient equation is easily derived by taking the direct derivative of the error in constitutive equation functional with respect to the design variables. The feasibility of the proposed inverse approaches is demonstrated through a series of numerical and physical experiments. Results show that the proposed inverse approaches have the potential to characterize spatially-varying elastic and viscoelastic properties of solids in realistic settings. Furthermore, it will be shown that the inverse approach based on the concept of error in constitutive equation outperformed the L2-adjoint inverse approach.
Note: a Piezo Tip/Tilt Platform: structure, kinematics, and experiments.
Du, Z; Su, Y; Yang, W; Dong, W
2014-04-01
A Piezo Tip/Tilt Platform (PT(2)P) is presented with its structure, kinematics, and preliminary experiments. Two essential models of the presented PT(2)P, an equivalent hinge of the flexure hinge and a simplified model of the transmission mechanism, are discussed with the analysis on the structure of the PT(2)P. Based on these models, the inverse kinematics of the PT(2)P is derived. Two experiments are conducted on a prototype of the PT(2)P. The kinematic model is verified with experimental results, which also indicate that the resolution and the repeatability of the PT(2)P is, respectively, better than 0.50 ?rad and 0.25 ?rad. PMID:24784680
Basic concepts of kinematic-wave models
Miller, J.E.
1984-01-01
The kinematic-wave model is one of a number of approximations of the dynamic-wave model. The dynamic-wave model describes one-dimensional shallow-water waves (unsteady, gradually varied, open-channel flow). The report provides a basic reference on the theory and application of kinematic-wave models and describes the limitations of the model in relation to the other approximations of the dynamic-wave model. In the kinematic-wave approximation, a number of the terms in the equation of motion are assumed to be insignificant. The equation of motion is replaced by an equation describing uniform flow. Thus, the kinematic-wave model is described by the continuity equation and a uniform flow equation such as the well-known Chezy or Manning formulas. Kinematic-wave models are applicable to overland flow where lateral inflow is continuously added and is a large part of the total flow. For channel-routing applications, the kinematic-wave model always predicts a steeper wave with less dispersion and attenuation than actually occurs. The effect of the accumulation of errors in the kinematic-wave model shows that the approximations made in the development of the kinematic-wave equations are not generally justified for most channel-routing applications. Modified flow-routing models can be used which help to stop the accumulation of error that occurs when the kinematic-wave model is applied. (USGS)
NASA Astrophysics Data System (ADS)
Huda, Syamsul; Takeda, Yukio
This paper concerns kinematics and dimensional synthesis of a three universal-revolute-universal (3-URU) pure rotational parallel mechanism. The mechanism is composed of a base, a platform and three symmetric limbs consisting of U-R-U joints. This mechanism is a spatial non-overconstrained mechanism with three degrees of freedom. The joints in each limb are so arranged to perform pure rotational motion of the platform around a specific point. Equations for inverse displacement analysis and singularities were derived to investigate the relationship of the kinematic constants to the solution of the inverse kinematics and singularities. Based on the results, a dimensional synthesis procedure for the 3-URU parallel mechanism considering singularities and the workspace was proposed. A numerical example was also presented to illustrate the synthesis method.
Ballistic representation for kinematic access
NASA Astrophysics Data System (ADS)
Alfano, Salvatore
2011-01-01
This work uses simple two-body orbital dynamics to initially determine the kinematic access for a ballistic vehicle. Primarily this analysis was developed to assess when a rocket body might conjunct with an orbiting satellite platform. A family of access opportunities can be represented as a volume for a specific rocket relative to its launch platform. Alternately, the opportunities can be represented as a geographical footprint relative to aircraft or satellite position that encompasses all possible launcher locations for a specific rocket. A thrusting rocket is treated as a ballistic vehicle that receives all its energy at launch and follows a coasting trajectory. To do so, the rocket's burnout energy is used to find its equivalent initial velocity for a given launcher's altitude. Three kinematic access solutions are then found that account for spherical Earth rotation. One solution finds the maximum range for an ascent-only trajectory while another solution accommodates a descending trajectory. In addition, the ascent engagement for the descending trajectory is used to depict a rapid access scenario. These preliminary solutions are formulated to address ground-, sea-, or air-launched vehicles.
Kinematics of primate midfoot flexibility.
Greiner, Thomas M; Ball, Kevin A
2014-12-01
This study describes a unique assessment of primate intrinsic foot joint kinematics based upon bone pin rigid cluster tracking. It challenges the assumption that human evolution resulted in a reduction of midfoot flexibility, which has been identified in other primates as the "midtarsal break." Rigid cluster pins were inserted into the foot bones of human, chimpanzee, baboon, and macaque cadavers. The positions of these bone pins were monitored during a plantarflexion-dorsiflexion movement cycle. Analysis resolved flexion-extension movement patterns and the associated orientation of rotational axes for the talonavicular, calcaneocuboid, and lateral cubometatarsal joints. Results show that midfoot flexibility occurs primarily at the talonavicular and cubometatarsal joints. The rotational magnitudes are roughly similar between humans and chimps. There is also a similarity among evaluated primates in the observed rotations of the lateral cubometatarsal joint, but there was much greater rotation observed for the talonavicular joint, which may serve to differentiate monkeys from the hominines. It appears that the capability for a midtarsal break is present within the human foot. A consideration of the joint axes shows that the medial and lateral joints have opposing orientations, which has been associated with a rigid locking mechanism in the human foot. However, the potential for this same mechanism also appears in the chimpanzee foot. These findings demonstrate a functional similarity within the midfoot of the hominines. Therefore, the kinematic capabilities and restrictions for the skeletal linkages of the human foot may not be as unique as has been previously suggested. PMID:25234343
Development of a sensor coordinated kinematic model for neural network controller training
NASA Technical Reports Server (NTRS)
Jorgensen, Charles C.
1990-01-01
A robotic benchmark problem useful for evaluating alternative neural network controllers is presented. Specifically, it derives two camera models and the kinematic equations of a multiple degree of freedom manipulator whose end effector is under observation. The mapping developed include forward and inverse translations from binocular images to 3-D target position and the inverse kinematics of mapping point positions into manipulator commands in joint space. Implementation is detailed for a three degree of freedom manipulator with one revolute joint at the base and two prismatic joints on the arms. The example is restricted to operate within a unit cube with arm links of 0.6 and 0.4 units respectively. The development is presented in the context of more complex simulations and a logical path for extension of the benchmark to higher degree of freedom manipulators is presented.
Robust adaptive kinematic control of redundant robots
NASA Technical Reports Server (NTRS)
Tarokh, M.; Zuck, D. D.
1992-01-01
The paper presents a general method for the resolution of redundancy that combines the Jacobian pseudoinverse and augmentation approaches. A direct adaptive control scheme is developed to generate joint angle trajectories for achieving desired end-effector motion as well as additional user defined tasks. The scheme ensures arbitrarily small errors between the desired and the actual motion of the manipulator. Explicit bounds on the errors are established that are directly related to the mismatch between actual and estimated pseudoinverse Jacobian matrix, motion velocity and the controller gain. It is shown that the scheme is tolerant of the mismatch and consequently only infrequent pseudoinverse computations are needed during a typical robot motion. As a result, the scheme is computationally fast, and can be implemented for real-time control of redundant robots. A method is incorporated to cope with the robot singularities allowing the manipulator to get very close or even pass through a singularity while maintaining a good tracking performance and acceptable joint velocities. Computer simulations and experimental results are provided in support of the theoretical developments.
NASA Astrophysics Data System (ADS)
Lu, Qipeng; Li, Yongjun; Peng, Zhongqi
2012-05-01
Six-bar parallel mechanism is now widely applied in synchrotron radiation beamline, while the six-dimensional adjustment is difficult and inefficient for lack of theoretical direction. This paper introduces a special six-bar parallel mechanism. By means of coordinate transformations, the inverse kinematics of six-bar parallel mechanism is studied, and the precise equations for six bars' lengths are obtained. Based on the inverse kinematics, forward kinematics of six-bar parallel mechanism is obtained with trust region method working for nonlinear optimization. The corresponding MATLAB program is also designed. The results show that trust region method is an effective way to solve forward kinematics, and the program is stable, reliable and rapid. This method has small errors with linear precision of 10-12 mm and rotational precision of 10-15 deg. Using differential snail adjustment, monochromator chamber's attitude can reach a linear resolution of 5 ÎĽm and a rotational resolution of 3â€ł, which entirely satisfies the practical requirements.
Goal driven kinematic simulation of flexible arm robot for space station missions
NASA Technical Reports Server (NTRS)
Janssen, P.; Choudry, A.
1987-01-01
Flexible arms offer a great degree of flexibility in maneuvering in the space environment. The problem of transporting an astronaut for extra-vehicular activity using a space station based flexible arm robot was studied. Inverse kinematic solutions of the multilink structure were developed. The technique is goal driven and can support decision making for configuration selection as required for stability and obstacle avoidance. Details of this technique and results are given.
NASA Astrophysics Data System (ADS)
Stoica, Alin; Pisla, Doina; Andras, Szilaghyi; Gherman, Bogdan; Gyurka, Bela-Zoltan; Plitea, Nicolae
2013-03-01
In the last ten years, due to development in robotic assisted surgery, the minimally invasive surgery has greatly changed. Until now, the vast majority of robots used in surgery, have serial structures. Due to the orientation parallel module, the structure is able to reduce the pressure exerted on the entrance point in the patient's abdominal wall. The parallel robot can also handle both a laparoscope as well an active instrument for different surgical procedures. The advantage of this parallel structure is that the geometric model has been obtained through an analytical approach. The kinematic modelling of a new parallel architecture, the inverse and direct geometric model and the inverse and direct kinematic models for velocities and accelerations are being determined. The paper will demonstrate that with this parallel structure, one can obtain the necessary workspace required for a minimally invasive operation. The robot workspace was generated using the inverse geometric model. An indepth study of different types of singularity is performed, allowing the development of safe control algorithms of the experimental model. Some kinematic simulation results and the experimental model of the robot are presented in the paper.
NASA Technical Reports Server (NTRS)
Gough, D.
1984-01-01
Helioseismological inversion, as with the inversion of any other data, is divided into three phases. The first is the solution of the so-called forward problem: namely, the calculation of the eigenfrequencies of a theoretical equilibrium state. The second is an attempt to understand the results, either empirically by determining how those frequencies vary as chosen parameters defining the equilibrium model are varied, or analytically from asymptotic expansions in limiting cases of high order or degree. The third phase is to pose and solve an inverse problem, which seeks to find a plausible equilibrium model of the Sun whose eigenfrequencies are consistent with observation. The three phases are briefly discussed in this review, and the third, which is not yet widely used in helioseismology, is illustrated with some selected inversions of artificial solar data.
Control Algorithms For Kinematically Redundant Manipulators
NASA Technical Reports Server (NTRS)
Wegner, David R.
1995-01-01
Report presents improved algorithms for controlling kinematically redundant robotic manipulators, producing unique configuration for each end-effector location. Furthermore, they generally produce configurations in which no interference between robot boom and payload or base structures. Report presents comparison between various other robot-kinematic algorithms.
Kinematic Event Patterns in Speech: Special Problems.
ERIC Educational Resources Information Center
Westbury, John R.; Severson, Elizabeth J.; Lindstrom, Mary J.
2000-01-01
Results from a new analysis of synchronous acoustic and fleshpoint-kinematic data, recorded from 53 normal young-adult speakers of American English, are reported. The kinematic data represent speech-related actions of the tongue blade and dorsum, both lips, and the mandible, during the test words, "special" and "problem," and were drawn from anâ€¦
Kinematics of the free throw in basketball
NASA Astrophysics Data System (ADS)
Tan, A.; Miller, G.
1981-06-01
The kinematics of the two basic styles of free throw in basketball are discussed. It is shown that from a purely kinematic and trajectory point of view, the overhand push shot is preferable to the underhand loop shot. The advantages of the underhand shot lie in the actual execution of the shot.
Kinematic Event Patterns in Speech: Special Problems.
ERIC Educational Resources Information Center
Westbury, John R.; Severson, Elizabeth J.; Lindstrom, Mary J.
2000-01-01
Results from a new analysis of synchronous acoustic and fleshpoint-kinematic data, recorded from 53 normal young-adult speakers of American English, are reported. The kinematic data represent speech-related actions of the tongue blade and dorsum, both lips, and the mandible, during the test words, "special" and "problem," and were drawn from an…
Kinematic model of southern California
Weldon, R.; Humphreys, E.
1986-02-01
A kinematic model for southern California, based on late-Quaternary slip rates and orientations of major faults in the region, is proposed. Internally consistent motions are determined assuming that these faults bound rigid blocks. Relative to North America, most of California west of the San Andreas fault is moving parallel to the San Andreas fault through the Transverse Ranges and not parallel to the motion of the Pacific plate. The velocities of the blocks are calculated along several paths in southern California that begin in the Mojave Desert and end off the California coast. A path that crosses the western Transverse Ranges accumulates the accepted relative North America-Pacific plate velocity, whereas paths to the north and south result in a significant missing component of motion, implying the existence of a zone of active deformation in southern California. 70 references.
Bayesian kinematic earthquake source models
NASA Astrophysics Data System (ADS)
Minson, S. E.; Simons, M.; Beck, J. L.; Genrich, J. F.; Galetzka, J. E.; Chowdhury, F.; Owen, S. E.; Webb, F.; Comte, D.; Glass, B.; Leiva, C.; Ortega, F. H.
2009-12-01
Most coseismic, postseismic, and interseismic slip models are based on highly regularized optimizations which yield one solution which satisfies the data given a particular set of regularizing constraints. This regularization hampers our ability to answer basic questions such as whether seismic and aseismic slip overlap or instead rupture separate portions of the fault zone. We present a Bayesian methodology for generating kinematic earthquake source models with a focus on large subduction zone earthquakes. Unlike classical optimization approaches, Bayesian techniques sample the ensemble of all acceptable models presented as an a posteriori probability density function (PDF), and thus we can explore the entire solution space to determine, for example, which model parameters are well determined and which are not, or what is the likelihood that two slip distributions overlap in space. Bayesian sampling also has the advantage that all a priori knowledge of the source process can be used to mold the a posteriori ensemble of models. Although very powerful, Bayesian methods have up to now been of limited use in geophysical modeling because they are only computationally feasible for problems with a small number of free parameters due to what is called the "curse of dimensionality." However, our methodology can successfully sample solution spaces of many hundreds of parameters, which is sufficient to produce finite fault kinematic earthquake models. Our algorithm is a modification of the tempered Markov chain Monte Carlo (tempered MCMC or TMCMC) method. In our algorithm, we sample a "tempered" a posteriori PDF using many MCMC simulations running in parallel and evolutionary computation in which models which fit the data poorly are preferentially eliminated in favor of models which better predict the data. We present results for both synthetic test problems as well as for the 2007 Mw 7.8 Tocopilla, Chile earthquake, the latter of which is constrained by InSAR, local high-rate GPS, and teleseismic observations.
The inverse electroencephalography pipeline
NASA Astrophysics Data System (ADS)
Weinstein, David Michael
The inverse electroencephalography (EEG) problem is defined as determining which regions of the brain are active based on remote measurements recorded with scalp EEG electrodes. An accurate solution to this problem would benefit both fundamental neuroscience research and clinical neuroscience applications. However, constructing accurate patient-specific inverse EEG solutions requires complex modeling, simulation, and visualization algorithms, and to date only a few systems have been developed that provide such capabilities. In this dissertation, a computational system for generating and investigating patient-specific inverse EEG solutions is introduced, and the requirements for each stage of this Inverse EEG Pipeline are defined and discussed. While the requirements of many of the stages are satisfied with existing algorithms, others have motivated research into novel modeling and simulation methods. The principal technical results of this work include novel surface-based volume modeling techniques, an efficient construction for the EEG lead field, and the Open Source release of the Inverse EEG Pipeline software for use by the bioelectric field research community. In this work, the Inverse EEG Pipeline is applied to three research problems in neurology: comparing focal and distributed source imaging algorithms; separating measurements into independent activation components for multifocal epilepsy; and localizing the cortical activity that produces the P300 effect in schizophrenia.
Automated kinematic generator for surgical robotic systems.
Jung, David L; Dixon, Warren E; Pin, FranĂ§ois G
2004-01-01
Unlike traditional assembly line robotic systems that have a fixed kinematic structure associated with a single tool for a structured task, next-generation robotic surgical assist systems will be required to use an array of end-effector tools. Once a robot is connected with a tool, the kinematic equations of motion are altered. Given the need to accommodate evolving surgical challenges and to alleviate the restrictions imposed by the confined minimally invasive environment, new surgical tools may resemble small flexible snakes rather than rigid, cable driven instruments. Connecting to these developing articulated tools will significantly alter the overall kinematic structure of a robotic system. In this paper we present a technique for real-time automated generation and evaluation of manipulator kinematic equations that exhibits the combined advantages of existing methods-speed and flexibility to kinematic change--without their disadvantages. PMID:15544260
Seth, Ajay; Matias, Ricardo; Veloso, AntĂłnio P.; Delp, Scott L.
2016-01-01
The complexity of shoulder mechanics combined with the movement of skin relative to the scapula makes it difficult to measure shoulder kinematics with sufficient accuracy to distinguish between symptomatic and asymptomatic individuals. Multibody skeletal models can improve motion capture accuracy by reducing the space of possible joint movements, and models are used widely to improve measurement of lower limb kinematics. In this study, we developed a rigid-body model of a scapulothoracic joint to describe the kinematics of the scapula relative to the thorax. This model describes scapular kinematics with four degrees of freedom: 1) elevation and 2) abduction of the scapula on an ellipsoidal thoracic surface, 3) upward rotation of the scapula normal to the thoracic surface, and 4) internal rotation of the scapula to lift the medial border of the scapula off the surface of the thorax. The surface dimensions and joint axes can be customized to match an individualâ€™s anthropometry. We compared the model to â€śgold standardâ€ť bone-pin kinematics collected during three shoulder tasks and found modeled scapular kinematics to be accurate to within 2mm root-mean-squared error for individual bone-pin markers across all markers and movement tasks. As an additional test, we added random and systematic noise to the bone-pin marker data and found that the model reduced kinematic variability due to noise by 65% compared to Euler angles computed without the model. Our scapulothoracic joint model can be used for inverse and forward dynamics analyses and to compute joint reaction loads. The computational performance of the scapulothoracic joint model is well suited for real-time applications; it is freely available for use with OpenSim 3.2, and is customizable and usable with other OpenSim models. PMID:26734761
Seth, Ajay; Matias, Ricardo; Veloso, António P; Delp, Scott L
2016-01-01
The complexity of shoulder mechanics combined with the movement of skin relative to the scapula makes it difficult to measure shoulder kinematics with sufficient accuracy to distinguish between symptomatic and asymptomatic individuals. Multibody skeletal models can improve motion capture accuracy by reducing the space of possible joint movements, and models are used widely to improve measurement of lower limb kinematics. In this study, we developed a rigid-body model of a scapulothoracic joint to describe the kinematics of the scapula relative to the thorax. This model describes scapular kinematics with four degrees of freedom: 1) elevation and 2) abduction of the scapula on an ellipsoidal thoracic surface, 3) upward rotation of the scapula normal to the thoracic surface, and 4) internal rotation of the scapula to lift the medial border of the scapula off the surface of the thorax. The surface dimensions and joint axes can be customized to match an individual's anthropometry. We compared the model to "gold standard" bone-pin kinematics collected during three shoulder tasks and found modeled scapular kinematics to be accurate to within 2mm root-mean-squared error for individual bone-pin markers across all markers and movement tasks. As an additional test, we added random and systematic noise to the bone-pin marker data and found that the model reduced kinematic variability due to noise by 65% compared to Euler angles computed without the model. Our scapulothoracic joint model can be used for inverse and forward dynamics analyses and to compute joint reaction loads. The computational performance of the scapulothoracic joint model is well suited for real-time applications; it is freely available for use with OpenSim 3.2, and is customizable and usable with other OpenSim models. PMID:26734761
NASA Astrophysics Data System (ADS)
Platonov, V. P.
2014-02-01
In the past four years a theory has been developed for finding fundamental units in hyperelliptic fields, and on basis of this theory innovative and efficient algorithms for computing them have been constructed and implemented. A new local-global principle was discovered which gives a criterion for the existence of non-trivial units in hyperelliptic fields. The natural connection between the problem of computing fundamental units and the problem of torsion in Jacobian varieties of hyperelliptic curves over the rational number field has led to breakthrough results in the solution of this problem. The main results in the present survey were largely obtained using a symbiosis of deep theory, efficient algorithms, and supercomputing. Such a symbiosis will play an ever increasing role in the mathematics of the 21st century. Bibliography: 27 titles.
NASA Astrophysics Data System (ADS)
Viallet, M.; Goffrey, T.; Baraffe, I.; Folini, D.; Geroux, C.; Popov, M. V.; Pratt, J.; Walder, R.
2016-02-01
This work is a continuation of our efforts to develop an efficient implicit solver for multidimensional hydrodynamics for the purpose of studying important physical processes in stellar interiors, such as turbulent convection and overshooting. We present an implicit solver that results from the combination of a Jacobian-free Newton-Krylov method and a preconditioning technique tailored to the inviscid, compressible equations of stellar hydrodynamics. We assess the accuracy and performance of the solver for both 2D and 3D problems for Mach numbers down to 10-6. Although our applications concern flows in stellar interiors, the method can be applied to general advection and/or diffusion-dominated flows. The method presented in this paper opens up new avenues in 3D modeling of realistic stellar interiors allowing the study of important problems in stellar structure and evolution.
Bernsen, Erik; Dijkstra, Henk A.; Thies, Jonas; Wubs, Fred W.
2010-10-20
In present-day forward time stepping ocean-climate models, capturing both the wind-driven and thermohaline components, a substantial amount of CPU time is needed in a so-called spin-up simulation to determine an equilibrium solution. In this paper, we present methodology based on Jacobian-Free Newton-Krylov methods to reduce the computational time for such a spin-up problem. We apply the method to an idealized configuration of a state-of-the-art ocean model, the Modular Ocean Model version 4 (MOM4). It is shown that a typical speed-up of a factor 10-25 with respect to the original MOM4 code can be achieved and that this speed-up increases with increasing horizontal resolution.
Pant-tilt Platform Design Based on Parallel Kinematics
NASA Astrophysics Data System (ADS)
Majarena, A. C.; Santolaria, J.; Aguilar, J. J.; Pastor, J.; Cajal, Cajal
2009-11-01
A new long distance measurement system design, based on parallel kinematics, is presented in this paper. This system has two degrees of freedom for positioning and orientating two high precision cameras. In this document is presented the system design. Several configurations have been analyzed and the components needed such as actuators, linear captators (to measure the displacement), spherical ball-and-socket joints and universal joints, have been selected. The developed model allows us to obtain the kinematic joint variables, depending on geometric parameters, by means of the resolution of opened chains for each leg. The direct model allows us to obtain the platform position and orientation for a determined displacement values. Once the matrix transformation (which describes the coordinates of the platform reference system respect to the base reference system) is obtained, the actuators elongation can be found out through the inverse model with numeric or geometric methods. The design optimization, by means of the analysis of anchorage points and the study of singularities (analysis of the limited platform positions, depending on maximum strut lengths and maximum angle that joints can turn), allows us to optimize the workspace of the platform.
A Kinematically Consistent Two-Point Correlation Function
NASA Technical Reports Server (NTRS)
Ristorcelli, J. R.
1998-01-01
A simple kinematically consistent expression for the longitudinal two-point correlation function related to both the integral length scale and the Taylor microscale is obtained. On the inner scale, in a region of width inversely proportional to the turbulent Reynolds number, the function has the appropriate curvature at the origin. The expression for two-point correlation is related to the nonlinear cascade rate, or dissipation epsilon, a quantity that is carried as part of a typical single-point turbulence closure simulation. Constructing an expression for the two-point correlation whose curvature at the origin is the Taylor microscale incorporates one of the fundamental quantities characterizing turbulence, epsilon, into a model for the two-point correlation function. The integral of the function also gives, as is required, an outer integral length scale of the turbulence independent of viscosity. The proposed expression is obtained by kinematic arguments; the intention is to produce a practically applicable expression in terms of simple elementary functions that allow an analytical evaluation, by asymptotic methods, of diverse functionals relevant to single-point turbulence closures. Using the expression devised an example of the asymptotic method by which functionals of the two-point correlation can be evaluated is given.
Dual velocity graphs in spatial kinematics
NASA Astrophysics Data System (ADS)
Baciu, George
1996-03-01
This article introduces a high-level topological representation for general multibody systems, the spatial directed graph. This simplified topological structure emphasizes the principal aspects of motion in multilink systems and forms a concise representation for the entire class of kinematically constrained multibody systems. It is shown that certain kinematic invariants with respect to this representation allow the simple formulation of kinematic constraints. In this context, it is observed that the only variables that are amenable to an operational algebra associated with this graph are the dual velocities. This formalism represents the starting point for the automatic generation of motion equations for generic multibody systems with applications in motion animation, virtual reality, robotics.
Electromagnetic inverse scattering
NASA Technical Reports Server (NTRS)
Bojarski, N. N.
1972-01-01
A three-dimensional electromagnetic inverse scattering identity, based on the physical optics approximation, is developed for the monostatic scattered far field cross section of perfect conductors. Uniqueness of this inverse identity is proven. This identity requires complete scattering information for all frequencies and aspect angles. A nonsingular integral equation is developed for the arbitrary case of incomplete frequence and/or aspect angle scattering information. A general closed-form solution to this integral equation is developed, which yields the shape of the scatterer from such incomplete information. A specific practical radar solution is presented. The resolution of this solution is developed, yielding short-pulse target resolution radar system parameter equations. The special cases of two- and one-dimensional inverse scattering and the special case of a priori knowledge of scatterer symmetry are treated in some detail. The merits of this solution over the conventional radar imaging technique are discussed.
Inversion for dielectric relaxation spectra
NASA Astrophysics Data System (ADS)
Morgan, Frank Dale; Lesmes, David P.
1994-01-01
A new least squares inversion algorithm is used to invert the real part of dielectric data for a spectrum of relaxation times. This inverse problem is inherently unstable; however, by transforming the linear inverse problem into log-space, the inversion iterates towards the true solution. Inversion of the theoretical distributions of Debye, Cole-Cole, and Davidson-Cole, show that this inversion method is stable, even when up to 5% of Gaussian noise is added to the data. Inversion of dielectric measurements on water, n-pentanol alcohol, and Morrison sandstone, illustrate the ability of this method to invert for relaxation-time distributions of arbitrary shape.
Karaoulis, M.; Revil, A.; Werkema, D.D.; Minsley, B.J.; Woodruff, W.F.; Kemna, A.
2011-01-01
Induced polarization (more precisely the magnitude and phase of impedance of the subsurface) is measured using a network of electrodes located at the ground surface or in boreholes. This method yields important information related to the distribution of permeability and contaminants in the shallow subsurface. We propose a new time-lapse 3-D modelling and inversion algorithm to image the evolution of complex conductivity over time. We discretize the subsurface using hexahedron cells. Each cell is assigned a complex resistivity or conductivity value. Using the finite-element approach, we model the in-phase and out-of-phase (quadrature) electrical potentials on the 3-D grid, which are then transformed into apparent complex resistivity. Inhomogeneous Dirichlet boundary conditions are used at the boundary of the domain. The calculation of the Jacobian matrix is based on the principles of reciprocity. The goal of time-lapse inversion is to determine the change in the complex resistivity of each cell of the spatial grid as a function of time. Each model along the time axis is called a 'reference space model'. This approach can be simplified into an inverse problem looking for the optimum of several reference space models using the approximation that the material properties vary linearly in time between two subsequent reference models. Regularizations in both space domain and time domain reduce inversion artefacts and improve the stability of the inversion problem. In addition, the use of the time-lapse equations allows the simultaneous inversion of data obtained at different times in just one inversion step (4-D inversion). The advantages of this new inversion algorithm are demonstrated on synthetic time-lapse data resulting from the simulation of a salt tracer test in a heterogeneous random material described by an anisotropic semi-variogram. ?? 2011 The Authors Geophysical Journal International ?? 2011 RAS.
Kinematics of normal lingual diadokokinesis
NASA Astrophysics Data System (ADS)
Flanagan, Kevin P.; Dembowski, James S.
2002-05-01
Speech-language clinicians use diadochokinetic (DDK) tasks as a behavioral measure of the status of the speech production system. The articulator kinematics of these repetitive syllable productions has been relatively little studied (most studies of speech DDK have been acoustic). As a result, many clinicians misunderstand the relationship between syllable rate and movement parameters, such as rate of articulator movement and range of articulator movement. For example, clinicians assume that because ``kuh'' syllable repetitions are relatively slow, tongue dorsum movements must be slow. However, Westbury and Dembowski [Ann. Bull. RILP No. 27 (1993)] showed that the tongue dorsum may produce larger and faster movements than other tongue points (such as the tongue tip). Therefore, syllable repetition rates may not reflect movement speeds for individual articulator points. This study replicates and extends these findings, using a larger speaker sample encompassing a wider age range. The goal of this study is to further clarify the relationship between articulator speed, range of articulator motion, and syllable rate. That is, it seeks to examine whether syllable rate is related to how quickly the tongue moves or how far the tongue moves. Data are derived from the University of Wisconsin X-ray Microbeam Database.
Edge-driven microplate kinematics
Schouten, Hans; Klitgord, Kim D.; Gallo, David G.
1993-01-01
It is known from plate tectonic reconstructions that oceanic microplates undergo rapid rotation about a vertical axis and that the instantaneous rotation axes describing the microplate's motion relative to the bounding major plates are frequently located close to its margins with those plates, close to the tips of propagating rifts. We propose a class of edge-driven block models to illustrate how slip across the microplate margins, block rotation, and propagation of rifting may be related to the relative motion of the plates on either side. An important feature of these edge-driven models is that the instantaneous rotation axes are always located on the margins between block and two bounding plates. According to those models the pseudofaults or traces of disrupted seafloor resulting from the propagation of rifting between microplate and major plates may be used independently to approximately trace the continuous kinematic evolution of the microplate back in time. Pseudofault geometries and matching rotations of the Easter microplate show that for most of its 5 m.y. history, block rotation could be driven by the drag of the Nazca and Pacific plates on the microplate's edges rather than by a shear flow of mantle underneath.
Hart, K.A.
1994-01-01
During the Intensive Observation Period (IOP), several periods of water vapor and temperature inversions near the 0 deg C level were observed. Satellite and radiosonde data from TOGA COARE are used to document the large-scale conditions and thermodynamic and kinematic structures present during three extended periods in which moisture and temperature inversions near the freezing level were very pronounced. Observations from each case are synthesized into schematics which represent typical structures of the inversion phenomena. Frequency distributions of the inversion phenomena along with climatological humidity and temperature profiles are calculated for the four-month IOP.
The kinematics of evolved planetary nebulae
NASA Astrophysics Data System (ADS)
Pereyra, E. Margarita; Richer, Michael G.; LĂłpez, Jose-Alberto
2012-08-01
We have selected a group of 85 evolved planetary nebulae to study their kinematic characteristic based on spatially resolved, long-slit echelle spectroscopy. The data have been drawn from the San Pedro MĂˇrtir Kinematic Catalogue of PNe. The aim is to characterize in detail the global kinematics of PNe at advanced stages of evolution with the largest sample of homogenous data used to date for this purpose. The results reveal groups that share kinematic and photo-ionization characteristics of the nebular shell at the different late stages under study. The expansion velocities are typically larger than seen in earlier evolutionary stages, with the largest velocities occurring in objects with very weak or absent [N II]Î»Î»6548, 6584 emission line. These results shall serve to be compared to predictions of hydrodynamical models.
Kinematic modeling of folding above listric propagating thrusts
NASA Astrophysics Data System (ADS)
Cardozo, Nestor; Brandenburg, J. P.
2014-03-01
We describe a kinematic approach to simulate folds above listric propagating thrusts. The model is based on a pre-defined circular thrust geometry with a maximum central angle beyond which the thrust is planar, inclined shear above the circular thrust, and trishear in front of the thrust. Provided the trajectory of thrust propagation is established, the model can be run forward and backwards. We use this last feature to implement a global simulated annealing, inverse modeling strategy. This inverse modeling strategy is applied to synthetic folds as well as two real examples in offshore Venezuela and the Niger Delta toe-thrust system. These three examples illustrate the benefits of the algorithm, particularly in predicting the possible range of models that can fit the structures. Thrust geometry, depth to detachment level, and backlimb geometry have high impact in model parameters such as backlimb shear angle and fault slip; while forelimb geometry is critical to constrain parameters such as fault propagation to fault slip ratio and trishear angle. Steep to overturned beds in forelimb areas are often not imaged by seismic, so in the absence of additional well data, considering all possible thrust-fold geometries is critical for the modeling and whatever prediction (e.g. hydrocarbon trap integrity) is made from it.
Kinematic Analysis of Cepheus OB3
NASA Astrophysics Data System (ADS)
Trullols, E.; Jordi, C.; Galadi-Enriquez, D.
1997-08-01
24 early type stars were selected in the Cepheus OB3 region and the surrounding area on the basis of their relationship to the Cepheus OB3 association or their photometric compatiblility with this group. A kinematic study using Hipparcos data did not show significant differences between the well known members and the remaining stars. Because some stars overlap Cepheus OB2 region, a connexion between both groups cannot be ruled out. Kinematic ages for the young and old subgroups are computed.
Regge kinematics in soft collinear effective theory
Donoghue, John F.; Wyler, Daniel
2010-06-01
We discuss the kinematics of the particles that make up a Reggeon in field theory, using the terminology of the soft collinear effective theory (SCET). Reggeization sums a series of strongly ordered collinear emissions resulting in an overall Reggeon exchange that falls in the Glauber or Coulomb kinematic region. This is an extremely multiscale problem and appears to fall outside of the usual organizing scheme of SCET.
Kinematical coincidence method in transfer reactions
NASA Astrophysics Data System (ADS)
Acosta, L.; Amorini, F.; Auditore, L.; Berceanu, I.; Cardella, G.; Chatterjiee, M. B.; De Filippo, E.; Francalanza, L.; Gianě, R.; Grassi, L.; Grzeszczuk, A.; La Guidara, E.; Lanzalone, G.; Lombardo, I.; Loria, D.; Minniti, T.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Pop, A.; Porto, F.; Rizzo, F.; Rosato, E.; Russotto, P.; Santoro, S.; Trifirň, A.; Trimarchi, M.; Verde, G.; Vigilante, M.
2013-07-01
A new method to extract high resolution angular distributions from kinematical coincidence measurements in binary reactions is presented. Kinematics is used to extract the center of mass angular distribution from the measured energy spectrum of light particles. Results obtained in the case of 10Be+p?9Be+d reaction measured with the CHIMERA detector are shown. An angular resolution of few degrees in the center of mass is obtained. The range of applicability of the method is discussed.
NASA Astrophysics Data System (ADS)
Clare, R. B.; Levinger, J. S.
1981-02-01
We use the formalism of hyperspherical harmonics to calculate several moments for the triton photoeffect, for a Volkov spin-independent potential. First, we improve the accuracy of Maleki's calculations of the moments Ď2 and Ď3 by including more terms in the hyperspherical expansion. We also calculate moments Ď0 and Ď1 for a Serber mixture. We find reasonable agreement between our moments found by sum rules and those found from the cross sections calculated by Fang et al. and Levinger-Fitzgibbon. We then develop a technique of inversion of a finite number of moments by making the assumption that the cross section can be written as a sum of several Laguerre polynomials multiplied by a decreasing exponential. We test our inversion technique successfully on several model potentials. We then modify it and apply it to the five moments (Ď-1 to Ď3) for a force without exchange, and find fair agreement with Fang's values of the cross section. Finally, we apply the inversion technique to our three moments (Ď-1,Ď0,and Ď1) for a Serber mixture, and find reasonable agreement with Gorbunov's measurements of the 3He photoeffect. NUCLEAR REACTIONS Triton photoeffects, hyperspherical harmonics, moments of photoeffect, inversion of moments.
Non-linear inverse scattering: High resolution quantitative breast tissue tomography
Wiskin, J.; Borup, D. T.; Johnson, S. A.; Berggren, M.
2012-01-01
Recent published results in inverse scattering generally show the difficulty in dealing with moderate to high contrast inhomogeneities when employing linearized or iteratively linearized algorithms (e.g., distorted Born iterative method). This paper presents a fully nonlinear algorithm utilizing full wave field data, that results in ultrasound computed tomographic images from a laboratory breast scanner, and shows several such unique images from volunteer subjects. The forward problem, data collection process and inverse scattering algorithm used are discussed. A functional that represents the “best fit” between predicted and measured data is minimized, and therefore requires a very fast forward problem solver, Jacobian calculation, and gradient estimation, all of which are described. The data collection device is described. The algorithm and device yield quantitative estimates of human breast tissue in vivo. Several high resolution images, measuring ?150 by 150 wavelengths, obtained from the 2D inverse scattering algorithms, using data collected from a first prototype, are shown and discussed. The quantitative values are compared with previous published work. PMID:22559356
Enhancement of near-surface elastic full waveform inversion results in regions of low sensitivities
NASA Astrophysics Data System (ADS)
Nuber, André; Manukyan, Edgar; Maurer, Hansruedi
2015-11-01
Elastic full waveform inversion of high-resolution seismic data is a potentially very powerful option for imaging the shallow subsurface. Unfortunately, the success of traditional full waveform inversion applied to such problems is limited by a very uneven sensitivity distribution, which can be attributed to the uneven amplitudes of body and surface waves. As a result, very shallow structures are well resolved by fitting the large amplitude surface waves, but the imaging quality decreases rapidly with depth. To account for uneven sensitivity distributions, we present a novel scaling approach that enhances weak sensitivities in regions of interest. To this end, the column sums of the Jacobian matrix - each of them corresponding to one model parameter - are equalized prior to updating the model. The performance of this methodology is demonstrated by inverting two synthetic, but realistic, data sets. Both the P- and S-wave velocity images were improved significantly by applying the new scaling technique. Our results are particularly relevant for shallow elastic full waveform inversion problems, but we also see benefits of our technique for other surface-based geophysical methods, such as geoelectrics or electromagnetics.
Can a pseudo-dynamic source inversion approach improve earthquake source imaging?
NASA Astrophysics Data System (ADS)
Zhang, Youbing; Song, Seok Goo; Dalguer, Luis; Clinton, John
2014-05-01
Imaging a high resolution spatio-temporal slip distribution of an earthquake rupture is a core research goal in seismology. In general we expect to obtain a higher quality source image by improving the observational input data (e.g. using more, higher quality, near field stations). However, recent studies show that increasing the surface station density alone does not significantly improve source inversion results (Custodio et al. 2005; Zhang et al. in review). Song et al. (2009) and Song and Dalguer (2013) found interesting correlation structures between kinematic source parameters (e.g. slip, peak slip velocity and rupture velocity) obtained both from kinematic inversion and dynamic modeling. These correlation structures that effectively regularize the model space may improve source imaging more than by simply improving the observational data. In this 'pseudo-dynamic' source inversion, source images are constrained by both physical constraints derived from rupture dynamics as well all the observational data, without compromising the computational efficiency of kinematic inversion. We investigate the efficiency of the pseudo-dynamic source inversion using synthetic dynamic rupture models. Our target model is a buried vertical strike-slip event (Mw 7.3) in a homogeneous half space. In the inversion, we model low frequency (below 1Hz) waveforms using a genetic algorithm in a Bayesian framework (Moneli et al. 2008). A dynamically consistent regularized Yoffe function (Tinti, et al. 2005) was applied as a single-window slip velocity function. We have first implemented the autocorrelation of slip in the prior distribution in the Bayesian inversion - preliminary results show that estimated kinematic source models closely match the target dynamic model. The prior information describing the auto-correlation of source parameters (e.g. slip) improves the imaging of spatial distribution of source parameters. By implementing both auto- and cross-correlation of kinematic source parameters, we can regularize the model space in a more physics-based manner and improve the source imaging more significantly compared to using traditional smoothing constraints. Further investigation is needed to tune the related parameters of pseudo-dynamic source inversion and relative weighting between the prior and the likelihood function in the Bayesian inversion.
Inverse consistent non-rigid image registration based on robust point set matching
2014-01-01
Background Robust point matching (RPM) has been extensively used in non-rigid registration of images to robustly register two sets of image points. However, except for the location at control points, RPM cannot estimate the consistent correspondence between two images because RPM is a unidirectional image matching approach. Therefore, it is an important issue to make an improvement in image registration based on RPM. Methods In our work, a consistent image registration approach based on the point sets matching is proposed to incorporate the property of inverse consistency and improve registration accuracy. Instead of only estimating the forward transformation between the source point sets and the target point sets in state-of-the-art RPM algorithms, the forward and backward transformations between two point sets are estimated concurrently in our algorithm. The inverse consistency constraints are introduced to the cost function of RPM and the fuzzy correspondences between two point sets are estimated based on both the forward and backward transformations simultaneously. A modified consistent landmark thin-plate spline registration is discussed in detail to find the forward and backward transformations during the optimization of RPM. The similarity of image content is also incorporated into point matching in order to improve image matching. Results Synthetic data sets, medical images are employed to demonstrate and validate the performance of our approach. The inverse consistent errors of our algorithm are smaller than RPM. Especially, the topology of transformations is preserved well for our algorithm for the large deformation between point sets. Moreover, the distance errors of our algorithm are similar to that of RPM, and they maintain a downward trend as whole, which demonstrates the convergence of our algorithm. The registration errors for image registrations are evaluated also. Again, our algorithm achieves the lower registration errors in same iteration number. The determinant of the Jacobian matrix of the deformation field is used to analyse the smoothness of the forward and backward transformations. The forward and backward transformations estimated by our algorithm are smooth for small deformation. For registration of lung slices and individual brain slices, large or small determinant of the Jacobian matrix of the deformation fields are observed. Conclusions Results indicate the improvement of the proposed algorithm in bi-directional image registration and the decrease of the inverse consistent errors of the forward and the reverse transformations between two images. PMID:25559889
NASA Technical Reports Server (NTRS)
Bayo, Eduardo; Ledesma, Ragnar
1993-01-01
A technique is presented for solving the inverse dynamics of flexible planar multibody systems. This technique yields the non-causal joint efforts (inverse dynamics) as well as the internal states (inverse kinematics) that produce a prescribed nominal trajectory of the end effector. A non-recursive global Lagrangian approach is used in formulating the equations for motion as well as in solving the inverse dynamics equations. Contrary to the recursive method previously presented, the proposed method solves the inverse problem in a systematic and direct manner for both open-chain as well as closed-chain configurations. Numerical simulation shows that the proposed procedure provides an excellent tracking of the desired end effector trajectory.
High-Resolution Inverse-Based Determination of Seismic-Velocity Structure in Basins
NASA Astrophysics Data System (ADS)
Akcelik, V.; Bielak, J.; Epanomeritakis, I.; Ghattas, O.
2004-12-01
Starting with the pioneering work of Aki, Christoffersson, and Husebye in 1976, there has been an increasing interest in developing inversion techniques for determining the three-dimensional crustal velocity structure in seismic regions. In this paper we describe a methodology that capitalizes on recent advances in optimization methods to adapt, extend, and refine powerful nonlinear Newton-Krylov adjoint-based inverse wave propagation algorithms to two- and three-dimensional velocity structure and kinematic source inversion problems. We present results of high resolution models for two-dimensional sedimentary valleys undergoing antiplane motion, and three dimensional acoustic approximations of models of the San Fernando Valley using parallel scalable inversion algorithms that overcome many of the difficulties particular to inverse heterogeneous wave propagation problems.
Atarod, Mohammad; Frank, Cyril B; Shrive, Nigel G
2014-03-01
The interactions between different tissues within the knee joint and between different kinematic DOF and joint flexion during normal gait were investigated. These interactions change following ACL transection, in both short (4 weeks) and long (20 weeks) term. Ten skeletally mature sheep were used in control (N = 5) and experimental (N = 5) groups. The 6-DOF stifle joint motion was first measured during normal gait. The control group were then euthanized and mounted on a unique robotic testing platform for kinetic measurements. The experimental group underwent ACL transection surgery, and kinematics measurements were repeated 4 and 20 weeks post-operatively. The experimental group were then euthanized and underwent kinetic assessment using the robotic system. Results indicated significant couplings between joint flexion vs. abduction and internal tibial rotation, as well as medial, anterior, and superior tibial translations during both normal and ACL-deficient gait. Distinct kinetic interactions were also observed between different tissues within the knee joint. Direct relationships were found between ACL vs. LM/MM, and PCL vs. MCL loads during normal gait; inverse relationships were detected between ACL vs. PCL and PCL vs. LM/MM loads. These kinetic interaction patterns were considerably altered by ACL injury. Significant inter-subject variability in joint kinematics and tissue loading patterns during gait was also observed. This study provides further understanding of the in vivo function of different tissues within the knee joint and their couplings with joint kinematics during normal gait and over time following ACL transection. PMID:24046151
Statistical Methods for Estimation of Direct and Differential Kinematics of the Vocal Tract
Lammert, Adam; Goldstein, Louis; Narayanan, Shrikanth; Iskarous, Khalil
2012-01-01
We present and evaluate two statistical methods for estimating kinematic relationships of the speech production system: Artificial Neural Networks and Locally-Weighted Regression. The work is motivated by the need to characterize this motor system, with particular focus on estimating differential aspects of kinematics. Kinematic analysis will facilitate progress in a variety of areas, including the nature of speech production goals, articulatory redundancy and, relatedly, acoustic-to-articulatory inversion. Statistical methods must be used to estimate these relationships from data since they are infeasible to express in closed form. Statistical models are optimized and evaluated â€“ using a heldout data validation procedure â€“ on two sets of synthetic speech data. The theoretical and practical advantages of both methods are also discussed. It is shown that both direct and differential kinematics can be estimated with high accuracy, even for complex, nonlinear relationships. Locally-Weighted Regression displays the best overall performance, which may be due to practical advantages in its training procedure. Moreover, accurate estimation can be achieved using only a modest amount of training data, as judged by convergence of performance. The algorithms are also applied to real-time MRI data, and the results are generally consistent with those obtained from synthetic data. PMID:24052685
Inverse problems in diffraction
NASA Technical Reports Server (NTRS)
Mikheev, Andrew G.; Shamaev, Aleksey S.
1991-01-01
A two-dimensional problem of diffraction of a plane electromagnetic wave on a smooth 2 pi-periodic surface is considered. A numerical algorithm solving this problem is developed. An inverse problem of determination of the shape of 2 pi-periodic surface using the performance data of reverse scattering is considered. The inverse problem was solved by means of minimization of the residual functional with the help of the gradient descent method. The initial data were calculated with the help of the numerical method. On each step of the iterative method of minimization, the residual functional was calculated approximately with the help of the small slope method. The examples of the shape determination are considered.
NASA Astrophysics Data System (ADS)
Kim, Sunghwan; Mitropoulos, Alexander N.; Spitzberg, Joshua D.; Tao, Hu; Kaplan, David L.; Omenetto, Fiorenzo G.
2012-12-01
Periodic nanostructures provide the facility to control and manipulate the flow of light through their lattices. Three-dimensional photonic crystals enable the controlled design of structural colour, which can be varied by infiltrating the structure with different (typically liquid) fillers. Here, we report three-dimensional photonic crystals composed entirely of a purified natural protein (silk fibroin). The biocompatibility of this protein, as well as its favourable material properties and ease of biological functionalization, present opportunities for otherwise unattainable device applications such as bioresorbable integration of structural colour within living tissue or lattice functionalization by means of organic and inorganic material doping. We present a silk inverse opal that demonstrates a pseudo-photonic bandgap in the visible spectrum and show its associated structural colour beneath biological tissue. We also leverage silk's facile dopability to manufacture a gold nanoparticle silk inverse opal and demonstrate patterned heating mediated by enhancement of nanoparticle absorption at the band-edge frequency of the photonic crystal.
Intersections, ideals, and inversion
Vasco, D.W.
1998-10-01
Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly onedimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons.
Interplanetary stream magnetism - Kinematic effects
NASA Technical Reports Server (NTRS)
Burlaga, L. F.; Barouch, E.
1976-01-01
The particle density and the magnetic-field intensity and direction are calculated for volume elements of the solar wind as a function of the initial magnetic-field direction and the initial speed gradient. It is assumed that the velocity is constant and radial. These assumptions are approximately valid between about 0.1 and 1.0 AU for many streams. Time profiles of the particle density, field intensity, and velocity are calculated for corotating streams, neglecting effects of pressure gradients. The compression and rarefaction of the magnetic field depend sensitively on the initial field direction. By averaging over a typical stream, it is found that the average radial field intensity is inversely proportional to the square of the heliocentric distance, whereas the average intensity in the direction of the planets' motion does not vary in a simple way, consistent with deep space observations. Changes of field direction may be very large, depending on the initial angle; but when the initial angle at 0.1 AU is such that the base of the field line corotates with the sun, the spiral angle is the preferred direction at 1 AU. The theory is also applicable to nonstationary flows.
Kinematic and Spatial Substructure in NGC 2264
NASA Astrophysics Data System (ADS)
Tobin, John J.; Hartmann, Lee; F?rész, Gabor; Hsu, Wen-Hsin; Mateo, Mario
2015-04-01
We present an expanded kinematic study of the young cluster NGC 2264 based upon optical radial velocities measured using multi-fiber echelle spectroscopy at the 6.5 m MMT and Magellan telescopes. We report radial velocities for 695 stars, of which approximately 407 stars are confirmed or very likely members. Our results more than double the number of members with radial velocities from F?rész et al., resulting in a much better defined kinematic relationship between the stellar population and the associated molecular gas. In particular, we find that there is a significant subset of stars that are systematically blueshifted with respect to the molecular (13CO) gas. The detection of Lithium absorption and/or infrared excesses in this blueshifted population suggests that at least some of these stars are cluster members; we suggest some speculative scenarios to explain their kinematics. Our results also more clearly define the redshifted population of stars in the northern end of the cluster; we suggest that the stellar and gas kinematics of this region are the result of a bubble driven by the wind from O7 star S Mon. Our results emphasize the complexity of the spatial and kinematic structure of NGC 2264, important for eventually building up a comprehensive picture of cluster formation. Observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.
Zou, Ling; Zhao, Haihua; Zhang, Hongbin
2015-09-01
The majority of the existing reactor system analysis codes were developed using low-order numerical schemes in both space and time. In many nuclear thermalâ€“hydraulics applications, it is desirable to use higher-order numerical schemes to reduce numerical errors. High-resolution spatial discretization schemes provide high order spatial accuracy in smooth regions and capture sharp spatial discontinuity without nonphysical spatial oscillations. In this work, we adapted an existing high-resolution spatial discretization scheme on staggered grids in two-phase flow applications. Fully implicit time integration schemes were also implemented to reduce numerical errors from operator-splitting types of time integration schemes. The resulting nonlinear system has been successfully solved using the Jacobian-free Newtonâ€“Krylov (JFNK) method. The high-resolution spatial discretization and high-order fully implicit time integration numerical schemes were tested and numerically verified for several two-phase test problems, including a two-phase advection problem, a two-phase advection with phase appearance/disappearance problem, and the water faucet problem. Numerical results clearly demonstrated the advantages of using such high-resolution spatial and high-order temporal numerical schemes to significantly reduce numerical diffusion and therefore improve accuracy. Our study also demonstrated that the JFNK method is stable and robust in solving two-phase flow problems, even when phase appearance/disappearance exists.
NASA Astrophysics Data System (ADS)
Briane, M.; Casado DĂaz, J.
2016-04-01
In this paper a new div-curl result is established in an open set Î© of RN, N â‰Ą 2, for the product Ďn áąˇÎ·n of two sequences of vector-valued functions Ďn, Î·n such that Ďn is bounded in Lp(Î©) N, Î·n is bounded in Lq(Î©) N, with 1 / p + 1 / q = 1 + 1 / (N - 1), and such that divĎn, curlÎ·n are compact in suitable spaces. The new assumption is that the product converges weakly in W - 1 , 1 (Î©). The approach is also new in the topic, and is based on a compactness result for bounded sequences in W 1 , q (Î©) through a suitable selection of annuli on which the gradients are not too high, in the spirit of [26,32] and using the imbedding of W 1 , q into Lpâ€§ for the unit sphere of RN. The div-curl result is applied to the homogenization of equi-coercive systems whose coefficients are equi-bounded in LĎ (Î©) for some Ď >N-1/2 if N > 2, or in L1 (Î©) if N = 2. It also allows us to prove a weak continuity result for the Jacobian for bounded sequences in W 1 , N - 1 (Î©) satisfying an alternative assumption to the Lâž-strong estimate of [8]. Two examples show the sharpness of the results.
Salinger, Andy; Evans, Katherine J; Lemieux, Jean-Francois; Holland, David; Payne, Tony; Price, Stephen; Knoll, Dana
2011-01-01
We have implemented the Jacobian-free Newton-Krylov (JFNK) method for solving the rst-order ice sheet momentum equation in order to improve the numerical performance of the Community Ice Sheet Model (CISM), the land ice component of the Community Earth System Model (CESM). Our JFNK implementation is based on signicant re-use of existing code. For example, our physics-based preconditioner uses the original Picard linear solver in CISM. For several test cases spanning a range of geometries and boundary conditions, our JFNK implementation is 1.84-3.62 times more efficient than the standard Picard solver in CISM. Importantly, this computational gain of JFNK over the Picard solver increases when rening the grid. Global convergence of the JFNK solver has been signicantly improved by rescaling the equation for the basal boundary condition and through the use of an inexact Newton method. While a diverse set of test cases show that our JFNK implementation is usually robust, for some problems it may fail to converge with increasing resolution (as does the Picard solver). Globalization through parameter continuation did not remedy this problem and future work to improve robustness will explore a combination of Picard and JFNK and the use of homotopy methods.
Inverse avalanches on Abelian sandpiles
Chau, H.F. Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080 )
1994-11-01
A simple and computationally efficient way of finding inverse avalanches for Abelian sandpiles, called the inverse particle addition operator, is presented. In addition, the method is shown to be optimal in the sense that it requires the minimum amount of computation among methods of the same kind. The method is also conceptually succinct because avalanche and inverse avalanche are placed in the same footing.
NASA Technical Reports Server (NTRS)
Hennessey, Michael P.; Huang, Paul C.; Bunnell, Charles T.
1989-01-01
An efficient approach to cartesian motion and force control of a 7 degree of freedom (DOF) manipulator is presented. It is based on extending the active stiffness controller to the 7 DOF case in general and use of an efficient version of the gradient projection technique for solving the inverse kinematics problem. Cooperative control is achieved through appropriate configuration of individual manipulator controllers. In addition, other aspects of trajectory generation using standard techniques are integrated into the controller. The method is then applied to a specific manipulator of interest (Robotics Research T-710). Simulation of the kinematics, dynamics, and control are provided in the context of several scenarios: one pertaining to a noncontact pick and place operation; one relating to contour following where contact is made between the manipulator and environment; and one pertaining to cooperative control.
SMACK - SMOOTHING FOR AIRCRAFT KINEMATICS
NASA Technical Reports Server (NTRS)
Bach, R.
1994-01-01
The computer program SMACK (SMoothing for AirCraft Kinematics) is designed to provide flightpath reconstruction of aircraft forces and motions from measurements that are noisy or incomplete. Additionally, SMACK provides a check on instrument accuracy and data consistency. The program can be used to analyze data from flight-test experiments prior to their use in performance, stability and control, or aerodynamic modeling calculations. It can also be used in the analysis of aircraft accidents, where the actual forces and motions may have to be determined from a very limited data set. Application of a state-estimation method for flightpath reconstruction is possible because aircraft forces and motions are related by well-known equations of motion. The task of postflight state estimation is known as a nonlinear, fixed-interval smoothing problem. SMACK utilizes a backward-filter, forward-smoother algorithm to solve the problem. The equations of motion are used to produce estimates that are compared with their corresponding measurement time histories. The procedure is iterative, providing improved state estimates until a minimum squared-error measure is achieved. In the SMACK program, the state and measurement models together represent a finite-difference approximation for the six-degree-of-freedom dynamics of a rigid body. The models are used to generate time histories which are likely to be found in a flight-test measurement set. These include onboard variables such as Euler angles, angular rates, and linear accelerations as well as tracking variables such as slant range, bearing, and elevation. Any bias or scale-factor errors associated with the state or measurement models are appended to the state vector and treated as constant but unknown parameters. The SMACK documentation covers the derivation of the solution algorithm, describes the state and measurement models, and presents several application examples that should help the analyst recognize the potential advantages of using state estimation. Complete instructions are given for preparing a coding list for problem solution by SMACK. The use of SMACK as part of an overall flight-test methodology is illustrated, as well as its application for analysis of a windshear accident. The details required for installing the program are presented, including sample output listings to facilitate testing. SMACK is written in FORTRAN 77 for DEC VAX series computers running VMS. Two versions of the source code are provided, a single precision version, which can be ported to Cray series computers, and a VAX double precision version. SMACK can call routines from the commercial package IMSL, or replacement routines which are provided can be used. SMACK solution variables to be plotted are written to an ASCII plot file. A sample plotting program, which is designed to be used with the DISSPLA graphics package, is included; however this program can easily be modified for use with other xy plotting packages. The double precision version requires 10Mb of RAM for execution under VMS. SMACK is available in DEC VAX BACKUP format on a 9-track 1600 BPI magnetic tape (standard distribution) or on a TK50 tape cartridge. This program was developed in 1991. DEC, VAX, and VMS are trademarks of Digital Equipment Corporation. DISSPLA is a trademark of Computer Associates, Inc. IMSL is a registered trademark of IMSL, Inc.
Highly damped kinematic coupling for precision instruments
Hale, Layton C. (Livermore, CA); Jensen, Steven A. (Livermore, CA)
2001-01-01
A highly damped kinematic coupling for precision instruments. The kinematic coupling provides support while causing essentially no influence to its nature shape, with such influences coming, for example, from manufacturing tolerances, temperature changes, or ground motion. The coupling uses three ball-cone constraints, each combined with a released flexural degree of freedom. This arrangement enables a gain of higher load capacity and stiffness, but can also significantly reduce the friction level in proportion to the ball radius divided by the distance between the ball and the hinge axis. The blade flexures reduces somewhat the stiffness of the coupling and provides an ideal location to apply constrained-layer damping which is accomplished by attaching a viscoelastic layer and a constraining layer on opposite sides of each of the blade flexures. The three identical ball-cone flexures provide a damped coupling mechanism to kinematically support the projection optics system of the extreme ultraviolet lithography (EUVL) system, or other load-sensitive apparatus.
Dark energy as a kinematic effect
NASA Astrophysics Data System (ADS)
Jennen, H.; Pereira, J. G.
2016-03-01
We present a generalization of teleparallel gravity that is consistent with local spacetime kinematics regulated by the de Sitter group SO(1 , 4) . The mathematical structure of teleparallel gravity is shown to be given by a nonlinear Riemann-Cartan geometry without curvature, which inspires us to build the generalization on top of a de Sitter-Cartan geometry with a cosmological function. The cosmological function is given its own dynamics and naturally emerges nonminimally coupled to the gravitational field in a manner akin to teleparallel dark energy models or scalar-tensor theories in general relativity. New in the theory here presented, the cosmological function gives rise to a kinematic contribution in the deviation equation for the world lines of adjacent free-falling particles. While having its own dynamics, dark energy manifests itself in the local kinematics of spacetime.
Kinematics and Control of Robot Manipulators
NASA Astrophysics Data System (ADS)
Paden, Bradley Evan
This dissertation focuses on the kinematics and control of robot manipulators. The contribution to kinematics is a fundamental theorem on the design of manipulators with six revolute joints. The theorem states, roughly speaking, that manipulators which have six revolute joints and are modeled after the human arm are optimal and essentially unique. In developing the mathematical framework to prove this theorem, we define precisely the notions of length of a manipulator, well-connected-workspace, and work-volume. We contribute to control a set of analysis techniques for the design of variable structure (sliding mode) controllers for manipulators. The organization of the dissertation is the following. After introductory remarks in chapter one, the group of proper rigid motions, G, is introduced in chapter two. The tangent bundle of G is introduced and it is shown that the velocity of a rigid body can be represented by an element in the Lie algebra of G (commonly called a twist). Further, rigid motions which are exponentials of twists are used to describe four commonly occurring subproblems in robot kinematics. In chapter three, the exponentials of twists are used to write the forward kinematic map of robot manipulators and the subproblems of chapter two are used to solve the Stanford manipulator and an elbow manipulator. Chapter four focuses on manipulator singularities. Twist coordinates are used to find critical points of the forward kinematic map. The contribution to kinematics is contained in chapter five where a mathematical framework for studying the relationship between the design of 6R manipulators and their performance is developed. Chapter seven contains the contribution to control. The work of A. F. Filippov on differential equations with discontinuous right-hand-side and the work of F. H. Clarke on generalized gradients are combined to obtain a calculus for analyzing nonsmooth gradient systems. The techniques developed are applied to design a simple variable structure controller for the nonlinear dynamics of robot manipulators.
Hexapod kinematics for secondary mirror aberration control .
NASA Astrophysics Data System (ADS)
Schipani, P.
This work deals with active correction of the aberrations in a telescope by moving the secondary mirror. A special attention is dedicated to the case of a secondary mirror whose motions are controlled by a 6-6 Stewart Platform (generally called by astronomers simply "hexapod", even if this term is more general). The kinematics of the device is studied. The non trivial forward kinematics problem is solved by an iterative algorithm fitting the necessities of an active optics system and fast enough to be used in a closed loop feedback control.
Discrepancies in kinematic calculations of HOLZ lines.
Eades, J A; Moore, S; Pfullmann, T; Hangas, J
1993-04-15
We have found significant differences between the results of computer simulations of HOLZ line patterns. The computations in question are made in the kinematical approximation. After trivial errors are eliminated the programs fall into two groups. There is a discrepancy between the two that increases with distance from the zone axis. The difference is small but not negligible at the level of precision used in determining lattice parameters or strain. We show which of the two is correct in the kinematic approximation and that the discrepancy between the two groups is of the order of the error introduced by dynamical interaction. PMID:8490236
Kinematic Distances of Galactic Planetary Nebulae
NASA Astrophysics Data System (ADS)
Yang, A. Y.; Tian, W. W.; Zhu, H.; Leahy, D. A.; Wu, D.
2016-03-01
We construct H i absorption spectra for 18 planetary nebulae (PNs) and their background sources using data from the International Galactic Plane Survey. We estimate the kinematic distances of these PNs, among which 15 objectsâ€™ kinematic distances are obtained for the first time. The distance uncertainties of 13 PNs range from 10% to 50%, which is a significant improvement with uncertainties of a factor of two or three smaller than most previous distance measurements. We confirm that PN G030.2â€‘00.1 is not a PN because of its large distance found here.
Graph Theory Roots of Spatial Operators for Kinematics and Dynamics
NASA Technical Reports Server (NTRS)
Jain, Abhinandan
2011-01-01
Spatial operators have been used to analyze the dynamics of robotic multibody systems and to develop novel computational dynamics algorithms. Mass matrix factorization, inversion, diagonalization, and linearization are among several new insights obtained using such operators. While initially developed for serial rigid body manipulators, the spatial operators and the related mathematical analysis have been shown to extend very broadly including to tree and closed topology systems, to systems with flexible joints, links, etc. This work uses concepts from graph theory to explore the mathematical foundations of spatial operators. The goal is to study and characterize the properties of the spatial operators at an abstract level so that they can be applied to a broader range of dynamics problems. The rich mathematical properties of the kinematics and dynamics of robotic multibody systems has been an area of strong research interest for several decades. These properties are important to understand the inherent physical behavior of systems, for stability and control analysis, for the development of computational algorithms, and for model development of faithful models. Recurring patterns in spatial operators leads one to ask the more abstract question about the properties and characteristics of spatial operators that make them so broadly applicable. The idea is to step back from the specific application systems, and understand more deeply the generic requirements and properties of spatial operators, so that the insights and techniques are readily available across different kinematics and dynamics problems. In this work, techniques from graph theory were used to explore the abstract basis for the spatial operators. The close relationship between the mathematical properties of adjacency matrices for graphs and those of spatial operators and their kernels were established. The connections hold across very basic requirements on the system topology, the nature of the component bodies, the indexing schemes, etc. The relationship of the underlying structure is intimately connected with efficient, recursive computational algorithms. The results provide the foundational groundwork for a much broader look at the key problems in kinematics and dynamics. The properties of general graphs and trees of nodes and edge were examined, as well as the properties of adjacency matrices that are used to describe graph connectivity. The nilpotency property of such matrices for directed trees was reviewed, and the adjacency matrices were generalized to the notion of block weighted adjacency matrices that support block matrix elements. This leads us to the development of the notion of Spatial Kernel Operator SKO kernels. These kernels provide the basis for the development of SKO resolvent operators.
Kinetic and kinematic differences between deadlifts and goodmornings
2013-01-01
Background In order to improve training performance, as well as avoid overloading during prevention and rehabilitation exercises in patients, the aim of this study was to understand the biomechanical differences in the knee, hip and the back between the exercises “Goodmornings” (GMs) and “Deadlifts” (DLs). Methods The kinetics and kinematics of 13 subjects, performing GMs and DLs with an additional 25% (GMs), 25% and 50% (DLs) body weight (BW) on the barbell were analysed. Using the kinetic and kinematic data captured using a 3D motion analysis and force plates, an inverse approach with a quasi-static solution was used to calculate the sagittal moments and angles in the knee, hip and the trunk. The maximum moments and joint angles were statistically tested using ANOVA with a Bonferroni adjustment. Results The observed maximal flexion angle of the knee was 5.3?±?6.7° for GMs and 107.8?±?22.4° and 103.4?±?22.6° for DLs with 25% and 50% BW respectively. Of the hip, the maximal flexion angle was 25% smaller during GMs compared to DLs. No difference in kinematics of the trunk between the two exercises was observed. For DLs, the resulting sagittal moment in the knee was an external flexion moment, whereas during GMs an external extension moment was present. Importantly, no larger sagittal knee joint moments were observed when using a heavier weight on the barbell during DLs, but higher sagittal moments were found at the hip and L4/L5. Compared to GMs, DLs produced a lower sagittal moment at the hip using 25% BW while generating the same sagittal moment at L4/L5. Conclusions The two exercises exhibited different motion patterns for the lower extremities but not for the trunk. To strengthen the hip while including a large range of motion, DLs using 50% BW should be chosen. Due to their ability to avoid knee flexion or a knee flexion moment, GMs should be preferentially chosen over DLs as ACL rupture prevention exercises. Here, in order to shift the hamstring to quadriceps ratio towards the hamstrings, GMs should be favoured ahead of DLs using 50% BW before DLs using 25% BW. PMID:24314057
Geometry and Kinematics of the High Zagros Belt (Iran)
NASA Astrophysics Data System (ADS)
Tavakoli, S.; Frizon de lamotte, D.; Ringenbach, J.-C.; Ballard, J.-F.
2012-04-01
The High Zagros Belt (HZB) is the most internal part of the wider Zagros Fold-Thrust Belt (ZFTB). It is an elevated domain (up to 4400 m) bounded to the south by the High Zagros Fault (HZF), which we define as the southernmost principal thrust-fault carrying out Lower Paleozoic strata over Mesozoic or Cenozoic rocks. To the north the HZB is bounded either by the Main Zagros Thrust (MZT), which corresponds to the fundamental limit (Neo-Tethys suture) with the internal Sanandaj-Sirjan Zone (pertaining to the Eurasian Plate) or by the front of the discontinuous "Crush Zone" (CZ) in which are exposed rocks coming from the distal margin of the former Neo-Tethys Ocean. Following our definition the HZB, exists in two disconnected prominent and elevated domains: the Central and Eastern High Zagros (CHZB& EHZB) respectively. The CHZB is a funnel shape region with a length of about 450 Km and variable width between 40 to 80 Km broadening from the NW to the SE. We will present a new tectonic map of this region and four new balanced cross-sections with associated kinematic models. From a geometric point of view, we show the existence of an important intermediate décollement level located within Ordovician-Silurian shale. This décollement, together with the well-known Hormuz basal décollement, allows the development of duplexes confined at depth in the core of the anticlines. For the kinematics, we confirm a two-steps model with a first thin-skinned phase leading to the development of large detachment folds developed over the Hormuz salt layer. At this stage the different intermediate décollement levels were activated. The second phase is thick-skinned and corresponds to the inversion of deep-seated basement faults and occurrence oflarge out-of-sequence thrusts,responsible for the exhumation of Lower Paleozoic rocks. The Eastern High Zagros Belt is a more restricted area composed by three giant anticlines, namely the Gakhum, Faraghan and Kue-e-Khush anticlines. Here also, we will present a new tectonic map and balanced-sections crossing the three anticlines. From a geometric point of view, the most striking structure is a major back-thrust floored by Ordovician shale in the Faraghan anticline. We will show that this back-thrust developed during an early thin-skinned phase of deformation and is subsequently cut out by basement faults. Finally, we will present an integrated kinematic model for the whole HZB.
[Puerperal uterine inversion].
Slaoui, M A; Bouchikhi, C; Banani, A
2010-09-01
The uterine inversion defines itself anatomically as the invagination of the uterine bottom "finger of glove" until be able to at most express itself in the vulva. It is a dramatic accident of the delivery and a sporadic occurrence in countries with low medical entity, this rarity which can mislead the practitioner, the delay of the diagnosis ends in redoubtable complications even the maternal death. Through a retrospective study concerning six case reports brought together within CHU Hassan II of Fez spreading out over eight years and review of literature, we try to describe different aspects epidemiological, etiologic, therapeutic and prognosis of this rather particular entity. PMID:21086583
Calibration of parallel kinematic devices using sequential determination of kinematic parameters
JOKIEL JR.,BERNHARD; BIEG,LOTHAR F.; ZIEGERT,JOHN C.
2000-04-06
In PKM Machines, the Cartesian position and orientation of the tool point carried on the platform is obtained from a kinematic model of the particular machine. Accurate positioning of these machines relies on the accurate knowledge of the parameters of the kinematic model unique to the particular machine. The parameters in the kinematic model include the spatial locations of the joint centers on the machine base and moving platform, the initial strut lengths, and the strut displacements. The strut displacements are readily obtained from sensors on the machine. However, the remaining kinematic parameters (joint center locations, and initial strut lengths) are difficult to determine when these machines are in their fully assembled state. The size and complexity of these machines generally makes it difficult and somewhat undesirable to determine the remaining kinematic parameters by direct inspection such as in a coordinate measuring machine. In order for PKMs to be useful for precision positioning applications, techniques must be developed to quickly calibrate the machine by determining the kinematic parameters without disassembly of the machine. A number of authors have reported techniques for calibration of PKMs (Soons, Masory, Zhuang et. al., Ropponen). In two other papers, the authors have reported on work recently completed by the University of Florida and Sandia National Laboratories on calibration of PKMs, which describes a new technique to sequentially determine the kinematic parameters of an assembled parallel kinematic device. The technique described is intended to be used with a spatial coordinate measuring device such as a portable articulated CMM measuring arm (Romer, Faro, etc.), a Laser Ball Bar (LBB), or a laser tracker (SMX< API, etc.). The material to be presented is as follows: (1) methods to identify the kinematic parameters of 6--6 variant Stewart platform manipulators including joint center locations relative to the workable and spindle nose, and initial strut lengths, (2) and example of the application of the method, and (3) results from the application of the technique.
Gait Kinematic Analysis in Water Using Wearable Inertial Magnetic Sensors
Fantozzi, Silvia; Giovanardi, Andrea; Borra, Davide; Gatta, Giorgio
2015-01-01
Walking is one of the fundamental motor tasks executed during aquatic therapy. Previous kinematics analyses conducted using waterproofed video cameras were limited to the sagittal plane and to only one or two consecutive steps. Furthermore, the set-up and post-processing are time-consuming and thus do not allow a prompt assessment of the correct execution of the movements during the aquatic session therapy. The aim of the present study was to estimate the 3D joint kinematics of the lower limbs and thorax-pelvis joints in sagittal and frontal planes during underwater walking using wearable inertial and magnetic sensors. Eleven healthy adults were measured during walking both in shallow water and in dry-land conditions. Eight wearable inertial and magnetic sensors were inserted in waterproofed boxes and fixed to the body segments by means of elastic modular bands. A validated protocol (Outwalk) was used. Gait cycles were automatically segmented and selected if relevant intraclass correlation coefficients values were higher than 0.75. A total of 704 gait cycles for the lower limb joints were normalized in time and averaged to obtain the mean cycle of each joint, among participants. The mean speed in water was 40% lower than that of the dry-land condition. Longer stride duration and shorter stride distance were found in the underwater walking. In the sagittal plane, the knee was more flexed (â‰ 23Â°) and the ankle more dorsiflexed (â‰ 9Â°) at heel strike, and the hip was more flexed at toe-off (â‰ 13Â°) in water than on land. On the frontal plane in the underwater walking, smoother joint angle patterns were observed for thorax-pelvis and hip, and ankle was more inversed at toe-off (â‰ 7Â°) and showed a more inversed mean value (â‰ 7Â°). The results were mainly explained by the effect of the speed in the water as supported by the linear mixed models analysis performed. Thus, it seemed that the combination of speed and environment triggered modifications in the joint angles in underwater gait more than these two factors considered separately. The inertial and magnetic sensors, by means of fast set-up and data analysis, can supply an immediate gait analysis report to the therapist during the aquatic therapy session. PMID:26368131
Gait Kinematic Analysis in Water Using Wearable Inertial Magnetic Sensors.
Fantozzi, Silvia; Giovanardi, Andrea; Borra, Davide; Gatta, Giorgio
2015-01-01
Walking is one of the fundamental motor tasks executed during aquatic therapy. Previous kinematics analyses conducted using waterproofed video cameras were limited to the sagittal plane and to only one or two consecutive steps. Furthermore, the set-up and post-processing are time-consuming and thus do not allow a prompt assessment of the correct execution of the movements during the aquatic session therapy. The aim of the present study was to estimate the 3D joint kinematics of the lower limbs and thorax-pelvis joints in sagittal and frontal planes during underwater walking using wearable inertial and magnetic sensors. Eleven healthy adults were measured during walking both in shallow water and in dry-land conditions. Eight wearable inertial and magnetic sensors were inserted in waterproofed boxes and fixed to the body segments by means of elastic modular bands. A validated protocol (Outwalk) was used. Gait cycles were automatically segmented and selected if relevant intraclass correlation coefficients values were higher than 0.75. A total of 704 gait cycles for the lower limb joints were normalized in time and averaged to obtain the mean cycle of each joint, among participants. The mean speed in water was 40% lower than that of the dry-land condition. Longer stride duration and shorter stride distance were found in the underwater walking. In the sagittal plane, the knee was more flexed (? 23°) and the ankle more dorsiflexed (? 9°) at heel strike, and the hip was more flexed at toe-off (? 13°) in water than on land. On the frontal plane in the underwater walking, smoother joint angle patterns were observed for thorax-pelvis and hip, and ankle was more inversed at toe-off (? 7°) and showed a more inversed mean value (? 7°). The results were mainly explained by the effect of the speed in the water as supported by the linear mixed models analysis performed. Thus, it seemed that the combination of speed and environment triggered modifications in the joint angles in underwater gait more than these two factors considered separately. The inertial and magnetic sensors, by means of fast set-up and data analysis, can supply an immediate gait analysis report to the therapist during the aquatic therapy session. PMID:26368131
Kinematics of the Ethiopian Rift and Absolute motion of Africa and Somalia Plates
NASA Astrophysics Data System (ADS)
Muluneh, A. A.; Cuffaro, M.; Doglioni, C.
2013-12-01
The Ethiopian Rift (ER), in the northern part of East African Rift System (EARS), forms a boundary zone accommodating differential motion between Africa and Somalia Plates. Its orientation was influenced by the inherited Pan-African collisional system and related lithospheric fabric. We present the kinematics of ER derived from compilation of geodetic velocities, focal mechanism inversions, structural data analysis, and construction of geological profiles. GPS velocity field shows a systematic eastward magnitude increase in NE direction in the central ER. In the same region, incremental extensional strain axes recorded by earthquake focal mechanism and fault slip inversion show ?N1000E orientation. This deviation between GPS velocity trajectories and orientation of incremental extensional strain is developed due to left lateral transtensional deformation. This interpretation is consistent with the en-échelon pattern of tensional and transtensional faults, the distribution of the volcanic centers, and the asymmetry of the rift itself. Small amount of vertical axis blocks rotation, sinistral strike slip faults and dyke intrusions in the rift accommodate the transtensional deformation. We analyzed the kinematics of ER relative to Deep and Shallow Hot Spot Reference Frames (HSRF). Comparison between the two reference frames shows different kinematics in ER and also Africa and Somalia plate motion both in magnitude and direction. Plate spreading direction in shallow HSRF (i.e. the source of the plumes locates in the asthenosphere) and the trend of ER deviate by about 27°. Shearing and extension across the plate boundary zone contribute both to the style of deformation and overall kinematics in the rift. We conclude that the observed long wavelength kinematics and tectonics are consequences of faster SW ward motion of Africa than Somalia in the shallow HSRF. This reference frame seems more consistent with the geophysical and geological constraints in the Rift. The faster SW motion of Africa with respect to Somalia plate is due to a possibly lower viscosity in the top asthenosphere (Low-Velocity Zone) beneath Africa. These findings have significant implications for the evolution of continental rifting in transtensional settings and provide evidence for the kinematics and tectonics of the Ethiopian rift in the context of the Africa-Somalia plate interaction in the mantle reference frame.
Transfer reaction studies in inverse kinematics with the magnetic spectrometer PRISMA
NASA Astrophysics Data System (ADS)
Corradi, L.
2015-01-01
The large solid angle magnetic spectrometers, in combination with large gamma arrays, allowed to perform reaction mechanism and nuclear structure studies in different regions of the nuclear chart, especially in the neutron-rich direction. By studying transfer of multiple pairs valuable information on nucleon-nucleon correlations can be derived, especially from measurements performed below the Coulomb barrier. There is growing interest in the study of the properties of the heavy binary partner, in the Pb and in the actinides regions, crucial also for astrophysics.
Inverse-kinematics one-neutron pickup with fast rare-isotope beams
Gade, A.; Baugher, T.; Brown, B. A.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Stroberg, S. R.; Tostevin, J. A.; Bazin, D.; Campbell, C. M.; Grinyer, G. F.; Weisshaar, D.; Winkler, R.; Meierbachtol, K.; Walsh, K. A.
2011-05-15
Measurements and reaction model calculations are reported for single-neutron pickup reactions onto a fast {sup 22}Mg secondary beam at 84 MeV per nucleon. Measurements made on both carbon and beryllium targets, having very different structures, were used to investigate the likely nature of the pickup reaction mechanism. The measurements involve thick reaction targets and {gamma}-ray spectroscopy of the projectile-like reaction residue for final-state resolution, which permit experiments with low incident beam rates compared to traditional low-energy transfer reactions. From measured longitudinal momentum distributions we show that the {sup 12}C({sup 22}Mg,{sup 23}Mg+{gamma})X reaction largely proceeds as a direct two-body reaction, with the neutron transfer producing bound {sup 11}C target residues. The corresponding reaction on the {sup 9}Be target seems to largely leave the {sup 8}Be residual nucleus unbound at excitation energies high in the continuum. We discuss the possible use of such fast-beam one-neutron pickup reactions to track single-particle strength in exotic nuclei and also their expected sensitivity to neutron high-l (intruder) states, which are often direct indicators of shell evolution and the disappearance of magic numbers in the exotic regime.
Inverse-kinematics one-neutron pickup with fast rare-isotope beams
NASA Astrophysics Data System (ADS)
Gade, A.; Tostevin, J. A.; Baugher, T.; Bazin, D.; Brown, B. A.; Campbell, C. M.; Glasmacher, T.; Grinyer, G. F.; McDaniel, S.; Meierbachtol, K.; Ratkiewicz, A.; Stroberg, S. R.; Walsh, K. A.; Weisshaar, D.; Winkler, R.
2011-05-01
Measurements and reaction model calculations are reported for single-neutron pickup reactions onto a fast Mg22 secondary beam at 84 MeV per nucleon. Measurements made on both carbon and beryllium targets, having very different structures, were used to investigate the likely nature of the pickup reaction mechanism. The measurements involve thick reaction targets and ?-ray spectroscopy of the projectile-like reaction residue for final-state resolution, which permit experiments with low incident beam rates compared to traditional low-energy transfer reactions. From measured longitudinal momentum distributions we show that the 12C(22Mg,23Mg+?)X reaction largely proceeds as a direct two-body reaction, with the neutron transfer producing bound C11 target residues. The corresponding reaction on the Be9 target seems to largely leave the Be8 residual nucleus unbound at excitation energies high in the continuum. We discuss the possible use of such fast-beam one-neutron pickup reactions to track single-particle strength in exotic nuclei and also their expected sensitivity to neutron high-? (intruder) states, which are often direct indicators of shell evolution and the disappearance of magic numbers in the exotic regime.
Inverse-kinematics proton scattering from 46Ar with a liquid hydrogen target and GRETINA
NASA Astrophysics Data System (ADS)
Glowacki, Matt; Ursinus College Nuclear Structure Group Team
2013-10-01
The Ursinus College nuclear structure group performed an experiment at the National Superconducting Cyclotron Laboratory at Michigan State University in May. We sent a super-cocktail beam of exotic nuclei through a liquid hydrogen target that was cooled to 16 K. We measured these gamma rays in coincidence with outgoing beam nuclei. Then, we compared the gamma-ray spectra with simulations to determine gamma-ray intensities, which are related to the cross sections of populating collective excited states of the nucleus in these collisions. These will help us better understand nuclear shell structure. My work is focused on 46Ar, a test case for which a similar measurement for cross sections have already been made. Preliminary results will be presented.
NASA Astrophysics Data System (ADS)
Deverchere, J.; Yelles, K.; Bracene, R.; Mercier de Lepinay, B. F.; Cattaneo, A.; Medaouri, M.; Gaullier, V.; Babonneau, N.; Ratzov, G.; Boudiaf, A.; Graindorge, D.; Kherroubi, A.; Strzerzynski, P. H.; Authemayou, C.; Djellit, H.; Heddar, A.; Maradja'03; Maradja-Samra'05 Scientific Teams
2011-12-01
The reasons to study the Algerian margin (Western Mediterranean) are at least threefold: (1) the seismic hazard offshore is obviously present but unconstrained, (2) the way the opening of the Algerian basin occurred is highly debated, and (3) this margin represents one of the rare examples on Earth of an ongoing subduction inception. We present an overview of recent findings on the tectonic evolution of this margin, where most of the plate convergence between Africa and Europe is taken up today, mostly from cruises MARADJA and MARADJA2/SAMRA led by joint Algerian and French teams. Large, overlapping active thrust faults and folds apparently dominate the seismotectonic pattern from the Atlas domain on land to the foot of the margin offshore, with a clear segmentation. Strain is distributed across the whole area, with a significant part of the relative plate convergence taken up offshore. Fault activity offshore is tenuous and most often indirect (Plio-Quaternary growth strata, folds, uplifted basins, scars and slope breaks). Along the eastern margin, faults form stepwise, en-Ă©chelon systems on the slope and in the deep basin. Some thrusts identified turn to fault-propagation folds at the sub-surface. Thrusts interact with the sediment flux, Messinian salt and seafloor currents, forming complex structures at deep-sea fans and scarps or scars on the main slope breaks. The 2003 Mw 6.9 Boumerdes rupture is correlated segmented cumulative scarps on the slope and at the foot of the margin. Using various VHR seismic reflection and coring analyses, we show that the record of turbidite deposition since ca. 10.000 yrs can be identified and correlated over long distances within or across large segments of the margin affected by the 1954, 1980 and 2003 events. The consequences in term of earthquake size and recovery of their recurrences (identification of paleo-events) are explored and discussed. Although we cannot associate the triggering of large turbidity currents to a given fault, we find that the Algerian margin gathers favourable conditions to reconstruct times series of turbidites associated to significant earthquakes. Finally, we show that the structures inherited from the Algerian basin opening and from the Alpine belt building (AlKaPeCa blocks migration and collision) determine for a large part the size, style and location of this strain pattern. The overall geometry indicates the predominance of back thrusts, implying underthrusting of the young oceanic crust, although large dextral strike-slip structures may guide deformation at some places on land. The recent (probably less than 3 Ma) reactivation of the Algerian margin is strongly influenced by the subduction of the Tethyan Maghrebian ocean, implying not only an important roll-back of the slab, but also strong thermal, magmatic and isostatic effects of the slab evolution at depth.
Block model of western US kinematics from inversion of geodetic, fault slip, and earthquake data
NASA Astrophysics Data System (ADS)
McCaffrey, R.
2003-12-01
The active deformation of the southwestern US (30° to 41° N) is represented by a finite number of rotating, elastic spherical caps. Horizontal GPS velocities (1583), fault slip rates (94), and earthquake slip vectors (116) are inverted for block angular velocities, locking on block-bounding faults, and the rotation of individual GPS velocity fields relative to North America. GPS velocities are modeled as a combination of rigid block rotations and elastic strain rates resulting from interactions of adjacent blocks across bounding faults. The resulting Pacific - North America pole is indistinguishable from that of Beavan et al. (2001) and satisfies spreading in the Gulf of California and earthquake slip vectors in addition to GPS. The largest blocks, the Sierra Nevada - Great Valley and the eastern Basin and Range, show internal strain rates, after removing the elastic component, of only a few nanostrain/a, demonstrating long term approximately rigid behavior. Most fault slip data are satisfied except that the San Jacinto fault appears to be significantly faster than inferred from geology while the Coachella and San Bernardino segments of the San Andreas fault are slower, suggesting the San Andreas system is straightening out in Southern California. Vertical axis rotation rates for most blocks are clockwise and in magnitude more like the Pacific than North America. One exception is the eastern Basin and Range (242° E to 248° E) which rotates slowly anticlockwise about a pole offshore Baja.
A kinematic model of KĂˇrmĂˇn gaiting in rainbow trout
Akanyeti, Otar; Liao, James C.
2013-01-01
SUMMARY A mechanistic understanding of how fishes swim in unsteady flows is challenging despite its prevalence in nature. Previous kinematic studies of fish KĂˇrmĂˇn gaiting in a vortex street behind a cylinder only report time-averaged measurements, precluding our ability to formally describe motions on a cycle-by-cycle basis. Here we present the first analytical model that describes the swimming kinematics of KĂˇrmĂˇn gaiting trout with 70â€“90% accuracy. We found that body bending kinematics can be modelled with a travelling wave equation, which has also been shown to accurately model free-stream swimming kinematics. However, free-stream swimming and KĂˇrmĂˇn gaiting are separated in the parameter space; the amplitude, wavelength and frequency values of the traveling wave equation are substantially different for each behavior. During KĂˇrmĂˇn gaiting, the wave is initiated at the body center, which is 0.2L (where L is total body length) further down the body compared with the initiation point in free-stream swimming. The wave travels with a constant speed, which is higher than the nominal flow speed just as in free-stream swimming. In addition to undulation, we observed that KĂˇrmĂˇn gaiting fish also exhibit substantial lateral translations and body rotations, which can constitute up to 75% of the behavior. These motions are periodic and their frequencies also match the vortex shedding frequency. There is an inverse correlation between head angle and body angle: when the body rotates in one direction, the head of the fish turns into the opposite direction. Our kinematic model mathematically describes how fish swim in vortical flows in real time and provides a platform to better understand the effects of flow variations as well as the contribution of muscle activity during corrective motions. PMID:24115054
Kinematic time migration and demigration of reflections in pre-stack seismic data
NASA Astrophysics Data System (ADS)
Iversen, Einar; Tygel, Martin; Ursin, BjĂ¸rn; de Hoop, Maarten V.
2012-06-01
In kinematic time migration one maps the time, slope and curvature characteristics of seismic reflection events, referred to as reflection-time parameters, from the recording domain of the seismic data to the time-migration domain. The inverse process is kinematic time demigration. We generalize kinematic time migration and demigration in several respects: the reflection-time parameters may belong to arbitrary source-receiver offsets; local heterogeneity of the time-migration velocity model is accounted for; the mapping operations do not depend specifically on the type of diffraction-time function and the parametrization of the velocity model. Time-migration and time-demigration spreading matrices are obtained as byproducts of the mapping operations. These matrices yield a paraxial expression for the connection between midpoint and image-point gather locations of mapped reflection events. Also, we obtain the time-migration counterpart of the so-called second duality theorem in Kirchhoff depth migration. Diffractions and reflections are assumed to be without conversion, and sources and receivers are located along the same measurement surface. Our framework enables the identification of a full set of first- and second-order reflection-time parameters from time-migrated seismic data followed by a kinematic demigration to the recording domain. The idea of this route is to 'undo' eventual errors introduced by time migration and result in reliable estimation of recording-domain invariants, that is, parameters insensitive to the time-migration velocity model. The developed concepts associated with time migration are of interest in reflection seismic and global earth applications. Two numerical examples demonstrate the potential of kinematic time migration and demigration techniques in seismic time imaging and velocity-model building.
Hierarchical Bayesian Inversion for the Centroid Moment Tensor
NASA Astrophysics Data System (ADS)
Mustac, M.; Tkalcic, H.
2014-12-01
Kinematic point source inversions using data from complex tectonic settings (e.g. geothermal or volcanic areas and mines) often result in large non-double-couple components. Examining events with mechanisms more complex than shear motion on a planar fault requires a sophisticated inversion method. We have developed a technique within the probabilistic Bayesian framework that combines previous knowledge about the mechanism with the information from the data and results in a posterior probability distribution for the model parameters. It is capable of yielding parameter uncertainties, which cannot be analytically calculated for a non-linear inversion that includes the source location. The code uses time-series of displacements of regional earthquakes and explosions with moderate magnitudes to compute the centroid location and the seismic moment tensor. The noise is also treated as an unknown in the inversion, in order to determine the level of data fit. As a result, the model complexity (i.e. the contribution of isotropic and compensated linear vector dipole components) is determined by the data themself. Furthermore, the noise weights the contribution of each waveform and the noise covariance matrix accounts for both observational and theoretical errors. The code has been extensively tested in synthetic experiments with a variety of focal mechanisms and different types of noise added to synthetic waveforms. It showed fast convergence of the centroid location, accompanied with thorough sampling of the moment tensor parameters leading to narrow posterior distributions. Subsequently, it is being applied to waveforms from earthquakes that occurred in various tectonic environments.
Internal kinematics of H II galaxies
NASA Astrophysics Data System (ADS)
Carvalho, M. S.; Plana, H.
2014-10-01
H II galaxies are dwarf galaxies characterized by high stellar formation rate with spectrum dominated by strong emission lines, superimposed on a weak stellar continuum. The study of internal kinematics of these objects may be realized using the observed emission lines. Based on these lines we obtained monochromatic intensity, velocity dispersion and radial velocity maps. We have studied the internal kinematics of two H II galaxies: UM 461 and CTS 1020, observed with the Gemini South telescope using the GMOS instrument equipped with an IFU. We aim to investigate the origin of the line-broadening observed on emission lines from the use of kinematics diagnostic diagrams: I vs Ď, I vs V, eV vs Ď. The analysis of these diagrams was based on the Cometary Stirring Model that allows us to identify, for example, the presence of expanding shells and stellar winds. We found that radial velocity and velocity dispersion maps, for each galaxy, show a different kinematical pattern, although both are H II galaxies. CTS 1020 shows a velocity gradient consistent with a rotating disc with a velocity amplitude of Ëś 40 km s^{-1}. On the other hand UM 461 does not exhibit a typical pattern of a rotating system, despite of the observed velocity gradient in both emission nuclei.
Action Experience Changes Attention to Kinematic Cues
Filippi, Courtney A.; Woodward, Amanda L.
2016-01-01
The current study used remote corneal reflection eye-tracking to examine the relationship between motor experience and action anticipation in 13-months-old infants. To measure online anticipation of actions infants watched videos where the actorâ€™s hand provided kinematic information (in its orientation) about the type of object that the actor was going to reach for. The actorâ€™s hand orientation either matched the orientation of a rod (congruent cue) or did not match the orientation of the rod (incongruent cue). To examine relations between motor experience and action anticipation, we used a 2 (reach first vs. observe first) Ă— 2 (congruent kinematic cue vs. incongruent kinematic cue) between-subjects design. We show that 13-months-old infants in the observe first condition spontaneously generate rapid online visual predictions to congruent hand orientation cues and do not visually anticipate when presented incongruent cues. We further demonstrate that the speed that these infants generate predictions to congruent motor cues is correlated with their own ability to pre-shape their hands. Finally, we demonstrate that following reaching experience, infants generate rapid predictions to both congruent and incongruent hand shape cuesâ€”suggesting that short-term experience changes attention to kinematics. PMID:26913012
Kinematic Measurements from YouTube Videos
ERIC Educational Resources Information Center
Ruiz, Michael J.
2009-01-01
Video analysis of motion has been in use now for some time. However, some teachers may not have video equipment or may be looking for innovative ways to engage students with interesting applications at no cost. The recent advent of YouTube offers opportunities for students to measure kinematic properties of real-life events using their computers.…
Compton Effect with Non-Relativistic Kinematics
ERIC Educational Resources Information Center
Shivalingaswamy, T.; Kagali, B. A.
2011-01-01
In deducing the change of wavelength of x-rays scattered by atomic electrons, one normally makes use of relativistic kinematics for electrons. However, recoiling energies of the electrons are of the order of a few keV which is less than 0.2% of their rest energies. Hence the authors may ask whether relativistic formulae are really necessary. Inâ€¦
Kinematics of foldable discrete space cranes
NASA Technical Reports Server (NTRS)
Nayfeh, A. H.
1985-01-01
Exact kinematic description of a NASA proposed prototype foldable-deployable discrete space crane are presented. A computer program is developed which maps the geometry of the crane once controlling parameters are specified. The program uses a building block type approach in which it calculates the local coordinates of each repeating cell and then combines them with respect to a global coordinates system.
Collecting kinematics data over long time intervals
NASA Astrophysics Data System (ADS)
Euler, Manfred; Braune, Gert; Schaal, Soenke; Zollman, Dean
2000-10-01
Data collection and analysis in real-world situations has been enhanced by combining an electronic bicycle speedometer, audiotape for data storage and computer analysis. Using a computer, distance, speed, acceleration, and time results can be obtained from the audiotape. The system has been used effectively to improve learning and motivation while students are learning kinematics.
KINEMATICS OF STELLAR POPULATIONS IN POSTSTARBURST GALAXIES
Hiner, Kyle D.; Canalizo, Gabriela E-mail: khiner@astro-udec.cl
2015-01-20
Poststarburst galaxies host a population of early-type stars (A or F) but simultaneously lack indicators of ongoing star formation such as [O II] emission. Two distinct stellar populations have been identified in these systems: a young poststarburst population superimposed on an older host population. We present a study of nine poststarburst galaxies with the following objectives: (1) to investigate whether and how kinematical differences between the young and old populations of stars can be measured, and (2) to gain insight into the formation mechanism of the young population in these systems. We fit high signal-to-noise spectra with two independent populations in distinct spectral regions: the Balmer region, the Mg IB region, and the Ca triplet when available. We show that the kinematics of the two populations largely track one another if measured in the Balmer region with high signal-to-noise data. Results from examining the Faber-Jackson relation and the fundamental plane indicate that these objects are not kinematically disturbed relative to more evolved spheroids. A case study of the internal kinematics of one object in our sample shows it to be pressure supported and not rotationally dominated. Overall our results are consistent with merger-induced starburst scenarios where the young population is observed during the later stages of the merger.
Constrained tri-sphere kinematic positioning system
Viola, Robert J (Jackson, WY)
2010-12-14
A scalable and adaptable, six-degree-of-freedom, kinematic positioning system is described. The system can position objects supported on top of, or suspended from, jacks comprising constrained joints. The system is compatible with extreme low temperature or high vacuum environments. When constant adjustment is not required a removable motor unit is available.
Chemical tagging of stellar kinematic groups
NASA Astrophysics Data System (ADS)
Tabernero, H. M.; Montes, D.; González Hernández, J. I.
2013-05-01
Stellar Kinematic Groups are kinematical coherent groups of stars which might share a common origin. These groups spread through the Galaxy over time due to tidal effects caused by galactic rotation and disc heating, however the chemical information survives. The aim of chemical tagging is to show that abundances of every chemical element must be homogeneus among candidate members. We have studied the case of the Hyades Supercluster and the Ursa Major Moving Group for kinematically selected FGK stars, based on high-resolution spectroscopic observations obtained at the 1.2 m Mercator Telescope with the HERMES Spectrograph. Stellar atmospheric parameters (T_{eff}, log{g}, ? and [Fe/H]) have been determined using an own-implemented automatic code (StePar) which makes use of the sensibility from iron EWs measured in the spectra. We have derived the chemical abundances of several elements and their [X/Fe] ratios. Thus, we finally perform a careful differential abundance analysis using a known member of each cluster as a reference star, with the aim to clarify the origin of these kinematical groups.
Stellar Archeology : Chemical Compositions and Kinematics
NASA Astrophysics Data System (ADS)
Stringer, Bayard; Carney, Bruce
2011-10-01
The Î»-CDM model of cosmology predicts a hierarchical formation mechanism of galaxies, with smaller units accreting to construct larger ones. The detection of merger events in external galaxies is well known, and the detection and analysis of merger remnants in the Milky Way is a key component in piecing together the history of our home galaxy. Statistical analyses of stellar kinematics in the solar neighborhood reveal much kinematic structure in the Galactic disk, but it is not readily apparent whether this structure is extragalactic or dynamical in origin. The most prominent structures are quickly identified as well known moving groups of stars such as the Hercules, Sirius, and Hyades stellar streams. Additionally, a subset of kinematically selected stars observed at McDonald Observatory are members of a stellar stream putatively identified by Amina Helmi as part of a merger remnant. A semi-automated, high resolution spectral analysis is applied to 504 F and G dwarf stars, and the results are amenable to Kolmogorov-Smirnov membership hypothesis testing. In all four cases, the kinematic streams have chemistries roughly consistent with the Galactic disk trends, although the statistical analyses suggest some subtle differences.
Computer Software & Programing Utilization in Kinematics.
ERIC Educational Resources Information Center
Zahraee, Mohammad A.; And Others
This paper discusses two software packages used in kinematics courses at Purdue University, Calumet (Indiana) and some algorithms written by students for cam design. The first software package, 4BAR, requires the user to define the particular four bar linkage in terms of lengths of the individual links and the angle and distance to the coupler…
KINEMATIC DISTANCE ASSIGNMENTS WITH H I ABSORPTION
Jones, Courtney; Dickey, John M.
2012-07-01
Using H I absorption spectra from the International Galactic Plane Survey, a new method is implemented to resolve the kinematic distance ambiguity for 75 H II regions with known systemic velocities from radio recombination lines. A further 40 kinematic distance determinations are made for H II region candidates without known systemic velocities through an investigation of the presence of H I absorption around the terminal velocity. New kinematic distance determinations can be used to further constrain spiral arm parameters and the location and extent of other structures in the Milky Way disk. H I absorption toward continuum sources beyond the solar circle is also investigated. Follow-up studies of H I at higher resolution than the 1' to 2' of existing Galactic Plane Surveys will provide kinematic distances to many more H II regions on the far side of the Galactic center. On the basis of the velocity channel summation technique developed in this paper, a much larger sample of H II regions will be analyzed in a future paper to remove the near-far distance ambiguity.
Kinematic Measurements from YouTube Videos
ERIC Educational Resources Information Center
Ruiz, Michael J.
2009-01-01
Video analysis of motion has been in use now for some time. However, some teachers may not have video equipment or may be looking for innovative ways to engage students with interesting applications at no cost. The recent advent of YouTube offers opportunities for students to measure kinematic properties of real-life events using their computers.â€¦
Friction-based design of kinematic couplings
Hale, L C
1998-07-30
Friction affects several aspects important to the design of kinematic couplings, but particularly the ability to reach its centered position is fundamental (In this paper, the term kinematic coupling refers to any connection device based on pairs of contacting surfaces that provide six constraints in an ideal sense). It becomes centered when all pairs of contacting surfaces are fully seated even though a small uncertainty may exist about the exact center where potential energy is minimum. For many applications, centering ability is a good indicator for optimizing the coupling design. Typically, the coupling design process has been largely heuristic based on a few guidelines [Slocum, 1992]. Several simple kinematic couplings (for example, a symmetric three-vee coupling) are compared for centering ability using closed-form equations. More general configurations lacking obvious symmetries are difficult to model in this way. A unique kinematic coupling for large interchangeable optics assemblies in the National Ignition Facility motivated the development of a computer program to optimize centering ability. However, space limits the description of the program to the basic algorithm. Currently the program is written in MathcadTM Plus 6 and is available upon request.
Lower extremity kinematics of athletics curve sprinting.
Alt, Tobias; Heinrich, Kai; Funken, Johannes; Potthast, Wolfgang
2015-01-01
Curve running requires the generation of centripetal force altering the movement pattern in comparison to the straight path run. The question arises which kinematic modulations emerge while bend sprinting at high velocities. It has been suggested that during curve sprints the legs fulfil different functions. A three-dimensional motion analysis (16 high-speed cameras) was conducted to compare the segmental kinematics of the lower extremity during the stance phases of linear and curve sprints (radius: 36.5 m) of six sprinters of national competitive level. Peak joint angles substantially differed in the frontal and transversal plane whereas sagittal plane kinematics remained unchanged. During the prolonged left stance phase (left: 107.5 ms, right: 95.7 ms, straight: 104.4 ms) the maximum values of ankle eversion (left: 12.7°, right: 2.6°, straight: 6.6°), hip adduction (left: 13.8°, right: 5.5°, straight: 8.8°) and hip external rotation (left: 21.6°, right: 12.9°, straight: 16.7°) were significantly higher. The inside leg seemed to stabilise the movement in the frontal plane (eversion-adduction strategy) whereas the outside leg provided and controlled the motion in the horizontal plane (rotation strategy). These results extend the principal understanding of the effects of curve sprinting on lower extremity kinematics. This helps to increase the understanding of nonlinear human bipedal locomotion, which in turn might lead to improvements in athletic performance and injury prevention. PMID:25495196
ANALYTIC MODELING OF THE MORETON WAVE KINEMATICS
Temmer, M.; Veronig, A. M.
2009-09-10
The issue whether Moreton waves are flare-ignited or coronal mass ejection (CME)-driven, or a combination of both, is still a matter of debate. We develop an analytical model describing the evolution of a large-amplitude coronal wave emitted by the expansion of a circular source surface in order to mimic the evolution of a Moreton wave. The model results are confronted with observations of a strong Moreton wave observed in association with the X3.8/3B flare/CME event from 2005 January 17. Using different input parameters for the expansion of the source region, either derived from the real CME observations (assuming that the upward moving CME drives the wave), or synthetically generated scenarios (expanding flare region, lateral expansion of the CME flanks), we calculate the kinematics of the associated Moreton wave signature. Those model input parameters are determined which fit the observed Moreton wave kinematics best. Using the measured kinematics of the upward moving CME as the model input, we are not able to reproduce the observed Moreton wave kinematics. The observations of the Moreton wave can be reproduced only by applying a strong and impulsive acceleration for the source region expansion acting in a piston mechanism scenario. Based on these results we propose that the expansion of the flaring region or the lateral expansion of the CME flanks is more likely the driver of the Moreton wave than the upward moving CME front.
The kinematic algebras from the scattering equations
NASA Astrophysics Data System (ADS)
Monteiro, Ricardo; O'Connell, Donal
2014-03-01
We study kinematic algebras associated to the recently proposed scattering equations, which arise in the description of the scattering of massless particles. In particular, we describe the role that these algebras play in the BCJ duality between colour and kinematics in gauge theory, and its relation to gravity. We find that the scattering equations are a consistency condition for a self-dual-type vertex which is associated to each solution of those equations. We also identify an extension of the anti-self-dual vertex, such that the two vertices are not conjugate in general. Both vertices correspond to the structure constants of Lie algebras. We give a prescription for the use of the generators of these Lie algebras in trivalent graphs that leads to a natural set of BCJ numerators. In particular, we write BCJ numerators for each contribution to the amplitude associated to a solution of the scattering equations. This leads to a decomposition of the determinant of a certain kinematic matrix, which appears naturally in the amplitudes, in terms of trivalent graphs. We also present the kinematic analogues of colour traces, according to these algebras, and the associated decomposition of that determinant.
Compton Effect with Non-Relativistic Kinematics
ERIC Educational Resources Information Center
Shivalingaswamy, T.; Kagali, B. A.
2011-01-01
In deducing the change of wavelength of x-rays scattered by atomic electrons, one normally makes use of relativistic kinematics for electrons. However, recoiling energies of the electrons are of the order of a few keV which is less than 0.2% of their rest energies. Hence the authors may ask whether relativistic formulae are really necessary. In…
2. 5D Kirchhoff Inversion Theory applied to VSP data
Dong, Wenjie, H. . Dept. of Earth, Atmospheric and Planetary Sciences); Bleistein, N. . Center for Wave Phenomena)
1992-01-01
Offset VSP (or Walk-away VSP) and Crosshole Tomography are special commonshot experiments. In the former, the receiver array is in a borehole with the source at the surface. In the latter, both receiver array and source array are in boreholes. For these two recording configurations, a two-and-one-half dimensional (2.5D) inversion is the method of choice if amplitude information of the data is used to extract medium parameters. By 2.5D, we mean 3D wave propagation within a 2D medium. Similar to the 2.5D inversion formulation of surface line seismic data, we formulate an inversion algorithm in the paper for VSP geometry. The resulting formula is equally applicable to Crosshole experiments. Our basic assumption is that wave propagation is governed by the acoustic wave equation. We also assume VSP data are high frequency so that the asymptotic evaluation of integrals is justified. This inversion algorithm consists of two transform kernels, which, when applied to VSP or Crosshole data, produce the subsurface reflector map. For one kernel, the reflector map is delineated by the singular functions of interface with peak amplitude being the angularly dependent geometrical optics reflection coefficient. For the other, we obtain the same reflector map, but the amplitude of the singular function is the product of the cosine of the incident angle with the reflection coefficient. From these two outputs, lower medium propagation speed can be estimated if densities are known. To estimate both the speed and density of the lower medium, two independent inversions, illuminating points on the reflector from distinct incidence angles, are needed. In practice, many experiments are used to limit the effect of noise. The inversion operator is tested on synthetic data for both kinematic (imaging) and dynamic (amplitude details) performance, and on field VSP data for imaging only. The results highlight the advantages and limitations of the method.
[TKA kinematics. In vivo techniques and results].
von Eisenhart-Rothe, R; Vogl, T; Englmeier, K-H; Dennis, D A
2007-07-01
Until now it remains less clear to what extent the different types of endoprostheses can simulate the physiological motion pattern of the knee joint. The aim of this study was to present fluoroscopy and functional MRI as well as the results of these in vivo imaging techniques for TKA kinematics. Videofluoroscopy is a dynamic investigation, analyzing the subjects under fluoroscopic surveillance during different activities. Three-dimensional (3D) kinematics were recovered from the two-dimensional fluoroscopic images using a model-fitting technique. Kinematic analysis with functional MRI was performed in an open MR system at different flexion angles with external loads being applied during imaging. Femoropatellar and femorotibial 3D kinematics were analyzed by image postprocessing. The findings in healthy knees obtained with functional MRI under static conditions are in good agreement with the fluoroscopic outcome under dynamic conditions. In all investigated TKA in the mean an increased external rotated position of the femur relative to the tibia was observed at full extension, while the amount of external rotation during knee flexion was decreased. Although there was great variability among the individuals, differences were observed between the TKA-groups (e.g. posterior stabilized vs PCL retaining). Significant changes of femorotibial and femoropatellar kinematics were found in TKA compared to healthy knees, which may lead to early aseptic loosening or increased polyethylene wear The presented techniques and results allow for advanced in vivo diagnostics and may help to improve the design of TKA and to enhance the long-term performance. PMID:17593348
Kinematic Optimization in Birds, Bats and Ornithopters
NASA Astrophysics Data System (ADS)
Reichert, Todd
Birds and bats employ a variety of advanced wing motions in the efficient production of thrust. The purpose of this thesis is to quantify the benefit of these advanced wing motions, determine the optimal theoretical wing kinematics for a given flight condition, and to develop a methodology for applying the results in the optimal design of flapping-wing aircraft (ornithopters). To this end, a medium-fidelity, combined aero-structural model has been developed that is capable of simulating the advanced kinematics seen in bird flight, as well as the highly non-linear structural deformations typical of high-aspect ratio wings. Five unique methods of thrust production observed in natural species have been isolated, quantified and thoroughly investigated for their dependence on Reynolds number, airfoil selection, frequency, amplitude and relative phasing. A gradient-based optimization algorithm has been employed to determined the wing kinematics that result in the minimum required power for a generalized aircraft or species in any given flight condition. In addition to the theoretical work, with the help of an extended team, the methodology was applied to the design and construction of the world's first successful human-powered ornithopter. The Snowbird Human-Powered Ornithopter, is used as an example aircraft to show how additional design constraints can pose limits on the optimal kinematics. The results show significant trends that give insight into the kinematic operation of natural species. The general result is that additional complexity, whether it be larger twisting deformations or advanced wing-folding mechanisms, allows for the possibility of more efficient flight. At its theoretical optimum, the efficiency of flapping-wings exceeds that of current rotors and propellers, although these efficiencies are quite difficult to achieve in practice.
The Maiden Voyage of a Kinematics Robot
NASA Astrophysics Data System (ADS)
Greenwolfe, Matthew L.
2015-04-01
In a Montessori preschool classroom, students work independently on tasks that absorb their attention in part because the apparatus are carefully designed to make mistakes directly observable and limit exploration to one aspect or dimension. Control of error inheres in the apparatus itself, so that teacher intervention can be minimal.1 Inspired by this example, I created a robotic kinematics apparatus that also shapes the inquiry experience. Students program the robot by drawing kinematic graphs on a computer and then observe its motion. Exploration is at once limited to constant velocity and constant acceleration motion, yet open to complex multi-segment examples difficult to achieve in the lab in other ways. The robot precisely and reliably produces the motion described by the students' graphs, so that the apparatus itself provides immediate visual feedback about whether their understanding is correct as they are free to explore within the hard-coded limits. In particular, the kinematic robot enables hands-on study of multi-segment constant velocity situations, which lays a far stronger foundation for the study of accelerated motion. When correction is anonymous—just between one group of lab partners and their robot—students using the kinematic robot tend to flow right back to work because they view the correction as an integral part of the inquiry learning process. By contrast, when correction occurs by the teacher and/or in public (e.g., returning a graded assignment or pointing out student misconceptions during class), students all too often treat the event as the endpoint to inquiry. Furthermore, quantitative evidence shows a large gain from pre-test to post-test scores using the Test of Understanding Graphs in Kinematics (TUG-K).
Digital seismic inverse methods
Robinson, E.A.
1984-01-01
This mathematically based text presents the basic geophysical models used today. It is designed as a text or reference information for courses in geophysics, and also as a professional reference. It presents following contents; the seismic method as a communication system, the design of high-resolution digital filters; principles of digital wiener filtering; sampling geophysical data, filter theory and wave propagation; random processes; spectral estimation; predictive decomposition of seismic traces; multichannel z-transforms and minimum delay; the spectral function of a layered system and the determination of waveforms at depth; deconvolution; spectral approach to geophysical inversion by Lorentz, Fourier, and radon transforms; dynamic predictive deconvolution; the normal incidence synthetic seismogram; maximum entropy and the relationship of the partial autocorrelation to the reflection coefficients of a layered system; maximum entropy spectral decomposition of a seismogram into its minimum entropy component plus noise; optimum stacking techniques; optimum digital filters for signal-to-noise ratio enhancement; bibliography, and index.
NASA Astrophysics Data System (ADS)
Suortti, Pekka
2016-04-01
A novel concept for a high resolution Compton spectrometer is introduced. 88 keV radiation from an Inverse Compton Compact Source is focused using crossed cylindrically bent Laue-type Si perfect crystals, and dispersed on the sample with a constant energy gradient. Dispersion is compensated exactly at a Ge crystal analyzer, so that the same wavelength shift is observed for all wavelengths of the incident beam. The ThomX source is used as a concrete example. Detailed dimensions and flux estimates at successive locations of the spectrometer are given, and the performance is compared with the dispersion compensating spectrometer at ID15 of the ESRF. The momentum resolution is better than 0.1 atomic units in both cases. The intensity of scattering with the compact source is an order of magnitude smaller, but still adequate for high resolution Compton profile measurements.
Stress inversion assumptions review
NASA Astrophysics Data System (ADS)
Lejri, Mostfa; Maerten, Frantz; Maerten, Laurent; Joonnenkindt, Jean Pierre; Soliva, Roger
2014-05-01
Wallace (1951) and Bott (1959) were the first to introduce the idea that the slip on each fault surface has the same direction and sense as the maximum shear stress resolved on that surface. This hypothesis are based on the assumptions that (i) faults are planar, (ii) blocks are rigid, (iii) neither stress perturbations nor block rotations along fault surfaces occur and (iv), the applied stress state is uniform. However, this simplified hypothesis is questionable since complex fault geometries, heterogeneous fault slip directions, evidences of stress perturbations in microstructures and block rotations along fault surfaces were reported in the literature. Earlier numerical geomechanical models confirmed that the striation lines (slip vectors) are not necessarily parallel to the maximum shear stress vector but is consistent with local stress perturbations. This leads us to ask as to what extent the Wallace and Bott simplifications are reliable as a basis hypothesis for stress inversion. In this presentation, a geomechanical multi-parametric study using 3D boundary element method (BEM), covering (i) fault geometries such as intersected faults or corrugated fault surfaces, (ii) the full range of Andersonian state of stress, (iii) fault friction, (iv) half space effect and (v), rock properties, is performed in order to understand the effect of each parameter on the angular misfit between geomechanical slip vectors and the resolved shear stresses. It is shown that significant angular misfits can be found under specific configurations and therefore we conclude that stress inversions based on the Wallace-Bott hypothesis might sometime give results that should be interpreted with care. Major observations are that (i) applying optimum tectonic stress conditions on complex fault geometries can increase the angular misfit, (ii) elastic material properties, combined to half-space effect, can enhance this effect, and (iii) an increase of the sliding friction leads to a reduction of this misfit.
Inverse magnetorheological fluids.
Rodríguez-Arco, L; López-López, M T; Zubarev, A Y; Gdula, K; Durán, J D G
2014-09-01
We report a new kind of field-responsive fluid consisting of suspensions of diamagnetic (DM) and ferromagnetic (FM) microparticles in ferrofluids. We designate them as inverse magnetorheological (IMR) fluids for analogy with inverse ferrofluids (IFFs). Observations on the particle self-assembly in IMR fluids upon magnetic field application showed that DM and FM microparticles were assembled into alternating chains oriented along the field direction. We explain such assembly on the basis of the dipolar interaction energy between particles. We also present results on the rheological properties of IMR fluids and, for comparison, those of IFFs and bidispersed magnetorheological (MR) fluids. Interestingly, we found that upon magnetic field application, the rheological properties of IMR fluids were enhanced with respect to bidispersed MR fluids with the same FM particle concentration, by an amount greater than the sum of the isolated contribution of DM particles. Furthermore, the field-induced yield stress was moderately increased when up to 30% of the total FM particle content was replaced with DM particles. Beyond this point, the dependence of the yield stress on the DM content was non-monotonic, as expected for FM concentrations decreasing to zero. We explain these synergistic results by two separate phenomena: the formation of exclusion areas for FM particles due to the perturbation of the magnetic field by DM particles and the dipole-dipole interaction between DM and FM particles, which enhances the field-induced structures. Based on the second phenomenon, we present a theoretical model for the yield stress that semi-quantitatively predicts the experimental results. PMID:25022363
Upper Limb Assessment in Tetraplegia: Clinical, Functional and Kinematic Correlations
ERIC Educational Resources Information Center
Cacho, Enio Walker Azevedo; de Oliveira, Roberta; Ortolan, Rodrigo L.; Varoto, Renato; Cliquet, Alberto
2011-01-01
The aim of this study was to correlate clinical and functional evaluations with kinematic variables of upper limp reach-to-grasp movement in patients with tetraplegia. Twenty chronic patients were selected to perform reach-to-grasp kinematic assessment using a target placed at a distance equal to the arm's length. Kinematic variables (hand peakâ€¦
Upper Limb Assessment in Tetraplegia: Clinical, Functional and Kinematic Correlations
ERIC Educational Resources Information Center
Cacho, Enio Walker Azevedo; de Oliveira, Roberta; Ortolan, Rodrigo L.; Varoto, Renato; Cliquet, Alberto
2011-01-01
The aim of this study was to correlate clinical and functional evaluations with kinematic variables of upper limp reach-to-grasp movement in patients with tetraplegia. Twenty chronic patients were selected to perform reach-to-grasp kinematic assessment using a target placed at a distance equal to the arm's length. Kinematic variables (hand peak…
Wavelet Sparse Approximate Inverse Preconditioners
NASA Technical Reports Server (NTRS)
Chan, Tony F.; Tang, W.-P.; Wan, W. L.
1996-01-01
There is an increasing interest in using sparse approximate inverses as preconditioners for Krylov subspace iterative methods. Recent studies of Grote and Huckle and Chow and Saad also show that sparse approximate inverse preconditioner can be effective for a variety of matrices, e.g. Harwell-Boeing collections. Nonetheless a drawback is that it requires rapid decay of the inverse entries so that sparse approximate inverse is possible. However, for the class of matrices that, come from elliptic PDE problems, this assumption may not necessarily hold. Our main idea is to look for a basis, other than the standard one, such that a sparse representation of the inverse is feasible. A crucial observation is that the kind of matrices we are interested in typically have a piecewise smooth inverse. We exploit this fact, by applying wavelet techniques to construct a better sparse approximate inverse in the wavelet basis. We shall justify theoretically and numerically that our approach is effective for matrices with smooth inverse. We emphasize that in this paper we have only presented the idea of wavelet approximate inverses and demonstrated its potential but have not yet developed a highly refined and efficient algorithm.
Tongue-jaw kinematic correlates of /s/ spectra
NASA Astrophysics Data System (ADS)
Dembowski, James S.; Crumb, Richard K.
2001-05-01
Frequencies of spectral peaks for fricatives are determined by the size of the resonating cavity anterior to the place of articulatory constriction in the upper vocal tract. For /s/, this cavity size may be altered through anterior-posterior (a-p) movements of the tongue blade forming the constriction, changes of jaw height, and degree of lip protrusion. With respect to intensity, modeling studies suggest that intensity of fricative spectral peaks may be related to degree of articulatory constriction. These spectral-kinematic relationships have been little studied in natural speech. This study used data from the University of Wisconsin X-Ray Microbeam Database to examine the relationship between spectral peaks and movements of the tongue and jaw in the /s/ productions of one normal speaker. Results showed no relationship between a-p tongue position and frequency of spectral peaks. However, a significant inverse correlation related peak between frequency and jaw opening. Thus, for this speaker jaw height appeared a more important determinant of spectral variability for /s/ than tongue position. Additional results showed a significant relationship between peak intensity and distance of the tongue blade from the palate. These natural speech data will be discussed with respect to models and theories of fricative production.
3D kinematics using dual quaternions: theory and applications in neuroscience.
Leclercq, Guillaume; Lefčvre, Philippe; Blohm, Gunnar
2013-01-01
In behavioral neuroscience, many experiments are developed in 1 or 2 spatial dimensions, but when scientists tackle problems in 3-dimensions (3D), they often face problems or new challenges. Results obtained for lower dimensions are not always extendable in 3D. In motor planning of eye, gaze or arm movements, or sensorimotor transformation problems, the 3D kinematics of external (stimuli) or internal (body parts) must often be considered: how to describe the 3D position and orientation of these objects and link them together? We describe how dual quaternions provide a convenient way to describe the 3D kinematics for position only (point transformation) or for combined position and orientation (through line transformation), easily modeling rotations, translations or screw motions or combinations of these. We also derive expressions for the velocities of points and lines as well as the transformation velocities. Then, we apply these tools to a motor planning task for manual tracking and to the modeling of forward and inverse kinematics of a seven-dof three-link arm to show the interest of dual quaternions as a tool to build models for these kinds of applications. PMID:23443667
PASTERNAK-JĂšNIOR, Braulio; de SOUSA NETO, Manoel DamiĂŁo; DIONĂŤSIO, Valdeci Carlos; PĂ‰CORA, Jesus Djalma; SILVA, Ricardo Gariba
2012-01-01
Objective This study assessed the muscular activity during root canal preparation through kinematics, kinetics, and electromyography (EMG). Material and Methods The operators prepared one canal with RaCe rotary instruments and another with Flexo-files. The kinematics of the major joints was reconstructed using an optoelectronic system and electromyographic responses of the flexor carpi radialis, extensor carpi radialis, brachioradialis, biceps brachii, triceps brachii, middle deltoid, and upper trapezius were recorded. The joint torques of the shoulder, elbow and wrist were calculated using inverse dynamics. In the kinematic analysis, angular movements of the wrist and elbow were classified as low risk factors for work-related musculoskeletal disorders. With respect to the shoulder, the classification was medium-risk. Results There was no significant difference revealed by the kinetic reports. The EMG results showed that for the middle deltoid and upper trapezius the rotary instrumentation elicited higher values. The flexor carpi radialis and extensor carpi radialis, as well as the brachioradialis showed a higher value with the manual method. Conclusion The muscular recruitment for accomplishment of articular movements for root canal preparation with either the rotary or manual techniques is distinct. Nevertheless, the rotary instrument presented less difficulty in the generation of the joint torque in each articulation, thus, presenting a greater uniformity of joint torques. PMID:22437679
3D kinematics using dual quaternions: theory and applications in neuroscience
Leclercq, Guillaume; LefĂ¨vre, Philippe; Blohm, Gunnar
2013-01-01
In behavioral neuroscience, many experiments are developed in 1 or 2 spatial dimensions, but when scientists tackle problems in 3-dimensions (3D), they often face problems or new challenges. Results obtained for lower dimensions are not always extendable in 3D. In motor planning of eye, gaze or arm movements, or sensorimotor transformation problems, the 3D kinematics of external (stimuli) or internal (body parts) must often be considered: how to describe the 3D position and orientation of these objects and link them together? We describe how dual quaternions provide a convenient way to describe the 3D kinematics for position only (point transformation) or for combined position and orientation (through line transformation), easily modeling rotations, translations or screw motions or combinations of these. We also derive expressions for the velocities of points and lines as well as the transformation velocities. Then, we apply these tools to a motor planning task for manual tracking and to the modeling of forward and inverse kinematics of a seven-dof three-link arm to show the interest of dual quaternions as a tool to build models for these kinds of applications. PMID:23443667
McDonnell, Lisa K; Hume, Patria A; Nolte, Volker
2013-09-01
The aim of this narrative review was to propose a deterministic model based on a review of previous research documenting the evidence for the associations between average kayak velocity and kinematic variables in sprint kayaking. Literature was reviewed after searching electronic databases using key words 'kayak,' 'biomechanics,' 'velocity,' 'kinematics,' and 'performance.' Our kinematic deterministic model for sprint kayaking performance shows that the average kayak velocity is determined by kayak stroke displacement and stroke time. Stroke time had the strongest correlation with 200-m race time (r = 0.86, p < 0.001), and stroke rate (inversely proportional to stroke time) was strongly correlated with average horizontal velocity over two consecutive strokes at race pace (r = -0.83, p < 0.05). Increased stroke rate via decreased absolute water phase time and increased relative water phase time were indicative of more elite performance. There was no significant relationship between stroke displacement and velocity; however, a large decrease in stroke displacement may be detrimental to performance. Individual characteristics may be responsible for a paddlers' ability to achieve and sustain a given stroke rate. Coaches should theoretically focus interventions on increasing stroke rate while maintaining stroke displacement; however this hypothesis should be confirmed with prospective studies. PMID:24245047
Quantum imaging and inverse scattering.
Schotland, John C
2010-10-15
We consider the inverse scattering problem that arises in two-photon quantum imaging with interferometric measurements. We show that the two-point correlation function of the field contains information about the scattering medium at a spatial frequency of twice the Rayleigh bandwidth. The linearized inverse problem, however, yields reconstructions with a resolution of ?/2, where ? is the wavelength of light. PMID:20967049
Modular theory of inverse systems
NASA Technical Reports Server (NTRS)
1979-01-01
The relationship between multivariable zeros and inverse systems was explored. A definition of zero module is given in such a way that it is basis independent. The existence of essential right and left inverses were established. The way in which the abstract zero module captured previous definitions of multivariable zeros is explained and examples are presented.
Kinematic measurements using an infrared sensor
NASA Astrophysics Data System (ADS)
Marinho, F.; Paulucci, L.
2016-03-01
The use of an infrared sensor as a new alternative to measure position as a function of time in kinematic experiments was investigated using a microcontroller as the data acquisition and control device. These are versatile sensors that offer advantages over typical ultrasound devices. The setup described in this paper enables students to develop their own experiments, promoting opportunities for learning physical concepts such as the different types of forces that can act on a body (gravitational, elastic, drag, etc) and the resulting types of movements with good sensitivity within the 4â€“30 cm range. As a proof of concept we also present the application of a prototype designed to record the kinematics of mass-spring systems.
A comparison of kinematic recording instruments.
Eckhouse, R H; Penny, M A; Maulucci, R A
1996-12-01
Kinematics, the study of motion, is employed in numerous biomechanics and human performance investigations. The types of instrumentation used in these studies vary at fundamental technical levels, making it difficult to relate results from studies carried out at different laboratories using different instrumentation. A project was designed to compare two commonly used types of kinematic recording techniques, i.e., the 6 df electromagnetic tracker system and the video motion analysis system. A four-level testing and comparison method was conducted involving static and dynamic inanimate objects, as well as human subjects under static and dynamic conditions. It was demonstrated that for rigid body inanimate objects the two systems produce nearly identical values under stationary conditions and are comparable under moving conditions. The systems show only trivial discrepancies in static human body measurements, and perform in qualitatively similar ways on human motion. PMID:9087888
The kinematic advantage of electric cars
NASA Astrophysics Data System (ADS)
Meyn, Jan-Peter
2015-11-01
Acceleration of a common car with with a turbocharged diesel engine is compared to the same type with an electric motor in terms of kinematics. Starting from a state of rest, the electric car reaches a distant spot earlier than the diesel car, even though the latter has a better specification for engine power and average acceleration from 0 to 100 km h-1. A three phase model of acceleration as a function of time fits the data of the electric car accurately. The first phase is a quadratic growth of acceleration in time. It is shown that the tenfold higher coefficient for the first phase accounts for most of the kinematic advantage of the electric car.
On the kinematic age of RZ Psc
NASA Astrophysics Data System (ADS)
Potravnov, I. S.; Grinin, V. P.
2013-11-01
RZ Psc belongs to the family of young UX Ori stars whose photometric activity is due to strong extinction variations in the circumstellar disks surrounding them. However, in contrast to all the remaining stars of this type, no evidence of youth has been detected for RZ Psc until recently. A rough estimate of the star's kinematic age was made for the first time in our previous paper (Grinin et al. 2010). It shows that RZ Psc is intermediate in its evolutionary status between young stars in Orion and stars with debris disks. In this paper, we provide a refined estimate of the kinematic age for the star confirming this conclusion. According to this estimate, the age of RZ Psc is approximately 25 Â± 5 Myr at M * = 1 M âŠ™.
Identification of top quarks using kinematic variables
Abe, F.; Akimoto, H.; Akopian, A.; Albrow, M.G.; Amendolia, S.R.; Amidei, D.; Antos, J.; Anway-Wiese, C.; Aota, S.; Apollinari, G.; Asakawa, T.; Ashmanskas, W.; Atac, M.; Auchincloss, P.; Azfar, F.; Azzi-Bacchetta, P.; Bacchetta, N.; Badgett, W.; Bagdasarov, S.; Bailey, M.W.; Bao, J.; de Barbaro, P.; Barbaro-Galtieri, A.; Barnes, V.E.; Barnett, B.A.; Bartalini, P.; Bauer, G.; Baumann, T.; Bedeschi, F.; Behrends, S.; Belforte, S.; Bellettini, G.; Bellinger, J.; Benjamin, D.; Benlloch, J.; Bensinger, J.; Benton, D.; Beretvas, A.; Berge, J.P.; Bertolucci, S.; Bhatti, A.; Biery, K.; Binkley, M.; Bisello, D.; Blair, R.E.; Blocker, C.; Bodek, A.; Bokhari, W.; Bolognesi, V.; Bortoletto, D.; Boudreau, J.; Brandenburg, G.; Breccia, L.; Bromberg, C.; Buckley-Geer, E.; Budd, H.S.; Burkett, K.; Busetto, G.; Byon-Wagner, A.; Byrum, K.L.; Cammerata, J.; Campagnari, C.; Campbell, M.; Caner, A.; Carithers, W.; Carlsmith, D.; Castro, A.; Cauz, D.; Cen, Y.; Cervelli, F.; Chao, H.Y.; Chapman, J.; Cheng, M.; Chiarelli, G.; Chikamatsu, T.; Chiou, C.N.; Christofek, L.; Cihangir, S.; Clark, A.G.; Cobal, M.; Contreras, M.; Conway, J.; Cooper, J.; Cordelli, M.; Couyoumtzelis, C.; Crane, D.; Cronin-Hennessy, D.; Culbertson, R.; Cunningham, J.D.; Daniels, T.; DeJongh, F.; Delchamps, S.; Dell`Agnello, S.; Dell`Orso, M.; Demortier, L.; Denby, B.; Deninno, M.; Derwent, P.F.; Devlin, T.; Dickson, M.; Dittmann, J.R.; Donati, S.; Drucker, R.B.; Dunn, A.; Eddy, N.; Einsweiler, K.; Elias, J.E.; Ely, R.; Engels, E. Jr.; Errede, D.; Errede, S.; Fan, Q.; Fiori, I.; Flaugher, B.; Foster, G.W.; Franklin, M.; Frautschi, M.; Freeman, J.; Friedman, J.; Frisch, H.; Fuess, T.A.; Fukui, Y.; Funaki, S.; Gagliardi, G.; Galeotti, S.; Gallinaro, M.; Garcia-Sciveres, M.; Garfinkel, A.F.; Gay, C.; Geer, S.; Gerdes, D.W.; Giannetti, P.; Giokaris, N.; Giromini, P.; Gladney, L.; Glenzinski, D.; Gold, M.; Gonzalez, J.; Gordon, A.; Goshaw, A.T.; Goulianos, K.; Grassmann, H.; Groer, L.; Grosso-Pilcher, C.; CDF Collabora..
1995-09-01
We have used a kinematic technique to distinguish top quark pair production from background in {ital p{bar p}} collisions at {radical}{ital s}=1.8 TeV, applied to 67 pb{sup {minus}1} of data. We define a sample of {ital W}+{ge}3 jet events in which the jets are produced at large angles relative to the incident beams. In this sample, we find an excess of events with large jet transverse energies relative to expectations from background. The excess is consistent with top quark production; a large fraction of events in this kinematic region contains {ital b} jets. We interpret these results as evidence that most of the selected events are from {ital t{bar t}} decay.
Inverse problem in hydrogeology
NASA Astrophysics Data System (ADS)
Carrera, JesĂşs; Alcolea, AndrĂ©s; Medina, AgustĂn; Hidalgo, Juan; Slooten, Luit J.
2005-03-01
The state of the groundwater inverse problem is synthesized. Emphasis is placed on aquifer characterization, where modelers have to deal with conceptual model uncertainty (notably spatial and temporal variability), scale dependence, many types of unknown parameters (transmissivity, recharge, boundary conditions, etc.), nonlinearity, and often low sensitivity of state variables (typically heads and concentrations) to aquifer properties. Because of these difficulties, calibration cannot be separated from the modeling process, as it is sometimes done in other fields. Instead, it should be viewed as one step in the process of understanding aquifer behavior. In fact, it is shown that actual parameter estimation methods do not differ from each other in the essence, though they may differ in the computational details. It is argued that there is ample room for improvement in groundwater inversion: development of user-friendly codes, accommodation of variability through geostatistics, incorporation of geological information and different types of data (temperature, occurrence and concentration of isotopes, age, etc.), proper accounting of uncertainty, etc. Despite this, even with existing codes, automatic calibration facilitates enormously the task of modeling. Therefore, it is contended that its use should become standard practice. L'Ă©tat du problĂ¨me inverse des eaux souterraines est synthĂ©tisĂ©. L'accent est placĂ© sur la caractĂ©risation de l'aquifĂ¨re, oĂą les modĂ©lisateurs doivent jouer avec l'incertitude des modĂ¨les conceptuels (notamment la variabilitĂ© spatiale et temporelle), les facteurs d'Ă©chelle, plusieurs inconnues sur diffĂ©rents paramĂ¨tres (transmissivitĂ©, recharge, conditions aux limites, etc.), la non linĂ©aritĂ©, et souvent la sensibilitĂ© de plusieurs variables d'Ă©tat (charges hydrauliques, concentrations) des propriĂ©tĂ©s de l'aquifĂ¨re. A cause de ces difficultĂ©s, le calibrage ne peut ĂŞtresĂ©parĂ© du processus de modĂ©lisation, comme c'est le cas dans d'autres cas de figure. Par ailleurs, il peut ĂŞtre vu comme une des Ă©tapes dans le processus de dĂ©termination du comportement de l'aquifĂ¨re. Il est montrĂ© que les mĂ©thodes d'Ă©valuation des paramĂ¨tres actuels ne diffĂ¨rent pas si ce n'est dans les dĂ©tails des calculs informatiques. Il est montrĂ© qu'il existe une large panoplie de techniques d'inversion : codes de calcul utilisables par tout-un-chacun, accommodation de la variabilitĂ© via la gĂ©ostatistique, incorporation d'informations gĂ©ologiques et de diffĂ©rents types de donnĂ©es (tempĂ©rature, occurrence, concentration en isotopes, Ă˘ge, etc.), dĂ©termination de l'incertitude. Vu ces dĂ©veloppements, la calibration automatique facilite Ă©normĂ©ment la modĂ©lisation. Par ailleurs, il est souhaitable que son utilisation devienne une pratique standardisĂ©e. Se sintetiza el estado del problema inverso en aguas subterrĂˇneas. El Ă©nfasis se ubica en la caracterizaciĂłn de acuĂferos, donde los modeladores tienen que enfrentar la incertidumbre del modelo conceptual (principalmente variabilidad temporal y espacial), dependencia de escala, muchos tipos de parĂˇmetros desconocidos (transmisividad, recarga, condiciones limitantes, etc), no linealidad, y frecuentemente baja sensibilidad de variables de estado (tĂpicamente presiones y concentraciones) a las propiedades del acuĂfero. Debido a estas dificultades, no puede separarse la calibraciĂłn de los procesos de modelado, como frecuentemente se hace en otros campos. En su lugar, debe de visualizarse como un paso en el proceso de enten dimiento del comportamiento del acuĂfero. En realidad, se muestra que los mĂ©todos reales de estimaciĂłn de parĂˇmetros no difieren uno del otro en lo esencial, aunque sĂ pueden diferir en los detalles computacionales. Se discute que existe amplio espacio para la mejora del problema inverso en aguas subterrĂˇneas: desarrollo de cĂłdigos amigables alusuario, acomodamiento de variabilidad a travĂ©s de geoestadĂstica, incorporaciĂłn de informaciĂłn geolĂłgica y diferentes tipos de datos (temperatura, presencia y concentraciĂłn de isĂłtopos, edad, etc), explicaciĂłn apropiada de incertidumbre, etc. A pesar de esto, aĂşn con los cĂłdigos existentes, la calibraciĂłn automĂˇtica facilita enormemente la tarea de modelado. Por lo tanto, se sostiene que su uso deberĂa de convertirse en prĂˇctica standard.
First-order ball-bearing kinematics
NASA Technical Reports Server (NTRS)
Kingsbury, E.
1985-01-01
Two first-order equations are given connecting geometry and internal motions in an angular-contact ball bearing. Total speed, kinematic equivalence, basic speed ratio, and modal speed ratio are defined and discussed; charts are given for the speed ratios covering all bearings and all rotational modes. Instances where specific first-order assumptions might fail are discussed, and the resulting effects on bearing performance reviewed.
Missing Mass Measurement Using Kinematic Cusp
Kim, Ian-Woo
2010-02-10
We propose a new method for mass measurement of missing energy particle using cusp structure in the kinematic distribution. We consider a resonance particle decay into a pair of missing energy particles and a pair of visible particles and show invariant mass and angular distribution have non-smooth profiles. The cusp location only depends on mass parameters. Invariant mass and angular distribution are complementary in visibility of the cusp.
A kinematical approach to conformal cosmology
NASA Astrophysics Data System (ADS)
Varieschi, Gabriele Umberto
2010-04-01
We present an alternative cosmology based on conformal gravity, as originally introduced by H. Weyl and recently revisited by P. Mannheim and D. Kazanas. Unlike past similar attempts our approach is a purely kinematical application of the conformal symmetry to the Universe, through a critical reanalysis of fundamental astrophysical observations, such as the cosmological redshift and others. As a result of this novel approach we obtain a closed-form expression for the cosmic scale factor R( t) and a revised interpretation of the space-time coordinates usually employed in cosmology. New fundamental cosmological parameters are introduced and evaluated. This emerging new cosmology does not seem to possess any of the controversial features of the current standard model, such as the presence of dark matter, dark energy or of a cosmological constant, the existence of the horizon problem or of an inflationary phase. Comparing our results with current conformal cosmologies in the literature, we note that our kinematic cosmology is equivalent to conformal gravity with a cosmological constant at late (or early) cosmological times. The cosmic scale factor and the evolution of the Universe are described in terms of several dimensionless quantitites, among which a new cosmological variable ? emerges as a natural cosmic time. The mathematical connections between all these quantities are described in details and a relationship is established with the original kinematic cosmology by L. Infeld and A. Schild. The mathematical foundations of our kinematical conformal cosmology will need to be checked against current astrophysical experimental data, before this new model can become a viable alternative to the standard theory.
Efficient Kinematic Computations For 7-DOF Manipulators
NASA Technical Reports Server (NTRS)
Seraji, Homayoun; Long, Mark K.; Kreutz-Delgado, Kenneth
1994-01-01
Efficient algorithms for forward kinematic mappings of seven-degree-of-freedom (7-DOF) robotic manipulator having revolute joints developed on basis of representation of redundant DOF in terms of parameter called "arm angle." Continuing effort to exploit redundancy in manipulator according to concept of basic and additional tasks. Concept also discussed in "Configuration-Control Scheme Copes With Singularities" (NPO-18556) and "Increasing the Dexterity of Redundant Robots" (NPO-17801).
Analyzing Robotic Kinematics Via Computed Simulations
NASA Technical Reports Server (NTRS)
Carnahan, Timothy M.
1992-01-01
Computing system assists in evaluation of kinematics of conceptual robot. Displays positions and motions of robotic manipulator within work cell. Also displays interactions between robotic manipulator and other objects. Results of simulation displayed on graphical computer workstation. System includes both off-the-shelf software originally developed for automotive industry and specially developed software. Simulation system also used to design human-equivalent hand, to model optical train in infrared system, and to develop graphical interface for teleoperator simulation system.
Kinematics and dynamics of sphenisciform wings
NASA Astrophysics Data System (ADS)
Noca, Flavio; Crisinel, Fabien; Munier, Pierre
2011-11-01
Three-dimensional scans of three different species of taxidermied penguins (Aptenodytes patagonicus, Pygoscelis papua, and Spheniscus magellanicus) have been performed. A three-dimensional reproduction of an African penguin (Sphenicus demersus) wing was manufactured and tested in a hydrodynamic channel. A six-degree-of-freedom robot was programmed to perform the three dimensional kinematics, obtained from actual footage. A six-component force balance was used to retrieve the dynamics of the wing motion. Results will be presented and discussed.
Graph Models of Automobile Gears - Kinematics
NASA Astrophysics Data System (ADS)
Drewniak, J.; KopeÄ‡, J.; ZawiĹ›lak, S.
2014-08-01
In the present paper, kinematical analysis of an automotive gear is described. Versatile graph based methods have been utilized for this purpose. An application of mixed, contour and bond graphs gives the same results. It allows the detection of possible mistakes as well as a deeper insight into the designed artifact. The graphs can also be used for further analyses which will be published in a separate document
Kinematics of Hooke universal joint robot wrists
NASA Technical Reports Server (NTRS)
Mckinney, William S., Jr.
1988-01-01
The singularity problem associated with wrist mechanisms commonly found on industrial manipulators can be alleviated by redesigning the wrist so that it functions as a three-axis gimbal system. This paper discussess the kinematics of gimbal robot wrists made of one and two Hooke universal joints. Derivations of the resolved rate motion control equations for the single and double Hooke universal joint wrists are presented using the three-axis gimbal system as a theoretical wrist model.
The Galactic kinematics of cataclysmic variables
NASA Astrophysics Data System (ADS)
Ak, T.; Bilir, S.; Özdönmez, A.; Soydugan, F.; Soydugan, E.; Püsküllü, Ç.; Ak, S.; Eker, Z.
2015-05-01
Kinematical properties of CVs were investigated according to population types and orbital periods, using the space velocities computed from recently updated systemic velocities, proper motions and parallaxes. Reliability of collected space velocity data was refined by removing 34 systems with largest space velocity errors. The 216 CVs in the refined sample were shown to have a dispersion of 53.70±7.41 km s-1 corresponding to a mean kinematical age of 5.29±1.35 Gyr. Population types of CVs were identified using their Galactic orbital parameters. According to the population analysis, seven old thin disc, nine thick disc and one halo CV were found in the sample, indicating that 94 % of CVs in the Solar Neighbourhood belong to the thin-disc component of the Galaxy. Mean kinematical ages 3.40±1.03 and 3.90±1.28 Gyr are for the non-magnetic thin-disc CVs below and above the period gap, respectively. There is not a meaningful difference between the velocity dispersions below and above the gap. Velocity dispersions of the non-magnetic thin-disc systems below and above the gap are 24.95±3.46 and 26.60±4.18 km s-1, respectively. This result is not in agreement with the standard formation and evolution theory of CVs. The mean kinematical ages of the CV groups in various orbital period intervals increase towards shorter orbital periods. This is in agreement with the standard theory for the evolution of CVs. Rate of orbital period change was found to be dP/ dt=-1.62(±0.15)×10-5 sec yr-1.
Kinematical Test Theories for Special Relativity
NASA Astrophysics Data System (ADS)
Lämmerzahl, Claus; Braxmaier, Claus; Dittus, Hansjörg; Müller, Holger; Peters, Achim; Schiller, Stephan
A comparison of certain kinematical test theories for Special Relativity including the Robertson and Mansouri-Sext test theories is presented and the accuracy of the experimental results testing Special Relativity are expressed in terms of the parameters appearing in these test theories. The theoretical results are applied to the most precise experimental results obtained recently for the isotropy of light propagation and the constancy of the speed of light.
Polarization of inverse plasmon scattering
NASA Technical Reports Server (NTRS)
Windsor, R. A.; Kellogg, P. J.
1974-01-01
The scattering of electrostatic plasma waves by a flux of ultrarelativistic electrons passing through a plasma gives rise to a radiation spectrum which is similar to a synchrotron radiation spectrum. This mechanism, first considered by Gailitis and Tsytovich, is analagous to inverse Compton scattering, and we have named it inverse plasmon scattering. For a power-law electron flux, both inverse plasmon scattering and synchrotron radiation have the same spectral index. In an attempt to distinguish between these mechanisms, we have calculated the polarization level expected from inverse plasmon scattering. The polarization level found is similar to that obtained from a synchrotron radiation source. This means that the radiation produced by two mechanisms, synchrotron radiation and inverse plasmon scattering, is indistinguishable; and this attempt to differentiate between them by polarization effects has been unsuccessful.
NASA Astrophysics Data System (ADS)
Saini, Indu; Singh, Vijay Pal
2016-03-01
Isomorphism identification is a difficult problem in kinematic chains (KC). There are a number of methods proposed by many researchers to detect the isomorphism and inversion of kinematic chain but each has its own shortcomings. Purpose of this paper is to give an efficient and reliable method for detection of isomorphism and inversion among the KC which can be less time consuming among many other related techniques. An attempt has been made to provide satisfactory solution to detection of isomorphism by using Hamming method. The Hamming Number is computed by using the direct method of writing the Hamming matrix, which save time and effort. Link Hamming string which is defined as the string obtained by concatenating the link Hamming number and the frequency of individual Hamming numbers in that row is then formed. Finally, chain Hamming string defined as the string obtained by the concatenation of the chain Hamming number and the link Hamming strings in descending order is formed. This method is implemented on the nine links two degree of freedom.
Kinematic adaptations to tripedal locomotion in dogs.
Goldner, B; Fuchs, A; Nolte, I; Schilling, N
2015-05-01
Limb amputation often represents the only treatment option for canine patients with certain diseases or injuries of the appendicular system. Previous studies have investigated adaptations to tripedal locomotion in dogs but there is a lack of understanding of biomechanical compensatory mechanisms. This study evaluated the kinematic differences between quadrupedal and tripedal locomotion in nine healthy dogs running on a treadmill. The loss of the right pelvic limb was simulated using an Ehmer sling. Kinematic gait analysis included spatio-temporal comparisons of limb, joint and segment angles of the remaining pelvic and both thoracic limbs. The following key parameters were compared between quadrupedal and tripedal conditions: angles at touch-down and lift-off, minimum and maximum joint angles, plus range of motion. Significant differences in angular excursion were identified in several joints of each limb during both stance and swing phases. The most pronounced differences concerned the remaining pelvic limb, followed by the contralateral thoracic limb and, to a lesser degree, the ipsilateral thoracic limb. The thoracic limbs were, in general, more retracted, consistent with pelvic limb unloading and previous observations of bodyweight re-distribution in amputees. Proximal limb segments showed more distinct changes than distal ones. Particularly, the persistently greater anteversion of the pelvis probably affects the axial system. Overall, tripedal locomotion requires concerted kinematic adjustments of both the appendicular and axial systems, and consequently preventive, therapeutic and rehabilitative care of canine amputees should involve the whole musculoskeletal apparatus. PMID:25862392
Morphologic and kinematic characteristics of elite sprinters.
Coh, M; Milanovi?, D; Kampmiller, T
2001-12-01
The purpose of the study was to ascertain the basic morphologic and kinematic characteristics of elite sprinters. The sample included 24 sprinters, with times over a 100 m distance between 10.21 s and 11.19 s. Morphologic characteristics of the sprinters were measured with a test battery of 17 measures, obtained according to the methodology prescribed by the International Biologic Programme (IBP). The kinematic variables were obtained from a flying start 20 m run and a 20 m run with a low start, with the technology of a contact carpet (ERGO TESTER-Bosco). Stride frequency and length, duration of contact and flight phases were registered. Time parameters were measured with a system of infrared photocells (BROWER Timing System). T-test showed that elite sprinters do not differ significantly in morphologic characteristics (p > 0.05) from the 100 m results point of view. However, statistically significant differences were obtained in starting acceleration and maximal velocity. The most important kinematic parameters for generating differences between the elite sprinters are contact time and stride frequency. PMID:11811291
First APOGEE Results on Galactic Bulge Kinematics
NASA Astrophysics Data System (ADS)
Nidever, David L.; Allende Prieto, C.; Bizyaev, D.; Frinchaboy, P. M.; Garcia Perez, A. E.; Holtzman, J.; Majewski, S. R.; Schiavon, R.; Skrutskie, M. F.; Zasowski, G.
2012-01-01
The SDSS-III Apache Point Observatory Galactic Evolution Experiment (APOGEE) will obtain high resolution (R 22,500) and high S/N ( 100 per pixel) H-band spectra of 100,000 giant stars in the Milky Way disk, bulge and halo to study the chemical and kinematical evolution of the Milky Way Galaxy. APOGEE will be able to probe deep into regions of our galaxy that were previously hidden by a thick veil of dust. I will present first APOGEE results on the Galactic bulge kinematics using commissioning data in 18 fields. Our reduction pipeline currently delivers radial velocites with accuracies of 0.2 km/s for the majority of our target stars. These RVs are used to derive accurate rotation curves and velocity dispersion profiles for our bulge fields, many of them in regions not previously probed. We compare our results to other surveys and to N-body models and confirm that the bulge is dominated by a bar to large longitudes. We also find the first evidence for kinematical substructure in our bulge fields.
Scapula Kinematics of Youth Baseball Players
Oliver, Gretchen; Weimar, Wendi
2015-01-01
Literature has revealed the importance of quantifying resting scapular posture in overhead athletes as well as quantifying scapular kinematics during dynamic movement. Prior to this project much of the attention in throwing research had been focused on the position of the humerus without description of the positioning of the scapula. Therefore, it was the purpose of this study to present scapular kinematics during pitching in youth baseball players. Twenty-five youth baseball players (age 11.3 + 1.0 years; body height 152.4 + 9.0 cm; body mass 47.5 + 11.3 kg), with no history of injury, participated in the study. Scapular kinematics at the events of maximum humeral external rotation (MER) and maximum humeral internal rotation (MIR) during the pitching motion were assessed three-dimensionally while pitching fastballs for strikes. Results revealed that at the event of MER, the scapula was in a position of retraction, upward rotation and a posterior tilt. While at the event of MIR, the scapula was protracted, upward rotated and tilted anteriorly. PMID:26839605
Kinematic definition of ram sperm hyperactivation.
Mortimer, S T; Maxwell, W M
1999-01-01
Although it is known that ram spermatozoa exhibit hyperactivated motility under capacitating conditions, quantitative analyses of the head and flagellar movement of washed ram spermatozoa have not been published. Motile spermatozoa were recovered from semen by swim-up into HSOF medium, and their movement in 30-microm-deep chambers was videorecorded. Spermatozoa of interest were identified during tape playback (hyperactivated spermatozoa were identified by visual assessment of flagellar movement) and sequential head and tail images were traced onto overhead projector film attached to the video monitor. The flagellar movement characteristics beat angle (FBA), beat envelope (FBE) and curvature ratio (FCR) were determined by first principles, and head centroid kinematics were determined using Cartesian methods. Hyperactivated spermatozoa had significantly higher FBA and FBE and significantly lower FCR values than non-hyperactivated spermatozoa (all P<0.0001). The centroid kinematic values were also found to be significantly different, and kinematic criteria for ram sperm hyperactivation were developed. These criteria were refined by consideration of 60-Hz CASA-derived trajectories, and ram sperm hyperactivation was defined by: VCL > 250.0 microm s(-1) and VSL < or = 100.0 microm s(-1) and LTN < or = 30% and ALHmax > or = 9.0 microm. PMID:10680999
New Kinematical Constraints on Cosmic Acceleration
Rapetti, David; Allen, Steve W.; Amin, Mustafa A.; Blandford, Roger; /-KIPAC, Menlo Park
2007-05-25
We present and employ a new kinematical approach to ''dark energy'' studies. We construct models in terms of the dimensionless second and third derivatives of the scale factor a(t) with respect to cosmic time t, namely the present-day value of the deceleration parameter q{sub 0} and the cosmic jerk parameter, j(t). An elegant feature of this parameterization is that all {Lambda}CDM models have j(t)=1 (constant), which facilitates simple tests for departures from the {Lambda}CDM paradigm. Applying our model to redshift-independent distance measurements, from type Ia supernovae and X-ray cluster gas mass fraction measurements, we obtain clear statistical evidence for a late time transition from a decelerating to an accelerating phase. For a flat model with constant jerk, j(t)=j, we measure q{sub 0}=-0.81 {+-} 0.14 and j=2.16 +0.81 -0.75, results that are consistent with {Lambda}CDM at about the 1{sigma} confidence level. In comparison to dynamical analyses, the kinematical approach uses a different model set and employs a minimum of prior information, being independent of any particular gravity theory. The results obtained with this new approach therefore provide important additional information and we argue that both kinematical and dynamical techniques should be employed in future dark energy studies, where possible.
Scapula Kinematics of Youth Baseball Players.
Oliver, Gretchen; Weimar, Wendi
2015-12-22
Literature has revealed the importance of quantifying resting scapular posture in overhead athletes as well as quantifying scapular kinematics during dynamic movement. Prior to this project much of the attention in throwing research had been focused on the position of the humerus without description of the positioning of the scapula. Therefore, it was the purpose of this study to present scapular kinematics during pitching in youth baseball players. Twenty-five youth baseball players (age 11.3 + 1.0 years; body height 152.4 + 9.0 cm; body mass 47.5 + 11.3 kg), with no history of injury, participated in the study. Scapular kinematics at the events of maximum humeral external rotation (MER) and maximum humeral internal rotation (MIR) during the pitching motion were assessed three-dimensionally while pitching fastballs for strikes. Results revealed that at the event of MER, the scapula was in a position of retraction, upward rotation and a posterior tilt. While at the event of MIR, the scapula was protracted, upward rotated and tilted anteriorly. PMID:26839605
Computational tool for comparison of kinematic mechanisms and commonly used kinematic models
Hollerbach, K.; Hollister, A.M.; Van Vorhis, R.L.
1997-03-01
Accurate, reliable, and reproducible methods to measure the movements of human joints have been elusive. Currently, three-dimensional recording methods are used to track the motion of one segment relative to another as the joint moves. Six parameters describe the moving segment`s location and orientation relative to the reference segment: three translations (x, y, and z) and three rotations (yaw, pitch and roll) in the reference frame. The raw data can be difficult to interpret. For this reason, several methods have been developed to measure the motion of human joints and to describe the resulting data. For example, instant helical axes or screw deviation axes (Kinzell et al., 1972), the Joint Coordinate System of Grood and Suntay (1983), and the Euler angle method have been used to describe the movements of bones relative to each other. None of these methods takes into account the physical kinematic mechanism producing the joint motion. More recently, Lupichuk (1995) has developed an algorithm to find, for an arbitrary revolute, the axis` position and orientation in three- dimensional space. Each of these methods has advantages and disadvantages in analyzing joint kinematics. The authors have developed software to provide a means of comparing these methods for arbitrary, single degree of freedom, kinematic mechanisms. Our objective is to demonstrate the software and to show how it can be used to compare the results from the different kinematic models as they are applied to specific kinematic mechanisms.
Kinematics of Haro 11: The miniature Antennae
NASA Astrophysics Data System (ADS)
Östlin, G.; Marquart, T.; Cumming, R. J.; Fathi, K.; Bergvall, N.; Adamo, A.; Amram, P.; Hayes, M.
2015-11-01
Luminous blue compact galaxies are among the most active galaxies in the local Universe in terms of their star formation rate per unit mass. They are rare at the current cosmic epoch, but were more abundant in the past and may be seen as the local analogues of higher red shift Lyman break galaxies. Studies of their kinematics is key to understanding what triggers their unusually active star formation. In this work, we investigate the kinematics of stars and ionised gas in Haro 11, one of the most luminous blue compact galaxies in the local Universe. Previous works have indicated that many of these galaxies may be triggered by galaxy mergers. We have employed Fabry-Perot interferometry, long-slit spectroscopy, and integral field unit (IFU) spectroscopy to explore the kinematics of Haro 11. We target the near-infrared calcium triplet, and use cross-correlation and penalised pixel fitting techniques to derive the stellar velocity field and velocity dispersion. We analyse ionised gas through emission lines from hydrogen, [O iii], and [S iii]. When spectral resolution and signal to noise allows, we investigate the line profile in detail and identify multiple velocity components when present. The spectra reveal a complex velocity field whose components, both stellar and gaseous, we attempt to disentangle. We find that to first order, the velocity field and velocity dispersions derived from stars and ionised gas agree. Hence the complexities reveal real dynamical disturbances providing further evidence for a merger in Haro 11. Through decomposition of emission lines, we find evidence for kinematically distinct components, for instance, a tidal arm. The ionised gas velocity field can be traced to large galactocentric radii, and shows significant velocity dispersion even far out in the halo. If interpreted as virial motions, this indicates that Haro 11 may have a mass of ~1011 M?. Haro 11 shows many resemblances with the famous Antennae galaxies both morphologically and kinematically, but it is much denser, which is the likely explanation for the higher star formation efficiency in Haro 11. Based on observations collected at the European Southern Observatory, Paranal, Chile, under observing programmes 71.B-0602, 074.B-0771(A), 074.B-0802A.
Inverse adaptive cluster sampling.
Christman, M C; Lan, F
2001-12-01
Consider a population in which the variable of interest tends to be at or near zero for many of the population units but a subgroup exhibits values distinctly different from zero. Such a population can be described as rare in the sense that the proportion of elements having nonzero values is very small. Obtaining an estimate of a population parameter such as the mean or total that is nonzero is difficult under classical fixed sample-size designs since there is a reasonable probability that a fixed sample size will yield all zeroes. We consider inverse sampling designs that use stopping rules based on the number of rare units observed in the sample. We look at two stopping rules in detail and derive unbiased estimators of the population total. The estimators do not rely on knowing what proportion of the population exhibit the rare trait but instead use an estimated value. Hence, the estimators are similar to those developed for poststratification sampling designs. We also incorporate adaptive cluster sampling into the sampling design to allow for the case where the rare elements tend to cluster within the population in some manner. The formulas for the variances of the estimators do not allow direct analytic comparison of the efficiency of the various designs and stopping rules, so we provide the results of a small simulation study to obtain some insight into the differences among the stopping rules and sampling approaches. The results indicate that a modified stopping rule that incorporates an adaptive sampling component and utilizes an initial random sample of fixed size is the best in the sense of having the smallest variance. PMID:11764249
A quantitative comparison of two kinematic protocols for lumbar segment motion during gait.
Kiernan, D; Malone, A; O'Brien, T; Simms, C K
2015-02-01
During gait analysis, motion of the lumbar region is tracked either by means of a 2-dimensional assessment with markers placed along the spine or a 3-dimensional assessment treating the lumbar region as a rigid segment. The rigid segment assumption is necessary for inverse dynamic calculations further up the kinematic chain. In the absence of a reference standard, the choice of model is mostly based on clinical experience. However, the potential exists for large differences in kinematic output if different protocols are used. The aim of this study was to determine the influence of using two 3-dimensional lumbar segment protocols on the resultant kinematic output during gait. The first protocol was a skin surface rigid protocol with markers placed across the lumbar region while the second consisted of a rigid cluster utilizing active markers applied over the 3rd lumbar vertebra. Data from both protocols were compared through simultaneous recording during gait. Overall variability was lower in 4 out of 6 measures for the skin surface protocol. Ensemble average graphs demonstrated similar mean profiles between protocols. However, Functional Limits of Agreement demonstrated only a poor to moderate agreement. This trend was confirmed with a poor to moderate waveform similarity (CMC range 0.29-0.71). This study demonstrates that the protocol used to track lumbar segment kinematics is an important consideration for clinical and research purposes. Greater variability recorded by the rigid cluster during lumbar rotation suggests the skin surface protocol may be more suited to studies where axial rotation is a consideration. PMID:25701013
Goal Directed Model Inversion: A Study of Dynamic Behavior
NASA Technical Reports Server (NTRS)
Colombano, Silvano P.; Compton, Michael; Raghavan, Bharathi; Lum, Henry, Jr. (Technical Monitor)
1994-01-01
Goal Directed Model Inversion (GDMI) is an algorithm designed to generalize supervised learning to the case where target outputs are not available to the learning system. The output of the learning system becomes the input to some external device or transformation, and only the output of this device or transformation can be compared to a desired target. The fundamental driving mechanism of GDMI is to learn from success. Given that a wrong outcome is achieved, one notes that the action that produced that outcome 0 "would have been right if the outcome had been the desired one." The algorithm then proceeds as follows: (1) store the action that produced the wrong outcome as a "target" (2) redefine the wrong outcome as a desired goal (3) submit the new desired goal to the system (4) compare the new action with the target action and modify the system by using a suitable algorithm for credit assignment (Back propagation in our example) (5) resubmit the original goal. Prior publications by our group in this area focused on demonstrating empirical results based on the inverse kinematic problem for a simulated robotic arm. In this paper we apply the inversion process to much simpler analytic functions in order to elucidate the dynamic behavior of the system and to determine the sensitivity of the learning process to various parameters. This understanding will be necessary for the acceptance of GDMI as a practical tool.
Influence of kinematic redundancy on the singularity-free workspace of parallel kinematic machines
NASA Astrophysics Data System (ADS)
Kotlarski, Jens; Heimann, Bodo; Ortmaier, Tobias
2012-06-01
In this paper the effect of kinematic redundancy in order to reduce the singularity loci of the direct kinematics and to increase the operational, i.e., singularityfree, workspace is demonstrated. The proposed approach consists of additional prismatic actuators allowing one or more base joints to move linearly. As a result, a selective reconfiguration can be performed in order to avoid singular configurations. Exemplarily, kinematically redundant schemes of four structures, the 3 RRR, the 3R PR, the 6U PS, and the 6 RUS, are considered. The relationship between the redundancy and the operational workspace is studied and several analysis examples demonstrate the effectiveness of the proposed concept. Furthermore, the additional benefit of an increasing number of redundant actuators is discussed.
Inverse melting and inverse freezing: A spin model
NASA Astrophysics Data System (ADS)
Schupper, Nurith; Shnerb, Nadav M.
2005-10-01
Systems of highly degenerate ordered or frozen state may exhibit inverse melting (reversible crystallization upon heating) or inverse freezing (reversible glass transition upon heating). This phenomenon is reviewed, and a list of experimental demonstrations and theoretical models is presented. A simple spin model for inverse melting is introduced and solved analytically for infinite range, constant paramagnetic exchange interaction. The random exchange analogue of this model yields inverse freezing, as implied by the analytic solution based on the replica trick. The qualitative features of this system (generalized Blume-Capel spin model) are shown to resemble a large class of inverse melting phenomena. The appearance of inverse melting is related to an exact rescaling of one of the interaction parameters that measures the entropy of the system. For the case of almost degenerate spin states, perturbative expansion is presented, and the first three terms correspond to the empiric formula for the Flory-Huggins ? parameter in the theory of polymer melts. The possible microscopic origin of this ? parameter and the limitations of the Flory-Huggins theory where the state degeneracy is associated with the different conformations of a single polymer or with the spatial structures of two interacting molecules are discussed.
NASA Astrophysics Data System (ADS)
Cardenas, Rolando
The Border Ranges Fault System (BRFS) bounds the Cook Inlet and Susitna Basins, and is an important petroleum province within south-central Alaska. A primary goal of our research is to test several plausible models of structure along the BRFS using a novel three-dimensional inversion technique utilizing gravity data, constrained with other geophysical, borehole and surface geological information. This research involves the development of 3D inversion modeling software using C++ Builder from Embarcadero's XE2 Suite. The novel inversion approach directly models known geology with a priori uncertainties assigned to the geologic model to allow researchers to compare alternative interpretations. This technique was developed to evaluate three-dimensional structure in regions of complex and poorly known geology. Our software computes the density solution of a geologic structure by utilizing its location within the gravity field as well as the gridded surface files of known topography and subsurface units. The total gravitational effect of each body is calculated with a series of semi-infinite vertical line elements which improves the computational efficiency of computing forward models of structures with extremely complex geometry. The inversion algorithm considers a priori geophysical constraints and uncertainties due to gravity measurements, surface file inconsistencies, and forward calculations in the model solution. In addition, a Kalman-based filtering estimator is used to minimize our observation and processing noise. The estimator allows the a posteriori covariance matrix to avoid its dependence on the non-singularity of the Jacobian (model) matrix.
NASA Astrophysics Data System (ADS)
Sirovich, Livio; Pettenati, Franco; Cavallini, Fabio
2013-12-01
inverted the regional pattern of intensities of the catastrophic earthquake of 1694 in the southern Apennines and determined the geometrical and kinematic characteristics of its source, including the double-couple orientation (strike angle 299° ± 10°, dip 54° ± 12°, and rake 309° ± 11°; pure dip-slip solution not precluded). The objective nonlinear inversion was performed using the simple 11 parameter kinematic-function model (KF) with a niching genetic algorithm technique. The similarity between the pattern of the field intensities of the 1694 earthquake and the synthetic pattern is striking. This result is supported by the fact that our inversion technique was verified in the study area, where it was able to again find the source of the Ms 6.9 Irpinia 1980 earthquake, known from instruments and from field surveys of the rupture. This type of inversion enables researchers to exploit the extensive intensity data from Italy and other countries to extend the knowledge of seismotectonic activity to preinstrumental times. New paleoseismological evidence and even published descriptions of the fault rupture by witnesses of the 1694 earthquake were found, confirming our results. We also present and apply a new algorithm, of general interest, to calculate disorientations between double-couples via standard linear algebra. The 3-D rotations that bring the pairwise orthogonal unit vectors that were estimated by our intensity inversion into the instrumental triples of the 1980 Irpinia earthquake, assumed as benchmarks, provide verification of our algorithm.
Inversion layer MOS solar cells
NASA Technical Reports Server (NTRS)
Ho, Fat Duen
1986-01-01
Inversion layer (IL) Metal Oxide Semiconductor (MOS) solar cells were fabricated. The fabrication technique and problems are discussed. A plan for modeling IL cells is presented. Future work in this area is addressed.
Temperature Inversions Have Cold Bottoms.
ERIC Educational Resources Information Center
Bohren, Craig F.; Brown, Gail M.
1982-01-01
Uses discussion and illustrations of several demonstrations on air temperature differences and atmospheric stability to explain the phenomena of temperature inversions. Relates this to the smog in Los Angeles and discusses the implications. (DC)
NASA Astrophysics Data System (ADS)
Mahan, G. D.
2014-09-01
We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikely to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.
Mahan, G. D.
2014-09-21
We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikely to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.
Computation of inverse magnetic cascades
NASA Technical Reports Server (NTRS)
Montgomery, D.
1981-01-01
Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to Tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed.
Athletic Footwear, Leg Stiffness, and Running Kinematics
Bishop, Mark; Fiolkowski, Paul; Conrad, Bryan; Brunt, Denis; Horodyski, MaryBeth
2006-01-01
Context: The leg acts as a linear spring during running and hopping and adapts to the stiffness of the surface, maintaining constant total stiffness of the leg-surface system. Introducing a substance (eg, footwear) may affect the stiffness of the leg in response to changes in surface stiffness. Objective: To determine if the type of athletic footwear affects the regulation of leg stiffness in dynamic activities. Design: Repeated-measures design. Setting: Motion analysis laboratory. Patients or Other Participants: Nine healthy adults (age = 28 ± 6.8 years, mass = 71.6 ± 12.9 kg) free from lower extremity injuries. Intervention(s): Subjects hopped at 2.2 Hz on a forceplate under 3 footwear conditions (barefoot, low-cost footwear, high-cost footwear). Subjects ran on a treadmill at 2 speeds (2.23 m/s, 3.58 m/s) under the same footwear conditions. Main Outcome Measure(s): Limb stiffness was calculated from forceplate data. Kinematic data (knee and ankle angles at initial contact and peak joint excursion after contact) were collected during running. We calculated 1-way repeated-measures (stiffness) and 2-way (speed by footwear) repeated-measures analyses of variance (running kinematics) to test the dependent variables. Results: A significant increase in leg stiffness from the barefoot to the “cushioned” shoe condition was noted during hopping. When running shod, runners landed in more dorsiflexion but had less ankle motion than when running barefoot. No differences were seen between the types of shoes. The primary kinematic difference was identified as running speed increased: runners landed in more knee flexion. At the ankle, barefoot runners increased ankle motion to a significantly greater extent than did shod runners as speed increased. Conclusions: Footwear influences the maintenance of stiffness in the lower extremity during hopping and joint excursion at the ankle in running. Differences in cushioning properties of the shoes tested did not appear to be significant. PMID:17273463
A Kinematical Approach to Dark Energy Studies
Rapetti, David; Allen, Steven W.; Amin, Mustafa A.; Blandford, Roger D.; /KIPAC, Menlo Park
2006-06-06
We present and employ a new kinematical approach to cosmological ''dark energy'' studies. We construct models in terms of the dimensionless second and third derivatives of the scale factor a(t) with respect to cosmic time t, namely the present-day value of the deceleration parameter q{sub 0} and the cosmic jerk parameter, j(t). An elegant feature of this parameterization is that all {Lambda}CDM models have j(t) = 1 (constant), which facilitates simple tests for departures from the {Lambda}CDM paradigm. Applying our model to the three best available sets of redshift-independent distance measurements, from type Ia supernovae and X-ray cluster gas mass fraction measurements, we obtain clear statistical evidence for a late time transition from a decelerating to an accelerating phase. For a flat model with constant jerk, j(t) = j, we measure q{sub 0} = -0.81 {+-} 0.14 and j = 2.16{sub -0.75}{sup +0.81}, results that are consistent with {Lambda}CDM at about the 1{sigma} confidence level. A standard ''dynamical'' analysis of the same data, employing the Friedmann equations and modeling the dark energy as a fluid with an equation of state parameter, w (constant), gives {Omega}{sub m} = 0.306{sub -0.040}{sup +0.042} and w = -1.15{sub -0.18}{sup +0.14}, also consistent with {Lambda}CDM at about the 1{sigma} level. In comparison to dynamical analyses, the kinematical approach uses a different model set and employs a minimum of prior information, being independent of any particular gravity theory. The results obtained with this new approach therefore provide important additional information and we argue that both kinematical and dynamical techniques should be employed in future dark energy studies, where possible. Our results provide further interesting support for the concordance {Lambda}CDM paradigm.
Kinematics of transition during human accelerated sprinting
Nagahara, Ryu; Matsubayashi, Takeo; Matsuo, Akifumi; Zushi, Koji
2014-01-01
ABSTRACT This study investigated kinematics of human accelerated sprinting through 50?m and examined whether there is transition and changes in acceleration strategies during the entire acceleration phase. Twelve male sprinters performed a 60-m sprint, during which step-to-step kinematics were captured using 60 infrared cameras. To detect the transition during the acceleration phase, the mean height of the whole-body centre of gravity (CG) during the support phase was adopted as a measure. Detection methods found two transitions during the entire acceleration phase of maximal sprinting, and the acceleration phase could thus be divided into initial, middle, and final sections. Discriminable kinematic changes were found when the sprinters crossed the detected first transition—the foot contacting the ground in front of the CG, the knee-joint starting to flex during the support phase, terminating an increase in step frequency—and second transition—the termination of changes in body postures and the start of a slight decrease in the intensity of hip-joint movements, thus validating the employed methods. In each acceleration section, different contributions of lower-extremity segments to increase in the CG forward velocity—thigh and shank for the initial section, thigh, shank, and foot for the middle section, shank and foot for the final section—were verified, establishing different acceleration strategies during the entire acceleration phase. In conclusion, there are presumably two transitions during human maximal accelerated sprinting that divide the entire acceleration phase into three sections, and different acceleration strategies represented by the contributions of the segments for running speed are employed. PMID:24996923
Uncertainty Propagation in Calibration of Parallel Kinematic Machines
JOKIEL JR.,BERNHARD; ZIERGERT,JOHN C.
1999-11-02
Over the last decade, multi-axis machine tools and robots based on parallel kinematic mechanisms (PKMs) have been developed and marketed worldwide. Positional accuracy in these machines is controlled by accurate knowledge of the kinematic parameters which consists of the joint center locations and distances between joint pairs. Since these machines tend to be rather large in size, the kinematic parameters (joint center locations, and initial strut lengths) are difficult to determine when these machines are in their fully assembled state. Work recently completed by the University of Florida and Sandia National Laboratories has yielded a method for determining all of the kinematic parameters of an assembled parallel kinematic device. This paper contains a brief synopsis of the calibration method created, an error budget, an uncertainty analysis for the recovered kinematic parameters and the propagation of these uncertainties to the tool tip.
Cosmological Applications of the Gaussian Kinematic Formula
NASA Astrophysics Data System (ADS)
Fantaye, Yabebal T.; Marinucci, Domenico
2014-05-01
The Gaussian Kinematic Formula (GKF, see Adler and Taylor (2007,2011)) is an extremely powerful tool allowing for explicit analytic predictions of expected values of Minkowski functionals under realistic experimental conditions for cosmological data collections. In this paper, we implement Minkowski functionals on multipoles and needlet components of CMB fields, thus allowing a better control of cosmic variance and extraction of information on both harmonic and real domains; we then exploit the GKF to provide their expected values on spherical maps, in the presence of arbitrary sky masks, and under nonGaussian circumstances.
Quantum simulation of noncausal kinematic transformations.
Alvarez-Rodriguez, U; Casanova, J; Lamata, L; Solano, E
2013-08-30
We propose the implementation of Galileo group symmetry operations or, in general, linear coordinate transformations in a quantum simulator. With an appropriate encoding, unitary gates applied to our quantum system give rise to Galilean boosts or spatial and time parity operations in the simulated dynamics. This framework provides us with a flexible toolbox that enhances the versatility of quantum simulation theory, allowing the direct access to dynamical quantities that would otherwise require full tomography. Furthermore, this method enables the study of noncausal kinematics and phenomena beyond special relativity in a quantum controllable system. PMID:24033011
The Stellar Kinematics of Extragalactic Bulges
NASA Astrophysics Data System (ADS)
Falcón-Barroso, Jesús
Galactic bulges are complex systems. Once thought to be small-scale versions of elliptical galaxies, advances in astronomical instrumentation (spectroscopy in particular) has revealed a wealth of photometric and kinematic substructure in otherwise simple-looking components. This review provides an overview of how our perspective on galactic bulges has changed over the years. While it is mainly focused on aspects related to the dynamical state of their stars, there will be natural connections to other properties (e.g. morphology, stellar populations) discussed in other reviews in this volume.
Failure tolerant operation of kinematically redundant manipulators
NASA Technical Reports Server (NTRS)
Lewis, Christopher L.; Maciejewski, Anthony A.
1994-01-01
Redundant manipulators may compensate for failed joints with their additional degrees of freedom. In this paper such a manipulator is considered fault tolerant if it can guarantee completion of a task after any one of its joints has failed. This fault tolerance of kinematically redundant manipulators is insured here. Methods to analyze the manipulator's work space find regions inherently suitable for critical tasks because of their high level of failure tolerance. Constraints are then placed on the manipulator's range of motion to guarantee completion of a task.
Kinematic bias in cosmological distance measurement
NASA Astrophysics Data System (ADS)
Kaiser, Nick; Hudson, Michael J.
2015-11-01
Recent calculations using non-linear relativistic cosmological perturbation theory show biases in the mean luminosity distance and distance modulus at low redshift. We show that these effects may be understood very simply as a non-relativistic, and purely kinematic, Malmquist-like bias, and we describe how the effect changes if one averages over sources that are limited by apparent magnitude. This effect is essentially identical to the distance bias from small-scale random velocities that has previously been considered by astronomers, though we find that the standard formula overestimates the homogeneous bias by a factor 2.
Kinematic Measurements from YouTube Videos
NASA Astrophysics Data System (ADS)
Ruiz, Michael J.
2009-04-01
Video analysis of motion has been in use now for some time.1-3 However, some teachers may not have video equipment or may be looking for innovative ways to engage students with interesting applications at no cost. The recent advent of YouTube offers opportunities for students to measure kinematic properties of real-life events using their computers. This paper provides examples such as measuring the average speed of a winning horse at the Kentucky Derby, plotting speed versus time from watching the speedometer of a high-performance bike, and determining acceleration for circular motion of amusement park rides.
Kinematics of Low Surface Brightness Galaxies
NASA Astrophysics Data System (ADS)
Cardullo, A.; Pizzella, A.; Corsini, E. M.; Bertola, F.
2008-10-01
We analyzed the kinematic of 12 low surface-brightness (LSB) galaxies to study the correlation between the disk circular velocity V_{c} and the central velocity dispersion of the spheroidal component Ď_{0}. This relation has been claimed to be either the same power-law relation tep{buy} or a different linear one tep{piz} with respect to high surface-brightness (HSB) galaxies. We confirm here that LSB and HSB galaxies follow two different linear V_{c}-Ď_{0} relations.
Changes in knee kinematics following total knee arthroplasty.
Akbari Shandiz, Mohsen; Boulos, Paul; Saevarsson, Stefan Karl; Yoo, Sam; Miller, Stephen; Anglin, Carolyn
2016-04-01
Total knee arthroplasty (TKA) changes the knee joint in both intentional and unintentional, known and unknown, ways. Patellofemoral and tibiofemoral kinematics play an important role in postoperative pain, function, satisfaction and revision, yet are largely unknown. Preoperative kinematics, postoperative kinematics or changes in kinematics may help identify causes of poor clinical outcome. Patellofemoral kinematics are challenging to record since the patella is obscured by the metal femoral component in X-ray and moves under the skin. The purpose of this study was to determine the kinematic degrees of freedom having significant changes and to evaluate the variability in individual changes to allow future study of patients with poor clinical outcomes. We prospectively studied the 6 degrees of freedom patellofemoral and tibiofemoral weightbearing kinematics, tibiofemoral contact points and helical axes of rotation of nine subjects before and at least 1â€‰year after total knee arthroplasty using clinically available computed tomography and radiographic imaging systems. Normal kinematics for healthy individuals were identified from the literature. Significant differences existed between pre-TKA and post-TKA kinematics, with the post-TKA kinematics being closer to normal. While on average the pre-total knee arthroplasty knees in this group displayed no pivoting (only translation), individually only five knees displayed this behaviour (of these, two showed lateral pivoting, one showed medial pivoting and one showed central pivoting). There was considerable variability postoperatively as well (five central, two lateral and two medial pivoting). Both preop and postop, flexion behaviour was more hinge-like medially and more rolling laterally. Helical axes were more consistent postop for this group. An inclusive understanding of the pre-TKA and post-TKA kinematics and changes in kinematics due to total knee arthroplasty could improve implant design, patient diagnosis and surgical technique. PMID:26936959
Kinematic Rupture Process Of Karakocan-Elazig Earthquake, Eastern Turkey
NASA Astrophysics Data System (ADS)
Bekler, F. N.; Ozel, N. M.; Tanircan, G. B.
2012-04-01
An earthquake (Mw=5.9) hit Elazig in the eastern part of Turkey on March 8, 2010 at 02:32 (GMT). It is located midway between the provincial capital of Elaz?? and Bingöl with coordinates reported as 38o48.42N and 40o5.99E by Bogazici University Kandilli Observatory and Earthquake Research Institute (KOERI). Source characterization and slip history were estimated the main and four moderate size earthquake almost at the same location. The earthquake occurred at one of the tectonically very active East Anatolian Fault zone starts at the Karl?ova triple junction, where it meets the North Anatolian fault to the NE. Multi time-window linear waveform inversion technique (MTWIT) was applied to strong ground motion (SGM) data. Theoretical Green's functions between subfaults and stations were calculated by a Discrete Wave Number Method (DWNM) using 1-D velocity structure. Inversion technique used in this study yields a non unique solution. Therefore various rupture models have been tried until both observed and synthetic data were matched. Results show simple patterns in slip distributions. Maximum slip is 0.78 and seismic moment is 1.435E+25 dyne.cm from the kinematic rupture process of the strike slip faulting. In this study, we searched a stable 1-D crustal velocity model with low RMS misfit to construct the theoretical Green's function between each sub-fault and each station among the 4 different models. These are Preliminary Reference Earth Model (PREM; Dziewonski and Anderson, 1981), International Association of Seismology and the Physics of the Earth's Interior (IASP91) (Kennett and Engdahl, 1991), Kandilli Observatory and Earthquake Research Institute (KOERI) earthquake location model, explosion model (Gurbuz, 2004). We have collected previous studies Rebollar et al., (2001), Ichinose et al., (1997), Abdel-Fattah (2002), Somerville et al., (1999), Wells and Coppersmith (1994) on source information of moderate size earthquakes occurred worldwide and compared with our results. Results were compared with those of similar size earthquakes around the world and a new empirical relationship was proposed between seismic moment and rupture area. We expect our findings provide usefull information to resolving rupture mechanisms and triggering of the events in Eastern Anatoion Region. Key Words: Rupture Process, Elazig Earthquake, Eastern Turkey
Kalman filtering, smoothing and recursive robot arm forward and inverse dynamics
NASA Technical Reports Server (NTRS)
Rodriguez, G.
1986-01-01
The inverse and forward dynamics problems for multi-link serial manipulators are solved by using recursive techniques from linear filtering and smoothing theory. The pivotal step is to cast the system dynamics and kinematics as a two-point boundary-value problem. Solution of this problem leads to filtering and smoothing techniques identical to the equations of Kalman filtering and Bryson-Frazier fixed time-interval smoothing. The solutions prescribe an inward filtering recursion to compute a sequence of constraint moments and forces followed by an outward recursion to determine a corresponding sequence of angular and linear accelerations. In addition to providing techniques to compute joint accelerations from applied joint moments (and vice versa), the report provides an approach to evaluate recursively the composite multi-link system inertia matrix and its inverse. The report lays the foundation for the potential use of filtering and smoothing techniques in robot inverse and forward dynamics and in robot control design.
Discrete wavelet transform: a tool in smoothing kinematic data.
Ismail, A R; Asfour, S S
1999-03-01
Motion analysis systems typically introduce noise to the displacement data recorded. Butterworth digital filters have been used to smooth the displacement data in order to obtain smoothed velocities and accelerations. However, this technique does not yield satisfactory results, especially when dealing with complex kinematic motions that occupy the low- and high-frequency bands. The use of the discrete wavelet transform, as an alternative to digital filters, is presented in this paper. The transform passes the original signal through two complementary low- and high-pass FIR filters and decomposes the signal into an approximation function and a detail function. Further decomposition of the signal results in transforming the signal into a hierarchy set of orthogonal approximation and detail functions. A reverse process is employed to perfectly reconstruct the signal (inverse transform) back from its approximation and detail functions. The discrete wavelet transform was applied to the displacement data recorded by Pezzack et al., 1977. The smoothed displacement data were twice differentiated and compared to Pezzack et al.'s acceleration data in order to choose the most appropriate filter coefficients and decomposition level on the basis of maximizing the percentage of retained energy (PRE) and minimizing the root mean square error (RMSE). Daubechies wavelet of the fourth order (Db4) at the second decomposition level showed better results than both the biorthogonal and Coiflet wavelets (PRE = 97.5%, RMSE = 4.7 rad s-2). The Db4 wavelet was then used to compress complex displacement data obtained from a noisy mathematically generated function. Results clearly indicate superiority of this new smoothing approach over traditional filters. PMID:10093032
Inverse Compton Scattering in Mildly Relativistic Plasma
NASA Technical Reports Server (NTRS)
Molnar, S. M.; Birkinshaw, M.
1998-01-01
We investigated the effect of inverse Compton scattering in mildly relativistic static and moving plasmas with low optical depth using Monte Carlo simulations, and calculated the Sunyaev-Zel'dovich effect in the cosmic background radiation. Our semi-analytic method is based on a separation of photon diffusion in frequency and real space. We use Monte Carlo simulation to derive the intensity and frequency of the scattered photons for a monochromatic incoming radiation. The outgoing spectrum is determined by integrating over the spectrum of the incoming radiation using the intensity to determine the correct weight. This method makes it possible to study the emerging radiation as a function of frequency and direction. As a first application we have studied the effects of finite optical depth and gas infall on the Sunyaev-Zel'dovich effect (not possible with the extended Kompaneets equation) and discuss the parameter range in which the Boltzmann equation and its expansions can be used. For high temperature clusters (k(sub B)T(sub e) greater than or approximately equal to 15 keV) relativistic corrections based on a fifth order expansion of the extended Kompaneets equation seriously underestimate the Sunyaev-Zel'dovich effect at high frequencies. The contribution from plasma infall is less important for reasonable velocities. We give a convenient analytical expression for the dependence of the cross-over frequency on temperature, optical depth, and gas infall speed. Optical depth effects are often more important than relativistic corrections, and should be taken into account for high-precision work, but are smaller than the typical kinematic effect from cluster radial velocities.
Geometric deviation modeling by kinematic matrix based on Lagrangian coordinate
NASA Astrophysics Data System (ADS)
Liu, Weidong; Hu, Yueming; Liu, Yu; Dai, Wanyi
2015-09-01
Typical representation of dimension and geometric accuracy is limited to the self-representation of dimension and geometric deviation based on geometry variation thinking, yet the interactivity affection of geometric variation and gesture variation of multi-rigid body is not included. In this paper, a kinematic matrix model based on Lagrangian coordinate is introduced, with the purpose of unified model for geometric variation and gesture variation and their interactive and integrated analysis. Kinematic model with joint, local base and movable base is built. The ideal feature of functional geometry is treated as the base body; the fitting feature of functional geometry is treated as the adjacent movable body; the local base of the kinematic model is fixed onto the ideal geometry, and the movable base of the kinematic model is fixed onto the fitting geometry. Furthermore, the geometric deviation is treated as relative location or rotation variation between the movable base and the local base, and it's expressed by the Lagrangian coordinate. Moreover, kinematic matrix based on Lagrangian coordinate for different types of geometry tolerance zones is constructed, and total freedom for each kinematic model is discussed. Finally, the Lagrangian coordinate library, kinematic matrix library for geometric deviation modeling is illustrated, and an example of block and piston fits is introduced. Dimension and geometric tolerances of the shaft and hole fitting feature are constructed by kinematic matrix and Lagrangian coordinate, and the results indicate that the proposed kinematic matrix is capable and robust in dimension and geometric tolerances modeling.
[Application and development of kinematical alighment during total knee arthroplasty].
Zhang Guo-dong; Yang, Chen; Yang, Guang; Qi, Xin
2015-12-01
Kinematical alignment during total knee arthroplasty is an emerging process, and draws more and more attentions from scholars. Knee joint is close to normal joint after TKA through kinematical alighment, which has good clinical results and functional scores, and not increase failure probility. Thus, it may increase joint stress of patella-femur joint, lead to patellar maltracking and increase abrasion. The paper summarized defination and basical principle, operative method, clinical outcomes and deficiency of kinematical alignment during total knee arthroplasty, in order to choose a better way for kinematical alignment during total knee arthroplasty. PMID:26911130
The 2011, Mw 6.2, Christchurch earthquakes (New Zealand): faults geometry and source kinematics
NASA Astrophysics Data System (ADS)
Toraldo Serra, E.; Delouis, B.; Emolo, A.; Zollo, A.
2012-12-01
The geometrical characteristics and the space-time distribution of the kinematic source parameters of the 21 February 2011, Mw 6.2, Christchurch earthquake, New Zealand, have been inferred through a joint inversion of geodetic and strong-motion data. The geodetic data consist of both Global Position System (GPS), from campaign and continuous stations, and Synthetic Aperture Radar (SAR) interferograms from two ascending satellite tracks. The strong-motion data have been recorded at 10 stations located in the Canterbury Plane, offering a quite good azimuthal coverage of the event. Before performing the data inversion, several preliminary analyses on individual data-sets have been carried out, in order to find the optimal lay-out for the inversion. In particular, the consistency between GPS and InSAR data was checked and some GPS measurements, characterized by large errors, were excluded from the data-set. The strong-motion analyses were instead primarily addressed, to identify the reliable frequency range to be used, through the analysis of stability of S-wave polarization. The kinematic rupture model was obtained using the nonlinear joint inversion scheme proposed by Delouis et al. (2000), which is based on the simulated annealing algorithm. In particular, for any sub-source in which the fault plane is discretized, we explore for the direction, duration and amplitude of the slip vector, and for the rupture offset time. The geometry and orientation of the fault plane to be used in the inversion procedure is preliminarily inferred from the analysis of the geodetic data. In order to account for the complex pattern of the superficial deformation data (especially of the InSAR data), we adopted a source model consisting of two partially overlapping fault segments, whose dimensions are 15x11 and 7x7 km2, and striking at 60o and 10o, respectively. From the data inversion we found a slip distribution for the largest plane characterized by a high slip area, with a maximum amplitude of 4.2 m, localized at NE of the hypocenter. The second fault plane activated with a delay of about 4s, and a maximum slip of 2 m. Moreover, the total Source Time Function considering the two events has a total duration of about 7 s. The global seismic moment resulting from the joint inversion is about 3.0x1025 dyne cm (Mw 6.2), with an average rupture velocity of 2.0 km/s, and most of the energy release occurring on the main fault plane. The source parameters resolution is studied using both the single and joint data-sets, and applying the errors analysis for the retrieved kinematic rupture model.
APOGEE Kinematics. I. Overview of the Kinematics of the Galactic Bulge as Mapped By APOGEE
NASA Astrophysics Data System (ADS)
Ness, M.; Zasowski, G.; Johnson, J. A.; Athanassoula, E.; Majewski, S. R.; GarcĂa PĂ©rez, A. E.; Bird, J.; Nidever, D.; Schneider, Donald P.; Sobeck, J.; Frinchaboy, P.; Pan, Kaike; Bizyaev, Dmitry; Oravetz, Daniel; Simmons, Audrey
2016-03-01
We present the stellar kinematics across the Galactic bulge and into the disk at positive longitudes from the SDSS-III APOGEE spectroscopic survey of the Milky Way. APOGEE includes extensive coverage of the stellar populations of the bulge along the midplane and near-plane regions. From these data, we have produced kinematic maps of 10,000 stars across longitudes of 0Â° < l < 65Â°, and primarily across latitudes of | b| < 5Â° in the bulge region. The APOGEE data reveal that the bulge is cylindrically rotating across all latitudes and is kinematically hottest at the very center of the bulge, with the smallest gradients in both kinematic and chemical space inside the innermost region (| l,b| ) < (5Â°, 5Â°). The results from APOGEE show good agreement with data from other surveys at higher latitudes and a remarkable similarity to the rotation and dispersion maps of barred galaxies viewed edge-on. The thin bar that is reported to be present in the inner disk within a narrow latitude range of | b| < 2Â° appears to have a corresponding signature in [{Fe}/{{H}}] and [Î± /{Fe}]. Stars with [{Fe}/{{H}}] > â€‘0.5 have dispersion and rotation profiles that are similar to that of N-body models of boxy/peanut bulges. There is a smooth kinematic transition from the thin bar and boxy bulge (l,| b| ) < (15Â°, 12Â°) out to the disk for stars with [{Fe}/{{H}}] > â€‘1.0, and the chemodynamics across (l, b) suggests that the stars in the inner Galaxy with [{Fe}/{{H}}] > â€‘1.0 originate in the disk.
Nonlinear particle kinematics of ocean waves
NASA Astrophysics Data System (ADS)
Sclavounos, Paul D.
2005-09-01
A fundamental relation is derived governing the Lagrangian kinematics of fluid particles on the surface of nonlinear ocean waves which may be known only stochastically. The horizontal trajectories of fluid particles on the free surface are shown to obey a pair of coupled nonlinear Ricatti-type ordinary differential equations driven by the temporal and spatial gradients of the free-surface elevation defined relative to an Eulerian frame. This equation is explicit in that it does not require the solution of a fully nonlinear potential flow free-surface problem and may be viewed as a deterministic or stochastic equation depending on the interpretation of the definition of the free-surface elevation. It is free of empirical corrections often used to estimate the particle kinematics above the calm water surface, is valid in potential flow and for waves of large steepness in two and three dimensions and in waters of all depths and may be used for the evaluation of the extreme unsteady loads exerted on surface piercing vertical circular cylinders by steep random waves.
The kinematics of turbulent boundary layer structure
NASA Technical Reports Server (NTRS)
Robinson, Stephen Kern
1991-01-01
The long history of research into the internal structure of turbulent boundary layers has not provided a unified picture of the physics responsible for turbulence production and dissipation. The goals of the present research are to: (1) define the current state of boundary layer structure knowledge; and (2) utilize direct numerical simulation results to help close the unresolved issues identified in part A and to unify the fragmented knowledge of various coherent motions into a consistent kinematic model of boundary layer structure. The results of the current study show that all classes of coherent motion in the low Reynolds number turbulent boundary layer may be related to vortical structures, but that no single form of vortex is representative of the wide variety of vortical structures observed. In particular, ejection and sweep motions, as well as entrainment from the free-streem are shown to have strong spatial and temporal relationships with vortical structures. Disturbances of vortex size, location, and intensity show that quasi-streamwise vortices dominate the buffer region, while transverse vortices and vortical arches dominate the wake region. Both types of vortical structure are common in the log region. The interrelationships between the various structures and the population distributions of vortices are combined into a conceptual kinematic model for the boundary layer. Aspects of vortical structure dynamics are also postulated, based on time-sequence animations of the numerically simulated flow.
Gait kinematic analysis evaluates hindlimb revascularization.
Ríos, Amelia; Delgado, Alexandra; Escalante, Bruno; Santana, Jesús
2011-01-01
Peripheral arterial occlusive disease is described as vascular disorders associated with ischemia and may be the result of an obstructive vascular process or a lost revascularization response. We have shown that gait locomotion analysis by video filming represents an integrative model for the evaluation of mechanisms involved in the process of ischemia-induced revascularization. However, analysis by this method can be subjective and perception errors may be occurring. We present the optimization of a quantifiable, noninvasive, reproducible method that analyzes ankle kinematics in rats using a two-dimensional digital video system. Gait dynamics were filmed in hindlimb ischemic rats with a high speed digital video camera. Images were collected and analyzed at 125 frames per second. An algorithm using interactive data language (IDL) was devised to assess different parameters. In ischemic rats, stride time and knee joint angle remained altered 10 days post-surgery compared with sham animals. Gait kinematics were outlined in a highly reliable way by this computational analysis and corroborated the notion of hindlimb movement recovery associated with the revascularization process. PMID:22423574
The kinematics of break-thrust folds
NASA Astrophysics Data System (ADS)
Fischer, M. P.; Woodward, N. B.; Mitchell, M. M.
1992-04-01
The kinematics of asymmetric, open to close, often overturned thrust-related folds are commonly explained with fault-propagation or detachment fold models. Field observations of thrust-related folds exposed in Tennessee, Virginia, Wyoming and Montana that exhibit this geometry indicate that models of fault-propagation and detachment folds do not adequately describe the kinematics of these structures. Existing models of fault-propagation and detachment folding employ migrating, kink-shaped hinges and relate fold geometry entirely to fault geometry, slip and to the thickness of the basal detachment layers. The models exclude the relation between fold shape and amplitude, and they do not predict a correlation between competent-layer thickness and fold wavelength as expected from buckling theory. Thrust-related folds examined in this study exhibit unique distributions of fabrics in the hinges and forelimbs which demonstrate a lack of hinge migration. Furthermore, the ratios of dominant member thickness to fold wavelenght agree with those expected for folds controlled by a single layer and they are within the expected range for folds with multiple, evenly spaced, harmonically deforming layers. Our analyses suggest these folds evolved from an initial, brief stage of sinusoidal buckling to a later stage of fixed-hinge kinking and thrusting. Thrust-related folds which exhibit a geometry and mesofabric distribution suggesting this type of evolution are defined as break-thrust folds.
Nuclear Rings in Galaxies - A Kinematic Perspective
NASA Technical Reports Server (NTRS)
Mazzuca, Lisa M.; Swaters, Robert A.; Knapen, Johan H.; Veilleux, Sylvain
2011-01-01
We combine DensePak integral field unit and TAURUS Fabry-Perot observations of 13 nuclear rings to show an interconnection between the kinematic properties of the rings and their resonant origin. The nuclear rings have regular and symmetric kinematics, and lack strong non-circular motions. This symmetry, coupled with a direct relationship between the position angles and ellipticities of the rings and those of their host galaxies, indicate the rings are in the same plane as the disc and are circular. From the rotation curves derived, we have estimated the compactness (v(sup 2)/r) up to the turnover radius, which is where the nuclear rings reside. We find that there is evidence of a correlation between compactness and ring width and size. Radially wide rings are less compact, and thus have lower mass concentration. The compactness increases as the ring width decreases. We also find that the nuclear ring size is dependent on the bar strength, with weaker bars allowing rings of any size to form.
The kinematic signature of voluntary actions.
Becchio, Cristina; Zanatto, Debora; Straulino, Elisa; Cavallo, Andrea; Sartori, Giuseppe; Castiello, Umberto
2014-10-01
Research in the field of psychology and cognitive neuroscience has begun to explore the functional underpinnings of voluntary actions and how they differ from stimulus-driven actions. From these studies one can conclude that the two action modes differ with respect to their neural and behavioural correlates. So far, however, no study has investigated whether the voluntary and stimulus-driven actions also differ in terms of motor programming. We report two experiments in which participants had to perform either voluntary or stimulus-driven reach-to-grasp actions upon the same stimulus. Using kinematic methods, in Experiment 1 we obtained evidence that voluntary actions and stimulus-driven actions translate into differential movement patterns. Results for Experiments 2 suggest that selecting what to do, when to act, and whether to act are characterized by specific kinematic signatures and affect different aspects of the reach-to-grasp movement in a selective fashion. These findings add to current models of volition suggesting that voluntary action control results from an interplay of dissociable subfunctions related to specific decision components: what action execute, when to execute an action, and whether to execute any action. PMID:25264611
Friction Stir Welding at MSFC: Kinematics
NASA Technical Reports Server (NTRS)
Nunes, A. C., Jr.
2001-01-01
In 1991 The Welding Institute of the United Kingdom patented the Friction Stir Welding (FSW) process. In FSW a rotating pin-tool is inserted into a weld seam and literally stirs the faying surfaces together as it moves up the seam. By April 2000 the American Welding Society International Welding and Fabricating Exposition featured several exhibits of commercial FSW processes and the 81st Annual Convention devoted a technical session to the process. The FSW process is of interest to Marshall Space Flight Center (MSFC) as a means of avoiding hot-cracking problems presented by the 2195 aluminum-lithium alloy, which is the primary constituent of the Lightweight Space Shuttle External Tank. The process has been under development at MSFC for External Tank applications since the early 1990's. Early development of the FSW process proceeded by cut-and-try empirical methods. A substantial and complex body of data resulted. A theoretical model was wanted to deal with the complexity and reduce the data to concepts serviceable for process diagnostics, optimization, parameter selection, etc. A first step in understanding the FSW process is to determine the kinematics, i.e., the flow field in the metal in the vicinity of the pin-tool. Given the kinematics, the dynamics, i.e., the forces, can be targeted. Given a completed model of the FSW process, attempts at rational design of tools and selection of process parameters can be made.
Multiplanar breast kinematics during different exercise modalities.
Risius, Deborah; Milligan, Alexandra; Mills, Chris; Scurr, Joanna
2015-01-01
Multiplanar breast movement reduction is crucial to increasing physical activity participation amongst women. To date, research has focused on breast movement during running, but until breast movement is understood during different exercise modalities, the breast support requirements for specific activities are unknown. To understand breast support requirements during different exercise modalities, this study aimed to determine multiplanar breast kinematics during running, jumping and agility tasks. Sixteen 32D participants had markers attached to their right nipple and torso. Relative multiplanar breast displacement was calculated during bare-breasted treadmill running (10 kph), maximum countermovement jumping and an agility t-test. Exercise modality influenced the magnitude and direction of breast displacement, velocity and acceleration (p < .05). Jumping produced greater vertical breast displacement (.09 m) but less mediolateral breast displacement (.05 m) than running or the agility task, but agility tasks produced the highest multiplanar breast velocities and acceleration. Breast movement during jumping was predominantly in the vertical direction, whereas the agility task produced a greater percentage of mediolateral breast acceleration than running or jumping. Exercise modality impacted upon the magnitude and distribution of bare-breasted multiplanar breast kinematics in this homogenous 32D cohort. Therefore, to reduce breast movement in women of a 32D bra size, manufacturers may wish to design sport-specific products, with greater vertical support for exercise modalities incorporating jumping and greater mediolateral support for agility tasks. PMID:24942053
THE KINEMATICS OF PRIMATE MIDFOOT FLEXIBILITY
Greiner, Thomas M.; Ball, Kevin A.
2015-01-01
This study describes a unique assessment of primate intrinsic foot joint kinematics based upon bone pin rigid cluster tracking. It challenges the assumption that human evolution resulted in a reduction of midfoot flexibility, which has been identified in other primates as the “midtarsal break.” Rigid cluster pins were inserted into the foot bones of human, chimpanzee, baboon and macaque cadavers. The positions of these bone pins were monitored during a plantarflexion-dorsiflexion movement cycle. Analysis resolved flexion-extension movement patterns and the associated orientation of rotational axes for the talonavicular, calcaneocuboid and lateral cubometatarsal joints. Results show that midfoot flexibility occurs primarily at the talonavicular and cubometatarsal joints. The rotational magnitudes are roughly similar between humans and chimps. There is also a similarity among evaluated primates in the observed rotations of the lateral cubometatarsal joint, but there was much greater rotation observed for the talonavicular joint, which may serve to differentiate monkeys from the hominines. It appears that the capability for a midtarsal break is present within the human foot. A consideration of the joint axes shows that the medial and lateral joints have opposing orientations, which has been associated with a rigid locking mechanism in the human foot. However, the potential for this same mechanism also appears in the chimpanzee foot. These findings demonstrate a functional similarity within the midfoot of the hominines. Therefore, the kinematic capabilities and restrictions for the skeletal linkages of the human foot may not be as unique as has been previously suggested. PMID:25234343
Kinematics of unconstrained tactile texture exploration.
Callier, Thierri; Saal, Hannes P; Davis-Berg, Elizabeth C; Bensmaia, Sliman J
2015-04-01
A hallmark of tactile texture exploration is that it involves movement between skin and surface. When we scan a surface, small texture-specific vibrations are produced in the skin, and specialized cutaneous mechanoreceptors convert these vibrations into highly repeatable, precise, and informative temporal spiking patterns in tactile afferents. Both texture-elicited vibrations and afferent responses are highly dependent on exploratory kinematics, however; indeed, these dilate or contract systematically with decreases or increases in scanning speed, respectively. These profound changes in the peripheral response that accompany changes in scanning speed and other parameters of texture scanning raise the question as to whether exploratory behaviors change depending on what surface is explored or what information is sought about that surface. To address this question, we measure and analyze the kinematics as subjects explore textured surfaces to evaluate different types of texture information, namely the textures' roughness, hardness, and slipperiness. We find that the exploratory movements are dependent both on the perceptual task, as has been previously shown, but also on the texture that is scanned. We discuss the implications of our findings regarding the neural coding and perception of texture. PMID:25744883
Rapid directivity detection by azimuthal amplitude spectra inversion
NASA Astrophysics Data System (ADS)
Cesca, Simone; Heimann, Sebastian; Dahm, Torsten
2011-01-01
An early detection of the presence of rupture directivity plays a major role in the correct estimation of ground motions and risks associated to the earthquake occurrence. We present here a simple method for a fast detection of rupture directivity, which may be additionally used to discriminate fault and auxiliary planes and have first estimations of important kinematic source parameters, such as rupture length and rupture time. Our method is based on the inversion of amplitude spectra from P-wave seismograms to derive the apparent duration at each station and on the successive modelling of its azimuthal behaviour. Synthetic waveforms are built assuming a spatial point source approximation, and the finite apparent duration of the spatial point source is interpreted in terms of rupture directivity. Since synthetic seismograms for a point source are calculated very quickly, the presence of directivity may be detected within few seconds, once a focal mechanism has been derived. The method is here first tested using synthetic datasets, both for linear and planar sources, and then successfully applied to recent Mw 6.2-6.8 shallow earthquakes in Peloponnese, Greece. The method is suitable for automated application and may be used to improve kinematic waveform modelling approaches.
Source Inversion of Glacial Earthquakes
NASA Astrophysics Data System (ADS)
Sergeant, A.; Mangeney, A.; Stutzmann, E.; Montagner, J. P.; Moretti, L.; Castelnau, O.; Yastrebov, V.
2014-12-01
Glacial earthquakes are very-long-period seismic events originating from fast moving marine-terminating glaciers, primarily in Greenland. They consist in large surface waves with dominant periods between 35 and 150 s that are detectable teleseismically. Several studies report a clear temporal and spatial correlation between major glacial earthquakes and the capsize of large, newly calved icebergs. The teleseismic waveform modeling shows that the seismic data are well-explained by a landslide-type source. Long-period seismic waves would result from the force exerted by the iceberg on the glacier and the underlying earth during its collapse. We propose here a method of waveform inversion to retrieve the source-time function of glacial earthquakes. The inversion is carried out in the frequency domain. Taking the inverse Fourier transform of the frequency components determined by the inversion we then obtain time series of forces in the East, North and vertical directions. The recent installation of high-quality seismic networks in Greenland provides valuable data to improve the analysis of the dynamic of such events. We use broadband data from the GLISN experiment to investigate the source process of major glacial earthquakes in the 20-100 s period band. We test the robustness of the method by showing the stability of the inverted source when different stations with varying epicentral distances are used in the inversion. Since observed waveforms used in the inversion are limited in a particular frequency band, the estimated source-time functions are bandpassed. Though their comparison to filtered classical centroid single force models used in other studies shows that the seismogenic process is more complex. We repeated the inversion for several events around Greenland to obtain statistics on different sources. We give a first order interpretation of the dynamic of the inverted sources when applicable.
NASA Astrophysics Data System (ADS)
Yilmaz, H.; Over, S.; Ozden, S.
2006-11-01
In this study we determined the stress regime acting along the East Anatolian Fault Zone between Turkoglu (Kahramanmaras) and Celikhan (Adiyaman), from the Neocene to present-day, based on the inversion of striations measured on faults and on the focal mechanisms of earthquakes having magnitudes greater than 5.0. The inversions yield a strike-slip stress regime with a reverse component (i.e., transpression) operative in the Neocene to present with a consistent N-to NW-trending ?1 axis 156 ± 11° and an E- to NE-trending ?3 axis, 67 ± 9°?3, producing left-lateral motion along the East Anatolian Fault Zone. The inversions of focal mechanisms yield a strike-slip stress deviator characterized by an approximately N-S (N1°W)-trending ?1 and an approximately E-W (N89°E)-trending ?3 axis. Both the kinematic analysis and structural observations indicate that the stress regime operating in the study area has had a transpressional character, giving rise to the Mio-Pliocene compressive structures (reverse faults, thrusts and folds) observed in the study area. Field observations allow estimation of a Pliocene age for the strike-slip East Anatolian Fault Zone.
Timothy C. Johnson; Roeof J. Versteeg; Andy Ward; Frederick D. Day-Lewis; Andre Revil
2010-09-01
Electrical geophysical methods have found wide use in the growing discipline of hydrogeophysics, both for characterizing the electrical properties of the subsurface, and for monitoring subsurface processes in terms of the spatiotemporal changes in subsurface conductivity, chargeability, and source currents they govern. Current multichannel and multielectrode data collections systems are able to collect large amounts of data in relatively short periods of time. However, practitioners are often unable to fully utilize these large data sets and the information they contain due to the processing limitations of standard desktop computers. This limitation can be addressed by utilizing the storage and processing capabilities of high-performance parallel computing environments. We present a parallel distributed-memory forward and inverse modeling algorithm for analyzing resistivity and time-domain induced polarization data. The primary components of the parallel computations include distributed computation of the pole solutions in forward mode, distributed storage and computation of the Jacobian matrix in inverse mode, and parallel execution of the inverse equation solver. We demonstrate the corresponding parallel code for three efforts: (1) resistivity characterization of the Hanford 300 Area Integrated Field Research Challenge site in Hanford, WA; (2) resistivity characterization of a volcanic island in the southern Tyrrhenian Sea in Italy; and (3) resistivity and IP monitoring of biostimulation at a superfund site in Brandywine, MD. Inverse analysis of each of these data sets would be limited (or impossible) in a standard serial computing environment which underscores the need for high-performance computing to fully utilize the potential of electrical geophysical methods in hydrogeophysical applications.
Optimization and geophysical inverse problems
Barhen, J.; Berryman, J.G.; Borcea, L.; Dennis, J.; de Groot-Hedlin, C.; Gilbert, F.; Gill, P.; Heinkenschloss, M.; Johnson, L.; McEvilly, T.; More, J.; Newman, G.; Oldenburg, D.; Parker, P.; Porto, B.; Sen, M.; Torczon, V.; Vasco, D.; Woodward, N.B.
2000-10-01
A fundamental part of geophysics is to make inferences about the interior of the earth on the basis of data collected at or near the surface of the earth. In almost all cases these measured data are only indirectly related to the properties of the earth that are of interest, so an inverse problem must be solved in order to obtain estimates of the physical properties within the earth. In February of 1999 the U.S. Department of Energy sponsored a workshop that was intended to examine the methods currently being used to solve geophysical inverse problems and to consider what new approaches should be explored in the future. The interdisciplinary area between inverse problems in geophysics and optimization methods in mathematics was specifically targeted as one where an interchange of ideas was likely to be fruitful. Thus about half of the participants were actively involved in solving geophysical inverse problems and about half were actively involved in research on general optimization methods. This report presents some of the topics that were explored at the workshop and the conclusions that were reached. In general, the objective of a geophysical inverse problem is to find an earth model, described by a set of physical parameters, that is consistent with the observational data. It is usually assumed that the forward problem, that of calculating simulated data for an earth model, is well enough understood so that reasonably accurate synthetic data can be generated for an arbitrary model. The inverse problem is then posed as an optimization problem, where the function to be optimized is variously called the objective function, misfit function, or fitness function. The objective function is typically some measure of the difference between observational data and synthetic data calculated for a trial model. However, because of incomplete and inaccurate data, the objective function often incorporates some additional form of regularization, such as a measure of smoothness or distance from a prior model. Various other constraints may also be imposed upon the process. Inverse problems are not restricted to geophysics, but can be found in a wide variety of disciplines where inferences must be made on the basis of indirect measurements. For instance, most imaging problems, whether in the field of medicine or non-destructive evaluation, require the solution of an inverse problem. In this report, however, the examples used for illustration are taken exclusively from the field of geophysics. The generalization of these examples to other disciplines should be straightforward, as all are based on standard second-order partial differential equations of physics. In fact, sometimes the non-geophysical inverse problems are significantly easier to treat (as in medical imaging) because the limitations on data collection, and in particular on multiple views, are not so severe as they generally are in geophysics. This report begins with an introduction to geophysical inverse problems by briefly describing four canonical problems that are typical of those commonly encountered in geophysics. Next the connection with optimization methods is made by presenting a general formulation of geophysical inverse problems. This leads into the main subject of this report, a discussion of methods for solving such problems with an emphasis upon newer approaches that have not yet become prominent in geophysics. A separate section is devoted to a subject that is not encountered in all optimization problems but is particularly important in geophysics, the need for a careful appraisal of the results in terms of their resolution and uncertainty. The impact on geophysical inverse problems of continuously improving computational resources is then discussed. The main results are then brought together in a final summary and conclusions section.
Stability of rapid finite-fault inversion for the 2014 Mw6.1 South Napa earthquake
NASA Astrophysics Data System (ADS)
Zhang, Yong; Wang, Rongjiang; Chen, Yun-Tai
2015-12-01
Local seismograms are useful for rapidly reconstructing kinematic finite-fault sources, but the results often depend not only on the data coverage but also on uncertainties of parameters (e.g., hypocentral location and fault geometry) used as a priori information during the inversion. An automatic scheme was applied to offline tests for the 2014 South Napa earthquake. In the case of retrospective full-waveform inversions, a network with station spacing of 10 km within the epicentral distance of 30 km is able to provide adequate stable key source parameters if the preestimated hypocenter and fault orientation are accurate of ±5 km and ±15°, respectively. In simulated real-time inversions, the magnitude reaches Mw6.0 at 13 s, and the slip distribution matches that from the retrospective inversion at about 22-28 s after the origin time of the earthquake. These results are meaningful for estimating the lead time of a catastrophic seismic event.
Zero-Inertial Recession for a Kinematic Wave Model
Technology Transfer Automated Retrieval System (TEKTRAN)
Kinematic-wave models of surface irrigation assume a fixed relationship between depth and discharge (typically, normal depth). When surface irrigation inflow is cut off, the calculated upstream flow depth goes to zero, since the discharge is zero. For short time steps, use of the Kinematic Wave mode...
Lingual Kinematics during Rapid Syllable Repetition in Parkinson's Disease
ERIC Educational Resources Information Center
Wong, Min Ney; Murdoch, Bruce E.; Whelan, Brooke-Mai
2012-01-01
Background: Rapid syllable repetition tasks are commonly used in the assessment of motor speech disorders. However, little is known about the articulatory kinematics during rapid syllable repetition in individuals with Parkinson's disease (PD). Aims: To investigate and compare lingual kinematics during rapid syllable repetition in dysarthric…
Kinematic Signatures of Telic and Atelic Events in ASL Predicates
ERIC Educational Resources Information Center
Malaia, Evie; Wilbur, Ronnie B.
2012-01-01
This article presents an experimental investigation of kinematics of verb sign production in American Sign Language (ASL) using motion capture data. The results confirm that event structure differences in the meaning of the verbs are reflected in the kinematic formation: for example, in the telic verbs (throw, hit), the end-point of the event is…
A School Experiment in Kinematics: Shooting from a Ballistic Cart
ERIC Educational Resources Information Center
Kranjc, T.; Razpet, N.
2011-01-01
Many physics textbooks start with kinematics. In the lab, students observe the motions, describe and make predictions, and get acquainted with basic kinematics quantities and their meaning. Then they can perform calculations and compare the results with experimental findings. In this paper we describe an experiment that is not often done, but is…
Lingual Kinematics during Rapid Syllable Repetition in Parkinson's Disease
ERIC Educational Resources Information Center
Wong, Min Ney; Murdoch, Bruce E.; Whelan, Brooke-Mai
2012-01-01
Background: Rapid syllable repetition tasks are commonly used in the assessment of motor speech disorders. However, little is known about the articulatory kinematics during rapid syllable repetition in individuals with Parkinson's disease (PD). Aims: To investigate and compare lingual kinematics during rapid syllable repetition in dysarthricâ€¦
A School Experiment in Kinematics: Shooting from a Ballistic Cart
ERIC Educational Resources Information Center
Kranjc, T.; Razpet, N.
2011-01-01
Many physics textbooks start with kinematics. In the lab, students observe the motions, describe and make predictions, and get acquainted with basic kinematics quantities and their meaning. Then they can perform calculations and compare the results with experimental findings. In this paper we describe an experiment that is not often done, but isâ€¦
The impact of tibial torsion measurements on gait analysis kinematics
Lucareli, Paulo Roberto Garcia; Santos, Nadia Maria; Godoy, Wagner De; Bernal, Milena Moreira Barreto; Paes, Ângela Tavares; Ramalho, Amancio
2014-01-01
Objective: To measure and compare tibial torsion values as assessed by goniometry and three-dimensional kinematics. In addition, the impact of each one of these measurements on kinematic and kinetic results for normal gait was determined. Methods: Twenty-three healthy and fully ambulatory patients were assessed, 11 women and 12 men, from 20 to 40 years old. Data were collected at a laboratory for the three-dimensional analysis of movement with 10 cameras and two force plates. Tibial torsion measurements were obtained using goniometry and three-dimensional kinematics based on the Plug-in Gait model. Afterwards, both procedures were compared, and the impact of each result was assessed on the kinematic and kinetic modeling of the knee and ankle. Results: Pearson's linear correlation coefficient (r=0,504) showed a moderate correlation between the three-dimensional kinematics and goniometry, and between the changes in the measurements. Regarding the processed kinematic and kinetic results for every torsion position, no significant differences were noticed among any of the studied variables (p>0.05). Conclusion: Although statistical correlation among tibial torsion angles by goniometry and three-dimensional kinematic were moderate, kinematic and kinetic analysis of the joints did not reveal any significant changes. Level of Evidence I, Diagnostic Studies - Investigating a Diagnostic Test. PMID:25328438
Damage identification using inverse methods.
Friswell, Michael I
2007-02-15
This paper gives an overview of the use of inverse methods in damage detection and location, using measured vibration data. Inverse problems require the use of a model and the identification of uncertain parameters of this model. Damage is often local in nature and although the effect of the loss of stiffness may require only a small number of parameters, the lack of knowledge of the location means that a large number of candidate parameters must be included. This paper discusses a number of problems that exist with this approach to health monitoring, including modelling error, environmental effects, damage localization and regularization. PMID:17255045
Darwin's “strange inversion of reasoning”
Dennett, Daniel
2009-01-01
Darwin's theory of evolution by natural selection unifies the world of physics with the world of meaning and purpose by proposing a deeply counterintuitive “inversion of reasoning” (according to a 19th century critic): “to make a perfect and beautiful machine, it is not requisite to know how to make it” [MacKenzie RB (1868) (Nisbet & Co., London)]. Turing proposed a similar inversion: to be a perfect and beautiful computing machine, it is not requisite to know what arithmetic is. Together, these ideas help to explain how we human intelligences came to be able to discern the reasons for all of the adaptations of life, including our own. PMID:19528651
Darwin's "strange inversion of reasoning".
Dennett, Daniel
2009-06-16
Darwin's theory of evolution by natural selection unifies the world of physics with the world of meaning and purpose by proposing a deeply counterintuitive "inversion of reasoning" (according to a 19th century critic): "to make a perfect and beautiful machine, it is not requisite to know how to make it" [MacKenzie RB (1868) (Nisbet & Co., London)]. Turing proposed a similar inversion: to be a perfect and beautiful computing machine, it is not requisite to know what arithmetic is. Together, these ideas help to explain how we human intelligences came to be able to discern the reasons for all of the adaptations of life, including our own. PMID:19528651
Unraveling L_{n,k}: Grassmannian Kinematics
Kaplan, Jared; /SLAC
2010-02-15
It was recently proposed that the leading singularities of the S-Matrix of N = 4 super Yang-Mills theory arise as the residues of a contour integral over a Grassmannian manifold, with space-time locality encoded through residue theorems generalizing Cauchy's theorem to more than one variable. We provide a method to identify the residue corresponding to any leading singularity, and we carry this out explicitly for all leading singularities at tree level and one-loop. We also give several examples at higher loops, including all generic two-loop leading singularities and an interesting four-loop object. As an example we consider a 12-pt N{sup 4}MHV leading singularity at two loops that has a kinematic structure involving double square roots. Our analysis results in a simple picture for how the topological structure of loop graphs is reflected in various substructures within the Grassmannian.
Global and regional kinematics from SLR stations
NASA Technical Reports Server (NTRS)
Dunn, Peter J.
1994-01-01
The stations of the Global Laser Tracking Network have significantly contributed to the measurement of plate kinematics. The expanding network of progressively improved instruments clearly demonstrates the systems' centimeter positioning accuracy. Several satellite laser ranging (SLR) analysis groups have adopted techniques to distill geodynamic information from the Lageos-1 satellite observations using orbital arc lengths from an hour to a decade. SLR observations now provide the scale for the International Terrestrial Reference System and help to define the Earth's polar motion in this system. Agreement between positions separately determined with SLR, VLBI and GPS systems has been established at the level of a few centimeters in position and a few millimeters per year in horizontal velocity.
Kinematic tests of exotic flat cosmological models
NASA Technical Reports Server (NTRS)
Charlton, Jane C.; Turner, Michael S.
1987-01-01
Theoretical prejudice and inflationary models of the very early universe strongly favor the flat, Einstein-de Sitter model of the universe. At present the observational data conflict with this prejudice. This conflict can be resolved by considering flat models of the universe which posses a smooth component of energy density. The kinematics of such models, where the smooth component is relativistic particles, a cosmological term, a network of light strings, or fast-moving, light strings is studied in detail. The observational tests which can be used to discriminate between these models are also discussed. These tests include the magnitude-redshift, lookback time-redshift, angular size-redshift, and comoving volume-redshift diagrams and the growth of density fluctuations.
Top quark kinematics and mass determination
Williams, H.H.
1994-10-01
An analysis is presented of 10 W + {ge} 3 jet events, each with evidence for the presence of a b quark, that were recently observed by the CDF collaboration. Seven of these events include a fourth jet and can be explicitly reconstructed as t{bar t} production. The best estimate of the top quark mass is M{sub t} = 174 {+-} 10{sub {minus}12}{sup +13} GeV/c{sup 2}. A study has also been performed to see if the kinematical properties of events with W + {ge} 3 jets gives evidence for top production. An excess of events with large jet energies, compared to that expected from direct production of W + {ge} 3 jets, is observed. A large fraction of these events also contain a b-quark and a fourth jet.
Kinematics of trajectories in classical mechanics
NASA Astrophysics Data System (ADS)
Shaikh, Rajibul; Kar, Sayan; DasGupta, Anirvan
2014-05-01
In this paper, we show how the study of kinematics of a family of trajectories of a classical mechanical system may be unified within the framework of analysis of geodesic flows in Riemannian geometry and relativity. After setting up the general formalism, we explore it through studies on various one- and two-dimensional systems. Quantities like expansion, shear and rotation (ESR), which are more familiar to the relativist, now reappear while studying such families of trajectories in configuration space, in very simple mechanical systems. The convergence/divergence of a family of trajectories during the course of time evolution, the shear and twist of the area enclosing the family, and the focusing/defocusing of the trajectories within a finite time are investigated analytically for these systems. The understanding of the configuration space developed through such investigations is elaborated upon, and possible future avenues are pointed out.
Adjustable link for kinematic mounting systems
Hale, Layton C. (Livermore, CA)
1997-01-01
An adjustable link for kinematic mounting systems. The adjustable link is a low-cost, passive device that provides backlash-free adjustment along its single constraint direction and flexural freedom in all other directions. The adjustable link comprises two spheres, two sockets in which the spheres are adjustable retain, and a connection link threadly connected at each end to the spheres, to provide a single direction of restraint and to adjust the length or distance between the sockets. Six such adjustable links provide for six degrees of freedom for mounting an instrument on a support. The adjustable link has applications in any machine or instrument requiring precision adjustment in six degrees of freedom, isolation from deformations of the supporting platform, and/or additional structural damping. The damping is accomplished by using a hollow connection link that contains an inner rod and a viscoelastic separation layer between the two.
Uncertainty quantification in kinematic wave models
Wang, Peng; Tartakovsky, Daniel M.
2012-10-01
We developed a probabilistic approach to quantify parametric uncertainty in first-order hyperbolic conservation laws (kinematic wave equations). The approach relies on the derivation of a deterministic equation for the cumulative density function (CDF) of the system state, in which probabilistic descriptions (probability density functions or PDFs) of the system parameters and/or initial and boundary conditions serve as inputs. In contrast to PDF equations, which are often used in other contexts, CDF equations allow for straightforward and unambiguous determination of boundary conditions with respect to sample variables.The accuracy and robustness of solutions of the CDF equation for one such system, the Saint-Venant equations of river flows, were investigated via comparison with Monte Carlo simulations.
Kinematic gait analysis in equine carpal lameness.
Back, W; Barneveld, A; van Weeren, P R; van den Bogert, A J
1993-01-01
Gait analysis plays a major role in the clinical evaluation of equine lameness. It is generally accepted that the clinician expresses the grade of lameness as a subjective score. In this study lameness was objectively assessed using a standardized transient lameness model, in which lameness was induced by intra-articular injection of bacterial endotoxin into the radiocarpal joint of ponies. Lameness was scored by an experienced clinician, and locomotion was recorded simultaneously using a CODA-3 apparatus. The obtained kinematic gait parameters correlated well with the clinical lameness score and also provided possibilities to objectively study the locomotor disturbances of the lame limb in more detail at the walk and trot. PMID:8470470
Kinematic tests of exotic flat cosmological models
Charlton, J.C.; Turner, M.S.
1986-05-01
Theoretical prejudice and inflationary models of the very early Universe strongly favor the flat, Einstein-deSitter model of the Universe. At present the observational data conflict with this prejudice. This conflict can be resolved by considering flat models of the Universe which possess a smooth component by energy density. We study in detail the kinematics of such models, where the smooth component is relativistic particles, a cosmological term, a network of light strings, or fast-moving, light strings. We also discuss the observational tests which can be used to discriminate between these models. These tests include the magnitude-redshift, lookback time-redshift, angular size-redshift, and comoving volume-redshift diagrams and the growth of density fluctuations.
A kinematic model of southern California.
Weldon, R.; Humphreys, E.
1986-01-01
We propose a kinematic model for southern California based on late Quaternary slip rates and orientations of major faults in the region. Internally consistent motions are determined assuming that these faults bound rigid blocks. The velocities of the blocks are calculated along several paths that begin in the Mojave Desert and end off the California coast. A path that crosses the western Transverse Ranges accumulates the accepted relative North America-Pacific plate velocity, whereas paths to the north and south result in a significant missing component of motion. This implies the existence of a zone of active deformation in southern California that is interpreted to include the western Transverse Ranges and northwest trending, predominately strike-slip faults close to the coast both north and south of the Transverse Ranges. Strain on this system accounts for about a third of the total North America- Pacific plate motion. -from Authors
Reproducing the kinematics of damped Lyman ? systems
NASA Astrophysics Data System (ADS)
Bird, Simeon; Haehnelt, Martin; Neeleman, Marcel; Genel, Shy; Vogelsberger, Mark; Hernquist, Lars
2015-02-01
We examine the kinematic structure of damped Lyman ? systems (DLAs) in a series of cosmological hydrodynamic simulations using the AREPO code. We are able to match the distribution of velocity widths of associated low-ionization metal absorbers substantially better than earlier work. Our simulations produce a population of DLAs dominated by haloes with virial velocities around 70 km s-1, consistent with a picture of relatively small, faint objects. In addition, we reproduce the observed correlation between velocity width and metallicity and the equivalent width distribution of Si II. Some discrepancies of moderate statistical significance remain; too many of our spectra show absorption concentrated at the edge of the profile and there are slight differences in the exact shape of the velocity width distribution. We show that the improvement over previous work is mostly due to our strong feedback from star formation and our detailed modelling of the metal ionization state.
Relativistic kinematics for motion faster than light
NASA Technical Reports Server (NTRS)
Jones, R. T.
1982-01-01
The use of conformal coordinates in relativistic kinematics is illustrated and a simple extension of the theory of motions faster than light is provided. An object traveling at a speed greater than light discloses its presence by appearing suddenly at a point, splitting into two apparent objects which then recede from each other at sublight velocities. According to the present theory motion at speeds faster than light would not benefit a space traveler, since the twin paradox becomes inverted at such speeds. In Einstein's theory travel at the velocity of light in an intertial system is equivalent to infinite velocity for the traveler. In the present theory the converse is also true; travel at infinite velocity is equivalent to the velocity of light for the traveler.
Galactic kinematics derived from classical cepheids
NASA Astrophysics Data System (ADS)
Zhu, Zi
On the basis of radial velocity and Hipparcos proper motion data, we have analyzed the galactic kinematics of classical Cepheids. Using the 3-D Ogorodnikov-Milne model we have determined the rotational velocity of the Galaxy to be V0 = 240.5 ± 10.2 km/s, on assuming a glactocentric distance of the Sun of R0 = 8.5 kpc. The results clearly indicate a contracting motion in the solar neighbourhood of (?V ???)/R = -2.60 ± 1.07 km s -1 kpc -1, along the direction of galactic rotation. Possible reason for this motion is discussed. The solar motion found here is S? = 18.78 ± 0.86 km/s in the direction l? = 54.4° ± 2.9° and b? = +26.6° ± 2.6°.
Adjustable link for kinematic mounting systems
Hale, L.C.
1997-07-01
An adjustable link for kinematic mounting systems is disclosed. The adjustable link is a low-cost, passive device that provides backlash-free adjustment along its single constraint direction and flexural freedom in all other directions. The adjustable link comprises two spheres, two sockets in which the spheres are adjustable retain, and a connection link threadly connected at each end to the spheres, to provide a single direction of restraint and to adjust the length or distance between the sockets. Six such adjustable links provide for six degrees of freedom for mounting an instrument on a support. The adjustable link has applications in any machine or instrument requiring precision adjustment in six degrees of freedom, isolation from deformations of the supporting platform, and/or additional structural damping. The damping is accomplished by using a hollow connection link that contains an inner rod and a viscoelastic separation layer between the two. 3 figs.
Robot Calibration Using Iteration and Differential Kinematics
NASA Astrophysics Data System (ADS)
Ye, S. H.; Wang, Y.; Ren, Y. J.; Li, D. K.
2006-10-01
In the applications of seam laser tracking welding robot and general measuring robot station based on stereo vision, the robot calibration is the most difficult step during the whole system calibration progress. Many calibration methods were put forward, but the exact location of base frame has to be known no matter which method was employed. However, the accurate base frame location is hard to be known. In order to obtain the position of base coordinate, this paper presents a novel iterative algorithm which can also get parameters' deviations at the same time. It was a method of employing differential kinematics to solve link parameters' deviations and approaching real values step-by-step. In the end, experiment validation was provided.
Collision kinematics in the western external Alps
NASA Astrophysics Data System (ADS)
Bellahsen, N.; Mouthereau, F.; Boutoux, A.; Bellanger, M.; Lacombe, O.; Jolivet, L.; Rolland, Y.
2014-06-01
The kinematics of the collision in Western Alps are investigated through five balanced cross sections of the whole external domain from the Oisans to the Mont Blanc massif. These cross sections were built using published data for the Jura and subalpine fold-and-thrust belts and new structural and field analysis for the External Crystalline Massifs. Five units are defined: the sedimentary nappes from innermost parts of the external zone (e.g., ultra-Dauphinois/Helvetic), the crystalline units with their dysharmonically folded cover (e.g., Morcles nappe), sedimentary nappes over the frontal parts of the crystalline massifs (the Aravis-Granier unit), the subalpine belts (e.g., Vercors, Chartreuse, Bauges, and Bornes), and the Jura. Except for the ultra-Dauphinois nappes, the shortening, including the cover shortening, always corresponds to basement shortening. The total amount of shortening increases from south (28 km, 20%) to north (66 km, 27%). Moreover, the shortening is slightly older in the south than in the north; deepwater turbidites (flysch) and shallow marine to freshwater clastics (molasse) basins are more developed in the north; pressure and temperature conditions are higher in the north; the average uplift rates are about 3 times higher in the north and more localized in space. We propose that these differences are due to along-strike variations in the structure of the European continental margin inherited from Mesozoic times. We then build five palinspastic maps: one at Cretaceous times showing the inherited European Mesozoic margin structure and four from Priabonian to upper Miocene times showing the collision kinematics and the related rotation of Adria.
Kinematics of Visually-Guided Eye Movements
Hess, Bernhard J. M.; Thomassen, Jakob S.
2014-01-01
One of the hallmarks of an eye movement that follows Listing’s law is the half-angle rule that says that the angular velocity of the eye tilts by half the angle of eccentricity of the line of sight relative to primary eye position. Since all visually-guided eye movements in the regime of far viewing follow Listing’s law (with the head still and upright), the question about its origin is of considerable importance. Here, we provide theoretical and experimental evidence that Listing’s law results from a unique motor strategy that allows minimizing ocular torsion while smoothly tracking objects of interest along any path in visual space. The strategy consists in compounding conventional ocular rotations in meridian planes, that is in horizontal, vertical and oblique directions (which are all torsion-free) with small linear displacements of the eye in the frontal plane. Such compound rotation-displacements of the eye can explain the kinematic paradox that the fixation point may rotate in one plane while the eye rotates in other planes. Its unique signature is the half-angle law in the position domain, which means that the rotation plane of the eye tilts by half-the angle of gaze eccentricity. We show that this law does not readily generalize to the velocity domain of visually-guided eye movements because the angular eye velocity is the sum of two terms, one associated with rotations in meridian planes and one associated with displacements of the eye in the frontal plane. While the first term does not depend on eye position the second term does depend on eye position. We show that compounded rotation - displacements perfectly predict the average smooth kinematics of the eye during steady- state pursuit in both the position and velocity domain. PMID:24751602
Numerical analysis of kinematic soil-pile interaction
Castelli, Francesco; Maugeri, Michele; Mylonakis, George
2008-07-08
In the present study, the response of singles pile to kinematic seismic loading is investigated using the computer program SAP2000. The objectives of the study are: (1) to develop a numerical model that can realistically simulate kinematic soil-structure interaction for piles accounting for discontinuity conditions at the pile-soil interface, energy dissipation and wave propagation; (2) to use the model for evaluating kinematic interaction effects on pile response as function of input ground motion; and (3) to present a case study in which theoretical predictions are compared with results obtained from other formulations. To evaluate the effects of kinematic loading, the responses of both the free-field soil (with no piles) and the pile were compared. Time history and static pushover analyses were conducted to estimate the displacement and kinematic pile bending under seismic loadings.
Bosco, G; Eian, J; Poppele, R E
2005-12-01
Previous work from this laboratory has shown that activity in the dorsal spinocerebellar tract (DSCT) relates strongly to global hindlimb kinematics variables during passive displacements of the hindlimb. A linear relationship to limb axis orientation and length variables accounts for most of the response variance for passive limb positioning and movement. Here we extend those observations to more natural movements by examining the information carried by the DSCT during passive stepping movements on a treadmill, and we compare it to information transmitted during passive robot-driven hindlimb movements. Using a principal component analysis approach, we found that a linear relationship between the responses and hindlimb kinematics was comparable across experimental conditions. We also observed systematic non-linearities in this relationship for both types of movement that could be attributed to events corresponding to the touch-down and lift-off phases of the movement. We concluded that proprioceptive information transmitted to the cerebellum by the DSCT during locomotion has at least two major components. One component is associated with limb kinematics (limb orientation) and may be more or less related to the metrics of the step (stride length, for example) or its velocity. The other component is associated with limb length and/or limb loading, and it may signal some aspect of limb stiffness. PMID:16261337
Visualization of dual-arm robot motion space under kinematic constraints
Tarn, T.J. ); De, P.K. ); Bejczy, A.K. ); Li, Z. )
1995-02-01
This article presents a technique for determining and visualizing the geometric motion capabilities of dual-arm robotic systems when the arms work on an object in a closed kinematic chain configuration, taking account of robot arms' base placements, object dimensions, object holding and contact constraints, and space occupancy conflicts of the two arms' links. The constrained and object orientation restricted motion space in general can be visualized as a complex 3D object with hidden unreachable holes or cavities of varying shapes. An automated visualization methodology is presented together with its graphical implementation, illustrated by an example. The methodology is an inverse computer vision technique in the sense that it creates rather than recognizes visual forms. 18 refs., 5 figs.
Kinematic modeling of a double octahedral Variable Geometry Truss (VGT) as an extensible gimbal
NASA Technical Reports Server (NTRS)
Williams, Robert L., II
1994-01-01
This paper presents the complete forward and inverse kinematics solutions for control of the three degree-of-freedom (DOF) double octahedral variable geometry truss (VGT) module as an extensible gimbal. A VGT is a truss structure partially comprised of linearly actuated members. A VGT can be used as joints in a large, lightweight, high load-bearing manipulator for earth- and space-based remote operations, plus industrial applications. The results have been used to control the NASA VGT hardware as an extensible gimbal, demonstrating the capability of this device to be a joint in a VGT-based manipulator. This work is an integral part of a VGT-based manipulator design, simulation, and control tool.
Action Understanding as Inverse Planning
ERIC Educational Resources Information Center
Baker, Chris L.; Saxe, Rebecca; Tenenbaum, Joshua B.
2009-01-01
Humans are adept at inferring the mental states underlying other agents' actions, such as goals, beliefs, desires, emotions and other thoughts. We propose a computational framework based on Bayesian inverse planning for modeling human action understanding. The framework represents an intuitive theory of intentional agents' behavior based on the…
Design, analysis and testing of a parallel-kinematic high-bandwidth XY nanopositioning stage
NASA Astrophysics Data System (ADS)
Li, Chun-Xia; Gu, Guo-Ying; Yang, Mei-Ju; Zhu, Li-Min
2013-12-01
This paper presents the design, analysis, and testing of a parallel-kinematic high-bandwidth XY nanopositioning stage driven by piezoelectric stack actuators. The stage is designed with two kinematic chains. In each kinematic chain, the end-effector of the stage is connected to the base by two symmetrically distributed flexure modules, respectively. Each flexure module comprises a fixed-fixed beam and a parallelogram flexure serving as two orthogonal prismatic joints. With the purpose to achieve high resonance frequencies of the stage, a novel center-thickened beam which has large stiffness is proposed to act as the fixed-fixed beam. The center-thickened beam also contributes to reducing cross-coupling and restricting parasitic motion. To decouple the motion in two axes totally, a symmetric configuration is adopted for the parallelogram flexures. Based on the analytical models established in static and dynamic analysis, the dimensions of the stage are optimized in order to maximize the first resonance frequency. Then finite element analysis is utilized to validate the design and a prototype of the stage is fabricated for performance tests. According to the results of static and dynamic tests, the resonance frequencies of the developed stage are over 13.6 kHz and the workspace is 11.2 ?m × 11.6 ?m with the cross-coupling between two axes less than 0.52%. It is clearly demonstrated that the developed stage has high resonance frequencies, a relatively large travel range, and nearly decoupled performance between two axes. For high-speed tracking performance tests, an inversion-based feedforward controller is implemented for the stage to compensate for the positioning errors caused by mechanical vibration. The experimental results show that good tracking performance at high speed is achieved, which validates the effectiveness of the developed stage.
Jung, Yihwan; Jung, Moonki; Lee, Kunwoo; Koo, Seungbum
2014-08-22
Kinetic analysis of walking requires joint kinematics and ground reaction force (GRF) measurement, which are typically obtained from a force plate. GRF is difficult to measure in certain cases such as slope walking, stair climbing, and track running. Nevertheless, estimating GRF continues to be of great interest for simulating human walking. The purpose of the study was to develop reaction force models placed on the sole of the foot to estimate full GRF when only joint kinematics are provided (Type-I), and to estimate ground contact shear forces when both joint kinematics and foot pressure are provided (Type-II and Type-II-val). The GRF estimation models were attached to a commercial full body skeletal model using the AnyBody Modeling System, which has an inverse dynamics-based optimization solver. The anterior-posterior shear force and medial-lateral shear force could be estimated with approximate accuracies of 6% BW and 2% BW in all three methods, respectively. Vertical force could be estimated in the Type-I model with an accuracy of 13.75% BW. The accuracy of the force estimation was the highest during the mid-single-stance period with an average RMS for errors of 3.10% BW, 1.48% BW, and 7.48% BW for anterior-posterior force, medial-lateral force, and vertical force, respectively. The proposed GRF estimation models could predict full and partial GRF with high accuracy. The design of the contact elements of the proposed model should make it applicable to various activities where installation of a force measurement system is difficult, including track running and treadmill walking. PMID:24917473
Remy, Christian D.; Thelen, Darryl G.
2010-01-01
Background Forward dynamic simulation provides a powerful framework for characterizing in vivo loads, and for predicting changes in movement due to injury, impairment or surgical intervention. However, the computational challenge of generating simulations has greatly limited the use and application of forward dynamic models for simulating human gait. Methods In this study, we introduce an optimal estimation approach to effciently solve for generalized accelerations that satisfy the overall equations of motion and best agree with measured kinematics and ground reaction forces. The estimated accelerations are numerically integrated to enforce dynamic consistency over time, resulting in a forward dynamic simulation. Numerical optimization is then used to determine a set of initial generalized coordinates and speeds that produce a simulation that is most consistent with the measured motion over a full cycle of gait. The proposed method was evaluated with synthetically created kinematics and forceplate data in which both random noise and bias errors were introduced. We also applied the method to experimental gait data collected from five young healthy adults walking at a preferred speed. Results and Conclusions We show that the proposed residual elimination algorithm (REA) converges to an accurate solution, reduces the detrimental effects of kinematic measurement errors on joint moments, and eliminates the need for residual forces that arise in standard inverse dynamics. The greatest improvements in joint kinetics were observed proximally, with the algorithm reducing joint moment errors due to marker noise by over 20% at the hip and over 50% at the low back. Simulated joint angles were generally within 1 deg of recorded values when REA was used to generate a simulation from experimental gait data. REA can thus be used as a basis for generating accurate simulations of subject-specific gait dynamics. PMID:19154064
Design, analysis and testing of a parallel-kinematic high-bandwidth XY nanopositioning stage
Li, Chun-Xia; Gu, Guo-Ying; Yang, Mei-Ju; Zhu, Li-Min
2013-12-15
This paper presents the design, analysis, and testing of a parallel-kinematic high-bandwidth XY nanopositioning stage driven by piezoelectric stack actuators. The stage is designed with two kinematic chains. In each kinematic chain, the end-effector of the stage is connected to the base by two symmetrically distributed flexure modules, respectively. Each flexure module comprises a fixed-fixed beam and a parallelogram flexure serving as two orthogonal prismatic joints. With the purpose to achieve high resonance frequencies of the stage, a novel center-thickened beam which has large stiffness is proposed to act as the fixed-fixed beam. The center-thickened beam also contributes to reducing cross-coupling and restricting parasitic motion. To decouple the motion in two axes totally, a symmetric configuration is adopted for the parallelogram flexures. Based on the analytical models established in static and dynamic analysis, the dimensions of the stage are optimized in order to maximize the first resonance frequency. Then finite element analysis is utilized to validate the design and a prototype of the stage is fabricated for performance tests. According to the results of static and dynamic tests, the resonance frequencies of the developed stage are over 13.6 kHz and the workspace is 11.2â€‰ÎĽm Ă— 11.6â€‰ÎĽm with the cross-coupling between two axes less than 0.52%. It is clearly demonstrated that the developed stage has high resonance frequencies, a relatively large travel range, and nearly decoupled performance between two axes. For high-speed tracking performance tests, an inversion-based feedforward controller is implemented for the stage to compensate for the positioning errors caused by mechanical vibration. The experimental results show that good tracking performance at high speed is achieved, which validates the effectiveness of the developed stage.