Kinematic Linkage Research Articles

Hip Arthroscopy in High Level Baseball Players (SS-31)

Hip disorders are known to be especially problematic in sports that place a premium on kinematic rotational velocity such as baseball with its intricate kinetics of the throwing motion and batting. There have been no studies reporting specifically on the role of hip arthroscopy in this population. The purpose of this study is to report the outcomes of hip arthroscopy in high level (college & professional) baseball players. All patients undergoing hip arthroscopy are prospectively assessed with a modified Harris hip score performed preoperatively and then postoperatively at 3, 12, 24, 60 and 120 months. From this prospectively gathered database, 41 athletes including 45 hips (3 bilateral) were identified who competed at the scholarship intercollegiate or professional level and had achieved minimum one-year follow-up. This cohort represents the substance of this report. There was 100% follow-up at an average of 44 months (range 12-120 months). The average age was 23 years (range 18-34 years). There were 23 collegiate (1 bilateral) and 18 professional baseball players (2 bilateral) including 10 who competed at the major league level. There were 19 pitchers, 8 outfielders, and 14 infielders (6 third basemen; 6 catchers). Among the pitchers, the push leg was involved in 12, the stride leg in 6, and1 both. The average improvement was 11 points (preop 81; postop 92). These players successfully returned to baseball following 42 of the 44 procedures (95%) at an average of 4.3 months (range 3-8 months). There were numerous diagnoses including: labral tears 32, cam FAI 16, combined FAI 12, pincer FAI 1, acetabular chondral lesion 36 (grade IV 12; grade III 17; grade II 1; grade I 6), femoral chondral lesions 1 grade IV, loose bodies 7, ruptured ligamentum teres 8, posterior acetabular fractures 2, and 1 snapping iliopsoas tendon; and there were various procedures performed including femoroplasty 28, acetabuloplasty 13, labral refixation 9, labral repair 1, labral debridement 30, chondroplasty 27 (10 microfractures), loose body removal 7, and 1 iliopsoas release. There were no complications although 2 players underwent repeat arthroscopy. The hip is an essential element in the complex kinematic linkage of the throwing and batting mechanics in baseball. Thus, hip disorders can be a significant cause of dysfunction and source of disability. This data spans more than a dozen years, spanning numerous technical advancements but demonstrates that hip arthroscopy in properly selected athletes can be successful in terms of improved outcome scores and return to baseball.

Conceptual design optimisation of a constant-velocity coupling

The Thompson Coupling is a novel constant velocity joint that operates using the robust double Cardan mechanism. Constant velocity and determinate linkage kinematics are maintained by a spherical pantograph. This mechanism forms an extra loop attached to the intermediate shaft in the double Cardan linkage, and consequently constrains this shaft to bisect the axis of input and output. To date, there has been little presented on the closed-form kinematics of this component. Closed-form expressions for its motion and the rotation of the double Cardan joint are derived by consideration of spherical linkage kinematics, and presented in this work. These expressions are then used to drive basic conceptual design optimisation, whose goal is to reduce induced driveline vibration. The findings of this optimisation are discussed with respect to the current design of the Thompson joint. Improvements in induced driveline vibration are possible, subject to the satisfaction of other coupling design criteria.

Fundamental Laws of Rolling-Element Bearing Mechanics and Diagnostic Methods FAM-C and FDM-A

Rolling-element bearings have been used in the engineering practice since the very beginning of the XIX century. The scientific literature on the subject is therefore rich. As rotational speeds of bearing shafts were getting higher, new problems appeared. Quite a new challenge to be faced were turbine engines with very high rotational speeds that considerably augmented both the scope of problems and the demand for fast and reliable diagnostic methods. The FDM-A diagnostic method (FM frequency modulation, D direct current, C - the level of the methods advancement) has been based on measurements of frequency modulation of the component of pulsation whereas the FAM-C method (FM frequency modulation, C alternating current, C - the level of the methods advancement, i.e. applications in the form of an automatic tester are in use) has been based on measurements of the alternating-current frequency. Both the methods have been developed at ITWL (Air Force Institute of Technology), Warsaw, Poland. Accuracy of these methods essentially results from the natural synchronization of the sampling signal with the angular velocity of kinematic links under examination. The methods enable abrasive wear of a given subassembly to be determined and localised in the course of the power plants regular operation. Possible is determination of numerous parameters of the bearings themselves, the bearing nodes, and the rotating (compressor-turbine) assembly, just to mention the degree of the rolling friction for any of the bearings, the smoothness of motion of the bearing cage, sizes of radial clearances, the level of abrasive wear of contact surfaces of both the bearing cage and the rolling element. A diagnostic unit is fitted to any item, e.g. an electrical joint, supplied with DC or AC voltage. What has been presented in the paper is findings from the performance testing of the aircraft turbine engine: the role of the generator observer has been played by a DC generator and a three-phase tachogenerator.

U-Pb zircon age constraints on two episodes of Paleoproterozoic magmatism and development of the Grizzly Creek shear zone, White River Uplift, western Colorado, U.S.A.

New U-Pb zircon ages from Precambrian exposures in the White River Uplift of western Colorado reveal at least two episodes of Proterozoic granitic magmatism and help to constrain the age of the 1-km-thick Grizzly Creek shear zone. Gneissic granite exposed along Mitchell Canyon northwest of Glenwood Springs, crystallized at 1765±9 Ma and is the oldest igneous unit recognized in the area. The gneissic foliation is defined by alternating layers of biotite and elongated pink K-feldspar up to 5 cm in size, and the fabric strikes west-northwest and dips moderately to steeply north. Cross-cutting relationships with gneissic country rocks and other igneous units exposed in adjacent drainages were not observed. However, deformation and metamorphism are inferred to be between the age of intrusion (ca. 1765 Ma) and the age of younger, unfoliated, coarse-grained to K-feldspar megacrystic granite exposed near the mouth of No Name Canyon, which crystallized at 1743±8 Ma. This younger granite is cut by the Grizzly Creek shear zone to the north and only contains a locally developed magmatic foliation south of the shear zone. Foliated to mylonitic, fine-grained biotite granite exposed in the hanging wall of the shear zone along No Name Canyon crystallized at 1745±10 Ma, suggesting that it might be related to coarse-grained granite exposed in the shear zone footwall. These new ages define two granitic magmatic events in this area at ca. 1765 and 1745 Ma and provide a maximum age of deformation in the Grizzly Creek shear zone of 1743 Ma. Similarities in the orientation, structural style, and kinematics between the Grizzly Creek shear zone and other well-documented structures in the region raise the possibility that the shear zone records multiple episodes of both Paleoproterozoic and Mesoproterozoic (ca. 1.4 Ga) deformation, in which case the younger events would have occurred in the absence of local magmatism. Thus, the Grizzly Creek shear zone might represent a kinematic link between major crustal shear zones to the north and south throughout crustal assembly and stabilization in southern Laurentia, but details of the timing and kinematic relationships between these structures remain uncertain.

Parametric study of the behavior of double toggle switching mechanisms

The paper identified and characterized a special multi-degree of freedom toggle behavior, called double toggle, observed in a typical MCCB switching mechanism. For an idealized system, the condition of toggle sequence is derived geometrically. The existing tools available in a multi-body dynamics package are used for exploring the dynamic behavior of such systems parametrically. The double toggle mechanism is found to make the system insensitive to the operator's behavior; however, the system is vulnerable under extreme usage. The linkage kinematics and stopper locations are found to have dominant role on the behavior of the system. It is revealed that the operating time is immune to the inertial property of the input link and sensitive to that of the output link. Novel designs exploiting this observation, in terms of spring and toggle placements, to enhance switching performance have also been reported in the paper. Detailed study revealed that strategic placement of the spring helps in selective alteration of system performance. Thus, the study establishes the critical importance of the kinematic design of MCCB over the dynamic parameters.

Role of the Palaeogene–Recent sinistral El-Kabir Lineament and the associated transtensional Neogene–Recent El-Kabir Basin (northern Syria) in distributed deformation between the African and Eurasian plates

Abstract The El-Kabir Lineament and the El-Kabir Basin further south form part of the southernmost of several sinistral strike-slip lineaments that characterize the distributed Africa–Eurasian collision zone in the easternmost Mediterranean region. Based on onshore field evidence and offshore two-dimensional (2D) seismic evidence, the El-Kabir fault lineament is interpreted as a sinistral strike-slip fault zone that was active at least from Middle Eocene time onwards. The El-Kabir Lineament was probably active in a transpressional mode during Middle Eocene–Early Miocene(?). The fault lineament was then active in a transtensional mode during Miocene–Recent time. The transtension resulted in the formation of the adjacent NE–SW El-Kabir Basin. Continuing subsidence provided the accommodation space for thick sediment accumulation (>3 km) within the El-Kabir Basin and its offshore extension (roughly corresponding to the Latakia Basin). Offshore 2D seismic data confirm that the basin is fault-bounded and that it continued to be active during Pliocene–Recent time. To the NE, the NE–SW El-Kabir Lineament is truncated and offset by the north–south-trending Dead Sea Transform Fault Zone (Ghab Graben), which propagated northwards during the Pliocene. The inferred Neogene–Recent transtension is explicable by kinematic linkage with oceanic crust in the easternmost Mediterranean that is likely to have experienced contemporaneous subduction zone rollback.

Multiple metamorphic events revealed by zircons from the Diancang Shan−Ailao Shan metamorphic complex, southeastern Tibetan Plateau

Analyses of mineral inclusions within complexly zoned zircons, combined with SIMS UPb ages for various domains within the zircons, provide evidence of the origin and multistage metamorphic evolution of the Diancang Shan−Ailao Shan metamorphic complex, southeastern Tibetan Plateau. Zircons separated from paragneisses, amphibolites, garnet pyroxenites, and marbles were subdivided into inherited (magmatic or detrital) and metamorphic zircons based on cathodoluminescence (CL) and Laser Raman spectroscopy. Weakly zoned, inherited detrital zircons from paragneisses yield ages of 700−540Ma, 1000−800Ma, ~1800Ma, and 2550−2450Ma, and contain inclusion assemblages of Qtz+Kfs+Pl+Ap, recording widespread geological events throughout the ancient Gondwana continent. In contrast, clearly zoned, inherited magmatic zircons in amphibolites and garnet pyroxenites yield ages of ~778−773Ma and contain Cpx+Pl±Qtz+Ap inclusions, representing the crystallization age of the mafic protolith. Metamorphic zircons also record discrete Early−Middle Triassic and the Eocene−Oligocene thermal events. Homogeneous metamorphic zircons with low Th/U ratios (<0.1) contain high-pressure (HP)-diagnostic Grt+Ky+Phe/Mus+Kfs+Qtz+Ap, and Grt+Cpx+Pl±Qtz inclusions in paragneisses, and amphibolites and garnet pyroxenites, respectively, suggesting their formation at 650−720°C and ~14kb. These HP zircons yield 206Pb/238U ages of 249−230Ma, indicating an Early−Middle Triassic HP metamorphic event in the Diancang Shan−Ailao Shan complex belt. Two groups of Eocene−Oligocene metamorphic zircons are also present. One of the groups comprises homogenous zircons with low Th/U ratios (<0.1) that contain medium-pressure (MP) amphibolite–granulite facies Grt+Ky+St+Bt+Kfs+Qtz, Grt+Cpx+Hb+Pl, and Dol+Cal+Ap in paragneisses, amphibolites, and marbles. These assemblages are stable at peak pressure−temperature (P−T) conditions of 720°C−760°C and 8.0−9.6kb, and yield consistent Eocene ages (44−36 Ma). The second group is homogeneous and all zircons have similar Th/U ratios, but contain distinct low-pressure (LP) Grt+Sil+Bt+Kfs+Qtz+Ap, Opx±Cpx±Grt+Hb+Pl, Cal±Cpx+Ap inclusions in paragneisses, amphibolites and garnet pyroxenites, and marbles, recording post-peak P−T conditions of 700°C−750°C and 5.0−6.5kb, and yielding younger Oligocene metamorphic ages (32−25Ma). 40Ar/39Ar analyses of biotite, muscovite, and amphibole yield the youngest ages (25−14Ma, Miocene) related to late cooling during retrogressive metamorphism under conditions of 520°C−620°C and 4.0−4.5kb.These new data suggest a clockwise P−T−t path for the Diancang Shan−Ailao Shan metamorphic complex belt, typical of continent−continent collision, indicating collision−subduction tectonism prior to the strong, left-lateral, ductile deformation along the Ailao Shan−Red River (ASRR) shear zone that started at ~32Ma and lasted until 25Ma, causing mid-crustal (18−25km depth) high-temperature metamorphic conditions. Continued uplift, and a slowing of left-lateral ductile shearing occurred at ~25−14Ma at a depth of 10−15km and under relatively low-temperature conditions. This temporal and kinematic link between left-lateral shearing along the ASRR and the opening of the South China Sea supports the occurrence of the block extrusion of Indochina from Eurasia along lithospheric-scale strike-up faults.

Orientations of wrist axes of rotation influence torque required to hold the hand against gravity: A simulation study of the nonimpaired and surgically salvaged wrist

The wrist is a complex kinematic link connecting the forearm and hand. The kinematic design of the wrist is permanently altered during surgical salvage procedures, such as proximal row carpectomy (PRC) and scaphoid-excision four-corner fusion (SE4CF), which have the unintended consequence of long-term functional impairments to both the wrist and hand. We developed simulations of the nonimpaired, PRC, and SE4CF wrists to evaluate if surgically altered wrist kinematics contribute to functional impairments. Specifically, as a step toward understanding the connection between kinematics and function, we examined the torque necessary to statically maintain functional postures. All simulations included only bone geometry and joint kinematics; soft tissues were excluded. Our simulations demonstrate that the torque necessary to maintain a functional posture is influenced by the orientations of the flexion and deviation axes of rotation relative to each other and the anatomical planes of the radius. The magnitude of torque required to hold the hand against gravity decreased in simulations of the PRC wrist compared to the nonimpaired wrist. In contrast, the torque required increased relative to the nonimpaired wrist in simulations of the SE4CF wrist. These divergent results are directly related to how motion is coupled between the flexion–extension and deviation axes of rotation. This study highlights that, even without considering the effects of soft tissues, changing the kinematic design of the wrist influences function; therefore, kinematics should be considered when surgically redesigning the wrist.

Tectonic and sedimentary response to subduction and incipient continental collision in southern Cyprus, easternmost Mediterranean region

Abstract Evidence mainly from Neogene–Recent sedimentary units and penetrative structures (faults and folds) is used to constrain stress regimes in Cyprus. Following c. south-vergent folding/thrusting, a regional change to extension activated several depocentres during the Late Miocene–Early Pliocene. Fault analysis establishes that kinematic linkages existed between the four Late Miocene basins in southern and western Cyprus. During Late Pliocene(?)–Early Pleistocene time there was a switch to c. east–west left-lateral strike-slip/transpression and fault reactivation. Late Pleistocene growth folding in western coastal Cyprus is explained by reactivation of extensional faults in a left-lateral stress regime. The timing of neotectonic faulting/folding in several areas is constrained by optically stimulated luminescence dating. Existing tectonic models involving north–south collision, left-lateral strike-slip and post-collisional suture tightening are problematic in certain respects. A new model is proposed in which Late Miocene extensional basin formation relates to northward subduction coupled with rollback of the African plate. Subduction culminated in collision of the Eratosthenes Seamount, the leading edge of the African plate, with the Cyprus active margin ( c. 3 Ma). This initiated regional uplift focused on the Troodos Massif. Cyprus was by then coupled with Anatolia as it escaped westwards towards the Aegean subduction zone, giving rise to dominantly strike-slip-related structures in southern Cyprus during the Late Pliocene–Recent.

The Influence of Visual Motion on Motor Learning

How does visual perception shape the way we coordinate movements? Recent studies suggest that the brain organizes movements based on minimizing reaching errors in the presence of motor and sensory noise. We present an alternative hypothesis in which movement trajectories also result from acquired knowledge about the geometrical properties of the object that the brain is controlling. To test this hypothesis, we asked human subjects to control a simulated kinematic linkage by continuous finger motion, a completely novel experience. This paradigm removed all biases arising from influences of limb dynamics and past experience. Subjects were exposed to two different types of visual feedback; some saw the entire simulated linkage and others saw only the moving extremity. Consistent with our hypothesis, subjects learned to move the simulated linkage along geodesic lines corresponding to the geometrical structure of the observed motion. Thus, optimizing final accuracy is not the unique determinant of trajectory formation.

The Study on Selection of human Model for Controllability Evaluation According to Working Postures

Objective: The purpose of this study was to suggest appropriate human model for ergonomic evaluation considering working postures on 3D space. Background: Traditionally extreme design rules have been widely utilized at the stage of designing products. Body size of 5th percentile and 95th percentile in stature has been generally selected for controllability and clearance evaluation, respectively. However, these rules had limitations in reflecting working posture in ergonomic evaluation. Method: In order to define working posture on 3D space, not only sagittal plane but also lateral plane was considered. Kinematic linkage body model was utilized for representation of working posture. By utilizing the anthropometric data of 2,836 South Korean male populations, the point cloud for end points of linkage models was derived. The individuals who were lacking in certain controllability were selected as human models for the evaluation. Result: In case of standing posture it was found that conventional approach is proper for all controllability evaluations. Contrary to standing posture, tall people had less controllability on control location below shoulder point in sitting posture. Conclusion: From the derived proper range on controllability, ergonomic evaluation rule was suggested according to working posture especially in standing and sitting. Application: The results of the study are expected to aid in selection of appropriate human model for ergonomic evaluation and to improve the usability of products and work space.

Inverse methods for modeling non-rigid plate kinematics: Application to mesozoic plate reconstructions of the Central Atlantic

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.

Termination of the northwestern Basin and Range province into a clockwise rotating region of transtension and volcanism, southeast Oregon

New data indicate that northeast-directed extensional faulting characterizes slip across the Brothers fault zone (BFZ), which marks the northern limit of the northwestern Basin and Range (NWBR) extensional province in southeastern Oregon. Structural separation across individual north-northeast striking NWBR faults decreases to zero south of the BFZ. Field relationships and cross-sections demonstrate limited kinematic linkage and independent evolution of the two fault systems since ∼7 Ma. West-directed extension accumulated on NWBR faults at 0.01 mm/yr and lengthened northward after 7.05 Ma. BFZ faults accumulated northeast-directed extension at rates of 0.01 mm/yr since 5.68 Ma. Deformation coincides with periods of heightened basaltic magmatism in the High Lava Plains, implying that volcanism weakened the crust and promoted extension in the BFZ. In a new model, we reconcile the observed northward diminishing rate and clockwise motion of the modern NWBR deformation field with regional geology. The BFZ defines a small circle about the pole of rotation and separates a stable block to the NE from the extending region to the south. Faults to the south are growing northward, consistent with the northward decrease in rate and magnitude of extension in the NWBR.

Source contamination and tectonomagmatic signals of overlapping Early to Middle Miocene orogenic magmas associated with shallow continental subduction and asthenospheric mantle flows in Western Anatolia: A record from Simav (Kütahya) region

The disappearances of mafic shoshonitic and ultrapotassic magma prior to Late Oligocene in Western Anatolia post-collisional tectonic settings, and the sudden appearance of Early-Middle Miocene potassic lavas with orogenic geochemical signatures, indicate a striking change of mantle sources during the Early-Middle Miocene period, and require a special explanation. In this regard, the Simav (Kütahya) region of Western Anatolia represents a critical area, where the Early-Middle Miocene mafic potassic (shoshonite, absarokite, ultrapotassic) and high-K calc-alkaline (andesite, dacite-rhyolite, granite) series rocks overlap in the extensional geotectonic setting in a back-arc position. The appraisal of petrological data obtained from Simav igneous complex indicates that there is a remarkable geochemical and isotopic similarity (e.g., negative Eu anomalies; Nb–Ta depletions; high Sr, low Nd and variable Pb isotope compositions) between coevally generated mafic potassic and high-K calc-alkaline magma series. The near primitive mafic potassic (MHKS) lavas with high Sr isotope compositions require a heterogeneous mantle source contaminated with crustal materials. Dragged and delaminated crustal components, caused by shallow continental subduction and the late arrived subducted terrigenous sediments from the Aegean trench are likely candidate sources of continental materials incorporated into the mantle source of the Simav mafic potassic (MHKS) magmas. The nature of these components also played a significant role in the compositional variations of Simav mafic series rocks. The Simav mafic potassic (MHKS) magmas were derived from a crust-contaminated, subduction-modified (metasomatized) EM-II type mantle source, interacting with influxed asthenosphere in a back-arc mantle wedge, whereas mixing of lower crustal silicic melts with underplated potassic mafic magmas resulted in coeval high-K calc-alkaline rocks, matched by the extent of crustal contamination observed in the more evolved silicic rocks. The petrogenesis of the Simav magmatism was triggered by multiple driving forces with kinematic linkage: such as asthenospheric mantle flows, trench retreat, shallow continental subduction, regional extensional uplifting (e.g., Menderes Massif), and concomitant extension and delaminations of subducted (accreted) crust and mantle lithosphere. Considering the Late Tertiary geodynamic picture of the Western Anatolia back-arc extensional province, the initiation of post-collisional potassic and ultrapotassic magma pulses, as a tectonomagmatic precursor, provide evidence for (i) the timing of last stage of regional uplifting (e.g., Menderes Massif) and onset of extensional basin formations in different periods, and (ii) rapid tectonic transitions.

Kinematic Analysis on Multi-Bar Linkage of Loader Working Device Based on Transformation Theory of Mechanisms

By using the traditional Assur Groups method analysis multi-bar linkage kinematics parameters with an advanced plane connecting rod, complex nonlinear equations should be solved. To solve this tedious and error-prone problem，The senior Assur Groups should be transformed into combination of second grade Assur Groups, virtual single component and constraints single component with the aid of the theory of senior Assur Groups transformation. The problem can be simplified. Based on the transformation theory of mechanisms, the eight-bar linkage working device of loader was analysised. The results showed the method could avoid the nonlinear equations, reduce the computation amounts and enhance the computing rate. It could be applied in various forms of senior Assur Groups

Internal combustion engines on the basis of crank mechanism with dual kinematic links

Представлен краткий анализ технических решений по кривошипно-шатунным механизмам (КШМ). Предложен КШМ со сдвоенными кинематическими связями и показано его преимущество, выявленное на основе анализа кинематических параметров дезаксиальных КШМ. Дана методика графического построения кривой перемещения поршня в зависимости от угла поворота кривошипа коленчатого вала. Приведена индикаторная диаграмма цикла, реализованная КШМ со сдвоенными кинематическими связями.

Obstacle avoidance of redundant manipulators using neural networks based reinforcement learning

This paper proposes a new approach for solving the problem of obstacle avoidance during manipulation tasks performed by redundant manipulators. The developed solution is based on a double neural network that uses Q-learning reinforcement technique. Q-learning has been applied in robotics for attaining obstacle free navigation or computing path planning problems. Most studies solve inverse kinematics and obstacle avoidance problems using variations of the classical Jacobian matrix approach, or by minimizing redundancy resolution of manipulators operating in known environments. Researchers who tried to use neural networks for solving inverse kinematics often dealt with only one obstacle present in the working field. This paper focuses on calculating inverse kinematics and obstacle avoidance for complex unknown environments, with multiple obstacles in the working field. Q-learning is used together with neural networks in order to plan and execute arm movements at each time instant. The algorithm developed for general redundant kinematic link chains has been tested on the particular case of PowerCube manipulator. Before implementing the solution on the real robot, the simulation was integrated in an immersive virtual environment for better movement analysis and safer testing. The study results show that the proposed approach has a good average speed and a satisfying target reaching success rate.

On performance enhancement of parallel kinematic machine

This paper proposes a spatial three degrees of freedom (DOF) parallel kinematic machine enhanced by a passive leg and a web-based remote control system. First, the geometric model of the parallel kinematic machine is addressed. In the mechanism, a fourth kinematic link--a passive link connecting the base center to the moving platform center--is introduced. Each of the three parallel limbs is actuated by one prismatic joint, respectively. The additional link has three passive DOF, namely two rotations around x and y axes and one translation along z axis. With the existence of this link, the unwanted motion of the tool (located in the moving platform) is constrained. The fourth link also enhances the global stiffness of the structure and distributes the torque from machining. With the kinematic model, a web-based remote control approach is applied. The concept of the web-based remote manipulation approach is introduced and the principles behind the method are explored in detail. Finally, a remote manipulation is demonstrated to the proposed structure using web-based remote control concept.

Neck muscle paths and moment arms are significantly affected by wrapping surface parameters

In this paper, we studied the effects of wrapping surfaces on muscle paths and moment arms of the neck muscle, semispinalis capitis. Sensitivities to wrapping surface size and the kinematic linkage to vertebral segments were evaluated. Kinematic linkage, but not radius, significantly affected the accuracy of model muscle paths compared to centroid paths from images. Both radius and linkage affected the moment arm significantly. Wrapping surfaces that provided the best match to centroid paths over a range of postures had consistent moment arms. For some wrapping surfaces with poor matches to the centroid path, a kinematic method (tendon excursion) predicted flexion moment arms in certain postures, whereas geometric method (distance to instant centre) predicted extension. This occurred because the muscle lengthened as it wrapped around the surface. This study highlights the sensitivity of moment arms to wrapping surface parameters and the importance of including multiple postures when evaluating muscle paths and moment arm.

Potential For Intracranial Movements in Pterosaurs

Based on comparative anatomical, morphological, and phylogenetic considerations the potential of pterosaurs for cranial kinesis is assessed. Our investigation shows that whereas skeletally mature derived pterodactyloids have completely fused, rigid and doubtlessly akinetic skulls, skeletally immature derived pterodactyloids and more basal pterosaurs possess key features in the morphology of their otic and basal joints that are suggestive of cranial kinesis, namely streptostyly. In addition, pterosaurs exhibit an evolutionarily informative trend in the degree of cranial ossification, where it is low in most nonpterodactyloids (here named bifenestratans), intermediate in Rhamphorhynchus and Archaeopterodactyloidea, and high in derived pterodactyloids. Incomplete fusion could also indicate loose connections between skull elements. However, another crucial anatomical requirement of a kinetic skull, the permissive kinematic linkage is absent in all pterosaurian taxa. The fact, that the presence of permissive kinematic linkages in the skull is also a prerequisite of all types of cranial kinesis, provides hard evidence that all members of Pterosauria had akinetic skulls. Thus, the presence of the morphological attributes indicative of intracranial movements in some pterosaurs must be explained on grounds other than real potential for cranial kinesis. It could either be of mechanical or ontogenetic importance, or both. Alternatively, it might be considered as the morphological remnant of a real, kinetic skull possessed by the diapsid ancestors of pterosaurs.