Complex Shape Changes Research Articles

Wireless Control System of Reconfigurable Flexible Process-Equipment

The reconfigurable flexible process-equipment developed for machining complex shape and size changes in the scope of large thin-walled parts usually consists of dozens or even hundreds of positioning/support units. During the control process, each unit communicates with the host computer to get control commands and simultaneously feedback internal state information. For large complex system composed of many subsystems, the traditional cable connection based on field bus technology is high control costs and the complexity of the control circuit is hard to build and manage. To solve this problem, this paper puts forward a new way of wireless communication with the cable network technology and drive positioning/support unit in order. This paper focuses on the overall structure of the proposed system, host computer control system, lower computer control system and wireless communication module as well as the implementation hardware circuits and software algorithm. In addition, some solutions of related issues are discussed. The research shows that the proposed system has high stability and reliability, and it provides an effective way to the control and communication of complex system which fully meets the requirements of reconfigurable flexible process-equipment.

A meshfree level-set method for topological shape optimization of compliant multiphysics actuators

This paper proposes a topology optimization method for compliant multiphysics actuators of geometrically nonlinear structures using meshfree Galerkin weak-forms and level set methods. The design boundary is implicitly represented as the zero level set of a higher-dimensional level set function, leading to a level set model capable of handling complex shape and topological changes with flexibilities. A family of compactly supported radial basis functions (CSRBFs) is firstly used to interpolate the level set function of Lipschitz continuity, and then augmented to construct the shape function for meshless approximation by satisfying basic requirements, in particular the predetermined consistency and the Kronecker delta function property. A meshless Galerkin method (MGM) with global weak-forms is established to implement the discretization of the state equations. The design of actuators is transformed into an easier size optimization from a more difficult shape and topology optimization. The design boundary evolution is just a question of advancing the discrete level set function in time by updating the design variables of the size optimization. Compared to most conventional level set methods, the proposed meshless level set method is able to implement the free moving boundary discontinuities without remeshing, and unify two different numerical procedures in propagating the discrete level set function (e.g. Eulerian grid) and approximating the state equation (e.g. Lagrangian mesh), respectively. This method can also avoid numerical difficulties in solving a series of complicate Hamilton–Jacobi partial differential equations (PDEs) with explicit time schemes. Two typical numerical examples are used to demonstrate the effectiveness of the proposed method.

Size matters, but so does shape: quantifying complex shape changes in a sexually selected trait in stalk-eyed flies (Diptera: Diopsidae)

The elaborate morphologies of sexually selected ornaments are ubiquitous across the animal kingdom. In studies investigating these traits, ornament size is frequently the focus, and empirical evidence supports its positive correlation with fitness. Yet shape plays an important role and, surprisingly, is often overlooked. Shape frequently changes with size, influenced by biomechanical, developmental, or performance constraints. Therefore, shape can provide additional insights into the morphological differences between individuals and the potential limits on sexual trait exaggeration. Here, we used landmark-based geometric morphometric methods on a sexually dimorphic species of stalk-eyed fly (Teleopsis dalmanni) to examine patterns of sexual shape dimorphism. Our analyses reveal a significant difference in head shape between the sexes, with males exhibiting smaller eye bulbs, thinner stalks, and smaller heads than females. Additionally, as eyestalk length increases within each sex, a similar pattern of shape change was observed as that observed between sexes. This pattern of shape change may be the result of constraints acting against further ornament exaggeration, and we suggest that this may significantly impact the whole-organism performance in stalk-eyed flies. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 104–113.

MICROWAVE IMAGING OF DIELECTRIC CYLINDERS USING LEVEL SET METHOD AND CONJUGATE GRADIENT ALGORITHM

In this paper, a level set method for shape reconstruction problems is considered. By measuring the scattered fleld, we tried to retrieve the localisation and permittivity of buried objects. The forward problem is solved by the method of moments. For solving the inverse problem, we adopt an evolution approach. Therefore, we introduce a level set technique witch is ∞exible in handling complex shape changes. A conjugate gradient-based method is used in order to deflne iterative updates for the level set functions with the goal to minimize a given least squares data misflt functional. In particular, the proposed method is capable of creating new holes inside the design domain, which makes the flnal design independent of initial guess and reduces the probability of converging to a local minimum. Experimental results demonstrate the feasibility and efiectiveness of the proposed technique.

Coupling ALE Technique and Harmonic Parametrization to Describe Concurrent and Successive Elementary Cell Deformations

We present here an extension of our finite element model of the Drosophila embryo to consider the interdependence of successive morphogenetic movements. A novel approach is used, which couples the Arbitrary Lagrangian Eulerian formulation with the harmonicparametrization. The combination of the two techniques allows to constantly update the deforming embryo geometry and simultaneously build an associated system of curvilinear coordinates. Thus, we are able to exactly describe the elementary cell deformations responsible for each biological event that are then defined with respect to the dynamic middle surface of the embryonic tissue and to their relative reference configuration. Both the active and the passive deformations occurring to the cells are considered through the deformation gradient decomposition. We develop a concurrent simulation of three morphogenetic movements: the ventral furrow invagination, the cephalic furrow formation and the germ band extension. The results show a consistent similarity with respect to the physical phenomena. More generally, the numerical approach that we propose could constitute a powerful tool to rigorously describe and simulate complex shape changes in biological systems.

Experimental study on the behaviors and shape changes of premixed hydrogen–air flames propagating in horizontal duct

The behaviors and shape changes of premixed hydrogen–air flames at various equivalence ratios propagating in half-open and closed horizontal ducts are experimentally investigated using high-speed schlieren imaging and pressure sensors. The study shows that the premixed hydrogen–air flame undergoes more complex shape changes and exhibits more distinct characteristics than that of other gaseous fuels. One of the outstanding findings is that obvious distortion happens to tulip flame after its full formation when equivalence ratio ranges from 0.84 to 4.22 in the closed duct. The salient tulip flame distortions are specially scrutinized and distinguished from the classical tulip collapse and disappearance. The dynamics of distorting tulip flame is different from that of classical tulip flame. The normal tulip flame can be reproduced after the first distortion followed by another distortion. The initiation of flame shape changes coincides with the deceleration both of pressure rise and flame front speed for flames with tulip distortions. And the formation and dynamics of tulip/distorting tulip flames depend on the mixture composition.

Bentho-pelagic divergence of cichlid feeding architecture was prodigious and consistent during multiple adaptive radiations within African rift-lakes.

BackgroundHow particular changes in functional morphology can repeatedly promote ecological diversification is an active area of evolutionary investigation. The African rift-lake cichlids offer a calibrated time series of the most dramatic adaptive radiations of vertebrate trophic morphology yet described, and the replicate nature of these events provides a unique opportunity to test whether common changes in functional morphology have repeatedly facilitated their ecological success.Methodology/Principal FindingsSpecimens from 87 genera of cichlid fishes endemic to Lakes Tanganyka, Malawi and Victoria were dissected in order to examine the functional morphology of cichlid feeding. We quantified shape using geometric morphometrics and compared patterns of morphological diversity using a series of analytical tests. The primary axes of divergence were conserved among all three radiations, and the most prevalent changes involved the size of the preorbital region of the skull. Even the fishes from the youngest of these lakes (Victoria), which exhibit the lowest amount of skull shape disparity, have undergone extensive preorbital evolution relative to other craniofacial traits. Such changes have large effects on feeding biomechanics, and can promote expansion into a wide array of niches along a bentho-pelagic ecomorphological axis.Conclusions/SignificanceHere we show that specific changes in trophic anatomy have evolved repeatedly in the African rift lakes, and our results suggest that simple morphological alterations that have large ecological consequences are likely to constitute critical components of adaptive radiations in functional morphology. Such shifts may precede more complex shape changes as lineages diversify into unoccupied niches. The data presented here, combined with observations of other fish lineages, suggest that the preorbital region represents an evolutionary module that can respond quickly to natural selection when fishes colonize new lakes. Characterizing the changes in cichlid trophic morphology that have contributed to their extraordinary adaptive radiations has broad evolutionary implications, and such studies are necessary for directing future investigations into the proximate mechanisms that have shaped these spectacular phenomena.

Developmental plasticity in fish exposed to a water velocity gradient: a complex response

Developmental plasticity plays a major role in evolution and provides an excellent context for unravelling the ecological implication of variation in abiotic factors to which developing fish are subjected. Water velocity has been known to induce plasticity in salmonids, but the ontogenetic component of these changes is poorly documented. Newly hatched specimens of rainbow trout (Oncorhynchus mykiss) were reared in four constant water velocity treatments (0.4, 0.8, 1.6 and 3.2 cm/sec) for a period of 100 days. Traditional and geometric morphometrics were used complementarily to characterize morphological changes among treatments throughout ontogeny and demonstrated early and complex developmental plasticity in O. mykiss. Certain traits display a constant direction of change, whereas other traits present a break point at 20-25 mm ( approximately 40-60 dph) indicating a modification in the nature of changes between developmental stages. Plasticity in response to water velocity was detected from very early on (15-20 mm; approximately 20-40 dph) and concerned mostly fin-related traits. Body-related traits did not respond conformingly to functional expectations as fishes reared in the fastest velocity treatment show a robust body shape more comparable to that of fish from the slowest treatment than do fish from the intermediate velocity. The noncongruence between treatment and response gradient suggests that different combinations of water velocity have the potential to lead to diverging interpretation of plasticity, both in an ecological and evolutionary context. Overall, the complex shape changes observed in O. mykiss stress the importance of paying better attention to actual functional requirements and adaptations that occur at levels other than hydrodynamics.

Investigation of clustered actuation in tensegrity structures

As tensegrity research is moving away from static structures toward active structures it is becoming critical that new actuation strategies and comprehensive active structures theories are developed to fully exploit the properties of tensegrity structures. In this paper a new general tensegrity paradigm is presented that incorporates a concept referred to as clustered actuation. Clustered actuation exploits the existence of cable elements in a tensegrity structure by allowing cables to be run over frictionless pulleys or through frictionless loops at the nodes. This actuation strategy is a scalable solution that can be utilized for active structures that incorporate many active elements and can reduce the number of actuators necessary for complex shape changes. Clustered actuation also has secondary benefits, specifically reducing the force requirements of actuators in dynamic structures, reducing the number of pre-stress modes to potentially one global mode and relieving element size limitations that occur with embedded actuation. Newly formulated clustered equilibrium equations are developed using energy methods and are shown to be a generalization of the classic tensegrity governing equations. Pre-stress analysis, mechanism analysis and stability of clustered structures are discussed. Lastly, examples compare the mechanics of a clustered structure to an equivalent classic structure and the utility of clustering is highlighted by allowing for actuation throughout a class 1 (no bar-to-bar connections) tensegrity while not embedding the actuators into the structure.

Suction generation in white-spotted bamboo sharksChiloscyllium plagiosum

After the divergence of chondrichthyans and teleostomes, the structure of the feeding apparatus also diverged leading to alterations in the suction mechanism. In this study we investigated the mechanism for suction generation during feeding in white-spotted bamboo sharks, Chiloscyllium plagiosum and compared it with that in teleosts. The internal movement of cranial elements and pressure in the buccal, hyoid and pharyngeal cavities that are directly responsible for suction generation was quantified using sonomicrometry and pressure transducers. Backward stepwise multiple linear regressions were used to explore the relationship between expansion and pressure, accounting for 60-96% of the variation in pressure among capture events. The progression of anterior to posterior expansion in the buccal, hyoid and pharyngeal cavities is accompanied by the sequential onset of subambient pressure in these cavities as prey is drawn into the mouth. Gape opening triggers the onset of subambient pressure in the oropharyngeal cavities. Peak gape area coincides with peak subambient buccal pressure. Increased velocity of hyoid area expansion is primarily responsible for generating peak subambient pressure in the buccal and hyoid regions. Pharyngeal expansion appears to function as a sink to receive water influx from the mouth, much like that of compensatory suction in bidirectional aquatic feeders. Interestingly, C. plagiosum generates large suction pressures while paradoxically compressing the buccal cavity laterally, delaying the time to peak pressure. This represents a fundamental difference from the mechanism used to generate suction in teleost fishes. Interestingly, pressure in the three cavities peaks in the posterior to anterior direction. The complex shape changes that the buccal cavity undergoes indicate that, as in teleosts, unsteady flow predominates during suction feeding. Several kinematic variables function together, with great variation over long gape cycles to generate the low subambient pressures used by C. plagiosum to capture prey.

SU-GG-T-54: On-Line Adaptive IMRT for Prostate Cancer

Purpose: This study proposes a novel on‐line IGRT technique that can modify the original IMRT plan to match with the “anatomy‐of‐the‐day” within few minutes. The performance of this technique is compared with current on‐line IGRT strategies using bone/soft‐tissue based alignment. Method and Materials: Six prostate IMRT patients were studied. An initial IMRT plan was designed on a commercial treatment planning system, using five/seven co‐planar 15‐MV beams. The plan information was exported to an in‐house adaptive planning system. Five daily CBCTimages of each patient were analyzed. Daily GTVs (prostate and seminal vesicles), bladders and rectums were contoured on each CBCT. The original plan dose distribution was deformed to match the daily anatomy and to serve as prescription dose distribution for the daily re‐optimization of the original plan. The re‐optimization process utilized linear programming technique which can reach the solution within less than two minutes. The delivered dose distributions were compared among the ART versus alignment based IGRT techniques. Three bone and soft‐tissue based alignment techniques: Bone10, Soft5, and Soft10, were included. The number 5 and 10 indicate the PTV margins; with Adapt indicating ART technique with 5mm margin. Results: The average GTV D99 doses for all six patients are 99%–100%, 65%–98%, 87%–99%, and 95%–99% for Adapt, Bone10, Soft5, and Soft10 plans respectively. The Bone10 missed GTV coverage at D99 and D95 in 2 of the 6 patients, while the Soft5 technique also missed D95 coverage in 3 patients. The Soft10 and Adapt techniques show adequate GTV coverage for all. Compare to Soft5, the Adapt technique shows improvement on bladder/rectal sparing when local volume/shape variation occurs. Conclusion: This demonstrates the advantage of the online ART technique over patient alignment techniques in handling complex anatomical positioning and shape changes during prostate IMRT treatment. Conflict of Interest: Research sponsored by Varian Medical Systems.

Adaptive Finite Element Method for a Phase Field Bending Elasticity Model of Vesicle Membrane Deformations

In this paper, a three-dimensional adaptive finite element method is developed for a variational phase field bending elasticity model of vesicle membrane deformations. Using a mixed finite element formulation, residual type a posteriori error estimates are derived for the associated nonlinear system of equations and, they are used to introduce the mesh refinement and coarsening. The resulting mesh adaptivity significantly improves the efficiency of the phase field simulation of vesicle membranes and enhances its capability in handling complex shape and topological changes. The effectiveness of the adaptive method is further demonstrated through numerical examples.

Optimal Shape Design of the Electromagnetic Devices in a Level Set Based Implicit Moving Boundary Framework

In this paper we present a new framework to approach the problem of Electro- magnetic shape optimization. We use a level set method with an implicit moving interface model. Such level set models are ∞exible in handling complex shape changes. Furthermore, by using a simple Hamilton-jacobi equation, the movement of the implicit interface is driven by a transformation of objective and the constraints into a speed function that deflnes the level set propagation. The numerical result shows the validity of the present technique. DOI: 10.2529/PIERS060906022153

Interaction of Oxide Surfaces with Water: Environmental Transmission Electron Microscopy of MgO Hydroxylation

Environmental transmission electron microscopy (ETEM) is opening an important window for in situ studies of interaction of water with oxides. Studies of MgO smoke nanocrystals under partial pressures of water ranging from 10 mTorr to 10 Torr found their {100} neutral surfaces to be extremely resistant to dissociative adsorption of water and hydroxylation, in agreement with recent theoretical predictions. ETEM observations of electron irradiation driven MgO smoke nanocrystal hydroxylation displayed the anticipated volume expansion, but revealed complex shape changes with elongations toward oxide corners. The reaction rate was found to increase with electron flux at constant water pressure. In situ selected area diffraction studies of MgO single crystals showed that the hydroxide grows with its basal (0001) plane parallel to the polar MgO (111) planes. This is the same crystallographic relationship as in dehydroxylation experiments, but with four variants. Electron energy loss spectroscopy found oxygen K-edge changes consistent with bulk hydroxylation.

SU-FF-J-48: A Slice-By-Slice CT-Guided Adaptive Radiation Therapy Technique for Twisting Targets

Purpose: To investigate a CT-guided adaptive radiation therapy technique capable of correcting for complex shape changes, including twisting around the longitudinal axis, such as found when treating head and neck patients with a head rotation. Method and Materials: For co-planar beams, the dose in an axial plane is primarily associated with the positions of a single MLC pair. We start with a primary plan, and automatically generate several secondary plans with gantry angles offset by regular increments. MLC sequences for each plan are calculated keeping MUs and number of segments constant for a given beam (fluences are different). Bulk registration (3D) of planning and daily CT images gives global shifts. Slice-by-slice (2D) registration gives local shifts and rotations about the longitudinal axis for each axial slice. The daily MLC sequence is then created for each axial slice/MLC leaf pair combination, by taking the MLC positions from the pre-calculated plan with the nearest rotation, and shifting using a beams-eye-view calculation to account for local linear shifts. A planning study was carried out using two MR images of a healthy volunteer, contoured to simulate a base-of-tongue treatment: One with the head straight (used to simulate the plan image) and one with the head tilted to the left (the daily image). Results: On a slice-by-slice basis, local rotations in the daily image varied from 2 – 31degrees. Local shifts ranged from −0.2 – 0.5cm and −0.4 – 0.0cm in right-left and posterior-anterior directions, respectively. The adapted treatment gave good target coverage, and kept the daily cord dose below the limit used in the original plan (65%, equivalent to 46Gy over 35 fractions). Conclusion: This technique may be useful for adaptive radiation therapy of targets where twisting around the longitudinal axis is significant. These results also demonstrate the feasibility of combining MLC sequences from different pre-approved treatment plans.

Rho GTPase function in flies: insights from a developmental and organismal perspective

Morphogenesis is a key event in the development of a multicellular organism and is reliant on coordinated transcriptional and signal transduction events. To establish the segmented body plan that underlies much of metazoan development, individual cells and groups of cells must respond to exogenous signals with complex movements and shape changes. One class of proteins that plays a pivotal role in the interpretation of extracellular cues into cellular behavior is the Rho family of small GTPases. These molecular switches are essential components of a growing number of signaling pathways, many of which regulate actin cytoskeletal remodeling. Much of our understanding of Rho biology has come from work done in cell culture. More recently, the fruit fly Drosophila melanogaster has emerged as an excellent genetic system for the study of these proteins in a developmental and organismal context. Studies in flies have greatly enhanced our understanding of pathways involving Rho GTPases and their roles in development.

Automatic Moving Object Extraction for Content-Based Applications

Rapid developments in the Internet and multimedia applications allow us to access large amounts of image and video data. While significant progress has been made in digital data compression, content-based functionalities are still quite limited. Many existing techniques in content-based retrieval are based on global visual features extracted from the entire image. In order to provide more efficient content-based functionalities for video applications, it is necessary to extract meaningful video objects from scenes to enable object-based representation of video content. Object-based representation is also introduced by MPEG-4 to enable content-based functionality and high coding efficiency. In this paper, we propose a new algorithm that automatically extracts meaningful video objects from video sequences. The algorithm begins with the robust motion segmentation on the first two successive frames. To detect moving objects, segmented regions are grouped together according to their spatial similarity. A binary object model for each moving object is automatically derived and tracked in subsequent frames using the generalized Hausdorff distance. The object model is updated for each frame to accommodate for complex motions and shape changes of the object. Experimental results using different types of video sequences are presented to demonstrate the efficiency and accuracy of our proposed algorithm.

Right ventricular volume measurement using the conductance catheter method: validation in excised porcine hearts.

The conductance catheter method for measuring right ventricular (RV) volume changes was assessed in seven excised porcine hearts. A 5-FG conductance catheter was placed within a latex balloon and positioned in the RV cavity of seven freshly excised porcine hearts. Conductance was recorded while saline was withdrawn from the intraventricular balloon in 2 ml decrements. Linear regression analysis of measured conductance versus reference volumes was computed. The effect of left ventricular (LV) filling and catheter length on conductance derived RV volume was also determined. Conductance derived volumes were highly correlated with reference volumes [R2 0.976, standard deviation (SD) 0.035]. The mean gradient of regression was 0.97 (SD 0.10), and it was not significantly affected by LV volume alterations. However, when we analyzed LV filling, a small but significant increase in the y-intercept was observed (LV empty 3.11 ml, SD 1.71; LV full 4.58, SD 2.39; p = 0.008). Introduction of the catheter through either the tricuspid or pulmonary orifices were both effective in ventricular volume measurement. The effect of mismatch between the catheter length and the RV long axis dimension was evaluated by changing the position of the active sensing electrodes along the catheter body. Conductance measurements, obtained from catheters shorter than the long axis of the RV, still maintained a highly linear correlation with real volume, but regression gradients were significantly reduced (long 0.975, SD 0.087; medium 0.787, SD 0.094; small 0.589, SD 0.091; p < 0.001). These results show that a conductance catheter of appropriate length can accurately measure RV volume, despite the complex shape and geometric changes associated with ventricular filling.

Dynacortin Is a Novel Actin Bundling Protein That Localizes to Dynamic Actin Structures

Dynacortin is a novel protein that was discovered in a genetic suppressor screen of a Dictyostelium discoideum cytokinesis-deficient mutant cell line devoid of the cleavage furrow actin bundling protein, cortexillin I. While dynacortin is highly enriched in the cortex, particularly in cell-surface protrusions, it is excluded from the cleavage furrow cortex during cytokinesis. Here, we describe the biochemical characterization of this new protein. Purified dynacortin is an 80-kDa dimer with a large 5.7-nm Stokes radius. Dynacortin cross-links actin filaments into parallel arrays with a mole ratio of one dimer to 1.3 actin monomers and a 3.1 microm K(d). Using total internal reflection fluorescence microscopy, GFP-dynacortin and the actin bundling protein coronin-GFP are seen to concentrate in highly dynamic cortical structures with assembly and disassembly half-lives of about 15 s. These results indicate that cells have evolved different actin-filament cross-linking proteins with complementary cellular distributions that collaborate to orchestrate complex cell shape changes.

Improving the robustness of parametric shape tracking with switched multiple models

This paper addresses the problem of tracking objects with complex motion dynamics or shape changes. It is assumed that some of the visual features detected in the image (e.g., edge strokes) are outliers i.e., they do not belong to the object boundary. A robust tracking algorithm is proposed which allows to efficiently track an object with complex shape or motion changes in clutter environments. The algorithm relies on the use of multiple models, i.e., a bank of stochastic motion models switched according to a probabilistic mechanism. Robust filtering methods are used to estimate the label of the active model as well as the state trajectory.