Theoretical morphology of modular organisms: geometric constraints of branch and dissepiment width and spacing in fenestrate bryozoans

2002 ◽  
Vol 223 (1) ◽  
pp. 79-122
Author(s):  
Robert W. Starcher ◽  
George R. Jr. McGhee
Keyword(s):  
Geometric Constraints ◽  
Modular Organisms ◽  
Theoretical Morphology

Theoretical morphology of hinge and shell form in Bivalvia: geometric constraints derived from space conflict between umbones

Paleobiology ◽  
2000 ◽  
Vol 26 (4) ◽  
pp. 606-624 ◽  
Author(s):  
Takao Ubukata
Keyword(s):  
Computer Simulation ◽  
Anterior Part ◽  
Large Degree ◽  
Ventral Side ◽  
Mutual Interference ◽  
Geometric Constraints ◽  
Geometric Properties ◽  
Shell Form ◽  
Theoretical Morphology

Geometric properties of the shells of 123 species of extant Bivalvia were analyzed from the viewpoint of theoretical morphology. The effects of shell form and the structure of ligament on the interumbonal space and the maximum shell opening received particular attention. The results of computer simulation and morphospace analysis indicate that possessing both prosogyrous shell form and an extended hinge without the parivincular ligament tends to cause space conflict between umbones or dorsal shell margins of right and left valves. To a large degree, a prosogyrous shell form with a long parivincular ligament helps shell opening without umbonal conflict, if the shell is flat enough to avoid the mutual interference between dorsal shell margins of closed valves. Extension of the ligament and plunging of the anterior part of the coiling axis into the ventral side provide enough space along the dorsal shell margins in which a parivincular ligament and its substrata are developed.

Fenestrate graptolite theoretical morphology: Geometric constraints on lophophore shape and arrangement in extinct hemichordates

2003 ◽  
Vol 77 (2) ◽  
pp. 360-367 ◽  
Author(s):  
Robert W. Starcher ◽  
George R. McGhee
Keyword(s):  
Geometric Analysis ◽  
Close Packing ◽  
Geometric Constraints ◽  
Theoretical Morphology ◽  
Packing Arrangement

A geometric analysis of lophophore shape and arrangement in the fenestrate dendroid graptolite genus Dictyonema reveals that the shape of the zooid domain in the majority of Dictyonema species colonies is highly elliptical, with the long axis of the ellipse perpendicular to the proximodistal axis of the stipe. A complex lophophore, bilaterally symmetrical and consisting of two tentaculated arms that are laterally directed and perpendicular to the stipe axis, provides the best geometric solution to completely filling the elliptical zooid domain seen in the majority of Dictyonema species.Working under the assumption that fenestrate graptolites, like fenestrate bryozoans, needed to form a continuous filtering surface with contact between adjacent lophophores, two optimum close-parking models exist for lophophores with elliptical zooid domains: either a proximodistal-row arrangement or a lateral-row arrangement of the lophophores. Of the two possible geometries, the most probable close-packing arrangement of hypothetical biplumed lophophores within the fenestrate graptolite meshwork is in proximodistal rows.

Fenestrate theoretical morphology: geometric constraints on lophophore shape and arrangement in extinct Bryozoa

Paleobiology ◽  
2000 ◽  
Vol 26 (1) ◽  
pp. 116-136 ◽  
Author(s):  
Robert W. Starcher ◽  
George R. McGhee
Keyword(s):  
Geometric Analysis ◽  
Close Packing ◽  
Geometric Constraints ◽  
Actual Distribution ◽  
Size And Shape ◽  
The Third ◽  
Theoretical Morphology

A geometric analysis of fenestrate bryozoan lophophore shape and arrangement is conducted by creating a theoretical morphospace of apertural positioning within the colonial meshwork. Working from the assumption that fenestrate bryozoans needed to form a continuous filtering surface with contact between adjacent lophophores, we show that within the morphospace three regions exist for optimum close-packing of lophophores with circular projections; all other close-packing configurations in the morphospace require the existence of noncircular lophophores.Examination of the actual distribution of 251 fenestrate colonies within the morphospace reveals that the morphospace regions occupied by fenestellids and polyporids are displaced and have little overlap, but that they are very similar in size and shape that the colonies scale similarly. With increasing size, fenestrate meshworks expand laterally faster than the branches widen and the proximodistal spacing of the apertures increases, apparently because the larger zooids require disproportionately more room for their lophophores.Two of the optimum close-packing regions of the morphospace are occupied by fenestrates. The positioning of the fenestellid region within the morphospace suggests that these biserial bryozoans followed a proximodistal-row placement of the lophophores that the lophophores were generally equitentacular, with circular projections. The positioning of the polyporid region within the morphospace suggests that these polyserial bryozoans followed a diagonal-row placement of the lophophores that the lophophores were heteromorphic, with medial lophophores on the branch being more equitentacular whereas the laterally placed lophophores were obliquely truncate. The third optimum close-packing region in the morphospace, corresponding to a hypothetical lateral-row placement of the lophophores within the colony, is unoccupied. We suggest that hypothetical fenestrate morphologies in the vacant region of morphospace have branches that would be too narrow to support normally shaped zooids that the lateral-row placement of the lophophores would have required the branches of the colony to have been perfectly aligned throughout growth.

Parallel Glide: A Fundamentally Different Type of Dislocation Motion in Ultrathin Metal Films

2003 ◽  
Vol 779 ◽  
Author(s):  
T. John Balk ◽  
Gerhard Dehm ◽  
Eduard Arzt
Keyword(s):  
Thermal Cycling ◽  
Grain Boundaries ◽  
Film Surface ◽  
Metal Films ◽  
Geometric Constraints ◽  
Film Stress ◽  
Diffusional Creep ◽  
Creep Model ◽  
Substrate Interface ◽  
Film Substrate

AbstractWhen confronted by severe geometric constraints, dislocations may respond in unforeseen ways. One example of such unexpected behavior is parallel glide in unpassivated, ultrathin (200 nm and thinner) metal films. This involves the glide of dislocations parallel to and very near the film/substrate interface, following their emission from grain boundaries. In situ transmission electron microscopy reveals that this mechanism dominates the thermomechanical behavior of ultrathin, unpassivated copper films. However, according to Schmid's law, the biaxial film stress that evolves during thermal cycling does not generate a resolved shear stress parallel to the film/substrate interface and therefore should not drive such motion. Instead, it is proposed that the observed dislocations are generated as a result of atomic diffusion into the grain boundaries. This provides experimental support for the constrained diffusional creep model of Gao et al.[1], in which they described the diffusional exchange of atoms between the unpassivated film surface and grain boundaries at high temperatures, a process that can locally relax the film stress near those boundaries. In the grains where it is observed, parallel glide can account for the plastic strain generated within a film during thermal cycling. One feature of this mechanism at the nanoscale is that, as grain size decreases, eventually a single dislocation suffices to mediate plasticity in an entire grain during thermal cycling. Parallel glide is a new example of the interactions between dislocations and the surface/interface, which are likely to increase in importance during the persistent miniaturization of thin film geometries.

The Origin of a New Kind of Science From the Life Sciences

2020 ◽  
Vol 30 (1) ◽  
pp. 131-158
Keyword(s):  
Natural Philosophy ◽  
Human Life ◽  
Natural Sciences ◽  
Natural Phenomenon ◽  
Dominican Order ◽  
Cultural Traditions ◽  
Knowledge Based ◽  
Living Things ◽  
Theoretical Morphology ◽  
Living Nature

Science in the modern era began with a process of synthesis; the natural sciences in particular emerged through a coalescence of several cultural traditions. Scientific knowledge arose in a series of several separate events as mathematics, philology, physics and biology emerged independently. Scientific ideas about natural life developed via a synthesis of three types of knowledge. (1) There was the tradition of herbalism as a type of knowledge of nature, and this approach remained close to the Aristotelian tradition of describing nature with a bookish method centered on descriptive practice. (2) The scholastic tradition clarified existing concepts and formed new ones. Its role was crucial in supplying nascent science with its set of cognitive tools. (3) The alchemical tradition provided experimental knowledge of nature as applied to human life. It was particularly important in building the skills needed to connect theoretical systems with reality. This synthesis in natural philosophy was the basis of Linnaean reforms. However, theoretical morphology was cen¬tral to Linnaeus’ thinking and, its features were responsible for the success of his system. Theoretical morphology offered ways to decide how a natural phenomenon should be reduced and divided into parts in order to serve as an object of scientific cognition. Essential theoretical precepts for this morphology were formulated by Andrea Cesalpino in De plantis libri XVI (1583). Hence, the origin of the natural sciences as a study of living nature should properly be traced to the 16th century. This strand in the development of the new scientific approach in Europe through studying living things should also be connected with earlier (medieval) efforts of the Dominican Order (promoting purer versions of Aristotelianism), while another strand which led to the appearance of physics and other more mathematically expressed branches of the natural sciences belongs to the Franciscan orders (more influenced by Neoplatonism). Science emerged then as profound and experimentally verifiable theoretical knowledge based on ideation through the construction of the objects of experimental research.

scholarly journals Geometric property-based convolutional neural network for indoor object detection

2021 ◽  
Vol 18 (1) ◽  
pp. 172988142199332
Author(s):  
Xintao Ding ◽  
Boquan Li ◽  
Jinbao Wang
Keyword(s):  
Neural Network ◽  
Object Detection ◽  
Convolutional Neural Network ◽  
Geometric Property ◽  
Ground Truth ◽  
Geometric Constraints ◽  
Depth Information ◽  
Training Set ◽  
Object Knowledge ◽  
The Mean

Indoor object detection is a very demanding and important task for robot applications. Object knowledge, such as two-dimensional (2D) shape and depth information, may be helpful for detection. In this article, we focus on region-based convolutional neural network (CNN) detector and propose a geometric property-based Faster R-CNN method (GP-Faster) for indoor object detection. GP-Faster incorporates geometric property in Faster R-CNN to improve the detection performance. In detail, we first use mesh grids that are the intersections of direct and inverse proportion functions to generate appropriate anchors for indoor objects. After the anchors are regressed to the regions of interest produced by a region proposal network (RPN-RoIs), we then use 2D geometric constraints to refine the RPN-RoIs, in which the 2D constraint of every classification is a convex hull region enclosing the width and height coordinates of the ground-truth boxes on the training set. Comparison experiments are implemented on two indoor datasets SUN2012 and NYUv2. Since the depth information is available in NYUv2, we involve depth constraints in GP-Faster and propose 3D geometric property-based Faster R-CNN (DGP-Faster) on NYUv2. The experimental results show that both GP-Faster and DGP-Faster increase the performance of the mean average precision.

Recognition of teaching method effects based on grid model simplification and artificial intelligence

2020 ◽  
pp. 1-11
Author(s):  
Guo Yunfeng ◽  
Li Jing
Keyword(s):  
Artificial Intelligence ◽  
Teaching Method ◽  
Evaluation Model ◽  
Geometric Constraints ◽  
Sorting Algorithm ◽  
Grid Model ◽  
Model Based ◽  
Refinement Method ◽  
Method Effects ◽  
Structure Simplification

In order to improve the effect of the teaching method evaluation model, based on the grid model, this paper constructs an artificial intelligence model based on the grid model. Moreover, this paper proposes a hexahedral grid structure simplification method based on weighted sorting, which comprehensively sorts the elimination order of candidate base complexes in the grid with three sets of sorting items of width, deformation and price improvement. At the same time, for the elimination order of basic complex strings, this paper also proposes a corresponding priority sorting algorithm. In addition, this paper proposes a smoothing regularization method based on the local parameterization method of the improved SLIM algorithm, which uses the regularized unit as the reference unit in the local mapping in the SLIM algorithm. Furthermore, this paper proposes an adaptive refinement method that maintains the uniformity of the grid and reduces the surface error, which can better slow down the occurrence of geometric constraints caused by insufficient number of elements in the process of grid simplification. Finally, this paper designs experiments to study the performance of the model. The research results show that the model constructed in this paper is effective.

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