Добірка наукової літератури з теми "Vogel spiral"

ABSTRACTSpire-bearing brachiopods formally comprise four different rhynchonelliform orders. A calcified spiral brachidium (presumably supporting a spirolophe when alive) and variable median fold and sulcus (probably aiding separation of incurrent from excurrent flows) are peculiar characteristics they all share. Inferences regarding feeding current systems for these extinct taxa have long remained controversial. Two rival models (the Williams–Ager model and the Rudwick–Vogel model) have been developed, each of which has gained supporters as well as critics over the years. In this present paper they are both contrasted and reassessed on the basis of available evidence, together with a new approach that combines: (a) a morpho-functional analysis applying the plankton net as a suitable seston-collecting paradigm; (b) a review of actualistic data showing that all extant spirolophes are functionally inhalant (irrespective of water entering the valves laterally or not); (c) an evaluation of known outcomes from flume experiments yielding consistent empirical results where gaping shells are oriented transversally and dorsally upcurrent; and (d) a reappraisal of the distributions of certain epizoobionts and endosymbionts revealing compatible patterns. The evidence thus accumulated supports the main conclusion that, in most groups (with laterally tapering spiralia), the inhalant current was located medially with the exhalant currents on either side; only in atrypides (with centrally to dorsally tapering spiralia) does the reverse situation appear to have occurred.

We present experiments of microwave transport in planar Vogel spirals arrays of high permittivity dielectric constant. Despite the lack of disorder, wave transport in certain frequency regions is dominated by localized modes. We characterize these modes spatially, and find that in contrary to disorder induced Anderson localization, their radial decay does not only decay exponentially, but some modes are found to decay according to a power law or to a Gaussian profile. Nevertheless, by extracting experimentally the Thouless conductance, we find that the region where these Gaussian and power law modes exist are regions of low Thouless conductance, similarly to what is expected for Anderson localization. This study unveil the rich modal structure associated with these aperiodic point patterns, and pave the way toward a better understanding of wave localization in general.

Au sens large, le terme de localisation ondulatoire fait référence à un phénomène où les ondes sont spatialement confinées dans de petites régions de l'espace sans la contrainte de barrières matérielles. Dans cette thèse, nous étudions (analytiquement, numériquement et expérimentalement) différents mécanismes physiques collectifs pour localiser spatialement, et donc pour contrôler les ondes électromagnétiques. En particulier, nous nous concentrons sur le rôle des potentiels non corrélés et corrélés, ainsi que sur des effets topologiques pour réaliser le confinement des ondes. Les études analytiques et numériques sont réalisées dans le cadre d'une approche récente de la modélisation de la localisation d'Anderson appelée théorie du paysage de localisation. D'autre part, des expériences sont réalisées à l'aide d'une plate-forme micro-ondes composée de petits cylindres diélectriques placés à l'intérieur d'une cavité constituée de deux plaques métalliques. La cavité met en œuvre un système d'ondes propagatives, où nous pouvons contrôler efficacement la permittivité locale au moyen des cylindres agissant comme des diffuseurs, ou comme un système de de liaison forte analogique, où, dans ce cas, les cylindres diélectriques jouent le rôle de résonateurs. Dans un premier temps, nous étendons le champ d'application de l'approche du paysage de localisation à une large classe de systèmes de liaison forte unidimensionnels et bidimensionnels en présence d'un désordre non corrélé, où des fonctions propres localisées apparaissent en bord de bande. Nous démontrons comment la théorie du paysage de localisation est capable de prédire avec précision non seulement les emplacements, mais aussi les énergies des fonctions propres localisées dans les régimes de basse et de haute énergie. Ensuite, en utilisant notre cavité expérimentale comme système de propagation, nous réalisons des expériences de transport de micro-ondes dans des réseaux planaires bidimensionnels. Les expériences sont réalisées sur un réseau désordonné et sur une spirale de Vogel apériodique à partir de laquelle nous caractérisons les structures modales électromagnétiques dans l'espace réel. Nos résultats révèlent que les systèmes apériodiques possèdent une grande variété de modes à longue durée de vie - avec des décroissances spatiales gaussiennes, exponentielles et en loi de puissance - qui sont capables de survivre même dans un environnement tridimensionnel. Ceci est confirmé par différentes quantités de transport telles que la densité d'états, le temps de décroissance caractéristique et la conductance de Thouless qui sont également accessibles expérimentalement. À l'inverse, nous montrons que les états propres dans les milieux désordonnés traditionnels sont toujours limités à des décroissances radiales exponentielles avec d'importantes fuites dès que les systèmes ne sont plus bidimensionnels. Enfin, nous utilisons la configuration expérimentale de liaison forte pour étudier la propagation des états hélicoïdaux topologiques. En particulier, nous analysons expérimentalement un ensemble de structures en nid d'abeille construites à l'aide d'un réseau triangulaire avec une cellule unitaire hexagonale, qui sont caractérisées par l'invariant topologique Z_2. En accédant à la structure modale dans l'espace réel et à la densité d'états, nos résultats révèlent la possibilité d'ouvrir une bande interdite topologique, peuplée d'états de bord localisés en bordure de la structure. Nous démontrons la nature unidirectionelle de la propagation de ces états de bord hélicoïdaux contre-propagatifs. Dans l'ensemble, nos résultats démontrent qu'il est possible de modéliser, de contrôler et de localiser les ondes électromagnétiques non seulement du point de vue d'Anderson, mais aussi au-delà. Grâce aux différents jalons que nous avons posés, nous ouvrons une voie vers l'hypothétique localisation d'Anderson des ondes électromagnétiques tridimensionnelles
In a broad sense, the term wave localization refers to a phenomenon where waves are spatially confined in small regions of the space without any bounding material barriers.In this Thesis, we investigate (analytically, numerically and experimentally) different physical collective mechanisms to spatially localize, and therefore, to control electromagnetic waves. Specifically, we focus on the role of uncorrelated and correlated potentials, as well as of topological effects to achieve wave confinement. Analytical and numerical studies are accomplished in the framework of a recent approach in the modeling of Anderson localization called localization landscape theory. On the other hand, experiments are performed using a microwave platform composed by small dielectric cylinders placed inside a cavity made of two metallic plates. The cavity implements a propagative wave system, where we can efficiently control the local permittivity by means of the cylinders acting as scatterers, or as an analogic tight-binding system, where, in this case, the dielectric cylinders play the role of resonators.First, we extend the scope of the localization landscape approach to a wide class of one and two dimensional tight-binding systems in the presence of uncorrelated disorder, where localized eigenfunctions appear in both band-edges. We demonstrate how the landscape theory is able to predict accurately not only the locations, but also the energies of localized eigenfunctions in the low- and high-energy regimes. Later, by using our experimental cavity as a propagative system, we perform microwave transport experiments in two dimensional planar arrays. Experiments are carried out on a disordered lattice and on an aperiodic Vogel spiral from where we characterize the electromagnetic modal structures in real space. Our results reveals that aperiodic systems can carry a rich variety of long-lived modes—with Gaussian, exponential, and power law spatial decays—which are able to survive even in a three-dimensional environment. This is supported by different transport quantities such as the density of states, the characteristic decay time, and the Thouless conductance that are also experimentally accessible. On the contrary, we show that the eigenstates in traditional disordered media are always limited to exponential radial decays with leaking features beyond two-dimensions.Finally, we use the experimental tight-binding configuration to investigate the propagation of topological helical states. Particularly, we experimentally analyze a set of honeycomb-like structures built using a triangular lattice with an hexagonal unit cell, which are characterized by the Z_2 topological invariant. By recovering the modal structure in real space and the density of states, our results reveal the possibility to open a topological gap, dwelt by edge states that lives in the border of the structure.We demonstrate the unidirectional counterpropagative features of such helical edge states.Taken together, our results demonstrate that it is possible to model, control and localize electromagnetic waves not only within, but beyond Anderson's conception. Thanks to the crossroads we have taken, we have mapped out an itinerary that brings us closer to the main avenue leading perhaps to Anderson localization of three dimensional electromagnetic waves

Background: Normal pressure hydrocephalus (NPH) has been an ongoing and challenging field of research for the past decades because two main issues are still not fully understood: the pathophysiologic mechanisms underlying ventricular enlargement and prediction of outcome after surgery. Purpose: To evaluate changes in diffusion tensor imaging (DTI) derived parameters in patients with suspected normal pressure hydrocephalus before and after withdrawal of cerebrospinal fluid (CSF). Material and Methods: Twenty-four consecutive patients with clinical and radiological suspicion of NPH and 14 agematched control subjects were examined with DTI on a clinical 3T scanner. Patients were examined before and 6–36 h after CSF drainage (interval between scans, 5 days). Fifteen patients were finally included in data analysis. Fractional anisotropy (FA) and mean, parallel, and radial diffusivity (MD, PD, RD) were evaluated using a combination of a ROI-based approach and a whole-brain voxel-by-voxel analysis. Results: Alteration of DTI parameters in patients with suspected NPH is regionally different. Compared to the control group, we found an elevation of FA in the subcortical white matter (SCWM) and corpus callosum, whereas the other diffusion parameters showed an increase throughout the brain in variable extent.We also found a slight normalization of RD in the SCWM in patients after lumbar drainage. Conclusion: Our results show that DWI parameters are regionally dependent and reflect multifactorial (patho-) physiological mechanisms, which need to be interpreted carefully. It seems that improvement of gait is caused by a decrease of interstitial water deposition in the SCWM.

碩士
國立臺灣科技大學
機械工程系
102
Face milling is a popular cutting method in mass production of spiral bevel gears. A CNC machine with five-axis simultaneous control system is demanded to implement face milling. This cutting method needs multi-axis movement and its tool design is complex. Therefore, in order to avoid collision, the simulation of tool paths and material removal should be performed previously to verify the correctness of NC codes. The study aims to develop a dedicated cutting simulation software for face-milled spiral bevel gears. Visual C# 2010 integrated with OpenGL is used as a foundation to develop the simulation program. Here, a voxel method for cutting simulation is employed. The mathematical model of tool surface is first established. The solid model of work gear is composed by cubes in which voxels are used to store the positions and values of those vertexes. According to the NC code, the relative positions between the tool and the work gear are determined through the coordinate transformations. And then, Boolean difference operation between the gear work and tool is made to simulate gear cutting. Moreover, the marching cube algorithm is adopted to improve the display resolution of produced tooth surfaces which are save as STL (Stereolithography) format. In order to verify the correctness of NC codes, an evaluation method is proposed to obtain tooth surface deviations between the produced STL surfaces and theoretical surfaces. And, the volume removal is obtained in real-time cutting simulation, which can be used as a beneficial data for further reach in optimization of NC tool paths.

Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is an effective symptomatic treatment for pharmacoresistant dystonic syndromes. The relationship between grey matter volume and intracortical inhibition of the primary motor cortex (MI) in regard to the effectiveness and the state (ON/OFF) of GPi DBS was analysed in the first study. The grey matter of chronically treated patients showed hypertrophy of the supplementary motor area and cerebellar vermis whereas this difference was more significant in patients with a better clinical outcome. The grey matter of the cerebellar hemispheres of the patients showed positive correlation with the improvement of an intracortical inhibition which was generally less effective in patients regardless of the GPi DBS state. Moreover, we showed the same level of SICI in the good responders as in the healthy controls, while in non-responders was the SICI decreased. In the second study, by using paired associative stimulation (PAS) we studied the influence of primary somatosensory cortex (SI) on the MI excitability in dystonia in regards to the effectiveness of GPi DBS. SI PAS decreased the MI excitability in the GPi DBS ON state while switching the stimulation off decreased an inhibitory effect of SI on MI excitability. Non-responders showed a...

Digital Linguistics (DL) is an interdisciplinary study that identifies human language as a digital evolution of mammal analog vocal sign communications, founded on the vertebrate spinal sign reflex mechanism [Tokumaru 2017 a/b, 2018 a/b/c/d]. Analog signs are unique with their physical sound waveforms but limited in number, whilst human digital word signs are infinite by permutation of their logical property, phonemes. The first digital evolution took place 66,000 years ago with South African Neolithic industries, Howiesons Poort, when linguistic humans acquired a hypertrophied mandibular bone to house a descended larynx for vowel accented syllables containing logical properties of phonemes and morae. Morae made each syllable distinctive in the time axis and enabled grammatical modulation by alternately transmitting conceptual and grammatical syllables. The sign reflex mechanism is an unconscious self-protection and life-support mechanism, operated by immune cell networks inside the ventricle system. DL identified cellular and molecular structures for the sign (=concept) device as a B lymphocyte (or, in other words, Mobile Ad-Hoc Networking Neuron), connects to sensory, conceptual and networking memories, which consist of its meanings [Table 1]. Its antibodies can network with antigens of CSF-Contacting Neurons at the brainstem reticular formation and of Microglia cells at the neocortex [Figure 1]. It is plausible that the 3D structure of the antigen molecule takes the shape of word sound waveform multiplexing intensity and pitch, and that specifically pairing the antibody molecule consists of three CDRs (Complementality Defining Regions) in the Antibody Variable Region network with the logic of dichotomy and dualism. As sign reflex deals with survival issues such as food, safety and reproduction, it is stubborn, passive and inflexible: It does not spontaneously look for something new, and it is not designed to revise itself. These characteristics are not desirable for the development of human intelligence, and thus are to be overcome. All the word, sensory and network memories in the brain must be acquired postnatally through individual learning and thought. The reason and intelligence of humans depend on how correctly and efficiently humans learn new words and acquire appropriate meanings for them.