Ultra high resolution stepper motors design, development, performance and application

The design and development of stepper motors with steps in the 10 arc sec to 2 arc min range is described. Some of the problem areas, e.g. rotor suspension, tribology aspects and environmental conditions are covered. A summary of achieved test results and the employment in different mechanisms already developed and tested is presented to give some examples of the possible use of this interesting device. Adaptations to military and commercial requirements are proposed and show the wide range of possible applications

Reproduction of the cavitating flows patterns in several nozzles geometries by using calibrated turbulence and cavitation models

Cavitating flow is a complex phenomenon related with turbulent and multiphase flows with mass transfer between the liquid and gaseous phases. This flow is affected by several factors as surrounding pressure, the local state of the turbulence, the non-condensable dissolved gases concentration and others effects. To study this kind of flow, several numerical models have been developed and they are now available in commercial and in-house software. A numerical model for cavitating flows involves a multiphase model, including both mass transfer and turbulence submodels. Inside of a commercial or an in-house numerical code there are several options and possible combinations of these submodels. A selection of the more suitable combination from this broad offer is a difficult task, involving then a subsequent careful calibration of the models selected, due to the fact that the default values for the calibration parameters that have these submodels, are related to simple flow conditions, i.e., simple geometries and flows without any detachment. Under cavitation conditions, these conditions are not the common situation. This work deals with the enhancement of some previous results obtained that allow to say that it is possible to capture several cavitating flows characteristics, improving a ‘standard’ numerical (i.e., without any calibration) simulation by means of a detailed tuning of the production/dissipation coefficients present in the equations of the Eddy Viscosity Models for turbulence, and other parameters related to the two-phase state of the flow. The numerical results obtained were compared against experimental data for pressure, velocity and the structure of the two-phase cavity. It is demonstrated that a careful calibration of both the turbulence and the cavitation submodels used is of paramount importance, because there is a very close relation between the turbulence state of the flow and the cavitation inception/developing conditions. A suitable calibration work allows also diminish the mesh size, saving a lot of computational resources or the use of more sophisticated strategies for turbulence simulations (e.g., Large Eddy Simulations). Those are very expensive in terms of the necessary computational resources required. A more general conclusions than obtained in previous works are presented, because results for other different nozzles configurations were obtained.Publicado en: Mecánica Computacional vol. XXXV, no. 15Facultad de Ingenierí

XNect: Real-time Multi-person 3D Human Pose Estimation with a Single RGB Camera

We present a real-time approach for multi-person 3D motion capture at over 30 fps using a single RGB camera. It operates in generic scenes and is robust to difficult occlusions both by other people and objects. Our method operates in subsequent stages. The first stage is a convolutional neural network (CNN) that estimates 2D and 3D pose features along with identity assignments for all visible joints of all individuals. We contribute a new architecture for this CNN, called SelecSLS Net, that uses novel selective long and short range skip connections to improve the information flow allowing for a drastically faster network without compromising accuracy. In the second stage, a fully-connected neural network turns the possibly partial (on account of occlusion) 2D pose and 3D pose features for each subject into a complete 3D pose estimate per individual. The third stage applies space-time skeletal model fitting to the predicted 2D and 3D pose per subject to further reconcile the 2D and 3D pose, and enforce temporal coherence. Our method returns the full skeletal pose in joint angles for each subject. This is a further key distinction from previous work that neither extracted global body positions nor joint angle results of a coherent skeleton in real time for multi-person scenes. The proposed system runs on consumer hardware at a previously unseen speed of more than 30 fps given 512x320 images as input while achieving state-of-the-art accuracy, which we will demonstrate on a range of challenging real-world scenes

Reproduction of the cavitating flows patterns in several nozzles geometries by using calibrated turbulence and cavitation models

Cavitating flow is a complex phenomenon related with turbulent and multiphase flows with mass transfer between the liquid and gaseous phases. This flow is affected by several factors as surrounding pressure, the local state of the turbulence, the non-condensable dissolved gases concentration and others effects. To study this kind of flow, several numerical models have been developed and they are now available in commercial and in-house software. A numerical model for cavitating flows involves a multiphase model, including both mass transfer and turbulence submodels. Inside of a commercial or an in-house numerical code there are several options and possible combinations of these submodels. A selection of the more suitable combination from this broad offer is a difficult task, involving then a subsequent careful calibration of the models selected, due to the fact that the default values for the calibration parameters that have these submodels, are related to simple flow conditions, i.e., simple geometries and flows without any detachment. Under cavitation conditions, these conditions are not the common situation. This work deals with the enhancement of some previous results obtained that allow to say that it is possible to capture several cavitating flows characteristics, improving a ‘standard’ numerical (i.e., without any calibration) simulation by means of a detailed tuning of the production/dissipation coefficients present in the equations of the Eddy Viscosity Models for turbulence, and other parameters related to the two-phase state of the flow. The numerical results obtained were compared against experimental data for pressure, velocity and the structure of the two-phase cavity. It is demonstrated that a careful calibration of both the turbulence and the cavitation submodels used is of paramount importance, because there is a very close relation between the turbulence state of the flow and the cavitation inception/developing conditions. A suitable calibration work allows also diminish the mesh size, saving a lot of computational resources or the use of more sophisticated strategies for turbulence simulations (e.g., Large Eddy Simulations). Those are very expensive in terms of the necessary computational resources required. A more general conclusions than obtained in previous works are presented, because results for other different nozzles configurations were obtained.Publicado en: Mecánica Computacional vol. XXXV, no. 15Facultad de Ingenierí

Reproduction of the cavitating flows patterns in several nozzles geometries by using calibrated turbulence and cavitation models

Cavitating flow is a complex phenomenon related with turbulent and multiphase flows with mass transfer between the liquid and gaseous phases. This flow is affected by several factors as surrounding pressure, the local state of the turbulence, the non-condensable dissolved gases concentration and others effects. To study this kind of flow, several numerical models have been developed and they are now available in commercial and in-house software. A numerical model for cavitating flows involves a multiphase model, including both mass transfer and turbulence submodels. Inside of a commercial or an in-house numerical code there are several options and possible combinations of these submodels. A selection of the more suitable combination from this broad offer is a difficult task, involving then a subsequent careful calibration of the models selected, due to the fact that the default values for the calibration parameters that have these submodels, are related to simple flow conditions, i.e., simple geometries and flows without any detachment. Under cavitation conditions, these conditions are not the common situation. This work deals with the enhancement of some previous results obtained that allow to say that it is possible to capture several cavitating flows characteristics, improving a ‘standard’ numerical (i.e., without any calibration) simulation by means of a detailed tuning of the production/dissipation coefficients present in the equations of the Eddy Viscosity Models for turbulence, and other parameters related to the two-phase state of the flow. The numerical results obtained were compared against experimental data for pressure, velocity and the structure of the two-phase cavity. It is demonstrated that a careful calibration of both the turbulence and the cavitation submodels used is of paramount importance, because there is a very close relation between the turbulence state of the flow and the cavitation inception/developing conditions. A suitable calibration work allows also diminish the mesh size, saving a lot of computational resources or the use of more sophisticated strategies for turbulence simulations (e.g., Large Eddy Simulations). Those are very expensive in terms of the necessary computational resources required. A more general conclusions than obtained in previous works are presented, because results for other different nozzles configurations were obtained.Publicado en: Mecánica Computacional vol. XXXV, no. 15Facultad de Ingenierí

Shape Evasion: Preventing Body Shape Inference of Multi-Stage Approaches

Modern approaches to pose and body shape estimation have recently achieved strong performance even under challenging real-world conditions. Even from a single image of a clothed person, a realistic looking body shape can be inferred that captures a users' weight group and body shape type well. This opens up a whole spectrum of applications -- in particular in fashion -- where virtual try-on and recommendation systems can make use of these new and automatized cues. However, a realistic depiction of the undressed body is regarded highly private and therefore might not be consented by most people. Hence, we ask if the automatic extraction of such information can be effectively evaded. While adversarial perturbations have been shown to be effective for manipulating the output of machine learning models -- in particular, end-to-end deep learning approaches -- state of the art shape estimation methods are composed of multiple stages. We perform the first investigation of different strategies that can be used to effectively manipulate the automatic shape estimation while preserving the overall appearance of the original image

The Mobilization of Actinides by Microbial Ligands Taking into Consideration the Final Storage of Nuclear Waste - Interactions of Selected Actinides U(VI), Cm(III), and Np(V) with Pyoverdins Secreted by Pseudomonas fluorescens and Related Model Compounds (Final Report BMBF Project No.: 02E9985)

The groundwater bacterium Pseudomonas fluorescens (CCUG 32456) isolated at a depth of 70 m in the Äspö Hard Rock Laboratory secretes a pyoverdin-mixture with four main components (two pyoverdins and two ferribactins). The dominant influence of the pyoverdins of this mixture could be demonstrated by an absorption spectroscopy study. The comparison of the stability constants of U(VI), Cm(III), and Np(V) species with ligands simulating the functional groups of the pyoverdins results in the following order of complex strength: pyoverdins (PYO) > trihydroxamate (DFO) > catecholates (NAP, 6­HQ) > simple hydroxamates (SHA, BHA). The pyoverdin chromophore functionality shows a large affinity to bind actinides. As a result, pyoverdins are also able to complex and to mobilize elements other than Fe(III) at a considerably high efficiency. It is known that EDTA may form the strongest actinide complexes among the various organic components in nuclear wastes. The stability constants of 1:1 species formed between Cm(III) and U(VI) and pyoverdins are by a factor of 1.05 and 1.3, respectively, larger compared to the corresponding EDTA stability constants. The Np(V)-PYO stability constant is even by a factor of 1.83 greater than the EDTA stability constant. The identified Np(V)-PYO species belong to the strongest Np(V) species with organic material reported so far. All identified species influence the actinide speciation within the biologically relevant pH range. The metal binding properties of microbes are mainly determined by functional groups of their cell wall (LPS: Gram-negative bacteria and PG: Gram-positive bacteria). On the basis of the determined stability constants raw estimates are possible, if actinides prefer to interact with the microbial cell wall components or with the secreted pyoverdin bioligands. By taking pH 5 as an example, U(VI)-PYO interactions are slightly stronger than those observed with LPS and PG. For Cm(III) we found a much stronger affinity to aqueous pyoverdin species than to functional groups of the cell wall compartments. A similar behavior was observed for Np(V). This shows the importance of indirect interaction processes between actinides and bioligands secreted by resident microbes

Two Approaches to Dislocation Nucleation in the Supported Heteroepitaxial Equilibrium Islanding Phenomenon

We study the dislocation formation in 2D nanoscopic islands with two methods, the Molecular Static method and the Phase Field Crystal method. It is found that both methods indicate the same qualitative stages of the nucleation process. The dislocations nucleate at the film-substrate contact point and the energy decreases monotonously when the dislocations are farther away from the island-wetting film contact points than the distance of the highest energy barrier.Comment: 4 page

Weak formulation for singular diffusion equation with dynamic boundary condition

In this paper, we propose a weak formulation of the singular diffusion equation subject to the dynamic boundary condition. The weak formulation is based on a reformulation method by an evolution equation including the subdifferential of a governing convex energy. Under suitable assumptions, the principal results of this study are stated in forms of Main Theorems A and B, which are respectively to verify: the adequacy of the weak formulation; the common property between the weak solutions and those in regular problems of standard PDEs.Comment: 23 page

Formation and stability of self-assembled coherent islands in highly mismatched heteroepitaxy

We study the energetics of island formation in Stranski-Krastanow growth within a parameter-free approach. It is shown that an optimum island size exists for a given coverage and island density if changes in the wetting layer morphology after the 3D transition are properly taken into account. Our approach reproduces well the experimental island size dependence on coverage, and indicates that the critical layer thickness depends on growth conditions. The present study provides a new explanation for the (frequently found) rather narrow size distribution of self-assembled coherent islands.Comment: 4 pages, 5 figures, In print, Phys. Rev. Lett. Other related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm