Assessment of Human Hemodynamics under Hyper- and Microgravity: Results of two Aachen University Parabolic Flight Experiments

Astronauts complain about fluid shifts from their lower extremities to their head caused by weightlessness during their flight into space. For a study of this phenomenon, RWTH Aachen University and Charité University Berlin participated in a joint project on two parabolic flight campaigns of the German Aerospace Centre (DLR) in September 2005 and June 2006. During these campaigns, the characteristics of the rapid fluid shifts during hyper- and micro gravity were measured by a combination of PPG and PPGI optoelectronic sensor concepts.

Inverse boundary value problem for the Helmholtz equation: quantitative conditional Lipschitz stability estimates

We study the inverse boundary value problem for the Helmholtz equation using the Dirichlet-to-Neumann map at selected frequencies as the data. A conditional Lipschitz stability estimate for the inverse problem holds in the case of wavespeeds that are a linear combination of piecewise constant functions (following a domain partition) and gives a framework in which the scheme converges. The stability constant grows exponentially as the number of subdomains in the domain partition increases. We establish an order optimal upper bound for the stability constant. We eventually realize computational experiments to demonstrate the stability constant evolution for three dimensional wavespeed reconstruction.Comment: 21 pages, 7 figures. arXiv admin note: text overlap with arXiv:1406.239

Bayesian weak lensing tomography: Reconstructing the 3D large-scale distribution of matter with a lognormal prior

We present a Bayesian reconstruction algorithm that infers the three-dimensional large-scale matter distribution from the weak gravitational lensing effects measured in the image shapes of galaxies. The algorithm is designed to also work with non-Gaussian posterior distributions which arise, for example, from a non-Gaussian prior distribution. In this work, we use a lognormal prior and compare the reconstruction results to a Gaussian prior in a suite of increasingly realistic tests on mock data. We find that in cases of high noise levels (i.e. for low source galaxy densities and/or high shape measurement uncertainties), both normal and lognormal priors lead to reconstructions of comparable quality, but with the lognormal reconstruction being prone to mass-sheet degeneracy. In the low-noise regime and on small scales, the lognormal model produces better reconstructions than the normal model: The lognormal model 1) enforces non-negative densities, while negative densities are present when a normal prior is employed, 2) better traces the extremal values and the skewness of the true underlying distribution, and 3) yields a higher pixel-wise correlation between the reconstruction and the true density.Comment: 23 pages, 12 figures; updated to match version accepted for publication in PR

Совершенствование технологического процесса изготовления станины

В ходе выполнения проекта был произведен анализ существующего технологического процесса изготовления станины. Были выявлены положительные и отрицательные стороны. При проектировании технологического процесса было выполнено следующее: выбраны базы и схемы установки; разработана маршрутная и операционная технология; определены технологические допуски, припуски на операционные размеры; выбрано оборудование, приспособления и инструмент; рассчитаны режимы резания. В конструкторской части были сконструированы два новых приспособления для закрепления детали.In the course of the project, an analysis of the existing technological process of manufacturing the frame has been made. Positive and negative aspects have been identified. When designing the technological process, the following has been done: the database and scheme installation have been selected; the route and the operating technology have been designed; the technological tolerances, allowances and operating dimensions have been defined, equipment, devices and tools have been chosen, cutting data have been calculated. In the design part two new fixtures to secure the part have been developed