Investigation of Boundary Conditions for Flexible Multibody Spacecraft Dynamics

In support of both the Space Shuttle and International Space Station programs, a set of generic multibody dynamics algorithms integrated within the Trick simulation environment have addressed the variety of on-orbit manipulator simulation requirements for engineering analysis, procedures development and crew familiarization/training at the NASA Johnson Space Center (JSC). Enhancements to these dynamics algorithms are now being driven by a new set of Constellation program requirements for flexible multibody spacecraft simulation. One particular issue that has been discussed within the NASA community is the assumption of cantilever-type flexible body boundary conditions. This assumption has been commonly utilized within manipulator multibody dynamics formulations as it simplifies the computation of relative motion for articulated flexible topologies. Moreover, its use for modeling of space-based manipulators such as the Shuttle Remote Manipulator System (SRMS) and Space Station Remote Manipulator System (SSRMS) has been extensively validated against flight data. For more general flexible spacecraft applications, however, the assumption of cantilever-type boundary conditions may not be sufficient. This paper describes the boundary condition assumptions that were used in the original formulation, demonstrates that this formulation can be augmented to accommodate systems in which the assumption of cantilever boundary conditions no longer applies, and verifies the approach through comparison with an independent model previously validated against experimental hardware test data from a spacecraft flexible dynamics emulator

Super-capacitor energy storage system to recuperate regenerative braking energy in elevator operation of high buildings

In operating phases of elevators, accelerating, braking modes occur frequently, so braking energy recuperation of elevators has contributed considerably to decrease the total electric energy consumption for operating elevators in multi-floor buildings. In this paper, the supercapacitor energy storage system is used to recover regenerative braking energy of elevators when they operate down full-load and up no-load, reducing fluctuation of voltage on DC bus as well. Therefore, super-capacitor energy storage system (SCESS) will be parallel with line utility to recuperate regenerative braking energy in braking phase and support energy for acceleration phase. The surplus energy will be stored in the supercapacitors thanks to a DC-DC converter capable of exchanging energy bidirectionally in buck/boost modes, and designing control strategy including two control loops. Inner loop-current loop: controlling charge/discharge process of supercapacitors by current iL complying with operation characteristic of elevator; Outer loop-voltage loop: managing UDC-link at a fixed value. Simulation results with elevator system of the ten-floor building, Hanoi, Vietnam installed SCESS have been verified on MATLAB Simulink, SimPowerSystem with saving energy level about 30%

Protocol for Seahorse Analysis of Ex Vivo Mouse Brown and White Adipose Tissues

The mitochondrial stress test is a gold-standard approach for assessing adipose tissue physiological functions and pathological changes. Here, we present a protocol for conducting Seahorse assays using ex vivo mouse brown and white adipose depots. We describe steps for rehydrating the cartridge, preparing freshly harvested fat depots, placing them onto an islet capture plate, and incubating them in a non-CO2 incubator. We then detail procedures for adding mitochondrial stressor solutions and conducting the mitochondrial stress test using the Seahorse XFe24 Analyzer. For complete details on the use and execution of this protocol, please refer to An et al.1

HETEROAGGREGATION BETWEEN ENGINEERED NANOMATERIALS AND HEMATITE NANOPARTICLES IN AQUATIC ENVIRONMENTS

The rapid growth in the use of engineered nanomaterials for industrial and research applications, as well as in consumer products, will inevitably result in the release of these nanomaterials into the environment. In natural and subsurface waters, engineered nanomaterials can undergo aggregation with each other (homoaggregation) or with other types of nanoparticles such as naturally occurring colloids (NOCs) (heteroaggregation). Since the concentration of engineered nanomaterials in natural aquatic systems is likely to be much lower than that of NOCs, heteroaggregation is expected to play a more important role than homoaggregation in determining the environmental fate and transport of engineered nanomaterials. While homoaggregation of engineered nanomaterials has been extensively investigated, the heteroaggregation behavior of these nanomaterials has rarely been studied and therefore is not well understood. The objectives of this dissertation work were to investigate the heteroaggregation of engineered nanomaterials with hematite nanoparticles (HemNPs), a model NOC, and the effects of heteroaggregation on the antimicrobial activity of engineered nanomaterials. The engineered nanomaterials studied in this dissertation work were carbon nanotubes (CNTs) and silver nanoparticles (AgNPs). The first part of the dissertation effort focused on the heteroaggregation between CNTs and HemNPs. The rate and mechanism of CNT–HemNP heteroaggregation were demonstrated to depend on the concentration ratios of the two nanomaterials. Heteroaggregation rates were found to increase with increasing CNT/HemNP concentration ratio up to a point and to then decrease with further increase in the concentration ratio. In the presence of humic acid, the maximum heteroaggregation rate was observed to decrease when the humic acid concentration was increased. As the CNT–HemNP heteroaggregates were exposed to solution chemistries where there should be electrostatic and electrosteric repulsion between these nanoparticles, the strength of the heteroaggregates was presumably weakened, thus making the heteroaggregates more susceptible to disaggregation. The heteroaggregation behavior of two other carbon-based nanomaterials, namely, graphene oxide nanosheets and fullerene (C60) nanoparticles, with HemNPs was also investigated and compared with that of CNTs with HemNPs. The second part of the dissertation effort focused on the homoaggregation behavior of citrate- and polyvinylpyrrolidone (PVP)-coated AgNPs in different solution chemistries. The nature of homoaggregation of citrate-coated AgNPs NaCl solution was shown to be in excellent agreement with the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. PVP was found to be a more effective stabilizer than citrate in both monovalent (NaCl) and divalent (CaCl2 and MgCl2) electrolyte solutions. The adsorption of humic acid on citrate- and PVP-coated AgNPs was found to increase the colloidal stability of these nanoparticles in NaCl solutions and also at low CaCl2 concentrations. Conversely, humic acid was observed to enhance the homoaggregation kinetics of both AgNPs at high CaCl2 concentrations. In addition, the heteroaggregation between citrate-coated AgNPs and HemNPs was demonstrated to reduce the antimicrobial activity of AgNPs toward Escherichia coli bacteria. To our knowledge, this work is the first to describe this effect

Die Grenzen der Markennutzung

Das Gesetz gewährt dem Inhaber einer Marke ein ausschließliches, aber nicht schrankenloses Recht. Vielmehr sehen unter anderem die §§ 23, 24 MarkenG bzw. Artikel 14, 15 UMV Ausnahmen von diesem ausschließlichen Recht vor. In der vorliegenden Bachelorarbeit wird zum einen als Vorfrage untersucht, weshalb diese Schranken existieren. Zum anderen geht die Arbeit aber im Fokus der Frage nach, wo auch diesen Schranken Grenzen gesetzt werden(müssen), d.h. an welcher Stelle das Recht eines Dritten zur Markennutzung endet. In der heutigen modernen Gesellschaft ist die Frage nach diesen Grenzen der Markennutzung höchst relevant: Im Zeitalter von Kommunikation und Internet muss vor allem im Bereich des Online-Vertriebs geklärt werden, inwieweit Dritte berechtigt sind, fremde Marken im geschäftlichen Verkehr zu benutzen

Exploring the Cosmic Reionization Epoch in Frequency Space: An Improved Approach to Remove the Foreground in 21 cm Tomography

Aiming to correctly restore the redshifted 21 cm signals emitted by the neutral hydrogen during the cosmic reionization processes, we re-examine the separation approaches based on the quadratic polynomial fitting technique in frequency space to investigate whether they works satisfactorily with complex foreground, by quantitatively evaluate the quality of restored 21 cm signals in terms of sample statistics. We construct the foreground model to characterize both spatial and spectral substructures of the real sky, and use it to simulate the observed radio spectra. By comparing between different separation approaches through statistical analysis of restored 21 cm spectra and corresponding power spectra, as well as their constraints on the mean halo bias $b$ and average ionization fraction $x_e$ of the reionization processes, at $z=8$ and the noise level of 60 mK we find that, although the complex foreground can be well approximated with quadratic polynomial expansion, a significant part of Mpc-scale components of the 21 cm signals (75% for $\gtrsim 6h^{-1}$ Mpc scales and 34% for $\gtrsim 1h^{-1}$ Mpc scales) is lost because it tends to be mis-identified as part of the foreground when single-narrow-segment separation approach is applied. The best restoration of the 21 cm signals and the tightest determination of $b$ and $x_e$ can be obtained with the three-narrow-segment fitting technique as proposed in this paper. Similar results can be obtained at other redshifts.Comment: 33 pages, 14 figures. Accepted for publication in Ap

Linked-List-Based Multibody Dynamics (MBDyn) Engine

This new release of MBDyn is a software engine that calculates the dynamics states of kinematic, rigid, or flexible multibody systems. An MBDyn multibody system may consist of multiple groups of articulated chains, trees, or closed-loop topologies. Transient topologies are handled through conservation of energy and momentum. The solution for rigid-body systems is exact, and several configurable levels of nonlinear term fidelity are available for flexible dynamics systems. The algorithms have been optimized for efficiency and can be used for both non-real-time (NRT) and real-time (RT) simulations. Interfaces are currently compatible with NASA's Trick Simulation Environment. This new release represents a significant advance in capability and ease of use. The two most significant new additions are an application programming interface (API) that clarifies and simplifies use of MBDyn, and a link-list infrastructure that allows a single MBDyn instance to propagate an arbitrary number of interacting groups of multibody top ologies. MBDyn calculates state and state derivative vectors for integration using an external integration routine. A Trickcompatible interface is provided for initialization, data logging, integration, and input/output