Real-Time Noncoherent UWB Positioning Radar With Millimeter Range Accuracy: Theory and Experiment

In this paper, we propose a novel architecture for ultra-wideband (UWB) positioning systems, which combines the architectures of carrier-based UWB systems and traditional energy detection-based UWB systems. By implementing the novel architecture, we have successfully developed a standalone noncoherent system for positioning both static and dynamic targets in an indoor environment with approximately 2 and 5 mm of 3-D accuracy, respectively. The results are considered a great milestone in developing such technology. 1-D and 3-D experiments have been carried out and validated using an optical reference system, which provides better than 0.3-mm 3-D accuracy. This type of indoor high-accuracy wireless localization system has many unique applications including robot control, surgical navigation, sensitive material monitoring, and asset tracking.      

GC–MS analysis of oxysterols and their formation in cultivated liver cells (HepG2)

Oxysterols play a key role in many (patho)physiological processes and they are potential biomarkers for oxidative stress in several diseases. Here we developed a rapid gas chromatographic-mass spectrometry-based method for the separation and quantification of 11 biologically relevant oxysterols bearing hydroxy, epoxy, and dihydroxy groups. Efficient chromatographic separation (resolution ≥ 1.9) was achieved using a medium polarity 35%-diphenyl/65%-dimethyl polysiloxane stationary phase material (30 m × 0.25 mm inner diameter and 0.25 μm film thickness). Based on thorough analysis of the fragmentation during electron ionization we developed a strategy to deduce structural information of the oxysterols. Optimized sample preparation includes (i) extraction with a mixture of n-hexane/iso-propanol, (ii) removal of cholesterol by solid phase extraction with unmodified silica, and (iii) trimethylsilylation. The method was successfully applied on the analysis of brain samples, showing consistent results with previous studies and a good intra- and interday precision of ≤20%. Finally, we used the method for the investigation of oxysterol formation during oxidative stress in HepG2 cells. Incubation with tert-butyl hydroperoxide led to a massive increase in free radical formed oxysterols (7-keto-chol > 7β-OH-chol >> 7α-OH-chol), while 24 h incubation with the glutathione peroxidase 4 inhibitor RSL3 showed no increase in oxidative stress based on the oxysterol pattern. Overall, the new method described here enables the robust analysis of a biologically meaningful pattern of oxysterols with high sensitivity and precision allowing us to gain new insights in the biological formation and role of oxysterols.     

Increase of regression speed of combustion through oxidizer doping

This paper presents an innovative method to increase the regression speed of a solid fuel grain by using oxidizer doping. The results obtained on a propulsion application showing the performance parameters as an output of a numerical model are provided. Two models are given that predict the regression speed increase for embedding wires and for oxidizer doping with a factor of ～2 to 3. Also, it is shown that this increase of the regression speed by using a low oxidizer doping percentage, which is based on the assumption that at a higher doping rate the combustion instabilities, can lead to detonations. Next, a thermochemical model for the combustion within the oxidizer doping model is afforded. For this model, the burn is assumed to take place around the surface of each of the oxidizer particles, being composed of two different burning processes: one is the burning on the surface of the solid fuel grain and the other is the burning between the solid fuel and the solid oxidizer. For a non-doped fuel grain, the burning takes place only on the surface of the fuel grain. Finally, a potential application of such propulsion units to small satellite launchers is presented, and a case study of such a vehicle intended to place a 50 kg payload on a low earth orbit (300 to 500 km altitude) is described. The modelling proposed is based on the assumption that the use of solid methane makes this launcher environmentally friendly.     

Two Sources Are Better than One for Increasing the Kolmogorov Complexity of Infinite Sequences

The randomness rate of an infinite binary sequence is characterized by the sequence of ratios between the Kolmogorov complexity and the length of the initial segments of the sequence. It is known that there is no effective procedure that transforms one input sequence into another sequence with higher randomness rate. By contrast, we display such a uniform effective procedure having as input two independent sequences with positive but arbitrarily small constant randomness rate. Moreover the transformation is a truth-table reduction and the output has randomness rate arbitrarily close to 1.     

Genotoxic potential of aqueous extracts of Artemisia verlotorum on the cell cycle of Allium cepa

Artemisia verlotorum, popularly ‘infalivina’, is a medicinal herb used for respiratory, circulatory and digestive treatments. Antiproliferative and genotoxic effects of A. verlotorum aqueous extracts in three different concentrations (6, 32 and 48 g/L) were evaluated on the Allium cepa cell cycle. Results clearly showed a significant difference using the χ² test (p = 0.05) among treatments with a decrease in the mitotic index as the concentration of the extract increased. Extracts of A. verlotorum proved to be genotoxic and showed antiproliferative potential on the A. cepa cell cycle. This study suggests the use of infusions of A. verloturum for medicinal purposes only after selecting suitable concentrations.     

Evidence of Tin Oxide Recrystallization in Opacified Lead Glazes

Tin oxide (SnO₂) particles that are a few hundred nanometers in size and are embedded in a lead glaze act as a white opacifier. The insolubility of SnO₂ particles in a lead glaze is responsible for this microstructure. Although it is assumed that SnO₂ particles do not react during the glaze formation, we demonstrate that the development of metastable phases prior to the fusion of the PbO-SiO₂-SnO₂ mixture allows the SnO₂ particles to react and then recrystallize subsequent to the fusion of the mixture. The recrystallization of SnO₂ occurs during heating and/or cooling until the temperature is sufficiently low and/or the tin supply is exhausted.     

Sekundärströmung in Schaufel(ring)gittern mit Pfeilung und V-Stellung — eine Literaturstudie

One goal in designing fluid machinery is to maximise the efficiency. The rotor and the stator of such machines are comprised of rotating and stationary cascades. In addition to the main flow a secondary flow develops which depends on the operation point. The efficiency of the cascade is affected by this flow. The secondary flow, including the gap flow, can reach up to 20–40% of the total hyraulic losses in modern axial flow turbines. A reduction of these losses can remarkably affect the efficiency. In order to achieve this an exact understanding of the formation and the development of the secondary flow is required. If the designer properly understands the secondary flows, the interaction between them and the parameters which influence the secondary flows, it is possible to design cascades with reduced secondary losses by using proper design criteria. Shape and extend of the secondary flow mainly depend on flow parameters and geometric parameters. Flow parameters are, for example, the incidence angle, the boundary layer thickness and the turbulence. Geometric parameters are for example the distribution of the blade load, shape and radius of the leading edge, the aspect ratio, boundary layer fences, dihedral and sweep of the blade. The latter two geometric criteria can be regarded efficient means to model the pressure on the endwalls and, therefore, the development of the secondary flow.     

A study on common malware families evolution in 2012

With the exponential growth of malware in the last 5 years, the number of polymorphic malware increased as well. The aim of this paper is to describe the evolution throughout a year of four major malware families (FakeAlert, Sirefef, ZBot and Vundo). The analysis has been made in terms of polymorphic mechanisms with regards to the polymorphic mechanisms (such as changes in the packer module, changes in the geometry of file, variation of version information from the resource directory or different methods used to modify the icon of one file) which have been used in order to avoid their detection by anti-malware systems. The malware files were collected every week throughout one year’s time. For each family we have recorded the new variants and the updates that were added to the old ones in order to avoid detection. We have managed to examine more than 1,000 new versions of such files. The current article includes an additional study case. The latter focuses on the methods that have been used by the FakeAlert malware family in order to modify their icons.     

A Lateral Restraining Device for Large Telescope Mirrors

Abstract

Telescope mirrors—like every rigid body—have six degrees of freedom (DOFs) to move: translation along three axes of space and rotation around these three axes. Hydraulic support systems, which are designed to hold the mirror in the required best optical shape, have to couple all six DOFs between the mirror and its supporting cell structure. While three DOFs are covered by the axial support system and two DOFs by the lateral support system, the last degree of freedom often remains uncovered. A good example is the lateral support system for the 8 m primary mirror of ESO's Very Large Telescope, which did not couple movements along the horizontal axis between the mirror and its cell and therefore required a lateral restraining device. Based on this example, a general method is shown how to control all degrees of freedom at a given supporting force distribution without any unwanted additional forces. According to the theory of modal control, a hydraulic network is used to decouple the oil flow to the hydraulic actuators and thereby to control the components of the supporting forces independently. The theory may be applied for other hydraulic support systems, too.     

A continuum phase field model for fracture

A phase field model based on a regularized version of the variational formulation of brittle fracture is introduced. The influences of the regularization parameter that controls the interface width between broken and undamaged material and of the mobility constant of the evolution equation are studied in finite element simulations. A generalized Eshelby tensor is derived and analyzed for mode I loading in order to evaluate the energy release rate of the diffuse phase field cracks. The numerical implementation is performed with finite elements and an implicit time integration scheme. The configurational forces are computed in a postprocessing step after the coupled problem of mechanical balance equations and the evolution equation is solved. Some of the numerical results are compared to analytical results from classical Griffith theory.