Laboratory tests of a motorized snow surface hardness gage

A motor-driven, spherical probe controlled by a handheld calculator and a microprocessor developed to measure the force and probe travel distance needed to break individual snow surface elements was tested for consistency and reliability. Consistency tests were run on automatic pencil leads; reliability tests on ice rods. Both proved satisfactory. Tests on two man-made snow surfaces showed the probe capable of measuring the strength of individual snow surface elements. Brittle failure occurred in such elements at loads varying from 0.200 to 174.631 grams (median 11.560 grams) for 118 samples. Probe travel distance varied from 0.003 to 0.099 mm (median 0.017 mm). The load needed to cause the first break was less than 1 gram for 21 (18%) of the samples.     

Calculation of propulsion forces in EDS-MAGLEV transport systems with superconducting coils

Contents The paper describes an analytical three-dimensional method which allows the determination of the propulsion force produced by air core long stator linear synchronous motors in EDS-MAGLEV transport systems, using super-conducting coils both for motor field winding and for vehicle levitation. The method, which allows to take into account the finite thickness of the coils, is based on the variation of the magnetic energy stored in the field and armature (over-lapped or non-overlapped) windings of the motor. The application of the method to an experimental Japanese prototype gives good concordance with the experimental data.

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Berechnung der Antriebskraft bei EDM-MAGLEV Beförderungssystemen mit supraleitenden Spulen

Übersicht Im Artikel wird ein analytisch-dreidimensionales Verfahren beschrieben, das die Berechnung der Antriebskraft erlaubt, die bei überschnellen Beförderungssystemen wie EDS-MAGLEV durch lineare Langstator-Synchronmotoren entsteht, wobei Supraleitungsspulen sowohl zur Motorerregung als auch zur magnetischen Levitation des Fahrzeuges verwendet werden. Das Verfahren berücksichtigt die endliche Spulendicke und geht aus von der Änderung der magnetischen Energie, die in den Anker- und Erregerwicklungen (Zylinder- sowie Wellenwicklungen) des Motors gespeichert ist. Die Werte der Antriebskraft, die durch die Anwendung dieses Verfahrens auf einen in Japan ausgeführten Experimentalprototyp ermittelt werden, weisen eine gute Übereinstimmung mit den experimentellen Werten auf.

     

Transport Properties,Local Coordination,and Thermal Stability of the Water/Diethylmethylammonium Methanesulfonate Binary System

Ammonium based protic ionic liquids are highlighted for their great potential to sustain proton transport in proton exchange membrane (PEM) fuel cells. Yet, there remain questions concerning the effect of water produced by the fuel cell at the cathode side on the performance of the ionic liquid. In this contribution we report the effect of water on the transport properties and the local coordination in the binary system of the protic ionic liquid diethylmethylammonium methanesulfonate ([DEMA][OMs]) and water, employing ¹H NMR, Raman, and infrared spectroscopy. We observe that the self‐diffusion of cations and anions increases with the water content and that cations and anions diffuse at the same rate at all concentrations investigated. ¹H NMR and vibrational spectroscopy, on the other hand, indicate that added water interacts primarily with the anion and slightly affects the ionicity of the ionic liquid. In addition, by investigating the thermal stability of the binary system we find that although [DEMA][OMs] displays a continuous loss of water upon increasing temperature a fraction of water molecules can be retained even above 120 °C, and that the complete loss of water is immediately followed by decomposition, which is observed to occur at about 185 °C.     

Immunological Response to Biodegradable Magnesium Implants

The use of biodegradable magnesium implants in pediatric trauma surgery would render surgical interventions for implant removal after tissue healing unnecessary, thereby preventing stress to the children and reducing therapy costs. In this study, we report on the immunological response to biodegradable magnesium implants—as an important aspect in evaluating biocompatibility—tested in a growing rat model. The focus of this study was to investigate the response of the innate immune system to either fast or slow degrading magnesium pins, which were implanted into the femoral bones of 5-week-old rats. The main alloying element of the fast-degrading alloy (ZX50) was Zn, while it was Y in the slow-degrading implant (WZ21). Our results demonstrate that degrading magnesium implants beneficially influence the immune system, especially in the first postoperative weeks but also during tissue healing and early bone remodeling. However, rodents with WZ21 pins showed a slightly decreased phagocytic ability during bone remodeling when the degradation rate reached its maximum. This may be due to the high release rate of the rare earth-element yttrium, which is potentially toxic. From our results we conclude that magnesium implants have a beneficial effect on the innate immune system but that there are some concerns regarding the use of yttrium-alloyed magnesium implants, especially in pediatric patients.     

High-Strength Low-Alloy (HSLA) Mg–Zn–Ca Alloys with Excellent Biodegradation Performance

This article deals with the development of fine-grained high-strength low-alloy (HSLA) magnesium alloys intended for use as biodegradable implant material. The alloys contain solely low amounts of Zn and Ca as alloying elements. We illustrate the development path starting from the high-Zn-containing ZX50 (MgZn5Ca0.25) alloy with conventional purity, to an ultrahigh-purity ZX50 modification, and further to the ultrahigh-purity Zn-lean alloy ZX10 (MgZn1Ca0.3). It is shown that alloys with high Zn-content are prone to biocorrosion in various environments, most probably because of the presence of the intermetallic phase Mg₆Zn₃Ca₂. A reduction of the Zn content results in (Mg,Zn)₂Ca phase formation. This phase is less noble than the Mg-matrix and therefore, in contrast to Mg₆Zn₃Ca₂, does not act as cathodic site. A fine-grained microstructure is achieved by the controlled formation of fine and homogeneously distributed (Mg,Zn)₂Ca precipitates, which influence dynamic recrystallization and grain growth during hot forming. Such design scheme is comparable to that of HSLA steels, where low amounts of alloying elements are intended to produce a very fine dispersion of particles to increase the material’s strength by refining the grain size. Consequently our new, ultrapure ZX10 alloy exhibits high strength (yield strength R _p = 240 MPa, ultimate tensile strength R _m = 255 MPa) and simultaneously high ductility (elongation to fracture A = 27%), as well as low mechanical anisotropy. Because of the anodic nature of the (Mg,Zn)₂Ca particles used in the HSLA concept, the in vivo degradation in a rat femur implantation study is very slow and homogeneous without clinically observable hydrogen evolution, making the ZX10 alloy a promising material for biodegradable implants.     

Nonlinear model and constrained ML for removing back-to-front interferences from recto–verso documents

In this paper, we approach the removal of back-to-front interferences from scans of double-sided documents as a blind source separation problem, and extend our previous linear mixing model to a more effective nonlinear mixing model. We consider the front and back ideal images as two individual patterns overlapped in the observed recto and verso scans, and apply an unsupervised constrained maximum likelihood technique to separate them. Through several real examples, we show that the results obtained by this approach are much better than the ones obtained through data decorrelation or independent component analysis. As compared to approaches based on segmentation/classification, which often aim at cleaning a foreground text by removing all the textured background, one of the advantages of our method is that cleaning does not alter genuine features of the document, such as color or other structures it may contain. This is particularly interesting when the document has a historical importance, since its readability can be improved while maintaining the original appearance.     

Characterisation of hydrodynamics induced by air injection related to membrane fouling behaviour

The study focuses on fine bubble and spherical cap bubble injection in case of outside/in fibres immersed in a tank. The objectives are to quantify liquid circulations and shear stresses along the membrane and to understand their effects on the fouling resistance. Thus, both filtration experiments and hydrodynamic characterisation were performed in the same aeration conditions. Only particle cake deposit was studied as fouling mode and the hydrodynamics was characterized experimentally by 2-phase flow particle image velocimetry (PIV) and numerically with the CFD code FLUENT. Results presented in this paper are limited to tight hollow-fibres to well understand hydrodynamics without fibre motion. One important result is that mean values of wall shear stress are very low (maximum 0.25 Pa) eliminating the wall shear stress as a mechanism able to explain filtration performances for a non-confined aeration without fibre displacement. In addition, an analysis has been conducted in terms of horizontal liquid flow toward the membrane. The quantification of this flow allowed to conclude that i) for a given local bubble flow rate, there is no influence of the kind of aeration on this horizontal flow rate; and ii) the filtration performances can be correlated with this horizontal flow. The reason might be an over concentration of particles near the membrane surface induced by this flow.     

On the use of second-order derivatives and metamodel-based Monte-Carlo for uncertainty estimation in aerodynamics

This article addresses the delicate issue of estimating physical uncertainties in aerodynamics. Usually, flow simulations are performed in a fully deterministic approach, although in real life operational uncertainty arises due to unpredictable factors that alter the flow conditions. In this article, we present and compare two methods to account for uncertainty in aerodynamic simulation. Firstly, automatic differentiation tools are used to estimate first- and second-order derivatives of aerodynamic coefficients with respect to uncertain variables, yielding an estimate of expectation and variance values (Method of Moments). Secondly, metamodelling techniques (radial basis functions, kriging) are employed in conjunction with Monte-Carlo simulations to derive statistical information. These methods are demonstrated for 3D Eulerian flows around the wing of a business aircraft at different regimes subject to uncertain Mach number and angle of attack.