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[en] We consider the most feasible ways to significantly improve the sensitivity of spectroscopic methods for detection and measurement of trace concentrations of greenhouse gas molecules in the atmosphere. The proposed methods are based on combining light fluxes from a number of spectral components of the specified molecule on the same photodetector, taking into account the characteristic features of the transmission spectrum of devices utilizing multipath interference effects.
[en] Adduct formation is a common ionization method in electrospray ionization mass spectrometry (ESI/MS). However, this process is poorly understood and complicated to control. We demonstrate possibilities to control adduct formation via mobile phase additives in ESI positive mode for 17 oxygen and nitrogen bases. Mobile phase additives were found to be a very effective measure for manipulating the formation efficiencies of adducts. An appropriate choice of additive may increase sensitivity by up to three orders of magnitude. In general, sodium adduct [M + Na]+ and protonated molecule [M + H]+ formation efficiencies were found to be in good correlation; however, the former were significantly more influenced by mobile phase properties. Although the highest formation efficiencies for both species were observed in water/acetonitrile mixtures not containing additives, the repeatability of the formation efficiencies was found to be improved by additives. It is concluded that mobile phase additives are powerful, yet not limiting factors, for altering adduct formation. .
[en] A method of calculating the optimal operating parameters of a centrifuge cascade for separating multicomponent mixtures of isotopes is developed. A computational scheme is proposed for calculating the parameters of a cascade and the distribution of the centrifuges over the stages with a prescribed total number of centrifuges in different variants of optimization. Calculations showing the particulars of optimization and the efficacy of the developed method are presented.
[en] The scheme of the propulsion unit with walking mechanism for a wheeled planetary rover is considered. The walking mechanism permits to convert the chassis in a transport position, displacement of rover’s center of mass so as to optimize the load on motor wheels. In wheeled motion the walking mechanism realize function of the active suspension for adaptation of the locomotion system to the surface features. On friable soils where wheeled locomotion is difficult or impossible, wheel-walking mode improves trafficability.
[en] The stress relaxation behaviors of magnetorheological (MR) gels under stepwise shear loading are systematically investigated. The particle-enhanced effect, the magneto-induced effect, and the temperature-enhanced effect on the stress relaxation of MR gels (MRG) are discussed. For further analysis of the magneto-induced stress relaxation mechanism in MRG, a phenomenological model is established to describe the stress relaxation behavior of the matrix and the magnetic particle chains. All characteristic parameters introduced in the model, i.e. relaxation time, instantaneous modulus, and stable modulus, have well-defined physical meanings and are fitted based on the experimental results. The influence of each parameter on the macroscopic response is discussed and it is found that the relaxation stress induced by the magneto-mechanical coupling effect plays an important role in the stress relaxation process of MRG. (paper)
[en] Highlights: •A dendritic matrix and a eutectic / typify the microstructure of the Mg-12 wt.%Zn alloy. •The eutectic mixture has two morphologies: lamellae and rods, the latter increasing with decreasing cooling rates. •Eutectic spacing (λ) and the growth rate (V) are related by the Jackson-Hunt equation: λ2V = constant. •Non-equilibrium MgZn2 and Mg4Zn7 nanoparticles are distributed throughout the matrix.
[en] The studied predictive model of behavior viscosimetric is the model of K.A. Petersen . The dominant idea of this method is to characterize the viscosity of a fluid from two models taken as a reference in passing through a reduced pressure. The method is corresponding state with two references. This study shows that this method is dependent on the choice of reference and for each of the possibilities of C10/C6H6 and C1/C10 references . The results were investigated for four different weight ratios. It shows that the introduction of an adjusted coefficient does not improve significantly compared to results without adjustment factor, which appears to be the best choice. Regarding the influence of the choice of references, generally the two couples appear suitable but we noted that the choice is not necessary. In the case of mixtures containing at least one aromatic, the results are correct, especially if one takes the ratio of adjustment and our ratio without adjustment compared to that of K. A. PETERSEN. The experimental results of the viscosity exhibit a good agreement with the calculated values. We can predict that the relative improvement is the finding that the introduction of the second body of reference (C10) from the model states corresponding to a reference (C1) of the authors. (paper)
[en] Additive alignment inside a polymer composite significantly affects the physical properties of the material. Many studies have attempted to predict, measure, and control additive alignment inside polymer composites with the aim of enhancing their properties. The objective of this study is to analyze additive alignment inside a mixture of ball-milled carbon fibers and liquid polydimethylsiloxane flowing in a channel. To this end, an image-processing method was developed to more quickly and accurately analyze the additive alignment in images obtained from flow visualization experiments. A process was developed to calculate the angle and length of an additive according to its location and the time at which the image was captured, by analyzing a sequence of images obtained from an optical microscope with a high-speed camera. The proposed process was applied to images composed of arbitrarily drawn lines and actual flow visualization images, and the results were verified by being compared with those of calculations based on the Hough transform or with directly measured values.
[en] Wireless sensor networks (WSNs) are promising technology in structural health monitoring (SHM) applications for their low cost and high efficiency. The limited wireless sensors and restricted power resources in WSNs highlight the significance of optimal wireless sensor placement (OWSP) during designing SHM systems to enable the most useful information to be captured and to achieve the longest network lifetime. This paper presents a holistic approach, including an optimization criterion and a solution algorithm, for optimally deploying self-organizing multi-hop WSNs on large-scale structures. The combination of information effectiveness represented by the modal independence and the network performance specified by the network connectivity and network lifetime is first formulated to evaluate the performance of wireless sensor configurations. Then, an information-fusing firefly algorithm (IFFA) is developed to solve the OWSP problem. The step sizes drawn from a Lévy distribution are adopted to drive fireflies toward brighter individuals. Following the movement with Lévy flights, information about the contributions of wireless sensors to the objective function as carried by the fireflies is fused and applied to move inferior wireless sensors to better locations. The reliability of the proposed approach is verified via a numerical example on a long-span suspension bridge. The results demonstrate that the evaluation criterion provides a good performance metric of wireless sensor configurations, and the IFFA outperforms the simple discrete firefly algorithm. (paper)
[en] The study simulates of aerosol dynamics including coagulation, deposition and source reinforcement. Typical applications are for nuclear reactor aerosols, aerosol reaction chambers and the production of purified materials. The model determines the aerosol number and volume distributions for an arbitrary number of particle-size classes, called sections. The user specifies the initial aerosol size distribution and the source generation rate of each component in each section. For spatially homogeneous aerosol of uniform chemical composition, the aerosol dynamic equation is solved in closed volume to simulate the radionuclide particle transport in the containment. The effects of initial conditions on the aerosol distribution, boundary layer thickness and the aerosol behaviour under source reinforcement (external source) are considered