A Test of Two Methods for Waste Rock Drainage Quality Prediction: Aqua Regia Extraction and Single-addition Net-acid Generation Test Leachate Analysis

Mine Water and the Environment - The mobility of contaminants from mine waste can be assessed using different extraction methods. Aqua regia (AR) extraction is the most commonly used method in...     

Statistical analysis of control parameters in evolutionary map L-systems-based topology optimization

Map L-systems-based parametrization, also referred to as the cellular division method, is a generative encoding, suitable for topology optimization. The parametrization is compact due to its ability to reuse its elements, and therefore capable of covering a large design space with relatively few design variables. Map L-systems are often evolved using genetic algorithms (GAs). A key implementation detail of such procedures, as with most GA-based geometry searches, is the choice of parameters controlling the operation of the evolutionary process. The optimal choice of these in conventional optimization formulations is highly problem-specific—far less so, however, when the GA evolves an L-systems encoding and does not act directly on the geometry. This is because the L-system encoding is, itself, independent of the geometry. We study the effects of different control parameters by conducting a statistical test of over 400 parameter combinations on five test cases, for which the global optima are known. The best-performing parameter combinations are reported as a Pareto front of the average number of objective function evaluations and ranking based on the average of optimized fitnesses. Finally, three Pareto-optimal parameter combinations are selected and applied to an optimization problem of maximizing the fundamental natural frequency of an integrally stiffened aluminum panel. The best of the resulting designs has a higher fundamental natural frequency than the baseline design by a margin of 11.2%.     

Breakdown of Zero-Energy Quantum Hall State in Graphene in the Light of Current Fluctuations and Shot Noise

We have investigated the cross-over from Zener tunneling of single charge carriers to avalanche type of bunched electron transport in a suspended graphene Corbino disk in the zeroth Landau level. At low bias, we find a tunneling current that follows the gyrotropic Zener tunneling behavior. At larger bias, we find an avalanche type of transport that sets in at a smaller current the larger the magnetic field is. The low-frequency noise indicates strong bunching of the electrons in the avalanches. On the basis of the measured low-frequency switching noise power, we deduce the characteristic switching rates of the avalanche sequence. The simultaneous microwave shot noise measurement also reveals intrinsic correlations within the avalanche pulses and indicate a decrease in correlations with increasing bias.     

MRI quality assurance based on 3D FLAIR brain images

Objective

Quality assurance (QA) of magnetic resonance imaging (MRI) often relies on imaging phantoms with suitable structures and uniform regions. However, the connection between phantom measurements and actual clinical image quality is ambiguous. Thus, it is desirable to measure objective image quality directly from clinical images.

Materials and methods

In this work, four measurements suitable for clinical image QA were presented: image resolution, contrast-to-noise ratio, quality index and bias index. The methods were applied to a large cohort of clinical 3D FLAIR volumes over a test period of 9.5 months. The results were compared with phantom QA. Additionally, the effect of patient movement on the presented measures was studied.

Results

A connection between the presented clinical QA methods and scanner performance was observed: the values reacted to MRI equipment breakdowns that occurred during the study period. No apparent correlation with phantom QA results was found. The patient movement was found to have a significant effect on the resolution and contrast-to-noise ratio values.

Discussion

QA based on clinical images provides a direct method for following MRI scanner performance. The methods could be used to detect problems, and potentially reduce scanner downtime. Furthermore, with the presented methodologies comparisons could be made between different sequences and imaging settings. In the future, an online QA system could recognize insufficient image quality and suggest an immediate re-scan.

     

Cu–H-MCM-41, H-MCM-41 and Na-MCM-41 Mesoporous Molecular Sieve Catalysts for Isomerization of 1-Butene to Isobutene

Cu–H-MCM-41, H-MCM-41 and Na-MCM-41 mesoporous molecular sieve catalysts were synthesized, characterized and investigated in the isomerization of 1-butene to isobutene. Introduction of copper in MCM-41 was found to play a positive role in enhancing the conversion of 1-butene and yield of isobutene and Cu–H-MCM-41 exhibited higher conversion of 1-butene and yield to isobutene than H-MCM-41 and Na-MCM-41 catalysts. The pretreatments of Cu–H-MCM-41 catalyst with synthetic air or hydrogen were observed to influence the 1-butene conversion, yield of isobutene and selectivity to isobutene. Pre-treated with the synthetic air the Cu–H-MCM-41-Ox catalyst exhibited higher conversion of 1-butene, yield of isobutene and selectivity to isobutene than hydrogen pre-treated Cu–H-MCM-41-Red. The reason for such a behavior of Cu–H-MCM-41-Red is the reduction of copper species to metallic form. The X-ray powder diffraction pattern of Cu–H-MCM-41-Red exhibited a peak attributed to the reduction of Cu²⁺ to Cu⁰. FTIR spectra of adsorbed pyridine showed the presence of Brønsted and Lewis acid sites in the H-MCM-41, Na-MCM-41 and Cu–H-MCM-41 catalysts.     

The comparison of particle oxidation and surface structure of diesel soot particles between fossil fuel and novel renewable diesel fuel

Conventional fossil diesel fuel and renewable diesel fuel based on hydrotreated vegetable oils (HVO) were compared regarding the oxidation characteristics of the generated soot particulate. The comparison was performed by utilizing a high-temperature oxidation tandem differential mobility analyser in which monodisperse soot aerosol was first selected and then heated in a high-temperature furnace. The particle size reduction caused by oxidation during the furnace treatment was then measured as a function of furnace temperature. The results indicate that soot oxidation is very similar between the studied fuels. This is supported by the obtained HR-TEM images and EELS-spectra which were practically indistinguishable between different fuels and engine conditions. The similar oxidation properties and surface structure between fossil and HVO-based diesel fuels imply that the oxidative aftertreatment devices designed for fossil diesel should work well also with the studied renewable diesel fuel.     

芬兰Jávri酒店

正Jávri Lodge是一家精品酒店,位于芬兰拉普兰地区Saariselk?附近。建筑曾是芬兰在位时间最长的总统Urho Kekkonen的滑雪度假屋,这里曾接待过不少皇室宾客、大国政要,甚至伊朗国王。后来酒店扩建,新建了主入口、餐厅和四间客房。从外观上看新增了三个铜板表皮的体量,分别位于原有建筑的前方和上方。酒店的宾客常常在附近进行各种户外活动,因此该酒店旨在为宾客提供一个温暖舒适的休息场所。在抵达酒店入口蜿蜒的走道上,铜灯笼静静伫立两旁,与铜质表皮的主入口遥相呼应。道路两边是旧旅馆房屋的原木墙     

Wetting behaviour and direct observation of thermally responsive polystyrene‐block‐poly(N‐isopropylacrylamide)‐block‐polystyrene electrospun fibres in aqueous environment

Electrospun fibres of thermally responsive triblock copolymer polystyrene‐block‐poly(N‐isopropylacrylamide)‐block‐polystyrene were prepared. Fibre morphology and swelling were studied below and above the lower critical solution temperature of poly(N‐isopropylacrylamide) (PNIPAM) using cryo‐electron microscopy. Cryo‐transmission electron microscopy showed that the fibre diameter increased up to 150% after immersion in water at 20 °C. In contrast, at 45 °C the fibre diameter increased considerably less. The sessile drop technique was used to characterize temperature‐dependent wetting of fibre mats. Contact angle (θ_CA) measurements revealed that a block copolymer fibre mat changed from hydrophobic (θ_CA > 90°) to hydrophilic (θ_CA < 90°) state within seconds after applying a water droplet on it at 20 °C. At 40 °C the initial contact angle was measured to be higher (135°) and it decreased much less than at 20 °C during the first minute of measurement. We observed using scanning electron microscopy that the electrospun fibres of the block copolymer having 77 wt% of PNIPAM lost their cylindrical shape and changed from fibres to thin sheets at both 20 and 40 °C within seconds after applying water on the fibres. Fibres having 55 wt% of PNIPAM were observed to be stable in water at both 20 and 40 °C, which resulted, surprisingly, in fibre mats with the strongest effects on thermally sensitive wetting. We discuss the surprising results and the implications that the evolution of fibre surface roughness has on the long‐term wetting behaviour, demonstrating a self‐adaptable hydrophilicity/hydrophobicity nature of the fibre mats. © 2013 Society of Chemical Industry     

Modelling and analysing a distributed dynamic channel allocation algorithm for mobile computing using high-level net methods

A distributed dynamic channel allocation algorithm has been proposed in [11]. In this paper the algorithm is modelled using predicate/transition nets. The same model can be used for any number of cell and channel configurations. The Maria reachability analyser has been used to analyse the protocol for some configurations. These are deadlock-free and are shown to satisfy the requirement that the same channel is never allocated to two neighbouring cells. The suitability of high-level nets for the modelling and analysis of distributed algorithms is discussed. Published online: 24 August 2001     

Characterizing geometric distortions of 3D sequences in clinical head MRI

Objective

Phantoms are often used to estimate the geometric accuracy in magnetic resonance imaging (MRI). However, the distortions may differ between anatomical and phantom images. This study aimed to investigate the applicability of a phantom-based and a test-subject-based method in evaluating geometric distortion present in clinical head-imaging sequences.

Materials and methods

We imaged a 3D-printed phantom and test subjects with two MRI scanners using two clinical head-imaging 3D sequences with varying patient-table positions and receiver bandwidths. The geometric distortions were evaluated through nonrigid registrations: the displaced acquisitions were compared against the ideal isocenter positioning, and the varied bandwidth volumes against the volume with the highest bandwidth. The phantom acquisitions were also registered to a computed tomography scan.

Results

Geometric distortion magnitudes increased with larger table displacements and were in good agreement between the phantom and test-subject acquisitions. The effect of increased distortions with decreasing receiver bandwidth was more prominent for test-subject acquisitions.

Conclusion

Presented results emphasize the sensitivity of the geometric accuracy to positioning and imaging parameters. Phantom limitations may become an issue with some sequence types, encouraging the use of anatomical images for evaluating the geometric accuracy.