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关键词： climate change   flow regime   headwaters   Sierra Nevada   stream biodiversity  

摘要： We studied benthic macroinvertebrate communities in 12 mid-elevation mountain streams in the Sierra Nevada, California. Data were collected at nine times (seven springs and two autumns) over a 14-year period of variable hydrological conditions, including years of flood and extreme unprecedented drought. The taxonomic and trait structures of communities were similar during wet and average springs but became increasingly different as drought continued and smaller streams became intermittent. The density of total invertebrates, primarily chironomids, increased during the drought years, but the richness and abundance of mayfly, stonefly, and caddisfly (EPT) taxa declined during the late drought. During the late drought, the proportions of rheophilic, semivoltine taxa with clinger or swimmer behavioural habits decreased, whereas small, stress-tolerant taxa with burrower and climber habits increased. Collector-gatherers dominated in all periods, but during the severe drought the relative abundance of micropredators increased and filterers, shredders, and grazers decreased. We also found greater changes in community structure between spring runoff and autumn base flow conditions in an average than a wet year. However, spring to autumn population growth rates were much greater during the wet than average year. Invertebrate richness and EPT abundance decreased and community structure showed large changes when stream discharge fell below 1-10L/s, but remained relatively constant across a range of higher flows. During the severe drought, there were significant declines in the densities of 40% of the common EPT taxa compared to average and wet years, but chironomid, mite, and other invertebrate taxa showed variable responses. Invertebrate diversity, community structure, and ecosystem functions in small, headwater streams are especially vulnerable to drought conditions, which are expected to increase in frequency and intensity with climate change in the Sierra Nevada and other m

关键词： Iron-based superconductivity   Superfluid density   Interband pairing   Gap anisotropy  

摘要： We study the temperature evolution behaviors of the superfluid density in the iron-based superconductors based on the two-orbital t - J(1) - J(2) model. It was revealed that the superfluid density exhibits the exotic positive curvature behavior when approaching T-c. The theoretical results are qualitatively consistent with the experimental observations. The positive curvature behavior of the superfluid density is attributed to the effects of the weak interband pairing coupling. Combining with the experimental observations, this indicates that the interband coupling strength is distinct between different iron-based compounds.

关键词： Air classification   Cyclonic classifier   CFD   Classification performance   Industrial application  

摘要： Due to the low particle classification accuracy or powder production of static air classifiers, a new cyclonic classifier with middle primary and secondary tangential inlets and feed tube was designed. The flow field and classification performance of the lab-scale classifier were investigated numerically and experimentally. The industrial cyclonic classifier's performance was also on-site tested. The simulated results show that the classifier has a main flow characterized by an upper upward vortex and a downer reverse-flow. The secondary air forms the other two vortexes with high tangential velocity near the wall and high axial velocity at the center, which helps to wash the fine particles and accelerate their discharge. The primary and secondary air occupies the separated space with a sharp dynamic boundary in the classifier regardless of inlet air velocity. The experimental lab-scale classifier has a maximum Newton efficiency of 88% with coarse product yield of 92%. The industrial classifier has been used to classify the waste microsilica for the reutilization, which well meets the industrial requirements of the classification efficiency and energy consumption. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： microfluidics   3D flow focusing   3D particle focusing   particle   cell imaging   bioMEMS   unsupervised learning   neural networks   variational inference  

摘要： Single-cell analysis commonly requires the confinement of cell suspensions in an analysis chamber or the precise positioning of single cells in small channels. Hydrodynamic flow focusing has been broadly utilized to achieve stream confinement in microchannels for such applications. As imaging flow cytometry gains popularity, the need for imaging-compatible microfluidic devices that allow for precise confinement of single cells in small volumes becomes increasingly important. At the same time, high-throughput single-cell imaging of cell populations produces vast amounts of complex data, which gives rise to the need for versatile algorithms for image analysis. In this work, we present a microfluidics-based platform for single-cell imaging in-flow and subsequent image analysis using variational autoencoders for unsupervised characterization of cellular mixtures. We use simple and robust Y-shaped microfluidic devices and demonstrate precise 3D particle confinement towards the microscope slide for high-resolution imaging. To demonstrate applicability, we use these devices to confine heterogeneous mixtures of yeast species, brightfield-image them in-flow and demonstrate fully unsupervised, as well as few-shot classification of single-cell images with 88% accuracy.

关键词： Wireless pebble   packed-Bed FHR   Support Vector Machine   Machine Learning   Nuclear Engineering  

摘要： In the first study, a novel wireless pebble for scale experiments is developed, and a simple heat transfer experiment is conducted to determine the difference in the local heat transfer coefficient. Based on the fact that the use of Dowtherm A between approximately 57–87 °C is an alternative to the normal use of the FliBe temperature range of 600–700°C, a new-concept wireless device in a scaled experiment is introduced. This device consists of a 63.5 mm diameter metal shell and contains a built-in customized circuit board and battery for driving temperature measurements and wireless data transfer. The circuit board used for receiving temperature measurements from several type K thermocouples is based on the ATmega328 microprocessor (MCU). This board collects temperature at multiple points and send data to the receiver wirelessly. Also, the results from the experiment on the wireless communication between multiple devices are presented. The single wireless pebble did not change the value of the averaged heat transfer coefficient, even when the airflow rate changed and the attachment structure of Thermocouple (TC) was changed. Because the averaged heat transfer coefficient did not change significantly in the orientation of the internal heater, it could easily expand into several wireless pebbles. Lastly, the demonstration of three multiple wireless pebbles indicates that our suggested wireless pebbles can greatly help to estimate the local heat transfer coefficient. The results of the validation process will be extended to multiple wireless pebbles in future packed pebble-beds. This research is applicable to a case study for scaled experiments with packed pebble-beds for fluoride salt-cooled high-temperature reactors. We expect that this study will provide an experimental basis for pebbles for those who wish to use a non-invasive wireless device, which offer a powerful approach to investigating heat transfer coefficients in a non-invasive manner and to designing rando

关键词： post-Newtonian approximation   gravitational waves   neutron stars   black holes  

摘要： We revisit the problem of flux-balance equations for isolated post-Newtonian matter systems due to the emission of gravitational waves. In particular we show by a local derivation confined to the system, using the expression of radiation-reaction forces up to the 3.5 PN order, that not only the energy, angular momentum and linear momentum of the system, but also the position of its center of mass, obey some (non-trivial) flux-balance equations. The balance equation for the center-of-mass position completes the description of the secular evolution by gravitational waves of relativistic post-Newtonian isolated matter systems. We then confirm this result by a direct computation of the gravitational-wave fluxes at future null infinity, obtaining the full multipole-moment expansion of the flux associated with the center-of-mass position (probably new with this paper), and rederiving as well the known multipole-moment expansions of the fluxes of energy, angular momentum and linear momentum. We also check our analysis by a direct calculation of radiation-reaction effects in the case of compact binary systems.

关键词： anthropogenic influences   classification   cluster analysis   hydrologic regime   random forest   regionalization   ungaged watersheds   watershed hydrology  

摘要： Watershed hydrology has often focused on modelling studies of individual watersheds, which consider each river system as unique. Classification is an alternative approach that instead focuses on the similarities among different watersheds. Although both supervised and unsupervised hydrologic classifications have been developed, few previous studies have used classification to assess the degree of anthropogenic modification of hydrologic regime. Here, we conducted an unsupervised hydrologic classification of 189 U.S. Geological Survey gages, including 41 minimally impacted gages from the Hydro-Climatic Data Network (HCDN), in the five major interstate river basins in the U.S. state of Alabama. For the natural classification, the most significant predictor variables for cluster membership were related to compressive strength of bedrock, bedrock depth, hydraulic conductivity, elevation, temperature, and soil texture, and several land-cover variables were also significant in the anthropogenic classification. We then developed two random-forest models: one based on all 189 gages using both natural and anthropogenic variables from the Stream-Catchment (StreamCat) dataset and one based on the 41 HCDN gages using natural StreamCat variables only. We used the random-forest models to predict natural and anthropogenic normative hydrologic class for over 158,000 National Hydrography Dataset Plus catchments in the study area. Catchments that changed their class between the natural and anthropogenic classifications can be identified as those that have a large amount of anthropogenic influences on their hydrologic regime, including many catchments on the coast, in the north-western Coastal Plain, in the Interior Low Plateaus, and in the Piedmont. Using unsupervised hydrologic classifications is a promising approach for uncovering the physical processes that affect hydrologic regime. There are also potential applications in river management, including predicting the hydrologic beha

关键词： Biohydrogen production   Immobilised cells   Hydrodynamic characteristics   Minimum fluidization velocity   Terminal velocity   Fluidized bed reactor  

摘要： A mathematical model of minimum fluidization velocity (U-mf ) was developed based on the hydrodynamic characteristics of the fluidized bed reactors (FBR) with immobilised cells attached to activated carbon at thermophilic biohydrogen fermentation. The maximum hydrogen productivity rate of 7.8 mmolH(2) /L.h and hydrogen yield of 2.2 molH(2) /mol of sugar consumed was obtained when the HRT was shortened from 48 h to 6 h. The presence of the immobilised cells enriched the biomass composition in the FBR from 4.9 to 7.1 g VSS/L and maximum energy generated was 58.7 KJ H-2/L.d. The FBR had to be operated at a high U(mf)( )of 0.05-0.44 cm/s and a low terminal velocity of 2.11 cm/s to prevent the immobilised cells from washed out from the FBR, hence achieved an adequate fluidization system. A screening of the microbial population by DGGE revealed that the T. thermosaccharolyticum sp. was dominant for all the HRTs, thereby indicating that this bacterium is resilient towards environmental disturbances. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.