Modelling of the enar-field distribution of pollutants from a coastal outfall subject to tidal currents

Pollutant distribution from a coastal outfall is studied accounting for tidal currents. The problem is solved using k-eps model. The constants in the logarithmic law for vertical velocity profile in the bbl (bottom boundary layer) are obtained by processing experimental data from a current profiler. The near-field distribution of pollutant concentration at different distances from the diffusor are obtained for different times, in terms of ambient flow velocity and outfall discharge characteristics

Crowdsourcing in China: Exploring the Work Experience of Solo Crowdworkers and Crowdfarm Workers

Recent research highlights the potential of crowdsourcing in China. Yet very few studies explore the workplace context and experiences of Chinese crowdworkers. Those that do, focus mainly on the work experiences of solo crowdworkers but do not deal with issues pertaining to the substantial amount of people working in ‘crowdfarms’. This article addresses this gap as one of its primary concerns. Drawing on a study that involves 48 participants, our research explores, compares and contrasts the work experiences of solo crowdworkers to those of crowdfarm workers. Our findings illustrate that the work experiences and context of the solo workers and crowdfarm workers are substantially different, with regards to their motivations, the ways they engage with crowdsourcing, the tasks they work on, and the crowdsourcing platforms they utilize. Overall, our study contributes to furthering the understandings on the work experiences of crowdworkers in China

GWAS Identifies Novel Susceptibility Loci on 6p21.32 and 21q21.3 for Hepatocellular Carcinoma in Chronic Hepatitis B Virus Carriers

Genome-wide association studies (GWAS) have recently identified KIF1B as susceptibility locus for hepatitis B virus (HBV)–related hepatocellular carcinoma (HCC). To further identify novel susceptibility loci associated with HBV–related HCC and replicate the previously reported association, we performed a large three-stage GWAS in the Han Chinese population. 523,663 autosomal SNPs in 1,538 HBV–positive HCC patients and 1,465 chronic HBV carriers were genotyped for the discovery stage. Top candidate SNPs were genotyped in the initial validation samples of 2,112 HBV–positive HCC cases and 2,208 HBV carriers and then in the second validation samples of 1,021 cases and 1,491 HBV carriers. We discovered two novel associations at rs9272105 (HLA-DQA1/DRB1) on 6p21.32 (OR = 1.30, P = 1.13×$10^{−19}$) and rs455804 (GRIK1) on 21q21.3 (OR = 0.84, P = 1.86×$10^{−8}$), which were further replicated in the fourth independent sample of 1,298 cases and 1,026 controls (rs9272105: OR = 1.25, P = 1.71×$10^{−4}$; rs455804: OR = 0.84, P = 6.92×$10^{−3}$). We also revealed the associations of HLA-DRB1*0405 and 0901*0602, which could partially account for the association at rs9272105. The association at rs455804 implicates GRIK1 as a novel susceptibility gene for HBV–related HCC, suggesting the involvement of glutamate signaling in the development of HBV–related HCC

Etude numérique d'écoulements turbulents tridimensionnels dans un habitacle (couplage avec les transferts de chaleur et de masse)

Dans cette étude, 3 sortes de ventilation 3D ont été considérées: ventilation isotherme, ventilation avec transfert de chaleur ou de masse et ventilation avec transfert de chaleur et de masse. L'un des buts est de valider les modèles de turbulence pour leur capacité à simuler des écoulements de ventilation et d'évaluer la fiabilité de ces modèles pour la prédiction correcte de la ventilation générale. L'objectif à long terme est d'évaluer la possibilité d'employer la CFD pour prédire les écoulements de ventilation à l'intérieur d'une cabine spatiale dans les conditions d'apesanteur. Le modèle de turbulence SST k-? donne la meilleure prédiction pour un grand choix d'écoulements de ventilation. Une étude préliminaire d'un écoulement de ventilation complexe avec transfert de chaleur et de masse montre que l'environnement de microgravité a une influence très importante sur l'écoulement de l'air, la distribution de température et de polluant à l'intérieur de l'habitacle.In this study, three kinds of 3D ventilation problems have been considered: isothermal ventilation, ventilation with coupled heat or mass transfer and ventilation with simultaneous heat and mass transfer. The focus is to validate the turbulence models and modeling methods for their capability of simulating such ventilation flows and to evaluate their performances for the correct prediction of the above general ventilation problems. The long-term objective is to evaluate the possibility of using CFD to investigate the ventilation flows and the associated heat and mass transfer processes inside a spacecraft cabin under microgravity. It is found that the SST k-? turbulence model yields the best overall prediction for a wide range of ventilation flows. A preliminary study of a ventilation flow under normal-g and zero-g conditions shows that the microgravity environment has very strong influences on the air flow pattern and temperature and contaminant distributions inside the cabin.AIX-MARSEILLE1-Inst.Médit.tech (130552107) / SudocAIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Dynamic optimization of tracked vehicle power train based on torsional vibration analysis

Aiming at the vehicle power train, system dynamic optimization is profoundly studied based on the system torsional vibration characteristics analysis. First, based on the concentrated mass method, the general torsional vibration model of vehicle power train is established and solved after parameters’ (inertia, stiffness, and damping) matrix and mathematic constraint conditions are acquired. Furthermore, both free vibration and forced vibration characteristics are analyzed. Second, the effects of the coupling stiffness on the dynamics behaviors of power train are thoroughly analyzed. The sensitivity analysis procedure is explored. And sensitivity models of both free and forced vibration feature parameters are deduced. Finally, dynamic optimization theory model and program are constructed based on genetic algorithm. The optimization results indicate that the proposed optimization method could contribute to the sharp attenuation of system torsional vibration

Integrated Carbon Footprint and Economic Performance of Five Types of Dominant Cropping Systems in China’s Semiarid Zone

Crop production requires large areas of land and makes an important contribution to greenhouse gas emissions. Cleaner production of all crop types could be of great significance to realizing carbon neutrality as soon as possible. The present study adopted life cycle assessment (LCA) combined with the profit accounting method of input-output to compare the differences in greenhouse gas emissions in the entire life cycle of apple (Malus pumila Mill.), grain maize (Zea mays L.), wheat (Triticum aestivum L.), silage maize (Zea mays L.), and alfalfa (Medicago sativa Linn.) production in eastern Gansu Province with three functional units, including per ha of land, per ton of product, and per 10,000 yuan of output value. The results showed that apple had the largest carbon footprint per ha. Wheat had the largest carbon footprint per ton of product and per 10,000 yuan output. The results of LCA inventory sensitivity analysis showed that the main sources of greenhouse gas emissions for all crops were the production process of agricultural materials such as chemical fertilizer, machinery, and agricultural film. In particular, the excessive input of chemical fertilizer was the driving factor resulting in greenhouse gas emissions. Based on the study results, this paper also puts forward certain suggestions on the future land use of the cropping systems in the study area

Torsional Vibration Attenuation Characteristics and Stiffness Identification of Flexible Coupling in Vehicle Power Train

Flexible coupling is one of the crucial components for vibration attenuation used in vehicle power train. Vibration attenuation characteristics and stiffness identification of flexible coupling are profoundly studied aiming at one vehicle power train. Firstly, the dynamics model of each crucial transmission component in power train is constructed. And the torsional vibration model of power train is established according to the concentrated mass method. The effects of coupling stiffness on vibration responses of power train are thoroughly analyzed based on system concentrated mass dynamics model. Secondly, the sensitivities of natural frequency and main forced vibration response parameters are calculated. The coupling stiffness is proved to be a sensitive parameter. Finally, taking the Geislinger coupling as an example, the damping and stiffness characteristics are acquired according to the parameter identification method based on the quantity of test data. The results provide the theory basis for the dynamics optimization of power train

Hydrodeoxygenation of aliphatic acid over NiFe intermetallic compounds: Insights into the mechanism via model compound study

Hydrodeoxygenation (HDO) is a promising way to produce the second generation bio-diesel from aliphatic acid based biomass. Compared with the monometallic Ni/SiO2, appropriate introduction of Fe results in the complete conversion of lauric acid and nearly 100% yield of alkane as well as satisfactory stability on conversion. Further study on mechanism shows that the NiFe intermetallic compounds (IMC) catalyst promotes the ratedetermining step, i.e., C11H23COOH → C11H23CHO, which is attributed to the synergistic effect of Ni-Fe bimetallic sites according to the characterization and calculation. For one thing, strong spin polarization enhances the interaction between Fe sites and aliphatic acid, and the subsequent dissociation of C-OH bond indicated by the DOS and transition state analysis. For another, dissociation of H2 on Ni site is promoted because of the higher charge density around Ni in the IMC according to the in-suit FTIR and Bader analysis. However, with the repeated use of the catalyst, the selectivity to alkane decreased gradually, which is ascribed to the oxidation of metal Ni-Fe bimetallic sites. This demonstrates that the reduced Ni-Fe bimetallic sites rather than the oxidized ones are the active phases in the HDO of aliphatic acid to produce alkanes with the NiFe IMC

YOLOv4-MN3 for PCB Surface Defect Detection

Surface defect detection for printed circuit board (PCB) is indispensable for managing PCB production quality. However, automatic detection of PCB surface defects is still a challenging task because, even within the same category of surface defect, defects present great differences in morphology and pattern. Although many computer vision-based detectors have been established to handle these problems, current detectors struggle to achieve high detection accuracy, fast detection speed and low memory consumption simultaneously. To address those issues, we propose a cost-effective deep learning (DL)-based detector based on the cutting-edge YOLOv4 to detect PCB surface defect quickly and efficiently. The YOLOv4 is improved upon with respect to its backbone network and the activation function in its neck/prediction network. The improved YOLOv4 is evaluated with a customized dataset, collected from a PCB factory. The experimental results show that the improved detector achieved a high performance, scoring 98.64% on mean average precision (mAP) at 56.98 frames per second (FPS), outperforming the other compared SOTA detectors. Furthermore, the improved YOLOv4 reduced the parameter space of YOLOv4 from 63.96 M to 39.59 M and the number of multiply-accumulate operations (Madds) from 59.75 G to 26.15 G