Biophysical controls on light response of net CO<inf>2</inf>exchange in a winter wheat field in the North China Plain

To investigate the impacts of biophysical factors on light response of net ecosystem exchange (NEE), CO2 flux was measured using the eddy covariance technique in a winter wheat field in the North China Plain from 2003 to 2006. A rectangular hyperbolic function was used to describe NEE light response. Maximum photosynthetic capacity (Pmax) was 46.6±4.0 μmol CO2 m-2 s-1 and initial light use efficiency (α) 0.059±0.006 μmol μmol-1 in April-May, two or three times as high as those in March. Stepwise multiple linear regressions showed that Pmax increased with the increase in leaf area index (LAI), canopy conductance (gc) and air temperature (Ta) but declined with increasing vapor pressure deficit (VPD) (P25°C or VPD>1.1-1.3 kPa, NEE residual increased with the increase in Ta and VPD (P<0.001), indicating that temperature and water stress occurred. When gc was more than 14 mm s-1 in March and May and 26 mm s-1 in April, the NEE residuals decline disappeared, or even turned into an increase in gc(P<0.01), implying shifts from stomatal limitation to non-stomatal limitation on NEE. Although the differences between sunny and cloudy sky conditions were unremarkable for light response parameters, simulated net CO2 uptake under the same radiation intensity averaged 18% higher in cloudy days than in sunny days during the year 2003-2006. It is necessary to include these effects in relevant carbon cycle models to improve our estimation of carbon balance at regional and global scales. © 2014 Tong et al

Vibration Parameter Optimization of a Linear Vibrating Banana Screen Using DEM 3D Simulation

In this paper, the effects of vibration parameters of a banana screen, i.e. frequency, amplitude and vibration direction angle, on the screening efficiency per unit time were studied using the discrete element method (DEM). The simulations were validated according to data collected from an experimental prototype screen. Functional relationships between vibration parameters and screening efficiency per unit time are presented. The results showed that the screening efficiency per unit time first displays an increase and later a decrease when the frequency, amplitude or vibration direction angle increased respectively. Vibration parameter optimization was also investigated, using an orthogonal experiment. Based on the banana screen model, it can be concluded that when the frequency is 22 Hz, the amplitude is 2.2 mm and the vibration direction angle is 39°, the screening efficiency of a banana screen is optimal

Electro-spraying and catalytic combustion characteristics of ethanol in meso-scale combustors with steel and platinum meshes

© 2018 Elsevier Ltd An experimental study on electro-spraying and catalytic combustion of ethanol at meso-scale is carried out. The electro-spraying process of ethanol is visualized and four typical spraying modes are identified. Based on droplet size measurements by a Phase Doppler Anemometer, the spraying at the cone-jet or multi-jet mode is suitable for meso-scale combustion. Two meso-combustors without and with the platinum catalyst, denoted as combustor A and combustor B, respectively, are designed to conduct the comparative experiments. The flame temperature at the cone-jet mode is higher than those at other modes when equivalence ratio φ = 1.0, and for the combustor with catalyst, fuel-lean conditions are favorable for stable combustion. It is also found that the carbon monoxide mole fraction in the exhaust decreases by at least 25% due to the catalytic effect. At the cone-jet electro-spraying mode, the combustion efficiencies of ethanol reach the highest value for both combustor A and combustor B due to smaller droplet size and more uniform droplet size distribution. Under the same conditions, combustion efficiency of ethanol can be improved by 4.5% for combustor B, which proves that the platinum catalyst can accelerate the decomposition of ethanol

Interactions of soil moisture and plant community properties in meadows restored from abandoned farmlands on the Sanjiang Plain, China

Abstract Soil moisture is a major driving force of plant community succession in restored meadows. Existing studies mainly focus on diversity-productivity relationships. However, studies which determine the effects of soil moisture on the plant community properties in restored meadows are lacking. In this study, we conducted a chronosequence analysis of the interactions between soil water content variation and plant community properties in meadows following passive restoration (3-, 5-, 9-, 14-, 17-, 21-year restoration) of abandoned farmlands on the Sanjiang Plain, China. Results showed that the plant community was characterized by ruderal plants in the initial year of succession, and then by perennial plants such as Calamagrostis angustifolia and Carex spp. in older restored meadows. Similarity of restored community to target site increased across succession time whereas species diversity gradually decreased. Plant height, coverage and biomass increased with restoration time, with plant density being the exception. The community height, coverage and root/shoot ratio were positively related to the water content in the surface soil layer (0–10 cm). Conversely, plant density was significantly and negatively related with soil moisture at 0–10 cm soil depth. Plant diversity (Shannon index, Richness index and evenness) was closely correlated to soil water content at the soil depth of 0–10 cm. Our findings indicate that vegetation of cultivated meadows could be effectively restored by passive restoration. Change of plant species diversity is an especially important response to hydrological recovery in restored meadows on the Sanjiang Plain

The observation of a positive magnetoresistance and close correlation among lattice, spin and charge around TC in antipervoskite SnCMn3

The temperature dependences of magnetization, electrical transport, and thermal transport properties of antiperovskite compound SnCMn3 have been investigated systematically. A positive magnetoresistance (~11%) is observed around the ferrimagnetic-paramagnetic transition (TC ~ 280 K) in the field of 50 kOe, which can be attributed to the field-induced magnetic phase transition. The abnormalities of resistivity, Seebeck coefficient, normal Hall effect and thermal conductivity near TC are suggested to be associated with an abrupt reconstruction of electronic structure. Further, our results indicate an essential interaction among lattice, spin and charge degrees of freedom around TC. Such an interaction among various degrees of freedom associated with sudden phase transition is suggested to be characteristic of Mn-based antiperovskite compounds.Comment: 13 pages, 5 figure

Environment Sensing Considering the Occlusion Effect: A Multi-View Approach

In this paper, we consider the problem of sensing the environment within a wireless cellular framework. Specifically, multiple user equipments (UEs) send sounding signals to one or multiple base stations (BSs) and then a centralized processor retrieves the environmental information from all the channel information obtained at the BS(s). Taking into account the occlusion effect that is common in the wireless context, we make full use of the different views of the environment from different users and/or BS(s), and propose an effective sensing algorithm called GAMP-MVSVR (generalized-approximate-message-passing-based multi-view sparse vector reconstruction). In the proposed algorithm, a multi-layer factor graph is constructed to iteratively estimate the scattering coefficients of the cloud points and their occlusion relationship. In each iteration, the occlusion relationship between the cloud points of the sparse environment is recalculated according to a simple occlusion detection rule, and in turn, used to estimate the scattering coefficients of the cloud points. Our proposed algorithm can achieve improved sensing performance with multi-BS collaboration in addition to the multi-views from the UEs. The simulation results verify its convergence and effectiveness