Industrial wastewater containing refractory organics has posed serious threat towards ecology and human health. The activated sludge methods for biological treatment are regarded as the core treatment units for industrial wastewater purification, and bacteria in activated sludge wastewater treatment bioreactors play a central role. A better understanding of microbial communities in sludge can not only provide important guidance in stable operation of wastewater treatment systems, but also improve the removal of pollutants. The clear geographical differences of microbial community diversity among the activated sludge in domestic wastewater treatment processes were revealed by cluster analyses based on abundances of the operational taxonomic units or the genus/phyla assigned by pyrosequencing of 16S rDNA. Each industrial activated sludge system exhibited a unique bacterial community composition, which was clearly distinct from the common profile of bacterial phyla/classes observed in municipal plants. The community structures of activated sludge in coking wastewater treatment plants exhibited a similar community composition at each taxonomic level. The wastewater characteristics are likely to be the major determinant that drives bacterial composition at high taxonomic ranks. The operational parameters have a great impact on the bacterial community structure. In addition, a variety of PAHs-degrading bacteria are identified, and the key enzyme and pathway involved in PAH degradation are characterized. These results have potential applications for strengthening the biological degradation. This review highlights several promising areas to be explored in future.
In this paper, we show that any homogeneous 3-sphere in complex Grassmanians must be a 3-dimensional ρ(SU(2))-orbit in complex Grassmanians. Then we use the representation theory of SU(2) and SU(2)×SU(2) to present a method for the construction of homogeneous 3-spheres in complex Grassmanians.
An HCMU metric is an extremal Kähler metric with singularities on a compact Riemann surface. We prove an existence theorem of non-CSC HCMU metrics with conical singularities, and discuss the energy integral formula for general non-CSC HCMU metrics.
In this paper we present an elementary method to decide whether a system of multivariate polynomials with rational coefficients has a real solution. Based on our discussion of the method, an algorithm is shown, which implies that verifying a system of multivariate polynomials with rational coefficients has a real solution can be completed in finite steps.
The present work constructs the CVaR linear programming model of portfolio with the constraint of generalized entropy. We generate scenarios and probabilities of each asset yield in the portfolio using the K-means clustering method. Then we substitute them into the model. Finally we get the optimal investment weights for various assets. The feasibility of this model is certificated by testing a portfolio which contains eight selected stocks in Shenzhen stock market. Compared with MV model, this model not only incorporates more decentralized investment principle, but also has better performance in the future yields. This model has strong practicability.
Uncertainty principle is one of the fundamental principles in quantum mechanics. In this work, we derive two uncertainty equalities, which hold for all pairs of incompatible observables. We also obtain an uncertainty relation in weak measurement which captures the limitations on the preparation of pre- and post-selected ensemble and holds for two non-Hermitian operators corresponding to two non-commuting observables.
Linear stability of liquid metal flow driven by pressure gradient in a square duct is investigated under the influence of a transverse magnetic field. In this study, the duct walls perpendicular to the magnetic field and the left parallel wall are perfectly conducting,whereas the right parallel wall is insulating. Generalized eigenvalue problem was obtained and solved by 2D-Chebyshev collocation method. Growth rate curves and distributions of perturbations are obtained for different Hartmann numbers. There are two different modes that lead to the linear instability of the flow. The dominant unstable mode alters from one to the other during the increase of Ha from 20 to 21. When Ha≤20, the flow is destabilized by the inflectional instability. When Ha≥21, the instability is caused by a combined effect by the inflection point, shear in side layer, and the non-uniformity of the velocity along the z direction.
Liquid metal, serving as one of the most promising plasma facing components in future fusion reactors, will be controlled by both super annular magnetic field and plasma in high temperature, which will lead liquid metal leaving initial position to fusion core. Three specific instable phenomena are concerned in this paper: 1) sputtering of liquid metal by ion bombardment, 2) splashing of liquid metal under both magnetic and electric fields, and 3) dropping of liquid metal from fusion core onto liquid metal film. The previous researchers had a lot of profound studies on sputtering and droplet dropping onto liquid film,based on which we design new experiments to explore the generation of splash.Our experiments show that liquid metal free surface will gradually grow,and the droplets splash from liquid metal peaks, accompanied by secondary droplet formation.
Recently, Seoane et al. reported two new types of Rh(III)-catalyzed cycloadditons:1) the hetero-[5+2] cycloaddition of 2-hydroxystyrenes with alkynes leading to benzoxepines and 2)the carbo-[3+2] cycloaddition of 2-alkenylphenols with alkynes leading to spirocyclic products. Interestingly,in the two reactions the same catalyst and similar substrates were used but completely different products were obtained. To gain insight into the catalytic mechanisms and to unravel the origins of chemoselectivity differences, we herein present a comparative DFT mechanistic study on the two representative reactions. The results show that both cycloadditions consist of four steps,O—H deprotonation, C—H bond activation, alkyne migratory insertion, and reductive elimination. The reductive elimination step controls the chemoselectivity. When the steric effect is greater than the dearomatization effect, the reaction leads to the five-membered spirocyclic product. Otherwise the reaction produces the seven-membered heterocyclic product. We also found that the regioselectivity of C—H bond activation is determined by the ring tension in the transition states of C—H bond activation and alkyne insertion.
The reactions of tropone (cycloheptatrienone) gave the cycloaddition products frequently, and occasionally substitutions on the olefins bonds also occurred. For 1,2-dimethoxybenzene, previous studies concerned its condensation reactions with the different aldehydes or ketones,more limited to the aryl aldehydes or saturated aliphatic aldehydes and ketones, under the action of acid.We study the condensation reaction of conjugated polyene unsaturated ketone with o-dimethoxybenzene, and the results show that not only the dehydration condensation occurs under the action of acid, but also the interesting shrink ring rearrangement reaction occurs in which a seven-membered ring converts to a six-membered aromatic ring.
Through molecular dynamic simulations, we have investigated the adsorption behavior of cytochrome c on graphene oxide. Results indicate that graphene oxide has a great binding affinity towards cytochrome c. Analyses of root mean square deviation and gyration radius show that there is a large structural damage occurring in system P3 among all the systems. Our study shows that graphene oxide has the ability to deteriorate the native structure of cytochrome c.
Functional polycentricity is a new regional spatial structure in the world in the 21st century and it will show a great economic power under the influence of economic globalization and the new labor division. In this paper we judge whether the functional polycentricity exists in Yangtze River delta (YRD) using the method of social network analysis and functional polycentricity index. Then we calculate the polarization effect and diffusion effect to further certify the former conclusion. The results are given below. YRD gradually shows a trend of coordinated development ——the core cities as the power source combined with other small and medium-sized cities. YRD shows a rank-size distribution under the constraints of the urban hierarchy system, which is the base of a functional polycentricity. The functional polycentricity in YRD is the result of regional polarization effect and diffusion effect. The former effect comes from the large-scale gathering of APS (advanced producer services), and the latter comes from the regional spread of basic manufactures.
Most moonquakes recorded are deep moonquakes that occur at depths of 700-1 200 km, and have a period of about 27 days. We use parallel finite element method and a model with million grids to simulate the tidal stress field and displacement field of the moon numerically. The results show that the maximum shear stress varies with depth. If the moon has a liquid core with a radius of about 700 km or if the moon has a smaller core but the materials at the bottom of lunar mantle are partially molten, the depth of the maximum shear stress will coincide with the depth of the deep moonquakes. The proposition that the moon has a core is lack of sound seismological evidence.Our calculation provides another approach and our result inclines to the suggestion that the moon has a liquid core.
The boundary-element method (BEM) is widely used in the engineering and technology fields. However,applications of BEM in geosciences are relatively rare at the present. In this paper, we first describe the boundary-integral equations in Stokes flow problems with the Green's functions under several boundary conditions. Then, we discuss applications of BEM numerical modeling in plate subduction dynamics and subduction-zone seismic anisotropy. The results indicate that BEM can be used for solving many difficult problems in geodynamics.
A dataset of mesoscale eddies from October 1992 to April 2012 is used to study eddies in South China Sea (SCS). Eddies mainly generate along northeast-southwest direction in SCS and most of them prefer a westward propagation with meridional deflections. Eastward propagating eddies occur more frequently on the southwest of Luzon and the east of Vietnam,and are mainly controlled by the circulation in SCS. Seasonal variations of eddy distribution show inconsistent characteristics in different regions of SCS. Cyclonic (anticyclonic) eddies prefer to occur during spring (winter) on the southwest of Taiwan and southwest of Luzon. While in the northwest of Luzon and southeast of Vitnam,cyclonic eddies prefer winter and anticyclonic eddies more likely in autumn and summer,respectively. Correlation analysis shows that wind stress curl can hardly benefit the formation of eddies directly while the geographic vorticity plays a significant role.
A model for repeat-pass interferometric synthetic aperture radar (InSAR) is proposed to detect deformation based on distributed compressed sensing (DCS). DCS is applied to recover the signals from independent observations of multiple sensors, which are sparse in a transform domain and coherent with each other. We conduct a series of ground-based SAR experiments to compare the recovery performance using different imaging algorithms, such as compressed sensing (CS) and DCS. We find that images recovered by CS and DCS can preserve the phase information of the complex data and have better focus and lower sidelobes than those by Omega-k. Furthermore, by taking advantage of the joint sparsity among multiple scene echoes, DCS joint observation system can further reduce independent observations than CS and achieve scene reconstruction and deformation detection.
Three-dimensional synthetic aperture radar (3D SAR) imaging has the advantage of solving the problems of geometric distortions in 2D SAR imaging, such as layover and top-bottom inversion. The 3D SAR imaging has wide application prospects in military reconnaissance, disaster prediction, resource investigation, and terrain fusion. The 3D SAR imaging method is studied based on beam-forming principle in this work, and digital beam-forming is used in the azimuth and cross-track directions simultaneously to realize the 3D SAR imaging of the observed target. The distance approximation condition for 3D imaging processing is analyzed and its correctness is verified. Finally, the effectiveness and correctness of the model and algorithm are verified by the simulation data.
VideoSAR is a land imaging mode. By using VideoSAR, the radar data can be persistently collected on a target of interest,and then "movie-like" images can be created for an extended period of time. We derive the relation expression between frame rate limited by resolution and radar center frequency, and the VideoSAR images can be formed from both the non-overlapping and overlapping sub-apertures. This work provides a useful theoretic approach for designing the VideoSAR system. The theoretical results are validated through stationary target and moving target simulations at the frame rate of 37.50 fps.
This work aims at the images with intensive corners in the target area and sparse corners in the background area.To extract the edges of target area more accurately and more completely and to eliminate the background, a target edge detection method based on SUSAN operator and corner discriminant factor is proposed. First, the corners of image are extracted by SUSAN operator and the isolated noise points in the image are filtered. Then, target corner discriminant factor is defined for elimination of corners in the background area and preservation of corners in the target area. Finally, according to the similar standard of effectiveness, other edge points are detected based on the target corner standard and the target edges are obtained. A large number of experimental results show that, compared with Canny method, the improved bee colony method, and the improved non-subsampled contourlet modulus maxima method, the proposed method avoids the interference of background area effectively and locate the target area accurately. The obtained edge profile can be connected and is complete with abundant details. It has better subjective visual effect and stronger anti-noise ability with less running time.
A new algorithm of object-tracking based on collaborative representation is proposed. Within Bayes framework,the robust tracker is presented using the observation likelihood model based on the error reconstruction and the updating scheme accounting for occlusion. The error reconstruction is modelled by the l1 norm to tolerate the outlier, and the code coefficients are regularized by collaborative representation. Experimental results show that the proposed algorithm solves the problems of occlusion, scale changing, varying illumination, and cluttered background with high accuracy and robustness.