Relationship between Microbial Activity and the Formation of Polymetallic Concretions in the Central Pacific Ocean

Using the concept of the interactive water rock- microbe system of ocean floor, the microbialmineralization of ocean-floor polymetallic concretions in the central Pacific Ocean has been studied for the firsttime. Through the correlation and study of the microbial activity and formation mechanism of polymetallicconcretions, the microbial and chemical processes for. transforming mineralizing materials and the observationand determination of the concentration of mineralizing material in the system and the variation ofenvironmental parameters, this paper reveals the reaction rate and evolutionary direction of mineralizing com-ponents caused by microbial activity, expounds the microbial mineralization mechanism and formation modelof polymetallic concretions from the angle of microbial geochemical action, and suggests a threefold division ofthe microbial mineralization stages

Inhibition mechanisms of ammonia and sulfate in high-solids anaerobic digesters for food waste treatment: Microbial community and element distributions responses

The horizontal flow anaerobic digester indicated that high ammonia (2923 mg/L) and SO42-(3653 mg/L)would influence the performance of methane production with food waste as substrates.Therefore,bottle anaerobic digestion reactors were carried out to investigate the effect of ammonia/sulfate concentrations on the methane production.Experimental results manifested that the anaerobic digesters with an ammonia concentration of 3500 mg/L or sulfate of 1600 mg/L showed the best performance of methane production,with an average methane yield of 0.32 and 0.33 L (g VS)^(-1)d^(-1),respectively.Specifically,a higher ammonia (6500 mg/L) or sulfate (1600-3500 mg/L) level hindered the bioconversion of C from liquid to gas phase (2.68%or 1.73%CH_(4)-Gas,respectively),while insignificantly for the hydrolyzation of C and N from solid to liquid phase.Similar to sulfate,high ammonia nitrogen seriously inhibited the methanation process,leading to a significant carbon accumulation in the anaerobic reactor,especially for propionic acid.The predominant archaea Methanosarcina at genus level indicated that aceticlastic methanogenesis was the major methanogenic pathway.Meanwhile,high ammonia level suppressed the activity of Methanosarcina,while modest sulfate improved H_(2)-consuming methanogens activity.A large fraction of unclassified bacteria within the Firmicutes (43.78%-63.17%) and Bacteroidetes (24.20%-33.30%) phylum played an important role in substrates hydrolysis.

FEM COUPLING FIELD ITERATION AND ITS CONVERGENCE FOR A GMM ACTURATOR

The coupling iteration (CI) of the finite element method(FEM) is used to simulate the magnetic and mechanical characteristics for a GMM actuator. The convergent ability under different prestress and different load types is investigated. Then the calculated deformations are compared with the experimental values. The results convince that the CI of FEM is suitable for the simulation of energy coupling and transformation mechanism of the GMM. At last, the output deformation properties are studied under different input currents, showing that there is a good compromise between good linearity and large strain under the prestress 6 MPa.

FLOW AROUND A CIRCULAR CYLINDER USING A FINITE-VOLUME TVD SCHEME BASED ON A VECTOR TRANSFORMATION APPROACH

Flows around a circular cylinder displaying an unsteady vortex shedding process at the Reynolds numbers of 1000,3900 and 1×104 are studied using a finite-volume Total Variation Diminishing（TVD） scheme for solving the Unsteady Reynolds-Averaged Navier-Stokes（URANS） equations.An Elemental Velocity Vector Transformation（EVVT） approach is proposed for the local normal and tangential velocity transformation at the interfaces of main and satellite elements.The presented method is validated by comparing with the available experimental data and numerical results.It is shown that the two-dimensional TVD finite volume method with the Renormalization Group（RNG） turbulence model can be used to determine hydrodynamic forces and captures vortex shedding characteristics very well.

Regular Posit ion-Oriented Method for Mesh Smoothing

Mesh smoothing is an essential technique for the improvement of mesh quality in finite element analysis,due to the fact that mesh quality has a large impact on the convergence of the computational scheme and the accuracy of the numerical results.A novel mesh smoothing method based on regular-position-guided operations is presented in this paper.The method introduced here contains two main stages:The first stage computes the regular position of each vertex based on the shape of the element and conducts regular-position-oriented-based element transformations independently;the second stage determines the finial position of each vertex according to its surrounding elements with an assembly strategy.This method is not limited to planar triangular mesh,but applicable to surface polygonal mesh.Numerical experiments on various mesh models demonstrate the effectiveness and potential of this method.