Experiments on Downstream Fining of Gravel.?II: Wide and Sandy Runs

This is the second of two papers about experiments on downstream fining of gravel. Here we briefly summarize the complete series of runs described in the first paper, where the influence of sediment feed rate was evaluated in a narrow channel. We then present results for variation in two more conditions: sand content and channel width. The experiments were carried out in a long flume with an effective 40-m-long test section, with two different widths of 0.3 and 2.7 m. In addition, two sediment mixtures were used with different sand contents (i.e., 33 and 55%) with the remainder being gravel. The following results were obtained. The increase in channel width allowed the formation of transverse topography, enhanced the development of sediment patches, and increased the fining rate of gravel for D50 and finer percentiles. Increasing sand content rendered the long profile of the bed much more concave, caused marked patch development, and most notably increased the fining rate for all percentiles of gravel-sized bed material.     

Assessing Multicomponent DNAPL Biostabilization Potential.?II: Aroclor 1242

Aroclors are dense nonaqueous-phase liquids (DNAPLs) composed of polychlorinated biphenyls, which are common subsurface contaminants. Because complete remediation of Aroclor is very difficult, biostabilization may offer an alternative where risk reduction can be achieved without destruction of the DNAPL mass. The potential for aerobic in situ biostabilization of Aroclor 1242 was evaluated using laboratory protocols similar to those described in the companion paper. Total microbial concentrations increased and stabilized in both mixed and unmixed systems, while the respiring cells did not stabilize in either system. After 100 days, the DNAPL in mixed biometers was depleted in dichlorobiphenyls; the DNAPL composition in unmixed biometers did not change significantly. The total aqueous polychlorinated biphenyl concentration was lower in the unmixed than mixed biometers; both were below the predicted equilibrium concentration. After 100 days, the chronic toxicity of the aqueous phase to Cerodaphnia was greater in the biotreated systems than in the unbiotreated systems. The results indicate that aerobic microbiological activity may be insufficient to fully stabilize Aroclor in the subsurface, in contrast to the clear biostabilization potential of coal tar.     

Fiber Element for Cyclic Bending and Shear of RC Structures.?II: Verification

The fiber beam element with shear modeling developed in the companion paper is calibrated and verified by comparison with test data. The verification is carried out for the material constitutive behavior and for single beam and column elements using available test results from literature. A structural analysis of a shear sensitive viaduct pier subjected to ground input motion is presented. Details of the algebraic expressions used for the concrete and steel constitutive behaviors are provided.     

Spatial Postbuckling Analysis of Nonsymmetric Thin-Walled Frames.?II: Geometrically Nonlinear FE Procedures

In a companion paper, transformation rules of Rodriguez' finite rotations and semitangential rotations are derived, respectively, and their rotational properties are discussed. The shear deformable displacement field of nonsymmetric thin-walled space frames is introduced based on semitangential rotations and the potential energy corresponding to semitangential internal moments are consistently derived using the proposed displacement field. In this paper, for spatial postbuckling analysis of thin-walled space frames, the elastic strain energy including bending-torsion coupled terms and shear deformation effects is derived using transformations of displacements and stress resultants defined at the centroid and the centroid-shear center, respectively. Tangent stiffness matrices of the frame element are derived by using Hermitian polynomials including shear effects, and an improved corotational formulation is presented by separating rigid body motions and pure deformations from incremental displacements, calculating the corresponding generalized forces and updating direction cosines of frame elements. In addition, a scheme to evaluate load correction stiffness matrices due to the off-axis loading and conservative moments is addressed. FE solutions for the postbuckling are presented and compared with results by ABAQUS shell models.     

Experimental and Numerical Modeling Studies on Production of Mg by Vacuum Silicothermic Reduction of CaO·MgO

The silicothermic reduction to magnesium is now intensively used in industry. In this article, an experimental and numerical modeling study on the reduction process in the single briquette and in an industrial retort was carried out. The experimental study was first conducted, and the experimental results indicated that both the thickness (from 17~19 to 3~4 mm) and heating temperature (from 1323 K to 1473 K [1050 °C to 1200 °C]) play significant roles in the reduction process in the single briquette. A kinetics analysis on the experimental data under the conditions of 3 to 4 mm briquette and different heating temperature indicated that the magnesium reduction reaction is controlled by the phase interface model before an extent and is controlled by the diffusion model after that. Then, the numerical model was developed according to the experimental data and used to predict the magnesium reduction performances in retort. The model results were validated in good agreement with the industrial data. The model prediction indicated that the magnesium reducing promotes inside layer by layer, and the reducing in the retort concentrates in one or two layers. It is concluded that the reduction process in retort is controlled by the heat transfer and reaction itself, the reaction heat needed for briquette is large, and the heat transfer becomes the main limiting factor.     

PAC-Membrane Filtration Process.?I: Model Development

Adsorption is modeled when powdered activated carbon (PAC) is applied in continuous-flow reactors followed by membrane filtration units operated without carbon wastage between backwash events. Four reactor configurations are studied: (1) A membrane reactor dosed with a step input of PAC; (2) a continuous-flow stirred tank reactor dosed with a step input of PAC and followed by a membrane reactor; (3) a plug-flow reactor dosed with a step input of PAC and followed by a membrane reactor; and (4) a membrane reactor dosed with a pulse input of PAC at the beginning of the filtration cycle. A steady-state operation is considered to describe the adsorption process through the continuous-flow stirred tank reactor and plug-flow reactor, whereas adsorption in the membrane reactor is modeled as a non-steady-state process. Adsorption kinetics is assumed to occur by homogeneous surface diffusion, and adsorption equilibrium is described with the Freundlich isotherm model. Analytical solutions of the homogeneous surface diffusion model with no external mass transfer limitation are used to evaluate adsorbate concentrations in the solid phase as a function of time. Part II of this study presents model simulations and verification with experimental data obtained in a bench-scale apparatus.     

Finite Strain, Anisotropic Modified Cam Clay Model with Plastic Spin.?II: Application to Piezocone Test

Micromechanical and anisotropic behavior of soils is analyzed using the plastic spin and anisotropic modified Cam clay model (AMCCM) in an updated Lagrangian reference frame. The micromechanical behavior of soils is especially important in large strain problems. The anisotropic behavior inherently exists in soils. This study uses AMCCM with the plastic spin to evaluate the pore pressure response in cone penetration tests. This test is a typical example for large strain problems. The analytical results indicate that the predicted pore pressure is closer to the measured one when the plastic spin is incorporated in AMCCM. It also shows that the micromechanical behavior is paramount in the vicinity of the cone tip where large strains and rotations occur.     

Studies on the Properties of PT-MN Ceramics

ＳｔｕｄｉｅｓｏｎｔｈｅＰｒｏｐｅｒｔｉｅｓｏｆＰＴＭＮＣｅｒａｍｉｃｓＷａｎｇＣｈｅｎｇｊｉａｎ（王成建），ＸｉａｏＭｉｎｇｓｈａｎ（肖鸣山），ＺｈａｎｇＣｈｅｎｇｊｕ（张承琚）ＬａｎＪｉａｎｓｈｅｎｇ（兰建胜）（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓ...     

Spatial Postbuckling Analysis of Nonsymmetric Thin-Walled Frames.?I: Theoretical Considerations Based on Semitangential Property

To present the spatial postbuckling analysis procedures of shear deformable thin-walled space frames with nonsymmetric cross sections, theoretical considerations based on the semitangential rotation and the semitangential moment are presented. First, similarity and difference between Rodriguez' rotations and semitangential rotations are addressed. Next, the improved displacement field is introduced using the second-order terms of semitangential rotations and rotational properties of off-axis loads and conservative moments are discussed based on the proposed displacement field. Finally, it is deduced that the resulting potential energy due to stress resultants corresponds to semitangential bending and torsional moments. In a companion paper, the elastic strain energy including bending-torsion coupled terms and shear deformation effects is newly derived and a clearly consistent finite-element procedure is presented based on the updated Lagrangian corotational formulation. Tangent stiffness matrices of the thin-walled space frame element are derived using Hermitian polynomials considering shear deformation effects, and a new scheme to evaluate incremental member forces and load correction stiffness matrices due to off-axis loads is presented and its physical meaning is addressed. Furthermore, finite-element solutions displaying spatial postbuckling behaviors are evaluated and compared with available solutions.     

Studies on Electrolytic Codeposition of Lanthanum-Cobalt in Urea Melt

ＳｔｕｄｉｅｓｏｎＥｌｅｃｔｒｏｌｙｔｉｃＣｏｄｅｐｏｓｉｔｉｏｎｏｆＬａｎｔｈａｎｕｍ－ＣｏｂａｌｔｉｎＵｒｅａＭｅｌｔＱｉｕＫａｉｒｏｎｇ（丘开容），ＹａｎｇＱｉｑｉｎ（杨绮琴）（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＺｈｏｎｇｓｈａｎＵｎ...     

Studies on Expert System for Extraction of Rare Earths

An expert system has been developed,using LISP,for extraction of rare earths.The expert system was de-signed to mimic the deduction of chemists for rare earth separation.The knowledge base consists mainly of threeparts:(1)the extractant solvents common use and the separations of the individual rare earths;(2)the recom-mendation of process for the separation of mixed rare earths with extraetant P507;(3)the evaluation of econo-my for planning to build a rare earth factory The knowledge base of this system was organized as files includingframe files and rules.In addition,removing of the rules can be carried out in the file compiling window under theLISP environment.Both the forward-chaining and the reverse chaining were used simultaneously as the infer-ence strategies.The machine used was a microcomputer IBM PC-XT.     

Temperature Programmed Reduction Studies on CeO2-Containing Catalysts

Temperature programmed reduction (TPR) study was carried out for CeO2/A12O3 and CeO2/ZrO2 catalysts to evaluate oxygen storage property induced by a facile redox cycling of Ce ion. The CeO2/ZrO2 catalyst possesses excellent oxygen storage activity at 373 K after reduction above 1173 K although the oxygen storage of CeO2/Al2O3 catalyst after reduction above 1173 K is poor because of the formation of CeAlO3. Consequently, the oxygen storage on the CeO2/ZrO2 catalyst smoothly occurs from low temperatures when the catalyst is reduced even at high temperatures.     

Review of Studies on Rare Earth against Plant Disease

Agricultural application of rare earth (RE) has been generalized for several decades, and it is involved in crops, vegetables and stock raising in China. However, all the researches on RE mainly focus on the fields such as plant physiological activity, physiological and biochemical mechanism, sanitation toxicology and environmental security. Plant protection by using RE and the induced resistance of plant against diseases were summarized. The mechanism of rare earth against plant disease is highlighted, which includes following two aspects. First, RE elements can control some phytopathogen directly and reduce its virulence to host plant. Another possibility is that RE elements can affect host plant and induce the plant to produce some resistance to disease.     

Flutter and Buffeting Analysis.?I: Finite-Element and RPE Solution

A finite-element formulation is developed for analyzing flutter instability and buffeting response of long-span bridges and their interaction. The flutter derivatives, instead of the indicial functions used by previous researchers, are applied in the random parametric excitation (RPE) analysis. This application makes finite-element formulation possible and results in much less computational effort in RPE analysis than those of previous analyses. With the finite-element program developed in the present study, as many modes as desired can be easily included in the flutter and buffeting analyses. Users have the choice of RPE or eigenvalue method for flutter analysis and RPE or spectral method for buffeting analysis.     

Studies on the Voltammetric Behaviors of Rare Earth Ions-Amino Acids

The voltammetric behaviors of rare earth ions-amino acids were studied.The reduction potential of Eu~(3+)was shifted positively and the peak separation of the cathodic and anodic peaks in cyclic voltammogram de-creased when a certain amino acid was added to Eu~(3+) solution.Experimental results showed that Eu~(3+) was re-duced by way of forming complexes with amino acids which were adsorbed on mercury electrode surface.Whenhistidine and formaldehyde existed simultaneously in the solution containing Eu~(3+),a well-defined reversiblecatalytic prewave of Eu~(3+) was obtained.Meanwhile,the reduction current of formaldehyde increased greatlywith the addition of histidine.The mechanism was studied.Several other rare earth ions and amino acids werealso studied preliminarily.     

Studies on Rare Earth Complexes with Ethylene-1,2-Dioxydiacetic Acid

ＳｔｕｄｉｅｓｏｎＲａｒｅＥａｒｔｈＣｏｍｐｌｅｘｅｓｗｉｔｈＥｔｈｙｌｅｎｅ－１，２－ＤｉｏｘｙｄｉａｃｅｔｉｃＡｃｉｄＸｕｅＷｅｎ－Ｍｅｉ；（薛文梅）；ＣｕｉＹｕ－Ｘｉｎ；（崔育新）；ＹａｎｇＲｕ－Ｄｏｎｇ；（杨汝栋）（ＤｅｐａｒｔｍｅｎｔｏｆＣ...     

Studies on the Interaction between Yttrium and Human Erythrocyte Membrane

ＳｔｕｄｉｅｓｏｎｔｈｅＩｎｔｅｒａｃｔｉｏｎｂｅｔｗｅｅｎＹｔｔｒｉｕｍａｎｄＨｕｍａｎＥｒｙｔｈｒｏｃｙｔｅＭｅｍｂｒａｎｅＬｉＲｏｎｇｃｈａｎｇ（李荣昌）；ＤｕａｎＧｕａｎｇｈｅ（段广河）；ＬｉｕＭｅｉ（柳梅）；ＷａｎｇＫｕｉ（王夔）（Ｄｅｐａ...     

In-Situ Synchrotron Diffraction Studies on Transformation Strain Development in a High-Strength Quenched and Tempered Structural Steel—Part II. Martensitic Transformation

In-situ synchrotron diffraction studies on the kinetics of phase transformation and transformation strain development during bainitic transformation were presented in part I of the current article. In the current article, in-situ phase transformation behavior of a high-strength (830 MPa yield stress) quenched and tempered S690QL1 [Fe-0.16C-0.2Si-0.87Mn-0.33Cr-0.21Mo (wt. pct)] structural steel, during continuous cooling and under different mechanical loading conditions to promote martensitic transformation, has been studied. Time–temperature–load resolved 2D synchrotron diffraction patterns were recorded and used to calculate the phase fractions and lattice parameters of the phases during heating and cooling cycles under different loading conditions. In addition to the thermal expansion behavior, the effects of the applied stress on the elastic strains during the martensitic transformation were calculated. The results show that small tensile stresses applied at the transformation temperature do not change the kinetics of the phase transformation. The start temperature for the martensitic transformation increases with the increasing applied tensile stress. The elastic strains are not affected significantly with the increasing tensile stress. The variant selection during martensitic transformation under small applied loads (in the elastic region) is weak.     

XPS Studies on Rare Earth Oxide LSCO／YSZ Electrodes

The X-ray diffraction spectra and X-my photoelectron spectroscopy were measured for Sr-doped Lal-xSrx CoO3 materials with perovskite structure prepared by the solid-state reaction method. The influence of heat-treatment tempera-ture on the average crystal size of Lal-xSrx CoO3 was studied. The surface chemical states of Lal-xSrxCoO3 cathodes with different Sr-doped content were discussed. The experimental results show that average crystal size of Lal-xSrxCoO3 under the condition of heat-treatment in the range of 900- 1200℃ is larger than that at other temperatures, which is of benefit to forming porous electrodes. When La is replaced by Sr gradually, the oxygen vacancy concentration increases. It is of benefit to enhancing the transport property of oxygen ion.