Effects of rare earth on inclusions and corrosion resistance of 10PCuRE weathering steel

The types,morphologies and distributions of nonmetallic inclusions in Cu-P weathering steels with and without rare earth were analyzed through a quantitative image analyzer,scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)attached to SEM.Solid-soluble content of rare earth in the steels was analyzed by non-aqua electroanalysis and ICP.The results showed that rare earth modified the types and the morphologies of inclusions in the weathering steels.The small spherical rare earth oxysulfides and rare earth sulphides replaced the elongated MnS inclusions in the RE weathering steels.The rare earth inclusions dispersedly distributed and most inclusions were smaller than 2 μm in size.The optimum content of RE was 0.0065%-0.016% for 10PCuRE weathering steels containing about0.002% oxygen and 0.004% sulfur.Solid-soluble content of rare earth in steels was(14-20)x 10-6,which can act as a micro-alloying element.The corrosion resistance of 10PCuRE weathering steels and Q235 were studied by dry-wet cyclic immersion test.Their corrosion rates were obtained respectively.The polarization curves and pitting corrosion behaviors of weathering steels with and without rare earth were measured by electrochemical methods.The corrosion resistance of Cu-P weathering steels was improved by adding an appropriate amount of rare earth.Less and fewer rare earth inclusions largely decreased pitting susceptibility and rate of pit propagation.The pitting potential and the resistance against pitting corrosion of the RE weathering steel were significantly improved due to the modification of rare earth to inclusions.     

Lanthanide NIR luminescence for telecommunications, bioanalyses and solar energy conversion

Present-day advanced technologies heavily rely on the exciting magnetic and spectroscopic properties of lanthanide ions. In particular, their ability to generate well-characterized and intense near-infrared (NIR) luminescence is exploited in any modern fiber-optic telecommunication network. In this feature article, we first summarize the whereabouts underlying the design of highly luminescent NIR molecular edifices and materials. We then focus on describing the main trends in three applications related to this spectral range: telecommunications, biosciences, and solar energy conversion. In telecommunications, efforts concentrate presently on getting easily processable polymer-based waveguide amplifiers. Upconversion nanophosphors emitting in the visible after NIR excitation are now ubiquitous in many bioanalyses while their application to bio-imaging is still in its early stages; however, highly sensitive NIR-NIR systems start to be at hand for both in vitro and in vivo imaging, as well as dual probes combining magnetic resonance and optical imaging. Finally, both silicon-based and dye-sensitized solar cells benefit from the downconversion and upconversion capabilities of lanthanide ions to harvest UV and NIR solar light and to boost the overall quantum efficiency of these next-generation devices.     

Evaluation of D113 cation exchange resin for the removal of Eu(Ⅲ) from aqueous solution

Batch adsorption experiments were conducted for the adsorption of Eu(Ⅲ) ions from aqueous solution by D113 resin. The results indicated that D113 resin could adsorb Eu(Ⅲ) ion effectively from aqueous solution. The adsorption was strongly dependent on pH of the medium with enhanced adsorption as the pH turned from 3.50 to 7.00 and the optimal adsorption condition was in HAc-NaAc medium with pH value of 6.50. The maximum uptake capacity of Eu(Ⅲ) ions was 290.9 mg/g D113 at 298 K, at an initial pH value of 6.50. The overall adsorption process was best described by Lagergren-first-order kinetics. When Freundlich and Langmuir isotherms were tested, the latter had a better fit with the experimental data. The thermodynamic parameters such as free energy (G) which were all negative, indicated that the adsorption of Eu(Ⅲ) ions onto D113 resin was spontaneous and the positive value of enthalpy (H) showed that the adsorption was endothermic in nature. Thomas model was applied to experimental column data to determine the characteristic parameters of column useful for process design. Furthermore, Eu(Ⅲ) could be eluted by using 3.0 mol/L HCl solution and the D113 resin could be regenerated and reused.     

Phase structure and temperature dependent luminescence properties of Sr2LiSiO4F: Eu2+ and Sr2MgSi2O7: Eu2+ phosphors

Green-emitting Sr2LiSiO4F:Eu2+ and blue-emitting Sr2MgSi2O7:Eu2+ phosphors were synthesized by the conventional high temperature solid-state route,respectively.Their structures and photoluminescenee properties were comparatively investigated.It was found that the mixture phases of Sr2MgSi2O7 and SrF2 were obtained when a part of Sr2+ in Sr2LiSiO4F was replaced by some amount of Mg2+ in order to design the possible SrMgLiSiO4F:Eu2+ phosphor.Based on the photoluminescence analysis,Sr2LiSiO4F:Eu2+ phosphor exhibited a green broad emission band of main peak at 513 nm under the excitation of 365 nm,while the Sr2MgSi2O7:Eu2+ and SrMgLiSiO4F:Eu2+ phosphor showed blue emission centered at 467 nm.The temperature dependent photoluminescence properties and room temperature decay time for the three kinds of phosphors were also discussed in this paper.     

Er3+-substituted W-type barium ferrite: preparation and electromagnetic properties

Er3+-substituted W-type barium ferrites Ba1-xErx(Zn0.3Co0.7)2Fe16O27(x=0.00,0.05,0.10,0.15,0.20)were synthesized by polymer adsorbent combustion method.Samples were characterized by X-ray diffraction analysis(XRD),X-ray fluorescence(XRF),scanning electron microscopy(SEM)and network analyzer to investigate the relationships among Er3+concentration,crystal structure,surface mcrphology and electromagnetic properties.All the XRD patterns showed pure phase of W-type barium ferrite when x≤0.15,while the impurity phase of ErFeO3 appeared when x=0.20.The pure W-type barium ferrite showed a hexagonal flake shape.In addition,the microwave electromagnetic properties of samples were analyzed in the frequency range of 2-18 GHz.It was indicated that the electromagnetic properties were significantly improved when Er3+doping content was 0.10.The reasons were also discussed using electromagnetic theory.The optimized ferrite exhibited excellent microwave absoption performance.The maximum of reflection loss(RL)reached about-27.4 dB and RL was below-10dB at the frequency range from 8.4 GHz to 18 GHz,when the thickness was 2.6 mm.     

EXAFS investigation and luminescent properties of nanosized Tb: Lu2O3 phosphors

Nanosized terbium doped Lu2O3 phosphors were synthesized via a modified co-precipitation processing.The as-prepared Tb:Lu2O3 phosphors was consisted of well crystallized nanosized sphere particles with a diameter of about 30 nnx Local structure of Tb ions in Lu2O3 lattice was investigated by an analytical approach based on Fourier transformation of the extended X-ray absorption fine structure(EXAFS) data.X-ray near edge structure (XANES) spectra suggested that all Tb ions doped were tervalonce.EXAFS results indicated that Tb ions have entered the Lu2O3 cubic lattice by means of solid solution.The coordination number and first shell Tb-O distance dropped with the increasing of Tb concentration.Emission spectra of the phosphors was shown to be typical for Tb3+ with main components at 542,550 and 490 nm,derived from irradiative relaxation of 5D4 level.The emission intensity decreased severely with the increasing of Tb concentration from 1 mol.% to 15 tool.%,suggesting a significant concentration quenching above 1 mol.% Tb.The reduction of emission intensity was interpreted by higher distortion derived relaxation among the surface state resident Tb3+ ions.     

Multi-Pass Simulation of Heavy Plate Rolling Including Intermediate Forced Cooling

Thermomechanical Controlled Processing (TMCP) including accelerated cooling after the final hot rolling pass is a well-established technology,widely applied in HSLA steel plate production.However,there are still certain limitations,especially for thicker plate.The rolling schedule includes a long holding period (HP) after the roughing stage to allow the temperature to fall sufficiently for optimised TMCP during finishing.Intermediate Forced Cooling (IFC) applied during the HP can increase productivity by decreasing the required hold time,can restrict austenite grain growth,and can also improve the subsequent strain penetration in thick plate with further metallurgical benefits.Multi-pass plane strain compression (PSC) tests have been performed on the thermomechanical compression (TMC) machine at Sheffield University including different severities of IFC.Clearly it is impossible to simulate all aspects of the temperature and strain gradients present in thick plates in laboratory specimens,and most of the tests were conducted at temperatures and strains calculated by Finite Element modelling as relevant to specific positions through the plate thickness.However,some aspects of the gradients were addressed with tests using cold platens.The results have indeed shown that IFC can shorten the HP and reduce austenite grain growth and its variation across thick plate.     

Overview of Particles and Bubbles in Continuously Cast Steel

This paper gives an overview of phenomena associated with particles and bubbles in continuously cast steel. During steel processing from deoxidation to solidification the inclusion population undergoes changes with opportunities of removal. Flotation is an important separation mechanism. Inclusion particles may accumulate in the solidifying strand, thus forming enriched bands, which depend on the type of casting machine. Bubbles are created during inert gas injection. They also change in size, can float out, but also form accumulation bands. The interaction of bubbles and particles is discussed. Internal structure that recently has been observed on the inner surface of bubbles will be reviewed.     

烦恼 快乐 艺术——池莉“人生三部曲”解读

池莉的"人生三部曲"--<烦恼人生>、<不谈爱情>、<太阳出世>诉尽了普普通通的市民烦恼,小说中主人公被柴米油盐、吃喝拉撒、老婆孩子等琐事所烦着,从而构成他们的"烦恼人生".然而池莉通过自己的艺术创作,以积极的人生态度,又让读者体会到生活本身的快乐,"烦恼人生"中包含着"快乐人生".     

属性块在工程图形中的研究与应用

介绍了在工程图形中用属性块标注表面粗糙度的方法.采用属性块不仅能避免大量重复性的工作,还能节省大量的存储空间,具有提高绘图速度、质量,便于修改,资源共享等应用价值.     

Failure Resistance of Historic Stone Bridge Structure of Charles Bridge. II: Susceptibility to Floods

The paper is a follow-up to the first part devoted to an analogical problem investigated with a view to the degradation of the stone structure due to the effects of nonstress load, and it deals with the probability problem of the bridge structure collapse under the effect of an extreme flood wave. The paper presents the results of the numerical analysis of the response of the historic stone bridge structure of Charles Bridge of the 14th century to the flood wave effect simulated by angular rotation, subsidence, and shifting in the footing bottom of a bridge pier. Special focus is on the effect of interventions into the stone bridge structure dating back to the last major overhaul of 1967–1975, particularly, on the effect of the reinforced concrete slab (tie plate) connecting the opposite bridge breast walls increasing the rigidity of the breast walls and their structurally efficient connection to the vaults of the bridge arches. The numerical analyses performed point out the prevailing negative effects of the implemented interventions in terms of structural rigidity of the stone bridge structure exposed to the effect of a flood wave.     

Addition of Cobalt to Lead Anodes Used for Oxygen Evolution—A Literature Review

A review of the literature dealing with the effect of cobalt on lead-based anodes for oxygen evolution during electrolysis of sulfuric acid solutions verifies that the presence of cobalt at the anode–electrolyte interface, either as constituent of the anode material or as ions in the electrolyte, catalyzes the evolution of oxygen and reduces the corrosion of the anodes and the contamination by lead of metal cathodes produced during electrowinning. However, due to harmful effects of cobalt ions on the cathodic reaction in some processes, these benefits are limited to the electrowinning of copper. Efforts to develop a way of introducing cobalt at the anode–electrolyte interface without interfering with the cathodic reactions are reviewed in this paper. The use of lead–cobalt alloy anodes has had limited success due to issues arising from the low solubility of cobalt in lead, segregation during casting of the alloys, and nonuniform distribution of cobalt which affects the integrity of the anodes. This has been overcome in part lately by inclusion of cobalt into only the surface layer of a lead or lead alloy substrate, by thermal treatment of a cobalt salt to form a catalytic cobalt oxide surface species, or by electrodeposition of composite lead–cobalt oxide anodes. The last approach in particular has been actively investigated by several groups, but to our knowledge it is yet to find application in the industry. The review also critically examines the likely reaction mechanisms involved.     

Reliability-Based Optimal Design of Truss Structures Using Particle Swarm Optimization

In this work, the particle swarm optimization method is employed for the reliability-based optimal design of statically determinate truss structures. Particle swarm optimization is inspired by the social behavior of flocks (swarms) of birds and insects (particles). Every particle’s position represents a specific design. The algorithm searches the design space by adjusting the trajectories of the particles that comprise the swarm. These particles are attracted toward the positions of both their personal best solution and the best solution of the swarm in a stochastic manner. In typical structural optimization problems, safety is dealt with in a yes/no manner fulfilling the set of requirements imposed by codes of practice. Considering uncertainty for the problem parameters offers a measure to quantify safety. This measure provides a rational basis for the estimation of the reliability of the components and of the entire system. Incorporating the reliability into the structural optimization framework one can seek a reliability-based optimal design. For the problems examined herein, the reliability indexes of the structural elements are obtained from analytical expressions. The structure is subsequently analyzed as a series system of correlated elements and the Ditlevsen bounds are used for the calculation of its reliability index. The uncertain-random parameters considered in this work are the load, the yield-critical stress; and the cross sections of the elements. The considered design variables of the optimization problem are the cross-sectional areas of the groups, which control the size of the truss, and the heights and lengths that control the shape of the truss. The results of the optimization are presented for a 25-bar truss and a 30-bar arch and the robustness of the optimization scheme is discussed.     

New Orleans Levee System Performance during Hurricane Katrina: London Avenue and Orleans Canal South

Hurricane Katrina was one of the worst natural disasters in U.S. history. The effects of the hurricane were particularly devastating in the city of New Orleans. Most of the damage was due to the failure of the levee system that surrounds the city to protect it from flooding. This paper presents the results of centrifuge models conducted at Rensselaer Polytechnic Institute and the U.S. Army Corps of Engineers simulating the behavior of the levees at London Avenue North and South that failed during Hurricane Katrina. Those levees failed without being overtopped by the storm surge. Also included are the results of a centrifuge model of one levee section at Orleans Canal South, which did not fail during the hurricane. The key factor of the failure mechanism of the London Avenue levees was the formation of a gap between the flooded side of the levee and the sheetpile. This gap triggered a reduction of the strength at the foundation of the protected side of the levee. The results are fully consistent with field observations.     

Reliability-Based Design for External Stability of Mechanically Stabilized Earth Walls

A two-phase approach was used to develop a reliability-based design (RBD) method for external stability of mechanically stabilized earth (MSE) walls. In the first phase, a parametric study was conducted using Monte Carlo simulation to identify parameters that affect the probability of external failure of MSE walls. Three modes of failure were considered: sliding, overturning, and bearing capacity. External stability was assessed by treating the reinforced soil as a rigid mass using the same procedures employed for conventional gravity-type wall systems. Results from the parametric study indicate that the mean and coefficient of variation of the backfill friction angle are significant for sliding, the mean and coefficient of variation of the friction angle of the backfill and coefficient of variation of the unit weight of the backfill are significant for overturning, and the mean and coefficient of variation of the friction angle of the foundation soil and the mean of the backfill friction angle are significant for bearing capacity. In the second phase, a series of additional simulations was conducted where the significant parameters identified in the parametric study were varied over a broad range. Results of these simulations were used to develop a set of RBD charts for external stability of MSE walls. A comparison indicates that similar reinforcement lengths are obtained using RBD and conventional methods and that the inherent probability of external failure in conventional deterministic design is ? 0.001. This probability of external failure is similar to inherent probability of failure reported by other investigators for similar geotechnical structures.     

Artificial Ground Freezing of Fully Saturated Soil: Viscoelastic Behavior

The transport and mechanical properties of saturated soil drastically change when temperatures drop below the freezing temperature of water. During artificial ground freezing, this change of properties is exploited in order to minimize deformations during construction work and for groundwater control. Whereas for the latter only the size of the frozen-soil body is relevant, which is obtained by solving the thermal problem, the design of the ground-freezing work for support purposes requires information about the mechanical behavior of frozen soil. In addition to the quantification of the improvement of mechanical properties during freezing, information about the dilation associated with the 9% volume increase of water during freezing is required in order to assess the risk of damage to surface infrastructure caused by frost heave. In this paper, a micromechanics-based model for the prediction of both the aforementioned phase-change dilation and the elastic and viscous properties of freezing saturated soil is presented. Hereby, the macroscopic material behavior is related to the behavior of the different constituents such as soil particles, water, and ice. Combined with the solution of the thermal problem, the proposed model provides the basis for predictions of the performance of support structures composed of frozen soil.     

Pseudostatic Coefficient for Use in Simplified Seismic Slope Stability Evaluation

Pseudostatic slope stability procedures are commonly used in engineering practice. However, the selection of the seismic coefficient employed in the analysis is often based on precedence without due consideration of the amount of seismic displacement that constitutes satisfactory performance for each particular project and without incorporating the vastly different seismic exposure for sites around the world. In this Note, a rational basis for selecting the seismic coefficient is presented. The proposed procedure requires that the engineer establishes the project-specific allowable level of seismic displacement. The seismic response characteristics of the slope are represented by the fundamental period of the potential sliding mass, and the site-dependent seismic demand is characterized by the 5% damped elastic design spectral acceleration at the degraded period of the potential sliding mass. The level of uncertainty in the estimates of the seismic demand and displacement can be handled through the use of different percentile estimates of these values. With the proposed equations, the engineer can properly incorporate the amount of seismic displacement judged to be allowable and the seismic hazard at the site in the selection of the seismic coefficient.     

Influence of Precipitates on Hydraulic Performance of Permeable Reactive Barrier Filters

A study was conducted to elaborate a predictive model that deals with the hydraulic conductivity reduction of permeable reactive barriers (PRBs) used for the in situ treatment of contaminated groundwater. As PRBs are composed of reactive and permeable filters through which the contaminated groundwater flows, their longevity has to be studied from both hydraulic and chemical points of view. Therefore, one-dimensional (1D) column filtration experiments were performed at a pilot scale, and an integrated model based on the solution of the advection-reaction-dispersion (ARD) mass balance equation was developed to study the space and time evolution of the hydraulic conductivity. This model uses the well-known Kozeny-Carman relation, which considers that permeability depends on the porosity and specific surface of the porous media. The ARD equation is solved by using the PHREEQC software with numerous capacities on the chemical point of view. Thanks to specific assumptions on the geometry of the precipitations, by using the floating-spheres model and the introduction of the “balanced time principle,” the evolution of the profiles of conductivity are computed and compared with those deducted from differential pressure measurements in the laboratory. Results of numerical simulations conducted with the model show that the largest porosity reductions occur on a 10-cm-thick layer at the entrance of the PRB as a result of precipitation of calcite minerals (prefilter).     

采场充填料浆流动与离析规律的试验研究

为研究采场充填料浆流动规律及充填料浆离析分层对充填体强度的影响规律,开展了充填料浆流动相似模拟试验及采场原位充填体力学强度测试试验,研究结果表明：单点下料时充填料浆流动终态坡面趋向于正态分布。流动过程中充填料浆产生离析分层现象,主要表现为充填体物料的粒径沿料浆流动方向呈先增大后减小的趋势,充填体强度沿料浆流动方向呈先减小后增大再减小的倒转“S”形趋势。采场原位充填体强度在下料口附近与标准试块强度接近,在采场中间位置附近的充填体强度最小,在距离下料点采场长度7/10左右的位置充填体强度达到最大值。研究成果能够为充填采场下料管的数量及位置设计提供依据,从而保证充填体的整体质量。     

Leaching Behavior of Lead, Chromium (III), and Zinc in Cement/Metal Oxides Systems

This paper reports the study of the leaching behavior of cement/metal oxides mixtures containing lead, chromium (III) and zinc oxides. A fractional factorial design of experiments (24?1) was carried out considering four factors, the concentration of ZnO, Cr2O3, PbO, and Fe2O3 in the formulations. Iron oxide was also included in the experimental design as it is usually the main constituent of industrial wastes from thermal processes, where lead, chromium and zinc oxides are also found. After 56 days of curing, samples were subjected to the Acid Neutralization Capacity Test and the concentrations of Cr, Zn, and Pb were determined in the leachate at different pH after filtering. The output variables for the analysis of the experimental data were the concentration of metals at initial pH (in water), at pH 9, 7, and 4, and the acid neutralization capacity of the samples at pH 9. The analysis of the results indicates that the immobilization of Zn and Pb in Portland cement is poor; these metals behave as their amphoteric hydroxides. However, the leaching of Cr (III) is in the range found in the control sample, indicating that the stabilization of Cr (III) is successful.