bluuebunny/crossref_metadata_2025 huggingface dataset:
The Slope Deformation Forecast Model Based on Kalman Filter and Wavelet Neural Network
Authors: Shi Bing Jun , Ruan Yong Fen , Li Qi , Wu Yong Hong
Published: March 2013

Deformation is the macroscopic index for the structure of geotechnical engineering, it is important for the design and construction of geotechnical engineering to monitor the deformation and analyze the monitored data. Kalman filter can enhance the effectiveness of the monitored data and wavelet neural network has the favorable time－frequency localization features and self－learning function. Firstly, the monitored data has been filtered by Kalman filter, and then a deformation forecast model will be established by means of combining with neural network wavelet to predict the deformation of actual engineering. The result shows that the forecast model is successful and effective to forecast the slope deformation.
Research Experimental Teaching System Based on Innovative Practice Ability
Authors: Wu Tong Qing , Xu Nian Chun , Huang Lin Qing
Published: March 2013

The university is the talent base of a country, and the university laboratory is the cradle which trains the innovation talents. The experimental teaching is also an important link of the higher education innovation, which is playing the role that the theoretical teaching can not be substituted. If you want to foster innovation talents in universities, first of all, you should consummate the existing experimental teaching system, then you should construct the new one. Firstly, this paper is discussing the main problem of traditional experimental teaching system ,Based on “the plan for outstanding engineer education”,set up advanced teaching concept, construct the experimental teaching system of multi-level, multi-module, multi plurality, and establish perfect experimental teaching system.
Study on the Safeguard Measures of Civil Engineering "Outstanding Engineers" Training for New Colleges and Universities
Authors: Zhao Bao Yun , Huang Lin Qing
Published: March 2013

Establish a reasonable safeguard measures is one of the key factors for the successful training of the "outstanding engineers" in new colleges and universities. Aimed to solve the protection safeguard measures of "outstanding engineers" training for the new colleges and universities, in this paper a safeguards measures case of civil engineering "outstanding engineers" training program declare in Chongqing University of Science and Technology Chongqing was introduced systematically, and the organizational guarantee, teaching platform measure, teachers and funds etc safeguard measures of the "outstanding engineers" training were also discussed. we hope that this study can provide a advice or the references for the "outstanding engineers" training of new colleges and universities.
Practice of Slip Surface Depth of Highway Slope Determined by Synthetic Survey Method
Authors: Zhang Cheng Liang , Wang Chun , Liu Lei
Published: March 2013

The excavation roadbed was used in K29+450～900 sections of secondary highway from Gengma to Qingshui River. The design roadbed width was 12m, and after an excavation, the inclination of side slope was between 27 to 50 °. It is Nanting River below bed and the vertical distance is 20m between them. Under actions of external load, mountain slipping and river scouring, there appears an instable phenomenon in slope. The pile board wall had inclined which is located in the central section of one side of roadbed and close to K29+900 section after construction. The inclining range was larger and the inclination that was serious at pile head at the top reached about 2m. The research was focused on a side slope engineering in K29+450~900 sections and through site survey, the topography and geological features of slope were known and mastered. By drilling, high-density electric method and numerical simulation method, the depth and scope of slip surface were determined to provide a basis for governance programme of engineering reinforcement.
Finite Element Analysis with Joint Element for Model Pile under Vertical Loading
Authors: Wu Yang , Yamamoto Haruyuki
Published: March 2013

This paper presents the finite element analysis of the model pile loading test considering large deformation theory. The area around pile tip is concentrated with significant compressive and shear stresses. A constitutive model with particle crushing is adopted to describe the mechanical behavior of model ground. The jointed element is introduced in numerical analysis to simulate the interaction between pile and its surrounding soil. The predictions of the relationship between the normalized bearing stress and displacement are good agreeable with the test results. The influences of the joint element on the accuracy of the predicted values are obtained. The figures of distribution for displacement vectors with different penetration depth are shown and discussed.
Numerical Study for Water Waves Generated by Debris Flow
Authors: Zhang Rui Jin , Sun Hong Yue , Zhang Hong Zhan , Tokuzo Hosoyamada
Published: March 2013

Earthquake or rainfall can arouse landslide, which will cause debris flow. Free surface water waves generated by plunging of debris flow cause devastating damage on human life. In this study, a numerical scheme for debris flow and free surface water wave was developed based on shallow water approximation, in which the interaction between these two flows was included newly. Generation of waves by plunging of debris flow is highly non-linear phenomena. Original CIP method and first order up-wind scheme mixed with second order central derivative scheme were adopted to simulate collision of two initially separated fluids (debris flow and still water). Six cases have been adopted to simulate the generation, propagation and run-up of water waves generated by debris flow. The time series of these two flows for these six calculating cases show the interaction of these two flows. Numerical results for interaction of debris flow and generated water wave are quite satisfactory and reasonable.
Estimation Theory on Initial Prestress of Cables in Mega Steel Frame and Cable Bracing Structure
Authors: Tang Bai Jian , Wang Fei , Gu Sheng
Published: March 2013

How to estimate initial cable pretension is one of key problems for mega steel frame and cable bracing structure. In this structure, pre-stressed cables work as components of lateral resistance and elastic supports for mega-beams. Based on these two roles, two principles about determination of initial pretension in them were presented. One is that the residual tension will be near to zero in the most unfavorable condition. The other is that the mega-beam deformation, not showing inverted-arch shape, meets Chinese code requirements in the normal service state. According to these two rules and superposition principle of structural deformation, the relationship between the mega-beam deformation and the cable force under vertical and horizontal loading were established. Further, the detailed calculating formulae and determination method about initial cable pretension were given. They are useful for preliminary design and qualitative analysis of mega steel frame and cable bracing structure.
Deflection Calculation on Reinforced Concrete Beams Strengthened by Externally Prestressing Transverse Tensioning Method
Authors: Liu Jin Jun , Wang Tian Wen
Published: March 2013

Eight reinforced concrete beams (six externally reinforced and two contrast beams) were tested under primary or secondary load experiment. According to the test results, the existing specifications were applied to make calculations on short-term deflection which leaded to a large error. The secondary effect should be considered on calculating the deflection. Therefore, comparisons were made between the improved calculated value and test value on deflections of reinforced concrete beams strengthened by externally prestressed transverse tensioning method and they are in good agreement.
Effects of Web Height-Thickness Ratio on Longitudinal Residual Stresses of the Welded Monosymmetric I-Section
Authors: Zhang Zhuang Nan , Zhao Ya Nan , Jin Lu
Published: March 2013

This paper descries work carried out using ANSYS finite element techniques to evaluate the longitudinal residual stress distributions of the welded monosymmetric I-section in various web height-thickness ratios. From the analysis results, it is shown that, with the web height to thickness ratio increased, the peak values of residual tensile and compressive stress in flange decrease, and the peak residual tensile stress in web decrease too, but the peak residual compressive stress increase. Meanwhile, the distribution width of residual tensile stress in flange and the distribution width of residual compressive stress in web all present increasing trends. The magnitude of the maximum longitudinal residual tensile stresses in both the flange and web reach the yield stress fy, while the maximum residual compressive stress in wide and narrow flange is close to 0.4 fy and 0.3 fy respectively, and the peak value of compressive stress in web which closes to the wide flange and to the narrow flange is about 0.4fy and 0.3fy separately. With the change of height to thickness ratio of web, the distributive width of residual tensile stress in flange or web is about 0.3 times of flange width or web height.
Experiments on Cold-Formed Steel Lipped Channel Beams with Complex Edge Stiffeners and Web Holes
Authors: Wang Chun Gang , Liang Run Jia , Jia Lian Guang , Liu Hong
Published: March 2013

This paper presents an experimental investigation and a numerical analysis on the bending strength and behavior of cold-formed steel C-section and ∑-section beams with complex edge stiffeners and web holes. Local buckling, distortional buckling and interaction between local and distortional buckling were observed in the tests. The experimental results show that the stiffened web has great influence on member's bending strength. Compared with C-section specimens, the stiffness of the web stiffeners of ∑-section specimens reduced the influence of the holes. The finite element analysis results show good agreement with the experimental results in terms of bending strength and buckling mode.
Influence of Span-Depth Ratio to the Ductile Property in Prestressed Concrete Hollow Slab
Authors: Dong Han , Cui Xiu Qin , Lv Shi Ge
Published: March 2013

The numerical analysis method is applied to simulate the whole process of bending. Keeping the section dimensions and the types of loads constant in prestressed concrete hollow slab with mid-strength spiral-rib steel wire, strength of concrete, strength of steel bar, reinforcement ratio, span-depth ratio and stretching control stress are analyzed and compared. The influence of span-depth ratio to the ductile property in prestressed concrete hollow slab is discussed by numerical simulation.
Research on Behavior of RCS Composite Joints
Authors: Guo Zhi Feng , Men Jin Jie , Shi Qing Xuan , Tian Jian Bo
Published: March 2013

A 3-D finite element model (FEM) using ABAQUS was established to simulate the performance of the composite joints with reinforced concrete column and steel beam. Accurate material model, element type, and solution method were discussed in the model. The results from FEM are good agreement with the test results. Some composite joints, reinforced concrete (RC) column to steel beam were modeled based on the model. The mechanism of the composite joint was investigated based on the FEM.
Snow Distribution on Low-Rise Roofs and Practical Analysis Method
Authors: Li Fang Hui , Fan Meng , Gu Ming , Shen Shi Zhao
Published: March 2013

Snow related failures can have significant impact on the safety of people who occupy snow damaged buildings. So the research for snow distribution characteristics on the roofs can avoid personnel casualty and economic losses caused by heavy snowdrift. This paper outlines the current researches of snow distribution on surface of the different roofs and the methods of researching for snowdrifting. The practical calculation method of the snow load on the typical low rise buildings was investigated by comparison between the different countries load code for example China, America, Canada and Europe.
A Steel Headframe Structure before and after the Comparison and Analysis of the Performance of Process Modification
Authors: Sun Jin Peng , Jiao Jin Feng
Published: March 2013

Because the coal mine derrick technology needs, to be in from the original winch system of backward 10m based on a new set of new ground winch system, resulting in the original derrick structure stress state change. By using SAP2000 finite element software, the establishment of three-dimensional finite element model, the dynamic characteristics and technological transformation and bar stress were analyzed, for the coal mine derrick technological transformation to provide certain reference.
Axial Compressive Behavior of High- and Ultra High-Strength Concrete-Filled AFRP Tubes
Authors: Vincent Thomas , Ozbakkloglu Togay
Published: March 2013

Concrete-filled FRP tubes (CFFTs) have received significant research attention over the last two decades. However, the experimental studies on the behavior of CFFTs filled with high- and ultra high-strength concretes (HSC and UHSC) remain very limited. This paper presents the results of an experimental study on the compressive behavior of circular HSC- and UHSC-filled fiber reinforced polymer (FRP) tubes (HSCFFTs and UHSCFFTs). A total of 24 aramid fiber made CFFTs were tested under uniaxial compression to investigate the influences of concrete strength, amount of confinement and manufacturing method of FRP tubes. The influence of tube manufacturing method was investigated with specimens manufactured with either automated filament winding or manual wet lay-up techniques. In this paper the experimentally recorded stress-strain relationships are presented graphically and key experimental outcomes discussed. The results indicate that the manufacturing method of the FRP tubes significantly influence the compressive behavior of CFFTs.
Calculation Methods for Flexural Capacity of Normal Section of Concrete Beams Strengthened with Prestressed CFRP Plates
Authors: Zhang Jun , Deng Lang Ni , Liao Ling
Published: March 2013

Existing experimental studies showed that the reinforced concrete (RC) beams strengthened with prestressed carbon fiber-reinforced polymer (CFRP) plates had two possible flexural failure modes (including the compression failure and tension failure) according to the CFRP reinforcement ratio. Theoretical formulas based on the compatibility of strains and equilibrium of forces were presented to predict the nominal flexural strength of strengthened beams under the two failure modes, respectively. It can provide a reference for engineering application of strengthening design.
Comparative Analysis of Traditional Braced Wall System and Retaining Wall System with Pre-Stressed Wale and Square Pipe Struts
Authors: Kim Gwang Hee , Kwon Kyung Taek , Cho Hong Gyu , Shin Yoon Seok
Published: March 2013

H shape steel strut, which is the most commonly used material in traditional braced wall system (TBWS), has some disadvantage such as narrow strut spacing and cost ineffectiveness. Therefore, a newly retaining wall system with pre-stressed (PS) wale and square pipe struts is developed for widening strut spacing and saving construction costs. In this study, three cases, which are changed from TBWS with H shape steel strut to retaining wall system with PS wale and square pipe struts, are compared construction costs and constructability. This results reveal that construction costs is decreased by 46.9% on average and constructability is improved by decreasing the amount of material and widening the strut spacing.
Finite Element Analysis of Corrugated Mild Steel Damper
Authors: Shi Wen Long , Yan Jin Man , Liu Xuan
Published: March 2013

A new kind of mild steel damper which use corrugated plate as energy-intensive steel plate is proposed in this paper. The structures and energy dissipation principles of the new type damper are presented. The hysteretic performances of corrugated mild steel damper with different height-thickness ratio, or with the same height-thickness ratio but with different thickness are analysed by numerical simulation with ABAQUS platform and then parameter study on this kind of damper in detail. The results show that the corrugated steel damper has good and stable energy dissipation performance. The performance of energy consumption increases with the decreasing of height-thickness ratio. When at the same height-thickness ratio, the performance of energy consumption increases with the thickness of energy-intensive steel plate.
Finite-Element Study of Geometrical Parameters of Corrugated Web Girders
Authors: Hu Xiao Long , Wang Qing Yuan , Tan Lian Fei
Published: March 2013

This paper present the geometrical parameters were conducted to study how they impact the fatigue of the girders with corrugated web by a comprehensive finite element method. Different parameters, such as the oblique angle of the web, the radius of curvature between the web folds, the thickness and width of flange, the height of the beam were investigated. The research object were : promote the application of this structure, especially for corrugated steel web composite bridges on the fatigue design theory and method provide the standard. The numerical results show that geometrical parameters of girders with corrugated webs have great effect on the stress concentration of weld toes. In addition, weld depth and angle have greater impact on the fatigue of the beams with corrugated webs.
The Case Analysis of Adding-Storey and Strengthening Design of Certain Single-Span Steel Structure of High-Rise Building
Authors: Sun Hai Li , Jiao Jin Feng
Published: March 2013

A high-rise steel structure which has been used for 21 years and has horizontally single-span structure, hinged nodes of columns-beams and removed column bracings was added four stories directly and evaluated the aseismic performance. Analysis shows that as a complicated system engineering, reinforcement scheme selection should take feasibility, safety and economy into account. In the meanwhile, anti-seismic standards and later working life should be reasonably determined in order to achieve the goal which not only uses previous structure but also saves the cost. Improper use of existing building will increase irregular degree of structure which will increase the destructive effect of earthquake. In order to ensure the overall performance of reinforced structures, taking reasonable reinforcement scheme and feasible construction technique are necessary.
Research on the Dynamic Behaviors of Semi-Rigid CFST Frame-Shear Wall
Authors: Sun Xiu Li
Published: March 2013

Concrete filled steel tubular (CFST) structure is a new type of structure. Assuming that concrete filled steel stub frame-shear wall is continuous elastic structure with infinite degree of freedom, free vibration equation is built. Furthermore, the effects of semi-rigid connection on natural periods and frequencies are studied. The formula to calculate the coefficient of natural periods is deduced. ANSYS is employed to determine the modal analysis. The results obtained from finite element analysis are consistent well with those obtained from formula. The results show that semi-rigid connections tend to increase the natural period. However, the effect on higher modes is negligible. The seismic design suggestions of the semi-rigid concrete filled steel stub frame-shear wall are proposed. The proposed methods may supply references for the engineers.
Optimization of Steel Liner on Spiral Case Structure for a Large Hydropower Station
Authors: Wu Hai Lin , Qin Shi He , Du Xiao Fan
Published: March 2013

Traditionally, spiral case structure is classified as non-member bar reinforced concrete structure. It is improper to calculate reinforcement area according to the area of tensile stress figure, which often causes a lot of waste of reinforcement; it is particularly true for the spiral case structure with steel liner. In combination with the practice of a spiral case of the hydropower station, the different schemes are proposed by 3-D nonlinear FEM software ABAQUS to study the feasibility of thinning steel liner in this paper. It is indicated that magnitude of steel liner and the hoop reinforcement stress is of no obviously increasement, damaged region of concrete is of no significant variation and the cracking range of peripheral concrete is of the requirements when the rate of steel liner thinning is tiny. When the thinning rate is 10%, there is a significant increase in crack width, but it still can meet the requirements of the specification. Although the magnitude of the stresses is not beyond the strength requirement, the maximum cracking width of concrete is over the designed standards when the rate is up to 30%. In this case, the crack width is controlled by collocating the more reinforcement in local positions. It is concluded that steel liner thinning is reasonable and feasible; what’s more, the magnitude of thinning is very large when the more reinforcement are collocated without prejudice to construction. It can provide references for optimization of the steel liner for the similar projects.
Research on Simulation Technique for Fixed Guide Vanes in Axial Symmetric Models of Spiral Case
Authors: Zhang Hong Zhan , Li Xiao Jun , Ma Zhen Yue , Xiang Kun Shan
Published: March 2013

The axial symmetric model has been widely used in the research and design of spiral case structure in hydraulic power station due to its convenience, however, instead of a continuous entity, the fixed guide vanes are discretely distributed around the vertical axis of the unit, and there are some different opinions on the simulation techniques for the fixed guide vane in the existing research. Commonly used processing methods for fixed guide vanes in the spiral case axial symmetry model are summarized and two new simulation techniques on the basis of existing research are proposed. Static analyses for a practical spiral case with cushion layer are conducted using 4 axial symmetry models and a 3-D FEM model. The influences of simulation techniques for fixed guide vanes on the stress and their distribution of steel liner, concrete and fixed guide vanes are investigated. The rationality and applicability of each simulation technique for fixed guide vanes are discussed.
Reliability Analysis of the Vertical Bearing Capacity of Prestressed Pipe Pile Foundations
Authors: Liu Chun Yuan , Zhao Meng Xuan , Liu Yu
Published: March 2013

The paper introduces the basic principles of vertical bearing capacity of the pile by using static load test, establish the random site theory model of the bearing capacity of prestressed pipe pile foundations calculation, calculates and statistics the try count ratio of vertical bearing capacity of 144 prestressed pipe pile in Tianjin, work out calculation procedures of JC method, calculate reliability index of vertical bearing capacity and analyze calculation results. In the last, we build a model using the finite element software, analysis the displacement of pile top under earthquake, evaluates the horizontal bearing capacity of prestressed pipe pile.
Current Situation of Research on CFST and SRC
Authors: Zhao Bai Dong , Chen Pei Chao
Published: March 2013

This paper describes the research on CFST and SRC and makes a comparison between CFST and SRC in the earthquake and fire. Get the comparison of horizontal displacement and rotation of the beam and column nodes and the comparison of CFST and SRCs’ fire resistance. Providing experience for the future engineering research.
3D Temperature Field Prediction and Experiment Verification of Concrete Diaphragm of Box-Girder Bridge in Early Hardening Period
Authors: Zhou Yi Shu , Liu Jing Hong
Published: March 2013

Diaphragm is often used in box-girder bridge for controlling warping stress such those in midspan or transferring strong bearing reactions such those in ends of span. The results of a crack investigation of box-girder bridges showed that vertical cracks can be found on most diaphragms and formed in early stage of the concrete hardening. Temperature caused by hydration heat is an important factor for these cracking. Therefore temperature field prediction for the diaphragm is significant to prevent the concrete diaphragm cracking. In this paper, three-dimensional finite element analysis software ANSYS is used for simulating 3D temperature field of diaphragm of the concrete box girder bridge in all stages of construction. By calculating space temperature field of the diaphragm in different time hydration heat of the law is analyzed, combined with the measured temperature a comparative analysis to verify the validity of the temperature prediction method is conducted. The results show that simulation method is effective and accurate enough to predict the time-varying temperature field of the diaphragm.
Behaviour Analysis of Prestressed Concrete Deck-Tied Arch Bridge
Authors: Xiang Yi Qiang , Zhang Li Chang , Wu Qiang Qiang
Published: March 2013

The prestressed concrete deck-tied arch bridge doesn’t only have a long span, good appearance and economy, but also have the characteristics of low requirements to the foundation. It changes traditional tied arch bridge into deck-tied arch bridge, which looks like sunflower-shaped arch and prestressed steel strands are embedded in box girder on the top of the arch. Taking Yingbin Bridge as engineering background, the reasonable analysis model was established and behaviour of the bridge under design load was analyzed. The results shown that the design project is reasonable, prestressing force embedded in box girder can balance horizontal thrust in arch bridge effectively, improving the internal force of the main arch ring.
Comparison of Temperature Gradient Effect on Curved Concrete Box Girder Based on Different Codes
Authors: Zhao Min , Di Jin , Lu Wen Ru , Dai Jie , Qin Feng Jiang , Ning Li
Published: March 2013

Based on a project of "Study on Bearing Capacity and Design Method for Curved PC Box Girder Bridge"(number: 03-01K), which came from the Communications Department of Shaanxi Province, temperature gradient effect of curved concrete box girder was researched. Using Finite Element Method (FEM), the effect of temperature gradient stipulated in several codes (Britain bridge standard, Australia bridge specification, New Zealand bridge standard, Japan bridge standard, America bridge specification and China bridge code) were analyzed and compared with. The results show that the calculated stress caused by temperature gradient is relatively unfavorable according to the bridge specification of China, which indicated that it is safer to adhere to Chinese code.
Design of an Extra-Long Railway Overpass Bridges Construction Supporting Frame with Combat Readiness Equipments
Authors: Li Hai Chao , Chang Chun Wei , Yang Xiao Rong
Published: March 2013

For better combining the uses of combat readiness equipments in war and in peace, taking the design of an extra-long railway overpass bridge’s construction supporting frame for example, this paper probes into the application method of the combat readiness equipments used in bridge construction.
Evaluation of Stress Intensity Factor Range in the Prediction of Fatigue Crack Growth at Rib-to-Deck Welded Joints of Orthotropic Steel Decks
Authors: Shi Guang Yu , Li Xiao Xiao , Zhang Gao Nan
Published: March 2013

This paper studies the evaluation of the proper stress intensity factor ranges in the fracture mechanics-based fatigue analysis of the rib-to-deck welded joints of orthotropic steel decks. It is pointed out in the paper that the stress intensity factor ranges used in Paris law for the fatigue crack growth at a rib-to-deck welded joint can not be taken as a value proportional to the corresponding stress ranges since the compressive stresses are the dominant transverse stresses in the cyclic stresses under the action of truck traffics. The proper fatigue design loads to characterize the standard truck loading for the accurate calculation of the tensile transverse stresses at the rib-to-deck joints is also discussed in the paper. It is shown that the loads from two neighboring wheel-axles of heavy trucks have to be taken into account.
Research on Loading Model of Bracket in Multiple Mass Concrete Placement
Authors: Zeng De Rong , Ren Yin
Published: March 2013

Parametric design language in finite element analysis software ANSYS is adopted to establish the analysis model in the construction of the 0# block of a rigid frame bridge on the pier bracket in different times, simulating the placing process of the 0# block of this bridge with three times, and analyzing and understanding the deformation and stress distribution of the bracket and 0# block during each placement of the 0# block. The load participation coefficient of the concrete placed in the 0# block in subsequent 0# block construction is obtained by the analysis and comparison of the stresses of the bracket’s longitudinal beam in the 0# block placed in one time and the 0# block placed in different times. In the meantime, the numerical calculation is proved to be reliable and correct based on the calculation of multiple software programs and the comparison of field test data. These conclusions are meaningful for the design of the bracket for multiple mass 0# block placements, load calculation, and 0# block construction monitoring.
Isotope Exchange between 18O2 Gas and Mechanoactivated Oxide NdMnO3+δ
Authors: Fedorova O.M. , Fishman Anatoly Yakovlevich , Kurennykh Tatiana Eugenievna , Vykhodets Vladimir Borisovich , Vykhodets V.B.
Published: March 2013

sotope exchange of oxygen 18О2 with oxides NdMnO3+δ was investigated. The oxide was obtained from oxides Nd2O3 and Mn2O3 using a ceramic technology with annealing in air at 1400°C for 90 hours followed by cooling in a furnace. A planetary mill AGO-2 with a centrifugal factor of g = 60 was used for mechanical treatment of oxides. The study of isotope exchange was carried out by nuclear microanalysis. The concentration of the isotopes 18O and 16O in oxides was determined using a Van de Graaff accelerator and 18O(p, α)15N and 16O(d, p)17O* reactions at the energies of incident beams 762 and 900 keV. Isothermal annealing of powders was carried out in oxygen, enriched to 80% by the isotope 18O. It was established that the concentration of the isotope 18O in mechanically activated powders was several times higher than in the initial micropowder under the same conditions of annealing. The effect increased with increasing of mechanical activation time (30 - 300 s). The isotope exchange parameters connected with the processes at the boundaries of the particles of mechano-activated powder and within their volume were analyzed.
Nanometric AlNi Precipitation in a 84.68 wt.% Cu-11.25 wt.%Al-4.07 Wt%Ni Shape Memory Alloy
Authors: Hamouda Khaled , Chentouf S.M. , Bouabdallah M. , Cheniti H. , Amimer N.
Published: March 2013

A shape memory alloy with a nominal composition of 84.68 wt.% Cu-11.25 wt.%Al-4.07 wt.%Ni, has been studied. Polycrystalline specimens have been quenched into water at room temperature, after heat treatment of 15 minutes at a high temperature of 1123 K. Two successive cycles from room temperature to 923 K and inversely have been performed on the non equilibrium samples. The microstructural study presented in this work has been performed using TEM (Transmission Electron Microscopy) analysis, STEM (Scanning Transmission Electron Microscopy) analysis, X-ray diffraction analysis at a variable temperature. Nanometric phase precipitation of AlNi type was observed to appear in this alloy.
Elaboration and Characterization of Zinc-Based Foams
Authors: Azzaz Hamza , Sid-Ali Kaoua , Djaffar Dahmoun , Azzaz Mohamed
Published: March 2013

For over a decade, metal foams have attracted a growing research interest because of the development of certain production processes. The advantages of metal foams most cited in the scientific literature are their low weight. However, one of the obstacles to their use on an industrial scale is the dispersion of their mechanical properties, in part because of their microstructural heterogeneity.
Ionic Conductivity, Morphology and Transport Number of Lithium Ions in PMMA Based Gel Polymer Electrolytes
Authors: Othman Lisani , Isa Khairul Bahiyah Md. , Osman Zurina , Yahya Rosiyah
Published: March 2013

The gel polymer electrolytes (GPEs) composed of polymethylmethacrylate (PMMA) with lithium trifluoromethanesulfonate (LiCF3SO3) salt dissolved in a binary mixture of ethylene carbonate (EC) and propylene carbonate (PC) organic solvents have been prepared by the solution casting technique. The samples are prepared by varying the salt concentrations from 5 wt.% to 30 wt.%. Impedance spectroscopy measurement has been carried out to determine the ionic conductivity of the samples. The sample containing 25 wt.% of LiCF3SO3 salt exhibits the highest room temperature ionic conductivity of 2.56 x 10-3 S cm-1. The conductivity of the GPEs has been found to depend on the salt concentration added to the sample, while at higher salt concentration reveals a decrease in the ionic conductivity due to ions association. The temperature dependence of conductivity from 303 K to 373 K is found to obey the Arrhenius law. The ionic transference number, ti of GPEs has been estimated by the DC polarization method and the value is found to be 0.98, 0.93, and 0.97 for the sample containing 25 wt.%, 5 wt.% and 30 wt.% respectively. This result is consistent with the conductivity studies.
Numerical Solution of the Three-Dimensional Diffusion Equation in Solids with Arbitrary Geometry for the Convective Boundary Condition: Application in Drying
Authors: Farias V.S.O. , Pereira Silva Wilton , Silva e Silva C.M.D.P. , Silva L.D. , Gama F.J.A. , de Lima Antônio Gilson Barbosa
Published: March 2013

In this work, a numerical solution for the diffusion equation applied to solids with arbitrary shape considering convective boundary condition is presented. To this end, the diffusion equation, written in generalized coordinates, was discretized by the finite-volume method with a fully implicit formulation. The transport parameters and the dimensions of the solids are considered constant during all process. For each time step, the system of equations obtained for a given non-orthogonal structured mesh was solved by the Gauss-Seidel method. One computational code was developed in FORTRAN, using the CFV 6.6.0 Studio, in a Windows platform. The proposed solution was validated using analytical and numerical solutions of the diffusion equation for different geometries (parallelepiped and finite cylinder). The analysis and comparison of the results showed that the proposed solution provides correct results for the cases investigated. In order to verify the potential of the proposed numerical solution, we used experimental data of the drying of ceramic roof tiles for the following temperature: T = 55.6 °C. The analysis of the results and the statistical indicators enables to affirm that the developed numerical solution satisfactorily describes the drying processes in this temperature for the convective boundary condition.
Precipitation Processes in Mg-Y-Nd Alloys
Authors: Vlach Martin , Smola Bohumil , Císařová Hana , Stulíková Ivana
Published: March 2013

Successive precipitation processes in solution treated Mg3Y3Nd alloy were studied by electrical resistometry, by differential scanning calorimetry and by microhardness. The results were compared to those in the commercial WE43 alloy. Five various phases known from the Mg-Gd-and Mg-Nd-type decomposition sequences form, dissolute or transform in the Mg3Y3Nd alloy. The main difference in the WE43 precipitation sequence is the absence of the β1 phase particles. Electron microscopy confirmed that not the phase type of hardening particles but their morphology, size and orientation to the matrix determine the hardening effectiveness. Differential scanning calorimetry revealed exothermic effects connected to precipitation processes. Apparent activation energies of individual precipitation processes correspond to those in the MgTbNd and in MgNd alloys.
Response of Hot-Extruded Al-Mn-Sc-Zr Alloy to Annealing with Constant Heating Rate
Authors: Vlach Martin , Stulíková Ivana , Smola Bohumil , Císařová Hana , Kekule Tomáš , Málek Jaroslav , Tanprayoon Dhritti , Neubert Volkmar
Published: March 2013

The effect of hot extrusion at 350°C on microstructure, thermal, electrical and mechanical properties of the AlMnScZr alloy was studied. The samples of the cast and of the hot-extruded alloys were annealed from 20°C up to 600°C. Transmission and scanning electron microscopy and electron backscatter diffraction examinations of specimens quenched from temperatures of significant resistivity changes were used to identify microstructural processes responsible for these changes. The cast as well as hot-extruded alloy is characterized by a dispersion of fine coherent Al3Sc and/or Al3(Sc,Zr) particles, and furthermore the fine (sub) grain structure was observed in the hot-extruded alloy. Microhardness HV1 and resistivity values reflect different microstructure of the alloys accordingly. The distinct resistivity changes of the alloys are mainly caused by precipitation of Mn-containing particles. The apparent activation energy for the Al6Mn-phase precipitation in the hot-extruded alloy was also determined. The obtained results agree with those observed in the alloys prepared by powder metallurgy studied in our previous work.
An Insight into the Effect of Deformation on Carbide Dissolution in the Band Structure of Bearing Steel
Authors: Basirat Mitra , Fredriksson Hasse
Published: March 2013

Dendritic segregation in deformed samples remains in the form of band structure, which is a high-strained region. The present work investigates the effect of the uphill diffusion process, occurring during deformation, on the dissolution of carbide particles in the band structure. A series of hot compression tests are performed on the cast structure of bearing steel by using a hydraulic testing machine, MTS 810. Cylindrical specimens are deformed in a temperature range of 800°C to 900°C and at strain rates of 5s-1 and 0.5s-1. In order to eliminate the recovery process, samples are immediately quenched after the compression. The microsegregation of Cr, Mo, Mn and Si are investigated in the band structure, which shows a tendency of uphill diffusion during deformation process. The results show that the volume fraction of carbides varies with the increased straining. The results also show that deformation causes the fragmentation, dispersion of pearlite in the dendrites and the dissolution of spheroidized carbides in the band structure.
Analysis of Substructure of High-Mn Steels in the Context of Dominant Stress Mechanism
Authors: Jabłońska Magdalena , Śmiglewicz Anna
Published: March 2013

In last ten years, leading research centers have been directed to the development of high-Mn steels for manufacturing of parts for automotive industry. The discussed steels with different values of Mn, Al, and Si addition have a medium value of EBU. They usually demonstrate a dominant stress mechanism like twinning induced plasticity TWIP. During the plastic deformation, they may demonstrate a two stress mechanisms like sliding and twinning. The paper presents the results of an analysis of the substructure of high manganese steel after deformation by cold rolling in the context of dominant stress mechanism. The substructure was analyzed by scanning transmission electron microscopy. In the steels, close weaves of dislocations, dislocations tangles, twins and microtwins were observed. It was revealed that the detailed analysis of substructure of the investigated steels after cold deformation could be helpful in determination of the dominant stress mechanism. The obtained results may be used for development of these steels and their plastic deformation models.
Mechanical Properties and Fracture Behavior of Hot Extruded Mg-5Al-3Ca-xNd Alloys at Elevated Temperature
Authors: Son Hyeon Taek , Lee Kwang Jin , Kim Yong Hwan
Published: March 2013

In this study, effects of Nd addition on mechanical properties and fracture behaviors of as-extruded Mg-5Al-3Ca based alloy were investigated by a tensile test at elevated temperatures. For all temperatures, addition of Nd elements resulted in further increase of strength both yield and ultimate strength compared to the Mg-5Al-3Ca alloy. At 150°C, the ductility in Nd-added alloys is lower than that of no-Nd addition alloy. However, at 250°C, the ductility in Nd-added alloys is improved for no-Nd addition alloy because of fine grain and suppression of grain growth by formation of thermally stable Al2Nd intermetallic compounds.
Forced Convection Mechanism Failure in the Eye Can Cause Cataract
Authors: Dória Silva Humberto , Dória Silva E. , Pereira Dória Luiz Cláudio , Pereira Dória Cristiana , Pereira Dória Cristiane , Dória Silva Maria do Carmo Tatiana , Dória Silva Júnior Humberto , Dória Silva M.T.
Published: March 2013

Although the exact causes for presbyopia are not known with certainty, there is the general understanding that it is associated with aging. This is one of the major paradigms of science because the analysis of the symptoms observed during the treatment of presbyopia in the first author of this paper indicates that presbyopia is associated with metabolic dehydrated secretions that have accumulated in various parts of the eyes. As a process of accumulation it is not difficult to associate it statistically to aging. The metabolic secretions produced by the cells inside the human eye are accumulated simultaneously in the cornea, trabecular meshwork, in the lens and retina, subject only to its origin, however, the symptomatology is well characterized by the location of accumulation. Genetic factors are directly related to how the clumps of metabolic secretions occur and the accumulation form is very specific according to the movement of the eyes based on the activities performed by the patient, so any outcome is unpredictable. In this paper introduces the hypothesis that senile cataract may be caused by transport mechanism failure by forced convection of aqueous humour and metabolic mass produced by the lens cells. The evidence confirms the comparative interpretation of physiology and biochemical constituents of studies between old and young lenses published in scientific literature. Besides that the accumulation produces a loss of elasticity of the lens, due to excess volume and causes its opacity because the metabolic secretion is translucent. It shows evidence of the formation of floaters.
The Effects of CaF2 in Mica Glass-Ceramics
Authors: Ghasemzadeh M. , Nemati Ali
Published: March 2013

Different concentrations of CaF2 were incorporated in mica glass-ceramics to evaluate their effects on the crystallization and microstructure. The kinetics of phase transformations, and the microstructures of the final crystalline phase were found to be dependent on the concentration of nucleation agents.
The results showed that CaF2 in high concentration had a synergistic effect and enhanced the formation of interlocked mica crystals. Non-isothermal DTA experiments showed that the crystallization activation energies of base glasses were changed in the range of 235-405 kJ/mol, while the crystallization activation energies of samples with addition of CaF2 were changed in the range of 419-747 kJ/mol.
Design of Biogas Pipeline Energy and Sanitation
Authors: Junior Ederaldo Godoy , Camargo José Rui , Santos R.R. , Rezende F.S. , Cassula A. Matotta , Trindade E. Marques , Bertoncello Danieletto José Roberto
Published: March 2013

The study aimed at developing a methodology for the design and appropriate use of materials in the pipes for the collection and distribution of biogas. The increasing use of biogas for distributed generation in agro-industries, sewage treatment effluent and anaerobic landfills, and the absence of a specific standard for biogas pipes led to the development of the work. Because there is no standard for design and delivery of pipes for the collection and distribution of biogas, the main eco-efficient energy projects implemented in the country, units digester / bike generator 50 kVA to 200 kVA, were used duct poly vinyl chloride (PVC) that permeable to gases, suffers from contamination of biogas network to air, leaks, reduce the efficiency of filter retention of H2S and reduced life of the motor generator. The methane in biogas reacts with PVC and decomposition occurs, dissolution, swelling and loss of ductility of the tube. Since polyethylene is the material world-known and most suitable for transportation of gas fuels, and the fact that its raw material, ethylene in the chain of thermoplastics derived from petroleum, polyethylene comes before the PVC, which makes it more economical and safe.
Mass Transfer with Chemical Reactions in Porous Catalysts: A Discussion on the Criteria for the Internal and External Diffusion Limitations
Authors: Gültekin S.
Published: March 2013

In this study, criteria for internal mass transfer given in the literature were investigated by considering tortuosity (τ) in the porous catalysts. Uncertainties in τ, which may have values between 2 to 7, have a big impact on the effective diffusivity (Deff) which also affects the Thiele Modulus (Φ). Since effectiveness factor (η) is function of Φ, then the criteria given for limitations are questionable. The value of Deff, and in turn the value of Φ calculated for the τ=2 to 7. At low Φ the effects are very small, but when the Φ increases the effect becomes more pronounced. As a result, when using internal mass transfer limitations, one has to be very careful not to get trapped by the disguised kinetics, results of which may end up with disaster.
Refractive Index and Extinction Coefficient of ZnO:Al Thin Films Derived by Sol-Gel Dip Coating Technique
Authors: Baydogan Nilgun , Ozdurmusoglu T. , Çimenoğlu H. , Tugrul A.B.
Published: March 2013

Doped ZnO:Al thin films were deposited on glass substrates by the solgel dip technique. Optical parameters such as the refractive index and the extinction coefficient tend to change with increasing annealing temperature.
Accessing the Influence of Hess-Murray Law on Suspension Flow through Ramified Structures
Authors: Serrenho Ana , Miguel Antonio Ferreira
Published: March 2013

The present study focuses on fluid flow and particle transport in symmetric T-shaped structures formed by tubes with circular and square cross-section. The performances of optimized structures (i.e., structures designed based on constructal allometric laws for minimum flow resistance) and not optimized structures were studied. Flow resistance and particle penetration efficiency were studied both for laminar and turbulent flow regimes, and for micrometer and submicrometer particles. Optimized structures have been proven to perform better for fluid flow but they have a similar performance for particle transport.
Jahn-Teller Phase Transitions in Non-Stoichiometric Oxides with Perovskite Structure: Effect of Mechanical Activation
Authors: Fishman Anatoly Yakovlevich , Tkachev Nickolai
Published: March 2013

Structure phase transitions in nonstoichiometry oxides with perovskite structure were considered. The microscopic description of cooperative Jahn-Teller transition was suggested and the effects caused by mechanical activation of oxide systems (their conversion into nanostructural state, acceleration of oxidation-renewal reactions and immiscibility) were analized. The correspondence of the theoretical results to the data of experiment on phase states of mechanically activated oxide NdMnO3 is shown.