bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Chemical-Looping Combustion of Solid Fuels
Authors: Luo Ming , Wang Shu Zhong , Wang Long Fei
Published: April 2013

The chemical-looping combustion process of solid fuels has been investigated using thermogravimetric analysis (TGA). Experimental results showed that CuO showed high reactivity during reduction process with coal. The coal conversion rate increased with the increase of reaction temperature, and the optimum reaction temperature was about 800 °C. When CuO was supported on TiO2, the temperature to initiate the reaction decreased and the coal conversion rate also increased. Candlenut wood ash, which contained high amount of alkali metal, displayed catalytic activity in mixtures with coal during the CLC process. A key issue is to find the ways for increasing the gasification rates during the CLC process in an industrial process.
Experiments of Green High-Ductile Fiber Low Cementitious Composites
Authors: Cho Chang Geun , Lim Hyun Jin
Published: April 2013

The carbon dioxide (CO2) emission during the ordinary Portland cement (OPC) manufacturing process is up to about 7.0 % of global manmade CO2. The OPC is also known to have toxic substances. The purpose of current research is to develop an environmentally green and high-ductile fiber low-cement composite (HDFLC) in which the binder is mixed by replacing the amount of the cement of 60% as the ground granulated blast-furnace slag (GGBS) with or without using alkali activators. The material and mechanical characteristics of the HDFLC were evaluated experimentally by the slump flow, compression, and direct tension tests.
A Novel NiCl2-CuCl2/HMOR Catalyst for Direct Vapor-Phase Carbonylation of Methanol
Authors: Wang Hai Xia , Guo Wen Wen , Zhu Ling Jun
Published: April 2013

Direct vapor-phase methanol carbonylation, without any methyl iodide in the feed as a promoter, was carried out over NiCl2-CuCl2/HMOR catalysts. The results showed that NiCl2-CuCl2/HMOR catalysts exhibited high activity for methanol carbonylation. The optimum component of the composite catalyst was 5wt% NiCl2 and 15wt% CuCl2. In addition, the effects of reaction pressure and temperature on catalytic performance of 5%NiCl2-15%CuCl2/HMOR catalyst were investigated. It was revealed that methanol conversion of 84.2% and carbonylation selectivity of 73.5% could be obtained under the optimum reaction conditions of P=1.5MPa and T=623K.
Dissolving Effect of [BMIM]CI and DMSO to Straw under High Temperature Conditions
Authors: Yin Qin , Qu Guang Fei , Liu Chong Hui , Xie Yu Bing , Liu Yu Huan
Published: April 2013

Solubility and regeneration of garlic straw in [BimiCl and [BimiCl /DMSO dissolution system were examined under 100°C-260°C. The results showed that activation can enhance straw solubility greatly wherein the optimum activation was 0.5%. DMSO can effectively improve the solubility of straw and speed up the dissolution rate ,and the solubility of garlic straw in [BimiCl and [BimiCl /DMSO dissolution system increased with temperature increased and time passed, but the straw began carbonation when temperature exceeded 160°C. The chemical structure of the orihinal and regenerated garlic was analyzed by FT-IRXRD and TGA-DTA ,The ionic liquid could reduce crystallinity effectively and partially dissolve garlic by destructing the iner-and intra-molecular hydrogen bond among lignocelluloses, IL can be reused many times. Keywords: Garlic straw; solubility; IL
Determination of the Activation Energy for Formation and Migration of Thermal Vacancies in 401.0 Casting Aluminum Alloy
Authors: Kamel N.A. , Aly S.A. , Ibrahim A.A. , Badawi E.A.
Published: April 2013

Electrical techniques have been used to study the thermal vacancies in 401.0 casting aluminum alloy. Quenching experiments were usually performed on thin specimens to ensure a uniform quenching rate throughout the specimen. After grinding, polishing and etching, samples of 401.0 were homogenized for 12h at 673K and annealed for 90min., before quenched in water (277K) and then subjected to electrical measurements. From such measurements it is possible to deduce the vacancy formation enthalpy, which in combination with the results of self-diffusion measurements, give a value for the migration enthalpy of the vacancy.
A Study of the Effect of Natural Aging on Some Plastically Deformed Aluminum Alloys Using Two Different Techniques
Authors: Kamel N.A.
Published: April 2013

Electrical and mechanical techniques have been performed in order to study the effect of natural aging for up to more than 650 days on wrought (2024, 7075) and cast (AlSi11.35Mg0.23, AlSi10.9Mg0.17Sr0.06) aluminum alloys, after having been deformed at room temperature to 25% deformation. The results revealed that, unlike dislocations, point defects were removed from the samples under investigation except for 7075 alloy and this can be attributed to no point defect introduced in this particular sample during the deformation.
Effects of Part Geometry on Spring-Back/Spring-Go Feature in U-Bending Process
Authors: Phanitwong Wiriyakorn , Sontamino Arkarapon , Thipprakmas Sutasn
Published: April 2013

The U-bending process is a common sheet-metal forming process widely employed to fabricate sheet parts like channels, beams, and frames of various sizes applied in almost all industrial fields. In recent years, the precision requirements are increased on the U-bent parts. To achieve these requirements, in this study, the effects of part geometry on the spring-back/spring-go feature including work piece length, U-channel width, punch and die radii, and work piece thickness, were investigated by using the finite element method (FEM) and laboratory experiments. The FEM simulation results clearly revealed the influence of part geometry on spring-back/spring-go feature via the changes of stress distribution analyses on the bending allowance zone, the bottom of bent part, and the U-leg of bent part. Specifically, the part geometry affected on the bending characteristic on the bending allowance zone, as well as it affected on the spring-back feature. In addition, the part geometry also affected on the formation of reversed bending characteristic on the bottom and U-leg of bent parts, as well as it affected on the spring-go feature. The bending angle could be achieved by compensating these bending and reversed bending characteristics. Therefore, to meet the required bending angle, the suitable design of part geometry was strongly considered to maintain the balancing of the bending and reversed bending characteristics. The laboratory experiments were carried out to validate the accuracy of the FEM simulation results. The FEM simulation results showed good agreement with the experimental results with reference to the bending angle and bending force.
Thermo-Mechanical Hardening of Ultra High-Strength Steels
Authors: Homberg Werner , Rostek Tim
Published: April 2013

nnovative ultra high-strength steels have excellent mechanical properties which commonly relate to the materials martensitic microstructure. As thermal heat treatments are state-of-the-art for obtaining the desired microstructure, innovative thermo-mechanical treatments are likely to give rise to even better material qualities. This article highlights various aspects of innovative thermo-mechanical hardening strategies for the processing of ultra high-strength steels, involving both press hardening and friction spinning operations.
Enhanced Formability of Age-Hardenable Aluminium Alloys by Incremental Forming of Solution-Treated Blanks
Authors: Mohammadi Amirahmad , Vanhove Hans , van Bael Albert , Duflou Joost R.
Published: April 2013

The influence of thermal pre-treatment on the formability of a precipitation-hardening aluminium alloy AA-2024 has been studied for three different heat treatment conditions: annealed (O-temper), solution treated and quenched (W-temper) and solution heat treated, quenched and then cold worked (T-temper).The maximum draw angle has been determined and the geometrical accuracy of specific SPIF formed parts has been compared. It is found that the maximum forming angles of the blank formed in O-temper and W-temper conditions show a respective 41% and 32% increase to those of the T-temper condition (initial blank).The hardness of the material reduces significantly after annealing, while SPIF parts formed from W-temper blanks regain their initial hardness after natural aging.
Development of Accurate Numerical Models for Bending of Aluminum Tailored Blanks
Authors: Del Prete Antonio , Papadia Gabriele , Primo Teresa , Mariano Emilia
Published: April 2013

Nowadays the main target in the automotive field is the realization of lightweight and safe components. In this way it is possible to reduce costs and improve fuel consumption and, at the same time, enhance passenger safety. The use of tailored blanks has increased considerably in the automotive industry. Tailored blanks are a combination of different thicknesses or different materials, obtained by welding together two or more blanks, used in particular in car body panels. A new requirement in the automotive sector is the application of aluminum tailored blanks. The main target of this paper is the development of accurate numerical models for bending tailored blanks made from thin aluminum sheets, joined by laser welding, without filler metal. The FE bending simulations have been carried out using an explicit solver. The accuracy of the numerical models has been estimated and improved through a comparison with the results from an experimental study. The experimental tests have been performed using bending testing equipment, designed and developed by the authors. Three different bending radii have been tested. Tailored blanks, used as specimens, have been made by laser welding of thin Al6061 sheets. The considered outputs, used for the numerical-experimental comparison, are the punch force and the bending angle. The experimental results have been compared with the numerical ones in order to verify the accuracy of the FE model related to thickness and radius variations.
Manufacture of Accurate Titanium Cranio-Facial Implants with High Forming Angle Using Single Point Incremental Forming
Authors: Duflou Joost R. , Behera Amar Kumar , Vanhove Hans , Bertol Liciane S.
Published: April 2013

One of the key application areas of Single Point Incremental Forming is in the manufacture of parts for bio-medical applications. This paper discusses the challenges associated with the manufacture of cranio-facial implants with extreme forming angles using medical grade titanium sheets. While on one hand, the failure wall angle is an issue of concern, the parts also need to be manufactured with accuracy at the edges where the implants fit into the human body. Systematic steps taken to overcome these challenges, using intelligent intermediate part design, feature analysis and compensation, are discussed. A number of case studies illustrating the manufacture of accurate parts in aluminium, stainless steel and titanium grade-2 alloy are discussed.
Optimization of the Blank Holder Force Using Genetic Algorithm Method in Case of a U - Shaped Part
Authors: Albut Aurelian , Ciubotariu Vlad
Published: April 2013

In case of sheet metal forming the main dimensional errors are caused by the springback phenomena. The present work deals with numerical simulation related to draw bending and springback of U - shaped parts. The current paper is trying to prove out the important role of the blank holder force variation during the forming process. The Dynaform 5.8 software was used to simulate the forming process, in which the blank holder force varies in four steps between 0 and 50 kN. The factorial simulations test plan was made to cover completely the variation domain and 256 simulations were necessarily to be performed. The part obtained after each simulation is analyzed and measured to quantify the errors caused by springback. Parameters as: angle between flange and sidewall, angle between sidewall and part bottom, chamfer radius between part bottom and sidewall or chamfer radius between sidewall and flange are recorded in a data base. The initial simulations plan together with the generated data base is used as an input for the genetic algorithm optimization method. With the optimized process parameters a new simulation is made and the final shape of the part is compared with the ideal geometry. The shape of the part obtained with the optimized parameters is proving the capability of the proposed method.
A Low Cost Knowledge Based System Framework for Design of Bending Die
Authors: Panghal Deepak , Kumar Shailendra
Published: April 2013

This paper presents a low cost knowledge based system (KBS) framework for design of bending die. Considerations for development of KBS are discussed at some length. The proposed framework divides the task of development of expert system into different modules for major activities of bending die design. The procedure of development of KBS modules is also described at length. Production rules for each module are recommended to be coded in the AutoLISP language and designed to be loaded into the prompt area of AutoCAD or through user interface created using Visual Basic. Each module of the proposed framework is user interactive. Development of one module of the proposed framework is also described at length. This module is capable to assess manufacturability of bending sheet metal parts. An illustrative example is also included to demonstrate the usefulness of this module. The proposed system framework is flexible enough to accommodate new acquired knowledge. As the proposed system is implementable on a PC having AutoCAD software, therefore its low cost of implementation makes it affordable even by small scale sheet metal industries.
Mechanical Response of Ti-6Al-4V Alloy on Deformation at Moderate Temperatures
Authors: Merklein Marion , Hagenah Hinnerk , Kaupper Markus , Schaub Adam
Published: April 2013

Due to beneficial characteristics such as high specific strength, corrosion resistance and biocompatibility Ti-6Al-4V alloy has become the most important industrially produced titanium alloy during the last decades. Commonly used for aerospace technology and medical products, nowadays Ti-6Al-4V covers 50% of the worldwide produced titanium alloy parts. Different deformation operations as forging and casting as well as machining are used to shape titanium alloy components. For sheet metals, cost and time of fabrication can be reduced significantly via the near net shape technology sheet metal forming. Materials such as the α + β alloy Ti-6Al-4V with high yield stress and comparatively low elastic modules need to be formed at elevated temperatures to increase their formability. Numerical simulations are applied to calculate the forming behavior during the process and conclude the characteristics of the shaped part. Therefore in this paper the mechanical behavior of this titanium alloy is investigated by uniaxial tensile test within elevated temperatures ranging from 250 to 500 °C. Finally, the experimental results are adapted to models which predict the flow response in order to describe material behavior in finite element analysis of the forming process.
A Microstructural Investigation of Roll Formed Austenitic Stainless Steel
Authors: Yvell Karin , Lindgren Michael , Bexell Ulf
Published: April 2013

Due to high production rates and the possibility to form complex geometries roll forming has become an increasingly popular forming process for sheet metal. Increasing quantities of high strength steels are used today but can be difficult to form due to their low ductility. One way to partly overcome this problem is to heat the steel in the forming area thus locally increasing the ductility. In the present study partially heated cold rolled high strength AISI 301 type austenitic stainless steel was investigated using electron backscattered diffraction (EBSD), and the results were compared to microhardness measurements. The results show that partial heating will give an almost complete reverse martensite transformation, i.e. martensite (α ́) transforms to austenite (γ), close to the surfaces and grain growth in the middle of the steel sheet. The extension of the heat affected zone can be determined using either microhardness or EBSD measurements. Both these measurements can be used to determine the position of the neutral layer after roll forming. The hardness measurement cannot distinguish between microstructural features but the results are in good agreement with the EBSD results for volume fraction of α ́-martensite. A major advantage of using EBSD is the possibility to characterize and follow the microstructural development when heating and roll forming.
Deformation Mechanisms of Ti6Al4V Sheet Material during the Incremental Sheet Forming with Laser Heating
Authors: Mosecker Linda , Göttmann Alexander , Saeed-Akbari Alireza , Bleck Wolfgang , Bambach Markus , Hirt Gerhard
Published: April 2013

ncremental sheet metal forming (ISF) is a suitable process for the production of small batch sizes. Due to the minor tooling effort and low forming forces, ISF enables the production of large components with inexpensive and light machine set-ups. Hence, ISF is an interesting manufacturing technique for aeronautical applications. Sheet metal parts in aircrafts are often made of titanium and its alloys like the high strength alloy Ti Grade5 (Ti6Al4V). The characteristic low formability of Ti6Al4V at room temperature requires forming operations on this material to be carried out at the elevated temperatures. The interaction of heating and deformation cycles results in a microstructure evolution, which is believed to have a high impact on formability and product quality. In the present work, the temperature-dependent microstructural evolution of the as-deformed parts was investigated. Longitudinal pockets with different depths were formed using a laser-assisted ISF process. The microstructural evolution and hardening of the material were analyzed with respect to the local strain in different forming depths and pocket zones. The formability of the material together with the deformation depth and the sheet thickness-reduction were found to be strongly dependent on the applied process temperatures and the activated deformation mechanisms like dislocation glide and dynamic recrystallization.
Comprehensive Material Characterization for an Intermediate Heat Treatment
Authors: Lechner Michael , Kuppert Andreas , Merklein Marion
Published: April 2013

Encouraged by increasing climate regulations there is a trend to lightweight constructions in the transportation sector, particularly in the automotive industry. An auspicious possibility to reduce the weight of the vehicle is the substitution of conventional steel by aluminum alloys. However, aluminum has a low formability and therefore new technologies have to be found in order to enhance the materials spectrum of application. A new strategy to extend the process limit is the short-term aluminum intermediate heat treatment between two forming operations. Key idea is the partial adaption of the mechanical properties with a short term heat treatment. By the interaction of soft and hard areas the material flow during the forming operation can be improved and the formability can be enhanced. Prerequisite for a successful application of the technology and the numerical simulation is a comprehensive knowledge about the interaction of pre-straining and a subsequent short term heat treatment. Within this paper the mechanical properties in dependency of the two parameters will be presented and a process window for the heat treatment after first forming operations will be derived. Moreover, the influence of batch fluctuations and the impact of ageing will be demonstrated.
Time Dependent FLC Determination Comparison of Different Algorithms to Detect the Onset of Unstable Necking before Fracture
Authors: Hotz Walter , Merklein Marion , Kuppert Andreas , Friebe Harald , Klein Markus
Published: April 2013

The ISO standard 12004-2:2008E for the determination of forming limit curves based on the section method was approved in 2008. About 4 years of measuring experience in different laboratories has shown advantages and weaknesses of the standard and is leading to some minor changes in the specification. In the years from the development of this standard until today a further technical development of the optical measuring devices occurred, so that it is now possible to determine forming limit curves using the time history of the test. This procedure of determination is referred to a time dependent technique and could be the basis of the ISO 12004 part 2 proposal worked out by the work group Erweiterung FLC ISO 12004 of the German group of the IDDRG.
This publication recapitulates existing work which was carried out from the IDDRG work group regarding the determination of forming limit curves for sheet metal materials. On one hand known issues with the current section based approach are discussed and on the other hand it deals with a comparison of different algorithms to determine the FLC from the time history of the Nakajima test using strategies to identify the instant of onset of instable necking. The different time dependent algorithms [ utilised are automatically selecting the area where necking is leading to fracture and then analyze the time history of such points using the first or the second time derivative of the true major strain, or of the true thinning strain using methods like: correlation coefficient (modified method based on [2]), gliding correlation coefficient, linear best fit (modified method based on [3]) and gliding difference of mean to median. The resulting experimental FLC points are compared with the results from the section technique described in ISO 12004 part 2 and with the maximum strain values measured in each test. Further a large number of forming limit curves were determined and used for a comparison of these different methods to define the most promising time dependent algorithm, which was selected as a suggestion for the working group defining the new proposed ISO standard 12004 part 2.
The Influence of the Shielding Gas to the Static and Dynamic Strength Properties of Laser Welded Workhardened Nitrogen Alloyed Austenitic Stainless Steel
Authors: Keskitalo Markku , Mäntyjärvi Kari
Published: April 2013

As an interstitial atom, nitrogen strengthens the structure of austenitic stainless steel (ASS). It therefore has been used to increase the strength of ASS. On the other hand, work hardening of ASS is a common method to increase the strength of the sheet product. When a work-hardened structure is welded, the strength properties decreases at the melted zone and the heat-affected zone (HAZ) of the weld. The nitrogen content can also be reduced by the effect of the heat input of the weld. Because the width of the soft area of the HAZ depends on the energy input of the weld, the strength of the weld depends on energy input. Therefore, laser welding provides better strength to the welded structure. The role of the shielding gas is also significant. Argon shielding gas is inert, but nitrogen used as a shielding gas can strengthen the weld metal and HAZ microstructure. In this study, the effect of different shielding gases in the laser welding of AISI 201 LN TR type work-hardened ASS are tested and the results are reported. Both non-destructive material and destructive material tests are performed. According to the results of the tensile test, the use of nitrogen as a shielding gas strengthens the laser-welded structure. The results of the low-cycle fatigue test show that fatigue strength improves when nitrogen is used as the shielding gas.
On the Field Variables Influence on Bonding Phenomena during FSW Processes: Experimental and Numerical Study
Authors: Buffa Gianluca , Fratini Livan , Pellegrino Sergio , Micari Fabrizio
Published: April 2013

Solid state bonding recurs in several manufacturing processes, as Friction Stir Welding (FSW), Linear Friction Welding (LFW), extrusion of hollow profiles and Accumulative Roll Bonding (ARB). The former processes are nowadays of particular industrial interest because of the specific advantages with respect to the classic welding technologies. In FSW the solid state bonding is obtained between an undeformed cold material, already placed in the advancing side of the joint, and the hot material flow incoming from the retreating side. Proper conditions of pressure, temperature, strain and strain rate are needed in order to get the final effective bonding. In the paper experimental tests on butt joints made out of AA6061-T6 aluminum alloys are used to identify the sets of process parameters resulting either in sound or poor joints. The same process conditions have been simulated used an already developed model in order to highlight the actual bonding line and the values of the main field variables determining the soundness of the joints. Finally a correlation between process parameters values, field variables values and joint effectiveness is made.
Wear Behavior of a DLC-Coated Blanking and Deep Drawing Tool Combination
Authors: Flosky H. , Vollertsen Frank
Published: April 2013

In macro forming a DLC-coating can increase durability and decrease wear of a deep drawing tool. Due to size effects, the behavior in micro range can differ from the behavior in macro range. To investigate durability and wear in micro deep drawing a blanking and deep drawing tool combination was developed, capable of maximum stroke rate of 200 parts per minute. Experiments with copper foil (E-Cu58) of 0.05 mm thickness were performed to produce cylindrical micro cups with a diameter of 1 mm using the lubricant Lubrimax Edel C. The tool material is stainless steel (German standard 1.2379). The punch has a diameter of 0.9 mm and the die diameter is 1.06 mm. To increase durability and decrease wear in micro deep drawing a DLC-coated tool is used. DLC-coated and uncoated tools are compared in long term test regarding wear behavior. Furthermore, the die radii of the tools are measured optically and cross-sections of the tools are made to analyze the microstructure. Experiments show, that the DLC-coating starts to delaminate during the first 5000 strokes. By analyzing the cross section it can be recognized a high density of scattered carbides and pores with different sizes up to 35 μm in the tool material are visible, causing delamination. Furthermore, higher load and stress in micro forming provides delamination. Thus a high influence on the durability of the DLC-coatings base material can be reported in micro range.
Experimental Investigations of Different Tool Concepts for Rotary Peen Forming
Authors: Russig Christoph , Bambach Markus , Hirt Gerhard
Published: April 2013

Rotary Peen Forming (RPF) is a new peen forming process, comparable to Shot Peen Forming (SPF), in which the shot is held by a flexible connection and moved on a circular trajectory. Hence, RPF uses less machine components and therefore offers a compact machine design and a more flexible use than SPF. Just as conventional Shot Peen Forming the RPF process causes localized plastic deformation but involves tangential components which can create shear deformation in the plastic layer.
In this paper, three different RPF tool concepts are compared and the applicability of Rotary Peen Forming for the production of slightly curved parts is analyzed. The first design offers a stochastic impact distribution, the second design leads to deterministic impacts. The third one is a further enhancement of the previous designs and combines the advantages of both.
In contrast to previous tests a new, stiffer testing setup was used which offers good comparability of the tool concepts. Particularly the forming potential in terms of the realization of high curvatures and the surface quality are investigated.
Depending on the tool concept the surface quality differs significantly, but generally RPF allows the forming of curvatures that are commonly used for aerospace structural parts.
Study of Wear Properties of In Situ TiB/TiC Reinforced Ti1100 Composites
Authors: Gong Xiao Lu , Zhao Fei , Zhang Di
Published: April 2013

The tribological performances of in-situ (TiB + TiC) / Ti1100 composites prepared by casting and the matrix alloy were tested by pin-on disc mode. The worn surface and wear debris were investigated by SEM. The models of the composites during the wear process were simulated by ABAQUS FEA software. The analysis shows the stress distributions inside the composites under the different shear stress. The wear mechanism of the composites is probed.
Melt Processing of PolyVinyliDene Fluoride Based Composites Containing Mineral Microparticles
Authors: El Achaby M. , Essassi El Mokhtar , El Kacem Qaiss Abou
Published: April 2013

PolyVinyliDene Fluoride (PVDF)/Calcium carbonate (CaCO3) composites were processed with incorporation of different weight fractions (1, 2 and 10 wt %) of CaCO3 particles into PVDF matrix using melt blending method. The influence of CaCO3 on the structural, thermal and mechanical properties of PVDF polymer was evaluated by using a variety of technique of characterization such as scanning electron microscopy (SEM), X-Ray diffraction (XRD), differential scanning calometry (DSC), thermogravitometric analysis (TGA) and uni-axial tensile test. It was found that the addition of CaCO3 particles results in an increase of thermal stability and some selected tensile properties of PVDF polymer.
Behavior of Thermally Sprayed WC-Co Layers on 5086 Aluminum Alloy and 304 L Stainless Steel
Authors: Boualem N. , Raid A. , Ghaffor M.A. , Tlemçani A. , Derrar M.
Published: April 2013

Thermal spraying is a process for surface coating by projecting a material in powder or in wire form on a material with a previously prepared surface. The materials used in our study are 5086 aluminum alloy and 304 L stainless steel with various surface qualities: polished 120, mirror polished and sandblasted. The projection powder is a combination of "ceramic-metal" WC-Co whose average grain size is 30 microns. The layers thicknesses obtained after 3 passes vary between 90 and 120 microns depending on the operating conditions: gas protection, temperature and surface condition. Indentation tests at the substrate-layer interface and micrographic sections revealed the roughness importance to allow a better layers grip.
Analysis of Transient Hygrothermal Ageing Analysis of Hybrid Composite Materials in Asymmetric Environments
Authors: Boukert B. , Benkhedda A. , Bergheul S.
Published: April 2013

In recent years composite materials are widely used in the aerospace industry. The advantages of these materials are derived from their high strength, rigidity and lightness. More importantly, they have the potential to reduce the cost of construction, while improving structural reliability and increasing safety. Aircraft structural parts made of composite materials with polymeric matrix, subject to variables conditions and severe environments, require a good knowledge of their behavior under humidity and temperature. The matrix is very sensitive to these parameters. A degradation of properties is then observed [1-1.
Injection Molding of PP/CaCO3 Hybrid Composites Toughened with SEBS-g-MA Elastomer: Morphological and Tensile Properties
Authors: El Achaby Mounir , Essassi El Mokhtar , El Kacem Qaiss Abou
Published: April 2013

The aim of this work is to prepare, by extrusion, blends of polypropylene (PP)/styrene-ethylene-butadiene-styrene-g-maleic anhydride (SEBS-g-MA) at the ratios of 100/0, 95/5, 90/10, 85/15 80/20. Then, a amount of 10 wt% of calcium carbonate (CaCO3) was added to each polymer blend to prepare (PP/SEBS-g-MA)/CaCO3 composites with effective ratios of (100/0)/10 (95/5)/10, (90/10)/10, (85/15)/15 and (80/20)/10. Morphological and tensile properties of PP/SEBS-g-MA, PP/CaCO3 and (PP/SEBS-g-MA)/ CaCO3 were evaluated and compared. It was found that the presence of SEBS-g-MA improves the particle dispersion and interfacial adhesion. The tensile properties of PP polymer were affected by addition of SEBS-g-MA and/or CaCO3. Indeed, the addition of only SEBS-g-MA the youngs modulus and tensile strength of PP were remarkably decreased and the elongation at break was significantly increased. In contrast, the PP/ CaCO3 composites shows improved youngs modulus and tensile strength and reduced elongation at break in regard to neat PP. A balance between these selected properties was found in (PP/SEBS-g-MA)/CaCO3 composites, while the youngs, tensile strength and elongation at break were together increased. .
The relationship between prophetic preaching and performing the gift of prophecy in South Africa
Authors: De Klerk Ben J.
Published: April 2013

The goal of this article is to investigate the relationship between the liturgy of the worship service, where prophetic preaching is delivered, and the liturgy of life, where the gift of prophecy must be put into practice. In what way could the ‘prophets’ be equipped to become practitioners of the gift of prophecy? A short description is given of what is understood by prophetic preaching and the gift of prophecy in an effort to determine the relationship between these concepts. In a brief summary, burning questions in church life and in the South African society are addressed: in church life, the questions of extreme conservatism and extreme liberalism are scrutinised and in the South African society, corruption and inequality are investigated. In conclusion, a few guidelines are given for putting the gift of prophecy into practice in the liturgy of life.
Liturgie en Letterkunde - �n �Herfs�-liturgie vir Paasfees in die Suidelike Halfrond
Authors: Vos Casparus J.A. , Wepener Casparus J.
Published: April 2013

Liturgy and Literature � An Autumn liturgy for Easter in the Southern Hemisphere. The aim of this article was to explore possibilities regarding the liturgical inculturation of the Easter liturgy in the Southern Hemisphere. The Easter liturgy originated in the Northern Hemisphere, where it was and is celebrated during Spring with all its concomitant symbolism of new life. That symbolism seems to be lacking in the Easter liturgy in the Southern Hemisphere, where Easter occurs during Autumn. In order to address this issue an interdisciplinary exploration of the themes of both the Easter liturgy and the liturgical ordo was undertaken, as well as a study of Afrikaans poems about Autumn. An example of a liturgy making use of the ecumenical-protestant fourfold order of worship [ordinarium] and enriched with liturgical elements based on the poems studied here as well as some traditions relating to the Easter liturgy [proprium] is presented. As a whole this article serves as an example of how Liturgical Studies can seek alliances with other disciplines in order to address its own questions and for its own purposes.
Early productivity and crude protein content of establishing forage swards composed of combinations of native grass and legume species in mixed-grassland ecoregions
Authors: Mischkolz Jenalee M. , Schellenberg Michael P. , Lamb Eric G.
Published: April 2013

Mischkolz, J. M., Schellenberg, M. P. and Lamb, E. G. 2013. Early productivity and crude protein content of establishing forage swards composed of combinations of native grass and legume species in mixed-grassland ecoregions. Can. J. Plant Sci. 93: 445–454. We evaluated the early establishment productivity of forage swards of native, perennial, cool and warm season grasses, and legumes as they have the potential to provide non-invasive, productive, and drought resistant rangelands. Seven species with agronomic potential and a broad native geographic distribution were selected for testing including: nodding brome [Bromus anomalus (Coult.)], blue bunch wheatgrass [Pseudoregneria spicata (Pursh)], western wheatgrass [Pascopyrum smithii (Rydb.)], side oats grama [Bouteloua curtipendula (Michx.)], little blue stem [Schizachyrium scoparium (Michx.)], purple prairie clover [Dalea purpurea (Vent.)], and white prairie clover [Dalea candida (Willd.)]. Forage swards, including all seven monocultures, 21 two-species mixtures and a mixture with all species, were planted in two sites, Saskatoon and Swift Current, Saskatchewan. Western wheatgrass (WWG) had the highest overall plant density and the strongest effect on the forage yield of the forage swards; however, productivity and crude protein content were not reduced when other species were also included in the forage sward. Dalea spp. did not establish as well as the other species, but had the highest crude protein concentrations. This work provides insight into forage sward development at the establishment stage; additional work is required to determine long-term species impacts for well established forage swards.
A construction of hyperbolic Coxeter groups
Authors: Osajda Damian
Published: April 2013

We give a simple construction of Gromov hyperbolic Coxeter groups of arbitrarily large virtual cohomological dimension. Our construction provides new examples of such groups. Using this one can construct, e.g., new groups having some interesting asphericity properties.
Direct photolysis of carbonyl compounds dissolved in cloud and fog droplets
Authors: Epstein S. A. , Tapavicza E. , Furche F. , Nizkorodov S. A.
Published: April 2013

Abstract. Gas phase photolysis is an important tropospheric sink for many carbonyl compounds, however the significance of direct photolysis of carbonyl compounds dissolved in cloud and fog droplets is uncertain. We develop a theoretical approach to assess the importance of aqueous photolysis for a series of carbonyls that possess carboxyl and hydroxyl functional groups by comparison with rates of other atmospheric processes. We use computationally and experimentally derived Henry's law parameters, hydration equilibrium parameters, aqueous hydroxyl radical (OH) rate constants, and optical extinction coefficients to identify types of compounds that will not have competitive aqueous photolysis rates. We also present molecular dynamics simulations of atmospherically relevant carbonyl compounds designed to estimate gas and aqueous phase extinction coefficients. In addition, experiments designed to measure the photolysis rate of glyceraldehyde, an atmospherically relevant water soluble organic compound, reveal that aqueous quantum yields are highly molecule-specific and cannot be extrapolated from measurements of structurally similar compounds. We find that only three out of the 92 carbonyl compounds investigated, pyruvic acid, 3-oxobutanoic acid, and 3-oxopropanoic acid, may have aqueous photolysis rates that exceed the rate of oxidation by dissolved OH. For almost all carbonyl compounds lacking α, β conjugation, atmospheric removal by direct photolysis in cloud and fog droplets can be neglected.
Investigation of CO, C2H6 and aerosols in a boreal fire plume over eastern Canada during BORTAS 2011 using ground- and satellite-based observations, and model simulations
Authors: Griffin D. , Walker K. A. , Franklin J. E. , Parrington M. , Whaley C. , Hopper J. , Drummond J. R. , Palmer P. I. , Strong K. , Duck T. J. , Abboud I. , Bernath P. F. , Clerbaux C. , Coheur P.-F. , Curry K. R. , Dan L. , Hyer E. , Kliever J. , Lesins G. , Maurice M. , Saha A. , Tereszchuk K. , Weaver D.
Published: April 2013

Abstract. We present the results of total column measurements of CO, C2H6 and fine mode aerosol optical depth (AOD) during the "Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites" (BORTAS-B) campaign over Eastern Canada. Ground-based observations, using Fourier transform spectrometers (FTSs) and sun photometers, were carried out in July and August 2011. These measurements were taken in Halifax, Nova Scotia, which is an ideal location to monitor the outflow of boreal fires from North America, and also in Toronto, Ontario. Measurements of fine mode AOD enhancements were highly correlated with enhancements in coincident trace gas (CO and C2H6) observations between 19 and 21 July 2011, which is typical for a smoke plume event. In this paper, we focus on the identification of the origin and the transport of this smoke plume. We use back-trajectories calculated by the Canadian Meteorological Centre as well as FLEXPART forward-trajectories to demonstrate that the enhanced CO, C2H6 and fine mode AOD seen near Halifax and Toronto originated from forest fires in Northwestern Ontario that occurred between 17 and 19 July 2011. In addition, total column measurements of CO from the satellite-borne Infrared Atmospheric Sounding Interferometer (IASI) have been used to trace the smoke plume and to confirm the origin of the CO enhancement. Furthermore, the emission ratio (ERC2H6/CO) and the emission factor (EFC2H6) of C2H6 (with respect to the CO emission) were estimated from these ground-based observations. These C2H6 emission results from boreal fires in Northwestern Ontario agree well with C2H6 emission measurements from other boreal regions, and are relatively high compared to fires from other geographical regions. The ground-based CO and C2H6 observations were compared with outputs from the 3-D global chemical transport model GEOS-Chem, using the Fire Locating And Monitoring of Burning Emissions (FLAMBE) inventory. Agreement within the stated measurement uncertainty was found for the magnitude of the enhancement of the total columns of CO (~3%) and C2H6 (~8%) between the measured and modelled results. However, there is a small shift in time (of approximately 6 h) of arrival of the plume over Halifax between the results.
Daytime aerosol extinction profiles from the combination of CALIOP profiles and AERONET products
Authors: Marcos C. , Pedrós R. , Gómez-Amo J. L. , Sicard M. , Utrillas M. P. , Muñoz C. , Comerón A. , Martinez-Lozano J. A.
Published: April 2013

Abstract. The solar background illumination has a strong effect on CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) measurements, leading to a decrease in the signal-to-noise ratio of the lidar signal. Because of this, CALIOP level 2 data algorithms might be limited in the retrieval of the properties of the aerosols in the atmosphere. In this work, we present a methodology that combines CALIOP level 1 data with AERONET (Aerosol RObotic NETwork) measurements to retrieve aerosol extinction profiles and lidar ratios in daytime conditions. In this way, we fulfill a two-fold objective: first, we obtain more accurate daytime aerosol information; second, we supplement column integrated measurements from AERONET sun photometers with information about the vertical distribution of aerosols. The methodology has been applied to Burjassot (39.30° N, 0.25° W) and Barcelona (41.39° N, 2.11° E) AERONET stations in the Mediterranean coast of Spain in the period from June 2006 to September 2011. We have found good agreement for the extinction profiles in several study cases of ground lidar measurements in Barcelona, coincident with CALIOP overpasses. Finally, the methodology has proved to be useful for the study of special episodes such as Saharan dust outbreaks.
How much are households willing to contribute to the cost recovery of drinking water supply? Results from a household survey
Authors: Tarfasa S.
Published: April 2013

Abstract. Financial resources are crucial to improve existing urban drinking water supply in developing countries typically characterized by low cost recovery rates and high and rapidly growing demand for more reliable services. This study examines the willingness to pay for improved urban drinking water supply employing a choice model (CM) in an urban context in Ethiopia, Hawassa, with a household survey of 170 respondents. The design of the choice model allows the estimation of the values of two attributes of urban drinking water service (extra day water delivery per week and safer water). The findings indicate that households are willing to pay up to 60% extra for improved levels of water supply over and above their current water bill. Especially those households living in the poorest part of the city with the lowest service levels demonstrate that they are willing to pay more despite significant income constraints they are facing. Women value the improvement of water quality most, while a significant effect is found for averting behavior and expenditures. The estimated economic values can be used in policy appraisals of investment decisions.
Efficient GIS-based model-driven method for flood risk management and its application in central China
Authors: Liu Y. , Zhou J. Z. , Song L. X. , Zou Q. , Guo J. , Wang Y. R.
Published: April 2013

Abstract. In recent years, an important development in flood management is a focal shift from flood protection towards flood risk management. This change greatly promoted the progress of flood control research by the multidisciplinary way. Moreover, given the growing complexity and uncertainty in many decision situations of flood risk management, traditional methods, e.g. tight-coupling integration of one or more quantitative models, are not enough to provide decision support for managers. Within this context, this paper presents a beneficial approach for dynamic adaptation of support to the needs of the decision maker. The overall methodology combines various engineering and geoinformation methods to analyse flood risk as well as calculate major damage processes. The main innovation is the application of model-driven concepts, which are promising for loose-coupling of GIS and multidisciplinary models. This paper defines the new system as Model-driven Decision Support System (MDSS) and proposes its framework. Two characteristics differentiate the MDSS are as follows: (1) it is made accessible to a non-technical specialist and (2) it has a higher level of adaptability and reusability. Furthermore, the MDSS was employed to manage the flood risk in Jingjiang flood diversion area, located in central China near the Yangtze River. Compared with traditional solutions, we believe that this model-driven method is reasonable, reliable and flexible, thus has bright prospects of application for comprehensive flood risk management.
Effects of relative density and accumulated shear strain on post-liquefaction residual deformation
Authors: Kim J. , Kazama M. , Kwon Y.
Published: April 2013

Abstract. The damage caused by liquefaction, which occurs following an earthquake, is usually because of settlement and lateral spreading. Generally, the evaluation of liquefaction has been centered on settlement, that is, residual volumetric strain. However, in actual soil, residual shear and residual volumetric deformations occur simultaneously after an earthquake. Therefore, the simultaneous evaluation of the two phenomena and the clarification of their relationship are likely to evaluate post-liquefaction soil behaviors accurately. Hence, a quantitative evaluation of post-liquefaction damage will also be possible. In this study, the effects of relative density and accumulated shear strain on post-liquefaction residual deformations were reviewed through a series of undrained K0 control cylindrical torsional tests. In order to identify the relationship between residual shear and residual volumetric strains, this study proposed a new test method that integrates monotonic loading after cyclic loading, and K0 drain after cyclic loading-in other words, the combination of cyclic loading, monotonic loading, and the K0 drain. In addition, a control that maintained the K0 condition across all the processes of consolidation, cyclic loading, monotonic loading, and drainage was used to reproduce the anisotropy of in-situ ground. This K0 control was performed by controlling the axial strain, based on the assumption that under undrained conditions, axial and lateral strains occur simultaneously, and unless axial strain occurs, lateral strain does not occur. The test results confirmed that the restoration behaviors of effective stresses, which occur during monotonic loading and drainage after cyclic loading, respectively, result from mutually different structure restoration characteristics. In addition, in the ranges of 40~60% relative density and 50~100% accumulated shear strain, relative density was found to have greater effects than the number of cycles (accumulated shear strain).