bluuebunny/crossref_metadata_2025 huggingface dataset:
Struggle for Survival: The Status Quo for Shanghai’s Bus Lane System
Authors: Xu Fei Fei , Du Yu Chuan , Sun Li Jun
Published: September 2014

This paper provides the opportunity to present the performance evaluation results of Shanghai’s bus lane system in 2012. The evaluation results show that development of Shanghai’s bus lane system has fallen into a dilemma. The effectiveness of bus lanes was presenting a descending tendency. The average travel speed of bus lanes was only 14.6km/h, which was lower than the baseline of Shanghai’s transit metropolis construction targets. “Empty lane syndrome” existed in three newly implemented bus lanes. After 2010 Shanghai Expo, no new bus lane was built and the construction of bus lane came to a standstill. Lax enforcement resulted in high violation rates, which significantly reduced bus speed. Due to the increasing congestion in general purpose lanes and underutilization of bus lanes, attitudinal survey results revealed a negative public sentiment towards bus lanes. The grim situation urges a transition to sustainable development of bus lanes, namely, back to way to seek for efficiency and quality instead of blindly expansion.
Study of Setting of Bus Bay Stop Based on VISSIM
Authors: Wang Jian Jun , Huang Xin Ting , Zhao Ning
Published: September 2014

Setting state of bus stop affects the efficiency of the entire road system. Through discussing bus bay stop’s width, length and distance to intersection, a microscopic simulation was conducted in this paper. With a certain bus frequency, the total delay time of vehicles was analyzed under different road traffic in different forms of Da Yanta Bus Station in Xi’an. The results show that setting bus bay stops on the secondary roads which have large traffic flow can significantly reduce delay time, and can provide references for urban road design.
Traffic Congestion Identification and Analysis of Urban Road Network Based on Granular Computing
Authors: Yao Chen , Gu Jiu Chun , Yang Qi
Published: September 2014

This paper proposes a generalized model based on the granular computing to recognize and analyze the traffic congestion of urban road network. Using the method of quotient space to reduce the attributes associating with traffic congestion, the identification of traffic congestion evaluation system is established including 3 first class indexes and second class indexes of 11. The weight of evaluation indexes are sorted by value in descending order, which are calculated based on rough set theory. In order to improve the efficiency of traffic congestion identification, the appropriate granular is determined by the model parameter μ. When μ is larger, the identification is more effective and the run time of model is longer conversely. Experiments show when the value of μ is between 0.8 and 0.98, the effect of traffic congestion identification is comprehensive optimal.
Forecasting Agricultural Bio-Energy Potential of Beijing
Authors: Ma Rui Pu , Liu Jing
Published: September 2014

Energy is an irreplaceable factor for the socio-economic development of a national or regional. Firstly, the definition, advantages and disadvantages as well as application scope of several energy forecasting methods are presented. Secondly, according to the characteristics of biomass and the worldwide studies, the GM (1, 1) prediction mode, the exponential smoothing model and their weight combination model are selected to predict the main crop yields of Beijing. The comparative analysis shows that the weight combination model has higher accuracy and reliability. Thirdly, using crop yields data of Beijing from 2001 to 2012 establish weight combination forecasting model. 2013 to 2022 in Beijing’s crop yields are predicted by the weight combination model and the available quantity is predicted by the rate of grass valley and availability coefficient. Finally, the converted into standard energy coefficient is introduced to assess agricultural biomass potential. All provides a theoretical basis for the government to make appropriate energy policy.
Research Progress on Independent Temperature-Humidity Control Air Conditioning System
Authors: Liu Jian Long , Xia Xiao Qian , Xie Jie Nan , Liu Peng
Published: September 2014

This paper expounds the research idea and the method of temperature and humidity independent control system and its historical development process and research status and summarized its advantages. Through reading many researches about that aspect, pointing some existing problems of the system and proposed the research prospects.
The Measurement Model and its Application of the Green Building Life-Cycle Carbon Emissions
Authors: Wang Qun
Published: September 2014

By using life cycle theory, the main features of exiting data related to building carbon emissions and the various resources used in different building life cycle phases were analyzed in this article. Thus, an operational method for carbon emissions depended on simplified building life cycle was modeling. In addition, this article also verified the feasibility and validity of the model by calculating carbon emissions of one public building in feasibility stage.
Integrated Photovoltaic System Design and Key Points Analysis Based on Green Building
Authors: Jia Yan Gang , Liu Hai Yang , Su San Fu , Ding Shi Lei , Han Yu Qiang , Liu Yi , Zhang Xiao Song
Published: September 2014

Including architectural design、electrical design、system design, Green BIPV system design are analyzed, and the importance of the building fire and lightning protection design and the main points are pointed out. Further, the details of system design have also been given with specification and description. The photovoltaic system design elements and the importance are expounded through the photovoltalic project example analysis.
Wear Properties of Al-17Si Alloys with Variable Fe Levels Formed by Semi-Solid Process
Authors: Wu Shu Sen , Lin Chong , Lü Shu Lin , An Ping
Published: September 2014

The Fe-rich Al-Si alloys have the potential to be used to make wear-resistant parts. However, there has been few work devoted to study the wear behavior of the hypereutectic Al-Si alloys with about 2% Fe (mass %). In this work, the semi-solid slurry of the alloy was prepared by an ultrasonic vibration (USV) process. The effect of Fe content on dry sliding wear properties of the alloys rheo-casted after USV treatment was investigated. The wear tests were carried out using a pin-on-disc wear tester at four different loads of 50N, 100N, 150N and 200N at a constant sliding speed of 0.75m/s. The results show that the wear rate of USV treated alloy increases almost linearly as the applied load increases from 50 N to 200N. The alloys made with semi-solid process exhibited improved wear resistance at the entire applied load range in comparison to the conventional casting alloys. At the applied load of 50N, oxidative wear is the dominant mechanism for the alloys with USV treatment. At 200N, a combination of delamination and oxidation wear is the main wear mechanism. The wear resistance of Al-17Si alloys containing 2% to 3% Fe is closely related to the morphology, size and volume fraction of Fe-bearing compounds, which can be changed by USV semi-solid process.
Thermomechanical Modelling and Simulation of C38 Thixoextrusion Steel
Authors: Becker Eric , Langlois Laurent , Favier Véronique , Bigot Régis
Published: September 2014

The present paper focuses the modelling and the simulation of a direct thixoextrusion test achieved on C38 semi-solid steel. Many parameters related to thermal, mechanical, material features are involved but are currently unknown. Consequently to validate the modelling and the simulation, it is important to get various experimental informations during the test and to correlate them with simulated results. In a previous paper (Becker et al, 2008), the force-displacement curve, the temperature within the die, the macro and micro structure obtained for different process parameters during thixoextrusion of C38 were investigated. In this work, those results are correlated to those obtained by simulations of the processing. The simulations were performed using the commercial software Forge®. The thermal modelling is based on the heat equation and the thermal boundary conditions involving the heat losses, the thermal conduction within the semi-solid slug and the die and the plastic dissipation as heat source. The latent heat associated to the liquid-solid phase transformation is not considered here. The constitutive equation of the material is given by a multi-scale modelling based on micromechanics and homogenization techniques, labelled as micro-macro modelling (Favier et al, 2009). Friction is modelled using the usual modified Tresca equation. The parameters of the model are determined (i) using literature results and (ii) to match various experimental measurements obtained during the test and described in Becker et al (2008) such as the die temperature during the test and the load-displacement curve. Comparisons between experimental and simulated reveal the presence of complex temperature field and the presence of zones having very low viscosities. These zones contribute actively to the semi-solid material flow.
Rheological Behavior of Semisolid Hypoeutectic Cast Iron Alloyed to Chromium
Authors: Benati Davi Munhoz , Torres Luis Vanderlei , Zoqui Eugênio José
Published: September 2014

This paper proposes and tests new Fe-2.6wt%C-2.8wt%Cr-1.8wt%Si specially designed for thixoforming processing. Samples were heated to the semisolid state at 1195 °C and held at this temperature for 0, 30, 60 and 90s, and then subjected to compression tests. Two-platen compression tests were carried out in order to determine the semisolid behavior. The holding time in the semisolid range simulates the industrial heating process that is time-controlled rather than temperature controlled. Morphological characterization pointed to an as cast microstructure composed by pearlite matrix plus chromium based carbides and nodular graphite and heated conditions composed by pearlitic matrix plus chromium based carbides without free graphite. The semisolid behavior indicated that at 1195 °C the thixoforming procedure requires a maximum stress of 2.5 MPa and maximum apparent viscosity of 4.8x105 Pa.s for the 0s soaking time condition, 2.0 MPa and 4.6x105 Pa.s for 30 s, 1.7 MPa and 3.7x105 Pa.s for 60 s and 1.2MPa and 3.3x105 Pa.s for 90 s of holding time, best condition achieved.
Semi-Solid Metal Processing: "Unlimited" Flow Velocity without Turbulence in Thin Cast Sections
Authors: Jorstad John L. , Alexandrou Andreas N. , Mitsoulis Evan
Published: September 2014

The objective of this presentation is to show and explain why semisolid slurries can fill thin sections at seemingly unlimited flow velocity; the suitability of SSM parts with very thin sections is a characteristic of the process that is often overlooked by the industry. This fact provides a unique opportunity for new advanced applications of the process, not possible by any of the existing metal-mold casting methods.
3D Numerical and Experimental Investigation on Semi-Solid AlSi9Mg Alloy Slurry Prepared by Electromagnetic Stirring
Authors: Zhang Chen Yang , Zhao Sheng Dun , Yan Guan Hai , Wang Yong Fei
Published: September 2014

To prepare semi-solid AlSi9Mg alloy slurry, we simulated electromagnetic stirring (EMS) based on a coupled 3D model of electromagnetic field, temperature field, and flow field by sequentially coupling ANSOFT and FLUENT software. Results show that magnetic flux density and electromagnetic body force (EMF) decrease and exhibit non-uniform patterns as stirring frequency increases. However, magnetic flux density and EMF increase in proportion to the stirring current but become more inhomogeneous. As EMF increases, the flow velocity and the depth of vortex in the semi-solid slurry gradually increase; thus, slurry temperature decreases. The deviation in temperature is then reduced between the center and the edge. As a result, the microstructure of the slurry evolves from coarse rosette grains to fine and spheroidal ones. By comparison, turbulent flow is generated by excessive and more unevenly distributed EMF, which causes deterioration in microstructures, such as the formation of cavities in the semi-solid AlSi9Mg alloy slurry. Based on simulation and experimental results, our conclusion is that reasonable process parameters have been obtained and verified experimentally. These results also show the validity and reliability of EMS-prepared semi-solid AlSi9Mg alloy.
Simulation on the Thixocasting Process of the Turbocharger Impellers and Selection of the Viscosity Models
Authors: Zhang Fan , Hu Xiao Gang , Li Da Quan , He You Feng , Xu Xiao Jing , Zhu Qiang
Published: September 2014

The thixocasting technology is chosen to produce the turbocharger impellers as it is capable of producing castings with high precision dimension, free of oxide and shrinkage porosity defects and therefore long service life. The thixocasting turbocharger impellers have the similar mechanical property to those produced by forging and machine processes, but much less costs. In the thixocasting process, the semisolid slurry with certain solid fraction is injected into mould at a high speed. Since high viscosity and thixotropic characteristics, the semisolid slurry reveals unique flow condition and characteristics in the filling process. So, its very desirable for the die design, process optimization, and defect control to visualize the high-speed filling process of semisolid slurry by numerical simulation. In this paper, several commonly used viscosity models for semisolid slurry are analysed. The Power law cut-off model (PLCO) model is selected to simulate the filling process in the thixocasting process of the impellers of 319s alloy, compared with actual results by partial filling testing. The causes of the casting defects are also analysed, indicating that the simulation results can accurately reproduce the filling process of semisolid slurry, and PLCO model is a successful choice for simulating the filling process of semisolid slurry with high solid fraction.
Study on Refining Mechanism of Primary Si in Semi-Solid Al-25%Si Alloy Slurry Prepared by Rotating-Rod Induced Nucleation
Authors: Chen Zong Bao , Li Lu , Zhou Rong Feng , Jiang Ye Hua , Zhou Rong
Published: September 2014

In this paper, a new method for preparing semi-solid Al-25%Si alloy slurry named as Rotating-Rod Induced Nucleation (RRIN) was adopted. In this method, liquid metal (velocity 0.66 kg/s) flew toward a vertical stainless steel rod (45 mm in diameter) which was self-revolving on its axis. Molten alloy was spread around the rod surface under the effect of rotating, which caused supercooling and induced nucleation of primary Si in the molten metal. After spread around the rod, molten alloy flew off the rod and down to a graphite crucible. The influence of rotating speed on the microstructures in the semi-solid slurry was studied. The refining mechanism of primary Si was also analyzed according to the change of the spreading state, the number of primary Si particles (PSPs) in per unit area (N), and the distribution of PSPs size under a series of different rotating speeds (from 100 r/min to 1000 r/min, and at intervals of 100 r/min). The results showed that, under the lower rotating speeds such as 100 and 200 r/min, the molten alloy flew downward along the rod. With the rotating speed increasing, a molten alloy film around the rod was formed under the effect of the tangential force caused by the rotating rod, and the film thickness thinning, the spreading area and the N was increased. The uniform supercooling in the whole molten metal film was obtained under the condition of higher rotating speeds such as 500 and 600 r/min, which promoted nucleation of the PSPs significantly. It is called Rotating-Rod Induced Nucleation (RRIN). After spreading around the rod during short time, the molten metal film was thrown away the rod rapidly under the effect of centrifugal force, which prevented further supercooling and growth of PSPs. Under the condition of too higher rotating speed of the rod such as up to 700 r/min, the molten melt flew off from the rod apparently before spreading around the rod surface, molten metal film as mentioned above was destroyed, RRIN was weakened. The microstructure with fine PSPs (27 μm) was distributed uniformly in the semi-solid slab obtained under the condition of rotating speed of 600 r/min and pouring temperature of 785 °C in this experiment. Keyword: high silicon aluminum alloy; Rotating-Rod Induced Nucleation; Si phase; refinement.
Production of Aluminum/SiC/NiAl2O4 MMCs by Thixoforming of Recycled Chips
Authors: Ferreira Lygia Maria Policarpio , Robert Maria Helena , Bayraktar Emin
Published: September 2014

The work explores the production of Al/SiC and Al/SiC/NiAl2O4composites by thixoforming compacted mixtures of AA7075 machining chips and reinforcing particles. It is analyzed the influence of processing parameters in the various processing steps, such as mixing, compacting, heating and thixoforming, in the final quality of products. Results showed the general viability of producing composites by the proposed technique; the utilization of recycling material is particularly important in the high demanding energy processing sector, as the Al industry. NiAl2O4particles and, in less extent, also SiC particles, can penetrate into the liquid phase present in the thixotropic microstructure within the chip, promoting their disaggregation; reinforcement distribution in the composite depends on appropriate choose of processing parameters.
Microstructural Evolution of 7050 Aluminum Alloy Semisolid Billets Fabricated by RAP Process
Authors: Jiang Ju Fu , Du Zhi Ming , Wang Ying , Luo Shou Jing
Published: September 2014

In the present study, 7050 supplied in extruded state was heated to different temperatures below solidus or the semisolid state and microstructural evolution and coarsening were investigated. The results showed that complete recrystallisation only occurs after soaking for 5 minutes at 545°C, which is characterised by formation of a lot of fine equiaxed grains. RAP is suitable for fabricating high-quality semisolid billet of 7050 aluminum alloy with an average grain size ranging from 47.4 um to 70.5 um and a roundness ranging from 1.3 to 1.7. Grain growth occurs as the samples were soaked at 610°C and 615°Cfor prolonged soaking time. When the isothermal temperatures were 610°C and 615°C, the coarsening rate constants were 359.5μm3s-1 and 470.5μm3s-1, respectively, indicating an increase of coarsening rate constant (K) with the increasing isothermal temperature. Coarsening tends to occur via Ostwald ripening and coalescence. Ostwald ripening plays an important role during the whole coarsening process, but the grain coalescence only contributes to coarsening after soaking for 12 minutes. 625°C is an optimal temperature to keep cylinder shape of the sample due to collapse of the sample above this temperature, leading to difficult clamping.
Steels with High Temperature Carbides - New Possibilities for Semi-Solid State Processing
Authors: Jirková Hana , Rubešová Kateřina , Pileček Vít , Behúlová Mária
Published: September 2014

Semi-solid processing of steels is typically studied using high-alloy steels with higher carbon levels, as those offer a long freezing range which is favourable for conducting the process. The drawback to their application is their microstructure which typically consists of austenite grains embedded in ledeburitic network. This type of microstructure typically fails in brittle manner by fracturing along the interface of the hard network and ductile austenite grains. This is why a way was sought to altering or even inverting the configuration of the microstructure. Eventually, suitable steel chemistries were found which allow the inverted microstructure to be obtained. With regard to the high content of alloy additions, these steels have to be made by powder metallurgy methods. Five different steels of this kind were selected for the experimental programme. All contained high amounts of alloying elements and a large fraction of carbides. Their carbon content was taken into account as well, ranging from 0.55 to 3.4 %. Differences between the steels consisted in the levels of major alloying elements, namely chromium, vanadium, molybdenum, tungsten and cobalt. After suitable process parameters were found, semi-solid processing was used to prepare demonstration products. The transition through semi-solid state transformed the ferritic matrix to austenitic-martensitic one, in which the high-stability carbides were retained. The resulting microstructures were of unconventional nature where carbide particles were embedded in tough metal matrix. Their configuration was thus inverted in contrast to the ones typically obtained by semi-solid processing of tool steels.
The Refinement Mechanism of La-Ce Binary Alloy on Primary α Phase in A356 Alloy under Electromagnetic Stirring
Authors: Liu Zheng , Luo Hao Lin , Chen Qing Chun
Published: September 2014

The refining effects of La-Ce binary alloy on the primary α phase in semisolid A356 alloy prepared by electromagnetically stirred were researched, in which the refinement mechanism of the binary alloy on primary α phase were emphatically approached. The different amount of La-Ce was added into A356 melt, the melt was poured at 620°C and slightly electromagnetically stirred for 15s with an electromagnetic stirrer which was controlled by frequency conversion, then it was isothermally held at 615°C for 10min. The shape and size of primary α phase were measured, and the distribution of La and Ce was researched by SEM and EDS. The results indicated that the RE elements were easy to uniformly distribute around the primary α phase under electromagnetic stirring, and had the obvious refining effect on primary α phase in semisolid A356 alloy, in which there was the finer primary α phase with particle-like in the melt. The refinement mechanism of La-Ce binary alloy under electromagnetic stirring was concerned with the eutectic reaction between RE elements and Al in the melt, in which the α-Al phase resulted from the Al-RE eutectic reaction could serve as the nucleating site of the primary α phase during solidification of A356 alloy. The other reactant from the Al-RE eutectic reaction, Al11Ce3, was also directly used as nucleation of α phase during the solidification.
Effect of Hot Rolling and Equal-Channel Angular Pressing on Generation of Globular Microstructure in Semi-Solid Mg-3%Zn Alloy
Authors: Rogal Łukasz , Czerwiński Frank , Litynska-Dobrzyńska Lidia , Bobrowski Piotr , Wierzbica-Miernik Anna , Dutkiewicz Jan
Published: September 2014

A combination of hot rolling and equal channel angular pressing (ECAP) was explored to generate globular microstructures in the Mg-3%Zn alloy after re-heating to the semisolid state. It was found that the single-step deformation of as-cast alloy via hot rolling at 350°C with a thickness reduction of 50% refined the alloy microstructure by creating deformation bands of the Mg (α) phase with a size of the order of tenths of micrometers. After re-heating to 630 °C, the microstructure transformed into spheroidal morphologies with an average globule size of 82 μm. An additional deformation of the hot-rolled alloy by the ECAP method at 250 °C further refined the alloy microstructure to sub-micrometer grains of lath and equiaxed shapes. After re-heating of this microstructure to 630 °C the average globule size reached 62 μm, which is roughly 25% smaller than that achieved for the hot-rolled precursor. The role of strain-induced melt activation (SIMA) techniques in generation of globular morphologies in Mg-based alloys after partial re-melting is discussed.
Fracture Property Correlation of Rheocast (EMS) and Thixocast 6061 Aluminium Alloy
Authors: Singh Shailesh K. , Das Prosenjit , Chattopadhyay Kamanio , Dutta P.
Published: September 2014

The present study has been taken up to establish fracture property correlation of the semi solid processed 6061 aluminium alloy. Electro Magnetic Stirring (EMS) has been performed to get non-dendritic billets and then the alloy has been thixocast using a High pressure die casting machine. Tensile tests have been performed to estimate mechanical properties of the semi solid processed alloy. Fracture behaviour of the alloy has been investigated at the intermediate EMS cast state and subsequent final thixocast state, employing uniaxial tensile tests at 0.001s-1strain rate and at room temperature. Fracture surface morphology of the EMS cast state shows that the presence of micro porosity is responsible for crack initiation and final fracture. Our results confirm that the dimpled rupture of primary Al phase is responsible for improved mechanical properties in the thixocast state of the alloy.
Effect of Rolling-Remelting SIMA Process on Semi-Solid Microstructure of ZCuSn10 Alloy
Authors: Wang Jia , Lu De Hong , Xiao Han , Zhou Rong Feng , Zhou Rong , Wu Long Biao
Published: September 2014

Semi-solid billet of ZCuSn10 (Wt%: 88.25Cu, 10.48Sn) alloy is prepared by strain induced melt activated (SIMA) method which including rolling and remelting process. Firstly, ZCuSn10 alloy is casted, and rolling samples are cut from ingot casting. Secondly, the rolling samples are two pass or four pass rolled after holding 15 minutes at 450°C, then samples with 10% and 20% pre-deformation degree are obtained. The remelting samples are cut from pre-deformed samples. Lastly, the remelting samples are reheated up to 850°C or 875°C, water quenching after holding for 15 minutes. Then semi-solid microstructure of ZCuSn10 alloy is prepared. The semi-solid microstructure of ZCuSn10 alloy is observed and compared with annealed microstructure and microstructure of ZCuSn10 alloy directly remelted after casting. The results indicate that semi-solid microstructure of ZCuSn10 alloy by rolling-remelting SIMA process is uniform and fine grain, and spheroidization level of solid particle is well. The optimum semi-solid microstructure is obtained when alloy with pre-deformation 20% is remelted at 875°C for 15 minutes, the average grain diameter is about 75.80μm, shape factor is 1.62, and volume fraction of liquid phase reaches about 17.28%. Pre-deformation process plays a crucial role in grain refinement and spheroidization during SIMA process for preparing the semi-solid ZCuSn10 alloy, as pre-deformation degree and remelting temperature increases, volume fraction of liquid phase increases, the solid particles in semi-solid microstructure are smaller and rounder. The main mechanism of SIMA process preparing semi-solid billet of ZCuSn10 alloy is that pre-deformation breaks dendrites and stores energy of deformation into alloy, and promotes dendrites fusing through remelting process. Meanwhile, liquid phase occupies sharp corners of solid particles by Sn element diffusing from liquid phase into α solid phase, so that fine and uniform and globular α solid particles are gained.
Using Semi-Solid Extrusion for the Production of Aluminum-Nanocomposite Master Alloys
Authors: Weiss David , Black Michael
Published: September 2014

The production of nanoreinforced aluminum alloys in volume and quality suitable for subsequent shape casting has been problematic. Large specific surface area and high interfacial energy of the particles combined with high surface tension of the aluminum melt makes it difficult to add appreciable numbers of particles to the melt, even when later de-agglomerated by techniques such as ultrasonic cavitation. Previous work by the authors used semi-solid squeeze casting to produce master alloys for dilution into the casting alloy. While the technique was shown to be effective, the master alloy proved difficult to remelt and was expensive to produce. The objective of this new work was to use an extrusion process that could be more readily scaled to produce nanoreinforced aluminum master alloys. This paper describes the process developed for incorporation of nanoparticles using semi-solid extrusion and the results of alloys produced using that process.
A New Technology to Improve the Elongation of A356 Alloy
Authors: Zhang Yi Jie , Ma Nai Heng , Li Xian Feng , Wang Hao Wei
Published: September 2014

A356 alloy was widely used in automobile industry due to its excellent castability and comprehensive mechanical properties. But, with increasing demands of strictly safety of components, fatigue life of A356 alloy became the key properties which were considered seriously. To evaluate the time-consuming properties, elongation, as a replaced property, was employed for its easy testing and the relationship which was proportional to the fatigue life of materials. Semi-solid processing was proved that it can improve the elongation of materials while the mechanical properties still kept at the same level as original alloy. Presently, many semi-solid techniques were developed to produce various products, in which the additional equipment was necessary to form the semi-solid microstructure. Therefore, this work is aimed to development an easily technique to obtain the semi-solid microstructure. In present study, A356 alloy with typical semi-solid microstructure was obtained by addition of RE elements during melt processing. In addition, the melting and pouring process was kept the same as the normal gravity casting of A356 alloy. After the treatment, the elongation was 19.5% for A356 alloy with RE addition, which was much higher than that of 13% for normal A356 alloy. Microstructure observation showed that the morphology of Si was changed significantly, and the shape of spheroid was dominantly appeared other than short rod shape. The improvement of elongation was attributed to the morphology change of α-Al and eutectic Si.
New Generation of Brake Callipers to Improve Competitiveness and Energy Savings in Very High Performance Cars
Authors: Gattelli Ivano , Chiarmetta Gian Luigi , Boschini Marcello , Moschini Renzo , Rosso Mario , Peter Ildiko
Published: September 2014

This paper concerns with the optimisation of the innovative rheocasting process to produce a new generation of brake callipers, characterised by very high reliability and strength. The attained very promising properties favoured their use on a very high performance car and the presented technique can be further extended for other important challenging applications. The prototype components are produced using T6 heat treated A357 alloy. Results on the samples machined directly from the produced callipers are in detail described and analysed. Pieces exhibiting some small defects, individuated by non-destructive tests, as well as defectless pieces have been underlined to severe industrial tests, e.g. high pressure tight, as well as severe bench tests, and it has been observed that the proposed technological process assure the fulfilment of the requirements contained in standards.
SSM Provides Important Advantages; So, why has SSM Failed to Achieve Greater Market Share?
Authors: Jorstad John L.
Published: September 2014

Semi solid metal processing has numerous technical and economic advantages, such as viscous, non-turbulent flow (thus no air entrapment during casting), ability to fill ultra-thin sections (thus reduced part weight), little solidification shrinkage in the die (thus little or no porosity), minimum heat imparted to tooling (thus long tool life) and good response to T-5 aging (thus reduced heat treating costs). Still, SSM has never achieved a prominent position in the field of light metals casting Why? Perhaps the reason was largely the down economy of recent years and SSM will yet emerge with the prominence once expected of it.
Industrial Applications for Aluminum Semi-Solid Castings
Authors: Midson Stephen
Published: September 2014

The goal of this paper is to examine industrial applications for semi-solid castings, and to develop strategies necessary for the wider commercialization of the semi-solid casting process. The performance and production techniques of semi-solid castings are reviewed, with the goal of identifying commercial niches where semi-solid castings can provide clear benefits over other casting process. A comparison of mechanical properties between semi-solid castings and other casting processes is presented. In addition, this paper provides an evaluation of the features of the optimal semi-solid casting processes, examines the characteristics of components that would benefit for production by semi-solid casting and describe the types of quality systems that casters need to have in place to make these types of castings. Cost analyses are presented suggesting that rheocasting can complete well with other casting processes.
Effects of Post Heat Treatment on Microstructure and Mechanical Properties of RAP-Processed Cr-V-Mo Steel
Authors: Meng Yi , Sugiyama Sumio , Yanagimoto Jun
Published: September 2014

Owing to the phase segregation occurred during semisolid process, the ferroalloys products manufactured by semisolid process always exhibit inhomogeneous microstructure and poor mechanical properties. In this study, the post heat treatments including quenching treatment and tempering treatment with various processing parameters were carried out to improve the quality of Cr-V-Mo steel (JIS SKD61, AISI H13, DIN 1.2344) which processed by RAP (recrystallization and partial melting) processed. The microstructural characteristics (phase transformation, morphology of carbides, and distribution of alloying elements) and mechanical properties (hardness, tensile strength, elongation, impact toughness, and resistance to high-temperature wear) of specimens processed by RAP and heat treatments under various experimental conditions were investigated experimentally. Being quenched from 1050 °C after isothermal holding for 480 s and then tempered twice at 560 °C for 2 h, the microstructural evolution took placed in both former solid-phase and liquid-phase regions of the RAP-processed Cr-V-Mo steel specimen. During this post heat treatment strategy, the weakening of phase segregation, the redistribution of carbides, and the release of residual stress occurred and resulted in the improvement of microstructure and a good combination of mechanical properties.
The Mechanical Properties of Rheo-High Pressure Die Cast Al-Mg-Si-(Cu) 6xxx Series Alloys
Authors: Möller Heinrich , Daswa Pfarelo , Govender Gonasagren
Published: September 2014

Near-net shape casting of wrought aluminium alloys has proven to be difficult due to a tendency towards hot tearing during cooling. Rheo-high pressure die casting (R-HPDC), has been shown to be an effective method of producing near-net shape wrought aluminium alloy castings. Limited information is available regarding the mechanical properties of age-hardenable wrought Al-castings produced by semi-solid metal forming. The purpose of this study is to investigate the effects of chemical composition and natural pre-ageing on the hardness and mechanical properties of rheo-HPDC 6xxx series Al-Mg-Si-(Cu) alloys in the T6 temper condition. The effects of the addition of Cu, as well as the (Mg+Si) content and Mg:Si ratio of the alloys are quantified. Alloys that are included are Cu-free 6004 and 6082, as well as Cu-containing 6013, 6111 and 6066. It is shown that the addition of Cu and excess Si result in higher hardness and strength. Natural pre-ageing has a significant effect (positive for 6004 and negative for the others) on the T6 properties. Good strength values can be achieved, but ductility is dependent on factors such as hot tearing during casting and incipient melting during solution heat treatment.
Aluminum Segregation in ZA27 Rheocast Alloy
Authors: Pola Annalisa , Montesano Lorenzo , Gelfi Marcello , Roberti Roberto , La Vecchia Giovina Marina
Published: September 2014

Aluminum segregation in zinc alloys is a well-known problem during melting and casting. In molten Zn alloys, in fact, Al tends to float on the surface of the bath because of its lower density than zinc. The same problem also occurs during casting solidification, causing chemical gradients along part thickness and soundness problems. As a consequence, the use of high aluminum content zinc alloys, such as ZA27, can be limited.In this paper the effectiveness of rheocasting method on decreasing Al-segregation phenomenon in ZA27 was investigated. The slurry was obtained by using the ultrasound technique, starting from the fully liquid down to different solid fraction percentages. The metal was then cast into a permanent steel mold. The produced samples were completely characterized by metallographic analysis (optical and scanning electron microscope), to assess the microstructure modification induced by the treatment. Hardness tests were also performed to evaluate mechanical properties. For comparison, the same tests were performed on conventionally cast samples.The analyses show that the use of a semisolid alloy increases the homogeneity of the part in terms of hardness, chemical composition and microstructure; furthermore casting’s shrinkage porosity is significantly reduced.
Preparation of Globular Microstructure in H18 Steel for Semi Solid Processing with the Use of Boron Addition
Authors: Dutkiewicz Jan , Głownia Jan , Rogal Łukasz
Published: September 2014

Martensitic stainless steel was chosen for a semi-solid processing due to high mechanical properties and resistance to high temperature surface oxidation. Modified H18 martensitic steel (1.1 % - C, 18.9 % - Cr, 0.1 % - V, 0.7 % - Mo, 0,9 % - Si, 2.0 % - Mn, balance Fe, all in weight %) modified with addition of 0.01 % boron was applied as a feedstock for semi-solid range temperature experiments. The samples were heated up to 1330°C to obtain about 26% of the liquid phase followed by rapid quenching in water. The microstructure of the samples consisted of austenitic globular grains (average grain size 42 μm, about 78 % of volume) surrounded by a eutectic mixture (ferrite, and M7C3,M23C6carbides as identified by X-ray and electron diffraction). The initial hardness of as-cast sample was 357 HV5and that after quenching from liquidus solidus range was 422 HV5. The X-ray analysis confirmed the presence of 16% - α-Fe, 80% - γ-Fe and 4% - M7C3carbides in rapid quenched sample. The EDS analysis of a eutectic mixture was as follows: 6.2 % - C, 31.7 % Cr, 0.1 % - Mn, 0.6 % - Si, 61.2 % Fe. The chemical composition analysis of globular grains confirmed the presence of 2.0% C, 16.3 % - Cr, 1 % - Si, 1.7 % - Mn, 0.5 % - Mo, 78.5% Fe.
Effects of Cu on the Microstructures and Tensile Properties of Thixoformed Al-Si Alloys
Authors: Salleh Mohd Shukor , Omar Mohd Zaidi , Syarif Junaidi , Alhawari K.S. , Mohammed M.N.
Published: September 2014

In this study, the effects of copper content on the microstructures and tensile properties of thixoformed Al-5Si-xCu-0.5Fe (x =1.0, 2.0 and 3.0 wt. %) were investigated. For this study, three different alloys having various amounts of copper were prepared using cooling slope casting before thixoforming. The semi-solid liquid range for the alloys were estimated using the diffrential scanning calorimetry (DSC) analysis. The samples were thixoformed at 40% liquid fraction. Some of these samples were treated with a T6 aging process. The thixoformed and thixoformed T6 samples were then characterized by optical microscopy, scanning electron microscope (SEM) and energy dispersive X-ray (EDX) as well as tensile tests. The different phases formed in the thixoformed and thixoformed T6 samples were throughly investigated.The results indicate that as copper content increases, the tensile strength also increases, which might due to precipitation hardening. The thixoformed T6 alloys attained an ultimate tensile strength (UTS) as high as 303 MPa when Cu content is 3 wt%.
Putting J Chain Back on the Map: How Might Its Expression Define Plasma Cell Development?
Authors: Castro Caitlin D. , Flajnik Martin F.
Published: September 2014

Joining chain (J chain) is a small polypeptide that regulates multimerization of secretory IgM and IgA, the only two mammalian Igs capable of forming multimers. J chain also is required for poly-Ig receptor–mediated transport of these Ig classes across the mucosal epithelium. It is generally assumed that all plasma cells express J chain regardless of expressed isotype, despite the documented presence of J chain− plasma cells in mammals, specifically in all monomeric IgA-secreting cells and some IgG-secreting cells. Compared with most other immune molecules, J chain has not been studied extensively, in part because of technical limitations. Even the reported phenotype of the J chain–knockout mouse is often misunderstood or underappreciated. In this short review, we discuss J chain in light of the various proposed models of its expression and regulation, with an added focus on its evolutionary significance, as well as its expression in different B cell lineages/differentiation states.
Five challenges for disability-related research in sub-Saharan Africa
Authors: Swartz Leslie
Published: September 2014

Disability research in contemporary sub-Saharan Africa is developing rapidly, and this is something to be celebrated. This article reviews some contemporary developments and suggests that there are five central, and interrelated, challenges for the field. These challenges – experience, expertise, enumeration, evidence, and expectations – go to the heart of thinking about disability research in sub-Saharan Africa. An optimistic but appropriately critical approach to addressing these issues is suggested.
An archaeological search for the emergence of early humans in West Africa
Authors: Agai Jock M.
Published: September 2014

Fossils of early humans and their ancestors dating back to millions of years have not yet been found in West Africa. Tools made of bones, stones, and wood suggesting use by early humans or their ancestors have however been found in some parts of West Africa. This research investigates the possible origins and West African indigenous influences on the manufacture and use of these tools. The purpose of this research is to stimulate interest into the study of West African archaeology and palaeontology.
On a generalized Muskat–Brinkman type problem
Authors: Chemetov Nikolai , Neves Wladimir
Published: September 2014

We show the solvability of a multidimensional Muskat type initial boundary value problem. The proposed mathematical model describing the transport phenomena of non-homogeneous flow in porous media, relies on a generalized formulation of the Brinkman equation.
On the regularity of the free boundary for quasilinear obstacle problems
Authors: Challal Samia , Lyaghfouri Abdeslem , Rodrigues José Francisco , Teymurazyan Rafayel
Published: September 2014

We extend basic regularity of the free boundary of the obstacle problem to some classes of heterogeneous quasilinear elliptic operators with variable growth that includes, in particular, the

p(x)

-Laplacian. Under the assumption of Lipschitz continuity of the order of the power growth

p(x)>1

, we use the growth rate of the solution near the free boundary to obtain its porosity, which implies that the free boundary is of Lebesgue measure zero for

p(x)

-Laplacian type heterogeneous obstacle problems. Under additional assumptions on the operator heterogeneities and on data we show, in two different cases, that up to a negligible singular set of null perimeter the free boundary is the union of at most a countable family of

C^1

hypersurfaces: i) by extending directly the finiteness of the

(n-1)

-dimensional Hausdorff measure of the free boundary to the case of heterogeneous

p

-Laplacian type operators with constant

p, 1 < p <\infty

; ii) by proving the characteristic function of the coincidence set is of bounded variation in the case of non degenerate or non singular operators with variable power growth

p(x)>1

.
On sharp interface limits for diffuse interface models for two-phase flows
Authors: Abels Helmut , Lengeler Daniel
Published: September 2014

We discuss the sharp interface limit of a diffuse interface model for a two-phase flow of two partly miscible viscous Newtonian fluids of different densities, when a certain parameter

\epsilon > 0

related to the interface thickness tends to zero. In the case that the mobility stays positive or tends to zero slower than linearly in

\epsilon

we will prove that weak solutions tend to varifold solutions of a corresponding sharp interface model. But, if the mobility tends to zero faster than

\epsilon^3

we will show that certain radially symmetric solutions tend to functions, which will not satisfy the Young-Laplace law at the interface in the limit.
The Book of Ezra and Nehemiah
Authors: Batten Loring Woart
Published: September 2014

No abstract available.
Opposition in Discourse
Authors: Jeffries Lesley
Published: September 2014

Lesley Jeffries introduces a phenomenon which has not been given the attention it deserves - the contextual construction of oppositional meaning. These are opposites not recognisable as such out of context but that are clearly set up this way in the text concerned. The significance of oppositional meaning is well-known, and has been discussed by scholars for millennia, from Philosophy to Politics. But the main emphasis has always been on the conventional opposite: the opposite recognised by lexical semantics. Starting from socio-cultural viewpoints, moving to original research and then concluding with a new theoretical formulation, this book introduces and consolidates a significant new approach to the analysis of oppositional meaning. It closes with a discussion of the importance of constructed opposition in hegemonic practice and makes a case for the inclusion of opposition as a central tool of critical discourse analysis. It will be essential reading for researchers and graduates in stylistics, linguistics and language studies.
Ice nucleation by water-soluble macromolecules
Authors: Pummer B. G. , Budke C. , Augustin-Bauditz S. , Niedermeier D. , Felgitsch L. , Kampf C. J. , Huber R. G. , Liedl K. R. , Loerting T. , Moschen T. , Schauperl M. , Tollinger M. , Morris C. E. , Wex H. , Grothe H. , Pöschl U. , Koop T. , Fröhlich-Nowoisky J.
Published: September 2014

Abstract. Cloud glaciation is critically important for the global radiation budget (albedo) and for initiation of precipitation. But the freezing of pure water droplets requires cooling to temperatures as low as 235 K. Freezing at higher temperatures requires the presence of an ice nucleator, which is a foreign body in the water that functions as a template for arranging water molecules in an ice-like manner. It is often assumed that these ice nucleators have to be insoluble particles. We put in perspective that also dissolved single macromolecules can induce ice nucleation: they are several nanometers in size, which is also the size range of the necessary critical cluster. As the critical cluster size is temperature-dependent, we see a correlation between the size of such ice nucleating macromolecules and the ice nucleation temperature. Such ice nucleating macromolecules have been already found in many different biological species and are as manifold in their chemistry. Therefore, we additionally compare them to each other, based on a composition of former, recent and yet unpublished studies. Combining these data with calculations from Classical Nucleation Theory, we want to foster a more molecular view of ice nucleation among scientists.