bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Determination of Concrete Resistance of Various Composition to Water and De-Icing Chemicals
Authors: Kocáb Dalibor , Komárková Tereza , Králíková Monika , Misák Petr , Moravcová Bronislava
Published: September 2016

The focus of the project GAČR 13-18870S is the research in concrete durability determined primarily by its surface layer quality. The surface layer can be difficult to assess for which reason the project makes use of available standardised and non-standardised test methods by means of which the concrete surface layer or its internal structure can be examined. One of these methods which is commonly used is Determination of resistance of cement concrete surface to water and defrosting chemicals. The paper presents the results of experiments performed with concretes differing only in w/c ratio and plasticiser content. Two more methods were used during the research based on the action of a thawing solution upon the surface of the specimen during freezing and thawing. The only difference between these methods is the direction in which the thawing agent acts on the test surface. The presumed experiment outcome was the existence of a strong dependence of the outcomes of the methods on the w/c ratio. The performed analyses confirmed the experiment presumption.
Experimental Determination of the Influence of an Air Entraining Additive on the Resistance of Concrete to Chemical Defrosting Agents
Authors: Kocáb Dalibor , Misák Petr , Králíková Monika , Komárková Tereza
Published: September 2016

The paper describes the results of an experiment performed as part of the GAČR 13-18870S project dealing with the durability characteristics of the surface layer of hardened concrete. The paper aims to evaluate the experimental determination of the influence of an air entraining additive on the resistance of cement concrete to water and defrosting chemicals. For the purposes of the experiment 4 mixtures were prepared which differed in the amount of air entraining additive and the amount of cement. The test results were evaluated using statistical analysis of experiment.
Coefficients of Transverse Contraction of the Wood Cell Constituents and their Effect on the Cell Behavior
Authors: Hlavata Vera , Kuklík Pavel , Hataj Martin
Published: September 2016

Wood cells are composed of cellulose, hemicellulose, and lignin. Geometrically we can idealize them as a set of hollow cylinders touching each other on the cylinder surface. The continuous displacements and stress state transmission are assumed on the cylinder surfaces. The article investigates stress development which is influenced by the wood cell axial elongation. Material properties of individual constituents are generally described by nine parameters characterizing orthotropic elastic material. Transversely isotropic constitutive model of was chosen for simplification. The analytical solution of the stress state was driven by the ideas of displacement method. Material parameters have been estimated according to available literature. The main task of our investigation was focused on the effect of transversal contraction. The actual calculation results are surprising and lead to reflection. These considerations and conclusions are summarized at the end of the paper.
Comparison of Modulus of Elasticity of Glued Laminated Timber
Authors: Klapálek Pavel , Prošek Zdeněk , Králík Vlastimil
Published: September 2016

This article focuses on testing of glued laminated timber beams and researching their properties. The article mainly focuses on comparison of measured modulus of elasticity obtained by two different methods. First method used was method of spike which has non-destructive character. This method was used to measure properties of glued laminated timber (GLT) on macro mechanical level in form of modulus of elasticity. Second method was used to determine micromechanical properties of material and is called nanoindentation. Tested material will be also described the article along with principle of testing and presenting results. Those results of individual measurements will be compared with respect to percentage representation of individual phases on micromechanical levels to measurement on macromechanical level.
Bonded Joints in Water-Repellent Timber Structures
Authors: Daňková Jana , Majstríková Tereza , Mec Pavel
Published: September 2016

Water in liquid and gaseous form is the main factor which significantly affects degradation processes in the wood. The mechanism and rate of wooden degradation processes can be effectively influenced by appropriate methods and technologies for its protection. However new knowledge, based on the possibilities of application of modern physical and chemical analytical methods, confirms that most well-known and previously commonly used protective equipment damages wooden structure. Many chemical substances, which are included in preservatives such as organic and inorganic biocides, or also flame retardants, are declared to be environmentally unacceptable. Nowadays, environmentally friendly treatment technologies of wood have increased attention to the above reasons. Wooden treatment by silicones ranks among the technologies which repellent, fire resistant and corrosion effectiveness is demonstrated by many authors. This article presents results of the experimental study that deals with the mechanical properties of bonded joints in the wood treated by silicones.
Modification of Silica Gel by Nanosilica
Authors: Peterová Adéla , Kotlík Petr
Published: September 2016

Consolidants based on silica gel have been widely used for the consolidation of decaying monuments. Consolidants reinforce building materials by replacing cement that has decayed. However, silica gels are formed by polycondensation, during which process they shrink and may crack from the internal tension. Therefore, their lifetime is limited and the building materials have to be treated time and time again. In this study, we investigate whether silica nanoparticles are able to absorb the internal stress caused by gel solidification and, thereby, prevent crack propagation. We carried out a time domain study of the sol-gel process under a stable laboratory conditions.
Composition and Microstructure of Plasters in Convent of the Želiv Monastery (Czech Republic)
Authors: Rezek Petr , Martinec Petr , Ščučka Jiří , Majstríková Tereza
Published: September 2016

The paper deals with analyses of composition and structure of historic plasters from the convent building of the Želiv Monastery (Czech Republic). Composition and microstructure of plaster samples taken from the historic object have been assessed using both traditional and advanced analytical methods. The following techniques have been used for the assessment of binders and fine aggregates in plasters: optical microscopy of thin sections, mineralogical and petrographic analysis of separated components, infrared spectroscopy, and thermal analysis. Presented results show significant differences in character of the studied materials of varying age and demonstrate the effectiveness of the taken analytical approach.
Microscopy Measurement of Open Porosity as a Function of Hydrophobic Impregnation
Authors: Pernicová Radka
Published: September 2016

In this paper open porosity as a function of hydrophobic properties was examined. It was measured three kinds of porous building materials which differ in their structure and properties. Especially, concrete samples such as: aerated concrete (denote as AC), normal strength concrete (denote as NSC) and ultra high performance concrete (denote as UHPC). We were focused on measurement of open porosity and distribution of pores in structure by microscopic method. The result clearly shows that concrete samples differ in among of pores, its geometric shape and deep and mainly in its distributions.
Water Vapour Resistance Factors of Three Wall Surface Finishing
Authors: Nenadálová Šárka , Balík Lukáš , Rydval Milan , Bittner Tomáš
Published: September 2016

There are results of water vapour resistance factors of three compositions commonly used for wall finishing in the paper. The compositions are: basic adhesive diffusion mortar; basic adhesive diffusion mortar with silicate plaster; basic adhesive diffusion mortar with acrylic plaster. There are not only the results of water vapour resistance factors but there are also the discussions as well as the impacts of the border conditions, it means temperature, relative humidity and barometric air pressure in the paper.
Development of Lightweight, Remediation Plasters and Study of their Moisture Behavior
Authors: Hroudová Jitka , Zach Jiří , Sedlmajer Martin , Korjenic Azra
Published: September 2016

One of the strategic goals of Europe 2020 is the reduction of greenhouse gas emissions by 20 % by 2020 compared to year 1990 and increasing energy efficiency by 20 %. Closely related to the revitalization of structures necessary for reasons reduction of their unsatisfactory energy consumption and then also the construction of new building structures with minimal energy requirements by using less energy demanding materials, if is it possible from easily renewable resources. Currently, the structures involved a high degree of total energy consumption in the European Union, about 40 %.
Thermal insulating plasters with using lightweight aggregate based on recycled glass are the appropriate remediation materials for the rehabilitation of existing buildings, or even for thermal insulation of new structures. In view of the fact that historic buildings are often exposed to dampness and moisture, it is necessary for these redevelopment plasters also tackle studios moisture transport. The paper describes the results of the development of new insulating plasters that would have been reflected particularly in the rehabilitation of historic buildings and problematic details of building structures.
A Study of Crushed Glass as a Replacement for Cement in Cement Pastes
Authors: Zahálková Jana , Rovnaníková Pavla
Published: September 2016

The production of Portland cement is connected with high emissions of greenhouse gases, especially carbon dioxide, and the intensive consumption of energy and natural resources. The present trend is for the replacement of cement by reactive admixtures, which can include ground waste glass, a material which shows pozzolanic activity. This paper deals with the determination of the mechanical properties of cement pastes in which part of the cement mixture (5 to 30 %) was replaced by borosilicate glass. The process by which the hydration of the cement with ground glass began was monitored by an isothermal calorimeter.
Determination of Fracture Toughness by Single and Double Action Tensile Impact Fracture Tests
Authors: Major Zoltan , Miron Matei , Kallai Imre
Published: September 2016

The characterization of the loading rate dependence of the fracture behavior of polymers is of prime theoretical and practical interest for supporting demanding engineering applications. To gain more insight into the high rate fracture behavior of polymers, fracture tests were performed under tensile loading conditions up to 12 m/s loading rate using a neat model polymer (PVC grey) in this study. A conventional single actuator test set-up for compact tension C(T) specimens was developed based on the previous experience of the authors and implemented on a new high rate servohydraulic testing machine. In addition, a novel double action test set-up was developed by applying two twin actuators and implemented in a rigid horizontal test frame. The conventional load and force measurement was extended by instrumented test specimens and by a high speed optical strain analysis system for both set-ups. Force based fracture toughness values using the peak load values, KIcPL and displacement based values using the critical crack opening displacement (CTOD) KICCTOD were determined up to a loading rate of 10 m/s. While the KIcPL values decreased up to a loading rate 103 MPam1/2s-1 an increase with a high data scatter was observed above them. Corresponding to the CTOD values the calculated KICCTOD values revealed a slight decrease and moderate data scatter up to the maximal loading rate.
Effect of Displacement Rate on Sharp Millimeter Indentation
Authors: Yamada Hiroyuki , Hotta Midori , Ogasawara Nagahisa
Published: September 2016

Indentation is widely used to investigate the elastic and plastic properties of materials, which include strain rate dependence. However, the results of the general micro-indentation test were affected by the microscopic scale of materials (e.g., surface roughness, and crystal grain size distribution), since the displacement was small. In the present study, we develop the sharp millimeter indention expanded displacement without the microscopic scale of materials. Furthermore, the effect of displacement rate on the sharp millimeter indentation was evaluated using the quasi-static and impact indentation test. In this study, high purity aluminum, with 99.99 mass%, was selected as the material with strain rate dependence of strength. The quasi-static indentation test was performed using the universal testing machine at the displacement rate of 8.3×10-7 m/s, 8.3×10-6 m/s, and 8.3×10-5 m/s. The impact indention was carried out at the displacement rate of approximately 3×100 m/s. The loading curvature decreased with increasing displacement immediately after indentation, and then this value was convergent, regardless of the displacement rate. It was clear that this convergent value was affected by the displacement rate.
Experimental Characterization of Crack Growth Behavior in Adhesive Interface under Impact Loading
Authors: Oshima Sota , Ishida Hisayoshi , Tanegashima Ryota , Kusaka Takayuki , Takeda Tomo
Published: September 2016

A novel experimental method has been developed to evaluate the mode I crack growth behavior of adhesively bonded joints under impact loading. The split Hopkinson pressure bar (SHPB) technique and the digital image correlation (DIC) technique was employed to evaluate the crack growth behavior. To reduce the dynamic effects by controlling loading input of the SHPB apparatus, the fracture toughness was determined precisely based on static evaluation formula. To contrive the testing set-up, high loading rate was kept until the arrest of crack. The fracture toughness of titanium alloy/epoxy adhesively bonded joints during crack propagation was obtained successfully by using present method.
Impact Compressive Fracture of Synthetic Quartz Accompanied by Electromagnetic Phenomenon
Authors: Kobayashi Hidetoshi , Horikawa Keitaro , Tanigaki Kenichi , Ogawa Kinya
Published: September 2016

In order to clarify the relationship between the mechanical properties of synthetic quartz and the electromagnetic phenomena during its fracture, a series of uniaxial compression tests were carried out at quasi-static and dynamic rates. Not only the stress-strain curves but also the output of ferrite-core antenna located close to the specimens were measured in a shield box made of permalloy plates. Since the synthetic quartz has three characteristic axes, i.e. optical axis, electric axis and machine axis, the effect of loading direction on the mechanical properties and electromagnetic phenomena of quarts was also examined. The dynamic compressive strength was greater than those in static tests and there is strain-rate dependence in their strength of synthetic quartz. It was also found that there are not any remarkable differences due to the loading direction with respect to the intensity of electromagnetic waves measured in the dynamic compression tests, i.e. the electromagnetic phenomenon does not depend on the loading direction.
Validation of the Hardening Behaviors for Metallic Materials at High Strain Rate and Temperature by Using the Taylor Impact Test
Authors: Piao Ming Jun , Huh Hoon , Lee Ik Jin , Kim Hyung Won , Park Lee Ju
Published: September 2016

This paper is concerned with the validation of the dynamic hardening behaviors of metallic materials by comparing numerical and experimental results of the Taylor impact tests. Several uniaxial tensile tests are performed at different strain rates and temperatures by using three kinds of materials: 4130 steel (BCC); OFHC copper (FCC); and Ti6Al4V alloy (HCP). Uniaxial material tests are performed at a wide range of strain rates from 10−3 s−1 to 103 s−1. Moreover, tensile tests are performed at temperature of 25 °C and 200 °C at strain rates of 10−3 s−1, 10−1 s−1, and 102 s−1, respectively. A modified Johnson–Cook type thermal softening model is utilized for the accurate application of the thermal softening effect at different strain rates. The hardening behaviors of the three materials are characterized by comparing the seven sequentially deformed shapes of the projectile from numerical and experimental results of Taylor impact tests.
The Resistance of Structural Elements to Impact and Shock-Wave Load
Authors: Kruszka Leopold , Vorobiov Iurii , Ovcharova Nataliia
Published: September 2016

The ability of structural elements withstanding impact and shock-wave loading has been considered. The dynamic stress-strain state of structural elements at the stage of occurrence of large elastic-plastic deformation and fracture has been investigated, and different criteria of the structure strength has been used. The numerical and experimental results have been compared.
Analysis of the Sliding Contact Behavior of a Centrifugal Clutch
Authors: Liu Chih Hsing , Chiang Yen Pin
Published: September 2016

The analysis of the sliding contact behavior for friction lining is an important issue in design of centrifugal clutches. In this study, a numerical model based on the moment equilibrium and contact mechanics has been developed to analyze the dynamics of a commercial centrifugal clutch. The proposed dynamic model can estimate the rotational speed of initial contact, output torque, and contact pressure for friction lining during the clutch operation. The comparison of the numerical and experimental results for the output torque of the analyzed centrifugal clutch shows the simulation agrees well with the experimental data. The difference for the maximum output torque is around 1.9%, which shows the effectiveness of the proposed method. The proposed dynamic model can reduce unnecessary physical prototypes and experimental cost, and is expected to be used to improve the design of the centrifugal clutches.
Analysis of Shell Material Influence on Detonation Process in High Explosive Charge
Authors: Balagansky Igor , Vinogradov Alexey , Merzhievsky Lev , Matrosov Alexander , Stadnichenko Ivan
Published: September 2016

The influence of the shell material (copper and silicon carbide) on the detonation process in cylindrical high explosive charge is experimentally and numerically investigated. We observed the significant differences of wave pictures in the detonation products and in the shells, which were due to differences in the sound velocities in the shells and rapid destruction of the ceramic shell under explosion loading. The specific features of a wave picture at the interface HE/ceramics due to desensitization of explosive under loading by an advanced wave in the shell were detected. Those features lead to decreasing of detonation pressure, blurring of the detonation front, and to increasing of mass velocity behind detonation front that is typical for under-compressed detonation. On the symmetry axis of HE charge in the ceramic shell behind the detonation front the long zone with practically constant pressure was observed. We have identified the mechanism of transmission of disturbances from the periphery to the symmetry axis of the HE charge. The source of the emergence of this zone is identified as transverse waves propagating directly behind the detonation front from the periphery to the symmetry axis of the HE charge.
Effect of Detachment Speed on Adhesion Strength of Gecko Inspired Adhesive Devices
Authors: Sekiguchi Yu , Sato Chiaki
Published: September 2016

Gecko has a special micro hair on its foot to attach to a surface and climb walls. Mimicking its hair, easily detachable adhesive devices have been developed creating micro-structures on the surfaces. Adhesion strength of these devices changes with peeling direction. Therefore, this dependency enables a compatibility of strong adhesion and easy detachment. In this study, the effect of peeling speed on the adhesive strength of the devices is experimentally investigated.
Rheological Behavior and Fluidity of Semi-Solid SiCp/A357 Composites with Different SiC Addition Levels
Authors: Zhang Zhen Lin , Zhang Zhi Feng , Xu Jun , Mao Wei Min
Published: September 2016

The apparent viscosities of the semi-solid SiCp/A357 composites with 0vol.%, 10vol.% and 20vol.% SiC particles manufactured by stir casting were investigated using a Couette type viscometer, and the composite fluidity was examined with a test casting. The results showed that, the viscosities of the semi-solid SiCp/A357 composites decreased with an increase in shear rate, but increased with the increasing of solid fraction, and apparent viscosity of 10vol.% SiCp/A357 composite was the lower than that of 20vol.% SiCp/A357 composite at the same solid fraction; and the composite fluidity results were in a good agreement with the viscosity ones.
Comparison of Morphological Evolution of Al-7wt%Si-2.5wt%Cu Alloy Produced by Direct Chill Casting/Electromagnetic Stirring and ECAP
Authors: Torres Luis Vanderlei , Proni Cecilia Tereza W. , Zoqui Eugênio José
Published: September 2016

In semisolid state forming the thermodynamic control of the solid liquid transition is necessary but not sufficient condition for having a good processing. For thixoforming it is critical to have a refined microstructure that during the heating to the semisolid state, achieve a mixture of small spheres immerse in liquid, which is crucial in order to get the best rheological properties for the slurry. This work compares the morphological evolution at the semisolid state of the Al-7wt%Si-2.5wt%Cu alloy produced by a) direct chill casting under electromagnetic stirring (EMS) combined with grain refinement and b) processed via one single pass in an equal channel angular pressing. EMS introduces metal flow during solidification that allows the better distribution of the nuclei provide by the grain refiner. ECAP has emerged as a promising technique capable of imposing large homogeneous deformations in metals, that could leads to a optimal grain refining. The ECAP deformation occurs in a die that contains two channels of the same cross-sectional area and form an angle of 120°. The raw materials were submitted to a heating treatment in order to reach 60% liquid fraction, at soaking times of 0s, 30s, 90s and 210s and the microstructure was evaluated via B&W and color metalography. Comparing the two production processes, it is observed that the ECAP process is highly efficient: while the traditional EMS method produced grains about 150 μm size, ECAP technique achieved grains of 60 μm, providing a fully globular structure, which exhibit favorable characteristics for the thixoforming process reaching to apparent viscosity about 2*104Pa.s.
Microstructure and Properties of LPSO Phase Reinforced Mg Alloy Produced by Rheocasting
Authors: Lü Shu Lin , Yang Xiong , Wu Shu Sen , Fang Xiao Gang , Wang Jing
Published: September 2016

The long period stacking ordered (LPSO) phase reinforced Mg alloys have received many researches in recent years because of their excellent mechanical properties. However, the LPSO phase usually concentrates at the grain boundaries with a coarse network structure, which seriously deteriorates its strengthening effect. In this research, rheocasting and ultrasonic vibration (USV) process were firstly used to refine the LPSO phase in Mg alloy. The semisolid slurry of Mg96.9Y2Zn1Zr0.1 (at.%) alloy was prepared by USV and then formed by rheo-squeeze casting (RSC). The effects of USV and squeeze pressure on the microstructure and mechanical properties of this Mg alloy were investigated. The results show that the primary α-Mg and coarse LPSO phases were refined obviously by USV and RSC. The tensile strength and elongation of the RSC Mg96.9Y2Zn1Zr0.1 alloy were 232 MPa and 17.7% respectively, which were increased by 17.8% and 172.3% respectively compared to the conventional liquid casting alloy. The refinement mechanism of the LPSO phase in semisolid Mg alloy is also discussed.
Filling, Feeding and Defect Formation of Thick-Walled AlSi7Mg0.3 Semi-Solid Castings
Authors: Santos Jorge , Jarfors Anders E.W. , Dahle Arne K.
Published: September 2016

Aluminium semi-solid castings have gained increased attention due to their superior mechanical properties, lower porosity compared to conventional high pressure die cast material. These characteristics suggests that semi-solid casting should be suitable to produce thick-walled structural components, yet most successful applications of semisolid casting have been for thin-walled components. There is a lack of understanding on filling and feeding related defect formation for semi-solid castings with thick-walled cross-sections. In the current study an AlSi7Mg0.3 aluminium alloy was used to produce semi-solid castings with a wall thickness of 10mm using a Vertical High Pressure Die Casting machine. The RheoMetalTM process was used for slurry preparation. The primary solid α-Al fraction in the slurry was varied together with die temperature. The evaluation of the filling related events was made through interrupted shots, stopping the plunger at different positions. Microscopy of full castings and interrupted test samples were performed identifying the presence of surface segregation layer, shear bands, gas entrapment, shrinkage porosity as well as burst feeding.
Crystallization and Ripening Phenomena in Semi-Solid Steels
Authors: Modigell Michael , Pola Annalisa , Volkmann Torsten , Zang Christoph
Published: September 2016

Rheological properties, crystallization and ripening phenomena have been investigated for three different steel grades in the semi-solid state. For each steel grade detailed investigation has been performed via differential scanning calorimetry to quantify the solid fraction as a function of temperature. The experimental procedure for all samples has been as follows: the completely liquid samples were cooled with a constant rate under constant shearing to temperatures corresponding to solid fractions of 30 and 40%. Tracking the viscosity during this procedure allowed analyzing the crystallization kinetics and final ripening process, which differ for the different steel grades. Evaluating the viscosity data on the base of a combination of convection dominated ripening model and a modified Krieger-Dougherty equation gives valuable information of the microstructural evolution. This is validated by additionally quenching samples.
Rheo-Forming AZ91D Magnesium Alloy Using Enthalpy Equilibrium Electromagnetic-Stirring Process
Authors: Zhang Xiao Li , Wang Tong Min , Zhang Chao
Published: September 2016

An enthalpy equilibrium electromagnetic-stirring process was introduced to semisolid metal processing for rheoforming route. AZ91D was die-casted under normally liquid state of Mg alloy, semisolid state of Mg alloy stirred using traditional EM-stirrer and an enthalpy equilibrium EM-Stirrer, respectively. Further step, effect of pouring temperature on microstructures and tensile properties of castings was researched in the introduced process. Experimental results indicated that samples of rheo-diecasted in the introduced process showed globular primary solid particle microstructure and better comprehensive mechanical properties, typical microstructures consisting of globular primary α-Mg grains and pseudoeutectic organization was observed in the castings with low solid fraction, while in higher solid fraction, the microstructure comprised of agglomerating primary solid particles and Mg17Al12 of divorced eutectic. With decreasing pouring temperature, the density of primary solid particles increased greatly, the size of primary solid particle evolved to coarse.
The Study of A356 Alloy Rheo-Squeeze Casting Process
Authors: Yang Xiang Jie , He Yi , Zhu Yong Bo , Hu Chuan Lin , Guo Hong Min , Jing Yun Hai , Yi Guang Bin
Published: September 2016

In this paper, the castings of A356 alloy were made by the rheo-squeeze casting with slurry-making from the process of LSPSF. Experiments were designed to study the influence of three parameters in rheo-squeeze casting process, such as injection speed, mould preheating temperature and injection pressure, on castings performance. The results show that high-quality castings were produced with the injection speed of 0.5m/s ,the mould preheating temperature of 240°C, the injection pressure of 50MPa. The mechanical properties, such as the yield strength, tensile strength and elongation of the castings with T6 heat treatment are 241 MPa, 328MPa and 11.6%, respectively.
Microstructure and Rheological Properties of Semi-Solid 7075 Slurries Using SEED Rheocasting Process
Authors: Bolouri Amir , Zhao Qin Fu , Côté Pascal , Chen X. Grant
Published: September 2016

The SEED rheocasting process was used to produce semisolid slurries of high strength 7075 aluminum wrought alloys. The effects of the SEED processing parameters on the microstructure of semisolid slurries were studied. The impact of grain refinement on the grain morphology and size was investigated. The rheological properties of semisolid 7075 alloys were characterized at different solid fractions using a parallel plate compression viscometer. Results indicated that the grain refinement could greatly improve the globularity of α-Al grains and rheoformability. The relationships between viscosity and shear rate at different solid fractions in the transient state for both unrefined and refined semisolid slurries were evaluated and discussed.
Thixomolding® at 25 Years
Authors: Decker Raymond , LeBeau Stephen , Wilson Bill , Reagan John , Moskovich Nir , Bronfin Boris
Published: September 2016

The technical and commercial development of Thixomolding® of magnesium (Mg) alloys is described. Based on the MIT semi-solid casting discovery, Dow Chemical adaption to Mg and Thixomat technical findings, Thixomat commercialized this process world-wide with Japan Steel Works (JSW) and numerous licensees in 13 countries. Some 480 Thixomolding machines have been commissioned by JSW to produce a wide range of parts for application in the communication/electronic, auto, sporting goods and hand-held tool markets. The advantages over conventional casting of Mg have been established in cleanliness, safety, worker comfort, machine portability, longer die life and reduced scrap. The competiveness of Thixomolding Mg has been enhanced by more durable and less expensive machine parts, longer die life, higher raw material yields by using hot nozzles and amenability to using recycled Mg scrap. The portability of this “foundry inside a machine” and availability of pre-owned machines allows quick set-up of Thixomolding operations. Several technical advances in Thixomolding are described. Solids content was optimized. Hot nozzles increased the part yield to >90% of the granule Mg alloy feed. Special steel barrels and liners are available to substitute for expensive Superalloys. In addition to conventional AZ91D and AM60, a wide range of Mg alloys can be Thixomolded. With Dead Sea Magnesium, AM70-TH and AJX810-TH were developed for improved ductility or creep strength. Low porosity and fine grain size of Thixomolding open the door to blister-free thermomechanical processing (TTMP) to boost the tensile and fatigue strength and ductility.
Deformation Behavior of Semi-Solid ZCuSn10P1 Copper Alloy during Isothermal Compression
Authors: Wang Jia , Zhou Rong Feng , Xiao Han , Lu De Hong , Li Lu , Bai Dan
Published: September 2016

The isothermal compression tests of semi-solid ZCuSn10P1 alloy by strain induced melt activation (SIMA) process are carried out by Gleeble-1500 thermo-mechanical simulator, and the same tests are finished to samples of as-cast ZCuSn10P1 alloy. The deformation temperature respectively is 910°C, 920°C and 930°C, and the strain respectively is 0.4 and 0.6, the strain rate is 0.5s-1, 1s-1 and 10s-1. The experimental results indicate that the deformation resistance of semi-solid ZCuSn10P1 copper alloy with smaller, more uniform and rounder solid grain is about half of the as-cast ZCuSn10P1 copper alloy. The deformation resistance of ZCuSn10P1 alloy by SIMA process decreases with the deformation temperature increasing, and the deformation resistance increases with the strain rate increasing.
Research on Fabrication and Semisolid Processing of Semisolid Slurries of 7075 Aluminum Matrix Composites Reinforced with Nano-Sized SiC Particles
Authors: Jiang Ju Fu , Wang Ying , Luo Shou Jing
Published: September 2016

Semisolid slurries of 7075 aluminum matrix composite reinforced with nano-sized SiC particles were fabricated by ultrasonic assisted semisolid stirring (UASS) method. Rheoforming and thixoforming of typical cylindrical parts were investigated. The results show that high-quality semisolid slurries with spheroidal solid grain of 38 µm were fabricated by UASS. The nano-sized SiC particles were dispersed uniformly due to transient cavitation and acoustic streaming of ultrasonic wave and high and controllable viscosity of semisolid slurry. Typical cylindrical composite parts with good surface quality and complete filling were rheoformed and thixoformed successfully. Ultimate tensile strength (UTS) of the rheoformed and thixoformed composite parts are enhanced due to addition of nano-sized SiC particles. However, elongation decreased as compared to those of the matrix parts. Maximum UTS of 550 MPa was achieved in the thixoformed composite part with T6 treatment. Increase of dislocation density around the reinforcement particles leads to improvement of the strength and wear resistance of the composite.
Effects of Grain Refiner on the Microstructural Evolution during Making Semi-Solid Slurry of the A357 Alloy
Authors: Liang Xiao Kang , Li Da Quan , Luo Min , He You Feng , Zhang Fan , Zhu Qiang
Published: September 2016

The enthalpy equilibration method is a novel technique to produce globular grain structure in semi-solid slurry preparation. In this process, the liquid is firstly poured into a metallic crucible, which possesses low thermal conductivity and high thermal capacity. Homogeneous distribution of temperature within the metallic crucible is achieved by rotating the crucible and cold down to a temperature between liquidus and solidus, determined by the requirement of solid fraction. The semi-solid slurry is then transferred to a high pressure die caster. In order to achieve a spherical microstructure morphologies in the entire slurry, effects of grain refiners, in addition to the enthalpy equilibration method, on the microstructure of the slurries of A357 alloy were investigated. Quantitative metallographic measurements were applied to evaluate microstructural evolution and processing parameters were optimized.
Round-Robin of High-Frequency Test Methods by IPC-D24C Task Group
Authors: Oliver Glenn , Weldon Jonathan , Nwachukwu Chudy , Andresakis John , Coonrod John , Wynants David L. , DeGroot Don
Published: September 2016

Currently, there is no industry standard test method for measuring dielectric properties of circuit board materials at frequencies greater than ~10 GHz. Various material vendors and test laboratories apply different approaches to determine these properties. It is common for these different approaches to yield varying values of key properties such as permittivity and loss tangent. The D-24C Task Group of IPC has developed this round-robin program to assess these various methods from the “bottom up” to determine if standardized methods can be agreed upon to provide the industry with more accurate and valid characteristics of dielectrics used in high-frequency and high-speed applications.
High-Permittivity and Low-Loss Electromagnetic Composites Based on Co-fired Ba0.55Sr0.45TiO3 or MgCaTiO2 Microfillers for Additive Manufacturing and Their Application to 3-D Printed K-Band Antennas
Authors: Castro Juan , Rojas Eduardo , Weller Thomas , Wang Jing
Published: September 2016

Six types of high-permittivity and low-loss electromagnetic (EM) composites based on a polydimethylsiloxane (PDMS) or cyclo-olefin polymer (COP) host matrix, reinforced by Ba0.55Sr0.45TiO3 or MgCaTiO2 microparticle fillers with volume loading concentration up to 49 vol. %, have been prepared and characterized up to 20 GHz using cavity resonators. These high dielectric permittivity (high-k) ceramic powders were sintered at temperatures up to 1,500°C to further enhance their dielectric properties. The 49 vol. % loaded PDMS-Ba0.55Sr0.45TiO3 composites with 1,340°C sintered fillers have a relative permittivity (ɛr) of 23.51 and a loss tangent (tanδd) <0.047 at frequencies up to 20 GHz. Meanwhile, the 39 vol. % loaded PDMS-Ba0.55Sr0.45TiO3 composites with 1,340°C sintered fillers have a ɛr of 15.02 and a tanδd <0.042 at frequencies up to 16 GHz. On the other hand, the 37 vol. % loaded PDMS-MgCaTiO2 composites with 1,100°C sintered fillers have an ɛr of 12.19 and a tanδd <0.021 at frequencies up to 20 GHz. The 49 vol. % loaded PDMS-MgCaTiO2 composite specimen has a measured ɛr of 16.33 and tanδd <0.021 between 0.4 and 20 GHz. In addition, thin-sheet specimens made of 25 vol. % COP-MgCaTiO2 prepared by fused deposition modeling have a ɛr of 4.74 and a tanδd <0.0018 up to 17 GHz. Similarly, 25 vol. % COP-Ba0.55Sr0.45TiO3 samples have a ɛr of 4.92 and a tanδd <0.0115 at frequencies up to 17 GHz. For demonstration of a device prototype, a 19.6-GHz microstrip patch antenna was printed by employing a molded PDMS-MgCaTiO2 composite substrate and microdispensed silver ink (CB028) to form the conductive layer, achieving a 20-dB return loss and ~10% bandwidth. Evidently, these newly developed polymer-ceramic composites are well suited for applications up to the K-band and are amenable to be adopted by 3-D printing technologies.
Additive Manufacturing Design and Fabrication of Ceramic Cylindrical Ion Trap Mass Analyzer Chips for Miniaturized Mass Spectrometer Smart-Device (Internet of Things) Applications
Authors: Roman Patrick , Chen Xudong , Jones W. Kinzy , Karbasi A. , Newton C. Mike , Bates Travis , Denkins Jacob , Bhansali Shekhar
Published: September 2016

The current computing power and network capabilities of handheld smart devices is helping to drive the development of new sensors, enabling the Internet of things. A chip-based mass spectrometer technology promises to offer a smart-device autonomous microsystem chemical analysis capability for sample determination and process monitoring for multiple applications in a small low-power instrument package. This project focuses on the development of cylindrical ion trap (CIT) mass analyzer chips fabricated using three-dimensional (3-D) additive manufacturing (AM) and planar low temperature cofired ceramic thick film processes for a chip-based mass spectrometer microsystem. The CIT is a mass analyzer composed of planar electrodes and operates by trapping and ejecting sample ions based on their mass in a radiofrequency field. Because of its simplicity, CITs may be easily miniaturized and connected in tandem to achieve multiplexing. AM materials and methods enable enhanced trap miniaturization through micromachining and electrode patterning methods, fast and cost-effective prototyping, batch fabrication, and material formulation flexibility. The current design incorporates three parallel ceramic plate metalized electrodes making up a singular trap geometry in a 10-mm2 ceramic chip, forming a mass analyzer of reduced size, mass, and power, with enhanced material robustness for extended range use and in harsh environments. Unique processes have been developed to produce these devices which include conformal metallization layers, adhesion layers, ceramic paste formulations, sacrificial supporting materials, and cofiring methods. Additionally, 3-D printing brings a unique design and fabrication capability enabling novel structures, material blending, and heterogeneous integration. With true digital control, the designs are easily scalable and shape agnostic.
Injectable disease modifying agents in multiple sclerosis: pattern of medication use and clinical effectiveness
Authors: Järvinen Elina , Holmberg Markus , Sumelahti Marja-Liisa
Published: September 2016

The objective of this study was to assess long-term use, adherence and efficacy of injectable disease modifying agents (DMAs). Multiple Sclerosis (MS) patients diagnosed during 2002-2010 with early treatment start and at least one year in first choice medication were included in a large university district in Finland. Annualized relapse rates (ARR) during each treatment period were studied, and number of switches by medication evaluated. Use of health care facilities during 2002-2010 was assessed. In the study were included 113 MS patients; 15 (13%) switched medication. The mean duration of treatment period (128) was 3.8 years. In 77% (98/128) the treatment continued with the first DMA for (mean) 3.8 years, in 19% (25/128) with the second for 3.5 years and in 4% (5/128) with the third for 4.8 years. Mean ARR was 0.26, with 54% (69/128) of the periods relapse free. Mean ARR during the treatment periods with product switch was 0.41 before, and 0.28 after the switch, showing a trend towards better efficacy with the second DMA. The usage of health care resources remained within the guidelines. Long-term adherence to first choice DMA was observed, and a switch of product within the DMAs showed continuous adherence and efficacy. The efforts to seek a clinically effective and well tolerated agent within the first-line DMAs is warranted, leading to continued adherence and increased clinical effectiveness.
Experiential Bloom’s Taxonomy learning framework for point-of-care diagnostics training of primary healthcare workers
Authors: Mashamba-Thompson Tivani P. , Sartorius Benn , Stevens Fred C.J. , Drain Paul K.
Published: September 2016

No abstract available.
Regina Mundi: Serving the liberation movement in South Africa
Authors: Oliver Willem , Oliver Erna
Published: September 2016

The struggle for ‘non-white’ South Africans to eventually become liberated in this country was a very tough and bloody one. In the struggle the South African Native National Congress – later renamed to African National Congress – as a liberation movement played a decisive role from the beginning of the 20th century, as the mainstream churches failed in the previous three centuries to really contribute to the liberation process. However, the Regina Mundi Catholic Church in Soweto serves as a good example of a church that did not look the other way during the struggle. This church assisted the liberation movement in promoting freedom for everyone,serving as the platform for many a politician and even, at least once, as a shelter against the raining bullets of the police.
The gospel in context: Hiebert’s critical contextualisation and charismatic movements in Sierra Leone
Authors: Bangura Joseph B.
Published: September 2016

This article examines the process of contextualisation adopted by charismatic movements (CMs) in Sierra Leone. In it I use Hiebert’s model of critical contextualisation to evaluate the biblical depth and cultural sensitivity of the CMs’ contextualisation. Three ongoing cultural issues are especially highlighted as crucial and are used as the point of departure in the discussions: initiation ceremonies, polygamous marriage practices and ancestral rituals. The article concludes that, whilst the danger of syncretism is likely to occur where uncritical forms of contextualisation are employed, the CMs in Sierra Leone are attempting to address themes that are concurrent with the African sensibilities of its followers. This is an effort to build authentic forms of Christianity that are faithful to Holy Scripture and relevant to the setting in which they are developed.
Ouderlinge met preekvergunning: ‘n Herlewing van Dordtse Kerkorde artikel 8?
Authors: Strauss Piet
Published: September 2016

Elders with consent to preach: A revival of Church order of Dordt (DCO) art 8? There seems to be a need for members other than trained ministers to preach in Reformed Churches. This need comes to the fore especially during periods in which traditional academically trained ministers are lacking. The well-known Synod of Dordt (1618–1619) made provision for members with extraordinary (singular) gifts to become ministers of the Word. In this it was continuing a practice in the Reformed Churches in the Netherlands of the 16th century. Other reformed churches followed. In the Dutch Reformed Church elders with the necessary abilities who are trained in short spells are nowadays also used to preach the Word. This article investigates the latter in the light of the former and the content of article 8 of the Church order of Dordt (DCO).
Blended interaction: Implementing a bring-your-own-device approach versus provided tablet computers
Authors: Olivier Jako
Published: September 2016

Effective interaction in classes and real-time feedback are challenges that may occur in any classroom. In this regard, mobile technologies may act as a supplement in a so-called blended context. This article investigates the role a bring-your-own-device approach in comparison with an approach where similar tablet computers are provided, plays in terms of interaction and feedback in a linguistics class at third-year university level. In this way the gap in the literature regarding the implementation of blended learning in higher education in South Africa and especially in terms of the bring-your-own-device approach could be augmented. In this research a case study design was used and the data of two groups of third-years were gathered by means of qualitative methods. User statistics from a learning management system was collected, but the main data consisted of the observations and reflections of the lecturer, as well as feedback from students by means of short questionnaires. This data was analysed in an inductive manner in order to identify relevant themes and codes. Both a bring-your-own-device approach and the use of provided tablet computers could facilitate effective interaction and real-time feedback. Apart from the benefits, some limitations were identified in terms of access and skills among students. In this specific context, the bring-your-own-device approach seems to be the better option, but for other contexts solutions will have to be customised.
Interrupted aortic arch with isolated persistent left superior vena cava in patient with Turners syndrome
Authors: Kattea M Obadah , Smettei Osama A , Kattea Abdulrahman , Abazid Rami M
Published: September 2016

We present a case of 13-year-old female with Turner syndrome (TS), who presented with unexplained lower limbs swelling and ejection systolic murmur at the left second intercostal space. Suspicion of mild aortic coarctation was made by echocardiography. Computed tomography angiography (CTA) showed a complete interruption of the aortic arch (IAA) below the left subclavian artery with persistent left superior vena cava (PLSVC) and absent right SVC, defined as an isolated PLSVC. The patient underwent successful surgical correction after unsuccessful trial of transcatheter stent placement. We present this case of asymptomatic IAA to draw attention to the importance of CTA in diagnosing such rare anomalies and ruling out asymptomatic major cardiovascular abnormalities in patient with TS.