bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Mullite-Silica-Rich Glass Using Waste Foundry Sand
Authors: Xiang Ruo Fei , Li Yuan Bing , Qiu Yong Bin , Li Ya Wei , Xu Yue Ze , Li Shu Jing , Sang Shao Bai
Published: March 2014

Waste foundry sand is a kind of solid wastes produced during casting process, the casting output of China ranks first in the world for many years and the amount of waste foundry sand is huge. But the utilization rate of the waste foundry sand is low in China. It is not only a threat to the environment but also a waste.In this paper, waste foundry sand was taken as main starting material, adding proper amount of additives. The shaped samples were heated in the electric oven at the temperature of 1300°C, 1400°C and 1500°C respectively, the soaking time is 3h for all samples.The microstructure and phase composition of the samples were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The effect of the temperature on the synthesis of mullite-silica-rich glass was investigated. The results showed that the main phases were mullite and glass when the samples were heated at 1500°C, mullite grain grew well and formed network structure. This network was benefical to improve the thermal shock resistence.It opens up a new method to utilize the waste foundry sand.
Microstructure, Mechanical Properties, and Electrical Resistivities of Mica Glass-Ceramics with Flake Phlogopite and Waste Glass
Authors: Chen Yu Fei , Liu Yan Gai , Wu Xiao Wen , Huang Zhao Hui , Fang Ming Hao
Published: March 2014

Mica glass-ceramics can be applied in all kinds of electrical equipment, locomotive internal circuits in high-speed rail, ordinary electric locomotive and subway locomotive. In this study, mica glass-ceramics were prepared by sintering process using flake mica and waste glass as the main raw material with low cost. Different mica glass-ceramic samples were fabricated by changing the formula of raw materials, molding process and sintering temperature. X-ray diffraction, scanning electron microscopy, three-point bending test, and balanced-bridge technique were applied to investigate the phase, microstructure, mechanical and electrical resistivities of the samples, respectively. The results show that the optimum sintering temperature is 900 to 1000 °C holding for two hours, the desirable ratio is 70 wt% of mica powder while 30 wt% of glass powder. In that condition the sample could be less porosity, high flexural strength (63.3 MPa) and eligible electrical resistivity (0.4×1013 Ω·cm).
Fatigue Short Crack Growth and Mechanism of GH4133B Superalloy Used in Turbine Disk of Aero-Engine
Authors: Zhao Rong Guo , Li Wei , Jiang Yong Zhou , Luo Xi Yan , Li Jun Fei , Li Qi Bang , Liu Ya Feng , Yan Yi
Published: March 2014

The short fatigue crack growth tests for circular notched compact tension specimens of GH4133B superalloy used in turbine disk of aero-engine are carried out at ambient temperature and atmospheric pressure. The stress intensity factor ranges and the fatigue crack growth rates at various stress ratios are measured, and the corresponding effective stress intensity factor ranges considering the crack closure effect are calculated. It is shown that the effective stress intensity factor range ΔKeff, can be applied to describe the deceleration and acceleration of crack growth rate during the short crack propagation. The fatigue fracture surface morphologies in the short crack growth region are investigated using a scanning electron microscopy. It is found that there is a cleavage step between two adjacent radial striations, a series of early fatigue striations exist on the cleavage step, and some secondary cracks perpendicular to the direction of main crack propagation emerge on the fracture surface, the superalloy exhibits a mixed fracture mode in the short crack growth region, which reveals the microscopic mechanism of short crack propagation that the fatigue crack growth rate is primarily higher, and then gradually decreases with the propagation of short crack.
Effect of Al2O3 and MgO Additives on Dielectric Properties of BaZrxTi1-xO3-Based Ceramics
Authors: Feng Hong Jun , Ji Hui Ming , Li Xiao Lei , Wang Jian , Wang Da Hao
Published: March 2014

BaZrxTi1-xO3-based (BZT) ceramics with Al2O3 and MgO addtives were prepared by the conventional solid state method with BaCO3, ZrO2, TiO2, Al2O3 and MgO as raw materials and B2O3 and Li2CO3 as sintering additive. The morphologies were analysized by scanning electron microscopy (SEM). The dielectric constant and dielectric loss of ceramics were measured by LCR meter. The temperature dependences of dielectric constant were measured by high-low temperature incubator tank and LCR meter at 1 MHz and a temperature range-55 to 125 °C. The tunabilities were tested by C-T-V converter and LCR meter at 1 MHz at room temperature. The results show that with the increase of Zr/Ti, BZT ceramic dielectric constant increases, the loss increases, the Curie temperature moves to a lower temperature, and dielectric bias field coordination is relatively lower. The SEM images show that the grain size reaches about 1-2 μm when the sintering temperature is 1100 °C, and the addition of Al2O3 and MgO promote the grain growth and densification of the composite ceramics. The Curie peaks are broadened and depressed with the addition of Al2O3 and MgO. The tunability is improved to 9.59% under a DC electric field of 7.0 kV/cm after the addition of Al2O3. The dielectric constant and dielectric loss of BaZr0.25Ti0.75O3-30wt%Al2O3 and BaZr0.25Ti0.75O3-30wt%MgO are 586, 0.011 and 486, 0.003, respectively. The optimistic dielectric properties make it a promising candidate for the application of tunable capacitors and phase shifters.
Microstructure and Electrical Properties of Al2O3-Doped Ba0.9Ca0.1Ti0.8Zr0.2O3 Based Dielectric Ceramics
Authors: Wang Yue Ping , Wang Xiao Hui , Peng Zhi Jian , Li Long Tu
Published: March 2014

Al2O3-doped Ba0.9Ca0.1Ti0.8Zr0.2O3(short for BCTZ) based dielectric ceramics were fabricated by sintering samples at 1300°C for 2h with conventional ceramic processing method. The microstructure and electrical properties of the as-prepared samples were investigated. X-ray diffraction analysis showed that after the addition of Al2O3with the amount designed in this study, no new phase was examined in the detection limit. Through scanning electron microscopy it was found that the doping of Al2O3can help the growth of BCTZ grains, and the relative permittivities of the samples. The result of electrical properties indicated that the resistance and the break voltage of the samples could be improved to some extent with appropriate doping amount of Al2O3resulting in the highest dielectric constant ~17000, low dielectric loss <10%, and highest break voltage 8.4 kV/mm, respectively.
Low-Temperature Sintering and Microwave Dielectric Properties of (Ca0.9Mg0.1)SiO3 Ceramic with Li2CO3 Addition
Authors: Zhao Xin Hui , Wang Min Jia , Zhang Qi Long , Yang Hui
Published: March 2014

(Ca0.9Mg0.1)SiO3ceramics possess a low dielectric constant and a highQfvalue, however, the densification temperature of (Ca0.9Mg0.1)SiO3ceramics is higher than 1280°C. In this paper, the effect of Li2CO3addition on sinterability and dielectric properties of (Ca0.9Mg0.1)SiO3ceramics were studied. The phase presence and surface morphology were determined by XRD and SEM techniques, respectively. CaSiO3and Ca2MgSi2O7phases were observed. With the addition of >2.0 wt% Li2CO3, the sintering temperature of (Ca0.9Mg0.1)SiO3ceramic was significantly lowered, reaching to 1070°C. (Ca0.9Mg0.1)SiO3ceramics with 4wt% Li2CO3sintered at 1070°C for 3 h shows excellent dielectric properties:εr=5.91,Qf= 15300GHz (at 10GHz).
The Preparation and Characterization of Geopolymer Based Inorganic Membranes
Authors: Liu Jing , He Yan , Yuan Yuan , Huang Jing Lin , Cui Xue Min
Published: March 2014

In this work, the geopolymer based inorganic membranes, as a kind of new inorganic membranes, were synthesized with water-glass, metakaolin and deionized water. The resulting membranes were characterized by SEM, water flux and pore size. The results show that the membranes have high strength and water flux when these membranes were fabricated under the preparation condition: water-glass modulus of 1.1, Na/Al molar ratio of 0.8 and H2O/Na2O molar ratio of 18. Keywords:Geopolymer; Inorganic membranes; Preparation; Characterization
Low Temperature Sintering of (Ba0.98Ca0.02)(Sn0.04Ti0.96)O3 Ceramics Using CuO-B2O3 as a Sintering Additive
Authors: Zhou Jian Qiang , Chen Ke Pi
Published: March 2014

The effects of CuO-B2O3(CBO) additive on densification, microstructure, and electrical properties of (Ba0.98Ca0.02)(Sn0.04Ti0.96)O3(BCST) cermaics were investigated. The phase compositions, microstructure, dielectric, ferroelectric and piezoelectric properties of BCST ceramics were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), precision impedance analyzer, ferroelectric tester and quasi-static piezoelectric constant testing meter, respectively. The results show that CuO-B2O3(CBO) frit can improve the densification and promote low-temperature sintering of BCST ceramics prepared by a conventional solid-state reaction method. Dense BCST ceramics with CBO can be sintered at temperatures as low as 1175 °C, which is approximately 275 °C less than the sintering temperature of pure BCST. When sintered at 1200 °C, the optimized properties of the BCST ceramics with 0.5 wt% CBO were obtain asε= 1206,d33= 346 pC/N,kP= 0.39, tgδ = 0.009.
Effect of Sintering Temperature on the Structure and Piezoelectric Properties of Lead-Free 0.97K0.5Na0.5NbO3-0.03AlFeO3 Ceramics
Authors: Peng Ling , Jiang Min Hong , Gu Zheng Fei , Cheng Gang
Published: March 2014

Lead-free piezoelectric 0.97 K0.5Na0.5NbO3-0.03 AlFeO3(KNN-AF) ceramics were prepared at low temperature of 980 °C to 1020 °C by the conventional ceramic process. The effect of sintering temperature on the crystal structure, density and electrical properties of the ceramics was investigated. The results indicate that KNN-AF ceramics sintered at an low temperature of 1000 °C exhibit high electrical and piezoelectric properties, with piezoelectric constantd33=116ρC/N, and electromechanical coupling factorkp= 32.9%, polarization (Pr) wasPr=21.8 μC/cm2and curie temperatureTC=382°C. This also indicates that KNN-AF ceramics are promising candidate materials for lead-free piezoelectric applications.
Sensing Properties of YSZ-Based NO Sensors with Double-Perovskite (La0.8Sr0.2)2FeNiO6-δ Sensing Electrodes
Authors: Zhou Li Hong , Wu Hai Yan , Yuan Quan , Li Xiang Dong , Xu Pei Wei , Wang Rong , Xia Feng , Xiao Jian Zhong
Published: March 2014

The powder of (La0.8Sr0.2)2FeNiO6-δ (LSFN) oxide with double-perovskite structure was synthesized by polymeric precursor method. Then the YSZ-based NO sensors with LSFN sintered at different temperatures (1000, 1100, 1200 and 1300 °C) as sensitive electrode (SE) were fabricated. All samples were characterized by XRD. The morphologies of the LSFN-SEs were observed with ESEM. The NO sensing properties of the sensors were investigated in the operating temperature range of 350-650 °C in 10 vol. % O2. Results demonstrated that the sensor with LSFN-SE sintered at 1300 °C exhibited highest response to 500 ppm NO at 400 °C, which was about 85 mV. A linear relationship was obtained between the emf and the logarithm of NO concentration from 500 to 800 ppm at 400 and 500 °C. Moreover, both magnitude and slope to NO response decreased as operating temperature increased. And both the response time and recovery time shortened as temperature increased. But the recovery rate was slower than the response rate, especially at and below 450 °C. The optimal sensor response was obtained at 500-550 °C.
The Influence of Sintering Temperature on the Microstructure and Electrical Properties of BiFeO3 Ceramics
Authors: Deng Xiao Ling , Liu Xing Bing , Cai Wei , Fu Chun Lin , Huang Jia Mu
Published: March 2014

This study reports the synthesis of bismuth ferrite ceramics (BiFeO3, BFO) by the sol-gel method and the effect of different sintering temperatures (800 °C, 820 °C, 850 °C, 880 °C, 900 °C) on the crystal structure, morphology, dielectric properties and ferroelectric properties of the bismuth ferrite ceramics. It is observed that the bismuth ferrite phase are formed when the molar ratio of bismuth and ferric is 1.025 : 1, and the bismuth ferrite ceramics have less impurity phase at all the five sintering temperature. The morphology studies revealed that the grain of bismuth ferrite ceramics is spherical and the grain size increases with the increasing of the sintering temperature. When the bismuth ferrite ceramics with excessive bismuth sintered at 820 °C, it exhibits the higher dielectric constant and the lower dielectric loss, the remnant polarization and the coercive field are 0.35 μC/cm2 and 4.03kV/cm, respectively. The observed ferroelectricity in bismuth ferrite ceramics owes to the point defects associated with oxygen vacancy defects as well as the smaller size effect.
Structure and Magnetic Properties of Ti-Co Co-Cubstituted Barium Hexaferrite
Authors: Zhang Zheng Qiang , Xia Qing Lin , Guo Guang Hua , Zhang Hai Fa , Dong Cun Jun
Published: March 2014

Polycrystalline Ti-Co co-substituted M-type ferrites Ba (TiCo)xFe12-2xO19 (x=0.25,0.5, 0.75, 1.0 ) samples were prepared by the citrate precursor method. The particle structure and morphology of the products were characterized by X-ray powder diffraction (XRD) and Field Emission Scanning Electron Microscope (FE-SEM). The effects of the substitution rate on the magnetic properties of samples were analysed by magnetic measurement with the Vibrating Sample Magnetometer (VSM) of Physical Properties Measurement System (PPMS). The XRD patterns show that only one type of crystalline phase can be detected and the substitution did not change the crystal structure. The SEM micrographs of Ba (TiCo)xFe12-2xO19 calcined at 450 °C for 5h, and then 950°C for 5h show that the M-type ferrite particles were homogeneously shaped and the grain sizes had no obvious differences when the substitution rate changed. The magnetic hysteresis loops illustrate that the coercivity (Hc) decreased rapidly with the increasing of Ti-Co substitution, while the saturation magnetization (Ms) changed slowly.
Sintering Behavior and THz Absorption Properties of B2O3 Doped Ca[(Li1/3Nb2/3)0.95Zr0.15]O3 Ceramics
Authors: Hu Ming Zhe , Mu Kai Jun , Ding Zhao , Xiong Gang
Published: March 2014

In the present paper, the sintering behavior and the THz absorption properties of B2O3doped Ca [(Li1/3Nb2/3)0.95Zr0.15]O3(CLNZ) ceramics are investigated. The results indicate that the sintering temperature of CLNZ ceramic can be significantly lowered by the doping of B2O3. The crystal structure evolution, phase assemblage as well as the microstructure properties are investigated by XRD and SEM respectively. The sintering mechanism is investigated based on microstructure analysis, where the liquid phase sintering is proposed to control the whole sintering process. The relative density of the B2O3doped CLNZ ceramics possess the optimum value when the B2O3doping content x is 1.5wt%. The THz absorption properties of B2O3doped CLNZ ceramics sintered at 1020°C are investigated and are related to the microstructure, phase assemblage and crystal structure factors.
Effect of Grain Growth Inhibitors VC/Cr3C2 on WC-ZrO2-Ni Composite Mechanics
Authors: Yung Der Liang , Dong Min Jie , Hussainova Irina
Published: March 2014

The effect of VC and Cr3C2 grain growth inhibitors on mechanical properties of the WC-Ni-ZrO2 composites are studied in the present work. The microstructural features responsible for a change in mechanical properties are analysed. Addition of both VC and Cr3C2 results in increase in hardness of the WC-based system, but consequently in decrease in fracture toughness. The transformation toughening effect of ZrO2 is not effective for the loading conditions applied in this study.
Extractive-Pyrolytic Method for Au/MeOx Nanocomposites Production
Authors: Serga Vera , Kulikova Lidiya , Cvetkov Anton , Chikvaidze George , Kodols Maris
Published: March 2014

Au/MeOx(MeOx- SiO2, Al2O3and TiO2) nanocomposites have been produced by the extractive-pyrolytic method. An organic extract – a solution of n-trioctylammonium tetrachlorolaurate ([Oct3NH]AuCl4) in toluene – was used as a gold-containing precursor. The produced samples were analyzed by IR spectroscopy, X-ray diffraction and scanning electron microscopy. The performed studies have shown that the mean size of the metal crystallites vary within wide limits: on Al2O3from 60 nm to 35 nm; on SiO2from 33 nm to 23 nm; on TiO2from 50 nm to 13 nm.
Multi-Component Composites Based on Polypropylene, Ethylene-Octene Copolymer and Zinc Oxide
Authors: Bochkov Ivan , Merijs Meri Remo , Zicans Janis , Ivanova Tatjana , Grabis Janis
Published: March 2014

Multi-component blends of polypropylene (PP), ethylene-1-octene copolymer (EOC) and zinc oxide (ZnO) are prepared by melt mixing using two-roll mill. Samples prepared by compression moulding have been investigated by using differential scanning calorimeter (DSC). It is found that addition of ZnO particles decreases PP melting point and increases crystallinity degree of PP. ZnO works as nucleation agent for PP by increasing quantity of crystallization centers, but at the same time decreasing structure quality. Because of the structure change mechanical properties are affected. At lower nanoparticle concentration some reinforcement effect I observed, while at higher particles concentration brittlening occurs. Crystalline structure and particles nature increases thermal stability of PP and PP/EOC blends.
Properties of High Performance Concrete Containing Waste Glass Micro-Filler
Authors: Sahmenko Genadijs , Toropovs Nikolajs , Sutinis Matiss , Justs Janis
Published: March 2014

The article discusses possibilities for use fine ground glass obtained from fluorescent lamp utilisation as micro filler in High Performance Concrete (HPC). Investigated mix compositions are based on silica fume (SF) and SF combination with glass powder. Testing results indicates that replacing silica fume by additionally ground fluorescent glass (up to 50%) slightly increasing consumption of water and delaying setting time of cement paste. All HPC mixes with glass powder showing decreased early-age strength and considerable strength gain after long-term hardening. It is concluded, that the best way of glass application in HPC is use fine ground glass powder together with silica fume as complex admixture.
The Effect of Activator on the Properties of Low-Calcium Alkali-Activated Mortars
Authors: Bumanis Girts , Bajare Diana , Locs Janis
Published: March 2014

Properties of the low-calcium alkali-activated materials (AAMs) made from the metakaolin, waste glass and sand were tested in this research. Specimens with dimensions 40x40x160mm were prepared. The correlation between development of microstructure and concentration of NaOH solution used for preparing of the AAMs was observed. Structure investigation with SEM and FTIR was performed to describe the formation of microstructure in low-calcium AAMs. The research results aimed that the improvement of physical and mechanical properties of the AAMs with increasing the activator’s concentration from 2 to 10 mol/kg H2O were in concordance with the structure development of AAM. The 28 days old AAMs with a compressive strength up to 31MPa and water absorption lower than 2% were obtained by using activator with concentration 10 mol/kg H2O.
Calcium Phosphate Bone Cements Reinforced with Biodegradable Polymer Fibres for Drug Delivery
Authors: Irbe Zilgma , Loca Dagnija , Bistrova Ivita , Berzina-Cimdina Liga
Published: March 2014

Conventional calcium phosphate bone cements are self setting water based pastes. Recently pre-mixed calcium phosphate bone cements have been proposed that have non-aqueous fluid as liquid phase of the paste. Such cements thus only start setting reaction in contact with body fluids. In this work the properties (cohesion, compressive strength, phase composition) of pre-mixed calcium phosphate cements based on α-tricalcium phosphate and calcium dihydrogen phosphate monohydrate are described. Properties of several cement compositions are examined and compared to properties of β-tricalcium phosphate and calcium dihydrogen phosphate monohydrate based cements. It was found that α-tricalcium phosphate and calcium dihydrogen phosphate monohydrate based cements have higher compressive strength (10 - 15 MPa) than corresponding β-tricalcium phosphate and calcium dihydrogen phosphate monohydrate based cements (10 - 6 MPa). Out of examined cement paste liquids (glycerol, polyethylene glycol and polypropylene glycol) cements using glycerol as the liquid phase had higher compressive strength and are more cohesive.
Scale-Up of Wet Precipitation Calcium Phosphate Synthesis
Authors: Sokolova Marina , Putnins Andris , Kreicbergs Imants , Locs Janis
Published: March 2014

Within current research calcium phosphates were synthesized by wet chemical precipitation method in laboratory and pilot scale reactor. The aim of this work was to study the influence of main technological parameters of wet chemical precipitation synthesis and scale-up of laboratory synthesis. The results showed that it is possible to obtain calcium phosphates with different and reproducible phase compositions such as hydroxyapatite (HAp), β-tricalcium phosphate (β-TCP) and biphasic calcium phosphates (HAp/β-TCP) in pilot scale reactor. Using the method developed it was possible to increase the product yield more than 30 times compared to formerly used laboratory scale method.
Application of Ion Exchange Resins in the Separation of Valuable Compounds from Wood Pyrolysis Liquids
Authors: Meile Kristine , Zhurinsh Aivars , Spince Baiba , Dobele Galina
Published: March 2014

Biomass, such as wood, is an important renewable raw material for the production of various products. Since one of the main constituents of wood is cellulose, a polysaccharide, fast pyrolysis of wood yields liquid products with a noteworthy content of sugars. The purpose of the present study was to develop a method for the chromatographic separation of valuable compounds, such as levoglucosan, from the complex mixture of wood pyrolysis products by using an ion exchange resin column.
Electrochemical Studies of Nonstoichiometric TiO2-x Ceramic
Authors: Narkevica Inga , Reimanis Madars , Kleperis Janis , Ozolins Jurijs , Berzina-Cimdina Liga
Published: March 2014

TiO2 ceramic was prepared using extrusion technology and thermal treatment in two stages: sintering in air and subsequent annealing under high vacuum conditions. Sample thermal treatment in high vacuum conditions causes formation of nonstoichiometric titanium oxide ceramic. As a result electrical conductivity of the material significantly increases. Such a material can be used for electrode production for electrochemical water treatment.
Structure and Magnetic Properties of NdFeB Powder Prepared by Hydrogen Decrepitation and High-Energy Ball Milling
Authors: Mural Zoryana , Kollo Lauri , Traksmaa Rainer , Kallip Kaspar , Link Joosep , Veinthal Renno
Published: March 2014

An ingot of NdFeB alloy was disintegrated by hydrogen decrepitation (HD). High-energy ball milling technique with hard metal milling elements and balls was employed to refine HD powders down to particle size optimum for magnet processing. The experiments were performed according to experimental plan to optimize the milling parameters regarding particle size, contamination and magnetic properties of the powder. The effect of milling time, speed of rotation, ball-powder weight ratio (BPR) and amount of wet agent was investigated. The highest influence was shown to be from attritor speed of rotation, ball-to powder ratio and combined effect of milling wet agent and rotating speed. Unified parameter of estimated number of total ball impacts was calculated, which allows predicting the final particle size of the powder at different milling speeds. Magnetic moments of powders were measured.
Application of Pulse Electromagnetic Field for Metal Coatings Manufacturing
Authors: Mironov Viktor , Kolbe Matthias , Lapkovskis Vjaceslavs , Zemchenkovs Vjaceslavs , Boiko Irina
Published: March 2014

In current article, applications of pulsed electromagnetic fields (PEMF) for processing of powder parts obtaining bronze coating on a steel rod are presented. Experiments were carried out in Laboratory of Metal Forming Technology (University of Applied Sciences of Zwickau, Germany) and in Laboratory of Powder Materials (Riga Technical University, Latvia). An adhesion strength between steel and bronze parts was measured by means of a shearing test.
Heat Treatment of Ultrafine Grained High-Strength Aluminum Alloy
Authors: Pramono Agus , Kollo Lauri , Kallip Kaspar , Veinthal Renno , Gomon Jaana Kateriina
Published: March 2014

Aluminum is one of the nonferrous metals with very wide applications. It has unique properties such as light weight and it is ductile has additionally, lower melting point compared to iron. Equal Channel Angular Consolidation (ECAC) is manufacturing method to produce alloys with high strength by consolidation at elevated temperatures. ECAC method can produce a fine grain and combined with oxide inclusion from particle surfaces, high strength. This research will examine the applicability of Equal Channel Angular Consolidation to incorporate aluminum Al 7075 series powder at a temperature of 400OC under pressure of 400 MPa. The effects of heat treatment regimes on grain size of the ECAC samples are observed. The results show hardness of 7075 Aluminum series after ECAC process reaching 120 HV10 and decreases down to 110 HV10 after T6 heat treatment. Hardness further decreases after annealing process, down to 104 HV10. Decline in hardness is accompanied with the increased grain size, which accompanies increased ductility.
Three-Body Abrasive Wear of Reactive Sintered WC-Co Hardmetals with Grain Growth Inhibitors
Authors: Juhani Kristjan , Pirso Jüri , Tarraste Marek , Viljus Mart , Suurkivi Taavi
Published: March 2014

WC-Co hardmetals are widely known wear resistant materials, their properties depend strongly on the WC grain size; commonly fine grained materials exhibited higher properties. One opportunity to produce fine grained materials is reactive sintering. Reactive sintering is a novel processing method, where the synthesis of the carbide phase is combined with solid and liquid state sintering of the composite during a single heating cycle. WC-co hardmetals where synthesizedin situfrom the elemental powders of W, Co and C. To investigate the influence of grain growth inhibitors the Cr3C2and VC were also included to powder mixtures. To investigate the influence of carbon content composites with different amounts of C were produced. The microstructures, hardness and three-body abrasive wear resistance of reactive sintered WC-Co hardmetals with grain growth inhibitors depending on carbon content in initial powder mixture is exhibited.
Influence of Laser Hardening to the Sliding Wear Resistance of the PVD (Al,Ti)N-G and nACo® Coatings
Authors: Surzhenkov Andrei , Adoberg Eron , Antonov Maksim , Sergejev Fjodor , Mikli Valdek , Viljus Mart , Latokartano Jyrki , Kulu Priit
Published: March 2014

In the present article, the laser hardening of the carbon steel C45, previously coated by the physical vapour deposition (PVD) process, is studied. The (Al,Ti)N-G and nACo® (nc-AlxTi1-xN/α-Si3N4) coatings were applied. Nd:YAG laser with the laser beam power density of 1945 W/cm2 and scan speed of 300 mm/min was used for hardening process. Laser hardening lead to the formation of hardened layer under both coatings, consisting of austenite and ferrite. The approximate depth of the hardened layer and maximal microhardness was approximately 0.2 mm and 955 HV0.05 and 0.1 mm and 520 HV0.05 in the case of the (Al,Ti)N-G and the nACo® coating, respectively. After laser hardening the sliding wear of the (Al,Ti)N-G coating decreased by 1.25 times and of the nACo® coating by 1.05 times.
Investigation of Hydration Features of the Special Concrete with Aggregates of Various Metal Particles
Authors: Pundienė Ina , Mironov Viktor , Korjakins Aleksandrs , Spudulis Edmundas
Published: March 2014

This study presents an analysis of various size metal particle waste (MP) influences on Portland cement (PC) paste hydration course, concrete sample structure densification during hardening and physical-mechanical properties. Investigations have shown that MP filler accelerates maximum heat release rate in PC pastes. MP intensifies structure development in the early phase, but slows it down in later PC hydration period. After 28-days of hardening the compressive strength of the concrete samples without MP filler is about 20% higher than of samples with MP. When in concrete composition microsilica and MP fillers are used together, compressive strength of concrete sample composition is up to 50% higher than of samples with MP filler only.
Modifiers Influence on Fibers Containing Polylactic Acid Biocomposites Exploitation Properties
Authors: Reihmane Skaidrīte , Kajaks Janis , Akimova Karina
Published: March 2014

A lot of achievements of contemporary science are connected with green composites producing and properties investigation. Variations of matrices, reinforcement and their combinations are innumerable. This study is focused on polylactic acid based biocomposites exploitation properties (flexural strength and modulus, impact strength, microhardness and water uptake) investigation results. Different origin cellulose containing fibers (hemp, cotton, tetra package cellulose, and hard wood) without and with modification were used as reinforcement.
Portland Cement Based Lightweight Multifunctional Matrix with Different Kind of Additives Containing SiO2
Authors: Pundienė Ina , Kligys Modestas , Šeputytė-Jucikė Jurga
Published: March 2014

Additives containing SiO2 (ACS) and having pozzolanic properties such as metakaolin (MK), microsilica (MS) and milled autoclaved aerated concrete waste (MAACW) are promising materials for partially replacement of Portlandcement (PC) in matrix of lightweight building materials. Studies have shown that SA effects on the hydration process of PC matrix. The highest wetting heat release rate values were obtained using MS additive, and the lowest a mix of MS and MK additives. In a mix with both MS and MK additives, the maximal value of heat release rate was reached after 10 h and in a mix with MS additive after 13 h. MS additive extends while MK additive accelerates the hydration process of PC. The most effective plasticizer (P) was chosen according to the study of dynamic viscosity (DV) of PC matrix. It was fixed that surfactant (SU) in amount of 0.03 % (from PC) reduces the density of matrix about 30 % compared with the density of matrix without SU. Increased quantity of MAACW (from 5 to 15 % from PC) causes in increase of compressive strength of PC matrix (after 28 days curing) from 19 to 47 MPa.
Contact Fatigue Life Investigations and Wear Mechanisms of Different Case Hardened and Nidrided Steels
Authors: Trausmuth Andreas , Godor Istvan , Dietrich Alexander
Published: March 2014

The present work examines experimentally the local damage evolution and compares the differences in fatigue behaviour of case-hardened and plasma nitrided layers under rolling contact fatigue (RCF). The RCF experiments are accompanied by damage assessments. In order to assess experimentally the extreme conditions of point contact, the experiments are performed on a ball-on-rod (BoR) test rig. Results showed that nitrided surface get more important to RCF at lower contact pressure due to the comparable thin nitration depth, whereas at high contact stress the crack initiation starts on the surface of the compound layer and crack grow further in the diffusion layer. The carburised layer of case-hardened surfaces do not show any surface crack initiation.
Politicisation of performance appraisals
Authors: Swanepoel Sonia , Botha Petrus A. , Mangonyane Nancy B.
Published: March 2014

Orientation: Employees are a source of competitive advantage for organisations and human resource management seek to promote employee efficiency. One of the tools organisations utilise to achieve this goal is performance appraisals.Research purpose: The purpose of this study was to investigate the weaknesses in performance appraisal and to determine whether it is politicised in the North West Department of Health and Social Development in South Africa.Motivation for study: Many organisations either ignore the existence of politics in the appraisal process or assume that its impact can be minimised if they refine their appraisal instruments. Executives admit that, in appraising others, they often intentionally avoid meeting the goal of accuracy in favour of achieving goals that have more to do with exercising discretion and maintaining departmental effectiveness. Ironically, these same executives lament that the appraisals they receive often do not accurately represent their abilities and performance (Gioia & Longenecker, 1994).Research approach, design and method: Self-administered questionnaires were used as a means of collecting data and analysis was done through the use of the Statistical Package for the Social Sciences (SPSS).Main findings: The results of the study showed that respondents believe that performance appraisals are highly politicised.Practical/managerial implications: If used effectively, performance appraisals may improve employee productivity and efficiency as well as motivation and performance. However, if performance appraisal is perceived as unfair and political, it can diminish rather than enhance employee attitudes and performance.Contribution: Amongst others, it is recommended that managers should consider separating assessment for development and assessment for rewards.
INsPeCT: INtegrative Platform for Cancer Transcriptomics
Authors: Madhamshettiwar Piyush B. , Maetschke Stefan R. , Davis Melissa J. , Reverter Antonio , Ragan Mark A.
Published: March 2014

The emergence of transcriptomics, fuelled by high-throughput sequencing technologies, has changed the nature of cancer research and resulted in a massive accumulation of data. Computational analysis, integration, and data visualization are now major bottlenecks in cancer biology and translational research. Although many tools have been brought to bear on these problems, their use remains unnecessarily restricted to computational biologists, as many tools require scripting skills, data infrastructure, and powerful computational facilities. New user-friendly, integrative, and automated analytical approaches are required to make computational methods more generally useful to the research community. Here we present INsPeCT (INtegrative Platform for Cancer Transcriptomics), which allows users with basic computer skills to perform comprehensive in-silico analyses of microarray, ChlPseq, and RNA-seq data. INsPeCT supports the selection of interesting genes for advanced functional analysis. Included in its automated workflows are (i) a novel analytical framework, RMaNI (regulatory module network inference), which supports the inference of cancer subtype-specific transcriptional module networks and the analysis of modules; and (ii) WGCNA (weighted gene co-expression network analysis), which infers modules of highly correlated genes across microarray samples, associated with sample traits, eg survival time. INsPeCT is available free of cost from Bioinformatics Resource Australia-EMBL and can be accessed at http://inspect.braembl.org.au .
DNA Conformational Transitions Induced by Supercoiling Control Transcription in Chromatin
Authors: Luchnik Andrey N.
Published: March 2014

Regulation of transcription in eukaryotes is considered in the light of recent findings demonstrating the presence of negative and positive superhelical tension in chromatin. This tension induces conformational transitions in DNA duplex. Particularly, the transition into A-form renders DNA accessible and waylaying for initiation of transcription producing RNA molecules long known to belong to the A-conformation. Competition between conformational transitions in various DNA sequences for the energy of elastic spring opens a possibility for understanding of fine tuning of transcription at a distance.
The canonical ring of a 3-connected curve
Authors: Franciosi Marco , Tenni Elisa
Published: March 2014

Let

C

be a projective curve either reduced with planar singularities or contained in a smooth algebraic surface. We show that the canonical ring

R(C, \omega_C) = \bigoplus_{k\geq 0} H^0(C, {\omega_C}^{\otimes k})

is generated in degree 1 if

C

is 3-connected and not (honestly) hyperelliptic; we show moreover that

R(C, L)=\bigoplus_{k\geq 0} H^0(C,L^{\otimes k})

is generated in degree 1 if

C

is reduced with planar singularities and

L

is an invertible sheaf such that

\deg L_{|B} \geq 2p_a(B)+1

for every

B\subseteq C

.
External Factors Affecting Investment Decisions of Companies
Authors: Bialowolski Piotr , Weziak-Bialowolska Dorota
Published: March 2014

In this paper, we attempt to investigate the importance of certain external factors on the investment decisions made by Polish companies. With the use of data from the tailor-made Survey on Receivables, we (1) examine factors influencing investment decisions of companies in Poland; (2) assess the relation between branch, company size and investment factors; (3) evaluate the importance of the investment factors; and (4) determine the relative influence of these factors on the company-level investment reductions. The results show that first, although the problem of payment delays is the most important single issue determining the investment decisions of Polish companies, its importance decreases when analysed simultaneously with other issues. Second, among the indicators selected for an assessment of investment decisions, two driving forces determine the investment decisions of Polish companies - namely, macroeconomic factors and law-related factors, with the relative importance of the former lower than the latter. Third, there is a positive association between the importance of each of the two factors and the actual investment reductions, implying that among companies facing higher investment reductions, the importance of macroeconomic and law-related factors is higher.
Oud en nieuw - Kroniek van het Nederlands als vreemde taal
Authors: van Kalsbeek Alice
Published: March 2014

Deze kroniek van het Nederlands als vreemde taal bevindt zich op een hellend vlak, namelijk het vlak dat loopt van Nederlands als tweede taal naar Nederlands als moedertaal ofwel van NT2 naar NT1. Het is een vlak waar taalaanbieders en uitgevers in Nederland zich meer en meer op begeven. ‘We schuiven allemaal’, hoorde ik laatst een uitgever van een NT2-fonds zeggen. En ze bedoelde: in de richting van NT1, Nederlands als moedertaal. Vanwaar dat schuiven en waarom is het een hellend vlak?
Meertaligheid: Nederlands na Duits en Engels
Authors: Wenzel Veronika
Published: March 2014

Dutch is a typical 'third language'. Most learners have knowledge of other languages before they start to learn Dutch. One or two of these languages are closely related to Dutch, English and/or German. When L3-learners come across a new language for the first time, it can be observed that they try to make use of languages they learned before. Experienced language learners often perform better than less experienced subjects. Furthermore, prior research shows that related languages will contribute more to intelligibility than less related languages do.

The objects of this study were 42 German multilinguals reading a Dutch text without knowledge of this language. They mainly differ according to their language background and language learning experience. The results indicate that the experienced learners use more inferring strategies than the less experienced learners and that German is indeed the preferred source of transfer. However, the experienced multilinguals do not show a significantly different metalinguistic strategy pattern, and some regard Scandinavian words as being much more transferable than one might expect. This leads to the assumption that their explicit knowledge about language relatedness and their linguistic knowledge is not fully available in reading comprehension. Finally, the author offers some suggestions as to the direction explanations might take.
Het voorzetselvoorwerp en de hiërarchie der objecten
Authors: Vandeweghe Willy
Published: March 2014

It is a widely accepted view that Dutch (verbal) predicates can take a maximum of one prepositional object complement, the so-called ‘voorzetselvoorwerp’. If there is a second prepositional phrase in the sentence, it is relegated to the realm of adjuncts. This article argues for an analysis accommodating the possibility of two prepositional object complements with one predicate, just as in the case of nominal objects. These prepositional objects have, just like the nominal ones, to be distinguished internally on relational and hierarchical grounds.
Extrapositie
Authors: de Vries Mark
Published: March 2014

Modifiers and several other types of constituents can be right-extraposed across the right sentence bracket (the verbal pole) in Dutch. This article discusses what the conditions on such configurations are, how extraposed phrases can be distinguished from dislocated phrases, and how extraposition can be analyzed from a formal syntactic perspective. An extraposed phrase is part of the intonational and semantic domain of the host, and the process is limited to the finite clause. Nevertheless, it can cross certain island boundaries in terms of structural hierarchy, among other things. Such properties are problematic for movement and stranding theories of extraposition. Instead, I propose an alternative analysis in terms of specifying coordination. Furthermore, I argue that ellipsis plays a role. In effect, then, extraposition amounts to structural but not phonological repetition of a part of the clause, such that the extraposed phrase is base-generated within the additional part of the structure.
In situ measurement of atmospheric CO2 at the four WMO/GAW stations in China
Authors: Fang S. X. , Zhou L. X. , Tans P. P. , Ciais P. , Steinbacher M. , Xu L. , Luan T.
Published: March 2014

Abstract. Atmospheric carbon dioxide (CO2) mole fractions were continuously measured from January 2009 to December 2011 at four atmospheric observatories in China using cavity ring-down spectroscopy instruments. The stations are Lin'an (LAN), Longfengshan (LFS), Shangdianzi (SDZ), and Waliguan (WLG), which are regional (LAN, LFS, SDZ) or global (WLG) measurement stations of the World Meteorological Organization's Global Atmosphere Watch program (WMO/GAW). LAN is located near the megacity of Shanghai, in China's economically most developed region. LFS is in a forest and rice production area, close to the city of Harbin in northeastern China. SDZ is located 150 km northeast of Beijing. WLG, hosting the longest record of measured CO2 mole fractions in China, is a high-altitude site in northwestern China recording background CO2 concentration. The CO2 growth rates are 3.7 ± 1.2 ppm yr−1 for LAN, 2.7 ± 0.8 ppm yr−1 for LFS, 3.5 ± 1.6 ppm yr−1 for SDZ, and 2.2 ± 0.8 ppm yr−1 (1σ) for WLG during the period of 2009 to 2011. The highest annual mean CO2 mole fraction of 404.2 ± 3.9 ppm was observed at LAN in 2011. A comprehensive analysis of CO2 variations, their diurnal and seasonal cycles as well as the analysis of the influence of local sources on the CO2 mole fractions allows a characterization of the sampling sites and of the key processes driving the CO2 mole fractions. These data form a basis to improve our understanding of atmospheric CO2 variations in China and the underlying fluxes using atmospheric inversion models.
TEM analysis of the internal structures and mineralogy of Asian dust particles and the implications for optical modeling
Authors: Jeong G. Y. , Nousiainen T.
Published: March 2014

Abstract. Mineral dust interacts with incoming/outgoing electromagnetic radiation in the atmosphere. This interaction depends on the microphysical properties of the dust particles, including size, mineral composition, external morphology, and internal structure. Ideally all these properties should be accounted for in dust remote sensing, the modeling of single-scattering properties, and radiative effect assessment. There have been many reports on the microphysical characterizations of mineral dust, but no investigations of the internal structures or mineral composition of individual dust particles. We explored the interiors of Asian dust particles using the combined application of focused ion beam thin-slice preparation and high-resolution transmission electron microscopy. The results showed that individual dust particles consisted of numerous mineral grains, which were organized into several types of internal structure: single and polycrystalline cores of quartz, feldspars, calcite, and amphibole often with oriented clay coatings; individual clay agglomerates of nano-thin clay platelets showing preferred to random orientations commonly with coarser mineral inclusions; and platy coarse phyllosilicates (muscovite, biotite, and chlorite). Micron to submicron pores were scattered throughout the interior of particles. Clays in the coatings and agglomerates were dominated by nano-thin platelets of the clay minerals of illite-smectite series including illite, smectite, and their mixed layers with subordinate kaolinite and clay-size chlorite. Submicron iron oxide grains, dominantly goethite, were distributed throughout the clay agglomerates and coatings. Unlike the common assumptions and simplifications, we found that the analyzed dust particles were irregularly shaped with birefringent, polycrystalline, and polymineralic heterogeneous compositions. Accounting for this structural and mineralogical makeup may improve the remote sensing retrieval of dust and the evaluation of radiation effects, but will also require sophisticated single-scattering modeling. In particular, the observed internal structures of dust particles such as clay coatings, preferred orientation, embedded grains in clays, and pores, likely have a great impact on the light scattering of dust particles. The distribution and size of structural components with contrasting dielectric properties, such as iron oxides, should also be explicitly accounted for.
Validation of FORMOSAT-3/COSMIC level 2 "atmPrf" global temperature data in the stratosphere
Authors: Das U. , Pan C. J.
Published: March 2014

Abstract. GPS radio occultations by Formosa Satellite mission-3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) provide bending angle profiles, which are further processed to give profiles of temperature and water vapour in the lower atmosphere and electron density in the upper atmosphere. The level 2 "atmPrf" (atmospheric profile) product of version 2010.2640 gives temperature from surface to 0.2 hPa (~ 60 km). This is a dry temperature data product that does not include relative humidity in the inversion process and hence is reliable at altitudes < 100 hPa and erroneous at lower altitudes. In the current study we compare the COSMIC "atmPrf" data from December 2010 to November 2011 with other satellite (SABER/TIMED and MLS/Aura) temperatures from 50 to 0.2 hPa, COSMIC "wetPrf" data and reanalysis (NCEP, ERA-Interim and UKMO) outputs at 100, 10, 1 and 0.5 hPa pressure levels. The satellite comparisons show that below 1 hPa the observed median differences are most likely produced due to the biases in the retrievals of SABER and MLS. "atmPrf" and "wetPrf" temperatures compare extremely well in the common altitudes with differences being absolute zero between 200 and 10 hPa. When compared to reanalysis outputs, COSMIC seasonal means match NCEP and ECMWF seasonal mean temperatures very well, especially at 100 and 10 hPa. We conclude from this study that with the COSMIC dry temperature retrievals obtained from radio occultations of GPS, there is a 20 km extension of reliable data in the middle atmosphere. "atmPrf" data are of good quality and provide reliable and unprecedentedly large number of profiles at greater temporal and spatial resolutions for further studies and investigations of the middle atmosphere up to 1 hPa, i.e., approximately up to the stratopause at around 50 km.