bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Deposition Rate on the Structural, Morphological and Optical Properties of Brookite TiO2 Films Prepared by MOCVD
Authors: Wang Wei Guang , Wang Ming Xian , Feng Xian Jin , Ma Jin
Published: June 2017

Compared to anatase and rutile TiO2, the brookite TiO2 (b-TiO2) is relatively seldom investigated, because it is difficult to be prepared. In order to explore a scientific and effective approach to prepare high quality b-TiO2 crystalline films, the effects of deposition rate on the properties of b-TiO2 films prepared on yttria-stabilized zirconia (YSZ) (110) substrates by metal organic chemical vapor deposition (MOCVD) were investigated in this study. The structural analyses indicated that the b-TiO2 film prepared with the lowest deposition rate of 1.25 Å/min had the best single crystalline quality for which the epitaxial relationship between the film and substrate was determined as b-TiO2(120) || YSZ(110) with an in-plane epitaxial relationship of b-TiO2[001]|| YSZ[001] and b-TiO2[20]||YSZ[10]. The RMS surface roughness of the obtained films decreased from 7.02 to 1.11 nm as the deposition rate decreased. The average transmittances of all the obtained b-TiO2 films exceeded 90% in the visible range. The optical band gaps increased from 3.54 to 3.63 eV as the deposition rate decreased. Apparently, the deposition rate has a significant influence on the structural, morphological and optical properties. Therefore, it provides a practicable way to manipulate such properties of b-TiO2 films for different applications in the field of transparent optoelectronic devices.
Power-Efficient Phase Change Memory Using Silicon Carbide as a Buffer Layer
Authors: Guo Tian Qi , Song San Nian , Li Le , Shen Lan Lan , Lv Shi Long , Liu Bo , Wu Liang Cai , Song Zhi Tang , Qi Ming , Feng Song Lin
Published: June 2017

Power consumption has long been a great obstacle in phase change memory technology. Silicon carbide was introduced to be a buffer layer between the phase change material and the metal electrode in this work. The results showed that the new structure mitigated the energy consumption and maintained the advantage of high speed. This is attributed to the thin SiC buffer layer that helps confine the generated Joule heat inside the active phase change volume and form more conducting paths by the high efficiency of the heat utilization. Additionally, another key role — inhibition of the material separation, is conducive to achieving stable and sustainable electrical operations.
Preparation and Adsorption Properties of Fe/Chitosan/Fly Ash Composite
Authors: Li Bei Gang , Wang Min
Published: June 2017

Fly ash (FA), a kind of fine-powder solid waste, was utilized to prepare a novel Fe/chitosan/FA composite (Fe/CTS/FA) by the calcination and solution reaction with chitosan (CTS) and ferric iron. In combination with the adsorption for reactive turquoise blue KN-G (RTB KN-G) and direct sky blue 5B (DSB 5B) dyes, the main conditions of preparation and adsorption of Fe/CTS/FA were investigated. The composite was characterized with SEM, EDS, particle-size distribution and N2-gas adsorption-desorption technology. The results show that: (1) Fe/CTS/FA prepared by calcining FA at 500°C and further mixing reaction with CTS and FeCl3⋅6H2O solution according to the mass ratio of m(FA):m(CTS):m(Fe)=10:1:0.34 has excellent adsorption properties. The amount of adsorption is mainly affected by solution pH and reaches the equilibrium in 60 min for high-concentration RTB KN-G and DSB 5B dye wastewater with adsorption capacities of 892.95 mg/g and 615.65 mg/g, which are 16.28 and 32.56 times larger than those of FA, respectively. (2) The characterization results of Fe/CTS/FA indicate that CTS and iron hydroxides have been successfully loaded on FA. The surface morphology of Fe/CTS/FA is significantly changed, and the particle-size distribution is obviously smaller than that of FA.
Freeze-Drying Graphene Aerogels and their Adsorption Ability towards Organic Reagents
Authors: Wu Hai Kun , Li Xiao Min , Zhao Wen , Meng Zhe , Zhang Wen Jin , Qian Lei
Published: June 2017

Graphene (GR) aerogels with three-dimensional interconnected network were prepared from freeze drying graphene oxide (GO) dispersions for adsorbing organic reagents. Microstructures of GR aerogels were observed by field-emission scanning electron microscopy, and the components were analyzed by X-ray photoelectron spectroscopy and X-ray diffraction. Their adsorption abilities and recycling performances for organic reagents were investigated in detail. The results showed that the adsorption capacity of GR aerogels was dependent on the concentration of GO dispersion. For example, the adsorption capacity of ethanol increased from 7.04 to 32 g/g when the GO concentration changed from 5 to 10 mg/ml. The GR aerogels also exhibited good adsorption performance for other organic reagents, reaching 44.78, 93.41 and 56.56 g/g for cyclohexane, acetone and methanol, respectively. Moreover, the 7GR had good cyclic adsorption capacity for cyclohexane, acetone and methanol, and the relative standard deviation was 3.7%, 4.3%, 3%, respectively.
Dynamic Compression Properties of Ti-6Al-4V Titanium Alloy Extruded Sections
Authors: Liu Rui , Hui Song Xiao , Ye Wen Jun , Yu Yang , Song Xiao Yun
Published: June 2017

This paper aimed to study the dynamic compression properties of Ti-6Al-4V titanium alloy sections. The Ti-6Al-4V sections were extruded above the β-transus temperature with extruding ratio of 85, and then heat treated by conventional annealing at 750°C, or annealing at 1200°C by two routes. Dynamic compression properties were investigated by Split Hopkinson Pressure Bar system at strain rate of 3000±200 s-1. The results show that the dynamic compression properties of as-extruded specimens are comparable to the specimens after conventional annealing at 750°C. Compared to Widmannstatten microstructure with original beta grains in size of 200 μm ~ 300 μm obtained by conventional annealing, the microstructure obtained by annealing at 1200°C with coarse grains consisted of fine α-lamellae exhibits comparable dynamic strength but the capability of plastic deformation reduced about 20%. For the microstructure obtained by annealing at 1200°C with coarse grains consisted of coarse α-lamellae, the dynamic strength slightly decreased, while the capability of plastic deformation reduced about 60%.
Influence of Preparation Process on the Performance of Strain Hardening Cementitious Composite
Authors: Gao Song , Luo Jian Lin , Wang Xian Mao , Li Qiu Yi
Published: June 2017

The modification of matrix is an important method to improve the mechanical properties of strain hardening cementitious composite (SHCC). The influence of the properties of the matrix water binder ratio (W/B) and fresh state rheology on SHCC tensile behaviors are useful for the SHCC design. The W/B influences only on tensile strength, but not the stain capacity, if the fresh state workability remains uniform. On the other hand, the workability has a significant influence on SHCC strain capacity through its influence on the fiber distribution. Consequently, it is important to cast SHCC carefully and make sure the even fiber distribution to insure the bridging function and mechanical properties of SHCC.
Application of Polycarboxylate Superplasticizer in the Concrete
Authors: Huang Xing Qi , Li Xiao Rong , Zhang Da Wei , Xue Chang Jun , ZHANG A.Q.
Published: June 2017

Compared with the traditional water reducer, polycarboxylicwater-reducing agent exhibits the advantages of high water-reducing rate, cement paste fluidity and low slump loss, etc. The structure of polycarboxylates water reducing agent molecular is comb type. Water reducing agent can be used in the molecular design because it has high water reducing rate, low dosage, good slump stability, and have great potential in increase strength. In recent years, it has attracted many researchers' attention. Water reducing agent can block or destroy cement granular flocculation structure, through the surface function, complexation, electrostatic repulsion force and stereo repulsive force. Research on water reducing agent based on the application of poly carboxylic acid can realize functional design of water reducing agent, so as to promote the development of high-performance concrete.
Organic Functionalization and Properties of ZnO Nanosheets with Polymer Containing N-Vinyl Carbazole
Authors: Bian Lin , Lv Shi Sheng , Qiu Jian Xun , Zhang Xin Tao , Gao Ming Jun , He Xiao Chun , Ma Xing Fa , Li Guang
Published: June 2017

To make full use of the visible light more effectively, many studies are focuses on ZnO baesd nanocomposites. To modify the surface of ZnO with functional polymer is a very simple and effective approach. PVK (N-vinyl carbazole polymer) is one of typical organic functional materials, which is generally used as charge transfer materials for the applications of several organic electronic devices. Surface modification of ZnO nanosheets with polymer containing –COOH and N-vinyl carbazole group was performed with self-assembly process for improving the adsorption to visible light and properties of charge transfer in nanoscale. A series of characterizations were carried out by SEM (scanning electron microscopy), Fourier-Transform Infrared (FTIR) spectra, UV-Vis (Ultra-violet visible spectroscopy), et al. The adsorption of the nanocomposite was extended to the region of visible light. The photoconductivity response to weak visible light was studied based on interdigital electrodes of Au on flexible PET (polyethylene terephthalate) film substrate with casting method. The photocurrent of ZnO nanosheets modified with the polymer containing N-vinyl carbazole to weak visible light was changed greatly. The organic-inorganic nanocomposite showed good activities to visible light, with which it can be easily produced photo-induced charges, avoiding the recombination of charges produced by visible light. Photocatalytic efficiency was examined by selecting typical organic pollutants and some good results were obtained, showing much prospect in the fields of photocatalysts, nanoreactors, self-cleaning films, coatings, and organic pollutants treatment of environmental.
Dielectric Properties of Epoxy/Anhydride System in Long-Term Storage
Authors: Han Chun Miao , Peng Kang , Yang Liu , Zeng Zhi Bin
Published: June 2017

The change of dielectric properties of epoxy/anhydride systems during eleven months storing was investigated. Test systems were bisphenol-A epoxy cured by different content of methyl-hexahydrophthalic anhydride with a slow cooling process across Tg range included in their curing procedure to reduce residual stress. The results showed all the systems’ dielectric constant and dielectric loss angle tangent had a trend of down then up. The highest decreasing amplitudes were about 4% and 10% respectively. Possible explanations for these phenomena were proposed, and then some preliminary investigations were carried out like DSC and IR.
Rheological Behaviors of Graphene Oxide/Polyacrylonitrile Spinning Solutions
Authors: Li Feng Mei , Zheng Ying Ying , Wang Biao
Published: June 2017

The rheological behaviors of polyacrylonitrile (PAN) in NaSCN aqueous solutions containing different amount of Graphene oxide (GO) were investigated through both steady-state and dynamic rheological measurements. The parameters such as apparent viscosity (ηα), flow activation energy (Eη), structural viscosity index (Δη), storage modulus (G’), loss modulus (G’’) and mechanical loss factor (tanδ) were measured to illustrate the rheological behaviors of these solutions. The results showed that the apparent viscosity decreased with adding appropriate amount of GO, while the structural viscosity index, the flow activation energy and the mechanical loss factor of GO/PAN spinning solutions increased. Accordingly, a possible mechanism of GO effect on rheological behaviors of PAN solution was proposed in this work.
Gamma Irradiation Assisted Synthesis of Ag/rGO Composites and their Surface Properties
Authors: Liang Ying , Fang Bin , Lin Fang Fang , Zhu Xu Min
Published: June 2017

Ag/rGO composites were synthesized under gamma irradiation using silver nitrate and graphene oxide (GO) as the starting materials. Comparing with traditional methods, gamma irradiation is a simple and “green” technique. In the irradiation system, silver ions were reduced to silver nanoparticles (AgNPs) by the electrons generated from the radiolysis of solvent. GO nanosheets provided reactive sites for the formation of AgNPs and acted as a colloidal surfactant preventing the aggregation of AgNPs. Meanwhile, GO were partially reduced to reduced graphene oxide (rGO). X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, Raman spectra and UV-Vis absorption spectra were applied for the characterization of Ag/rGO composites. The results showed that the absorbed dose (3.1 kGy, 4.7 kGy, 9.4 kGy and 27.4 kGy) plays an important role in the size distribution of AgNPs and the reduction degree of GO nanosheetes. The Ag/rGO composites exhibit a broad absorption band at visible light due to the surface plasmon resonance of AgNPs. Because of the unique surface properties, Ag/rGO composites behave enhanced performance for the adsorption of organic dye from water.
Effect of Surface Treatment on the Mechanical Performance of PPTA-Pulp Reinforced Rubber Composites in Supercritical Carbon Dioxide Fluid
Authors: Qin Ming Lin , Liu Jing , Han Ke Qing , Yu Fan , Teng Cui Qing , Yu Mu Huo
Published: June 2017

A facile surface modification method for PPTA-pulp was developed to improve the adhesion to rubber matrix. Tensile strength tests and SEM were used to evaluate the adhesion of PPTA-pulp with rubber matrix, and the results indicated that surface treatment of PPTA pulp in supercritical carbon dioxide fluid was an efficient method to increase interfacial adhesion between PPTA-pulp and rubber matrix. Attenuated Toyal reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to investigate the surface structure and composition of untreated and treated PPTA-pulp in supercritical carbon dioxide fluid. The results indicated that the interaction of macromolecules, the crystal structure and the surface composition of PPTA-pulp changed during supercritical carbon dioxide fluid, particularly for the surface morphology and composition.
Processability and Thermal Property of Poly(Phenylene Sulfide)/Graphene Nanoplatelets Nanocomposites and their Fibers
Authors: Hu Ze Xu , Meng Si , Lu Qiu Xu , Xiang Heng Xue , Chen Zi Ye , Wei Pei Ling , Zhu Mei Fang
Published: June 2017

A new kind of functionalized graphene nanoplatelets (GNPs), poly (phenylene sulfide) (PPS) grafted GNPs (GNPs-g-PPS), have been successfully prepared by Friedel–Crafts reaction and in-situ grafting polymerization. In this paper, we produced PPS/GNPs-g-PPS and PPS/GNPs nanocomposite materials where PPS-g-GNPs and pristine GNPs acted as inorganic fillers. It was observed that PPS/GNPs-g-PPS exhibited superior spinnability due to its better compatibility and dispersibility of GNPs in the PPS matrix. Non-isothermal crystallization properties, thermal resistances and thermal stabilities were studied. The results showed that the crystallization behavior and thermal stability of PPS was strongly enhanced with only 1.0 wt.% GNPs-g-PPS added.
Preparation and Environmental Resistance of Dual-Wavelength Polypropylene Fluorescent Anti-Counterfeiting Fibers
Authors: Xu Yuan Yuan , Xia Wei Lan , Yang Ge Sheng , Zhang Hui Hui , Shao Hui Li
Published: June 2017

The UV short-wavelength/infrared excitable dual-wavelength fluorescent anti-counterfeiting polypropylene (PP) fibers were spun by the traditional melt spinning process. The effects of pH value, temperature, and solvents on the structure and properties of fibers were investigated by means of tensile tester, fluorescence spectrometer and scanning electron microscope (SEM), respectively. The results showed that the fibers could emit red light under the excitation of 254 nm wavelength UV light and emit green light under the excitation of 980 nm wavelength infrared light, which show the double anti-counterfeiting effects. The dual-wavelength fluorescent fibers showed stable mechanical properties in acid and alkali resistance, whereas the fluorescence properties of fibers decreased with the increase of processing time in acid and alkali solutions. With the extension of high temperature treatment time, the mechanical properties of fibers decreased slightly and tended to be stable, while the fluorescence performance of fibers decreased gradually. The influences of different organic solvents on the properties of fluorescent fibers were different, and the fibers showed relatively good solvent resistance.
Polyaniline Nanofibers Prepared with Binary Oxidant at the Presence of Para-Phenylenediamine
Authors: Qian Peng Fei , Li Tao , Liang Bang Lei , Qin Zong Yi
Published: June 2017

Polyaniline nanofibers were facially synthesized by the chemical polymerization with binary oxidant containing ammonium persulfate and ferric chloride at the presence of para-phenylenediamine. For a better comparison, the polymerization with single oxidant was also carried out. The effect of binary oxidant on the morphology and structure was systematically investigated for better understanding the role of oxidant in the formation of nanostructures. The morphology, chemical structure as well as crystalline and thermal property were characterized by field emission scanning electron microscopy, ultraviolet-visible absorption spectroscopy, Fourier transform infrared and Raman spectroscopy, X-ray diffraction and thermogravimetric analysis.
Effects of Multi-Walled Carbon Nanotubes on the Properties of Acrylonitrile Butadiene Styrene Nanocomposites Potentially Used for Fused Deposition Modeling
Authors: Zhu Jin , Wang Biao
Published: June 2017

Multi-walled carbon nanotubes (MWCNTs)/acrylonitrile butadiene styrene (ABS) nanocomposites were prepared by melt blending and then filaments were obtained by melt extrusion method. The Scanning electron microscope (SEM) exhibited good dispersion of MWCNTs in the SAN phase of the ABS matrix. The rheological results showed that incorporation of MWCNTs into ABS resulted in higher storage modulus (G′) and loss modulus (G′′) than those of ABS, especially at low frequencies. The tensile strength and modulus of MWCNT/ABS nanocomposite filaments substantially increased with the MWCNTs content while the elongation at break decreased. Additionally, the addition of MWCNTs decreased the coefficient of linear thermal expansion. This study provides a basis for further development of MWCNT/ABS nanocomposites used for FDM process with desirable mechanical properties and good dimension stability.
Microstructure Evolution and Mechanical Properties of Extruded Mg-Al-Zn-Sn Alloy Sheets
Authors: Yang Qing Shan , Liu Wen Jun , Yu Zu Jian
Published: June 2017

The microstructure and mechanical responses of the AZ31 with the addition of 1.8% Sn alloys have been studied and compared. Mg alloy sheets were prepared with metal model casting method and subsequent processes by conventional extrusion (CE) and differential speed extrusion (DSE). Mg alloys were hot extruded at 400oC with the extrusion ratio of 101:1. The microstructure of Mg alloy sheets was examined by optical microscopy (OM) and scanning electron microscope (SEM). The results indicated that the grains were dynamically recrystallized after the extrusion process. Moreover, DSE process dramatically enhanced the room temperature ductility of the extruded sheets. It was also presented that the Mg alloy processed by DSE exhibite a classical dimple structure as a result of slip accumulation and ductile tear.
Fabrication and Properties of Gas Atomized Gamma Titanium Aluminide Powders and PM Processing
Authors: Liu Na , Li Zhou , Xu Wen Yong , Zheng Liang , Liu Yang
Published: June 2017

Pre-alloyed gamma titanium aluminide powders were fabricated by argon gas atomization. The powder was hot isostatic pressed (HIP) at 1200°Cand 150MPa for 3h to obtain full density compact. The properties of the powders and the HIP’ed compacts were investigated in this work. The microstructure of the powder exhibited dendrite and cellular mixed image, resulted from rapid solidification and independent of particle size. The microstructural transition from cell to dendrite could be readily represented in a droplet or the droplets of different size. The transition was the result of the decrease of undercooling. XRD analysis result showed that the powder consisted of α2 phase and γ phase, coarse powder was mostly γ phase, while fine powder mostly α2 phase. After HIP, the near gamma microstructure showed an average γ-TiAl grains of approximately 6μm.
Effect of Alloying Elements on Volume Fraction of γ′ Phase in Power Metallurgy Nickel-Base Superalloy
Authors: Chen Yang , Tian Gao Feng , Zhou Lei , Wang Yue , Ma Guo Jun , Yang Jie , Zou Jin Wen
Published: June 2017

The effect of alloying elements on the volume fraction of γ′ phase at aging temperature was investigated. The results indicated the volume fraction of γ′ was mainly sensitive to Al, Ti, Nb, Ta, and Cr. Based on analyzing the chemical component and the volume fraction of γ′ phase of 20 kinds of nickel-base superalloys , a linear regression formula between the volume fraction of γ′ phase and alloying element content was established using Matlab software, and the formula was given as: Vγ′=21.06+5.76Al+0.41Co-0.95Cr+0.84Hf+2.15Nb+0.82Ta+3.06Ti, where the correlation coefficient r = 95.5%. This linear equation was more accurate compared with the three public empirical formulas.
First-Principles Investigation of Phase Stability, Elastic and Thermodynamic Properties in L12 Co3(Al,Mo,Ta) Phase
Authors: Yao Qiang , Lu Tong , Wang Qiong , Wang Yan , Zhu Yu Hong
Published: June 2017

First-principles calculations have been performed to investigate the phase stability, elastic, and thermodynamic properties of Co3(Al,Mo,Ta) with the L12 structure. Calculated elastic constants showed that Co3(Al,Mo,Ta) is mechanically stable and possesses intrinsic ductility. Young’s and shear moduli of polycrystalline Co3(Al,Mo,Ta) were calculated using the Voigt-Reuss-Hill approach. It was found that the shear and Young’s moduli of Co3(Al,Mo,Ta) were smaller than those of Co3(Al,W). States density indicated the existence of covalent-like bonding in Co3(Al,Mo,Ta). Temperature-dependent thermodynamic properties of Co3(Al,Mo,Ta) could be described satisfactorily using the Debye-Grüneisen approach, including entropy, enthalpy, heat capacity and linear thermal expansion coefficient, showing their significant temperature dependences. Furthermore the obtained data could be employed in the modeling of thermodynamic and mechanical properties of Co-based alloys to enable the design of high temperature alloys.
Effects of HIP Process on the Microstructure and Mechanical Properties of a Cast Superalloy
Authors: Yang Jin Xia , Sun Yuan , Zhou Dong Ling
Published: June 2017

The effects of HIP process on microstructure and mechanical properties of IN792 cast superalloy were studied. The results showed that HIP process produced more uniform and finer cubic γ′ than standard heat treatment. The difference of the mechanical properties should be caused by the microstructure changes. HIP process leads the homogeneous distribution of γ′ at dendritic arm and interdendritic area, and improved UTS and YS of tested alloy at 550°C. However, it played no role in increasing UTS and YS at room temperature and stress-rupture lives of 760°C/662MPa and decreased stress-rupture lives of 982°C/186MPa.
The Precipitation Behavior of γ′ Phase in Single Crystal Ni-Based DD6 Superalloy for Turbine Blade
Authors: Xue Yan Peng , Li Jia Rong , Zhao Jin Qian , Xiong J.C.
Published: June 2017

The precipitation behavior of γ′ precipitates in typical section dimensions of DD6 single crystal superalloy turbine blade was investigated experimentally during directional solidification process. The phase transformation temperatures in the single crystal Ni-based DD6 superalloy from DSC analysis and JmatPro simulation were basically in consistent with the isothermal solidification experiments. The solidification route of DD6 single crystal superalloy could be described as follows: L1 → γ + L2; L2 → (γ + γ′)eutectic + MC; γ → γ′/γ. With increasing continuous cooling rates, the primary γ′ precipitates tended to be refined, and the size distributions of the primary γ′ precipitates at every temperature measuring position followed the normal distribution. In comparison to the interdendritic regions, nearly a 60% reduction in the average sizes of the primary γ′ precipitates was measured in the dendritic core regions. The result of the primary γ′ size difference was strongly affected by the multi-component segregations between the interdendritic and dendritic regions, where the γ′ forming elements of Al and Ta segregated towards the interdendritic regions. Furthermore, the secondary γ′ precipitation was found to occur within a relatively wide corridor of γ matrix for low cooling rates (12.6, 23.3 and 29.7 °C/min) during the directional solidification process. The occurrence of the secondary γ′ precipitation resulted from the complex interaction of multiple thermodynamic and kinetic factors in the γ′ nucleation and the diffusion rate of γ′ forming elements.
Effect of Forging Processes on the Microstructure and Mechanical Properties of High Temperature Titanium Alloy Containing Erbium
Authors: Wang Zhen Qiang , Li Bo Long , Wang Tong Bo , Nie Zuo-Ren
Published: June 2017

A new high-temperature titanium alloy containing erbium was designed and fabricated. The influence of α+β forging process and β forging process on microstructure and mechanical properties of the alloy was studied. The microstructure, mechanical properties and fracture morphologies of the new high-temperature titanium alloy after different forging processes were characterized. The results showed that the forging process significantly affected the microstructure of the alloy. The alloy exhibits nearly equiaxed microstructure and lamellar microstructure after α+β and β forging, respectively. In addition, there were Er-rich phases in both forged alloys. The alloy with nearly equiaxed microstructure acquired a satisfactory comprehensive performance. However, the alloy with lamellar microstructure had higher strength and less plasticity. The tensile fracture of the alloy after α + β forging had more dimples, while cleavage plane was obvious in the alloy after β forging. Owing to the addition of erbium and the formation of Er-rich phases, forged alloys possess excellent strength. The Er-rich phase might be the main reason for the fracture.
Microstructure and Properties of the Co2NiWV0.5Mo1.5, Co2NiWV0.5Mo2, and Co2NiWV1.0Mo2 Multi-Principal Elements Alloys
Authors: Jiang Hui , Han Lin Ge , Chang Xiao Xue , Lu Yi Ping , Li Ting Ju
Published: June 2017

The Co2NiWV0.5Mo1.5, Co2NiWV0.5Mo2 and Co2NiWV1.0Mo2 multi-principal elements alloys were prepared by vacuum arc melting. The microstructure, compressive property and corrosion resistance of the alloys were investigated by means of X-ray diffraction, scanning electron microscope with energy dispersive spectroscopy, electrochemical workstation and material testing machine. Results indicated that all of these alloys were composed of primary dendrite with BCC structure. Inter-dendrite regions were filled with irregular and lamellar eutectics with a mixture of FCC solid solution and Co7Mo6-type μ phase. Compression tests indicated that fracture strength of Co2NiMo2V1.0W, Co2NiMo2V0.5W and Co2NiMo1.5V0.5W alloys was 2308MPa, 1983MPa and 1861MPa, respectively. The solid-solution strengthening of BCC matrix and μ phase were the two main factors to strengthen the alloys. Alloys corrosion resistance showed the alloy with higher Mo or lower V content has better corrosion resistance.
In Situ Laser Synthesis of High Entropy Alloy Coating on Ti-6Al-4V Alloy: Characterization of Microstructure and Properties
Authors: Cai Zhao Bing , Pang Xue Jia , Cui Xiu Fang , Wen Xin , Liu Zhe , Dong Mei Ling , Li Yang , Jin Guo
Published: June 2017

In order to improve the surface properties of Ti-6Al-4V, high-entropy alloy coatings were prepared by in-situ laser cladding on the surface of Ti-6Al-4V substrate. The microstructure, micro-hardness, corrosion resistance and wear resistance were investigated. The results showed that the high-entropy alloy coating was composed of BCC high-entropy alloy phase, α-Ti phase and (Ni, Co)Ti2 phase. The micro-hardness of the high-entropy alloy coatings is much higher than that of Ti-6Al-4V substrate. The coating also has a better corrosion resistance than Ti-6Al-4V substrate, even superior to 304SS in 3.5wt.% NaCl solution at room temperature. Compared with Ti-6Al-4V substrate, the high-entropy alloy coating has a greater wear resistance with the wear mass loss decreased 28.2% and 23.1%, respectively. Wear patterns of Ti-6Al-4V substrate and high-entropy alloy coatings are the coexistence of adhesive wear and abrasive wear, but the wear degree of high-entropy alloy coatings is lower.
Effect of Laser Shock Peening on the Surface Morphology of Metallic Glasses
Authors: Li Yan Sen , Zhang Kun , Duan Gui Hua , Xu Guang Yue , Wei Yu Hang , Wei Yan Peng , Wei Bing Chen
Published: June 2017

Laser shock peening is a promising effective approach for improving mechanical properties of metallic glass. In this work, laser shock peening was employed to study the surface morphologies of metallic glasses with different toughness. Numerous localized circular-or arc-shaped structures, with the size of 5~20 μm, were observed in the shock treated surface. The number of these unique localized structures has a close correlation to the ability of metallic glass to accommodate plastic deformation. In addition, the surface morphology evolution of Zr-based metallic glasses with different crystalline degrees is also discussed, indicating that the circular-or arc-shaped structures only appear in fully amorphous system.
Effect of Aging Temperature on Microstructure and Properties of V Alloyed High Manganese Austenitic Steel
Authors: Feng Yi Fan , Song Ren Bo , Peng Shi Guang , Cai Chang Hong , Tan Zhi Dong
Published: June 2017

The effect of aging temperature on microstructure and mechanical properties of Fe-16Mn-1.3C-0.3V steel was investigated. After a series of heat treatment experimental processes, including solution treatment at 1080 oC for 1 h then aging treatment at 350 oC, 400 oC, 450 oC, 500 oC and 550 oC for 1 h respectively, the microstructure of V alloyed high manganese austenitic steels were studied using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experimental steel had the best comprehensive performance after aging treated at 450 oC for 1 h. It presented hardness of 249HB, impact toughness of 215 J·cm-2, tensile strength of 707 MPa, yield strength of 421 MPa and elongation of 30.8%. With the aging temperature increased, the amount of precipitates increased and precipitates gradually transformed from globularity to needle. EDS analysis showed the most striking difference between two types carbides. That the globular carbide had a lot of vanadium element, which could cause the hardness of globular carbide higher than needle-like carbide. TEM showed the size of these globular carbide particles were 10~100 nm. SADP demonstrated that the fine globular precipitate was vanadium carbide (VC).
Corrosion Resistance of a Gradient Surface with Cr Alloying on Low-Carbon Steel
Authors: Yao Y. , Mao X.Y. , Shao L.J. , Chen H. , Yang H.Y. , Liang H.
Published: June 2017

As compared with the untreated one, the low-carbon steel with gradient alloying produced by impact peening showed an increase in corrosion resistance. Specifically, when the corrosion potential increased from-1061 mV to-603.5 mV, the corrosion current density decreased from 1.579×10-3 A/cm2 to 6.703×10-4 A/cm2, the capacitive arc radius increased, and there was no corrosion products viewed on the surface. The improvement in corrosion resistance could be attributed to the diffusion of Cr allowed by the large number of defects induced by the impact peening deformation. This also resulted in the formation of Fe-Cr solid solution, which helped to promote the formation of a passivation film.
Inducing Mucosal IgA: A Challenge for Vaccine Adjuvants and Delivery Systems
Authors: Boyaka Prosper N.
Published: June 2017

Mucosal IgA or secretory IgA (SIgA) are structurally equipped to resist chemical degradation in the harsh environment of mucosal surfaces and enzymes of host or microbial origin. Production of SIgA is finely regulated, and distinct T-independent and T-dependent mechanisms orchestrate Ig α class switching and SIgA responses against commensal and pathogenic microbes. Most infectious pathogens enter the host via mucosal surfaces. To provide a first line of protection at these entry ports, vaccines are being developed to induce pathogen-specific SIgA in addition to systemic immunity achieved by injected vaccines. Mucosal or epicutaneous delivery of vaccines helps target the inductive sites for SIgA responses. The efficacy of such vaccines relies on the identification and/or engineering of vaccine adjuvants capable of supporting the development of SIgA alongside systemic immunity and delivery systems that improve vaccine delivery to the targeted anatomic sites and immune cells.
Assessment of consistency in the dimension of gutta-percha cones of ProTaper Next and WaveOne with their corresponding number files
Authors: Bajaj Nitika , Monga Prashant , Mahajan Pardeep
Published: June 2017

Objectives: To compare the dimensions of gutta-percha (GP) cones of ProTaper Next (25/0.06) and WaveOne (25/0.08) in relation to their corresponding instruments of the same dimension, respectively. Materials and Methods: Two groups of GP cones were made with 25 cones in each group. Group 1 consisted of 25 GP cones # 25/0.06 (ProTaper Next). Group 2 consisted of 25 GP cones # 25/0.08 (WaveOne). Measurements were done at D1 (1 mm short of the tip), D3 (3 mm short of the tip), and D11 (11 mm short of the tip) for GP cones of both groups and were compared with their corresponding instruments. Results: Group 1 (ProTaper) 25/.06 GP points showed greater diameters than those of the corresponding instrument, which was statistically significant. Group 2 (WaveOne) 25/0.08 GP points showed greater diameters than those of the corresponding instrument which was statistically significant whereas it was nonsignificant at level D1. Conclusion: Diameters of both ProTaper Next and WaveOne GP cones were greater than their corresponding instruments. Hence, there are chances of under obturation with both systems.
Association of oral health behavior and the use of dental services with oral health literacy among adults in Tehran, Iran
Authors: Sistani Mohammad Mehdi Naghibi , Virtanen Jorma , Yazdani Reza , Murtomaa Heikki
Published: June 2017

Objective: To assess the association of oral health behavior (OHB) and the use of dental services with oral health literacy (OHL) among Iranian adults.Methods: This was a cross-sectional population study of a random sample of 1031 adults aged 18–65 in Tehran, Iran. We collected data on tooth brushing frequency, the consumption of sugary snacks and beverages, and time since last dental visit. To measure OHL, we used a validated OHL adults' questionnaire (OHL-AQ). In addition to descriptive analysis, we used multiple logistic regression models to assess the association of OHB and the most recent dental visit with OHL while controlling for socioeconomic and demographic factors.Results: The participants' mean age was 36.3 (standard deviation 12.9), and 51% were women. Of the participants, 81.3% reported brushing their teeth daily (≥1/day), 37.6% consumed sugary snacks or beverages between meals less than once daily (<1/day), and 36.8% used dental services within the past 6 months. In the adjusted models, high OHL scores significantly correlated with daily (≥1/day) tooth brushing (odds ratio [OR] = 1.97, 95% confidence interval [CI]: 1.30–2.98), the consumption of sugary snacks or beverages (<1/day between meals) (OR = 1.56, 95% CI: 1.13–2.15) and the recent use of dental services (≤6 months) (OR = 1.59, 95% CI: 1.15–2.21), respectively.Conclusions: OHL relates significantly to improved OHB and the use of dental services. Oral health promotion programs should, therefore, take into account improvements in adults' OHL, particularly in countries with developing health-care services.
El movimiento de los comuneros en Milpa Alta1
Authors: Korsbaek Leif , Bello Salgado Evelyn Guadalupe
Published: June 2017

El presente texto se refiere a la lucha de los comuneros en las comunidades originarias de Milpa Alta, es la delegación territorialmente más extensa pero con menos densidad de población, ubicada en el extremo sur de la Ciudad de México. En el primer apartado se introduce la sociedad plural de México y se presenta a Milpa Alta como parte de esa sociedad. En el segundo apartado se describe la suerte de la población indígena en México, tanto en lo cuantitativo como en lo cualitativo a través de los tiempos, y se estudia el proceso de legalización de esta población, en particular las consecuencias de la firma y la ratificación del Convenio 169 de la OIT y la rebelión de los zapatistas el primero de enero de 1994. El apartado medular del texto es el tercero, que es un estudio antropológico del proceso de lucha de los comuneros de Milpa Alta durante los años recientes, con base en entrevistas con una serie de líderes y participantes en esta lucha. En la breve conclusión se hace referencia a otras luchas similares y se plantea una evaluación de las perspectivas de la lucha de los comuneros.
La construcción del conocimiento realizando prácticas escolares reales
Authors: Vélez Torres Álvaro , Lara Lara Antonieta Paulina
Published: June 2017

El propósito del documento es presentar el análisis de tres actividades integradoras de conocimientos con alumnos del nivel medio superior que vinculan contenidos teóricos vistos en clase con aplicaciones prácticas de las materias de química, ecología y medio ambiente. Dichas actividades involucraron la producción de un coagulante orgánico –chitosan– obtenido de exoesqueletos de camarón para tratar agua residual generada del trapeado de pisos en el plantel, así como la implementación de un huerto escolar y la construcción de una planta de tratamiento manual de agua residual. La hipótesis planteó que los alumnos construyen nuevo conocimiento cuando vinculan los contenidos teóricos vistos en clase con su cotidianidad, porque es en la práctica diaria donde surgen los problemas y las soluciones racionales, empíricamente tratables. Se usó una metodología general cualitativa, así como varios métodos específicos para la obtención del coagulante y el huerto. Los alumnos corroboraron la hipótesis retomando la expresión generalizada de que aprenden haciendo.
Influence of common assumptions regarding aerosol composition and mixing state on predicted CCN concentration
Authors: Mahish Manasi , Jefferson Anne , Collins Don
Published: June 2017

Abstract. A 4-year record of aerosol size and hygroscopic growth factor distributions measured at the Department of Energy’s SGP ARM site in Oklahoma, U.S. were used to estimate supersaturation (S)-dependent cloud condensation nuclei concentrations (NCCN). Baseline or reference NCCN(S) spectra were estimated by using the data to create a matrix of size- and hygroscopicity-dependent number concentration (N) and then integrating for S > critical supersaturation (Sc) calculated for the same size and hygroscopicity pairs using κ-Köhler Theory. The accuracy of those estimates was assessed through comparison with the directly measured NCCN at the same site. Subsequently, NCCN was calculated using the same dataset but with an array of simplified treatments in which the aerosol was assumed to be either an internal or an external mixture and the hygroscopicity either assumed or based on averages derived from the growth factor distributions. The CCN spectra calculated using the simplified treatments were compared with those from the baseline approach to evaluate the impact of commonly used approximations. Among the simplified approaches, assuming the aerosol is an internal mixture with size-dependent hygroscopicity parameter (κ) resulted in estimates closest to those from the baseline approach over the range in S considered.
Measurements of wind turbulence parameters by a conically scanning coherent Doppler lidar in the atmospheric boundary layer
Authors: Smalikho Igor N. , Banakh Viktor A.
Published: June 2017

Abstract. The method and results of lidar studies of spatiotemporal variability of wind turbulence in the atmospheric boundary layer are reported. The measurements were conducted by a Stream Line pulsed coherent Doppler lidar with the use of conical scanning by a probing beam around the vertical axis. Lidar data are used to estimate the kinetic energy of turbulence, turbulent energy dissipation rate, integral scale of turbulence, and momentum fluxes. The dissipation rate was determined from the azimuth structure function of radial velocity within the inertial subrange of turbulence. When estimating the kinetic energy of turbulence from lidar data, we took into account the averaging of radial velocity over the sensing volume. The integral scale of turbulence was determined on the assumption that the structure of random irregularities of the wind field is described by the von Karman model. The domain of applicability of the used method and the accuracy of estimation of turbulence parameters were determined. Turbulence parameters estimated from Stream Line lidar measurement data and from data of a sonic anemometer were compared.
Impacts of temperature extremes on European vegetation during the growing season
Authors: Baumbach Lukas , Siegmund Jonatan F. , Mittermeier Magdalena , Donner Reik V.
Published: June 2017

Abstract. Temperature is a key factor controlling plant growth and vitality in the temperate climates of the mid-latitudes like in vast parts of the European continent. Beyond the effect of average conditions, the timings and magnitudes of temperature extremes play a particularly crucial role, which needs to be better understood in the context of projected future rises in the frequency and/or intensity of such events. In this work, we employ event coincidence analysis (ECA) to quantify the likelihood of simultaneous occurrences of extremes in daytime land surface temperature anomalies and the normalized difference vegetation index (NDVI). We perform this analysis for entire Europe based upon remote sensing data, differentiating between three periods corresponding to different stages of plant development during the growing season. In addition, we analyze the typical elevation and land cover type of the regions showing significantly large event coincidences rates to identify the most severely affected vegetation types. Our results reveal distinct spatio-temporal impact patterns in terms of extraordinarily large co-occurrence rates between several combinations of temperature and NDVI extremes. Croplands are among the most frequently affected land cover types, while elevation is found to have only a minor effect on the spatial distribution of corresponding extreme weather impacts. These findings provide important insights into the vulnerability of European terrestrial ecosystems to extreme temperature events and demonstrate how event-based statistics like ECA can provide a valuable perspective on environmental nexuses.
An Efficient Algorithm for Improved Doppler Profile Detection of MST Radar Signals
Authors: Padmaja Nimmagadda , Varadarajan Souri , Yashoda Polisetti , Ramyakrishna Enugonda
Published: June 2017

Abstract. An efficient algorithm based on Empirical Mode Decomposition (EMD) de-noising using soft threshold techniques for accurate doppler profile detection and Signal to Noise Ratio (SNR) improvement of MST Radar Signals is discussed in this paper. Hilbert Huang Transform (HHT) is a time-frequency analysis technique for processing radar echoes which constitutes EMD process that decomposes the non-stationary signals into Intrinsic Mode Functions (IMFs). HHT process has been applied on the time series data of MST (Mesosphere-Stratosphere–Troposphere) radar collected from NARL (National Atmospheric research Laboratory), Gadanki, India. Further, spectral moments were estimated and signal parameters such as mean doppler, signal power, noise power and SNR were calculated. Stacked doppler profile was plotted to observe the improvement in doppler detection. It has been observed that there is a considerable improvement in recognition of the doppler echo leading to improved Signal Power and SNR. The algorithm was tested for its efficacy on various data sets for all the 6 beams and the results of two data sets are presented.
GLOFRIM v1.0 – A globally applicable computational framework
for integrated hydrological-hydrodynamic modelling
Authors: Hoch Jannis M. , Neal Jeffrey C. , Baart Fedor , van Beek Rens , Winsemius Hessel C. , Bates Paul D. , Bierkens Marc F. P.
Published: June 2017

Abstract. To increase the representation of physical processes in inundation modelling, current research approaches aim to integrate both hydrological and hydrodynamic models. A previous study by Hoch et al. (2017) showed that spatially explicit coupling approaches can outperform stand-alone runs by single-purpose models as they combine spatially distributed model forcing by hydrological models with more sophisticated routing schemes in hydrodynamic models. We here present GLOFRIM, a globally applicable computational framework for integrated hydrological-hydrodynamic modelling, to facilitate such coupling approaches and to cater for an ensemble of models to be coupled. It currently allows for coupling the global hydrological model PCR-GLOBWB with either Delft3D Flexible Mesh (DFM), solving the full shallow-water equations and allowing for spatially flexible meshing, or LISFLOOD-FP (LFP), solving the local inertia equations and running on regular grids. The main advantages of the framework are its open and free access, its global applicability, its versatility, and its extensibility with other hydrological or hydrodynamic models. Before applying GLOFRIM to an actual test case, we benchmarked both DFM and LFP for a synthetic test case. Results show that for sub-critical flow conditions, discharge response to the same input signal is near identical for both models, which agrees with previous studies. We subsequently applied the framework to the Amazon River basin to test the framework thoroughly and, in addition, to perform a first-ever benchmark of flexible and regular grids at the large-scale. Both DFM and LFP produce comparable results in terms of simulated discharge with LFP exhibiting slightly higher accuracy as expressed by a Kling-Gupta-Efficiency of 0.82 compared to 0.76 for DFM. However, benchmarking inundation extent between DFM and LFP over the entire study area, a critical success index of 0.46 was obtained, indicating that the models disagree as often as they agree. Differences between models in both simulated discharge and inundation extent is to a large extent attributable to the gridding techniques employed. In fact, the result show that the numerical scheme of the inundation model and the gridding technique can contribute as strongly to deviations in simulated inundation extent as, unlike the global flood model inter-comparison by Trigg et al. (2016), we control for model forcing and boundary conditions. This study shows that the presented computational framework is robust and widely applicable. GLOFRIM is designed as open access and to be easily extendable, and thus we hope that other large-scale hydrological and hydrodynamic models will be added, eventually capturing more locally relevant processes as well as allowing for more robust model inter-comparison, benchmarking, and ensemble simulations of flood hazard at the large scale.