bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Press Formability of Pure Titanium Sheets
Authors: Pham Quoc Tuan , Kim Young Suk
Published: November 2016

Commercially pure titanium (CP Ti) has been actively used in plate heat exchangers due to its light weight, high specific strength, and excellent corrosion resistance. However compared with automotive steels and aluminum alloys, only limited research has been conducted on the plastic deformation characteristics and press formability of CP Ti sheets. In this study, the mechanical properties, including the anisotropic property and the stress-strain relation, of the CP Ti sheet are clarified in relation to press formability. A new proposed strain hardening model, Kim-Tuan equation, is successful in perfectly describing the stress evaluation for strain increment of this material during strain path. The forming limit curve (FLC) of the CP Ti sheet as a criterion for press formability was experimentally evaluated by punch stretching testing and analytically predicted via Hora’s modified maximum force criterion. The predicted FLC based on the Kim-Tuan strain hardening equation and the appropriate yield function correlates well with the experimental results of the punch stretching test.
Microstructure and Mechanical Properties of Multi-Pass Warm Rolled Ti-6Al-4V Alloy of Different Microstructures
Authors: Xu Yong , Yang Xiang Jie , Du Dan Ni
Published: November 2016

In this investigation three kinds of raw microstructure Ti-6Al-4V alloys were studied using two directional rolling on a conventional rolling mill. The effect of deformation on microstructure and mechanical properties has been attempted. Microstructural observation indicated that the size of the lamellar/equiaxed α grain was sharply decreased to submicro after multi-pass warm rolling. Tensile test results showed that the multi-pass warm rolling process was found to have a remarkable strengthening effect. The ultimate tensile strength and yield stress were increased by more than 10% and 25% respectively compared with unidirection rolled specimen, and the elongation has been increased by more than one times, and the maximum is up to 1.58 times. Meanwhile, the difference of the strength and elongation between in rolling direction and in transverse direction has been greatly reduced.
Effect of Plastic Deformation on Elastic and Plastic Recovery in CP-Titanium
Authors: Khayatzadeh Saber , Rahimi Salah , Blackwell Paul
Published: November 2016

The springback associated with cold deep drawing of sheet metals leads to undesired dimensional changes in the final products. This is often due to the heterogeneous plastic deformation in different areas of the intended geometry that creates various stress states throughout the part. The major objective of this study is to understand the interconnection between springback, level of plastic deformation, degradation of elastic modulus and strain recovery in a CP-Ti material. The mechanical properties of the sheet material and the dependency of mechanical properties on directionality are investigated by examining samples from three orientations of parallel to the rolling direction (RD), at 45° to RD and perpendicular to RD. The degradation of elastic modulus as a function of level of plastic deformation was explored for 0° and 45° samples by conducting multi-step uniaxial loading-unloading in tension.The experimental results showed that the mechanical properties vary for each direction, with the lowest elastic modulus along RD. A significant degradation was observed in elastic modulus (up to 50% reduction) with increased plastic deformation. This resulted in more strain relaxation compared to that associated with the initial elastic modulus. For stresses below 100MPa, a nonlinear (plastic) recovery was observed, resulting in additional relaxation in the total strain upon load removal in each step of the interrupted tests. This plastic recovery behaviour is observed to be dependent on sample orientation. It is concluded that accurate prediction of springback during sheet metal forming, requires a material model which takes into accounts the directional degradation of elastic modulus and the plastic recovery as a function of plastic deformation.
The Effect of Low-Intensity Static Magnetic Field on Ni-P-PTFE Electroless Composite Plating Coatings
Authors: Hou Jun Ying , Gao Hong Jiang , Liu Xiao Lin , Jiao Yu , Liu Li
Published: November 2016

A new processing concept has been developed to produce Ni-P-PTFE electroless composite coating. This method combines magnetic field and electroless composite plating techniques to prepare high-quality Ni-P-PTFE electroless composite coating. The influence of magnetic on composite plating process and coatings performance by changing some factors such as the plating time, magnetic field strength, magnetic field direction. The results indicate that the external magnetic field improved deposition rate and the PTFE particles content of composite coatings, meanwhile, some performances of composite coating like thickness, corrosion resistance, were effected by external magnetic field strength. Therefore, the method combines magnetic field and electroless completing techniques had a wide application prospect in the aspect of improving the properties of electroless composite coating.
Review of Research Progress on Size Effect in Micro-Forming
Authors: Qiu T.T. , Hou Ying Ke , Cao H.L.
Published: November 2016

Microforming process is a promising approach to manufacture microparts for its high productivity, high material usage and good part properties. However, when the part size is scaled down from macro to micro level, the deformation behaviors of materials change and the size effects occur. This makes it difficult to use microforming process in industry. In the last decade, many studies have been conducted with different test methods and materials. In this paper, the main test apparatus and the methods used to study the size effect and the significant results are reported.
Effects of Liquids on Physicochemical Properties of Fluorosilicone Rubber
Authors: Cheng Jun Mei , Zhao Shu Gao
Published: November 2016

An attempt has been undertaken to assess the effect of RP-3 jet fuel and 4109 lubricant on the mechanical, swelling properties and compression set of two kinds of fluorosilicone rubber (FSR) which are self-made and provided by Dow corning, and are marked as FSR A and FSR B respectively. Results showed that FSR B has better chemical resistance and comparable mechanical properties with that of FSR A, and are promising candidates for the development of high performance sealing materials.
Grain Refinement in an Al-Zn-Mg-Cu Casting Ingot
Authors: Wu Xiao Dong , Liao Bin , Yan Chang Jian , Huang Li , Cao Ling Fei
Published: November 2016

The grain refinement in a high specific strength Al-Zn-Mg-Cu casting ingot was studied by add different amount of Al-Ti-C and Al-Ti-B master alloys during casting. The optical microscopy observation shows that the grain size of ingot is greatly reduced when adding Al-Ti-B as low as 0.01 wt%. Both the average size and the size difference among samples from various locations of ingots are smaller when the alloy casted with Al-Ti-B, which indicates that Al-Ti-B is effecient for the grain refinement in the Al-Zn-Mg-Cu casting ingot.
Research of Preparing Parameters in the Complex Process on Microstructure in Semisolid A356 Alloy Slurry with Micro-Addition of La
Authors: Liu Zheng , Xu Li Na , Zhang Jia Yi , Bai Guang Zhu , Liu Xiao Mei
Published: November 2016

Based on the green and saving concept, a complex process preparing semisolid alloy slurry was developed, which was composed of the low superheat pouring and low frequency electromagnetic stirring. The semisolid A356-La slurry was prepared by the complex process, and the microstructure of the semisolid A356-La alloy was researched under the different preparing parameters in the complex process, such as the pouring temperature, electromagnetic stirring frequency, stirring time and micro-addition of La. The results indicated that it was feasible to reduce the addition of La and consumption of energy during the preparation of semisolid alloy slurry by optimizing the preparing parameters in the complex process. The suitable preparing parameters were obtained by the experiment, in which the pouring temperature was 630 °C, the frequency of electromagnetic stirring was 30 Hz, and the stirring time was 8 s. When semisolid A356 alloy slurry added 0.3 wt% La was prepared by the suitable preparing parameters in the complex process, the refining effects on microstructure in the semisolid A356-0.3La alloy was indistinguishable with that of the conventional addition amount of 0.6 wt% La in semisolid A356 alloy prepared by low superheat pouring.
Detection of Quench Induced Precipitation in Al Alloys by Dilatometry
Authors: Milkereit Benjamin , Reich Michael , Kessler Olaf
Published: November 2016

Quenching is a critical step during the strengthening age hardening of Aluminium alloys. To obtain optimal technological results, parts should be quenched with the upper critical cooling rate. The precipitation behaviour of Al alloys during cooling from solution annealing and thereby the critical cooling rates are typically investigated by in-situ measurements with differential scanning calorimetry (DSC). Conventional DSCs are limited at cooling rates below 10 Ks-1. Unfortunately, medium to high strength Al alloys typically have critical cooling rates between 10 and some 100 Ks-1. Recently it was shown that dilatometry is generally able for in-situ detection of precipitation in Al alloys. Dilatometry allows controlled cooling up to some 100 Ks-1 and therefore covers the cooling rate range relevant. In this work, we aim to show up and discuss possibilities and limitations of dilatometric detection of quench induced precipitates in 2xxx, and 7xxx Al alloys. The basic method will be presented and results will be compared with DSC work.
Stress Induced Precipitation during Quenching of Aluminium Alloys
Authors: Osten Julia , Lux Christian , Milkereit Benjamin , Reich Michael , Kessler Olaf
Published: November 2016

Quenching is an important step during age hardening of aluminium alloys. It significantly influences on microstructures, properties, residual stresses and component distortion. Due to high heat transfer, thermal stresses occur in quenched components. I.e., all premature precipitates during undercritical quenching form on condition of mechanical stresses. Opposite, quench sensitivity investigations, e.g. recording of continuous cooling precipitation diagrams, are usually performed in stress-free conditions and may therefore be incomplete. We have developed a new method of thermomechanical analysis and calorimetric reheating to investigate stress induced precipitation during quenching of aluminium alloys. For aluminium alloy 2024, it has been shown for the very first time that mechanical stresses during quenching also influence on quench-induced precipitation reactions.
Role of Pre-Deformation on Aging Precipitation Behavior of Al-Cu-Li Alloys
Authors: Li Jin Feng , Chen Yong Lai , Zhang Xu Hu , Zheng Zi Qiao
Published: November 2016

Predeformation on tensile properties and microstructure of three Al-Cu-Li alloys, 1460, 2050 and 2A96 was investigated. The strength of the alloys is enhanced by the predeformation. Meanwhile, predeformation impacts the precipitation of T1 (Al2CuLi) and θ′(θ′′) (Al2Cu) phases. The precipitation (nucleation rate) of T1 is accelerated by the predeormation, and the effect is increased with the predeformation degree. While, effect on θ′(θ′′) precipitation is dependent on the alloy composition feature. In the 2A96 alloy with a medium Cu/Li ratio, it is decelerated by the predeformation. In the 2050 alloy with high Cu/Li ratio and 1460 alloy with low Cu/Li ratio but subjected to two-step aging at 130°C and 160°C, the θ′(θ′′) precipitation is accelerated at lower predeformation but decelerated at higher predeformation.
Quantitative Measurement of Strain Field around η′ Phase in a 7000 Series Aluminum Alloy
Authors: Liu Fei , Bai Pu Cun , Hou Xiao Hu , Xing Yong Ming
Published: November 2016

The strain field of η′ phase in an aged 7000 series aluminum alloy has been investigated using a combination of high resolution transmission electron microscopy (HRTEM) and geometric phase analysis (GPA) technique in this paper, and strain components εxx, εyywere mapped, respectively. The results showed that the strain is mainly generated near the matrix/η′ phase interface and gradually decreases with distance increasing away from the interface. There were convergence and divergence regions of the strain within the η′ phase, and maximum strain occurred in the position where about 0.25 nm far from the interface, value of the maximum strains was about 2.54%.
APT Investigation of Effect of Minor Zr on Precipitation Strength of Al-Sc Alloy
Authors: Xue Na , Song Hui , Zhou Chang Bing , Wang Xiao Jiao , Liu Wen Qing
Published: November 2016

As-cast Al-Sc alloys and Zr-containing Al-Sc-Zr alloys were aged at 300°C for different times, the Al-Sc-Zr alloy showed more excellent precipitation strengthening. The atom probe tomography (APT) was applied to characterize the precipitates in the two alloys, the results show that the precipitates in Al-Sc-Zr alloy is smaller in size and is higher in number density than that in the Al-Sc alloy at same aging time, it is because that the Zr addition reduces the diffusion rate of Sc, and which retains the growth of precipitates and results in the excellent precipitation strengthening of Al-Sc-Zr alloy.
Effect of Annealing Conditions on Recrystallization of AA5182 Sheet
Authors: Guo Qian Ning , Lei Xiu Chuan , Sanders Jr Robert E. , Yang Xiao Fang , Liang Yan Xiang , Wang Lu , Fan Zhen Zhen
Published: November 2016

Alloy 5182 has been extensively used in the O temper for automotive sheet parts requiring high formability and moderate strength. The grain size of the sheet has been shown to impact strength, formability, and Lüdering behavior during forming. The present study examined the effect of heating rate on the recrystallization behavior of the alloy. Various heating rates, recovery treatments and annealing temperatures were used to manipulate the final grain size. Metallographic observations, EBSD and hardness tests were used during the research. The results are discussed in terms of operative recrystallization mechanisms for this alloy.
Combined Effect of Cold-Rolling and Aging on Precipitation and Recrystallization Behavior of Al-Er-Zr Alloy
Authors: Liu Tong Hui , Wen Sheng Ping , Wu Xiao Lan , Gao Kun Yuan , Huang Hui , Wang W. , Nie Zuo Ren
Published: November 2016

To investigate the effect of cold-rolling and aging on precipitation and recrystallization behavior of Al-0.04Er-0.08Zr (at. %) alloy, two thermo-mechanical processes containing peak aging + cold-rolling (A+CR) and cold-rolling + isochronal aging (CR+A) were studied. In A+CR process, the hardness of alloy under cold-rolled state was much higher than the maximum obtained during isochronal aging, due to the strong interaction between precipitates and dislocations or sub-grain boundaries. Furthermore, the recrystallization temperature was 475 °C as indicated by the hardness curve. The microstructure analysis revealed that the sample annealed at 525 °C for 1 h still don’t recrystallize fully. For CR+A, it turned out that the deformation play a small role in improving the maximum of hardness. But comparing with those without deformation, the existence of deformation accelerated the rate of precipitation process and obtained higher electrical conductivity.
A Study on the Deformation Dehaviours of Al-1.4Fe-0.2Mn Alloy Sheets
Authors: Pan Yan Feng , Zhao Pi Zhi , Shen Yi Fu , Shi Xiang Jun , Jiang Tao
Published: November 2016

The deformation behaviours and microstructure transformations during the cold rolling process of Al-1.4Fe-0.2Mn alloy sheets prepared from 99.7% pure aluminium were investigated by means of hardness-testing, transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS). The phenomena of work hardening and work softening were observed. The hardness of Al-1.4Fe-0.2Mn alloy sheets increased with the increasing of cold rolling reduction firstly, and reached to a peak at 80% cold rolling reduction, meaning work hardening. However, with further increasing of cold rolling reduction, the hardness decreased, which indicates work softening. During the initial deformation stage, the dislocation density and the number of sub-grain structures increased gradually, and many dislocations formed tangles, resulting in work hardening. When the cold rolling reduction exceeded 80%, the dislocation density decreased and sub-grain structures polygonized, leading to work softening. The forming of Mn, Fe and Si bearing compounds is an important reason for the work softening due to lowering solid solution content.
Correlation between Fracture Toughness and Quantitative Characterization of Microstructure in 7055 Aluminium Alloy
Authors: Yan Hong Wei , Li Xi Wu , Xiong Bai Qing , Zhang Yong An , Li Zhi Hui , Liu Hong Wei , Huang Shu Hui , Yan Li Zhen
Published: November 2016

Microstructure of high strength aluminum alloy have determinant effect on the properties, thus an effort has been made to investigation the relationship between fracture toughness and quantitative characteristics of microstructure in high strength aluminum alloy. Fracture toughness was tested for aluminum alloy specimens with various microstructure. The corresponding microstructure was observed by optical metallography and electron back-scattered diffraction, and quantitative characterization was conducted by further analysis of result obtained. Correlation between fracture toughness and parameters included grain size, percentage of recrystallization, substructure content and area fraction of residual phases was investigated. It was shown that percentage of recrystallization was a crucial factor for the fracture toughness, and correlations were established with proper and reasonable correction.
Characterization of Intergranular Corrosion Defects in a 2024 T351 Aluminium Alloy
Authors: de Bonfils-Lahovary M.L. , Laffont L. , Blanc Christine
Published: November 2016

In the 2xxx series alloys, intergranular corrosion is generally related to the strong reactivity of copper-rich intergranular precipitates leading to a copper enrichment of these particles. While the nature of the oxides formed inside the intergranular corrosion defects was assumed to strongly influence the intergranular corrosion propagation rate, it was not clearly identified due to the thickness of the oxide layer formed which required to use high resolution analytical techniques. The present work aims to characterize the intergranular corrosion defects formed for a 2024-T351 aluminum alloy after a 24 hours continuous immersion in a 1 M NaCl solution and compares the results to literature data concerning the oxide layers formed on copper-rich model alloys. A combination of focus ion beam (FIB) technique, transmission electron microscopy (TEM) observations and energy dispersive X-Ray spectroscopy (EDX) analyses was used to accurately characterize both the morphology and chemical composition of the intergranular corrosion defects. Results evidenced the dissolution of intergranular copper-rich particles, the formation of a 10-200 nm-thin metallic copper-rich layer at the oxide/metal interface and the incorporation of copper inside the amorphous alumina oxide film leading to the formation of structural defects of the oxide film.
Directionality and Column Arrangement Principles of Precipitates in Al-Mg-Si-(Cu) and Al-Mg-Cu Linked to Line Defect in Al
Authors: Andersen Sigmund J. , Marioara Calin D. , Friis Jesper , Bjørge R. , Du Qiang , Ringdalen I.G. , Wenner Sigurd , Mørtsell Eva A. , Holmestad Randi , Saito T. , Røyset Jostein , Reiso Oddvin
Published: November 2016

In the structures of all metastable precipitates in Al-Mg-Cu and Al-Mg-Si alloys, we find that column surrounding of an element column in the needle/lath direction order according to simple principles. Advanced transmission electron microscopy and DFT calculations support the principles originate with a line defect, which is a segment of a <100>Al column shifted to interstitial positions. We propose the defect aids solute decomposition by partitioning the FCC matrix locally into columns of fewer and higher number of nearest neighbours, which suit smaller and larger size solute atoms, respectively. The defect explains how <100> directionality of the precipitates can arise in a cluster. Ordering of a few defects leads naturally to GPB zones in Al-Mg-Cu and to β'' in Al-Mg-Si.
Optimization for Anodizing Conditions of 5A06 Aluminum Alloy Based on Doehlert Design Matrix Method
Authors: Li Ying Dong , Zhao Pi Zhi , Li Song Mei
Published: November 2016

The present study investigated the influence of intermetallic phases and anodizing parameters on anodic oxidation of 5A06 aluminum alloy by using Doehlert design matrix, in which the anodizing voltage, time and concentration of sulfuric acid were set as input variables while the quantity of electricity (Q) and the corrosion current (jcorr) were set as response values. The results showed that the residual particles after anodizing were mainly Si-containing phases. The thickness of anodic film increased linearly with the applied quantity of electricity and the anodic film exhibited high corrosion resistance when applied quantity of electricity increased more than 900C. Doehlert design matrix revealed that all regressions were significant, indicating that each second order model was adequate. The anodizing behavior and corrosion resistance could be predicted by the simulated model. An optimal anodizing parameters (16V, 20 min, 50g/L) were obtained by using desirability functions with satisfied degree of 0.987.
Application of Vertical-Type High-Speed Twin-Roll Casting for Up-Grade Recycling and Clad Sheets Fabrication of Aluminum Alloys
Authors: Kumai Shinji , Takayama Yusuke , Nakamura Ryoji , Shimosaka Daisuke , Harada Yohei , Kim Min Seok
Published: November 2016

A horizontal-type twin roll casting method has been popular for producing aluminum alloy strips, however, it is characterized by a relatively low productivity (1~6 m/min). In contrast, a vertical-type high-speed twin-roll casting method possesses an extremely high productivity (60~120 m/min (1~2 m/s)) and an excellent heat extraction ability. The rapid cooling effect provided significant microstructure refinement and mechanical properties improvement in various kinds of cast aluminum alloy products. Not only “product to product recycling” but also “up-grade recycling” can be achieved by making good use of these merits. Two examples of application showing the potential of vertical-type high-speed twin roll casting method are presented. (1) Several kinds of Al-Si base alloy were cast into the strips. Not only strength and toughness but also formability was increased in the twin roll cast products. In particular, great improvement in deformability shows the potential of the twin-roll cast aluminum alloy products as substitutes for some wrought aluminum alloy products. (2) The vertical-type tandem twin-roll caster was able to fabricate a clad strip by single step. The A4045/A3003/A4045 aluminum alloy clad sheets produced by the twin-roll casting showed better mechanical properties than the conventional hot-roll bonded clad sheets.
Study of an Accelerated Aging Process for Conductive Aluminum Alloys
Authors: Liao Heng Cheng , Liu Ye , Wang Qi Gui
Published: November 2016

An orthogonal hardness study of 4 factors (the step one aging temperature (T1) and time (t1), and step two aging temperature (T2) and time (t2)) with 3 levels was designed to optimize an accelerated aging process for a newly developed conductive aluminum alloy (Al-0.4wt.%Si-0.3wt.% Mg-0.3wt.%Ce). Statistical analysis of the experimental results indicates that the factor significance ranked from high to low is t2, T2, T1, and t1. The optimal aging process is 140°C×5h+220°C×5h. Experimental validation confirms that all the strength, hardness, elongation and conductivity with the optimized aging process exceed the predictions. Compared with the commonly used T7 process (190°C×20h), the optimized aging process leads to a more superior precipitation effect and much less time. TEM observation indicates the accelerated aging process significantly expedites the precipitating transformation even with much shorter aging time.
Effect of Zn, Mg, Cu, Zr on Microstructure and Properties of Laser Welding Aluminium Alloy
Authors: Zhao Zhi Hao , Liu Wen Qiang , Tao Kai , Chen Qi Chao , Wang Gao Song
Published: November 2016

A series of Al-6.3Zn-2.3Mg-2.3Cu-0.15Zr alloys with different reduce of Zn, Mg, Cu and Zr were prepared by ingot-metallurgy processing. The metallurgical structure and mechanical properties were investigated by optical microscope, scanning electron microscopy and other equipment. The results indicated that the ingot’s microstructures of the four alloys contain the phrases of η (MgZn2) and θ (Al2Cu), which mostly distribute at the grain boundaries in a shape of continuous network. After extrusion processing, the grain of laser welding aluminium alloy was elongated along the extrusion direction, therefore forming fibrous structures, and meanwhile the second phase particles with different degrees of fragmentation were arranged along the extrusion direction since the microstructure of extruded bars was inherited by the as-cast structure. Zr could significantly inhibit recrystallization of alloy; the recrystallization of the alloy with lower Zr was more obvious. As the content of Zr reduced, the tensile strength of alloy decreased, but the electrical conductivity and hardness increased. When the content of Cu was lower, the hardness were decreased.
Study on Thermal Physical Properties of Al-Si8-Cu2-Mg Alloy
Authors: Gao Liang , He Ping , Guo Gang Yin , Xiang Zheng Bo , Liu Fei
Published: November 2016

Parts of thermal physical properties of Al-Si8-Cu2-Mg alloy were studied. The curves were plotted showing the relationship between density, specific heat capacity, coefficient of thermal expansion and the variation of temperature for the first time with this alloy. The results show that the density was decreased when the temperature was raised, but the specific heat capacity and the coefficient of thermal expansion were first increased and then decreased. The solidus-liquidus temperatures, latent heat of fusion were studied, and the results show that the melting temperature range of this alloy was 507-596°C.
Modelling of Strain-Path Transients in Commercially Pure Aluminium
Authors: Qin Ji Sheng , Holmedal Bjørn , Hopperstad Oddsture
Published: November 2016

In the current work, the recently proposed homogeneous anisotropic hardening (HAH) model, featuring a distorted yield surface, is applied to commercially pure aluminium. A dislocation-based hardening rule is incorporated into the HAH model to describe the transient stagnation of the hardening rate during strain reversal. A cast and homogenized material with random texture previously investigated by Mánik et al. [1] is selected. The material is prestrained either by compression or rolling, and then tested in uniaxial tension to acquire either reverse softening or orthogonal hardening. The Bauschinger effect, the permanent softening during reverse loading and the hardening in the course of orthogonal loading are captured by the model. However, the permanent softening during orthogonal loading cannot be predicted, and the transient variations of the R-value predicted by the HAH model are neither in qualitative nor quantitative agreement with the experimental data.
Optimized Design of Aluminum Cross Car Beam (CCB) Based in Modal Strain Energy Analysis
Authors: Liu Bo , Qiu Zhong Cai , Yang Qin , Wang Ke , Wu Xian He
Published: November 2016

An aluminium cross car beam (CCB) for new energy is designed with CATIA. And then,modal analysis is taken by using simulation software-NASTRAN. As nature frequencies can't meet the design target, optimization is performed according to the modal strain energy contour. After structure is strengthen, the first vertical nature frequency of the aluminum CCB(mounted on trimmed car body,with closures and interiors) reaches 35.4Hz.While the first lateral nature frequency reaches 36.5 Hz. Besides,comparing to steel CCB,the weight of the aluminum CCB reduces by4.4 kilogram.
The Study of Change in Optical Properties of Highly AgNO3 Doped Poly Vinyl Alcohol Hydrosol
Authors: Vaghasiya Tusharkumar K.
Published: November 2016

Highly Ag doped PVA (20%wt., 35%wt., 40%wt.) were prepared by chemical reaction. The transmission and reflection spectra were recorded by UV-Vis-NIR spectrophotometer within the wavelength of 180nm-1200nm. The absorption has been evaluated by reflectance and transmittance spectra. Absorption coefficient, extinction coefficient, refractive index, optical conductivity and real and imaginary part of dielectric constant were calculated from optical spectra and plotted versus wavelength, it was shown that the adding of AgNO3 affect all these parameters by increasing their values. The optical band gap decreases with concentration of Ag increases. The diameter of doped silver nanoparticles has been estimated by assuming free particles behavior of conduction electron and calculated with the help of Surface Plasmon Resonance band of silver nanoparticles which is of the order of 14±0.5nm. Nearly symmetric shape and narrow FWHM of SPR band indicate that the synthesized silver nanoparticles are nearly spherical in shape. FTIR transmission spectra were recorded by single beam Fourier transform infrared spectrometer (Spectrum GX, Perkin Elmer, U.S.A.) in the spectral range of 4000 cm-1-400 cm-1. FTIR spectrum peaks correspond to molecular vibrations and chemical bonds, indicate the presence of silver in the PVA polymer structure.
Fabrication of an Enzymatic Biosensor Based on Gold Nanoparticles Modified Electrochemical Transducer for the Detection of Organophosphorus Compounds
Authors: Grace Rini , Sundar Keerthana , Mohan N. , Selvakumar D. , Kumar N.S.
Published: November 2016

A facile and sensitive enzyme based electrochemical transducer has been fabricated for the detection of organophosporus compounds. The enzyme, acetylcholinesterase, was covalently immobilized on gold nanoparticles deposited electrochemically over screen printed carbon working electrode. The electrodes were characterized by scanning electron microscopy, atomic force microscopy and electrochemical methods. The enzyme-substrate reactions and sensing studies were carried out at room temperature by cyclic voltammetry. The developed biosensor gave optimum response within 25 sec. for a substrate (acetylthiocholine) concentration of 0.0699 mM at pH. The electrode showed a linear response in the range between 0.2 and 1 ppb, and the detection limit was determined to be 0.6 ppb. Moreover the biosensor exhibited good reusability and stability thus, making it a promising tool for on-field detection of organophosphorus compounds.
Differing Effects of Fatigue and Depression on Hospitalizations in Men and Women With Heart Failure
Authors: Heo Seongkum , McSweeney Jean , Tsai Pao-Feng , Ounpraseuth Songthip
Published: November 2016

Background

In patients with heart failure, worsening of signs and symptoms and depression can affect hospitalization and also each other, resulting in synergistic effects on hospitalizations. A patient’s sex may play a role in these effects.

Objectives

To determine the effects of fatigue and depression on all-cause hospitalization rates in the total sample and in subgroups of men and women.

Methods

A secondary analysis was done of data collected January 1, 2010, through December 31, 2012 (N = 582; mean age, 63.2 years [SD, 14.4]). Data were collected on fatigue, depression, sample characteristics, vital signs, results of laboratory tests, medications, and frequency of hospitalization. Patients were categorized into 4 groups on the basis of the International Classification of Diseases, Ninth Revision: no fatigue or depression, fatigue only, depression only, and both fatigue and depression. General linear regression was used to analyze the data.

Results

In both the total sample and the subgroups, the number of hospitalizations in patients with both fatigue and depression was greater than the number in patients without either symptom. Among women, the number of hospitalizations in the fatigue-only group and in the depression-only group was greater than that in the group with neither symptom. In men, the number of hospitalizations in the fatigue-only group was greater than that in the group without either symptom.

Conclusion

Fatigue and depression do not have synergistic effects on hospitalization, but men and women differ in the effects of these symptoms on hospitalization.
Effectiveness of Arbuscular Mycorrhizal Fungi based biofertilizer on early growth of coconut seedlings
Authors: Ilangamudali I. M. P. S. , Senarathne S. H. S.
Published: November 2016

Coconut (Cocos nucifera L) is one of the predominant plantation crops in Sri Lanka. The success of a coconut plantation, in terms of its establishment as well as its future performance, is heavily dependent on the quality of the seedling used. Thus attention needs to pay to raise healthy seedlings in coconut nurseries. Coconut nurseries adopt different agronomic practices to produce good quality seedlings. In this process, applying mycorrhizal inoculants is becoming an increasingly common practice in plant nurseries. Therefore the effects of mycorrhizae based biofertilizer on root and shoot development of coconut seedlings was evaluated under nursery conditions for a period of seven months. The treatments were the presence of mycorrhizae based biofertilizer (T1) and absence of mycorrhizae based biofertilizer (T2). Application of mycorrhizae based biofertilizer had no significant effect on growth parameters tested in the early stages of seedling development up to four months. In contrast, the bio fertilizer significantly increased the numbers, volumes and dry weights of primary, secondary, tertiary and quaternary roots and stem girth at the latter stages of seedling growth. The leaf area and seedling height were not significantly increased by application of biofertilizer during the nursery period. These results revealed that the usage of mycorrhizae based biofertilizer positively affected root development and stem girth of coconut seedlings. The application of the mycorrhizae based biofertilizer seems to be beneficial to produce high quality seedlings with well developed roots and thus obtain good field establishment, thereby reducing the number casualties at early field establishment.
Assessing the performance of fruit colour based phenotypes of tall (Typica) coconuts (Cocos nucifera L.) in Sri Lanka
Authors: Perera S. A. C. N. , Kumarasinghe W. M. , Gunasekara T. M. C. P.
Published: November 2016

Sri Lanka tall (variety Typica, form typica) is the most widely cultivated coconut form in Sri Lanka. Sri Lanka tall coconuts display variation in fruit colour ranging from green to divergent brownish red (rathi). The growers' perception is that rathi seedlings are more vigorous and higher yielding than the green phenotype. A study was conducted to evaluate and compare the nut and copra yield and seedling vigour of phenotypic groups of green, rathi and intermediate coloured fruits. Secondary data for nut yield recorded over 21 years and husked nut weight of 30 nuts per palm collected over a year in 30 palms in each of the three phenotypes were used for analysis. Furthermore, primary data for seedling girth, height and leaf number in 30 palms each of rathi and green phenotypes were collected for analysis. The data was subjected to Analysis of variance using MINITAB 16. Nut yield or the husked nut weight of the three phenotypes was not significantly different. Significant differences were observed in seedling collar girth between rathi and green phenotypes, with rathi seedlings appearing more vigorous as indicated by the thicker stem compared to the green seedlings. It is concluded that, there are no differences in the nut and copra yield among different colour forms of Sri Lanka Tall coconuts while the rathi seedlings appear superior due to their thicker seedling girth.
A Role for Human Skin Mast Cells in Dengue Virus Infection and Systemic Spread
Authors: Troupin Andrea , Shirley Devon , Londono-Renteria Berlin , Watson Alan M. , McHale Cody , Hall Alex , Hartstone-Rose Adam , Klimstra William B. , Gomez Gregorio , Colpitts Tonya M.
Published: November 2016

Dengue virus (DENV) is a mosquito-borne flavivirus that causes serious global human disease and mortality. Skin immune cells are an important component of initial DENV infection and systemic spread. Here, we show that mast cells are a target of DENV in human skin and that DENV infection of skin mast cells induces degranulation and alters cytokine and growth factor expression profiles. Importantly, to our knowledge, we also demonstrate for the first time that DENV localizes within secretory granules in infected skin mast cells. In addition, DENV within extracellular granules was infectious in vitro and in vivo, trafficking through lymph to draining lymph nodes in mice. We demonstrate an important role for human skin mast cells in DENV infection and identify a novel mechanism for systemic spread of DENV infection from the initial peripheral mosquito injection site.
Acetylation Modulates IL-2 Receptor Signaling in T Cells
Authors: Kuwabara Taku , Kasai Hirotake , Kondo Motonari
Published: November 2016

Ligand binding to the cognate cytokine receptors activates intracellular signaling by recruiting protein tyrosine kinases and other protein modification enzymes. However, the roles of protein modifications other than phosphorylation remain unclear. In this study, we examine a novel regulatory mechanism of Stat5, based on its acetylation. As for phosphorylation, IL-2 induces the acetylation of signaling molecules, including Stat5, in the murine T cell line CTLL-2. Stat5 is acetylated in the cytoplasm by CREB-binding protein (CBP). Acetylated Lys696 and Lys700 on Stat5 are critical indicators for limited proteolysis, which leads to the generation of a truncated form of Stat5. In turn, the truncated form of Stat5 prevents transcription of the full-length form of Stat5. We also demonstrate that CBP physically associates with the IL-2 receptor β-chain. CBP, found in the nucleus in resting CTLL-2 cells, relocates to the cytoplasm after IL-2 stimulation in an MEK/ERK pathway–dependent manner. Thus, IL-2–mediated acetylation plays an important role in the modulation of cytokine signaling and T cell fate.
Survival after Pneumocystis jirovecii pneumonia requiring ventilation: A case report
Authors: Nethathe Gladness , Patel Nirav
Published: November 2016

Pneumocystis pneumonia (PCP) in patients with the human immunodeficiency virus (HIV) is associated with a high mortality rate, which increases substantially with the need for mechanical ventilation. Local experience of patients with PCP admitted to the intensive care unit has revealed mortality rates close to 100%. We present a case of a 39-year-old HIV-infected man diagnosed with PCP who was successfully weaned from mechanical ventilation after presenting with respiratory distress and severe hypoxaemia. A short review of the literature will also be presented.
Uncovering Web search strategies in South African higher education
Authors: Civilcharran Surika , Maharaj Manoj S.
Published: November 2016

Background: In spite of the enormous amount of information available on the Web and the fact that search engines are continuously evolving to enhance the search experience, students are nevertheless faced with the difficulty of effectively retrieving information. It is, therefore, imperative for the interaction between students and search tools to be understood and search strategies to be identified, in order to promote successful information retrieval.Objectives: This study identifies the Web search strategies used by postgraduate students and forms part of a wider study into information retrieval strategies used by postgraduate students at the University of KwaZulu-Natal (UKZN), Pietermaritzburg campus, South Africa. Method: Largely underpinned by Thatcher’s cognitive search strategies, the mixed-methods approach was utilised for this study, in which questionnaires were employed in Phase 1 and structured interviews in Phase 2. This article reports and reflects on the findings of Phase 2, which focus on identifying the Web search strategies employed by postgraduate students. The Phase 1 results were reported in Civilcharran, Hughes and Maharaj (2015).Results: Findings reveal the Web search strategies used for academic information retrieval. In spite of easy access to the invisible Web and the advent of meta-search engines, the use of Web search engines still remains the preferred search tool. The UKZN online library databases and especially the UKZN online library, Online Public Access Catalogue system, are being underutilised.Conclusion: Being ranked in the top three percent of the world’s universities, UKZN is investing in search tools that are not being used to their full potential. This evidence suggests an urgent need for students to be trained in Web searching and to have a greater exposure to a variety of search tools. This article is intended to further contribute to the design of undergraduate training programmes in order to deal with the information retrieval frustrations of novice users.
О некоторых проблемах, связанных с гипотезой Гильберта-Смита
Authors: Dranishnikov Alexander Nikolaevich
Published: November 2016

Гипотеза Гильберта-Смита утверждает, что если компактная группа действует свободно на многообразии, то она является группой Ли. В статье приводятся редукции гипотезы Гильберта-Смита в случае конечномерного пространства орбит к некоторым другим проблемам геометрической топологии, ключевой из которых является проблема о существенной последовательности линзовых пространств возрастающей размерности.
Библиография: 52 названия.
Проективные торические полиномиальные образующие в кольце комплексных кобордизмов
Authors: Solomadin Grigory Dmitrievich , Ustinovskiy Yury Mikhailovich
Published: November 2016

Согласно классическому результату Милнора и Новикова известно, что кольцо комплексных кобордизмов изоморфно градуированному кольцу полиномов от счетного числа образующих: $\Omega^U_*\simeq \mathbb Z[a_1,a_2,…]$, $\operatorname{deg}(a_i)=2i$. В статье решена известная задача построения геометрических представителей образующих $a_{i}$ среди гладких проективных торических многообразий, $a_n=[X^{n}]$, $\dim_{\mathbb C} X^{n}=n$. Доказательство основывается на использовании семейства эквивариантных модификаций (бирациональных изоморфизмов) $B_k(X)\to X$ произвольного комплексного гладкого многообразия $X$ комплексной размерности $n$ ($n\geqslant 2$, $k=0,…,n-2$), при которых изменение числа Милнора определяется лишь размерностью $n$ и значением параметра $k$, в частности не зависит от самого многообразия $X$.
Библиография: 22 названия.
Об объемах классических супермногообразий
Authors: Voronov Theodore Theodorovich
Published: November 2016

Рассмотрены объемы классических супермногообразий таких, как суперсфера, комплексное проективное суперпространство, и супермногообразия Штифеля и Грассмана, относительно естественных метрик или симплектических структур. Показано, что формулы для объемов этих супермногообразий могут быть получены с помощью аналитического продолжения по параметрам из формул для объемов соответствующих обычных многообразий (при некоторой универсальной нормализации объема). Объемы нетривиальных супермногообразий могут тождественно обращаться в нуль. Ф. А. Березин в 1970-х годах показал, что полная мера Хаара унитарной супергруппы $\mathbf{U}(n|m)$ обращается в нуль, кроме случаев $m=0$ или $n=0$, т.е. если супергруппа не сводится к обычной унитарной группе $\mathbf{U}(n)$ или $\mathbf{U}(m)$. Некоторое время назад Э. Виттен предположил, что лиувиллевский объем компактного четного симплектического супермногообразия всегда должен быть равен нулю (кроме обычных многообразий). В статье содержатся контрпримеры к этой гипотезе, а также получены простое объяснение теоремы Березина и ее обобщение на супермногообразие Штифеля $\mathbf{V}_{r|s}(\mathbf C^{n|m})$. Отмечена связь с недавними работами Р. Л. Мкртчяна и А. П. Веселова об универсальных формулах в теории алгебр Ли.
Библиография: 32 названия.
Малые накрытия над граф-ассоциэдрами и реализация циклов
Authors: Gaifullin Alexander Aleksandrovich
Published: November 2016

Ориентированное связное замкнутое многообразие $M^n$ называется $\mathrm{URC}$-многообразием, если для любого другого ориентированного связного замкнутого многообразия $N^n$ той же размерности найдется отображение ненулевой степени некоторого конечнолистного накрытия $\widehat{M}^n$ многообразия $M^n$ на многообразие $N^n$. Это условие эквивалентно следующему: любой $n$-мерный класс целочисленных гомологий любого топологического пространства $X$ может быть с некоторой кратностью реализован как образ фундаментального класса многообразия $\widehat{M}^n$, являющегося конечнолистным накрытием многообразия $M^n$, при непрерывном отображении $f\colon \widehat{M}^n\to X$. В 2007 г. автором было получено конструктивное доказательство классического результата Р. Тома о том, что любой целочисленный класс гомологий с некоторой кратностью реализуется образом фундаментального класса ориентированного гладкого многообразия. Из этой конструкции следует существование $\mathrm{URC}$-многообразий всех размерностей. Для важного класса многообразий - так называемых малых накрытий над граф-ассоциэдрами, отвечающими связным графам, - мы доказываем, что все они (или их ориентируемые двулистные накрытия) являются $\mathrm{URC}$-многообразиями. В частности, мы получаем, что двулистное накрытие малого накрытия над обычным ассоциэдром Сташефа является $\mathrm{URC}$-многообразием. В размерностях 4 и выше это многообразие гораздо проще, чем все примеры $\mathrm{URC}$-многообразий, которые были известны ранее.
Библиография: 39 названий.
Diagnosis of Visceral Leishmaniasis Using Peripheral Blood Microscopy in Ethiopia: A Prospective Phase-III Study of the Diagnostic Performance of Different Concentration Techniques Compared to Tissue Aspiration
Authors: Diro Ermias , Yansouni Cedric P. , Takele Yegnasew , Mengesha Bewketu , Lynen Lutgarde , Hailu Asrat , van Griensven Johan , Boelaert Marleen , Büscher Philippe
Published: November 2016

Visceral leishmaniasis (VL) is a fatal parasitic disease. Unfortunately, diagnosis of VL in east Africa currently relies on aspiration of tissue from the spleen or bone marrow, which is painful and potentially dangerous. We sought to determine whether peripheral blood could be used instead of invasive tissue aspirates to diagnose VL, using three parasite concentration techniques. Three hundred and one consecutive people suspected of having VL were recruited. Compared with microscopy of tissue aspirates, the diagnostic accuracy of peripheral blood microscopy was as follows: whole blood thin smear sensitivity 1.5% (95% confidence interval [CI] 0.0–8.3) and specificity 100% (95% CI 76.8–100); buffy-coat smear sensitivity 19.5% (95% CI 14.3–25.6) and specificity 98.9% (95% CI 94.1–100); peripheral blood mononuclear cell (PBMC) smear sensitivity 33.7% (95% CI 27.3–40.5) and specificity 95.7% (95% CI 89.6–98.6). Sensitivity of PBMC smears was significantly higher in human immunodeficiency virus (HIV)-coinfected patients (N = 48/301); two-sample test of proportions, P = 0.0097; sensitivity 55.9% (95% CI 37.9–72.8) and specificity 92.9% (95% CI 66.1–99.8), and correlated with the degree of parasite load in the tissue. Combining the results from smears of both PBMC and buffy coat yielded a sensitivity and specificity of 67.6% (95% CI 49.1–82.6) and 92.9% (95% CI 66.1–99.8), respectively, in HIV-coinfected patients. In this setting, VL could be ruled-in with peripheral blood microscopy in a substantial number of VL suspects and may reduce the number of tissue aspirations performed, particularly in HIV-coinfected patients. More sensitive and logistically feasible methods than light microscopy are needed to detect Leishmania donovani parasites present in blood.