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6xxx series (Al–Mg–Si) alloys are generally known to be greatly susceptible to localized corrosion, which is closely related to the presence of coarse intermetallic compounds (IMCs). In this work, the localized corrosion behaviour of two representative IMCs, namely β-Mg2Si and α-Al(Fe,Mn)Si, were investigated in a 6082 alloy (Al–Mg–Si–Mn-based). For the β-Mg2Si phase, a rapid de-alloying process is primarily observed. Subsequently, their surface will transform to the electric insulating SiO2layer, which tends to suppress the further corrosion in its periphery. However, it is found that the α-Al(Fe,Mn)Si phase surprisingly tends to be a potentially effective cathode to promote the initiation of stable localized corrosion, which is contrast with its outstanding corrosion-resistance. Careful examinations reveal that such abnormal corrosion behaviour of α-Al(Fe,Mn)Si is most likely to be relevant to the surface aggregation of Cu impurities, which is clarified by a large number of Cu-rich nanoparticles on its surfaces.

[Display omitted] • The influence of aspect ratio of particles on residual stress was investigated. • The pre-yield phenomenon was studied numerically. • An efficient method for introducing the effect of residual stresses to the stress-strain curves was developed. Thermal residual stress and strain (TRSS) in particle reinforced metal matrix composites (PRMMCs) are believed to cause strengthening effects, according to previous studies. Here, the representative volume element (RVE) based computational homogenization technique was used to study the tensile deformation of PRMMCs with different particle aspect ratios (AR). The influence of TRSS was assessed quantitatively via comparing simulations with or without the cooling process. It was found that the strengthening effect of TRSS was affected by the particle AR. With the average strengthening effect of TRSS, a fast method of introducing the strengthening effect of TRSS to the tensile behavior of PRMMCs was developed. The new method has reduced the computational cost by a factor 2. The effect of TRSS on continuous fiber-reinforced metal matrix composite was found to have a softening-effect during the entire tensile deformation process because of the pre-yield effect caused by the cooling process. [ABSTRACT FROM AUTHOR]

The hot deformation behaviors of the bimodal carbon nanotube reinforced 2009Al (CNT/2009Al) composite were studied by establishing processing map and characterizing the microstructure evolution. The results indicate that the grain size in the ultra-fine grained zones was stable during hot deformation, while the coarse grained zones were elongated with their long axis directions tending to be perpendicular to the compression direction. Low temperature with high strain rate (LTHR), as well as high temperature with low strain rate (HTLR) could increase the length/width ratio of the coarse grained zones. However, LTHR and HTLR could cause the instable deformation. The instable deformation at LTHR was induced by severe intragranular plastic deformation and the localized shear crack, while the instable deformation at HTLR resulted from the more deformation component at the coarse grained zones, and the micro-pore initiation due to CNT re-agglomeration at the boundaries between the coarse and the ultra-fine grained zones. [ABSTRACT FROM AUTHOR]

One of the most desired strengthening mechanisms in the carbon nanotube reinforced aluminum matrix composites (CNT/Al) composites is the load transfer strengthening mechanism (LTSM). However, a fundamental issue concerning the LTSM is that quantitative measurements of load partitioning in these composites during loading are very limited. In this study, in-situ neutron diffraction study on the tensile deformation of the 3 vol.% CNT/2009Al composite and the unreinforced 2009Al alloy was conducted. The {311} and {220} diffraction elastic constants (DECs) of the 2009Al alloy were determined. Using those DECs the average stress in the 2009Al matrix of the composite was calculated. Then the average stress in the CNTs was separated by using the stress equilibrium condition. Computational homogenization models were also applied to explain the stress evolution in each phase. Predicted results agree with experimental data. In the present case, the average stress in the CNTs reaches 1630 MPa at the yield strength of the composite based on linear regression of the measured data, which leads to an increment of yield strength by about 37 MPa. As the result of this work, an approach to quantify load partitioning in the CNTs is developed for the CNT/Al composites, which can be applied to optimize the mechanical properties of the composites. [ABSTRACT FROM AUTHOR]

The aim of this study was to optimize the protein hydrolysates from chicken liver with xylose under Maillard reaction (MR) conditions using response surface methodology. The correlation between the browning degree, grafting degree, and the antioxidant activities of the Maillard reaction products (MRPs) was investigated. The optimal reaction conditions were achieved with a reaction temperature of 138.78°C, an initial pH of 7.99, and a reaction time of 93.14 min. The grafting degree (41.98%) and browning degree (2.582) of chicken liver protein hydrolysate MRPs (CLPHM) were notably higher (P < 0.05) than those of protein MRPs (CLPM) and were significantly lower (P < 0.05) than those of sonicated hydrolysate MRPs (SCLPHM). The reducing power, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and hydroxyl radical scavenging of CLPM, CLPHM, and SCLPHM were significantly higher (P < 0.01) than those of the protein or hydrolysate substrates. The grafting degree and browning degree of CLPM, CLPHM, and SCLPHM had positive correlations with DPPH and hydroxyl radical scavenging activity. Hence, this study could enhance the added value of chicken liver by exhibiting the enhancements from ultrasound pretreatment and the MR. MRPs could have an effective and potential application in the food industry.

Abstract The effects of welding speed on the macroscopic and microscopic residual stresses (RSes) in friction stir welded 17 vol.% SiCp/2009Al-T4 composite plates were studied via neutron diffraction and an improved decoupled hierarchical multiscale modeling methods. Measurements showed that the macroscopic and total RSes had the largest variations in the longitudinal direction (LD). Increasing the welding speed led to higher values of measured LD macroscopic and total RSes in the matrix. The welding speed also significantly influenced the distributions and magnitudes of the microscopic RSes. The RSes were predicted via an improved hierarchical multiscale model, which includes a constant coefficient of friction based thermal model. The RSes in the composite plates before friction stir welding (FSW) were computed and then set as the initial states of the FSW process during modeling. This improved decoupled multiscale model provided improved predictions of the temperature and RSes compared with our previous model. [ABSTRACT FROM AUTHOR]

The deformation, damage and failure behaviors of 17 vol.% SiCp/2009Al composite were studied by microscopic finite element (FE) models based on a representative volume element (RVE) and a unit cell. The RVE having a 3D realistic microstructure was constructed via computational modeling technique, in which an interface phase with an average thickness of 50 nm was generated for assessing the effects of interfacial properties. Modeling results showed that the RVE based FE model was more accurate than the unit cell based one. Based on the RVE, the predicted stress-strain curve and the fracture morphology agreed well with the experimental results. Furthermore, lower interface strength resulted in lower flow stress and ductile damage of interface phase, thereby leading to decreased elongation. It was revealed that the stress concentration factor of SiC was ∼2.0: the average stress in SiC particles reached ∼1200 MPa, while that of the composite reached ∼600 MPa. [ABSTRACT FROM AUTHOR]

In the present paper, an algorithm is proposed to identify time delay parameters appearing in feedback loop of controlled systems in which the structural factors are prior known. The algorithm, connecting to the principle of least squares (LS) and the frequency–response function derived from harmonic balance method (HBM), provides a technique to fit the observed input–output data in frequency domain. Since the delay included in the exponential function can be of multi-values in frequency domain, the uniqueness of the identified results is also discussed so that the provided algorithm has completeness. As applications of the algorithm, a single degree of freedom and a two-degree of freedom systems are considered as two typical examples to display the validity of the algorithm. It is seen that the identified delay may be determined uniquely and may reach any desired accuracy by the present algorithm. It is also shown that the algorithm is simple but robust. [ABSTRACT FROM AUTHOR]

The present paper mainly focuses on the parameter identification of a vibration absorber coupled with time delay. The absorber is considered to be linear so that its frequency response function can be derived out and corresponding parameter identifiability can be proved conveniently. Using Newton-Raphson procedure, the transcendental frequency response function is linearized so that the parameters is identified in an iterative approach. This iteration process is verified to be a compressing mapping, which assures the algorithm's convergence. In the experiment, the time delay and the coupling gain are set artificially to check the algorithm's accuracy and robustness. The results show that this identification algorithm gives an accurate calibration to the system's dynamic parameters.

The present paper introduces a parameter identification algorithm into the experiment of a time delay coupled nonlinear system. The algorithm takes account into noise distortion correction in parameter identification. The distortion is treated as the increment of harmonic coefficient so that the Incremental Harmonic Balance (IHB) method is applied. In the experiment, the system parameters like damping and stiffness are prior unknown, whereas the active control parameters such as time delay and coupling ccuracy. Using the identified parameters, the simulated applicability in experimental application.

Dye-sensitized solar cells (DSSCs) have attracted extensive attention owning to their simple preparation prcess, low cost, and relatively high energy conversion efficiency. At present, most researches are focused on TiO2-based DSSC and high powder conversion efficiency of over 12.3% has been obtained. As a potential candidate, Zn2SnO4 has drawn increasing attention for DSSCs due to its attractive electrical and optical properties (Eg = 3.6 eV, electron mobility of 10–15 cm2V-1s-1). In this article, we maily reviewed the recent progress of Zn2SnO4-based DSSCs and put forward ideas for designing new Zn2SnO4 materials in future application for DSSCs.

Abstract: In real-world Web applications, information is often vague or ambiguous. Fuzzy XML databases have been proposed to manage data exchanges among different imprecise and uncertain XML documents. However, data collected from different data sources referring to the same real-world object may conflict. It is the task of the data management system to resolve the conflicts and integrate the data without any interference from a user. In order to integrate data from multiple autonomous fuzzy XML databases, an integration of fuzzy XML data has to be performed. In this paper, we take a first step in a fundamental consolidation of the fuzzy XML data model. In particular, we investigate the integration technique, which is designed to integrate fuzzy XML data collected from different data sources. We develop a basic framework for detecting conflicts and overlaps in fuzzy XML documents. In addition, we propose an approach for reconciling the fuzzy XML data collected from different data sources. [Copyright &y& Elsevier]

Ordered Co-Ni nanowires have been fabricated by alternating current (AC) electrodeposition method using anodic porous alumina as a template. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) test results reveal that the samples are polycrystalline with uniform diameters around 50 nm and lengths up to several micrometers. X-ray diffraction (XRD) pattern indicate the crystalline structure change from fcc to hcp as the Co composition increasing. Magnetic measurements show that the nanowires have high magnetic anisotropy with their easy axis parallel to the nanowire arrays. The coercivity (Hc) and squareness (Mr/Ms) are found to increase with the increase of ferromagnetic Co component.

A 3D realistic microstructure based computational homogenization model is proposed, in order to determine the temperature dependent effective coefficient of thermal expansion of particle reinforced metal matrix composites The model employed three-dimensional realistic microstructures with different domain sizes, where particles had random shape, sharp edges and were randomly distributed. The unit cell microstructure based model and classical analytical models were also presented for comparison. As an illustration of the model, a 17% vol. SiCp reinforced 2124Al composite was investigated. Its minimum RVE size is found to be δ = 15, where δ is called the size ratio and defined by the ratio between the side length of microstructure and the mean particle radius.

This research deals with the sensitivity of eight types of performance-designed high-strength concrete to the loading rate. Variations in the composition of the concrete produce the desired performance, for instance having null shrinkage or being able to be pumped at elevated heights without segregation, but they also produce variations in the fracture properties that are reported in this paper. We performed tests at five loading rates spanning six orders of magnitude in the displacement rate, from 1.74  10-5 mm/s to 17.4 mm/s. Load-displacement curves show that their peak is higher as the displacement rate increases, whereas the corresponding displacement is almost constant. Fracture energy also increases, but only for loading rates higher than 0.01 mm/s. We use a formula based on a cohesive law with a viscous term to study the results. The correlation of the formula to the experimental results is good and it allows us to obtain the theoretical value for the fracture energy under strictly static conditions. In addition, both the fracture energy and the characteristic length of the concretes used in the study diminish as the compressive strength of their aggregates increases.

Compared with the extensive research on properties of the fracture process zone (FPZ) under quasi-static loading conditions, much less information is available on its dynamic characterization, especially for high-strength concrete (HSC). This paper presents the very recent results of an experimental program aimed at disclosing the loading rate effect on the size and velocity of the (FPZ) in HSC. Eighteen three-point bending specimens were conducted under a wide range of loading rates from from 10-4 mm/s to 103 mm/s using either a servo-hydraulic machine or a self-designed drop-weight impact device. Four strain gauges mounted along the ligament of the specimen were used to measure the FPZ size. Surprisingly, the FPZ size remains almost constant (around 20 mm) when the loading rate varies seven orders of magnitude.

A type of basalt fibers polymer functional composites embedded with ZnO whiskers was prepared. The as-prepared composites exhibited good microwave absorption properties after the dispersion of ZnO whiskers in resin. The dynamic compressive properties of composites were investigated by the split Hopkinson pressure bar (SHPB) system. The macro- and micro-fracture morphology of composites was obtained by the scanning electron microscope (SEM). The experimental results showed that the as-prepared composites have excellent mechanical properties, and the compressive properties could be significantly affected by the strain rates in the in-plane direction, as well as in the normal direction. As the strain rate increased, the higher strength and elastic modulus are obtained. Under the dynamic compressive load in the normal direction, the main failure mode of composites is pure compression. On the other hand, longitudinal splitting and delamination of composites could be induced when loaded in the in-plane direction. The micro- interfacial crack, fiber fracture and plastic deformation of resin could be observed from the morphology of fractured composites.

A steady-state, two-dimensional numerical model has been used to describe coupled liquid steel's turbulent flow and heat transfer with solidification for Fe-C binary alloy in a crystallizer of inverse casting. The solid-liquid phase change phenomena have been modeled by using continuum formulations and considering the mushy zone as porous media. The turbulence flow in the crystallizer has been accounted for using a modified version of the low-Reynolds-number κ−ɛ turbulence model. The flow pattern in the liquid zone and the temperature distribution in the solid, mushy, and liquid regions have been predicted. The numerical analysis indicates that the residence time of the mother sheet in the crystallizer is one of the key parameters. The effects of some other main parameters on the solidification behavior have also been studied, such as the thickness and the initial temperature of the mother sheet, and the superheat degree of liquid steel. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(7): 582–592, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10112

High concentrations of metals Er, Cu and Zn, were potentiostatically electrodeposited into porous silicon (PS). Er doping was found to improve the room-temperature visible photoluminescence (PL) of PS, whereas Cu and Zn doping seemed to have a quenching effect. The current densities decreased exponentially with doping time in the entire electrodepositing processes of Er and Zn, which was true just in the beginning of Cu depositing. A phenomenological model based on the adsorption on the PS surface and the reduction of metal ions is proposed to explain the exponential dependence of the current density on doping time.

A reliable and sensitive gas chromatographic-mass spectrometric method was devised to determine the levels of bromazepam in human tissues. Bromazepam was extracted from body tissues using a three-step solvent extraction procedure. N-Desmethyldiazepam served as the internal standard. Selected ion monitoring withm/z 317 for bromazepam andm/z 270 for internal standard was used for quantitation. Calibration curves in all body tissues were linear over the concentration range from 50–500 ng/g. The lower detection limit in body tissues was 2–5 ng/g and the absolute recovery in body tissues was 27.8–68.0%. This method was used to determine the levels of bromazepam in tissues of an autopsied individual who had been prescribed psychotropic drugs and who was found dead in a car.

Spectroscopic and laser-pumped laser studies of Nd3+-doped LiKYF5and LiKGdF5are reported. The optical absorption and photoluminescence spectra are strongly polarised, the sense of polarisation of the 4I92→ 2F52, 2H92absorption near 800 nm being opposite to that of the 4F32→ 4I112laser emission near 1.05 μ. At ambient temperature (∼ 300 K) the luminescence decay times of excited Nd3+ions are in both hosts of order 480–490 μs, and strongly concentration dependent above 2 at.% Nd3+. Efficient laser action (∼ 25%) is observed under excitation with a long pulse Cr3+: LiSAF laser tuned to 797 nm, with low threshold energies of ca. 125 μJ.

Temperature and Yb3+concentration dependences of the Ho3+to Yb3+energy transfer process in KYF4are reported. The energy transfer rate from Ho3+to Yb3+increases asT4at low temperatures and depends quadratically on Yb3+concentration. The results are explained by a one-phonon-assisted nonradiative energy transfer process with an electric dipole-dipole interaction mechanism.

The effect on Nd3+Stark levels of substituting Gd for Y in YLiF4, KLiYF5, and YVO4laser crystals is slight, as demonstrated in our spectra and in our best-fit crystal-field parameters. Gd-based crystals maintain the spectral properties of Y-based crystals while allowing for larger Nd concentrations.

The TCSUH developed a passive radiative cooler, which is expected to be used in a spacecraft for the cooling of HTS microwave devices. For the demonstration of the cooler, in this work Hg system and Y123 HTS materials were used on the fabrication of loop antennas. The matching circuit was designed to let the antennas work at frequencies much lower than the resonant frequencies of the antennas. The measured results showed that as the temperature went down, the efficiencies of Hg and Y123 loop antennas increased 8dB and 8.5dB around 110K and 85K, respectively, but the increase of the Hg antenna was much slower.

We studied the effect of ‘microwave window’ on the performance of a high temperature superconducting antenna that was installed in a metal dewar with a low temperature superconducting magnet inside. Although the window was in the antenna's near and Fresnel zones, the signal attenuation induced by the ‘microwave window’ can be reduced to less than 1 dB in the far field. The configuration of the ‘microwave window’ is also presented.

A four element high Tcsuperconducting antenna array was designed and fabricated. Its measured E plane radiation patterns and gain improvement(1.2dB) relative to the comparable silver antenna were in good agreement with the calculated results.

Low-temperature magnetic relaxation phenomena have been studied in two samples consisting of nanocrystalline γ-Fe2O3and polymer in either water (as ferrofluid) or in potassium silicate (as glass). The relaxation of the magnetization follows a logarithmic law and the magnetic viscosity, S, tends to be independent of temperature below 2.1 K for the glass sample, giving evidence of macroscopic quantum tunneling of the magnetization.

A 4.5GHz circularly polarized YBCO microstrip antenna was designed and fabricated. Measurements showed that at 77K the superconducting antenna had about 3dB gain improvement over the comparable silver antenna, in agreement with the calculated results using the modified Green function method.

The power dependence of radiation efficiency of two circularly polarized superconducting microstrip antennas, fabricated from YBCO/LaAlO3films, was investigated. The study showed that this kind of HTS antennas could withstand 5W input power level, beyond which a sharp drop in the radiation efficiency was observed.

We report here on low temperature magnetic relaxation in the erbium orthoferrite ErFeO3. The variation of magnetic viscosity, S≡ ∂M/∂/∂ln t, with temperature shows three different regimes below 40 K. The most remarkable is that at T≤ 3 K where S(T)remains constant suggesting the occurrence of macroscopic quantum tunneling of the magnetization.