Corrosion resistance of a silane/ceria modified Mg--Al-layered double hydroxide on AA5005 aluminum alloy

The present work aimed at assessing the electrochemical behavior and the corrosion inhibition performance of Mg--Al-layered double hydroxide (LDH) coatings modified with methyltrimethoxysilane (MTMS) and cerium nitrate on AA5005 aluminum alloy. The chemical compositions and surface morphologies of the coatings were investigated by XRD, FT-IR and FE-SEM, while their corrosion resistance was evaluated by electrochemical and immersion tests. An optimum corrosion resistance of the composite coatings was obtained by adding 10⁻² mol·L⁻¹ cerium nitrate. An excess addition of cerium nitrate resulted in a loose structure and poor corrosion resistance of the coating. The corrosion mechanism of the composite coatings was proposed and discussed.     

A client-assisted interval caching strategy for video-on-demand systems

In a Video-on-Demand (VoD) system, in order to guarantee smooth playback of a video stream, sufficient resources (such as disk I/O (Input/Output) bandwidth, network bandwidth) have to be reserved in advance. Thus, given limited resources, the number of simultaneous streams can be supported by a video server is restricted. Due to the mechanical nature, the I/O subsystem is generally the performance bottleneck of a VoD system, and there have been a number of caching algorithms to overcome the disk bandwidth limitation. In this paper, we propose a novel caching strategy, referred to as client-assisted interval caching (CIC) scheme, to balance the requirements of I/O bandwidth and cache capacity in a cost-effective way. The CIC scheme tends to use the cache memory available in clients to serve the first few blocks of streams so as to dramatically reduce the demand on the I/O bandwidth of the server. Our objective is to maximize the number of requests that can be supported by the system and minimize the overall system cost. Simulations are carried out to study the performance of our proposed strategy under various conditions. The experimental results show the superior of CIC scheme to the tradition Interval Caching (IC) scheme, with respect to request accepted ratio and average servicing cost per stream.     

Phase transformation and nanocrystallite growth behavior of 2 mol% yttria-partially stabilized zirconia (2Y-PSZ) powders

Two mol% yttria-partially stabilized zirconia (2Y-PSZ) precursor powders were obtained through a co-precipitation process using ZrOCl₂.8H₂O and Y(NO₃)₃.6H₂O as starting materials. Phase transformation and crystallite growth behavior have been investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). XRD results show that the crystal structure to be composed of coexisting tetragonal ZrO₂ (t-ZrO₂) and monoclinic ZrO₂ (m-ZrO₂) when the 2Y-PSZ freeze dried precursor powders was calcined at 773–1273 K for 2 h. The fraction of m-ZrO₂ content is lower than 3.0 % when the calcination temperature is lower than 1073 K, whereas m-ZrO₂ content rapidly increases to 8.7 % with the increase of calcination temperature to 1273 K. The crystallite size of t-ZrO₂ increases from 12.3 to 30.2 nm when calcination temperature increased from 773 to 1273 K. In addition, the activation energy of t-ZrO₂ and m-ZrO₂ crytallite growth in 2Y-PSZ freeze dried precursor powders are 29.2 and 21.8 kJ/mol, respectively.     

Diffusion of Acetic and Propionic Acids from Chitosan-based Antimicrobial Packaging Films

The diffusion of acetic or propionic acids from thin (44 to 54 μm) chitosan‐based antimicrobial packaging films in which they were incorporated was measured after immersion of the films in water, and the effects of pH (5.7, 6.4, or 7.0) and temperature (4 °C, 10 °C, or 24 °C) on diffusion were investigated. The kinetics of acetic‐ and propionic‐acid release deviated from the Fickian model of diffusion. Diffusion was found to be unaffected by pH in the range of values tested, but a decrease in temperature from 24 °C to 4 °C resulted in a reduction of diffusion coefficients from 2.59 × 10^?12 m².s^?1 to 1.19 × 10^?12 m².s^?1 for acetic acid and from 1.87 × 10^?12 m².s^?1 to 0.91 × 10^?12 m².s^?1 for propionic acid. The effect of temperature on diffusion was well (r² > 0.9785) described by an Arrhenius‐type model with activation energies of 27.19 J.mole^?1 (acetic) and 24.27 J.mole^?1 (propionic). Incorporation of lauric acid or essential oils (cinnamaldehyde or eugenol) into the chitosan film at the time of preparation produced a subsequent reduction in the diffusion of acetic or propionic acid, and maximum effects were obtained with lauric acid and cinnamaldehyde incorporated to final concentrations of 1.0% and 0.5% (w/w), respectively.     

Analytical approaches of meat authentication in food

Meat industry sector is likely exposed to illegal practices which involve replacement of meat ingredients with other animal species. Meat products are commonly modified during processing, and the cases have been rampant in certain part of the world. Meanwhile, individual consumption patterns are affected by religious belief and health reason. For instance, Muslims and Jews are prohibited from consuming pork and allergic reaction to certain meat species affects choices of meat products. Thus, food authentication is vital as it offers protection to consumers from fraudulent act. Numerous authentication techniques have been developed to tackle food fraud issues. Authentication methods are categorised mainly as targeted analysis which provides quantitative outcome and non-targeted analysis which offers qualitative result. In the present review, both targeted and non-targeted analyses for meat species authentication are discussed based on previous research conducted using these methods and how they serve the purpose for authentication.     

Recent progress in the development and properties of novel metal matrix nanocomposites reinforced with carbon nanotubes and graphene nanosheets

One-dimensional carbon nanotubes and two-dimensional graphene nanosheets with unique electrical, mechanical and thermal properties are attractive reinforcements for fabricating light weight, high strength and high performance metal-matrix composites. Rapid advances of nanotechnology in recent years enable the development of advanced metal matrix nanocomposites for structural engineering and functional device applications. This review focuses on the recent development in the synthesis, property characterization and application of aluminum, magnesium, and transition metal-based composites reinforced with carbon nanotubes and graphene nanosheets. These include processing strategies of carbonaceous nanomaterials and their composites, mechanical and tribological responses, corrosion, electrical and thermal properties as well as hydrogen storage and electrocatalytic behaviors. The effects of nanomaterial dispersion in the metal matrix and the formation of interfacial precipitates on these properties are also addressed. Particular attention is paid to the fundamentals and the structure–property relationships of such novel nanocomposites.     

Intensity cultivation induced effects on soil organic carbon dynamic in the western cotton area of Burkina Faso

The soil organic carbon (SOC) dynamic is a key element of soil fertility in savannah ecosystems that form the key agricultural lands in sub-Saharan Africa. In the western part of Burkina Faso, the land use is mostly linked to cotton-based cropping systems. Use of mechanization, pesticides, and herbicides has induced modifications of the traditional shifting cultivation and increased the need for sustainable soil fertility management. The SOC dynamic was assessed based on a large typology of land cultivation intensity at Bondoukui. Thus, 102 farm plots were sampled at a soil depth of 0–15 cm, considering field–fallow successions, the cultivation phase duration, tillage intensity, and soil texture. Physical fractionation of SOC was carried out by separating the following particle size classes: 2,000–200, 200–50, 50–20, and 0–20 μm. The results exhibited an increase in SOC stock, and a lower depletion rate with increase in clay content. After a long-term fallow period, the land cultivation led to an annual loss of 31.5 g m⁻² (2%) of its organic carbon during the first 20 years. The different fractions of SOC content were affected by this depletion depending on cultivation intensity. The coarse SOC fraction (2,000–200 μm) was the most depleted. The ploughing-in of organic matter (manure, crop residues) and the low frequency of the tillage system produced low soil carbon loss compared with annual ploughing. Human-induced disturbances (wildfire, overgrazing, fuel wood collection, decreasing fallow duration, increasing crop duration) in savannah land did not permit the SOC levels to reach those of the shifting cultivation system.     

Development of biodegradable coatings for covered horizontal bunker‐stored silage

The addition of different plasticizers, thickeners and hydrophobic compounds such as fatty acids in biodegradable coatings has been evaluated using pH values and dry matter content as criteria in silage during one month of storage at room temperature under laboratory conditions. A base coating solution was prepared with whey protein concentrate, calcium caseinate and carboxymethylcellulose. From the base coating solution, derivative coating solutions were developed to evaluate the effect of plasticizers by incorporating glycerol at different concentrations and different ratios of sorbitol and glycerol. Thickening agents were also evaluated by adding fine silage powder, coarse silage powder, hay powder, or cornstarch. Derivative coating solutions were studied to evaluate the effect of fat constituents. Canola oil, beef fat, shortening, bees wax or candellila wax were added to the base solution following various procedures. Results showed that the addition of glycerol (320 g kg^?1) in the coating formulation resulted in a pH value of 5.21 after 31 days of storage without visible spoilage under the coating. The presence of plasticizer compounds avoids the appearance of cracking in the coating during the early stage of conservation. The pH of silage coated with formulations containing coarse or fine silage powder was preserved below 5 until day 17 as compared to the other formulations where the pH was preserved below 5 only for 10 days. The incorporation of beef fat in the coating formulation resulted in the lowest pH as compared to all the other fat compounds evaluated, showing a value of 4.61 at the end of storage. The addition of glycerol, coarse silage and beef fat in the same coating formulation recovered by a hydrophobic layer of zein stabilized the pH to 4.47 for 28 days of storage with a final dry matter content at 344.3 g kg^?1 without visible spoilage under the coating during all of the storage at room temperature. Copyright © 2004 Society of Chemical Industry     

Right-cyclic Hadamard coding schemes and fast Fourier transformsfor use in computing spectrum estimates in Hadamard-transformspectrometry

Two computationally efficient spectrum-recovery schemes were recently developed for use by Hadamard-transform spectrometers that have static and dynamic nonidealities in their encoding masks. These methods make use of a left-cyclic Hadamard encodement scheme and the ability to express the left-cyclic W_D matrix in factored form as W_D =ST_D. The matrix W_D describes the dynamic characteristics of and the encodement scheme for the mask. This paper focuses on the use of a right-cyclic Hadamard pattern to encode the mask and computationally efficient methods that can be used to obtain the spectrum-estimate. The major advantage of right-cyclic over left-cyclic encodement schemes is due to the resulting right-cyclic nature of both W _D and W_D^-1. Fast algorithms, such as a fast Fourier transform (FFT) or a Trench algorithm, that take advantage of the right-cyclic nature of W_D can be used to obtain W_D^-1 directly. In general, the number of mask elements is not an integer power of two, and non-radix-2 FFT's must be used to compute W_D^-1. Since W_D^-1 is right-cyclic, the vector-matrix product of W_D^-1 and the measurement vector can be expressed as a circular correlation and implemented indirectly via FFT's. With appropriate zero-padding of the vectors, radix-2 FFT's can be used for this computation. Various algorithms were used at each step in the overall computation of the spectrum-estimate, and the total computation times are presented and compared. The size of the mask is important in determining which algorithms are the most efficient in recovering the spectrum-estimate