Partial Oxidation of Propane Over Mo1V0.3Te0.23Nb0.12Ox Catalyst in a Fluidized Bed Reactor

A fluidized bed reactor, for the first time, was employed to investigate the partial oxidation of propane to acrylic acid over Mo₁V_0.3Te_0.23Nb_0.12O_x catalyst. Effects of temperature, oxygen concentration, steam concentration, space velocity, and dilution with different sizes of SiC were studied and discussed. The reaction in the fluidized bed was compared with the reaction in the classical fixed bed. The results indicated that at constant temperature propane conversion obtained in the fixed bed reactor was higher. But the fluidized bed recompensed it by higher acrylic acid selectivity leading to acrylic acid yields and formation rates considerably over the fixed bed. In the fluidized bed reactor, an enhancement in the acrylic acid selectivity was observed over fixed bed at similar conversions. It is suggested that passing a large portion of gas phase oxygen through bubbles allows operation under lower oxygen partial pressure, which favors the desired reaction path. With the heat sink feature of the diluent, the catalytic performance is more influenced by dilution in the fixed bed. However, hot spots are less likely to occur in the fluidized bed and dilution has little effect on the catalytic performance. However, propane conversion increases slightly by increasing SiC particle diameter due to better fluidization quality.     

Self-centring segmental retaining walls—A new construction system for retaining walls

This paper reports on an experimental study on a new self-centring retaining wall system. Four post-tensioned segmental retaining walls (PSRWs) were experimentally tested. Each of the walls was constructed using seven T-shaped concrete segments with a dry stack. The walls were tested under incrementally increasing cyclic lateral load. The effect of the wall height, levels of post-tensioning (PT) force, and bonded versus unbonded condition of PT reinforcement on the structural behavior of the PSRWs was investigated. The results showed that such PSRWs are structurally adequate for water retaining structures. According to the results, increasing the wall height decreases initial strength but increases the deformation capacity of the wall. The larger deformation capacity and ductility of PSRW make it a suitable structural system for fluctuating loads or deformation, e.g., seawall. It was also found that increasing the PT force increases the wall’s stiffness; however, reduces its ductility. The residual drift and the extent of damage of the unbonded PSRWs were significantly smaller than those of the bonded ones. Results suggest that this newly developed self-centring retaining wall can be a suitable structural system to retain lateral loads. Due to its unique deformation capacity and self-centring behavior, it can potentially be used for seawall application.     

Cumin seed meal as an alternative to wheat bran in commercial laying hen diets

To evaluate the nutritional significance of cumin seed meal (CSM) as a commercial poultry feedstuff on laying hen performance and quality of laid eggs, an experiment was conducted using 144 (48‐week‐old) laying hens receiving diets containing 0, 25 and 50 g CSM kg^?1 with or without polyethylene glycol (PEG 6000) and xylanase enzyme (Grindazym^? GP 15000) for 9 weeks. Body weight on the first and last days of the experiment and daily egg production and egg weight and weekly feed intake during the first, fifth and ninth weeks of the experiment were recorded. Shell weight, shell thickness, Haugh unit and yolk colour were measured during the last week of the experiment. The results showed that inclusion of CSM in laying hen diets had no negative influence on the parameters measured compared with the control diet (P > 0.05), but enhanced egg yolk colour (P < 0.05). PEG increased the daily feed intake of birds receiving CSM diets (P < 0.01) and tended to enhance daily egg production and egg weight, although not significantly. Grindazym decreased shell weight and thickness of laid eggs (P < 0.05) and tended to increase hen body weight, but had no influence on other parameters measured. The results demonstrated that CSM can be substituted for wheat bran in layer diets at 25 or 50 g kg^?1 dietary inclusion level without any adverse effect on hen performance or egg quality, and might enhance egg yolk colour. In view of the low price of CSM, it could be concluded that inclusion of CSM in the diet might be beneficial to the commercial laying hen industry and reduce the overall cost of egg production. Copyright © 2006 Society of Chemical Industry     

On the added value of multi-scale modeling of concrete

This review of the added value of multi-scale modeling of concrete is based on three representative examples. The first one is concerned with the analysis of experimental data, taken from four high-dynamic tests. The structural nature of the high-dynamic strength increase can be explained by using a multi-scale model. It accounts for the microstructure of the specimens. The second example refers to multi-scale thermoelastic analysis of concrete pavements, subjected to solar heating. A sensitivity analysis with respect to the internal relative humidity (RH) of concrete has underlined the great importance of the RH for an assessment of the risk of microcracking of concrete. The third example deals with multi-scale structural analysis of a real-scale test of a segmental tunnel ring. It has turned out that multi-scale modeling of concrete enables more reliable predictions of crack opening displacements in tunnel segments than macroscopic models taken from codes of practice. Overall, it is concluded that multi-scale models have indeed a significant added value. However, its degree varies with these examples. In any case, it can be assessed by means of a comparison of the results from three sources, namely, multi-scale structural analysis, conventional structural analysis, and experiments.     

High-Pressure Processing of Manuka Honey: Improvement of Antioxidant Activity,Preservation of Colour and Flow Behaviour

Manuka honey in New Zealand is known for its superior antimicrobial and antioxidant properties. However, these valuable properties are known to be compromised when raw honey goes through conventional thermal processing, thus reducing its final quality. As such, this present work is undertaken to assess the effect of high-pressure processing on quality of honey, namely, the antioxidant activity, colour and viscosity. The honey was subjected to different pressures (200–600 MPa) at ambient temperatures (25 to 33 °C) and combined with moderate temperatures (53 to 74 °C) for holding times (10 to 30 min). Thermal processing (49 to 70 °C) was also carried out for comparison purpose. In the absence of heat, the antioxidant activity of high-pressure processing (HPP)-treated samples (600 MPa, 10 min) was found to increase by about 30 % with no colour changes detected. The shear-thinning behaviour of the honey was also retained after HPP at ambient temperature, whereas for combined HPP–thermal treatment, no added benefit in antioxidant activity was observed particularly at higher temperature. Colour was significantly degraded when processed for ≥15 min at 70 °C and the flow behaviour was brought about from shear thinning to Newtonian. Thus, it can be concluded that the quality of honey can be enhanced by using high-pressure processing at ambient temperature.     

Adaptive sliding mode control of a piezo-actuated bilateral teleoperated micromanipulation system

Piezoelectric actuators are widely used in micro manipulation applications. However, hysteresis nonlinearity limits the accuracy of these actuators. This paper presents a novel approach for utilizing a piezoelectric nano-stage as the slave manipulator of a teleoperation system based on a sliding mode controller. The Prandtl-Ishlinskii (PI) model is used to model actuator hysteresis in feedforward scheme to cancel out this nonlinearity. The presented approach requires full state and force measurements at both the master and slave sides. Such a system is costly and also difficult to implement. Therefore, sliding mode unknown input observer (UIO) is proposed for full state and force estimations. Furthermore, the effects of uncertainties in the constant parameters on the estimated external forces should be eliminated. So, a robust adaptive controller is proposed and its stability is guaranteed through the Lyapunov criterion. Performance of the proposed control architecture is verified through experiments.     

CFD modeling of a boiler’s tubes rupture

This paper reports the results of a study on the reason for tubes damage in the superheater Platen section of the 320 MW Bisotoun power plant, Iran. The boiler has three types of superheater tubes and the damage occurs in a series of elbows belongs to the long tubes. A three-dimensional modeling was performed using an in-house computational fluid dynamics (CFD) code in order to explore the reason. The code has ability of simultaneous solving of the continuity, the Reynolds-Averaged Navier–Stokes (RANS) equations and employing the turbulence, combustion and radiation models. The whole boiler including; walls, burners, air channels, three types of tubes, etc., was modeled in the real scale. The boiler was meshed into almost 2,000,000 tetrahedral control volumes and the standard k–ε turbulence model and the Rosseland radiation model were used in the model. The theoretical results showed that the inlet 18.9 MPa saturated steam becomes superheated inside the tubes and exit at a pressure of 17.8 MPa. The predicted results showed that the temperature of the steam and tube’s wall in the long tubes is higher than the short and medium size tubes. In addition, the predicted steam mass flow rate in the long tube was lower than other ones. Therefore, it was concluded that the main reason for the rupture in the long tubes elbow is changing of the tube’s metal microstructure due to working in a temperature higher than the design temperature. In addition, the structural fatigue tension makes the last elbow of the long tube more ready for rupture in comparison with the other places. The concluded result was validated by observations from the photomicrograph of the tube’s metal samples taken from the damaged and undamaged sections.     

Cyclic biamperometry at micro-interdigitated electrodes

Cyclic biamperometry was studied as an analytical method for use with commercially available, comb-type, coplanar microinterdigitated electrodes (μIDEs), using the ferri-/ferrocyanide redox couple as a model analyte. The μIDEs studied in this work were made of gold that had been deposited onto a Ti/W adhesion layer on borosilicate glass chips and had 5 and 10 μm bands with equal gap sizes. Close proximity of the two working electrodes, and their interdigitation, resulted in signal amplification by redox cycling. Results were compared with those obtained by cyclic voltammetry, where one of the two IDE electrodes was used as the working electrode and external reference and auxiliary electrodes were used. Amplification factors of almost 20 were achieved due to redox cycling. Attempts to apply cyclic voltammetry to the μIDEs, with one of the combs as the working and the other as the auxiliary electrode, were unsuccessful due to corrosion of the auxiliary electrode comb. Results of this study, and the electrochemically unique feature of biamperometry to probe but not change the net contents of the medium under examination, suggest the applicability of scanning biamperometry at μIDEs to the very small volumes and electrochemical cell dimensions that are now of great interest.     

Dating silk by capillary electrophoresis mass spectrometry

A new capillary electrophoresis mass spectrometry (CE-MS) technique is introduced for age estimation of silk textiles based on amino acid racemization rates. With an L to D conversion half-life of ~2500 years for silk (B. mori) aspartic acid, the technique is capable of dating silk textiles ranging in age from several decades to a few-thousand-years-old. Analysis required only ~100 μg or less of silk fiber. Except for a 2 h acid hydrolysis at 110 °C, no other sample preparation is required. The CE-MS analysis takes ~20 min, consumes only nanoliters of the amino acid mixture, and provides both amino acid composition profiles and D/L ratios for ~11 amino acids.     

Structure Learning in Bayesian Networks Using Asexual Reproduction Optimization

A new structure learning approach for Bayesian networks based on asexual reproduction optimization (ARO) is proposed in this paper. ARO can be considered an evolutionary‐based algorithm that mathematically models the budding mechanism of asexual reproduction. In ARO, a parent produces a bud through a reproduction operator; thereafter, the parent and its bud compete to survive according to a performance index obtained from the underlying objective function of the optimization problem: This leads to the fitter individual. The convergence measure of ARO is analyzed. The proposed method is applied to real‐world and benchmark applications, while its effectiveness is demonstrated through computer simulations. Results of simulations show that ARO outperforms genetic algorithm (GA) because ARO results in a good structure and fast convergence rate in comparison with GA.