Interactions of thermally induced acoustic waves with buoyancy induced flows in rectangular enclosures

Acoustic waves are generated when a compressible-fluid is exposed to a rapidly varying heat flux along a confining wall. For an enclosure, these waves reverberate and eventually decay. Buoyancy-induced flows generated within an enclosure can be affected by the acoustic waves generated. The interactions of the acoustic waves produced by rapid heating of a wall with the buoyancy-induced flow in air filled rectangular enclosures are investigated numerically. For the present simulations, the bottom wall of the enclosure is heated rapidly with varying heating rates, while the top wall is held at the initial temperature of the air. The vertical walls of the enclosure are considered insulated. The compressible unsteady Navier–Stokes equations are solved by an explicit flux-corrected transport algorithm for the convection terms and by a central-differencing scheme for the viscous and conduction terms.     

Natural preservative ingredient from marine alga Ulva lactuca L.

The contents of total chlorophyll (T-Chl), carotenoids and phenolics compounds were quantified in the biomasses of Ulva lactuca grown either in normal or artificial sea water under indoor conditions. The antioxidant and antibacterial activities of U. lactuca crude organic extracts ( Ulva- COEs) were determined. Thirty-four compounds in Ulva- COEs were characterised by thin layer chromatography and high-performance liquid chromatography. The major compounds were chlorophyll a (Chl a ) (15.60–30.90%) and b (Chl b ) (12.20–14.89%) , 9-cis β-carotene (13.12–14.47%), α-carotene (11.44–11.47%) and all-trans β-carotene (6.16–29.70%, of total carotenoids).The Ulva- COEs exhibited remarkable antioxidant activity, with an IC₅₀ (concentration which causes a 50% of DPPH radical scavenging activity) values ranged from 16.5 and 18.7 μg mL⁻¹, which could be compared with the synthetic antioxidants: α-tocopherol (14.4 μg mL⁻¹), butylated hydroxyanisol (13.1 μg mL⁻¹) and butylated hydroxyltoluene (13.1 μg mL⁻¹). Also, Ulva- COEs exhibited great potential antibacterial activities against six bacterial strains, with minimal inhibitory concentration values ranged from 0.40 to 0.35 mg mL⁻¹.     

Mechanical properties of a-C:H and a-C:H/SiOx nanocomposite thin films prepared by ion-assisted plasma-enhanced chemical vapor deposition

a-C:H and a-C:H/SiO_x nanocomposite thin films were deposited on silicon, aluminum and polyimide substrates at 25 °C in an asymmetric 13.56 MHz r.f.-driven plasma reactor under heavy ion bombardment. Fourier transform infrared spectra of the films indicate that the nanocomposite filmsappears to consist of an atomic scale random network of a-C:H and SiO_x. Raman spectroscopy revealed that the sp² carbon fraction in the nanocomposite film was reduced compared with the a-C:H film. The intrinsic stress of both films increased with increasing negative bias voltage (−V_dc) at the substrate. However, the nanocomposite films exhibited lower intrinsic stress compared w with a-C:H-only films. Especially, a thin SiO_x-rich interlayer was very effective in reducing the film stress and enhancing the bonding strength at the interface. The interlayer allowed deposition of thick films of up to 5 μm. Also, the nanocomposite films were stable in 0.1 M NaOH solution and showed good microhardness.     

Optical performance of an asymmetric inverted absorber compound parabolic concentrating solar collector

A computer-based numerical model has been developed utilising ray trace techniques, to simulate the optical characteristics of asymmetric inverted absorber line axis compound parabolic concentrating solar collectors (IACPCs). Cognisance is taken of the separate effects of the beam and diffuse properties of the total insolation on the optical performance. Increasing absorber gap height was expected to increase convection heat loss suppression and overall collector performance at the expense of a reduction in optical efficiency. The results are presented as graphical analyses of optical efficiency versus height of absorber gap, reflectivity and, acceptance and ray input angles.     

Small heat shock proteins and toughness in intermediate pHu beef

Bull M. longissimus dorsi (n = 94) categorised into high (n = 28), intermediate (n = 14) and low (n = 52) ultimate pH (pH_u) were aged at − 1.5 °C for 28 days. Shear force was higher and more variable (p < 0.05) in intermediate pH_u samples during ageing. Titin, filamin and desmin degradation was also less extensive in intermediate pH_u samples compared to the other two pH categories. The extent of the decline of HSP20, HSP27 and αβ-crystallin concentrations during post mortem ageing was pH_u related such that high pH_u meat maintained the highest concentration of small heat shock proteins followed by intermediate and low pH_u meat. μ-Calpain autolysis was slowest in intermediate pH_u and cathepsin B activities remained consistently low during ageing in this group (p < 0.05). Meat toughness in the intermediate pH_u group may be attributed to the combination of a larger pool of sHSP with a sub-optimal cathepsin B activity and intermediary μ-calpain activities.     

Wettability determination of core samples through visual rock and fluid imaging during fluid injection

Reservoir rock wettability is a key factor in oil recovery, as it controls the location, flow, and distribution of reservoir fluids. However, proper assessment of wettability is not an easy task and provides a number of challenges. Wettability is in parts determined by the history of the oil reservoir through mechanisms such as aging and fouling. Hence direct measurements on freshly exposed rock surfaces (e.g. on core plugs) are critical and might not represent the true wettability within the sample. We present a new and fast method for wettability determination based on the optical observation of injected fluids, which allows for wettability determination independent from the surface wettability state of the sample. Fluid behavior within the boundaries of the capillary regime is driven by capillary forces and thus by wettability, which is exploited for our method. We show that a combined optical white-light and fluorescence imaging technique provides excellent contrast for reliable observations. Based on this imaging technique, we successfully distinguish core samples with different internal wettability, independent of their surface state.     

A new structure-preserving method of sampling for predicting self-similar traffic

The paper presents a structure-preserving method of sampling self-similar traffic with an application to network monitoring and resource provisioning. Based on the observation of the self-similarity of Internet traffic, we propose a new sampling technique (so-called the maximum-based sampling). We show that the resulting data suits perfectly for predicting the bandwidth required by upcoming traffic so that the resource provisioning can be done efficiently and intelligently especially for the context of IP over WDM networks. Hence, we prove mathematically that the proposed technique preserves the self-similarity of the traffic. Besides, experimental results using real Internet traffic show that unlike other sampling techniques (systematic sampling and stratified random sampling), the maximum-based sampling capture faithfully the traffic self-similarity. In order to assess the effect of the sampling technique impact on the performance of the traffic prediction,we undertake a series of prediction experiments using sampled traffic with the proposed technique and the other sampling techniques. A neurofuzzy model (α _SNF), the AutoRegressive Integrated Moving Average model (ARIMA) and the Linear Minimum Mean Square Error (LMMSE) are considered in this study for bandwidth prediction. Our experiments results show that the maximum-based sampled traffic—used for the identification of the prediction model—is the most suitable for predicting the traffic for different time scales.     

The effect of diffusion on two-dimensional problem of generalized thermoelasticity with Green–Naghdi theory

The present paper is concerned with the investigation of disturbances in a homogeneous, isotropic elastic medium with generalized thermoelastic diffusion. The formulation is applied to the generalized thermoelasticity based on the Green and Naghdi (GN) theory under the effect of diffusion. The analytical expressions for displacement components, stresses, temperature field, concentration and chemical potential are obtained in the physical domain by using the normal mode analysis. These expressions are calculated numerically for a copper-like material and depicted graphically. Effect of presence of diffusion is analyzed theoretically and numerically. Comparisons are made with the results predicted by the type II and type III in the presence and absence of diffusion.     

Value creating construction virtual teams: A case study in the construction sector

The research explores factors influencing knowledge value creation of virtual teams in the construction industry. Collectiveness and conscientiousness emerge as important socio-cultural enablers for value creation. Collectiveness represents the degree of cohesiveness and social relationships between virtual team members and conscientiousness represents an awareness of the situation and avoidance of uncertainty and risk by team members. Moreover, technology assets, human networks, social capital, intellectual capital, and change management are identified as essential ingredients that have the potential to ensure effective knowledge value creation.     

Enhancing antioxidant availability in wheat grains from plants grown under seawater stress in response to microalgae extract treatments

BACKGROUND: The present study was designed to investigate the enhanced antioxidant capacity of whole grains from wheat plants grown under seawater stress in response to microalgae extract treatment. RESULTS: The total carotenoid (TCAR), tocopherol (TOC), phenolic (TPC), and protein (PC) contents in whole grains of wheat plants irrigated with 10% and 20% (v/v) seawater (SW) in response to water extracts of microalgae Spirulina maxima (SME) and Chlorella ellipsoida (CEE) as well as exogenous plant growth enhancers of ascorbic acid and benzyladenine treatments were measured. The results showed that the levels of enhanced TCAR (range 0.08–0.14 g kg^?1), TOC (range 0.05–0.12 g kg^?1), TPC (range 0.80–2.96 g kg^?1) and PC (range 93.4–137.9 g kg^?1) in wheat grains of plants irrigated with 10% and 20% SW were significantly increased in response to SME and CEE treatments. Evaluation of antioxidant activity of ethanolic extracts of grains of SW‐stressed plants indicated that DPPH and TBAS radical scavenging activity was significantly increased in response to SME and CEE treatments and coincided with the increase in levels of antioxidant compounds present in each extract. The electrophoretic profiles of the grains of proteins of treated samples exhibited quite different patterns from those in control samples. CONCLUSION: The results suggest that the application of algal extracts to wheat plants irrigated with SW is useful for improvement of salinity tolerance. This effect can be triggered by the stimulation of antioxidant components and protein content. Copyright © 2009 Society of Chemical Industry