Numerical investigation of several physical and geometric parameters in the natural convection into trapezoidal cavities

Natural convection in trapezoidal cavities, especially those with two internal baffles in conjunction with an insulated floor, inclined top surface, and isothermal left-heated and isothermal right-cooled vertical walls, has been investigated numerically using the Element based Finite Volume Method (EbFVM). In numerical simulations, the effect of three inclination angles of the upper surface as well as the effect of the Rayleigh number (Ra), the Prandtl number (Pr), and the baffle’s height (H_b) on the stream functions, temperature profiles, and local and average Nusselt numbers has been investigated. A parametric study was performed for a wide range of Ra numbers (10³ ? Ra ? 10⁶) H_b heights (H_b = H¹/3, 2H¹/3, and H¹), Pr numbers (Pr = 0.7, 10 and 130), and top angle (θ) ranges from 10 to 20. A correlation for the average Nusselt number in terms of Pr and Ra numbers, and the inclination of the upper surface of the cavity is proposed for each baffle height investigated.     

Effect of different acid and lithium salt used in polyethylene glycol–titanium oxide based solvent-free electrolytes on electrochromic performance of WO3 thin films

Polymeric nanocomposites of polyethylene glycol (PEG) with titanium oxide compound, PEG–Ti, are solvent-free viscous materials obtained by sol–gel method in acidic medium. Lithium salt (LiX) has been added into PEG–Ti to form PEG–Ti–LiX polymeric electrolytes. Electrochromic devices based on tungsten oxide thin films and PEG–Ti–LiX electrolyte may show excellent optical contrast in the wavelength range from 300 to 2500 nm, however it depends on the type of lithium salt as well as the acid source used during the sol–gel process. With LiI, the color change speed of the devices is very fast, but they show a yellow color at bleaching state. The use of LiClO₄ makes the devices totally transparent in visible region, and the optical contrast is small. On the other hand, hydrochloric acid is good catalyst for hydrolysis of the titanium precursor during the sol–gel process, but it also originates the yellowish appearance of the devices. The substitution of HCl by acetic acid makes the devices more transparent in 250–500 nm, but the optical contrast as well as color change speed were deteriorated. Possible chemical reaction mechanisms during the formation of these polymeric electrolytes have been proposed to explain the relation between electrochromic performance of tungsten oxide and chemical composition of the electrolytes.     

Effect of chitosan coating in preventing deterioration and preserving the quality of fresh‐cut papaya ‘Maradol’

BACKGROUND: Chitosan can form antimicrobial, semi‐permeable barriers that limit gas exchange and reduces water loss in fruits. Consumer interest in fresh‐cut papaya fruit is leading to increasing demand because of its sensorial and antioxidant properties. However, papaya is a highly perishable product that is prone to loss of weight, loss of firmness and microbial attack. The aim of this study was to evaluate the effect of chitosan coatings on the overall quality of fresh‐cut papaya. Chitosan coatings of low (LMWC), medium (MMWC) and high (HMWC) molecular weights, at concentrations of 0.01 and 0.02 g mL^?1, were applied to fresh‐cut papaya cubes. The treated cubes were stored at 5 °C and changes in quality were evaluated. RESULTS: MMWC maintained the highest color values (L* and b*) and firmness. Chitosan coatings suppressed mesophilic plate count, and the growth of molds and yeast, compared to controls. The MMWC coatings at 0.02 g mL^?1 resulted in the highest antimicrobial activity and decreased the activity of the enzymes polygalacturonase and pectin methylesterase, followed by low and high MW chitosan coatings at 0.02 g mL^?1. CONCLUSION: The application of the MMWC treatment at 0.02 g mL^?1 could be used to reduce deteriorative processes, maintain quality and increase the shelf life of fresh‐cut papaya stored at 5 °C. Copyright © 2008 Society of Chemical Industry     

Integrating Outsourcing in the Maintenance Process

Outsourcing of software life cycle activities is a growing business area in many sectors influenced by Information Technologies. This fact, coupled with the usual lack of planning and high costs of software maintenance, may invite many organizations to outsource this important process of the software life cycle. Such outsourcing should be relied to a technological associate who can carry out this process using an adequate methodological foundation. In this paper we present the outsourcing strategy that we have integrated in MANTEMA, a methodology for software maintenance developed by our university and Atos ODS, a multinational organization which provides software maintenance services to third-party organizations.     

Influence of the chestnuts drying temperature on the rheological properties of their doughs

Chestnut flour doughs were prepared using chestnut air-dried at 45, 65, and 85 °C with constant load density (8.0 ± 0.6 kg/m²). Mixing curves of doughs using Mixolab^® device showed that chestnut flour doughs dried at 85 °C needed more water absorption to reach the target consistency, (1.1 ± 0.07 Nm). Thermorheological properties were evaluated by means of a controlled stress rheometer. All tested doughs showed shear-thinning behaviour in the steady-shear tests (0.001–1 s^?1). Oscillatory (1–100 rad s^?1 at 0.1% strain), temperature sweep (30–90 °C) and creep-recovery (loading 50 Pa for 60 s) tests showed that flour doughs from chestnuts dried at 85 °C provide interesting properties, particularly remarkable elasticity that is associated with starch gelatinisation. Experimental data were described using various rheological models.     

Semantic web technologies applied to software accessibility evaluation: a systematic literature review

Universal Access in the Information Society - Software accessibility is a current field of interest. Governments and organizations boost initiatives and legislations to assure universal access. On...     

Transformation During Aging of Niobium-Rich Carbides in Cast Heat-Resistant Alloys

Metallurgical and Materials Transactions A - The changes occurring in two heat-resistant alloys while aged at 750 °C for different periods of time were studied. Aging promoted...     

Property modifications of low-grade clay through physical treatments and its incidence in the pozzolanic activity

In the cement industry, it is usual to use calcined clays due to structural changes caused by thermal activations; however, there are other activation methods, such as mechanical activation by grinding. This method is not so common and has been relegated to the second level. Thus, in this work, the physical and mechanical changes in the structure of clays, induced by comminution processes, of standard clays and a low-grade kaolinitic multicomponent clay, derived from weathering of metamorphic rock, were evaluated. These changes were measured using X-ray fluorescence, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, specific surface area (SSA) by Brunauer–Emmett–Teller method, and lime fixing as a measure of pozzolanic activity. It was found that the milling process modified the structure of the clays and the pozzolanic activity, since the main reflection (001) disappeared, the dehydroxylation temperature decreased to a maximum differential of 150°C with 120 s of milling time, especially in T:O:T clays, and the SSA increased along with the lime fixing to a maximum of 119 m²/g and 46%, respectively. In this way, the milling process is effective for the mechanical activation of the clay, especially in multicomponent clay, making it interesting for use as supplementary cementitious material.