Poly(vinyl alcohol)/Fatty Acid Blends for Thermal Energy Storage

Abstract

This article is aimed to prepare the blends of poly(vinyl alcohol) (PVA) with fatty acids (lauric, myristic, palmitic, and stearic acids) as shape-stabilized phase change material (PCM), to prove the miscibility of fatty acids with the PVA by microscopic investigation and infrared (IR) spectroscopy, and to measure their melting temperature and the latent heat of fusion by differential scanning calorimetry (DSC) analysis methods. In the blends, the fatty acids, which are dispersed in the solid network of the polymer, act as latent heat thermal energy storage (LHTES) material during its solid-liquid phase change when the polymer (PVA) has function of supporting material because of its structural strength. Therefore, the shape-stabilized fatty acids can keep the same shape in a solid shape without leakage of liquid fatty acids by aid of PVA in solid state. The maximum mixture ratio for all fatty acids in the shape-stabilized form was found as 50 wt%. By using DSC analysis method, the melting temperatures and latent heats of the shape-stabilized lauric, myristic, palmitic and stearic acids were determined as 39.8, 50.2, 56.2, and 67.4°C and 96.4, 105.3, 121.6, and 132.6 J/g, respectively. The results indicate that the PVA/fatty acids blends as shape-stabilized PCM have great potential for passive solar LHTES applications in terms of their satisfactory thermal properties and utility advantage of without encapsulation.     

Numerical Analysis of a Tunnel Support Design in Conjunction with Empirical Methods

In this paper, preliminary support design of a tunnel was analyzed by numerical and empirical approaches. The case study for this analysis is a tunnel to be constructed on the Bilecik-Istanbul roadway in Turkey. The rock mass properties of the tunnel route and design support recommendations were obtained by using an empirical approach. The rock mass properties obtained from the empirical method were used as input parameters for the numerical analysis. The empirical and numerical results, in terms of support design, were evaluated. It was seen that the numerical analysis results supported by empirical values were logical and reliable.     

Polymers,composites, and characterization of conducting polyfuran and poly(2‐bromoaniline)

Polyfuran (PFu), poly(2‐bromoaniline) (P2BrAn), and poly(2‐bromoaniline)/polyfuran (P2BrAn/PFu) composites were synthesized by coupling using various solvents and oxidants. 2‐Bromoaniline (2BrAn) was polymerized using FeCl₃ and (NH₄)₂S₂O₈ in aqueous HCl medium. PFu was synthesized using FeCl₃ and SbCl₃ in anhydrous media (CHCl₃, CH₃CN). Furan was polymerized using both salts in CHCl₃ medium, whereas it could be polymerized using only FeCl₃ in CH₃CN medium. The new electrically conducting composites were prepared by chemical oxidative polymerization using polyfuran synthesized with SbCl₃ and poly(2‐bromoaniline). The polymers and composites were characterized using conductivity, magnetic susceptibility, infrared spectra (FTIR), UV‐Vis spectra, thermal analysis (TGA), and scanning electron microscopy (SEM) measurements. It was found that PFu(SbCl₃) has the lowest thermal stability. Thus, the thermal stability of PFu was increased by preparing composites. The chemical structures of P2BrAns and composites have been found from UV‐Vis results to contain quinone‐imine units along the polymer chain. Magnetic susceptibility measurements indicated that the polymers and composites were diamagnetic or paramagnetic. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2048–2057, 2005     

Graphical fault tree analysis for fatal falls in the construction industry

The current study applied a fault tree analysis to represent the causal relationships among events and causes that contributed to fatal falls in the construction industry. Four hundred and eleven work-related fatalities in the Taiwanese construction industry were analyzed in terms of age, gender, experience, falling site, falling height, company size, and the causes for each fatality. Given that most fatal accidents involve multiple events, the current study coded up to a maximum of three causes for each fall fatality. After the Boolean algebra and minimal cut set analyses, accident causes associated with each falling site can be presented as a fault tree to provide an overview of the basic causes, which could trigger fall fatalities in the construction industry. Graphical icons were designed for each falling site along with the associated accident causes to illustrate the fault tree in a graphical manner. A graphical fault tree can improve inter-disciplinary discussion of risk management and the communication of accident causation to first line supervisors.     

Characterization of UHF RFID tags fabricated directly on convex surfaces by pad printing

The possibility of pad printing in RFID tag antenna manufacturing is investigated. Passive UHF RFID tags were printed on flat and on convex surfaces with two different polymer thick-film silver inks. The effect of the ink and substrate material properties on tag antenna performance was examined. The goal was to provide information which is needed in adapting the pad-printing technique in RFID tag manufacture. The results show that pad printing is suitable for tag manufacturing on flat and on convex surfaces. The curvature of the substrate did not significantly affect the tag performance. It was more important to take into consideration other substrate properties, ink characteristics, morphology, and printing parameters. The best practice is to take these matters into consideration in the initial tag design process to ensure proper tag performance at the desired frequency.     

User involvement: a review of the benefits and challenges

User involvement is a widely accepted principle in development of usable systems. However, it is a vague concept covering many approaches. This study first clarifies the nature of user involvement and its expected benefits, and secondly reviews three streams of research, to evaluate the benefits and problems of varied user involvement approaches in practice. The particular focus of this study is on the early activities in the development process. An analysis of the literature suggests that user involvement has generally positive effects, especially on user satisfaction, and some evidence exists to suggest that taking users as a primary information source is an effective means of requirements capture. However, the role of users must be carefully considered and more cost-efficient practices are needed for gathering users' implicit needs and requirements in real product development contexts.     

Analysis of predistortion, equalization, and ISI cancellationtechniques in digital radio systems with nonlinear transmit amplifiers

An analysis made of the performance of predistortion, equalization, and intersymbol interference (ISI) cancellation techniques in compensating for the transmit amplifier nonlinearity in digital microwave radio systems. The study is carried out using the 64 QAM and 256 QAM signal formats and two values of the roll-off factor in the Nyquist pulse shaping. The simulated compensation techniques include three types of predistortion, two ISI cancellers, and several nonlinear equalizers with or without decision feedback. A basic result is that decision-feedback equalizers do not offer any significant advantage over nonrecursive equalizers. It is also shown that ISI cancelers with a memoryless equalizer as first-stage decision device do not perform any better than nonlinear equalizers of similar complexity. Another contribution an improved fifth-order analog signal predistortion technique is analyzed. The gain that can be achieved using a modified 256 QAM signal constellation that is more robust to nonlinear distortion is quantified     

Critical flux in cross-flow ultrafiltration of protein solutions

The effect of solute size relative to membrane pore size on the critical flux during the ultrafiltration of protein solutions was investigated using the constant pressure method. Hydrophilic regenerated cellulose membranes with a cut-off of 10, 30 and 100 kg mol⁻¹, model proteins and skimmed milk solutions were used. The critical flux mainly increased with the pore size of the ultrafiltration membrane. The lowest critical fluxes, 40-50 L m⁻²h⁻¹, were obtained with the retentive 10 kg mol⁻¹ cut-off membrane. This membrane had a very low permeability and, thus, the critical fluxes were achieved at high transmembrane pressures (TMP): 1.7-2.3 bar. With the 100 kg mol⁻¹ cut-off membrane critical fluxes were obtained at 0.2 bar TMP, which were around 100 L m⁻² h⁻¹, slightly declining with increasing protein molar mass. In skimmed milk experiments the permeate flux decreased when the protein molecules were enzymatically split to peptides. A critical flux for skimmed milk solution could not be found unless the protein concentration was diluted to 0.3-w% or lower. The results with model proteins were then compared to those obtained with skimmed milk resulting in β-lactoglobulin being the worst foulant.     

Reappraisal of the role of vegetables in the vitamin A status of mothers in Central Java, Indonesia

Food-based approaches for controlling vitamin A deficiency and its consequences, such as increased mortality, more severe morbidity, and anemia, have become increasingly important, thus prompting a reassessment of the relation between vitamin A intake and status. A nutrition surveillance system in Central Java, Indonesia, assessed the vitamin A intake and serum retinol concentration of women with a child < or =24 mo old with a semiquantitative 24-h recall method that categorized vitamin A-containing foods into 3 categories of plant foods and into 2 categories of animal foods and identified portions as small, medium, or large. Median vitamin A intake was 335 retinol equivalents (RE)/d (n = 600) and vitamin A intake from plant foods was 8 times higher than from animal foods. Serum retinol concentration was related to vitamin A intake in a dose-response manner. The multiple logistic regression model for predicting the chance for a serum retinol concentration greater than the observed median (> or = 1.37 micromol/L) included physiologic factors, vitamin A intake from plant [odds ratio (95% CI) per quartile: 1st, 1.00: 2nd, 1.23 (0.75, 2.02); 3rd, 1.60 (0.97, 2.63); and 4th, 2.06 (1.25, 3.40)] and animal [1st and 2nd, 1.00; 3rd, 1.31 (0.86, 2.02); and 4th, 2.18 (1.40. 3.42)] foods, home gardening [(no, 1.00; yes, 1.71 (1.12, 2.60)], and woman's education level [< or =primary school, 1.00; > or =secondary school, 1.51 (1.02, 2.22)]. Despite the fact that plant foods contributed 8 times as much vitamin A as did animal foods, serum retinol concentrations did not reflect this large difference. Home gardening and woman's education level seemed to reflect longer-term consumption of vitamin A-rich plant and animal foods, respectively.