Laterally supported sandwich panels subjected to large deflections—Part 1: Test apparatus design and experimental results

This paper deals with the experimental characterization of the structural behavior of sandwich panels under distributed transverse loadings. A configuration typically used in aircraft interior applications is considered: a simply supported rectangular plate fixed by bolts on the two longitudinal edges or on all four edges. The panel and joint stiffness are experimentally evaluated and a test apparatus is designed and instrumented to measure the reaction shear loads at the panel attachment bolts and the transverse deflection of the plate. The results demonstrate the importance of a nonlinear analysis for the design of this type of structure. A companion paper, describes the FE analysis procedure utilized to simulate the nonlinear behavior of the tested panels. The numerical results are validated against the experimental results.     

Study on characterization of pyrolysis and hydrolysis products of poly(vinyl chloride) waste

Poly(vinyl chloride) PVC pyrolysis and hydrolysis are conducted in a fixed bed reactor and in an autoclave, respectively, under different operating conditions such as the temperature and time. The product distribution is studied. For the PVC pyrolysis process, the main gas product is HCl (55% at 340°C), there is 9% hydrocarbon gas (C₁–C₅), the liquid product fraction is about 5% (at 340°C), and the solid residue fraction is about 31% (at 340°C). For the hydrolysis process, the main gas product is HCl (55.8% at 240°C) and the solid residue is about 49.6% (at 240°C). The pyrolysis liquid product is analyzed by using gas chromatography with magic‐angle spinning. Aromatic hydrocarbons are the main class (90%), of which the major part is benzene (33%). The residue produced through pyrolysis and hydrolysis is investigated by high‐resolution solid‐state ¹³C‐NMR. These details revealed by the high‐field NMR spectra provide importmant information about the chemical changes in the PVC pyrolysis and hydrolysis process. The mechanism of PVC hydrolysis dechlorination is also discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3252–3259, 2003     

Performance analysis of Energy Efficient Ethernet on video streaming servers

Current trends on traffic growth oversee a steady increase of video streaming services, and the subsequent development of the associated infrastructure to allocate and distribute such contents. One of the operational costs associated to this infrastructure is the power bill. Therefore any mechanism used to decrease it, reducing also the carbon footprint associated to it, is welcome. In this work we investigate the suitability of the recently standardized IEEE 802.3az Energy Efficient Ethernet (EEE) for video traffic generated by video-streaming servers. The conclusion of the analysis is positive about the achievable energy savings, due to the inherent features of traffic patterns of video-streaming servers which help reducing the number of transitions between active and low-power modes in EEE.     

Structural,Electrical, and Thermal Behavior of Graphite‐Polyaniline Composites with Increased Crystallinity

Conductive materials are at the forefront of materials science research because of the large number of applications that have been developed around their interesting and unique properties. This work reports for the first time a correlation between the structural, electrical, and thermal behavior of novel graphite‐polyaniline (G‐PANI) composites with electrical conductivities greater than either of the individual components. The G:PANI mass ratio was varied during synthesis of the composites (90:10, 95:5, 96:4, 97:3, and 98:2 G:PANI mass ratios) and the highest electrical conductivity was determined for the composite having a G:PANI mass ratio of 96:4. The structural changes related to this increase in electrical conductivity were clearly reflected by the Raman spectra of the new composites, which indicated an improved crystallinity through a better stacking along the c‐axis of graphite when PANI was present (as evidenced by the G and 2 × D modes at 1582 and 2684 cm⁻¹). X‐ray diffraction data showed a slight increase in the (0 0 2) graphite crystal plane distance that was associated with a dilute stage intercalation or a possible “pseudo‐intercalation” of the polymer species between the graphite layers facilitating charge transfer in the composites. It is proposed that polyaniline acts as a charge transfer component between basal planes of graphite. Thermogravimetric analyses of the samples showed similar trends for the thermal stability in accordance with the electrical conductivity, the Raman and X‐ray diffraction data. The potential impact of this work is evident in the many areas that utilize graphite as conductive filler in electrically conducting materials. The composites can be used for a large number of applications in nanoelectronics, electromagnetic interference shielding, rechargeable batteries or as other advanced nanocomposite materials with improved electrical, structural, and thermal properties.     

Optimisation of hydrothermal treatment for dehulling pigeon pea

This study was carried out to investigate the effect of hydrothermal treatment and drying time at a constant drying temperature of 50 °C on the dehulling behavior of pigeon pea seed. Response surface methodology (RSM) based on a two-factor, five-level, central composite design was employed to study the effect of the independent variables and optimize processing conditions. A second-order polynomial model described dehulling quality in terms of: (1) dehulled seeds, (2) undehulled seeds, (3) broken seeds, (4) powder loss and (5) dehulling efficiency. The process parameters showed significant effects on dehulled seeds and dehulling efficiency. The optimized processing conditions for maximum dehulled seeds, dehulling efficiency and minimum powder loss were a hydrothermal treatment time of 10.2 min and a drying time of 2.9 h.     

Synthesis and characterization of tanninsulfonic acid doped polyaniline–metal oxide nanocomposites

Composites of conducting polymers and metal oxides have a potential role in electronic devices because of their enhanced physical and electronic properties. An in situ synthesis of metal oxide nanocomposites of polyaniline (PANI) and tanninsulfonic acid doped PANI was carried out at ?10°C with two different ratios of aniline to sodium persulfate (oxidant) and the simultaneous incorporation of TiO₂, Al₂O₃, and ZnO nanopowders. The products were characterized by X‐ray diffraction (XRD), thermal analysis, spectroscopy, and electrical conductivity measurements. XRD and thermogravimetric analysis confirmed the presence of the metal oxide in the final product, whereas the spectroscopic characterization revealed interactions among the tannin, metal oxides, and PANI. The electrical properties were determined by four‐point‐probe bulk conductivity measurements. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Sintering of nanoscale silver coated textiles,a new approach to attain conductive fabrics for electromagnetic shielding

The demand for conductive textiles is increasing, owing to the need for lightweight and flexible conductive materials for a variety of applications, including electromagnetic shielding of electronic equipment. Herein we propose a process that combines the in situ synthesis of silver nanoparticles at the textile fibre surface followed by sintering of the nanoparticles to obtain highly conductive fabrics. The formation of silver particles at the nanoscale allowed for sintering to be performed efficiently, at reduced temperature and time, bestowing fabrics with high conductivity and capability of shielding electromagnetic radiation. The nanoparticle synthesis method entailed the precipitation of 2.0 g L⁻¹ silver nitrate and further reduction with citrate, with the formation of a deposit of silver nanoparticles at the fabric surface. The amount of silver deposited (up to 195 mg of silver per g of fabric) resulted in moderate electrical conductivity with sheet resistance of 803 Ω/sq. Upon sintering, this value decreased dramatically to 5.2 Ω/sq. The sintering process was monitored by SEM, which showed that sintering at 200 °C for 30 min resulted in maximal electrical conductivity with the lowest amount of silver deposited, while forming a homogenous surface. Fabrics submitted to these sintering conditions maintained their sheet resistance and shielding effectiveness values, even after eight washing cycles.     

Evaluation of line surge arrester failure rate for multipulse lightning stresses

This paper develops a method to analyze energy stresses on transmission line surge arresters. The approach computes the failure rate of arresters due to energy stresses, convolving the density probabilities of first and subsequent pulses. Multipulse stroke effects are considered in a 138 kV line case study, typical of single circuit lines, located in regions with high densities of ground flashes, in SE Brazil. The proposed method provides an improved insight into energy stress evaluation for selection of line surge arresters.     

Ultrahigh field induced strain and polarization response in electron irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer

 The influence of electron dosage on the field induced strain, dielectric constant, and polarization response has been investigated in electron irradiated poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) 50/50 copolymer. It was found that under suitable electron dosage an ultrahigh electrostrictive strain can be achieved. Interestingly, material after irradiation exhibits many features resembling those of relaxor ferroelectrics, suggesting that the electron irradiation breaks up the coherent polarization domain in normal ferroelectric P(VDF-TrFE) copolymer into nano-polar regions that transform the material into a relaxor ferroelectric. In addition, many of the material properties including the field induced polarization, the electrostrictive strain, and elastic modulus exhibit irregular change (non-monotonical) with electron dosage, indicating a complex relation among the crosslinking density, crystallinity, crystallite size, and molecular conformation in determining the material responses. Received: 10 June 1998 / Accepted: 30 July 1998