Nonlinear vibrations of laminated and sandwich rectangular plates with free edges. Part 2: Experiments & comparisons

Large-amplitude (geometrically nonlinear) forced vibrations of completely free sandwich rectangular plates are investigated experimentally. Harmonic excitation is applied by using an electro-dynamic exciter and the plate vibration is measured by using laser Doppler vibrometers. A scanning laser Doppler vibrometer is used for experimental modal analysis since it provides non-contact vibration measurements with very high spatial resolution. The large-amplitude vibration experiments are carried out by using a single point laser Doppler vibrometer and a stepped-sine testing procedure. The nonlinear frequency response curves are obtained by increasing and decreasing the excitation frequency in very small steps at specific force amplitudes controlled in a closed-loop. The experimental results are compared to numerical simulations obtained by reduced-order models and show very good agreement. The nonlinear damping is experimentally obtained as a function of the vibration amplitude

Diaphragmatic hernia following oesophagectomy for oesophageal cancer – Are we too radical?

Background: Diaphragmatic herniation (DH) of abdominal contents into the thorax after oesophageal resection is a recognised and serious complication of surgery. While differences in pressure between the abdominal and thoracic cavities are important, the size of the hiatal defect is something that can be influenced surgically. As with all oncological surgery, safe resection margins are essential without adversely affecting necessary anatomical structure and function. However very little has been published looking at the extent of the hiatal resection. We aim to present a case series of patients who developed DH herniation post operatively in order to raise discussion about the ideal extent of surgical resection required. Methods: We present a series of cases of two male and one female who had oesophagectomies for moderately and poorly differentiated adenocarcinomas of the lower oesophagus who developed post-operative DH. We then conducted a detailed literature review using Medline, Pubmed and Google Scholar to identify existing guidance to avoid this complication with particular emphasis on the extent of hiatal resection. Discussion: Extended incision and partial resection of the diaphragm are associated with an increased risk of postoperative DH formation. However, these more extensive excisions can ensure clear surgical margins. Post-operative herniation can be an early or late complication of surgery and despite the clear importance of hiatal resection only one paper has been published on this subject which recommends a more limited resection than was carried out in our cases. Conclusion: This case series investigated the recommended extent of hiatal dissection in oesophageal surgery. Currently there is no clear guidance available on this subject and further studies are needed to ascertain the optimum resection margin that results in the best balance of oncological parameters vs. post operative morbidity

Quantitative phase evolution during mechano-synthesis of Ti-Ni-Cu shape memory alloys

Cataloged from PDF version of article.Ti-41Ni-9Cu shape memory alloy was synthesized by mechanical alloying of pure elemental Ti, Ni, and Cu powders using high-energy ball milling. The qualitative and quantitative phase analyses of the as-milled powders were done by X-ray diffraction (XRD) using Rietveld refinement and the alloys microstructure was studied by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Concerning the results, by milling evolution, the dissolution of the primary materials occurred at different rates and a considerable amount of the amorphous phase as well as B19′-martensite and B2-austenite was created. The formation of Ni solid solution was also evidenced prior to its dissolution. It was found that at sufficient milling time, the mechano-crystallization of the amorphous phase occurred and at the end of milling, the B19′-martensite is the dominant phase of the structure. © 2012 Elsevier B.V. All rights reserve

Effect of milling Time on the Structure, Micro-hardness, and Thermal Behavior of Amorphous/Nanocrystalline TiNiCu Shape Memory Alloys Developed by Mechanical Alloying

Cataloged from PDF version of article.In the present paper, the effect of milling process on the chemical composition, structure, microhardness, and thermal behavior of Ti-41Ni-9Cu compounds developed by mechanical alloying was evaluated. The structural characteristic of the alloyed powders was evaluated by X-ray diffraction (XRD). The chemical composition homogeneity and the powder morphology and size were studied by scanning electron microscopy coupled with electron dispersive X-ray spectroscopy. Moreover, the Vickers micro-indentation hardness of the powders milled for different milling times was determined. Finally, the thermal behavior of the as-milled powders was studied by differential scanning calorimetery. According to the results, at the initial stages of milling (typically 0-12 h), the structure consisted of a Ni solid solution and amorphous phase, and by the milling evolution, nanocrystalline martensite (B19') and austenite (B2) phases were initially formed from the initial materials and then from the amorphous phase. It was found that by the milling development, the composition uniformity is increased, the inter-layer thickness is reduced, and the powders microhardness is initially increased, then reduced, and afterward re-increased. It was also realized that the thermal behavior of the alloyed powders and the structure of heat treated samples is considerably affected by the milling time. (C) 2013 Elsevier Ltd. All rights reserved

Social Achievement Goal Theory in Education: A Validity and Reliability Study

The objective of this study was to validate the Iranian version of the Social Achievement Goal Orientation Scale and test the Social Achievement Goal Orientation theory in the context of Iranian students. A total of 403 Iranian high school students completed a Social Achievement Goal Orientation Scale and an Achievement Goal Questionnaire. Exploratory and confirmatory factor analyses confirmed the hypothesized model of social achievement goals. The fit of the proposed three-factor model was promising and moderate support for the three factor structure of social goal orientation was found using scores from an abbreviated 13-item SAGOS. Graded Response Model showed an information function that was peaked at the upper end of the scale, indicating that severe social goal orientation is measured with most precision. Convergent validity for the new measure of social achievement goals was established. Findings generally supported the trichotomous framework of the social achievement goal orientation theory with Iranian students. Consistent with the academic goal orientation theory, findings indicated that social mastery and performance-approach and performance-avoidance goals had positive relationships with academic goals

Tuning dissipation dilution in 2D material resonators by MEMS-induced tension

Resonators based on two-dimensional (2D) materials have exceptional properties for application as nanomechanical sensors, which allows them to operate at high frequencies with high sensitivity. However, their performance as nanomechanical sensors is currently limited by their low quality ($Q$)-factor. Here, we make use of micro-electromechanical systems (MEMS) to apply pure in-plane mechanical strain, enhancing both their resonance frequency and Q-factor. In contrast to earlier work, the 2D material resonators are fabricated on the MEMS actuators without any wet processing steps, using a dry-transfer method. A platinum clamp, that is deposited by electron beam-induced deposition, is shown to be effective in fixing the 2D membrane to the MEMS and preventing slippage. By in-plane straining the membranes in a purely mechanical fashion, we increase the tensile energy, thereby diluting dissipation. This way, we show how dissipation dilution can increase the $Q$-factor of 2D material resonators by 91\%. The presented MEMS actuated dissipation dilution method does not only pave the way towards higher $Q$-factors in resonators based on 2D materials, but also provides a route toward studies of the intrinsic loss mechanisms of 2D materials in the monolayer limit.Comment: 20 pages, 15 figure

Capping agent effect on Pd-supported nanoparticles in the hydrogenation of furfural

The catalytic performance of a series of 1 wt % Pd/C catalysts prepared by the sol-immobilization method has been studied in the liquid-phase hydrogenation of furfural. The temperature range studied was 25\u201375 \ub0C, keeping the H2 pressure constant at 5 bar. The effect of the catalyst preparation using different capping agents containing oxygen or nitrogen groups was assessed. Polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and poly (diallyldimethylammonium chloride) (PDDA) were chosen. The catalysts were characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The characterization data suggest that the different capping agents affected the initial activity of the catalysts by adjusting the available Pd surface sites, without producing a significant change in the Pd particle size. The different activity of the three catalysts followed the trend: PdPVA/C > PdPDDA/C > PdPVP/C. In terms of selectivity to furfuryl alcohol, the opposite trend has been observed: PdPVP/C > PdPDDA/C > PdPVA/C. The different reactivity has been ascribed to the different shielding effect of the three ligands used; they influence the adsorption of the reactant on Pd active sites

Formation of B19', B2, and amorphous phases during mechano-synthesis of nanocrystalline NiTi intermetallics

Ni-50Ti shape memory alloy was synthesized by mechanical alloying of the elemental powders mixture under an argon gas atmosphere. The structural and microstructural properties of the alloyed powders were evaluated by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Moreover, the Vickers microhardness of the powders was estimated at different milling times. According to the results, by milling progression, the amount of the amorphous phase increased considerably and after sufficient milling time (48h), the mechano-crystallization of the amorphous phase into the more stable crystalline phases (i.e. B2 and B19') occurred. It was found that the particles size and microhardness were significantly affected by the formation of the amorphous, B2, and B19' phases. It was also deduced that, by appropriate heating and cooling cycles, the B2 and thermally-induced B19' phases can be created. Furthermore, it was inferred that the formation of undesirable intermetallic phases (particularly NiTi2) during the heating cycle was considerably reduced by milling time evolution. © 2013 Elsevier B.V

Effect of milling time on the structure, micro-hardness, and thermal behavior of amorphous/nanocrystalline TiNiCu shape memory alloys developed by mechanical alloying

In the present paper, the effect of milling process on the chemical composition, structure, microhardness, and thermal behavior of Ti-41Ni-9Cu compounds developed by mechanical alloying was evaluated. The structural characteristic of the alloyed powders was evaluated by X-ray diffraction (XRD). The chemical composition homogeneity and the powder morphology and size were studied by scanning electron microscopy coupled with electron dispersive X-ray spectroscopy. Moreover, the Vickers micro-indentation hardness of the powders milled for different milling times was determined. Finally, the thermal behavior of the as-milled powders was studied by differential scanning calorimetery. According to the results, at the initial stages of milling (typically 0-12. h), the structure consisted of a Ni solid solution and amorphous phase, and by the milling evolution, nanocrystalline martensite (B19') and austenite (B2) phases were initially formed from the initial materials and then from the amorphous phase. It was found that by the milling development, the composition uniformity is increased, the inter-layer thickness is reduced, and the powders microhardness is initially increased, then reduced, and afterward re-increased. It was also realized that the thermal behavior of the alloyed powders and the structure of heat treated samples is considerably affected by the milling time. © 2013 Elsevier Ltd

Impact of independent and non-independent parameters on various elements’ rejection by nanofiltration employed in groundwater treatment

Nanofiltration is one of the widely used robust methods in water sweetening throughout the world. This work highlights the comparison of the impact of independent and non-independent parameters on element rejection to treat groundwater of a region located in Qazvin province, Iran. A pilot-scale FILMTEC-NF90-4040 nanofilter membrane was applied. Samples were collected from three various wells and the volume of 50 cc was tested, each of which was tested three times, and then cations and anions were measured in raw water and treated water by ion chromatography. The data collection and operation of the system was performed by the 761 compact IC version 1.1 software where statistical analyses were performed with SPSS, version 19. Results showed that the degradation efficiency of divalent ions was greater than that of monovalent cations. The content of ion rejection in the nanofilter membrane was not an independent phenomenon. For instance, the results revealed that the presence of high magnesium ion is very effective in disposing sodium ion. At the same time, the rejection rate of ions does not always follow the Van’t Hoff series. Optimal pressure was determined to be 10 bar