Nonlinear vibration and rippling instability for embedded carbon nanotubes

Based on the rippling deformations, a nonlinear continuum elastic model is developed to analyze the transverse vibration of single-walled carbon nanotubes (SWCNTs) embedded on a Winkler elastic foundation. The nonlinear natural frequency has been derived analytically for typical boundary conditions using the perturbation method of multi-scales. The results indicate that the nonlinear resonant frequency due to the rippling is related to the stiffness of the foundation, the boundary conditions, the excitation load-to-damping ratio, and the diameter-to-length ratio. Moreover, the rippling instability of carbon nanotubes, as a structural instability, is introduced and the influences of several effective parameters on this kind of instability are widely discussed.     

Imidazolium-based Alkylsulfate Ionic Liquids and Removal of Sulfur Content From Model of Gasoline

Two ionic liquids, butyl-methyl-imidazolium octylsulfate, [BMIM][OCSO₄], and ethyl-methyl-imidazolium ethylsulfate, [EMIM][EtSO₄], were demonstrated to be effective for the removal of aromatic sulfur compounds such as benzothiophene and thiophene from model of gasoline. Organic compounds with higher aromatic π-electron density were favorably adsorbed by using ionic liquids. It was shown that the extractive ability of the alkylsulfate IL_s was dominated by the structure and size of cation and anion. The cation and anion structure and size of ionic liquids are important factors affecting the absorption capacity for aromatic compounds. It is found that [BMIM][OCSO₄] has the best effect on the selective removal of sulfur compounds from gasoline. Sulfur extractive selectivity for specified IL followed the order BT>T>3-MT>2-MT.     

Application of ANFIS to predict crop yield based on different energy inputs

In this paper, adaptive neuro-fuzzy inference system (ANFIS) was used to predict the grain yield of irrigated wheat in Abyek town of Ghazvin province, Iran. Due to large number of inputs (eight inputs) for ANFIS, the input vector was clustered into two groups and two networks were trained. Inputs for ANFIS 1 were diesel fuel, fertilizer and electricity energies and for ANFIS 2 were human labor, machinery, chemicals, water for irrigation and seed energies. The RMSE and R² values were found 0.013 and 0.996 for ANFIS 1 and 0.018 and 0.992 for ANFIS 2, respectively. These results showed that ANFIS 1 and ANFIS 2 could well predict the yield. Finally, the predicted values of the two networks were used as inputs to the third ANFIS. The results indicated that the energy inputs in ANFIS 1 have a greater impact on the final yield production than other energy inputs. Also, the RMSE and R² values for ANFIS 3 were 0.013 and 0.996, respectively. These results showed that ANFIS 1 and the combined network (ANFIS 3) could both predict the grain yield with good accuracy.     

Enhanced hydrogen reversibility of nanoconfined LiBH4–Mg(BH4)2

This study shows the hydrogen desorption kinetics and reversible hydrogen storage properties of 0.55LiBH₄–0.45Mg(BH₄)₂ melt-infiltrated in different nanoporous carbon aerogels with different BET surface areas of 689 or 2660 m²/g and pore volumes of 1.21 or 3.13 mL/g. These investigations clearly show a significantly improved hydrogen storage capacity after four cycles of hydrogen release and uptake for bulk 0.55LiBH₄–0.45Mg(BH₄)₂ and infiltrated in carbon aerogel and the high surface area scaffold, where 22, 36 and 58% of the initial hydrogen content remain after four cycles of hydrogen release and uptake, respectively. Nanoconfinement in high surface area carbon aerogel appears to facilitate hydrogen release illustrated by release of 13.3 wt% H₂ (93%) and only 8.4 wt% H₂ (58%) from bulk hydride in the first cycle using the same physical condition. Notably, nanoconfinement also appear to have a beneficial effect on hydrogen uptake, since 8.3 wt% H₂ (58%) is released from the high surface area scaffold and only 3.1 wt% H₂ (22%) from the bulk sample during the fourth hydrogen release.     

Development and Evaluation of a High-Volume Aerosol-into-Liquid Collector for Fine and Ultrafine Particulate Matter

This study presents a novel high-volume aerosol-into-liquid collector, developed to provide concentrated slurries of fine and/or ultrafine particulate matter (PM) to be used for unattended, in situ measurements of PM chemistry and toxicity. This system operates at 200 liters per minute (L/min) flow and utilizes the saturation–condensation, particle-to-droplet growth component of the versatile aerosol concentration enrichment system (VACES), growing fine or ultrafine PM to 3–4-μm droplets, in conjunction with a newly designed impactor, in which grown particles are collected gradually forming highly concentrated slurries. Laboratory evaluation results indicated an excellent overall system collection efficiency (over 90%) for both monodisperse and polydisperse particles in the range of 0.01 to 2 μm. Field evaluations illustrated that overall a very good agreement was obtained for most PM_2.5 species between the new aerosol collection system and the VACES/BioSampler tandem as well as filter samplers operating in parallel. Very good agreement between the new system and the VACES/BioSampler was also observed for reactive oxygen species (ROS) in ambient PM_2.5 samples, whereas lower ROS values were obtained from the water extracts of the filter, likely due to incomplete extraction of water insoluble redox active species collected on the filter substrate. Moreover, the field tests indicated that the new aerosol collection system could achieve continuous and unattended collection of concentrated suspensions for at least 2 to 3 days without any obvious shortcomings in its operation. Both laboratory and field evaluations of the high-volume aerosol-into-liquid collector suggest that this system is an effective technology for collection and characterization of ambient aerosols.

Copyright 2013 American Association for Aerosol Research     

Optimization of Sputtering Parameters for the Deposition of Low Resistivity Indium Tin Oxide Thin Films

Indium tin oxide(ITO) thin films have been deposited using RF sputtering technique at different pressures,RF powers,and substrate temperatures.Variations in surface morphology,optical properties,and film resistances were measured and analyzed.It is shown that a very low value of sheet resistance(1.96 Ω/sq.) can be achieved with suitable arrangement of the deposition experiments.First,at constant RF power,deposition at different pressure values is done,and the condition for achieving minimum sheet resistance(26.43 Ω/sq.) is found.In the next step,different values of RF powers are tried,while keeping the pressure fixed on the previously found minimum point(1–2 Pa).Finally,the minimum resistivity is obtained by sweeping the substrate temperatures,while keeping RF power and the working pressure at their optimum values.Furthermore,the effects of process parameters on properties,such as the surface morphology and the optical transmission,are discussed.Although the point of minimum resistivity does not coincide with that of the maximum transparency of ITO film,relatively acceptable values of transmittance(approximately 75% on a glass substrate with intrinsic transparency of 89%) can be obtained.     

Study the Heat Recovery Performance of Micro and Nano Metfoam Regenerators in Alpha Type Stirling Engine Conditions

This paper experimentally investigates the performance of micro and nano metfoam regenerators in alpha-type Stirling engine conditions. The thermal efficiency of this engine depends on performance of regenerator. Therefore, increase the heat recovery of regenerator raises the total efficiency. Accordingly, two types of regenerators from porous media are designed and simulated with different materials. Three-dimensional regenerator CFD simulation shows that randomize porous open cell metfoam made of silver as high conductivity and high heat capacity material is the best structure to fabricate metfoam regenerator. The porosity and matrix element diameter are optimized. The nano coating methodology enhances the activated surface. The regenerators are fabricated using casting polymer mold layer deposition. The nano silver particles are coated on the metfoam by sol-gel coating method. Experimental results show the improvement in regenerator percentage of heat recovery by 3.40% and 5.93% for micro metfoam and nano metfoam, respectively. The maximum improvement is achieved up to 8.65% in case of using the nano metfoam regenerator at 543 K.     

Multimedia document retrieval using speech and speaker recognition

Speech and speaker recognition systems are rapidly being deployed in real-world applications. In this paper, we discuss the details of a system and its components for indexing and retrieving multimedia content derived from broadcast news sources. The audio analysis component calls for real-time speech recognition for converting the audio to text and concurrent speaker analysis consisting of the segmentation of audio into acoustically homogeneous sections followed by speaker identification. The output of these two simultaneous processes is used to abstract statistics to automatically build indexes for text-based and speaker-based retrieval without user intervention. The real power of multimedia document processing is the possibility of Boolean queries in the form of combined text- and speaker-based user queries. Retrieval for such queries entails combining the results of individual text and speaker based searches. The underlying techniques discussed here can easily be extended to other speech-centric applications and transactions.     

Webometric analysis of Iranian universities of medical sciences

Introduction  There are many researches have been conducted on webometrics, especially the impacts of websites on each other and the web impact factor. However, there are few studies focusing on the websites of Iranian universities. This study analyzed the websites of Iranian universities of medical sciences according to the webometric indicators. Method and materials  In a cross-sectional study, the number of web pages, inlinks, external inlinks and also the overall and absolute web impact factors for Iranian universities of medical sciences with active exclusive websites were calculated and compared using AltaVista search engine. Finally, the websites were ranked based on these webometric indicators. Results  The results showed that the website of Tehran university of medical sciences with 49,300 web pages and 9860 inlinks was ranked first for the size and number of inlinks, while its impact factor was ranked 38th. Rafsanjan UMS with 15 web pages and 211 links had the highest rank for the web impact factor among Iranian universities of medical sciences. Discussions and conclusions  The study revealed that Iranian universities of medical sciences did not have much impact on the web and were not well known internationally. The major reason relies on linguistic barriers. Some of them also suffer from technical problems in their web design.     

Seasonal and Spatial Coarse Particle Elemental Concentrations in the Los Angeles Area

The concentrations of trace metals and elements in the coarse fraction of atmospheric particulate matter (CPM, particles smaller than 10 and larger than 2.5 μm in diameter, PM_10–2.5) and their spatial and temporal trends were investigated in the greater Los Angeles area. Ten distinct sampling sites were chosen to encompass a variety of CPM sources, including urban, rural, coastal, inland, and near-freeway sites. Time-integrated 24-h CPM samples were collected at each location once a week, for an entire year, from April 2008 to March 2009, to characterize drivers of the seasonal and spatial patterns of the CPM trace metal content. Metals were quantified using sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS).

Trace metals in CPM displayed distinct seasonal and temporal variations, and a principal component analysis (PCA) was performed to aid the identification of the CPM sources underlying these variations. The probable sources of each principal component were identified using elemental tracers. Major sources of CPM metals and elements identified were crustal and mineral matter, abrasive vehicular emissions, industrial, sea spray, and catalytic converters, explaining more than 80% of the total variance of CPM metal content. Mineral and crustal elements, most notably Fe, Ca, Al, Mg, K, Ti, and Mn, were the main contributors to the overall CPM mass, accounting for over 33% of the total variance, followed by abrasive vehicular markers such as Cu, Ba, and Sb, accounting for over 16% of the variance, with an increasing contribution in the urban sites. Temporal and spatial variations in each identified class of CPM sources were also investigated.