Numerical Investigation of the Effect of Vertical Load on the Lateral Response of Piles

The laboratory and field test data on the response of piles under the combined action of vertical and lateral loads is rather limited. The current practice for design of piles is to consider the vertical and lateral loads independent of each other. This paper presents some results from three-dimensional finite-element analyses that show the significant influence of vertical loads on a pile’s lateral response. The analyses were performed in both homogeneous clayey soils and homogeneous sandy soils. The results have shown that the influence of vertical loads on the lateral response of piles is to significantly increase the capacity in sandy soils and marginally decrease the capacity in clayey soils. In general, it was found that the effect of vertical loads in sandy soils is significant even for long piles, which are as long as 30 times the pile width, while in the case of clayey soils, the effect is not significant for piles beyond a length of 15 times the width of the pile. The design bending moments in the laterally loaded piles were also found to be dependent on the level of vertical load on the piles.     

A distributed laxity-based priority scheduling scheme for time-sensitive traffic in mobile ad hoc networks

Characteristics of Mobile Ad hoc Networks such as shared broadcast channel, bandwidth and battery power limitations, highly dynamic topology, and location dependent errors, make provisioning of quality of service (QoS) in such networks very difficult. The Medium Access Control (MAC) layer plays a very important role as far as QoS is concerned. The MAC layer is responsible for selecting the next packet to be transmitted and the timing of its transmission. We have proposed a new MAC layer protocol that includes a laxity-based priority scheduling scheme and an associated back-off scheme, for supporting time-sensitive traffic. In the proposed scheduling scheme, we select the next packet to be transmitted, based on its priority value which takes into consideration the uniform laxity budget of the packet, the current packet delivery ratio of the flow to which the packet belongs, and the packet delivery ratio desired by the user. The back-off mechanism devised by us grants a node access to the channel, based on the rank of its highest priority packet in comparison to other such packets queued at nodes in the neighborhood of the current node. We have studied the performance of our protocol that combines a packet scheduling scheme and a channel access scheme through simulation experiments, and the simulation results show that our protocol exhibits a significant improvement in packet delivery ratio under bounded end-to-end delay requirements, compared to the existing 802.11 DCF and the Distributed Priority Scheduling scheme proposed recently in [ACM Wireless Networks Journal 8 (5) (2002) 455–466; Proceedings of ACM MOBICOM '01, July 2001, pp. 200–209].     

Hydrothermally synthesized ZnO and Z-rGO nanorods: Effect of post-annealing temperature and rGO incorporation on hydrogen sensing

Journal of Materials Science: Materials in Electronics - In this work, hydrogen-sensing characteristics of zinc oxide nanorods and reduced graphene oxide-incorporated zinc oxide nanorods are...     

Synthesis and Study of Structural,Morphological and Magnetic Properties of ZnFe2O4 Nanoparticles

Superparamagnetic zinc ferrite (ZnFe₂O₄) nanoparticles were prepared by a surfactant assisted hydrothermal method and subjected to the heat treatment. The structure, vibrational, morphology, and magnetic properties of synthesized product were characterized by XRD, FT-IR, HR-SEM, and VSM measurements. XRD result confirms the formation of regular spinel structured ZnFe₂O₄ with space group of Fd3m and an average crystalline size was calculated as 21 nm and 28 nm for the samples annealed in air atmosphere at 300 °C and 600 °C. The HR-SEM image shows that the particles are in spherical shape with small aggregation. A room temperature superparamagnetic behavior was observed for both samples. The saturation magnetization (M _s) of 12.0 emu/g and 9.10 emu/g were observed for the samples annealed in air atmosphere at 300 °C and 600 °C, respectively.     

Structural,morphological and magnetic properties of hydrothermally synthesized ZnFe2O4 nanoparticles

Zinc ferrite (ZnFe₂O₄) nanoparticles were synthesized by a surfactant assisted hydrothermal method using different concentrations of ethylamine (EA) namely, 2, 4, 6, 8 and 10 ml. The powder X-ray diffraction measurements revealed that the amount of EA plays an important role in the formation of single phase ZnFe₂O₄ nanoparticles. The amount of 2 and 4 ml of EA yielded mixed phases of α-Fe₂O₃ and ZnFe₂O₄ whereas 6 ml of EA produced well crystalline and single phase ZnFe₂O₄ with regular spinel structures. Field emission scanning electron microscopy images revealed that ZnFe₂O₄ possess spherical shape, irrespective of the concentrations of EA. Magnetic characterizations revealed that the synthesized samples with EA concentrations 6, 8, 10 ml were superparamagnetic in nature at room temperature.     

Synthesis of superparamagnetic ZnFe2O4 nanoparticle by surfactant assisted hydrothermal method

Zinc ferrite (ZnFe₂O₄) ultrafine powder was synthesized by hydrothermal method using various amounts of cetyltrymethylammonium bromide (CTAB) as a surfactant. The phase purity, thermal stability, morphology, size and magnetic properties of the final products were studied. All the synthesized products were possessing normal spinel structure without any impurities. The crystalline size of synthesized products decreased with the increasing amounts of surfactant. Particles had narrow size distribution with an average particle size of 6.5 nm for 1.5 g of CTAB. Magnetic characterizations revealed that the synthesized products were superparamagnetic in nature.     

Synthesis and characterization of MWCNT impregnated with different loadings of SnO2 nanoparticles for hydrogen storage applications

Multi-walled carbon nanotubes (MWCNTs) loaded with different wt % of tin oxide (MWCNT: SnO₂) nanocomposites have been synthesized by impregnation method and their hydrogen uptake capacity is investigated. The hydrogen storage capacity of MWCNT: SnO₂ (3 wt %), MWCNT: SnO₂ (5 wt %), MWCNT: SnO₂ (7 wt %) and MWCNT: SnO₂ (9 wt %) composites is found to be 2.03, 1.95, 0.94 and 1.59 wt % respectively. The enhanced hydrogen storage capacity is due to SnOC bond formation and summative adsorption of hydrogen by MWCNT and SnO₂ nanoparticles. Moreover, physical/chemical properties of composites are examined by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, thermogravimetric and Raman analyses. Hydrogen adsorption and desorption behavior of the composites are analyzed using Raman and thermogravimetric analyses. The stored hydrogen is desorbed in the temperature range of 183 ?C-536 °C.     

Characterization and hydrogen storage properties of SnO2 functionalized MWCNT nanocomposites

Structural, spectral, morphological, thermal and hydrogen storage properties of the multi-walled carbon nanotubes functionalized with SnO₂ particles (MWCNT/SnO₂) heat treated at 300, 350 and 400 °C in air were systematically investigated. X-ray diffraction from (110), (101) and (211) planes of SnO₂, (002) plane of MWCNT and shift towards higher angle confirmed the formation of composites. XPS, Raman, FTIR and TGA analyses revealed that C–O bond on the surface of MWCNT acts as the nucleation sites for SnO₂ which resulted in a strong interaction between MWCNT and SnO₂. Presence of C, Sn and O was confirmed by EDX and XPS analyses. Hydrogen adsorption was carried out using hydrogenation set-up and H₂ adsorption/desorption behavior of the composites were studied employing Raman and thermogravimetric analyses. Size, morphology and interaction between MWCNT and SnO₂ were impacted significantly by the heat treatment which resulted in high hydrogen storage capacity of 2.13 and 2.62 wt % for 15 and 30 min hydrogenation time for the nanocomposite heat treated at 400 °C.     

Iridium oxide as low temperature NO/sub 2/-sensitive material for work function-based gas sensors

This paper presents the results on work function-based NO/sub 2/-sensing properties of iridium-oxide thin films at 130/spl deg/C. Films of 20-nm and 100-nm thickness were deposited on silicon substrates using dc sputtering followed by annealing in oxygen ambient. Sensitivity of these films to different concentrations of NO/sub 2/, H/sub 2/, CO, Cl/sub 2/, and NH/sub 3/ in synthetic air was measured using a Kelvin probe. It was observed that work function of 20-nm-thick iridium-oxide film changed by /spl sim/100 mV on exposure to 5-ppm NO/sub 2/ (German safety limit). Cross sensitivity to other gases (except NH/sub 3/) and interference of humidity was found to be negligibly small. The film was incorporated as a gate electrode in a hybrid suspended gate field effect transistor (HSGFET) structure to examine its suitability in FET-type sensors. The films were characterized using Rutherford backscattering spectroscopy, X-ray diffraction analysis, and scanning electron microscopy to determine their composition, phase, and surface morphology. The results suggest that iridium-oxide film is a promising material for the realization of a FET-based NO/sub 2/ sensor.