Thermal analysis of dry sleeve bearings — a comparison between analytical, numerical (finite element) and experimental results

Thermal analysis of a plastic sleeve bearing in dry operation was investigated experimentally by Floquet et al. [Trans. ASME, J. Lubr. Technol. 99 (1977) 277]. For a comparison with the experimental results, Kennedy [Trans. ASME, J. Tribol. 103 (1981) 90] developed a numerical approach using the finite element method (FEM) that included the development of finite element equations for the case of a moving body heat conduction. In this investigation, both the experimental results of Floquet [Docteur-Ingenier thesis, Université Claude Bernard, Lyon, 1978] and the numerical results of Kennedy were compared with the results of the analytical method developed using the classical heat source method introduced by Jaeger [Proc. Roy. Soc. NSW 76 (1942) 203] and the heat partition principles of Blok [Proc. Inst. Mech. Engrs. 2 (1937) 222], which involves matching of the temperatures on either side of the contact interface. The non-uniform distribution of heat partition (as one body is stationary and the other moving) along the interface is addressed by matching the temperatures at the interface between the stationary and the moving bodies in relative sliding contact using the functional analysis approach originally introduced by Chao and Trigger [Trans. ASME 72 (1955) 1107]. The analytical results are found to be in excellent agreement with both the experimental and the numerical results.     

A phenomenological model of polishing of silicon with diamond abrasive

A phenomenological model of polishing hemispherical silicon asperities with spherical diamond abrasives is presented. Removal of the asperity material is quantitatively determined by a removal rate constant K. It is based on our molecular dynamics (MD) simulation studies considering the probability of removal of asperity atoms by an abrasive. The dependence of the removal rate constant K on the diameter and velocity of abrasives, number of asperities and abrasives per unit area, and cutting depth has been investigated. The rate constant K is found to be insensitive to the density of asperities, but linearly dependent on the density of abrasives.     

Benzofuran–Chalcone Hybrids as Potential Multifunctional Agents against Alzheimer’s Disease: Synthesis and in vivo Studies with Transgenic Caenorhabditis elegans

In the search for effective multifunctional agents for the treatment of Alzheimer’s disease (AD), a series of novel hybrids incorporating benzofuran and chalcone fragments were designed and synthesized. These hybrids were screened by using a transgenic Caenorhabditis elegans model that expresses the human β‐amyloid (Aβ) peptide. Among the hybrids investigated, (E)‐3‐(7‐methyl‐2‐(4‐methylbenzoyl)benzofuran‐5‐yl)‐1‐phenylprop‐2‐en‐1‐one ( 4 f ), (E)‐3‐(2‐benzoyl‐7‐methylbenzofuran‐5‐yl)‐1‐phenylprop‐2‐en‐1‐one ( 4 i ), and (E)‐3‐(2‐benzoyl‐7‐methylbenzofuran‐5‐yl)‐1‐(thiophen‐2‐yl)prop‐2‐en‐1‐one ( 4 m ) significantly decreased Aβ aggregation and increased acetylcholine (ACh) levels along with the overall availability of ACh at the synaptic junction. These compounds were also found to decrease acetylcholinesterase (AChE) levels, reduce oxidative stress in the worms, lower lipid content, and to provide protection against chemically induced cholinergic neurodegeneration. Overall, the multifunctional effects of these hybrids qualify them as potential drug leads for further development in AD therapy.     

Radiative transfer based scaling of LAI retrievals from reflectance data of different resolutions

The problem of how the scale, or spatial resolution, of reflectance data impacts retrievals of vegetation leaf area index (LAI) is addressed in this article. We define the goal of scaling as the process by which it is established that LAI values derived from coarse resolution sensor data equal the arithmetic average of values derived independently from fine resolution sensor data. The increasing probability of land cover mixtures with decreasing resolution is defined as heterogeneity, which is a key concept in scaling studies. The effect of pixel heterogeneity on spectral reflectances and LAI retrievals is investigated with 1-km Advanced Very High Resolution Radiometer (AVHRR) data aggregated to different coarse spatial resolutions. It is shown that LAI retrieval errors at coarse resolution are inversely related to the proportion of the dominant land cover in such pixel. Further, large errors in LAI retrievals are incurred when forests are minority biomes in non-forest pixels compared to when forest biomes are mixed with one another, and vice versa. A physically based scaling with explicit spatial resolution-dependent radiative transfer formulation is developed. The successful application of this theory to scaling LAI retrievals from AVHRR data of different resolutions is demonstrated. These principles underlie our approach to the production and validation of LAI product from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multi-angle Imaging Spectroradiometer (MISR) aboard the TERRA platform.     

Ultrawideband Printed Elliptical Monopole Antennas

Parametric study of ultrawideband printed elliptical monopole antennas have been presented. Design curve for the length of the feed transmission line for various lower band edge frequencies has been generated. Variation of bandwidth with ellipticity ratio of these configurations has also been studied. Experiments have been performed to measure bandwidth and radiation patterns of these configurations, which tally well with simulated results. The elliptical configuration with ellipticity ratio of 1.1 gives ultrawide impedance bandwidth ratio of 12.4:1 as compared to 10.2:1 of the circular monopole antenna. This antenna introduces minimum ringing and distortion/dispersion of the pulse in time domain     

Wear of silicon carbide in high speed sliding

Attritious wear of silicon carbide rubbing against a cobalt base superalloy at high speed was studied using a scanning electron microscope (SEM) and an Auger electron spectroscope (AES). The SEM study of the wear area on the silicon carbide grain showed it to be very smooth. The AES study of the groove-like marking generated by a silicon carbide grain showed a heavy concentration of carbon in areas where submicron wear debris was present. No indication of chemical reaction of the abrasive with the work material was evident. Instead, it appears that the surface atoms on the abrasive are removed preferentially, layer by layer, by oxidation under high temperature and a favorably directed shear stress.     

Network Partitioning Recovery Mechanisms in WSANs: a Survey

Wireless sensor and actor networks (WSANs) are more promising and most addressing research field in the area of wireless sensor networks in recent scenario. It composed of possibly a large number of tiny, autonomous sensor devices and resources rich actor nodes equipped with wireless communication and computation capabilities. Actors collect sensors’ information and respond collaboratively to achieve an application specific mission. Since actors have to coordinate their operation, a strongly connected inter-actor network would be required at all the time in the network. Actor nodes may fail for many reasons (i.e. due of battery exhaustion or hardware failure due to hash environment etc.) and failures may convert connected network into disjoint networks. This can hinder sometimes not only the performance of network but also degrade the usefulness and effectiveness of the network. Thus, having a partitioning detection and connectivity restoration procedure at the time of failure occurs in the network is crucial for WSANs. In this paper, we review the present network partitioning recovery approaches and provide an overall view of this study by summarizing previous achievements.     

Influence of metal particles on the reduction properties of ceria-based materials studied by TPR

Temperature programmed reduction (TPR) investigations on ceria-based catalytic materials are presented. Pure ceria shows two major reduction regions around 790 K and 1100 K due to surface capping oxygen ions and bulk oxygen ions. The extent of reduction in the low temperature region depends greatly on the surface area of the sample. The remnant reduction features that appear below 700 K are ascribed to O²⁻ ions located at various low coordination sites on the oxide crystallites. The substitution of ZrO₂ (40–60%) in CeO₂ lattice decreases the overall reduction temperature of high surface area samples. Metal particles supported on low surface area CeO₂-ZrO₂ solid solutions induce bulk reduction of the support at low temperatures to a great extent. These observations provide a clue that the CeO₂-based oxide supports, irrespective of their surface area, can perform as good oxygen exchangers in the presence of metal particles, contributing indirectly to the overall catalytic activity.     

Simulation of dynamic crack growth using the generalized interpolation material point (GIMP) method

Dynamic crack growth is simulated by implementing a cohesive zone model in the generalized interpolation material point (GIMP) method. Multiple velocity fields are used in GIMP to enable handling of discrete discontinuity on either side of the interface. Multilevel refinement is adopted in the region around the crack-tip to resolve higher strain gradients. Numerical simulations of crack growth in a homogeneous elastic solid under mode-II plane strain conditions are conducted with the crack propagating along a weak interface. A parametric study is conducted with respect to varying impact speeds ranging from 5 m/s to 60 m/s and cohesive strengths from 4 to 35 MPa. Numerical results are compared qualitatively with the dynamic fracture experiments of Rosakis et al. [(1999) Science 284:1337–1340]. The simulations are capable of handling crack growth with crack-tip velocities in both sub-Rayleigh and intersonic regimes. Crack initiation and propagation are the natural outcome of the simulations incorporating the cohesive zone model. For various impact speeds, the sustained crack-tip velocity falls either in the sub-Rayleigh regime or in the region between (c _S is the shear wave speed) and c _D (c _D is the dilatational wave speed) of the bulk material. The Burridge–Andrews mechanism for transition of the crack-tip velocity from sub-Rayleigh to intersonic speed of the bulk material is observed for impact speeds ranging from 9.5 to 60 m/s (for normal and shear cohesive strengths of 24 MPa). Within the intersonic regime, sustained crack-tip velocities between 1.66 c _S (or 0.82 c _D ) and 1.94 c _S (or 0.95 c _D ) were obtained. For the cases simulated in this work, within the stable intersonic regime, the lowest intersonic crack-tip velocity obtained was 1.66 c _S (or 0.82 c _D ).     

On the machining of fiber reinforced plastic (FRP) composite laminates

With the increasing use of fiber reinforced plastic (FRP) composites outside the defense, space and aerospace industries, namely, civilian industries, machining of these materials is assuming a significant role. Unit cost rather than solely performance at any cost will be the consideration for the implementation of FRP composites to consumer industries. The current knowledge of machining FRP composites, unfortunately, is inadequate for its optimum utilization in many applications. This paper presents some observations made on the orthogonal machining of unidirectional carbon fiber reinforced plastic (UD-CFRP) laminates with different fiber orientations. Iosipescu shear test was adopted to evaluate the inplane shear strength of varied fiber angle test specimens. A model for predicting the cutting forces and the dependence of cutting direction on machinability requirements is presented.