Effects of random particle dispersion and size on the indentation behavior of SiC particle reinforced metal matrix composites

This study investigates the effects of particle size, volume fraction, random dispersion and local concentration underneath a spherical indenter on the indentation response of particle reinforced metal matrix Al 1080/SiC composites. The ceramic particles in certain sizes and volume fractions were randomly distributed through the composite structure in order to achieve a similar structure to an actual microstructure as possible. The particle size and volume fraction affected considerably indentation depths and deformed indentation surface profiles. The indentation depth increases with increasing particle size, but decreases with increasing particle volume fraction. The experimental indentation depths were in agreement with numerical indentation depths in case the local particle concentration effect is considered. The local particle concentration plays an important role on the peak indentation depth. For small particle sizes and large volume fractions the random particle distribution affects the deformed surface profiles as well as the indentation depths. However, its effect is minor on residual stress and strain distributions rather than levels in the indentation region.     

Synthetic Aperture Hitchhiker Imaging

We introduce a novel synthetic-aperture imaging method for radar systems that relies on sources of opportunity. We consider receivers that fly along arbitrary, but known, flight trajectories and develop a spatio-temporal correlation-based filtered-backprojection-type image reconstruction method. The method involves first correlating the measurements from two different receiver locations. This leads to a forward model where the radiance of the target scene is projected onto the intersection of certain hyperboloids with the surface topography. We next use microlocal techniques to develop a filtered-backprojection-type inversion method to recover the scene radiance. The method is applicable to both stationary and mobile, and cooperative and noncooperative sources of opportunity. Additionally, it is applicable to nonideal imaging scenarios such as those involving arbitrary flight trajectories, and has the desirable property of preserving the visible edges of the scene radiance. We present an analysis of the computational complexity of the image reconstruction method and demonstrate its performance in numerical simulations for single and multiple transmitters of opportunity.     

Extrudate swell behavior of glass fiber filled polyamide 6

This paper discusses the extrudate swell behavior of glass-filled polyamide 6. The key features of the experiments were the facility to extrude directly into a density matched oil kept at extrusion temperature and thus, the ability to measure the diameter of the extrudate of the glass-filled polyamide immediately upon exit from the die, without the extrudate contacting air and as a function of time in a chamber under isothermal and neutrally-buoyant conditions. The concentration and orientation of the fibers of the extrudates were also studied using X-ray radiography in a post-mortem fashion. A skin/core morphology, where uniaxially aligned fibers constitute the skin zone and the core contains a reduced concentration of fibers, was observed.     

The effects of heating rate on the dose response characteristics of TLD-200, TLD-300 and TLD-400

In the given study; the effects of heating rates on the dose response characteristics of CaF₂:Dy (TLD-200), CaF₂:Tm (TLD-300) and CaF₂:Mn (TLD-400) crystals have been investigated using the dose dependence curve and dose response function f(D). It was observed from the dose response functions that the linearity and behaviour of the TL glow peaks of TLD-200 and TLD-400 are affected, but the TLD-300 is not affected from the heating rate.     

Determination of surface energies and acidity‐basicity numbers of protonated and deprotonated forms of poly(sulfonic acid diphenyl aniline) by inverse gas chromatography

Protonated form of poly(sulfonic acid diphenyl aniline) (p‐PSDA) was synthesized through oxidative chemical polymerization of sodium salt of diphenylamino‐4‐sulfonic acid in hydrochloric acid and then, its deprotonated form (PSDA) was obtained by neutralization with aqueous ammonium hydroxide solution. The samples were characterized by thermal analysis and Fourier Transform Infrared, Ultraviolet‐visible, ¹H‐NMR spectroscopy techniques. Their dispersive surface energies as well as surface acidity and basicity were determined by inverse gas chromatography at temperatures between 313 and 353 K. The dispersive surface energy of p‐PSDA was found to be considerably lower but it increased with temperature while that of PSDA was close to those of conventional polymers and decreased slightly with temperature. According to the Schreiber's procedure, the surfaces of p‐PSDA and PSDA were found to be acidic and amphoteric, respectively. It was observed from the electron microscope images p‐PSDA chains can form self‐organized circular polydisperse micro‐sized aggregates in aqueous solutions while PSDA cannot self‐organize to form individual aggregates. POLYM. ENG. SCI., 55:1246–1254, 2015. © 2015 Society of Plastics Engineers     

RELIEF-MM: effective modality weighting for multimedia information retrieval

Fusing multimodal information in multimedia data usually improves the retrieval performance. One of the major issues in multimodal fusion is how to determine the best modalities. To combine the modalities more effectively, we propose a RELIEF-based modality weighting approach, named as RELIEF-MM. The original RELIEF algorithm is extended for weaknesses in several major issues: class-specific feature selection, complexities with multi-labeled data and noise, handling unbalanced datasets, and using the algorithm with classifier predictions. RELIEF-MM employs an improved weight estimation function, which exploits the representation and reliability capabilities of modalities, as well as the discrimination capability, without any increase in the computational complexity. The comprehensive experiments conducted on TRECVID 2007, TRECVID 2008 and CCV datasets validate RELIEF-MM as an efficient, accurate and robust way of modality weighting for multimedia data.     

Energy constrained multi-robot sensor-based coverage path planning using capacitated arc routing approach

Multi-robot sensor-based coverage path planning requires every point given in the workspace has to be covered at least by a sensor of a robot in the robot team. In this study, a novel algorithm was proposed for the sensor-based coverage of narrow environments by considering energy capacities of the robots. For this purpose, the environment was modeled by a Generalized Voronoi diagram-based graph to guarantee complete sensor-based coverage. Then, depending on the required arc set, a complete coverage route was created by using the Chinese Postman Problem or the Rural Postman Problem, and this route was partitioned among robots by considering energy capacities. Route partitioning was realized by modifying the Ulusoy partitioning algorithm which has polynomial complexity. This modification handles two different energy consumptions of mobile robots during sensor-based coverage, which was not considered before. The developed algorithm was coded in C++ and implemented on P3-DX mobile robots both in laboratory and in MobileSim simulation environments. It was shown that the convenient routes for energy constrained multi-robots could be generated by using the proposed algorithm in less than 1 s.     

Biosorption of copper(II) by Marrubium globosum subsp. globosum leaves powder: effect of chemical pretreatment

The study was aimed at determining the effect of chemical pretreatment on copper(II) biosorption by Marrubium globosum subsp. globosum leaves. The uptake capacity of the biomass was increased by chemical pretreatment when compared with the raw biomass. The results of biosorption experiments, carried out at the conditions of 50 mg l(-1) initial metal concentration and pH 5.5, showed that pretreating the biomass with alkali solutions (laundry detergent, sodium hydroxide and sodium bicarbonate, 0.5 M) improved the biosorption capacity of biomass (45.90, 45.78 and 43.91%, respectively) compared with raw biomass. Pretreatment with sulfuric and nitric acid solutions, 0.5 M, increased the biosorption capacity of biomass by 11.82 and 10.18%, respectively, while there was no considerable change in the biosorption capacity of biomass (0.35%) after pretreatment with formic acid solution, 0.5 M. Furthermore, sodium chloride and calcium chloride, 0.5 M, pretreatments resulted in the improvement in biosorption capacity of biomass (31.38 and 26.69%, respectively). FT-IR analysis revealed that hydroxyl and carboxyl functional groups were mainly responsible for copper(II) biosorption.