Creation of ultrafine-grained surfaces by large strain extrusion machining (LSEM)

Large strain extrusion machining (LSEM) is examined as a route for achieving controlled microstructure refinement at freshly generated surfaces in a single pass of the machining tool. It is shown that the extrusion ratio λ of LSEM, which is the ratio of the thickness of the chip to that of the preset depth of cut, controls the extent of the ultrafine-grained (UFG) zone. Microstructure analysis was performed using orientation imaging microscopy (OIM) and mechanical testing using nanoindentation was used to characterize the UFG microstructure beneath the freshly generated surfaces. The mechanics of deformation in LSEM were examined using infrared thermography and modeled. The present research demonstrates LSEM as a novel platform for tailoring surficial microstructures and controlling their spatial extents in fabricated components.     

Like-minded communities: bringing the familiarity and similarity together

Community detection in social networks is a well-studied problem. A community in social network is commonly defined as a group of people whose interactions within the group are more than outside the group. It is believed that people’s behavior can be linked to the behavior of their social neighborhood. While shared characteristics of communities have been used to validate the communities found, to the best of authors’ knowledge, it is not demonstrated in the literature that communities found using social interaction data are like-minded, i.e., they behave similarly in terms of their interest in items (e.g., movie, products). In this paper, we experimentally demonstrate, on a social networking movie rating dataset, that people who are interested in an item are socially better connected than the overall graph. Motivated by this fact, we propose a method for finding communities wherein like-mindedness is an explicit objective. We find small tight groups with many shared interests using a frequent item set mining approach and use these as building blocks for the core of these like-minded communities. We show that these communities have higher similarity in their interests compared to communities found using only the interaction information. We also compare our method against a baseline where the weight of edges are defined based on similarity in interests between nodes and show that our approach achieves far higher level of like-mindedness amongst the communities compared to this baseline as well.     

Roller bearing lubrication with shear thinning lubricants

Lubricants are continually being subjected to increasing mechanical shearing forces. Consequently the interest in materials of variable viscosity has increased. The problem of a roller bearing lubricated by a Casson fluid, which is a shear thinning lubricant, has been investigated; the non-sliding steady state and the squeezed film situation have been studied. At high speeds the load capacity of the Casson fluid is equal to that for a Newtonian fluid of the same viscosity. At low speeds the difference is significant; the Casson fluid film has a load capacity even if the velocities of both cylinders in contact are zero.     

Sequential polymer dosing for effective dewatering of ATAD sludges

Dewatering problems associated with the sludge from autothermal thermophilic aerobic digestion (ATAD) of sludge, result in large chemical conditioning costs for effective dewatering. A variety of chemical conditioners were used to improve dewatering, but none of them were able to dewater the sludge as desired at acceptable conditioning doses. It was found that during the digestion process, chemical precipitation of divalent cations occurred. Some of the ATAD sludge colloids were found to have a positive zeta potential and these were thought to be the precipitated divalent cations. Sequential polymer dosing using either iron or cationic polymer, followed by anionic polymer, was found to improve dewatering. The use of anionic polymer is essential and allows the use of smaller amounts of iron or cationic polymer for effective dewatering. The use of the less expensive anionic polymer along with cationic polymers has the potential to make the use of the ATAD process more economical.     

Examining Impacts of Spatial Correlation in Forward Error Correction Code

ABSTRACT

The utilization of Multiple Input Multiple Output – Orthogonal Frequency Division Multiplexing (MIMO-OFDM) has rapidly gained popularity because of its improved performance capabilities in terms of enhanced spatial diversity gain, reliability as well as the spatial multiplexing Gain. This paper discusses the effect of spatial correlation in Forward Error Correction of MIMO-OFDM system. Here, the four error correction codes, namely, Convolutional Code (CC), Low-Density Parity Check (LDPC-CC), and Reed-Solomon code (RSC-CC) is validated under three channel models, namely, Rayleigh, Rician and Additive White Gaussian Noise (AWGN). The analysis is performed using four modulation schemes such as Quadrature Phase Shift Keying (QPSK), Binary Phase Shift Keying (BPSK), Quadrature Amplitude Modulation (QAM)-16, and QAM-64. It is performed under three antenna configurations like 2 × 2, 2 × 4, and 4 × 4. Moreover, the Peak Signal to Noise Ratio (PSNR) is exploited to identify the image transmission, as well as the Bit Error Rate (BER), is exploited to identify the data transmission. In experimental results, the Turbo-CC displays better performance.     

Development of MIMO–OFDM system and forward error correction techniques since 2000s

The multi-input multi-output–orthogonal frequency division multiplexing (MIMO–OFDM) system serves as one of the most promising techniques that support high data rate and high performance in diverse fading channel conditions. The paper presents an overview of MIMO–OFDM wireless technology, covering advances in physical-layer design, various space–time codes, space–frequency codes and efficient concatenated forward error correction techniques, along with interleaving to yield reduced bit error rate performance (BER). Further, the paper presents the evolution of various performance metrics that are reported since the 2000s in the literature. The evolution outcome is examined using a quadratic nonlinear fitting function to assess the interesting performance metrics. Since BER versus SNR analysis is found as the interesting performance study of the MIMO–OFDM system, the current status of the achieved BER under varying SNR is reviewed and presented.     

Analysis of intermittent timing fault vulnerability

Continuous scaling of transistor feature size rapidly increases the effect of intermittent faults. These faults manifest as timing violations due to the combined effects of process variation, circuit wear-out, and variation in environmental conditions. In this paper, we combine all critical sources of intermittent faults in a comprehensive framework. Our experiments with the MIPS-789 processor reveal that at the 22nm technology node, the combined effect of all the factors can degrade the delay by 2.5X. Such gross delay degradation extending more than two cycles can render many recently proposed time borrowing techniques ineffective. We analyze three architectural techniques to mitigate intermittent faults and evaluate them using full system architectural simulation.     

Automatically generating taxonomy for grouping app reviews — a study of three apps

Software Quality Journal - App reviews often reflect end-users’ requests, issues or suggestions for supporting app maintenance and evolution. Hence, researchers have evaluated several...     

N-type silk fibroin/TiO2 nanocomposite transparent films: electrical and optical properties

This paper highlights the effect of different concentrations of titanium dioxide (TiO₂) nanoparticles on the electrical and optical properties of silk fibroin (SF). TiO₂ based SF nanocomposite films were prepared using the solvent casting method. Uniform dispersion and agglomeration of nanoparticles, in nanocomposite films, were observed by field emission SEM. The conductivity of pure SF and nanocomposite films was determined by a four-point probe and the TiO₂ nanoparticles were found to bring high conductivity to the nanocomposite films. Dielectric strength improved with the addition of nanoparticles to the SF matrix. Dielectric constant and capacitance of the pure SF and nanocomposite films were measured using an LCR meter, which showed a 10-fold enhancement on the addition of nanoparticles in SF. A very unusual property, i.e. negative resistance, was observed during LCR meter analysis for the nanocomposite films for a particular range of frequency (200–550 kHz), voltage (1 V) and current (0.5–1.5 μA). TiO₂ nanoparticles changed the semiconducting behavior of the SF films from p-type to n-type as measured by the Hall effect experiment. The optical properties of pure SF and nanocomposite films were measured using a UV–visible spectrophotometer. The increased concentration of nanoparticles in the SF has effectively enhanced the absorbing coefficient, refractive index and percentage transmittance and reduced the bandgap energy. These SF/TiO₂ nanocomposite films have shown the potential to be used as dielectric and high refractive index material for optoelectronics applications. © 2021 Society of Industrial Chemistry.     

Cetyl Trimethyl Ammonium Bromide Modified Montmorillonite-Doped Tasar Silk Fibroin/Polyvinyl Alcohol Blend 3D Nanowebs for Tissue Engineering Applications

Cetyl trimethyl ammonium bromide (CTAB) modified montmorillonite (MMT) clay (CTAB-MT) doped, tasar silk fibroin-polyvinyl alcohol blend-based 3D nanowebs are generated through electrospinning technique. The morphological analysis reveals the formation of interlinked 3D nanoweb-like architecture and high surface roughness through scanning electron microscopy (SEM) and atomic force microscopy, respectively. The existence of CTAB-MT in nanowebs is confirmed by Fourier transform infrared and complete exfoliation of clay in the polymer blend matrix along with the altered crystallinity of samples is indicated in X-ray diffraction. The incorporation of CTAB-MT clay has shown the enhancement of thermal and mechanical properties of nanoweb samples while the water uptake capacity is reduced and enzymatic biodegradability is found to slow down. The samples present excellent biocompatibility with no cytotoxicity in the Alamar blue assay and high attachment as well as spreading of L929 fibroblast cells covering the entire surface as observed in SEM. The CTAB-MT clay has imparted the samples with good antimicrobial activity against E. coli and S. aureus bacterial strains. The aforementioned properties of these CTAB-MT clay doped 3D nanowebs direct toward their suitability as a potential candidate for tissue engineering applications in the biomedical field.