Development of a Continuous Equal Channel Angular Extrusion (ECAE) Process

Equal Channel Angular Extrusion (ECAE) has great potential for developing ultrafine grain structure consisting of homogeneous and equiaxed grains dominated by high angle grain boundaries. In addition, the ECAE-processed specimens retain their original cross-section, providing capabilities of multi-passing. However, the process is discontinuous as the length of the billet is limited due to potential buckling of the extruding ram. This problem provides an opportunity of making the process continuous. The objectives of this study were to examine the feasibility of a process obtained by combining ECAE and Equal Channel Angular Drawing (ECAD), evaluate the potential of the combined process for continuous processing of sheet metal, and to analyze the mechanical response of sheet metal subjected to the ECAE and ECAD techniques using numerical study. Numerical analyses of ECAE and ECAD were performed using the commercial FE analysis package ABAQUS/explicit. Experimental data and analytical models available in literature were used to validate the numerical results. Parametric studies on the effects of drawing angle, and sheet thickness to die radius ratio (t/r), on reduction in thickness, strain uniformity and resulting microstructure are presented. Numerical results indicate that ECAD through a closed channel should be preferred over conventional drawing (open channel) operation as reduction in thickness is decreased by 2-3% after a single pass. In the experimental study, it was observed that during ECAD, the reduction in thickness increases by 2.5-3.5% per pass. Also, a higher reduction is observed in route C compared to route A. Use of sharper die corners (higher t/r ratios) and smaller channel intersection angles tend to increase this thickness reduction, and results in an increase in hardness i.e., results in strengthening. ECAD most likely results in a non-uniform microstructure with low fraction of high angle grain boundaries. In addition, for a given pass, the average hardness of the ECADprocessed samples is approximately half that of ECAE-processed samples. This suggests that ECAD alone may not be commercially viable. However, a significant improvement in minimizing reduction in thickness is achieved by providing a little gap between the sheet metal and support plates. From the numerical analyses, the proposed continuous process appears to be effective in retaining continuity of the drawing operation, minimizing the percent reduction in thickness and imparting higher plastic strains. It is believed that an experimental study of the process will reveal some more promising information

Morphological study of plantaris tendon and its surgical perspectives

Introduction: Plantaris tendon is a long, slender tendon having the property of stretching and can be converted into a thin sheath when stretched. The plantaris tendon has been used in various tendon repairs and also membrane created from plantaris tendon may be wrapped around tendon anastomosis. Materials and methods: In this study of 50 embalmed lower limbs, various parameters of the plantaris tendon i.e. length, breadth, thickness were measured. Data analyzed as numbers and mean value. The unpaired t test was used to study the significance of the differences in male and females and right and left plantaris tendon. Results: The total 25 adult cadavers studied of which 23 were males and 2 were females, out of these there were 25 left and 25 right limbs. It has been observed that the mean tendon length was more in male cadavers compared with female cadavers INTRODUCTION The origin of plantaris muscle is from the lateral supracondylar line of the popliteal surface of the femur just superior and medial to the lateral head of the gastrocnemius muscle as well as from the oblique popliteal ligament in the posterior aspect of the knee. 1,2,3 The muscle belly ranges from 7-13 cm long varying in its size and form when present, and the mean length of the tendon from its proximal 4,5 insertion to its distal insertion is 43.25 cm. The agenesis of the plantaris muscle may affect the Perspectives in Medical Research | September - December 2014 | Vol 2 | Issue 3 (33.38±7.430, 30.73±.957) whereas mean tendon breadth was slightly more in female cadavers as compa r ed with ma l e s (. 3085±.14115, .3125±.08539). The dimension of left side tendon in length (32.97±7.209, 33.36±7.256), breadth (.2940±.11962, .3236±.15332) and thickness (.056±.0369, .080±.0951) was slightly more on the left side compared with the right side. No statistical significance was obtained in the morphology of the tendon in the context of right and left side as well as male and female. Conclusion: As the plantaris tendon is a tensile and stretchable structure, it is used as a strong reinforcement membrane and can be useful for surgeons performing various reconstructive surgeries. In such scenario study of morphological characteristics of the tendon is of utmost importanc

Next-Generation Self-Organizing Communications Networks: Synergistic Application of Machine Learning and User-Centric Technologies

The telecommunications industry is going through a metamorphic journey where the 5G and 6G technologies will be deeply rooted in the society forever altering how people access and use information. In support of this transformation, this dissertation proposes a fundamental paradigm shift in the design, performance assessment, and optimization of wireless communications networks developing the next-generation self-organizing communications networks with the synergistic application of machine learning and user-centric technologies. This dissertation gives an overview of the concept of self-organizing networks (SONs), provides insight into the “hot” technology of machine learning (ML), and offers an intuitive understanding of the user-centric (UC) technology that form the foundation of the research initiatives conceived, implemented, and validated in this dissertation. A three-layered approach based on the synergistic application of SON, ML, and UC technologies is applied for anomaly detection, load balancing and capacity optimization, and radio access network-based notification area (RNA) configuration and management. In the first research initiative, ML is applied to learn and predict a UC key performance indicator that imports the effect of the end-user perception of the quality of service to achieve end-to-end service assurance and proactively detect dysfunctional network nodes enabling automatic detection and remediation of failing network nodes to mitigate network degradation in self-healing SON systems. In the second research initiative a UC and ML based methodology called US-OCSP (i.e. user-specific optimal capacity and shortest path) is developed that can be integrated with an auto or personal navigation system to provide routing that avoids congested network traffic and effects resource optimization enabling load balancing and capacity optimization in self-optimizing SON systems. In the third research initiative, a UC and ML-embedded clustering mechanism is developed for dynamic configuration and management of RAN-based notification areas (i.e. RAN-based paging areas) that can help achieve improved signaling and paging load to attain reduced latency and improved network capacity, while lowering power consumption supporting emerging 5G/6G applications and services that generate an extensive amount of random aperiodic and keep-alive data traffic in self-configuring SON systems. Finally, a high-level framework consisting of several core building blocks is provided to support UC and ML-infused network standardization that the network operators can adopt to shape the network of tomorrow

epr is transcribed from a sigma(D) promoter and is involved in swarming of Bacillus subtilis

Epr is a minor extracellular protease secreted by Bacillus subtilis 168. In this study, we show that epr is transcribed by E sigma (D), the RNA polymerase associated with transcription of genes involved in chemotaxis and motility. Disruption of epr abolished swarming of Bacillus subtilis, suggesting its involvement in motility

The carboxy terminal domain of Epr, a minor extracellular serine protease, is essential for the swarming motility of Bacillus subtilis 168

In this study we have investigated the role of Epr, a minor extracellular serine protease, in the swarming motility of Bacillus subtilis 168. We identified that the protease activity of Epr was dispensable for swarming. Since the protease activity of Epr was confined to its N-terminal domain, we hypothesized instead that its C-terminal domain (CTD) could be critical for swarming. Our study showed that not only the expression of Epr-CTD was necessary, but also its secretion was crucial for the swarming motility of B. subtilis 168