Energy Cooperation with Sleep Mechanism in Renewable Energy Assisted Cellular HetNets

The emerging fifth generation (5G) and beyond radio access networks are expected to be extremely dense and heterogeneous as compared to the current networks, involving a large number of different classes of base stations (BSs), namely macro, micro, femto and pico BSs. Among several performance requirements 5G and beyond systems aim to achieve, energy efficiency is one of the crucial requirements. In order to achieve energy-efficient design in dense heterogeneous 5G networks, various approaches in terms of resource allocation, off-loading techniques, hardware solutions and energy harvesting are being considered. In this regard, this paper develops an energy usage optimization framework in a cellular heterogeneous network (HetNet) consisting of a central macro-BS and a number of micro-BSs, equipped with renewable energy sources (RESs) such as solar panels and wind turbines. The proposed framework incorporates an energy cooperation mechanism along with a sleep mechanism (BS ON/OFF switching), in which the BSs having lean traffic are put into a sleep mode and their traffic load gets shared by the central BS. The surplus harvested energy from RESs of the sleeping BSs can then be sold back to the grid. An optimization problem for maximizing the utilization of RES and minimizing the usage of the traditional sources, such as utility and generator, is formulated and this mixed integer non-linear programming problem is solved through an interior point method. The presented results for various HetNet sizes demonstrate the significant savings in the energy cost with the proposed RES-enabled HetNet sleep mechanism model over the conventional approaches.

     

Fabrication and characterization of high extinction ratio transmission polarizers

In this paper, large area nanoimprint lithography on a trilayer resist stack for the nanofabrication of light polarizer was successfully carried out. Large area gratings with 10 mm × 10 mm area and 300 nm pitch were fabricated. The measurement results indicate that our polarizers exhibit extraordinarily high extinction ratio. It is observed that the extinction ratio is dependent on the wavelength. Theoretical simulation also agreed with our measured results very well. The poor reflective polarization property measured in this work was discussed.     

Failure analysis of an aero engine ball bearing

An aero engine failed due to the misalignment of the ball bearing fitted on the main shaft of the engine. The aero engine incorporates two independent compressors: a six-stage axial flow low-pressure compressor and a nine-stage axial flow high-pressure compressor. The bearing under consideration is a high-pressure-location bearing and is fitted at the rear of the nine-stage compressor. It was supposed to operate for at least 5000 h but failed catastrophically after 1300 h of operation and rendered the engine unserviceable. Unusually high stresses caused by misalignment and uneven axial loading resulted in the generation of fatigue crack(s) in the inner race. When the crack reached the critical size, the collar of the race fractured, causing subsequent damage. The cage also failed due to excessive stresses in the axial direction, and its material was smeared on the steel balls and the outer race.     

Effective polarization control of metallic planar chiral metamaterials with complementary rosette pattern fabricated by nanoimprint lithography

In this work the interaction between the metallic planar chiral metamaterials (PCM) with complementary rosette pattern and the incident electromagnetic wave was studied theoretically using finite difference time domain (FDTD) method. Both the evolution of the electric field distribution as the electromagnetic wave propagated through this PCM and the optic activity in near infrared range were investigated. By utilizing nanoimprint lithography technology, we successfully fabricated metallic PCM with complementary rosette pattern with period of 600 nm. The measurement results of polarization rotation capability indicate that by easily tuning the depth of the imprint depth in SU-8, the optical activity of this metallic PCM could be effectively controlled for specific wavelength.     

Coverage Differentiation Based Adaptive Tx-Power for Congestion and Awareness Control in VANETs

The use of Information and Communication Technology (ICT) as a copilot for the drivers has a potential to improve traffic safety and efficiency. A key challenge in integrating ICT in vehicular networks is to provide the mechanisms for the delivery of safety messages called beacons. In particular, finding the trade-off between providing sufficient coverage and controlling channel congestion remains the focus in the stipulated amendments for safety message transmissions. In this paper, we handle this trade-off by proposing a Multi-metric Power Control (MPC) approach, which uses application requirements and channel states to determine a transmit power for safety messages. The MPC gives a best-effort approach to satisfy the coverage range requirement of a message as specified by the application. Moreover, the concept distinguishes among message types to provide coverage differentiation. We show that the best-effort approach of providing coverage for different messages can control congestion and as a result improve awareness by minimizing beacon collisions. The performance analysis of MPC using discrete event simulation confirms its practicality.     

MRT letter: Visual attention driven framework for hysteroscopy video abstraction

Diagnostic hysteroscopy is a popular method for investigating the regions in the female reproductive system. The videos generated by hysteroscopy sessions of patients are recurrently archived in medical libraries. Gynecologists often need to browse these libraries in search of similar cases or for reviewing old videos of a patient. Diagnostic hysteroscopy videos contain a lot of information with abundant redundancy. Key frame extraction‐based video summarization can be used to reduce this huge amount of data. Moreover, key frames can be used for browsing and indexing of hysteroscopy videos. In this article, a domain specific visual attention driven framework for summarization of hysteroscopy videos is proposed. The visual attention model is materialized by computing saliency based on color, texture, and motion. The experimental results, in comparison with other techniques, demonstrate the efficacy of the proposed framework. Microsc. Res. Tech. 76:559–563, 2013. © 2013 Wiley Periodicals, Inc.     

Role of extruded texture on fatigue crack growth in a high strength aluminum alloy thick-walled cylinder

In present study, as a basic step for modeling the fatigue behavior of an extruded Al alloy cylinder, the fatigue crack growth data of the alloy was collected in two orientations. Microstructural analysis revealed that the material had recrystallized grains and clusters of constituent particles aligned in the direction of extrusion. Fatigue life of the samples revealed a shorter fatigue life representing a higher fatigue crack growth rate in transverse direction. The Paris constants C and m were found to be 4 × 10⁻¹¹ and 3.4 for the transverse orientation. The same constants were found to be 2 × 10⁻¹⁰ and 2.6 for the longitudinal direction. Post fracture analysis revealed that the topographical appearance of the fractured surfaces in two orientations was different. The mechanism of crack growth was the formation of striations. The present study revealed that the texture of the constituent particles created during extrusion process has a pronounced effect on the crack growth rate in two orientations. This paper was recommended for publication in revised form by Associate Editor Chongdu Cho Dr. M. A. Malik is a Professor in Department of Mechanical Engineering, College of Electrical and Mechanical Engineering, National University of Sciences and Technology, Rawalpindi, Pakistan. He graduated from Georgia Tech, USA with MS and PhD degrees in nuclear engineering. He has considerable working experience in nuclear research industry. He specializes in impurity transport and modeling and simulation techniques. His current research interests include structural analysis, reliability of materials and modeling and simulation of dynamic engineering systems. He has over 85 publications to his credit.     

A 32-bank 1 Gb self-strobing synchronous DRAM with 1 GByte/sbandwidth

This paper describes a 32-bank 1 Gb DRAM achieving 1 Gbyte/s (500 Mb/s/DQ pin) data bandwidth and the access time from RAS of 31 ns at V _cc=2.0 V and 25°C. The chip employs (1) a merged multibank architecture to minimize die area; (2) an extended small swing read operation and a single I/O line driving write scheme to reduce power consumption; (3) a self-strobing I/O schemes to achieve high bandwidth with low power dissipation; and (4) a block redundancy scheme with increased flexibility. The nonstitched chip with an area of 652 mm ² has been fabricated using 0.16 μm four-poly, four-metal CMOS process technology     

A unified analytical framework for distributed variable step size LMS algorithms in sensor networks

Internet of Things (IoT) is helping to create a smart world by connecting sensors in a seamless fashion. With the forthcoming fifth generation (5G) wireless communication systems, IoT is becoming increasingly important since 5G will be an important enabler for the IoT. Sensor networks for IoT are increasingly used in diverse areas, e.g., in situational and location awareness, leading to proliferation of sensors at the edge of physical world. There exist several variable step-size strategies in literature to improve the performance of diffusion-based Least Mean Square (LMS) algorithm for estimation in wireless sensor networks. However, a major drawback is the complexity in the theoretical analysis of the resultant algorithms. Researchers use several assumptions to find closed-form analytical solutions. This work presents a unified analytical framework for distributed variable step-size LMS algorithms. This analysis is then extended to the case of diffusion based wireless sensor networks for estimating a compressible system and steady state analysis is carried out. The approach is applied to several variable step-size strategies for compressible systems. Theoretical and simulation results are presented and compared with the existing algorithms to show the superiority of proposed work.