Comparison of fatigue life assessment by analytical,experimental and damage accumulation modelling approach for steel SAE 1045

Fatigue life assessment for two‐phase steel SAE 1045 has been carried out by experimental and simulation techniques. Analytical approach, termed as fatigue lifetime calculation, was employed making use of a load increase testing procedure and constant amplitude tests equipped with measurement techniques – plastic strain amplitude, change in temperature and change in electrical potential difference. The predicted fatigue life has been validated by constant amplitude tests and compared with fatigue life estimation by microstructure‐based simulation. Simulation has been carried out over the complete cross section of the specimen. The simulation uses damage accumulation in the gage section of the specimen culminating in the macro‐crack propagation, taking into account the inhomogeneous fatigue resistance of the material element. The results show that at the initial intervals of high cycle fatigue range at relatively higher stress amplitudes, the experimental and simulation results are in agreement; whereas in the (high cycle fatigue) region at relatively low stress amplitudes, the simulation results were found more optimistic and the corresponding fatigue scatter is also increased. Each scatter is attributed to the relatively small number of analysed models of the material structure. Scanning electron microscope was used to determine volume fraction of the microstructure for simulation. Fatigue fracture surface analysis shows that crack initiated from internal defect of material and crack propagation is driven by silicon oxide inclusion.     

High Performance Inverted RbCsFAPbI3 Perovskite Solar Cells Based on Interface Engineering and Defects Passivation

Lead halide-based perovskites solar cells (PSCs) are intriguing candidates for photovoltaic technology due to their high efficiency, low cost, and simple fabrication processes. Currently, PSCs with efficiencies of >25% are mainly based on methylammonium (MA)-free and bromide (Br) free, formamide lead iodide (FAPbI₃)-based perovskites, because MA is thermally unstable due to its volatile nature and Br incorporation will induce blue shift in the absorption spectrum. Therefore, MA-free, Br-free formamidine-based perovskites are drawing huge research attention in recent years. The hole transporting layer (HTL) is crucial in fabricating highly efficient and stable inverted p-i-n structured PSCs by enhancing charge extraction, lowering interfacial recombination, and altering band alignment, etc. Here, this work employs a NiO_x/PTAA bi-layer HTL combined with GuHCl (guanidinium hydrochloride) additive engineering and PEAI (phenylethylammonium iodide) passivation strategy to optimize the charge carrier dynamics and tune defects chemistry in the MA-free, Br-free RbCsFAPbI₃-based perovskite absorber, which boosts the device efficiency up to 22.78%. Additionally, the device retains 95% of its initial performance under continuous 1 sun equivalent LED light illumination at 45 °C for up to 500 h.     

An Access Control Scheme Using Heterogeneous Signcryption for IoT Environments

When the Wireless Sensor Network (WSN) is combined with the Internet of Things (IoT), it can be employed in a wide range of applications, such as agriculture, industry 4.0, health care, smart homes, among others. Accessing the big data generated by these applications in Cloud Servers (CSs), requires higher levels of authenticity and confidentiality during communication conducted through the Internet. Signcryption is one of the most promising approaches nowadays for overcoming such obstacles, due to its combined nature, i.e., signature and encryption. A number of researchers have developed schemes to address issues related to access control in the IoT literature, however, the majority of these schemes are based on homogeneous nature. This will be neither adequate nor practical for heterogeneous IoT environments. In addition, these schemes are based on bilinear pairing and elliptic curve cryptography, which further requires additional processing time and more communication overheads that is inappropriate for real-time communication. Consequently, this paper aims to solve the above-discussed issues, we proposed an access control scheme for IoT environments using heterogeneous signcryption scheme with the efficiency and security hardiness of hyperelliptic curve. Besides the security services such as replay attack prevention, confidentiality, integrity, unforgeability, non-repudiations, and forward secrecy, the proposed scheme has very low computational and communication costs, when it is compared to existing schemes. This is primarily because of hyperelliptic curve lighter nature of key and other parameters. The AVISPA tool is used to simulate the security requirements of our proposed scheme and the results were under two backbends (Constraint Logic-based Attack Searcher (CL-b-AtSER) and On-the-Fly Model Checker (ON-t-FL-MCR)) proved to be SAFE when the presented scheme is coded in HLPSL language. This scheme was proven to be capable of preventing a variety of attacks, including confidentiality, integrity, unforgeability, non-repudiation, forward secrecy, and replay attacks.

     

An Improved Dictionary Cracking Scheme Based on Multiple GPUs for Wi-Fi Network

The Internet has penetrated all aspects of human society and has promoted social progress. Cyber-crimes in many forms are commonplace and are dangerous to society and national security. Cybersecurity has become a major concern for citizens and governments. The Internet functions and software applications play a vital role in cybersecurity research and practice. Most of the cyber-attacks are based on exploits in system or application software. It is of utmost urgency to investigate software security problems. The demand for Wi-Fi applications is proliferating but the security problem is growing, requiring an optimal solution from researchers. To overcome the shortcomings of the wired equivalent privacy (WEP) algorithm, the existing literature proposed security schemes for Wi-Fi protected access (WPA)/WPA2. However, in practical applications, the WPA/WPA2 scheme still has some weaknesses that attackers exploit. To destroy a WPA/WPA2 security, it is necessary to get a PSK pre-shared key in pre-shared key mode, or an MSK master session key in the authentication mode. Brute-force cracking attacks can get a phase-shift keying (PSK) or a minimum shift keying (MSK). In real-world applications, many wireless local area networks (LANs) use the pre-shared key mode. Therefore, brute-force cracking of WPA/WPA2-PSK is important in that context. This article proposes a new mechanism to crack the Wi-Fi password using a graphical processing unit (GPU) and enhances the efficiency through parallel computing of multiple GPU chips. Experimental results show that the proposed algorithm is effective and provides a procedure to enhance the security of Wi-Fi networks.     

Efficient Algorithms for Cache-Throughput Analysis in Cellular-D2D 5G Networks

In this paper, we propose a two-tiered segment-based Device-to-Device (S-D2D) caching approach to decrease the startup and playback delay experienced by Video-on-Demand (VoD) users in a cellular network. In the S-D2D caching approach cache space of each mobile device is divided into two cache-blocks. The first cache-block reserve for caching and delivering the beginning portion of the most popular video files and the second cache-block caches the latter portion of the requested video files ‘fully or partially’ depending on the users’ video watching behaviour and popularity of videos. In this approach before caching, video is divided and grouped in a sequence of fixed-sized fragments called segments. To control the admission to both cache-blocks and improve the system throughput, we further propose and evaluate three cache admission control algorithms. We also propose a video segment access protocol to elaborate on how to cache and share the video segments in a segmentation based D2D caching architecture. We formulate an optimisation problem and find the optimal cache probability and beginning-segment size that maximise the cache-throughput probability of beginning-segments. To solve the non-convex cache-throughout maximisation problem, we derive an iterative algorithm, where the optimal solution is derived in each step. We used extensive simulations to evaluate the performance of our proposed S-D2D caching system.     

Measuring social media activity of scientific literature: an exhaustive comparison of scopus and novel altmetrics big data

This paper measures social media activities of 15 broad scientific disciplines indexed in Scopus database using Altmetric.com data. First, the presence of Altmetric.com data in Scopus database is investigated, overall and across disciplines. Second, a zero-truncated negative binomial model is used to determine the association of various factors with increasing or decreasing citations. Lastly, the effectiveness of altmetric indices to identify publications with high citation impact is comprehensively evaluated by deploying area under the curve (AUC)—an application of receiver operating characteristic. Results indicate a rapid increase in the presence of Altmetric.com data in Scopus database from 10.19% in 2011 to 20.46% in 2015. It was found that Blog count was the most important factor in the field of Health Professions and Nursing as it increased the number of citations by 38.6%, followed by Twitter count increasing the number of citations by 8% in the field of Physics and Astronomy. The results of receiver operating characteristic show that altmetric indices can be a good indicator to discriminate highly cited publications, with an encouragingly AUC = 0.725 between highly cited publications and total altmetric count. Overall, findings suggest that altmetrics can be used to distinguish highly cited publications. The implications of this research are significant in many different directions. Firstly, they set the basis for a further investigation of altmetrics efficiency to predict publications impact and most significantly promote new insights for the measurement of research outcome dissemination over social media.     

Quantifying diffused hydrogen in AISI-52100 bearing steel and in silver steel under tribo-mechanical action: Pure rotating bending, sliding-rotating bending, rolling-rotating bending and uni-axial tensile loading

Hydrogen embrittlement is often a catastrophic phenomenon of machine elements failure under cyclic stresses. This hydrogen is generated as a result of tribo-chemical and mechanical actions on the working surfaces. This hydrogen can have three different zones or stages of behaviour under tribo-mechanical actions. Firstly, it can strongly adsorb on the mating surfaces at a shallow subsurface zone and take up the load in the boundary-lubricating regime and reduce the coefficient of friction. At a second stage, it can diffuse to the deep subsurface zone where it might work together with Hertzian stresses and embrittle the subsurface zone. The last zone of hydrogen activity is the bulk of the bearing steel where it is known to collect under the action of tensile stresses and degrade the bearing steel and hence resulting in catastrophic failure. It is important and interesting to follow up the presence of hydrogen in these zones in order to predict the safe functioning of the machine elements. In addition to this a clear distinction must be made between the internal hydrogen embrittlement and environmental hydrogen embrittlement. Two important behaviours of hydrogen are studied and quantification was made by a melting sample technique. Dependence of hydrogen diffusion on the variation of tribo-mechanical action is shown in this work. This was done by studying the pure rotating bending, rotating bending with combination of sliding and rolling motion of the mating surfaces and uni-axial tensile experiments in pure water environment to see the diffusion of hydrogen into or out of the AISI-52100 bearing steel and in silver steel. Two different approaches were adopted in order to investigate the presence of hydrogen in three zones under the action of different stress states. The two techniques are melting sample technique by using hydrogen analyser and elastic recoil detection analysis, an ion beam technique. It is believed until now that hydrogen spread is homogeneous in the bearing steel. The results obtained showed that the inherent amount of hydrogen in steel samples is non-homogeneous and it was learnt that inherent amount of hydrogen in the steel samples is very important in order to support the boundary lubrication by hydrogen. Content of hydrogen in the steel samples showed a relation to the increasing number of cyclic stresses. The sliding-rotating bending stress state showed a considerable wear of the surfaces but the content of hydrogen was not very high in that sample when compared to the samples that were run under pure rotating bending stress state.     

Extending the theory of planned behavior (TPB) to explain online game playing among Malaysian undergraduate students

As the world moves into the web 2.0 era, everyone can connect virtually, and online game playing has become a trend. Online games are played over computer networks, usually over the Internet. Online games entail a number of advantages, such as the ability to connect to multiplayer games, although single-player online games are also rather popular. This exploratory study focused on modeling the determinants of actual use of online game playing. Many researchers have shown perceived enjoyment and flow experience as important drivers of actual use of online game playing. The theory of planned behavior has been used in this study. Data were collected from 1584 Universiti Sains Malaysia students with different backgrounds using a structured questionnaire. The findings show that perceived enjoyment has the strongest influence on actual use. Other variables found to influence actual usage include the level of perceived behavioral control, subjective norms, attitude, perceived enjoyment, and flow experience. Implications of this research for future researchers will also be discussed. We hope this research will increase researchers’ interest in further development in this sector and that the model will assist the games industry to identify factors that increase actual use by players.     

Location Privacy with Dynamic Pseudonym-Based Multiple Mix-Zones Generation over Road Networks

According to the recent studies, application related with safety associated with road networks must need verification of entities and messages. However, security of road network users like vehicles and drivers needs to be dealt with. Unique identity like pen names and certificates might get useful to ensure security. Pseudonym names and the special certificates are being considered as the basic building blocks to ensure security requirements for road networks. Nevertheless, apart from the seen advantages, road network communication might also generate certain privacy issues by giving opportunity to invader to track vehicles. One and for most basic technique is to solve this issue by means of using pen names by the vehicles and alter them time to time. Since executing the procedure of changing pen names has to increase overhead. By looking at such type of limitations, our given technique will produce top privacy level for the road network users by using dynamic pseudonyms based multiple mix zones scenario. This pseudonym based procedure will base upon vehicle’s acceleration, heading and displacement to execute dynamic pseudonym alteration. We have performed simulation by applying SUMO simulator. After having a detailed comparison with the current pseudonym change techniques, it has been verified that our given technique has shown enhanced performance in terms of acquiring top level privacy rate having few numbers of pseudonyms alteration; broad level of simulations and analysis has been elaborated the efficiency of the given technique.     

Wear resistance and friction coefficient of nano-SiO<Subscript>2</Subscript> and ash-filled HDPE/lignocellulosic fiber composites

This work comparatively evaluates the effect of nano-SiO₂ (at 2 and 3 wt%), rice husk and bagasse ash (at 5 and 10 wt%) on the wear resistance and friction coefficient of HDPE (high-density polyethylene)/lignocellulosic fiber composites. Rice husk and bagasse fibers at 50% by weight contents were mixed with HDPE and 2% maleic anhydride-grafted polyethylene as compatibilizer. SEM images showed a fairly appropriate connection between the polymer matrix and fillers. We found that the fillers improve the wear resistance, and the effect of nano-SiO₂ is more pronounced. The rice husk ash showed a better performance compared to the bagasse ash, probably due to greater SiO₂ content measured by X-ray fluorescence spectrometry. In contrast to nano-SiO₂, both ashes had a reducing effect on other mechanical strengths (Izod impact resistance, modulus of elasticity and modulus of rupture). All fillers remarkably increased the water absorption and thickness swelling. The water uptake of composites increased after wear.