Machining of polymeric composite is inevitable during assembly of components. In view of making holes on structural composites, drilling is essential and a study to optimize the machining parameters ...is very important. The present study has been made to investigate the defaces and cutting forces associated during drilling of natural fiber reinforced plastics. Plastic composite has been manufactured using chemically treated
vetiveria zizanioides
as the reinforcement and polyester as the matrix. The composite has been drilled several times on the basis of central composite design. Speed and feed rate of the spindle, point angle and diameter of the tool are considered as the input parameters. Deface of each hole during entry and exit, thrust force and torque have been measured as the output parameters. A fuzzy model has been created and a comparative study between the central composite design and fuzzy model is made. The design has been optimized with the objective of minimizing the output parameters and a set of confirmatory experiments have been conducted. The central composite model has been validated by comparing it with the fuzzy model and confirmatory runs. The comparison presented only a minimal error and hence the modeling by central composite design and fuzzy are consummate.
The need of composite material in industries is increasing day by day due to its competent characteristics with the traditional materials. The plastic composite materials made of polymers are used as ...structural elements in different fields. The present day polymeric composites are made by mainly focussing the natural fibers as reinforcements because of their usability, properties and cost. While preparing these new composites, utmost care must be taken for synthesizing the natural fibers and polymers before fabrication. Also, during the fabrication of a new composite the process and parameter selection plays a vital role. Once the composites are fabricated, it needs several machining operations as secondary processing. This paper gives a detailed review of different challenges during the synthesis, fabrication, characterization and machining of natural fiber reinforced plastic composites.
Predictability is important in decision-making in many fields, including transport. The ill-predictability of time-varying processes poses severe problems for traffic and transport planners. The ...sources of ill-predictability in traffic phenomena could be due to uncertainty and incompleteness of data and models and/or due to the complexity of the processes itself. Traffic counts at intersections are typically consistent and repetitive on the one hand and yet can be less predictable on the other hand, in which on any given time, unusual circumstances such as crashes and adverse weather can dramatically change the traffic condition. Understanding the various causes of high/low predictability in traffic counts is essential for better predictions and the choice of prediction methods. Here, we utilise the Hurst exponent metric from the fractal theory to quantify fluctuations and evaluate the predictability of intersection approach volumes. Data collected from 37 intersections in Sydney, Australia for one year are used. Further, we develop a random-effects linear regression model to quantify the effect of factors such as the day of the week, special event days, public holidays, rainfall, temperature, bus stops, and parking lanes on the predictability of traffic counts. We find that the theoretical predictability of traffic counts at signalised intersections is upwards of 0.80 (i.e., 80%) for most of the days, and the predictability is strongly associated with the day of the week. Public holidays, special event days, and weekends are better predictable than typical weekdays. Rainfall decreases predictability, and intersections with more parking spaces are highly predictable.
Autonomous vehicles are being viewed with scepticism in their ability to improve safety and the driving experience. A critical issue with automated driving at this stage of its development is that it ...is not yet reliable and safe. When automated driving fails, or is limited, the autonomous mode disengages and the drivers are expected to resume manual driving. For this transition to occur safely, it is imperative that drivers react in an appropriate and timely manner. Recent data released from the California trials provide compelling insights into the current factors influencing disengagements of autonomous mode. Here we show that the number of accidents observed has a significantly high correlation with the autonomous miles travelled. The reaction times to take control of the vehicle in the event of a disengagement was found to have a stable distribution across different companies at 0.83 seconds on average. However, there were differences observed in reaction times based on the type of disengagements, type of roadway and autonomous miles travelled. Lack of trust caused by the exposure to automated disengagements was found to increase the likelihood to take control of the vehicle manually. Further, with increased vehicle miles travelled the reaction times were found to increase, which suggests an increased level of trust with more vehicle miles travelled. We believe that this research would provide insurers, planners, traffic management officials and engineers fundamental insights into trust and reaction times that would help them design and engineer their systems.
Road traffic congestion continues to manifest and propagate in cities around the world. The recent technological advancements in intelligent traveler information have a strong influence on the route ...choice behavior of drivers by enabling them to be more flexible in selecting their routes. Measuring traffic congestion in a city, understanding its spatial dispersion, and investigating whether the congestion patterns are stable (temporally, such as on a day-to-day basis) are critical to developing effective traffic management strategies. In this study, with the help of Google Maps API, we gather traffic speed data of 29 cities across the world over a 40-day period. We present generalized congestion and network stability metrics to compare congestion levels between these cities. We find that (a) traffic congestion is related to macroeconomic characteristics such as per capita income and population density of these cities, (b) congestion patterns are mostly stable on a day-to-day basis, and (c) the rate of spatial dispersion of congestion is smaller in congested cities, i.e. the spatial heterogeneity is less sensitive to increase in delays. This study compares the traffic conditions across global cities on a common datum using crowdsourced data which is becoming readily available for research purposes. This information can potentially assist practitioners to tailor macroscopic network congestion and reliability management policies. The comparison of different cities can also lead to benchmarking and standardization of the policies that have been used to date.
The structural performance of metallic components is a significant challenge especially when it comes to operating conditions in real-world applications. Friction stir additive manufacturing (FSAM) ...is a solid-state additive manufacturing (AM) that provides controlled microstructure with homogenous grains and excellent structural performance. In this study, the FSAM technique was utilized to fabricate a lightweight laminated AA6061/AA7075 metal matrix composite with improved mechanical properties. The feasibility of the FSAM was demonstrated to build multi-functional, multi-material components for aerospace, automotive, and defence industries to enable lightweight, high-strength components. The FSAM tool was designed with an optimum shoulder length, shoulder diameter, pin length, and pin diameter considering the plate thickness. Afterward, optimized process parameters were designed using the Taguchi L9 orthogonal array (OA) technique. Microstructural features and their effect on mechanical properties such as microhardness and ultimate tensile strength (UTS) were evaluated in the FSAM build. FSAM build improved in microhardness (from 107±1.2 to 138.4 ±2.8 HV0.2) and tensile strength (from 310 to 384 MPa) as compared to base material AA6061. Corrosion resistance was also studied to understand the feasibility of the FSAM technique in various environmental conditions. The overall performance of the FSAM build shows promising results compared to the base materials.
Current transportation management systems rely on physical sensors that use traffic volume and queue-lengths. These physical sensors incur significant capital and maintenance costs. The ubiquity of ...mobile devices has made possible access to accurate and cheap traffic delay data. However, current traffic signal control algorithms do not accommodate the use of such data. In this paper, we propose a novel parsimonious model to utilize real-time crowdsourced delay data for traffic signal management. We demonstrate the versatility and effectiveness of the data and the proposed model on seven different intersections across three cities and two countries. This signal system provides an opportunity to leapfrog from physical sensors to low-cost, reliable crowdsourced data.
•The distribution of speed suggests speed variability decreases with increasing CAV penetration.•Robustness of the driving behaviour increases with increased CAV penetration.•Increased CAV ...penetration leads to greater exposure of critical crash events/conflicts but a reduction in crash severity.•The full-scale benefits of CAVs can only be achieved at 100 per cent CAV penetration.•Pareto optimality is identified under multi-criterion evaluation.
Connected and Automated Vehicle (CAV) technology, although in the development stage, is quickly expanding throughout the vehicle market. However, full market penetration will most likely require considerable planning as key stakeholders, manufacturers, consumers and governing agencies work together to determine optimal deployment strategies. Specifically, road safety is a critical challenge to the widespread deployment and adoption of this disruptive technology. During the transition period fleets will be composed of a combination of CAVs and conventional vehicles, and therefore it is imperative to investigate the repercussions of CAVs on traffic safety at different penetration rates. Since crash severity and frequency in conjunction reflect traffic safety, this study attempts to investigate the effect of CAVs on both crash severity and frequency through a microsimulation modelling exercise. VISSM microsimulation platform is used to simulate a case study of the M1 Geelong Ring Road network (Princes Freeway) in Victoria, Australia. Network performance is evaluated using performance metrics (Total System Travel Time, Delay) and kinematic variables (Speed, acceleration, jerk rate). Surrogate safety measures (time to collision, post encroachment time, etc.) are examined to inspect the safety in the network. The results indicate that the introduction of CAVs does not achieve the expected decrease in crash severity and rates involving manual vehicles, despite the improvement in network performance, given the demand and the set of parameters used in our operational CAV algorithm are intact. Additionally, the study identifies that the safety benefits of CAVs are not proportional to CAV penetration, and full-scale benefits of CAVs can only be achieved at 100 % CAV penetration. Further, considering network efficiency as a performance metric and total crash rate involving conventional vehicles as a safety metric, a Pareto frontier is extracted, for varying CAV operational behaviour. The results presented in this study provide insights into the impacts of CAVs on traffic safety valuable for insurance companies and other industry participants, enabling safety-related services and more enterprising business models.
Autonomous Vehicles (AVs) are being widely tested on public roads in several countries such as the USA, Canada, France, Germany, and Australia. For the transparent deployment of AVs in California, ...the California Department of Motor Vehicles (CA DMV) commissioned AV manufacturers to draft and publish reports on disengagements and crashes. These reports must be processed before any statistical analysis, which is cumbersome and time-consuming. Our dataset presents the processed disengagement data from 2014 to 2019, crash data till the 10
of March 2020 and supplementary road network and land-use data extracted from OpenStreetMap. Primary data are manually assessed and converted into an easily processed format. Our processed data will be advantageous to the research community and enable accelerated research in this domain. For example, the data can be utilised to discern trends in disengagement, observe the distribution of disengagement causes, and investigate the contributory factors of the crashes. Such investigations can subsequently improve the reporting protocols and make policies and laws for the smooth deployment of this disruptive technology.
This paper deals with the study of dimple type RF MEMS capacitive shunt switch using different meandering techniques for high isolation and low actuation voltage. The novelty of the proposed RF MEMS ...switch is it incorporates the meanders and dimples, which help to reduce the actuation voltage. The proposed switch structure is optimized, designed, and simulated with FEM analysis such as electromechanical and electromagnetic by using COMSOL and HFSS tools respectively. The best performance of the switch is observed by varying different parameters such as beam material, beam thickness, dielectric thickness, and airgap. The proposed switch with different meandering techniques attains the pull-in voltage in the range of 10.3-46 V, particularly the three uniform meander technique has low actuation voltage of 10.3 V. The RF performance of the device is particularly tuned in the range of 26.5-40 GHz frequency range and it is analyzed for all types of meanders. Among them, the non-uniform single meander has attained the best isolation of -54.13 dB at 40 GHz in the off state. The insertion and return losses of the device are -0.514 dB and -17.35 dB over 1-40 GHz frequency in on state.
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