Skid-steered vehicles (SSV) are gaining huge importance in the market due to their applications like construction, agricultural work, material handling etc. The accuracy of performing such tasks ...require a robust control algorithm. The design of such controller is very challenging task due to external disturbances caused by wheel-ground interaction and aerodynamic effects. This paper proposes robust fractional and integral order fuzzy sliding mode controllers (FSMC, FFSMC) for a skid-steered vehicles with varying coefficient of friction and a displaced center of gravity (CG). FFSMC controller reduces the outcome of forces generated as a result of ground tire interaction during skidding and friction variations. The proposed controllers are implemented for a four-wheel SSV under high-speed turning motion. A simulation environment is constructed by implementing the SSV dynamics with wheel-road model and the performance of the proposed algorithms is tested. The simulation test is conducted for a Pioneer-3AT (P-3AT) robot SSV vehicle with displaced CG and variable coefficient of tires friction. Simulation results demonstrate the efficiency of the proposed FFSMC algorithm in term of reduced state errors and minimum chattering. The proposed controller compensates the effect of different responses of the wheels generated as a result of variable CG. The chattering phenomenon generated by conventional SMCs is also minimized by fuzzy tuning approach.
Ti6Al4V is regarded as the “workhorse” in aerospace industry for its wide applications at high temperatures. Unique attributes are high strength to density ratio and outstanding material properties ...at high thermal conditions. This present-day work involves the pre-slotting on Ti6Al4V surface with the help of fibre Laser, followed by the operation of micro-milling on respective Laser engraved slots. Localized melting due to Laser ablation leads to the decrease in the surface contact between milling tool and material surface. Micro-milling in return helps to remove the Heat affected zones (HAZ) created during Laser engraving process. ANOVA helps to point out the contributing factors for burr width and height on both milling sides. Main effect plots generated during process optimization, help to point out optimal combination of input parameters for minimized burr width and height. Higher frequency of Laser helps to generate consistent slots. Lower rotational speeds are responsible for high values of burr width and height. Whereas high rotational speed leads to efficient chip removal, resulting in decreased burr width and height.
This study aims at characterisation of various densities of Rigid Polyurethane Foam (RPUF) under quasi-static tension and compression. The density of foam is key parameter in selection of suitability ...for structural applications. Various densities of RPUF are synthesised using commercial grade Polyols and Methylene diphenyl isocyanate (MDI). The ratio of mixing both constituents was maintained at 1:1.15 for polyol and MDI respectively. Free rise density of the foam was achieved at 234 kg/m3 and is considered the baseline density for comparison. The higher than baseline densities were achieved by blowing the mixture into a mould with variable pouring times and three densities in the range of 252 kg/m3, 303 kg/m3 and 353 kg/m3 were achieved. The tensile and compression specimens were prepared from the manufactured blocks. SEM images were taken from the blocks of various densities and uniform cell patterns were observed for all densities. The specimens were then tested under compressive and tensile loads. It was found that the specimen exhibit consistency in results and the density affects the mechanical properties directly. Optimum density of foam for energy absorption capability of RPUF based on specific work done is also estimated. A phenomenological model based on relative density of foam was developed to assess material behaviour which can reduce the requirement of test specimens for obtaining a set of particular material properties.
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In the past decade, different sensing mechanisms and algorithms have been developed to detect or estimate indoor occupancy. One of the most recent advancements is using networked sensor nodes to ...create a more comprehensive occupancy detection system where multiple sensors can identify human presence within more expansive areas while delivering enhanced accuracy compared to a system that relies on stand-alone sensor nodes. The present work reviews the studies from 2012 to 2022 that use networked sensor nodes to detect indoor occupancy, focusing on PIR-based sensors. Methods are compared based on pivotal ADPs that play a significant role in selecting an occupancy detection system for applications such as Health and Safety or occupant comfort. These parameters include accuracy, information requirement, maximum sensor failure and minimum observation rate, and feasible detection area. We briefly describe the overview of occupancy detection criteria used by each study and introduce a metric called “sensor node deployment density” through our analysis. This metric captures the strength of network-level data filtering and fusion algorithms found in the literature. It is hinged on the fact that a robust occupancy estimation algorithm requires a minimal number of nodes to estimate occupancy. This review only focuses on the occupancy estimation models for networked sensor nodes. It thus provides a standardized insight into networked nodes’ occupancy sensing pipelines, which employ data fusion strategies, network-level machine learning algorithms, and occupancy estimation algorithms. This review thus helps determine the suitability of the reviewed methods to a standard set of application areas by analyzing their gaps.
Climate change can adversely impact the thermal comfort and energy efficiency of the buildings stock. The South Asian countries are particularly vulnerable to the adverse impacts of climate change ...specially in the form of rising temperatures and increasing frequency of heat waves. The passive building design measures can be useful in mitigating and adapting to the climate change by increasing energy efficiency and reducing greenhouse gas (GHG) emissions. In this study various passive climate change adaptation measures (PCAMs) have been used individually and in form of combinations in order to analyze their impact on the energy efficacy of residential buildings in Pakistan. It has been found that the natural ventilation and front green wall are the most efficient options for reducing the overall energy consumption. By implementation of these PCAMs, cooling demand can be decreased by 27.75% while heating demand can be reduced by 35%. Secondly, the prospect of net zero-energy building and reduced CO
2
emissions are also studied. It has been shown that building can achieve net-zero energy on an annual basis at every orientation and it can attain the status of nearly zero-energy building on a monthly basis. Moreover, emitted CO
2
can be reduced by 31% by using the renewable energy.
Climate change and the urban heat island (UHI) effects are increasing heat stress and adversely impacting outdoor thermal comfort in urban areas. The study demonstrates that thermal comfort ...conditions can be improved by reducing air temperature and surface temperature with the integration of street trees into the urban environment. In this work, computational fluid dynamics (CFD) simulations using unsteady Reynolds-averaged Navier-Stokes (URANS) equations have been performed to analyze the cooling effect of street trees for heatwave period (18-22 June 2015) in a hot-humid urban environment. The results are then compared in-term-of air/surface temperature, flow-velocity and apparent temperature for the vegetation case, open-space case, and built case. The analysis shows that the vegetation can effectively decrease surrounding temperature (a reduction of 1.2 K), thereby reducing energy consumption and effectively promote thermal comfort conditions. The study findings will encourage city planners and citizens to take action for urban greening.
Tungsten inert gas (TIG) welding is type of arc welding with area of applications in food industry, pharmaceutical industry, chemical plants, marine, aerospace, medical devices, and implants, etc. ...TIG welding process involve several parameters. Many parameters are controllable by the operator, and these parameters have a direct or indirect impact on the microstructure and mechanical properties of the joints. In the present study, three TIG welding parameters, arc current, voltage, and shielding gas flow rate, were changed up to three levels and their effects on surface roughness, hardness and tensile strength were investigated. Experiments were carried out on a 3 mm thick plate of austenitic stainless steel AISI 316L utilizing a TIG welding equipment and were designed according to Taguchi L9 orthogonal array (OA). ER308L was used as filler material. Results were analyzed using signal to noise S/N ratio and analysis of variance. It was observed that, for optimization of each response, arc current is the most influential factor. Minimum surface roughness was achieved at parametric combination of current 125 A, voltage 18 V and gas flow rate 12 L/min. Maximum hardness was achieved at parametric combination of current 125 A, voltage 20 V and gas flow rate 9 L/min. Maximum tensile strength was achieved at parametric combination of current 100 A, voltage 18 V and gas flow rate 6 L/min.
The goal of this paper is to provide a novel computing approach that can be used to reduce the power consumption, size, and cost of wearable electronics. To achieve this goal, the use of ...microelectromechanical systems (MEMS) sensors for simultaneous sensing and computing is introduced. Specifically, by enabling sensing and computing locally at the MEMS sensor node and utilizing the usually unwanted pull in/out hysteresis, we may eliminate the need for cloud computing and reduce the use of analog-to-digital converters, sampling circuits, and digital processors. As a proof of concept, we show that a simulation model of a network of three commercially available MEMS accelerometers can classify a train of square and triangular acceleration signals inherently using pull-in and release hysteresis. Furthermore, we develop and fabricate a network with finger arrays of parallel plate actuators to facilitate coupling between MEMS devices in the network using actuating assemblies and biasing assemblies, thus bypassing the previously reported coupling challenge in MEMS neural networks.
Brick manufacturing sector is a major contributor to air pollution and greenhouse gas emissions in South Asian countries. This study investigates barriers and drivers relevant to the adoption of ...cleaner zig-zag kiln (ZZK) technology in Punjab, Pakistan by surveying 63 kiln owners. These survey respondents owned three different types of brick kiln i.e., ZZK, Fixed chimney bull’s trench kiln (FCBTK), and clamp type kiln (CTK). Roger’s model of innovation diffusion was adopted to access the determinants pertaining to relative advantage, compatibility, complexity, trialability and observability. Survey questionnaire included questions related to 35 factors (20 drivers and 15 barriers) and responses were recorded on Likert scale. These barrier and drivers covered variety of factors associated with regulatory, financial, technological, social, and environmental issues that may influence the perception and decision of kiln owners for the adoption of cleaner ZZK technology. Our results show that most important drivers pertain to economic benefits such as emissions fine reduction, decrease in fuel costs and year-round operations. Other high impact drivers relate to compatibility and similarity between ZZK and FCBTK construction and operations. Top-ranked barriers highlight the challenges associated with financial burden of retrofitting cost, higher salaries demanded by skilled workers, and maintenance issues for blower assembly. Mean scores for the determinants pertaining to the attributes of Roger’s model were computed. Our results show that both relative advantage and compatibility received highest mean scores. On the other hand, trialability and observability received lowest scores. Government, policy makers and other relevant stakeholders should focus on awareness campaigns, capacity building and training of labor, and developing financial instruments to provide loans to kiln owners for covering retrofit costs.
Abstract
Background
The highly contagious nature of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) places physicians in South Asia at high risk of contracting the infection. ...Accordingly, we conducted this study to provide an updated account of physician deaths in South Asia during the COVID-19 pandemic and to analyze and compare the different characteristics associated with physician mortality amongst the countries of the region.
Methods
We performed a cross-sectional study by using published news reports on the websites of news agencies from 9 selected countries in South Asia. Our study included only those physicians and doctors who died after contracting COVID-19 from their respective workplaces. All available data about the country of origin, type of, sex, age, medical or surgical specialty, and date of death were included.
Results
The total number of physician deaths reported due to COVID-19 in our study was 170, with half (87/170, 51%) of the deaths reported from Iran. Male physician deaths were reported to be 145 (145/170 = 85%). Internal Medicine (58.43%) was the most severely affected sub-specialty. The highest physician mortality rate in the general population recorded in Afghanistan (27/1000 deaths). General physicians from India OR = 11.00(95% CI = 1.06–114.08),
p
= 0.045 and public sector medical practitioners from Pakistan aOR = 4.52 (95% CI = 1.18–17.33),
p
= 0.028 were showing significant mortality when compared with other regions in multivariate logistic regression.
Conclusion
An increased number of physician deaths, owing to COVID-19, has been shown in South Asia. This could be due to decreased personal protective equipment and the poor health care management systems of the countries in the region to combat the pandemic. Future studies should provide detailed information of characteristics associated with physician mortalities along with the main complications arising due to the virus.
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