Dynamic Mechanical Analysis and Three-Body Abrasive Wear Behaviour of Thermoplastic Copolyester Elastomer Composites

Various amounts of short fibers (glass and carbon) and particulate fillers like polytetrafluoroethylene (PTFE), silicon carbide (SiC), and alumina (Al2O3) were systematically introduced into the thermoplastic copolyester elastomer (TCE) matrix for reinforcement purpose. The mechanical properties such as storage modulus, loss modulus, and Tan δ by dynamic mechanical analysis (DMA) and three-body abrasive wear performance on a dry sand rubber wheel abrasion tester have been investigated. For abrasive wear study, the experiments were planned according to L27 orthogonal array by considering three factors and three levels. The complex moduli for TCE hybrid composites were pushed to a higher level relative to the TCE filled PTFE composite. At lower temperatures (in the glassy region), the storage modulus increases with increase in wt.% of reinforcement (fiber + fillers) and the value is maximum for the composite with 40 wt.% reinforcement. The loss modulus and damping peaks were also found to be higher by the incorporation of SiC and Al2O3 microfillers. The routine abrasive wear test results indicated that TCE filled PTFE composite exhibited better abrasion resistance. Improvements in the abrasion resistance, however, have not been achieved by short-fiber and particlaute filler reinforcements. From the Taguchi’s experimental findings, optimal combination of control factors were obtained for minimum wear volume and also predictive correlations were proposed. Further, the worn surface morphology of the samples was discussed

Modelling of 3-Phase p-q Theory-Based Dynamic Load for Real-Time Simulation

This article proposes a new method of modelling dynamic loads based on instantaneous p-q theory, to be employed in large powers system network simulations in a digital real-time environment. Due to the use of computationally heavy blocks such as phase-locked-loop (PLL), mean calculation,and coordinate transformation blocks (e.g., abc–dq0), real-time simulation of large networks with dynamic loads can be challenging. In order to decrease the computational burden associated to the dynamic load modelling, a p-q theory-based approach for load modelling is proposed in this paper. This approach is based on the well-known p-q instantaneous theory developed for power electronics converters, and it consists only of linear controllers and of a minimal usage of control loops, reducing the required computational power. This improves real-time performance and allows larger scale simulations. The introduced p-q theory-based load (PQL) model has been tested on standard networks implemented in a digital real time simulator, such as the SimBench semi-urban medium voltage network and the 118-bus Distribution System, showing significant improvement in terms of computational capability with respect to standard load models (e.g., MATLAB/Simulink dynamic load)

Ferric reducing ability of plasma: a potential oxidative stress marker in stored plasma

Introduction: The ferric reducing ability of plasma (FRAP) assay is used for measuring the antioxidant capacity. FRAP is proportional to the molar concentration of the antioxidant capacity. This study attempts to analyze the possibilities of FRAP as an indicator of oxidative stress. Methods: Blood was drawn from male Wistar rats and stored for 20 days at 4○C in citrate phosphate dextrose adenine 1. The rats were divided into two groups: controls and experimentals. The experimentals were added with antioxidants — l-carnitine, curcumin, vitamin C (VC), and caffeic acid of varying concentrations — 10, 30, and 60 mM (n =5 for each group). Plasma was isolated from these samples at regular intervals (every 5 days), and FRAP and protein were assayed. Results were analyzed by two-way ANOVA, using GraphPad prism 6. FRAP was maintained in controls. Results: VC (ascorbic acid) was the most potent antioxidant in terms of FRAP during storage compared with the above antioxidants. This study emphasizes the use of FRAP as a potential marker of oxidative stress in plasma of stored blood. Conclusion: FRAP can be utilized as a reliable marker for determining the antioxidant capacity

Modulations in Oxidative Stress of Erythrocytes during Bacterial and Viral Infections

Oxidative stress (OS) occurs when the generation of free radicals and reactive oxygen species (ROS) overwhelms the antioxidant capacity. OS causes storage lesions which can be defined as a series of biochemical and biomechanical changes. Erythrocytes are constantly exposed to OS due to the presence of ROS, which are countered by the endogenous antioxidant system. Various irreversible changes that occur include fragmentation and aggregation of proteins and lipids. The changes in proteins, lipids and antioxidant capacity are used as OS biomarkers to assess the efficacy of the erythrocytes, post oxidative insult. Aging of erythrocytes is also associated with the changes in its physical, biochemical and physiological properties and OS causes its rapid aging. Bacterial and viral infections also cause OS which alters the erythrocytes’ antioxidant capacity. These modulations in its microenvironment are both beneficial in terms of protection against invading microorganisms as well as harmful to the erythrocytes, causing damage to surrounding cells and tissues. Thus, OS biomarkers can be used to gain insights into the effects of bacterial and viral infections on the erythrocyte microenvironment

Reactive Oxygen Species and Antioxidant Interactions in Erythrocytes

There is a continuous generation of reactive oxygen species (ROS) in erythrocytes due to their microenvironment. Reactive oxygen species (ROS) and reactive nitrogen species are well known as both harmful and beneficial species. They help in activating the antioxidant enzymes. However, overproduction of ROS can cause fatal damage to cell structures, including lipids and membranes, proteins and cause oxidative stress. Erythrocytes have effective antioxidant defenses to maintain their structure and functions. They protect these cells from damage and maintain their activities. Studies have reported that antioxidant interventions in various situations have proved beneficial to erythrocytes. Therefore, they can be employed as in vitro models for antioxidant and free radical interactions and also are ideal cell models for translational studies

PTEM based moving obstacle detection and avoidance for an unmanned ground vehicle

This study presents the development and implementation of an autonomous obstacle avoidance algorithm for an UGV (Unmanned Ground Vehicle). This research improves the prior work by enhancing the obstacle avoidance capability to handle moving obstacles as well as stationary obstacles. A mathematical representation of the area of operation with obstacles is formulated by PTEM (Probabilistic Threat Exposure Map). The PTEM quantifies the risk in being at a position in an area with different types of obstacles. A LRF (Laser Range Finder) sensor is mounted on the UGV for obstacle data in the area that is used to construct the PTEM. A guidance algorithm processes the PTEM and generates the speed and heading commands to steer the UGV to assigned waypoints while avoiding obstacles. The main contribution of this research is to improve the PTEM framework by updating it continuously as new LRF readings are obtained, on the contrary to the prior work with fixed PTEM. The improved PTEM construction algorithm is implemented in a MATLAB/Simulink simulation environment that includes models of the UGV, LRF, all the sensors and actuators needed for the control of the UGV. The performance of the algorithm is also demonstrated in real time experiments with an actual UGV system.Book ChapterConference Proceeding