Hybrid Feedback for Autonomous Navigation in Environments with Arbitrary Non-Convex Obstacles

We develop an autonomous navigation algorithm for a robot operating in two-dimensional environments containing obstacles, with arbitrary non-convex shapes, which can be in close proximity with each other, as long as there exists at least one safe path connecting the initial and the target location. The proposed navigation approach relies on a hybrid feedback to guarantee global asymptotic stabilization of the robot towards a predefined target location while ensuring the forward invariance of the obstacle-free workspace. The proposed hybrid feedback controller guarantees Zeno-free switching between the move-to-target mode and the obstacle-avoidance mode based on the proximity of the robot with respect to the obstacle-occupied workspace. An instrumental transformation that reshapes (virtually) the non-convex obstacles, in a non-conservative manner, is introduced to facilitate the design of the obstacle-avoidance strategy. Finally, we provide an algorithmic procedure for the sensor-based implementation of the proposed hybrid controller and validate its effectiveness through simulation results.Comment: arXiv admin note: text overlap with arXiv:2111.0938

A review of Mukta : An Ancient drug in Rasa Shastra

Rasa Shastra or preferably called as the ancient Indian Alchemy, deals with the preparation of medicines that has helped mankind since thousands of years. Rasa which means Mercury has been the chief area of interest for the Ancient Alchemists of Rasa Shastra. Along with safe use of Mercurial preparations as medicines since many years, Rasa Shastra also deals with preparation of other herbomineral compounds using varied drugs of plant as well as animal origin. One of the drug, that has been used widely in Rasa Shastra is Mukta or Pearl. There are several categories or groups of drugs (Varga) used in Rasa Shastra viz. Maharasas, Uparasas etc. whereas Mukta is classified under Ratna (precious gems) Varga. Mukta is a shining off white coloured hard spherical object found in sea shells. Due to its lucrative appearance it is widely used in jewelry, cosmetics, as well as in clothing. It is formed by deposition of several concentric layers of calcium carbonate and conchiolin around central nucleus. According to Rasa Shastra classics, Mukta has Madhura, Sheeta and Laghu properties. And so is widely used as a potent Pitta Shamaka. Its purification and Pishti processes are also mentioned in Rasa Shastra classics which makes pearl more potent to cure diseases. Mukta is also widely used in conditions like Amlapitta, Jwara, Daha etc

A Review on Pishti Kalpana

Rasa Shastra deals with the preparation of variety of medicaments and formulations that include Bhasmas, Kharaliya Rasayanas, Kupipakwa Rasayanas, etc. These sections of formulations also depend upon the different types of raw materials that are to be used in it as chief ingredients. Rasa Shastra has a vast and varied history of preparing these medicines and its safer use since thousands of years. Pishti is one such section of formulations that is chiefly used when the raw materials cannot tolerate heat but at the same time are very effective without heat treatment. In Rasa Shastra, mainly the drugs of animal origin or precious gems are subjected to levigation or trituration in a particular media to form a particular Pishti. The word Pishti literally means that which is finely triturated and made into a very fine powder similar to flour. Mukta Pishti, Prawal Pishti being some of the important examples

The state-of-the-art progress in cloud detection, identification, and tracking approaches: a systematic review

A cloud is a mass of water vapor floating in the atmosphere. It is visible from the ground and can remain at a variable height for some time. Clouds are very important because their interaction with the rest of the atmosphere has a decisive influence on weather, for instance by sunlight occlusion or by bringing rain. Weather denotes atmosphere behavior and is determinant in several human activities, such as agriculture or energy capture. Therefore, cloud detection is an important process about which several methods have been investigated and published in the literature. The aim of this paper is to review some of such proposals and the papers that have been analyzed and discussed can be, in general, classified into three types. The first one is devoted to the analysis and explanation of clouds and their types, and about existing imaging systems. Regarding cloud detection, dealt with in a second part, diverse methods have been analyzed, i.e., those based on the analysis of satellite images and those based on the analysis of images from cameras located on Earth. The last part is devoted to cloud forecast and tracking. Cloud detection from both systems rely on thresholding techniques and a few machine-learning algorithms. To compute the cloud motion vectors for cloud tracking, correlation-based methods are commonly used. A few machine-learning methods are also available in the literature for cloud tracking, and have been discussed in this paper too

Vehicle-to-Grid Integration for Enhancement of Grid: A Distributed Resource Allocation Approach

In the future grids, to reduce greenhouse gas emissions Electric Vehicles (EVs) seems to be an important means of transportation. One of the major disadvantages of the future grid is the demand-supply mismatch which can be mitigated by incorporating the EVs into the grid. The paper introduces the concept of the Distributed Resource Allocation (DRA) approach for incorporating a large number of Plug-in EV (PEVs) with the power grid utilizing the concept of achieving output consensus. The charging/discharging time of all the participating PEVs are separated with respect to time slots and are considered as strategies. The major aim of the paper is to obtain a favorable charging strategy for each grid-connected PEVs in such a way that it satisfies both grid objectives in terms of load profile smoothening and minimizing of load shifting as well as economic and social interests of vehicle owners i.e. a fair share of the rate of charging for all connected PEVs. The three-fold contribution of the paper in smoothening of load profile, load shifting minimization, and fair charging rate is validated using a representative case study. The results confirm improvement in load profile and also highlight a fair deal in the charging rate for each PEV

Microstructure characterization of Co–Cr–Mo–xTi alloys developed by micro-plasma based additive manufacturing for knee implants

This paper reports on effects of adding 2, 4 and 6 wt.% Ti to Co–Cr–Mo by micro-plasma based additive manufacturing (MPBAM) process on density, porosity, microstructure, phase formation, inter-diffusion zones, microhardness, and wear characteristics of the resultant alloy with an objective to develop better material for knee implant applications. Bulk and relative density found to decrease, and porosity increase with increase in Ti % to Co–Cr–Mo alloy. Co–Cr–Mo–4Ti alloy showed more pores and their uniform distribution. Microstructures of Co–Cr–Mo–2Ti and Co–Cr–Mo–4Ti alloys are porous and crack-free. Phase analysis of Co–Cr–Mo–4Ti revealed presence of α-Co, ε-Co, and β-titanium phases (having FCC, HCP, and BCC crystal structure respectively), inter-metallic CoTi2, and lamellar chromium carbides i.e. Cr7C3 and Cr23C6. It is confirmed by the phase mapping also. Inverse pole figure maps did not show any preferential orientation of grains and revealed presence of ε-Co phase matrix with traces of grains of chromium carbides and CoTi2 phases. Increasing Ti% in Co–Cr–Mo alloy increased formation of β-Ti and CoTi2 phases which have less hardness than the carbide phases therefore average microhardness of Co–Cr–Mo–2Ti alloy is found as the highest followed by Co–Cr–Mo–4Ti alloy. Coefficient of friction, specific wear rate, and wear volume increase with increase in Ti% in Co–Cr–Mo alloys due to decrease in microhardness and increase in porosity. It also increased ploughing and delamination in the worn track. This study found Co–Cr–Mo–4Ti as a better knee implant material due to its lesser density, uniform porous structure, absence of cracks, moderate microhardness, and wear characteristics