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Chandra Surface Thermophysical Experiment (ChaSTE) is one of the payloads flown onboard the Chandrayaan-3 lander. The objective of the experiment is in-situ investigation of thermal behaviour of outermost 100 mm layer of the lunar surface by deploying a thermal probe. The probe consists of 10 temperature sensors (Platinum RTDs) mounted at different locations along the length of the probe to measure lunar soil temperatures as a function of depth. A heater is also mounted on the probe for thermal conductivity measurements. The onboard electronics of ChaSTE has two parts, Front-End Electronics (FEE) and processing electronics (PE). The front-end electronics (FEE) card is responsible for carrying out necessary sensor signal conditioning,which includes exciting the RTD sensors,acquiring analog voltages and then converting the acquired analog signals to digital signals using an Analog to Digital Converter(ADC). The front-end card is further interfaced with the processing electronics card for digital processing and spacecraft interface.The calibration, characterisation and functional test activities of Front-End Electronics of ChaSTE were carried out with the objective of testing and ensuring proper functionality and performance.A two phase calibration process involving electronic offset correction and temperature calibration were carried out. All these activities were successfully completed and the results from them provided us with a really good understanding of the behaviour of the FEE under different thermal and electrical conditions as well as when subjected to the simulated conditions of the actual ChaSTE experiment. The performance of the ChaSTE front-end electronics was very much within the design margins and its behaviour in simulated lunar environment was as desired. The data from these activities is useful in the interpretation of the actual science data of ChaSTE., Comment: 15 pages, 14 figures

Contact mechanics models that can accurately estimate the contact conditions and, consequently predict wear must be developed for hip implants. This study analyses and verifies the existing Hertz and Fang analytical models applicable to hard-on-hard hip implants. The contact parameters, such as the maximum contact pressure, contact radius and the maximum deformation, are considered for the validation with FEM. Both analytical models fail to predict the contact conditions throughout a gait cycle. A novel data-driven ANN model is developed to comprehensively predict the contact conditions considering different input parameters. The analysis shows that cup thickness significantly affects the output contact conditions. Therefore, it is recommended to consider cup thickness in the analytical model interpretation for hard-on-hard hip implants., Comment: 42 pages, 23 figures and 4 tables

Several factors, such as the material, geometry, roughness, relative angular movement and loading conditions, influence the hip implant's lubrication regime, thereby affecting the friction and wear performance including longevity. In this study, a ball-on-plane model is considered to predict the lubrication regime across the entire gait cycle for the metal-on-metal and ceramic-on-ceramic hip implants. According to ISO 14242-1, a normal walking gait cycle is considered for the loads and rotations in the hip implant for this study. A comprehensive analysis is done to estimate the lubrication regime by considering different material combinations, body weights, femoral head sizes, clearances, and roughness across the entire gait cycle. The correlation coefficients show that the geometrical parameters are dominant in affecting the lubrication film thickness compared to the operational and material parameters. The femoral head size and body weight are found to be the most dominant and least dominant parameter respectively. Among the hard-on-hard tribo-pair, ceramics operate predominantly in the full-film lubrication regime compared to metals due to its fine surface finish. The present research suggests that in order to maximise the longevity of a hip implant, an orthopaedic surgeon should choose one with a larger femoral head diameter, less clearance, and an ultra-fine surface finish, regardless of any tribo-pair., Comment: 13 figures, 6 tables