EFFECTS OF PARTICLE SIZE AND SINTERING TEMPERATURE ON SUPERELASTICITY BEHAVIOR OF NiTi SHAPE MEMORY ALLOY USING NANOINDENTATION

The present study investigates the superelasticity properties of spark plasma sintered (SPS) nickel titanium shape memory alloy (NiTi SMA) with the influence of sintering temperature and particle size. The nanoindentation is conducted on the surface of the NiTi SMA at various loads such as 100, 300 and 500[Formula: see text]mN. The nanoindentation technique determines the quantitative results of elasto-plastic properties such as depth recovery in the form of superelasticity, stiffness, hardness and work recovery ratio from load–depth ([Formula: see text]–[Formula: see text]) data during loading and unloading of the indenter. Experimental findings show that the depth and work recovery ratio increases with the decrease of indentation load and particle size. In contrast, increasing the sintering temperature exhibited a better depth and work recovery due to the removal of pores which could enhance the reverse transformation. The contact stiffness is influenced by [Formula: see text] which leads to attain a maximum stiffness at the highest load (500[Formula: see text]mN) and particle size (45[Formula: see text][Formula: see text]m) along with the lowest sintering temperature (700∘C). NiTi alloy exhibited a maximum hardness of 9.46[Formula: see text]GPa when subjected to indent at the lowest load and particle size sintered at 800∘C. The present study reveals a better superelastic behavior in NiTi SMA by reducing the particle size and indentation load associated with the enhancement of sintering temperature.

Energetic and exergetic studies of modified CO2 transcritical refrigeration cycles

Thermodynamic analysis including energetic and exergetic analysis is carried out employing Engineering Equation Solver for the five modified cycles: dual expansion cycle, internal heat exchanger cycle, work recovery cycle, work recovery with internal heat exchanger cycle and vortex tube expansion cycle. Contours are developed to study the effect of gas cooler temperatures and evaporator temperatures on the system performance and optimum gas cooler pressure. The modified cycle with work recovery turbine offers relatively higher COP and higher exergetic efficiency with lower compressor discharge pressure. The exergy loss in compressor, gas cooler, throttle valve and vortex tube (VT) are considerably higher than that in internal heat exchanger (IHX), evaporator and turbine. It is observed that COP of modified cycle with VT is slightly less than that with IHX, whereas the cycle with work recovery turbine brings the highest COP with the improvement of 25% at the gas cooler exit temperature of 305 K and evaporator temperature of 248 K.

Body Temperature Responses During Phases of Work in Human Remains Detection Dogs Undergoing a Simulated Deployment

Body temperature responses were recorded during phases of work (waiting-to-work in close proximity to search site, active work in a search site, and post-work recovery crated in vehicle) in human remains detection dogs during search training. State or federally certified human remains detection dogs (n = 8) completed eight iterations of searching across multiple novel search environments to detect numerous scent sources including partial and complete, buried, hidden, or fully visible human remains. Internal temperature (Tgi) of the body was measured continuously using an ingestible thermistor in the gastrointestinal tract. Mean total phase times were: waiting-to-work: 9.17 min (±2.27); active work: 8:58 min (±2:49); and post-work recovery: 24:04 min (±10.59). Tgi was impacted by phase of work (p < 0.001) with a small increase during active work, with mean peak temperature 39.4 °C (±0.34 °C) during that period. Tgi continued to increase for a mean of 6:37 (±6:04) min into the post-work recovery phase in the handler’s vehicle with a mean peak Tgi of 39.66 °C (±0.41 °C). No significant increase in temperature was measured during the waiting-to-work phase, suggesting behaviors typical of anticipation of work did not appear to contribute to overall body temperature increase during the waiting-to-work recovery cycle. Continued increase of gastrointestinal body temperature several minutes after cessation of exercise indicates that risk of heat injury does not immediately stop when the dog stops exercising, although none of the dogs in this study reached clinically concerning body temperatures or displayed any behavioral signs suggestive of pending heat injury. More work is needed to better understand the impact of vehicle crating on post-work recovery temperatures in dogs.

Body Temperature Responses during Phases of Work in Human Remains Detection Dogs Undergoing a Simulated Deployment

Body temperature responses were recorded during phases of work (waiting to work in close proximity to search site, active work in a search site, and post-work recovery crated in vehicle) in human remains detection dogs during search training. State or federally certified human remains detection dogs (n = 8) completed eight iterations of searching, rotating through six different types of search environments to detect numerous scent sources including partial and complete, buried, hidden, or fully visible human remains. Internal temperature (Tgi) of the body was measured continuously using an ingestible thermistor in the gastrointestinal tract. Mean total phase times were: waiting to work: 9.17 minutes (&plusmn; 2.27); active work: 8:58 minutes (&plusmn; 2:49); and post work recovery: 24:04 minutes (&plusmn; 10.59). Tgi was impacted by phase of work (P &lt; 0.001) with a small increase during active work, with mean peak temperature 39.4 &deg;C (&plusmn; 0.34 &ordm;C) during that period. Tgi continued to increase for a mean of 7:37 (&plusmn; 6:04) minutes into the post-work recovery phase in the handler&rsquo;s vehicle with a mean peak Tgi of 39.66 &deg;C (&plusmn; 0.41 &ordm;C). No significant increase in temperature was measured during the waiting to work phase, suggesting anticipation of work did not appear to contribute to overall body temperature increase during the waiting to work recovery cycle. Continued increase of gastrointestinal body temperature several minutes after cessation of exercise indicates that risk of heat injury does not immediately stop when the dog stops exercising, although none of the dogs in this study reached clinically concerning body temperatures or displayed any behavioral signs suggestive of pending heat injury. More work is needed to better understand the impact of vehicle crating on post-work recovery temperatures in dogs.