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The influence of Cu doping on phase transition, thermal strain, and thermal expansion property of polycrystalline Ni50Mn23−xCuxGa27(x = 1, 3, 5, 6 and 7) alloys is investigated. The results show that with increasing Cu concentration, martensitic transformation gradually gets close to Curie transition. A magnetostructural transition (MST) is observed in samples with x = 6 and 7. Such MST can enhance magnitude of transformation strain. Besides, Ni50Mn23−xCuxGa27 alloys possess an isotropic, recoverable, and thermally stable thermal strain. Excitedly, Cu doping can effectively tune the phase transition, thermal strain, and thermal expansion properties of Ni50Mn23−xCuxGa27 alloys. Adjustable coefficients of thermal expansion from positive to negative are obtained by Cu‐doped Ni50Mn23−xCuxGa27 alloys. The average linear expansion coefficient (α) between −140.44 and −207.70 ppm K−1 is observed in samples with x = 6 and 7 for a narrow temperature span of 11–14 K. When the temperature span is about 72 K (x = 6) and 73 K (x = 7), which is the largest temperature span observed in Ni–Mn–Ga‐based alloys recently, the α values decrease to about −36 ppm K−1. These findings are beneficial for manipulating the thermal expansion property of Ni–Mn–Ga–Cu alloys and their multifunctional applications. [ABSTRACT FROM AUTHOR]

Intelligent drones or flying robots play a significant role in serving our society in applications such as rescue, inspection, agriculture, etc. Understanding the scene of the surroundings is an essential capability for further autonomous tasks. Intuitively, knowing the self-location of the UAV and creating a semantic 3D map is significant for fully autonomous tasks. However, integrating simultaneous localization, 3D reconstruction, and semantic segmentation together is a huge challenge for power-limited systems such as UAVs. To address this, we propose a real-time semantic mapping system that can help a power-limited UAV system to understand its location and surroundings. The proposed approach includes a modified visual SLAM with the direct method to accelerate the computationally intensive feature matching process and a real-time semantic segmentation module at the back end. The semantic module runs a lightweight network, BiSeNetV2, and performs segmentation only at key frames from the front-end SLAM task. Considering fast navigation and the on-board memory resources, we provide a real-time dense-map-building module to generate an OctoMap with the segmented semantic map. The proposed system is verified in real-time experiments on a UAV platform with a Jetson TX2 as the computation unit. A frame rate of around 12 Hz, with a semantic segmentation accuracy of around 89% demonstrates that our proposed system is computationally efficient while providing sufficient information for fully autonomous tasks such as rescue, inspection, etc. [ABSTRACT FROM AUTHOR]

Magnetocaloric materials with first-order phase transition are potential refrigerant media for solid state refrigeration. In this work, the Ni45Co5Mn35In15 alloy possesses a representative first-order martensitic transition (MT), which is found to be sensitive to both magnetic field and isostatic pressure with rates of ∼−6.4 K T−1 and ∼4.24 K kbar−1. Such an active response to multi-stimuli derives from the strong coupling of the spin and the lattice. A low magnetic field of 1 T can drive nearly 100% of the total entropy change corresponding to the whole transformation in this alloy. However, the prominent magnetocaloric effect (MCE) is almost irreversible owing to the intrinsic hysteresis of the first-order phase transition. By virtue of the strong magnetostructural coupling during the MT, a hydrostatic pressure assisted magnetic field loading loop has been constructed for eliminating the hysteresis and to a large extent improve the reversibility of the MCE. [ABSTRACT FROM AUTHOR]

Both the barocaloric effect (BCE) and its reversible behavior during martensitic transformation (MT) have been experimentally investigated in Ni 42.3 Co 7.9 Mn 38.8 Sn 11 quaternary Heusler alloy. The experimental results show that the studied alloy experiences the MT from the ferromagnetic L 2 1 -type cubic structure to the paramagnetic-like three-layered (3 M ) modulated monoclinic structure, resulting in a value of ∼1.1% for the relative volume change ε between two phases. Due to appearance of an enhanced ε , the migration rate of martensitic transformation with respect to the hydrostatic pressure reaches ∼4.7 K/kbar, while a high transition entropy change (∼28 J/kg K) is still maintained. Based on an indirectly estimated method, the calculated maximum value for isothermal entropy change Δ S T achieves ∼ -23 J/kg K with the pressure change of 6.2 kbar, which yields the values of ∼10 K for adiabatic temperature change Δ T a d and ∼786 J/kg for relative cooling power (RCP), performing a large BCE. According to the change of phase fraction at selected hydrostatic pressures, a detailed schematic diagram has been established to evaluate the reversibility of this effect. With applying an external cyclic pressure of 6.2 kbar, the maximum repeatable values calculated for both Δ S T and Δ T a d are decreased to ∼ -15 J/kg K and ∼5 K, respectively. This is attributed to an insufficient driving force, which can only partially transform this material, leading to a reversible MT appeared in the mixed state. [ABSTRACT FROM AUTHOR]

Abstract: The performances of solar cell arrays based on a Trough Concentrating Photovoltaic/Thermal (TCPV/T) system have been studied via both experiment and theoretical calculation. The I–V characteristics of the solar cell arrays and the output performances of the TCPV/T system demonstrated that among the investigated four types of solar cell arrays, the triple junction GaAs cells possessed good performance characteristics and the polysilicon cells exhibited poor performance characteristics under concentrating conditions. The optimum concentration ratios for the single crystalline silicon cell, the Super cells and the GaAs cells were also studied by experiments. The optimum concentration ratios for the single crystalline silicon cells and Super cells were 4.23 and 8.46 respectively, and the triple junction GaAs cells could work well at higher concentration ratio. Besides, some theoretical calculations and experiments were performed to explore the influences of the series resistances and the working temperature. When the series resistances Rs changed from 0Ω to 1Ω, the maximum power Pm of the single crystalline silicon, the polycrystalline silicon, the Super cell and the GaAs cell arrays decreased by 67.78%, 74.93%, 77.30% and 58.07% respectively. When the cell temperature increased by 1K, the short circuit current of the four types of solar cell arrays decreased by 0.11818A, 0.05364A, 0.01387A and 0.00215A respectively. The research results demonstrated that the output performance of the solar cell arrays with lower series resistance was better and the working temperature had a negative impact on the current under concentration. In addition, solar irradiation intensity had certain effects on the solar cell’s performance. For the crystalline silicon solar cell arrays, when the solar direct radiation exceeded a certain value, the I–V curves almost became a straight line and the output performances decreased due to the high series resistance leading to the high power loss. For the triple junction GaAs solar cell array, its performance was always excellent. [Copyright &y& Elsevier]

The structure, transition properties, and hydrostatic pressure (p) and magnetic field (B) dependence of transition temperatures and operation-temperature window (Δ T , defined as the temperature range of martensitic transition) were investigated in Ni 53 Mn 21 Ga 26 alloy. The results reveal that all the transition temperatures and Δ T increase almost linearly with increasing magnetic field and pressure. Particularly, a stronger dependence of peak temperature (T M) and Δ T on pressure, d T M /d p = 25.7 K/GPa and dΔ T /d p = 18.7–22.7 K/GPa, is observed in contrast with the smaller values of d T M /d B = 1.3 K/T and dΔ T /d B = 1.4–1.7 K/T found in Ni 53 Mn 21 Ga 26 alloy. Furthermore, the value of 25.7 K/GPa may be the largest shift in T M with pressure observed in polycrystalline Ni–Mn-Ga systems. Clearly, the sensitivities of T M and Δ T to pressure are much higher than those to magnetic field. These findings illustrate that applying hydrostatic pressure is beneficial to broaden Δ T in Ni 53 Mn 21 Ga 26 alloy. • Ni 53 Mn 21 Ga 26 alloy exhibits a magnetostructural transformation (MST). • Hydrostatic pressure effects on the phase transition properties and operation-temperature window (Δ T) have been studied. • A large shift in peak temperature with pressure of 25.7 K/GPa was observed. • A strong response of Δ T to pressure p , dΔ T /d p = 18.7–22.7 K/GPa, was reported. • Hydrostatic pressure can effectively broaden the operation-temperature window. [ABSTRACT FROM AUTHOR]