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Recently, photothermoelectric effect of thermoelectric materials has been hotly explored to develop self-powered and large bandwidth photodetectors working at ambient conditions. However, the key parameters for optimized photothermoelectric effect are still elusive. Here, based on the two-temperature model under static condition, we theoretically studied the key parameters to optimize the photothermoelectric performance of thermoelectric materials. Results verify that when the incident electromagnetic wave only generates electronic intra-band excitation, there is an ideal carrier concentration to optimize the photothermoelectric voltage; when the wavelength of a detected electromagnetic wave can resonantly excite quasi-particle (like phonons) except electrons, the photothermoelectric voltage can be enhanced significantly around the resonant wavelength regime; and when the electronic inter-band transition can be excited by an electromagnetic wave, photothermoelectric voltage is significantly increased due to the high optical absorption. As an example, the theoretical dependence of the photothermoelectric voltage of SnSe on wavelength is in line with the experimental result. This work elucidates the crucial parameters of thermoelectric materials to achieve the ideal photothermoelectric performance. [ABSTRACT FROM AUTHOR]

We experimentally demonstrated that composites, being effective in optimizing the thermoelectric performance, can also enhance photothermoelectric effects in this work. In detail, we employed an alternating-growth in chemical-vapor-transport to grow the SnSe–SnSe2 composite crystals. The photo-responsivities of SnSe–SnSe2 (atomic-weight-ratio as 44%–56%) composite are comparable to SnSe crystals in the visible band (444 and 532 nm). However, the responsivities of SnSe–SnSe2 have remarkable 27.3% enhancement than those of SnSe crystal at the near-infrared band (1310 and 1550 nm). Supported by optical spectroscopy and theoretical electronic band structure, the enhanced optical responsivity of SnSe–SnSe2 composites is due to the formation of P–N junctions at interfaces between SnSe and SnSe2, leading to more optical transition channels and corresponding optical absorptions in near-infrared band. Our work verifies that hetero-junction formed among constituent compounds in composites is effective in optimizing the photothermoelectric response of thermoelectric materials in certain electromagnetic bands, paving the way to develop photoelectric detection devices. [ABSTRACT FROM AUTHOR]

A new method is proposed for mobile robot visual servoing using model-free visual targets under dynamic scenes. In the first stage, the ratio of depth information is calculated by using the geometric relationship between feature points and images. For the second stage, the relationship between various coordinate systems can be calculated via homography decompositions and coordinate transformation. Finally, an adaptive controller is adopted to drive the mobile robot to the desired pose. Both the simulation and experimental results show that when the scene changes, the mobile robot can complete the stabilization control. That is, when the linear velocity v→0 and the angular velocity w→0, the error e→0, then the robot stabilization to the desired pose 0.0 m, 0.0 m, 0.0°. [ABSTRACT FROM AUTHOR]

Mytilopsis sallei, an invasive alien species, has strong reproductive ability and high adaptability. It can severely endanger biodiversity of intertidal ecosystem after invasion. The intertidal zones and oyster breeding areas in some coastal areas of Guangdong Province have been severely invaded by M. sallei. To examine the potential habitat of M. sallei in China, we established a potential habitat prediction model of M. sallei using Maxent and ArcGIS method for China and global scales. The model was verified by the method of receiver operating characteristic curve (ROC) analysis and field investigation. The results showed that M. sallei could distribute with high probabili-ty in the area between North and South America, South India in Asia, Sri Lanka, the south coast of the Yangtze River in China, and in Van Dimen Bay of the southern hemisphere. In China, M. sallei mainly distributed in coastal provinces south of Shanghai. The main environmental factors affecting the suitable distribution areas for M. sallei were water vapor pressure, temperature, and solar radiation. After ROC detection, the AUC values of both the training and testing sets were 0.996, indicating that the prediction reached an excellent level. Our results provide theoretical basis for the risk assessment and management of M. sallei, and complement the potential habitat prediction of invasive species in China.