[en] In an underwater imaging system, a refractive interface is introduced when a camera looks into the water-based environment, resulting in the usually linear rays of light bending and the commonly used pinhole camera model to be invalid. In this paper, a novel method to model and calibrate the underwater stereo system is proposed. Unlike most existing recent works that use vector operations to express light propagation, this paper remodels the underwater imaging system in the view of the light field, which is more organized and concise. Additionally, a forward projection error function, which is more accurate and efficient, is used for non-linear optimization to minimize the reprojection error. The proposed method allows improved accuracy compared with other methods and is evaluated in a set of experiments. (paper)

[en] Highlights: • U(VI) was primarily adsorbed on pyrrhotite and partially reduced by Fe"2"+ and S"2"−. • XAS demonstrated reductive co-precipitates of U(VI) on pyrrhotite after 168 h. • Inner-surface complexation dominated the U(VI) removal at pH > 5 by SCMs. - Abstract: The interaction mechanism of U(VI) on pyrrhotite was demonstrated by batch, spectroscopic and modeling techniques. Pyrite was selected as control group in this study. The removal of U(VI) on pyrite and pyrrhotite significantly decreased with increasing ionic strength from 0.001 to 0.1 mol/L at pH 2.0–6.0, whereas the no effect of ionic strength was observed at pH  > 6.0. The maximum removal capacity of U(VI) on pyrite and pyrrhotite calculated from Langmuir model was 10.20 and 21.34 mg g"−"1 at pH 4.0 and 333 K, respectively. The XPS analysis indicated the U(VI) was primarily adsorbed on pyrrhotite and pyrite and then approximately 15.5 and 9.8% of U(VI) were reduced to U(IV) by pyrrhotite and pyrite after 20 days, respectively. Based on the XANES analysis, the adsorption edge of uranium-containing pyrrhotite located between U"I"VO_2(s) and U"V"IO_2"2"+ spectra. The EXAFS analysis demonstrated the inner-sphere surface complexation of U(VI) on pyrrhotite due to the occurrence of U-S shell, whereas the U-U shell revealed the reductive co-precipitates of U(VI) on pyrrhotite/pyrite with increasing reaction times. The surface complexation modeling showed that outer- and inner-surface complexation dominated the U(VI) removal at pH < 4 and pH > 5.0, respectively. The findings presented herein play a crucial role in the removal of radionuclides on iron sulfide in environmental cleanup applications.

[en] Excellent thermoelectric cooling and power generation are simultaneously realized in an n-type PbTe-based thermoelectric material. The cooling temperature difference (ΔT) of ≈15.6 K, maximum power density of ≈0.4 W cm${}^{-<!--\; ???\; -->2}$ and conversion efficiency of ≈1.5% with T${}_C$ = 295 K and T${}_H$ = 765 K can be obtained in a single-leg device composed of PbTe-30%SnSe-1.5%Cu. This advanced thermoelectric performance in n-type PbTe-30%SnSe-1.5%Cu mainly originates from its high-ranged ZT value achieved through optimizing its bandgap, carrier density, and microstructure. The bandgap in PbTe is first reduced by SnSe alloying to facilitate the carrier transport properties at low temperature range (300-573 K). With further tuned carrier density, the average power factor increases from ≈10.2 µW cm${}^{-<!--\; ???\; -->1}$ K${}^{-<!--\; ???\; -->2}$ in Pb${}_{0.985}$Sb${}_{0.015}$Te-30%SnSe to ≈16.2 µW cm${}^{-<!--\; ???\; -->1}$ K${}^{-<!--\; ???\; -->2}$ in PbTe-30%SnSe-1.5%Cu at 300-773 K. Moreover, microstructure observation reveals high-density dislocations in PbTe-30% SnSe-1.5% Cu, which can dramatically suppress the room-temperature lattice thermal conductivity from ≈2.21 Wm${}^{-<!--\; ???\; -->1}$ K${}^{-<!--\; ???\; -->1}$ in Pb${}_{0.985}$Sb${}_{0.015}$Te to ≈0.53 Wm${}^{-<!--\; ???\; -->1}$ K${}^{-<!--\; ???\; -->1}$ in PbTe-30%SnSe-1.5%Cu. As a result, a room-temperature ZT value of ≈0.7 and high average ZT value (ZT${}_{ave}$) of ≈0.98 can be obtained in PbTe-30%SnSe-1.5%Cu at 300-573 K, which makes its performance comparable to the commercial n-type Bi${}_2$Te${}_3$-based thermoelectric material. (© 2022 Wiley-VCH GmbH)

[en] Mg${}_3$(Sb, Bi)${}_2$-based materials possess excellent room-temperature thermoelectric performance, while poor interfacial behaviors occur when connected with metal electrodes due to the strong chemical activity and volatility of Mg element. In this study, a high efficiency of 7.1% under a temperature difference of 230 K is achieved in n-Mg${}_3$(Sb, Bi)${}_2$/p-Bi${}_2$Te${}_3$ thermoelectric module. When changing the interfacial layer from Fe powder to Fe foil, it effectively prevents a significant diffusion of both Mg and Bi elements from the material matrix to the interfacial layer, resulting in an extremely low contact resistivity ≈3.4 µΩ cm${}^2$ that is almost one order lower than of that of Fe powder/Mg${}_3$(Sb, Bi)${}_2$ junction ≈30 µΩ cm${}^2$. Particularly, a thin diffusion layer with a width of ≈2 µm is initially observed in the unannealed Fe foil/Mg${}_3$(Sb, Bi)${}_2$ junction. Even after thermal aging at 573 K for 28 days, the diffusion-layer width is basically unchanged and its corresponding contact resistivity maintained as low as ≈5.8 µΩ cm${}^2$. Overall, this work provides deep insights into interfacial design and paves the way for high-performance and sustainable low-grade waste heat recovery. (© 2023 Wiley‐VCH GmbH)