摘要 : •Single-site FeN4 species are designed to dangle over axial carbon micropores (d-FeN4)•d-FeN4 shows much superior oxygen reduction reactivity to traditional FeN4•d-FeN4 facilitates the formation of singlet-state oxygen-containing species with optimized spin states by micropore•This work provides in-depth understanding of spin tuning for advanced catalyst designSingle-site metal atoms (SMAs) on supports are attracting extensive interest as new catalytic systems because of maximized atom utilization and superior performance. However, rational design of configuration-optimized SMAs with high activity from the perspectives of fundamental electron spin is highly challenging. Herein, N-coordinated Fe single atoms are successfully distributed over axial carbon micropores to form dangling-FeN4 centers (d-FeN4). This unique d-FeN4 demonstrates much higher intrinsic activity toward oxygen reduction reaction (ORR) in HClO4 than FeN4 without micropore underneath and commercial Pt/C. Both theoretical calculation and electronic structure characterization imply that d-FeN4 endows central Fe with medium spin (t2g4 eg1), which provides a spin channel for electron transition compared with FeN4 with low spin. This leads to the facile formation of the singlet state of oxygen-containing species from triplet oxygen during the ORR, thus showing faster kinetics than FeN4. This work provides an in-depth understanding of spin tuning on SMAs for advanced energy catalysis.

摘要 : The surface coverage of micro-nano structure seriously affects the spectroscopic conformity of the surface-enhanced Raman scattering (SERS) substrate. In the paper, the influence of the surface coverage on the spectrum is studied, and a method is proposed to eliminate the influence of surface coverage. First, the SERS substrate was prepared by using the lyotropic liquid crystal soft template and the relationship between the surface coverage and Raman spectral intensity is analyzed to obtain a formula. Then, based on the this formula, all measured spectral intensities are unified to the standard surface coverage, which is defined with the measured average spectral intensity corresponded surface coverage, thus, the influence of the surface coverage on the spectral intensity is elimanated. Finally, the effectiveness of the proposed method is verified with different SERS substrates and different test spot sizes on the same substrate. The fitting and experimental results show that the spectral intensity changes as an exponential function of the surface coverage, the coefficients of variation are reduced to about 6% for different substrates, the spectroscopic conformities of the substrate are improved more than twice or so for different measured spots, and the coefficients of variation linearly decrease with the spots increase. In a word, the proposed method can improve the spectroscopic conformity of the SERS substrate significantly, the quantitative and reliable detection of various material components will be realized. This work may greatly promote the application of the SERS substrate in multiple detection fields.

摘要 : GPS has a sharp performance decline in terms of accuracy indoors due to the complex building structure. A combined algorithm, targeting at received signal strength indication (RSSI) calibration optimisation, depending on deep neural network training via input vector Γ and the target output vector Ψ, termed reference signal optimisation algorithm (RSOA) is proposed to improve the positioning accuracy in the indoor Bluetooth positioning networks. Experimental results show that the relative error of the proposed RSOA between the estimated results and the measured ones can reach as low as 0.2%, and the absolute errors can be reduced to 0.13 m at most within 10 m.

摘要 : Two types of weak grating sensors with different packaging methods were developed using the weak grating strain monitoring technology. The strain of the steel beam after loading is measured and compared with the distributed optical fiber sensor. The experimental results show that the strain monitoring results obtained using weak grating agree well with those obtained using distributed optical fiber and theoretical calculation. The error between the calculated deflection of the steel beam and measured and theoretical values of the dial indicator is within 10%. The horizontal static load test results of an offshore steel pipe pile show that the deformation of the pile is mainly within the range of 60 m below the sea level. The deflection of steel pipe piles increases with the increase of load and decreases with the increase in pile depth. After 50 m buried depth, the steel pipe pile is almost no longer affected by horizontal thrust, and the deflection value is 0. In the horizontal static load test, the average error between the monitored deflection and actual deflection is 16 mm. Through the indoor model and practical engineering application, the feasibility and accuracy of weak grating in steel structure monitoring are proved, which provides technical support for similar projects.

摘要 : Aiming at the problem of secondary diffraction in aberration correction of an M-type Czerny-Turner spectrometer, we propose the anti-secondary diffraction condition for this optical structure under the coma-free condition. The main factors of secondary diffraction are analyzed and deduced theoretically. Combining the anti-secondary diffraction condition with the constraint coma-free condition, we built an M-type coma-free Czerny-Turner spectrometer. In order to verify the correctness of the theoretical analysis, the Zemax OpticStudio simulation software is used for a comparative experiment. The simulation results show that there is no secondary diffraction in the M-type optical path structure meeting the constraints, but there is secondary diffraction in the M-type optical path structure that does not meet the constraints, which is consistent with the theoretical analysis result. Under the condition that the incident slit width is 25 μm and the grating engraving line density is 600 line/mm, the spectral resolution of the optical system optimized by the software is better than 1 nm in the range of 200?500 nm.

摘要 : Susan Sontag's discussion and depiction of illness, especially AIDS, in her writings can help us better understand the metaphoric mechanism of illness in the Chinese film Love for Life. As one of the leading metaphors attached to AIDS, plague brings discrimination and prejudice against AIDS patients, whether they are to blame or not. Moreover, due to demonization, AIDS patients suffer from social death even when they are still alive. Love for Life challenges the taboo subject in China and makes an appeal that the body should not be treated as the vehicle of metaphors and that we need to break the illness–health dichotomy so as to shake off the metaphors of illness.

摘要 : The hollow cylinder torsional testing system (RHCA) was used to conduct true triaxial test on gray sandstone. Controlled conditional compression tests (?2??3), constant ?3 and variable ?2 conditional compression tests were carried out respectively. ?2 is the intermediate principal stress, ?3 is the maximum principal stress. Strength and failure characteristics were analyzed in detail, and intermediate principal stress effects, minimum principal stress effects, stress Lord angle effect and applicability of strength criterion were further analyzed. The results indicate that rock hollow cylindrical apparatus can realize the simulation of true triaxial stress path and the end friction can be avoided. The pressure difference between the inner and outer confining pressure has a great influence on the strength of the rock, especially under high confining pressure, a large pressure difference makes the strength of the rock weaken rapidly, resulting in severe damage. The intermediate principal stress has a significant effect on the strength of the rock and has an interval effect, and the minimum principal stress has a strengthening effect on the strength of the rock. This feature has an important guiding significance for the efficient and timely support of the rock mass in actual engineering excavation. Further, according to the obtained test results, the strength criteria used to describe the mechanical properties of the rock at this stage were analyzed. It is considered that the calculated rock strength obtained by using the exponent criteria can better reflect the stress state of rock and has a relatively good applicability. It can be used to evaluate the strength of rock in practical engineering.

摘要 : An optimized method for the design of progressive addition lens (PAL) is proposed in this study, aiming at the characteristics of the population that experiences a transition from myopia to presbyopia. The height expression of the surface of the PAL is proposed based on an aspherical formula, and a continuously varying conic coefficient is used to adjust the optical power and astigmatism distribution. Two PALs with an additional power of 1.5 dioptres were designed for comparison, using the spherical height and the aspheric height expression, respectively. The optical power and astigmatism distribution are given in the design results, and the free form verifier (FFV) of ROTLEX Ltd. in Israel is used to verify the results obtained via simulation. The results show that the optical power around the assembly centre of the optimized PAL annularly increases. The maximum astigmatism distribution of the lens does not exceed 1.25 dioptres, thereby not exceeding 83% of the additional power. In the area above the assembly centre, the astigmatism at any position is less than 0.5 dioptres. The length of the power stabilization zone in the near zone is approximately 20 mm. The optical power of the distance zone of the optimized PAL is annularly increased, which is beneficial to alleviate the asthenopia of myopia. The maximum astigmatism of the lens is considerably reduced, which is easily accepted by customers whose defect in vision has changed from myopia to presbyopia and wear PALs for the first time.

摘要 : Organic–inorganic hybrid perovskites (OHPs) with a rich reservoir of distinct physical attributes have been considered as promising resistive switching materials for next-generation electronic devices, including resistive random-access memory (RRAM) devices, artificial synapses, and logic operation. In this review, we first briefly introduce the structural and photoelectronic properties of OHPs materials, followed by elaborating the typical lateral/vertical device architectures and commonly-used device fabrication technologies. Secondly, recent progress of OHPs in three categories of RRAM, artificial synapses, and logic operation, including various materials design, outstanding electrical behaviors, and multifunctional applications, are well discussed. Besides, the operational mechanisms and performance improvement strategies are summarized in a recapitulative way. Finally, current challenges and future development prospects of OHPs-based devices are demonstrated to provide a better guideline for the next-generation technical revolution. This review offers an encouraging recognition that OHPs hold immense expectation to keep up with the upcoming big-data and artificial intelligence era.

摘要 : Dual-wavelength retinal imaging adaptive optics systems are suitable for high contrast and resolution imaging of retinal capillaries. The compensation of the Longitudinal Chromatic Aberrations (LCAs) in dual-wavelength adaptive systems is researched. The LCA is measured, the measured wavefronts are analyzed, and the arbitrary wavefront LCA compensation method is given. An adaptive correction experiment is carried out and the experimental results indicate that the root mean square error of the wavefront is reduced to 0.16 λ (λ=589 nm) and the retinal capillary resolution is improved to 6 μm. This work may be used for the clinical applications of retinal imaging.