- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Preparation and Two-Photon Photoluminescence Properties of Organic Inorganic Hybrid Perovskites (C6H5CH2NH3)2PbBr4 and (C6H5CH2NH3)2PbI4
摘要： Organic inorganic hybrid perovskites have potential applications in solar cells, electroluminescent devices and radiation detection because of their unique optoelectronic properties. In this paper, the perovskites (C6H5CH2NH3)2PbBr4 and (C6H5CH2NH3)2PbI4 were synthesized by solvent evaporation. The crystal structure, morphology, absorption spectrum, laser power dependence of the photoluminescence (PL) intensity and lifetime were studied. The results showed that the perovskites (C6H5CH2NH3)2PbBr4 and (C6H5CH2NH3)2PbI4 display a layered stacking structure of organic and inorganic components. The absorption peaks are located at 392 nm (3.16 eV) and 516 nm (2.40 eV), respectively. It was observed that the PL intensity and photoluminescence quantum yield (PLQY) increases with increasing laser power, and that the PL lifetime decreases with increasing laser power, which is mainly due to the non-geminate recombination.
关键词： perovskites,photoluminescence lifetime,two-photon excitation,photoluminescence spectrum
更新于2025-09-09 09:28:46
-
Space-Frequency Joint Contention Scheduling Algorithm based on AoD in SDM-EONs
摘要： Compared with elastic optical networks, spectrum contention problem may become more serious in space-division multiplexing elastic optical networks. Spectrum converters (SCs) can effectively resolve the problem of spectrum contention without additional delays, but SCs have the disadvantages of complicated technologies and high costs. To resolve the two problems aforesaid, taking into account the alleviated spectrum continuity constraint caused by the space dimension and the node flexibility introduced by architecture on demand (AoD), a space-frequency joint contention scheduling algorithm (SFJSA) based on AoD is proposed in this paper. SFJSA divides the contention scheduling process into two phases: scheduling in space domain and in frequency domain. It gives priority to resolve contention in the spatial domain, and then considers using spectrum converters in spectrum domain. In the stage of space switching, a weight formula is designed to balance the costs of spectrum selective switches and the loads of cores. In the stage of spectrum conversion, a concept of spectrum compactness is introduced to further optimize the utilization of spectrum resources and spectrum converters. The simulation results indicate that the proposed algorithm can reduce the number of spectrum converters required while improving the blocking performance, which means it achieves better blocking performance in a more cost-effective manner.
关键词： Space division multiplexing elastic optical networks,Bandwidth blocking probability,Architecture on demand,Spectrum converter,Space-Frequency Joint Scheduling
更新于2025-09-09 09:28:46
-
Comparative Study on Fluorescence Spectra of Chinese Medicine North and South Isatis Root Granules
摘要： Since the spectral imaging technology emerged, it has gained a lot of application achievements in the military field, precision agriculture and biomedical science. When the fluorescence spectrum imaging first applied to the detection of the feature resource of Chinese herbal medicine, the characteristics of holistic and ambiguity made it a new approach to the traditional Chinese medicine testing. In this paper, we applied this method to study the Chinese medicine north and south isatis root granules by comparing their fluorescence spectra. Using cluster analysis, the results showed that the north and south Banlangen can not be divided by ascription. And these indicate that there is a large difference in the quality of Banlangen granules on the market, and fluorescence spectrum imaging method can be used in monitoring the quality of Radix isatidis granules.
关键词： Chinese medicine,Radix isatidis granules,Fluorescence spectrum imaging,South isatis root granules
更新于2025-09-09 09:28:46
-
Contiguous polarisation spectra of the Earth from 300 to 850 nm measured by GOME-2 onboard MetOp-A
摘要： In this paper we present the ?rst contiguous high-resolution spectra of the Earth’s polarisation observed by a satellite instrument. The measurements of the Stokes fraction Q/I are performed by the spectrometer GOME-2 onboard the MetOp-A satellite. Polarisation measurements by GOME-2 are performed by onboard polarisation measurement devices (PMDs) and the high-resolution measurements discussed in this paper are taken in the special “PMD RAW” mode of operation. The spectral resolution of these PMD RAW polarisation measurements varies from 3 nm in the ultraviolet (UV) to 35 nm in the near-infrared wavelength range. We ?rst compare measurements of the polarisation from cloud-free scenes with radiative transfer calculations for a number of cases. We ?nd good agreement but also a spectral discrepancy at 800 nm, which we attribute to remaining imperfections in the calibration key data. Secondly, we study the polarisation of scenes with special scattering geometries that normally lead to near-zero Q/I . The GOME-2 polarisation spectra indeed show this behaviour and con?rm the existence of the small discrepancy found earlier. Thirdly, we study the Earth polarisation for a variety of scenes. This provides a blueprint of Q/I over land and sea surfaces for various degrees of cloud cover. Fourthly, we compare the spectral dependence of measurements of Q/I in the UV with the generalised distribution function proposed by Schutgens and Stammes (2002) to describe the shape of the UV polarisation spectrum. The GOME-2 data con?rm that these functions match the spectral behaviour captured by the GOME-2 PMD RAW mode.
关键词： Stokes fraction Q/I,UV polarisation spectrum,Earth polarisation,GOME-2,PMD RAW mode
更新于2025-09-09 09:28:46
-
Fundamental molecules of life are pigments which arose and co-evolved as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum
摘要： The driving force behind the origin and evolution of life has been the thermodynamic imperative of increasing the entropy production of the biosphere through increasing the global solar photon dissipation rate. In the upper atmosphere of today, oxygen and ozone derived from life processes are performing the short-wavelength UV-C and UV-B dissipation. On Earth’s surface, water and organic pigments in water facilitate the near-UV and visible photon dissipation. The first organic pigments probably formed, absorbed, and dissipated at those photochemically active wavelengths in the UV-C and UV-B that could have reached Earth’s surface during the Archean. Proliferation of these pigments can be understood as an autocatalytic photochemical process obeying non-equilibrium thermodynamic directives related to increasing solar photon dissipation rate. Under these directives, organic pigments would have evolved over time to increase the global photon dissipation rate by (1) increasing the ratio of their effective photon cross sections to their physical size, (2) decreasing their electronic excited state lifetimes, (3) quenching radiative de-excitation channels (e.g., fluorescence), (4) covering ever more completely the prevailing solar spectrum, and (5) proliferating and dispersing to cover an ever greater surface area of Earth. From knowledge of the evolution of the spectrum of G-type stars, and considering the most probable history of the transparency of Earth’s atmosphere, we construct the most probable Earth surface solar spectrum as a function of time and compare this with the history of molecular absorption maxima obtained from the available data in the literature. This comparison supports the conjecture that many fundamental molecules of life are pigments which arose, proliferated, and co-evolved as a response to dissipating the solar spectrum, supports the thermodynamic dissipation theory for the origin of life, constrains models for Earth’s early atmosphere, and sheds some new light on the origin of photosynthesis.
关键词： photosynthesis,thermodynamic dissipation,UV-C,solar spectrum,UV-B,Archean,organic pigments,origin of life
更新于2025-09-09 09:28:46
-
Resolution improvement of dipole source localization for artificial lateral lines based on multiple signal classification
摘要： The lateral line is a critical mechanosensory organ that enables fish to perceive the surroundings accurately and rapidly. Massive efforts have been made to build an artificial lateral line system rivaling that of fish for underwater vehicles. Dipole source localization has become a standard problem for evaluating the sensing capabilities of the developed systems. In this paper we propose, for the first time, the MUSIC (multiple signal classification) method in order to achieve high-resolution dipole source localization based on spatial spectrum estimation. We also present the MVDR (minimum variance distortionless response) method by making an improvement to the previous Capon’s method. Experiments are conducted on a linear prototype of lateral line canal and the localization performance of these two methods are compared. The results show that the MUSIC method provides an overall localization resolution improvement of 10.4% and maintains similar levels of localization accuracy compared with the MVDR method. Further studies show that the MUSIC method has the potential of localizing two closer incoherent dipole sources with a minimum lateral separation of 20 mm, versus 70 mm for the MVDR method, at a dipole-array distance of half the array length. Both localization methods have strong robustness to the vibrational state of the dipole source. Our work provides a promising and robust way to meet the high-resolution and multi-source sensing requirements of underwater vehicles.
关键词： resolution improvement,dipole source localization,multiple signal classification,artificial lateral line,spatial spectrum estimation
更新于2025-09-09 09:28:46
-
Estimating chlorophyll content from Eucalyptus dunnii leaves by reflectance values
摘要： This study aimed to estimate photosynthetic pigments contents from leaves of Eucalyptus dunni Maiden based on values of reflectance spectra of red, green and blue colors obtained with a digital color analyzer. We collected fifty leaves from the lower third of the crown of twenty trees including young as well as mature leaves. From each leaf an area of 14 cm2 of the leaf blade was cut in which we measured reflectance values on the red, green and blue spectra with a portable digital colorimeter, obtained relative index of chlorophyll with a SPAD – 502 and determined the content of the chlorophyll a, b, and a + b by classic method of solvent extraction. We submitted the data to multiple linear regression and nonlinear analysis at 5% of error probability. It was evaluated the occurrence of multicollinearity. The negative exponential model resulted in good fit when data from red spectrum was used for chlorophyll a, green spectrum for chlorophyll b and a + b, making possible correlation coefficients between the estimated values and the extracted above 0.85. Except for the chlorophyll a content, the accuracy in estimates of photosynthetic pigments were higher than estimated by the chlorophyll meter, even with linearity between methods. Therefore, it is possible to estimate photosynthetic pigments on E. dunni leaves through values of red and green wavelengths from a digital color analyser.
关键词： Colorimetry,Chlorophylls,Spectrum colors
更新于2025-09-09 09:28:46
-
Carbon dots modified WO2-NaxWO3 composite as UV-Vis-NIR broad spectrum-driven photocatalyst for overall water splitting
摘要： The utilization of solar energy and valid photocatalyst is one of the most effective strategies to achieve water splitting into hydrogen (H2) and oxygen (O2). Although enormous effort has been devoted to photocatalysts, the sunlight still cannot be fully utilized by the developed photocatalysts. It is important but remains challenging to develop a broad spectrum-driven photocatalyst for overall water splitting. Here, we design a UV-Vis-NIR broad spectrum-driven carbon dots modified WO2-NaxWO3 (WO2-NaxWO3-CDs) composite as photocatalyst for overall water splitting without requirement of any sacrificial agents or cocatalysts. When the concentration of CDs in the sample is 0.008 gCDs/gcatalyst, the WO2-NaxWO3-CDs shows the highest photocatalytic activity with stoichiometric ratio of H2/O2 evolutions and their rates are 0.05/0.02, 2.58/1.24, 4.74/2.28 μmol/h under UV (λ< 420 nm), visible (420 nm≤λ≤760 nm) and near-infrared (λ>760 nm) light irradiation, respectively. It is also impressive that the photocatalyst shows excellent stability for about 6 cycles of repetitive experiments. The WO2-NaxWO3-CDs composites functioned as broad spectrum-driven photocatalyst for overall water splitting should attribute to the synergistic effect of WO2-NaxWO3 and CDs, in which the WO2-NaxWO3 provides the suitable bandgap, while the CDs can enhance light absorption and accelerate separation efficiencies of photo-generated charge carriers.
关键词： CDs,overall water splitting,broad spectrum,WO2-NaxWO3,photocatalyst
更新于2025-09-09 09:28:46
-
An insight into the polarization mechanism of rutile based oxides with a wide doping levels in the TiO2-CuO-TaO2.5 ternary system
摘要： Excellent dielectric properties have been found in some acceptor-donor co-doped rutile TiO2 type materials, but the polarization mechanism has long been debated. In present work, the polarization behaviors of single solid solutions Ti1-x(Cu0.333Ta0.667)xO2 (0 < x ≤ 0.465) samples are systematically investigated by establishing the ternary phase diagram of Ti1-xCu2x-2.5yTayO2 (0.05 ≤ x ≤ 1, 0 ≤ y ≤ 0.667). Basing on the obtained phase diagram and the analysis about microstructure, element valence and dielectric behaviors of rutile Ti1-x(Cu0.333Ta0.667)xO2 compositions with various doping levels (x = 0%, 5%, 18%, 33% and 45%), it is demonstrated the existence of multiple polarization mechanisms in this ternary dielectric system, i.e. free carrier nearest-neighbor-hopping polarization as well as internal barrier and surface barrier layer capacitor effect, contribute together to the overall dielectric behaviors. This work would provide guidance to achieve new electronics material with desired structures and properties.
关键词： Impedance spectrum,Polarization mechanism,High doping level,Ternary phase diagram
更新于2025-09-09 09:28:46
-
Robust beam hardening artifacts reduction for computed tomography (CT) using spectrum modeling
摘要： The aim of this study was to develop a fast and accurate beam hardening correction method by modeling physical interactions between X-ray photons and materials for computed tomography (CT) imaging. The nonlinear attenuation process of the X-ray projection was modeled by reprojecting a template image with the estimated polychromatic spectrum. By adding the scaled difference of the monochromatic reprojection data and the polychromatic reprojection to the raw projection data, the raw projection data was mapped into the corresponding monochromatic projection data, which was used to reconstruct the beam hardening artifacts corrected images. The algorithm can also be implemented in image-domain which takes the uncorrected image volume as input when there is an adequate model of the spectrum. In this case, the scaled difference was reconstructed to yield a set of artifacts images which can be added directly to the uncorrected images. Numerical simulations, experimental phantom data, and animal data which were acquired on a modern diagnostic CT scanner (Discovery CT750 HD, GE Healthcare, WI, USA), and a modern C-Arm CT scanner (Artis Zee, Siemens Healthcare, Forchheim, Germany), respectively, were used to evaluate the proposed method. The results show the proposed method significantly reduced both cupping and streak artifacts, and successfully recovered the Housfield Units (HU) accuracy. Extensive studies suggest the proposed model-based method successfully corrects the beam hardening artifacts. This work is practically useful and is promising to be applied to commercial products.
关键词： Computed tomography,quantitative imaging,spectrum modeling,polychromatic forward projection,beam hardening correction
更新于2025-09-09 09:28:46