- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Towards Customized Spatial Resolution in TDLAS Tomography and Hugh McCann
摘要： Tunable diode laser absorption spectroscopy (TDLAS) tomography has been widely employed to spatially and temporally resolve gas parameters in combustion processes. The requirements placed on the spatial resolution of a tomographic image vary in industrial applications, depending on the size of the target field and the necessity to detect small features. Based on an optimized beam arrangement, this work proposes a scheme to customize the spatial resolution in the design of TDLAS tomography systems. To the best of our knowledge, the proposed scheme, for the first time, quantifies the impact on the spatial resolution of varying the number of samples of the imaging space, in both angular and linear dimensions. More importantly, the proposed scheme can be used to determine the most effective optical layout that would achieve a desired spatial resolution. The reduction in the system complexity will enable the sensor to be installed in practical combustors while maintaining reliability. Finally, we apply the proposed scheme in a case study based on experimental data previously acquired from an automotive engine.
关键词： tunable diode laser absorption spectroscopy (TDLAS),spatial resolution,combustion diagnosis,tomography,beam arrangement
更新于2025-09-11 14:15:04
-
Fingerprinting electronic structure of heme iron by ab initio modeling of metal L-edge X-ray absorption spectra
摘要： The capability of the multiconfigurational restricted active space approach to identify electronic structure from spectral fingerprints is explored by applying it to iron L-edge X-ray absorption spectroscopy (XAS) of three heme systems that represent the limiting descriptions of iron in the Fe-O2 bond, ferrous and ferric [Fe(P)(ImH)2]0/1+ (P = porphine,ImH = imidazole), and FeII(P). The level of agreement between experimental and simulated spectral shapes is calculated using the cosine similarity, which gives a quantitative and unbiased assignment. Further dimensions in fingerprinting are obtained from the L-edge branching ratio, the integrated absorption intensity, and the edge position. The results show how accurate ab initio simulations of metal L-edge XAS can complement calculations of relative energies to identify unknown species in chemical reactions.
关键词： multiconfigurational restricted active space,branching ratio,integrated absorption intensity,iron L-edge X-ray absorption spectroscopy,electronic structure,cosine similarity,edge position,heme systems,spectral fingerprints
更新于2025-09-10 09:29:36
-
Review of Incoherent Broadband Cavity-Enhanced Absorption Spectroscopy (IBBCEAS) for Gas Sensing
摘要： Incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) is of importance for gas detection in environmental monitoring. This review summarizes the unique properties, development and recent progress of the IBBCEAS technique. Principle of IBBCEAS for gas sensing is described, and the development of IBBCEAS from the perspective of system structure is elaborated, including light source, cavity and detection scheme. Performances of the reported IBBCEAS sensor system in laboratory and field measurements are reported. Potential applications of this technique are discussed.
关键词： supercontinuum light source,incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS),gas sensing,broadband light source,molecular spectroscopy
更新于2025-09-10 09:29:36
-
Green coloring of GaN single crystals introduced by Cr impurity
摘要： In this study unintentionally doped GaN grown by hydride vapor phase epitaxy that exhibits a sharply delimited region of green color was investigated. Optical analysis was performed by absorption and photoluminescence spectroscopy. An absorption band between 1.5 and 2.0 eV was found to be responsible for the green color and was related to a sharp emission at 1.193 eV by luminescence and excitation spectroscopy. The appearance of both optical signatures in the region of green color was related to an increase of Cr contamination detected by secondary ion mass spectrometry. We propose that the origin of green color as well as the emission line at 1.193 eV is attributed to internal transitions of Cr4+.
关键词： Crystal impurities,Photoluminescence spectroscopy,Bulk GaN,Hydride vapor phase epitaxy,Absorption spectroscopy
更新于2025-09-10 09:29:36
-
Principle of pulse oximetry
摘要： In the ICU, electrocardiogram (ECG) and SpO2 are required for patient monitoring. An ECG shows cardiac electrical activity, but pulse oximetry can measure the pulse rate and SpO2 using plethysmogram. Arterial blood drawing is not needed, and the SpO2 measurements are noninvasive, unlike SaO2 measurements. SpO2 is measured using a red light, an infrared light, and absorption spectroscopy. There are many factors affecting the measurement of SpO2. A low peripheral circulation and body movement can make the detection of the pulse wave difficult, greatly decreasing the accuracy of the SpO2 measurement. The solution for this disturbance to the measurement varies according to each maker. Understanding the principle of measurement is necessary for the interpretation of SpO2 values. There are two methods for measuring SpO2: transmittance and reflectance. The reflection type measures SpO2 at the supra-orbital artery, wherein arterial heartbeat is maintained at the time of a shock and the hypothermia. Moreover, the reflection type has a shorter discrimination time to SpO2 change than the finger of limb. This method is suitable for ICU patients with low peripheral perfusion and motion artifacts.
关键词： plethysmogram,absorption spectroscopy,SpO2,near-infrared spectroscopy,pulse oximeter
更新于2025-09-10 09:29:36
-
Tailoring the Optical Properties of Organic D-π-A Photosensitizers: Effect of Sulfur Introduction in the Acceptor Group
摘要： In this work, we present for the first time the synthesis and characterization of potential DSSC organic sensitizers whose cyanoacrylic acceptor/anchoring group was modified by replacement of oxygen with one or more sulfur atoms. Using known carboxylic acid dye DF15 as a reference, their TD-DFT computational analysis indicated that oxygen-sulfur substitution should induce a significant red-shift of the corresponding UV-Vis absorption spectra. Whereas synthesis of monothiocarboxylic derivatives of DF15 was successfully carried out, isolation of the analogous dithiocarboxylic acid proved impossible due to its very low stability: despite that, their relative spectroscopic properties could be compared by analyzing the corresponding benzylic esters. Combined computational and transient absorption spectroscopy studies suggested that photoexcited thiocarboxylic acid 1-SO and thioamide 1-SN were able to inject electrons into nanocrystalline TiO2, and indicated a similar charge injection efficiency for 1-SO relative to DF15. Preliminary DSSC studies showed that, when t-butylpyridine was present in the electrolyte solution, 1-SO was rapidly degraded; however, in the absence of basic additives 1-SO provided a sufficiently stable device, giving a slightly lower efficiency compared to carboxylic sensitizer DF15.
关键词： thiocarboxylic acid,transient absorption spectroscopy,thioamide,Organosulfur compounds,dye-sensitized solar cells
更新于2025-09-10 09:29:36
-
Increased nitrogen-vacancy centre creation yield in diamond through electron beam irradiation at high temperature
摘要： The nitrogen-vacancy (NV) centre is a fluorescent defect in diamond that is of critical importance for applications from ensemble sensing to biolabelling. Hence, understanding and optimising the creation of NV centres in diamond is vital for technological progress in these areas. We demonstrate that simultaneous electron irradiation and annealing of a high-pressure high-temperature diamond sample increases the NV centre creation efficiency from substitutional nitrogen defects by up to 117% with respect to a sample where the processes are carried out consecutively, but using the same process parameters. This increase in fluorescence is supported by visible and infrared absorption spectroscopy experiments. Our results pave the way for a more efficient creation of NV centres in diamond as well as higher overall NV densities in the future.
关键词： diamond,nitrogen-vacancy centre,high temperature,fluorescence,absorption spectroscopy,electron beam irradiation
更新于2025-09-10 09:29:36
-
[Nanostructure Science and Technology] Nanowire Electronics || X-Ray Spectroscopic Analysis of Electronic Properties of One-Dimensional Nanostructured Materials
摘要： Recent studies of the control of the shape and size of nanomaterials have enabled researchers to explore the development of energy storage and conversion applications in unprecedented detail. Nanomaterials can be exploited into green energy strategies if their surface architectures can be controlled by various treatment processes. Their remarkable behaviors arise in part from their small size, large surface area, and quantum con?nement. Nanomaterial science has various implications for environmental science and sustainability. Physical and chemical routes for controlling morphologies, crystal structures, and physical and chemical properties can be exploited to improve performance, expand the function, and extend lifetime of devices with energy storage and conversion applications. Such devices that involve nanomaterials include storage and conversion devices (energy storage, hydrogen generation, water-splitting and dye-sensitized solar cells (DSSC)), optical and electronic devices (semiconductors, photoelectrocatalytic, and waveguides), and environmental devices (sensors and adsorption/separation), among others. Such applications typically rely on emerging electrode designs, which support the realization of energy storage and conversion devices, whose manufacture can be done more ef?ciently by nanotechnology. The unique features of nanomaterials have been in the development of energy storage and conversion proved to be useful.
关键词： supercapacitors,nanomaterials,conversion,water-splitting,X-ray absorption spectroscopy,energy storage,MnO2,TiO2
更新于2025-09-10 09:29:36
-
Disentangling the Electron and Hole Dynamics in Janus CdSe/PbSe Nanocrystals through Variable Pump Transient Absorption Spectroscopy
摘要： CdSe/PbSe Janus hetero-nanocrystals (HNCs) represent an interesting system where structurally immiscible CdSe and PbSe co-exist in a single structure with intermixed electronic states. Here, we have investigated the carrier dynamics in Janus CdSe/PbSe HNCs through ultrafast transient absorption spectroscopy by selectively exciting either the CdSe or the PbSe domains. Upon excitation of the CdSe domain sub-picosecond hole transfer to the hybrid interfacial PbSe states were identified. On the other hand, the transfer of hot electron from PbSe to CdSe was evident upon creation of hot electrons in PbSe domain without exciting the CdSe domain. The photo-excited hot hole also gets transferred to the hybrid interfacial states in sub-ps time (~1ps) bleaching the corresponding transition. The decay of the localized hole was found to be much slower compared to the electron which can be beneficial for carrier extraction and multiexciton generation. The finding of hot electron transfer in a single structure and slow decay of holes can thus prove to be advantageous for future design of photovoltaic devices.
关键词： carrier dynamics,ultrafast transient absorption spectroscopy,CdSe/PbSe Janus hetero-nanocrystals,photovoltaic devices,hot electron transfer
更新于2025-09-10 09:29:36
-
Characterization and bioavailability of rainwater dissolved organic matter at the southeast coast of China using absorption spectroscopy and fluorescence EEM-PARAFAC
摘要： Rainwater brings considerable amounts of dissolved organic matter (DOM) from atmosphere to freshwater and marine environments, but little is known about the chemical composition and bioavailability of rainwater DOM. The quantity, quality, and bioavailability of DOM were investigated for 21 rain events at a coastal site in southeast China, using dissolved organic carbon (DOC) measurements, absorption spectroscopy, and fluorescence excitation-emission matrices-parallel factor analysis (EEM-PARAFAC). The DOC concentration ranged from 35 to 457 μM, which was affected by the prevailing monsoon, rainfall amount and terrestrial/anthropogenic inputs. The volume-weighted average DOC was 118 μM, corresponding to a rainwater DOC flux of 1.98 g m?2 yr?1. Four fluorescent components were identified with EEM-PARAFAC, including three humic-like components (C1-C3) and one tyrosine-like component C4. Absorption coefficient (aCDOM(300)) and fluorescence intensities of C2-C4 strongly correlated with DOC, indicating they can be used for DOC estimation. Rainwater DOM was characterized by low DOC-specific UV absorbance (SUVA254) and humification index (HIX), which indicated a low aromaticity and humification degree. Principal component analysis (PCA) based on DOM indices revealed two principal factors, which were related to the DOM concentration and humification degree respectively. PCA, together with air-mass trajectory analysis, successfully separated different rain events with variable inputs from living plants/local sources, soil organic matter/humified materials, and the marine source. Rainwater DOM generally showed a high bioavailability of 50% ± 19%, with higher degradability of non-chromophoric constituents and C1-C2 than other components. This study demonstrated the applicability of absorption and EEM-PARAFAC combined with PCA and air-mass trajectory analysis in differentiating rain events and tracking organic matter sources, and revealed different effects of microbial degradation on individual PARAFAC components in rainwater.
关键词： Dissolved organic matter,Absorption spectroscopy,EEM-PARAFAC,Rainwater,Bioavailability
更新于2025-09-10 09:29:36