共查询到20条相似文献,搜索用时 15 毫秒
1.
CO分子是监测大气污染气体的优异示踪气体,要实现对CO分子实时监控就需要做到对气体浓度的精确快速测量。气体分子浓度测量可以利用测量吸收光谱和谱线线形强度得到,CO的(3←0)泛频谱带是吸收较弱的跃迁波段,利用以干空气为缓冲气体的200μmol/mol的CO混合物,基于稳频的光腔衰荡装置测量了在温度293K、压力13~93kPa下的CO分子R支3条跃迁谱线的吸收光谱。HTP(Hartmann-Tran profile)线形被用来获得这些谱线的线形强度,测量结果的相对标准不确定度优于1%,与国际HITRAN、HITEMP和GEISA光谱数据库比较,相对偏差小于4%。 相似文献
2.
Mingli Wan Weiqing Zhai Yueli Song Yong Li Pengfei Ji Fengqun Zhou 《Journal of Modern Optics》2013,60(15):1264-1269
We theoretically investigate the plasmonic interaction between radiative localized surface plasmon resonances and subradiative propagating surface plasmon modes in a nanostructure consisting of a periodic array of gold nanobars and an optically thick gold film, separated by a silica dielectric spacer layer. A controllable transparency window within the broad dipole resonance profile is observed clearly in the reflectance spectra via tailoring the length of the bar, the periodicity of the nanoparticle array, or the incident angle of applied field, respectively, a classic analog of electromagnetically induced transparency (EIT). We believe that the last excitation configuration is particularly beneficial for the realization of active manipulation of plasmonic optical switching without using coupling/control fields required in the conventional EIT scheme. 相似文献
3.
By approximating the index distribution of a medium with electromagnetically induced transparency (EIT) as a gradient index (GRIN), propagation laws in the medium with EIT can be obtained. Transmission properties in an optical system with an EIT medium are analyzed. The results show that, unlike the case in the ordinary GRIN medium, the refractive index of EIT medium has the better controllability. Consequently, discussions are focused on how to conveniently manipulate the focal shift of the input in the EIT by means of controlling the index of the medium. Additionally, the speckle radius on the location of the actual focus can be diminished by adjusting some parameters in the EIT medium. 相似文献
4.
G. González J. M. J. Huttunen V. Kolehmainen A. Seppänen M. Vauhkonen 《Inverse Problems in Science & Engineering》2016,24(8):1411-1431
In electrical impedance tomography (EIT), two- or three-dimensional (2D or 3D) distribution of the electrical conductivity is reconstructed based on potential measurements from the surface of the object. In many industrial and medical applications of EIT, the conductivity distribution is discontinuous – due to, e.g. phase or tissue boundaries. Previous studies have shown that such features in the conductivity can be preserved by using total variation (TV) prior model in the EIT image reconstruction. Recently, both 2D and 3D TV models have been utilized in EIT simulation studies. This far, however, EIT reconstructions with TV models have been evaluated experimentally only in 2D cases or translationally invariant 3D cases. In this paper, an experimental study of EIT with a TV prior in a 3D geometry is presented. In addition, we propose the selection of the prior parameters in the TV model based on the prior information of materials in the target, and their conductivity ranges. The results demonstrate the robustness of the proposed parameter selection strategy, and verify that the use of the TV prior yields sharp reconstructions in 3D EIT. 相似文献
5.
Shangjie Ren Manuchehr Soleimani Yaoyuan Xu 《Inverse Problems in Science & Engineering》2018,26(7):1037-1061
Reconstruction of conductive inclusions in a homogeneous background medium is commonly seen in electrical impedance tomography (EIT). One of the methods to deal with the inclusion reconstruction problems is the shape-based method. With prior knowledge of conductivity of target inclusions, the boundary of inclusions is parameterized by several shape coefficients and recovered from EIT measurements. This paper presents a shape-based inclusion reconstruction method and its numerical implementation with boundary element method (BEM). A shape perturbation method (SPM) is proposed to calculate the shape sensitivity in EIT. To evaluate the accuracy of the presented method, a series of numerical tests are conducted. The characteristics of EIT shape sensitivity are analysed. Some factors influencing the reconstruction performance are discussed. 相似文献
6.
We report a new simple method for the signal enhancement of laser-induced breakdown spectroscopy using a pulsed buffer gas jet. The signal is enhanced up to more than 10 fold by using argon gas jets, which are injected through a pulsed nozzle onto the sample area to be analyzed. By synchronizing the buffer gas pulse with the laser pulse and optimizing the spatial arrangements between the gas jet and the sample surface, we have successfully exploited the useful properties of the buffer gas in open atmosphere. The signal-enhancement mechanism in our buffer gas jet has been discussed. Also, applications to various samples (metal, glass, and paper) have been demonstrated. 相似文献
7.
The Kerr nonlinear index of refraction for rubidium atoms is measured by using an optical ring cavity with and without electromagnetically induced transparency (EIT). Significant enhancement and inhibition of the Kerr nonlinear index is observed near resonance with EIT. The nonlinear index of refraction is measured as functions of probe and coupling frequency detunings, respectively, with and without the presence of EIT. A simple theoretical calculation including Doppler broadening is presented and is found to be in good qualitative agreement with the experimentally measured results. 相似文献
8.
Azeem Baig Mirza 《Journal of Modern Optics》2013,60(1):16-26
We explore the feasibility of attaining simultaneous electromagnetically induced transparency (EIT) and efficient nonlinear generation in different configurations of Doppler broadened diamond (double-cascade) systems such as, the frequency up-conversion, nearly degenerate and degenerate scheme. We show that EIT and nonlinear generation efficiency depend critically on the type of residual Doppler broadening present in each of the two cascade subsystems constituting the diamond system. Furthermore, it is observed that nonlinear generation with perfect EIT simultaneously in both subsystems is not possible as the process of nonlinear generation actually tends to oppose EIT. Yet in an extended medium, on resonance field propagation under matched conditions for probe and generated signal can occur when a balance (equilibrium) is established between these two competing processes. 相似文献
9.
10.
The results of an experimental investigation of a multinozzle gas-dynamic molecular-beam source, in which the working material
is introduced directly into a supersonic jet of a buffer gas, are presented. The source is designed to create slow cold beams
of atoms and molecules. Time-of-flight profiles of the beams of the N2 buffer gas and the working material SF6 formed by a source with six nozzles are presented. The measured parameters of the flow field of the buffer gas are compared
with the results of calculations for an axisymmetric nozzle with an inner body having an annular critical cross section. The
results obtained show that multinozzle designs can be used, in principle, in molecular-beam sources instead of axisymmetric
nozzles with an inner body. This permits relaxation of the requirements placed on the accuracy needed in fabricating such
sources, reduction of the buffer gas flow rate, and the employment of fairly simple schemes for recycling the buffer gas.
Pis’ma Zh. Tekh. Fiz. 23, 47–54 (October 26, 1997) 相似文献
11.
Cheng-Ning Huang Fang-Ming Yu Hung-Yuan Chung 《IEEE transactions on instrumentation and measurement》2008,57(6):1193-1198
This paper addresses a scanning data collection strategy in electrical impedance tomography (EIT) to enhance the quality of an impedance image by expanding the electrode number. This scanning EIT (SEIT) system rotates the electrode pairs at a small angle, and then, the measurement electrodes can scan around the circumference of a phantom tank. The numerical simulations examine the reconstructed result by using a cylindrical model with two conductivity varieties. The experimental results illustrate the reconstruction images with and without the SEIT from 2-D real measurement data. Compared with conventional EIT images, the images reconstructed from the scanning data collection strategy exhibit high resolution and are clearer. This paper provides a feasible configuration to reduce the noise and improve the resolution of the impedance image. 相似文献
12.
Single-particle levitation in conjunction with 264.3-nm laser excitation is used to measure the fluorescence emission of individual particles of Bacillus globigii spores. With precise humidity control, the fluorescence emission of wetted and desiccated Bacillus spore particles is measured from 300 to 450 nm. Comparison of spectra for Bacillus spores suspended in a standard buffer aqueous solution and for a desiccated 10-mum-diameter aggregate Bacillus spore particle shows that the spectra is virtually indistinguishable. However, at 85% relative humidity, corresponding to a 4.5M sodium chloride solution, the spore spectra redshifts by approximately 25 nm. It is postulated that the spectra redshifting is a result of specific interactions between the tyrosine fluorophore of the Bacillus spore and the phosphate moieties in the buffer solution. 相似文献
13.
A. I. Fedorov 《Technical Physics Letters》2000,26(7):625-627
The gas discharge and output radiation parameters were studied in XeCl lasers with various buffer gas compositions (argon vs. neon) and different types of excitation regimes (fast vs. quasi-stationary) in the preionization source. The intervals of specific energy for the neon-and argon-based buffer gas mixtures are 10–125 and 45–360 J/(l atm), respectively. The specific parameters of radiation in the neon-and argon-based buffer gas mixtures depend on the energy required for the UV preionization. For high-power UV preionization sources, the output parameters of lasers using argon-based gas mixtures may exceed those obtained with neonbased mixtures. 相似文献
14.
In this paper, ion sputtering of cathode material in a specific type of glow discharge—hollow cathode discharge (HCD)—is analyzed. To estimate both real sputtering yield and screening effect of the buffer gas, two different methods—combination of experimental and analytical approach (applicable for Ar buffer gas only) and use of Monte Carlo simulations—are used. The latter, which is introduced for the first time here, can be used for any buffer gas. Real sputtering yield Sk is estimated by Monte Carlo simulations for several commercial HCD lamps with Ne buffer gas: Ne-Li (0.046), Ne-As (0.862), Ne-Ca (0.337) and Ne-Cd (1.069). 相似文献
15.
16.
Rob H. Ireland David C. Barber 《International journal of imaging systems and technology》2007,17(6):379-382
Magnetic detection electrical impedance tomography (MD‐EIT) produces images of conductivity from magnetic field measurements taken around the body. The ill‐conditioned nature of the MD‐EIT inverse problem is improved by limiting the number of unknowns to be solved. In this article, a method of iterative grid refinement for MD‐EIT, which produces images significantly better than unconstrained solutions, is described. © 2008 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 379–382, 2007 相似文献
17.
J. S. Martins C. S. Moura R. M. F. Vargas 《Inverse Problems in Science & Engineering》2018,26(6):834-854
Image reconstruction in electrical impedance tomography (EIT) deals with an ill-posed and non-linear inverse problem. It has the objective of minimizing the difference between simulated (virtual) object data and electric voltage measurements performed on a non-simulated (real) object. In this paper, a new approach to the simulated annealing method applied to the reconstruction of EIT images is described. The main advantage of this approach is that all conductivity parameters are updated simultaneously. Most methods that employ simulated annealing to the problem of EIT usually evaluate each conductivity parameter individually resulting in high computational cost. The algorithm was tested both with computationally generated data and with measurements performed on a physical tank. In both cases, the method was able to make data inversion, determining the position, the dimensions and the conductivity of materials in an opaque object plane. 相似文献
18.
V.A. Sautenkov H. Li Y.V. Rostovtsev G.R. Welch J.P. Davis F.A. Narducci 《Journal of Modern Optics》2013,60(8):975-979
We have studied a time response of electromagnetically induced transparency (EIT) in a rubidium vapor to a rapid variation of optical phase. We have observed a very fast growth of the absorption when the phase of the optical field has been abruptly changed, followed by a slow return to the level of steady-state absorption. The recovery time decreases with increasing optical power. A simple theoretical analysis shows that under our experimental conditions the low power limit of the recovery time is determined by the ground relaxation time. In our case it is defined by a time-of-flight of rubidium atoms through laser beam. The obtained value of the ground state relaxation time is in a good agreement with result of direct measurements by ‘relaxation in the dark’ method. Our technique based on phase dynamics in EIT can be used for investigation of the ground state relaxation and the fast control of EIT. 相似文献
19.
一般采用气体流量计前加装缓冲器消除压缩机性能试验装置中气流脉动对测量精度的影响。本文分析2种适用于大型活塞式压缩机性能试验装置的缓冲器容积的计算方法,认为针对压缩机性能试验装置中的微小脉动气流,德国BORSIG的计算方法更加适合。搭建大型活塞式压缩机性能试验装置,利用经理论计算设计的缓冲器进行试验,发现即使在最大测试流量的情况下,缓冲器仍然可以很好地削减气流脉动的影响,从而大大提高压缩机试验装置的试验精度。 相似文献
20.
Rabia Jamil Abu Bakar Ali Muqaddar Abbas Fazal Badshah 《Journal of Modern Optics》2017,64(14):1457-1462
The Hartman effect is revisited using a Gaussian beam incident on a one-dimensional photonic crystal (1DPC) having a defect layer doped with four-level atoms. It is considered that each atom of the defect layer interacts with three driving fields, whereas a Gaussian beam of width w is used as a probe light to study Hartman effect. The atom–field interaction inside the defect layer exhibits electromagnetically induced transparency (EIT). The 1DPC acts as positive index material (PIM) and negative index material (NIM) corresponding to the normal and anomalous dispersion of the defect layer, respectively, via control of the phase associated with the driving fields and probe detuning. The positive and negative Hartman effects are noticed for PIM and NIM, respectively, via control of the relative phase corresponding to the driving fields and probe detuning. The advantage of using four-level EIT system is that a much smaller absorption of the transmitted beam occurs as compared to three-level EIT system corresponding to the anomalous dispersion, leading to negative Hartman effect. 相似文献