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DOUBLY-PERIODIC PHOTONIC CRYSTALS: SPECTRAL PROBLEMS ANALYSIS
摘要： The present work is devoted to the clari?cation of the conditions necessary for step-by-step justification of the possibility of reduction of the homogeneous system of linear algebraic equations for the spectral problems of 2-D photonic crystals by the plane waves method. The issues related to the algorithms and the numerical solutions of these spectral problems are analyzed. The possibility of analytical regularization is investigated, and the ways to improve the convergence of the obtained results are identi?ed.
关键词： spectral problems,plane waves method,photonic crystals,convergence,analytical regularization
更新于2025-09-23 15:21:01
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Pulmonary Bone Cement Embolism: CT Angiographic Evaluation with Material Decomposition Using Gemstone Spectral Imaging
摘要： We report a case of pulmonary bone cement embolism in a female who presented with dyspnea following multiple sessions of vertebroplasty. She underwent spectral CT pulmonary angiography and the diagnosis was made based on enhanced visualization of radiopaque cement material in the pulmonary arteries and a corresponding decrease in the parenchymal iodine content. Here, we describe the CT angiography findings of bone cement embolism with special emphasis on the potential benefits of spectral imaging, providing additional information on the material composition.
关键词： Bone cement,Spectral imaging,Pulmonary embolism,Dual-energy CT
更新于2025-09-23 15:21:01
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Peripapillary Retinal Nerve Fiber Layer Thickness Measured by Optical Coherence Tomography in Different Clinical Subtypes of Multiple Sclerosis
摘要： Background Multiple sclerosis (MS) is a chronic inflammatory demyelinating autoimmune disease of the central nervous system (CNS) with axonal degeneration as major determinant of neurological disability. Assessment of unmyelinated retinal nerve fibers using optical coherence tomography (OCT) may be useful for diagnosing the onset and rate of progression of neurodegeneration. Objective: To assess the incidence and severity of damage of the peripapillary retinal nerve fiber layer (RNFL) in two different MS subtypes: non-progressive [Prog(-)MS] and progressive [Prog(+)MS]. Methods 48 patients (96 eyes) with MS were included: 13 males, 35 females; aged 22-62 years (mean 38.8; SD ±10.02) in two subgroups: 26 Prog(-)MS and 22 Prog(+)MS. 3 subtypes of Prog(+)MS were identified by neurologist, according to Lublin criteria: 3 patients had PPMS (14%), 7 had SPMS(32%), 12 had PRMS(54%). RRMS subtype was considered a non-progressive phenotype, designated as Prog(-)MS. All 22 patients with progressive MS phenotypes were included in one group, designated as Prog(+)MS. Progressive disease can be defined over 1 year. The expanded EDSS score was determined by the treating MS specialist and confirmed by the study investigators through the records review. Definition included a 3-strata progression magnitude in the absence of a relapse, confirmed after 3 months within the leading Functional System and required an Expanded Disability Status Scale step ≥ 4 and pyramidal score ≥ 2. 11 Prog(-)MS (16 eyes) and 10 Prog(+)MS (13 eyes) patients had a history of optic neuritis (ON). EDSS score was 1.5-6.5 (mean 3.83±1.62) in the Prog(+)MS group and 1.0-3.5 (mean 1.40±0.57) in the Prog(-)MS. Control group: 31 healthy volunteers (3 males, 28 females), aged 20-62 years (mean 37.4 ±10.88). Peripapillary RNFL thickness was measured around the optic nerve head (ONH) using spectral-domain OCT (Topcon OCT 1000 MarkII, FastMap v. 3.40, Topcon, Japan). Scans were obtained according to OSCAR-IB consensus criteria. The generalized estimating equation model (GEE) was used in the statistical analysis to assess differences in RNFL thickness between Prog(-)MS and Prog(+)MS patients, taking into consideration history of ON, EDSS score, immunomodulatory therapy, MS progression, MS duration, age and gender. The protocol was approved by the Ethical Committee of the Medical Centre of Postgraduate Education, Warsaw, Poland and informed consent was obtained from all subjects. Results There was a significant difference between Prog(-)MS and Prog(+)MS groups for mean, nasal and superior quadrant of RNFL thickness. For individuals with a history of ON, significant differences were found between the two MS phenotypes regardless of RNFL thickness measurements. Conclusions A significant correlation was established between RNFL thickness and progression of neurodegeneration in MS patients with no regard to history of ON. RNFL thickness may be considered a MS biomarker and potential diagnostic tool for assessment of disease progression.
关键词： multiple sclerosis,spectral-domain optical coherence tomography,peripapillary retinal nerve fiber layer
更新于2025-09-23 15:21:01
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Disorganization of Retinal Inner Layers and Ellipsoid Zone Disruption Predict Visual Outcomes in Central Retinal Vein Occlusion
摘要： To assess the associations and predictive value of spectral-domain (SD) OCT inner and outer retinal structural parameters and visual acuity (VA) outcomes in macular edema (ME) secondary to central retinal vein occlusion (CRVO).
关键词： disorganization of retinal inner layers,visual acuity,ellipsoid zone disruption,macular edema,spectral-domain OCT,central retinal vein occlusion
更新于2025-09-23 15:21:01
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Changes in Retinal Layer Thickness in the?Contralateral Eye of Patients with Unilateral Neovascular Age-Related Macular Degeneration
摘要： To evaluate the thickness of the outer retinal layers and its relationship with visual function in fellow eyes of participants with unilateral neovascular age-related macular degeneration (AMD). Design: Longitudinal study. Participants: We enrolled 105 subjects with unilateral neovascular AMD from 3 clinical centers in Europe. Methods: The fellow eye, without advanced AMD, was selected for the study. Subjects were followed up with visits occurring every 6 months for 2 years. Spectral domain optical coherence tomography volume scans were collected at 3 clinical sites, in Belfast, Northern Ireland; Coimbra, Portugal; and Milan, Italy. Detailed manual segmentation of outer retinal layers was performed using the custom-designed and validated grading software 3D OCTOR. Thickness measurements for neurosensory retina, photoreceptor layer (PRL) outer segments, retinal pigment epithelium plus drusen (RPEtdrusen) complex, and choroidal layers from each sector of the standard macular grid were obtained. Measures of vison were distance visual acuity, near visual acuity, Smith-Kettlewell Institute low-luminance acuity score, and reading speed. Subjects were grouped based on the presence or absence of subretinal drusenoid deposits (SDDs) for further analysis. Main Outcome Measures: Change in thickness of retinal layers and change in measures of vision. Results: In all, 85 eyes were included in the analysis. The average duration of follow-up was 20.5 (cid:2) 5.8 months. By the ?nal visit, the RPEtdrusen complex was signi?cantly thinner when compared with baseline (29.7 mm vs. 34.09 mm; P ? 0.03). Low-luminance de?cit was signi?cantly worse at the ?nal visit (P < 0.001) and correlated with PRL outer segment thickness (r ? 0.33; P ?0.02). The RPEtdrusen complex was signi?cantly thicker in eyes with SDDs compared with that in those without SDDs (30.67 mm vs. 28.64 mm; P ? 0.02). PRL outer segments became signi?cantly thinner over time in eyes with SDDs compared with those in eyes without SDDs. Conclusions: The RPEtdrusen complex layer becomes thinner over time in fellow eyes of subjects with unilateral neovascular AMD. The rate of PRL outer segment thinning was higher in eyes with SDDs than in eyes without SDDs. These ?ndings are preliminary steps in the identi?cation of early biomarkers for detecting and monitoring the progression of AMD. Ophthalmology Retina 2018;-:1e10 a 2018 Published by Elsevier Inc. on behalf of the American Academy of Ophthalmology
关键词： spectral domain optical coherence tomography,visual function,retinal layer thickness,subretinal drusenoid deposits,age-related macular degeneration
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Experimental Study of the Spectral and Angular Solar Irradiance
摘要： We developed an experimental set-up and procedure to measure spectral and angular solar irradiance to accurately predict and optimize solar power plant performance. The set-up is comprised of a fiber coupled spectrometer mounted to a rotational stage which allows for 360? light capture. The lightweight and flexible design enables irradiance measurements at any location. Measurements were taken in Enschede, Netherlands and in Phoenix, AZ, USA. We find a strong location, dependence of spectro-angular irradiance on the surroundings and cloud coverage which needs to be considered when modelling and optimizing location dependent solar power plant output.
关键词： spectral albedo,Bifacial solar cells,spectral and angular irradiance,solar irradiance measurements
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International WIE Conference on Electrical and Computer Engineering (WIECON-ECE) - Bangalore, India (2019.11.15-2019.11.16)] 2019 IEEE International WIE Conference on Electrical and Computer Engineering (WIECON-ECE) - Closed-Loop Control of a DC-DC Four-Phase Interleaved Quadrupler for Solar Photovoltaic Applications
摘要： We propose ?lter banks in the graph spectral domain, where each ?lter is de?ned by a sum of sinusoidal waves. The main advantages of these ?lter banks are that (a) they have low approximation errors even if a lower-order shifted Chebyshev polynomial approximation is used, (b) the upper bound of the error after the pth order Chebyshev polynomial approximation can be calculated rigorously without complex calculations, and (c) their parameters can be ef?ciently obtained from any real-valued linear phase ?nite impulse response ?lter banks in regular signal processing. The proposed ?lter bank has the same ?lter characteristics as the corresponding classical ?lter bank in the frequency domain and inherits the original properties, such as tight frame and no DC leakage. Furthermore, their approximation orders can be determined from the desired approximation accuracy. The effectiveness of our approach is evaluated by comparing them with existing spectral graph wavelets and ?lter banks.
关键词： spectral graph wavelet,spectral graph ?lter bank,Graph signal processing,Chebyshev polynomial approximation
更新于2025-09-23 15:19:57
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Determination of uranium in ores using laser-induced breakdown spectroscopy combined with laser-induced fluorescence
摘要： The plasma emission spectrum of uranium in laser-induced breakdown spectroscopy (LIBS) is weak and susceptible to spectral interference, especially in a complex ore matrix. In this study, laser-induced breakdown spectroscopy combined with laser-induced fluorescence (LIBS-LIF) technology was proposed to enhance the spectral intensity of uranium in ores and eliminate spectral interference. Different combinations of excitation lines and analytical lines of the U element were investigated. In contrast with atomic lines, uranium ion lines are more suitable for determination of uranium. The relative number of U ions in plasma was studied for the best selection of excitation lines and analytical lines. The analytical performance of LIBS-LIF and LIBS for U determination in ores was compared. The results showed that all indicators had been significantly improved by LIBS-LIF. The slope, R2, LoD, RMSECV, ARE, and ARSD values of LIBS-LIF were 1.1 (cid:1) 105 counts per wt%, 0.998, 35 mg g(cid:3)1, 0.05 wt%, 6.69%, and 6.37%, respectively. This work demonstrates that LIBS-LIF has excellent potential in the exploration of uranium resources.
关键词： laser-induced breakdown spectroscopy,uranium,spectral interference,laser-induced fluorescence,ore matrix
更新于2025-09-23 15:19:57
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Evaluation of stress on metal surfaces by laser-induced breakdown spectroscopy
摘要： In this study, we evaluated the feasibility of using laser-induced breakdown spectroscopy (LIBS) to determine the stress generated in metal materials by comparing measured stress levels with those determined by x-ray diffraction (XRD). Magnesium (Mg) alloy specimens underwent impact stress generated under ultrasonic peening. Stainless steel specimens were subjected to bending stress. The reference stress for each specimen was measured using XRD. LIBS measurements were performed to determine the correlation between stress distribution and the ratio of ionic to atomic spectral line intensity. The stress distribution from the surface to the interior of the ultrasonic-peened specimens measured by LIBS showed a similar tendency to that measured by XRD, but there was a difference in the maximum measurable depth. Additionally, the tensile and compressive stress distributions measured by LIBS on bending specimens showed similar trends to those of XRD. From these results, it was possible to measure the correlation between the stress state of the metal matrix and the spectral line strength of LIBS, thus confirming the potential for stress measurement using LIBS.
关键词： laser-induced breakdown spectroscopy,mechanical stress,spectral line
更新于2025-09-23 15:19:57
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Polarization-Sensitive Self-Powered Type-II GeSe/MoS2 Van der Waals Heterojunction Photodetector
摘要： Polarization-sensitive photodetectors are highly desirable for high performance optical signal capture and stray light shielding in order to enhance the capability for detection and identification of targets in the dark, haze and other complex environments. Usually, filters and polarizers are utilized for conventional devices to achieve polarization-sensitive detection. Herein, to simplify the optical system, a 2-D self-powered polarization-sensitive photodetector is fabricated based on a stacked GeSe/MoS2 van der Waals (vdWs) heterojunction which facilitates efficient separation and transportation of the photogenerated carriers, due to type-II band alignment. Accordingly, a high performance self-powered photodetector is achieved with merits of a very large on-off ratio photocurrent at zero bias of currently 104 and a high responsivity (Rλ) of 105 mA/W with the external quantum efficiency (EQE) of 24.2%. Furthermore, a broad spectral photoresponse is extended from 380 nm to 1064 nm owing to the high absorption coefficient in a wide spectral region. One of the key benefits from these highly anisotropic orthorhombic structures of layered GeSe is self-powered polarization sensitive detection with a peak/valley ratio up to 2.95. This is realized irradiating with a 532 nm wavelength laser with which a maximum photoresponsivity of up to 590 mA/W is reached when the input polarization is parallel to the armchair direction. This work provides a facile route to fabricate self-powered polarization-sensitive photodetectors from GeSe/MoS2 vdW heterojunctions for integrated optoelectronic devices.
关键词： polarization sensitive photodetector,self-powered,type-II band alignment,GeSe/MoS2 heterojunction,broad spectral photoresponse
更新于2025-09-23 15:19:57