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Effect of the Orientation Schemes of the Energy Collection Element on the Optical Performance of a Parabolic Trough Concentrating Collector
摘要： While the circular shape is currently the proven optimum design of the energy collection element (ECE) of a parabolic trough collector, that is yet to be confirmed for parabolic trough concentrating collectors (PTCCs) like trough concentrating photovoltaic collectors and hybrid photovoltaic/thermal collectors. Orientation scheme of the ECE is expected to have significant effect on the optical performance including the irradiance distribution around the ECE and the optical efficiency, and therefore, on the overall energy performance of the PTCC. However, little progress addressing this issue has been reported in the literature. In this study, a thorough investigation has been conducted to determine the effect of the orientation schemes of ECE on the optical performance of a PTCC applying a state-of-the-art Monte Carlo ray tracing (MCRT) technique. The orientation schemes considered are a flat rectangular target and a hollow circular, semi-circular, triangular, inverted triangular, rectangular and rectangle on semi-circle (RSc). The effect of ECE defocus, Sun tracking error and trough rim angle on the optical performance is also investigated. The MCRT study reveals that the ECE orientation schemes with a curved surface at the trough end showed much higher optical efficiency than those with a linear surface under ideal conditions. ECEs among the linear surface group, the inverted triangular orientation exhibited the highest optical efficiency, whereas the flat and triangular ones exhibited the lowest optical efficiency, and the rectangular one was in between them. In the event of defocus and tracking errors, a significant portion of the concentrated light was observed to be intercepted by the surfaces of the rectangular and RSc ECEs that are perpendicular to the trough aperture. This is an extended version of a published work by the current authors, which will help to design an optically efficient ECE for a parabolic trough concentrating collector.
关键词： optical efficiency,optical performance,concentrating solar power,parabolic trough concentrating collector,irradiance distribution,Monte Carlo ray tracing
更新于2025-09-23 15:23:52
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Growth, optical, mechanical and thermal behavior of unidirectionally grown L-Glutaminium p-Toluenesulfonate crystal
摘要： Organic crystal of L-Glutaminium p-Toluenesulfonate (LGPT) was grown unidirectional by Sankaranarayanan and Ramasamy (SR) method. The grown crystal belongs to monoclinic crystal system with noncentrosymmetric space group P21. High resolution XRD confirms crystalline perfection of the grown crystal. Optical transmission shows that unidirectional grown crystal has higher transmittance and the lower cut-off wavelength is 290 nm. The emission wavelength of grown crystal is 410 nm and emission region is confirmed by luminescence spectra. The laser damage threshold value of unidirectional crystal has increased by 0.3 GW/cm2. The grown LGPT crystals belong to hard material category and it confirms the normal indentation size effect. The grown LGPT crystal is thermally stable upto 165 oC and decomposition of the molecules were elucidated by using TGA and DSC. Powder second harmonic generation measurement confirms the efficiency of the grown LGPT crystal is 0.8 times that of KDP.
关键词： Nonlinear optical materials,Crystal growth,Recrystallization,Optical properties
更新于2025-09-23 15:23:52
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Compact Transportable Optical Standard Based on a Single 171Yb+ Ion (“YBIS” Project)
摘要： The schematic diagram of the compact transportable optical frequency standard based on the quadrupole transition in a single 171Yb+ ion with a relative instability at the level of 5 · 10?16, less than 1 m3 in volume and less than 300 kg in weight is presented. The ionic trap and laser systems are described. Trapping and laser cooling of the 174Yb+ ion are experimentally demonstrated.
关键词： ytterbium ion,transportable frequency standard,optical clock
更新于2025-09-23 15:23:52
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Multi-Spectral Ship Detection Using Optical, Hyperspectral, and Microwave SAR Remote Sensing Data in Coastal Regions
摘要： The necessity of efficient monitoring of ships in coastal regions has been increasing over time. Multi-satellite observations make it possible to effectively monitor vessels. This study presents the results of ship detection methodology, applied to optical, hyperspectral, and microwave satellite images in the seas around the Korean Peninsula. Spectral matching algorithms are used to detect ships using hyperspectral images with hundreds of spectral channels and investigate the similarity between the spectra and in-situ measurements. In the case of SAR (Synthetic Aperture Radar) images, the Constant False Alarm Rate (CFAR) algorithm is used to discriminate the vessels from the backscattering coefficients of Sentinel-1B SAR and ALOS-2 PALSAR2 images. Validation results exhibited that the locations of the satellite-detected vessels showed good agreement with real-time location data within the Sentinel-1B coverage in the Korean coastal region. This study presented the probability of detection values of optical and SAR-based ship detection and discussed potential causes of the errors. This study also suggested a possibility for real-time operational use of vessel detection from multi-satellite images based on optical, hyperspectral, and SAR remote sensing, particularly in the inaccessible coastal regions off North Korea, for comprehensive coastal management and sustainability.
关键词： ship detection,coastal region,hyperspectral,sustainability,optical remote sensing,SAR
更新于2025-09-23 15:23:52
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Low-loss and broadband non-volatile phase-change directional coupler switches
摘要： An optical equivalent of the field-programmable gate array (FPGA) is of great interest to large-scale photonic integrated circuits. Previous programmable photonic devices relying on the weak, volatile thermo-optic or electro-optic effect usually suffer from a large footprint and high energy consumption. Phase change materials (PCMs) offer a promising solution due to the large non-volatile change in the refractive index upon phase transition. However, the large optical loss in PCMs poses a serious problem. Here, by exploiting an asymmetric directional coupler design, we demonstrate non-volatile PCM-clad silicon photonic 1 × 2 and 2 × 2 switches with a low insertion loss of ~1 dB and a compact coupling length of ~30 μm while maintaining a small crosstalk less than ?10 dB over a bandwidth of 30 nm. The reported optical switches will function as the building blocks of the meshes in the optical FPGAs for applications such as optical interconnects, neuromorphic computing, quantum computing, and microwave photonics.
关键词： Silicon photonics,Non-volatile,Optical switches,Phase-change materials,Reconfigurable photonics,Integrated photonic devices
更新于2025-09-23 15:23:52
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Soliton slow light for closed loop quantum systems
摘要： This paper describes the dynamics of solitonic pulse propagation in a closed loop quantum system comprised of five atomic energy levels. Although the propagation of an intense probe pulse suffers losses and broadening in linear regime, there exist specific conditions where the probe pulse is found to become robust during its propagation. We attribute this regime to the formation of an optical soliton with a slow group velocity because of the balance between the dispersion and Kerr optical nonlinearity. Results obtained are based on the theoretical model using the coupled Maxwell-Bloch equations for the nonlinear propagation.
关键词： Optical solitons,Kerr nonlinearity,Nonlinear pulse propagation,Closed-loop quantum system
更新于2025-09-23 15:23:52
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Spectral correction for handheld optoacoustic imaging by means of near-infrared optical tomography in reflection mode
摘要： In vivo imaging of tissue/vasculature oxygen saturation levels is of prime interest in many clinical applications. To this end, the feasibility of combining two distinct and complementary imaging modalities was investigated: optoacoustics (OA) and near-infrared tomography (NIROT), both operating noninvasively in reflection mode. Experiments were conducted on two optically heterogeneous phantoms mimicking tissue before and after the occurrence of a perturbation. OA imaging was used to resolve submillimetric vessel-like optical absorbers at depths up to 25 mm, but with a spectral distortion in the OA signals. NIROT measurements were utilized to image perturbations in the background and to estimate the light fluence inside the phantoms at the wavelength pair (760 nm, 830 nm). This enabled the spectral correction of the vessel-like absorbers' OA signals: the error in the ratio of the absorption coefficient at 830 nm to that at 760 nm was reduced from 60%-150% to 10%-20%. The results suggest that oxygen saturation (SO2) levels in arteries can be determined with <10% error and furthermore, that relative changes in vessels' SO2 can be monitored with even better accuracy. The outcome relies on a proper identification of the OA signals emanating from the studied vessels.
关键词： fluence compensation,near-infrared optical tomography,blood oxygen saturation,quantitative optoacoustic imaging,optoacoustic signal quantification,multimodal imaging,spectral correction
更新于2025-09-23 15:23:52
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Characterization of Abnormal Optic Nerve Head Morphology in Albinism Using Optical Coherence Tomography
摘要： PURPOSE. To characterize abnormalities in three-dimensional optic nerve head (ONH) morphology in people with albinism (PWA) using spectral-domain optical coherence tomography (SD-OCT) and to determine whether ONH abnormalities relate to other retinal and clinical abnormalities. METHODS. Spectral-domain OCT was used to obtain three-dimensional images from 56 PWA and 60 age- and sex-matched control subjects. B-scans were corrected for nystagmus-associated motion artefacts. Disc, cup, and rim ONH dimensions and peripapillary retinal nerve fiber layer (ppRNFL) thickness were calculated using Copernicus and ImageJ software. RESULTS. Median disc areas were similar in PWA (median ? 1.65 mm2) and controls (1.71 mm2, P ? 0.128), although discs were significantly elongated horizontally in PWA (P < 0.001). In contrast, median optic cup area in PWA (0.088 mm2) was 23.7% of that in controls (0.373 mm2, P < 0.001), with 39.4% of eyes in PWA not demonstrating a measurable optic cup. This led to significantly smaller cup to disc ratios in PWA (P < 0.001). Median rim volume in PWA (0.273 mm3) was 136.6% of that in controls (0.200 mm3). The ppRNFL was significantly thinner in PWA compared with controls (P < 0.001), especially in the temporal quadrant. In PWA, ppRNFL thickness was correlated to ganglion cell thickness at the central fovea (P ? 0.007). Several ONH abnormalities, such as cup to disc ratio, were related to higher refractive errors in PWA. CONCLUSIONS. In PWA, ocular maldevelopment is not just limited to the retina but also involves the ONH. Reduced ppRNFL thickness is consistent with previous reports of reduced ganglion cell numbers in PWA. The thicker rim volumes may be a result of incomplete maturation of the ONH.
关键词： albinism,optic nerve head,optical coherence tomography
更新于2025-09-23 15:23:52
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Synthesis of Bi <sub/>2</sub> O <sub/>3</sub> films, studying their optical, structural, and surface roughness properties
摘要： Reactive pulse laser deposition system was used to prepare Bi2O3 thin films at different laser fluence. It effect on the physical properties of thin films was investigated. A Polymorphous structure was obtaining from XRD results. While the obtained microscopic results from AFM show that grain size is varied between 33.48nm and 131.6 nm. The estimated band gap value from the optical transmission found to range from 1.7-2.9 eV.
关键词： Pulsed laser deposition,morphological properties,Optical properties,Bismuth trioxide,structural properties
更新于2025-09-23 15:23:52
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Alkali-metal-adsorbed g-GaN monolayer: ultralow work functions and optical properties
摘要： The electronic and optical properties of alkali-metal-adsorbed graphene-like gallium nitride (g-GaN) have been investigated using density functional theory. The results denote that alkali-metal-adsorbed g-GaN systems are stable compounds, with the most stable adsorption site being the center of the hexagonal ring. In addition, because of charge transfer from the alkali-metal atom to the host, the g-GaN layer shows clear n-type doping behavior. The adsorption of alkali metal atoms on g-GaN occurs via chemisorption. More importantly, the work function of g-GaN is substantially reduced following the adsorption of alkali-metal atoms. Specifically, the Cs-adsorbed g-GaN system shows an ultralow work function of 0.84 eV, which has great potential application in field-emission devices. In addition, the alkali-metal adsorption can lead to an increase in the static dielectric constant and extend the absorption spectrum of g-GaN.
关键词： Density functional theory,Optical properties,Field emission device,Adsorption,Work function,G-GaN
更新于2025-09-23 15:23:52