Spectral Filtration Research Articles

Experimental study of photovoltaic performance with a spectral filtration technique

The most significant challenge in the solar energy industry is the increase in PV temperature. Typically, the wavelength range throughout the terrestrial spectrum of the sun is 250 to 2500 nm, while that of the C-Si PV has a response between 750 and 1125 nm. This implies that PV cannot harness all photons for energy production, and an abundance of photons leads to an increase in PV temperature. This paper investigates the use of filters (Acrylic 6mm), (Acrylic 2.5mm), and (Polycarbonate 1.2mm) as heat-absorbing materials and spectrum filters for C-Si PV to improve PV performance and investigates various factors that impact the electrical features of PV. The ultraviolet, visible, and near-infrared spectrophotometer is used to perform a spectroscopic investigation of the filter. Following this analysis, the filter is transparent to the C-Si PV's response range of values. It has notable absorption in the infrared and ultraviolet spectrum zones. The experimental results, obtained from testing multiple filters in various scenarios with varying air gaps and irradiance levels using a solar simulator, showed a 9% decrease in temperature when using Acrylic 6mm at an airgap of 7cm and an irradiance of 850 W/m2. After increasing irradiance, using an Acrylic 6mm at an airgap of 7cm enhanced power by 16% and reduced temperature by 15.8%, with CPV at 1850 W/m2. The results obtained reveal that this technique helps to reduce PV temperature, increases lifetime, and enhances PV performance. Using filters depends on many factors because it was noticed that the average collected electrical power of the PV is dependent on the amount of irradiance, the air gap between the filter and the PV (the filter installation method), and the filter's absorption.

Low-cost dual-energy CBCT by spectral filtration of a dual focal spot X-ray source

Dual-energy cone beam computed tomography (DE-CBCT) has been shown to provide more information and improve performance compared to a conventional single energy spectrum CBCT. Here we report a low-cost DE-CBCT by spectral filtration of a carbon nanotube x-ray source array. The x-ray photons from two focal spots were filtered respectively by a low and a high energy filter. Projection images were collected by alternatively activating the two beams while the source array and detector rotated around the object, and were processed by a one-step materials decomposition and reconstruction method. The performance of the DE-CBCT scanner was evaluated by imaging a water-equivalent plastic phantom with inserts containing known densities of calcium or iodine and an anthropomorphic head phantom with dental implants. A mean energy separation of 15.5 keV was achieved at acceptable dose rates and imaging time. Accurate materials quantification was obtained by materials decomposition. Metal artifacts were reduced in the virtual monoenergetic images synthesized at high energies. The results demonstrated the feasibility of high quality DE-CBCT imaging by spectral filtration without using either an energy sensitive detector or rapid high voltage switching.

Imaging and characterization of optical emission from ex vivo tissue during conventional and UHDR PBS proton therapy

Objective. Imaging of optical photons emitted from tissue during radiotherapy is a promising technique for real-time visualization of treatment delivery, offering applications in dose verification, treatment monitoring, and retrospective treatment plan comparison. This research aims to explore the feasibility of intensified imaging of tissue luminescence during proton therapy (PT), under both conventional and ultra-high dose rate (UHDR) conditions. Approach. Conventional and UHDR pencil beam scanning (PBS) PT irradiation of fresh ex vivo porcine tissue and tissue-mimicking plastic phantom was imaged using intensified complementary metal-oxide-semiconductor(CMOS) cameras. The optical emission from tissue was characterized during conventional irradiation using both blue and red-sensitive intensifiers to ensure adequate spectral coverage. Spectral characterization was performed using bandpass filters between the lens and sensor. Imaging of conventional proton fields (240 MeV, 10 nA) was performed at 100 Hz frame rate, while UHDR PBS proton delivery (250 MeV, 99 nA) was recorded at 1 kHz frame rate. Dependence of optical emission yield on proton energy was studied using an optical tissue-mimicking plastic phantom and a range shifter. Finally, we demonstrated fast beam tracking capability of fast camera towards in vivo monitoring of FLASH PT. Main results. Under conventional treatment dose rates optical emission was imaged with single spot resolution. Spot profiles were found to agree with the treatment planning system calculation within >90% for all spectral bands and spot intensity was found to vary with spectral filtration. The resultant polychromatic emission presented a maximum intensity at 650 nm and decreasing signal at lower wavelengths, which is consistent with expected attenuation patterns of high fat and muscle tissue. For UHDR beam imaging, optical yield increased with higher proton energy. Imaging at 1 kHz allowed continuous monitoring of delivery during porcine tissue irradiation, with clear identification of individual dwell positions. The number of dwell positions matched the treatment plan in total and per row showing adequate temporal capability of iCMOS imaging. Significance. For the first time, this study characterizes optical emission from tissue during PT and demonstrates our capability of fast optical tracking of pencil proton beam on the tissue anatomy in both conventional and UHDR setting. Similar to the Cherenkov imaging in radiotherapy, this imaging modality could enable a seamless, independent validation of PT treatments.

Neurointerventions on two generations of angiography systems: Recent systems reduce radiation exposure by half

PurposeFluoroscopically-guided neurointervention may be associated with prolonged procedure time and substantial radiation exposure to the patient and staff. This study sought to examine technological features affecting the potential radiation exposure reduction of new angiography systems, compared to older systems, for neurointerventional procedures. MethodsConsecutive neurointerventional patients (2020–2022) were retrospectively analyzed. The air kerma at the reference point (Ka,r) and kerma-area product (KAP) were compared between Artis icono and Artis zee (Siemens) using statistical analyses (two-tailed t tests), where P < 0.05 is considered significant. X-ray tube potential and copper filtration were examined. Tests with an anthropomorphic phantom (Sun Nuclear) on Artis icono were conducted and entrance skin exposure and x-ray spectral half value layer were measured. Effective spectral filtration was characterized by x-ray spectral modeling. ResultsThe number of procedures was 1158 [median (range) age, 59 (7–95) years] on Artis zee and 1087 [60 (1–95) years] on Artis icono, without significant difference in age (p = 0.059) between cohorts. Ka,r was 925.4 (890.6–960.1) mGy [mean (95 % CI)] and KAP was 119.8 (115–124.5) Gy∙cm2 on Artis zee. The measures were 48–50 % lower on Artis icono, 440.5 (411.7–469.4) mGy (Ka,r) and 59.5 (55.4–63.6) Gy∙cm2 (KAP); while the difference in fluoroscopic time between the two generations of angiography systems was insignificant (p = 0.55). ConclusionsThe newer angiography system, with updated hardware and software, was found to result in half the radiation exposure compared to older technology of the same manufacturer, even though fluoroscopic time was similar.

Three new, UV spectrum filtration protocols for the synchronous quantification of ciprofloxacin HCl and ornidazole in the existence of ciprofloxacin-induced degradation compound

Three new spectrum filtration protocols have been developed and adapted to overcome some difficulties in dealing with highly overlapping triple drug mixtures by proposing new smart mathematical techniques that facilitate the resolution of the ternary mixture and the recovery of a filtrated zero-order spectrum (D0 spectrum) of each component without any overlapping from the accompanying components. The three established spectrophotometric protocols were conducted on the combination of ciprofloxacin hydrochloride and ornidazole as a green alternative to the usual chromatographic technique: the first protocol is ratio difference-isosbestic points coupled with ratio difference-areas under the curve (RD-ISO/RD-AUC); the second protocol is ratio difference-isosbestic points coupled with dual-wavelength equation (RD-ISO/DWE); and the third protocol is signal retrieval by zero-crossing point (SRZ). All three developed protocols have the power to recover a filtrated zero-order spectrum of each ornidazole and ciprofloxacin hydrochloride without any involvement from the ciprofloxacin-induced degradation substance through processing their spectral data either in the zero-order spectrum, ratio spectrum, or derivative spectrum. The correctness of the spectral filtration process for each protocol was checked by involving the spectral print recognition index to ensure the drug's purity and freeness from impurities or degradation products. The validation process was performed as per the directions of ICH, which confirmed the effectiveness of the elaborated protocols and their usability as daily analysis methods with a linearity range of (3.5–15 μg/ml) for ciprofloxacin in (RD-ISO/RD-AUC) and (RD-AUC/DWE) protocols and (1.5–15 μg/ml) in (SRZ) protocol; and a linearity range of (3–20 μg/ml) for ornidazole in (RD-ISO/RD-AUC) and (SRZ) protocols and (3–15 μg/ml) in (RD-ISO/DWE) protocol. A statistical comparison and greenness evaluation utilizing NEMI, AGREE, GAPI, and CALIFICAMET-HEXAGON tools were made with the reference approach, confirming no statistical variations and a better greenness profile for the newly established protocols.

Effect of tin spectral filtration on organ and effective dose in CT colonography and CT lung cancer screening.

Studies of tin spectral filtration have demonstrated potential in reducing radiation dose while maintaining image quality for unenhanced computed tomography (CT) scans. The extent of dose reduction, however, was commonly measured using the change in the scanner's reported CTDIvol . This method does not account for how tin filtration affects patient organ and effective dose. To investigate the effect of tin filtration on patient organ and effective dose for CT Lung Cancer Screening (LCS) and CT Colonography (CTC). A previously-developed Monte Carlo program was adapted to model a 96-row CT scanner (Somatom Force, Siemens Healthineers) with tin filtration capabilities at 100kV (100Sn) and 150kV (150Sn). The program was then validated using experimental CTDIvol measurements at all available kV (70-150kV) and tin-filtered kV options (100Sn and 150Sn). After validation, the program simulated LCS scans of the chest and CTC scan of the abdomen-pelvis for a population of 53 computational patient models from the extended cardiac-torso family. Each scan was performed using three different spectra: 120kV, 100Sn, and 150Sn. CTDIvol -normalized organ doses and DLP-normalized effective doses, commonly referred to as dose conversion factors, were compared between the different spectra. For all LCS and CTC scans, CTDIvol -normalized organ doses and DLP-normalized effective doses increased with increasing beam hardness (120kV, 100Sn, 150 Sn). For LCS, relative for 120kV, conversion factors for 100Sn produced a median increase in effective dose of 9%, with organ dose increases of 8% to lung, 5% to breast, 15% to thyroid, and 3% to skin. Conversion factors for 150Sn produced a median increase in effective dose of 20%, with organ dose increases of 16%, 18%, 26%, and 12% to these same organs, respectively. For CTC, relative for 120kV, conversion factors for 100Sn produced a median increase in effective dose of 12%, with organ dose increases of 9% to colon, 10% to liver, 11% to stomach, and 4% to skin. Conversion factors for 150Sn produced a median increase in effective dose of 21%, with organ dose increases of 16%, 17%, 19%, and 10% to these same organs, respectively. Results show that dose conversion factors are greater when using tin filtration and should be considered when evaluating tin's potential for dose reduction.

Photovoltaic/thermal (PV/T) solar collectors employing phase-change nano-capsules as spectral filters: Coupled, decoupled, and partially-coupled configurations

The ineffective utilization of solar radiation poses negative impacts on the performance of photovoltaic (PV) cells in terms of their efficiency and durability. For the first time, this study numerically introduces a comparative performance analysis between multiple PV/T configurations (thermally decoupled, coupled, and partially coupled) that employ nano-encapsulated phase-change material (nano-ePCM) dispersions. The dispersions act as multi-functional fluids that can optically filter incident radiation to fit the spectral response of Si PV cells, and serve as both heat carriers and storage media to effectively cool PV cells. The water-dispersed ePCM particles are made of silica shells and paraffin cores. The numerical model developed for the proposed configurations mainly comprises of three mathematical models (thermal, optical, and electrical) that are coupled together to simulate the performance of the novel systems. To ensure that the presented results are of high accuracy and credibility, the optical, electrical, and thermal models were rigorously validated against published data. Performance of the three PV/T configurations was comparatively analyzed upon varying the PCM core material, mass flowrate, channel depth, inlet and ambient temperatures, and wind speed. The utilized dispersion exhibited a 73.8% spectral match with Si PV cells, thus hinting at the effective spectral filtration capabilities of the designed fluid. When compared to similar PV/T configurations from different literatures, total exergy efficiency enhancements of 43.2%, 76.8%, and 2.6% were evident for the coupled, decoupled, and partially coupled systems, respectively. In addition, results have shown that the thermally decoupled system outperforms the coupled and partially coupled systems in terms of thermal performance but exhibits the poorest performance when superior electrical performance is desired.

Studying the Influence of the Interaction between Spectral Filtration and Slow Saturable Absorption on the Formation of Ultrashort Pulses in Optical Fiber Lasers

Studying the Influence of the Interaction between Spectral Filtration and Slow Saturable Absorption on the Formation of Ultrashort Pulses in Optical Fiber Lasers

Water liquid compatibility as a spectral splitting optical filtration fluid to six types of photovoltaic solar cells under high solar concentrations

The spectral-splitting optical filtration (SSOF) technique has attracted a lot of attention as a solution to the unnecessary portion of solar irradiation that can be stored as heat in the cells of conventional photovoltaic (PV) and photovoltaic/thermal (PV/T) systems. Transmitting the effective portion according to the SSOF fluid optical range and the spectral response of the integrated cell was the key solution proposed by this technique. The present study investigates the numerical feasibility of using liquid water, under six distinct solar concentration ratios, as a SSOF fluid for incident radiation on six types of PV cells with different spectral response ranges. For the 36 cases, the performance of PV and hybrid PV/T systems, represented as PV/Cooling fluid (PV/CF), with SSOF was evaluated and compared to their original performance without SSOF. In mid-July in Dhahran, Saudi Arabia, the functionality of each system was determined by analyzing the generated electrical and thermal energy over the course of a full day. In addition, the electrical efficiency and average PV temperature of the systems were estimated. In terms of spectral compatibility, the water SSOF was more compatible with three PV cells, out of the examined cells. At specified solar concentrations, depending on the engaged PV cell, the results demonstrated that integrating SSOF into the conventional PV and hybrid PV/CF systems produced more electricity at reduced PV temperatures, compared to the corresponding conventional system. In addition, the functionality was extended to increased solar concentrations. Due to the discrepancy in their spectral responses, the electrical energy and efficiency outputs of each cell type varied. When conventional systems were combined with SSOF, the spectral transmittance range of the liquid and the distinct spectral response ranges of the cells increased the number of possible combinations. p-Si and CIGS cells performed comparably in standalone PV and hybrid PV/CF systems, while CIGS and Perovskite cells performed comparably with SSOF. The m-Si and p-Si cells provided the most electrical energy and efficiency, while the a-Si cells were the least efficient, which thereafter influenced the selection of the highly functional system suitable for the PV cell type. At 8.2 suns and above, the hybrid SSOF/PV/CF system had the highest overall energy output and electrical efficiency, for all the examined cells, due to enhanced cooling and reduced solar radiation exposure.

Selective filtration of NMR signals arising from weakly- and strongly-coupled spin systems

Nuclear magnetic resonance (NMR) spectroscopy is a powerful technique for analyzing chemical and biological systems. However, in complex solutions with similar molecular components, NMR signals can overlap, making it challenging to distinguish and quantify individual species. In this paper, we introduce new spectral editing sequences that exploit the differences in nuclear spin interactions (J-couplings) between weakly- and strongly-coupled two-spin systems. These sequences selectively attenuate or nullify undesired spin magnetization while they preserve the desired signals, resulting in simplified NMR spectra and potentially facilitating single-species imaging applications. We demonstrate the effectiveness of our approach using a 31P spectral filtration method on a model system of nicotinamide dinucleotide (NAD), which exists in oxidized (NAD+) and reduced (NADH) forms. The presented sequences are robust to field inhomogeneity, do not require additional sub-spectra, and retain a significant portion of the original signal.

Continuous-wave single-frequency holmium-doped fiber laser based on saturable absorber

The single-frequency holmium-doped fiber laser with spectral filtration based on a dynamics filter formed in heavily holmium-doped fiber is presented. The continuous wave lasing on a single longitudinal mode in the spectral region of 2.1 μm with an output power of 1.6 mW is shown when the filtering fiber is cooled with liquid nitrogen. The optical signal-to-noise ratio and the relative intensity noise were more than 30 dB and — 62.8 dB Hz−1, respectively. The developed source can be used for gas spectroscopy as well as for remote atmosphere sensing of such gases as carbon dioxide, nitric oxide, ammonia, carbon monoxide and others.

Knock Recognition System in a PCCI Engine Powered by Diesel

The measurement of engine vibrations components is used to identify combustion phases in a single-cylinder PCCI diesel engine in this work. A single channel Knock transducer was used to measure engine vibration caused by combustion pressure forces and knocking tendency. The transducer is used to obtain the engine's frequency spectrum in the temporal domain. Categorization discrete wavelet analysis is used to isolate the observed vibration data. Spectral analysis and filtration of fragmented sections of the source signal are used in this approach. Fast Fourier transforms (FFT) and short-time Fourier transform (STFT) are used to investigating the discrete parts of the observed signals (STFT). In order to study engine events, time is given in milliseconds in the time-frequency domain. The engine knocking is determined from the observed signal using time-frequency analysis. The outcomes reveal that the engine events derived from vibration signals are closely connected to the premixing fuel ratio, as expected.

9.4: Plasmonic Nanostructure‐Loaded filtering film for Color Blindness Management

Optimization of filters for color blindness management was investigated to improve color vision on display devices. A model for simulation of CVD was built based on display primaries, twostage theory of human color vision and spectral filtration of filters. Spectral filtration of filters made of dye, nanostructures and multi‐layer dielectric filters was surveyed with varying primaries. Quantitative evaluation system of color contrast and naturalness were introduced into filter studies to optimize perceptual experience in both personal and public display products.

Feasibility of dual-energy CBCT by spectral filtration of a dual-focus CNT x-ray source.

Cone beam computed tomography (CBCT) is now widely used in dentistry and growing areas of medical imaging. The presence of strong metal artifacts is however a major concern of using CBCT especially in dentistry due to the presence of highly attenuating dental restorations, fixed appliances, and implants. Virtual monoenergetic images (VMIs) synthesized from dual energy CT (DECT) datasets are known to reduce metal artifacts. Although several techniques exist for DECT imaging, they in general come with significantly increased equipment cost and not available in dental clinics. The objectives of this study were to investigate the feasibility of developing a low-cost dual energy CBCT (DE-CBCT) by retrofitting a regular CBCT scanner with a carbon nanotube (CNT) x-ray source with dual focal spots and corresponding low-energy (LE) and high-energy (HE) spectral filters. A testbed with a CNT field emission x-ray source (NuRay Technology, Chang Zhou, China), a flat panel detector (Teledyne, Waterloo, Canada), and a rotating object stage was used for this feasibility study. Two distinct polychromatic x-ray spectra with the mean photon energies of 66.7keV and 86.3keV were produced at a fixed 120kVp x-ray tube voltage by using Al+Au and Al+Sn foils as the respective LE and HE filters attached to the exist window of the x-ray source. The HE filter attenuated the x-ray photons more than the LE filter. The calculated post-object air kerma rate of the HE beam was 31.7% of the LE beam. An anthropomorphic head phantom (RANDO, Nuclear Associates, Hicksville, NY) with metal beads was imaged using the testbed and the images were reconstructed using an iterative volumetric CT reconstruction algorithm. The VMIs were synthesized using an image-domain basis materials decomposition method with energy ranging from 30 to 150keV. The results were compared to the reconstructed images from a single energy clinical dental CBCT scanner (CS9300, Carestream Dental, Atlanta, GA). A significant reduction of the metal artifacts was observed in the VMI images synthesized at high energies compared to those from the same object imaged by the clinical dental CBCT scanner. The ability of the CNT x-ray source to generate the output needed to compensate the reduction of photon flux due to attenuation from the spectral filters and to maintain the CT imaging time was evaluated. The results demonstrated the feasibility of DE-CBCT imaging using the proposed approach. Metal artifact reduction was achieved in VMIs synthesized. The x-ray output needed for the proposed DE-CBCT can be generated by a fixed-anode CNT x-ray source.

Interaction between spectral filtration and slow relaxation saturable absorption during short pulse formation inside fiber lasers

Interaction between spectral filtration and slow relaxation saturable absorption during short pulse formation inside fiber lasers

Feasibility of dual-energy CBCT by spectral filtration of a dual-focus CNT x-ray source

Feasibility of dual-energy CBCT by spectral filtration of a dual-focus CNT x-ray source

Modes of wide-aperture acousto-optic diffraction in a uniaxial birefringent crystal

Acousto-optic (AO) anisotropic interaction in uniaxial birefringent crystals is a widespread and versatile approach to tunable spectral filtration of light. Its principal constraints are limited values of spectral and angular bandwidth restricting the light transmission and imaging performance of AO filters. A way to overcome these drawbacks is simultaneous Bragg diffraction of two or more light beams. In this paper, we discuss and compare the main features of four available modes of anisotropic wide-aperture AO interactions in uniaxial birefringent crystals. We calculate the angular aperture, spectral resolution and other parameters and estimate the spectral image quality features related to each one. Theoretical consideration and computational modeling are carried out for tellurium dioxide (TeO2)—the main AO crystal. Derived results are important for the development of AO imaging devices, particularly multi-channel AO tunable filters.

Influence of Spectral Filtration on Pulse Dynamics in Ring-Cavity Mamyshev Oscillator

Here we present a numerical study of pulsing build-up dynamics inside the fiber Mamyshev Oscillator (MO). The main scope of the investigation is to describe the influence of the spectral separation between the filters on self-starting MO dynamics and transition from multipulse to single-pulse generation regimes. It was found that Floquet stability analysis provides a straightforward way to determine whether the system will be self-starting or if it has to be excited by external source and predicts the repetition rate of the pulse train. We showed that spectrally overlapped bandpass filters provide reliable multi-pulse generation due to Faraday instability. Adiabatic increase in the spectral separation between the filters decreases the number of pulses down to single-pulse regime, therefore providing a flexible way to generate adjustable number of mode-locked pulses on demand.

Spectral Imaging Experiments with Various Optical Schemes Based on the Same AOTF.

Spectral image filtration by means of acousto-optical tunable filters (AOTFs) has multiple applications. For its implementation, a few different optical schemes are in use. They differ in image quality, number of coupling components, dimensions and alignment complexity. To choose the optical system of AOTF-based spectral imager properly, many factors have to be considered. Though various schemes of acousto-optic (AO) filtration have been tested and discussed, their comparative analysis has not been reported up to now. In this study, we assembled the four most popular schemes (confocal, collimating, tandem and double-path) using the same AO cells and experimentally compared their main features. Depending on the application, each scheme may be the basis of compact cost-effective spectral imaging devices.

A Performance Evaluation and Inter-laboratory Comparison of Community Face Coverings Media in the Context of COVID-19 Pandemic

During the recent pandemic of SARS-CoV-2, and as a reaction to the worldwide shortage of surgical masks, several countries have introduced new types of masks named “community face coverings” (CoFC). To ensure the quality of such devices and their relevance to slow down the virus spreading, a quick reaction of the certification organisms was necessary to fix the minimal acceptable performances requirements. Moreover, many laboratories involved in the aerosol research field have been asked to perform tests in a quick time according to (CEN, 2020) proposed by the European committee for standardization. This specification imposes a minimal air permeability of 96 L m–2 s–1 for a 100 Pa pressure drop and a minimal filtration efficiency of 70% for 3 µm diameter particles. In the present article, an intercomparison of efficiencies and permeabilities measured by 3 laboratories has been performed. Results are in good agreement considering the heterogeneity of the material samples (within 27% in terms of filtration efficiency and less than 20% in terms of permeability). On this basis, an analysis of 233 materials made of woven, non-woven and mixed fibrous material has been done in terms of filtration efficiency and air permeability. For some of them, measurements have been performed for 0.2 µm, 1 µm and 3 µm particle diameters. As expected, no deterministic correlation could be determined to link these efficiencies to the permeability of the considered samples. However, a trend could be identified for woven and mixed materials with an increase of filtration efficiency when the air permeability decreases. The same exercise has been conducted to link the filtration efficiency measured at 3 µm to the one for lower diameters. Finally, a discussion on the kind of material that is the most relevant to manufacture CoFC supported by spectral filtration efficiency values (from 0.02 µm to 3 µm) is proposed.