Background Losses Research Articles

Flare Removal Model Based on Sparse-UFormer Networks.

When a camera lens is directly faced with a strong light source, image flare commonly occurs, significantly reducing the clarity and texture of the photo and interfering with image processing tasks that rely on visual sensors, such as image segmentation and feature extraction. A novel flare removal network, the Sparse-UFormer neural network, has been developed. The network integrates two core components onto the UFormer architecture: the mixed-scale feed-forward network (MSFN) and top-k sparse attention (TKSA), creating the sparse-transformer module. The MSFN module captures rich multi-scale information, enabling the more effective addressing of flare interference in images. The TKSA module, designed with a sparsity strategy, focuses on key features within the image, thereby significantly enhancing the precision and efficiency of flare removal. Furthermore, in the design of the loss function, besides the conventional flare, background, and reconstruction losses, a structural similarity index loss has been incorporated to ensure the preservation of image details and structure while removing the flare. Ensuring the minimal loss of image information is a fundamental premise for effective image restoration. The proposed method has been demonstrated to achieve state-of-the-art performance on the Flare7K++ test dataset and in challenging real-world scenarios, proving its effectiveness in removing flare artefacts from images.

Improvement of Efficiency in 976 nm Fiber Amplifier by Spectral Filtering in Yb-Doped Fiber with Absorbing Rods Embedded in the Cladding

A novel Yb-doped fiber design for improved lasing near 976 nm based on spectral filtering of the amplified spontaneous emission near 1030 nm was realized and investigated. A very sharp short-pass filter was implemented by adding appropriately chosen high-index absorbing rods into the silica cladding. In this case, the resonant interaction of the core mode with the high-index rod mode could be controlled by fiber bending, which allows for the precise adjustment of the stop-band position. It was shown that the utilization of Sm-doped absorbing rods allows one to achieve very high absorption of emission at unwanted wavelengths, but it also adds background losses for the pump near 915 nm and for the signal at 976 nm. Despite this fact, the improvement of efficiency in the 976 nm fiber amplifier, after shifting the stop-band to 1000 nm, was clearly demonstrated. Based on theoretical calculations, it was shown that, after optimizing the fiber parameters, a further twofold improvement in efficiency was possible despite the excess losses at the pump and signal wavelengths.

Quantum illumination using polarization-path entangled single photons for low reflectivity object detection in a noisy background.

Detecting object with low reflectivity embedded within a noisy background is a challenging task. Quantum correlations between pairs of quantum states of light, though are highly sensitive to background noise and losses, offer advantages over traditional illumination methods. Instead of using correlated photon pairs which are sensitive, we experimentally demonstrate the advantage of using heralded single-photons entangled in polarization and path degree of freedom for quantum illumination. In the study, the object of different reflectivity is placed along the path of the signal in a variable thermal background before taking the joint measurements and calculating the quantum correlations. We show the significant advantage of using non-interferometric measurements along the multiple paths for single photon to isolate the signal from the background noise and outperform in detecting and ranging the low reflectivity objects even when the signal-to-noise ratio is as low as 0.03. Decrease in visibility of polarization along the signal path also results in similar observations. This will have direct relevance to the development of single-photon based quantum LiDAR and quantum imaging.

A deductible comparison of cost per-loss, cost per-payment event, loss elimination ratio under exponentially and lognormally distributed severities

The maximum amount of losses retained by the insured under deductible policy modifications is usually set as part of the terms of the policy conditions. The objective of this study are to (i) estimate mean losses of an insured risk by means of the operational behavior of density function with deductible modifications and (ii) compare the mean severities under exponentially and log-normally distributed arbitrary policy in a cost per loss and cost per payment contingencies. The results show that despite the established fact in literature that log-normal severity distribution has a thicker tail than the exponential distribution, its cost per loss payment is correspondingly lower than the corresponding values of the exponential mean loss. Computational evidence over the trend of the change in the loss eliminated in the domain for which deductible has been defined revealed that the cost per loss amount is less than the cost per payment amount in the two models. The method can be used to estimate aggregate claims as the deductible level increases for every scheme holder and such that the estimated claims could be compared with the hypothetical observed claims which can be arrived at by applying the hypothetical deductible value to the background losses.

Heralded single-pixel imaging with high loss-resistance and noise-robustness

Imaging with non-classically correlated photon-pairs takes advantages over classical limits in terms of sensitivity and a signal-to-noise ratio. However, it is still a challenge to achieve a strong resilience to background noise and losses for practical applications. In this work, we present heralded single-pixel imaging that is remarkably robust against bright background noise and severe signal losses. Using a strong temporal correlation between a photon-pair and joint measurement-based imaging method, we achieve the suppression of noise up to 1000 times larger than the signal and also demonstrate the correlation-induced SNR enhancement factor of over 200 against 70 times larger noise and a 90% signal loss compared to non-time-gated classical imaging. Our work enables correlated imaging with a highly scalable photon capacity.

Near-Maximal Two-Photon Entanglement for Optical Quantum Communication at 2.1μm

The 2- to 2.5-$\ensuremath{\mu}$m waveband enjoys reduced solar background and low propagation losses in the atmosphere and hollow-core optical fibers. However, harnessing these advantages for optical quantum communications has proved challenging due to a lack of suitable quantum light sources and detectors. The authors demonstrate in this waveband a source of entangled photons that is suitable for generating secure keys for quantum key distribution, and provide device-independent certification of the entanglement. These results are promising for the future implementation of device-independent secure optical quantum communications in daylight.

Two-step manufacturing of hundreds of meter-long silicon micrometer-size core optical fibers with less than 0.2 dB/cm background losses

This work reports on the fabrication and the characterization of hybrid optical fibers with silicon core and silica cladding. Adopting a two-step manufacturing technique derived from the stack-and-draw method, silicon-core fibers with core dimensions ranging from about 0.8 μm to 3.5 μm have been successively drawn into hundreds of meter-long fibers. A 3.3 μm diameter core fiber has been more extensively characterized and background losses for this as-drawn fiber are less than 0.2 dB/cm between 1250 nm and 1650 nm, with a minimum of 0.12 dB/cm around 1600 nm. The crystalline state of the core and the limited impact of oxygen contamination were confirmed by Raman scattering, x-ray diffraction, HR-STEM, and ToF-SIMS analysis. Transmission peaks associated with specific modal distributions are evidenced under certain injection conditions and their positions are shown to be in good accordance with mode cut-off wavelengths of a step-index silicon-core fiber.

DETERMINATION OF OIL AND OIL PRODUCT LOSSES FROM EVAPORATION WHEN LOADING VEHICLES

Background Losses of oil and oil products from evaporation when they are loaded into tankers, automobile and railway tanks at points that are not equipped with steam recovery units are inevitable. This also leads to environmental pollution and may lead to the formation of explosive concentrations in the air of the working area. Therefore, the control of losses of oil and oil products from evaporation at filling points is an urgent task. Aims and Objectives The purpose of this article is to develop a method for calculating losses of oil and petroleum products from evaporation at filling points. Results A formula has been obtained for calculating the loss of oil and oil products from evaporation based on the results of measuring the mass content of hydrocarbons in a vapor-air mixture. It is shown that the previously proposed formulas of P.R. Rivkin for this purpose do not take into account a large number of significant factors.

Simulations of radiation effects on erbium–ytterbium co-doped fiber amplifiers for space applications

An improved model of erbium–ytterbium codoped fiber amplifier (EYDFA) considering the effects of radiation is proposed. In this model, terms of radiation-induced losses are introduced into power propagation equations, combined with the simplified rate equations to simulate radiation effects on EYDFA performances related to space missions. A method for recovering background losses and radiation-induced losses of EYDFA is illustrated. Numerical simulation tools are based on a homemade particle swarm optimization procedure. In the experimental aspect, two amplifiers of the same type were irradiated with Co60 gamma rays up to a total dose of 10 and 50 krad, respectively. Compared with the experimental data, the curve of output power drawn by the model is in good agreement with the experimentally measured values, validating the validity of the theoretical model. Using this method that combined experimental testing of online monitoring with theoretical simulation provides a new way to evaluate the performance degradation of commercial amplifiers in a radiation environment.

BonoFill-II, from bench to bedside: A novel autologous cell-based, tissue-engineered product in line to replace bone autografts for large segmental bone defect applications

Background & Aim Significant losses of bone tissues that are often too large to heal occur in >10% of all open fractures and present an urgent clinical challenge associated with grave morbidities and huge healthcare costs. Bone autografting, the therapeutic standard in such cases, has a 50% complication rate, with persistent infection or non-union present in 18% of the patients, and further surgery required in 36% of them. Bone tissue engineering technologies have been widely suggested as an alternative to autografts. Such technologies were tested in segmental animal bone defects up to 5 cm long, with success reported mostly for defects under 2.5 cm. This size (or equivalent product volume) is also the upper limit for tissue-engineered bone grafts in clinical development. Considering that much larger defects, with a mean of 5.5 cm, are encountered in the clinic, Bonus is developing autologous tissue-engineered bone grafts for the treatment of defects larger than 2.5 cm. Methods, Results & Conclusion Bonus utilizes proprietary procedures to isolate adipose tissue-derived mesenchymal cells from patients’ lipoaspirates, seed them on mineral scaffold particles, and culture them in a specially designed bioreactor (Fig. 1). The expansion of the cells on this scaffold increases their osteo-inducibility, allowing a controlled osteoinduction process that possibly also retains some of these cells’ additional regenerative functions. This possibility is exemplified by the higher levels of osteogenic and other genes related to angiogenesis and ECM remodeling expressed by 3D-osteoinduced cells, compared to the 2D ones. After their osteoinduction, the cells and scaffold are washed and formulated into the final product—BonoFill-II. In a preclinical study, BonoFill-II applied to a 3.2 cm defect in a sheep tibia led to a full recovery in 12 weeks (N=7), as well as a full bridging of a 10.5 cm defect (Fig. 2). A phase I/II clinical trial is currently underway testing BonoFill-II in patients with bone defects ≥2.5 cm. So far, we have treated patients with defects up to 8.5 cm long and a history of 2-7 failed prior interventions, with a few representatives that can exemplify this study safety and efficacy (Fig. 3). The performance of BonoFill-II was also tested in Phase I/II trial in patients in need of a bone transplant in the upper maxilla with complete success reported. Overall, the solid underlying science and innovative technologies developed by Bonus position BonoFill-II as a promising alternative to bone autografts.

Impact of shaping optical fiber preforms based on grinding and a CO2 laser on the inner-cladding losses of shaped double-clad fibers.

We experimentally compared for the first time, two techniques of optical fiber preform shaping based on the mechanical grinding and thermal CO2 laser processing from the point of the inner-cladding losses. The shaped preforms were fabricated of coreless pure silica technical rods as well as high purity silica Heraeus F300 rods and drawn them into coreless multimode fibers with various inner-cladding geometries coated with a low index fluorinated polymers. The background losses of the fibers were measured via the cut-back method and compared to the losses of the unshaped fibers with a circular cross-section. Results show that both preform-shaping techniques would induce additional losses in the inner-cladding. High surface scattering losses were observed in the mechanically-grinded fibers. On the other hand, the mechanical grinding retains the advantage of a significant reduction of attenuation peaks attributed to OH-groups that penetrated into the preform surface during the preform collapse. On the contrary, CO2 laser thermal-shaping provides the advantage of quick, fully automated shaping with smooth surface finish and induces much lower scattering losses, but it is not so effective in removing water penetrated surface layer of the preform so that OH-groups diffuse deeper towards the preform center. Additionally, laser thermal-shaping allows processing the preform to complex shapes which are more effective in scrambling cladding modes. Some of the absorption peaks of OH-groups and fluorinated polymers may be rather close to common pumping wavelengths and this should be considered in the design of the double-clad fibers and selection of proper shaping technology.

Instability of supersonic cold streams feeding galaxies – IV. Survival of radiatively cooling streams

ABSTRACT We study the effects of Kelvin–Helmholtz Instability (KHI) on the cold streams that feed massive haloes at high redshift, generalizing our earlier results to include the effects of radiative cooling and heating from a UV background, using analytic models and high resolution idealized simulations. We currently do not consider self-shielding, thermal conduction, or gravity. A key parameter in determining the fate of the streams is the ratio of the cooling time in the turbulent mixing layer which forms between the stream and the background following the onset of the instability, $t_{\rm cool,\, mix}$, to the time in which the mixing layer expands to the width of the stream in the non-radiative case, tshear. This can be converted into a critical stream radius, Rs, crit, such that $R_{\rm s}/R_{\rm s,crit}=t_{\rm shear}/t_{\rm cool,\, mix}$. If Rs < Rs, crit, the non-linear evolution proceeds similarly to the non-radiative case studied by Mandelker et al. If Rs > Rs,crit, which we find to almost always be the case for astrophysical cold streams, the stream is not disrupted by KHI. Rather, background mass cools and condenses on to the stream, and can increase the mass of cold gas by a factor of ∼3 within 10 stream sound crossing times. The mass entrainment induces thermal energy losses from the background and kinetic energy losses from the stream, which we model analytically. Roughly half of the dissipated energy is radiated away from gas with $T \lt 5\times 10^4\, {\rm K}$, suggesting much of it will be emitted in Ly α.

Sustainable Aquaculture Futures

Sustainable Aquaculture Futures

Measuring Neutron Lifetime on an IBR-2 Pulsed Neutron Source

A new method of measuring neutron lifetimes on pulsed neutron sources based on changes in the neutron spectrum during the time of the neutron transit along a rather large path length due to their decay is proposed. The main advantage of this method is the use of relative measurements. Simulating the experiment made it possible to explore the influence of background and neutron losses caused by both the interaction with residual gas and the different level of detector efficiency on the systematic errors. All parameters can be measured experimentally.

High Average Power Thulium-Doped Silica Fiber Lasers: Review of Systems and Concepts

Thulium-doped fiber lasers (TDFLs) have had the second highest growth in average output power next to ytterbium-doped fiber lasers. This has been enabled by access to high power, high brightness ∼790-nm pump diodes in conjunction with the cross-relaxation process that improves laser efficiency. While numerous high power TDFLs have been recently demonstrated, a 1-kW result from 2010 remains the highest output power system reported to date. This paper reviews these systems and the concepts behind high power TDFLs. The spectroscopic properties of Tm3+ -doped silica are first detailed, revealing complex processes and large variations among published measurements. Notable multi-100 W TDFLs are then summarized, with outputs ranging from 1908 to 2130 nm. Another route for power scaling is to in-band pump with another TDFL to enable >90% efficiencies. Both 790- and 1900-nm pumped TDFL architectures are theoretically modeled based on currently available systems. Hindered by high background losses and available pump sources, achieving >4 kW like ytterbium-fiber systems will be a substantial challenge.

Effect of the preform fabrication process on the properties of all-silica optical fibres

In this paper, we present a detailed comparison of technical capabilities of processes for the fabrication of all-silica optical fibre preforms with the use of an atmospheric pressure radio frequency plasma (POVD process) and low-pressure microwave plasma (PCVD process) and analyse the origin of the difference in optical properties between fibres produced by these methods. It is shown that the higher temperature of the core material and the higher oxygen partial pressure in preform fabrication by the POVD process lead to an increase in optical losses in the visible and UV spectral regions in the silica fibres with low hydroxyl (OH) content and a decrease in the solarisation resistance of the fibres with high OH content, i.e. to a more rapid increase in background losses in response to UV irradiation. No such drawbacks are detected in the case of the growth of reflective layers by the PCVD process.

Parallel Low-Loss Measurement of Multiple Atomic Qubits.

We demonstrate low-loss measurement of the hyperfine ground state of rubidium atoms by state dependent fluorescence detection in a dipole trap array of five sites. The presence of atoms and their internal states are minimally altered by utilizing circularly polarized probe light and a strictly controlled quantization axis. We achieve mean state detection fidelity of 97% without correcting for imperfect state preparation or background losses, and 98.7% when corrected. After state detection and correction for background losses, the probability of atom loss due to the state measurement is <2% and the initial hyperfine state is preserved with >98% probability.

A spatio-temporal analysis of forest loss related to cocaine trafficking in Central America

A growing body of evidence suggests that criminal activities associated with drug trafficking networks are a progressively important driver of forest loss in Central America. However, the scale at which drug trafficking represents a driver of forest loss is not presently known. We estimated the degree to which narcotics trafficking may contribute to forest loss using an unsupervised spatial clustering of 15 spatial and temporal forest loss patch metrics developed from global forest change data. We distinguished anomalous forest loss from background loss patches for each country exhibiting potential ‘narco-capitalized’ signatures which showed a statistically significant dissimilarity from other patches in terms of size, timing, and rate of forest loss. We also compared annual anomalous forest loss with the number of cocaine shipments and volume of cocaine seized, lost, or delivered at country- and department-level. For Honduras, results from linear mixed effects models showed a highly significant relationship between anomalous forest loss and the timing of increased drug trafficking (F = 9.90, p = 0.009) that also differed significantly from temporal patterns of background forest loss (t-ratio = 2.98, p = 0.004). Other locations of high forest loss in Central America showed mixed results. The timing of increased trafficking was not significantly related to anomalous forest loss in Guatemala and Nicaragua, but significantly differed in patch size compared to background losses. We estimated that cocaine trafficking could account for between 15% and 30% of annual national forest loss in these three countries over the past decade, and 30% to 60% of loss occurred within nationally and internationally designated protected areas. Cocaine trafficking is likely to have severe and lasting consequences in terms of maintaining moist tropical forest cover in Central America. Addressing forest loss in these and other tropical locations will require a stronger linkage between national and international drug interdiction and conservation policies.

Interaction-Assisted Quantum Tunneling of a Bose-Einstein Condensate Out of a Single Trapping Well.

We experimentally study tunneling of Bose-condensed ^{87}Rb atoms prepared in a quasibound state and observe a nonexponential decay caused by interatomic interactions. A combination of a magnetic quadrupole trap and a thin 1.3 μm barrier created using a blue-detuned sheet of light is used to tailor traps with controllable depth and tunneling rate. The escape dynamics strongly depend on the mean-field energy, which gives rise to three distinct regimes-classical spilling over the barrier, quantum tunneling, and decay dominated by background losses. We show that the tunneling rate depends exponentially on the chemical potential. Our results show good agreement with numerical solutions of the 3D Gross-Pitaevskii equation.

Background losses of woody plant foliage to insects show variable relationships with plant functional traits across the globe

Summary Despite a long history of research, we lack a comprehensive understanding of the reasons behind pronounced variation in foliar losses to insects among plant species. Our aim was to test the hypothesis that plant functional traits and/or ecological strategies are good predictors of the background losses of woody plant foliage to insects (i.e. losses occurring when herbivore populations are at their ‘normal’ densities) at the global scale. We conducted a quantitative synthesis of published and original data on foliar losses of 793 species of woody plants belonging to 128 families from ca. 500 localities world‐wide, representing tropical, temperate and polar climate zones. The background foliar losses to insects varied among plant life forms, increasing from dwarf shrubs to large trees, and were higher in inherently fast‐growing species than in slow‐growing species. These patterns supported predictions of both the apparency and growth rate (resource availability) hypotheses for data combined across localities, but only outside the tropics. Foliar losses to insects slightly but significantly increased with specific leaf area (SLA) in all climate zones. No differences were noted in background herbivory between woody plant species with deciduous and evergreen foliage, with different shade tolerance and with different successional status. Synthesis. Factors affecting the distribution of herbivory among species of woody plants differed among the climate zones, and the predictive power of at least some of the theories/hypotheses addressing plant–herbivore interactions at large spatial scales varies among climates and/or biomes. The average background losses of woody plant foliage to insects across localities can be predicted from the inherent growth rate of the plant species, its life form and SLA, although these plant characteristics jointly explain only a minor part of the total variation observed in the primary data.