Miracle-dz/UniFAR-FTUs huggingface dataset:
Characteristics of suspended sediment in Sentinel-1 synthetic aperture radar observations

ABSTRACT The main purpose of this study is to quantitatively examine the characteristics of suspended sediment on synthetic aperture radar (SAR) observations of sea roughness. In this work, seven Sentinel-1 (S-1) SAR images in 2019 acquired in the Interferometric Wide-swath (IW) mode at vertical-vertical (VV) polarization channel were collected, where Yangtze River freshwater dominants and suspended sediment concentration (SSC) are higher in continental shelf of East China Sea (ECS). These images were collocated with waves simulated from WAVEWATCH-III (WW3) and SSC inverted from the Haiyang-1C (HY-1C) Coastal Zone Imager (CZI) image. The comparison of WW3-simulated SWH yielded a 0.45-m root-mean-square error (RMSE) with a 0.78 correlation (COR) when comparing the simulations with the measurements from Haiyang-2B (HY-2B). The SAR-measured normalized radar cross-section (NRCS) is linearly related with the HY-1 C SSC at SSC > 1200 mg l–1, which is caused by the change of dielectric constant of sea water and viscosity. Moreover, the NRCS is simulated by the three-scale radar backscattering model. It is generally found that HY-1 C SSC enhances the NRCS in difference between simulations and observations up to 8 dB at SSC of 2000 mg l–1, which could distort the accuracy of SAR wind retrieval.
Google Earth Engine for large-scale land use and land cover mapping: an object-based classification approach using spectral, textural and topographical factors

ABSTRACT Mapping the distribution and type of land use and land cover (LULC) is essential for watershed management. The Tigris-Euphrates basin is a transboundary region in the Middle East shared between six countries, but a recent fine-scale LULC map of the area is lacking. Using Landsat-8 time series, a 30-m resolution LULC map was produced for the Tigris-Euphrates basin. In total, 1184 Landsat scenes were processed within the Google Earth Engine (GEE). For the collection of ground truth data, differential manifestations of green cover were considered by dividing the study area into five climatic regions and the training samples were taken from each sub-region. To account for the temporal variation of LULC types, six two-month interval composite layers, including the spectral and thermal bands of Landsat-8, texture and spectral indices, as well as topographic factors were created for the target year 2019. Image segmentation and classification were performed using the simple non-iterative clustering (SNIC) and Random Forest (RF) algorithms, respectively. A computationally effective parallel processing approach was developed, which created a number of tiles and sub-tiles and a bulk command was converted into smaller parallel commands. The generated LULC map showed a satisfactory overall accuracy of 91.7%, with the highest User’s accuracy in water and wetland, and the lowest in rainfed crop and rangeland and the highest Producer’s accuracy in water and barren areas, and the lowest in garden and rangeland. This study highlights the necessity of using multi-temporal data for LULC mapping, in particular, multi-temporal NDVI, for the separation of different green cover types in arid and semi-arid environment.
Field determination of nitrate using nitrate reductase

Nitrate is routinely measured in a variety of substrates - water, tissues, soils, and foods - both in the field and in laboratory settings. The most commonly used nitrate test methods involve the reduction of nitrate to nitrite via a copper-cadmium reagent, followed by reaction of the nitrite with the Griess dye reagents. The resulting color is translated into a nitrate concentration by comparison with a calibrated color chart or comparator, or by reading the absorbance in a spectrophotometer. This basic method is reliable and sufficiently sensitive for many applications. However, the cadmium reagent is quite toxic. The trend today is for continued increase in concern for worker health and safety; in addition, there are increasing costs and logistical problems associated with regulatory constraints on transport and disposal of hazardous materials. Some suppliers have substituted a zinc-based reagent powder for the cadmium in an effort to reduce toxicity. We describe here an enzyme-based nitrate detection method as an improvement on the basic Griess method that demonstrates equal or superior sensitivity, superior selectivity, and is more environmentally benign. Comparisons between the enzyme-based method and some standard field test kits being used today are made.
Measurements with a capacitance gauge for sub-nanometer thermal expansion characterization of optical components

The ability to measure small thermal expansion of precision components can be critical to the performance of precision instruments such as optical telescopes. The methods available to measure nanometer and sub-nanometer dimensional changes on optical elements is very limited. This white paper explores the ability of the capacitance gauge to measure expansion of optical elements in the sub-nanometer range.
The polymer nanocomposites embedded particles size and agglomeration effect on the effective refractive index tuning

The polymer nanocomposites have attracted increasing attention in the optical components that are miniaturized and integrated with wearable or portable electronics due to the polymer processibility and the tunability of the refractive index (RI) by adding nanoparticles. However, the lack of models predicting the composites’ RI attributed to the morphology, physical properties, as well as volume fraction of the nanoparticles poses difficulties in the design. This study investigates the effect of the size and agglomeration condition of the nanoparticles on the effective RI based on a Finite Element Analysis (FEA) method simulating the Fabry-Pérot resonance within the composite film. The result showed that larger particles (or particle clusters) could reinforce the RI of nanocomposites compared with the well-dispersed small particles. The particle-cluster model had lower RI than the single-solid-particle model with the same effective particle diameter, demonstrating that the particle cluster provides less scattering intensity than the single-solid-particle.
Exploring Parental Identities: How Single Black Males Understand Fatherhood in the Absence of Their Fathers

This qualitative study was exploratory in nature and involved the collection and analysis of data from Single Black fathers in Northern California raised without a father in the home. Fathers in our study shared that they navigate their roles as single fathers through trial and error and by making a personal commitment to do what is necessary for the well-being of their children; they refuse to allow obstacle to get in their way of their effort to be a responsible, caring father. The absence of their fathers was a prevalent factor that increased the devotion they have for their children.
Barriers for Entering the Digital World: Exploring Customer Value Co-destruction in Self-Service Technologies

The value co-creation scholarly work has been criticized for neglecting the possible failures in the collaborative value creation process, which is termed as ‘value co-destruction’. Additionally, both the value co-creation and available limited research work in value co-destruction have overly attended on actor-to-actor interactions taking place in traditional service encounters, disregarding the practical movement towards the provision of services via technological platforms. Though there are ample studies that recognize factors influencing customer acceptance or rejections of technologies, a very limited number of studies have focused on exploring how and why customer collaboration with self-service technologies (SSTs) goes wrong due to the failures in the co-creation process. Therefore, this study attempts to understand how ‘value co-destruction’ takes place in the SSTs. Following a qualitative inquiry, using semi-structured interviews with 25 individuals, 15 reasons for co-destruction that vary among different customer demographics were found and classified into four integrative themes as ‘inabilities in co-learning’, ‘poor co-operation’, ‘problems with connecting’ and ‘poor corrective actions’. The findings fill the gap in the literature by addressing value co-destruction in technological interfaces, particularly in the SST context. Further, it will help practitioners to design and deliver value-enhancing self-service technological interfaces, resulting in none or minimum difficulties for customers.
Luxury Shopping Websites: The Impact of ‘Hygiene’ Design Factors on Trust and Distrust

Though luxury products have unique characteristics that predominantly influence online luxury behaviour, study on luxury shopping websites has received little attention in academic literature. This research investigates how hygiene factors of website design attributes (information quality, functional quality and situational normality) impact on trust and distrust on luxury shopping websites. Free simulation experiments were conducted with 386 subjects and data were collected using a structured questionnaire for this study. The study found that information quality and functional quality have a strong effect on trust and distrust on luxury shopping websites. This study also found that these factors not only act as hygiene factors but also as motivating factors in the luxury context. Surprisingly, situational normality is negatively related to trust and positively related to distrust in the study. Managerial implications regarding the development of luxury websites and research opportunities are discussed.
Frequency comb based absolute frequency reference design for future spaceborne multi species differential absorption lidar systems for green-house gases monitoring

The Lidar Emitter and Multi-species greenhouse gases Observation iNstrument (LEMON) is a novel Differential Absorption Lidar (DIAL) sensor concept for greenhouse gases and water vapor measurements from space.1,2 It is based on a versatile transmitter allowing for addressing various absorption lines of different molecules. This highly flexible emitter design requires a universal frequency referencing scheme. Here we present a concept employing a 1 GHz frequency comb, which allows the absolute referencing over a spectral range from 0.95 μm to 1.15 μm. By using an intermediate frequency doubling stage, this allows for DIAL measurements on CO2, H2O/HDO, and CH4 in the 2 μm range. Absolute referencing is obtained by using a GPS disciplined oscillator as the common time base for frequency measurements. The concept of the LEMON Frequency Reference UnIT (FRUIT) is designed to match the requirements of the vibration loads associated with airborne operation to allow implementation on the airborne demonstrator for LEMON. In addition, the requirements for a future space development are considered in the design. For example, radiation critical items have been identified and radiation tested within the project and a compact wavemeter design has been implemented.
Optical adhesion of photocurable emulsion droplets using laser trapping

As represented by "Lab on a Tip" using microchannels, the miniaturization of manufacturing and inspection processes attracts widespread interest. Therefore, many micro-tool fabrication techniques using optical tweezers have been reported. Most reported methods focus on assembling trapped microbeads, and it was necessary to have a photocurable resin phase and surface modification process to assemble solid beads. However, because many procedures such as dispersion of microbeads and removal from the resin solution were required, flexible one-step fabrication is difficult with previous methods. This study proposed a direct adhesion and assembly of the photocurable resin droplets dispersed in the aqueous solution. Since the photocurable droplets work as both base material and an adhesive, a flexible one-step fabrication of micro-tools can be achieved. It was experimentally found that the morphology of emulsion droplets in contact significantly affects the adhesion. Generally, oil-in-water emulsion droplets are stabilized by a surfactant, and adhesion between droplets can be disturbed by a surfactant bilayer. By controlling the contact angle between the droplets, the optically trapped droplets successfully adhered together with photopolymerization. Furthermore, combining the various diameter and materials of emulsion droplets using microfluidic channels, more functional and complex microtools can be expected.
Comparison of stacked actuator and bimorph mirrors for scattered laser-beam focusing

Bimorph deformable mirrors can be successively used to improve focusing of a laser beam passed through a moderately scattering medium with optical density in the range of 1 . 10. In this paper we investigate the efficiency of the stacked actuator deformable mirror with 61 piezo stacks and clear aperture of 60 mm. We demonstrate that such kind of mirrors also can be used to optimize the focal spot in the far-field. Shack-Hartmann sensor was used to measure the averaged wavefront distortions and CCD camera was used to estimate the intensity distribution of the focal spot in the far-field.
The TIR instrument on TRISHNA satellite: a precursor of high resolution observation missions in the thermal infrared domain

The TRISHNA program marks a step further in the fruitful cooperation built between CNES and ISRO since many years, through a new Earth observation mission dedicated to the improvement of water cycle understanding and water resource management. Thanks to its unprecedented high spatial resolution in the thermal infrared domain, together with a high revisit frequency, TRISHNA mission will significantly contribute to the detection of ecosystem stress and to the optimization of water use in agriculture in a context of global climate change. This paper presents the TRISHNA mission context and main requirements, gives an overview of TRISHNA system architecture and describes TIR (Thermal InfraRed) instrument design with a highlight on its specific innovative features and the current development status.
Performance limitations in optical retarders

Materials commonly used for making waveplates or retarders all have measured performance deviations from what might be expected. These materials include crystals such as quartz, magnesium fluoride and sapphire, polymers and nematic and ferro-electric liquid crystals. Some deviations result from manufacturing errors but many are inherent properties of the birefringent materials used. These effects create systematic errors in polarimetry and in other applications where precise knowledge of polarization is important. We will discuss our quantitative measurements of the sometimes unexpected presence of elliptical retardance, retardance fringes and birefringence nonuniformities as well as other effects.
FCI instrument on-board MeteoSat Third Generation satellite: design and development status

2020 has been a key year in the MeteoSat Third Generation (MTG), with the integration and tests of the Flexible Combined Imager (FCI) proto-flight model(PFM). The FCI is the imaging instrument of the MeteoSat Third Generation mission, whose first satellite MTG-I1 will be launched in the second half of 2022. Its large spectral coverage, its fast and flexible scanning, associated with demanding radiometric and optical performances will allow a step forward in Europe weather nowcasting. In 2018, three complementary development models were successfully integrated and tested. The Engineering Model validated the optical and radiometric performances of the detection chain. The Structural and Thermal Model qualified the robustness of the design against launch and in-orbit environments and validated the consistency with the thermal and microvibration mathematical model predictions. The Avionic Test Bench with the software which reached a very good level of maturity, validated the control, command and data handling of the instrument. The completion of these developments enabled to successfully hold the instrument Critical Design Review (CDR) end 2018. In 2019, the two main components of the instrument, namely the telescope assembly and the detection control electronics assembly (DCEA) successfully passed the acceptance tests and have been delivered. The article will present first an overview of the instrument design and the main outcomes of the development models. Then, it will discuss the up-to-date status of the FCI PFM development. Finally, it will introduce the overall planning for the four FCI models to be delivered to the MTG-I satellite series. This work has been performed under an ESA contract to Thales Alenia Space-France.
Behind optothermal trapping of photothermally-induced microbubbles

We present 3D steady-state trapping and manipulation of vapor microbubbles in pure ethanol by optothermal effects induced by low power CW laser. Light absorption from silver nanoparticles photodeposited on the core of a multi-mode optical fiber is used as a heat source to induce microbubbles of several diameters. The optothermal effects generated by the light absorption of light bulk absorption modulates the microbubble wall's surface tension inducing both longitudinal and transversal forces just like optical forces, generating a 3D potential well. By numerical simulations, we find expressions to describe both the temperature profiles and the convective currents. Besides, using an array of three optical fibers with silver nanoparticles photodeposited on their cores we show the transmission of microbubbles from one fiber to another by switching the laser radiation from the CW lasers.
A method to improve the optical coupling into the bioinspired peptide micro-waveguides using aberrated objective

Significant research has been done to develop functional bio-inspired nano-architectures for photonic, biomedical and energy storage applications. Among these, peptide nanostructures are the prime candidates with unique optical properties, like the wide optical transparency, high refractive index contrast, and optical nonlinearity. In this work, a linear aromatic diphenylalanine peptide, which is the core motif of Alzheimer-amyloid protein, is self-assembled into open-end hexagonal microtubes. The waveguiding aspects of the tubes are studied with high NA objectives acting as a major optical component to couple light into one of the ends of the tubes. Our study tells that the micro-waveguide’s performance with chromatically aberrated i.e uncorrected objective is far better than the corrected one giving a higher dynamical range, higher signal-to-noise ratio, and higher guided peak resolution, thus making it more suitable for fine measurements. The experimental results are verified using the finite difference time domain method. The higher resolution, higher scan depth, and color selectivity with the aberrated objectives indicate deploying these waveguides in biosensing and other applications.
An improved programmable grating array based wavefront sensor

An improved programmable grating array based wavefront sensor (GAWS) is proposed which is capable of estimating the incident wavefront more accurately, by generating an array of uniform intensity +1 order spots with negligible contribution from unwanted higher order spots. The duty cycle of each grating element of the proposed sensor is effectively varied in order to independently control the intensity of each +1 order spot. Furthermore, random binarisation technique is implemented on the diffraction grating array to reduce the contribution from undesirable higher order spots by disintegrating them into noise. Proof-of-principle simulation results are presented to demonstrate the working of the proposed GAWS in comparison to the conventional GAWS, for non-uniform intensity of the +1 order spots.
Upconversion nanocrystal emission rate enhancement using double nanoholes

Here we use optical trapping to isolate single Yb/Er-doped upconversion nanocrystals in plasmonic double nanohole apertures and show that the geometry of the aperture can be tuned to give high emission rate en- hancement. The double nanohole apertures show additional enhancement over the rectangular apertures that were previously demonstrated by our group, producing enough enhancement to observe emission at 400 nm and 1550 nm with 980 nm excitation—not seen in our group’s previous work with rectangular apertures. A facile method for tuning the geometry of double nanohole apertures by adjusting the plasma etching time in the colloidal lithography fabrication process is discussed. We find that a double nanohole with a cusp separation of 32 nm yields the greatest emission enhancement with multiple plasmonic resonances which enhance both the excitation and emission wavelengths. The emission enhancement for the DNH with 32 nm cusp separation was found to be a factor of 54, 44, and 31 greater than the rectangular apertures used in our group’s previous work, for wavelengths of 650 nm, 550 nm, and 400 nm. This result shows that double nanohole apertures can be tuned for emission enhancement as required by specific applications.
Structuring acoustic fields for particle manipulation

We present a powerful and efficient technique to structure acoustic fields, based on the use of active diffraction elements, which can be designed in practically arbitrary shapes and can be operated within a broad spectral range of ultrasonic frequencies in air. Two kinds of structured fields are demonstrated: focused acoustic vortices and the simultaneous generation of multiple acoustic Bessel beams of different topological charges, well separated among each other along the propagation axis. In both cases, the main parameters of the field can be finely and continuously tuned by setting the operation frequency. Experimental results show very good agreement with theoretical analysis and numerical simulations.
Introducing ‘low cost large scale’ hydrophobic SERS substrate

Large-area nano-patterned surfaces invoking hydrophobicity hold great significance for Surface Enhanced RamanSpectroscopy or SERS substrates. Conventionally, these structures are fabricated using state-of-the-art litho-graphic techniques. These techniques while being efficient, are complex and are cost-ineffective. Here, we report a low-cost, facile and scalable solution for fabrication of periodic array of metallic nanocones using colloidal lithography and reactive ion etching process. Nanocone array coated with gold thin film serves as a hydrophobicsurface with plasmonic properties. Hydrophobicity on the cones helps to keep the analyte molecule localized near the tip of nanocones where, due to plasmonic behavior of metal thin film i.e. field enhancement by the metal gives rise to significant SERS. We validate this concept through our fabricated substrate via detection ofRhodamine 6G molecules using Raman spectroscopy and report the limit of detection upto 1 nM.
Defect detection in additive manufactured products with a new photonics procedure: a case study

We describe a new photonics procedure developed for non-destructive testing of additive manufactured (AM) parts and present a case study for inspection of AM brackets to detect and reject parts containing printing defects. This is an update of a previously presented paper of the work in progress to develop an Authentication Sensing System Using Resonance Evaluation Spectroscopy (ASSURES). The principle of operation is based on the concept that a part’s vibration spectrum (set of resonant frequencies) is uniquely determined by its dimensions, material parameters, and interior flaws. The vibration spectrum of a part can be measured remotely with a laser vibrometer, and the presence of defects or a change in material parameters can be inferred from a change in the part’s vibration spectrum (shifts in the resonant frequencies). The spectrum of a part can be measured and compared in a few seconds to a known “good” part, a “good” reference spectrum, or to other parts in the batch.