Three-dimensional rainbow refractometry.

We propose a new, to the best of our knowledge, rainbow technique called three-dimensional rainbow refractometry (TDRR), with a cylindrical lens in the signal collecting system. With a TDRR model based on the ray transfer matrix developed, it is proved that the tilt angle of the rainbow signal is related to the axial position of the droplet, which helps to obtain the 3D position. By converting rainbow scattering angle calibration into the system parameter calibration, a new rainbow data processing program is written in combination with the model to obtain the refractive index and the particle size. With TDRR, we measured a monodisperse droplet stream of deionized water at room temperature for experimental validation and obtained the refractive index with an absolute error of less than 0.0015, the droplet size with an error within ±5%, and the axial position with an error within ±3%, which demonstrated a high accuracy of TDRR.

Spectroscopic Techniques and Hydrogen-Sensitive Compounds: A New Horizon in Hydrogen Detection.

Detecting hydrogen leaks remains a pivotal challenge demanding robust solutions. Among diverse detection techniques, the fiber-optic method distinguishes itself through unique benefits, such as its distributed measurement properties. The adoption of hydrogen-sensitive materials coated on fibers has gained significant traction in research circles, credited to its operational simplicity and exceptional adaptability across varied conditions. This manuscript offers an exhaustive investigation into hydrogen-sensitive materials and their incorporation into fiber-optic hydrogen sensors. The research profoundly analyzes the sensor architectures, performance indicators, and the spectrum of sensing materials. A detailed understanding of these sensors' potentials and constraints emerges through rigorous examination, juxtaposition, and holistic discourse. Furthermore, this analysis judiciously assesses the inherent challenges tied to these systems, simultaneously highlighting potential pathways for future innovation. By spotlighting the hurdles and opportunities, this paper furnishes a view on hydrogen sensing technology, particularly related to optical fiber-based applications.

Advances in air pollution control for vessels in China.

Vessel emissions have contributed a great deal to air quality deterioration in China. Hence, the Chinese government has promulgated a series of stringent emission regulations. It is in this context that vessel emission control technology research is in full swing. In particular, during the 13th Five-Year Plan, the air pollution control technology of vessels has greatly improved. Vessel emission control has followed two main governance routes: source emission reduction and aftertreatment technology. Source control focuses on alternative fuels, with two main directions, the development of new fuels and the modification of existing fuels. Moreover, after-treatment technologies have also been developed, including wet desulfurization technology using seawater or alkaline liquids as wet washing liquids and selective catalytic reduction (SCR) for the control of NOx emission. Due to China's increasingly stringent emissions standards and regulations, work on the development of clean alternative fuels and further upgrading the collaborative application of after-treatment technologies to meet the near-zero-emissions requirements of vessels is still necessary.

Advances in the treatment of multi-pollutant flue gas in China's building materials industry.

In most of the world's building material industries, the control of flue gas pollutants mainly focuses on a single pollutant. However, given the large capacity and high contribution of China's building materials industry to global air pollution, the need to develop multi-pollutant emission reduction technology is urgent. Recently, China has focused on reducing the emissions of flue gas pollutants in the building materials industry, established many key research and development projects, and gradually implemented more stringent pollutant emission limits. This project focuses on the most recent advances in flue gas emission control technology in China's building materials industry, including denitration, dust removal, desulfurization, synergistic multi-pollutant emission reduction, and the construction of pilot research and demonstration projects for pollutant removal in several building material industries. On this basis, revised pollutant limits in flue gas emitted in China's building material industry are proposed.

Advances in air pollution control for key industries in China during the 13th five-year plan.

Industrial development is an essential foundation of the national economy, but the industry is also the largest source of air pollution, of which power plants, iron and steel, building materials, and other industries emit large amounts of pollutants. Therefore, the Chinese government has promulgated a series of stringent emission regulations, and it is against this backdrop that research into air pollution control technologies for key industrial sectors is in full swing. In particular, during the 13th Five-Year Plan, breakthroughs have been made in pollution control technology for key industrial sectors. A multi-pollutant treatment technology system of desulfurization, denitrification, and dust collection, which applies to key industries such as power plants, steel, and building materials, has been developed. High-performance materials for the treatment of different pollutants, such as denitrification catalysts and desulfurization absorbers, were developed. At the same time, multi-pollutant synergistic removal technologies for flue gas in various industries have also become a hot research topic, with important breakthroughs in the synergistic removal of NOx, SOx, and Hg. Due to the increasingly stringent emission standards and regulations in China, there is still a need to work on the development of multi-pollutant synergistic technologies and further research and development of synergistic abatement technologies for CO2 to meet the requirements of ultra-low emissions in industrial sectors.

Technology development and cost analysis of multiple pollutant abatement for ultra-low emission coal-fired power plants in China.

The implementation of ultra-low emission (ULE) limits (SO2: 35 mg/m3, NOx: 50 mg/m3, PM: 10 mg/m3) promoted the development of flue gas treatment technologies in China. Pollutant control technology development for Chinese coal-fired power plants was summarized and an analysis of the applicability and cost of pollutant control technologies was conducted. Detailed data were collected from 30 ultra-low emission coal-fired units across China. Based on a cost analysis model, the average unit power generation incremental costs were 0.0144 and 0.0095 CNY/(kW·hr) for SO2 and NOx control technologies, respectively. The unit power generation incremental cost of twin spray tower technology was 7.2% higher than that of dual-loop spray tower technology. The effect of key parameters on operating cost was analyzed. The unit power generation incremental cost increased because of increments in the electricity price for SO2 control technology and the price of the reductant in NOx control technology. With high sulfur content or NOx concentration, the unit power generation incremental cost caused by pollutant control increased, whereas the unit pollutant abatement cost decreased. However, the annual operating hours or load increased, thereby leading to a decline in unit power generation incremental cost and unit pollutant abatement cost.

Accurate droplet depth displacement measurement with time-resolved astigmatic interferometric particle imaging.

The astigmatic interferometric particle imaging (AIPI) model reveals that the fringe orientation shifts with droplet depth displacement, and their relationships are quantitatively formulated. The depth displacement is directly evaluated from the relative angular shift of the fringes with angular cross power spectral density, and this algorithm isolates the uncertainty of droplet depth position from depth displacement. Proof-of-concept experiments on micrometer-sized transparent droplets with a 5 kHz AIPI system demonstrates that droplet three-dimensional (3D) trajectories are accurately obtained with the accuracy of depth displacement up to tens of micrometers, improving an order of magnitude from hundreds of microns in a traditional Lagrangian framework by comparing droplet depth positions.

Synthetic aperture rainbow refractometry.

This work proposed a synthetic aperture rainbow refractometry (SARR) by synthesizing rainbow signals of the same droplet with dual-wavelength laser beams, in order to increase the aperture of rainbow refractometry. In this way, the SARR can apply to long distance and small droplets measurement. An achromatic imaging system, which simultaneously records while separating the two rainbow signals in two channels of a color image, is elaborately designed. A data processing algorithm is developed to retrieve the optimal droplet refractive index and size. Numerical simulations of different droplet sizes from 10 µm to 200 µm certify the viability of the SARR. Proof-of-concept experiments of micron-sized ethanol droplets are performed with 1650 mm measurement distance. Results show that the SARR can accurately measure droplet refractive index and size with uncertainties of 2.3 × 10-4 and 2µm, respectively. The feasibility and accuracy of the proposed SARR are successfully demonstrated, paving the way for rainbow refractometry applied to large-scale industrial applications.

Paeoniflorin attenuates monocrotaline-induced pulmonary arterial hypertension in rats by suppressing TAK1-MAPK/NF-κB pathways.

Pulmonary arterial hypertension (PAH) characterized by pulmonary vascular remodeling is a lethal disease. Paeoniflorin (PF) is a monoterpene glycoside with numerous beneficial functions, such as vasodilation, anti-inflammation and immunomodulation. This study aims to investigate the effects of PF on monocrotaline (MCT)-induced PAH rats. Our data showed that both prophylactic or therapeutic administration of PF alleviated MCT-induced increasing of right ventricular systolic pressure (RVSP), prevented right ventricle hypertrophy and pulmonary arterial remodeling, as well as inhibited inflammatory cell infiltration around pulmonary arteries. Meanwhile, PF blocked MCT-induced endothelial-mesenchymal transition (EndMT) as indicated by the restored expression of endothelial markers in lung. Moreover, PF inhibited MCT-induced down-regulation of bone morphogenetic protein receptor 2 (BMPR2) and suppressed MCT-induced phosphorylation of transforming growth factor-ß (TGFß) activated kinase 1 (TAK1) in vivo. In vitro studies indicated that PF prevented human pulmonary arterial smooth muscle cells (PASMCs) from platelet-derived growth factor-BB (PDGF-BB)-stimulated proliferation and migration. PF also partially reversed TGFß1, interleukin-1ß (IL-1ß) and tumor necrosis factor (TNF-α) co-stimulated endothelial-to-mesenchymal transition (EndMT) in cultured human pulmonary artery endothelial cells (HPAECs). Signaling pathway analysis demonstrated that the underlying mechanism might be associated with the inhibition of TAK1-MAPK/NF-κB pathways. Taken together, our results suggested that PF could be a potential drug for the treatment of PAH.

Surface temperature measurement of cooling and heating droplets by rainbow refractometry.

Rainbow refractometry was used to measure the temperature and size of transparent spherical particles. In practice, however, there are limitations to the application of heating and cooling droplets, as the temperature measured is neither the average nor the surface or core temperature of the droplet. Reported here is an exploitation of this technique for droplet surface temperature determination. Droplet surface tension was measured by detecting the evolution of interference fringes of oscillating droplets. The dependence of surface tension on temperature facilitated the study of surface temperature of an evaporating droplet with time. Moving ethanol, n-heptane, and n-decane droplets were investigated under heating and cooling conditions. The capabilities and limitations of rainbow refractometry were verified by comparing the droplet temperature values measured directly by rainbow refractometry with the surface temperature.

A Method for Medical Microscopic Images' Sharpness Evaluation Based on NSST and Variance by Combining Time and Frequency Domains.

An algorithm for a sharpness evaluation of microscopic images based on non-subsampled shearlet wave transform (NSST) and variance is proposed in the present study for the purpose of improving the noise immunity and accuracy of a microscope's image autofocus. First, images are decomposed with the NSST algorithm; then, the decomposed sub-band images are subjected to variance to obtain the energy of the sub-band coefficients; and finally, the evaluation value is obtained from the ratio of the energy of the high- and low-frequency sub-band coefficients. The experimental results show that the proposed algorithm delivers better noise immunity performance than other methods reviewed by this study while maintaining high sensitivity.

Astigmatic dual-beam interferometric particle imaging for metal droplet 3D position and size measurement.

We propose astigmatic dual-beam interferometric particle imaging (ADIPI) to simultaneously measure the three-dimensional (3D) position and size of spherical metal droplets. A theoretical model reveals that the orientation and spacing of the ADIPI fringes generated from the two reflections propagating through an astigmatic imaging system relate to the depth position and size, respectively. Proof-of-concept experiments on micron-sized gallium droplets are performed, and the tilted fringes in elliptical patterns are observed in the ADIPI interferogram, confirming theoretical predictions. Droplet 3D position and size are determined with ADIPI, and the relative discrepancies are within 5% and 2% compared to those with a dual-view digital inline holography system, demonstrating the feasibility and high accuracy of ADIPI.

Planar rainbow refractometry.

Rainbow refractometry has been used in the past to measure size and refractive index of spherical particles, typically droplets in a spray. In the present study, conventional optical configurations for point measurements or line measurements have been extended to allow also the particle position in a plane to be determined, and hence, the designation planar rainbow refractometry. However, this extension introduces challenges in accurately calibrating the 2D scattering angles with the image coordinates. This challenge has been met using a novel calibration method, employing a monodispersed droplet stream traversed through the measurement plane. Experiments confirm achievable horizontal and vertical position accuracies of 0.42 mm and 0.36 mm, respectively, and a refractive index uncertainty of 2×10-4.

Measurement of airblast atomization of low temperature kerosene with 25 kHz digital holography.

Atomization of low temperature fuel is of great importance in a jet engine combustor, and its visualization and diagnostics are challenging, especially in the presence of shreds and ligaments. A 25 kHz picosecond pulsed digital inline holography system is applied to measure the spray produced by an airblast atomizer with low temperature kerosene. The breakup process of shreds and ligaments of -37∘C kerosene are visualized and analyzed, revealing the transition of liquid jet disintegrating into droplets under the atomizing air film. Three-dimensional positions and size distributions of droplets in spray are acquired. It is found that a decrease in the kerosene temperature increases shreds and ligaments in the spray, which eventually leads to reduction of droplet density and increase of droplet size, while increasing the air pressure can compensate the degradation. This work also demonstrates that high speed holographic imaging is a powerful tool in spray diagnostics and liquid breakup visualization.

Surface tension and viscosity measurement of oscillating droplet using rainbow refractometry.

We extend rainbow refractometry to quantify the oscillations of a droplet in its fundamental mode. The oscillation parameters (frequency and amplitude damping), extracted using the time-resolved rainbow angular shift, are utilized to measure surface tension and viscosity of the liquid. Proof-of-concept experiments on an oscillating droplet stream produced by a monodisperse droplet generator are conducted. Results show that the relative measurement errors of surface tension and viscosity are 1.5% and 8.4% for water and 5.3% and 2.5% for ethanol. This approach provides an alternative mean for characterizing liquid surface properties, e.g., dynamic surface tension and viscosity, especially for liquids with a low Ohnesorge number.

Phase critical angle scattering for measurement of transient nanoscale growth rate of a micron-sized bubble.

We developed phase critical angle scattering (PCAS) to simultaneously measure the spherical and transparent bubble size at the micron scale and transient bubble growth at the nanoscale. The theoretical derivation of PCAS reveals that the phase of the fine structure of critical angle scattering caused by reflection and first-order refraction is highly sensitive to and linearly shifts with bubble diameter growth. Experiments on a single growing bubble are implemented with a Fourier imaging system. The results show that the PCAS technique can measure the tiny bubble growth down to tens of nanometers, providing a promising tool for accurate characterization of bubble dynamics.

Accurate detection of small particles in digital holography using fully convolutional networks.

Particle detection is a key procedure in particle field characterization with digital holography. Due to various background noises, spurious small particles might be generated and real small particles might be lost during particle detection. Therefore, accurate small particle detection remains a challenge in the research of energy and combustion. A deep learning method based on modified fully convolutional networks is proposed to detect small opaque particles (e.g., coal particles) on extended focus images. The model is tested by several experiments and proved to have good small particle detection accuracy.

Three-dimensional dynamic measurement of irregular stringy objects via digital holography.

Dynamic stringy objects such as liquid rims and ligaments are frequently observed in important applications such as the multiphase breakup of fuel droplets. We develop a new method based on digital in-line holography to automatically measure complicated stringy objects. A static spring mounted on a rotator is measured to validate the effectiveness and accuracy of the method. The sections are extracted along the skeleton of the spring in a depth-of-field extended image and then sized and located as individual particles using a hybrid method. The surface points of sections are stitched together to visualize the entire spring. Local thickness errors smaller than 5.3%, and z errors smaller than 230 µm are achieved. This method is applied to characterize the spatial-temporal features of the liquid rim formed in the bag-type regime of the aerodynamic breakup of a falling drop. The evolution of the rim/ligament structures is continuously captured in seven frames, lasting in 1.58 ms. This Letter extends the application of digital holography as an effective 3D diagnostic tool.

Three-dimensional characterization of debris clouds under hypervelocity impact with pulsed digital inline holography.

The increasing space debris poses a great threat to in-orbit spacecraft and satellites, because its hypervelocity impact can bring about fatal mechanical and electrical damage to them. This work applies pulsed digital inline holography (DIH) to measure three-dimensional (3D) positions and shapes of the debris clouds generated by the hypervelocity impact in the Whipple shield. Detailed operation procedures of synchronizing the pulse DIH system with the impact event and removing the strong plasma radiation are presented, ensuring the successful capture of the transient state of ultrafast ejecta. Experiments on a 2.25 mm aluminum sphere impacting a 0.5 mm thickness aluminum target plate with a velocity of 3.6 km/s are carried out at the Hypervelocity Impact Research Center of the China Aerodynamics Research and Development Center, and results show that the holographic fringes are clearly recorded and the debris fragments are reconstructed and located accurately, agreeing well with the results measured by laser shadowgraph. This work demonstrates the powerful capability and great potential of DIH in the diagnostics of hypervelocity impact.