Angle Spread Research Articles

Research on a measurement method for spatio-temporal distribution of fragments based on a high-speed camera network

To reliably measure multiple spatio-temporal distribution parameters of fragments in the blast field, a measurement method for spatio-temporal distribution of fragments based on a high-speed camera network is proposed. The method is based on the principle of binocular stereo vision measurement and consists of four steps: fragment image acquisition, target detection of multi-view images, fitting of motion trajectory, and calculation of the spatio-temporal distribution parameters. The test results demonstrate that the method can simultaneously measure multiple parameters in the intersecting field of view. Compared with the measurement results of the array target, the absolute value of the measurement relative error of velocity was less than 1.5%, and the measurement results of scatter angle and distribution density were consistent. It indicates that the measurement results of the proposed method are reliable, and the method is a feasible and effective measurement method for spatio-temporal distribution parameters of fragments in the explosion filed.

Synergism and molecular mismatch in rhamnolipid/CTAC catanionic surfactant mixtures

Rhamnolipids represent a promising class of biosurfactants, whose industrial exploitation could potentially reduce the ecological impact of surfactant-based formulations. In this direction, the rational design of rhamnolipid mixtures with other surfactants constitutes a strategic field of research.In this work, we combine mono-rhamnolipid (mRha) with the cationic surfactant cetyltrimethylammonium chloride (CTAC). The study is conducted at pH = 7.1, so that the mRha carboxylic group is dissociated and catanionic mRha-CTAC mixtures form. The system is investigated across the entire composition range by surface tension and conductivity measurements, which show a strong synergism between the two surfactants in forming mixed aggregates, specifically in mRha-rich mixtures. No coacervation or precipitation is observed, due to the strong asymmetry between the surfactant molecular architectures, with mRha presenting a bulky headgroup and two relatively short tails compared to the single long tail of CTAC. Dynamic Light Scattering (DLS) and Small Angle Neutron Scattering (SANS) experiments show that, while the single surfactants predominantly form small micelles, their mixing results in the spontaneous formation of vesicles. Within the vesicle bilayer, the termini of the longer surfactant tails fold, assuming disordered conformations, as probed by Electron Paramagnetic Resonance (EPR) measurements.These results point to the rational design of rhamnolipid-based catanionic mixtures as a suitable tool to optimize their structural properties, constituting a solid basis for their practical applications.

Polyphenyltriazoles on Kombucha‐Derived Bacterial Cellulose: Synthesis, Structural Evaluation and Hydrophobicity

AbstractBacterial cellulose‐based materials have diverse applications as leather‐like materials, wound‐healing materials, and optoelectronic materials etc. Particularly, functionalization by polymer or organic compounds can help improve specific properties to diversify application areas. In this work, we reported a facile approach to functionalize Kombucha‐derived bacterial cellulose (BC) by AB‐type “Graft Through” click polymerization reaction. Since by this technique, the polymer was anchored on the surfaces as well as was produced in solution, and it provided the flexibility of detailed characterization on the surface as well as in a solution. Apart from standard spectroscopic characterization techniques, multinuclear solid‐state 13C, 29Si, and 15N NMR spectroscopic studies were undertaken extensively for finding the detailed structural information unambiguously. Thermal analysis, X‐Ray Diffraction analysis, and Small Angle Scattering (SAXS) was undertaken to understand the crystallinity and fibrous properties of the bacterial cellulose materials, while various microscopic analyses were undertaken for morphological studies. Those are particularly helpful in understanding the hydrophobicity of the materials an essential parameter for diversifying the application areas of the materials.

Synchrotron radiation stability with meV-level energy resolution: in situ characterization.

One of the most critical parameters in synchrotron radiation (SR) experiments is the stability of the photon energy, which is primarily affected by the stability of the light source and the optical elements in the beamline. Due to the characteristics of SR and the use of dispersive elements such as monochromators in the beamline, the change of the beam position is usually accompanied by the change of energy and flux, while most traditional beam monitoring methods are based on the direct or indirect measurement of total flux, and are therefore sensitive to the beam position only, having no energy resolution. In this paper, an in situ monitoring system has been designed to measure the short-term (jitter) and long-term (drift) characteristics of the energy variation in the SR beamline. The system consists of a double-crystal monochromator, an orthogonal analysis crystal, and an X-ray imaging detector, which could decouple the angle and energy spread of the photon beam based on the dispersion effect in Bragg diffraction. The time response and the energy resolution of the system could reach millisecond and millielectron volt level, respectively.

A novel design of a retarding field electron energy analyzer with a cavity electrode providing extremely high energy resolution

An electron energy analyzer based on the retarding electrostatic field generated by a cavity electrode was prototyped, where the designed energy resolution is smaller than 10 meV at acceleration voltages Vo less than 5 kV and a half angle spread θo less than 20 mrad for the incident electron beams with the scanning voltage range of 3 V. Precise energy resolution, however, has not been recognized experimentally because of the difficulties of equipping such a narrow energy spread electron source. This paper describes the principle of the newly developed energy analyzer and shows the obtained energy spectra from a Schottky emitter ZrO/W(100) with a tip of the curvature radius of 1.5 μm, which could highly reproduce the theoretically expected spectra at various emitter temperatures because of its predominantly thermal emission.

Predicting buoyant jet characteristics: a machine learning approach.

We study positively buoyant miscible jets through high-speed imaging and planar laser-induced fluorescence methods, and we rely on supervised machine learning techniques to predict jet characteristics. These include, in particular, predictions to the laminar length and spread angle, over a wide range of Reynolds and Archimedes numbers. To make these predictions, we use linear regression, support vector regression, random forests, K-nearest neighbour, and artificial neural network algorithms. We evaluate the performance of the aforementioned models using various standard metrics, finding that the random forest algorithm is the best for predicting our jet characteristics. We also discover that this algorithm outperforms a recent empirical correlation, resulting in a significant increase in accuracy, especially for predicting the laminar length.

Physico-chemical characterization of Synperonic™ 91/5 self-assembly behaviour in water

We studied the self-assembled aggregates of Synperonic™ 91/5 (SYN) in water solution. This surfactant presents the peculiarity of having an odd number of aliphatic carbons, with a tail composed of C9H19 and C11H23, and the headgroup having an average of 5 ethoxy units. While the general family of CiEOj nonionic surfactants has been widely studied, there is little knowledge for the case of surfactants with odd-number carbons. For this reason, we carried out an in depth physico-chemical characterization of water solutions containing SYN in the wide range of concentration from 2 % to 50 % (i.e. 0.05–1.4 M), considering that high concentrated systems are relevant for industrial applications. This class of surfactants is also interesting as remediation agent since they can incorporate different polluting molecules, both polar and nonpolar, such as volatile Organic Compounds (VOCs) and Dense Non Aqueous Phase liquids (DNAPLs). The rheological and transport properties of SYN solutions were investigated through diffusion coefficients and viscosity, while shape and size of self-assemblies were determined by Dynamic Light Scattering and by Small Angle Scattering of Neutrons (SANS) and X-rays (SAXS). Results show that SYN generally behaves as other nonionic surfactants in dilute solutions, but shows some peculiarity of aggregate packing at high concentration. We recently demonstrated the efficiency of the Synperonic™ family of surfactants in solubilising trichloroethylene (TCE), in particular above a critical concentration of 0.1 M, thus being a good candidate for remediation purposes. Here, the solubility of TCE was correlated with the number and the size of micelles at different surfactant concentrations. Our work helps filling a gap in the literature about technical grade surfactants with odd-number carbons, and the results can help in assessing the performances of Synperonic™ products for technical tasks.

Fabrication of Ultralarge Curvature Folding-Resistant Polyimide Films by Widening the Elastic Range and Intermolecular Slippery Spacing

As the electrons advanced toward foldable and lightweight characteristics, fabricating polyimide (PI) substrates resisting large curvature folding under an ultralow folding radius posed a significant challenge for flexible electronics. Here, one polyimide film (PICu) was fabricated by introducing Cu2+ and benzimidazole, whose elastic range and intermolecular slippery spacing were widened thanks to the point-to-face multi-coordination structure with larger attraction distance and variable bond angles, and it was fortunately equipped with greatly enhanced folding resistance even under an ultralarge curvature. First, the folding radius was confirmed to have an exponential impact on the tested folding reliability, as folding times of pure PI to form creases decreased sharply from 300,000 to 3000 with the folding radius dropping from 2 to 0.25 mm. In contrast, no crease was formed on PICu films even after folding over 200,000 times under an ultralow folding radius of 0.25 mm. Importantly, the folding radius was almost 10 times smaller than that in current reports (2–3 mm). In addition, the spread angle of PICu films after static folding at 80 °C was 50–78% larger than that of pure PI films with the folding radius decreased from 2 to 0.25 mm, demonstrating the excellent dynamic and static folding resistance of PICu films under an ultralarge curvature.

Ultralarge Curvature Folding Resistance of Polyimide Films Based on Spring-Like Folding Segments.

With the trend toward lighter and thinner flexible electronics, developing foldable polymeric substrates that can withstand ultralow folding radiuses has become an urgent issue. Here, a strategy to develop polyimide (PI) films with excellent dynamic and static folding resistance under an ultralarge curvature through copolymerizing one "unidirectional diamine" with classic PMDA-ODA PIs to achieve a kind of folding-chain PI (FPI). It was theoretically and experimentally confirmed that the spring-like folding structure equipped PI films with an enhanced elastic behavior and thus an excellent ability to endure a large curvature. Among them, FPI-20 did not show any crease even after folding over 200000 times under a folding radius of 0.5 mm, while creases were observed on pure PI film only after folding 1000 times. It is noteworthy that the folding radius was almost 5 times smaller than that in current reports (2-3 mm). Meanwhile, the spread angle of FPI-20 films after static folding at 80 °C under a 0.5 mm folding radius get 51% larger than that of films, showing the remarkable static folding resistance.

DOA estimation method for incoherently distributed sources based on spatial–temporal generalized ESPRIT

This paper proposes a spatial–temporal generalized ESPRIT parameter estimation method to solve the estimation problem of the central angles and spread angles of incoherently distributed sources. To begin with, a virtual array covariance matrix is built by conducting time-delay autocorrelation operation on the original received data. The central angles are then estimated with the generalized shift invariance property inside the virtual array manifold. Next, the spread angles are obtained with resorting to the estimated central angles and the central moments of the angular distribution function. Compared with the existing algorithm, the proposed algorithm does not require the signal to have non-circular characteristics, and has higher parameter estimation accuracy and can distinguish more sources. In addition, the proposed method is robust to types of spread angles, as verified by a series of simulation results.

Variation in the Root System Architecture of Peach × (Peach × Almond) Backcrosses.

The spatial arrangement and growth pattern of root systems, defined by the root system architecture (RSA), influences plant productivity and adaptation to soil environments, playing an important role in sustainable horticulture. Florida's peach production area covers contrasting soil types, making it necessary to identify rootstocks that exhibit soil-type-specific advantageous root traits. In this sense, the wide genetic diversity of the Prunus genus allows the breeding of rootstock genotypes with contrasting root traits. The evaluation of root traits expressed in young seedlings and plantlets facilitates the early selection of desirable phenotypes in rootstock breeding. Plantlets from three peach × (peach × almond) backcross populations were vegetatively propagated and grown in rhizoboxes. These backcross populations were identified as BC1251, BC1256, and BC1260 and studied in a completely randomized design. Scanned images of the entire root systems of the plantlets were analyzed for total root length distribution by diameter classes, root dry weight by depth horizons, root morphological components, structural root parameters, and root spreading angles. The BC1260 progeny presented a shallower root system and lower root growth. Backcross BC1251 progeny exhibited a more vigorous and deeper root system at narrower root angles, potentially allowing it to explore and exploit water and nutrients in deep sandy entisols from the Florida central ridge.

Radio Channel Measurements and Characterization in Substation Scenarios for Power Grid Internet of Things

Wireless communication technologies play a key role to support the implementation of power grid Internet of Things (PIoT). An in-depth knowledge of the radio channel is vital to the application of wireless communication technologies in PIoT. This paper investigates the radio channel measurements and characterization for PIoT substation scenarios. A novel channel sounder is designed for achieving omnidirectional measurements and phased array antennas based directional measurements, and a directional multipath components extraction algorithm is proposed. The channel sounding system is verified and is used to perform a series of 3.35 GHz omnidirectional and directional channel measurements in four substation scenarios, involving a 10 kV switch room, a 110 kV GIS room, a semi-indoor 110 kV substation and an outdoor 220 kV substation. Based on the measured channel impulse responses data, both large-scale and small-scale fading characteristics of substation channels are extracted and analyzed. Empirical models of path loss, shadow fading, Ricean K-factor and root-mean-square (RMS) delay spread are proposed. In addition, results of RMS angle spread of departure and RMS angle spread of arrival are presented. These results will provide useful reference for the deployment and optimization of wireless communication networks in PIoT substation scenarios.

Comparative Study of the Parameter Acquisition Methods for the Cauer Thermal Network Model of an IGBT Module

Under the operating conditions of high power and high switching frequency, an insulated gate bipolar transistor (IGBT) chip can produce relatively large power loss, causing the junction temperature to rise rapidly; consequently, the reliability of the IGBT module can be seriously affected. Therefore, it is necessary to accurately predict the junction temperature of the IGBT chip. The resistance capacitance (RC) thermal network model is a commonly used method for IGBT junction temperature prediction. In this paper, the model parameters are obtained by two methods to establish the Cauer thermal network models of the IGBT module. The first method is to experimentally obtain the transient thermal impedance curve of the IGBT module and the structure function and then extract the individual thermal parameters of the Cauer thermal network model; the second method is to obtain the thermal parameters of the thermal network model directly by using theoretical formulas that consider the influence of the heat spreading angle. The predicted junction temperatures of the Cauer thermal network models established by the two methods are compared with the junction temperatures obtained from infrared (IR) measurements during the power cycling test, the junction temperatures measured by the temperature-sensitive electrical parameter (TSEP) method, and the junction temperatures calculated by finite element (FE) analysis. Additionally, the Cauer thermal network models established by the two methods are compared and verified. The results indicate that the Cauer thermal network model established based on theoretical formulas can accurately predict the maximum junction temperature of the IGBT chip, and the calculated temperature for each layer, from the IGBT chip layer to the ceramic layer, also accords well with the FE results. The Cauer thermal network model established based on the experimental test and the structure function can accurately predict the average junction temperature of the IGBT chip.

Motion of a Debris Line Source Under Currents and Waves: Experimental Study

Debris impact has an important role in structural damage during extreme coastal events. Understanding the transport of debris and the characteristic of its motion is crucial because the debris impact depends on debris motion. This study investigated floating debris dispersion and motion by conducting laboratory experiments that considered the effects of a structural array, or a gridded layout of city-like buildings. Physical model experiments were conducted for two different hydrodynamic conditions: (1) current only; and (2) current + wave combined cases. Debris was released from a certain height in a repeatable way. Visual data were collected by four overhead video cameras and a particle tracking algorithm was implemented to track debris motion. Onshore debris spreading was much larger in the current + wave combined cases than in the current only trials. The results indicated that the structural array restricted the lateral spreading of debris onshore, and between the buildings, the spread of the particles approached a Gaussian distribution as the particles move inland. The offshore dispersion of debris particles was slightly higher when structures were present due to the additional turbulence that was created by the reflected waves. Debris spreading angles (θs) were calculated for each case and compared with the angles used in the current engineering practice. The presented results aimed to increase the current knowledge on debris motion and spreading during extreme events, such that engineers might build more resilient coastal communities.

Thermal Circuit Models of Microstrip Lines Based on Precise Heat Spreading Angles and Convection Boundary Conditions

In this paper, the equivalent thermal circuits of microstrip lines are proposed based on the equivalent heat spreading angle (ESA) model and convection boundary conditions. Unlike the conventional constant-angle assumption, the ESAs corresponding to the situations of conductor and dielectric losses of microstrip lines are determined precisely by means of the modified parallel-plate model, which are associated with the geometry and material of the microstrip lines. Further, different kinds of boundary conditions are considered in the thermal circuit models, especially the impact of heat convection condition which matters in realistic situations. In addition, the thermal circuit models are extended to the case of coupled microstrip lines. The calculated results of the proposed model agree well with those simulated by the multiphysics solver.

Spray dynamics of synthetic dimethyl carbonate and its blends with gasoline

Synthetic dimethyl carbonate (DMC) is a promising alternative or oxygenated additive fuel to reduce not only CO2 but also particle number (PN) emissions from gasoline direct injection (GDI) engines. Despite many investigations on the engine performance of DMC-gasoline blends in the literature, limited reports can be found focusing on their spray characteristics. However, a comprehensive understanding of spray characteristics is crucial to interpret the results of GDI engine tests. Therefore, this study was to examine the near-nozzle spray dynamics of the DMC-gasoline blends by using the X-ray phase contrast imaging technique. First, the fuel properties of the synthetic DMC and regular gasoline blends were quantified. Then, the near-nozzle spray dynamics were examined in both non-evaporating and evaporating conditions, and discussions were made accordingly to link the near-nozzle spray dynamics with fuel properties. It is found that increasing DMC content could enlarge the spray spreading angle and reduce the near-nozzle spray velocity by up to +22 % and –18 %, respectively. The near-nozzle-exit spray velocity depends sharply on the fuel density as the DMC content varies in the blends. However, this dependency gradually becomes insignificant as the spray propagating distance increases. Pure DMC has the largest Sauter mean diameter (SMD) and least droplet number than other blends, but they tend to be consistent as the ambient gas temperature increases. The existing empirical correlation is still feasible to predict the SMD of the DMC-gasoline blends, but certain tuning of the constants is necessary. Within the experimental conditions in this study, the DMC-gasoline blends should undergo the same spray breakup regime, i.e., the atomization regime.

Controlling the beam angle spread of carbon implantation for improvement of bin map defect in V-NAND flash memory

As the shrinkage of devices accelerates and the vertical layers increase, beam angle spread of carbon ion implantation (C IIP) for the silicon selective epitaxial growth (Si-SEG) areas in V-NAND is one of the most critical parameters related with bin map defects. The roles of C IIP in Si-SEGs are that it can suppress channeling effect of boron IIP and diffusion limitation of boron dopants during subsequent annealing processes. In this study, beam angle spread was reduced by 36% and the center-to-edge beam angle skew of wafer was reduced to less than 1° by optimizing the specification of tracking magnet and the beam angle mean. After applying the improved process conditions and effective interlocks, the bin defective rate was controlled less than 0.5% successfully.

Multi-Wavelength Spot-Array Beams Based on Tunable Dammann Grating Metasurface

The structured light projection (SLP) method occupies a crucial position in three-dimensional (3D) imaging technology. Different working wavelengths of structured light can be employed depending on the situation. However, there are few structured lights that can be modulated based on wavelength at present. Therefore, we have comprehensively investigated and designed a Dammann grating (DG) based on metasurface, which can be controlled through multi-beam interference (MBI) to achieve a change of the working wavelength. In this work, we can convert the straight waveguide to the helical waveguide by fine-tuning the related parameters of the incident lights and generate 5 × 5 diffraction spot arrays in the wavelength range of 480–510 nm and 950–1020 nm, respectively. Furthermore, the metasurfaces exhibit good performance. For example, their spread angles can be up to 44° × 44° and they can reach a conversion efficiency of over ≥50% while maintaining a contrast ratio of roughly 40%. Compared with traditional structured light, it can be used in different working wavelengths and has a broader application range in 3D sensing systems.

Resonant Scattering of Radiation Belt Electrons at Saturn by Ion Cyclotron Waves

AbstractBy constructing an empirical model of the spectral and latitudinal distribution of ion cyclotron waves on the basis of Cassini datasets, we investigate the resonant interactions between ion cyclotron waves and radiation belt electrons at Saturn. Calculations based on quasi‐linear bounce‐averaged diffusion coefficients show that at Saturn ion cyclotron waves can efficiently pitch angle scatter >∼1 MeV to tens of MeV electrons into the loss cone thereby inducing precipitation loss, while the mixed and momentum scattering effects are typically negligible. The resultant electron loss timescales range from a few to tens of minutes, which in fact decrease significantly with increasing L‐shell at L = 4–6. We also find that the kinetic effects introduced by pick‐up ring particles cause distinct changes in pitch angle scattering efficiency for lower energy electrons (<3 MeV at L = 5). Our results demonstrate that ion cyclotron waves play a significant role in the dynamics of Saturn's radiation belt electrons.

Introduction of Research Work on Laser Proton Acceleration and Its Application Carried out on Compact Laser–Plasma Accelerator at Peking University

Laser plasma acceleration has made remarkable progress in the last few decades, but it also faces many challenges. Although the high gradient is a great potential advantage, the beam quality of the laser accelerator has a certain gap, or it is different from that of traditional accelerators. Therefore, it is important to explore and utilize its own features. In this article, some recent research progress on laser proton acceleration and its irradiation application, which was carried out on the compact laser plasma accelerator (CLAPA) platform at Peking University, have been introduced. By combining a TW laser accelerator and a monoenergetic beamline, proton beams with energies of less than 10 MeV, an energy spread of less than 1%, and with several to tens of pC charge, have been stably produced and transported in CLAPA. The beamline is an object–image point analyzing system, which ensures the transmission efficiency and the energy selection accuracy for proton beams with large initial divergence angle and energy spread. A spread-out Bragg peak (SOBP) is produced with high precision beam control, which preliminarily proved the feasibility of the laser accelerator for radiotherapy. Some application experiments based on laser-accelerated proton beams have also been carried out, such as proton radiograph, preparation of graphene on SiC, ultra-high dose FLASH radiation of cancer cells, and ion-beam trace probes for plasma diagnosis. The above applications take advantage of the unique characteristics of laser-driven protons, such as a micron scale point source, an ultra-short pulse duration, a wide energy spectrum, etc. A new laser-driven proton therapy facility (CLAPA II) is being designed and is under construction at Peking University. The 100 MeV proton beams will be produced via laser–plasma interaction by using a 2-PW laser, which may promote the real-world applications of laser accelerators in malignant tumor treatment soon.