Single Angle Research Articles

Changing the optical properties of poly(methyl methacrylate) superficial films during UV irradiation

In this work, the simple spectroscopic method is presented to study the change of the optical constants n and k of the poly(methyl methacrylate), UV-irradiated. The infrared reflection-absorption spectra were recorded at a single incidence angle. The reflection-absorption spectra of the poly(methyl methacrylate) thin films were processed using classical dispersion analysis and a fitting program to obtain optical constants n and k. The shift, the variation of intensity, or broadening of the absorption bands during the UV degradation, were watched in the extinction coefficient k spectrum. The changes in the extinction spectrum of UV-irradiated polymer films are consistent with the photodegradation mechanisms described in the literature.

Time‐dependent failure of off‐axis loaded unidirectional glass/iPP composites

AbstractIn our previous study, we demonstrated that the time‐dependent failure of transversely loaded UD (unidirectional) glass/iPP is fully plasticity‐controlled and proposed a lifetime prediction method based on plasticity to predict transverse failure. In the present work, extending our previous study to other off‐axis angles, we aim to investigate the effect of the off‐axis angle on the time‐dependent failure of UD glass/iPP, and to propose a lifetime prediction method for the off‐axis failure. Glass/iPP specimens with different off‐axis angles are tested at various strain rates, creep, and fatigue loads to characterize the anisotropic, time‐dependent mechanical response. It is demonstrated that the influences of strain rate and fiber orientation angle on tensile strength are multiplicatively separable; also referred to as factorizable, enabling one to characterize the angle dependence at a single strain rate and the strain rate dependence at a single angle. Moreover, similar to transverse loading, off‐axis failure is also observed to be plasticity‐controlled. Based on these observations, the lifetime prediction method for the plasticity‐controlled transverse failure is extended to off‐axis loading using the aforementioned factorazibility, which resulted in lifetime predictions in agreement with the experimental creep and fatigue data.

Attitude Stabilization Control of Autonomous Underwater Vehicle Based on Decoupling Algorithm and PSO-ADRC.

Autonomous Underwater Vehicle are widely used in industries, such as marine resource exploitation and fish farming, but they are often subject to a large amount of interference which cause poor control stability, while performing their tasks. A decoupling control algorithm is proposed and A single control volume–single attitude angle model is constructed for the problem of severe coupling in the control system of attitude of six degrees of freedom Autonomous Underwater Vehicle. Aiming at the problem of complex Active Disturbance Rejection Control (ADRC) adjustment relying on manual experience, the PSO-ADRC algorithm is proposed to realize the automatic adjustment of its parameters, which improves the anti-interference ability and control accuracy of Autonomous Underwater Vehicle in dynamic environment. The anti-interference ability and control accuracy of the method were verified through experiments.

Cryogenic electron microscopy approaches that combine images and tilt series.

Cryogenic electron microscopy can be widely applied to biological specimens from the molecular to the cellular scale. In single-particle analysis, 3D structures may be obtained in high resolution by averaging 2D images of single particles in random orientations. For pleomorphic specimens, structures may be obtained by recording the tilt series of a single example of the specimen and calculating tomograms. Where many copies of a single structure such as a protein or nucleic acid assembly are present within the tomogram, averaging of the sub-volumes (subtomogram averaging) has been successfully applied. The choice of data collection method for any given specimen may depend on the structural question of interest and is determined by the radiation sensitivity of the specimen. Here, we survey some recent developments on the use of hybrid methods for recording and analysing data from radiation-sensitive biological specimens. These include single-particle reconstruction from 2D images where additional views are recorded at a single tilt angle of the specimen and methods where image tilt series, initially used for tomogram reconstruction, are processed as individual single-particle images. There is a continuum of approaches now available to maximize structural information obtained from the specimen.

Study on the cutting mechanism of randomly deflected truncated cone shape single abrasive grain

Based on the random distribution characteristic of abrasive grains for the grinding wheel circumferential surface during the manufacturing process, considering the grinding parameters and deflection parameters comprehensively, a randomly deflected truncated cone shape single abrasive grain cutting simulation model was established. Then, studying its cutting mechanism, i.e., the trajectory length value by numerical method and formula method was compared, the consequence indicates that the error is extremely small; this demonstrates the accuracy of the numerical method. The calculation and analysis of the workpiece cutting surface topography and the undeformed chip shape were carried out; it shows that the cutting surface topography and the undeformed chip shape are coincident. And the calculation results of the model were compared to verify. The influence laws of each grinding process parameter on the material removal volume (MRV) and material removal rate (MRR) were investigated; the results display that the grinding method affects the changing pattern of MRV and MRR; when the grinding method was up-grinding, a high wheel speed or a small wheel diameter is able to enhance the MRR; the MRV and MRR are increments with the increasing workpiece feed speed or abrasive grain cutting depth; and the MRV and MRR decrease with the raising of the absolute value of single abrasive grain deflection angle. The situation is a similar or opposite trend in down grinding. This work can provide a theoretical reference for the selection and optimization of parameters and further lay a foundation for the research in the grinding mechanism of the grinding wheel.

Effects of T2 * on accuracy and precision of dynamic T1 measurements using the single reference variable flip angle method: a simulation study.

To study in simulation and in theory the accuracy and precision of dynamic T1 measurements obtained using the previously published single-reference variable flip angle (SR-VFA) technique, with a focus on the effects of dynamic changes in T2 * on the calculation. Monte Carlo simulations were performed over 1000 noisy iterations for the VFA method, the SR-VFA method, and a proposed method, SR-VFA with a T2 * correction (SR-VFA-T2 *). Dynamic T1 estimates were calculated analytically for each method, with signals modeled by the steady-state spoiled gradient echo equation. The mean and standard deviation of these estimates were calculated and compared to truth, while varying repetition time (TR), baseline and dynamic T1 , echo time (TE), baseline and dynamic T2 *, flip angles, and the number of averages on baseline scans. Additionally, the variance of T1 in the SR-VFA and SR-VFA-T2 * methods was derived analytically based on the theory of propagation of errors. This equation was used to produce an inverse-variance weighted linear combination to improve T1 mapping precision in the SR-VFA-T2 * method. Flip angle sensitivity of dynamic T1 precision in the SR-VFA and SR-VFA-T2 * methods was also performed. Substantial bias can be produced by the SR-VFA method when the ratio of the T2 * decay of the dynamic signal versus that of the baseline signals deviates from 1, with a 0.01 deviation leading to approximately a 1% bias in cases of high SNR and TR ≫ T1 . This bias can be corrected by estimating the baseline and dynamic T2 * values in this ratio via multiecho measurements. The bias and precision of the SR-VFA-T2 * method, when normalized to scan time, is found to rival and sometimes improve upon the two flip angle VFA method when an inverse variance weighted linear combination is applied across its multiecho T1 maps. The analytic variance equation presented is found to be accurate within 1% relative to the Monte Carlo simulations over a broad parameter space. Flip angle ranges that maximize SR-VFA and SR-VFA-T2 *T1 precision over a broad parameter space are given, and each is defined relative to TR and T1 . Multiecho SR-VFA-T2 * T1 mapping is found in simulation and theory to be a promising alternative to the VFA method that maintains speed of the SR-VFA method with accuracy and precision similar to the VFA method.

Measurements of Aquatic Particle Volume Scattering Function up to 178.5° in the East China Sea

Particulate volume scattering function (VSF), especially at angles larger than 170°, is of particular importance for interpreting ocean optical remote sensing signals and underwater imagery. In this study, a laboratory-based VSF instrument (VSFlab) adopting the periscopic optical system was developed to obtain VSF measurements from 1°–178.5°. In the VSFlab, a new prism design that simply combines a single prism and a neutral density filter was proposed to more efficiently reduce the stray light in the backward direction, while a detailed calibration procedure was given. A full validation based on standard beads of various sizes and a comparison with the results from LISST-VSF and POLVSM indicated that the VSFlab can provide reliable results from 1° to 178.5°. VSFlab measurements in the East China Sea (ECS) exhibited a moderate increase (not more than 5 times) in VSF from 170° to 178.5° rather than a sharp increase of more than one order of magnitude presented in other instrument results measured in other coastal regions. The estimates of the particulate backscattering coefficient using single angle scattering measurements near 120° or 140° and suitable χp were justified. Two types of the VSFs with different size distribution and shape parameters in the ECS can be distinguished based on the variability of χp after 155°. The measured VSF could provide a basis for the parameterization of VSF in the radiative transfer model and the variability of χp in the backward direction had the potential to be used to characterize the particles in the coastal region of the ECS.

Rockfall Kinematics from Massive Rock Cliffs: Outlier Boulders and Flyrock from Whitney Portal, California, Rockfalls

ABSTRACT Geologic conditions and topographic setting are among the most critical factors for assessing rockfall hazards. However, other subtle features of rockfall motion may also govern the runout of rockfall debris, particularly for those sourced from massive cliffs where debris can have substantial momentum during transport. Rocks may undergo collisions with trees and talus boulders, with the latter potentially generating flyrock—launched rock pieces resulting from boulder collisions that follow distinctively different paths than the majority of debris. Collectively, these intricacies of rockfall kinematics may substantially govern the hazards expected from rockfall to both persons and infrastructure located beneath steep cliffs. Here, we investigate the kinematics, including outlier boulder and flyrock trajectories, of seismically triggered rockfalls on 24 June 2020 that damaged campground facilities near Whitney Portal, CA, a heavily used outdoor recreation gateway to the Sierra Nevada mountains. Our results, obtained in part by rockfall runout model simulations, indicate that outlier boulder trajectories resulted from opportunities provided by less steep terrain beyond the talus edge. The influence of trees, initially thought to have served a protective capacity in attenuating rockfall energy, appears to have been negligible for the large boulder volumes (>50 m3) mobilized, although they did potentially deflect the trajectory of flyrock debris. Rockfall outlier boulders from the event were comparable in volume and runout distance to prehistoric boulders located beyond the talus slope, thereby providing some level of confidence in the use of a single rockfall shadow angle for estimating future rockfall hazards at the site.

Segmented guidance law for single moving mass controlled reentry vehicle with multiple constraints

This paper addresses the problem of low guidance accuracy when the traditional guidance method is adopted on the single moving mass controlled reentry vehicle (SMMCRV) with multiple constraints. More specifically, the range and the velocity cannot be controlled accurately by the single bank angle. To solve the aforementioned problems, the segmented guidance law is employed for the reentry phase to achieve the goal of considerable range adjustment and meeting multiple constraints, which consists of the reference trajectory planning & tracking method and the modified rolling guidance law, making full use of the range adjustment capability of the high-altitude phase and the deceleration capacity of the low-altitude phase. For the high-altitude phase, it is difficult to guarantee the precise control of the velocity and range with the bank angle. Therefore, the varying-weight trajectory planning method and adaptive trajectory tracking method considering the combination between tracking errors are employed. In addition, to decrease the influence caused by the lateral motion and the multiple changing rolling direction, the lateral logic and improved B-spline fitting method are also proposed. For the low-altitude phase, the lateral deviation is counteracted by the high speed rotation. Considering the influence on the stability of the SMMCRV caused by the too high rotation, the nonlinear error angle command is designed and the finite-time guidance law is proposed to obtain the high guidance accuracy. Compared with the traditional method, lower terminal velocity dispersion, higher terminal accuracy and lower rotation speed can be obtained, which can be also demonstrated by the numerical simulation.

Angle-dependent effects in DLS measurements of polydisperse particles

Dynamic light scattering (DLS) is widely used for analyzing biological polymers and colloids. Its application to nanoparticles in medicine is becoming increasingly important with the recent emergence of prominent lipid nanoparticle (LNP)-based products, such as the SARS-CoV-2 vaccines from Pfizer, Inc.-BioNTech (BNT162b2) and Moderna, Inc. (mRNA-1273). DLS plays an important role in the characterization and quality control of nanoparticle-based therapeutics and vaccines. However, most DLS instruments have a single detection angle θ, and the amplitude of the scattering vector, q, varies among them according to the relationship q = (4πn/λ 0) sin(θ/2), where λ 0 is the laser wavelength. Results for identical, polydisperse samples among instruments of varying q yield different hydrodynamic diameters, because, as particles become larger they scatter less light at higher q, so that higher-q instruments will under-sample large particles in polydisperse populations, and report higher z-average diffusion coefficients, and hence smaller effective hydrodynamic diameters than lower-q instruments. As particle size reaches the Mie regime the scattering envelope manifests angular maxima and minima, and the monotonic decrease of average size versus q is lost. The discrepancy among instruments of different q is hence fundamental, and not merely technical. This work examines results for different q-value instruments, using mixtures of monodisperse latex sphere standards, for which experimental measurements agree well with computations, and also polydisperse solutions of physically-degraded LNPs, for which results follow expected trends. Mie effects on broad unimodal populations are also considered. There is no way to predict results between two instruments with different q for samples of unknown particle size distributions. Initial analysis of the polydispersity index among different instruments shows a technical difference due to method of autocorrelation analysis, in addition to the fundamental q-effect.

Mean scattering angle method for direct simulation Monte Carlo.

In order to predict the postcollision velocities in the binary collision, one needs the deflection angle given by the solution of the trajectory equation of classical mechanics. In the direct simulation Monte Carlo, it has been conventional to assume that the scattering is isotropic taking the hard sphere scattering law (the variable hard sphere model). Because the simulation carries out the ensemble average, and thus the collisional deflections should be averaged at the end, it is proposed to use the preaveraged deflection angle for each collision. This is a representative single deflection angle simulation. The present work postulates a method to estimate the mean deflection angles for arbitrary force models considering the differential cross section formula and the trajectory equation. For hard spheres, the representative single deflection simulation of normal shock waves recovers the conventional computations within 3%. For Maxwell molecules, the conventional simulation in which the isotropic scattering law is taken can exactly be reproduced by the single deflection when the representative angle is adjusted to the mean deflection angle together with the reference diameter obtained in the present method. It has been observed that the Maxwell-molecule-representative for the single angle simulation reproduces the conventional computations of any isotropic scattering models including hard spheres.

The impact of heterogeneous environmental regulations on the technology innovation of urban green energy: a study based on the panel threshold model

<abstract> <p>Since the Porter hypothesis was proposed, environmental regulation has been recognized as a critical factor influencing technology innovation. However, there is no unified conclusion on whether the relationship between the two is linear or non-linear, and environmental regulation is always examined from single angles. Therefore, according to the difference of environmental regulation implementation subjects, this paper divides environmental regulation into formal regulation and informal regulation. Utilizing the panel data of 281 prefecture-level and above cities in China from 2011-2019, the non-linear effects of heterogeneous environmental regulations on green energy technology innovation are analyzed based on the panel threshold model, and the non-linear relationship between the two under the difference in urban economic development level is further considered. The results indicate that: (1) The threshold effect of the environmental regulations on China's green energy technology innovation is significant, and there is heterogeneity in the effects of different environmental regulations. (2) At present, positive relationship are observed between the informal environmental regulation and green energy technology innovation in China, while the formal environmental regulation exerts a significant inhibitory effect on green energy technology innovation. (3) The level of regional economic development plays a significantly positive role in moderating the relationship between environmental regulation and green energy innovation. However, there exists a certain heterogeneity in the moderating role between the formal regulation-innovation link and informal regulation-innovation relationship. This study provides a reference for further clarifying the relationship between heterogeneous environmental regulations and green energy technology innovation.</p> </abstract>

Thoracolumbar kyphosis in postmenopausal osteoporosis patients without vertebral compression fractures.

BackgroundTo investigate whether thoracolumbar kyphosis (TLK) of the spine is related to the reduction of bone mineral density (BMD) in postmenopausal osteoporosis women, and whether BMD of postmenopausal osteoporosis women can predict the occurrence of TLK.MethodsThis retrospective cohort study included 224 postmenopausal female patients hospitalized for osteoporosis from December 2017 to December 2020, and the control group included 270 postmenopausal female patients hospitalized for thoracolumbar degenerative diseases. The age, body mass index (BMI), visual analogue scale (VAS), and BMD of the lumbar spine [BMD(L)] and femoral neck [BMD(F)] of all patients during admission were recorded. We measured and recorded the Cobb angle of thoracolumbar and the height of the thoracolumbar intervertebral space in the spinal X-ray lateral radiograph. The Pearson and Spearman correlation coefficients were used to calculate the correlation between each parameter in the group. The Chi-square test was used for categorical variables, the independent-sample t-test was used for normally distributed continuous variables, and two-sample non-parametric tests were used for non-normally distributed variables. Binary logistic regression analysis and receiver operating characteristic (ROC) curves were applied to determine independent risk factors and cut-off values, respectively.ResultsThere were significant differences in the BMD(L), BMD(F), thoracolumbar junction Cobb angle, lumbar spine Cobb angle, T11/12-L1/2 height difference of the posterior and anterior edge of intervertebral space (HDPAIS), single vertebra Cobb angle (SVC), procollagen type 1 N-terminal propeptide (PINP) and 25-hydroxyvitamin D [25-(OH)D] between the study and control groups. Through binary logistic regression analysis, we found that BMD(L), PINP, bone alkaline phosphatase, and 25-(OH)D were independent risk factors for future TLK in postmenopausal women. According to the ROC curve, the prediction accuracy of BMD(L) was the highest. By calculating the critical value, we found that when the BMD(L) T-score <−1.65, postmenopausal women were more likely to develop TLK.ConclusionsIn postmenopausal osteoporosis patients, TLK will occur even if there is no compression fracture, and when the BMD(L) T-score <−1.65, postmenopausal women are more likely to develop TLK in the future.

Angle-Resolved Spectrophotometry for the Optical Characterization of Material Surfaces

Surface reflectance is a practical metric of the optical performance of a material. Applications, such as glass manufacturing, light sensing, satellite reflectors, and photovoltaics, depend on their reflectance properties and generalized optical performance. Reflectance measurements are rarely reported comprehensively, with only a single angle of incidence common in most datasets. Here, we present a new spectrophotometry system capable of performing angle-, wavelength-, and polarization-resolved reflectance measurements on various surfaces. Data from such a system yields significant information regarding the everyday, real-world performance of said materials. We perform exemplar studies by characterizing several standard thin-film antireflectance coatings and comparing the results to their known theoretical optical response. We also present results from measurements on an optical insulating material as well as a selection of wall paints to showcase the versatility of the technique. We highlight the parallels between measurement and theory, while analyzing the realistic implications of the measurements on their respective material’s practical performance under real-world conditions.

Calculation method of stability bearing capacity of transmission tower angle steel considering semi-rigid constraint

Abstract The angle steel member is the most commonly used component form of the transmission tower structure. Considering its connection characteristics, we must deal with its stability analysis under semi-rigid constraint conditions for the proper study of the overall structure’s mechanical performance. Therefore, in order to establish a simple and high-precision method suitable for the ultimate bearing capacity analysis of the transmission tower, we build the refined finite element models of typical steel tower joints, analyze its moment-rotation curve and utilize simulation technique of spring elements to acquire the calculation method of its single angle stability bearing capacity, which is considering initial imperfection and residual stress. Furthermore, we analyze its bearing capacity under different constraint conditions such as rigid, semi-rigid and articulated connection. The results show that it is necessary to consider joint stiffness in the bearing capacity analyses. Finally, it’s confirmed that the calculation results of this method agree well with the experimental data, which validates its high accuracy. Therefore, the method provides technical support for high efficient component stability simulation in overall stability analyses of the transmission steel tower.

Optimum Switching Angle Of Switched Reluctance Motor Using Response Surface Methodology

Switched Reluctance Motor has numerous advantages compared to another electric motor. Simple structure, low-cost production, robustness, and high fault tolerance have been remarkable milestones. Still, the problem of excitation angle at power converter becomes crucial, especially for traction use, requiring higher torque at low speed for starting and acceleration. Therefore, this research emphasized finding the optimum excitation angle at low speed using Response Surface Methodology, a practical application to achieve the highest torque, as indicated by the best speed in the constant torque region. As a result, using Matlab simulation, the adaptive combination of optimum angles reached 2691 rpm quicker than a single excitation angle with 2568 rpm, an increase of 4.79% higher speed using RSM optimization. According to the experimental data, the adaptive combination of optimum angle achieved 2475 rpm better than the single excitation angle reached 2340 rpm, an increase of 5.77% higher speed using the Response Surface Methodology.

Reflection coefficient frequency-dependent inversion of a planar interface with spherical waves: Using critical and post-critical angles

As a zero-order approximation of spherical wave theory, plane wave theory based on the Zoepprtizs equations and various linear approximations has been widely used in seismic exploration, such as prestack inversion, deconvolution and Q compensation. Since localized sources excited in field acquisition usually produce spherical wavefronts, the plane wave approximation fails to correctly utilize post-critical information and frequency-dependent characteristics have been completely neglected. Unlike conventional prestack inversion using multiple angles, the existence of frequency dependency makes the inversion using reflected record of a single angle possible. Therefore, the feasibility of frequency-dependent inversion of a planar interface using one angle is analyzed and investigated. A strategy of choosing frequency-band in frequency-domain inversion is given by fitting the geometric distribution of reflection coefficients on a complex plane. The sensitivity, resolution matrix and objective function are adopted to analyze the coupled relationship between different parameters and to determine the parameters to be inverted. Combining a global optimal algorithm, the effectiveness of frequency-dependent inversion is verified using synthetic data and cross-well seismic data. The velocity and density parameters are well-inverted, especially when the data of critical offset is included. Moreover, the inversion uniting frequency-dependency with multiple angles offers more accurate estimations for both density and velocity parameters.

Inherent structure landscape of hard spheres confined to narrow cylindrical channels.

The inherent structure landscape for a system of hard spheres confined to a hard cylindrical channel, such that spheres can only contact their first and second neighbors, is studied using an analytical model that extends previous results [Phys. Rev. Lett. 115, 025702 (2015)PRLTAO0031-900710.1103/PhysRevLett.115.025702] to provide a comprehensive picture of jammed packings over a range of packing densities. In the model, a packing is described as an arrangement of k helical sections, separated by defects, that have alternating helical twist directions and where all spheres satisfy local jamming constraints. The structure of each helical section is determined by a single helical twist angle, and a jammed packing is obtained by minimizing the length of the channel per particle with respect to the k helical section angles. An analysis of a small system of N=20 spheres shows that the basins on the inherent structure landscape associated with these helical arrangements split into a number of distinct jammed states separated by low barriers giving rise to a degree of hierarchical organization. The model accurately predicts the geometric properties of packings generated using the Lubachevsky and Stillinger compression scheme (N=10^{4}) and provides insight into the nature of the probability distribution of helical section lengths.

A shortcut to the thermodynamic limit for quantum many-body calculations of metals

Computationally efficient and accurate quantum mechanical approximations to solve the many-electron Schrödinger equation are crucial for computational materials science. Methods such as coupled cluster theory show potential for widespread adoption if computational cost bottlenecks can be removed. For example, extremely dense k-point grids are required to model long-range electronic correlation effects, particularly for metals. Although these grids can be made more effective by averaging calculations over an offset (or twist angle), the resultant cost in time for coupled cluster theory is prohibitive. We show here that a single special twist angle can be found using the transition structure factor, which provides the same benefit as twist averaging with one or two orders of magnitude reduction in computational time. We demonstrate that this not only works for metal systems but also is applicable to a broader range of materials, including insulators and semiconductors.

Energy and CO2 emissions modeling for unconventional machining industry considering processing characteristics

Unconventional machining of WEDM (Wire Electrical Discharge Machining) is playing an increasingly important role in the manufacturing industry. The processing efficiency and resource consumption of this method are research hotspots from the perspective of sustainable development. Energy and CO2 emissions modeling of process machining have been recognized as an effective and economical ways to achieve energy-saving, emission-reducing and to improve process efficiency. However, the predictive modeling of energy and CO2 emissions in unconventional machining of WEDM machining has not been thoroughly fully studied. This paper proposes a predictive model of energy consumption and CO2 emissions in WEDM process considering process characteristics. The application of the energy and CO2 emissions model proposed in this paper in an example shows that the model's energy consumption prediction accuracy for single part processing reaches 96.5%, and the energy consumption prediction accuracy for batch processing is above 99%. A new standard for cutting fluid substitution with the best machining stability and energy consumption is proposed. In the example, it is also shown that the corners in the geometric structure will reduce the processing energy consumption. The smaller the number of single folding angles, the more energy consumption will be reduced. The processing energy consumption per unit area has a greater deviation when the thickness is low, and the thickness of the workpiece will also affect the life of the electrode wire. It depends on the number of multi-layer stacks and the life of electrode wires; the quality of machine tool auxiliary materials has a greater impact on energy consumption, with a difference of up to 40% in energy consumption. The results of this research can better understand the energy consumption and CO2 emissions characteristics of the unconventional machining of WEDM.