Small Changes In Angle Research Articles

Developments regarding Type II secondary sonic booms and topography

Type II secondary sonic booms are those that reflect from the primary boom carpet, enter the stratosphere, and turn back toward the ground if the upper atmospheric winds are favorable. A study initially described by the authors at the Forum Acusticum meeting in September 2023 predicted that the Type II secondary sonic boom rays could be profoundly affected by small angle changes in the topography of the ground. The current work provides an update on those ray tracing predictions, namely, that the amplitudes of Type II secondary sonic booms are substantially reduced by the topography. Such results may explain why secondary sonic booms historically have been reported for supersonic operations over water but not for over land. A grid refinement study will also be summarized. [Work supported by the FAA through ASCENT Project 57 under the supervision of Sandy Liu. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the FAA.]

High-Precision Small-Angle Measurement of Laser-Fiber Autocollimation Using Common-Path Polarized Light Difference

The laser autocollimation measurement method is an important technique for the precise measurement of small angles. However, the beam drift significantly affects the accuracy and stability of laser autocollimation. This paper is the first to present a laser-fiber autocollimation method for measuring small angles with the difference of common-path polarized light. In principle, this method greatly reduces the laser beam drift caused by various factors and significantly improves the measurement accuracy and stability. The effects of the factors affecting beam drift on small-angle measurement were analyzed and simulated. A corresponding measurement system was developed with the capability to measure not only small angular changes in a single object, but also relatively small angular changes between two objects, and a series of experiments were conducted. The results indicated that the angle measurement stability was improved by 90%–98% using the difference of common-path polarized light to compensate the beam drift caused by mechanical structure drift, vibration, and environmental disturbance. Extremely high measurement stability of 0.07" in 10 h and 0.04" in 2 h was obtained at 500 mm. Furthermore, the measurement system was effectively utilized to measure the thermal stability of a star sensor bracket of a satellite, yielding a thermal stability of 0.15"/°C to meet the on-orbit operational stability requirement of 0.25"/°C. Thus, this new method compensates for beam drift in the autocollimation measurement of small angle changes in a single object and relatively small angular changes between two objects.

Sacral interface pressure can be alleviated by repositioning with a small-angle change using an automated bed in patients with spinal cord injury

Aim of the studyThis study aimed to compare interface pressure and total contact area of the sacral region in different positions, including small-angle changes, in patients with spinal cord injury (SCI). Furthermore, we analyzed the clinical factors influencing pressure to identify the pressure injury (PI) high-risk group. Materials and methodsAn intervention was conducted for patients with paraplegia (n = 30) with SCI. In the first and second trials, interface pressure and total contact area of the sacral region were recorded from large- and small-angled positions using the automatic repositioning bed, which can change the angle of the back, lateral tilt, and knee. ResultsPositions with back raised ≥45° showed significantly higher pressure on the sacrum than most other positions. The pressure and contact area differences were statistically insignificant for combinations of small-angled changes <30°.Additionally, the duration of injury (β = 0.51, p = 0.010) and neurological level of injury (NLI) (β = −0.47, p = 0.020) were significant independent predictors of average pressure. Similarly, the duration of injury (β = 0.64, p = 0.001), the Korean version of the spinal cord independence measure-III (β = −0.52, p = 0.017), and body mass index (BMI; β = −0.34, p = 0.041) were significant independent predictors of peak pressure. ConclusionsFor repositioning, combinations of small-angle changes <30° effectively reduce pressure on the sacral region in patients with SCI. Lower BMI, longer duration of injury, lower functioning score, and NLI ≥ T7 are predictors of high sacral pressures, which increase the risk for PI. Therefore, patients with these predictors require strict management.

Angle dependent structural colors with full-visible-spectrum and narrow-angle change properties for anti-counterfeiting

Photonic crystals (PCs) are widely investigated for applications in anti-counterfeiting, sensing, and displaying. And PCs exhibit obvious advantages over traditional pigments and dyes, including environmental friendliness, vivid structural colors, and color durability. However, less variety and low sensitivity of structural colors seriously limit their practical applications. Here, a nano-grating PC film, which featurs bright angle-dependent structural colors over the whole visible spectrum via small angle change, was made by the facile and low-cost inverted nanoimprint. By tuning the incidence angle from 25° to 60°, continuous structural colors can be perceived ranging from violet to wine accompanying red-shift of reflection peaks from 450 nm to 670 nm. Further, the film material of polydimethylsiloxane enables their mechanical flexibility and stability of the structural color. They can be readily patterned and applied as an anti-counterfeiting mark in university logo, which makes them promisingly practical as anti-counterfeiting materials.

Concept of self-excited unsteady flow control on a compressor blade and its preliminary proof by numerical simulation

This paper presents a new concept of self-excited unsteady flow control technique on a compressor blade using a passive fluidic oscillator. This concept, as an unsteady flow control method, has the advantages that no additional air source or power supply needs to be introduced and no complex actuators or movable parts are included. Numerical simulations show that the passive fluidic oscillator will reduce the total pressure loss coefficient of the compressor cascade by 4.2% to 2.8% when the inlet Mach number of the compressor blade ranges from 0.28 to 0.39. The time domain and frequency spectrum analysis prove the unsteadiness of the jet produced by the passive fluidic oscillator. Within the Mach number scope, the reduced jet velocity equals approximately 0.68 to 0.7 and the reduced jet frequency equals nearly 1.1 to 1.2. This finding agrees with the order-of-magnitude study result that the jet parameters are compatible with the compressor (the reduced jet velocity and frequency are in the order of magnitude of 1) at the design point, and it conforms to the self-adaptivity of the passive fluidic oscillator in a certain degree (the reduced jet velocity and frequency are nearly invariant) at off-design points (providing small changes in angles of attack), which most passive flow control methods do not share.

Spectral CT using a fine grid structure and varying x-ray incidence angle.

Interest in spectral computed tomography (CT) for diagnostics and therapy evaluation has been growing. Data acquisitions with distinct spectral sensitivities provide the ability to discriminate multiple materials, quantitative density estimates, and reduced artifacts due to energy dependencies. We introduce a novel spectral CT concept that includes a fine-pitch grid structure for prefiltration of the x-ray beam. We develop physical models for grid designs and illustrate the basic operating principles wherein small angulations of the incident x rays results significant filtration and spectral shaping of the beam. We fabricate a prototype grid with tungsten lamellae. We compare x-ray spectra induced by this filter as a function of incidence angle in both simulation students and in physical measurements. The grid is also integrated onto a CT test bench where we scanned an iodinated phantom with clinically relevant concentrations (5, 10, 20, and 50mgI/mL) to demonstrate the ability to perform spectral CT acquisitions and material decomposition. X-ray spectrometer measurements reveal diverse and controllable spectral shaping with small angle changes that are in agreement with simulation studies. Critical angles where the characteristics of the induced spectrum changes dramatically are identified. Reconstructions of projection data for two angulations separated by 2° was reconstructed and material decomposition into iodine and water images shows good agreement with the known iodine concentrations. This work demonstrates the feasibility of the grid-based approach to enable spectral CT data acquisitions and accurate material decompositions. On-going and future studies will investigate the potential of this novel concept as a relatively simple upgrade to standard energy-integrating CT.

3D-Printed Tilt Sensor Based on an Embedded Two-Mode Fiber Interferometer

A 3D-printed tilt fiber sensor using a two-mode fiber interferometer (TMFI) as the sensing mechanism has been demonstrated. The TMFI was constructed by splicing single-mode fibers (SMF-28s) at both ends of a two-mode fiber (TMF) to generate a comb-like interference spectrum that is sensitive to bending. A 3D-printed cantilever with a weight attached to one end was used to induce bending as the structure was tilted and by embedding the TMFI onto the 3D printed cantilever, different tilt angles can be measured, as a result of the bending of the fiber. The TMFI exhibited a linear response towards the tilt angles, $\theta $ , with a responsivity of $1\times 10^{-2}$ nm/deg at negative $\theta$ (0 to −90°) and $5 \times 10^{-3}$ nm/deg at positive $\theta$ (0 to 90°), respectively. The sensor was able to detect small angle changes in increments as small as 1° and it performs better than embedded FBG sensors. The tilt sensor proposed has a small formfactor and simple design, as well as being cost-effective and light-weight, thus showing significant potential for a variety of civil engineering applications.

Technique for measuring very small angle changes.

A method for making accurate and precise measurements of small angles is described using an interferometer and a test fixture with reference control surfaces. The test is relatively insensitive to test fixture alignment. Typical measurement uncertainties are better than 0.2 arcsec (1σ). This technique is applicable for verifying the angular stability of opto-mechanical systems that must undergo rigorous environmental testing.

Dual-axis optical spatial heterodyning angle measurements using CMOS sensor color crosstalk

A simple, yet precise, optical angle measurement device was developed by analyzing the light interference pattern from a modified Lloyd’s mirror interferometer combined with a CMOS camera sensor. The resulting spatially heterodyned signal was very sensitive to small angle changes from an incident low-power laser beam, with an accuracy better than 8.9 arcsec over a range of 1.47 degrees. Measurement dead zones, estimated to have an angular span of ± 0.96 arcmin, occurred in the middle of the device’s measurement range at a critical angle where the pitches of the light interference pattern and the CMOS sensor array were equal. Also, a proof-of-concept test successfully demonstrated the use of this device for dual-axis angle measurements using a single CMOS sensor.

Electron Injection for Direct Acceleration by A Gaussian Laser Field Under the Influence of Azimuth Magnetic Field

Electron injection for direct acceleration by a circularly polarized Gaussian laser field under the influence of azimuth magnetic field is studied. The electron energy gain, \(\gamma\) versus electron's injection angle \(\delta\) at different values laser intensity parameters and laser spot size shows the energy enhancement on increasing the parameters. For a small change in angle of injection then there appears a significant change in electron energy gain also for the variation of energy gain and magnetic field energy gain increases when value of \(\delta\) $ is 8.5, 8.0, 13.5 and 13, respectively. It is observed that \(\delta\) should be small and optimized for appropriate momentum to maximize the electron energy gain due to a relativistic longitudinal momentum and the variation of the scattering angle of the electron \(\theta\) with respect to electron's injection angle \(\delta\) in the presence of magnetic field shows a relatively lower scattering is observed with optimized values of injection angle in the presence of magnetic field.

Superelastic Carbon Aerogel with Ultrahigh and Wide-Range Linear Sensitivity.

Compressible and elastic carbon materials offer many advantages and have promising applications in various electronic devices. However, fabricating carbon materials with super elasticity, fatigue resistance, and high and wide-range linear sensitivity for pressure or strain remains a great challenge. Herein, a facile and sustainable route is developed to fabricate a carbon aerogel with not only superior mechanical performances but also exceptionally high and wide-range linear sensitivity by using chitosan as a renewable carbon source and cellulose nanocrystal as a nanoreinforcement or support. The as-prepared carbon aerogel with wave-shaped layers shows high compressibility, super elasticity, stable strain-current response, and excellent fatigue resistance (94% height retention after 50 000 cycles). More importantly, it demonstrates both an ultrahigh sensitivity of 103.5 kPa-1 and a very wide linear range of 0-18 kPa. In addition, the carbon aerogel has a very low detection limit (1.0 Pa for pressure and 0.05% for strain). The carbon aerogel also can be bended to detect a small angle change. These superiorities render its applications in various wearable devices.

Intranasal Medication Administration Using a Squeeze Bottle Atomizer Results in Overdosing if Deployed in Supine Patients.

Vasoconstrictors and local anesthetics are commonly administered using a squeeze bottle atomizer to the nasal mucosa to reduce edema, limit bleeding, and provide analgesia. Despite widespread use, there are few clinical guidelines that address technical details related to safe administration. The purpose of this study was to quantify, via simulation, the amount of liquid delivered to the nasal mucosa when patients are in the supine and upright positions and administration parameters that would reliably provide the desired amount of medication per spray. A convenience sample of 10 anesthesia residents was studied. Providers were instructed to use a 25-mL dip and tube nasal squeeze bottle to administer the test solution (sterile water) to a mannequin in the upright (90° elevation) and supine (0° elevation) position. After mannequin testing, additional testing was completed with the spray bottles at 0°, 15°, 30°, 45°, and 90° to determine the relationship between the angles of administration and the amount of liquid dispensed. The mean volume delivered per spray was substantially greater when administered in the supine position (0.56 ± 0.22 mL) compared with the upright position (0.041 ± 0.02 mL, difference = 0.52 mL, 95% confidence interval [CI], 0.37-0.67 mL, P < .001). Converting the administered volume to the dose of phenylephrine that would be administered using our standard 0.25% solution, an estimated additional 1300 mcg is delivered per spray in the supine position compared with the upright position (95% CI, 925-1675 mcg, P < .001). Administration with a delivery angle of ≤30° resulted in significantly more volume than when the bottle was oriented at a 90° angle. The volume dispensed at 45° was not different from the volume delivered at 90° (0.032 ± 0.006 mL vs 0.030 ± 0.005 mL, P = .34). We found a 14-fold increase in the volume (ie, dose) delivered per spray when a nasal squeeze bottle was used with a mannequin in the supine position compared with the upright position. Given the reported toxicity from the use of intranasal medication and the inadvertent overdosing that occurs when squeeze bottle atomizers are used in clinical practice, our data suggest that all intranasal drugs should be administered with a precise, metered-dose device. If a metered-dose device is unavailable, the medication should be delivered at an angle of ≥45°; however, we recommend administering the drug with the patient in the sitting position and the bottle at 90° because only a small change in angle below 45° will result in a substantial increase in medication delivered.

Effect of tilt on the performance of a quarter-wave prism retarder

The rhomb-type achromatic prism retarder utilizes the phase difference introduced at the glass–air interface, where the beam of light undergoes total internal reflection. With the proper choice of glass materials and the number of total internal reflection, it is possible to obtain a desired phase difference. The phase difference introduced is also dependent on the angle of incidence of the light beam at the glass–air interface. A small change in angle of incidence causes a considerable change in phase difference. The change in the phase difference introduced with the change in external angle of incidence of the light beam in an achromatic prism-type quarter-wave retarder is studied both theoretically and experimentally. The experimental results obtained are found to be in accordance with the theoretical results.

Integrating Photonics with Luminescent Solar Concentrators: Optical Transport in the Presence of Photonic Mirrors

Luminescent solar concentrators downshift and concentrate the incident solar spectrum onto adjacent solar cells. In this paper we study the combination of highly performing luminescent nanocrystals with photonic structures to guide light to the edge of the concentrator. While one approach is to use a wavelength-selective Bragg mirror to reduce escape cone losses, we find that this also requires nearly perfect mirrors and luminophore quantum yield. The key issue is that light is trapped inside the concentrator in modes that inefficiently propagate toward the edge, leading to luminophore reabsorption and losses to imperfect mirrors. To overcome this difficulty, we use modeling to study the use of meta-mirrors that shift propagating photons to larger angles, minimizing interactions with the reabsorbing luminophores and mirrors. We find that this design favors mirrors with small changes in angle, separated from the luminophore–polymer layer by an air gap. This research indicates that a combination of photonic...

The influence of curing time on the shear strength of fluidized fly ash

Abstract The paper presents results of research on the influence of compaction and air and water curing on angle of internal friction and cohesion of fluidized fly ash from “Połaniec” Power Plant. It was stated that the increase in compaction resulted in an insignificant increase of the angle of internal friction and a quite significant increase of cohesion. While the type and time of curing had a great influence on the angle of internal friction and cohesion. The highest values of angle of internal friction were obtained in the air curing, and the lowest in the water curing whereas in case of cohesion there was an inverse relation. The rise of curing time resulted in largely increased cohesion and small changes of angle of internal friction.

"Difficult back", turns into "less difficult back" by ultrasonography.

"Difficult back", turns into "less difficult back" by ultrasonography.

Development of an x-ray prism for analyzer based imaging systems

Analyzer crystal based imaging techniques such as diffraction enhanced imaging (DEI) and multiple imaging radiography (MIR) utilize the Bragg peak of perfect crystal diffraction to convert angular changes into intensity changes. These x-ray techniques extend the capability of conventional radiography, which derives image contrast from absorption, by providing large intensity changes for small angle changes introduced from the x-ray beam traversing the sample. Objects that have very little absorption contrast may have considerable refraction and ultrasmall angle x-ray scattering contrast improving visualization and extending the utility of x-ray imaging. To improve on the current DEI technique an x-ray prism (XRP) was designed and included in the imaging system. The XRP allows the analyzer crystal to be aligned anywhere on the rocking curve without physically moving the analyzer from the Bragg angle. By using the XRP to set the rocking curve alignment rather than moving the analyzer crystal physically the needed angle sensitivity is changed from submicroradians for direct mechanical movement of the analyzer crystal to tens of milliradians for movement of the XRP angle. However, this improvement in angle positioning comes at the cost of absorption loss in the XRP and depends on the x-ray energy. In addition to using an XRP for crystal alignment it has the potential for scanning quickly through the entire rocking curve. This has the benefit of collecting all the required data for image reconstruction in a single measurement thereby removing some problems with motion artifacts which remain a concern in current DEI/MIR systems especially for living animals.

Measurement of Probe Angle for Ultrasound Evaluation of Articular Cartilage Using "Rise-to-Peak Time"

Background. Ultrasound evaluation of articular cartilage is not accurate if the ultrasound probe is not perpendicular to the cartilage surface. However a probe angle adjustment is difficult because of the manual procedure and the lack of angle index for the measurer. The aim of this study is to propose “Rise-to-Peak time” as an index of probe angle and to evaluate its effectiveness in evaluating articular cartilage surfaces. Methods. The “Rise-to-Peak time” is defined as the time interval between the rise of the first peak (50% amplitude of the first peak) and the first positive peak following the minimum peak of the echo. The relationship between the Rise-to-Peak time and probe angle was evaluated using several reflection surfaces including that of articular cartilage. Findings. The “Rise-to-Peak time” increased monotonically with increases in the angle between the probe and the reflection surface, and showed good agreement with calculated values for small angle changes (<3 degrees). Interpretation. The “Rise-to-Peak time” provides an index of probe angle in the ultrasound measurement of articular cartilage. Availability of echo-amplitude correction using the “Rise-to-Peak time” is evaluated.

Mechanical Mixture Simulation Devices for Determining and Calibrating Internal Angle of Gyration in Superpave Gyratory Compactor

Since 1993, asphalt technologists have recognized the importance of maintaining a tight tolerance on the angle of gyration used in the Superpave® gyratory compactor. Small changes in angle were shown to affect significantly the percentage of air voids in a compacted mix specimen and, in the design phase, to affect the design asphalt binder content. Through the years since its implementation, there have been significant advancements in the understanding of the Superpave gyratory compactor. Implementation research indicated that the internal angle of gyration was the compaction parameter of importance and that it did not directly relate to the measured external angle of gyration. Continuing to seek improvements in reproducibility of test results, the industry developed several devices that mechanically simulate the stiffness of an asphalt mixture so that determination and calibration of the internal angle of gyration can be accomplished without the necessity of compacting mixture specimens. The purpose of this research was to improve the determination and subsequent calibration of the dynamic internal angle of gyration for the Superpave gyratory compactor by evaluating the use of the mechanical mixture simulation devices. The results of the research indicate that mechanical mixture simulation devices can be used to effectively determine and calibrate the internal angle of gyration. By streamlining and standardizing the process for determining and calibrating the internal angle, it is expected that the variation in the bulk specific gravity (or percentage of air voids) of a compacted mixture specimen between user agencies and producers will be significantly reduced.

Mechanical Mixture Simulation Devices for Determining and Calibrating Internal Angle of Gyration in Superpave Gyratory Compactor

Since 1993, asphalt technologists have recognized the importance of maintaining a tight tolerance on the angle of gyration used in the Superpave® gyratory compactor. Small changes in angle were shown to affect significantly the percentage of air voids in a compacted mix specimen and, in the design phase, to affect the design asphalt binder content. Through the years since its implementation, there have been significant advancements in the understanding of the Superpave gyratory compactor. Implementation research indicated that the internal angle of gyration was the compaction parameter of importance and that it did not directly relate to the measured external angle of gyration. Continuing to seek improvements in reproducibility of test results, the industry developed several devices that mechanically simulate the stiffness of an asphalt mixture so that determination and calibration of the internal angle of gyration can be accomplished without the necessity of compacting mixture specimens. The purpose of this research was to improve the determination and subsequent calibration of the dynamic internal angle of gyration for the Superpave gyratory compactor by evaluating the use of the mechanical mixture simulation devices. The results of the research indicate that mechanical mixture simulation devices can be used to effectively determine and calibrate the internal angle of gyration. By streamlining and standardizing the process for determining and calibrating the internal angle, it is expected that the variation in the bulk specific gravity (or percentage of air voids) of a compacted mixture specimen between user agencies and producers will be significantly reduced.