Scan Angle Research Articles

The influence of the raster angle on the dimensional accuracy of FDM-printed PLA, PETG, and ABS tensile specimens

3D printing is a rapidly advancing method in digital manufacturing techniques and produces objects in layers. Fused Deposition Modelling (FDM) is a 3D printing technology where the material is melted in a hot nozzle and then placed on a build platform to create a prototype layer by layer. In this study, the effects of different raster angles (0°, 45°, 90°, 45°/-45°, 0°/90°) on dimensional accuracy for PLA, PETG and ABS materials produced using FDM were investigated. The results show that PETG generally shows higher dimensional deviations compared to PLA and ABS, and samples with a scan angle of 90° generally have lower deviation percentages than other angles. Width deviations (approximately 1.5% on average) were lower than thickness deviations (approximately 9.5% on average). Analysis of the cross-sectional areas shows that all samples are above the theoretical area (41.6 mm2). PETG samples with a scan angle of 45°/-45° exhibit the largest cross-sectional area (46.78 mm2), while ABS samples with a scan angle of 90° exhibit the smallest (45.46 mm2). This study is important to understand the impact of material selection and raster angle on dimensional accuracy, and it is recommended to account for cross-sectional deviations and calculate the stress based on the actual cross-sectional area to achieve more accurate results in applications requiring precise measurements. These data offer valuable information for those interested in 3D printing and its professionals and can lead to further research in this field, so that printing techniques can be further developed and product quality can be improved.

Discovery of macrocyclic CDK2/4/6 inhibitors with improved potency and DMPK properties through a highly efficient macrocyclic drug design platform

Cyclin-dependent kinases (CDKs) are critical cell cycle regulators that are often overexpressed in tumors, making them promising targets for anti-cancer therapies. Despite substantial advancements in optimizing the selectivity and drug-like properties of CDK inhibitors, safety of multi-target inhibitors remains a significant challenge. Macrocyclization is a promising drug discovery strategy to improve the pharmacological properties of existing compounds. Here we report the development of a macrocyclization platform that enabled the highly efficient discovery of a novel, macrocyclic CDK2/4/6 inhibitor from an acyclic precursor (NUV422). Using dihedral angle scan and structure-based, computer-aided drug design to select an optimal ring-closing site and linker length for the macrocycle, we identified compound 8 as a potent new CDK2/4/6 inhibitor with optimized cellular potency and safety profile compared to NUV422. Our platform leverages both experimentally-solved as well as generative chemistry-derived macrocyclic structures and can be deployed to streamline the design of macrocyclic new drugs from acyclic starting compounds, yielding macrocyclic compounds with enhanced potency and improved drug-like properties.

Research on reconstruction of diffraction tomography based on prior information

Under coherent light illumination, several approaches need either angle scanning or diffuser rotating to reconstruct the image through opaque scattering media. We propose a linear model to restore the hidden object through the actual power spectrum with disturbance of the scattering layer. The experimental results confirm that, the algorithm quickly converge to the only correct reconstruction solution with the accuracy power spectrum pattern of Fourier transform, and the method can reconstruct the high accuracy image of the object hidden by the scattering media with one-shot power spectrum.

Scan Angle Analysis of Airborne Lidar Data for Missing Return Approximation in Urban Areas

The density and uniformity of lidar data play crucial roles in the cor-responding data processing steps. One factor influencing point density and spacing in lidar data is the presence of empty pulses, where no return is detected. Missing returns can occur due to atmospheric absorption, specular and diffusive reflection, etc. To address this issue and enhance point density, this paper introduces a novel method for approximating missing returns in airborne lidar data collected over urban areas. This technique focuses on approximating returns for empty pulses that hit spots near abrupt slope changes on building and ground surfaces. The proposed methodology is validated through experiments using a lidar data set from downtown Dublin, Ireland. The collected data contained numerous gaps associated with wet surfaces, as well as missing returns on vertical and oblique surfaces.

Wide-Angle Scanning and High Isolation Dual-Polarized Base Station Antennas for Sub-6 GHz Applications

This paper presents a wide-angle scanning and high isolation base station antenna array. The antenna element employs a compact dual-polarized umbrella-shaped printed dipole with a small size of 0.23λ0 × 0.23λ0 × 0.26λ0, which provides the possibility for a small element spacing array. The antenna element possesses wide 3 dB beamwidth of 84.6∘ benefiting from the pulling down of the dipole arms. Then, a dual-layer metal superstrate structure and metal wall is adopted to mitigate different kinds of mutual coupling between the dual-polarized antenna elements in the array. Owing to the wide beamwidth of the element and the low mutual coupling between the elements, the final 4×6 antenna array can achieve a good beam-scanning capability with maximum scanning angle up to ±55∘ and a small gain variation of less than 3 dB over the operation band 3.3-3.8 GHz. The fabricated array shows the measured isolation between all ports of the antennas is increased to more than 20 dB. Scanning characteristics also agree well with the simulated results. With the merits of wideband, low-cost (simple design and easy fabrication), wide-angle beam-scanning capacity, and good radiation performance, the proposed design has potential for application in 5G base stationsystems.

Synthesis of Antenna Array Radiation Pattern at Large Scanning Angles Using Genetic Algorithm

At present, in most modern communication systems, for example, in modern satellite terminals, the use of scanning beam antennas, i. e. antenna arrays is assumed. At the same time, at large scanning angles, the side lobe level (SLL) increases strongly and decrease in the gain is observed. In this regard, the problem of finding a procedure for synthesizing an amplitude-phase distribution (APD) with low SLL and high gain (G) at large scanning angles comes up. One of the ways to reduce SLL and compensate for the decrease in G is to synthesize the optimal APD (in terms of the maximum G and minimum SLL) using optimization algorithms. At the same time, taking into account the characteristics of the radiation pattern of the array emitters requires numerical electrodynamic calculation. The goal of this paper is to develop a procedure for the synthesis of APD with low SLL for linear and rectangular antenna arrays at various, including large, scanning angles and compensation for G reduction using a genetic algorithm and numerical electrodynamic calculation. The methods for studying the characteristics of antenna radiators are numerical electrodynamic modeling by the finite element method (FEM) in Ansys HFSS computer-aided design system and optimization of the APD for a given radiation pattern(RP) by a random search method using partial diagrams of antenna elements. The novelty is the combination of accurate numerical electrodynamic calculation of the RP of antenna elements and optimization search for APD for the synthesis of the required RP using partial diagrams. As a result, a procedure for APD synthesis of linear and uniform rectangular equidistant (for example, 8- and 64-element) antenna arrays has been developed, taking into account the exact electrodynamic characteristics of antenna elements and their mutual resistance. Radiation patterns were obtained taking into account the effect of neighboring elements, with the help of which, using a genetic algorithm, APDs on emitters were found at different scanning angles. The change in SLL and G of the antenna array is analyzed at different scanning angles using different APDs. The proposed algorithm allows to synthesize APD for a RP with low SLL and high G at scanning angles up to 40° for linear antenna array and up to 80° in the case of a uniform rectangular antenna array. The results of this work are relevant in the problems of radiation pattern synthesis, since the proposed solution provides a significant gain in the radiation pattern synthesis rate of APD of linear and rectangular antenna arrays, especially for systems with a large number of antenna elements. At the same time, it is possible to maintain a high G at large scanning angles, and achieve a significant reduction of SLL.

Beam Steering Technology of Optical Phased Array Based on Silicon Photonic Integrated Chip.

Light detection and ranging (LiDAR) is widely used in scenarios such as autonomous driving, imaging, remote sensing surveying, and space communication due to its advantages of high ranging accuracy and large scanning angle. Optical phased array (OPA) has been studied as an important solution for achieving all-solid-state scanning. In this work, the recent research progress in improving the beam steering performance of the OPA based on silicon photonic integrated chips was reviewed. An optimization scheme for aperiodic OPA is proposed.

Shared‐Aperture 2‐Bit Coding Metasurface for Simultaneous Manipulation of Space Wave and Surface Wave

AbstractA shared‐aperture 2‐bit coding metasurface for simultaneously and independently manipulating space wave and surface wave is proposed in this paper. When the proposed coding metasurface is expected to modulate space wave, the unit cells can control the reflection phase. The reflected wave becomes various according to the specific coding sequence. When the proposed coding metasurface acts as spoof surface plasmon polaritons (SSPP) transmission line, the unit cells can modulate the surface impedance. With periodic modulation to the surface impedance, electromagnetic wave can be radiated into free space and the radiation beam scans as frequency changes. Space wave modulator works at 22.5 GHz, while the surface wave modulator works during the frequency range of 6.5–11.4 GHz. The total scanning angle of the radiated beam of surface wave modulator covers from −54° to 52°, with an average gain of 10.64 dBi. Simultaneous manipulation of both space wave and surface wave by a single metasurface makes the proposed device promising in the new radar and satellite communication systems with compact requirement.

Wide-angle scanning and Wideband millimeter-wave phased array with Enhanced Isolation using Novel Triple-function Electric Walls

A wide-angle scanning millimeter-wave (mm-wave) phased array with enhanced bandwidth and isolation using novel triple-function electric walls (TEWs) is presented in this work. First, a novel concept for element beamwidth broadening is proposed by using a suspended horizontal magnetic current (SHMC) with a conical pattern. Then, based on this concept, an antenna element is designed using the proposed TEWs. TEWs not only broaden the element beamwidth by forming a suspended horizontal magnetic current(SHMC), but also widen the element bandwidth by introducing a new mode. Meanwhile, the proposed TEWs can be used as a band-stop filter in the array to reduce the mutual coupling. Based on the three beneficial functions of the proposed TEWs, a wide-angle scanning mm wave phased array with enhanced bandwidth and isolation is designed. Measured results show that the phased array achieves an active impedance bandwidth of 19.3% (24.7-30 GHz) and a good isolation of more than 15 dB. Meanwhile, a wide 3 dB scanning angle larger than ±74° is achieved by the proposed array with the maximum scanning angle of ±80° at 27 GHz.

Development of a near-infrared single-photon 3D imaging LiDAR based on 64×64 InGaAs/InP array detector and Risley-prism scanner.

A near-infrared single-photon lidar system, equipped with a 64×64 resolution array and a Risley prism scanner, has been engineered for daytime long-range and high-resolution 3D imaging. The system's detector, leveraging Geiger-mode InGaAs/InP avalanche photodiode technology, attains a single-photon detection efficiency of over 15% at the lidar's 1064 nm wavelength. This efficiency, in tandem with a narrow pulsed laser that boasts a single-pulse energy of 0.5 mJ, facilitates 3D imaging capabilities for distances reaching approximately 6 kilometers. The Risley scanner, composing two counter-rotating wedge prisms, is designed to perform scanning measurements across a 6-degree circular field-of-view. Precision calibration of the scanning angle and the beam's absolute direction was achieved using a precision dual-axis turntable and a collimator, culminating in 3D imaging with an exceptional scanning resolution of 28 arcseconds. Additionally, this work has developed a novel spatial domain local statistical filtering framework, specifically designed to separate daytime background noise photons from the signal photons, enhancing the system's imaging efficacy in varied lighting conditions. This paper showcases the advantages of array-based single-photon lidar image-side scanning technology in simultaneously achieving high resolution, a wide field-of-view, and extended detection range.

Characterization of Anisotropic Shape Memory Behavior of Thermoresponsive Components in 4D Printing.

Four-dimensional (4D) printing has emerged as a promising manufacturing technology in recent years and revolutionized products by adding shape-morphing capabilities when exposed to certain stimuli. Increasing research attention has been dedicated to studying the shape memory behaviors of the 4D fabricated structures. However, in-depth discussions on quantifying the influence of process parameters on shape fixity and recovery properties are limited, and the anisotropy induced by the layer-wise fabrication nature is significantly underreported. To further exploit the shape memory property of 4D printed structures, it is essential to investigate the process-induced anisotropic shape memory behaviors. In this study, the effects of critical process parameters on anisotropy in shape memory properties are mathematically quantified; meanwhile, the feasibility of tailoring the anisotropy of 4D printed parts is examined with joint consideration of total build time. Different scanning patterns are experimentally analyzed for their influence on anisotropic behaviors. It is found that the Triangle scanning pattern often leads to the best shape memory behaviors in different directions. The outcome of this study confirms the existence of anisotropy in both shape fixity and shape recovery ratios. In addition, the results also reveal that a smaller scanning angle tends to minimize the anisotropy and total fabrication time while ensuring satisfactory shape memory performance. Furthermore, layer thickness shows negligible effects on anisotropy, while the scanning angle and shape memory temperature suggest the opposite.

Analyzer-free hard x-ray interferometry

Objective. To enable practical interferometry-based phase contrast CT using standard incoherent x-ray sources, we propose an imaging system where the analyzer grating is replaced by a high-resolution detector. Since there is no need to perform multiple exposures (with the analyzer grating at different positions) at each scan angle, this scheme is compatible with continuous-rotation CT apparatus, and has the potential to reduce patient radiation dose and patient motion artifacts. Approach. Grating-based x-ray interferometry is a well-studied technique for imaging soft tissues and highly scattering objects embedded in such tissues. In addition to the traditional x-ray absorption-based image, this technique allows reconstruction of the object phase and small-angle scattering information. When using conventional incoherent, polychromatic, hard x-ray tubes as sources, three gratings are usually employed. To sufficiently resolve the pattern generated in these interferometers with contemporary x-ray detectors, an analyzer grating is used, and consequently multiple images need to be acquired for each view angle. This adds complexity to the imaging system, slows image acquisition and thus increases sensitivity to patient motion, and is not dose efficient. By simulating image formation based on wave propagation, and proposing a novel phase retrieval algorithm based on a virtual grating, we assess the potential of a analyzer-grating-free system to overcome these limitations. Main results. We demonstrate that the removal of the analyzer-grating can produce equal image contrast-to-noise ratio at reduced dose (by a factor of 5), without prolonging scan duration. Significance. By demonstrating that an analyzer-free CT system, in conjuction with an efficient phase retrieval algorithm, can overcome the prohibitive dose and workflow penalties associated grating-stepping, an alternative path towards realizing clinical inteferometric CT appears possible.

A New Method for the Compaction Quality Inspection of High Rockfill Dams Based on 3D Laser Scanning Technology

The compaction quality is directly related to the deformation and stability of the rockfill dam. Measuring the test pit volume efficiently and accurately is the most critical step during the compaction quality inspection. A new method for calculating the test pit volume based on point cloud data is proposed. An auxiliary device that can change the scanning distance and angle of the handheld 3D laser scanner is developed to collect the initial point cloud. The segmentation method of the initial point cloud data including the test pit and the compaction surface outside the pit is to divide the data into two parts according to the order number of the segmentation point, after slicing and sorting point clouds, which is the key to ensuring the computational precision. The segmentation points are the adjacent two points with the greatest order number difference in these point clouds whose distance from the line connecting the end points of the slicing point clouds is less than dz. The compaction surface point clouds are used to construct a plane by the least-squares algorithm so that the closed three-dimensional model is formed by registering it with the test pit point clouds. After converting the test pit surface to the horizontal plane by the Rodrigues formula, the test pit point clouds are divided into n2 parts with equal projection areas on the horizontal plane, and n2 prisms are constructed using them and their projection areas. The test pit volume is the sum of the intersection space volumes of all prisms and the test pit model, and the intersection space is determined by comparing the Z-values of point clouds. The new method was programmed in MATLAB and applied to the Shuangjiangkou rockfill dam with a height of 315 m. The relative error of volume results between the new method and the old water-filling method is 0.14–2.31%. The cause of the error is analyzed, and it is proved that the results of the new method are closer to the real volume of the test pit in theory. This method reduces the inspection cost but greatly improves the level of precision, efficiency, and intelligence for compaction quality inspection.

Water-Immersible MEMS Mirror with a Large Optical Aperture.

This paper presents a two-axis AlScN-based water-immersible MEMS mirror fabricated in an 8-inch MEMS process. Compared with other studies, this device has a larger optical aperture 10 mm in diameter. The resonant frequencies of the device are 1011 Hz in air and 342 Hz in water. The scanning angle reaches ±5° and ±2° at resonant frequencies in air and water, respectively. The cavitation phenomenon is observed when the device is operating in water, which leads the device to electrical failure. To address this issue, a device with reduced resonant frequencies-246 Hz and 152 Hz in air and water-is characterized, through which the bubbles can be effectively prohibited. This MEMS mirror could potentially be used in ultrasound and photoacoustic microscopy applications.

Thinned array distribution with grating lobe canceller at any scan angle for automotive radar applications

Abstract A novel thinned antenna element distribution for cancelling grating lobes (GLs) as well as for reducing phase shifters (PSs) is presented for a two-dimensional phased-array automotive radar application. First, an efficient clustering technique of vertical adjacent elements is employed with array thinning for a PS reduction of 66.7%. In the proposed distribution, several single-element radiators (non-clustered antenna elements) are placed in the vertical direction with specific spacing in a grid of 16 × 12 (192) elements with λ/2 pitch. This disrupts the periodicity of phase-centers after element-clustering and takes a role as steerable GL canceller with capabilities of tracking and nullifying the GL at any scan angle. The proposed distribution enables beam steering up to ±60° in the azimuth plane, as well as ±25° in the elevation plane with cancelled GL and sidelobes. Furthermore, the proposed distribution has been efficiently calibrated with all elements activated by introducing the code division multiple access technique. To the best of the authors’ knowledge, this work represents the first fully calibrated state-of-the-art thinned distribution phased-array including a novel steerable GL canceller to track and nullify GLs.

Bone microarchitecture and strength assessment in adults with osteogenesis imperfecta using HR-pQCT: normative comparison and challenges.

Data on bone microarchitecture in osteogenesis imperfecta (OI) are scarce. The aim of this cross-sectional study was to assess bone microarchitecture and strength in a large cohort of adults with OI using high-resolution peripheral quantitative computed tomography (HR-pQCT) and to evaluate challenges of using HR-pQCT in this cohort. Second-generation HR-pQCT scans were obtained at the distal radius and tibia in 118 men and women with Sillence OI type I, III, or IV using an extremity-length-dependent scan protocol. In total, 102 radius and 105 tibia scans of sufficient quality could be obtained, of which 11 radius scans (11%) and 14 tibia scans (13%) had a deviated axial scan angle as compared with axial angle data of 13 young women. In the scans without a deviated axial angle and compared with normative HR-pQCT data, Z-scores at the radius for trabecular bone mineral density (BMD), number, and separation were -1.6 ± 1.3, -2.5 ± 1.4, and -2.7 (IQR: 2.7), respectively. They were -1.4 ± 1.5 and -1.1 ± 1.2 for stiffness and failure load and between ±1 for trabecular thickness and cortical bone parameters. Z-scores were significantly lower for total and trabecular BMD, stiffness, failure load, and cortical area and thickness at the tibia. Additionally, local microarchitectural inhomogeneities were observed, most pronounced being trabecular void volumes. In the scans with a deviated axial angle, the proportion of Z-scores <-4 or >4 was significantly higher for trabecular BMD and separation (radius) or most total and trabecular bone parameters (tibia). To conclude, especially trabecular bone microarchitecture and bone strength were impaired in adults with OI. HR-pQCT may be used without challenges in most adults with OI, but approximately 12% of the scans may have a deviated axial angle in OI due to bone deformities or scan positioning limitations. Furthermore, standard HR-pQCT parameters may not always be reliable due to microarchitectural inhomogeneities nor fully reflect all inhomogeneities.

Direct voxel classification from x-ray projections for 3D pore detection applied to laser sintered parts

X-ray computed tomography (XCT) is a validated and frequently used tool to verify part geometry and to perform a non-destructive inspection of additive manufacturing parts. However, the acquisition of a large number of x-ray projections generates long inspection times. This conflicts with a high throughput of the production process and hinders the integration of XCT as an in-line quality control procedure for low-end parts. In this paper, we propose a method to obtain three-dimensional (3D) information of the internal pores from a limited view or limited angle scan. The method combines a forward projection model of a cone-beam x-ray system and a deep learning neural network to directly classify each individual voxel, based on the x-ray projections in order to avoid the reconstruction and segmentation step. Accompanying reconstruction artifacts for limited view and limited angle XCT scans are thereby reduced, while preserving 3D information of the pores, defects or inclusions inside the material. The method is validated on real x-ray projections of polymer laser sintered industrial parts and shows a significant reduction in the required x-ray projections, hence acquisition time.

Wide-Angle Beam Steering Closed-Form Pillbox Antenna Fed by Substrate-Integrated Waveguide Horn for On-the-Move Satellite Communications

Wide-angle mechanical beam steering for on-the-move satellite communications is presented in this paper based on a closed-form pillbox antenna system. It includes three main parts: a fixed-feed part, which is a substrate-integrated waveguide (SIW) horn with an extended aperture attached to a parabolic reflector; a novel quasi-optical system, which is a single coupling slot alongside and without spacing from the parabolic reflector; and a radiating disc, which is a leaky-wave metallic pattern. To make the antenna compact, pillbox-based feeding is implemented underneath the metallic patterns. The antenna is designed based on a substrate-guided grounded concept using leaky-wave metallic patterns operating at 20 GHz. Beam scanning is achieved using mechanical rotation of the leaky-wave metallic patterns. The proposed antenna has an overall size of 340 × 335 × 2 mm3, a gain of 23.2 dBi, wide beam scanning range of 120°, from −60° to +60° in the azimuthal plane, and a low side lobe level of −17.8 dB at a maximum scan angle of 60°. The proposed antenna terminal is suitable for next-generation ubiquitous connectivity for households and small businesses in remote areas, ships, unmanned aerial vehicles, and disaster management.

Dynamic wake field reconstruction of wind turbine through Physics-Informed Neural Network and Sparse LiDAR data

Real-time acquisition of dynamic wake field information has garnered substantial attention in the wind farm industry, as it provides a crucial data source for intelligent wind farm monitoring and control. However, the existing wind measurement technologies, such as light detection and ranging (LiDAR), are limited to sparse data point measurements. This paper explores the utilization of a Physics-Informed Neural Network (PINN) to reconstruct wind turbine wake dynamics, specifically focusing on the influence of active wind turbine yaw operation on wake evolution. The methodology involves creating a tailored loss function that combines sparse wake measurement data with the Navier-Stokes (NS) equations. More precisely, the neural network incorporates the NS equations as constraints to guide the prediction of physical quantities in the output, including downwind velocity, crosswind velocity, and pressure. Taking the dynamic wake during yawing as a case study, the proposed method showcases remarkable universality and robustness across diverse scenarios involving varying scanning angle intervals, measurement point spacings, frequencies, and noise levels. It successfully captures the dynamic trends in wake evolution during yawing and accurately forecasts the wake trajectory and deflection. Even when tested with actual wake measurement data, the method can still effectively reconstruct the flow field, indicating significant potential for the real wind farm yaw control.

Stable scanning angle, polarization-insensitive band-stop frequency selective surface for wireless communication

Stable scanning angle, polarization-insensitive band-stop frequency selective surface for wireless communication