Flat Objects Research Articles

Intense laser interaction with micro-bars

Intense laser fields interact very differently with micrometric rough surfaces than with flat objects. The interaction features high laser energy absorption and increased emission of MeV electrons, ions, and of hard x-rays. In this work, we irradiated isolated, translationally-symmetric objects in the form of micrometric Au bars. The interaction resulted in the emission of two forward-directed electron jets having a small opening angle, a narrow energy spread in the MeV range, and a positive angle to energy correlation. Our numerical simulations show that following ionization, those electrons that are pulled into vacuum near the object’s edge, remain in-phase with the laser pulse for long enough so that the Lorentz force they experience drive them around the object’s edge. After these electrons pass the object, they form attosecond duration bunches and interact with the laser field over large distances in vacuum in confined volumes that trap and accelerate them within a narrow range of momentum. The selectivity in energy of the interaction, its directionality, and the preservation of the attosecond duration of the electron bunches over large distances, offer new means for designing future laser-based light sources.

A Single-Actuator Four-Finger Adaptive Gripper for Robotic Assembly

Efficiently grasping and releasing objects using robotic grippers is an essential step in robotic assembly. This paper presents a low-cost four-finger adaptive gripper capable of performing stable and reliable grasping operations on irregular-shaped flat objects. Unlike other grasping systems in the fixture-to-fixture robotic assembly, the assembly process using the proposed gripper does not rely on any vision systems or six-axis force/torque sensors. Specifically, assuming that the relative position <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\bm {\Lambda }$</tex-math></inline-formula> between the two fixtures is known, such assembly tasks can be accomplished simply by performing a predefined motion of a robot arm only related to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\bm {\Lambda }$</tex-math></inline-formula> . This is mainly because the developed gripper not only adapts to the shape and size of the grasped object, but also keeps its position and posture relative to the gripper unchanged throughout the grasping process. A novel underactuated grasping mechanism consisting of an X-shaped differential mechanism and two seesaw ones is proposed to perform adaptive and stable fingertip grasps with more contact points. The kinematics and statics of the gripper-object system are derived for the analysis and design of the gripper. The proposed gripper is fabricated, and a grasping system is built using a commercial robot arm (UR5) to verify its capability for adaptive grasps and assembly of difficult-to-handle flat objects. Experimental results show that it is effective to grasp objects with uncertain shape/size and position, control the grasping force, and accomplish the fixture-to-fixture assembly, etc.

A Dual-Arm Robot That Manipulates Heavy Plates With the Support of a Vacuum Lifter

A vacuum lifter is widely used to hold and pick up large, heavy, and flat objects. Conventionally, when using a vacuum lifter, a human worker watches the state of a running vacuum lifter and adjusts the object&#x2019;s pose to maintain balance. In this work, we propose using a dual-arm robot to replace the human workers and develop planning and control methods for a dual-arm robot to raise a heavy plate with the help of a vacuum lifter. The methods help the robot determine its actions by considering the vacuum lifer&#x2019;s suction position and suction force limits. The essence of the methods is two-fold. First, we build a Manipulation State Graph (MSG) to store the weighted logical relations of various plate contact states and robot/vacuum lifter configurations, and search the graph to plan efficient and low-cost robot manipulation sequences. Second, we develop a velocity-based impedance controller to coordinate the robot and the vacuum lifter when lifting an object. With its help, a robot can follow the vacuum lifter&#x2019;s motion and realize compliant robot-vacuum lifter collaboration. Real-world experiments are carried out to investigate the proposed planning and control methods. The results show that a robot can effectively and flexibly work together with a vacuum lifter to manipulate large and heavy plate-like objects with the methods&#x2019; support. <i>Note to Practitioners</i>&#x2014;This paper is motivated by the vacuum lifters used for transporting heavy plates in a factory that produces building materials. In the factory, a human worker attaches the suction cup of a vacuum lifter to a plate and controls the vacuum lifter to pull the plate up. Meanwhile, another human worker moves and lifts the plate to a goal pose, following the vacuum lifter while maintaining balance. The job is dangerous as the plate is heavy, and the vacuum lifter is not always strong enough to hold the plate firmly. Inspired by the usage and safety problem, we in this paper develop a planning and control method for a dual-arm robot to replace humans. The robot coordinates its motion to work with the vacuum lifter and performs lifting tasks. The vacuum lifter could remain operated by a human worker or be actuated by signals from the dual-arm robot or other third-party machines. The work is complementary to our previous study that developed planners for robots to use pulley blocks. They together provide extensive knowledge for using low-payload collaboratively robots to manipulate heavy plates.

Filter-based solutions for finite and infinite edge diffraction

Sound diffraction occurs at (building) corners, objects and openings, prominently affecting occluded and reflected sounds. Here, a physically-based, parametric filter model for diffraction at arbitrary wedges is presented. The model connects existing high-frequency asymptotic and exact solutions in geometrical acoustics using up to four half-order low-pass filters. Compact expressions for the transfer function and impulse response of the singly diffracted field are derived, with errors below 0.1 dB. A filter modification is suggested to account for the exact solution at low frequencies. The filter solution is further simplified to approximate the spectral effects of diffraction from finite wedges and objects composed thereof, referred to as universal diffraction filter approximation (UDFA). A computationally highly-efficient recursive filter implementation is presented and it is demonstrated that diffraction from flat finite objects like plates or apertures can be closely approximated. To account for effects of higher-order diffraction at the object, a heuristic filter extension is suggested. The presented filter-based diffraction solution is suited for the prediction and simulation of sound propagation including non-specular reflections in architectural acoustics. For virtual acoustics, UDFA provides an efficient and accurate approximation of edge diffraction to account for perceptually relevant frequency-dependent attenuation, extendable to arbitrary objects.

The multi-scale fusion reconstruction algorithm of CT and CL

Computed tomography (CT) is a widely used nondestructive testing (NDT) technique for material research, paleontology research and other fields. However, it is difficult for CT to reconstruct flat objects at high magnification ratios. Computed laminography (CL) enables high-resolution imaging for flat objects due to its unique scanning geometry. A challenging task for CL image reconstruction is to deal with the cross-section artifacts resulting from the incomplete projection data acquired from the CL scan. An effective multi-scale fusion reconstruction algorithm of CT and CL was proposed in this paper. The algorithm combining the advantages of the two scanning geometries, low-resolution CT data was used to compensate for the data missing in CL projection domain, and the cross-section artifacts were reduced. Experiments on paleontological fossils and multilayer printed circuit boards (PCB) were performed, where CT and CL data from different systems and scanning conditions. The results showed that the method can effectively suppress the cross-section artifacts of CL and obtain high-resolution reconstructed images.

Comparative Analysis of Cooling Methods for Dynamic Infrared Thermography (DIRT)-Based Skin Cancer Diagnosis

Skin cancer is a significant global health issue, placing a growing burden on individuals and society. Conventional diagnostic methods like visual examination and biopsy have limitations in invasiveness and accuracy. As a result, alternative tools such as infrared thermography have gained attention in skin cancer diagnosis. Tissue-mimicking phantoms have been instrumental in facilitating research in this field, offering controlled environments. While they do not fully replicate human skin complexity, physical skin models provide stability, ease of fabrication, and control over properties. Agarose phantoms are employed in this study. This research focused on testing and comparing cooling techniques for human skin in the context of skin cancer diagnosis using dynamic infrared thermography. Six cooling methods were investigated: a cool pack, an aluminum medal, ice, alcohol, a vortex cooler and a Zimmer Cryo 6 cooler. The experimental setup involved an infrared camera (Optris Xi400) with microscope optics positioned above an agar phantom mimicking flat skin and an ulcerating skin lesion. Based on experiments conducted on the skin phantom, it was observed that convective cooling methods offered more consistent and uniform cooling. Conversely, conductive methods proved effective for flat objects but posed challenges in achieving uniform cooling for bulging skin or ulcerated lesions. Ice or alcohol were deemed unsuitable due to artifacts influencing the infrared radiation and thermal camera view. A decision matrix assessed cooling techniques based on criteria such as uniformity, repeatability, view obstruction, efficiency, workload, patient comfort, clinical suitability, noise exposure, consumables, additional equipment, and price. The Zimmer Cryo 6 cooler emerged as the most suitable cooling method after evaluating various factors.

Hunting for the candidates of misclassified sources in LSP BL Lacs using machine learning

ABSTRACT An equivalent–width-based classification may cause the erroneous judgement to the flat spectrum radio quasars (FSRQs) and BL Lacerate objects (BL Lac) due to the diluting the line features by dramatic variations in the jet continuum flux. To help address the issue, this work explores the possible intrinsic classification on the basis of a random forest supervised machine learning algorithm. In order to do so, we compile a sample of 1680 Fermi blazars that have both gamma-rays and radio-frequencies data available from the 4LAC-DR2 catalogue, which includes 1352 training and validation samples and 328 forecast samples. By studying the results for all of the different combinations of 23 characteristic parameters, we found that there are 178 optimal parameter combinations (OPCs) with the highest accuracy (≃98.89 per cent). Using the combined classification results from the nine combinations of these OPCs to the 328 forecast samples, we predict that there are 113 true BL Lacs (TBLs) and 157 false BL Lacs (FBLs) that are possible intrinsically FSRQs misclassified as BL Lacs. The FBLs show a clear separation from TBLs and FSRQs in the gamma-ray photon spectral index, Γph, and X-band radio flux, logFR, plot. Phenomenally, existence a BL Lac to FSRQ (B-to-F) transition zone is suggested, where the FBLs are in the stage of transition from BL Lacs to FSRQs. Comparing the LSP changing-look blazars (CLBs) reported in the literatures, the majority of LSP CLBs are located at the B-to-F zone. We argue that the FBLs located at B-to-F transition zone are the most likely candidates of CLBs.

An anisotropic alternating regularization-based reconstruction algorithm for cone beam computed laminography

Computed laminography (CL) is a promising tool for non-destructive visualization of the internal structures of relatively flat objects. However, CL scanning characteristics lead to the absence of projection data along certain directions. When applying conventional algorithms to cone-beam CL projections, the reconstructed images will be deteriorated by cone angle artifacts. Motivated by this finding, we proposed a CL reconstruction model based on anisotropic alternating regularization (AAR) and its numerical solver. The model contains three regularization terms. l0 norm of image gradient is employed as the x- and the y-direction regularizers to perform edge-preserving smoothing. And relative total variance (RTV) is used as the z-direction regularizer to recover inter-slice structures. Experiments on both disk and PCB phantoms demonstrate that our algorithm is effective at preserving image edges, eliminating inter-slice aliasing and denoising.

APPLICATIONS OF ROTATIONAL MANIPULATORS IN THE MANUFACTURE AND CHARACTERIZATION OF HIGHLY CURVED THIN FILMS

AbstractWhat do common devices such as smartphones, CD’s and solar panels all have in common? They are all examples of innovative technology that is still limited to flat, rigid geometries. This is primarily due to the limitations of the manufacturing processes used to create components within these devices, key among them the thin polymer films produced through spin coating.Spin coating is a technique used due to its ability to effectively create uniform films on the scale of micro or nanometres. However, it relies on a planar substrate to produce uniform layers, thus restricting the design of components manufactured using this process to simple, flat objects. As the requirement for curved device geometries expands, complex alternative fabrication methods are being implemented in industry.For spin coating to remain relevant, a viable process for controlling the fluid flow over curved surfaces must be developed. This research investigates the hypothesis that coating distributions can be controlled through optimized rotation of a curved substrate. Where a multi-axis rotational manipulator and novel characterization system have been developed to investigate the fabrication of curved devices using the improved spin coating technique.

Optimized Centroid-Based Clustering of Dense Nearly-square Point Clouds by the Hexagonal Pattern

Abstract An approach to optimize centroid-based clustering of flat objects is suggested, which is practically important for efficiently solving metric facility location problems. In such problems, the task is to find the best warehouse locations to optimally service a given set of consumers. An example is assigning mobiles to base stations of a wireless communication network. We suggest a hexagonal-pattern-based approach to partition flat nodes into clusters quicker than the k-means algorithm and its modifications do. First, a hexagonal cell lattice is applied to nodes to approximately determine centroids of the clusters. Then the centroids are used as initial centroids to start the k-means algorithm. The suggested method is efficient for centroid-based clustering of dense nearly-square point clouds of 0.1 million points and greater by using no fewer than 6 lattice cells along an axis. Compared to k-means, our method is at least 10 % faster and it is about 0.01 to 0.07 % more accurate in regular Euclidean distances. In squared Euclidean distances, the accuracy gain is 0.14 to 0.21 %. Applying a hexagonal cell lattice determines an upper bound of the clustering quality gap.

Recent insights on advancements and substantial transformations in food printing technology from 3 to 7D.

Food printing using 3D, 4D, and 5D printing processes has received a lot of interest as a result of rising living standards and increased customer desire for new foods. In the food industry, 3D as well as 4D printing are extremely effective methods for additive manufacturing. The 3D printing technology produces flat objects with a variety of mechanical strengths. The strength of the object depends on the type of material used and the printing process. Printing structures with the most complex geometric, such as curved surfaces, necessitates the usage of supplementary material. The 4D printing procedure necessitates additional stimuli in order to adjust the aspect of the generated geometry. These obstacles can be addressed by employing 5D printing techniques, which prints the product in three motions and two rotational axes without the use of additional support material. These emerging innovations are likely to result in substantial advancements in all industries, including the manufacturing of high-quality food products. Food printing technology can be used to create long shelf-life products by printing food with protective coatings that prevent oxidation and degradation. Foods can also be printed in specific shapes or sizes to reduce surface area exposed to air. 6D printed objects can be created as a result of 5D printing because it is regarded as a by-product of 5D printing technology. 6D printing can save time and money by using the right processing parameters to create strong materials that are more sensitive to stimuli. 7D printing can enable more efficient production processes, reduce costs, and enable the development of products that are more complex and intricate than what is achievable with traditional manufacturing methods. The revolutionary change brought by food printing technologies in the field of applications, research and development, processing, advantages in food industry have been discussed in this paper.

Vibration Distribution Measurement of Car Door and Engine Head Using OPPA Vibration Distribution Analyzer

In order to address the issue of vibration, it is crucial to accurately measure the vibration distribution. The authors previously developed the one-pitch phase analysis (OPPA) method, which allows for rapidly capturing the three-dimensional shape of a flat object. By integrating this method into a system, an OPPA vibration distribution measurement system was created, utilizing a line light source consisting of LEDs or optical fibers and also a high-speed camera to measure the vibrations of three-dimensional objects without physical contact. To further extend the application of the OPPA method to larger objects, such as cars, in this paper, a new system is introduced using a commercially available projector using a liquid crystal display (LCD) instead of a liner light source and a glass grating. This new system, which employs an ultra-short throw projector, is highly sensitive in displacement measurements and provides a wide-area analysis. These kinds of projectors produce noises at the frequency of the cooling fan and the refresh rate of the LCD. However, in this study, these noise sources were also examined. The capabilities of the new system are demonstrated through its application to the measurement of vibrations in a car door and an engine head. The measurement system and examples of its application are presented.

A Soft Gripper with Granular Jamming and Electroadhesive Properties

In recent years, there has been a growing interest in the development of universal soft grippers that can handle objects of varying form factors (including flat objects), surface conditions (including moistened or oily objects), and mechanical properties (deformable and fragile). Yet, there is no single gripper that can gently grip objects with such a wide range of properties. Herein, a soft gripper that combines granular jamming (GJ) and electroadhesion (EA) to gently grasp and release a large set of diverse objects is presented. The gripper can operate in GJ mode only, in EA mode only, or in a combination mode that simultaneously activates GJ and EA. In GJ mode, the gripper can grasp objects with different surface properties, lift objects 38 times its own weight using negative pressure, and release objects by applying positive pressure, but has difficulty in handling flat and fragile objects. In EA mode, the gripper can manipulate flat and fragile objects but encounters difficulties with different surface properties such as oily or moisture. In the combination mode, the gripper can generate grasping forces up to 35% higher than in the GJ mode for all object sizes and certain shapes such as a cylinder. An interactive preprint version of the article can be found here: https://doi.org/10.22541/au.166937296.61200374/v1.

Geometric parameters sensitivity evaluation based on projection trajectories for X-ray cone-beam computed laminography.

X-ray cone-beam computed laminography (CL) is widely used for large flat objects that computed tomography (CT) cannot investigate. The rotation angle of axis tilt makes geometric correction of CL system more complicated and has more uncertain factors. Therefore, it is necessary to evaluate sensitivity of the geometric parameters of CL system in advance. This study aims to objectively and comprehensively evaluate sensitivity of CL geometric parameters based on the projection trajectory. This study proposes the Minimum Deviation Unit (MDU) to evaluate sensitivity of CL geometric parameters. First, the projection trajectory formulas are derived according to the spatial relationship of CL system geometric parameters. Next, the MDU of the geometric parameters is obtained based on the projection trajectories and used as the evaluation index to measure the sensitivity of parameters. Then, the influence of the rotation angle of the axis tilt and magnification on the MDU of the parameters is analyzed. At low magnification, three susceptible parameters (η, u0, v0) with MDU less than 1 (° or mm) must be calibrated accurately to avoid geometric artifacts. The sensitivity of CL parameters increases as the magnification increases, and all parameters become highly sensitive when the magnification power is greater than 10. The results of this study have important guiding significance for the subsequent further parameter calibration.

The Role Classifiers Play in Selecting the Referent of a Word

An important cue to the meaning of a new noun is its accompanying classifier. For example, in English, X in “a sheet of X” should refer to a broad, flat object. A classifier is required in Chinese to quantify nouns. Using children’s overt responses in an object/picture selection task, past research found reliable semantic knowledge of classifiers in Mandarin-reared children at around age three. However, it is unclear how children’s semantic knowledge differs across different types of classifiers and how this difference develops with age. Here we use an arguably more sensitive measure of children’s language knowledge (the intermodal preferential-looking paradigm) to examine Mandarin-reared three-, four-, and five-year-olds’ semantic knowledge of four types of classifiers indicating animacy (human vs. animal distinction), configuration (how objects are arrayed), object shape, and vehicle function. Multiple factors were matched across classifier types: the number of classifiers, perceived familiarity and perceived typicality of the target, and the visual similarity of the two images paired together. Children’s performances differed across classifier types, as they were better with animacy classifiers than with configuration and vehicle function classifiers. Their comprehension was reliable for animacy, object shape, and vehicle function classifiers but not for configuration classifiers. Furthermore, we did not find conclusive evidence for an age-dependent improvement in the child’s performance. The analysis, including the oldest (five-year-olds) and youngest (three-year-olds) children, revealed a marginally significant age effect.

Using Neural Networks to Differentiate Newly Discovered BL Lacertae Objects and FSRQs among the 4FGL Unassociated Sources Employing Gamma-Ray, X-Ray, UV/Optical, and IR Data

Among the ∼2157 unassociated sources in the third data release (DR3) of the fourth Fermi catalog, ∼1200 were observed with the Neil Gehrels Swift Observatory pointed instruments. These observations yielded 238 high signal-to-noise ratio X-ray sources within the 95% Fermi uncertainty regions. Recently, Kerby et al. employed neural networks to find blazar candidates among these 238 X-ray counterparts to the 4FGL unassociated sources and found 112 likely blazar counterpart sources. A complete sample of blazars, along with their subclassification, is a necessary step to help understand the puzzle of the blazar sequence and for the overall completeness of the gamma-ray emitting blazar class in the Fermi catalog. We employed a multi-perceptron neural network classifier to identify flat spectrum radio quasars (FSRQs) and BL Lac objects among these 112 blazar candidates using the gamma-ray, X-ray, UV/optical, and IR properties. This classifier provided probability estimates for each source to be associated with one or the other category, such that P fsrq represents the probability for a source to be associated with the FSRQ subclass. Using this approach, four FSRQs and 50 BL Lac objects are classified as such with >99% confidence, while the remaining 58 blazars could not be unambiguously classified as either BL Lac objects or FSRQs.

Octopus‐Inspired Suction Cups with Embedded Strain Sensors for Object Recognition

The octopus has unique capacities are sources of inspiration in developing soft robotic‐enabling technologies. Herein, soft, sensorized, suction cups inspired by the suckers of Octopus vulgaris are presented. The suction cups using direct casting are fabricated, so that materials with different mechanical properties can be combined to optimize sensing and grasping capabilities. The artificial suckers integrate four embedded strain sensors, individually characterized and placed in a 90° configuration along the rim of the suction cup. Based on this arrangement, how well the sensory suction cup can detect 1) the direction and 2) the angle (from 30° to 90°) of a touched inclined surface and 3) the stiffness of a touched flat object (shore hardness between 0010 and D50) both in air and underwater is evaluated. Data processing on neural networks is based using a multilayer perceptron to perform regression on individual properties. The results show a mean absolute error of 0.98 for angles, 0.02 for directions, and 97.9% and 93.5% of accuracy for the material classification in air and underwater, respectively. In view of the results and scalability in manufacturing, the proposed artificial suckers would seem to be highly effective solutions for soft robotics, including blind exploration and object recognition.

Development of a General-purpose Gripper with Selectable Gripping Method by Jamming Transfer and Adhesion

In recent years, the use of robots has been considered due to the labor shortage. In this situation, the utilization of soft robot grippers that can grasp various objects is expected in the industrial world. The purpose of this study is to develop a soft robotic hand with an adhesion pad attached to a jamming gripper to enable grasping of flat and complex shaped objects. The gripper we have developed can be switched between a jamming gripper and a suction pad by switch control. This makes it possible to perform grasping according to the object. We applied a load to the gripper and conducted a gripping experiment on a complex-shaped object or a flat object. As a result, the gripping success rate of the jamming gripper increased as the applied load increased, and a stable gripping success rate was obtained on the adhesion side. Therefore, it can be seen that the gripper in this study satisfies the sufficient performance.

A Universal Filter Approximation of Edge Diffraction for Geometrical Acoustics

Sound propagation in urban and indoor environments often involves diffraction at corners, finite objects and openings, resulting in perceptually relevant frequency-dependent attenuation. Geometrical acoustics (GA) have become a de-facto standard for the prediction and simulation of sound propagation and real-time virtual acoustics, including effects of edge diffraction. However, methods to account for edge diffraction often assume infinite edges, such as the uniform theory of diffraction, or are computationally involved, such as the Biot-Tolstoy-Medwin-Svensson (BTMS) method. Particularly for interactive auralization, an efficient approximation of edge diffraction is desirable. Here, an extension of GA to account for diffraction with simple-to-derive parameters and a time-domain recursive filter implementation is suggested. This universal diffraction filter approximation (UDFA) describes diffraction from infinite and finite wedges using a combination of first-order and (fractional) half-order low-pass filters to account for the frequency-dependent attenuation of the diffracted incident and reflected sound field. The physically-based UDFA exactly matches asymptotic solutions for infinite wedges and provides approximations for finite wedges. It is demonstrated that first-order diffraction from flat finite objects like a plate or an aperture can be described by combining the filters for each edge. To account for effects of higher-order diffraction, an additional heuristic filter extension is suggested.

Optimization of the Printing Parameters to Improve the Surface Roughness in Fused Deposition Modeling

A better surface finish is an essential requirement of any component in particular medical components. The recent development in additive manufacturing technology produces components with a good surface finish. However, the optimization of process parameters helps to achieve a better surface finish. This paper focuses on the optimization of printing parameters of the surface roughness of a flat object developed from an FDM printer. FDM (Fused Deposition Modeling) is a layer-by-layer deposition process to develop 3D objects. It uses solid-state material (Filament) to print the product by melting and depositing the material on the printing bed. Several factors in the FDM process can affect the product’s quality. The parameters such as printing temperature, bed temperature, printing speed, fill density, layer thickness, and air gap influence the quality of the printed products. This investigation has considered printing temperature, layer height, and printing as process parameters. In addition, the parameter affecting the printed object’s surface finish is determined using ANOVA optimization and S/N ratios. PLA (Polylactic Acid) is taken as study material which is one of the feedstocks used in polymer filament and finds its applications in implant printing and medical tools.