3-D calibration method and algorithm for freehand image of phased array ultrasonic testing

Phased array ultrasonic testing (UT) is an advanced technique applying ultrasound wave vibration theory to detect the flaw in tested materials by imaging. In this research, computer 3-D visualization of the flaw through calibrating the ultrasonic phased array image is proposed. 3-D calibration for ultrasonic phased array image is a procedure to calculate the spatial transformation matrix, spatial relationship between the US image plane and the tracker attached to the UT probe. The calibration method depends on a cross-string phantom and the corresponding algorithm. The phantom with a set of crosses guiding the operator quickly to find the scanning plane. The ten string crosses in the scanning plane provide the coordinates and spatial vectors for the calibration algorithm, thus the calibration algorithm can be realized based on the least-squares fitting method of the homologous points matching. Select the points having different distances and angles with the reference point to calculate the matrix and average them as the final result. The results show that the scanning plane positioning time is no more than 5 s. The precision and the accuracy results are the same as that is obtained through the other published methods in the medical 3-D ultrasound image calibration. The results make the 3-D flaw model reconstruction possible in phased array ultrasonic NDT. It will reduce the difficulties in the flaw recognizing and localization

N-(2-Pyridylmethyleneamino)dehydro­abietylamine

The title compound {systematic name: 1-[(1R,4aS,10aR)-7-isopropyl-1,2,3,4,4a,9,10,10a-octa­hydro­phenanthren-1-yl]-N-[(E)-2-pyridylmethyleneamino]methanamine}, C26H33N2, has been synthesized from dehydro­abietylamine. The two cyclo­hexane rings form a trans ring junction with classic chair and half-chair conformations, respectively, whereas the benzene and pyridine rings are almost planar, and the dihedral angle between them is 80.4°. The two methyl groups directly attached to the tricyclic nucleus are on the same side of the tricyclic hydro­phenanthrene structure

Fast voice-coil scanning optical-resolution photoacoustic microscopy

We developed a photoacoustic imaging system that has real-time imaging capability with optical resolution. The imaging system is capable of scanning at 20 Hz over a 9 mm range and up to 40 Hz over a 1 mm scanning range. A focused laser beam provides a lateral resolution of 3.4 μm as measured in an optically nonscattering medium. Flows of micrometer-sized carbon particles or whole blood in a silicone tube and individual red blood cells (RBCs) in mouse ear capillaries were also imaged in real time, demonstrating the capability to image highly dynamic processes in vivo at a micrometer-scale resolution

Prompt Learning with Optimal Transport for Vision-Language Models

With the increasing attention to large vision-language models such as CLIP, there has been a significant amount of effort dedicated to building efficient prompts. Unlike conventional methods of only learning one single prompt, we propose to learn multiple comprehensive prompts to describe diverse characteristics of categories such as intrinsic attributes or extrinsic contexts. However, directly matching each prompt to the same visual feature is problematic, as it pushes the prompts to converge to one point. To solve this problem, we propose to apply optimal transport to match the vision and text modalities. Specifically, we first model images and the categories with visual and textual feature sets. Then, we apply a two-stage optimization strategy to learn the prompts. In the inner loop, we optimize the optimal transport distance to align visual features and prompts by the Sinkhorn algorithm, while in the outer loop, we learn the prompts by this distance from the supervised data. Extensive experiments are conducted on the few-shot recognition task and the improvement demonstrates the superiority of our method

A novel circularly polarized filtering antenna with high out‐of‐band radiation rejection level

In this paper, a circularly polarized filtering antenna with high out‐of‐band radiation rejection level is proposed. The entire design consists of a patch and a filtering feeding network, which are connected by metallic pins. First, a high‐selectivity filtering power divider is constructed utilizing two shunted bandpass filter. Next, a 90° phase difference could be realized by adjusting the length of the two outputs of the power divider. The measured transmission coefficient of the feeding network is 6.3 dB at 2 GHz. The measured axial ratio is below 3 dB within the operating band of the proposed antenna, which represents the effectiveness of the proposed feeding network. In addition, the obvious radiation nulls can be found from the antenna measurement because of the transmission zeros introducing by the filtering power divider. The measured gain is 5.73 dB at 2 GHz and decreases dramatically in stopband. Specially, the measured gain is −30 and −41 dB at 1.95 and 2.06 GHz. The proposed antenna has an excellent filtering characteristic compared with those without the filtering feeding network. To sum up, the proposed antenna and filtering power divider are promising in the modern wireless communication systems.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140028/1/mop30929.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/140028/2/mop30929_am.pd

Superluminal pulse reflection from a weakly absorbing dielectric slab

Group delay for a reflected light pulse from a weakly absorbing dielectric slab is theoretically investigated, and large negative group delay is found for weak absorption near a resonance of the slab ($Re(kd)=m\pi$). The group delays for both the reflected and transmitted pulses will be saturated with the increase of the absorption.Comment: 13pages, 3figure