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In a satellite-denied environment, a swarm of drones is capable of achieving relative positioning and navigation by leveraging the high-precision ranging capabilities of the inter-drone data link. However, because of factors such as high drone mobility, complex and time-varying channel environments, electromagnetic interference, and poor communication link quality, distance errors and even missing distance values between some nodes are inevitable. To address these issues, this paper proposes a low-rank optimization algorithm based on the eigenvalue scaling of the distance matrix. By gradually limiting the eigenvalues of the observed distance matrix, the algorithm reduces the rank of the matrix, bringing the observed distance matrix closer to the true value without errors or missing data. This process filters out distance errors, estimates and completes missing distance elements, and ensures high-precision calculations for subsequent topology perception and relative positioning. Simulation experiments demonstrate that the algorithm exhibits significant error filtering and missing element completion capabilities. Using the F-norm metric to measure the relative deviation from the true value, the algorithm can optimize the relative deviation of the observed distance matrix from 11.18% to 0.25%. Simultaneously, it reduces the relative positioning error from 518.05 m to 35.24 m, achieving robust topology perception and relative positioning for the drone swarm formation.

An autonomous place recognition system is essential for scenarios where GPS is useless, such as underground tunnels. However, it is difficult to use existing algorithms to fully utilize the small number of effective features in underground tunnel data, and recognition accuracy is difficult to guarantee. In order to solve this challenge, an efficient point cloud position recognition algorithm, named Dual-Attention Transformer Network (DAT-Net), is proposed in this paper. The algorithm firstly adopts the farthest point downsampling module to eliminate the invalid redundant points in the point cloud data and retain the basic shape of the point cloud, which reduces the size of the point cloud and, at the same time, reduces the influence of the invalid point cloud on the data analysis. After that, this paper proposes the dual-attention Transformer module to facilitate local information exchange by utilizing the multi-head self-attention mechanism. It extracts local descriptors and integrates highly discriminative global descriptors based on global context with the help of a feature fusion layer to obtain a more accurate and robust global feature representation. Experimental results show that the method proposed in this paper achieves an average F1 score of 0.841 on the SubT-Tunnel dataset and outperforms many existing state-of-the-art algorithms in recognition accuracy and robustness tests.

Generalized space-time-frequency index modulation (GSTFIM) inherits the drawbacks of the conventional orthogonal frequency-division multiplex (OFDM), such as being sensitive to carrier frequency offset (CFO). For a robust design against this problem, in this contribution, a novel construction of a message passing (MP)-aided detector is developed for GSTFIM systems to combat the influence of CFO, while offering a flexible tradeoff between transmission performance and computational complexity. Through complexity analysis and simulation results, we demonstrate that, in the context of CFO, with a careful design, the developed MP detector is capable of approaching traditional GSTFIM with maximum likelihood (ML) detection, and of offering better performance at lower complexity compared to its minimum mean-square-error (MMSE)-aided counterpart.

Focusing of wafer plane is an essential factor to determine the ultimate feature size of the stepper such as projection lithographic system. Based on Michelson interferometeric system, this paper demonstrates an interferometric focusing scheme for projection lithography to coaxially locate the ideal focal plane of the projective objective. The collimated incident laser beam is divided into the reference arm and object arm. The latter propagates through the objective lens and then interferes with the slightly deflected reference beam that reflected back by a fixed mirror, giving rise to an interferential pattern on the CCD. Any amounts of defocusing can be directly indicated from the demodulated phase of the interferential pattern. In this manner, the focusing sensitivity at nanometer scale is experimentally attainable, which shows great superiority over traditional methods, particularly the limited focal length of current projective objective lens.

Focusing and leveling are two imperative processes to adjust the wafer onto the ideal focal plane of projection lithography tools. Based on moiré fringes formed by particularly designed dual-grating marks, the four-channel focusing and leveling scheme is proposed and demonstrated. These relationships between the tilted amount of wafer, the vertical defocusing amount, and the phase distributions of moiré fringes are deduced. A single-channel experimental setup is constructed to verify the performances of proposed method. Results indicate that the tilted amount and the vertical defocusing amount can be precisely detected with accuracy at 10-4 rad and several nanometers level, respectively, and therefore meet the demand of the high-demanding focusing and leveling processes.

Abstract Background Crohn’s disease (CD) patients require varying levels of supportive care. In order to facilitate caregivers and nurses in precisely evaluating the caregiving requirements of these patients, we developed the CD-specific Care Needs Scale (CD-CNS). Methods This study employed a mixed-methods approach, integrating qualitative and quantitative methodologies. The initial items of the scale were developed through qualitative interviews, Delphi expert consultation, and literature review, while the final items were refined through clinical testing. Qualitative interviews were conducted based on the supportive care needs framework and Maslow’s hierarchy of needs, and scale items were constructed through a literature search and qualitative interviews. The initial version of the scale with 45 items was obtained after the items were verified and modified by expert consultation. A total of 250 CD patients admitted to the gastroenterology department of a hospital in China were selected for verification of the initial version of the scale. A self-designed general questionnaire was used to obtain patients’ medical history and sociodemographic data, and the Chinese version of the Inflammatory Bowel Disease Questionnaire (IBDQ) was used as the criterion. Exploratory factor analysis (EFA) was performed on the CD-CNS to evaluate the dimensions, factor structure, reliability, criterion validity, and construct validity. Results EFA identified 5 dimensions and retained 27 items with strong internal consistency reliability (α = 0.940). The Cronbach’s α coefficients for each dimension ranged from 0.824 to 0.921. Criterion validity was assessed using Spearman’s coefficient, which demonstrated a significant correlation with the IBDQ (P

Abstract Background Previous studies reported that transnasal ileus tube was a new and useful method for rapid relief of small intestinal obstruction. However, no study reported the impacts of the transnasal ileus tube for Crohn’s disease combined with intestinal obstruction. We aimed to describe the strategy to the small intestine obstruction caused by Crohn’s disease on the basis of transnasal ileus tube insertion. Methods From November 2019 to November 2021, the data of 6 hospitalized patients with CD, diagnosed and conservatively treated in The Second Hospital of Nanjing, were not relived and retrospectively collected. After the insertion of transnasal ileus tube, demographic information, clinical features and treatment data were extracted from medical records. Results Six Crohn’s disease patients with intestinal obstruction were included. Half of them were male. The patients aged from 29 to 70 years. Five patients had chronic intestinal obstruction more than one year. Three patients had intestinal surgery history. One patient had colonic abdominal fistula and anastomotic fistula, when she took intermittent usage of sulfsalazine and steroid. On admission, all the patients had abdominal pain, distention and mass. Five patients had anemia, low albumin and cholinesterase. All CDAI scores were more than 400. Compared to 19 patients with incomplete intestinal obstruction improved by nasogastric decompression tube, 6 patients with intestinal obstruction catheter had significant difference in time for relieving abdominal pain and distension (p = 0.003), time for alleviating abnormal mass (p ≤ 0.01), drainage volume (p = 0.004), and preoperative CDAI score (p = 0.001). Compared with X-ray image before insertion, complete remission of obstruction of 5 patients were observed in intestinal cavity after insertion. After 1–2 months nutrition, all the patients had small intestine resection and ileostomy, half of them underwent colectomy and fistula repair, and 4 patients were performed enterolysis at the same time, the residual small intestine length ranging from 250 to 400 cm. 1 patient had permanent ileostomy;1 patient had abdominal infection after operation. The typical manifestations of acute and chronic inflammation, transmural inflammation, pseudopolyps and serous fiber hyperplasia could be seen in pathological findings of patients 1 to 5. All the patients continued enteral nutrition after surgery. Four patients were treated with infliximab or vedolizumab. Conclusion The current intestinal obstruction catheter which is used to treat patients with Crohn's combined obstruction can afford quick clinical remission, longer nutrition time, and suitable preoperative CDAI score for operation, which is worthy of wildly being used.