Improving Matching Accuracy of Underwater Gravity Matching Navigation Based on Iterative Optimal Annulus Point Method with a Novel Grid Topology

In this study, we improve the matching accuracy of underwater gravity matching navigation. Firstly, the Iterative Optimal Annulus Point (IOAP) method with a novel grid topology is proposed for breaking through the inherent grid structure limit of the canonical gravity matching algorithm and enhancing its underwater gravity matching accuracy. The theory of IOAP is as follows: (1) small-annulus matching and positioning mechanism on the tracking starting point is developed by employing the starting point and drift error of the INS (Inertial Navigation System), the fixed rotation angle, etc. The optimal matching location of the starting point is obtained by matching and comparing the matched points in this small-annulus grid, which contributes to heightening the initial-position error insensitivity of the algorithms. (2) Variable-angle three-layer annulus matching and positioning mechanisms on the tracking ending point were constructed by using the optimal matching location of the starting point and combining the tracking direction-and-distance information of the INS and the cumulative drift error, etc. It is used to generate the annulus matching points with the ring-type grid topology. (3) The optimal matching position of the ending point in this annulus is obtained by iteratively calculating the evaluation index value of the matching points and following the evaluation index optimal rule. Secondly, we comprehensively consider the main performance evaluation indexes of the underwater gravity matching algorithms, such as the statistical indicators of the matching accuracy, the average matching time and the matching success rate, and take them as a basis of the pros and cons of the matching analysis. Furthermore, under conditions that include different scale searching regions or different reference-angle ring radii, the statistical results verify that the IOAP had a different matching ability and better robustness. Finally, several trajectories with the starting points from different areas and the ending points in different gravity ranges are tested and compared to carry out the numerical simulations. These results indicate that the IOAP has many advantages, such as a high matching accuracy and strong positioning applicability in different gravity regions. Compared with the TERCOM (terrain contour matching algorithm), its average matching accuracy was the highest, increased by 40.39%.

A novel adaptive slicing algorithm based on ameliorative area ratio and accurate cusp height for 3D printing

Purpose Adaptive slicing is a key step in three-dimensional (3D) printing as it is closely related to the building time and the surface quality. This study aims to develop a novel adaptive slicing method based on ameliorative area ratio and accurate cusp height for 3D printing using stereolithography (STL) models. Design/methodology/approach The proposed method consists of two stages. In the first stage, the STL model is sliced with constant layer thickness, where an improved algorithm for generating active triangular patches, the list is developed to preprocess the model faster. In the second stage, the model is first divided into several blocks according to the number of contours, then an axis-aligned bounding box-based contour matching algorithm and a polygons intersection algorithm are given to compare the geometric information between several successive layers, which will determine whether these layers can be merged to one. Findings Several benchmarks are applied to verify this new method. Developed method has also been compared with the uniform slicing method and two existing adaptive slicing methods to demonstrate its effectiveness in slicing. Originality/value Compared with other methods, the method leads to fewer layers whilst keeping the geometric error within a given threshold. It demonstrates that the proposed slicing method can reach a trade-off between the building time and the surface quality.

A Hybrid Landmark and Contour-Matching Image Registration Model

In this manuscript, we propose a novel hybrid Landmark and Contour-Matching (LCM) image registration model to align image pairs. The proposed model uses image contour information to supplement missing edge information in between exact landmarks. We demonstrate that the model circumvent the drawbacks associated with an straightforward application of the Thin Plate Spline (TPS) registration technique.The proposed model provides higher post-registration Dice similarity between the reference and registered template images by improving the image overlap away from major landmarks and visually reduces the appearance of the ''unnatural bending'' typically present in TPS-registered images. We also show that naively increasing the number of landmarks in a TPS model does not always guarantee an accurate registration result. We indicate how the proposed model using even less number of exact landmarks along with additional approximate contour information provided suitable results, as opposed to the TPS model. Lastly, the proposed model produces physically relevant registration results with improved Dice similarity indices even when landmark localization errors are present in data.Overall, the proposed Landmark and Contour-Matching (LCM) model increases the flexibility of the TPS approach especially when only a few landmarks can be defined, when defining too many landmarks leads to high oscillations in the registration transformations, or when the identification of exact landmarks is susceptible to human error.

MANAGEMENT OF ACQUIRED SOFT TISSUE DEFECTS OF FACE

Background: Since time immemorial, soft-tissue defects of face due to injuries have been documented in literature and even depicted in sculptures, reflecting the image of society. Facial injuries themselves are rarely life-threatening, but are indicators of the energy of injury. Soft-tissue defects of the face can arise out of various causes which may include simple or complex contused lacerations with loss of tissue, avulsions, bites and burns. Common etiologies are road traffic accidents, foreign bodies, defects secondary to tumor excision, homicidal trauma, thermal, chemical and electrical burn, suicidal injuries, human bites, animal bites, gunshot injuries and blast injuries. The management of acquired soft tissue defects of face requires precise planning and coverage by a modality which is functionally and aesthetically pleasant. Objectives: To study the epidemiology of acquired soft tissue defects of face. To restore the aesthetics of the face by resorting to appropriate modality of reconstruction. Materials & Methods: This study was conducted in the Department of Surgery, Govt. Medical College Jammu, J&K, India and included 40 patients having been diagnosed with acquired soft-tissue defects of the face admitted in surgery ward from November 2018 to October 2019 (Prospective study). All the defects were evaluated for size, depth, and status of the base of the defect (presence of gross contamination or infection, integrity, and viability of the wound edges) along with evaluation and documentation of cranial nerve function, particularly the facial and trigeminal nerves. The management depended upon the defect site, size, status and type. 52.5 % patients underwent flap coverage whereas 22.5% underwent skin grafting for coverage of defects. 25% of the patients underwent primary closure of the facial defects. Results: Majority of the patients had restoration of anatomy and normal function after reconstructive procedures with colour and contour matching of that of the recipient site. No major complication was encountered in any of the patients. Conclusion: Acquired soft tissue defects of the face can be reconstructed by a variety of modalities which should not only be functionally adequate but also aesthetically appealing. Flaps are a versatile modality of reconstruction with the choice of flap being governed by the site and size of the defect.