Individual Pieces Research Articles

Application of Integral Invariants to Apictorial Jigsaw Puzzle Assembly

We present a method for the automatic assembly of apictorial jigsaw puzzles. This method relies on integral area invariants for shape matching and an optimization process to aggregate shape matches into a final puzzle assembly. Assumptions about individual piece shape or arrangement are not necessary. We illustrate our method by solving example puzzles of various shapes and sizes.

The Art of Mbira: Musical Inheritance and LegacyMbira's Restless Dance: An Archive of Improvisation, Vols. 1 & 2

The Art of Mbira: Musical Inheritance and LegacyMbira's Restless Dance: An Archive of Improvisation, Vols. 1 & 2

A TECHNOLOGY FOR PRODUCING THE SMALL VESSEL HULL BY THE ADDITIVE MANUFACTURING METHODS

The issues of the technological complex for manufacturing the hull of a small vessel obtained using additive manufacturing methods are considered in the paper. The purpose of the work is to study the emerging problems, issues, patterns, rules and norms of the process of 3D-printing the hull of a small vessel. The objectives of the paper include presentation of previously obtained calculated and experimental results for printing and assembling the ship hull; development of a method for assembling a hull using additive technology; comparative analysis of the labor intensity of manufacturing ship hulls using traditional and additive technologies; studying the issues of the slipway period of building the hull after completing printing work. The main methods for solving problems include well-known fundamentals in the technology of shipbuilding, ship repair, optimization of ships, technical and economic analysis, materials science, etc.; information about the production of marine equipment objects by additive manufacturing from filaments; the results of our own calculations and experiments for the production of a small vessel hull using additive technologies; well-known industry regulations and standards for working with fiberglass in shipbuilding. The technique of printing and assembling the hull of a small vessel, the necessary preliminary computational-analytical and experimental studies for redesigning the hull structure for additive manufacturing, the problems arising during and after printing and assembling the hull, and the analysis of the labor intensity of manufacturing the hull using additive and traditional technologies are considered. It has been found that not all types of small vessels will have advantages in terms of labor intensity in their additive manufacturing; it is possible to use incremental production. With the right organization of production management, additive technologies will have an advantage in terms of the laboriousness of the technological process in the production of hulls of kayak-type ships, and similar structures in terms of geometry and weight, with individual piece production.

CT Scan-Based Robotic-Arm Assisted Total Hip Arthroplasty: What Do Today's Highest-Quality Studies Tell Us?

Total hip arthroplasty (THA) aims to restore function and reduce pain for patients suffering from hip pathologies. However, some procedures require revision THA, with the most common reasons including: mechanical failure, aseptic loosening, infection, and component malposition leading to dislocations. Computed tomography (CT) scan-based, three-dimensional imaging operating techniques can help address some of these issues by helping to provide more optimal implant positioning, which can potentially confer improved outcomes. To date, only a few studies have evaluated the utilization of CT scan-based robotic-arm assisted THA in total hip arthroplasty, and those that do are not necessarily of the high-methodological quality. Therefore, the purpose of this review was to select the most recent and good- to high-quality studies focusing on robotic-assisted THA, to help provide a more comprehensive representation of postoperative outcomes. Specifically, we evaluated each study independently as well as performed a cumulative assessment of this most recent high-quality data. An extensive, cross-platform search of total hip arthroplasty on August 1, 2022 was performed. Studies were included only if they addressed robotic-assisted THA in comparison to manual techniques. Additional inclusion criteria consisted of studies scoring excellent (100 to 85 points) or good (84 to 70 points) based on their Coleman methodology score. Studies were evaluated as individual pieces of work, as well as a cumulative assessment. Specific outcomes evaluated were: component placement in safe zones, leg- length discrepancies, dislocation rates, clinical outcomes, patient clinical scores, patient-reported outcome measures (PROMS), lengths of stay, and costs. Overall, 24 studies were included for analyses. CT scan-based robotic-arm assisted THA had some potential key advantages as compared to manual techniques. Specifically, robotic-assisted THA was associated with more accurate component placement in safe zones, fewer chances of leg-length discrepancies, and lower risks of dislocation. Patient satisfaction and reported outcome measures were superior for CT scan-based robotic-arm assisted THA. Costs were also lower. Overall, 23 of 24 studies were positive for this technology, with one study of cases done between 2010 and 2014 more neutral. The robot led to positive findings for component placement in safe zones, leg-length discrepancies, dislocation rates, clinical outcomes, PROMS, lengths of stay, and costs. The current literature suggests potential advantages for CT scan-based robotic-arm assisted THA compared to manual THA. Surgeons should consider CT scan-based robotic-arm assisted THA for their patients given the multiple added benefits of improved clinical scores and PROMS, less dislocations (with a few exceptions reported), more component placements in safe zones, less leg-length discrepancies, decreased lengths of stay, and decreased episode-of-care costs.

Awful Archives: Conspiracy Theory, Rhetoric, and Acts of Evidence

Awful Archives: Conspiracy Theory, Rhetoric, and Acts of Evidence

How to Detect Concealed Crime Knowledge in Situations With Little Information Using the Forced Choice Test

The Forced Choice Test (FCT) can be used to detect concealed crime knowledge, but it requires more evidence than typically available from a crime to be constructed. We propose a method to repeat individual pieces of evidence to achieve the necessary test length, hence widening the practical applicability. According to our method, FCT trials are created so that on each trial examinees are presented with a novel and unique decision between two answer alternatives even if a specific piece of information is presented again. We argue that if the decision in each trial is unique, the properties and diagnosticity of a traditional FCT can be maintained. In experiment 1, we provide a proof of concept by comparing our novel method with a traditional FCT and demonstrate that an FCT with repeated presentation of the same evidence has diagnostic value (AUC = .69) albeit less so than a traditional FCT (AUC = .86). In experiment 2, we put our novel FCT to the test in a situation with insufficient information for a traditional FCT alongside the Concealed Information Test (CIT), which also detects concealed information but relies on psychophysiological indices. Both, the FCT (AUC = .81) and CIT (AUC = .83) were diagnostic and combining them increased the detection accuracy even further (AUC = .91). If replicated, our novel FCT increase practical applicability of the FCT in general and in conjunction with the CIT.

Building on Solid Ground: Foundational Knowledge and the Dynamics of Innovation

How do changes in knowledge uncertainty dynamically shape the rate and direction of innovation? I develop a novel typology of knowledge based on the degree of uncertainty and synthesis across individual pieces of knowledge. To empirically explore the role of foundational knowledge—integrative knowledge with low uncertainty—I study how 135 clinical practice guidelines published 1990-2011 by cardiology professional medical societies shape the use of the 14,390 underlying articles and associated research subfields they incorporate. Employing a difference-in-differences approach, I find articles cited by a clinical practice guideline have a marked increase in citations, acting to diffuse the underlying knowledge by bringing in new researchers, compared to control articles carefully matched on observables. Subfields included in the guideline have a large and sustained increase in the flow of articles into the field, which are more likely to be themselves highly cited. Rather than the aperture of subsequent innovation narrowing, subfields shift towards more disruptive, more intellectually distant, and more translational research, with only a small increase in incremental clinical research. In particular, this shift is larger for those subfields that are more technologically immature. As developing foundational knowledge requires the investment of resources and time, this shows how commitment can facilitate breakthrough innovation.

IsoBugView

Database applications frequently use weaker isolation levels, such as Read Committed, for better performance, which may lead to bugs that do not happen under Serializable. Although a number of works have proposed methods to identify such isolation-related bugs, the difficulty of analyzing reported bugs is often underestimated, since these bugs often involve multiple complicated transactions interleaved in a specific order and they often require users' feedback to improve the accuracy of bug analysis. This paper presents IsoBugView, a tool to visualize isolation bugs and incorporate users' feedback: to address the challenge that a complicated bug may include much information and thus is hard to present, IsoBugView displays a high-level overview of the bug first and displays further information of individual pieces if the developer needs further investigation. To incorporate users' feedback, IsoBugView embeds hook functions into the backend analysis tool to preprocess a dependency graph and postprocess a found cycle and further allows a user to apply predefined hook functions in its graphic user interface. Our experience shows that IsoBugView has greatly improved our productivity of analyzing isolation bugs.

Color Depth

Color Depth is a material-based research project investigating the optical and structural properties of thick glass. The research is driven by an interest in optical gradients of transparency and color, which are designed through a manipulation of geometric form and composition. These qualities can be attributed to the interrelated optical effects created through reflection, refraction, and volume color, in direct correlation to the geometry of individual glass pieces and overall glass assemblies. An example of this can be seen in viewing a monolithic volume of glass that would appear to change color by varying the depths of its form. This concept was originally discussed in Josef Albers’ Interaction of Colour, and applied more specifically to glass in recent essays by Heike Brachlow. Color Depth utilizes this phenomenon of perceived color variation to construct and analyze architectural glass forms in both physical prototypes and design speculation. To evaluate architectural design opportunities, a multi-objective optimization workflow simulates and evaluates varying glass colors, forms, and compositions to achieve a desired visual effect. Additionally, the digital optimization process reveals patterns and visual effects that further the understanding of optical gradients when applied in an architectural context with various seasonal and diurnal environments. Keying into the geometry of glass– to deploy changes in color, darkness, or translucency—Color Depth ties together the physical attributes of a material system with its surrounding light.

Curtain of Glass – Textured by Stone

The new World Trade Center site was rebuilt after 9/11 comprising seven mayor skyscrapers around the memorial site and the 9/11 museum. Between WTC 2 and WTC 3, Santiago Calatrava’s Oculus Station spans its wings in the NY air while finally, the complex is completed by the “The Ronald O. Perelman Performing Arts Center”. This building sets a one-in-a-kind visual appearance to the area. Its four-sided, 42 m tall, even facade is made from 4736 equal-sized insulated glass panes. More specifically, the architectural vision is to create a marble stone front covered with glass which results in a stone-glass laminate as a part of an insulated glass unit. The marble shows a distinguished white face with crisp black veining. Each of the four elevations of the building impresses with a perfect symmetry and veins touching at the vertical center line. So, the design team at Josef Gartner was challenged to set-up a logistics chain from quarry in Portugal where the stone panels were cut and catalogued to glass production of laminated glass in France and IGUs in Germany and assembly of curtain wall mega-panels at Gartner in Germany up to the site in Lower Manhattan. Our in-house logistics concept, customized for this project, guarantees that each individual piece of stone finds its correct and unique spot defined by the architect on the 7,000 m2 surface – a large-scale game of “Matching Pairs”. The steel base building provides a cantilevering roof that holds 128 hot-rolled steel mullions. Each 36 m in length with one intermediate lateral support only. This allows the visitor to experience a clear and unobstructed view along the transom-free facade elements that carry the translucent stone-wall. During the day, it appears white from the outside and shines with an amber-glow during the night when the interior space is illuminated. We show the use of a novel stone-glass product that is exposed to a variety of requirements. The logistics chain is described from quarry to site making sure that the architectural and economical demand is met along the whole process. Finally, the team connects all branches in facade design using stone, aluminum, glass and architectural exposed structural steel assembled in one landmark project.

The Strength of Pine (Pinus sylvestris L.) Sawn Timber in Correlation with Selected Wood Defects.

Pine timber of Polish origin intended for structural purposes is characterized by significant variability in the quality parameters. Technological suitability determined on the basis of relevant international classifications is based on the assessment of both selected mechanical and physical properties of wood. Moreover, the description of visual properties is also a valuable indicator regarding defect distribution. In the group of quality features playing a crucial role in the classification of sawn timber, there are knots, disruptions of grains, cracks, etc. Thus, the aim of the research was to determine the correlation between the presence of selected defects and the strength properties of individual timber pieces. This type of study is based on a nondestructive test method that allows for high optimization of sawn materials processing. In the case of sawn timber of Polish origin, the modulus of elasticity (MOE) determined using the sonic test is commonly used as a criterion. The research material was harvested from southern Poland. The results of the conducted studies confirmed a correlation between an increasing occurrence of particular types of defects and the results of MOE. Furthermore, as a result of the performed investigations, no significant effect of narrow surface cracks on strength properties was observed.

Indian Ocean Narratives, Tidalectics, and Perth’s Centre for Stories

Abstract This essay argues that contemporary literary anthologies of Indian Ocean narratives offer a distinctive way of representing the diversity of voices and experiences that traverse the ocean and connect the different countries and cultures along its rim. Whereas the single-author historical or historiographical novel is often the focus of Indian Ocean literary scholarship, this essay examines Ways of Being Here and Wave after Wave, anthologies produced under the rubric of Indian Ocean mentorship and writing projects by the Centre for Stories located in Perth, Western Australia. While the anthologies do share some thematic similarities with Indian Ocean novels, this essay draws on Kamau Brathwaite’s thinking to argue that the anthologies have a tidalectical aesthetic connecting their different individual pieces, which unfolds as readers move through their pages. This tidalectical aesthetic, in which there is no resolving synthesis but rather a series of interconnected and overlapping lived experiences and emotional struggles produced by multiple authors, may be a better way of representing contemporary Indian Ocean narratives that circles back to issues of migration, racism, and resistance at the very southeastern edge of the Indian Ocean.

“Thy Words Do Finde Me Out”: Aaron Kunin’s Love Three

“Thy Words Do Finde Me Out”: Aaron Kunin’s <i>Love Three</i>

A systematic mapping study on automated analysis of privacy policies

A privacy policy describes the operations an organization carries out on its users’ personal data and how it applies data protection principles. The automated analysis of privacy policies is a multidisciplinary research topic producing a growing but scattered body of knowledge. We address this gap by conducting a systematic mapping study which provides an overview of the field, identifies research opportunities, and suggests future research lines. Our study analyzed 39 papers from the 1097 publications found on the topic, to find what information can be automatically extracted from policies presented as textual documents, what this information is applied to, and what analysis techniques are being used. We observe that the techniques found can identify individual pieces of information from the policies with good results. However, further advances are needed to put them in context and provide valuable insight to end-users, organizations dealing with data protection laws and data protection authorities.

Creation of Three‐Dimensional Pedagogical Models of Genetic Mutations

A genetic mutation is a change of one or more bases in the DNA sequence that may alter the structure and ability of the resulting protein product to function properly. In this study, we created three‐dimensional (3D) pedagogical models for teaching genetic mutations. SolidWorks©, 3D modeling software was used to create the models showing the three main types of DNA mutations: (i) point mutation, (ii) frameshift mutation, and (iii) insertion mutation. The models were 3D printed using a selective laser sintering (SLS) machine. Further, the printed models are strong enough to absorb physical mishandling by the users such as accidental drops. User instructions accompanying the models were developed.The models were created to allow the individual nucleotide bases adenine (A), thymine (T), guanine (G), cytosine (C) and uracil (U) to be attached or removed from the DNA and mRNA backbone and moved around easily by using magnets embedded into the individual pieces. Other ease of use features include color coding and labeling emphasize the difference between the four nucleotides in DNA. Further, as an example of real‐life mutations, we also created a unique model explaining the formation of cyclobutane thymine‐thymine (T‐T) dimers following exposure of DNA to ultraviolet B (UV‐B) radiations. UV‐B radiation in the region of 290‐320 nm is absorbed by skin cells resulting in DNA damage and mutated DNA which can lead to skin cancer. The 3D model showing cyclobutane dimers should help the students gain a deeper understanding of DNA damage, and skin cancer at the biochemical level. Ultraviolet light can break bonds in adjacent thymine bases. New covalent bonds are formed, linking the two thymine bases, forming cyclobutane T‐T dimers. We believe that models will enhance in‐depth hands‐on learning of the genetic mutations.

MP58-10 A NOVEL APPROACH FOR 3D RECONSTRUCTION OF THE PROSTATE GLAND THAT ALLOWS TUMOUR LOCATION, VOLUME ESTIMATION, AND GLEASON CHARACTERIZATION

You have accessJournal of UrologyCME1 May 2022MP58-10 A NOVEL APPROACH FOR 3D RECONSTRUCTION OF THE PROSTATE GLAND THAT ALLOWS TUMOUR LOCATION, VOLUME ESTIMATION, AND GLEASON CHARACTERIZATION Pedro Oliveira, Avaneesh Meena, Saikiran Bonthu, Nitin Singhal, Ashwin Sachdeva, Yatin Jain, and Vijay Ramani Pedro OliveiraPedro Oliveira More articles by this author , Avaneesh MeenaAvaneesh Meena More articles by this author , Saikiran BonthuSaikiran Bonthu More articles by this author , Nitin SinghalNitin Singhal More articles by this author , Ashwin SachdevaAshwin Sachdeva More articles by this author , Yatin JainYatin Jain More articles by this author , and Vijay RamaniVijay Ramani More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002641.10AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: We propose a novel approach for identification (ID) of clinical significant PCa on mpMRI based upon retrospective comparison of in vivo mpMRI images to spatially concordant digitally-scanned post-prostatectomy H&E images. Steps: 1) localisation and Gleason grading of tumour foci; 2) reconstruction of H&E slides in 3D; 3) alignment of reconstructed histology to mpMRI images; 4) labelling of aggressive prostate cancer on mpMRI images using reconstructed 3D histology; 5) training a deep learning-based model for unsupervised segmentation of aggressive PCa foci using mpMRI images and transferred labels. Using this approach, the extent of cancer can be mapped directly onto mpMRI enabling accurate segmentation of voxels corresponding to tumour foci, including ID of mpMRI-invisible lesions using radiomic features. METHODS: The step 2 is presented herein. Whole-mount histopathological sections from totally embedded radical prostatectomy specimens, with correspondent diagnostic pre-biopsy mpMRI, were used. Apex and base tissue blocks were cut perpendicular to the axial plane, with the central portion of the gland sliced in 4 mm thick sections. H&E whole-mount slides were digitised at 40x. 3D reconstruction was performed using a novel computational strategy that includes: 1) angular alignment of individual macrodissected tissue pieces using colour ink markers; 2) scale alignment to fit the pieces on a pre-defined bounding box; 3) generation of intermediate layers between two pieces; 4) normal vector estimation; and 5) Poisson reconstruction to generate the triangular mesh. RESULTS: The volume estimate from the original prostate specimen was compared to the reconstructed volume to assess the 3D reconstruction performance with a correlation of 85%-88%. Because the base and apex portions are not discarded, we establish a high correlation between the reconstructed 3D histopathological volume and actual prostate volume. Further, this methodology allowed ID not only of independent tumour foci within the gland but also 3D reconstruction of the different Gleason patterns with accurate estimation of tumour volume and prognostic Grade Group. CONCLUSIONS: A method for reconstructing 3D prostate volumes from 2D histology images has been presented. The development of radiomic and deep learning algorithms to automatically detect prostate cancer on MRI will be aided by the accurate labelling of tumour foci on mpMRI images using our 3D reconstruction approach. Source of Funding: NHS/Aira-Matrix Project PO01 © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e995 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Pedro Oliveira More articles by this author Avaneesh Meena More articles by this author Saikiran Bonthu More articles by this author Nitin Singhal More articles by this author Ashwin Sachdeva More articles by this author Yatin Jain More articles by this author Vijay Ramani More articles by this author Expand All Advertisement PDF DownloadLoading ...

Comparing Multi-Arm Robotics for In-Space Assembly

Robotic In-space assembly (ISA) is the next step to building larger and more permanent structures in orbit. Determining the best robot for ISA is difficult as it will not only depend on the structure being assembled but on how it is assembled. This analysis shows how changing some key design parameters can influence different robotic systems for ISA. This study focuses on the construction of a 20 m linear truss structure but also expands to a 10 and 50 m truss. Two categories of robots are included in this study: a stationary robot and a mobile robot which crawls along the structure. Both the stationary and crawling robotic systems utilize two planar dexterous manipulators to assemble individual truss pieces into a linear truss. In the case of the stationary robotic system a single long positioning leg is used to move the two dexterous arms into position. The crawling robotic system uses two planar manipulators to crawl along the truss. A systems level analysis is presented which details how the forces from the robotic systems drive the mass of the truss and also how the size of the truss segments drive the requirements of the robotic system. This analysis shows how changing some key design parameters can influence each of the different robotic systems and the truss design itself. The estimated masses of the robotic systems and the truss and the assembly time are presented. There are trade-offs to every robot design and understanding those trade-offs is essential to building a system that is not only efficient but also cost-effective.

Thermal Properties of Hemp Shives Used as Insulation Material in Construction Industry

The article presents the results of studies concerning raw hemp shives obtained from the Polish crop of industrial hemp as a loose-fill thermal insulation material. The study focuses mainly on the measurements of the pore size distribution, thermal conductivity and air permeability of material. An increase in the value of the thermal conductivity coefficient (0.049–0.052 W/(m·K)) was demonstrated with an increase in the bulk density. The porosity of the individual pieces of shives is 78.7% and the predominant number of pores is in the diameter range of 0.9–3 μm. The paper also presents an example of the use of the tested material as thermal insulation of the wooden frame wall. The heat flow analysis was performed in various wall variants (insulation thickness: 100, 200 and 300 mm and pressure difference 0, 5, 10 and 15 Pa). A clear influence of the variables on the temperature distribution was observed.

Being You: A New Science of Consciousness by Anil Seth

Reviewed by: Being You: A New Science of Consciousness by Anil Seth Felix Haas Anil Seth Being You: A New Science of Consciousness New York. Dutton. 2021. 352 pages. THEORIZING ABOUT consciousness was long left to philosophers. Venturing into the field as a neuroscientist was risking ridicule and, possibly, career suicide, until things started changing in the 1980s and ’90s. Even though the decades since have seen several prototheories of consciousness develop, we still seem far from a full theory, or even an accepted analytical definition of what consciousness means. Many neuroscientists and philosophers thus fall back on a working definition that equates the existence of an agent’s subjective inner experience with what it means for that agent to be conscious. Anil Seth—a director of the Sackler Centre for Consciousness Science in Sussex, England—too follows this definition in his recent book, Being You. This much-anticipated publication goes on to present the author’s views on central topics connected to consciousness, often developing surprisingly counterintuitive arguments with strong epistemological implications. In the philosophy of consciousness, people are frequently classified by their stance on the so-called hard problem of consciousness—the question of how and why our brains’ neuronal activity should be accompanied by any subjective experience at all. Interestingly, Seth falls somewhat in the middle of the usual two camps: he does not think that the question posed by the hard problem is inherently meaningless but also does not believe that facing it head-on will lead to any real progress. Rather, he maintains research should focus on [End Page 72] what he calls the “real problem” of consciousness: “why a particular pattern of brain activity . . . maps to a particular kind of conscious experience.” This does not directly explain why consciousness exists in the first place (i.e., the hard problem), but the hope is that building more explanatory bridges between neuronal activity and different subjective experiences will diminish, if not dissolve, the need to answer the hard problem at all. In tackling this so-called real problem, perception takes a pivotal role in Seth’s thinking. He proposes that perception does not happen outside-in, with external physical signals being detected and processed to constitute our view of the world, but rather inside-out. According to Seth, our brains constantly make predictions about the causes of our sensory signals. Perception then “happens through a continual process of prediction error minimization.” What sounds technical should not conceal the magnitude of this claim: Seth proposes that we do not see, hear, or smell the world as it is, but rather that we live in what he calls a “controlled hallucination.” We only have an internal model (a “hallucination”) of the world and our bodies. This model is continuously updated and corrected (“controlled”) through new incoming signals. What we normally refer to as a “hallucination” is but a failure of the control step of this process. But Seth extends the role of prediction far beyond the perception of our environment and bodies. He sees our emotions as being “control-oriented perceptions which regulate [our] body’s” temperature, blood sugar, and other “essential variables.” Even the notion of our self is a prediction of our mind, one which, just as any prediction, can disintegrate to various degrees—most completely under the influence of large doses of psychedelics, or due to damage or disease. Lastly, Seth discusses the possibility of consciousness emerging in artificial intelligence. He argues that our brains’ principal function—to control our bodies’ essential variables—firmly connects our consciousness with our biology. However, the pivotal role that our biology plays in the structure of our minds does not rule out the possibility of artificial consciousness in principle. Seth thus suggests that it might require silicon-based minds to mimic certain aspects of our evolved embodied minds to become conscious. Despite much progress, the scientific field of consciousness is still in its infancy. We might hold a growing number of individual puzzle pieces and ideas but are likely still far from finding a single theoretical frame that can put them all together. What is exciting to the researcher might be frustrating to the novice. Each introductory text comes...

On the trail of a comet’s tail: A particle tracking algorithm for comet 67P/Churyumov-Gerasimenko

Context.During the post-perihelion phase of the European Space Agency’s Rosetta mission to comet67P, the Optical, Spectroscopic, and Infrared Remote Imaging System on board the spacecraft took numerous image sequences of the near-nucleus coma, with many showing the motion of individual pieces of debris ejected from active surface areas into space.Aims.We aim to track the motion of individual particles in these image sequences and derive their projected velocities and accelerations. This should help us to constrain their point of origin on the surface, understand the forces that influence their dynamics in the inner coma, and predict whether they will fall back to the surface or escape to interplanetary space.Methods.We have developed an algorithm that tracks the motion of particles appearing as point sources in image sequences. Our algorithm employs a point source detection software to locate the particles and then exploits the image sequences’ pair-nature to reconstruct the particle tracks and derive the projected velocities and accelerations. We also constrained the particle size from their brightness.Results.Our algorithm identified 2268 tracks in a sample image sequence. Manual inspection not only found that 1187 (∼52%) of them are likely genuine, but in combination with runs on simulated data it also revealed a simple criterion related to the completeness of a track to single out a large subset of the genuine tracks without the need for manual intervention. A tentative analysis of a small (n = 89) group of particles exemplifies how our data can be used, and provides first results on the particles’ velocity, acceleration, and radius distributions, which agree with previous work.