Parallel Tracks Research Articles

Discontinuity of overhanging melt track in selective laser melting process

This study shares a side-by-side numerical and experimental examination on the features of overhanging structure in the SLM process. The simulation model was achieved by incorporating Fresnel reflections in the laser beam through the ray-tracing model. The CFD model was employed to investigate different overhanging situations, including perpendicular and parallel overhanging melt tracks on a cuboid block, as well as parallel melt tracks on an inclined block. The process parameters are found to strongly affect the surface morphologies of the overhanging melt track where voids caused by interfacial instability and geometrical defects namely discontinuities were observed. The subsequent defects caused by the discontinuity have also been investigated in both simulation and experiment. In the range of this study, it found that high laser power alleviates the discontinuity phenomenon of the overhanging melt track. However, by applying high laser power at high energy density, the high value of melt pool depth was formed, causing warpage to the overhanging printed part. Nevertheless, employing high laser power while maintaining low energy density can eliminate phenomenon such as irregular pores, partially-melted powder, deep melt pool formation and geometrical inaccuracy.

PDCAT: a framework for fast, robust, and occlusion resilient fiducial marker tracking

Square binary patterns have become the de facto fiducial marker for most computer vision applications. Existing tracking solutions suffer a number of limitations, such as the low frame-rate and sensitivity to partial occlusions. This work aims at overcoming these limitations, by exploiting temporal information in video-sequences. We propose a parallel detection, compensation and tracking (PDCAT) framework, which can be integrated into any binary marker system. Our solution is capable of recovering markers even when they become mostly occluded. Furthermore, the low processing time of the tracking task makes PDCAT more than an order of magnitude faster than a track-by-detect solution. This is particularly important for embedded computer vision applications, wherein the detection run at a very low frame rate. In the experiments conducted on an embedded computer, the processing frame rate of the track-by-detect solution was merely 11 FPS. Our solution, on the other hand, was capable of processing more than 100 FPS.

New York University Grossman School of Medicine.

New York University Grossman School of Medicine.

Penn State College of Medicine.

Penn State College of Medicine.

University of Nebraska Medical Center College of Medicine.

University of Nebraska Medical Center College of Medicine.

Hackensack Meridian School of Medicine at Seton Hall University.

Hackensack Meridian School of Medicine at Seton Hall University.

Western Michigan University Homer Stryker M.D. School of Medicine.

Western Michigan University Homer Stryker M.D. School of Medicine.

Texas Tech University Health Sciences Center School of Medicine, Lubbock.

Texas Tech University Health Sciences Center School of Medicine, Lubbock.

Texas A&M University College of Medicine.

Texas A&M University College of Medicine.

Charles E. Schmidt College of Medicine at Florida Atlantic University.

Charles E. Schmidt College of Medicine at Florida Atlantic University.

McGovern Medical School at The University of Texas Health Science Center at Houston.

McGovern Medical School at The University of Texas Health Science Center at Houston.

Western University Schulich School of Medicine & Dentistry.

Western University Schulich School of Medicine & Dentistry.

University of South Alabama College of Medicine.

University of South Alabama College of Medicine.

The role of reconstructive surgery after soft tissue sarcoma resection

Soft tissue sarcomas are rare malignant tumors with pejorative prognosis. They require a multidisciplinary approach in a specialized hospital belonging to the NetSarc network in France. In all cases treated with curative intent, the objective of excision surgery is to achieve wide, microscopically negative margins (R0 according to the UICC classification). When growing on a limb, sarcomas may threaten functionally relevant structures and even lead to amputation. Nowadays, when combined with radiation therapy, wide exeresis limb-sparing surgery is achievable in 90 to 95% of the cases, of which 25% will nevertheless require reconstructive surgery to preserve the limb, to limit postoperative complications and to manage possible sequelae. Progress in reparative surgery, particularly in microsurgery, has helped not only to improve limb salvage rates but also to create wider margins without altering oncologic goals of curative resection. After determining the range of resection, reconstructive surgery should be tailored to address the tissue defect. The converse is to be strongly discouraged. The extent of resection must not be compromised or reduced in order to facilitate reconstructive surgery. A plastic surgeon must master all the flap techniques, including microsurgery, while taking into account the impact of preoperative and postoperative radiation therapy on previously irradiated tissues or on wounds requiring adjuvant therapy. Recent developments, especially as regards perforator flaps, have helped to enhanced the quality of reconstruction procedure while reducing donor site morbidity. In our experience, perforator flaps are a workhorse in reconstructive surgeries subsequent to soft tissue sarcoma of the extremities. On a parallel track, lipofilling (otherwise known as fat grafting or fat transfer) has become the first-line treatment for patients with post-surgical functional or cosmetic sequalae. It is performed after long-term follow-up during disease-free survival. Strict clinical examination and MRI are mandatory prior to programming any local procedure. Usually, three to four sessions of fat grafting are needed to enhance local trophicity or the cosmetic aspect. Sequalae treatments are of great interest in terms of psychological as well as functional outcome.

The parallel tracks of kHz QPOs in low-mass X-ray binary 4U 1728−34: explorer of the bimodal accretion modes

ABSTRACT Parallel tracks in the relation between the lower kilohertz quasi-periodic oscillation (kHz QPO) frequency ν1 and the X-ray intensity I have been observed in the neutron star low-mass X-ray binary (NS-LMXB) 4U 1728−34, and we try to ascribe these phenomena to the bimodal accretion modes, i.e. the disc accretion and radial accretion. For the source with one constant radial accretion rate $\dot{M}_{\rm r}$, as the increase of the disc accretion rate $\dot{M}_{\rm d}$, the NS magnetosphere-disc radius can shrink from ∼18 to ∼16 km, while ν1 increases from ∼670 to ∼870 Hz. Then, due to the increase of the kHz QPO frequency and total X-ray intensity Itot, the source will trace out an oblique track in ν1–I relation. While, if the source enters another constant radial accretion rate due to the variation of the accretion environment, the increase of the disc accretion rate can arise another parallel track in ν1–I relation. Finally, the reliability of the theoretical assumptions, the variability of the accretion radius and accretion rate, as well as the dependence of the two accretion modes, are also investigated and discussed.

Ecological characterization of cold-seep epifauna in the South China Sea

Site F, an active cold seep situated on the northeastern continental slope of the South China Sea (SCS), has not been systematically surveyed since its first discovery in 2007. Here we report the results of a ROV transect survey of this cold seep conducted in 2018, which mapped the distribution of the substrates and quantified epifauna along parallel dive tracks. The site, measuring 180 m × 180 m, is characterized by a central part of authigenic carbonate outcrops with crevices releasing gas bubbles, which support high densities of bathymodiolin mussels Gigantidas platifrons (up to 273 individuals m−2) and galatheid squat lobsters Shinkaia crosnieri (up to 300 individuals m−2). On more condensed carbonate crusts, G. platifrons and the munidopsid squat lobsters Munidopsis spp. are present at low densities. The outskirts of the site are dominated by soft sediment, with bacterial mats and sparsely distributed G. platifrons and their shells, as well as the vestimentiferan tubeworm Paraescarpia echinospica. Sampling in various locations of the cold seep yields 10 new records of epibenthic animals as determined by watching the captured videos, morphological analysis as well as sequencing the COI and 16S rRNA gene sequences. Stable isotope analysis showed that biogenic methane is the main carbon source for most of the macrobenthos in this community. Many of these SCS cold seep macrobenthos have been reported from hydrothermal vents of the Okinawa Trough, indicating high connectivity between the two chemosynthesis-based communities in the Western Pacific.

A dual-track transition to global carbon pricing

ABSTRACT Unilateral climate policies have been unable to achieve intended emissions reductions. We argue that international harmonization of climate policy beyond the Paris Agreement is the only way forward and that global carbon pricing, either through a tax or market, is the best available instrument to manage this. A foundation has already been laid, as current carbon pricing initiatives cover about 20% of global CO2 emissions. Since it limits free-riding by countries/jurisdictions, global carbon pricing is, in principle, behaviourally easier to negotiate than other instruments, such as emission targets or technical standards. To overcome political resistance, we propose a dynamic strategy consisting of two parallel tracks and five transition phases. The first track entails assembly of a carbon-pricing coalition that expands over time and exerts moral and economic pressure on non-members to join. The second track involves refocusing UN intergovernmental climate change negotiations on carbon pricing, potentially involving initially heterogeneous prices reflecting distinct income levels of countries, which then gradually converge. The dual tracks are designed to reinforce one another, increasing the likelihood of a successful outcome. The proposal results in a transition trajectory consisting of two interactive tracks and five phases, with specific attention to inequity within and among countries. We illustrate how such an approach could function with either a carbon tax or market. Key policy insights International harmonization of climate policies is required to achieve the deep cuts in emissions needed to meet the Paris Agreement’s 2°C or 1.5°C target. A focus on carbon pricing – either through taxation or emissions trading – has multiple strengths: it can be easily compared and harmonized among countries; it can be gradually strengthened over time; it moderates freeriding and fear of competitiveness losses; and it automatically generates revenues to compensate low-income households and countries. Formation of a carbon-pricing coalition would enable such a group to speak with a single, powerful voice at UN climate change conferences. It would put economic and moral pressure on non-members, stimulating them to join and show a constructive attitude in ongoing UN climate change negotiations.

The Photographic Gaze Meets the Medical Gaze: Two Cross-Dressing Men in Christer Strömholm’s Place Blanche

In 1963, Christer Strömholm photographed the cross-dressing men Zizou and Carla on successive days in a Paris bar. The images are unique in Strömholm’s Place Blanche archive in that in one photograph Zizou is the “man” and Carla the “woman,” and in the other they switch. Who were Zizou and Carla? Strömholm’s captions for the images do not say. But two years after he photographed them the men were interviewed by a medical school Ph.D. student for a thesis on trans and gender non-conforming prostitutes in Paris. Denise Fidanza’s completed thesis contains detailed summaries of the men’s elicited self-stories. What can be learned about Zizou and Carla by comparing the photographic and verbal evidence? To what extent do the sources align? My analysis reveals that the information conveyed by Strömholm’s photographs and Fidanza’s interviews exists on largely parallel tracks. Indeed, given that the men are identified only by aliases, without the corroborating visual evidence of a distinctive tattoo on Carla’s left arm and a small photograph of Zizou in Fidanza’s thesis, a conclusive match would be impossible. Considered together, Strömholm’s photographs and Fidanza’s interviews provide rich insights into the lives of two marginalized queer men in 1960s Paris.

A Distributed Approach for the Implementation of Geometric Reconstruction-Based Visual SLAM Systems

SUMMARYVisual simultaneous localization and mapping (VSLAM) is a relevant solution for vehicle localization and mapping environments. However, it is computationally expensive because it demands large computational effort, making it a non-real-time solution. The VSLAM systems that employ geometric reconstructions are based on the parallel processing paradigm developed in the Parallel Tracking and Mapping (PTAM) algorithm. This type of system was created for processors that have exactly two cores. The various SLAM methods based on the PTAM were also not designed to scale to all the cores of modern processors nor to function as a distributed system. Therefore, we propose a modification to the pipeline for the execution of well-known VSLAM systems so that they can be scaled to all available processors during execution, thereby increasing their performance in terms of processing time. We explain the principles behind this modification via a study of the threads in the SLAM systems based on PTAM. We validate our results with experiments describing the behavior of the original ORB-SLAM system and the modified version.

Christian Education and Spiritual Formation: Recent History and Future Prospects

Throughout the 1980s and 1990s, Christian education and spiritual formation existed in an uneasy tension, running on parallel tracks but also developing mutual points of intersection. This article traces the growing connections between these movements in the last two decades of the twentieth century, the changing emphases in this relationship since 2000, and the need for further cross-fertilization between the two fields as ministries face the challenges of the twenty-first century.