43,766 research outputs found

    Hull design and calculation of the propulsion plant of a freezer trawler of 640 m3

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    RESUMEN: El presente proyecto se redacta para la Escuela Técnica Superior de Náutica de la Universidad de Cantabria, donde se presenta como Trabajo de Fin de Grado, teniendo como objetivos fundamentales el diseño del casco y el cálculo de la planta propulsora de un buque arrastrero congelador factoría de 640 m3. En primer lugar, se diseña el casco del buque. Para ello, y por medio de una serie de cálculos empleando regresiones, se obtienen las dimensiones, de una forma aproximada, que debe tener el buque. A continuación, se realiza un estudio sobre dichas medidas, con el objeto de conseguir el buque más viable económicamente empleando un método basado en la combinación de dichas relaciones dimensionales, estableciendo así un límite superior e inferior y seleccionando la alternativa más económica. Partiendo de los datos de dicha alternativa, se modela el casco del buque y se realiza el alisado empleando los softwares MAXURF Modeler y ProSurf. Empleando el software MAXURF Stability, se calcula la resistencia al avance del casco, la cual se empleará para obtener la potencia que debe suministrar el motor principal del buque. Por último, se realiza una búsqueda en catálogos del motor que más se ajuste a las necesidades y se selecciona la línea de ejes, el alternador y la reductora que deberán ser instalados.ABSTRACT: This project has been drawn up for the School of Nautical Studies at the University of Cantabria, and is presented as an end of course project. The fundamental objectives are the hull design and calculation of the propulsión plant of a freezer trawler of 640 m3. First, the hull of the ship is designed. To do this, and through several calculations using regressions, the approximate dimensions that the vessel must have are obtained. Next, a study is carried out on these measures, in order to achieve the most economically viable vessel using a method based on the combination of dimensional relationships, establishing an upper and lower limit and selecting the most economical alternative. Based on the data of this alternative, the hull of the ship is modeled and smoothing is performed using the MAXURF Modeler and ProSurf software. Using the MAXURF Stability software, total resistance of the hull is calculated, which will be used to obtain the power required by the main engine of the ship. Finally, the most appropriate engine is searched in catalogs as well as the engine shaft, the alternator and the gearbox that must be installed.Grado en Ingeniería Marin

    Meso-scale FDM material layout design strategies under manufacturability constraints and fracture conditions

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    In the manufacturability-driven design (MDD) perspective, manufacturability of the product or system is the most important of the design requirements. In addition to being able to ensure that complex designs (e.g., topology optimization) are manufacturable with a given process or process family, MDD also helps mechanical designers to take advantage of unique process-material effects generated during manufacturing. One of the most recognizable examples of this comes from the scanning-type family of additive manufacturing (AM) processes; the most notable and familiar member of this family is the fused deposition modeling (FDM) or fused filament fabrication (FFF) process. This process works by selectively depositing uniform, approximately isotropic beads or elements of molten thermoplastic material (typically structural engineering plastics) in a series of pre-specified traces to build each layer of the part. There are many interesting 2-D and 3-D mechanical design problems that can be explored by designing the layout of these elements. The resulting structured, hierarchical material (which is both manufacturable and customized layer-by-layer within the limits of the process and material) can be defined as a manufacturing process-driven structured material (MPDSM). This dissertation explores several practical methods for designing these element layouts for 2-D and 3-D meso-scale mechanical problems, focusing ultimately on design-for-fracture. Three different fracture conditions are explored: (1) cases where a crack must be prevented or stopped, (2) cases where the crack must be encouraged or accelerated, and (3) cases where cracks must grow in a simple pre-determined pattern. Several new design tools, including a mapping method for the FDM manufacturability constraints, three major literature reviews, the collection, organization, and analysis of several large (qualitative and quantitative) multi-scale datasets on the fracture behavior of FDM-processed materials, some new experimental equipment, and the refinement of a fast and simple g-code generator based on commercially-available software, were developed and refined to support the design of MPDSMs under fracture conditions. The refined design method and rules were experimentally validated using a series of case studies (involving both design and physical testing of the designs) at the end of the dissertation. Finally, a simple design guide for practicing engineers who are not experts in advanced solid mechanics nor process-tailored materials was developed from the results of this project.U of I OnlyAuthor's request

    CM Mic and other ER UMa stars showing standstills

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    We analyzed All-Sky Automated Survey for Supernovae (ASAS-SN), Asteroid Terrestrial-impact Last Alert System (ATLAS) and Transiting Exoplanet Survey Satellite (TESS) observations of CM Mic and found that this object belongs to a small group of ER UMa stars showing standstills. In addition to typical ER UMa-type cycles, the object showed standstills between 2017 and 2019 July, and in 2022. The supercycles varied between 49 and 83 d. In 2015, the object showed outbursts with a cycle length of ~35 d. An analysis of TESS observations during the 2020 July outburst detected superhumps with a mean period of 0.080251(6) d (value after the full development of superhumps). We also studied other ER UMa stars showing standstills mainly using Zwicky Transient Facility (ZTF) data. DDE 48, MGAB-V728 and ZTF18abmpkbj mostly showed ER UMa-type supercycles but showed one or two standstills. MGAB-V3488 was mostly in ER UMa states with short (~25 d) supercycles in 2020-2022 similar to RZ LMi. This object also showed long standstills. PS1-3PI J181732.65+101954.6 showed ER UMa-type supercycles up to 2020 May and entered a long standstill. ZTF18abncpgs showed standstills most of the time, but also showed ER UMa-type supercycles occasionally between standstills. ZTF19aarsljl is a likely member of this group. MGAB-V284 showed a pattern similar to ER UMa stars showing standstills but with a longer time-scale of normal outbursts. This object seems to be an ER UMa star with standstills above the period gap. None of the objects we studied showed a superoutburst arising from a long standstill, as recorded in NY Ser in 2018, although the 2019 June-July superoutburst of PS1-3PI J181732.65+101954.6 might have been an exception.Comment: 33 pages, 20 figures, VSOLJ Variable Star Bulletin No. 11

    Fragmentation of the High-mass "Starless'' Core G10.21-0.31: a Coherent Evolutionary Picture for Star Formation

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    G10.21-0.31 is a 70 μ\mum-dark high-mass starless core (M>300M>300 M\mathrm{M_{\odot}} within r<0.15r<0.15 pc) identified in SpitzerSpitzer, HerschelHerschel, and APEX continuum surveys, and is believed to harbor the initial stages of high-mass star formation. We present ALMA and SMA observations to resolve the internal structure of this promising high-mass starless core. Sensitive high-resolution ALMA 1.3 mm dust continuum emission reveals three cores of mass ranging 11-18 M\mathrm{M_{\odot}}, characterized by a turbulent fragmentation. Core 1, 2, and 3 represent a coherent evolution at three different evolutionary stages, characterized by outflows (CO, SiO), gas temperature (H2CO\mathrm{H_2CO}), and deuteration (N2D+/N2H+\mathrm{N_2D^+/N_2H^+}). We confirm the potential to form high-mass stars in G10.21 and explore the evolution path of high-mass star formation. Yet, no high-mass prestellar core is present in G10.21. This suggests a dynamical star formation where cores grow in mass over time.Comment: 30 pages, 13 figures; accepted for publication in Ap

    unTimely: a Full-sky, Time-domain unWISE Catalog

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    We present the unTimely Catalog, a deep time-domain catalog of detections based on Wide-field Infrared Survey Explorer (WISE) and NEOWISE observations spanning the 2010 through 2020 time period. Detections are extracted from “time-resolved unWISE coadds,” which stack together each biannual sky pass of WISE imaging to create a set of ∼16 all-sky maps (per band), each much deeper and cleaner than individual WISE exposures. unTimely incorporates the W1 (3.4 μ m) and W2 (4.6 μ m) channels, meaning that our data set effectively consists of ∼32 full-sky unWISE catalogs. We run the crowdsource crowded-field point-source photometry pipeline (Schlafly et al. 2018) on each epochal coadd independently, with low detection thresholds: S/N = 4.0 (2.5) in W1 (W2). In total, we tabulate and publicly release 23.5 billion (19.9 billion) detections at W1 (W2). unTimely is ∼1.3 mag deeper than the WISE/NEOWISE Single Exposure Source Tables near the ecliptic, with further enhanced depth toward higher ecliptic latitudes. The unTimely Catalog is primarily designed to enable novel searches for faint, fast-moving objects, such as Y dwarfs and/or late-type (T/Y) subdwarfs in the Milky Way’s thick disk or halo. unTimely will also facilitate other time-domain science applications, such as all-sky studies of quasar variability at mid-infrared wavelengths over a decade-long time baseline

    EMPRESS. XI. SDSS and JWST Search for Local and z~4-5 Extremely Metal-Poor Galaxies (EMPGs): Clustering and Chemical Properties of Local EMPGs

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    We search for local extremely metal-poor galaxies (EMPGs), selecting photometric candidates by broadband color excess and machine-learning techniques with the SDSS photometric data. After removing stellar contaminants by shallow spectroscopy with Seimei and Nayuta telescopes, we confirm that three candidates are EMPGs with 0.05--0.1 ZZ_\odot by deep Magellan/MagE spectroscopy for faint {\sc[Oiii]}λ\lambda4363 lines. Using a statistical sample consisting of 105 spectroscopically-confirmed EMPGs taken from our study and the literature, we calculate cross-correlation function (CCF) of the EMPGs and all SDSS galaxies to quantify environments of EMPGs. Comparing another CCF of all SDSS galaxies and comparison SDSS galaxies in the same stellar mass range (107.0108.4M10^{7.0}-10^{8.4} M_\odot), we find no significant (>1σ>1\sigma) difference between these two CCFs. We also compare mass-metallicity relations (MZRs) of the EMPGs and those of galaxies at zz\sim 0--4 with a steady chemical evolution model and find that the EMPG MZR is comparable with the model prediction on average. These clustering and chemical properties of EMPGs are explained by a scenario of stochastic metal-poor gas accretion on metal-rich galaxies showing metal-poor star formation. Extending the broadband color-excess technique to a high-zz EMPG search, we select 17 candidates of zz\sim 4--5 EMPGs with the deep (30\simeq30 mag) near-infrared JWST/NIRCam images obtained by ERO and ERS programs. We find galaxy candidates with negligible {\sc[Oiii]}λλ\lambda\lambda4959,5007 emission weaker than the local EMPGs and known high-zz galaxies, suggesting that some of these candidates may fall in 0--0.01 ZZ_\odot, which potentially break the lowest metallicity limit known to date

    GEE Training Manual on Use of Earth Observation data and Google Earth Engine monitoring and early warning of floods and droughts in Zambia

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    This training manual supported participants in learning the pre-processing tool to provide the user with enhanced time-series processing capabilities and access to various open-source satellite data, learning basic scripts in Google Earth Engine for activities related to floods and drought in showcasing the application of water resource management. Specifically, the experts will give more focus to Google’s Earth Engine platform to showcase large- and small-scale scientific analysis and visualization of geospatial datasets. The codes and step by step procedure are given in the manual

    Building data management capabilities to address data protection regulations: Learnings from EU-GDPR

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    The European Union’s General Data Protection Regulation (EU-GDPR) has initiated a paradigm shift in data protection toward greater choice and sovereignty for individuals and more accountability for organizations. Its strict rules have inspired data protection regulations in other parts of the world. However, many organizations are facing difficulty complying with the EU-GDPR: these new types of data protection regulations cannot be addressed by an adaptation of contractual frameworks, but require a fundamental reconceptualization of how companies store and process personal data on an enterprise-wide level. In this paper, we introduce the resource-based view as a theoretical lens to explain the lengthy trajectories towards compliance and argue that these regulations require companies to build dedicated, enterprise-wide data management capabilities. Following a design science research approach, we propose a theoretically and empirically grounded capability model for the EU-GDPR that integrates the interpretation of legal texts, findings from EU-GDPR-related publications, and practical insights from focus groups with experts from 22 companies and four EU-GDPR projects. Our study advances interdisciplinary research at the intersection between IS and law: First, the proposed capability model adds to the regulatory compliance management literature by connecting abstract compliance requirements to three groups of capabilities and the resources required for their implementation, and second, it provides an enterprise-wide perspective that integrates and extends the fragmented body of research on EU-GDPR. Practitioners may use the capability model to assess their current status and set up systematic approaches toward compliance with an increasing number of data protection regulations
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