4,522 research outputs found

    Simulation of metal powder packing behaviour in laser-based powder bed fusion

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    Laser-based powder bed fusion (L-PBF) is a method of additive manufacturing, in which metal powder is fused into solid parts, layer by layer. L-PBF shows high promise for manufacture of functional Tungsten parts, but the development of Tungsten powder feedstock for L-PBF processing is demanding and expensive. Therefore, computer simulation is explored as a possible tool for Tungsten powder feedstock development at EOS Finland Oy, with whom this thesis was made. The aim of this thesis was to develop a simulation model of the recoating process of an EOS M 290 L-PBF system, as well as a validation method for the simulation. The validated simulation model can be used to evaluate the applicability of the used simulation software (FLOW-3D DEM) in powder material development, and possibly use the model as a platform for future application with Tungsten powder. In order to reduce complexity and uncertainties, the irregular Tungsten powder is not yet simulated, and a well-known, spherical EOS IN718 powder feedstock was used instead. The validation experiment is based on building a low, enclosed wall using the M 290 L-PBF system. Recoated powder is trapped inside as the enclosure is being built, making it possible to remove the sampled powder from a known volume. This enables measuring the powder packing density (PD) of the powder bed. The experiment was repeated five times and some sources of error were also quantified. Average PD was found to be 52 % with a standard deviation of 0.2 %. The simulation was modelled after the IN718 powder and corresponding process used in the M 290 system. Material-related input values were found by dynamic image analysis, pycnometry, rheometry, and from literature. PD was measured with six different methods, and the method considered as most analogous to the practical validation experiment yielded a PD of 52 %. Various particle behavior phenomena were also observed and analyzed. Many of the powder bed characterization methods found in literature were not applicable to L-PBF processing or were not representative of the simulated conditions. Many simulation studies were also found to use no validation, or used a validation method which is not based on the investigated phenomena. The validation model developed in this thesis accurately represents the simulated conditions and is found to produce reliable and repeatable results. The simulation model was parametrized with values acquired from practical experiments or literature and closely matched the validation experiment, and could therefore be considered a truthful representation of the powder recoating process of an EOS M 290. The model can be used as a platform for future development of Tungsten powder simulation

    Comparing the Performance of Initial Coin Offerings to Crowdfunded Equity Ventures

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    Uncertainty in markets increases the likelihood of market failure due to volatility and suboptimal functioning. While initial coin offerings (ICOs) and crowdfunded equity (CFE) offerings may improve functioning in growing markets, there is a lack of knowledge and understanding pertaining to the relative efficiency and behavior of ICO markets compared to CFE markets, potentially perpetuating and thwarting the various communities they are intended to serve. The purpose of this correlational study was to compare a group of ICOs with a group of CFE offerings to identify predictive factors of funding outcomes related to both capital offering types. Efficient market hypothesis was the study’s theoretical foundation, and analysis of variance was used to answer the research question, which examined whether capital offering type predicted the amount of funds raised while controlling for access to the offering companies’ secondary control factors: historical financial data, pro forma financial projections, detailed product descriptions, video of product demonstrations, company website, company history, company leadership, and company investors. Relying on a random sample of 115 campaigns (84 ICOs and 31 CFE) from websites ICOdrops.com, localstake.com, fundable.com, and mainvest.com, results showed differences in mean funds raised between CFEs and ICOs (346,075comparedto346,075 compared to 4,756,464, respectively). ANOVA results showed no single secondary control factors and only one two-factor interaction (company leadership and company investors) influenced mean funds raised. This study may contribute to positive social change by informing best practices among market participants including entrepreneurs, regulators, scholars, and investors

    A Cybersecurity review of Healthcare Industry

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    Antecedentes La ciberseguridad no es un concepto nuevo de nuestros días. Desde los años 60 la ciberseguridad ha sido un ámbito de discusión e investigación. Aunque los mecanismos de defensa en materia de seguridad han evolucionado, las capacidades del atacante también se han incrementado de igual o mayor manera. Prueba de este hecho es la precaria situación en materia de ciberseguridad de muchas empresas, que ha llevado a un incremento de ataques de ransomware y el establecimiento de grandes organizaciones criminales dedicadas al cibercrimen. Esta situación, evidencia la necesidad de avances e inversión en ciberseguridad en multitud de sectores, siendo especialmente relevante en la protección de infraestructuras críticas. Se conoce como infraestructuras críticas aquellas infraestructuras estratégicas cuyo funcionamiento es indispensable y no permite soluciones alternativas, por lo que su perturbación o destrucción tendría un grave impacto sobre los servicios esenciales. Dentro de esta categorización se encuentran los servicios e infraestructuras sanitarias. Estas infraestructuras ofrecen un servicio, cuya interrupción conlleva graves consecuencias, como la pérdida de vidas humanas. Un ciberataque puede afectar a estos servicios sanitarios, llevando a su paralización total o parcial, como se ha visto en recientes incidentes, llevando incluso a la pérdida de vidas humanas. Además, este tipo de servicios contienen multitud de información personal de carácter altamente sensible. Los datos médicos son un tipo de datos con alto valor en mercados ilegales, y por tanto objetivos de ataques centrados en su robo. Por otra parte, se debe mencionar, que al igual que otros sectores, actualmente los servicios sanitarios se encuentran en un proceso de digitalización. Esta evolución, ha obviado la ciberseguridad en la mayoría de sus desarrollos, contribuyendo al crecimiento y gravedad de los ataques previamente mencionados. - Metodología e investigación El trabajo presentado en esta tesis sigue claramente un método experimental y deductivo. Está investigación se ha centrado en evaluar el estado de la ciberseguridad en infraestructuras sanitarias y proponer mejoras y mecanismos de detección de ciberataques. Las tres publicaciones científicas incluidas en esta tesis buscan dar soluciones y evaluar problemas actuales en el ámbito de las infraestructuras y sistemas sanitarios. La primera publicación, 'Mobile malware detection using machine learning techniques', se centró en desarrollar nuevas técnicas de detección de amenazas basadas en el uso de tecnologías de inteligencia artificial y ‘machine learning’. Esta investigación fue capaz de desarrollar un método de detección de aplicaciones potencialmente no deseadas y maliciosas en entornos móviles de tipo Android. Además, tanto en el diseño y creación se tuvo en cuenta las necesidades específicas de los entornos sanitarios. Buscando ofrecer una implantación sencilla y viable de acorde las necesidades de estos centros, obteniéndose resultados satisfactorios. La segunda publicación, 'Interconnection Between Darknets', buscaba identificar y detectar robos y venta de datos médicos en darknets. El desarrollo de esta investigación conllevó el descubrimiento y prueba de la interconexión entre distintas darknets. La búsqueda y el análisis de información en este tipo de redes permitió demostrar como distintas redes comparten información y referencias entre ellas. El análisis de una darknet implica la necesidad de analizar otras, para obtener una información más completa de la primera. Finalmente, la última publicación, 'Security and privacy issues of data-over-sound technologies used in IoT healthcare devices' buscó investigar y evaluar la seguridad de dispositivos médicos IoT ('Internet of Things'). Para desarrollar esta investigación se adquirió un dispositivo médico, un electrocardiógrafo portable, actualmente en uso por diversos hospitales. Las pruebas realizadas sobre este dispositivo fueron capaces de descubrir múltiples fallos de ciberseguridad. Estos descubrimientos evidenciaron la carencia de certificaciones y revisiones obligatorias en materia ciberseguridad en productos sanitarios, comercializados actualmente. Desgraciadamente la falta de presupuesto dedicado a investigación no permitió la adquisición de varios dispositivos médicos, para su posterior evaluación en ciberseguridad. - Conclusiones La realización de los trabajos e investigaciones previamente mencionadas permitió obtener las siguientes conclusiones. Partiendo de la necesidad en mecanismos de ciberseguridad de las infraestructuras sanitarias, se debe tener en cuenta su particularidad diseño y funcionamiento. Las pruebas y mecanismos de ciberseguridad diseñados han de ser aplicables en entornos reales. Desgraciadamente actualmente en las infraestructuras sanitarias hay sistemas tecnológicos imposibles de actualizar o modificar. Multitud de máquinas de tratamiento y diagnostico cuentan con software y sistemas operativos propietarios a los cuales los administradores y empleados no tienen acceso. Teniendo en cuenta esta situación, se deben desarrollar medidas que permitan su aplicación en este ecosistema y que en la medida de los posible puedan reducir y paliar el riesgo ofrecido por estos sistemas. Esta conclusión viene ligada a la falta de seguridad en dispositivos médicos. La mayoría de los dispositivos médicos no han seguido un proceso de diseño seguro y no han sido sometidos a pruebas de seguridad por parte de los fabricantes, al suponer esto un coste directo en el desarrollo del producto. La única solución en este aspecto es la aplicación de una legislación que fuerce a los fabricantes a cumplir estándares de seguridad. Y aunque actualmente se ha avanzado en este aspecto regulatorio, se tardaran años o décadas en sustituir los dispositivos inseguros. La imposibilidad de actualizar, o fallos relacionados con el hardware de los productos, hacen imposible la solución de todos los fallos de seguridad que se descubran. Abocando al reemplazo del dispositivo, cuando exista una alternativa satisfactoria en materia de ciberseguridad. Por esta razón es necesario diseñar nuevos mecanismos de ciberseguridad que puedan ser aplicados actualmente y puedan mitigar estos riesgos en este periodo de transición. Finalmente, en materia de robo de datos. Aunque las investigaciones preliminares realizadas en esta tesis no consiguieron realizar ningún descubrimiento significativo en el robo y venta de datos. Actualmente las darknets, en concreto la red Tor, se han convertido un punto clave en el modelo de Ransomware as a Business (RaaB), al ofrecer sitios webs de extorsión y contacto con estos grupos

    It's (DOM) Clobbering Time: Attack Techniques, Prevalence, and Defenses

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    DOM Clobbering is a type of code-less injection attack where attackers insert a piece of non-script, seemingly benign HTML markup into a webpage and transform it to executable code by exploiting the unforeseen interactions between JavaScript code and the runtime environment. The attack techniques, browser behaviours, and vulnerable code patterns that enable DOM Clobbering has not been studied yet, and in this paper, we undertake one of the first evaluations of the state of DOM Clobbering on the Web platform. Starting with a comprehensive survey of existing literature and dynamic analysis of 19 different mobile and desktop browsers, we systematize DOM Clobbering attacks, uncovering 31.4K distinct markups that use five different techniques to unexpectedly overwrite JavaScript variables in at least one browser. Then, we use our systematization to identify and characterize program instructions that can be overwritten by DOM Clobbering, and use it to present TheThing, an automated system that detects clobberable data flows to security-sensitive instructions. We instantiate TheThing on the top of the Tranco top 5K sites, quantifying the prevalence and impact of DOM Clobbering in the wild. Our evaluation uncovers that DOM Clobbering vulnerabilities are ubiquitous, with a total of 9,467 vulnerable data flows across 491 affected sites, making it possible to mount arbitrary code execution, open redirections, or client-side request forgery attacks also against popular websites such as Fandom, Trello, Vimeo, TripAdvisor, WikiBooks and GitHub, that were not exploitable through the traditional attack vectors. Finally, in this paper, we also evaluate the robustness of the existing countermeasures, such as HTML sanitizers and Content Security Policy, against DOM Clobbering

    Advances in Binders for Construction Materials

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    The global binder production for construction materials is approximately 7.5 billion tons per year, contributing ~6% to the global anthropogenic atmospheric CO2 emissions. Reducing this carbon footprint is a key aim of the construction industry, and current research focuses on developing new innovative ways to attain more sustainable binders and concrete/mortars as a real alternative to the current global demand for Portland cement.With this aim, several potential alternative binders are currently being investigated by scientists worldwide, based on calcium aluminate cement, calcium sulfoaluminate cement, alkali-activated binders, calcined clay limestone cements, nanomaterials, or supersulfated cements. This Special Issue presents contributions that address research and practical advances in i) alternative binder manufacturing processes; ii) chemical, microstructural, and structural characterization of unhydrated binders and of hydrated systems; iii) the properties and modelling of concrete and mortars; iv) applications and durability of concrete and mortars; and v) the conservation and repair of historic concrete/mortar structures using alternative binders.We believe this Special Issue will be of high interest in the binder industry and construction community, based upon the novelty and quality of the results and the real potential application of the findings to the practice and industry

    Weather or not? The role of international sanctions and climate on food prices in Iran

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    IntroductionThe scarcity of resources have affected food production, which has challenged the ability of Iran to provide adequate food for the population. Iterative and mounting sanctions on Iran by the international community have seriously eroded Iran's access to agricultural technology and resources to support a growing population. Limited moisture availability also affects Iran's agricultural production. The aim of this study was to analyze the influence of inflation, international sanctions, weather disturbances, and domestic crop production on the price of rice, wheat and lentils from 2010 to 2021 in Iran.MethodData were obtained from the statistical yearbooks of the Ministry of Agriculture in Iran, Statistical Center of Iran, and the Central Bank of Iran. We analyzed econometric measures of food prices, including CPI, food inflation, subsidy reform plan and sanctions to estimate economic relationships. After deflating the food prices through CPI and detrending the time series to resolve the non-linear issue, we used monthly Climate Hazards group Infrared Precipitation with Stations (CHIRPS) precipitation data to analyze the influence of weather disturbances on food prices.Results and discussionThe price of goods not only provides an important indicator of the balance between agricultural production and market demand, but also has strong impacts on food affordability and food security. This novel study used a combination of economic and climate factors to analyze the food prices in Iran. Our statistical modeling framework found that the monthly precipitation on domestic food prices, and ultimately food access, in the country is much less important than the international sanctions, lowering Iran's productive capability and negatively impacting its food security

    Anime Studies: media-specific approaches to neon genesis evangelion

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    Anime Studies: Media-Specific Approaches to Neon Genesis Evangelion aims at advancing the study of anime, understood as largely TV-based genre fiction rendered in cel, or cel-look, animation with a strong affinity to participatory cultures and media convergence. Making Neon Genesis Evangelion (Shin Seiki Evangerion, 1995-96) its central case and nodal point, this volumen forground anime as a media with clearly recognizable aesthetic properties, (sub)cultural affordances and situated discourses

    International Academic Symposium of Social Science 2022

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    This conference proceedings gathers work and research presented at the International Academic Symposium of Social Science 2022 (IASSC2022) held on July 3, 2022, in Kota Bharu, Kelantan, Malaysia. The conference was jointly organized by the Faculty of Information Management of Universiti Teknologi MARA Kelantan Branch, Malaysia; University of Malaya, Malaysia; Universitas Pembangunan Nasional Veteran Jakarta, Indonesia; Universitas Ngudi Waluyo, Indonesia; Camarines Sur Polytechnic Colleges, Philippines; and UCSI University, Malaysia. Featuring experienced keynote speakers from Malaysia, Australia, and England, this proceeding provides an opportunity for researchers, postgraduate students, and industry practitioners to gain knowledge and understanding of advanced topics concerning digital transformations in the perspective of the social sciences and information systems, focusing on issues, challenges, impacts, and theoretical foundations. This conference proceedings will assist in shaping the future of the academy and industry by compiling state-of-the-art works and future trends in the digital transformation of the social sciences and the field of information systems. It is also considered an interactive platform that enables academicians, practitioners and students from various institutions and industries to collaborate

    Strawberry Production Guide For the Northeast, Midwest, and Eastern Canada 2nd Edition

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    This guide is intended as a comprehensive resource for both novice and experienced strawberry growers in northeastern North America. It provides information on all aspects of strawberry culture. The second edition has been updated and revised throughout, and includes expanded and new information on variety selection (Ch. 3), production systems (Ch. 4), harvesting, handling and transportation (Ch. 12), marketing (Ch. 13) and budgeting/economics (Ch. 14). In addition, a new section on diagnosing problems in strawberry plantings has been added (Ch. 15)
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