Multi-axial fatigue strength of structural bolts in slip-critical connections under combined cyclic axial and shear demands

2018 Summer.Includes bibliographical references.High-Strength bolts are used extensively in structures and are regarded as the better option for connections subjected to fatigue as compared to welds and rivets. Studies have shown the superior resistance to fatigue and conclude that it should not be an issue when a bolt is properly pre-tensioned. Nevertheless, a recent application of properly pre-tensioned bolts subjected to shear stress reversals shows extensive fatigue cracking and total severing of up to 50% of the bolts in the connections. Sufficient evidence, based on experimental testing and field observations, exist to suggest the possibility of fully pre-tensioned bolts coming loose due to shear stress reversals. The problem of transverse vibrational loosening of bolts has been extensively researched as well as the issue of bolt fatigue. Only recently have they been considered together although no studies of this interaction have been done on high-strength bolts. Certain mechanisms mark the onset of bolt loosening and fatigue when bolts are subjected to cyclic shear or shear combined with tension. In this study, causes of bolt loosening and fatigue failure of bolted connections are explored. Especially the study pertains to structural bolts that are subjected to cyclic loads in multiple directions with shear reversals, which are typical of mitre gate to pintle socket connections. Certain mechanisms mark the onset of bolt loosening and fatigue when bolts are subjected to cyclic shear or shear combined with tension. The actual mechanisms and limits at which this occurs are explored in the literature and experimentally and recommendations are provided

Photochemical cross-linking study of polymers containing diacetylene groups in their main chain and azobenzene compounds as pendant groups

Photochemical cross-linking studies at different temperatures (room temperature, Tg and maximum exothermal of crosslinking peak) are shown for three series of polymers containing diacetylene-groups in the main chain and polar chromophores derived from benzene, azo- and di-azobenzene, as pendant groups. We establish the optimal irradiation time and temperature that permit them being poled and cross-linked with minimal dye-degradation. The degradation process was followed by a diminution of the respective maximum absorption peak. These conditions could extend the mean life-time of the second order nonlinear optical properties, studied previously. Photochemical cross-linking at each polymer´s Tg (50-130°C) was the most convenient process. It took less than 10 min and was monitored by IR spectroscop

Mexican Organizations: Alignment, ICTs and Leadership

Regardless of their classification and size, organizations face challenges that require the use of Information and Communication Technologies (ICTs) in order to overcome them. Once organizations identify and create their strategy, organization’s strategy alignment with ICTs becomes a necessity. Organizations’ management has different leadership styles that impact their outcomes; in addition, could influence such alignment. Mexican organizations, like their counterparts in other countries, implement controls for their operations. These controls demand strong support of tools that involve ICTs. Consequently, a strong differentiator is the adoption of ICTs that support their substantive work, regardless of its size. What does impact these organizations is the destination given to the investment in ICTs to support their processes. Past research in the strategic alignment of ICTs has made significant progress since the emergence of the Strategic Alignment Model (Henderson and Venkatraman 1993). Talon et al. (2016) proposed an approach, in which the alignment between the ICTs and the organizations’ objectives is given at the process level: lack of ICT support for critical activities in a specific process (ICT Deficit), ICTs fully support the key processes/macroprocesses (Alignment of ICTs), and finally surplus ICT resources (ICT surplus). The latter approach is what the present study uses for alignment measurement Goleman (2000) proposes six styles of leadership, coercive, authoritative, affiliative, democratic, pacesetting and coaching. He argues that, taken individually, they seem to have a unique and direct impact on the work climate of a company, division or team and, in turn, on financial performance. Furthermore, he believes that leaders who used styles that positively affected the climate had markedly better financial outcomes than those who did not. The main argument underlying the studies discussed previously is that organizations will function well when the key ICT resources, infrastructure, associated technical/administrative skills, and knowledge assets are aligned with the organizations’ strategy. The main objective of the present research is to identify whether such alignment is oriented to the macroprocesses/key processes of the organization. Those that are key to the type of strategy defined by the organization, and measure its deficit, alignment or surplus, whether they are applicable. In addition, intends to identify whether the leadership style in the organization influences the degree of alignment and execution of such strategy

ALMA polarimetry measures magnetically aligned dust grains in the torus of NGC 1068

The obscuring structure surrounding active galactic nuclei (AGN) can be explained as a dust and gas flow cycle that fundamentally connects the AGN with their host galaxies. This structure is believed to be associated with dusty winds driven by radiation pressure. However, the role of magnetic fields, which are invoked in almost all models for accretion onto a supermassive black hole and outflows, is not thoroughly studied. Here we report the first detection of polarized thermal emission by means of magnetically aligned dust grains in the dusty torus of NGC 1068 using ALMA Cycle 4 polarimetric dust continuum observations ($0.07"$, $4.2$ pc; 348.5 GHz, $860$ $\mu$m). The polarized torus has an asymmetric variation across the equatorial axis with a peak polarization of $3.7\pm0.5$\% and position angle of $109\pm2^{\circ}$ (B-vector) at $\sim8$ pc east from the core. We compute synthetic polarimetric observations of magnetically aligned dust grains assuming a toroidal magnetic field and homogeneous grain alignment. We conclude that the measured 860 $\mu$m continuum polarization arises from magnetically aligned dust grains in an optically thin region of the torus. The asymmetric polarization across the equatorial axis of the torus arises from 1) an inhomogeneous optical depth, and 2) a variation of the velocity dispersion, i.e. variation of the magnetic field turbulence at sub-pc scales, from the eastern to the western region of the torus. These observations and modeling constrain the torus properties beyond spectral energy distribution results. This study strongly supports that magnetic fields up to a few pc contribute to the accretion flow onto the active nuclei.Comment: 19 pages, 11 figures (Accepted for Publication to ApJ

Evaluacion del sistema de drenaje en canal abierto en el cultivo de banano (Musa AAA) en la finca La bomba

El presente estudio se realizó en los suelos de la finca Bomba", corregimiento de Orihueca, Municipio de Ciénaga, Departamento del Magdalena. El corregimiento de Orihueca se encuentra enmarcado en los siguientes límites: por el Norte con el río Rio Frío, por el este con la carretera que de Ciénaga conduce a Fundación, por el Oeste con terrenos que dan a la Ciénaga Grande de Santa Marta y por el Sur con la Quebrada Orihueca. La finca La Bomba limita por el Norte con, la parcela Osario Serrano Alberto y con Inversiones urbanas rurales, al sur con la finca de Dávila - y Pedro, por el Este con las fincas de Navarro y Antonio Torres, por el Oeste con camino en medio. La zona bananera está entre las siguientes o coordenadas: Longitud Oeste 74 21' - 74 24"; latitud o Norte: 11 01' - 10 22'. La finca presenta un área aproximada de 46,5 Has, el relieve es plano con pendiente de 0 - 1%, con una altura de 15 m.s.n.m una precipitación promedio anual de 1.31e mm, una o temperatura media de 28 C y la humedad relativa es de 20,57, los suelos son permeables, con un PH variable predominando el ligeramente ácido. La zona se encuentra influenciada por los vientos alisios que soplan durante los meses de Diciembre a Marzo alcanzando velocidades de 10 1 m/seg. La investigación se inició en el mes de enero de 1.993 y - finalizó en enero de 1.994. Durante este período se llevó cabo el trabajo de campo que partió como primera medida un reconocimiento del terreno, las instalaciones que poseían la finca y el estado en que se encontraba. Para evaluar los resultados y establecer el diseño del drenaje propuesto se tuvo en cuenta los siguientes parámetros: Profundidad efectiva, clase de textura del suelo, conductividad hidráulica, retención de humedad, salinidad del suelo, salinidad del agua de riego, profundidad del nivel freático, profundidad de la capa impermeable, infiltración, precipitación promedia, evaporación y temperatura de la zora. Los resultados señalan que para establecer un correcto diseño de drenaje fue necesario además de las evaluaciones de los parámetros anteriores, establecer el espaciamiento entre drenes terciarios para lo cual se utilizó la fórmula de Houghoutd, encontrándose que dicho espaciamiento depende no solo de las características físicas de los suelos, sino de la profundidad en la cual se encuentra ubicada la capa impermeable del suelo que para nuestro caso es de 17,42 m. El diseño actual y el diseño propuesto presentan igual número de canales secundarios y primarios con 10 y uno respectivamente, el diseño propuesto presenta además canales terciarios ubicados a 50 metros de separación entre ellos; necesarios para una evacuación rápida y eficiente de las aguas de escorrentía después de una fuerte precipitación. Es claramente notorio que en el diseño propuesto las áreas para los canales secundarios y primarios son más reducidas que las áreas de los canales del diseño actual, trayendo como consecuencia un sobre diseño en el drenaje externo, reflejándose esto en un incremento de los costos de excavación además por los ingresos dejados de percibir al no cultivarse las áreas que actualmente se encuentran ocupadas por los canales del diseño actual

A New Methodology for Vibration Error Compensation of Optical Encoders

Optical encoders are sensors based on grating interference patterns. Tolerances inherent to the manufacturing process can induce errors in the position accuracy as the measurement signals stand apart from the ideal conditions. In case the encoder is working under vibrations, the oscillating movement of the scanning head is registered by the encoder system as a displacement, introducing an error into the counter to be added up to graduation, system and installation errors. Behavior improvement can be based on different techniques trying to compensate the error from measurement signals processing. In this work a new “ad hoc” methodology is presented to compensate the error of the encoder when is working under the influence of vibration. The methodology is based on fitting techniques to the Lissajous figure of the deteriorated measurement signals and the use of a look up table, giving as a result a compensation procedure in which a higher accuracy of the sensor is obtained

Impacto del Dólar en la Deuda Externa en el Sector Privado

El presente documento brinda informacion respecto al impacto del precio del dolar en Colombia

UniDA: Uniform Device Access Framework for Human Interaction Environments

Human interaction environments (HIE) must be understood as any place where people carry out their daily life, including their work, family life, leisure and social life, interacting with technology to enhance or facilitate the experience. The integration of technology in these environments has been achieved in a disorderly and incompatible way, with devices operating in isolated islands with artificial edges delimited by the manufacturers. In this paper we are presenting the UniDA framework, an integral solution for the development of systems that require the integration and interoperation of devices and technologies in HIEs. It provides developers and installers with a uniform conceptual framework capable of modelling an HIE, together with a set of libraries, tools and devices to build distributed instrumentation networks with support for transparent integration of other technologies. A series of use case examples and a comparison to many of the existing technologies in the field has been included in order to show the benefits of using UniDA

The Tucana/Horologium, Columba, AB Doradus, and Argus Associations: New Members and Dusty Debris Disks

We propose 35 star systems within ~70 pc of Earth as newly identified members of nearby young stellar kinematic groups; these identifications include the first A- and late-B type members of the AB Doradus moving group and field Argus Association. All but one of the 35 systems contain a bright solar- or earlier-type star that should make an excellent target for the next generation of adaptive optics (AO) imaging systems on large telescopes. AO imaging has revealed four massive planets in orbit around the {\lambda} Boo star HR 8799. Initially the planets were of uncertain mass due in large part to the uncertain age of the star. We find that HR 8799 is a likely member of the ~30 Myr old Columba Association implying planet masses ~6 times that of Jupiter. We consider Spitzer Space Telescope MIPS photometry of stars in the ~30 Myr old Tucana/Horologium and Columba Associations, the ~40 Myr old field Argus Association, and the ~70 Myr old AB Doradus moving group. The percentage of stars in these young stellar groups that display excess emission above the stellar photosphere at 24 and 70 \mu m wavelengths - indicative of the presence of a dusty debris disk - is compared with corresponding percentages for members of 11 open clusters and stellar associations with ages between 8 and 750 Myr, thus elucidating the decay of debris disks with time.Comment: Accepted for publication in Ap

Selección De Personal Para El Banco Del Llano S.A

N/AEl proyecto se centra en mejorar la selección de personal en el Banco del Llano S.A., un banco en Colombia orientado hacia la atención al cliente y la expansión nacional. Enfrenta desafíos en el mercado laboral, como la brecha de habilidades y la diversidad cultural. Se inicia con una introducción sobre la importancia de la selección de personal en un entorno competitivo, abordando sesgos y discriminación respaldados por investigaciones. Se justifica el proyecto citando expertos en recursos humanos, enfatizando la relevancia estratégica de mejorar los procesos de selección. Se busca identificar fortalezas y debilidades en el proceso de selección del banco, con el argumento de que una selección efectiva no solo beneficia comercialmente a la entidad, sino que también tiene un impacto social positivo mediante la generación de empleo y el fortalecimiento organizativo. Los objetivos incluyen optimizar el proceso de selección con un modelo eficaz que promueva la diversidad, utilizar pruebas y evaluaciones para identificar candidatos adecuados, y explorar la evolución de la gestión humana, enfocándose en el talento como ventaja competitiva. Se mencionan detalles legales que respaldan el proceso de selección, como la Ley de Protección de Datos Personales y leyes que garantizan la igualdad de oportunidades y la protección contra la discriminación. La metodología de investigación es mixta, combinando enfoques cualitativos y cuantitativos, y se describe la población objetivo, el tamaño de la muestra y las técnicas de análisis de datos. Los resultados resaltan la necesidad de innovación, especialmente la incorporación de inteligencia artificial para reducir sesgos. Se hacen recomendaciones, como adoptar tecnologías emergentes, desarrollar programas de formación innovadores y estrategias para la diversidad e inclusión, y monitorear las tendencias laborales.The project focuses on improving staff selection at Banco del Llano S.A., a bank in Colombia oriented towards customer service and national expansion. It faces challenges in the labour market, such as skills gap and cultural diversity. It begins with an introduction on the importance of staff selection in a competitive environment, addressing biases and discrimination supported by research. The project is justified by quoting human resources experts, emphasizing the strategic relevance of improving selection processes. It seeks to identify strengths and weaknesses in the selection process of the bank, arguing that an effective selection not only benefits the entity commercially, but also has a positive social impact through employment generation and organizational strengthening. Objectives include optimizing the selection process with an effective model that promotes diversity, using tests and evaluations to identify suitable candidates, and exploring the evolution of human management, focusing on talent as a competitive advantage. Legal details supporting the selection process are mentioned, such as the Personal Data Protection Act and laws guaranteeing equal opportunities and protection against discrimination. The research methodology is mixed, combining qualitative and quantitative approaches, and describes the target population, sample size and data analysis techniques. The results highlight the need for innovation, especially the incorporation of artificial intelligence to reduce biases. Recommendations are made, such as adopting emerging technologies, developing innovative training programs and strategies for diversity and inclusion, and monitoring work trends