32,331 research outputs found

    Miniaturización de antenas tipo microstrip mediante recubrimientos con materiales ferroeléctricos

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    La limitaci√≥n en el espacio donde se dispone la antena dentro de un dispositivo electr√≥nico ha promovido la investigaci√≥n de alternativas que permitan el desarrollo de antenas miniaturizadas con una amplia capacidad de emisi√≥n y recepci√≥n, siendo los materiales ferroel√©ctricos una de las opciones m√°s acertadas para reducir el tama√Īo de las antenas sin generar cambios significativos en el dise√Īo. Adicionalmente, estos materiales pueden ser obtenidos por diferentes t√©cnicas, dentro de las que sobresale sol-gel por su flexibilidad en deposici√≥n de pel√≠cula. Por ello, el presente trabajo se centra en la evaluaci√≥n del factor de miniaturizaci√≥n de antenas de parche microstrip recubiertas con materiales ferroel√©ctricos tales como titanato de estroncio (STO), titanato de bario-estroncio (BSTO), y titanato de bario (BTO), obtenidos v√≠a sol-gel y depositados mediante spin coating a 3000 rpm (20 s) con tratamiento t√©rmico a 700 ¬įC (1 h, 1 ¬įC/min). Estas antenas fueron dise√Īadas y simuladas dentro de un rango de frecuencia entre 1 y 8.5 GHz; se fabricaron por fotolitograf√≠a usando substratos de al√ļmina de 635 m con metalizaci√≥n en oro (3.0 m) y capa de adherencia de n√≠quel-cromo (0.2 m), para ser caracterizadas con el uso de un analizador vectorial de red (VNA). La ejecuci√≥n de esta investigaci√≥n se verific√≥ mediante difracci√≥n de rayos X, mostrando la presencia de estructuras cristalinas en fase perovskita c√ļbica, con par√°metros de red para STO, BSTO y BTO de 3.9012 ¬Ī 0.0049 √Ö, 3.9631 ¬Ī 0.0055 √Ö, y 4.0268 ¬Ī 0.0119 √Ö, respectivamente. La caracterizaci√≥n microestructural y morfol√≥gica permiti√≥ establecer las condiciones de deposici√≥n y de tratamiento t√©rmico de la pel√≠cula que permitieran uniformidad, homogeneidad y adherencia aceptable de la capa con poca presencia de defectos superficiales. Por su parte, la espectroscop√≠a de rayos X de energ√≠a dispersa cuantific√≥ composiciones elementales para STO de 1.48 ¬Ī 0.13 % wt Sr, y 0.54 ¬Ī 0.07 % wt Ti; BSTO: 0.69 ¬Ī 0.22 % wt Ba, 1.22 ¬Ī 0.12 % wt Sr, 0.63 ¬Ī 0.09 % wt Ti, y 6.05 ¬Ī 0.85 % wt O; y para BTO de 1.28 ¬Ī 0.23 % wt Ba, 0.74 ¬Ī 0.09 % wt Ti, y 7.28 ¬Ī 0.92 % O; todos estos materiales analizados en forma de pel√≠cula cristalizada y depositada sobre Al2O3/Ni-Cr/Au. Los espesores obtenidos para las pel√≠culas de STO, BSTO, y BTO fueron: 2.8130, 4.1070, y 3.9217 m; con constante diel√©ctrica de 92, 136, y 232; tangente de p√©rdida de 0.0112, 0.0104, y 0.0080, con operaci√≥n en 4.116 GHz (-12.6000 dB), 4.0800 GHz (-10.0900 dB), y 4.0200 GHz (-10.0900 dB), respectivamente para STO, BSTO y BTO. Por otro lado, las antenas recubiertas con STO, BSTO y BTO evidenciaron tasas de miniaturizaci√≥n de 4.7 %, 7.0 %, y 15.6 %, con frecuencia de operaci√≥n en 2.5925 GHz, 2.5300 GHz, y 2.2950 GHz, respectivamente. De este modo se comprob√≥ dentro de las instalaciones de la Universidad EAFIT la aplicabilidad de las pel√≠culas ferroel√©ctricas en los procesos de miniaturizaci√≥n de antenas

    Building body identities - exploring the world of female bodybuilders

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    This thesis explores how female bodybuilders seek to develop and maintain a viable sense of self despite being stigmatized by the gendered foundations of what Erving Goffman (1983) refers to as the 'interaction order'; the unavoidable presentational context in which identities are forged during the course of social life. Placed in the context of an overview of the historical treatment of women's bodies, and a concern with the development of bodybuilding as a specific form of body modification, the research draws upon a unique two year ethnographic study based in the South of England, complemented by interviews with twenty-six female bodybuilders, all of whom live in the U.K. By mapping these extraordinary women's lives, the research illuminates the pivotal spaces and essential lived experiences that make up the female bodybuilder. Whilst the women appear to be embarking on an 'empowering' radical body project for themselves, the consequences of their activity remains culturally ambivalent. This research exposes the 'Janus-faced' nature of female bodybuilding, exploring the ways in which the women negotiate, accommodate and resist pressures to engage in more orthodox and feminine activities and appearances

    Exploring the effects of spinal cord stimulation for freezing of gait in parkinsonian patients

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    Dopaminergic replacement therapies (e.g. levodopa) provide limited to no response for axial motor symptoms including gait dysfunction and freezing of gait (FOG) in Parkinson’s disease (PD) and Richardson’s syndrome progressive supranuclear palsy (PSP-RS) patients. Dopaminergic-resistant FOG may be a sensorimotor processing issue that does not involve basal ganglia (nigrostriatal) impairment. Recent studies suggest that spinal cord stimulation (SCS) has positive yet variable effects for dopaminergic-resistant gait and FOG in parkinsonian patients. Further studies investigating the mechanism of SCS, optimal stimulation parameters, and longevity of effects for alleviating FOG are warranted. The hypothesis of the research described in this thesis is that mid-thoracic, dorsal SCS effectively reduces FOG by modulating the sensory processing system in gait and may have a dopaminergic effect in individuals with FOG. The primary objective was to understand the relationship between FOG reduction, improvements in upper limb visual-motor performance, modulation of cortical activity and striatal dopaminergic innervation in 7 PD participants. FOG reduction was associated with changes in upper limb reaction time, speed and accuracy measured using robotic target reaching choice tasks. Modulation of resting-state, sensorimotor cortical activity, recorded using electroencephalography, was significantly associated with FOG reduction while participants were OFF-levodopa. Thus, SCS may alleviate FOG by modulating cortical activity associated with motor planning and sensory perception. Changes to striatal dopaminergic innervation, measured using a dopamine transporter marker, were associated with visual-motor performance improvements. Axial and appendicular motor features may be mediated by non-dopaminergic and dopaminergic pathways, respectively. The secondary objective was to demonstrate the short- and long-term effects of SCS for alleviating dopaminergic-resistant FOG and gait dysfunction in 5 PD and 3 PSP-RS participants without back/leg pain. SCS programming was individualized based on which setting best improved gait and/or FOG responses per participant using objective gait analysis. Significant improvements in stride velocity, step length and reduced FOG frequency were observed in all PD participants with up to 3-years of SCS. Similar gait and FOG improvements were observed in all PSP-RS participants up to 6-months. SCS is a promising therapeutic option for parkinsonian patients with FOG by possibly influencing cortical and subcortical structures involved in locomotion physiology

    Examination of a Brief, Self-Paced Online Self-Compassion Intervention Targeting Intuitive Eating and Body Image Outcomes among Men and Women

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    Ideals for appearance and body image are pervasive in Western culture in which men and women are portrayed with unrealistic and often unattainable standards (Ferguson, 2013; Martin, 2010). Exposure and reinforcement have created a culture of social acceptance and internalization of these ideals, contributing to pervasive body image disturbance (i.e., body dissatisfaction; Fallon et al., 2014; Stice, 2001; Thompson & Stice, 2001; Thompson et al., 1999). Research has suggested that body dissatisfaction is expressed differently across sexes (Grossbard et al., 2008), with attention to thin ideals among women and muscular ideals among men. Body dissatisfaction has been linked to numerous poor outcomes, including dieting, unhealthy weight control behaviors, disordered eating, and increased psychopathology. Although dieting is one of the primary mechanisms employed to reduce body dissatisfaction (Thompson & Stice, 2001), research has shown that such efforts are contraindicated as dieting predicts weight gain over time (Pietil√ɬ§inen et al., 2012) as well as preoccupation with food, disordered eating, eating disorders, emotional distress, and higher body dissatisfaction (Grabe et al., 2007; Johnson & Wardle, 2005; Neumark- Sztianer et al., 2006; Paxton et al., 2006; Tiggemann, 2005). Restrictive dietary behaviors suppress physiological cues to eat (e.g., hunger) that presents a vulnerability to eating in response to alternative cues, both internal (e.g., emotions) and external (e.g., availability of food). Intuitive eating is a non-restrictive approach to eating that encourages adherence to internal physiological cues to indicate when, what, and how much to eat (Tylka, 2006) and has demonstrated an inverse relationship with disordered eating, restrained eating, food preoccupation, dieting, body dissatisfaction, and negative affect (Bruce & Ricciardelli, 2016). Self-compassion, relating to oneself in a caring and supportive manner (Neff, 2003a), has been proposed as a pathway to increase intuitive eating and reduce body dissatisfaction (Neff & Knox, 2017; Schoenefeld & Webb, 2013; Webb & Hardin, 2016). Research has highlighted the efficacy of self-compassion interventions in addressing weight-related concerns (Rahimi-Ardabili et al., 2018) as well as brief experiential exercises for reducing body dissatisfaction (Moffitt et al., 2018). Additionally, there is a growing body of evidence supporting the efficacy of internet-based self-compassion interventions (Mak et al., 2018; Kelman et al., 2018; Nadeau et al., 2020). The purpose of the current study was to examine the effectiveness of a brief, self-paced online self-compassion intervention targeting body image and adaptive eating behaviors and potential mechanisms of change (e.g., self-compassion and psychological flexibility) among undergraduate men and women. This study also examined outcomes among men and women in the area of self-compassion, body dissatisfaction, and intuitive eating as research has highlighted the need to determine who benefits more from self-compassion interventions (Rahimi-Ardabili et al., 2018). The study compared a one-hour, self-guided online self-compassion intervention to an active control condition. The intervention was comprised of psychoeducation, experiential exercises, and mindfulness practice designed to increase self-compassion surrounding body image and eating behaviors. In contrast, the active control condition consisted of self-care recommendations and self-assessments for nutrition, exercise, and sleep. The study was administered over three parts (e.g., baseline, intervention, and follow-up) in which variables of interest were assessed at each time point. Outcome variables included self-compassion, intuitive eating, disordered eating, body appreciation, muscle dysmorphia, internalized weight bias, fear of self-compassion, and psychological inflexibility. Participants were randomized on a 2:1 intervention to control ratio at the second time point in order to make comparisons between groups while simultaneously having sufficient power for examining mediation and moderation within the treatment condition. Overall, 1023 individuals (64% women, Mage = 18.9, 67.4% white) signed informed consent and participated in at least one part of the study whereas 101 participants (71% women, Mage = 19.3, 71% white) completed all three study portions. As predicted, self-compassion was correlated with all variables of interest, and all study variables were correlated with each other (p < .01). In contrast to hypothesized outcomes, the self-compassion condition failed to demonstrate improvements across time or between conditions on all study outcomes. These results persisted when participants were screened for levels of intuitive eating as well. Contrary to prediction, internalized weight bias, muscle dysmorphia, and fear of self-compassion demonstrated increased levels within the intervention condition and decreases in the control condition. There were significant gender differences on multiple outcome variables, with men demonstrating higher levels of self-compassion and body appreciation whereas women endorsed higher levels of disordered eating, internalized weight bias, muscle dysmorphia, and psychological inflexibility. Additionally, there were significant gender interactions for internalized weight bias, body appreciation, and muscle dysmorphia. The interactions existed such that men demonstrated increased internalized weight bias and muscle dysmorphia across time whereas women displayed decreased weight bias and muscle dysmorphia. The opposite pattern was found within body appreciation; women demonstrated increased body appreciation across time while men reported decreased levels of body appreciation. Despite this study√Ę‚ā¨‚ĄĘs intent to examine underlying mechanisms of change, the condition in which participants were randomly selected did not have any relationship, positive or negative, with the outcome variables of interest. As such, mediation within the current study was not conducted as it would violate statistical assumptions required to examine this hypothesis. Finally, upon examining the moderating relationship of fear of self-compassion between self-compassion and outcome variables, there were main effects for self-compassion on intuitive eating, emotional eating, internalized weight bias, body appreciation, and psychological inflexibility as well as main effects of fear of self-compassion on psychological inflexibility. There were significant interactions for intuitive eating and emotional eating, such that as fear of self-compassion increased, the effect of self-compassion on intuitive eating decreased, and the effect of self-compassion on reducing emotional eating behaviors decreased. Overall, the brief, self-paced online intervention delivered in the current study did not prove to be an effective means for improving self-compassion, intuitive eating, body appreciation, disordered eating, muscle dysmorphia, and psychological inflexibility. Nevertheless, the relationships between self-compassion and outcome variables of interest throughout the study mirror that of the existing literature. Findings from this study, in general, were also consistent with differences between men and women despite a gap in the research for intervention outcomes. Although fear of self-compassion demonstrated a moderating effect on the relationship between self-compassion and intuitive eating as well as emotional eating, this does not account for the lack of significant findings. The context surrounding this study, such as the COVID-19 pandemic, provided a considerable challenge to examining the efficacy of the current intervention. However, the findings of this study suggest future research will likely need to identify ways to enhance the delivery of experiential exercises that encourage engagement, provide a safe and warm environment for participants, and create flexibility and willingness surrounding painful and difficult experiences in order to undermine internalized and socially accepted beliefs about body image and eating behaviors

    Hybrid Perovskite Thin Film

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    Hybrid perovskite thin film offers diverse advantages like low cost deposition techniques, less material consumption and superior optoelectronic properties. These merits including high voltage and high efficiency performance in a wide range of high light intensity are sufficient to distinguish perovskite thin films/devices from their contenders as a thin film technology with greater potential for industrial applications. Perovskite thin film technology demonstrates potency in a variety of applications in optoelectronic devices especially photovoltaic applications. The National Renewable Energy Laboratory (NREL) of the USA categorizes a number of thin films technologies including perovskite thin film, as emerging photovoltaics with the bulk of them yet to be commercially applied but are still in the research or developmental stage. In this chapter, various processing methods and material combinations as well as current trends in this technology are subjects of discussion

    Siamese-Based Attention Learning Networks for Robust Visual Object Tracking

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    Tracking with the siamese network has recently gained enormous popularity in visual object tracking by using the template-matching mechanism. However, using only the template-matching process is susceptible to robust target tracking because of its inability to learn better discrimination between target and background. Several attention-learning are introduced to the underlying siamese network to enhance the target feature representation, which helps to improve the discrimination ability of the tracking framework. The attention mechanism is beneficial for focusing on the particular target feature by utilizing relevant weight gain. This chapter presents an in-depth overview and analysis of attention learning-based siamese trackers. We also perform extensive experiments to compare state-of-the-art methods. Furthermore, we also summarize our study by highlighting the key findings to provide insights into future visual object tracking developments

    The Linear and Nonlinear Relationship between Infrastructure and FDI in India

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    The study examines the linear and nonlinear relationship between Infrastructure and FDI, to understand whether there is a significant difference or not concerning the FDI equity inflows to infrastructure projects. The ARDL and Granger causality methods to cointegration; propose the existence of long-run function in two-directional causalities between foreign direct investment and infrastructure, whereas the nonlinear autoregressive distributed lag (ARDL) validates the asymmetries in the relationship between FDI and Infrastructure. The outcomes of the study are that foreign direct investment inflows are significant to improve the infrastructure projects in various sectors, in the short-run and long run. As enlightening infrastructure is dynamic to attract FDI, outcomes will be predominantly valuable to policymakers and related to the emerging markets
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