IMRT QA using machine learning: A multi-institutional validation.

PurposeTo validate a machine learning approach to Virtual intensity-modulated radiation therapy (IMRT) quality assurance (QA) for accurately predicting gamma passing rates using different measurement approaches at different institutions.MethodsA Virtual IMRT QA framework was previously developed using a machine learning algorithm based on 498 IMRT plans, in which QA measurements were performed using diode-array detectors and a 3%local/3 mm with 10% threshold at Institution 1. An independent set of 139 IMRT measurements from a different institution, Institution 2, with QA data based on portal dosimetry using the same gamma index, was used to test the mathematical framework. Only pixels with ≥10% of the maximum calibrated units (CU) or dose were included in the comparison. Plans were characterized by 90 different complexity metrics. A weighted poison regression with Lasso regularization was trained to predict passing rates using the complexity metrics as input.ResultsThe methodology predicted passing rates within 3% accuracy for all composite plans measured using diode-array detectors at Institution 1, and within 3.5% for 120 of 139 plans using portal dosimetry measurements performed on a per-beam basis at Institution 2. The remaining measurements (19) had large areas of low CU, where portal dosimetry has a larger disagreement with the calculated dose and as such, the failure was expected. These beams need further modeling in the treatment planning system to correct the under-response in low-dose regions. Important features selected by Lasso to predict gamma passing rates were as follows: complete irradiated area outline (CIAO), jaw position, fraction of MLC leafs with gaps smaller than 20 or 5 mm, fraction of area receiving less than 50% of the total CU, fraction of the area receiving dose from penumbra, weighted average irregularity factor, and duty cycle.ConclusionsWe have demonstrated that Virtual IMRT QA can predict passing rates using different measurement techniques and across multiple institutions. Prediction of QA passing rates can have profound implications on the current IMRT process

3D product authenticity model for online retail: An invariance analysis

This study investigates the effects of different levels of invariance analysis on three dimensional (3D) product authenticity model (3DPAM) constructs in the e- retailing context. A hypothetical retailer Web site presents a variety of laptops using 3D product visualisations. The proposed conceptual model achieves acceptable fit and the hypothesised paths are all valid. We empirically investigate the invariance across the subgroups to validate the results of our 3DPAM. We concluded that the 3D product authenticity model construct was invariant for our sample across different gender, level of education and study backgrounds. These findings suggested that all our subgroups conceptualised the 3DPAM similarly. Also the results show some non-invariance results for the structural and latent mean models. The gender group posits a non-invariance latent mean model. Study backgrounds group reveals a non-invariance result for the structural model. These findings allowed us to understand the 3DPAMs validity in the e-retail context. Managerial implications are explained

Measuring the degree of virtualization. An empirical analysis in two Austrian industries.

Strategic management literature suggests that especially in young and dynamic industries Virtual Corporations are more likely to emerge, as this type of organization is flexible enough to deal with rapidly changing environments. This paper challenges the proposition that environ-mental uncertainty and technological change lead to organizational adaptation towards virtual structures. We analyzed companies of two Austrian industries, data processing and engineering, which are characterized by different rates of innovation and environmental uncertainty, and compare their strategic, structural, and process characteristics by measuring their Degree of Virtualization. Results indicate almost no difference in the Degree of Virtualization. From these findings, we draw implications for the theoretical concept of Virtual Corpora-tions as well as for empirical research. (author's abstract)Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science

Imagen de destino en redes sociales virtuales

Since destination image is an important construct for tourism research, cities and regions try to understand and to develop a positive image in order to guarantee the number of visitors and the tourism revenue. The main objective of this article was to develop a model of evaluation of destination image through the use of pictures shared in virtual social networks. We propose that the image of a destination can be analyzed through the way tourists picture the destination in virtual social networks. Hence, we have developed a measurement to evaluate destination image based on pictures posted on Instagram, and we made a model to analyze destination image based on pictures shared in virtual social network. Our method was composed by an analysis of 1,500 pictures of three important destinations in Brazil (Foz do Iguaçú, Rio de Janeiro, and Salvador). Our results contribute to tourism research by indicating that it is possible to determine the main characteristics of a destination by the pictures in virtual social networks, and by providing a 5-dimension model to do so. This study contributes to tourism research in two venues. First, we propose a method for evaluating destination image based on pictures posted in social media rather than the usual questionnaires. This may help scholars by providing an alternative way of evaluating destination image without recall, social desirability and non-response bias. And secondly, this study also contributes to practitioners and public policy in tourism by showing which characteristics of a destination image are more prominent to the destination image, based on virtual social networks.Como a imagem de destino é um importante construto para a pesquisa em turismo, as cidades e regiões tentam desenvolver uma imagem positiva para garantir o número de visitantes e a receita. O objetivo deste artigo é desenvolver um modelo de avaliação de imagem de destino através do uso de imagens compartilhadas em redes sociais virtuais. Propomos que a imagem de um destino possa ser analisada pela maneira como os turistas imaginam o destino em redes sociais virtuais. Assim, desenvolvemos uma medida para avaliar a imagem de destino com base em fotos publicadas no Instagram. Nosso método foi composto por uma análise de 1500 fotos de três importantes destinos no Brasil (Foz do Iguaçu, Rio de Janeiro e Salvador). Nossos resultados contribuem para a pesquisa em turismo, indicando que é possível determinar as principais características de um destino pelas imagens em redes sociais virtuais e fornecendo um modelo de 5 dimensões para fazê-lo. Este estudo contribui para a pesquisa em turismo em dois locais: propomos um método para avaliar a imagem de destino com base em imagens postadas em mídias sociais, em vez dos questionários usuais. Isso pode ajudar os estudiosos, fornecendo uma maneira alternativa de avaliar a imagem de destino sem recordação, desejo social e viés de não-resposta. Este estudo também contribui para os profissionais e políticas públicas em turismo, mostrando quais características de uma imagem de destino são mais proeminentes para a imagem de destino com base em redes sociais virtuais.Dado que la imagen de destino es una construcción importante para la investigación turística, las ciudades y regiones intentan entender y desarrollar una imagen positiva para garantizar el número de visitantes y los ingresos del turismo. El objetivo principal de este artículo es desarrollar un modelo de evaluación de la imagen de destino mediante el uso de imágenes compartidas en redes sociales virtuales. Proponemos que la imagen de un destino se pueda analizar a través de la forma en que los turistas representan el destino en las redes sociales virtuales. Por lo tanto, desarrollamos una medida para evaluar la imagen de destino basada en imágenes publicadas en Instagram y desarrollamos un modelo para analizar la imagen de destino basada en imágenes compartidas en una red social virtual. Nuestro método fue compuesto por un análisis de 1500 imágenes de tres destinos importantes en Brasil (Foz do Iguaçú, Río de Janeiro y Salvador). Nuestros resultados contribuyen a la investigación turística en tanto indican que es posible determinar las características principales de un destino por las imágenes en las redes sociales virtuales, y proporcionan un modelo de cinco dimensiones para hacerlo. Este estudio contribuye a la investigación turística en dos espacios. Por un lado, proponemos un método para evaluar la imagen de destino basada en imágenes publicadas en las redes sociales en lugar de los cuestionarios habituales; esto puede ayudar a los académicos al proporcionar una forma alternativa de evaluar la imagen de destino sin recordar la conveniencia social y el sesgo de no respuesta. Y por otro lado, este estudio también resulta provechoso para los profesionales y las políticas públicas en turismo al mostrar qué características de una imagen de destino son más prominentes a la imagen de destino basada en redes sociales virtuales.https://revistas.udem.edu.co/index.php/anagramas/article/view/252

Frequency support characteristics of grid-interactive power converters based on the synchronous power controller

Grid-interactive converters with primary frequency control and inertia emulation have emerged and are promising for future renewable generation plants because of the contribution in power system stabilization. This paper gives a synchronous active power control solution for gridinteractive converters , as a way to emulate synchronous generators for inerita characteristics and load sharing. As design considerations, the virtual angle stability and transient response are both analyzed, and the detailed implementation structure is also given without entailing any difficulty in practice. The analytical and experimental validation of frequency support characteristics differentiates the work from other publications on generator emulation control. The 10 kW simulation and experimental frequency sweep tests on a regenerative source test bed present good performance of the proposed control in showing inertia and droop characteristics, as well as the controllable transient response.Peer ReviewedPostprint (author's final draft

Using authentic 3D product visualisation for an electrical online retailer

This study investigates the effects of authentic three dimensional (3D) product visualisation versus 3D telepresence on consumers’ virtual experience. A hypothetical electrical retailer Web site presents a variety of laptops using 3D product visualisations for the within-subjects laboratory experiments. The first experiment uses two-way repeated measures ANOVA to determine the effects of the antecedents on 3D authenticity. In a second experiment, a one-way ANOVA compares telepresence and authenticity scores. This research uses a U.K. sample to investigate the effects of control and animated colours on 3D authenticity and the effects of 3D authenticity on experiential and instrumental values. The results reveal significant differences between telepresence and authenticity constructs. Authenticity is more significant in simulating an online retailer’s products, and control and animated colours represent the main antecedents of authenticity. Moreover, experiential and instrumental values represent the main consequences of 3D authenticity

Probabilistic simulation for the certification of railway vehicles

The present dynamic certification process that is based on experiments has been essentially built on the basis of experience. The introduction of simulation techniques into this process would be of great interest. However, an accurate simulation of complex, nonlinear systems is a difficult task, in particular when rare events (for example, unstable behaviour) are considered. After analysing the system and the currently utilized procedure, this paper proposes a method to achieve, in some particular cases, a simulation-based certification. It focuses on the need for precise and representative excitations (running conditions) and on their variable nature. A probabilistic approach is therefore proposed and illustrated using an example. First, this paper presents a short description of the vehicle / track system and of the experimental procedure. The proposed simulation process is then described. The requirement to analyse a set of running conditions that is at least as large as the one tested experimentally is explained. In the third section, a sensitivity analysis to determine the most influential parameters of the system is reported. Finally, the proposed method is summarized and an application is presented

Highly efficient impulse-radio ultra-wideband cavity-backed slot antenna in stacked air-filled substrate integrated waveguide technology

An impulse-radio ultra-wideband (IR-UWB) cavity-backed slot antenna covering the [5.9803; 6.9989] GHz frequency band of the IEEE 802.15.4a-2011 standard is designed and implemented in an air-filled substrate integrated waveguide (AFSIW) technology for localization applications with an accuracy of at least 3 cm. By relying on both frequency and time-domain optimization, the antenna achieves excellent IR-UWB characteristics. In free-space conditions, an impedance bandwidth of 1.92 GHz (or 29.4%), a total efficiency higher than 89%, a front-to-back ratio of at least 12.1 dB, and a gain higher than 6.3 dBi are measured in the frequency domain. Furthermore, a system fidelity factor larger than 98% and a relative group delay smaller than 100 ps are measured in the time domain within the 3 dB beamwidth of the antenna. As a result, the measured time-of-arrival of a transmitted Gaussian pulse, for different angles of arrival, exhibits variations smaller than 100 ps, corresponding to a maximum distance estimation error of 3 cm. Additionally, the antenna is validated in a real-life worst-case deployment scenario, showing that its characteristics remain stable in a large variety of deployment scenarios. Finally, the difference in frequency-and time-domain performance is studied between the antenna implemented in AFSIW and in dielectric filled substrate integrated waveguide (DFSIW) technology. We conclude that DFSIW technology is less suitable for the envisaged precision IR-UWB localization application

A metric for collaborative networks

The objective of this paper is to provide a metric that could be used to define success in acollaborative network. Design/methodology/approach - The methodology of this research consists of four stages: Review, Constructing, Testing and Description. Review stage comprised of a critical review of theliterature in order to understand the characteristics of collaborative network organisations and thereasons behind the successes and failures in collaborative networks. Construction stage resulted indevelopment of a metric for collaborative networks. Testing stage tested the model through case studyin a collaborative networks organisation. The outcome of the case study was discussed at thedescription stage to assess usability and usefulness of the metric for participants in turn to generatec onclusions