430 research outputs found

    Unsupervised domain adaptation for medical imaging segmentation with self-ensembling

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    Recent advances in deep learning methods have come to define the state-of-the-art for many medical imaging applications, surpassing even human judgment in several tasks. Those models, however, when trained to reduce the empirical risk on a single domain, fail to generalize when applied to other domains, a very common scenario in medical imaging due to the variability of images and anatomical structures, even across the same imaging modality. In this work, we extend the method of unsupervised domain adaptation using self-ensembling for the semantic segmentation task and explore multiple facets of the method on a small and realistic publicly-available magnetic resonance (MRI) dataset. Through an extensive evaluation, we show that self-ensembling can indeed improve the generalization of the models even when using a small amount of unlabelled data.Comment: 15 pages, 9 figure

    The High-Speed Longitudinal Stability and Control of the Bell P-39N-1 Airplane as Calculated from Propeller-Off Tests of a 0.35-Scale Model

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    This report presents the results of tests of a .35-scale model of the Bell P-39N-1 airplane. Included are the longitudinal-stability and -control characteristics of the airplane as indicated by tests of the model equipped with each of two different sets of elevators. The results indicate good longitudinal stability and control throughout the speed range encounterable in flight. The variation of estimated stick force with speed was less when the model was equipped with elevators constructed to the theoretical design dimensions than when equipped with elevators as built to scale from measurements of the corresponding parts of the actual airplane. The predicted stick forces required to produce the normal accelerations attainable in flight are within the limits specified by the Army Air Forces

    Energetic analysis and optimal design of a CHP plant in a frozen food processing factory through a dynamical simulation model

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    The proper design of cogeneration plants requires the choice of the technologies that best fits the ratio between heating and power loads. In this paper, a dynamical procedure of selecting and dimensioning a cogeneration plant, using deep and detailed energy, exergy and economic analysis of the entire production process of a frozen food production factory is proposed. The results highlight that a design method, based on a dynamic simulation, optimizes the energy efficiency of the food processing plant involved in the experimental test. Indeed, by considering the overall efficiency of the CHP + National grid system, the energy efficiency is 6% higher in the case of dynamic compared to a static design, resulting in better overall use of resources with a possible lower level of environmental impact. Moreover, the CHP plant designed with the proposed method generates electrical energy which appropriately matches that required by the process, with a surplus/deficit less than 4%, while the classic method never covers the amount required and results in a deficit greater than 20%. Finally, the annual savings of the solution derived from the dynamic method is 12% higher than that obtained with a traditional design technique. Considering the greater absolute cost of the cogeneration plant, this dynamic approach results in more profitable annual investment margins for the company

    The relationship of sex and sexual orientation to self-esteem, body shape satisfaction, and eating disorder symptomatology

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    There is increasing interest in understanding what role, if any, sex and sexual orientation play in body dissatisfaction, its correlates to distress, and its relationship to disordered eating. The goals of the present study were to examine: (a) differences in sex and sexual orientation in internalization of societal pressure to modify physical appearance, components of body image dissatisfaction, self-esteem, and eating disorder symptomatology and (b) whether the internalization-eating disorder symptomatology was mediated by the different components of body image dissatisfaction and low self-esteem. The present data support several key trends in the literature: men generally reported less body dissatisfaction, internalization of socio-cultural standards of beauty, drive for thinness, and disordered eating, but a greater drive for muscularity than women; results also indicated that different components of body image dissatisfaction and low self-esteem partially mediated the relationship between internalization and eating disorder symptomatology. Gay men reported significantly more body dissatisfaction, internalization, eating disorder symptomatology, drive for thinness, and drive for muscularity than heterosexual men. Compared to heterosexual women, lesbians reported increased drive for muscularity, lower self-esteem, and lower internalization; however, they did not significantly differ on body dissatisfaction, drive for thinness or disordered eating. Correlation coefficients between body shape dissatisfaction and several aspects of mental distress were significantly larger for gay men than heterosexual men; the same coefficients did not differ between lesbian women and heterosexual women. Results of path analyses indicated that the relationship between internalization and disordered eating differs for gay and heterosexual men but not for lesbian and heterosexual women. These results call attention to lesbians as a generally understudied population

    Thermal analysis of a cold room

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    The purpose of this research was to study the storage of fresh raw horticultural material processed and frozen in an industrial plant in southern Italy. A simulation technique (validated by experimental tests) was used giving the chance to evaluate the effect of bins location on the cooling capacity of the cold room avoiding expensive experimental tests. An external cooling system and an intermediate fluid ensure the cooling of the products. The air is distributed inside the cold room by two blowers that provide the forced convection of the air itself. First of all, experimental tests were carried out to validate the preliminary results obtained from the previous experiment, and then the authors carried out a computational fluid dynamic (CFD) analysis in order to verify where a good arrangement of the storage bins is achieved inside the room. The tests were carried out in summer (July) on zucchini and peppers. The important deviations in the temperature of the product are mainly due to the different position occupied by the bins in the room. In fact, they are positioned at different distances and heights from the forced convection fans. Both simulation and experimental results show that the raw material cooled in the shortest possible time was the one placed to the shortest distance from the wall and at the lowest height of the room because of the low heat transfer through the floor. By increasing the distance from the access door through which the most significant heat transfer takes place, there is a small variation due to the optimal position of the storage bins inside the room, which still allows a good distribution of air

    Thermo-fluid-dynamic characteristics of confluent jets for distribution of treated air in small environment

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    The diffusion of the air through nozzles and/or diffusers has been studied extensively thanks to the numerous examples of environmental conditioning systems and in general of systems in which the flow of matter escapes from particular openings. In this paper, we studied closed and small environments requiring thermo-hygrometric and ventilation control. Air jets are used to mix the treated air within the environment. The widespread diffusion of this technology, mainly conceived for large environments, justifies the characterization of a particular type of system realized by the authors. The first results of experimental tests carried out with a particular air conditioning system are showed in the present work. The particularity of the system consists in a low construction cost, possibility of modifications and operation according to the characteristics and needs to different agricultural species. This initial phase of the research related to the isothermal regime, allowed by the conditioning system, aimed to characterize the fluid-dynamic behaviour of the air diffusion systems realized with perforated surfaces. First tests were carried out in a specifically designed climatic room whose climate conditions are strictly controlled by a suitable control system under isothermal conditions. Moreover, an ad-hoc designed experimental device was used. It consists of a pantograph kinematic structure carrying the probes around in the fluid dynamic field. It allows measuring air velocity in different points in stationary or slowing enough transient conditions. The experimental data was used to validate the computational fluid dynamics (CFD) model to predict the internal airflow velocity distribution

    Minimax Manifold Estimation

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    We find the minimax rate of convergence in Hausdorff distance for estimating a manifold M of dimension d embedded in R-D given a noisy sample from the manifold. Under certain conditions, we show that the optimal rate of convergence is n(-2/(2+d)). Thus, the minimax rate depends only on the dimension of the manifold, not on the dimension of the space in which M is embedded

    Test-time Unsupervised Domain Adaptation

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    Convolutional neural networks trained on publicly available medical imaging datasets (source domain) rarely generalise to different scanners or acquisition protocols (target domain). This motivates the active field of domain adaptation. While some approaches to the problem require labeled data from the target domain, others adopt an unsupervised approach to domain adaptation (UDA). Evaluating UDA methods consists of measuring the model's ability to generalise to unseen data in the target domain. In this work, we argue that this is not as useful as adapting to the test set directly. We therefore propose an evaluation framework where we perform test-time UDA on each subject separately. We show that models adapted to a specific target subject from the target domain outperform a domain adaptation method which has seen more data of the target domain but not this specific target subject. This result supports the thesis that unsupervised domain adaptation should be used at test-time, even if only using a single target-domain subjectComment: Accepted at MICCAI 202
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