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- PublicationDesign and health: An interdisciplinary baseline experience of product design for health needs of the Chilean elderly(2021-02-01)Abstract Objective: Describing the results of a User-Centered Design workshop using Challenge Based Learning or CBL, where students from Chilean industrial design and health degrees, developed solutions to resolve health problems among the elderly. Method: It was a pre-experimental study; 45 university students took part in a workshop: 39 from Industrial Design, 3 from Speech Therapy, 2 from Medical Technology and 1 from Medicine. In this workshop, the students, using CBL in disciplinary heterogeneous groups, faced a 3-week challenge to develop products to overcome a health problem for an elderly person. Once the product was presented, the professors and students assessed the conceptual proposals, using a semantic differential. The students also evaluated the workshop with a perception survey. Results: Both the students and professors positively evaluated the usefulness and functionality of the conceptual proposals; although, the industrial design students were more critical about these aspects. The originality of proposals evaluated was the worst. Regarding the workshop, all students (100%) felt that instructions were clear as were the three moments of design, with problem definition stage best evaluated. Conclusions: The CBL is shown to be an educational tool that allows training professionals in product design and in developing health technology that is suitable for the users' needs. Regarding the process, heterogeneous make-up of the groups and clear external guide appear as essential for CBL to work well. Keywords: challenge-based learning, elderly, interdisciplinary, higher education. Continuous...
- PublicationSustainability and urban metabolism(2020-01-01)The concept of urban metabolism was introduced by Wolman in 1965 [1], following insights and suggestions coming from ancient Marxism and the early ecologist theories.
- PublicationApproximate Nonlinear Discrete-Time Models Based on B-Spline Functions(2020-01-01)We consider the discretization of continuous-time nonlinear systems described by normal forms. In particular, we consider the case when the input to the system is generated by a B-spline hold device to obtain an approximate discrete-time model. It is shown that the corresponding sampled-data model and its accuracy (measured in terms of the local truncation error) depend on the smoothness of the input and on the applied integration strategy, namely, the truncated Taylor series expansion. Moreover, the sampling zero dynamics of the discrete-time model are asymptotically characterized as the sampling period goes to zero, and it is shown that these zero dynamics converge to the asymptotic sampling zeros of the linear case.
- PublicationStep-up partial power DC-DC converters for two-stage PV systems with interleaved current performance(2018-02-01)This work presents a partial power converter allowing us to obtain, with a single DC-DC converter, the same feature as the classical interleaved operation of two converters. More precisely, the proposed topology performs similarly as the input-parallel output-series (IPOS) configuration reducing the current ripple at the input of the system and dividing the individual converters power rating, compared to a single converter. The proposed topology consists of a partial DC-DC converter processing only a fraction of the total power, thus allowing high efficiency. Experimental results are provided to validate the proposed converter topology with a Flyback-based 100 W test bench with a transformer turns ratio n 1 = n 2 . Experimental results show high performances reducing the input current ripple around 30 % , further increasing the conversion efficiency.
- PublicationAnalysis of Solar Chimneys in Different Climate Zones - Case of Social Housing in Ecuador(2017-11-04)The aim of this research is to simulate the performance of a solar chimney located in different macro-zones in Ecuador. The proposed solar chimney model was simulated using a python script in order to predict the temperature distribution and the mass flow over time. The results obtained were firstly compared with experimental data for dry-warm climate. Then, the model was evaluated and tested in real weather conditions: dry-warm, moist-warm and rainycold. In addition, the assumed chimney dimensions were chosen according to the literature for the studied conditions. In spite of evaluating the best nightly ventilation, different chimney wall materials were tested: solid brick, common brick and reinforced concrete. The results showed that concrete in a dry-warm climate, a metallic layer on the gap with solid brick in a moist–warm climate and reinforced concrete in a rainy cold climate used for the absorbent wall improve the thermal inertia of the social housing.

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- PublicationTechnology acceptance model: Worried about the cultural influence?(2014-01-01)The Technology Acceptance Model (TAM) has shown in the USA that the Perceived Usefulness (PU) and the Perceived ease-of-use (PEU) determine the intention to use (IU) a specific technology or information system. In this research, the TAM model is validated in Chile, considering the cultural factors of this country, through an application of the model to university students. The results show that the TAM model works in Chile, regardless of the studied technology or the cultural aspects of the country. Finally, new questions arise related to this topic such as the influence of the intensity of use, familiarity with the technology and the individual’s reference group for the technologies aimed to encourage communication among people.
- PublicationCataclysmic Variables from Sloan Digital Sky Survey - V. The search for period bouncers continues(2023-11-01)SDSS-V is carrying out a dedicated survey for white dwarfs, single, and in binaries, and we report the analysis of the spectroscopy of 118 cataclysmic variables (CVs) and CV candidates obtained during the final plug plate observations of SDSS. We identify eight new CVs, spectroscopically confirm 53 and refute 11 published CV candidates, and we report 21 new or improved orbital periods. The orbital period distribution of the SDSS-V CVs does not clearly exhibit a period gap. In common with previous studies, the distribution shows that spectroscopically identified CVs have a larger proportion of short-period systems compared to samples identified from photometric variability. Remarkably, despite a systematic search, we find very few period bouncers. We estimate the space density of period bouncers to be , i.e. they represent only a few per cent of the total CV population. This suggests that during their final phase of evolution, CVs either destroy the donor, e.g. via a merger, or that they become detached and cease mass transfer.
- PublicationExamination of kt-factorization in a Yukawa theory(2024-04-01)We discuss the upper limit, kmax, of the transverse-momentum integration performed in the kt-factorization formula. Based on explicit calculations in the Yukawa theory and the study of seminal papers, we argue that kmax is equal to the factorization scale μF used to factorize the cross section into an off-shell hard coefficient and a universal factor. There is consequently a relation between kmax and the definition of unintegrated parton densities (UPDFs). The use of an inconsistent relation leads potentially to the overestimation of the cross section, which has been observed, e.g., in D-meson production [1]. One of our conclusions is that UPDFs related to collinear PDFs by an integration up to μ ∼ Q, where Q is the hard scale and μ the scale in the collinear PDFs, imply that ∼ Q2. Integrating the transverse-momentum significantly above may result in the overestimation of the cross section. On the opposite, for UPDFs related to the collinear ones by an integration of the transverse momentum up to infinity, any > Q2 is fine.
- PublicationIdentification of Continuous-Time Linear Parameter Varying Systems with Noisy Scheduling Variable Using Local Regression(2024-01-01)Some nonlinear systems can be represented through linear parameter varying models. In this work, we address the estimation of continuous-time linear parameter varying models in output error form, using a refined instrumental variable method. A distinguished feature of a linear parameter varying model is that it has parameters that depend on an external signal called the scheduling variable. In this paper, we assume that the scheduling variable is noisy, a condition which is often met in practice, but not frequently considered in the literature. On the other hand, there are applications in which the noise-free version of the scheduling variable is smooth. Under such scenario we can simply filter the scheduling variable before estimating the linear parameter model. Nonetheless, there are cases where special smoothing techniques are required. In this study, we consider one of these special cases, and we use the well-known local regression method as smoothing technique. A numerical example based on a Monte Carlo simulation shows the benefits of the proposed approach.