EQUIVALENT MODELS FOR PHOTOVOLTAIC CELL – A REVIEW

Over the years, the contribution of photovoltaic energy to an eco-friendly world is continually increasing. Photovoltaic (PV) cells are commonly modelled as circuits, so finding the appropriate circuit model parameters of PV cells is crucial for performance evaluation, control, efficiency computations and maximum power point tracking of solar PV systems. The problem of finding circuit model of solar PV cells is referred to as “PV cell equivalent model problem”. In this paper, the existing research works on PV cell model parameter estimation problem are classified according to error quali-quantitative analysis, number of parameters, translation equations and PV technology. The existent models were discussed pointing out its different levels of approximation. A qualitative comparative ranking was made and four models were found to be the best ones for simulating PV cells. Besides, based on the conducted review, some recommendations for future research are provided

A BRIEF REVIEW ON THE ADVANTAGES, HINDRANCES AND ECONOMIC FEASIBILITY OF STIRLING ENGINES AS A DISTRIBUTED GENERATION SOURCE AND COGENERATION TECHNOLOGY

The present paper aims to provide a brief review of the potentiality and economic feasibility of the Stirling engine as a distributed generation source and cogeneration technology. Another objective was the determination of hindrances which may be preventing the feasibility of the Stirling technology. With these intentions, a research based on a combination of preselected keywords was performed at the Metasearch of CAPES (Brazil's Higher Education Coordination of Personnel Perfecting). No filters in relation to the research period or to particular geographical regions were employed, thus publications until 2017’s middle were included and the research was conducted on a global level. Next, the selection of papers which contained some of the keywords was made, consisting initially of the read of the publications’ abstracts. The remaining ones were then further explored and had their relevant information incorporated, according to the scope of this work. It is worth mentioning that other accredited sources which dealt with important aspects of the topic were also included. Furthermore, a table containing some examples of products concerning the application of the Stirling engine as a distributed generation and cogeneration technology is presented. Ultimately, it is concluded that the Stirling technology, despite its advantages and suitability regarding the proposed applications, is not yet commercially feasible, having currently only a minor presence in the market. This scenario can be attributed to the need for further research and technical development as well as cost reduction

Quality of life trajectories in breast cancer patients: an updated analysis 5 years after diagnosis

Letter to the editorThis work was funded by FEDER through the Operational Programme Competitiveness and Internationalization and national funding from the Foundation for Science and Technology—FCT (Portuguese Ministry of Science, Technology and Higher Education) under the project ‘A five-year prospective cohort study on the neurological complications of breast cancer: frequency and impact in patient-reported outcomes’ (POCI-01-0145-FEDER-016867, Ref. PTDC/DTP-EPI/7183/2014), and national funding from FCT under the Unidade de Investigação em Epidemiologia—Instituto de Saúde Pública da Universidade do Porto (EPIUnit) (POCI-01-0145-FEDER-016867, Ref. PTDC/DTP-EPI/7183/2014), and national funding from FCT under the Unidade de Investigação em Epidemiologia - Instituto de Saúde Pública da Universidade do Porto (EPIUnit) (info:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UIDB/04750/2020/PT). LLC was funded under the scope of the project ‘NEON-PC—Neuro-oncological complications of prostate cancer: longitudinal study of cognitive decline’ (POCI01–0145-FEDER-032358; ref. PTDC/SAU-EPI/32358/2017). Individual grants attributed to NA (SFRH/BD/119390/2016) and FF (SFRH/BD/92630/2013) were funded by FCT and the ‘Programa Operacional Capital Humano’ (POCH/FSE). Data management activities up to the first year of follow-up were supported by the Chair on Pain Medicine of the Faculty of Medicine, University of Porto, and by the Grünenthal Foundation—Portugal

Manifestation of finite temperature size effects in nanogranular magnetic graphite

In addition to the double phase transition (with the Curie temperatures T_C=300K and T_{Ct}=144K), a low-temperature anomaly in the dependence of the magnetization is observed in the bulk magnetic graphite (with an average granular size of L=10nm), which is attributed to manifestation of the size effects below the quantum temperature. The best fits of the high-temperature data (using the mean-field Curie-Weiss and Bloch expressions) produced reasonable estimates for the model parameters, such as defects mediated effective spin exchange energy J=12meV (which defines the intragranular Curie temperature T_C) and proximity mediated interactions between neighboring grains (through potential barriers created by thin layers of non-magnetic graphite) with energy J_t=exp(-d/s)J=5.8meV (which defines the intergranular Curie temperature T_{Ct}) with d=1.5nm and s=2nm being the intergranular distance and characteristic length, respectively

Quality of life trajectories during the first three years after diagnosis of breast cancer: the NEON-BC study

Background We aimed to identify and characterize quality of life trajectories up to 3 years after breast cancer diagnosis. Methods A total of 460 patients were evaluated at baseline (before treatments), and after 1- and 3-years. Patient-reported outcomes, including quality of life (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30, QLQ-C30), anxiety, depression and sleep quality, were assessed in all evaluations. Model-based clustering was used to identify quality of life trajectories. Results We identified four trajectories without intersection during 3 years. The two trajectories characterized by better quality of life depicted relatively stable scores; in the other trajectories, quality of life worsened until 1 year, though in one of them the score at 3 years improved. Sociodemographic and clinical characteristics at baseline did not differ between trajectories, except for mastectomy, which was higher in the worst trajectory. Anxiety, depression and poor sleep quality increased from the best to the worst trajectory. Conclusions The type of surgery and the variation of other patient-reported outcomes were associated with the course of quality of life over 3 years. More research to understand the heterogeneity of individual trajectories within these major patterns of variation is needed.This work was funded by FEDER through the Operational Programme Competitiveness and Internationalization and national funding from the Foundation for Science and Technology—FCT (Portuguese Ministry of Science, Technology and Higher Education) under the project ‘A five-year prospective cohort study on the neurological complications of breast cancer: frequency and impact in patient-reported outcomes’ (POCI-01-0145-FEDER-016867, Ref. PTDC/DTP-EPI/7183/2014) and the Unidade de Investigação em Epidemiologia—Instituto de Saúde Pública da Universidade do Porto (EPIUnit) (POCI-01-0145-FEDER-006862; Ref. UID/DTP/04750/2019). LC was also funded under the scope of the project “NEON-PC - Neuro-oncological complications of prostate cancer: longitudinal study of cognitive decline” (POCI01-0145-FEDER-032358; ref. PTDC/SAU-EPI/32358/2017). Individual grants attributed to NA (SFRH/BD/119390/2016) and FF (SFRH/BD/92630/2013) were funded by FCT and the ‘Programa Operacional Capital Humano’ (POCH/FSE). Data management activities up to the first year of follow-up were supported by the Chair on Pain Medicine of the Faculty of Medicine, University of Porto and by the Grünenthal Foundation—Portugal

The Highly Miniaturised Radiation Monitor

We present the design and preliminary calibration results of a novel highly miniaturised particle radiation monitor (HMRM) for spacecraft use. The HMRM device comprises a telescopic configuration of active pixel sensors enclosed in a titanium shield, with an estimated total mass of 52 g and volume of 15 cm$^3$. The monitor is intended to provide real-time dosimetry and identification of energetic charged particles in fluxes of up to 10$^8$ cm$^{-2}$ s$^{-1}$ (omnidirectional). Achieving this capability with such a small instrument could open new prospects for radiation detection in space.Comment: 17 pages, 15 figure

Dynamical reentrance and geometry imposed quantization effects in Nb-AlOx-Nb Josephson junction arrays

In this paper, we report on different phenomena related to the magnetic properties of artificially prepared highly ordered (periodic) two-dimensional Josephson junction arrays (2D-JJA) of both shunted and unshunted Nb-AlOx-Nb tunnel junctions. By employing mutual-inductance measurements and using a high-sensitive bridge, we have thoroughly investigated (both experimentally and theoretically) the temperature and magnetic field dependence of complex AC susceptibility of 2D-JJA. We also demonstrate the use of the scanning SQUID microscope for imaging the local flux distribution within our unshunted arrays

Random Sequential Adsorption: From Continuum to Lattice and Pre-Patterned Substrates

The random sequential adsorption (RSA) model has served as a paradigm for diverse phenomena in physical chemistry, as well as in other areas such as biology, ecology, and sociology. In the present work, we survey aspects of the RSA model with emphasis on the approach to and properties of jammed states obtained for large times in continuum deposition versus that on lattice substrates, and on pre-patterned surfaces. The latter model has been of recent interest in the context of efforts to use pre-patterning as a tool to improve selfassembly in micro- and nanoscale surface structure engineering