24 research outputs found
Investigation of the inductor’s parasitic capacitance in the high frequency switching of the high voltage cascode GaN HEMT
No full textThe concept of the More Electric Aircraft, where the majority of the aircraft’s secondary needs will be supplied by electrical power, is under continuous research over a number of years in order to conform the recent demand for more efficient and environmentally friendly aircrafts. Advancements in power electronics have contributed towards the realization of that demand, by introducing lightweight, high-power density and highly efficient in harsh environment power electronics. The increase in power density of power electronic systems was made feasible, so far, by developments in the semiconductors field, namely by semiconductors that can operate at higher switching frequencies and generate less power loss. Wide-bandgap devices, such as Gallium Nitride (GaN) transistors, have emerged as possible candidates to replace silicon and even silicon carbide devices in various power conversion applications offering potential benefits for high frequency power conversion due to their intrinsic material properties. Another step towards higher power densities is to utilize appropriate circuit topologies since they can reduce the stress upon the components and the cooling requirements. However, as the frequency goes up, the switching behavior of the device is not only influenced by the die itself and the device package’s and circuit’s parasitic elements can not be neglected any more. One of these parasitic elements is the the equivalent parasitic capacitance (EPC) of the magnetic component, which is part of almost every topology. This thesis project aims at two things: first, to observe the switching behavior of a high-voltage cascode GaN High Electron Mobility Transistor (HEMT) under inductive clamped load condition, which is the same commutation mode for the power devices as switching in a PWM, hard-switching type converter and second, to investigate the influence of the magnetic component’s EPC on the switching behavior of the GaN HEMT. For this, an analytical loss model of the device was developed and a double-pulse tester (DPT), which is considered to be a very good example of that load condition, was optimally designed and manufactured in order to verify the analytical model. Two pulses are launched to the device under test (DUT) and the switching transitions of the DUT can be captured for any desired current and voltage rating under hard-switching conditions. Moreover, when operating under that load conditions, applying active devices with reverse recovery charge has significant influence on the switching behavior of the DUT, so both cases will be examined. Finally, in order to characterize the device and eventually verify the analytical loss model, current and voltage measurements need to be taken during the turn-on and turn-off switching transitions. As the GaN HEMT is capable of switching are very high speed, there are issues and limitations that need to be taken into consideration in order to ensure the fidelity and the accuracy of these high frequency measurementsElectrical Power EngineeringElectrical Engineering, Mathematics and Computer Scienc
Multivariate GARCH models for large-scale applications : a survey
No full textThis chapter provides a survey of various multivariate GARCH specifications that model the temporal dependence in the second moment of multivariate return series processes. The survey is focused on feasible multivariate GARCH models for large-scale applications, as well as on recent contributions in outlier-robust MGARCH analysis and the use of high-frequency returns or the score for covariance modeling. We discuss their likelihood-based estimation and application to forecasting and simulation with software implementations in the R-programming language.</p
Multivariate GARCH models for large-scale applications: A survey
No full textThis chapter provides a survey of various multivariate GARCH specifications that model the temporal dependence in the second moment of multivariate return series processes. The survey is focused on feasible multivariate GARCH models for large-scale applications, as well as on recent contributions in outlier-robust MGARCH analysis and the use of high-frequency returns or the score for covariance modeling. We discuss their likelihood-based estimation and application to forecasting and simulation with software implementations in the R-programming language
Depression as a Mediator or Moderator Between Preparatory Grief and Sense of Dignity in Patients With Advanced Cancer
No full textThe objectives of the study were to evaluate the relationship between depression, preparatory grief, and loss of dignity in patients with advanced cancer and whether depression has a mediator and/or a mediator role between preparatory grief and dignity. The participants were 120 patients with advanced cancer who completed the Greek version of the Patient Dignity Inventory, the Greek Hospital Anxiety and Depression Scale, and the Preparatory Grief in Advanced Cancer Patients questionnaire. Depression was highly correlated with preparatory grief and loss of dignity. Additionally, strong relationship was found between preparatory grief and loss of dignity. Mediation analyses revealed that preparatory grief influenced loss of dignity as well as indirectly by its effect on depression. However, there was not any affect of depression as moderator. The effect of depression on preparatory grief in patients with advanced cancer and dignity emphasizing the need for further research to confirm the current relationship as well as the need for treatment of depression. © The Author(s) 2019
Psychometric Properties of the Patients’ Satisfaction Instrument FAMCARE-P13 in a Palliative Care Unit
No full textPurpose: To investigate the psychometric properties of the Greek 13-item measure of patients’ satisfaction (FAMCARE-P13) in palliative care setting. Methods: A hundred patients completed the FAMCARE-P13. Exploratory factor analysis and confirmatory factor analysis (CFA) have been conducted. Two factors’ solution was revealed from CFA. The questionnaire was administered to an initial validation sample and then for test–retest in a sample of 40 patients 3 days later. The Rosenberg Self-Esteem Scale measuring global self-esteem has been also used as a gold standard for construct validity. Subscale and known groups validity have also been tested for FAMCARE-P13s’ validity. Results: A reduced 13-item version of our measure (FAMCARE-P13) possessed 2-factor structure with high reliability. Patient satisfaction was correlated with physical distress, communication and relationship with health-care providers, and caregiver satisfaction. Conclusions: We recommend the use of the Greek FAMCARE-P13 to assess care satisfaction of patients with advanced-stage cancer. © 2016, © The Author(s) 2016
Validity and reliability of the Greek version of the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form
No full textBackground: The aim of our study is to prove the validity and reliability of the Greek translated version of the self-report section of the American Shoulder and Elbow Surgeons (ASES) questionnaire. Methods: A total of 108 patients with various shoulder disorders were evaluated at two different orthopedic centers. All patients answered the Greek ASES questionnaire as well as the previously validated Greek version of the Disability Arm Shoulder and Hand score. Three days after the first evaluation, a subgroup of 40 individuals was randomly selected to complete again the Greek ASES text to prove its reliability, after the test-retest procedure. Reliability was tested with Cronbach's alpha, stability by calculating the intraclass correlation coefficient and by Blant Altman plot and structural validity with the confirmatory factor analysis. Results: The internal consistency of the ASES functional score and the ASES total score was 0.925 and 0.750 respectively. The intraclass correlation coefficient between initial assessment and reassessment of the ASES functional and total score was 0.951 and 0.938 (P < .001), respectively. The correlation coefficients correlation between the ASES functional and total scores with DASH total score were −0.881 and −0.759 (P < .001), respectively. Conclusions: The Greek ASES version proved to be equivalent to the English original version in evaluating different shoulder disorders in the Greek population. © 2021 The Author
Author Correction: Mutational signatures reveal the role of RAD52 in p53-independent p21-driven genomic instability (Genome Biology, (2018), 19, 1, (37), 10.1186/s13059-018-1401-9)
No full textFollowing publication of the original article [1], the authors identified an error in additional file 1. Two minor typing errors were discovered in legends S2 and S6. The updated additional file 1 is given in this correction article. © The Author(s) 2022
Study protocol of a randomised controlled trial for the effectiveness of a functional partial body weight support treadmill training (FPBWSTT) on motor and functional skills of children with ataxia
No full textINTRODUCTION: A great heterogeneity characterises the paediatric population with ataxia, which has been studied poorly. The lack of postural control and coordination, in addition with features of the 'ataxic' gait are linked with functional limitations. Studies on physiotherapy interventions for children with ataxia are highly needed for identifying optimal training strategies for improving motor and functional related skills. METHODS AND ANALYSIS: A stratified randomised control clinical trial of a 4-week functional partial body weight support treadmill training, (5 days/week 45 min/day) and 2-month follow-up period will be applied in children with ataxia, aged 8-18 years old with Gross Motor Function Classification System II-IV. Participants will be allocated to experimental group (intervention and usual care) or control group (usual care), using stratified randomisation process into two strata (progressive and non-progressive ataxia). Participants will be assessed at baseline, by the end of the 4-week period and by the end of a 2-month period as a follow-up measurement. Motor and functional skills will be assessed using the Gross Motor Function Measure-D and E, the Pediatric Balance Scale, the 10-meter walk test, the 6-minute walk test, the Scale for Assessment and Rating Ataxia, the timed up and go test and children's spatiotemporal gait features will be assessed through GaitSens software recording over a 2 min low treadmill gait speed, while three-dimensional gait analysis will be performed for kinetic and kinematic analysis of the lower limbs in all three levels of movement. Two-way mixed Analysis of Variance (ANOVA) with factors 'intervention' (between group) and 'time' (within group) will be used for the analysis of all parameters. Analysis of Covariance (ANCOVA) will be used in case of imbalance of baseline measurements. Statistical significance will be set at p<0.05 using the statistical package SPSS V.21.00. ETHICS AND DISSEMINATION: University of West Attica (study's protocol: 14η/26-04-2021) and 'ATTIKON' General University Hospital of Athens (study's protocol: Γ ΠΑΙΔ, ΕΒΔ 149/20-3-2020). Trial results of the main trial will be submitted for publication in a peer-reviewed journal and/or international conference. TRAIL REGISTRATION NUMBER: ISRCTN54463720. © Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ
The incidence of place of death in Greek patients with cancer in 1995 and 2005
No full textPurpose: To describe where (home or hospital) patients with cancer die in Greece, in 1995 and 2005. Methods: We used data from patients with cancer, who died in Greece in 1995 and 2005, and we studied the location changes of death in the 3 major geographical areas of Greece (Macedonia: North Greece, Central Greece, and Crete: South Greece). Results: In Central Greece and Crete, death incidences for 60 to 69, 70 to 79, and 80+ age groups decreased from 1995 to 2005. In Crete, in 1995, male and female death incidences for 80+ age group dying at home was higher than the corresponding one dying in hospital. Conclusion: It seemed that in Greece, more cancer patients are dying in hospitals. Geographical and socioeconomic criteria might affect the place of death of a patient with cancer. © 2009 The Author(s)
Self-efficacy, depression, and physical distress in males and females with cancer
No full textAims: To examine the relationship between self-efficacy with depression and physical distressing symptoms in males and females with cancer. Methods: A total of 41 males and 49 females with cancer completed the General Perceived Self-Efficacy Scale (GSE), depression scale, from the Hospital Anxiety and Depression Scale (HAD-D), and the MD Anderson Symptom Inventory (MDASI). Results: Correlations were found between depression and self-efficacy in males (r = -.501, P=.001) and females (r = -.588, P <. 0005). The multivariate regression analysis revealed that education and depression could influence self-efficacy in male population. Urogenital versus breast cancer as well as depression seemed to influence females' self-efficacy. Conclusions: Patients who had higher self-efficacy had lower depressive symptoms. Men with depressive symptoms and women with breast cancer and depression are more likely to have low self-efficacy than patients with other cancer types. © The Author(s) 2010
