Stability analysis and active stabilization of DC microgrid clusters using adaptive controllers

This report presents a small-signal model of a DC Microgrid (MG) cluster and its control system. In the closed loop control system, proportional-integral (PI) controllers and two active stabilization methods, namely the droop loop and the feed-forward compensation loop, are used. A consensus-based distributed control framework is used to control the output voltages of the MGs and power flow between the MGs. Simulations of the small-signal model on MATLAB/Simulink demonstrate that the control system successfully stabilizes the DC MG cluster at a particular operating point, as it is able to reject sudden changes in voltage, current, or load demand. The PI controllers are then replaced with adaptive PI controllers, and simulation results show that the adaptive PI controllers better stabilize the system against sudden load changes and current disturbances. Hardware-in-the-loop simulations on OPAL-RT verify that the adaptive PI controllers and feed-forward compensation loop stabilize the system more rapidly, as the MG voltages settle faster to the steady state. This report concludes with some possible future extensions to this project, and my reflections.Bachelor of Engineering (Electrical and Electronic Engineering

Double Heterojunction Crystalline Silicon Solar Cells: From Doped Silicon to Dopant-Free Passivating Contacts

Carrier-selective passivating contacts for effective electron and hole extraction are crucial to the attainment of high efficiency in crystalline silicon (Si) solar cells. In this comprehensive review, the principle of carrier extraction and recombination mechanisms in conventional industrial Si solar cells are discussed first. Passivating contacts based on (i) amorphous hydrogenated Si and (ii) polysilicon/silicon oxide are next reviewed, with emphasis on carrier selectivity mechanisms including contact layer band alignment with silicon, and localized carrier transport in ultrathin oxides. More recent developments in dopant-free passivating contacts deposited by lower-cost fabrication processes with lower thermal budget are then described. This third category of non-Si based electron- and hole-selective passivating contacts include transition metal oxides, alkali/alkali earth metal fluorides and organic conjugated polymers. The photovoltaic performance of asymmetric double heterojunction Si solar cells fabricated using these non-Si passivating contacts and their stability in damp heat conditions are discussed and compared with Si based passivating contacts

Double heterojunction crystalline silicon solar cells: from doped silicon to dopant-free passivating contacts

Carrier-selective passivating contacts for effective electron and hole extraction are crucial to the attainment of high efficiency in crystalline silicon (Si) solar cells. In this comprehensive review, the principle of carrier extraction and recombination mechanisms in conventional industrial Si solar cells are discussed first. Passivating contacts based on (i) amorphous hydrogenated Si and (ii) polysilicon/silicon oxide are next reviewed, with emphasis on carrier selectivity mechanisms including contact layer band alignment with silicon, and localized carrier transport in ultrathin oxides. More recent developments in dopant-free passivating contacts deposited by lower-cost fabrication processes with lower thermal budget are then described. This third category of non-Si based electron- and hole-selective passivating contacts include transition metal oxides, alkali/alkali earth metal fluorides and organic conjugated polymers. The photovoltaic performance of asymmetric double heterojunction Si solar cells fabricated using these non-Si passivating contacts and their stability in damp heat conditions are discussed and compared with Si based passivating contacts.Published versio

Growth Performance and Meat Quality of Broiler Chickens Supplemented with in Drinking Water

A feeding trial was conducted to investigate effects of Bacillus licheniformis on growth performance and meat quality of broilers. Nine hundred one-d-old broiler chicks were randomly assigned to 3 experimental groups with three replicate pens of 100 broiler chicks. Three treatments were i) control, ii) basal diets supplemented with 1 ml of B. licheniformis for each in feed water per day iii) basal diets supplemented with 2 ml of B. licheniformis per chick in feed water per day. The supplementation of B. licheniformis significantly increased body weight in grower chickens (p<0.05), and significantly improved the feed conversion in 3 to 6 and 0 to 6 wk feeding period compared with the control group (p<0.05). Additionally, the supplement also resulted in increased protein and free amino acid contents, and decreased fat content in chicken breast fillet (p<0.05). Furthermore, improvement in sensory attributes was observed in broilers fed with the probiotic. In conclusion, B. licheniformis treatments resulted in a significant increase (p<0.05) in broiler productivity based on an index taking into account daily weight gain and feed conversion rate. Meanwhile, the probiotic contributed towards an improvement of the chemical, nutritional and sensorial characteristics of breast fillet. Overall, the study indicates that B. licheniformis can be used as a growth promoter and meat quality enhancer in broiler poultry

A scoping review and theory‐informed conceptual model of professional identity formation in medical education

AbstractIntroductionProfessional identity formation (PIF) is a central tenet of effective medical education. However, efforts to support, assess and study PIF are hindered by unclear definitions and conceptualisations of what it means to ‘think, act, and feel like a physician’. Gaps in understanding PIF, and by extension, its support mechanisms, can predispose individuals towards disengaged or unprofessional conduct and institutions towards short‐sighted or reactionary responses to systemic issues.MethodsA Systematic Evidence‐Based Approach‐guided systematic scoping review of PIF theories was conducted related to medical students, trainees and practising doctors, published between 1 January 2000 and 31 December 2021 in PubMed, Embase, ERIC and Scopus databases.ResultsA total of 2441 abstracts were reviewed, 607 full‐text articles evaluated and 204 articles included. The domains identified were understanding PIF through the lens of pivotal theories and characterising PIF by delineating the underlying factors that influence it and processes that define it.ConclusionsBased on regnant theories and frameworks related to self‐concepts of identity and personhood, the relationships between key PIF influences, processes and outcomes were examined. A theory‐backed integrated conceptual model was proposed to delineate the interconnected relationships among these, aiming to untangle some of the complexities inherent to PIF, to shed light on existing practices and to identify shortcomings in our understanding so as to develop mechanisms in support of its multifaceted, interlinked components.</jats:sec

Assessing professional identity formation (PIF) amongst medical students in Oncology and Palliative Medicine postings: a SEBA guided scoping review

Abstract Background Introduction to a multi-professional team who are working and caring for the dying, and facing complex moral and ethical dilemmas during Oncology and Palliative Medicine postings influence a medical student’s professional identity formation (PIF). However, limited appreciation of PIF, inadequate assessments and insufficient support jeopardise this opportunity to shape how medical students think, feel and act as future physicians. To address this gap, a systematic scoping review (SSR) of PIF assessment methods is proposed. Methods A Systematic Evidence-based Approach (SEBA) guided SSR of assessments of PIF in medical schools published between 1st January 2000 and 31st December 2021 in PubMed, Embase, ERIC and Scopus databases was carried out. Included articles were concurrently content and thematically analysed using SEBA’s Split Approach and the themes and categories identified were combined using SEBA’s Jigsaw Perspective. The review hinged on the following questions: “what is known about the assessment of professional identity formation amongst medical students?”, “what are the theories and principles guiding the assessment of professional identity formation amongst medical students?”, “what factors influence PIF in medical students?”, “what are the tools used to assess PIF in medical students?”, and “what considerations impact the implementation of PIF assessment tools amongst medical students?”. Results Two thousand four hundred thirty six abstracts were reviewed, 602 full-text articles were evaluated, and 88 articles were included. The 3 domains identified were 1) theories, 2) assessment, and 3) implementation in assessing PIF. Differing attention to the different aspects of the PIF process impairs evaluations, jeopardise timely and appropriate support of medical students and hinder effective implementation of PIF assessments. Conclusion The Krishna-Pisupati model combines current theories and concepts of PIF to provide a more holistic perspective of the PIF process. Under the aegis of this model, Palliative Care and Oncology postings are envisaged as Communities of Practice influencing self-concepts of personhood and identity and shaping how medical students see their roles and responsibilities as future physicians. These insights allow the forwarding of nine recommendations to improve assessments of PIF and shape the design of a PIF-specific tool that can direct timely and personalized support of medical students. </jats:sec