Performance Modelling and Optimisation of NoSQL Database Systems

The 8th International Workshop on Performance Modeling, Evaluation, and Optimization of Ubiquitous Computing and Networked Systems (PMEO-UCNS'09)

Welcome to PMEO-UCNS'10! This is the 9 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> International Workshop on Performance Modeling, Evaluation, and Optimization of Ubiquitous Computing and Networked Systems is being held in conjunction with IPDPS'10.

Accurate modeling of direct-detection lightwave systems is required for system performance assessment and optimization, especially in the presence of impairments. System optimization, though, is generally numerically intensive and notably so when trying to accommodate the full range of impairments that are representative of practical systems.

A framework for the design, modeling and optimization of biomedical systems

In the field of urban and green mobility, electric car-sharing networks have recently emerged as one of the promising alternatives, dealing with both environmental and transportation issues. Despite the increasing success of the shared mobility concept over the world, the design and management of such urban mobility systems implies strategic, tactical and operational challenges. To support designers and operators, all these issues constitute an emerging and challenging research topic, aiming to develop techniques and tools for modeling, analysis and optimization of such complex systems. In this contribution, based on the modeling and analysis power of stochastic timed Petri nets, a discrete event simulation approach is developed, taking into account their dynamic behavior complexities due to their self-service mode and characteristics including capacities of the stations, energy availability, rebalancing and maintenance activities. A real-life application is presented, to demonstrate the applicability and the potential of the proposed modeling and simulation analysis approach. <i>Note to Practitioners</i>&#x2014;To support designers, providers and managers of shared mobility programs, performance and optimization models and decision-making tools are needed. In this contribution, we deals with a powerful and modular stochastic timed Petri net methodology suitable for performance modeling and simulation analysis of such complex dynamical systems. The authors believe that this discrete event dynamic approach has significant promise for the future and to influence economic viability and operational efficiency of such emerging urban transportation systems.

The need for performance has motivated the increasing adoption of solid-state drives (SSD) both in personal computers and data centers. However, the high cost per gigabyte and reduced lifetime hinder the thorough replacement of hard disk drives (HDD) with SSDs. To mitigate these issues, several architectures have been conceived based on hybrid storage systems, but performance and dependability models have not been proposed to better assess such different architectures. This paper presents an approach based on stochastic models for performance and availability modeling of hybrid storage systems, using stochastic Petri nets (SPN) and reliability block diagrams (RBD). A case study based on OpenStack Swift platform is adopted to demonstrate the feasibility of the proposed approach.

“Securing the Digital Frontier: Navigating Cyber Threats in Cloud, Network, and Information Security” offers a comprehensive exploration of the intricate landscape of Cyber security, meticulously designed to equip readers with a robust understanding of contemporary challenges and proactive strategies. With an elaborate Table of Contents spanning thirteen chapters, the book embarks on a journey that starts with laying the groundwork in Chapter 1, providing a holistic Introduction to Cyber security. Here, readers delve into the nuances of the digital realm, tracing the Evolution of Cyber Threats, and comprehending the Historical Milestones that have shaped the field. It underscores the paramount Importance of Cyber security in Modern Society and elucidates the Current State of Cyber security Challenges while speculating on Future Projections and Trends, emphasizing the Interdisciplinary Nature of Cyber security. Moving forward, Chapter 2 delves into the Fundamentals of Information Security, elucidating the CIA Triad – Confidentiality, Integrity, and Availability. It navigates through Risk Management, Compliance, and Regulatory Frameworks, shedding light on Security Policies and Procedures alongside the significance of Security Awareness Training and Incident Response Planning. Subsequent chapters systematically dissect various domains of Cyber security, from Network Security (Chapter 3) to Cloud Security (Chapter 4), Endpoint Security (Chapter 5), and Identity and Access Management (Chapter 6). Each chapter meticulously examines core concepts, methodologies, and best practices essential for fortifying digital infrastructures against evolving threats. The discourse extends to Data Protection (Chapter 7), Threat Intelligence and Detection (Chapter 8), and Incident Response and Management (Chapter 9), offering invaluable insights into encryption techniques, threat hunting strategies, and incident triage frameworks. Furthermore, Security Operations and Monitoring (Chapter 10) elucidates the pivotal role of Security Operations Centers (SOCs), Vulnerability Management, and Red Team vs. Blue Team Exercises in bolstering cyber defenses. Chapter 11 ventures into Emerging Technologies and Threats, contemplating the security ramifications of IoT, AI, Quantum Computing, Block chain, AR, VR, and Biometric Authentication. Meanwhile, Chapter 12 explores the realm of Ethical Hacking and Penetration Testing, unraveling methodologies for ethical hacking, vulnerability assessment, and social engineering mitigation. Finally, Chapter 13 prognosticates on Future Trends and Challenges, accentuating the imperative of addressing the Skills Gap, fostering Global Collaboration, and navigating Regulatory Challenges amidst burgeoning technological advancements. It underscores the ethical considerations paramount in Cyber security endeavors while advocating for resilience-building strategies against escalating cyber threats. In essence, “Securing the Digital Frontier” transcends the realms of a conventional Cyber security manual, emerging as an indispensable compendium for Cyber security professionals, aspiring enthusiasts, and stakeholders navigating the ever-evolving digital ecosystem. It amalgamates theoretical insights with practical wisdom, empowering readers to navigate the complex terrain of cyber threats with confidence and acumen.

Chapter 13 - IT Operational Security Plan

Due to the tremendous growth in the evolution of telecommunication system and wireless networks, recent developments in telecommunication system and wireless communication technologies and mobile networks has posed various challenges to the researchers in the field of performance modelling. These challenges require effective performance evaluation tools, techniques and methodologies to design new protocols and robust solutions before a global and wide-scale integrated broadband infrastructure of convergent multi-service networks can be established towards the next generation of telecommunication system with efficient support of multimedia applications. As a result, performance modelling and evaluation has gained increasing importance. This special issue solicits papers on advances in the analytical and simulation based modelling and evaluation of new challenges in the telecommunication systems. Papers in this special issue were selected from the IEEE International Workshop on Performance Modelling and Evaluation in Computer and Telecommunication Networks (PMECT2008) in conjunction with the 17th IEEE International Conference on Computer Communications and Networks (ICCCN 2008), held in August 4–7, 2008 at Virgin Islands, USA. These papers were selected by the scientific

We investigate optimization of system performance in the below scenario: capturing and transmitting videos by single or multiple video sensors using distributed video coding (DVC) over ad hoc networks. There is an intrinsic contradiction in this scenario that could affect the system performance: the contradiction between the decoding quality and network lifetime. In this paper, we propose a joint optimization between the decoding quality and network lifetime using a quantitative metric of system performance, which is defined as the amount of collected visual information during the operational time of the video sensor. Based on the proposed metric, an optimal encoding rate is determined, which results in an optimal system performance. The simulation results show that the optimal encoding rate can be determined to achieve the optimal system performance.KeywordsDistributed video codingad hoc networksenergyoptimization

The potential for blockchain to transform several industries, including cybersecurity, has piqued the interest of many different sectors. This abstract delves into the relationship between blockchain and cybersecurity, showcasing how the two may work together to strengthen data security. The present cybersecurity scenario prompted this study to examine existing blockchain-based security solutions. In this study, we looked at the ways blockchain technology maintains the security triangle. The results show that blockchain has a lot of promise for solving current cybersecurity problems, especially with IoT, data ownership and integrity, and network security. However, high-cost complexity, regulatory barriers, and technology immaturity all hinder wider implementation. As a result, using blockchain-based solutions in cybersecurity requires careful consideration of how well they apply to the particular requirements of an organisation, as well as the establishment of precise implementation objectives and the navigation of potential obstacles. This pertinent systematic review sheds light on several subjects that should be explored further as fields for cyber and blockchain security research, education, and practice, including blockchain security in the IoT, blockchain security for AI data, and sidechain security.

Current Opinion in Allergy and Clinical Immunology was launched in 2001. It is one of a successful series of review journals whose unique format is designed to provide a systematic and critical assessment of the literature as presented in the many primary journals. The fields of allergy and clinical immunology are divided into 14 sections that are reviewed once a year. Each section is assigned a Section Editor, a leading authority in the area, who identifies the most important topics at that time. Here we are pleased to introduce the Journal's Editors and Section Editors for this issue. EDITORS Mark BallowMark BallowDr Mark Ballow received his MD from the University of Chicago Pritzker School of Medicine, USA. After a pediatric residency at Yale-New Haven Hospital, USA, he completed an immunology fellowship at the University of Minnesota Hospitals, USA. He was the Chief of Clinical and Experimental Immunology at Walter Reed Army Medical Center, USA. He was then appointed as Chief of the Division of Clinical Immunology in the Department of Pediatrics at the University of Connecticut, USA from 1975 to 1988, and became Chief of the Division of Allergy/Clinical Immunology and Pediatric Rheumatology, and Program Director of the Allergy/Immunology fellowship program at The Women and Children's Hospital of Buffalo, State University of New York at Buffalo, USA from 1988 to 2012. He is presently Training Program Director of the Allergy/Immunology Fellowship program at University of South Florida, Allergy & Immunology Division at All Children's Hospital in St Petersburg, FL. Dr Ballow is certified by the American Board of Pediatrics, American Board of Allergy & Immunology (ABAI), and in Clinical Laboratory Immunology. He was on the Board of Directors of the ABAI from 1992–1998. He has served on four editorial boards including the Journal of Allergy and Clinical Immunology (1984–1989; 1995–2000), and is an Ad Hoc reviewer for a number of pediatric, allergy and immunology journals. He has recently been appointed to the editorial board of Journal of Allergy and Clinical Immunology: In Practice. Dr Ballow has served as an ad hoc member of several NIH study sections, and was a member of the committee that published the first Allergy and Immunology Medical Knowledge Self Assessment Program (MK-SAP), and was a member of the new 3rd edition AI-MK-SAP. Dr Ballow is a Fellow of the American Academy of Asthma, Allergy and Immunology, and has served on the Board of Directors of the Academy (1996–1999), and has chaired the A/I Training Program Directors, Basic Clinical immunology Interest Section, and the Post-graduate Education Program. He was President of the American Academy of Allergy, Asthma and Immunology in 2010–2011. Dr Ballow is a member of the Clinical Immunology Society, the Florida Allergy Society, and the American College of Allergy, Asthma and Immunology. He also has served on the Blood Product Advisory Committee of the FDA. Dr Ballow's major clinical interests include chronic sinusitis, primary immune deficiency disorders, and the uses and mechanisms of action of Intravenous Immune Globulin (IGIV). His research interests include the immunology of the newborn infant and the immunoregulatory effects of IVIG, Vitamin A and retinoic acid. G. Walter CanonicaG. Walter CanonicaProfessor Giorgio Walter Canonica is Director of the Allergy & Respiratory Diseases Clinic, Genoa University, Italy, a GALEN Centre of Excellence. Professor Canonica first specialised in pulmonary diseases after having received his medical degree from the University of Genoa, Italy. He then specialised in Allergy and Clinical Immunology at Florence University, Italy. He subsequently conducted clinical immunology and allergology research in several European universities and institutes, in addition to two years at the Medical University of South Carolina, USA. Since returning to the University of Genoa in 1995, Professor Canonica has held a number of academic positions including Director of the Speciality School of Allergy and Clinical Immunology, Director of the Specialty School of Pulmonary Diseases and Chairman of Chairman of the Dept of Medical Specialties (University Hospital S. Martino Genoa, Italy). He is Board Member of ARIA (Allergic Rhinitis and its impact Asthma) guidelines) and GALEN (Global Allergy and Asthma European Network). Professor Canonica's research interests include examination of the molecular events and interactions between immunocompetent cells, inflammatory cells and epithelial cells in allergic inflammation and airway remodelling. He is particularly involved in new strategies in the treatment of allergic disease, including biological response modifiers, such as specific immunotherapy (with a special focus on SLIT – sublingual immunotherapy - and Severe Asthma treatment with biologics). Professor Canonica has published extensively in international journals and acts as a referee of many immunology journals. In addition, Professor Canonica is a member of a number of societies, he was President of World Allergy Organization 2008/09. He is also currently President of Global Asthma Association - Interasma. He was President of SIMeR (Italian Society of Respiratory Medicine) 2000–2003 and he is Honorary President of this same Society since 2007. He is currently President of SIAAIC Italian Society of Allergy, Asthma and Clinical Immunology (2014–2017). SECTION EDITORS Ruby PawankarRuby PawankarProf. Ruby Pawankar MD, PhD, FRCP (UK), FAAAAI is currently the Immediate Past President of the World Allergy Organization (WAO) and was WAO President from January 2012 to December 2013, after serving as a member of the Board of Directors since 2001, as Treasurer 2008–2009 and as President-Elect 2010–2011. She is currently also the President of the Indian Academy of Allergy. She is Professor of Allergy in the Department of Pediatrics at Nippon Medical School, Tokyo, Japan, and Guest Professor at the Kyung Hee University School of Medicine in Seoul, Korea and the Showa University School of Medicine in Tokyo, Japan. After graduating in medicine from the Armed Forces Medical College, Pune, India, Prof. Pawankar did her residency and post-graduation from BJ Medical College, Pune, India. Thereafter, she trained in Allergy & Clinical Immunology at the Nippon Medical School and Juntendo University School of Medicine in Tokyo, Japan from where she obtained her doctorate. Prof. Pawankar serves on numerous committees and boards of many academic organizations and grant reviews, is a Member/Fellow of organizations including the Collegium International Allergolicum, the American Academy of Allergy, Asthma and Immunology, the American College of Allergy and Immunology, the European Academy of Allergy and Clinical Immunology and the Japanese Society of Allergology. She has delivered several orations/named lectures nationally and internationally including the SK Malik Oration and DN Shivpuri Oration. She is a recipient of many academic awards including the World Achievement Award in Allergy from Thailand; the International Distinguished Fellow Award from the American College of Allergy, Asthma & Immunology; and especially the Pravasi Bharatiya Samman Award from the President of India for excellence in medicine. Prof. Pawankar's research has focused on the cellular and molecular mechanisms of allergy, immune cells like mast cells and T cells, epithelial cell-immune cell interactions, novel roles of IgE, mast cell-IgE cascade, environmental pollution, immunotherapy and novel therapies for respiratory allergies. In 1995, she was the first to report on the increased presence and role of gamma delta T cells in allergic rhinitis. In 1997, she was among the first to show that mast cells in perennial allergic rhinitis exhibit increased expression of the IgE receptor as well as being a major source of the obligatory pro- allergic Th2 cytokines interleukin IL-4, and IL-13 capable of driving local allergen-specific IgE synthesis by B lymphocytes and has formed the basis of the successful therapeutic targeting of these cytokines with biological therapeutics. Her research and educational activities have been strongly translational as it applies to clinical science. This has resulted in 411 publications including peer-reviewed original articles in: Journal of Allergy and Clinical Immunology, Journal of Clinical Investigation, Journal of Immunology, Blood, American Journal of Respiratory and Critical Care Medicine, Allergy, Clinical & Experimental Allergy, International Archives of Allergy and Immunology, Current Opinion in Allergy and Clinical Immunology etc, and invited reviews and book chapters. She is an Editor/ Associate Editor of peer-reviewed journals such as: International Archives of Allergy, Clinical Experimental Immunology, Current Opinion in Allergy and Clinical Immunology etc., and books including the 6 volume book ‘Allergy Frontiers’, the WAO White Book on Allergy, Update on Respiratory Disorders, and is a co-author of several consensus documents. She has mentored over 30 fellows from Japan and abroad. Prof. Pawankar has chaired as President and organized several international congresses including: the 10th Trans Pacific Allergy Congress in Mumbai, India; the first and the Middle East Allergy Congress, in 2009 and 2011 respectively; the WAO International Scientific Conference (WISC) 2012, India; the World Allergy Asthma Congress 2013, Milan, Italy, as well as several educational programs and has been a visiting faculty to lecture at several institutions such as Harvard Medical School, USA; the University of Wisconsin, USA; Imperial College, London, UK; Catholic University, Argentina; the University of Sao Paolo, Brazil and Mahidol University, Thailand. At an organizational level, her vision is to create a channel of dialogue with all stakeholders to address the unmet global public health issue of asthma and allergies in the context of non-communicable diseases (NCDs) via an integrated approach that could lead to increased resources for research, improved patient care, better health care delivery, and preventative strategies. David P. SkonerDavid P. SkonerDr David P. Skoner is Director of the Division of Allergy, Asthma, and Immunology in the Department of Medicine of Allegheny General Hospital in Pittsburgh, Pennsylvania, USA. He is also Professor of Medicine at the Temple University School of Medicine in Philadelphia, Pennsylvania, USA and Clinical Professor of Pediatrics, West Virginia University School of Medicine, USA. Previously, he was Associate Professor of Pediatrics and Otolaryngology at the University of Pittsburgh, School of Medicine, USA and has served as the Chief of the Section of Allergy/Immunology and Director of the Allergy and Immunology Training Program at the Children's Hospital of Pittsburgh, USA. Dr Skoner received his BS degree from Juniata College in Huntingdon, Pennsylvania, USA and his MD degree from Temple University in Philadelphia, Pennsylvania, USA. He served his residency in general pediatrics at Children's Hospital in Cincinnati, Ohio, USA, and he completed his fellowship in allergy/immunology at Children's Hospital in Pittsburgh. His current research interests include the relationships between respiratory viruses, asthma, immunity, and stress; the relationship between viral and allergen-induced nasal inflammation and middle ear disease; and the efficacy and safety (HPA axis function and growth in children) of inhaled and intranasal steroids. Dr Skoner has received NIH funding and written more than 100 articles and given more than 200 presentations on respiratory disease. His articles and abstracts have been published in many leading journals, including Pediatrics, Journal of Allergy and Clinical Immunology, Pediatric Research, American Journal of Respiratory and Critical Care Medicine, The Journal of the American Medical Association, and American Review of Respiratory Disease. Dr Skoner serves on the editorial advisory boards of the journals Current Allergy and Asthma Reports, and Current Opinion in Allergy and Clinical Immunology, and previously served on the editorial board of the American Journal of Rhinology. He is a Fellow of the American Academy of Pediatrics and a member of the Society of Pediatric Research, the American Academy of Allergy, Asthma and Immunology, the American College of Allergy, Asthma & Immunology, the Association for Research in Otolaryngology, and the American Pediatric Society. He has been recognized as one of America's ‘Top Doctors’ (Pediatric Allergy & Immunology, Castle Connolly Medical Ltd.) from 2001 to 2014, as one of the Most Influential Doctors by USA TODAY (http://www.usatoday.com/yourlife/health/most-influential-doctors.htm), and as a U.S. News Top Doctor (www.usnews.com/top-doctors). He was invited to join the Best Pharmaceuticals for Children Act (BPCA) Pediatric Asthma Therapeutics Group convened by the National Institute of Child Health and Human Development. Dr Skoner co-founded the Nemacolin Asthma Conference (www.ahn.org/nemacolin-asthma), a continuing medical education (CME) program that attracts a national and an international audience and faculty, now in its ninth year. He also founded and is the President of ‘For Your Good Health’ (www.fygh.org), a Pennsylvania non-profit corporation that brings together asthma stakeholders in the development and implementation of state-of the-art programs to educate children with asthma and their caregivers about the disease and its management. The aim of these programs is to reduce asthma's impact on patients, caregivers, the community, and the healthcare system by helping the patients to lead near-normal lives. He also serves on the board of the non-profit Greater Pittsburgh Allergy Asthma and Immunology Society (GPAAIS), which serves to educate and inform physicians and other health care providers. Dr Skoner was selected as a finalist in the category of ‘Health Care Provider: Physician’ for the 2013 Pittsburgh Business Times Health Care Heroes Awards. J. Andrew GrantJ. Andrew GrantDr Grant is a native of Florida and received his undergraduate degree from Harvard University, USA, in biochemical sciences. After attending Duke Medical School, USA, he did a residency in internal medicine at New York Hospital – Cornell Medical Center in New York City, USA. He did a fellowship in immunology with Leroy Hood at the National Institutes of Health and an allergy-immunology clinical fellowship at Johns Hopkins University, USA, with Phillip Norman and Lawrence Lichtenstein. In 1973, he established the first basic and clinical research program in allergy in Texas at the University of Texas Medical Branch in Galveston, USA. Presently he is Clinical Professor in the Departments of Medicine and Microbiology-Immunology and training program Director in Allergy-Immunology at that institution. He has served as Division Director and Vice Chair for Research within the Department of Internal Medicine. He vacations during the summer months in Colorado and has been appointed Clinical Professor at University of Colorado Medical School, USA. Dr Grant has been an active member of the American Academy of Allergy, Asthma and Immunology for over four decades. His contributions to this organization include chairing the Program Directors Assembly, Mechanisms of Allergy Interest Section, Postgraduate Education Committee, Scientific Workshops and Exhibits Committee, and Immunotherapy Committee. He served on the Editorial Board of the Journal of Allergy and Clinical Immunology. He founded In-training Examination for Allergy-Immunology postdoctoral fellows, the first subspecialty exam of its type. Dr Grant served as President of the Texas Allergy Asthma and Immunology Society and a Director of the American Board of Allergy and Immunology, and a member of the Residency Review Committee for Allergy and Immunology. He chaired the Pulmonary Allergy Drugs Advisory Committee of the Food and Drugs Administration and currently is a member of the Allergenic Products Advisory Committee. He was a visiting professor at the National Heart and Lung Institute with Professor Barry Kay in 1994. Dr Grant's research interests have included mechanisms of cellular activation especially the role of chemokines and novel therapies for allergic disorders. Currently he is emphasizing management of difficult patients with urticaria and angioedema. He has authored over 190 publications and chapters and 175 presentations at national and international meetings. Peter Howarth Professor Peter Howarth is Professor of Allergy and Respiratory Medicine and Honorary Consultant Physician within Medicine at the University of Southampton with a clinical and research focus on asthma, particularly severe asthma, and allergy. Professor Howarth has supervised over 20 PhD and DM students (scientists and clinicians) and his research involves Local, National and International collaboration. He has participated in EU funded collaborative programmes, such as BIOAIR and GA2LEN, focusing respectively on severe asthma and allergic diseases, and is joint work package 4 lead for UBIOPRED, the EU/EFPIA funded IMI programme on severe asthma. Professor Howarth has published over 200 peer reviewed papers and lectured extensively at National and International specialist society meetings as an invited speaker. Professor Howarth has contributed to National, European and International (World Health Organisation) guidelines on the management of rhinitis and asthma. He has been on the council of The British Society of Allergy and Clinical Immunology, advisor on allergy to Asthma UK and has been chairman of the board of trustees of Allergy UK. He is currently President of Allergy UK and a trustee of AAIR.

Modern software systems provide many configuration options which significantly influence their non-functional properties. To understand and predict the effect of configuration options, several sampling and learning strategies have been proposed, albeit often with significant cost to cover the highly dimensional configuration space. Recently, transfer learning has been applied to reduce the effort of constructing performance models by transferring knowledge about performance behavior across environments. While this line of research is promising to learn more accurate models at a lower cost, it is unclear why and when transfer learning works for performance modeling. To shed light on when it is beneficial to apply transfer learning, we conducted an empirical study on four popular software systems, varying software configurations and environmental conditions, such as hardware, workload, and software versions, to identify the key knowledge pieces that can be exploited for transfer learning. Our results show that in small environmental changes (e.g., homogeneous workload change), by applying a linear transformation to the performance model, we can understand the performance behavior of the target environment, while for severe environmental changes (e.g., drastic workload change) we can transfer only knowledge that makes sampling more efficient, e.g., by reducing the dimensionality of the configuration space.

Performance modelling and estimation of computer systems is a vital facility for any software engineer. Thus any computer-aided software engineering environment should contain tools to support this. The need to provide tools to support systematic experimentation with performance models is examined and a solution is discussed, building on the idea of an experimental frame, originally introduced by Zeigler in Ref. 1. The inter-working of these tools and the support tools in a proposed integrated modelling support environment is considered. The tools discussed are an experimental plan editor, an experiment executor and an animator. This report is based on a deliverable***! of the Alvey project SE/059 ‘Improved methods for performance modelling (SIMMER)’, but has been edited to be more self-contained.

Semprius, a producer of high concentration photovoltaic (CPV) modules with world record efficiency, has developed capabilities for modeling field performance of CPV modules using two performance models: PVsyst and Semprius Performance Model (SPM). Modeling with PVsyst relies on the definition of a PAN file which is described here. SPM is the result of Semprius' collaboration with Sandia National Laboratory to develop software that can accurately model the field performance of Semprius CPV systems. The performance of both PVsyst and SPM is demonstrated for Semprius CPV by validation against actual Semprius CPV systems operating in the field, one in Tucson and one at Sandia National Labs, NM. These comparisons suggest that both of these models can accurately predict annual AC energy yield to within 1-3 percent.