Control of Distributed Uninterruptible Power Supply Systems

In the last years, the use of distributed uninterruptible power supply (UPS) systems has been growing into the market, becoming an alternative to large conventional UPS systems. In addition, with the increasing interest in renewable energy integration and distributed generation, distributed UPS systems can be a suitable solution for storage energy in micro grids. This paper depicts the most important control schemes for the parallel operation of UPS systems. Active load-sharing techniques and droop control approaches are described. The recent improvements and variants of these control techniques are presented

Der platonische Nietzsche

Mit der Behauptung, dass seine eigene Philosophie als »umgedrehter Platonismus« verstanden werden soll, stellt Nietzsche seine Beziehung zum platonischen System dar. Dieses Forschungsprojekt sucht nach einer neuen Variation dieser Darstellung, um die philosophischen Analogien beider Autoren aufzuspüren. Das erste Kapitel beschäftigt sich mit einer Erläuterung des Begriffes „umgedrehter Platonismus“, womit die Differenz zwischen diesen beiden Systemen definiert wird. Diese Diskrepanz ist spürbar in vier verschiedene Bereichen: metaphysisch, axiologisch, gnoseologisch und ästhetisch. Das zweite Kapitel behandelt die Rolle des Apollinischen und des Dionysischen in der nietzscheschen Theorie. Die beiden Konzepte werden mit dem des platonischen Eros verglichen, da diese es dem Menschen ermöglichen, die sinnliche Welt zu verlassen und eine Ur-Realität kennenzulernen. Das dritte Kapitel analysiert die Verurteilung der Kunst in Platon’s „Staat“. Der griechische Philosoph strebt die wahre Kenntnis an und verbindet seine ästhetischen Überlegungen mit der Idee der Wahrheit. Nietzsche bearbeitet diese Verbindung zwischen Ästhetik und Erkenntnistheorie unter dem Begriff »amor fati«. Das vierte Kapitel ist der Physiologie der Liebe gewidmet. Nietzsche verwandelt der Erkenntnisprozess in eine leidenschaftliche Liebe. Die Erkenntnis nimmt die Form einer Passion an und kristallisiert sich allmählich und nach einem langen Prozess mit Höhen und Tiefen in »amor fati«. »Amor fati« schafft eine Ästhetisierung der Erkenntnis und Epistemologiesierung der Ästhetik. Somit liegt Nietzsches Erkenntnistheorie parallel zu jener Platons.By claiming that his philosophy should be understood as “inverted Platonism” Nietzsche defined his relationship to the Platonic system. This research project aims to articulate a new understanding of this relationship by analyzing philosophical similarities between the two authors'' respective philosophies. The first chapter is dedicated to the explanation of the term “inverted Platonism” and articulates the differences between Plato''s and Nietzsche''s systems. These discrepancies are manifested in four main areas: the metaphysical, the axiological, the gnosiological and the aesthetic. The second chapter deals with the roles of the Apollonian and the Dionysian in Nietzschean theory. Both concepts are compared with the Platonic Eros, as they invite man to abandon the sensual world and instead to commune with the very origin of reality. The third chapter analyzes Plato´s denunciation of art in “The Republic”. The Greek philosopher seeks true knowledge and connects his aesthetic concerns with the idea of Truth. Nietzsche refers to the cynosure between aesthetics and cognitive theory as “amor fati”. The fourth chapter is dedicated to the physiology of love. Nietzsche transforms the cognitive process into a passionate love. Cognition assumes the shape of passion, slowly crystallizing over time, with many twists and turns, into “amor fati”. “Amor fati” aestheticizes cognition and epistemologizes aesthetics. Therefore Nietzsche''s cognitive theory is actually equivalent to that of Plato

Prevalence of Vitamin D Inadequacy Among Chinese Postmenopausal Women: A Nationwide, Multicenter, Cross-Sectional Study

Purpose: We aimed to investigate the status of serum 25-hydroxyvitamin D [25(OH)D] among Chinese postmenopausal women in a multicenter cross-sectional study.Methods: Non-institutionalized postmenopausal women aged ≥55 years were recruited from urban and rural areas in 7 geographically different regions in China. Subject enrollment was executed during the summer and the winter. Vitamin D insufficiency and deficiency were defined as 25(OH)D < 30 and< 20 ng/ml, and was measured by liquid chromatography-tandem mass spectrometry. Women were referred to a dual-energy x-ray absorptiometry (DXA) if they had a medium-to-high fracture risk suggested by Osteoporosis Self-Assessment Tool for Asians (OSTA).Results: Among all subjects, 91.2% (1,535/1,684, 95%CI: 89.7, 92.5) had vitamin D insufficiency and 61.3% had vitamin D deficiency (1,033/1,684, 95%CI: 59.0, 63.7). The prevalence of vitamin D deficiency was significantly higher in urban dwellers (64.9 vs. 57.7% in rural, P = 0.002) and in winter-enrolled subjects (84.7 vs. 41.3% in summer, P < 0.0001). The prevalence of vitamin D inadequacy did not increase in trend by latitude and was numerically lower in women who had high fracture risk and osteoporosis. A non-curvilinear change of intact parathyroid hormone (iPTH) levels was observed at 25(OH)D >16.78 ng/mL.Conclusions: The prevalence of vitamin D inadequacy was remarkable among Chinese postmenopausal women and independent of fracture risk assessed by OSTA or osteoporosis suggested by DXA. Winter season, urban residence, however not latitude, were significantly associated with a higher likelihood of vitamin D deficiency. Optimal vitamin D status for iPTH and bone-related outcomes merits further investigation in this population

Mapping adipose and muscle tissue expression quantitative trait loci in African Americans to identify genes for type 2 diabetes and obesity

Relative to European Americans, type 2 diabetes (T2D) is more prevalent in African Americans (AAs). Genetic variation may modulate transcript abundance in insulin-responsive tissues and contribute to risk; yet published studies identifying expression quantitative trait loci (eQTLs) in African ancestry populations are restricted to blood cells. This study aims to develop a map of genetically regulated transcripts expressed in tissues important for glucose homeostasis in AAs, critical for identifying the genetic etiology of T2D and related traits. Quantitative measures of adipose and muscle gene expression, and genotypic data were integrated in 260 non-diabetic AAs to identify expression regulatory variants. Their roles in genetic susceptibility to T2D, and related metabolic phenotypes were evaluated by mining GWAS datasets. eQTL analysis identified 1,971 and 2,078 cis-eGenes in adipose and muscle, respectively. Cis-eQTLs for 885 transcripts including top cis-eGenes CHURC1, USMG5, and ERAP2, were identified in both tissues. 62.1% of top cis-eSNPs were within ±50kb of transcription start sites and cis-eGenes were enriched for mitochondrial transcripts. Mining GWAS databases revealed association of cis-eSNPs for more than 50 genes with T2D (e.g. PIK3C2A, RBMS1, UFSP1), gluco-metabolic phenotypes, (e.g. INPP5E, SNX17, ERAP2, FN3KRP), and obesity (e.g. POMC, CPEB4). Integration of GWAS meta-analysis data from AA cohorts revealed the most significant association for cis-eSNPs of ATP5SL and MCCC1 genes, with T2D and BMI, respectively. This study developed the first comprehensive map of adipose and muscle tissue eQTLs in AAs (publically accessible at https://mdsetaa.phs.wakehealth.edu) and identified genetically-regulated transcripts for delineating genetic causes of T2D, and related metabolic phenotypes

VOT and VFT-Based hybrid digital hysteresis control for UPS inverter

When the digital hysteresis current control (DHCC) strategy is applied to control the uninterruptible power supply (UPS) inverter, here are some issues such as large hysteresis tracking error caused by sampling interval and severe switching frequency swing caused by rapid change rate of inductor current. To address these issues, this paper presents a digital control strategy based on the hybrid digital hysteresis current control (HDHCC) of variable opening time (VOT) and variable falling time (VFT) for UPS inverter. Firstly, the HDHCC structure is established and the working principle of the inverter system is described in detail. Then, the tracking error and switching frequency error of the DHCC are derived. Based on the performance requirement of quasi-constant frequency control of UPS inverter, VOT and VFT control criteria without the dependency of circuit parameters are given. The experimental results demonstrate that the hybrid digital hysteresis control strategy based on VOT and VFT has the advantages of high current tracking accuracy, accurate switching frequency control, small output voltage waveform distortion, and simple implementation

Multi-Resonant-Based Sliding Mode Control of DFIG-Based Wind System under Unbalanced and Harmonic Network Conditions

In general, the integral sliding mode control (ISMC) with an integral sliding surface would lead to tracking errors under unbalanced and harmonic grid voltage conditions. In order to eliminate tracking errors under these conditions, multi-resonant items are added to the conventional integral sliding surface in the proposed strategy, which can be called multi-resonant-based sliding mode control (MRSMC). A comparison of tracking precision on the ISMC and MRSMC is analyzed. In order to regulate the system powers directly, the errors of instantaneous active and reactive powers are selected as the state variables. Finally, the output current harmonics and a majority of the doubly-fed induction generator’s (DFIG) electromagnetic torque pulsations can be removed under unbalanced and harmonic grid voltage conditions. Simulation and experimental results are presented to verify the correctness and effectiveness of the proposed strategy

Towards an applied mathematics for computer science

SIGLEGBUnited Kingdo

Numerical simulation of end restraint effects on triaxial strength of soil

Concern for possible adverse effects of end restraint in triaxial compression testing is almost as old as the technique of conducting such tests. A finite element model is established to study the influence of end restraint effects on drained triaxial strength of soil in this paper. Results from simulations with free ends are compared with those from simulations with restraint ends. The comparison revealed that the obtained shear strengths from simulations with free ends and restraint ends are almost the same for non-dilative soil. With the increase in dilation angle, the relationship between the average deviatoric stress of all of the elements in the specimen and the vertical displacement did not show any change. However, the stress in the specimen with free ends was uniform while the stress in the specimen with fixed ends was not uniform. The investigation shows that the end restraints only influence the stress distribution in the specimen and do not influence the overall behaviour of it for drained triaxial tests