scholarly journals Propagation of Voltage Deviations in a Power System

Electronics ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 949
Author(s):  
Tomasz Okon ◽  
Kazimierz Wilkosz
Keyword(s):  
Power System ◽  
Case Studies ◽  
Measurement Data ◽  
Theoretical Background ◽  
Original Method ◽  
Operational Experience ◽  
Remedial Measures ◽  
Time Points ◽  
General Candidate ◽  
Time Point

The paper deals with voltage profiles in a power system. The analysis of these profiles is important due to the requirement that the Root-Mean-Squared (RMS) values of nodal voltages should be within certain ranges, as well as to ensure desired power flows in a power system. In both cases, it is desirable to indicate points in a power system where it is reasonable to apply remedial measures to meet the requirements for RMS values of nodal voltages, or to effectively control the power flows in a power system. In general, candidate nodes for remediation are established based on operational experience or measurement data from a certain time point (sometimes from several time points). The paper presents a method that provides a basis for determining the aforementioned candidate nodes based on the behavior of a system over a certain period of time, which is an unquestionable advantage of this proposal. In order to achieve the abovementioned goal, the method provides for the analysis of propagation of voltage RMS value deviations in a power system. The analysis of correlational relationships between the RMS values of nodal voltages is used for this. After presentation of the theoretical background, the new original method is described in the paper. Then, case studies showing the utilization of that method are presented. At the end of the paper, features of the proposed method are enumerated.

Large qualitative models of complex chemical and bioengineering processes

1991 ◽  
Vol 56 (10) ◽  
pp. 2107-2141 ◽  
Author(s):  
Mirko Dohnal
Keyword(s):  
Case Studies ◽  
Chemical Process ◽  
Ad Hoc ◽  
Chemical Reactor ◽  
Theoretical Background ◽  
Qualitative Model ◽  
Complex Chemical ◽  
Practical Applications ◽  
Qualitative Models ◽  
Decomposition Principle

Qualitative model is a theoretical background of commonsense. Complex qualitative models can have prohibitively many solutions (qualitative states). Therefore a qualitative analogy of such classical quantitative tools as e.g. the decomposition is developed. Practical applications of decomposition principle is nearly always ad hoc. Therefore two case studies are presented in details, a chemical process (mixer, chemical reactor, separator) and an anaerobic fermentor.

scholarly journals Series Compensation of Transmission Systems: A Literature Survey

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1717
Author(s):  
Camilo Andrés Ordóñez ◽  
Antonio Gómez-Expósito ◽  
José María Maza-Ortega
Keyword(s):  
Steady State ◽  
Power Systems ◽  
Power System ◽  
Case Studies ◽  
Electronic Devices ◽  
Literature Survey ◽  
Power Electronic ◽  
Transmission Systems ◽  
Series Compensation ◽  
Near Future

This paper reviews the basics of series compensation in transmission systems through a literature survey. The benefits that this technology brings to enhance the steady state and dynamic operation of power systems are analyzed. The review outlines the evolution of the series compensation technologies, from mechanically operated switches to line- and self-commutated power electronic devices, covering control issues, different applications, practical realizations, and case studies. Finally, the paper closes with the major challenges that this technology will face in the near future to achieve a fully decarbonized power system.

scholarly journals Cytotoxicity assessment of different doses of ozonated water on dental pulp cells

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Ferdiye Küçük ◽  
Sibel Yıldırım ◽  
Serap Çetiner
Keyword(s):  
Cell Viability ◽  
Repeated Measures ◽  
Dental Pulp ◽  
Control Group ◽  
Dental Pulp Cells ◽  
Time Points ◽  
Significant Difference ◽  
Pulp Cells ◽  
Time Point ◽  
Ozonated Water

Abstract Background The purpose of this study was to assess the cytotoxicity of various concentrations of ozonated water (OW) on human primary dental pulp cells. Methods Human primary dental pulp cells were isolated from exfoliated primary canine teeth of an 11-year-old patient with good systemic and oral health. Afterwards, cells were divided into 6 experimental groups; four groups of OW in concentrations of 2 mg/L, 4 mg/L, 8 mg/L, and 16 mg/L, untreated control group, and cell culture without cells. Cytotoxicity was evaluated after exposure for 5-min exposure using Mosmann’s Tetrazolium Toxicity (MTT) assay at 0 h and 48 h time points. Data were analyzed using a repeated measures analysis of variance and Post-hoc tests were performed using Bonferroni correction for multiple comparisons. Results All experimental groups showed proliferation at 0 h time point. However, all groups also experienced a decrease in overtime at 48 h time point (p < 0.05). At both time points 2 mg/L OW showed the highest cell viability as well as proliferation. At 0 h time point, the increase in cell viability for all experimental groups was found statistically significant when compared to positive control group (p < 0.05). At 48 h time point, although 8 mg/L and 16 mg/L OW showed statistically significant reduction in compare to 0 h time point, 2 mg/L and 4 mg/L OW groups didn’t experience any statistically significant difference (p < 0.05). Conclusion Considering our findings, due to ozonated water's induced a higher proliferation rate of dental pulp cells, indicating their biocompatibility and a possible adjuvant on irrigating agent in regenerative endodontic procedures.

scholarly journals Levels of physical activity in four domains and affective wellbeing before and during the Covid-19 pandemic

2021 ◽  
Vol 79 (1) ◽  
Author(s):  
Eliane S. Engels ◽  
Michael Mutz ◽  
Yolanda Demetriou ◽  
Anne K. Reimers
Keyword(s):  
Mental Health ◽  
Physical Activity ◽  
Protective Factor ◽  
Total Sample ◽  
Poor Mental Health ◽  
German Population ◽  
Time Points ◽  
Sport And Exercise ◽  
Over Time ◽  
Time Point

Abstract Background Latest studies indicated that the general mental health level is low during the pandemic. Probably, this deterioration of the mental health situation is partly due to declines in physical activity. The aim of this study was to investigate differences in and the association between affective wellbeing and levels of different domains of physical activity at three time points before and during the pandemic. Method We used a nationwide online panel with a trend data design encompassing a total sample of N = 3517, representing the German population (> 14 years). Four different activity domains (sport and exercise, light outdoor activity, housework/gardening, active travel) and affective wellbeing (positive and negative affect) were assessed at three time points before and during the Covid-19 pandemic (October 2019, March 2020, October 2020). Results Multivariate analyses of variance (MANOVA) indicate differences regarding affective wellbeing over the three time points with the lowest values at the second time point. Levels of activity in the four domains differed significantly over time with the strongest decrease for sport and exercise from the first to the second time point. Partial correlations indicated that the relationships between sport and exercise and positive affect were most consistent over time. Conclusions Overall, our findings suggest that physical activity plays a particularly important role in the pandemic period as a protective factor against poor mental health. Especially sports and exercise seem to be supportive and should be encouraged, e.g. by providing additional support in finding adequate outdoor, home-based or digital substitutes.

scholarly journals Knee Muscle Strength Recovery in the Early Period After ACL Reconstruction

2014 ◽  
Vol 2 (11_suppl3) ◽  
pp. 2325967114S0014
Author(s):  
Gulcan Harput ◽  
Hasan Erkan Kılınc ◽  
Hamza Özer ◽  
Gül Baltacı ◽  
Carl G. Mattacola
Keyword(s):  
Acl Reconstruction ◽  
Early Period ◽  
Quadriceps Strength ◽  
Isometric Strength ◽  
Time Points ◽  
Hamstring Muscles ◽  
Significant Difference ◽  
Isometric Torque ◽  
Over Time ◽  
Time Point

Objectives: The aim of this study was to investigate quadriceps and hamstrings isometric strength at 4, 8 and 12 week time points following ACL Reconstruction (ACLR) and to document the strength changes of these muscles over time. The primary hypothesis was that there would be significant increases in quadriceps and hamstring muscle strengths between the 4th, 8th and 12th weeks following ACLR. The secondary hypothesis was that the quadriceps index would be higher than hamstring index at 12th week after ACLR. Methods: Thirty patients (Mean ± SD [age, 29.1±2.3yrs; weight, 77.3±13.2kg; height, 172.1±7.1cm; BMI, 21.2±3.5kg/m2, time to surgery: 7.1±7.2 months]) who underwent ACLR with Hamstring Tendon Autograft (HTG) were enrolled in this study. The isometric strength of quadriceps and hamstring muscles was measured on an isokinetic dynamometer at 60° knee flexion angle at 4th, 8th and 12th weeks after surgery. The recovery of quadriceps and hamstring muscles strength following rehabilitation was expressed as a Quadriceps Index (QI) and Hamstring Index (HI) and calculated with the following formula:[(maximum voluntary isometric torque of the involved limb / maximum voluntary isometric torque by uninvolved limb) × 100]. Torque output of the involved and uninvolved limbs and quadriceps and hamstring indexes were used for the statistical analysis. A repeated measures of ANOVA was used to determine the strength changes of quadriceps and hamstrings over time. Results: Quadriceps and Hamstrings strengths significantly increased over time for both involved (Quadriceps: F (2,46)=58.3, p<0.001, Hamstring: F (2,46)=35.7, p<0.001) and uninvolved limb (Quadriceps: F(2,46)=17.9, p<0.001, Hamstring: F(2,46)=56.9, p=0.001 ). Quadriceps strength was higher at 12th week when compared to the 8 and 4 week time points for the involved limb (p<0.001), and it was higher at 8th week when compared to 4 week time point for the involved limb (p<0.001). For the uninvolved limb, quadriceps strength was also higher at 12th week when compared to the 8 (p=0.02) and 4 week time point (p<0.001), and higher at 8 week when compared to the 4 week time point (p=0.02). Hamstring strength was higher at 12 week when compared to the 8 and 4 week time points (p<0.001) and it was higher at 8 week when compared to 4 week time point for the involved limb (p<0.001). For the uninvolved limb hamstring strength was also higher at 12 week when compared to 4 week time point (p=0.01). There was no significant difference between the 4 and 8 week time points (p>0.05) or between the 8 and 12 week time points (p=0.07). Quadriceps and hamstring indexes significantly changed from 4th weeks (QI:57.9, HI:54.4 ) to 8th weeks (QI:78.8, HI:69.9 ) and from 8th weeks to 12th weeks (QI:82, HI:75.7 ) (p<0.001); however, there was no difference between indexes at the 12-week time point (p=0.17). Conclusion: Isometric strength of quadriceps and hamstring muscles for the involved and uninvolved limb increased during the early period of ACLR. The results of this study could be a baseline for clinicians while prescribing a rehabilitation protocol for ACLR patients with HTG to better appreciate expected strength changes of the muscles in the early phase.

scholarly journals Virus isolation studies suggest short-term variations in abundance in natural cyanophage populations of the Indian Ocean

2006 ◽  
Vol 86 (3) ◽  
pp. 499-505 ◽  
Author(s):  
Martha R.J. Clokie ◽  
Andrew D. Millard ◽  
Jaytry Y. Mehta ◽  
Nicholas H. Mann
Keyword(s):  
Indian Ocean ◽  
Surface Waters ◽  
Molecular Diversity ◽  
Virus Isolation ◽  
Short Term ◽  
Distinct Subgroup ◽  
Time Points ◽  
The Indian Ocean ◽  
Long Timescales ◽  
Time Point

Cyanophage abundance has been shown to fluctuate over long timescales and with depth, but little is known about how it varies over short timescales. Previous short-term studies have relied on counting total virus numbers and therefore the phages which infect cyanobacteria cannot be distinguished from the total count.In this study, an isolation-based approach was used to determine cyanophage abundance from water samples collected over a depth profile for a 24 h period from the Indian Ocean. Samples were used to infect Synechococcus sp. WH7803 and the number of plaque forming units (pfu) at each time point and depth were counted. At 10 m phage numbers were similar for most time-points, but there was a distinct peak in abundance at 0100 hours. Phage numbers were lower at 25 m and 50 m and did not show such strong temporal variation. No phages were found below this depth. Therefore, we conclude that only the abundance of phages in surface waters showed a clear temporal pattern over a short timescale. Fifty phages from a range of depths and time points were isolated and purified. The molecular diversity of these phages was estimated using a section of the phage-encoded psbD gene and the results from a phylogenetic analysis do not suggest that phages from the deeper waters form a distinct subgroup.

Continuity and Variation in Germanic and Romance

2021 ◽  
Keyword(s):  
Case Studies ◽  
Historical Linguistics ◽  
Theoretical Background ◽  
Romance Languages ◽  
Left Periphery ◽  
Central Importance ◽  
Discourse Pragmatics ◽  
Indispensable Tool ◽  
The Relationship ◽  
People Today

This volume offers a range of synchronic and diachronic case studies in comparative Germanic and Romance morphosyntax. These two language families, spoken by over a billion people today, have been of central importance throughout the development linguistics, yet many significant questions about the relationship between the two families remain. Following an introduction that sets out the methodological, empirical, and theoretical background to the book, the volume is divided into three parts which deal with the morphosyntax of subjects and the inflectional layer inversion, discourse pragmatics, and the left periphery, and continuity and variation beyond the clause. The approaches used by the authors of individual chapters are diverse, making use of the latest digitized corpora and presenting a mixture of well-known and understudied data from standard and non-standard Germanic and Romance languages. Many of the chapters challenge received wisdom about the relationship between these two important language families. This volume will be an indispensable tool to researchers and students in Germanic and Romance linguistics, historical linguistics, grammatical theory, and language relationships.

The USE IT Model Case Studies

2011 ◽  
pp. 177-191 ◽  
Author(s):  
Margreet B. Michel-Verkerke ◽  
Roel W. Schuring ◽  
Ton A.M. Spil
Keyword(s):  
Multiple Sclerosis ◽  
Case Studies ◽  
General Practitioners ◽  
Mobile Device ◽  
Theoretical Background ◽  
Model Case ◽  
Stroke Service ◽  
Ex Post ◽  
Ex Ante ◽  
Healthcare Processes

In the previous two chapters, the determinants and theoretical background of the USE IT model is discussed. In this chapter, the application of the USE IT model in three cases are described to show the value and benefits of the USE IT model in practice. The USE IT model has four determinants: resistance, relevance, requirements, and resources. It can be used ex ante and ex post. The USE IT model is applied ex ante to find relevance and appropriate choices to overcome resistance for an ICT support of the multiple sclerosis (MS) healthcare chain and the rheumatism care guide, and as well ex ante as ex post in a local stroke service to measure the feasibility of a mobile device for general practitioners. The USE IT model proved to be very helpful not only in revealing the most urgent and relevant problems but also in discovering the crucial obstacles and prerequisites for implementing a solution to these problems. By that, the USE IT model served as a strong tool to decide whether healthcare processes should be supported by ICT and, if so, what processes should be used and how.

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