scholarly journals Impact of Control Loops on the Passivity Properties of Grid-Forming Converters with Fault-Ride through Capability

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6036
Author(s):  
Mebtu Beza ◽  
Massimo Bongiorno ◽  
Anant Narula
Keyword(s):  
Renewable Energy Sources ◽  
Experimental Tests ◽  
Power Electronic ◽  
Power Electronic Converters ◽  
Input Admittance ◽  
Factors Affecting ◽  
Control Loops ◽  
Fault Ride Through ◽  
Main Factors ◽  
The Impact

Due to the increasing integration of renewable energy sources (RES) and a corresponding reduction of conventional generating units, there is nowadays a demand from the power-electronic converters to provide grid-forming properties through proper control of the converter systems. This paper aims to evaluate the impact of various control loops in a grid-forming control strategy equipped with a fault-ride through capability on the passivity properties of the converter system. Through the analysis of the frequency-dependent input admittance of the converter, the main factors affecting the passivity properties are identified. A simplified analytical model is derived in order to propose possible control modifications to enhance the system’s passivity at various frequencies of interest and the findings are validated through detailed time-domain simulations and experimental tests.

ANALYSIS OF BLOOD FLOW PASSING THROUGH AORTIC AND MITRAL VALVES USING A COMPUTATIONAL MODEL OF CONCENTRATED PARAMETERS

2014 ◽  
Vol 26 (06) ◽  
pp. 1450068
Author(s):  
J. Del Río Palma ◽  
E. Romero V. ◽  
M. Cerrolaza
Keyword(s):  
Blood Flow ◽  
Heart Valves ◽  
Computational Models ◽  
Flow Behavior ◽  
Flow Analysis ◽  
High Mobility ◽  
Abnormal Behavior ◽  
Factors Affecting ◽  
Main Factors ◽  
The Impact

Blood flow has been extensively studied because of its close relationship with cardiovascular disease. Heart valves blood flow analysis is particularly complex due to the high mobility of its leaflets, a fact that has stimulated the development of computational models aimed to its better understanding. For studying heart valves blood flow, we developed a mathematical model derived from clinical observations based on echocardiographic images, which describe valve leaflets motion and its influence on blood flow. This work presents a concentrated-parameters-based model of heart valves blood flow that takes into consideration five main factors affecting such a flow in the mitral and aortic valves. This model considers factors that are related to blood fluid and valve leaflets characteristics. Considering the main factors involved, it was found that blood flow exhibit an abnormal behavior in response to small variations (less than 10%) in blood pressure gradient or in leaflets stiffness. Likewise, after changing the roughness of the leaflets, the impact is smaller, only slightly affecting blood flow behavior with changes beyond 30%. Moreover, it was observed that the influence of fluid vortices originated behind the valves can be disregarded and the kinetic energy induced by them is almost negligible.

scholarly journals Factors affecting the decision for routine health checkup: evidence from survey data in Khanh Hoa province

2020 ◽  
Vol 4 (4) ◽  
pp. First
Author(s):  
Phạm Thành Thái ◽  
Võ Chí Nam
Keyword(s):  
Survey Data ◽  
Scientific Method ◽  
Education Level ◽  
Health Checkup ◽  
Factors Affecting ◽  
Logit Regression ◽  
The World ◽  
Main Factors ◽  
Logit Regression Model ◽  
The Impact

Routine health checkup is the simplest and most scientific method for early detection, minimizing harm, and preventing complications of diseases. However, until now, only a fraction of the population is aware of its importance. Studies in the world and in Vietnam show that the proportion of the population having routine health checkups remains modest. Understanding which factors affect the decision to have routine health checkups is important in creating a system and environment that encourage people to have regular health checkups. The study is based on the survey data of 420 people in Khanh Hoa province to identify the main factors affecting their decision of routine health checkups, using the Logit regression model. The results shows that factors affecting decisions on routine health checkups include: education level, occupation, income, age, chronic illness, waiting time, and the impact of cost. The study also determines that gender and marital status have no effect on regular health checkups. The results highlight the importance of taking into consideration the priorities of time and cost when developing policies to encourage regular health checkups in the population.

scholarly journals Claim study of contractors in Commercial Berth Project in Duqm Port in Oman

2021 ◽  
Vol 10 (3) ◽  
Author(s):  
Omar Khaleel ◽  
Sultan Mohamed Al Mandhari
Keyword(s):  
Weather Conditions ◽  
Time Frame ◽  
Site Management ◽  
Sultanate Of Oman ◽  
Key Factors ◽  
Factors Affecting ◽  
Five Factors ◽  
Main Factors ◽  
Poor Site ◽  
The Impact

The claim during the implementation of projects is very important for the contractor and the consultant. As for the owner, it is considered expensive and cumbersome,and therefore the project contract must be very clear so that there are no gaps or defects against the owner.The aim of this research is to analyze and study deeply contractor's claim.The objectives of this study are to study the main factors for the contractor's claim to the commercial pier project in the Sultanate of Oman,including eleven factors. The second objective is to study the impact of the contractor's claim on the commercial pier project in the Sultanate of Oman, and it includes five factors, as the questionnaire was distributed to customers and various segments of society.The results of analyzing 16 factors to identify the key factors and the impact of the study of the contractors claim conclude that the main factors affecting the contactor's claim to the pier project.The factors and impacts are valid to the study after conducting analysis on the obtained data. The factors include the development unexpected weather conditions, inconsideration of the time frame, government approval of delays,poor coordination with the project parties, poor site management and supervision,a change in the clients requirements, the lack of experienced staff, incompetence among teams, low items in the bill of products,and misunderstanding the scope of work and specifications.The impacts to the completion of the Berth project include payment delays, delays in the extension of time,issuing variation order,value implementation engineering and cost reduction,and contractor's performance.

scholarly journals Simulation-Based Research on Driver Visibility of Black-and-White Striped Vehicles

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Pei Xie ◽  
Qing Li ◽  
Tong Zhu ◽  
Minghua Cao ◽  
Runqing Zhao
Keyword(s):  
Target Identification ◽  
Primary Objective ◽  
Color Analysis ◽  
Factors Affecting ◽  
Black And White ◽  
Lighting Conditions ◽  
Simulation Based ◽  
Main Factors ◽  
The Impact ◽  
Vehicle Size

The vehicle color is considered to be a significant factor affecting driver visibility. The primary objective of this study is therefore to determine the impact of black-and-white striped vehicles (BWVs) on driver visibility through simulation-based experiments. In these experiments, subjects were asked to perform front and rear target identification tasks under daylight and twilight conditions. Then, a 2 (lighting conditions) × 2 (vehicle size) × 5 (vehicle color) analysis of variance was conducted for each task. Under the front identification scenario, the main factors affecting visibility were found to be lighting conditions, vehicle size, vehicle color, and the interactions between these factors. Under the rear identification scenario, lighting conditions and vehicle color were found to be the main factors. The results of this study demonstrate that driver visibility of BWVs is poorer than that of other colors of vehicles and that BWV visibility is susceptible to lighting conditions.

Assessment of the impact of structural changes in sown areas on grain yields during the implementation of state programs

2021 ◽  
pp. 58-65
Author(s):  
V. V. Demichev ◽  
A. V. Panin ◽  
V. I. Khoruzhy ◽  
E. V. Khudyakova
Keyword(s):  
Grain Yield ◽  
Structural Changes ◽  
Mineral Fertilizers ◽  
Index Method ◽  
Factors Affecting ◽  
Main Factors ◽  
Leguminous Crops ◽  
State Programs ◽  
The Impact ◽  
Structural Shifts

The article analyzes the dynamics and provides a forecast for 2021 of the yield of grain and leguminous crops in Russia. According to the results of the analysis for the period from 2006 to 2019, the average annual increase in yield by 0.6 center per ha was revealed for all categories of farms. The average grain yield in the forecast year will be in the range of 26.5 to 29.6 center per ha. The main focus of this article is on the assessment of the impact of structural shifts in sown areas on the yield of cereals and legumes. According to the results of the index method, it was found that due to changes in the regional structure of grain crops, the yield in Russia as a whole increased by an average of 5%. Based on the constructed regression model, it is concluded that the main factors affecting the grain yield are the productivity of the climate and the number of mineral fertilizers applied.

Wastage of conserved fodder when feeding livestock

2010 ◽  
Vol 50 (6) ◽  
pp. 400 ◽  
Author(s):  
C. R. Stockdale
Keyword(s):  
Beef Cattle ◽  
Dairy Cattle ◽  
Present Review ◽  
Factors Affecting ◽  
Storage Method ◽  
The Mean ◽  
Main Factors ◽  
Wet Weather ◽  
The Cost ◽  
The Impact

The objective of the present review was to establish levels of conserved fodder wastage when feeding livestock (sheep, beef cattle, dairy cattle) under various conditions and using various feed-out systems, and to determine the factors affecting wastage. The mean wastage of hay recorded in the literature reviewed was 17% of the DM offered, but the range was from 4 to 77%. The main factors affecting the degree of wastage were storage method, packaging method, method of feeding out, amount of fodder on offer and its palatability and/or quality and the impact of wet weather. Although the emphasis was on hay, the principles should also apply to silage. If wastage was 40% rather than 5%, the cost of feeding conserved fodder to livestock would be a third greater than producers might expect or budget on.

scholarly journals Sustainability of denitrifying bioreactors with various fill media

2017 ◽  
Vol 63 (No. 10) ◽  
pp. 442-448 ◽  
Author(s):  
Malá Jitka ◽  
Bílková Zuzana ◽  
Hrich Karel ◽  
Schrimpelová Kateřina ◽  
Kriška Michal ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Hydraulic Retention Time ◽  
Agricultural Runoff ◽  
Factors Affecting ◽  
Pine Sawdust ◽  
Spruce Wood ◽  
Main Factors ◽  
Agricultural Areas ◽  
The Impact

Nitrogen losses from utilised agricultural areas are responsible for water quality degradation and eutrophication. Denitrifying bioreactors can be used to reduce high nitrate concentrations in agricultural runoff in situ. The main factors affecting their function are the bioreactor fill medium and process parameters such as hydraulic retention time, temperature and inlet concentration of nitrates. The paper presents the results of laboratory experiments achieved with bioreactors filled with eight different wood-based materials, namely mulch, a mixture of spruce and pine sawdust, a mixture of pine and larch bark, and chips made of oak, poplar, larch, beech, and spruce wood. A sustainability index was used to assess the impact of the bioreactor on the environment. The best results were shown by beech, mulch and poplar and were achieved with hydraulic retention times 1.6–0.7–2.2 days, respectively, and inlet NO<sub>3</sub><sup>–</sup>-N concentration of 43.1 mg/L.

scholarly journals Factors affecting food choice in Greek primary-school students: ELPYDES study

2008 ◽  
Vol 11 (6) ◽  
pp. 639-646 ◽  
Author(s):  
Grigoris Risvas ◽  
Demosthenes B Panagiotakos ◽  
Antonis Zampelas
Keyword(s):  
Nutrition Education ◽  
Food Choice ◽  
Primary Schools ◽  
Environmental Changes ◽  
School Students ◽  
Factors Affecting ◽  
Explained Variation ◽  
Main Factors ◽  
Main Meal ◽  
The Impact

AbstractObjectiveTo measure factors affecting food choice in a sample of Greek schoolchildren attending 5th and 6th grade.DesignThree self-administered questionnaires were distributed to the participants – one on nutritional knowledge, one on self-efficacy and social support for dietary change and a food-frequency questionnaire.SettingOne hundred Greek primary schools from Attica and Thessaloniki regions.SubjectsIn total, 2439 students in 5th and 6th grades.ResultsPrincipal components analysis was applied to extract the main factors affecting food choice of our subjects. Six components were derived explaining 66% of the total variation in factors affecting food choice. The first component was characterised by readiness to make the healthier choice when competitive foods are considered (explained variation 29%); the second was characterised by the impact of parents, friends and advertisements on students’ choices and also the impact of taste, smell and cooking method on the consumption of vegetables (explained variation 11%); the third component was characterised by readiness to choose fresh foods instead of ready-to-eat, pre-packaged choices as a main meal and awareness of the health value of fruits and vegetables (explained variation 8%); the other components mainly expressed the interdependence of the main factors.ConclusionsNutrition education and health promotion programs in Greece must include family members and activities regarding food preparation, as well as education and environmental changes in schools. Public health measures must include regulation of advertising. Moreover, the categorisation of foods as ‘healthier but less tasty’ and ‘appealing but unhealthy’ needs to be challenged in the future, since balanced nutrition is founded in variety and norm.

scholarly journals On the Existence and Uniqueness of the ODE Solution and Its Approximation Using the Means Averaging Approach for the Class of Power Electronic Converters

Mathematics ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1146
Author(s):  
Santolo Meo ◽  
Luisa Toscano
Keyword(s):  
Local Existence ◽  
Experimental Tests ◽  
Power Converter ◽  
Power Electronic ◽  
Power Electronic Converters ◽  
Effective System ◽  
The Cauchy Problem ◽  
Analytical Proof ◽  
Power Electronics Converter ◽  
Averaged Model

Power electronic converters are mathematically represented by a system of ordinary differential equations discontinuous right-hand side that does not verify the conditions of the Cauchy-Lipschitz Theorem. More generally, for the properties that characterize their discontinuous behavior, they represent a particular class of systems on which little has been investigated over the years. The purpose of the paper is to prove the existence of at least one global solution in Filippov’s sense to the Cauchy problem related to the mathematical model of a power converter and also to calculate the error in norm between this solution and the integral of its averaged approximation. The main results are the proof of this theorem and the analytical formulation that provides to calculate the cited error. The demonstration starts by a proof of local existence provided by Filippov himself and already present in the literature for a particular class of systems and this demonstration is generalized to the class of electronic power converters, exploiting the non-chattering property of this class of systems. The obtained results are extremely useful for estimating the accuracy of the averaged model used for analysis or control of the effective system. In the paper, the goodness of the analytical proof is supported by experimental tests carried out on a converter prototype representing the class of power electronics converter.

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