Virtual Synchronous Generator Based Current Synchronous Detection Scheme for a Virtual Inertia Emulation in SmartGrids

Authors:Arvind Parwa, Martin Fregelius, Dalmo Cardosa Silva, Tatiana Potapenko, Johannes Hjalmarsson, James Kelly, Irina Temiz, Janaina Goncalves de Oliveira,
Cecilia Boström, Mats Leijon

ABSTRACT
Renewable energy sources, such as photovoltaic wind turbines, and wave power converters, use power converters to connect to the grid which causes a loss in rotational inertia. The attempt to meet the increasing energy demand means that the interest for the integration of renewable energy sources in the existing power system is growing, but such integration poses challenges to the operating stability. Power converters play a major role in the evolution of power system towards SmartGrids, by regulating as virtual synchronous generators. The concept of virtual synchronous generators requires an energy storage system with power converters to emulate virtual inertia similar to the dynamics of traditional synchronous generators. In this paper, a dynamic droop control for the estimation of fundamental reference sources is implemented in the control loop of the converter, including active and reactive power components acting as a mechanical input to the virtual synchronous generator and the virtual excitation controller. An inertia coefficient and a droop coefficient are implemented in the control loop. The proposed controller uses a current synchronous detection scheme to emulate a virtual inertia from the virtual synchronous generators. In this study, a wave energy converter as the power source is used and a power management of virtual synchronous generators to control the frequency deviation and the terminal voltage is implemented. The dynamic control scheme based on a current synchronous detection scheme is presented in detail with a power management control. Finally, we carried out numerical simulations and verified the scheme through the experimental results in a microgrid structure.

Source:

Journal: Energy and Power Engineering
DOI: 10.4236/epe.2019.113007(PDF)
Paper Id: 91095 (metadata)

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An Analysis of the Determinants of Arbitrage Spread

Author:Etienne Redor

ABSTRACT
This study examines the determinants of arbitrage spread of S&P 500 firms between 2004 and 2014. We find that bid hostility, the relative size of the target compared to the potential bidder and the acquisition premium paid by the bidding firm are associated with greater arbitrage spread while the proportion of cash in the offer and target termination fees are associated with smaller arbitrage spread.

Source:

Journal: Theoretical Economics Letters
DOI: 10.4236/tel.2019.93034(PDF)
Paper Id: 91064 (metadata)

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Interprofessional Team-Based Learning: A Revealing Process for Cultivating Professional Identity among Nursing Students

Authors:Kitty Chan, Frances K. Y. Wong, Lap Ki Chan, Fraide A. Ganotice Jr.

ABSTRACT
Background: Nurses are significant healthcare team members. It is vital to examine their gains in an interprofessional education (IPE). Purpose: We aimed to examine the perceived benefits of interprofessional team-based learning (IPTBL) on the entry level nursing students. Methods: Content analysis was adopted to identify categories in the reflections of the entry-level undergraduate nursing student IPTBL experiences. Results: There were 205 (male = 34) undergraduate nursing students (response rate 82.2%) participating in the present study. In line with the Interprofessional Education Collaborative Report (IPEC) core competencies, four categories were identified: 1) Values/Ethics for Interprofessional Practice, 2) Roles/Responsibilities, 3) Interprofessional Communication, and 4) Teams and Teamwork. A new category emerged—individual learning outcomes. Conclusion: Through IP interactions and the expectation of the IP team, the nursing students had built confidence and defined the nurses’ roles.

Source:

Journal: Open Journal of Nursing
DOI: 10.4236/ojn.2019.93025(PDF)
Paper Id: 91027 (metadata)

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The Role of Family in Dealing with Juvenile Delinquency

Author:Rosemary Kakonzi Mwangangi

ABSTRACT
The overall purpose of the study was to explore the relationship between various family-related factors and crime. The study also attempted to ascertain whether those factors can act as causative agents for “juvenile delinquency”. The study postulated that although there are different factors that impact on the development of child character, the family plays a central role in child development and consequentially impacting on the character of a child. In order to critically analyze the hypothesis of study, the paper reviewed the concepts of juvenile delinquency and family. Although the paper centered on the family factors influencing delinquency, it equally attached premium on the non-family factors influencing levels of juvenile delinquency. The study found out that there are several notable family-related factors that impact on child crime. These include parental attitudes, the degree of family cohesion, physical violence, and uninvolved parenting. There are also non-family factors that impact on juvenile delinquency, which include the failure of the juvenile justice system, poverty, a lack of access to education, drug abuse and genetic problems.

Source:

Journal: Open Journal of Social Sciences


DOI: 10.4236/jss.2019.73004(PDF)
Paper Id: 90991 (metadata)

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Spitzer IRAC Colors of Nebulae Associated with Star-Forming Regions

Authors: Yoichi Itoh, Yumiko Oasa

ABSTRACT
Star-forming regions are often associated with nebulosity. In this study, we investigated infrared diffuse emission in Spitzer IRAC images. The infrared nebula L1527 traces outflows emanating from a low-mass protostar. The nebular color is consistent with the color of a stellar photosphere with large extinction. Nebulae around the HII region W5-East are bright in the infrared. These colors are consistent with the model color of dust containing polycyclic aromatic hydrocarbon (PAH). The strength of ultraviolet irradiation of the nebulae and the small dust fraction were deduced from the infrared colors of the nebulae. We found that the edges of the nebulae are irradiated by strong ultraviolet radiation and have abundant small dust. Dust at the surface of the molecular cloud is thought to be destroyed by ultraviolet radiation from an early-type star.

Source:

Journal: International Journal of Astronomy and Astrophysics
DOI: 10.4236/ijaa.2019.91004(PDF)
Paper Id: 90959 (metadata)

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Design of Printed Dipole Array for Omnidirectional Radiation Pattern

Author: Jean-Marie Floc’h

ABSTRACT
In this paper, we describe 2 kinds of printed dipole arrays and compare the performances of these arrays in term of reflexion coefficient, radiation pattern and dimensions. It is interesting to design array in order to obtain better performances in term of omnidirectional radiation pattern in comparison with single element. We choose this elementary source in order to obtain compact array with good performances. These antenna arrays are designed to have omnidirectional radiation pattern with horizontal polarization. We present an application dedicated to compact base station in the last section.

Source:

Journal: Wireless Engineering and Technology
DOI: 10.4236/wet.2019.102002(PDF)
Paper Id: 90949 (metadata)

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Impaired Executive Function in Everyday Life: A Predictor of OCD Relapse?

Authors: Nathalie Fournet, Ouafae Achachi1, Arnaud Roy, Jérémy Besnard,
Céline Lancelot, Didier Le Gall, Martine Bouvard

ABSTRACT
Objectives: In the present study, we set out to establish whether executive function in everyday life is impaired in obsessive-compulsive disorder patients, and if it is more impaired (or not) in patients who relapsed after cognitive behavioural therapy than in treatment-naïve obsessive-compulsive disorder patients. Method: The Behavior Rating Inventory of Executive Function— Adult Version (BRIEF-A) was used to measure executive function in everyday life in three groups of 19 participants: treatment-naïve obsessive-compulsive disorderpatients, obsessive-compulsive disorder patients having relapsed after CBT, and healthy controls. Results: The BRIEF-A results revealed an impairment in executive function in the treatment-naïve and relapsed obsessive-compulsive disorder groups, relative to the healthy control group. There was no significant difference in executive function between the two groups of patients. Conclusions: These results show that impaired executive function is not associated with relapse in patients with obsessive-compulsive disorder having undergone cognitive behavioural therapy.

Source:

Journal: Journal of Behavioral and Brain Science
DOI: 10.4236/jbbs.2019.93008(PDF)
Paper Id: 90922 (metadata)

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Assessment of Turbulence Models on Bridge-Pier Scour Using Flow-3D

Authors: Chandara Man, Genguang Zhang, Vouchleang Hong, Shuang Zhou, Yulin Feng

ABSTRACT
The main purpose of this paper is to analyze the influence of different turbulence flow models on scouring pit of bridge-pier. Flow-3D software is applied in line with the purpose. The key motivation for this study is to contribute to the Flow-3D software by means of some modification and adjustment in the sediment scour model and shallow water model. An assessment of turbulence model adopted with the parameters of the Melville experiment to estimate the maximum scour-depth was performed. In the simulation results, the alternate eddy formation and shedding were repeated while the Karman vortex street formed behind the pier for the large eddy simulation LES turbulence model is more realistic in the flow phenomenon. The results of the scour development of large eddy simulation (LES) turbulence model were found to be more satisfied than the Renormalized group (RNG) turbulence model and close to the prior experiment results. The simulated scour results were significantly different with the observed data collected from previous literature in the reason of some unsuitability of meshing method in Flow-3D software.

Source:

Journal: World Journal of Engineering and Technology
DOI: 10.4236/wjet.2019.72016(PDF)
Paper Id: 90901 (metadata)

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Classification of Beach Based on Beach-Surf-Zone Morphodynamics—A Case Study

Author: V. R. Shamjiorcid

ABSTRACT
The beach classifications based on theoretical and numerical modelling study are more in literature. The paper discusses a case study regarding the morphological response of sandy beach to the monsoonal waves and its classifications based on the energy conditions. The sediment dynamics associated with morphological changes are functions of incident wave climate, sediment characteristics and other environmental factors. The study establishes quantitative relationships between incident wave energy flux, fall speed parameters, grain size and wave steepness, and classifies beach in accordance with energy conditions using different empirical functions. A criterion for sediment transport direction with different wave climate is also proposed and validated in the field conditions.

Source:

Journal: Open Journal of Marine Science
DOI: 10.4236/ojms.2019.92005(PDF)
Paper Id: 90890 (metadata)

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Analysis and Design of Different Methods to Reach Optimum Power in Butler Matrix

Authors: Shahideh Kiehbadroudinezhad, Jean-François Bousquet, Michael Cada,
Adib Shahabi, Mohammad Ali Kiehbadroudinezhad

ABSTRACT
With the increasing demand for high speed reliable communications, smart antennas, such as the Butler Matrix array, can be used to develop a system that increases the performance of a wireless system. The Butler matrix is a switched beam array system which can produce orthogonal uniform beams. The main objective is to improve the efficiency of the power in a 90-degree bend. Also, the double-mitered bend is particularly interesting since it provides a substantially lower reflection coefficient and a lower value of S12 at a frequency of 2.4 GHz compared to an unmitered one. Therefore, this paper describes an optimum design using a double-mitered method with a 2 × 2 and a 4 × 4 Butler Matrix array, operating at 2.4 GHz which is used in wireless systems with an FR4 substrate.

Source:

Journal: International Journal of Communications, Network and System Sciences
DOI: 10.4236/ijcns.2019.122003(PDF)
Paper Id: 90867 (metadata)

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