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Abstract

Frequency regulation is in a first line of preference for an interconnected power system. Presence of nonlinearities in the generation systems further raises the complexity level of the problem. In this scenario, this article presents a robust Automatic Generation Control (AGC) mechanism to maintain the frequency and tie-line power of the power system to their nominal values. A Coefficient Diagram Method (CDM) based AGC mechanism including an AC/DC tie-line and Unified Power Flow Controller (UPFC) has been developed and the performance in handling the frequency regulation has been analyzed. The nonlinearities such as Governor Dead-Band (GDB) and Generation Rate Constraint (GRC) are included in the system to analyze the proposed AGC scheme in a more realistic approach. The AC/DC tie-line and UPFC which are included in the proposed AGC scheme provides an immense strength to handle the active power variation as-well-as frequency regulation. To develop a more effective AGC scheme, the parameters of an AC/DC tie-line and UPFC are optimized by successful implementation of the Fruit Fly Optimization Algorithm (FOA). The justification of the proposed AGC scheme has been carried out through a step by step verification such as justifying the CDM based controller, effectiveness of the proposed scheme and robustness of the system against parameters variation. The CDM based controller has been compared with the conventional controllers to elevate the effectiveness and the supremacy of the proposed AGC scheme has been examined by comparing with previously published work. The design and simulation of the work has been carried out by the MATLAB/Simulink® tool box.

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Authors and Affiliations

A.K. Sahani
Ravi Shankaro
Murali Sariki
Rajib Kumar Mandal
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Abstract

Duration of construction projects can be reduced by harmonizing construction processes: adjusting productivity rates of specialized crews and enabling the crews to work in parallel as in a production line. This is achievable in the case of projects whose scope can be divided into units where a similar type of work needs to be conducted in the same sequence. A number of repetitive project scheduling methods have been developed to assist the planner in minimizing the execution time and smoothing resource profiles. However, the workflow, especially in construction, is subject to disturbance, and the actual process durations are likely to vary from the as-scheduled ones. The inherent variability of process durations results not only in delays of a particular process in a particular unit but also in the propagation of disruptions throughout the initially well-harmonized schedule. To counteract the negative effects of process duration variability, a number of proactive scheduling methods have been developed. They consist in some form of predicting the conditions to occur in the course of the project and implementing a strategy to mitigate disturbance propagation. This paper puts forward a method of scheduling repetitive heterogeneous processes. The method aims to reduce idle time of crews. It is based on allocating time buffers in the form of breaks between processes conducted within units. The merits of the method are illustrated by an example and assessed in the course of a simulation experiment.
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Authors and Affiliations

Piotr Jaśkowski
1
ORCID: ORCID
Sławomir Biruk
1
ORCID: ORCID
Michał Krzemiński
2
ORCID: ORCID

  1. Lublin University of Technology, Faculty of Civil Engineering and Architecture, Nadbystrzycka str.40, 20-618 Lublin, Poland
  2. Warsaw University of Technology, Faculty of Civil Engineering, Armii Ludowej str. 16, 00-637 Warsaw, Poland
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Abstract

The coexistence of two congeneric amphipods, boreal Gammarus oceanicus, and arctic G. setosus, was studied during the summer seasons of 2017-2019 in the region of Isfjorden, Forlandsundet, and Prins Karl Forland island in the west-central part of the Svalbard archipelago (Arctic). Across the study area species distribution often overlapped, but the domination patterns mirrored environmental conditions preferred by each species. Both species, however, were able to survive in suboptimal conditions. On a small spatial scale (in one sample) the species were separated, which may suggest an antagonistic relationship between them. The ongoing changes in the environment of Svalbard will likely affect these two species differently. The increasing intrusion of Atlantic waters will probably favor the further expansion of G. oceanicus along the Svalbard coasts. This will be due to the gradual advance of the existing population, as an influx of individuals from the Nordic seas seems unlikely. G. setosus will remain the dominant species in cold-water areas such as the inner fjords and the northeastern coast of Svalbard and may find new suitable habitats in lagoons or estuaries fed by melting glaciers. Despite predicted changes in the distribution range of both species, their future coexistence should still be possible due to the wide range of environmental tolerance and the heterogeneity of the Svalbard coastal habitats.
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Authors and Affiliations

Jan Marcin Węsławski
1
ORCID: ORCID
Joanna Legeżyńska
1
ORCID: ORCID
Lech Kotwicki
1
ORCID: ORCID
Mikołaj Mazurkiewicz
1
ORCID: ORCID
Sergej Olenin
2
ORCID: ORCID

  1. Institute of Oceanology Polish Academy of Sciences, Powstańców Warszawy 55, Sopot 81-712, Poland
  2. Marine Research Institute, Klaipėda University, Universiteto al. 17, 92294, Klaipėda, Lithuania
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Abstract

Penguin bones from the La Meseta Formation (Seymour Island, Antarctic Peninsula) are the only record of Eocene Antarctic Sphenisciformes. Being an abundant component of the youngest unit of the formation (Telm7), they are not so common in earlier strata. Here, I present the oldest penguin remains from the La Meseta Formation (Telm1-Telm2), often bearing close resemblance to their counterparts from younger units. Addressing the recent findings in fossil penguin systematics, I suggest there is too weak a basis for erecting new Eocene Antarctic taxa based on non-tarsometatarsal elements of penguin skeletons, and considering Oligocene species part of the studied assemblage. Finally, I conclude if the common ancestor of extant Sphenisciformes lived in the Eocene Antarctic (as suggested recently), penguins referred to Delphinornis seem to be prime candidates to that position.

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Authors and Affiliations

Piotr Jadwiszczak
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Abstract

This article presents some cultural, historical and linguistic insights on the names of the Szczutowskie and Urszulewskie Lakes, both situated in the historical Dobrzyńskie Lakeland, today on the border between the Mazovian and Kuyavian-Pomeranian Voivodeships (the historical border between Polish and Prussian-Teutonic states). The author also takes into account the description of the local place and terrain names, showing a common relation with the natural landscape, in which the two lakes are immersed.

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Authors and Affiliations

Artur Gałkowski

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