130,752 research outputs found
Duabanga taylorii Jayaweera (Sonneratiaceae) a putative hybrid
No full textThe differentiating characters of Duabanga grandiflora (Roxb. ex DC.) Walp., D. moluccana Bl., and D. taylorii Jayaweera are given. Most characters of D. taylorii appear to be intermediate between those of the other two species; a few characters represent combinations of those of the two other species; one character is not shared by the other species. From this evidence it is supposed that D. taylorii is a hybrid. This suggestion is sustained by the history of the specimens on which D. taylorii is based. An attempt to count chromosomes of D. taylorii and D. grandiflora failed, probably due to the unsuitability of the fixative for this purpose
Grid integration of renewable energy systems
No full textThe percentage of renewable power demand met by renewable power generators is increasing rapidly. This growth is driven by environmental concerns, government policies and decreasing cost of technologies. However, as the penetration of renewable power sources increases, new challenges in system planning and operation are becoming evident. There are short term operational challenges as well as long term planning challenges due to the intermittent nature of renewable power generation primarily from wind and solar photovoltaics. The study of grid integration of renewables is concerned with determining the optimal technical and regulatory framework that can effectively manage the short term and long term challenges of large scale renewable power penetration. Operational challenges of this chapter include maintaining frequency and voltage stability due to intermittency as well as network congestion. Planning challenges include allocating long term capacity credits of wind and solar power generation. Currently, the cost of a number of balancing technologies is expected to play a major role in overall viability of renewable power generation. This includes energy storage, demand side management, and dynamic ratings of assets. Smart grids are expected to provide the platform for utilizing the full potential of renewable power generation as well as balancing the technologies
Fundamentals of power systems
No full textThe chapter describes the history, evolution, and fundamental analysis frameworks of a power system. Power systems started modestly as small scale DC systems. As the dependence on electricity has increased, the complexities and demands placed on electricity have also been increased. The chapter begins with a description of the history of power systems and then describes major events that have shaped the modern power system industry. A description of the basic power system components are presented along with analysis techniques of load flow, optimal power dispatch, and transient stability. The chapter fundamentals will aid in a better understanding of the remaining chapters
Modelling and simulation of power systems
No full textThis chapter presents major modelling and simulation techniques applied in power systems research. As the smart grids will be a journey through the modern power system environment, it is vital to know how these models and techniques are applied in a traditional power grid environment and how they can make advances to realize smart grid objectives. The chapter describes optimization techniques applied in power systems research and then extended to incorporate stochastic elements. The chapter ends with a brief exploration into the Monte Carlo simulation based research
Micro grid planning and operation
No full textIncreasing penetrations of renewable power as well as deregulation of electricity markets have seen a rise around the world. A Micro Grid is a smaller entity that can intelligently control and coordinate distributed energy resources with the support of intelligent controllers and other necessary architecture. However, achieving such objectives that lead to a smart operation require significant advances to planning and operation of the Micro Grid as the collective operation of Micro Grids can potentially provide business cases. Roles of Micro Grids include improving reliability, resilience and security at the normal and emergency operating conditions of the power grid. Each mode of operation presents challenges such as frequency control in islanded mode and voltage control in grid connect mode. Micro Grid control strategies may be classified into grid following and grid forming and further into interactive or non-interactive. Most control hierarchies combine centralised as well as decentralised control. This chapter investigates specific challenges in a Micro Grid, planning and operation, control strategies as well as realistic studies of micro grids
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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