3,811 research outputs found
AC vs. DC Boost Converters: A Detailed Conduction Loss Comparison
Studies have shown the efficiency benefits of DC dis- tribution systems are largely due to the superior performance of DC/DC converters. Nonetheless, these studies are often based on product data that differs widely in manufacturer and operating voltage. This work develops a rigorous loss model to theoretically compare the efficiency of a DC/DC and an AC/DC PFC boost converter. It ensures each converter has the same components and equivalent operating voltages. The results show AC boost converters below 500 W to have 2.9 to 4.2 times the loss of DC
An Efficiency-Focused Design of Direct-DC Loads in Buildings
Despite the recent interest in direct current (DC) power distribution in buildings, the market for DC-ready loads remains small. The existing DC loads in various products or research test beds are not always designed to efficiently leverage the benefits of DC. This work addresses a pressing need for a study into the development of efficient DC loads. In particular, it focuses on documenting and demonstrating how to best leverage a DC input to eliminate or improve conversion stages in a load’s power converter. This work identifies how typical building loads can benefit from DC input, including bath fans, refrigerators, task lights, and zone lighting. It then details the development of several prototypes that demonstrate efficiency savings with DC. The most efficient direct-DC loads are explicitly designed for DC from the ground up, rather than from an AC modification
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DC Power Distribution in Buildings
Overview of the current state of DC power distribution and its benefits. Delivered at a seminar at National Tsing Hua University, Taiwan
How Teachers Can Integrate Absent Narratives Into Their Manifest Destiny Curriculum To Better Understand The Experiences Of People Of Color
The research question addressed in this project was, how can teachers integrate absent narratives into their Manifest Destiny curriculum to better understand the experiences of people of color? It documents one teacher’s reasons for modifying a Manifest Destiny and Pre- Civil War unit in a mainstream, high school-level curriculum, that incorporates absent narratives of people of color negatively affected by American expansion. The author documents through research that many curriculum textbooks and standards do not adequately mention what happens to people of color when the U.S. takes over territory through expansion. The author includes research related to why absent narratives are important to any curriculum, putting it in the context of Critical Race Theory and Culturally Relevant Pedagogy as essential to understanding the experiences of people of color throughout history. Following the Understanding by Design curriculum process by Wiggins and McTighe, the redesign is based on students creating an artistic representation that showcases what they have learned in class and through their own research on how a certain group or groups became disadvantaged as a result of the U.S. achieving its goal of extending from the Atlantic to Pacific Oceans. The author concludes that it is possible to successfully implement absent narratives into Manifest Destiny curriculum and beyond to allow students to better understand the experiences of people of color. While there are limitations related to curriculum time constraints and standards, it is in every educator’s best interest to integrate absent narratives where and whenever possible
Statistical Extraction of Multilingual Natural Language Patterns for RDF Predicates: Algorithms and Applications
The Data Web has undergone a tremendous growth period.
It currently consists of more then 3300 publicly available knowledge bases describing millions of resources from various domains, such as life sciences, government or geography, with over 89 billion facts.
In the same way, the Document Web grew to the state where approximately 4.55 billion websites exist, 300 million photos are uploaded on Facebook as well as 3.5 billion Google searches are performed on average every day.
However, there is a gap between the Document Web and the Data Web, since for example knowledge bases available on the Data Web are most commonly extracted from structured or semi-structured sources, but the majority of information available on the Web is contained in unstructured sources such as news articles, blog post, photos, forum discussions, etc.
As a result, data on the Data Web not only misses a significant fragment of information but also suffers from a lack of actuality since typical extraction methods are time-consuming and can only be carried out periodically.
Furthermore, provenance information is rarely taken into consideration and therefore gets lost in the transformation process.
In addition, users are accustomed to entering keyword queries to satisfy their information needs.
With the availability of machine-readable knowledge bases, lay users could be empowered to issue more specific questions and get more precise answers.
In this thesis, we address the problem of Relation Extraction, one of the key challenges pertaining to closing the gap between the Document Web and the Data Web by four means.
First, we present a distant supervision approach that allows finding multilingual natural language representations of formal relations already contained in the Data Web.
We use these natural language representations to find sentences on the Document Web that contain unseen instances of this relation between two entities.
Second, we address the problem of data actuality by presenting a real-time data stream RDF extraction framework and utilize this framework to extract RDF from RSS news feeds.
Third, we present a novel fact validation algorithm, based on natural language representations, able to not only verify or falsify a given triple, but also to find trustworthy sources for it on the Web and estimating a time scope in which the triple holds true.
The features used by this algorithm to determine if a website is indeed trustworthy are used as provenance information and therewith help to create metadata for facts in the Data Web.
Finally, we present a question answering system that uses the natural language representations to map natural language question to formal SPARQL queries, allowing lay users to make use of the large amounts of data available on the Data Web to satisfy their information need
Atom Scattering from Disordered Surfaces in the Sudden Approximation: Double Collisions Effects and Quantum Liquids
The Sudden Approximation (SA) for scattering of atoms from surfaces is
generalized to allow for double collision events and scattering from
time-dependent quantum liquid surfaces. The resulting new schemes retain the
simplicity of the original SA, while requiring little extra computational
effort. The results suggest that inert atom (and in particular He) scattering
can be used profitably to study hitherto unexplored forms of complex surface
disorder.Comment: 15 pages, 1 figure. Related papers available at
http://neon.cchem.berkeley.edu/~dan
Determinants of participation in child’s education and alternative activities in Pakistan
Using data from Pakistan, this study analyzed the effect of various individual, household, and community level characteristics on the probability that children engage in different activities. According to the existing trend of their prevalence, we considered five child’s activities, namely: secular schooling; religious education; child labor; a combination of child labor and secular schooling; and inactivity (including leisure). Data was collected through field surveys conducted in over 40 villages in four Pakistani provinces: Balochistan, Khyber Paktunkhwa, Punjab, and Sind. A total of 963 households were interviewed on the activities of 2,496 children. Multinomial Probit model was used for the analyses. Results indicated that parental perception had significant relationship to the probability of engagement in secular school attendance, religious education, and child labor. In addition, we investigated the relationships between participation in the different child activities with location (rural/urban) and children’s gender. We detected a lower probability of attending secular school and a higher probability of engaging in child labor among female children in rural areas. We also found that even parents who openly expressed appreciation of the importance of secular schooling were more likely to send male children to school than female children.Child productivity, Child’s activities, Parental perception, Gender, Community/Rural/Urban Development, Labor and Human Capital, Teaching/Communication/Extension/Profession,
Laser Cooling of Molecular Anions
We propose a scheme for laser cooling of negatively charged molecules. We
briefly summarise the requirements for such laser cooling and we identify a
number of potential candidates. A detailed computation study with C, the
most studied molecular anion, is carried out. Simulations of 3D laser cooling
in a gas phase show that this molecule could be cooled down to below 1 mK in
only a few tens of milliseconds, using standard lasers. Sisyphus cooling, where
no photo-detachment process is present, as well as Doppler laser cooling of
trapped C, are also simulated. This cooling scheme has an impact on the
study of cold molecules, molecular anions, charged particle sources and
antimatter physics
Sandhill crane population monitoring, modeling, and harvest decision making
Includes bibliographical references.2015 Fall.To view the abstract, please see the full text of the document
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The effectiveness of partnership approach in community development.
This study explores the concept of partnership in community development programs. The purpose of this study is to investigate the concept of partnership, and acquire a comprehensive understanding of community development programs called partnership programs. In the past few years the international development community, especially the nongovernment organization (NGO) community, has been discussing the importance of establishing partnerships between organizations and people from the developed countries with organizations and people from the emerging nations. Also, during the past fifty years community development programs have become the dominant type of development program for communities working together to improve the living condition of the community members. In the last few years a new concept called, partnerships and community partnerships is being heard as a new type of development program. What are these partnerships? How are they different from community development programs? Are these partnerships worthwhile? And if they are, how, and to whom? These questions need to be answered in order to decide if and how development organizations should implement partnership programs. The following research hopes to answer these questions. Six programs have been studied, five short cases and one longer case study. The issue of power and empowerment have been examined in detail because it is important to understand exactly how partnership members empower themselves to improve their lives for themselves. Three other dimensions used in this dissertation to understand partnerships are: different types of teaching pedagogies, participation, and different types of community development organizations. By examining partnership programs through these four dimensions the author was able to better understand and explain why and how partnership programs are different from community development partnership programs of the past. The study concludes with a description of what partnership pedagogy is, and how the author believes that creating partnerships in development is one way of transforming our institutions into more effective systems for human beings to work and live together
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