1,064,223 research outputs found
Toric bases for 6D F-theory models
We find all smooth toric bases that support elliptically fibered Calabi-Yau
threefolds, using the intersection structure of the irreducible effective
divisors on the base. These bases can be used for F-theory constructions of
six-dimensional quantum supergravity theories. There are 61,539 distinct
possible toric bases. The associated 6D supergravity theories have a number of
tensor multiplets ranging from 0 to 193. For each base an explicit Weierstrass
parameterization can be determined in terms of the toric data. The toric
counting of parameters matches with the gravitational anomaly constraint on
massless fields. For bases associated with theories having a large number of
tensor multiplets, there is a large non-Higgsable gauge group containing
multiple irreducible gauge group factors, particularly those having algebras
e_8, f_4 and (g_2 + su(2)) with minimal (non-Higgsable) matter.Comment: 39 pages, 13 figures, one appendix; ancillary data file contains list
of 61,539 bases; v2: minor correctio
A Global Database of Domestic and International Tourist Numbers at National and Subnational Level
We present a new, global data base on tourist destinations. The data base differs from other data bases in that it includes both domestic and international tourists; and it contains data, for the most important destinations, data at national level as well as at lower administrative levels. Missing observations are interpolated using statistical models. The data are freely accessible on the internet.Tourism, Data
A GLOBAL DATABASE OF DOMESTIC AND INTERNATIONAL TOURIST NUMBERS AT NATIONAL AND SUBNATIONAL LEVEL
We present a new, global data base on tourist destinations. The data base differs from other data bases in that it includes both domestic and international tourists; and it contains data, for the most important destinations, data at national level as well as at lower administrative levels. Missing observations are interpolated using statistical models. The data are freely accessible on the internet.tourism, data
Multipurpose Interactive NASA Information Systems (MINIS)
The Multipurpose Interactive NASA Information System was developed to provide remote, interactive information retrieval capability for various types of data bases to be processed on different types of small and medium size computers. Use of the system for three different data bases is decribed: (1) LANDSAT photo look-up, (2) land use, and (3) census/socioeconomic. Each of the data base elements is shown together with other detailed information that a user would require to contact the system remotely, to transmit inquiries on commands, and to receive the results of the queries or commands
LDEF materials data bases
The Long Duration Exposure Facility (LDEF) and the accompanying experiments were composed of and contained a wide variety of materials representing the largest collection of materials flown in low Earth orbit (LEO) and retrieved for ground based analysis to date. The results and implications of the mechanical, thermal, optical, and electrical data from these materials are the foundation on which future LEO space missions will be built. The LDEF Materials Special Investigation Group (MSIG) has been charged with establishing and developing data bases to document these materials and their performance to assure not only that the data are archived for future generations but also that the data are available to the spacecraft user community in an easily accessed, user-friendly form. This paper discusses the format and content of the three data bases developed or being developed to accomplish this task. The hardware and software requirements for each of these three data bases are discussed along with current availability of the data bases. This paper also serves as a user's guide to the MAPTIS LDEF Materials Data Base
Learning over Knowledge-Base Embeddings for Recommendation
State-of-the-art recommendation algorithms -- especially the collaborative
filtering (CF) based approaches with shallow or deep models -- usually work
with various unstructured information sources for recommendation, such as
textual reviews, visual images, and various implicit or explicit feedbacks.
Though structured knowledge bases were considered in content-based approaches,
they have been largely neglected recently due to the availability of vast
amount of data, and the learning power of many complex models.
However, structured knowledge bases exhibit unique advantages in personalized
recommendation systems. When the explicit knowledge about users and items is
considered for recommendation, the system could provide highly customized
recommendations based on users' historical behaviors. A great challenge for
using knowledge bases for recommendation is how to integrated large-scale
structured and unstructured data, while taking advantage of collaborative
filtering for highly accurate performance. Recent achievements on knowledge
base embedding sheds light on this problem, which makes it possible to learn
user and item representations while preserving the structure of their
relationship with external knowledge. In this work, we propose to reason over
knowledge base embeddings for personalized recommendation. Specifically, we
propose a knowledge base representation learning approach to embed
heterogeneous entities for recommendation. Experimental results on real-world
dataset verified the superior performance of our approach compared with
state-of-the-art baselines
A Survey of Volunteered Open Geo-Knowledge Bases in the Semantic Web
Over the past decade, rapid advances in web technologies, coupled with
innovative models of spatial data collection and consumption, have generated a
robust growth in geo-referenced information, resulting in spatial information
overload. Increasing 'geographic intelligence' in traditional text-based
information retrieval has become a prominent approach to respond to this issue
and to fulfill users' spatial information needs. Numerous efforts in the
Semantic Geospatial Web, Volunteered Geographic Information (VGI), and the
Linking Open Data initiative have converged in a constellation of open
knowledge bases, freely available online. In this article, we survey these open
knowledge bases, focusing on their geospatial dimension. Particular attention
is devoted to the crucial issue of the quality of geo-knowledge bases, as well
as of crowdsourced data. A new knowledge base, the OpenStreetMap Semantic
Network, is outlined as our contribution to this area. Research directions in
information integration and Geographic Information Retrieval (GIR) are then
reviewed, with a critical discussion of their current limitations and future
prospects
Testing the Tax Competition Theory: How Elastic are National Tax Bases in OECD Countries?
To what extent do countries' corporate income tax (CIT) rates attract foreign tax bases? What are the revenue implications of a unilateral tax reduction when tax bases are internationally mobile? These questions are explored using a panel of annual data from 17 OECD countries spanning the period 1982 to 2005. We find significant international fiscal externalities in the form of CIT-induced resource flows. The magnitude, however, indicates that the extent of international corporate tax base mobility is rather modest. Moreover, we find that, on average, a unilateral CIT reduction results in a less-than-proportional increase in the CIT base, thus reducing CIT revenues. The results are robust across a wide range of specifications and point to potential gains from international tax policy coordination.tax competition, corporate income tax base elasticity, instrumental variables, international fiscal externalities, Laffer curve, panel data estimation
- âŠ