14,151 research outputs found
Spartan Daily, October 25, 1995
Volume 105, Issue 39https://scholarworks.sjsu.edu/spartandaily/8754/thumbnail.jp
The second-phase development of the China JinPing underground Laboratory
During 2013-2015 an expansion of the China JinPing underground Laboratory
(CJPL) will be undertaken along a main branch of a bypass tunnel in the JinPing
tunnel complex. This second phase of CJPL will increase laboratory space to
approximately 96,000 m^3, which can be compared to the existing CJPL-I volume
of 4,000 m^3. One design configuration has eight additional hall spaces, each
over 60 m long and approximately 12 m in width, with overburdens of about 2.4
km of rock, oriented parallel to and away from the main water transport and
auto traffic tunnels. Concurrent with the excavation activities, planning is
underway for dark matter and other rare-event detectors, as well as for
geophysics/engineering and other coupled multi-disciplinary sensors. In the
town meeting on 8 September, 2013 at Asilomar, CA, associated with the 13th
International Conference on Topics in Astroparticle and Underground Physics
(TAUP), presentations and panel discussions addressed plans for one-ton
expansions of the current CJPL germanium detector array of the China Darkmatter
EXperiment (CDEX) collaboration and of the duel-phase xenon detector of the
Panda-X collaboration, as well as possible new detector initiatives for dark
matter studies, low-energy solar neutrino detection, neutrinoless double beta
searches, and geoneutrinos. JinPing was also discussed as a site for a
low-energy nuclear astrophysics accelerator. Geophysics/engineering
opportunities include acoustic and micro-seismic monitoring of rock bursts
during and after excavation, coupled-process in situ measurements, local,
regional, and global monitoring of seismically induced radon emission, and
electromagnetic signals.Comment: 9 pages, 3 figures. 13th International Conference on Topics in
Astroparticle and Underground Physics, TAUP 201
Ion lasers-the early years
The paper is a personal, anecdotal history of the discovery and early development of ion lasers, particularly the argon ion laser. A brief discussion of the mechanisms that make this laser work, and the engineering challenges and developments that make it practical are included. Some early applications in night reconnaissance and imaging are include
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Thorium Energy Futures
The potential for thorium as an alternative or supplement to uranium in fission power generation has long been recognised, and several reactors, of various types, have already operated using thorium-based fuels. Accelerator Driven Subcritical (ADS) systems have benefits and drawbacks when compared to conventional critical thorium reactors, for both solid and molten salt fuels. None of the four options – liquid or solid, with or without an accelerator – can yet be rated as better or worse than the other three, given today's knowledge. We outline the research that will be necessary to lead to an informed choice
Query-Driven Sampling for Collective Entity Resolution
Probabilistic databases play a preeminent role in the processing and
management of uncertain data. Recently, many database research efforts have
integrated probabilistic models into databases to support tasks such as
information extraction and labeling. Many of these efforts are based on batch
oriented inference which inhibits a realtime workflow. One important task is
entity resolution (ER). ER is the process of determining records (mentions) in
a database that correspond to the same real-world entity. Traditional pairwise
ER methods can lead to inconsistencies and low accuracy due to localized
decisions. Leading ER systems solve this problem by collectively resolving all
records using a probabilistic graphical model and Markov chain Monte Carlo
(MCMC) inference. However, for large datasets this is an extremely expensive
process. One key observation is that, such exhaustive ER process incurs a huge
up-front cost, which is wasteful in practice because most users are interested
in only a small subset of entities. In this paper, we advocate pay-as-you-go
entity resolution by developing a number of query-driven collective ER
techniques. We introduce two classes of SQL queries that involve ER operators
--- selection-driven ER and join-driven ER. We implement novel variations of
the MCMC Metropolis Hastings algorithm to generate biased samples and
selectivity-based scheduling algorithms to support the two classes of ER
queries. Finally, we show that query-driven ER algorithms can converge and
return results within minutes over a database populated with the extraction
from a newswire dataset containing 71 million mentions
Probabilistic Graphical Model Representation in Phylogenetics
Recent years have seen a rapid expansion of the model space explored in
statistical phylogenetics, emphasizing the need for new approaches to
statistical model representation and software development. Clear communication
and representation of the chosen model is crucial for: (1) reproducibility of
an analysis, (2) model development and (3) software design. Moreover, a
unified, clear and understandable framework for model representation lowers the
barrier for beginners and non-specialists to grasp complex phylogenetic models,
including their assumptions and parameter/variable dependencies.
Graphical modeling is a unifying framework that has gained in popularity in
the statistical literature in recent years. The core idea is to break complex
models into conditionally independent distributions. The strength lies in the
comprehensibility, flexibility, and adaptability of this formalism, and the
large body of computational work based on it. Graphical models are well-suited
to teach statistical models, to facilitate communication among phylogeneticists
and in the development of generic software for simulation and statistical
inference.
Here, we provide an introduction to graphical models for phylogeneticists and
extend the standard graphical model representation to the realm of
phylogenetics. We introduce a new graphical model component, tree plates, to
capture the changing structure of the subgraph corresponding to a phylogenetic
tree. We describe a range of phylogenetic models using the graphical model
framework and introduce modules to simplify the representation of standard
components in large and complex models. Phylogenetic model graphs can be
readily used in simulation, maximum likelihood inference, and Bayesian
inference using, for example, Metropolis-Hastings or Gibbs sampling of the
posterior distribution
Arguments for a "U.S. Kamioka": SNOLab and its Implications for North American Underground Science Planning
We argue for a cost-effective, long-term North American underground science
strategy based on partnership with Canada and initial construction of a modest
U.S. Stage I laboratory designed to complement SNOLab. We show, by reviewing
the requirements of detectors now in the R&D phase, that SNOLab and a properly
designed U.S. Stage I facility would be capable of meeting the needs of North
America's next wave of underground experiments. We discuss one opportunity for
creating a Stage I laboratory, the Pioneer tunnel in Washington State, a site
that could be developed to provide dedicated, clean, horizontal access. This
unused tunnel, part of the deepest (1040 m) tunnel system in the U.S., would
allow the U.S. to establish, at low risk and low cost, a laboratory at a depth
(2.12 km.w.e., or kilometers of water equivalent) quite similar to that of the
Japanese laboratory Kamioka (2.04 km.w.e.). We describe studies of cosmic ray
attenuation important to properly locating such a laboratory, and the tunnel
improvements that would be required to produce an optimal Stage I facility. We
also discuss possibilities for far-future Stage II (3.62 km.w.e.) and Stage III
(5.00 km.w.e.) developments at the Pioneer tunnel, should future North American
needs for deep space exceed that available at SNOLab.Comment: 23 pages, 10 figures; revised version includes discusion about
neutrino-factory magic baseline
Impact cratering experiments into highly porous bodies
Asteroids represent both an opportunity and a risk. Their pristine environment captures the early collision evolution of the solar system; while their inherent ground impact potential could result in the mass extinction of life. Amongst the many possibilities of asteroid deflection, kinematic impactors have been theoretically proven to be a promising technique. However, this is primarily based on modelling rocky, brittle bodies. Little experimental consideration has been made for highly porous bodies. Therefore to advance current mitigation scenarios a series of experiments have been conducted. Under an accelerated reference frame this aimed to assess the impact cratering response of highly porous asteroids. All events were examined relative to the increasing levels of porosity and the impact’s resultant morphological profile. This included crater shape and depth, and the ejecta profile. The latter was considered critical in assessing the overall contribution to the momentum enhancement exchange of any kinematic impact event
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