29,588 research outputs found
Analysis of rainfall over northern Peru during El Nino: A PCDS application
In an examination of GOES satellite data during the 1982 through 1983 El Nino period, the appearance of lee wave cloud patterns was revealed. A correlation was hypothesized relating an anomalous easterly flow across the Andes with the appearance of these wave patterns and with the subsequent onset of intense rainfall. The cloud patterns are belived to be associated with the El Nino period and could be viewed as precursors to significant changes in weather patterns. The ultimate goal of the researchers will be the ability to predict occurrences of rainstorms associated with the appearance of lee waves and related cloud patterns as harbingers of destruction caused by flooding, huaycos, and other catastrophic consequences of heavy and abnormal rainfall. Rainfall data from about 70 stations in northern Peru from 1980 through 1984 were formatted to be utilized within the Pilot Climate Data System (PCDS). This time period includes the 1982 through 1983 El Nino period. As an example of the approach, a well-pronounced lee wave pattern was shown from a GOES satellite image of April 4, 1983. The ground truth data were then displayed via the PCDS to graphically demonstrate the increase in intensity and areal distribution of rainfall in the northern Peruvian area in the next 4 to 5 days
Core-competitive Auctions
One of the major drawbacks of the celebrated VCG auction is its low (or zero)
revenue even when the agents have high value for the goods and a {\em
competitive} outcome could have generated a significant revenue. A competitive
outcome is one for which it is impossible for the seller and a subset of buyers
to `block' the auction by defecting and negotiating an outcome with higher
payoffs for themselves. This corresponds to the well-known concept of {\em
core} in cooperative game theory.
In particular, VCG revenue is known to be not competitive when the goods
being sold have complementarities. A bottleneck here is an impossibility result
showing that there is no auction that simultaneously achieves competitive
prices (a core outcome) and incentive-compatibility.
In this paper we try to overcome the above impossibility result by asking the
following natural question: is it possible to design an incentive-compatible
auction whose revenue is comparable (even if less) to a competitive outcome?
Towards this, we define a notion of {\em core-competitive} auctions. We say
that an incentive-compatible auction is -core-competitive if its
revenue is at least fraction of the minimum revenue of a
core-outcome. We study the Text-and-Image setting. In this setting, there is an
ad slot which can be filled with either a single image ad or text ads. We
design an core-competitive randomized auction and an
competitive deterministic auction for the Text-and-Image
setting. We also show that both factors are tight
Exact Nonperturbative Unitary Amplitudes for 1->N Transitions
I present an extension to arbitrary N of a previously proposed field
theoretic model, in which unitary amplitudes for processes were
obtained. The Born amplitude in this extension has the behavior
expected in a bosonic field theory. Unitarity
is violated when , or when Numerical
solutions of the coupled Schr\"odinger equations shows that for weak coupling
and a large range of N>\ncrit, the exact unitary amplitude is reasonably fit
by a factorized expression |A(1->N)| \sim (0.73 /N) \cdot \exp{(-0.025/\g2)}.
The very small size of the coefficient 1/\g2 , indicative of a very weak
exponential suppression, is not in accord with standard discussions based on
saddle point analysis, which give a coefficient The weak dependence
on could have experimental implications in theories where the exponential
suppression is weak (as in this model). Non-perturbative contributions to
few-point correlation functions in this theory would arise at order $K\ \simeq\
\left((0.05/\g2)+ 2\ ln{N}\right)/ \ ln{(1/\g2)}\g2.$Comment: 11 pages, 3 figures (not included
Recommended from our members
Cost of Florida's Ban on Adoption by GLB Individuals and Same-Sex Couples
This memo estimates the impact on children and the cost to the State of Florida of the current prohibition on adoption by gay, lesbian, and bisexual (GLB) individuals and same-sex couples. We use data about the number of children adopted each year as a way to estimate the number of GLB individuals and same-sex couples who would be likely to serve as adoptive parents if the ban were not in place. Prohibiting GLB individuals and same-sex couples from adopting means that 165 children must remain in foster care or must have alternative adoptive homes recruited for them. As a result, we estimate that the ban costs the State of Florida over 3.4 million dollars in the first year
Ion composition in a noctilucent cloud
Ion composition at mesospheric altitudes was measured and compared between high and mid-latitude sites under summer daytime conditions. Rocket-borne measurements were made with pumped quadrupole ion mass spectrometers. The mid-latitude data were obtained at Wallops Island, Virginia on June 30, 1973, at 1510 LMT. Large quantities of hydronium cluster ions were observed through 109+, with maximum concentrations at 55+ and 73+. Also, cluster ions of nitric oxide were observed through 84+. The high latitude launch occurred at Kiruna, Sweden on August 2, 1973, at 0700 LMT following visual sighting of a noctilucent cloud on the prior evening. The data near mesopause shows cluster ions, but also a preponderance of heavy ions between 90 and 145 AMU, with groupings 18 AMU apart but unrelated to the more typical cluster ions. One possible set of consistent identifications leads to iron and iron oxide hydrates. These results may suggest the presence of metallic particulates and ions which form hydrated clusters ions
A Palladium-Catalyzed Vinylcyclopropane (3 + 2) Cycloaddition Approach to the Melodinus Alkaloids
A palladium-catalyzed (3 + 2) cycloaddition of a vinylcyclopropane and a β-nitrostyrene is employed to rapidly assemble the cyclopentane core of the Melodinus alkaloids. The ABCD ring system of the natural product family is prepared in six steps from commercially available materials
Diffraction of wave packets in space and time
The phenomenon of wave packet diffraction in space and time is described. It
consists in a diffraction pattern whose spatial location progresses with time.
The pattern is produced by wave packet quantum scattering off an attractive or
repulsive time independent potential. An analytical formula for the pattern at
is derived both in one dimension and in three dimensions. The
condition for the pattern to exist is developed. The phenomenon is shown
numerically and analytically for the Dirac equation in one dimension also. An
experiment for the verification of the phenomenon is described and simulated
numerically.Comment: replaces quant-ph 0008077, 0008107, Journal of physics, A, in pres
Recommended from our members
The Effects of Marriage Equality in Massachusetts: A survey of the experiences and impact of marriage on same-sex couples
May 17th, 2009 marks the 5th year of marriage equality in the state of Massachusetts. To mark this anniversary, the Massachusetts Department of Public Health conducted the largest survey to date of married same-sex couples, the Health and Marriage Equality in Massachusetts (HMEM) survey. During the past year, four other states have extended marriage to same-sex couples and several other states are considering marriage legislation. The HMEM data allows us to address important questions that arise as other states consider whether to extend marriage to same-sex couples. The data provides answers to several key questions: Who is getting married? Why are same-sex couples getting married? What impact has marriage had on same-sex relationships? And, what impact has marriage had on the children of same-sex couples
Recommended from our members
The Fiscal Impact of Extending Federal Benefits to Same-Sex Domestic Partners
This report finds that offering health and other benefits to the same-sex partners of federal employees would add 675 million, a small percentage of the federal budget. The report also takes into account the added federal income taxes that will be paid by federal employees if they sign a partner up for health insurance. It estimates the cost of including partners in retirement benefits, work injury and death compensation, and travel and relocation expenses. Many benefits offered to federal employees, such as life insurance and family and medical leave, can be offered to domestic partners at no additional cost to the federal government
Expansion-limited aggregation of nanoclusters in a single-pulse laser-produced plume
Formation of carbon nanoclusters in a single-laser-pulse created ablation plume was studied both in vacuum and in a noble gas environment at various pressures. The developed theory provides cluster radius dependence on combination of laser parameters, properties of ablated material, and type and pressure of an ambient gas in agreement with experiments. The experiments were performed on carbon nanoclusters formed by laser ablation of graphite targets with 12 picosecond 532 nm laser pulses at MHz-range repetition rate in a broad range of ambient He, Ar, Kr, and Xe gas pressures from 2× 10-2 to 1500 Torr. The experimental results confirmed our theoretical prediction that the average size of the nanoparticles depends weakly on the type of the ambient gas used, and is determined exclusively by the single laser pulse parameters even at the repetition rate as high as 28 MHz with the time gap 36 ns between the pulses. The most important finding relates to the fact that in vacuum the cluster size is mainly determined by hydrodynamic expansion of the plume while in the ambient gas it is controlled by atomic diffusion in the gas. We demonstrate that the ultrashort pulses can be used for production of clusters with the size less than the critical value, which separates the particles with properties drastically different from those of a material in a bulk. The presented results of experiments on formation of carbon nanoclusters are in close agreement with the theoretical scaling. The developed theory is applicable for cluster formation from any monatomic material, such as silicon for example
- …