421 research outputs found
Optimal Storage Rack Design for a 3-dimensional Compact AS/RS
In this paper, we consider a newly-designed compact three-dimensional automated storage and retrieval system (AS/RS). The system consists of an automated crane taking care of movements in the horizontal and vertical direction. A gravity conveying mechanism takes care of the depth movement. Our research objective is to analyze the system performance and optimally dimension of the system. We estimate the crane’s expected travel time for single-command cycles. From the expected travel time, we calculate the optimal ratio between three dimensions that minimizes the travel time for a random storage strategy. In addition, we derive an approximate closed-form travel time expression for dual command cycles. Finally, we illustrate the findings of the study by a practical example.AS/RS;Warehousing;Order Picking;Travel Time Model;Compact Storage Rack Design
Optimal Storage Rack Design for a 3-dimensional Compact AS/RS
In this paper, we consider a newly-designed compact three-dimensional automated storage and retrieval system (AS/RS). The system consists of an automated crane taking care of movements in the horizontal and vertical direction. A gravity conveying mechanism takes care of the depth movement. Our research objective is to analyze the system performance and optimally dimension of the system. We estimate the crane’s expected travel time for single-command cycles. From the expected travel time, we calculate the optimal ratio between three dimensions that minimizes the travel time for a random storage strategy. In addition, we derive an approximate closed-form travel time expression for dual command cycles. Finally, we illustrate the findings of the study by a practical example
Highly stable perylenediimide based self-assembled monolayers studied by spectroelectrochemistry
Perylenediimide (PDI) based self-assembled monolayers (SAMs) have been studied by quartz crystal microbalance, X-ray photoelectron spectroscopy, cyclic voltammetry and spectroelectrochemistry (SEC). The high stability of PDI based SAMs has allowed probing very low signals by absorption and emission SEC and extracting voltabsorptograms. The wavelengths of absorption maxima of PDI, anion radical and dianion species. In contrast, the magnitudes of the molar extinction coefficient of the reduced forms were not preserved in SAM. The quenching of PDI fluorescence was confirmed on gold substrate
A Potential Galaxy Threshing System in the Cosmos Field
We report on the discovery of a new potential galaxy threshing system in the
COSMOS 2 square degree field using the prime-focus camera, Suprime-Cam, on the
8.2 m Subaru Telescope. This system consists of a giant elliptical galaxy with
and a tidally disrupted satellite galaxy with at a photometric redshift of . This redshift is
consistent with the spectroscopic redshift of 0.079 for the giant elliptical
galaxy obtained from the Sloan Digital Sky Survey (SDSS) archive. The
luminosity masses of the two galaxies are
and , respectively. The distance between the
two galaxies is greater than 100 kpc. The two tidal tails emanating from the
satellite galaxy extend over 150 kpc. This system would be the second
well-defined galaxy threshing system found so far.Comment: 17 pages, 7 figures, accepted for the COSMOS special issue of ApJ
Invariant Synthesis for Incomplete Verification Engines
We propose a framework for synthesizing inductive invariants for incomplete
verification engines, which soundly reduce logical problems in undecidable
theories to decidable theories. Our framework is based on the counter-example
guided inductive synthesis principle (CEGIS) and allows verification engines to
communicate non-provability information to guide invariant synthesis. We show
precisely how the verification engine can compute such non-provability
information and how to build effective learning algorithms when invariants are
expressed as Boolean combinations of a fixed set of predicates. Moreover, we
evaluate our framework in two verification settings, one in which verification
engines need to handle quantified formulas and one in which verification
engines have to reason about heap properties expressed in an expressive but
undecidable separation logic. Our experiments show that our invariant synthesis
framework based on non-provability information can both effectively synthesize
inductive invariants and adequately strengthen contracts across a large suite
of programs
Population density, water supply, and the risk of dengue fever in Vietnam: cohort study and spatial analysis.
BACKGROUND: Aedes aegypti, the major vector of dengue viruses, often breeds in water storage containers used by households without tap water supply, and occurs in high numbers even in dense urban areas. We analysed the interaction between human population density and lack of tap water as a cause of dengue fever outbreaks with the aim of identifying geographic areas at highest risk. METHODS AND FINDINGS: We conducted an individual-level cohort study in a population of 75,000 geo-referenced households in Vietnam over the course of two epidemics, on the basis of dengue hospital admissions (n = 3,013). We applied space-time scan statistics and mathematical models to confirm the findings. We identified a surprisingly narrow range of critical human population densities between around 3,000 to 7,000 people/km² prone to dengue outbreaks. In the study area, this population density was typical of villages and some peri-urban areas. Scan statistics showed that areas with a high population density or adequate water supply did not experience severe outbreaks. The risk of dengue was higher in rural than in urban areas, largely explained by lack of piped water supply, and in human population densities more often falling within the critical range. Mathematical modeling suggests that simple assumptions regarding area-level vector/host ratios may explain the occurrence of outbreaks. CONCLUSIONS: Rural areas may contribute at least as much to the dissemination of dengue fever as cities. Improving water supply and vector control in areas with a human population density critical for dengue transmission could increase the efficiency of control efforts. Please see later in the article for the Editors' Summary
Dark Matter and Gas Concentrations in the NGC 4532 / DDO 137 System
Neutral hydrogen synthesis mapping of NGC 4532 and DDO 137, a pair of Sm galaxies on the edge of the Virgo cluster, is used to determine rotation curves for each of the galaxies and to resolve the structure and kinematics of three distinct HI concentrations embedded in an extended envelope of diffuse HI discovered in earlier Arecibo studies of the system. The HI masses of the three concentrations do not appear to be sufficient for them to be self-gravitating; however, their HImasses and dynamical masses are very similar to those of faint Im galaxies in the Virgo cluster. The peak HI column density of each of the clouds is close to the star formation threshold, but CCD images in B and R reveal no trace of stars nor star formation. If the system is gravitationally bound and in Virial equilibrium, we find its total mass to be ten times that within the outermost HI contours of the individual galaxies and clouds. Thirty-seven percent of the total HI lies outside the boundaries of the individual galaxies as determined by the VLA mapping; 28% cannot be ascribed to either galaxy nor to the discrete concentrations. One possible way to account for the velocity field and the large quantity of diffuse gas is to assume that DDO 137, the gas concentrations and other apparent tidal features are due to gas infall into clumps within the dark matter potential of the group, and that prior to the interaction the group consisted of an irregular galaxy (NGC 4532) and a large, star-poor HI cloud like HI 1225+01 (Giovanelli et al. 1991)
Plasmodium knowlesi malaria in Vietnam: some clarifications
A recently published comment on a report of Plasmodium knowlesi infections in Vietnam states that this may not accurately represent the situation in the study area because the PCR primers used may cross-hybridize with Plasmodium vivax. Nevertheless, P. knowlesi infections have been confirmed by sequencing. In addition, a neighbour-joining tree based on the 18S S-Type SSUrRNA gene shows that the Vietnamese samples clearly cluster with the P. knowlesi isolates identified in Malaysia and are distinct from the corresponding P. vivax sequences. All samples came from asymptomatic individuals who did not consult for fever during the months preceding or following the survey, indicating that asymptomatic P. knowlesi infections occur in this population, although this does not exclude the occurrence of symptomatic cases. Large-scale studies to determine the extent and the epidemiology of P. knowlesi malaria in Vietnam are further needed
Lattice Blind Signatures with Forward Security
Blind signatures play an important role in both electronic cash and
electronic voting systems. Blind signatures should be secure against various
attacks (such as signature forgeries). The work puts a special attention to
secret key exposure attacks, which totally break digital signatures. Signatures
that resist secret key exposure attacks are called forward secure in the sense
that disclosure of a current secret key does not compromise past secret keys.
This means that forward-secure signatures must include a mechanism for
secret-key evolution over time periods.
This paper gives a construction of the first blind signature that is forward
secure. The construction is based on the SIS assumption in the lattice setting.
The core techniques applied are the binary tree data structure for the time
periods and the trapdoor delegation for the key-evolution mechanism.Comment: ACISP 202
The XMM-LSS survey. Survey design and first results
We have designed a medium deep large area X-ray survey with XMM - the XMM
Large Scale Structure survey, XMM-LSS - with the scope of extending the
cosmological tests attempted using ROSAT cluster samples to two redshift bins
between 0<z<1 while maintaining the precision of earlier studies. Two main
goals have constrained the survey design: the evolutionary study of the
cluster-cluster correlation function and of the cluster number density. The
results are promising and, so far, in accordance with our predictions as to the
survey sensitivity and cluster number density. The feasibility of the programme
is demonstrated and further X-ray coverage is awaited in order to proceed with
a truly significant statistical analysis. (Abridged)Comment: Published in Journal of Cosmology and Astroparticle Physic
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