331 research outputs found
Twin bent functions and Clifford algebras
This paper examines a pair of bent functions on and their
relationship to a necessary condition for the existence of an automorphism of
an edge-coloured graph whose colours are defined by the properties of a
canonical basis for the real representation of the Clifford algebra
Some other necessary conditions are also briefly examined.Comment: 11 pages. Preprint edited so that theorem numbers, etc. match those
in the published book chapter. Final post-submission paragraph added to
Section 6. in "Algebraic Design Theory and Hadamard Matrices: ADTHM,
Lethbridge, Alberta, Canada, July 2014", Charles J. Colbourn (editor), pp.
189-199, 201
Vulnerability assessment to trihalomethane exposure in water distribution system.
Chlorination is an effective and cheap disinfectant for preventing waterborne diseases-causing microorganisms, but its compounds tend to react with the natural organic matter (NOM), forming potentially harmful and unwanted disinfection by-products (DBPs) such as trihalomethanes (THMs), haloacetic acids (HAAs), and others. The present paper proposes a methodology for estimating the vulnerability with respect to users' exposure to DPBs in water distribution systems (WDSs). The presented application considers total THMs (TTHMs) concentration, but the methodology can be used also for other types of DPBs. Five vulnerability indexes are adopted that furnish different kinds of information about the exposure. The methodology is applied to five case studies, and the results suggest that the introduced indexes identify different critical areas in respect to elevated concentrations of TTHMs. In this way, the use of the proposed methodology allows identifying the higher risk nodes with respect to the different kinds of exposure, whether it is a short period of exposure to high TTHMs values, or chronic exposure to low concentrations. The application of the methodology furnishes useful information for an optimal WDS management, for planning system modifications and district sectorization taking into account water quality
A Pre-screening Procedure for Pollution Source Identification in Sewer Systems
Illicit intrusions in Sewer Systems (SSs), modifying the wastewater characteristics, may create problems to the treatment plant
and/or to the final recipient water body. For this reason, the source identification (SI) problem is becoming an important issue
also in SSs. For large real systems, the computational burden might make the SI methodologies impractical. In this paper a prescreening
procedure, based on the pollution matrix concept, is introduced and applied before the SI methodology. Selecting a
group of possible candidate nodes and cutting consequently the scheme, a significant improvement both in terms of time and the
accuracy is obtained
Optimal Placement of Water Quality Monitoring Stations in Sewer Systems: An Information Theory Approach
A core problem associated with the water quality monitoring in the sewer system is the optimal placement of a limited number of
monitoring sites. A methodology is provided for optimally design water quality monitoring stations in sewer networks. The
methodology is based on information theory, formulated as a multi-objective optimization problem and solved using NSGA-II.
Computer code is written to estimate two entropy quantities, namely Joint Entropy, a measure of information content, and Total
Correlation, a measure of redundancy, which are maximized and minimized, respectively. The test on a real sewer network
suggests the effectiveness of the proposed methodology
Hyperpolarizability and operational magic wavelength in an optical lattice clock
Optical clocks benefit from tight atomic confinement enabling extended
interrogation times as well as Doppler- and recoil-free operation. However,
these benefits come at the cost of frequency shifts that, if not properly
controlled, may degrade clock accuracy. Numerous theoretical studies have
predicted optical lattice clock frequency shifts that scale nonlinearly with
trap depth. To experimentally observe and constrain these shifts in an
Yb optical lattice clock, we construct a lattice enhancement cavity
that exaggerates the light shifts. We observe an atomic temperature that is
proportional to the optical trap depth, fundamentally altering the scaling of
trap-induced light shifts and simplifying their parametrization. We identify an
"operational" magic wavelength where frequency shifts are insensitive to
changes in trap depth. These measurements and scaling analysis constitute an
essential systematic characterization for clock operation at the
level and beyond.Comment: 5 + 2 pages, 3 figures, added supplementa
Optimizing the linearity in high-speed photodiodes
Analog photonic links require high-fidelity, high-speed optical-to-electrical
conversion for applications such as radio-over-fiber, synchronization at
kilometer-scale facilities, and low-noise electronic signal generation.
Photodetector nonlinearity is a particularly vexing problem, causing signal
distortion and excess noise, especially in systems utilizing ultrashort optical
pulses. Here we show that photodetectors designed for high power handling and
high linearity can perform optical-to-electrical conversion of ultrashort
optical pulses with unprecedented linearity over a large photocurrent range. We
also show that the broadband, complex impedance of the circuit following the
photodiode modifies the linearity significantly. By externally manipulating the
circuit impedance, we extend the detector's linear range to higher
photocurrents, with over 50 dB rejection of amplitude-to-phase conversion for
photocurrents up to 40 mA. This represents a 1000-fold improvement over
state-of-the-art photodiodes and significantly extends the attainable microwave
power by a factor of four. As such, we eliminate the long-standing requirement
in ultrashort pulse detection of precise tuning of the photodiode's operating
parameters (average photocurrent, bias voltage or temperature) to coincide with
a nonlinearity minimum. These results should also apply more generally to
reduce nonlinear distortion in a range of other microwave photonics
applications
A dedicated protocol and environment for central venous catheter removal in pediatric patients affected by oncohematological diseases
The removal of long-term central venous catheters (CVCs) is not performed according to evidence-based guidelines, thus conveying the message that it is a procedure of secondary importance. Our study aims at comparing the experience at Bambino Gesù Pediatric Hospital before and after the implementation of a dedicated protocol and the identification of a specific area to perform such a procedure under the so-called nonoperating room anesthesia (NORA)
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