83,513 research outputs found
Multivariate adaptive regression splines for estimating riverine constituent concentrations
Regression-based methods are commonly used for riverine constituent concentration/flux estimation, which is essential for guiding water quality protection practices and environmental decision making. This paper developed a multivariate adaptive regression splines model for estimating riverine constituent concentrations (MARS-EC). The process, interpretability and flexibility of the MARS-EC modelling approach, was demonstrated for total nitrogen in the Patuxent River, a major river input to Chesapeake Bay. Model accuracy and uncertainty of the MARS-EC approach was further analysed using nitrate plus nitrite datasets from eight tributary rivers to Chesapeake Bay. Results showed that the MARS-EC approach integrated the advantages of both parametric and nonparametric regression methods, and model accuracy was demonstrated to be superior to the traditionally used ESTIMATOR model. MARS-EC is flexible and allows consideration of auxiliary variables; the variables and interactions can be selected automatically. MARS-EC does not constrain concentration-predictor curves to be constant but rather is able to identify shifts in these curves from mathematical expressions and visual graphics. The MARS-EC approach provides an effective and complementary tool along with existing approaches for estimating riverine constituent concentrations
Fermi gas in harmonic oscillator potentials
Assuming the validity of grand canonical statistics, we study the properties
of a spin-polarized Fermi gas in harmonic traps. Universal forms of Fermi
temperature , internal energy and the specific heat per particle of
the trapped Fermi gas are calculated as a {\it function} of particle number,
and the results compared with those of infinite number particles.Comment: 8 pages, 1 figure, LATE
Hertz-level Measurement of the 40Ca+ 4s 2S1/2-3d 2D5/2 Clock Transition Frequency With Respect to the SI Second through GPS
We report a frequency measurement of the clock transition of a single ^40Ca^+
ion trapped and laser cooled in a miniature ring Paul trap with 10^-15 level
uncertainty. In the measurement, we used an optical frequency comb referenced
to a Hydrogen maser, which was calibrated to the SI second through the Global
Positioning System (GPS). Two rounds of measurements were taken in May and June
2011, respectively. The frequency was measured to be 411 042 129 776 393.0(1.6)
Hz with a fractional uncertainty of 3.9{\times}10^-15 in a total averaging time
of > 2{\times}10^6 s within 32 days
Cutting the last wires for mobile communications by microwave power transfer
published_or_final_versio
Analysis of the influence to productivity of software corrective maintenance using an economic model
© 2014 IEEE. This paper presents an economic model for productivity of software corrective maintenance. The productivity is modeled using economic value of the maintenance process as the output, and the pre-committed fixed cost and variable cost as input. The relationship of the economic value and these cost components are modeled using analytical theory of investment. The values of corrective maintenance process are analyzed. A simulation approach is demonstrated to analyze the influences to the productivity in corrective maintenance. This approach provides a tool to identify and analyze the optimal parameters in productivity using the economic model and simulation
Calibration and Precise Detection of the Irregular Drift of the Tidal Zero Point for a short/medium term Tide Station
The tide gauge is one of the most important auxiliary sensors in
hydrographic surveying. Medium and short-term tide stations are established using
pressure-type tide gauges to achieve the water level control for the depth measurement
along the coast. Affected by the complex marine environment, one of the main factors in
determining the accuracy of the water depth measurement is the irregular drift of the
tidal zero point, which is usually deter-mined during the engineering practice. However,
the relevant theoretical research on detection and correction lags. In this paper, the
occurence of irregular drift about tidal zero is analyzed, and a mathematical model for
precise processing of drift detection and correc-tion is proposed. Based on the processing
of nearly one month of simultaneous tide data at the long-term Dinghai station, the
temporary station at Gangxin, as well as the long-term Dafeng station and temporary
Sanyazi station, the effect of two daily average sea surface calculation methods on
different constituents are analyzed. The results show that the new proposed model is
suitable for the precise processing of irregular drift of tide zero point. After the tide
zero point correction, the accuracy of the water level observation data of the short-term
Gangxin and Sanyazi tide stations is improved from decimetre (dm) to centime-tre (cm)
levels.El mareógrafo es uno de los sensores auxiliares más importantes en
los levantamientos hidrográficos. Las estaciones de mareas de medio y corto plazo se
establecen utilizando mareógrafos de presión afÃn de lograr el nivel del mar para el
control de la medición de profundidad a lo largo de la costa. Afectado por el complejo
entorno marino, uno de los principales factores en la determinación de la precisión en la
medición de la profundidad del mar es la deriva irregular del punto cero de la marea, que
generalmente está basado en la práctica de la ingenierÃa. Sin embargo, la investigación
teórica pertinente sobre la detección y la corrección toma su tiempo. En este artÃculo, se
analiza la ocurrencia de deriva irregular sobre el punto cero de la marea, y se propone un
modelo matemático para el procesado preciso de la detección y corrección de la deriva.
Basándose en el proceso de casi un mes de datos de mareas obtenidos simultáneamente en la
estación Dinghai de largo plazo, en la estación temporal de Gangxin, y también en la
estación Dafeng de largo plazo y la estación temporal de Sanyazi, se ha analizado el
efecto de dos métodos diarios de cálculo de la superficie media del mar en diferentes
componentes. Los resultados muestran que el nuevo modelo propuesto es adecuado para el
proceso preciso de la deriva irregular del punto cero de la marea. Después de la
corrección del punto cero de la marea, se ha mejorado la precisión de los datos de
observación del nivel del mar de las estaciones de marea de corto plazo de Gangxin y
Sanyazi, de niveles de decÃmetros (dm) a centÃmetros (cm).Le marégraphe est l’un des capteurs auxiliaires les plus importants
en matière de levés hydrographiques. Les observatoires de marée de courte/moyenne durée
sont établis à l’aide de marégraphes à pression servant à observer le niveau de la mer en
vue de mesurer les profondeurs le long de la côte. Affecté par l’environnement maritime
complexe, l’un des principaux facteurs permettant de déterminer la précision de la mesure
de la profondeur d’eau est la dérive irrégulière du zéro hydrographique, qui repose
habituelle-ment sur les pratiques d’ingénierie. Toutefois, la recherche théorique
appropriée en matière de détection et de correction a pris du retard. Dans l’article qui
suit, l’occurrence de la érive irrégulière du zéro hydrographique est analysée et un
modèle mathématique pour le traitement précis de la détection et de la correction de la
dérive est proposé. A partir de presqu’un mois de données de marées simultanées
recueillies à l’observatoire Dinghai de longue durée, à l’observatoire temporaire de
Gangxin, ainsi qu’à l’observatoire Dafeng de longue durée et à l’observatoire temporaire
de Sanyazi, les effets de deux méthodes de calcul quotidiennes du niveau moyen de la mer
sur différentes composantes harmoniques sont analysés. Les résultats montrent que le
nouveau modèle proposé convient pour le traitement précis de la dérive irrégulière du zéro
hydrographique. Après la correction du zéro hydrographique, la précision des données sur
l’observation du niveau de la mer des stations de courte durée de Gangxin et de Sanyazi
est améliorée et passe de l’ordre du décimètre (dm) au centimètre (cm)
Scheme for sharing classical information via tripartite entangled states
We investigate schemes for quantum secret sharing and quantum dense coding
via tripartite entangled states. We present a scheme for sharing classical
information via entanglement swapping using two tripartite entangled GHZ
states. In order to throw light upon the security affairs of the quantum dense
coding protocol, we also suggest a secure quantum dense coding scheme via W
state in analogy with the theory of sharing information among involved users.Comment: 4 pages, no figure. A complete rewrritten vession, accepted for
publication in Chinese Physic
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