380 research outputs found
Probabilistic Anomaly Detection in Natural Gas Time Series Data
This paper introduces a probabilistic approach to anomaly detection, specifically in natural gas time series data. In the natural gas field, there are various types of anomalies, each of which is induced by a range of causes and sources. The causes of a set of anomalies are examined and categorized, and a Bayesian maximum likelihood classifier learns the temporal structures of known anomalies. Given previously unseen time series data, the system detects anomalies using a linear regression model with weather inputs, after which the anomalies are tested for false positives and classified using a Bayesian classifier. The method can also identify anomalies of an unknown origin. Thus, the likelihood of a data point being anomalous is given for anomalies of both known and unknown origins. This probabilistic anomaly detection method is tested on a reported natural gas consumption data set
Data Improving in Time Series Using ARX and ANN Models
Anomalous data can negatively impact energy forecasting by causing model parameters to be incorrectly estimated. This paper presents two approaches for the detection and imputation of anomalies in time series data. Autoregressive with exogenous inputs (ARX) and artificial neural network (ANN) models are used to extract the characteristics of time series. Anomalies are detected by performing hypothesis testing on the extrema of the residuals, and the anomalous data points are imputed using the ARX and ANN models. Because the anomalies affect the model coefficients, the data cleaning process is performed iteratively. The models are re-learned on “cleaner” data after an anomaly is imputed. The anomalous data are reimputed to each iteration using the updated ARX and ANN models. The ARX and ANN data cleaning models are evaluated on natural gas time series data. This paper demonstrates that the proposed approaches are able to identify and impute anomalous data points. Forecasting models learned on the unclean data and the cleaned data are tested on an uncleaned out-of-sample dataset. The forecasting model learned on the cleaned data outperforms the model learned on the unclean data with 1.67% improvement in the mean absolute percentage errors and a 32.8% improvement in the root mean squared error. Existing challenges include correctly identifying specific types of anomalies such as negative flows
The effective mass of atom-radiation field system and the cavity-field Wigner distribution in the presence of a homogeneous gravitational field in the Jaynes-Cummings model
The effective mass that approximately describes the effect of a classical
homogeneous gravitational field on an interacting atom-radiation field system
is determined within the framework of the Jaynes-Cummings model.
By taking into account both the atomic motion and gravitational field, a full
quantum treatment of the internal and external dynamics of the atom is
presented. By solving exactly the Schrodinger equation in the interaction
picture, the evolving state of the system is found. Influence of a classical
homogeneous gravitational field on the energy eigenvalues, the effective mass
of atom-radiation field system and the Wigner distribution of the radiation
field are studied, when initially the radiation field is prepared in a coherent
state and the two-level atom is in a coherent superposition of the excited and
ground states.Comment: 12 pages, 9 figure
Dissociation and ionization of small molecules steered by external noise
We show that ionization and dissociation can be influenced separately in a
molecule with appropriate external noise. Specifically we investigate the
hydrogen molecular ion under a stochastic force quantum mechanically beyond the
Born-Oppenheimer approximation. We find that up to 30% of dissociation without
ionization can be achieved by suitably tuning the forcing parameters.Comment: 13 pages, 6 figure
Convex ordering and quantification of quantumness
The characterization of physical systems requires a comprehensive
understanding of quantum effects. One aspect is a proper quantification of the
strength of such quantum phenomena. Here, a general convex ordering of quantum
states will be introduced which is based on the algebraic definition of
classical states. This definition resolves the ambiguity of the quantumness
quantification using topological distance measures. Classical operations on
quantum states will be considered to further generalize the ordering
prescription. Our technique can be used for a natural and unambiguous
quantification of general quantum properties whose classical reference has a
convex structure. We apply this method to typical scenarios in quantum optics
and quantum information theory to study measures which are based on the
fundamental quantum superposition principle.Comment: 9 pages, 2 figures, revised version; published in special issue "150
years of Margarita and Vladimir Man'ko
Mean parity of single quantum excitation of some optical fields in thermal environments
The mean parity (the Wigner function at the origin) of excited binomial
states, excited coherent states and excited thermal states in thermal channel
is investigated in details. It is found that the single-photon excited binomial
state and the single-photon excited coherent state exhibit certain similarity
in the aspect of their mean parity in the thermal channel. We show the negative
mean parity can be regarded as an indicator of nonclassicality of single-photon
excitation of optical fields with a little coherence, especially for the
single-photon excited thermal states.Comment: 4 pages, 4 figures, RevTex4; PACS numbers: 42.50.Dv, 03.65.Yz,
05.40.Ca; Three typo errors have been correcte
Bifurcation and Chaos in Coupled Ratchets exhibiting Synchronized Dynamics
The bifurcation and chaotic behaviour of unidirectionally coupled
deterministic ratchets is studied as a function of the driving force amplitude
() and frequency (). A classification of the various types of
bifurcations likely to be encountered in this system was done by examining the
stability of the steady state in linear response as well as constructing a
two-parameter phase diagram in the () plane. Numerical explorations
revealed varieties of bifurcation sequences including quasiperiodic route to
chaos. Besides, the familiar period-doubling and crises route to chaos
exhibited by the one-dimensional ratchet were also found. In addition, the
coupled ratchets display symmetry-breaking, saddle-nodes and bubbles of
bifurcations. Chaotic behaviour is characterized by using the sensitivity to
initial condition as well as the Lyapunov exponent spectrum; while a perusal of
the phase space projected in the Poincar cross-section confirms some
of the striking features.Comment: 7 pages; 8 figure
Does the Advice to Assume the Knee-Chest Position at the 36th to 37th Weeks of Gestation Reduce the Incidence of Breech Presentation at Delivery?
Breech presentation remains a hazard for the mother and her fetus. To reduce its incidence at delivery, postural techniques have been used, among which the kneechest position. The objective of this study was to assess the effectiveness of this position on cephalic version of breech presentation. It was a prospective randomized study in a group of 102 women with viable fetuses in breech presentation at 36 to 37 weeks of gestation. The 49 womenof the intervention group assumed the knee-chest position for 15 minutes three times a day for one week. The control group had 53 cases. The study and control groups were reviewed after a week to assess the fetal presentation. The version rate was 61% and 20% in intervention and in control groups, respectively (P value = .03). This position should be advised to women with fetus in breech between 36 and 37 weeks of gestation
Performance and carcass characteristics of broilers fed boiled cowpea (Vigna unguiculata L Walp) and or black common bean (Phaseolus vulgaris) meal diets
A total of 256 broiler chicks were used to evaluate the effect of replacing meat meal with boiled cowpea and/or black common bean on the performance and carcass characteristics of broilers. At the starterphase, boiled cowpea and or black common bean meal constituted 11% of S1, S2 and a 1:1 ratio of boiled cowpea and black common (S3) diets replacing 100% of meat meal and 25% of fish meal. For thefinisher phase, 14% boiled cowpea (F1), 14% boiled black common bean (F2) and an equal proportion (1:1) of boiled cowpea and black common bean meals (F3) were used to replace 100% meat meal and25% fish meal. During the starter period, feed intake and weight gain were significantly (P 0.05)difference was observed between treatment groups for feed conversion ratio and feed cost for the production of 1 kg live body weight. At finisher, broilers started with the control starter diet and finishedwith any of the test diets significantly (P < 0.05) consumed more feed and acquired heavier weights compared to the other dietary combinations. Feed cost was significantly (P < 0.05) lower for birdsstarted the control starter diet and finished with either the control finisher diet or boiled cowpea diets. Carcass yield was significantly (P < 0.05) higher for birds finished with boiled cowpea diet compared tothe other treatments. Cowpea and black common bean boiled for 30 min under uncontrolled temperature and pressure could not be recommended for broiler's diet formulation
- …