scholarly journals FAILURE SIMULATION OF ELEMENTS OF THE CITY ELECTRIC NETWORK (10 KV) BY THE EXAMPLE OF THE PRAVOBEREZHNIY DISTRICT OF THE IRKUTSK CITY

2021 ◽  
pp. 87-98
Author(s):  
Ya.M. Ivanyo ◽  
◽  
I.V. Naumov ◽  
M.N. Polkovskaya ◽  
◽  
...  
Keyword(s):  
Least Squares Method ◽  
Nonlinear Models ◽  
Electrical Network ◽  
Electric Networks ◽  
Statistical Parameters ◽  
Polynomial Trend ◽  
Seasonal Model ◽  
Forecast Models ◽  
June July ◽  
The City

The paper presents mathematical models for probabil-istic evaluation and forecasting of emergency shutdowns in electric networks by the example of the Pravoberezhniy District of the Irkutsk City from 2008 through 2017. At the first stage, the autocorrelation function of the parameter series is determined to estimate its randomness. According to the calculated statistical parameters and the consent criteria, a number of equipmentfailures may be described by a three-parameter gamma distribution. A method of two-level identification of extreme (maximum and minimum) values of the parameter under study is proposed; accord-ing to this method, a significant polynomial trend is ob-tained for predicting the largest number of failures. The evaluation of the presence of trends based on monthly data showed that polynomial and power trends may be used to predict failures on electric networks. At the same time, sig-nificant trends were identifiedonly for January, February, May and December. At the next stage, trend-seasonal models are constructed; the least squares method is used to calculate their components. According to the obtained seasonality indices, the greatest increase in emergency shutdowns takes place in April and July, and a decrease -in February and March. On the basis of the correlation-regression model, factor models of failures of electrical network elements and the accumulated average daily tem-peratures for months and time are constructed. Linear and nonlinear models with and without trends are obtained. To evaluate the accuracy of the forecasts of the obtained models, the results of the retrospective forecast for 2017 were compared with the actual values. According to the resultsobtained for predicting failures on electric networks in February, June, July and September, the best result is shown by a trend-seasonal model, in May -a polynomial trend, in November -a factorial one taking into account time, in March, May and October-a nonlinear regression equation, and in December -a power trend. There are no qualitative forecast models for the months of January, April, and August. In this regard, the values of emergency shut-downs on these months may be estimated using a proba-bilistic model.

Seasonal Variation of Suicide in the City of São Paulo, Brazil, 1996–2010

Crisis ◽  
2014 ◽  
Vol 35 (1) ◽  
pp. 5-9 ◽  
Author(s):  
Daniel Hideki Bando ◽  
Fernando Madalena Volpe
Keyword(s):  
Seasonal Pattern ◽  
Total Sample ◽  
Sao Paulo ◽  
Seasonal Patterns ◽  
São Paulo ◽  
Health Statistics ◽  
Males And Females ◽  
June July ◽  
The City ◽  
Over Time

Background: In light of the few reports from intertropical latitudes and their conflicting results, we aimed to replicate and update the investigation of seasonal patterns of suicide occurrences in the city of São Paulo, Brazil. Methods: Data relating to male and female suicides were extracted from the Mortality Information Enhancement Program (PRO-AIM), the official health statistics of the municipality of São Paulo. Seasonality was assessed by studying distribution of suicides over time using cosinor analyses. Results: There were 6,916 registered suicides (76.7% men), with an average of 39.0 ± 7.0 observed suicides per month. For the total sample and for both sexes, cosinor analysis estimated a significant seasonal pattern. For the total sample and for males suicide peaked in November (late spring) with a trough in May–June (late autumn). For females, the estimated peak occurred in January, and the trough in June–July. Conclusions: A seasonal pattern of suicides was found for both males and females, peaking in spring/summer and dipping in fall/winter. The scarcity of reports from intertropical latitudes warrants promoting more studies in this area.

scholarly journals High honeybee abundances reduce wild bee abundances on flowers in the city of Munich

Oecologia ◽  
2021 ◽  
Author(s):  
Susanne S. Renner ◽  
Marie Sophie Graf ◽  
Zoe Hentschel ◽  
Helen Krause ◽  
Andreas Fleischmann
Keyword(s):  
Apis Mellifera ◽  
Adjacent Area ◽  
Exploitative Competition ◽  
Wild Bees ◽  
European Cities ◽  
Urban Garden ◽  
Wild Bee ◽  
June July ◽  
The City ◽  
Clear Support

AbstractThe increase in managed honeybees (Apis mellifera) in many European cities has unknown effects on the densities of wild bees through competition. To investigate this, we monitored honeybees and non-honeybees from 01 April to 31 July 2019 and 2020 at 29 species of plants representing diverse taxonomic and floral-functional types in a large urban garden in the city of Munich in which the same plant species were cultivated in both years. No bee hives were present in the focal garden, and all bee hives in the adjacent area were closely monitored by interviewing the relevant bee keepers in both 2019 and 2020. Honeybee numbers were similar in April of both years, but increased from May to July 2020 compared to 2019. The higher densities correlated with a significant increase in shifts from wild bee to honeybee visits in May/June/July, while visitor spectra in April 2019 and 2020 remained the same. Most of the species that experienced a shift to honeybee visits in 2020 were visited mostly or exclusively for their nectar. There were no shifts towards increased wild bee visits in any species. These results from a flower-rich garden have implications for the discussion of whether urban bee keeping might negatively impact wild bees. We found clear support that high honeybee densities result in exploitative competition at numerous types of flowers.

scholarly journals The use of the nonlinear models in the growth of pears of ‘Shinseiki’ cultivar

2017 ◽  
Vol 48 (1) ◽  
Author(s):  
Thais Destefani Ribeiro ◽  
Taciana Villela Savian ◽  
Tales Jesus Fernandes ◽  
Joel Augusto Muniz
Keyword(s):  
Logistic Model ◽  
Least Squares Method ◽  
Nonlinear Models ◽  
Logistic Models ◽  
Information Criterion ◽  
Fruit Weight ◽  
Coefficient Of Determination ◽  
Pear Fruit ◽  
Asian Pear ◽  
Residual Correlations

ABSTRACT: The goal of this study was to elucidate the growth and development of the Asian pear fruit, on the grounds of length, diameter and fresh weight determined over time, using the non-linear Gompertz and Logistic models. The specifications of the models were assessed utilizing the R statistical software, via the least squares method and iterative Gauss-Newton process (DRAPER & SMITH, 2014). The residual standard deviation, adjusted coefficient of determination and the Akaike information criterion were used to compare the models. The residual correlations, observed in the data for length and diameter, were modeled using the second-order regression process to render the residuals independent. The logistic model was highly suitable in demonstrating the data, revealing the Asian pear fruit growth to be sigmoid in shape, showing remarkable development for three variables. It showed an average of up to 125 days for length and diameter and 140 days for fresh fruit weight, with values of 72mm length, 80mm diameter and 224g heavy fat.

scholarly journals ON THE MANAGEMENT OF URBAN ELECTRIC NETWORKS IN THE CONDITIONS OF THE SMART GRID

2018 ◽  
Vol 61 (1) ◽  
pp. 15-27 ◽  
Author(s):  
M. А. Fursanov ◽  
A. A. Zalotoy
Keyword(s):  
Smart Grid ◽  
Electric Power ◽  
Power Transmission ◽  
Electrical Networks ◽  
Electric Networks ◽  
Urban Networks ◽  
Theoretical Criterion ◽  
Active Power Losses ◽  
And Control ◽  
The City

The issues of prospective operation of the city electric networks in the conditions of the MART GRID, which will be quite different as compared to the traditional understanding and approaches, are under consideration. This requires the selection and application of appropriate analytical criteria and approaches to assessment, analysis and control of the networks. With this regard the following criteria are recommended: in a particular case – the optimal (minimal) technological electric power consumption (losses), while in general – economically reasonable (minimal) cost value of electric power transmission. It should be also borne in mind that contemporary urban networks are actively saturated with distributed sources of small generation that have radically changed the structure of electrical networks; therefore, account for such sources is an absolutely necessary objective of management regimes of urban electric networks, both traditional and in associated with the SMART GRID. A case of the analysis and control of urban electric 10 kV networks with distributed small sources of generation has been developed and presented according to the theoretical criterion of minimum relative active power losses in the circuit as a control case. The conducted research makes it possible to determine the magnitude of the tolerance network mode from the point of the theoretical minimum. 

scholarly journals Optimal Attack against Autoregressive Models by Manipulating the Environment

2020 ◽  
Vol 34 (04) ◽  
pp. 3545-3552
Author(s):  
Yiding Chen ◽  
Xiaojin Zhu
Keyword(s):  
Predictive Control ◽  
Linear Models ◽  
Nonlinear Models ◽  
Linear Quadratic Regulator ◽  
Black Box ◽  
Combine System ◽  
Linear Quadratic ◽  
Time Series Forecast ◽  
Forecast Models ◽  
Adversarial Attack

We describe an optimal adversarial attack formulation against autoregressive time series forecast using Linear Quadratic Regulator (LQR). In this threat model, the environment evolves according to a dynamical system; an autoregressive model observes the current environment state and predicts its future values; an attacker has the ability to modify the environment state in order to manipulate future autoregressive forecasts. The attacker's goal is to force autoregressive forecasts into tracking a target trajectory while minimizing its attack expenditure. In the white-box setting where the attacker knows the environment and forecast models, we present the optimal attack using LQR for linear models, and Model Predictive Control (MPC) for nonlinear models. In the black-box setting, we combine system identification and MPC. Experiments demonstrate the effectiveness of our attacks.

PREWEANING PATTERNS OF GROWTH IN THREE BREED GROUPS OF ANGE BEEF CALVES

1987 ◽  
Vol 67 (3) ◽  
pp. 653-661 ◽  
Author(s):  
B. AHUNU ◽  
M. MAKARECHIAN
Keyword(s):  
Growth Rate ◽  
Least Squares Method ◽  
Average Daily Gain ◽  
Late Summer ◽  
University Of Alberta ◽  
Bull Calves ◽  
Absolute Growth ◽  
The Mean ◽  
June July ◽  
The University

Preweaning weight records of 2856 spring-born calves raised at the University of Alberta cattle ranch during a 15-yr period were used in this study. Calving occurred mainly in April and May every year. Calves from three breed groups: Hereford (HE), Beef Synthetic (SY) and Beef Crossbred (XB) were weighed at birth, and in late June, July and August and at weaning in mid-October. They were classified as early, mid-season and late-born according to their birth dates. Average daily gain (ADG) between two consecutive weighings and relative growth rate (RGR) at each interval were analyzed by the least squares method and the adjusted means were plotted against the mean ages of the calves classified at 2-wk intervals to determine the pattern of changes in ADG and RGR with the increase in age of the calf. The SY calves had the highest ADG and RGR followed by the XB and HE (P < 0.05). Bull calves exhibited significantly higher (P < 0.05) absolute growth rate than heifer calves but the sexes were not different in RGR. Preweaning ADG reached a peak when calves were between 110 and 120 d old and declined thereafter. The decline in RGR was linear during the preweaning period. The mean growth rates of the early and mid-season calves were significantly (P < 0.05) higher than that of the late-born calves, and early-born calves showed more consistent gain than the mid-season and late-born calves. A pronounced decline in gain was observed for mid-season and late-born calves in late summer when pasture condition deteriorated indicating that early weaning and supplementation of calves' diet at that stage might be beneficial in sustaining growth rate of the calves. Key words: Cattle (beef), preweaning growth, calf (beef)

scholarly journals PASSIVE DOSIMETRY: COMPARATIVE STUDY BETWEEN TWO EVALUATION METHODS OF OCCUPATIONAL EXPOSURE TO PESTICIDES

2019 ◽  
Vol 7 (9) ◽  
pp. 52-62
Author(s):  
Francisco Alves Pinheiro ◽  
José Lourenço Do Egito ◽  
Paulo José Adissi
Keyword(s):  
Data Analysis ◽  
Working Conditions ◽  
Pesticide Exposure ◽  
Statistical Parameters ◽  
Paired Samples ◽  
Census Methods ◽  
Student’S T ◽  
Sample Method ◽  
The City ◽  
Student’S T Test

The present study aims to compare the passive dosimetry sampling and census methods for the evaluation of pesticide exposure. The studies were carried out in the city of Petrolina - PE, in the São Francisco River Valley, under three working conditions: weeds, grape and acerola cultivation with the use of a hand-held sprayer in the Brazilian summer. For data analysis, descriptive statistical parameters and Student's T-test were used to compare the means of paired samples. Both methods evaluated the simulated manual application of pesticides. Given the results, it was concluded that there was a high discrepancy between exposure assessments in all treatments, with the sample method showing overestimated values, with differences greater than 200% and that the census method showed more reliable and accurate results with greater efficiency.

scholarly journals STUDY OF THE NATURE OF OVERVOLTAGES IN THE ELECTRICAL NETWORK ARISING FROM VOLTAGE TRANSFORMERS

2021 ◽  
pp. 28-36
Author(s):  
Oleksii Hanus ◽  
Kostiantyn Starkov
Keyword(s):  
Transient Process ◽  
Distribution System ◽  
Forced Oscillations ◽  
Electrical Network ◽  
Secondary Circuit ◽  
Electric Networks ◽  
Voltage Transformer ◽  
Secondary Resistance ◽  
Non Linear ◽  
Secondary Winding

A non-linear dynamic mathematical model of voltage transformer has been considered and overvoltages arising on the elements of voltage transformer equivalent circuit during transient processes have been investigated. The influence of voltage transformer secondary circuit capacitance on overvoltage multiplicity in the primary circuits and the duration of transients has been determined. The advantages of approximation of nonlinearity of voltage transformers by hyperbolic sine are used. Mathematical expressions determining the nature of changes in the forced and free components of the transient process in an electrical network with a voltage transformer have been obtained. It is shown that with the increase of the electric network capacitance the duration of the transition process damping increases and the frequency of the forced oscillations and the level of overvoltage decrease. It is proved that even small, in comparison with the primary nominal sinusoidal voltage, aperiodic components of the voltage transient process can lead to significant overvoltages during voltage transformer outages. It has been substantiated that both the secondary resistance and the switching torque influence the overvoltage multiplicity arising in the primary winding of voltage transformers. It is shown that the closed secondary winding worsens the disconnection process of non-linear inductance of voltage transformers. The values to which overvoltages increase in this case are determined. According to the results of calculations it is determined that with open secondary winding of voltage transformers the duration of transient process significantly increases. It has been found that the decrease of frequency of forced oscillations, which occurs in this case, is accompanied by an increase of currents in the primary winding of the voltage transformer, which is dangerous in terms of thermal stability of the winding insulation. It is shown, that closing the secondary winding of voltage transformers leads to significant reduction of transient damping time. It is suggested that this algorithm can be used to provide a rapid breakdown (suppression) of ferroresonant processes. The effectiveness of such a measure of stopping of ferroresonance processes as short-term shunting of secondary winding of voltage transformers has been investigated. The correlation of parameters of electric networks (capacity of busbar sections, nonlinearity of characteristics of voltage transformers, disconnection torque, etc.) at which ferroresonance process may occur and consideration of which may allow, in terms of prevention of ferroresonance processes, to identify substations (electric networks) that require more detailed research has been determined. The results of analytical studies were tested in the electric networks of JSC "Kharkivoblenergo" and used in the electricity distribution system for the selection of specific voltage transformers for certain configurations of electrical networks.

scholarly journals Electric network topology and method of transmission of electric energy

2019 ◽  
Vol 21 (4) ◽  
pp. 95-103
Author(s):  
N. I. Smolentsev ◽  
L. M. Chetoshnikova
Keyword(s):  
Energy Storage ◽  
Network Topology ◽  
Information Technologies ◽  
Electric Energy ◽  
Electrical Energy ◽  
Electrical Network ◽  
Energy Storage Devices ◽  
Electric Networks ◽  
Storage Devices ◽  
Asynchronous Method

The purpose of the work is to reduce losses and increase energy saving in electric networks. To achieve this goal, a multilevel topology of the electrical network and an asynchronous method for transferring electrical energy between nodes including a load, energy sources, energy storage devices connected in an appropriate manner are proposed. It is shown by the mathematical method that this network topology allows using energy storage devices controlled appropriately and using tele-information technologies to optimize the balance of electric energy in the network, achieving equality of the generated and consumed electricity. Such a network topology and a method of transmitting electrical energy can be the basis of digital technologies in the energy sector (ENERNET).

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