1,752 research outputs found
A comparative study of the Lasso-type and heuristic model selection methods
Get PDFThis study presents a first comparative analysis of Lasso-type (Lasso, adaptive Lasso, elastic net) and heuristic subset selection methods. Although the Lasso has shown success in many situations, it has some limitations. In particular, inconsistent results are obtained for pairwise strongly correlated predictors. An alternative to the Lasso is constituted by model selection based on information criteria (IC), which remains consistent in the situation mentioned. However, these criteria are hard to optimize due to a discrete search space. To overcome this problem, an optimization heuristic (Genetic Algorithm) is applied. Monte-Carlo simulation results are reported to illustrate the performance of the methods.Model selection, Lasso, adaptive Lasso, elastic net, heuristic methods, genetic algorithms
ABOUT OPTIMAL DATES OF SATELLITE IMAGES ACQUISITION FOR ARABLE SOIL MAPPING
No full textThe state of the exposed surface of arable soils strongly varies in time and depends on properties of the upper soil horizon, meteorological conditions, and specific character of its usage. A change of the arable soil surface has a significant effect on their image on remote sensing data. For the maximum extraction of information about the spatial heterogeneities of soil properties satellite survey must be carried out before the first treatment of the surface of arable soils in spring
Elektroluminestsentsi-alased tööd. VIII, Kilestruktuurid = Труды по электролюминесценции. Пленочные структуры
Get PDF• Келк Э.Х., Ребане К.-С.К. Пленочные люминофоры и история их открытия
• E. Kelk, K.-S. Rebane. The story of discovery of thin luminescent layers. Summary
• Власенко H.A., Копытко Ю.В., Куриленко Б.В., Савин А.К., Цыркунов Ю.А. Пленочные электролюминесцентные источники света повышенн
• N. Vlasenko, Yu. Kopytko, B. Kurilenko, A. Savin, Yu. Cyrkunov. Thin film electroluminescent panels with improved brightness based on ZnS. Summary
• Вишeвa Т.П., Власенко H.A. Копытко, Ю. В., Пухлий Ж .A., Дыркунов Ю.А. Изменение спектра электролюминесценции пленок ZnS, леги
• T. Tisheva, N. Vlasenko, Yu. Kopytko, J. Puhly, Yu. Cyrkunov. Alteration of electroluminescent spectrum of manganese doped ZnS films. Summary
• Васильченко В.П., Каск A.K. Электрофизические свойства электролюмино^ора постоянного тока на базе ZnS: Мп
• V. Vasilchenko, A. Kask. Electrophysical properties of ZnS: Mn direct current electroluminophor. Summary
• Кыласов В.А., Серобабин М.Т., Корнева Р.В. Эффект потемнения электролюминесцентных слоев
• V. Kysalov, M. Serobabin, R. Korneva. The darkening effect of electroluminescent layers. Summary
• Кыласов В.А., Лямичев И.Я., Орлов И.Н. Оптические свойства электролюминесцентного конденсатора
• V. Kylasov, I. Iyamichev, I. Orlov. Official properties of electroluminescent capacitor. Summary
• Mитягин A.D., Уустаре Т.О. Использование метода мягкой рентгеновской спектроскопии потенциалов возбуждения для анализа поверхно
• Mityagin, T. Uustare. Application of sort X-ray appearance potential spectroscopy to the analysis of surface of AIII BV compounds. Summary
• Hымм. У.Х. Инфракрасная люминесценция в сульфидах цинка и кадмия и центр меди в регулярном узле
• U. Nõmm. Infrared luminescence in ZnS and CdS and substitutional copper center. Summary
• Айдлa A.K., Кире Я.Я. Роль мелких центров чувствительности в процессах долговременной релаксации фотопроводимости и послесвечен
• Aidla, J. Kirs. Role of shallow sensitizing centres in long-term relaxation process of photoconductivity and afterglow in cadmium sulphide single crystals. Summary
• Айдлa A.K. Влияние мелких центров чувствительности на люкс-амперные характеристики монокристаллов сульфида кадмия
• Aidla. Effect of shallow sensitizing centers on the dependence of photoconductivity upon excitation intensity in cadmium sulphide single crystals. Summary
• Содержаниеhttp://tartu.ester.ee/record=b1173416~S1*es
Dynamics of non-newtonian oscillator
No full textFor an explanation of curves of rotation of spiral galaxies the changed form of the second law of Newton is offered. For the purpose of possible experimental registration in terrestrial conditions of the changed law the model of non-newtonian oscillator is offered. Precisely and in various approximations the task about oscillations of non-newtonian oscillator is solved
THE USE OF NDVI PROFILES FOR ESTIMATING THE QUALITY OF ARABLE LANDS (EXEMPLIFIED BY THE BAKSAN REGION IN KABARDINO-BALKARIA)
No full textA new approach to estimating the quality of arable lands was developed as based upon MODIS-derived satellite data. The essence of the approach consists in an expert analysis of NDVI curves created separately for different crop groups in the last 10–12 years as well as the inter-annual variability of the NDVI seasonal maximum, whose value was used as an indicator for the crop state and yield on different fields. The nature of NDVI curves allowed expertly classifying the groups, characterizing the winter, early spring and late spring crops. The approach to estimating the quality of arable lands was approved on the example of the Baksan region in Kabardino-Balkaria. All the arable lands have been comprehensively analyzed in the region, the mask of which was created by visual interpretation of field boundaries using LANDSAT satellite data. The temporary NDVI profiles were obtained by the satellite service VEGA. Based upon the given method all the fields in the region were classified according to the quality of arable lands. The obtained data may be used in cadastre surveys for objective estimate of lands and optimal arrangement of the main agricultural crops in this Republic, being applicable in the other regions of the Russian Federation
Overlapping sub-sampling and invariance to initial conditions
No full textThis paper studies the use of the overlapping blocking scheme in unit root autoregression. When the underlying process is that of a random walk, the blocks’ initial conditions are not fixed, but are equal to the sum of all the previous observations’ error terms. When non- overlapping subsamples are used, as first shown by Chambers and Kyriacou (2010), these initial conditions do not disappear asymptotically. In this paper we show that a simple way of overcoming this issue is to use overlapping blocks. By doing so, the effect of these initial conditions vanishes asymptotically. An application of these findings to jackknife estimators indicates that an estimator based on moving-blocks is able to provide obvious reductions to the mean square erro
Satellite based assessment of agronomically important properties of agricultural soils with consideration of their surface state
Get PDFSatellite data have been used for a long time to assess various properties of arable soils. At the same time, there are certain difficulties associated with the fact that a number of agronomically important soil properties do not directly affect spectral reflectance of their surface, which complicates the remote assessment of such properties. In addition, to obtain reproducible models, it is necessary to take into account the state of the open soil surface during the survey. The aim of the study was to demonstrate a method for detecting agronomically important properties of arable soils based on Landsat 8-9 OLI satellite data and including information about the state of their open surface using the example of a test field in the Serebryano-Prudsky district of the Moscow region. Depending on the soil property, R2cv of the models developed based on Landsat 8-9 OLI satellite data varied from 0.57 to 0.91. The best models with R2cv>0.8 were obtained for organic matter and properties higly correlated with it such as the content of exchangeable calcium and magnesium cations, the content of total nitrogen, pH of water and salt extracts. The involvement of information on the state of the open surface of arable soils for most properties made it possible to obtain models of higher quality and predictive ability, regardless of the survey period. Based on the models obtained, maps of the spatial variation of agronomically important properties of arable soils were constructed as part of the demonstration of the method. The resulting models can be used for remote monitoring of the analyzed properties of arable soils of the test field. At the same time, for such properties as the content of exchangeable potassium and phosphorus compounds, it is necessary to search for the approaches that will take into account their high variability, as well as to perform a prior assessment of the informativity of the survey periods in which the open soil surface is not transformed
Possibilities of remote sensing monitoring of soil fertility indicators of arable soils
No full textOn the example of the test field located in the Tula region (Russia), the possibility of using remote sensing data for mapping the fertility of arable soils is considered. Analysis of ground-based spectrometry data showed that the correlation between the spectral reflectance of the surface of arable soils and fertility indicators increases with an increase in wavelength. The maximum value of the correlation coefficient for mobile phosphorus was 0.84, for humus content - -0.83, for mobile potassium - -0.7, for pH - -0.86, for exchangeable calcium - -0.88, for exchangeable magnesium - 0.67. When analysing the Sentinel-2 satellite data, the correlation coefficients turned out to be higher than in the case of ground-based spectrometry data. Band 5 of Sentinel-2 was found to be the most informative for the detection of most of the analysed parameters of soil fertility. Depending on the property, the R2cv of the models varied from 0.47 to 0.93. The best models were obtained for pH, humus, mobile phosphorus, and exchangeable calcium. Based on regression models, maps of fertility indicators of arable soils for the test field were produced. The obtained models can be used to organize operational monitoring of the main parameters of soil fertility in the field. © Published under licence by IOP Publishing Ltd
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