HF-Induced Modifications of the Electron Density Profile in the Earth’s Ionosphere Using the Pump Frequencies near the Fourth Electron Gyroharmonic

We discuss results on plasma density profile modifications in the F-region ionosphere that are caused by HF heating with the frequency f0 in the range [(−150 kHz)–(+75 kHz)] around the fourth electron gyroharmonic 4fc. The experiments were conducted at the HAARP facility in June 2014. A multi-frequency Doppler sounder (MDS), which measures the phase and amplitude of reflected sounding radio waves, complemented by the observations of the stimulated electromagnetic emission (SEE) were used for the diagnostics of the plasma perturbations. We detected noticeable plasma expulsion from the reflection region of the pumping wave and from the upper hybrid region, where the expulsion from the latter was strongly suppressed for f0 ≈ 4fc. The plasma expulsion from the upper hybrid region was accompanied by the sounding wave’s anomalous absorption (AA) slower development for f0 ≈ 4fc. Furthermore, slower development and weaker expulsion were detected for the height region between the pump wave reflection and upper hybrid altitudes. The combined MDS and SEE allowed for establishing an interconnection between different manifestations of the HF-induced ionospheric turbulence and determining the altitude of the most effective pump wave energy input to ionospheric plasma by using the dependence on the offset between f0 and 4fc.

Hilbert–Schmidt Independence Criterion Subspace Learning on Hybrid Region Covariance Descriptor for Image Classification

The region covariance descriptor (RCD), which is known as a symmetric positive definite (SPD) matrix, is commonly used in image representation. As SPD manifolds have a non-Euclidean geometry, Euclidean machine learning methods are not directly applicable to them. In this work, an improved covariance descriptor called the hybrid region covariance descriptor (HRCD) is proposed. The HRCD incorporates the mean feature information into the RCD to improve the latter’s discriminative performance. To address the non-Euclidean properties of SPD manifolds, this study also proposes an algorithm called the Hilbert-Schmidt independence criterion subspace learning (HSIC-SL) for SPD manifolds. The HSIC-SL algorithm is aimed at improving classification accuracy. This algorithm is a kernel function that embeds SPD matrices into the reproducing kernel Hilbert space and further maps them to a linear space. To make the mapping consider the correlation between SPD matrices and linear projection, this method introduces global HSIC maximization to the model. The proposed method is compared with existing methods and is proved to be highly accurate and valid by classification experiments on the HRCD and HSIC-SL using the COIL-20, ETH-80, QMUL, face data FERET, and Brodatz datasets.

Influence of Sowing Times and Agricultural Plant Care on Water Consumption and Productivity of Sunflower Hybrid Region

When growing sunflower in the southern steppe of Ukraine, the main limiting factor is moisture. The amount of water consumed and the intensity of its consumption by plants depends on environmental factors and biological characteristics of sunflower. Therefore, it is important to ensure the rational use of available moisture in the soil by crop plants. The aim of our research was to establish the impact of sowing dates, application of soil herbicide and crop care methods on water consumption and productivity of sunflower hybrid Region in the southern steppe of Ukraine. The research was conducted in 2011-2013 in the fields of the Institute of Oilseeds of UAAS. The sunflower of the Region hybrid was sown with a row spacing of 70 cm and a sowing rate of 50,000 similar seeds per hectare in three terms: the first (I) – at a soil temperature of 6-8 °С; the second (II) – at a soil temperature of 10-12 °C; third (III) – at a soil temperature of 14-16 °C. Variants of crop care methods: 1 – before and post-emergence harrowing + 1 inter-row tillage; 2 – pre-emergence harrowing + 2 interrow cultivation; 3 – 2 inter-row treatments on herbicide and herbicide (application of soil herbicide harnes – 2.5 l/ha under pre-sowing cultivation) backgrounds. According to the results of three years of research, it was found that the timing of sowing and different methods of crop care on herbicide and non-herbicide backgrounds affected the water consumption and productivity of sunflower hybrid Region. Depending on the sowing period, the total moisture reserves in the soil layer 0-150 cm at the beginning of the growing season were equal to: 420.9 mm for the first; 410.3 mm for the other; 385.0 mm for the third. The amount of precipitation, taking into account the utilization factor for three years on average, was equal to: 150.9, 147.9 and 148.5 mm, respectively. Given the moisture reserves at the beginning of the growing season and productive precipitation, the total water consumption of sunflower hybrid Region was different in terms of sowing and was depending on the application of the herbicide and crop care: for the first – 301.0-316.3 mm; for the other – 292.6-301.0 mm; for the third – 263.1-278.2 mm. Sowing at a later date led to a decrease in total water consumption of sunflower by 8.4-17.3 mm in the second term and 37.9-43.6 mm in the third term compared to the first. For three sowing dates on both herbicide and herbicide-free backgrounds, the lowest total water consumption was observed in the variant with pre- and post-emergence harrowing and one inter-row tillage. According to the results of average three-year studies, moisture was most effectively used by sunflower plants of the Region hybrid in second-term crops, ie water consumption coefficients were lower (1207-1229 m3/t). During the first and third sowing periods, they increased in accordance with 1550-1628 and 1302-1331 m3/t, respectively. Regarding the backgrounds of herbicide application, during the first and second sowing periods, moisture was used more effectively against the background of soil herbicide application. And for the third sowing period, on the contrary, the coefficient was lower by 15-18 m3/t on a herbicide-free background. The lowest indicators of the water consumption coefficient were observed during the second sowing period against the background of soil herbicide application in the variants with pre-emergence harrowing + 2 inter-row treatments (1209 m3/t) and two inter-row treatments (1207 m3/t). On average, over three years of research, depending on the background of herbicide application and crop care, higher yields of sunflower hybrid Region (2.38-2.49 t/ha) were obtained during the second sowing period, which is 0.44-0, 52 and 0.35-0.43 t/ha exceeded this figure for the first and third terms, respectively. It should be noted that the most effective application of soil herbicide was during the first sowing period, the yield increase was 0.10-0.12 t/ha. During the second sowing period, it was lower – 0.06-0.07 t/ha. In the absence of weeds in the third sowing period, the application of soil herbicide was not effective. The increase in yield (0.01-0.03 t/ha) was within the NIR. Among the methods of crop care, the most effective options were: pre-harvest harrowing + 2 inter-row tillage and 2 inter-row tillage. The highest yield of sunflower hybrid Region (2.49 t/ha) was obtained during the second sowing period at the soil temperature at the depth of seed wrapping 10-12 °C with the application of soil herbicide and pre-emergence harrowing and two inter-row tillage. According to the results of the fat content in the seeds, the influence of agricultural techniques studied in the experiment was not observed. For the first term of sowing the fat content was 46.6-46.8 %, for the second term - 46.1-46.4 % and for the third term – 46.2-46.3 %. An important indicator of sunflower productivity is the yield of oil per unit area. According to the results of research, depending on the yield obtained under the influence of the background of herbicide application and crop care, higher oil yields (966-1017 kg/ha) were observed during the second sowing period, which is 173-203 and 143-179 kg/ha exceeded this figure for the first and third terms, respectively. The highest oil yields were observed during the second sowing period against the background of soil herbicide application in the variants with pre-emergence harrowing + 2 inter-row tillage (1017 kg/ha) and two inter-row tillage (1010 kg/ha).

Experimental and numerical investigation of the transition zone of locally steel-reinforced joining areas under combined tension–bending loading

In modern lightweight structures, the use of fasteners is preferred to other joining techniques. An approach to increase the bearing strength is the local metal hybridisation, where carbon fibre-reinforced plastics layers are substituted locally by metal foils of the same thickness. The local replacement leads to a transition zone between the hybrid region and the pure carbon fibre-reinforced plastics region. The present work deals with the investigation of different transition zone patterns of carbon fibre-reinforced plastics-steel hybrid specimens in combined tension–bending tests and accompanying non-linear static simulation. The simulation includes delamination and intralaminar damage with the use of a cohesive zone model and Cuntze’s failure mode concept. Furthermore, residual thermal stresses are considered. A satisfying agreement of test and simulation is achieved, which allows the identification of beneficial transition zone configurations and also validates the numerical model for further parametric studies.