scholarly journals Improved Imaging Model in the Presence of Multiplicative Spatially Extended Cloaking Interference

2021 ◽  
Vol 11 (11) ◽  
pp. 189-198
Author(s):  
Hennadii Khudov ◽  
◽  
Igor Ruban ◽  
Oleksandr Makoveichuk ◽  
Yevhen Stepanenko ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Image Brightness ◽  
Transmitted Radiation ◽  
Imaging Model ◽  
Visible Wavelength Range ◽  
Spatially Extended ◽  
Medium Layer ◽  
Distorted Region ◽  
Masking Interference ◽  
Upper Boundary

The paper proposes an improved imaging model in the presence of multiplicative spatially extended cloaking interference. The model take into account the effect of multiplicative masking interference. To simplify the calculations of the image brightness in the distorted region the diagram technique is used. Unlike the known ones, the model takes into account the concentration of the distorting medium in a narrow squat layer, the primary reflection of solar radiation from the upper boundary of the distorting layer and subsequent multiple re-reflections of the transmitted radiation of the visible wavelength range from the earth’s surface and the upper boundary of the distorting medium layer. A technique for finding and taking into account the reflection and re-reflection coefficients of radiation to restore distorted images is proposed. The results of experimental studies are presented. For the experiment, the image of the territory of Iraq during the 2003 "Freedom for Iraq" hostilities was selected. Keywords— image, model, multiplicative, extended cloaking interference, spacecraft, reflection, coefficient

scholarly journals Investigation of the tip injection for stall control in a transonic compressor with inlet distortion

2021 ◽  
Vol 5 ◽  
pp. 28-38
Author(s):  
Wenqiang Zhang ◽  
Mehdi Vahdati
Keyword(s):  
Experimental Studies ◽  
Flow Region ◽  
Main Flow ◽  
Test Case ◽  
Stall Margin ◽  
Transonic Compressor ◽  
Inlet Distortion ◽  
Distorted Region ◽  
Tip Injection ◽  
Stall Control

Experimental studies have shown that tip injection upstream of the rotor can extend its operational range when subjected to circumferential inlet distortion. Typically, injectors are placed uniformly around the annulus. However, such arrangement consumes a large amount of high-pressure air and decreases the overall efficiency of the compression system. The aim of this paper is to minimise the amount of the injected air by determining the most effective circumferential location for the injector. In this study, NASA stage 35 was used as the test case. The experiment was conducted with a circumferential total pressure distortion of 120 degrees. In the first part of this paper, numerical simulations were compared against the experimental data and good match was obtained. In the second part, tip injection at three different positions were tested: the clean flow region (Position 1), the distorted region (Position 2) and the border between the clean and distorted regions (Position 3). It was found that a mild injection (0.66% of the main flow) at Position 2 and Position 3 can extend the stall margin by 1.8% and 2.7%, respectively. No obvious improvement was observed for the injection at Position 1. With a larger injection of 1.5% of main flow at Position 3, the stall margin improved further with no efficiency loss.

scholarly journals Instability of a homogeneous flow from a lumped source in the presence of special boundary conditions on a free surface

2019 ◽  
Vol 213 ◽  
pp. 02074 ◽  
Author(s):  
Anastasia Shmyrova ◽  
Andrey Shmyrov
Keyword(s):  
Boundary Conditions ◽  
Vortex Flow ◽  
Hydrodynamic Instability ◽  
Experimental Studies ◽  
Spatial Separation ◽  
Surface Flow ◽  
Water Volume ◽  
Reverse Situation ◽  
Surface Active ◽  
Upper Boundary

In this work, experimental studies were carried out to investigate the structure of a surface flow and to understand potential mechanisms leading to the formation of this type instability. The surface flow was generated by feeding water through three sources: a lumped source with free upper boundary, a slot gap, and a lumped source for inducing a capillary-driven Marangoni flow. For flow visualization, a traditional light knife technique was used. The application of a method of spatial separation of the water volume into two isolated parts whose common surface remained unchanged and the realization of a reverse situation with a divided surface made it possible to study in detail the surface flow structure and to determine the conditions for the appearance of such hydrodynamic instability. It is shown that the formation of a vortex flow is caused by the interaction between the coordinate of the flow homogeneous along the transverse flow and the layer of a surface-active substance adsorbed at the interface. The obtained experimental results demonstrate the importance of setting different boundary conditions for potential and vortex velocity components of a convective flow in the region near the interface occupied by a surfactant.

Experimental study of liquid movement in free elementary convective cells

Energetika ◽  
2015 ◽  
Vol 61 (2) ◽  
Author(s):  
Liudmyla Bozbiei ◽  
Boris Borts ◽  
Yuri Kazarinov ◽  
Andrey Kostikov ◽  
Viktor Tkachenko
Keyword(s):  
Mass Transfer ◽  
Boundary Conditions ◽  
Solid Wall ◽  
Large Diameter ◽  
Experimental Studies ◽  
Maximum Velocity ◽  
A Cell ◽  
Convective Cells ◽  
Liquid Movement ◽  
Upper Boundary

Elementary convection cells (ECC) are formed in horizontal layers of liquid heated from below, and they are experimentally investigated in this work. Results of experimental studies were adequately described by the theoretical model of ECC. It is shown that the addition of aluminum powder to oil transforms oil to a suspension, such that boundary conditions on the solid wall can be regarded as free because there is a slip through the tape of pure oil. Change in the character of boundary conditions is confirmed by the results of numerical processing of experimental results on formation of convective rings on the layer surface by other authors. Two independent methods for determining the velocity of mass transfer in cells with various diameters are described in the article. For cells with a large diameter (17 mm), the maximum velocity of mass transfer was measured at the upper boundary on a deflection angle of the probe. Measured in this way velocity was equal to V<sub>Oil</sub> ≈ 0.2 mm/sec. For cells with a smaller diameter (2 mm), the velocity of oil on the surface of a cell was measured using an optical method and constituted the value from 3.5 mm/s to 5.2 mm/s.

scholarly journals The Image Brightness Control System Dedicated For The Autonomous Unmanned Aerial Vehicle

2014 ◽  
Vol 32 (1) ◽  
pp. 71-82 ◽  
Author(s):  
Jakub Cieśluk ◽  
Zdzisław Gosiewski
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Vision System ◽  
Experimental Studies ◽  
Dynamic Environment ◽  
Cmos Camera ◽  
Real Time Control ◽  
Image Brightness ◽  
Time Control ◽  
Aerial Vehicles ◽  
Aerial Vehicle

Abstract The investigations of systems which allow to avoid obstacles by the unmanned aerial vehicles (UAV) are presented in the paper. The systems are designed to enable the full autonomous UAV flight in unknown, dynamic environment. Presented solutions enable to real-time control of the image brightness, without significantly disturbing the objectivity of the vision system. Single board ADSP-BF537 computer with built-in CMOS camera was used in the experimental studies. The final stage of the task is to perform fully autonomous missions of flying object with the real obstacles on its trajectory.

scholarly journals Investigation of Ways of Dynamic Range Expansion for Broadband Receiver Microwave Devices in Multi-Signal Mode

2018 ◽  
pp. 85-90
Author(s):  
S. A. Bogdanov ◽  
P. V. Kupriyanov ◽  
S. V. Nikolaev ◽  
S. A. Petrov
Keyword(s):  
Output Power ◽  
Dynamic Range ◽  
Experimental Studies ◽  
Technical Solution ◽  
Third Order ◽  
Measurement Results ◽  
Signal Mode ◽  
Output Amplifier ◽  
Intermodulation Distortions ◽  
Upper Boundary

 The article investigates ways to expand the dynamic range of broadband microwave receiving devices. The task is to lim-it the output signals while increasing the upper boundary of the dynamic range by the criterion of the thirdorder inter-modulation component suppression. The main relations  determining the dynamic range boundary conditions are pre-sented. Experimental studies of three variants of constructing the broadband microwave receiver output path in two-ton mode of operation are carried out for:– an output amplifier with a point of 1 dB of output power compression at the level corresponding to safe output power;– a powerful output amplifier with a passive diode limiter on the output;– a powerful output amplifier with an automatic attenuation adjustment circuit connected to its input.The measurement results of the magnitude of intermodulation distortions suppression and output power are presented as a function of the input signal level for various nonlinear elements. Based on the analysis of the measured characteristics, an optimal technical solution is found for constructing an output path. The dynamic range is extended by more than 20 dB. Suppression of intermodulation components of the third order exceeds 60 dB. Effective functioning of the broadband receiver in multisign mode is ensured.

scholarly journals Theoretical and experimental studies of dielectric two-dimensional Bragg structures for development of spatially-extended heterolasers

2018 ◽  
Vol 195 ◽  
pp. 02012
Author(s):  
N.Yu. Peskov ◽  
V.R. Baryshev ◽  
N.S. Ginzburg ◽  
E.R. Kocharovskaya ◽  
A.M. Malkin ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Two Dimensional ◽  
Bragg Structures ◽  
Spatially Extended

Field-Ion Microscopy of BCC Metals: A Study of Image Differences and Topographical Variations

1973 ◽  
Vol 31 ◽  
pp. 114-115
Author(s):  
O. T. Inal ◽  
L. E. Murr
Keyword(s):  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Surface Atom ◽  
Image Brightness ◽  
Field Ion Microscopy ◽  
Topographic Features ◽  
Bcc Metals ◽  
Electron Orbital ◽  
Ion Microscopy ◽  
Field Ion Microscope

When sharp metal filaments of W, Fe, Nb or Ta are observed in the field-ion microscope (FIM), their appearance is differentiated primarily by variations in regional brightness. This regional brightness, particularly prominent at liquid nitrogen temperature has been attributed in the main to chemical specificity which manifests itself in a paricular array of surface-atom electron-orbital configurations.Recently, anomalous image brightness and streaks in both fcc and bee materials observed in the FIM have been shown to be the result of surface asperities and related topographic features which arise by the unsystematic etching of the emission-tip end forms.

3-D reconstruction and analysis of mammalian mitotic spindle structure

1992 ◽  
Vol 50 (1) ◽  
pp. 578-579
Author(s):  
Kent McDonald ◽  
David Mastronarde ◽  
Rubai Ding ◽  
Eileen O'Toole ◽  
J. Richard McIntosh
Keyword(s):  
Cross Sections ◽  
Mitotic Spindle ◽  
Experimental Studies ◽  
Video Camera ◽  
Three Dimensions ◽  
Mitotic Spindles ◽  
Black And White ◽  
Reconstruction Methods ◽  
Spindle Structure ◽  
Tissue Culture Line

Mammalian spindles are generally large and may contain over a thousand microtubules (MTs). For this reason they are difficult to reconstruct in three dimensions and many researchers have chosen to study the smaller and simpler spindles of lower eukaryotes. Nevertheless, the mammalian spindle is used for many experimental studies and it would be useful to know its detailed structure.We have been using serial cross sections and computer reconstruction methods to analyze MT distributions in mitotic spindles of PtK cells, a mammalian tissue culture line. Images from EM negatives are digtized on a light box by a Dage MTI video camera containing a black and white Saticon tube. The signal is digitized by a Parallax 1280 graphics device in a MicroVax III computer. Microtubules are digitized at a magnification such that each is 10-12 pixels in diameter.

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