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Multi-Band Cylindrical Dielectric Resonator Antenna Using Permittivity Variation in Azimuth Direction

Multi-Band Cylindrical Dielectric Resonator Antenna Using Permittivity Variation in Azimuth Direction

A dual- and triple-band cylindrical dielectric resonator antenna (CDRA) using varying permittivity in azimuth-direction fed by coaxial probe is proposed in this paper. The proposed structure is constructed using different materials having different permittivites in azimuth direction in cylindrical dielectric resonator (DR). The operating band can be scaled up or down by adjusting the design parameters. Dual-band and triple-band with equal segment CDRA have been fabricated using commercially available microwave laminates to validate the simulation results. In terms of radiation pattern, dual-band CDRA shows less cross-polar influence around 40 dB down in the direction of maximum radiation in yz-plane.

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Glacier motion estimation using SAR offset-tracking procedures

Glacier motion estimation using SAR offset-tracking procedures

offsets depends on the presence of nearly identical features in the two SAR images at the scale of the employed patches. When coherence is retained, the speckle pattern of the two images is correlated, and intensity tracking with small image patches can be performed to remarkable accuracy. Incoherent intensity tracking is also feasible but requires large image patches. In order to increase the estimation accuracy, oversampling rates are applied to the image patches, and a two-dimensional (2-D) regression fit to model the correlation function around the peak is determined with a four-point interpolation. The location of the peak of the 2-D cross-correlation function yields the image offset. Confidence in the offset estimate is measured by comparing the height of the correlation peak relative to the average level of the correlation function to supply a correlation signal-to-noise ratio (SNR). Coarse information on the slant-range and azimuth offsets is used to guide the search of the cross-correlation maximum. The image-patch size may be adapted to a specific case. For the present study with ERS SAR data, we systematically used patch sizes of 64 64 single-look pixels, which corresponds to around 1300 m in the ground-range direction and 250 m in the azimuth direction. C. Coherence Tracking

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A weighted least squares solution for space intersection of spaceborne stereo SAR data

A weighted least squares solution for space intersection of spaceborne stereo SAR data

The need for GCPs is less when good orbit data is available and when there are minimal errors in the orthogonal relation- ship between the azimuth direction (the resultant velocity vector considering the Earth rotation) and the range (the resultant range vector relating the sensor to a ground point). Hence, reasonable results have been obtained with ERS data with no GCPs [7]. However, the orbit data for RADARSAT is not as accurate as for ERS and the reliability of the orthogonal relationship be- tween the azimuth direction and the range is uncertain, hence it is necessary to refine the intersection method to allow for these possible errors. It is proposed in this paper that the weighting matrix in the least squares adjustment be designed to solve these problems. In general, the proposed weighting matrix helps make the radargrammetric model insensitive to the effects from the azimuth timing error as well as those from the uncertain orthog- onal relationship between the azimuth direction and the range. The method presented is designed to use the minimum number of GCPs and to give a better solution than, or at least similar to, the traditional methods. The use of the weighting matrix for de- termining unknown ground points, leading to the generation of DEMs [8], is described in Section II. A revised error model for the algorithm is discussed in Section III to show the robustness of the proposed method and to be compared with the test results. The paper demonstrates the proposed radargrammetric model is not only robust to the error from uncertain orthogonal rela- tionship between the azimuth direction and the range, but also independent from the need of accurate orbit data and of GCPs,

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An Improved SASS Model for Sea Clutter Reflectivity at Ku band

An Improved SASS Model for Sea Clutter Reflectivity at Ku band

in crosswind direction, and then followed by a medium value in downwind direction. Furthermore, the minimum value of improved SASS model in Fig.3(a) is illustrated with a tendency towards downwind direction, which has been revealed in [7] for the backscatter of SASS model was always with the strongest value at the upwind direction and a minimum value not exactly at the crosswind direction but rather towards the downwind direction. The Nathanson data and the NRL model have no variation since they are averaged over azimuth direction. The backscatter values of Nathanson data are -23 dB and -14 dB with no error likely at grazing angles of 30  and 60  , respectively [5]. Less deviations are shown between the improved SASS data and the Nathanson data. The HYB model is removed in Fig.3(b) since the grazing angle of 60  is out of its valid range.

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Landslides Monitoring with a Squint Angle Based on GBSAR

Landslides Monitoring with a Squint Angle Based on GBSAR

A novel SAR imaging algorithm originated from the conventional range doppler algorithm is introduced and implemented in the paper to solve the image defocus problem in GBSAR imaging with a squint angle. The proposed algorithm is proposed by compensating the phase error in azimuth direction and range direction, respectively. Experiments results verify that the proposed algorithm is effective in landslide monitoring. It can be used to image scatters which are far away from the radar sensor in azimuth direction.

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The mechanics of azimuth control in jumping by froghopper insects

The mechanics of azimuth control in jumping by froghopper insects

Many animals move so fast that there is no time for sensory feedback to correct possible errors. The biomechanics of the limbs participating in such movements appear to be configured to simplify neural control. To test this general principle, we analysed how froghopper insects control the azimuth direction of their rapid jumps, using high speed video of the natural movements and modelling to understand the mechanics of the hind legs. We show that froghoppers control azimuth by altering the initial orientation of the hind tibiae; their mean angle relative to the midline closely predicts the take-off azimuth. This applies to jumps powered by both hind legs, or by one hind leg. Modelling suggests that moving the two hind legs at different times relative to each other could also control azimuth, but measurements of natural jumping showed that the movements of the hind legs were synchronised to within 32  s of each other. The maximum timing difference observed (67  s) would only allow control of azimuth over 0.4  deg. to either side of the midline. Increasing the timing differences between the hind legs is also energetically inefficient because it decreases the energy available and causes losses of energy to body spin; froghoppers with just one hind leg spin six times faster than intact ones. Take-off velocities also fall. The mechanism of azimuth control results from the mechanics of the hind legs and the resulting force vectors of their tibiae. This enables froghoppers to have a simple transform between initial body position and motion trajectory, therefore potentially simplifying neural control.

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The cosmology of Inca huacas

The cosmology of Inca huacas

Chinkana is an outcropping of limestone and is one of the two principle huacas of Chinchero (Figure 10-11). Chinkana lies low on the eastern end of Chinchero’s central valley and has been extensively carved on all sides with such as seats, stairs, shelves and niches. A stream was routed to pass beneath the base of the rock on its western side, likely to energize the huaca through camay (Figure 10-12). A niche by the creek faces 346.3° and a notch on the horizon that is inclined by 12.0° up. Chinkana faces Titikaka and the approximate direction of the December solstice sunset. Chinkana is located at S13°-23.27’; W072°-02.58’ and 3724 masl. The short distance between the GPS coordinates of Chinkana and Titikaka may be a factor in the discrepancy between the GPS azimuth and true azimuth.

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3D Millimeter Wave Image by Combined Active and Passive System

3D Millimeter Wave Image by Combined Active and Passive System

• Span 3D image by fusing two images. As the sensors are not of compatible dimensionality, we make use of the azimuth information which is aligned and shared by the two images and span a 3D space of azimuth-elevation-range. Specifically, (1) for an nonzero pixel in the radiometric image, label its azimuth angle and record the radiometric temperature; (2) check the radar range profile at this azimuth angle and search all the nonzero values, record their ranges and profile intensities; (3) in the 3D range-azimuth-elevation coordinate system, the fused value is only assigned for points selected in step (2) by the root mean square of radar profile intensity and radiometric temperature, while the fused values are zeros for other points.

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Coherent radar clutter statistics.

Coherent radar clutter statistics.

The statistical models studied in Chapter 3 assume a uniformly distributed phase for the detected field. The resultant phase is the sum o f the phase contribution from individual scatterers within a resolution cell. The phase return from a scat- terer is the sum o f the phase o f the backscattering coefficient and the two-way path from the scatterer to the sensor. Therefore, the orientation and the position o f the individual scatterer determine its phase and hence the phase distribution o f the detected field. W hen the cell dimensions are several wavelengths in size then the phase overlaps many times as the co-ordinate values o f individual scatterers span from the near to far range and from left to right azimuth o f a range cell. In such strong scattering regime the phase o f the detected field will be uniformly dis­ tributed and the detected field can be adequately represented by the statistical models described in Chapter 3. It was shown that when the effective num ber o f scatterers fluctuates according to a negative binomial distribution the resultant field statistics are K-distributed. However, when the resolution ceU is only a few w ave­ lengths in depth the scatterers wül not have a uniformly distributed phase. Also if there is a bright target immersed in a resolution cell otherwise containing scatterers with uniformly distributed phase the net effect will again be a non-uniformly dis­ tributed phase for the detected field. In the random walk representation o f the scattering process the non-uniform phase manifests as a bias in the random walk. This type o f scattering is termed ‘weak scattering’.

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Effect of Tilt angle and Azimuth angle on Solar Output and Optimum Tilt and Azimuth angle for Chandigarh, India

Effect of Tilt angle and Azimuth angle on Solar Output and Optimum Tilt and Azimuth angle for Chandigarh, India

All the inputs in mechanical design and electrical design are same as before in study of tilt angle only the azimuth angle is varied between 120 degrees to 240 degrees where 180 degree is true south. The tilt angle is now freezed to 20 degrees which is optimum tile angle for Chandigarh according to annual AC energy generated. Then following inputs are provided:

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Wind turbine wake measurements with automatically adjusting scanning trajectories in a multi-Doppler lidar setup

Wind turbine wake measurements with automatically adjusting scanning trajectories in a multi-Doppler lidar setup

Coherent Doppler lidar instruments for wind speed mea- surement have been widely used in atmospheric sciences since the late 20th century (Frehlich et al., 1998; Reite- buch et al., 2001; Smalikho, 2003). Because of their good performance within the atmospheric boundary layer, their high availability and capability to measure continuously, they have become increasingly interesting for wind-energy re- search as well (Emeis et al., 2007; Frehlich and Kelley, 2008). Conically scanning lidars (operating in the so-called velocity azimuth display, or VAD, mode) are useful for mea- suring vertical profiles of wind speed and wind direction in the range between 50 m and the boundary-layer top. They can also be used to estimate dissipation rate and turbulent kinetic energy (TKE; Kumer et al., 2016). More advanced scanning scenarios can be performed with instruments that have full hemispherical scanning capabilities and thus allow arbitrary volumes of the atmosphere to be scanned. Such sys- tems have been deployed in the past to measure wind turbine wakes by scanning through them either horizontally (in so- called plan-position indicator, or PPI, mode) or vertically (in so-called range–height indicator mode, short: RHI) (Käsler et al., 2010; Smalikho et al., 2013), thus showing their prop- agation path. A drawback of measurements with single lidars is that only radial wind velocities along the line of sight of the laser beam can be retrieved. To overcome this limitation, multiple lidars can be deployed with intersecting beams that allow a geometric reconstruction of the meteorological wind components (so-called dual-Doppler technique for the appli- cation of two lidars or multi-Doppler as the more general term; Calhoun et al., 2006; Choukulkar et al., 2017; Drechsel et al., 2009; Mann et al., 2009; Newman et al., 2016). Exam- ples for multi-lidar measurements of wind turbine wakes are for example Iungo et al. (2013), who placed dual-Doppler measurement points in the wake to retrieve vertical and hor- izontal wind speed at these points. Van Dooren et al. (2016) combined PPI scans to retrieve the horizontal wind speeds at hub height in the wake and its horizontal propagation.

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The cosmology of Inca huacas

The cosmology of Inca huacas

Kenko Chico (Figure 9-12) is located near Kenko Grande to its southwest, separated by a ravine and a small stream. Kenko Chico contains a stone stairway leading to its summit, terraces, and large stone blocks similar in size to many of those used at Sacsahuaman. It is surrounded by a moat and exhibits many carvings, such as steps and seats, in its limestone. Kenko Chico is oriented generally east-west and, while not a structural alignment, Nevado Ausangate can be viewed on the horizon in the direction of the December solstice sunrise. The central staircase is aligned north and south.

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Accounting for the effects of sastrugi in the CERES clear-sky Antarctic shortwave angular distribution models

Accounting for the effects of sastrugi in the CERES clear-sky Antarctic shortwave angular distribution models

Abstract. The Cloud and the Earth’s Radiant Energy System (CERES) instruments on NASA’s Terra, Aqua and Soumi NPP satellites are used to provide a long-term measurement of Earth’s energy budget. To accomplish this, the radiances measured by the instruments must be inverted to fluxes by the use of a scene-type-dependent angular distribution model (ADM). For permanent snow scenes over Antarctica, short- wave (SW) ADMs are created by compositing radiance mea- surements over the full viewing zenith and azimuth range. However, the presence of small-scale wind blown rough- ness features called sastrugi cause the BRDF (bidirectional reflectance distribution function) of the snow to vary sig- nificantly based upon the solar azimuth angle and location. This can result in monthly regional biases between − 12 and 7.5 Wm −2 in the inverted TOA (top-of-atmosphere) SW flux. The bias is assessed by comparing the CERES shortwave fluxes derived from nadir observations with those from all viewing zenith angles, as the sastrugi affect fluxes inverted from the oblique viewing angles more than for the nadir viewing angles. In this paper we further describe the clear- sky Antarctic ADMs from Su et al. (2015). These ADMs ac- count for the sastrugi effect by using measurements from the Multi-Angle Imaging Spectro-Radiometer (MISR) instru- ment to derive statistical relationships between radiance from different viewing angles. We show here that these ADMs re- duce the bias and artifacts in the CERES SW flux caused by sastrugi, both locally and Antarctic-wide. The regional monthly biases from sastrugi are reduced to between −5 and 7 Wm −2 , and the monthly-mean biases over Antarctica are reduced by up to 0.64 Wm −2 , a decrease of 74 %. These im-

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Applying rotorcraft modelling technology to renewable energy research

Applying rotorcraft modelling technology to renewable energy research

used by the wind turbine community. This prob- lem bears striking similarities to that associated with the interaction between the main and tail ro- tors of a conventional helicopter. This interaction can have a strong negative influence on the flight mechanics of the helicopter. Significant unsteadi- ness in the tail rotor loading is encountered un- der certain flight conditions, but the character of the unsteadiness can depend on the direction of rotation of the tail rotor. VTM simulations of the aerodynamic interaction between the main and tail rotors of a helicopter show distinct differences in the behaviour of the system in left and right cross- wind flight that are consistent with flight experi- ence — the greatest fluctuations in loading or con- trol input are required in left sideways flight (for a counter-clockwise rotating rotor) and are gener- ally more extreme for a system with tail rotor ro- tating top-forward than top-aft. Although not yet fully understood, the observed behaviour, in the helicopter context, appears to originate in a global unsteadiness in the flow field that arises in the pro- cess whereby the tail rotor wake merges with the wake of the main rotor.

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Analysis on the Azimuth Shift of a Moving Target in SAR Image

Analysis on the Azimuth Shift of a Moving Target in SAR Image

In this paper, we conduct a detailed theoretical analysis on the azimuth shift issue of a moving target in SAR image whose spectrum may entirely situate within a PRF band or spans in two neighboring PRF bands. The analyzed results are summarized and validated by simulations. Based on the derived analytical formulas, one can get the correct azimuth shift for a moving target with arbitrary velocity, which is beneficial for moving targets relocation in SAR image processing.

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A Numerical Study of Thickness Effect of the Symmetric NACA 4-Digit Airfoils on Self Starting Capability of a 1kW H-Type Vertical Axis Wind Turbine

A Numerical Study of Thickness Effect of the Symmetric NACA 4-Digit Airfoils on Self Starting Capability of a 1kW H-Type Vertical Axis Wind Turbine

It is noted that during the startup procedure, the total moment of three blades is highly correlated to the moment affected on blade 1 as shown later on Fig. 16 and Fig. 17. Looking the variation of the moment coefficient of blade 1 with different velocities, at the same starting azimuth position condition, θ = 0°, and for particular NACA 0015 airfoil, as shown in Fig. 16, is the simplest way to investigate effect of wind velocity on startup time. Note that the moment contribute to start up process nearly constant in function of wind velocity when blade 1 has the azimuth position of [45°, 120°]. The main difference in magnitude of the maximum moment coefficient on blade 1 can be observed when the azimuth position of blade 1 is [0°, 45°].

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Aerodynamic response of a hovering rotor to ramp change in pitch input

Aerodynamic response of a hovering rotor to ramp change in pitch input

CHRONoS (Compressible High Resolution Over- set mesh Navier–StOkes Solver) is a vertex cen- tered finite volume code for the solution of the Navier–Stokes equations on structured overset meshes. While the primary algorithm uses a hybrid RANS/LES coupling to represent the unresolved scales of the flow, in the present study the solver was employed in a fully turbulent RANS mode in which the Spalart-Allmaras turbulence model (Ref. 10) is integrated to the blade surface. The near-blade domain was discretized using a body- conforming mesh with dimension 229 × 71 × 67 cells in the chordwise, spanwise and normal directions, respectively. This mesh was then overset inside a half-cylindrical background mesh with dimension 121 × 91 × 91 cells in the azimuthal, vertical and radial directions, respectively. The azimuthal pe- riodicity of the flow field of the two-bladed rotor system allowed the simulation to be performed on the mesh of a single blade together with its asso- ciated half-cylindrical background mesh. A hole with constant topology was cut in the rigidly ro- tating background mesh and local searches and in- terpolations were performed at every time-step to account for the motion of the blade mesh relative to the background mesh. A third-order Weighted Es- sentially Non-oscillatory scheme (Ref. 7), based on the AUSM-DV flux splitting method (Ref. 8) was used to discretize the inviscid terms. The viscous terms were computed using second order central differencing. Second order accurate implicit time integration was used with the Diagonalized Di- agonally Dominant Alternating Direction Implicit scheme (Ref. 11). 2880 time steps per revolution

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ARRP: Azimuth Restricted Routing Protocol for Ad Hoc Networks

ARRP: Azimuth Restricted Routing Protocol for Ad Hoc Networks

In this paper we propose a routing protocol that takes advantage of position information of nodes. Azimuth Restricted Routing Protocol computes the azimuth angle between the source and destination node position. Based on this azimuth angle, a flooding range is calculated. Intermediate nodes takes forwarding decision based on this flooding angle. Each node adds its location information into the RREQ and RREP it generates. RREQ additionally carry the computed range based on the destination position. Whenever a node receives a control packet it updates the routing table, adding the position information. When the source has the position information of destination it range based flooding else it is broadcasted over the entire network.

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Article Estimating Ocean Vector Winds and Currents Using a Ka-band Pencil-Beam Doppler Scatterometer

Article Estimating Ocean Vector Winds and Currents Using a Ka-band Pencil-Beam Doppler Scatterometer

Figure 17. Collocated DopplerScatt and model data histograms after filtering. From left to right, relative frequency of: backscatter, incidence angle, relative azimuth to model direction, and model wind speed. In total there are about 7.2 million data points. Zero degrees relative azimuth corresponds to the upwind direction. In spite of conical scanning, the azimuth angles are not uniformly distributed because we have discarded pixels very near the coast, which lie predominantly in one direction.

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Comparison and validation of top of atmosphere (toa) radiance of oceansat 2 ocm sensor

Comparison and validation of top of atmosphere (toa) radiance of oceansat 2 ocm sensor

Prosoft 7.7. The average of the wind for the period 1000 to 1400 hrs local time provides the wind speed, wind direction and salinity from CTD are casts at the NIO, Goa. All data were mostly collected around noon time to secure a high sun zenith angle and when the ship was stationary to avoid white caps in the sensors' fields of view. To derive OCM2_GAC data, the image analysis software, SeaDAS house module by National Institute of Oceanography (NIO), Goa is used.

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