Calculation of the incidence angle modifier of a Linear Fresnel Collector: The proposed declination and zenith angle model compared to the biaxial factored approach

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

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Atomic force microscopy (AFM) of the topography of silicon surfaces exposed to ion beams

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130298 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1132-1133

Author(s):

Mark Denker ◽

Jennifer Wall ◽

Mark Ray ◽

Richard Linton

Keyword(s):

Secondary Ion Mass Spectrometry ◽

Incidence Angle ◽

Ion Beam ◽

Depth Profiling ◽

Depth Resolution ◽

Ion Beams ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Trace Impurities ◽

Energy Dose

Reactive ion beams such as O2+ and Cs+ are used in Secondary Ion Mass Spectrometry (SIMS) to analyze solids for trace impurities. Primary beam properties such as energy, dose, and incidence angle can be systematically varied to optimize depth resolution versus sensitivity tradeoffs for a given SIMS depth profiling application. However, it is generally observed that the sputtering process causes surface roughening, typically represented by nanometer-sized features such as cones, pits, pyramids, and ripples. A roughened surface will degrade the depth resolution of the SIMS data. The purpose of this study is to examine the relationship of the roughness of the surface to the primary ion beam energy, dose, and incidence angle. AFM offers the ability to quantitatively probe this surface roughness. For the initial investigations, the sample chosen was <100> silicon, and the ion beam was O2+.Work to date by other researchers typically employed Scanning Tunneling Microscopy (STM) to probe the surface topography.

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Principle and practice of high-resolution imaging with a field-emission TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121090 ◽

1992 ◽

Vol 50 (1) ◽

pp. 138-139

Author(s):

Max T. Otten ◽

Wim M.J. Coene

Keyword(s):

High Resolution ◽

Field Emission ◽

Incidence Angle ◽

Temporal Coherence ◽

Energy Spread ◽

High Resolution Imaging ◽

Major Improvement ◽

High Resolution Images ◽

Resolution Imaging

High-resolution imaging with a LaB6 instrument is limited by the spatial and temporal coherence, with little contrast remaining beyond the point resolution. A Field Emission Gun (FEG) reduces the incidence angle by a factor 5 to 10 and the energy spread by 2 to 3. Since the incidence angle is the dominant limitation for LaB6 the FEG provides a major improvement in contrast transfer, reducing the information limit to roughly one half of the point resolution. The strong improvement, predicted from high-resolution theory, can be seen readily in diffractograms (Fig. 1) and high-resolution images (Fig. 2). Even if the information in the image is limited deliberately to the point resolution by using an objective aperture, the improved contrast transfer close to the point resolution (Fig. 1) is already worthwhile.

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Calculating the aerodynamics of vertical axis wind turbines

Vietnam Journal of Mechanics ◽

10.15625/0866-7136/34/3/2358 ◽

2012 ◽

Vol 34 (3) ◽

pp. 169-184 ◽

Cited By ~ 1

Author(s):

Hoang Thi Bich Ngoc

Keyword(s):

Wind Turbine ◽

Incidence Angle ◽

Vertical Axis ◽

Rotor Blades ◽

Vertical Axis Wind Turbine ◽

Horizontal Axis Wind Turbine ◽

Velocity Triangle ◽

Relationship Of ◽

The Relationship

Vertical axis wind turbine technology has been applied last years, very long after horizontal axis wind turbine technology. Aerodynamic problems of vertical axis wind machines are discussible. An important problem is the determination of the incidence law in the interaction between wind and rotor blades. The focus of the work is to establish equations of the incidence depending on the blade azimuth, and to solve them. From these results, aerodynamic torques and power can be calculated. The incidence angle is a parameter of velocity triangle, and both the factors depend not only on the blade azimuth but also on the ratio of rotational speed and horizontal speed. The built computational program allows theoretically selecting the relationship of geometric parameters of wind turbine in accordance with requirements on power, wind speed and installation conditions.

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Ripple Formation during Oblique Angle Etching

Coatings ◽

10.3390/coatings9040272 ◽

2019 ◽

Vol 9 (4) ◽

pp. 272

Author(s):

Mehmet F. Cansizoglu ◽

Mesut Yurukcu ◽

Tansel Karabacak

Keyword(s):

Plasma Etching ◽

Incidence Angle ◽

Incident Beam ◽

Root Mean Square Roughness ◽

Sticking Coefficient ◽

Oblique Angle ◽

Nano Fabrication ◽

Ripple Formation ◽

Rapid Formation ◽

Roughness Analysis

Chemical removal of materials from the surface is a fundamental step in micro- and nano-fabrication processes. In conventional plasma etching, etchant molecules are non-directional and perform a uniform etching over the surface. However, using a highly directional obliquely incident beam of etching agent, it can be possible to engineer surfaces in the micro- or nano- scales. Surfaces can be patterned with periodic morphologies like ripples and mounds by controlling parameters including the incidence angle with the surface and sticking coefficient of etching particles. In this study, the dynamic evolution of a rippled morphology has been investigated during oblique angle etching (OAE) using Monte Carlo simulations. Fourier space and roughness analysis were performed on the resulting simulated surfaces. The ripple formation was observed to originate from re-emission and shadowing effects during OAE. Our results show that the ripple wavelength and root-mean-square roughness evolved at a more stable rate with accompanying quasi-periodic ripple formation at higher etching angles (θ > 60°) and at sticking coefficient values (Sc) 0.5 ≤ Sc ≤ 1. On the other hand, smaller etching angle (θ < 60°) and lower sticking coefficient values lead to a rapid formation of wider and deeper ripples. This result of this study can be helpful to develop new surface patterning techniques by etching.

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Rotor Wake Generated Unsteady Aerodynamic Response of a Compressor Stator

Journal of Engineering for Power ◽

10.1115/1.3446415 ◽

1978 ◽

Vol 100 (4) ◽

pp. 664-675 ◽

Cited By ~ 25

Author(s):

S. Fleeter ◽

R. L. Jay ◽

W. A. Bennett

Keyword(s):

Pressure Difference ◽

Second Harmonic ◽

Incidence Angle ◽

Dynamic Pressure ◽

Pressure Differential ◽

Phase Lag ◽

Trailing Edge ◽

Unsteady Pressure ◽

Forcing Function ◽

Reduced Frequency

An experimental investigation was conducted to determine the fluctuating pressure distribution on a stationary vane row, with the primary source of excitation being the wakes from the upstream rotor blades. This was accomplished in a large scale, low speed, single stage research compressor. The forcing function, the velocity defect created by the rotor wakes, was measured with a crossed hot-wire probe. The aerodynamic response on the vanes was measured by means of flush mounted high response dynamic pressure transducers. The dynamic data were analyzed to determine the chordwise distribution of the dynamic pressure coefficient and aerodynamic phase lag as referenced to a transverse gust at the vane leading edge. Vane suction and pressure surface data as well as the pressure difference across the vane were obtained for reduced frequency values ranging from 3.65 to 16.80 and for an incidence angle range of 35.5 deg. The pressure difference data were correlated with a state-of-the-art aerodynamic cascade transverse gust analysis. The correlation was quite good for all reduced frequency values for small values of incidence. For the more negative incidence angle data points, it was shown that a convected wake phenomena not modeled in the analysis existed. Both the first and second harmonic unsteady pressure differential magnitude data decrease in the chordwise direction. The second harmonic magnitude data attains a value very nearly zero at the vane trailing edge transducer location, while the first harmonic data is still finite, albeit small, at this location. That the magnitude of the unsteady pressure differential data approaches zero near to the trailing edge, particularly the second harmonic data which has reduced frequency values to 16.8, is significant in that it reflects upon the validity of the Kutta condition for unsteady flows.

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Investigation of the selective color-changing mechanism of Dynastes tityus beetle (Coleoptera: Scarabaeidae)

Scientific Reports ◽

10.1038/s41598-020-80699-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jiyu Sun ◽

Wei Wu ◽

Limei Tian ◽

Wei Li ◽

Fang Zhang ◽

...

Keyword(s):

Focused Ion Beam ◽

Color Change ◽

Incidence Angle ◽

Ion Beam ◽

Three Dimensional ◽

Water Infiltration ◽

Photonic Materials ◽

Local Color ◽

Water Contact ◽

Color Changes

AbstractNot only does the Dynastes tityus beetle display a reversible color change controlled by differences in humidity, but also, the elytron scale can change color from yellow-green to deep-brown in specified shapes. The results obtained by focused ion beam-scanning electron microscopy (FIB-SEM), show that the epicuticle (EPI) is a permeable layer, and the exocuticle (EXO) is a three-dimensional photonic crystal. To investigate the mechanism of the reversible color change, experiments were conducted to determine the water contact angle, surface chemical composition, and optical reflectance, and the reflective spectrum was simulated. The water on the surface began to permeate into the elytron via the surface elemental composition and channels in the EPI. A structural unit (SU) in the EXO allows local color changes in varied shapes. The reflectance of both yellow-green and deep-brown elytra increases as the incidence angle increases from 0° to 60°. The microstructure and changes in the refractive index are the main factors that influence the process of reversible color change. According to the simulation, the lower reflectance causing the color change to deep-brown results from water infiltration, which increases light absorption. Meanwhile, the waxy layer has no effect on the reflection of light. This study lays the foundation to manufacture engineered photonic materials that undergo controllable changes in iridescent color.

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Adaptive Ultrasound-Based Tractor Localization for Semi-Autonomous Vineyard Operations

Agronomy ◽

10.3390/agronomy11020287 ◽

2021 ◽

Vol 11 (2) ◽

pp. 287

Author(s):

Matteo Corno ◽

Sara Furioli ◽

Paolo Cesana ◽

Sergio M. Savaresi

Keyword(s):

Autonomous Navigation ◽

Incidence Angle ◽

Autonomous Driving ◽

Localization Algorithm ◽

Robust Performance ◽

Cluttered Environment ◽

Experimental Campaign ◽

Commercial Applications ◽

Agricultural Tractors ◽

Selection Stage

Autonomous driving is greatly impacting intensive and precise agriculture. Matter-of-factly, the first commercial applications of autonomous driving were in autonomous navigation of agricultural tractors in open fields. As the technology improves, the possibility of using autonomous or semi-autonomous tractors in orchards and vineyards is becoming commercially profitable. These scenarios offer more challenges as the vehicle needs to position itself with respect to a more cluttered environment. This paper presents an adaptive localization system for (semi-) autonomous navigation of agricultural tractors in vineyards that is based on ultrasonic automotive sensors. The system estimates the distance from the left vineyard row and the incidence angle. The paper shows that a single tuning of the localization algorithm does not provide robust performance in all vegetation scenarios. We solve this issue by implementing an Extended Kalman Filter (EKF) and by introducing an adaptive data selection stage that automatically adapts to the vegetation conditions and discards invalid measurements. An extensive experimental campaign validates the main features of the localization algorithm. In particular, we show that the Root Mean Square Error (RMSE) of the distance is 16 cm, while the angular RMSE is 2.6 degrees.

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Magnetic plasmons induced in a dielectric-metal heterostructure by optical magnetism

Nanophotonics ◽

10.1515/nanoph-2021-0146 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Shulei Li ◽

Lidan Zhou ◽

Mingcheng Panmai ◽

Jin Xiang ◽

Sheng Lan

Keyword(s):

Transverse Electric ◽

Incidence Angle ◽

High Sensitivity ◽

Critical Value ◽

Transverse Magnetic ◽

Quality Factors ◽

Light Spectrum ◽

Optical Resonances ◽

Scattering Spectra ◽

Plasmon Polaritons

Abstract We investigate numerically and experimentally the optical properties of the transverse electric (TE) waves supported by a dielectric-metal heterostructure. They are considered as the counterparts of the surface plasmon polaritons (i.e., the transverse magnetic (TM) waves) which have been extensively studied in the last several decades. We show that TE waves with resonant wavelengths in the visible light spectrum can be excited in a dielectric-metal heterostructure when the optical thickness of the dielectric layer exceeds a critical value. We reveal that the electric and magnetic field distributions for the TE waves are spatially separated, leading to higher quality factors or narrow linewidths as compared with the TM waves. We calculate the thickness, refractive index and incidence angle dispersion relations for the TE waves supported by a dielectric-metal heterostructure. In experiments, we observe optical resonances with linewidths as narrow as ∼10 nm in the reflection or scattering spectra of the TE waves excited in a Si3N4/Ag heterostructure. Finally, we demonstrate the applications of the lowest-order TE wave excited in a Si3N4/Ag heterostructure in optical display with good chromaticity and optical sensing with high sensitivity.

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