Off-axis Non-rotationally Symmetric Superposition Square Spot Uniform Concentration Fresnel Lens

With the improvement of the optical properties of the modern TEM objective lenses the point resolution is pushed beyond 0.2 nm. The objective lens of the CM300 UltraTwin combines a Cs of 0. 65 mm with a Cc of 1.4 mm. At 300 kV this results in a point resolution of 0.17 nm. Together with a high-brightness field-emission gun with an energy spread of 0.8 eV the information limit is pushed down to 0.1 nm. The rotationally symmetric part of the phase contrast transfer function (pctf), whose first zero at Scherzer focus determines the point resolution, is mainly determined by the Cs and defocus. Apart from the rotationally symmetric part there is also the non-rotationally symmetric part of the pctf. Here the main contributors are not only two-fold astigmatism and beam tilt but also three-fold astigmatism. The two-fold astigmatism together with the beam tilt can be corrected in a straight-forward way using the coma-free alignment and the objective stigmator. However, this only works well when the coefficient of three-fold astigmatism is negligible compared to the other aberration coefficients. Unfortunately this is not generally the case with the modern high-resolution objective lenses. Measurements done at a CM300 SuperTwin FEG showed a three fold-astigmatism of 1100 nm which is consistent with measurements done by others. A three-fold astigmatism of 1000 nm already sinificantly influences the image at a spatial frequency corresponding to 0.2 nm which is even above the point resolution of the objective lens. In principle it is possible to correct for the three-fold astigmatism a posteriori when through-focus series are taken or when off-axis holography is employed. This is, however not possible for single images. The only possibility is then to correct for the three-fold astigmatism in the microscope by the addition of a hexapole corrector near the objective lens.

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New Feasible Concepts of Aberration Correction for Realizing High-Resolution Electron Microscopes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179762 ◽

1990 ◽

Vol 48 (1) ◽

pp. 202-203

Author(s):

H. Rose

Keyword(s):

Spherical Aberration ◽

Wave Length ◽

Electron Wave ◽

Optical Lens ◽

Resolution Electron ◽

Rotationally Symmetric ◽

Electron Microscopes ◽

The Cost ◽

Imaging Performance ◽

Acceleration Voltage

The imaging performance of the light optical lens systems has reached such a degree of perfection that nowadays numerical apertures of about 1 can be utilized. Compared to this state of development the objective lenses of electron microscopes are rather poor allowing at most usable apertures somewhat smaller than 10-2 . This severe shortcoming is due to the unavoidable axial chromatic and spherical aberration of rotationally symmetric electron lenses employed so far in all electron microscopes.The resolution of such electron microscopes can only be improved by increasing the accelerating voltage which shortens the electron wave length. Unfortunately, this procedure is rather ineffective because the achievable gain in resolution is only proportional to λ1/4 for a fixed magnetic field strength determined by the magnetic saturation of the pole pieces. Moreover, increasing the acceleration voltage results in deleterious knock-on processes and in extreme difficulties to stabilize the high voltage. Last not least the cost increase exponentially with voltage.

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Far-Infrared Fresnel Lens for Thermal Imaging

IEEJ Transactions on Sensors and Micromachines ◽

10.1541/ieejsmas.133.274 ◽

2013 ◽

Vol 133 (7) ◽

pp. 274-279

Author(s):

Tomoyuki Takahata ◽

Kiyoshi Matsumoto ◽

Isao Shimoyama

Keyword(s):

Thermal Imaging ◽

Far Infrared ◽

Fresnel Lens

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See-Through Aerial Concave Display by Use of Fresnel Lens and AIRR with Polarization Modulation

Proceedings of the International Display Workshops ◽

10.36463/idw.2019.0150 ◽

2019 ◽

pp. 150

Author(s):

Shuto Hatsumi ◽

Kazuki Shimose ◽

Masaki Yasugi ◽

Hirotsugu Yamamoto

Keyword(s):

Fresnel Lens ◽

Polarization Modulation

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Mixed fluid cosmological model in f(R, T) gravity

Canadian Journal of Physics ◽

10.1139/cjp-2019-0494 ◽

2020 ◽

Vol 98 (11) ◽

pp. 1015-1022 ◽

Cited By ~ 1

Author(s):

Parbati Sahoo ◽

Barkha Taori ◽

K.L. Mahanta

Keyword(s):

Cosmological Model ◽

Bianchi Type ◽

Type I ◽

Time Varying ◽

Eos Parameter ◽

Barotropic Fluid ◽

Rotationally Symmetric ◽

Expansion Of The Universe ◽

The Universe ◽

Mixed Fluid

We construct a locally rotationally symmetric (LRS) Bianchi type-I cosmological model in f(R, T) theory of gravity when the source of gravitation is a mixture of barotropic fluid and dark energy (DE) by employing a time-varying deceleration parameter. We observe through the behavior of the state finder parameters (r, s) that our model begins from the Einstein static era and goes to ΛCDM era. The equation of state (EOS) parameter (ωd) for DE varies from the phantom (ω < –1) phase to quintessence (ω > –1) phase, which is consistent with observational results. It is found that the discussed model can reproduce the current accelerating phase of the expansion of the universe.

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Rotationally symmetric flow of Reiner-Rivlin fluid over a heated porous wall using numerical approach

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/09544062211034204 ◽

2021 ◽

pp. 095440622110342

Author(s):

Talat Rafiq ◽

M Mustafa ◽

Junaid Ahmad Khan

Keyword(s):

Boundary Layer ◽

Layer Structure ◽

Full Range ◽

Porous Wall ◽

Symmetric Flow ◽

Axial Velocity Component ◽

Suction Velocity ◽

Rotationally Symmetric ◽

Non Linear System ◽

Rotationally Symmetric Flow

This research features one parameter family of solutions representing rotationally symmetric flow of non-Newtonian fluid obeying Reiner-Rivlin model. Such flows take place over a revolving plane permeable surface through origin such that fluid at infinity also undergoes uniform rotation about the vertical axis. Heat transfer accompanied with viscous heating effect is also analyzed. A similarity solution is proposed that results into a coupled non-linear system with four unknowns. Boundary layer structure is characterized by a parameter [Formula: see text] that compares angular velocity of external flow with that of the rotating surface. Solutions are developed by a well-known package bvp4c of MATLAB for full range of [Formula: see text]. Flow pattern for different choices of [Formula: see text] is scrutinized by computing both 2 D and 3 D streamlines. It is further noted that value of suction velocity is important with regards to the sign of axial velocity component. Boundary layer suppresses considerably whenever the surface is permeable. For sufficiently high suction velocity with [Formula: see text], entire fluid undergoes rigid body rotation. In no suction case, axially upward flow accelerates for increasing values of parameter [Formula: see text] in the range [Formula: see text], whereas opposite trend is apparent in the case [Formula: see text]. Results for normalized wall shear and Nusselt number are scrutinized for various choices of embedded parameters.

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Electrical Tuning of Fresnel Lens in Reflection

ACS Photonics ◽

10.1021/acsphotonics.1c00520 ◽

2021 ◽

Author(s):

Christopher Damgaard-Carstensen ◽

Martin Thomaschewski ◽

Fei Ding ◽

Sergey I. Bozhevolnyi

Keyword(s):

Fresnel Lens

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Design and Evaluation of the Fresnel-Lens Based Solar Concentrator System Through a Statistical-Algorithmic Approach

Volume 8B: Heat Transfer and Thermal Engineering ◽

10.1115/imece2018-87023 ◽

2018 ◽

Cited By ~ 2

Author(s):

Hassan Qandil ◽

Weihuan Zhao

Keyword(s):

High Temperature ◽

High Efficiency ◽

Incident Light ◽

Thermal Analyses ◽

Solar Spectrum ◽

Chromatic Aberration ◽

Fresnel Lens ◽

Optimum Number ◽

Solar Concentrator ◽

Receiver System

A novel non-imaging Fresnel-lens-based solar concentrator-receiver system has been investigated to achieve high-efficiency photon and heat outputs with minimized effect of chromatic aberrations. Two types of non-imaging Fresnel lenses, a spot-flat lens and a dome-shaped lens, are designed through a statistical algorithm incorporated in MATLAB. The algorithm optimizes the lens design via a statistical ray-tracing methodology of the incident light, considering the chromatic aberration of solar spectrum, the lens-receiver spacing and aperture sizes, and the optimum number of prism grooves. An equal-groove-width of the Poly-methyl-methacrylate (PMMA) prisms is adopted in the model. The main target is to maximize ray intensity on the receiver’s aperture, and therefore, achieve the highest possible heat flux and output concentration temperature. The algorithm outputs prism and system geometries of the Fresnel-lens concentrator. The lenses coupled with solar receivers are simulated by COMSOL Multiphysics. It combines both optical and thermal analyses for the lens and receiver to study the optimum lens structure for high solar flux output. The optimized solar concentrator-receiver system can be applied to various devices which require high temperature inputs, such as concentrated photovoltaics (CPV), high-temperature stirling engine, etc.

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Quantum Kasner transition in a locally rotationally symmetric Bianchi II universe

Physical Review D ◽

10.1103/physrevd.104.024006 ◽

2021 ◽

Vol 104 (2) ◽

Author(s):

Ana Alonso-Serrano ◽

David Brizuela ◽

Sara F. Uria

Keyword(s):

Locally Rotationally Symmetric ◽

Rotationally Symmetric

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