scholarly journals Effect of Particle Sizes on the Efficiency of Fluorinated Nanodiamond Neutron Reflectors

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3067
Author(s):  
Aleksander Aleksenskii ◽  
Marcus Bleuel ◽  
Alexei Bosak ◽  
Alexandra Chumakova ◽  
Artur Dideikin ◽  
...  
Keyword(s):  
Incidence Angle ◽  
Particle Sizes ◽  
Detonation Nanodiamond ◽  
Velocity Range ◽  
Initial Size ◽  
Cold Neutrons ◽  
Small Incidence ◽  
Reflector Geometry ◽  
Overall Efficiency ◽  
Upper Boundary

Over a decade ago, it was confirmed that detonation nanodiamond (DND) powders reflect very cold neutrons (VCNs) diffusively at any incidence angle and that they reflect cold neutrons quasi-specularly at small incidence angles. In the present publication, we report the results of a study on the effect of particle sizes on the overall efficiency of neutron reflectors made of DNDs. To perform this study, we separated, by centrifugation, the fraction of finer DND nanoparticles (which are referred to as S-DNDs here) from a broad initial size distribution and experimentally and theoretically compared the performance of such a neutron reflector with that from deagglomerated fluorinated DNDs (DF-DNDs). Typical commercially available DNDs with the size of ~4.3 nm are close to the optimum for VCNs with a typical velocity of ~50 m/s, while smaller and larger DNDs are more efficient for faster and slower VCN velocities, respectively. Simulations show that, for a realistic reflector geometry, the replacement of DF-DNDs (a reflector with the best achieved performance) by S-DNDs (with smaller size DNDs) increases the neutron albedo in the velocity range above ~60 m/s. This increase in the albedo results in an increase in the density of faster VCNs in such a reflector cavity of up to ~25% as well as an increase in the upper boundary of the velocities of efficient VCN reflection.

X-ray depth profiling of iron oxide thin films

1988 ◽  
Vol 3 (2) ◽  
pp. 351-356 ◽  
Author(s):  
Michael F. Toney ◽  
Ting C. Huang ◽  
Sean Brennan ◽  
Zophia Rek
Keyword(s):  
Incidence Angle ◽  
Depth Profiling ◽  
Grazing Incidence ◽  
Outward Diffusion ◽  
X Ray ◽  
X Ray Scattering ◽  
Α Phase ◽  
Small Incidence ◽  
Pattern Characteristic ◽  
Fe Ions

A nominally γ-Fe2O3 thin film (oxidized from an Fe3O4 film) has been structurally depth profiled using x-ray scattering in a grazing incidence, asymmetric Bragg geometry. By varying the grazing incidence angle, the x-ray penetration depth is varied from tens of Angstroms to several thousand Angstroms, slightly larger than the film thickness. At small incidence angles a diffraction pattern characteristic of α-Fe2O3 is observed, while at larger angles the pattern is predominantly from γ-Fe2O3, showing that there is a surface layer of α-Fe2O3. These results are quantified and the thickness of the α phase found to be 90 Å. The presence of the α phase explains a nonferromagnetic layer observed previously. These data together with magnetic and chemical data suggest that the nonferromagnetic layer forms during oxidation of the Fe3O4 film due to outward diffusion of Fe ions and their subsequent oxidation to form α-Fe2O3

Grazing incidence synchrotron x-ray diffraction method for analyzing thin films

1987 ◽  
Vol 2 (4) ◽  
pp. 471-477 ◽  
Author(s):  
G. Lim ◽  
W. Parrish ◽  
C. Ortiz ◽  
M. Bellotto ◽  
M. Hart
Keyword(s):  
Thin Films ◽  
Penetration Depth ◽  
Incidence Angle ◽  
Depth Profiling ◽  
Diffraction Method ◽  
Grazing Incidence ◽  
Parallel Beam ◽  
X Ray ◽  
Small Incidence ◽  
Iron Oxide Films

A method using synchrotron radiation parallel beam x-ray optics with a small incidence angle α on the specimen and 2Θ-detector scanning is described for depth profiling analysis of thin films. The instrumentation is the same as used for Θ:2Θ synchrotron parallel beam powder diffractometry, except that the specimen is uncoupled from the detector. There is no profile distortion. Below the critical angle for total reflection αc, the top tens of Angstroms are sampled. Depth profiling is controlled to a few Angstroms using a small α and 0.005° steps. The penetration depth increases to several hundred Angstroms as α approaches αc. Above αc there is a rapid increase in penetration depth to a thousand Angstroms or more and the profiling cannot be sensitively controlled. At grazing incidence the peaks are shifted several tenths of a degree by the x-ray refraction and an experimental procedure for calculating the shifts is described. The method is illustrated with an analysis of iron oxide films.

Wake Formation for an Oscillating Small-Incidence-Angle Cylinder Pair in Cross-Flow

2011 ◽  
Author(s):  
Mir M. Hayder
Keyword(s):  
Incidence Angle ◽  
Flow Direction ◽  
Incident Angle ◽  
Cross Flow ◽  
Wake Flow ◽  
Circular Cylinders ◽  
Mean Flow ◽  
Small Incidence ◽  
The Mean ◽  
Wake Formation

The wake region of a pair of equal-diameter staggered circular cylinders in cross-flow is investigated experimentally for Reynolds numbers, based on the mean flow velocity, U, and the cylinder diameter, D, within the range 540 ≤ Re ≤ 755. The centre-to-centre pitch ratio and stagger angle of the cylinders at their mean position are P/D = 2.0 and α = 16°, respectively. In an earlier study, wake formation of a small-incident-angle cylinder pair was investigated for forced oscillation (transverse to the flow direction) of the upstream cylinder only. The present study is aimed to reveal the modification of the wake when the oscillation is shifted from the upstream to downstream cylinder or vice versa. Results with cylinder excitation frequencies in the range 0.07 ≤ feD/U ≤ 1.10 are reported. It is observed that for both upstream and downstream cylinder oscillations with frequency feD/U ≤ 0.10 the wake flow patterns remain essentially the same as those of the corresponding static cases. However, for frequency feD/U > 0.10 the wake undergoes considerable modification vis-a`-vis when the cylinders are stationary, and the flow pattern within the wake is strongly dependent on feD/U value. As also observed in the previous study, there are distinct regions of synchronization between the dominant wake periodicities and the cylinder oscillation over the whole range of feD/U. These synchronizations involve sub- and super-harmonics as well as fundamental synchronizations and are the result of the formation of two rows of vortices, one on either side of the combined wake of the cylinder pair. The manner in which the wake responds to the cylinder oscillation depends strongly on whether it is the upstream or downstream cylinder which is oscillating. Flow-visualization images suggests that the synchronizations on the mean-flow side of the downstream cylinder occur from the outer vortices shed by the downstream cylinder, and those on the mean-flow side of the upstream cylinder occur from the vortices formed by the interaction of the two gap shear layers and the outer shear layer separated from the upstream cylinder.

Sound Transmission through Lightweight All-Metallic Sandwich Panels with Corrugated Cores

2008 ◽  
Vol 47-50 ◽  
pp. 57-60 ◽  
Author(s):  
Feng Xian Xin ◽  
T.J. Lu ◽  
Chang Chen
Keyword(s):  
Inclination Angle ◽  
Transmission Loss ◽  
Cell Model ◽  
Incidence Angle ◽  
Sandwich Panels ◽  
Sound Transmission ◽  
Lumped Mass ◽  
Space Harmonic ◽  
The Core ◽  
Small Incidence

The transmission of sound through all-metallic sandwich panels with corrugated cores is investigated using the space-harmonic method. The sandwich panel is modeled as two parallel panels connected by uniformly distributed translational springs and rotational springs, with the mass of the core sheets taken as lumped mass. Based on the periodicity of the panel structure, a unit cell model is developed to provide the effective translational and rotational stiffness of the core. The model is used to investigate the influence of sound incidence angle and the inclination angle between facesheet and core sheet on the sound transmission loss (STL) of the sandwich structure. The results show that the inclination angle has a significant effect on STL, and sandwich panels with corrugated cores are more suitable for the insulation of sound having small incidence angle.

Study of Abrasive Water Jet Polishing Technology

2011 ◽  
Vol 487 ◽  
pp. 327-331 ◽  
Author(s):  
Cui Lian Che ◽  
Chuan Zhen Huang ◽  
Jun Wang ◽  
Hong Tao Zhu
Keyword(s):  
Flow Structure ◽  
Incidence Angle ◽  
Necessary Condition ◽  
Abrasive Water Jet ◽  
Removal Mechanism ◽  
Polishing Process ◽  
Small Incidence ◽  
Ductile Removal ◽  
Abrasive Size ◽  
The Ideal

In this paper, the influence of the incidence angle and abrasive mesh on the polishing quality is analyzed during AWJ polishing process. Through the study on the jet flow structure, it is obtained the standoff of AWJ polishing is chosen within the jet basic section. According to the experiments for AWJ Polishing quartz, it is better to remove material by ductile removal mechanism choosing small incidence angle, low pressure and small abrasive size. The ductile removal mechanism of the polished material is a necessary condition for the ideal polishing results

The Design and Testing of a Low Reaction Turbine Blade Profile for HP and IP Steam Flow Path

2016 ◽  
Author(s):  
Guoliang Deng ◽  
Qi Sun ◽  
Qilin Wu ◽  
Xiaoping Fan ◽  
Mingyan Yin ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Mass Flow ◽  
Incidence Angle ◽  
Steam Flow ◽  
Geometry Design ◽  
Multi Stage ◽  
Measured Efficiency ◽  
Real Mass ◽  
Overall Efficiency ◽  
Profile Loss

The design of a low reaction turbine blade profiles was carried out to improve the steam flow efficiency. The blade profiles geometry design for both the stationary and moving blades and reprofiling of them are done using Vista ATBlade, according to the aerodynamic analysis results from the cascade analysis code MISES. The original stator profile is aft-loaded, and the new one present in this paper is highly-aft-loaded (HAL) to depress the development of secondary flow further, while maintaining even lower profile loss and wider incidence angle tolerance. The newly designed moving blade is more robust compared with the original one, thus it has larger aspect ratio under the same blade section average stress level, and with better incidence tolerant capability as well. The planar cascade air tests were first carried out to verify the stator profile loss improvement, with a decrease of energy loss coefficient of almost 0.8% obtained under the Reynolds number of about 1e6. Then the annular cascade air tests with fully 360 degrees stator blades installed were conducted to validate the reduction of endwall loss and the profile loss as well, and to measure the mass flow capability (real mass flow/ideal mass flow). Finally, two three-stage tests for the original blades and the new one were developed to verify the improvement under real multi-stages flow conditions. All the stages for both tests are designed with the hub reaction of about 15%, without interstage swirl, in the design condition. The flow probes at upstream of first stage stator and downstream of last stage moving blade, the hydraulic dynamometer and the flowmeter are used to test the overall efficiency. Three traverse planes are located at the upstream, middle and downstream of the second stage to measure the flow properties using five hole pneumatic probes. The test results showed a increase of overall efficiency of about 1.5%. The CFD simulations showed very good agreement of mass flow capability with the tests, for both the stator annular and multi-stage tests. The application of the newly designed blade profiles in SanHe subcritical reheat 300MW steam turbine (16.7MPa/537°C/537°C) retrofit gives the final proof of the efficiency improvement. The measured efficiency showed remarkable performance, with an increase of efficiency of 1.5%–2.2% for both the HP and IP cylinder.

Corrections for Residual Stress in X- Ray Grazing Incidence Technique

2008 ◽  
Vol 571-572 ◽  
pp. 289-294 ◽  
Author(s):  
Sebastian Wroński ◽  
Krzysztof Wierzbanowski ◽  
Andrzej Baczmanski ◽  
Chedly Braham ◽  
Alain Lodini
Keyword(s):  
Incidence Angle ◽  
Wave Length ◽  
Grazing Incidence ◽  
Sample Surface ◽  
Peak Position ◽  
Ferrite Powder ◽  
X Ray ◽  
Wave Refraction ◽  
Small Incidence ◽  
Α Angle

Grazing incidence technique can be used to study samples with important stress gradients. The stress can be measured at very small depths, of the order of a few μm. The penetration depth of radiation is almost constant in a wide 2θ range for a given incidence angle α. It can be changed by an appropriate selection of α angle. This enables the investigation of stress variation with depth below the sample surface. There are, however, some factors which have to be corrected in this technique. The most important one is the X-ray wave refraction: it changes the wave length and direction of the beam inside a sample. These two effects cause some shift of a peak position and they have to be taken into account. For small incidence angles (α≤100) the corrections are significant and can modify the measured stress even of 70 MPa. The refraction correction decreases with increasing of the incidence angle. The corrections were tested on ferrite powder and on the ground AISI316L steel samples.

scholarly journals Arctic Sea Ice Classification Based on CFOSAT SWIM Data at Multiple Small Incidence Angles

2021 ◽  
Vol 14 (1) ◽  
pp. 91
Author(s):  
Meijie Liu ◽  
Ran Yan ◽  
Jie Zhang ◽  
Ying Xu ◽  
Ping Chen ◽  
...  
Keyword(s):  
Sea Ice ◽  
Sea Water ◽  
Incidence Angle ◽  
Arctic Sea Ice ◽  
Detection Methods ◽  
The Arctic ◽  
Support Vector ◽  
Remote Sensors ◽  
Arctic Sea ◽  
Small Incidence

Sea ice type is the key parameter of Arctic sea ice monitoring. Microwave remote sensors with medium incidence and normal incidence modes are the primary detection methods for sea ice types. The Surface Wave Investigation and Monitoring instrument (SWIM) on the China-France Oceanography Satellite (CFOSAT) is a new type of sensor with a small incidence angle detection mode that is different from traditional remote sensors. The method of sea ice detection using SWIM data is also under development. The research reported here concerns ice classification using SWIM data in the Arctic from October 2019 to April 2020. Six waveform features are extracted from the SWIM echo data at small incidence angles, then the distinguishing capabilities of a single feature are analyzed using the Kolmogorov-Smirnov distance. The classifiers of the k-nearest neighbor and support vector machine are established and chosen based on single features. Moreover, sea ice classification based on multi-feature combinations is carried out using the chosen KNN classifier, and optimal combinations are developed. Compared with sea ice charts, the overall accuracy is up to 81% using the optimal classifier and a multi-feature combination at 2°. The results reveal that SWIM data can be used to classify sea water and sea ice types. Moreover, the optimal multi-feature combinations with the KNN method are applied to sea ice classification in the local regions. The classification results are analyzed using Sentinel-1 SAR images. In general, it is concluded that these multifeature combinations with the KNN method are effective in sea ice classification using SWIM data. Our work confirms the potential of sea ice classification based on the new SWIM sensor, and highlight the new sea ice monitoring technology and application of remote sensing at small incidence angles.

Effect of Wall Roughness on the Dynamics of Unsteady Cavitation

2005 ◽  
Vol 127 (4) ◽  
pp. 726-733 ◽  
Author(s):  
Olivier Coutier-Delgosha ◽  
Jean-François Devillers ◽  
Mireille Leriche ◽  
Thierry Pichon
Keyword(s):  
Smooth Surface ◽  
Cavity Length ◽  
Incidence Angle ◽  
Vertical Wall ◽  
Suction Side ◽  
General Effect ◽  
Wall Roughness ◽  
Cloud Cavitation ◽  
Fast Fourier Transform Analysis ◽  
Small Incidence

The present paper is devoted to the experimental study of unsteady cavitation on the suction side of a two-dimensional foil section positioned in a cavitation tunnel with a small incidence angle. When the pressure is decreased in the tunnel, a sheet of cavitation characterized by large amplitude fluctuations is obtained on the foil. The present study focuses on the effects of the foil wall roughness on the cavity unsteady behavior. Four different sizes d of irregularities have been tested, from the smooth surface to a 400μm grain size. The characteristic frequency of the flow unsteadiness is investigated by analyzing the data measured by a pressure transducer mounted flush on one vertical wall of the test section, whereas the mean cavity length is obtained by visual measurements on the foil side. Several types of cloud cavitation are identified in the case of the smooth surface. The effect of roughness is a significant decrease of the cavity length and a large increase of the oscillation frequency. It results in Strouhal numbers higher than the classical values obtained for partial cavity fluctuations. Moreover, the cavitation cycle is disorganized by the increase of the roughness, as it can be detected by the fast fourier transform analysis of the pressure signal. The general effect is a reduction of the pressure fluctuation intensity.

Analytic Model of Proprotor Forces and Moments at High Incidence

2021 ◽  
Author(s):  
Yuchen Leng ◽  
Thierry Jardin ◽  
Jean-Marc Moschetta ◽  
Murat Bronz
Keyword(s):  
Incidence Angle ◽  
Analysis Tool ◽  
Blade Element Theory ◽  
High Incidence ◽  
Small Incidence ◽  
Classical Models ◽  
Flight Regimes ◽  
Thrust And Torque ◽  
Element Theory ◽  
Blade Element

The paper presents an analytical model for estimation of proprotor aerodynamic loads at elevated incidence angles. Previous theories have concentrated on either small incidence angle for aircraft stability analysis or edge-wise flow for helicopter forward flight. This development attempted an engineering method that covers the full incidence angle range from 0 to π/2. Blade element theory was applied to known proprotor geometry, and off-axis loads including normal force and in-plane moment were obtained in closed form based on thrust and torque in axial condition. The model was found to be sufficiently accurate over a broader flight conditions compared to classical models, and computationally more efficient than numerical methods. Hence it could be easily used as a preliminary design and analysis tool for future convertible aircraft proprotors. The paper further discusses a dedicated wind tunnel campaign on proprotor off-axis load measurement. Experimental data from the test campaign was considered in model validation. The results suggested that the model was capable to accurately estimate proprotor performance in nominal flight regimes.

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