HIGH-FREQUENCY DIFFRACTION BY A SPHERE

1961 ◽  
Vol 39 (10) ◽  
pp. 1486-1494
Author(s):  
C. L. Tang
Keyword(s):  
Plane Wave ◽  
High Frequency ◽  
Rotational Symmetry ◽  
Asymptotic Series ◽  
Three Dimensional ◽  
Shadow Region ◽  
High Frequencies ◽  
Present Procedure ◽  
Dimensional Object

A systematic procedure is given for the determination of the asymptotic series directly from the Helmholtz equation and the boundary conditions for the field in the shadow region of a sphere illuminated by a plane wave at high frequencies. The first two terms in the series for the shadow region, including the regions near the axial caustic and the boundary layer near the surface of the sphere, are explicitly evaluated. The present procedure can be generalized to any smooth convex three-dimensional object with a rotational symmetry, illuminated by a plane wave in the direction of the axis of rotational symmetry.

scholarly journals Generation of Novel-Substrate-Accepting Biphenyl Dioxygenases through Segmental Random Mutagenesis and Identification of Residues Involved in Enzyme Specificity

2006 ◽  
Vol 72 (3) ◽  
pp. 2191-2199 ◽  
Author(s):  
Marco Zielinski ◽  
Silke Kahl ◽  
Christine Standfuß-Gabisch ◽  
Beatriz Cámara ◽  
Michael Seeger ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Random Mutagenesis ◽  
Major Influence ◽  
Enzyme Specificity ◽  
Three Dimensional Model ◽  
Wild Type Enzyme ◽  
High Frequencies ◽  
Burkholderia Xenovorans ◽  
Function Relationship

ABSTRACT Aryl-hydroxylating dioxygenases are of interest for the degradation of persistant aromatic pollutants, such as polychlorobiphenyls (PCBs), or as catalysts for the functionalization of aromatic scaffolds. In order to achieve dioxygenation of technical mixtures of PCBs, enzymes with broadened or altered substrate ranges are essential. To alter the substrate specificity of the biphenyl dioxygenase (BphA) of Burkholderia xenovorans LB400, we applied a directed evolution approach that used structure-function relationship data to target random mutageneses to specific segments of the enzyme. The limitation of random amino acid (AA) substitutions to regions that are critical for substrate binding and the exclusion of AA exchanges from positions that are essential for catalytic activity yielded enzyme variants of interest at comparatively high frequencies. After only a single mutagenic cycle, 10 beneficial variants were detected in a library of fewer than 1,000 active enzymes. Compared to the parental BphA, they showed between 5- and 200-fold increased turnover of chlorinated biphenyls, with substituent patterns that rendered them largely recalcitrant to attack by BphA-LB400. Determination of their sequences identified AAs that prevent the acceptance of specific PCBs by the wild-type enzyme, such as Pro334 and Phe384. The results suggest prime targets for subsequent cycles of BphA modification. Correlations with a three-dimensional model of the enzyme indicated that most of the exchanges with major influence on substrate turnover do not involve pocket-lining residues and had not been predictable through structural modeling.

A Model for the Fast Determination of Modal Sound Transmission of Large Rectangular Opening

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Jiazhu Li ◽  
Rui Zhang ◽  
Shen Chen ◽  
Can Li ◽  
Jian Chen
Keyword(s):  
Wave Equations ◽  
Three Dimensional ◽  
Sound Transmission ◽  
Computational Effort ◽  
Sound Insulation ◽  
Fast Determination ◽  
High Frequencies ◽  
Higher Order Modes ◽  
Insulation Performance

Abstract The existence of openings affects the sound insulation performance of structures significantly. The determination of sound transmission through large rectangular openings is often time-consuming, because of the large number of modes, especially if there is a need to go to high frequencies. A model is proposed and detailed based on three-dimensional wave equations, the transfer matrix method, and modal superposition. The viscous and thermal boundary layer effects have been concerned; hence, the model accuracy for narrow slits was improved. The computational effort is significantly decreased by neglecting the cross-modal sound transmission. The accuracy of this model is validated by comparing it with the existing model, the measurement, and the acoustic finite element method. The study of sound transmission behavior of higher-order modes is performed. The modal sound transmission is predicted and compared for several modes. The phenomenon that is different from that of the plane wave situation is found and discussed.

Silencer for high-frequency turbocharger compressor noise via an acoustic straightener

2021 ◽  
Vol 263 (5) ◽  
pp. 1744-1755
Author(s):  
Pranav Sriganesh ◽  
Rick Dehner ◽  
Ahmet Selamet
Keyword(s):  
Wave Propagation ◽  
Plane Wave ◽  
High Frequency ◽  
Three Dimensional ◽  
Mean Flow ◽  
Analytical Treatment ◽  
Underlying Assumption ◽  
Wide Range ◽  
Plane Wave Propagation ◽  
Dimensional Wave

Decades of successful research and development on automotive silencers for engine breathing systems have brought about significant reductions in emitted engine noise. A majority of this research has pursued airborne noise at relatively low frequencies, which typically involve plane wave propagation. However, with the increasing demand for downsized turbocharged engines in passenger cars, high-frequency compressor noise has become a challenge in engine induction systems. Elevated frequencies promote multi-dimensional wave propagation rendering at times conventional silencer treatments ineffective due to the underlying assumption of one-dimensional wave propagation in their design. The present work focuses on developing a high-frequency silencer that targets tonal noise at the blade-pass frequency within the compressor inlet duct for a wide range of rotational speeds. The approach features a novel "acoustic straightener" that creates exclusive plane wave propagation near the silencing elements. An analytical treatment is combined with a three-dimensional acoustic finite element method to guide the early design process. The effects of mean flow and nonlinearities on acoustics are then captured by three-dimensional computational fluid dynamics simulations. The configuration developed by the current computational effort will set the stage for further refinement through future experiments.

Colloidal nanocrystal superlattices as phononic crystals: plane wave expansion modeling of phonon band structure

RSC Advances ◽  
2016 ◽  
Vol 6 (50) ◽  
pp. 44578-44587 ◽  
Author(s):  
Seid M. Sadat ◽  
Robert Y. Wang
Keyword(s):  
Band Structure ◽  
Plane Wave ◽  
High Frequency ◽  
Three Dimensional ◽  
Organic Matrix ◽  
Phononic Crystals ◽  
Periodic Array ◽  
Plane Wave Expansion ◽  
Phonon Band ◽  
Nanocrystal Superlattices

Colloidal nanocrystal superlattices are a natural platform for high frequency three-dimensional phononic crystals (~102 GHz) because they consist of a periodic array of hard nanoparticles in a soft organic matrix.

High Frequency (27.12 MHz) Activation of the Radical Curing of Unsaturated Polyesters in Styrene Solution

1996 ◽  
Vol 430 ◽  
Author(s):  
P. Alazard ◽  
A. Gourdenne
Keyword(s):  
Transition Temperature ◽  
Benzoyl Peroxide ◽  
High Frequency ◽  
Steel Plates ◽  
Crosslinking Reaction ◽  
High Frequencies ◽  
Unsaturated Polyesters ◽  
Radical Initiator ◽  
Electrical Voltage

AbstractThe crosslinking reaction of a divinylester resin of epoxy-acrylic type in styrene solution is activated by high frequencies at 27.12 MHz. The samples to be cured are positionned betweeen two parallel steel plates used as electrodes and an electrical voltage is applied. A parametrical study is described, where the applied electrical voltage, or power, and the concentration of benzoyl peroxide, which is the radical initiator, are taken into account. The optimization of the electromagnetic curing is performed through the determination of the glassy transition temperature of the final products.

scholarly journals Detection of clear sky instants from high frequencies pyranometric measurements of global horizontal irradiance

2021 ◽  
Vol 229 ◽  
pp. 01008
Author(s):  
Omaima El Alani ◽  
Hicham Ghennioui ◽  
Abdellatif Ghennioui ◽  
Fatima-ezzahra Dahr
Keyword(s):  
High Frequency ◽  
Resource Assessment ◽  
High Frequencies ◽  
Energy Field ◽  
Clear Sky ◽  
Stable Conditions ◽  
Soil Measurements ◽  
Solar Resource

Solar resource assessment by clear sky models is of great importance in the solar energy field: verifying the performance of photovoltaic systems during stable conditions, clouds effects evaluation, the determination of geographical areas where irradiation is more uncertain and the preparation of forecasts with sky cameras. But before using these models they must be validated against high performances soil measurements. Since there is no radiometric sensor that measures clear-sky radiation, then historical clear-sky time periods must be identified only from long-term allsky irradiation records. The contribution of this study is to exploit the ground measurements, analyze them and retrieve the information they contain concerning the clear sky instants. The study will be performed by comparing the clear sky instants identified by an algorithm proposed by Reno and Hansen with a physical clear sky model. This comparison is made using high frequency global horizontal irradiation (GHI) data from high performances meteorological station installed at Benguerir in Morocco.

scholarly journals Detection of clear sky instants from high frequencies pyranometric measurements of global horizontal irradiance

2021 ◽  
Vol 297 ◽  
pp. 01028
Author(s):  
Omaima El Alani ◽  
Hicham Ghennioui ◽  
Abdellatif Ghennioui ◽  
Fatima-ezzahra Dahr
Keyword(s):  
High Frequency ◽  
Resource Assessment ◽  
High Frequencies ◽  
Energy Field ◽  
Clear Sky ◽  
Stable Conditions ◽  
Soil Measurements ◽  
Solar Resource

Solar resource assessment by clear sky models is of great importance in the solar energy field: verifying the performance of photovoltaic systems during stable conditions, clouds effects evaluation, the determination of geographical areas where irradiation is more uncertain and the preparation of forecasts with sky cameras. But before using these models they must be validated against high performances soil measurements. Since there is no radiometric sensor that measures clear-sky radiation, then historical clear-sky time periods must be identified only from long-term all-sky irradiation records. The contribution of this study is to exploit the ground measurements, analyze them and retrieve the information they contain concerning the clear sky instants. The study will be performed by comparing the clear sky instants identified by an algorithm proposed by Reno and Hansen with a physical clear sky model. This comparison is made using high frequency global horizontal irradiation (GHI) data from high performances meteorological station installed at Benguerir in Morocco.

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