Scattering from Many Centers in One Dimension

1975 ◽  
Vol 53 (9) ◽  
pp. 874-881 ◽  
Author(s):  
K. K. Bajaj ◽  
Y. Nogami
Keyword(s):  
Cross Section ◽  
Forward Scattering ◽  
Scattering Cross Section ◽  
One Dimension ◽  
Laboratory System ◽  
Dimensional Model ◽  
One Dimensional ◽  
Scattering Cross ◽  
Low Energies ◽  
Nucleus Scattering

The accuracies of the fixed scatterer approximation (FSA) and the Glauber approximation (GA) are examined for an exactly soluble, one dimensional model which simulates nucleon–nucleus scattering. These approximations are found to work well at unexpectedly low energies. For example, the errors in the FSA and GA for the 'nucleon–deuteron' forward scattering cross section at 10 MeV (laboratory system) are only 5 and 7% respectively. The reason for this success is examined.

scholarly journals Post-flight analysis of detailed size distributions of warm cloud droplets, as determined in situ by cloud and aerosol spectrometers

2021 ◽  
Author(s):  
Sorin Nicolae Vâjâiac ◽  
Andreea Calcan ◽  
Robert Oscar David ◽  
Denisa-Elena Moacă ◽  
Gabriela Iorga ◽  
...  
Keyword(s):  
Cross Section ◽  
Forward Scattering ◽  
Scattering Cross Section ◽  
Size Distributions ◽  
Cloud Droplets ◽  
Cloud Particle ◽  
Fine Grid ◽  
Scattering Cross ◽  
Cloud Parameters

Abstract. Warm clouds, consisting of liquid cloud droplets, play an important role in modulating the amount of incoming solar radiation to Earth’s surface and thus, the climate. The size and number concentration of these cloud droplets control the reflectance of the cloud, the formation of precipitation and ultimately, the lifetime of the cloud. Therefore, in situ observations of the number and diameter of cloud droplets are frequently performed with cloud and aerosol spectrometers, which determine the optical diameters of cloud particles (in the range of up to a few tens of microns) by measuring their forward scattering cross sections in visible light and comparing these values with Mie-theoretical computations. The use of such instruments must rely on a fast working scheme consisting of a limited pre-defined uneven grid of cross section values that corresponds to a theoretically derived uneven set of size intervals (bins). However, as more detailed structural analyses of warm clouds are needed to improve future climate projects, we present a new numerical post-flight methodology using recorded particle-by-particle sample files. The Mie formalism produces a complicated relationship between a particle’s diameter and its forward scattering cross section. This relationship cannot be expressed in an analytically closed form and it should be numerically computed point by point, over a certain grid of diameter values. The optimal resolution required for constructing the diagram of this relationship is therefore analysed. Cloud particle statistics are further assessed using a fine grid of particle diameters in order to capture the finest details of the cloud particle size distributions. The possibility and the usefulness of using coarser size grids, with either uneven or equal intervals is also discussed. For coarse equidistant size grids, the general expressions of cloud microphysical parameters are calculated and the ensuing relative errors are discussed in detail. The proposed methodology is further applied to a subset of measured data and it is shown that the overall uncertainties in computing various cloud parameters are mainly driven by the measurement errors of the forward scattering cross section for each particle. Finally, the influence of the relatively large imprecision in the real and imaginary parts of the refractive index of cloud droplets on the size distributions and on the ensuing cloud parameters is analysed. It is concluded that, in the presence of high atmospheric loads of hydrophilic and light absorbing aerosols, such imprecisions may drastically affect the reliability of the cloud data obtained with cloud and aerosol spectrometers. Some complementary measurements for improving the quality of the cloud droplet size distributions obtained in post-flight analyses are suggested.

Design of Acoustic Cloak Using Generative Modeling and Gradient-Based Optimization

2021 ◽  
Vol 263 (3) ◽  
pp. 3511-3522
Author(s):  
Linwei Zhuo ◽  
Feruza Amirkulova
Keyword(s):  
Cross Section ◽  
Scattering Cross Section ◽  
Objective Functions ◽  
Total Scattering ◽  
One Dimensional ◽  
Scattering Cross ◽  
Generative Modeling ◽  
Wide Range ◽  
Total Scattering Cross Section ◽  
Gradient Based

Metamaterials are engineered composites that can achieved electromagnetic and mechanical properties that do not exist in natural materials by rearranging their structures. Due to the complexity of the objective functions, it is difficult to find the globally optimized solutions in metameterial design. This talk outlines a gradient-based optimization with generative networks that can search for the globally optimized cloaking devices over a wide range of parameters. The GLO-Net[1] model was developed originally for one-dimensional nano-photonic metagratings is generalized in this work to design two-dimensional broadband acoustic cloaking devices by perturbing positions of each scatterer in planar configuration of cylindrical scatterers. Such optimized cloaking devices can efficiently suppress the total scattering cross section to the minimum at certain parameters over range of wavenumbers. During training each iteration, a generative model generates a batch of metamaterials and compute the total scattering cross section and its gradients using an in-house built multiple scattering MATLAB solver. To evaluate our approach, we compare our obtained results with fmincon in MATLAB. Reference: [1] Jiaqi Jiang and Jonathan A. Fan. Simulator-based training of generative neural networks for the inverse design of metasurfaces. Nanophotonics, 9(5):1059-1069, nov 2019.

scholarly journals Elastic and Inelastic Alpha Transfer in the \(^{16}\)O+\(^{12}\)C Scattering

2021 ◽  
Vol 31 (4) ◽  
Author(s):  
Nguyen Tri Toan Phuc ◽  
Nguyen Hoang Phuc ◽  
Dao Tien Khoa
Keyword(s):  
Cross Section ◽  
Heavy Ion ◽  
Scattering Cross Section ◽  
Transition Strength ◽  
Valence Nucleon ◽  
The Core ◽  
Scattering Cross ◽  
Oscillatory Pattern ◽  
Low Energies ◽  
Reaction Channels

The elastic scattering cross section measured at energies \(E\lesssim 10\) MeV/nucleon for some light heavy-ion systems having two identical cores like \(^{16}\)O+\(^{12}\)C exhibits an enhanced oscillatory pattern at the backward angles. Such a pattern is known to be due to the transfer of the valence nucleon or cluster between the two identical cores. In particular, the elastic \(\alpha\) transfer has been shown to originate directly from the core-exchange symmetry in the elastic \(^{16}\)O+\(^{12}\)C scattering. Given the strong transition strength of the $2^+_1$ state of $^{12}$C and its large overlap with the $^{16}$O ground state, it is natural to expect a similar \(\alpha\) transfer process (or inelastic \(\alpha\) transfer) to take place in the inelastic \(^{16}\)O+\(^{12}\)C scattering. The present work provides a realistic coupled channel description of the \(\alpha\) transfer in the inelastic \(^{16}\)O+\(^{12}\)C scattering at low energies. Based on the results of the 4 coupled reaction-channels calculation, we show a significant contribution of the \(\alpha\) transfer to the inelastic \(^{16}\)O+\(^{12}\)C scattering cross section at the backward angles. These results suggest that the explicit coupling to the \(\alpha\) transfer channels is crucial in the studies of the elastic and inelastic scattering of a nucleus-nucleus system with the core-exchange symmetry.

scholarly journals Post-flight analysis of detailed size distributions of warm cloud droplets, as determined in situ by cloud and aerosol spectrometers

2021 ◽  
Vol 14 (10) ◽  
pp. 6777-6794
Author(s):  
Sorin Nicolae Vâjâiac ◽  
Andreea Calcan ◽  
Robert Oscar David ◽  
Denisa-Elena Moacă ◽  
Gabriela Iorga ◽  
...  
Keyword(s):  
Cross Section ◽  
Forward Scattering ◽  
Scattering Cross Section ◽  
Size Distributions ◽  
Cloud Droplets ◽  
Cloud Particle ◽  
Fine Grid ◽  
Scattering Cross ◽  
Cloud Parameters

Abstract. Warm clouds, consisting of liquid cloud droplets, play an important role in modulating the amount of incoming solar radiation to Earth's surface and thus the climate. The size and number concentration of these cloud droplets control the reflectance of the cloud, the formation of precipitation and ultimately the lifetime of the cloud. Therefore, in situ observations of the number and diameter of cloud droplets are frequently performed with cloud and aerosol spectrometers, which determine the optical diameters of cloud particles (in the range of up to a few tens of micrometers) by measuring their forward-scattering cross sections in visible light and comparing these values with Mie theoretical computations. The use of such instruments must rely on a fast working scheme consisting of a limited pre-defined uneven grid of cross section values that corresponds to a theoretically derived uneven set of size intervals (bins). However, as more detailed structural analyses of warm clouds are needed to improve future climate projects, we present a new numerical post-flight methodology using recorded particle-by-particle sample files. The Mie formalism produces a complicated relationship between a particle's diameter and its forward-scattering cross section. This relationship cannot be expressed in an analytically closed form, and it should be numerically computed point by point, over a certain grid of diameter values. The optimal resolution required for constructing the diagram of this relationship is therefore analyzed. Cloud particle statistics are further assessed using a fine grid of particle diameters in order to capture the finest details of the cloud particle size distributions. The possibility and the usefulness of using coarser size grids, with either uneven or equal intervals, is also discussed. For coarse equidistant size grids, the general expressions of cloud microphysical parameters are calculated and the ensuing relative errors are discussed in detail. The proposed methodology is further applied to a subset of measured data, and it is shown that the overall uncertainties in computing various cloud parameters are mainly driven by the measurement errors of the forward-scattering cross section for each particle. Finally, the influence of the relatively large imprecision in the real and imaginary parts of the refractive index of cloud droplets on the size distributions and on the ensuing cloud parameters is analyzed. It is concluded that, in the presence of high atmospheric loads of hydrophilic and light-absorbing aerosols, such imprecisions may drastically affect the reliability of the cloud data obtained with cloud and aerosol spectrometers. Some complementary measurements for improving the quality of the cloud droplet size distributions obtained in post-flight analyses are suggested.

Measurements of the π−p → π0n forward scattering cross section in the energy region 400–600 MeV

1978 ◽  
Vol 140 (2) ◽  
pp. 279-284 ◽  
Author(s):  
A.V. Kravtsov ◽  
L.A. Kuzmin ◽  
O.N. Nemozhenko ◽  
D.L. Nikolaev ◽  
T.S. Serebrova ◽  
...  
Keyword(s):  
Cross Section ◽  
Energy Region ◽  
Forward Scattering ◽  
Scattering Cross Section ◽  
Scattering Cross
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