Vibration problem of a spherical tank containing jet propellant: numerical simulations

This document is the final report on the joint research project on vibration problem of a spherical tank containing jet propellant between IHI, Japan and SES, University of Southampton, UK. The background of the project is described. The fundamental principles and numerical method used in numerical simulations are presented. The detailed FEA models for each studied cases are given. The calculation results are presented using tables, curves, figures as well as the attached data files. The available experiment results are listed to compare with the numerical calculations. The calculation results show a fundamental agreement with the experiment results. The numerical analysis confirms that:1)Due to water – tank interaction, the natural frequencies of the water – tank system are decreased with the water level increase. For the 25% water level, the natural frequencies, especially heave mode frequency, shows a significant decrease compared with the empty case. However, with continuing increase the filed water more than 25% level, the decrease gradient of the natural frequencies gradually tends to zero. In the 100% water case, the natural frequency of heave mode is about 200 Hz which can not equal zero.2)Considering free surface wave effect produces a lot of sloshing modes of very low frequencies compared with the natural frequencies of the dry tank structure. Therefore, for dynamic response analysis with high frequency excitations, the free surface wave may be neglected. However, to assess loads caused by sloshing modes, the free surface waves have to be considered.3)There exist relative big deformations at the four tank support places in several vibration modes, which may produce a large local stress at support places to cause the product fail in vibration environment. A strengthen local design at the support places is needed.4)The dynamic response results are affected by damping coefficients of all modes used in the dynamic response analysis. The damping coefficients are approximately presented and therefore, the numerical results are good reference for practical designs.The report confirms that the original purpose of this joint research project has well completed by IHI and SES

Recognizing basal cell carcinoma on smartphone‐captured digital histopathology images with a deep neural network

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154530/1/bjd18026.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154530/2/bjd18026_am.pd

A Green's function approach to transmission of massless Dirac fermions in graphene through an array of random scatterers

We consider the transmission of massless Dirac fermions through an array of short range scatterers which are modeled as randomly positioned $\delta$- function like potentials along the x-axis. We particularly discuss the interplay between disorder-induced localization that is the hallmark of a non-relativistic system and two important properties of such massless Dirac fermions, namely, complete transmission at normal incidence and periodic dependence of transmission coefficient on the strength of the barrier that leads to a periodic resonant transmission. This leads to two different types of conductance behavior as a function of the system size at the resonant and the off-resonance strengths of the delta function potential. We explain this behavior of the conductance in terms of the transmission through a pair of such barriers using a Green's function based approach. The method helps to understand such disordered transport in terms of well known optical phenomena such as Fabry Perot resonances.Comment: 22 double spaced single column pages. 15 .eps figure

Critical behavior of the two-dimensional N-component Landau-Ginzburg Hamiltonian with cubic anisotropy

We study the two-dimensional N-component Landau-Ginzburg Hamiltonian with cubic anisotropy. We compute and analyze the fixed-dimension perturbative expansion of the renormalization-group functions to four loops. The relations of these models with N-color Ashkin-Teller models, discrete cubic models, planar model with fourth order anisotropy, and structural phase transition in adsorbed monolayers are discussed. Our results for N=2 (XY model with cubic anisotropy) are compatible with the existence of a line of fixed points joining the Ising and the O(2) fixed points. Along this line the exponent $\eta$ has the constant value 1/4, while the exponent $\nu$ runs in a continuous and monotonic way from 1 to $\infty$ (from Ising to O(2)). For N\geq 3 we find a cubic fixed point in the region $u, v \geq 0$, which is marginally stable or unstable according to the sign of the perturbation. For the physical relevant case of N=3 we find the exponents $\eta=0.17(8)$ and $\nu=1.3(3)$ at the cubic transition.Comment: 14 pages, 9 figure

Quantifying atmospheric nitrogen deposition through a nationwide monitoring network across China

A Nationwide Nitrogen Deposition Monitoring Network (NNDMN) containing 43 monitoring sites was established in China to measure gaseous NH3, NO2, and HNO3 and particulate NH4+ and NO3− in air and/or precipitation from 2010 to 2014. Wet/bulk deposition fluxes of Nr species were collected by precipitation gauge method and measured by continuous-flow analyzer; dry deposition fluxes were estimated using airborne concentration measurements and inferential models. Our observations reveal large spatial variations of atmospheric Nr concentrations and dry and wet/bulk Nr deposition. On a national basis, the annual average concentrations (1.3–47.0 μg N m−3) and dry plus wet/bulk deposition fluxes (2.9–83.3 kg N ha−1 yr−1) of inorganic Nr species are ranked by land use as urban > rural > background sites and by regions as north China > southeast China > southwest China > northeast China > northwest China > Tibetan Plateau, reflecting the impact of anthropogenic Nr emission. Average dry and wet/bulk N deposition fluxes were 20.6 ± 11.2 (mean ± standard deviation) and 19.3 ± 9.2 kg N ha−1 yr−1 across China, with reduced N deposition dominating both dry and wet/bulk deposition. Our results suggest atmospheric dry N deposition is equally important to wet/bulk N deposition at the national scale. Therefore, both deposition forms should be included when considering the impacts of N deposition on environment and ecosystem health

A power flow mode theory based on a system's damping distribution and power flow design approaches

A power flow mode theory is developed to describe the natural power flow behaviour of a dynamic system based on its inherent damping distribution. The system's characteristic-damping matrix is constructed and it is shown that the eigenvalues and eigenvectors of this matrix identify natural power flow characteristics. These eigenvectors, or power flow mode vectors, are chosen as a set of base-vectors spanning the power flow space and completely describe the power flow in the system. The generalized coordinate of the velocity vector decomposed in this space defines the power flow response vector. A time-averaged power flow expression and theorems relating to its estimation are presented.Based on this theory, power flow design approaches are proposed to identify energy flow patterns satisfying vibration control requirements. The mode control factor defines the measure of the correlation between a power flow mode and a natural vibration mode of the system. Power flow design theorems are presented providing guidelines to construct damping distributions maximizing power dissipation or to suppress/retain a particular vibration mode and/or a motion.The developed damping-based power flow mode theory is compared with a mobility-based power flow model. It is shown that the proposed power flow model provides insight into the power flow dissipation mechanisms in dynamic systems.Examples are presented to demonstrate the applicability of the power flow mode theory and the power flow design approach. These examples demonstrate the generality of the theory, including non-symmetric damping matrices, and illustrate power flow design applications through modifications of the system's damping distribution using passive and/or active control components

A novel method for power flow design and control based on power flow mode theory

In a previous study, a generalized power flow mode theory was proposed to describe the power flow behaviour of a dynamical system based on the inherent characteristics of the system’s damping distribution. By extending this theory, a power flow design and control mathematical model is developed which allows control of energy flow patterns, thus reducing or retaining vibratory energy flow in a particular vibration mode of the system. This is achieved through analyzing energy flow characteristics and designing an appropriate damping distribution in the system to adjust its characteristic damping factors and power flow mode vectors. To meet different vibration control requirements, new design criteria are proposed so as to dissipate maximum vibration energy and/or to control power flow in a specific vibration mode of the system. This mathematical model is demonstrated through an example of a suspension system with two degrees of freedom for which the power flow dissipation corresponding to selected control cases are presented. This study provides a novel approach to design a dynamical system from the perspective of energy flow patterns

Power flow analysis for a floating sandwich raft isolation system using a higher-order theory

A higher-order sandwich theory is implemented in conjunction with an equivalent mobility-based power flow progressive method to determine power flow for a sandwich configured floating raft vibration isolation system. The power spectrum changes in whole frequency range effectively when core materials’ properties change. It is also shown that the loss factors of the sandwich configured floating raft influence the power flow transmitted to the foundation effectively in the medium- to high-frequency range and that the resonant peak cannot be avoided by increasing damping only in high-frequency ranges which is not found in floating raft isolation systems with isotropic beams

Power flow analysis for a floating sandwich raft isolation system using a higher-order theory

A higher-order sandwich theory is implemented in conjunction with an equivalent mobility-based power flow progressive method to determine power flow for a sandwich configured floating raft vibration isolation system. The power spectrum changes in whole frequency range effectively when core materials’ properties change. It is also shown that the loss factors of the sandwich configured floating raft influence the power flow transmitted to the foundation effectively in the medium- to high-frequency range and that the resonant peak cannot be avoided by increasing damping only in high-frequency ranges which is not found in floating raft isolation systems with isotropic beams