Reduced-Order Modeling of Mistuned Bladed Disks in Contact with Dry Friction Ring Dampers

Bladed disks (blisks) used in turbomachinery applications frequently operate under severe forcing conditions, which can lead to high levels of dynamics responses and pre-mature high cycle fatigue (HCF). Small blade-to-blade variations in structural properties, referred to as mistuning, result in strain energy localization, drastically amplifying blisk forced responses, and accelerate HCF. To quantitatively capture the effect of mistuning, it is necessary to develop efficient computational methods to predict the free and forced responses of blisks with various types of mistuning patterns. Due to the high geometric complexity of commercial blisks, full-order finite element (FE) blisk models contain many degrees of freedom (DOFs). Direct structural analyses with such FE models are computationally cumbersome or practically infeasible. Moreover, to prevent blisks from reaching HCF, frictional damping sources are introduced to dissipate vibrational energy and reduce the level of forced responses. Frictional damping is nonlinear in nature, and adds complexity into the blisk systems. Thus, robust and accurate reduced-order models must be developed to predict fast the dynamic responses of blisks with various mistuning and frictional damping sources. The main objective of this study is to develop a framework that involves several novel reduced-order modeling techniques. This framework is capable of efficiently and accurately capturing linear and nonlinear dynamic responses of blisks with small blade material variations, large changes in blisk mass, stiffness, and geometry, and dry friction ring dampers. Moreover, this framework serves as a powerful tool in designing friction dampers with optimal design parameters.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/137043/1/weihant_1.pd

Virtual prototyping with surface reconstruction and freeform geometric modeling using level-set method

More and more products with complex geometries are being designed and manufactured by computer aided design (CAD) and rapid prototyping (RP) technologies. Freeform surface is a geometrical feature widely used in modern products like car bodies, airfoils and turbine blades as well as in aesthetic artifacts. How to efficiently design and generate digital prototypes with freeform surfaces is an important issue in CAD. This paper presents the development of a Virtual Sculpting system and addresses the issues of surface reconstruction from dexel data structures and freeform geometric modeling using the level-set method from distance field structure. Our virtual sculpting method is based on the metaphor of carving a solid block into a 3D freeform object using a 3D haptic input device integrated with the computer visualization. This dissertation presents the result of the study and consists primarily of four papers --Abstract, page iv

IkamvaYouth

IkamvaYouth is a non-profit organization in South Africa that would benefit from a streamlined system that expedites registration and optimizes communication for volunteers and learners. IkamvaYouth currently has multiple mediums for registering users, which is hard to track and manage. Our solution is to make a product for volunteers and learners. The learners will be able to identify the nearest branch. The volunteers will be able to identify the nearest branch and register for a position at that branch. The primary considerations for an application in South Africa is that it is practical and usable. The solution provide is based on web technologies to deal with the devices in South Africa, particularly focusing on data usage. The final step of the project entails the deployment of the application by Global Social Benefit Fellowship students who will be implementing the application in South Africa with the organization

CFDP: Common Frequency Domain Pruning

As the saying goes, sometimes less is more -- and when it comes to neural networks, that couldn't be more true. Enter pruning, the art of selectively trimming away unnecessary parts of a network to create a more streamlined, efficient architecture. In this paper, we introduce a novel end-to-end pipeline for model pruning via the frequency domain. This work aims to shed light on the interoperability of intermediate model outputs and their significance beyond the spatial domain. Our method, dubbed Common Frequency Domain Pruning (CFDP) aims to extrapolate common frequency characteristics defined over the feature maps to rank the individual channels of a layer based on their level of importance in learning the representation. By harnessing the power of CFDP, we have achieved state-of-the-art results on CIFAR-10 with GoogLeNet reaching an accuracy of 95.25%, that is, +0.2% from the original model. We also outperform all benchmarks and match the original model's performance on ImageNet, using only 55% of the trainable parameters and 60% of the FLOPs. In addition to notable performances, models produced via CFDP exhibit robustness to a variety of configurations including pruning from untrained neural architectures, and resistance to adversarial attacks. The implementation code can be found at https://github.com/Skhaki18/CFDP.Comment: CVPR ECV 2023 Accepted Pape

Reflection Spectrum of Two Level Atoms by an Evanescent Laser Wave

An exact solution and numerical calculation of the reflection of two level atoms by atomic mirror are presented. The curve of reflection coefficient against Rabi frequency calculated shows some new features, and the physical machanism underlying is analyzed

The Dissipation in Laser and in Coherent State

The general process in lasers is defined in the photon number representation d rho(sub n)/dt = mu(sub 0)(u - mu(sub 1) u(exp 2) + mu(sub 2) u(exp 2) + mu(sub 3) u(exp 3)...)rho(sub n), where u is the matrix change operation u rho(sub n) = rho(sub n - 1) - rho(sub n), and mu(sub 1), mu(sub 2),...are the coefficients. In the same way as previous papers, we deduced the generating function G(sub 0)(z,t)