Morphology of Thin Sheets in the Lame Setup and Beyond

We present a general analytical approach to study the wrinkling phenomena in the Lame, sheet on drop, drop on sheet, and twisted ribbon setups. In the partially single-mode wrinkle pattern, we employ the boundary layer analysis to regularize the divergence in the energy and obtain the optimal wavenumber. In the multi-mode wrinkle pattern scenario, we consider the effects of the boundary condition, meniscus, and the geometry of the setup separately on the energies and obtain scaling results for the wavenumber of the multi-mode pattern due to each effect. Lastly, a wrinkle-to-fold transition is discussed in the Lame setup, with our main finding that this transition is triggered by geometry of the annulus alone which minimizes the surface energ

The Development and Application of Rhodamine-Based Fluorescent Sensors

Fluorescent sensors are a very promising method for the elucidation of pathologically relevant analytes in complex cellular environments, enabling a deeper understanding of the processes behind health and disease. Rhodamines are highly favorable fluorophores for fluorescent sensors due to their excellent photophysical properties. In this work, several rhodamine-based fluorescent sensors applying sulfur-containing recognition groups have been designed and synthesized. Platinum-based chemotherapeutics have long been successfully used in the clinic for cancer treatment. Fluorescent sensors for platinum drugs and their metabolites are urgently required. Chapter Two describes work towards a rhodamine-based fluorescent sensor, which can selectively respond to Pt(Cl)2(H2O)2, a key metabolite of platinum- based drugs in aqueous environments. While Fenton chemistry has long been known to play a role in inducing cellular stress, the roles that Fenton chemistry plays in pathological processes remain unclear. Chapter Three presents a rhodamine-based fluorescent sensor, RTFt1, which applies both recognition and reactivity strategies to sense the Fenton reactants. The utility of RTFt1 in sensing the Fenton chemistry accompanies ferroptosis and cisplatin-induced cytotoxicity was also demonstrated. Hypochlorous acid is one of the most important ROS, with significant roles in both health and disease. Chapter Four describes investigations of an analogue of RTFt1, RTFt-dimer, that was found to give a selective turn-on response to HOCl. RTFt-dimer was applied to investigations of HOCl in cellular environments, demonstrating that it could be further used to understand HOCl-related biological processes. Considering their versatile application and the diverse sensing strategies by which they can operate, this work confirms that rhodamine-based fluorescent sensors are a powerful tool, and are expected to uncover a greater understanding of biology

The semi-analytical method for damping of tubular transition layer damping structure

To solve the limited vibration consumption of the traditional tubular damping structure (TTDS), the tubular transition layer damping structure (TTLDS) is proposed; Based on viscoelastic materials and theories of thin cylindrical shells, the governing equation, the first order matrix differential equation describing vibration of TTLDS under harmonic excitation, is derived by considering the interaction between all layers and the dissipation caused by the shear deformation for transition layer and damping layer. By using the extended homogeneous capacity precision integration method to solve the control equation, a semi-analytical method for studying the vibration and damping characteristics of TTLDS is given. By way of comparison, the correctness of the method provided in paper is verified. At last, the influence of thickness, material and location of transition layer on damping effect is analyzed. The results show that the change for the thickness or material of the transition layer can make the structural damping effect change greatly, while the change for location of the transition layer plays only a few roles on the structural damping effect

Sparse decomposition based on ADMM dictionary learning for fault feature extraction of rolling element bearing

Sparse decomposition is a novel method for the fault diagnosis of rolling element bearing, whether the construction of dictionary model is good or not will directly affect the results of sparse decomposition. In order to effectively extract the fault characteristics of rolling element bearing, a sparse decomposition method based on the over-complete dictionary learning of alternating direction method of multipliers (ADMM) is presented in this paper. In the process of dictionary learning, ADMM is used to update the atoms of the dictionary. Compared with the K-SVD dictionary learning and non-learning dictionary method, the learned ADMM dictionary has a better structure and faster speed in the sparse decomposition. The ADMM dictionary learning method combined with the orthogonal matching pursuit (OMP) is used to implement the sparse decomposition of the vibration signal. The envelope spectrum technique is used to analyze the results of the sparse decomposition for the fault feature extraction of the rolling element bearing. The experimental results show that the ADMM dictionary learning method can updates the dictionary atoms to better fit the original signal data than K-SVD dictionary learning, the high frequency noise in the vibration signal of the rolling bearing can be effectively suppressed, and the fault characteristic frequency can be highlighted, which is very favorable for the fault diagnosis of the rolling element bearing

Characterization of four vaccine-related polioviruses including two intertypic type 3/type 2 recombinants associated with aseptic encephalitis

Temperature sensitivity of 4 poliovirus type 3 isolates. (DOC 31 kb

Geometry-driven folding of a floating annular sheet

Predicting the large-amplitude deformations of thin elastic sheets is difficult due to the complications of self contact, geometric nonlinearities, and a multitude of low-lying energy states. We study a simple twodimensional setting where an annular polymer sheet floating on an air-water interface is subjected to different tensions on the inner and outer rims. The sheet folds and wrinkles into many distinct morphologies that break axisymmetry. These states can be understood within a recent geometric approach for determining the gross shape of extremely bendable yet inextensible sheets by extremizing an appropriate area functional. Our analysis explains the remarkable feature that the observed buckling transitions between wrinkled and folded shapes are insensitive to the bending rigidity of the sheet

Geometry-driven folding of a floating annular sheet

Predicting the large-amplitude deformations of thin elastic sheets is difficult due to the complications of self contact, geometric nonlinearities, and a multitude of low-lying energy states. We study a simple twodimensional setting where an annular polymer sheet floating on an air-water interface is subjected to different tensions on the inner and outer rims. The sheet folds and wrinkles into many distinct morphologies that break axisymmetry. These states can be understood within a recent geometric approach for determining the gross shape of extremely bendable yet inextensible sheets by extremizing an appropriate area functional. Our analysis explains the remarkable feature that the observed buckling transitions between wrinkled and folded shapes are insensitive to the bending rigidity of the sheet

A comparative analysis of numerical approaches to the mechanics of elastic sheets

Numerically simulating deformations in thin elastic sheets is a challenging problem in computational mechanics due to destabilizing compressive stresses that result in wrinkling. Determining the location, structure, and evolution of wrinkles in these problems has important implications in design and is an area of increasing interest in the fields of physics and engineering. In this work, several numerical approaches previously proposed to model equilibrium deformations in thin elastic sheets are compared. These include standard finite element-based static post-buckling approaches as well as a recently proposed method based on dynamic relaxation, which are applied to the problem of an annular sheet with opposed tractions where wrinkling is a key feature. Numerical solutions are compared to analytic predictions of the ground state, enabling a quantitative evaluation of the predictive power of the various methods. Results indicate that static finite element approaches produce local minima that are highly sensitive to initial imperfections, relying on a priori knowledge of the equilibrium wrinkling pattern to generate optimal results. In contrast, dynamic relaxation is much less sensitive to initial imperfections and can generate low-energy solutions for a wide variety of loading conditions without requiring knowledge of the equilibrium solution beforehand.Engineering and Applied Science