Snapping shrimp is the well-known source of biological sound in subtidal zone. Sounds were created by imploding a cavitation bubble which is generated under the tensile forces of the claw after a high-velocity water jet has been formed. The sounds of snapping shrimp is not only for attacking and defending, but also for communicating with each others. These sounds thus become the material of studying complex behavior arisen from interaction between individuals. This paper studies the change of fractal dimension of snapping shrimp¡¦s noises in different condition of environment. Sounds of snapping shrimp in Chigu lagoon and Tanshui estuary were recorded respectively. With the help of computer software to edit and calculate, the fractal dimension was taken as indicator for the complexity of communication. The behavior was assumed to be affected by many factors at the same time. Analysis of multiple regression with fractal dimension as dependent variables show that the fractal dimensions increased with night time, water temperature, and the ebb tide, but decrease with light intensity. Diurnal hour is the most significant factor in Chigu area. Analysis of Tanshui¡¦s data showed fractal dimension decrease with water depth.

Thesis (Ph. D.)--University of Minnesota, 1912. / "Reprinted from the American journal of anatomy, vol. 14. no. 2, January, 1913." "Literature cited": p. 163-164.

Crosslinked polymers or elastomers are examples of soft, synthetic material that can bend, crease, snap, wrinkle in response to external stimulus like pH, humidity, electric field or swelling. If a droplet of favorable solvent is placed on top of a thin, elastomer beam, it bends drastically to accommodate the excessive swelling stress. Keeping the solvent and its volume constant if we just increase the thickness of the beam, microscopic surface creases appear on the top surface. In this thesis, we experimentally characterize this transition between global bending to surface creasing. Closing of Venus flytrap leaves is a classic example of well known snap-through instability. A knowledge of the timescale of snapping is crucial in designing advanced functional materials. We perform the simplest experiment of poking an soft, elastomer arch at its apex till it snaps. Combining our experiments with analytical model we are able to predict the purely geometric nature of the snapping timescale. We also develop a simple scaling law that captures the dynamics of jumping toy poppers. / Master of Science

This work focuses on understanding deformation mechanisms and responsiveness associated with the wrinkling, folding, and snapping of thin polymer films. We demonstrated the use of elastic instabilities in confined regimes, such as the crumpling and snapping of surface attached sheets. We gained fundamental insight into a thin film's ability to localize strain. By taking advantage of geometric strain localization we were able to develop new strategies for responsive surfaces that will have a broad impact on adhesive, optical, and patterning applications. Using the rapid closure of the Venus flytrap's leafets as dictated by the onset of a snap instability as motivation, we created surfaces with patterned structures to transition through a snap instability at a prescribed stress state. This mechanism causes surface topography to change over large lateral length scales and very short timescales. Changes in the stress state can be related to triggers such as chemical swelling, light-induced architecture transitions, mechanical pressure, or voltage. The primary advantages of the snap transition are that the magnitude of change, the rate of change, and the sensitivity to change can be dictated by a balance of materials properties and geometry. The patterned structures that exhibit these dynamics are elastomeric shells that geometrically localize strain and can snap between concave and convex curvatures. We have demonstrated the control of the microlens shell geometry and that the transition time follows scaling relationships presented for the Venus flytrap. Furthermore, the microlens arrays have been demonstrated as surfaces that can alter wettability. Using a similar novel processing technique, microarrays of freestanding elastomeric plates were placed in equibiaxial compression to fabricate crumpled morphologies with strain localized regions that are difficult to attain through traditional patterning techniques. The microstructures that form can be initially described using classical plate buckling theory for circular plates under an applied compressive strain. Upon the application of increasing compressive strain, axisymmetric microstructures undergo a secondary bifurcation into highly curved, nonaxisymmetric structures. The inherent interplay between geometry and strain in these systems provides a mechanism for generating responsiveness in the structures. By swelling the elastomeric plates with a compatible solvent, we demonstrated the microstructures ability to reversibly switch between axisymmetric and nonaxisymmetric geometries. To further explore the localization of strain in materials, we have fabricated sharply folded films of glassy, homogenous polymers directly on rigid substrates. The films were uniaxially compressed and buckle after delaminating from the substrate. As the applied strain is increased, we observed strain localization at the center of the delaminated features. We found that normally brittle, polystyrene films can accommodate excessive compressive strains without fracture by undergoing these strain localizing fold events. This technique provided a unique way to examine the curvature and stability of folded features, but was not adequate for understanding the onset of folding. By taking thin films, either glassy or elastomeric, and simply lifting them from the surface of water, we observed and quantified the wrinkle-to-fold transition in an axisymmetric geometry. The films initially wrinkle as they are lifted with a wavelength that is determined by the film thickness and material properties. The wrinkle-to-fold transition is analogous to the transition observed in uniaxially compressed films, but the axisymmetric geometry caused the fold to act as a disclination that increased the radial stress in the film, thereby decreasing the wavelength of the remaining wrinkles. Further straining the films caused the remaining wrinkles to collapse into a discrete number of folds that is independent of film thickness and material properties.

Highly nonlinear structures exhibit complex responses to external loads, and often become unstable. In this thesis, I consider structures with either a nonlinear geometric response or material response. Geometrically nonlinear bistable shells have two stable configurations and can reversibly change between them via snap-through instabilities. This snap-through behavior can cause large geometric deformations in response to small changes in loading, and thus is ideal for designing various devices. For materially nonlinear structures, one recent focus is the potential to utilize granular jamming to construct structures. However, it is not yet fully understood how the stability of such nonlinear structures is governed by geometric and materials properties. This thesis aims to answer this question and propose design guidelines for engineering applications. This research will focus on the statics and dynamics of spherical shells, prestressed bistable shells and elastogranular columns. For spherical shells, we aim to find out under what geometric criteria can a shell be turned inside out, and as the shell goes through the snap-through instability, what dictates the shape and speed of it. Geometric criteria to predict whether a spherical shell is bistable or monostable is proposed based on precisely fabricated soft spherical shells. Point load indentation tests were performed to determine how stable a spherical shell is in its everted configuration. The results show a distinct difference between shallow shells and deep shells, which led to further studies on the snapping dynamics of spherical shells. High speed videos are recorded to track the motion of the apex of an everted spherical shell during its snap-through process, and we find that as the spherical shell goes from shallow to deep, the axisymmetric snapping will transform into asymmetric snapping. This change in snapping modes greatly affects the snapping dynamics of the everted spherical shells, and the shapes they adopt through the instability. Besides spherical shells, we also analyzed prestressed, bistable, cylindrical shells. Prestressed bistable shells fabricated by stretching and bonding multiple layers of elastomers can have various geometric shapes and can snap under external stimuli, but the governing parameters for the fabrication and snapping are not known yet. An analytical model was proposed based on non-Euclidean Plate Theory to predict the mean curvature of the prestressed shell, and the amount of stimulus that is needed to trigger the snapping. Numerical simulations are performed to compare with the analytical results. Based on the proposed theory, for given fabrication parameters and material properties, the final mean curvature of the bistable prestressed shell can be predicted accurately, as well as the amount of stretch that is needed to trigger snapping. This study can be used to design smart actuators or other soft, smart devices. To study material nonlinear structures, we use a mixture of grains and rods to enable the formation of stable structures via granular jamming. Understanding how these constituents govern the mechanical properties of the jammed structures is crucial for devising relevant engineering designs. We examine freestanding columns composed of rocks and string, and propose a simple physical model to explain the resulting structure’s mechanical behavior. The results indicate that exterior fiber mainly contributes to stiffness, while interior fiber increases the stored elastic energy and absorbed total energy of the structures under certain external load. By assembling the grains and strings in an engineer way, structures with robust mechanical properties can be formed. The results provide guidelines that allow the design of jammed elastogranular structures with desired mechanical properties. The research results of this thesis will open and guide a variety of possibilities in designing functional responsive devices or jamming structures.

Soft materials and compliant structures often undergo significant deformation without failure, a unique feature making them distinct from classical rigid materials. These substantial deformations provide a means for faster or more energy efficient deformations, which can be achieved by taking advantage of elastic instabilities. We intend to utilize structural instabilities to generate advanced functionality within soft materials. In particular, we use the buckling of thin, flexible plates to control or enhance the flow of fluid in a micro channel. The buckling deformation is created or altered via two different stimuli, first a mechanical strain and then an electrical signal. We investigate the behavior of each system under different conditions experimentally, numerically, or theoretically. We also show that the coupled interaction between fluid and the soft film plays a critical role in the shape of deformation and consequently in the functionality of the mechanism. We first embed a buckled thin film in a fluid channel within a soft device. By applying a mechanical strain to the device, we show both experimentally and numerically that the height of the buckled film changes accordingly as does the flow rate. We then offer an analytical solution by extending the classical lubrication theory to higher-order terms as a means to more accurately describe the flow in a channel with a buckled thin film, and in general, the flow in channels with any constrictions provided the Reynolds number is low. Next, we use an electrical signal to make a confined dielectric film undergo out-of-plane buckling deformation. The thin film is sandwiched between two flexible electrodes and the mechanism is implemented in a microfluidic device to pump the fluid into a micro channel. We show that the critical buckling voltage at which the thin film buckles out of the plane is mainly a function of voltage while the shape of deformation and so the functionality of this mechanism depend considerably on the applied boundary conditions. Finally, we enhance the fluid-soft structure response of the actuating mechanism by substituting flexible electrodes with fluid electrodes, resulting in a significant increase in the actuation frequency as well as a reduction in the critical buckling voltage. / Ph. D.

This study attempted to examine three aspects of Equus caballus foal snapping behavior. First, it suggested that the previous theoretical explanation for snapping established by behavioral researchers was incorrect. Second, as a means of suggesting an alternative hypothesis, this study proposed that snapping behavior could be a modified play response that was elicited when foals were confused by the complex social signals displayed by conspecifics. Finally, this project tested the aforementioned hypothesis by recording interactions between foals and conspecifics and analyzing the snapping intensity with each subject's previous level of social experience. There were two indicators utilized to establish social experience. First, the "age" of the foal was employed as a measure of overall life experience and development. Second, the number of hours per day the foal was exposed to conspecifics gave an effective measure of the amount of time the subject had an opportunity to learn the complex Equine visual communication (referred to as "out-time"). / Master of Science

Patent information can provide up-to-date technological data that accelerate the development of new products and the improvement of technology. They also can provide a most useful survey of known solution possibilities, which avoid duplication and the resources wasting. Therefore, this study focuses on the patent searching and analysis of the mechanical overload protection devices. Patent information are fed into computer databases and stored for design around activities. The connections between biology and technology be called as bionics or biomimetics can lead to very useful and novel technical solution. This study introduced special underwater creatures ¡§snapping shrimp¡¨ which have a large claw can generate the snapping action. This action inspires us to find a new technical solution that using the liquid cohesion to store and release the energy. In the end, using the patent information and the new solution to achieve the new design of mechanical overload protection devices, include ¡§Force-Type¡¨ and ¡§Torque-Type¡¨.

Local twitch responses (LTRs) can be elicited by snapping palpation of myofascial trigger points (TrP) or TrP injections. Objective: To characterize the LTR elicited by TrP injection and snapping palpation on surface electromyography (sEMG) in subjects with myofascial pain in 14 female subjects. Methods: Surface EMG electrodes were placed around the TrP and a control site on the trapezius muscle. Then the following protocol was carried out: tension and contraction of the ipsilateral trapezius muscle, baseline resting activity (five minutes), snapping palpation of the TrP and the control sites, TrP injection, and final resting activity (five minutes). The following data were recorded: pain ratings, areas of referred pain, presence of LTR, and sEMG recordings. Results: During the TrP injection, the investigator found LTRs in only 36% of the subjects, while 64% of the subjects reported that they felt the LTR, and the sEMG recorded only one LTR in one subject. Despite the low percentage of LTRs elicited clinically (36%), a large number of subjects (71%) reported more than 50% immediate reduction in pain intensity after the TrP injection. Conclusion: The sEMG is unable to register the LTR elicited by snapping palpation and TrP injection.

The conversion of natural habitat to urban areas has lasting impacts on wildlife and biodiversity. Known effects to urban wildlife include direct mortality while crossing roads, reduced species diversity, and habitat fragmentation and degradation. Among wildlife occupying urban areas, turtle populations can be particularly impacted in anthropogenic landscapes. Snapping Turtle (<i>Chelydra serpentina</i>) is one of the most common species found within urban wetlands, but populations are beginning to show declines in northern portions of their geographic range. The preservation and management of this species is aided by knowledge related to its spatial ecology. I investigated <i>C. serpentina</i> home range, movement, habitat use, and habitat selection in a midwestern USA urban wetland complex during two active seasons (May-August 2019 and 2020) using radiotelemetry. Home range sizes and movement did not differ between sex or sample year except the mean movement of males decreased from 2019 to 2020. No differences in mean monthly movement were found between sexes but mean monthly movement did differ between month and year. Habitat use was skewed during the active season and did not differ between sex or year, but there were positive habitat associations between forested wetlands and modal centers of activity (MCA). Habitat selection was tested at two spatial scales by comparing random points to home ranges and turtle locations using Euclidean Distance Analysis. Turtles appeared to select home ranges from available habitat site-wide but did not select habitat within home ranges. Home range selection included semi-permanent open water, trail, road/barrier, permanent open water, scrub-shrub, ditches, shoreline, and vegetated ponds, while upland forest, field and agriculture habitat were avoided. Home ranges appear to be constrained by available habitat and movement differences between years may be due to anthropogenic change in water levels. The use of space seems to be more affected by wetland size and connectivity than proximity to barriers, which suggests that management practices that protect turtles from accessing roads and railways will benefit populations. Additionally, habitat selection and association indicate that ditches are utilized as corridors between wetland areas. When feasible, increasing the connectivity of large wetlands containing many habitat types should have positive impacts on the persistence of populations in human dominated landscapes.