The single-degree-of-freedom (SDOF) system is the most widely used model for vibration isolation systems. The SDOF system is a simple but worthy model because it quantifies many results of an isolation system. For instance, a SDOF model predicts that the high frequency transmissibility increases when the isolator has passive damping although this does not occur for an isolator implementing active damping. A severe limitation of this system is that it cannot be used when the base and/or equipment are flexible. System flexibility has been considered in previous literature but the flexibility has always been approximated which leads to truncation errors. The analysis used in this work is more sophisticated in that it can model the system flexibility without the use of any approximations. Therefore, the true effects of system flexibility can be analyzed analytically. Current literature has not fully explored the choice of mount frequency or actuator placement for flexible systems either. It is commonly suggested that isolators should be designed with a low-frequency mount. That is, the isolator frequency should be much lower than any of the system frequencies. It is shown that these isolators tend to perform best in an overall sense; however, mount frequencies designed between system modes tend to have a coupling effect. That is, the lower frequencies have such a strong interaction between each other that when isolator damping is present, multiple system modes are attenuated. Also, when the base and equipment are flexible, isolator placement becomes a critical issue. For low-frequency mount designs, the first natural frequency can shift as much as 15.6% for various isolator placements. For a mid-frequency mount design, the shift of the first three modes can be as high as 34.9%, 26.6% and 11.3%, respectively, for varying isolator placements. NOTE: (03/2011) An updated copy of this ETD was added after there were patron reports of problems with the file. / Ph. D.

Thèse de doctorat : Génie civil : Villeurbanne, INSA : 2002. / Thèse : 2002ISAL0045. Titre provenant de l'écran-titre. Bibliogr. p.173-186.

An interrogation of male behavior in isolated masculine spaces through short stories, an essay, and chapters from a novel-in-progress.

Base isolated buildings are well known to provide enhanced performance due to minimized accelerations and decreased interstory drifts. However, the reduced demands are obtained at the expense of large displacements at the isolation layer. This study investigates an innovative system, termed ‘dual isolation’, which applies two layers of isolation, one at the base and one mid-story to resolve this issue. An analytical solution for the equation of motion of the proposed system is developed based on linear isolation theory. This creates a foundation to assess the behavior of various types of seismic protection systems and to select the damping, mass and frequency ratio that leads to an optimal dual isolation design. Time history responses of the dual isolation system with viscous damping are compared to those of a conventional isolation counterpart to examine the effectiveness of the system. The system reduces first floor displacements by 40% on average, while the roof displacement is increased by roughly 15%. This results in reduced design forces for the structure. In addition, accelerations, especially above the second isolation layer, are significantly decreased. By reducing story shears and accelerations, the dual isolation system limits damage to both structural and nonstructural systems and components, thereby increasing global system performance. / Thesis / Master of Applied Science (MASc)

Current rates of excessive alcohol use and abuse among young adults are recognized as a major problem by scholars across a wide variety of fields. Here, I take a social psychological approach to understanding why individuals drink to excess, examining the unique role that a specific form of social isolation called existential isolation (feeling alone in one’s experiences of the world; Yalom, 1980; Pinel, Long, Murdoch, & Helm, 2017) may play in predicting alcohol use and abuse. The relationship between existential isolation and alcohol use is explored using both correlational and cross-lagged designs. Results indicate that existential isolation predicts alcohol use above and beyond a more traditional measure of social isolation, though not in the hypothesized direction (i.e. social isolation is associated with more alcohol use, whereas existential isolation is associated with less). Further, negative emotional symptoms (depression, anxiety, and stress) and racial identity emerged as significant moderators of this effect. Exploratory analyses considering a reversal of the hypothesized causal direction (i.e. alcohol use now predicting feelings of existential isolation) revealed a significant two-way interaction between current and lifetime alcohol use and a significant three-way interaction between current alcohol use, desire for existential connection, and motivations to use alcohol for social purposes. Implications of these general findings are discussed, including that 1) they identify a seemingly positive outcome of drinking that may play a role in perpetuating problematic alcohol use, and 2) conversely, they may illustrate a “dark side of sobriety.” This research serves as a first step into distinguishing between aspects of social isolation in the realm of alcohol use and abuse. Future research is necessary in order to identify the mechanisms underlying this effect and inform the development of more effective alcohol-related interventions.

Thesis (B.A.)--Haverford College, Dept. of Psychology, 2009. / Includes bibliographical references.

Thesis (B.A.)--Haverford College, Dept. of Psychology, 2009. / Includes bibliographical references.

Combining shock and vibration isolation into a single isolation system package is explored through the use of an air spring in parallel with a controlled magnetorheological fluid damper. The benefits of combining shock and vibration isolation into a single package is discussed. Modeling and control issues are investigated and test and simulation results are discussed. It is shown that this hybrid isolation system provides significantly increased performance over current state-of-the-art passive systems. Also explored is the feasibility of scavenging and storing ambient shipboard vibration energy for use in powering the isolation system. To date the literature has not adequately explored the direct design of a combined shock and vibration isolation system. As shock and vibration isolation are typically conflicting goals, the traditional approach has been to design separate shock and vibration isolation systems and operate them in parallel. This approach invariably leads to compromises in terms of the performance of both systems. Additionally, while considerable research has been performed on magnetorheological fluids and devices based on these fluids, there has been little research performed on the use of these fluids in devices that are subjected to high velocities such as the velocity seen by a ship exposed to underwater near-miss explosive events. Also missing from the literature is any research involving the scavenging and storage of ambient shipboard vibration energy. While the focus of this work is on the use of this scavenged energy to power the subject isolation system, many other uses for this energy can be envisioned. Experimental and analytical results from this research clearly show the advantages of this hybrid isolation system. Drop tests show that inputs as great as 167 g's were reduced to 3.42 g's above mount at 1.11 inches of deflection using a Velocity Feedback controller suggested by the author. When contrasted with typical test results with similar inputs, the subject isolation system achieved reductions in above mount accelerations of 300% and reductions in mount deflections of 200% over current state-of-the-art passive shipboard isolation systems. Furthermore, simulations using a validated model of the isolation system suggest that this performance improvement can be achieved in multi-degree-of-freedom isolation systems as well. It was shown that above mount accelerations in the vertical and athwartship directions could be effectively limited to a predefined value, while achieving the absolute minimum mount defections, using an Acceleration Limiting Bang-Bang controller suggested by the author. Further experimentation suggests that the subject isolation system could be entirely self-powered from scavenged ambient shipboard vibration energy. An experiment using an energy scavenging and storage system consisting of a Piezoelectric Stack Generator and a bank of ultracapacitors showed that enough energy could be harvested to power the isolation system though several shock events. / Ph. D.

No description available.

No description available.