Fresh air ventilation openings or windows are essential to most buildings but the openings allow considerable portions of noise to be transmitted from the outdoor into the indoor environment. This project studies relevant theoretical models through accurate numerical solutions, and seeks better designs to gain extra noise attenuation through the openings. The spectral method of Chebyshev collocation and the corresponding technique of out-going wave boundary conditions, for both ducted and flanged opening, are developed as numerical tools and validated by analytical examples. After establishing the numerical tools, two prototype problems are studied. The first is one in which there is no special sound attenuation device. The configuration includes aperture of negligible thickness, aperture of finite thickness and aperture of semi-infinite length. The characteristics of the noise transmission through aperture of finite thickness are investigated with examples of sonic boom and traffic noise. The second prototype problem is the sound attenuation performance of side-branch design of the ducted opening. Side-branch configurations including porous material, single micro-perforated panel, double-layer micro-perforated panels, parallel micro-perforated panels and parallel micro-perforated panels with connected cavity are investigated. They are tested individually with parameters optimized for each of two examples of noise sources. The sound attenuation performances compared using appropriate subjective ratings of the noise sources. It is found that the parallel micro-perforated panels give the best performance for the sonic boom and the double-layer micro-perforated panels serve as the best substitute for the porous material with traffic noise source. Results from experiment are also presented to validate some numerical results. / published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

Self-control is arguably one of the most beneficial adaptations of the agentic self. It enables humans to alter spontaneous, impulsive responses in order to fit one’s goals and standards. Variations in self-control capacity are strong predictors of a wide array of individual and societal outcomes including psychological adjustment, academic achievement, physical health, financial condition, and criminality. In this respect, investigating how to prevent self-control failures is a promising way for psychologists to improve human well-being. To this end, it is important for researchers to understand why people fail to control themselves. The limited-energy model suggests that self-control behaviors draw on a limited, depletable internal resource. People will become more vulnerable to self-control failures if the internal energy is depleted by prior use. Research demonstrates that an initial volitional act would undermine subsequent self-control performance as if the initial exertion exhausts an internal resource that is required for all self-control behaviors. This phenomenon is known as ego-depletion. Although much research lends credence to the validity of the ego-depletion phenomenon, little is known about its underlying psychological mechanisms. To fill this research gap, the present research tested a self-efficacy account of ego-depletion, which suggests that reduction in self-efficacy mediates the effect of initial self-control exertion on subsequent performance. A series of four experiments were conducted to examine the self-efficacy account. Experiment 1 found that initial self-control exertion resulted in lower self-efficacy to regulate eating habits. Two subsequent experiments found that self-efficacy mediated the negative effect of initial self-control exertion on mental calculation performance under distraction (experiment 2) and persistence on anagrams (experiment 3). In experiment 4, self-efficacy explained how implicit theory of willpower moderated the ego-depletion effect. In particular, participants who believed that “willpower is unlimited” were less affected by ego-depletion because their self-efficacy did not decrease after initial exertion. Taken together, the current data suggest that self-efficacy is one of the cognitive processes underlying ego-depletion. Moreover, the current research distinguishes task-specific, prospective self-efficacy from other positive beliefs such as retrospective confidence of the initial task (experiment 2 and 4), outcome expectation (experiment 3) and general confidence in one’s ability (experiment 4). It shows that among these positive beliefs, only self-efficacy serves a mediation role in ego-depletion. The current findings not only enrich the self-efficacy theory by identifying a potential source of efficacy belief, but also contribute to a fuller mechanistic understanding of self-control failures. Implications for intervention and human agency are discussed. / published_or_final_version / Psychology / Doctoral / Doctor of Philosophy

With the development of the industry and the society, noise pollution becomes increasingly severe, especially in large cities. Generally, there are three major noise sources, namely industrial noise, traffic noise and community noise. In response, several measurements have been developed to achieve effective noise control. Examples of noise control methods are reduction of noise at source and abatement of noise during the transmission. Since noise sources are more difficult to control, and sometimes already fixed, noise control during sound transmission is more broadly applied. Traditional passive noise control techniques include Helmholtz resonators and noise absorption materials like felt, glass mineral. The sound absorption materials (SAM) are found to be efficient in attenuating noise in high frequency domain, but their performance at low frequencies is quite poor. On the other hand, the Helmholtz resonator works perfect at any target frequency but suffers from its narrow absorption bandwidth, so that it’s only effective within a limited frequency band. As an innovative solution to passive noise control problem, micro-perforated panel absorber (MPPA) has attracted great interest in recent years. It turns out to be a competitive alternative to sound absorption materials and Helmholtz resonator. The parallel and series arrangement of MPPAs backed with cavities of different depths allows them to obtain decent noise absorption performance over a relatively broad frequency range. However, the performance of MPPA is restricted by its volume, as large volume is demanded for decent low-frequency absorption, which is also the case for noise absorption materials. In this thesis, a potential way to improve the low-frequency performance of the MPPA without occupying extra volume is proposed and implemented to tests. The focus is the adjustment of speed of sound and it is beneficial in different applications such as the following. In low frequency noise control, the size of the absorber in at least one dimension is often related to the wavelength and it is often too long. With a reduced speed of sound one can reduce this size while keeping the overall volume constant. Along this line of thinking, the effect of cavity configuration on its acoustic properties is investigated by two steps. Firstly, the property of a waveguide consisting of several identical elements is studied. The number of element is chosen to magnify the effect of the configuration. It turns out the irregularity of the duct shape can slow down the speed of sound of the plane wave by increasing the acoustic mass. Secondly, the absorption performance of an MPPA backed with an irregular cavity is evaluated. The shape of the cavity is the same as the element in the first step. In advance, the parallel arrangement of two MPPAs backed with irregular cavities is investigated, in order to look into the effect of cavity shape on inter-resonator interaction. The final results indicate that cavity design is an effective method to enhance the noise absorption performance of the MPPA arrays in the low-frequency domain. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

The fundamental problem of managing an inventory over time in the presence of stochastic demand is one of the core problems of operations research. This thesis is motivated by the need (in both government and industry) to understand such complex inventory systems used to model many of society's most important problems. In particular, we investigate simple, efficient and robust inventory policies for several fundamental models commonly used in the study of stochastic inventory systems. Some of these policies have been already implemented in practice and we provide strong theoretic support for their practical utilization in industry. Furthermore, the results on the performance of these policies often yield a rule-of-thumb that is applicable in a variety of settings.

published_or_final_version / abstract / toc / Mathematics / Doctoral / Doctor of Philosophy

published_or_final_version / Industrial Engineering / Master / Master of Philosophy

published_or_final_version / Mathematics / Master / Master of Philosophy

No description available.

This thesis develops the theoretical construct of "relatedness." Relatedness is defined as a sense of connectedness or meaning which provides for acceptance and serenity in the face of "the things I cannot change" and is an empirical extension of the work of Victor Frankl in Man's Search for Meaning. To examine the possible interaction between locus of control and an hypothesized "relatedness" phenomenon, four hundred forty four students of introductory psychology at the University of Arizona were given the Rotter Social Reaction Inventory and the Antonovsky Sense of Coherence Scale. A subscale measuring relatedness was constructed by factor analysis of Rotter and Antonovsky items combined. Five subscales of the Rotter were identified by factor analysis. Correlation was performed between the Relatedness subscale and the Rotter and its various subscales. Regression procedures were applied using Relatedness and Sex as independent variables and the Rotter as the dependent variable.

No description available.