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Vertical Acoustic Propagation in the Non-Homogeneous Layered Atmosphere for a Time-Harmonic, Compact Source
Get PDFIn this work we study vertical, acoustic propagation in a non-homogeneous media for a spatially-compact, time-harmonic source. An analytical, 2-layer model is developed representing the acoustic pressure disturbance propagating in the atmosphere. The validity of the model spans the distance from the Earth\u27s surface to 30,000 meters. This includes the troposphere (adiabatic), ozone layer (isothermal), and part of the stratosphere (isothermal). The results of the model derivation in the adiabatic region yield pressure solutions as Bessel functions of the First (J) and Second (Y) Kind of order with an argument of (where represents a dimensionless frequency and is a dimensionless vertical height in z (vertical coordinate)). For an added second layer (isothermal region), the pressure solution is a decaying sinusoidal, exponential function above the first layer.
In particular, the vertical, acoustic propagation is examined for various configurations. These are divided into 2 basic classes. The first class consists of examining the pressure response function when the source is located on boundary interfaces, while the second class consists of situations where the source is arbitrarily located within a finite layer. In all instances, a time-harmonic, compact source is implicitly understood. However, each class requires a different method of solution. The first class conforms to a general boundary value problem, while the second requires the use of Green\u27s functions method.
In investigating problems of the first class, 3 different scenarios are examined. In the first case, we apply our model to a semi-infinite medium with a time-harmonic source () located on the ground. In the next 2 cases, a semi-infinite medium is overlain on the previous medium at a height of z=13,000 meters. Thus, there exist two boundaries: the ground and the layer interface between the 2 media. Sources placed at these interfaces represent the 2nd and 3rd scenarios, respectively. The solutions to all 3 cases are of the form , where \textit{A} and \textit{B} are constants determined by the boundary conditions.
For the 2nd class, we examine the application to a time-harmonic, compact source placed arbitrarily within the 1st layer. The method of Green\u27s functions is used to obtain a particular solution for the model equations. This result is compared with a Fast Field Program (FFP) which was developed to test these solutions. The results show that the response given by the Green\u27s function compares favorably with that of the FFP.
Keywords: Linear Acoustics, Inhomogeneous Medium, Layered Atmosphere, Boundary Value Problem, Green\u27s Function Metho
Naholo
No full textA collection of photos from different ecosystems across Louisiana that express the death of the land through images of skeleton trees/plants, ghost swamps, and oil rigs in the Gulf
Human Serum Albumin Nanoparticles for the Treatment of Hepatocellular Carcinoma
Get PDFHepatocellular carcinoma (HCC) is an aggressive and destructive cancer of the liver. Currently available treatment plans are locoregional therapies aimed to decrease tumor burden, resection that surgically removes the tumor, or systemic therapies for advanced stage to extend survival. However, decompensation post-locoregional treatment and recurrence rates for HCC remain high despite the different treatment modalities. There is a great need for alternative and more effective treatment methods that will further dampen tumor burden while decreasing the risk of intra- and extrahepatic spread. The goal of this project was to develop a non-invasive therapeutic treatment to target HCC cells using human serum albumin particles (HSAPs).
In this study, nanoparticles were prepared using human serum albumin (HSA) and synthesized to house gold nanorods (AuNRs). The AuNR-HSAPs were incubated with hepatic cell lines under different stresses of chemotherapy drug, doxorubicin, with near-infrared laser irradiation. Metabolic activity and viability were determined via MTT assay and flow cytometry.
Particle uptake in HCC lines was confirmed. AuNRs were sufficient to cause metabolic stress and reduce viability by 10-25% in a cell line dependent manner. The combination of AuNRs and laser irradiation did not significantly impact viability that differed from AuNRs alone in any of the cell lines tested, doxorubicin doses chosen were aimed to decrease viability by 10%. The combination of AuNRs, laser irradiation, and doxorubicin provided the largest decrease in viability. However, it was not statistically significant from the control
Investigation on the Impacts of Vessel Flooding on Roll Motion
Get PDFThis thesis develops a method to analyze the roll response of a vessel during a damaged (flooded) scenario. This was done by developing a time-domain method in which the damaged compartment was flooding while the ship is simultaneously subjected to a seaway. The KRISO containership was used as a test hull and was subjected to three flooding conditions. These flooding conditions involved flooding Hold 5, Hold 3, and Hold 1 separately. Newmark’s Beta method for linear acceleration was used to solve the roll motion of equation in which the hydrodynamic coefficients A44, B44, and C44 were predetermined from linear strip theory for various drafts and trim angles. The roll response in the transient flooding state and the steady state, after flooding ceased (fully damaged state), while in wave action was simulated and plotted. The amplitudes from the initial and damaged steady states were recorded at the given wave frequency and wave amplitude, to generate the roll response amplitude operators for the vessel from wave frequency ω = 0.1 rad/s to ω = 2.1 rad/s. Analysis of the RAO curves revealed that the KRISO was not made significantly more unstable by the flooding, for the conditions that were considered, for nearly all wave frequencies except the natural frequency of 0.5 rad/s
Impact of Relative Liquidity of Stocks and Bonds on the Financing and Investment Decisions of a Firm
Get PDFThe dissertation consists of two essays. The first essay investigates if market illiquidity is a significant determinant of capital structure decisions. We hypothesize that firms would likely compare the illiquidity of two sources of external funding at a given point in time and issue the one with lower illiquidity. Therefore, if the level of illiquidity is a key driver of firms’ capital structure decisions in that year, the higher the level of stocks illiquidity, the more of its financing needs are satisfied by the issuance of debt, and the higher the level of bonds illiquidity, the less of its financing needs are satisfied by the issuance of debt. We find that illiquidity of the two sources of external funding affects significantly the capital structure decisions of U.S. firms over the sample period 2003-2018. Specifically, the coefficient of relative bonds illiquidity is negative, large, and strongly significant regardless of leverage measurement, and the coefficient of relative stocks illiquidity is positive, large, and strongly significant regardless of leverage measurement.
The second essay investigates if markets illiquidity is a significant determinant of investment decisions. We argue that an increase in investment opportunities due to an increase in bonds liquidity is for the decrease of the firm’s cost of capital and the decrease in its issuance cost. With a lower cost of capital and a higher ability to issue securities, firms are able to undertake more investment opportunities. We find that bonds and stocks illiquidity affect significantly the investment decisions of U.S. firms over the sample period 2003-2018. Specifically, the coefficients of bonds and stocks illiquidity are negative, large, and strongly significant regardless of investment measurement. Also, we find the effect of bonds illiquidity is more pronounced for financially constrained firms using different financial constraints measures
Crossroads and Crow Feathers
Get PDFThis thesis uses the short story form to examine the influence of myth, magick, and the supernatural on the interstitial areas of the United States. The power of words as a force for change figures prominently in these stories. This thesis looks at the monstrous as it moves in the darkness and in the minds of humans, but also at the tremendous depths of compassion and courage we find in ourselves when faced with monstrous situations
Inside the Black Box of Mentoring: African-American Adolescents, Youth Mentoring, and Stereotype Threat Conditions
Get PDFDespite a narrowing trend over the past forty years, the racial academic performance gap between non-Asian-American minority students and European-American students remains an overarching issue in K-12 schooling according to the Stanford Center for Education Policy Analysis (2017). Du Bois’s (1903) theory of double consciousness is implicated in the performance gap phenomenon. Though not explicitly connected, Steele and Aronson’s 1995 study revealed stereotype threat (STT) to be an empirical explanation of the negative impact of double consciousness. Steele et al.’s study revealed a psycho-social contributor to the racial academic performance gap, STT. STT is characterized by performance suppression caused by the fear of fulfilling a negative stereotype or the fear of being judged based on a negative stereotype attributed to one’s social identity group. The activation of this phenomenon is related to identity threatening cues, a systemic issue laden in the academic environment (Purdie-Vaughns, Steele, Davies, Ditlmann, & Crosby, 2008). To date, over 300 studies have been conducted on STT according to a meta-analysis conducted by Pennington, Heim, Levy, and Larkin (2016). Though certain experimental studies featuring mentoring as a vehicle for shifting stereotype narratives have yielded useful practices for STT reduction (Good et al., 2003), qualitative design, which is seldomly employed in the STT field, may produce an understanding of the phenomenon that is not possible through a deductive approach (Ezzy, 2002; van Kaam, 1966). The purpose of this phenomenological study was to explore African-American adolescent student perceptions of the impact that mentoring has on their schooling experiences while under STT conditions. The findings of this study demonstrated that African-American adolescents perceived mentoring to positively impact their schooling experiences and helped them to cope with STT activating cues in the environment. The participants discussed structural aspects of the relationships, personality attributes of the mentor, and specific mentor guidance. Participants also discussed a documented STT intervention that fell outside of the parameters of their mentoring relationships that positively impacted their schooling experiences and abilities to cope with STT cues – affirmations (Cohen, Garcia, Apfel, & Master, 2006; Walton et al., 2012). Recommendations for practice and future research are presented
Examining the Development of Career Identity within a College Preparatory School: A Case Study
Get PDFRecent college graduates are clearly facing significant labor market challenges and statistics show that college graduates will more likely find themselves unemployed or underemployed rather than gainfully employed in the current job market. The purpose of this study was to examine the career identity development of non-public high school seniors taking a career preparation program involving internships within all career pathways, not just those requiring a bachelor’s degree or higher. Individual interviews were conducted with ten students, the program director, and four site coordinators to gain the insight from their experiences with the career development course. Results from this study indicated that students experienced a high level of student engagement in the program, exposure to real-world experience in careers, and meaningful relationships with adults who participated in the program. Findings in this study also indicated how self-awareness and self-confidence gained from participating in the program lead to the development of a positive career identity. This study can be used to inform schools and school districts of the value of internships on the development of career identity