<p> In experimental microdosimetry one of the goals is to measure the absorbed dose in microscopic volumes of tissue. The traditional spherical tissue-equivalent proportional counter (TEPC) is the most common detector currently used for microdosimetry. A new microdosimetric detector based on a thick gas electron multiplier (THGEM) was developed. To investigate the feasibility of the THGEM type detector for microdosimetry, a prototype detector was designed and manufactured. The THGEM detector is robust, easy to manufacture and is cost effective. The THGEM foil is composed of a thin FR4-epoxy insulator coated with copper on both sides. The THGEM contains 32 holes each with a diameter of 0.35 mm and pitch of 0.64 mm. The sensitive volume of the detector is a right cylinder with a diameter of ~5 mm and height of ~5 mm and is located in the center of the detector. Systematic tests were conducted at the McMaster Accelerator Laboratory to investigate its overall performance. A neutron-gamma ray radiation field was generated using the 7Li(p,n) reaction. The detector was operated at low bias voltages initially to test the stability and then the relative multiplication gain was measured as a function of the operating high voltage. The detector performance was observed with different THGEM insulator thicknesses ranging from 0.12 mm to 1.48 mm. The multiplication gain was assessed and both neutron and gamma-ray radiation was detected by the THGEM detector. The spectra obtained with the THGEM detector were analyzed and compared to the data collected with the standard spherical TEPC. The investigations provided information about the THGEM detector operation for microdosimetry and the THGEM microdosimetric spectra observed are comparable to the standard TEPC data.</p> / Thesis / Doctor of Philosophy (PhD)

No description available.

A new beta-ray detector using the Thick Gas Electron Multiplier (THGEM) technology is presented. Traditional proportional counters have been considered the standard for many decades for radiation contamination monitoring. However, it has always been challenging to detect low energy beta-emitters such as 3H and 14C. In order to extend the low energy cut-off of these beta particles, it is important to keep the electron multiplication gain as high as possible. To accomplish this goal, we have developed a new gaseous beta-ray detector using THGEMs. Founded on previous THGEM avalanche simulations [1] and predecessor detectors, a novel prototype THGEM beta-ray detector was designed and fabricated. Its signal performance, effective gain and gain stability were comprehensively studied for single and double-THGEM configurations using an alpha source. The first time THGEM detector response to beta-rays was observed for various operating conditions and compared with Monte Carlo N-Particle Transport 6 (MCNP6) Monte Carlo simulations. / Thesis / Master of Science (MSc)

Nowadays, the apparent promise of Big Data is that of being able to understand in real-time people's behavior in their daily lives. However, as big as these data are, many useful variables describing the person's context (e.g., where she is, with whom she is, what she is doing, and her feelings and emotions) are still unavailable. Therefore, people are, at best, thinly described. A former solution is to collect Big Thick Data via blending techniques, combining sensor data sources with high-quality ethnographic data, to generate a dense representation of the person's context. As attractive as the proposal is, the approach is difficult to integrate into research paradigms dealing with Big Data, given the high cost of data collection, integration, and the expertise needed to manage them. Starting from a quantified approach to Big Thick Data, based on the notion of situational context, this thesis proposes a methodology, to design, collect, and prepare reliable and valid quantified Big Thick Data for the purposes of their reuse. Furthermore, the methodology is supported by a set of services to foster its replicability. The methodology has been applied in 4 case studies involving many domain experts and 10,000+ participants from 10 countries. The diverse applications of the methodology and the reuse of the data for multiple applications demonstrate its inner validity and reliability.

A new family of dielectric materials has been studied, individually as thick-film capacitors and as buried components incorporated in second-order lowpass and bandpass RC active filter circuits. The materials were electrically characterized in terms of the variation of dielectric constant and dissipation factor with frequency. The performance of the filter circuit is related to the characteristics of the dielectric materials. An analysis of the circuit is developed which accounts for the capacitor losses. / Master of Science

This work presents a method based on time domain techniques to characterize and model thick film inductor structures. The method is a time domain reflection (TOR) measurement which measures the input port's reflection transfer function of the component under test. The reflection from a short circuit is acquired as the reference waveform, while the reflection from the sample is acquired as the response waveform. From the information contained in both waveforms the complex impedance Z(jω) of the sample can be calculated. This information is used for modeling the inductor by fitting the data to a network model. This thesis also presents a technique for the modeling and the characterization of multilayer thick film inductors over the frequency range from DC to a few GHz. The modeling technique is based on the use of Time Domain Reflectometry (TDR) measurements to reveal the transmission structure equivalent network of the multilayer thick film inductor. The equivalent network model is then analyzed using a computer network analysis program to characterize the inductor performance. Other thick film inductor structures modeled in this work are: the spiral conductor is printed directly on the ceramic substrate, the spiral is printed on a ferrite layer, the spiral is printed on the substrate with the ferrite layer on top, and finally, two interconnected spiral layers sandwiching ferrite (or dielectric) layers. / M.S.

First described by physician William Dietz in 1995, the "Food Insecurity-Obesity Paradox" (FIOP) attempts to explain the biology and behaviors of people who are simultaneously overweight and food-insecure. I was introduced to this theory as a Behavioral Health graduate student and, in that context, was taught to understand it as a fact. My personal experiences as a Black woman, however, alongside ongoing engagement with Black feminist thought and critical medical sociology, have taught me otherwise. This disssertation takes Dietz's theory as a starting point in order to argue that Black women in the US experience fatphobic and racial discrimination while being "cared for" by western institutional medicine. I argue that discourses like the FIOP, though framed as benevolent clinical theories, do more harm than good: not only do they multiply pathologize so-called "fat" Black women by drawing on disparaging stereotypes, but they simultaneously ignore the specific health and wellness needs that emerge at the intersection of weight, size, skin color, gender, ability, and economic class. My broader dissertation project is an interdisciplinary critique of pathologizing discourses about Black women, including medically "legitimate" ones like the FIOP. Via critical analysis of these discourses, and employing Black feminist and medical sociological perspectives, I explore how stereotypes of Black women correlate with how these women are perceived and treated by physicians and other health professionals. These racialized perceptions and forms of discriminatory medical treatment are instances of what has been labeled, variously, as a racial formation (Omi and Winant, 1997), a matrix of domination (Patricia Hill Collins, 1990) and a racial ideology (Feagin, 2006). These processes are further extended by physicians who use these pathologizing discourses and practices to advance their own careers. Black feminist theorists have described the multiple marginalizations experienced by contemporary Black women in the US and my project places weight and body size within this marginalizing dynamic. After tracing the long history of medical "othering" of Black women by science, I show the persistence of these ideologies in contemporary medical practice. My interviews with Black women investigate their lived experiences of these ideologies and practices, and allow women to speak for themselves in a space that so often speaks for them. / Doctor of Philosophy / Black women's historical experiences in the US, including my own story, are akin to what Black feminist Melissa Harris-Perry in her book, Sister Citizen: Shame, Stereotypes, and Black Women in America (2011), calls the crooked room. Applying Harris-Perry's theorization of the crooked room to how medical institutions operate to cause Black thick women to be so quickly categorized as diseased, I have developed the concept of the Crooked Room of Medicine (CRoM) to describe the mental, emotional, and physical struggles Black women face at the intersection of race and gender stereotypes and false narratives particularly in medical settings. I utilize and build upon Black feminist theoretical frameworks as well as my own personal narrative to investigate how a society that is built on racialized and gendered systems has implications for how the large Black female body is interpreted as unhealthy and diseased when treated within these social and medical settings. Building on Tressie McMillan Cottom's scholarship, I utilize a methodology of what I call Thick Studies to develop a Gender Race Weight (GRW) matrix from the crooked room of medicine, to map out our experiences and develop a theory that focuses on healing. The result of Black women's disproportionately poor health outcomes is a result of a complex environment of barriers from quality health care, to racism, and stress correlated with the distinct social experiences of Black womanhood in U.S. society (Chinn. Martin, Redmond 2021). The heaviness of generational racialized trauma is still in our DNA (Degruy-Leary 2017). Racism and gender discrimination have profound impacts on the well-being of Black women. I argue for a holistic health treatment that addresses mind, body, emotion, and spirit and for an acknowledgement of Black women's knowledge of health and healing in relation to Black women, weight, and medical space.

Ceramic substrates play an important role in thick film hybrid microelectronic circuits. Existing substrates such as alumina and beryllia do not meet satisfactorily the desired requirements. The newly developed aluminum nitride (<i>AIN</i>) substrate shows a great deal of promise and potentially embraces the best qualities of alumina and beryllia. The objective of this dissertation is to study the electrical properties, thick film interaction, and environmental effects on <i>AIN</i> substrates, and also to examine the performance of this material for high power - high frequency hybrid thick film applications. In particular, wideband dielectric constant measurements of A1N and other ceramic substrates are performed, oxidization and humidity effects on surface properties of <i>AIN</i> are addressed, and short and long term aging effects on several circuit parameters are studied. To evaluate the performance of <i>AIN</i> in high power and high frequency applications, two circuits; an impulse generator and a power converter, are realized, tested and compared with those on alumina substrates. The thick film circuits realized on <i>AIN</i> perform considerably better than those on alumina. / Ph. D.

The initiation and propagation of adiabatic shear bands is analyzed numerically for an impulsively loaded thick-walled steel tube. A circumferential V-notch located at the outer surface of the center of the tube provides a stress concentration. The material is modeled as strain hardening, strain-rate hardening and thermal softening. The dynamic loading conditions considered are pure torsion, axial pressure combined with torsion, and internal pressure combined with torsion. Because of the stress concentration, a shear band will first initiate in an element adjoining the notch tip and propagate radially inwards through the thickness of the tube. The speed of propagation and the amount of energy required to drive a shear band through the material are calculated. The effects of the pressure preload and the depth of the notch are studied. Also, the influence of thermal softening is investigated by modeling it after a relation proposed by Zhou et al. <i>[Vita removed July 18, 2008 CK/GMc 2/2/2012]<i> / Master of Science

This dissertation presents methods for wideband characterization and modeling of magnetic materials and structures over a wide frequency range (dc to a few GHz). A method for modeling the thick film inductor structures at high frequencies is presented in this dissertation. The thick film inductor under test is printed and located in shunt connection at the end of a reference transmission line. Time Domain Reflectometry (TDR) technique is used to measure the response waveform from the inductor under test. The response from a short circuit at the location of the inductor is acquired as the reference waveform. The two acquired waveforms are then transformed into the frequency domain using the Fast Fourier Transform algorithm (FFT). The reflection coefficient is then computed as the ratio between the Fourier Transforms of the response and reference waveforms. From the information contained, the complex impedance of the structure under study can be calculated. This information is used for modeling that structure by fitting the data to the network model using the computer network analysis program. Experimental and simulated response waveforms are compared and brought to a close match by changing the model components values. A cavity-like sample holder filled with ferrite material ls proposed in this dissertation to measure the complex permeability of the magnetic material filling this cavity. The cavity walls are deposited on a coaxially shaped sample using thick film techniques. The reflection coefficient from the cavity under study is measured by adapting the cavity to the end of a transmission line. The full field analysis of this proposed configuration is used to determine a relationship between the complex permeability of the ferrite material and the measured reflection coefficient. The method of moments ls used to achieve this task. Computer simulation experiments are performed to test the sensitivity of the technique and to predict the performance over the desired frequency range. Actual experimentation as well as verifications of these measurements are conducted to verify the merit of the proposed technique. / Ph. D. / incomplete_metadata