Indiana University-Purdue University Indianapolis (IUPUI) / In this dissertation, a beyond-CMOS approach to Static Random Access Memory (SRAM) design is investigated using exploratory transistors including Tunnel Field Effect Transistor (TFET), Carbon Nanotube Field Effect Transistor (CNFET) and Graphene NanoRibbon Field Effect Transistor (GNRFET). A Figure-of-Merit (FOM) based comparison of 6-transistor (6T) and a modified 8-transistor (8T) single-port SRAMs designed using exploratory devices, and contemporary devices such as a FinFET and a CMOS process, highlighted the performance benefits of GNRFETs and power benefits of TFETs. The results obtained from the this work show that GNRFET-based SRAM have very high performance with a worst-case memory access time of 27.7 ps for a 16x4-bit 4-word array of 256-bitcells. CNFET-based SRAM bitcell consume the lowest average power during read/write simulations at 3.84 uW, while TFET-based SRAM bitcell show the best overall average and static power consumption at 4.79 uW and 57.8 pW respectively. A comparison of these exploratory devices with FinFET and planar CMOS showed that FinFET-based SRAM bitcell consumed the lowest static power at 39.8 pW and CMOS-based SRAM had the best read, write and hold static noise margins at 201 mV, 438 mV and 413 mV respectively. Further, the modification of 8T-SRAMs via dual wordlines for individually controlling read and write operations for uni-directional transistors TFET and CNFET show improvement in read static noise margin (RSNM). In dual wordline CNFET 8T-SRAM, an RSNM improvement of approximately 23.6x from 6 mV to 142 mV was observed by suppressing the read wordline (RWL) from a nominal supply of 0.71 V down to 0.61 V. In dual wordline TFET 8T-SRAM, an RSNM improvement of approximately 16.2x from 5 mV to 81 mV was observed by suppressing the RWL from a nominal supply of 0.6 V down to 0.3 V. Next, the dissertation explores whether the robustness of SRAM arrays can be improved. Specifically, the robustness related to noise margin during the write operation was investigated by implementing a negative bitline (NBL) voltage scheme. NBL improves the write static noise margin (WSNM) of the SRAM bitcells in the row of the array to which the data is written during a write operation. However, this may cause degraded hold static noise margin (HSNM) of un-accessed cells in the array. Applying a negative wordline voltage (NWL) on un-accessed cells during NBL shows that the NWL can counter the degraded HSNM of un-accessed cells due to NBL. The scheme, titled as NBLWL, also allows the supply of a lower NBL, resulting in higher WSNM and write-ability benefits of accessed row. By applying a complementary negative wordline voltage to counter the half-select condition in columns, the WSNM of cells in accessed rows was boosted by 10.9% when compared to a work where no negative bitline was applied. In addition, the HSNM of un-accessed cells remain the same as in the case where no negative bitline was implemented. Essentially, a 10.9% boost in WSNM without any degradation of HSNM in un-accessed cells is observed. The dissertation also focuses on the impact of process-related variations in SRAM arrays to correlate and characterize silicon data to simulation data. This can help designers remove pessimistic margins that are placed on critical signals to account for expected process variation. Removing these pessimistic margins on critical data paths that dictate the memory access time results in performance benefits for the SRAM array. This is achieved via an in-situ silicon monitor titled SRAM process and ageing sensor (SPAS), which can be used for silicon and ageing characterization, and silicon debug. The SPAS scheme is based on a process variation tolerant technique called RAZOR that compares the data arriving on the output of the sense amplifiers during the read operation. This scheme can estimate the impact of process variation and ageing induced slow-down on critical path during read operation of an array with high accuracy. The estimation accuracy in a commercially available 65nm CMOS technology for a 16x16 array at TT, and global SS and FF corners at nominal supply and testing temperature were found to be 99.2%, 94.9% and 96.5% respectively. Finally, redundant columns, an architectural-level scheme for tolerating failing SRAM bitcells in arrays without compromising performance and yield, is studied. Redundant columns are extra columns that are programmed when bitcells in the regular columns of an array are slower or have higher leakage than expected post-silicon. The regular columns are often permanently disabled and remain unused for the chip lifetime once redundant columns are enabled. In the SRRC scheme proposed in this thesis, the regular columns are only temporarily disabled, and re-used at a later time in chip life cycle once the previously awakened redundant columns become slower than the disabled regular columns. Essentially, the scheme can identify and temporarily disable the slowest column in an array until other mitigating factors slow down active columns. This allows the array to operate at a memory access time closer to the target access time regardless of other mitigating factors slowing down bitcells in arrays during chip life cycle. An approximate 76.4% reduction in memory access time was observed from a 16x16 array from simulations in a commercially available 65nm CMOS technology with respect to a work where no redundancy was employed.

Unmanned Aircraft Systems (UAS) face one common challenge when integrating with the existing manned aircraft population in the National Airspace System (NAS). To unlock the full efficiency of UAS, the UAS integrator must comply with an onboard pilot’s requirement to see-and-avoid other aircraft while operating. Commercially available Detect-and-Avoid (DAA) sensor technologies have been developed to attempt to comply with this requirement. UAS integrators must use these sensors to meet or exceed the performance of a human pilot. This thesis covers research done to integrate an array of commercially made DAA sensors with a large Group 3 UAS both in hardware and software that was later flight tested and evaluated for usability. A fast-time simulation is presented using the principles of the National Aeronautics and Space Administration's (NASA) Detect-and-AvoID Alerting Logic for Unmanned Systems (DAIDALUS). Last, open-source tools are presented to assist future integrators in validating their DAA solutions.

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Everything that humans have ever touched, created or built something from consists of a type of matter that only makes up 15 percent of the total matter in the universe. The remaining 85 percent is attributed to dark matter, a so far not discovered and non-luminous type of matter. In this thesis a potential dark matter particle candidate has been studied by investigating an extension of the SU(2) symmetry into a dark gauge sector, where the new sector is connected to the standard model through a vector-like fermion portal. In order to understand how such an extension is made, the Lagrangian density of the standard model and its different gauge sectors were derived. The cross sections of the process of pair production of dark matter particles and tau leptons in the final state due to proton-proton collisions at the LHC was simulated with the software \texttt{MadGraph}. The cross sections were used to draw significance contours for the exclusion and discovery regions for parts of the parameter space of the new model, for current and projected luminosities of the LHC. The projected luminosity scans also consider how lowering the uncertainty in the number of background events through hypothetical improvements to detectors would impact the exclusion and discovery contours. The significance contours were combined with relic density constraints, derived from comparisons between measurements of the Planck telescope and calculations from the software \texttt{MicrOMEGAs}. The resulting graphs show that there are non-forbidden regions of the parameter space that are significant for exclusion and discovery for luminosity of current searches. Increasing the luminosity while keeping the uncertainty in the number of background events the same yielded only minor increases to the exclusion and discovery contours. Combining the projected luminosities with improvements to the background uncertainty instead produced exclusion and discovery regions that were significantly larger than those for the current luminosity.

This study examined the demographic characteristics and education-related experiences of adults age 50 and beyond enrolled in graduate degree programs on the academic campus of Virginia Commonwealth University. The major focus for this study was to identify and examine the experiences of adults age 50 and older enrolled in graduate degree programs. The population for the study included 113 adults age 50 and older who were enrolled in graduate degree programs on the academic campus of Virginia Commonwealth University between fall 1995 and fall 1996. Surveys were mailed to these potential participants with a total of96 individuals responding. A focus group interview was also conducted in the fall semester of 1996 to gain further insight regarding their experiences; the respondents were eager to share their responses during this session. The findings in this study revealed that older adults in graduate degree programs at Virginia Commonwealth University were between the ages of 50 to 62, were more often married than not, had no children under the age of eighteen in the household, and most completed their last degree in 1979. The results of the survey revealed that most of the adults did not have negative feelings about their experiences. Overall, these students felt very positive about their educational-related experiences. There were, however, several administrative concerns associated with the selected demographics of gender, occupation, income, marital status, age and major field of study, and .the education-related experiences of these adults. While most respondents agreed that it was very difficult to maintain their family, work and personal life while earning this degree, they were overall satisfied with their experiences and felt challenged even though their socializing time was significantly reduced. The respondents were not as satisfied with the administration and staff because they were not available for support after work hours when they had concerns that needed addressing. They also felt their classrooms were not adequately prepared to accommodate the older learners, especially in regard to having appropriate visual equipment and adequately designed desks for older students. The data obtained will be useful to Virginia Commonwealth University in making decisions relative to improving existing services, developing innovative programs, designing policies and procedures that will improve recruitment, retention, and completion of adults age 50 and beyond in graduate programs. Further study is needed from this population of students to ascertain whether there are additional experiences that should be examined and explored. A replication of the study may reveal additional information not addressed in this study. / Ph. D.

Local governments during the past few years have been increasingly hard-pressed to make ends meet. Fiscally conservative times are now a political reality with which all of government must learn to cope. Many local officials have responded to this problem by introducing some new and innovative management techniques. But despite its potential economic and political advantages, interlocal cooperation has not received adequate attention as a cutback management technique. This study is therefore designed to increase our understanding of interlocal cooperation by: (1) updating the information currently in existence on interlocal cooperation in the state of Virginia; (2) analyzing, evaluating and describing the administrative processes and structures of illustrative examples of interlocal cooperation in the state; and (3) assessing the relationship between interlocal cooperation and various political, social, economic and demographic characteristics of the state’s political subdivisions. The methodology used in this study includes: (1) state-wide mail survey, (2) data analysis, (3) examination of illustrative examples of interlocal cooperation, and (4) literature review. Major research findings were: 1. There appears to be a relationship between population size, population growth, education, median household incomes, per capita income and per capita market values of real estate and interlocal cooperation in the State of Virginia, but the relationship is very weak indeed. 2. There is no appreciable differentiation by local governmental units in Virginia with regard to interlocal cooperation. 3. There is no appreciable difference between metropolitan and non-metropolitan jurisdictions in Virginia with regard to interlocal cooperation. 4. Virginia cities tend to use written agreement and contract more often than do either counties or towns. Counties are more apt to use contributions of cash and/or other resources than are either cities or towns. Towns, more often than cities or counties use unwritten/informal agreement. 5. Metropolitan jurisdictions used written agreement and contract more often than any other form of interlocal agreement. Non-metropolitan localities were found to use unwritten/informal agreement most often. 6. Virginia cities tend to cooperate more in the functional area of health and welfare, while towns form more agreements in the areas of administration and public safety. 7. There is more interlocal cooperation between counties and towns than between any other combinations of governmental units in the state. 8. Virginia counties and towns participate more often in interlocal agreement than do cities. 9. An overwhelming majority of local officials in the state considered economies of scale to be the major driving force behind their communities’ interlocal agreement. 10. Surprisingly, fear of annexation was not considered by Virginia local officials as the major reason for their communities’ reluctance to enter into interlocal cooperation. 11. In the state of Virginia, joint operation occurs more frequently in those public services requiring large capital outlays. / Ph. D.

This paper examines peri-urban space existing separate from the urban fabric and often in between urban and rural landscapes. This is a largely neglected area and often considered by each side as belonging to the other. Contemporary studies identify two sides associated with the rural-urban fringe: the expanding built settlements and ebbing countryside, ignoring significance and the circumstance of the spaces. The peri-urban fringe is a planning opportunity, which provides services beyond simple human habitat or wasteland of undesirable function. Through this study I intend to present the peri-urban interface as an intricate element of the urban infrastructure. This paper examines a series of case studies, which display peri-urban land-use planning and design through established areas, boundaries, and buffers spanning North America, Western Europe and Australia. Each area is examined to determine scope, program, and ecological and social impacts. The data informs positive and negative impacts within the peri-urban area. The peri-urban fringe spaces take on many forms and functions. Successful sites enrich the associated urban communities, whereas unsuccessful sites, which often exist in conflict with abutting environments, reduce quality of life and essential ecological processes. The peri-urban interface varies with many scales and circumstances, which affect quality of life for the urban population. Planning in the PUI is essential in promoting healthy populations and ecologies. Scale, program and accessibility determine how effectiveness of a peri-urban interface. Through this study, I want to identify significant value of the peri-urban interface as an opportunity and asset for the urban landscape. / Master of Landscape Architecture