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- Genre: Masters Thesis
Description
The primary goal of this thesis is to evaluate the influence of ethyl vinyl acetate (EVA) and polyolefin elastomer (POE) encapsulant types on the glass-glass (GG) photovoltaic (PV) module reliability. The influence of these two encapsulant types on the reliability of GG modules was compared with baseline glass-polymer backsheet (GB) modules for a benchmarking purpose. Three sets of modules, with four modules in each set, were constructed with two substrates types i.e. glass-glass (GG) and glass- polymer backsheet (GB); and 2 encapsulants types i.e. ethyl vinyl acetate (EVA) and polyolefin elastomer (POE). Each module set was subjected to the following accelerated tests as specified in the International Electrotechnical Commission (IEC) standard and Qualification Plus protocol of NREL: Ultraviolet (UV) 250 kWh/m2; Thermal Cycling (TC) 200 cycles; Damp Heat (DH) 1250 hours. To identify the failure modes and reliability issues of the stressed modules, several module-level non-destructive characterizations were carried out and they include colorimetry, UV-Vis-NIR spectral reflectance, ultraviolet fluorescence (UVF) imaging, electroluminescence (EL) imaging, and infrared (IR) imaging. The above-mentioned characterizations were performed on the front side of the modules both before the stress tests (i.e. pre-stress) and after the stress tests (i.e. post-stress). The UV-250 extended stress results indicated slight changes in the reflectance on the non-cell area of EVA modules probably due to minor adhesion loss at the cell and module edges. From the DH-1250 extended stress tests, significant changes, in both encapsulant types modules, were observed in reflectance and UVF images indicating early stages of delamination. In the case of the TC-200 stress test, practically no changes were observed in all sets of modules. From the above short-term stress tests, it appears although not conclusive at this stage of the analysis, delamination seems to be the only failure mode that could possibly be affecting the module performance, as observed from UV and DH extended stress tests. All these stress tests need to be continued to identify the wear-out failure modes and their impacts on the performance parameters of PV modules.
ContributorsBhaskaran, Rahul (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Phelan, Patrick (Thesis advisor) / Wang, Liping (Committee member) / Arizona State University (Publisher)
Created2020
Description
Ecotourism is defined as a traveling distance where tourist interact with environment and enjoy nature. It is a market segment in the tourism sector that can provide several benefits if managed properly. Although ecotourism can provide economic benefits for Saudi Arabia, there is not enough attention granted to ecotourism facilities and services in desert sites. The current study attempts to fill this gap by aiming to explore families’ perceptions of environmental desert settings that support their ecotourism needs and to identify opportunities to develop services, expand activities areas, and infrastructures. Ultimately, this study addresses families’ ecotourism needs for the promotion of sustainable desert ecotourism development that is inclusive to most Saudi tourists. This study uses qualitative research methods, including observations, surveys and interviews of families who have visited Saudi Arabian deserts between December 2019 and March 2020. The findings are analyzed and translated into a set of design guidelines for existing and for new sustainable ecotourist sites within Saudi Arabian desert environments. The implications of this study are two-fold: to (1) educate the design industry to take into account ecotourism visitors’ perceptions of environmental settings and infrastructures needs without compromising its natural resources; and (2) highlight the value of sustainable ecotourism so that decision makers take an action to ensure stability of the growing market demand of desert tourism. This study concludes with a discussion of findings reached that can promote more sustainable ecotourism experiences at Saudi Arabian desert sites.
ContributorsAlfadhli, Amirah (Author) / Zingoni, Milagros MZ (Thesis advisor) / Brunner, Lori LB (Committee member) / Vogt, Christine CV (Committee member) / Arizona State University (Publisher)
Created2020
Description
Employee wellbeing is a top concern for many organizations as its been linked to job performance and organizational commitment (Colquit, LePine, & Wesson, 2019). Research suggests that overall wellbeing is important to employees as well. Organizations are significantly investing into upgrading workplace environments, and there is a need for a clear understanding of how those improvements truly impact employee wellbeing. Current workplace research reveals that the open-office floorplan accounts for more than 70% of office layouts in the United States and is most commonly used for the benefits of collaboration and efficiency (Gallup, 2017). However, the open office layout ranks poorly in current employee wellbeing studies with a number of office environment stressors such as noise, distractions, and privacy concerns noted to impact employee wellbeing (C. Bodin-Danielsson, 2016; Haynes, Suckley, & Nunnington, 2017). The knowledge work performed in office environments require high amounts of cognitive tasks and when combined with filtering distractions in the workplace it can increase strains caused by common office stressors, thereby impacting employee wellbeing (Bridger & Brasher, 2011). This study will examine common stressors from the open office environment and compare employee’s perceptions of their work environment before and after renovations, as well as observations and behavioral mapping that record how the built environment influences the behaviors of the occupants. This research seeks to understand how wellbeing in the open office is affected by its different physical environmental settings, and how this environment influences employee’s behaviors. The end research goal is to see if there is a significant correlation of physical work environment and workplace behaviors that are common in the open office to help understand how the designed interior workplace impacts the wellbeing of its users.
ContributorsFrederick, Laura (Author) / Zingoni Phielipp, Milagros (Thesis advisor) / Brunner, Lori (Thesis advisor) / Trinh, Mai (Committee member) / Pijem, Maria (Committee member) / Arizona State University (Publisher)
Created2020
Description
In recent years, with the increase in the number of students studying abroad, the psychological problems of international students have attracted more and more attention. At the same time, due to the stigma and stereotypes of mental illness, international students have encountered difficulties in using campus psychological counseling services of overseas universities. Gamification is a concept that applies the elements of games to non-gaming fields. It is being widely used in various fields. This study aims to conduct user research for designing a better experience and service design for international students using campus psychological counseling by using gamification. The study was conducted using an extensive literature review as well as quantitative and qualitative research methods including a focus group, an online survey, and an interview to explore the main sources of pressure for international students and their perception on-campus counseling service. Furthermore, this study tried to explore the feasibility of online services and how gamification be applied to the services. The results showed that international students have been reported to have psychological pressure on some special issues, and few international students used campus counseling. International students who have used campus psychological counseling services also expressed their dissatisfaction with campus psychological counseling. Additionally, the study showed the feasibility of online services and the acceptance of core drives of gamification. The conclusion can be summarized as a user research for future service design in the campus counseling system, which includes expected functions and some gamified ways of online services. Because the results showed that online services cannot replace face-to-face consulting services, how to combine online and offline services, and how to let gamification reach its full potential will be further discussed.
ContributorsXu, Wei (Author) / Takamura, John (Thesis advisor) / Mejia, G. Mauricio (Committee member) / Johnson, Mina C. (Committee member) / Arizona State University (Publisher)
Created2020
Description
In the current photovoltaic (PV) industry, the O&M (operations and maintenance) personnel in the field primarily utilize three approaches to identify the underperforming or defective modules in a string: i) EL (electroluminescence) imaging of all the modules in the string; ii) IR (infrared) thermal imaging of all the modules in the string; and, iii) current-voltage (I-V) curve tracing of all the modules in the string. In the first and second approaches, the EL images are used to detect the modules with broken cells, and the IR images are used to detect the modules with hotspot cells, respectively. These two methods may identify the modules with defective cells only semi-qualitatively, but not accurately and quantitatively. The third method, I-V curve tracing, is a quantitative method to identify the underperforming modules in a string, but it is an extremely time consuming, labor-intensive, and highly ambient conditions dependent method. Since the I-V curves of individual modules in a string are obtained by disconnecting them individually at different irradiance levels, module operating temperatures, angle of incidences (AOI) and air-masses/spectra, all these measured curves are required to be translated to a single reporting condition (SRC) of a single irradiance, single temperature, single AOI and single spectrum. These translations are not only time consuming but are also prone to inaccuracy due to inherent issues in the translation models. Therefore, the current challenges in using the traditional I-V tracers are related to: i) obtaining I-V curves simultaneously of all the modules and substrings in a string at a single irradiance, operating temperature, irradiance spectrum and angle of incidence due to changing weather parameters and sun positions during the measurements, ii) safety of field personnel when disconnecting and reconnecting of cables in high voltage systems (especially field aged connectors), and iii) enormous time and hardship for the test personnel in harsh outdoor climatic conditions. In this thesis work, a non-contact I-V (NCIV) curve tracing tool has been integrated and implemented to address the above mentioned three challenges of the traditional I-V tracers.
This work compares I-V curves obtained using a traditional I-V curve tracer with the I-V curves obtained using a NCIV curve tracer for the string, substring and individual modules of crystalline silicon (c-Si) and cadmium telluride (CdTe) technologies. The NCIV curve tracer equipment used in this study was integrated using three commercially available components: non-contact voltmeters (NCV) with voltage probes to measure the voltages of substrings/modules in a string, a hall sensor to measure the string current and a DAS (data acquisition system) for simultaneous collection of the voltage data obtained from the NCVs and the current data obtained from the hall sensor. This study demonstrates the concept and accuracy of the NCIV curve tracer by comparing the I-V curves obtained using a traditional capacitor-based tracer and the NCIV curve tracer in a three-module string of c-Si modules and of CdTe modules under natural sunlight with uniform light conditions on all the modules in the string and with partially shading one or more of the modules in the string to simulate and quantitatively detect the underperforming module(s) in a string.
This work compares I-V curves obtained using a traditional I-V curve tracer with the I-V curves obtained using a NCIV curve tracer for the string, substring and individual modules of crystalline silicon (c-Si) and cadmium telluride (CdTe) technologies. The NCIV curve tracer equipment used in this study was integrated using three commercially available components: non-contact voltmeters (NCV) with voltage probes to measure the voltages of substrings/modules in a string, a hall sensor to measure the string current and a DAS (data acquisition system) for simultaneous collection of the voltage data obtained from the NCVs and the current data obtained from the hall sensor. This study demonstrates the concept and accuracy of the NCIV curve tracer by comparing the I-V curves obtained using a traditional capacitor-based tracer and the NCIV curve tracer in a three-module string of c-Si modules and of CdTe modules under natural sunlight with uniform light conditions on all the modules in the string and with partially shading one or more of the modules in the string to simulate and quantitatively detect the underperforming module(s) in a string.
ContributorsMurali, Sanjay (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Srinivasan, Devarajan (Committee member) / Rogers, Bradley (Committee member) / Arizona State University (Publisher)
Created2020
Description
In many biological research studies, including speech analysis, clinical research, and prediction studies, the validity of the study is dependent on the effectiveness of the training data set to represent the target population. For example, in speech analysis, if one is performing emotion classification based on speech, the performance of the classifier is mainly dependent on the number and quality of the training data set. For small sample sizes and unbalanced data, classifiers developed in this context may be focusing on the differences in the training data set rather than emotion (e.g., focusing on gender, age, and dialect).
This thesis evaluates several sampling methods and a non-parametric approach to sample sizes required to minimize the effect of these nuisance variables on classification performance. This work specifically focused on speech analysis applications, and hence the work was done with speech features like Mel-Frequency Cepstral Coefficients (MFCC) and Filter Bank Cepstral Coefficients (FBCC). The non-parametric divergence (D_p divergence) measure was used to study the difference between different sampling schemes (Stratified and Multistage sampling) and the changes due to the sentence types in the sampling set for the process.
This thesis evaluates several sampling methods and a non-parametric approach to sample sizes required to minimize the effect of these nuisance variables on classification performance. This work specifically focused on speech analysis applications, and hence the work was done with speech features like Mel-Frequency Cepstral Coefficients (MFCC) and Filter Bank Cepstral Coefficients (FBCC). The non-parametric divergence (D_p divergence) measure was used to study the difference between different sampling schemes (Stratified and Multistage sampling) and the changes due to the sentence types in the sampling set for the process.
ContributorsMariajohn, Aaquila (Author) / Berisha, Visar (Thesis advisor) / Spanias, Andreas (Committee member) / Liss, Julie (Committee member) / Arizona State University (Publisher)
Created2020
Description
The following document describes the hardware implementation and analysis of Temporal Interference Mitigation using High-Level Synthesis. As the problem of spectral congestion becomes more chronic and widespread, Electromagnetic radio frequency (RF) based systems are posing as viable solution to this problem. Among the existing RF methods Cooperation based systems have been a solution to a host of congestion problems. One of the most important elements of RF receiver is the spatially adaptive part of the receiver. Temporal Mitigation is vital technique employed at the receiver for signal recovery and future propagation along the radar chain.
The computationally intensive parts of temporal mitigation are identified and hardware accelerated. The hardware implementation is based on sequential approach with optimizations applied on the individual components for better performance.
An extensive analysis using a range of fixed point data types is performed to find the optimal data type necessary.
Finally a hybrid combination of data types for different components of temporal mitigation is proposed based on results from the above analysis.
The computationally intensive parts of temporal mitigation are identified and hardware accelerated. The hardware implementation is based on sequential approach with optimizations applied on the individual components for better performance.
An extensive analysis using a range of fixed point data types is performed to find the optimal data type necessary.
Finally a hybrid combination of data types for different components of temporal mitigation is proposed based on results from the above analysis.
ContributorsSiddiqui, Saquib Ahmad (Author) / Bliss, Daniel (Thesis advisor) / Chakrabarti, Chaitali (Committee member) / Ogras, Umit Y. (Committee member) / Jayasuriya, Suren (Committee member) / Arizona State University (Publisher)
Created2020
Description
This thesis introduces a new robotic leg design with three degrees of freedom that
can be adapted for both bipedal and quadrupedal locomotive systems, and serves as
a blueprint for designers attempting to create low cost robot legs capable of balancing
and walking. Currently, bipedal leg designs are mostly rigid and have not strongly
taken into account the advantages/disadvantages of using an active ankle, as opposed
to a passive ankle, for balancing. This design uses low-cost compliant materials, but
the materials used are thick enough to mimic rigid properties under low stresses, so
this paper will treat the links as rigid materials. A new leg design has been created
that contains three degrees of freedom that can be adapted to contain either a passive
ankle using springs, or an actively controlled ankle using an additional actuator. This
thesis largely aims to focus on the ankle and foot design of the robot and the torque
and speed requirements of the design for motor selection. The dynamics of the system,
including height, foot width, weight, and resistances will be analyzed to determine
how to improve design performance. Model-based control techniques will be used to
control the angle of the leg for balancing. In doing so, it will also be shown that it
is possible to implement model-based control techniques on robots made of laminate
materials.
can be adapted for both bipedal and quadrupedal locomotive systems, and serves as
a blueprint for designers attempting to create low cost robot legs capable of balancing
and walking. Currently, bipedal leg designs are mostly rigid and have not strongly
taken into account the advantages/disadvantages of using an active ankle, as opposed
to a passive ankle, for balancing. This design uses low-cost compliant materials, but
the materials used are thick enough to mimic rigid properties under low stresses, so
this paper will treat the links as rigid materials. A new leg design has been created
that contains three degrees of freedom that can be adapted to contain either a passive
ankle using springs, or an actively controlled ankle using an additional actuator. This
thesis largely aims to focus on the ankle and foot design of the robot and the torque
and speed requirements of the design for motor selection. The dynamics of the system,
including height, foot width, weight, and resistances will be analyzed to determine
how to improve design performance. Model-based control techniques will be used to
control the angle of the leg for balancing. In doing so, it will also be shown that it
is possible to implement model-based control techniques on robots made of laminate
materials.
ContributorsShafa, Taha A (Author) / Aukes, Daniel M (Thesis advisor) / Rogers, Bradley (Committee member) / Zhang, Wenlong (Committee member) / Arizona State University (Publisher)
Created2020
Description
Detecting areas of change between two synthetic aperture radar (SAR) images of the same scene, taken at different times is generally performed using two approaches. Non-coherent change detection is performed using the sample variance ratio detector, and displays a good performance in detecting areas of significant changes. Coherent change detection can be implemented using the classical coherence estimator, which does better at detecting subtle changes, like vehicle tracks. A two-stage detector was proposed by Cha et al., where the sample variance ratio forms the first stage, and the second stage comprises of Berger's alternative coherence estimator.
A modification to the first stage of the two-stage detector is proposed in this study, which significantly simplifies the analysis of the this detector. Cha et al. have used a heuristic approach to determine the thresholds for this two-stage detector. In this study, the probability density function for the modified two-stage detector is derived, and using this probability density function, an approach for determining the thresholds for this two-dimensional detection problem has been proposed. The proposed method of threshold selection reveals an interesting behavior shown by the two-stage detector. With the help of theoretical receiver operating characteristic analysis, it is shown that the two-stage detector gives a better detection performance as compared to the other three detectors. However, the Berger's estimator proves to be a simpler alternative, since it gives only a slightly poorer performance as compared to the two-stage detector. All the four detectors have also been implemented on a SAR data set, and it is shown that the two-stage detector and the Berger's estimator generate images where the areas showing change are easily visible.
A modification to the first stage of the two-stage detector is proposed in this study, which significantly simplifies the analysis of the this detector. Cha et al. have used a heuristic approach to determine the thresholds for this two-stage detector. In this study, the probability density function for the modified two-stage detector is derived, and using this probability density function, an approach for determining the thresholds for this two-dimensional detection problem has been proposed. The proposed method of threshold selection reveals an interesting behavior shown by the two-stage detector. With the help of theoretical receiver operating characteristic analysis, it is shown that the two-stage detector gives a better detection performance as compared to the other three detectors. However, the Berger's estimator proves to be a simpler alternative, since it gives only a slightly poorer performance as compared to the two-stage detector. All the four detectors have also been implemented on a SAR data set, and it is shown that the two-stage detector and the Berger's estimator generate images where the areas showing change are easily visible.
ContributorsBondre, Akshay Sunil (Author) / Richmond, Christ D (Thesis advisor) / Papandreou-Suppappola, Antonia (Committee member) / Bliss, Daniel W (Committee member) / Arizona State University (Publisher)
Created2020
Description
Energy is one of the wheels on which the modern world runs. Therefore, standards and limits have been devised to maintain the stability and reliability of the power grid. This research shows a simple methodology for increasing the amount of Inverter-based Renewable Generation (IRG), which is also known as Inverter-based Resources (IBR), for that considers the voltage and frequency limits specified by the Western Electricity Coordinating Council (WECC) Transmission Planning (TPL) criteria, and the tie line power flow limits between the area-under-study and its neighbors under contingency conditions. A WECC power flow and dynamic file is analyzed and modified in this research to demonstrate the performance of the methodology. GE's Positive Sequence Load Flow (PSLF) software is used to conduct this research and Python was used to analyze the output data.
The thesis explains in detail how the system with 11% of IRG operated before conducting any adjustments (addition of IRG) and what procedures were modified to make the system run correctly. The adjustments made to the dynamic models are also explained in depth to give a clearer picture of how each adjustment affects the system performance. A list of proposed IRG units along with their locations were provided by SRP, a power utility in Arizona, which were to be integrated into the power flow and dynamic files. In the process of finding the maximum IRG penetration threshold, three sensitivities were also considered, namely, momentary cessation due to low voltages, transmission vs. distribution connected solar generation, and stalling of induction motors. Finally, the thesis discusses how the system reacts to the aforementioned modifications, and how IRG penetration threshold gets adjusted with regards to the different sensitivities applied to the system.
The thesis explains in detail how the system with 11% of IRG operated before conducting any adjustments (addition of IRG) and what procedures were modified to make the system run correctly. The adjustments made to the dynamic models are also explained in depth to give a clearer picture of how each adjustment affects the system performance. A list of proposed IRG units along with their locations were provided by SRP, a power utility in Arizona, which were to be integrated into the power flow and dynamic files. In the process of finding the maximum IRG penetration threshold, three sensitivities were also considered, namely, momentary cessation due to low voltages, transmission vs. distribution connected solar generation, and stalling of induction motors. Finally, the thesis discusses how the system reacts to the aforementioned modifications, and how IRG penetration threshold gets adjusted with regards to the different sensitivities applied to the system.
ContributorsAlbhrani, Hashem A M H S (Author) / Pal, Anamitra (Thesis advisor) / Holbert, Keith E. (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2020