The Impact of Socioeconomic Status on College Students’ Experiences

This qualitative research project examines the role of socioeconomic status in shaping the experiences of students attending Pearson College, an elite liberal arts college in Southern California. One hour-long, semi-structured interviews were conducted with ten Asian Pacific Islander Desi American (APIDA) students in order to better understand APIDA student experiences and their views on the college’s efforts to support class-based diversity and inclusion. Findings include insights into challenges faced by college students, how they understand privilege and identity, and where college students find support. These results have implications for Pearson College, and similar liberal arts colleges, to implement changes to better support students that are reporting significant mental health challenges and feelings of alienation. In addition, this work adds to the broader national conversation around income inequality and social mobility in higher education. As more and more young people across the country attend college, it is imperative to ask who “diversity and inclusion” college initiatives are truly benefiting

Development of a γ’ Precipitation Hardening Ni-Base Superalloy for Additive Manufacturing

The performance of superalloy materials at high temperatures is what makes gas turbine technology possible. Continual improvement in superalloy properties and resultant elevation of operating temperatures drives higher efficiency and reduced environmental impact in both aerospace and energy applications. Given the technological and commercial significance of superalloys, their adoption into Additive Manufacturing is of vital importance. The Additive Manufacturing of nickel-base superalloys aims to optimize function through geometric complexity of engineered parts, while reducing product development and marketing times. However, there are challenges to overcome before these materials can be used in serial production. Most superalloys are susceptible to cracking when processed in laser-powder bed fusion processes, and cracking mechanisms must be understood and mitigated in order to produce fully-dense parts. Another challenge is in the postprocessing stage. Additively manufactured microstructures are unlike cast or wrought microstructures, and heat treatment regimens must be re-formulated based on the different starting microstructure. Inconel 939 is a cast Ni-base superalloy for service above 800°C and is widely used in hot-sections of industrial gas turbine engines. This thesis presents a study of the cracking behaviour of IN939, and based on fractographic results, shows solidification cracking to be the primary mechanism responsible. The design of heat-treatment necessitated a comprehensive study of the starting microstructure. This was performed by thermal analysis and metallography and equated to simulation results. Heat treatment trials were conducted and the resulting microstructure and room temperature mechanical properties were characterized. Results showed significant differences in the fractions and morphologies of strengthening phases, compared to the conventionally cast material, while room temperature mechanical properties were better or comparable. The obtained results form a basis for proceeding with high-temperature and creep testing of the material to prove its viability in AM

Laser powder bed fusion processing and heat treatment of Ni-base superalloys: microstructure and properties

Nickel-base superalloys are indispensable materials for the energy and aerospace industries. The additive manufacturing (AM) of these materials by powder bed fusion – laser beam (PBF-LB) presents a valuable opportunity to improve component performance and ease manufacturing and supply chain complexity in these industries. However, only a limited number of Ni-base superalloys are currently available for PBF-LB. This is due to several challenges encountered during PBF-LB processing, including microcracking, post-process cracking, development of an AM-specific microstructure, and lack of heat treatment optimization.The aim of this thesis study is to develop better understanding of the extent of these issues in different superalloys, their causes, and potential remedies. To understand aspects of processability, the alloy Haynes\uae 282\uae was studied to assess its feasibility for manufacture by means of PBF-LB, including susceptibility to cracking. Results showed excellent processibility of Haynes\uae 282\uae by PBF-LB, allowing to reach full-density crack-free components over the wide range of energy input, while also being resistant to post-process cracking.Conventionally manufactured superalloys – cast or wrought – are currently considered as the benchmark in terms of mechanical performance. The microstructure and mechanical performance of PBF-LB processed Haynes\uae 282\uae after standard heat treatment was evaluated and compared to its wrought counterpart from the literature. PBF-LB processed Haynes\uae 282\uae showed finer grain sizes and discontinuous grain boundary carbides compared to wrought microstructure. Despite excellent room temperature tensile properties, clear anisotropy in high temperature mechanical performance of PBF-LB processed Haynes\uae 282\uae was observed, which is proposed to be addressed by heat treatment optimization.Heat treatment is a critical post processing step for any precipitation strengthened alloy, and this is especially true for PBF-LB processed superalloys. Heat treatments developed for cast or wrought alloys may not be optimal for the same alloys in PBF-LB processed form because PBF-LB processed superalloys have a starting microstructure that is very different from equivalent cast or wrought microstructures. This aspect was studied in detail by evaluation of the as-built microstructure of Inconel 939, a high γ’-fraction superalloy. No γ’ precipitates were found in the as-built microstructure, however, η phase was found at inter-dendritic regions. This secondary phase was observed to grow upon ageing, lowering the ductility of the material. This demonstrates the importance of a solution treatment for Inconel 939, regardless of γ’ in the as-built condition. Further study also aimed to optimize the ageing heat treatment steps for PBF-LB manufactured Inconel 939. This resulted in a proposed ageing heat treatment which is shorter than the one used for conventional cast Inconel 939, which also produces improved and more isotropic tensile performance. Another aspect of heat treatment in PBF-LB processing is potential contamination of an alloy from the stress relief heat treatment carried out while a part is fused to a dissimilar building platform material. This was addressed in a study on Haynes\uae 282\uae built onto a carbon steel building platform. The study showed that no large-scale change in chemical composition occurred, suggesting that steel platforms are suitable for use with Ni-base superalloys

Theoretical and experimental investigations of lead chalcogenides quantum confined structures for solar cell application

Solar cell has gained much attention due to its simple design and similarity to dye sensitized solar cells (DSSC), in which the QCS replaces the dye molecules. The QCSs are able to yield more than one exciton upon absorption of a single photon with sufficient energy, a multiple exciton generation (MEG). Theoretically, MEG could increase the efficiency of a PV device ≥ 60%, however QCSCs could deliver an insignificant PV conversion efficiency (PCE) of only ca. 16.6%. This doctoral research therefore aims to: (i) investigate the effect of energy level alignment of the lowest unoccupied molecular orbital of the fluorophore (LUMOfluorophore), with the conduction band minimum of MOS (CBMMOS) on the electron injection efficiency from the fluorophore to the MOS, (ii) determine the geometry of lead chalcogenides QCS (< their exciton Bohr radius) that would exhibit MEG using ab-initio density functional theory (DFT) calculations, (iii) identify the simulated geometries of lead chalcogenides that could be synthesized using a vacuum thermal evaporator (TE) and (iv) investigate the effect of the addition of activated carbon (AC) on the morphology and optoelectronic properties of the lead sulphide (PbS) fabricated using a vacuum TE, and the electron injection efficiency from the fluorophore to the MOS. The results of the study show that the ideal energy level alignment between LUMOfluorophore (-4.0 eV) and CBMMOS (-4.1 eV) supported an efficient electron injection from the fluorophore to the MOS, with an injection efficiency as high as ca. 97%. The structural geometry of PbS, PbSe and PbTe that exhibit MEG were identified viz., (PbS)40, (PbS)74, (PbS)80, (PbSe)16, (PbSe)30, (PbSe)32, (PbSe)50, (PbSe)74, (PbTe)12, (PbTe)16, (PbTe)44, (PbTe)50 and (PbTe)74 with the size of 3.49 nm, 4.86 nm, 4.58 nm, 2.63 nm, 3.20 nm, 3.29 nm, 4.03 nm, 5.02 nm, 2.52 nm, 2.69 nm, 3.90 nm, 4.16 nm and 4.84 nm respectively. The optoelectronic properties of (PbS)80, (PbSe)30 and (PbTe)50 QCS that were obtained from ab-initio DFT calculations were in good agreement the PbS, PbSe and PbTe thin films; which compared based on the first excitonic peaks of the fabricated thin films (nano-sphere morphology) to the PbS, PbSe and PbTe realistic cluster models, which resulted in similarities of 92.93%, 99.38% and 95.49% respectively. The PbS nano-tubules with a size range of 41-76 nm were yielded after the addition of AC with a specific surface area of 80 m 2/g (AC80). PbS nano-sheets with a size range of 36-95 nm were yielded after the addition of AC with a specific surface area of 650 m2/g (AC650). PbS nano-sheets (size range: 33-63 nm) were yielded after the addition of AC with a specific surface area of 1560 m2/g (AC1560). Optoelectronic properties of the fabricated PbS thin films with the addition of AC80, AC650 and AC1560 were similar to that of the (PbS)80 realistic model; determined based on the positions of the first excitonic peaks, which recorded 90.1%, 96.1% and 92.8% of similarity, respectively. The electron injection efficiencies from PbS-AC80, PbS-AC650 and PbS-AC1560 conjugates to the MOS were determined to be 18.48%, 62.71% and 87.18%, respectively. In conclusion, a PbS thin film possessing a nano-sphere morphology and exhibiting MEG could be fabricated using TE without the addition of AC

Strategic aspects of the Afghan conflict: maximization of national interests

Call number: LD2668 .T4 PLSC 1987 B87Master of ArtsPolitical Scienc

Microstructure and mechanical properties of Haynes 282 superalloy produced by laser powder bed fusion

Ni-base superalloys are essential materials for high-temperature applications in the energy and aerospace sectors. Significant benefits in design, function, and manufacture of high-temperature components may be realized from additive manufacturing (AM) of these materials. However, because of cracking issues during AM fabrication, only a handful of materials have been tried and qualified. This article provides an initial evaluation of theprocessability and properties of Haynes 282 by laser-powder bed fusion (LPBF), which is a relatively new Ni-base superalloy with properties superior to those of many legacy wrought superalloys. The results demonstrated that crack-free Haynes 282 can be manufactured by means of LPBF with full density. The mechanical properties at ambient temperature exceeded the properties of the reference material in the as-built and heat-treated conditions, albeit with significant anisotropy. Mechanical properties at 800 ◦C indicated that the yield strength of heattreated Haynes 282 by LPBF was comparable to that of the reference material, however, ductility was significantly reduced. Promising stress rupture performance also indicates that Haynes 282 is an ideal candidate for adoption in additive manufacturing, especially if heat treatments can be re-designed for the additively manufactured as-built microstructure

On as-built microstructure and necessity of solution treatment in additively manufactured Inconel 939

Increased adoption of additively manufactured superalloys has led to the consideration of revised heat treatment approaches for these materials. The rapid cooling during additive manufacturing processes has been seen to suppress gamma prime (γ′) precipitation, which has raised the possibilities for omitting the high-temperature solution treatment step that usually precedes ageing heat treatment for these alloys. In this work, the as-built microstructure of a high gamma prime fraction superalloy Inconel 939 is presented, where the absence of any\ua0γ′ precipitation is notable. However, transmission electron microscopy shows the presence of nano-sized Eta (η) phase. It is shown that the omission of solution treatment leads to the growth of the deleterious\ua0η\ua0phase upon ageing, which results in embrittlement in tensile loading. It is concluded that at least for this particular alloy the solution treatment plays a critical role in the establishment of the required microstructure and hence cannot be omitted from the heat treatment

Planetarium pedagogy and technical learning experience: an investigation from instructional perspectives

The research focused on the National Planetarium Kuala Lumpur’s education programs, investigating the types and target audiences. It examined the educational theories and strategies used, including multiple intelligence theory and cooperative learning. The study also explored the alignment of astrophysics in Pearson Edexcel International General Certificate of Secondary Education (IGCSE) Physics with the Planetarium’s programs. Document analysis and participant observation were employed. The results revealed two program types: on-site and online. The programs showed alignment with IGCSE Physics and utilized theories like social cognitive theory. The National Planetarium positively impacted students through multi-intelligence theory, sociocultural theory, experiential theory, and constructivism. Gamification and group activities enhanced the learning experience. The Planetarium’s ability to simulate astronomical events made it an effective medium for instructional science institutions. Overall, the study highlighted the diverse education programs of the National Planetarium Kuala Lumpur, their alignment with IGCSE Physics, and their positive impact on students’ personal, physical, and social contexts

Student’s acceptance of e-learning during the COVID-19 pandemic

Electronic learning (e-learning) has become the main method of teaching and learning for many educational institutions during the COVID-19 pandemic. The purpose of this study is to investigate the students’ acceptance of e-learning during the COVID-19 pandemic. Quantitative research methods were utilized in order to obtain the necessary data. A total of 100 respondents from three science courses, which were Biology (ED247), Chemistry (ED260), and Physics (ED248) in the Faculty of Education, University Teknologi MARA, Puncak Alam answered a questionnaire given via Google Forms. The IBM SPSS version 25.0 software was used for data analysis. The results show that the students’ acceptance towards e-learning is low based on research question 1 (mean=3.05, SD=.796), research question 2 (mean=1.18, SD=.386), research question 3 (mean=1.18, SD=.435) and research question 4 (mean=1.44, SD=.608). In conclusion, the student’s acceptance of e-learning during the COVID-19 pandemic is significant to improve an educational process by creating and sustaining meaningful learning