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- Title
- A Network Analysis to Examine the Construct of Acculturative Stress in Mexican Americans
- Creator
- Mosqueda, Andrea I
- Date
- 2020
- Description
-
Acculturative stress (AS) is a negative consequence of acculturation and occurs when acculturation is problematic for the individual. There is...
Show moreAcculturative stress (AS) is a negative consequence of acculturation and occurs when acculturation is problematic for the individual. There is a substantial variation in AS phenomena across different cultural/ethnic groups, across individual variables (e.g., sex, age, education, attitude, cognitive style), and across social variables (e.g., contact, social support, status). There does not seem to be one specific way in which AS affects all groups or individuals. Elevated levels of AS are associated with multiple manifest difficulties, including family dysfunction, geographical separation from family, low-income levels, and non-positive expectations for the future. AS has been associated with outcomes such as anxiety, depression, suicidal ideation, and feelings of isolation and alienation. Using a network analysis approach, this exploratory study examined the structure of the construct of AS as represented in the Social, Attitudinal, Familial, and Environmental (SAFE) AS Scale, a measure used to assess the AS construct across four contexts. Results of the network analysis of AS aspects suggest that the AS construct is best understood as a latent variable rather than as a network of interacting AS aspects, and that distress is related to particular aspects of AS. The present study findings suggest a particular model of relations between latent AS, its manifest aspects, and clinical outcomes. Further research can help to better understand the relationship between individual AS aspects (i.e., treatment targets) and treatment goals of impacting AS-related outcomes (e.g., distress), as well as the mechanisms of change.
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- Title
- Technology News, January 08, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-01-08, 1946-01-08
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, February 05, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-02-05, 1946-02-05
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, January 29, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-01-29, 1946-01-29
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, June 04, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-06-04, 1946-06-04
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, April 30, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-04-30, 1946-04-30
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, June 11, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-06-11, 1946-06-11
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, June 18, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-06-18, 1946-06-18
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, December 18, 1945
- Creator
- Illinois Institute of Technology
- Date
- 1945-12-18, 1945-12-18
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, January 15, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-01-15, 1946-01-15
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, March 11, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-03-11, 1946-03-11
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, March 19, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-03-19, 1946-03-19
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- Technology News, April 16, 1946
- Creator
- Illinois Institute of Technology
- Date
- 1946-04-16, 1946-04-16
- Collection
- Technology News Microfilm collection, 1928-1981
- Title
- COMPUTATIONAL MODELLING OF FALLING FILM FLOW AND HEAT TRANSFER OVER HORIZONTAL TUBES
- Creator
- Karmakar, Avijit
- Date
- 2021
- Description
-
In this study, numerical simulations based on the volume of fluid (VOF) method are conducted to investigate the hydrodynamic behavior,...
Show moreIn this study, numerical simulations based on the volume of fluid (VOF) method are conducted to investigate the hydrodynamic behavior, sensible heat transfer behavior, and tube surface wettability effects for a falling film over heated horizontal tubes encountered in falling film heat exchangers. The Reynolds number ranges from 15 - 210, covering the droplet, jet (inline and staggered), and sheet flow modes. To consider evaporation under liquid film waviness and gas (vapor and air) flow effects, a simplified case was studied for the wavy liquid film over a heated vertical surface with the surrounding gas flowing in either co-current or counter-current direction. The OpenFOAM CFD solver has been used to conduct the numerical simulations.For hydrodynamics, the liquid film thickness and interface velocity variation for all the flow modes are presented. In droplet mode, the movement of the liquid waves formed by the drop impact causes an over 350% change in film thickness. A dimple around the jet impingement region in the steady inline jet mode is formed with a relative change in film thickness by 40%. The base of the impinging jets possess ripples of wavelengths 0.3-1.0 times the capillary length. For the steady staggered jet mode, the neighboring jets interact to develop crest and stable segments with film thickness ratio of 1.7. Finally, for the sheet mode, interfacial waves are seen to travel along the tube periphery with amplitudes of about 20% of the nominal film thickness. A set of correlations have been presented to predict film thickness and interfacial velocity with RMSE = 0.2 for 80% of the data.The local Nusselt number (Nu) distribution depends on the flow features in each mode. In the droplet mode, the Nu value varies significantly as the droplet impinges and the remnant liquid-bridge retracts (peak instantaneous Nu = 6), followed by wave propagation with peak Nu = 0.25. For the jet modes, the local maximum in Nu occurs off-center to the impingement location with peak Nu = 3.1 for the inline jet mode and Nu = 2.7 for the staggered jet mode, while for other locations, Nu varies as inversely proportional to film thickness. Substantial variations in the Nu value are also recorded in the middle of the two impinging jets with Nu = 0.95 in the inline jet mode, and Nu = 0.60 in the crest region of the staggered jet mode. In the sheet mode, the Nu varies with the thickness of the traversing liquid waves. Lower Nu values were recorded beneath the crest location of the liquid waves, which increases (1.4 - 11.6%) abruptly at the advancing fronts of the waves. The temperature distribution in the liquid film in each of the modes was examined to evaluate the mechanism of heat transfer process. This study also compares the Nu distribution with the available analytical heat transfer models.The tube surface wettability results present the liquid film thickness, the wetted areas, and the Nusselt number (Nu) over the tube surface. The resistance imposed by the increasing contact angles inhibits the extent of the liquid spreading over the tube surface, and this, in turn, influences film thickness and wetted areas. A significant decrement in the heat transfer rate from the tube surfaces was observed as the equilibrium contact angle increased from 2 to 175 degrees. The local distributions of the Nu over the tube surface are strongly influenced by the flow recirculation in the liquid bulk.Finally, for wavy film evaporation under gas flow effects, the results show a 15% and 16% enhancement in time-averaged Sherwood number (Sh) due to film waviness (sinusoidal and solitary) with gas flow rate, Qg = +50 and Qg = -50, respectively. This enhancement in the Sh for both the waves further increases by 11% with Qg =+800 and by 196% with Qg = -800. Closer examination of the mass transfer process over a wave demonstrates that with Qg = +50, the concentration of the gas side streamlines at the trough locations of the wave leads to higher values of Sh than the rest of the locations. However, with Qg = +800, although the overall Sh increases, vortices appear at the wave trough locations, leading to decreased local Sh values than the surrounding locations.
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- Title
- REVEALING LINGUISTIC BIAS
- Creator
- Karmarkar, Sathyaveer S.
- Date
- 2021
- Description
-
Readers currently face bias in articles written by writers who focus more on partiality towards any person or organization than showing the...
Show moreReaders currently face bias in articles written by writers who focus more on partiality towards any person or organization than showing the real facts. The study aims to detect and reveal such bias against them and try to portray real facts without any partiality against any person or organization. The data is fetched by selecting various articles from Google, especially those containing some bias in them. The bias was checked by measuring the subjectivity and polarity of the article using multiple libraries such as NLTK etc. We created a google form to take readers’ views showing them randomly either the biased article or the improved article after changing bias and getting their opinions.
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- Title
- IRREGULAR GROWTH AND INTERFACIAL EFFECT IN THIN FILM MULTILAYER STRUCTURES FOR USES IN PHOTOCATHODE APPLICATIONS
- Creator
- Lee, ZhengRong
- Date
- 2021
- Description
-
Improving photocathode performance by increasing the electron density while lowering the angular spread of emitted electrons can improve...
Show moreImproving photocathode performance by increasing the electron density while lowering the angular spread of emitted electrons can improve particle accelerator performance, expanding the reach of both fundamental and applied science. Materials science expertise is needed to design new photocathodes with these desired properties. Nemeth, et al, determined that a multilayered photocathode structure consisting of MgO/Ag/MgO could be engineered for higher brightness and lower dispersion [Nemeth, et al, Phys. Rev. Lett. 104, 046801 (2010)]. The dispersion of the surface bands impacts the angular spread of the emitted beam, and the model predicted that the bands could be tuned by precisely controlling the layer thicknesses of the multilayer structure. We synthesized and probed this MgO/Ag/MgO system experimentally. We measured the work function, emittance, and quantum efficiency of multilayer photocathodes with different MgO layer thicknesses to compare with theoretical predictions. We observed that although the general trend was as predicted, the measurements and the model were not in exact agreement [Velasquez, et al, Appl. Surf. Sci. 360, 762 (2016)]. In this work, we have undertaken a study of the electronic structure of the interfaces to explore how these observed deviations may have originated. It is possible that the fabrication process leads to non-ideal interfaces compared to those constructed in the simulations. To study how the fabrication affects the interfaces, hard X-ray photoemission spectroscopy(HAXPES) was used to probe the chemistry of the buried interfaces within the thin film multilayer structure of Ag and MgO. In these multilayer structures, we observed that the silver layers were predominantly metallic. A small high binding energy (ΔE = 0.69 eV) peak was also observed in the Ag 3d core level in the samples. This peak is shifted in the opposite direction of the binding energy shift in silver oxides, suggesting that this peak is not due to the formation of silver oxides at the interfaces with the MgO. Two possible explanations for the origin of this peak then are charge transfer at the interface from the Ag to the oxide monolayer or the formation of silver nanoparticles during the growth process. Based upon simple depth profiling analysis, we postulate the former is the more likely explanation. In addition, the O 1s and Mg 1s core level indicated the presence of Mg(OH)2. The MgO layers react with H2O in the vacuum chamber or ideal gas used as a buffer during sample transfer. Since the theory predicts a strong dependence upon the number of MgO layers surrounding the Ag, the formation of Mg(OH)2 likely contributes to the non- ideal behavior, even given the similarity in the electronic structure to MgO (large band gap insulator) and Mg(OH)2. The speed at which this reaction occurs would significantly limit the lifetime and the utility of the MgO/Ag multilayer photocathodes. In order to custom engineer multilayer photocathodes, complete control over the growth process will be needed to ensure that the ideal surfaces are formed. Using non-reactive materials would greatly increase the lifetime of the engineered photocathodes.
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- Title
- INVESTIGATION OF STRUCTURE AND PROCESSING EFFECTS ON THE ELECTROCHEMICAL PERFORMANCE OF COBALT-FREE, LITHIUM- AND MANGANESE-RICH LAYERED OXIDE CATHODE FOR LIBS
- Creator
- Kucuk, Kamil
- Date
- 2021
- Description
-
Rechargeable Li-ion batteries (LIBs) have been widely used in a diverse range of energy storage systems because of their high energy and power...
Show moreRechargeable Li-ion batteries (LIBs) have been widely used in a diverse range of energy storage systems because of their high energy and power density, low self-discharge, and tolerable memory effect, compared to the conventional alkaline, lead acid, and nickel-cadmium (Ni/Cd) batteries. [2] Since not only cathodes materials control the energy density of a cell, but also the capacity of cathode material characteristically restricts the cell capacity (as well as about 40% of the cell cost results from the cost of cathode raw materials), the majority of studies on LIBs have been carried out on developing alternative cathodes with higher energy, lower cost, and more environmentally friendliness. [2], [3] From this perspective, both Co-free and lithium- & manganese-rich (LMRO) layered oxide MNF cathodes, Li1.2(MnxNiyFez)O2, have recently attracted great attention in lithium-ion battery (LIB) research for electric vehicles and energy storage devices due to their high capacities of over 250 mAhg−1 and being eco-friendly and inexpensive compared to the cobalt-based Li-rich Li1.2(NixMnyCoz)O2 and Ni-rich Li(NixMnyCoz)O2 (NMC), and LiCoO2 commercial cathodes. Replacing toxic and expensive Co in the LMRO cathodes with environmentally friendly and much cheaper Fe element has been extensively studied over the last two decades. It was suggested by Aryal, S. et. al., in 2018. [4] that the Li1.2(Mn0.50Ni0.20Fe0.10)O2 (MNF502010) Co-free LMRO MNF cathodes seem better in terms of capacity-retention with higher discharge capacity and less voltage fade compared to other MNF compositions. However, the MNF502010 cathode still suffers from its lower experimental capacity, compared to its expected theoretical capacity (270-455 mAhg−1), as well as capacity decay, voltage fade, poor rate capability, and thermal instability. In this dissertation, it is reported that comparable specific discharge capacity with less amount of voltage fading and capacity decay can be achieved by fluorine doping, synthesizing materials in large amounts (0.1 mol synthesis at least) with two-step firing, and then washing the obtained nanocomposites with H3PO4 to create Li3PO4 layer on the surface of bulk MNF composites. The specific discharge capacity and cycling performance of the Co-free MNF502010 cathodes were studied and enhanced by using and optimizing these approaches in this work for the first time. However, voltage fading and capacity decay are still remaining challenges, even if they are remarkably mitigated by applying these approaches. Structural changes due to layered to spinel transformation, less amount of monoclinic phase activation leading to structural deformation occurring after 1st charge, dissolution of the transition metals (TM), and oxygen release (loss of lattice oxygen) from the MNF material upon following electrochemical cycling at higher voltage (≥ 4.5V ) seem the main reasons behind these challenges, specifically the voltage fading and capacity decay.A series of fluorine-doped/undoped, Co-free MNF502010 nanocomposite cathode materials (Li1.2(Mn0.50Ni0.20Fe0.10)O2(1−x)F2x, briefly F-doped MNF) were synthesized by using a sol-gel technique. Firstly (Chapter 4), the fluorine was substituted for oxygen in the parent MNF compound in different fractions (0.00, 0.025, 0.05,0.075, 0.10, which means 0%, 2.5%, 5.0%, 7.5%, and 10%), in order to optimize the amount of fluorine for better performance; secondly (Chapter 5), a large batch (0.1mol, 10 times more than the previous batch) of 5%F-doped material was prepared by a modified sol-gel synthesis which is modified by heating at 700 ◦C for different time-periods; 7.5 hours (7.5h), 15 hours (15h, two-step firing, 7.5h + rest for 12h + 7.5h), instead of heating directly 15 hours (d15h), as done in the first chapter; finally (Chapter 6), H3PO4 treatment resulting in a non-uniform Li3PO4 layer on the bulk surface. These approaches were respectively applied on doped/undoped MNF502010 nano-composites, in order to overcome the challenges already mentioned above. Finally, the effects of these approaches on the structural, morphological, and electrochemical properties of MNF cathode materials were investigated by means of powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray (EDS) analysis, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic charge-discharge cycling, and X-ray absorption spectroscopy (XAS, an element specific probe technique). Specifically, ex-situ XAS was performed at the Mn, Ni, and Fe K-edge and used to detect the changes both in the oxidation state of the transition metal (TM) ions and their local environments in order to get a better understanding of the improved performance of the composite materials, as well as their failure mechanism. Moreover, the EXAFS data were modeled to gain insight into the influence of these approaches on the electrochemical performance of both pristine (uncycled) and cycled electrodes (after the 100th discharge). From correlating the electrochemical performance of the modified/unmodified MNF nano-composite cathodes to their XANES and EXAFS analysis, the ability to achieve higher specific capacity is strongly dependent on the formation of a well-ordered layered structure and the amount of monoclinic component (Li2MnO3) activation resulting in higher redox-activity of the Mn cations. The long-term cyclability or capacity retention can be enhanced by heating the resulting powders with a two-step firing (instead of directly 15 hours) and washing them with 1wt%H3PO4 solution to create a Li3PO4 conductive and protective layer.
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