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Hot Forging Die Design Optimization Using FEM Analysis for Near-Net Forming of 18CrNiMo7-6 Steel Pinion Shaft
No full textThe objective of the presented work was to develop a new forging process for a pinion shaft as a component of a wind turbine. A study of near-net-shape forming using Deform 3D software was performed to reduce operational cost, time, and material scrap; enhance specific properties; increase productivity. Near-net forged products have good dimensional accuracy and continuous metal flow lines, which are characteristic of improved mechanical properties. To avoid the traditional trial-and-error experimental method, the process and tool design were accomplished with a careful and detailed numerical simulation approach. In the present work, the Finite Element Method was used to develop a process model for the existing hot forging process of the 18CrNiMo7-6 steel pinion shaft used in a wind turbine. The developed numerical process model was validated via experiment including a comparison of the metal flow lines from the FEM model with the metallography results of the forged part. Two new die designs were proposed, and the simulation results were compared to the actual process to achieve improved geometry. The results for the new geometries showed improvements in terms of the die cavity filling for the new proposed dies and better results in grain flow orientation. Compared to the initial non-optimized die, the new designs improved the mechanical properties and savings associated with the lower volume of required raw material and fewer finishing operations. Considering the applied stresses and wear in the new near-net shape, the die geometry shall be updated to accommodate more severe solicitations. Naturally, all the improvements carried out are dependent on other factors such as the conditions of the equipment, operator skills, lubrication, and other variables. A surface heat treatment is also suggested for stress relief as a reliability improvement.</jats:p
Patriarchal Anxieties and Masculine Sexual Privilege in Contemporary Urban Mali
No full text The neoliberal transformation of Mali\u27s burgeoning capital city, Bamako, has undermined men\u27s capacity to provide for their households and dependents even as it has boosted women\u27s economic participation, leading senior males to express mounting anxieties over their declining economic power. As more men find themselves unable to assure economic stability for the women and children under their charge, many double down in their bid to exercise authority over women, particularly their wives. Some men use polygynous marriage as a means of performing certain masculine ideals, acquiring social prestige despite their diminished roles as breadwinners. Others find maintaining multiple female partners outside marriage similarly useful for offsetting their economic disadvantages. Based on ethnographic fieldwork and interviews with men and women in Bamako, this paper examines the extent to which modern masculinity in the city remains predicated on the control of women and their bodies. </jats:p
Firearms Are Now the Leading Cause of Traumatic Brain Injury Related Mortality in Children
No full textUsing benthic macroinvertebrates as bioindicators to evaluate the impact of anthropogenic stressors on water quality and sediment properties of a West African lagoon
No full textPhosphorus adsorption using chemical and metal chloride activated biochars: Isotherms, kinetics and mechanism study
No full textK2 Optical Emission from OJ 287 and Other γ-Ray Blazars on Hours-to-weeks Timescales from 2014 to 2018
No full textAbstract
We present second observations by K2 of OJ 287 and seven other γ-ray active galactic nuclei (AGNs) obtained in 2017–2018, second and third observations of the lobe-dominated, steep-spectrum quasar 3C 207, and observations of nine additional blazars not previously observed with K2. The AGNs were observed simultaneously with K2 and the Fermi Large Area Telescope for 51–81 days. Our full sample, observed in 2014–2018, contained 16 BL Lacertae objects (BL Lacs), nine flat-spectrum radio quasars (FSRQs), and four other γ-ray AGNs. Twelve BL Lacs and seven FSRQs exhibited fast, jagged light curves, while four BL Lacs and two FSRQs had slow, smooth light curves. Some objects changed their red-noise character significantly between repeated K2 observations. The optical characteristics of OJ 287 derived from the short-cadence K2 light curves changed between observations made before and after the predicted passage of the suspected secondary supermassive black hole through the accretion disk of the primary supermassive black hole. The average slopes of the periodogram power spectral densities of the BL Lacs’ and FSRQs’ light curves differed significantly, by ≈12%, with the BL Lac slopes being steeper, and a Kolmogorov–Smirnov test with a p-value of 0.039 indicates that these samples probably come from different populations; however, this result is not as strongly supported by power spectral response (PSRESP) analyses. Differences in the origin of the jets from the ergosphere or accretion disk in these two classes could produce such a disparity, as could different sizes or locations of emission regions within the jets.</jats:p
Molecular Simulation of the Interaction of Diclofenac with Halogen (F, Cl, Br)-Encapsulated Ga12As12 Nanoclusters
No full textSignificance of Short‐Wavelength Magnetic Anomaly Low Along the East Pacific Rise Axis, 9°50′N
No full textAbstractMagnetic anomaly variations near mid‐ocean ridge spreading centers are sensitive to a variety of crustal accretionary processes as well as geomagnetic field variations when the crust forms. We collected near‐bottom vector magnetic anomaly data during a series of 21 autonomous underwater vehicle Sentry dives near 9°50′N on the East Pacific Rise (EPR) covering ∼26 km along‐axis. These data document the 2–3 km wide axial anomaly high that is commonly observed at fast‐spreading ridges but also reveal the presence of a superimposed ∼800 m full wavelength anomaly low. The anomaly low is continuous for ≥13 km along axis and may extend over the entire survey region. A more detailed survey of hydrothermal vents near 9°50.3′N reveals ∼100 m diameter magnetic lows, which are misaligned relative to active vents and therefore cannot explain the continuous axial low. The axial magnetization low persists in magnetic inversions with variable extrusive source thickness, indicating that to the extent to which layer 2A constitutes the sole magnetic source, variations in its thickness alone cannot account for the axial low. Lava accumulation models illustrate that high geomagnetic intensity over the past ∼2.5 kyr, and decreasing intensity over the past ∼900 years, are both consistent with the broad axial anomaly high and the superimposed shorter wavelength low. The continuity of this axial low, and similar features elsewhere on the EPR suggests, that either crustal accretionary processes responsible for this anomaly are common among fast‐spread ridges, or that the observed magnetization low may partially reflect global geomagnetic intensity fluctuations.</jats:p
Assessing the causal effect of long-term exposure to air pollution on cognitive decline in middle-aged and older adults Empirical evidence from a nationwide longitudinal cohort
No full textThree Essays on Applied Microeconomics
No full textThe first chapter studies the changes in doctors\u27 decisions when they are at the beginning or the end of their shifts using the Florida Emergency Department Dataset. I find that patients have shorter lengths of stay, have lower medical expenditure, and receive fewer procedures if taken care of by doctors at the end of their shifts. On the other hand, patients have a longer length of stay, higher medical expenditure, and receive more medical expenditure if taken care of by doctors who just start their shifts. In addition, I employ generalized random forest models to explore heterogeneous effects among doctors and patients with different characteristics.Chapter 2 explores how doctors\u27 medical decisions are affected by their colleagues\u27 medical schools. Specifically, I study how doctors adjust their decisions when working with colleagues from the top 20 schools or with colleagues from the same schools. We find that patients experience longer length of stay if the ratio of their doctors\u27 colleagues graduating from the top 20 medical schools increases. On the other hand, patients\u27 medical expenditure, number of procedures received, and their health outcome are not affected by their doctors\u27 colleagues\u27 education background. In addition, I do not find significant change in doctors\u27 medical behaviors when working with colleagues from the same schools. Females are underrepresented in the Engineering domain. In Taiwan, after controlling for test scores, females are found to have a 15% lower likelihood of being admitted to Engineering majors compared to males. To explore potential factors encouraging females pursuing degrees in Engineering, Chapter 3 first studies how students \u27 university and subject field choices are affected by the earlier cohorts of their high schools who graduated a year earlier. The finding reveals strong preference among students for universities which many of their earlier cohort admitted to in the previous year. In addition, for females with weaker academic background, the probabilities for choosing subject fields in the Engineering domain increases as more of their female earlier cohorts admitted to those fields. Last, the research uncovers a willingness among students to compromise university-major pairs\u27 qualities to study the majors in the same subject fields or the same universities as their earlier cohorts