705 research outputs found
Numerical Simulation of Continuous Extraction of Li<sup>+</sup> from High Mg<sup>2+</sup>/Li<sup>+</sup> Ratio Brines Based on Free Flow Ion Concentration Polarization Microfluidic System
No full textIon concentration polarization (ICP) is a promising mechanism for concentrating and/or separating charged molecules. This work simulates the extraction of Li+ ions in a diluted high Mg2+/Li+ ratio salt lake brines based on free flow ICP focusing (FF-ICPF). The model solution of diluted brine continuously flows through the system with Li+ slightly concentrated and Mg2+ significantly removed by ICP driven by external pressure and perpendicular electric field. In a typical case, our results showed that this system could focus Li+ concentration by ~1.28 times while decreasing the Mg2+/Li+ ratio by about 85% (from 40 to 5.85). Although Li+ and Mg2+ ions are not separated as an end product, which is preferably required by the lithium industry, this method is capable of decreasing the Mg2+/Li+ ratio significantly and has great potential as a preprocessing technology for lithium extraction from salt lake brines
High-voltage performance of concentration-gradient Li[Ni<sub>0.6</sub>Co<sub>0.2</sub>Mn<sub>0.2</sub>]O<sub>2</sub> layered oxide cathode materials for lithium batteries
No full textHigh-voltage performance concentration-gradient Li[Ni0.6Co0.2Mn0.2]O2 (CG-NCM622) layered oxide cathodes consisting of Li[Ni0.8Co0.1Mn0.1]O2 cores and stable outer layers of Li[Ni1/3Co1/3Mn1/3]O2 were synthesized via co-precipitation.</p
U-U and Th-U ages over the last 820,000 years from Devils Hole calcite (NV, USA) for palaeo water table reconstruction
No full textU-series measurements to constrain the age of Devils Hole cave 2's submerged calcite (Nevada, USA). Samples originate from 11 horizontally drilled cores of 0.1 to 1.3m length and 2.5cm diameter. They were taken from the hanging wall at elevations between +3.2 m and +19.5 m relative to the modern water table. Sampling was done between the years 2015 and 2023. A resurvey of the elevation of all sample locations was done in 2023. Samples for dating are all taken from mammillary calcite which precipitates from the groundwater underneath the water table. The sequence of mammillary calcite and Folia which only grows at the water table surface allow to reconstruct a water table history. Depending on the sequence of mammillary calcite and Folia, samples represent the following types: (i) the water table increased above this elevation, (d) the water table decrease to below this elevation, (b) water table rose briefly above this elevation and then dropped below it again, (x) water table was above this elevation (see method section of Steidle et al. (2024) for details). Both, 230Th/U ages and 234U/U ages were calculated. The latter method could be applied under the assumption that initial 234U/U concentration are correlated with d18O and d13C stable isotope ratios (Li et al., 2021). The ages range from 820,000 to 350,000 years ago and show that the water table oscillations are in sync with global climate shifts where Interglacials are marked by a low water table and vice versa glacials are marked by a high water table (Steidle et al., 2024)
The Application of Infrared Spectral Radiances and Fluxes for Arctic Climate Monitoring and Cloud Phase Determination from Space
No full textThe Arctic climate is strongly influenced by infrared (IR) radiation emitted and absorbed by greenhouse gases, clouds, and the surface. As the Arctic continues to rapidly change, it is crucial to further understand how changes in such geophysical variables influence changes in IR flux at the Arctic surface and the top-of-atmosphere. Cloud phase (i.e., ice, liquid, and mixed) can affect the clouds’ overall contributions to the IR fluxes. However, the spatial and temporal occurrences of Arctic cloud phase are not well characterized.
Satellite observations of spectrally resolved IR fluxes can be used to connect changes in the atmosphere and surface to broadband IR flux changes, however, such studies have not been performed in the Arctic. Spectral IR radiances can be used for satellite-based cloud phase retrievals, but conventional methods using the mid-IR window region (~800-1250 cm-1) have limitations in polar regions, especially for mixed phase clouds. It may be possible to improve Arctic mid-IR cloud phase retrievals with far-IR (<~600 cm-1) measurements. However, few studies have investigated far-IR cloud phase retrievals from space.
Overall, this dissertation studies the potential and limitations of spectral mid-IR and far-IR radiances and fluxes for monitoring Arctic IR radiation and identifying cloud phase from space. It contains four studies. The first study examines the trends of zonal mean spectral outgoing longwave radiation (OLR) and greenhouse efficiencies (GHE) in the Arctic from 2003 to 2016 using spectral flux derived from collocated Atmospheric IR Sounder (AIRS) and the Clouds and the Earth's Radiant Energy System observations in conjunction with AIRS retrievals. Positive and negative trends in Arctic OLR and GHE are observed across the far-IR and mid-IR spectral regions, depending on the season, and the largest positive OLR and GHE trends occur in spring. Sensitivity studies reveal that surface temperature increases contribute most to the OLR and GHE trends, but the effects of atmospheric humidity and temperature are discernable.
In the second study, AIRS cloud phase retrievals, which were never evaluated over the Arctic, are evaluated against four years of combined CloudSat and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation measurements over the Arctic Ocean. AIRS classification skill for single-layer ice- and liquid-phase clouds ranges from 85%–95% and 22%–32%, respectively. Most unknown and liquid AIRS phase classifications correspond to mixed-phase clouds.
The third study explores the synergy between the far- and mid-IR for polar ice cloud detection. A far-IR brightness temperature difference (BTD) test is developed and applied to simulated IR radiances and the results are compared to those from a mid-IR BTD test. Scattering leads to the far-IR being most sensitive to small ice particles, and the increase of cloud optical depth contributing to stronger far-IR BTD signals. Synergy between the mid-IR and far-IR is most useful for identifying cloud ice particles with an effective diameter around 40 µm.
The final study examines the sensitivity of simulated 11 µm brightness temperature (BT11) to cloud ice changes within Arctic liquid-topped mixed phase clouds (LTMs). It was determined that BT11 can be sensitive to cloud ice for a range of commonly observed Arctic LTMs. By utilizing channels in the mid- and far-IR, it may be possible to use BTD tests together with a machine learning approach to detect Arctic LTMs from space.PhDAtmospheric, Oceanic & Space ScienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/174592/1/coltenp_1.pd
Validating eDNA Measurements of the Richness and Abundance of Anurans at a Large Scale
No full text<ol>
<li>In some situations, environmental DNA (eDNA) metabarcoding is a more accurate tool for measuring species richness of a taxon than conventional methods. Whether this tool can reliably estimate the abundance of a taxon remains unresolved.</li>
<li>We examined the reliability of metabarcoding for measuring anuran diversity compared to a commonly used traditional line transect method (TLTM) through the replicate sampling of three visits across 71 waterbodies (ponds or reservoirs) in Liuheng, China. We also investigated the relative contributions of species-specific characteristics and the physiochemical properties of a waterbody on the relative read count across species and waterbodies.</li>
<li>We found that eDNA metabarcoding had a higher detection probability for each of seven anuran species found in the sampling region than TLTM. Furthermore, the relative read count estimated by metabarcoding was positively correlated with the density or relative density of individuals identified with the TLTM across waterbodies for every species. Species-specific characteristics of anurans, such as density, relative density, body mass, biomass and relative biomass, accounted for substantial variations in the read count across species and waterbodies, while physiochemical factors, including pH, temperature, water volume, vegetation and elevation, had little effect on the read count.</li>
<li class="15">Our results based on robust sampling suggest that metabarcoding enables more reliable and efficient measurements of anuran occurrence at a large scale during a short-term survey (within 15 days) than that obtained by the TLTM, and offers an alternative tool for quantifications of anuran abundance. Density or biomass is better and more reliable indicator of anuran abundance associated with read count than relative density or relative biomass.</li>
</ol><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100001809<br>Award Number: 3,203,007,031,872,240</p>
ESSAYS ON ENVIRONMENTAL POLICIES IN THE TRANSPORTATION SECTOR
No full textThis dissertation consists of three essays studying the effects of environmental regulations and policies in the transportation sector in China. The first chapter studies the effectiveness, efficiency, and distributional effect of using trade restrictions on used vehicles to protect the local environment. Leveraging comprehensive data on the bilateral trade of vehicles across Chinese prefecture cities and the staggered rollout of import restrictions on used vehicles implemented by city governments from 2013 to 2015, this chapter shows empirical evidence that import restrictions reduce net imports of used vehicles, and cities’ import restrictions are strategic complements. With a multi-sector multi-region structural trade model, this study shows that unilaterally restricting imports of used vehicles leads to welfare trade-offs between economic losses vs. environmental benefits. Restricting heavy-polluting vehicles makes some cities better off, especially lower-income cities. However, decentralized restrictions are socially inefficient due to strategic interactions, and the effectiveness and efficiency of using import restrictions as an environmental instrument are limited compared to emission taxes. The second chapter, joint with Jie Bai, Danxia Xie, and Shanjun Li, explores the import restrictions on used vehicles in China from the perspective of local protectionism. Leveraging the universe of new and used vehicle registration/sales data and the staggered removal of the restriction across cities from 2016 to 2018, this analysis shows that the removal of restriction led to a sharp increase in the cross-city flow of used vehicles but had no significant impacts on local air quality in the short run. Interestingly, the new vehicle market points to a prisoner’s dilemma among city governments: a unilateral removal of the policy would reduce new vehicle sales in a city but increase new vehicle sales in other cities. The effect is stronger in cities with a large automobile industry. The findings highlight alternative motives behind local environmental regulations and the need for coordinated efforts at the national level. The third chapter, joint with Shanjun Li, Xianglei Zhu, Yiding Ma, and Fan Zhang, examines the effectiveness of various policy measures that underlie the rapid development of the EV market in China, based on detailed data on EV sales, local and central government incentive programs, and charging stations in 150 cities from 2015 to 2018. This research finds that consumer subsidies for vehicle purchases accounted for more than half of EV sales in China. Nevertheless, investments in charging infrastructure were much more cost-effective than consumer subsidies. An inexpensive policy that merely provided EVs with a distinctive, green license plate was strikingly effective. These findings demonstrate the varying efficacy of different policy instruments and highlight the critical role of the government in promoting clean technologies
Global Simulation of Nitrate and Ammonium Aerosols and Their Radiative Effects and Comparison of Satellite-Based and Modeled Aerosol Indirect Forcing.
No full textLarge uncertainties exist in estimates of aerosol direct and indirect radiative effects on climate. In this dissertation, we improve the representation of nitrate and ammonium in the global model and evaluate their radiative effects. We also improve understanding why satellite-based estimates of aerosol indirect forcing are consistently lower than global model estimates.
The formation of nitrate and ammonium on five types of externally mixed pre-existing aerosols is taken into account in the global chemistry transport model. Compared with the treatment assuming the internal mixture, this work predicts lower burden, higher sources (sinks) and therefore shorter lifetimes of aerosol nitrate and ammonium. Nitrate and ammonium are found to exhibit two counteracting direct effects on pre-existing aerosols. The inclusion of ammonium and nitrate can boost scattering efficiency of sulfate and organic matter but lower scattering characteristics of sea salt due to their lower hygroscopicity than that of sea salt. The anthropogenic forcing of nitrate and ammonium at the top of atmosphere (TOA) are estimated to be -0.11 W m-2. Nitrate and ammonium also affect aerosol activation and the reflectivity of clouds. The first aerosol indirect forcing induced by anthropogenic nitrate and ammonium is estimated to be -0.1 W m-2 at TOA.
By using an offline radiative transfer model combined with statistical slopes of a proxy of cloud properties (ln(Nd)) versus a proxy of aerosol properties (ln(AOD) or ln(AI)) based on either only PD values of aerosol and cloud properties or PD and PI values, we found that statistical slopes based on the temporal variation of PD and PI values of Nd and AOD would be steeper than those only based on the spatial variation of PD values because the spatial variation of PD values does not include magnitude of AOD and Nd as small as those in the PI simulation. As a result, the associated error in aerosol indirect forcing can be between a factor of 3 to more than a factor of 6 on a global average basis if one uses slopes of ln(Nd) versus ln(AOD) to estimate PI Nd or about ±25-35% if one uses ln(AI).PhDAtmospheric and Space SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91511/1/lixum_1.pd
Educational achievement of Asian-American students: A generational perspective.
No full textThis study investigated how family-, individual-, and school-related factors together influence the learning of Asian American students during the first two years of high school, in comparison to that of Caucasian students. The author employed a generational perspective and defined first-generation Asian American students as those who were born in Asia and late emigrated to the United States with their parents; the second generation as those who were born in the United States, but have one or both Asian-born parents; and the third generation as those who were American-born, as were both of their parents. Using the first two waves of the National Educational Longitudinal Study of 1988, the first two generations of Asian American students were found to be advantaged over their Caucasian counterparts in terms of parents' educational background and expectations, and students' own learning attitudes and behaviors. The learning of these two generations is determined largely by their high educational goals, by the extraordinary effort expended in pursuit of these goals, and by good use of school academic resources. Third-generation Asian American students are similar to Caucasians in terms of family background and learning characteristics. For these groups, academic ability is a major factor determining their educational expectations, engagement, and their choice of courses. School curricular structure also exerts a great influence on their course-taking behaviors. A constrained, academically-focused curriculum, coupled with high graduation requirements, can "push" Caucasian and third-generation Asian American students to take more academic courses. The author offered several alternative explanations for these differential learning attitudes and behaviors across the three generation of Asian American students, and for the relationships of these attributes to the learning outcomes. These include differences in Asian and American cultural beliefs about the relative contribution of ability and effort to learning; recent selective immigration of Asians based on motivation, ability, or educational levels; and differential perceptions for the three generations of Asian American students of their status and mobility opportunities in the United States.PhDEducationUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104928/1/9624587.pdfDescription of 9624587.pdf : Restricted to UM users only
Research on Fault Fuzzy Clustering Method for Reducing False Alarm by New Three States Demarcation
No full text- …
