1,119 research outputs found
The Studious University: A Marxist-Psychoanalytic Groundwork
How a pedagogy of study can work against the neoliberal university, from a psychoanalytic-Marxist perspective
Re-Taking the Test
Application of Avital Ronnell's theory of the "test drive" to high-stakes standardized testing in K-12 schooling
An analysis of the kinetics for oil agglomeration of coal
In batch tests with graphite, 2 min. were required to produce a maximum shift towards larger particle sizes in the distribution curves for a stirring speed of 21,000 rpm, slurry concentration of 2 wt%, and oil dosage of 10 v/w%. For a stirring speed of 650 rpm, 4 min. were required for the maximum shift. When the oil was pre-emulsified and then added to the slurry, the maximum shift required 1 min. at 650 rpm. In all these cases, the distribution curves showed particle size reductions after their maximum shift. In the case of 650 rpm, the shift was all the way back to nearly the feed size distribution;For emulsion characterization, the nonpolar oils (tetralin and a heptane/heptanol mixture) were more stable than the polar oil (heptane) and an ultrasonic treatment produced the most turbid emulsions;In batch studies with Australian coal from the Ulan mine, emulsification decreased the time needed for agglomeration and created slightly more compact spherical agglomerates. Although the use of heptane (a nonpolar oil) created more selective agglomeration of the organic matter, its use caused the agglomeration to proceed at a slower rate. Of the three oils used, heptane, tetralin, and the heptane/heptanol combination, the mixture of heptane/heptanol produced the fastest agglomeration;In continuous runs employing Upper Freeport coal, there were runs where the size of the agglomerates was limited to about 1000 [mu]m or smaller. In these runs, application of the layering mechanism in the population balance did a good job in modelling the particle growth. For runs where agglomeration produced particles that were much larger than 1000 [mu]m, the layering model was able to fit the size distribution for small particle sizes, while a Gaussian distribution was able to fit the distribution for large particle sizes. The Gaussian distribution was useful for two purposes: (1) for determining the influence of the operating parameters on the particle size distribution data, and (2) to serve as an explicit functional form when employing a coalescence/breakage model. Thus, some of the continuous runs produced distributions that were explained by assuming growth by layering, while other continuous runs produced distributions that were explained by both layering (small particle sizes) and coalescence/breakage (large particle sizes)
Evaluation of laboratory and field techniques to improve portland cement concrete performance
This dissertation is presented as a compilation of five papers. Each paper is presented as a chapter in the dissertation and includes a short literature review, research data, significant findings, and references. A general conclusion section follows the main body of the dissertation and summarizes the significant findings and includes recommendations for further research.;The first paper presents a paste and concrete laboratory study investigating the two-stage mixing process and its effects on portland cement concrete mix consistency and concrete performance. In the paste study, mixing energy was varied to determine the effects on rheological and compressive strength properties. The concrete study investigated the two-stage mixing process and its effects on fresh and hardened concrete properties.;The second paper details a new characterization procedure for portland cement using the heat signature. A Type I/II portland cement was used to determine the effects of initial water and initial cement temperature on the heat signature of the paste. Several other portland cements, including blended cements, were also investigated to show the differences in cement chemistry when comparing the heat generation curves.;The third paper investigates the effects of differing air entraining agent, water reducing agents, and supplementary cementitious materials on the air void structure of fresh mortar samples. The air void analyzer was used to document the air void structure and identify anomalies or incompatible material combinations. Cubes were cast for compressive strength testing at seven days to show incompatible combinations in terms of retarded strength gain.;The fourth paper uses AVA data from a sixteen state pooled fund study to evaluate the AVA sampling locations. Samples were obtained from the slip formed concrete surface on vibrators and between vibrators from sixteen states. AVA samples were obtained before the paver on three states. Statistical analysis (t-test) was conducted at an alpha level of 0.05 to determine significance.;The fifth paper presents data on the heat signature of ternary mixes. The heat signatures were characterized and the results were modeled using slope 1 and slope 2, maximum temperature, time to maximum temperature, area under the heat signature curve, initial set, and final set
Master of Science
thesisThe Sky-scan Atmospheric Monitoring Instrument (SAMI) consists of a low pro-fi le, autonomous unmanned aerial vehicle (UAV) that provides a platform for remotely sampling airborne contaminants in real-time over large distances. In this manner, the SAMI may be used to acquire pollutant concentration at various altitudes, relevant, for example, to smokestack emissions, and in high-risk locations where conditions hazardous to humans may exist. The SAMI system employs an innovative miniaturized pollution measurement device that captures discrete gas samples at programmed intervals during flight and records the corresponding pollutant concentration using an on-board data logger. The pollution measurement device integrates seamlessly with the body of the UAV and directly interfaces with the autopilot hardware/software. The pollution measurement device draws/expels gas into/out of the sampling chamber by taking advantage of the pressure drop that naturally occurs over the surface of the aircraft. This eliminates the need for an external pump, thereby aff ording signifi cant weight and cost savings. The present thesis documents the response characteristics of the SAMI system and demonstrates the functionality of the system for the specifi c pollutant carbon monoxide (CO). The potential application is real-time monitoring of air pollution dispersion due to automobile traffic
Influence of subgrade improvement and non-uniformity on pavement performance
This thesis contains results from three projects describing self-cementing fly ash stabilization of RAP-soil mixtures, stabilization of limestone screenings for use as a structural layer in road construction, and finite element modeling results of various subgrade materials including self-cementing fly ash stabilized subgrade, natural subgrade, granular subbase, and hydrated fly ash. The first project shows that self-cementing fly ash stabilization of RAP-soil mixtures is economically feasible and structurally capable of supporting construction traffic. The increase stiffness from the addition of self-cementing fly ash increases capacity ensuring long term pavement performance. Addition of self-cementing fly ash increases the consolidated shear strength about five times. The second project shows construction operations and field results proving that stabilization of limestone screenings is viable, cost effective, and produces an adequate structural layer for road construction. The measured moisture-density curves for manufactured sand and limestone screenings are about the same, and the moisture-strength curves show a dramatic decrease in strength beyond the optimum moisture content for strength. Durability testing concluded that CKD stabilized manufactured sand and limestone screenings are not viable construction alternatives, and the addition of class C fly ash with CKD significantly increased the durability of the mixtures. The third project concluded that a link exists between subgrade non-uniformity and pavement performance. Field testing, with the DCP, Clegg Impact Hammer, nuclear density gauge, and GeoGauge, and statistical analysis of subgrade materials concluded that granular subbase, self-cementing fly ash treated subgrade, and HFA decrease the variability of field results. Finite element modeling analysis proved that a link exists between subgrade non-uniformity and pavement performance. Uniform modeling conditions produced lower average deflections and stresses increasing pavement life. Statistical analysis concluded that modeling uniform subgrade conditions produce average stresses that have less variability than those for non-uniform modeling conditions. Pavement response reliability increased with the addition of uniform subgrade, proving that subgrade non-uniformity influences pavement performance
The Geopolitics of Digital Technology Innovation: Assessing Strengths and Challenges of Germany's Innovation Ecosystem
The COVID-era public and private investment influx into Germany’s digital technology R&D is reversing amid inflation, fiscal consolidation, and geopolitical pressures coming from the Zeitenwende. Germany's future in an EU that is among the top-tier technology powers requires a profound and rapid transition of the country's R&D strengths into data-intensive, systems-centric areas of IoT and deep technology that are linked to the domestic manufacturing base. New policy approaches in three areas - money, markets, and minds - are needed. New technologies such as robotics, artificial intelligence (AI), advanced material science, biotech, and quantum computing tend to have broad general-purpose applications. But uncoordinated funding vehicles, universities' civil clauses, and restrictive visa and onboarding guidelines for skilled foreign workers slow innovation in these sectors and hamper German techno-geopolitical competitiveness
Association of inferior vena cava filter placement for venous thromboembolic disease and a contraindication to anticoagulation with 30-day mortality
Importance: Despite the absence of data from randomized clinical trials, professional societies recommend inferior vena cava (IVC) filters for patients with venous thromboembolic disease (VTE) and a contraindication to anticoagulation therapy. Prior observational studies of IVC filters have suggested a mortality benefit associated with IVC filter insertion but have often failed to adjust for immortal time bias, which is the time before IVC filter insertion, during which death can only occur in the control group.
Objective: To determine the association of IVC filter placement with 30-day mortality after adjustment for immortal time bias.
Design, Setting, and Participants: This comparative effectiveness, retrospective cohort study used a population-based sample of hospitalized patients with VTE and a contraindication to anticoagulation using the State Inpatient Database and the State Emergency Department Database, part of the Healthcare Cost and Utilization Project of the Agency for Healthcare Research and Quality, from hospitals in California (January 1, 2005, to December 31, 2011), Florida (January 1, 2005, to December 31, 2013), and New York (January 1, 2005, to December 31, 2012). Data analysis was conducted from September 15, 2015, to March 14, 2018.
Exposure: Inferior vena cava filter placement.
Main Outcomes and Measures: Multivariable Cox proportional hazard models were constructed with IVC filters as a time-dependent variable that adjusts for immortal time bias. The Cox model was further adjusted using the propensity score as an adjustment variable.
Results: Of 126 030 patients with VTE, 61 281 (48.6%) were male and the mean (SD) age was 66.9 (16.6) years. In this cohort, 45 771 (36.3%) were treated with an IVC filter, whereas 80 259 (63.7%) did not receive a filter. In the Cox model with IVC filter status analyzed as a time-dependent variable to account for immortal time bias, IVC filter placement was associated with a significantly increased hazard ratio of 30-day mortality (1.18; 95% CI, 1.13-1.22; P \u3c .001). When the propensity score was included in the Cox model, IVC filter placement remained associated with an increased hazard ratio of 30-day mortality (1.18; 95% CI, 1.13-1.22; P \u3c .001).
Conclusions and Relevance: After adjustment for immortal time bias, IVC filter placement was associated with increased 30-day mortality in patients with VTE and a contraindication to anticoagulation. Randomized clinical trials are needed to determine the efficacy of IVC filter placement in patients with VTE and a contraindication to anticoagulation
Germany's Economic Security and Technology: Optimizing Export Control, Investment Screening and Market Access Instruments
Technological development and increasingly fraught US-China competition have geopolitical consequences for technology access. The erosion of post-Cold War multilateral dual-use technology export control regimes, such as the Wassenaar Arrangement, and investment and other control frameworks have led to national, EU, and ad hoc measures, such as the restrictions on Russian semiconductor access following the invasion of Ukraine
Technology and Industrial Policy in an Age of Systemic Competition: Safeguarding Germany's Technology Stack and Innovation Industrial Strength
As one of the world's most globalized economies, Germany is confronting a challenging international environment characterized by aggressive subsidies, a global race for control of key technologies such as advanced chips, and vulnerable supply chains for critical components. Increased energy costs - induced by Russia's war on Ukraine - are also straining Germany's industrial model. Germany's industrial economy is simultaneously undergoing a fundamental transformation from precision-based engineering to systems-based manufactured products. With this shift, a competitive digital technology stack is becoming a key repository for future industrial competitiveness. Yet, the country struggles to capture value in fast-growing markets like that for cloud and edge infrastructure. It also faces risks from its exposure to untrustworthy technology vendors and potential geopolitical disruptions to fragile hardware supply chains
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