RF Studies of Soot and Ammonia Loadings on a Combined Particulate Filter and SCR Catalyst

Modern diesels employ a particulate filter (DPF) to reduce soot emissions. Additionally, the selective catalytic reduction (SCR) of NOx by NH3 stored on the SCR catalyst reduces NOx emissions. In some vehicles the functions of these aftertreatment components are combined in the SDPF, a DPF having a SCR washcoat. The RF resonant method has been shown to be an alternative tool for measuring the DPF\u27s soot loading and the SCR\u27s NH3 loading. For both applications, the transmitted electromagnetic signal between antennae placed on either side of the catalyst change with loading. Here we report the influence of the RF signal on both soot and NH3 loadings on a SDPF segment. We show that the attenuation of the RF signal by soot is much larger than that caused by saturating it with 400 ppm NH3. By taking the mean RF signal amplitude measured over a wide range of frequencies, we demonstrate a method for determination of the soot loading even in the presence of stored NH3. For light soot loadings, before the RF attenuation by soot cause the resonant modes to disappear in the spectra, we demonstrate a method for the simultaneous determination of both the soot and NH3 loadings

Final design report of a personnel launch system and a family of heavy lift launch vehicles

The objective was to design both a Personnel Launch System (PLS) and a family of Heavy Lift Launch Vehicles (FHLLVs) that provide low cost and efficient operation in missions not suited for the Shuttle. The PLS vehicle is designed primarily for space station crew rotation and emergency crew return. The final design of the PLS vehicle and its interior is given. The mission of the FHLLVs is to place large, massive payloads into Earth orbit with payload flexibility being considered foremost in the design. The final design of three launch vehicles was found to yield a payload capacity range from 20 to 200 mt. These designs include the use of multistaged, high thrust liquid engines mounted on the core stages of the rocket

Dosimeter-Type NOx Sensing Properties of KMnO4 and Its Electrical Conductivity during Temperature Programmed Desorption

An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release

Radio-Frequency-Based NH₃-Selective Catalytic Reduction Catalyst Control : Studies on Temperature Dependency and Humidity Influences

The upcoming more stringent automotive emission legislations and current developments have promoted new technologies for more precise and reliable catalyst control. For this purpose, radio-frequency-based (RF) catalyst state determination offers the only approach for directly measuring the NH3 loading on selective catalytic reduction (SCR) catalysts and the state of other catalysts and filter systems. Recently, the ability of this technique to directly control the urea dosing on a current NH3 storing zeolite catalyst has been demonstrated on an engine dynamometer for the first time and this paper continues that work. Therefore, a well-known serial-type and zeolite-based SCR catalyst (Cu-SSZ-13) was investigated under deliberately chosen high space velocities. At first, the full functionality of the RF system with Cu-SSZ-13 as sample was tested successfully. By direct RF-based NH3 storage control, the influence of the storage degree on the catalyst performance, i.e., on NOx conversion and NH3 slip, was investigated in a temperature range between 250 and 400 °C. For each operation point, an ideal and a critical NH3 storage degree was found and analyzed in the whole temperature range. Based on the data of all experimental runs, temperature dependent calibration functions were developed as a basis for upcoming tests under transient conditions. Additionally, the influence of exhaust humidity was observed with special focus on cold start water and its effects to the RF signals

Radio-Frequency-Controlled Urea Dosing for NH3-SCR Catalysts : NH3 Storage Influence to Catalyst Performance under Transient Conditions

Current developments in exhaust gas aftertreatment led to a huge mistrust in diesel driven passenger cars due to their NOx emissions being too high. The selective catalytic reduction (SCR) with ammonia (NH3) as reducing agent is the only approach today with the capability to meet upcoming emission limits. Therefore, the radio-frequency-based (RF) catalyst state determination to monitor the NH3 loading on SCR catalysts has a huge potential in emission reduction. Recent work on this topic proved the basic capability of this technique under realistic conditions on an engine test bench. In these studies, an RF system calibration for the serial type SCR catalyst Cu-SSZ-13 was developed and different approaches for a temperature dependent NH3 storage were determined. This paper continues this work and uses a fully calibrated RF-SCR system under transient conditions to compare different directly measured and controlled NH3 storage levels, and NH3 target curves. It could be clearly demonstrated that the right NH3 target curve, together with a direct control on the desired level by the RF system, is able to operate the SCR system with the maximum possible NOx conversion efficiency and without NH3 slip

Dual Mode NOx Sensor: Measuring Both the Accumulated Amount and Instantaneous Level at Low Concentrations

The accumulating-type (or integrating-type) NOx sensor principle offers two operation modes to measure low levels of NOx: The direct signal gives the total amount dosed over a time interval and its derivative the instantaneous concentration. With a linear sensor response, no baseline drift, and both response times and recovery times in the range of the gas exchange time of the test bench (5 to 7 s), the integrating sensor is well suited to reliably detect low levels of NOx. Experimental results are presented demonstrating the sensor’s integrating properties for the total amount detection and its sensitivity to both NO and to NO2. We also show the correlation between the derivative of the sensor signal and the known gas concentration. The long-term detection of NOx in the sub-ppm range (e.g., for air quality measurements) is discussed. Additionally, a self-adaption of the measurement range taking advantage of the temperature dependency of the sensitivity is addressed

Teaching at the sharp end of correctional education theory and practice

This research investigates and advances knowledge of the factors that shape the teaching role and hinder education delivery in the United States' jail system. This is an area in which little research has been undertaken. Correctional teachers work with incarcerated adults in jails and prisons. This research comprises a series of closely related investigative studies that critically explore historical, political, and ideological factors that determine the intent and purported outcomes of education programs in jails. This approach leads to a comprehensive case study of a jail correctional education program. In the course of the investigative studies I point to how correctional education has capitulated to penal trends and powerful political agendas that drive correctional and education policy, some of which appear to be diametrically opposed to the interests of teachers and inmate students. The findings leading from the case study point to why teaching in such a setting is logistically, institutionally and politically complicated, and excessively so. I elucidate how a preferred teaching role is constrained by a divisive workplace culture, a range of institutional problems and, not least, a complex inmate student population. These matters are magnified by convoluted education policies including high stake standardized testing. In the course of the case study, I provide examples of how teachers working in a jail setting attempt to navigate the many pressures and demands on their time armed with finite resources and an education model which in many respects defines their role as teachers

Gender differences in two motivational pathways to political conservatism

Gender differences in strategic interests provide a theoretical framework to account for the heterogeneous landscape of gender differences in political preferences. Men's greater scores on social dominance orientation are consistent with a preference for social hierarchy, and women's greater scores on sexual disgust, a construct tapping aversions to sexually adventurous behavior, are consistent with a preference for restricted sexuality. We analyze how these psychological motives relate to political orientation (N = 757) and find that (a) there are indirect effects of gender on conservatism through social dominance orientation and sexual disgust, (b) there is a suppressor effect such that controlling for the indirect effect through sexual disgust leads the direct effect of gender to become substantially larger, (c) gender moderates the effect of sexual disgust on conservatism such that sexual disgust is a stronger predictor of conservatism among women, and (d) conservative moral foundations mediate the effect of sexual disgust on political conservatism