Polyethylenimine (PEI) has been shown to be promising for direct air capture (DAC) of carbon dioxide and has potential for commercial scale-up globally. Laboratory scale processes include multiple ...steps, such as mixing, solvent extraction, vacuum application, sonication, and various flushes and activation steps. It is critical to properly control these operating parameters to achieve higher capture capacity as a result of the optimized material configuration. This study adopts previously published pelletization processes for PEI-infiltrated mesoporous foam silica (mesoporous silica foam) to uncover the adsorption mechanisms and optimize the associated fabrication steps, such as sonication, to achieve higher sorbent productivity. A high capture capacity was achieved at 46 °C for 75 wt % PEI loading (2.27 mmol/g) followed by PEI_MSF 70 (1.81 mmol/g) and PEI_MSF 80 (1.44 mmol/g). As part of the optimization, sonication parameters of frequency, amplitude, and time were modified for PEI_MSF 75 sorbent, which resulted in the highest uptake capacity of 3.04 mmol/g (sonicated at 40 kHz and a wave amplitude of 50% for 30 s). These preliminary results would tend to prove that sonication energy affects carbon capture capacity, although there is still a lack of understanding regarding the exact underlying mechanism, suggesting the need for further investigation. It is important to note that the present work is focused on the adsorption mechanisms and not desorption or durability of the capture performance. Ongoing research addresses these factors. This paper is intended to establish baseline DAC behavior of a promising capture medium and begins probing the optimization spectrum by considering the effects of sonication energy on adsorption. Ongoing work intends to address potential abbreviations of the full range of process steps and furthers the understanding of kinetics by considering the desorption and resorption attributes.
We report the results of a limited number of measurements that were performed to compare the upload performance of a RaptorQ-based file transfer protocol to SFTP in a mobile environment. In ...particular, we measured times required to transfer files from a laptop in a vehicle and tethered to the Internet via an iPhone hotspot to a stationary host located on the Internet and having a manually assigned IP address. Even though our RaptorQ-based protocol is in its very early stages of development, we found that the file transfer times of the two protocols are comparable in the stationary environment even without doing any specific optimization work on the RaptorQ-based protocol. We also found that SFTP was very prone to stalling whenever we passed through a region where propagation is poor whereas, in the same propagation environment, the RaptorQ-based protocol tended to make use the available bandwidth and complete the file transfer but with a reduced file transfer time.
IC manufacturers will often adopt new cassette materials for particulate control, dimensional stability, and improved thermal properties. In order to maintain tool performance, in some cases the ...introduction of these new materials introduce new demands on the vacuum system. Six cassette materials have been tested in a medium current implanter using eight pump configurations. The results show that preventing water in the load lock from getting to the process chamber is important to maximize tool throughput. This paper discusses what options are currently available to compensate for new vacuum demands that are related to hygroscopic cassette materials.
Recent advances in soil moisture remote sensing have
produced satellite data sets with improved soil moisture mapping under
vegetation and with higher spatial and temporal resolutions. In this study,
...we evaluate the potential of a new, experimental version of the Advanced Scatterometer (ASCAT) soil water index data set for multiple objective calibrations of a conceptual hydrologic model. The analysis is performed in 213 catchments in Austria for the period 2000–2014. An HBV (Hydrologiska Byråns Vattenbalansavdelning)-type hydrologic model is calibrated based on runoff
data, ASCAT soil moisture data, and Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover data for various
calibration variants. Results show that the inclusion of soil moisture data
in the calibration mainly improves the soil moisture simulations, the
inclusion of snow data mainly improves the snow simulations, and the inclusion of both of them improves both soil moisture and snow simulations to almost the same extent. The snow data are more efficient at improving snow simulations than the soil moisture data are at improving soil moisture simulations. The improvements of both runoff and soil moisture model efficiencies are larger in low elevation and agricultural catchments than in others. The calibrated snow-related parameters are strongly affected by including snow data and, to a lesser extent, by soil moisture data. In contrast, the soil-related parameters are only affected by the inclusion of soil moisture data. The results indicate that the use of multiple remote sensing products in hydrological modeling can improve the representation of hydrological fluxes and prediction of runoff hydrographs at the catchment scale.
The recent advances in remote sensing provide opportunities for estimating the parameters of conceptual hydrologic models more reliably. However, the question of whether and to what extent the use of ...satellite data in model calibration may assist in transferring model parameters to ungauged catchments has not been fully resolved. The aim of this study is to evaluate the efficiency of different methods for transferring model parameters obtained by multiple-objective calibrations to ungauged sites and to assess the model performance in terms of runoff, soil moisture, and snow cover predictions relative to existing regionalization approaches. The model parameters are calibrated to daily runoff, satellite soil moisture (Advanced Scatterometer – ASCAT), and snow cover (Moderate Resolution Imaging Spectroradiometer – MODIS) data. The assessment is based on 213 catchments situated in different physiographic and climate zones of Austria. For the transfer of model parameters, eight methods (global and local variants of arithmetic mean, regression, spatial proximity, and similarity) are examined in two periods, i.e., the period in which the model is calibrated (2000–2010) and an independent validation period (2010–2014). The predictive accuracy is evaluated by the leave-one-out cross-validation. The results show that the method by which the model is calibrated in the gauged catchment has a larger impact on runoff prediction accuracy in the ungauged catchments than the choice of the parameter transfer method. The best transfer methods are global and local similarity and the kriging approach. The performance of the transfer methods differs between lowland and alpine catchments. While the soil moisture and snow cover prediction efficiencies are higher in lowland catchments, the runoff prediction efficiency is higher in alpine catchments. A comparison of the model transfer methods, based on parameters calibrated to runoff, snow cover, and soil moisture with those based on parameters calibrated to runoff, only indicates that the former outperforms the latter in terms of simulating soil moisture and snow cover. The performance of simulating runoff is similar, and the accuracy depends mainly on the weight given to the runoff objective in the multiple-objective calibrations.
► We compare design flood estimates from flood frequency statistics and rainfall runoff models. ► Statistical estimates can be too low when a step change in the flood frequency curve occurs. ► Runoff ...model estimates are too high when chosen design storms are too large. ► Design flood dominating runoff components have to be represented correctly.
Design floods for a given location at a stream can be estimated by a number of approaches including flood frequency statistics and the design storm method. If applied to the same catchment the two methods often yield quite different results. The aim of this paper is to contribute to understanding the reasons for these differences. A case study is performed for 10 alpine catchments in Tyrol, Austria, where the 100-year floods are estimated by (a) flood frequency statistics and (b) an event based runoff model. To identify the sources of the differences of the two methods, the 100-year floods are also estimated by (c) Monte Carlo simulations using a continuous runoff model. The results show that, in most catchments, the event based model gives larger flood estimates than flood frequency statistics. The reasons for the differences depend on the catchment characteristics and different rainfall inputs that were applied. For catchments with a high storage capacity the Monte Carlo simulations indicate a step change in the flood frequency curve when a storage threshold is exceeded which is not captured by flood frequency statistics. Flood frequency statistics therefore tends to underestimate the floods in these catchments. For catchments with a low storage capacity or significant surface runoff, no step change occurs, but in three catchments the design storms used were larger than those read from the IDF (intensity duration frequency) curve leading to an overestimation of the design floods. Finally, also the correct representation of flood dominating runoff components was shown to influence design flood results. Geologic information on the catchments was essential for identifying the reasons for the mismatch of the flood estimates.
The perfluorinated sulfonic acid membranes used in direct alcohol fuel cells cause low faradaic efficiency and performance due to alcohol absorption and permeation. Thus, a measurement setup is ...sought that enables a direct evaluation of the suitability of polymer electrolytes for this application. A 3D‐printed diffusion cell setup capable of measuring the interaction between the organic solvents, such as alcohols, and a proton exchange membrane via confocal Raman microscopy is introduced. The cell design employs flow channels to mimic the flow fields of electrochemical cell tests. Exemplarily, information on the interaction of membranes like Nafion 212 and the composite membrane Nafion XL with 1 m solutions of organic solvents such as 2‐propanol, acetone, and ethanol are provided to demonstrate the applicability of this setup. The Raman diffusion cell is capable of quantifying the preferred solvent uptake, which is characterized by the sorption coefficient, the permeability, and the concentration gradient within the membrane. These properties can be obtained in situ and in a time‐resolved manner. Thus, this diffusion cell setup is a powerful and accessible tool for screening membrane compatibility with various liquids.
A 3D printed diffusion cell setup for confocal Raman microscopy is introduced, which is capable of giving insight into the interactions between polymeric membranes, e.g., polymer electrolytes used in direct alcohol fuel cells, and different organic solvents. The design allows for determining time‐dependent concentration profiles within complex composite membranes, their through‐plane swelling, permeability, and preferred solvent uptake.
Empirical distribution functions of flood peaks in small catchments sometimes show discontinuities in the slope; that is, the largest flood peaks are significantly larger than the rest of the record. ...The aim of this paper is to understand whether these discontinuities, or step changes, can be a consistent effect of hydrological processes. We conducted field surveys in two Austrian alpine catchments 73 km2in size to map the spatial patterns of surface runoff generation and hydrogeologic storage. On the basis of this information, we selected the parameters of a distributed continuous runoff model, which is designed to simulate well the point when the storage capacity of the catchment is exhausted. Then we calibrated a stochastic rainfall model and performed Monte Carlo simulations of runoff to generate flood frequency curves for the two catchments. The curves exhibit a step change around a return period of 30 years. An analysis of the storage capacities suggests that this step change is due to a threshold of storage capacity being exceeded, which causes fast surface runoff in large parts of the catchments. The threshold occurs when the storage within the catchment is spatially rather uniform. To identify step changes, reliable estimates of the catchment storage capacity are needed on the basis of detailed hydrogeological information. The occurrence of a step change is of importance for estimating low‐probability floods since the flood estimates with the step change accounted for can be significantly different from those based on commonly used distribution functions. We therefore suggest that step changes in the flood frequency curve of small catchments can be real and their possible presence should be taken into account in design flood estimation.
Key Points
For the examined catchments step changes in the flood frequency curve are real
In this case they are caused by threshold processes related to storage capacity
Step changes significantly affect flood design values
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