Computational Homogenisation of Polycrystalline Elastoplastic Microstructures at Finite Deformation

During sheet bulk metal forming processes, both flat geometries and three-dimensional structures change their shape while undergoing large plastic deformations. As for metal forming processes, FE-simulations are often done before in-situ experiments, a very accurate model for respective structures is required, performing well at small geometries possessing small curvatures as forms with wide as well as lateral characteristics.Because of the crystalline nature of metals, certain anisotropies have to be taken into account. Macroscopically observable plastic deformation is traced back to dislocations within considered slip systems in the crystals causing plastic anisotropy on the microscopic and the macroscopic level.A crystal plasticity model for finite deformations is used to model the behaviour of polycrystalline materials in representative volume elements (RVEs) on the microstructure. In order to circumvent singularities stemming from the linear dependency of the slip system vectors, a viscoplastic power-law is introduced providing the evolution of the plastic slips and slip resistances. The model is validated with experimental microstructural data under deformation. Through homogenisation and optimisation techniques, effective stress-strain curves are determined and can be compared to results from real forming processes, leading to an effective elastoplastic material model which is suitable for processes in the sheet bulk metal forming field

Surrogate cloud fields generated with the Iterative Amplitude Adapted Fourier Transform algorithm

A new method of generating two-dimensional and three-dimensional cloud fields is presented, which share several important statistical properties with real measured cloud fields.Well-known algorithms such as the Fourier method and the Bounded Cascade method generate fields with a specified Fourier spectrum. The new iterative method allows for the specification of both the power spectrum and the amplitude distribution of the parameter of interest, e.g. the liquid water content or liquid water path. As such, the method is well suited to generate cloud fields based on measured data, and it is able to generate broken cloud fields. Important applications of such cloud fields are e.g. closure studies. The algorithm can be supplied with additional spatial constraints which can reduce the number of measured cases needed for such studies. In this study the suitability of the algorithm for radiative questions is evaluated by comparing the radiative properties of cloud fields from cloud resolving models of cumulus and stratocumulus with their surrogate fields at nadir, and for a solar zenith angle of 0◦ and 60◦. The cumulus surrogate clouds ended up to be identical to the large eddy simulation (LES) clouds on which they are based, except for translations and reflections. The root mean square differences of the stratocumulus transmittance and reflectance fields are less than 0.03% of the radiative budget. The radiances and mean actinic fluxes fit better than 2%. These results demonstrate that these LES clouds are well described from a radiative point of view, using only a power spectrum together with an amplitude distribution

Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.

BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700

Revisiting Liquid Water Content Retrievals in Warm Stratified Clouds: The Modified Frisch

Accurate observations of liquid water content (LWC) in warm stratiform clouds are important for quantifying their radiative and hydrological effects and for studying aerosol-cloud interactions. Retrieving LWC from radar reflectivity under drizzling or nondrizzling conditions has been investigated for several decades by the cloud remote sensing community. However, no physically plausible framework exists to address the biases introduced by drizzle on existing retrieval techniques. We present the modified Frisch retrieval (ModFrisch), which combines radar and microwave radiometer measurements to retrieve LWC in both nondrizzling and drizzling conditions. It is shown, using a 1-D steady state microphysical model and a radar simulator, that the uncertainty of ModFrisch is up to four times smaller than the uncertainty of similar retrievals under drizzling conditions, enabling LWC profiling with an accuracy of 20%. The performance of the ModFrisch technique is evaluated using 1year of observations. Plain Language Summary It is important to measure the vertical structure of clouds accurately to create reliable climatological records and to investigate how well clouds can be predicted by weather and climate models. A commonly used technique to determine the liquid water content of stratified clouds is based on two standard instruments: a radar, providing profile information, and a microwave radiometer providing the total amount of liquid in the cloud. However, if the cloud droplets are too big (larger than about 50-70m), the vertical profile of the radar measurement cannot be related to the profile of liquid water content. Unfortunately, most stratus clouds contain liquid drops (drizzle) that exceed that critical size leading to a big lack of accurate data. In our study, we separate the cloud into two regions: the upper part of the cloud where drizzle has no significant influence and the lower part where drizzle is present. In the upper part, we apply a commonly used retrieval while assuming a linearly increasing liquid water content in the lower part, which has been shown to be valid in previous studies. Thus, we can potentially provide a more reliable basis of observational liquid water contents to constrain model simulations

Ground-Based Temperature and Humidity Profiling Using Spectral Infrared and Microwave Observations. Part II: Actual Retrieval Performance in Clear-Sky and Cloudy Conditions

Although current upper-air observing systems provide an impressive array of observations, many are deficient in observing the temporal evolution of the boundary layer thermodynamic profile. Ground-based remote sensing instruments such as the multichannel microwave radiometer (MWR) and Atmospheric Emitted Radiance Interferometer (AERI) are able to provide profiles of temperature and water vapor through the boundary layer at 5-min resolution or better. Previous work compared these instruments through optimal-estimation retrievals on simulated clear-sky spectra to evaluate the retrieval accuracy and information content of each instrument. In this study, this method is duplicated using real observations from collocated MWR and AERI instruments from a field campaign in southwestern Germany. When compared with radiosondes, this study confirms the previous results that AERI retrievals are more accurate than MWR retrievals in clear-sky and below-cloud-base profiling. These results demonstrate that the AERI has nearly 2 times as much information as the MWR

Advances in continuously profiling the thermodynamic state of the boundary layer: integration of measurements and methods

This paper describes advances in ground-based thermodynamic profiling of the lower troposphere through sensor synergy. The well-documented integrated profiling technique (IPT), which uses a microwave profiler, a cloud radar, and a ceilometer to simultaneously retrieve vertical profiles of temperature, humidity, and liquid water content (LWC) of nonprecipitating clouds, is further developed toward an enhanced performance in the boundary layer and lower troposphere. For a more accurate temperature profile, this is accomplished by including an elevation scanning measurement modus of the microwave profiler. Height-dependent RMS accuracies of temperature (humidity) ranging from 0.3 to 0.9 K (0.5–0.8 g m−3) in the boundary layer are derived from retrieval simulations and confirmed experimentally with measurements at distinct heights taken during the 2005 International Lindenberg Campaign for Assessment of Humidity and Cloud Profiling Systems and its Impact on High-Resolution Modeling (LAUNCH) of the German Weather Service. Temperature inversions, especially of the lower boundary layer, are captured in a very satisfactory way by using the elevation scanning mode. To improve the quality of liquid water content measurements in clouds the authors incorporate a sophisticated target classification scheme developed within the European cloud observing network CloudNet. It allows the detailed discrimination between different types of backscatterers detected by cloud radar and ceilometer. Finally, to allow IPT application also to drizzling cases, an LWC profiling method is integrated. This technique classifies the detected hydrometeors into three different size classes using certain thresholds determined by radar reflectivity and/or ceilometer extinction profiles. By inclusion into IPT, the retrieved profiles are made consistent with the measurements of the microwave profiler and an LWC a priori profile. Results of IPT application to 13 days of the LAUNCH campaign are analyzed, and the importance of integrated profiling for model evaluation is underlined

Information content of millimeter observations for hydrometeor properties in mid-latitudes.

23-27 october 200