Simultaneous parametric material and topology optimization with constrained material grading

We consider the problem of parametric material and simultaneous topology optimization of an elastic continuum. To ensure existence of solutions to the proposed optimization problem and to enable the imposition of a deliberate maximal material grading, two approaches are adopted and combined. The first imposes pointwise bounds on design variable gradients, whilst the second applies a filtering technique based on a convolution product. For the topology optimization, the parametrized material is multiplied with a penalized continuous density variable. We suggest a finite element discretization of the problem and provide a proof of convergence for the finite element solutions to solutions of the continuous problem. The convergence proof also implies the absence of checkerboards. The concepts are demonstrated by means of numerical examples using a number of different material parametrizations and comparing the results to global lower bounds.     

Experimental automobile-pedestrian injuries

Fifteen fresh cadaver impacts were conducted in simulation of pedestrian-automobile accidents. The test sled configuration simulated an automobile bumper and hood in "standard" and "nosedive" situations as well as "hard" and "soft" impact surfaces. Instrumentation and film demonstrated large axial compression forces in the struck leg and considerable angular velocity of the torso in all modes. Dissection revealed primary injury at the impact site at low velocities with added remote injury at high velocities. Fracture of the lateral tibial plateau was most common. Lowering the bumper height offered the greatest protection against injury at moderate impact velocities.     

An operational tool to quality control 2D radar reflectivity data for assimilation in COSMO-DE

An operational tool has been designed to enhance the quality of 2D radar reflectivity data for assimilation in COSMO-DE within the German Weather Service (DWD). This article describes the operational algorithms including their testing, the creation of local and composite quality-index fields and their application to improve data assimilation. In the first step, algorithms have been developed and tested to define and identify some of the most severe errors in radar data: corrupt images, low-reflectivity phenomena, which occur under special meteorological conditions, spokes, rings and clutter remnants/speckles. The algorithms use simple but effective tests based on statistical and textural characteristics of spurious signals. The results are stored in an 8-bit quality-index field created concurrently with the radar data at each radar station. It contains quality flags for each individual range bin plus some header information on the overall quality of the underlying data set. The independent coding of error bits enables a differentiated a posteriori decision on whether a range bin is to be used for a given application. These local quality index fields are then used to create a radar precipitation composite, accompanied by a quality-index composite, covering Germany. This tool has now been applied operationally throughout the German radar network. As a result, the radar data quality in data assimilation could be increased.     

Effect of temporal aggregation on multiple time series in the frequency domain

The effect of temporal aggregation on bivariate spectral measures is investigated. First, the low‐frequency regression coefficient turns out to be invariant under aggregation irrespective of differencing, with the exception of when the aggregation of flow and stock variables is combined. Second, the long‐run squared coherency is invariant with respect to aggregation irrespective of differencing. Third, for frequencies different from zero, limiting results for a growing aggregation level m are obtained equal to those at frequency 0 of the underlying basic series. Hence, all frequency domain information is distorted by aggregation apart from the long‐run one. This also holds true for the phase angle that always approaches zero with growing aggregation level m. The sole exception to these findings is the case of the skip sampling stationary series. Moreover, for finite aggregation level, one may exactly quantify the aggregational effect on each cycle of interest. Numerical examples illustrate our results.     

Influence of pH of the adsorbent on the properties of edible oils and fats

Journal of the American Oil Chemists' Society -     

Amount of subarachnoid blood and vasospasm: current aspects. A transcranial Doppler study

Subsequent to admission after aneurysmal subarachnoid haemorrhage (SAH), 120 patients (74 women and 46 men) underwent microsurgical clipping of a total of 158 cerebral aneurysms within 96 hours after the bleed. Their mean age was 46 (20-91) years. Computed tomography (CT) findings were graded according to the modified Fisher scale and all patients had daily transcranial doppler (TCD) recordings of their basal cerebral arteries. In 19% of SAH was grade I on CT, in 44% grade II and in 37% grade III. The rate of patients who developed severe vasospasm as documented by TCD (mean blood flow velocities exceeding 160 cm/s on 2 or more consecutive days) was 39% for grade I patients, 26% for grade II patients and 34% for patients with SAH grade III on the initial CT. There was no difference in the rate of occurrence of severe vasospasm, when the patients were split into 2 groups according to the time of performance of the initial CT scan-within 24 hours, and 48-80 hours after SAH, respectively. It is concluded that the amount of subarachnoid blood on the initial CT scan should no longer be used as the indicator for occurrence and severity of the multifactorial entity vasospasm.     

Warm ischemic tolerance in collapsed pulmonary grafts is limited to 1 hour

OBJECTIVE: To determine the length of warm ischemic tolerance in pulmonary grafts from non-heart-beating donors. SUMMARY BACKGROUND DATA: If lungs could be retrieved for transplant after circulatory arrest, the shortage of donors might be significantly alleviated. Great concern, however, exists about the length of tolerable warm ischemia before cold preservation of pulmonary grafts retrieved from such non-heart-beating donors. METHODS: The authors compared the influence of an increasing postmortem interval on graft function in an isolated, room air-ventilated rabbit lung model during blood reperfusion up to 4 hours. Four groups of cadavers (four animals per group) were studied. In group 1, lungs were immediately reperfused. In the other groups, cadavers with lungs deflated were left at room temperature for 1 hour (group 2), 2 hours (group 3), or 4 hours (group 4). RESULTS: Pulmonary vascular resistance was enhanced in all ischemic groups compared with the control group. An increase was noted with longer postmortem intervals in peak airway pressure and in weight gain. A concomitant decline was observed in the venoarterial oxygen pressure gradient caused by progressive edema formation, as reflected by the wet-to-dry weight ratio at the end of reperfusion. CONCLUSIONS: Warm ischemia resulted in increased pulmonary vascular resistance. Graft function in lungs retrieved 1 hour after death was not significantly worse than in nonischemic lungs. Therefore, 60 minutes of warm ischemia with the lung collapsed may be tolerated before cold storage. Further studies are necessary to investigate whether lungs retrieved from non-heart-beating donors will become a realistic alternative for transplant.