Aluminium alloy based hydrogen storage tank operated with sodium aluminium hexahydride Na3AlH6

Here we present the development of an aluminium alloy based hydrogen storage tank, charged with Ti-doped sodium aluminium hexahydride Na₃AlH₆. This hydride has a theoretical hydrogen storage capacity of 3 mass-% and can be operated at lower pressure compared to sodium alanate NaAlH₄. The tank was made of aluminium alloy EN AW 6082 T6. The heat transfer was realised through an oil flow in a bayonet heat exchanger, manufactured by extrusion moulding from aluminium alloy EN AW 6060 T6. Na₃AlH₆ is prepared from 4 mol-% TiCl₃ doped sodium aluminium tetrahydride NaAlH₄ by addition of two moles of sodium hydride NaH in ball milling process. The hydrogen storage tank was filled with 213 g of doped Na₃AlH₆ in dehydrogenated state. Maximum of 3.6 g (1.7 mass-% of the hydride mass) of hydrogen was released from the hydride at approximately 450 K and the same hydrogen mass was consumed at 2.5 MPa hydrogenation pressure. 45 cycle tests (rehydrogenation and dehydrogenation) were carried out without any failure of the tank or its components. Operation of the tank under real conditions indicated the possibility for applications with stationary HT-PEM fuel cell systems.     

Sensitivity-based feedforward and feedback control for uncertain systems

In many control applications, we are interested in accurate trajectory tracking. This is especially true for cases in which exact analytic solutions are not available because initial states are not consistent with the desired state or output trajectories or because parameters are significantly uncertain. In these cases, control strategies can be derived on the basis of a verified sensitivity analysis. For that purpose, we have to define suitable performance indices which describe the deviation between the actual and desired trajectories. In this paper, an overview of different sensitivity-based control procedures is given. These procedures include tracking control for systems with bounded parameter uncertainties as well as measurement errors described by interval variables. Moreover, we present a first verified approach to automatic path following by means of an automatic modification of desired output trajectories. This procedure is necessary in cases in which exact trajectory tracking is not possible due to the violation of control constraints.     

Optimizing main-memory join on modern hardware

In the past decade, the exponential growth in commodity CPU's speed has far outpaced advances in memory latency. A second trend is that CPU performance advances are not only brought by increased clock rates, but also by increasing parallelism inside the CPU. Current database systems have not yet adapted to these trends and show poor utilization of both CPU and memory resources on current hardware. In this paper, we show how these resources can be optimized for large joins and translate these insights into guidelines for future database architectures, encompassing data structures, algorithms, cost modeling and implementation. In particular, we discuss how vertically fragmented data structures optimize cache performance on sequential data access. On the algorithmic side, we refine the partitioned hash-join with a new partitioning algorithm called "radix-cluster", which is specifically designed to optimize memory access. The performance of this algorithm is quantified using a detailed analytical model that incorporates memory access costs in terms of a limited number of parameters, such as cache sizes and miss penalties. We also present a calibration tool that extracts such parameters automatically from any computer hardware. The accuracy of our models is proven by exhaustive experiments conducted with the Monet database system on three different hardware platforms. Finally, we investigate the effect of implementation techniques that optimize CPU resource usage. Our experiments show that large joins can be accelerated almost an order of magnitude on modern RISC hardware when both memory and CPU resources are optimized     

NEGO — Group decision support system

There are two major frameworks for decision making: maximizing and satisficing. A combination of both may be used to describe group decision making (GDM). In the satisficing approach, decision makers (DMs) formulate aspiriation levels or demands which take the form of constraints. Choosing from among different decisions, DMs take into account their preferences or wants, which take the form of objective functions.GDM is divided into two stages: first, each DM makes a decision, and second, DMs negotiate so as to achieve a compromise decision. Negotiating is an iterative process. Negotiations are completed when all demands have been met.The group decision support system “NEGO” assists DMs in finding a compromise. It has been used for solving a GDM problem at the corporate level and is currently utilized in management courses.     

Correlation of esophageal conductance measurements with aortic and left ventricular diameters and stroke volume

Esophageal conductance measurements were correlated with hemodynamic events in 9 dogs chronically instrumented for measurement of left ventricular (LV) and aortic pressures, LV short axis and descending aortic diameters, and aortic blood flow. A four-electrode conductance catheter was positioned in the esophagus. Both an internal and an internal/external configuration were examined during anesthesia with hemodilution, pulmonary lavage and dobutamine infusion. LV stroke volume was altered by caval occlusion at each intervention. Stroke conductance was highly correlated to aortic or LV diameters and stroke volume over a range of diameters depending on the electrode configuration. Esophageal conductance measurements are directly influenced by local hemodynamic events adjacent to the site of measurement.     

Cr(VI)/Cr(III) and As(V)/As(III) ratio assessments in Jordanian spent oil shale produced by aerobic combustion and Anaerobic Pyrolysis

With the increase in the awareness of the public in the environmental impact of oil shale utilization, it is of interest to reveal the mobility of potentially toxic trace elements in spent oil shale. Therefore, the Cr and As oxidation state in a representative Jordanian oil shale sample from the El-Lajjoun area were investigated upon different lab-scale furnace treatments. The anaerobic pyrolysis was performed in a retort flushed by nitrogen gas at temperatures in between 600 and 800 °C (pyrolytic oil shale, POS). The aerobic combustion was simply performed in porcelain cups heated in a muffle furnace for 4 h at temperatures in between 700 and 1000 °C (burned oil shale, BOS). The high loss-on-ignition in the BOS samples of up to 370 g kg(-1) results from both calcium carbonate and organic carbon degradation. The LOI leads to enrichment in the Cr concentrations from 480 mg kg(-1) in the original oil shale up to 675 mg kg(-1) in the ≥ 850 °C BOS samples. Arsenic concentrations were not much elevated beyond that in the average shale standard (13 mg kg(-1)). Synchrotron-based X-ray absorption near-edge structure (XANES) analysis revealed that within the original oil shale the oxidation states of Cr and As were lower than after its aerobic combustion. Cr(VI) increased from 0% in the untreated or pyrolyzed oil shale up to 60% in the BOS ash combusted at 850 °C, while As(V) increased from 64% in the original oil shale up to 100% in the BOS ash at 700 °C. No Cr was released from original oil shale and POS products by the European compliance leaching test CEN/TC 292 EN 12457-1 (1:2 solid/water ratio, 24 h shaking), whereas leachates from BOS samples showed Cr release in the order of one mmol L(-1). The leachable Cr content is dominated by chromate as revealed by catalytic adsorptive stripping voltammetry (CAdSV) which could cause harmful contamination of surface and groundwater in the semiarid environment of Jordan.