Electrical impedance tomography using the extended Kalman filter

In this paper, we propose an algorithm that, using the extended Kalman filter, solves the inverse problem of estimating the conductivity/resistivity distribution in electrical impedance tomography (EIT). The algorithm estimates conductivity/resistivity in a wide range. The purpose of this investigation is to provide information for setting and controlling air volume and pressure delivered to patients under artificial ventilation. We show that, when the standard deviation of the measurement noise level raises up to 5% of the maximal measured voltage, the conductivity estimates converge to the expected vector within 7% accuracy of the maximal conductivity value, under numerical simulations, with spatial a priori information. A two-phase identification procedure is proposed. A cylindrical phantom with saline solution is used for experimental evaluation. An abrupt modification on the resistivity distribution of this solution is caused by the immersion of a glass object. Estimates of electrode contact impedances and images of the glass object are presented.     

Characteristics of the thick,compound refractive lens

A compound refractive lens (CRL), consisting of a series of N closely spaced lens elements each of which contributes a small fraction of the total focusing, can be used to focus x rays or neutrons. The thickness of a CRL can be comparable to its focal length, whereupon a thick-lens analysis must be performed. In contrast with the conventional optical lens, where the ray inside the lens follows a straight line, the ray inside the CRL is continually changing direction because of the multiple refracting surfaces. Thus the matrix representation for the thick CRL is quite different from that for the thick optical lens. Principal planes can be defined such that the thick-lens matrix can be converted to that of a thin lens. For a thick lens the focal length is greater than for a thin lens with the same lens curvature, but this lengthening effect is less for the CRL than for the conventional optical lens.     

Effects of triton WR 1339 and heparin on the transfer of surface lipids from triglyceride-rich emulsions to high density lipoproteins in rats

The influence of lipolytic mechanisms on the transfer of phospholipids and unesterified cholesterol from artificial emulsions, serving as chylomicron models to other plasma lipoproteins, mainly high density lipoproteins (HDL) were testedin vivo. The emulsions labeled with radioactive lipids were injected into the bloodstream of rats (controls) and the results were compared with those obtained from rats that had previously been treated with Triton WR 1339 or heparin. Plasma clearance and the distribution of cholesteryl esters, phospholipids and unesterified cholesterol in the different plasma lipoprotein fractions were then determined. Whereas virtually no cholesteryl esters were found in d>1.006 g/mL density fraction of the three experimental groups, 2.8±1.3% of the injected phospholipids were in the 1.063–1.210 g/L density fraction of the Triton treated rats, and 12.6±5.4% of the heparin treated rats, as compared to 10.1±1.7% in controls. This indicates that lipolysis directly influences phospholipid transfer to HDL. In contrast, free-cholesterol transfer to HDL, besides being less pronounced than phospholipid transfer, was enhanced by Triton and diminished by heparin, indicating that lipolytic mechanisms were not important determinants in this process. This work is part of a Privatdozent Thesis by the corresponding author.     

The solution polymerization of hexachlorocyclotriphosphazene

Summary The polymerization of hexachlorocyclotriphosphazene (trimer) is studied in different solvents. A soluble low molecular weight polymer is obtained when benzene is the solvent, a highly cross-linked polymer when cyclohexane is the solvent, and a mixture of soluble and insoluble polymers results when the solvent is chlorobenzene. The conversion-concentration curve for the trimer shows a dependence of the amount of soluble and insoluble polymer formed on the trimer concentration. No polymerization took place when the solvent was toluene, nitrobenzene or THF, but a reaction between solvent and trimer was detected.     

Adaptive changes in Δ9 desaturase activity in rat liver

The Δ9 desaturase activity and the¹⁴C radioactivity of the de novo synthesized fatty acids incorporated into microsomal lipids and serum triglycerides were measured under different nutritional conditions. The results obtained indicate a correlation between the values of the three parameters studied after starvation or after refeeding Purina chow or either a high carbohydrate or a high protein diet. These data suggest that liver lipogenesis and Δ9 desaturase activities respond to the same regulatory factors.     

仿生土木工程研究进展与展望

随着城镇化水平不断提升,中国每年新增建筑面积约20亿m²,大规模基础设施建设对土木工程理论和技术创新的要求越来越高。学者们通过研究自然界的增强增韧、水下黏合、钻孔掘进和轻质高强等现象发现,生物体具有独特的外部形态和组织结构,通过模仿生物体的外部形态、结构特征或运动机理可为土木工程技术创新和可持续发展提供新思路、新原理和新理论。从仿生材料、仿生结构和仿生机械与构筑物3个方面阐述仿生学在土木工程中的应用,列举典型的应用案例,并对仿生土木工程进行总结和展望,为未来的研究提供基础材料。作为新兴的研究方向,仿生土木工程基础理论尚不完善,仿生土木工程涉及生物、材料、结构等多学科的交叉,需要开展不同领域间的协同合作研究。     

Influence of adhesive fillets on fatigue behaviour of single-strap composite repairs

The objective of this work is to analyse the influence of adhesive fillets on the fatigue/fracture behaviour of single-strap adhesive repairs of carbon-epoxy composites. A cohesive zone model (CZM) appropriate for high-cycle fatigue analysis was employed. A preliminary model validation was performed using results ensuing from experimental testing of single-strap adhesive repairs without fillets. Subsequently, the numerical model was used to investigate the effect of outer, inner and both (outer and inner) fillets on the quasi-static strengths and on the fatigue lives of these repairs. It was concluded that inner fillets provide the best option concerning the increase of fatigue life or a maximum fatigue load for a given planned service-life of the repaired component.     

Moving boundary approach to forecast tight oil production

A novel semianalytical production predictive tool for tight reservoirs based on the application of material balance on a transient linear flow system is developed in this paper. This method considers two important regions during transient production of oil reservoirs: the saturated region where gas evolves and flows with oil, and the undersaturated region where only oil flows. A zonal moving boundary approach is used to evolve the two regions as the reservoir pressure gradually decreases. A semianalytical method is used to calculate pressures in the various regions and volumetric expansions. For both black oil and volatile oil scenarios, calculations from this analytical framework are able to match reservoir pressures, oil and gas rates, and cumulative gas–oil ratios determined using a reservoir simulator. The model was also applied to wells in tight reservoirs around the United States such as the Bakken (ND) and the Eagle Ford (TX) with reasonable success.     

Impairment-aware fixed-alternate BSR routing heuristics applied to elastic optical networks

The Journal of Supercomputing - The introduction of elastic optical networks (EONs) leads to new challenges, such as the problem of routing, modulation level, and spectrum assignment. In...