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Dynamics and Control technologies play a central role in the development and operation of decision support systems of modern air traffic management systems. Recent emergence of Global Navigation Satellite Systems and satellite-based augmentation systems have enabled higher precision execution of aircraft trajectories, opening-up the potential for the implementing more quantitative air traffic management approaches. Already, this navigation capability is enabling higher traffic through puts, and safer operation of aircraft in the proximity of the terrain at several major airports in the US. This paper discusses the aircraft trajectory optimization, conflict resolution algorithms, and traffic flow management problems which form the essential components of the evolving air traffic management system. It will be shown that Optimal Control Theory, Model Predictive Control and the Discrete Event Systems theory form the underlying analytical machinery in this domain. Finally, the paper will outline some of the algorithms for realizing the Trajectory Based Operations concept, currently being developed for future air traffic management. [ABSTRACT FROM AUTHOR]

Abstract: Paraelectric PLT(lead lanthanium titanate) thin films were prepared by dc magnetron sputtering with multi element metal target. In order to crystallize the as-deposited PLT thin films to the cubic perovskite phase, post-heat treatment was applied at the temperatures from 450 to 750°C. The composition of PLT(28) thin film was: Pb, 0.72; La, 0.28; Ti, 0.88; O, 2.9. The dielectric characteristics were essentially dependent on the changes in the chemical composition and crystalline phase with variation of annealing treatment. The dielectric constant increased and dissipation factor decreased slightly, as the post-annealing temperature increased. The dielectric constant and dissipation factor at low electric field measurement of the capacitors with highest dielectric properties were 1216 and 0.018, respectively. [Copyright &y& Elsevier]

Abstract: The bipolar plates in polymer electrolyte membrane fuel cells (PEMFC) typically have been made of polymer resin-impregnated graphite. However, because of their expensive cost and for difficulties to design the gas flow field channels to machine, it should be considered to search out the alternative materials from graphite to carbon–carbon composite and carbon–polymer composites. Therefore, several kinds of composite plates for PEMFC are currently under development to easy produce and reduce cost, stack volume and weight. In this work, we present the preparation method and characterization of alternative bipolar plate material, which can be researched for the application of PEMFC vehicle. Bulk resistance of the plate was measured with a four-point probe method. The electrical conductivity of polymer composite plate was 4.40 × 103 S/cm. On the other hand, the electrical interfacial resistance of the polymer composite plate valued at 1.87mΩcm2 and that of graphite was 0.26mΩcm2 under the holding pressure of 140N/cm2 at the applied current of 5A. And the performance of alternative materials bipolar plate for PEMFC with 25 and 50cm2 were evaluated at various conditions. The single cell performance was more than 0.37W/cm2 (0.77W/g) for polymer composite bipolar plate at 50°C under atmospheric pressure in external humidified hydrogen and oxygen condition. As the results, we could show the results that the alternative material bipolar plates were favorable in the aspect of electrical and physical properties compared with those of the commercialized resin-impregnated graphite plates. [Copyright &y& Elsevier]

Abstract This paper reports the effect of the global behaviour of three-legged jack-up rigs due to the reinstallation of spudcan footings next to seabed footprints. Two reinstallation scenarios are discussed: (i) two legs first installed on flat ground, and then the third leg installed near a footprint (representing what is known as leg-by-leg preloading); and (ii) the three legs installed simultaneously (representing simultaneous preloading). The spudcan-soil interaction was simulated using a coupled Eulerian-Lagrangian (CEL) approach. A simplified global jack-up model was developed by considering an equivalent beam model for the hull and legs. The results of the jack-up installations are compared against the responses of the more common modelling of a spudcan with a fixed head condition. A detailed parametric study assessing the consequences of spudcan-footprint interactions, such as the risk of the jack-up and spudcan sliding towards the footprint centre, overturning of the jack-up rig and of structural failure of the jack-up leg due to excessive stresses, is also discussed. The ability of a recently developed novel spudcan with a flat base and 4 holes, coupled with the global jack-up model, to mitigate the consequences of spudcan-footprint interactions is highlighted. Highlights • New global modelling techniques: three-legged jack-up rigs considering spudcan-footprint interactions. • Two different installation scenarios: (a) leg-by-leg preloading; (b) simultaneous preloading. • Extensive parametric investigation: (a) spudcan sliding; (b) overturning of the jack-up rig; (c) the novel spudcan effect. • Structural integrity analyses were also carried out to identify the potential leg failure due to spudcan-footprint interactions. [ABSTRACT FROM AUTHOR]

Abstract The horizontal force and moment induced on a spudcan as it penetrates next to an existing seabed footprint have been identified as one of the key challenges in the offshore oil and gas industry. This paper assesses the potential of changing and then optimising the spudcan foundation shape to mitigate the spudcan-footprint interaction. Large-deformation finite-element (LDFE) analyses are performed using the Coupled Eulerian-Lagrangian (CEL) approach with the simple elastic-perfectly plastic Tresca soil model modified to enable strain softening and to incorporate strain-rate dependency of the shear strength. The spudcan shape was optimised by parametric analyses varying the spudcan’s skirt length, underside profile, and number of holes through the spudcan periphery. A spudcan with a flatter (or even concave) underside profile and with holes was shown to significantly reduce the induced horizontal force and moment during reinstallation next to an existing footprint. However, use of skirts has an adverse influence. Based on the results, an optimised spudcan shape is proposed. [ABSTRACT FROM AUTHOR]

This paper reports the effect of the remoulded soil strength of a footprint on the reinstallation of jack-up rigs near the footprint. The footprint creation is from an earlier spudcan penetration and extraction process in which the soil is remoulded. Dissipation of pore pressures between the footprint creation and jack-up reinstallation causes further consolidation of the soil around the footprint. Large-deformation finite-element (LDFE) analyses were performed using the Coupled Eulerian-Lagrangian (CEL) approach. A recently developed novel spudcan shape with a flat base and four holes is studied to mitigate spudcan-footprint interactions during spudcan reinstallation. The installation of a whole three-legged jack-up rig is modelled considering a simplified global jack-up unit. The LDFE results were validated against existing centrifuge test data prior to undertaking a detailed parametric study, assessing the effects of consolidation occurred after footprint creation, the offset distance of spudcan installation from the footprint centre, and spudcan shape. Compared to a footprint of the same shape, but virgin intact soil strength, the footprint with remoulded soil strength enhances the maximum horizontal force, maximum moment, maximum lateral displacement, and rotation, by 12–20%. The critical offset distance is found to be one spudcan diameter with the spudcan centre being at the crest of the footprint. The novel spudcan shape is shown to be effective at easing spudcan-footprint interactions, reducing horizontal force, moment, lateral displacement and rotation by about 50%; and total stress on the jack-up leg by 41%. [ABSTRACT FROM AUTHOR]

This paper investigates the potential for using skirted foundations as an alternative to spudcans in an attempt to mitigate punch-through failure of jack-up rigs during installation and preloading in sand-over-clay deposits. The results from a series of numerical analyses on the skirt length were presented in combination with different conditions of sand-over-clay deposit. Three-dimensional large deformation finite element (LDFE) analyses were carried out using the coupled Eulerian-Lagrangian approach. The sand was represented with a modified Mohr-Coulomb model and the clay with an extended Tresca model. The results showed that the likelihood and severity of punch-through increased with (i) increasing the thickness of the sand layer, (ii) increasing the strength of the clay layer, and (iii) reducing the strength non-homogeneity of the clay layer. The degree of mitigation was increased with increasing the skirt length. An optimal skirt length of 0.25 D was suggested accounting for the rig towing constraint. Prediction models have been proposed for assessing (i) the potential for punch-through failure, and (ii) the resistance profile for skirted foundations penetrating sand-over-clay deposits. • Effect of different skirt length on mitigation of punch-through in sand-over-clay was investigated. • Longer skirt is better, but the skirt length of a quarter of the foundation diameter would be recommended. • Prediction models were proposed for skirted foundations penetrating sand-over-clay deposits. [ABSTRACT FROM AUTHOR]

Abstract: Upregulation of hypoxia-inducible factor-1α (HIF-1α) in response to ischemic states has been suggested to have a role in the development of chronic allograft nephropathy. Deposition of C4d in the peritubular capillaries of renal allografts has been reported to be a sensitive marker of acute humoral rejection. The purpose of this study was to determine the effects of HIF-1α expression and C4d deposition in implantation biopsies of renal allografts. Implantation biopsies and 22 rejection proved biopsies were performed in 54 renal transplant recipients between December 1996 and July 1999. The mean follow-up was 82.8 months. Immunohistochemical studies were performed using a mouse monoclonal antibody for HIF-1α expression and a rabbit polyclonal antibody for C4d detection. HIF-1α was demonstrated in 19 of 54 implantation biopsies (35%), and C4d deposition in one (1.9%). The HIF-1α–positive group included a higher percentage of deceased donor organs (66.4% vs 17.1%; P = .002) and longer mean cold ischemia times (261.3 ± 231 vs 103 ± 40 min; P = .008) compared with the HIF-1α–negative group. The relative risks (95% confidence intervals) of expression of HIF-1α for allograft rejection, chronic allograft nephropathy, and graft loss were 1.53 (0.82–2.87), 0.61 (0.06–5.50), and 2.45 (0.62–9.85). The C4d-positive patient developed acute accelerated rejection on postoperative day 4. In the present study, the expression of HIF-1α showed a significant correlation with the use of a deceased donor kidney and with cold ischemia time. However, there were no significant effects on the prognosis for a graft after implantation of a kidney with HIF-1α expression. [Copyright &y& Elsevier]