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The Gravity Recovery and Climate Experiment (GRACE) satellite mission measures the Earth’s gravity field since March 2002. We propose a new filtering procedure for post-processing GRACE-based monthly gravity field solutions provided in the form of spherical harmonic coefficients. The procedure is tuned for the optimal estimation of linear trends and other signal components that show a systematic behavior over long time intervals. The key element of the developed methodology is the statistically optimal Wiener-type filter which makes use of the full covariance matrices of noise and signal. The developed methodology is applied to determine the mass balance of the Greenland ice sheet, both per drainage system and integrated, as well as the mass balance of the ice caps on the islands surrounding Greenland. The estimations are performed for three 2-year time intervals (2003–2004, 2005–2006, and 2007–2008), as well as for the 6-year time interval (2003–2008). The study confirms a significant difference in the behavior of the drainage systems over time. The average 6-year rate of mass loss in Greenland is estimated as 165 ± 15 Gt/year. The rate of mass loss of the ice caps on Ellesmere Island (together with Devon Island), Baffin Island, Iceland, and Svalbard is found to be 22 ± 4, 21 ± 6, 17 ± 9, and 6 ± 2 Gt/year, respectively. All these estimates are corrected for the effect of glacial isostatic adjustment., Geoscience and Remote Sensing, Civil Engineering and Geosciences

The Gravity Recovery and Climate Experiment (GRACE) satellite mission measures the Earth’s gravity field since March 2002. We propose a new filtering procedure for post-processing GRACE-based monthly gravity field solutions provided in the form of spherical harmonic coefficients. The procedure is tuned for the optimal estimation of linear trends and other signal components that show a systematic behavior over long time intervals. The key element of the developed methodology is the statistically optimal Wiener-type filter which makes use of the full covariance matrices of noise and signal. The developed methodology is applied to determine the mass balance of the Greenland ice sheet, both per drainage system and integrated, as well as the mass balance of the ice caps on the islands surrounding Greenland. The estimations are performed for three 2-year time intervals (2003–2004, 2005–2006, and 2007–2008), as well as for the 6-year time interval (2003–2008). The study confirms a significant difference in the behavior of the drainage systems over time. The average 6-year rate of mass loss in Greenland is estimated as 165 ± 15 Gt/year. The rate of mass loss of the ice caps on Ellesmere Island (together with Devon Island), Baffin Island, Iceland, and Svalbard is found to be 22 ± 4, 21 ± 6, 17 ± 9, and 6 ± 2 Gt/year, respectively. All these estimates are corrected for the effect of glacial isostatic adjustment., Geoscience and Remote Sensing, Civil Engineering and Geosciences

Graphene is an exceptionally thin semiconductor that consists of only one atomic layer of carbon atoms. The electrons in graphene live in a strictly two-dimensional (2D) world. In addition to this remarkable 2Dness, it is also peculiar that the behavior of the electrons in graphene is governed by the Dirac equation rather than the well known Schrödinger’s equation, leading to the discovery of several new physics phenomena. Such unusual properties of graphene have stirred up great excitements since it was first isolated in the lab about five years ago. In this thesis, we investigate the low temperature transport properties of the electrons and holes in several graphene based nano-devices. Overall, two topics are explored in this thesis. First we engineer an energy gap in graphene, which is naturally a zero-gap semiconductor, and further form quantum dot devices on the gapped graphene. The low temperature electronic transport properties of the confined electrons are then studied experimentally in such graphene dots. In a second project,we fabricated Josephson junction devices on graphene using a high critical field superconductor as leads. Here the goal is to research on the interactions between the electrons from graphene and the Cooper pairs from the superconductor in the quantum Hall regime., Kavli Institute of Nanoscience Delft, Applied Sciences

DEOS, Aerospace Engineering

Graphene is an exceptionally thin semiconductor that consists of only one atomic layer of carbon atoms. The electrons in graphene live in a strictly two-dimensional (2D) world. In addition to this remarkable 2Dness, it is also peculiar that the behavior of the electrons in graphene is governed by the Dirac equation rather than the well known Schrödinger’s equation, leading to the discovery of several new physics phenomena. Such unusual properties of graphene have stirred up great excitements since it was first isolated in the lab about five years ago. In this thesis, we investigate the low temperature transport properties of the electrons and holes in several graphene based nano-devices. Overall, two topics are explored in this thesis. First we engineer an energy gap in graphene, which is naturally a zero-gap semiconductor, and further form quantum dot devices on the gapped graphene. The low temperature electronic transport properties of the confined electrons are then studied experimentally in such graphene dots. In a second project,we fabricated Josephson junction devices on graphene using a high critical field superconductor as leads. Here the goal is to research on the interactions between the electrons from graphene and the Cooper pairs from the superconductor in the quantum Hall regime., Kavli Institute of Nanoscience Delft, Applied Sciences

DEOS, Aerospace Engineering

Udgivelsesdato: 2009

Purpose: To analyze the potential association of programmed cell death 1 (PDCD1) with Vogt-Koyanagi-Harada (VKH) syndrome in a Chinese Han population. Methods: Three single nucleotide polymorphism (SNPs), PD-1.3G/A, PD-1.5C/T, and PD-1.6G/A, were genotyped in 247 VKH patients and 289 age-, sex-, and ethnically-matched healthy controls using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. The associations of genotypes and alleles with VKH syndrome were analyzed. Results: All genotype distributions in healthy controls were in Hardy-Weinberg equilibrium. The genotype and allele frequencies of PD-1.3, PD-1.5, and PD-1.6 were not different between patients with VKH syndrome and healthy controls. No significant difference was observed according to the status of human leukocyte antigen (HLA)-DR4 and HLA-DRw53. Compared to the controls, lower frequencies of the PD-1.5C genotype and allele frequencies were observed in VKH patients with extraocular findings. Conclusions: PD-1.3 and PD-1.6 polymorphisms are not associated with the susceptibility to VKH syndrome in the Chinese Han population. However, PD-1.5 may be negatively associated with the occurrence of extraocular manifestations of VKH syndrome.

Udgivelsesdato: 2009

The liner, a composite made from a combination of different materials, is designed to be firmly attached to the inside of a ball mill by magnetic attraction and to attract in its turn pieces of abraded grinding balls, which form a natural and permanent protective layer. The liner's three-part structure, with a metallic outer shell, permanent magnets and elastic rubber layer, is described in detail amd its mechanism, magnetic field distribution, application in China and overseas, economic benefits and safety performance are discussed. Twenty years of development and use have shown that the liner has a service life of more than 6 years, with a saving of 8-10% of balls and 5-7% of power as well as a 1% increase in operational time. It has been widely used in large, medium and small iron ore processing plants and its application is being extended to nonferorous ad gold mines., The liner, a composite made from a combination of different materials, is designed to be firmly attached to the inside of a ball mill by magnetic attraction and to attract in its turn pieces of abraded grinding balls, which form a natural and permanent protective layer. The liner's three-part structure, with a metallic outer shell, permanent magnets and elastic rubber layer, is described in detail amd its mechanism, magnetic field distribution, application in China and overseas, economic benefits and safety performance are discussed. Twenty years of development and use have shown that the liner has a service life of more than 6 years, with a saving of 8-10% of balls and 5-7% of power as well as a 1% increase in operational time. It has been widely used in large, medium and small iron ore processing plants and its application is being extended to nonferorous ad gold mines.

Udgivelsesdato: 2008

Udgivelsesdato: 2008

Geoscience and Remote Sensing, Civil Engineering and Geosciences

Geoscience and Remote Sensing, Civil Engineering and Geosciences

Iron ore consumption has doubled several times due to the rapid development of the ironmaking industry in China, resulting in a worse quality of iron ores in the past decade. Therefore, the efficient utilisation of poor quality iron ore resources is of great importance for the sustainable development of the ironmaking industry. In this work, a new method for optimisation of blast furnace burdens was studied based on the primary slag formation behaviour because it has significant influence on the formation of the cohesive zone. The results showed that there was obvious interaction between sinter and acid iron ores at high temperature, and the primary slag formation behaviour was clearly improved by the high-temperature interaction. Poor quality lump ore could be utilised together with high basicity sinter and self-fluxed pellets to enhance the high-temperature interaction. Besides, increasing CaO and MgO content in blast furnace burdens would further improve their primary slag formation behaviour and the performance of the cohesive zone. (Authors)., Iron ore consumption has doubled several times due to the rapid development of the ironmaking industry in China, resulting in a worse quality of iron ores in the past decade. Therefore, the efficient utilisation of poor quality iron ore resources is of great importance for the sustainable development of the ironmaking industry. In this work, a new method for optimisation of blast furnace burdens was studied based on the primary slag formation behaviour because it has significant influence on the formation of the cohesive zone. The results showed that there was obvious interaction between sinter and acid iron ores at high temperature, and the primary slag formation behaviour was clearly improved by the high-temperature interaction. Poor quality lump ore could be utilised together with high basicity sinter and self-fluxed pellets to enhance the high-temperature interaction. Besides, increasing CaO and MgO content in blast furnace burdens would further improve their primary slag formation behaviour and the performance of the cohesive zone. (Authors).

Solid particle flow patterns in the moving bed zone of a melter/gasifier were studied using discrete element method (DEM). Interparticle forces were calculated using the Hertz-Mindlin no-slip contact model. The simulation results of the solid particle flow patterns agree well with the experimental results exhibited by tracer particles. The solid particle flow pattern and descending velocity were studied, as well as the effect of the discharge rate of solid particles in the raceway on solid particle flow pattern in the moving bed. Results show that the moving bed could be divided into four subdomains based on the velocity of solid particles. A stagnation zone with semielliptic geometry is formed at the central bottom of the moving bed during drainage of solid particles. Furthermore, the simulated results of compressive force among solid particles in the moving bed zone indicate that the deadman zone undergoes a high degree of compressive force, especially at the centre of the gasifier. This finding implies that more compressive force-resistant solid material should be placed at the centre zone by manipulating solid particles fed into the melter/gasifier. (Authors.), Solid particle flow patterns in the moving bed zone of a melter/gasifier were studied using discrete element method (DEM). Interparticle forces were calculated using the Hertz-Mindlin no-slip contact model. The simulation results of the solid particle flow patterns agree well with the experimental results exhibited by tracer particles. The solid particle flow pattern and descending velocity were studied, as well as the effect of the discharge rate of solid particles in the raceway on solid particle flow pattern in the moving bed. Results show that the moving bed could be divided into four subdomains based on the velocity of solid particles. A stagnation zone with semielliptic geometry is formed at the central bottom of the moving bed during drainage of solid particles. Furthermore, the simulated results of compressive force among solid particles in the moving bed zone indicate that the deadman zone undergoes a high degree of compressive force, especially at the centre of the gasifier. This finding implies that more compressive force-resistant solid material should be placed at the centre zone by manipulating solid particles fed into the melter/gasifier. (Authors.)