世界铁矿石烧结法发展现状

世界铁矿石烧结法发展现状［澳大利亚］Ｐ·Ｒ·道森第四部分烧结工艺１烧结能耗烧结生产所需能耗约占整个钢铁工业总能耗的６．７％。图１所示为有代表性的烧结能耗的变化情况。德国１９８９年的烧结能耗为１７５８ＭＪ／ｔ烧结矿，而１９８２年的能耗为２５１５ＭＪ／ｔ...     

铜熔炼工艺设备及其应用

铜熔炼工艺设备及其应用简单地说，硫化铜精矿是由各种天然的铜矿物和脉石所组成。虽然铜矿物的种类较多，但是一般包含铜和铁的硫化物。同时含有不同量的各种稀少元素，如各种杂质和金与银。目前的大多数炼铜厂仍采用两段冶炼法。第一段称熔炼阶段，在此阶段使炉料熔化并...     

Corrections for nonuniform sampling distortions in magnetic resonance imagery

A technique for estimating and correcting nonuniform sampling distortions in magnetic resonance imagery is presented. The technique consists of first estimating the sampling grid distortion using a parametric model, and then estimating the uniformly sampled data by interpolation on the nonuniform grid. Parameterized models for two particular sampling grid distortion are presented. Maximum likelihood and maximum a posteriori estimators are developed for these distortions. Using computer simulated data, these estimators are shown to perform well.     

Linograms in image reconstruction from projections

The notion of a linogram is introduced. It corresponds to the notion of a sinogram in the conventional representation of projection data in image reconstruction. In the sinogram, points which correspond to rays which go through a fixed point in the cross section to be reconstructed all fall on a sinusoidal curve. In the linogram, however, these points fall on a straight line. Thus, backprojection corresponds to integration along straight lines in the linogram. A theorem is proved expressing the backprojection operator in terms of the Radon transform and simple changes of variables. Consequences of this theorem are discussed. A novel image reconstruction method based on the theorem is presented.     

Invited article: development of high-field superconducting Ioffe magnetic traps

We describe the design, construction, and performance of three generations of superconducting Ioffe magnetic traps. The first two are low current traps, built from four racetrack shaped quadrupole coils and two solenoid assemblies. Coils are wet wound with multifilament NbTi superconducting wires embedded in epoxy matrices. The magnet bore diameters are 51 and 105 mm with identical trap depths of 1.0 T at their operating currents and at 4.2 K. A third trap uses a high current accelerator-type quadrupole magnet and two low current solenoids. This trap has a bore diameter of 140 mm and tested trap depth of 2.8 T. Both low current traps show signs of excessive training. The high current hybrid trap, on the other hand, exhibits good training behavior and is amenable to quench protection.     

Photon counting with passively quenched germanium avalanche

We demonstrate photon counting in germanium avalanche photodiodes biased beyond breakdown and quenched with a simple series resistance circuit. The devices show moderate (> 7%) quantum efficiency with limited afterpulsing and dark counts and subnanosecond jitter.