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991.
During a core melt accident, a pressurization of the containment has to be expected, which could lead to a failure of the containment due to overpressurization. This failure mode is expected to be the most likely one for large dry containments under accident conditions. Also during a core melt accident, a large quantity of hydrogen may be generated, giving the potential of a loss of containment integrity due to violent hydrogen combustion. Timely venting of the containment atmosphere can prevent overpressurization and may perhaps make the hydrogen situation in the containment less severe. This paper discusses the thermodynamic consequences of different vent strategies for a large German PWR during core melt accidents. 相似文献
992.
To deal with circulated bills in various conditions regarding size, shape, and rigidity, we have developed a new bill-stacking
cassette that can accept and re-dispense various-sized bills. This cassette stacks the bills upright by using deforming guides
and sheet rollers under our newly developed “phase control”. It was experimentally verified by stacking tests that the cassette
can handle bills in various conditions; thus, we conclude that the new cassette is practical for stacking circulated bills
and re-dispensing them securely.
Received: 14 August 2001/Accepted: 11 December 2001 相似文献
993.
The rheological behavior and microstructure of semi-solid aluminum alloys were studied using a novel apparatus, the drop-forge
viscometer (DFV). The viscometer determines force from the second-derivative-of-displacement data with respect to time and
permits calculations of viscosities at shear rates in excess of 1000 s−1. Alternatively, the DFV can be operated like a conventional parallel-plate viscometer, attaining shear rates as low as 10−5 s−1. Rapid compression experiments (in the DFV) result in first rapidly increasing, then decreasing, shear rates. In a typical
experiment, the viscosity decreased from about 100 to 1 Pa·s as the shear rate increased from approximately 200 to 1300 s−1 in less than 4 ms. The viscosity later increased to about 10 Pa·s as the shear rate decreased from 1300 to 30 s−1 over 2 ms. The minimum viscosity obtained depended on the maximum shear rate, not the duration of shear. The dual observed
phenomena of (1) a very rapid drop of viscosity with increasing shear rate followed by (2) a relatively slow increase of viscosity
with decreasing shear rate thereafter have potential significance for future machine and process design. For example, it should
be possible to form higher fraction solid slurries than is now feasible by applying vigorous shear to semi-solid slurries
just before the metal is introduced to the die entrance. The DFV was used to calculate viscosity as a function of shear rate
for samples produced by the commercial strain-induced, melt-activated (SIMA) and magnetohydrodynamic (MHD) methods, as well
as the recently developed Massachusetts Institute of Technology (MIT) method. Isothermal experiments were conducted between
fraction solid of 0.44 and 0.67 for the various alloys (corresponding to a temperature range of 579 °C to 611 °C). The viscosity
of the commercial semi-solid Al-Si alloys A357 and A356 produced by the various methods was similar. Separation of liquid
and solid phases was not observed in rapid compression experiments shorter than 10 ms, either visually or with energy-dispersive
spectroscopy (EDS) characterization. At low compression velocities, segregation was observed and increased with increasing
amounts of strain. The maximum fraction solid compressed at high and low shear rates were 0.67 and 0.69, respectively. 相似文献
994.
995.
The stabilization problem for selected relative equilibria of an underactuated rigid body, modelling a simple underwater vehicle, moving in an ideal fluid is addressed. State feedback control laws achieving local asymptotic stability of a forward motion and of a diving/rising with forward/reverse motion are proposed. The control design exploits the Hamiltonian nature of the system to be controlled and it is based on the so-called interconnection and damping assignment (IDA) procedure. Simulation results complete the work. 相似文献
996.
This paper introduces a graphic methodology that makes it possible to compare over a wide range of probabilities the revenues that a generator obtains using different policies to decide how much energy to sell under long-term contracts and how much on the spot market. Examples are based on results for the Colombian Power System 相似文献
997.
J. Balakrishnan W. A. Sethares C. R. Johnson 《International Journal of Adaptive Control and Signal Processing》2002,16(4):309-323
A method of approximate channel identification is proposed that is based on a simplification of the correlation estimator. Despite the numerical simplification (no multiplications or additions are required, only comparisons and an accumulator), the performance of the proposed estimator is not significantly worse than that of the standard correlation estimator. A free (user selectable) parameter moves ‘smoothly’ from a situation with small sum‐squared channel estimation error but hard‐to‐identify channel peaks, to one with a larger sum‐squared estimation error but easy‐to‐identify channel peaks. The proposed estimator is shown to be biased and its behaviour is analysed in a number of situations. Applications of the proposed estimator to sparsity detection, symbol timing recovery and to the initialization of blind equalizers are suggested. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
998.
Generation of self-oscillations under unstable stationary states of nonlinear control systems, which may contain delay of complicated nature (the Andronov–Hopf bifurcation), and approximate design of self-oscillating states and their asymptotes are studied with the help of pulse-frequency characteristics of the linear component of a system. 相似文献
999.
1000.