Delay considerttion has been a major issue in design and test of high performance digital circuits . The assumption of input signal change occurring only when all internal nodes are stable restricts the increase of cl...Delay considerttion has been a major issue in design and test of high performance digital circuits . The assumption of input signal change occurring only when all internal nodes are stable restricts the increase of clock frequency. It is no longer true for wave pipelining circuits. However, previous logical delay models are based on the assumption. In addition, the stable time of a robust delay test generally depends on the longest sensitizable path delay. Thus , a new delay model is desirable. This paper explores the necessity first. Then, Boolean process to analytically describe the logical and timing behavior of a digital circuit is reviewed . The concept of sensitization is redefined precisely in this paper. Based on the new concept of sensitization, an analytical delay model is introduced . As a result , many untestable delay faults under the logical delay model can be tested if the output waveforms can be sampled at more time points. The longest sensitiaable path length is computed for circuit design and delay test .展开更多
Recently, non-equilibrium plasma assisted combustion （PAC） has been found to be promising in reducing the ignition delay time in hypersonic propulsion system. NO x produced by non-equilibrium plasma can react with i...Recently, non-equilibrium plasma assisted combustion （PAC） has been found to be promising in reducing the ignition delay time in hypersonic propulsion system. NO x produced by non-equilibrium plasma can react with intermediates during the fuel oxidation process and thereby has influence on the combustion process. In this study, the effects of NO x addition on the ignition process of both the homogeneous ethylene/air mixtures and the non-premixed diffusion layer are examined numerically. The detailed chemistry for ethylene oxidization together with the NO x sub-mechanism is included in the simulation. Reaction path analysis and sensitivity analysis are conducted to give a mechanistic interpretation for the ignition enhancement by NO x addition. It is found that for both the homogenous and non-premixed ignition processes at normal and elevated pressures, NO 2 addition has little influence on the ignition delay time while NO addition can significantly promote the ignition process. The ignition enhancement is found to be caused by the promotion in hydroxyl radical production which quickly oxidizes ethylene. The promotion in hydroxyl radical production by NO addition is achieved in two ways：one is the direct production of OH through the reaction HO2＋NO = NO2＋OH, and the other is the indirect production of OH through the reactions NO＋O2=NO2＋O and C2H4＋O = C2H3＋OH. Moreover, it is found that similar to the homogeneous ignition process, the acceleration of the diffusion layer ignition is also controlled by the reaction HO2＋NO = NO2＋OH.展开更多
文摘Delay considerttion has been a major issue in design and test of high performance digital circuits . The assumption of input signal change occurring only when all internal nodes are stable restricts the increase of clock frequency. It is no longer true for wave pipelining circuits. However, previous logical delay models are based on the assumption. In addition, the stable time of a robust delay test generally depends on the longest sensitizable path delay. Thus , a new delay model is desirable. This paper explores the necessity first. Then, Boolean process to analytically describe the logical and timing behavior of a digital circuit is reviewed . The concept of sensitization is redefined precisely in this paper. Based on the new concept of sensitization, an analytical delay model is introduced . As a result , many untestable delay faults under the logical delay model can be tested if the output waveforms can be sampled at more time points. The longest sensitiaable path length is computed for circuit design and delay test .
基金Beijing Municipal Natural Science Foundation(Grant No.3102016)National Natural Science Foundation of China(Grant Nos.50976003,51136005)for funding this work
文摘Recently, non-equilibrium plasma assisted combustion （PAC） has been found to be promising in reducing the ignition delay time in hypersonic propulsion system. NO x produced by non-equilibrium plasma can react with intermediates during the fuel oxidation process and thereby has influence on the combustion process. In this study, the effects of NO x addition on the ignition process of both the homogeneous ethylene/air mixtures and the non-premixed diffusion layer are examined numerically. The detailed chemistry for ethylene oxidization together with the NO x sub-mechanism is included in the simulation. Reaction path analysis and sensitivity analysis are conducted to give a mechanistic interpretation for the ignition enhancement by NO x addition. It is found that for both the homogenous and non-premixed ignition processes at normal and elevated pressures, NO 2 addition has little influence on the ignition delay time while NO addition can significantly promote the ignition process. The ignition enhancement is found to be caused by the promotion in hydroxyl radical production which quickly oxidizes ethylene. The promotion in hydroxyl radical production by NO addition is achieved in two ways：one is the direct production of OH through the reaction HO2＋NO = NO2＋OH, and the other is the indirect production of OH through the reactions NO＋O2=NO2＋O and C2H4＋O = C2H3＋OH. Moreover, it is found that similar to the homogeneous ignition process, the acceleration of the diffusion layer ignition is also controlled by the reaction HO2＋NO = NO2＋OH.
