A novel front-end circuit designed for PMT signals processing considering the solution of "Time Walk" correction is discussed in this paper. We are trying to apply the TOT (Time over Threshold) technique to ...A novel front-end circuit designed for PMT signals processing considering the solution of "Time Walk" correction is discussed in this paper. We are trying to apply the TOT (Time over Threshold) technique to our research. Different from traditional ways, where amplitude is measured, time width is measured for slew correction here, which takes the advantage of TDC. Expensive fast ADCs are abandoned and the whole time measurement electronics design becomes more effective and economical. Test boards have been developed and a convenient method is introduced to evaluate our TOT technique. Results have shown that a 10ps slew correction resolution is achieved throughout the amplitude range from -108mV to -2000mV for negative signals of both 5 ns leading and trailing edge with 10 ns 50%-50% pulse width.展开更多
High precision time measurement is required in the readout of the neutron wall and TOF walls in the external target experiment of the Cooling Storage Ring(CSR) project in the Heavy Ion Research Facility in Lanzhou(HIR...High precision time measurement is required in the readout of the neutron wall and TOF walls in the external target experiment of the Cooling Storage Ring(CSR) project in the Heavy Ion Research Facility in Lanzhou(HIRFL).Considering the time walk correction,both time and charge are measured in the readout electronics.In this 16-channel measurement module,time and charge information are digitized by TDCs at the same time based on the Time-Over-Threshold(TOT) method;meanwhile,by employing high-density ASIC chips,the electronics complexity is effectively reduced.Test results indicate that this module achieves a time resolution better than 25 ps and a charge resolution better than 5%over the input amplitude range from 50 mV to 3V.展开更多
In this paper, an SEIRS epidemic model with pulse vaccination and two time delays is proposed. By using stroboscopic map and comparison principle, the disease-free periodic solution(DFPS for short) is obtained and the...In this paper, an SEIRS epidemic model with pulse vaccination and two time delays is proposed. By using stroboscopic map and comparison principle, the disease-free periodic solution(DFPS for short) is obtained and the global asymptotic stability of the DFPS is proved. The sufficient conditions for the permanence of the model are obtained. In addition, numerical simulations are done to confirm our theoretical results.展开更多
A certain formation pressure level must be kept due to the threshold pressure of the low-permeability reser-voir during the seepage. Advanced water injection can keep the formation pressure at a higher level and keep ...A certain formation pressure level must be kept due to the threshold pressure of the low-permeability reser-voir during the seepage. Advanced water injection can keep the formation pressure at a higher level and keep a higher pressure gradient, which is an effective way to develop low-permeability reservoir. Based on the mechanism of advanced water injection and characteristic of porous flow in low permeability reservoir, a seepage model considering threshold pressure gradient is established to determine the formation pressure distribution at anytime as the water is injected at a constant speed. The optimum water injection time for the advanced water injection technology can be determined by using this model. The calculated result coincides basically with the numerical simulation result, which indicates that the model put forward in this paper is feasible.展开更多
Long departure-taxi-out time leads to significant airport surface congestion, fuel-burn costs, and excessive emissions of greenhouse gases. To reduce these undesirable effects, a Predicted taxi-out time-based Dynamic ...Long departure-taxi-out time leads to significant airport surface congestion, fuel-burn costs, and excessive emissions of greenhouse gases. To reduce these undesirable effects, a Predicted taxi-out time-based Dynamic Pushback Control(PDPC) method is proposed. The implementation of this method requires two steps: first, the taxi-out times for aircraft are predicted by the leastsquares support-vector regression approach of which the parameters are optimized by an introduced improved Firefly algorithm. Then, a dynamic pushback control model equipped with a linear gate-hold penalty function is built, along with a proposed iterative taxiway queue-threshold optimization algorithm for solving the model. A case study with data obtained from Beijing International airport(PEK) is presented. The taxi-out time prediction model achieves predictive accuracy within 3 min and 5 min by 84.71% and 95.66%, respectively. The results of the proposed pushback method show that total operation cost and fuel-burn cost achieve a 14.0% and 21.1%reduction, respectively, as compared to the traditional K-control policy.(3) From the perspective of implementation, using PDPC policy can significantly reduce the queue length in taxiway and taxi-out time. The total operation cost and fuel-burn cost can be curtailed by 37.2% and 52.1%,respectively, as compared to the non-enforcement of any pushback control mechanism. These results show that the proposed pushback control model can reduce fuel-burn costs and airport surface congestion effectively.展开更多
In this paper we consider the problem of determining the optimal time to buy an asset in a position of an uptrend or downtrend in the financial market and currency market as well as other markets. Asset price is model...In this paper we consider the problem of determining the optimal time to buy an asset in a position of an uptrend or downtrend in the financial market and currency market as well as other markets. Asset price is modeled as a geometric Brownian motion with drift being a two-state Markov chain. Based on observations of asset prices, investors want to detect the change points of price trends as accurately as possible, so that they can make the decision to buy. Using filtering techniques and stochastic analysis, we will develop the optimal boundary at which investors implement their decisions when the posterior probability process reaches a certain threshold.展开更多
基金Supported by National Natural Science Foundation of China (10405023)National Large-Scale Science Project BEPCII
文摘A novel front-end circuit designed for PMT signals processing considering the solution of "Time Walk" correction is discussed in this paper. We are trying to apply the TOT (Time over Threshold) technique to our research. Different from traditional ways, where amplitude is measured, time width is measured for slew correction here, which takes the advantage of TDC. Expensive fast ADCs are abandoned and the whole time measurement electronics design becomes more effective and economical. Test boards have been developed and a convenient method is introduced to evaluate our TOT technique. Results have shown that a 10ps slew correction resolution is achieved throughout the amplitude range from -108mV to -2000mV for negative signals of both 5 ns leading and trailing edge with 10 ns 50%-50% pulse width.
基金Supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(No.KJCX2-YW-N27)the National Natural Science Foundation of China(No.11079003)
文摘High precision time measurement is required in the readout of the neutron wall and TOF walls in the external target experiment of the Cooling Storage Ring(CSR) project in the Heavy Ion Research Facility in Lanzhou(HIRFL).Considering the time walk correction,both time and charge are measured in the readout electronics.In this 16-channel measurement module,time and charge information are digitized by TDCs at the same time based on the Time-Over-Threshold(TOT) method;meanwhile,by employing high-density ASIC chips,the electronics complexity is effectively reduced.Test results indicate that this module achieves a time resolution better than 25 ps and a charge resolution better than 5%over the input amplitude range from 50 mV to 3V.
基金The Natural Science Basic Research Plan in Shaanxi Province of China(2018JM1011)Natural Science Basic Research Plan in Shaanxi Province of China(2017JQ1014)NSF of China(11701041)
文摘In this paper, an SEIRS epidemic model with pulse vaccination and two time delays is proposed. By using stroboscopic map and comparison principle, the disease-free periodic solution(DFPS for short) is obtained and the global asymptotic stability of the DFPS is proved. The sufficient conditions for the permanence of the model are obtained. In addition, numerical simulations are done to confirm our theoretical results.
文摘A certain formation pressure level must be kept due to the threshold pressure of the low-permeability reser-voir during the seepage. Advanced water injection can keep the formation pressure at a higher level and keep a higher pressure gradient, which is an effective way to develop low-permeability reservoir. Based on the mechanism of advanced water injection and characteristic of porous flow in low permeability reservoir, a seepage model considering threshold pressure gradient is established to determine the formation pressure distribution at anytime as the water is injected at a constant speed. The optimum water injection time for the advanced water injection technology can be determined by using this model. The calculated result coincides basically with the numerical simulation result, which indicates that the model put forward in this paper is feasible.
基金partially supported by the National Natural Science Foundation of China-Civil Aviation Joint Fund(Nos.U1533203,U1233124.)
文摘Long departure-taxi-out time leads to significant airport surface congestion, fuel-burn costs, and excessive emissions of greenhouse gases. To reduce these undesirable effects, a Predicted taxi-out time-based Dynamic Pushback Control(PDPC) method is proposed. The implementation of this method requires two steps: first, the taxi-out times for aircraft are predicted by the leastsquares support-vector regression approach of which the parameters are optimized by an introduced improved Firefly algorithm. Then, a dynamic pushback control model equipped with a linear gate-hold penalty function is built, along with a proposed iterative taxiway queue-threshold optimization algorithm for solving the model. A case study with data obtained from Beijing International airport(PEK) is presented. The taxi-out time prediction model achieves predictive accuracy within 3 min and 5 min by 84.71% and 95.66%, respectively. The results of the proposed pushback method show that total operation cost and fuel-burn cost achieve a 14.0% and 21.1%reduction, respectively, as compared to the traditional K-control policy.(3) From the perspective of implementation, using PDPC policy can significantly reduce the queue length in taxiway and taxi-out time. The total operation cost and fuel-burn cost can be curtailed by 37.2% and 52.1%,respectively, as compared to the non-enforcement of any pushback control mechanism. These results show that the proposed pushback control model can reduce fuel-burn costs and airport surface congestion effectively.
文摘In this paper we consider the problem of determining the optimal time to buy an asset in a position of an uptrend or downtrend in the financial market and currency market as well as other markets. Asset price is modeled as a geometric Brownian motion with drift being a two-state Markov chain. Based on observations of asset prices, investors want to detect the change points of price trends as accurately as possible, so that they can make the decision to buy. Using filtering techniques and stochastic analysis, we will develop the optimal boundary at which investors implement their decisions when the posterior probability process reaches a certain threshold.
