In this paper, the speed gradient （SG） model is extended to describe the traffic flow on two-lane freeways. Terms related to lane change are added into the continuity equations and velocity dynamic equations. The em...In this paper, the speed gradient （SG） model is extended to describe the traffic flow on two-lane freeways. Terms related to lane change are added into the continuity equations and velocity dynamic equations. The empirically observed two-lane phenomena, such as lane usage inversion and lane change rate versus density, are reproduced by extended SG model. The local cluster effect is also investigated by numerical simulations.展开更多
A potential acceleration of a quantum open system is of fundamental interest in quantum computation, quantum communication, and quantum metrology. In this paper, we investigate the ＂quantum speed-up capacity＂ which ...A potential acceleration of a quantum open system is of fundamental interest in quantum computation, quantum communication, and quantum metrology. In this paper, we investigate the ＂quantum speed-up capacity＂ which reveals the potential ability of a quantum system to be accelerated. We explore the evolutions of the speed-up capacity in different quantum channels for two-qubit states. We find that although the dynamics of the capacity is varying in different kinds of channels, it is positive in most situations which are considered in the context except one case in the amplitude-damping channel. We give the reasons for the different features of the dynamics. Anyway, the speed-up capacity can be improved by the memory effect. We find two ways which may be used to control the capacity in an experiment： selecting an appropriate coefficient of an initial state or changing the memory degree of environments.展开更多
Studies conducted on crashes at rural intersections of state highways and local roads/streets with two-way stop control have proved that the problem was likely poor judgment by the stopped driver on the minor approach...Studies conducted on crashes at rural intersections of state highways and local roads/streets with two-way stop control have proved that the problem was likely poor judgment by the stopped driver on the minor approach of the speed of an oncoming vehicle and/or safe gap in traffic on the major highway. Several mitigating strategies have been suggested and studied in various studies to improve safety at the two-way stop control rural intersections and at other rural highway segments. There are also several low-cost techniques used, mostly in foreign countries, to slow drivers on major highways as they enter small towns and villages, e.g., narrowing pavement lines, establishing visual gateways, etc. Lowered speeds would decrease crash severity. In this study, four strategies including solar speed display units, mobile speed trailers, optical speed bars, and colored pavement were tested and assessed in some locations in Kansas. The results of this research indicate that both solar speed display units and mobile speed trailers are effective in speed reduction at the desired points, but optical speed bars and colored pavements do not yield reliable results. Additional studies and longer term studies, should be conducted.展开更多
As one weak topic in research of debris flow,abrasion of debris flow shortens obviously application life of control structure composed of concrete.High_speed drainage structure,one of the most effective techniques to ...As one weak topic in research of debris flow,abrasion of debris flow shortens obviously application life of control structure composed of concrete.High_speed drainage structure,one of the most effective techniques to control giant debris flow disaster,has shortened one_third application life due to abrasion by debris flow.Based on velocity calculation method founded by two_phase theory,research of abrasion mechanism of debris flow to high_speed drainage structure was made.The mechanism includes both abrasion mechanism of homogeneous sizing and shearing mechanism of particle of debris flow to high_speed drainage trough structure.Further abrasion equations of both sizing and particle were established by Newton movement theory of debris flow.And abrasion amount formula of the high_speed drainage trough structure is set up by dimensional analysis.Amount to calculating in the formula is consistent with testing data in_situ,which is valuable in design of high_speed drainage structure.展开更多
A two-streak high-speed photography measuring system is designed, which can successfully record the reactive shock front and the reaction profile within the run distance of shock initiation under two-dimensional shock...A two-streak high-speed photography measuring system is designed, which can successfully record the reactive shock front and the reaction profile within the run distance of shock initiation under two-dimensional shock initiation. The strong reaction delay time and the shape of reaction shock front are determined in the cast composition B (RDX/TNT/60/40). A low level reaction zone has been found and analyzed..展开更多
This paper presents a variable speed control strategy for wind turbines in order to capture maximum wind power.Wind turbines are modeled as a two-mass drive-train system with generator torque control.Based on the obta...This paper presents a variable speed control strategy for wind turbines in order to capture maximum wind power.Wind turbines are modeled as a two-mass drive-train system with generator torque control.Based on the obtained wind turbine model,variable speed control schemes are developed.Nonlinear tracking controllers are designed to achieve asymptotic tracking for a prescribed rotor speed reference signal so as to yield maximum wind power capture.Due to the difficulty of torsional angle measurement,an observer-based control scheme that uses only rotor speed information is further developed for global asymptotic output tracking.The effectiveness of the proposed control methods is illustrated by simulation results.展开更多
The aim of this study is to investigate CO2 two-phase nozzle flow in terms of both experimental and analytical aspects for the optimum design of two-phase flow nozzle of CO2 two-phase flow ejector. In the experiment, ...The aim of this study is to investigate CO2 two-phase nozzle flow in terms of both experimental and analytical aspects for the optimum design of two-phase flow nozzle of CO2 two-phase flow ejector. In the experiment, it is measured that the temperature profile in the stream-wise direction of a divergent-convergent nozzle through which CO2 in the supercritical pressure condition is blown down into the atmosphere. In the analysis, a one-dimensional model which assumes steady, adiabatic, frictionless, and equilibrium is proposed. In the convergent part of the nozzle the flow is treated as single-phase flow of liquid, whereas in the divergent part the flow is treated as separated two-phase flow with saturated condition. The analytical results indicate that the temperature and the pressure decrease rapidly in the divergent part, and the void fraction increases immediately near the throat. Although this analysis is quite simple, the analytical results can follow the experimental results well within this study.展开更多
文摘In this paper, the speed gradient （SG） model is extended to describe the traffic flow on two-lane freeways. Terms related to lane change are added into the continuity equations and velocity dynamic equations. The empirically observed two-lane phenomena, such as lane usage inversion and lane change rate versus density, are reproduced by extended SG model. The local cluster effect is also investigated by numerical simulations.
基金supported by the EU FP7 Marie–Curie Career Integration Fund(Grant No.631883)the Royal Society Research Fund(Grant No.RG150036)the Fundamental Research Fund for the Central Universities,China(Grant No.2018IB010)
文摘A potential acceleration of a quantum open system is of fundamental interest in quantum computation, quantum communication, and quantum metrology. In this paper, we investigate the ＂quantum speed-up capacity＂ which reveals the potential ability of a quantum system to be accelerated. We explore the evolutions of the speed-up capacity in different quantum channels for two-qubit states. We find that although the dynamics of the capacity is varying in different kinds of channels, it is positive in most situations which are considered in the context except one case in the amplitude-damping channel. We give the reasons for the different features of the dynamics. Anyway, the speed-up capacity can be improved by the memory effect. We find two ways which may be used to control the capacity in an experiment： selecting an appropriate coefficient of an initial state or changing the memory degree of environments.
文摘Studies conducted on crashes at rural intersections of state highways and local roads/streets with two-way stop control have proved that the problem was likely poor judgment by the stopped driver on the minor approach of the speed of an oncoming vehicle and/or safe gap in traffic on the major highway. Several mitigating strategies have been suggested and studied in various studies to improve safety at the two-way stop control rural intersections and at other rural highway segments. There are also several low-cost techniques used, mostly in foreign countries, to slow drivers on major highways as they enter small towns and villages, e.g., narrowing pavement lines, establishing visual gateways, etc. Lowered speeds would decrease crash severity. In this study, four strategies including solar speed display units, mobile speed trailers, optical speed bars, and colored pavement were tested and assessed in some locations in Kansas. The results of this research indicate that both solar speed display units and mobile speed trailers are effective in speed reduction at the desired points, but optical speed bars and colored pavements do not yield reliable results. Additional studies and longer term studies, should be conducted.
文摘As one weak topic in research of debris flow,abrasion of debris flow shortens obviously application life of control structure composed of concrete.High_speed drainage structure,one of the most effective techniques to control giant debris flow disaster,has shortened one_third application life due to abrasion by debris flow.Based on velocity calculation method founded by two_phase theory,research of abrasion mechanism of debris flow to high_speed drainage structure was made.The mechanism includes both abrasion mechanism of homogeneous sizing and shearing mechanism of particle of debris flow to high_speed drainage trough structure.Further abrasion equations of both sizing and particle were established by Newton movement theory of debris flow.And abrasion amount formula of the high_speed drainage trough structure is set up by dimensional analysis.Amount to calculating in the formula is consistent with testing data in_situ,which is valuable in design of high_speed drainage structure.
文摘A two-streak high-speed photography measuring system is designed, which can successfully record the reactive shock front and the reaction profile within the run distance of shock initiation under two-dimensional shock initiation. The strong reaction delay time and the shape of reaction shock front are determined in the cast composition B (RDX/TNT/60/40). A low level reaction zone has been found and analyzed..
基金supported by the Key Project of National Natural Science Foundation of China(61533009)the 111 Project(B08015)the Research Projects(KQC201105300002A,JCY20130329152125731,JCYJ20150403161923519)
文摘This paper presents a variable speed control strategy for wind turbines in order to capture maximum wind power.Wind turbines are modeled as a two-mass drive-train system with generator torque control.Based on the obtained wind turbine model,variable speed control schemes are developed.Nonlinear tracking controllers are designed to achieve asymptotic tracking for a prescribed rotor speed reference signal so as to yield maximum wind power capture.Due to the difficulty of torsional angle measurement,an observer-based control scheme that uses only rotor speed information is further developed for global asymptotic output tracking.The effectiveness of the proposed control methods is illustrated by simulation results.
文摘The aim of this study is to investigate CO2 two-phase nozzle flow in terms of both experimental and analytical aspects for the optimum design of two-phase flow nozzle of CO2 two-phase flow ejector. In the experiment, it is measured that the temperature profile in the stream-wise direction of a divergent-convergent nozzle through which CO2 in the supercritical pressure condition is blown down into the atmosphere. In the analysis, a one-dimensional model which assumes steady, adiabatic, frictionless, and equilibrium is proposed. In the convergent part of the nozzle the flow is treated as single-phase flow of liquid, whereas in the divergent part the flow is treated as separated two-phase flow with saturated condition. The analytical results indicate that the temperature and the pressure decrease rapidly in the divergent part, and the void fraction increases immediately near the throat. Although this analysis is quite simple, the analytical results can follow the experimental results well within this study.
