与双模腔场发生多光子相互作用的纠缠双原子的纠缠演化特性

研究了二能级偶极耦合的两个纠缠原子通过多光子相互作用与双模腔场进行耦系统中原子纠缠的演化特性.分析表明,两个原子之间的纠缠具有不规则演化特性,原子的纠缠与两原子的初始状态、偶极作用、叠加态参数以及跃迁光子数有关.     

Tavis-Cummings模型中耦合双原子纠缠度的演化特性

主要考虑Tavis-Cummings(T-C)模型中有偶极-偶极相互作用的双原子和单模相干光场相互作用时原子间的纠缠演化规律.文章给出了模型中系统时间演化算符的具体形式,并且给出了两原子初始均处于基态时不同耦合程度下原子之间的纠缠演化曲线和原子布居差演化曲线,发现原子之间始终是纠缠的,纠缠度随时间作周期性振荡,振荡幅度和周期都与原子间的耦合强度密切相关,同时原子间纠缠度的演化与原子布居差的坍塌-恢复有关联.     

四原子TaVis-Cummings模型中两体及多体纠缠的研究

首先,研究4个二能级原子与1个单模腔场相互作用下量子系统的演化情况,在此基础上,再运用concurrence和tangle两种度量对4个二能级原子之间及与腔场的相互纠缠的周期性演化进行计算并对其结果进行讨论和分析.通过比较两种度量之间的关系发现此量子系统只存在两体纠缠,而不存在多体之间的纠缠,另外,在恰当选择时间的情况...     

Tavis-Cummings模型中耦合双原子纠缠度的演化特性

主要考虑Tavis-Cumm ings(T-C)模型中有偶极-偶极相互作用的双原子和单模相干光场相互作用时原子间的纠缠演化规律.文章给出了模型中系统时间演化算符的具体形式,并且给出了两原子初始均处于基态时不同耦合程度下原子之间的纠缠演化曲线和原子布居差演化曲线,发现原子之间始终是纠缠的,纠缠度随时间作周期性振荡,振荡幅度和周期都与原子间的耦合强度密切相关,同时原子间纠缠度的演化与原子布居差的坍塌-恢复有关联.     

伊辛模型实现量子态存储和调节

考虑利用腔QED理论模拟伊辛模型,双原子在腔中演化之后,可以实现特定量子态的稳定存储,调节相互作用时间和外驱动场的频率可以实现最大纠缠态的制备.     

一般Jaynes—Cummings模型中内在相干性的解除

利用Ｍｉｌｂｕｒｎ理论，给出了初始时二能级原子处于激发态与光场处于相干态的一般Ｊａｙｎｅｓ－Ｃｕｍｍｉｎｇｓ模型密度算符的精确解。     

原子-光力混合系统的机械压缩和纠缠研究

传统光力系统中产生强机械压缩一般需要光场衰减率小于机械振子频率（可分辨边带条件），在实验室极难实现。针对光力系统在高不可分辨边带（光场衰减率远大于机械振子频率）条件下产生强机械压缩及稳态纠缠问题，提出利用两个两能级原子系综和两束不同强度激光共同调制光力系统，放宽可分辨边带条件的限制。研究结果表明：将两个原子系综放入光力学系统中，即使在高不可分辨的边带状态下，也能实现超过3 dB的强机械压缩；光场和机械振子之间的稳态纠缠也可产生。     

基于压缩库产生的磁子阻塞

基于近年来微波腔与磁子相互作用的实验进展以及非线性库理论，提出将腔-磁系统与压缩库耦合，分析其中的磁子阻塞效应，以实现磁性量子级的操控。在一个受驱动的微波腔中放置一个钇铁石榴石小球，球体中的Kittel模与微波腔模耦合，同时腔场与压缩真空库耦合。通过数值求解系统的量子主方程，详细分析了关联函数受耦合强度、失谐量、耗散率等因素的影响。从理论上证明了与压缩库耦合的腔-磁系统可以产生单磁子阻塞和双磁子阻塞，并且可以通过调节驱动强度或者失谐量灵活地在单磁子阻塞、双磁子阻塞、双磁子隧穿之间进行切换。所提出的磁子阻塞方案主要由压缩库的非线性诱导得到，为腔-磁系统实现单磁子和双磁子阻塞提供了一种可能的新途径。     

基于腔QED的量子网络即时通讯

提出了一种在实验上可行的利用腔QED实现的量子通信方案.这种方案的优点是原子与腔相互作用时在经典驱动和大失谐的条件下,不再受腔衰减和热场的影响,Bell基的测量转变为原子态的测量,从而使多人之间的量子即时通信较容易实现.     

方腔内热磁致空气自然对流数值研究

建立了处于空间中的孤立永磁体产生的永磁场中的二维方腔热磁自然对流模型,并通过数值计算的方法研究了方腔内空气在重力和磁化力驱动下的自然对流现象.在瑞利数105和磁场强度0.5~3.5T范围内,研究了梯度磁场对自然对流的抑制作用,给出了方腔内磁浮升力场,温度场、流场的变化以及方腔内壁面的换热特性.结果表明:高剩磁钕铁硼永磁体磁场可以明显的抑制方腔内自然对流,与重力场自然对流相比,方腔内流场和温度场发生了明显的变化,剩磁3.5T时Nu减小达47%.     

Excitonic Doppler-Rabi Oscillations in a Moving Organic Slab

It is theoretically shown that excitonic Doppler-Rabi oscillations can occur in an organic slab moving along the axis ofa high-Qcavity. Due to the √N enhancement of the vacuum Rabi frequency, this effect can be more easily observed than that in a moving two-level atom.     

居住区共享停车泊位分配模型

为了提高停车泊位利用率,减少停车后步行距离,根据商业区和居住区停车需求时段的错峰特征,建立共享停车泊位利用率最大化和步行距离最小化的双目标泊位分配模型.模型考虑了停车泊位供需空间和时间冲突特征,界定了模型的边界约束条件,采用粒子群多目标搜索算法求解.以聊城市金鼎商圈为例,调研了商业区和居住区的停车泊位数量、高峰时段停车需求和平均步行距离等模型参数.通过算法仿真,实验结果验证了模型的可行性.研究结果表明,建立的停车共享分配模型可用于居住区共享停车泊位分配,有效地提高了泊位利用率,降低了停车后的平均步行距离.     

Study on the squeezing effect of open-ended pipe piles

During the installation of a pipe pile, the soil around the pile will be squeezed out. This paper deals with this squeezing effect of open-ended pipe piles using the cylindrical cavity expansion theory. The characteristics of soil with different tension and compression modnli and dilation are involved by applying the elastic theory with different moduli and logarithmic strain. The closed-form solutions of the radius of the plastic region, the displacement of the boundary between the plastic region and the elastic region and the expansion pressure on the external surface of the pipe piles are obtained. When obtaining these solutions, the soil ping in the open-ended pipe pile is considered by employing an incremental filling ratio to quantify the degree of soil plugging. Moreover, the effects of the ratio of tension and compression moduli, angle of dilation and incremental filling ratio on the radius of the plastic region and the expansion pressure on the external surface of the pipe pile are investigated. The parametric analyses show that it is necessary and important to consider the difference between the tension modulus and compression modulus, dilation angle and incremental filling ratio for studying the squeezing effect of open-ended pipe pile installation. It is concluded that the analytical solutions presented in this paper are suitable for studying the squeezing effect of open-ended pipe piles.     

机动车混合交通占有率-流量模型研究

在交通流基本参数模型中,密度参数难以直接获取,占有率-流量模型具有较强的实用价值。提出占有率分析单元概念,分析混合交通不同跟车组合下,大型车辆混入对分析单元中占有率参数的影响机理,综合分析单元出现概率,得出在占有率-流量模型中,原始占有率难以反映出大型车辆对交通流影响效应的结论,随后基于车头时距和大车率修正原始占有率,最终建立了机动车混合交通情况下的占有率-流量模型,并用北京快速路实测数据对模型进行了检验,证明占有率修正之后,占有率-流量模型更加精确。此模型等式两边都考虑了大型车辆的影响效应,具有更好的实际物理意义。     

An improved general bidirectional progression model for arterial

Optimal control of arterial signals is critical for the effective operation of urban road network. With the goal of providing reasonable allocation of bidirectional green time while maximizing general bidirectional traffic progression along the arterial, this paper develops an improved general bidirectional coordinated progression model for arterial based on Maxband model. In the model, a proportional coefficient of bidirectional bandwidth demands is introduced and calibrated by adopting average link queue occupancy. The calibration method takes full account of actual traffic volume and capacity of each link, which helps to provide optimal control performance. Additionally, new constraints are added into the model and enable the model with two features: it can automatically select two-way or one-way progression, and the involved intersection unit can be either one-phase-one-approach or bidirectional symmetric release mode. The results of extensive simulation studies indicate that the improved model outperforms existing methods, markedly increasing the utilization of available bidirectional green time.     

基于离散分布的智能停车诱导系统中空余泊位数的预测研究

本文根据城市公共停车场泊位占有率在时间上表现出的周期性及其随时间的变化趋势,不考虑其由于受各种随机因素影响所表现出的不确定性,将车辆进出停车场的行为看成可描述事件。利用离散分布模型描述行为进行,建立数学模型,表达经过某段时间后停车场的空余停泊位数。最后通过算例计算验证模型的可行性,可用于停车诱导屏的泊位预测。     

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交通流密度是衡量道路服务水平的指标之一. 当交通流中车辆长度和速度变化较大时,占有率则可以更好地反映交通流密度状况. 占有率的测定能够考虑到车辆的长度和速度变化,但是其值受到测量区域长度的影响,并且在混合交通情况下测量值缺乏准确性. 对于没有车道行驶规则的混合交通流,应当以整条路段为单位进行交通流分析. 因此本文提出了“区域占有率”的概念,且利用仿真技术验证其有效性. 对混合交通流条件下的占有率和区域占有率进行比较分析,区域占有率可以更合理地描述混合交通流的密度. 同时,得出混合交通条件下的区域占有率和交通流速度关系,证明了混合交通流条件下区域占有率提出的合理性和准确性.     

Methodology for Determination of Concentration of Hetrogeneous Traffic

Traffic density provides an indication of the level of service being provided to the road users. When the length and speed of the vehicles in a traffic stream varies significantly, however, it has been found that the concept of occupancy, rather than density, is more appropriate to describe traffic concentration. This is because of the reason that occupancy takes into account the variation in the speed and length of vehicles in its measurement. The value of occupancy, however, changes with change in the detection-zone length. Also, the measure occupancy is not appropriate under heterogeneous traffic conditions, as the traffic has no lane discipline and hence, it is necessary to consider the whole of the width of the road as single unit to analyze the traffic flow. Hence, a new concept named, “area-occupancy” is proposed. Simulation technique has been used to validate the concept of area-occupancy. To check for the validity of the concept, the occupancy and area-occupancy of a homogeneous traffic stream were related to the density of the stream and it was found that area-occupancy can be a substitute for occupancy. Then, the concept of area-occupancy was applied for heterogeneous traffic and a relationship was developed between area-occupancy and traffic stream speed. The developed relationship is found to be logical indicating the appropriateness of the area-occupancy concept for heterogeneous traffic conditions.     

考虑驾驶行为异质性的城市快速路合流区仿真模型

为研究城市快速路合流区车辆运行规律，基于车辆自然轨迹数据，提出考虑驾驶行为异质性的合流区元胞自动机仿真模型。模型将合流区分为上游区域、合流区域及下游区域，3个区域由11条路段组成。首先，利用Kalman滤波算法对自然轨迹数据进行降噪处理；然后，计算每辆车驾驶行为特征参数并进行K-means聚类分析，结合聚类效果评价指标Silhouette系数将驾驶行为分为：保守-谨慎型、激进-谨慎型、保守-轻率型及激进-轻率型这4种类型；最后，依据分类结果， 建立考虑加速度、随机慢化概率异质性的跟驰模型和考虑换道安全间距、换道决策的多级异质性换道模型。在各空间占有率的情境下，基于Matlab进行数值仿真，统计同质驾驶行为和异质驾驶 行为条件下，合流区域车道的流量、密度、速度、时空位置及换道频率等参数。仿真结果表明：在空间占有率为10%~20%时，同质交通流相比异质交通流更容易产生局部交通拥堵和交通流失效情境，并且同质交通流量峰值比异质交通量小27.1%；随着空间占有率的增加，同质车辆和异质车辆驾驶频率均呈现增加-稳定-下降的趋势，而异质驾驶行为换道频率的极大值比同质交通流高 20.74%。     

PB位相相干态的振幅平方压缩特性

研究了ＰＢ位相相干态的振幅平方压缩特性。结果表明，对于ｓ〉４的ＰＢ位相相干态均可存在振幅平方压缩特性，并给出了振幅平方压缩条件。