直驱式波浪发电用磁场调制横向磁通发电机的设计与分析

基于直线发电机的直驱式波浪发电系统可以直接将波浪能转化为电能,具有结构简单和效率高等优点。然而,由于波浪速度较低,造成直驱式波浪发电机体积庞大和功率密度较低,为解决这个问题,该文基于磁齿轮和磁场调制电机的增速效应,结合横向磁通电机的横向磁路,提出一种用于波浪发电的新型磁场调制横向磁通直线发电机结构。首先,介绍发电机的结构、工作原理和磁场调制机理,采用多目标优化法对发电机电磁结构进行优化设计;研究不同极槽配比和调制器倾斜角度对发电机电磁性能的影响;计算发电机对应不同电枢电流的损耗和效率,对比该结构、交叉绕组结构和现有文献中横向磁通直线电机的功率密度;最后,制造样机并搭建实验测试平台,测量发电机推力和反电势,证明所提出拓扑结构的合理性和有限元计算结果的准确性。

神经先验增强的抗干扰鲁棒自动驾驶导航

自动驾驶车辆广泛依赖感知系统来进行城市导航和环境理解,然而现有研究大多局限于良好的城市驾驶环境,在恶劣天气以及外部干扰下导致的传感器故障和感知失灵等严重影响现有自动驾驶系统的实际落地。为此提出了一种基于神经先验的自动驾驶信息重建算法,通过对大范围自动驾驶场景的隐式建模密集地存储场景几何先验,并基于注意力机制结合隐式神经先验进行自动驾驶感知信息的鲁棒重建,最终提出一个通用的自动驾驶导航鲁棒性增强框架。在CARLA自动驾驶模拟器仿真实验中,该算法显著提升了多个现有自动驾驶模型在外部干扰下的导航性能,使自动驾驶模型在攻击和干扰下的性能衰减率从82.74%下降到了8.84%,证明了所提方法的通用性和有效性。

Controlling quantum discord dynamics in cavity QED systems by applying a classical driving field with phase decoherence

We investigate a two=level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of the atom and cavity field as the time turns to infinity. We also find that the stationary quantum discord can be increased by applying a classical driving field. Furthermore, we explore the quantum discord dynamics of two identical non=interacting two-level atoms independently interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence. Results show that the quantum discord between two atoms is more robust than entanglement under phase decoherence and the classical driving field can help to improve the amount of quantum discord of the two atoms.

Sub- and Super-Luminal Phenomena in a Doubly Driven Four-Level System

With the occurrence of an adding driving field, the properties of the dispersion and the absorption of a four-level system are changed greatly. The system can produce the normal and anomalous dispersion regions with proper parameters. Here, the driving fields can be seemed as knobs to manipulate the group velocity of a weak probe field between subluminal and superluminal.

Model calibration concerning risk coefficients of driving safety field model

Driving safety field(DSF) model has been proposed to represent comprehensive driving risk formed by interactions of driver-vehicle-road in mixed traffic environment. In this work, we establish an optimization model based on grey relation degree analysis to calibrate risk coefficients of DSF model. To solve the optimum solution, a genetic algorithm is employed. Finally, the DSF model is verified through a real-world driving experiment. Results show that the DSF model is consistent with driver's hazard perception and more sensitive than TTC. Moreover, the proposed DSF model offers a novel way for criticality assessment and decision-making of advanced driver assistance systems and intelligent connected vehicles.

Creating unconventional geometric phase gate using squeeze-like operator assisted by strong driving field

Based on the idea that a squeezing process can be thought of as a total cumulative effect of a large number of tiny squeezing processes, we define a squeeze-like operator with a time-dependent squeeze parameter. Applying this operator to and combining with a system which includes a two-photon interaction between two atoms and an initial vacuum cavity field, and resorting to a resonant strong driving classical field, we obtain an unconventional geometric phase gate with a shorter gating time.

Fluorescence properties in a single driven four-level atomic system

The spontaneous emission decay dynamics of a tripod configuration four-level atom driven by a single laser field is studied. Under different initial conditions, we discuss the effects of quantum interference and detuning of external driving field on atomic spontaneous emission properties. For the larger detuning, the interesting phenomena of the spectral line narrowing are found which stem from the contribution of external driving field.

Generation of W-Type Entangled Coherent States of Three-Cavity Fields by a Driving Classical Field

A scheme is proposed to generate the W-type entangled coherent states of three-cavity field. The scheme is based on the resonant atom-field interaction, thus the interaction time between the atom and the cavity is greatly reduced, which is important in view of decoherence. Furthermore, the scheme does not need accurate adjustment of the interaction time.

Controlling the Directed Quantum Transport of Ultracold Atoms in an Optical Lattice with a Periodic Driving Field

We propose a new method to control the directed quantum transport of ultracold atoms in a one-dimensional optical lattice. In this proposal, the effective tunneling between the neighboring sites can be adjusted via coherent destruction of tunneling by tuning the phase of the external field, instead of using the driving field intensity or the frequency, thus the directed quantum transport of ultracold atoms can be coherently controlled in a nmch easier manner. Our proposal overcomes the major drawback of the method used by Creffield et al [Phys. Rev. Lett. 99 （2007） 110501], and can be implemented, in principle, in any one-dimensional optical lattice. Some potential applications of the scheme are also discussed.

Quantum coherence preservation of atom with a classical driving field under non-Markovian environment

The exact dynamics of an open quantum system consisting of one qubit driven by a classical driving field is investigated. Our attention is focused on the influences of single-and two-photon excitations on the dynamics of quantum coherence and quantum entanglement. It is shown that the atomic coherence can be improved or even maintained by the classical driving field, the non-Markovian effect, and the atom-reservoir detuning. The interconversion between the atomic coherence and the atom-reservoir entanglement exists and can be controlled by the appropriate conditions. The conservation of coherence for different partitions is explored, and the dynamics of a system with two-photon excitations is different from the case of single-photon excitation.

Modulating the Lasing Performance of the Quantum Dot-Cavity System by Adding a Resonant Driving Field

We propose a new scheme on modulating the lasing performance of a quantum dot-cavity system. Compared to the conventional above-band pump, in our new scheme an additional resonant driving field is applied on the quantum dot-cavity system. By employing the master equation theory and the Jaynes-Cummings model, we are able to study the interesting phenomenon of the coupling system. To compare the different behaviors between using our new scheme and the conventional method,we carry out investigatioin for both the 'good system'and 'more realistic system', characterizing several important parameters, such as the cavity population, exciton population and the second-order correlation function at zero time delay. Through numerical simulations,we demonstrate that for both the good system and more realistic system, their lasing regimes can be displaced into other regimes in the presence of a resonant driving field.

Lower Bounds on Negative Energy Densities for the Scalar Field in Flat Spacetime

We obtain a lower bound on the spacetime-weighted average of the energy density for the scalar field in four-dimensional flat spacetime. The bound takes the form of a quantum inequality. The inequality does not rely on the quantum state and its form is only related to the weights, namely the spacetime sampling functions which are assumed to be smooth, positive and compactly supported. It is found that the inequality is just equal to the temporal quantum energy inequality. When the characteristic length of the temporal sampling function tends to zero, the lower bound becomes divergent. This is consistent with the fact that the spatial restriction on negative energy density does not exist in four-dimensional spacetime.

Field Weakening Control of a Separately Excited DC Motor Using Neural Network Optemized by Social Spider Algorithm

This paper presents the speed control of a separately excited DC motor using Neural Network (NN) controller in field weakening region. In armature control, speed controller has been used in outer loop while current controller in inner loop is used. The function of NN is to predict the field current that realizes the field weakening to drive the motor over rated speed. The parameters of NN are optimized by the Social Spider Optimization (SSO) algorithm. The system has been implemented using MATLAB/SIMULINK software. The simulation results show that the proposed method gives a good performance and is feasible to be applied instead of others conventional combined control methods.

激波管模拟产生近场爆炸冲击波

激波管可以在实验室环境下模拟爆炸产生冲击波,具有参数易于控制和测量手段准确多样等优势,在爆炸冲击效应的研究中被广泛应用。但与真实爆炸相比,尤其是近场爆炸,激波管产生的冲击波存在正压作用时间难以缩短、超压峰值难以提升的困难。通过对激波管运行理论和数值模拟分析发现:缩短正压作用时间的关键是让反射稀疏波尽快追上入射激波;提升超压峰值的关键是提高驱动气体的驱动能力。为此,设计了一种驱动段为锥形截面的激波管,使得反射稀疏波更快地追上入射激波,从而有效减小激波管设备长度并缩短正压作用时间;同时,采用正向爆轰驱动技术,利用化学能代替高压空气驱动提高驱动气体声速,在低爆轰初始压力下可以获得高的超压峰值。数值计算结果表明,在入射激波马赫数(MS=2.0)相同条件下,相对于等截面驱动方式,采用锥形截面驱动方式时,激波管长度可以减少近2/3,正压作用时间可以缩短近1/2。激波管实验结果表明,锥形截面驱动激波管产生的超压曲线满足近场爆炸冲击波形要求,并获得了超压峰值为64.7~813.4 kPa、正压作用时间为1.7~4.8 ms的爆炸冲击波波形。该研究可为近场爆炸冲击波致伤及装备防护效应评价实验提供参考。

Recent Results on Field Reversed Configurations from the Translation, Confinement and Sustainment Experiment

The field-reversed configuration (FRC) offers an attractive alternative approach to magnetically confined fusion because of its extremely high β, simple linear geometry, and natural divertor for helium ash removal. Multi-hundred eV and high density FRCs have been produced using the standard Field Reversed Theta Pinch (RFTP) method, with a confinement scaling that leads to fusion conditions. These FRCs are, however, limited to only tens of mWb fluxes and sub-msec lifetime. Recent progress has been made in building up the flux and sustaining the FRC current using Rotating Magnetic Fields (RMF) in the Translation, Sustainment, and Confinement (TCS) facility at the University of Washington. TCS has demonstrated formation and steady-state sustainment of standard, flux-confined, prolate FRCs. The RMF also provides stability for the n = 2 rotational mode, which is the dominant global instability observed experimentally. Simple calculations show that a strong radially inward force imposed by the RMF increases proportionally to any local outward deformation of the plasma cross section. Evidence of this has been experimentally demonstrated, and the effects of various RMF antenna geometries studied. High temperature FRCs could also be produced in TCS by translating high energy plasmoids formed in the normal theta pinch manner into the confinement chamber containing the RMF antennas. Extremely interesting results were obtained for this translation and capture process. The plasmoids can survive the violent dynamics of supersonic reflections off magnetic mirror structures, producing a stable high-β, near-FRC state with substantial flux conversion from toroidal to poloidal. This is a tribute not only to the robustness of FRCs, but also to the tendency of an FRC to assume a preferred state for a magnetized plasma. The magnetic helicity, as inferred by a simple interpretive model, is approximately preserved, possibly conforming to a high-β relaxation principle.

考虑周车主观侵略性的智能车辆换道优化策略

智能车辆换道策略是智能驾驶技术的重要组成部分,在不同场景下的适应能力对于高品质自动驾驶尤为重要。在异质交通流中,智能车辆认知属性的不同会引起换道车辆换道意图及轨迹规划的差异。该策略利用车辆行驶空间、行驶效率参数建立车辆的决策代价函数,采用模糊理论从速度系数、空间系数、车道分布等角度实现对周围车辆主观侵略性的量化描述,在此基础上,通过智能驾驶员模型(IDM)预测周车对换道车辆换道意图的行为响应,并根据预测信息优化换道决策。在轨迹规划过程中,将车辆换道轨迹解耦为车辆换道路径及行驶速度,利用车辆主观侵略性及车辆行驶安全场评估车辆换道行驶风险,并将行驶安全场与二次规划相融合,从安全性、舒适性、参考线偏差等角度进行路径及速度优化。仿真结果表明,该优化策略通过换道决策可以有效提高道路通行效率,相较固定五次多项式与单独的安全场换道轨迹,可以有效降低换道过程中横向速度与横向加速度的幅值,改善换道过程中的行驶舒适性。

Numerical Simulation of Modified Radial Electric Field by LHCD

Based on the electron’s radial force equilibrium, the profiles of radial electric field in OH and LHCD phase are calculated by using a simulation code. The dependences of radial electron field on electron density and its profile and different current ratio, Irf/Ip, are given. The connections between the improvement of plasma confinement and the modified radial electric field by LHCD are discussed by comparing the calculated results with the experimental results.

基于风险场的不同认知次任务下接管风险评估模型

为有效评估不同认知次任务下L3级自动驾驶车辆接管时的风险,开展了驾驶接管风险评估模型研究。设计了城市快速路紧急接管场景并开展不同认知次任务下的驾驶模拟试验。考虑轨迹场、势能场和行为场因素,构建了接管风险评估模型。采用接管风险指数法,验证了所建模型的有效性。结合实测数据,量化不同认知次任务和回避操作类型对接管风险场场强的影响。结果表明:被试者进行接管操作后1~9 s内模型接管风险指数分布情况的M-W检验和K-S检验结果均为p<0.05,说明模型可以有效评估车辆在接管过程中的接管风险。此外,模型接管风险指数的均方根误差均值(0.062)小于碰撞时间倒数的均方根误差均值(0.098),说明模型在表征风险的准确性方面要优于碰撞时间倒数。研究结果可为接管过程中的车辆运行风险评估和避撞设计提供借鉴和参考。

邯郸山前平原地下水流场演变及其驱动力

20世纪60年代初邯郸山前平原浅层地下水位大幅下降,地下水降落漏斗逐渐形成,地下水流场剧烈演变,采用时间序列分析、相关分析、水均衡等方法,分析了邯郸山前平原浅层地下水流场的演变规律及其驱动力,并计算了1981—2019年各影响因素对地下水流场演变的贡献率,结果表明:1960年以前邯郸山前平原浅层地下水流场演变主要受自然因素驱动,1960年以后地下水流场演变的驱动力由自然因素演化为人为因素和自然因素,地下水源汇项逐渐发生变化;邯郸山前平原排泄项对地下水流场演变的贡献率大于补给项,降水入渗和地下水开采始终是浅层地下水流场演变的主要驱动力;1981—2000年降水入渗补给量和开采量对浅层地下水流场演变的贡献率为80.82%,2001—2019年降水入渗补给量和开采量对浅层地下水流场演变的贡献率为75.79%,浅层地下水流场演变的驱动力趋于多元化。

基于行车风险场的自动驾驶接管风险评估模型

为评估L3级自动驾驶的接管风险,降低接管过程中的事故率,设计城市快速路接管场景并开展驾驶模拟实验,以行车风险场理论为基础,采用动态和静态风险分布函数反映其他交通单元对接管风险的影响,引入车辆性能概率因子对自动驾驶接管过程中的事故发生概率进行表征,同时考虑接管反应时间的影响,构建自动驾驶接管风险评估模型,基于驾驶模拟实验获取接管反应时间数据和车辆轨迹数据对模型参数进行标定,并与碰撞时间倒数进行对比,验证模型的有效性。结果表明:驾驶员接管后1~9 s内模型计算所得的接管风险指数的变化趋势与碰撞时间倒数一致,但接管过程中风险指数的均方根误差均值(0.059)相较于碰撞时间倒数的均方根误差均值(0.093)下降了37%。构建的模型能够有效评估驾驶员的接管风险,且模型在表征风险的准确性方面优于碰撞时间倒数。