Direct Observation on H-Elimination Enhancement from C_(2)H_(4) through Non-Adiabatic Process by Femtosecond Laser Induced Coulomb Explosion

Ethylene, the simplest model of a carbon-carbon double bond system, is pivotal in numerous chemical and biological processes. By employing intense infrared laser pump-probe techniques alongside coincidence measurements, we investigate the ultrafast non-adiabatic dynamics involved in the breakage of carbon-carbon double bonds and hydrogen elimination in dissociation of ethylene. Our study entails analyzing the dynamic kinetic energy release spectra to assess three bond-breaking scenarios, movements of nuclei, and structural changes around the carbon atoms. This allows us to evaluate the relaxation dynamics and characteristics of various dissociative states. Notably, we observe a significant rise in the yield of fragments resulting from C–H bond breakage with the delay time extended, suggesting non-adiabatic coupling through conical intersections from C–C bond breakage as a probable cause.

Quantum State-Resolved Nonadiabatic Dynamics of the H+NaF→Na+HF Reaction

The H+NaF reaction is investigated at the quantum state-resolved level using the time-dependent wavepacket method based on a set of accurate diabatic potential energy surfaces.Oscillatory structures in the total reaction probability indicate the presence of the short-lived intermediate complex.

Balancing the Quantum Speed Limit and Instantaneous Energy Cost in Adiabatic Quantum Evolution

Adiabatic time-optimal quantum controls are extensively used in quantum technologies to break the constraints imposed by short coherence times.However,practically it is crucial to consider the trade-off between the quantum evolution speed and instantaneous energy cost of process because of the constraints in the available control Hamiltonian.Here,we experimentally show that using a transmon qubit that,even in the presence of vanishing energy gaps,it is possible to reach a highly time-optimal adiabatic quantum driving at low energy cost in the whole evolution process.This validates the recently derived general solution of the quantum Zermelo navigation problem,paving the way for energy-efficient quantum control which is usually overlooked in conventional speed-up schemes,including the well-known counter-diabatic driving.By designing the control Hamiltonian based on the quantum speed limit bound quantified by the changing rate of phase in the interaction picture,we reveal the relationship between the quantum speed limit and instantaneous energy cost.Consequently,we demonstrate fast and high-fidelity quantum adiabatic processes by employing energy-efficient driving strengths,indicating a promising strategy for expanding the applications of time-optimal quantum controls in superconducting quantum circuits.

Ion acoustic solitary waves in an adiabatic dusty plasma:Roles of superthermal electrons,ion loss and ionization

We investigate propagation of dust ion acoustic solitary wave(DIASW)in a multicomponent dusty plasma with adiabatic ions,superthermal electrons,and stationary dust.The reductive perturbation method is employed to derive the damped Korteweg-de Vries(DKdV)equation which describes DIASW.The result reveals that the adiabaticity of ions significantly modifies the basic features of the DIASW.The ionization effect makes the solitary wave grow,while collisions reduce the growth rate and even lead to the damping.With the increases in ionization cross sectionΔσ/σ_(0),ion-to-electron density ratioδ_(ie)and superthermal electrons parameterκ,the effect of ionization on DIASW enhances.

Fast population transfer with a superconducting qutrit via non-Hermitian shortcut to adiabaticity

Non-Hermitian dissipation dynamics,capable of turning the conventionally detrimental decoherence effects to useful resources for state engineering,is highly attractive to quantum information processing.In this work,an effective scheme is developed for implementing fast population transfer with a superconducting qutrit via the non-Hermitian shortcut to adiabaticity(STA).We first deal with aΛ-configuration interaction between the qutrit and microwave drivings,in which the dephasing-assisted qubit state inversion requiring an overlarge dephasing rate is constructed non-adiabatically.After introducing a feasible ancillary driving that directly acts upon the qubit states,the target state transfer can be well realized but with an accessible qubit dephasing rate.Moreover,a high fidelity could be numerically obtained in the considered system.The strategy could provide a new route towards the non-Hermitian shortcut operations on superconducting quantum circuits.

Charge self-trapping in two strand biomolecules:Adiabatic polaron approach

We investigate the properties of the excess charge(electron, hole) introduced into a two-strand biomolecule. We consider the possibility that the stable soliton excitation can be formed due to interaction of excess charge with the phonon subsystem. The influence of overlap of the molecular orbitals between adjacent structure elements of the macromolecular chain on the soliton properties is discussed. Special attention is paid to the influence of the overlapping of the molecular orbitals between structure elements placed on the different chains. Using the literature values of the basic energy parameters of the two-chain biomolecular structures, possible types of soliton solutions are discussed.

Comparative study on the flame retardancy of CO_(2) and N_(2) during coal adiabatic oxidation process

To test the effectiveness of N_(2) and CO_(2) in preventing coal from spontaneously combusting,researchers used an adiabatic oxidation apparatus to conduct an experiment with different temperature starting points.Non-adsorbed helium(He)was used as a reference gas,and coal and oxygen concentration temperature variations were analyzed after inerting.The results showed that He had the best cooling effect,N_(2) was second,and CO_(2) was the worst.At 70℃and 110℃,the impact of different gases on reducing oxygen concentration and the cooling effect was the same.However,at the starting temperature of 150℃,CO_(2) was less effective in lowering oxygen concentration at the later stage than He and N_(2).N_(2) and CO_(2) can prolong the flame retardation time of inert gas and reduce oxygen displacement with an initial temperature increase.When the starting temperature is the same,N_(2) injection cools coal samples and replaces oxygen more effectively than CO_(2) injection.The flame retardancy of inert gas is the combined result of the cooling effect of inert gas and the replacement of oxygen.These findings are essential for using inert flame retardant technology in the goaf.

锂离子动力电池充放电热跟踪系统设计

为实现18650锂离子电池在室温下以1 C倍率充放电时产热测量的绝热环境,设计一种基于电池温度与环境温度跟随策略的锂离子动力电池充放电热跟踪系统,采用硅胶加热片对绝热温控腔体进行加热,STM32单片机和LM2596电源管理芯片搭建可调节电源实现驱动。利用Matlab对绝热箱温控系统进行模型辨识,提出一种Smith预估模糊PID算法进行控制。仿真与实验结果表明:绝热箱内电池温度与环境温度的最大跟踪误差不超过0.5℃,具有响应速度快、误差小等优点,能够满足18650锂离子电池在室温下以1 C倍率充放电时产热测量的需求。

堆石混凝土绝热温升曲线特征及速率模型

为了探究堆石混凝土温升机制,对6种不同堆石率、3种不同初始浇筑温度、3种不同堆石级配的堆石混凝土进行绝热温升试验。分析堆石率、初始浇筑温度、堆石级配对堆石混凝土绝热温升和温升速率曲线的影响规律。并在绝热温升规律的基础上,提出一种通用的堆石混凝土绝热温升速率模型,用于描述绝热温升速率随龄期的变化规律。绝热温升速率模型简单,对堆石混凝土绝热温升和温升速率的描述具有较好的效果。研究结果为建立混凝土绝热温升模型奠定了基础,并有望推动通过动力学研究分析堆石混凝土的温升机理。

预制孪晶对AZ31镁合金绝热剪切敏感性的影响

为了分析不同孪晶体积分数对材料绝热剪切敏感性的影响,预制具有不同孪晶体积分数的AZ31镁合金。采用分离式霍普金森压杆在200℃、944 s^(-1)条件下对AZ31镁合金帽状试样进行高速冲击试验,采用电子背散射衍射仪和光学显微镜对试样在高应变速率变形前后的微观组织进行观察,计算了试样发生绝热剪切时的吸收能量,比较了绝热剪切带内外的显微硬度。结果表明:不同孪晶体积分数试样内均产生了绝热剪切带,随着孪晶体积分数的增加,绝热剪切带宽度和吸收能量减小,而绝热剪切敏感性增大。

TA1纯钛绝热剪切行为及变形机制

利用分离式霍普金森压杆实验装置,对TA1纯钛帽形试样进行高应变速率下的动态冲击实验,并利用金相显微镜(OM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和电子背散射衍射(EBSD)技术研究了不同应变速率下纯钛的绝热剪切行为及变形机制。结果表明:在动态加载下,纯钛帽形试样的强迫剪切区出现明显的绝热剪切带。随着应变速率的增加,绝热剪切带宽度变窄,长度增加,表现出较大的绝热剪切敏感性。纯钛绝热剪切带中心区的变形机制是由绝热温升和剧烈塑性变形的共同作用而发生的几何动态再结晶,过渡区的变形机制以位错滑移为主,孪生变形辅助,而基体的塑性变形机制为位错滑移和孪生共同主导。

饱和湿大气中惯性重力内波不稳定判据的探讨

为分析饱和湿斜压大气中任意频率的惯性重力内波的稳定性,利用非静力平衡Boussinesq近似的方程组,在饱和湿斜压大气中考虑湿绝热过程,着重分析讨论任意频率的惯性重力内波不稳定的充分条件(即判据),主要得出:当饱和湿斜压大气的位温经向梯度与饱和相当位温经向梯度之和大于零时,波动不稳定的必要条件是波动向北倾斜;反之,波动不稳定的必要条件是波动向南倾斜。在基流、基本温度场分布不同的饱和湿斜压环境大气中,任意频率惯性重力内波的不稳定判据呈多种不同的表达式,变化复杂。一般情况下,波动不稳定的充分条件即不稳定判据是饱和湿斜压环境大气不仅满足动热力参数Δ大于零,且波动等位相面的倾斜度必须位于与Δ有关的两个参数值A_(1)、A_(2)之间。当位温经向梯度与饱和假相当位温经向梯度的方向相反,波动相对更稳定。如果惯性重力内波发生不稳定,饱和湿斜压环境大气的等饱和相当位温面的倾斜度可能超过等绝对动量面的倾斜度,也可能小于等绝对动量面的倾斜度。

计及AA-CAES与PTC集成的综合能源系统运行优化与性能分析

为进一步发挥综合能源系统的多能互补优势,提出一种计及先进绝热压缩空气储能(AA-CAES)与槽式太阳能集热器(PTC)集成的综合能源系统(IES-PTC-CAES)优化运行策略。首先,对AA-CAES、PTC以及系统中其他设备进行分析并建立相应模型;进而以经济性、环保性和能效性为优化目标,以设备运行的关键参数为优化变量,基于分时电价建立了协同优化策略,并通过K-means算法将模拟出的典型年负荷聚类为典型日负荷;最终,使用并行式的遗传算法对系统进行寻优,得到不同目标下IES-PTC-CAES的最优运行策略。结果表明:与参考系统相比,IES-PTC-CAES系统经济目标下总成本降低了14.61万元,环保目标下二氧化碳排放量减少了6194.38 kg。

超细晶纯钛动态力学响应及变形机制

采用分离式霍普金森压杆技术在应变速率为2000~3000 s^(-1)和温度为300~450℃条件下对超细晶纯钛进行了动态冲击实验,研究了其动态力学响应及变形机制,并利用扫描电子显微镜和透射电子显微镜对变形后的微观组织进行了表征。结果表明:超细晶纯钛的真应力-真应变曲线呈现出明显的“双应力峰”特征,随着应变速率的增加和温度的降低,其屈服强度和流变应力提高,表现出正应变速率敏感性和负温度敏感性。在应变速率为2000~3000 s^(-1)的范围内,超细晶纯钛的应变速率敏感性指数m为0.12~0.17。当应变速率大于2500 s^(-1)时,超细晶纯钛试样出现绝热剪切带,绝热剪切带产生的临界应变为0.316。在动态冲击载荷下,超细晶纯钛的变形机制由低温时的位错密度增加和位错胞形成转变为高温时的几何动态再结晶和晶粒粗化。

Adiabatic shear fracture in Ti-6Al-4V alloy

Separated specimens of Ti-6Al-4V alloy were dynamically loaded at a strain rate of 3 900 s-1 using a split Hopkinson pressure bar（SHPB） apparatus.The fracture features of the separated specimens were investigated by a scanning electron microscope.The results show that adiabatic shear failure occurs in the tested specimens,and two typical areas（dimple and smooth areas） with different features are alternatively distributed on the whole fracture surface.The dimple areas originate from voids generation and coalescence,exhibiting ductile fracture characteristics.Simultaneously,ultrafine grains（UFGs） and microcracks among grains are observed on the smooth areas,indicating that the emergence of UFG areas is caused by the propagation of microcracks along grain boundaries and exhibits brittle fracture characteristics.Fracture occurring in adiabatic shear bands is not uniform and ultimate rupture is resulted from ductile and brittle fracture modes.

基于火-储联合循环的冷热电三联供系统多运行模式热力性能分析

综合考虑绝热压缩空气储能及火电机组的特点和不足,该文从能量转化及利用机理出发,提出将二者耦合集成的火-储联合循环概念以及一种基于该循环的新型冷热电多能联供系统,并对该系统进行性能评估和特性分析。基于构建的热力模型,分别研究纯电及热电、冷电联产3种典型场景下热能综合利用方式对重要参数及性能的影响规律。结果显示,在最优集成方案下,储能系统的循环效率可提高2.61%。在热电和冷电模式下,循环效率可进一步提升至77%及70.13%。火-储集成能够显著提高能源综合利用水平,在多能联产模式下性能提升更为明显。此外,通过敏感性分析得到典型运行模式下热能利用的合理方式。该文结果能够指导火-储耦合集成系统优化设计及运行,可为火电机组与压缩空气-储能高效发展提供一种新思路。

应变速率对TB6钛合金绝热剪切敏感性的影响

在室温下采用分离式霍普金森压杆对TB6钛合金帽型试样进行动态加载,研究了应变速率对TB6钛合金绝热剪切敏感性的影响。结果表明,应变速率1950~2510 s^(-1)时,4组试样均表现出明显的应变硬化效应;在绝热温升作用下,4组试样均发生热塑失稳形成绝热剪切带;受冲击载荷和材料晶粒尺寸影响,基体和绝热剪切带之间的过渡区域变形梯度不明显;热剪切带内100 nm等轴晶的形成是旋转动态再结晶机制作用的结果。通过观察金相、表征绝热剪切敏感性及计算扩展能发现,TB6钛合金绝热剪切敏感性随应变速率增加而增加。

新型磁热效应直接测量仪的研制与性能测试

基于Halbach旋转原理,设计三种尺寸的中空圆柱形NdFeB永磁磁体。利用有限元法计算的结果表明,NdFeB永磁磁体中间空隙处可产生匀强磁场,磁感应强度分别为1.0 T、1.5 T和2.0 T,方向和主磁体的磁化方向相同。NdFeB永磁磁体中轴线上磁场分布的测试结果和计算结果相吻合,误差在5%以内。基于绝热温变的直接测量法,研制磁热效应直接测量仪。对典型磁热材Gd的测试结果表明,磁热效应直接测量仪可准确测量磁热材料的绝热温变,精度在0.2℃以内。该磁热效应直接测量仪对样品的形状要求较低,测量时间短,测试过程简便。

高温下多主元合金的动态变形行为与本构建模

为加速多主元合金在航空工业领域的应用,将航空发动机经常面临的高温高应变率耦合环境作为实验条件,在5种温度下开展了CoCrFeNiMn多主元合金的动态压缩实验和变形后试样的塑性变形机理微观表征。结果表明:在1273 K的高温环境中,多主元合金的动态屈服强度可达200 MPa,表现出较好的耐高温性能;随着动态塑性应变的增加,材料内部出现了晶粒粗化的现象,并且在晶界处具有更高的亚结构孕育能力。此外,量化了不同环境温度下动态塑性变形过程中绝热温升的变化规律,指出了现有动态本构关系对CoCrFeNiMn多主元合金在宽温度域内动态应力-应变关系预测能力的不足。最后,通过解耦分析初始屈服与塑性流动阶段的温度效应,建立了一个指数形式的唯象动态本构方程。该本构方程可用于预测冲击载荷作用下宽温度域内多主元合金的屈服强度和塑性流动规律。

基于临界半衰期的连续流反应热安全风险评估方法

为了更好地评估连续流反应热安全风险,研究以通道式反应器为例,通过构建基于热量衡算和物料衡算的反应体系模型,对连续流反应体系的实际传热量和热安全风险进行了研究。针对通道式反应器进口端的绝热温升反应现象,提出了临界半衰期作为热安全判据的方法,获得了具有热安全高风险的两大反应条件,分别为:当目标反应产热总量大于800 J·g^(-1),且该反应在反应温度下半衰期小于临界半衰期;当分解反应产热总量大于800 J·g^(-1),且目标反应在反应温度下半衰期小于临界半衰期,同时分解反应在100%MTSR(工艺反应能够达到的最高温度)下半衰期也小于临界半衰期。并且通过氯苯硝化反应验证其准确性和实用性,结果显示,通道式反应器在该条件下可发生分解爆炸反应,证实了该评估方法可用于确定连续流反应热安全的高风险条件。