Properties of collective flow and pion production in intermediate-energy heavy-ion collisions with a relativistic quantum molecular dynamics model

The relativistic mean-field approach was implemented in the Lanzhou quantum molecular dynamics transport model(LQMD.RMF). Using the LQMD.RMF, the properties of collective flow and pion production were investigated systematically for nuclear reactions with various isospin asymmetries. The directed and elliptic flows of the LQMD.RMF are able to describe the experimental data of STAR Collaboration. The directed flow difference between free neutrons and protons was associated with the stiffness of the symmetry energy, that is, a softer symmetry energy led to a larger flow difference. For various collision energies, the ratio between the π^(-) and π^(+) yields increased with a decrease in the slope parameter of the symmetry energy. When the collision energy was 270 MeV/nucleon, the single ratio of the pion transverse momentum spectra also increased with decreasing slope parameter of the symmetry energy in both nearly symmetric and neutron-rich systems.However, it is difficult to constrain the stiffness of the symmetry energy with the double ratio because of the lack of threshold energy correction on the pion production.

Modeling Submicron Particles Collection in Laminar Forced Convection Gas Flow by a Rectangular Venturi Scrubber

Venturi scrubbers are usually used for large particles cleaning in turbulent gaseous flow. In this work, submicron particles scrubbing in laminar forced convection dusty air flow in a rectangular venturi scrubber have been numerically simulated. Hydrodynamics effects and scrubbing process are investigated in detail. Results are presented as flow velocity, axial pressure, streamlines pattern, particles and droplets mass fraction profile, and collect efficiency. They show that venturi scrubbers can be efficient for submicron particles scrubbing. In fact, a better collect efficiency is obtained at high particles-droplets residence time, high ratio droplets concentration/particles concentration, low venturi diameter ratioand low Reynolds numbers. There is a critical Reynolds number value for which the collect efficiency becomes very low and tends to be constant.

Effects of sequential decay on collective flows and nuclear stopping power in heavy-ion collisions at intermediate energies

In this study, the rapidity distribution, collective flows, and nuclear stopping power in ^(197)Au+^(197)Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics(UrQMD) model with GEMINI++ code. The UrQMD model was adopted to simulate the dynamic evolution of heavy-ion collisions, whereas the GEMINI++ code was used to simulate the decay of primary fragments produced by UrQMD. The calculated results were compared with the INDRA and FOPI experimental data. It was found that the rapidity distribution, collective flows, and nuclear stopping power were affected to a certain extent by the decay of primary fragments, especially at lower beam energies. Furthermore, the experimental data of the collective flows and nuclear stopping power at the investigated beam energies were better reproduced when the sequential decay effect was included.

Articles collection published in Neural Regeneration Research 2011

Neural Regeneration Research （NRR, ISSN 1675-5374, CN11-5422/R）, an English language journal published in China every ten days, is dedicated to presenting peer-reviewed, evidenced based scholarly research in neuroregeneration, including neural stem cells, nerve tissue engineering, gene therapy, and traditional Chinese medicine.

Jade Articles Collected in Tibetan Museum

Since the Yuan Dynasty, Tibet has been formally part of the territory of China. By keeping abreast with developments in the hinterland, Tibet has maintained close relations with other provinces in China and kept up to date. Mutual interactions were frequent i.e. Tibetans presented tributes to the central government and vice versa, the central governments bestowed largess on Tibetans. The largess included Buddhist statues, porcelains, silks, satins, and fabulous jade ornaments. In book entitled "Memoir of...

Collective flow and hydrodynamics in large and small systems at the LHC

In this article,we briefly review the recent progress on collective flow and hydrodynamics in large and small systems at the Large Hadron Collider(LHC),which includes the following topics:extracting the QGP viscosity from the flow data,initial-state fluctuations and final-state correlations at 2.76 A TeV Pb-Pb collisions,correlations,and collective flow in high-energy p-Pb and p-p collisions.

Identification method of crowded passenger flow based on automatic fare collection data of Nanjing Metro

To relieve traffic congestion in urban rail transit stations,a new identification method of crowded passenger flow based on automatic fare collection data is proposed.First,passenger travel characteristics are analyzed by observing the temporal distribution of inflow passengers each hour and the spatial distribution concerning cross-section passenger flow.Secondly,the identification method of crowded passenger flow is proposed to calculate the threshold via the probability density function fitted by Matlab and classify the early-warning situation based on the threshold obtained.Finally,a case study of Xinjiekou station is conducted to prove the validity and practicability of the proposed method.Compared to the traditional methods,the proposed comprehensive method can remove defects such as efficiency and delay.Furthermore,the proposed method is suitable for other rail transit companies equipped with automatic fare collection systems.

Collective Flows of 16O＋16O Collisions with α-Clustering Configurations

The main purpose of the present work is to discuss whether or not the collective flows in heavy-ion collision at the Fermi energy can be taken as a tool to investigate the cluster configuration in light nuclei. In practice, within an extended quantum molecular dynamics model, four a-clustering （linear chain, kite, square and tetrahedron） configurations of 16O are employed in the initialization, 16O＋16O around the Fermi energy （40-60 MeV/nucleon） with impact parameter 1-3fro are simulated, and the directed and elliptic flows are analyzed. It is found that collective flows are influenced by the different a-clustering configurations, and the directed flow of free protons is more sensitive to the initial cluster configuration than the elliptic flow. Nuclear reaction at the Fermi energy can be taken as a useful way to study cluster configuration in light nuclei.

Collective flow and nuclear stopping in heavy ion collisions in Fermi energy domain

The effects of the in-medium nucleon-nucleon(NN) elastic cross section on the observables in heavy ion collisions in the Fermi energy domain are investigated within the framework of the ultrarelativistic quantum molecular dynamics model. The results simulated using medium correction factors of F=σ_(NN)^(in-medium)/σ_(NN)^(free)=0.2,0.3,0.5,and the density-and momentum-dependent factor obtained from the FU3 FP1 parametrization are compared with the FOPI and INDRA experimental data. It is found that the calculations using the correction factors F=0.2 and 0.5 reproduce the experimental data(i.e.,collective flow and nuclear stopping) at 40 and 150 MeV/nucleon, respectively. Calculations with the FU3 FP1 parametrization can best fit these experimental data. These conclusions can be confirmed in both^(197)Au+^(197)Au and^(129)Xe+^(120)Sn.

Effects of the HMT on Nucleon Collective Flows within BUU Transport Model

Within the framework of a semiclassical Boltzmann-Uehling-Uhlenbeck （BUU） transport model, the high mo- mentum tail （HMT） effects of nucleon momentum distribution in the nucleus on the nucleon collective flows are studied in semieentral Au＋Au collisions. The HMT due to the isospin-dependent short-range correlations causes a smaller value of the collective flows. We find that the HMT effects on the nucleon collective flows are remarkable at beam energy of 300 MeV/nucleon and become weak as the incident beam energy increases. The results indicate that for the collective flow studies at intermediate energies, the HMT of nucleon momentum distribution in nucleus should be taken into account in transport models.

Momentum-Dependent Symmetry Potential from Nuclear Collective Flows in Heavy Ion Collisions at Intermediate Energies

Within the isospin-dependent quantum molecular dynamics model, we investigate the nuclear collective flows produced in semi-central 197 Au＋197 Au collisions at intermediate energies. The neutron proton differential flows and difference of neutron proton collective flows are sensitive to the momentum-dependent symmetry potential. This sensitivity is less affected by both the isoscalar part of nuclear equation of state and in-medium nucleon- nucleon cross sections. Moreover, this sensitivity becomes pronounced with increasing the rapidity cut.

The Time Evolution of Radial Collective Flow in Reaction of ^(197)Au with ^(197)Au at 150 MeV/u

Dynamical time evolution for central collision of 197 Au on 197Au at 150 MeV/u is in-vestigated by using Isospin-dependent Quantum Molecular Dynamics （IQMD） calculation. Thepreequilibrium emission, its influence and the time evolution of radial collective flow are dis-cussed in detail.

社保费征管与企业投资——基于社会保险法实施的准自然实验

经济下行压力下,稳投资是关系国计民生的重大战略方向。以社会保险法实施为准自然实验,采用双重差分法探究社保费征管对企业投资的影响,研究发现:社保费征管加强显著提升了企业投资,该效应在超额雇佣、行业竞争激烈、外部社保压力大以及由税务部门征收社保费的企业更为明显。机制检验表明,社保费征管加强会通过“要素替代效应”促进企业投资,同时也会产生“现金流约束效应”抑制企业投资,而前者为核心作用机制。进一步研究显示,社会保险法实施后,企业会增加创新投入和债务融资,最终提高了企业绩效和企业价值。

基于YOLO模型的车流量实时采集系统研究

对于一座现代化城市来说,合理的交通规划是一个城市高效运行的关键,作为交通规划的关键信息的城市车流量信息,原本需要人工进行识别、获取、验证的提取方式,随着计算机视觉技术的蓬勃发展弊端尽显,终将退出历史的舞台。为了提高城市车流量信息的准确性和及时性,利用现有的计算机技术设计一种基于YOLO模型的车流量实时采集系统。该系统基于YOLO视觉检测模型,采用DeepSORT算法对检测到的目标车辆进行跟踪识别、判断车辆的运行状态、实现当前路段的车流量统计、对已记录车流量信息进行可视化展示以及数据输出等。该系统可以有效地代替传统消耗人力的死板工作,实现自动化数据收集以及道路交通情况的快速监测。该系统操作简单,交互性强,为城市的交通管理和交通规划提供准确实时的信息数据。

集体统筹与中国式农业现代化的可能路径

有关农业现代化的讨论通常围绕农业规模化展开。要理解中国式农业现代化的独特性,需要将之放在与全球其他国家对比的基础上。西方国家的农业现代化转型是为了给自己的工业化提供条件,但中国今天的农业现代化转型发生在工业化的中后期,发生在城市工商资本过剩的背景下,因而中国农业转型受到了资本下乡的推动。从中国农业规模化的实践来看,常见的有土地规模化和服务规模化两种路径,但这两种路径都是由资本主导的,小农户被锁定在利润低、风险高的生产环节,总体上处于被动地位。由于中国仍有大量的小农户只能依赖农业收益来维持生计,因而中国的农业现代化要考虑如何在保护小农户的基础上实现规模经营,保证粮食安全。在土地集体所有制之下,一些地区探索了以保护小农户为基础的农业规模化实践。村集体通过对细碎土地的整合,或通过将小农户组织起来对接公共服务或市场化服务,也可以推动农业规模经营。以小农户组织化为基础的农业现代化,是中国式农业现代化不同于他国的独特创新。中国式农业现代化的实现涉及道路选择问题,要发展小农户组织化为基础的农业现代化,需要为村集体的统筹经营留出空间。

基于幅度和相位融合的微波两相流测量系统设计

针对油井开采过程中需要对各相含量进行精确预测以调整开采策略的实际问题,设计了一种基于微波法的油水两相流检测系统。该系统利用微波在不同介质中透射能力的差异,构建了一套包含微波信号源、功率放大器、功率分配器、检波器和STM32F103ZET6核心板的硬件电路系统,通过编写AD采集和串口通信的软件代码,来接收检波器端幅度和相位数据。在数据处理方面,分别对幅度数据、相位数据和幅度-相位融合数据采用BP神经网络的方法预测含水率。实验表明:在使用融合数据时,预测准确度可以提高至96.33%,取得了较理想的效果。

乌东德水电站尾水集鱼平台集鱼效果影响因素分析

为研究乌东德水电站尾水集鱼平台集鱼效果与诱鱼措施、下游水文要素等影响因素之间的关系,通过分析2021年4~10月乌东德水电站右岸尾水集鱼平台运行数据以及同期水文数据,采用数据对比分析法初步提出了水文指标变化与集鱼效果之间的趋势关系。数据分析显示:金沙江中游江段投放肉食型饵料诱鱼增益效果更好;6~7月开启灯光诱鱼,可显著提升光照敏感鱼类的收集率;短时间的下泄流量增加对刺激鱼类洄游,增加集鱼数量没有明显作用,而超过5 d以上连续的下泄流量增加可以刺激鱼类洄游,提升集鱼数量。研究成果可为优化金沙江中游水电站生态调度以及提升集鱼系统集鱼效率提供支撑。

泥石流承灾体群体效应特征反演——以7·12四川平武县黑水沟泥石流为例

群体建筑结构的分布格局、结构形式等因素影响泥石流冲击过程和致灾表现。泥石流冲击存在绕流现象、放大作用和遮蔽效应,泥石流与建筑群之间存在复杂的流固耦合模态,但针对这类泥石流承灾体群体效应的过程与机制仍不清晰。本研究通过野外调查、物理实验和数值模拟等方法,调查泥石流承灾体群体效应特征,反演泥石流冲击流场分布和建筑损伤过程,提出了一套建筑群对泥石流的承灾动力响应特征分析方法。研究结果表明:(1)泥石流流场存在放大作用。面对泥石流冲击,建筑群的破坏导致沟道区域流速增加20%,建筑群区域流速增加46%。(2)泥石流流场存在绕流现象。建筑群阻碍泥石流直进输运,导致建筑拐角之间存在局部压力高度集中现象。(3)在建筑群中存在明显的遮蔽效应。失去建筑的上游遮蔽保护可使下游建筑受到的泥石流冲击强度增加120%。(4)泥石流致灾过程中,建筑群周边与内部的泥石流冲击特征差异明显。在建筑群外围,受前排建筑破坏的影响,泥石流流线后排建筑受泥石流冲击时刻提前10 s,泥石流冲击强度增加速率达2.1倍;(5)泥石流对建筑群内建筑冲击强度分为冲击力急剧增加—缓慢增加—逐渐稳定三个阶段,对应泥石流流深增高、缓慢淤积过程。研究结果可以为泥石流易发区村落城镇的建筑规划布局和防灾减灾措施提供科学参考。

基于Netflow的网络流量监测系统研究

网络流量测量是认识网络规律、了解网络行为的前提工作。文章从网络流量监测系统的需求出发,提出了一种基于Netflow的网络流量监测系统的解决方案,重点阐述了网络流量监测系统的总体结构设计、数据包的采集和流量数据统计等内容。同时采用Vis-ual C++6.0技术设计该方案的平台架构,指出了实现网络流量监测系统的关键技术和方法,实现了网络流量监测和管理;该系统的实现可以有效地监控网络流量状况。

生产要素下乡的障碍性因素及破解之策——基于S县J农业项目的调查研究

城乡要素的双向有序流动是在我国实施乡村振兴的战略背景之下,实现城乡融合发展的关键支撑,而城乡融合则是建立在生产要素双向自由流动的基础之上的,但是当前我国的城乡要素却只呈现出由乡村向城市的单向流动,从城市向乡村的流动还存在着障碍。为了深入研究生产要素下乡的障碍性因素,本文采取案例分析法,通过对S县J农业项目落地过程的考察和分析,研究发现阻碍生产要素下乡的主要障碍性因素为:由于在我国现行的农村土地制度、政策、运行机制之中均存在着与现代农业及乡村旅游业发展不相适应的成分,因而由此引发的农用地供地障碍和农村集体经营性建设用地供地障碍。为了破解生产要素下乡的障碍性因素,本文提出如下建议:1)我国应以土地确权为基础,积极开展对农用地经营权的股份化改革,从而可以将农用地经营权“化零为整”集中管理,最终以达到解决农用地规模化流转困难的目的。2)我国应通过重新研究制定乡镇的行政区划标准,来进行相应的调整改革,从而以打破土地流转的行政壁垒。3)我国应对农村集体经营性建设用地的空间置换机制进行深入改革,并完善相应的土地入市机制,从而可以将农村分散、闲置的集体经营性建设用地整合利用,并可以为生产要素下乡提供足够的空间载体。4)我国应优化农村集体建设用地的空间布局,促使其可以充分发挥出集聚产业要素、保障社会服务、促进文化发展等诸多功能,进而以形成主城区与区域中心镇相结合的空间格局,并可以为生产要素下乡提供畅通的渠道。