Self-organized phenomena of pedestrian counter flow in a channel under periodic boundary conditions

In this paper we investigate self-organized phenomena such as lane formation generated by pedestrian counter flow in a channel.The lattice gas model is extended to take the effect of walkers in the opposite direction into account simultaneously when they are in the view field of a walker,i.e.,walkers tend to follow the leaders in the same direction and avoid conflicts with those walking towards them.The improved model is then used to mimic pedestrian counter flow in a channel under periodic boundary conditions.Numerical simulations show that lane formation is well reproduced,and this process is rather rapid which coincides with real pedestrian traffic.The average velocity and critical density are found to increase to some degree with the consideration of view field.

Effect of following strength on pedestrian counter flow

This paper proposes a modified lattice gas model to simulate pedestrian counter flow by considering the effect of following strength which can lead to appropriate responses to some complicated situations. Periodic and open boundary conditions are adopted respectively. The simulation results show that the presented model can reproduce some essential features of pedestrian counter flows, e.g., the lane formation and segregation effect. The fundamental diagrams show that the complete jamming density is independent of the system size only when the width W and the length L are larger than some critical values respectively, and the larger asymmetrical conditions can better avoid the occurrence of deadlock phenomena. For the mixed pedestrian flow, it can be found that the jamming cluster is mainly caused by those walkers breaking the traffic rules, and the underlying mechanism is analysed. Furthermore, the comparison of simulation results and the experimental data is performed, it is shown that this modified model is reasonable and more realistic to simulate and analyse pedestrian counter flow.

Flow Rate Measurement of Gravity Infusion Set and Functional Evaluation of Drop Counter: A Pilot Study

Developing a novel drop counter by introducing the Internet of Things concept has been vigorously conducted in recent years. Understanding the newly introduced drop counter’s flow rate control accuracy and flow rate count feature is essential for improving safety in infusion management. This study aimed to verify if the new drop counters could secure accurate flow rate and drip count by conducting actual flow rate measurements using gravimetry and functional evaluation. A drop counter was attached to each drip chamber of the infusion set, and an IV drip was conducted at the 100 ml/h flow rate. The weight of discharged physiological saline was measured to plot trumpet curves. Next, three different types of drop counters were evaluated to determine if they maintained drip count accuracy according to the changes in their position angles. The flow rate errors in all conditions indicated trumpet-like curves, exhibiting an overall error range within ±10% in all observation windows. Although every drop counter successfully detected and measured dripping, it was challenging in some counters to detect dripping when the drip chamber was tilted. In comparing adult and pediatric IV sets, the adult IV set was found to be less likely to detect dripping in the angled position. No significant differences in results were confirmed between high and low flow rates, suggesting that the drop count function would not be affected by the flow rate in the ranges of typical infusion practices. Doppler sensors have a wide range of measurements and high sensitivity;the dripping was detected successfully even when the drip chamber was tilted, probably due to the advantages of these sensors. In contrast, miscounts occurred in those equipped with infrared sensors, which could not detect light intensity changes in tilted positions. Understanding the tendencies in flow rate errors in infusion can be valuable information for infusion management.

Reaction zone characterization of counter-flow diffusion flame with diluted and preheated reactants

Reaction zone characteristics were studied using hydroxy radical planar laser-induced fluorescence （OH-PLIF） technique for a counter-flow preheated （CH4＋N2）/（Air＋N2） diluted diffusion flames. The effects of preheat temperature and dilute ratio on the reaction zone characteristics were investigated by demonstrating the OH intensity distribution and reaction zone thickness from OH-PLIF images. Under the experimental conditions of constant cold flow velocity, the results show that the OH intensity and reaction zone thickness decrease with the increase of dilute ratio at constant preheat temperature and increase with preheat temperature at fixed dilute ratio. The OH maximum intensity shifts towards the ＂lean＂ side of counter flow at constant preheat temperature, and it shifts towards the fuel side with the increase of dilute ratio of fuel stream and towards the oxidizer side with the increase of dilute ratio of oxidizer stream respectively. The feasibility of OH as a reaction zone marker in this diluted combustion is verified further. The variation of diffusion and chemical reaction rate of reactants due to preheat and dilution contributes to the reaction zone characteristics simultaneously. The effect of strain on the flame reaction zone should be included in the future work.

Comparison of Co-Current and Counter-Current Flow Fields on Extraction Performance in Micro-Channels

Several applications such as liquid-liquid extraction in micro-fluidic devices are concerned with the flow of two immiscible liquid phases. The commonly observed flow regimes in these systems are slug-flow and stratified flow. The latter regime in micro-channels has the inherent advantage that separation of the two liquids at the exit is efficient. Recently extraction in a stratified counter-current flow has been studied experimentally and it has been shown to be more efficient than co-current flow. An analytical as well as a numerical method to determine the steady-state solution of the corresponding convection-diffusion equation for the two flow-fields is presented. It is shown that the counter-current process is superior to the co-current process for the same set of parameters and operating conditions. A simplified model is proposed to analyse the process when diffusion in the transverse direction is not rate limiting. Different approaches to determining mass transfer coefficient are compared. The concept of log mean temperature difference used in design of heat exchangers is extended to describe mass transfer in the system.

轴流式对旋除尘风机的结构优化与性能研究

为了提高轴流式对旋除尘风机的除尘性能,研究各个参数相互之间的干扰,对其一级叶轮叶片数量、二级叶轮叶片数量、一二级叶轮距离、风筒直径和叶轮至进口距离这5个主要的结构参数进行优化改进和参数匹配。采取正交试验法,通过FLUENT对各结构参数下的风机除尘过程进行模拟仿真试验,分析风机除尘作业时内部流场和进出口速度、压力分布情况,给出综合评价风机除尘性能公式,得到轴流式对旋除尘风机各个参数的影响程度由大到小分别为一级叶轮叶片数量、风筒直径、二级叶轮叶片数量、一二级叶轮距离、叶轮至进口距离,并通过计算分析得到风机结构的最佳参数组合。

流气式低本底α/β测量仪的串道特征及干扰修正

研究了一系列α、β金属平面源、粉末源及薄层样法自制面源在流气式低本底α/β测量仪上的串道现象。结果显示:^(90)Sr-^(90)Y金属面源以及 ^(14)C,^(137)Cs,^(90)Sr-^(90)Y, ^(40)K粉末源β对α通道的串道比均在0.1%以下,基本可以忽略不计;α金属平面源串道比大小规律表现为 ^(210)Po<^(209)Po<^(239)Pu<^(239)Pu-^(241)Am混合源<241Am,范围为3.49%~25.4%,发射不同能量粒子的α金属源的串道比差异较大。由于衰变过程产生的内转换电子、俄歇电子以及X射线等在β道产生响应,241Am源的串道比明显高于其他源,241Am粉末源的串道比随单位面积质量厚度增加而增大。α粒子对β通道的串道现象较明显,并与样品制源方式有关,主要是不同制源方式造成的自吸收差异导致的,总体有α粉末源串道比>薄层样法自制α面源>α金属平面源,测量时应重点考虑α粒子对β放射性的串道干扰。通过210Po加标样及牡蛎样品经放化分析制成的电镀源验证,对待测样品源进行一定厚度的铝箔或纸片覆盖,可以有效的减小α粒子对β通道的串道干扰;也可以直接利用串道比对测量计数进行修正,此时需要考虑待测样品源和串道比刻度源的一致性,否则会导致修正结果的偏差较大。

基于HPC的网络安全应用研究综述

随着网络安全技术的发展,基于硬件的网络安全解决方案受到广泛关注和研究。近年来,使用硬件性能计数器(Hardware Performance Counter,HPC)检测恶意软件的研究不断出现,并发展到控制流完整性检测和侧信道攻击检测等领域。对基于HPC的网络安全技术进行了研究总结。首先概述了现有基于HPC的网络空间安全应用相关技术方案;其次对基于HPC的网络安全应用技术方法进行了分类,总结了其特点和适用场景;最后讨论了HPC安全研究的发展趋势和仍需解决的挑战。

环形异向流浅层流场油滴流动及分离特性研究

目前关于环形多层异向流浅层流道内液滴流动和油水分离特性的研究尚不够深入。为此,借助流体动力学方法,对环形异向流浅层流道内分散油滴运移分离特性和多层浅层流道速度分布特性进行分析。研究结果表明:环形异向流浅层流道内油滴浮升至斜板表面所需板长为96 mm,小于理论计算所需板长122 mm;浅层通道内层间速度分布对分离效率影响较大,下层流道入口速度峰值为0.00805 m/s,环形多层浅层通道内油相浮升过程中会遇到交叉流,显著影响浅层通道分离效率;滑移距离是影响浅层通道间分离效率的重要因素,当板长为350 mm、油滴粒径为50μm时,滑移距离占板长38.35%。所得结论可为基于浅层沉降强化分离理论的紧凑型采出水处理设备结构创新优化设计提供理论支撑。

一种基于双重Counter Bloom Filter的长流识别算法

提出了一种基于双层Counter Bloom Filter的长流识别算法(algorithm based on double counter bloom filter for long flows identification,简称CCBF).该算法使用两层Counter Bloom Filter结构,将长流过滤和长流存在分开处理.分析了该算法的误判率,通过模拟数据分析了算法错误率和内存资源限制的关系,并在相同内存资源限制的条件下,将该算法与类似算法的准确性进行了比较.结果表明,在数据量较大的情况下,该算法具有比现有算法更小的平均错误率;对算法的时间效率分析表明,该算法可以达到1500kpps的处理速度.各项指标反映出,该算法可以应用于大规模主干网的长流监测.

李岚教授治疗小儿肺炎支原体肺炎经验

[目的]总结李岚教授辨证论治小儿肺炎支原体肺炎的临证经验。[方法]通过搜集整理住院病历、跟师侍诊病案,查阅相关古籍及文献资料,阐述李师对该病病因病机的认识,分析其诊疗思路,并附验案二则以资验证。[结果]李师认为,小儿肺炎支原体肺炎病因多责之于外感之风邪及小儿肺脾本虚,临床分期可分为初期、极期、恢复期三期。在治疗中,总体以宣肺开闭为基本治则,同时采用清热涤痰、活血化瘀、回阳救逆、扶正祛邪等治法,临床辨证施治,屡获佳效。验案一辨证为极期(心阳虚衰证),治法为回阳救逆,以参附龙牡救逆汤为主方,同时选用黄芪、茯苓补气健脾、扶正祛邪。验案二辨证为极期(痰热闭肺证),治法为清热涤痰、宣肺开闭,以麻杏石甘汤合千金苇茎汤为主方,考虑兼有瘀血阻滞,选用桃仁、丹参活血化瘀;在恢复期时,选用白术、太子参培土生金、健脾益气。[结论]李师辨证论治小儿肺炎支原体肺炎,灵活运用中医药治疗,解决小儿肺炎支原体肺炎极期高热难退、恢复期咳嗽咳痰迁延不愈等问题,疗效显著,其经验值得临床学习及推广。

超低本底流气式正比计数器在样品总α/β测量中串道影响修正

超低本底流气式正比计数器是样品总α/β测量的理想探测器,但本身具有较强的串道现象,影响样品测量的准确性。系统研究了流气式正比计数器在同一质量厚度、不同241 Am和40 K质量分数下α→β、β→α串道影响,建立了总α/β串道修正的二元方程,并与遮盖修正法进行对比,对自制的25组α/β模拟粉末样品进行了测量和串道修正。结果显示α→β串道影响较大,修正因子随着α计数率的变化并非恒定值;β→α串道修正因子影响较小,其平均值为0.001;遮盖修正法对模拟粉末样品中β测量结果的修正效果较差,其相对偏差绝对值介于1.4%~45.0%;二元方程修正法对模拟粉末样品中β测量结果的修正效果较好,其相对偏差绝对值介于0~5.5%。

双支点对转轴承腔两相流动及换热特性的数值研究

为探究双支点对转轴承腔两相流动及换热特性,利用耦合的CLSVOF两相流方法开展数值研究,对比高低压轴同转、对转形式下的轴承腔流动及换热特征,重点探讨对转条件下,高低压轴转速及双侧供油流量对轴承腔壁面油气分布特征与换热特性的影响。结果表明:不同转向下轴承腔壁面油膜形成过程类似,滑油在壁面以油滴、油矢、油带形式分布;同转形式下壁面流线旋向相同,对转形式下壁面流线旋向则相反,对转提高了轴承腔壁面剪切力及湍流强度,平均换热系数相对提升了16.47%;对转转速越大或转速比越高时,壁面滑油体积分数增大而油膜厚度降低,油膜流速平均增加72.95%,双侧供油量或供油流量比越大时,壁面滑油体积分数与油膜厚度均上升,油膜流速平均增加31.02%;增加转速与供油流量均可提高壁面热流密度,增大换热系数,采用双支点对转形式布局能够一定程度提高轴承腔换热性能,有利于保障发动机的安全可靠运转。

运行方式对闭式冷却塔换热性能影响研究

运用Matlab GUI功能开发闭式冷却塔校核软件,利用该闭式冷却塔校核软件计算在不同空气流向、不同热流体流向、有无填料的条件下闭式冷却塔的总换热量及热流体温下降情况,并对其进行对比分析,研究得出不同淋水温度、不同空气干球温度下换热性能最优的闭式冷却塔运行方式。

煤矿对旋轴流通风机的振动响应特性分析

为进一步探究煤矿对旋轴流通风机设备可能的优化路径,从振动响应分析的角度着手,对煤矿轴流通风机流场进行仿真分析,通过分析压力-时间变化情况,探究不同轴向间隙和径向间隙对煤矿对旋轴流通风机的振动响应特征。并根据分析结果,确定了较为合理的轴向间隙与径向间隙取值范围,以期为后续的对旋轴流通风机优化设计提供更多参考借鉴。

径向间隙对煤矿对旋轴流通风机性能的影响分析

为进一步探究煤矿对旋轴流通风机径向间隙对风机性能的影响,以某小型煤矿企业的局部对旋轴流通风机为研究对象,对其进行建模与仿真分析,确定了稳态与非稳态两种情况下,不同径向间隙对风机性能的整体影响作用.结果显示,当降低径向间隙时,有助于增加风机压头和对气流做功,但与此同时,较小的径向间隙也将导致风机的气动噪声问题更为突出,对风机流量也将产生一定的不利影响,由此确定将径向间隙控制在叶片直径的0.8%~1%范围较为合理,以此为后续的煤矿对旋轴流通风机径向间隙优化设计工作提供参考借鉴.

对旋轴流通风机轴向间距对性能影响分析

以FBDCZ-8-NO27型对旋轴流通风机为例,模拟分析了轴向间距对旋轴流通风机性能的影响。首先,将通风机规格尺寸、材料特性等参数录入到CFD软件内,由该软件自动构建出通风机及流体的有限元模型,并根据研究需求划分网格,然后以此为基础,分别从稳态与非稳态两个方面出发,模拟分析了三种轴向间距条件下通风机性能的变化情况,以设计出最佳的通风机轴向间距,提升通风机性能,使其在煤矿生产作业中发挥出更大的作用。

气体流量对磁控溅射氮化镍薄膜对电极性能的影响

目的:开发性能卓越、成本经济的对电极,优化氮化镍薄膜制备工艺。方法:使用直流磁控反应溅射技术探究气体(氮气、氩气)流量对薄膜对电极的性能及组装成染料敏化太阳能电池的光电转化效率的影响。利用X射线衍射仪分析薄膜物相组成、紫外-可见分光光度计对薄膜透光度进行分析、太阳光模拟器和数字源表测定电池的光电转换效率。结果:氮化镍薄膜为四方相Ni2N物质,在通入固定Ar流量(16 mL·min^(-1))的条件下,电池光电转换效率随N2通入量的增加而增加;在通入固定N2流量(10 mL·min^(-1))的条件下,电池光电转换效率随Ar通入量的增加而减小,未通入Ar时为最优(η=2.87%),这与Ar流量为16 mL·min^(-1)、N2流量为10 mL·min^(-1)条件下的电池光电转换效率非常接近,但制备成本更低。此时薄膜透光率接近40%,满足将其作为半透明光伏窗以实现绿色低碳建筑的要求。结论:半透明光伏窗不仅具备窗户的采光功能,还能通过光伏组件发电以降低能耗,为染料敏化太阳能电池和光伏建筑一体化技术相结合提供了可能性,具备较大的节能潜力。

Weather induced subtidal flows through multiple inlets of an arctic microtidal lagoon

Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In this paper, wind-driven exchange flows in the micro-tidal Elson Lagoon of northern Alaska with multiple inlets of contrasting widths and depths are studied with in situ observations, statistical analysis, numerical experiments, a regression model on the basis of dynamics, and remote sensing data. Water velocity profiles were obtained from a bottom deployed acoustic Doppler current profiler(ADCP) in the northwestern Eluitkak Pass connecting the Beaufort Sea to the Elson Lagoon during a 4.9 day ice-free period in the summer of 2013. The subtidal flow is found correlated with wind(R^2 value ～96%). Frequently occurring east, northeast and north winds from the arctic atmospheric high-and low-pressure systems push water from the Beaufort Sea into the lagoon through the wide inlets on the eastern side of the lagoon, resulting in an outward flow against the wind at the narrow northwestern inlet. The counter-wind flow is a result of an uneven wind forcing acting through the asymmetric inlets and depth,an effect of "torque" or vorticity. Under northwest wind, the exchange flow at the northwestern inlet reverses its direction, with inward flows through the upwind northwestern inlet and outward flows through the downwind eastern inlets. A regression model is established based on the momentum equations and Taylor series expansions. The model is used to predict flows in July and August of 2015 and July of 2017, supported by available Landsat satellite images. About 73%–80% of the time the flows at Eluitkak Pass are out of Elson Lagoon for the summer of 2015 and 2017. Numerical experiments are conducted to corroborate the findings and illustrate the effects under various wind conditions. A quasi-steady state balance between wind force and surface pressure gradient is confirmed.

一种基于孔板压差原理的流量控制系统

为了解决海拔与温湿度因素影响气体流量采集精度的问题,在研究了孔板压差流量控制原理、温湿度和大气压对气体采集流量精度影响的基础上,提出了一种基于孔板压差流量法的流量控制系统。首先,设计了流量孔板结构,开发了数据信号采集与信号放大电路,对传统温湿度流量补偿公式进行了改进,提高了不同环境条件下的孔板流量测量精度;然后,基于脉宽调制(PWM)的气泵控制算法,设计了比例-积分-微分(PID)参数动态调节算法和压差零点自校准方法;设计了人机交互界面,完成了采样流量、孔板大小和压差传感器量程参数的灵活设置;最后,为了验证流量控制系统的精度,研制了流量控制系统样机,并开展了系统实验。实验及研究结果表明:所开发的流量控制系统示值误差在1.12%以内,符合尘埃粒子计数器流量校准规范的要求,克服了由于环境因素导致气体采集流量误差大的问题,在尘埃粒子计数器领域具有较好的应用价值。