Pressure ranges of velocity splitting of ablated particles produced by pulsed laser deposition in different inert gases

The transport of ablated particles produced by single pulsed-laser ablation is simulated via Monte Carlo method. The pressure ranges of velocity splitting of ablated particles in different inert gases are investigated. The result shows that the range of velocity splitting decreases with the atomic mass of the ambient gas increasing. The ambient gas whose atomic mass is more than that of Kr cannot induce the velocity splitting of ablated particles. The results are explained by the underdamping model and the inertia flow model.

Proper Particle Size Range for Resistance to Chemical Oxidation: A Perspective on the Recalcitrance of Beanpod Biochar for Soil Carbon Sequestration

The effect of particle size on the recalcitrance of biochar against oxidation has been regarded as one of the most important factors influencing its stability and transportation in soils. Little is known about the peculiar stability of different particle sizes under chemical oxidation conditions. In this study, several sizes of biochar particles derived from beanpod were produced,and their stabilities were tested by using acid dichromate and hydrogen peroxide. We discovered that the 60-100 mesh size of particles produced at 400 and 500 ℃ showed the least carbon loss under the oxidation of both dichromate and hydrogen peroxide. In addition, this particle size also shows great stability at 600 and 700 ℃, but this stability was not observed below 300 °C for all temperature-dependent biochars. Medium-sized particles composed of exclusively heterogeneous components produced a biochar at temperatures over 400 ℃ with comparatively stronger chemical anti-oxidation characteristics. The chemical recalcitrance of biochar should be reevaluated based on particle size before soil application.

基于图像分析的掘进工作面粉尘颗粒检测方法

基于光散射原理测定粉尘质量浓度只能定时定点手动检测,实时性差,且只能检测出粉尘质量浓度,并不能给出粒径分布范围。目前基于图像分析的粉尘颗粒检测研究主要是针对粉尘质量浓度或粒径分布进行单方面研究,并不能实现粉尘质量浓度和粒径分布范围的同时检测。针对上述问题,提出了一种基于图像分析的掘进工作面粉尘颗粒检测方法,探究图像特征与粉尘质量浓度、粒径分布间的关系。通过粉尘样本收集及图像采集装置,采集粉尘颗粒图像并获取采集图像时的粉尘质量浓度。编写粉尘样本图像处理算法,提取图像的灰度特征、纹理特征、几何特征相关参数。对提取的图像特征与实测粉尘质量浓度进行相关性分析,选取相关性较大的图像特征作为参数建立回归数学模型。提取粉尘颗粒对象像素点个数,结合转换系数,基于几何当量等效面积径计算粉尘粒径大小及分布范围。实验结果表明:实测粉尘质量浓度与建立的图像特征多元非线性回归模型数学模型计算值间的平均相对误差为12.37%,标准实测粒径与几何当量等效面积径得到的粒径分布间的最大相对误差为8.63%,平均相对误差为6.37%,验证了基于图像特征的粉尘质量浓度回归数学模型和基于几何当量等效面积径分布数学模型的准确性。

纳米气泡浮选过程强化研究进展

浮选是低品质矿及煤分选提质的有效手段,其中微细粒浮选难题突出,而纳米气泡则是解决该难题的重要途径,但关于纳米气泡浮选过程强化的诸多基础科学问题仍未解决。为促进微细粒纳米气泡浮选过程强化技术的开发,重点围绕浮选过程中纳米气泡的界面选择性成核动力学、界面纳米气泡超常稳定性机理及纳米气泡强化颗粒-气泡捕获效率微观作用机制等三个关键科学问题,介绍了笔者团队在纳米气泡浮选过程强化方向的最新研究进展。研究结果表明:纳米气泡的选择性成核是纳米气泡浮选过程强化的关键,而纳米气泡的稳定性则是纳米气泡浮选过程强化的前提;纳米气泡浮选过程强化的机制主要包括促进颗粒絮团与缩短诱导时间,其内在作用机制来自纳米气泡长程疏水引力与边界滑移的协同作用。笔者团队的研究阐明了纳米气泡固-液界面选择性成核的能量作用机制,提出了基于界面高密度气层自动补偿的界面纳米气泡稳定性机理,建立了微纳力学-边界滑移协同驱动的纳米气泡强化浮选界面作用机制,进一步丰富发展了现代浮选基础理论,为开发微细粒纳米气泡浮选过程强化技术提供了一定的指导。

再生粗骨料取代率及粒径对混凝土抗压性能影响试验研究

为研究单轴受压情况下再生粗骨料粒径范围、取代率对再生混凝土抗压性能的影响规律,分别以粒径范围5~10、10~20和20~31.5 mm,以及取代率分别为0%、10%、30%和50%为参量设计制作再生混凝土棱柱体试件,并对其开展单轴抗压性能试验研究。结果表明:在取代率相同时,粒径范围为5~10 mm时再生混凝土的抗压强度及峰值应变均比粒径范围为10~20、20~31.5 mm时的大;在粒径范围相同情况下,随取代率增大,再生混凝土抗压强度呈现出逐渐减小的变化趋势,而峰值应变则呈现出逐渐增大的变化趋势。根据试验数据,得出了再生混凝土抗压强度和峰值应变的函数关系式。

基于环路补偿的增程式发电机组稳压控制策略研究

在增程式发电机组永磁同步发电机的稳压控制实验过程中,传统电压电流双闭环控制方式虽然能够得到稳定的直流母线电压,但在突加负载实验时存在电压波动较大、恢复时间较长的问题。对电压环路进行改进设计,在原有双闭环基础上加入转矩内环补偿,经过仿真实验与传递函数伯德图分析,验证了该方法能够有效抑制电压波动并提升响应速度。为提升控制效果,考虑将PI控制与免疫粒子群算法相结合,实现发电机控制器PI参数自整定,满足发电机组不同电机的变参数需求。算法运行结果表明,相较于传统试凑方法,稳压精度得到进一步提升。

灌区田间渠系水工建筑物循环冻胀机理试验探究

高分子聚合物颗粒轻质土中,原料黏土取自三江平原青龙山灌区田间配套支渠堤坝。由低液限黏土、粉煤灰、减水外加剂、硅酸盐水泥、水、高分子聚合物颗粒按选定比例混合,经搅拌机械翻拌成混合料。这种混合料具有密度比小,热效率传导慢,热效阻隔强和保温效果优等特点。为了深入探究预防冻胀破坏成因成效,拓展预制混凝土矩型槽在渠道应用条件,利用模拟冻融循环试验,对颗粒轻质土的保温效能及预防冻胀破坏进行实测和论证,为颗粒混合轻质土在三江平原季节冰冻地区的典型推广确定理论依据和使用方法,使灌区田间配套渠系水工建筑物在季节冻胀区的冻胀损坏降至最低。

基于标准粒子群的起重机摄影测量方法

大型起重机械的安全性评估与关键尺寸或关键点是高度关联的,文中针对如何高效稳定地获取其三维坐标这一问题,提出一种基于标准粒子群的起重机摄影测量方法。传统相机像主距标定方法主要采用定制的标定板或采用穷举法在一定范围内搜索,但两者的计算精度和计算效率已无法满足目前工程应用中的需求。现提出一种面向起重机的双目相机像主距的标定方法,该方法利用双目测距的数学原理结合粒子群优化算法,将粒子群优化算法(PSO)引入到相机标定中,通过迭代找到最优解,粒子通过自己的经验和同伴中最好的经验来决定下一步的行动。将标准粒子群搜索算法融合到摄影测量方法中,获得精准的有效焦距后,完成起重机关键尺寸的测量。以门式起重机为实验对象进行实验,实验结果表明,相比传统的穷举法,所提方法在速度上具有明显优势,且测量精度能够满足工程需要。

Operating range of magnetic stabilization flow regime for magnetized fluidized bed with Geldart-B magnetizable and nonmagnetizable particles

The magnetic stabilization flow regime could also be created forGeldart-Bnonmagnetizable particles pro-vided some magnetizable particles are introduced and the magnetic field is applied.This study aimed toexplore the size(d_(pM))and density(ρ_(pM))effects of magnetizable particles on its operating range.The upperlimit(Umb;)could not be determined from the △P_(b)-U_(g)↓curve but could from analyzing the variation of △P_(b)-fluctuation with increasing U_(g).Due to the variation of U_(mfH)(lower limit)with d_(pM) and ppw,both U_(mbH)-U_(mfH) and(U_(mbH)-U_(mfH))/U_(mfH) were used to quantify the operating range of magnetic stabilization.U_(mbH)-U_(mfH) varied hardly with ρ_(pM) but increased significantly with decreasing ρ_(pM).(U_(mbH)-U_(mfH))/U_(mfH)increased as d_(pM) or ρ_(pM) decreased.lt was more difficult for the nonmagnetizable particles to escape fromthe network formed by the smaller/lighter magnetizable particles.For the same magnitude of change,dp had a stronger effect than ρ_(pM) on(U_(mbH)-U_(mfH))/U_(mfH).Neither U_(mbH)-U_(mfH) nor(U_(mbH)-U_(mfH):)/Uma variedmonotonously with the minimum fluidization velocity of the magnetizable particles,indicating that nostraightforward criterion for matching the magnetizable particles to the given nonmagnetizable particlescould be established based on their minimum fluidization velocities to maximize the operating range ofmagnetic stabilization.

Measurement on soil deformation caused by expanded-base pile in transparent soil using particle image velocimetry (PIV)

A new small-scale geotechnical physical model in 1-g and unconfined condition, combining the transparent soil, close-range photogrammetry and particle image velocimetry(PIV), was employed, which provides a non-intrusively internal deformation measurement approach to monitor the internal deformation of soil caused by expanded-base pile jacking with casing. The transparent soil was made of fused quartz and its refractive index matched blended oil, adding reflective particles(glass beads). Closerange photogrammetry was employed to record the images of the process of casing jacking and extraction in transparent soil, allowing the use of Matlab-based Geo-PIV to figure out the displacement field converted from image space to object space. Analysis of test results indicates that the maximum displacement caused by casing jacking for expandedconical-base pile is decreased by 29% compared with that for expanded-flat-base pile. The main movement happens at the early stage of casing extraction. The maximum displacement caused by casing extraction for the conical base is about 43% of that for the flatbase, while the affected zone caused by casing extraction for the conical base accounts for about 1/3 of that for the flat base. The contraction for horizontal displacements tends to decrease with the depth increasing. By contrast, the contraction under pile base decreases with the increasing of displacement. The displacements generated by jacking a conventional pile having a diameter equal to the casing diameter of the expanded-base pile were comparable to the net displacement taking place due to expanded-base pile installation for the conical base pile.

A New Method to Determine the Maximum Value of the Track Length of Alpha Particle in CR-39 Detector

The aim of this paper is to determine the maximum values of the track length (Lmax) of alpha particles in Nuclear Track Detector (type CR-39) using a new method by taking the relation between the etching time and the diameter square of alpha particle with different energies at constant bulk etch rate VB (1.45 μm/hr) by using TRACK_TEST program from Brun et al. function and Yu et al. function. Using the new equation, the maximum values of the track lengths of alpha particles measured in CR-39 detector have been found to be in a good agreement with the values measured by using Brun et al. function and Yu et al. function in TRACK_TEST program.

基于激光跟踪小空间搜索的运动轨迹生成方法

以实时跟踪监控多个运动目标为出发点,提出基于激光跟踪小空间搜索的运动轨迹生成方法。激光跟踪测距仪以采集到的激光点和运动目标像素坐标为依据,构建激光自主瞄准模式瞄准运动目标,引导激光靠近运动目标并缩短二者间距离,利用激光跟踪测距仪的小空间搜索性能确定运动目标质心,实现运动目标精准定位检测;采用均值漂移粒子滤波跟踪算法,以检测所得的运动目标位置作为初始粒子跟踪运动目标,获取运动目标跟踪效果图;结合轨迹生成模块,生成运动目标轨迹。实际应用结果表明,检测及跟踪多个运动目标时,准确性高,且生成运动目标轨迹完整且与实际运动轨迹一致,生成结果准确无遗漏可达100%,检测目标车辆的时间均在2.5 s以下,分别低于文献方法2.5 s和1.9 s,降低了检测时间,并且具备性能稳定、实用性强优势。

土坝坝基土的渗透淤堵试验研究

该文选取太行山研究区内某水库坝基处土样,通过室内筛分,分析其颗粒级配组成,再进行人工配比,模拟其天然土体状态,进行室内渗透性及淤堵效应研究。为不同水头条件下配比最佳粒径的淤堵材料提供参考。

基于超宽带非对称双边双程测距的矿山井下定位跟踪算法研究

在地下矿山建立稳定、有效、高精度的人员定位系统和算法,对矿井事故灾害的灾时指导逃生和灾后救援等方面起着至关重要的作用。基于超宽带定位测距系统,进行了室内非对称双边双程测距试验,利用粒子群算法、Taylor级数迭代等智能算法完成对目标的定位,以期获得更精确的定位解析,相较于传统的Wi-Fi通信系统及射频识别人员定位管理方法,能够在保证实时性的同时,有效、准确地提供遇险人员的位置及周边地形状况,达到了厘米级定位精度,实现了井下精确定位,为井下救援工作提供技术支持。

高超声速滑翔飞行器运动性能分析

防御方对来袭高超声速滑翔飞行器存在运动建模颗粒度过粗和难以过细等问题。在给出弹道几何模型的基础上,运用升阻比表示的滑翔段至末段运动模型定量评估分析了高超声速滑翔飞行器远程打击、末段毁伤、低空突防、快速打击、侧向绕飞突防等能力,采用4种典型高超声速滑翔飞行器对性能分析结论进行了校验。分析结果表明:高超声速滑翔飞行器大气层内高速飞行的同时会极大地延长其飞行时间,可观的横向机动距离需要牺牲较远的纵向射程。

考虑动态功率区间和制氢效率的电转氢(P2H)设备容量配置优化

考虑大规模风电固有的间歇性、波动性影响,采用电转氢技术将弃风电量转化为可存储再利用的清洁氢能,助力碳达峰与碳中和战略目标。该文选用碱性电解槽作为电转氢设备,研究其制氢效率曲线,构建运行区间规划与经济性规划相结合的优化配置模型。首先分析电解槽平滑跟踪动态功率的区间范围,对设备充当电负荷的运行能力进行限制。然后在此基础上,以设备全生命周期成本与电氢市场交易成本整体最小为目标,对设备容量进行经济性优化。最后采用混沌粒子群优化算法求解模型。算例结果表明,在保障设备产氢质量同时,可有效提升系统运行可靠性并降低投资成本和弃风率。研究成果实现电转氢设备作为灵活负载跟踪可再生能源的功率波动。

中非某铜钴精矿工艺矿物学特性及影响分析

采用化学分析、扫描电镜和矿物自动分析系统(AMICS)等综合手段对中非某铜钴精矿中铜钴载体矿物种类、相对含量、工艺粒度和嵌布特征进行了详细的工艺矿物学研究。结果表明,矿石中主要的有价元素铜、钴品位分别为13.64%和13.20%,其中铜主要赋存在黄铜矿、硫铁铜矿等独立硫化铜矿物中;钴以类质同象替代或独立矿物的形式赋存在黄铁矿和硫铜钴矿中。铜钴硫精矿中50%以上的矿物粒径集中在13.5~45.0μm,多呈不规则粒状分布。铜钴载体矿物连生关系复杂,存在黄铜矿-含钴黄铁矿,黄铜矿-硫铜钴矿、硫铁铜矿-黄铜矿等两相或多相类型的连生体。铜钴精矿中含铜矿物种类多,硫铜钴矿含杂较高,铜钴硫化物连生关系复杂是影响铜钴精矿后续冶炼工艺的主要因素。研究结果为同类型铜钴资源的开发利用提供了借鉴和参考。

侧限条件下钙质砂颗粒破碎与蠕变特征

通过侧限条件下的蠕变试验,基于近景摄影测量技术对试验过程的动态捕捉,探讨了钙质砂的颗粒破碎与蠕变特征。侧限条件下,钙质砂的蠕变随时间的增加而增加,蠕变变形与时间关系符合Burgers模型,蠕变变形可分为减速蠕变阶段和稳态蠕变阶段,即,蠕变速率随时间增加先减小,后稳定。钙质砂的蠕变特性受应力条件和粒径影响。轴向应力越大,蠕变速率和蠕变量越大;低应力下,蠕变量随粒径增大而减小;高应力下,受颗粒破碎的影响,钙质砂的蠕变以及蠕变速率均随粒径增大而增大。与硅质砂相比,钙质砂的蠕变在较低应力(≤0.1 MPa)时,由于钙质砂具有多棱角特性,颗粒间嵌固力较大,限制颗粒间位移产生,蠕变较小;随着应力增大,钙质砂开始产生颗粒破碎,增加了钙质砂试样变形,蠕变逐渐显著并超过硅质砂的蠕变。钙质砂的颗粒破碎特性随粒径和应力增大而增大,其中粒径>5 mm的试样在竖向应力0.7 MPa附近开始破碎;蠕变过程中的试样变形由完整颗粒和破碎后的颗粒沿裂隙和内外孔隙移动提供。

Multiple model particle flter track-before-detect for range ambiguous radar

The middle pulse repetition frequency（MPRF）and high pulse repetition frequency（HPRF）modes are widely adopted in airborne pulse Doppler（PD）radar systems,which results in the problem that the range measurement of targets is ambiguous.The existing data processing based range ambiguity resolving methods work well on the condition that the signal-to-noise ratio（SNR）is high enough.In this paper,a multiple model particle flter（MMPF）based track-beforedetect（TBD）method is proposed to address the problem of target detection and tracking with range ambiguous radar in low-SNR environment.By introducing a discrete variable that denotes whether a target is present or not and the discrete pulse interval number（PIN）as components of the target state vector,and modeling the incremental variable of the PIN as a three-state Markov chain,the proposed algorithm converts the problem of range ambiguity resolving into a hybrid state fltering problem.At last,the hybrid fltering problem is implemented by a MMPF-based TBD method in the Bayesian framework.Simulation results demonstrate that the proposed Bayesian approach can estimate target state as well as the PIN simultaneously,and succeeds in detecting and tracking weak targets with the range ambiguous radar.Simulation results also show that the performance of the proposed method is superior to that of the multiple hypothesis（MH）method in low-SNR environment.

基于动态CRE偏置选择的干扰抑制策略

随着无线通信用户数量的指数性增长,宏小区用户数量超负荷,边缘用户受邻近微小区的干扰逐步加剧,导致整个小区的通信服务质量降低。为解决这些问题,针对双层无线异构网络场景,结合粒子群优化算法和小区范围扩展技术动态地调整微小区服务区域,寻找出小区范围扩展最优偏置值,缓解宏小区高热点区域负载压力并提高系统用户平均传输速率。仿真结果表明,相比静态小区范围扩展偏置值算法,利用动态小区范围扩展偏置选择的宏小区用户数量下降了近10%,即卸载了部分宏用户使其接入微小区,达到为宏小区减负的效果;微小区边缘用户的信干噪比相应提高了约2 dB,系统用户平均传输速率提高,整个小区的通信服务质量有较大提升。