FEM-DEM coupled modeling of cone penetration tests in lunar soil

Cone penetration test(CPT)is an appropriate technique for quickly determining the geotechnical properties of lunar soil,which is valuable for in situ lunar exploration.Utilizing a typical coupling method recently developed by the authors,a finite element method(FEM)-discrete element method(DEM)coupled model of CPTs is obtained.A series of CPTs in lunar soil are simulated to qualitatively reveal the flow of particles and the development of resistance throughout the penetration process.In addition,the effects of major factors,such as penetration velocity,penetration depth,cone tip angle,and the low gravity on the Moon surface are investigated.

Cone model for two surface foundations on layered soil

In this paper, the cone model is applied to the vibration analysis of two foundations on a layered soil half space. In the analysis, the total stress field in the subsoil is divided into the free-field and the scattering field. Seed＇s simplified method is adopted for the free-field analysis, while the cone model is proposed for analyzing the dynamic scattering stress wave field. The shear stress field and the compressive stress field in the layered stratum with two scattering sources are calculated by shear cone and compressive cone, respectively. Furthermore, the stress fields in the subsoil with two foundations are divided into six zones, and the P wave and S wave are analyzed in each zone. Numerical results are provided to illustrate features of the added stress field for two surface foundations under vertical and horizontal sinusoidal force excitation. The proposed cone model may be useful in handling some of the complex problems associated with multi-scattering sources.

Model Test Study on Ice-Induced Vibrations of Compliant Multi-Cone Structures

For the study on the ice-induced vibration of a compliant mono-cone structure,a series of model tests were performed from 2004 to 2006.In these tests,the ice sheet before the compliant conical structure was found to be failed in two-time breaking.Based on this important finding,model tests study of the ice force on a compliant multi-cone structure were performed from 2006 to 2007.In these tests,the ice sheet broke before each single cone non-simultaneously.The exciting energy of the total ice force was found to be in a wide range of frequencies,and the structure can be easily excited with nonlinear resonance.

Electromagnetic Properties of S11 States in a Light Cone Quark Model

Using relativistic spin-flavor wave functions of a Lorentz-covariant light cone quark model, we calculate the electromagnetic form factors of two S11 resonances, N（1535） and N（1650）, and the helicity amplitudes A1/2 and S1/2 for electroexcitation of the S11 resonances from the nucleon. The electromagnetic form factors of these S11 resonances are found to be similar to those of the nucleon in shape, while the charge form factor of neutral N（1650） is nearly zero. The relative peak height of the S11 charge form factors is controlled by the mixing angle common to both resonance wave functions. As in most quark models, there is a systematic overestimate of A1/2 in both N（1535） and N（1650） cases at the photon point. A sizeable S1/2 for all cases is produced as suggested by experiments.

Technique for Estimating the Cone Bearing Smoothing Parameters

Cone penetration testing (CPT) is an extensively utilized and cost effective tool for geotechnical site characterization. CPT consists of pushing at a constant rate an electronic cone into penetrable soils and recording the resistance to the cone tip (qc value). The measured qc values (after correction for the pore water pressure) are utilized to estimate soil type and associated soil properties based predominantly on empirical correlations. The most common cone tips have associated areas of 10 cm2 and 15 cm2. Investigators also utilized significantly larger cone tips (33 cm2 and 40 cm2) so that gravelly soils can be penetrated. Small cone tips (2 cm2 and 5 cm2) are utilized for shallow soil investigations. The cone tip resistance measured at a particular depth is affected by the values above and below the depth of interest which results in a smoothing or blurring of the true bearing values. Extensive work has been carried out in mathematically modelling the smoothing function which results in the blurred cone bearing measurements. This paper outlines a technique which facilitates estimating the dominant parameters of the cone smoothing function from processing real cone bearing data sets. This cone calibration technique is referred to as the so-called CPSPE algorithm. The mathematical details of the CPSPE algorithm are outlined in this paper along with the results from a challenging test bed simulation.

京津冀平原浅层地下水漏斗演变规律与影响因素

为研究华北地区河湖生态补水对地下水漏斗演变的影响,以京津冀平原浅层地下水漏斗2003年至2022年的相对变化作为识别目标,从气象因素、地形因素、人为因素和含水层水力学特性4个方面进行考虑,选取8个具体指标构建特征变量数据集,使用逻辑回归(logistic regression, LR)、支持向量机(support vector machine, SVM)和随机森林(random forest, RF)方法建立漏斗演变识别模型,并利用敏感度、特异度和决定系数R^(2)对拟合效果进行对比评价,结果显示随机森林为最优模型。进而利用模型分析研究区地下水漏斗演变规律,阐明具体因素对漏斗演变的影响作用。研究表明:京津冀平原区浅层地下水漏斗在2010年之前整体呈扩张趋势,之后在部分地区呈现缩减和消失的态势。河湖补水前,地下水漏斗发展主要受开采影响,其重要度约50%;2018年后河湖补水对抑制漏斗扩张发挥了较为明显的作用,重要度达16%。从发展过程来看,地下水开采依然是控制京津冀平原浅层地下水漏斗变化最重要的因素。对比宁柏隆和高蠡清两个典型浅层地下水漏斗的发展变化可知,河道生态补水对宁柏隆漏斗变化的贡献率接近10%,而对高蠡清漏斗变化影响的重要度仅为1%,因此持续的河流生态补水对宁柏隆漏斗水位恢复会产生积极影响,而对于高蠡清漏斗则需要以水源置换压减农业灌溉地下水量为关键手段实现水位恢复。

基于CFD仿真的浮子流量传感器设计

针对小流量测量精度低等问题,文中提出了一种基于6DOF模型和浮子流量传感器工作原理的浮子流量传感器CFD仿真方法,基于该仿真方法,设计了一种流量范围为60~600 mL/h用于水流量检测的浮子流量传感器。结果显示:当传感器的关键结构参数锥管锥半角为0.1°、浮子直径为2.98 mm时,浮子流量传感器性能达到最优。通过实流实验验证了设计方案的可行性。

考虑交通流量和用户行为不确定性的加氢站选址优化模型

加氢站是氢能产业发展的重要基础设施,其布局选址对于氢能在交通领域的推广应用至关重要。为此,提出一种加氢站的选址优化方法。首先,分别以运营商追求捕获交通流量最大化、客户追求获得加氢服务可能性最大化为上、下层目标函数构建了双层规划模型,并引入机会约束规划理论处理了交通流量的不确定性。该模型考虑了客户路径选择的行为特性,能够为交通流量不确定性下的加氢站选址提供重要借鉴。其次,利用KKT条件和确定性等价将所提机会约束双层规划模型转化为了单层的混合整数二阶锥规划问题以实现高效求解。最后,为验证该模型的有效性,以长三角地区交通网络为案例进行了仿真分析。

基于线框模型的卷烟燃烧锥三维形态分析

【目的】生成卷烟燃烧锥的完整三维形态模型,提取燃烧锥的高度、表面积、体积和偏离角等参数,为建立卷烟燃烧性能评价体系提供支撑。【方法】将带有燃烧锥的卷烟放置在高精度旋转平台,通过智能手机采集燃烧锥的视频并转换为图像,通过图像分割及边缘提取获取燃烧锥的边缘坐标,采用线框模型建立燃烧锥的三维形态,计算燃烧锥的高度、表面积、体积和偏离角,分析偏离角的分布特点。【结果】利用该方法建立的卷烟燃烧锥三维模型曲面连续平滑,实现了燃烧锥的三维形态的精准测定,优于常规的测定方法。

CONE模型与地基动力液化的非线性有效应力分析

在分析建筑物地基的地震(或振动)液化时,为了简化分析土壤-地基的动力相互作用,引入Cone模型,在总应力分析的方法基础上,结合了Martin等提出的孔隙水压力发展模型,并且考虑土壤发生液化的动力非线性过程中材料刚度退化的影响,提出了可以直接求解各区域的孔隙水压力的有效应力简化分析法,并进行液化可能性判别。

基于无模型拟合法和模型拟合法的樟子松松果热解动力学研究

利用TA Q600同步热分析仪,在空气氛围下,2~3 mg粒径为250~420μm的樟子松松果颗粒以10、15、20、25 K/min的升温速率线性升温至1073 K左右,采用模型拟合法(Coats-Redfern法、Zsako法、Satava-Sestak法)和无模型拟合法(KAS法、Doyle法、FWO法)对松果热解动力学参数进行求解和比较,计算反应活化能E值、指前因子A。结果表明:松果热解主要包括4个阶段,主要质量损失阶段失重率占85%以上。无模型拟合法得到平均活化能分别为74.3 kJ/mol(Doyle法)、71.8 kJ/mol(FWO法)、68.3 kJ/mol(KAS法),且KAS法的活化能与指前因子曲线拟合R 2>0.95;模型拟合法得到平均活化能为65.4 kJ/mol(Zsako法)、62.4 kJ/mol(Satava-Sestak法)、56.4 kJ/mol(Coats-Redfern),且Zsako法、Satava-Sestak法的平均活化能更接近无模型较准确的活化能,其中Satava-Sestak法的指前因子可反映热解反应机理的复杂性。建议将KAS法与Satava-Sestak法结合,更好地评价樟子松松果的燃烧性。

基于Cone Beam CT图像的呼吸运动分析

呼吸运动是有一定规律性的运动,传统呼吸运动模型用公式描述,不能准确反映不同病人的特点或同一病人不同时期的特点,无法满足实时准确分析的需要。为此,我们提出了一种通过跟踪病人自由呼吸状态下所采集的Cone Beam CT图像序列中的横隔膜的运动来建立病人呼吸运动模型的方法。该方法建立的模型与传统的呼吸运动理论模型非常相似,证明了它是可行且有效的,同时该方法更能实时准确地反映病人的呼吸运动规律,具有很高的临床实用价值。

基于分布式新能源与配网网络重构的降损技术

考虑分布式新能源出力随机性对调控策略执行效果的影响,研究了基于电压风险评估和主动重构的日前调度技术。基于光伏出力预测和负荷预测,以电压安全概率风险最小为目标,以开合联络开关为控制变量,应用二阶锥松弛过的Distflow潮流模型进行求解,获取电压安全概率风险最小的配网重构方案。通过对IEEE 33节点配网进行算例分析,仿真结果验证了所提基于电压风险评估与主动重构的日前降损策略的可行性。

基于人工神经网络的多源数据融合技术在浅层纵波速度调查中的应用

微测井是地震勘探中常用的一种近地表纵波速度调查方法,在场地条件和施工成本受限的情况下,该方法得到的速度解释剖面常存在横向分辨率不足的问题。利用静力触探法布设方便、成本低廉的优势,提出一种利用人工神经网络模型关联地层阻力和地层波速的方法,以期通过少量实测微测井实现大范围纵波速度结构的有效预测。该方法的实施流程如下:(1)两两配对静力触探和微测井数据以生成控制点位,以岩性变化为网络分裂条件,输入层神经元接收锥尖阻力、侧摩阻力和深度数据,输出层神经元接收纵波速度,在中间设置多个全连接隐藏层;(2)通过前馈训练机制更新隐藏层神经元参数;(3)将非控制点位的静力触探数据输入到训练好的神经网络模型以获取全区近地表纵波速度结构剖面。在苏北某场地进行方法测试和数据分析,结果证实岩性分层的精细度和训练样本量是决定模型表现的两个关键因素。人工神经网络法预测浅层纵波速度的准确率超过90%,在可靠性、分辨率以及鲁棒性方面都超越了现有的经验公式法,可以辅助判断地下虚反射界面和低降速带分布范围,是提高地震勘探浅层速度调查精度和效率的有益探索。

Model Test Study of Dynamic Ice Force on Compliant Conical Structures

To study ice-induced vibration of a compliant conical structure, a series of model tests were performed from 2004 to 2005. In the tests, the ice sheet before the compliant conical structure was found to fail in two-time breaking. From 2005 to 2006, this type of ice failure was studied through more groups of tests. The tests show that two-time breaking is the typical failure of ice before steep conical structures, and is controlled by other factors at the same time, such as ice speed and the angle of the cone.

Disappearance of the Dirac cone in silicene due to the presence of an electric field

Using the two-dimensional ionic Hubbard model as a simple basis for describing the electronic structure of silicene in the presence of an electric field induced by the substrate, we use the coherent-potential approximation to calculate tbe zero-temperature phase diagram and the associated spectral function at half filling. We find that any degree of symmetry- breaking induced by the electric field causes the silicene structure to lose its Dirac fermion characteristics, thus providing a simple mechanism for the disappearance of the Dirac cone.

Effect of Penetration Rates on the Piezocone Penetration Test in the Yellow River Delta Silt

Partial drainage often occurs during piezocone penetration testing on Yellow River Delta silt because of its intermediate physical and mechanical properties between those of sand and clay.Yet,there is no accurate understanding for the range of penetra-tion rates to trigger the partial drainage of silt soils.In order to fully investigate cone penetration rate effects under partial drainage condi-tions,indoor 1 g penetration model tests and numerical simulations of cavity expansion at variable penetration rates were carried out on the Yellow River Delta silt.The boundary effect of the model tests and the variation of key parameters at the different cavity ex-pansion rates were analyzed.The 1 g penetration model test results and numerical simulations results consistently indicated that the penetration rate to trigger the partially drainage of typical silt varied at least three orders of magnitude.The numerical simulations also provide the reference values for the penetration resistance corresponding to zero dilation and zero viscosity at any given normalized penetration rate for silt in Yellow River Delta.These geotechnical properties can be used for the design of offshore platforms in Yel-low River Delta,and the understanding of cone penetration rate effects under the partially drained conditions would provide some technical support for geohazard evaluation of offshore platforms.

ALGORITHM FOR GENERATING DEM BASED ON CONE

Digital elevation model (DEM) has a variety of applications in GIS and CAD.It is the basic model for generating three_dimensional terrain feature.Generally speaking,there are two methods for building DEM.One is based upon the digital terrain model of discrete points,and is characterized by fast speed and low precision.The other is based upon triangular digital terrain model,and slow speed and high precision are the features of the method.Combining the advantages of the two methods,an algorithm for generating DEM with discrete points is presented in this paper.When interpolating elevation,this method can create a triangle which includes interpolating point and the elevation of the interpolating point can be obtained from the triangle.The method has the advantage of fast speed,high precision and less memory.

Analyzing and Projecting Soil Moisture and Cone Penetrability Variations in Forest Soils

This article details how forest soil moisture content (MC) and subsequent resistances to cone penetration (referred below as Cone Index, CI) vary by daily weather, season, topography, site and soil properties across eleven harvest blocks in northwestern New Brunswick. The MC- and CI-affecting soil variables refer to density, texture, organic matter content, coarse fragment content, and topographic position (i.e., elevation, and the seasonally affected cartographic depth-to-water (DTW) pattern). The harvest blocks were transect-sampled inside and outside their wood-forwarding tracks at varying times throughout the year. In detail, 61% of the pore-filled moisture content (MCPS) determinations inside and outside the tracks could be related to topographic position, coarse fragments, bulk density, and forest cover type specifications. In addition, 40% of the CI variations could be related to soil depth, MCPS, and block-specific cover type. Actual versus model-projected uncertainties amounted to ΔMCPS ≤ ± 15% and ΔCI ≤ ± 0.5 MPa, 8 times out of 10. Block-centered MC and CI projections were obtained through: 1) daily hydrological modelling using daily precipitation and air temperature weather-station records nearest each block, and 2) digitally mapped variations in soil properties, elevation, DTW and forest cover type, done at 10 m resolution.

RobustL_1 model reduction for stochastic time-delay systems

This paper investigates the problem of robust L1 model reduction for continuous-time uncertain stochastic time-delay systems. For a given mean-square stable system, our purpose is to construct reduced-order systems, such that the error system between these two models is mean-square asymptotically stable and has a guaranteed L1 (also called peak-to-peak) performance. The peak-to-peak gain criterion is first established for stochastic time-delay systems, and the corresponding model reduction problem is solved by using projection lemma. Sufficient conditions are obtained for the existence of admissible reduced-order models in terms of linear matrix inequalities (LMIs) plus matrix inverse constraints. Since these obtained conditions are not expressed as strict LMIs, the cone complementarity linearization (CCL) method is exploited to cast them into nonlinear minimization problems subject to LMI constraints, which can be readily solved by standard numerical software. In addition, the development of reduced-order models with special structures, such as the delay-free model, is also presented. The efficiency of the proposed methods is demonstrated via a numerical example.