Jet formation and penetration performance of a double-layer charge liner with chemically-deposited tungsten as the inner liner

This paper proposes a type of double-layer charge liner fabricated using chemical vapor deposition(CVD)that has tungsten as its inner liner.The feasibility of this design was evaluated through penetration tests.Double-layer charge liners were fabricated by using CVD to deposit tungsten layers on the inner surfaces of pure T2 copper liners.The microstructures of the tungsten layers were analyzed using a scanning electron microscope(SEM).The feasibility analysis was carried out by pulsed X-rays,slug-retrieval test and static penetration tests.The shaped charge jet forming and penetration law of inner tungsten-coated double-layer liner were studied by numerical simulation method.The results showed that the double-layer liners could form well-shaped jets.The errors between the X-ray test results and the numerical results were within 11.07%.A slug-retrieval test was found that the retrieved slug was similar to a numerically simulated slug.Compared with the traditional pure copper shaped charge jet,the penetration depth of the double-layer shaped charge liner increased by 11.4% and>10.8% respectively.In summary,the test results are good,and the numerical simulation is in good agreement with the test,which verified the feasibility of using the CVD method to fabricate double-layer charge liners with a high-density and high-strength refractory metal as the inner liner.

Formation behaviors of rod-like reactive shaped charge penetrator and their effects on damage capability

Formation behaviors of rod-like reactive shaped charge penetrator(RRSCP)and their effects on damage capability are investigated by experiments and numerical simulations.The pulsed X-ray technology and a spaced aluminum/steel plate with the thicknesses of 5 mm/100 mm are used.Three types of sphericalsegment aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with Cu contents of 0%,46.6%,and 66%are fabricated and tested.The experimental results show that the reactive liners can form excellent rod-shaped penetrators with tail skirts under the shaped charge effect,but the tail skirts disappear over time.Moreover,rupturing damage to the aluminum plate and penetration to the steel plate are caused by the RRSCP impact.From simulation analysis,the RRSCP is formed by a mechanically and chemically coupled response with the reactive liner activated by shock in its outer walls and bottom and then backward overturning,forming a leading reactive penetrator and a following chemical energy cluster.The unique formation structure determines the damage modes of the aluminum plate and the steel plate.Further analysis indicates that the formation behaviors and damage capability of Al-PTFE-Cu RRSCP strongly depend on Cu content.With increasing Cu content,the velocity,activation extent,and reaction extent of Al-PTFE-Cu RRSCP decrease,which contribute to elongation and alleviate the negative effects of chemical reactions on elongation,significantly increasing the length-diameter ratio and thus enhancing the capability of steel plate penetration.However,the lower activation extent and energetic density will weaken the RRSCP's capability of causing rupturing damage to the aluminum plate.

Comparative analysis of phase extraction methods based on phase-stepping and shifting curve in grating interferometry

Two phase extraction methods which are based separately on phase-stepping and shifting curve are mainly used in phase-sensitive imaging in gating interferometry to determine the x-ray phase shift induced by an object in the beam. In this paper, the authors perform a full comparative analysis and present the main virtues and limitations of these two methods according to the theoretical analysis of the grating interferometry.

矩形空洞探地雷达成像曲线厚度变化规律研究

由于城市基础建设不断地翻新改造,引发城市地下空洞滋生问题。通过探地雷达扫描技术,对地下矩形空洞整个探测过程进行研究,将探测过程划分为四个阶段,研究了成像曲线厚度变化规律。对探地雷达水平运行时矩形空洞的成像曲线厚度变化规律进行分析,对不同大小下的矩形空洞点测时曲线厚度进行研究,并通过实际探测案例来解释矩形空洞成像曲线厚度变化规律,结果表明探地雷达探测矩形空洞时其成像曲线厚度为先增加后减小的对称曲线,其曲线厚度最大处在图像上为水平弧段两端,位于实际矩形空洞对角线附近;雷达点测时成像曲线厚度随矩形空洞变大而增加,在图像上表现为空洞越大线条越粗。

配电网分布式发电渗透率极限值定义与计算方法

未来配电网接入分布式发电的比例将不断提高,为此提出了分布式发电(distributed generation,DG)渗透率极限值的定义及计算方法。首先,利用消纳能力曲线和负荷时序特性得到按时间分布的消纳能力。其次,在此基础上定义功率、容量和能量3个渗透率极限值。将渗透率极限值定义为保证任一时刻DG出力不超过该时刻消纳能力下的渗透率的最大值。再次,给出渗透率极限值的计算方法。根据DG容量及其时序出力特性和按时间分布的消纳能力确定DG容量极限值,进而得到渗透率极限值。最后,用IEEE 33节点算例进行验证,与现有方法比较表明,所得结果更为准确。定义的渗透率极限值易于使用,在满足安全性前提下,为衡量DG接入配电网程度提供了重要的参考指标。

改良雨水生物滞留系统截留微塑料效果及影响因素探究

选取聚乙烯(PE,疏水)和聚苯乙烯乳胶微球(PS,亲水)两种使用广泛且在水环境中频繁检出的微塑料为代表,对基质为90%砂土+10%给水厂污泥的雨水生物滞留系统在不同水力停留时间、离子强度、pH值和阳离子类型条件下截留微塑料的效果进行了研究。结果表明,当进水中两种微塑料的丰度分别为5.0×10^(4),5.3×10^(4)个/L、HRT为10 min时,微塑料在改良雨水生物滞留系统中开始穿透及完全穿透时间较传统雨水生物滞留系统均明显后移。在改良雨水生物滞留系统中,HRT由10 min提升至30 min后,聚乙烯开始穿透从90 min(9 FVs)后移至360 min(12 FVs),聚苯乙烯乳胶微球开始穿透从40 min(4 FVs)后移至240 min(8 FVs);高离子强度时(50.0 mmol/L)系统对微塑料的截留能力更强;pH及阳离子类型对微塑料的截留效果无明显影响。

高速铁路微膨胀泥岩破碎土非饱和渗透特性研究

非饱和渗透系数是非饱和膨胀泥岩土体渗流分析及水-力耦合研究的基础,对工程建设和工程病害预防具有重要意义。以新疆哈密地区微膨胀泥岩破碎土为例,制备4种不同初始干密度重塑土样,采用压力板法和滤纸法试验测量其土-水特征曲线,采用变水头试验测量土样饱和渗透系数;通过自主研制的土柱渗流试验装置进行恒定体积条件下一维土柱入渗试验,探究湿润锋前进法和瞬态剖面法的适用性,以获得不同初始干密度土体的非饱和渗透性曲线,并结合试验值对Childs和Collis-Geroge (CCG)渗透系数预测模型进行修正。结果表明:新疆哈密微膨胀泥岩破碎土的基质吸力范围为1~10^(5)kPa,渗透系数范围为10^(-9)~10^(-4)cm·s^(-1);试验土样初始干密度越大,大孔隙占比越小,阻渗作用越明显;CCG渗透系数预测模型可较好地反映土体渗透性曲线发展趋势,但在量值上随吸力的增加逐渐“远离”土体实测渗透性曲线;修正后的CCG渗透系数预测模型可反映不同初始干密度下土体渗透性曲线的发展规律。

基于硝酸钠联合焙烧改性天然沸石的水体氨氮动态吸附特性研究

目的:通过硝酸钠浸渍联合焙烧改性天然沸石(NZ),开发出一种氨氮高性能吸附剂,研究改性NZ对水体中氨氮的动态吸附特性及穿透曲线,并与NZ的氨氮动态吸附能力做出对比。方法:考察在不同初始氨氮质量浓度、进水流量和柱深条件下氨氮的去除情况和穿透曲线,运用Thomas模型、Yoon-Nelson模型和BDST模型对吸附过程拟合。结果:当初始氨氮质量浓度为5 mg·L^(-1)、进水流量为20 mL·min^(-1)、柱深为8 cm时,对氨氮的吸附容量达6.81 mg·g^(-1),远大于NZ吸附容量2.18 mg·g^(-1)。结论:硝酸钠联合焙烧改性沸石可提高对氨氮的吸附能力,动态流实验结果为改性沸石实际应用提供了有力指导。

A Comprehensive Investigation on Shear Performance of Improved Perfobond Connector

This paper presents an easily installed improved perfobond connector (PBL) designed to reduce the shearconcentration of PBL. The improvement of PBL lies in changing the straight penetrating rebar to the Z-typepenetrating rebar. To study the shear performance of improved PBL, two PBL test specimens which containstraight penetrating rebar and six improved PBL test specimens which contain Z-type penetrating rebars weredesigned and fabricated, and push-out tests of these eight test specimens were carried out to investigate andcompare the shear behavior of PBL. Additionally, Finite Element Analysis (FEA) models of the PBL specimenswere established and validated against the test results. Through FEA, the effects of concrete grade, perforatedplate’s aperture, Z-type penetrating rebar’s diameter, Z-type penetrating rebar’s bending angle, and bending lengthon shear behaviors were discussed. The results indicate that (1) Compared with PBL specimens with straightpenetrating rebars, Z-type penetrating rebar can significantly improve the shear resistance and shear stiffnessof the specimens. This enhanced performance can be mainly attributed to the increased adhesion of the transverserebar. (2) By comparing the load-slip curve, the slip of PBL test specimens which contain straight penetratingrebar increases rapidly and the bearing capacity decreases rapidly after concrete craking, while the bearingcapacity of Z-type penetrating rebar specimens decreases first and then increases gradually, showing betterductility. (3) The stress of the PBL shear connector with Z-type penetrating rebar is more uniform than thePBL shear connector with straight penetrating rebar, and the overall deformation is more uniform. (4) The higherthe concrete grade, the higher the shear bearing capacity and the better ductility of the new PBL. Increasing theaperture of the perforated plate or the diameter of the rebar has a very limited effect on the improvement of theshear capacity of PBL. Through the systematic analysis of the mechanical properties of Z-type penetrating rebarPBL specimen, the experimental reference is provided for improving the structure and design of new type PBL.

腐殖酸和pH对典型轮胎磨损颗粒迁移行为的影响机制

轮胎磨损颗粒(Tire wear particles,TWPs)作为微塑料(Microplastics,MPs)的重要种类之一,当下其生态风险已受到生态学家的高度重视。通常,颗粒型污染物的环境行为过程是其生态风险的重要影响因素。然而,TWPs在土壤等多孔介质中的迁移过程及影响机制至今尚未见报道。选择冷冻破碎制备的冷冻破碎轮胎磨损颗粒(C-TWPs)以及道路磨损产生的滚动摩擦轮胎磨损颗粒(R-TWPs)和滑动摩擦轮胎磨损颗粒(S-TWPs)为典型研究对象,以石英砂柱来模拟研究TWPs在土壤等环境多孔介质中的迁移行为,并探究天然有机物腐殖酸(HA)及不同pH(4、7和10)环境对以上三种类型TWPs迁移行为的影响。结果显示:HA(50 mg·L^(-1))能够显著增强三种类型TWPs的迁移性,并且在HA(50 mg·L^(-1))存在下,不同pH(4、7和10)对TWPs迁移行为影响不同,中碱性环境(pH=7/10)更有利于TWPs的迁移。主要原因在于,HA存在或(和)中碱性环境有利于(同时)增大TWPs和石英砂颗粒表面的Zeta电位值(绝对值),此时,一方面TWPs的分散性得到改善,有较小的粒径分布,另一方面增加了TWPs和石英砂颗粒间的静电排斥力,有助于TWPs的迁移。值得注意的是,HA存在和不同pH环境条件下,低温破碎制备的C-TWPs的迁移性较R-TWPs和S-TWPs强,主要由于C-TWPs制备时携带有较多的负电荷、较小的等电点和较强的疏水性,上述性质也可促使其吸附更多的HA,从而加强其电负性;而R-TWPs和S-TWPs由于粘附了道路矿物、金属盐或灰尘而减弱以上性质,表面具有较小的电负性。研究结果揭示了不同类型TWPs在自然界中地球化学迁移行为的差异性,并暗示了研究源头性质(排放方式)以确定同种材质微塑料环境行为及生态风险内在差异的必要性。

辽西北风沙地不同林龄樟子松土壤大孔隙特征

土壤大孔隙是土壤水分、空气、化学物质及污染物优先运移的主要通道,与地表径流及土壤渗透性之间具有密切关系。为明晰不同林龄樟子松土壤大孔隙特征,以辽西北风沙地不同林龄(对照样地、24 a、38 a和49 a)、不同土层(0~50 cm)樟子松人工林为研究对象,采用野外染色示踪试验,基于室内水分穿透曲线和Poiseulle方程,分析不同林龄樟子松土壤大孔隙特征及其影响因素。结果表明:不同林龄樟子松染色和非染色区渗透速率存在较明显差异性,染色区水分渗透速率较非染色区提高近60%;土壤大孔隙半径分布在0.52~3.66 mm之间,其孔隙半径均值为0.69 mm,并随土层的加深而减少;樟子松土壤大孔隙与林龄、土层深度的变化存在显著差异,在不同林龄中,樟子松大孔隙半径与出流速率的关系具有显著线性相关性。研究结果可为深入理解辽西北风沙地樟子松土壤大孔隙特征及其对土壤水分运动的影响机理提供理论依据。

枯草芽孢杆菌hs032对盐碱土理化性质及弥散能力的影响

为了探究微生物对盐碱土壤理化特性及溶质弥散能力的影响,以一株分离自盐碱土的高产胞外多糖枯草芽孢杆菌(Bacillus subtilis)hs032为试验对象,设置5个施用水平(5、7、9、15和20 mL/kg)开展了室内培养试验。结果显示:相较对照组,菌株hs032能够显著提高土壤微生物和多糖含量(P<0.05);试验结束时(30 d)土壤团聚体含量平均增加7.2 g/kg,容重平均降低31%,孔隙度平均升高11.8%,可溶性盐含量下降41.5%,p H下降至7.16~7.41。添加菌株hs032会使土壤的穿透曲线右移,土壤孔隙水流速增高,弥散系数降低。总之,枯草芽孢杆菌hs032能够明显改善土壤理化性质和水盐运移参数,对盐碱土壤治理工作具有一定的实际应用价值。

基于孔压静力触探的大直径单桩p-y曲线分析

【目的】水平受荷桩的p-y曲线法已广泛用于描述桩-土相互作用并预测桩在水平荷载下的行为,特别是在海上风电机大直径单桩的理论分析中。孔压静力触探试验(piezocone penetration test,简称CPTu)作为一种效率高、精确度好的原位测试手段,克服了传统室内试验获得土工参数的过程中土样存在扰动、结果准确性较差的缺点。该试验可以通过测量三个基本参数(修正锥尖阻力qt、侧壁摩阻力fs以及孔隙水压力u2)随深度变化的连续剖面来解译土体的物理力学参数,从而在p-y曲线模型的建立中提供关键数据。【方法】利用渤海海域某场区的CPTu数据,完成了以下研究任务:(1)基于CPTu触探响应结果,对该场区海洋土体进行分类,以及物理与力学参数的反演,包括土体密度、弹性模量、有效内摩擦角及有效黏聚力;(2)将CPTu反演参数代入三维有限元分析模型中,模拟直径为5 m的钢管桩在最大荷载为20 MN时的水平受荷响应;(3)基于CPTu测试数据,提出一套土抗力计算公式;(4)将现有p-y曲线模型中相关参数通过CPTu触探响应结果进行反演,之后对比分析上述p-y曲线模型。【结果】形成了一套基于CPTu且适用于土体分层情况较为复杂的p-y曲线公式,该公式与有限元方法对比结果良好。【结论】结果表明,提出的基于CPTu的土抗力公式经过有限元模拟检验后能快速、准确地反映大直径单桩的水平受荷响应。该公式不仅为渤海海域内大直径单桩的工程实践提供了有力的理论支持,还为相似海洋环境的工程设计与分析提供了完全基于CPTu研究大直径单桩的新思路。

地下水示踪试验中穿透曲线的解析——以平果县平南赤泥堆场地下岩溶系统为例

地下水示踪试验中的穿透曲线解译是一项重要的技术,通过这一技术,可以获得关于地下岩溶管道的信息,如管道的尺寸、连通性、分布和方向等。然而,在实际应用中,仍存在许多问题需要解决,以提高对穿透曲线的解释准确性和可靠性。以平果县平南赤泥堆场地下岩溶系统为例,利用荧光计获取示踪数据结合Qtracer2软件对示踪剂回收率、平均滞留时间、弥散系数、地下水平均流速等参数进行计算,并结合当前被广泛认同的结论对穿透曲线中的多峰、异常波动等现象进行解释。由于本次研究区的岩溶管道规模小,将岩溶管道的复杂性降低到了可计算程度,对并联岩溶管道长度近似值进行计算,最后排除曲线尾部的峰值为溶质暂态存储现象,分析表明研究区属于多管道岩溶系统,地下水主要表现为“岩溶水扩散流”特征。本研究为地下水数值模型提供了依据,为研究如何分析岩溶复杂介质运移特征提供参考。

贯入法检测特细砂砌筑砂浆抗压强度的测强曲线研究

针对重庆地区特细砂砌筑砂浆的性能差异,设计制作不同强度等级的砂浆试件,对组测定其贯入深度和抗压强度,拟合建立贯入法检测特细砂砌筑砂浆抗压强度的专用测强曲线。试验结果验证了贯入法统一测强曲线应用于重庆地区特细砂砌筑砂浆的检测误差,同时表明所建立的专用测强曲线较统一测强曲线检测精度更高,更接近砌筑砂浆的实际强度。专用测强曲线可作为既有砌体结构房屋砂浆强度检测鉴定的参考,亦可作为贯入法检测砌筑砂浆强度地方标准编制的基础数据。

A new method for information retrieval in two-dimensional grating-based X-ray phase contrast imaging

Grating-based X-ray phase contrast imaging has been demonstrated to he an extremely powerful phase-sensitive imaging technique. By using two-dimensional （2D） gratings, the observable contrast is extended to two refraction directions. Recently, we have developed a novel reverse-projection （RP） method, which is capable of retrieving the object information efficiently with one-dimensional （1D） grating-based phase contrast imaging. In this contribution, we present its extension to the 2D grating-based X-ray phase contrast imaging, named the two-dimensional reverse- projection （2D-RP） method, for information retrieval. The method takes into account the nonlinear contributions of two refraction directions and allows the retrieval of the absorption, the horizontal and the vertical refraction images. The obtained information can be used for the reconstruction of the three-dimensionak phase gradient field, and for an improved phase map retrieval and reconstruction. Numerical experiments are carried out, and the results confirm the validity of the 2D-RP method.

Retrieval of multiple scattering contrast from x-ray analyzer-based imaging

We present a moment-based alternative approach to retrieve multiple scattering contrasts from x-ray analyzer-based imaging. By use of the properties of moments of convolutions, the multiple-image radiography approach is theoretically validated. Furthermore, higher order moments of the object scattering distribution, inaccessible in multiple-image radiography, are simultaneously provided by this alternative approach. It is experimentally demonstrated that the skew and kurtosis information related to the distribution of sub-pixel features within the object can be obtained from those complementary contrasts. Finally, the sensitivity of the retrieved multiple scattering contrasts is investigated experimentally. The finding that the sensitivity is inversely proportional to the square root of the detected photon number essentially indicates that the retrieval of moments with an order higher than two can be achieved without increasing exposure time or dose. The presented alternative approach provides an access to the exploitation of multiple scattering contrasts, which is expected to be useful in biomedical research, materials science, security screening, etc.

武汉汉江湾桥主桥设计关键技术

武汉汉江湾桥主桥为(132+408+132)m中承式连续钢桁拱桥,桥面车行道按双向6车道布置,并预留拓宽至8车道条件。主桥拱肋采用变高度N形桁式两主桁钢桁架结构。主桁标准间距34 m,汉口岸边跨受限于总体线形,主桁间距由34 m变化至39.5 m。主桁中支点附近下弦杆根据受力要求采用Q690qE高性能桥梁钢。车行道桥面采用正交异性钢桥面板,车行道桥面下U形纵肋与钢桥面采用全熔透焊接设计。通过主桁节点弯折、钢桥面横坡变化等构造措施简化了主桁、联结系、桥面系的空间关系,降低了杆件制造难度,实现了桥面结构的曲线变宽。

基于静力触探的黏土中桩基p-y曲线研究

将华能灌云海上风电场试桩试验实测数据与4种基于CPT测试的黏土p-y曲线方法的理论计算结果进行对比。对比显示:传统的p-y曲线因其原始试验的局限性会显著低估桩侧土体的极限土反力,使桩基设计偏于保守;而双曲线型的p-y曲线虽然高估桩侧土反力,但是对桩侧土体初始刚度预测较准。根据以上对比分析结果,采用Matlab回归函数进行模型集成,将传统型p-y曲线模型与双曲线型p-y曲线模型结合,提出一种基于CPT测试的适用于黏土的复合p-y曲线模型。最后通过与已有工程实例实测数据进行对比,验证了新提出方法的可靠性。该方法可为黏土中水平受荷桩基计算提供新途径。

不同金属污染物在含钙高岭土中的运移特性试验研究

重金属在土壤中的运移过程极其复杂,土壤的性质和结构不同,对运移也会造成影响.通过将不同浓度的Ca^(2+)溶液加入高岭土来模拟真实的含钙土壤,研究高岭土含钙量对Cu^(2+)、Pb^(2+)、Zn^(2+)运移规律的影响,并分析Cu^(2+)、Pb^(2+)、Zn^(2+)在含钙高岭土中的运移规律.得出结论:随着高岭土含钙量的增加,Cu^(2+)、Pb^(2+)、Zn^(2+)的初始穿透时间和运移平衡时间都有不同程度的缩短,其中对Zn^(2+)初始穿透和运移平衡时间影响的差距最大,且高岭土对Cu^(2+)、Zn^(2+)的吸附量都减少,对Pb^(2+)的吸附量几乎不变;Cu^(2+)、Pb^(2+)、Zn^(2+)三种离子中,Pb^(2+)达到初始穿透和运移平衡的时间最长且吸附量最大,而Zn^(2+)达到初始穿透和运移平衡的时间最短且吸附量最小.