Ballistic performances of the hourglass lattice sandwich structures under high-velocity fragments

In this paper,the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments.Attention is paid to elucidating the influences of rod cross-section dimensions,structure height,structure layer,and rod inclination angle on the deformation mode,ballistic performances,and ability to change the ballistic direction of fragments.The results show that the ballistic performances of hourglass lattice sandwich structures are mainly affected by their structural parameters.In this respect,structural parameters optimization of the hourglass lattice sandwich structures enable one to effectively improve their ballistic limit velocity and,consequently,ballistic performances.

Research on High-Velocity Impact Damage Monitoring Method of CFRP Based on Guided Wave

Carbon fiber-reinforced polymer(CFRP)is widely used in aerospace applications.This kind of material may face the threat of high-velocity impact in the process of dedicated service,and the relevant research mainly considers the impact resistance of the material,and lacks the high-velocity impact damage monitoring research of CFRP.To solve this problem,a real high-velocity impact damage experiment and structural health monitoring(SHM)method of CFRP plate based on piezoelectric guided wave is proposed.The results show that CFRP has obvious perforation damage and fiber breakage when high-velocity impact occurs.It is also proved that guided wave SHM technology can be effectively used in the monitoring of such damage,and the damage can be reflected by quantifying the signal changes and damage index(DI).It provides a reference for further research on guided wave structure monitoring of high/hyper-velocity impact damage of CFRP.

Influence of particle size on property of Ti-6Al-4V alloy prepared by high-velocity compaction

Three Ti-6Al-4V alloy powders with median diameters of 103, 66 and 44 pm, respectively, were pressed by high-velocity compaction （HVC） technology and then sintered in vacuum. The effects of particle sizes on forming as well as properties of sintered samples were investigated. The results show that fine powders are more difficult to press than coarse powders and its compact density is lower too. But the sintered density of fine powders is obviously higher than that of coarse powders. Compared with the powders with 103 and 66 ~un in diameter, the green density with 44 ~rn diameter powders is lower, which is 85.1% of theoretical density （TD） at an impact energy of 913 J. After sintering at 1300 ~C for 2,5 h, the sintered density of the compacts with 44 pm diameter powders is the highest, and reaches 98.2% of TD. Moreover, the sintered sample with 44 pan in diameter has the highest hardness and compressive strength, which are HV 354 and 1265 MPa, respectively.

季冻影响下路用CFB灰混凝土孔隙特征及动态力学性能研究

通过室内冻融循环试验和SHPB动力学试验,探究冻融循环对CFB灰混凝土孔隙率的影响特征,分析高应变率作用下冻融循环次数和CFB灰掺量对混凝土动态力学性能的影响。根据公路建设季冻灾害与动载扰动的影响规律,分析CFB灰混凝土的路用可行性。研究表明:在冻融循环作用下,CFB灰混凝土的孔隙率与混凝土可承受的冻融循环次数呈对数关系,CFB灰掺量的增加使混凝土密实度提高,孔隙率减小;随着冻融循环次数的增加,混凝土的动态弹性模量、动态抗压强度呈对数减小,动态峰值应变呈对数增加,掺量为20%的CFB灰混凝土具有较强的动态抗压性能;在公路建设中,掺量不大于20%的CFB灰能有效降低混凝土孔隙率、提高动荷载承载力、改善混凝土的抗冻性。研究成果对于探究CFB灰混凝土力学性能、促进CFB灰混凝土在公路建设中的应用具有重要意义。

CFB飞灰压浆料的制备及高强微膨胀机理研究

利用循环流化床燃煤固硫灰(CFB飞灰)的活性与膨胀性制备压浆料,研究了CFB飞灰掺量和水胶比对压浆料工作性能、强度和膨胀率的影响;CFB飞灰与矿粉以不同比例复配,对比研究了CFB飞灰压浆料的高强微膨胀特性,并采用XRD与SEM分析验证。结果表明,随CFB飞灰替代水泥掺量的增加,压浆料的需水性增强,抗压强度降低,20%(质量分数)CFB飞灰的试样28 d抗压强度与基样接近,可达85.8 MPa,而抗折强度先升高后降低,膨胀率一直升高。随用水量的增加,压浆料的膨胀率降低但均为正值。随CFB飞灰取代矿粉率的提高,压浆料的工作性能降低,28 d抗压强度先升高后降低,其中20%(质量分数)CFB飞灰、10%(质量分数)矿粉复合的试样28 d抗压强度最高,为99.8 MPa,膨胀率一直升高。通过CFB飞灰与矿粉复合配制了各项性能均满足铁标要求的压浆料。CFB飞灰不仅自身水化产生膨胀,还能激活矿粉活性,产生复合增强作用。

High-velocity frictional behavior of Longmenshan fault gouge from Hongkou outcrop and its implications for dynamic weakening of fault during the 2008 Wenchuan earthquake

High-velocity friction experiments were conducted on clayey fault gouge collected from Hongkou outcrop of Beichuan fault, located at the southwestern part of Longmenshan fault system that caused the disastrous 2008 Wenchuan earthquake. The ultimate purpose of this study is to reproduce this earthquake by modeling based on measured frictional properties. Dry gouge of about 1 mm in thickness was deformed dry at slip rates of 0.01 to 1.3 m/s and at normal stresses of 0.61 to 3.04 MPa, using a rotary-shear high-velocity frictional testing machine. The gouge displays slip weakening behavior as initial peak friction decays towards steady-state values after a given displacement. Both peak friction and steady-state friction remain high at slow slip rates are exam- ined and gouge only exhibits dramatic weakening at high slip rates, with steady-state friction coefficient values of about 0.1 to 0.2. Specific fracture energy ranges from 1 to 4 MN/m in our results and this is of the same order as seismically determined values. Low friction coefficients measured on experimental faults are in broad agree- ment with lack of thermal anomaly observed from temperature measurements in WFSD-1 drill hole （Wenchuan Earthquake Fault Scientific Drilling Project）, which can be explained by even smaller friction coefficient for the Wenchuan earthquake fault. High-velocity friction experiments with pore water needs to be done to see if even smaller friction is attained or not. Shiny slickenside surfaces form at high slip rates, but not at slow slip rates. Slip zone with slickenside surface changes its color to dark brown and forms duplex-like microstructures, which are similar to those microstructures found in the fault gouges from the Hongkou outcrop. Detailed comparisons between experimentally deformed gouge samples and WFSD drill cores in the future will reveal how much we could reproduce the dynamic weakening processes in operation in fault zones during Wenchuan earthquake at present.

A rotary-shear low to high-velocity friction apparatus in Beijing to study rock friction at plate to seismic slip rates

This paper reviews 19 apparatuses having highvelocity capabilities,describes a rotary-shear low to highvelocity friction apparatus installed at Institute of Geology,China Earthquake Administration,and reports results from velocity-jump tests on Pingxi fault gouge to illustrate technical problems in conducting velocity-stepping tests at high velocities.The apparatus is capable of producing plate to seismic velocities（44 mm/a to 2.1 m/s for specimens of 40 mm in diameter）,using a 22 kW servomotor with a gear/belt system having three velocity ranges.A speed range can be changed by 103 or 106by using five electromagnetic clutches without stopping the motor.Two cam clutches allow fivefold velocity steps,and the motor speed can be increased from zero to 1,500 rpm in 0.1-0.2 s by changing the controlling voltage.A unique feature of the apparatus is a large specimen chamber where different specimen assemblies can be installed easily.In addition to a standard specimen assembly for friction experiments,two pressure vessels were made for pore pressures to 70 MPa;one at room temperature and the other at temperatures to 500 °C.Velocity step tests are needed to see if the framework of rate-and-state friction is applicable or not at high velocities.We report results from velocity jump tests from 1.4 mm/s to 1.4 m/s on yellowish gouge from a Pingxi fault zone,located at the northeastern part of the Longmenshan fault system that caused the 2008 Wenchuan earthquake.An instantaneous increase in friction followed by dramatic slip weakening was observed for the yellowish gouge with smooth sliding surfaces of host rock,but no instantaneous response was recognized for the same gouge with roughened sliding surfaces.Instantaneous and transient frictional properties upon velocity steps cannot be separated easily at high velocities,and technical improvements for velocity step tests are suggested.

A novel approach to predict green density by high-velocity compaction based on the materials informatics method

High-velocity compaction is an advanced compaction technique to obtain high-density compacts at a compaction velocity of ≤10 m/s. It was applied to various metallic powders and was verified to achieve a density greater than 7.5 g/cm^3 for the Fe-based powders. The ability to rapidly and accurately predict the green density of compacts is important, especially as an alternative to costly and time-consuming materials design by trial and error. In this paper, we propose a machine-learning approach based on materials informatics to predict the green density of compacts using relevant material descriptors, including chemical composition, powder properties, and compaction energy. We investigated four models using an experimental dataset for appropriate model selection and found the multilayer perceptron model worked well, providing distinguished prediction performance, with a high correlation coefficient and low error values. Applying this model, we predicted the green density of nine materials on the basis of specific processing parameters. The predicted green density agreed very well with the experimental results for each material, with an inaccuracy less than 2%. The prediction accuracy of the developed method was thus confirmed by comparison with experimental results.

基于TF-NGO算法的CFB锅炉床温系统建模研究

床温是循环流化床(CFB)锅炉重要的运行参数之一。针对床温耦合性强、干扰因素多、控制复杂的问题,亟需建立床温的数学模型,以实现床温控制,从而保证CFB锅炉安全、平稳地运行。为此,首先引入了混沌映射、切线飞行(TF)和柯西变异策略改进北方苍鹰优化(NGO)算法,并用实际工况的系统模型测试TF-NGO算法。测试结果表明,TF-NGO算法拥有更快的收敛速度和更高的寻优精度。其次,采集并预处理山西某电厂350 MW超临界CFB锅炉的现场运行数据。最后,采用TF-NGO算法对所建模型的参数进行辨识,并用实际工况数据进行模型验证。辨识和验证结果表明,由TF-NGO算法辨识的床温模型与实际输出拟合度高,能有效反映床温的动态特性,证明所建模型的有效性。该研究为后续对350 MW超临界CFB锅炉床温的优化控制研究奠定了基础。

Internal structures and high-velocity frictional properties of Longmenshan fault zone at Shenxigou activated during the 2008 Wenchuan earthquake

This paper reports internal structures of a wide fault zone at Shenxigou,Dujiangyan,Sichuan province,China,and high-velocity frictional properties of the fault gouge collected near the coseismic slip zone during the 2008 Wenchuan earthquake.Vertical offset and horizontal displacement at the trench site were 2.8 m（NW side up）and 4.8 m（right-lateral）,respectively.The fault zone formed in Triassic sandstone,siltstone,and shale about 500 m away from the Yingxiu-Beichuan fault,a major fault in the Longmenshan fault system.A trench survey across the coseismic fault,and observations of outcrops and drill cores down to a depth of 57 m revealed that the fault zone consists of fault gouge and fault breccia of about0.5 and 250-300 m in widths,respectively,and that the fault strikes N62°E and dips 68° to NW.Quaternary conglomerates were recovered beneath the fault in the drilling,so that the fault moved at least 55 m along the coseismic slip zone,experiencing about 18 events of similar sizes.The fault core is composed of grayish gouge（GG） and blackish gouge（BG） with very complex slip-zone structures.BG contains low-crystalline graphite of about 30 %.High-velocity friction experiments were conducted at normal stresses of 0.6-2.1 MPa and slip rates of 0.1-2.1 m/s.Both GG and BG exhibit dramatic slip weakening at constant high slip rates that can be described as an exponential decay from peak friction coefficient lpto steadystate friction coefficient lssover a slip-weakening distance Dc.Deformation of GG and BG is characterized by overlapped slip-zone structures and development of sharp slickenside surfaces,respectively.Comparison of our data with those reported for other outcrops indicates that the high-velocity frictional properties of the Longmenshan fault zones are quite uniform and the high-velocity weakening must have promoted dynamic rupture propagation during the Wenchuan earthquake.

Influence of High-Velocity Blood Flow on Right-to-Left Shunt in Patients with Patent Foramen Ovale during the Valsalva Maneuver

In this study, we investigated the changes in the right-to-left shunt (RLS) of the patent foramen ovale (PFO) at different phases of the Valsalva maneuver and analyzed the possible mechanisms. The study population consisted of 57 patients with symptoms highly suggestive of a PFO. These patients had been diagnosed with apsychia, migraine with aura, cerebral infarction, transient ischemic attack (TIA), and cerebral ischemia with unknown cause. Routine echocardiography was performed in all patients to rule out a cardiac malformation. Contrast-transcranial Doppler (c-TCD) and contrast-enhanced transthoracic echocardiography (c-TTE) were used to visualize and quantify the RLS. The standard apical four chamber view was used to observe the changes of E peak, A peak, and velocity-time integral (VTI) ratio of tricuspid blood flow during the strain phase and release phase of the Valsalva maneuver. Paired t-test was used to compare E peak, A peak, and VTI ratio of tricuspid blood flow during the different phases. The right-to-left shunt across the PFO (PFO-RLS) was graded in the two phases and compared by Kruskal-Wallis test. Compared with the strain phase of the Valsalva maneuver, the parameters of E, A, and VTI in diastolic period in patients with PFO-RLS at the release phase were significantly increased [54.30 ± 13.65 cm/s vs 100.35 ± 21.11 cm/s, 42.21 ± 12.32 cm/s vs 57.30 ± 18.88 cm/s, 10.34 ± 3.27 cm/s vs 19.58 ± 4.56 cm/s, respectively], and the difference was statistically significant. The positive consequence of PFO-RLS, as diagnosed by c-TTE with the Valsalva maneuver at the release phase of the Valsalva maneuver, was significantly higher than that at the strain phase of the Valsalva maneuver. At the beginning of release phase of the Valsalva maneuver, decreased intrathoracic pressure led to increased venous backflow into the right atrium. Thus, high-velocity blood flow rapidly pushed the PFO open, which resulted in a significant increase in the PFO-RLS. Therefore, the increase of the PFO-RLS during the Valsalva maneuver is caused by the impact of high-velocity blood flow the PFO.

Fe-based amorphous coating prepared using high-velocity oxygen fuel and its corrosion behavior in static lead-bismuth eutectic alloy

The Fe_(949.7)Cr_(18)Mn_(1.9)Mo_(7.4)W_(1.6)B_(15.2)C_(3.8)Si_(2) amorphous coating was deposited on T91 steel substrate by using the high-velocity oxygen fuel(HVOF)spray technique to enhance the corrosion resistance of T91 stainless steel in liquid lead-bismuth eutectic(LBE).The corrosion behavior of the T91 steel and coating exposed to oxygen-saturated LBE at 400℃ for 500 h was investigated.Results showed that the T91 substrate was severely corroded and covered by a homogeneously distributed dual-layer oxide on the interface contacted to LBE,consisting of an outer magnetite layer and an inner Fe-Cr spinel layer.Meanwhile,the amorphous coating with a high glass transition temperature(Tg=550℃)and crystallization temperature(T_(x)=600℃)exhibited dramatically enhanced thermal stability and corrosion resistance.No visible LBE penetration was observed,although small amounts of Fe_(3)O_(4),Cr_(2)O_(3),and PbO were found on the coating surface.In addition,the amorphicity and interface bonding of the coating layer remained unchanged after the LBE corrosion.The Fe-based amorphous coating can act as a stable barrier layer in liquid LBE and have great application potential for long-term service in LBE-cooled fast reactors.

Use of low-frequency signals to improve imaging quality under high-velocity basalt

Wave equation wave field numerical modeling technology is applied to the observation that deep layer imaging is difficult below a screening layer of high-velocity basalt. Three simple high-velocity basalt models are designed on the basis of basalt formation characteristics. The analysis of deep-layer reflection seismic signal energy shows that lowfrequency seismic signals are capable of both penetrating the thin high-velocity basalt layer and reducing the diffraction noise caused by the rough surfaces. The simulation experiment of a complete 2D basalt model confirms that the low-frequency signals can be used to boost the quality of deep-layer imaging under the high-velocity basalt layer and achieve good results in low-pass filter processing of actual data.

生物质CFB氮氧化物排放建模与优化控制

由于生物质循环流化床(CFB)燃烧不稳定,为实现负荷波动过程中机组NO_(x)的动态预测,从锅炉燃烧机理切入,建立了氧量模型与即燃碳模型;对炉内NO_(x)自生成与自还原机理进行分析,并结合数学建模的方法,建立了NO_(x)动态排放模型。进行给料量、二次风量开环阶跃试验;分析NO_(x)排放与氧量耦合情况,采用简化对角解耦与前馈补偿解耦法解除耦合。结合某130 t/h生物质CFB实际运行数据进行仿真试验。结果表明:模型拥有较好的预测效果,能反映氧量及NO_(x)排放过程的动态特性,可实现给料量控制NO_(x)排放质量浓度、二次风控制氧体积分数的单回路控制,所设计的NO_(x)排放质量浓度模型及解耦控制方法可以为今后生物质CFB机组适应动态运行以及智能控制策略设计提供参考。

Comparative investigation of microstructure and high-temperature oxidation resistance of high-velocity oxy-fuel sprayed CoNiCrAlY/nano-Al_(2)O_(3) composite coatings using satellited powders

Satellited CoNiCrAlY–Al_(2)O_(3)feedstocks with 2wt%, 4wt%, and 6wt% oxide nanoparticles and pure CoNiCrAlY powder were deposited by the high-velocity oxy fuel process on an Inconel738 superalloy substrate. The oxidation test was performed at 1050℃ for 5, 50, 100,150, 200, and 400 h. The microstructure and phase composition of powders and coatings were characterized by scanning electron microscopy and X-ray diffraction, respectively. The bonding strength of the coatings was also evaluated. The results proved that with the increase in the percentage of nanoparticles(from 2wt% to 6wt%), the amount of porosity(from 1vol% to 4.7vol%), unmelted particles, and roughness of the coatings(from 4.8 to 8.8 μm) increased, and the bonding strength decreased from 71 to 48 MPa. The thicknesses of the thermally grown oxide layer of pure and composite coatings(2wt%, 4wt%, and 6wt%) after 400 h oxidation were measured as 6.5, 5.5, 7.6, and 8.1 μm, respectively.The CoNiCrAlY–2wt% Al_(2)O_(3)coating showed the highest oxidation resistance due to the diffusion barrier effect of well-dispersed nanoparticles. The CoNiCrAlY–6wt% Al_(2)O_(3)coating had the lowest oxidation resistance due to its rough surface morphology and porous microstructure.

CFB灰渣混凝土的组成设计与应用研究

随着循环流化床(CFB)锅炉清洁燃烧技术的大规模应用,所排放的CFB灰渣的处理成为亟待解决的问题。本文以碎石作粗集料、CFB炉渣作细集料以及CFB飞灰作矿物掺合料来制备CFB灰渣混凝土,探讨了CFB炉渣砂率、CFB飞灰掺量对CFB灰渣混凝土的工作性能与力学性能的影响,优化设计了CFB灰渣混凝土配合比,对比研究了CFB灰渣混凝土与机制砂混凝土抗Cl-渗透性能、抗冻性和干燥收缩等耐久性能,并进行了CFB灰渣混凝土小型预制构件的工程应用。结果表明:随着CFB炉渣砂率的增加,CFB灰渣混凝土的抗压强度先增大后降低,随着CFB飞灰掺量的增加,CFB灰渣混凝土的坍落度逐渐降低,抗压强度先增大后降低,优化的最佳配合比为水泥280 kg/m^(3)、CFB飞灰120 kg/m^(3)、矿粉40 kg/m^(3)、CFB炉渣620 kg/m^(3)、碎石1 013 kg/m^(3)、水223 kg/m^(3)、减水剂8.8 kg/m^(3);相比于机制砂混凝土,CFB灰渣混凝土具有良好的抗Cl-渗透性能、抗冻性和较小的干燥收缩,且采用CFB灰渣混凝土制备的小型预制构件在实际工程中具有更好的应用效果。

CFB炉渣细骨料纤维砂浆干燥收缩特性研究

为了实现CFB炉渣的高效利用,提高预拌砂浆的抗裂性,以粉煤灰取代量(体积分数)、CFB炉渣细骨料取代量(体积分数)和PVA纤维掺量(体积分数)为因素,设计正交试验方案L_(16)(4~5),试验研究CFB炉渣细骨料纤维砂浆的干燥收缩特性,分析作用规律,建立回归模型。结果表明:增加粉煤灰取代量可以提高CFB炉渣砂浆稠度,增加CFB炉渣取代量和PVA纤维掺量不利于砂浆稠度的提升;粉煤灰取代量、CFB炉渣取代量为CFB炉渣纤维砂浆的干燥收缩特别显著性影响因素,PVA纤维掺量为显著性影响因素;粉煤灰取代量、PVA纤维掺量对CFB炉渣纤维砂浆的干燥收缩起明显的抑制作用,CFB炉渣使砂浆的干燥收缩呈先降低后增大的变化趋势;砂浆干燥收缩的模型预测相对残差在±5%以内,模型预测结果准确可信。

CFB灰渣对水泥稳定红砂岩集料的增强改性作用

针对红砂岩均质性差,红砂岩集料性能和水泥稳定红砂岩集料路用性能不明确的问题,以水泥稳定石灰岩集料为对照,分别研究了红砂岩粗、细集料取代率。研究了循环流化床(CFB)炉渣、CFB飞灰掺量对水泥稳定红砂岩集料7 d无侧限抗压强度、长期强度、抗干缩性能和抗冻性能的影响规律。采用SEM揭示了CFB灰渣对水泥稳定红砂岩集料的改性作用机理。结果表明:红砂岩集料的组成成分和物理性能与粒径大小存在明显相关性,集料粒径越小,集料中的黏土矿物含量越高,压碎值越低,塑性指数越高,表明可以通过破碎筛分将不同类型红砂岩分离,提高红砂岩集料均质性。水泥稳定红砂岩集料的强度、抗裂性能、抗冻性受红砂岩粗集料替代率影响小,受红砂岩细集料替代率影响大。采用CFB炉渣和CFB飞灰作复合细集料可显著提高水泥稳定红砂岩集料的路用性能。与同水泥掺量水泥稳定石灰石集料相比,经改性后的水泥稳定红砂岩集料7 d无侧限抗压强度高0.8 MPa,干缩应变低49.5%,抗冻性持平。从SEM的试验结果中可以观察到针棒状钙矾石和絮状C—S—H凝胶,这表明CFB灰渣的水化产物起到了胶结增强作用,针棒状钙矾石形成产生的膨胀与CFB炉渣的多孔“内养生”作用可协同降低干缩、防止冻融破坏。

超临界CFB锅炉水冷壁管分区段热应力分析

为确保循环流化床锅炉水冷壁的正常运行,以避免发生蠕变变形、高温腐蚀等生产事故。以600 MW超临界循环流化床(circulating fluidized bed,CFB)锅炉为研究对象,建立了水冷壁温度应力场数值模型。并利用分区段炉膛热力计算理论和新IAPWS-IF97公式,对运行状态中水冷壁分区段进行壁温和热应力分析。结果表明:各区段管壁温度与应力场分布变化一致,但由于工质焓值和高温烟气的交叉作用,区段5存在最高壁温与最大热应力。进一步对区段5进行传热恶化分析可得,管壁最高温度部位发生转移,且壁温与热应力最大值皆超过设计值,可能导致水冷管爆管或断裂。随后针对安全隐患,通过数值模拟方法从降低局部热负荷和控制质量流速的角度来防止锅炉传热恶化,为锅炉安全监测提供了有效建议与防治手段。

300 MW CFB锅炉旋风分离器改造数值模拟研究

旋风分离器分离性能会显著影响循环流化床锅炉的运行。为解决某300 MW循环流化床锅炉旋风分离器分离器性能差的问题,基于欧拉-拉格朗日框架,使用UGNX12.0软件对该300 MW循环流化床锅炉的炉膛、旋风分离器、返料阀按照实际尺寸1∶1建立全回路几何模型,根据实际参数设置边界条件,并通过Barracuda软件进行数值模拟,分析旋风分离器烟道入口各参数(入口烟道高度、入口烟道宽度、入口下倾角大小及中心筒插入深度)对旋风分离器效率及压降的影响;综合考虑分离器的分离效率、压降以及磨损量,提出了2个改造方案。仿真结果表明:炉膛内压力模拟值与实际值的偏差均在5%以内,模拟结果较为精确;2个方案在各负荷下均能提升旋风分离器分离性能,方案1满负荷下效率相较于较改造前提升了0.260%,压降降低了13.1 Pa,方案2满负荷下效率相较于改造前提升了0.240%,压降降低了53.7 Pa;随着负荷降低,旋风分离器效率提升逐渐不明显,在300、260和160 MW负荷下,方案1分别提升0.263%、0.178%和0.023%,方案2分别提升0.243%、0.174%和0.020%。