Characteristics of non-thermal AC arcs in multi-arc generator

To obtain large-volume non-thermal arc plasma(NTAP), a multiple NTAP generator with three pairs of electrodes has been developed. The arc plasma characteristics, including dynamic process, spatial distribution, and rotation velocity in the discharge zone, were investigated by high speed photograph and image processing methods. The results showed that the dynamic behaviors and spatial distribution of the arc plasma were strongly related to the electrode configuration.A swirl flow of multi-arc plasma was formed by adjusting the electrode configuration, and a steady luminance area was clearly observed in the center of the discharge zone. Moreover, the size of the luminance area increased by decreasing the gas flow rate. The electrical connection in series could be formed between/among these arc columns with their respective driving power supplies in the multi-arc dynamic evolution process. An approximately periodical process of acceleration and deceleration of the arc rotation velocity was observed in the multi-arc generator with swirl flow configuration. In general, the mean velocity of arc rotation was higher in the multi-arc generator with swirl flow configuration when a pair of electrodes driven by a power supply were opposite to each other rather than adjacent.

Structure and Tribological Properties of CrTiAlN Coatings Deposited by Multi-Arc Ion Plating

CrTiAIN coatings were prepared by using a home-made industrial scale multi-arc ion plating system. The coatings were found to be composites of face-center-cubic CrN and TiN. The surface roughness, microhardness, and tribological properties of the films were significantly affected by the nitrogen pressure and dc-pulsed bias voltage applied to the substrate. The CrTiA1N coatings with the smoothest surfaces were obtained at optimum conditions of nitrogen pressure of 5.0 Pa and bias voltage of -200 V. The samples were found to exhibit a hardness of 2900 HV0.05 with an average friction coefficient of 0.16 and wear rate of 1.5× 10^-16 m^3/N.m against cemented carbide.

Dynamic characteristics of multi-arc thermal plasma in four types of electrode configurations

The enhanced volume of thermal plasma is produced by a multi-arc thermal plasma generator with three pairs of discharge electrodes driven by three directed current power suppliers.Combined with a high-speed camera and an oscilloscope,which acquire optical and electric signals synchronously,the dynamic behavior of different kinds of multi-arc discharge adjusted by the electrode arrangement is investigated.Also,the spatial distributions and instability of the arc discharge are analyzed in four electrode configurations using the gray value statistical method.It is found that the cathodic arcs mainly show a contracting state,while the anodic arcs have a trend of transition from shrinkage to a diffusion-like state with the increase of the discharge current.As a result of the adjustment of the electrode configuration,a high temperature region formed in the center of the discharge region in configurations of adjacent electrodes with opposite flow distribution and opposite electrodes with swirl flow distribution due to severe fluctuation of arcs.The discharge voltage rises with increased discharge current in this novel multi-arc plasma generator.It is also found that anode ablation mainly occurs on the conical surface at the copper electrode tip,while cathode erosion mainly occurs on the surface of the inserted tungsten and the nearby copper.

EXPERIMENTAL STUDY ON SUPERFICIAL COAT OF GEARS OF NITRIDED 32Cr2MoV COATED WITH TiN FILM BY MULTI-ARC ION PLATING

After 32CrMoV is selected to manufacture nitrided gears coated with TiN by multi-arc ion plating, all of these uncoated gears and coated gears run in the gearbox under the same initial conditions so as to compare their difference concerning properties and microstructure. Experiment results indicate that tooth surface of the coated-TiN gears does not suffer surface abnormalities in meshed zone. Instead, the gears with nitrided case exhibit an abrasion mark on the meshed zone of tooth surface, which results in more weight loss of nitrided gears. The morphology of the surface suggests TiN film with more than 2 000 HV is so dense and smooth that coated-TiN gears have higher wear resistance compared with the uncoated gears. The microstructure of coated-TiN gears is finer, hardness is higher and its distribution of coated-TiN gears is more reliable than uncoated ones, which makes nitride layer combined with TiN film tightly. Consequently, the wear-resistance of gears has been dramatically promoted.

Wear-resistance and anti-scuffing of multi-arc ion plating molybdenum films

The multi-arc ion plating technology was employed to prepare the molybdenum films with thickness of 3 μm on the AISI 1045 steel. The wear and scuffing tests were carried out on the ball-on-disc tester. AFM and SEM equipped with EDS were adopted to observe and analyze the morphologies and element compositions of surface,cross-section and worn scar of the Mo film. The phase structure was studied by XRD and the bonding strength between Mo film and substrate was measured by scratching tester. The tribological experiments show that the Mo film possesses a good wear-resistance and an excellent anti-scuffing property. The failure mechanism of Mo film under extreme condition is flaking off.

STUDIES OF Cr-O THIN FILNS DEPOSITED BY MULTI-ARC ION PLATING

This paper presents the formation of Cr-O thin films on an iron substrate by multi-arc ion plating, which are intended to be used as a thermal radiation absorbent in electronic vacuum devices. Only oxygen was used as a reaction gas during deposition, the Cr-O thin film, must have high adhesion and low outgassing rate. The scratch test shows that the critical load, for an applicable Cr-O thin film deposited in oxygen atmosphere alone at a pressure of 8×10-1 Pa, was as high as 6kg.

Structure and wear resistance of TiN and TiAlN coatings on AZ91 alloy deposited by multi-arc ion plating

In order to investigate the microstructure of TiN and TiAlN coatings and their effect on the wear resistance of Mg alloy, TiN and TiAlN coatings were deposited on AZ91 magnesium alloy by multi-arc ion plating technology.TiN and Ti70Al30N coatings were prepared on the substrate,respectively,which exhibited dark golden color and compact microstructure.The microstructures of TiN and Ti70Al30N coatings were investigated by X-ray diffractometry(XRD)and scanning electron microscopy(SEM).The micro-hardness and wear resistance of TiN and Ti70Al30N coatings were investigated in comparison with the uncoated AZ91 alloy. The XRD peaks assigned to TiN and TiAlN phases are found.The hardness of TiN coatings is two times as high as that of AZ91 alloy, and Ti70Al30N coating exhibits the highest hardness.The wear resistance of the hard coatings increases obviously as result of their high hardness.

STUDY ON HIGH TEMPERATURE PERFORMANCES OF MCrAlX COATINGS DEPOSITED BY MULTI-ARC ION PLATING

NCoCrAlSiYHf and CoNiCrAlTaY coatings which belong to protective Al 2O 3 scale forming type were deposited by multi arc ion plating technique . The effect of deposition process parameters on qualities of the coatings was discussed. The high temperature oxidation performances isothermal oxidation with 950℃ / 500h and 1100℃ / 100h were studied. And also, the hot corrosion performances at 700℃ and 800℃, with molten mixed salt composed of 75%wt Na 2SO 4 and 25%wt NaCl were investigated. Then the high temperature protection decaying mechanisms were proposed.

MULTI-ARC BASIN SYSTEM OF THE KUNLUN OROGENIC BELT AND PAN-CATHYSIAN CONTINENTAL ACCRETION

After Rodinia supercontinent was disintegrated in Late Proterozoic, an ocean, namely, Tethys Ocean, occurred between Gondwana continental group and Pan-Cathaysian continental group from Late Proterozoic to Mesozoic. From Early Paleozoic to Mesozoic, Tethys Ocean was subducted toward Pan-Cathaysian block group, which results in backarc expansion, arc-land collision and forearc accretion. When the backarc basin expands and reaches the small oceanic basin, ophiolite melange will be generated. As accretion had already occurred in the south of the continental margin in the earlier stage, the succeeding backarc expansion and the frontal arc position were migrated toward south correspondingly. Therefore, multiple ophiolite belts and magmatic rock belts occurred, and show a trend of decreasing age from north toward south. As the continental margin was split and migrated toward south and reached a high latitude position, i.e., with the shortening and subduction of oceanic crust, the sedimentary bodies at high latitude was accreted continuously toward low latitude area together with the formation of oceanic island, mixing of cold-type and warm-type organism was generated. Moreover,blocks split and separated from Pan-Cathaysian or Gondwana continental group cannot traverse the oceanic median ridge and joins with another continental block. As a result, the Kunlun belt on the SW margin of the Pan-Cathaysian land was resulted from the multi-arc orogenesis such as the backarc seabed expansion, arc-arc collision, arc-land collision oceanic bed, and the continuous southward accretion process.

自适应模糊神经网络多信息融合串联型电弧故障检测方法

针对低压交流串联电弧故障因其特殊性难以识别的问题,在实验室建立了实验平台,采集不同负载下的正常和电弧故障的电流波形数据,提出一种自适应模糊神经网络(adaptive neuro fuzzy inference system,ANFIS)多信息融合串联型电弧故障检测方法,通过多层次特征参数提取,对自适应模糊神经网络进行训练、测试。结果表明,该方法可以有效地克服反向传播(back propagation,BP)神经网络故障诊断中收敛速度慢、误差精度大的缺点,得到更为精准、理想的诊断结果。

空间燃料电池金属钛表面复合涂层制备与性能研究

金属Ti因其密度小(仅为不锈钢的0.6倍)和比强度高等特点,是轻量化空间燃料电池金属板材料的首要选择,但其在弱酸性环境中长时间工作容易被腐蚀。为了改善金属Ti双极板耐蚀性,采用多弧离子镀技术在金属Ti表面制备了由Ti过渡层及TiN表层构成的Ti/TiN复合涂层,研究制备工艺参数对Ti/TiN复合涂层微观结构及力学、电化学性能的影响规律。利用场发射扫描电子显微镜(SEM)分析涂层的微观形貌,利用X射线衍射仪分析涂层的相组成,利用纳米压痕仪评价涂层的力学性能,利用电化学工作站评价涂层在模拟质子交换膜燃料电池(PEMFC)阴极工作环境下的耐蚀性。结果表明:制备工艺参数优化后的Ti/TiN复合涂层具有优异的表面质量和良好的耐蚀性,腐蚀电流密度为6.383μA/cm^(2),是金属Ti腐蚀电流密度的0.6倍,Ti/TiN复合涂层显著提高了金属Ti的耐蚀性,可为空间燃料电池金属双极板表面改性提供技术支持。

2Cr13钢离子渗氮和WCrAlTiSiN离子镀复合处理及电化学行为

马氏体不锈钢的常规表面改性方法基本局限在单一化学热处理或镀膜,对表面性能的提升有限。对2Cr13不锈钢进行离子渗氮与多弧离子镀WCrAlTiSiN纳米多层涂层复合强化处理,研究其在天然海水环境中的耐腐蚀性能。采用不同的表面强化工艺,即未处理(Untreated)、低温渗氮处理(LPN)、高温渗氮处理(HPN)、单一镀膜处理(Coating)、低温渗氮+镀膜处理(LPN+C)和高温渗氮+镀膜处理(HPN+C)。采用X射线衍射、光学显微镜、透射电子显微镜和维氏硬度计对不同样品的组织结构、化学成分和硬度等进行表征。采用电化学阻抗法和动态电位极化法对2Cr13在天然黄海海水中的电化学行为进行测试。试验结果表明:WCrAlTiSiN涂层可在一定程度上提升腐蚀性能,但是溶液中的Cl^(−)通过较薄单一涂层的缺陷侵入基体。LPN样品因渗氮层的存在提升了一定的耐腐蚀性能,而HPN样品因为渗氮温度过高而导致CrN大量析出,使得样品表面出现“贫Cr”现象,耐腐蚀性能下降。复合处理样品的渗氮层-WCrAlTiSiN涂层可形成保护屏障,有效阻止电荷转移和电流从阳极流向阴极,提高2Cr13钢在海水环境中的耐腐蚀性能。通过离子渗氮-多弧离子镀WCrAlTiSiN纳米涂层复合强化方法可有效提升马氏体不锈钢在海水中的耐腐蚀性能。

High temperature oxidation resistance of CrN/(Ti,Al,Zr,Cr)N bilayer films deposited by multi-arc ion plating

CrN/（Ti,Al,Zr,Cr） N bilayer films were successfully deposited on cemented carbide（ WC-8% Co） substrates by multi-arc ion plating process using two Ti-Al-Zr alloy targets and one pure Cr target. As a result of bilayered structure and addition of alloying elements（ e. g. Al and Cr）,the films exhibited excellent high temperature oxidation resistance under both short-term isothermal（ up to 800 ℃） and long-term cyclic（ up to 600 ℃） exposure conditions. Combined with pre-established outstanding tribological properties（ e. g. maximum hardness of 4 000HV0. 01 and maximum adhesion strength over 200 N）,these observations make such films quite a promising candidate to extend the cutting tool life span and boost the performance in high-productivity,high-speed and high-feed cutting or in dry machining conditions.

镍铁矿热炉熔炼过程中的多物理场耦合

建立了一个三维多物理场耦合模型,揭示矿热炉运行过程中电磁、温度、化学反应间的相互作用机理该模型不仅将电磁理论、多相流动、传热、还原反应整合到统一的计算框架中,还通过用户自定义函数(UDFs)将电弧热、焦耳热和化学反应热加入到能量方程源项中研究了不同电极插入深度下的熔池温度分布,并分析了熔池不同位置处的还原反应量结果表明:随着电极插入深度的增加,熔池温度不断升高在磁场作用下,熔池底部温度分布均匀熔池区内氧化镍比铁氧化物还原更彻底,而坩埚区内镍铁氧化物均被彻底还原当电极插入深度为21m和22m时,有助于提高炉料温度,适用于升温阶段当电极插入深度为20m时,炉料温度和铁氧化物的还原量更为均衡,适用于稳定熔炼阶段。

方位多波束弧形阵列SAR成像方法研究

弧形阵列合成孔径雷达(Synthetic Aperture Radar,简称SAR)是一种广域观测的新体制微波成像系统,相比于线性阵列合成孔径雷达,弧形阵列SAR能够有效克服常规成像雷达前视、侧视、下视等观测视角单一的问题,弥补了常规成像模式的不足。方位多波束技术是星载合成孔径雷达系统获取高分辨宽覆盖测绘能力的重要技术途径。本文首先构建了多波束弧形阵列SAR系统的方位向多通道信号模型,并通过传统的方位多通道重建方法进行成像仿真,成像结果出现虚假目标,由于传统的多通道重建方法适用于大多数线性阵列,所以通过分析回波斜距的数学几何模型推导出了多波束弧形阵列SAR相比于线性阵列SAR多了一个附加相位,与弧形阵列天线结构相结合,附加相位由子孔径角度引起,因此方位多通道回波数据中相位误差是由多通道弧形阵列SAR的子孔径角度引起,从而导致多通道不均衡,所以传统的多通道重建方法不能够直接用于弧形阵列SAR的成像处理中,为了实现弧形阵列SAR系统的静止目标聚焦成像,提出了适用于弧形阵列SAR系统的方位多通道重建方法,在进行多通道重构和合并之前,对方位通道间的附加相位进行补偿,避免方位欠采样,然后根据弧形阵列方位多通道脉冲响应重构方位多通道数据,该方法可以很好的抑制了虚假目标,最后通过仿真实验验证了该方法的可行性。

蒙特卡罗模拟机架和多叶准直器误差对旋转放疗剂量的影响

研究在常规直线加速器实施快速旋转调强放疗(IMAT)治疗过程中,内置多叶准直器(MLCs)和机架旋转误差对放疗剂量的影响。随机选择7例脑胶质瘤患者,并在常规直线加速器Varian 23EX上设计IMAT计划,对MLCs和机架分别引入不同大小误差。通过不一致指数和剂量体积直方图(DVH)评估引入误差对IMAT放疗临床剂量的影响。对于单侧MLCs随机误差,当MLCs随机误差达2 mm时计划靶体积平均剂量(PTV-Dmean)增加了约2.7%。当MLCs一侧外扩MLC-1 mm、MLC-2 mm、MLC-rnd时导致其PTV-Dmean平均偏差分别为1.12%、2.15%和1.15%,晶体的平均剂量偏差分别为5.25%、9.97%和5.49%。对于MLC两组叶片分别偏移±2 mm时导致PTV平均剂量的最大偏差为0.8%,晶体和脑干的最大剂量和平均剂量分别增加了11.4%、15.8%和1.99%、1.07%。引入机架角度误差,计划靶体积最小剂量(PTV-Dmin)和PTV-Dmean最大剂量分别降低了2.75%和0.35%。导致危及器官(OAR)的DVH的剂量学偏差变化较大,尤其对于晶体当机架偏差为(−2°)时晶体的最大剂量和平均剂量分别偏高达16.9%和38.5%。机架和MLCs误差对OAR的受量均产生较大剂量偏差。随机误差导致的MLCs剂量偏差受叶片位移误差的大小以及在特定弧段处的射束子野权重影响,MLCs误差(−2 mm或+2 mm)时产生的剂量偏差最大。机架旋转误差对靶区PTV剂量分布的影响不大,但是对于OAR会产生较大的剂量偏差。

多向钢节点电弧增材制造摆动工艺参数优化

基于二次回归通用旋转设计试验方法对多向钢节点电弧增材制造摆动工艺参数进行优化。建立了摆动工艺参数送丝速度、焊枪移动速度及单边摆动幅度与堆积金属宽度和高度之间的3D响应模型,并分析验证了模型的可靠性。研究了单个摆动工艺参数和摆动工艺参数交互作用对堆积金属宽度和高度的影响。利用建立的3D响应模型优化了六向钢节点电弧增材制造摆动工艺参数,采用优化的摆动工艺参数电弧增材制造六向钢节点,制造的六向钢节点平均尺寸偏差为±1.30mm,成形精度较高。

Oxidation behavior of TiAlZrCr/(Ti,Al,Zr,Cr)N gradient films deposited by multi-arc ion plating

The two Ti-Al-Zr targets and one pure Cr target were used to prepare the TiAlZrCr/（Ti, Al, Zr, Cr）N gradient films on high speed steel （WlSCr4V） substrates by multi-arc ion plating technique. Short-term isothermal （at 600 ℃, 700 ℃, 800℃ and 900 ℃ for 4 h） and long-terra cyclic （at 700℃ and 800℃ for 100 h） high temperature oxidation behavior of the gradient films were studied. Then the oxide scales formed on the film specimens were characterized by scanning electron microscopy （SEM）, energy dispersion X-ray spectroscopy （EDS） and X-ray diffraction （XRD）. It was showed that, under short-term isothermal condition, the high temperature oxidation resistance of the gradient film was excellent up to 800 ℃ and an oxide scale comprising TiO2 was observed. On the other hand, under long-term cyclic high temDerature condition, the oxidation resistance of the gradient film was excellent at about 700 ℃.

MLC运动误差对不同射野面积的鼻咽癌容积调强计划的影响

目的 研究多叶准直器运动误差(Multi-Leaf Collimator Error,MLC_(error))对不同射野平均面积(Mean Aperture Area,MAA)的鼻咽癌容积调强的影响。方法 选取30例鼻咽癌患者为研究对象,每例患者的原始计划导出后使用Python编译,依据不同的MLC_(error)制作6组模拟计划(±0.2 mm、±0.5 mm和±1.0 mm)。对比原始计划与模拟计划的剂量学参数和验证通过率,分析MLC_(error)和MAA对计划验证的影响。其中,将鼻咽肿瘤计划靶区(Planning Target Volume,PTV)与颈部转移淋巴结肿瘤靶区通过布尔运算整合为PTV69。结果 随着MLC_(error)的变化(-1~1 mm),PTV69、原发灶高危亚临床靶区和中危亚临床靶区的剂量梯度分别为6.1、6.0、6.3%/mm(P<0.05);危及器官(Organ At Risk,OAR)的剂量梯度均高于靶区剂量梯度。脊髓、脑干、左侧腮腺、右侧腮腺、口腔和喉的剂量梯度分别为10.6、10.5、12.3、12.0、8.1、11.2%/mm(P<0.05)。在对射野面积、MLC_(error)及验证通过率关系的研究中发现,不同MAA计划的验证通过率差异随MLC_(error)的增加而增大;当MLC_(error)误差达到±1.0 mm时,不同MAA计划的验证通过率差异最大(51.7%~90.2%)。结论 相较于靶区,控制MLC_(error)更有利于OAR的保护。对于鼻咽癌等复杂的放疗计划,建议将MLC_(error)精度控制在0.5 mm以内并降低小子野使用,以保护危及器官,保证计划执行的精确度。