Improvement of X-Band Polarization Radar Melting Layer Recognition by the Bayesian Method and ITS Impact on Hydrometeor Classification

Using melting layer(ML)and non-melting layer(NML)data observed with the X-band dual linear polarization Doppler weather radar(X-POL)in Shunyi,Beijing,the reflectivity(ZH),differential reflectivity(ZDR),and correlation coefficient(CC)in the ML and NML are obtained in several stable precipitation processes.The prior probability density distributions(PDDs)of the ZH,ZDR and CC are calculated first,and then the probabilities of ZH,ZDR and CC at each radar gate are determined(PBB in the ML and PNB in the NML)by the Bayesian method.When PBB>PNB the gate belongs to the ML,and when PBB<PNB the gate belongs to the NML.The ML identification results with the Bayesian method are contrasUsing melting layer(ML)and non-melting layer(NML)data observed with the X-band dual linear polarization Doppler weather radar(X-POL)in Shunyi,Beijing,the reflectivity(ZH),differential reflectivity(ZDR),and correlation coefficient(CC)in the ML and NML are obtained in several stable precipitation processes.The prior probability density distributions(PDDs)of the ZH,ZDR and CC are calculated first,and then the probabilities of ZH,ZDR and CC at each radar gate are determined(PBB in the ML and PNB in the NML)by the Bayesian method.When PBB>PNB the gate belongs to the ML,and when PBB<PNB the gate belongs to the NML.The ML identification results with the Bayesian method are contrasted under the conditions of the independent PDDs and joint PDDs of the ZH,ZDR and CC.The results suggest that MLs can be identified effectively,although there are slight differences between the two methods.Because the values of the polarization parameters are similar in light rain and dry snow,it is difficult for the polarization radar to distinguish them.After using the Bayesian method to identify the ML,light rain and dry snow can be effectively separated with the X-POL observed data.ted under the conditions of the independent PDDs and joint PDDs of the ZH,ZDR and CC.The results suggest that MLs can be identified effectively,although there are slight differences between the two methods.Because the values of the polarization parameters are similar in light rain and dry snow,it is difficult for the polarization radar to distinguish them.After using the Bayesian method to identify the ML,light rain and dry snow can be effectively separated with the X-POL observed data.

Microstructures and properties of the nitrided layers fabricated on titanium substrate by direct current nitrogen arc melting technique

The nitrided layers mainly containing TiN dendrites were fabricated by direct current nitrogen arc melting method. The test results show that the layers are harder and more resistant to wear than the titanium substrate. Arc traveling speeds and arc currents have an effect on both the microstructures and the properties of the layers. Decreasing the arc traveling speed or increasing the arc current can obviously enhance the hardness and the wear resistance of the nitrided layers.

Microstructures of surface modification layer on Q235 steel produced by laser melt injection of WC

WC powder was injected onto the surface of Q235 steel by laser melt injection (LMI). The influence of process parameters was studied. The microstructure and composition of the coatings were analyzed by SEM, XRD and EDS. The hardness and wear-resistant property of the coatings and Q235 steel were measured. The results show that LMI layer can be achieved only under the condition that process parameters meet the strict requirements. By optimizing the process parameter, excellent coatings can be acquired by injecting WC powder onto the surface of Q235 steel. The microstructure in the coatings is complex, which consists of WC, W2C and M6C(Fe3W3C-Fe4W2C) phases. The difference of Fe3W3C microstructure in different zones of the coatings is obvious. Both the compositions of the reaction layers around the particle and dendrite precipitation carbides in the upper coating are Fe3W3C. The average hardness of LMI layer is above HV 900, which is about four times that of Q235 steel. The friction coefficient of LMI layer is only one quarter that of the substrate, which indicates that the wear resistance of the coatings is enhanced sharply.

Process analysis of direct laser melting to fabricate layered hybrid beads

The successful fabrication of layered hybrid beads by DLM process is limited by dissimilar melting ranges of different powders.For the application of DLM process into manufacturing industries,target mechanical properties of final product must be achieved.Process analysis was performed for the DLM fabrication of layered hybrid beads by using stainless steel (SS 316L) and titanium powders.For the analysis of fabrication characteristics,single hybrid bead was formed using SS316L powder onto the base plate and then Ti powder was melted onto the previous melted layer.In addition,multi-layer hybrid beads were fabricated for the analysis of the layering effects between them.From these studies,the effects of the processing parameters,such as laser power,scan rate and scan line spacing on surface morphology were characterized and optimum processing conditions for the DLM fabrication of layered hybrid beads were developed.

FORMATION OF THE CRUSTAL MELTING LAYER AND ITS RELATIONS TO THE DEFORMATION OF CONTINENTAL CRUST:AN EXAMPLEFROM SOUTHEAST CHINA

Unlike the magma intrusion model,the in- situ melting hypothesis advanced in the lastdecade regards the upper crustas a closed system,and granite as the resultof the materialswithin system changing from order (protolith) to disorder (melts) and to new order(granite) with the variations of entropy of the system.The various geological and geochemi-cal data from the Mesozoic granitesof southeast China are explained logically and systemical-ly by the hypothesis,concluding that they should be originated from the melting of pro-toliths.According to the hypothesis,melts generated from in- situ melting are of layer- likewithin the crustand batholithsare the protruding parts of the uppersurface of the layer (de-fined as the Melting Interface,MI for short) .On the basis the author tries to discuss thesource of heatfor the Mesozoic crustal melting in southeast China.

Selective laser melting of Fe-Ni-Cr layer on AISI H13 tool steel

An attempt to fabricate Fe-Ni-Cr coating on AISI H13 tool steel was performed with selective laser melting.Fe-Ni-Cr coating was produced by experimental facilities consisting of a 200 W fiber laser which can be focused to 80 μm and atmospheric chamber which can control atmospheric pressure with N2 or Ar.Coating layer was fabricated with various process parameters such as laser power,scan rate and fill spacing.Surface quality and coating thickness were measured and analyzed.Three different surface patterns,such as typeⅠ,typeⅡand type Ⅲ,are shown with various test conditions and smooth regular pattern is obtained under the conditions as 10 μm of fill spacing,50-350 mm/s of scan rate and 40 μm of fill spacing,10-150 mm/s of scan rate.The maximum coating thickness is increased with power elevation or scan rate drop,and average thickness of 10 μm fill spacing is lower than that of 40 μm fill spacing.

贵州省不同强度区域性凝冻过程环流形势对比分析

利用贵州省84个气象站逐日观测资料以及再分析资料,对4种不同强度区域性凝冻过程进行对比分析。结果表明:500 hPa位势高度场上中高纬度的亚洲东部区域距平场呈现“+-”的分布或有切断低压分布,贝加尔湖至中国华北地区以经向环流为主;850 hPa风场上云南南部以南受偏南风和西南风控制,并且在江南至华南存在西南或西风急流,是4种不同强度凝冻过程中形势场共性特征。500 hPa高度场上中高纬度地区呈两槽一脊或一槽一脊分布;风场上850 hPa东北风回流和700 hPa西南急流形成上暖下冷的形势场,同时850 hPa形成稳定低层切变线;温度场上存在冷暖冷的夹心结构,近地面层0℃线维持在900 hPa以下,均是较强等级以上的区域性凝冻过程中形势场共性特征。而对于一般性区域性凝冻过程,500 hPa位势高度场上呈多槽脊分布,风场上是否存在东北风回流和低层切变线,温度场上是否存在冷暖冷的夹心结构以及近地面层0℃线位置等特征均不统一。温度剖面图上,当近地面层0℃线位置最低时或出现冷暖冷的夹心结构时段与凝冻过程影响范围最广、灾情最重的时间段对应。

激光熔凝处理对P20钢组织及性能的影响

目的提高P20模具钢的表面硬度和耐磨性能。方法采用激光熔凝技术对P20模具钢表面进行强化处理。通过硬度梯度检测和摩擦磨损测试,分别评价熔凝层的硬度分布特征和耐磨性能,并通过光学显微镜和扫描电子显微镜对熔凝层及磨痕形貌进行分析。结果使用激光输出功率为500W、光斑直径为2.5mm、聚焦透镜距离为40 mm、扫描速度为6 mm/s、搭接率为45%、氮气保护的激光熔凝工艺所得熔凝层的组织细小,无脱碳、畸变、裂纹等缺陷,熔凝处理质量高。熔凝过程中单道激光熔凝层呈半椭圆形分布,最大深度为610~620μm。熔凝处理后表面硬度提升显著,熔凝层的硬度分布与熔凝层的区域位置有关,具有较高硬度且硬度保持基本稳定的熔凝层深度约为400μm;单道激光熔凝层最高硬度可达460~480HV,重叠影响区即双熔凝区的最高硬度在540~560HV之间,即熔凝层硬度普遍较基体硬度提高了60%以上。此外,P20模具钢经过激光熔凝处理后耐磨性能提升明显,其平均摩擦因数约为0.85,熔凝处理的磨损失重较未处理的试样减少了约61%,其磨损机制主要表现为磨粒磨损和少量的黏着磨损或剥落脱离。结论激光熔凝处理能够显著提高P20模具钢的表面硬度和耐磨性能,试验采用的激光熔凝工艺可在P20钢表面获得硬度较高且稳定可靠的熔凝层深度在400μm左右,能将P20模具钢的表面硬度及耐磨性提高60%以上。

河北省一次层状云冰相粒子及融化层微物理特性研究

层状云中冰粒子、融化层及以下粒子微物理特性演变规律的科学认识对于中国云降水参数化、降水预报及人工影响天气研究具有重要意义。利用2019年8月24日河北省一次层状云飞机观测资料,分析云中负温层、融化层及以下粒子群微物理特性的演变。研究表明,云中负温层冰相粒子以聚合体为主,部分区域存在霰粒子。云中冰相粒子通过凇附、碰连和贝吉龙过程增长。相对来说,上升气流较强及相对湿度较高云区的冰相粒子数浓度较高、粒子谱较宽。融化层中,中等大小粒子数浓度存在增大趋势,说明融化层中不同粒径冰相粒子的融化速率存在差异。研究发现,高相对湿度区(RH≥95%)粒子融化速率较低相对湿度区(RH<95%)快,低相对湿度区中表面融化的粒子蒸发吸收潜热,使环境温度降低,减缓粒子融化速率。融化层高相对湿度区降水粒子谱分布的截距大于低相对湿度区,斜率与低相对湿度区接近。融化层降水粒子负指数谱分布的截距与斜率均大于负温层,0℃层高度以下HVPS探测到的粒子谱分布参数N_(0)与λ呈正相关,线性函数能较好地拟合二者的关系。对于D_(max)大于1000μm的降水粒子,谱参数λ与D_(max)呈负相关,幂函数能较好地拟合二者的关系。数值研究发现,0℃层之下云内存在混合相态粒子,观测和模拟结果均发现0℃层之下中等大小的粒子数浓度更高。分档方案数值模拟得到的降水粒子平均谱的截距与观测资料一致,但斜率大于观测结果。研究结合飞机观测资料与模式,对云内融化层中粒子微物理特性有了更加深入的认识。

共和盆地深部构造格架及其对干热岩热源的影响

干热型地热资源作为一种新型的地热资源形式,是一种发展前景广阔的新型清洁能源。青海省共和盆地位于青藏高原东北缘,区域地质活动丰富,为干热岩的形成创造了良好的条件。因此,研究共和盆地构造格架与干热岩成热模式,对地热资源勘探具有重要意义。笔者基于重力异常归一化总水平导数垂向导数技术(NVDR-THDR)和重磁异常融合方法划分了共和盆地的断裂构造格架,共识别深大断裂20条,有9条是前人未识别断裂。其中,F1-15推断断裂作为共和盆地东西分界断裂,对共和盆地干热岩成因具有重要意义。基于超低频大地电磁测深剖面及重力异常归一化总梯度的反演结果显示,共和盆地地幔物质向上运移并加热和侵蚀岩石圈底部,导致岩石圈底部发生熔融减薄。盆地东部和西部均存在自青海南山及贵南南山向盆地的逆冲推覆构造,但深部地质结构存在明显差异。盆地西部地质体挤压变形程度强于盆地东部,西部盆地深部地质体密度结构呈“八”字型特征,表现为压陷盆地的特征,断裂发育较少;而东部盆地大量发育深大断裂,为深部的热源物质和热量提供了传输通道。因此,认为共和盆地干热岩热源以地幔热流传导供热和壳内部分熔融层供热为主,放射性元素衰变生热为辅,盆地东部相较于西部更具备干热岩成藏条件。

毫米波雷达在台风外围云系研究中的应用

为评估台风条件下毫米波雷达的探测表现,利用上海2018年和2019年4个台风影响期间的毫米波雷达数据,结合雨滴谱仪、静止卫星、S波段天气雷达等资料,探讨了利用毫米波雷达研究台风外围云系的可能性。结果表明:毫米波雷达探测台风外围区域具有良好的性能,对于云降水结构的垂直探测具有一定应用潜力;在降水强度低于5 mm·h^(-1)时雷达对于云顶高度的探测较为准确;提出一种融化层亮带判别方法,亮带识别结果与探空观测一致。对比毫米波雷达与S波段天气雷达降水强度反演,结果显示利用毫米波雷达衰减特征能够实现降水强度廓线的反演,但需要对存在显著雨滴碰并增长的降水进行识别并订正,可为毫米波雷达探测台风外围云系提供参考依据。

钨丝增强非晶复合材料弹芯高速侵彻熔化快凝层研究

对钨丝增强非晶复合材料弹芯高速侵彻靶板时产生的熔化快凝层进行了扫描电镜观察、能谱分析和X衍射分析,研究了弹靶作用下界面温升机理。结果表明,与传统钨合金相比,钨丝增强非晶复合材料具有更好的“自锐”效应,侵彻能力得到了有效提升;熔化快凝层生成温度应高于1670℃,高温效应有助于提升其侵彻能力;熔化快凝层成分包含靶板材料(Fe、Cr、Mn)和弹芯材料(Zr、Ti、Cu、Ni、W)。其中W的原子分数仅有3.15%,且W元素主要以熔化或熔解方式存在于熔化快凝层中;非晶复合材料弹芯侵彻靶板时反喷物中存在TiW相。弹靶作用界面巨大的冲击导致弹靶材料受到冲击压缩并发生塑性变形、断裂等,引起弹靶作用界面温度急剧升高。

COPRA双层熔池湍流模型优选

为了预测下封头内双层熔池的流动和传热过程,基于不同湍流模型,同时采用凝固熔化模型对堆芯熔池研究装置(corium pool research apparatus,COPRA)双层熔池实验进行计算流体力学(CFD)数值模拟,通过数值计算获得准稳态下熔池的温度、沿壁面的热流密度与内壁面壳层的分布,将模拟结果与实验值进行比较,评价不同湍流模型的适用性和准确性,并进行湍流模型优选。结果表明,壁面模化大涡模拟(WMLES)湍流模型对下封头内双层熔融池流动与传热模拟的准确性和适用性最好;基于WMLES湍流模型,氧化层温度随着熔池高度增大而增大,氧化层上部存在强烈的湍流,在熔池底部的壳层最厚。

日钢高炉高铝矿冶炼的优化措施

日钢高炉高铝矿冶炼过程中,面临烧结矿的软熔性能变化大,炉渣熔化温度及黏度上升等问题。为此,采取一系列优化措施:①不同矿种优化搭配,烧结矿加块矿,槽下高、低碱度烧结矿块矿混匀,改善炉料软熔性能;②在厚焦层基础上探索合适矿层厚度,适当减薄矿层,炉腰矿层厚度维持在0.35m左右,以利于改善矿石熔化性,增强炉况抗波动能力;③提镁降钙,优化渣相,二元碱度控制在1.25,(MgO)<15%,镁铝比维持在0.75左右,保证炉渣的流动性和稳定性。采用以上措施后,日钢高炉炉况顺行,抗波动能力增强,燃料消耗长期维持在较低水平。

滑动电接触界面沉积层对电枢熔化的抑制效应研究

维持良好的滑动电接触性能是实现电磁轨道发射高频率和高效率工作的重要保证。重复发射时,轨道表面沉积层影响电枢表面熔化特性,进而改变接触状态,从而影响滑动电接触性能,因此有必要对沉积层作用下的电枢熔化特性进行分析。首先,通过分析沉积层受热过程,建立了沉积层熔化判断模型,并提出沉积层熔化判断条件;其次,基于沉积层熔化特性,建立了沉积层作用下的电枢熔化磨损计算模型,分析不同电流条件下沉积层熔化特性发现,载流量越大,沉积层熔化范围越大,并且启动低速阶段沉积层能够发生熔化,高速阶段沉积层不容易发生熔化;最后,开展重复发射试验,通过理论分析结合试验验证对电枢熔化的抑制特性进行研究。结果表明:沉积层厚度随着发射次数逐渐增加,沉积层全部熔化状态下,电枢最大熔化深度随发射次数呈逐渐减小的趋势。模型计算结果与试验测量结果变化趋势相同,说明沉积层熔化对电枢熔化有抑制效应。该文所建立模型及分析结果对深入理解重复发射时枢轨界面熔化磨损机理、提高滑动电接触性能具有重要意义。

环境湿度影响人工催化消减雨效果的数值模拟研究

利用耦合了碘化银催化过程的WRF(Weather Research and Forecast)模式,对2014年8月16日南京青奥会开幕式当天实施的人工催化作业开展数值模拟,评估催化效果并通过敏感性数值试验调查低空环境干层对催化效果的影响。结果表明,催化作业产生了减雨效果,低空干区的存在是影响催化效果的关键。当低空存在深厚的相对湿度很小的干层时,催化导致减雨效果;当增加低层的相对湿度即弱化低空干层,催化减雨效果减弱甚至出现增雨效果。催化增强了雪的形成过程但减弱了雪的增长过程尤其是凝华增长,导致雪粒子浓度增加但粒径减小,融化产生更多的小雨滴增强了蒸发过程,最终导致地面降水减少。

一种高压压合的高频PCB层偏改善研究

对一种结构为“芯板+半固化片(PP)+芯板”的4层高频印制电路板(PCB)进行研究,鉴于其PP流动性较低,采用高压的方式压合,会导致严重的层间偏移问题。通过不同的排板方式,包括PIN钉定位压合工艺(PIN+LAM)、电磁热熔+PIN和铆钉+PIN 3种方法,研究不同排板方式对层偏的影响,结合层偏数据从原理上对不同的排板方式进行分析论证,为改善类似PCB层偏问题提供理论支持。

某电站锅炉水冷壁补焊层裂纹原因分析

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