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.

Identification of structural entities in NdF_3-LiF melts with cryoscopic method

Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculations,NdF4- was identified as the most likely Nd-F entity in the melts in which the mole fraction of NdF3 was lower than 20%,considering only one single Nd species in the melt,and which was formed in accordance with Temkin model or Flood model.Then,activities of different components in the melts were researched.The results show that activity of LiF decreases,and that of NdF3 increases with increasing the mole fraction of NdF3.The value of activity coefficient of NdF3 is higher than 1,and that of LiF is lower than 1.

Preparation of AZ91D magnesium alloy semi-solid billet by new strain induced melt activated method

New strain induced melt activated (new SIMA) method for preparing AZ91D magnesium alloy semi-solid billet is introduced by applying equal channel angular extrusion into strain induced step in SIMA method, by which semi-solid billet with fine spheroidal grains and average grain size of 18 μm can be prepared. Furthermore, average grain size of semi-solid billet is reduced with increasing extrusion pass of AZ91D magnesium alloy obtained in ECAE process. By using semi-solid billet prepared by new SIMA, thixoforged magazine plates component with high mechanical properties such as yield strength of 201.4 MPa, ultimate tensile strength of 321.8 MPa and elongation of 15.3%, can be obtained.

Preparation of Thermosensitive Microcapsules Containing Water Soluble Powder by Melting Dispersion Cooling Method

It was tried to prepare the thermosensitive microcapsules containing the water soluble solid powder by the melting dispersion cooling method and to establish the optimum preparation conditions. As a model water soluble solid powder, sodium hydrogen carbonate was adopted in order to generate carbon dioxide gas and as a thermosensitive shell material, olefin resin with the melting point of ca. 40°C was used. In the experiment, the concentration of olefin resin in the shell material solution was mainly changed together with the concentrations of the oil soluble surfactant species and the α-tocopherol as a modifier of shell. Addition of α-tocopherol into the shell material solution could prevent the core from breaking away during the microencapsulation process and result in the higher microencapsulation efficiency, because the dispersion stability of solid powder in the shell material solution could be increased due to the increase in affinity between the shell material solution and solid powder. Also, the microencapsulation efficiency increased with the concentration of olefin resin, became maximum at 50 wt% and then, decreased. The microcapsules were found to begin melting at 36°C and to generate carbon dioxide gas.

Ultravilolet-radiation-induced graft polymerization of acrylamide onto the melt-blown polypropylene filter element by dynamic method

By dynamic method under UV irradiation, commercial melt-blown polypropylene （PPMB） filter element was modified with acrylamide （AAm） using benzophenone （BP） as initiator. Attenuated total reflection-Fourier transform infrared spectroscopy and scanning electron microscope verified that polyacrylamide chain was grafted on the fiber surface of PPMB filter element. Elemental content analysis with energy dispersive X-ray of fibers revealed that the polymerization content in the inner part of filter element was relatively higher than that in the outer. Degree of grafting changed with initiator concentration, monomer concentration, reaction temperature and reached 2.6% at the reaction condition： CBp=0.06 mol/L, CAAm=2.0 mol/L, irradiation time： 80 min, temperature： 60℃. Relative water flux altered with the hydrophilicity and pore size of filter element. In the antifouling test, the modified filter gave greater flux recovery （approximately 70%） after filtration of the water extract of Liuweidihuang, suggesting that the fouling layer was more easily reversible due to the hydrophilic nature of the modified filter.

STUDY ON SLOW-RELEASE CHARACTERISTICS OF MICROCAPSULES WITH EMULSION NON-SOLVENT ADDITION METHOD

An O / W emulsion non-solvent addition method was used to prepare ethyleellulose (EC) microcapsules of water soluble pharmaceutical (theophylline). The solvent and non-solvent reagents used in this work were toluene and cyclohexane. The effects of polymer concentration, core wall ratio and particle size on the kinetics as well as the dissolution rate of the drug were investigated. The results show that the dissolution rate increases with the increasing of polymer concentration and core wall ratio. The release of microcapsules prepared with different procedures can be selectively profiled with first order and Higuchi matrix kinetic models.

A Data Treatment Method of Carbon Saturated Solubility in Fe-C-Cr Melt

Based on the current situation of studying the thermodynamic property of Fe-C-Cr melt using the carbon saturated solubility, an experimental data treatment method of the carbon saturated solubility was put forward. With this method a linear relationship ex- pression of the carbon saturated solubility in Fe-C-Cr melt was obtained, which intercept is dependent on temperature and independent of third component [Cr], but which slope is dependent on third component [Cr] and independent of temperature. Through this expression activity interaction coefficients at different temperatures were calculated and the relationship between activity interaction coefficients and temperature is also obtained.

Structural and electrical characterization of Cu_(2)ZnSnS_(4) ingot material grown by melting method

In this work,a Cu_(2)ZnSnS_(4)(CZTS)ingot is grown via a melting method,then cooled;the resulting molten stoichiomet-ric mixture is sealed off in a quartz ampoule under vacuum.The CZTS powder chemical composition analyses are determined us-ing energy dispersive spectroscopy,and revealing the slightly Cu-rich and Zn-poor character of the ingot.Powder X-ray diffrac-tion analysis reveals a crystalline structure with a kesterite phase formation,and a preferred orientation of(112)plane.The lat-tice constants of the a-and c-axes,calculated based on the XRD analyses,are a=5.40Åand c=10.84Å.Based on Hall measure-ments at room temperature,we find that the crystal exhibits p-type conductivity,with a high concentration of 1018 cm^(-3),a res-istivity of 1.7Ωcm,and a mobility of 10.69 cm^(2)V-1s-1.Activation energies are estimated based on an Arrhenius plot of conductiv-ity versus 1/T,for a temperature range of 80-350 K,measuring 35 and 160 meV in low-and high-temperature regimes,respect-ively,which is attributed to complex defects(2CuZn+SnZn)and antisite defects(CuZn),respectively.The observed scattering mech-anisms are attributed to ionized impurities and acoustic phonons at low and high temperatures,respectively.The extracted band-gap is 1.37 eV.

Preparation of Microcapsules Containing Aqueous Solution of Azur B with Melting Dispersion Cooling Method and Application to DNA Amplification Detector

Microcapsules containing the aqueous solution of Azur B of a water soluble dye were prepared with the melting dispersion cooling method and applied to the amplification detector of plant DNA. Paraffin wax with melting temperature of 75°C was used as the shell material. In the experiment, the aqueous solution (W) of Azur B as the core material was dispersed in the melted paraffin wax (O) to form the (W/O) emulsion and then, the (W/O) emulsion was dispersed in the silicon oil (O’) as the continuous phase to form the (W/O)/O’ emulsion at 85°C. After formation of the (W/O)/O’ emulsion, the microcapsules were prepared by cooling the (W/O)/O’ emulsion to 50°C. The microcapsules were prepared by changing the concentration of oil soluble surfactant in the (W/O) emulsion and the volume of the (W/O) emulsion in the (W/O)/O’ emulsion. The microencapsulation efficiency increased with the concentration of oil soluble surfactant and finally became 100% under the optimum conditions. Furthermore, the microcapsules were melted down at temperature of 85°C to reveal the sharp thermal responsibility and to release the aqueous solution of Azur B. As a result, it was found that the microcapsules were able to be applied to the amplification detector of plant DNA by utilizing the reaction between DNA and Azur B.

Organic Melt Crystallization as a Method for Synthesis of Supramolecular Complexes

The most simple method for solventless synthesis of supramolecular complex of CMCR·2BPY·BZP, [CMCR = C-methylcalix[4]resorcinarene, BPY = 4,4'-bipyridine, BZP = benzophenone], is proposed. Although CMCR by itself is high melting point compound (above 300°C), CMCR was found to be dissolved in melt mixture of BPY and BZPeven below 120°C. In the mixture of the three components, the reaction occurs to form CMCR·2BPY·BZP supramolecular complex.

High-temperature thermal stability of C/C−ZrC−SiC composites via region labeling method

To investigate the thermal stability of ceramic-matrix composites,three kinds of C/C−ZrC−SiC composites with different Zr/Si molar ratios were synthesized by reactive melt infiltration.Employing region labeling method,the high-temperature thermal stability of the composites was systematically studied by changing the temperature and holding time of thermal treatment.Results show that the mass loss rate of low Si composites has a growth trend with increasing temperature,and a crystal transformation from β-SiC toα-SiC occurs in the composites.In the calibrated area,SiC phase experiences Ostwald ripening and volume change with location migration,while ZrC phase experiences a re-sintering process with diffusion.Moreover,it is found that increasing temperature has a more obvious effect on the thermal stability than extending holding time,which is mainly attributed to the faster diffusion rate of atoms.

The Processes-Based Attributes of Four Major Surface Melting Events over the Antarctic Ross Ice Shelf

The Ross-Amundsen sector is experiencing an accelerating warming trend and a more intensive advective influx of marine air streams.As a result,massive surface melting events of the ice shelf are occurring more frequently,which puts the West Antarctica Ice Sheet at greater risk of degradation.This study shows the connection between surface melting and the prominent intrusion of warm and humid air flows from lower latitudes.By applying the Climate Feedback-Response Analysis Method(CFRAM),the temporal surge of the downward longwave(LW)fluxes over the surface of the Ross Ice Shelf(RIS)and adjacent regions are identified for four historically massive RIS surface melting events.The melting events are decomposed to identify which physical mechanisms are the main contributors.We found that intrusions of warm and humid airflow from lower latitudes are conducive to warm air temperature and water vapor anomalies,as well as cloud development.These changes exert a combined impact on the abnormal enhancement of the downward LW surface radiative fluxes,significantly contributing to surface warming and the resultant massive melting of ice.

Effect of Initial Geometry on Surface Flatness after Arc Welding Analyzed with MPS Method

The flow behavior in a typical arc welding process is very complex and features rapid melting and solidification. In this work, the flow in the melted region was determined by the effect of surface tension, viscosity, and gravity. Two-dimensional change of the geometry of the melted region was analyzed using the MPS （moving particle semi-implicit） method to melt a small upper plate in a hole at the center of a base plate. The relation between the initial geometry of the upper plate and the surface flatness after welding was calculated. The calculation results showed that the upper plate with a triangular notch at its center minimized the surface unevenness after welding. The depth of notch and thickness of the upper plate were optimized.

One-step Eco-friendly Fabrication of Antibacterial Polyester Via On-line Amination Reaction by Melt Coextrusion

The work is dedicated to develop a one-step eco-friendly method to prepare antibacterial polyethylene terephthalate(PET).We report a one-step eco-friendly method to manufacture antibacterial PET via on-line amination reaction by melt coextrusion.Beside evenly mixing of poly(hexamethylene guanidine)(PHMG)and PET in the melt coextrusion procedure,the amination reaction also occurred between PHMG and PET under high temperature(230-270℃).The antibacterial ability of composite PET showed obvious PHMG concentration dependence,and antibacterial activity reached more than 99%when PHMG content was 2.5 wt%.Moreover,LIVE/DEAD fluorescence test further confirmed that the composite PET could kill bacteria quickly and efiectively(within 30 min);while negligible cytotoxicity was observed to HSF and HUVEC cells.Onestep eco-friendly fabrication of composite antibacterial PET was accomplished by on-line melt coextrusion.The composite antibacterial PET has potential use in multiple fields to combat with pathogenic including textiles,packaging materials,decoration materials and biomedical devices,etc.

惰气熔融-红外吸收/热导法同时测定无烟煤中氮和氢

首次使用惰气熔融-红外吸收/热导法实现无烟煤中氮、氢元素的同时、快速、准确测定.探究分析条件,发现当称样量为0.0300 g,分析功率为5500 W,氮元素的积分延迟时间为15 s,集成时间为55 s,氢元素的积分延迟时间为5 s,集成时间为85 s,且使用石墨套埚时,氮氢元素的释放最完全、合理.方法中氮、氢校准曲线的相关系数分别为0.9949、0.9940,检出限分别为0.321%、0.189%,定量限分别为0.326%、0.194%,精密度分别为3.60%、0.63%,满足线性关系及方法要求.惰气熔融-红外吸收/热导法重复性好、高效便捷、操作和维护简单,可用于无烟煤中氮、氢元素的定量检测.

基于离散元法的SLM刮刀倾角对粉末铺展行为的影响研究

刮刀倾角对选区激光熔化过程粉末铺展行为有重要影响.基于离散元法建立铺粉数值模型,对不同刮刀倾角的铺粉过程及粉层质量进行模拟研究.针对不同的刮刀倾角,提出一个量化指标对粉层铺展的致密度和均匀性进行综合评估,获得刮刀倾角对粉层质量的影响规律.根据颗粒分布及运动特征将粉堆颗粒体系划分为底层区、斜坡区、刮刀影响区和内部区4个区域.针对各区域进行铺粉过程动力学机理的深入研究,包括颗粒运动轨迹和速度场、刮刀前方剪切带、颗粒间力链分布及演化等.研究发现:刮刀倾角小于0时,颗粒体系难以形成完整的环流运动,剪切带较小,流向沉积层的颗粒较少,颗粒间强力链较少,刮刀间隙前方易形成力拱导致颗粒堵塞,进而形成空斑使得沉积层的致密度和均匀性较低.刮刀倾角大于0时,颗粒体系的环流运动较充分,剪切带较大,流向沉积层的颗粒增多,随倾角增大强力链增多,刮刀压实作用增强,有利于沉积层致密度和均匀性的提高.本研究为优化工艺参数、提高粉层沉积质量提供了理论基础.

负载花色苷的抗酸性羧甲基壳聚糖凝胶微球的缓释研究

为拓宽壳聚糖基水凝胶的应用范围,构筑可食用的花色苷(ACNs)递送体系,采用反相乳液法,以玉米油为连续相,水杨醛(SA)为交联剂,制备了具有抗酸性能的载ACNs羧甲基壳聚糖(CMCS)凝胶微球(ACNs/CMCS-SA),表征了其结构和形貌,研究了其稳定性、溶胀性能和缓释性能。结果表明,ACNs/CMCSSA具有微米级粒径,表面光滑呈圆形;ACNs/CMCS-SA在酸性条件下稳定性良好,溶胀和缓释过程展现pH响应性;ACNs的释放行为符合Weibull模型,pH7和9时为扩散和骨架溶蚀复合释放机制控制,pH3和5时为菲克扩散和Case Ⅱ transport(0级-溶胀依赖性释放)联合释放机制控制。ACNs/CMCS-SA制备方法简单,过程绿色;对ACNs展现良好的胃酸保护和肠道释放性能,为环境友好型药物包封材料的开发和ACNs的应用提供了理论和实践参考。

一种基于物质点法的熔冰仿真方法

为了解决拉格朗日法模拟熔冰时产生的穿模现象,提出一种基于物质点法的熔冰仿真方法。首先,将欧拉空间中的每个拉格朗日粒子视为固-液双相耦合的集合体,实现固相到液相的平稳过渡;其次,在物质点法背景网格上计算热能,采用预处理共轭梯度法求解相变过程的温度线性系统;最后,对潜热现象进行处理,引入虚拟水模型,通过限制虚拟水的移动来实现对冰块外部水流现象的仿真。实验结果表明,该方法不仅能够利用物质点法处理自碰撞的优势解决穿模现象,而且能模拟出真实的潜热过程的水流现象。

基于改进SHRP融冰试验的氯盐融雪剂性能研究

氯盐融雪剂因其融冰除雪性能优异、价格低廉、易于获取而得到广泛应用。为探究氯盐融雪剂的温度适用性不同、标准不统一、撒布方式粗略等问题,该文通过改进的SHRP融冰试验,分析了温度、固液态及撒布方式对NaCl、CaCl_(2)、MgCl_(2) 3种常用氯盐融雪剂除冰性能的影响。试验结果表明:氯盐融雪剂的除冰性能对温度具有显著的敏感性;MgCl_(2)、CaCl_(2)两种融雪剂在融化过程中存在“放热”效应;同种氯盐融雪剂在固态下的融冰效率高于液态下的;同种氯盐融雪剂在不同撒布方式下融冰效率不同,其中,在线性撒布下除冰能力最强。根据试验结果,建议使用固态线性撒布的方式,并根据环境温度选择适宜的融雪剂。

致密铼粒的制备研究

为了制备致密铼粒,采用粉末冶金法和电弧熔炼法分别处理5N铼粉。结果表明:当压坯压力为20 MPa、烧结温度2 000℃、烧结时间4 h时,在氢气气氛下烧结后制得致密铼粒,其致密度达到92.33%,且晶粒尺寸为8~20μm,其微观形貌呈现多孔状且具有较多孔洞缺陷;而电弧熔炼法所得铼粒微观形貌平整无缺陷,其致密度高达99.95%,优于粉末冶金法所得铼粒的致密度,但其晶粒尺寸偏大,其值为700~1 500μm。