共查询到18条相似文献,搜索用时 62 毫秒
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基于固体和液体散裂靶,近期国内外研究学者提出了一种新概念重金属颗粒流散裂靶。加速器驱动次临界系统(ADS)中重金属散裂靶在高能质子轰击作用下,出现能量沉积现象,而这些热量必须进行有效冷却以保证ADS的安全性。本文针对这种新概念颗粒流靶对靶区产生的高额热量的导出效果进行了模拟分析。首先采用蒙特卡罗程序计算450 Me V质子束轰击钨靶后能量沉积的空间分布,并将此作为颗粒流的体热源输入,基于计算流体力学-离散单元法(CFD-DEM)耦合方法对ADS靶区两种不同直径颗粒流的输运过程进行了模拟研究。结果表明,随颗粒直径的减小,靶区内温度分布更为均匀,颗粒流的流动特性更接近流体,颗粒导热性能增强;颗粒流靶中热应力可局限在单个颗粒内部而承受更高的能量沉积,具有更高的安全限值以及更广阔的应用前景。 相似文献
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本文以正丁醇中卤离子(I~-或Br~-)与卤代烷烃(C_(16)H_(33)Br或C_(16)H_(33)I)的交换反应为例,首次采用示踪原子法研究卤素非同位素交换反应的动力学,并与同位素交换结果做了比较。发现反应符合S_N2机构。不同交换反应的速度有显著差异,次序为碘-碘交换>碘-溴交换>溴-碘交换>溴-溴交换。利用溶剂效应解释了这一次序。测得了这几种交换的若干动力学参数等。本文介绍的方法对于用示踪原子法定量探讨S_N2机构的有机化学反应具有普遍意义。 相似文献
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水稻白叶枯病(Xanthomonas oryzae)是重要的细菌病害之一,十九世纪末发生于日本,六十年代起逐渐传播于亚洲各国,在中国原仅发生于南方稻区,现已传播北方各省。在大发生年份造成严重为害,要想弄清白叶枯细菌的侵染规律,必须采用先进的检测方法。目前,国内外用分离培养、噬菌体法、镜检观察喷菌法、浓缩接种法和反向间接血凝法进行了大量的研究工作。这些方法对种子、稻株、杂草和稻田水等带菌的检验起了很大作用。但对检验病菌的侵染来源及植物体内微量细菌的潜伏存在有一定的困难。我们经过五年试验,初步探索出白叶枯细菌的~(14)C标记、制样和测量方法。 相似文献
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本文搭建了一个快速预测燃料棒模态特征及流致振动响应的降阶模型(ROM)。首先,基于有限元分析软件ANSYS的批处理功能得到不同刚度下燃料棒的模态数据,将模态数据组装成快照矩阵。接着,基于商用数学软件MATLAB和半经验公式批量计算燃料棒的流致振动响应,将流致振动响应数据组装成快照矩阵。然后,采用本征正交分解(POD)方法将快照矩阵投影到低维空间,并根据特征值大小选出能量占比最高的POD模态。基于选出的POD模态将快照矩阵重构回物理空间,实现了模态和流致振动响应的快速计算。研究发现:对于1阶模态和流致振动响应的重构,刚度越小所需要的POD模态数量越多;对于相同刚度下不同阶模态的重构,模态阶次越高,所需要的POD模态数量越多。本文研究结果对于燃料棒模态特征和流致振动响应的快速计算具有一定的意义。 相似文献
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采用二分掩膜技术向溅射沉积的(Co6Ag94)薄膜中组合注入Fe离子,制备成具有不同Fe含量的16单元Fe-(Co6Ag94)颗粒膜磁光芯片。对制备态和退火态的Fe-(Co6Ag94)颗粒膜的物相进行了XRD研究。不同退火温度下,物相的演变反映出了退火过程中Co、Fe相和FeCo相纳米微晶的析出长大过程。采用原子力显微镜(AFM)对薄膜表面的研究结果表明,在退火过程中形成了嵌于基底中的纳米颗粒相。对制备态和不同温度退火后芯片各单元的磁光性能进行了测量,结果表明极向Kerr旋转角晚随着注入Fe含量的增加而增大,这可归因于颗粒膜中铁磁相的增多。在500℃以下,随着退火温度的增加,Fe-(Co6Ag94)颗粒膜的克尔磁光效应增加。对不同温度退火的样品进行穆斯堡尔谱测量,结果证明一定尺寸纳米Fe微晶颗粒的出现是磁光效应提高的主要原因之一。 相似文献
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Jiang-Feng Wan Sheng Zhang Yuan Tian Ping Lin Guanghui Yang 《Journal of Nuclear Science and Technology》2016,53(11):1809-1815
The spallation target is one of the key components of an accelerator-driven subcritical system (ADS). Following previous designs such as plate targets, rod targets, rotating targets, and liquid metal targets, the gravity-driven dense granular-flow target (DGT), which combines the advantages of solid and liquid metal targets, becomes a new attractive choice. The geometry of DGT consists of a cylindrical hopper and an internal coaxial cylindrical beam pipe. In this paper, using discrete element method simulations on graphics processing units, we research into the relations of the flow rate with the geometrical as well as the material parameters. For geometrical parameters, it is found that the existence of an internal pipe does not influence the flow rate when the distance from the bottom of the pipe to orifice is large enough. The results also reveal how the material parameters influence the flow rate. The whole research is helpful for the design of DGT. 相似文献
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A generator of the gliding arc jet (GAJ), which is driven by a transverse magnetic field, is developed to produce non-equilibrium plasma at atmospheric pressure. The gas temperature is estimated using the spectrum of OH radicals to be about 2400±400 K. The determinations of electron temperature and electron density by using a line-ratio method are elaborated for the gliding arc jet plasma. This line-ratio method is based on a collisional-radiative model. The experiment results show that electron temperature is about 1.0 eV and electron density is about 6.9×1014 cm-3 . Obviously, the plasma of GAJ is in a non-equilibrium state. 相似文献
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用^133Xe清除法测量了18名正常人,8例股骨头坏死和7例股骨颈处骨病人股骨颈局部血流灌注,并就骨坏死(或骨折)病人与正常人股骨颈局部血流灌注进行了分析比较,以研究骨病变后血流灌注的变化,结果表明,正常成年人股骨颈局部血流灌注均值7.22±0.53mL/(100g.min)8例股骨坏死病人的坏死侧与正常人股骨颈局部血流灌注均值之间存在显著性差异(t=6.028,P〈0.001),坏死侧血流灌注要 相似文献
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《Journal of Nuclear Science and Technology》2013,50(10):1300-1312
Relocation and freezing of molten core materials mixed with solid phases are among the important thermal-hydraulic phenomena in core disruptive accidents of a liquid-metal-cooled reactor (LMR). To simulate such behavior of molten metal mixed with solid particles flowing onto cold structures, a computational framework was investigated using two moving particle methods, namely, the finite volume particle (FVP) method and the distinct element method (DEM). In FVP, the fluid movement and phase changes are modeled through neighboring fluid particle interactions. For mixed-flow calculations, FVP was coupled with DEM to represent interactions between solid particles and between solid particles and the wall. A 3D computer code developed for solid-liquid mixture flows was validated by a series of pure-and mixed-melt freezing experiments using a low-melting-point alloy. A comparison between the results of experiments and simulations demonstrates that the present computational framework based on FVP and DEM is applicable to numerical simulations of solid-liquid mixture flows with freezing process under solid particle influences. 相似文献
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G C DAS 《等离子体科学和技术》2020,22(12):125302-125302
Our interest is to study the nonlinear wave phenomena in complex plasma constituents with Maxwellian electrons and ions. The main aim is to use a new method known as the (G'/G) method to exhibit the effects of dust charge fluctuations on the evolution of nonlinear waves. The coherent features of the shock and solitary waves along with the generation of high-energy waves have been amplified through the solution of the Korteweg–de Vries–Burgers equation, and the different natures of the waves were found successfully. Results are discussed graphically with the thoughtful choice of typical plasma parameters from different space plasma environments, exactly those found in cosmic dusty plasmas laden in ionospheric auroral region, radial spokes of Saturn's rings, planetary nebulae and solar F-corona region. All conclusions are in good accordance with the actual occurrences and could be of interest to further investigations of space. Moreover, the applicability of the present method is hoped to be a great enhancement by its use as ingenious mechanism used to evaluate the soliton dynamics and Burgers shock waves. 相似文献
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Excitation functions of (n,p) reactions for stable isotopes of Cr,Fe and Ni from threshold to 20 MeV
The excitation functions of (n,p) reactions for the stable isotopes of Cr, Fe and Ni were calculated using EMPIRE 3.0 β1 (ARCOLE) from threshold to 20 MeV. The cross-sections are calculated using full featured Hauser–Feshbach statistical model with pre-equilibrium effects by invoking DEGAS option in the code. A good agreement between the calculated and experimental data (EXFOR data base) as well as evaluated data is obtained with option of neutron and proton potentials by Koning (Global) and HFB parity dependent nuclear level density. This is an important step to the validation of nuclear model with superior predictive power. The compound nucleus and pre-equilibrium reaction mechanisms as well as the isotopic effects were also studied. 相似文献
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本文用γ辐射技术,在硅橡胶膜(Silastic)上接枝丙烯酰胺单体(AAM),用不同接枝率的Silastic-AAM膜通过叠氮化后对羊抗人IgG和出血热单克隆抗体(E_5)进行了偶联固定化。同位素~(125)碘标记方法对固定在Silastic-AAM膜上的羊抗人IgG量与接枝率的关系,以及抗体量与其免疫活性的关系进行了测定,得到了适于固定化的抗体偶联反应液最适浓度和最佳接枝率范围;用ELISA法对Silastic-AAM膜固定化的出血热(E_5)单抗进行了免疫活性实验,得到了承某一实验条件下具有明显的阳性反应。结果表明,经适当改进,本法对临床诊断有一定应用价值。 相似文献