场冷和零场冷过程中磁化强度的模型化与数值模拟

通过采用蒙特卡罗模拟方法和磁通运动的热激活模型（ＴＡＦＭ） ,本文计算了在场冷（ＦＣ）和零场冷（ＺＦＣ） 过程中的磁场位形及磁化强度．基于简单的ＫｉｍＡｎｄｅｒｓｏｎ 模型的Ｕ（ｊ） 依赖关系,主要的实验结果都可以较好的被模拟．计算表明,在零场冷中,磁场位形非常接近Ｂｅａｎ 临界态模型,而在场冷中则相反,表现的是磁通冻结的图象．零场冷和场冷中的磁化强度都很强的依赖于钉扎势和临界电流密度,而只微弱的依赖于温度变化的速度     

FEB聚变实验增殖堆氚投料量及氚回收的研究

运用三维ＭｏｎｔｅＣａｒｌｏ程序ＭＯＲＳＥ＿ＣＧＴ，计算了变实验增堆ＦＥＢ满功率运行１０ｄ后外侧包层各区中的氚浓度、运行１天后的内侧包层各区中的氚浓度及运行１ＦＰＹ后Ｂｅ球中的氚投料量，设计了ＦＥＢ堆现场氚的分布流程图。采用组合于燃料净化系统和低温分馏法从等离子体排出气体中回收氚，讨论了从液态锂中回收氚的几种方案用于ＦＥＢ的可行性。     

BaZn2(GeMn)0-2Fe15-6O27六角铁氧体的磁晶各向异性

用标准陶瓷工艺制备了ＢａＺｎ２（ＧｅＭｎ）０－２Ｆｅ１５－６Ｏ２７六角铁氧体．假设Ｇｅ４＋取代了４ｅ和４ｆⅣ中的Ｆｅ３＋,能够很好地解释实验结果．利用分子场理论和Ｈ．Ｂ．Ｃａｌｌｅｎ单离子各向异性模型计算了ＢａＺｎ２（ＧｅＭｎ）０－２Ｆｅ１５－６Ｏ２７次点阵之间的交换参数和各次点阵对磁晶各向异性的贡献,并对实验结果进行了拟合．结果表明,１２ｋ和２ｄ次点阵对磁晶各向异性有较大的贡献 关键词：     

EuBa2Cu3O7的化学键性质和穆斯堡尔谱研究

利用电介质的平均能带模型计算了ＥｕＢａ２Ｃｕ３Ｏ７的化学键参数,得到Ｃｕ（１）－Ｏ键的平均共价性为０．４１４,Ｃｕ（２）－Ｏ键的平均共价性为０．２８１,应用由共价性和极化率定义的化学环境因子计算了＾５７Ｆｅ、＾１１９Ｓｎ在ＥｕＢａ２Ｃｕ３Ｏ７中的穆斯堡尔同质异能位移,确定了＾５７Ｆｅ、＾１１９Ｓｎ的价态和占位情况。     

丙酮酸分子结构与振动光谱的密度泛函理论研究

用密度泛函方法ＢＬＹＰ、Ｂ３ＬＹＰ和从头算Ｈａｒｔｒｅｅ－Ｆｏｃｋ（ＨＦ）方法在６－３１Ｇ＊基组水平上对丙酮酸分子的几何结构（甲基的重叠式和交错式两种构象）和振动光谱分别进行了优化和计算,并给出了各种频率所对应的红外强度及拉曼活性,对光谱进行了指认,结果表明：在丙酮酸分子的两种构象中,重叠式比较稳定,Ｂ３ＬＹＰ计算得到的构型参数与实验结果比较一致;在振动频率的计算中,ＢＬＹＰ未标度力场所计算的非Ｃ     

储存环上的放射性核束流品质计算

为给兰州重离子加速器冷却储存环（ＨＩＲＦＬ－ＣＳＲ）注入放射性核束（ＲＩＢ）提供初始参数，及为ＣＳＲ上ＲＩＢ分离谱仪的物理设计提供依据，对最近几年发展起来的利用弹核碎裂（ＰＦ）、双消色散分离谱仪在线获取和分离所需ＲＩＢ的参数计算方法，进行了系统的总结；给设计中的ＣＳＲ－ＲＩＢ分离谱仪设定一组束流光学参数，在此基础上对一组具有代表性的反应道的部分参数进行了初步计算，并用ＧＡＮＩＬ发展的相关程序ＬＩＳＥ进行了验证．理论与实验均表明，在目前对ＰＦ反应机制尚不能精确描述的情况下，对ＲＩＢ产额的计算结果达到１～２数量级的精度；对ＲＩＢ横向发射度和动量散度的计算结果相对准确. The calculation of the parameters of RIB produced by the projectile fragmentation and separated by an achromatic spectrometer is firstly summarized. The calculation method to the RSPC(the RIB spectrometer between CSR main ring and the experimental ring) is then described. The final results of the yield, the energy spread and the transversal emittance of some typical RIB has been obtained.     

钠长石玻璃中挥发份的振动光谱研究

利用高挥发份凝胶在高压下熔制出钠长石玻璃进行Ｒａｍａｎ光谱与红外光谱研究。结果表，ＣＯ２以气体分子形式而不是以ＣＯ＾－３的形式溶解在玻璃熔液中，并认为拉曼光谱中的１５５０ｃｍ＾－１谱带是由溶解于玻璃熔体中的分子Ｏ２振动引起的，实验表明它与ＣＯ２在钠长石玻璃中的溶解度随玻璃熔制的压力与温度变化存在负相关性。     

聚变实验增殖堆FEB-E放射性废物处置指标的计算

应用中子输运程序ＢＩＳＯＮ３．０、增殖堆放射性计算程序ＦＤＫＲ、剂量率计算程序ＤＯＳＥ完成了聚变实验增殖堆ＦＥＢ－Ｅ的放射性、核废物特性及废物处置额定容量（ＷＤＲ）的计算。结果表明,在停堆以后几周内,ＦＥＢ－Ｅ设计的经一壁和包层结构材料满足１０ＣＦＲ６１Ｃ级核废物处置额定容量的要求。对包层中的重要锕系元素＾２３２Ｕ、＾２３７Ｎｐ的含量也作了计算分析。     

煤粉挥发份析出规律的研究

本文提出了粉煤挥发份析出的通用热解模型。该模型与现有的其他模型相比,主要特点是挥发份析出时的化学动力学参数E、K不随煤种变化,仅是颗粒最终温度T_∞的函数。这是一个新的结论。本文还得到了E(或K)和T_∞间的关系,它适用于所有的煤种。若在一定条件下得到粉煤挥发份的最终产量V_∞,则可用该模型预示任何煤种的挥发份析出过程。 本文报道了烟煤、褐煤、劣质烟煤、贫煤在高温下降炉中、加热气体为Ar、N_2和He的条件下,其挥发份的析出过程。煤颗粒的加热速率大于10~4K/s,直径从35μm—100μm,温度范围为973—1773K,取样时颗粒的冷却速率大于10~5K/s。确定挥发份的产量利用灰作示踪剂。气体在高温反应炉内的流动是层流运动,且颗粒在下降过程中弥散很小。     

PGBs对高能e~＋e~－湮没产生顶夸克对的单圈量子效应

在一代Ｔｅｃｈｎｉｃｏｌｏｒ（ＴＣ）模型中计算了ＰＧＢｓ（ＰｓｅｕｄｏＧｏｌｄｅｎｓｔｏｎｅＢｏｓｏｎｓ）对高能ｅ＋ｅ－→ｔｔ过程的单圈量子效应．给出了重整化的形状因子和矩阵元．计算了ＰＧＢｓ对总截面前后不对称参数ＡＦＢ和左右不对称参数ＡＬＲ的虚贡献，结果表明选取适当的参数值，新物理对以上可测量的贡献最大分别可达：－１２．３％、－３．３％和－１１．７％．在下一代对撞机上这一理论结果能为ＴＣ理论打开实验的窗口．同样的计算表明ＰＧＢｓ对ｅ＋ｅ－→ｂｂ过程的单圈贡献小于－１．０％．     

Measurement and kinetics of elemental and atomic potassium release from a burning biomass pellet

Combining polarizing-filtered planar laser-induced fluorescence (PLIF) with simultaneous laser absorption, quantitative laser-induced breakdown spectroscopy (LIBS) and two-color pyrometry, the potassium release during the combustion of biomass fuels (corn straw and poplar) has been investigated. The temporal release profiles of volatile atomic potassium and potassium compounds from a corn straw show a single peak. The woody biomass, poplar, produces a dual-maxima distribution for potassium and potassium compounds. For both biomass samples, the highest concentrations of released atomic potassium and potassium compounds occur in the devolatilization stage. The mass ratios between volatile atomic potassium and potassium compounds in the corn straw and poplar cases are 0.77% and 0.79%, respectively. These values agree well with chemical equilibrium predictions that 0.68% of total potassium will be in atomic form. A two-step kinetic model of potassium release has been developed, which gives better predictions during the devolatilization stage than the existing single-step model. Finally, a map of potassium transformation processes during combustion is developed. Starting with inorganic and organic potassium, there are eight proposed transformation pathways including five proposed release pathways that occur during the combustion. The pathways describe the transformation of potassium between the fuel volatile matter, char, and ash. Potassium release during the devolatilization stage is due to pyrolysis and evaporation; during the char burnout stage, potassium release is due to char oxidation and decomposition; and during the ash cooking stage, potassium release is caused by reactions between the ash and H₂O in the co-flow.     

Systematic characterization of drug release profiles from finite-sized hydrogels

Diffusion is often used as the primary method of molecular transport in drug delivery schemes. We present a systematic investigation of the Weibull and Peppas functions as useful tools in quantifying drug release profiles. The data is obtained from 2D simulated hydrogels and diffusion is modeled using an exact enumeration scheme. We show the fitting parameters to be largely time-dependent and therefore unreliable in indicating fundamental characteristics of the underlying physical mechanism. The parameters in the Weibull function however, have a stable regime when characterizing release profiles; we propose a simple iterative test that can be used to ensure that one is in this stable regime. Also, the mechanism of diffusion is shown to be independent of obstacle density in hydrogels that are larger than their respective characteristic lengths; a homogeneous obstacle distribution can therefore be replaced by an effective viscosity.     

The Weibull-log Weibull transition of the interoccurrence time statistics in the two-dimensional Burridge-Knopoff Earthquake model

In analyzing synthetic earthquake catalogs created by a two-dimensional Burridge-Knopoff model, we have found that a probability distribution of the interoccurrence times, the time intervals between successive events, can be described clearly by the superposition of the Weibull distribution and the log-Weibull distribution. In addition, the interoccurrence time statistics depend on frictional properties and stiffness of a fault and exhibit the Weibull-log Weibull transition, which states that the distribution function changes from the log-Weibull regime to the Weibull regime when the threshold of magnitude is increased. We reinforce a new insight into this model; the model can be recognized as a mechanical model providing a framework of the Weibull-log Weibull transition.     

CO_2在与高振动激发NaH碰撞中的量子态分辨能量再分配

利用简并受激超拉曼泵浦激发NaH基态到高位振动态(ν″=14,J″=20)。研究了NaH(14,20)与CO_2(00°0)间的振转能量转移。利用吸收系数和瞬时Doppler线宽,得到不同池温下NaH(14,20)分子密度,测量CO_2(00°0,J)与NaH高振动态碰撞前后的瞬时泛频激光感应荧光谱线的相对强度,确定了CO_2(00°0,J=2~80)的初生态布居,它们呈现双指数转动分布。拟合实验数据得到两个转动温度T_(rot)=(650±80)和(1 531±150)K。较冷的分布约占CO_2(00°0)的79%,它是由弹性或弱非弹性碰撞产生的,因而CO_2只有很小的转动激发。另有21%的CO_2(00°0)较大地增加了转动能,故有较热的转动温度。对碰撞产生的CO_2(00°0,J)进行高分辨率瞬时泛频荧光谱线的轮廓测量,得到各转动态平移能的改变。对于CO_2(00°0,J=56~80),转移能从582cm~(-1)(对于J=60)增加到2 973cm~(-1)(对于J=80)。探测转动态布居数的改变,得到各转动态的产生速率系数k_(app)~J之和为(7.2±1.8)×10~(-10) cm~3·mol~(-1)·s~(-1),而平均倒空速率系数〈kdep〉=(6.9±1.7)×10~(-10)cm~3·mol~(-1)·s~(-1)。     

Strength statistics and the distribution of earthquake interevent times

The Weibull distribution is often used to model the earthquake interevent times distribution (ITD). We propose a link between the earthquake ITD on single faults with the Earth’s crustal shear strength distribution by means of a phenomenological stick–slip model. For single faults or fault systems with homogeneous strength statistics and power-law stress accumulation we obtain the Weibull ITD. We prove that the moduli of the interevent times and crustal shear strength are linearly related, while the time scale is an algebraic function of the scale of crustal shear strength. We also show that logarithmic stress accumulation leads to the log-Weibull ITD. We investigate deviations of the ITD tails from the Weibull model due to sampling bias, magnitude cutoff thresholds, and non-homogeneous strength parameters. Assuming the Gutenberg–Richter law and independence of the Weibull modulus on the magnitude threshold, we deduce that the interevent time scale drops exponentially with the magnitude threshold. We demonstrate that a microearthquake sequence from the island of Crete and a seismic sequence from Southern California conform reasonably well to the Weibull model.     

燃烧驱动气动CO2激光器几种液体燃料性能差异的数值模拟

 在甲苯、苯、煤油和乙醇四种不同液体燃料燃烧驱动条件下,对气动CO₂激光器燃烧室的平衡组分、小信号增益沿流场方向的分布及激光器的输出功率进行了数值模拟,计算对比分析了该四种燃料的性能。计算结果表明甲苯是气动CO₂激光器四种燃料中最为理想的燃料。     

石墨烯形核初期Cu(111)面上CxHy团簇生成的理论研究

采用基于密度泛函理论的第一原理计算方法,我们研究了Cu(111)表面上石墨烯成核生长过程中CxHy小团簇的吸附和生成行为. 计算结果表明：随着氢原子饱和度、氢原子个数的增大,CxHy团簇的形成能减小,碳原子与铜表面的平均距离增加,C-C键的平均键长呈增大趋势. 然而,当生成的CxHy团簇具有空间对称结构时,在一定程度上打破了上述规律性. 令人惊奇的是,形成的C3H4和C3H5对称团簇具有类似石墨烯的空间结构,这类结构可能在石墨烯的形成过程中起着重要的作用.     

石墨烯形核初期Cu(111)面上C_xH_y团簇生成的理论研究

采用基于密度泛函理论的第一原理计算方法,我们研究了Cu(111)表面上石墨烯成核生长过程中CxHy小团簇的吸附和生成行为.计算结果表明:随着氢原子饱和度、氢原子个数的增大,CxHy团簇的形成能减小,碳原子与铜表面的平均距离增加,C-C键的平均键长呈增大趋势.然而,当生成的CxHy团簇具有空间对称结构时,在一定程度上打破了上述规律性.令人惊奇的是,形成的C3H4和C3H5对称团簇具有类似石墨烯的空间结构,这类结构可能在石墨烯的形成过程中起着重要的作用.     

Approximation of the erosion zone profile in planar magnetrons with a disk cathode

We have proposed a universal approximation of the normalized erosion zone profile of planar magnetrons with a disk cathode by a composite function that includes the probability density function for the minimal distribution of extremal values for the region from the center of the disk cathode to the maximum of the erosion zone and the survival Weibull distribution function (from the maximum to the outer boundary of the sputtering zone). The accuracy of the approximation has been verified for six magnetrons differing in the cathode size or in the design of the magnetic systems. In all cases, good agreement has been observed between the approximation and experimentally measured values. The results reported here can be used to analyze processes that occur on the cathode during sputtering and to refine the calculations of coating profiles.     

轻组份燃料对乳化油蒸发与着火影响的研究

本文研究了较组份添加剂对单滴乳化油着火规律的影响。实验采用挂滴法。实验中,测量了体积比为十二烷：正庚烷：水6：0：4,5：1：4,4：2：4,3：3：4的着火延迟时间。实验结果和数值计算表明,在乳化油中加入易挥发添加剂能有效缩短乳化油的着火延迟时间,着火延迟时间随着添加剂加入量的增加而缩短,当易挥发添加剂含量较大时,着火延迟随着添加剂加入量的增加,变化越来越缓慢。这一结果对解决在掺水量大的条件下保证柴油机中乳化燃料的正常点火与启动具有实用价值。