托卡马克等离子体中电子温度梯度不稳定性的粒子模拟编码

本文简述了环形等离子体中电子温度梯度不稳定性的动力学特征粒子模拟的数学方程。给出了计算程序框图以及输入数据变量说明等；计算方法部分和数值模拟结果可参阅文献。在编码中，我们采用四阶自动变步长积分方法。该方法通过每积分一步计算的误差估计公式来帮助编制自动调整积分步长。     

负磁剪切环形等离子体中的电子温度梯度不稳定性研究

本文用本征模积分方程研究了环形等离子体中磁剪切为负时由电子温度梯度驱动的不稳定性。考虑了电子的全部动力学效应，强调了稳定性阈值附近的模式行为及相应的湍性输运，给出了磁剪切为负的临界梯度的拟合公式。     

具有广义协变的包含重力场贡献的重力场方程

利用半度规λ^(α)_μ表象的数学工具定义一个对广义坐标具有协变形式的重力场矢势函数ω^(α)_μ≡-cλ^(α)_μ，给出一个具有广义协变的包含重力场贡献的重力场方程R_μν-g_μνR/2+Λg_μν=8πG(T^(Ⅰ)_μν+T^(Ⅱ)_μν) 关键词： 重力场方程 协变形式 能量-动量张量 量子化     

托卡马克中电子温度梯度不稳定性的数值研究

用本征模积分方程研究了环形等离子体中的电子温度梯度不稳定性，在接近不稳定性阈值的参数区域内对模和输运的特征进行了研究。文中引入了一个新的积分参数，将实平面的积分解析延拓到复平面。这样可以同时对增长模和阻尼模进行研究。对被积函数的奇点进行了处理，给出了临界梯度的拟合公式，与有关的实验进行了比较，计算结果接近实验测量值。     

BF+2注入多晶硅栅F迁移特性的分析与模拟

在深入分析BF⁺₂注入多晶硅栅F在多晶硅栅中迁移特性的基础上，建立了F在多晶硅栅中的迁移方程.采用有限差分法，模拟了BF⁺₂注入多晶硅栅F在多晶硅栅中的分布.模拟结果与二次离子质谱(SIMS)分析结果相符.给出了80keV，2×10¹⁵cm^-2 BF⁺₂注入多晶硅栅900℃，30min退火条件下F在多晶硅中的发射系数e=6×10关键词：     

BaVS3晶格动力学研究

采用基于密度泛函理论的平面波赝势方法,在局域密度近似下采用线性响应的密度泛函微扰理论研究了具有六角结构的BaVS₃化合物的晶格动力学性质,得到了整个声子谱.计算得到的Γ点拉曼频率和实验数据进行了比较,其中E²_2g模、A_1g模和实验测量值符合得比较好.对于E³_2g模,采用线性响应计算的结果与实验值差别较大.对该模应用冻结声子方法研究后认为差异主要是由于E³_2g模的较强的非谐性引起的.此外V原子在平面内的振动模E¹_2u出现了虚频.虚频的出现预示着六角相的BaVS₃结构的不稳定性,从而很好地解释了该材料由六角相到正交相的结构相变. 关键词： 晶格动力学 密度泛函 赝势方法 3')" href="#">BaVS₃     

电子温度各向异性对螺旋波等离子体中电磁模式的传播及功率沉积特性的影响

采用考虑粒子温度各向异性热等离子体介电张量模型,借助磁化、均匀密度分布等离子体中电磁波的一般色散关系,在低磁场、低气压螺旋波等离子体典型参量条件下,理论分析了电子温度各向异性对电磁模式传播特性和角向对称模功率沉积的影响.研究结果表明:对于给定的纵向静磁场B₀(或波频率ω),存在一个临界波频率ω_cr(或纵向静磁场B_0,cr),当ω>ω_cr(或B₀0,cr)时,电子回旋谐波遭受的阻尼开始显著增大;相比粒子温度各向同性情形,粒子温度各向异性彻底改变了波的传播特性,即相位常数和衰减常数均出现峰值现象;在考虑电子有限拉莫尔半径效应和电子温度各向异性情形下,Trivelpiece-Gould (TG)波碰撞阻尼在整个电磁波功率沉积中占据主导地位,电子纵向温度T_e,//存在某一临界值,在此临界值处TG波功率沉积出现峰值P_abs,TG,且随着T_e,⊥/T_e,//的减小,...     

高能粒子对托卡马克气球模稳定作用的数值分析

用数值方法分析了高能捕获粒子对托卡马克气球模不稳定性的影响.利用变步长RKF积分方法求解了相应的微分-积分方程边值问题.数值结果表明,气球模不稳定区随高能粒子压强增大而缩小,充分说明了高能捕获粒子能部分或全部抑制气球模不稳定性.     

径向积分的解析计算

本文阐明的方法能方便地求出径向积分ⁿ₁^l₁F_Lⁿ₂^l₂(q)≡∫₀^∞> (R_n1^l₁(αr)jL(Kr)R_n2^l₂(αr)r²dr(q≡(K)/(α))的解析表达式。文中给出了L=0,1,2情况下各个径向积分的解析式,同时还以多重求和的形式络出了对各种量子数L,n₁,l₁,n₂,l₂适用的径向积分表达式。     

Mn5Ge2.7M0.3 (M=Ga，Al，Sn) 化合物的磁性和磁熵变

研究了Mn₅Ge_2.7M_0.3(M=Ga，Al，Sn)化合物的磁性和磁熵变. x射线衍射实验表明，研究的化合物均呈六角Mn₅Si₃型结构. 三种原子对Ge原子的替代，使得平均Mn原子磁矩下降，但居里温度没有明显的变化. 由于磁矩的降低，导致磁熵变值的下降，在磁场变化为4.0×10⁶A·m^-1时，对应于M=Ga，Al和Sn的样品，最大磁熵变值ΔS^max_Ｍ分别为6.1，6.3和5.3J·kg^-1K^-1，但磁熵变峰值的半高宽ΔＴ_ＦＷＨＭ有所增加. 另外，Mn₅Ge_2.7M_0.3(M=Ga，Al，Sn)化合物在高于居里温度的Arrott曲线上出现了一个不连续点，即样品在一定温度下的顺磁磁化率在某一临界磁场下发生了突变，临界磁场与温度几乎呈正比关系.这可能是由于样品在加一定磁场时3d带的费米能级发生了变化，使得有效电子数的减少所致. 关键词： 居里温度 平均Mn原子磁矩 磁熵变 Arrott图     

Thermal expansion of sodium nitrate (I)

The thermal expansion coefficients, α, of sodium nitrate have been measured along the trigonal axis of the crystal (α_∥) and in a direction perpendicular to this axis (α_⊥) by means of a Fizeau interferometer in the temperature range 77–300 K. α_∥ is large, while α_⊥ is relatively small, showing a large anisotropy. The results have been compared with earlier observations and the possible origin of large anisotropy has been suggested. Some details are given of the cryostat used for this experiment.     

Crystal field investigation on the magnetic properties of Yb in Yb(CF3SO3)3·9H2O

Ytterbium tri-fluoromethanesulfonate (YbTFMS) single crystals are prepared from the slow evaporation of the aqueous solution of YbTFMS and the principal magnetic susceptibility perpendicular to the c-axis of the hexagonal crystal (χ_⊥) is measured from 300 K down to 13 K. Principal magnetic anisotropy Δχ(=χ_∥−χ_⊥) is measured from 300 K down to 80 K which provides principal magnetic susceptibility parallel to the c-axis (χ_∥) down to 80 K. Very good theoretical simulation of the observed magnetic properties of YbTFMS has been obtained using one electron crystal field (CF) analysis having C_3h site symmetry. No signature of ordering effect in the observed magnetic data is noticed down to the lowest temperature (13 K) attained, indicating the inter-ionic interaction to be of predominantly dipolar type. The calculated g-values are found to be g_∥=2.67 and g_⊥=2.51, respectively. CF analysis provides the electronic specific heat which gives two Schottky anomalies in its thermal variation down to ∼13 K. The temperature dependences of quadrupole splitting and hyperfine heat capacity are studied from the necessary information obtained from the CF analysis.     

A nearly zero temperature gradient furnace system for high pressure multi-anvil experiments

A new furnace system with an almost zero temperature gradient throughout the sample area was designed for multi-anvil high pressure experiments. Test experiments of the new design were performed using 18/11 and 25/15 cell assemblies at 4?GPa, 1400°C and 1500°C, respectively. The temperature field within the sample capsules appeared to be very homogenous as indicated by Mg₂Si₂O₆–MgCaSi₂O₆ two-pyroxene thermometry, by direct temperature measurements using two thermocouples within the same assembly, and by distribution of solid and liquid phases in the sample capsule. The temperature gradient is estimated to be <2.4°C/mm over an area of 4?×?5?mm² within the furnace. It is significantly lower than standard multi-anvil experiments with straight or stepped furnace systems, which are at the levels of 20–200°C/mm.     

Low temperature ESR of K2Pt(CN)4Br0.3. 3.2 H2O

Electron spin resonance has been observed in high purity single crystals of K₂Pt(CN)₄Br_0.3·3.2H₂O, (KCP), in the temperature range of 4.22–80 K. Two types of paramagnetic species are found to dominate the spectrum. One of these is an inhomogeneously broadened line showing no resolved hyperfine splitting and having g_∥ = 1.946 ± 0.003 and g⊥ = 2.340 ± 0.003. The second paramagnet is identified as a Cu²⁺ impurity center with g_∥ = 2.231 ± 0.003, g⊥ = 2.079 ± 0.002 and hyperfine tensor A_∥ = 467 MHz, A_⊥ = 70 MHz.     

Effect of the spin-orbit interaction of Ni2+ ions with a triplet orbital ground state on the magnetostriction of NiFe0.5Cr1.5O4 ferrite

The magnetization σ and the longitudinal (λ_∥) and transverse (λ_⊥) magnetostrictions of the NiFe_0.5Cr_1.5O₄ ferrite containing the tetrahedral ions Ni²⁺ with the triplet orbital ground state have been investigated for the first time at a temperature of 4.2 K in fields up to 55 kOe. It is revealed that the NiFe_0.5Cr_1.5O₄ ferrite exhibits an anomalously large magnetic anisotropy (H _c=12.5 kOe) and magnetostrictions (λ_∥≈?870×10^?6 and λ_⊥≈800×10^?6). In strong fields, the magnetostrictions λ_∥ and λ_⊥ are found to be anisotropic in character; i.e., the susceptibility Δλ_∥p and Δλ_⊥p. The conclusion is drawn that the studied compound is characterized by two paraprocesses: one paraprocess in the B sublattice has an exchange nature, and the second process in the A sublattice is due to the spin-orbit interaction of Ni _A ²⁺ ions.     

Gradient measurement technique to identify phase transitions in nano-dispersed liquid crystalline compounds

Characterization and phase transitions in pure and 0.5% BaTiO₃ nano-dispersed liquid crystalline (LC) N-(p-n-heptyloxybenzylidene)-p-n-nonyloxy aniline, 7O.O9, com-pounds are carried out using a polarizing microscope attached with hot stage and camera. We observed that when any of these images are distorted, different local structures suffer from various degradations in a gradient magnitude. So, we examined the pixel-wise gradient magnitude similarity between the reference and distorted images combined with a novel pooling strategy – the standard deviation of the GMS map – to determine the overall phase transition variations. In this regard, MATLAB software is used for gradient measurement technique to identify the phase transitions and transition temperature of the pure and nano-dispersed LC compounds. The image analysis of this method proposed is in good agreement with the standard methods like polarizing microscope (POM) and differential scanning calorimeter (DSC). 0.5% BaTiO₃ nano-dispersed 7O.O9 compound induces cholesteric phase quenching the nematic phase, which the pure compound exhibits.     

Evolution of the d∥ band across the metal-insulator transition in VO2

We studied the evolution of the electronic structure of VO₂ across the metal-insulator transition. The electronic structure was calculated using the standard TB-LMTO-ASA method. The calculated DOS was compared to previous photoemission and X-ray absorption spectra. The electronic structure is discussed in terms of the usual molecular-orbital scheme. In the metallic phase, the d_∥ band appears at the bottom of the V 3d bands and crosses the Fermi level. In the insulating phase, the d_∥ band is split around 2 eV opening a pseudo band gap at the Fermi level. The largest effect of the splitting appears in the unoccupied part of the d_∥ band. The calculated value of the splitting accounts for 77% of the experimental value, 2.6 eV. The results suggest that electron-lattice interaction seems to be the dominant factor in the splitting of the d_∥ band.     

四角或三角畸变立方晶场中(3d)1过渡金属离子的劈裂因子

对四角或三角畸变立方晶场中的(3d)¹离子,在已有的静电晶场理论的基础上,采用“集团模型”,进一步引入Γ_∥, Γ_⊥及K_∥, K_⊥,R_∥, R_⊥,并考虑E_g混入T_2g,导出适用于四角或三角畸变立方晶场各种可能情况的g_∥, g_⊥公式。讨论了g_∥, g 关键词：     

关于辐射在双麦克斯韦等离子体中散射的结构因子

文献[1]在计算双麦克斯韦等离子体的辐射散射结构因子的时候,区分T_⊥≥T_∥和T_⊥≤T_∥两种情况,得到两个不同形式的解析表达式。本文指出,区分这两种情况是没有必要的,可以得到具有更高精确度的统一解析表达式。 关键词：     

Infrared and Raman spectra of GeSe2

Far infrared room temperature reflectivity spectra have been measured with polarized light for single crystal GeSe₂ in the range 40–400 cm^-1 for all three principal directions. Altogether 15 “Reststrahlen” peaks were observed, seven for E∥a, six for E∥b and only two for E∥c. Optical parameters were calculated using both Kramers-Krönig integration and a fitting procedure. A nonpolarized Raman spectrum of GeSe₂ was also measured. 17 Raman active lines were observed. The strongest one was at 213cm^-1.