高分辨差分比热测量方法及在高温超导体研究中的应用

差分比热实验方法是测量两个样品的比热差,具有高达万分之一的比热测量分辨率,适合测量相变时微小的比热变化及宽温区的电子比热.文章介绍了高分辨连续升温差分比热实验的测量原理和测量方法,并以铜氧化物高温超导体Y0.8Ca0.2Ba2Cu3O6+x为例,介绍了差分比热实验手段在宽温区电子比热的获得、正常态赝能隙及超导凝聚能研究等方面的应用.     

熔融织构Y0.8Ca0.2Ba2Cu3Oy的电子比热

采用热驰豫方法在0到9T范围内测量了熔融织构Y0.8Ca0.2Ba2Cu3O y的比热.零场下,2～180K的比热结果可以用Einstein模型来描述.通过4-Einstein峰拟合声子谱的方法,我们分别处理了不同磁场下超导转变附近的比热,获得了晶格比热和不同磁场下的电子比热,并将实验结果与London模型的计算结果进行对比,发现London模型能够很好地模拟出我们的实验结果.     

关于二硼化镁超导体比热的一点探索

在双带密度泛函理论的基础上,研究了双能隙超导体MgB2的超导态的比热跃变ΔC(T)与能隙的关系,指出了比热跃变的主要原因,并在转变温度Tc时将ΔC(T)/Tc的理论计算值与实验值作了对比,结果符合得很好。     

比热演示实验的探索与改进

分析了初中教材中比热演示实验的缺点，指出水浴法不能用于该演示实验，给出用电炉加热改进实验的方法。     

铜银合金比热的分子动力学模拟

本文采用嵌入原子模型对铜银合金的比热进行了分子动力学模拟，得到了铜银合金从深过冷态到熔点以上温度范围内的比热以及比热随温度的变化规律，并从内聚能的角度分析了铜银合金比热与温度的关系。与已有的铜镍合金的比热随温度变化规律的报道不同，本文的模拟结果和理论分析表明铜银合金的比热在 ８００ Ｋ～１９００ Ｋ的温度范围内基本为一恒值，其过冷液态下的比热可由熔点以上的比热外推得到。     

Zr-Ti-Cu-Ni-Be大块非晶低温比热

测量了Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5大块非晶及不同退火条件的样品在液氦温区的比热.低温下的比热数据可用电子比热和声子比热两部分的贡献来拟合,发现非晶的电子比热系数γ值比其他样品大,德拜温度从非晶到平衡相依次增大,并从电子态密度和德拜理论出发,初步解释了这种差异. 关键词： 低温比热 大块非晶     

T2铜的低温比热

在1.4—27K的温区内测量了纯度为99.9％的国产T_2铜的比热,得出了T_2铜的电子比热系数γ为0.68mJ·mol_(-1)·K_(-2),德拜温度θ_D为339.7K。与国外的比热数据比较,显然在纯度相同的条件下,比热数据是一致的,且可以互换。     

层状材料中一个简单晶格模型的比热计算

本文采用Born 势和简单立方结构计算了层状材料的晶格比热. 发现当层伏材料层厚较小时(约在十几层以内) , 界面态对晶格比热有明显影响。但随层厚增大, 比热下降, 且基本与界面态及层厚无关. 文中还比较了准周期超晶格与周期超晶格两者的晶格比热。 关键词：     

高温超导体的电子比热研究

在vanHove奇异性背景下,从BardeenGooperSchrieffer超导理论和二维紧束缚能带结构出发,推导了各向异性的d波序参量方程和d波的电子比热公式,并研究了在临界温度Tc处的电子比热跃变和低温下电子比热的温度行为及掺杂关系.得出了考虑到vanHove奇异性可以提高Tc处的比热跃变以及d波低温电子比热与温度的平方成线性关系的结论. 关键词：     

熔融织构Y0．8Ca0．2Ba2Cu3Oy的电子比热

采用热驰豫方法在0到9T范围内测量了熔融织构Y0．8Ca0．2Ba2Cu3Oy的比热．零场下，2-180K的比热结果可以用Einstein模型来描述．通过4-Einstein峰拟合声子谱的方法，我们分别处理了不同磁场下超导转变附近的比热，获得了晶格比热和不同磁场下的电子比热，并将实验结果与London模型的计算结果进行对比，发现London模型能够很好地模拟出我们的实验结果．     

关于"太阳在银河系中所受引力与到银心距离r的关系"的讨论

讨论了银道面内的引力场强分布和太阳在银河系中所受引力与到银心距离r的关系，指出引力场强g并不是与r的平方成反比，这是由于银河系的大小和形状不能忽略造成的．强调了万有引力定律的适用条件．     

On the calculation of the bremsstrahlung in the region of the plasma frequency

On the basis of the classical theory of radiation produced in incomplete Coulomb interaction, a formula is derived for the coefficient of the bremsstrahlung of fully ionized plasma. In the region of rectilinear approximation a comparison is made with the results of the quantum formula derived from the Born approximation. Furthermore, the influence of dispersion upon the emission coefficient is taken into account; some relations for the region of dispersion are given.     

On the predictability of the positions of the convergence zones in the ocean

The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized.     

Dependence of the Intensity of the Spectral Lines and the Composition of the Sample and the Plasma Parameters of the Unipolar Arc

The investigation was made of the dependence of the intensity of Tl, Ga, Mo, Mg, Mn, Sn, Bi, Ni, Zn, Pt and Au spectral lines and the plasma parameters (temperature T, electron concentration n_e, degree of 6 ionnization α) from concentration of lithium additive.     

Extracting the wavefunction of the LSP at the LHC

We consider associated production of squarks and gluinos with the lightest supersymmetric particle (LSP), or states nearly degenerate in mass with it. Though sub-dominant to pair production of color SU(3)-charged superpartners, these processes are directly sensitive to the wavefunction composition of the lightest neutralinos. Exploiting event-shape variables - including some introduced here for the first time - we are able to identify the composition of the LSP by selecting events involving a single high-pT jet recoiling against missing transverse energy. We illustrate the proposed technique on a set of benchmark cases and propose methods for applying these results in more realistic experimental environments.     

Set the controls for the heart of the Sun

In this paper we describe experiments conducted with high-power lasers that are attempting to replicate, for a very short time and in miniature, conditions found in the Sun. Experiments to date have reached conditions in the outer part of the Sun. To reach the Sun's centre requires compression of material to very much greater than solid density and heating to over ten million degrees. To achieve this, a new class of experiments and a new generation of high-power lasers are required.     

On the Question of the Source of the Apokamp

Technical Physics - The object of this work is the apokamp—a new type of plasma jet, which is formed from a bright offshoot emerging at the bending point of a channel of a high-voltage...