Nd2O3掺杂对SnO2气敏性质的影响

SnO_2是目前应用最广的一种气敏材料。我们曾经报道掺入La_2O_3,CeO_2,Pr_6O_(11),和Nd_2O_3后可使半导体元件的灵敏度提高,尤以对乙醇、乙醚、丙酮为显著。掺Nd_2O_3元件对乙炔的灵敏度也有提高。本文考察了SnO_2粒度和被测气氛的物化性质对掺Nd_2O_3元件灵敏度的影响。SnO_2采用水解SnCl_4法制备,纯度经光谱分析测定合格,试样用标准筛分目。在SnO_2中加1wt%Nd_2O_3(光谱纯)和适量水及甲基纤维素,混磨15分钟。将制成的悬浊液滴在一对铂     

Comments on “power-law falloff in the Kosterlitz-Thouless phase of a two-dimensional lattice Coulomb gas”

A simple argument is presented by which one can show that the critical inverse temperature _c of a two-dimensional Coulomb gas (standard or hard-core) with activityz satisfies , where in the low-activity limit. Previous results yield .     

Superdegenerate point in FCC phase diagram: CVM and Monte Carlo investigations

We investigate the topology of the phase diagram of binary alloys on the fee lattice with first-neighbor antiferromagnetic interactions around the superdegenerate point, where the L1₀ and L1₂ phases meet. We treat the system as a hard-constraint lattice gas, following a procedure previously described by Lebowitzet al. We perform cluster variation method calculations in theT0 limit and Monte Carlo simulations directly atT=0 K on the ground states of the superdegenerate point. We find that: (i) there is no disordered phase in the neighborhood of this point; (ii) a phase L for which two of the four cubic sublattices have the same average occupancy and each of the two others are different appears between L1₀ and L1₂; (iii) the transition L/L1₂ is of first order.     

Vicious random walkers in the limit of a large number of walkers

The vicious random walker problem on a line is studied in the limit of a large number of walkers. The multidimensional integral representing the probability that thep walkers will survive a timet (denotedP _t ^(p) ) is shown to be analogous to the partition function of a particular one-component Coulomb gas. By assuming the existence of the thermodynamic limit for the Coulomb gas, one can deduce asymptotic formulas forP _t ^(p) in the large-p, large-t limit. A straightforward analysis gives rigorous asymptotic formulas for the probability that after a timet the walkers are in their initial configuration (this event is termed a reunion). Consequently, asymptotic formulas for the conditional probability of a reunion, given that all walkers survive, are derived. Also, an asymptotic formula for the conditional probability density that any walker will arrive at a particular point in timet, given that allp walkers survive, is calculated in the limittp.     

Computer simulation of some dynamical properties of the Lorentz gas

We carried out molecular dynamics simulations of a Lorentz gas, consisting of a lone hydrogen molecule moving in a sea of stationary argon atoms. A Lennard-Jones form was assumed for the H₂-Ar potential. The calculations were performed at a reduced temperatureK ^* =kT/_{H 2–Ar} = 4.64 and at reduced densities ^*= _{Ar Ar} ³ in the range 0.074–0.414. The placement of Ar atoms was assumed to be random rather than dictated by equilibrium considerations. We followed the trajectories of many H₂ molecules, each of which is assigned in turn a velocity given by the Maxwell-Boltzmann distribution at the temperature of the simulation. Solving the equations of motion classically, we obtained the translational part of the incoherent dynamic structure factor for the H₂ molecule,S _tr(q, ). This was convoluted with the rotational structure factorS _rot(q, ) calculated assuming unhindered rotation to obtain the total structure factorS(q, ). Our results agree well with experimental data on this function obtained by Egelstaffet al. At the highest density ( ^*=0.414) we studied the dependence ofS(q, ) on system size (number of Ar atoms), number of H₂ molecules for which trajectories are generated, and the length of time over which these trajectories are followed.     

顶空气相色谱法测定延生护宝液中甲醇残留量

本文用顶空气相色谱法，以ＧＤＸ－１０１为固定相，测定了延生护宝液中甲醇残留量，方法的回收率在８５．９％－１０１．６％之间，变异系数０．３％，最小检出量１．０ｍｇ／Ｌ。     

衍生化气相色谱法测定3-氨基-1, 2-丙二醇的含量

建立衍生化气相色谱法测定非离子型X-CT造影剂碘海醇中间体3-氨基-1,2-丙二醇的含量.将试样经过三氟乙酸酐(TFAA)在50℃下衍生30 min后,用配有FID检测器的气相色谱仪SE-54毛细管柱(30 m×0.25 mm×0.25μm)进行测定,在选定的实验条件下,测定的相对标准偏差为0.921%,加样回收率为99.2%.结果重现性好,准确度高,方法简便易行.     

顶空毛细管气相色谱法测定非那雄胺中有机溶剂的残留量

建立了顶空毛细管气相色谱法测定非那雄胺中二氯甲烷和氯仿两种有机溶剂残留量的方法,并讨论了平衡温度、平衡时间、盐效应对测定的影响。分析结果表明:该法可将两种残留有机溶剂完全分离,具有较好的线性(相关系数分别为0.999 7和0.999 8),检出限为3.2μg/L和0.094μg/L,测定结果的相对标准偏差分别为1.33%和0.89%,样品回收率分别为94%和96%。     

气固射流床射流深度的研究

在３００×５１×２６００ｍｍ的二维射流床中，采用多路毕托管测试系统，对包括三种双组份混合物在内的五种物料的射流深度进行了考察。结果表明，射流管径、射流气速对射流深度都有影响，本文尤其考察了环隙气量与射流深度的关系，发现在同样的射流气速下，环隙气速增大则射流深度降低，得出了综合各种影响因素的关联式。