新型金属蜂窝板燃烧器的高效燃烧现象分析

新型金属蜂窝板燃烧器是通过采用双层或多层金属薄片制成,能有效地解决普通燃气灶具燃烧器存在的不足,使产品结构更加合理完善,性能更加稳定可靠,能效更加优越。本文以红外燃气灶具的核心部件—新型金属蜂窝板燃烧器为研究对象,利用红外摄像仪对红外燃气灶具和普通燃气灶具进行了对比研究。结果表明,红外燃气灶的火焰集中,温度分布均匀,燃烧效率比普通燃气灶高12.7%。     

Higher order solutions of Lieb-Liniger integral equation

We study higher order solutions of Lieb-Liniger integral equation for a one-dimensional δ-function Bose gas. By use of the power series expansion method, the integral equation is solved and the correction terms which improve the Bogoliubov theory are calculated analytically in the weak coupling regime. Physical quantities such as the ground state energy and the chemical potential are represented by a dimensionless parameter γ=c/ρ, where c is the interaction strength and ρ is the number density of particles while the quasi-momentum distribution function is expressed in terms of a dimensionless parameter λ=c/K, where K is the cut-off momentum.     

High coercive Nd-Fe-B magnets fabricated via two-step sintering

The fabrication of Nd₁₁Dy₄Fe_76.5TM_2.5B₆ (TM=Co, Cu, Al, and Nb: at%) sintered magnets via a two-step sintering process was demonstrated. A densification of greater than 99% was achieved using the two-step sintering of the Nd-Fe-B powder. This process produced a sample with an average grain size of 6.2 μm in the Nd₂Fe₁₄B phase, resulting in an enhancement of the coercivity compared to that of the isothermally sintered sample. The suppression of grain growth was considered to be affected by the relatively low temperature during the two-step sintering and by the presence of a B-rich phase at the triple junction. Consequently, the two-step sintering process led to suppression of grain growth and a uniform grain size distribution, which resulted in improved magnetic properties, in particular in the intrinsic coercivity.     

An alternative approach to calculate the density of states in nonextensive statistical mechanics

A relation between the generalized partition function (Tsallis) and density of states is established by using the method of integral transform which enables reducing some integral equations into the algebraic equations. Inverse Mellin transformation of this equation gives the density of states. Similar relation is also hold the for standard partition function (Boltzmann-Gibbs) and the density of states. Using these relations, we recover the density of states for the classical ideal gas within both statistics.     

多特征波长窗法检测痕量甲醛气体的研究

为了克服化学检测痕量甲醛气体速度慢、有耗材、采样区域局限等缺点,实现快速准确地检测甲醛气体的浓度,设计了一种多特征波长窗的方法。根据甲醛及主要干扰气体的特征光谱选择相干度最小的多组特征波长,特征波长个数分别选用3,4和5个,同时配合相应的多组窄带滤光片。当光源依次通过这些窗口及气室后,由PCI-2TE-13型红外探测器采集,并经相关算法反演样气中的甲醛浓度。实验针对新装修的房屋、建材商场、超市及公园四种环境下采集的样气中的甲醛进行定量分析。实验结果与ARCSpectro-A-MIR型红外光谱仪的检测结果相比较,结果表明,采用多特征波长窗法在10μg.m-3以上的检测结果均与标准值相近,其平均误差均小于5%,满足实际应用的要求,并且具有实时检测、不中毒等优点。     

Delta-shocks and vacuum states in the vanishing pressure limit of solutions to the isentropic Euler equations for modified Chaplygin gas

The phenomena of concentration and cavitation and the formation of δ-shocks and vacuum states in solutions to the isentropic Euler equations for a modified Chaplygin gas are analyzed as the double parameter pressure vanishes. Firstly, the Riemann problem of the isentropic Euler equations for a modified Chaplygin gas is solved analytically. Secondly, it is rigorously shown that, as the pressure vanishes, any two-shock Riemann solution to the isentropic Euler equations for a modified Chaplygin gas tends to a δ-shock solution to the transport equations, and the intermediate density between the two shocks tends to a weighted δ-measure that forms the δ-shock; any two-rarefaction-wave Riemann solution to the isentropic Euler equations for a modified Chaplygin gas tends to a two-contact-discontinuity solution to the transport equations, the nonvacuum intermediate state between the two rarefaction waves tends to a vacuum state. Finally, some numerical results exhibiting the formation of δ-shocks and vacuum states are presented as the pressure decreases.     

考虑基岩向井筒供气的气藏压裂水平井产能预测模型

基于等效井径模型,综合考虑各裂缝不同参数、裂缝变质量入流和井筒变质量流动等因素的影响,建立并求解了基岩和压裂缝同时向井筒供气的井筒与气藏耦合的压裂水平井产能预测模型.研究分析了压裂水平井产能敏感因素.结果表明:压裂水平井的产能随裂缝条数、裂缝半长、裂缝间距的增加而增加;为获得较高的产能,压裂时应尽可能保持裂缝与井筒垂直;压裂缝条数一定时,裂缝越长、间距越大,压裂缝产能贡献越大,而裂缝越短、间距越小时,基岩向井筒供气的贡献越大,压裂缝贡献相对较小.研究成果为气藏压裂水平井设计提供了科学依据.     

天然气消费量的偏最小二乘支持向量机预测

结合偏最小二乘法和支持向量机的优缺点,提出基于偏最小二乘支持向量机的天然气消费量预测模型。首先,利用偏最小二乘法确定影响天然气消费量的新综合变量,建立以新综合变量为输入,天然气消费量为输出的支持向量机模型,对天然气消费量进行了预测;然后,与多元回归、偏最小二乘回归、普通支持向量机做误差检验比较,验证该方法的可行性与正确性。结果表明,此天然气消费量预测模型具有较高的精确度和应用价值。     

Flux growth and characterizations of NdPO4 single crystals

Neodymium phosphate single crystals, NdPO₄, have been grown by a flux growth method using Li₂CO₃-2MoO₃ as a flux. The as-grown crystals were characterized by X-ray powder diffraction(XRPD), differential thermal analysis (DTA) and thermogravimetric analysis (TG) techniques. The results show that the as-grown crystals were well crystallized. The crystal was stable over the temperature range from 26 to 1200 °C in N₂. The specific heat of NdPO₄ crystal at room temperature was 0.41 J/g °C. The absorption and the fluorescence spectra of NdPO₄ crystal were also measured at room temperature.