Free Structures in Division Rings

Makar–Limanov's conjecture states that, if a division ring D is finitely generated and infinite dimensional over its center k, then D contains a free k-subalgebra of rank 2. In this work, we will investigate the existence of such structures in D, the division ring of fractions of the skew polynomial ring L[t; σ], where t is a variable and σ is a k-automorphism of L. For instance, we prove Makar-Limanov's conjecture when either L is the function field of an abelian variety or the function field of the n-dimensional projective space.     

低温工况下翅片管换热器的设计计算

采用分段模型将气化压力高于介质临界压力的翅片管换热器内低温介质的气化过程分为液相、气相两个传热区。同时考虑气化过程中翅片管表面结霜情况,对低温介质在翅片管换热器内的吸热气化过程进行传热分析,给出了适合各分区传热特性的计算关联式,为工程设计提供参考。     

Nonlinear dynamics of the heartbeat: II. Subharmonic bifurcations of the cardiac interbeat interval in sinus node disease

Changing the coupling of electronic relaxation oscillators may be associated with the emergence of complex periodic behavior. The electrocardiographic record of a patient with the “sick sinus syndrome” demonstrated periodic behavior including subharmonic bifurcations in an attractor of his interbeat interval. Such nonlinear dynamics which may emerge from alterations in the coupling of oscillating pacemakers are not predicted by traditional models in cardiac electrophysiology. An understanding of the nonlinear behavior of physical and mathematical systems may generalize to pathophysiological processes.     

粘土力学强度分层中的模糊数学模型

本文依据宁波北仑港海上大量的粘性土工程地质勘察资料和土工试验数据,以传统地质分层为背景,力学强度分层为目标,建立了一套模糊数学评判模型,并用计算机进行数据处理,定量地划分了粘性土的力学强度。     

A new method for the carrier-free production of 90y from 90sr-90y mixture and 89sr from neutron-irradiated y2o3

The extraction of strontium(II) and yttrium(III) ions from aqueous solutions at various pH values into methyl isobutyl ketone containing I-phenyl-3-methyl-4-caprylpyrazolone-5 is described. Quantitative extraction of Sr and Y at pH 8.6–10 and pH 2.8–5.4 respectively is utilized for the carrier-free production of ⁹⁰Y from ⁹⁰Sr–⁹⁰Y mixtures and ⁸⁹Sr from neutron-irradiated yttrium oxide. A clean separation of these elements from each other and more than 95% calculated activities were recovered     

Use of ir and 13c-nmr data in the retrieval of functional groups for computer-aided structure determination

Computer-aided interpretation of ¹³C-n.m.r. and i.r. spectra of organic molecules (m.w. ? 500) is done by an artificial intelligence approach. The output of the proposed ASSIGNER system is a list of functional groups which are reasonable candidates for the final structural isomers. The procedure of finding possible functional groups and the main features of the filtering steps are outlined. One search is worked out in detail to demonstrate the capability of the system.     

Kinetic treatment of unsegmented flow systems : Part 2. Detailed Treatment of Flow-Injection Systems with Gradient Chamber

A kinetic model is utilized for a detailed mathematical treatment and experimental evaluation of single-channel and dual-channel flow injection systems that include a gradient chamber. The kinetic model includes three distinct stages in the process, namely clearing reactant from the gradient chamber by first portions of sample, continued entry of sample into the gradient chamber, and decrease of determinant concentration in the gradient chamber via dilution and reaction with reagent. Equations predict entirely different behavioral patterns for different conditions and these predictions are verified experimentally for a wide range of conditions. The data show that the variable-time kinetic model is superior to the titration models previously utilized to describe these flow systems. The principal limitation of the kinetic equations involves an assumption of plug flow that is not completely valid. The extent of deviations from ideal behavior depend on conditions, but are negligible at low concentrations (0–50 mmol l^-1) and can be 10% or larger at higher concentrations (100 mmol l^-1). While equations are not exact, they are useful in predicting performance characteristics for a variety of conditions and experimental approaches.     

Quenching of aromatic hydrocarbon triplet states by stable carbon free radicals

Quenching of the triplet states of a series of polynuclear aromatic hydrocarbons in solution by three members of the bis-biphenylene allyl radical family has been studied. Bimolecular rate constants for the quenching process have values corresponding to a diffusion controlled process; in contrast to quenching by nitroxide radicals, there is no clear dependence of quenching rate constant on the triplet energy of the hydrocarbon being quenched. It is proposed that the mechanism leading to quenching is based on an exchange interaction between the tree radical and the triplet state.     

Magnetic properties of iron-intercalated titanium diselenide

Powder samples of Fe_xTiSe₂ (0.00 ≤ x ≤ 0.50) have been prepared by direct reaction of high purity elements. Crystal parameters were determined by the Debye-Scherrer powder diffraction technique. Magnetic susceptibility measurements were made by the Faraday method in the temperature range 1.5–300 K and indicated magnetic odering for compositions with x > 0.03. The magnetic ordering temperature, T_m, was observed to move to higher temperature with increasing iron concentration. These results have been interpreted in terms of a spin-glass model for low iron concentrations (x < 0.2) and antiferromagnetism for high concentrations (x > 0.2).     

Sensitized multiphoton dissociation of UF6 IN SF6-UF6 mixtures by a tea CO2 laser

UF₆ undergoes decomposition in the presence of SF₆ when mixtures of both are irradiated with a TEA CO₂ laser. The mechanism for UF₆ decomposition may involve vibrational energy transfer from excited SF₆ and laser absorption from the same laser pulse by excited UF₆ in its vibrational quasi-continuum