西曲煤显微组分化学结构的研究

应用红外光谱和电子顺磁共振对西曲煤显微组分的分子结构和自由基性质进行了研究。结果表明:镜质组、半镜质组和惰质组的芳碳率分别为0.84、0.91和0.93,镜质组分子结构单元中含有较多的脂肪取代基和螯形醌基;显微组分的自由基浓度(10~(18)spins/g):镜质组3.87,半镜质组18.98,惰质组40.10。镜质组自由基为较小的含氧型芳香π自由基,情质组自由基为巨大的纯芳香π自由基;半镜质组的分子结构和自由基性质均介于镜质组和惰质组之间。     

600MW汽轮发电机空载谐振现象及原因分析

本文示出了哈尔滨第三发电厂６００ＭＷ机组汽轮发电机空载谐振现象,分析了产生谐波的原因及危害,提出了谐振的防范措施。     

Photo-Induced Effect of the Electron-Spin Resonance on the Charge-Ordered State in Pr0.65Ca0.35MnO3

Electron-spin resonance (ESR) for the charge-ordered state in well-characterized Pr_0.65Ca_0.35MnO₃ exhibited significant change of both the absorption profile and the effective spin susceptibility upon injection of laser light with photon energy of 1.17 eV provided by Nd-YAG laser. The increase of the effective spin susceptibility was clearly found out thanks to the injection of photons in the temperature range 90 K–80 K, which is below the transition temperature from the antiferromagnetic charge ordered state to the canted antiferromagnetic spin alternation state, T _CAF125 K. The temperature dependence of the change of the ESR profile excludes the possibility of heating by laser light. The present result suggests that a kind of photo-induced insulator–metal transition may occur due to propagation of the delocalized carriers via probable double exchange interaction in the charge-ordering collapsed state created by the injection of photons.     

Nonequilibrium Thermodynamics of Mesoscopic Systems

The Markovian dynamics of a Brownian particle is derived in the case that the local temperature is a stochastic variable. The isolated mesoscopic particle plus environment system is analyzed in the microcanonical ensemble by means of nonlinear-process projection methods. The ensuing generalized Kramers FokkerPlanck equation involves a thermodynamic potential of mean force that is different from the canonical free energy, and the conditional entropy (or availability) emerges as the relevant steady-state potential. By coupling the system to a heat bath, we provide a microscopic foundation for the phenomenological theory of nonisothermal activation in mesoscopic systems. In the second part of this article, we then prove the existence of an availability potential governing the nonisothermal features of a Josephson junction in a SQUID, by studying the Josephson internal energy (and entropy) for T T _c in a model of two BCS superconductors coupled by a tunneling Hamiltonian. The predicted periodic dependence of the junction's T _c as a function of the flux in the SQUID has meanwhile been confirmed experimentally.     

Electron Spin Resonance in Pr0.65Ca0.35MnO3

The magnetic behavior of the distorted perovskite manganese, Pr_0.65Ca_0.35MnO₃ was studied by X-band electron spin resonance for powder samples. We observed the onset of the charge-ordered state at T _CO215 K, the antiferromagnetic transition with the peak of the ESR linewidth, H _p–p at T _AF180 K and the canted antiferromagnetic transition at T _CAF125 K associated with the abrupt increase of both the effective magnetization and H _p–p . Below 90 K, the absorption intensity profile becomes weakened with decreasing temperature suggesting the existence of some kind of magnetic disorder below 90 K, which is responsible for a part of evidence of the existence of the spin-glass state as has been proposed by Yoshizawa et al., Phys. Rev. B 52, 1689 (1996).     

Robust LQ Regulator for Jump Linear Systems with Uncertain Parameters

This paper deals with the robustness stabilizability of the class of linear systems with Markovian jumping parameters and unknown but bounded uncertainties. Under the assumption of the complete access to the system's states and its modes, we establish the robust stabilizability result under norm bounded uncertainties and also under structured uncertainties. We give the conditions under which the class of uncertain linear systems with jumping parameters will remain stable.     

Filtration of Colloidal Suspensions – MRI Investigation and Numerical Simulation

The principle mechanisms of solid‐liquid separation processes are sedimentation and filtration, both including the formation and compression of a liquid‐saturated bulk. The compressive properties of the bulk determine the operating parameters of solid‐liquid separation devices and the achievable separation results. Information about the solids volume fraction of the bulk is essential for a better understanding of the physical mechanisms and precise modeling. A numerical model for the calculation of the local solids volume fraction during formation and compression of filter cakes and sediments was developed. The calculated results are compared with experimental NMR data.     

Characterization of Structure and Transport in Porous Media by Pulsed Field Gradient (PFG) NMR Technique. Part I: Master Curve and Characteristic Inner Length

Systematic experimental studies focusing on the practical application of observation time dependent pulsed‐field‐gradient (PFG) NMR were performed. The objective was to provide engineering scientists with a reliable experimental tool for characterizing the structure and transport in fluid‐filled porous media. Observation time dependent self‐diffusion in glass bead packs as model systems was investigated, where the diffusing species (molecules of the solvent or dissolved particles) served as probes for the confining geometry in the porous medium. First, the basic question whether the obtainable structure information is independent of the actual mobility of the diffusing probe particles was examined experimentally. It could be demonstrated that plotting the normalized time‐dependent diffusion coefficient D(t)/D₀ versus the actual migration length l_D(t) during a given observation time t indeed yields a characteristic “master curve” that is independent of the mobility of the diffusing species, thus reflecting, as desired for a reliable method, solely the effects of the confining geometry of the porous system of interest. It was further shown that from the master curve a new quantity, i.e., a “characteristic inner length” or “correlation length” ξ_D can be derived that corresponds to a path length in the porous medium, after which particles in the pore fluid experience an averaged restricting geometry and diffuse with an effective diffusion coefficient D_eff. It turned out that ξ_D is surprisingly short, that is, in the order of the bead radius. Moreover, it was demonstrated that normalization of this migration length with the bead radius yields a common master curve for all monodisperse bead packs used and thus, it is obviously possible to derive and record master curves for different kinds of packs, beds or other porous media as references that can be used to characterize or certify the kind of the porous matrix of interest.     

Estimation of model quality

This paper provides an introduction to recent work on the problem of quantifying errors in the estimation of models for dynamic systems. This is a very large field. We therefore concentrate on approaches that have been motivated by the need for reliable models for control system design. This will involve a discussion of efforts that go under the titles of ‘estimation in ’, ‘worst-case estimation’, ‘estimation in ℓ₁’ and ‘stochastic embedding of undermodelling’. A central theme of this survey is to examine these new methods with reference to the classic bias/variance tradeoff in model structure selection.     

Nondestructive quality evaluation of fresh prunes by NMR spectroscopy

The potential for utilizing nuclear magnetic resonance measurements for evaluating the quality of fresh prunes was investigated. In a 2 T magnetic flux density, the chemical shift between proton hydrogens of soluble solids and those of water is less than 100 Hz. The band width of the water resonance spectrum of fruits is relatively large and therefore it is difficult to resolve between the spectral peaks of water and soluble solids. Measurements with a 100 mm Birdcage coil failed to resolve between the resonance peaks of soluble solids and water. Good resolution was achieved with a 20 mm diameter Surface coil. Signals (free induction decay) of 30 sugar prunes were acquired, and the spectra were calculated. Tuning and matching the coil before each measurement were not necessary, and the results were better when the magnetic field was not shimmed. The ratio of the soluble solids peak height to the water peak height correlated well (r = 0.907) with the soluble solids content of the prunes, as estimated by a refractometer.