干空气和冷冻水联产除湿空调节能特性研究

本文提出了一种将转轮除湿和再生式蒸发冷却相结合来实现干空气和冷冻水联产的除湿空调系统,以各组成部件为基础,建立了该系统的计算模型,并对其节能特性进行了分析.结果表明,ARI夏季工况下,干空气和冷冻水联产空调的热力COP在1左右,电力COP可达9.03,相应电力消耗和CO2排量比常规空调减少72.69%之多.存在使系统具有较好性能结构的再生温度范围.可以通过改变干空气比来调节潜/显热处理能力,进而实现无能量浪费地提供全部所需冷量.     

Extrinsic versus intrinsic high-field and high-frequency EPR properties of magnetic materials

Performing high-field and high-frequency electron paramagnetic resonance (HFHFEPR) experiments on a one-dimensional (1-D) magnetic system, we put in evidence a number of effects that can be attributed to extrinsic properties of the sample and have to be distinguished from the intrinsic physical properties of the investigated system. We have studied a 1-D molecular-based magnetic system made up by trivalent gadolinium ions (Gd³⁺) and the nitronyl-nitroxide radicals (NIT-Et = 2-ethyl-4,4,5,5,-tetramethyl-4,5-dihydro-1-H-imidazolyl-1-oxyl-3-oxide). In addition to showing the effects of short-range magnetic correlation on HFHFEPR spectra of this compound, this paper is also intended to be a starting point of an investigation of the methods according to which HFHFEPR spectra should be performed in order to estimate the importance, minimize and possibly correct the effects of orientation, propagation and demagnetization phenomena when dealing with magnetic materials.     

Relaxation Limit for Aw-Rascle System

We study the relaxation limit for the Aw-Rascle system of traffic flow. For this we apply the theory of invariant regions and the compensated compactness method to get global existence of Cauchy problem for a particular Aw-Rascle system with source, where the source is the relaxation term, and we show the convergence of this solutions to the equilibrium state.     

Facile synthesis of 3‐substituted [1,2,4]triazino[3,4‐f]purine‐4,6,8‐trione derivatives

A new synthetic route to build the [1,2,4]triazino[3,4‐ f]purine nucleus is described. The novel [1,2,4]‐triazino[3,4‐ f]purine‐4,6,8(l H,7 H,9 H)‐trione derivatives were obtained by condensation of 8‐hydrazinotheophylline with appropriate glyoxylic acids via the intermediate hydrazones.     

Dependence on relaxation times of longitudinally detected paramagnetic resonance

The spin system longitudinal magnetization at resonance, irradiated by two nearly resonant transversal waves, oscillates. The oscillation for low signal intensities depends linearly on the product T₁·T₂. This effect allows to resolve overlapping spectra which are usually not detectable.     

A X-band ESR apparatus using a Whispering Gallery Mode dielectric resonator

The behaviour of a disc-shaped dielectric resonator (DR) working in the Whispering-Gallery Modes (WGM) when used for X-band ESR experiments has been tested. It has been verified that the WGM in the resonator can be excited by using the microwave bridge of a Bruker spectrometer. The microwave field is well confined in the DR also in the absence of metal shieldings as demonstrated by the high Q values of the detected resonances. A large number of such resonances has been detected from eight up to twelve gigahertz making the DR a very broadband device. ESR spectra of various powder and aqueous samples have been obtained and compared with those of the same samples recorded by using a metal cavity. The relative amplitude of the spectra demonstrated that for aqueous samples the sensitivity of DR is similar to that of the metallic cavity. Further investigations are in progress to enhance the overall performance.     

A multifrequency EPR approach to travertine characterisation

The understanding of processes that give rise to travertine deposits is important. This is so because of its widespread use as decorative material, but more so in environmental studies due to the significance, by proxy, of travertine in climatology. In this paper, a multifrequency EPR spectroscopy study of the behaviour of an ubiquitary vicariant of Ca in calcite, Mn(II), is presented. EPR spectra were obtained from a natural sample at 9.5 (X-band), 95, 190, and 285GHz, and interpreted through numerical simulation. An analysis of the distribution of the zero-field splitting interaction revealed the source of some unexpected spectral features in the width of the lines in the X-band. By contrast, the homogeneous broadening plays only a minor role. Moreover, field-dependent anisotropies of the Zeeman and hyperfine tensors were observed at higher frequency. On the basis of results garnered in this study, the ZFS interaction of Mn(II) has been ascribed to the microstructural anomalies of the Mn(II) distribution in calcite. This may be considered as the fingerprint of the physical-chemical conditions at the time of travertine deposition. As a consequence, X-band EPR spectroscopy represents a specific tool to investigate the genesis, and to check the homogeneity of Mn(II) distribution in travertines as well as in other calcite-based materials.     

How and why the characterization of magnetic materials can give directions in the methodological development in high field–high frequency EPR

The experimental problems linked to the use of the ultra-wide band high field-high frequency Electron Paramagnetic Resonance (HF²-EPR) spectrometers are illustrated with some key examples. The single pass technique is critically analyzed and compared with other techniques. Propagation and magnetic field dependent phenomena are illustrated with the aid of three key examples and discussed. The possible actions to be taken in order to minimize and possibly eliminate these extrinsic effects affecting the spectra obtained with the single pass technique are proposed. Future instrumental developments are discussed in the light of the experience acquired in this study.