Spatial or flow velocity phase encoding gradients in NMR imaging

We describe time modulated field gradient sequences able to selectively phase encode spatial location or flow velocity in NMR Signals. Two flow conditions are presented: constant flow velocity and simple harmonic flow superposed on steady flow. In each case we show that specific modulated gradients are available in order to discriminate between stationary and mobile protons. The methods are presented in the one dimensional case. The advantages of the phase modulation for flow analysis are the following: the method is sensitive to flow direction, unaffected by the T₂, and the stationary and flow parameters are quantifiable factors.     

The HN method for half-space Albedo and constant source problems for isotropic and anisotropic scattering kernels

The H_N method, which is developed recently, is used to solve the half-space albedo and the half-space constant source problems for both isotropic and extremely anisotropic scattering kernels. It has been shown that the method solves the problems in a concise manner and leads to fast converging numerical results as shown in tables.     

A modified PGSE for measuring diffusion in the presence of static magnetic field gradients

With a proper timing of pi pulses, it is possible to reduce the effect of the static internal magnetic field gradient on the measurement of diffusion with the pulsed gradient spin echo (PGSE). A pulse sequence that in the first order eliminates the effect of weak internal static gradients in a standard PGSE experiment is introduced. The method should be applied in the cases, where strong and short magnetic gradient pulses are used to investigate the motion of liquid in heterogeneous samples with large susceptibility differences such as porous media.     

Four-component gas/water/oil displacements in one dimension: part II,example solutions

In this article analytical solutions are constructed for a system of conservation laws modeling compositional flow of four components in three phases using the method of characteristics (MOC). Every component partitions between all phases present, and the equilibrium volume ratios of the components in each phase are fixed. Riemann problems modeling the injection of carbon dioxide and water in a depleted oil reservoir are studied, and the sensitivity of the solutions to changes in boundary conditions is analyzed. Finally the MOC solutions are compared to simulated displacements.     

A systematic experimental study on the phase behavior of complex fluid mixtures up to near-critical region

The near-critical phase behavior of five synthetic reservoir fluid mixtures has been systematically studied using a ROP (France) high-pressure PVT system. The C₇⁺-content in the prepared samples ranges from 6.67 to 11.15 mol%. Through a series of constant composition expansion experiments performed in the temperature range of 303–433 K, the compressibility factor of compressed fluid (in the single-phase region), partial pressure–temperature (P–T) phase envelope, total molar volume and liquid volume fraction in the two-phase region have been measured for each sample. In addition, the critical point data of three samples were determined.     

川芎药材中常量和微量元素的测定

采用火焰原子吸收光谱法测定了8种川芎样品中Mg、Fe、Mn、Zn 4种常量、微量元素的含量。元素的回收率在95.8%—100.8%之间,RSD均不大于1.634%,方法稳定可靠。结果表明,川芎样品中常量、微量元素含量丰富,依次为Mg>Fe>Zn>Mn,其中Mg的含量在3500μg·g^-1以上。川芎药材中高含量的Mg是否与其活血行气,祛风止痛功效有关,待进一步研究。本研究可为深入了解和探讨川芎常量和微量元素及药效机理提供参考。     

Electrical field on non-ceramic insulators and its relation to contact angles for constant volume droplets

The presence of water droplets on the surface of insulators provides intensification of the electric field, which are caused by the non-uniform voltage distribution and dielectric properties of the different materials. The degree of Electric field (E-field) intensification at the triple joint, the region where water, the non-ceramic dielectric and the air are in contact, must be carefully analyzed, because under certain conditions, breakdown voltages can be reached, sometimes, under very little or no contamination at all, which can cause the insulator wettability, tracking, flashover and degradation. In this paper, variations of the electrical field over two polymer compounds widely used in the insulator manufacturing industry, Silicone Rubber (SIR) and High Density Polyethylene (HDPE), are analyzed on a 2D geometry with respect to contact angles of constant volume water droplets. The Electrical field is also computed as a function of relative water droplets distances.     

Low complexity PPN-FBMC Receivers with improved sliding window equalizers

Bandwidth and latency in future 5G and beyond multiple access systems are two extremely important metrics for which the requirements are very strict. Filter Bank Multi-Carrier (FBMC) is a promising scheme that can satisfy many future requirements due to its advantageous spectral characteristics. However, the required computational complexity is one of its major drawbacks. In this paper, we propose two improved receiver structures for the PolyPhase Network (PPN) based FBMC receivers. These improved structures reduce the complexity of the receivers to almost half of the conventional PPN receivers taking advantage of the real valued signal processing. We also investigate the Sliding Window (SW) equalizer technique to enable the implementation of the proposed structures in multipath environments. Furthermore, we propose two modifications to the SW equalization method. First, by using the Hopping Discrete Fourier Transform (HDFT) the complexity requirements can be reduced. Second, by applying overlapped windows the overall system performance in terms of bit error rate can be improved.     

A classification of unitary invariant weakly complex Berwald metrics of constant holomorphic curvature

In this paper, we give a characterization of strongly pseudoconvex complex Finsler metric F which is unitary invariant. A necessary and sufficient condition for F to be a weakly complex Berwald metric and a necessary and sufficient condition for F to be a weakly Kähler Finsler metric are given, respectively. We also give a classification of unitary invariant weakly complex Berwald metrics which are of constant holomorphic curvatures.