Uniform sampling Subject

Sample subjected to uniform tensile stress Tensile strength... 

After the proof-of-principle that covariance proves robust in the case of sparsely sampled data sets, non-uniformly sampled data were finally subjected to covariance processing for the analysis of anisotropic liquid crystal samples investigated by natural abundance 2D NMR [38]. A natural abundance deuterium (NAD) Q-COSY with a z-gradient filter, Q-COSY Fz, was used for data acquisition [69,70]. The sequence involves cancellation of diagonal peaks. As NUS scheme, exponentially weighted deterministic on-grid sampling was employed [71]. Yet, quantitative direct... 

In Eqn. 3 the first term represents the shear deformation, the second term represents the volume change due to the mean stress and the third term represents the volume change due to the sintering potential. A uniform compact of any shape shrinks according to the third term if it is unconstrained and not subject to any external force. Therefore this term as a whole can be determined from free sintering experiment using uniform samples according to that... 

Speaking pictorially, the quasiergodic hypothesis implies that the trajectory of a single system, while it does not cover phase space, uniformly samples phase space. Questions regarding ergodlc properties of Hamiltonian systems are extremely complicated, and the subject is under active study today. But in practice an MD system is not quite Hamiltonian, because solving the equations of motion as finite difference equations Introduces a certain randomness Into the phase space trajectory. This property of the trajectory, which will be discussed In detail In Section III, presumably justifies the quasiergodic hypothesis for an MD system. 

Improper sampling can introduce errors originating at the surface (8.7) because x-ray emission spectrography operates only on a surface layer of critical thickness (6.4). Powders are particularly subject to errors that result from segregation and lack of uniformity in general (7.8, 7.15). Nonuniform residues from the evaporation of solutions can be troublesome. 

There are two main types of viscometer rotary instruments and tubular, often capillary, viscometers. When dealing with non-Newtonian fluids, it is desirable to use a viscometer that subjects the whole of the sample to the same shear rate and two such devices, the cone and plate viscometer and the narrow gap coaxial cylinders viscometer, will be considered first. With other instruments, which impose a non-uniform shear rate, the proper analysis of the measurements is more complicated. 

For simplicity and convenience, sampling at evenly spaced intervals over a population is often used in place of random sampling For example, a field may be divided into uniform segments, and a sample taken from the center of each segment This procedure is generally subject to more bias than random sampling Should periodicity in the population be present or suspected, segments to be sampled should be selected with the... 

Some of the procedures used to assess mixture uniformity (e.g. the visual inspection of spectra) are subjective. Those based on mathematical parameters are objective. However, most require spectral information from homogeneous samples, so criteria can be established only after the process is finished. 

The current transfer problem that had been identified with low temperature superconducting composites deserves additional mention for the high temperature superconductors, that in the bulk material are frequently not fully dense. Making the electrical connection in such a manner as to obtain uniform current distribution throughout the cross section of the material is difficult. The method described by Jin, et al. (24) with embedded wires or particles may provide for a significant improvement but the present techniques used to determine the critical current by a surface contact on the ceramic sample are subject to this problem. A discussion for the multifilamentary wire of NbsSn is provided by Goodrich and Fickett (30) and this discussion is likely to be similar to the high temperature materials that are not fully dense. 

To improve the meso-structural order and stability of the mesoporous silica ropes, a postsynthesis ammonia hydrothermal treatment (at 100 °C) was invoked. As indicated by the XRD profile in Fig. 3A, 4-5, sharp features are readily observed in ammonia hydrothermal treated samples. Moreover, after the post-synthesis ammonia treatment, the sample also possesses a sharp capillary condensation at p/po 0.35(Fig. 3B) corresponding to a much narrower BJH pore size distribution of ca. 0.12 nm (at FWHM). In other words, the mesostructures are not only more uniform but also more stable when subjected to the post-synthesis treatment. The morphology of the silica ropes remained unchanged during the ammonia hydrothermal process. The mesostructures remain intact under hydrothermal at 100 °C in water even for extended reaction time (> 12 h). 

The effects of post-synthesis alumination on purely siliceous MCM-41 material with A1(NC>3)3 on acidity have been studied by FTIR, NH3-TPD, and IPA decomposition reaction. The FTIR results of pyridine absorption show that both Lewis and Bronsted acid sites are increased by the post-modification. The amount of NH3 adsorbed on the alumina-modified MCM-41 samples increases with the loading of Al onto the surface of MCM-41. Due to the improved acidity, the alumina-modified MCM-41 materials show considerably higher catalytic activity for dehydration of isopropanol than purely siliceous MCM-41. In addition, XRD and N2 adsorption results show that all MCM-41 samples maintained their uniform hexagonal mesoporous structure well after they have been subjected to post-synthesis alumination with the loading of Al species on Si-MCM-41 varied from 0.1 wt. % up to 10 wt. % (calculated based on AI2O3). 

---