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31.
An efficient, reliable and easily programmed method for solving systems of equilibrium stage separation devices is described. The method is an extension of an algorithm developed by Ishii and Otto(9) for single columns. It solves all equations simultaneously, takes advantage of the basic tridiagonal matrix form form of the linearized steady state equations and can handle configurations which include distillation columns, absorbers and reboiled absorbers. The solution for a thermally coupled distillation system is presented. 相似文献
32.
Erik E Luther Fred F. Lange Dale S. Pearson 《Journal of the American Ceramic Society》1995,78(8):2009-2014
Two different methods are used to coat silicon nitride particles with an alumina precursor to make Si3 N4 behave like Al2 O3 in aqueous slurries. The first method involves the precipitation of an aluminum hydroxycarbonate from dissolved Al(NO3 )3 during the decomposition of urea. In the second method, dry silicon nitride powder is reacted with aluminum tri- sec -butoxide in hexane at room temperature. Both methods produce a coated powder in which the electrophoretic and rheological properties of aqueous slurries mimic those of alumina. When salt is added to slurries consisting of coated Si3 N4 powder, all rheological evidence suggests the presence of a short-range repulsive potential that produces a weakly attractive particle network similar to that previously reported for Al2 O3 powder. Although electrophoretic and rheological data showed that the coated powder behaved like Al2 O3 , consolidation data indicated that slurries of coated powder with added salt did not pack to high density. In addition, these bodies were not plastic as found for bodies consolidated from dispersed and salt-added Al2 O3 slurries. 相似文献
33.
Mari Lou Balmer Fred F. Lange Carlos G. Levi 《Journal of the American Ceramic Society》1994,77(8):2069-2075
Aqueous solutions of zirconium acetate and aluminum nitrate were spray pyrolyzed at 250°C and upquenched to different temperatures to yield metastable solid solutions of composition Zr(1− x ) Alx O(2− x /2) . An amorphous oxide forms first during pyrolysis which subsequently crystallizes as a single phase for x ≤ 0.57 (≤40 mol% Al2 O3 ). The crystallization temperature increased with Al2 O3 content. Electron diffraction, supported by Raman spectroscopy, indicates that the initial phase is tetragonal. At higher temperatures, the initial solid solation partitions to other metastable phases, viz., t -ZrO2 +γ-Al2 O3 , prior to achieving their equilibrium phase assemblage, m -ZrO2 +α-Al2 O3 . Partitioning yields a nanocomposite microstructure with grain sizes of 20–100 nm, compared to the 3 to 5 nm in the initial, single phase. Compositions containing 45 to 50 mol% Al2 O3 concurrently crystallize and partition. The structure selected during crystallization and the partitioning phenomena are discussed in terms of diffusional constraints during crystallization, which are conceptually similar to those operating during rapid solidification. 相似文献
34.
At temperature above 300°C the glycosyl units of cellulose are simultaneously depolymerized to a tar and decomposed to a char by evolution of H2O, CO, and CO2. When the glycosyl units are depleted, a stable char is formed containing about 30% aliphatic and 70% aromatic components. The aliphatic component is formed first, but on further heating is converted to polycyclic aromatic structures. The chars formed at lower temperatures are more combustible because the aliphatic component of the char is highly pyrophoric and is oxidized almost at the same temperature at which it is formed (~360°C). The aromatic component, however, is less reactive and is oxidized at ~520°C. Consequently, the chars formed at higher temperatures are less combustible. It has been shown that (NH4)2HPO4, which is a well-known flame retardant and smoldering inhibitor, lowers the pyrolysis temperature and increases the char yield by accelerating the decomposition reactions. This affects the composition of the intermediate chars but the final products have about the same composition irrespective of additives. (NH4)2HPO4 also lowers the rate of oxidation of the aromatic component and the corresponding heat release. NaCl, which is an enhancer of smoldering combustion, has a slight stabilizing effect on pyrolysis of cellulose. It lowers the oxidation temperature of the aromatic component and dramatically increases its rate. The corresponding heat release is also increased due to complete oxidation to CO2. The rate of oxidation calculated from the dynamic thermal analysis data is more than tripled by NaCl and significantly reduced by (NH4)2HPO4. 相似文献
35.
The crystal state binding of sodium ditbionite to deoxyhemoglobinis reported. Dithionite has been used extensively to deoxygenatehemoglobin and myoglobin and there has been considerable interestamong users of dithionite about its effect on protein structureand binding site(s). We have determined that dithionite bindsto deoxygenated hemoglobin crystals at the interface of twomolecules in the crystal lattice. Specific residues involvedin hydrogen bonds or salt interactions with dithionite includeHisll6 and Hisll7 of the ft subunit and Lysl6 of the ß2subunit of the adjacent hemoglobin molecule. No binding wasobserved at the symmetry related Hisll6 and 117 ß1 residues.We have shown that dithionite does not affect the native hemoglobinstructure or the binding of several allosteric inhibitors tohemoglobin and can be used to mount T state crystals in theair 相似文献
36.
Definition of the problem:
Being satisfied with one’s work depends on professional autonomy, which is attributed to the medical profession to a high degree, combined with specialized knowledge and moral authority for vital questions. That is why physicians enjoy a high reputation. At the beginning of a person's medical career, moral competence is developed nearly completely, but specialized knowledge must be learned. Hospitals, in which further medical education regularly takes place, are still traditionally hierarchically organized today. Unfortunately, feudalistic or military structures hinder autonomous moral decisions and cause structural irresponsibility.Arguments:
Obstructions and pressure by superiors, financial restrictions, arrogance and trying to make one's mark are shown in typical conflict situations. Stress, discontent, moral conflicts and illness, even including burn out are possible. Commitment and creativity by employees are prevented and mistakes cannot be constructively managed. Thus, patients may suffer unreasonably or be hurt.Conclusion:
There is a risk to subordinate moral principles under other interests, not only with subordinates but also with superiors. Ways to create a culture that promotes autonomy among physicians and between different professions are discussed. Therefore it is necessary to institutionalize communication based on a reciprocal high regard in a team with people treated as equal partners, who are then able to discuss moral questions in a discourse. 相似文献37.
Lourenço André Rota Bulò Samuel Rebagliati Nicola Fred Ana L. N. Figueiredo Mário A. T. Pelillo Marcello 《Machine Learning》2015,98(1-2):331-357
Machine Learning - Clustering ensemble methods produce a consensus partition of a set of data points by combining the results of a collection of base clustering algorithms. In the evidence... 相似文献
38.
This paper presents procedures for efficient design sensitivity analysis for shape memory alloy (SMA) structures modeled with shell elements. Availability of sensitivity information at low computational cost can dramatically improve the efficiency of the optimization process, as it enables use of efficient gradient-based optimization algorithms. The formulation and computation of design sensitivities of SMA shell structures using the direct differentiation method is considered, in a steady state electro-thermo-mechanical finite element context. Finite difference, semi-analytical and refined semi-analytical sensitivity analysis approaches are considered and compared in terms of efficiency, accuracy and implementation effort, based on a representative finite element model of a miniature SMA gripper. 相似文献
39.
Work on single tone frequency estimation has focused on uniformly sampled data. However, it has been shown that, for a given number of samples, more information on the frequency of a signal can be gained by non-uniform sampling schemes [M. Wieler, S. Trittler, F.A. Hamprecht, Optimal design for single tone frequency estimation, Digital Signal Process., in press]. Unfortunately, an optimum sampling pattern (that, for example, minimizes the Cramér–Rao bound) does not automatically have a fast and simple algorithm for frequency estimation associated with it. For application in an interferometric measurement system, an algorithm is needed that gathers as much information as possible from a low number of samples, while at the same time keeping the computational effort sufficiently low to process millions of time series in a few seconds. This paper proposes a simple approximation to the optimum sampling pattern by using uniformly sampled blocks of data and further proposes to estimate phase and frequency in each of these blocks and to exploit these intermediate results in the final estimation. An approach to do so is investigated in detail. Results are compared to the Cramér–Rao bound (CRB), and it is shown that this algorithm almost reaches this limit on the variance of unbiased estimators, at a computational complexity lower than that of a typical FFT-based approach. For samples and a signal-to-noise ratio of 10, the standard deviation of the frequency estimate is lower by more than 50% compared to uniform sampling. In addition, the algorithm can easily be applied to poorly characterized systems, e.g. systems for which the noise is not known exactly. Finally, we demonstrate that the proposed strategy yields results that are within 3% of the theoretically achievable accuracy for the theoretically optimum sampling pattern. 相似文献
40.
Fred Glover 《OR Spectrum》1995,17(2-3):125-137
Scatter search and genetic algorithms have originated from somewhat different traditions and perspectives, yet exhibit features that are strongly complementary. Links between the approaches have increased in recent years as variants of genetic algorithms have been introduced that embody themes in closer harmony with those of scatter search. Some researchers are now beginning to take advantage of these connections by identifying additional ways to incorporate elements of scatter search into genetic algorithm approaches. There remain aspects of the scatter approach that have not been exploited in conjunction with genetic algorithms, yet that provide ways to achieve goals that are basic to the genetic algorithm design. Part of the gap in implementing hybrids of these procedures may derive from relying too literally on the genetic metaphor, which in its narrower interpretation does not readily accommodate the strategic elements underlying scatter search. The theme of this paper is to show there are benefits to be gained by going beyond a perspective constrained too tightly by the connotations of the term genetic. We show that the scatter search framework directly leads to processes for combining solutions that exhibit special properties for exploiting combinatorial optimization problems. In the setting of zero-one integer programming, we identify a mapping that gives new ways to create combined solutions, producing constructions calledstar-paths for exploring the zero-one solution space. Star-path trajectories have the special property of lying within regions assured to include optimal solutions. They also can be exploited in association with both cutting plane and extreme point solution approaches. These outcomes motivate a deeper look into current conceptions of appropriate ways to combine solutions, and disclose there are more powerful methods to derive information from these combinations than those traditionally applied.This research is supported in part by the Joint Air Force Office of Scientific Research and Office of Naval Research Contract No. F49620-90-C-0033 at the University of Colorado 相似文献