T (Mx+q)=0, Mx+q≥0, x≥0 has a solution. We explain how one can use the polyhedral structure of the set of all triangulations
of a finite point set to determine if an n×n matrix M is a Q-matrix. Our implementation of the algorithm is practical for
deciding the Q-nature for all M with n≤8.
Received May 30, 1997 / Revised version received June 12, 1998
Published online November 24, 1998 相似文献
This paper introduces thelocally Farkas-Minkowski (LFM) linear inequality systems in a finite dimensional Euclidean space. These systems are those ones that satisfy that any consequence
of the system that is active at some solution point is also a consequence of some finite subsystem. This class includes the
Farkas-Minkowski systems and verifies most of the properties that these systems possess. Moreover, it contains the locally
polyhedral systems, which are the natural external representation of quasi-polyhedral sets. TheLFM systems appear to be the natural external representation of closed convex sets. A characterization based on their properties
under the union of systems is provided. In linear semi-infinite programming, theLFM property is the more general constraint qualification such that the Karush-Kuhn-Tucker condition characterizes the optimal
points. Furthermore, the pair of Haar dual problems has no duality gap. 相似文献
CO2-switchable oligomeric surfactants have good viscosity-reducing properties; however, the complex synthesis of surfactants limits their application. In this study, a CO2-switchable “pseudo”-tetrameric surfactant oleic acid (OA)/cyclic polyamine (cyclen) was prepared by simple mixing and subsequently used to reduce the viscosity of heavy oil. The surface activity of OA/cyclen was explored by a surface tensiometer and a potential for viscosity reduction was revealed. The CO2 switchability of OA/cyclen was investigated by alternately introducing CO2 and N2, and OA/cyclen was confirmed to exhibit a reversible CO2-switching performance. The emulsification and viscosity reduction analyses elucidated that a molar ratio of OA/cyclen of 4:1 formed the “pseudo”-tetrameric surfactants, and the emulsions of water and heavy oil with OA/cyclen have good stability and low viscosity and can be destabilized quickly by introducing CO2. The findings reported in this study reveal that it is feasible to prepare CO2-switchable pseudo-tetrameric surfactants with viscosity-reducing properties by simple mixing, thus providing a pathway for the emulsification and demulsification of heavy oil by using the CO2-switchable “pseudo”-oligomeric surfactants. 相似文献
The efficient and straightforward NHC-rhodium-catalyzed thiol-silane and thiol-germanane coupling reactions, leading to new classes of functionalized SQ-based materials, are presented for the first time. The proposed strategies use commercially available reagents and show a broad functional groups tolerance, which opens a possibility of effective synthetic procedures of biologically active compounds. 相似文献
The trisilanol isobutyl polyhedral oligomeric silsesquioxane(POSS) was fabricated into liquid-like nanoparticle organic hybrid materials(NOHMs) with γ-(2,3-epoxypropoxy)propytrimethoxysilane as corona and polyetheramine M2070 as canopy, and the product was called liquid-like POSS NOHM. The liquid-like POSS NOHM has a low viscosity at room temperature without any solvent and the mass fraction of trisilanol isobutyl POSS was 23.38%. The liquid-like POSS NOHM shows great CO2 capturing property with a capacity of 2.108 mmol/g(pCO2=6 MPa). The physical adsorption increased obviously with the pressure going up and it may make a difference between liquid-like POSS NOHMs and traditional monoethamolamine(MEA) based CO2 absorbent. The recycle property was also studied. The NOHM behaved as fresh product even after 10 cycles. 相似文献
Isotactic polypropylene(iPP) was modified by the introduction of polyhedral oligomeric silsesquio- xanes(POSS) and 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol(DMDBS). Chemical combination of (3-mercapto)- propyl-heptaisobutyl POSS with DMDBS(POSS-DMDBS), and physical mixing of DMDBS with octaisobutyl POSS (iso-POSS/DMDBS) or trisilanolisobutyl POSS(tri-POSS/DMDBS) were applied respectively to modifying iPP, and the effects of POSS and DMDBS on crystallization, rheological and mechanical properties of iPP were systematically investigated. The results indicate that iso-POSS/DMDBS and tri-POSS/DMDBS were more effective than POSS-DMDBS on the improvement of the crystallization behavior of iPP due to the higher crystallization temperature, while the crystallinity of iPP containing POSS-DMDBS was enhanced, approximately approached to that of iPP containing tri-POSS/DMDBS. The tensile strength of iPP with POSS-DMDBS was significantly increased from 34 MPa to 40 MPa, as high as that of iPP with iso-POSS/DMDBS. The different effects caused by the specific interaction between POSS and DMDBS could possibly be applied in the modification of iPP. 相似文献
A novel well‐defined amphiphilic block copolymer, with the polyhedral oligomeric silsesquioxane (POSS) moiety at the junction of the two blocks of polystyrene and poly(ethylene oxide) (PEO), was designed and synthesized. First, a macroinitiator containing a POSS moiety and a PEO chain was prepared and then atom transfer radical polymerization of styrene was carried out in the presence of the macroinitiator in bulk. The polymerization results show that the process bears the characteristics of controlled/living free radical polymerizations. The structure and molecular weight of the polymers were characterized by GPC, 1H NMR, and FT‐IR spectroscopy. The self‐assembly behaviors of the polymers was investigated by TEM and SEM. It was observed that the polymers can self‐assemble into vesicles in aqueous solution.