An Improved Reachability Analysis Method for Strongly Linear Hybrid Systems

in Lecture Notes in Computer Science (1997), 1254

This paper addresses the exact computation of the set of reachable states of a linear hybrid system. It proposes an approach that is an extension of classical state-space exploration. This approach uses a ... [more ▼]

This paper addresses the exact computation of the set of reachable states of a linear hybrid system. It proposes an approach that is an extension of classical state-space exploration. This approach uses a new operation, based on a cycle analysis in the control graph of the system, for generating sets of reachable states, as well as a powerful representation system for sets of values. The method broadens the range of hybrid systems for which a finite and exact representation of the set of reachable states can be computed. In particular, the state-space exploration may be performed even if the set of variable values reachable at a given control location cannot be expressed as a finite union of convex regions. The technique is illustrated on a very simple example. [less ▲]

Improved separation and quantification of dioxin and furan congeners using Novel low-bleed capillary gas chromatography columns and mass spectrometry

in Organohalogen Compounds (2004), 66

Improved separation of the 209 polychlorinated biphenyl congeners using comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry

in Journal of Chromatography. A (2004), 1040(2), 227-238

The separation of the 209 polychlorinated biphenyl (PCB) congeners has been studied using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOFMS). Four ... [more ▼]

The separation of the 209 polychlorinated biphenyl (PCB) congeners has been studied using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOFMS). Four column combinations based on thermally stable phases, DB-1/HT-8, DB-XLB/HT-8, DB-XLB/BPX-50, and HT-8/BPX-50, have been investigated. The HT-8/BPX-50 set produced the best separation. The distribution of the 100 to 150 ms wide peaks was highly structured in the chromatographic space and based on the degree of ortho-substitution within each separated homologue series. A total of 192 congeners were resolved in 146 min (1.3 analyte per min) using this column set. Eight coelutions involved 17 congeners. Among them, seven congeners were present in Aroclors at levels >1.0 wt.% (CBs 33, 47, 48, 95, 97, 163, 187). Except for CBs 47 and 48, none of the major constituents of commercial mixtures were coeluting. CB 138 was well separated from CBs 163 and 164 in the second dimension. For all column sets, CBs 20, 33, and 109 always coeluted with other PCBs. The 12 toxic dioxin-like congeners (CBs 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, 189), and the seven European Union marker PCBs (CBs 28, 52, 101, 118, 138, 153, 180) were separated from any interfering congeners. This was not the case for the other investigated column sets. [less ▲]

Improved stability and transient behaviour of generalized-alpha time integrators for constrained flexible systems

Conference (2011, November)

An Improved Test to Study the Changes in Membrane Permeability During Rehydration of Freeze-Dried Weissella paramesenteroides LC11

in The Open Biotechnology Journal (2010), 4

The objective of this study was to assess changes in membrane permeability during rehydration of freeze-dried Weissella paramesenteroides LC11. Viability was assessed using the electrical conductivity ... [more ▼]

The objective of this study was to assess changes in membrane permeability during rehydration of freeze-dried Weissella paramesenteroides LC11. Viability was assessed using the electrical conductivity measurement (ms cm-1 g-1 dry weight) and the plate count method (cfu g-1 dry weight). The symptoms of injury included an increase in the electrolyte leakage during the first 4 h of rehydration in Milli Q water and a decrease in the survival rate (about 64%), suggesting an increase in membrane permeability during dehydration. During rehydration of the freeze-dried strain, an increase in the temperature, NaCl or monosodium glutamate concentration and a decrease in H+ concentration resulted in an increase in the electrolyte leakage and a decrease in the survival rate (from about 5% to 97%, with respect to the treatment made). However, a decrease in the electrolyte leakage was observed with increasing glycerol, sucrose or maltodextrin and resulted in the maintenance of cell viability. Change in membrane permeability might lead to electrolyte leakage during rehydration and, ultimately, cell death. The electrolyte leakage assay associated with the plate count method, a quick and inexpensive method, could be used to evaluate dried bacteria resistance to dehydration. [less ▲]

Improved use of serial laboratory data in acute myocardial infarction

in Clinical Chemistry (1983), 28

An improved weighting method with multibounds formulation and convex programming for multicriteria structural optimization

in International Journal for Numerical Methods in Engineering (2001), 52(9), 889-902

This paper presents an improved weighting method for multicriteria structural optimization. By introducing artificial design variables, here called as multibounds formulation (MBF), we demonstrate ... [more ▼]

This paper presents an improved weighting method for multicriteria structural optimization. By introducing artificial design variables, here called as multibounds formulation (MBF), we demonstrate mathematically that the weighting combination of criteria can be transformed into a simplified problem with a linear objective function. This is a unified formulation for one criterion and multicriteria problems. Due to the uncoupling of involved criteria after the transformation, the extension and the adaptation of monotonic approximation-based convex programming methods such as the convex linearization (CONLIN) or the method of moving asymptotes (MMA)are made possible to solve multicriteria problems as efficiently as for one criterion problems. In this work, a multicriteria optimization tool is developed by integrating the multibounds formulation with the CONLIN optimizer and the ABAQUS finite element analysis system. Some numerical examples are taken into account to show the efficiency of this approach. [less ▲]

Improvement by solubilization in DMPC liposomes of PPME photodynamic effect - A study in human colon cancer cells HCT-116

Conference (2004)

Improvement in HSS grade for early stands of hot strip mills - Metallurgical features and mechanical properties assessment

in Proceedings of the 43rd Seminar of Rollings (2007)

Aurora and Kosmos grades are HSS alloys belonging to the complex Fe-Cr-C-X system, where X is a strong carbide former element of the V, Mo or W type. Both alloys were metallurgically characterised prior ... [more ▼]

Aurora and Kosmos grades are HSS alloys belonging to the complex Fe-Cr-C-X system, where X is a strong carbide former element of the V, Mo or W type. Both alloys were metallurgically characterised prior to their comparison. Metallurgical analyses involved phases identification and carbides quantification by using Scanning Electron Microscopy and Energy Dispersive X rays. Differential Thermal Analysis was performed to allow a better understanding of the solidification sequence of studied alloys while mechanical tests performed were compressive at room temperature and bulk hardness at usual service temperatures. An attempt was made in order to connect experimental results to the good behaviour in operation of Aurora grade. In fact Aurora grade appeared to exhibit strong metallurgical differences when compared to Kosmos grade, especially as concern in nature and amount of carbides. [less ▲]

Improvement in the methylene blue adsorption capacity and photocatalytic activity of H2-reduced rutile-TiO2 caused by Ni(II)porphyrin preadsorption

in Applied Catalysis B : Environmental (2011), 106

H2-reduced rutile-TiO2 xerogel (Ti-700), obtained via the sol–gel process, was found to strongly adsorb the Ni(II)-5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrin (NiTCPP) from a methanolic solution ... [more ▼]

H2-reduced rutile-TiO2 xerogel (Ti-700), obtained via the sol–gel process, was found to strongly adsorb the Ni(II)-5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrin (NiTCPP) from a methanolic solution, despite its very low specific surface area (SBET ≈ 2 m2 g−1). UV/vis spectroscopy analysis showed that after calcination at 700 ◦C and reduction under H2 flow at 400 ◦C, the TiO2-xerogel increased its NiTCPP-adsorption capacity by surface area unit by up to 120 times. The effect of the porphyrin presence in the catalytic performances of TiO2-xerogels was studied through three kinetics models: (i) the pseudo-first-order kinetic model; (ii) the pseudo-second-order kinetic model, which are used to describe the adsorption rate based on the adsorption capacity of the catalysts; and (iii) the Langmuir–Hinshelwood kinetic model which is used to describe the photocatalytic degradation rate of methylene blue (MB). A significant improvement in the efficiency of Ti-700 was observed after the porphyrin-adsorption process (NiTCPP/Ti-700): MB-adsorption capacity at equilibrium and the apparent MB-photoconversion constant, kapp, of NiTCPP/Ti-700 were both up to 2 times higher than those observed for the Ti-700. [less ▲]