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991.
Since Markowitz (1952) formulated the portfolio selection problem, many researchers have developed models aggregating simultaneously several conflicting attributes such as: the return on investment, risk and liquidity. The portfolio manager generally seeks the best combination of stocks/assets that meets his/her investment objectives. The Goal Programming (GP) model is widely applied to finance and portfolio management. The aim of this paper is to present the different variants of the GP model that have been applied to the financial portfolio selection problem from the 1970s to nowadays. 相似文献
992.
In this paper we propose methods for computing Fresnel integrals based on truncated trapezium rule approximations to integrals on the real line, these trapezium rules modified to take into account poles of the integrand near the real axis. Our starting point is a method for computation of the error function of complex argument due to Matta and Reichel (J Math Phys 34:298–307, 1956) and Hunter and Regan (Math Comp 26:539–541, 1972). We construct approximations which we prove are exponentially convergent as a function of \(N\) , the number of quadrature points, obtaining explicit error bounds which show that accuracies of \(10^{-15}\) uniformly on the real line are achieved with \(N=12\) , this confirmed by computations. The approximations we obtain are attractive, additionally, in that they maintain small relative errors for small and large argument, are analytic on the real axis (echoing the analyticity of the Fresnel integrals), and are straightforward to implement. 相似文献
993.
Giovanna Citti Maria Manfredini Andrea Pinamonti Francesco Serra Cassano 《Calculus of Variations and Partial Differential Equations》2014,49(3-4):1279-1308
We characterize intrinsic Lipschitz functions as maps which can be approximated by a sequence of smooth maps, with pointwise convergent intrinsic gradient. We also provide an estimate of the Lipschitz constant of an intrinsic Lipschitz function in terms of the $L^{\infty }$ -norm of its intrinsic gradient. 相似文献
994.
Laura Tositti Enio Bueno Pereira Silvia Sandrini Davide Capra Ottavio Tubertini Maria Giovanna Bettoli 《International journal of environmental analytical chemistry》2013,93(5):259-274
This work reports the first results of atmospheric radon measurements performed at the Italian Antarctic station located at Terra Nova Bay (74.69°S; 164.12°E) during summer campaigns of 1995-96, 1996-97 and 1997-98. Mean222Rn concentrations was 0.51 - 0.43 Bq mm3 (median = 0.37 Bq mm3), and ranged from 0.01 to 2.74 Bq mm3 . On the average, these values were considered high, in comparison to results reported for other sites in Antarctica at equivalent latitudes. This could be explained by two causes: radon data for Terra Nova Bay were only for the summer period, when the ice-free area is at its maximum and thus the radon emission to the atmosphere; and by the larger ice-free area at Terra Nova Bay compared, for example, to measurements taken at another Antarctic site by the same technique (Ferraz station - 62°05'S; 058°23.5'W). The mean 222Rn to 220Rn activity ratio was 4.4 - 4.2, ranging between 0.1 and 45.3. The highest ratios indicated that some of observed surges of concentration of 222Rn could be attributed to not local sources. Lower radon concentrations were observed during katabatic wind events. The diurnal radon variation followed the general trend observed for continental areas located at lower latitudes. 相似文献
995.
Lavinia de Ferri Pier Paolo Lottici Andrea Lorenzi Angelo Montenero Giovanna Vezzalini 《Journal of Sol-Gel Science and Technology》2013,66(2):253-263
Medieval glass is commonly attacked by atmospheric pollutants conveyed by water, triggering the corrosion process. Current conservation strategies aim to maintain window glass in its original context, and so it is necessary to protect it from further degradation. Sol–gel technology is very effective for the preparation of protective films, using Si-alkoxide precursors chemically similar to the substrate. The present work discusses water-repellent hybrid sol–gel coatings made from tetra-ethyl-ortho-silicate with different quantities of Si-alkoxides, functionalized with various alkyl groups. The coatings were deposited using the dip-coating technique and characterized by UV–VIS and FT-IR spectroscopy. Static and dynamic contact angle measurements showed an overall homogeneity of the coatings and indicated improved water-repellency when functionalized by long alkyl chains. The coatings with best performance in terms of transparency and contact angle, and with the lowest organic content, were selected and applied to medieval-like glass samples. Colorimetric characterization was carried out using a spectrophotometric scanner before and after application of the coatings and no significant color changes were found. The electron microscopy images revealed relatively even, crack-free coatings, especially with higher organic contents. Contact angle and colorimetric measurements were repeated after accelerated ageing by exposure to UV light and an SO2-saturated atmosphere. A significant decrease in the contact angle was observed only for the samples treated at the highest SO2 concentration. The silica-based materials did not give reaction by-products, were water-repellent, compatible with the substrate, colorless, transparent, and stable under exposure to chemicals and light, thereby satisfying the main requirements for the conservation of Cultural Heritage. 相似文献
996.
Giovanna Longhi Alberto Ceselli Sandro L. Fornili Sergio Abbate Leopoldo Ceraulo Vincenzo Turco Liveri 《Journal of mass spectrometry : JMS》2013,48(4):478-486
The behavior of aqueous solutions of sodium bis(2‐ethylhexyl)sulfosuccinate (AOTNa) subject to electrospray ionization (ESI) has been investigated by molecular dynamics (MD) simulations at three temperatures (350, 500 and 800 K). We consider several types of water nanodroplets containing AOTNa molecules and composed of a fixed number of water molecules (1000), N0AOT AOT? anions (N0AOT = 0, 5, 10) and N0Na sodium ions (N0Na = 0, 5, 10, 15, 20): in a short time scale (less than 1 ns), the AOTNa molecules, initially forming direct micelles in the interior of the water nanodroplets, are observed in all cases to diffuse nearby the nanodroplet surface, so that the hydrophilic heads and sodium ions become surrounded by water molecules, whereas the alkyl chains lay at the droplet surface. Meanwhile, evaporation of water molecules and of solvated sodium ions occurs, leading to a decrease of the droplet size and charge. At 350 K, no ejection of neutral or charged surfactant molecules is observed, whereas at 500 K, some fragmentation occurs, and at 800 K, this event becomes more frequent. The interplay of all these processes, which depend on the values of temperature, N0AOT and N0Na eventually leads to anhydrous charged surfactant aggregates with prevalence of monocharged ones, in agreement with experimental results of ESI mass spectrometry. The quantitative analysis of the MD trajectories allows to evidence molecular details potentially useful in designing future ESI experimental conditions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
997.
Mariana Loredana Dianu Angela Kriza Adina Magdalena Musuc 《Journal of Thermal Analysis and Calorimetry》2013,112(2):585-593
A bidentate/tridentate 5-bromosalycilaldehyde isonicotinoylhydrazone Schiff base was synthesized by condensing 5-bromosalycilaldehyde with isonicotinoylhydrazine. Cu(II), Co(II), Ni(II), Mn(II) and Zn(II) complexes of this chelating ligand were synthesized using nitrates of these metals. The ligand and the complexes were characterized by elemental analysis, UV–Vis, IR and EPR spectroscopy, conductance and magnetic susceptibility measurements, fluorescence, cyclic voltammetry and thermogravimetric analysis. The ligand and Zn(II) complex exhibits solid-state photoluminescence at room temperature. 相似文献
998.
999.
Diego R. Alcoba Alicia Torre Luis Lain Ofelia B. Oña Josep M. Oliva 《International journal of quantum chemistry》2014,114(14):952-958
This work studies the ability of the two‐center local spin quantities, provided by the partitioning of the expectation value of the spin‐squared operator corresponding to N‐electron systems, for determining spin‐exchange coupling constants within the Heisenberg spin Hamiltonian model. The spin‐exchange parameters, which characterize this Hamiltonian for a determined system, have been evaluated in the HeH2 aggregate and in several clusters (n = 2, 3, 4) with different geometrical arrangements, using internuclear distances larger than the equilibrium ones (beyond the bonding regions). The results found have been analyzed and compared with those arising from other approaches, showing the feasibility of our methodology. © 2014 Wiley Periodicals, Inc. 相似文献
1000.
Oliver Strohmeier Silke Laßmann Bianca Riedel Daniel Mark Günter Roth Martin Werner Roland Zengerle Felix von Stetten 《Mikrochimica acta》2014,181(13-14):1681-1688
Point Mutations on the Kirsten rat sarcoma viral oncogene homolog (KRAS) have been identified as an important predictive biomarker for response to cancer therapy targeting the epidermal growth factor receptor. KRAS mutations are prevalent in up to 40 % of all colorectal carcinomas, and routinely conducted KRAS genotyping is becoming mandatory to predict therapy success and to reduce therapy costs. We report a low-cost, disposable and ready-to-use centrifugal microfluidic cartridge (termed GeneSlice) containing preloaded primers and probes. The GeneSlice cartridge enables the parallel detection of the seven most relevant KRAS point mutations by allele-specific real-time PCR. It represents a cost effective alternative to dideoxy-sequencing with a faster time-to-result (~ 2 h versus up to 20 h in case of dd-sequencing). Microfluidic processing of the GeneSlice along with allele-specific amplification and real-time detection are conducted in a slightly modified, commercially available PCR thermocycler. Intra-chip standard deviation of Cq values on the GeneSlices is negligible (GeneSlice 1: Cq,std.dev. = 0.13; GeneSlice 2: Cq,std.dev?=?0.26). In 23 of 24 experiments, the data for genotyping 6 cancer cell lines (n?=?4 per cell line) agreed with dd-sequencing. Additionally, DNA derived from microdissected formalin-fixed and paraffin embedded colorectal carcinomas of two cases was genotyped correctly and reproducibly (n?=?3 per patient; one GeneSlice excluded from evaluation). The GeneSlice therefore clearly demonstrated the potential to become a valuable tool for routine diagnostics of KRAS mutations by reducing costs and hands-on time. Figure