排序方式: 共有155条查询结果,搜索用时 15 毫秒
21.
We propose a new optimal control model of product goodwill in a segmented market where the state variable behaviour is described by a partial differential equation of the Lotka–Sharp–McKendrick type. In order to maximize the sum of discounted profits over a finite time horizon, we control the marketing communication activities which influence the state equation and the boundary condition. Moreover, we introduce the mathematical representation of heterogeneous electronic word of mouth. Based on the semigroup approach, we prove the existence and uniqueness of optimal controls. Using a maximum principle, we describe a numerical algorithm to find the optimal solution. Finally, we examine several examples on the optimal goodwill model and discover two types of marketing strategies. 相似文献
22.
23.
Podstawka-Proniewicz E Piergies N Skołuba D Kafarski P Kim Y Proniewicz LM 《The journal of physical chemistry. A》2011,115(40):11067-11078
This study reports the Raman (FT-Raman) and absorption infrared (FT-IR) spectra, based on calculated wavenumbers and normal modes of vibrations, of the following compounds: L-Leu-D-NH-CH(Me)-PO(3)H(2) (LI), L-Leu-NH-C(Me)(2)-PO(3)H(2) (LII), L-Leu-D-NH-CH(Et)-PO(3)H(2) (LIII), L-Leu-L-NH-CH(Et)-PO(3)H(2) (LIV), L-Leu-L-NH-CH(EtOH)-PO(3)H(2) (LV), L-Leu-NH-C(Me)(Et)-PO(3)H(2) (LVI), L-Leu-L-NH-CH(PrA)-PO(3)H(2) (LVII), L-Leu-L-NH-CH(c-Pr)-PO(3)H(2) (LVIII), L-Leu-L-NH-CH(t-Bu)-PO(3)H(2) (LIX), L-Leu-L-NH-CH(BuA)-PO(3)H(2) (LX), L-Leu-L-NH-CH(c-Bu)-PO(3)H(2) (LXI), and L-Leu-L-NH-C(Adm)-PO(3)H(2) (LXII). The equilibrium geometries and vibrational wavenumbers were calculated using density functional theory (DFT) at the B3LYP, 6-311++G** level using Gaussian 03, Raint, GaussSum 0.8, and Gar2ped software. We briefly compare and analyze the experimental and calculated vibrational wavenumbers in the range 4000-400 cm(-1). In addition, the Raman wavenumbers are compared to those from the surface-enhanced Raman scattering (SERS) spectra for the phosphono analogues of l-leucine (l-Leu) adsorbed on a colloidal silver surface in an aqueous solution. The geometries of these molecules etched on the silver surface were deduced from observed changes in both the intensity and broadness of Raman bands in the spectra of the bound versus free species. For example, LVI appears to adsorb onto the colloidal silver particles mainly through the amine group and amide bond, which assists in the adsorption process, whereas LII shows strongly enhanced SERS bands due to the rocking, twisting, and stretching vibrations of the N(amid)C(sg)(Me)(2)P fragment, suggesting that this peptide's interaction with the silver surface occurs mainly via this fragment. On the other hand, the most dominant SERS bands of LIII and LIV due to the P═O bond stretches reflect P═O···Ag complex formation. 相似文献
24.
Elżbieta Greiner-Wronowa Dominika Zabiegaj Paolo Piccardo 《Applied Physics A: Materials Science & Processing》2013,113(4):999-1008
This paper contributes to the investigations on history, technology, and degradation of middle age objects (metallic rings with mounted glass beads) recently excavated under the Main Square in Krakow (Poland). Moreover, they were discovered in soil layers differing by chemical composition and microclimate parameters. Historical material is indeed very limited in terms of quantity and sample size, and the following nondestructive analyses were applied: scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD), and X-ray fluorescence spectroscopy (XRF). The glass and the metal were separately tested. Metallography on cross-sections (by both optical and scanning electron microscopy) was applied only on microfragments sampled from metallic rings. The achieved results pointed out how the local microclimate affected the degradation of the analyzed rings developing locally different corrosion processes. Each tested glass of “ring eye” shows a specific chemical composition. All glass pieces were covered by silica gel, and locally more advanced corrosion has been found. 相似文献
25.
A spacer-equipped tetrasaccharide, p-aminocyclohexylethyl alpha-l-Colp-(1-->2)-beta-d-Galp-(1-->3)-[alpha-l-Colp-(1-->4)]-beta-D-GlcpNAc, containing a 4,6-cyclic phosphate in the galactose residue, has been synthesised. The structure corresponds to a part of the repeating unit of the capsular (and lipo-) polysaccharide of the endemic bacteria Vibrio cholerae type O139 synonym Bengal. The synthetic strategy allows continuous syntheses of the complete O139 hexasaccharide repeating unit as well as of the structurally related repeating unit of serotype O22. Starting from ethyl 2-azido-4,6-O-benzylidene-2-deoxy-1-thio-beta-D-glucopyranoside, a thioglycoside tetrasaccharide donor block was constructed through two orthogonal glycosylations with glycosyl bromide donors. First, a properly protected galactose moiety was introduced using silver triflate as promoter and subsequently the two colitose residues, carrying electron-withdrawing protecting groups for stability reasons, under halide-assisted conditions. The tetrasaccharide block was then linked to the spacer in a NIS-TMSOTf-promoted coupling. Transformation of the azido group into an acetamido group using H2S followed by removal of temporary protecting acetyl groups gave a 4',6'-diol, which was next phosphorylated with methyl dichlorophosphate and deprotected to yield the 4,6-cyclic phosphate tetrasaccharide target structure. 相似文献
26.
Dominika Bogusz 《Journal of Optimization Theory and Applications》2013,156(3):650-682
We consider an infinite-horizon optimal control problem with the cost functional described either by an integral over an unbounded interval (a Lebesgue integral) or by a limit of integrals (an improper Lebesgue integral). We prove some theorems on the existence of solutions to such problems. The proofs are based on appropriate lower closure theorems and some extensions of Olech’s theorem on the lower semicontinuity of an integral functional; these extensions cover the cases of functionals described by an integral over an unbounded interval and by a limit of integrals. 相似文献
27.
Trojanowska A Lewicka-Szczebak D Jedrysek MO Kurasiewicz M Wassenaar LI Izydorczyk K 《Isotopes in environmental and health studies》2008,44(2):163-175
The stable isotopic analyses of molecular oxygen dissolved in water (delta18O(DO)) and dissolved inorganic carbon (delta13C(DIC)), supplemented with basic chemical measurements, have been carried out on a diurnal basis to better understand the dynamics of photosynthesis and respiration in freshwater systems. Our observations have been carried out in a lowland dam reservoir, the Sulejow Lake (central Poland), during the summer cyanobacterial bloom. All data obtained, isotopic, hydrochemical, and biological, show a high mutual consistency. Namely, the lowest delta18O(DO) values, obtained at 10:00 and 14:00 (16.0 and 15.5 per thousand, respectively), correspond to the highest amount of cyanobacterial cells observed (66 and 63 mg dm(-3), respectively), whereas the minimum delta13C(DIC) (-10.6 per thousand) obtained at 22:00 corresponds to the maximum content of organic matter (110 mg dm(-3)). This evidence suggests that isotopic assays of delta18O(DO) and delta13C(DIC) are a reliable tool for the quantitative study of biochemical processes in freshwater systems. 相似文献
28.
We consider the conformal flow model derived in Bizoń et al. (2017) as a normal form for the conformally invariant cubic wave equation on 𝕊3. We prove that the energy attains a global constrained maximum at a family of particular stationary solutions that we call the ground state family. Using this fact and spectral properties of the linearized flow (which are interesting in their own right due to a supersymmetric structure), we prove nonlinear orbital stability of the ground state family. The main difficulty in the proof is due to the degeneracy of the ground state family as a constrained maximizer of the energy. © 2019 Wiley Periodicals, Inc. 相似文献
29.
3T3 and VH10 cells were subjected to oxidative damage by hydroxyl radicals generated from Cu(II) ions and ascorbate. The presence of reactive oxygen and nitrogen species in cells was determined using fluorescent dyes. MitoQ—a mitochondrially targeted antioxidant—was examined to prevent cell death and was compared with trolox as a reference standard serving as an antioxidant. MitoQ at lower concentrations (up to 500 nM) prevented damage of mitochondria and thereby increased viability of cells. However, at higher concentrations (over 500 nM) MitoQ decreased the viability of both strains of cells. The last observation indicates that the application of MitoQ should be evaluated also from the point of its cell-destructive potential. 相似文献
30.