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101.
Hanan Luss 《The Journal of the Operational Research Society》1977,28(2):275-284
In this paper we describe a model for systems in which the customers usually reserve the required facilities in advance. The model has been developed for a communication network which provides visual conferencing services. We concentrate upon a network with a single pair of cities. Each customer calls the reservation office and specifies the desired day, starting time and holding time for his conference. A scheduler either satisfies the customer's request or offers him up to two alternatives which he may or may not accept. Various performance indices of the system, such as the proportion of lost customers, the proportion of rescheduled customers and the facilities' occupancy rate, are derived. Numerical examples and applications are discussed. 相似文献
102.
We consider minimax optimization problems where each term in the objective function is a continuous, strictly decreasing function of a single variable and the constraints are linear. We develop relaxation-based algorithms to solve such problems. At each iteration, a relaxed minimax problem is solved, providing either an optimal solution or a better lower bound. We develop a general methodology for such relaxation schemes for the minimax optimization problem. The feasibility tests and formulation of subsequent relaxed problems can be done by using Phase I of the Simplex method and the Farkas multipliers provided by the final Simplex tableau when the corresponding problem is infeasible. Such relaxation-based algorithms are particularly attractive when the minimax optimization problem exhibits additional structure. We explore special structures for which the relaxed problem is formulated as a minimax problem with knapsack type constraints; efficient algorithms exist to solve such problems. The relaxation schemes are also adapted to solve certain resource allocation problems with substitutable resources. There, instead of Phase I of the Simplex method, a max-flow algorithm is used to test feasibility and formulate new relaxed problems.Corresponding author.Work was partially done while visiting AT&T Bell Laboratories. 相似文献
103.
Summary The reactions of 2,2-biquinoline(biq) with M(PhCN)2X2 (M=Pd; X=Cl or Br; M=Pt, X=Cl, Br or I), K2PtCl4 and RhCl3·3H2O and of 2-(2-pyridyl)quinoline (pq) with K2PtCl4 and RhCl3·3H2O have been investigated. The isolated complexescis-[Pd(biq)X2] (X=Cl or Br),cis-[Pt(biq)Cl2],cis-[Pt(biq)Cl2]·H2O,trans-[Pt(biq)2Br2]·5H2O, [Pt3(biq)2I6],mer-[Rh(biq)Cl3-(H2O)] andmer-[Rh(pq)Cl3(H2O)] have been characterized by elemental analyses, conductivity measurements, i.r., electronic, and1H n.m.r. spectra. The reaction of pq with K2PtCl4 in 1M H2SO4 gave the salt 2-(2-pyridyl) quinolinium tetrachloroplatinate(II) pentahydrate, (pqH)2[PtCl4]·5H2O; when the reaction was carried out in aqueous acetone,cis-[Pt(pq)Cl2] was obtained. A new method for the synthesis ofcis-[Rh(biq)2X2]X (X=Cl or Br) is described; both compounds have been further characterized by1H n.m.r. 相似文献
104.
Coordination complexes have been used extensively as the photoactive component of artificial photosynthetic devices. While polynuclear arrays increase the probability of light absorption, the incorporation of the stereogenic Ru(2,2'-bipyridine)(3)(2+) motif gives rise to diastereomeric mixtures whereas the achiral Ru(2,2':6',2"-terpyridine)(2)(2+) motif creates stereopure polynuclear complexes. Thus, polynuclear arrays composed of ruthenium(II) complexes of tridentate ligands are the targets of choice for light-harvesting devices. As Ru(II) complexes of tridentate ligands have short excited state lifetimes at room temperature (r. t.), considerable effort has been focused on trying to increase their r. t. luminescence lifetime for practical applications. This tutorial review will report on the sophisticated synthetic strategies currently in use to enhance the room temperature photophysical properties of Ru(II) complexes of tridentate ligands. 相似文献
105.
Ahmed A. Mohamed Hanan E. Abdou Michael D. Irwin José M. López-de-Luzuriaga John P. Fackler Jr. 《Journal of Cluster Science》2003,14(3):253-266
The structures of the tetragold(I) formamidinate cluster complexes, [Au4(ArNC(H)NAr)4], Ar=C6H4-4-OMe (1), C6H3-3,5-Cl (2), C6H4-4-Me (3), have been characterized by x-ray crystallography. The range of AuAu distances is 2.8–3.0 Å. The angles at AuAuAu are acute and obtuse 70 and 109°, 88 and 91°, and 63 and 116° in 1, 2, and 3, respectively. The four gold atoms are located at the corner of a rhomboid with the formamidinate ligands bridged above and below the near plane of the four Au(I) atoms. The tetranuclear gold(I) complexes show a bright blue-green luminescence under UV light, with an emission at 490 nm and a weak emission at 530 nm in the solid state, at room temp and 77 K. The oxidation of the formamidinate cluster, 1, has been studied electrochemically in 0.1 M Bu4NPF6/CH2Cl2 at a Pt working electrode with different scan rates. Three waves were obtained, 0.75, 0.95, and 1.09V vs. Ag/AgCl at a scan rate of 500 mV/s, the three waves are reversible. The potentials are independent of the scan rate in the range 50 mV/s to 3 V/s. The current at the third wave is larger than those at the first two. 相似文献
106.
M. S. Abdelmonem A. A. Naqvi Ghada Al-Misned Hanan Al-Ghamdi 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(3):685-690
Effect of neutron source-moderator geometry has been studied on the performance of a thermal neutron capture-based prompt
gamma neutron activation analysis (PGNAA) setup. In the study prompt gamma-ray and thermal neutron yield was calculated for
various positions of the neutron source inside 3–10 cm long high density polyethylene moderators. The study has been carried
out for a Portland cement sample using Monte Carlo calculations. The maximum yields of the thermal neutrons and prompt gamma-rays
have been observed for a neutron source at a distance of 1 cm from the sample. The maximum yield of the 1.94 and 6.42 MeV
prompt gamma-ray from a Portland cement sample has been observed for moderators having length equal to or greater than 7 cm.
The yield of both gamma rays is 2.57 times higher than the previously reported value for a PGNAA setup with the source placed
outside a 5 cm thick moderator. The higher yield of gamma rays will result in higher sensitivity of the PGNAA setup. 相似文献
107.
Wang J Hanan GS Loiseau F Campagna S 《Chemical communications (Cambridge, England)》2004,(18):2068-2069
A novel series of ruthenium terpyridine complexes with bichromophoric units separated by more than 1 nm display an extraordinary enhancement of their luminescence lifetimes when compared to the parent Ru(tpy)2(2+) chromophore (tpy = 2,2':6',2"-terpyridine). 相似文献
108.
Fang YQ Taylor NJ Hanan GS Loiseau F Passalacqua R Campagna S Nierengarten H Van Dorsselaer A 《Journal of the American Chemical Society》2002,124(27):7912-7913
Several ruthenium(II) complexes with new tridentate polypyridine ligands have been prepared, and their photophysical properties have been studied. The new tridentate ligands are tpy-modified systems (tpy = 2,2':6',2' '-terpyridine) in which aromatic substituents designed to be coplanar with the tpy moiety are introduced, with the aim of enhancing delocalization in the acceptor ligand of the potentially luminescent metal-to-ligand charge-transfer (MLCT) state and increasing the MLCT-MC energy gap (MC = metal-centered excited state). Indeed, the Ru(II) complexes obtained with this new family of tridentate ligands exhibit long-lived luminescence at room temperature (up to 200 ns). The enhanced luminescence properties of these complexes support this design strategy and are superior to those of the model Ru(tpy)22+ compound and compare favorably with those of the best Ru(II) complexes with tridentate ligands reported so far. 相似文献
109.
Mechanistic Features of the TiO2 Heterogeneous Photocatalysis of Arsenic and Uranyl Nitrate in Aqueous Suspensions Studied by the Stopped‐Flow Technique
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Dr. Jorge M. Meichtry Dr. Ivana K. Levy Dr. Hanan H. Mohamed Dr. Ralf Dillert Prof. Detlef W. Bahnemann Prof. Marta I. Litter 《Chemphyschem》2016,17(6):885-892
The dynamics of the transfer of electrons stored in TiO2 nanoparticles to AsIII, AsV, and uranyl nitrate in water was investigated by using the stopped‐flow technique. Suspensions of TiO2 nanoparticles with stored trapped electrons (etrap?) were mixed with solutions of acceptor species to evaluate the reactivity by following the temporal evolution of etrap? by the decrease in the absorbance at λ=600 nm. The results indicate that AsV and AsIII cannot be reduced by etrap? under the reaction conditions. In addition, it was observed that the presence of AsV and AsIII strongly modified the reaction rate between O2 and etrap?: an increase in the rate was observed if AsV was present and a decrease in the rate was observed in the presence of AsIII. In contrast with the As system, UVI was observed to react easily with etrap? and UIV formation was observed spectroscopically at λ=650 nm. The possible competence of UVI and NO3? for their reduction by etrap? was analyzed. The inhibition of the UVI photocatalytic reduction by O2 could be attributed to the fast oxidation of UV and/or UIV. 相似文献
110.
Nourhan Samy Elmalahany Muhammed Abdel-Hamied Abdel-Tawab Hanan M. Elwy Hussein M. Fahmy Rasha M. El Nashar 《Electroanalysis》2023,35(5):e202200313
Saxagliptin (Saxa) belongs to a new generation of antidiabetic pharmaceutical compounds used in combination with healthy diet and exercise to lower blood glucose levels in patients with type 2 diabetes mellitus (T2DM). In this work, we report for the first time a molecularly imprinted polymer (MIP) based electrochemical sensor for the determination of Saxa. Computational calculations were performed, based on which five MIPs were synthesized using Saxa as a template, itaconic acid as a monomer, crosslinked with ethylene glycol dimethacrylate and Di methyl sulfoxide (DMSO) as a porogen with different ratios. Non-covalent interaction (NCI) analysis has been also conducted, and the obtained isosurface analysis was used for graphical visualization of NCI that could occur in real space as well as for the discrimination between hydrogen bond interaction, Van Der Waals attraction and spatial repulsion. The optimized polymer was incorporated as a modifier for designing an electrochemical sensor comprising MIP and Multiwalled carbon nanotubes (MwCNT) within carbon paste electrode (CPE). The operational variables including incubation time, pH, scan rate, and accumulation time were optimized. The sensor showed linearity over the concentration range (1 × 10−9–1 × 10−15 M) with low limit of detection (LOD) 8 × 10−16 and 2 × 10−16 M on using DPV and EIS, respectively. The sensor was successfully applied for pharmaceutical formulations, urine, and human serum samples with recovery range between 97.45–100.64 %. 相似文献