Simulation-based Selectee Lane queueing design for passenger checkpoint screening

There are two kinds of passenger checkpoint screening lanes in a typical US airport: a Normal Lane and a Selectee Lane that has enhanced scrutiny. The Selectee Lane is not effectively utilized in some airports due to the small amount of passengers selected to go through it. In this paper, we propose a simulation-based Selectee Lane queueing design framework to study how to effectively utilize the Selectee Lane resource. We assume that passengers are classified into several risk classes via some passenger prescreening system. We consider how to assign passengers from different risk classes to the Selectee Lane based on how many passengers are already in the Selectee Lane. The main objective is to maximize the screening system’s probability of true alarm. We first discuss a steady-state model, formulate it as a nonlinear binary integer program, and propose a rule-based heuristic. Then, a simulation framework is constructed and a neighborhood search procedure is proposed to generate possible solutions based on the heuristic solution of the steady-state model. Using the passenger arrival patterns from a medium-size airport, we conduct a detailed case study. We observe that the heuristic solution from the steady-state model results in more than 4% relative increase in probability of true alarm with respect to the current practice. Moreover, starting from the heuristic solution, we obtain even better solutions in terms of both probability of true alarm and expected time in system via a neighborhood search procedure.     

2D → 3D corrugated structure self-assembled from 4,4′-methylenebis(N-(pyridin-2-ylmethylene)aniline and terephthalic acid: Crystal structure and selective anion separations via anion exchange

A new flexible cationic Zn(II)metal organic framework, {[Zn₂(BDC)_1.5(L)(DMF)]NO₃·DMF·solvent}_n, MOF 1 , which is a corrugated two-dimensional network, was synthesized by self-assembly of Zn(NO₃)₂.6H₂O with 4,4′-methylenebis(N-(pyridin-2-ylmethylene)aniline as a neutral ligand and terephthalic acid in dimethyl formamide (DMF) as solvent and characterized by X-ray diffraction. Because of the presence of uncoordinated nitrate (NO₃⁻) ions in the channels, the compound was employed for ion-exchange applications. We report a detailed study of the host–guest interaction for a cationic metal–organic framework (MOF) that can reversibly capture nitrate. The recrystallization of the MOF was evaluated by monitoring the anion exchange dynamics using a combination of powder X-ray diffraction and Fourier transform infrared spectra with various kinds of foreign anions. This MOF showed fast and highly efficient Cr₂O₇²⁻ and CrO₄²⁻, N₃⁻, MnO₄⁻, and SCN⁻ exchange. The trapping capacities of Cr₂O₇²⁻, CrO₄²⁻, N₃⁻, MnO₄⁻, and SCN⁻ were 105,138, 44,104, and 25mg/g at 25°C after 3h, respectively, and there was good recyclability for capturing N₃⁻ and SCN⁻. {[Zn₂(BDC)_1.5(L)(DMF)]NO₃}_n exhibited anion exchange selectivity of SCN⁻ in a solution containing a mixture of 0.025mmol N₃⁻, SCN⁻, CrO₄⁻²⁻, Cr₂O₇²⁻, and MnO₄⁻ for 3h and exhibited anion exchange selectivity for SCN⁻ and Cr₂O₇²⁻ in a solution containing a mixture of 0.001mmol N₃⁻, SCN⁻, CrO₄²⁻, Cr₂O₇²⁻, and MnO₄⁻.     

{4‐Bromo‐2‐[2‐(5‐bromo‐2‐oxido­benzyl­idene­amino­methyl)­phenyl­imino­methyl]­phenolato‐κ4O,N,N′,O′}nickel(II)

In the title complex, [Ni(C₂₁H₁₄Br₂N₂O₂)], the Ni^II atom is coordinated by the two imine N and two phenolate O atoms of the Schiff base ligand in a tetrahedrally distorted square‐planar geometry. The Ni—N and Ni—O distances are within the ranges expected for Ni–Schiff base derivatives. Intermolecular C—H⋯O hydrogen bonds link the mol­ecules into centrosymmetric dimers, forming (12) (A) and (10) (B) rings. These dimers combine to form a supramolecular ABAB… aggregate which propagates along the [100] direction.     

Thermodynamic investigations on shape selective separation behaviors of poly(4-vinylpyridine)-grafted silica for polycyclic aromatic hydrocarbons in both normal-phase and reversed-phase high-performance liquid chromatography

With the successful implementation of poly(4-vinylpyridine)-grafted silica prepared by grafting-from approach (GF-VP(n)) as a stationary phase for the separation of polycyclic aromatic hydrocarbons (PAHs) in normal-phase HPLC, this paper describes the chromatographic retention behaviors of PAHs with GF-VP(n) in reversed-phase HPLC. Significantly higher retention factor along with enhanced shape selectivity were observed with GF-VP(n). Thermodynamic study on the retention behaviors of PAHs with GF-VP(n) in normal-phase and reversed-phase HPLC revealed that retention of PAHs was exothermic in both phases. Furthermore, higher entropic contribution was observed in reversed-phase HPLC compared to normal-phase HPLC.     

Unexpected one-pot synthesis of new polycyclic coumarin[4,3-c]pyridine derivatives via a tandem hetero-Diels-Alder and 1,3-dipolar cycloaddition reaction

O-Methyl-4-coumarincarbaldehyde oxime reacted as an azadiene with electron-deficient and electron-rich dienophiles to give, via one-step hetero-Diels-Alder cycloaddition reactions, the corresponding 5H-coumarin[4,3-c]pyridin-5-ones. When excess of the dienophile was used, fused azatetracyclo derivatives were also formed via a tandem Diels-Alder and 1,3-dipolar cycloaddition reaction of the dienophile to an azomethine ylide formed by the intermediate 2,3-dihydro-5H-coumarin[4,3-c]pyridine-5-one. The regio- and stereoselectivities of the new compounds correspond well with spectroscopic (2D NMR) and theoretical data. A possible mechanistic scheme is provided.     

Synthesis,Characterization and X‐ray Structures of AMTT‐Type Schiff bases and two CuI Complexes (AMTT= 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione)

The reaction of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT) with 4‐methylbenzaldehyde and 4‐methoxybenzaldehyde in ethanol led to the iminic derivatives ‐4‐(4‐methylbenzylideneamino)‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)thione ( L1 ) and 4‐(4‐methoxybenzyl‐ideneamino)‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione ( L2 ). The reaction of L1 with CuCl in the presence of triphenylphosphane as co‐ligand in methanol/chloroform solution gave the Cu^I complex containing L1 , [Cu( L1 )(PPh₃)₂Cl]·0.5CH₃OH·0.25CHCl₃ ( 1 ). Treatment of L2 with the same metal salt in a molar ratio of 1:1 in methanol and further addition of a solution of PPh₃ in chloroform led to the complex [Cu( L2 )(PPh₃)₂Cl]·2.5CHCl₃ ( 2 ). The complexes and L1 were characterized by IR and NMR spectroscopy as well as by X‐ray diffraction studies. In both complexes, the Schiff base ligand is coordinated to the copper ion through its sulfur atom. The other coordination sites around the copper ion are occupied by two triphenylphosphane molecules and one chloride ion. Therefore, each Cu^I ion is in a distorted tetrahedral environment. Crystal data for L1 at ?100 °C: space group P2₁/n with a = 720.5(1), b = 1140.6(1), c = 1426.3(2) pm, β = 91.25(1)°, Z = 4, R₁ = 0.03, for 1 at ?120 °C : space group with a = 1286.3(1), b = 1740.3(1), c = 2060.2(1) pm, α = 79.085(6), β = 83.827(5), γ = 76.688(6)°, Z = 4, R₁ = 0.0649 and for 2 at ?80 °C : space group with a = 1183.7(2), b = 1370.1(2), c = 1812.1(3) pm, α = 85.69(2), β = 88.52(2), γ = 64.89(2)°, Z = 2, R₁ = 0.0488.     

Assouad-Nagata dimension via Lipschitz extensions

In the first part of the paper we show how to relate several dimension theories (asymptotic dimension with Higson property, asymptotic dimension of Gromov and capacity dimension of Buyalo [7]) to Assouad-Nagata dimension. This is done by applying two functors on the Lipschitz category of metric spaces: microscopic and macroscopic. In the second part we identify (among spaces of finite Assouad-Nagata dimension) spaces of Assouad-Nagata dimension at most n as those for which the n-sphere S ⁿ is a Lipschitz extensor. Large scale and small scale analogues of that result are given. The author was partially supported by Grant No.2004047 from the United States-Israel Binational Science Foundation (BSF), Jerusalem, Israel. The author was supported by Grant AP2004-2494 from the Ministerio de Educacion y Ciencia, Spain. He thanks the Department of Mathematics of University of Tennessee for their hospitality.     

Dynamical Instability Causes the Demise of a Supercooled Tetrahedral Liquid

We investigate the relaxation mechanism of a supercooled tetrahedral liquid at its limit of stability using isothermal isobaric (NPT) Monte Carlo simulations. In similarity with systems which are far from equilibrium but near the onset of jamming (O’Hern et al. in Phys Rev Lett 93:165702, 2004), we find that the relaxation is characterized by two time-scales: the decay of long-wavelength (slow) fluctuations of potential energy is controlled by the slope \([\partial (G/N)/\partial \phi ]\) of the Gibbs free energy (G) at a unique value of per particle potential energy \(\phi = \phi _{{\tiny mid}}\). The short-wavelength (fast) fluctuations are controlled by the bath temperature T. The relaxation of the supercooled liquid is initiated with a dynamical crossover after which the potential energy fluctuations are biased towards values progressively lesser than \(\phi _{{\tiny mid}}\). The dynamical crossover leads to the change of time-scale, i.e., the decay of long-wavelength potential energy fluctuations (intermediate stage of relaxation). Because of the condition [\(\partial ^2 (G/N)/\partial \phi ^2 = 0\)] at \(\phi = \phi _{{\tiny mid}}\), the slope \([\partial (G/N)/\partial \phi ]\) has a unique value and governs the intermediate stage of relaxation, which ends just after the crossover. In the subsequent stage, there is a relatively rapid crystallization due to lack of long-wavelength fluctuations and the instability at \(\phi _{{\tiny mid}}\), i.e., the condition that G decreases as configurations with potential energies lower than \(\phi _{{\tiny mid}}\) are accessed. The dynamical crossover point and the associated change in the time-scale of fluctuations is found to be consistent with the previous studies.     

A Geometrically Exact Incremental Variational Formulation for Phase Field Models in Micromagnetics

Magnetic materials have been finding increasingly wide areas of application. We focus here on the continuum modeling of such materials and present an incremental variational principle for a dissipative micro-magneto-elastic model. It describes the quasi-static evolution of both magnetically as well as mechanically driven magnetic domains, which also incorporates the surrounding free space. Furthermore, the algorithmic preservation of the geometrical nature of the variables is an important challenge from the numerical perspective and to this end we present a novel FE discretization whereby the geometric property of the magnetization director is pointwise exactly preserved by nonlinear rotational updates at the nodes. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)