Quantitative comparison between crowd models for evacuation planning and evaluation

Crowd simulation is rapidly becoming a standard tool for evacuation planning and evaluation. However, the many crowd models in the literature are structurally different, and few have been rigorously calibrated against real-world egress data, especially in emergency situations. In this paper we describe a procedure to quantitatively compare different crowd models or between models and real-world data. We simulated three models: (1) the lattice gas model, (2) the social force model, and (3) the RVO2 model, and obtained the distributions of six observables: (1) evacuation time, (2) zoned evacuation time, (3) passage density, (4) total distance traveled, (5) inconvenience, and (6) flow rate. We then used the DISTATIS procedure to compute the compromise matrix of statistical distances between the three models. Projecting the three models onto the first two principal components of the compromise matrix, we find the lattice gas and RVO2 models are similar in terms of the evacuation time, passage density, and flow rates, whereas the social force and RVO2 models are similar in terms of the total distance traveled. Most importantly, we find that the zoned evacuation times of the three models to be very different from each other. Thus we propose to use this variable, if it can be measured, as the key test between different models, and also between models and the real world. Finally, we compared the model flow rates against the flow rate of an emergency evacuation during the May 2008 Sichuan earthquake, and found the social force model agrees best with this real data.     

Balance of nanostructure and bimetallic interactions in Pt model fuel cell catalysts: in situ XAS and DFT study

We have studied the effect of nanostructuring in Pt monolayer model electrocatalysts on a Rh(111) single-crystal substrate on the adsorption strength of chemisorbed species. In situ high energy resolution fluorescence detection X-ray absorption spectroscopy at the Pt L(3) edge reveals characteristic changes of the shape and intensity of the "white-line" due to chemisorption of atomic hydrogen (H(ad)) at low potentials and oxygen-containing species (O/OH(ad)) at high potentials. On a uniform, two-dimensional Pt monolayer grown by Pt evaporation in ultrahigh vacuum, we observe a significant destabilization of both H(ad) and O/OH(ad) due to strain and ligand effects induced by the underlying Rh(111) substrate. When Pt is deposited via a wet-chemical route, by contrast, three-dimensional Pt islands are formed. In this case, strain and Rh ligand effects are balanced with higher local thickness of the Pt islands as well as higher defect density, shifting H and OH adsorption energies back toward pure Pt. Using density functional theory, we calculate O adsorption energies and corresponding local ORR activities for fcc 3-fold hollow sites with various local geometries that are present in the three-dimensional Pt islands.     

Development of polyaniline microarray electrodes for cadmium analysis

Disposable screen-printed electrodes (SPCE) were modified using a cosmetic product to partially block the electrode surface in order to obtain a microelectrode array. The microarrays formed were electropolymerized with aniline. Scanning electron microscopy was used to evaluate the modified and polymerized electrode surface. Electrochemical characteristics of the constructed sensor for cadmium analysis were evaluated by cyclic and square-wave voltammetry. Optimized stripping procedure in which the preconcentration of cadmium was achieved by depositing at ?1.20 V (vs. Ag/AgCl) resulted in a well defined anodic peak at approximately ?0.7 V at pH 4.6. The achieved limit of detection was 4 × 10^?9 mol dm^?3. Spray modified and polymerized microarray electrodes were successfully applied to quantify cadmium in fish sample digests.     

Electronic transport between Au surface and scanning tunnelling microscope tip via a multipodal cyclodextrin host–metallo‐guest supramolecular system

An elementary supramolecular conducting system was constructed using a novel (±)‐thioctic acid‐functionalized β‐cyclodextrin host deposited on a gold (Au) surface and an iridium‐bearing guest molecule with biphenyl tails to insert specifically into the cyclodextrin cavity. The resulting supramolecular system was used to investigate remote electron communication between the flat Au surface and the platinum (Pt)/iridium (Ir) tip of a scanning tunnelling microscope. The morphology of the surfaces after successive deposition of host molecules followed by guest molecules was investigated. Formation of features of 2 nm size was shown on the Au surface functionalised with the supramolecular system. I–V spectroscopic analysis of the tunnelling current through this supramolecular layer revealed the relation between the effective barrier height and tunnelling distance. Thus, in the supramolecular host–metallo‐guest system, a small increase of conductance is observed, compared to the layer without the guest. This can be attributed to the presence of the Ir‐guest, which eventually creates intermediate energy states between the Au substrate and the Pt/Ir tip. Copyright © 2011 John Wiley & Sons, Ltd.     

Manifestation of the Gouy phase in vector-vortex beams

Experimental measurements of the twirl and changes in the anisotropy of the constant intensity ellipse, and the rotation of the polarization singular lemon pattern a generalized vector-vortex beam experiences around the two foci due to the converging and diverging conical waves and in between, are presented and interpreted as being due to the universal form of the Gouy phase, φ(G)=mπ/2.     

The development and optimization of a modified single-drop microextraction method for organochlorine pesticides determination by gas chromatography-tandem mass spectrometry

We have developed a new method for single-drop microextraction (SDME) for the preconcentration of organochlorine pesticides (OCP) from complex matrices. It is based on the use of a silicone ring at the tip of the syringe. A 5 μL drop of n-hexane is applied to an aqueous extract containing the OCP and found to be adequate to preconcentrate the OCPs prior to analysis by GC in combination with tandem mass spectrometry. Fourteen OCP were determined using this technique in combination with programmable temperature vaporization. It is shown to have many advantages over traditional split/splitless injection. The effects of kind of organic solvent, exposure time, agitation and organic drop volume were optimized. Relative recoveries range from 59 to 117 %, with repeatabilities of <15 % (coefficient of variation) were achieved. The limits of detection range from 0.002 to 0.150 μg kg^?1. The method was applied to the preconcentration of OCPs in fresh strawberry, strawberry jam, and soil.

Pore Scale Modeling of Reactive Transport Involved in Geologic CO<Subscript>2</Subscript> Sequestration

We apply a multi-component reactive transport lattice Boltzmann model developed in previous studies for modeling the injection of a CO₂-saturated brine into various porous media structures at temperatures T = 25 and 80°C. In the various cases considered the porous medium consists initially of calcite with varying grain size and shape. A chemical system consisting of Na⁺, Ca²⁺, Mg²⁺, H⁺, CO₂^°(aq){{\rm CO}_2^{\circ}{\rm (aq)}}, and Cl⁻ is considered. Flow and transport by advection and diffusion of aqueous species, combined with homogeneous reactions occurring in the bulk fluid, as well as the dissolution of calcite and precipitation of dolomite are simulated at the pore scale. The effects of the structure of the porous media on reactive transport are investigated. The results are compared with a continuum-scale model and the discrepancies between the pore- and continuum-scale models are discussed. This study sheds some light on the fundamental physics occurring at the pore scale for reactive transport involved in geologic CO₂ sequestration.     

Effect of substrate temperature on the properties of vacuum evaporated indium selenide thin films

Thin films of InSe were obtained by thermal evaporation techniques on glass substrates maintained at various temperatures (T_sb = 30°, 400°C). X‐ray diffraction analysis showed the occurrence of amorphous to polycrystalline transformation in the films deposited at higher substrate temperature (400°C). The polycrystalline films were found to have a hexagonal lattice. Compositions of these films have been characterized by EDAX and the surface analysis by scanning electron microscopy. Optical properties of the films, investigated by using spectrophotometer transmittance spectra in the wavelength range (300 – 1100 nm), were explained in terms of substrate temperatures. Films formed at room temperature showed an optical band gap (E_g^opt) 1.56 eV; where as the films formed at 400°C were found to have a E_g^opt of 1.92 eV. The increase in the value of E_g^opt with T_sb treatment is interpreted in terms of the density of states model as proposed by Mott and Davis. The analysis of current ‐Voltage characteristics, based on space charge limited currents (SCLC) measurements, confirms the exponential decrease of density of states from the conduction band edge towards the Fermi level for both the amorphous and polycrystalline films. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of substrate temperature on the properties of vacuum evaporated InSb films

Indium Antimonide (InSb) thin films were grown onto well cleaned glass substrates at different substrate temperatures (303, 373 and 473 K) by vacuum evaporation. The elemental composition of the deposited InSb film was found to be 52.9% (In) and 47.1% (Sb). X‐ray diffraction studies confirm the polycrystallinity of the films and the films show preferential orientation along the (111) plane. The particle size (D), dislocation density (δ) and strain (ε) were evaluated. The particle size increases with the increase of substrate temperature, which was found to be in the range from 22.36 to 32.59 nm. In Laser Raman study, the presence of longitudinal mode (LO) confirms that the deposited films were having the crystalline nature. Raman peak located at 191.26 cm^–1 shift towards the lower frequencies and narrows with increase in deposition temperature. This indicates that the crystallinity is improved in the films deposited at higher substrate temperatures. Hall measurements indicate that the films were p‐type, having carrier concentration ≅10¹⁶ cm^–3 and mobility (4–7.7) ×10³ cm²/Vs. It is observed that the carrier concentration (N) decreases and the Hall mobility (μ) increases with the increase of substrate temperature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation and characterization of electrodeposited indium selenide thin films

Indium Selenide (InSe) thin films were deposited from a mixture of Indium chloride and selenium dioxide in aqueous solution by electrodeposition technique on Indium Tin oxide coated glass substrates. The effects of the parameters during deposition such as current density, deposition potential versus saturated calomel electrode, pH value and concentration of source material were studied. X‐ray diffraction studies were carried out on the films to analyze the microstructure using an x‐ray diffractometer and were examined by RAMAN spectroscopy. The Raman peak position did not change much with chemical concentrations. Raman scattering due to the (LO) phonon was observed at 211 cm^–1. Optical absorption studies were performed with a double beam ultra violet‐visible –NIR spectrophotometer in the wavelength 300–1100 nm. The surface morphology of the layer was examined using a scanning electron micrograph. The composition of the films was studied using an Energy Dispersive Analysis by X‐Rays (EDAX).