A graph-theoretic approach to interval scheduling on dedicated unrelated parallel machines

We study the problem of scheduling n non-preemptive jobs on m unrelated parallel machines. Each machine can process a specified subset of the jobs. If a job is assigned to a machine, then it occupies a specified time interval on the machine. Each assignment of a job to a machine yields a value. The objective is to find a subset of the jobs and their feasible assignments to the machines such that the total value is maximized. The problem is NP-hard in the strong sense. We reduce the problem to finding a maximum weight clique in a graph and survey available solution methods. Furthermore, based on the peculiar properties of graphs, we propose an exact solution algorithm and five heuristics. We conduct computer experiments to assess the performance of our and other existing heuristics. The computational results show that our heuristics outperform the existing heuristics.     

Reduction of Graphene Oxide by Aniline with Its Concomitant Oxidative Polymerization

Graphene oxide (GO) nanosheets are readily reduced by aniline above room temperature in an aqueous acid medium, with the aniline simultaneously undergoing oxidative polymerization to produce the reduced graphene oxide‐polyaniline nanofiber (RGO‐PANi) composites. The resulting RGO‐PANi composites and RGO (after dissolution of PANi) were characterized by XPS, XRD analysis, TGA, UV–visible absorption spectroscopy, and TEM. It was also found that the RGO‐PANi composites exhibit good specific capacitance during galvanostatic charging–discharging when used as capacitor electrodes.

     

Reaction pathways of Sc+ (3D, 1D) and Fe+ (6D, 4F) with acetone in the gas phase: metal ion oxidation and acetone deethanization

The reactions of Sc⁺ (³D, ¹D) and Fe⁺ (⁶D, ⁴ F) with acetone have been investigated in both high‐ and low‐spin states using density functional theory. Our calculations have indicated that oxidation of Sc⁺ by acetone can take place by (1) metal‐mediated H migration, (2) direct methyl‐H shift and/or (3) C = O insertion. The most energetically favorable pathway is metal‐mediated H migration followed by intramolecular ScO⁺ rotation and dissociation. For the deethanization of acetone mediated by Fe⁺, the reaction occurs on either the quartet or sextet surfaces through five elementary steps, i.e. encounter complexation, C–C bond activation, methyl migration, C–C coupling and non‐reactive dissociation. The rate‐determining step along the quartet‐state potential‐energy surface (PES) is similar to that in the case of Ni⁺ (² F, 3d⁹), namely the methyl‐migration step. For the sextet‐state PES, however, the energy barrier for methyl migration is lower than that for C–C bond activation, and the rate‐determining step is C–C coupling. In general, the low‐spin‐state pathways are lower in energy than the high‐spin‐state pathways; therefore, the reaction pathways for the oxidation of Sc⁺ and the Fe⁺‐mediated deethanization of acetone mostly involve the low‐spin states. Copyright © 2012 John Wiley & Sons, Ltd.     

Perception of urban park soundscape

A number of studies have been initiated to explore how to improve the soundscape quality in urban parks. However, good soundscape quality in parks cannot be provided without a thorough understanding of the complex relationships among sound, environment, and individuals. As acoustic comfort is considered to be an important outcome of soundscape quality, this study investigates the relative impacts of the factors influencing acoustic comfort evaluation by formulating a multivariate ordered logit model. This study also explores the inter-relationships among acoustic comfort evaluation, acceptability of the environment, and preference to stay in a park using a path model. A total of 595 valid responses were obtained from interview surveys administered in four parks in Hong Kong while objective sound measurements were carried out at the survey spots concurrently. The findings unveil that acoustic comfort evaluation, besides visual comfort evaluation of landscape, also plays an important role on users' acceptability of the urban park environment. Compared with all the studied acoustic related factors, acoustic comfort evaluation serves as a better proxy for park users' preference to stay in urban parks. Hearing the breeze will significantly increase the likelihood of individuals in giving high acoustic comfort evaluation. Conversely, hearing the sounds from heavy vehicles or sounds from bikes will significantly reduce the likelihood in giving a high acoustic evaluation.     

Curriculum traditions in Berlin and Hong Kong: a comparative case study of the implemented mathematics curriculum

Many studies (such as Pepin in Learners and pedagogy, Sage Publications, London, 1999; Kaiser in ZDM 34(6):241–257, 2002; Park and Leung in Mathematics education in different cultural traditions: a comparative study of East Asia and the West. The 13th ICMI Study, pp. 227–238, Springer, New York, 2006) have revealed that there is a strong dependence on cultural traditions in mathematics teaching in different countries. Education in Germany is influenced by the Central and North European Didaktik tradition (Westbury in Teaching as a reflective practice: the German Didaktik tradition, L. Erlbaum Associates, Mahwah, pp. 15–39, 2000), while that in East Asia is influenced by Confucian heritage culture. However, there have not been studies investigating the relationships between these two cultural traditions and their influences on teaching and learning. This study aims at filling this gap in knowledge. Some commonalities in the aims and beliefs in the underlying philosophies in education in traditional China and Germany were found and are presented in this paper. Specifically, the relationship between cultural traditions and the implemented mathematics curriculum was investigated, using Berlin and Hong Kong as examples. It was found that culture affects the implemented curriculum in a complicated way and that other factors such as the intended curriculum and textbooks may also influence the implemented curriculum.     

On the study of the effects of sea views, greenery views and personal characteristics on noise annoyance perception at homes

Noise annoyance has caused significant adverse impacts on human beings and numerous efforts have been spent on mitigating annoyance problems. Natural greenery has been shown to be able to moderate annoyance problems at home but this conclusion was drawn without properly controlling the potential confounding factors. Furthermore, few have explored the moderation effect of a sea view. Accordingly, this study formulated a multivariate model to examine the impacts of natural views as well as personal characteristics on annoyance perception. A housing estate was selected in Hong Kong as the survey site for which some of the residents were exposed to greenery views, sea views, or both from their homes. Eight hundred and sixty-one responses were collected via questionnaire surveys and analyzed using an ordered logit model. The results suggest that both a greenery view and a sea view can moderate annoyance responses. Several individual's personal characteristics are found to affect individuals' annoyance perception. The duration of time spent daily at home is shown to have an influence on the moderation impact exerted by a greenery view, while the age of an individual is shown to have an influence on noise moderation effect exerted by a sea view.     

An investigation of gold adsorption from a binary mixture with selective mesoporous silica adsorbents

Gold-selective adsorbents were prepared from mesoporous MCM-41 silica by grafting organic amine groups (i.e., RNH2, R2NH, and R3N; R=propyl). NH2-MCM-41, NRH-MCM-41, and NR2-MCM-41 displayed strong affinity for gold and at 1 mmol/g loading adsorbed 0.40, 0.33, and 0.20 mmol/g of gold. Copper and nickel were not adsorbed on these adsorbents. Grafting surface chemical moieties introduces heterogeneity on an otherwise uniform MCM-41 pore surface and metal adsorption is best described by the Freundlich adsorption model. A series of binary adsorption equilibrium studies with NH2-MCM-41 containing 2.2 mmol RNH2/g shows that NH2-MCM-41 adsorbs only gold from solutions containing copper and nickel with an adsorption capacity of 0.6 mol of Au/mol of RNH2 (1.1 mmol of Au/g of NH2-MCM-41). Copper and nickel were not adsorbed by NH2-MCM-41 regardless of the solution concentration, composition, and pH (i.e., 2 to 4) in the presence of gold. The LeVan and Vermeulen adsorption model based on a single component Freundlich isotherm and corrected for the anion effect accurately predicted the binary adsorptions. The adsorbed gold was completely recovered by a simple acid wash and the recovered gold solution is 99% pure. The regenerated NH2-MCM-41 remained 100% selective for gold removal and exhibited the same adsorption capacity even after several uses.     

Synthesis and characterization of random and block copolymers with pendant rhenium diimine complexes by controlled radical polymerization

We report the polymerization of rhenium‐containing methacrylates by atom transfer radical polymerization. The structure of the monomer was confirmed by X‐ray crystallography, which showed the bulkiness of the metal‐complex moiety. The rhenium complexes were polymerized in the presence of copper(I) bromide, 1,1,4,7,7‐pentamethyldiethylenetriamine, and methyl 2‐bromopropionate. They were copolymerized with methyl methacrylate in different monomer ratios. An ABA triblock copolymer was also synthesized with poly(methyl methacrylate) as the macroinitiator. When 2,2′‐bipyridine was used as the ligand for the copper catalyst in the polymerizations, it underwent a ligand exchange process with the iminopyridine ligand in the monomer. The neutral rhenium complex in the homopolymers and copolymers could be converted into ionic forms by the replacement of the chloride with an imidazole ligand, and the solubility of the resulting ionic polymers was greatly enhanced. The photosensitizing properties of the doped and undoped polymer films were investigated by the measurement of the photocurrent response under an externally applied electric field. The photoconductivities of the polymers were approximately 10^?12–10^?13 Ω^?1 cm^?1. The experimental quantum efficiencies were simulated with Onsager's theory, and they showed that the initial quantum yield and thermalization distance were 10^?3 and 1.7 nm, respectively. Transmission electron microscopy showed that the rhenium complexes aggregated to form domains with dimensions of approximately 20–30 nm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1292–1308, 2005     

Ionic‐liquid‐based dispersive liquid–liquid microextraction for high‐throughput multiple food contaminant screening

This paper describes an innovation of dispersive liquid–liquid microextraction enabling multiple‐component analysis of eight high‐priority food contaminants in two chemically distinctive families: Sudan dyes and phthalate plasticizers. To provide convenient sample handling for solid and solid‐containing matrices, a modified dispersive liquid–liquid microextraction procedure used an extractant precoated frit to perform simultaneous filtration, solvent mixing, and phase dispersion in one simple step. A binary ionic liquid extractant system was carefully tuned to deliver high quality analysis based only on affordable LC with diode array detector instrumentation. The method is comprehensively validated for robust quantification with good precision (6.9–9.8% RSD) in a linear 2–1000 μg/L range. Having accomplished enrichment factors up to 451, the treatment enables sensitive detection at 0.09–1.01 μg/L levels. Analysis of six high‐risk solid condiments and sauces further verified its practical applicability within a 70–120% recovery range. Compared to other approaches, the current dispersive liquid–liquid microextraction treatment offers major advantages in terms of minimal solvent (1.5 mL) and sample (0.1 g) consumption, ultra‐high analytical throughput (6 min), and the ability to handle complex solid matrices. The idea of performing simultaneous analysis for multiple contaminants presented here fosters a more effective mode of operation in food control routines.