Bin Clusters Research Articles

Optimization models for clustering of solid waste collection process

In Jordan, the waste collection process incurs high transportation and operation costs. The main reasons for the high transportation costs are inefficient clustering and poor routing systems. In response, this research proposes a mathematical model for optimal clustering of garbage containers or bins (referred to as customers) for solid waste collection. The model’s objective function is to define the customers of each cluster such that the transportation costs within each cluster and between the hubs and depots are minimized, and the satisfaction of the clusters’ demand mean and variance is maximized. The optimization model was illustrated on solid waste collection for 20 customers, where the results showed that the proposed model is found to be effective in optimizing the waste collection process. In practice, this approach can be utilized in waste management for planning waste collection processes with minimal transportation costs while maximizing operational capacity.

Raman spectroscopy of GaSb1−xBix alloys with high Bi content

We report on the crystal morphology and Raman scattering features of high structural quality GaSb1−xBix alloys grown by molecular beam epitaxy with a high Bi content (x up to ∼0.10). The Raman spectra were measured at room temperature with different laser excitation wavelengths of 532 nm, 633 nm, and 785 nm. We observed well-defined Bi-induced Raman peaks associated with atomic Bin clusters and GaBi vibrational modes. Remarkably, some Bi-induced Raman modes were strongly enhanced when the laser energy was selected near an optical transition for the 5.8%Bi sample. This effect was attributed to a Raman resonant effect near an excited optical transition of the GaSbBi layer and has been used to identify the nature of the observed Raman peaks.

Structural, electronic, vibrational and optical properties of Bin clusters

The neutral, anionic and cationic bismuth clusters with the size n up to 14 are investigated by using B3LYP functional within the regime of density functional theory and the LAN2DZ basis set. By analysis of the geometries of the Bi[Formula: see text] (n = 2–14) clusters, where cationic and anionic bismuth clusters are largely similar to those of neutral ones, a periodic effect by adding units with one to four atoms into smaller cluster to form larger cluster is drawn for the stable structures of bismuth clusters. An even–odd alteration is shown for the properties of the clusters, such as the calculated binding energies and dissociation energies, as well as frontier orbital energies, electron affinities, ionization energies. All the properties indicate that the Bi4 cluster is the most possible existence in bismuth-containing materials, which supports the most recent experiment. The orbital compositions, infrared and Raman activities and the ultraviolet absorption of the most possible tetramer bismuth cluster are given in detail to reveal the periodic tendency of adding bismuth atoms and the stability of tetramer bismuth cluster.

Measuring cluster masses with CMB lensing: a statistical approach

We present a method for measuring the masses of galaxy clusters using the imprint of their gravitational lensing signal on the cosmic microwave background (CMB) temperature anisotropies. The method first reconstructs the projected gravitational potential with a quadratic estimator and then applies a matched filter to extract cluster mass. The approach is well-suited for statistical analyses that bin clusters according to other mass proxies. We find that current experiments, such as Planck, the South Pole Telescope and the Atacama Cosmology Telescope, can practically implement such a statistical methodology, and that future experiments will reach sensitivities sufficient for individual measurements of massive systems. As illustration, we use simulations of Planck observations to demonstrate that it is possible to constrain the mass scale of a set of 62 massive clusters with prior information from X-ray observations, similar to the published Planck ESZ-XMM sample. We examine the effect of the thermal (tSZ) and kinetic (kSZ) Sunyaev-Zeldovich (SZ) signals, finding that the impact of the kSZ remains small in this context. The stronger tSZ signal, however, must be actively removed from the CMB maps by component separation techniques prior to reconstruction of the gravitational potential. Our study of two such methods highlights the importance of broad frequency coverage for this purpose. A companion paper presents application to the Planck data on the ESZ-XMM sample.

Structure and dynamics in liquid bismuth and Bi(n) clusters: a density functional study.

Density functional/molecular dynamics simulations with more than 500 atoms have been performed on liquid bismuth at 573, 773, 923, and 1023 K and on neutral Bi clusters with up to 14 atoms. There are similar structural patterns (coordination numbers, bond angles, and ring patterns) in the liquid and the clusters, with significant differences from the rhombohedral crystalline form. We study the details of the structure (structure factor, pair, and cavity distribution functions) and dynamical properties (vibration frequencies, diffusion constants, power spectra), and compare with experimental results where available. While the three short covalent bonds typical to pnictogens are characteristic in both liquid and clusters, the number of large voids and the total cavity volume is much larger in the liquid at 1023 K, with larger local concentration variations. The inclusion of spin-orbit coupling results in a lowering of the cohesive energies in Bin clusters of 0.3-0.5 eV/atom.

On the dust content of galaxy clusters

We present a study to estimate the dust content in galaxy clusters by using one the most complete existing catalogues of galaxy clusters based on SDSS data and following two methods: the first one compares the colours of samples of galaxies in the background of clusters with those of galaxies in the field. Using this method, we have explored clustercentric distances up to 6 Mpc. The galaxies used in this first method were selected from the SDSS-DR9, among those having reliable photometry and accurate estimation of photometric redshifts. The results are largely independent of the galactic cut applied. At |b|>20 deg., the sample contains 56,985 clusters in the redshift range 0.05<z<0.68 (the mean redshift is 0.30) and ~5.3x10^6 galaxies. The second method computes the contribution of dust in clusters of galaxies to the far infrared sky. That is estimated indirectly by measuring the effect of clusters in the E(B-V) extinction map. Using the first method, we did not find any dependence with clustercentric distance in the colours of background galaxies. This allows us to constrain the mass of dust in the intracluster media, M_dust<8.4x10^9 M_sun (95% C.L.) within a cluster radius of 3 Mpc. With the second method, which averages the extinction of all clusters, we find a surface integral of the excess of colour g-i of 3.4+/-0.1 millimag Mpc^2. This is equivalent to ~60 times the far infrared luminosity of a Milky Way-like galaxy. By assumming similar properties for the dust, we can estimate a total dust mass per cluster of ~2x10^9 M_sun, which is compatible with the hypothesis that the dust is within the spiral galaxies of a cluster. Separating the clusters in 5x5 bins in redshift and richness, we confirm previous findings of a clear increase in luminosity with a redshift that agrees with the trend expected from current models.

Re-print of “Sputtering of polymers by keV clusters: Microscopic views of the molecular dynamics”

This article reviews the results of molecular dynamics simulations of cluster sputtering of hydrocarbon polymers obtained in the last few years and expand them with unpublished data of Ar cluster bombardment. The targets are molecular solids of linear hydrocarbons, polyethylene and polystyrene, including a polyethylene substrate decorated with adsorbed globular macromolecules. The projectiles are (hydro)carbon and Arn clusters, from small to massive, as well as Bin and Au400 clusters. The study focuses on the dynamics of cratering and sputtering, using a coarse-grained representation of the samples, on the study of molecular fragmentation, crosslinking and free H formation, using a fully atomistic model, and on the conditions of desorption of macromolecules by massive clusters. The results explain the similarities and differences between several cluster types and sizes and, to a large extent, the sputtering yields of Arn clusters and their ‘universal’ dependence on the scaled cluster energy, as observed in the experiments. They also demonstrate the reduction of sample fragmentation and crosslinking when going to larger clusters and the incidence angle dependence of intact macromolecule emission. Recent experimental validations obtained in our laboratory are also introduced and comparisons with data obtained by other groups are discussed in order to present a more complete picture of the physics of cluster bombardment of organic solids and polymers.

Sputtering of polymers by keV clusters: Microscopic views of the molecular dynamics

This article reviews the results of molecular dynamics simulations of cluster sputtering of hydrocarbon polymers obtained in the last few years and expand them with unpublished data of Ar cluster bombardment. The targets are molecular solids of linear hydrocarbons, polyethylene and polystyrene, including a polyethylene substrate decorated with adsorbed globular macromolecules. The projectiles are (hydro)carbon and Arn clusters, from small to massive, as well as Bin and Au400 clusters. The study focuses on the dynamics of cratering and sputtering, using a coarse-grained representation of the samples, on the study of molecular fragmentation, crosslinking and free H formation, using a fully atomistic model, and on the conditions of desorption of macromolecules by massive clusters. The results explain the similarities and differences between several cluster types and sizes and, to a large extent, the sputtering yields of Arn clusters and their ‘universal’ dependence on the scaled cluster energy, as observed in the experiments. They also demonstrate the reduction of sample fragmentation and crosslinking when going to larger clusters and the incidence angle dependence of intact macromolecule emission. Recent experimental validations obtained in our laboratory are also introduced and comparisons with data obtained by other groups are discussed in order to present a more complete picture of the physics of cluster bombardment of organic solids and polymers.

On the analogy between photoluminescence and carrier-type reversal in Bi- and Pb-doped glasses

Reaction order in Bi-doped oxide glasses depends on the optical basicity of the glass host. Red and NIR photoluminescence (PL) bands result from Bi(2+) and Bin clusters, respectively. Very similar centers are present in Bi- and Pb-doped oxide and chalcogenide glasses. Bi-implanted and Bi melt-doped chalcogenide glasses display new PL bands, indicating that new Bi centers are formed. Bi-related PL bands have been observed in glasses with very similar compositions to those in which carrier-type reversal has been observed, indicating that these phenomena are related to the same Bi centers, which we suggest are interstitial Bi(2+) and Bi clusters.

Computer Simulations of the Sputtering of Metallic, Organic, and Metal–Organic Surfaces with Bin and C60 Projectiles

This study focuses on the microscopic modeling of 0–25 keV Bi1–3–5 and C60 cluster impacts on three different targets (Au crystal, adsorbed Au nanoparticle, and organic solid), using molecular dynamics simulations, and on the comparison of the calculated quantities with recent experimental results, reported in the literature or obtained in our laboratory. The sputtering statistics are reported, showing nonlinearity of the sputtering yields with the number of cluster atoms at the same incident velocity for Bi1–5 bombardment. They are compared to experiments (especially for the organic target), and the microscopic explanation of the observations is analyzed. The results show that the respective behaviors and performances of the different projectiles are strongly dependent on the target, with clusters of heavy Bi atoms being more efficient at sputtering gold and, conversely, fullerene clusters inducing the largest sputtering yields of the organic material (mass matching). For organic targets, some important and novel conclusions of this work are the following: (i) The increase of the sputtering yield when going from Bi atoms to Bi clusters is insufficient to explain the much larger increase of characteristic ion yields, suggesting a projectile-dependent ionization probability. (ii) The extent of molecular fragmentation follows the order of Bi > Bi3 > Bi5 > C60, that is, softer emission with larger clusters. (iii) Even 5–10 keV Bi atoms create collective molecular motions and craters in the polymeric solid, though the collision cascades are rather dilute. Finally, a second series of simulations performed at low energies predict that 0.1–1 keV Bin clusters should not provide better results for sputtering and depth profiling than isoenergetic single atoms.

Electric dipole moments and polarizabilities of small Bin (n = 2–24, 40, 80) clusters

AbstractThe electric dipole moments (EDMs) and polarizabilities of small Bin (n = 2–24, 40, 80) clusters are investigated by the finite field method within density functional theory (DFT). The results show that both dipole moments and polarizabilities have even–odd oscillation behaviors, and they strongly depend on geometrical structures and electronic structures. High symmetry structure prohibits the occurrence of EDMs on Bi clusters. The increasing polarizabilities of Bi clusters are attributed to the inherent novel chain‐like geometrical evolution, which is significantly different from the characters observed in metal clusters or semiconductor clusters.

Sampling error of areal average rainfall due to radar partial coverage

Areal average rainfall is important as it is used as an input for most rainfall-runoff analysis in Hydrology and Water Resources. Different from traditional methods of using rain gauge data, the use of radar rainfall for the estimation of areal average rainfall is very straightforward. However, in some cases with severe terrain blockages, the value of the incomplete radar information is of serious concern. This study investigated this problem and derived an equation for estimating the error involved in the areal average rainfall due to partial radar coverage of a basin or sub-basin. When only partial radar information is available, the sampling error decreases with increasing radar coverage and the number of radar bin clusters. As an application example, this study considered the Han River Basin with its rainfall observations using the Ganghwa rain radar. Among a total of 24 mid-sized sub-basins in the Han River Basin evaluated, only five sub-basins were fully covered by the radar and three were totally uncovered. The remaining 16 sub-basins were covered partially by radar leading to incomplete radar information. The results show that the sampling error ranged from several % to tens % of standard deviation of the areal average rainfall depending on the relative areal radar coverage.

CROSS-CORRELATION WEAK LENSING OF SDSS GALAXY CLUSTERS. III. MASS-TO-LIGHT RATIOS

We present measurements of the excess mass-to-light ratio (M/L) measured around MaxBCG galaxy clusters observed in the Sloan Digital Sky Survey. This red-sequence cluster sample includes objects from small groups with M200 ∼ 5 × 1012 h−1 M☉ to clusters with M200 ∼ 1015 h−1 M☉. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean for clusters in bins of richness and optical luminosity. We also measure the excess luminosity density measured in the z = 0.25 i band. For both mass and light, we de-project the profiles to produce three-dimensional mass and light profiles over scales from 25 h−1 kpc to 22 h−1 Mpc. From these profiles we calculate the cumulative excess mass ΔM(r) and excess light ΔL(r) as a function of separation from the BCG. On small scales, where , the integrated mass-to-light profile (ΔM/ΔL)(r) may be interpreted as the cluster M/L. We find the (ΔM/ΔL)200, the M/L within r200, scales with cluster mass as a power law with index 0.33 ± 0.02. On large scales, where , the ΔM/ΔL approaches an asymptotic value independent of cluster richness. For small groups, the mean (ΔM/ΔL)200 is much smaller than the asymptotic value, while for large clusters (ΔM/ΔL)200 is consistent with the asymptotic value. This asymptotic value should be proportional to the mean M/L of the universe 〈M/L〉. We find 〈M/L〉b−2M/L = 362 ± 54h (statistical). There is additional uncertainty in the overall calibration at the ∼10% level. The parameter b2M/L is primarily a function of the bias of the L ≲ L* galaxies used as light tracers, and should be of order unity. Multiplying by the luminosity density in the same bandpass we find Ωmb−2M/L = 0.20 ± 0.03, independent of the Hubble parameter.

N-Point Hough transform for line detection

In this paper, we introduce the N-point Hough transform for the detection of a large number of planar lines in a noisy image. The N-point Hough transform yields the randomized Hough transform and the three-point Hough transform if we set N = 2 and N = 3 , respectively. From the viewpoint of the number of sample points required for the computation of lines, the N-point Hough transform is a generalization of the usual randomized Hough transform. The three-point Hough transform is introduced to increase the speed of the randomized Hough transform; the third point is used to avoid the selection of meaningless first and second sample points, which are used for the computation of the parameters of a line. This additional sample point guarantees the accuracy and robustness of a line detected using the first and second sample points. The N-point Hough transform evaluates the accuracy and robustness of a computed line using additional ( N - 2 ) points for each line. The evaluation in the N-point Hough transform is achieved by counting the cardinality of sample points in the neighborhood of this line as the support of the sample points for the acceptance of this line. First, to define the neighborhood of a line mathematically, in this paper we clarify the relationship between a line and a set of parameters in the voting space using geometric duality. This relationship allows us to define a metric in the voting space. The metric is used for the clustering of bins in the spherical voting space to guarantee the accurate and robust computation of lines. Finally, we evaluate the performance of the N-point Hough transform by comparing it with the randomized Hough transform, which is the two-point Hough transform in our framework of the voting method. This comparative study shows the geometric and computational advantages of the N-point Hough transform.

Structural and electronic properties of Bin (n = 2-14) clusters from density-functional calculations

The structural and electronic properties of Bi n (n = 2-14) clusters have been systematically studied using gradient-corrected density-functional theory. For each cluster size, a number of structural isomers were constructed and optimized to search for the lowest-energy structure. The competition of several structural patterns such as cages, superclusters, and layered structures leads to the alternating appearance of these configurations as global minima. Although the tendency of Bi to form puckered-layer structures is already well-known, the electronic states of Bi n clusters are still far from that of the bulk. As well, a remarkable even-odd atom number oscillation is observed in the structural and electronic properties of the clusters, implying that the stability of Bi n clusters is mainly dominated by the electron shell effect rather than by geometrical packing. The theoretically calculated values for electron affinities agree well with available experimental data.

The evolution of [O ii] emission from cluster galaxies

We investigate the evolution of the star formation rate in cluster galaxies. We complement data from the Canadian Network for Observational Cosmology 1 (CNOC1) cluster survey (0.15 < z < 0.6) with measurements from galaxy clusters in the Two-degree Field (2dF) galaxy redshift survey (0.05 < z < 0.1) and measurements from recently published work on higher-redshift clusters, up to almost z= 1. We focus our attention on galaxies in the cluster core, i.e. galaxies with r < 0.7h−170 Mpc. Averaging over clusters in redshift bins, we find that the fraction of galaxies with strong [Oii] emission is ≲20 per cent in cluster cores, and the fraction evolves little with redshift. In contrast, field galaxies from the survey show a very strong increase over the same redshift range. It thus appears that the environment in the cores of rich clusters is hostile to star formation at all the redshifts studied. We compare this result with the evolution of the colours of galaxies in cluster cores, first reported by Butcher and Oemler. Using the same galaxies for our analysis of the [Oii] emission, we confirm that the fraction of blue galaxies, which are defined as galaxies 0.2 mag bluer in the rest-frame B–V than the red sequence of each cluster, increases strongly with redshift. Because the colours of galaxies retain a memory of their recent star formation history, while emission from the [Oii] line does not, we suggest that these two results can best be reconciled if the rate at which the clusters are being assembled is higher in the past, and the galaxies from which it is being assembled are typically bluer.

Meta-analysis of genome-wide scans for hypertension and blood pressure in Caucasians shows evidence of susceptibility regions on chromosomes 2 and 3.

Individual genome-wide scans of blood pressure (BP) and hypertension (HT) have shown inconsistent results. The aim of this study was to investigate whether there was any consistent evidence of linkage across multiple studies with similar ethnicity. We applied the genome-search meta-analysis method (GSMA) to nine published genome-wide scans of BP (n = 5) and HT (n = 4) from Caucasian populations. For each study, the genome was divided into 120 bins and ranked according to the maximum evidence of linkage within each bin. The ranks were summed and averaged across studies and significance levels were estimated, on the basis of a distribution function of summed ranks or permutation tests without (PU) or with (PW) a study sample size weighting factor. Chromosome 3p14.1-q12.3 showed consistent evidence of linkage to HT (PU = 0.0001 and PW = 0.0001), diastolic BP (DBP) (PU = 0.007 and PW = 0.02), HT and DBP pooled (PU = 0.00002 and PW = 0.0001) and HT and systolic BP (SBP) pooled (PU = 0.0003 and PW = 0.0005). Chromosome 2p12-q22.1 showed evidence of linkage to HT (PU = 0.003 and PW = 0.009), DBP (PU = 0.05 and PW = NS), HT and DBP pooled (PU = 0.001 and PW = 0.004) and HT and SBP pooled (PU = 0.001 and P W = 0.005). The summed ranks of the HT analysis correlated significantly with those of the DBP (r = 0.20, P = 0.03) but not with those of the SBP. Both loci showed clustering of significant bins in the analysis of HT and DBP. We conclude that modest or non-significant linkage on chromosomes 3p14.1-q12.3 and 2p12-q22.1 in each individual study translates into genome-wide significant or highly suggestive linkages to HT and DBP in our GSMA analysis.

Inflammatory bowel disease susceptibility loci defined by genome scan meta-analysis of 1952 affected relative pairs

Crohn's disease and ulcerative colitis (the inflammatory bowel diseases) have a strong genetic component. Although over 20 putative susceptibility loci have been identified by individual genome scans, the majority of these loci have not been replicated. Many individual studies are at the lower limit of acceptable power for complex disease linkage analysis. Genome scan meta-analysis (GSMA), by use of sample sizes an order of magnitude greater than individual linkage studies, has increased power to detect novel loci, may confirm or refute regions detected in smaller individual studies, and enables regions to be prioritized for further gene identification efforts. Genome scan data (markers, significance scores) were obtained from 10 separate studies and meta-analysis was performed using the GSMA method. These studies comprised 1952 inflammatory bowel disease, 1068 Crohn's disease and 457 ulcerative colitis affected relative pairs. Study results were divided into 34 cM chromosomal bins, ranked, weighted by study size, summed across studies and bin-by-bin significance obtained by simulation. A region on chromosome 6p (containing the HLA) met genome wide significance for inflammatory bowel disease. Loci meeting suggestive significance for inflammatory bowel disease were 2q, 3q, 5q, 7q and 16 (NOD2/CARD15 region); Crohn's disease, 2q, 3q, 6p, 16 (NOD2/CARD15 region), 17q, 19p; and ulcerative colitis, 2q. Clustering of adjacent bins was observed for chromosomes 6p, 16, 19p. The meta-analysis has identified novel loci and prioritized genomic regions for further gene identification studies.

Electronic spin-spin coupling in rare earth doped semiconductor and semimetal clusters

Coupling between electronic spins in rare earth doped TeN and BiN clusters is investigated by size selective Stern—Gerlach deflection experiments. The results are interpreted in terms of Dy3+(Te N )3− and Dy3+(Bi N )3− structures. This magnetochemical approach is consistent with a Zener type exchange spin coupling between valence electrons and the localized electrons in the impurity core.

Laser fluorescence studies of metal clusters: Spectroscopy of molecular bismuth

The electronic spectra of Bin clusters in solid Ne and Ar matrices are studied by absorption and laser induced fluorescence techniques. The Bi2 ?→? spectrum appears to be unperturbed by the solid medium. A second, slightly lower lying excited electronic state may also be due to Bi2. Spectra belonging to another bismuth cluster, most likely to Bi4 are also observed and analyzed. The vibrational frequencies of the emitting species are determined. The spectrum is consistent with a Td structure for the tetramer, but shows no evidence of Jahn–Teller distortions.