Narrow Results

The Connection Machine CM-2 computer represents the state of the art in supercomputer performance at this time, with peak rates of over 20 Gflops in 32-bit precision. While theoretical peak rates are essentially never attained, remarkable performance is possible on real applications. We discuss a number of CM-2 applications including implicit and explicit PDE solvers as well as spectral methods. We demonstrate delivered performance over a gigaflop in each case, and ranging as high as 3.8 gigaflops in the case of conjugate gradient solution of elliptic PDE.

We describe 2D and 3D Fast Helmholtz and Poisson Direct Solvers for the CM-2 and provide performance data for them on grids with up to 4 million points and using 65,536 processors. Performance of 1.1 Gflops is attained in 2D, and over 850 Mflops in 3D. The solution of the Helmholtz equation on a 2048×2048 grid takes under half a second, and on a 128×128×256 3D grid it requires .54 seconds. We have iteratively solved more general elliptic PDE by conjugate gradient methods at 3.8 Gflops. The fast solver has been used to provide a pre-conditioner for the conjugate gradient solver, which is then limited in performance to 1.3 Gflops, but results in far fewer iterations.

We also describe several partial and complete applications ranging from oil reservoir simulation to oceanographic modeling. In the latter case we present the first results of spectral models running on the CM-2. We emphasize the issues involved in attaining these levels of performance and compare in most cases with CRAY-XMP performance for the same algorithm. All results are for algorithms written in a high-level language.

Threats associated with bioaerosol weapons have been around for several decades. However, with the recent political developments that changed the image and dynamics of the international order and security, the visibility and importance of these bioaerosol threats have considerably increased. Over the last few years, Defence Research and Development Canada has investigated the spectrometric LIDAR-based standoff bioaerosol detection technique to address this menace. This technique has the advantages of rapidly monitoring the atmosphere over wide areas without physical intrusions and reporting an approaching threat before it reaches sensitive sites. However, it has the disadvantages of providing a quality of information that degrades as a function of range and bioaerosol concentration. In order to determine the importance of these disadvantages, Canada initiated in 1999 the SINBAHD (Standoff Integrated Bioaerosol Active Hyperspectral Detection) project investigating the standoff detection and characterization of threatening biological clouds by Laser-Induced Fluorescence (LIF) and intensified range-gated spectrometric detection techniques. This article reports an overview of the different lessons learned with this program. Finally, the BioSense project, a Technology Demonstration Program aiming at the next generation of wide area standoff bioaerosol sensing, mapping, tracking and classifying systems, is introduced.

Heavy loads of aerosols in the air have considerable health effects in individuals who suffer from chronic breathing difficulties. This problem is more acute in the Middle-East, where dust storms in winter and spring transverse from the neighboring deserts into dense populated areas. Discrimination between the dust types and association with their source can assist in assessment of the expected health effects. A method is introduced to characterize the properties of dense dust clouds with passive IR spectral measurements. First, we introduce a model based on the solution of the appropriate radiative transfer equations. Model predictions are presented and discussed. Actual field measurements of silicone-oil aerosol clouds with an IR spectro-radiometer are analyzed and compared with the theoretical model predictions. Silicone-oil aerosol clouds have been used instead of dust in our research, since they are composed of one compound in the form of spherical droplets and their release is easily controlled and repetitive. Both the theoretical model and the experimental results clearly show that discrimination between different dust types using IR spectral measurements is feasible. The dependence of this technique on measurement conditions, its limitations, and the future work needed for its practical application of this technique is discussed.

We analyze two theoretical approaches to ensemble averaging for integrable systems in quantum chaos, spectral averaging (SA) and parametric averaging (PA). For SA, we introduce a new procedure, namely, rescaled spectral averaging (RSA). Unlike traditional SA, it can describe the correlation function of spectral staircase (CFSS) and produce persistent oscillations of the interval level number variance (IV). PA while not as accurate as RSA for the CFSS and IV, can also produce persistent oscillations of the global level number variance (GV) and better describes saturation level rigidity as a function of the running energy. Overall, it is the most reliable method for a wide range of statistics.

Finding the sources of sound in large nonlinear fields via direct simulation currently requires excessive computational cost. This paper describes a simple technique for efficiently solving the multidimensional nonlinear Euler equations that significantly reduces this cost and demonstrates a useful approach for validating high order nonlinear methods. Up to 15th order accuracy in space and time methods were compared and it is shown that an algorithm with a fixed design accuracy approaches its maximal utility and then its usefulness exponentially decays unless higher accuracy is used. It is concluded that at least a 7th order method is required to efficiently propagate a harmonic wave using the nonlinear Euler equations to a distance of five wavelengths while maintaining an overall error tolerance that is low enough to capture both the mean flow and the acoustics.

Theoretical exploration of network structure significance requires a range of different networks for comparison. Here, we present a new method to construct networks in a spatial setting that uses spectral methods in combination with a probability distribution function. Nearly all previous algorithms for network construction have assumed randomized distribution of links or a distribution dependent on the degree of the nodes. We relax those assumptions. Our algorithm is capable of creating spectral networks along a gradient from random to highly clustered or diverse networks. Number of nodes and link density are specified from start and the structure is tuned by three parameters (γ, σ, κ). The structure is measured by fragmentation, degree assortativity, clustering and group betweenness of the networks. The parameter γ regulates the aggregation in the spatial node pattern and σ and κ regulates the probability of link forming.

A new series of mono-/di-aminated meso-tetraarylporphyrins has been synthesized and characterized by conventional spectroscopic methods. Crystal structure analysis shows that interactions involving halogens are the major contributors, and the relative contributions are 56% and 53% respectively for MB2c and MB3c. All the compounds were electrochemically analyzed under different reaction conditions and showed a positive shift in the reduction and oxidation potentials. The HOMO–LUMO energy gap was altered with respect to the nature of the supporting electrolyte and reference electrodes used. The linear behavior of Randles-Sevcik plots indicate that the redox processes are diffusion controlled; the first reduction/oxidation is a reversible one-electron step whereas the second reduction/oxidation is a quasi-reversible one-electron process. Results also reveal that the mono-aminated porphyrins are more electron deficient than non-aminated and di-aminated porphyrins.

Two $\beta$-substituted Pd(II) porphyrins, (PdTPP(NO${}_2)$Ph₂ and PdTPP(Ph)${}_4)$, were synthesized and characterized by various spectroscopic techniques, and their spectral and electrochemical redox properties were investigated with respect to PdTPP. The single-crystal X-ray structure of PdTPP(NO${}_2)$-Ph₂ revealed saddle-shape conformation of the macrocyclic core of porphyrin. DFT studies revealed nonplanar saddle shape conformation of PdTPP(Ph)₄ with an average deviation of $\beta$-pyrrole carbon atoms from the porphyrin mean plane ($\mathrm{\Delta }$C${}_{\beta }$ = ± 0.751 Å) and also 24 core atoms ($\mathrm{\Delta }$24 = ± 0.368 Å) as compared to PdTPP(NO${}_2)$Ph₂ ($\mathrm{\Delta }$C${}_{\beta }$ = 0.649 Å and $\mathrm{\Delta }$24 = ± 0.317 Å) due to more $\beta$-pyrrole substitution. Both PdTPP(NO${}_2)$Ph₂ and PdTPP(Ph)₄ exhibited 13-19 nm and 49-59 nm red-shift in the Soret and Q${}_{x(0,0)}$ bands as compared to PdTPP, respectively. PdTPP(NO${}_2)$Ph₂ exhibited a very high dipole moment (7.32 D) as compared to PdTPP(Ph)₄ (0.239 D) due to the “push-pull” effect of electron donor (phenyl) and acceptor (-NO${}_2)$ groups at the $\beta$-pyrrole positions of the macrocycle. The redox potentials of PdTPP(NO${}_2)$Ph₂ anodically shifted ($\mathrm{\Delta }$E = 0.2-0.4V) as compared to PdTPP and PdTPP(Ph)₄ due to the presence of $\beta$-phenyl groups and the strong electron-withdrawing effect of the nitro group. Hence the HOMO-LUMO energy gap of PdTPP(NO${}_2)$Ph₂ decreased by 0.20 V and 0.28 V as compared to PdTPP(Ph)₄ and PdTPP, respectively.

Threats associated with bioaerosol weapons have been around for several decades. However, with the recent political developments that changed the image and dynamics of the international order and security, the visibility and importance of these bioaerosol threats have considerably increased. Over the last few years, Defence Research and Development Canada has investigated the spectrometric LIDAR-based standoff bioaerosol detection technique to address this menace. This technique has the advantages of rapidly monitoring the atmosphere over wide areas without physical intrusions and reporting an approaching threat before it reaches sensitive sites. However, it has the disadvantages of providing a quality of information that degrades as a function of range and bioaerosol concentration. In order to determine the importance of these disadvantages, Canada initiated in 1999 the SINBAHD (Standoff Integrated Bioaerosol Active Hyperspectral Detection) project investigating the standoff detection and characterization of threatening biological clouds by Laser-Induced Fluorescence (LIF) and intensified range-gated spectrometric detection techniques. This article reports an overview of the different lessons learned with this program. Finally, the BioSense project, a Technology Demonstration Program aiming at the next generation of wide area standoff bioaerosol sensing, mapping, tracking and classifying systems, is introduced.

Heavy loads of aerosols in the air have considerable health effects in individuals who suffer from chronic breathing difficulties. This problem is more acute in the Middle-East, where dust storms in winter and spring transverse from the neighboring deserts into dense populated areas. Discrimination between the dust types and association with their source can assist in assessment of the expected health effects. A method is introduced to characterize the properties of dense dust clouds with passive IR spectral measurements. First, we introduce a model based on the solution of the appropriate radiative transfer equations. Model predictions are presented and discussed. Actual field measurements of silicone-oil aerosol clouds with an IR spectro-radiometer are analyzed and compared with the theoretical model predictions. Silicone-oil aerosol clouds have been used instead of dust in our research, since they are composed of one compound in the form of spherical droplets and their release is easily controlled and repetitive. Both the theoretical model and the experimental results clearly show that discrimination between different dust types using IR spectral measurements is feasible. The dependence of this technique on measurement conditions, its limitations, and the future work needed for its practical application of this technique is discussed.