United States Army Research Office

Article OBBTree: a hierarchical structure for rapid interference detection Share on Authors: S. Gottschalk Department of Computer Science, University of North Carolina, Chapel Hill, NC Department of Computer Science, University of North Carolina, Chapel Hill, NCView Profile , M. C. Lin Department of Computer Science, University of North Carolina, Chapel Hill, NC and U.S. Army Research Office Department of Computer Science, University of North Carolina, Chapel Hill, NC and U.S. Army Research OfficeView Profile , D. Manocha Department of Computer Science, University of North Carolina, Chapel Hill, NC Department of Computer Science, University of North Carolina, Chapel Hill, NCView Profile Authors Info & Claims SIGGRAPH '96: Proceedings of the 23rd annual conference on Computer graphics and interactive techniquesAugust 1996 Pages 171–180https://doi.org/10.1145/237170.237244Online:01 August 1996Publication History 959citation5,396DownloadsMetricsTotal Citations959Total Downloads5,396Last 12 Months262Last 6 weeks40 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

A survey of microstrip antenna elements is presented, with emphasis on theoretical and practical design techniques. Available substrate materials are reviewed along with the relation between dielectric constant tolerance and resonant frequency of microstrip patches. Several theoretical analysis techniques are summarized, including transmission-line and modal-expansion (cavity) techniques as well as numerical methods such as the method of moments and finite-element techniques. Practical procedures are given for both standard rectangular and circular patches, as well as variations on those designs including circularly polarized microstrip patches. The quality, bandwidth, and efficiency factors of typical patch designs are discussed. Microstrip dipole and conformal antennas are summarized. Finally, critical needs for further research and development for this antenna are identified.

An accurate spin-polarized exchange-only Kohn-Sham (KS) potential is constructed from a consideration of the optimized-effective-potential (OEP) method. A detailed analysis of the OEP integral equation for the exchange-only case results in a set of conditions which are manifestly satisfied by the exact OEP; these conditions are employed to construct an approximate OEP, ${\mathit{V}}_{\mathit{x}\mathrm{\ensuremath{\sigma}}}$, and therefore an approximate KS exchange-only potential as a functional of KS orbitals. Further, it is shown that this ${\mathit{V}}_{\mathit{x}\mathrm{\ensuremath{\sigma}}}$ can be derived analytically based on a simple approximation of the Green's functions in the OEP integral equation. The constructed potential, although approximate, contains many of the key analytic features of the exact KS potential: it reduces to the exact KS result in the homogeneous-electron-gas limit, approaches -1/r as r\ensuremath{\rightarrow}\ensuremath{\infty}, yields highest occupied-orbital energy eigenvalues ${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{m}\mathrm{\ensuremath{\sigma}}}$ that satisfy Koopmans's theorem, and exhibits an integer discontinuity when considered as a function of fractional occupancy of the highest-energy occupied single-particle state of a given spin projection \ensuremath{\sigma}. In addition ${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{m}\mathrm{\ensuremath{\sigma}}}$ nearly exactly satisfies Janak's theorem. The approximate OEP is a simple but remarkably accurate representation of the exact, numerically derived exchange-only OEP.Detailed numerical results obtained by employing ${\mathit{V}}_{\mathit{x}\mathrm{\ensuremath{\sigma}}}$ as the exchange-only potential for ten atoms with closed subshells yield total energies, Hartree potentials, single-particle expectation values, and ${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{m}}$ which are in excellent agreement with both exact OEP and Hartree-Fock (HF) results and represent a significant improvement over the results obtained by employing other exchange-only potentials. Similarly, the properties of alkali-metal atoms are calculated including the separate spin-up and spin-down densities to obtain results in excellent agreement with those of spin-unrestricted OEP and HF methods. Finally, we demonstrate the accuracy of ${\mathit{V}}_{\mathit{x}\mathrm{\ensuremath{\sigma}}}$ by calculating the total energy, ${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{m}\mathrm{\ensuremath{\uparrow}}}$, and ${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{m}\mathrm{\ensuremath{\downarrow}}}$ as a function of fractional filling f, of the highest occupied single-particle orbital for the magnesium atom (Z=12) from N=9--12 electrons and find excellent agreement with both spin-unrestricted OEP and HF results even when ${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{m}\mathrm{\ensuremath{\sigma}}}$ is strongly dependent on f. In addition we display the integer discontinuity in ${\mathit{V}}_{\mathit{x}\mathrm{\ensuremath{\sigma}}}$ when the highest-energy spin subshell begins to be filled.

Flexible and lightweight energy storage systems have received tremendous interest recently due to their potential applications in wearable electronics, roll-up displays, and other devices. To manufacture such systems, flexible electrodes with desired mechanical and electrochemical properties are critical. Herein we present a novel method to fabricate conductive, highly flexible, and robust film supercapacitor electrodes based on graphene/MnO(2)/CNTs nanocomposites. The synergistic effects from graphene, CNTs, and MnO(2) deliver outstanding mechanical properties (tensile strength of 48 MPa) and superior electrochemical activity that were not achieved by any of these components alone. These flexible electrodes allow highly active material loading (71 wt % MnO(2)), areal density (8.80 mg/cm(2)), and high specific capacitance (372 F/g) with excellent rate capability for supercapacitors without the need of current collectors and binders. The film can also be wound around 0.5 mm diameter rods for fabricating full cells with high performance, showing significant potential in flexible energy storage devices.

We introduce a control network protocol, try-once-discard (TOD), for networked control systems (NCS), and provide, for the first time, an analytic proof of global exponential stability for both the new protocol and the commonly used statically scheduled access methods. Controllers are designed without regarding the presence of the network in the feedback loop, so consequently many controller design techniques may be employed. The performance of the new network protocol and the statically scheduled protocols are compared in simulations.

In recent years, the field of terahertz (THz) science and technology has entered a completely new phase of unprecedented expansion that is generating ever growing levels of broad-based international attention. In particular,there have been important advances in state-of-the-art THz technology and very enthusiastic growth in research activities associated with related scientific and industrial applications. One can legitimately argue that the potential payoffs of THz sensing and imaging (THz S&I) to application areas such as defense, security, biology and medicine are the major drivers of this new phenomenon. However, there remain major science and technology "gaps" in the THz regime that must be reconciled before many of the perceived payoffs ever become realizable. Therefore, it is natural to ask the question "Is now the time for THz?" or rather, are these recent events just a repeat of previous cycles in THz overenthusiasm that have been witnessed during the last century? The main goal of this paper is to consider some of the most promising THz S&I applications within the specific context of their particular science and technology challenges in an attempt to credibly judge (or speculate on) their future potential.

The integral equation originally derived by Sharp and Horton for the optimized effective potential (OEP) is exactly transformed into an equivalent form from which it is manifestly clear that the OEP, ${\mathit{V}}_{\mathit{x}\mathrm{\ensuremath{\sigma}}}^{0}$(r), is an implicit functional of only {${\mathit{n}}_{\mathit{i}\mathrm{\ensuremath{\sigma}}}$}, the orbital densities of the occupied states {${\mathrm{\ensuremath{\psi}}}_{\mathit{i}\mathrm{\ensuremath{\sigma}}}$}, and the corresponding single-particle exchange potentials {${\mathit{v}}_{\mathit{i}\mathrm{\ensuremath{\sigma}}}$}. Furthermore, the transformed OEP has exactly the same form as one recently developed by the authors [Phys. Rev. A 45, 101 (1992)] from a more heuristic approach, the only difference being that in the present work a term proportional to the gradient of ${\mathit{n}}_{\mathit{i}\mathrm{\ensuremath{\sigma}}}$ is added to each ${\mathit{v}}_{\mathit{i}\mathrm{\ensuremath{\sigma}}}$ whose average value when taken over the i\ensuremath{\sigma} state is zero. This result leads to the natural development of an iterative approximation for ${\mathit{V}}_{\mathit{x}\mathrm{\ensuremath{\sigma}}}^{0}$, with the zeroth approximation being given by our previous result. The application of this technique to the calculation of the total energy and highest-energy single-particle eigenvalue for selected atoms is presented. In addition, we note that our results are applicable to the calculation of the OEP for any assumed exchange-correlation functional ${\mathit{E}}_{\mathrm{xc}}$[{${\mathrm{\ensuremath{\psi}}}_{\mathit{i}\mathrm{\ensuremath{\sigma}}}$}], where ${\mathit{v}}_{\mathit{i}\mathrm{\ensuremath{\sigma}}}$ is taken as the appropriate functional derivative of ${\mathit{E}}_{\mathrm{xc}}$. In the case that ${\mathit{E}}_{\mathrm{xc}}$ is a functional of {${\mathit{n}}_{\mathit{i}\mathrm{\ensuremath{\sigma}}}$} only, as in the case of the local-density approximation with self-interaction correction, the resulting ${\mathit{V}}_{\mathrm{xc}\mathrm{\ensuremath{\sigma}}}^{0}$ is a functional of the {${\mathit{n}}_{\mathit{i}\mathrm{\ensuremath{\sigma}}}$} only.

Mg alloys are among the lightest alloys but they are usually weak. Here we report a new mechanism to make them ultrastrong while maintaining good ductility. Stacking faults with nanoscale spacing were introduced into a Mg–8.5Gd–2.3Y–1.8Ag–0.4Zr (wt%) alloy by conventional hot rolling, which produced a yield strength of ∼575 MPa, an ultimate strength of ∼600 MPa, and a uniform elongation of ∼5.2 %. Low stacking fault (SF) energy enabled the introduction of a high density of SFs, which impeded dislocation slip and promoted dislocation accumulation. These findings provide guidance for developing Mg alloys with superior mechanical properties.

The flow induced by a vortex ring approaching a plane wall on a trajectory normal to the wall is investigated for an incompressible fluid which is otherwise stagnant. The detailed characteristics of the interaction of the ring with the flow near the surface have been observed experimentally for a wide variety of laminar rings, using dye in water to visualize the flow in the ring as well as near the plane surface. Numerical solutions are obtained for the trajectory of the ring as well as for the unsteady boundary-layer flow that develops on the wall. The experimental and theoretical results show that an unsteady separation develops in the boundary-layer flow, in the form of a secondary ring attached to the wall. A period of explosive boundary-layer growth then ensues and a strong viscous-inviscid interaction occurs in the form of the ejection of the secondary vortex ring from the boundary layer. The primary ring then interacts with the secondary ring and in some cases was observed to induce the formation of a third, tertiary, ring near the wall. The details of this process are investigated over a wide Reynolds number range. The results clearly show how one vortex ring can produce another, through an unsteady interaction with a viscous flow near the wall.

Very efficient power combining of solid-state millimeter-wave sources may be obtained through the application of quasi-optical resonators and monotfthic source arrays. Through the theory of reiterative wavebeams (beam modes) with application of the Lorentz reciprocity theorem, it is shown that planar source arrays containing 25 individual elements or more result in very efficient power transfer of energy from the source arrays to the fundamental wave-beam mode. It is further shown that for identical sources within a properly designed quasi-optical power combiner, the output power tends to increase much faster that number of source elements.

Catching photons: Visible light, an amine reductant, and a [Ru(bpy)3]2+ photocatalyst can be used to mediate the addition of glycosyl halides into alkenes to synthesize important C-glycosides (see scheme). This method shows the growing potential of photocatalysis to effectively drive useful and difficult chemical transformations. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

The Bonin archipelago represents an uplifted fore-arc terrain which exposes the products of Eocene supra-subduction zone magmatism. Chichijima, at the centre of the chain, represents the type locality for the high-Mg andesitic lava termed boninite. The range of extrusives which constitute the boninite series volcanics are present on Chichijima, and are disposed in the sequence boninite-andesite-dacite with increasing height in the volcano-stratigraphy. Progression to evolved compositions within the Chichijima boninite series is controlled by crystal fractionation from a boninite parental magma containing ∼ 15% MgO. Olivine and clinoenstatite are the initial liquidus phases, but extraction of enstatitic orthopyroxene, followed by clinopyroxene and plagioclase, is responsible for the general evolution from boninite, through andesite, to dacite. Some andesites within the overlying Mikazukiyama Formation are petrographically distinct from the main boninite series in containing magnetite phenocrysts and a high proportion of plagioclase. As such, these andesites have affinities with the calc-alkaline series. Major and trace element data for 74 boninitic series rocks from Chichijima are presented. Although major element variation is dominantly controlled by high-level crystal fractionation, the large variations in incompatiable trace element concentrations at high MgO compositions cannot be explained by this mechanism. Nd, Pb, and Sr isotopic data indicate the following: (1) a strong overprint on 87Sr/86Sr by seawater alteration; (2) Pb isotopes lie above the northern hemisphere reference line (NHRL) and are thus similar to the <30-Ma are and basin lavas of the Izu—Bonin system, and (3) εNd(40 Ma) ranges between 2.8 and 6.8 within the boninite series volcanics. Differences in rare-earth elements (REE), Zr, Ti, and 143Nd/144Nd at similar degrees of fractionation can be explained by the addition of a component of fixed composition from the down-going oceanic crustal slab to a variably depleted source region within the overlying wedge. Data presented for Sm/Zr and Ti/Zr indicate that boninite series volcanics are characterized by low values for both of these ratios. In particular, boninites appear to have uniquely low Sm/Zr ratios. These characteristics may be the result of slab melting in the presence of residual amphibole; the resultant melt could combine with typical slab dehydration fluids and infiltrate the overlying mantle wedge. Such a fluid—melt component could mix either with shallow mantle or directly with primitive melts from depleted mantle. Trace elements, REE, and isotope data thus point to a model for boninite genesis which requires tightly constrained pressure—temperature conditions in the slab combined with melting of a variably depleted source in the overlying wedge. Such constraints are rarely met except during the subduction of juvenile oceanic crust beneath a young, hot overriding plate.

The electrophilic activation of alkenes by transition-metal catalysts is a fundamental step in a rapidly growing number of catalytic processes. Although palladium is the best known metal for this purpose, the special properties of its third-row cousin platinum (strong metal-ligand bonds and slow substitution kinetics) have enabled the development of transformations that are initiated by addition to the C=C bonds by protic carbon, nitrogen, oxygen, and phosphorus nucleophiles, as well as alkene or arene nucleophiles. Additionally, reactivity profiles, which are often unique to platinum, provide wholly new reaction products. This Review concerns platinum-catalyzed electrophilic alkene activation reactions, with a special emphasis on the mechanistic properties of known systems, on the differences between platinum and palladium catalysts, and on the prospects for the development of new systems.

In this paper we describe an accumulative approach to move beyond simple incorporation of conductive carbon nanostructures, such as graphene and carbon nanotubes, to improve the performance of metal oxide/hydroxide based electrodes in energy storage applications. In this approach we first synthesize Co–Ni double hydroxides/graphene binary composites through a co-precipitation process. We then assemble these composites into films (∼6 mg cm−2) by integrating with carbon nanotubes that can be used directly as electrodes. Experimental results indicate that the synergistic contributions from nanotubes, graphene and cobalt substitution enabled electrodes with substantially improved energy storage performance metrics. With 50% Co and 50% Ni (i.e. Co0.5Ni0.5(OH)2), the composite exhibited a remarkable maximum specific capacitance of 2360 F g−1 (360 mA h g−1) at 0.5 A g−1 and still maintained a specific capacitance as high as 2030 F g−1 at 20 A g−1 (∼86% retention). More importantly, the double hydroxides exhibited tunable redox behavior that can be controlled by the ratio between cobalt and nickel. These results demonstrate the importance of the rational design of functional composites and the large-scale assembly strategies for fabricating electrodes with improved performance and tunability for energy storage applications.

Here the authors report systematic studies on the epitaxial growth and properties of Zn1−xCuxO (x=0.02–0.1) thin films deposited onto sapphire c-plane single crystals using pulsed-laser deposition. X-ray diffraction and high resolution transmission electron microscopy (HRTEM) were employed to study the epitaxial relations of Zn1−xCuxO with the substrate, and x-ray photoelectron spectroscopy was used to establish the bonding characteristics and oxidation states of copper inside the ZnO host. Room temperature ferromagnetism was observed in the Zn1−xCuxO films with magnetic moment per Cu atom decreasing with an increasing Cu content. The presence of any magnetic phase was ruled out using HRTEM. Thus, the ferromagnetism was attributed to Cu ions substituted into the ZnO lattice.

No abstract available.

Fungal peritonitis is a rare complication in patients on continuous ambulatory peritoneal dialysis. We report five recent cases and their management. The fungi isolated were Candida albicans, C. parapsilosis, Exophiala jeanselmei, Drechslera spicifera, and a Fusarium species. Chemotherapy was attempted with various regimens including oral ketoconazole, intravenous or intraperitoneal amphotericin B, and oral flucytosine. Pharmacokinetic studies were done in two patients receiving treatment with one of these drugs. Three patients were cured of their fungal infection. Three patients whose Tenckhoff catheters were left in situ died, whereas two patients whose catheters were removed survived. Our experience suggests that removal of the peritoneal catheter should be considered once the diagnosis of fungal peritonitis is established.

The use of self-assembled InAs-GaAs quantum dots in photoconductive intersubband detectors in the far-infrared is presented. Far-infrared absorption is observed in self-assembled quantum dots in the 6-18-/spl mu/m range for subband-subband and subband-continuum transitions. Photoconductive quantum-dot intersubband detectors were fabricated and demonstrate tunable operating wavelengths between 6-18 /spl mu/m using subband-subband or subband-continuum transitions. The use of AlAs barriers allows further tuning to shorter wavelengths of 3-7 /spl mu/m. Subband-continuum quantum dot intersubband detectors show encouraging normal incidence performance characteristics at T=40 K, with responsivities of 10-100 mA/W, detectivities of 1-10 /spl times/10/sup 9/ cm/spl middot/Hz/sup 1/2//W and large photoconductive gain up to g=12 for a ten-layer quantum-dot heterostructure. With improvements in device structure, self-assembled quantum dots can be expected to provide intrinsic normal incidence broad-band detectors with advantages over quantum wells.

Measurement of the room temperature forward bias current-voltage behavior of InGaN/AlGaN double heterostructure blue light-emitting diodes demonstrates a significant departure from the usual Is exp(qV/ nkT) behavior where n is the ideality factor which varies between 1 and 2. The observed current-voltage behavior at room temperature may be represented as I=2.7×10−11 exp(5.7V) which suggests a tunneling mechanism. Measurement of the electroluminescence for currents from 0.5 to 100 mA demonstrates that the emission peak shifts to higher energy while increasing in intensity. The shifting peak spectra is due to band filling, a process which results from the injection of holes via tunneling into an empty acceptor impurity band and vacant valence band tails. At currents near 100 mA, a non-shifting band-to-band emission approaches the intensity of the shifting peak spectra. The active layer of these diodes is codoped with both the donor Si and the acceptor Zn.

This paper presents a restricted overview of Fractal Physiology focusing on the complexity of the human body and the characterization of that complexity through fractal measures and their dynamics, with fractal dynamics being described by the fractional calculus. Not only are anatomical structures (Grizzi and Chiriva-Internati, 2005), such as the convoluted surface of the brain, the lining of the bowel, neural networks and placenta, fractal, but the output of dynamical physiologic networks are fractal as well (Bassingthwaighte et al., 1994). The time series for the inter-beat intervals of the heart, inter-breath intervals and inter-stride intervals have all been shown to be fractal and/or multifractal statistical phenomena. Consequently, the fractal dimension turns out to be a significantly better indicator of organismic functions in health and disease than the traditional average measures, such as heart rate, breathing rate, and stride rate. The observation that human physiology is primarily fractal was first made in the 1980s, based on the analysis of a limited number of datasets. We review some of these phenomena herein by applying an allometric aggregation approach to the processing of physiologic time series. This straight forward method establishes the scaling behavior of complex physiologic networks and some dynamic models capable of generating such scaling are reviewed. These models include simple and fractional random walks, which describe how the scaling of correlation functions and probability densities are related to time series data. Subsequently, it is suggested that a proper methodology for describing the dynamics of fractal time series may well be the fractional calculus, either through the fractional Langevin equation or the fractional diffusion equation. A fractional operator (derivative or integral) acting on a fractal function, yields another fractal function, allowing us to construct a fractional Langevin equation to describe the evolution of a fractal statistical process. Control of physiologic complexity is one of the goals of medicine, in particular, understanding and controlling physiological networks in order to ensure their proper operation. We emphasize the difference between homeostatic and allometric control mechanisms. Homeostatic control has a negative feedback character, which is both local and rapid. Allometric control, on the other hand, is a relatively new concept that takes into account long-time memory, correlations that are inverse power law in time, as well as long-range interactions in complex phenomena as manifest by inverse power-law distributions in the network variable. We hypothesize that allometric control maintains the fractal character of erratic physiologic time series to enhance the robustness of physiological networks. Moreover, allometric control can often be described using the fractional calculus to capture the dynamics of complex physiologic networks.