cssi/SciSciGPT-SciSciNet huggingface dataset:
Ranging airport pseudolite for local area augmentation

This paper discusses the integration of an airport pseudolite (APL) into a local area augmented differential GPS based precision approach system. A prototype architecture is described that is being used to develop requirements for the local area augmentation system. Key features of this prototype system are presented along with its current performance. Key features discussed include the use of a multipath limiting antenna, APL signal structure factors, a unique APL automatic gain control, and GPS blanking technique to maximize APL tracking performance, while minimizing the electromagnetic interference to nominal DGPS performance.
On the vibrations of lumped parameter systems governed by differential-algebraic equations

Abstract In this paper, we consider the vibratory motions of lumped parameter systems wherein the components of the system cannot be described by constitutive expressions for the force in terms of appropriate kinematical quantities. Such physical systems reduce to a system of differential-algebraic equations, which invariably need to be solved numerically. To illustrate the issues with clarity, we consider a simple system in which the dashpot is assumed to contain a “Bingham” fluid for which one cannot describe the force in the dashpot as a function of the velocity. On the other hand, one can express the velocity as a function of the force.
Electronic Coherence in Mixed-Valence Systems: Spectral Analysis

The electron transfer kinetics of mixed-valence systems is studied via solving the eigenstructure of the two-state nonadiabatic diffusion operator for a wide range of electronic coupling constants and energy bias constants. The calculated spectral structure consists of three branches in the eigendiagram: a real branch corresponding to exponential or multiexponential decay, and two symmetric branches corresponding to population oscillations between donor and acceptor states. The observed electronic coherence is shown as a result of underdamped Rabi oscillations in an overdamped solvent environment. The time evolution of electron population is calculated by applying the propagator constructed from the eigensolution to the nonequilibrium initial preparation, and it agrees perfectly with the result of a direct numerical propagation of the density matrix. The resulting population dynamics confirms that increasing the energy bias destroys electronic coherence.
Thermal expansion and phase transitions of α-AlF3

Abstract ReO3-type materials are of interest for their potential low or negative thermal expansion. Many metal trifluorides MF3 adopt the cubic form of this structure at elevated temperatures, which rhombohedrally distorts upon cooling. The rhombohedral form displays strong positive volume thermal expansion, but cubic MF3 display much lower and sometimes negative thermal expansion. The expansion behavior of α-AlF3 was characterized via synchrotron powder diffraction between 323 and 1177 K. α-AlF3 is rhombohedral at ambient conditions and displays strongly anisotropic thermal expansion. The volume coefficient of thermal expansion (CTE), αV, at 500 K is ~86 ppm K−1, but the linear CTE along the c-axis, αc, is close to zero. α-AlF3 becomes cubic on heating to ~713 K and continues to show positive thermal expansion above the phase transition (αV(900 K) ~25 ppm K−1).
On the Nature and Location of the Microlenses

This paper uses the caustic-crossing events in the microlens data sets to explore the nature and location of the lenses. We conclude that (1) the large majority of lenses, whether they are luminous or dark, are likely to be binaries; (2) blending is an important feature of all the data sets; and (3) most of the LMC/SMC events to date are due to lenses in the Magellanic Clouds, if, as is suspected, the caustic-crossing events along the directions to the Magellanic Clouds are due to lenses located in the Clouds. Although these conclusions are based on a very small number of events, they are subject to a variety of detailed tests. If they are correct, a large fraction of lenses along the direction to the LMC may be ordinary stellar binary systems, just as are the majority of the lenses along the direction to the Bulge. Thus, a better understanding of the larger-than-anticipated value derived for the Bulge optical depth may allow us to better interpret the large value derived for the optical depth to the LMC. Indeed, binarity and blending in the data sets may illuminate connections among several other puzzles: the dearth of binary-source light curves, the dearth of non-caustic-crossing, perturbed, binary-lens events, and the dearth of obviously blended point-lens events.
A Thermodynamic Model for Receptor Clustering

Intracellular signaling often arises from ligand-induced oligomerization of cell surface receptors. This oligomerization or clustering process is fundamentally a cooperative behavior between near-neighbor receptor molecules; the properties of this cooperative process clearly affect the signal transduction. Recent investigations have revealed the molecular basis of receptor-receptor interactions, but a simple theoretical framework for using these data to predict cluster formation has been lacking. Here, we propose a simple, coarse-grained, phenomenological model for ligand-modulated receptor interactions and discuss its equilibrium properties via mean-field theory. The existence of a first-order transition for this model has immediate implications for the robustness of the cellular signaling response.
Existence of invariant tori in three dimensional maps with degeneracy

Abstract We prove a KAM-type result for the persistence of two-dimensional invariant tori in perturbations of integrable action–angle–angle maps with degeneracy, satisfying the intersection property. Such degenerate action–angle–angle maps arise upon generic perturbation of three-dimensional volume-preserving vector fields, which are invariant under volume-preserving action of S 1 when there is no motion in the group action direction for the unperturbed map. This situation is analogous to degeneracy in Hamiltonian systems. The degenerate nature of the map and the unequal number of action and angle variables make the persistence proof non-standard. The persistence of the invariant tori as predicted by our result has implications for the existence of barriers to transport in three-dimensional incompressible fluid flows. Simulation results indicating existence of two-dimensional tori in a perturbation of swirling Hill’s spherical vortex flow are presented.
Susceptibility of vancomycin-resistant enterococci to environmental disinfectants.

Objective To determine the susceptibilities of vancomycin-resistant and -sensitive enterococci (VRE and VSE) to various concentrations of commonly used, commercial, hospital-grade disinfectants. Design A microbial suspension test using inocula of 10(8) cells per mL in a disinfectant test dilution was used to determine inactivation kinetics of the test strains. In each test, 1-mL aliquots were removed from the cell-disinfectant mixtures at 15 and 30 seconds and then at 1-minute intervals for 5 minutes and neutralized. Appropriate serial dilutions were plated on agar medium for enumeration of survivors. Results VRE and VSE challenge inocula (in the absence of any additional protein or serum challenge) were below the limit of detection (5 colony-forming units/mL) after 15 seconds' exposure to the manufacturers' suggested use-dilutions of quaternary ammonium, phenolic, or iodophor germicidal detergents. In subsequent tests, when the disinfectants were diluted far beyond-the recommended use-dilutions (extended dilution), no differences were demonstrated between the susceptibilities of VRE and VSE. Conclusions VRE and VSE are sensitive to a spectrum of commonly used environmental disinfectants and have parallel inactivation rates when challenged with extended dilutions of these products. Our findings did not demonstrate a relationship between antibiotic and germicide resistance. Routine disinfection and housekeeping protocols presently used in hospitals need not be altered due to concerns about the potential for environmentally mediated transmission of antibiotic-resistant microorganisms.
Combinatorial optimization in geometry

In this paper we extend and unify the results of [Rivin, Ann. of Math. 143 (1996)] and [Rivin, Ann. of Math. 139 (1994)]. As a consequence, the results of [Rivin, Ann. of Math. 143 (1996)] are generalized from the framework of ideal polyhedra in H^3 to that of singular Euclidean structures on surfaces, possibly with an infinite number of singularities (by contrast, the results of [Rivin, Ann. of Math. 143 (1996)] can be viewed as applying to the case of non-singular structures on the disk, with a finite number of distinguished points). This leads to a fairly complete understanding of the moduli space of such Euclidean structures and thus, by the results of [Penner, Comm. Math. Phys. 113 (1987) 299-339; Epstein, Penner, J. Differential Geom. 27 (1988) 67-80; Naatanen, Penner, Bull. London Math. Soc. 6 (1991) 568-574] the author [Rivin, Ann. of Math. 139 (1994); Rivin, in: Lecture Notes in Pure and Appl. Math., Vol. 156, 1994], and others, further insights into the geometry and topology of the Riemann moduli space. The basic objects studied are the canonical Delaunay triangulations associated to the aforementioned Euclidean structures. The basic tools, in addition to the results of [Rivin, Ann. of Math. 139 (1994)] and combinatorial geometry are methods of combinatorial optimization-linear programming and network flow analysis; hence the results mentioned above are not only effective but also efficient. Some applications of these methods to three-dimensional topology are also given (to prove a result of Casson's).
Methane: a menace surfaces.

The article examines the environmental impact of the thawing of the Arctic permafrost, such as the creation of lakes that emit methane (CH4) gas. According to the author, methane, which is a greenhouse gas, could accelerate global warming. Topics include an overview of the environmental conditions in the Arctic, the role of anaerobic decomposition in methane production, and an in-depth discussion on research measuring methane emissions from Siberian and Alaskan lakes. INSETS: BURSTING BUBBLES;HYDRATES: DEEPER TROUBLE.
α-Ketocyclopropane ring-opening reactions via O-stannyl ketyls

Abstract Three tricyclo[3.3.0.0 2,8 ]octane-3-one ring systems were treated with nBu 3 SnH which produced different cyclopropane cleavage products depending on the location and type of substituent present.
Ferrocenes derived from isodicyclopentadiene and tricyclo[5.2.1.02,6]deca-2,5,8-triene

Abstract The ferrocene derivatives of isodicyclopentadiene and tricyclo[5.2.1.0 2,6 ]deca-2,5,8-triene were synthesized and studied by 2D 1 H NMR (COSY and NOESY). The results of the studies indicated the presence of all possible isomers ( exo,exo, exo,endo, and endo,endo ) in each case, although the exo,exo isomeric distribution was favored for each compound. This contrasts somewhat with the findings in earlier studies which predicts the exo,exo isomers to be the sole species formed from these cyclopentadienyl ligands.
Models for monolayers adsorbed on a square substrate

Abstract Motivated by recent experimental studies of Hg and Pb monolayers on Cu(001) we introduce a zero temperature model of a monolayer adsorbed on a square substrate. Lennard-Jones potentials are used to describe the interaction between pairs of adlayer-adlayer and adlayer-substrate atoms. We study a special case in which the monolayer atoms form a perfect square structure and the lattice constant, position and orientation with respect to the substrate can vary to minimize the energy. We introduce a rule based on the Farey tree construction to generate systematically the most energetically favored phases and use it to calculate the phase diagram in this model.
Employee spinouts, social networks, and family firms

Recently collected data show that, within any manufacturing industry, vertically integrated firms tend to have larger, higher productivity plants, account for the bulk of sales, and also sell externally most of the inputs they produce. In a weak contracting environment characteristic of developing countries, vertically integrated firms are vulnerable to employee “spinouts”: managers of input divisions can start their own firms, making customized inputs formerly provided internally subject to hold-up and capturing the profits formerly made from external sales of generic inputs. This vulnerability is shown to lead to inefficiently low entry. Vertically integrated firms can fight back by hiring managers for their input divisions who are members of networks that informally sanction hold-ups or children who keep profits “in the family” even if they spin out. This is shown to predict the association of co-ethnic networks with high rates of entrepreneurship and the prominence of family-owned business groups in d...
The impact of charge symmetry and charge independence breaking on the properties of neutrons and protons in isospin-asymmetric nuclear matter

We investigate the effects of charge independence and charge symmetry breaking in neutron-rich matter. We consider neutron and proton properties in isospin-asymmetric matter at normal densities as well as the high-density neutron matter equation of state and the bulk properties of neutron stars. We find charge symmetry and charge independence breaking effects to be very small.
A Thermal, Thermoelastic, and Wear Simulation of a High-Energy Sliding Contact Problem

This paper describes an investigation of the sliding contact problem encountered in high-energy disk brakes. The analysis includes a simulation modeling, using the finite element method, of the thermoelastic instabilities that cause transient changes in contact to occur on the friction surface. In order to include the effect of wear of the concentrated contacts on the friction surface, a wear criterion is proposed that results in prediction of wear rates for disk brakes that are quite close to experimentally determined wear rates. The thermal analysis shows that the transient temperature distribution in a disk brake can be determined more accurately by use of this thermomechanical analysis than by a more conventional analysis that assumes constant contact conditions. It is also shown that lower, more desirable, temperatures in disk brakes can be attained by increasing the volume, the thermal conductivity, and especially, the heat capacity of the brake components.
Choosing the sexual orientation of children.

Many people believe that a person's sexual orientation is genetic. Given the widespread prejudice against, and hatred of, homosexuals in many societies, it seems likely that many parents will be interested in using genetic technologies to prevent the birth of children who will not be heterosexual. This paper considers the moral and legal implications of such procedures (whether or not they would work). It is argued that the availability of procedures to select the sexual orientation of children would contribute to discrimination and prejudice against lesbians, gay men and bisexuals and, more generally, undermine the maintenance of a just society. These effects carry significant weight in determining whether genetic technologies should be developed and whether their use is, or should be, legally permissible and morally acceptable.
Evaporation kinetics of laser heated silica in reactive and inert gases based on near-equilibrium dynamics

Evaporation kinetics of fused silica were measured up to ≈3000K using CO2 laser heating, while solid-gas phase chemistry of silica was assessed with hydrogen, air, and nitrogen. Enhanced evaporation in hydrogen was attributed to an additional reduction pathway, while oxidizing conditions pushed the reaction backwards. The observed mass transport limitations supported use of a near-equilibrium analysis for interpreting kinetic data. A semi-empirical model of the evaporation kinetics is derived that accounts for heating, gas chemistry and transport properties. The approach described should have application to materials laser processing, and in applications requiring knowledge of thermal decomposition chemistry under extreme temperatures.
Transient Elastic and Viscoelastic Thermal Stresses During Laser Drilling of Ceramics

Lasers appear to be particularly well suited to drill and shape hard and brittle ceramics, which are almost impossible to netshape to tight tolerances, and are presently machined in industry only by diamond grinding. Unfortunately, the large, focussed heat fluxes that allow the ready melting and ablation of material, also result in large localized thermal stresses within the narrow heat-affected zone, which can lead to microcracks, significant decrease in bending strength, and even catastrophic failure. In order to assess the where, when, and what stresses occur during laser drilling, that are responsible for cracks and decrease in strength, elastic and viscoelastic stress models have been incorporated into our two-dimensional drilling code. The code is able to predict temporal temperature fields as well as the receding solid surface during CW or pulsed laser drilling. Using the resulting drill geometry and temperature fields as well as the receding solid surface during CW of pulsed laser drilling. Using the resulting drill geometry and temperature field, elastic stresses as well as viscoelastic stresses are calculated as they develop and decay during the drilling process. The viscosity of the ceramic is treated as temperature-dependent, limiting viscoelastic effects to a thin layer near the ablation front where the ceramic has softened.
Epoxide deoxygenation mediated by Salen complexes

Abstract N,N′ -Bis(3,5-di- tert -butylsalicylidene)-1,2-cyclohexanediaminocobalt(II) ( 1 ) catalyzes the reductive deoxygenation of epoxides by Na(Hg) in THF, with 5–10 catalytic turnovers. The simpler N,N′ -bis(salicylidene)-ethylenediaminocobalt(II) [Co(Salen) 2 ] ( 16 ) failed to catalyze deoygenations in THF but did in DMF.
Computer viruses and related threats to computer and network integrity

Abstract Computer viruses, worms, Trojan horses, and other exotic-sounding computer security have become a subject of considerable interest and concern in the computing and communications communities. This brief paper discusses the kinds of threats to security that such programs represent, and suggests some reasonable actions that computer and network users and owners can take to help minimize the risks. These threats are just beginning to be thoroughly studied, and this paper will by no means provide answers to all the problems they present. It is intended only to make the reader aware of the most essential definitions and issues, and to provide some references to further reading.
Computer graphics and computer aided design in mechanical engineering at the University of Minnesota

Abstract Engineering design in industry is changing as a result of the application of the new tools provided by the digital computer and interactive computer graphics. This shift is placing new demands on engineering curricula. The engineering graduate today must be trained in the use of the computer and computer graphics as a design tool—in much the same way that engineers in the past used the slide rule and today use the hand-held calculator. This paper summarizes the efforts to integrate computer graphics and computer aided design into the design curriculum in the Mechanical Engineering Department at the University of Minnesota. Specific software packages have been developed for use in teaching engineering graphics and mechanism synthesis and analysis. These packages are discussed in detail, including the hardware used.
(-)-Dioxosantadienic acid: hydrogen-bonding patterns in a bicyclic sesquiterpenoid keto acid and its monohydrate.

The an­hydrous form, (I), of the title compound, (−)-2-(1,2,3,4,4a,7-hexa­hydro-4a,8-di­methyl-1,7-dioxo-2-naphthyl)­propionic acid, C15H18O4, derived from a naturally occurring sesquiterpenoid, has two mol­ecules in the asymmetric unit, (I) and (I′), differing in the conformations of the saturated ring and the carboxyl group. The compound aggregates as carboxyl-to-ketone hydrogen-bonding catemers [O⋯O = 2.776 (3) and 2.775 (3) A]. Two crystallographically independent sets of single-strand hydrogen-bonding helices with opposite end-to-end orientation pass through the cell in the b direction, one consisting exclusively of mol­ecules of (I) and the other entirely of (I′). Three C—H⋯O=C close contacts are found in (I). The monohydrate, C15H18O4·H2O, (II), with two mol­ecules of (I) plus two water mol­ecules in its asymmetric unit, forms a complex three-dimensional hydrogen-bonding network including acid-to-water, water-to-acid, water-to-ketone, water-to-water and acid-to-acid hydrogen bonds, plus three C—H⋯O=C close contacts. In both (I) and (II), only the ketone remote from the acid is involved in hydrogen bonding.
Organophosphoro(thioperoxoic) acids: Direct observation and reactivity

Abstract Peracid oxidation of organophosphorothioic acids yields novel organophosphoro(thioperoxoic) acids (PSOH-isomers) and tentatively their POSH-isomers evident by 31 p NMR spectroscopy. These acids or their further oxidation products are phosphorylating and sulfurylating agents.
Road network circuity in metropolitan areas

Circuity, the ratio of network to Euclidean distances, describes the directness of trips and the efficiency of transportation networks. This paper measures the circuity of the fifty-one most populated Metropolitan Statistical Areas (MSAs) in the United States and identifies trends in those circuities between 1990 and 2010. Overall circuity has increased between 1990 and 2010: random points have not only become farther apart in distance, their shortest network path has become more circuitous, suggesting that the more recently constructed parts of street networks are laid out more circuitously than older parts of the network. Over this period thirty-five MSAs experienced a statistically significant increase in circuity (six experienced a significant decrease). As expected, short trips are more circuitous than long trips. A new circuity distance-decay function describes how circuity varies with distance within metropolitan areas. The parameters of this function have changed from 1990 to 2010.
PHI: a conceptual foundation for design hypermedia

Abstract PHI (Procedural Hierarchy of Issues) extends the IBIS (Issue-Based Information System) method developed by Rittel to support an argumentative approach to design. PHI extends that approach, because it uses an additional argumentative process and deals with a greater range of design issues. PHI has recently gained recognition as the conceptual foundation for a number of design hypermedia systems.
An Examination of Memory Conjunction Errors in Multiple Client Audit Environments

This study is the first in an auditing context to examine auditor susceptibility to memory conjunction errors, a type of systematic memory error that is related to the memory reconstruction process. Conjunction errors occur when memory traces associated with one event are incorrectly attributed to another event during memory reconstruction. Auditors may be particularly susceptible to memory conjunction errors due to their simultaneous exposure to multiple audit clients and their use of standardized audit forms and checklists to capture information. Unrecognized, such errors could adversely affect the efficiency and/or effectiveness of the financial statement audit process. We conducted an experiment that employed practicing audit professionals addressing multiple audit clients. Consistent with our hypotheses, the results indicate that memory conjunction errors in an audit environment are a complex function of (1) the consistency between the audit evidence recalled from an unrelated audit and the character...
Supplier Relations and the Market Context: A Theory of Handshakes

Abstract This paper analyzes the degree of formality in industrial procurement. Contracts impose cost discipline on suppliers, but stifle cooperative innovation; noncontractual procurement provides cooperation but poor cost discipline. However, cost discipline comes naturally when there is not much vertical integration, because the promise of finding an alternative buyer to use as a bargaining threat enhances the supplier's incentive to make efficiency-enhancing investments. Thus, highly integrated industries use contracts, while less integrated industries do business on handshakes. In the latter, cooperative innovations flourish. This may help explain some international comparisons and changes in business practices observed over time.
A Short Efficient Analytical Satellite Theory

A simplified analytical solution for the motion of an artificial Earth satellite under the combined influences of the zonal harmonics through J4 and a nonrotating spherically symmetric power density function atmosphere is given. This solution has been obtained by simplification of a more extensive analytical solution previously published by the author. The simplified version has nearly the same accuracy, yet has only about 16% the formula amount of the full theory. Comparison is made with two other widely used simplfied analytical theories of comparable size. Our solution is found to consistently produce equal or superior prediction accuracies. For low-altitude, high-drag satellites, the improvement can approach a factor of 10 or more.
On the stability of bubble functions and a stabilized mixed finite element formulation for the Stokes problem

In this paper we investigate the relationship between stabilized and enriched finite element formulations for the Stokes problem. We also present a new stabilized mixed formulation for which the stability parameter is derived purely by the method of weighted residuals. This new formulation allows equal-order interpolation for the velocity and pressure fields. Finally, we show by counterexample that a direct equivalence between subgrid-based stabilized finite element methods and Galerkin methods enriched by bubble functions cannot be constructed for quadrilateral and hexahedral elements using standard bubble functions. Copyright © 2008 John Wiley & Sons, Ltd.
Challenging the Fringe

Sometimes it is helpful to stand back from the everyday routines of our practices and evaluate the bases for our treatment methods. Our daily routines are often filled with clinical procedures that are successful and proper for our patients. They are proper because we have selected them specifically for our patient’s needs. But what makes them so appropriate? Perhaps an analogy may be helpful.
Learning situation-dependent costs: Improving planning from probabilistic robot execution

Abstract Physical domains are notoriously hard to model completely and correctly, especially to capture the dynamics of the environment. In this article, we present Rogue , a robot that learns from its execution experiences. Since actions may have different costs under different conditions, we introduce the concept of situation-dependent rules, in which situational features are attached to the costs or probabilities, reflecting patterns and dynamics encountered in the environment. Rogue extracts learning opportunities from massive, continual, probabilistic execution traces. It then correlates these learning opportunities with environmental features, creating situation-dependent costs for its actions. We present the development and use of these rules for a robotic path planner. Our empirical results show that situation-dependent rules effectively improve the planner’s model of the environment, thus allowing the planner to predict and avoid failures, to create plans that are tailored to the real world, and to respond to a changing environment.
Synthesis of 2-Aryl-3-cyanophthalimidines and Related Analogs

Abstract A series of novel 3-cyano- and related 3-substituted phthalmidines have been synthesized from acyclic precursors, some of which were isolated.
Ferroelectric-like SrTiO3 surface dipoles probed by graphene

The electrical transport properties of graphene are greatly influenced by its environment. Owing to its high dielectric constant, strontium titanate (STO) is expected to suppress the long-range charged impurity scattering and consequently to enhance the mobility. However, the absence of such enhancement has caused some controversies regarding the scattering mechanism. In graphene devices transferred from SiO2 to STO using a newly developed technique, we observe a moderate mobility enhancement near the Dirac point, which is the point of charge neutrality achieved by adjusting the Fermi level. While bulk STO is not known as a ferroelectric material, its surface was previously reported to exhibit an outward displacement of oxygen atoms and ferroelectric-like dipole moment. When placed on STO, graphene shows strong and asymmetric hysteresis in resistivity, which is consistent with the dipole picture associated with the oxygen displacement. The hysteretic response of the surface dipole moment diminishes the polarizability, therefore weakens the ability of STO to screen the Coulomb potential of the impurities.
Localization of polymers in a finite medium with fixed random obstacles

In this paper we investigate the conformation statistics of a Gaussian chain embedded in a medium of finite size, in the presence of quenched random obstacles. The similarities and differences between the case of random obstacles and the case of a Gaussian random potential are elucidated. The connection with the density of states of electrons in a metal with random repulsive impurities of finite range is discussed. We also interpret the results obtained in some previous numerical simulations.
A connection between complex-temperature properties of the 1D and 2D spin s Ising model

Abstract Although the physical properties of the 2D and 1D Ising models are quite different, we point out an interesting connection between their complex-temperature phase diagrams. We carry out an exact determination of the complex-temperature phase diagram for the 1D Ising model for arbitrary spin s and show that in the u s = e −K s 2 plane (i) it consists of Nc,1D = 4s2 infinite regions separated by an equal number of boundary curves where the free energy is nonanalytic; (ii) these curves extend from the origin to complex infinity, and in both limits are oriented along the angles θ n = (1 + 2n)π 4s 2 , for n = 0,…,4s2 − 1; (iii) of these curves, there are Nc,NE,1D = Nc,NW,1D = [s2] in the first and second (NE and NW) quadrants; and (iv) there is a boundary curve (line) along the negative real us axis if and only if s is half-integral. We note a close relation between these results and the number of arcs of zeros protruding into the FM phase in our recent calculation of partition function zeros for the 2D spin s Ising model.
Direct adaptive cancellation of periodic disturbances for multivariable plants

A multivariable adaptive scheme is proposed that is designed to reject periodic disturbances of unknown frequency at multiple sensor locations. The case of square systems is considered, as well as the common case where there are more sensors than actuators (overdetermined systems). The disturbances are assumed to contain multiple harmonics associated with a single fundamental frequency, as is the case if the source of the disturbances is a rotating machine. Accordingly, the control inputs are selected to be periodic signals with a frequency determined by a single frequency estimate. Although the adaptive scheme is highly nonlinear, approximations yield an analysis that enables a linear time-invariant design of the algorithm. The analysis also gives useful information about the dynamic behavior of the system and the selection of the design parameters. Experimental results show that the proposed scheme is able to significantly reduce acoustic noises with constant or time-varying frequency at multiple locations in an enclosure.
Palladium-catalyzed highly chemo- and regioselective formal [2+2+2] sequential cycloaddition of alkynes: a renaissance of the well known trimerization reaction?

A new concept of highly chemo- and regioselective formation of the benzene ring by a palladium-catalyzed formal [2 + 2 + 2] sequential intermolecular trimerization of alkynes is proposed. Homodimerization of terminal alkynes and subsequent [4 + 2] benzannulation with diynes gives tetrasubstituted benzenes in moderate to good yields. The introduction of two different alkynes (terminal and internal) in the first step of the sequence allows for construction of pentasubstituted benzenes from three different acyclic acetylenic units. In all cases the tetra- and pentasubstituted benzenes are formed as a single reaction product without being accompanied by any of regio- or chemoisomers. A significant acceleration of the sequential trimerization reaction in the presence of Lewis acid/phosphine combined system was observed. Mechanistic studies reveal that the Lewis acid assisted isomerization of the E-enyne formed in the first step of the sequence to the more reactive Z-isomer is responsible for the observed accel...
Experimental wing and canard jet-flap aerodynamics

The effects of upper surface blowing on the aerodynamics of a 1/2-span wing/body/canard configuration are shown. The results expand a data base that is limited at high subsonic Mach numbers (M = 0.6-0.9), data that are needed if computational techniques are to be developed for the complex flowfields generated by jet blowing. At lift coefficients greater than about 1.0, the thrust removed drag coefficient was lower with jet blowing than without jet blowing. This favorable effect increased with increasing jet blowing coefficient, and, for a fixed coefficient, simultaneous wing/canard jet blowing was slightly more effective than blowing either surface alone.
Parental Behaviors and Beliefs, Child Temperament, and Attachment Disorganization

This research examined alternative mechanisms in the etiology of attachment disorganization. The authors hypothesized that negative intrusive parenting would significantly predict children's attachment disorganization at age 12 months within a diverse community sample. Of more substantial interest, the authors tested moderational mechanisms in the association between negative intrusive parenting, parental strong belief in discipline and control, child difficult temperament, and children's attachment disorganization. Using a multiple regression analytic approach, this research found that negative intrusive parenting significantly predicted children's attachment disorganization. This prediction was more significantly related to children's levels of attachment disorganization when it was paired with stronger rather than weaker parental beliefs in discipline and control. In contrast, when children had difficult temperament at 6 months, it was only when parents held very weak beliefs in discipline and control that children were at higher risk for attachment disorganization. Implications of the findings were discussed accordingly.
Benefits of Solar/Fossil Hybrid Gas Turbine Systems

The potential benefits of solar/fossil hybrid gas turbine power systems were assessed. Both retrofit and new systems were considered from the aspects of cost of electricity, fuel conservation, operational mode, technology requirements, and fuels flexibility. Hybrid retrofit (repowering) of existing combustion (simple Brayton cycle) turbines can provide near-term fuel savings and solar experience, while new and advanced recuperated or combined cycle systems may be an attractive fuel saving and economically competitive vehicle to transition from today's gas and oil-fired powerplants to other more abundant fuels.
Control of noisy differential-drive vehicles from time-bounded temporal logic specifications

We address the problem of controlling a noisy differential drive mobile robot such that the probability of satisfying a specification given as a bounded linear temporal logic formula over a set of properties at the regions in the environment is maximized. We assume that the vehicle can determine its precise initial position in a known map of the environment. However, motivated by practical limitations, we assume that the vehicle is equipped with noisy actuators and, during its motion in the environment, it can only measure the angular velocity of its wheels using limited accuracy incremental encoders. Assuming the duration of the motion is finite, we map the measurements to a Markov decision process (MDP). We use recent results in statistical model checking to obtain an MDP control policy that maximizes the probability of satisfaction. We translate this policy to a vehicle feedback control strategy and show that the probability that the vehicle satisfies the specification in the environment is bounded from below by the probability of satisfying the specification on the MDP. We illustrate our method with simulations and experimental results.
Hamiltonian maps and transport in structured fluids

Abstract Structures such as waves, jets, and vortices have a dramatic impact on the transport properties of a flow. Passive tracer transport in incompressible two-dimensional flows is described by Hamiltonian dynamics, and, for idealized structures, the system is typically integrable. When such structures are perturbed, chaotic trajectories can result which can significantly change the transport properties. It is proposed that the transport due to the chaotic regions can be efficiently calculated using Hamiltonian mappings designed specifically for the structure of interest. As an example, a new map is constructed, appropriate for studying transport by propagating isolated vortices. It is found that a perturbed vortex will trap fluid parcels for varying lengths of time, and that the distribution of such trapping times has slopes which are independent of the amplitudes both the vortex and the perturbation.
Measuring macroscopic diffusion of positive muons in metals

We have discussed some schemes for measuring the diffusion coefficient for positive muons in metals, using diffusion over macroscopic distances. The method offers some promise of yielding diffusion information over wider temperature ranges and a greater variety of metals than the presently used technique. The major difficulty in applying the laminate scheme will be fabricating suitable, well-characterized targets that are thick enough to stop a significant fraction of the μ+ beam. The use of a surface (i.e., 4 MeV) μ+ beam appears most promising, but this brings with it formidable technical problems in heating and cooling the targets. We may hope that these problems will be attacked vigorously and effectively in the near future.
A CONVENIENT METHOD FOR THE SYNTHESIS OF 1,8-BIS(PYRIDIN- 3-OXY)OCT-4-ENE-2,6-DIYNE

A convenient and rapid synthesis of the title compound is described. The key step in the procedure is the Stephens Castro coupling of 3-prop-2-ynyloxy-pyridine with cis-1,2-dichloroethylene and subsequent column purification in the final stage.
The little Higgs from a simple group

We present a model of electroweak symmetry breaking in which the Higgs boson is a pseudo-Nambu-Goldstone boson. By embedding the standard models SU(2) × U(1) into an SU(4) × U(1) gauge group, one-loop quadratic divergences to the Higgs mass from gauge and top loops are canceled automatically with the minimal particle content. The potential contains a Higgs quartic coupling which does not introduce one-loop quadratic divergences. Our theory is weakly coupled at the electroweak scale, it has new weakly coupled particles at the TeV scale and a cutoff above 10 TeV, all without fine tuning. We discuss the spectrum of the model and estimate the constraints from electroweak precision measurements.
Fluctuations of the empirical quantiles of independent Brownian motions

Abstract We consider iid Brownian motions, B j ( t ) , where B j ( 0 ) has a rapidly decreasing, smooth density function f . The empirical quantiles, or pointwise order statistics, are denoted by B j : n ( t ) , and we consider a sequence Q n ( t ) = B j ( n ) : n ( t ) , where j ( n ) / n → α ∈ ( 0 , 1 ) . This sequence converges in probability to q ( t ) , the α -quantile of the law of B j ( t ) . We first show convergence in law in C [ 0 , ∞ ) of F n = n 1 / 2 ( Q n − q ) . We then investigate properties of the limit process F , including its local covariance structure, and Holder-continuity and variations of its sample paths. In particular, we find that F has the same local properties as fBm with Hurst parameter H = 1 / 4 .
Surface Roughness Studies for Wind Tunnel Models Used in High Reynolds Number Testing

This paper focuses on stylus and optical techniques for the measurement of surface roughness in wind tunnel models. The stylus instruments provide detailed information, such as surface profiles and area maps, that may then be used either to calculate statistical properties (i.e., the rms surface roughness) or to study individual surface peaks or other features. By contrast, certain optical techniques yield area-averaged statistical properties of the surface roughness directly. Two instruments that use the technique of optical angular scattering are compared. One is a research instrument that has been developed to study the basic scattering phenomena by testing the optical theories and surface models used in inverse calculations of statistical roughness parameters. The second instrument is more compact and is under development as a hand held, on-line device to be used during manufacture of wind tunnel models for the National Transonic Facility at NASA Langley Research Center. The scattering geometries for the two instruments are compared and results from these instruments and the stylus technique are shown for roughness specimens that are typical of the surface finish of wind tunnel models.
A queueing theory description of fat-tailed price returns in imperfect financial markets

In a financial market, for agents with long investment horizons or at times of severe market stress, it is often changes in the asset price that act as the trigger for transactions or shifts in investment position. This suggests the use of price thresholds to simulate agent behavior over much longer timescales than are currently used in models of order-books. We show that many phenomena, routinely ignored in efficient market theory, can be systematically introduced into an otherwise efficient market, resulting in models that robustly replicate the most important stylized facts. We then demonstrate a close link between such threshold models and queueing theory, with large price changes corresponding to the busy periods of a single-server queue. The distribution of the busy periods is known to have excess kurtosis and non-exponential decay under various assumptions on the queue parameters. Such an approach may prove useful in the development of mathematical models for rapid deleveraging and panics in financial markets, and the stress-testing of financial institutions.
Early evidence on balloon performance

Balloon loans have become increasingly popular in recent years. For this reason, it is important to understand their features, assess their potential risks, and monitor their early performance. This article focuses on these topics. The first section discusses balloon characteristics and mortgage choice. The second section discusses expected balloon performance. The third section provides an econometric model for monitoring current performance. The fourth and fifth sections describe the data and results, respectively. The final section summarizes the article and offers some concluding remarks. The fundamental conclusions are that (1) early balloon performance is slightly worse than expected (i.e., balloons are not matching fixed-rate performance prior to balloon reset dates); (2) balloon performance is, however, within the range expected over the full term of the loans (i.e., performance worse than fixed-rate performance, but better than ARM performance); and (3) balloons have important characteristics that help mitigate systematic risk.
Constructing invariants for hybrid systems

We present a new method for generating algebraic invariants of hybrid systems. The method reduces the invariant generation problem to a constraint solving problem using techniques from the theory of ideals over polynomial rings. Starting with a template invariant--a polynomial equality over the system variables with unknown coefficients--constraints are generated on the coefficients guaranteeing that the solutions are inductive invariants. To control the complexity of the constraint solving, several stronger conditions that imply inductiveness are proposed, thus allowing a trade-off between the complexity of the invariant generation process and the strength of the resulting invariants.
Sovereign wealth fund investment and the return-to-risk performance of target firms

Abstract This paper investigates the relationship between sovereign wealth fund (SWF) investment and the return-to-risk performance of target firms. Specifically, we find that target firm raw returns decline following SWF investment. Though risk also declines following SWF investment, we find that SWF investment is associated with a reduction in the compensation of risk over the 5 years following acquisition. Firm volatility decomposition suggests that idiosyncratic risk is what mainly drives these impacts toward decline. Employing a multinomial logit framework wherein combinations of target returns and risk movements are categorized, we see that, in cases of foreign investment, SWFs’ target firm performance most closely resembles that of other government-owned firms. The observed results are inconsistent with predictions of higher volatility and improved returns due to monitoring firm activities from the institutional investor literature. This suggests that SWFs may not provide some of the benefits that are offered by other institutional investors.
Double Perovskites as Anode Materials for Solid-Oxide Fuel Cells

Extensive efforts to develop a solid-oxide fuel cell for transportation, the bottoming cycle of a power plant, and distributed generation of electric energy are motivated by a need for greater fuel efficiency and reduced air pollution. Barriers to the introduction of hydrogen as the fuel have stimulated interest in developing an anode material that can be used with natural gas under operating temperatures 650 degrees C < T < 1000 degrees C. Here we report identification of the double perovskites Sr2Mg(1-x)MnxMoO(6-delta) that meet the requirements for long-term stability with tolerance to sulfur and show a superior single-cell performance in hydrogen and methane.