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none given. Paper discusses connecting schools to the information superhighway and its implications for society.
This paper presents a unified and efficient method of solving the inverse kinematics for 6 d.o.f. serial connections of two 3 d.o.f. serial and parallel manipulators.
This paper applies dynamical systems techniques to the problem of heteroclinic connections and resonance transitions in the planar circular restricted three-body problem.
A Series Connected Buck-Boost Regulator (SCBBR) that switches only a fraction of the input power, resulting in relatively high efficiencies. The SCBBR has multiple operating modes including a buck, a boost, and a current limiting mode, so that an output voltage of the SCBBR ranges from below the source voltage to above the source voltage.
The Bayesian and statistical mechanical communities often share the same objective in their work - estimating and integrating probability distribution functions (pdfs) describing stochastic systems, models or processes. Frequently, these pdfs are complex functions of random variables exhibiting multiple, well separated local minima. Conventional strategies for sampling such pdfs are inefficient, sometimes leading to an apparent non-ergodic behavior. Several recently developed techniques for handling this problem have been successfully applied in statistical mechanics. In the multicanonical and Wang-Landau Monte Carlo (MC) methods, the correct pdfs are recovered from uniform sampling of the parameter space by iteratively establishing proper weighting factors connecting these distributions. Trivial generalizations allow for sampling from any chosen pdf. The closely related transition matrix method relies on estimating transition probabilities between different states. All these methods proved to generate estimates of pdfs with high statistical accuracy. In another MC technique, parallel tempering, several random walks, each corresponding to a different value of a parameter (e.g. "temperature"), are generated and occasionally exchanged using the Metropolis criterion. This method can be considered as a statistically correct version of simulated annealing. An alternative approach is to represent the set of independent variables as a Hamiltonian system. Considerab!e progress has been made in understanding how to ensure that the system obeys the equipartition theorem or, equivalently, that coupling between the variables is correctly described. Then a host of techniques developed for dynamical systems can be used. Among them, probably the most powerful is the Adaptive Biasing Force method, in which thermodynamic integration and biased sampling are combined to yield very efficient estimates of pdfs. The third class of methods deals with transitions between states described by rate constants. These problems are isomorphic with chemical kinetics problems. Recently, several efficient techniques for this purpose have been developed based on the approach originally proposed by Gillespie. Although the utility of the techniques mentioned above for Bayesian problems has not been determined, further research along these lines is warranted
The dramatic changes seen in the X-ray spectral and timing properties of accreting black hole candidates (BHCs) provide important clues about the accretion and jet formation processes that occur in these systems. Dividing the different source behaviors into spectral states provides a framework for studying BHCs. To date, there have been three main classification schemes with Luminosity-based, Component-based, or Transition-based criteria. The canonical, Luminosity-based criteria and physical models that are based on this concept do not provide clear explanations for several phenomena, including hysteresis of spectral states and the presence of jets. I discuss the re-definitions of states, focusing on an application of the Component-based states to more than 400 RXTE observations of the recurrent BHC 4U 1630^17. We compare the X-ray properties for the recent 2002-2004 outburst to those of an earlier (1998) outburst, during which radio jets were observed. The results suggest a connection between hysteresis of states and major jet ejections, and it is possible that both of these are related to the evolution of the inner radius of the optically thick accretion disk.
A Series Connected Buck-Boost Regulator (SCBBR) that switches only a fraction of the input power, resulting in relatively high efficiencies. The SCBBR has multiple operating modes including a buck, a boost, and a current limiting mode, so that an output voltage of the SCBBR ranges from below the source voltage to above the source voltage.
The connection between the accretion process that powers AGN and the formation of jets is still poorly understood. Here we tackle this issue using new, deep Chandra and XMM-Newton observations of tlie cores of three powerful radio loud quasars: 1136-135, 1150+497 (Chandra), and 0723+679 (XMM-Newton), in the redshift range z=0.3-0.8. These sources are known from our previous Chandra siiapsliot survey to liave kpc-scale X-ray jets. In 1136-135 and 1150-1+497; evidence is found for the presence of diffuse thermal X-ray emission around the cores; on scales of 40-50 kpc and with luminosity L(sub 0.3-2 kev approx. 10(sup 43) erg per second, suggesting thermal emission from the host galaxy or a galaxy group. The X-ray continua of the cores in the three sources are described by an upward-curved (concave) broken power law, with photon indices GAMMA (sub soft) approx. 1.8 - 2.1 and GAMMA (sub hard) approx. 1.7 below and above approx. equal to 2 keV, respectively. There is evidence for an uiiresolved Fe K alpha line with EW approx. 70 eV in the three quasars. The Spectral Energy Distributions of the sources can be well described by a mix of jet and disk emission, with the jet dominating the radio and hard X-rays (via synchrotron and external Compton) and the disk dominating the optical/UV through soft X-rays. The ratio of the jet-to-disk powers is approx. 1, consistent with those derived for a number of gamma ray emitting blazars. This indicates that near equality of accretion and jet power may be common in powerful radio-loud AGN.
A new, lower cost fluorinated dianhydride based on the phenyltrifluoroethylidene (3F) connecting linkage was invented by the principal author in the early 1980's. New 3F condensation and addition cured polyimides were synthesized with the newly discovered 3F dianhydride and the previously known 3F diamine. As controls, polyimides based on the somewhat analogous higher cost hexafluoroisopropylidene (6F) linkage were also prepared. The short term thermal oxidative stability (TOS), determined by thermal gravimetric analysis (TGA), and the glass transition temperatures (Tg) of 3F dianhydride polyimides were found to be similar to 6F dianhydride polyimides, but the Tg was slightly higher for 3F diamine polyimides than 6F diamine polyimides. Unfortunately, in real time testing, long term TOS of 3F polymers was clearly inferior to 6F polymers. This was due to a 3 to 5 fold greater rate of loss of trifluoromethyl group from 3F versus 6F linkages. However, at shorter times or lower temperatures, 3F TOS was almost comparable to 6F TOS. The wide scope of the 3F technology was also demonstrated to have distinct unique advantages over 6F technology through the use of the 3F pendant phenyl ring as a synthetic site to introduce other functional groups. These groups have been used for the control or modification of polymer properties; an advantage lacking within 6F technology. The synthetic ease by which 3F can be introduced into various types of monomers has lead to the explosion of advanced 3F polyimides and other high performance advanced 3F polymers in the prior decade of 3F polymer literature as cited herein; covering polyimides, substituted polyimides, at least ten types of nonpolyimide 3F polymer modifications, and also the government's nine 3F U.S. patents and corporations' nine 3F U.S. patents.
The dramatic changes seen in the X-ray spectral and timing properties of accreting black hole candidates (BHCs) provide important clues about the accretion and jet formation processes that occur in these systems. Dividing the different source behaviors into spectral states provides a framework for studying BHCs. To date, there have been three main classification schemes with Luminosity-based, Component-based, or Transition-based criteria. The canonical, Luminosity-based criteria and physical models that are based on this concept do not provide clear explanations for several phenomena, including hysteresis of spectral states and the presence of jets. I discuss the re-definitions of states, focusing on an application of the Component-based states to more than 400 RXTE observations of the recurrent BHC 4U 1630-47. We compare the X-ray properties for the recent 2002-2004 outburst to those of an earlier (1998) outburst, during which radio jets were observed. The results suggest a connection between hysteresis of states and major jet ejections, and it is possible that both of these are related to the evolution of the inner radius of the optically thick accretion disk.
A quick-connect fastener of a relatively-simple straightforward design is arranged with a tubular body adapted to be engaged against an attachment fitting in coincidental alignment with an opening in that fitting. A tubular collet having flexible fingers projecting from its forward end is arranged in the fastener body to be shifted forwardly by an elongated expander member coaxially arranged within the tubular collet for advancing the collet fingers into the opening in the attachment fitting. Biasing means are arranged between the elongated expander member and a rotatable actuator which is threadedly mounted within the tubular collet so as to be rotated for urging the expander member into engagement with the collet fingers. A first coupling member is arranged on the rotatable actuator to be accessible from outside of the fastener so that a second coupling member on the distal end of a flexible shaft can be introduced into the fastener body and coupled to the first coupling member to enable a typical actuating tool coupled to the shaft outside of the fastener body to be operated for advancing the outwardly-enlarged ends of the collet fingers into the opening in the attachment fitting and thereafter rotating the actuator member to expand the fingers within the opening for releasably latching the fastener to that attachment fitting. Upon expansion of the collet fingers, the biasing means impose a biasing force on the expander to releasably retain the fingers in their latching positions.
The Direct Connect Combustor Durability Rig (DCR) will provide NASA a flexible and efficient test bed to demonstrate the durability of actively cooled scramjet engine structure, static and dynamic sealing technologies, and thermal management techniques. The DCR shall be hydrogen fueled and cooled, and test hydrogen coolded structural panels at Mach 5 and 7. Actively cooled Haynes 188 superalloy DCR structural panels exposed to the combustion environment shall have electrodischarge machined (EDM) internal cooling holes with flowing liquid hydrogen. Hydrogen combustion could therefore produce severe thermal conditions that could challenge low cycle fatigue durability of this material. The objective of this study was to assess low cycle fatigue capability of Haynes 188 for DCR application. Tests were performed at 25 and 650 C, in hydrogen and helium environments, using specimens with low stress ground (LSG) and electro-discharge machined (EDM) surface finish. Initial fatigue tests in helium and hydrogen indicate the low cycle fatigue life capability of Haynes 188 in hydrogen appears quite satisfactory for the DCR application. Fatigue capability did not decrease with increasing test temperature. Fatigue capability also did not decrease with EDM surface finish. Failure evaluations indicate retention of ductility in all conditions. Additional tests are planned to reconfirm these positive trends.
Spatiotemporal patterns in soil moisture and vegetation water content across mainland Australia were investigated from 1998 through 2005, using TRMMITMI passive microwave observations. The Empirical Orthogonal Function technique was used to extract dominant spatial and temporal patterns in retrieved estimates of moisture content for the top 1-cm of soil (theta) and vegetation moisture content (via optical depth tau). The dominant temporal theta and tau patterns were strongly correlated to El Nino/Southern Oscillation (ENSO) in spring (3 = 0.90), and to a progressively lesser extent autumn, summer and winter. The Indian Ocean Dipole (IOD) index also explained part of the variation in spring 8 and z. Cluster analysis suggested that the regions most affected by ENS0 are mainly located in eastern Australia. The results suggest that the drought conditions experienced in eastern Australia since 2000 an clearly expressed in these satellite observations have a strong connection with ENSO patterns.
We investigate the intraseasonal (30-90 day) variations in satellite-observed tropical total ozone (O3) and their connection to the Madden-Julian Oscillation (MJO). Tropical total O3 intraseasonal variations are large (approximately +/- 10 DU) and comparable to those in annual and interannual time scales. These O3 anomalies are mainly evident in the subtropics over the Pacific an eastern; hemisphere and propagate slowly eastward (approximately 5 m s-1). The subtropical negative (positive) O3 anomalies are typically collocated with the subtropical upper troposphere anticyclones (cyclones) generated by equatorial MJO convection and flank or lie to the west of the equatorial enhanced (suppressed) MJO convection. The subtropical O3 are anticorrelated with geopotential height anomalies near the tropopause and thus mainly associated with the O3 variability in the stratosphere rather the troposphere. Over the equatorial regions, total O3 anomalies are small.
An objective of the Hypersonic International Flight Research Experimentation (HIFiRE) Program Flight 2 is to provide validation data for high enthalpy scramjet prediction tools through a single flight test and accompanying ground tests of the HIFiRE Direct Connect Rig (HDCR) tested in the NASA LaRC Arc Heated Scramjet Test Facility (AHSTF). The HDCR is a full-scale, copper heat sink structure designed to simulate the isolator entrance conditions and isolator, pilot, and combustor section of the HIFiRE flight test experiment flowpath and is fully instrumented to assess combustion performance over a range of operating conditions simulating flight from Mach 5.5 to 8.5 and for various fueling schemes. As part of the instrumentation package, temperature and heat flux sensors were provided along the flowpath surface and also imbedded in the structure. The purpose of this paper is to demonstrate that the surface heat flux and wall temperature of the Zirconia coated copper wall can be obtained with a water-cooled heat flux gage and a sub-surface temperature measurement. An algorithm was developed which used these two measurements to reconstruct the surface conditions along the flowpath. Determinations of the surface conditions of the Zirconia coating were conducted for a variety of conditions.
A recent assessment of suprathermal electron heat flux dropouts (HFDs) in the solar wind eliminated 90% as possible signatures of field lines disconnected from the Sun at both ends (Pagel et al., 2005b). The primary reason for elimination was the presence of a residual field-aligned strahl presumably signaling field lines connected to the Sun. Using high-time-resolution data from the Wind spacecraft, this paper tests whether the residual strahls were an artifact of averaging over pitch angle distributions (PADs) with and without strahls. An automated search for PADs without strahls (flat PADs) yields an occurrence rate of only 14% within HFDs, but a detailed case study shows that these flat PADs are imbedded within intervals of nearly flat PADs, that is, PADS with residual strahls that cannot be artifacts of averaging. An attractive alternative is that the residual strahls result from intermixing of originally back-scattered fluxes (haloes) of unequal intensities on field lines that have either disconnected or interchange reconnected at the Sun. A reevaluation of reported streaming of higher-energy electrons in HFDs suggests a similar cause. While the high-time-resolution data show high variability of PAD profiles within HFDs, this paper reopens the possibility that a substantial fraction signal disconnection or interchange reconnection. Estimated occurrence rates of fields having undergone these processes based upon published HFD rates are of the same order of magnitude as the surprisingly low values of 1-5% recently predicted by a model of a balanced heliospheric flux budget (Owens and Crooker, 2007).
Finding strongly connected components (SCCs) in the state-space of discrete-state models is a critical task in formal verification of LTL and fair CTL properties, but the potentially huge number of reachable states and SCCs constitutes a formidable challenge. This paper is concerned with computing the sets of states in SCCs or terminal SCCs of asynchronous systems. Because of its advantages in many applications, we employ saturation on two previously proposed approaches: the Xie-Beerel algorithm and transitive closure. First, saturation speeds up state-space exploration when computing each SCC in the Xie-Beerel algorithm. Then, our main contribution is a novel algorithm to compute the transitive closure using saturation. Experimental results indicate that our improved algorithms achieve a clear speedup over previous algorithms in some cases. With the help of the new transitive closure computation algorithm, up to 10(exp 150) SCCs can be explored within a few seconds.
Determining the source at the Sun of the slow solar wind is one of the major unsolved problems in solar and heliospheric physics. First, we review the existing theories for the slow wind and argue that they have difficulty accounting for both the observed composition of the wind and its large angular extent. A new theory in which the slow wind originates from the continuous opening and closing of narrow open field corridors, the S-Web model, is described. Support for the S-Web model is derived from MHD solutions for the quasisteady corona and wind during the time of the August 1, 2008 eclipse. Additionally, we perform fully dynamic numerical simulations of the corona and heliosphere in order to test the S-Web model as well as the interchange model proposed by Fisk and co-workers. We discuss the implications of our simulations for the competing theories and for understanding the corona - heliosphere connection, in general.