Science.gov

Sample records for discrete hypoechoic ring

  1. Spring flood reconstruction from continuous and discrete tree ring series

    NASA Astrophysics Data System (ADS)

    Boucher, ÉTienne; Ouarda, Taha B. M. J.; BéGin, Yves; Nicault, Antoine

    2011-07-01

    This study proposes a method to reconstruct past spring flood discharge from continuous and discrete tree ring chronologies, since both have their respective strengths and weaknesses in northern environments. Ring width or density series provide uninterrupted records that are indirectly linked to regional discharge through a concomitant effect of climate on tree growth and streamflow. Conversely, discrete event chronologies constitute conspicuous records of past high water levels since they are constructed from trees that are directly damaged by the flood. However, the uncertainty of discrete series increases toward the past, and their relationships with spring discharge are often nonlinear. To take advantage of these two sources of information, we introduce a new transfer model technique on the basis of generalized additive model (GAM) theory. The incorporation of discrete predictors and the evaluation of the robustness of the nonlinear relationships are assessed using a jackknife procedure. We exemplify our approach in a reconstruction of May water supplies to the Caniapiscau hydroelectric reservoir in northern Quebec, Canada. We used earlywood density measurements as continuous variables and ice-scar dates around Lake Montausier in the James Bay area as a discrete variable. Strong calibration (0.57 < 0.61 < 0.75) and validation (0.27 < 0.44 < 0.58) R2 statistics were obtained, thus highlighting the usefulness of the model. Our reconstruction suggests that, since ˜1965, spring floods have become more intense and variable in comparison with the last 150 years. We argue that a similar procedure can be used in each case where discrete and continuous tree ring proxies are used together to reconstruct past spring floods.

  2. On sound transmission into a stiffened cylindrical shell with rings and stringers treated as discrete elements

    NASA Technical Reports Server (NTRS)

    Koval, L. R.

    1980-01-01

    In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the transmission of an oblique plane sound wave into a finite cylindrical shell stiffened by stringers and ring frames. The rings and stringers are modeled as discrete structural elements. The numerical case studied was typical of a narrow-bodied jet transport fuselage. The numerical results show that the ring-frequency dip in the transmission loss curve that is present for a monocoque shell is still present in the case of a stiffened shell. The ring frequency effect is a result of the cylindrical geometry of the shell. Below the ring frequency, stiffening does not appear to have any significant effect on transmission loss, but above the ring frequency, stiffeners can enhance the transmission loss of a cylindrical shell.

  3. Hypoechoic media: a landmark for intravascular ultrasonic imaging

    NASA Astrophysics Data System (ADS)

    Gussenhoven, Elma J.; Bom, Nicolaas; Li, Wenguang; van Urk, Hero; Pietermann, Herman; van Suylen, Robert J.; Salem, H. K.

    1991-05-01

    This paper describes the in vitro (40 MHz) and in vivo (30 MHz) results of studies performed on human vessels using a mechanically rotated single element ultrasonic imaging system. The in vitro images were matched with the corresponding histologic cross-sections. Morphology of vessels and possibility to determine the extent of atherosclerosis were assessed by two blinded observers. Echographic images with an echolucent zone were seen to correspond with muscular type of arteries. The echographic images showing no echographic distinction between the various layers were seen to correspond with either elastic type of arteries, veins, veins used for bypass, or bypass Goretex grafts. The extent of atherosclerosis could only be assessed in the muscular type of artery. The data showed close correlation with histology (r = 0.89). In vivo studies (30 patients) revealed a characteristic three-layered appearance of the distal iliac and femoral artery. Normal cross-sections were readily differentiated from non- obstructive and obstructive lesions. In all these patients the hypoechoic muscular media served as an important landmark.

  4. Quantitation of hypoechoic lesions for the prediction and Gleason grading of prostate cancer: a prospective study.

    PubMed

    Lee, Kwang Suk; Koo, Kyo Chul; Chung, Byung Ha

    2018-03-05

    Hypoechoic lesions are not included as indicators for prostate biopsy. To discriminate the features of hypoechoic lesions, we investigated the ultrasonographic characteristics of hypoechoic lesions using numerical analysis in image. In addition, we evaluated previously suggested subjective parameters on hypoechoic lesion. We performed one-core targeted biopsy (TBx) for each hypoechoic lesion in up to two lesions in each patient before the 12-core systemic biopsy was obtained between July 2015 and May 2016. Image analysis data were analyzed using grayscale values and Hounsfield units (HU) to measure heterogeneity. Subjective evaluation of hypoechoic lesions including hypoechoicity, irregularity, vascularity, and microcalcification was also validated. Of 157 patients (median age = 67.1 years, median prostate-specific antigen = 6.21 ng/mL) included in the study, 77 (49.0%) were diagnosed with prostate cancer (PCa), and 39 (17.0%) diagnoses were confirmed by the results of targeted cores. The existence of hypoechoic lesions was not a final predictor for PCa detection. In multivariate analysis using a combination of clinical and quantitative image analyses, the grayscale value was identified as a significant predictive factor for the presence of PCa and high-grade disease (Gleason score ≥ 7) on target lesions. The combination of clinical and image variables had the highest area under the curve (0.890) for detecting PCa in TBx. The proposed method for the quantitation of hypoechoic lesions using grayscale images and HU is simple. Combined with the current clinical approaches, quantitative scoring of lesions can be useful for detecting PCa and making more precise diagnoses.

  5. Continuum and discrete pulsed cavity ring down laser absorption spectra of Br2 vapor.

    PubMed

    Sharma, Ramesh C; Huang, Hong-Yi; Chuang, Wang-Ting; Lin, King-Chuen

    2005-07-01

    The absorption cross-sections at room temperature are reported for the first time, of Br2 vapor in overlapping bound-free and bound-bound transition of A(3)pi1u <-- Xsigma(g)+, X(1)pi1u <-- X(1)sigma(g)+ and B(3)pi0u <-- X(1)sigma(g)+, using cavity ring down spectroscopy (CRDS) technique. We reported here, the A(3)pi1u <-- X(1)sigma(g)+, transition is included along with the two stronger X(1)pi1u <-- X(1)sigma(g)+ and B(3)pi0u <-- X(1)sigma(g) transitions of Br2. We obtained discrete absorption cross-section in the rotational structure, the continuum absorption cross-sections, and were also able to measure the absorption cross-section in separate contribution of A(3)pi1u <-- X(1)sigma(g)+, (1)pi1u <-- X(1)sigma(g)+, and B(3)pi0u <-- X(1)sigma(g)+ transitions using CRDS method to use quantum yield of Br*((2)P(1/2)). We obtained absorption cross-section order 10(-19) cm2 and detection 10(13) molecule cm(-3) (1 mTorr) of Br2. The absorption cross-sections are increasing with increasing excitation energy in the wavelength region 510-535 nm.

  6. From ring-in-ring to sphere-in-sphere: self-assembly of discrete 2D and 3D architectures with increasing stability.

    PubMed

    Sun, Bin; Wang, Ming; Lou, Zhichao; Huang, Mingjun; Xu, Chenglong; Li, Xiaohong; Chen, Li-Jun; Yu, Yihua; Davis, Grant L; Xu, Bingqian; Yang, Hai-Bo; Li, Xiaopeng

    2015-02-04

    Directed by increasing the density of coordination sites (DOCS) to increase the stability of assemblies, discrete 2D ring-in-rings and 3D sphere-in-sphere were designed and self-assembled by one tetratopic pyridyl-based ligand with 180° diplatinum(II) acceptors and naked Pd(II), respectively. The high DOCS resulted by multitopic ligand provided more geometric constraints to form discrete structures with high stability. Compared to reported supramolecular hexagons and polyhedra by ditotpic ligands, the self-assembly of such giant architectures using multitopic ligands with all rigid backbone emphasized the structural integrity with precise preorganization of entire architecture, and required elaborate synthetic operations for ligand preparation. In-depth structural characterization was conducted to support desired structures, including multinuclear NMR ((1)H, (31)P, and (13)C) analysis, 2D NMR spectroscopy (COSY and NOESY), diffusion-ordered NMR spectroscopy (DOSY), multidimensional mass spectrometry, TEM and AFM. Furthermore, a quantitative definition of DOCS was proposed to compare 2D and 3D structures and correlate the DOCS and stability of assemblies in a quantitative manner. Finally, ring-in-rings in DMSO or DMF could undergo hierarchical self-assembly into the ordered nanostructures and generated translucent supramolecular metallogels.

  7. Causes of Avascular Hypoechoic Testicular Lesions Detected at Scrotal Ultrasound: Can They Be Considered Benign?

    PubMed

    Ma, Weining; Sarasohn, Debra; Zheng, Junting; Vargas, Hebert A; Bach, Ariadne

    2017-07-01

    The purposes of this study were to determine the cause of avascular hypoechoic lesions detected at scrotal ultrasound and to assess usefulness of sonographic and clinical features in differentiating benign from malignant etiologic factors. This retrospective study included 58 patients with avascular hypoechoic lesions detected at testicular ultrasound. The sonographic features recorded were lesion size and margins and presence of peripheral vascularity and focal calcifications. Also recorded were patient age, symptoms, risk factors, lesion palpability, and levels of serum tumor markers. The reference standard was pathologic results or at least 2-year stability documented with serial follow-up ultrasound studies. Features associated with malignant, including burnt-out, lesions and benign lesions were examined by Fisher exact test, Wilcox-on rank sum test, and the generalized estimating equations method for multivariable models. Sixty-three lesions were identified in 58 patients; 40 of the 63 (63.5%) were benign. Patients with malignant lesions had elevated serum tumor marker levels more often than patients who had benign lesions (26.1% versus 5.7%, p = 0.043). The clinical palpability of lesions and history of testicular cancer were not statistically significantly different between patients with malignant and those with benign lesions. Poorly defined margins of a lesion and focal calcification within the lesion were more often found in malignant lesions. Maximal size of a lesion and peripheral vascularity were not associated with either the benign or the malignant nature of a lesion. Although most avascular hypoechoic testicular lesions are benign, a substantial proportion are malignant. The ultrasound characteristics of a lesion, the patient's clinical presentation, and serum tumor marker status may be useful in differentiating malignant from benign lesions.

  8. Rings

    SciTech Connect

    Davis, R.L.

    1989-01-01

    The essence of vortex physics is that at certain low-energy scales elementary excitations of a point particle theory can behave like strings rather than particles. Vortices are the resulting string-like solutions; their thickness sets the distance scale beyond which physics is string-like rather than particle-like. String degrees of freedom are massless in the sense that excitations on a string can have an arbitrarily low frequency. Non-string degrees of freedom correspond to massive particles and are absent from the low energy spectrum. This article considers only field theories with vortices at low energies. The possible existence of a class of solitonsmore » in these vortex theories will be discussed. They are vortex rings: they are localized and finite in energy, and able to carry the quantum numbers of point particles. Rings are thus particle-like solutions of a vortex theory, which is itself a limit of a point particle field theory.« less

  9. Hepatic colon cancer metastases in mice: dynamic in vivo correlation with hypoechoic rims visible at US.

    PubMed

    Kruskal, J B; Thomas, P; Nasser, I; Cay, O; Kane, R A

    2000-06-01

    To use videomicroscopy of tumor-bearing livers of live mice to depict tumors directly to determine the exact nature of rims seen on corresponding ultrasonographic (US) scans. Seventy-six hepatic colorectal cancer metastases were studied in exteriorized livers of 18 mice by using intravital microscopy, US, and histologic examination of the same tumors. Hypoechoic rims correlated with distended sinusoidal spaces in vivo. These spaces surrounded only locally invasive tumors (mean diameter, 0.85 mm) that had obstructed the supplying terminal portal venules. These spaces, containing adherent leukocytes and tumor cells, gave rise to new tumor vasculature. Results of histologic examination of rims (portal inflammation, congested or compressed sinusoids, cell atrophy) correlated with leukocyte endothelial adherence, occluded sinusoids, and new vessel formation in vivo. Unlike results from previous studies, dynamic in vivo observations of peritumoral rims demonstrated distended sinusoidal spaces giving rise to new tumor-penetrating vessels. These sinusoids arose around locally invasive tumors and were associated with more advanced intrahepatic disease. These dynamic observations provide a pathophysiologic explanation for previous histologic correlates of peritumoral rims.

  10. In vivo observation of the hypo-echoic "black hole" phenomenon in rat arterial bloodstream: a preliminary Study.

    PubMed

    Nam, Kweon-Ho; Paeng, Dong-Guk

    2014-07-01

    The "black hole," a hypo-echoic hole at the center of the bloodstream surrounded by a hyper-echoic zone in cross-sectional views, has been observed in ultrasound backscattering measurements of blood with red blood cell aggregation in in vitro studies. We investigated whether the phenomenon occurs in the in vivo arterial bloodstream of rats using a high-frequency ultrasound imaging system. Longitudinal and cross-sectional ultrasound images of the rat common carotid artery (CCA) and abdominal aorta were obtained using a 40-MHz ultrasound system. A high-frame-rate retrospective imaging mode was employed to precisely examine the dynamic changes in blood echogenicity in the arteries. When the imaging was performed with non-invasive scanning, blood echogenicity was very low in the CCA as compared with the surrounding tissues, exhibiting no hypo-echoic zone at the center of the vessel. Invasive imaging of the CCA by incising the skin and subcutaneous tissues at the imaging area provided clearer and brighter blood echo images, showing the "black hole" phenomenon near the center of the vessel in longitudinal view. The "black hole" was also observed in the abdominal aorta under direct imaging after laparotomy. The aortic "black hole" was clearly observed in both longitudinal and cross-sectional views. Although the "black hole" was always observed near the center of the arteries during the diastolic phase, it dissipated or was off-center along with the asymmetric arterial wall dilation at systole. In conclusion, we report the first in vivo observation of the hypo-echoic "black hole" caused by the radial variation of red blood cell aggregation in arterial bloodstream. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  11. System for δ13C-CO2 and xCO2 analysis of discrete gas samples by cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Dickinson, Dane; Bodé, Samuel; Boeckx, Pascal

    2017-11-01

    A method was devised for analysing small discrete gas samples (50 mL syringe) by cavity ring-down spectroscopy (CRDS). Measurements were accomplished by inletting 50 mL syringed samples into an isotopic-CO2 CRDS analyser (Picarro G2131-i) between baseline readings of a reference air standard, which produced sharp peaks in the CRDS data feed. A custom software script was developed to manage the measurement process and aggregate sample data in real time. The method was successfully tested with CO2 mole fractions (xCO2) ranging from < 0.1 to > 20 000 ppm and δ13C-CO2 values from -100 up to +30 000 ‰ in comparison to VPDB (Vienna Pee Dee Belemnite). Throughput was typically 10 samples h-1, with 13 h-1 possible under ideal conditions. The measurement failure rate in routine use was ca. 1 %. Calibration to correct for memory effects was performed with gravimetric gas standards ranging from 0.05 to 2109 ppm xCO2 and δ13C-CO2 levels varying from -27.3 to +21 740 ‰. Repeatability tests demonstrated that method precision for 50 mL samples was ca. 0.05 % in xCO2 and 0.15 ‰ in δ13C-CO2 for CO2 compositions from 300 to 2000 ppm with natural abundance 13C. Long-term method consistency was tested over a 9-month period, with results showing no systematic measurement drift over time. Standardised analysis of discrete gas samples expands the scope of application for isotopic-CO2 CRDS and enhances its potential for replacing conventional isotope ratio measurement techniques. Our method involves minimal set-up costs and can be readily implemented in Picarro G2131-i and G2201-i analysers or tailored for use with other CRDS instruments and trace gases.

  12. Saturn's rings

    NASA Technical Reports Server (NTRS)

    2000-01-01

    When seen from the unlit side, the rings of Saturn present a much different appearance from that familiar to telescopic observers. Relatively opaque areas like the B Ring turn black, while lightly populated zones, such as the C Ring and the Cassini Division, prove to excellent diffuse transmitters of sunlight. The A Ring, with intermediate opacity, is at an intermediate level of brightness.

  13. Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Cuzzi, J. N.

    2014-12-01

    The rings are changing before our eyes; structure varies on all timescales and unexpected things have been discovered. Many questions have been answered, but some answers remain elusive (see Cuzzi et al 2010 for a review). Here we highlight the major ring science progress over the mission to date, and describe new observations planned for Cassini's final three years. Ring Composition and particle sizes: The rings are nearly all water ice with no other ices - so why are they reddish? The C Ring and Cassini Division are "dirtier" than the more massive B and A Rings, as shown by near-IR and, recently, microwave observations. Particle sizes, from stellar and radio occultations, vary from place to place. Ring structure, micro and macro: numerous spiral density waves and ubiquitous "self-gravity wakes" reveal processes which fostered planet formation in the solar system and elsewhere. However, big puzzles remain regarding the main ring divisions, the C Ring plateau structures, and the B Ring irregular structure. Moonlets, inside and out, seen and unseen: Two gaps contain sizeable moonlets, but more gaps seem to contain none; even smaller embedded "propeller" objects wander, systematically or randomly, through the A ring. Rubble pile ringmoons just outside the rings may escaped from the rings, and the recently discovered "Peggy" may be trying this as we watch. Impact bombardment of the rings: Comet fragments set the rings to rippling on century-timescales, and boulders crash through hourly; meanwhile, the constant hail of infalling Kuiper belt material has a lower mass flux than previously thought. Origin and Age of the Rings: The ring mass and bombardment play key roles. The ring mass is well known everywhere but in the B Ring (where most of it is). New models suggest how tidal breakup of evolving moons may have formed massive ancient rings, of which the current ring is just a shadow. During its last three years, the Cassini tour profile will allow entirely new

  14. Ring World

    NASA Image and Video Library

    2007-03-01

    Our robotic emissary, flying high above Saturn, captured this view of an alien copper-colored ring world. The overexposed planet has deliberately been removed to show the unlit rings alone, seen from an elevation of 60 degrees

  15. Ring Herding

    NASA Image and Video Library

    2007-07-09

    Prometheus pulls material from the tortured F ring in this highly detailed view. The aftereffects of the moon other recent encounters with the ring are visible above as dark channels in the inner ringlet

  16. Neptune's rings

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This 591-second exposure of the rings of Neptune were taken with the clear filter by the Voyager 2 wide-angle camera. The two main rings are clearly visible and appear complete over the region imaged. Also visible in this image is the inner faint ring and the faint band which extends smoothly from the ring roughly halfway between the two bright rings. Both of these newly discovered rings are broad and much fainter than the two narrow rings. The bright glare is due to over-exposure of the crescent on Neptune. Numerous bright stars are evident in the background. Both bright rings have material throughout their entire orbit, and are therefore continuous. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.

  17. Neptune Rings

    NASA Image and Video Library

    1999-10-29

    This 591-second exposure of the rings of Neptune were taken with the clear filter by NASA Voyager 2 wide-angle camera. The two main rings are clearly visible and appear complete over the region imaged.

  18. Ring Backdrop

    NASA Image and Video Library

    2011-01-03

    Saturn moon Enceladus brightly reflects sunlight before a backdrop of the planet rings and the rings shadows cast onto the planet. NASA Cassini spacecraft captured this snapshot during its flyby of the moon on Nov. 30, 2010.

  19. Ring Shines

    NASA Image and Video Library

    2012-11-19

    The rich dynamics of Saturn F ring are seen in this image taken by NASA Cassini spacecraft. Most of the features are believed to be due to the ring interactions with its shepherd moons or with small moonlets embedded within the ring itself.

  20. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Tiscareno, Matthew S.

    Planetary rings are the only nearby astrophysical disks and the only disks that have been investigated by spacecraft (especially the Cassini spacecraft orbiting Saturn). Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 10- 7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close range and in real time in planetary rings.We review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We then review planetary rings by type. The A, B, and C rings of Saturn, plus the Cassini Division, comprise our solar system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are found both at Uranus (where they comprise the main rings entirely) and at Saturn (where they are embedded in the broad disk) and are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally confined arcs at Neptune, Saturn, and Jupiter. Finally, every known ring system includes a substantial component of diffuse dusty rings.Planetary rings have shown themselves to be useful as detectors of planetary processes around them, including the planetary magnetic field and interplanetary impactors as well as the gravity of nearby perturbing moons. Experimental rings science has made great progress in recent decades, especially numerical simulations of self-gravity wakes and other processes but also laboratory investigations of coefficient of restitution and spectroscopic ground truth. The age of self-sustained ring systems is a matter of

  1. Discrete Thermodynamics

    DOE PAGES

    Margolin, L. G.; Hunter, A.

    2017-10-18

    Here, we consider the dependence of velocity probability distribution functions on the finite size of a thermodynamic system. We are motivated by applications to computational fluid dynamics, hence discrete thermodynamics. We then begin by describing a coarsening process that represents geometric renormalization. Then, based only on the requirements of conservation, we demonstrate that the pervasive assumption of local thermodynamic equilibrium is not form invariant. We develop a perturbative correction that restores form invariance to second-order in a small parameter associated with macroscopic gradients. Finally, we interpret the corrections in terms of unresolved kinetic energy and discuss the implications of ourmore » results both in theory and as applied to numerical simulation.« less

  2. Ultrasound findings of diffuse metastasis of gastric signet-ring-cell carcinoma to the thyroid gland.

    PubMed

    Morita, Koji; Sakamoto, Takahiko; Ota, Shuji; Masugi, Hideo; Chikuta, Ikumi; Mashimo, Yamato; Edo, Naoki; Tokairin, Takuo; Seki, Nobuhiko; Ishikawa, Toshio

    2017-01-01

    It has been shown that metastases to the thyroid from extrathyroidal malignancies occur as solitary or multiple nodules, or may involve the whole thyroid gland diffusely. However, diffuse metastasis of gastric cancer to the thyroid is extremely rare. Here, we report a case of a 74-year-old woman with diffuse infiltration of gastric adenocarcinoma (signet-ring-cell carcinoma/poorly differentiated adenocarcinoma) cells in the thyroid. The pathological diagnosis was made based on upper gastrointestinal endoscopy with biopsy and fine-needle aspiration cytology of the thyroid. An 18F-FDG PET/CT revealed multiple lesions with increased uptake, including the bilateral thyroid gland. On thyroid ultrasound examination, diffuse enlargement with internal heterogeneity and hypoechoic reticular lines was observed. On color Doppler imaging, a blood-flow signal was not detected in these hypoechoic lines. These findings were similar to those of diffuse metastases caused by other primary cancers, such as lung cancer, as reported earlier. Therefore, the presence of hypoechoic reticular lines without blood-flow signals is probably common to diffuse thyroid metastasis from any origin and an important diagnostic finding. This is the first report to show detailed ultrasound findings of diffuse gastric cancer metastasis to the thyroid gland using color Doppler.

  3. Planetary Rings

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.

    1994-01-01

    Just over two decades ago, Jim Pollack made a critical contribution to our understanding of planetary ring particle properties, and resolved a major apparent paradox between radar reflection and radio emission observations. At the time, particle properties were about all there were to study about planetary rings, and the fundamental questions were, why is Saturn the only planet with rings, how big are the particles, and what are they made of? Since then, we have received an avalanche of observations of planetary ring systems, both from spacecraft and from Earth. Meanwhile, we have seen steady progress in our understanding of the myriad ways in which gravity, fluid and statistical mechanics, and electromagnetism can combine to shape the distribution of the submicron-to-several-meter size particles which comprise ring systems into the complex webs of structure that we now know them to display. Insights gained from studies of these giant dynamical analogs have carried over into improved understanding of the formation of the planets themselves from particle disks, a subject very close to Jim's heart. The now-complete reconnaissance of the gas giant planets by spacecraft has revealed that ring systems are invariably found in association with families of regular satellites, and there is ark emerging perspective that they are not only physically but causally linked. There is also mounting evidence that many features or aspects of all planetary ring systems, if not the ring systems themselves, are considerably younger than the solar system

  4. Vascular ring

    MedlinePlus

    Right aortic arch with aberrant subclavian and left ligamentum ateriosus; Congenital heart defect - vascular ring; Birth defect ... well in most cases and often relieves symptoms right away. Severe breathing problems may take months to ...

  5. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Nicholson, P. D.

    2001-11-01

    A revolution in the studies in planetary rings studies occurred in the period 1977--1981, with the serendipitous discovery of the narrow, dark rings of Uranus, the first Voyager images of the tenuous jovian ring system, and the many spectacular images returned during the twin Voyager flybys of Saturn. In subsequent years, ground-based stellar occultations, HST observations, and the Voyager flybys of Uranus (1986) and Neptune (1989), as well as a handful of Galileo images, provided much additional information. Along with the completely unsuspected wealth of detail these observations revealed came an unwelcome problem: are the rings ancient or are we privileged to live at a special time in history? The answer to this still-vexing question may lie in the complex gravitational interactions recent studies have revealed between the rings and their retinues of attendant satellites. Among the four known ring systems, we see elegant examples of Lindblad and corotation resonances (first invoked in the context of galactic disks), electromagnetic resonances, spiral density waves and bending waves, narrow ringlets which exhibit internal modes due to collective instabilities, sharp-edged gaps maintained via tidal torques from embedded moonlets, and tenuous dust belts created by meteoroid impact onto parent bodies. Perhaps most puzzling is Saturn's multi-stranded, clumpy F ring, which continues to defy a simple explanation 20 years after it was first glimpsed in grainy images taken by Pioneer 11. Voyager and HST images reveal a complex, probably chaotic, dynamical interaction between unseen parent bodies within this ring and its two shepherd satellites, Pandora and Prometheus. The work described here reflects contributions by Joe Burns, Jeff Cuzzi, Luke Dones, Dick French, Peter Goldreich, Colleen McGhee, Carolyn Porco, Mark Showalter, and Bruno Sicardy, as well as those of the author. This research has been supported by NASA's Planetary Geology and Geophysics program and the

  6. Saturn Ring

    NASA Image and Video Library

    2007-12-12

    Like Earth, Saturn has an invisible ring of energetic ions trapped in its magnetic field. This feature is known as a "ring current." This ring current has been imaged with a special camera on Cassini sensitive to energetic neutral atoms. This is a false color map of the intensity of the energetic neutral atoms emitted from the ring current through a processed called charged exchange. In this process a trapped energetic ion steals and electron from cold gas atoms and becomes neutral and escapes the magnetic field. The Cassini Magnetospheric Imaging Instrument's ion and neutral camera records the intensity of the escaping particles, which provides a map of the ring current. In this image, the colors represent the intensity of the neutral emission, which is a reflection of the trapped ions. This "ring" is much farther from Saturn (roughly five times farther) than Saturn's famous icy rings. Red in the image represents the higher intensity of the particles, while blue is less intense. Saturn's ring current had not been mapped before on a global scale, only "snippets" or areas were mapped previously but not in this detail. This instrument allows scientists to produce movies (see PIA10083) that show how this ring changes over time. These movies reveal a dynamic system, which is usually not as uniform as depicted in this image. The ring current is doughnut shaped but in some instances it appears as if someone took a bite out of it. This image was obtained on March 19, 2007, at a latitude of about 54.5 degrees and radial distance 1.5 million kilometres (920,000 miles). Saturn is at the center, and the dotted circles represent the orbits of the moon's Rhea and Titan. The Z axis points parallel to Saturn's spin axis, the X axis points roughly sunward in the sun-spin axis plane, and the Y axis completes the system, pointing roughly toward dusk. The ion and neutral camera's field of view is marked by the white line and accounts for the cut-off of the image on the left. The

  7. Jupiter's Rings

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Annotated Version

    The New Horizons Long Range Reconnaissance Imager (LORRI) snapped this photo of Jupiter's ring system on February 24, 2007, from a distance of 7.1 million kilometers (4.4 million miles).

    This processed image shows a narrow ring, about 1,000 kilometers (600 miles) wide, with a fainter sheet of material inside it. The faint glow extending in from the ring is likely caused by fine dust that diffuses in toward Jupiter. This is the outer tip of the 'halo,' a cloud of dust that extends down to Jupiter's cloud tops. The dust will glow much brighter in pictures taken after New Horizons passes to the far side of Jupiter and looks back at the rings, which will then be sunlit from behind.

    Jupiter's ring system was discovered in 1979, when astronomers spied it in a single image taken by the Voyager 1 spacecraft. Months later, Voyager 2 carried out more extensive imaging of the system. It has since been examined by NASA's Galileo and Cassini spacecraft, as well as by the Hubble Space Telescope and large ground-based observatories.

  8. Fiber Ring Optical Gyroscope (FROG)

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The design, construction, and testing of a one meter diameter fiber ring optical gyro, using 1.57 kilometers of single mode fiber, are described. The various noise components: electronic, thermal, mechanical, and optical, were evaluated. Both dc and ac methods were used. An attempt was made to measure the Earth rotation rate; however, the results were questionable because of the optical and electronic noise present. It was concluded that fiber ring optical gyroscopes using all discrete components have many serious problems that can only be overcome by discarding the discrete approach and adapting an all integrated optic technique that has the laser source, modulator, detector, beamsplitters, and bias element on a single chip.

  9. Ring coolers

    NASA Astrophysics Data System (ADS)

    Palmer, R. B.

    2003-08-01

    The simulated performance of three different 6D muon cooling rings is presented. Two of these used solenoid focusing and one used quadrupoles. All three performed better than the linear cooling channel described in Study-2 (Ozaki S, Palmer R B, Zisman M S and Gallardo J C 2001 BNL-52623). The best example increased the 6D phase space density by a factor of 162, compared with the linear channel's factor of only 15. However, none of the simulations used fully realistic magnetic fields, and absorber and radio frequency (RF) cavity windows were not included. Injection/extraction is discussed.

  10. RADIOGRAPHIC AND ULTRASONOGRAPHIC ABDOMINAL ANATOMY IN CAPTIVE RING-TAILED LEMURS (LEMUR CATTA).

    PubMed

    Makungu, Modesta; du Plessis, Wencke M; Barrows, Michelle; Groenewald, Hermanus B; Koeppel, Katja N

    2016-06-01

    The ring-tailed lemur (Lemur catta) is primarily distributed in south and southwestern Madagascar. It is classified as an endangered species by the International Union for Conservation of Nature. Various abdominal diseases, such as hepatic lipidosis, intestinal ulcers, cystitis, urinary tract obstruction, and neoplasia (e.g., colonic adenocarcinoma and cholangiocarcinoma), have been reported in this species. The aim of this study was to describe the normal radiographic and ultrasonographic abdominal anatomy in captive ring-tailed lemurs to provide guidance for clinical use. Radiography of the abdomen and ultrasonography of the liver, spleen, kidneys, and urinary bladder were performed in 13 and 9 healthy captive ring-tailed lemurs, respectively, during their annual health examinations. Normal radiographic and ultrasonographic reference ranges for abdominal organs were established and ratios were calculated. The majority (12/13) of animals had seven lumbar vertebrae. The sacrum had mainly (12/13) three segments. Abdominal serosal detail was excellent in all animals, and hypaxial muscles were conspicuous in the majority (11/13) of animals. The spleen was frequently (12/13) seen on the ventrodorsal (VD) view and rarely (3/13) on the right lateral (RL) view. The liver was less prominent and well contained within the ribcage. The pylorus was mostly (11/13) located to the right of the midline. The right and left kidneys were visible on the RL and VD views, with the right kidney positioned more cranial and dorsal to the left kidney. On ultrasonography, the kidneys appeared ovoid on transverse and longitudinal views. The medulla was hypoechoic to the renal cortex. The renal cortex was frequently (8/9) isoechoic and rarely (1/9) hyperechoic to the splenic parenchyma. The liver parenchyma was hypoechoic (5/5) to the renal cortex. Knowledge of the normal radiographic and ultrasonographic abdominal anatomy of ring-tailed lemurs may be useful in the diagnosis of diseases and in

  11. Discrete quadratic cavity solitons.

    PubMed

    Egorov, O; Peschel, U; Lederer, F

    2005-05-01

    We predict the existence of various types of discrete solitons in arrays of coupled optical cavities endowed with a quadratic nonlinearity. We derive mean-field equations and determine their range of validity by comparing results with those from the original round-trip model. By using an analytical approach we identify domains in parameter space where solitons can potentially exist and describe their asymptotic behavior. Taking advantage of these results, we numerically find discrete solitons of different topologies. Some of them are unique to discrete models. Ultimately, we study the stability of these soliton solutions and find that discreteness appreciably influences this behavior.

  12. Ringing phenomenon of the fiber ring resonator.

    PubMed

    Ying, Diqing; Ma, Huilian; Jin, Zhonghe

    2007-08-01

    A resonator fiber-optic gyro (R-FOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A fiber ring resonator is the core sensing element in the R-FOG. When the frequency of the fiber ring resonator input laser is swept linearly with time, ringing of the output resonance curve is observed. The output field of the fiber ring resonator is derived from the superposition of the light transmitted through the directional coupler directly and the multiple light components circulated in the fiber ring resonator when the frequency of the laser is swept. The amplitude and phase of the output field are analyzed, and it is found that the difference in time for different light components in the fiber ring resonator to reach a point of destructive interference causes the ringing phenomenon. Finally the ringing phenomenon is observed in experiments, and the experimental results agree with the theoretical analysis well.

  13. Discrete Mathematics Re "Tooled."

    ERIC Educational Resources Information Center

    Grassl, Richard M.; Mingus, Tabitha T. Y.

    1999-01-01

    Indicates the importance of teaching discrete mathematics. Describes how the use of technology can enhance the teaching and learning of discrete mathematics. Explorations using Excel, Derive, and the TI-92 proved how preservice and inservice teachers experienced a new dimension in problem solving and discovery. (ASK)

  14. The Ring Sculptor

    NASA Image and Video Library

    2006-09-08

    Prometheus zooms across the Cassini spacecraft field of view, attended by faint streamers and deep gores in the F ring. This movie sequence of five images shows the F ring shepherd moon shaping the ring inner edge

  15. Asymmetric dipolar ring

    DOEpatents

    Prosandeev, Sergey A.; Ponomareva, Inna V.; Kornev, Igor A.; Bellaiche, Laurent M.

    2010-11-16

    A device having a dipolar ring surrounding an interior region that is disposed asymmetrically on the ring. The dipolar ring generates a toroidal moment switchable between at least two stable states by a homogeneous field applied to the dipolar ring in the plane of the ring. The ring may be made of ferroelectric or magnetic material. In the former case, the homogeneous field is an electric field and in the latter case, the homogeneous field is a magnetic field.

  16. Rotating Monopole-Antimonopole Pairs and Vortex Rings

    NASA Astrophysics Data System (ADS)

    Neemann, Ulrike; Kunz, Jutta; Kleihaus, Burkhard

    2008-09-01

    We discuss dyons and electrically charged monopole-antimonopole pairs and vortex rings in Einstein-Yang-Mills-Higgs theory. The solutions are stationary, axially symmetric and asymptotically flat. In monopole-antimonopole pair solutions the Higgs field vanishes at two discrete points along the symmetry axis. In vortex ring solutions the Higgs field vanishes on a ring, centered around the symmetry axis. The dyons represent non-static solutions with vanishing angular momentum. In contrast to the dyons the monopole-antimonopole pairs and vortex rings possess vanishing magnetic charge, but finite angular momentum, equaling n times their electric charge. The dependence of the solutions on the strength of gravity is studied.

  17. Stirling engine piston ring

    DOEpatents

    Howarth, Roy B.

    1983-01-01

    A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

  18. Uranus Tenth Ring

    NASA Image and Video Library

    1996-01-29

    On Jan. 23, 1986, NASA Voyager 2 discovered a tenth ring orbiting Uranus. The tenth ring is about midway between the bright, outermost epsilon ring and the next ring down, called delta. http://photojournal.jpl.nasa.gov/catalog/PIA00035

  19. The Discrete Hanging Cable

    ERIC Educational Resources Information Center

    Peters, James V.

    2004-01-01

    Using the methods of finite difference equations the discrete analogue of the parabolic and catenary cable are analysed. The fibonacci numbers and the golden ratio arise in the treatment of the catenary.

  20. New Dust Belts of Uranus: One Ring, Two Ring, Red Ring, Blue Ring

    SciTech Connect

    de Pater, I; Hammel, H B; Gibbard, S G

    2006-02-02

    We compare near-infrared observations of the recently discovered outer rings of Uranus with HST results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/2003 U 1 is probably produced via impacts into the embedded moon Mab, which apparently orbits at a location where non-gravitational perturbations favor the survival and spreading of sub-micron sized dust. R/2003 U 2 more closely resembles Saturn's G ring.

  1. The Discrete Wavelet Transform

    DTIC Science & Technology

    1991-06-01

    B-1 ,.iii FIGURES 1.1 A wavelet filter bank structure ..................................... 2 2.1 Diagram illustrating the dialation and...abstract decompositions of discrete time series. Their wide sweeping significance, however, lies in their interpretation as wavelet transforms. In a general...parameter transform wn in the scale- time plane. Following terminology to be intro- duced, wi is the (decimated) discrete wavelet transform. become the

  2. Basin-ring spacing on the Moon, Mercury, and Mars

    USGS Publications Warehouse

    Pike, R.J.; Spudis, P.D.

    1987-01-01

    Radial spacing between concentric rings of impact basins that lack central peaks is statistically similar and nonrandom on the Moon, Mercury, and Mars, both inside and outside the main ring. One spacing interval, (2.0 ?? 0.3)0.5D, or an integer multiple of it, dominates most basin rings. Three analytical approaches yield similar results from 296 remapped or newly mapped rings of 67 multi-ringed basins: least-squares of rank-grouped rings, least-squares of rank and ring diameter for each basin, and averaged ratios of adjacent rings. Analysis of 106 rings of 53 two-ring basins by the first and third methods yields an integer multiple (2 ??) of 2.00.5D. There are two exceptions: (1) Rings adjacent to the main ring of multi-ring basins are consistently spaced at a slightly, but significantly, larger interval, (2.1 ?? 0.3)0.5D; (2) The 88 rings of 44 protobasins (large peak-plus-inner-ring craters) are spaced at an entirely different interval (3.3 ?? 0.6)0.5D. The statistically constant and target-invariant spacing of so many rings suggests that this characteristic may constrain formational models of impact basins on the terrestrial planets. The key elements of such a constraint include: (1) ring positions may not have been located by the same process(es) that formed ring topography; (2) ring location and emplacement of ring topography need not be coeval; (3) ring location, but not necessarily the mode of ring emplacement, reflects one process that operated at the time of impact; and (4) the process yields similarly-disposed topographic features that are spatially discrete at 20.5D intervals, or some multiple, rather than continuous. These four elements suggest that some type of wave mechanism dominates the location, but not necessarily the formation, of basin rings. The waves may be standing, rather than travelling. The ring topography itself may be emplaced at impact by this and/or other mechanisms and may reflect additional, including post-impact, influences. ?? 1987

  3. Jupiter's Main Ring/Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts - - a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, outside the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the figure's far left side. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa (top image). A faint mist of particles can be seen above and below the main rings. This vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the

  4. Particle sizes in Saturn's rings from UVIS stellar occultations 1. Variations with ring region

    NASA Astrophysics Data System (ADS)

    Colwell, J. E.; Esposito, L. W.; Cooney, J. H.

    2018-01-01

    The Cassini spacecraft's Ultraviolet Imaging Spectrograph (UVIS) includes a high speed photometer (HSP) that has observed stellar occultations by Saturn's rings with a radial resolution of ∼10 m. In the absence of intervening ring material, the time series of measurements by the HSP is described by Poisson statistics in which the variance equals the mean. The finite sizes of the ring particles occulting the star lead to a variance that is larger than the mean due to correlations in the blocking of photons due to finite particle size and due to random variations in the number of individual particles in each measurement area. This effect was first exploited by Showalter and Nicholson (1990) with the stellar occultation observed by Voyager 2. At a given optical depth, a larger excess variance corresponds to larger particles or clumps that results in greater variation of the signal from measurement to measurement. Here we present analysis of the excess variance in occultations observed by Cassini UVIS. We observe differences in the best-fitting particle size in different ring regions. The C ring plateaus show a distinctly smaller effective particle size, R, than the background C ring, while the background C ring itself shows a positive correlation between R and optical depth. The innermost 700 km of the B ring has a distribution of excess variance with optical depth that is consistent with the C ring ramp and C ring but not with the remainder of the B1 region. The Cassini Division, while similar to the C ring in spectral and structural properties, has different trends in effective particle size with optical depth. There are discrete jumps in R on either side of the Cassini Division ramp, while the C ring ramp shows a smooth transition in R from the C ring to the B ring. The A ring is dominated by self-gravity wakes whose shadow size depends on the occultation geometry. The spectral ;halo; regions around the strongest density waves in the A ring correspond to

  5. Localized Perturbations in Saturn's C Ring

    NASA Astrophysics Data System (ADS)

    Spitale, Joseph N.; Tiscareno, Matthew S.

    2016-10-01

    Years of high-resolution imaging of Saturn's rings have revealed many examples of perturbations arising from local causes. For example, the presence of 100-m-scale and smaller moonlets is inferred in the A ring based on the propeller-shaped disturbances that they create (Tiscareno et al. 2006, 2010); the F ring is shaped by regular collisions with its shepherd Prometheus, as well as with other smaller bodies orbiting in the vicinity (Murray et al. 2005, 2008); the "wisps" on the outer edge of the Keeler gap (Porco et al. 2005) may mark the locations of small moonlets that have emerged from the A ring (Tiscareno and Arnault 2015); wakes in the Huygens ringlet imply the presence of two multi-km bodies, and the irregular shape of its inner edge suggests the presence of many smaller bodies (Spitale and Hahn 2016); based on shadow measurements, the B ring contains an embedded 300-m object that produces a small propeller-shaped disturbance (Spitale and Porco 2010; Spitale and Tiscareno 2012).Here, we present evidence for localized perturbations in the C ring. The ringlet embedded in the Bond gap, near 1.470 Saturn radii, shows discrete clumps orbiting at the Keplerian rate in images spanning about eight years. The clumps are not detected in all image sequences at the expected longitudes. The Dawes ringlet, near 1.495 Saturn radii, has an irregular edge that does not appear as a simple superposition of low-wavenumber normal modes.

  6. Rings of non-spherical, axisymmetric bodies

    NASA Astrophysics Data System (ADS)

    Gupta, Akash; Nadkarni-Ghosh, Sharvari; Sharma, Ishan

    2018-01-01

    We investigate the dynamical behavior of rings around bodies whose shapes depart considerably from that of a sphere. To this end, we have developed a new self-gravitating discrete element N-body code, and employed a local simulation method to simulate a patch of the ring. The central body is modeled as a symmetric (oblate or prolate) ellipsoid, or defined through the characteristic frequencies (circular, vertical, epicyclic) that represent its gravitational field. Through our simulations we explore how a ring's behavior - characterized by dynamical properties like impact frequency, granular temperature, number density, vertical thickness and radial width - varies with the changing gravitational potential of the central body. We also contrast properties of rings about large central bodies (e.g. Saturn) with those of smaller ones (e.g. Chariklo). Finally, we investigate how the characteristic frequencies of a central body, restricted to being a solid of revolution with an equatorial plane of symmetry, affect the ring dynamics. The latter process may be employed to qualitatively understand the dynamics of rings about any symmetric solid of revolution.

  7. Discrete Newtonian cosmology: perturbations

    NASA Astrophysics Data System (ADS)

    Ellis, George F. R.; Gibbons, Gary W.

    2015-03-01

    In a previous paper (Gibbons and Ellis 2014 Discrete Newtonian cosmology Class. Quantum Grav. 31 025003), we showed how a finite system of discrete particles interacting with each other via Newtonian gravitational attraction would lead to precisely the same dynamical equations for homothetic motion as in the case of the pressure-free Friedmann-Lemaître-Robertson-Walker cosmological models of general relativity theory, provided the distribution of particles obeys the central configuration equation. In this paper we show that one can obtain perturbed such Newtonian solutions that give the same linearized structure growth equations as in the general relativity case. We also obtain the Dmitriev-Zel’dovich equations for subsystems in this discrete gravitational model, and show how it leads to the conclusion that voids have an apparent negative mass.

  8. Discrete Driver Assistance

    NASA Astrophysics Data System (ADS)

    Klette, Reinhard; Jiang, Ruyi; Morales, Sandino; Vaudrey, Tobi

    Applying computer technology, such as computer vision in driver assistance, implies that processes and data are modeled as being discretized rather than being continuous. The area of stereo vision provides various examples how concepts known in discrete mathematics (e.g., pixel adjacency graphs, belief propagation, dynamic programming, max-flow/min-cut, or digital straight lines) are applied when aiming for efficient and accurate pixel correspondence solutions. The paper reviews such developments for a reader in discrete mathematics who is interested in applied research (in particular, in vision-based driver assistance). As a second subject, the paper also discusses lane detection and tracking, which is a particular task in driver assistance; recently the Euclidean distance transform proved to be a very appropriate tool for obtaining a fairly robust solution.

  9. Unfocused F Ring

    NASA Image and Video Library

    2007-04-02

    The F ring dissolves into a fuzzy stream of particles -- rather different from its usual appearance of a narrow, bright core flanked by dimmer ringlets. Also notable here is the bright clump of material that flanks the ring core

  10. Rings Through Atmosphere

    NASA Image and Video Library

    2010-05-26

    NASA Cassini spacecraft looks toward the limb of Saturn and, on the right of this image, views part of the rings through the planet atmosphere. Saturn atmosphere can distort the view of the rings from some angles.

  11. New dust belts of Uranus: one ring, two ring, red ring, blue ring.

    PubMed

    de Pater, Imke; Hammel, Heidi B; Gibbard, Seran G; Showalter, Mark R

    2006-04-07

    We compared near-infrared observations of the recently discovered outer rings of Uranus with Hubble Space Telescope results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/2003 U 1 is probably produced by impacts into the embedded moon Mab, which apparently orbits at a location where nongravitational perturbations favor the survival and spreading of submicron-sized dust. R/2003 U 2 more closely resembles Saturn's G ring, which is red, a typical color for dusty rings.

  12. Rings Around a Crescent

    NASA Image and Video Library

    2010-11-01

    A crescent Saturn appears nestled within encircling rings in this image captured by NASA Cassini spacecraft. Clouds swirl through the atmosphere of the planet. Prometheus appears as a speck above the rings near the middle of the image.

  13. Budding F Ring

    NASA Image and Video Library

    2007-03-27

    The brilliant core of the F ring displays a breakaway clump of material, possibly related to the other objects the Cassini spacecraft has witnessed in the dynamic ring in the past few years of observations

  14. Saturn's F-Ring

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This narrow-angle camera image of Saturn's F Ring was taken through the Clear filter while at a distance of 6.9 million km from Saturn on 8 November 1980. The brightness variations of this tightly-constrained ring shown here indicate that the ring is less uniform in makeup than the larger rings. JPL managed the Voyager Project for NASA's Office of Space Science

  15. Discrete Warehouse Problem

    DTIC Science & Technology

    1988-12-01

    December 1988 UILU-ENG-88-2263 ACT-105 COORDINATED SCIENCE LABORATORY College of Engineering y Applied Computation Theory I<el I I DISCRETE WAREHOUSE...remote robot and it can manage to move about with the help of only one hole, whereas an H -robot needs a new hole 3 every time it advances a step. Then

  16. Discretion in Administrative Law.

    ERIC Educational Resources Information Center

    Grey, J.

    1979-01-01

    Clarifies the concept of discretion, demonstrates how far the courts have been willing to tolerate it, and charts some new paths that appear to be opening before those who advocate wide judicial review. Available from the Osgoode Hall Law School, York University, 4700 Keele Street, Downsview, Ontario, Canada, M3J 2R5; $8.00/issue. (Author/IRT)

  17. What Is Discrete Mathematics?

    ERIC Educational Resources Information Center

    Sharp, Karen Tobey

    This paper cites information received from a number of sources, e.g., mathematics teachers in two-year colleges, publishers, and convention speakers, about the nature of discrete mathematics and about what topics a course in this subject should contain. Note is taken of the book edited by Ralston and Young which discusses the future of college…

  18. Dusty D Ring

    NASA Image and Video Library

    2014-02-24

    Saturn D ring is easy to overlook since it trapped between the brighter C ring and the planet itself. In this view from NASA Cassini spacecraft, all that can be seen of the D ring is the faint and narrow arc as it stretches from top right of the ima

  19. So Long, C Ring

    NASA Image and Video Library

    2017-11-13

    Saturn's C ring is home to a surprisingly rich array of structures and textures. Much of the structure seen in the outer portions of Saturn's rings is the result of gravitational perturbations on ring particles by moons of Saturn. Such interactions are called resonances. However, scientists are not clear as to the origin of the structures seen in this image which has captured an inner ring region sparsely populated with particles, making interactions between ring particles rare, and with few satellite resonances. In this image, a bright and narrow ringlet located toward the outer edge of the C ring is flanked by two broader features called plateaus, each about 100 miles (160 kilometers) wide. Plateaus are unique to the C ring. Cassini data indicates that the plateaus do not necessarily contain more ring material than the C ring at large, but the ring particles in the plateaus may be smaller, enhancing their brightness. This view looks toward the sunlit side of the rings from about 53 degrees above the ring plane. The image was taken in green light with the Cassini spacecraft narrow-angle camera on Aug. 14, 2017. The view was acquired at a distance of approximately 117,000 miles (189,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 74 degrees. Image scale is 3,000 feet (1 kilometer) per pixel. The Cassini spacecraft ended its mission on Sept. 15, 2017. https://photojournal.jpl.nasa.gov/catalog/PIA21356

  20. Nonlinear antiresonant ring interferometer.

    PubMed

    Otsuka, K

    1983-09-01

    A beam-splitter ring-mirror configuration employing a Kerr-like nonlinear medium, that is, a nonlinear antiresonant ring interferometer, is proposed for several optical functional devices. The basic idea behind the configuration is derived from the formation of a nonlinear refractive-index grating in a Kerr-like medium inside the unbalanced ring.

  1. Ladder-like Ring

    NASA Image and Video Library

    2013-05-27

    Forever changing, the F ring takes on a ladder-like appearance in this recent image from NASA Cassini spacecraft. Scientists believe that interactions between the F ring and the moons Prometheus and Pandora cause the dynamic structure of the ring.

  2. The Jumping Ring Experiment

    ERIC Educational Resources Information Center

    Baylie, M.; Ford, P. J.; Mathlin, G. P.; Palmer, C.

    2009-01-01

    The jumping ring experiment has become central to liquid nitrogen shows given as part of the outreach and open day activities carried out within the University of Bath. The basic principles of the experiment are described as well as the effect of changing the geometry of the rings and their metallurgical state. In general, aluminium rings are…

  3. Rings Around Uranus

    ERIC Educational Resources Information Center

    Maran, Stephen P.

    1977-01-01

    Events leading up to the discovery of the rings of Uranus are described. The methods used and the logic behind the methods are explained. Data collected to prove the existence of the rings are outlined and theories concerning the presence of planetary rings are presented. (AJ)

  4. Eyeing the E Ring

    NASA Image and Video Library

    2009-12-24

    NASA Cassini spacecraft takes a look at Saturn diffuse E ring which is formed from icy material spewing out of the south pole of the moon Enceladus. The E ring is seen nearly edge-on from slightly above the northern side of Saturn ring plane.

  5. Mapping magnetoelastic response of terfenol-D ring structure

    NASA Astrophysics Data System (ADS)

    Youssef, George; Newacheck, Scott; Lopez, Mario

    2017-05-01

    The magneto-elastic response of a Terfenol-D (Tb.3Dy.7Fe1.92) ring has been experimentally investigated and analyzed. Ring structures give rise to complex behavior based on the interaction of the magnetic field with the material, which is further compounded with anisotropies associated with mechanical and magnetic properties. Discrete strain measurements were used to construct magnetostriction maps, which are used to elucidate the non-uniformity of the strain distribution due to geometrical factors and magnetic field interactions, namely, magnetic shielding and stable onion state in the ring structure.

  6. Saturn's largest ring.

    PubMed

    Verbiscer, Anne J; Skrutskie, Michael F; Hamilton, Douglas P

    2009-10-22

    Most planetary rings in the Solar System lie within a few radii of their host body, because at these distances gravitational accelerations inhibit satellite formation. The best known exceptions are Jupiter's gossamer rings and Saturn's E ring, broad sheets of dust that extend outward until they fade from view at five to ten planetary radii. Source satellites continuously supply the dust, which is subsequently lost in collisions or by radial transport. Here we report that Saturn has an enormous ring associated with its outer moon Phoebe, extending from at least 128R(S) to 207R(S) (Saturn's radius R(S) is 60,330 km). The ring's vertical thickness of 40R(S) matches the range of vertical motion of Phoebe along its orbit. Dynamical considerations argue that these ring particles span the Saturnian system from the main rings to the edges of interplanetary space. The ring's normal optical depth of approximately 2 x 10(-8) is comparable to that of Jupiter's faintest gossamer ring, although its particle number density is several hundred times smaller. Repeated impacts on Phoebe, from both interplanetary and circumplanetary particle populations, probably keep the ring populated with material. Ring particles smaller than centimetres in size slowly migrate inward and many of them ultimately strike the dark leading face of Iapetus.

  7. The contraceptive vaginal ring.

    PubMed

    Edwardson, Jill; Jamshidi, Roxanne

    2010-03-01

    The contraceptive vaginal ring offers effective contraception that is self-administered, requires less frequent dosing than many other forms of contraception, and provides low doses of hormones. NuvaRing (Organon, Oss, The Netherlands), the only contraceptive vaginal ring approved for use in the United States, contains etonogestrel and ethinyl estradiol. It is inserted into the vagina for 3 weeks, followed by a 1-week ring-free period, and works by inhibiting ovulation. Most women note a beneficial effect on bleeding profiles and are satisfied with NuvaRing. Commonly reported adverse events include vaginitis, leukorrhea, headaches, and device-related events such as discomfort. Serious adverse events are rare. In Chile and Peru, progesterone-only vaginal contraceptive rings are available for nursing women. Studies are ongoing examining new formulations of vaginal contraceptive rings. Thieme Medical Publishers.

  8. Fast Supervised Discrete Hashing.

    PubMed

    Gui, Jie; Liu, Tongliang; Sun, Zhenan; Tao, Dacheng; Tan, Tieniu

    2018-02-01

    Learning-based hashing algorithms are "hot topics" because they can greatly increase the scale at which existing methods operate. In this paper, we propose a new learning-based hashing method called "fast supervised discrete hashing" (FSDH) based on "supervised discrete hashing" (SDH). Regressing the training examples (or hash code) to the corresponding class labels is widely used in ordinary least squares regression. Rather than adopting this method, FSDH uses a very simple yet effective regression of the class labels of training examples to the corresponding hash code to accelerate the algorithm. To the best of our knowledge, this strategy has not previously been used for hashing. Traditional SDH decomposes the optimization into three sub-problems, with the most critical sub-problem - discrete optimization for binary hash codes - solved using iterative discrete cyclic coordinate descent (DCC), which is time-consuming. However, FSDH has a closed-form solution and only requires a single rather than iterative hash code-solving step, which is highly efficient. Furthermore, FSDH is usually faster than SDH for solving the projection matrix for least squares regression, making FSDH generally faster than SDH. For example, our results show that FSDH is about 12-times faster than SDH when the number of hashing bits is 128 on the CIFAR-10 data base, and FSDH is about 151-times faster than FastHash when the number of hashing bits is 64 on the MNIST data-base. Our experimental results show that FSDH is not only fast, but also outperforms other comparative methods.

  9. The Structure of Saturn's F Ring

    NASA Astrophysics Data System (ADS)

    Murray, C. D.; Attree, N. O.; Cooper, N. J.; Williams, G. A.

    2012-04-01

    In stark contrast to the ordered regularity of the planet's main rings, Cassini images of Saturn's F ring show a diversity of structures on a variety of scales. The ring is located ~3000km beyond the edge of the A ring and Cassini ISS images reveal a core (radial width ~50km) with localised radial distortions (~50km), as well as occasional spiral strands that can extend to ~200km on either side. High-resolution images also show discrete structures on smaller scales (~10km) in addition to several types of clumps in or around the core and the strands. Despite this the F ring can still be modelled as a uniformly precessing, eccentric, inclined ring suggesting that it has sufficient mass for the effects of self-gravity or collisions to be important in maintaining this configuration. The perturbing effect of the nearby satellite Prometheus is now well understood (Murray et al., 2005) as is its role in producing clumps of material which then interact with the ring and strands (Beurle et al., 2010). The production of the largest strands is linked to collisions between the ring's core and the object S/2004 S 6 (Murray et al., 2008) although additional objects may be involved. Such collisions produce "jets" of material that subsequently undergo Keplerian shear to produce the spiral strands. Cassini images have now provided direct evidence for the existence of a population of small objects (radius <1km) colliding with the ring. The impact velocities are ~ 5 m/s implying a source of objects with orbits similar to that of the F ring; this is consistent with what might be expected for objects formed in the core and perturbed by Prometheus. It is now possible to understand the morphology and dynamic nature of the F ring as being due to the gravitational and collisional effects of a variety of nearby objects, ranging in size from Prometheus (mean radius ~40km) down to sub-km objects orbiting close to the core.

  10. Lebedev discrete variable representation

    NASA Astrophysics Data System (ADS)

    Haxton, Daniel J.

    2007-12-01

    We describe the construction of a Lebedev discrete variable representation (DVR) (Dickinson and Certain 1968 J. Chem. Phys. 49 4209, Lill, Parker and Light 1982 Chem. Phys. Lett. 89 483, Light, Hamilton and Lill 1985 J. Chem. Phys. 82 1400). This DVR is based upon a new algorithm for constructing a generalized DVR in one or more dimensions. The novel part of this algorithm is a contraction of the underlying functional basis that is based upon the given points and weights. The contraction allows us to define a set of basis functions and a set of points, of equal number, for which the transformation between the 'point basis' and the 'function basis' is neither singular nor close to it. We present both a strictly orthogonal and a discretely orthogonal version of the Lebedev DVR, which are based on the octahedrally symmetric Lebedev quadratures for the sphere. The discretely orthogonal DVR is a classic generalized DVR (Light, Hamilton and Lill 1985 J. Chem. Phys. 82 1400) and the strictly orthogonal version is similar to a diagonalization DVR. These DVRs perform well in test calculations. The algorithm is general and should be applicable to nonseparable bases in many dimensions.

  11. Discrete Subaortic Stenosis

    PubMed Central

    Darcin, Osman Tansel; Yagdi, Tahir; Atay, Yuksel; Engin, Cagatay; Levent, Erturk; Buket, Suat; Alayunt, Emin Alp

    2003-01-01

    Discrete subaortic stenosis, which is an obstructing lesion of the left ventricular outflow tract, remains a surgical challenge. The recurrence rate is high despite sufficient conventional resection. We retrospectively reviewed the results of surgery for discrete subaortic stenosis at our institution from September 1995 through March 2001. Twenty-one patients with this lesion underwent surgical treatment during this period. Excision of the fibromuscular membrane with myectomy was performed in all of the patients. Follow-up in all patients ranged from 7 to 67 months (mean follow-up period, 39.57 ± 15.46 months). The mean systolic gradient between the left ventricle and the aorta decreased from 59.23 ± 35.38 mmHg preoperatively to 9.47 ± 9.91 mmHg postoperatively. There was no instance of heart block that required a permanent pacemaker, nor of bacterial endocarditis. There was no early or late postoperative death. A 22nd patient, who had 3+ aortic regurgitation, required aortic valve replacement and was excluded from the study. Two of the patients (9.5%) underwent reoperation because of recurrent gradient and residual ventricular septal defect. Our results suggest that fibromuscular membrane excision combined with myectomy in patients with discrete subaortic stenosis produces sufficient relief of obstruction with low morbidity. (Tex Heart Inst J 2003;30:286–92) PMID:14677738

  12. Discrete Lorentz symmetry and discrete time translational symmetry

    NASA Astrophysics Data System (ADS)

    Wang, Pei

    2018-02-01

    The Lorentz symmetry and the space and time translational symmetry are fundamental symmetries of nature. Crystals are the manifestation of the continuous space translational symmetry being spontaneously broken into a discrete one. We argue that, following the space translational symmetry, the continuous Lorentz symmetry should also be broken into a discrete one, which further implies that the continuous time translational symmetry is broken into a discrete one. We deduce all the possible discrete Lorentz and discrete time translational symmetries in 1+1-dimensional spacetime, and show how to build a field theory or a lattice field theory that has these symmetries.

  13. Surge in the Ring

    NASA Image and Video Library

    2016-08-29

    An ethereal, glowing spot appears on Saturn's B ring in this view from NASA's Cassini spacecraft. There is nothing particular about that place in the rings that produces the glowing effect -- instead, it is an example of an "opposition surge" making that area on the rings appear extra bright. An opposition surge occurs when the Sun is directly behind the observer looking toward the rings. The particular geometry of this observation makes the point in the rings appear much, much brighter than would otherwise be expected. This view looks toward the sunlit side of the rings from about 28 degrees above the ring plane. The image was taken in visible light with the Cassini wide-angle camera on June 26, 2016. The view was acquired at a distance of approximately 940,000 miles (1.5 million kilometers) from the rings and at a Sun-ring-spacecraft, or phase, angle of 0 degrees. Image scale on the rings at center is 56 miles (90 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20496

  14. Traceable Ring Signature

    NASA Astrophysics Data System (ADS)

    Fujisaki, Eiichiro; Suzuki, Koutarou

    The ring signature allows a signer to leak secrets anonymously, without the risk of identity escrow. At the same time, the ring signature provides great flexibility: No group manager, no special setup, and the dynamics of group choice. The ring signature is, however, vulnerable to malicious or irresponsible signers in some applications, because of its anonymity. In this paper, we propose a traceable ring signature scheme. A traceable ring scheme is a ring signature except that it can restrict “excessive” anonymity. The traceable ring signature has a tag that consists of a list of ring members and an issue that refers to, for instance, a social affair or an election. A ring member can make any signed but anonymous opinion regarding the issue, but only once (per tag). If the member submits another signed opinion, possibly pretending to be another person who supports the first opinion, the identity of the member is immediately revealed. If the member submits the same opinion, for instance, voting “yes” regarding the same issue twice, everyone can see that these two are linked. The traceable ring signature can suit to many applications, such as an anonymous voting on a BBS. We formalize the security definitions for this primitive and show an efficient and simple construction in the random oracle model.

  15. The ring laser gyro

    NASA Astrophysics Data System (ADS)

    Chow, W. W.; Gea-Banacloche, J.; Pedrotti, L. M.; Sanders, V. E.; Schleich, W.; Scully, M. O.

    1985-01-01

    This paper presents a review of both active and passive ring laser devices. The operating principles of the ring laser are developed and discussed, with special emphasis given to the problems associated with the achievement of greater sensitivity and stability. First-principle treatments of the nature of quantum noise in the ring laser gyro and various methods designed to avoid low-rotation-rate lock-in are presented. Descriptions of state-of-the-art devices and current and proposed applications (including a proposed test of metric theories of gravity using a passive cavity ring laser) are given.

  16. Tiny Mimas, Huge Rings

    NASA Image and Video Library

    2016-11-28

    Saturn's icy moon Mimas is dwarfed by the planet's enormous rings. Because Mimas (near lower left) appears tiny by comparison, it might seem that the rings would be far more massive, but this is not the case. Scientists think the rings are no more than a few times as massive as Mimas, or perhaps just a fraction of Mimas' mass. Cassini is expected to determine the mass of Saturn's rings to within just a few hundredths of Mimas' mass as the mission winds down by tracking radio signals from the spacecraft as it flies close to the rings. The rings, which are made of small, icy particles spread over a vast area, are extremely thin -- generally no thicker than the height of a house. Thus, despite their giant proportions, the rings contain a surprisingly small amount of material. Mimas is 246 miles (396 kilometers) wide. This view looks toward the sunlit side of the rings from about 6 degrees above the ring plane. The image was taken in red light with the Cassini spacecraft wide-angle camera on July 21, 2016. The view was obtained at a distance of approximately 564,000 miles (907,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 31 degrees. Image scale is 34 miles (54 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20509

  17. Nonlinear antiresonant ring interferometer

    NASA Astrophysics Data System (ADS)

    Otsuka, K.

    1983-09-01

    A new nonlinear ring interferometer is proposed which embodies a beam-splitter ring-mirror configuration containing a Kerr-like nonlinear medium. Theoretical calculations are presented which show that this system is characterized by frequency-independent nonlinear interference. This interference is due to the nonreciprocal phase shift of the counter propagating waves in the unbalanced ring which is a result of the formation of a refractive-index grating. Potential applications of the nonlinear antiresonant ring interferometer to optical logic and functional devices are examined.

  18. Faint D Ring

    NASA Image and Video Library

    2015-04-27

    Not all of Saturn's rings are created equal: here the C and D rings appear side-by-side, but the C ring, which occupies the bottom half of this image, clearly outshines its neighbor. The D ring appears fainter than the C ring because it is comprised of less material. However, even rings as thin as the D ring can pose hazards to spacecraft. Given the high speeds at which Cassini travels, impacts with particles just fractions of a millimeter in size have the potential to damage key spacecraft components and instruments. Nonetheless, near the end of Cassini's mission, navigators plan to thread the spacecraft's orbit through the narrow region between the D ring and the top of Saturn's atmosphere. This view looks toward the unilluminated side of the rings from about 12 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 11, 2015. The view was acquired at a distance of approximately 372,000 miles (599,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 133 degrees. Image scale is 2.2 miles (3.6 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/pia18313

  19. Jupiter Ring Halo

    NASA Image and Video Library

    1998-03-26

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age. Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal "halo" is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest being

  20. Jupiter's Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow.

    A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest

  1. Renormalization for Discrete Optimization

    NASA Astrophysics Data System (ADS)

    Houdayer, J.; Martin, O. C.

    1999-08-01

    The renormalization group has proven to be a very powerful tool in physics for treating systems with many length scales. Here we show how it can be adapted to provide a new class of algorithms for discrete optimization. The heart of our method uses renormalization and recursion, and these processes are embedded in a genetic algorithm. The system is self-consistently optimized on all scales, leading to a high probability of finding the ground state configuration. To demonstrate the generality of such an approach, we perform tests on traveling salesman and spin glass problems. The results show that our ``genetic renormalization algorithm'' is extremely powerful.

  2. Discrete Dynamics Lab

    NASA Astrophysics Data System (ADS)

    Wuensche, Andrew

    DDLab is interactive graphics software for creating, visualizing, and analyzing many aspects of Cellular Automata, Random Boolean Networks, and Discrete Dynamical Networks in general and studying their behavior, both from the time-series perspective — space-time patterns, and from the state-space perspective — attractor basins. DDLab is relevant to research, applications, and education in the fields of complexity, self-organization, emergent phenomena, chaos, collision-based computing, neural networks, content addressable memory, genetic regulatory networks, dynamical encryption, generative art and music, and the study of the abstract mathematical/physical/dynamical phenomena in their own right.

  3. Discretization of time series data.

    PubMed

    Dimitrova, Elena S; Licona, M Paola Vera; McGee, John; Laubenbacher, Reinhard

    2010-06-01

    An increasing number of algorithms for biochemical network inference from experimental data require discrete data as input. For example, dynamic Bayesian network methods and methods that use the framework of finite dynamical systems, such as Boolean networks, all take discrete input. Experimental data, however, are typically continuous and represented by computer floating point numbers. The translation from continuous to discrete data is crucial in preserving the variable dependencies and thus has a significant impact on the performance of the network inference algorithms. We compare the performance of two such algorithms that use discrete data using several different discretization algorithms. One of the inference methods uses a dynamic Bayesian network framework, the other-a time-and state-discrete dynamical system framework. The discretization algorithms are quantile, interval discretization, and a new algorithm introduced in this article, SSD. SSD is especially designed for short time series data and is capable of determining the optimal number of discretization states. The experiments show that both inference methods perform better with SSD than with the other methods. In addition, SSD is demonstrated to preserve the dynamic features of the time series, as well as to be robust to noise in the experimental data. A C++ implementation of SSD is available from the authors at http://polymath.vbi.vt.edu/discretization .

  4. Discretization of Time Series Data

    PubMed Central

    Licona, M. Paola Vera; McGee, John; Laubenbacher, Reinhard

    2010-01-01

    Abstract An increasing number of algorithms for biochemical network inference from experimental data require discrete data as input. For example, dynamic Bayesian network methods and methods that use the framework of finite dynamical systems, such as Boolean networks, all take discrete input. Experimental data, however, are typically continuous and represented by computer floating point numbers. The translation from continuous to discrete data is crucial in preserving the variable dependencies and thus has a significant impact on the performance of the network inference algorithms. We compare the performance of two such algorithms that use discrete data using several different discretization algorithms. One of the inference methods uses a dynamic Bayesian network framework, the other—a time-and state-discrete dynamical system framework. The discretization algorithms are quantile, interval discretization, and a new algorithm introduced in this article, SSD. SSD is especially designed for short time series data and is capable of determining the optimal number of discretization states. The experiments show that both inference methods perform better with SSD than with the other methods. In addition, SSD is demonstrated to preserve the dynamic features of the time series, as well as to be robust to noise in the experimental data. A C++ implementation of SSD is available from the authors at http://polymath.vbi.vt.edu/discretization. PMID:20583929

  5. Contraceptive vaginal ring.

    PubMed

    Madden, Tessa; Blumenthal, Paul

    2007-12-01

    The vaginal contraceptive ring is comprised of ethinyl vinyl acetate that releases ethinyl estradiol and the third-generation progestin, etonorgestrel. It was approved by the Food and Drug Administration in 2001. The vaginal contraceptive ring is highly efficacious with a Pearl Index of 1.18 and an efficacy of 99.1%. Effectiveness is similar with actual use.

  6. Inner B Ring Terminus

    NASA Image and Video Library

    2009-09-21

    This mosaic, part of a larger mosaic of images captured by NASA Cassini Orbiter just hours before exact equinox at Saturn, shows that the spiral corrugation in the planet’s inner rings continues right up to the inner B ring.

  7. Lower esophageal ring (Schatzki)

    MedlinePlus

    ... narrowed area to stretch the ring. Sometimes, a balloon is placed in the area and inflated, to help widen the ring. Outlook (Prognosis) Swallowing problems may return. You may need repeat treatment. When to Contact a Medical Professional Call your health care provider if you ...

  8. Improved gas ring laser

    NASA Technical Reports Server (NTRS)

    Coccoli, J. D.; Lawson, J. R.

    1968-01-01

    Minimizing mode coupling improves sensing resolution of a gas ring laser in a gimballess gyroscope system or inertial rotation sensor. The piezoelectric-driven corner mirrors of the ring laser are oscillated in a direction parallel to their surfaces and the plane of rotation.

  9. A-ring Propeller

    NASA Image and Video Library

    2010-08-26

    A propeller-shaped structure, created by an unseen moon, can be seen in Saturn A ring and looks like a small, dark line interrupting the bright surrounding ring material in the upper left of this image taken by NASA Cassini spacecraft.

  10. Splinters of Rings

    NASA Image and Video Library

    2009-12-28

    Saturn shadow interrupts the planet rings, leaving just thin slivers of the rings visible in this image, which shows a pair of the planet small moons. Helene is in the center top of the image, Epimetheus is in the lower right.

  11. Rings of Neptune

    NASA Image and Video Library

    1999-07-25

    These two 591-second exposures of the rings of Neptune were taken with the clear filter by the NASA Voyager 2 wide-angle camera on Aug. 26, 1989. The two main rings are clearly visible and appear complete over the region imaged.

  12. Smoke Ring Physics

    ERIC Educational Resources Information Center

    Huggins, Elisha

    2011-01-01

    The behavior of smoke rings, tornados, and quantized vortex rings in superfluid helium has many features in common. These features can be described by the same mathematics we use when introducing Ampere's law in an introductory physics course. We discuss these common features. (Contains 7 figures.)

  13. Birth Control Ring

    MedlinePlus

    ... It? The birth control ring is a soft, flexible, doughnut-shaped ring about 2 inches (5 centimeters) in diameter. It is inserted into the vagina, where it slowly releases hormones — the chemicals the body makes to control organ function — through the vaginal wall into the ...

  14. Uranus Ring System

    NASA Image and Video Library

    1996-01-29

    This image captured by NASA's Voyager 2 in 1986 revealed a continuous distribution of small particles throughout the Uranus ring system. This unique geometry, the highest phase angle at which Voyager imaged the rings, allowed us to see lanes of fine dust. http://photojournal.jpl.nasa.gov/catalog/PIA00142

  15. Contactless Magnetic Slip Ring

    NASA Technical Reports Server (NTRS)

    Kumagai, Hiroyuki (Inventor); Deardon, Joe D. (Inventor)

    1997-01-01

    A contactless magnetic slip ring is disclosed having a primary coil and a secondary coil. The primary and secondary coils are preferably magnetically coupled together, in a highly reliable efficient manner, by a magnetic layered core. One of the secondary and primary coils is rotatable and the contactless magnetic slip ring provides a substantially constant output.

  16. Imaging rings in ring imaging Cherenkov counters

    SciTech Connect

    Ratcliff, Blair N

    2002-11-25

    The general concepts used to form images in Ring Imaging Cherenkov (RICH) counters are described and their performance properties compared. Particular attention is paid to issues associated with imaging in the time dimension, especially in Detectors of Internally Reflected Cherenkov light (DIRCs).

  17. Jupiter Main Ring/Ring Halo

    NASA Image and Video Library

    1998-03-26

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age. http://photojournal.jpl.nasa.gov/catalog/PIA00701

  18. Jupiter's Rings: Sharpest View

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The New Horizons spacecraft took the best images of Jupiter's charcoal-black rings as it approached and then looked back at Jupiter. The top image was taken on approach, showing three well-defined lanes of gravel- to boulder-sized material composing the bulk of the rings, as well as lesser amounts of material between the rings. New Horizons snapped the lower image after it had passed Jupiter on February 28, 2007, and looked back in a direction toward the sun. The image is sharply focused, though it appears fuzzy due to the cloud of dust-sized particles enveloping the rings. The dust is brightly illuminated in the same way the dust on a dirty windshield lights up when you drive toward a 'low' sun. The narrow rings are confined in their orbits by small 'shepherding' moons.

  19. Jupiter Ring, With Orion

    NASA Image and Video Library

    2017-05-25

    As NASA's Juno spacecraft flew through the narrow gap between Jupiter's radiation belts and the planet during its first science flyby, Perijove 1, on August 27, 2016, the Stellar Reference Unit (SRU-1) star camera collected the first image of Jupiter's ring taken from the inside looking out. The bright bands in the center of the image are the main ring of Jupiter's ring system. While taking the ring image, the SRU was viewing the constellation Orion. The bright star above the main ring is Betelgeuse, and Orion's belt can be seen in the lower right. Juno's Radiation Monitoring Investigation actively retrieves and analyzes the noise signatures from penetrating radiation in the images of the spacecraft's star cameras and science instruments at Jupiter. https://photojournal.jpl.nasa.gov/catalog/PIA21644

  20. Saturn's ring region

    NASA Technical Reports Server (NTRS)

    1981-01-01

    This long exposure of the ring region about 150,000 to 200,000 kilometers (90,000 to 120,000 miles) from the center of Saturn captured the very faint G-ring, seen at left. The ring was discovered by Voyager 1 last fall at a similar phase angle. Voyager 2 was about 305,000 km. (189,000 mi.) away when it took this image Aug. 26. The small rectangular dots forming a regular pattern are reseau (reference) marks on the Voyager vidicon camera. The high-resolution detail in the A-ring has been washed out by the very long exposure needed to bring out the very tenuous G-ring. The Voyager project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.

  1. Jupiter's Main Ring

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa. A faint mist of particles can be seen above and below the main rings; this vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic.

    Jupiter's main ring is a thin strand of material encircling the planet. The diffuse innermost boundary begins at approximately 123,000 km. The main ring's outer radius is found to be

  2. STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED BY ARCHITECTURAL FINISH. TENSION RING ROLLER SUPPORT AT COLUMN OBSCURED BY COLUMN COVERINGS. - Houston Astrodome, 8400 Kirby Drive, Houston, Harris County, TX

  3. Manpower Analysis Using Discrete Simulation

    DTIC Science & Technology

    2015-12-01

    building using Discrete Event Simulation (DES) and experimentation using Design of Experiments (DOE). We derived five metamodels to identify the most...objectives were met. 14. SUBJECT TERMS manpower policy analysis, discrete event simulation, Simkit 15. NUMBER OF PAGES 85 16. PRICE CODE 17. SECURITY...using Discrete Event Simulation (DES) and experimentation using Design of Experiments (DOE). We derived five metamodels to identify the most

  4. Discrete bisoliton fiber laser

    PubMed Central

    Liu, X. M.; Han, X. X.; Yao, X. K.

    2016-01-01

    Dissipative solitons, which result from the intricate balance between dispersion and nonlinearity as well as gain and loss, are of the fundamental scientific interest and numerous important applications. Here, we report a fiber laser that generates bisoliton – two consecutive dissipative solitons that preserve a fixed separation between them. Deviations from this separation result in its restoration. It is also found that these bisolitons have multiple discrete equilibrium distances with the quantized separations, as is confirmed by the theoretical analysis and the experimental observations. The main feature of our laser is the anomalous dispersion that is increased by an order of magnitude in comparison to previous studies. Then the spectral filtering effect plays a significant role in pulse-shaping. The proposed laser has the potential applications in optical communications and high-resolution optics for coding and transmission of information in higher-level modulation formats. PMID:27767075

  5. Discretization of Differential Equations

    NASA Astrophysics Data System (ADS)

    Scherer, Philipp O. J.

    The simplest approach to discretize a differential equation replaces differential quotients by quotients of finite differences. For the space variables this method works best on a regular grid. Finite volume methods, which are very popular in computational fluid dynamics, take averages over small control volumes and can be easily used with irregular grids. Finite elements and finite volumes belong to the general class of finite element methods which are prominent in the engineering sciences and use an expansion in piecewise polynomials with small support. Spectral methods, on the other hand, expand the solution as a linear combination of global basis functions. A general concept is the method of weighted residuals. Most popular is Galerkin's method. The simpler point collocation and sub-domain collocation methods fulfill the differential equation only at certain points or averaged over certain control volumes. The more demanding least-squares method has become popular in computational fluid dynamics and computational electrodynamics.

  6. Immigration and Prosecutorial Discretion

    PubMed Central

    Apollonio, Dorie; Lochner, Todd; Heddens, Myriah

    2015-01-01

    Immigration has become an increasingly salient national issue in the US, and the Department of Justice recently increased federal efforts to prosecute immigration offenses. This shift, however, relies on the cooperation of US attorneys and their assistants. Traditionally federal prosecutors have enjoyed enormous discretion and have been responsive to local concerns. To consider how the centralized goal of immigration enforcement may have influenced federal prosecutors in regional offices, we review their prosecution of immigration offenses in California using over a decade's worth of data. Our findings suggest that although centralizing forces influence immigration prosecutions, individual US attorneys' offices retain distinct characteristics. Local factors influence federal prosecutors' behavior in different ways depending on the office. Contrary to expectations, unemployment rates did not affect prosecutors' willingness to pursue immigration offenses, nor did local popular opinion about illegal immigration. PMID:26146530

  7. Immigration and Prosecutorial Discretion.

    PubMed

    Apollonio, Dorie; Lochner, Todd; Heddens, Myriah

    Immigration has become an increasingly salient national issue in the US, and the Department of Justice recently increased federal efforts to prosecute immigration offenses. This shift, however, relies on the cooperation of US attorneys and their assistants. Traditionally federal prosecutors have enjoyed enormous discretion and have been responsive to local concerns. To consider how the centralized goal of immigration enforcement may have influenced federal prosecutors in regional offices, we review their prosecution of immigration offenses in California using over a decade's worth of data. Our findings suggest that although centralizing forces influence immigration prosecutions, individual US attorneys' offices retain distinct characteristics. Local factors influence federal prosecutors' behavior in different ways depending on the office. Contrary to expectations, unemployment rates did not affect prosecutors' willingness to pursue immigration offenses, nor did local popular opinion about illegal immigration.

  8. Dynamic discrete tomography

    NASA Astrophysics Data System (ADS)

    Alpers, Andreas; Gritzmann, Peter

    2018-03-01

    We consider the problem of reconstructing the paths of a set of points over time, where, at each of a finite set of moments in time the current positions of points in space are only accessible through some small number of their x-rays. This particular particle tracking problem, with applications, e.g. in plasma physics, is the basic problem in dynamic discrete tomography. We introduce and analyze various different algorithmic models. In particular, we determine the computational complexity of the problem (and various of its relatives) and derive algorithms that can be used in practice. As a byproduct we provide new results on constrained variants of min-cost flow and matching problems.

  9. Earth: A Ringed Planet?

    NASA Astrophysics Data System (ADS)

    Hancock, L. O.; Povenmire, H.

    2010-12-01

    Among the most beautiful findings of the Space Age have been the discoveries of planetary rings. Not only Saturn but also Jupiter, Uranus and Neptune have rings; Saturn’s ring system has structures newly discovered; even Saturn's moon Rhea itself has a ring. All these are apparently supplied by material from the planetary moons (Rhea's ring by Rhea itself). The question naturally arises, why should the Earth not have a ring, and on the other hand, if it does, why has it not been observed? No rings have yet been observed in the inner solar system, but after all, rings in the inner solar system might simply tend to be fainter and more transient than those of the outer solar system: the inner solar system is more affected by the solar wind, and the Sun’s perturbing gravitational influence is greater. J.A. O’Keefe first suggested (1980) that Earth might have a ring system of its own. An Earth ring could account for some climate events. O’Keefe remarked that formation or thickening of a ring system in Earth’s equatorial plane could drive glaciation by deepening the chill of the winter hemisphere. (It is very well established that volcanic dust is an effective agent for the extinction of sunlight; this factor can be overwhelmingly apparent in eclipse observations.) O’Keefe died in 2000 and the speculation was not pursued, but the idea of an Earth ring has a prima facie reasonableness that calls for its renewed consideration. The program of this note is to hypothesize that, as O’Keefe proposed: (a) an Earth ring system exists; (b) it affects Earth's weather and climate; (c) the tektite strewn fields comprise filaments of the ring fallen to Earth's surface on various occasions of disturbance by comets or asteroids. On this basis, and drawing on the world's weather records, together with the Twentieth Century Reanalysis by NCEP/CIRES covering the period 1870-2010 and the geology of the tektite strewn fields, we herein propose the hypothesized Earth ring

  10. Gored of the Rings

    NASA Image and Video Library

    2014-06-09

    Prometheus is caught in the act of creating gores and streamers in the F ring. Scientists believe that Prometheus and its partner-moon Pandora are responsible for much of the structure in the F ring as shown by NASA Cassini spacecraft. The orbit of Prometheus (53 miles, or 86 kilometers across) regularly brings it into the F ring. When this happens, it creates gores, or channels, in the ring where it entered. Prometheus then draws ring material with it as it exits the ring, leaving streamers in its wake. This process creates the pattern of structures seen in this image. This process is described in detail, along with a movie of Prometheus creating one of the streamer/channel features, in PIA08397. This view looks toward the sunlit side of the rings from about 8.6 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 11, 2014. The view was acquired at a distance of approximately 1.3 million miles (2.1 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 147 degrees. Image scale is 8 miles (13 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18270

  11. Seal ring installation tool

    NASA Technical Reports Server (NTRS)

    Haselmaier, L. Haynes (Inventor)

    2004-01-01

    A seal ring tool that allows an installer to position a primary seal ring between hub ends of pipe flanges that are being assembled together. The tool includes a pivoting handle member and extension arms attached to the pivoting handle member. The ends of the arms have side indentation type longitudinal grooves angled toward one another for holding the primary seal ring in place between the hubs of respective pipes that are to be attached together. The arms of the tool can also have flat sides that can be used to abut against an optional second larger seal that is supported within a groove in one of the hub ends so that the second hub end can then be moved against the other side of the primary seal ring. Once the seal ring is positioned between the pipe hubs, the pipe hubs can be moved about the seal ring due to the flat sides of the arms of the tool. The tool eliminates the chances of damaging and contaminating seal rings being installed within pipe hubs that are being attached to one another.

  12. Dynamics of the Uranian Rings

    NASA Technical Reports Server (NTRS)

    Dermott, S. F.

    1984-01-01

    Some of the problems of the shepherding satellite model of Goldreich ant tremaine are discussed. The following topics are studied: (1) optical depths of the all the observed narrow rings; (2) satellite and ring separation timescales; (3) ring edge sharpness; (4) shock formation in narrow rings; (5) the existence of small satellites near the Uranian rings; and (6) the apse and node alignments of the eccentric and inclined rings.

  13. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025879 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  14. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025872 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  15. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025868 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  16. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025866 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  17. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025870 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  18. Theodolite Ring Lights

    NASA Technical Reports Server (NTRS)

    Clark, David

    2006-01-01

    Theodolite ring lights have been invented to ease a difficulty encountered in the well-established optical-metrology practice of using highly reflective spherical tooling balls as position references. A theodolite ring light produces a more easily visible reflection and eliminates the need for an autocollimating device. A theodolite ring light is a very bright light source that is well centered on the optical axis of the instrument. It can be fabricated, easily and inexpensively, for use on a theodolite or telescope of any diameter.

  19. Faint Ring, Bright Arc

    NASA Image and Video Library

    2010-01-12

    In this image taken by NASA Cassini spacecraft, the bright arc in Saturn faint G ring contains a little something special. Although it cant be seen here, the tiny moonlet Aegaeon orbits within the bright arc.

  20. In, Around, Beyond Rings

    NASA Image and Video Library

    2011-10-24

    A quartet of Saturn moons, from tiny to huge, surround and are embedded within the planet rings in this Cassini composition. Saturn largest moon, Titan, in the background, and the moon north polar hood is clearly visible.

  1. Outer B Ring Edge

    NASA Image and Video Library

    2004-12-03

    This image NASA Cassini spacecraft shows subtle, wavelike patterns, hundreds of narrow features resembling a record grooves in Saturn outer B-ring, and a noticeable abrupt change in overall brightness beyond the dark gap near the right.

  2. Hexagon and Rings

    NASA Image and Video Library

    2013-02-04

    Saturn north polar hexagon basks in the Sun light now that spring has come to the northern hemisphere. Many smaller storms dot the north polar region and Saturn signature rings put in an appearance in the background.

  3. Highlights in planetary rings

    NASA Astrophysics Data System (ADS)

    Porco, Carolyn C.

    1995-07-01

    There is a rich phenomenology within the planetary rings surrounding the giant planets, most of it discovered by the Voyagers during their historic tours of t he outer solar system in the 1980s. In the last decade, there have been two detailed IUGG reviews of planetary rings. Cuzzi [1983] covered the time period from 1979-1983 which included the Pioneer 11 encounter with Saturn (1979), the Voyager 1 and 2 encounters with Jupiter (1979) and with Saturn (1980 and 1981). Nicholson and Dones [1991] reviewed the developments in the field between 1984 and 1991, a period of time which included the Voyager 2 Uranus (1986) and Neptune (1989) encounters. (References t o additional reviews of planetary rings and related fields can be found in Nicholson and Dones [1991].) Rather than being comprehensive in nature, this review will concentrate on only those areas of ring research in which particularly promising developments have occurred in the last half decade.

  4. Rings and Enceladus

    NASA Image and Video Library

    2012-02-06

    A crescent Enceladus appears with Saturn rings in this view of the moon from NASA Cassini spacecraft. The famed jets of water ice emanating from the south polar region of the moon are faintly visible here.

  5. Rings and Waves

    NASA Image and Video Library

    2013-09-30

    Saturn A ring is decorated with several kinds of waves. NASA Cassini spacecraft has captured a host of density waves, a bending wave, and the edge waves on the edge of the Keeler gap caused by the small moon Daphnis.

  6. High Plains Ring

    NASA Image and Video Library

    2006-08-18

    This MOC image shows a ring marking the location of a nearly-filled, nearly-buried impact crater on the martian northern plains. Remnants of bright, seasonal frost occur in some polygonal cracks on the plain

  7. Discrete Mathematics and Its Applications

    ERIC Educational Resources Information Center

    Oxley, Alan

    2010-01-01

    The article gives ideas that lecturers of undergraduate Discrete Mathematics courses can use in order to make the subject more interesting for students and encourage them to undertake further studies in the subject. It is possible to teach Discrete Mathematics with little or no reference to computing. However, students are more likely to be…

  8. Saturn's dynamic D ring

    USGS Publications Warehouse

    Hedman, M.M.; Burns, J.A.; Showalter, M.R.; Porco, C.C.; Nicholson, P.D.; Bosh, A.S.; Tiscareno, M.S.; Brown, R.H.; Buratti, B.J.; Baines, K.H.; Clark, R.

    2007-01-01

    The Cassini spacecraft has provided the first clear images of the D ring since the Voyager missions. These observations show that the structure of the D ring has undergone significant changes over the last 25 years. The brightest of the three ringlets seen in the Voyager images (named D72), has transformed from a narrow, <40-km wide ringlet to a much broader and more diffuse 250-km wide feature. In addition, its center of light has shifted inwards by over 200 km relative to other features in the D ring. Cassini also finds that the locations of other narrow features in the D ring and the structure of the diffuse material in the D ring differ from those measured by Voyager. Furthermore, Cassini has detected additional ringlets and structures in the D ring that were not observed by Voyager. These include a sheet of material just interior to the inner edge of the C ring that is only observable at phase angles below about 60??. New photometric and spectroscopic data from the ISS (Imaging Science Subsystem) and VIMS (Visual and Infrared Mapping Spectrometer) instruments onboard Cassini show the D ring contains a variety of different particle populations with typical particle sizes ranging from 1 to 100 microns. High-resolution images reveal fine-scale structures in the D ring that appear to be variable in time and/or longitude. Particularly interesting is a remarkably regular, periodic structure with a wavelength of ??? 30 ?? km extending between orbital radii of 73,200 and 74,000 km. A similar structure was previously observed in 1995 during the occultation of the star GSC5249-01240, at which time it had a wavelength of ??? 60 ?? km. We interpret this structure as a periodic vertical corrugation in the D ring produced by differential nodal regression of an initially inclined ring. We speculate that this structure may have formed in response to an impact with a comet or meteoroid in early 1984. ?? 2006 Elsevier Inc. All rights reserved.

  9. Discrete dynamics versus analytic dynamics

    NASA Astrophysics Data System (ADS)

    Toxvaerd, Søren

    2014-01-01

    For discrete classical Molecular dynamics obtained by the "Verlet" algorithm (VA) with the time increment h there exists a shadow Hamiltonian tilde{H} with energy tilde{E}(h), for which the discrete particle positions lie on the analytic trajectories for tilde{H}. Here, we proof that there, independent of such an analytic analogy, exists an exact hidden energy invariance E* for VA dynamics. The fact that the discrete VA dynamics has the same invariances as Newtonian dynamics raises the question, which of the formulations that are correct, or alternatively, the most appropriate formulation of classical dynamics. In this context the relation between the discrete VA dynamics and the (general) discrete dynamics investigated by Lee [Phys. Lett. B 122, 217 (1983)] is presented and discussed.

  10. Discreteness inducing coexistence

    NASA Astrophysics Data System (ADS)

    dos Santos, Renato Vieira

    2013-12-01

    Consider two species that diffuse through space. Consider further that they differ only in initial densities and, possibly, in diffusion constants. Otherwise they are identical. What happens if they compete with each other in the same environment? What is the influence of the discrete nature of the interactions on the final destination? And what are the influence of diffusion and additive fluctuations corresponding to random migration and immigration of individuals? This paper aims to answer these questions for a particular competition model that incorporates intra and interspecific competition between the species. Based on mean field theory, the model has a stationary state dependent on the initial density conditions. We investigate how this initial density dependence is affected by the presence of demographic multiplicative noise and additive noise in space and time. There are three main conclusions: (1) Additive noise favors denser populations at the expense of the less dense, ratifying the competitive exclusion principle. (2) Demographic noise, on the other hand, favors less dense populations at the expense of the denser ones, inducing equal densities at the quasi-stationary state, violating the aforementioned principle. (3) The slower species always suffers the more deleterious effects of statistical fluctuations in a homogeneous medium.

  11. Propellers in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

    2014-04-01

    Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings [5, 8]. Even if the objects are too small to be directly observed, each creates a much larger gravitational imprint on the surrounding ring material. These strongly depend on the mass of the object and range from "S" like propeller-shaped structures for about 100m-sized icy bodies to the opening of circumferential gaps as in the case of the embedded moons Pan and Daphnis and their corresponding Encke and Keeler Gaps. Since the beginning of the Cassini mission many of these smaller objects (~ 100m in size) have been identified in Saturn's A ring through their propeller signature in the images [10, 7, 9, 11]. Furthermore, recent Cassini observations indicate the possible existence of objects embedded even in Saturn's B and C ring [6, 2]. In this paper we present our new results about by now classical A ring propellers and more enigmatic B ring population. Due to the presence of self-gravity wakes the analysis of propeller brightness in ISS images always bears some ambiguity [7, 9] and consequently the exact morphology of propellers is not a settled issue. In 2008 we obtained a fortunate Cassini Ultraviolet Imaging Spectrograph (UVIS) occultation of the largest A ring propeller Bleriot. Utilizing Cassini ISS images we obtain Bleriot orbit and demonstrate that UVIS Persei Rev42 occultation did cut across Bleriot about 100km downstream from the center. The occultation itself shows a prominent partial gap and higher density outer flanking wakes, while their orientation is consistent with a downstream cut. While in the UVIS occultation the partial gap is more prominent than the flanking wakes, the features mostly seen in Bleriot images are actually flanking wakes. One of the most interesting aspects of the A ring propellers are their wanderings, or longitudinal deviations from a pure circular orbit [11]. We numerically investigated the possibility of simple moon

  12. Selective synthesis of iridium(iii)-derived molecular Borromean rings, [2]catenane and ring-in-ring macrocycles via coordination-driven self-assembly.

    PubMed

    Singh, Nem; Kim, Dongwook; Kim, Dong Hwan; Kim, Eun-Hee; Kim, Hyunuk; Lah, Myoung Soo; Chi, Ki-Whan

    2017-01-03

    This paper reports the formation of unprecedented iridium(iii)-derived topological macrocycles. Discrete molecular Borromean rings 1 and 3 in pure form are synthesized via coordination-driven self-assembly of an acceptor [(Cp*Ir) 2 (OO∩OO)](OTf) 2 (Cp* = pentamethylcyclopentadienyl, OO∩OO = 6,11-dioxido-5,12-naphthacenedione) (A) with dipyridyl donors 1,4-bis(4-pyridinylethynyl)benzene (L 1 ) and 2,5-bis(4-pyridinylethynyl)thiophene (L 2 ) respectively in methanol. Self-assembly using the same acceptor under similar conditions with two other donors 9,10-bis(4-pyridinylethynyl)anthracene (L 3 ) and 1,4-di(4-pyridinylethynyl)buta-1,3-diyne (L 4 ) resulted in [2]catenane 5 and non-catenane ring-in-ring topological macrocycle 7 respectively. Rectangular macrocycles 2, 4, 6, and 8 were respectively obtained when the self-assembly of acceptor A with one of the donors L 1 -L 4 was carried out under dilute conditions in nitromethane or methanol. All these new macrocycles were characterized by 1 H and 13 C NMR, 2D NMR, ESI-MS and elemental analyses. Single crystal X-ray structures of Borromean rings 1 and 3, and ring-in-ring macrocycle 7 revealed that the length and functionality of donors enabling CHπ and ππ interactions govern the topology.

  13. Ring correlations in random networks.

    PubMed

    Sadjadi, Mahdi; Thorpe, M F

    2016-12-01

    We examine the correlations between rings in random network glasses in two dimensions as a function of their separation. Initially, we use the topological separation (measured by the number of intervening rings), but this leads to pseudo-long-range correlations due to a lack of topological charge neutrality in the shells surrounding a central ring. This effect is associated with the noncircular nature of the shells. It is, therefore, necessary to use the geometrical distance between ring centers. Hence we find a generalization of the Aboav-Weaire law out to larger distances, with the correlations between rings decaying away when two rings are more than about three rings apart.

  14. DC-Powered Jumping Ring

    NASA Astrophysics Data System (ADS)

    Jeffery, Rondo N.; Amiri, Farhang

    2016-02-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant differences from the AC case. In particular, the ring does not fly off the core but rises a short distance and then falls back. If the ring jumps high enough, the rising and the falling motion of the ring does not follow simple vertical motion of a projectile. This indicates that there are additional forces on the ring in each part of its motion. Four possible stages of the motion of the ring with DC are identified, which result from the ring current changing directions during the jump in response to a changing magnetic flux through the moving ring.

  15. Propellers in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

    2013-12-01

    Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings. Even if the objects are too small to be directly observed, each creates a much larger gravitational imprint on the surrounding ring material. These strongly depend on the mass of the object and range from "S" like propeller-shaped structures for about 100m-sized icy bodies to the opening of circumferential gaps as in the case of the embedded moons Pan and Daphnis and their corresponding Encke and Keeler Gaps. Since the beginning of the Cassini mission many of these smaller objects (~<500m in size) have been indirectly identified in Saturn's A ring through their propeller signature in the images. Furthermore, recent Cassini observations indicate the possible existence of objects embedded even in Saturn's B and C ring. In this paper we present evidence for the existence of propellers in Saturn's B ring by combining data from Cassini Ultraviolet Imaging Spectrograph (UVIS) and Imaging Science Subsystem (ISS) experiments. We show evidence that B ring seems to harbor two distinct populations of propellers: "big" propellers covering tens of degrees in azimuth situated in the densest part of B ring, and "small" propellers in less dense inner B ring that are similar in size and shape to known A ring propellers. The population of "big" propellers is exemplified with a single object which is observed for 5 years of Cassini data. The object is seen as a very elongated bright stripe (40 degrees wide) in unlit Cassini images, and dark stripe in lit geometries. In total we report observing the feature in images at 18 different epochs between 2005 and 2010. In UVIS occultations we observe this feature as an optical depth depletion in 14 out of 93 occultation cuts at corrotating longitudes compatible with imaging data. Combining the available Cassini data we infer that the object is a partial gap located at r=112,921km embedded in the high optical depth region of the B

  16. Two F Ring Views

    NASA Technical Reports Server (NTRS)

    2005-01-01

    These views, taken two hours apart, demonstrate the dramatic variability in the structure of Saturn's intriguing F ring.

    In the image at the left, ringlets in the F ring and Encke Gap display distinctive kinks, and there is a bright patch of material on the F ring's inner edge. Saturn's moon Janus (181 kilometers, or 113 miles across) is shown here, partly illuminated by reflected light from the planet.

    At the right, Prometheus (102 kilometers, or 63 miles across) orbits ahead of the radial striations in the F ring, called 'drapes' by scientists. The drapes appear to be caused by successive passes of Prometheus as it reaches the greatest distance (apoapse) in its orbit of Saturn. Also in this image, the outermost ringlet visible in the Encke Gap displays distinctive bright patches.

    These views were obtained from about three degrees below the ring plane.

    The images were taken in visible light with the Cassini spacecraft narrow-angle camera on June 29, 2005, when Cassini was about 1.5 million kilometers (900,000 miles) from Saturn. The image scale is about 9 kilometers (6 miles) per pixel.

  17. Piston Ring Pressure Distribution

    NASA Technical Reports Server (NTRS)

    Kuhn, M.

    1943-01-01

    The discovery and introduction of the internal combustion engine has resulted in a very rapid development in machines utilizing the action of a piston. Design has been limited by the internal components of the engine, which has been subjected to ever increasing thermal and mechanical stresses, Of these internal engine components, the piston and piston rings are of particular importance and the momentary position of engine development is not seldom dependent upon the development of both of the components, The piston ring is a well-known component and has been used in its present shape in the steam engine of the last century, Corresponding to its importance, the piston ring has been a rich field for creative activity and it is noteworthy that in spite of this the ring has maintained its shape through the many years. From the many and complicated designs which have been suggested as a packing between piston and cylinder wall hardly one suggestion has remained which does not resemble the original design of cast iron rectangular ring.

  18. Epsilon ring of Uranus

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Voyager 2 acquired this high-resolution image of the epsilon ring of Uranus on Jan. 23, 1986, from a distance of 1.12 million kilometers (690,000 miles). This clear-filter image from Voyager's narrow-angle camera has a resolution of about 10 km (6 mi). The epsilon ring, approximately 100 km (60 mi) wide at this location, clearly shows a structural variation. Visible here are a broad, bright outer component about 40 km (25 mi) wide; a darker middle region of comparable width; and a narrow, bright inner strip about 15 km (9 mi) wide. The epsilon-ring structure seen by Voyager is similar to that observed from the ground with stellar-occultation techniques. This frame represents the first Voyager image that resolves these features within the epsilon ring. The occasional fuzzy splotches on the outer and inner parts of the ring are artifacts left by the removal of reseau marks (used for making measurements on the image). The Voyager project is managed for NASA by the Jet Propulsion Laboratory.

  19. Dynamics of Polar Rings in Oblate and Triaxial Potentials

    NASA Astrophysics Data System (ADS)

    Sparke, Linda S.; Arnaboldi, Magda

    1993-12-01

    A number of early type galaxies show a polar ring of gas, dust and stars lying roughly perpendicular to the apparent major axis of the central galaxy. We have studied the dynamics of a self-gravitating ring which is inclined to the principal planes of a triaxial galactic potential tumbling about its short axis; in a steadily-precessing equilibrium state, the precession rate of the ring in the potential must be equal to the tumbling speed of the triaxial figure. As in an oblate galaxy, both stable and unstable equilibria exist: in the tumbling triaxial potential, there are stable equilibria bending towards the equator, if the ring is light, and towards the pole, at higher ring mass. The former are similar to the `anomalous retrograde orbits', while the latter resemble the stable equilibria for a self-gravitating ring in an oblate potential. Following the time evolution of unstable polar rings shows that in an oblate galaxy potential, even if the ring is not sufficiently massive to be stabilised, self-gravity can still cause the characteristic warp up towards the pole. In the triaxial potential, when the inclination of the polar ring is not such that its precession rate matches the galaxy tumbling speed, the ring can wobble gently in a quasiperiodic manner if it is massive enough, but is disrupted if its mass is too low. Some polar rings are not mirror-symmetric about the center of the galaxy, but have a banana or `C' shaped bend: these distortions may represent axisymmetric bending modes. The sideways displacement of an isolated ring or disk represents a neutrally stable mode of zero frequency; in the central galaxy potential, this can become an m=0 bending mode, which remains discrete when the galaxy is not too massive in relation to the ring. The curvature of the mode is sensitive to the core radius of the galaxy halo. The mode is not spontaneously unstable, so the bending must be excited by an encounter, or during the accretion of ring material. Send preprint

  20. Child sex rings.

    PubMed Central

    Wild, N J; Wynne, J M

    1986-01-01

    Details of 11 child sex rings identified in one working class community were obtained by interviewing investigating police officers and examining health and social services records. The rings contained 14 adult male perpetrators and 175 children aged 6-15 years. Most perpetrators used child ringleaders to recruit victims; others became a "family friend" or obtained a position of authority over children. Secrecy was encouraged and bribery, threats, and peer pressure used to induce participation in sexual activities. Offences reported included fondling, masturbation, pornography, and oral, vaginal, and anal intercourse. Eleven perpetrators were successfully prosecuted; all but one received a sentence of three years or less. Behavioural problems were common among those children who had participated for a long time. Child sex rings are difficult to detect and may be common. Many children are seriously abused as a consequence of them. PMID:3730803

  1. Child sex rings.

    PubMed

    Wild, N J; Wynne, J M

    1986-07-19

    Details of 11 child sex rings identified in one working class community were obtained by interviewing investigating police officers and examining health and social services records. The rings contained 14 adult male perpetrators and 175 children aged 6-15 years. Most perpetrators used child ringleaders to recruit victims; others became a "family friend" or obtained a position of authority over children. Secrecy was encouraged and bribery, threats, and peer pressure used to induce participation in sexual activities. Offences reported included fondling, masturbation, pornography, and oral, vaginal, and anal intercourse. Eleven perpetrators were successfully prosecuted; all but one received a sentence of three years or less. Behavioural problems were common among those children who had participated for a long time. Child sex rings are difficult to detect and may be common. Many children are seriously abused as a consequence of them.

  2. Unidirectional ring lasers

    DOEpatents

    Hohimer, John P.; Craft, David C.

    1994-01-01

    Unidirectional ring lasers formed by integrating nonreciprocal optical elements into the resonant ring cavity. These optical elements either attenuate light traveling in a nonpreferred direction or amplify light traveling in a preferred direction. In one preferred embodiment the resonant cavity takes the form of a circle with an S-shaped crossover waveguide connected to two points on the interior of the cavity such that light traveling in a nonpreferred direction is diverted from the cavity into the crossover waveguide and reinjected out of the other end of the crossover waveguide into the cavity as light traveling in the preferred direction.

  3. GUARD RING SEMICONDUCTOR JUNCTION

    DOEpatents

    Goulding, F.S.; Hansen, W.L.

    1963-12-01

    A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

  4. Unidirectional ring lasers

    DOEpatents

    Hohimer, J.P.; Craft, D.C.

    1994-09-20

    Unidirectional ring lasers formed by integrating nonreciprocal optical elements into the resonant ring cavity is disclosed. These optical elements either attenuate light traveling in a nonpreferred direction or amplify light traveling in a preferred direction. In one preferred embodiment the resonant cavity takes the form of a circle with an S-shaped crossover waveguide connected to two points on the interior of the cavity such that light traveling in a nonpreferred direction is diverted from the cavity into the crossover waveguide and reinjected out of the other end of the crossover waveguide into the cavity as light traveling in the preferred direction. 21 figs.

  5. Satellite Rings Movie

    NASA Image and Video Library

    2000-12-30

    This brief movie clip (of which the release image is a still frame), taken by NASA's Cassini spacecraft as it approached Jupiter, shows the motions, over a 16 hour-period, of two satellites embedded in Jupiter's ring. The moon Adrastea is the fainter of the two, and Metis the brighter. Images such as these will be used to refine the orbits of the two bodies. The movie was made from images taken during a 40-hour sequence of the Jovian ring on December 11, 2000. http://photojournal.jpl.nasa.gov/catalog/PIA02872

  6. Saturn's Rings, the Yarkovsky Effects, and the Ring of Fire

    NASA Technical Reports Server (NTRS)

    Rubincam, David Parry

    2004-01-01

    The dimensions of Saturn's A and B rings may be determined by the seasonal Yarkovsky effect and the Yarkovsky-Schach effect; the two effects confine the rings between approximately 1.68 and approximately 2.23 Saturn radii, in reasonable agreement with the observed values of 1.525 and 2.267. The C ring may be sparsely populated because its particles are transients on their way to Saturn; the infall may create a luminous Ring of Fire around Saturn's equator. The ring system may be young: in the past heat flow from Saturn's interior much above its present value would not permit rings to exist.

  7. Directed self-assembly of proteins into discrete radial patterns

    PubMed Central

    Thakur, Garima; Prashanthi, Kovur; Thundat, Thomas

    2013-01-01

    Unlike physical patterning of materials at nanometer scale, manipulating soft matter such as biomolecules into patterns is still in its infancy. Self-assembled monolayer (SAM) with surface density gradient has the capability to drive biomolecules in specific directions to create hierarchical and discrete structures. Here, we report on a two-step process of self-assembly of the human serum albumin (HSA) protein into discrete ring structures based on density gradient of SAM. The methodology involves first creating a 2-dimensional (2D) polyethylene glycol (PEG) islands with responsive carboxyl functionalities. Incubation of proteins on such pre-patterned surfaces results in direct self-assembly of protein molecules around PEG islands. Immobilization and adsorption of protein on such structures over time evolve into the self-assembled patterns. PMID:23719678

  8. Interaction of multiple co-axial co-rotating vortex rings

    NASA Astrophysics Data System (ADS)

    Qin, Suyang; Liu, Hong; Liu, Xiaoyu; Xiang, Yang

    2015-11-01

    Fish and birds gain hydrodynamic force from a wake of discrete or linked vortex chain, which is the existence form of vortex rings in nature. Vortex rings with the same formation time are generated successively with different time interval by a piston-cylinder arrangement, and the velocity fields are measured using DPIV. The motion of multiple interacting vortex rings is first reported in laboratorial experiments. Besides the most attracting leapfrogging phenomenon, two other phenomena, suction and weak influence, are also clearly presented using the method of Lagrangian coherent structures. Due to the induced effect of wake vortex rings, the formation process of the forming vortex rings is different from that of a single isolated vortex ring, indicating that another distinct timescale exists, together with formation number proposed by Gharib (1998 JFM), determining the mechanisms of vortex rings. When the rear vortex ring leapfrogs, the limiting case is that the rear contracting ring is axis-touching. If an axis-touching ring is further squeezed by the wake vortex, the vortex structure will collapse, which can be explained by Kelvin-Benjamin variational principle. According to this principle, it is impossible for two optimal formed vortex rings to leapfrog. Financial support from the State Key Development Program of Basic Research of China (2014CB744802) is gratefully acknowledged.

  9. Retrieval of Composition and Shadowing Properties of Saturn's Rings from Cassini UVIS Spectra

    NASA Astrophysics Data System (ADS)

    Bradley, E. T.; Colwell, J. E.; Esposito, L. W.

    2017-12-01

    The rings of Saturn consist of centimeter-to-meter sized particles that are covered by a layer of regolith whose grains consist of water ice and some small amount of contaminant that is delivered to the rings through micrometeorite impacts. The mixing of the water ice and meteoritic material is affected by inter-particle collisions and from the meteoritic impacts. Two types of mixtures considered in this investigation are 1) discrete grains of water ice and contaminant and 2) grains of water ice with inclusions of contaminant embedded within the grain. The rough regolith-covered surfaces may result in shadowing between grains that darkens the observed rings reflectance spectra. We compared reflectance spectra of the rings at far ultraviolet wavelengths taken by the Cassini UVIS to models of the rings that include a shadowing function with both types of mixtures and with different contaminant materials. One contaminant that we used was the dark material of Comet 67P, where we retrieved the single scattering albedo at UVIS wavelengths from reflectance spectra measured by the ALICE spectrograph on the Rosetta spacecraft. We compared the reflectance over a range of phase angles with a Hapke model that included macroscopic roughness in order to account for shadowing in the Comet 67P material. We retrieved the ring particle albedo at discrete radial regions in the rings using reflectance spectra over a wide range of phase angles. We corrected the retrieved ring particle albedo for roughness using the shadowing function and then compared the "smooth" ring particle albedo to compositional models. We found that a two-component discrete grain model consisting of greater than ninety percent water ice and contaminant from either Triton tholin or material spectrally similar to Comet 67P were indistinguishable when compared to the UVIS spectra. This suggests a common darkening material and/or processing between the rings and Comet 67P.

  10. Making Molecular Borromean Rings

    ERIC Educational Resources Information Center

    Pentecost, Cari D.; Tangchaivang, Nichol; Cantrill, Stuart J.; Chichak, Kelly S.; Peters, Andrea J.; Stoddart, Fraser J.

    2007-01-01

    A procedure that requires seven 4-hour blocks of time to allow undergraduate students to prepare the molecular Borromean rings (BRs) on a gram-scale in 90% yield is described. The experiment would serve as a nice capstone project to culminate any comprehensive organic laboratory course and expose students to fundamental concepts, symmetry point…

  11. Ring of Stellar Death

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image from NASA's Spitzer Space Telescope shows a dying star (center) surrounded by a cloud of glowing gas and dust. Thanks to Spitzer's dust-piercing infrared eyes, the new image also highlights a never-before-seen feature -- a giant ring of material (red) slightly offset from the cloud's core. This clumpy ring consists of material that was expelled from the aging star.

    The star and its cloud halo constitute a 'planetary nebula' called NGC 246. When a star like our own Sun begins to run out of fuel, its core shrinks and heats up, boiling off the star's outer layers. Leftover material shoots outward, expanding in shells around the star. This ejected material is then bombarded with ultraviolet light from the central star's fiery surface, producing huge, glowing clouds -- planetary nebulas -- that look like giant jellyfish in space.

    In this image, the expelled gases appear green, and the ring of expelled material appears red. Astronomers believe the ring is likely made of hydrogen molecules that were ejected from the star in the form of atoms, then cooled to make hydrogen pairs. The new data will help explain how planetary nebulas take shape, and how they nourish future generations of stars.

    This image composite was taken on Dec. 6, 2003, by Spitzer's infrared array camera, and is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

  12. PSSC Turbo Ring Flinger

    NASA Astrophysics Data System (ADS)

    McAlexander, Aaron

    2005-12-01

    This is a description of an inexpensive version of the Thompson's jumping ring demonstration apparatus, which provides for a spectacular demonstration of Lenz's law. The device has the additional capability of being used to demonstrate the opposing nature of inductive and capacitive reactance.

  13. Rings In Between

    NASA Image and Video Library

    2011-12-05

    Saturn rings lie between a pair of moons in this view from NASA Cassini spacecraft that features Mimas and Prometheus. Mimas is the more noticeable of the two moons at top left, Prometheus is near the center of image and closest to Cassini.

  14. Flushing Ring for EDM

    NASA Technical Reports Server (NTRS)

    Earwood, L.

    1985-01-01

    Removing debris more quickly lowers cutting time. Operation, cutting oil and pressurized air supplied to ring placed around workpiece. Air forces oil through small holes and agitates oil as it flows over workpiece. High flow rate and agitation dislodge and remove debris. Electrical discharge removes material from workpiece faster.

  15. Reading, Writing, and Rings!

    ERIC Educational Resources Information Center

    Aschbacher, Pamela; Li, Erika; Hammon, Art

    2008-01-01

    "Reading, Writing, and Rings!" was created by a team of elementary teachers, literacy experts, and scientists in order to integrate science and literacy. These free units bring students inside NASA's Cassini-Huygens mission to Saturn. The authors--a science teacher and education outreach specialist and two evaluators of educational programs--have…

  16. Ring laser scatterometer

    DOEpatents

    Ackermann, Mark; Diels, Jean-Claude

    2005-06-28

    A scatterometer utilizes the dead zone resulting from lockup caused by scatter from a sample located in the optical path of a ring laser at a location where counter-rotating pulses cross. The frequency of one pulse relative to the other is varied across the lockup dead zone.

  17. Rings from Close Encounters

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-09-01

    Weve recently discovered narrow sets of rings around two minor planets orbiting in our solar system. How did these rings form? A new study shows that they could be a result of close encounters between the minor planets and giants like Jupiter or Neptune.Unexpected Ring SystemsPositions of the centaurs in our solar system (green). Giant planets (red), Jupiter trojans (grey), scattered disk objects (tan) and Kuiper belt objects (blue) are also shown. [WilyD]Centaurs are minor planets in our solar system that orbit between Jupiter and Neptune. These bodies of which there are roughly 44,000 with diameters larger than 1 km have dynamically unstable orbits that cross paths with those of one or more giant planets.Recent occultation observations of two centaurs, 10199 Chariklo and 2060 Chiron, revealed that these bodies both host narrow ring systems. Besides our four giant planets, Chariklo and Chiron are the only other bodies in the solar system known to have rings. But how did these rings form?Scientists have proposed several models, implicating collisions, disruption of a primordial satellite, or dusty outgassing. But a team of scientists led by Ryuki Hyodo (Paris Institute of Earth Physics, Kobe University) has recently proposed an alternative scenario: what if the rings were formed from partial disruption of the centaur itself, after it crossed just a little too close to a giant planet?Tidal Forces from a GiantHyodo and collaborators first used past studies of centaur orbits to estimate that roughly 10% of centaurs experience close encounters (passing within a distance of ~2x the planetary radius) with a giant planet during their million-year lifetime. The team then performed a series of simulations of close encounters between a giant planet and a differentiated centaur a body in which the rocky material has sunk to form a dense silicate core, surrounded by an icy mantle.Some snapshots of simulation outcomes (click for a closer look!) for different initial states of

  18. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

  19. Analytical and experimental studies of natural vibrations modes of ring-stiffened truncated-cone shells with variable theoretical ring fixity

    NASA Technical Reports Server (NTRS)

    Naumann, E. C.; Catherines, D. S.; Walton, W. C., Jr.

    1971-01-01

    Experimental and analytical investigations of the vibratory behavior of ring-stiffened truncated-cone shells are described. Vibration tests were conducted on 60 deg conical shells having up to four ring stiffeners and for free-free and clamped-free edge constraints and 9 deg conical shells, for two thicknesses, each with two angle rings and for free-free, free-clamped, and clamped-clamped edge constraints. The analytical method is based on linear thin shell theory, employing the Rayleigh-Ritz method. Discrete rings are represented as composed of one or more segments, each of which is a short truncated-cone shell of uniform thickness. Equations of constraint are used to join a ring and shell along a circumferential line connection. Excellent agreement was obtained for comparisons of experimental and calculated frequencies.

  20. Distributed Relaxation for Conservative Discretizations

    NASA Technical Reports Server (NTRS)

    Diskin, Boris; Thomas, James L.

    2001-01-01

    A multigrid method is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work that is a small (less than 10) multiple of the operation count in one target-grid residual evaluation. The way to achieve this efficiency is the distributed relaxation approach. TME solvers employing distributed relaxation have already been demonstrated for nonconservative formulations of high-Reynolds-number viscous incompressible and subsonic compressible flow regimes. The purpose of this paper is to provide foundations for applications of distributed relaxation to conservative discretizations. A direct correspondence between the primitive variable interpolations for calculating fluxes in conservative finite-volume discretizations and stencils of the discretized derivatives in the nonconservative formulation has been established. Based on this correspondence, one can arrive at a conservative discretization which is very efficiently solved with a nonconservative relaxation scheme and this is demonstrated for conservative discretization of the quasi one-dimensional Euler equations. Formulations for both staggered and collocated grid arrangements are considered and extensions of the general procedure to multiple dimensions are discussed.

  1. Formation of lunar basin rings

    NASA Technical Reports Server (NTRS)

    Hodges, C. A.; Wilhelms, D. E.

    1978-01-01

    The outer rings of impact basins are interpreted as the bounding rings of the excavated basin cavities analogous to Copernicus-type crater rim crests. It is suggested that the inner rings are strata from depth uplifted during excavation of the transient cavity. Spacing relations and morphology appear to indicate a transition from central peaks to rings but not from terraces to rings. Evidence related to terrestrial craters with rings or peaks produced by meteorite impacts suggests that one or more crater rims may form inside the main, outer crater rim, resulting in nested craters. There is some evidence that peaks grade into inner rings as material is ejected from their cores in progressively larger impacts. Multiply layered materials may produce multiple rings by differential excavation of the layers.

  2. Inorganic glass ceramic slip rings

    NASA Technical Reports Server (NTRS)

    Glossbrenner, E. W.; Cole, S. R.

    1972-01-01

    Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

  3. Atlas and the F Ring

    NASA Image and Video Library

    2007-03-29

    The Cassini spacecraft gazes toward the multiple strands of the ever-changing F ring, also sighting Atlas at its station just beyond the A ring edge. A few faint background stars are visible in the image

  4. A ring galaxy in Canes Venatici and related ring galaxies

    SciTech Connect

    Wakamatsu, Ken-ichi; Nishida, M.T.

    1991-04-01

    A spectroscopic observation was made of a ring-shaped object in Canes Venatici. A bright knot at the edge of the ring has a recession velocity of 10,960 + or - 30 km/s and so is confirmed as an extragalactic object. It shows no sign of nuclear activity but appears to be an H II region of intermediate excitation class. The linear diameter of the ring is 14.2 + or - 0.8 kpc, a typical size for ring galaxies. Recession velocities of several other ring galaxies are also given. 24 refs.

  5. F Ring Bright Core Clumps

    NASA Image and Video Library

    2010-07-20

    Bright clumps of ring material and a fan-like structure appear near the core of Saturn tenuous F ring in this mosaic of images from NASA Cassini spacecraft. Such features suggest the existence of additional objects in the F ring.

  6. Monolithic Unidirectional Planar Ring Laser

    NASA Technical Reports Server (NTRS)

    Nilsson, Alan C.; Byer, Robert L.

    1990-01-01

    Operation based on induced birefringence of stressed laser medium. Unidirectional operation of ring laser made possible by polarization-dependent differential loss induced by some combination of reciprocal and nonreciprocal polarization effects. Concept arises from theoretical analysis of monolithic unidirectional nonplanar ring laser described in article, "Monolithic Unidirectional Nonplanar Ring Laser" (LAR-14146). Potential for use in metrology and spectroscopy.

  7. Uranus: the rings are black.

    PubMed

    Sinton, W M

    1977-11-04

    An upper limit of 0.05 is established for the geometric albedo of the newly discovered rings of Uranus. In view of this very low albedo, the particles of the rings cannot be ice-covered as are those of rings A and B of Saturn.

  8. Uranus Rings and Two Moons

    NASA Image and Video Library

    1999-06-19

    Voyager 2 has discovered two hepherd satellites associated with the rings of Uranus. The two moons, designated 1986U7 and 1986U8, are seen here on either side of the bright epsilon ring; all nine of the known Uranian rings are visible.

  9. DC-Powered Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Farhang, Amiri

    2016-01-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant…

  10. Integrable structure in discrete shell membrane theory

    PubMed Central

    Schief, W. K.

    2014-01-01

    We present natural discrete analogues of two integrable classes of shell membranes. By construction, these discrete shell membranes are in equilibrium with respect to suitably chosen internal stresses and external forces. The integrability of the underlying equilibrium equations is proved by relating the geometry of the discrete shell membranes to discrete O surface theory. We establish connections with generalized barycentric coordinates and nine-point centres and identify a discrete version of the classical Gauss equation of surface theory. PMID:24808755

  11. Geometry of discrete quantum computing

    NASA Astrophysics Data System (ADS)

    Hanson, Andrew J.; Ortiz, Gerardo; Sabry, Amr; Tai, Yu-Tsung

    2013-05-01

    Conventional quantum computing entails a geometry based on the description of an n-qubit state using 2n infinite precision complex numbers denoting a vector in a Hilbert space. Such numbers are in general uncomputable using any real-world resources, and, if we have the idea of physical law as some kind of computational algorithm of the universe, we would be compelled to alter our descriptions of physics to be consistent with computable numbers. Our purpose here is to examine the geometric implications of using finite fields Fp and finite complexified fields \\mathbf {F}_{p^2} (based on primes p congruent to 3 (mod4)) as the basis for computations in a theory of discrete quantum computing, which would therefore become a computable theory. Because the states of a discrete n-qubit system are in principle enumerable, we are able to determine the proportions of entangled and unentangled states. In particular, we extend the Hopf fibration that defines the irreducible state space of conventional continuous n-qubit theories (which is the complex projective space \\mathbf {CP}^{2^{n}-1}) to an analogous discrete geometry in which the Hopf circle for any n is found to be a discrete set of p + 1 points. The tally of unit-length n-qubit states is given, and reduced via the generalized Hopf fibration to \\mathbf {DCP}^{2^{n}-1}, the discrete analogue of the complex projective space, which has p^{2^{n}-1} (p-1)\\,\\prod _{k=1}^{n-1} ( p^{2^{k}}+1) irreducible states. Using a measure of entanglement, the purity, we explore the entanglement features of discrete quantum states and find that the n-qubit states based on the complexified field \\mathbf {F}_{p^2} have pn(p - 1)n unentangled states (the product of the tally for a single qubit) with purity 1, and they have pn + 1(p - 1)(p + 1)n - 1 maximally entangled states with purity zero.

  12. Resonances in Saturn's rings

    NASA Technical Reports Server (NTRS)

    Lissauer, J. J.; Cuzzi, J. N.

    1982-01-01

    The locations and strengths of the major resonances of Saturn's known moons with particles orbiting within Saturn's rings are calculated. The resonant effects of an outer satellite on Saturn's rings is analyzed by Fourier expanding the satellite's potential, and it is found that the forcing at an l:(m-1) resonance depends on the moon's eccentricity to the (l-m) power. As most of Saturn's inner moons are in very nearly circular orbits, only their strongest resonances, with l = m and l = m+1, are calculated. For Mimas, which has a somewhat larger eccentricity, resonances with l = m+2 are also computed. All of the resonances of these forms which are located between Saturn's cloud tops and 2.267 Saturn radii are tabulated, except some of those due to tiny 1980 S28.

  13. Which Ringed Planet...!?

    NASA Astrophysics Data System (ADS)

    2002-12-01

    Don't worry - you are not the only one who thought this was a nice amateur photo of planet Saturn, Lord of the Rings in our Solar System! But then the relative brightness and positions of the moons may appear somewhat unfamiliar... and the ring system does look unusually bright when compared to the planetary disk...?? Well, it is not Saturn, but Uranus , the next giant planet further out, located at a distance of about 3,000 million km, or 20 times the distance between the Sun and the Earth. The photo shows Uranus surrounded by its rings and some of the moons, as they appear on a near-infrared image that was obtained in the K s -band (at wavelength 2.2 µm) with the ISAAC multi-mode instrument on the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory (Chile) . The exposure was made on November 19, 2002 (03:00 hrs UT) during a planetary research programme. The observing conditions were excellent (seeing 0.5 arcsec) and the exposure lasted 5 min. The angular diameter of Uranus is about 3.5 arcsec. The observers at ISAAC were Emmanuel Lellouch and Thérése Encrenaz of the Observatoire de Paris (France) and Jean-Gabriel Cuby and Andreas Jaunsen (both ESO-Chile). The rings The rings of Uranus were discovered in 1977, from observations during a stellar occultation event by astronomer teams at the Kuiper Airborne Observatory (KAO) and the Perth Observatory (Australia). Just before and after the planet moved in front of the (occulted) star, the surrounding rings caused the starlight to dim for short intervals of time. Photos obtained from the Voyager-2 spacecraft in 1986 showed a multitude of very tenuous rings. These rings are almost undetectable from the Earth in visible light. However, on the present VLT near-infrared picture, the contrast between the rings and the planet is strongly enhanced. At the particular wavelength at which this observation was made, the infalling sunlight is almost completely absorbed by gaseous methane present in the planetary atmosphere

  14. Discovery of Jupiter's 'gossamer' ring.

    PubMed

    Showalter, M R; Burns, J A; Cuzzi, J N; Pollack, J B

    Jupiter's ring system has previously been described as being composed of a 'bright' narrow ring and an interior, vertically-extended halo. The one image which reveals this morphology most clearly is Voyager 2's parting shot of the Jupiter system, a wide-angle (WA) view of the ring ansa in forward-scattered light (FDS 20693.02). The bright ring is plainly visible, and the halo appears after slight contrast enhancement. By further enhancement of this image we have discovered an additional ring, which is far fainter than either of the (already faint) components previously identified, extending to a radius of 210,000 km.

  15. Planetary ring dynamics and morphology

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.; Durisen, Richard H.; Shu, Frank H.

    1987-01-01

    Evidence for a moonlet belt in the region between Saturn's close-in moonrings Pandora and Prometheus is discussed. It is argued that little-known observations of magnetospheric electron density by Pioneer 11 imply substantial, ongoing injections of mass into the 2000 km region which surrounds the F ring. A hypothesis is presented that these events result naturally from interparticle collisions between the smaller members of an optically thin belt of moonlets. Also discussed is work on Uranus ring structure and photometry, image processing and analysis of the Jonian ring strucure, photometric and structural studies of the A ring of Saturn, and improvements to an image processing system for ring studies.

  16. Helmet latching and attaching ring

    NASA Technical Reports Server (NTRS)

    Chase, E. W.; Viikinsalo, S. J. (Inventor)

    1970-01-01

    A neck ring releasably secured to a pressurized garment carries an open-ended ring normally in the engagement position fitted into an annular groove and adapted to fit into a complementary annular groove formed in a helmet. Camming means formed on the inner surface at the end of the helmet engages the open-ended ring to retract the same and allow for one motion donning even when the garment is pressurized. A projection on the end of the split ring is engageable to physically retract the split ring.

  17. Discrete space charge affected field emission: Flat and hemisphere emitters

    SciTech Connect

    Jensen, Kevin L., E-mail: kevin.jensen@nrl.navy.mil; Shiffler, Donald A.; Tang, Wilkin

    2015-05-21

    Models of space-charge affected thermal-field emission from protrusions, able to incorporate the effects of both surface roughness and elongated field emitter structures in beam optics codes, are desirable but difficult. The models proposed here treat the meso-scale diode region separate from the micro-scale regions characteristic of the emission sites. The consequences of discrete emission events are given for both one-dimensional (sheets of charge) and three dimensional (rings of charge) models: in the former, results converge to steady state conditions found by theory (e.g., Rokhlenko et al. [J. Appl. Phys. 107, 014904 (2010)]) but show oscillatory structure as they do. Surfacemore » roughness or geometric features are handled using a ring of charge model, from which the image charges are found and used to modify the apex field and emitted current. The roughness model is shown to have additional constraints related to the discrete nature of electron charge. The ability of a unit cell model to treat field emitter structures and incorporate surface roughness effects inside a beam optics code is assessed.« less

  18. A season in Saturn's rings: Cycling, recycling and ring history

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.; Meinke, B. K.; Albers, N.; Sremcevic, M.

    2012-04-01

    Cassini experiments have watched Saturn's ring system evolve before our eyes. Images and occultations show changes and transient events. The rings are a dynamic and complex geophysical system, incompletely modeled as a single-phase fluid. Key Cassini observations: High resolution images show straw, propellers, embedded moonlets, and F ring objects. Multiple UVIS, RSS and VIMS occutlations indicate multimodal ringlet and edge structure, including free and forced modes along with stochastic perturbations that are most likely caused by nearby mass concentrations. Vertical excursions are evident at ring edges and in other perturbed regions. The rings are occasionally hit by meteorites that leave a signature that may last centuries; meteoritic dust pollutes the rings. Temperature, reflectance and transmission spectra are influenced by the dynamical state of the ring particles. Saturn's Equinox 2009: Oblique lighting exposed vertical structure and embedded objects. The rings were the coldest ever. Images inspired new occultation and spectral analysis that show abundant structure in the perturbed regions. The rings are more variable and complex than we had expected prior to this seasonal viewing geometry. Sub-kilometer structure in power spectral analysis: Wavelet analysis shows features in the strongest density waves and at the shepherded outer edge of the B ring. Edges are variable as shown by multiple occultations and occultations of double stars. F ring kittens: 25 features seen in the first 102 occultations show a weak correlation with Prometheus location. We interpret these features as temporary aggregations. Simulation results indicate that accretion must be enhanced to match the kittens' size distribution. Images show that Prometheus triggers the formation of transient objects. Propellers and ghosts: Occulations and images provide evidence for small moonlets in the A, B and C rings. These indicate accretion occurs inside the classical Roche limit. Implications

  19. Discrete input equipment design study

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The study to improve the reliability of the LUT system by discrete input equipment (DIE) is reported. Subjects discussed include: specifications, packaging, aircraft integrated systems, and word formats DIE. It is recommended that maximal use of advanced technology be made, particularly the "know how' developed on the Saturn project.

  20. Ring-rolling design of yaw ring for wind turbines

    NASA Astrophysics Data System (ADS)

    Yeom, Jong-Taek; Kim, Jeoung Han; Hong, Jae-Keun; Lee, Jin Mo; Kim, Kook Joo; Kim, Tae Ok; Kim, Nam Yong; Chang, Hi Sang

    2014-05-01

    In this work, a ring-rolling process to formulate ring-shaped components for a wind turbine is designed by means of a simulation and in an experimental approach. The target of the ring-rolling design is a yaw ring with an outer diameter of approximately 3,130 mm. The ring-rolling design includes the design of the geometry and the optimization of the process variables. A calculation method was used for the geometry design, in this case for the initial billet and the pre-form (or blank) sizes, and for the final rolled ring shape. Also, a deformation map-based approach was utilized to determine the initial ring-rolling temperature and feed rate of the mandrel. A three-dimensional finite element method was used to predict the formation of rolling defects and the deformed shape in the ring-rolled components. The design criteria are to achieve uniform distributions of the strains and temperatures as well as defect-free ring-shaped components. Finally, an optimum process design to obtain a sound large-scale yaw ring without defects is proposed. It is validated by comparisons between the experimental data and the FE analysis results.

  1. New Views of Jupiter's Rings

    NASA Astrophysics Data System (ADS)

    Burns, J. A.

    1998-09-01

    Jupiter's rings are the archetype of ethereal planetary rings (very-low optical-depth bands containing micron-sized "dust"). As a result of much improved observations by Galileo (Ockert-Bell* -- most citations are et al. and Icarus in press* or this meeting) and Keck (de Pater*), we now understand the nature of such rings. The ring has three components: a 104 km-thick toroidal halo (1.4-1.7 RJ; normal optical depth t = 10-6), a thin main ring (1.7-1.8 RJ; t = 10-6), and a pair of exterior gossamer rings (1.8-3.5RJ; t = 10-7). The main ring has patchy ( 20-30 percent) brightness. The ring is reddish and its particles satisfy a -2.5 differential power-law size distribution. Because particle lifetimes are brief, the rings must be continually regenerated, by collisions into parent bodies, which may be unseen or may be the known small ring-moons (Thomas*, Simonelli). The gossamer ring seems to be collisional ejecta derived from the ring-moons Amalthea and Thebe, and evolving inward by Poynting-Robertson drag (Burns). The particles drift through many electromagnetic resonances, clustering around synchronous orbit, which produce jumps in the particles' inclinations (Hamilton). The main ring is probably debris from Adrastea and Metis, which orbit in the equatorial plane. The halo particles are driven vertically by electromagnetic forces, which may be resonant (Schaffer & Burns) or not (Horanyi & Cravens). When halo orbits become highly distorted, particles are lost into Jupiter. Similar faint rings may be attendant to all small, close-in satellites (Showalter).

  2. Tree Rings: Timekeepers of the Past.

    ERIC Educational Resources Information Center

    Phipps, R. L.; McGowan, J.

    One of a series of general interest publications on science issues, this booklet describes the uses of tree rings in historical and biological recordkeeping. Separate sections cover the following topics: dating of tree rings, dating with tree rings, tree ring formation, tree ring identification, sample collections, tree ring cross dating, tree…

  3. High Plains Ring

    NASA Technical Reports Server (NTRS)

    2006-01-01

    18 August 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a ring marking the location of a nearly-filled, nearly-buried impact crater on the martian northern plains. Remnants of bright, seasonal frost occur in some polygonal cracks on the plain.

    Location near: 62.9oN, 96.0oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Spring

  4. Clusters in storage rings

    NASA Astrophysics Data System (ADS)

    Hvelplund, P.; Andersen, J. U.; Hansen, K.

    1999-01-01

    Anions of fullerenes and small metal clusters have been stored in the storage rings ASTRID and ELISA. Decays on a millisecond time scale are due to electron emission from metastable excited states. For the fullerenes the decay curves have been interpreted in terms of thermionic emission quenched by radiative cooling. The stored clusters were heated by a Nd:YAG laser resulting in increased emission rates. With an OPO laser this effect was used to study the wavelength dependence of the absorption of light in hot C60- ion molecules.

  5. Ring currents in azulene

    NASA Astrophysics Data System (ADS)

    Paxton, A. T.; Todorov, T. N.; Elena, A. M.

    2009-11-01

    We propose a self consistent polarisable ion tight binding theory for the study of push-pull processes in aromatic molecules. We find that the method quantitatively reproduces ab initio calculations of dipole moments and polarisability. We apply the scheme in a simulation which solves the time dependent Schrödinger equation to follow the relaxation of azulene from the second excited to the ground states. We observe rather spectacular oscillating ring currents which we explain in terms of interference between the HOMO and LUMO states.

  6. Observational studies of Saturn's rings

    NASA Technical Reports Server (NTRS)

    Porco, Carolyn C.

    1987-01-01

    Several noteworthy phenomena in Saturn's rings were investigated which have until now received an inadequate amount of attention. Among these are the periodic variation of the spokes in the B ring and eccentric features throughout the rings. One of the major discoveries by Voyager was the existence of eccentric features within the predominantly circular rings of Saturn. Several of these nonaxisymmetric features are narrow elliptical rings which share many characteristics with the rings of Uranus. In recent work, two narrow ringlets were added to the list of eccentric features in the rings of Saturn. Voyager imaging and occultation data are now in hand, as well as image-processing software which allows accurate absolute positional measurements to be made in Voyager imaging data. Work is in progress to re-examine this region of Saturn's rings and to study the possibility of a dynamical interaction between the outer B ring edge, the Huygens ringlet and the nearby Mimas 2:1 resonance. An understanding of the kinematics and dynamics of this region promises to yield important clues to a matter of great interest in both theoretical and observation ring studies.

  7. Saturn ring temperature variations with approaching ring equinox

    NASA Astrophysics Data System (ADS)

    Spilker, L.; Leyrat, C.; Flandes, A.; Altobelli, N.; Pilorz, S.; Ferrari, C.; Edgington, S.

    2009-04-01

    Cassini's Composite Infrared Spectrometer (CIRS) has acquired a wide-ranging set of thermal measurements of Saturn's main rings (A, B, C and Cassini Division) at solar elevations ranging from less than one degree to 24 degrees. At Saturn equinox in August the solar elevation angle will reach zero as the sun traverses from the south to north side of the rings. For the data acquired to date, temperatures were retrieved for the lit and unlit rings over a variety of ring geometries that include solar elevation, as well as spacecraft elevation, phase angle and local hour angle. To first order, the largest temperature changes on the lit face of the rings are driven by variations in phase angle while differences in temperature with changing spacecraft elevation and local time are a secondary effect. Decreasing ring temperature with decreasing solar elevation are observed for both the lit and unlit faces of the rings after phase angle and local time effects are taken into account. As the solar elevation continues to decrease, the ring temperatures are decreasing in a non-linear fashion. The difference in temperature between the lit and unlit sides of the rings is decreasing also with decreasing solar elevation. Using ring thermal models developed by Leyrat we extrapolate to the expected minimum ring temperatures at equinox for our planned CIRS ring observations. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA and at CEA Saclay supported by the "Programme National de Planetologie". Copyright 2009 California Institute of Technology. Government sponsorship acknowledged.

  8. Contraceptive vaginal rings.

    PubMed

    Harwood, B; Mishell, D R

    2001-12-01

    Contraceptive vaginal rings (CVRs) contain sex steroids that diffuse through a plastic polymer ring at a constant rate and are absorbed directly through the vaginal epithelium into the systemic circulation. This delivery system provides many advantages over oral contraceptives (OCs), including avoidance of the first-pass effect through the liver, constant serum steroid levels, longer duration of use, and greater bioavailability of the hormones. CVRs containing progestin only are designed for continuous use for 3 to 6 months. Those containing progesterone alone are indicated for use in women who are breastfeeding. Large clinical trials of progestin-containing CVRs demonstrated good efficacy and safety of the CVR, with continuation rates similar to that of OCs. CVRs containing a combination of estrogen and progestin are designed to be used for 1 to 12 months in a cyclic manner similar to OCs, with withdrawal bleeding in the fourth week of each cycle. In clinical trials these CVRs have typical use efficacies similar to OCs, with an acceptable pattern of bleeding.

  9. Ring Image Analyzer

    NASA Technical Reports Server (NTRS)

    Strekalov, Dmitry V.

    2012-01-01

    Ring Image Analyzer software analyzes images to recognize elliptical patterns. It determines the ellipse parameters (axes ratio, centroid coordinate, tilt angle). The program attempts to recognize elliptical fringes (e.g., Newton Rings) on a photograph and determine their centroid position, the short-to-long-axis ratio, and the angle of rotation of the long axis relative to the horizontal direction on the photograph. These capabilities are important in interferometric imaging and control of surfaces. In particular, this program has been developed and applied for determining the rim shape of precision-machined optical whispering gallery mode resonators. The program relies on a unique image recognition algorithm aimed at recognizing elliptical shapes, but can be easily adapted to other geometric shapes. It is robust against non-elliptical details of the image and against noise. Interferometric analysis of precision-machined surfaces remains an important technological instrument in hardware development and quality analysis. This software automates and increases the accuracy of this technique. The software has been developed for the needs of an R&TD-funded project and has become an important asset for the future research proposal to NASA as well as other agencies.

  10. Vortex and Rings

    NASA Image and Video Library

    2014-07-07

    NASA Cassini spacecraft captures three magnificent sights at once: Saturn north polar vortex and hexagon along with its expansive rings. The hexagon, which is wider than two Earths, owes its appearance to the jet stream that forms its perimeter. The jet stream forms a six-lobed, stationary wave which wraps around the north polar regions at a latitude of roughly 77 degrees North. This view looks toward the sunlit side of the rings from about 37 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on April 2, 2014 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 1.4 million miles (2.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 43 degrees. Image scale is 81 miles (131 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18274

  11. A FORTRAN Program for Discrete Discriminant Analysis

    ERIC Educational Resources Information Center

    Boone, James O.; Brewer, James K.

    1976-01-01

    A Fortran program is presented for discriminant analysis of discrete variables. The program assumes discrete, nominal data with no distributional, variance-covariance assumptions. The program handles a maximum of fifty predictor variables and twelve outcome groups. (Author/JKS)

  12. Dark Energy from Discrete Spacetime

    PubMed Central

    Trout, Aaron D.

    2013-01-01

    Dark energy accounts for most of the matter-energy content of our universe, yet current theories of its origin rely on radical physical assumptions such as the holographic principle or controversial anthropic arguments. We give a better motivated explanation for dark energy, claiming that it arises from a small negative scalar-curvature present even in empty spacetime. The vacuum has this curvature because spacetime is fundamentally discrete and there are more ways for a discrete geometry to have negative curvature than positive. We explicitly compute this effect using a variant of the well known dynamical-triangulations (DT) model for quantum gravity. Our model predicts a time-varying non-zero cosmological constant with a current value, in natural units, in agreement with observation. This calculation is made possible by a novel characterization of the possible DT action values combined with numerical evidence concerning their degeneracies. PMID:24312502

  13. Dark energy from discrete spacetime.

    PubMed

    Trout, Aaron D

    2013-01-01

    Dark energy accounts for most of the matter-energy content of our universe, yet current theories of its origin rely on radical physical assumptions such as the holographic principle or controversial anthropic arguments. We give a better motivated explanation for dark energy, claiming that it arises from a small negative scalar-curvature present even in empty spacetime. The vacuum has this curvature because spacetime is fundamentally discrete and there are more ways for a discrete geometry to have negative curvature than positive. We explicitly compute this effect using a variant of the well known dynamical-triangulations (DT) model for quantum gravity. Our model predicts a time-varying non-zero cosmological constant with a current value, [Formula: see text] in natural units, in agreement with observation. This calculation is made possible by a novel characterization of the possible DT action values combined with numerical evidence concerning their degeneracies.

  14. Saturn's Rings and Associated Ring Plasma Cavity: Evidence for Slow Ring Erosion

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Kurth, W. S.; Gurnett, D. A.; Persoon, A. M.; MacDowall, R. J.

    2017-01-01

    We re-examine the radio and plasma wave observations obtained during the Cassini Saturn orbit insertion period, as the spacecraft flew over the northern ring surface into a radial distance of 1.3 Rs (over the C-ring). Voyager era studies suggest the rings are a source of micro-meteoroid generated plasma and dust, with theorized peak impact-created plasma outflows over the densest portion of the rings (central B-ring). In sharp contrast, the Cassini Radio and Plasma Wave System (RPWS) observations identify the presence of a ring-plasma cavity located in the central portion of the B-ring, with little evidence of impact-related plasma. While previous Voyager era studies have predicted unstable ion orbits over the C- ring, leading to field-aligned plasma transport to Saturns ionosphere, the Cassini RPWS observations do not reveal evidence for such instability-created plasma fountains. Given the passive ring loss processes observed by Cassini, we find that the ring lifetimes should extend >10(exp 9) years, and that there is limited evidence for prompt destruction (loss in <100 Myrs).

  15. Observability of discretized partial differential equations

    NASA Technical Reports Server (NTRS)

    Cohn, Stephen E.; Dee, Dick P.

    1988-01-01

    It is shown that complete observability of the discrete model used to assimilate data from a linear partial differential equation (PDE) system is necessary and sufficient for asymptotic stability of the data assimilation process. The observability theory for discrete systems is reviewed and applied to obtain simple observability tests for discretized constant-coefficient PDEs. Examples are used to show how numerical dispersion can result in discrete dynamics with multiple eigenvalues, thereby detracting from observability.

  16. Speckle noise reduction in ultrasound biomedical B-scan images using discrete topological derivative.

    PubMed

    Damodaran, Nedumaran; Ramamurthy, Sivakumar; Velusamy, Sekar; Manickam, Gayathri Kanakaraj

    2012-02-01

    Over three decades, several despeckling techniques have been developed by researchers to reduce the speckle noise inherently present in ultrasound B-scan images without losing the diagnostic information. The topological derivative (TD) is the recently adopted technique in the area of biomedical image processing. In this work, we computed the topological derivative for an appropriate function associated to the ultrasound B-scan image gradient by assigning a diffusion factor k, which indicates the cost endowed to that particular image. In this article, a novel image denoising approach, called discrete topological derivative (DTD) has been implemented. The algorithm has been developed in MATLAB7.1 and tested over 200 ultrasound B-scan images of several organs such as the liver, kidney, gall bladder and pancreas. Further, the performance of the DTD algorithm has been estimated by calculating important performance metrics. A comparative study was carried out between the DTD and the traditional despeckling techniques. The calculated peak signal-to-noise ratio (PSNR) (the ratio between the maximum possible power of a signal and the power of corrupting noise that affects the fidelity of its representation) value of the DTD despeckled liver image is found to be 28 which is comparable with the outperformed speckle reducing anisotropic diffusion (SRAD) filter. SRAD filter is an edge-sensitive diffusion method for speckled images of ultrasonic and radar imaging applications. Canny edge detection and visual inspection of DTD filtered images by the trained radiologist found that the DTD algorithm preserves the hypoechoic and hyperechoic regions resulting in improved diagnosis as well as tissue characterization. Copyright © 2012 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  17. Interference in discrete Wigner functions

    SciTech Connect

    Cormick, Cecilia; Paz, Juan Pablo

    2006-12-15

    We analyze some features of the class of discrete Wigner functions that was recently introduced by Gibbons et al. [Phys. Rev. A 70, 062101 (2004)] to represent quantum states of systems with power-of-prime dimensional Hilbert spaces. We consider ''cat'' states obtained as coherent superpositions of states with positive Wigner function; for such states we show that the oscillations of the discrete Wigner function typically spread over the entire discrete phase space (including the regions where the two interfering states are localized). This is a generic property, which is in sharp contrast with the usual attributes of Wigner functions that makemore » them useful candidates to display the existence of quantum coherence through oscillations. However, it is possible to find subsets of cat states with a natural phase-space representation, in which the oscillatory regions remain localized. We show that this can be done for interesting families of stabilizer states used in quantum error-correcting codes, and illustrate this by analyzing the phase-space representation of the five-qubit error-correcting code.« less

  18. Formation of lunar basin rings

    USGS Publications Warehouse

    Hodges, C.A.; Wilhelms, D.E.

    1978-01-01

    The origin of the multiple concentric rings that characterize lunar impact basins, and the probable depth and diameter of the transient crater have been widely debated. As an alternative to prevailing "megaterrace" hypotheses, we propose that the outer scarps or mountain rings that delineate the topographic rims of basins-the Cordilleran at Orientale, the Apennine at Imbrium, and the Altai at Nectaris-define the transient cavities, enlarged relatively little by slumping, and thus are analogous to the rim crests of craters like Copernicus; inner rings are uplifted rims of craters nested within the transient cavity. The magnitude of slumping that occurs on all scarps is insufficient to produce major inner rings from the outer. These conclusions are based largely on the observed gradational sequence in lunar central uplifts:. from simple peaks through somewhat annular clusters of peaks, peak and ring combinations and double ring basins, culminating in multiring structures that may also include peaks. In contrast, belts of slump terraces are not gradational with inner rings. Terrestrial analogs suggest two possible mechanisms for producing rings. In some cases, peaks may expand into rings as material is ejected from their cores, as apparently occurred at Gosses Bluff, Australia. A second process, differential excavation of lithologically diverse layers, has produced nested experimental craters and is, we suspect, instrumental in the formation of terrestrial ringed impact craters. Peak expansion could produce double-ring structures in homogeneous materials, but differential excavation is probably required to produce multiring and peak-in-ring configurations in large lunar impact structures. Our interpretation of the representative lunar multiring basin Orientale is consistent with formation of three rings in three layers detected seismically in part of the Moon-the Cordillera (basin-bounding) ring in the upper crust, the composite Montes Rook ring in the underlying

  19. Images of Jupiter's Sulfur Ring.

    PubMed

    Pilcher, C B

    1980-01-11

    Images of the ring of singly ionized sulfur encircling Jupiter obtained on two successive nights in April 1979 show that the ring characteristics may change dramatically in approximately 24 hours. On the first night the ring was narrow and confined to the magnetic equator inside Io's orbit. On the second it was confined symmetrically about the centrifugal symmetry surface and showed considerable radial structure, including a "fan" extending to Io's orbit. Many of the differences in the ring on the two nights can be explained in terms of differences in sulfur plasma temperature.

  20. Saturn's Rings Edge-on

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In one of nature's most dramatic examples of 'now-you see-them, now-you-don't', NASA's Hubble Space Telescope captured Saturn on May 22, 1995 as the planet's magnificent ring system turned edge-on. This ring-plane crossing occurs approximately every 15 years when the Earth passes through Saturn's ring plane.

    For comparison, the top picture was taken by Hubble on December 1, 1994 and shows the rings in a more familiar configuration for Earth observers.

    The bottom picture was taken shortly before the ring plane crossing. The rings do not disappear completely because the edge of the rings reflects sunlight. The dark band across the middle of Saturn is the shadow of the rings cast on the planet (the Sun is almost 3 degrees above the ring plane.) The bright stripe directly above the ring shadow is caused by sunlight reflected off the rings onto Saturn's atmosphere. Two of Saturn's icy moons are visible as tiny starlike objects in or near the ring plane. They are, from left to right, Tethys (slightly above the ring plane) and Dione.

    This observation will be used to determine the time of ring-plane crossing and the thickness of the main rings and to search for as yet undiscovered satellites. Knowledge of the exact time of ring-plane crossing will lead to an improved determination of the rate at which Saturn 'wobbles' about its axis (polar precession).

    Both pictures were taken with Hubble's Wide Field Planetary Camera 2. The top image was taken in visible light. Saturn's disk appears different in the bottom image because a narrowband filter (which only lets through light that is not absorbed by methane gas in Saturn's atmosphere) was used to reduce the bright glare of the planet. Though Saturn is approximately 900 million miles away, Hubble can see details as small as 450 miles across.

    The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science

  1. Split ring containment attachment device

    DOEpatents

    Sammel, Alfred G.

    1996-01-01

    A containment attachment device 10 for operatively connecting a glovebag 200 to plastic sheeting 100 covering hazardous material. The device 10 includes an inner split ring member 20 connected on one end 22 to a middle ring member 30 wherein the free end 21 of the split ring member 20 is inserted through a slit 101 in the plastic sheeting 100 to captively engage a generally circular portion of the plastic sheeting 100. A collar potion 41 having an outer ring portion 42 is provided with fastening means 51 for securing the device 10 together wherein the glovebag 200 is operatively connected to the collar portion 41.

  2. Discrete fractional solutions of a Legendre equation

    NASA Astrophysics Data System (ADS)

    Yılmazer, Resat

    2018-01-01

    One of the most popular research interests of science and engineering is the fractional calculus theory in recent times. Discrete fractional calculus has also an important position in fractional calculus. In this work, we acquire new discrete fractional solutions of the homogeneous and non homogeneous Legendre differential equation by using discrete fractional nabla operator.

  3. Embryonic ring closure: Actomyosin rings do the two-step

    PubMed Central

    2016-01-01

    Actomyosin rings drive numerous closure processes, but the mechanisms by which they contract are still poorly understood. In this issue, Xue and Sokac (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201608025) show that actomyosin ring closure during Drosophila melanogaster cellularization uses two steps, only one of which involves Myosin-2. PMID:27799371

  4. Rings Around the Pole

    NASA Image and Video Library

    2005-01-20

    Atmospheric features in Saturn's north polar region are revealed in spectacular detail in this Cassini image, taken in the near infrared spectral region, where methane gas is not very absorbing. The dark shadows of Saturn's rings drape across the planet, creating the illusion of atmospheric bands. Dots of bright clouds give the appearance that this is an active place. The image was taken with the Cassini spacecraft wide angle camera on Dec. 14, 2004, at a distance of 717,800 kilometers (446,100 miles) from Saturn through a filter sensitive to wavelengths of infrared light centered at 939 nanometers. The image scale is about 43 kilometers (27 miles) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA06567

  5. Coiffured black rings

    NASA Astrophysics Data System (ADS)

    Bena, Iosif; Ross, Simon F.; Warner, Nicholas P.

    2014-08-01

    We describe a new type of hair on supersymmetric black string and black ring solutions, which produces the largest known violation of black hole uniqueness, parameterized by an arbitrary function and hence an infinite number of continuous parameters. The new solutions can have non-trivial density profiles for the electric fields along the horizon, and yet have a geometry that is regular, although generically not infinitely differentiable, at the horizon. Both neutral and charged probes can cross the horizon without experiencing divergent forces. We also find restricted examples, parameterized by a few arbitrary continuous parameters, where the charge densities fluctuate but the metric does not and hence is completely differentiable. Our new class of solutions owes its existence to a mechanism reminiscent of the Q-ball: in the simplest examples the metric has more symmetry than the matter that supports it.

  6. Review of the combined contraceptive vaginal ring, NuvaRing.

    PubMed

    Roumen, Frans Jme

    2008-04-01

    The purpose of this review was to test contraceptive efficacy, cycle control, tolerability, and acceptability as found in the non-comparative studies with NuvaRing((R)) by those found in the randomized trials comparing NuvaRing and combined oral contraceptives (COCs). All large non-comparative studies and all relevant randomized controlled trials (RCTs) between NuvaRing and a COC up to and including December 2006 were analyzed. Two large multi-center registration studies, 1 large daily clinical practice study, and 6 RCTs comparing NuvaRing and a COC were identified. The findings in the non-comparative studies were confirmed in the RCTs. Contraceptive efficacy was high showing no significant differences in comparison with the COC; cycle control was good and consistently better than that of the COC; compliance was high and comparable with that of the pill; the incidence of adverse events such as breast tenderness, headache, and nausea was low, but not lower than with the COC despite a halving of the systemic exposure to ethinyl estradiol (EE) with NuvaRing compared with a 30-mug EE-containing COC; the incidence of local and ring-related events was low but higher than with the COC, leading to higher discontinuation rates among NuvaRing users; acceptability was high and comparable between both contraceptives, resulting in a global improvement of sexual function with both methods. After study completion, women using NuvaRing were more likely to continue with their method than women using a COC. The good results with respect to contraceptive efficacy, cycle control, tolerability, and acceptability as achieved with NuvaRing in the large non-comparative registration studies were confirmed in the RCTs comparing NuvaRing with different COCs.

  7. Space-Time Discrete KPZ Equation

    NASA Astrophysics Data System (ADS)

    Cannizzaro, G.; Matetski, K.

    2018-03-01

    We study a general family of space-time discretizations of the KPZ equation and show that they converge to its solution. The approach we follow makes use of basic elements of the theory of regularity structures (Hairer in Invent Math 198(2):269-504, 2014) as well as its discrete counterpart (Hairer and Matetski in Discretizations of rough stochastic PDEs, 2015. arXiv:1511.06937). Since the discretization is in both space and time and we allow non-standard discretization for the product, the methods mentioned above have to be suitably modified in order to accommodate the structure of the models under study.

  8. Simulating the Smallest Ring World of Chariklo

    NASA Astrophysics Data System (ADS)

    Michikoshi, Shugo; Kokubo, Eiichiro

    2017-03-01

    A ring system consisting of two dense narrow rings has been discovered around Centaur Chariklo. The existence of these rings around a small object poses various questions about their origin, stability, and lifetime. In order to understand the nature of Chariklo’s rings, we perform global N-body simulations of the self-gravitating collisional particle rings for the first time. We find that Chariklo should be denser than the ring material in order to avoid the rapid diffusion of the rings. If Chariklo is denser than the ring material, fine spiral structures called self-gravity wakes occur in the inner ring. These wakes accelerate the viscous spreading of the ring significantly and typically occur on timescales of about 100 {years} for m-sized ring particles, which is considerably shorter than the timescales suggested in previous studies. The existence of these narrow rings implies smaller ring particles or the existence of shepherding satellites.

  9. Contraceptive vaginal rings: a review.

    PubMed

    Brache, Vivian; Faundes, Anibal

    2010-11-01

    Development efforts on contraceptive vaginal rings were initiated over 40 years ago based on two principles: the capacity of the vaginal epithelium to absorb steroids and the capacity of elastomers to release these hormones at a nearly constant rate. Numerous models of contraceptive vaginal rings (CVRs) have been studied, but only two have reached the market: NuvaRing, a combined ring that releases etonogestrel (ENG) and ethinylestradiol (EE), and Progering, a progesterone-releasing ring for use in lactating women. The main advantages of CVRs are their effectiveness (similar to or slightly better than the pill), ease of use without the need of remembering a daily routine, user's ability to control initiation and discontinuation, nearly constant release rate allowing for lower doses, greater bioavailability and good cycle control with the combined ring. The main disadvantages are related to the mode of delivery; CVRs may cause vaginal discharge and complaints, ring expulsion is not uncommon, the ring may be felt during coitus and vaginal insertion may be unpleasant for some women. The studies reviewed in this article provide evidence that CVRs are safe, effective and highly acceptable to women. There is no doubt that CVRs offer a new, effective contraceptive option to women, expanding their available choices of hormonal contraception. Copyright © 2010 Elsevier Inc. All rights reserved.

  10. Nardò Ring, Italy

    NASA Image and Video Library

    2008-04-08

    The Nardò Ring is a striking visual feature from space, and astronauts have photographed it several times. The Ring is a race car test track in Italy. This image was acquired by NASA Terra satellite on August 17. 2007.

  11. Biomechanics of Corneal Ring Implants

    PubMed Central

    2015-01-01

    Purpose: To evaluate the biomechanics of corneal ring implants by providing a related mathematical theory and biomechanical model for the treatment of myopia and keratoconus. Methods: The spherical dome model considers the inhomogeneity of the tunica of the eye, dimensions of the cornea, lamellar structure of the corneal stroma, and asphericity of the cornea. It is used in this study for calculating a strengthening factor sf for the characterization of different ring-shaped corneal implant designs. The strengthening factor is a measure of the amount of strengthening of the cornea induced by the implant. Results: For ring segments and incomplete rings, sf = 1.0, which indicates that these implants are not able to strengthen the cornea. The intracorneal continuous complete ring (MyoRing) has a strengthening factor of up to sf = 3.2. The MyoRing is, therefore, able to strengthen the cornea significantly. Conclusions: The result of the presented biomechanical analysis of different ring-shaped corneal implant designs can explain the different postoperative clinical results of different implant types in myopia and keratoconus. PMID:26312619

  12. Running Rings Around the Web.

    ERIC Educational Resources Information Center

    McDermott, Irene E.

    1999-01-01

    Describes the development and current status of WebRing, a service that links related Web sites into a central hub. Discusses it as a viable alternative to other search engines and examines issues of free speech, use by the business sector, and implications for WebRing after its purchase by Yahoo! (LRW)

  13. Uranus Rings in False Color

    NASA Image and Video Library

    1996-01-29

    This false-color view of the rings of Uranus was made from images taken by NASA Voyager 2 on Jan. 21, 1986. All nine known rings are visible here; the somewhat fainter, pastel lines seen between them are contributed by the computer enhancement. http://photojournal.jpl.nasa.gov/catalog/PIA00033

  14. Inflatable Rings For Temporary Sealing

    NASA Technical Reports Server (NTRS)

    Lesh, Paul L.; Richards, Cuyler H.

    1992-01-01

    Inflatable rings seal joint. After inflation, space pressurized to test for leakage through joint. Rings protect surface of aperture from contact with metal structure of plug, and accommodate out-of-roundness and irregular surface contours without leaking. Pressure seal requires no preparation or cleanup.

  15. How Jupiter's Ring Was Discovered.

    ERIC Educational Resources Information Center

    Elliot, James; Kerr, Richard

    1985-01-01

    "Rings" (by astronomer James Elliot and science writer Richard Kerr) is a nontechnical book about the discovery and exploration of ring systems from the time of Galileo to the era of the Voyager spacecraft. One of this book's chapters is presented. (JN)

  16. The Search for Ringed Exoplanets

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-04-01

    Are planetary rings as common in our galaxy as they are in our solar system? A new study demonstrates how we might search for ringed exoplanets and then possibly finds one!Saturns Elsewhere?Artists illustration of the super ring system around exoplanet J1407b. This is the only exoplanet weve found with rings, but its not at all like Saturn. [Ron Miller]Our solar system is filled with moons and planetary rings, so it stands to reason that exoplanetary systems should exhibit the same features. But though weve been in the planet-hunting game for decades, weve only found one exoplanet thats surrounded by a ring system. Whats more, that system J1407b has enormous rings that are vastly different from the modest, Saturn-like rings that we might expect to be more commonplace.Have we not discovered ringed exoplanets just because theyre hard to identify? Or is it because theyre not out there? A team of scientists led by Masataka Aizawa (University of Tokyo) has set out to answer this question by conducting a systematic search for rings around long-period planet candidates.The transit light curve of KIC 10403228, shown with three models: the best-fitting planet-only model (blue) and the two best-fitting planet+ring models (green and red). [Aizawa et al. 2017]The Hunt BeginsWhy long-period planets? Rings are expected to be unstable as the planet gets closer to the central star. Whats more, the planet needs to be far enough away from the stars warmth for the icy rings to exist. The authors therefore select from the collection of candidate transiting planets 89 long-period candidates that might be able to host rings.Aizawa and collaborators then fit single-planet models (with no rings) to the light curves of these planets and search for anomalies curves that arent fit well by these standard models. Particularly suspicious characteristics include a long ingress/egress as the planet moves across the face of the star, and asymmetry of the transit shape.After applying a series of

  17. Advances in microbicide vaginal rings.

    PubMed

    Malcolm, R Karl; Edwards, Karen-Leigh; Kiser, Patrick; Romano, Joseph; Smith, Thomas J

    2010-12-01

    Vaginal ring devices capable of providing sustained/controlled release of incorporated actives are already marketed for steroidal contraception and estrogen replacement therapy. In recent years, there has been considerable interest in developing similar ring devices for the administration of microbicidal compounds to prevent vaginal HIV transmission. Intended to be worn continuously, such coitally independent microbicide rings are being developed to maintain effective vaginal microbicide concentrations over many weeks or months, thereby overcoming issues around timing of product application, user compliance and acceptability associated with more conventional semi-solid formulations. In this article, an overview of vaginal ring technologies is presented, followed by a review of recent advances and issues pertaining to their application for the delivery of HIV microbicides. This article forms part of a special supplement on presentations covering intravaginal rings, based on the symposium "Trends in Microbicide Formulations", held on 25 and 26 January 2010, Arlington, VA. Copyright © 2010 Elsevier B.V. All rights reserved.

  18. Discrete Control of Continuous Processes.

    DTIC Science & Technology

    1981-11-01

    80-30 SEP 81 6. PERFORMING O1G. REPORT NUMBER LIDS-FR-I 165 7 AUTHOR(s) 8. CONTRACT OR GRANT NUMAER(s) Timothy L. Johnson and Martin E. Kaliski F49620...Room 35-205B Cambridge, Massachusetts 02139 Acting Contract Monitor: Dr. Bernard Epstein Principal Investigators: Timothy L. Johnson, Visiting Research...formalized the notion of a discrete- time coder and have exhibited canonical structures S. Raney , G., "Sequential Functions," Assoc. for three classes of

  19. Ring Buffered Network Bus

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This report describes the research effort to demonstrate the integration of a data sharing technology, Ring Buffered Network Bus, in development by Dryden Flight Research Center, with an engine simulation application, the Java Gas Turbine Simulator, in development at the University of Toledo under a grant from the Glenn Research Center. The objective of this task was to examine the application of the RBNB technologies as a key component in the data sharing, health monitoring and system wide modeling elements of the NASA Aviation Safety Program (AVSP) [Golding, 1997]. System-wide monitoring and modeling of aircraft and air safety systems will require access to all data sources which are relative factors when monitoring or modeling the national airspace such as radar, weather, aircraft performance, engine performance, schedule and planning, airport configuration, flight operations, etc. The data sharing portion of the overall AVSP program is responsible for providing the hardware and software architecture to access and distribute data, including real-time flight operations data, among all of the AVSP elements. The integration of an engine code capable of numerically "flying" through recorded flight paths and weather data using a software tool that allows for distributed access of data to this engine code demonstrates initial steps toward building a system capable of monitoring and modeling the National Airspace.

  20. Particle properties and processes in Uranus' rings

    NASA Technical Reports Server (NTRS)

    Esposito, L. W.; Brahic, A.; Burns, J. A.; Marouf, Essam A.

    1991-01-01

    The particle properties and processes in the Uranian rings are analyzed from Voyager observations and ground-based data. Occultation observations of the epsilon ring are interpreted to yield an effective size of the ring particles that exceeds 70 cm, a surface mass density that exceeds 80 g/sq cm, and a ring vertical thickness greater than tens of meters for solid ice particles. The particles forming the classic rings are dark and gray, with albedo of 0.014 +/-0.004. It is argued that the small amount of dust that exists in the classical rings and between the rings in bands is created by erosion of ring particles and unseen satellites resulting from collisions and micrometeoroid bombardment. As proposed for regions of the other known ring systems, new ring material can be continually created by the destruction of small moons near the rings, which may explain the youthful appearance of the Uranian rings.

  1. Glittering Trail in Saturn F Ring

    NASA Image and Video Library

    2012-04-23

    One of the glittering trails caused by small objects punching through Saturn F ring is highlighted in this image from NASA Cassini spacecraft. These trails show how the F ring, the outermost of Saturn main rings, is constantly changing.

  2. Modeling piston-ring dynamics, blowby, and ring-twist effects

    SciTech Connect

    Tian, T.; Noordzij, L.B.; Wong, V.W.

    1996-12-31

    A ring-dynamics and gas-flow model has been developed to study ring/groove contact, blowby, and the influence of ring static twist, keystone ring/groove configurations, and other piston and ring parameters. The model is developed for a ring pack with three rings. The dynamics of the top two rings and the gas pressures in the regions above the oil control ring are simulated. Distributions of oil film thickness and surface roughness on the groove and ring surfaces are assumed in the model to calculate the forces generated by the ring/groove contact. Ring static and dynamic twists are considered as well as differentmore » keystone ring/groove configurations. Ring dynamics and gas flows are coupled in the formulation and an implicit scheme is implemented, enabling the model to resolve detailed events such as ring flutter. Studies on a spark ignition engine found that static twist or, more generally speaking, the relative angle between rings and their grooves, has great influence on ring/groove contact characteristics, ring stability, and blowby. Ring flutter is found to occur for the second ring with a negative static twist under normal operating conditions and for the top ring with a negative static twist under high-speed/low-load operating conditions. Studies on a diesel engine show that different keystone ring/groove configurations result in different twist behaviors of the ring that may affect the wear pattern of the keystone ring running surfaces.« less

  3. Stellar Occultations by Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Nicholson, Philip; Hedman, Matthew; French, Richard G.; Ansty, Todd

    2018-04-01

    On 15 September 2017 the Cassini mission came to an end when the spacecraft made a controlled entry into the planet's atmosphere. Over the preceding 13 years the Visual and Infrared Mapping Spectrometer (VIMS) instrument successfully observed over 170 stellar occultations by Saturn's rings, greatly increasing the available data set for high-resolution studies of the rings' structure and dynamics. Ring opening angles, B_\\ast ranged from 1.06° to 74.18°, while spacecraft ranges varied from 220,000 to 3,014,000 km. The effective radial resolution of the data is determined by a combination of Fresnel diffraction, stellar diameter and sampling rate, but is typically 150-300~m. We will briefly review the overall data set, before looking at examples of dynamical studies carried out with it over the past decade. These include modeling the geometry of self-gravity wakes in the A and B rings, evidence for viscous over-stability in the inner A ring, studies of eccentric, inclined and more complex orbital perturbations on the edges of isolated ringlets and narrow gaps, identification of density and bending waves in the C ring driven by both internal oscillations and gravity anomalies in Saturn, and the first reliable estimates of surface mass density in the central B ring.{\\bf References:} French \\etal\\ (2016a, 2016b, 2017), Hedman \\etal\\ (2007, 2010, 2014), Hedman \\& Nicholson (2013, 2014, 2016), Nicholson \\& Hedman (2010, 2016), Nicholson \\etal\\ (2014a, 2014b).

  4. A Discretized Method for Deriving Vortex Impulse from Volumetric Datasets

    NASA Astrophysics Data System (ADS)

    Buckman, Noam; Mendelson, Leah; Techet, Alexandra

    2015-11-01

    Many biological and mechanical systems transfer momentum through a fluid by creating vortical structures. To study this mechanism, we derive a method for extracting impulse and its time derivative from flow fields observed in experiments and simulations. We begin by discretizing a thin-cored vortex filament, and extend the model to account for finite vortex core thickness and asymmetric distributions of vorticity. By solely using velocity fields to extract vortex cores and calculate circulation, this method is applicable to 3D PIV datasets, even with low spatial resolution flow fields and measurement noise. To assess the performance of this analysis method, we simulate vortex rings and arbitrary vortex structures using OpenFOAM computational fluid dynamics software and analyze the wake momentum using this model in order to validate this method. We further examine a piston-vortex experiment, using 3D synthetic particle image velocimetry (SAPIV) to capture velocity fields. Strengths, limitations, and improvements to the framework are discussed.

  5. Comments on collision mechanics in ring systems. [planetary rings

    NASA Technical Reports Server (NTRS)

    Hartmann, W. K.

    1982-01-01

    Collisions within planetary ring systems, especially Saturn's, are discussed. The particles may have coherent icy cores and less coherent granular or frosty surface layers, consistent with thermal eclipse observations. Collisions do not cause catastrophic fragmentation of the particles, although minor surface erosion and reaccretion is possible. Evolution by collisional fragmentation is thus not as important as in the asteroid belt. Models suggest that the fractional number of projectile masses dislodged when solid (or solid-core) projectiles strike solid ice or granular surface layers does not exceed the order of 10 to the minus 7th to minus 9th power. Even at this rate, the half life of ring particles would be less than the age of the solar system in crowded ring regions unless there was very efficient reaccretion. A plausible ring particle model involves solid ice cores with granular surface layers that exchange material by slow erosion and efficient reaccretion; the granular layers protect the cores from rapid erosion.

  6. Ladder supported ring bar circuit

    NASA Technical Reports Server (NTRS)

    Kosmahl, H. G. (Inventor)

    1983-01-01

    An improved slow wave circuit especially useful in backward wave oscillators includes a slow wave circuit in a waveguide. The slow wave circuit is comprised of rings disposed between and attached to respective stubs. The stubs are attached to opposing sidewalls of the waveguide. To the end that opposed, interacting magnetic fields will be established to provide a very high coupling impedance for the slow wave structure, axially orientated bars are connected between rings in alternate spaces and adjacent to the attachment points of stubs. Similarly, axial bars are connected between rings in the spaces which do not include bars and at points adjacent to the attachment of bars.

  7. Researches on the Piston Ring

    NASA Technical Reports Server (NTRS)

    Ehihara, Keikiti

    1944-01-01

    In internal combustion engines, steam engines, air compressors, and so forth, the piston ring plays an important role. Especially, the recent development of Diesel engines which require a high compression pressure for their working, makes, nowadays, the packing action of the piston ring far more important than ever. Though a number of papers have been published in regard to researches on the problem of the piston ring, none has yet dealt with an exact measurement of pressure exerted on the cylinder wall at any given point of the ring. The only paper that can be traced on this subject so far is Mr. Nakagawa's report on the determination of the relative distribution of pressure on the cylinder wall, but the measuring method adopted therein appears to need further consideration. No exact idea has yet been obtained as to how the obturation of gas between the piston and cylinder, the frictional resistance of the piston, and the wear of the cylinder wall are affected by the intensity and the distribution of the radial pressure of the piston ring. Consequently, the author has endeavored, by employing an apparatus of his own invention, to get an exact determination of the pressure distribution of the piston ring. By means of a newly devised ring tester, to which piezoelectricity of quartz was applied, the distribution of the radial pressure of many sample rings on the market was accurately determined. Since many famous piston rings show very irregular pressure distribution, the author investigated and achieved a manufacturing process of the piston ring which will exert uniform pressure on the cylinder wall. Temperature effects on the configuration and on the mean spring power have also been studied. Further, the tests were performed to ascertain how the gas tightness of the piston ring may be affected by the number or spring power. The researches as to the frictional resistance between the piston ring and the cylinder wall were carried out, too. The procedure of study, and

  8. Reflex ring laser amplifier system

    DOEpatents

    Summers, Mark A.

    1985-01-01

    A laser pulse is injected into an unstable ring resonator-amplifier structure. Inside this resonator the laser pulse is amplified, spatially filtered and magnified. The laser pulse is recirculated in the resonator, being amplified, filtered and magnified on each pass. The magnification is chosen so that the beam passes through the amplifier in concentric non-overlapping regions similar to a single pass MOPA. After a number of passes around the ring resonator the laser pulse is spatially large enough to exit the ring resonator system by passing around an output mirror.

  9. SPHERES-RINGS Time Lapse

    NASA Image and Video Library

    2014-07-10

    ISS040-E-059467 (10 July 2014) --- In the International Space Station's Kibo laboratory, European Space Agency astronaut Alexander Gerst and NASA astronaut Reid Wiseman (mostly obscured), both Expedition 40 flight engineers, conduct a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  10. SPHERES-RINGS Time Lapse

    NASA Image and Video Library

    2014-07-10

    ISS040-E-059344 (10 July 2014) --- In the International Space Station’s Kibo laboratory, NASA astronaut Reid Wiseman (left) and European Space Agency astronaut Alexander Gerst, both Expedition 40 flight engineers, conduct a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  11. SPHERES-RINGS Time Lapse

    NASA Image and Video Library

    2014-07-10

    ISS040-E-059478 (10 July 2014) --- In the International Space Station's Kibo laboratory, European Space Agency astronaut Alexander Gerst (left) and NASA astronaut Reid Wiseman, both Expedition 40 flight engineers, conduct a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  12. Review of the vaginal contraceptive ring (NuvaRing).

    PubMed

    Shimoni, Noa'a; Westhoff, Carolyn

    2008-10-01

    NuvaRing represents another useful contraceptive option for women. The vaginal administration confers benefits and women do not appear to dislike this route of hormone delivery. Efficacy and cycle control are the least comparable to conventional COCs and adverse events are minimal, though vaginal side effects are reported more commonly. Women may find that trying to insert the ring in the clinic will allay any concerns they have with regard to insertion and removal.

  13. Modeling of Electromagnetic Scattering by Discrete and Discretely Heterogeneous Random Media by Using Numerically Exact Solutions of the Maxwell Equations

    NASA Technical Reports Server (NTRS)

    Dlugach, Janna M.; Mishchenko, Michael I.

    2017-01-01

    In this paper, we discuss some aspects of numerical modeling of electromagnetic scattering by discrete random medium by using numerically exact solutions of the macroscopic Maxwell equations. Typical examples of such media are clouds of interstellar dust, clouds of interplanetary dust in the Solar system, dusty atmospheres of comets, particulate planetary rings, clouds in planetary atmospheres, aerosol particles with numerous inclusions and so on. Our study is based on the results of extensive computations of different characteristics of electromagnetic scattering obtained by using the superposition T-matrix method which represents a direct computer solver of the macroscopic Maxwell equations for an arbitrary multisphere configuration. As a result, in particular, we clarify the range of applicability of the low-density theories of radiative transfer and coherent backscattering as well as of widely used effective-medium approximations.

  14. Statistical discrete particle simulation studies

    NASA Technical Reports Server (NTRS)

    Mcdonald, Jeffrey D.

    1992-01-01

    A particle simulation code was developed that is suited to Multiple Instruction Multiple Data multiprocessor computers. The resulting code is designed to be portable between a large class of multiprocessor computer architectures, including hypercubes (e.g., Intel iPSC/860), shared memory machines (e.g., Cray, SGI, DASH), and simple uniprocessors (e.g., SUN, VAX, IBM PC). This code provides a powerful general framework that can be adapted to specific applications, such as thermomechanical modeling, general 3-D geometry support, or visualization support via a codeveloped CPlot data reduction and visualization system. Chemistry models were implemented and validated with comparison to continuum solutions of thermochemically relaxing gas mixtures and with experimental results from the high speed flow about a circular cylinder. Furthermore, the exchange of energy between translational and internal modes was modeled. New models were developed, combining greater efficiency than earlier phenomenological models. They offer greater physical detail by addressing vibrational energy as a discretely distributed quantity.

  15. Multigrid methods for isogeometric discretization

    PubMed Central

    Gahalaut, K.P.S.; Kraus, J.K.; Tomar, S.K.

    2013-01-01

    We present (geometric) multigrid methods for isogeometric discretization of scalar second order elliptic problems. The smoothing property of the relaxation method, and the approximation property of the intergrid transfer operators are analyzed. These properties, when used in the framework of classical multigrid theory, imply uniform convergence of two-grid and multigrid methods. Supporting numerical results are provided for the smoothing property, the approximation property, convergence factor and iterations count for V-, W- and F-cycles, and the linear dependence of V-cycle convergence on the smoothing steps. For two dimensions, numerical results include the problems with variable coefficients, simple multi-patch geometry, a quarter annulus, and the dependence of convergence behavior on refinement levels ℓ, whereas for three dimensions, only the constant coefficient problem in a unit cube is considered. The numerical results are complete up to polynomial order p=4, and for C0 and Cp-1 smoothness. PMID:24511168

  16. Multigrid methods for isogeometric discretization.

    PubMed

    Gahalaut, K P S; Kraus, J K; Tomar, S K

    2013-01-01

    We present (geometric) multigrid methods for isogeometric discretization of scalar second order elliptic problems. The smoothing property of the relaxation method, and the approximation property of the intergrid transfer operators are analyzed. These properties, when used in the framework of classical multigrid theory, imply uniform convergence of two-grid and multigrid methods. Supporting numerical results are provided for the smoothing property, the approximation property, convergence factor and iterations count for V -, W - and F -cycles, and the linear dependence of V -cycle convergence on the smoothing steps. For two dimensions, numerical results include the problems with variable coefficients, simple multi-patch geometry, a quarter annulus, and the dependence of convergence behavior on refinement levels [Formula: see text], whereas for three dimensions, only the constant coefficient problem in a unit cube is considered. The numerical results are complete up to polynomial order [Formula: see text], and for [Formula: see text] and [Formula: see text] smoothness.

  17. Classicality in discrete Wigner functions

    SciTech Connect

    Cormick, Cecilia; Galvao, Ernesto F.; Gottesman, Daniel

    2006-01-15

    Gibbons et al., [Phys. Rev. A 70, 062101 (2004)] have recently defined discrete Wigner functions W to represent quantum states in a Hilbert space with finite dimension. We show that such a class of Wigner functions W can be defined so that the only pure states having non-negative W for all such functions are stabilizer states, as conjectured by Galvao, [Phys. Rev. A 71, 042302 (2005)]. We also show that the unitaries preserving non-negativity of W for all definitions of W in the class form a subgroup of the Clifford group. This means pure states with non-negative W and theirmore » associated unitary dynamics are classical in the sense of admitting an efficient classical simulation scheme using the stabilizer formalism.« less

  18. Discrete modelling of drapery systems

    NASA Astrophysics Data System (ADS)

    Thoeni, Klaus; Giacomini, Anna

    2016-04-01

    Drapery systems are an efficient and cost-effective measure in preventing and controlling rockfall hazards on rock slopes. The simplest form consists of a row of ground anchors along the top of the slope connected to a horizontal support cable from which a wire mesh is suspended down the face of the slope. Such systems are generally referred to as simple or unsecured draperies (Badger and Duffy 2012). Variations such as secured draperies, where a pattern of ground anchors is incorporated within the field of the mesh, and hybrid systems, where the upper part of an unsecured drapery is elevated to intercept rockfalls originating upslope of the installation, are becoming more and more popular. This work presents a discrete element framework for simulation of unsecured drapery systems and its variations. The numerical model is based on the classical discrete element method (DEM) and implemented into the open-source framework YADE (Šmilauer et al., 2010). The model takes all relevant interactions between block, drapery and slope into account (Thoeni et al., 2014) and was calibrated and validated based on full-scale experiments (Giacomini et al., 2012).The block is modelled as a rigid clump made of spherical particles which allows any shape to be approximated. The drapery is represented by a set of spherical particle with remote interactions. The behaviour of the remote interactions is governed by the constitutive behaviour of the wire and generally corresponds to a piecewise linear stress-strain relation (Thoeni et al., 2013). The same concept is used to model wire ropes. The rock slope is represented by rigid triangular elements where material properties (e.g., normal coefficient of restitution, friction angle) are assigned to each triangle. The capabilities of the developed model to simulate drapery systems and estimate the residual hazard involved with such systems is shown. References Badger, T.C., Duffy, J.D. (2012) Drapery systems. In: Turner, A.K., Schuster R

  19. Scalar discrete nonlinear multipoint boundary value problems

    NASA Astrophysics Data System (ADS)

    Rodriguez, Jesus; Taylor, Padraic

    2007-06-01

    In this paper we provide sufficient conditions for the existence of solutions to scalar discrete nonlinear multipoint boundary value problems. By allowing more general boundary conditions and by imposing less restrictions on the nonlinearities, we obtain results that extend previous work in the area of discrete boundary value problems [Debra L. Etheridge, Jesus Rodriguez, Periodic solutions of nonlinear discrete-time systems, Appl. Anal. 62 (1996) 119-137; Debra L. Etheridge, Jesus Rodriguez, Scalar discrete nonlinear two-point boundary value problems, J. Difference Equ. Appl. 4 (1998) 127-144].

  20. Ultraviolet Ring Around the Galaxies

    NASA Image and Video Library

    2010-08-11

    Astronomers have found unexpected rings and arcs of ultraviolet light around a selection of galaxies, four of which are shown here as viewed by NASA and the European Space Agency Hubble Space Telescope.

  1. Vortex rings in Bose gas

    SciTech Connect

    Belyaev, S. T., E-mail: bst@kiae.ru

    2016-06-15

    We consider excitations that exist, in addition to phonons, in the ideal Bose gas at zero temperature. These excitations are vortex rings whose energy spectrum is similar to the roton one in liquid helium.

  2. Propeller Churns the A Ring

    NASA Image and Video Library

    2010-07-08

    This image is part of a set of images obtained by NASA Cassini spacecraft showing a propeller-shaped structure created by a hidden, embedded moon moving through one of Saturn rings. An animation is available at the Photojournal.

  3. Large Double-ringed Basin

    NASA Image and Video Library

    2000-08-05

    Taken about 40 minutes before NASA Mariner 10 made its close approach to Mercury on Sept. 21,1974, this picture shows a large double-ringed basin center of picture located in the planet south polar region

  4. Ring lasers - a brief history

    NASA Astrophysics Data System (ADS)

    Klein, Tony

    2017-10-01

    Used these days in inertial navigation, ring lasers are also used in recording the tiniest variations in the Earth's spin, as well in detecting earthquakes and even the drift of continents. How did it all begin?

  5. Biglobal stability of vortex rings

    NASA Astrophysics Data System (ADS)

    Balakrishna, Naveen; Mathew, Joseph; Samanta, Arnab

    2017-11-01

    Shear layers of low-speed round jets are known to roll up via Kelvin-Helmholtz-like instability into vortex rings, which are then susceptible to azimuthal instability. Using an inviscid linear stability analysis, Widnall and Tsai (1977) found for a thin vortex ring the most unstable azimuthal mode to depend upon the core to ring radius ratio and the core vorticity distribution. In addition, the outside straining field deforms this ring core into the shape of an ellipse. In this work, both the azimuthal and elliptic instabilities are investigated using a linear biglobal stability framework. It is formulated as a standard eigensystem in cylindrical polar coordinates with Fourier decomposition along the azimuthal direction, while Chebyshev collocation points are used in other directions. We explore the role of viscosity on instability, which has not been studied before in detail.

  6. The Composition of Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Clark, R. N.; Cuzzi, J.; Filacchione, G.; Cruikshank, D. P.; Curchin, J. M.; Hoefen, T. M.; Nicholson, P. D.; Hedman, M.; Brown, R. H.; Buratti, B. J.; Baines, K. H.; Nelson, R. M.

    2008-12-01

    The Cassini spacecraft has obtained a unique collection of data about Saturn's rings, as it has observed the rings from 0 to 180 degrees in phase angle, and on both lit and unlit sides. Identification of trace contaminants, especially organic compounds, requires that spectra of the rings be uncontaminated by light from Saturn. The Cassini Visual and Infrared Mapping Spectrometer (VIMS) has acquired 0.35 to 5.1 micron, high spatial resolution spectroscopic data near the shadow of Saturn on the rings where scattered light is at a minimum. At low phase angles, the ring spectra show classic crystalline-ice spectral features except for a contaminant causing a UV absorption. VIMS spectra at 180-degree phase angle are generally flat, with only a weak positive feature at 2.86 microns in spectra of the F-ring. The general transmission decrease is due to large ring particles completely blocking light. The 2.86-micron feature indicates the presence of fine ice dust, where the ice's index of refraction is near 1.0, and light is not refracted or diffracted. There are no indications of interparticle scattering in the VIMS data at any phase angle. The lack of interparticle scattering indicates that the dense A and B rings must be very thin, approaching a monolayer, but rigorous constraints have yet to be modeled. Previous studies used tholins and amorphous carbon for the contaminant causing the UV absorption, but these models display additional absorptions and spectral structure in the near infrared not seen in VIMS data. Clark et al. (Icarus, v193, p372, 2008) modeled the changing blue peak and UV absorber observed on Phoebe, Iapetus, Hyperion, and Dione with amorphous carbon and nano-sized hematite. Nanohematite has muted spectral features compared to larger grained hematite, due to crystal field effects at the surfaces of small grains. Nanohematite has a strong UV absorber that matches the steep UV slope observed in spectra of Saturn's rings and has no strong IR absorptions

  7. Standard Fibre Optic Ring LANs

    NASA Astrophysics Data System (ADS)

    Beale, N. C. L.

    1985-08-01

    The paper begins with a reminder of the particular need for standards in LANs. We then describe the requirements of High Integrity LANs. Current developments in LAN standards are then outlined. It is argued that the requirements of industrial LANs lead ideally to reconfiguring fibre optic rings, for which there are two major emerging standards. These two (IEEE 802.5 and ANSI FDDI) and the Cambridge Ring are discussed and compared. One implementation - the HILAN is discussed.

  8. Ring resonant cavities for spectroscopy

    DOEpatents

    Zare, R.N.; Martin, J.; Paldus, B.A.; Xie, J.

    1999-06-15

    Ring-shaped resonant cavities for spectroscopy allow a reduction in optical feedback to the light source, and provide information on the interaction of both s- and p-polarized light with samples. A laser light source is locked to a single cavity mode. An intracavity acousto-optic modulator may be used to couple light into the cavity. The cavity geometry is particularly useful for Cavity Ring-Down Spectroscopy (CRDS). 6 figs.

  9. Ring resonant cavities for spectroscopy

    DOEpatents

    Zare, Richard N.; Martin, Juergen; Paldus, Barbara A.; Xie, Jinchun

    1999-01-01

    Ring-shaped resonant cavities for spectroscopy allow a reduction in optical feedback to the light source, and provide information on the interaction of both s- and p-polarized light with samples. A laser light source is locked to a single cavity mode. An intracavity acousto-optic modulator may be used to couple light into the cavity. The cavity geometry is particularly useful for Cavity Ring-Down Spectroscopy (CRDS).

  10. Collar nut and thrust ring

    DOEpatents

    Lowery, Guy B.

    1991-01-01

    A collar nut comprises a hollow cylinder having fine interior threads at one end for threadably engaging a pump mechanical seal assembly and an inwardly depending flange at the other end. The flange has an enlarged portion with a groove for receiving an O-ring for sealing against the intrusion of pumpage from the exterior. The enlarged portion engages a thrust ring about the pump shaft for crushing a hard O-ring, such as a graphite O-ring. The hard O-ring seals the interior of the mechanical seal assembly and pump housing against the loss of lubricants or leakage of pumpage. The fine threads of the hollow cylinder provide the mechanical advantage for crushing the hard O-ring evenly and easily with a hand tool from the side of the collar nut rather than by tightening a plurality of bolts from the end and streamlines the exterior surface of the mechanical seal. The collar nut avoids the spatial requirements of bolt heads at the end of a seal and associated bolt head turbulence.

  11. Faint F Ring and Prometheus

    NASA Image and Video Library

    2016-11-21

    Surface features are visible on Saturn's moon Prometheus in this view from NASA's Cassini spacecraft. Most of Cassini's images of Prometheus are too distant to resolve individual craters, making views like this a rare treat. Saturn's narrow F ring, which makes a diagonal line beginning at top center, appears bright and bold in some Cassini views, but not here. Since the sun is nearly behind Cassini in this image, most of the light hitting the F ring is being scattered away from the camera, making it appear dim. Light-scattering behavior like this is typical of rings comprised of small particles, such as the F ring. This view looks toward the unilluminated side of the rings from about 14 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 24, 2016. The view was acquired at a distance of approximately 226,000 miles (364,000 kilometers) from Prometheus and at a sun-Prometheus-spacecraft, or phase, angle of 51 degrees. Image scale is 1.2 miles (2 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20508

  12. Multisoliton solutions of integrable discrete and semi-discrete principal chiral equations

    NASA Astrophysics Data System (ADS)

    Riaz, H. Wajahat A.; ul Hassan, Mahmood

    2018-01-01

    Using a quasideterminant Darboux transformation matrix, we construct soliton solutions of nonlinear integrable discrete and semi-discrete principal chiral equations (PCEs). A Darboux transformation is defined for the matrix solutions of the discrete PCE in terms of matrix solutions to the Lax pair. The solutions are expressed in terms of quasideterminants. By taking continuum limit of one independent discrete variable, we also compute quasideterminant solutions of semi-discrete PCEs. Explicit expressions of one and two soliton solutions of the discrete PCE are obtained from a seed solution by using properties of quasideterminants. It has been shown that the soliton solutions of the discrete system reduce to those of semi-discrete and usual continuum PCEs by applying appropriate limits.

  13. Screw split ring resonator as building block of three-dimensional chiral metamaterials

    NASA Astrophysics Data System (ADS)

    Liao, Yong; Yang, Shizhong; Shi, Lina

    2014-01-01

    We proposed and numerically investigated the influence of spatial topology on the infrared frequency region response of chiral metamaterials based on discrete deformed split ring resonators. Compared with the well studied continuous helix, the proposed metamaterials with discrete topology exhibit broad band chiral electromagnetic response. It is shown that the conversion between left and right circular polarization waves for our model is much broader than the continuous helix model. The observed cross-coupling between electric and magnetic fields results from the chiral electric currents on the resonators due to the broken mirror symmetry. The findings are useful for the design of future real three-dimensional chiral metamaterials with tunable optical response.

  14. Sources and Losses of Ring Current Ions

    NASA Technical Reports Server (NTRS)

    Chen, Sheng-Hsien; Fok, Mei-Ching H.; Angeloupoulos, Vassilis

    2010-01-01

    During geomagnetic quiet times, in-situ measurements of ring current energetic ions (few to few tens of keVs) from THEMIS spacecraft often exhibit multiple ion populations at discrete energies that extend from the inner magnetosphere to the magnetopause at dayside or plasma sheet at nightside. During geomagnetic storm times, the levels of fluxes as well as the mean energies of these ions elevated dramatically and the more smooth distributions in energies and distances during quiet times are disrupted into clusters of ion populations with more confined spatial extends. This reveals local plasma heating processes that might have come into play. Several processes have been proposed. Magnetotail dipolarization, sudden enhancement of field-aligned current, local current disruptions, and plasma waves are possible mechanisms to heat the ions locally as well as strong convections of energetic ions directly from the magnetotail due to reconnections. We will examine two geomagnetic storms on October 11, 2008 and July 22, 2009 to reveal possible heating mechanisms. We will analyze in-situ plasma and magnetic field measurements from THEMIS, GOES, and DMSP for the events to study the ion pitch angle distributions and magnetic field perturbations in the auroral ionosphere and inner magnetosphere where the plasma heating processes occur.

  15. Clumps in the F Ring

    NASA Image and Video Library

    2004-03-12

    Scientists have only a rough idea of the lifetime of clumps in Saturn's rings - a mystery that Cassini may help answer. The latest images taken by the Cassini-Huygens spacecraft show clumps seemingly embedded within Saturn's narrow, outermost F ring. The narrow angle camera took the images on Feb. 23, 2004, from a distance of 62.9 million kilometers (39 million miles). The two images taken nearly two hours apart show these clumps as they revolve about the planet. The small dot at center right in the second image is one of Saturn's small moons, Janus, which is 181 kilometers, (112 miles) across. Like all particles in Saturn's ring system, these clump features orbit the planet in the same direction in which the planet rotates. This direction is clockwise as seen from Cassini's southern vantage point below the ring plane. Two clumps in particular, one of them extended, is visible in the upper part of the F ring in the image on the left, and in the lower part of the ring in the image on the right. Other knot-like irregularities in the ring's brightness are visible in the image on the right. The core of the F ring is about 50 kilometers (31miles) wide, and from Cassini's current distance, is not fully visible. The imaging team enhanced the contrast of the images and magnified them to aid visibility of the F ring and the clump features. The camera took the images with the green filter, which is centered at 568 nanometers. The image scale is 377 kilometers (234 miles) per pixel. NASA's two Voyager spacecraft that flew past Saturn in 1980 and 1981 were the first to see these clumps. The Voyager data suggest that the clumps change very little and can be tracked as they orbit for 30 days or more. No clump survived from the time of the first Voyager flyby to the Voyager 2 flyby nine months later. Scientists are not certain of the cause of these features. Among the theories proposed are meteoroid bombardments and inter-particle collisions in the F ring. http

  16. Accretion in Saturn's F Ring

    NASA Astrophysics Data System (ADS)

    Meinke, B. K.; Esposito, L. W.; Stewart, G.

    2012-12-01

    Saturn's F ring is the solar system's principal natural laboratory for direct observation of accretion and disruption processes. The ring resides in the Roche zone, where tidal disruption competes with self-gravity, which allows us to observe the lifecycle of moonlets. Just as nearby moons create structure at the B ring edge (Esposito et al. 2012) and the Keeler gap (Murray 2007), the F ring "shepherding" moons Prometheus and Pandora stir up ring material and create observably changing structures on timescales of days to decades. In fact, Beurle et al (2010) show that Prometheus makes it possible for "distended, yet gravitationally coherent clumps" to form in the F ring, and Barbara and Esposito (2002) predicted a population of ~1 km bodies in the ring. In addition to the observations over the last three decades, the Cassini Ultraviolet Imaging Spectrograph (UVIS) has detected 27 statistically significant features in 101 occultations by Saturn's F ring since July 2004. Seventeen of those 27 features are associated with clumps of ring material. Two features are opaque in occultation, which makes them candidates for solid objects, which we refer to as Moonlets. The 15 other features partially block stellar signal for 22 m to just over 3.7 km along the radial expanse of the occultation. Upon visual inspection of the occultation profile, these features resemble Icicles, thus we will refer to them as such here. The density enhancements responsible for such signal attenuations are likely due to transient clumping of material, evidence that aggregations of material are ubiquitous in the F ring. Our lengthy observing campaign reveals that Icicles are likely transient clumps, while Moonlets are possible solid objects. Optical depth is an indicator of clumping because more-densely aggregated material blocks more light; therefore, it is natural to imagine moonlets as later evolutionary stage of icicle, when looser clumps of material compact to form a feature that appears

  17. Double acting stirling engine piston ring

    DOEpatents

    Howarth, Roy B.

    1986-01-01

    A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

  18. Plasma deposited rider rings for hot displacer

    DOEpatents

    Kroebig, Helmut L.

    1976-01-01

    A hot cylinder for a cryogenic refrigerator having two plasma spray deposited rider rings of a corrosion and abrasion resistant material provided in the rider ring grooves, wherein the rider rings are machined to the desired diameter and width after deposition. The rider rings have gas flow flats machined on their outer surface.

  19. Discrete/PWM Ballast-Resistor Controller

    NASA Technical Reports Server (NTRS)

    King, Roger J.

    1994-01-01

    Circuit offers low switching loss and automatic compensation for failure of ballast resistor. Discrete/PWM ballast-resistor controller improved shunt voltage-regulator circuit designed to supply power from high-resistance source to low-impedance bus. Provides both coarse discrete voltage levels (by switching of ballast resistors) and continuous fine control of voltage via pulse-width modulation.

  20. Center for Efficient Exascale Discretizations Software Suite

    SciTech Connect

    Kolev, Tzanio; Dobrev, Veselin; Tomov, Vladimir

    2017-08-30

    The CEED Software suite is a collection of generally applicable software tools focusing on the following computational motives: PDE discretizations on unstructured meshes, high-order finite element and spectral element methods and unstructured adaptive mesh refinement. All of this software is being developed as part of CEED, a co-design Center for Efficient Exascale Discretizations, within DOE's Exascale Computing Project (ECP) program.

  1. Covariance control of discrete stochastic bilinear systems

    NASA Technical Reports Server (NTRS)

    Skelton, R. E.; Kherat, S. M.; Yaz, E.

    1991-01-01

    The covariances that certain bilinear stochastic discrete time systems may possess are characterized. An explicit parameterization of all controllers that assign such covariances is given. The state feedback assignability and robustness of the system are discussed from a deterministic point of view. This work extends the theory of covariance control for continuous time bilinear systems to a discrete time setting.

  2. Current Density and Continuity in Discretized Models

    ERIC Educational Resources Information Center

    Boykin, Timothy B.; Luisier, Mathieu; Klimeck, Gerhard

    2010-01-01

    Discrete approaches have long been used in numerical modelling of physical systems in both research and teaching. Discrete versions of the Schrodinger equation employing either one or several basis functions per mesh point are often used by senior undergraduates and beginning graduate students in computational physics projects. In studying…

  3. Methods for discrete solitons in nonlinear lattices.

    PubMed

    Ablowitz, Mark J; Musslimani, Ziad H; Biondini, Gino

    2002-02-01

    A method to find discrete solitons in nonlinear lattices is introduced. Using nonlinear optical waveguide arrays as a prototype application, both stationary and traveling-wave solitons are investigated. In the limit of small wave velocity, a fully discrete perturbative analysis yields formulas for the mode shapes and velocity.

  4. Conservative discretization of the Landau collision integral

    DOE PAGES

    Hirvijoki, E.; Adams, M. F.

    2017-03-28

    Here we describe a density, momentum-, and energy-conserving discretization of the nonlinear Landau collision integral. The method is suitable for both the finite-element and discontinuous Galerkin methods and does not require structured meshes. The conservation laws for the discretization are proven algebraically and demonstrated numerically for an axially symmetric nonlinear relaxation problem using a finite-element implementation.

  5. Discretization vs. Rounding Error in Euler's Method

    ERIC Educational Resources Information Center

    Borges, Carlos F.

    2011-01-01

    Euler's method for solving initial value problems is an excellent vehicle for observing the relationship between discretization error and rounding error in numerical computation. Reductions in stepsize, in order to decrease discretization error, necessarily increase the number of steps and so introduce additional rounding error. The problem is…

  6. Concentric ring flywheel without expansion separators

    DOEpatents

    Kuklo, T.C.

    1999-08-24

    A concentric ring flywheel wherein the adjacent rings are configured to eliminate the need for differential expansion separators between the adjacent rings. This is accomplished by forming a circumferential step on an outer surface of an inner concentric ring and forming a matching circumferential step on the inner surface of an adjacent outer concentric ring. During operation the circumferential steps allow the rings to differentially expand due to the difference in the radius of the rings without the formation of gaps therebetween, thereby eliminating the need for expansion separators to take up the gaps formed by differential expansion. 3 figs.

  7. Concentric ring flywheel without expansion separators

    DOEpatents

    Kuklo, Thomas C.

    1999-01-01

    A concentric ring flywheel wherein the adjacent rings are configured to eliminate the need for differential expansion separators between the adjacent rings. This is accomplished by forming a circumferential step on an outer surface of an inner concentric ring and forming a matching circumferential step on the inner surface of an adjacent outer concentric ring. During operation the circumferential steps allow the rings to differentially expand due to the difference in the radius of the rings without the formation of gaps therebetween, thereby eliminating the need for expansion separators to take up the gaps formed by differential expansion.

  8. Active control of turbomachine discrete tones

    NASA Astrophysics Data System (ADS)

    Fleeter, Sanford

    This paper was directed at active control of discrete frequency noise generated by subsonic blade rows through cancellation of the blade row interaction generated propagating acoustic waves. First discrete frequency noise generated by a rotor and stator in a duct was analyzed to determine the propagating acoustic pressure waves. Then a mathematical model was developed to analyze and predict the active control of discrete frequency noise generated by subsonic blade rows through cancellation of the propagating acoustic waves, accomplished by utilizing oscillating airfoil surfaces to generate additional control propagating pressure waves. These control waves interact with the propagating acoustic waves, thereby, in principle, canceling the acoustic waves and thus, the far field discrete frequency tones. This model was then applied to a fan exit guide vane to investigate active airfoil surface techniques for control of the propagating acoustic waves, and thus the far field discrete frequency tones, generated by blade row interactions.

  9. Discrete frequency slice wavelet transform

    NASA Astrophysics Data System (ADS)

    Yan, Zhonghong; Tao, Ting; Jiang, Zhongwei; Wang, Haibin

    2017-11-01

    This paper introduces a new kind of Time-Frequency Representation (TFR) method called Discrete Frequency Slice Wavelet Transform (DFSWT). It is an improved version of Frequency Slice Wavelet Transform (FSWT). The previous researches on FSWT show that it is a new efficient TFR in an easy way without strict limitation as traditional wavelet theory. DFSWT as well as FSWT are defined directly in frequency domain, and still keep its properties in time-frequency domain as FSWT decomposition, reconstruction and filter design, etc. However, the original signal is decomposed and reconstructed on a Chosen Frequency Domains (CFD) as need of application. CFD means that the decomposition and reconstruction are not completed on all frequency components. At first, it is important to discuss the necessary condition of CFD to reconstruct the original signal. And then based on norm l2, an optimization algorithm is introduced to reconstruct the original signal even accurately. Finally, for a test example, the TFR analysis of a real life signal is shown. Some conclusions are drawn that the concept of CFD is very useful to application, and the DFSWT can become a simple and easy tool of TFR method, and also provide a new idea of low speed sampling of high frequency signal in applications.

  10. On the formation of ring galaxies

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Ting; Jiang, Ing-Guey

    2011-08-01

    The formation scenario of ring galaxies is addressed in this paper. We focus on the P-type ring galaxies presented in Madore, Nelson & Petrillo (2009), particularly on the axis-symmetric ones. Our simulations show that a ring can form through the collision of disc and dwarf galaxies, and the locations, widths, and density contrasts of the ring are well determined. We find that a ring galaxy such as AM 2302-322 can be produced by this collision scenario.

  11. Softened-Stainless-Steel O-Rings

    NASA Technical Reports Server (NTRS)

    Marquis, G. A.; Waters, William I.

    1993-01-01

    In fabrication of O-ring of new type, tube of 304 stainless steel bent around mandril into circle and welded closed into ring. Ring annealed in furnace to make it soft and highly ductile. In this condition, used as crushable, deformable O-ring seal. O-ring replacements used in variety of atmospheres and temperatures, relatively inexpensive, fabricated with minimum amount of work, amenable to one-of-a-kind production, reusable, and environmentally benign.

  12. Archiving of Planetary Ring Data

    NASA Technical Reports Server (NTRS)

    Elliot, James L.

    2001-01-01

    Stellar occultation data provide our only Earth-based means of probing planetary rings at kilometer spatial resolution. The occultation data archive at MIT contains original data and analysis products of stellar occultations by the ring systems of the planets Jupiter, Saturn, Uranus, and Neptune observed by members of the group (and other groups) from 1977 to the present. During this time period, several media have been used to record and store the original and processed data: (1) chart records; (2) printed output, (3) audio reel tape; (4) audio cassette tape; (5) 7-track, 1/2-inch computer tape; (6) 9-track, 1/2-inch computer tape at 800, 1600, and 6250 bpi; (7) NOVA disk platters (2.5 and 5.0 Mbyte); (8) write once optical disks; (9) punched cards; and (10) read-write optical disks. With the rapid change of computer technology over this time period, some of these media have become not only obsolete, but nearly extinct. In particular, it has become nearly impossible to find any facilities that can still read 800 bpi tapes, which contain the only copies of several important data sets for the ring system of Uranus. In particular, we have an extensive ring data collection that includes data sets for the following Uranian ring occultations: U0, U11, U12, U13, U14, U25, U17, and U36.

  13. Instantaneous Frequency and Damping from Transient Ring-Down Data

    SciTech Connect

    Kuether, Robert J.; Brake, Matthew Robert

    2015-10-01

    Broadband impact excitation in structural dynamics is a common technique used to detect and characterize nonlinearities in mechanical systems since it excites many frequencies of a structure at once and can be applied with a variety of boundary conditions. Non-stationary time signals from transient ring-down measurements require time-frequency analysis tools to observe variations in frequency and energy dissipation as the response evolves. This work uses the short-time Fourier transform to estimate the instantaneous frequency and damping ratio from either measured or simulated transient ring-down data. By combining the discrete Fourier transform with an expanding or contracting window function that movesmore » along the time axis, the resulting spectrum is used to estimate the instantaneous frequencies, damping and complex Fourier coefficients. This method is demonstrated on a multi-degree-of-freedom beam with a cubic spring attachment, and investigates the amplitudefrequency dependence in connection to the undamped nonlinear normal modes. A second example shows the results from experiment ring-down response on a beam with a lap joint, and reveals how the system behaves as energy dissipates.« less

  14. Interaction of the BKCa channel gating ring with dendrotoxins

    PubMed Central

    Takacs, Zoltan; Imredy, John P; Bingham, Jon-Paul; Zhorov, Boris S; Moczydlowski, Edward G

    2014-01-01

    Two classes of small homologous basic proteins, mamba snake dendrotoxins (DTX) and bovine pancreatic trypsin inhibitor (BPTI), block the large conductance Ca2+-activated K+ channel (BKCa, KCa1.1) by production of discrete subconductance events when added to the intracellular side of the membrane. This toxin-channel interaction is unlikely to be pharmacologically relevant to the action of mamba venom, but as a fortuitous ligand-protein interaction, it has certain biophysical implications for the mechanism of BKCa channel gating. In this work we examined the subconductance behavior of 9 natural dendrotoxin homologs and 6 charge neutralization mutants of δ-dendrotoxin in the context of current structural information on the intracellular gating ring domain of the BKCa channel. Calculation of an electrostatic surface map of the BKCa gating ring based on the Poisson-Boltzmann equation reveals a predominantly electronegative surface due to an abundance of solvent-accessible side chains of negatively charged amino acids. Available structure-activity information suggests that cationic DTX/BPTI molecules bind by electrostatic attraction to site(s) on the gating ring located in or near the cytoplasmic side portals where the inactivation ball peptide of the β2 subunit enters to block the channel. Such an interaction may decrease the apparent unitary conductance by altering the dynamic balance of open versus closed states of BKCa channel activation gating. PMID:25483585

  15. Traversable wormholes: The Roman ring

    SciTech Connect

    Visser, M.

    1997-04-01

    In this Brief Report I introduce yet another class of geometries for which semiclassical chronology protection theorems are of dubious physical reliability. I consider a {ital {open_quotes}Roman ring{close_quotes}} of traversable wormholes, wherein a number of wormholes are arranged in a ring in such a manner that no subset of wormholes is near chronology violation, though the combined system can be arbitrarily close to chronology violation. I show that (with enough wormholes in the ring) the gravitational vacuum polarization (the expectation value of the quantum stress-energy tensor) can be made arbitrarily small. In particular, the back reaction can be kept arbitrarilymore » small all the way to the {open_quotes}reliability horizon,{close_quotes} so that semiclassical quantum gravity becomes unreliable before the gravitational back reaction becomes large. {copyright} {ital 1997} {ital The American Physical Society}« less

  16. CMB lensing and giant rings

    NASA Astrophysics Data System (ADS)

    Rathaus, Ben; Itzhaki, Nissan

    2012-05-01

    We study the CMB lensing signature of a pre-inationary particle (PIP), assuming it is responsible for the giant rings anomaly that was found recently in the WMAP data. Simulating Planck-like data we find that generically the CMB lensing signal to noise ratio associated with such a PIP is quite small and it would be difficult to cross correlate the temperature giant rings with the CMB lensing signal. However, if the pre-inationary particle is also responsible for the bulk flow measured from the local large scale structure, which happens to point roughly at the same direction as the giant rings, then the CMB lensing signal to noise ratio is fairly significant.

  17. Hawking radiation from an acoustic black hole on an ion ring.

    PubMed

    Horstmann, B; Reznik, B; Fagnocchi, S; Cirac, J I

    2010-06-25

    In this Letter we propose to simulate acoustic black holes with ions in rings. If the ions are rotating with a stationary and inhomogeneous velocity profile, regions can appear where the ion velocity exceeds the group velocity of the phonons. In these regions phonons are trapped like light in black holes, even though we have a discrete field theory and a nonlinear dispersion relation. We study the appearance of Hawking radiation in this setup and propose a scheme to detect it.

  18. Hawking Radiation from an Acoustic Black Hole on an Ion Ring

    SciTech Connect

    Horstmann, B.; Cirac, J. I.; Reznik, B.

    2010-06-25

    In this Letter we propose to simulate acoustic black holes with ions in rings. If the ions are rotating with a stationary and inhomogeneous velocity profile, regions can appear where the ion velocity exceeds the group velocity of the phonons. In these regions phonons are trapped like light in black holes, even though we have a discrete field theory and a nonlinear dispersion relation. We study the appearance of Hawking radiation in this setup and propose a scheme to detect it.

  19. On the definition of discrete hydrodynamic variables

    NASA Astrophysics Data System (ADS)

    Español, Pep; Zúñiga, Ignacio

    2009-10-01

    The Green-Kubo formula for discrete hydrodynamic variables involves information about not only the fluid transport coefficients but also about discrete versions of the differential operators that govern the evolution of the discrete variables. This gives an intimate connection between discretization procedures in fluid dynamics and coarse-graining procedures used to obtain hydrodynamic behavior of molecular fluids. We observed that a natural definition of discrete hydrodynamic variables in terms of Voronoi cells leads to a Green-Kubo formula which is divergent, rendering the full coarse-graining strategy useless. In order to understand this subtle issue, in the present paper we consider the coarse graining of noninteracting Brownian particles. The discrete hydrodynamic variable for this problem is the number of particles within Voronoi cells. Thanks to the simplicity of the model we spot the origin of the singular behavior of the correlation functions. We offer an alternative definition, based on the concept of a Delaunay cell that behaves properly, suggesting the use of the Delaunay construction for the coarse graining of molecular fluids at the discrete hydrodynamic level.

  20. Textures in the C Ring

    NASA Image and Video Library

    2017-07-24

    Recent images of features in Saturn's C ring called "plateaus" have deepened the mystery surrounding them. It turns out that these bright bands have a streaky texture that is very different from the textures of the regions around them. The central feature in this image, called Plateau P1, is found approximately 47,300 miles (76,200 kilometers) from Saturn's center. It is situated amid some undulating structure that characterizes this region of the C ring. None of this structure is well understood. This image reveals three different textures with different kinds of structure. The plateau itself is shot through with elongated streaks, while the brighter parts of the undulating structure have more clumpy texture that is similar to the "straw" seen previously in the A ring, and the dimmer parts of the undulating structure have no apparent texture at all. These textures provide information about different ways in which the ring particles are interacting with each other, though scientists have not yet worked out what it all means. Plateau regions are brighter than their surroundings, and have sharp edges. Recent evidence indicates that the plateaus do not actually contain more material than their surroundings, nor are they different in their chemical composition, which would mean that their greater brightness is likely due to smaller particle sizes. (If a given amount of mass is broken into smaller particles, it will spread out more [i.e., it will have more surface area].) These texture differences may give a clue about processes at the particle level that create the larger structures that Cassini has observed from greater distance throughout its mission at Saturn. These images were taken with the camera moving in sync with the orbits of individual ring particles. Therefore, any elongated structures are truly there in the rings, and are not an artifact of particles moving during the exposure (i.e., smear). This image was taken on June 4, 2017, with the Cassini spacecraft

  1. Discretization of quaternionic continuous wavelet transforms

    NASA Astrophysics Data System (ADS)

    Askari Hemmat, A.; Thirulogasanthar, K.; Krzyżak, A.

    2017-07-01

    A scheme to form a basis and a frame for a Hilbert space of quaternion valued square integrable function from a basis and a frame, respectively, of a Hilbert space of complex valued square integrable functions is introduced. Using the discretization techniques for 2D-continuous wavelet transform of the SIM(2) group, the quaternionic continuous wavelet transform, living in a complex valued Hilbert space of square integrable functions, of the quaternion wavelet group is discretized, and thereby, a discrete frame for quaternion valued Hilbert space of square integrable functions is obtained.

  2. Hairs of discrete symmetries and gravity

    NASA Astrophysics Data System (ADS)

    Choi, Kang Sin; Kim, Jihn E.; Kyae, Bumseok; Nam, Soonkeon

    2017-06-01

    Gauge symmetries are known to be respected by gravity because gauge charges carry flux lines, but global charges do not carry flux lines and are not conserved by gravitational interaction. For discrete symmetries, they are spontaneously broken in the Universe, forming domain walls. Since the realization of discrete symmetries in the Universe must involve the vacuum expectation values of Higgs fields, a string-like configuration (hair) at the intersection of domain walls in the Higgs vacua can be realized. Therefore, we argue that discrete charges are also respected by gravity.

  3. INVITED TALK: Dynamics Of Planetary Rings

    NASA Astrophysics Data System (ADS)

    Tiscareno, Matthew S.

    2011-04-01

    Planetary rings are the only nearby astrophysical disks, and the only disks that have been investigated by spacecraft (especially the Cassini spacecraft orbiting Saturn). Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 1e-7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close-range and in real-time in planetary rings. We will review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We will then review planetary rings by type. The A, B, and C rings of Saturn, plus the Cassini Division, comprise our solar system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are found both at Uranus (where they comprise the main rings entirely) and at Saturn (where they are embedded in the broad disk), and are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally-confined arcs both at Saturn, Jupiter, and Neptune. Finally, every known ring system includes a substantial component of diffuse dusty rings.

  4. Evidence for Break-Up of Clumps in Dynamically Stirred Regions of Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Colwell, J. E.; Sega, D. N.; Jerousek, R. G.; Cooney, J. H.; Esposito, L. W.

    2017-12-01

    Stellar occultations of Saturn's rings observed by the Cassini Ultraviolet Imaging Spectrograph (UVIS) High Speed Photometer (HSP) record stellar brightness seen through the rings as photon counts that are described by Poisson counting statistics in the absence of intervening ring material. The variance in the data increases above counting statistics due to the discrete sizes of the ring particles, with larger particles leading to a larger variance at a given optical depth. We take advantage of the high spatial resolution and multiple viewing geometries of the UVIS occultations to study variations in particle size near and within strongly perturbed regions of Saturn's A ring, in particular the strong first order Lindblad resonances with Janus and the Mimas 5:3 Lindblad resonance and inner vertical resonance. The variance shows changes in the area-weighted particle size between peaks and troughs in the density waves as well as an overall decrease in particle size in the broad "halo" regions that bracket the strong Janus Lindblad resonances in the A ring. In addition we see a decrease in particle size at the location of the Mimas 5:3 bending wave wavetrain itself, and an increase in optical depth at the location of the wave when viewed from high elevation angles out of the ring plane. Taken together, these observations suggest that clumps of particles, perhaps the ubiquitous A ring self-gravity wakes, are disaggregated in the bending wave, even though standard bending wave theory does not predict enhanced collision velocities. We also examine the skewness, a higher order moment of the occultation data, that is diagnostic of asymmetries in the particle size distribution. We use Monte Carlo simulations of occultations to match the first three moments of the data (the signal mean, or equivalently the optical depth, the variance, and the skewness) to illustrate differences in ring particle size in these perturbed regions.

  5. Thomson's Jumping Ring Over a Long Coil

    NASA Astrophysics Data System (ADS)

    Jeffery, Rondo N.; Amiri, Farhang

    2018-03-01

    The classic jumping ring apparatus consists of a coil with an iron core that extends out of the coil. A copper or aluminum ring placed over the iron core jumps upward when AC power is applied to the coil. In this paper we will examine a modified design of the jumping ring apparatus, called the "long-coil design." It allows the ring to jump upward or downward, depending on the starting position of the ring. These features shed significant light on the study of the force that causes the ring to jump.

  6. Cavity-locked ring down spectroscopy

    DOEpatents

    Zare, Richard N.; Paldus, Barbara A.; Harb, Charles C.; Spence, Thomas

    2000-01-01

    Distinct locking and sampling light beams are used in a cavity ring-down spectroscopy (CRDS) system to perform multiple ring-down measurements while the laser and ring-down cavity are continuously locked. The sampling and locking light beams have different frequencies, to ensure that the sampling and locking light are decoupled within the cavity. Preferably, the ring-down cavity is ring-shaped, the sampling light is s-polarized, and the locking light is p-polarized. Transmitted sampling light is used for ring-down measurements, while reflected locking light is used for locking in a Pound-Drever scheme.

  7. The formation of Jupiter's faint rings

    PubMed

    Burns; Showalter; Hamilton; Nicholson; de Pater I; Ockert-Bell; Thomas

    1999-05-14

    Observations by the Galileo spacecraft and the Keck telescope showed that Jupiter's outermost (gossamer) ring is actually two rings circumscribed by the orbits of the small satellites Amalthea and Thebe. The gossamer rings' unique morphology-especially the rectangular end profiles at the satellite's orbit and the enhanced intensities along the top and bottom edges of the rings-can be explained by collisional ejecta lost from the inclined satellites. The ejecta evolves inward under Poynting-Robertson drag. This mechanism may also explain the origin of Jupiter's main ring and suggests that faint rings may accompany all small inner satellites of the other jovian planets.

  8. Rings on strings in excitable media

    NASA Astrophysics Data System (ADS)

    Maucher, Fabian; Sutcliffe, Paul

    2018-02-01

    We study the dynamics and interaction of coaxial vortex rings in the FitzHugh–Nagumo excitable medium. We find that threading vortex rings with a vortex string results in significant qualitative differences in their evolution and interaction. In particular, threading prevents the annihilation of rings in a head-on collision, allows generic ring overtaking, and can even reverse the direction of motion of a ring. We identify that an important mechanism for producing this new behaviour is that threaded vortex rings interact indirectly via induced twisting of the threading vortex string.

  9. Ring Network with VLAN Tag

    NASA Astrophysics Data System (ADS)

    Shimizu, Hiroshi

    The proposed Ring Network with VLAN Tag offers the features of wrapping/steering control functions and 1+1 path protection function, keeping the compatibility with Ethernet media access control scheme. The key technology for “Path concept” is VLAN tag swapping operation. A set of primary and back-up paths is defined between ring nodes, which are distinguished by a flag bit in VLAN tag field. On failure detection, the path is switched within the path set by the tag swapping. Tag swapping at the failure detection node, while tag swapping at the source node achieves staring operation, achieves Wrapping operation. The restoration behavior is almost the same as that of Resilient Packet Ring (RPR). Since the tag swapping control is based on hardware processing, high-speed operation is also expected. Furthermore, because the paths are independently designed from the physical topology, the scheme can be applied to other networks than physical ring networks. The proposed scheme will fit to the path control for next generation Ethernet over WDM system.

  10. Conical O-ring seal

    DOEpatents

    Chalfant, Jr., Gordon G.

    1984-01-01

    A shipping container for radioactive or other hazardous materials which has a conical-shaped closure containing grooves in the conical surface thereof and an O-ring seal incorporated in each of such grooves. The closure and seal provide a much stronger, tighter and compact containment than with a conventional flanged joint.

  11. Conical O-ring seal

    DOEpatents

    Chalfant, G.G. Jr.

    A shipping container for radioactive or other hazardous materials has a conical-shaped closure containing grooves in the conical surface thereof and an O-ring seal incorporated in each of such grooves. The closure and seal provide a much stronger, tighter and compact containment than with a conventional flanged joint.

  12. Barred Ring Galaxy NGC 1291

    NASA Image and Video Library

    2005-05-05

    This ultraviolet image left and visual image right from NASA Galaxy Evolution Explorer is of the barred ring galaxy NGC 1291. The VIS image is dominated by the inner disk and bar. The UV image is dominated by the low surface brightness outer arms.

  13. Alkaline ring complexes in Sudan

    NASA Astrophysics Data System (ADS)

    Vail, J. R.

    An anorogenic petrographic province containing nearly 100 alkaline ring complexes extends across Sudan. These anorogenic complexes are distinct from late-orogenic granite-gabbro, calcalkaline plutonic centres particularly in the eastern part of Sudan, many of which also take the form of ring complexes. The biggest, most closely spaces, and most numerous ring complexes occur in a discontinuous belt of alkali granites and syenites, rarer foid syenites, and associated extrusive trachytes, rhyolites and ignimbrites exposed intermittently across 100 km from the Bayuda Desert and Nile River Valley near Khartoum to northern Kordofan Province and the Nuba Mountains region of central Sudan. These complexes range in age from Ordovician to Jurassic, but show no progressive change in age or distribution pattern other than a tendency to align locally in NW-trending bands, which might reflect zones of weakness in the underlying basement rocks. Mesozoic syenites and alkali granites forming plugs and ring complexes lie in a belt parallel to the coast in the Red Sea Hills of eastern Sudan. In the north-west of the country, alkali granites and foid syenites of Tertiary age crop out in the basement inlier of J. Uweinat, and Mesozoic granites, syenites and foid syenites form igneous plutons in Equatoria Province in the extreme south.

  14. Looking for rings and things

    NASA Astrophysics Data System (ADS)

    Kenworthy, Matthew

    2017-04-01

    It's not often that an astronomical object gets its own dedicated observatory, but as the planet Beta Pictoris b moves in front of its host star, its every move will be watched by bRing, eager to discover more about the planet's Hill sphere, explains Matthew Kenworthy.

  15. Reducing Neuronal Networks to Discrete Dynamics

    PubMed Central

    Terman, David; Ahn, Sungwoo; Wang, Xueying; Just, Winfried

    2008-01-01

    We consider a general class of purely inhibitory and excitatory-inhibitory neuronal networks, with a general class of network architectures, and characterize the complex firing patterns that emerge. Our strategy for studying these networks is to first reduce them to a discrete model. In the discrete model, each neuron is represented as a finite number of states and there are rules for how a neuron transitions from one state to another. In this paper, we rigorously demonstrate that the continuous neuronal model can be reduced to the discrete model if the intrinsic and synaptic properties of the cells are chosen appropriately. In a companion paper [1], we analyze the discrete model. PMID:18443649

  16. Running Parallel Discrete Event Simulators on Sierra

    SciTech Connect

    Barnes, P. D.; Jefferson, D. R.

    2015-12-03

    In this proposal we consider porting the ROSS/Charm++ simulator and the discrete event models that run under its control so that they run on the Sierra architecture and make efficient use of the Volta GPUs.

  17. Comparing the Discrete and Continuous Logistic Models

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2008-01-01

    The solutions of the discrete logistic growth model based on a difference equation and the continuous logistic growth model based on a differential equation are compared and contrasted. The investigation is conducted using a dynamic interactive spreadsheet. (Contains 5 figures.)

  18. Radix Representation of Triangular Discrete Grid System

    NASA Astrophysics Data System (ADS)

    Ben, J.; Li, Y. L.; Wang, R.

    2016-11-01

    Discrete Global Grid Systems (DGGSs) are spatial references that use a hierarchical tessellation of cells to partition and address the entire globe. It provides an organizational structure that permits fast integration between multiple sources of large and variable geospatial data. Although many endeavors have been done to describe certain discrete grid systems, there still lack of a uniform mathematical framework for them. This paper simplifies the planar class I aperture 4 triangular discrete grid system into a hierarchical lattice model which is proved to be a radix system in the complex number plane. Mathematical properties of the radix system reveal the discrete grid system is equivalent to the set of complex numbers with special form. The conclusion provides a potential way to build a uniform mathematical framework of DGGS and can be used to design efficient encoding and spatial operation scheme for DGGS.

  19. The discrete-time compensated Kalman filter

    NASA Technical Reports Server (NTRS)

    Lee, W. H.; Athans, M.

    1978-01-01

    A suboptimal dynamic compensator to be used in conjunction with the ordinary discrete time Kalman filter was derived. The resultant compensated Kalman Filter has the property that steady state bias estimation errors, resulting from modelling errors, were eliminated.

  20. Optimum Energy Extraction from Coherent Vortex Rings Passing Tangentially Over Flexible Plates

    NASA Astrophysics Data System (ADS)

    Pirnia, Alireza; Browning, Emily A.; Peterson, Sean D.; Erath, Byron D.

    2017-11-01

    Coherent vortical structures can incite self-sustained oscillations in flexible membranes. This concept has recently gained interest for energy extraction from ambient environments. In this study the special case of a vortex ring passing tangentially over a cantilevered flexible plate is investigated. This problem is governed by the Kirchhoff-Love plate equation, which can be expressed in terms of a non-dimensional mass parameter of the plate, non-dimensional pressure loading induced by the vortex ring, and a Strouhal (St) number which expresses the duration of pressure loading relative to the period of plate oscillation. For a plate with a fixed mass parameter immersed in a fluid environment, the St number specifies the beam dynamics and the energy exchange process. The aim of this study is to identify the St number corresponding to maximum energy exchange between plates and vortex rings. The energy exchange process between the vortex ring and the plate is investigated over a range of 0.3 discrete and periodic vortex ring loadings, as well as varying vortex ring to plate distances. The optimum value of St number that maximizes energy transfer is reported in each case and an empirical correlation is provided for predictive purposes. Supported by the National Science Foundation (NSF) under Grant No. CBET-1511761, and the Natural Sciences and Engineering Research Council of Canada (NSERC), under Grant No. 05778-2015.

  1. Properties of a metamaterial element: Analytical solutions and numerical simulations for a singly split double ring

    NASA Astrophysics Data System (ADS)

    Shamonin, M.; Shamonina, E.; Kalinin, V.; Solymar, L.

    2004-04-01

    An equivalent circuit, consisting of bulk and distributed elements, is derived for describing the properties of a potential metamaterial element capable of providing negative effective permeability. It is the singly split double ring (SSDR), a special case of the split ring resonator (J. B. Pendry et al., IEEE Trans. Microwave Theory Tech. 47, 2075 (1999)), obtained when the gap capacitance in the inner ring is infinitely large. The variables are the inter-ring voltage and the currents flowing in the inner and outer rings. The excitation is assumed in the form of a spatially constant temporally varying magnetic field. The functions, showing the angular variation of the variables, are found by solving a set of differential equations with boundary conditions imposed at the position of the split. It is shown from the analytical solution that the SSDR can have resonant frequencies in the full spectrum from very low to very high frequencies. It is pointed out in particular that whenever the mean diameter of the ring is equal to an odd multiple of the half wavelength it is always possible to find a set of parameters which will give rise to resonance. As examples the resonant frequencies are determined for eight sets of parameters. Results are also derived by replacing the distributed circuit with a number of discrete circuits. It is finally shown that the results obtained from the equivalent circuit model are in excellent agreement with those derived from the MICRO-STRIPES numerical package which solves Maxwell's equations in the time domain.

  2. High-Speed Ring Bus

    NASA Technical Reports Server (NTRS)

    Wysocky, Terry; Kopf, Edward, Jr.; Katanyoutananti, Sunant; Steiner, Carl; Balian, Harry

    2010-01-01

    The high-speed ring bus at the Jet Propulsion Laboratory (JPL) allows for future growth trends in spacecraft seen with future scientific missions. This innovation constitutes an enhancement of the 1393 bus as documented in the Institute of Electrical and Electronics Engineers (IEEE) 1393-1999 standard for a spaceborne fiber-optic data bus. It allows for high-bandwidth and time synchronization of all nodes on the ring. The JPL ring bus allows for interconnection of active units with autonomous operation and increased fault handling at high bandwidths. It minimizes the flight software interface with an intelligent physical layer design that has few states to manage as well as simplified testability. The design will soon be documented in the AS-1393 standard (Serial Hi-Rel Ring Network for Aerospace Applications). The framework is designed for "Class A" spacecraft operation and provides redundant data paths. It is based on "fault containment regions" and "redundant functional regions (RFR)" and has a method for allocating cables that completely supports the redundancy in spacecraft design, allowing for a complete RFR to fail. This design reduces the mass of the bus by incorporating both the Control Unit and the Data Unit in the same hardware. The standard uses ATM (asynchronous transfer mode) packets, standardized by ITU-T, ANSI, ETSI, and the ATM Forum. The IEEE-1393 standard uses the UNI form of the packet and provides no protection for the data portion of the cell. The JPL design adds optional formatting to this data portion. This design extends fault protection beyond that of the interconnect. This includes adding protection to the data portion that is contained within the Bus Interface Units (BIUs) and by adding to the signal interface between the Data Host and the JPL 1393 Ring Bus. Data transfer on the ring bus does not involve a master or initiator. Following bus protocol, any BIU may transmit data on the ring whenever it has data received from its host. There

  3. F Ring Mini-Jets

    NASA Astrophysics Data System (ADS)

    Attree, N.; Murray, C.; Cooper, N. J.; Williams, G.

    2012-12-01

    Mini-jets are small, (~50 km) linear features observed in Cassini images to be emanating from Saturn's F ring; they are believed to be produced by collisions with a local population of moonlets. An analysis of one such feature, observed over the course of a ~7.5 h sequence as its length changed from ~75 km to ~250 km while it simultaneously appeared to collapse back into the core, supports the collisional theory of their origin [1]. Orbit determination suggests that this mini-jet consisted of ring material displaced by a ~1 m/s collision with a nearby object, resulting in paths relative to the core that are due to a combination of keplerian shear and epicyclic motion. The colliding object itself is likely to be too small to resolve in these images but represents just one member of a population of F ring moonlets. Such a population has been investigated by UVIS occultations [2], and other methods, but generally remains unresolved in Cassini images. Collisional features such as this mini-jet therefore provide an additional tracer for the region's moonlet population. In this talk we will present the results of recent work in measuring and describing a subset of ~350 catalogued mini-jets, applying knowledge gained from the original mini-jet feature. Their distribution in space and time, proximity to Prometheus and evolution are all examined in an effort to place constraints on the properties of the underlying population of colliding objects. References [1] N. O. Attree, C. D. Murray, N. J. Cooper, and G. A. Williams. Detection of low velocity collisions in Saturn's F ring. Ap. J. Lett. (In press). [1] B. K. Meinke, L. W. Esposito, N. Albers, and M. Sremevi. Classification of F ring features observed in cassini UVIS occultations. Icarus, 218(1):545 - 554, 2012.

  4. Discrete mechanics, "time machines" and hybrid systems

    NASA Astrophysics Data System (ADS)

    Elze, Hans-Thomas

    2013-09-01

    Modifying the discrete mechanics proposed by T.D. Lee, we construct a class of discrete classical Hamiltonian systems, in which time is one of the dynamical variables. This includes a toy model of "time machines" which can travel forward and backward in time and which differ from models based on closed timelike curves (CTCs). In the continuum limit, we explore the interaction between such time reversing machines and quantum mechanical objects, employing a recent description of quantum-classical hybrids.

  5. Creative Visualization in Discrete Global Grid System

    NASA Astrophysics Data System (ADS)

    Etemad, K.; Samavati, F.; Sherlock, M. J.

    2016-12-01

    Discrete Global Grid System (DGGS) is a disruptive method for developing digital representation of the Earth. In DGGS, to create a multiresolution representation of the Earth, the surface of the Earth is discretized to a hierarchy of indexed (mostly) regular cells. In this talk, an overview of research projects and recent achievements from my group related to DGGS is provided. This covers example works in large geospatial data processing and streaming, as well as creative visualization and interaction in the context of DGGS.

  6. Nonlinear integrodifferential equations as discrete systems

    NASA Astrophysics Data System (ADS)

    Tamizhmani, K. M.; Satsuma, J.; Grammaticos, B.; Ramani, A.

    1999-06-01

    We analyse a class of integrodifferential equations of the `intermediate long wave' (ILW) type. We show that these equations can be formally interpreted as discrete, differential-difference systems. This allows us to link equations of this type with previous results of ours involving differential-delay equations and, on the basis of this, propose new integrable equations of ILW type. Finally, we extend this approach to pure difference equations and propose ILW forms for the discrete lattice KdV equation.

  7. Discrete Surface Modelling Using Partial Differential Equations

    PubMed Central

    Xu, Guoliang; Pan, Qing; Bajaj, Chandrajit L.

    2009-01-01

    We use various nonlinear partial differential equations to efficiently solve several surface modelling problems, including surface blending, N-sided hole filling and free-form surface fitting. The nonlinear equations used include two second order flows, two fourth order flows and two sixth order flows. These nonlinear equations are discretized based on discrete differential geometry operators. The proposed approach is simple, efficient and gives very desirable results, for a range of surface models, possibly having sharp creases and corners. PMID:19830268

  8. Separable two-dimensional discrete Hartley transform

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.; Poirson, Allen

    1986-01-01

    Bracewell has proposed the Discrete Hartley Transform (DHT) as a substitute for the Discrete Fourier Transform (DFT), particularly as a means of convolution. Here, it is shown that the most natural extension of the DHT to two dimensions fails to be separate in the two dimensions, and is therefore inefficient. An alternative separable form is considered, corresponding convolution theorem is derived. That the DHT is unlikely to provide faster convolution than the DFT is also discussed.

  9. Discrete retardance second harmonic generation ellipsometry.

    PubMed

    Dehen, Christopher J; Everly, R Michael; Plocinik, Ryan M; Hedderich, Hartmut G; Simpson, Garth J

    2007-01-01

    A new instrument was constructed to perform discrete retardance nonlinear optical ellipsometry (DR-NOE). The focus of the design was to perform second harmonic generation NOE while maximizing sample and application flexibility and minimizing data acquisition time. The discrete retardance configuration results in relatively simple computational algorithms for performing nonlinear optical ellipsometric analysis. NOE analysis of a disperse red 19 monolayer yielded results that were consistent with previously reported values for the same surface system, but with significantly reduced acquisition times.

  10. Discrete Event Component Architecture for Modeling Ships

    DTIC Science & Technology

    2010-07-01

    12 vttxtx )()( 00  ),,( 00 vxt 7/14/2010 2010 MOVES Research Summit Mover Event Graph Component 137/14/2010 2010 MOVES Research Summit Mover Manager ...Discrete Event Component Architecture for Modeling Ships Arnie Buss Research Associate Professor MOVES Institute abuss@nps.edu 831-656-7582 http...REPORT DATE JUL 2010 2. REPORT TYPE 3. DATES COVERED 00-00-2010 to 00-00-2010 4. TITLE AND SUBTITLE Discrete Event Component Architecture

  11. Discrete Event Simulation of Distributed Team Communication

    DTIC Science & Technology

    2012-03-22

    DISCRETE EVENT SIMULATION OF DISTRIBUTED TEAM COMMUNICATION THESIS Travis J. Pond, 2nd Lieutenant, USAF AFIT/GSE/ENV/12-M07 DEPARTMENT OF THE AIR...copyright protection in the United States. AFIT/GSE/ENV/12-M07 DISCRETE EVENT SIMULATION OF DISTRIBUTED TEAM COMMUNICATION THESIS Presented to the Faculty...Department of Systems Engineering Graduate School of Engineering and Management Air Force Institute of Technology Air University Air Education and

  12. Ring Current Decay During Northward Turnings of The Interplanetary Magnetic Field

    NASA Astrophysics Data System (ADS)

    Monreal MacMahon, R.; Llop, C.; Miranda, R.

    The ring current formation and energization is thought to be the main consequence of geomagnetic storms and its strength is characterized by the Dst index which evolu- tion satisfies a simple and well-known differential equation introduced by Burton et al. (1975). Since then, several attempts and approaches have been done to study the evolution of the ring current whether introducing discrete values or continuous func- tions for the decay time involved. In this work, we study the character of the recovery phase of magnetic storms in response to well defined northward turnings of the inter- planetary magnetic field using our functional form of the decay time of ring current particles introduced previously.

  13. Discretization of continuous features in clinical datasets.

    PubMed

    Maslove, David M; Podchiyska, Tanya; Lowe, Henry J

    2013-05-01

    The increasing availability of clinical data from electronic medical records (EMRs) has created opportunities for secondary uses of health information. When used in machine learning classification, many data features must first be transformed by discretization. To evaluate six discretization strategies, both supervised and unsupervised, using EMR data. We classified laboratory data (arterial blood gas (ABG) measurements) and physiologic data (cardiac output (CO) measurements) derived from adult patients in the intensive care unit using decision trees and naïve Bayes classifiers. Continuous features were partitioned using two supervised, and four unsupervised discretization strategies. The resulting classification accuracy was compared with that obtained with the original, continuous data. Supervised methods were more accurate and consistent than unsupervised, but tended to produce larger decision trees. Among the unsupervised methods, equal frequency and k-means performed well overall, while equal width was significantly less accurate. This is, we believe, the first dedicated evaluation of discretization strategies using EMR data. It is unlikely that any one discretization method applies universally to EMR data. Performance was influenced by the choice of class labels and, in the case of unsupervised methods, the number of intervals. In selecting the number of intervals there is generally a trade-off between greater accuracy and greater consistency. In general, supervised methods yield higher accuracy, but are constrained to a single specific application. Unsupervised methods do not require class labels and can produce discretized data that can be used for multiple purposes.

  14. Recent advances in discrete dipole approximation

    NASA Astrophysics Data System (ADS)

    Flatau, P. J.

    2012-12-01

    I will describe recent advances and results related to Discrete Dipole Approximation. I will concentrate on Discrete Dipole Scattering (DDSCAT) code which has been jointly developed by myself and Bruce T. Draine. Discussion will concentrate on calculation of scattering and absorption by isolated particles (e.g., dust grains, ice crystals), calculations of scattering by periodic structures with applications to studies of scattering and absorption by periodic arrangement of finite cylinders, cubes, etc), very fast near field calculation, ways to display scattering targets and their composition using three dimensional graphical codes. I will discuss possible extensions. References Flatau, P. J. and Draine, B. T., 2012, Fast near field calculations in the discrete dipole approximation for regular rectilinear grids, Optics Express, 20, 1247-1252. Draine B. T. and Flatau P. J., 2008, Discrete-dipole approximation for periodic targets: theory and tests , J. Opt. Soc. Am. A., 25, 2693-2703. Draine BT and Flatau PJ, 2012, User Guide for the Discrete Dipole Approximation Code DDSCAT 7.2, arXiv:1202.3424v3.ear field calculations (Fast near field calculations in the discrete dipole approximation for regular rectilinear grids P. J. Flatau and B. T. Draine, Optics Express, Vol. 20, Issue 2, pp. 1247-1252 (2012))

  15. Discrete differential geometry: the nonplanar quadrilateral mesh.

    PubMed

    Twining, Carole J; Marsland, Stephen

    2012-06-01

    We consider the problem of constructing a discrete differential geometry defined on nonplanar quadrilateral meshes. Physical models on discrete nonflat spaces are of inherent interest, as well as being used in applications such as computation for electromagnetism, fluid mechanics, and image analysis. However, the majority of analysis has focused on triangulated meshes. We consider two approaches: discretizing the tensor calculus, and a discrete mesh version of differential forms. While these two approaches are equivalent in the continuum, we show that this is not true in the discrete case. Nevertheless, we show that it is possible to construct mesh versions of the Levi-Civita connection (and hence the tensorial covariant derivative and the associated covariant exterior derivative), the torsion, and the curvature. We show how discrete analogs of the usual vector integral theorems are constructed in such a way that the appropriate conservation laws hold exactly on the mesh, rather than only as approximations to the continuum limit. We demonstrate the success of our method by constructing a mesh version of classical electromagnetism and discuss how our formalism could be used to deal with other physical models, such as fluids.

  16. Development of a container for handling, testing, and storing discrete microelectronic components

    NASA Technical Reports Server (NTRS)

    Filip, G. L.; Caruso, S. V.

    1972-01-01

    A container has been developed for handling, testing, burning-in, and storing discrete microelectronic components without removal from the protective package. The package was designed to accommodate the leadless inverted device and other carrier-mounted active devices and chip-type discrete resistors and capacitors. Before the indicated development, components were handled and tested in various ways, some of which resulted in damage or contamination. The basic design of the container utilizes precision machined printed circuit boards and chemically milled (photoetched) contact springs. Included in this design for protection is an O-ring-sealed cover. Methods of fabrication and limitations of the current hardware are presented. Current applications of and possible extensions to the technology are discussed.

  17. Evidence for the relative depths and energies of phreatomagmatic explosions recorded in tephra rings

    NASA Astrophysics Data System (ADS)

    Graettinger, Alison H.; Valentine, Greg A.

    2017-12-01

    Experimental work and field observations have inspired the revision of conceptual models of how maar-diatreme eruptions progress and the effects of variable energy, depth, and lateral position of explosions during an eruption sequence. This study reevaluates natural tephra ring deposits to test these new models against the depositional record. Two incised tephra rings in the Hopi Buttes Volcanic Field are revisited, and published tephra ring stratigraphic studies are compared to identify trends within tephra rings. Five major facies were recognized and interpreted as the result of different transportation and depositional processes and found to be common at these volcanoes. Tephra rings often contain evidence of repeated discrete phreatomagmatic explosions in the form of couplets of two facies: (1) massive lapilli tuffs and tuff breccias and (2) overlying thinly stratified to cross-stratified tuffs and lapilli tuffs. The occurrence of repeating layers of either facies and the occurrence of couplets are used to interpret major trends in the relative depth of phreatomagmatic explosions that contribute to these eruptions. For deposits related to near-optimal scaled depth explosions, estimates of the mass of ejected material and initial ejection velocity can be used to approximate the explosion energy. The 19 stratigraphic sections compared indicate that near-optimal scaled depth explosions are common and that the explosion locations can migrate both upward and downward during an eruption, suggesting a complex interplay between water availability and magma flux. Reverse to normal coarse-tail graded tuff breccias inferred to be the product of closely timed phreatomagmatic explosions, and deposits of magmatic gas-driven explosions, were observed interspersed with discrete explosion deposits. This study not only provides a framework for more detailed interpretations of eruption sequences from tephra rings but also highlights the gap in our understanding of syn

  18. Planetary science: Shepherds of Saturn's ring

    NASA Astrophysics Data System (ADS)

    Crida, Aurélien

    2015-09-01

    Saturn's F ring is chaperoned on both sides by the tiny moons Prometheus and Pandora. Numerical simulations show that this celestial ballet can result from the collision of two aggregates that evolved out of Saturn's main rings.

  19. How to Remove a Stuck Ring Safely

    MedlinePlus

    ... Hand Safety Fireworks Safety Lawnmower Safety Snowblower safety Pumpkin Carving Gardening Safety Turkey Carving Removing a Ring ... Hand Safety Fireworks Safety Lawnmower Safety Snowblower safety Pumpkin Carving Gardening Safety Turkey Carving Removing a Ring ...

  20. The "Polar Light Sign" is a useful tool to detect discrete membranous supravalvular mitral stenosis.

    PubMed

    Hertwig, Christine; Haas, Nikolaus A; Habash, Sheeraz; Hanslik, Andreas; Kececioglu, Deniz; Sandica, Eugen; Laser, Kai-Thorsten

    2015-02-01

    Mitral valve stenosis caused by a discrete supravalvular membrane is a rare congenital malformation haemodynamically leading to significant mitral valve stenosis. When the supravalvular mitral stenosis consists of a discrete supravalvular membrane adherent to the mitral valve, it is usually not clearly detectable by routine echocardiography. We report about the typical echocardiographic finding in three young patients with this rare form of a discrete membranous supravalvular stenosis caused by a membrane adherent to the mitral valve. These cases present a typical echocardiographic feature in colour Doppler generated by the pathognomonic supramitral flow acceleration. Whereas typical supravalvular mitral stenosis caused by cor triatriatum or a clearly visible supravalvular ring is easily detectable by echocardiography, a discrete supravalvular membrane adjacent to the mitral valve leaflets resembling valvular mitral stenosis is difficult to differentiate by routine echocardiography. In our opinion, this colour phenomenon does resemble the visual impression of polar lights in the northern hemisphere; owing to its typical appearance, it may therefore be named as "Polar Light Sign". This phenomenon may help to detect this anatomical entity by echocardiography in time and therefore improve the prognosis for repair.

  1. Optical fiber having wave-guiding rings

    DOEpatents

    Messerly, Michael J [Danville, CA; Dawson, Jay W [Livermore, CA; Beach, Raymond J [Livermore, CA; Barty, Christopher P. J. [Hayward, CA

    2011-03-15

    A waveguide includes a cladding region that has a refractive index that is substantially uniform and surrounds a wave-guiding region that has an average index that is close to the index of the cladding. The wave-guiding region also contains a thin ring or series of rings that have an index or indices that differ significantly from the index of the cladding. The ring or rings enable the structure to guide light.

  2. EDGE-ON VIEW OF SATURN'S RINGS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is a NASA Hubble Space Telescope snapshot of Saturn with its rings barely visible. Normally, astronomers see Saturn with its rings tilted. Earth was almost in the plane of Saturn's rings, thus the rings appear edge-on. In this view, Saturn's largest moon, Titan, is casting a shadow on Saturn. Titan's atmosphere is a dark brown haze. The other moons appear white because of their bright, icy surfaces. Four moons - from left to right, Mimas, Tethys, Janus, and Enceladus - are clustered around the edge of Saturn's rings on the right. Two other moons appear in front of the ring plane. Prometheus is on the right edge; Pandora, on the left. The rings also are casting a shadow on Saturn because the Sun was above the ring plane. [bottom] - This photograph shows Saturn with its rings slightly tilted. The moon called Dione, on the lower right, is casting a long, thin shadow across the whole ring system due to the setting Sun on the ring plane. The moon on the upper left of Saturn is Tethys. Astronomers also are studying the unusual appearance of Saturn's rings. The bottom image displays a faint, narrow ring, the F-ring just outside the main ring, which normally is invisible from Earth. Close to the edge of Saturn's disk, the front section of rings seem brighter and more yellow than the back due to the additional lumination by yellowish Saturn. The color images were assembled from separate exposures taken August 6 (top) and November 17 (bottom), 1995 with the Wide Field Planetary Camera-2. CREDIT: Erich Karkoschka (University of Arizona Lunar and Planetary Lab) and NASA

  3. The Phase Shift in the Jumping Ring

    NASA Astrophysics Data System (ADS)

    Jeffery, Rondo N.; Amiri, Farhang

    2008-09-01

    The popular physics demonstration experiment known as Thomson's Jumping Ring (JR) has been variously explained as a simple example of Lenz's law, or as the result of a phase shift of the ring current relative to the induced emf. The failure of the first-quadrant Lenz's law explanation is shown by the time the ring takes to jump and by levitation. A method is given for measuring the phase shift with results for aluminum and brass rings.

  4. Techniques for computing the discrete Fourier transform using the quadratic residue Fermat number systems

    NASA Technical Reports Server (NTRS)

    Truong, T. K.; Chang, J. J.; Hsu, I. S.; Pei, D. Y.; Reed, I. S.

    1986-01-01

    The complex integer multiplier and adder over the direct sum of two copies of finite field developed by Cozzens and Finkelstein (1985) is specialized to the direct sum of the rings of integers modulo Fermat numbers. Such multiplication over the rings of integers modulo Fermat numbers can be performed by means of two integer multiplications, whereas the complex integer multiplication requires three integer multiplications. Such multiplications and additions can be used in the implementation of a discrete Fourier transform (DFT) of a sequence of complex numbers. The advantage of the present approach is that the number of multiplications needed to compute a systolic array of the DFT can be reduced substantially. The architectural designs using this approach are regular, simple, expandable and, therefore, naturally suitable for VLSI implementation.

  5. A Ring Construction Using Finite Directed Graphs

    ERIC Educational Resources Information Center

    Bardzell, Michael

    2012-01-01

    In this paper we discuss an interesting class of noncommutative rings which can be constructed using finite directed graphs. This construction also creates a vector space. These structures provide undergraduate students connections between ring theory and graph theory and, among other things, allow them to see a ring unity element that looks quite…

  6. Anomalous dark growth rings in black cherry

    Treesearch

    Robert P. Long; David W. Trimpey; Michael C. Wiemann; Susan L. Stout

    2012-01-01

    Anomalous dark growth rings have been observed in black cherry (Prunus serotina) sawlogs from northwestern Pennsylvania making the logs unsuitable for veneer products. Thirty-six cross sections with dark rings, each traceable to one of ten stands, were obtained from a local mill and sections were dated and annual ring widths were measured. One or...

  7. Rings of uranus: invisible and impossible?

    PubMed

    VAN Flandern, T C

    1979-06-08

    Neither the dynamical nor the optical properties of the rings of Uranus are easily understood, unless it is assumed that they are not rings in the ordinary sense but simply volatile material in the orbits of several individual small satellites. It is possible that other natural satellites may also leave such rings in their wakes.

  8. O-ring gasket test fixture

    NASA Technical Reports Server (NTRS)

    Turner, James Eric (Inventor); Mccluney, Donald Scott (Inventor)

    1991-01-01

    An apparatus is presented for testing O-ring gaskets under a variety of temperature, pressure, and dynamic loading conditions. Specifically, this apparatus has the ability to simulate a dynamic loading condition where the sealing surface in contact with the O-ring moves both away from and axially along the face of the O-ring.

  9. The Phase Shift in the Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Amiri, Farhang

    2008-01-01

    The popular physics demonstration experiment known as Thomson's Jumping Ring (JR) has been variously explained as a simple example of Lenz's law, or as the result of a phase shift of the ring current relative to the induced emf. The failure of the first-quadrant Lenz's law explanation is shown by the time the ring takes to jump and by levitation.…

  10. On the consistency between nearest-neighbor peridynamic discretizations and discretized classical elasticity models

    DOE PAGES

    Seleson, Pablo; Du, Qiang; Parks, Michael L.

    2016-08-16

    The peridynamic theory of solid mechanics is a nonlocal reformulation of the classical continuum mechanics theory. At the continuum level, it has been demonstrated that classical (local) elasticity is a special case of peridynamics. Such a connection between these theories has not been extensively explored at the discrete level. This paper investigates the consistency between nearest-neighbor discretizations of linear elastic peridynamic models and finite difference discretizations of the Navier–Cauchy equation of classical elasticity. While nearest-neighbor discretizations in peridynamics have been numerically observed to present grid-dependent crack paths or spurious microcracks, this paper focuses on a different, analytical aspect of suchmore » discretizations. We demonstrate that, even in the absence of cracks, such discretizations may be problematic unless a proper selection of weights is used. Specifically, we demonstrate that using the standard meshfree approach in peridynamics, nearest-neighbor discretizations do not reduce, in general, to discretizations of corresponding classical models. We study nodal-based quadratures for the discretization of peridynamic models, and we derive quadrature weights that result in consistency between nearest-neighbor discretizations of peridynamic models and discretized classical models. The quadrature weights that lead to such consistency are, however, model-/discretization-dependent. We motivate the choice of those quadrature weights through a quadratic approximation of displacement fields. The stability of nearest-neighbor peridynamic schemes is demonstrated through a Fourier mode analysis. Finally, an approach based on a normalization of peridynamic constitutive constants at the discrete level is explored. This approach results in the desired consistency for one-dimensional models, but does not work in higher dimensions. The results of the work presented in this paper suggest that even though nearest

  11. Drag of buoyant vortex rings

    NASA Astrophysics Data System (ADS)

    Vasel-Be-Hagh, Ahmadreza; Carriveau, Rupp; Ting, David S.-K.; Turner, John Stewart

    2015-10-01

    Extending from the model proposed by Vasel-Be-Hagh et al. [J. Fluid Mech. 769, 522 (2015), 10.1017/jfm.2015.126], a perturbation analysis is performed to modify Turner's radius by taking into account the viscous effect. The modified radius includes two terms; the zeroth-order solution representing the effect of buoyancy, and the first-order perturbation correction describing the influence of viscosity. The zeroth-order solution is explicit Turner's radius; the first-order perturbation modification, however, includes the drag coefficient, which is unknown and of interest. Fitting the photographically measured radius into the modified equation yields the time history of the drag coefficient of the corresponding buoyant vortex ring. To give further clarification, the proposed model is applied to calculate the drag coefficient of a buoyant vortex ring at a Bond number of approximately 85; a similar procedure can be applied at other Bond numbers.

  12. Dynamics of coorbital satellite rings

    NASA Technical Reports Server (NTRS)

    Salo, H.; Yoder, C. F.

    1988-01-01

    The dynamical behavior of a coorbital satellite ring is studied for N = 2-9 satellites, in terms of a simplified dynamical description, in which the motion is reduced to the separation angles between satellites. The number and stability of different kinds of stationary configurations is explored, revealing that equally spaced rings are not stable against small perturbations for N not greater than 6, while for N = 2-8 there exists another, stable compact solution. Integrations of exact equations confirm these results. Moreover, the systems are found to display chaotic characteristics for a certain range of energy. The behavior can be interpreted in terms of maximum velocity curves, defining the allowed region of the motion in the phase space.

  13. Behavioral Mapless Navigation Using Rings

    NASA Technical Reports Server (NTRS)

    Monroe, Randall P.; Miller, Samuel A.; Bradley, Arthur T.

    2012-01-01

    This paper presents work on the development and implementation of a novel approach to robotic navigation. In this system, map-building and localization for obstacle avoidance are discarded in favor of moment-by-moment behavioral processing of the sonar sensor data. To accomplish this, we developed a network of behaviors that communicate through the passing of rings, data structures that are similar in form to the sonar data itself and express the decisions of each behavior. Through the use of these rings, behaviors can moderate each other, conflicting impulses can be mediated, and designers can easily connect modules to create complex emergent navigational techniques. We discuss the development of a number of these modules and their successful use as a navigation system in the Trinity omnidirectional robot.

  14. Enhancing Geometric Phases Sensitivity in Atomic Coupled Ring Interferometers by Modulating Inter-Ring Distance

    NASA Astrophysics Data System (ADS)

    Toland, John; Romano, Eleni

    2017-04-01

    Previous theoretical work in the study of transmission properties of cold atoms in coupled ring waveguide structures has indicated that the sensitivity to geometrical phase shifts be greatly enhanced by increasing the number of rings in the array or by changing the relative size of the rings in an array of the coupled waveguides. The coupled ring structures in these simulations assumed zero distance between rings. Our research addresses how increasing the inter-ring distance of the chain of N rings affects the rotational sensitivity of a ring array interferometer. We determine the sensitivity of a ring array gyroscope by calculating the slopes of the transmission function with respect to phase at the sharpest transmission resonance in the transmission function. The distance between rings is parameterized as the product of the wave number k and the distance between the rings d, while the size of the rings is parameterized by the product of k and the ring circumference L. The transmission is periodic with oscillatory regions and zero transmission gap regions. Our results show that modulating the inter-ring distance near kd = 0 . 5 π leads to sharp transmission resonances with slopes that are orders of magnitude greater than those in ring arrays with directly connected rings. CILES, NASA.

  15. Ball-joint grounding ring

    NASA Technical Reports Server (NTRS)

    Aperlo, P. J. A.; Buck, P. A.; Weldon, V. A.

    1981-01-01

    In ball and socket joint where electrical insulator such as polytetrafluoroethylene is used as line to minimize friction, good electrical contact across joint may be needed for lightning protection or to prevent static-charge build-up. Electrical contact is maintained by ring of spring-loaded fingers mounted in socket. It may be useful in industry for cranes, trailers, and other applications requiring ball and socket joint.

  16. The Friction of Piston Rings

    NASA Technical Reports Server (NTRS)

    Tischbein, Hans W

    1945-01-01

    The coefficient of friction between piston ring and cylinder liner was measured in relation to gliding acceleration, pressure, temperature, quantity of oil and quality of oil. Comparing former lubrication-technical tests, conclusions were drawn as to the state of friction. The coefficients of friction as figured out according to the hydrodynamic theory were compared with those measured by tests. Special tests were made on "oiliness." The highest permissible pressure was measured and the ratio of pressure discussed.

  17. Reflex ring laser amplifier system

    DOEpatents

    Summers, M.A.

    1983-08-31

    The invention is a method and apparatus for providing a reflex ring laser system for amplifying an input laser pulse. The invention is particularly useful in laser fusion experiments where efficient production of high-energy and high power laser pulses is required. The invention comprises a large aperture laser amplifier in an unstable ring resonator which includes a combination spatial filter and beam expander having a magnification greater than unity. An input pulse is injected into the resonator, e.g., through an aperture in an input mirror. The injected pulse passes through the amplifier and spatial filter/expander components on each pass around the ring. The unstable resonator is designed to permit only a predetermined number of passes before the amplified pulse exits the resonator. On the first pass through the amplifier, the beam fills only a small central region of the gain medium. On each successive pass, the beam has been expanded to fill the next concentric non-overlapping region of the gain medium.

  18. Gibbs Ringing in Diffusion MRI

    PubMed Central

    Veraart, Jelle; Fieremans, Els; Jelescu, Ileana O.; Knoll, Florian; Novikov, Dmitry S.

    2016-01-01

    Purpose To study and reduce the effect of Gibbs ringing artifact on computed diffusion parameters. Methods We reduce the ringing by extrapolating the k-space of each diffusion weighted image beyond the measured part by selecting an adequate regularization term. We evaluate several regularization terms and tune the regularization parameter to find the best compromise between anatomical accuracy of the reconstructed image and suppression of the Gibbs artifact. Results We demonstrate empirically and analytically that the Gibbs artifact, which is typically observed near sharp edges in magnetic resonance images, has a significant impact on the quantification of diffusion model parameters, even for infinitesimal diffusion weighting. We find the second order total generalized variation to be a good choice for the penalty term to regularize the extrapolation of the k-space, as it provides a parsimonious representation of images, a practically full suppression of Gibbs ringing, and the absence of staircasing artifacts typical for total variation methods. Conclusions Regularized extrapolation of the k-space data significantly reduces truncation artifacts without compromising spatial resolution in comparison to the default option of window filtering. In particular, accuracy of estimating diffusion tensor imaging and diffusion kurtosis imaging parameters improves so much that unconstrained fits become possible. PMID:26257388

  19. Discrete stochastic analogs of Erlang epidemic models.

    PubMed

    Getz, Wayne M; Dougherty, Eric R

    2018-12-01

    Erlang differential equation models of epidemic processes provide more realistic disease-class transition dynamics from susceptible (S) to exposed (E) to infectious (I) and removed (R) categories than the ubiquitous SEIR model. The latter is itself is at one end of the spectrum of Erlang SE[Formula: see text]I[Formula: see text]R models with [Formula: see text] concatenated E compartments and [Formula: see text] concatenated I compartments. Discrete-time models, however, are computationally much simpler to simulate and fit to epidemic outbreak data than continuous-time differential equations, and are also much more readily extended to include demographic and other types of stochasticity. Here we formulate discrete-time deterministic analogs of the Erlang models, and their stochastic extension, based on a time-to-go distributional principle. Depending on which distributions are used (e.g. discretized Erlang, Gamma, Beta, or Uniform distributions), we demonstrate that our formulation represents both a discretization of Erlang epidemic models and generalizations thereof. We consider the challenges of fitting SE[Formula: see text]I[Formula: see text]R models and our discrete-time analog to data (the recent outbreak of Ebola in Liberia). We demonstrate that the latter performs much better than the former; although confining fits to strict SEIR formulations reduces the numerical challenges, but sacrifices best-fit likelihood scores by at least 7%.

  20. Discrete Mathematics in the Schools. DIMACS Series in Discrete Mathematics and Theoretical Computer Science, Volume 36.

    ERIC Educational Resources Information Center

    Rosenstein, Joseph G., Ed.; Franzblau, Deborah S., Ed.; Roberts, Fred S., Ed.

    This book is a collection of articles by experienced educators and explains why and how discrete mathematics should be taught in K-12 classrooms. It includes evidence for "why" and practical guidance for "how" and also discusses how discrete mathematics can be used as a vehicle for achieving the broader goals of the major…

  1. Modeling equinox temperature variations in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Spilker, L. J.; Ferrari, C. C.; Morishima, R.

    2011-12-01

    For a few days around Saturn ring equinox, the Cassini Composite Infrared Spectrometer (CIRS) obtained data on Saturn's rings at different local times and phase angles. We examine results from 15 scans taken near equinox. The sun was shining on the south side of the rings prior to the equinox crossing. The solar elevation angle in the 15 scans varied between -0.00007 degrees and 0.036 degrees and the phase angle ranged from 30 degrees to 147 degrees. The equinox geometry is unique because the sun is edge-on to the rings. Saturn heating dominates while solar heating is at a minimum. The ring temperature varies between the lit and unlit sides of the A and B rings when the sun is the dominant heat source. With the sun shining on the rings the temperature of the lit rings decreases with increasing phase angle and the ring temperature in the shadow is less than the ring temperature at noon. At equinox the ring temperature does not decrease with increasing phase angle and the temperature at noon is no longer greater than the temperature in the shadow. As the solar elevation angle decreased the last few degrees, the ring temperatures on the lit and unlit sides rapidly decreased to the coldest temperatures observed thus far. At equinox radial and longitudinal temperature variations are observed in the A, B and C rings and the Cassini Division. The radial temperature variations result both from the decreasing Saturn solid angle with increasing distance from the planet and varying optical depth as the screening effect of optically thicker rings limits the heat contribution to primarily one hemisphere of Saturn. Both monolayer and multilayer models can explain the radial variations in ring temperature except for the A ring. A ring model fits produce temperatures that are lower than observed temperatures perhaps because of the effects from gravitational wakes, density waves and bending waves that are not included in the models. Saturn ring temperatures near equinox also vary

  2. Wavelength-tunable optical ring resonators

    DOEpatents

    Watts, Michael R [Albuquerque, NM; Trotter, Douglas C [Albuquerque, NM; Young, Ralph W [Albuquerque, NM; Nielson, Gregory N [Albuquerque, NM

    2009-11-10

    Optical ring resonator devices are disclosed that can be used for optical filtering, modulation or switching, or for use as photodetectors or sensors. These devices can be formed as microdisk ring resonators, or as open-ring resonators with an optical waveguide having a width that varies adiabatically. Electrical and mechanical connections to the open-ring resonators are made near a maximum width of the optical waveguide to minimize losses and thereby provide a high resonator Q. The ring resonators can be tuned using an integral electrical heater, or an integral semiconductor junction.

  3. Wavelength-tunable optical ring resonators

    DOEpatents

    Watts, Michael R [Albuquerque, NM; Trotter, Douglas C [Albuquerque, NM; Young, Ralph W [Albuquerque, NM; Nielson, Gregory N [Albuquerque, NM

    2011-07-19

    Optical ring resonator devices are disclosed that can be used for optical filtering, modulation or switching, or for use as photodetectors or sensors. These devices can be formed as microdisk ring resonators, or as open-ring resonators with an optical waveguide having a width that varies adiabatically. Electrical and mechanical connections to the open-ring resonators are made near a maximum width of the optical waveguide to minimize losses and thereby provide a high resonator Q. The ring resonators can be tuned using an integral electrical heater, or an integral semiconductor junction.

  4. Signal and power roll ring testing update

    NASA Technical Reports Server (NTRS)

    Smith, Dennis W.

    1989-01-01

    The development of the roll ring as a long-life, low-torque alternative to the slip ring is discussed. A roll ring consists of one or more circular flexures captured by their own spring force in the annular space between two concentric conductors or contact rings. The advantages of roll rings over other types of electrical transfer devices are: extremely low drag torque, high transfer efficiencies in high-power configurations, extremely low wear debris generation, long life, and low weight for high-power applications.

  5. Vaginal rings for delivery of HIV microbicides

    PubMed Central

    Malcolm, R Karl; Fetherston, Susan M; McCoy, Clare F; Boyd, Peter; Major, Ian

    2012-01-01

    Following the successful development of long-acting steroid-releasing vaginal ring devices for the treatment of menopausal symptoms and contraception, there is now considerable interest in applying similar devices to the controlled release of microbicides against HIV. In this review article, the vaginal ring concept is first considered within the wider context of the early advances in controlled-release technology, before describing the various types of ring device available today. The remainder of the article highlights the key developments in HIV microbicide-releasing vaginal rings, with a particular focus on the dapivirine ring that is presently in late-stage clinical testing. PMID:23204872

  6. Noncircular features in Saturn's rings II: The C ring

    NASA Astrophysics Data System (ADS)

    Nicholson, Philip D.; French, Richard G.; McGhee-French, Colleen A.; Hedman, Matthew M.; Marouf, Essam A.; Colwell, Joshua E.; Lonergan, Katherine; Sepersky, Talia

    2014-10-01

    We present a comprehensive survey of sharp-edged features in Saturn's C ring, using data from radio and stellar occultation experiments carried out by the Cassini spacecraft over a period of more than five years. Over 100 occultations are included in the combined data set, enabling us to identify systematic radial perturbations as small as 200 m on the edges of ringlets and gaps. We systematically examine all of the noncircular features in the C ring, refine the eccentricities, precession rates and width variations of the known eccentric ringlets, identify connections between several noncircular gap and ringlet edges and nearby satellite resonances, and report the discovery of a host of free normal modes on ring and gap edges. We confirm a close association between the Titan (or Colombo) ringlet (a = 77878.7 km) and the Titan 1:0 apsidal resonance: the apoapse of the ringlet is nearly aligned with Titan's mean longitude, and the pattern speed closely matches Titan's mean motion. Similar forced perturbations associated with the Titan resonance are detectable in more than two dozen other features located throughout the inner C ring as far as 3500 km from the Titan resonance. The inner edge of the Titan ringlet exhibits several strong outer Lindblad resonance (OLR-type) normal modes, and scans of the outer edge reveal inner Lindblad resonance (ILR-type) normal modes. The Maxwell ringlet (a = 87,510 km), in contrast, appears to be a freely-precessing eccentric ringlet, with post-fit RMS residuals for the inner and outer edges of only 0.23 and 0.16 km, respectively. The best-fitting edge precession rates differ by over 10 times the estimated uncertainty in the rate of the inner edge, consistent with a slow libration about an equilibrium configuration on a decadal timescale. Using self-gravity models for ringlet apse alignment, we estimate the masses and surface densities of the Titan and Maxwell ringlets. The Bond ringlet (a = 88,710 km), about 17 km wide, shows no free

  7. Leapfrogging of multiple coaxial viscous vortex rings

    SciTech Connect

    Cheng, M., E-mail: chengm@ihpc.a-star.edu.sg; Lou, J.; Lim, T. T.

    2015-03-15

    A recent theoretical study [Borisov, Kilin, and Mamaev, “The dynamics of vortex rings: Leapfrogging, choreographies and the stability problem,” Regular Chaotic Dyn. 18, 33 (2013); Borisov et al., “The dynamics of vortex rings: Leapfrogging in an ideal and viscous fluid,” Fluid Dyn. Res. 46, 031415 (2014)] shows that when three coaxial vortex rings travel in the same direction in an incompressible ideal fluid, each of the vortex rings alternately slips through (or leapfrogs) the other two ahead. Here, we use a lattice Boltzmann method to simulate viscous vortex rings with an identical initial circulation, radius, and separation distance with themore » aim of studying how viscous effect influences the outcomes of the leapfrogging process. For the case of two identical vortex rings, our computation shows that leapfrogging can be achieved only under certain favorable conditions, which depend on Reynolds number, vortex core size, and initial separation distance between the two rings. For the case of three coaxial vortex rings, the result differs from the inviscid model and shows that the second vortex ring always slips through the leading ring first, followed by the third ring slipping through the other two ahead. A simple physical model is proposed to explain the observed behavior.« less

  8. Nuclear Rings in Galaxies - A Kinematic Perspective

    NASA Technical Reports Server (NTRS)

    Mazzuca, Lisa M.; Swaters, Robert A.; Knapen, Johan H.; Veilleux, Sylvain

    2011-01-01

    We combine DensePak integral field unit and TAURUS Fabry-Perot observations of 13 nuclear rings to show an interconnection between the kinematic properties of the rings and their resonant origin. The nuclear rings have regular and symmetric kinematics, and lack strong non-circular motions. This symmetry, coupled with a direct relationship between the position angles and ellipticities of the rings and those of their host galaxies, indicate the rings are in the same plane as the disc and are circular. From the rotation curves derived, we have estimated the compactness (v(sup 2)/r) up to the turnover radius, which is where the nuclear rings reside. We find that there is evidence of a correlation between compactness and ring width and size. Radially wide rings are less compact, and thus have lower mass concentration. The compactness increases as the ring width decreases. We also find that the nuclear ring size is dependent on the bar strength, with weaker bars allowing rings of any size to form.

  9. Simulations of light scattering in planetary rings

    NASA Technical Reports Server (NTRS)

    Dones, L.; Cuzzi, J. N.; Showalter, M. R.

    1989-01-01

    The current status of efforts to model light scattering in the Uranian and Saturnian rings is briefly reviewed, with an emphasis on the treatment of thin, vertically warped, or clumpy rings. Consideration is given to observations of an opposition surge in the rings (indicating that they are physically thick) and possible reasons for the failure of classical models to predict the forward-scattering characteristics of the B and inner A rings of Saturn, the quadrupole brightness variations in the A ring, the increase in reflectivity with optical depth in the A and B rings, the increase in brightness with solar and observer angle in the B ring, and systematic brightness variations in images of the inner Cassini division. It is pointed out that some of these discrepancies are eliminated by the use of a ray-tracing simulation code which determines the singly scattered light from a layer one or many particles thick.

  10. Discrete-time Markovian stochastic Petri nets

    NASA Technical Reports Server (NTRS)

    Ciardo, Gianfranco

    1995-01-01

    We revisit and extend the original definition of discrete-time stochastic Petri nets, by allowing the firing times to have a 'defective discrete phase distribution'. We show that this formalism still corresponds to an underlying discrete-time Markov chain. The structure of the state for this process describes both the marking of the Petri net and the phase of the firing time for each transition, resulting in a large state space. We then modify the well-known power method to perform a transient analysis even when the state space is infinite, subject to the condition that only a finite number of states can be reached in a finite amount of time. Since the memory requirements might still be excessive, we suggest a bounding technique based on truncation.

  11. An algebra of discrete event processes

    NASA Technical Reports Server (NTRS)

    Heymann, Michael; Meyer, George

    1991-01-01

    This report deals with an algebraic framework for modeling and control of discrete event processes. The report consists of two parts. The first part is introductory, and consists of a tutorial survey of the theory of concurrency in the spirit of Hoare's CSP, and an examination of the suitability of such an algebraic framework for dealing with various aspects of discrete event control. To this end a new concurrency operator is introduced and it is shown how the resulting framework can be applied. It is further shown that a suitable theory that deals with the new concurrency operator must be developed. In the second part of the report the formal algebra of discrete event control is developed. At the present time the second part of the report is still an incomplete and occasionally tentative working paper.

  12. Direct Discrete Method for Neutronic Calculations

    SciTech Connect

    Vosoughi, Naser; Akbar Salehi, Ali; Shahriari, Majid

    2002-07-01

    The objective of this paper is to introduce a new direct method for neutronic calculations. This method which is named Direct Discrete Method, is simpler than the neutron Transport equation and also more compatible with physical meaning of problems. This method is based on physic of problem and with meshing of the desired geometry, writing the balance equation for each mesh intervals and with notice to the conjunction between these mesh intervals, produce the final discrete equations series without production of neutron transport differential equation and mandatory passing from differential equation bridge. We have produced neutron discrete equations for amore » cylindrical shape with two boundary conditions in one group energy. The correction of the results from this method are tested with MCNP-4B code execution. (authors)« less

  13. The ultimatum game: Discrete vs. continuous offers

    NASA Astrophysics Data System (ADS)

    Dishon-Berkovits, Miriam; Berkovits, Richard

    2014-09-01

    In many experimental setups in social-sciences, psychology and economy the subjects are requested to accept or dispense monetary compensation which is usually given in discrete units. Using computer and mathematical modeling we show that in the framework of studying the dynamics of acceptance of proposals in the ultimatum game, the long time dynamics of acceptance of offers in the game are completely different for discrete vs. continuous offers. For discrete values the dynamics follow an exponential behavior. However, for continuous offers the dynamics are described by a power-law. This is shown using an agent based computer simulation as well as by utilizing an analytical solution of a mean-field equation describing the model. These findings have implications to the design and interpretation of socio-economical experiments beyond the ultimatum game.

  14. Discrete Roughness Transition for Hypersonic Flight Vehicles

    NASA Technical Reports Server (NTRS)

    Berry, Scott A.; Horvath, Thomas J.

    2007-01-01

    The importance of discrete roughness and the correlations developed to predict the onset of boundary layer transition on hypersonic flight vehicles are discussed. The paper is organized by hypersonic vehicle applications characterized in a general sense by the boundary layer: slender with hypersonic conditions at the edge of the boundary layer, moderately blunt with supersonic, and blunt with subsonic. This paper is intended to be a review of recent discrete roughness transition work completed at NASA Langley Research Center in support of agency flight test programs. First, a review is provided of discrete roughness wind tunnel data and the resulting correlations that were developed. Then, results obtained from flight vehicles, in particular the recently flown Hyper-X and Shuttle missions, are discussed and compared to the ground-based correlations.

  15. Designing perturbative metamaterials from discrete models.

    PubMed

    Matlack, Kathryn H; Serra-Garcia, Marc; Palermo, Antonio; Huber, Sebastian D; Daraio, Chiara

    2018-04-01

    Identifying material geometries that lead to metamaterials with desired functionalities presents a challenge for the field. Discrete, or reduced-order, models provide a concise description of complex phenomena, such as negative refraction, or topological surface states; therefore, the combination of geometric building blocks to replicate discrete models presenting the desired features represents a promising approach. However, there is no reliable way to solve such an inverse problem. Here, we introduce 'perturbative metamaterials', a class of metamaterials consisting of weakly interacting unit cells. The weak interaction allows us to associate each element of the discrete model with individual geometric features of the metamaterial, thereby enabling a systematic design process. We demonstrate our approach by designing two-dimensional elastic metamaterials that realize Veselago lenses, zero-dispersion bands and topological surface phonons. While our selected examples are within the mechanical domain, the same design principle can be applied to acoustic, thermal and photonic metamaterials composed of weakly interacting unit cells.

  16. Feasibility of a ring FEL at low emittance storage rings

    NASA Astrophysics Data System (ADS)

    Agapov, I.

    2015-09-01

    A scheme for generating coherent radiation at latest generation low emittance storage rings such as PETRA III at DESY (Balewski et al., 2004 [1]) is proposed. The scheme is based on focusing and subsequent defocusing of the electron beam in the longitudinal phase space at the undulator location. The expected performance characteristics are estimated for radiation in the wavelength range of 500-1500 eV. It is shown that the average brightness is increased by several orders of magnitude compared to spontaneous undulator radiation, which can open new perspectives for photon-hungry soft X-ray spectroscopy techniques.

  17. Limit sets for the discrete spectrum of complex Jacobi matrices

    NASA Astrophysics Data System (ADS)

    Golinskii, L. B.; Egorova, I. E.

    2005-06-01

    The discrete spectrum of complex Jacobi matrices that are compact perturbations of the discrete Laplacian is studied. The precise stabilization rate (in the sense of order) of the matrix elements ensuring the finiteness of the discrete spectrum is found. An example of a Jacobi matrix with discrete spectrum having a unique limit point is constructed. These results are discrete analogues of Pavlov's well-known results on Schrödinger operators with complex potential on a half-axis.

  18. Cortical Neural Computation by Discrete Results Hypothesis.

    PubMed

    Castejon, Carlos; Nuñez, Angel

    2016-01-01

    One of the most challenging problems we face in neuroscience is to understand how the cortex performs computations. There is increasing evidence that the power of the cortical processing is produced by populations of neurons forming dynamic neuronal ensembles. Theoretical proposals and multineuronal experimental studies have revealed that ensembles of neurons can form emergent functional units. However, how these ensembles are implicated in cortical computations is still a mystery. Although cell ensembles have been associated with brain rhythms, the functional interaction remains largely unclear. It is still unknown how spatially distributed neuronal activity can be temporally integrated to contribute to cortical computations. A theoretical explanation integrating spatial and temporal aspects of cortical processing is still lacking. In this Hypothesis and Theory article, we propose a new functional theoretical framework to explain the computational roles of these ensembles in cortical processing. We suggest that complex neural computations underlying cortical processing could be temporally discrete and that sensory information would need to be quantized to be computed by the cerebral cortex. Accordingly, we propose that cortical processing is produced by the computation of discrete spatio-temporal functional units that we have called "Discrete Results" (Discrete Results Hypothesis). This hypothesis represents a novel functional mechanism by which information processing is computed in the cortex. Furthermore, we propose that precise dynamic sequences of "Discrete Results" is the mechanism used by the cortex to extract, code, memorize and transmit neural information. The novel "Discrete Results" concept has the ability to match the spatial and temporal aspects of cortical processing. We discuss the possible neural underpinnings of these functional computational units and describe the empirical evidence supporting our hypothesis. We propose that fast-spiking (FS

  19. Cortical Neural Computation by Discrete Results Hypothesis

    PubMed Central

    Castejon, Carlos; Nuñez, Angel

    2016-01-01

    One of the most challenging problems we face in neuroscience is to understand how the cortex performs computations. There is increasing evidence that the power of the cortical processing is produced by populations of neurons forming dynamic neuronal ensembles. Theoretical proposals and multineuronal experimental studies have revealed that ensembles of neurons can form emergent functional units. However, how these ensembles are implicated in cortical computations is still a mystery. Although cell ensembles have been associated with brain rhythms, the functional interaction remains largely unclear. It is still unknown how spatially distributed neuronal activity can be temporally integrated to contribute to cortical computations. A theoretical explanation integrating spatial and temporal aspects of cortical processing is still lacking. In this Hypothesis and Theory article, we propose a new functional theoretical framework to explain the computational roles of these ensembles in cortical processing. We suggest that complex neural computations underlying cortical processing could be temporally discrete and that sensory information would need to be quantized to be computed by the cerebral cortex. Accordingly, we propose that cortical processing is produced by the computation of discrete spatio-temporal functional units that we have called “Discrete Results” (Discrete Results Hypothesis). This hypothesis represents a novel functional mechanism by which information processing is computed in the cortex. Furthermore, we propose that precise dynamic sequences of “Discrete Results” is the mechanism used by the cortex to extract, code, memorize and transmit neural information. The novel “Discrete Results” concept has the ability to match the spatial and temporal aspects of cortical processing. We discuss the possible neural underpinnings of these functional computational units and describe the empirical evidence supporting our hypothesis. We propose that fast

  20. Current status of contraceptive vaginal rings.

    PubMed

    Brache, Vivian; Payán, Luis José; Faundes, Aníbal

    2013-03-01

    Contraceptive vaginal rings (CVR) offer a new, effective contraceptive option, expanding the available choices of hormonal contraception. Various ring prototypes have been evaluated: progestin-only rings and combined progestin-estrogen rings, as well as different combination of progestins and estrogens. The progestin-only ring is intended for continuous use, whereas the combined ring has been designed for cyclic 3-week in/1-week out use, although several studies have explored alternative schemes of extended use. However, only two ring designs have reached the market: NuvaRing, a 1-month combined ring that releases etonogestrel and ethinylestradiol, and Progering, a 3-month progesterone-releasing ring for use in lactating women. A one year Nestorone/ethinyl estradiol CVR is approaching the final stages of development, as the Population Council is preparing to submit a new drug application to the Food and Drug Administration. The main advantages of CVRs are their effectiveness (similar or slightly better than the pill), ease of use without the need of remembering a daily routine, user ability to control initiation and discontinuation, nearly constant release rate allowing for lower doses, greater bioavailability and good cycle control with the combined ring, in comparison with oral contraceptives. Current prototypes in development include rings releasing progesterone receptor modulators, which would provide estrogen-free contraception, as well as combined rings releasing estradiol, instead of ethinyl-estradiol, providing a safer profile. Furthermore, intensive efforts towards developing dual protection rings, providing both contraception and protection against reproductive tract infections, offer hope that this greatly needed technology will soon undergo clinical testing and will be in the hands of women worldwide in the near future. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. Compatible Discretizations for Continuous Dynamical Systems

    NASA Astrophysics Data System (ADS)

    Kojouharov, H. V.; Dimitrov, D. T.

    2008-10-01

    In this paper, we briefly review the history of the nonstandard finite difference (NSFD) methods and their application to a wide range of physical and biological problems. Emphasis is given on the use of the nonstandard discretization ideas to the numerical solution of continuous dynamical systems. In that context, specific examples of positive and elementary stable nonstandard (PESN) finite difference schemes are presented. We also outline possible future research directions for the construction of structural property-preserving numerical methods and discuss some open problems in the general area of nonstandard discretizations of differential equations.

  2. Hybrid Discrete-Continuous Markov Decision Processes

    NASA Technical Reports Server (NTRS)

    Feng, Zhengzhu; Dearden, Richard; Meuleau, Nicholas; Washington, Rich

    2003-01-01

    This paper proposes a Markov decision process (MDP) model that features both discrete and continuous state variables. We extend previous work by Boyan and Littman on the mono-dimensional time-dependent MDP to multiple dimensions. We present the principle of lazy discretization, and piecewise constant and linear approximations of the model. Having to deal with several continuous dimensions raises several new problems that require new solutions. In the (piecewise) linear case, we use techniques from partially- observable MDPs (POMDPS) to represent value functions as sets of linear functions attached to different partitions of the state space.

  3. Model reduction for discrete bilinear systems

    NASA Technical Reports Server (NTRS)

    King, A. M.; Skelton, R. E.

    1987-01-01

    A model reduction method for discrete bilinear systems is developed which matches q sets of Volterra and covariance parameters. These parameters are shown to represent both deterministic and stochastic attributes of the discrete bilinear system. A reduced order model which matches these q sets of parameters is defined to be a q-Volterra covariance equivalent realization (q-Volterra COVER). An algorithm is presented which constructs a class of q-Volterra COVERs parameterized by solutions to a Hermitian, quadratic, matrix equation. The algorithm is applied to a bilinear model of a robot manipulator.

  4. Reliability of hybrid microcircuit discrete components

    NASA Technical Reports Server (NTRS)

    Allen, R. V.

    1972-01-01

    Data accumulated during 4 years of research and evaluation of ceramic chip capacitors, ceramic carrier mounted active devices, beam-lead transistors, and chip resistors are presented. Life and temperature coefficient test data, and optical and scanning electron microscope photographs of device failures are presented and the failure modes are described. Particular interest is given to discrete component qualification, power burn-in, and procedures for testing and screening discrete components. Burn-in requirements and test data will be given in support of 100 percent burn-in policy on all NASA flight programs.

  5. Synchronization Of Parallel Discrete Event Simulations

    NASA Technical Reports Server (NTRS)

    Steinman, Jeffrey S.

    1992-01-01

    Adaptive, parallel, discrete-event-simulation-synchronization algorithm, Breathing Time Buckets, developed in Synchronous Parallel Environment for Emulation and Discrete Event Simulation (SPEEDES) operating system. Algorithm allows parallel simulations to process events optimistically in fluctuating time cycles that naturally adapt while simulation in progress. Combines best of optimistic and conservative synchronization strategies while avoiding major disadvantages. Algorithm processes events optimistically in time cycles adapting while simulation in progress. Well suited for modeling communication networks, for large-scale war games, for simulated flights of aircraft, for simulations of computer equipment, for mathematical modeling, for interactive engineering simulations, and for depictions of flows of information.

  6. Einstein Ring in Distant Universe

    NASA Astrophysics Data System (ADS)

    2005-06-01

    Using ESO's Very Large Telescope, Rémi Cabanac and his European colleagues have discovered an amazing cosmic mirage, known to scientists as an Einstein Ring. This cosmic mirage, dubbed FOR J0332-3557, is seen towards the southern constellation Fornax (the Furnace), and is remarkable on at least two counts. First, it is a bright, almost complete Einstein ring. Second, it is the farthest ever found. ESO PR Photo 20a/05 ESO PR Photo 20a/05 Deep Image of a Region in Fornax (FORS/VLT) [Preview - JPEG: 400 x 434 pix - 60k] [Normal - JPEG: 800 x 867 pix - 276k] [Full Res - JPEG: 1859 x 2015 pix - 3.8M] ESO PR Photo 20b/05 ESO PR Photo 20b/05 Zoom-in on the Newly Found Einstein Ring (FORS/VLT) [Preview - JPEG: 400 x 575 pix - 168k] [Normal - JPEG: 630 x 906 pix - 880k] Caption: ESO PR Photo 20a/05 is a composite image taken in two bands (B and R) with VLT/FORS1 of a small portion of the sky (field-of-view 7x7' or 1/15th of the area of the full moon). The faintest object seen in the image has a magnitude 26, that is, it is 100 million times fainter than what can be observed with the unaided eye. The bright elliptical galaxy on the lower-left quadrant is a dwarf galaxy part of a large nearby cluster in the Fornax constellation. As for all deep images of the sky, this field shows a variety of objects, the brightest ponctual sources being stars from our Galaxy. By far the field is dominated by thousands of faint background galaxies the colours of which are related to the age of their dominant stellar population, their dust content and their distance. The newly found Einstein ring is visible in the top right part of the image. ESO PR Photo 20b/05 zooms-in on the position of the newly found cosmic mirage. ESO PR Photo 20c/05 ESO PR Photo 20c/05 Einstein Ring in Distant Universe (FORS/VLT) [Preview - JPEG: 400 x 584 pix - 104k] [Normal - JPEG: 800 x 1168 pix - 292k] [Full Res - JPEG: 1502 x 2192 pix - 684k] Caption of ESO PR Photo 20c/05: The left image is magnified and centred

  7. The combined contraceptive vaginal ring, NuvaRing, and tampon co-usage.

    PubMed

    Verhoeven, Carole H J; Dieben, Th O M

    2004-03-01

    We investigated the effect of tampon co-usage on systemic exposure to etonogestrel (ENG) and ethinylestradiol (EE) from the combined contraceptive vaginal ring, NuvaRing. One cycle of ring use consists of 3 weeks of ring use followed by a 1-week ring-free period. Fourteen healthy women were randomized to use both NuvaRing and tampons (Kotex( regular) or NuvaRing alone for one cycle; participants then switched to the alternate treatment regimen for a second cycle of ring use. The first tampon was self-administered on day 8 of the interaction cycle; 4 tampons a day were used for 3 consecutive days. Tampon co-usage did not result in any changes in serum ENG or EE concentrations and is thus not expected to compromise the ring's contraceptive efficacy.

  8. Ring magnet firing angle control

    DOEpatents

    Knott, M.J.; Lewis, L.G.; Rabe, H.H.

    1975-10-21

    A device is provided for controlling the firing angles of thyratrons (rectifiers) in a ring magnet power supply. A phase lock loop develops a smooth ac signal of frequency equal to and in phase with the frequency of the voltage wave developed by the main generator of the power supply. A counter that counts from zero to a particular number each cycle of the main generator voltage wave is synchronized with the smooth AC signal of the phase lock loop. Gates compare the number in the counter with predetermined desired firing angles for each thyratron and with coincidence the proper thyratron is fired at the predetermined firing angle.

  9. Ring resonator based SOI biosensors

    NASA Astrophysics Data System (ADS)

    Bienstman, P.; Werquin, S.; Lerma Arce, C.; Witters, D.; Puers, R.; Lammertyn, J.; Claes, T.; Hallynck, E.; Hoste, J.-W.; Martens, D.

    2013-02-01

    In this paper, two recent advances in silicon ring resonator biosensors are presented. First, we address the problem that due to the high index contrast, small deviations from perfect symmetry lift the degeneracy of the normal resonator mode. This severely deteriorates the quality of the output signal. To address this, we discuss an integrated interferometric approach to give access to the unsplit, high-quality normal modes of the microring resonator. Second, we demonstrate how digital microfluidics can be used for effective fluid delivery to nanophotonic microring resonator sensors fully constructed in SOI.

  10. Saturn's Rings in Ultraviolet Light

    NASA Image and Video Library

    2017-12-08

    Saturn's Rings in Ultraviolet Light Credit: NASA and E. Karkoschka (University of Arizona) The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute conducts Hubble science operations. Goddard is responsible for HST project management, including mission and science operations, servicing missions, and all associated development activities. To learn more about the Hubble Space Telescope go here: www.nasa.gov/mission_pages/hubble/main/index.html

  11. Saturn's E Ring in Ultraviolet Light

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Visible from Earth only at times of ring plane crossing, Saturn's tenuous E Ring was discovered during the 1966 crossings and imaged again in 1980. From these observations, its color is known to be distinctively blue. The E Ring was captured in ultraviolet light for the first time in this image taken with HST's Wide Field and Planetary Camera on 9 August 1995. Five individual images taken with a broadband 3000 A filter were combined, amounting to a total exposure time of 2200 sec. Shorter exposure images were also obtained with blue, red and infrared filters in order to characterize the ring's color. The peak brightness of the E Ring occurs at 3.9 Saturn radii (235,000 km), coinciding with the orbit of Enceladus. In the HST images it can be traced out to a maximum distance of approximately 8 Rs (480,000 km). The vertical thickness of the ring, on the other hand, is smallest at Enceladus' orbit, with the ring puffing up noticeably at larger distances to 15,000 km or more thick. Also visible in this image, between the E Ring and the overexposed outermost part of the main rings near the lower edge of the frame, is the tenuous, thin, 6000 km-wide G Ring at 2.8 Rs (170,000 km). This is among the first earth-based observations of the G Ring, which was discovered by the Pioneer 11 spacecraft in 1979. Noticeably thinner than the E Ring and more neutral in color, the G Ring is thought to be composed of larger, macroscopic particles, and to pose a significant hazard to spacecraft. The faint diagonal band in the lower right part of the image is due to diffracted light from the heavily-overexposed planet. Credit: Phil Nicholson (Cornell University), Mark Showalter (NASA-Ames/Stanford) and NASA

  12. Saturn's rings thickness with the shadow hiding

    NASA Astrophysics Data System (ADS)

    Deau, Estelle; Brahic, André; Porco, Carolyn

    Using the Hapke shadow hiding model on various curves phases of ISS/Cassini, we were able to compute the thickness of Saturn's rings through the photometric filling factor. Our results show that diffuse rings (C ring and Cassini Division) are distributed in a monolayer with a thickness from a few centimeters to 5 meters. This seems to suggest that the layer is smaller than the larger particles. For the A and B rings, we find a thickness ranging from 10 to 20 meters, then leading to multiple layers of particles. Our results for the A ring are systematically lower than the values derived by density waves (Tiscareno et al., 2007) and dynamical simulations of Salo and Kaarjalainen (2003). For the first one, this can be explain by the fact the vertical height of the density waves are the upper limit of the real height. Indeed, the wakes (Julian & Toomre, 1966; Salo 1995) conduce the viscosity in the A ring (Daisaka et al., 2001), and produce random speeds greater in the ring plane than in the vertical direction (Daisaka & Ida, 1999), thereby reducing the thickness given by the vertical random speed used to compute the vertical height. However, for the latter one, simulations lead in all the cases (A and B rings such as C ring and Cassini Division) to vertical height of few meters. This constancy can be explained by the fact that simulations take a size distribution too truncated, and a coefficient of restitution rather simple (indeed, rings reflect different surface conditions related to the optical depth, thus the Bridges' law could not promote only one type of collisions). Finally, our results prefer monolayer (layer smaller than the larger particles which allow multilayer of smaller particules) for the faint rings (C ring and Cassini Division) and multilayer for the A and B rings.

  13. Discrete component S-band power amplifier

    NASA Technical Reports Server (NTRS)

    Block, A. F.

    1972-01-01

    A spacecraft S-band power amplifier for Nimbus satellite is reported that achieves stability by use of moderate Q input and output circuits. The discrete component amplifier uses distributed inductance and small piston capacitors for resonance and impedance matching of the transistor to 50 ohm input and output.

  14. Electroless plating apparatus for discrete microsized particles

    DOEpatents

    Mayer, Anton

    1978-01-01

    Method and apparatus are disclosed for producing very uniform coatings of a desired material on discrete microsized particles by electroless techniques. Agglomeration or bridging of the particles during the deposition process is prevented by imparting a sufficiently random motion to the particles that they are not in contact with each other for a time sufficient for such to occur.

  15. Electrolytic plating apparatus for discrete microsized particles

    DOEpatents

    Mayer, Anton

    1976-11-30

    Method and apparatus are disclosed for electrolytically producing very uniform coatings of a desired material on discrete microsized particles. Agglomeration or bridging of the particles during the deposition process is prevented by imparting a sufficiently random motion to the particles that they are not in contact with a powered cathode for a time sufficient for such to occur.

  16. Discrete wavelength-locked external cavity laser

    NASA Technical Reports Server (NTRS)

    Pilgrim, Jeffrey S. (Inventor); Silver, Joel A. (Inventor)

    2005-01-01

    An external cavity laser (and method of generating laser light) comprising: a laser light source; means for collimating light output by the laser light source; a diffraction grating receiving collimated light; a cavity feedback mirror reflecting light received from the diffraction grating back to the diffraction grating; and means for reliably tuning the external cavity laser to discrete wavelengths.

  17. Discrete Gust Model for Launch Vehicle Assessments

    NASA Technical Reports Server (NTRS)

    Leahy, Frank B.

    2008-01-01

    Analysis of spacecraft vehicle responses to atmospheric wind gusts during flight is important in the establishment of vehicle design structural requirements and operational capability. Typically, wind gust models can be either a spectral type determined by a random process having a wide range of wavelengths, or a discrete type having a single gust of predetermined magnitude and shape. Classical discrete models used by NASA during the Apollo and Space Shuttle Programs included a 9 m/sec quasi-square-wave gust with variable wavelength from 60 to 300 m. A later study derived discrete gust from a military specification (MIL-SPEC) document that used a "1-cosine" shape. The MIL-SPEC document contains a curve of non-dimensional gust magnitude as a function of non-dimensional gust half-wavelength based on the Dryden spectral model, but fails to list the equation necessary to reproduce the curve. Therefore, previous studies could only estimate a value of gust magnitude from the curve, or attempt to fit a function to it. This paper presents the development of the MIL-SPEC curve, and provides the necessary information to calculate discrete gust magnitudes as a function of both gust half-wavelength and the desired probability level of exceeding a specified gust magnitude.

  18. Discrete filters for large eddy simulation

    NASA Astrophysics Data System (ADS)

    Sagaut, P.; Grohens, R.

    1999-12-01

    This paper summarizes several results relative to discrete filters for subgrid-scale (SGS) models based on a multi-level filtering procedure. First, a theoretical study of discrete filters in physical space is performed. The analysis is done in the uniform one-dimensional case, and is then extended to the general multi-dimensional case for arbitrary structured and unstructured meshes. Some equivalence classes for the discrete filters are defined, based either on a differential approximation or the associated transfer function. Methods for the definition of discrete filters are proposed in the general case, including the approximation of continuous convolution filters. Second, the sensitivity of several SGS models with respect to the test filter is investigated. The selected models are: the dynamic Smagorinsky model, the mixed scale model (MSM), the selective MSM and the Liu-Meneveau-Katz (LMK) similarity model. Improved versions, which explicitly account for the spectral width of the test filter of the MSM and the LMK similarity model are proposed. The analysis, which reveals a significant influence of the test filter, is done through a priori testing on a 1283 field issued from the large eddy simulation (LES) of freely decaying homogeneous isotropic turbulence. Copyright

  19. A Note on Discrete Mathematics and Calculus.

    ERIC Educational Resources Information Center

    O'Reilly, Thomas J.

    1987-01-01

    Much of the current literature on the topic of discrete mathematics and calculus during the first two years of an undergraduate mathematics curriculum is cited. A relationship between the recursive integration formulas and recursively defined polynomials is described. A Pascal program is included. (Author/RH)

  20. Discrete Mathematics Course Supported by CAS MATHEMATICA

    ERIC Educational Resources Information Center

    Ivanov, O. A.; Ivanova, V. V.; Saltan, A. A.

    2017-01-01

    In this paper, we discuss examples of assignments for a course in discrete mathematics for undergraduate students majoring in business informatics. We consider several problems with computer-based solutions and discuss general strategies for using computers in teaching mathematics and its applications. In order to evaluate the effectiveness of our…

  1. Geometric Representations for Discrete Fourier Transforms

    NASA Technical Reports Server (NTRS)

    Cambell, C. W.

    1986-01-01

    Simple geometric representations show symmetry and periodicity of discrete Fourier transforms (DFT's). Help in visualizing requirements for storing and manipulating transform value in computations. Representations useful in any number of dimensions, but particularly in one-, two-, and three-dimensional cases often encountered in practice.

  2. Web-Based Implementation of Discrete Mathematics

    ERIC Educational Resources Information Center

    Love, Tanzy; Keinert, Fritz; Shelley, Mack

    2006-01-01

    The Department of Mathematics at Iowa State University teaches a freshman-level Discrete Mathematics course with total enrollment of about 1,800 students per year. The traditional format includes large lectures, with about 150 students each, taught by faculty and temporary instructors in two class sessions per week and recitation sections, with…

  3. Kinematics of foldable discrete space cranes

    NASA Technical Reports Server (NTRS)

    Nayfeh, A. H.

    1985-01-01

    Exact kinematic description of a NASA proposed prototype foldable-deployable discrete space crane are presented. A computer program is developed which maps the geometry of the crane once controlling parameters are specified. The program uses a building block type approach in which it calculates the local coordinates of each repeating cell and then combines them with respect to a global coordinates system.

  4. Discrete control of resonant wave energy devices.

    PubMed

    Clément, A H; Babarit, A

    2012-01-28

    Aiming at amplifying the energy productive motion of wave energy converters (WECs) in response to irregular sea waves, the strategies of discrete control presented here feature some major advantages over continuous control, which is known to require, for optimal operation, a bidirectional power take-off able to re-inject energy into the WEC system during parts of the oscillation cycles. Three different discrete control strategies are described: latching control, declutching control and the combination of both, which we term latched-operating-declutched control. It is shown that any of these methods can be applied with great benefit, not only to mono-resonant WEC oscillators, but also to bi-resonant and multi-resonant systems. For some of these applications, it is shown how these three discrete control strategies can be optimally defined, either by analytical solution for regular waves, or numerically, by applying the optimal command theory in irregular waves. Applied to a model of a seven degree-of-freedom system (the SEAREV WEC) to estimate its annual production on several production sites, the most efficient of these discrete control strategies was shown to double the energy production, regardless of the resource level of the site, which may be considered as a real breakthrough, rather than a marginal improvement.

  5. Applied Behavior Analysis: Beyond Discrete Trial Teaching

    ERIC Educational Resources Information Center

    Steege, Mark W.; Mace, F. Charles; Perry, Lora; Longenecker, Harold

    2007-01-01

    We discuss the problem of autism-specific special education programs representing themselves as Applied Behavior Analysis (ABA) programs when the only ABA intervention employed is Discrete Trial Teaching (DTT), and often for limited portions of the school day. Although DTT has many advantages to recommend its use, it is not well suited to teach…

  6. Attractors for discrete periodic dynamical systems

    Treesearch

    John E. Franke; James F. Selgrade

    2003-01-01

    A mathematical framework is introduced to study attractors of discrete, nonautonomous dynamical systems which depend periodically on time. A structure theorem for such attractors is established which says that the attractor of a time-periodic dynamical system is the unin of attractors of appropriate autonomous maps. If the nonautonomous system is a perturbation of an...

  7. 5 CFR 572.102 - Agency discretion.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... and transportation or interview expenses in filling any position, the agency should consider such factors as availability of funds as well as the desirability of conducting interviews for a particular job... TRANSPORTATION EXPENSES; NEW APPOINTEES AND INTERVIEWS § 572.102 Agency discretion. Payment of travel expenses...

  8. Stable discrete representation of relativistically drifting plasmas

    DOE PAGES

    Kirchen, M.; Lehe, R.; Godfrey, B. B.; ...

    2016-10-10

    Representing the electrodynamics of relativistically drifting particle ensembles in discrete, co-propagating Galilean coordinates enables the derivation of a Particle-In-Cell algorithm that is intrinsically free of the numerical Cherenkov instability for plasmas flowing at a uniform velocity. Application of the method is shown by modeling plasma accelerators in a Lorentz-transformed optimal frame of reference.

  9. 5 CFR 572.102 - Agency discretion.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... TRANSPORTATION EXPENSES; NEW APPOINTEES AND INTERVIEWS § 572.102 Agency discretion. Payment of travel expenses... and transportation or interview expenses in filling any position, the agency should consider such factors as availability of funds as well as the desirability of conducting interviews for a particular job...

  10. The cryogenic storage ring CSR

    NASA Astrophysics Data System (ADS)

    von Hahn, R.; Becker, A.; Berg, F.; Blaum, K.; Breitenfeldt, C.; Fadil, H.; Fellenberger, F.; Froese, M.; George, S.; Göck, J.; Grieser, M.; Grussie, F.; Guerin, E. A.; Heber, O.; Herwig, P.; Karthein, J.; Krantz, C.; Kreckel, H.; Lange, M.; Laux, F.; Lohmann, S.; Menk, S.; Meyer, C.; Mishra, P. M.; Novotný, O.; O'Connor, A. P.; Orlov, D. A.; Rappaport, M. L.; Repnow, R.; Saurabh, S.; Schippers, S.; Schröter, C. D.; Schwalm, D.; Schweikhard, L.; Sieber, T.; Shornikov, A.; Spruck, K.; Sunil Kumar, S.; Ullrich, J.; Urbain, X.; Vogel, S.; Wilhelm, P.; Wolf, A.; Zajfman, D.

    2016-06-01

    An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm-3 is derived, equivalent to a room-temperature pressure below 10-14 mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.

  11. The cryogenic storage ring CSR.

    PubMed

    von Hahn, R; Becker, A; Berg, F; Blaum, K; Breitenfeldt, C; Fadil, H; Fellenberger, F; Froese, M; George, S; Göck, J; Grieser, M; Grussie, F; Guerin, E A; Heber, O; Herwig, P; Karthein, J; Krantz, C; Kreckel, H; Lange, M; Laux, F; Lohmann, S; Menk, S; Meyer, C; Mishra, P M; Novotný, O; O'Connor, A P; Orlov, D A; Rappaport, M L; Repnow, R; Saurabh, S; Schippers, S; Schröter, C D; Schwalm, D; Schweikhard, L; Sieber, T; Shornikov, A; Spruck, K; Sunil Kumar, S; Ullrich, J; Urbain, X; Vogel, S; Wilhelm, P; Wolf, A; Zajfman, D

    2016-06-01

    An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm(-3) is derived, equivalent to a room-temperature pressure below 10(-14) mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.

  12. New diols with imidazoquinazoline ring

    NASA Astrophysics Data System (ADS)

    Szyszkowska, Agnieszka; Klasek, Antonin; Pawlędzio, Sylwia; Trzybiński, Damian; Woźniak, Krzysztof; Zarzyka, Iwona

    2018-02-01

    The objective of these studies was to synthesize and characterize new diols with an imidazoquinazoline ring. New diols were obtained in reactions of 2,6-bis-(ethoxycarbonylmethyl)-1-phenylimidazo[1,5-c]quinazoline-3,5-dione with excess of ethylene glycol or in reaction of 1-phenyl-2H,6H-imidazo[1,5-c]quinazoline-3,5-dione with 2-M excess of ethylene oxide. The products were isolated at high yield and characterized by instrumental methods (IR, 1H- and 13C-NMR, MS-ESI, UV, TGA). The structure of 2,6-bis(2-hydroxyethyl)-1-phenylimidazo[1,5-c]quinazoline-3,5-dione (BEFIQ) was also investigated by single-crystal X-ray diffraction. BEFIQ crystallizes in the monoclinic P21/n space group with two molecules in the asymmetric unit of the crystal lattice. The nature of the packing of molecules in the crystal lattice of BEFIQ was investigated by Hirshfeld surface analysis. The described methods enable the synthesis of new diols with an imidazoquinazoline ring. The new diols are quite soluble in typical organic solvents. Therefore, they can be used as raw materials for the synthesis of thermally stable polymers, and they can also have biological activity.

  13. Electrostatic, inductive ring probe bandwidth

    NASA Astrophysics Data System (ADS)

    Gajewski, Juliusz B.

    1996-12-01

    Electrostatic, inductive, non-intrusive probes are employed for measuring the electric charge as well as the mass flow rate, volume loading, and mean flow velocity of solid particles especially while travelling through pipes of pneumatic transport or in ambient air when a flux of those particles forms a rather compact column-like jet of a nearly constant cross sectional area. The bandwidth of such measuring devices is a very important factor which should be determined carefully, or even planned in advance, before designing the probe itself intended for the use under well defined conditions. In the paper the bandwidth of the inductive ring probes is discussed. To find the probe bandwidth the derivation of a general formula is presented along with the accepted assumptions and an original way of formulation and consideration of that problem. The general formula obtained is an inductive ring probe frequency response function and permits the bandwidth of any inductive, non-intrusive probe, sensor, transducer, etc, to be easily determined for given mean flow velocities of particles and probe widths.

  14. Infant differential behavioral responding to discrete emotions.

    PubMed

    Walle, Eric A; Reschke, Peter J; Camras, Linda A; Campos, Joseph J

    2017-10-01

    Emotional communication regulates the behaviors of social partners. Research on individuals' responding to others' emotions typically compares responses to a single negative emotion compared with responses to a neutral or positive emotion. Furthermore, coding of such responses routinely measure surface level features of the behavior (e.g., approach vs. avoidance) rather than its underlying function (e.g., the goal of the approach or avoidant behavior). This investigation examined infants' responding to others' emotional displays across 5 discrete emotions: joy, sadness, fear, anger, and disgust. Specifically, 16-, 19-, and 24-month-old infants observed an adult communicate a discrete emotion toward a stimulus during a naturalistic interaction. Infants' responses were coded to capture the function of their behaviors (e.g., exploration, prosocial behavior, and security seeking). The results revealed a number of instances indicating that infants use different functional behaviors in response to discrete emotions. Differences in behaviors across emotions were clearest in the 24-month-old infants, though younger infants also demonstrated some differential use of behaviors in response to discrete emotions. This is the first comprehensive study to identify differences in how infants respond with goal-directed behaviors to discrete emotions. Additionally, the inclusion of a function-based coding scheme and interpersonal paradigms may be informative for future emotion research with children and adults. Possible developmental accounts for the observed behaviors and the benefits of coding techniques emphasizing the function of social behavior over their form are discussed. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  15. Dynamical Evolution of Ring-Satellite Systems

    NASA Technical Reports Server (NTRS)

    Ohtsuki, Keiji

    2005-01-01

    The goal of this research was to understand dynamical processes related to the evolution of size distribution of particles in planetary rings and application of theoretical results to explain features in the present rings of giant planets. We studied velocity evolution and accretion rates of ring particles in the Roche zone. We developed a new numerical code for the evolution of ring particle size distribution, which takes into account the above results for particle velocity evolution and accretion rates. We also studied radial diffusion rate of ring particles due to inelastic collisions and gravitational encounters. Many of these results can be also applied to dynamical evolution of a planetesimal disk. Finally, we studied rotation rates of moonlets and particles in planetary rings, which would influence the accretional evolution of these bodies. We describe our key accomplishments during the past three years in more detail in the following.

  16. Cooling system for three hook ring segment

    SciTech Connect

    Campbell, Christian X.; Eng, Darryl; Lee, Ching-Pang

    2014-08-26

    A triple hook ring segment including forward, midsection and aft mounting hooks for engagement with respective hangers formed on a ring segment carrier for supporting a ring segment panel, and defining a forward high pressure chamber and an aft low pressure chamber on opposing sides of the midsection mounting hook. An isolation plate is provided on the aft side of the midsection mounting hook to form an isolation chamber between the aft low pressure chamber and the ring segment panel. High pressure air is supplied to the forward chamber and flows to the isolation chamber through crossover passages in themore » midsection hook. The isolation chamber provides convection cooling air to an aft portion of the ring segment panel and enables a reduction of air pressure in the aft low pressure chamber to reduce leakage flow of cooling air from the ring segment.« less

  17. Cooling system for three hook ring segment

    DOEpatents

    Campbell, Christian X.; Eng, Darryl; Lee, Ching-Pang; Patat, Harry

    2014-08-26

    A triple hook ring segment including forward, midsection and aft mounting hooks for engagement with respective hangers formed on a ring segment carrier for supporting a ring segment panel, and defining a forward high pressure chamber and an aft low pressure chamber on opposing sides of the midsection mounting hook. An isolation plate is provided on the aft side of the midsection mounting hook to form an isolation chamber between the aft low pressure chamber and the ring segment panel. High pressure air is supplied to the forward chamber and flows to the isolation chamber through crossover passages in the midsection hook. The isolation chamber provides convection cooling air to an aft portion of the ring segment panel and enables a reduction of air pressure in the aft low pressure chamber to reduce leakage flow of cooling air from the ring segment.

  18. Report of the eRHIC Ring-Ring Working Group

    SciTech Connect

    Aschenauer, E. C.; Berg, S.; Blaskiewicz, M.

    2015-10-13

    This report evaluates the ring-ring option for eRHIC as a lower risk alternative to the linac-ring option. The reduced risk goes along with a reduced initial luminosity performance. However, a luminosity upgrade path is kept open. This upgrade path consists of two branches, with the ultimate upgrade being either a ring-ring or a linac-ring scheme. The linac-ring upgrade could be almost identical to the proposed linac-ring scheme, which is based on an ERL in the RHIC tunnel. This linac-ring version has been studied in great detail over the past ten years, and its significant risks are known. On the othermore » hand, no detailed work on an ultimate performance ring-ring scenario has been performed yet, other than the development of a consistent parameter set. Pursuing the ring-ring upgrade path introduces high risks and requires significant design work that is beyond the scope of this report.« less

  19. Signet ring lymphoma: a potential diagnostic mishap.

    PubMed

    Krause, John R

    2013-07-01

    Signet ring lymphomas are proliferations of malignant lymphoid cells containing cytoplasmic inclusions or vacuoles that displace the nucleus to the side, imparting a "signet ring" appearance. These signet ring cells, particularly those with cytoplasmic vacuoles, may be mistaken for an adenocarcinoma rather than a lymphoma, if sufficient material is not available to differentiate the case by immunohistochemical stains or flow cytometry. The pathologist must also be aware of this entity so that appropriate studies may be untaken.

  20. Saturn’s ring temperatures at equinox

    NASA Astrophysics Data System (ADS)

    Spilker, Linda J.; Ferrari, C.; Morishima, R.

    2013-10-01

    Modeling the thermal emission of Saturn's rings is challenging due to the numerous heating sources as well as the structural properties of the disk and of the particles that are closely related. At equinox, however, the main rings are externally heated by Saturn alone and the problem is somewhat simplified. We test the abilities of our current models to reproduce the temperatures observed with the Cassini CIRS instrument around equinox in August 2009. A simple semi-analytic model which includes mutual shadowing effects can mostly explain the radial profile of the equinox ring temperatures, except the model predicts lower temperatures than those observed for the A ring. The temperature variation at a given saturnocentric radius is primarily caused by observational geometry variations relative to Saturn. The observed temperature increases with decreasing Saturn-ring-observer angle. In addition, we found evidence that the leading hemispheres of particles are warmer than the trailing hemispheres at least for the C ring and probably for the A and B rings as well. This is explained if some fraction of particles has spin rates lower than the synchronous rotation rate as predicted by N-body simulations. The spin model for a monolayer ring (Ferrari, C., Leyrat, C., 2006, Astron. Astrophys. 447, 745-760) can fit the temperature variations with spacecraft longitude observed in the C ring with currently known thermal properties and a mixing of slow and fast rotators. The multilayer model (Morishima, R., Salo, H., Ohtsuki, K., 2009, Icarus 201, 634-654) can reproduce the temperatures of the B and C rings but gives A ring temperatures that are significantly lower than those observed as does the simple semi-analytic model. More advanced models which take into account self-gravity wakes may explain the A ring temperature behavior.

  1. Saturn’s ring temperatures at equinox

    NASA Astrophysics Data System (ADS)

    Spilker, Linda; Ferrari, Cecile; Morishima, Ryuji

    2013-09-01

    Modeling the thermal emission of Saturn’s rings is challenging due to the numerous heating sources as well as the structural properties of the disk and of the particles that are closely related. At equinox, however, rings are externally heated by Saturn alone and the problem is somewhat simplified. We test the abilities of our current models to reproduce the temperatures observed with the Cassini-CIRS instrument around equinox in August 2009. A simple semi-analytic model with the mutual shadowing effect can mostly explain the radial profile of the equinox ring temperatures, except the model predicts lower temperatures than those observed for the A ring. The temperature variation at a given saturnocentric radius is primarily caused by observational geometry variations relative to Saturn. The observed temperature increases with decreasing Saturn-ring-observer angle. In addition, we found evidence that the leading hemispheres of particles are warmer than the trailing hemispheres at least for the C ring and probably for the A and B rings as well. This is explained if some fraction of particles has spin rates lower than the synchronous rotation rate as predicted by N-body simulations. The spin model for a monolayer ring (Ferrari, C., Leyrat, C. [2006]. Astron. Astrophys. 447, 745-760) can fit the temperature variations with spacecraft longitude observed in the C ring with currently known thermal properties and a mixing of slow and fast rotators. The multilayer model (Morishima, R., Salo, H., Ohtsuki, K. [2009]. Icarus 201, 634-654) can reproduce the temperatures of the B and C rings but gives A ring temperatures that are significantly lower than those observed as does the simple semi-analytic model. More advanced models which take into account self-gravity wakes may explain the A ring temperature behavior.

  2. Interferometric ring lasers and optical devices

    DOEpatents

    Hohimer, J.P.; Craft, D.C.

    1995-03-14

    Two ring diode lasers are optically coupled together to produce tunable, stable output through a Y-junction output coupler which may also be a laser diode or can be an active waveguide. These devices demonstrate a sharp peak in light output with an excellent side-mode-rejection ratio. The rings can also be made of passive or active waveguide material. With additional rings the device is a tunable optical multiplexer/demultiplexer. 11 figs.

  3. Saturn Ring Data Analysis and Thermal Modeling

    NASA Technical Reports Server (NTRS)

    Dobson, Coleman

    2011-01-01

    CIRS, VIMS, UVIS, and ISS (Cassini's Composite Infrared Specrtometer, Visual and Infrared Mapping Spectrometer, Ultra Violet Imaging Spectrometer and Imaging Science Subsystem, respectively), have each operated in a multidimensional observation space and have acquired scans of the lit and unlit rings at multiple phase angles. To better understand physical and dynamical ring particle parametric dependence, we co-registered profiles from these three instruments, taken at a wide range of wavelengths, from ultraviolet through the thermal infrared, to associate changes in ring particle temperature with changes in observed brightness, specifically with albedos inferred by ISS, UVIS and VIMS. We work in a parameter space where the solar elevation range is constrained to 12 deg - 14 deg and the chosen radial region is the B3 region of the B ring; this region is the most optically thick region in Saturn's rings. From this compilation of multiple wavelength data, we construct and fit phase curves and color ratios using independent dynamical thermal models for ring structure and overplot Saturn, Saturn ring, and Solar spectra. Analysis of phase curve construction and color ratios reveals thermal emission to fall within the extrema of the ISS bandwidth and a geometrical dependence of reddening on phase angle, respectively. Analysis of spectra reveals Cassini CIRS Saturn spectra dominate Cassini CIRS B3 Ring Spectra from 19 to 1000 microns, while Earth-based B Ring Spectrum dominates Earth-based Saturn Spectrum from 0.4 to 4 microns. From our fits we test out dynamical thermal models; from the phase curves we derive ring albedos and non-lambertian properties of the ring particle surfaces; and from the color ratios we examine multiple scattering within the regolith of ring particles.

  4. Interferometric ring lasers and optical devices

    DOEpatents

    Hohimer, John P.; Craft, David C.

    1995-01-01

    Two ring diode lasers are optically coupled together to produce tunable, stable output through a Y-junction output coupler which may also be a laser diode or can be an active waveguide. These devices demonstrate a sharp peak in light output with an excellent side-mode-rejection ratio. The rings can also be made of passive or active waveguide material. With additional rings the device is a tunable optical multiplexer/demultiplexer.

  5. On the potential of large ring lasers

    NASA Astrophysics Data System (ADS)

    Stedman, G. E.; Hurst, R. B.; Schreiber, K. U.

    2007-11-01

    We describe a new ring laser with area A = 833 m 2 and update performance statistics for several such machines. Chaio and Anandan [R.Y. Chaio, J. Anandan, Gen. Relat. Gravit. 14 (1982) 515-521] judged ring lasers inferior to matter interferometers as possible detectors of gravitational waves. However, we note that geophysically interesting results have been obtained from large ring lasers and that there is still a lot of room for improvements.

  6. The CO emission of ring galaxies.

    NASA Astrophysics Data System (ADS)

    Horellou, C.; Casoli, F.; Combes, F.; Dupraz, C.

    1995-06-01

    Using the 15m SEST and 30m IRAM telescope we have observed 16 ring galaxies in the 2CO10 transition and detected 14. Six ring galaxies have been detected in the ^12^CO(2-1) line. The Cartwheel, often considered as the prototype of ring galaxies, has not been detected. We suggest that the weak CO emission of this galaxy is due to its low metallicity. The observations do not exclude the possibility that the Cartwheel may be H_2_rich and actively forming stars. We also present new HI detections of six rings. We have compared the CO emission of the ring galaxies with that of the distance-limited sample of Sage (1993a,b) and found that ring galaxies are bright in CO compared to normal galaxies. If the standard conversion factor from CO emissivities into H_2_column densities holds for ring galaxies, this suggests that a large amount of molecular gas is available for star formation and that ring galaxies are actively forming stars. This result is in agreement with the high far-infrared luminosities of ring galaxies. We have also observed two Hoag-type objects in CO but have detected neither of them.

  7. Development of a liquid metal slip ring

    NASA Technical Reports Server (NTRS)

    Weinberger, S. M.

    1972-01-01

    A liquid metal slip ring/solar orientation mechanism was designed and a model tested. This was a follow-up of previous efforts for the development of a gallium liquid metal slip ring in which the major problem was the formation and ejection of debris. A number of slip ring design approaches were studied. The probe design concept was fully implemented with detail drawings and a model was successfully tested for dielectric strength, shock vibration, acceleration and operation. The conclusions are that a gallium liquid metal slip ring/solar orientation mechanism is feasible and that the problem of debris formation and ejection has been successfully solved.

  8. Edge-on View of Saturn's Rings

    NASA Technical Reports Server (NTRS)

    1996-01-01

    TOP - This is a NASA Hubble Space Telescope snapshot of Saturn with its rings barely visible. Normally, astronomers see Saturn with its rings tilted. Earth was almost in the plane of Saturn's rings, thus the rings appear edge-on.

    In this view, Saturn's largest moon, Titan, is casting a shadow on Saturn. Titan's atmosphere is a dark brown haze. The other moons appear white because of their bright, icy surfaces. Four moons - from left to right, Mimas, Tethys, Janus, and Enceladus - are clustered around the edge of Saturn's rings on the right. Two other moons appear in front of the ring plane. Prometheus is on the right edge; Pandora, on the left. The rings also are casting a shadow on Saturn because the Sun was above the ring plane.

    BOTTOM - This photograph shows Saturn with its rings slightly tilted. The moon called Dione, on the lower right, is casting a long, thin shadow across the whole ring system due to the setting Sun on the ring plane. The moon on the upper left of Saturn is Tethys.

    Astronomers also are studying the unusual appearance of Saturn's rings. The bottom image displays a faint, narrow ring, the F-ring just outside the main ring, which normally is invisible from Earth. Close to the edge of Saturn's disk, the front section of rings seem brighter and more yellow than the back due to the additional lumination by yellowish Saturn.

    The color images were assembled from separate exposures taken August 6 (top) and November 17 (bottom), 1995 with the Wide Field Planetary Camera-2.

    The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

    This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

  9. Condenser for illuminating a ring field

    DOEpatents

    Sweatt, William C.

    1994-01-01

    A series of segments of a parent aspheric mirror having one foci at at a si-point source of radiation and the other foci at the radius of a ring field have all but one or all of their beams translated and rotated by sets of mirrors such that all of the beams pass through the real entrance pupil of a ring field camera about one of the beams and fall onto the ring field radius as a coincident image as an arc of the ring field.

  10. Vortex rings in radially confined domains

    NASA Astrophysics Data System (ADS)

    Stewart, Kelley C.; Vlachos, Pavlos P.

    2012-10-01

    The dynamics of vortex rings generated within confined domains are relevant to important hydrodynamic processes such as flow past heart valves or severe arterial constrictions. However, despite their importance, these flows have not received much attention to date. This study examines the development and evolution of radially confined vortex rings. Time-resolved digital particle image velocimetry was used to investigate two levels of radial confinement and a range of vortex ring strengths. We found that for severely confined vortex rings, the formation time and peak circulation values were unaffected for L/D 0 < 4 cases and slightly affected for larger L/D 0 cases. After pinch-off, circulation decay was observed with an approximately constant normalized circulation decay rate. We found that with increasing circulation strength, the nondimensional time delay between the pinch-off and the onset of circulation decay reduced due to an increased vortex ring diameter within the confinement domain and a reduction in the necessary time for the surface induced and core vorticity regions to interact. This study uncovers the dynamics of radially confined vortex rings and show that the nondimensional rate of circulation decay is dependent on the vortex ring confinement ratio (ratio of the vortex ring orifice diameter to the diameter of the outer cylinder), and the time delay between the vortex pinch-off and the onset of circulation is dependent on the vortex ring circulation strength.

  11. Condenser for illuminating a ring field

    DOEpatents

    Sweatt, W.C.

    1994-11-01

    A series of segments of a parent aspheric mirror having one foci at a point source of radiation and the other foci at the radius of a ring field have all but one or all of their beams translated and rotated by sets of mirrors such that all of the beams pass through the real entrance pupil of a ring field camera about one of the beams and fall onto the ring field radius as a coincident image as an arc of the ring field. 5 figs.

  12. What Perturbs the ggrdgr Rings of Uranus?

    PubMed

    French, R G; Kangas, J A; Elliot, J L

    1986-01-31

    The gamma and delta rings have by far the largest radial perturbations of any of the nine known Uranian rings. These two rings deviate from Keplerian orbits, having typical root-mean-square residuals of about 3 kilometers (compared to a few hundred meters for the other seven known rings). Possible causes for the perturbations include nearby shepherd satellites and Lindblad resonances. If shepherd satellites are responsible, they could be as large as several tens of kilometers in diameter. The perturbation patterns of the gamma and delta rings have been examined for evidence of Lindblad resonances of azimuthal wave number m = 0, 1, 2, 3, and 4. The beta ring radial residuals are well matched by a 2:1 Lindblad resonance. If this represents a real physical phenomenon and is not an artifact of undersampling, then the most plausible interpretation is that there is an undiscovered satellite orbiting 76,522 +/- 8 kilometers from Uranus, with an orbital period of 15.3595 +/- 0.0001 hours and a radius of 75 to 100 kilometers. Such a satellite would be easily detected by the Voyager spacecraft when it encounters Uranus. The 2:1 resonance location is 41 +/- 9 kilometers inside the delta ring, which makes it unlikely that the resonance is due to a viscous instability within the ring. In contrast, no low-order Lindblad resonance matches the gamma ring perturbations, which are probably caused by one or more shepherd satellites large enough to be clearly visible in Voyager images.

  13. Corneal iron ring after hyperopic photorefractive keratectomy.

    PubMed

    Bilgihan, K; Akata, F; Gürelik, G; Adigüzel, U; Akpinar, M; Hasanreisoğlu, B

    1999-05-01

    To report the incidence and course of corneal iron deposition after hyperopic photorefractive keratectomy (PRK). Gazi University, Medical School, Department of Ophthalmology, Ankara, Turkey. Between January 1995 and December 1997, 62 eyes had PRK to correct hyperopia. Nine eyes developed corneal iron ring 5 to 8 months (mean 6.25 months +/- 1.3 [SD]) after PRK for hyperopia. The rings persisted during the mean follow-up of 19 +/- 11.09 months. The ring-shaped iron deposition after PRK for hyperopia must be differentiated from the Fleischer ring. Our results suggest that the slitlamp findings of peripheral corneal iron deposition in hyperopic PRK patients correlate with achieved correction.

  14. Dual wavelength SOA based fiber ring laser

    NASA Astrophysics Data System (ADS)

    Omran, Haitham; Kotb, Hussein E.; Khalil, Diaa

    2017-02-01

    In this paper we present a novel dual wavelength SOA based fiber ring laser. The ring laser combines the effect of SOA gain starving at the edge of the gain spectrum and the polarization state in the PM fiber ring to generate a dual wavelength laser at 1452.7 nm and 1454.5 nm with single mode operation verified. With the proposed technique, single wavelength single mode laser operation can be easily obtained by adjusting the SOA pumping current and the ring polarization state.

  15. Apse-Alignment of the Uranian Rings

    NASA Technical Reports Server (NTRS)

    Mosqueira, I.; Estrada, P. R.

    2000-01-01

    An explanation of the dynamical mechanism for apse-alignment of the eccentric Uranian rings is necessary before observations can be used to determine properties such as ring masses, particle sizes, and elasticities. The leading model relies on the ring self-gravity to accomplish this task, yet it yields equilibrium masses which are not in accord with Voyager radio measurements. We explore possible solutions such that the self-gravity and the collisional terms are both involved in the process of apse-alignment. We consider limits that correspond to a hot and a cold ring, and show that pressure terms may play a significant role in the equilibrium conditions for the narrow Uranian rings. In the cold ring case, where the scale height of the ring near periapse is comparable to the ring particle size, we introduce a new pressure correction pertaining to a region of the ring where the particles are locked in their relative positions and jammed against their neighbors, and the velocity dispersion is so low that the collisions are nearly elastic. In this case, we find a solution such that the ring self-gravity maintains apse-alignment against both differential precession (m = 1 mode) and the fluid pressure. We apply this model to the Uranian alpha ring, and show that, compared to the previous self-gravity model, the mass estimate for this ring increases by an order of magnitude. In the case of a hot ring, where the scale height can reach a value as much as fifty times larger than a particle size, we find velocity dispersion profiles that result in pressure forces which act in such a way as to alter the ring equilibrium conditions, again leading to a ring mass increase of an order of magnitude; however, such a velocity dispersion profile would require a different mechanism than is currently envisioned for establishing heating/cooling balance in a finite-sized, inelastic particle ring. Finally, we introduce an important correction to the model of Chiang and Goldreich.

  16. The Conversion of Wiswesser Line Notations to Ring Codes. I. The Conversion of Ring Systems

    ERIC Educational Resources Information Center

    Granito, Charles E.; And Others

    1972-01-01

    The computerized conversion of Wiswesser Line Notations to Ring Codes, using a two-part approach, and the set of computer programs generated for the conversion of ring systems are described. (9 references) (Author)

  17. Concentric ring flywheel with hooked ring carbon fiber separator/torque coupler

    DOEpatents

    Kuklo, T.C.

    1999-07-20

    A concentric ring flywheel with expandable separators, which function as torque couplers, between the rings to take up the gap formed between adjacent rings due to differential expansion between different radius rings during rotation of the flywheel. The expandable separators or torque couplers include a hook-like section at an upper end which is positioned over an inner ring and a shelf-like or flange section at a lower end onto which the next adjacent outer ring is positioned. As the concentric rings are rotated the gap formed by the differential expansion there between is partially taken up by the expandable separators or torque couplers to maintain torque and centering attachment of the concentric rings. 2 figs.

  18. Concentric ring flywheel with hooked ring carbon fiber separator/torque coupler

    DOEpatents

    Kuklo, Thomas C.

    1999-01-01

    A concentric ring flywheel with expandable separators, which function as torque couplers, between the rings to take up the gap formed between adjacent rings due to differential expansion between different radius rings during rotation of the flywheel. The expandable separators or torque couplers include a hook-like section at an upper end which is positioned over an inner ring and a shelf-like or flange section at a lower end onto which the next adjacent outer ring is positioned. As the concentric rings are rotated the gap formed by the differential expansion there between is partially taken up by the expandable separators or torque couplers to maintain torque and centering attachment of the concentric rings.

  19. Mechanical support of a ceramic gas turbine vane ring

    DOEpatents

    Shi, Jun; Green, Kevin E.; Mosher, Daniel A.; Holowczak, John E.; Reinhardt, Gregory E.

    2010-07-27

    An assembly for mounting a ceramic turbine vane ring onto a turbine support casing comprises a first metal clamping ring and a second metal clamping ring. The first metal clamping ring is configured to engage with a first side of a tab member of the ceramic turbine vane ring. The second metal clamping ring is configured to engage with a second side of the tab member such that the tab member is disposed between the first and second metal clamping rings.

  20. A Pauson-Khand and ring-expansion approach to the aquariane ring system.

    PubMed

    Thornton, Paul D; Burnell, D Jean

    2006-07-20

    [Structure: see text] The carbocyclic ring system of the aquariolide diterpenes has been synthesized by two routes involving a diastereoselective Pauson-Khand reaction and subsequent ring expansion. In one route, a tetracyclic enone was elaborated to generate the nine-membered ring by Grob fragmentation. In the second approach, a spirocyclic tricycle underwent a facile anionic oxy-Cope rearrangement to complete the synthesis of the desired ring system.

  1. THE REVITALIZED NSLS VUV RING.

    SciTech Connect

    HULBERT,S.L.

    1999-10-13

    A status report on the revitalization of the NSLS VUV ring will be presented, concentrating on three areas: (1) the four infrared ports (U2A/B, U4IR, U10A/B, and U12IR), (2) conversion of out-of-date toroidal grating monochromators to spherical grating type (U4A, U7A, and U12A), and (3) new insertion device beamlines (U5UA and U13UB). All of these beamlines were designed (new ones) or upgraded (old ones) to serve a specific scientific need represented by the PRTs (both NSLS and non-NSLS based) involved. Therefore, an overview of the scientific programs served by these new beamlines will be given, as well as a summarymore » of the beamline optical designs and operating performance.« less

  2. The revitalized NSLS VUV ring

    SciTech Connect

    Hulbert, S.L.

    1999-10-13

    A status report on the revitalization of the NSLS VUV ring will be presented, concentrating on three areas: (1) the four infrared ports (U2A/B, U4IR, U10A/B, and U12IR), (2) conversion of out-of-date toroidal grating monochromators to spherical grating type (U4A, U7A, and U12A), and (3) new insertion device beamlines (U5UA and U13UB). All of these beamlines were designed (new ones) or upgraded (old ones) to serve a specific scientific need represented by the PRTs (both NSLS and non-NSLS based) involved. Therefore, an overview of the scientific programs served by these new beamlines will be given, as well as a summarymore » of the beamline optical designs and operating performance.« less

  3. Smoke ring for a halo

    NASA Image and Video Library

    2015-10-26

    Two stars shine through the centre of a ring of cascading dust in this image taken by the NASA/ESA Hubble Space Telescope. The star system is named DI Cha, and while only two stars are apparent, it is actually a quadruple system containing two sets of binary stars. As this is a relatively young star system it is surrounded by dust. The young stars are moulding the dust into a wispy wrap. The host of this alluring interaction between dust and star is the Chamaeleon I dark cloud — one of three such clouds that comprise a large star-forming region known as the Chamaeleon Complex. DI Cha's juvenility is not remarkable within this region. In fact, the entire system is among not only the youngest but also the closest collections of newly formed stars to be found and so provides an ideal target for studies of star formation.

  4. Formation dynamics in geostationary ring

    NASA Astrophysics Data System (ADS)

    Spiridonova, Sofya

    2016-08-01

    A relative motion model for a satellite formation composed of two Earth-orbiting spacecraft located in the geostationary ring is developed taking into account major gravitational and non-gravitational forces. A previously existing model featuring perturbation due to J_2 is enhanced by the perturbations due to solar radiation pressure arising from unequal area-to-mass ratios, as well as the secular and long-periodic gravitational perturbations due to the Sun and the Moon. The extended relative motion model is validated using several typical formation geometries against a reference generated by numerical integration of the absolute orbits of the two spacecraft. The results of this work can find application in future on-orbit servicing and formation flying missions in near-geostationary orbit.

  5. The cryogenic storage ring CSR

    SciTech Connect

    Hahn, R. von; Becker, A.; Berg, F.

    2016-06-15

    An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbitmore » shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm{sup −3} is derived, equivalent to a room-temperature pressure below 10{sup −14} mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.« less

  6. What confines the rings of Saturn?

    NASA Astrophysics Data System (ADS)

    Tajeddine, Radwan; Nicholson, Philip D.; El Moutamid, Maryame; Longaretti, Pierre-Yves; Burns, Joseph A.

    2017-10-01

    The viscous spreading of planetary rings is believed to be counteracted by satellite torques, either through an individual resonance or through overlapping resonances (when the satellite is close to the ring edge). For the A ring of Saturn, it has been commonly believed that the satellite Janus alone can prevent the ring from spreading via its 7:6 Lindblad resonance. We discuss this common misconception and show that, in reality, the A ring is confined by the contributions from the group of satellites Pan, Atlas, Prometheus, Pandora, Janus, Epimetheus, and Mimas, whose resonances gradually decrease the angular momentum flux transported outward through the ring via density and bending waves. We further argue that this decrease in angular momentum flux occurs through the mechanism of ‘flux reversal’.We find that the Janus 7:6 torque is relatively feeble, as is the comparable torque of the nearby small satellite Atlas, each amounting to less than one-tenth of the angular momentum transport carried by the A ring. But the cumulative torques of the many other satellite resonances in the A ring sufficiently reduce the angular momentum flux through the rings so that the torques due to Janus and Atlas are effective in confining the outer edge of the ring.Furthermore, we use the magnitude of the satellites’ resonance torques to estimate the effective viscosity profile across the A ring, showing that it decreases from ~50 cm2 s-1 at the inner edge to less than ~11 cm2 s-1 at the outer edge. The gradual estimated decrease of the angular momentum flux and effective viscosity are roughly consistent with results obtained by balancing the shepherding torques from Pan and Daphnis with the viscous torque at the edges of the Encke and Keeler gaps, as well as the edge of the A ring.On the other hand, the Mimas 2:1 Lindblad resonance alone seems to be capable of confining the edge of the B ring, and contrary to the situation in the A ring, we show that the effective viscosity

  7. Cassini RADAR Backscatter Measurements of Saturn Rings

    NASA Astrophysics Data System (ADS)

    West, R. D.; Janssen, M. A.; Cuzzi, J. N.; Anderson, Y. Z.; Hamilton, G.

    2016-12-01

    The Cassini mission is now heading into its last year of observations. Part of the mission plan includes orbits that bring the spacecraft close to Saturn's rings prior to deorbiting into Saturn's atmosphere. First, a series of F-ring orbits will cross the ring plane just outside of the F-ring, and then a series of Proximal orbits will cross the ring plane inside of the D-ring - just above the cloud tops. These orbits are providing a unique opportunity to obtain backscatter measurements and relatively high-resolution brightness temperature measurements from the rings. In one F-ring orbit and three Proximal orbits, the spacecraft will scan the rings with the radar central beam and obtain backscatter measurements as a function of radial distance with some variation of incidence angle. These radar observations will be designed to sweep the A through C rings with varying bandwidth chirps selected to optimize the tradeoff between radial resolution and measurement variance. Pulse compression will deliver radial resolutions varying from about 200 m to around 4 km depending on the bandwidth used. These measurements will provide a 1-D profile of backscatter obtained at 2.2 cm wavelength that will complement similar passive profiles obtained at optical, infrared, and microwave wavelengths. This presentation will summarize the detailed designs and tradeoffs made for these observations. Such measurements will further constrain and inform models of the composition and structure of the ring particle distributions. This work is supported by the NASA Cassini Program at JPL - CalTech.

  8. Is Discrete Mathematics the New Math of the Eighties?

    ERIC Educational Resources Information Center

    Hart, Eric W.

    1985-01-01

    Considered are what discrete mathematics includes, some parallels and differences between new math and discrete mathematics (listed in a table), and lessons to be learned. A list of references is included. (MNS)

  9. The combined contraceptive vaginal ring, NuvaRing: an international study of user acceptability.

    PubMed

    Novák, A; de la Loge, C; Abetz, L; van der Meulen, E A

    2003-03-01

    The acceptability of the combined contraceptive vaginal ring, NuvaRing, was assessed during two trials conducted in North America and Europe. Women completed a questionnaire about the ring's clarity of instructions, ease of use, sexual comfort, cycle-related characteristics and satisfaction after 3, 6 and 13 cycles of use. A total of 1,950 women (82% of those recruited) completed a questionnaire at cycle 3. At baseline, 66% of participants preferred oral contraceptives, but after three cycles of ring use 81% preferred the ring. On study completion, 97% agreed that the instructions for use were clear; 85% of women and 71% of their partners never/rarely felt the ring during intercourse and 94% of partners never/rarely minded that the woman was using the ring. Overall acceptance was high, 96% were satisfied with the ring and 97% would recommend the ring. Similar responses were seen for women who prematurely discontinued from the studies, except that slightly fewer women were satisfied (60%) and would recommend the ring (75%). Reasons for liking the ring included 'not having to remember anything' (45%) and 'ease of use' (27%). In conclusion, there is a high level of user and partner acceptability for the contraceptive ring.

  10. Special relativity in a discrete quantum universe

    NASA Astrophysics Data System (ADS)

    Bisio, Alessandro; D'Ariano, Giacomo Mauro; Perinotti, Paolo

    2016-10-01

    The hypothesis of a discrete fabric of the universe, the "Planck scale," is always on stage since it solves mathematical and conceptual problems in the infinitely small. However, it clashes with special relativity, which is designed for the continuum. Here, we show how the clash can be overcome within a discrete quantum theory where the evolution of fields is described by a quantum cellular automaton. The reconciliation is achieved by defining the change of observer as a change of representation of the dynamics, without any reference to space-time. We use the relativity principle, i.e., the invariance of dynamics under change of inertial observer, to identify a change of inertial frame with a symmetry of the dynamics. We consider the full group of such symmetries, and recover the usual Lorentz group in the relativistic regime of low energies, while at the Planck scale the covariance is nonlinearly distorted.

  11. Discrete Spectrum Reconstruction Using Integral Approximation Algorithm.

    PubMed

    Sizikov, Valery; Sidorov, Denis

    2017-07-01

    An inverse problem in spectroscopy is considered. The objective is to restore the discrete spectrum from observed spectrum data, taking into account the spectrometer's line spread function. The problem is reduced to solution of a system of linear-nonlinear equations (SLNE) with respect to intensities and frequencies of the discrete spectral lines. The SLNE is linear with respect to lines' intensities and nonlinear with respect to the lines' frequencies. The integral approximation algorithm is proposed for the solution of this SLNE. The algorithm combines solution of linear integral equations with solution of a system of linear algebraic equations and avoids nonlinear equations. Numerical examples of the application of the technique, both to synthetic and experimental spectra, demonstrate the efficacy of the proposed approach in enabling an effective enhancement of the spectrometer's resolution.

  12. Hydraulically controlled discrete sampling from open boreholes

    USGS Publications Warehouse

    Harte, Philip T.

    2013-01-01

    Groundwater sampling from open boreholes in fractured-rock aquifers is particularly challenging because of mixing and dilution of fluid within the borehole from multiple fractures. This note presents an alternative to traditional sampling in open boreholes with packer assemblies. The alternative system called ZONFLO (zonal flow) is based on hydraulic control of borehole flow conditions. Fluid from discrete fractures zones are hydraulically isolated allowing for the collection of representative samples. In rough-faced open boreholes and formations with less competent rock, hydraulic containment may offer an attractive alternative to physical containment with packers. Preliminary test results indicate a discrete zone can be effectively hydraulically isolated from other zones within a borehole for the purpose of groundwater sampling using this new method.

  13. Multiple Autonomous Discrete Event Controllers for Constellations

    NASA Technical Reports Server (NTRS)

    Esposito, Timothy C.

    2003-01-01

    The Multiple Autonomous Discrete Event Controllers for Constellations (MADECC) project is an effort within the National Aeronautics and Space Administration Goddard Space Flight Center's (NASA/GSFC) Information Systems Division to develop autonomous positioning and attitude control for constellation satellites. It will be accomplished using traditional control theory and advanced coordination algorithms developed by the Johns Hopkins University Applied Physics Laboratory (JHU/APL). This capability will be demonstrated in the discrete event control test-bed located at JHU/APL. This project will be modeled for the Leonardo constellation mission, but is intended to be adaptable to any constellation mission. To develop a common software architecture. the controllers will only model very high-level responses. For instance, after determining that a maneuver must be made. the MADECC system will output B (Delta)V (velocity change) value. Lower level systems must then decide which thrusters to fire and for how long to achieve that (Delta)V.

  14. Muscle contraction generates discrete sound bursts.

    PubMed Central

    Brozovich, F V; Pollack, G H

    1983-01-01

    Isolated frog sartorius muscles were stimulated to shorten under lightly loaded conditions. A piezoelectric transducer was placed alongside the muscle to record sounds generated during contraction. Shortening was accompanied by the generation of a series of discrete sound bursts. The bursts were found to be moderately repeatable among successive contractions; 44% repeated from contraction to contraction. The duration of each sound burst was on the order of 400 mus, and the temperature dependence of the interval between successive bursts had a Q10 of approximately 2. Sound intensity was variable: average acoustic power ranged from 0.05-0.4 mW/g, or approximately 1% of the heat generated during contraction. The generation of discrete bursts of sound during contraction, rather than continuous sound, implies that contractile behavior may be discontinuous. Images FIGURE 3 FIGURE 4 FIGURE 6 PMID:6600629

  15. Juxtaposed color halftoning relying on discrete lines.

    PubMed

    Babaei, Vahid; Hersch, Roger D

    2013-02-01

    Most halftoning techniques allow screen dots to overlap. They rely on the assumption that the inks are transparent, i.e., the inks do not scatter a significant portion of the light back to the air. However, many special effect inks, such as metallic inks, iridescent inks, or pigmented inks, are not transparent. In order to create halftone images, halftone dots formed by such inks should be juxtaposed, i.e., printed side by side. We propose an efficient juxtaposed color halftoning technique for placing any desired number of colorant layers side by side without overlapping. The method uses a monochrome library of screen elements made of discrete lines with rational thicknesses. Discrete line juxtaposed color halftoning is performed efficiently by multiple accesses to the screen element library.

  16. A Discrete Convolution Modelfor Phase Transitions

    NASA Astrophysics Data System (ADS)

    Bates, Peter W.; Chmaj, Adam

    We study a discrete convolution model for Ising-like phase transitions. This nonlocal model is derived as an l2-gradient flow for a Helmholtz free energy functional with general long range interactions. We construct traveling waves and stationary solutions, and study their uniqueness and stability. In particular, we find some criteria for ``propagation'' and ``pinning'', and compare our results with those for a previously studied continuum convolution model.

  17. Additive discrete 1D linear canonical transform

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Healy, John J.; Guo, Chang-liang; Sheridan, John T.

    2015-09-01

    The continuous linear canonical transforms (LCT) can describe a wide variety of wave field propagations through paraxial (first order) optical systems. Digital algorithms to numerically calculate the LCT are therefore important in modelling scalar wave field propagations and are also of interest for many digital signal processing applications. The continuous LCT is additive, but discretization can remove this property. In this paper we discuss three special cases of the LCT for which constraints can be identified to ensure the DLCT is additive.

  18. Exponential-modified discrete Lindley distribution.

    PubMed

    Yilmaz, Mehmet; Hameldarbandi, Monireh; Acik Kemaloglu, Sibel

    2016-01-01

    In this study, we have considered a series system composed of stochastically independent M-component where M is a random variable having the zero truncated modified discrete Lindley distribution. This distribution is newly introduced by transforming on original parameter. The properties of the distribution of the lifetime of above system have been examined under the given circumstances and also parameters of this new lifetime distribution are estimated by using moments, maximum likelihood and EM-algorithm.

  19. Program For Parallel Discrete-Event Simulation

    NASA Technical Reports Server (NTRS)

    Beckman, Brian C.; Blume, Leo R.; Geiselman, John S.; Presley, Matthew T.; Wedel, John J., Jr.; Bellenot, Steven F.; Diloreto, Michael; Hontalas, Philip J.; Reiher, Peter L.; Weiland, Frederick P.

    1991-01-01

    User does not have to add any special logic to aid in synchronization. Time Warp Operating System (TWOS) computer program is special-purpose operating system designed to support parallel discrete-event simulation. Complete implementation of Time Warp mechanism. Supports only simulations and other computations designed for virtual time. Time Warp Simulator (TWSIM) subdirectory contains sequential simulation engine interface-compatible with TWOS. TWOS and TWSIM written in, and support simulations in, C programming language.

  20. Continuous limit of discrete quantum walks

    NASA Astrophysics Data System (ADS)

    M N, Dheeraj; Brun, Todd A.

    2015-06-01

    Quantum walks can be defined in two quite distinct ways: discrete-time and continuous-time quantum walks (DTQWs and CTQWs). For classical random walks, there is a natural sense in which continuous-time walks are a limit of discrete-time walks. Quantum mechanically, in the discrete-time case, an additional "coin space" must be appended for the walk to have nontrivial time evolution. Continuous-time quantum walks, however, have no such constraints. This means that there is no completely straightforward way to treat a CTQW as a limit of a DTQW, as can be done in the classical case. Various approaches to this problem have been taken in the past. We give a construction for walks on d -regular, d -colorable graphs when the coin flip operator is Hermitian: from a standard DTQW we construct a family of discrete-time walks with a well-defined continuous-time limit on a related graph. One can think of this limit as a "coined" continuous-time walk. We show that these CTQWs share some properties with coined DTQWs. In particular, we look at a spatial search by a DTQW over the two-dimensional (2D) torus (a grid with periodic boundary conditions) of size √{N }×√{N } , where it was shown that a coined DTQW can search in time O (√{N }logN ) , but a standard CTQW takes Ω (N ) time to search for a marked element. The continuous limit of the DTQW search over the 2D torus exhibits the O (√{N }logN ) scaling, like the coined walk it is derived from. We also look at the effects of graph symmetry on the limiting walk, and show that the properties are similar to those of the DTQW as shown in Krovi and Brun, Phys. Rev. A 75, 062332 (2007), 10.1103/PhysRevA.75.062332.

  1. Bessel-zernike discrete variable representation basis.

    PubMed

    Cerjan, Charles

    2006-04-27

    The connection between the Bessel discrete variable basis expansion and a specific form of an orthogonal set of Jacobi polynomials is demonstrated. These so-called Zernike polynomials provide alternative series expansions of suitable functions over the unit interval. Expressing a Bessel function in a Zernike expansion provides a straightforward method of generating series identities. Furthermore, the Zernike polynomials may also be used to efficiently evaluate the Hankel transform for rapidly decaying functions or functions with finite support.

  2. Discrete sequence prediction and its applications

    NASA Technical Reports Server (NTRS)

    Laird, Philip

    1992-01-01

    Learning from experience to predict sequences of discrete symbols is a fundamental problem in machine learning with many applications. We apply sequence prediction using a simple and practical sequence-prediction algorithm, called TDAG. The TDAG algorithm is first tested by comparing its performance with some common data compression algorithms. Then it is adapted to the detailed requirements of dynamic program optimization, with excellent results.

  3. Remarks on a New Possible Discretization Scheme for Gauge Theories

    NASA Astrophysics Data System (ADS)

    Magnot, Jean-Pierre

    2018-03-01

    We propose here a new discretization method for a class of continuum gauge theories which action functionals are polynomials of the curvature. Based on the notion of holonomy, this discretization procedure appears gauge-invariant for discretized analogs of Yang-Mills theories, and hence gauge-fixing is fully rigorous for these discretized action functionals. Heuristic parts are forwarded to the quantization procedure via Feynman integrals and the meaning of the heuristic infinite dimensional Lebesgue integral is questioned.

  4. Police investigations: discretion denied yet undeniably exercised

    PubMed Central

    Belur, J.; Tilley, N.; Osrin, D.; Daruwalla, N.; Kumar, M.; Tiwari, V.

    2014-01-01

    Police investigations involve determining whether a crime has been committed, and if so what type of crime, who has committed it and whether there is the evidence to charge the perpetrators. Drawing on fieldwork in Delhi and Mumbai, this paper explores how police investigations unfolded in the specific context of women’s deaths by burning in India. In particular, it focuses on the use of discretion despite its denial by those exercising it. In India, there are distinctive statutes relating to women’s suspicious deaths, reflecting the widespread expectation that the bride’s family will pay a dowry to the groom’s family and the tensions to which this may on occasion give rise in the early years of a marriage. Often, there are conflicting claims influencing how the woman’s death is classified. These in turn affect police investigation. The nature and direction of police discretion in investigating women’s deaths by burning reflect in part the unique nature of the legislation and the particular sensitivities in relation to these types of death. They also highlight processes that are liable to be at work in any crime investigation. It was found that police officers exercised unacknowledged discretion at seven specific points in the investigative process, with potentially significant consequences for the achievement of just outcomes: first response, recording the victim’s ‘dying declaration’, inquest, registering of the ‘First Information Report’, collecting evidence, arrest and framing of the charges. PMID:26376482

  5. Adenocarcinoma metastasis causing discrete extraocular muscle enlargement.

    PubMed

    Slagle, William Scott; Eckermann, Daniel R; Musick, Angela N; Slagle, Amber M

    2009-07-01

    Discrete extraocular muscle (EOM) metastasis is rarely reported. Clinical signs and symptoms of EOM metastasis can often be indistinguishable from primary idiopathic orbital myositis, posing a significant clinical challenge. A case of a 61-year-old man with acute-onset unilateral periorbital pain and diplopia is presented. Magnetic resonance imaging showed an isolated edematous superior rectus/levator muscle complex with an isointense T2-weighted signal, supporting a diagnosis of orbital myositis. He was started on corticosteroids, with resolution of pain and improved motilities. Subsequently, his condition worsened. Repeat imaging results suggested the possibility of neoplastic infiltration of the muscle because of the newly demonstrated hyperintensity of the T2-weighted signal and perineural extension along the trigeminal nerve. Fine-needle aspiration biopsy showed adenocarcinoma cytology in the muscle. This case illustrates discrete adenocarcinoma metastasis of an EOM, initially displaying characteristics predominantly consistent with orbital myositis. There is a paucity of epidemiologic data on EOM cancer, and clinical characteristics are derived only from a selection of case reports in the literature. Thus, the predominant features of global orbital metastatic cancer versus primary inflammation are highlighted in this presentation. This case shows that the variable characteristics of each process prohibit identification of any clinical feature that would prove pathognomonic for either disorder. The varied practice philosophies and standard of care regarding the proper time to biopsy are reviewed. This case shows the importance of early referral for orbital biopsy, even in the presentation of isolated, discretely edematous, and painful EOM enlargement.

  6. Discrete phase space based on finite fields

    SciTech Connect

    Gibbons, Kathleen S.; Department of Theology, University of Notre Dame, Notre Dame, Indiana 46617; Hoffman, Matthew J.

    2004-12-01

    The original Wigner function provides a way of representing in phase space the quantum states of systems with continuous degrees of freedom. Wigner functions have also been developed for discrete quantum systems, one popular version being defined on a 2Nx2N discrete phase space for a system with N orthogonal states. Here we investigate an alternative class of discrete Wigner functions, in which the field of real numbers that labels the axes of continuous phase space is replaced by a finite field having N elements. There exists such a field if and only if N is a power of a prime;more » so our formulation can be applied directly only to systems for which the state-space dimension takes such a value. Though this condition may seem limiting, we note that any quantum computer based on qubits meets the condition and can thus be accommodated within our scheme. The geometry of our NxN phase space also leads naturally to a method of constructing a complete set of N+1 mutually unbiased bases for the state space.« less

  7. Meshes optimized for discrete exterior calculus (DEC).

    SciTech Connect

    Mousley, Sarah C.; Deakin, Michael; Knupp, Patrick

    2017-12-01

    We study the optimization of an energy function used by the meshing community to measure and improve mesh quality. This energy is non-traditional because it is dependent on both the primal triangulation and its dual Voronoi (power) diagram. The energy is a measure of the mesh's quality for usage in Discrete Exterior Calculus (DEC), a method for numerically solving PDEs. In DEC, the PDE domain is triangulated and this mesh is used to obtain discrete approximations of the continuous operators in the PDE. The energy of a mesh gives an upper bound on the error of the discrete diagonal approximationmore » of the Hodge star operator. In practice, one begins with an initial mesh and then makes adjustments to produce a mesh of lower energy. However, we have discovered several shortcomings in directly optimizing this energy, e.g. its non-convexity, and we show that the search for an optimized mesh may lead to mesh inversion (malformed triangles). We propose a new energy function to address some of these issues.« less

  8. Discrete Deterministic and Stochastic Petri Nets

    NASA Technical Reports Server (NTRS)

    Zijal, Robert; Ciardo, Gianfranco

    1996-01-01

    Petri nets augmented with timing specifications gained a wide acceptance in the area of performance and reliability evaluation of complex systems exhibiting concurrency, synchronization, and conflicts. The state space of time-extended Petri nets is mapped onto its basic underlying stochastic process, which can be shown to be Markovian under the assumption of exponentially distributed firing times. The integration of exponentially and non-exponentially distributed timing is still one of the major problems for the analysis and was first attacked for continuous time Petri nets at the cost of structural or analytical restrictions. We propose a discrete deterministic and stochastic Petri net (DDSPN) formalism with no imposed structural or analytical restrictions where transitions can fire either in zero time or according to arbitrary firing times that can be represented as the time to absorption in a finite absorbing discrete time Markov chain (DTMC). Exponentially distributed firing times are then approximated arbitrarily well by geometric distributions. Deterministic firing times are a special case of the geometric distribution. The underlying stochastic process of a DDSPN is then also a DTMC, from which the transient and stationary solution can be obtained by standard techniques. A comprehensive algorithm and some state space reduction techniques for the analysis of DDSPNs are presented comprising the automatic detection of conflicts and confusions, which removes a major obstacle for the analysis of discrete time models.

  9. Discrete dynamic modeling of cellular signaling networks.

    PubMed

    Albert, Réka; Wang, Rui-Sheng

    2009-01-01

    Understanding signal transduction in cellular systems is a central issue in systems biology. Numerous experiments from different laboratories generate an abundance of individual components and causal interactions mediating environmental and developmental signals. However, for many signal transduction systems there is insufficient information on the overall structure and the molecular mechanisms involved in the signaling network. Moreover, lack of kinetic and temporal information makes it difficult to construct quantitative models of signal transduction pathways. Discrete dynamic modeling, combined with network analysis, provides an effective way to integrate fragmentary knowledge of regulatory interactions into a predictive mathematical model which is able to describe the time evolution of the system without the requirement for kinetic parameters. This chapter introduces the fundamental concepts of discrete dynamic modeling, particularly focusing on Boolean dynamic models. We describe this method step-by-step in the context of cellular signaling networks. Several variants of Boolean dynamic models including threshold Boolean networks and piecewise linear systems are also covered, followed by two examples of successful application of discrete dynamic modeling in cell biology.

  10. Ring chromosome 13 and ambiguous genitalia.

    PubMed

    Ozsu, Elif; Yeşiltepe Mutlu, Gül; Ipekçi, Belkıs

    2014-01-01

    Ambiguous genitalia, known to be associated with sex chromosome disorders, may also be seen with autosomal chromosome anomalies. Herein, we report a case with ambiguous genitalia and ring chromosome 13. Ring chromosome 13 is a rare genetic anomaly in which the loss of genetic material determines the clinical spectrum.

  11. Evolution of Vortex Rings Exiting Inclined Cylinders

    NASA Astrophysics Data System (ADS)

    Longmire, E. K.; Webster, D. R.; Reetz, M.; Gefroh, D.

    1996-11-01

    Vortex rings initiated in cylinders with exit incline lengths of 0, D/4, and D/2 were investigated for Reynolds numbers up to 30,000. The fluid exiting each cylinder was visualized with an ionized bromothymol blue solution, and velocity fields were obtained with PIV. In each inclined case, vortex rings form at angles smaller than the cylinder incline angle. Entrainment of ambient fluid on the short side of the cylinder is much stronger than that on the long side. This results in a larger circulation about the short side of the ring and a greater propagation velocity on that side. The incline angle of the ring thus decreases as it moves downstream. Behind the ring core, an impulsive wave of entrained ambient fluid flows parallel to the cylinder exit plane. Some of this fluid is wrapped into the core, while the rest is ejected outward past the long cylinder edge. The vortex ring dynamics differ significantly from those observed in jets from inclined nozzles where neighboring rings are connected by straining zones, and ring incline angles increase with downstream distance.

  12. 21 CFR 870.3800 - Annuloplasty ring.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Annuloplasty ring. 870.3800 Section 870.3800 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3800 Annuloplasty ring. (a...

  13. 21 CFR 870.3800 - Annuloplasty ring.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Annuloplasty ring. 870.3800 Section 870.3800 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3800 Annuloplasty ring. (a...

  14. 21 CFR 870.3800 - Annuloplasty ring.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Annuloplasty ring. 870.3800 Section 870.3800 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3800 Annuloplasty ring. (a...

  15. 21 CFR 870.3800 - Annuloplasty ring.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Annuloplasty ring. 870.3800 Section 870.3800 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3800 Annuloplasty ring. (a...

  16. 21 CFR 870.3800 - Annuloplasty ring.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Annuloplasty ring. 870.3800 Section 870.3800 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3800 Annuloplasty ring. (a...

  17. A comparison of chronologies from tree rings

    Treesearch

    Kurt H. Riitters

    1990-01-01

    Forty-five-year ring width index chronologies were estimated by five mean-value functions applied to 183 ring width series from four similar sites. The effects of autocorrelation on the comparisons among mean-value functions were explored by fitting box-Jenkins models to individual-tree index services prior to pooling (prewhitening), and to the pooled chronologies...

  18. Ring Counts in Second-Growth Baldcypress

    Treesearch

    W. R. Beaufait; T. C. Nelson

    1957-01-01

    Many thrifty, second-growth baldcypress trees (Taxodium distichum) [L.] Rich. ) appear to lay down several rings each year. These false rings may cause foresters to underestimate the growth potential of a highly prized species by overestimating the age of sample trees.

  19. The multi-bend achromat storage rings

    SciTech Connect

    Eriksson, Mikael

    2016-07-27

    Not very long ago, the 3{sup rd} generation storage ring technology was judged as mature. Most of the 3{sup rd} generation storage rings used the Double-Bend Achromat (DBA) or Triple-Bend Achromat (TBA) concepts. It was however a well-known fact that increasing the number of magnet cells in the rings is a powerful way of decreasing the electron beam emittance and thus the source brilliance, but at the penalty of increasing the size and cost of the rings. Preserving the Dynamic Aperture (DA) in the rings became also an issue when increasing the number of magnet cells. The Multi-Bend Achromat (MBA)more » concept, including a miniaturization of the ring elements, has now drastically changed the picture. The MBA rings, now in construction or being planned, offer orders of magnitudes higher brilliance than rings of conventional designs. Several light sources around the world are now implementing or planning to implement this MBA concept. This article touches on the science drivers for higher brilliance. We will then describe the MBA concept with its advantages as well as its challenges. A short survey of the MBA activity around the world will also be presented. The author apologies for focusing on the MAX IV project regarding technical solutions. This is motivated by that MAX IV is the facility he knows best and it might be regarded as a fore-runner for the MBA concept.« less

  20. Two cases of halo scalp ring.

    PubMed

    Douri, Thaer Hasan

    2016-11-15

    Halo scalp ring (HSR) is a rare form of non-scarring annular alopecia that is attributed to caput succedaneum. It arises perinatally because of prolonged pressure on the scalp by the cervix during or before the delivery. We report two new cases of halo scalp ring in full term pregnancy - newborns.

  1. Coefficient rings of formal group laws

    SciTech Connect

    Buchstaber, V M; Ustinov, A V

    2015-11-30

    We describe the coefficient rings of universal formal group laws which arise in algebraic geometry, algebraic topology and their application to mathematical physics. We also describe the homomorphisms of these coefficient rings coming from reductions of one formal group law to another. The proofs are based on the number-theoretic properties of binomial coefficients. Bibliography: 37 titles.

  2. 5 CFR 7.1 - Discretion in filling vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Discretion in filling vacancies. 7.1 Section 7.1 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE RULES GENERAL PROVISIONS (RULE VII) § 7.1 Discretion in filling vacancies. In his discretion, an appointing officer may fill any position in the competitive service either...

  3. 5 CFR 7.1 - Discretion in filling vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Discretion in filling vacancies. 7.1 Section 7.1 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE RULES GENERAL PROVISIONS (RULE VII) § 7.1 Discretion in filling vacancies. In his discretion, an appointing officer may fill any position in the competitive service either...

  4. Process Design by FEM Simulation for Shape Ring Rolling of Large-Sized Ring

    SciTech Connect

    Lee, Y. S.; Lee, M. W.; Park, S. S.

    2010-06-15

    Ring rolling process is usually used to fabricate large-sized ring, such as, tower flange for wind power electric generator. Many kinds of seamless ring are used in wind power electric generator and manufactured by ring rolling process. In general, final part is machined after forming with shape of plain square section. Since interests for near net shaping of seamless ring have been increased gradually because of green energy, it is necessary to develop the technology for shape ring rolling with respect to the market demands and cost. Therefore, we studied the process and die design for shape ring rolling ofmore » large sized ring over 3,500 mm out diameter by experiment and FEM simulation. Ring rolling process is very difficult to solve by FEM method because of equilibrium state and size effect, etc. Moreover, shape ring rolling is more difficult to solve the problem that two plastic deformation zones are different each other, that is main roll and conical roll. Also since conical roll has a shape, deformation velocity field is very much complex and the deformed section passed axial roll is different section and velocity field. The FE simulations are performed to analyze process variables affected in forming of profiled ring. Therefore, the main features of used FE model are: (1) it adopts a transient or unsteady state full ring mesh to model the deformation processes and shape development; (2) the mandrel and conical rolls are modeled using coupled heat-transfer elements; (3) the model involves the full process from blank through perform to final profiled ring. From these calculated results, we have proposed the mechanisms of various tools, such as mandrel and conical roll. The calculated results are compared experimental results. Calculated results can predict the tilting of profiled ring and then process variables to form large sized ring.« less

  5. Molecular organization of cytokinesis nodes and contractile rings by super-resolution fluorescence microscopy of live fission yeast

    PubMed Central

    Laplante, Caroline; Huang, Fang; Tebbs, Irene R.; Bewersdorf, Joerg; Pollard, Thomas D.

    2016-01-01

    Cytokinesis in animals, fungi, and amoebas depends on the constriction of a contractile ring built from a common set of conserved proteins. Many fundamental questions remain about how these proteins organize to generate the necessary tension for cytokinesis. Using quantitative high-speed fluorescence photoactivation localization microscopy (FPALM), we probed this question in live fission yeast cells at unprecedented resolution. We show that nodes, protein assembly precursors to the contractile ring, are discrete structural units with stoichiometric ratios and distinct distributions of constituent proteins. Anillin Mid1p, Fes/CIP4 homology-Bin/amphiphysin/Rvs (F-BAR) Cdc15p, IQ motif containing GTPase-activating protein (IQGAP) Rng2p, and formin Cdc12p form the base of the node that anchors the ends of myosin II tails to the plasma membrane, with myosin II heads extending into the cytoplasm. This general node organization persists in the contractile ring where nodes move bidirectionally during constriction. We observed the dynamics of the actin network during cytokinesis, starting with the extension of short actin strands from nodes, which sometimes connected neighboring nodes. Later in cytokinesis, a broad network of thick bundles coalesced into a tight ring around the equator of the cell. The actin ring was ∼125 nm wide and ∼125 nm thick. These observations establish the organization of the proteins in the functional units of a cytokinetic contractile ring. PMID:27647921

  6. Analysis of a laterally loaded ring with a hinged cross section.

    NASA Technical Reports Server (NTRS)

    Williams, H. E.

    1972-01-01

    A ring assembly constructed by lacing together three elements into a basic channel cross section is analyzed. The ring is supported at three equidistant points and loaded by a uniform distribution of radial and transverse loads. Bulkheads may be introduced at discrete cross sections to prevent distortion. The purpose of this analysis is to determine the behavior of the deflection as the number and location of the bulkheads and the degree of rigidity of the supports are varied. The method of analysis is an application of the Principle of Virtual Work within the framework of small displacement theory. Numerical results are presented for the geometrical parameters of a model. An important result is the observation that bulkheads have virtually no effect on the deflections of the web.

  7. Tuning the size of a redox-active tetrathiafulvalene-based self-assembled ring

    PubMed Central

    Bivaud, Sébastien; Croué, Vincent; Allain, Magali; Pop, Flavia

    2015-01-01

    Summary The synthesis of a new Pd coordination-driven self-assembled ring M6L3 constructed from a concave tetrapyridyl π-extended tetrathiafulvalene ligand (exTTF) is described. The same ligand is also able to self-assemble in a M4L2 mode as previously described. Herein, we demonstrate that the bulkiness of the ancillary groups in the Pd complex allows for modulating the size and the shape of the resulting discrete self-assembly, which therefore incorporate two (M4L2) or three (M6L3) electroactive exTTF sidewalls. PMID:26124899

  8. Characterization of Fractures in the Chicxulub Peak Ring: Preliminary Results from IODP/ICDP Expedition 364

    NASA Astrophysics Data System (ADS)

    McCall, N.; Gulick, S. P. S.; Morgan, J. V.; Hall, B. J.; Jones, L.; Expedition 364 Science Party, I. I.

    2017-12-01

    During Expedition 364, IODP/ICDP drilled the peak ring of the Chicxulub impact crater at Site M0077, recovering core from 505.7 to 1334.7 mbsf. The core has been imaged via X-ray Computer Tomography (CT) as a noninvasive method to create a 3-dimensional model of the core, providing information on the density and internal structure at a 0.3 mm resolution. Results from the expedition show that from 748 mbsf and deeper the peak ring is largely composed of uplifted and fractured granitic basement rocks originally sourced from approximately 8-10 km depth. Impact crater modeling suggests the peak ring was formed through dynamic collapse of a rebounding central peak within 10 minutes of impact, requiring the target rocks to temporarily behave as a viscous fluid. The newly recovered core provides a rare opportunity to investigate the cratering process, specifically how the granite was weakened, as well as the extent of the hydrothermal system created after the impact. Based on the CT data, we identify four classes of fractures based on their CT facies deforming the granitoids: pervasive fine fractures, discrete fine fractures, discrete filled fractures, and discrete open fractures. Pervasive fine fractures were most commonly found proximal to dikes and impact melt rock. Discrete filled fractures often displayed a cataclastic texture. We present density trends for the different facies and compare these to petrophysical properties (density, NGR, P-wave seismic velocity). Fractured areas have a lower density than the surrounding granite, as do most filled fractures. This reduction suggests that fluid migrating through the peak ring in the wake of the impact either deposited lower density minerals within the fractures and/or altered the original fracture fill. The extent and duration of fluid flow recorded in these fractures will assist in the characterization of the post-impact hydrothermal system. Future work includes combining information from CT images with thin sections

  9. Micro Ring Grating Spectrometer with Adjustable Aperture

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor); Choi, Sang H. (Inventor)

    2012-01-01

    A spectrometer includes a micro-ring grating device having coaxially-aligned ring gratings for diffracting incident light onto a target focal point, a detection device for detecting light intensity, one or more actuators, and an adjustable aperture device defining a circular aperture. The aperture circumscribes a target focal point, and directs a light to the detection device. The aperture device is selectively adjustable using the actuators to select a portion of a frequency band for transmission to the detection device. A method of detecting intensity of a selected band of incident light includes directing incident light onto coaxially-aligned ring gratings of a micro-ring grating device, and diffracting the selected band onto a target focal point using the ring gratings. The method includes using an actuator to adjust an aperture device and pass a selected portion of the frequency band to a detection device for measuring the intensity of the selected portion.

  10. Cassini CIRS Observations of Saturn's Rings

    NASA Technical Reports Server (NTRS)

    Spilker, Linda J.; Pilorz, Stuart H.; Wallis, Brad D.; Brooks, Shawn M.; Edgington, Scott G.; Flasar, F. Michael; Pearl, John C.; Showalter, Mark R.; Ferrari, Cecile; Achterberg, Richard K.

    2005-01-01

    In the spring of 2004, during Cassini s approach to Saturn, the Cassini Composite Infrared Spectrometer (CIRS) began acquiring thermal spectra of Saturn s rings. CIRS is a Fourier-transform spectrometer that measures radiation in the thermal infrared from 7 microns to 1 millimeter (1400 to 10/cm). CIRS has a set of 21 detectors, consisting of two 1 x 10 linear arrays with a pixel size of 0.3 mrad, and one 4 mrad circular detector. Just after the completion of the Saturn orbit insertion (SOI) burn, CIRS performed an especially high spatial resolution scan of portions of Saturn s A, B and C rings. In the months following SOI, additional ring measurements have been obtained, including radial scans on the lit and unlit sides of the rings, and azimuthal scans across the shadowed regions of the A, B and C rings.

  11. The Circumnuclear Starburst Ring in NGC 1097

    NASA Astrophysics Data System (ADS)

    Thackeray-Lacko, Beverly; Stierwalt, Sabrina; Sheth, Kartik

    2016-01-01

    The circumnuclear ring in galaxy NGC 1097 is bursting with star formation at a rate of five solar masses per year as previously measured through Hα emission. The rate of star formation drops by a factor of one thousand outside the circumnuclear ring. We characterize the behavior of the dust in this region by measuring the spectral energy distribution focused exclusively on the circumnuclear ring using a selective variety of high resolution science images spanning wavelengths from ultraviolet to infrared, and adding proprietary high resolution radio data from Atacoma Large Millimeter Array (ALMA) in Chile. High resolution radio data obtained from ALMA allows us to constrain the shape of the spectral energy distribution curve specifically at longer wavelengths, and therefore the rate of star formation within the circumnuclear ring. Comparing the spectral energy distribution of the entire galaxy with that of the circumnuclear ring indicates how starburst activity influences the galactic spectral energy distribution.

  12. Monlithic nonplanar ring oscillator and method

    NASA Technical Reports Server (NTRS)

    Nilsson, Alan C. (Inventor); Byer, Robert L. (Inventor)

    1991-01-01

    A monolithic nonplanar ring oscillator having an optically isotropic solid-state laser body for propagating laser radiation about a nonplanar ring path internal to the laser body is disclosed. The monolithic laser body is configured to produce a 2N reflection nonplanar ring light path, where N is an integer greater than or equal to 2, comprising 2N-1 total internal reflections and one reflection at a coupler in a single round trip. Undirectional traveling wave oscillation of the laser is induced by the geometry of the nonplanar ring path together with the effect of an applied magnetic field and partial polarizer characteristics of the oblique reflection from the coupler. The 6-reflection nonplanar ring oscillator makes possible otpimal unidirectional oscillation (low loss for the oscillating direction of propagation and, simultaneously high loss for the nonoscillating direction of propagation) in monolithic NPROs using materials with index of refraction smaller than the square root of 3, for example, laser glass.

  13. An evolving view of Saturn's dynamic rings.

    PubMed

    Cuzzi, J N; Burns, J A; Charnoz, S; Clark, R N; Colwell, J E; Dones, L; Esposito, L W; Filacchione, G; French, R G; Hedman, M M; Kempf, S; Marouf, E A; Murray, C D; Nicholson, P D; Porco, C C; Schmidt, J; Showalter, M R; Spilker, L J; Spitale, J N; Srama, R; Sremcević, M; Tiscareno, M S; Weiss, J

    2010-03-19

    We review our understanding of Saturn's rings after nearly 6 years of observations by the Cassini spacecraft. Saturn's rings are composed mostly of water ice but also contain an undetermined reddish contaminant. The rings exhibit a range of structure across many spatial scales; some of this involves the interplay of the fluid nature and the self-gravity of innumerable orbiting centimeter- to meter-sized particles, and the effects of several peripheral and embedded moonlets, but much remains unexplained. A few aspects of ring structure change on time scales as short as days. It remains unclear whether the vigorous evolutionary processes to which the rings are subject imply a much younger age than that of the solar system. Processes on view at Saturn have parallels in circumstellar disks.

  14. Saturn's B and C-rings

    NASA Technical Reports Server (NTRS)

    1981-01-01

    This view focusing on Saturn's C-ring (and to a lesser extent, the B-ring at top and left) was compiled from three separate images taken through ultraviolet, clear and green filters. On Aug. 23, when it acquired these frames, Voyager 2 was 2.7 million kilometers (1.7 million miles) from the planet. More than 60 bright and dark ringlets are evident here; the small, bland squares are caused by the removal of reseau (reference) marks during processing. In general, C-ring material is very bland and gray, the color of dirty ice. Color differences between this ring and the B-ring indicate differing surface compositions for the material composing these complex structures.

    JPL manages the Voyager project for NASA's Office of Space Science.

  15. Tree rings and monsoon season rainfall variability in the Southwestern US: Strategies for sensitive chronology development

    NASA Astrophysics Data System (ADS)

    Griffin, D.; Meko, D. M.; Touchan, R.; Woodhouse, C. A.; Leavitt, S. W.; Castro, C. L.

    2009-12-01

    The climate of southwestern North America is characterized by two seasonally discrete precipitation regimes. Frontal storms deliver cool season precipitation whereas warm season rainfall is associated with the North American Monsoon. For the cool season, tree-ring reconstructions have revealed a detailed history of moisture variability across the region for the last 500-1000 years. These reconstructions have been developed primarily from annual ring-width chronologies, which are not typically useful for reconstructing the warm season rainfall variability. However, using chronologies developed from the intra-annual, anatomically distinguishable components of the growth ring, commonly referred to as earlywood (EW) and latewood (LW), great potential exists for reconstructing monsoon-season moisture variability in the region. Towards this end, we are currently developing a network of EW and corresponding LW chronologies from moisture-sensitive tree-ring sites around the southwestern United States. We have updated over forty tree-ring collections to 2009 and are measuring EW and LW width of the modern and archived specimens. Here we report results from an experiment designed to refine and improve the published methods for developing LW chronologies that are sensitive to monsoon-season precipitation. Challenges we face include 1) the evaluation of competing techniques for the treatment of intra-annual latewood density variations (i.e. “false” rings), 2) the assessment of sample signal strength in LW-width time series, particularly since LW-width variability often diminishes substantially with increasing biological age, 3) the improvement of statistical techniques for removing the covariance between EW and LW, a step proven to be necessary for developing chronologies sensitive to warm season precipitation in the region.

  16. Minimum weight design of ring and stringer stiffeners for axially compressed cylindrical shells with and without internal pressure

    NASA Technical Reports Server (NTRS)

    Block, D. L.

    1972-01-01

    Results of analytical study to determine desirable ring and stringer stiffener parameters and proportions for axially compressed stiffened isotropic cylinders with and without internal pressure are presented. This investigation examines the panel and general instability buckling modes of a stiffened cylindrical shell and from this determines desirable stiffener parameters and proportions. Classical buckling equations are used which retain the important effects of the stiffeners. The results determined by using the simpler classical buckling equations are then spot checked and verified using buckling equations which considered discrete ring stiffeners and nonlinear prebuckling deformations. For both rings and stringers, T-shaped stiffeners are preferable and the effects to stiffener shape are much more pronounced at low or zero values of the internal pressure parameter. Simple analytical expressions are developed and presented which express the stiffener area parameter, the ratio of stiffener area and elastics to shell wall area and elastic modulus, in terms of the cylinder geometry and internal pressure parameter.

  17. Effects of Meteoroid Erosion in Planetary Rings

    NASA Technical Reports Server (NTRS)

    Durisen, Richard H.

    1995-01-01

    This grant supported continuing studies of the effects of ballistic transport on the evolution of Saturn's rings. Ballistic transport, as used in this context, refers to the net transport of mass and angular momentum caused by the exchange of meteoroid impact ejecta between neighboring ring regions (Ip 1983, 1984, Morfill et al. 1983, Lissauer 1984, Durisen 1984a,b). The characteristic time scale associated with this process is the gross erosion time t(sub g) the time it would take a ring region to be completed eroded if all impact ejecta were lost. This time scale is estimated to be about 10(exp 5) to 10(exp 6) years for a ring region with normal optical depth tau approximately 1. Earlier work by myself and collaborators developed the physical theory and simulation techniques to model this process (Durisen et al. 1989, Cuzzi and Durisen 1990). Detailed simulations, supported in part by this grant, have demonstrated that ballistic transport can produce observed structures in Saturn's rings, especially at and near the inner edges of the A and B Rings (Durisen et al. 1992, 1996). The structures of interest in the real rings are illustrated in Figures 1 and 2. Most of these structures were previously unexplained. The computational results plus analytic treatments place useful constraints on fundamental ring properties, including the indication of a relatively young ring age less than or equal 10(exp 8) years (see reviews by Nicholson and Dones 1991, Esposito 1993, Cuzzi 1995, and Porco 1995). This grant also supported development of the faster computational algorithms necessary to permit longer evolutions. Resulting simplications in the ballistic transport equations permitted an analytic linear stability analysis (Durisen 1995), which has provided considerable insight into ballistic transport processes and applications to Saturn's rings. All these accomplishments are described in more detail below.

  18. Caldera Collapse at Ossipee Ring Complex

    NASA Astrophysics Data System (ADS)

    Kennedy, B.; Stix, J.

    2004-05-01

    The collapse of a magma chamber often forms a caldera at the surface and a ring dyke at depth. The Ossipee Ring Complex, dated at 125 Ma and part of the White Mountain Igneous Province in New Hampshire, it contains volcanic rocks, landslide breccias and a 10 km-diameter ring dyke. We hypothesize that caldera collapse was responsible for the accumulation of volcanic rocks, formation of breccias and the ring dyke. To understand the relationships between the different magmas and textures within the ring dyke, we made detailed maps, and collected samples for chemical and textural analysis. Pyroclastic rhyolite and mafic breccias have accumulated within the ring dyke. The majority of the ring dyke is crystal-rich quartz syenite. Pyroclastic and porphyritic rhyolite are also widespread in the quartz syenite and occur as diffuse blobs and dyke-like bodies. Mafic rocks also occur as mingled dykes, blobs and streaks within the ring dyke. Our observations allow us to place the eruptive and intrusive processes sequentially. First, basaltic dykes intruded the pre-collapse volcanic edifice. This was followed by rhyolitic eruptions of lavas and pyroclastic rocks, which caused the collapse of the magma chamber roof. During collapse, large landslides cascaded into the caldera from the caldera walls. Finally, crystal-rich quartz syenite, and mafic magma intruded the ring fault producing the ring dyke. The rhyolite and porphyritic quartz syenite and have very similar textures and mineralogy, which indicates that they evolved in the same magma chamber. We propose that the collapse of the chamber's roof promoted (1) the separation and eruption of the rhyolite from the quartz syenite crystal mush, (2) magma mixing at the base of a stratified chamber, (3) and the rise and intrusion of new magma.

  19. Electro-optical hybrid slip ring

    NASA Astrophysics Data System (ADS)

    Hong, En

    2005-11-01

    The slip ring is a rotary electrical interface, collector, swivel or rotary joint. It is a physical system that can perform continuous data transfer and data exchange between a stationary and a rotating structure. A slip ring is generally used to transfer data or power from an unrestrained, continuously rotating electro-mechanical system in real-time, thereby simplifying operations and eliminating damage-prone wires dangling from moving joints. Slip rings are widely used for testing, evaluating, developing and improving various technical equipment and facilities with rotating parts. They are widely used in industry, especially in manufacturing industries employing turbo machinery, as in aviation, shipbuilding, aerospace, defense, and in precise facilities having rotating parts such as medical Computerized Tomography (CT) and MRI scanners and so forth. Therefore, any improvement in slip ring technology can impact large markets. Research and development in this field will have broad prospects long into the future. The goal in developing the current slip ring technology is to improve and increase the reliability, stability, anti-interference, and high data fidelity between rotating and stationary structures. Up to now, there have been numerous approaches used for signal and data transfer utilizing a slip ring such as metal contacts, wires, radio transmission, and even liquid media. However, all suffer from drawbacks such as data transfer speed limitations, reliability, stability, electro-magnetic interference and durability. The purpose of the current research is to break through these basic limitations using an optical solution, thereby improving performance in current slip ring applications. This dissertation introduces a novel Electro-Optical Hybrid Slip Ring technology, which makes "through the air" digital-optical communication between stationary and rotating systems a reality with high data transfer speed, better reliability and low interference susceptibility

  20. What Confines the Rings of Saturn?

    NASA Astrophysics Data System (ADS)

    Tajeddine, Radwan; Nicholson, Philip D.; Longaretti, Pierre-Yves; El Moutamid, Maryame; Burns, Joseph A.

    2017-10-01

    The viscous spreading of planetary rings is believed to be counteracted by satellite torques, through either an individual resonance or overlapping resonances. For the A ring of Saturn, it has been commonly believed that the satellite Janus alone can prevent the ring from spreading, via its 7:6 Lindblad resonance. We discuss this common misconception and show that, in reality, the A ring is confined by the contributions from the group of satellites Pan, Atlas, Prometheus, Pandora, Janus, Epimetheus, and Mimas, whose cumulative torques from various resonances gradually decrease the angular momentum flux transported outward through the ring via density and bending waves. We further argue that this decrease in angular momentum flux occurs through “flux reversal.” Furthermore, we use the magnitude of the satellites’ resonance torques to estimate the effective viscosity profile across the A ring, showing that it decreases with radius from ˜50 cm2 s-1 to less than ˜10 cm2 s-1. The gradual estimated decrease of the angular momentum flux and effective viscosity are roughly consistent with results obtained by balancing the shepherding torques from Pan and Daphnis with the viscous torque at the edges of the Encke and Keeler gaps, as well as the edge of the A ring. On the other hand, the Mimas 2:1 Lindblad resonance alone seems to be capable of confining the edge of the B ring, and contrary to the situation in the A ring, we show that the effective viscosity across the B ring is relatively constant at ˜24-30 cm2 s-1.

  1. Dynamic LES of Colliding Vortex Rings Using a 3D Vortex Method

    NASA Astrophysics Data System (ADS)

    Mansfield, John R.; Knio, Omar M.; Meneveau, Charles

    1999-06-01

    A Lagrangian particle method is used to simulate the collision of coaxial vortex rings in three dimensions. The scheme combines a 3D, adaptive, viscous, vortex element method with a dynamic eddy viscosity model of the subfilter scale stresses. The vortex method is based on discretization of the vorticity field into Lagrangian vortex elements and transport of the elements along particle trajectories. The computations incorporate a mesh redistribution algorithm which creates new elements in regions of high strain and locally redistributes the vorticity field into a smaller number of elements when particles tend to cluster. The subfilter scale vorticity model consists of approximating the effect of unresolved vorticity stresses using a gradient-diffusion eddy viscosity model, following the development in Part I (J. R. Mansfield, O. M. Knio, and C. Meneveau, J. Comput. Phys.145, 693 (1998)). Dynamic implementation of the model relies on determining model coefficients through test-filtering the Lagrangian particle representation of the filtered vorticity field. Computations of ring collisions show that, combined, the mesh redistribution scheme and subfilter scale model result in a robust scheme that can be extended into the late stages of evolution of the flow. In addition, it is shown that the Lagrangian LES scheme captures several experimentally observed features of the ring collisions, including turbulent breakdown into small-scale structures and the generation of small-scale radially propagating vortex rings.

  2. Direct numerical modeling of Saturn's dense rings at high optical depth

    NASA Astrophysics Data System (ADS)

    Richardson, Derek C.; Ballouz, Ronald-Louis; Morishima, Ryuji

    2015-11-01

    Saturn's B ring exhibits complex optical depth structure of uncertain origin. We are investigating the extent to which viscous overstability and/or gravitational wakes can give rise to this structure, via discrete particle numerical simulations. We use the parallelized N-body tree code pkdgrav with a soft-sphere collision model for detailed treatment of particle collisional physics, including multi-point persistent contact with static, sliding, rolling, and twisting friction forces. This enables us to perform local simulations with millions of particles, realistic sizes, and configurable material properties in high-optical-depth ring patches with near-linear scaling across multiple processors. Recent code improvements to the collision search algorithm provide a further roughly factor of 2 speedup. We present results from the first year of this study in which a library of simulations with different optical depths was constructed. Parameters explored include normal (dynamical) optical depths between 0.5 (approximately 100,000 particles) and 4.0 (approximately 8.3 million particles) in ring patches of dimension 6 by 6 critical Toomre wavelengths, using material parameters ranging from highly elastic smooth spheres to rough "gravel"-like particles. We also vary the particle internal densities to enhance (low density)/suppress (high density) viscous overstability in order to compare against gravitational instability in these different regimes. These libraries will be used to carry out simulated observations for comparison with Cassini CIRS temperature measurements and UVIS occulation data of Saturn's dense rings.

  3. Galactic rings revisited - I. CVRHS classifications of 3962 ringed galaxies from the Galaxy Zoo 2 Database

    NASA Astrophysics Data System (ADS)

    Buta, Ronald J.

    2017-11-01

    Rings are important and characteristic features of disc-shaped galaxies. This paper is the first in a series that re-visits galactic rings with the goals of further understanding the nature of the features and for examining their role in the secular evolution of galaxy structure. The series begins with a new sample of 3962 galaxies drawn from the Galaxy Zoo 2 citizen science data base, selected because zoo volunteers recognized a ring-shaped pattern in the morphology as seen in Sloan Digital Sky Survey colour images. The galaxies are classified within the framework of the Comprehensive de Vaucouleurs revised Hubble-Sandage system. It is found that zoo volunteers cued on the same kinds of ring-like features that were recognized in the 1995 Catalogue of Southern Ringed Galaxies. This paper presents the full catalogue of morphological classifications, comparisons with other sources of classifications and some histograms designed mainly to highlight the content of the catalogue. The advantages of the sample are its large size and the generally good quality of the images; the main disadvantage is the low physical resolution that limits the detectability of linearly small rings such as nuclear rings. The catalogue includes mainly inner and outer disc rings and lenses. Cataclysmic (`encounter-driven') rings (such as ring and polar ring galaxies) are recognized in less than 1 per cent of the sample.

  4. The combined contraceptive vaginal ring (NuvaRing): evaluation of the clinical and pharmacological evidence.

    PubMed

    Gruber, Christian J

    2006-05-01

    The NuvaRing((R)) is a vaginal ring contraceptive that releases a daily dose of 15 microg ethinylestradiol and 120 microg etonogestrel through the vaginal epithelium, thereby avoiding the daily fluctuations in serum levels typically observed with combined oral contraceptives. Each ring is designed for a single 3-week use followed by a 1-week ring-free period. The ring offers robust inhibition of ovulation, yielding a Pearl Index of 0.65 for European women in registration trials. The ring has the same contraindications as combined oral contraceptives. The vaginal ring is a highly effective, safe and well-tolerated method of hormonal contraception designed for reproductive-aged women who desire freedom from the daily pill.

  5. Residual hormone levels in used contraceptive rings as a measurement of adherence to vaginal ring use.

    PubMed

    Haaland, Richard E; Holder, Angela; Evans-Strickfaden, Tammy; Nyagol, Beatrice; Makanga, Mumbi; Oyaro, Boaz; Humwa, Felix; Williams, Tiffany; McLellan-Lemal, Eleanor; Desai, Mitesh; Huey, Michael J

    2017-06-01

    This study sought to measure residual contraceptive hormone levels in vaginal rings as an adherence marker for monitoring product use in clinical trials. Residual etonogestrel and ethinyl estradiol levels from used NuvaRings® of 26 self-reported adherent women enrolled in a clinical trial of vaginal ring acceptability were compared to those from 16 women who used NuvaRing® as their contraceptive choice. Twenty-one (81%) clinical trial rings had contraceptive hormone levels within the range of those used as a contraceptive choice. Five returned rings had unused or discordant levels of residual contraceptive hormones. Residual vaginal ring drug levels could help assess adherence in clinical trials. Published by Elsevier Inc.

  6. The remote sensing of Saturn's rings. 1: The magnetic alinement of the ring particles

    NASA Technical Reports Server (NTRS)

    Evans, L. C.

    1973-01-01

    Because of the potential implications for the optical properties of Saturn's rings, the orientation of nonspherical ring particles at equilibrium is investigated with respect to four stochastic influences: interactions with the interplanetary medium, interactions with the expected magnetic field of Saturn, thermal fluctuations due to the internal temperature of the ring particles; collisions between ring particles. The solution of the homogeneous Fokker-Planck equation for nearly spherical spheroids is presented and investigated in general. Values of the pertinent physical parameters in the vicinity of Saturn are estimated, and the implications for the alignment of the ring particles are investigated. It is concluded that for some alignment mechanisms, small ring particles can be expected to be almost completely aligned. This alignment results in each particle spinning around its shortest body axis with this axis parallel to the magnetic field direction (perpendicular to the ring plane).

  7. Accidental ingestion of BiTine ring and a note on inefficient ring separation forceps.

    PubMed

    Baghele, Om Nemichand; Baghele, Mangala Om

    2011-01-01

    Accidental ingestion of medium-to-large instruments is relatively uncommon during dental treatment but can be potentially dangerous. A case of BiTine ring ingestion is presented with a note on inefficient ring separation forceps. A 28-year-old male patient accidentally ingested the BiTine ring (2 cm diameter, 0.5 cm outward projections) while it was being applied to a distoproximal cavity in tooth # 19. The ring placement forceps were excessively flexible; bending of the beaks towards the ring combined with a poor no-slippage mechanism led to sudden disengagement of the ring and accelerated movement towards the pharynx. We followed the patient with bulk forming agents and radiographs. Fortunately the ring passed out without any complications. Checking equipment and methods is as important as taking precautions against any preventable medical emergency. It is the responsibility of the clinician to check, verify and then use any instrument/equipment.

  8. Structure of a BRCA1/BARD1 Complex: a Heterodimeric RING-RING Interaction

    SciTech Connect

    Brzovic, Peter S.; Rajagopal, Ponni; Hoyt, David W.

    2001-10-01

    The N-terminal RING domain of the breast and ovarian cancer tumor suppressor BRCA1 interacts with multiple cognate proteins, including the RING protein, BARD1. Proper function of the BRCA1 RING domain is critical, as evidenced by the many cancer-predisposing mutations found within this domain. We present the solution structure of the N-terminal RING domain heterodimer of BRCA1 and BARD1. Comparison with the RAG1 RING homodimer reveals the structural diversity of complexes formed by interactions between different RING domains. The BRCA1/BARD1 structure provides a model for its ubiquitin ligase activity, illustrates how the BRCA1 RING domain can be involved in associations withmore » multiple protein partners, and provdes a framework for understanding cancer-causing mutations at the molecular level.« less

  9. Smoke Ring for a Halo

    NASA Image and Video Library

    2017-12-08

    Two stars shine through the center of a ring of cascading dust in this image taken by the NASA/ESA Hubble Space Telescope. The star system is named DI Cha, and while only two stars are apparent, it is actually a quadruple system containing two sets of binary stars. As this is a relatively young star system it is surrounded by dust. The young stars are molding the dust into a wispy wrap. The host of this alluring interaction between dust and star is the Chamaeleon I dark cloud — one of three such clouds that comprise a large star-forming region known as the Chamaeleon Complex. DI Cha's juvenility is not remarkable within this region. In fact, the entire system is among not only the youngest but also the closest collections of newly formed stars to be found and so provides an ideal target for studies of star formation. Image credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  10. Wedding ring shaped excitation coil

    DOEpatents

    MacLennan, Donald A.; Tsai, Peter

    2001-01-01

    A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and/or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency.

  11. Using discretization for extending the set of predictive features

    NASA Astrophysics Data System (ADS)

    Rosenfeld, Avi; Illuz, Ron; Gottesman, Dovid; Last, Mark

    2018-12-01

    To date, attribute discretization is typically performed by replacing the original set of continuous features with a transposed set of discrete ones. This paper provides support for a new idea that discretized features should often be used in addition to existing features and as such, datasets should be extended, and not replaced, by discretization. We also claim that discretization algorithms should be developed with the explicit purpose of enriching a non-discretized dataset with discretized values. We present such an algorithm, D-MIAT, a supervised algorithm that discretizes data based on minority interesting attribute thresholds. D-MIAT only generates new features when strong indications exist for one of the target values needing to be learned and thus is intended to be used in addition to the original data. We present extensive empirical results demonstrating the success of using D-MIAT on 28 benchmark datasets. We also demonstrate that 10 other discretization algorithms can also be used to generate features that yield improved performance when used in combination with the original non-discretized data. Our results show that the best predictive performance is attained using a combination of the original dataset with added features from a "standard" supervised discretization algorithm and D-MIAT.

  12. Flow ring valve is simple, quick-acting

    NASA Technical Reports Server (NTRS)

    Lindfors, J. A.

    1966-01-01

    Two porting rings, one within the other, control gas or liquid flow by using seal buttons as the sliding valve closers. Multiporting within the ring allows close control of the flow by the slight rotation of the outer porting ring.

  13. Rings of Uranus at 1.44 kilometers

    NASA Image and Video Library

    1998-11-11

    The outer rings of Uranus are visible in this image, obtained by NASA Voyager 2 on Jan. 23, 1986. The outermost and brightest ring, called epsilon, is visible along with the fainter and narrower delta and gamma rings from left.

  14. The tilt effect for Saturn's rings

    NASA Technical Reports Server (NTRS)

    Esposito, L. W.; Lumme, K.

    1977-01-01

    Multiple-scattering computations are carried out to explain the variation of the observed brightness of the A and B rings of Saturn with declination of the earth and sun. These computations are performed by a doubling scheme for a homogeneous plane-parallel scattering medium. A range of choices is tested for the phase function, albedo for single scattering, and optical depth of both the rings. Isotropic scattering and several other simple phase functions are ruled out, and it is found that the phase function must be moderately peaked in both the forward and backward directions. The tilt effect can be explained by multiple scattering in a homogeneous layer, but, for ring B, this requires a single-scattering albedo in excess of 0.8. The brightest part of ring B must have an optical depth greater than 0.9. It is found that the tilt effect for ring A can be reproduced by particles having the same properties as those in ring B with the optical depth for the A ring in the range 0.4 to 0.6.

  15. Gored Clump in Saturn F Ring

    NASA Image and Video Library

    2015-10-19

    Saturn's dynamic F ring contains many different types of features to keep scientists perplexed. In this image we see features ring scientists call "gores," to the right of the bright clump, and a "jet," to the left of the bright spot. Thanks to the ring's interaction with the moons Prometheus and Pandora, and perhaps a host of smaller moonlets hidden in its core, the F ring is a constantly changing structure, with features that form, fade and re-appear on timescales of hours to days. This view looks toward the unilluminated side of the rings from about 7 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 15, 2015. The view was acquired at a distance of approximately 295,000 miles (475,000 kilometers) from Saturn and at a Sun-ring-spacecraft, or phase, angle of 117 degrees. Image scale is 1.8 miles (2.9 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18337

  16. Saturn's Ring Images/Dynamics by Cassini

    NASA Astrophysics Data System (ADS)

    Burns, J. A.; Tiscareno, M. S.

    2005-12-01

    Since its orbit insertion in mid-2004, the Cassini spacecraft has been able to view Saturn's magnificent rings at various phase and elevation angles, with resolutions ranging from ~200 m on orbit insertion, through a km or two during typical closest approaches, up to many tens of km at distant apoapses. Significant changes have occurred in isolated regions of the rings between the Voyager encounters a quarter century ago and the continuing observations over the last eighteen months. This talk will focus on observations and understandings of the past year. As time permits, we will discuss bending and density wave structures (emphasizing the changes in those caused by the switching orbits of Janus and Epimetheus); features that are temporally variable over short times (F ring, Encke ringlets, ring edges) and longer (D and G rings); odd patterns (short streaks, "straw", "knots" and "turbulence"); and interactions with adjacent satellites, especially those embedded in the Encke and Keeler gaps. Since the spacecraft will spend most of Fall 2005 near the ring plane, we anticipate few discoveries during this period; this should allow us time to do a better job at interpreting those data currently in hand. As J. C. Maxwell wrote in 1857, we are "still grinding at Saturn's rings."

  17. Evolution and stability of ring species

    PubMed Central

    Martins, Ayana B.; de Aguiar, Marcus A. M.; Bar-Yam, Yaneer

    2013-01-01

    Neutral models, in which genetic change arises through random variation without fitness differences, have proven remarkably successful in describing observed patterns of biodiversity, despite the manifest role of selection in evolution. Here we investigate the effect of barriers on biodiversity by simulating the expansion of a population around a barrier to form a ring species, in which the two ends of the population are reproductively isolated despite ongoing gene flow around the ring. We compare the spatial and genetic properties of a neutral agent-based population model to the greenish warblers’ complex, a well-documented example of an actual ring species in nature. Our results match the distribution of subspecies, the principal components of genetic diversity, and the linear spatial–genetic correlation of the observed data, even though selection is expected to be important for traits of this species. We find that ring species are often unstable to speciation or mixing but can persist for extended times depending on species and landscape features. For the greenish warblers, our analysis implies that the expanded area near the point of secondary contact is important for extending the duration of the ring, and thus, for the opportunity to observe this ring species. Nevertheless it also suggests the ring will break up into multiple species in 10,000 to 50,000 y. These results imply that simulations can be used to accurately describe empirical data for complex spatial–genetic traits of an individual species. PMID:23479635

  18. A COLLISIONAL ORIGIN FOR THE LEO RING

    SciTech Connect

    Michel-Dansac, Leo; Emsellem, Eric; Duc, Pierre-Alain

    2010-07-10

    Extended H I structures around galaxies are of prime importance for probing galaxy formation scenarios. The giant H I ring in the Leo group is one of the largest and most intriguing H I structures in the nearby universe. Whether it consists of primordial gas, as suggested by the apparent absence of any optical counterpart and the absence of an obvious physical connection to nearby galaxies, or of gas expelled from a galaxy in a collision is actively debated. We present deep wide field-of-view optical images of the ring region obtained with MegaCam on the CFHT. They reveal optical counterpartsmore » to several H I and UV condensations along the ring, in the g', r', and i' bands, which likely correspond to stellar associations formed within the gaseous ring. Analyzing the spectral energy distribution of one of these star-forming regions, we found it to be typical for a star-forming region in pre-enriched tidal debris. We then use simulations to test the hypothesis that the Leo ring results from a head-on collision between Leo group members NGC 3384 and M96. According to our model which is able to explain, at least qualitatively, the main observational properties of the system, the Leo ring is consistent with being a collisional ring. It is thus likely another example of extended intergalactic gas made-up of pre-enriched collisional debris.« less

  19. Rational reprogramming of fungal polyketide first-ring cyclization.

    PubMed

    Xu, Yuquan; Zhou, Tong; Zhou, Zhengfu; Su, Shiyou; Roberts, Sue A; Montfort, William R; Zeng, Jia; Chen, Ming; Zhang, Wei; Lin, Min; Zhan, Jixun; Molnár, István

    2013-04-02

    Resorcylic acid lactones and dihydroxyphenylacetic acid lactones represent important pharmacophores with heat shock response and immune system modulatory activities. The biosynthesis of these fungal polyketides involves a pair of collaborating iterative polyketide synthases (iPKSs): a highly reducing iPKS with product that is further elaborated by a nonreducing iPKS (nrPKS) to yield a 1,3-benzenediol moiety bridged by a macrolactone. Biosynthesis of unreduced polyketides requires the sequestration and programmed cyclization of highly reactive poly-β-ketoacyl intermediates to channel these uncommitted, pluripotent substrates to defined subsets of the polyketide structural space. Catalyzed by product template (PT) domains of the fungal nrPKSs and discrete aromatase/cyclase enzymes in bacteria, regiospecific first-ring aldol cyclizations result in characteristically different polyketide folding modes. However, a few fungal polyketides, including the dihydroxyphenylacetic acid lactone dehydrocurvularin, derive from a folding event that is analogous to the bacterial folding mode. The structural basis of such a drastic difference in the way a PT domain acts has not been investigated until now. We report here that the fungal vs. bacterial folding mode difference is portable on creating hybrid enzymes, and we structurally characterize the resulting unnatural products. Using structure-guided active site engineering, we unravel structural contributions to regiospecific aldol condensations and show that reshaping the cyclization chamber of a PT domain by only three selected point mutations is sufficient to reprogram the dehydrocurvularin nrPKS to produce polyketides with a fungal fold. Such rational control of first-ring cyclizations will facilitate efforts to the engineered biosynthesis of novel chemical diversity from natural unreduced polyketides.

  20. Rational reprogramming of fungal polyketide first-ring cyclization

    PubMed Central

    Xu, Yuquan; Zhou, Tong; Zhou, Zhengfu; Su, Shiyou; Roberts, Sue A.; Montfort, William R.; Zeng, Jia; Chen, Ming; Zhang, Wei; Lin, Min; Zhan, Jixun; Molnár, István

    2013-01-01

    Resorcylic acid lactones and dihydroxyphenylacetic acid lactones represent important pharmacophores with heat shock response and immune system modulatory activities. The biosynthesis of these fungal polyketides involves a pair of collaborating iterative polyketide synthases (iPKSs): a highly reducing iPKS with product that is further elaborated by a nonreducing iPKS (nrPKS) to yield a 1,3-benzenediol moiety bridged by a macrolactone. Biosynthesis of unreduced polyketides requires the sequestration and programmed cyclization of highly reactive poly-β-ketoacyl intermediates to channel these uncommitted, pluripotent substrates to defined subsets of the polyketide structural space. Catalyzed by product template (PT) domains of the fungal nrPKSs and discrete aromatase/cyclase enzymes in bacteria, regiospecific first-ring aldol cyclizations result in characteristically different polyketide folding modes. However, a few fungal polyketides, including the dihydroxyphenylacetic acid lactone dehydrocurvularin, derive from a folding event that is analogous to the bacterial folding mode. The structural basis of such a drastic difference in the way a PT domain acts has not been investigated until now. We report here that the fungal vs. bacterial folding mode difference is portable on creating hybrid enzymes, and we structurally characterize the resulting unnatural products. Using structure-guided active site engineering, we unravel structural contributions to regiospecific aldol condensations and show that reshaping the cyclization chamber of a PT domain by only three selected point mutations is sufficient to reprogram the dehydrocurvularin nrPKS to produce polyketides with a fungal fold. Such rational control of first-ring cyclizations will facilitate efforts to the engineered biosynthesis of novel chemical diversity from natural unreduced polyketides. PMID:23509261