Academic literature on the topic 'Annular groove'
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Journal articles on the topic "Annular groove":
1
Thawornsathit, Phongsakorn, Ekachai Juntasaro, Hwanjit Rattanasonti, Putapon Pengpad, Karoon Saejok, Chana Leepattarapongpan, Ekalak Chaowicharat, and Wutthinan Jeamsaksiri. "Enhancing Performance of a MEMS-Based Piezoresistive Pressure Sensor by Groove: Investigation of Groove Design Using Finite Element Method." Micromachines 13, no. 12 (December 17, 2022): 2247. http://dx.doi.org/10.3390/mi13122247.
Abstract:
The optimal groove design of a MEMS piezoresistive pressure sensor for ultra-low pressure measurement is proposed in this work. Two designs of the local groove and one design of the annular groove are investigated. The sensitivity and linearity of the sensor are investigated due to the variations of two dimensionless geometric parameters of these grooves. The finite element method is used to determine the stress and deflection of the diaphragm in order to find the sensor performances. The sensor performances can be enhanced by creating the annular or local groove on the diaphragm with the optimal dimensionless groove depth and length. In contrast, the performances are diminished when the local groove is created on the beam at the piezoresistor. The sensitivity can be increased by increasing the dimensionless groove length and depth. However, to maintain low nonlinearity error, the annular and local grooves should be created on the top of the diaphragm. With the optimal designs of annular and local grooves, the net volume of the annular groove is four times greater than that of the local groove. Finally, the functional forms of the stress and deflection of the diaphragm are constructed for both annular and local groove cases.
2
Robrecht, Robin M., and Peter F. Pelz. "Lubrication Film Friction Model for Grooved Annular Seals." International Journal of Turbomachinery, Propulsion and Power 8, no. 4 (November 10, 2023): 45. http://dx.doi.org/10.3390/ijtpp8040045.
Abstract:
Grooved liquid annular seals have a significant influence on the design of turbomachines. Corresponding lubrication film models need to account for the different friction behavior of the grooves compared to plain seals. However, there is a lack of reliable and validated models for this purpose. Thus, the applicability of a friction factor model is explored and a calibration method is presented. A single square groove is investigated by means of 96 steady-state RANS simulations for different operation conditions and groove geometries. The results are used to calibrate the friction model and successfully verify it in terms of the pressure drop over the groove. For validation, two full grooved seals with relatively large square grooves were investigated by experiment. The friction model was incorporated in a lubrication model and compared to the measurement data for the pressure difference and the resulting force for specified leakage and eccentricity. The model predictions for the pressure difference can be considered very good. The force predictions show significant deviation, but can be considered acceptable given the low force magnitudes and measurement uncertainty. The results offer a general validity to our friction model approach, assumptions and the calibration method.
3
Yifang, Sun, O. G. Grebenikov, and O. O. Vendin. "ВПЛИВ КІЛЬЦЕВИХ КАНАВОК ХОЛОДНОГО ОБТИСКУ НА ДОВГОВІЧНІСТЬ ПАНЕЛЕЙ КРИЛА З ФУНКЦІОНАЛЬНИМИ ОТВОРАМИ." Open Information and Computer Integrated Technologies, no. 99 (June 24, 2024): 22–31. http://dx.doi.org/10.32620/oikit.2023.99.02.
Abstract:
This article studies in detail the method of cold extrusion annular grooves to solve the problem of aircraft fatigue life extension that reduces the fatigue life of aircraft wing panels due to functional holes. This method is a very simple and effective anti-fatigue manufacturing technology. In order to simulate the different wing panels with functional holes, the experiment is designed to extrude the specimen with different extrusion forces to obtain annular grooves of different depths. Fatigue tests are conducted on specimens with annular grooves. The test results show that: 1) Cold extrusion annular grooves can extend the fatigue life of wing panels with functional holes; 2) The fatigue life of wing panels with functional holes is affected by the depth of the cold extrusion annular groove. The fatigue life changes in an inverted "V" shape as the depth of the cold extrusion annular groove increases; 3) When cold extrusion annular groove depth is 0.26mm, the fatigue life of specimen with holes is maximum, and the fatigue life is increased by 2.35~32.9 times when specimen thickness is 5 mm
4
Childs, Dara W., Luis E. Rodriguez, Vito Cullotta, Adnan Al-Ghasem, and Matthew Graviss. "Rotordynamic-Coefficients and Static (Equilibrium Loci and Leakage) Characteristics for Short, Laminar-flow Annular Seals." Journal of Tribology 128, no. 2 (September 28, 2005): 378–87. http://dx.doi.org/10.1115/1.2164468.
Abstract:
Test results are presented for laminar-flow seals that are representative of buffered-flow oil seals in centrifugal compressors. The seals are short (L∕D≅0.21), with a diameter of 117mm and a clearance-to-radius ratio 0.0007. A smooth seal, a seal with one central groove, and a seal with three grooves were tested. Groove geometries employed are representative of industrial practice for compressors with a groove-depth to clearance ratio on the order of 6. Tests were conducted at 4000, 7000, and 10,000rpm shaft speed with delta pressures across the seals of 21, 45, and 69bars. For all cases, the flow was laminar. The seals were tested from a centered position out to an eccentricity ratio of 0.7. Static data included leakage and equilibrium loci for a range of loads. Direct and cross-coupled stiffness and damping coefficients and direct mass coefficients were determined from dynamic tests. For the smooth seal, comparisons between measurements and predictions were reasonable for the direct and cross-coupled stiffness and damping coefficients; however, measured added mass coefficients were roughly ten times larger than predicted. Predictions for the grooved seals from a “deep-groove” model that assumed zero pressure oscillations in the grooves greatly over predicted the influence of the grooves. In a centered position, smooth and grooved seals had comparable leakage performance. At higher eccentricity ratios, the grooved seals leaked modestly more. For eccentricity ratios less than approximately 0.3, the grooved seals and the smooth seal had qualitatively similar static and dynamic characteristics. In terms of cross-coupled stiffness coefficients, the grooved seals were less stable than the smooth seal at eccentricity ratios greater than approximately 0.5 but had significantly lower cross-coupled coefficients at reduced eccentricity ratios between zero and 0.3. A grooved centered seal is more stable than a smooth centered seal. The smooth seal had higher damping than the grooved seals and had moderately better centering capabilities.
5
Yen, S. C., and C. L. Shih. "Improving Combustion Intensity and Modulating Flame Behaviors Using Helical-Grooved Cones." Journal of Mechanics 29, no. 2 (December 20, 2012): 273–80. http://dx.doi.org/10.1017/jmech.2012.134.
Abstract:
AbstractFour helical-grooved cones were installed behind an unconfined combustion nozzle to increase the bluff-body effect and turbulence intensity (T.I.). The cone configurations included a smooth cone and the other three cones cut with 1, 2 and 3 helical v-grooves. Experimental results showed that the helical v-grooves transformed the axial momentum (or the axial velocity) to the angular momentum (or the angular velocity). TheT.I.was enhanced by increasing the tangential component of fuel-jet momentum. The direct photography and thermocouple were utilized to observe the flame structures and to delineate the characteristic flame modes, flame length, temperature distribution, and combustion intensity. The flame modes were classified as jet flame, flickering flame, bubble flame, recirculation flame, lifted flame and ring flame. The flame length decreases as the groove number increases. The increasedT.I.and groove number (or bluff-body effect) improve the fuel-air mixing. The total combustion intensity increases with annular-air jet and with the groove number.
6
Редин, И. И., and М. А. Шевченко. "УЛУЧШЕНИЕ ТОПЛИВНОЙ ЭФФЕКТИВНОСТИ ГАЗОТУРБИННОГО ДВИГАТЕЛЯ УСТАНОВКОЙ В КОМПРЕССОРЕ НАДРОТОРНОГО УСТРОЙСТВА." Open Information and Computer Integrated Technologies, no. 81 (November 16, 2018): 72–85. http://dx.doi.org/10.32620/oikit.2018.81.08.
Abstract:
The analysis of the influence of annular grooves on the flow in the compressor rotor air gas channel and the axial compressor characteristics as well as on the fuel efficiency of the gas turbine engine is presented. The hypothetical mechanism of the flow effect in the cavity of the annular groove on the main flow in the tip end of the blade air-foil of the axial compressor stage is outlined. The effectiveness of the casing treatment in the form of single annular groove, width is 20% of the axial projection of the chord of the tip end section of the blade is shown experimentally in a single-stage and multi-stage axial compressor system. The increase of the compressor efficiency with ten single annular grooves installed above the leading edges of the blades of each stage, has reduced the specific fuel consumption of the serial GTE in its main operating modes.
7
Razzzaque, M. Mahbubur, and Takahisa Kato. "Effects of a Groove on the Behavior of a Squeeze Film Between a Grooved and a Plain Rotating Annular Disk." Journal of Tribology 121, no. 4 (October 1, 1999): 808–15. http://dx.doi.org/10.1115/1.2834139.
Abstract:
A model simulating the squeezing process of an annular disk rotating against a grooved counterpart has been developed. Grooving effects are incorporated using the narrow groove assumption. Disks are considered impermeable, rigid, perfectly aligned, and smooth. It is assumed that the fluid film is isothermal and obeys Reynolds equation. The governing equations derived from the model are solved numerically. The effects of groove geometry, orientation and applied load on film thickness, transmitted torque, speed, squeeze time, and viscous power dissipation have been calculated and analyzed. It has been found that angular orientation significantly affects the squeezing process. Squeeze time and power dissipation are less for grooves with angular orientation in the range 40–60 deg.
8
Childs, Dara W., Matthew Graviss, and Luis E. Rodriguez. "Influence of Groove Size on the Static and Rotordynamic Characteristics of Short, Laminar-Flow Annular Seals." Journal of Tribology 129, no. 2 (January 5, 2007): 398–406. http://dx.doi.org/10.1115/1.2647471.
Abstract:
Test results are presented for a smooth seal and three centrally grooved seals that are representative of buffered-flow oil seals in centrifugal compressors. The seals are short (L∕D≅0.21), with a diameter of 117mm and a nominal radial clearance of 0.085mm, netting the clearance-to-radius ratio 0.0015. The grooves have groove depth to clearance ratios (Dg∕Cr) of 5, 10, and 15. Test conditions include three shaft speeds from 4000rpm to 10,000rpm, three inlet oil pressures from 24bar to 70bar, and seal eccentricity ratios from 0 (centered) to 0.7. Dynamic results include stiffness, damping, and added-mass coefficients; static results include stator position, attitude angles, and seal leakage. Stiffness, damping, and mass coefficients plus leakage are compared for the seal geometries. Results show that all rotordynamic coefficients consistently decrease with increasing seal groove depths, and seal leakage is largely unchanged. Comparisons are also made between experimental results and predictions from a computer program based on a Reynolds + energy equation model. The model includes the assumption that a groove is large enough to create separate lands within the seal, creating a zero or negligible pressure perturbation within the groove. Test results show that even the deepest groove depth tested is not deep enough to satisfy this assumption.
9
Lin, Zhimin, Ruixia Yang, Haihong Yang, Liangbi Wang, Yongheng Zhang, and Anning Guo. "Parametric effect of the interrupted annular groove fin on flow and heat transfer characteristics of a finned circular tube heat exchanger." Thermal Science, no. 00 (2022): 40. http://dx.doi.org/10.2298/tsci211015040l.
Abstract:
The influences of the geometrical parameters of interrupted annular groove fin (IAGF) mainly including the annular groove diameter, the groove arc length, and the fin spacing, on the fin side thermal-hydraulic characteristics of a finned circular tube exchanger were numerically investigated by actualizing the custom FORTRAN programing with SIMPLE algorithm in a nonorthogonal curvilinear coordinate system, and the regression formulas of average Nusselt number and friction factor with flow parameters and geometrical parameters were obtained. Compared with the referential plain fin, IAGF could significantly improve thermal performance under the same pumping power constraint, and Nusselt number is closely germane to the secondary flow, which implies that the fin side heat transfer is depended entirely on the secondary flow strength. For Nusselt number, the annular groove diameter and the groove arc length have positive effect, while the fin pitch, the groove circumferential and radial locations have negative effect. The dominant parameters influencing on friction factor in turn are the fin pitch, the groove radial location, and the annular groove diameter. The optimal annular groove diameter is screened, and found that the optimal annular groove diameter is closely related with Reynolds number under the same pumping power constraint, while under the same mass flow rate constraint that is scarcely related with Reynolds number.
10
Childs, D. W., S. A. Nolan, and J. J. Kilgore. "Test Results for Turbulent Annular Seals, Using Smooth Rotors and Helically Grooved Stators." Journal of Tribology 112, no. 2 (April 1, 1990): 254–58. http://dx.doi.org/10.1115/1.2920250.
Abstract:
Test results, consisting of leakage data, friction factors, and rotordynamic force coefficients, are presented for seven annular seals using smooth rotors and helically-grooved stators. All seals have the same nominal clearances and groove depths. The helix angles vary from zero (circumferential grooving) to 70 deg. The number of grooves and the leakage rates increase steadily with increasing helix angles. Helically-grooved stators leak more than smooth seals for helix angles greater than 30 deg. The effective direct stiffness of the seals first decreases and then increases with increasing helix angles. Contrary to theoretical predictions (Kim and Childs 1987), the effective net damping was relatively insensitive to changes in the helix angles.
Dissertations / Theses on the topic "Annular groove":
1
Graviss, Matthew Sheridan. "The influence of a central groove on static and dynamic characteristics of an annular liquid seal with laminar flow." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/2359.
Abstract:
This thesis provides experimental static and dynamic results for four pairs of
seals, including a pair of smooth seals and three pairs of centrally grooved seals. The
grooved seals have groove depth to clearance ratios (Dg/C) of 5, 10, and 15. The radial
clearance of each test seal is 0.0891 mm. Test conditions include three shaft rotational
speeds from 4000 to 10000 rpm, three inlet oil pressures from 24 to 70 bars, and seal
dimensionless eccentricities from 0 (centered) to 0.7. For each pair of test seals, dynamic
results include stiffness and damping coefficients; static results include stator position,
attitude angles, and seal leakage. Stiffness, damping, and leakage are compared among
the seal pairs with various groove depths. Results show that all rotordynamic coefficients
consistently decrease with increasing seal groove depths, and seal leakage remains
constant through varying groove depths. Additionally, a comparison is made between
experimental results of all test seals and XLLubeGT. XLLubeGT is a computer model
developed at Texas A&M University, which uses a Reynolds equation + energy equation
model to predict dynamic performance of a grooved seal. It operates on the assumption
that the groove is large enough to create separate lands within the seal, creating a zero or
negligible pressure perturbation across the seal. A comparison with XLLubeGT shows
that even the seal with the largest groove depth tested is not deep enough to agree with
XLLubeGT predictions.
2
Le, Mentec Guichon Ronan. "Caractérisation et Optimisation d'assemblages sertis hydrauliquement." Electronic Thesis or Diss., Ecole centrale de Nantes, 2023. http://www.theses.fr/2023ECDN0044.
Abstract:
Le sertissage de tubes représente un enjeu important en ingénierie car c’est un besoin récurrent dans presque toutes les industries ayant besoin de solidariser des pièces tubulaires entre elles. On retrouve notamment ces assemblages dans l’industrie navale de défense pour la propulsion des bâtiments de surface ou des sous-marins. Au fil des années, de nombreux chercheurs se sont intéressés aux liaisons serties avec pour but de déterminer les paramètres procédé, géométriques et matériaux prépondérants en vue de les dimensionner de façon optimale. Afin d’augmenter leur résistance, ils ont essayé d’implanter une gorge au sein de la liaison en préconisant certaines formes géométriques mais en occultant les critères de conception indispensables à la tenue de la liaison dans le temps. Plus tard, nous avons assisté à l'émergence des procédés dynamiques qui grâce aux grandes vitesses de déformations qu'ils génèrent, permettent de réduire le retour élastique dans certains cas. Cela peut donc être un autre moyen de rendre des liaisons serties plus résistantes. Le premier objectif de ce travail de thèse consiste à construire et fiabiliser un modèle numérique de simulation du sertissage par expansion hydraulique (quasi-statique) en vue de proposer un profil de gorge annulaire optimisé respectant des critères de conception. Le second axe vise à analyser dans quelle mesure le sertissage électrohydraulique (dynamique) présente des bénéfices supplémentaires en termes de résistance à l'arrachement et d'étanchéité en comparaison d’un procédé quasi-statiqueTube crimping is a major challenge in engineering because it is a recurring requirement in nearly all industries that need toconnect tubular parts together. These assemblies are particularly found in the defense naval industry for the propulsion of surface vessels or submarines. Over the years, numerous researchers have been interested in crimped joints with the aim of determining the predominant process, geometric, and material parameters for optimal sizing. To increase their strength, they have attempted to introduce a groove within the joint by recommending certain geometric shapes but neglecting essentialdesign criteria necessary for the long-term integrity of the assembly. Later, we witnessed the emergence of dynamic processes that, thanks to the high strain rates they generate, can reduce springback in certain cases. This can, therefore, be another way to produce crimped joints more resilient. The primary objective of this thesis work is to build and validate a numerical simulation model of crimping by hydraulic expansion (quasistatic) in order to propose an optimized annulargroove profile respecting design criteria. The second one aims to analyze to what extent electrohydraulic crimping (dynamic) offers additional benefits in terms of pull-out strength and tightness compared to a quasi-static process
3
Wilkes, Kevin Wood. "Rotordynamic analysis of circumferentially grooved annular pump seals with turbulent flow and inlet swirl /." This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-12302008-063353/.
4
Wilkes, Kevin. "Rotordynamic analysis of circumferentially grooved annular pump seals with turbulent flow and inlet swirl." Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/46444.
Abstract:
In this thesis an analysis is developed to predict the leakage and dynamic characteristics for circumferentially grooved turbulent annular seals used in turbopumps. The flow in the groove is modelled using turbulent shear layer theory and an entrance loss model is applied at the inlet and land regions of the seal. The governing equations are derived using Hirs’ turbulent lubrication theory. The equations are expanded to yield zeroth and first order perturbation equations for small rotor displacements about a centered position. The leakage and velocity distribution is obtained from a numerical solution of the zeroth order equations. The first order equations define the dynamic pressure distribution which is integrated to yield the fluid force reactions. The model predictions are compared to test results for smooth walled and grooved seals. The model shows good qualitative agreement with experimental test results for seal leakage and rotordynamic coefficients. Actual quantitative agreement is unresolved given the high level of experimental uncertainty in the test results.Master of Science
5
Bruno, François. "Optimisation des modes de Lamb à vitesse de groupe nulle engendrés par laser et évaluation locale de structures collées." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC147/document.
Abstract:
Les structures planes supportent la propagation de modes de Lamb, dont certains présentent une vitesse de groupe nulle et une vitesse de phase finie. Ces modes ZGV, favorablement engendrés et détectés par ultrasons laser, donnent lieu à des résonances locales étroites qui sont sensibles à l'épaisseur, aux propriétés élastiques et aux conditions de surface. Dans le premier volet de cette thèse, l'optimisation spatiale de la source laser (Faisceau rectangle ou Gaussien, anneau à profil rectangle ou Gaussien obtenu à l'aide d'un axicon) est étudiée afin d'améliorer la génération d'un mode de Lamb de longueur d'onde λ. Il est démontré que le rayon optimal d'un faisceau Gaussien est égal à λ/π. Les résultats théoriques sont en bon accord avec les simulations semi-analytiques et les mesures réalisées à la fréquence du mode ZGV S1S2 dans une plaque de Duralumin. Le second volet est dédié au contrôle de plaques collées par résonance ZGV. Ces structures sont décrites par un modèle rhéologique adhésif faisant intervenir des raideurs d'interface. La sensibilité des fréquences ZGV aux paramètres de la couche d'adhésif et aux raideurs d'interface est étudiée. La mesure des résonances ZGV a conduit à l'obtention des cartes de raideurs et d'épaisseur de colle. Elle a également permis de différencier des assemblages à tenue mécanique contrôléeFor some Lamb modes propagating in plane structures, the group velocity vanishes while the phase velocity remains finite. These modes are associated with local and narrow resonances and are sensitive to thickness, elastic properties and boundary conditions. Laser ultrasound techniques are well suited to generate and detect these resonances. In the first part of this thesis, spatial optimization of laser sources (Top-Hat and Gaussian beam, rectangular and Gaussian ring produced by an axicon-lens system) are studied in order to enhance the generation of a Lamb mode at wavelength λ. Optimal radius of a Gaussian beam is demonstrated to be λ/π. Theoretical results are shown to be in a good agreement with semi-analytical simulation and experimental results performed in a Duralumin plate at the S1S2-ZGV mode frequency. The second part of this work is dedicated to the use of ZGV resonances for the inspection of bonded plates. Trilayers are described by rheological model where interfaces are modelized by stiffnesses. The sensitivity of ZGV frequencies to the interfacial stiffnesses as well as adhesive layer parameters has been studied. Stiffnesses and adhesive thickness maps have been extracted from ZGV resonance measurements. In addition, ZGV mode measurements have been shown to allow the differenciation of controled bond strengh samples
6
Vandevelde, Ségolène. "Y'a pas de suie sans feu ! : étude micro-chronologique des concrétions fuligineuses. Étude de cas : le site paléolithique de la Grotte Mandrin (France)." Thesis, Paris 1, 2019. http://www.theses.fr/2019PA01H103.
Abstract:
L’étude des sociétés passées passe par la compréhension de leur organisation sociale. Une des fenêtres pour y accéder est l’étude des schèmes de mobilité et des dynamiques d’occupation du territoire, qui ne sont accessibles qu’avec une haute résolution temporelle. Si cette résolution micro-chronologique (sub-annuelle à décennale) est accessible aux ethnologues, elle ne l’est généralement pas aux archéologues préhistoriens, dont les assemblages archéologiques sont malheureusement presque exclusivement cumulatifs et se forment pour la plupart sur le temps long. Dans l’optique d’atteindre une haute résolution temporelle en archéologie, l’objet de cette thèse de Doctorat a été de développer la Fuliginochronologie (de fuligine : suie), étude microchronologique des dépôts de suie prisonniers dans des concrétions calcaires, témoins des occupations humaines dans les cavités. L’analyse de cet objet géoarchéologique consiste ainsi en une étude anthropologique des sociétés passées. Le corpus d’étude de la thèse est constitué de fragments de parois recouverts de concrétions fuligineuses et collectés dans les douze niveaux archéologiques pléistocènes de la Grotte Mandrin (Malataverne, Drôme, France), attribués au Paléolithique moyen et à la transition entre Paléolithique moyen et Paléolithique supérieur, et dans un treizième niveau holocène contenant principalement des vestiges de crémations néolithiques. Le site se situe en moyenne vallée du Rhône, rive gauche (est), et surplombe un bras mort du fleuve, au niveau d’un rétrécissement : le défilé de Donzère, donnant à l’abri une position privilégiée dans le paysage à la croisée de différents biotopes. Des analyses complémentaires (...) ont permis de démontrer le potentiel de datation des concrétions fuligineuses, de mieux comprendre leur genèse et les processus post-dépositionnels les affectant, et surtout de démontrer la nature annuelle des doublets de calcite qui les constituent et qui sont observables pour la plupart des échantillons. L’observation microscopique de lames minces et/ou de sections polies réalisées dans l’axe de croissance des concrétions révèle que ce qui pouvait apparaître comme une unique lamine noire à l’œil nu ou à faible grossissement se résout généralement en une multitude de fins films de suie de quelques micromètres d’épaisseur. Les codes-barres inventoriés sont ensuite mis en correspondance afin de reconstruire la chronique des occupations humaines dans l’abri pour chaque niveau archéologique. L’étude conjointe des films de suie et des doublets de calcite permet quant à elle de caler les chroniques sur une échelle de temps microchronologique. À ce jour, peu d’études se sont intéressées à ce matériau et, pour la première fois ici, nous avons pu construire les chroniques des occupations humaines dans un abri-sous-roche pour l’ensemble des niveaux archéologiques du site : la Grotte Mandrin. Parmi les résultats, nous avons notamment pu déterminer un Nombre Minimum d’Occupations par niveau archéologique, ou encore mettre en évidence des dynamiques d’occupation du site (et dans une certaine mesure du territoire), différentes entre les niveaux archéologiques, via l’identification de rythmes d’occupation intégrés au cycle annuel de nomadisme ou au sein de cycles pluriannuels. Cette finesse de perception, jusqu’ici inaccessible pour l’étude des populations anciennes, permet également de démontrer que la succession entre les derniers Néanderthaliens et les premiers Homo sapiens régionaux s’est faite, sur ce site, en un temps très court qui peut être évalué à un an, indiquant une contemporanéité de ces deux humanités, sur un même territoire. Les perspectives de recherche de la fuliginochronologie sont diverses. Cette méthode microchronologique présente un large domaine d’application tant chronologique que géographique, puisqu’elle peut être appliquée partout dans le monde et pour toutes périodes, tant que des feux ont été faits à proximité de concrétions activesThe study of past societies requires an understanding of their social organization. One way to do study it is to focus on mobility patterns and land use dynamics, which are only accessible with a high temporal resolution. While micro-chronological resolution (sub-annual to decennial) is accessible to ethnologists, it is generally not accessible to prehistoric archaeologists, whose archaeological assemblages are unfortunately almost exclusively cumulative and are mostly formed over a long period of time. The aim of this PhD thesis was to develop fuliginochronology (of fuliginous: sooty) as a technique to reach a high temporal resolution in archaeological settings. Fuliginochronology is the micro-chronological study of soot deposits trapped in limestone concretions, which are evidence of human occupations in caves. The analysis of this geoarchaeological phenomenon thus consists of an anthropological study of past societies. The thesis corpus consists is composed of fragments of walls covered with sooty concretions and collected in the twelve Pleistocene archaeological levels of the Grotte Mandrin site (Malataverne, Drôme, France). These are attributed to the Middle Palaeolithic and the transition between the Middle and Upper Palaeolithic. A thirteenth Holocene level contains mainly remains of Neolithic cremations. The site is located in the middle Rhône valley, left bank (east), and overlooks a dead arm of the river, at the level of a narrowing: the Donzère defile, giving the shelter a privileged position in the landscape at the crossroads of different biotopes. Additional analyses (…) demonstrated the dating potential of sooty concretions. These studies also helped to better understand the genesis and the post-depositional alterations of the concretions. Moreover, they provided evidence demonstrating the annual nature of the calcite doublets that constitute them and that are observable for most samples. Microscopic observation of thin, and/or polished, sections made in the concretion’s growth axis reveals that what appears as a single black lamina to the naked eye generally resolves as a multitude of thin soot films a few micrometres thick which can resemble a barcode. These ‘barcodes’ can be inventoried and aligned to reconstruct longer sequences and the chronicle of human occupations in the shelter for each archaeological level. The joint study of soot films and calcite doublets allows us to set the chronicles on a micro-chronological time scale. Few studies have been carried out on this type of material. This work represents the first attempt to build the chronicles of occupations across all archaeological levels in a rock shelter. Among the results, The Minimum Number of Occupations per archaeological level was determined, and occupation rhythms integrated into the annual cycle of nomadism or within multi-year cycles were identified. This highlights the dynamics of occupation of the site (and, to a certain degree, of the territory) that are different between the archaeological levels. This finesse of perception, hitherto inaccessible for the study of ancient populations, also makes it possible to demonstrate that the succession between the last Neanderthals and the first regional Homo sapiens took place on this site in a very short time, a single year, indicating the contemporaneity of these two humanities on the same territory. The research applications of fuliginochronology are diverse. This micro-chronological method has a wide field of application both chronologically and geographically, since it can be applied anywhere in the world and for any period of time, as long as fires have been made in the vicinity of active concretions
7
Lhuillier, Jean-Baptiste. "Le cyber-actionnaire : adaptation du droit des sociétés à l’évolution des technologies d’information et de communication. Étude en droits européen, français et allemand comparés." Thesis, Paris 10, 2015. http://www.theses.fr/2015PA100142/document.
Abstract:
Dès la loi NRE de 2001, le législateur français s’est intéressé à l’utilisation de la voie électroniqueen période d’assemblée générale des actionnaires. Il laisse au pouvoir réglementaire la liberté deposer les modalités de toute forme d’interaction à distance entre la société anonyme et sesactionnaires. Le régime juridique allemand relatif aux assemblées générales a quant à lui étémodernisé en profondeur par la seule ARUG de 2009. Cette loi transpose la directiveeuropéenne 2007/36/CE du 11 juillet 2007 concernant l’exercice de certains droits desactionnaires de sociétés cotées. Ces textes ont conçu un actionnaire qui utiliserait la voieélectronique pour faciliter l’exercice de ses droits, un « cyber-actionnaire ». Si les textes françaisont bien pour objectif de faciliter l’exercice des droits de l’actionnaire, un nouveau cadre juridiquesemble s’être greffé sur la réglementation connue jusqu’alors. À trop chercher à s’en distinguer,notamment pour marquer la nouveauté, un régime juridique spécial semble s’être constitué, alorsque le droit allemand paraît aisément assimiler la voie électronique aux modes traditionnels decommunication. Or l’on ne fait pas face à une nouvelle catégorie d’actionnaires qui justifierait untraitement particulier. Le cyber-actionnaire n’est qu’un actionnaire exerçant par voie électroniqueses droits relatifs à l’information, à la communication et à la prise de décision collective enpériode d’assemblée générale. Pour s’en convaincre, la présente étude tire le bilan del’implication de la voie électronique en droit des sociétés par actions français et allemandThis study looks into the introduction of electronic means in French and German company law.The French legislator already introduced the possibility of participating in shareholders annualgeneral meetings via electronic means in 2001. The law on New Economic Regulations led thegovernment to set the conditions of all the electronic communication between companies andtheir shareholders. In Germany, mainly the ARUG from 2009 modernized the law related to theAGM, by transposing the European directive from 11th July 2007 on the exercise of certain rightsof shareholders in listed companies. The new laws have a shareholder in mind, who would useelectronic means to facilitate the exercise of his rights before and during the AGM, a “cybershareholder”.While the German law seeks to assimilate the electronic communication with thetraditional correspondence, the varying French decrees seem to distinguish between a new legalregime and a traditional one. However, there is no need for a new category of shareholders,which could justify a special legal foundation. The cyber-shareholder is just a shareholderexercising his rights related to information, communication and collective decision-making in theAGM via electronic means
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BULGINI, Giulia. "Il progetto pedagogico della Rai: la televisione di Stato nei primi vent’anni. Il caso de ‹‹L’Approdo››." Doctoral thesis, 2018. http://hdl.handle.net/11393/251123.
Abstract:
Non c’è dubbio sul fatto che la RAI, dal 1954 a oggi, abbia contribuito in misura considerevole a determinare la fisionomia dell’immaginario collettivo e dell’identità culturale dell’Italia. Si tratta di un assunto che, a distanza di più di sessant’anni, resta sempre di grande attualità, per chi si occupa della questione televisiva (e non solo). Ma a differenza di quanto avveniva nel passato, quando la tv appariva più preoccupata dei reali interessi dei cittadini, oggi essa sembra rispondere prevalentemente a dinamiche di mercato, in grado di alterarne la funzione etica e sociale. E nonostante il livello di istruzione e di benessere economico si siano evidentemente alzati, in questi ultimi anni si è assistito a programmi di sempre più bassa qualità e in controtendenza a un incremento del potere modellante e suggestivo sull’immaginario dei telespettatori. C’è di più: l’interesse verso la tv ha coinvolto anche gli storici dell’epoca contemporanea, i quali hanno iniziato a prendere coscienza che le produzioni audiovisive sono strumenti imprescindibili per la ricerca. Se si pensa ad esempio al ‹‹boom economico›› del Paese, negli anni Cinquanta e Sessanta, non si può non considerare che la tv, insieme agli altri media, abbia contributo a raccontare e allo stesso tempo ad accelerare i progressi economici e sociali di quell’epoca.
Partendo, dunque, dal presupposto che la televisione da sempre esercita un potere decisivo sulla collettività, si è scelto di concentrarsi sulla fase meno indagata della sua storia, quella della televisione delle origini: ‹‹migliore›› perché senza competitor, ‹‹autentica›› perché incontestabile e soprattutto ‹‹pedagogica›› perché è di istruzione e di formazione che, quell’Italia appena uscita dalla guerra, aveva più urgenza. La storia della televisione italiana inizia il 3 gennaio 1954, con la nascita del servizio pubblico televisivo e insieme di un mezzo che, di lì a poco, avrebbe completamente rivoluzionato la società italiana, trasformandola in una civiltà di massa. Si accorciano le distanze territoriali e insieme culturali e la società inizia a omologarsi nei gusti, poi nei consumi e infine nel pensiero. Il punto d’arrivo si colloca negli anni Settanta, quando ha termine il monopolio della RAI, che fino a quel momento era stato visto come il garante del pluralismo culturale. La RAI passa dal controllo governativo a quello parlamentare, mentre si assiste al boom delle televisioni private e alla necessità della tv di Stato di stare al passo con la concorrenza, attraverso una produzione diversa da quella degli esordi. Dunque cambia la tv, come pure cambia la sua funzione e la forma mentis di chi ne detiene le redini. Ne risulta un’indagine trasversale, che passa nel mezzo di molteplici discipline che afferiscono alla materia televisiva e che non evita di porsi quelle domande scomode, necessarie tuttavia a comprendere la verità sugli artefici della prima RAI e sui loro obiettivi. E allora: qual era il valore attribuito alla televisione degli esordi? Era davvero uno strumento pedagogico? Sulla base di quali presupposti? Chi scriveva i palinsesti di quegli anni? Chi e perché sceglieva temi e format televisivi? Chi decideva, in ultima analisi, la forma da dare all’identità culturale nazionale attraverso questo nuovo apparecchio?
Il metodo di ricerca si è articolato su tre distinte fasi di lavoro. In primis si è puntato a individuare e raccogliere bibliografia, sitografia, studi e materiale bibliografico reperibile a livello nazionale e internazionale sulla storia della televisione italiana e sulla sua programmazione nel primo ventennio. In particolare sono stati presi in esame i programmi scolastici ed educativi (Telescuola, Non è mai troppo tardi), la Tv dei Ragazzi e i programmi divulgativi culturali. Successivamente si è resa necessaria una definizione degli elementi per l’analisi dei programmi presi in esame, operazione resa possibile grazie alla consultazione del Catalogo multimediale della Rai. In questa seconda parte della ricerca si è voluto puntare i riflettori su ‹‹L’Approdo››, la storia, le peculiarità e gli obiettivi di quella che a ragione potrebbe essere definita una vera e propria impresa culturale, declinata in tutte le sue forme: radiofonica, di rivista cartacea e televisiva. In ultimo, sulla base dell’analisi dei materiali d’archivio, sono state realizzate interviste e ricerche all’interno dei palazzi della Rai per constatare la fondatezza e l’attendibilità dell’ipotesi relativa agli obiettivi educativi sottesi ai format televisivi presi in esame.
Le conclusioni di questa ricerca hanno portato a sostenere che la tv delle origini, con tutti i suoi limiti, era uno strumento pedagogico e di coesione sociale. E se ciò appare come un aspetto ampiamente verificabile, oltreché evidente, qualora si voglia prendere in esame la televisione scolastica ed educativa di quegli anni, meno scontato risulta invece dimostrarlo se si decide – come si è fatto – di prendere in esame un programma divulgativo culturale come ‹‹L’Approdo››, che rientra nell’esperienza televisiva definita di ‹‹educazione permanente››. Ripercorrere la storia della trasmissione culturale più longeva della tv italiana degli esordi, per avvalorarne la funzione educativa, si è rivelata una strada interessante da battere, per quanto innegabilmente controversa, proprio per il principale intento insito nella trasmissione: diffondere la cultura ‹‹alta›› a milioni di telespettatori che erano praticamente digiuni della materia. Un obiettivo che alla fine della disamina si è rivelato centrato, grazie alla qualità della trasmissione, al suo autorevole e prestigioso groupe d'intellectuels, agli ascolti registrati dal ‹‹Servizio Opinioni›› e alla potenzialità divulgativa e penetrante della tv, nel suo saper trasmettere qualunque tematica, anche quelle artistiche e letterarie. Dunque se la prima conclusione di questo studio induce a considerare che la tv del primo ventennio era pedagogica, la seconda è che ‹‹L’Approdo›› tv di questa televisione fu un’espressione felice. ‹‹L’Approdo›› conserva ancora oggi un fascino innegabile, non foss’altro per la tenacia con la quale i letterati difesero l’idea stessa della cultura classica dal trionfo lento e inesorabile della società mediatica. Come pure appare ammirevole e lungimirante il tentativo, mai azzardato prima, di far incontrare la cultura con i nuovi media. Si potrebbe dire che ‹‹L’Approdo›› oggi rappresenti una rubrica del passato di inimmaginata modernità e, nel contempo, una memoria storica, lunga più di trent’anni, che proietta nel futuro la ricerca storica grazie al suo repertorio eccezionale di immagini e fatti che parlano di arte, di letteratura, di cultura, di editoria e di società e che raccontano il nostro Paese e la sua identità culturale, la stessa che la televisione da sempre contribuisce a riflettere e a delineare.
Lo studio è partito da un’accurata analisi delle fonti, focalizzando l’attenzione, in primo luogo, sugli ‹‹Annuari della Rai›› (che contengono le Relazioni del Cda Rai, le Relazioni del Collegio Sindacale, i Bilanci dell’Esercizio e gli Estratti del Verbale dell’Assemblea Ordinaria). Altre fonti prese in esame sono gli stati gli opuscoli di ‹‹Servizio Opinioni››, le pubblicazioni relative a studi e ricerche in materia di televisione e pedagogia e le riviste edite dalla Rai Eri: ‹‹Radiocorriere tv››, ‹‹L’Approdo Letterario››, ‹‹Notizie Rai››, ‹‹La nostra RAI››, ‹‹Video››. Negli ultimi anni la Rai ha messo a disposizione del pubblico una cospicua varietà di video trasmessi dalle origini a oggi (www.techeaperte.it): si tratta del Catalogo Multimediale della Rai, che si è rivelato fondamentale al fine della realizzazione della presente ricerca. Altre sedi indispensabili per la realizzazione di questa ricerca si sono rivelate le due Biblioteche romane della Rai di Viale Mazzini e di via Teulada.
Books on the topic "Annular groove":
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Lynch, Tony. The official Byker Grove annual. London: Grandreams Ltd., 1989.
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Division, Alberta Assessment Services. You asked about annual general assessments: The Spruce Grove experience. Edmonton: The Division, 1987.
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United States. National Aeronautics and Space Administration., ed. Physics of heat pipe rewetting: Annual status report for the period April 1, 1991 - March 31, 1992. [Washington, DC?: National Aeronautics and Space Administration, 1992.
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Workshop, on Microprogramming (18th 1985 Pacific Grove Calif ). Micro 18: Proceedings, the 18th annual Workshop on Microprogramming, Pacific Grove, California, December 3-6, 1985. Washington, D.C: IEEE Computer Society Press, 1985.
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Non-Volatile Memory Technology Symposium (9th 2008 Pacific Grove, CA). 2008 9th Annual Non-Volatile Memory Technology Symposium: Proceedings : Pacific Grove, California, 11-14 November 2008. Piscataway, NJ: IEEE, 2008.
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Chambers, Jeanne C. Using resistance and resilience concepts to reduce impacts of invasive annual grasses and altered fire regimes on the sagebrush ecosystem and greater sage-grouse: A strategic multi-scale approach. Fort Collins, CO: U.S. Dept. of Agriculture, Forest Service, Rocky Mountain Research Station, 2014.
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International Conference on Industrial Electronics, Control, and Instrumentation (1990 Pacific Grove, Calif.). IECON' 90: 16th annual conference of IEEE Industrial Electronics Society : November 27-30, 1990, Asilomar Conference Center, Pacific Grove, California. New York, NY: Institute of Electrical and Electronics Engineers, 1990.
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Keeler, Charles Augustus. A service for the cremation of care: As inspired by the annual ritual performed at the Bohemian Grove, Monte Rio, California. [San Francisco]: Lands End Press, 1989.
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N, Heine John, Crane Nicole L, Moss Landing Marine Laboratories, Diving Officers of Monterey Bay., and American Academy of Underwater Sciences., eds. Diving for science--1993: Proceedings of the American Academy of Underwater Sciences thirteenth annual scientific diving symposium, September 19-22, 1993, Asilomar Conference Center, Pacific Grove, California. Nahant, MA: American Academy of Underwater Sciences, 1993.
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Pacific Climate Workshop (18th 2001 Asilomar Conference Grounds). Proceedings of the Eighteenth Annual Pacific Climate Workshop: Asilomar Conference Grounds, Pacific Grove, California, March 18-21, 2001 : climate variability of the eastern North Pacific and western North America. [Sacramento, Calif.]: Interagency Ecological Program for the Sacramento-San Joaquin Estuary, 2002.
Book chapters on the topic "Annular groove":
1
Beck, Jeffrey L., Thomas J. Christiansen, Kirk W. Davies, Jonathan B. Dinkins, Adrian P. Monroe, David E. Naugle, and Michael A. Schroeder. "Sage-Grouse." In Rangeland Wildlife Ecology and Conservation, 295–338. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-34037-6_10.
Abstract:
AbstractIn this chapter, we summarize the ecology and conservation issues affecting greater (Centrocercus urophasianus) and Gunnison (C. minimus) sage-grouse, iconic and obligate species of rangelands in the sagebrush (Artemisia spp.) biome in western North America. Greater sage-grouse are noted for their ability to migrate, whereas Gunnison sage-grouse localize near leks year-round. Seasonal habitats include breeding habitat where males display at communal leks, nesting habitat composed of dense sagebrush and herbaceous plants to conceal nests, mesic summer habitats where broods are reared, and winter habitat, characterized by access to sagebrush for cover and forage. While two-thirds of sage-grouse habitat occurs on public lands, private land conservation is the focus of national groups including the USDA-NRCS Sage-Grouse Initiative. Sage-grouse are a species of great conservation concern due to population declines associated with loss and fragmentation of more than half of the sagebrush biome. Wildlife and land management agencies have been increasingly proactive in monitoring trends in sage-grouse populations (e.g., lek count index), adapting regulations to reduce harvest on declining populations, and in designing and implementing conservation policies such as core areas to conserve sage-grouse habitats and populations. Much of the remaining sagebrush habitat is threatened by altered fire regimes, invasive annual grasses and noxious weeds, encroaching piñon (Pinus edulis and monophylla)-juniper (Juniperus spp.) woodlands, sagebrush conversion, anthropogenic development, and climate change. Several diseases affect sage-grouse, but to date, disease has not been a widespread cause of declines. Proper livestock grazing and limited hunting appear to be sustainable with sage-grouse, whereas improper grazing, increasing free-roaming equid populations, and sagebrush conversion are primary concerns for future conservation. Research has identified additional concerns for sage-grouse including effects from fence collisions, predation from common ravens (Corvus corax), and reduced habitat effectiveness resulting from grouse avoidance of anthropogenic infrastructure. There is a need for future research evaluating sage-grouse habitat restoration practices following improper rangeland management, habitat alteration from invasive species and fire, effects on small and isolated populations, and effects from diseases.
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Benes, J., and E. Kasal. "New Fully Non-invasive Hemodynamic Monitoring Technologies: Groovy or Paltry Tools." In Annual Update in Intensive Care and Emergency Medicine, 249–58. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-13761-2_18.
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Xiao, Xiang, and Shunshan Feng. "Ballistic Characteristics on Oblique Penetrating Multi-Layer Aluminium Targets by Annular Groove Projectile." In Advances in Transdisciplinary Engineering. IOS Press, 2023. http://dx.doi.org/10.3233/atde230427.
Abstract:
With the development of complex terminal effects, the semi penetration effect of annular groove projectiles on multi-layer targets has obtained increasing attention. In this paper, based on the theory of cavity expansion, a comparative analysis model is established for the oblique penetration of annular groove projectile and ogive-nosed projectile into multi-layer targets. The FEM analysis software LS-DYNA is used to simulate and calculate the time history curves of projectile velocity, axis deviation angle, and axis angular velocity. In addition, the micro rheological behavior of the target material in the groove during oblique penetration was studied. The results show that the radial offset of the annular groove projectile is less than that of the pointed projectile, and the larger the landing angle, the greater the projectile offset. The penetration resistance of target decreases with the increase in layers of target, while the DOP and lateral deviation of the projectile increase. This analysis model can provide analytical basis for related applications.
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Zuccarello, Bernardo. "Use of Hybrid Methods (Hole-Drilling and Ring-Core) for the Analysis of the RS on Welded Joints." In Welding Principles and Application [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.102051.
Abstract:
The hybrid methods (HMs) for the residual stress (RS) analysis, such as the well-known hole-drilling method (HDM) and the ring-core method (RCM), have been widely developed since 80’. They are mechanical methods based on the partial relaxation of the RSs that occur when a proper geometry variation of the analysed component is introduced by drilling a hole (HDM) or a proper annular groove (RCM). The RS computation is performed by measuring the strains relaxed on surface and then by combine properly such measured strains with the influence coefficients previously computed accurately by using a numerical codes that consider the geometry of the particular component to be examined. In such a manner, the HMs can be potentially applied to any RS distribution independently from the cause that have caused them. In more detail, the HMs can be used for the analysis of the RS on welded joint by using both classical welding methods, as MIG or TIG processes, or modern methods as friction stir welding, etc. In the present chapter, after a brief presentation of the theory of the HMs, their application to various cases of welding joints are treated, and the possible limitation are discussed.
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Lambert, Frank. "The Battle of Ole Miss." In The Battle of Ole Miss, 105–27. Oxford University PressNew York, NY, 2009. http://dx.doi.org/10.1093/oso/9780195380422.003.0007.
Abstract:
Abstract On Friday, September 28, 1962, the Ole Miss campus was a tranquil setting for a student body abuzz with excitement and anticipation. Situated on almost a thousand acres of rolling hills and dotted with hardwood groves, the picturesque campus in north Mississippi, dormant over the hot summer, was now alive with all the activities of a new academic year. Students had completed registration for the fall semester and were attending their first classes. Hundreds of pledges had joined fraternities and sororities during rush week, an annual ritual at Ole Miss with its rich Greek tradition. The nationally ranked football team had won its first game against Memphis State and was traveling to Jackson to play the University of Kentucky on Saturday. Indeed, about half of the roughly 4,500 students would make the 175-mile trip down to the state capital for a weekend of revelry and football.
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Gussow, Adam. "Turnaround." In Whose Blues?, 252–76. University of North Carolina Press, 2020. http://dx.doi.org/10.5149/northcarolina/9781469660363.003.0012.
Abstract:
The twelfth and final “bar” of Whose Blues? offers a handful of thematic and anecdotal explorations: a prismatic view of the blues in the second decade of the third millennium, as Black bluesist heritage claims wrestle with the music’s postmodern condition. What happens when we add Asia—a sampling of younger bluesmen from Japan, China, and India—to our reckoning? Is there a significant statistical disparity between African American and white blues performers in contemporary American blues festivals and awards ceremonies, and at what point does that disparity become objectionable? What might a white blues scholar have to learn by attending the all-Black Jus’ Blues Music Foundation’s annual awards ceremony in Tunica, Mississippi? What sort of blues is being played and sung by the best younger African American bluesmen when they get together in Cleveland, Mississippi—the town where W. C. Handy first had his revelation about the power of the blues more than a hundred years earlier? This chapter ends with a capsule portrait of Akarsha “Aki” Kumar, a Silicon Valley bluesman from Mumbai and former software engineer at Adobe who has reinvented himself in the age of Trump, blending jump blues grooves with Bollywood lyrics and costumes.
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Davis*, Evan, and John Kay†. "Corporate Governance, Take-overs, and the Role of the Non-executive Director." In European Mergers and Merger Policy, 200–216. Oxford University PressOxford, 1993. http://dx.doi.org/10.1093/oso/9780198773450.003.0006.
Abstract:
Abstract Imagine a system of government in which there are annual elections, but these are almost never contested. Whenever they are, the incumbent government wins by an overwhelming majority. All the information about the state of the nation which the voters receive is controlled and distributed by the government and is glossy and self-congratulatory in tone. Changes in the senior leadership do take place, normally through an orderly process of retirement in which the incumbent leaders select and groom their successors. Occasionally there is more violent change. Sometimes this takes the form of an internal coup d’ètat. Or it may occur as a result of the intervention of the hostile government of another state. This is not a description of Eastern Europe before perestroika and glasnost. It is a description of the system by which public companies in Britain are controlled and governed.
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Robinson, James. "Saints’ Cults and Celebrity: The Medieval Legacy." In The Middle Ages in the Modern World. British Academy, 2017. http://dx.doi.org/10.5871/bacad/9780197266144.003.0007.
Abstract:
This chapter is based on Robinson’s experience as a curator of medieval material culture. It relates especially to his interest in relic veneration that culminated in the 2011 Treasures of Heaven exhibition at the British Museum. In order to make saints' cults accessible to modern audiences, he draws on the parallels between medieval devotion to saints and modern devotion to celebrities, chiefly through: crucifixion iconography (James Dean, Jim Morrison), pilgrimage to a shrine and annual commemoration (Elvis Presley/Graceland), perverse satisfaction at the death of a saint/celebrity, importance of clothes as reliquaries that enshrined a living form and are therefore imbued with the quality of the previous owner (Marilyn Monroe's gowns, Michael Jackson’s diamante glove), and fame for charitable works (Princess Diana, Audrey Hepburn). Princess Diana emerges as particularly close to a medieval saint with her healing touch, her glowing presence as a groomed but emotionally damaged figure, a virgin princess both detrimental and beneficial to the monarchy. The chapter highlights the importance of significant objects to medievalist practice, and Robinson draws on his experiences in sourcing modern as well as medieval devotional objects for exhibition, including issues of ownership, accessibility and value of such objects at auctions.
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Herz, Norman, and Ervan G. Garrison. "Other Chronological Methods." In Geological Methods for Archaeology. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195090246.003.0011.
Abstract:
Dendrochronology relies on the seasonal changes in the wood growth of trees that result in the annual production of rings; each ring starts with large cell elements associated with spring and ends with small cell elements associated with summer and autumn growth. The age of the tree is known by counting these rings. The sequence of rings produced over the years is distinctive and shared by trees of the same species over a broad region. In the western and southwestern United States, the bristlecone pine from the White Mountains of California and the eastern Great Basin has allowed the establishment of a tree-ring chronology of 10,000 years. The California bristlecone pines are found west of the Sierra escarpment's White Mountains, on the Trans-Sierra Valley slopes. The oldest groves of the trees are at an altitude of 13,000 ft (3936 m), with a few hundred trees. The oldest living tree is "Methuselah," at 4,700 years, while some of the dead trees have ages of 8,000 years. Shaped by the wind, their silvery trunks have tightly packed ring sequences. The growth of trees, which occurs from spring to autumn, is marked each year by the formation of a new ring of wood cells. The thickness of the rings is a function of the temperature and precipitation at the time of their formation. The trees of a region experience the same variations in climate and, therefore, present the same series of growth rings for the same data (period) sequence. In 1911, an astronomer, A. E. Douglass, was studying tree rings to correlate them with s spots and climatic changes. He succeeded in establishing one of the most precise dating t hniques used in archaeology. In order for the technique to be used, the tree rings must contain an arrangement of both narrow and wide rings that vary considerably in width. Each of the rings found within the cross section is called an annual ring. A wide annual ring signifies plentiful moisture in the soil, whereas a narrow ring signifies insufficient moisture in the soil for robust growth.
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Varzally, Allison. "Conclusion." In Children of Reunion. University of North Carolina Press, 2017. http://dx.doi.org/10.5149/northcarolina/9781469630915.003.0006.
Abstract:
2015: Tung Nguyen and Merrie Li—siblings born in Vietnam who reconnected in the United States in the 1980s—mourned the passing of their Vietnamese mother and puzzled over the discovery that the American man whom Tung believed was his father was not. A large group of Amerasians organized by Jimmy Miller gathered in Seattle for an annual celebration, reflection, and call to political action. During the festive evening of dancing and dining, they honored their successes, paid tribute to Vietnam veterans, and recommitted to helping those who remained in Vietnam. Adoptee Tiffany Chi Goodson, who spent one year in Hanoi, where she taught English and yoga, hosted monthly music events, and served street youth under the auspices of the nonprofit Blue Children’s Foundation, relocated to South Africa with and soon married Chris, a fellow volunteer and traveler whom she met in Southeast Asia. “Operation Babylift: Perspectives and Legacies,” an exhibit documenting and inviting exchanges on the subjects of adoption and the airlifts, opened in San Francisco’s Presidio. The bilingual, interactive space featured artifacts from Operation Babylift, text panels interpreting key events, a set of dialogues that paired adoptees with Presidio volunteers, and notecards—each asking a question such as “What conversation do you want to begin?” “What memories or stories do you want to share?” and “What question do you have about Operation Babylift?”—for visitors to complete and display on a peg-filled wall. National and regional media outlets used the occasion of the fortieth anniversary of the U.S. withdrawal from Vietnam to explore the recollections of aging veterans and the status of Vietnamese communities stretching from Philadelphia and Houston to San Jose and Garden Grove, California. The coverage not only replayed familiar themes of exile, anti-Communism, despair, and courageous adaptation but also noted the waning poignancy of the war and shifting priorities among American-born Vietnamese....
Conference papers on the topic "Annular groove":
1
Fang, Zhi, Zhigang Li, Jun Li, and Zhenping Feng. "Numerical Investigations on the Static and Rotordynamic Characteristics of Hole-Pattern Seals With Annular or Pocket Grooves on Seal Stator." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90776.
Abstract:
Abstract Annular damper seals, such as hole-pattern seals, are widely used to control leakage and enhance rotordynamic stability in turbomachinery, especially for the balance-piston seal in the straight-through compressor, and the center seal in the back-to-back compressor. To avoid or minimize negative static stiffness, annular grooves on seal stator have been used to increase direct static stiffness of hole-pattern seals by dividing one long seal to several shorter seal sections. However, few literatures are available for understanding the influences of annular grooves on seal static and rotordynamic characteristics. To understand the comprehensive effects of grooves on the static and rotordynamic characteristics of annular seals, a proposed three-dimensional (3D) transient CFD-based method was used for predictions of rotordynamic characteristics of hole-pattern seals, based on the multi-frequency one-dimensional rotor oscillating model and mesh deformation technique. Moreover, a 3D steady CFD-based method based on the mesh deformation technique was also utilized to predict static characteristics of hole-pattern seals. The accuracy and reliability of the present transient CFD-based method were demonstrated with experimental data of frequency-dependent rotordynamic coefficients of an experimental hole-pattern seal (HPS) at three inlet preswirl conditions (μ0 = −0.2441, 0, 0.598). The leakage flow rates, static and rotordynamic force coefficients were computed for three types of HPS (one without grooves - HPS, one with annular grooves on stator - HPS-AG, and one with pocket grooves on stator – HPS-PG) with three axial locations of grooves (20%, 40%, 60% of seal axial length) at zero and positive inlet preswirl conditions. The effects of groove types (annular and pocket grooves) and groove locations on the static and rotordynamic coefficients of HPS were numerically discussed. Numerical results show that the annular groove and pocket groove on the seal stator both produce a significantly increase in static stiffness, and the HPS-PG seal possesses relatively optimal static stiffness. The annular groove and pocket groove both result in slight increase (less than 5%) in leakage flow rate. The annular groove will significantly weaken the seal dynamic stiffness capability but weakly influence the seal net damping capability. However, the pocket groove shows weakly influences on the dynamic stiffness and damping characteristics. This suggests that the pocket groove is a more suitable design to improve the static and rotordynamic characteristic. The rotordynamic force coefficients show strong dependence on the annular groove location for the HPS-AG seal, but are insensitive to the pocket groove location for the HPS-PG seal. The optimal location of annular groove is strongly related to the inlet preswirl conditions. The increasing swirl velocity induced by the annular groove results in the decrease in stiffness and damping of the HPS-AG seal.
2
Peng, Xu-Dong, Li-Li Tan, Ji-Yun Li, Song-En Sheng, and Shao-Xian Bai. "Numerical Analysis of Dry Gas Face Seals With Spiral Groove and Inner Annular Groove." In 2008 Second International Conference on Integration and Commercialization of Micro and Nanosystems. ASMEDC, 2008. http://dx.doi.org/10.1115/micronano2008-70185.
Abstract:
A two-dimensional Reynolds equation was established for isothermal compressible gas between the two faces of a dry gas face seal with both spiral grooves and an inner annular groove onto the hard face. The opening force, the leakage rate, the axial film stiffness and the film stiffness to leakage ratio were calculated by finite element method. The comparisons with the sealing performances of a typical gas face seal only with spiral grooves onto its hard face were made. The effects of the face geometric parameters on the static behavior of such a seal were analyzed. The optimization principle for geometric parameters of a dry gas face seals with spiral grooves and an inner annular groove was presented. The recommended geometric parameters of spiral grooves and circular groove presented by optimization can ensure larger axial stiffness while lower leakage rates.
3
Paudel, Wisher, Cori Watson, and Houston G. Wood. "The Impact of Adding a Labyrinth Surface to an Optimal Helical Seal Design." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-87089.
Abstract:
Non-contacting annular seals are used in rotating machinery to reduce the flow of working fluid across a pressure differential. Helical and labyrinth grooved seals are two types of non-contacting annular seals frequently used between the impeller stages in a pump and at the balance drum. Labyrinth seals have circumferential grooves cut into the surface of the rotor, the stator, or both. They function to reduce leakage by dissipating kinetic energy as fluid expands in the grooves and then is forced to contract in the jet stream region. Helical groove seals have continuously cut grooves on either or both the rotor and stator surfaces. Like labyrinth seals, they reduce leakage through dissipation of kinetic energy, but have the added mechanism of functioning as a pump to push the fluid back towards the high-pressure region. Previous work has shown that mixed helical-labyrinth seals with labyrinth grooves on stator and helical grooves on rotor or labyrinth grooves on rotor and helical grooves on stator have an approximately 45% lower leakage than an optimized helical groove seal with grooves just on the stator in a high pressure application. The primary objective of this study is to determine whether the same performance gains can also be achieved in a low pressure application. Simulations were run in ANSYS CFX for seal designs with a helical stator and labyrinth rotor. Several labyrinth design parameters including the number of grooves and the groove width and depth are varied while the helical variables such as the groove width and depth as well as helix angle are kept constant. The data obtained are analyzed using backward regression methods and various response plots to determine the relationship between the design parameters and mass flow and power loss. The optimized helical design was simulated and the axial pressure profiles of the designs were compared to analyze the mechanism of the mixed helical-labyrinth seal. Then, the same labyrinth seal designs were simulated for a labyrinth rotor and a smooth stator to determine whether the optimal number of grooves, groove width and groove depth change due to the helical stator. The findings of this study show the effectiveness of mixed helical labyrinth grooved seals for both low and high pressure cases, and thus their efficiency and reliability for numerous industrial applications.
4
Huang, Jin, Zhen Qiao, and Yi Zhou. "Gap Analysis of Annular Groove MR Brake." In 5th International Conference on Civil Engineering and Transportation. Paris, France: Atlantis Press, 2015. http://dx.doi.org/10.2991/iccet-15.2015.5.
5
San Andrés, Luis, Tingcheng Wu, Hideaki Maeda, and Ono Tomoki. "A Computational Fluid Dynamics Modified Bulk Flow Analysis for Circumferentially Shallow Grooved Liquid Seals." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63492.
Abstract:
In straight-through centrifugal pumps, a grooved seal acts as a balance piston to equilibrate the full pressure rise across the pump. As the groove pattern breaks the development of fluid swirl, this seal type offers lesser leakage and lower cross-coupled stiffnesses than a similar size and clearance annular seal. Bulk-flow models predict expediently the static and dynamic force characteristics of annular seals; however they lack accuracy for grooved seals. Computational fluid dynamics (CFD) methods give more accurate results, but are not computationally efficient. This paper presents a modified bulk-flow model to predict the rotordynamic force coefficients of shallow depth circumferentially grooved liquid seals with an accuracy comparable to a CFD solution but with a simulation time of bulk-flow analyses. The procedure utilizes the results of CFD to evaluate the bulk flow velocity field and the friction factors for a 73 grooves annular seal (depth/clearance dg/ Cr = 0.98 and length/diameter L/D = 0.9) operating under various sets of axial pressure drop and rotor speed. In a groove, the flow divides into a jet through the film land and a strong recirculation zone. The penetration angle (α), specifying the streamline separation in the groove cavity, is a function of the operating conditions; an increase in rotor speed or a lower pressure difference increases α. This angle plays a prominent role to evaluate the stator friction factor and has a marked influence on the seal direct stiffness. In the bulk-flow code the friction factor model (f = nRem) is modified with the CFD extracted penetration angle (α) to account for the flow separation in the groove cavity. The flow rate predicted by the modified bulk-flow code shows good agreement with a measured result (6% difference). A perturbation of the flow field is performed on the bulk-flow equations to evaluate the reaction forces on the rotor surface. Compared to the rotordynamic force coefficients derived from the CFD results, the modified bulk-flow code predicts rotordynamic force coefficients within 10%, except that the cross-coupled damping coefficient is over-predicted up to 14%. An example test seal with a few grooves (L/D = 0.5, dg/Cr = 2.5) serves to further validate the predictions of the modified bulk-flow model. Compared to the original bulk-flow analysis, the current method shows a significant improvement in the predicted rotordynamic force coefficients, the direct stiffness and damping coefficients in particular.
6
Wu, Tingcheng, and Luis San Andrés. "Pump Grooved Seals: A CFD Approach to Improve Bulk-Flow Model Predictions." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90499.
Abstract:
Abstract In multiple stage centrifugal pumps, balance pistons, often comprising a grooved annular seal, equilibrate the full pressure rise across the pump. Grooves in the stator break the evolution of fluid swirl and increase mechanical energy dissipation; hence, a grooved seal offers a lesser leakage and lower cross-coupled stiffness than a similar size uniform clearance seal. To date bulk-flow models (BFMs) expediently predict leakage and rotor dynamic force coefficients of grooved seals; however, they lack accuracy for any other geometry besides rectangular. Note scalloped and triangular (serrated) groove seals are not uncommon. In these cases, computational fluid dynamics (CFD) models seals of complex shape to produce leakage and force coefficients. Alas CFD is not yet ready for routine engineer practice. Hence, an intermediate procedure presently takes an accurate two-dimensional (2D) CFD model of a smaller flow region, namely a single groove and adjacent land, to produce stator and rotor surface wall friction factors, expressed as functions of the Reynolds numbers, for integration into an existing BFM and ready prediction of seal leakage and force coefficients. The selected groove-land section is well within the seal length and far away from the effects of the inlet condition. The analysis takes three water lubricated seals with distinct groove shapes: rectangular, scalloped and triangular. Each seal, with length/diameter L/D = 0.4, has 44 grooves of shallow depth dg ∼ clearance Cr, and operates at a rotor speed equal to 5,588 rpm (78 m/s surface speed) and with a pressure drop of 14.9 MPa. The method validity is asserted when 2D (single groove-land) and 3D (whole seal) predictions for pressure and velocity fields are compared against each other. The CFD predictions, 2D and 3D, show the triangular groove seal has the largest leakage, 41% greater than the rectangular groove seal does, albeit producing the smallest cross-coupled stiffnesses and whirl frequency ratio. On the other hand, the triangular groove seal has the largest direct stiffness and damping coefficients. The scalloped groove seal shows similar rotordynamic force coefficients as the rectangular groove seal but leaks 13% more. For the three seal groove types, the modified BFM predicts leakage that is less than 6% away from that delivered by CFD, whereas the seal stiffnesses (both direct and cross-coupled) differ by 13%, the direct damping coefficients by 18%, and the added mass coefficients are within 30%. The procedure introduced extends the applicability of a BFM to predict the dynamic performance of grooved seals with distinctive shapes.
7
Watson, Cori, and Houston G. Wood. "Developing an Optimal Helix Angle As a Function of Pressure for Helical Groove Seals." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69322.
Abstract:
Helical groove seals are non-contacting annular seals used in pumps between impeller stages and at the balance drum. These seals have helically machined grooves on the surface of the rotor and/or stator. They work to sustain a pressure difference given a mass flow rate of the impeller through two flow phenomena which can be characterized by their flow direction. Fluid flowing axially dissipates kinetic energy through turbulent mixing as fluid is pushed through the jet stream region and mixes in the larger groove region, thus producing a pressure differential. Fluid flowing in the groove direction rotates with the rotor wall and is positively displaced toward the high pressure region, essentially acting as a screw pump. Previous work with optimization of helical groove seals has shown that the ideal helix angle of the seal is steeper for lower pressure applications and shallower for higher pressure applications. This is due to lower pressure applications having higher circumferential velocity in the grooves. In high pressure applications, the groove circumferential velocity has even been shown to be negative, and therefore the fluid leaks out the end of the grooves. The objective of this study is to use computational fluid dynamics simulations to find the optimal helix angle of the seal given the pressure differential. To accomplish this goal, simulations were run in ANSYS CFX for various inlet pressures, given zero gauge outlet pressure, and the helix angle of the grooves are varied. The helical grooves seals in this study have grooves on only the stator surface. The number of grooves is varied with the angle to keep the axial cross section of the seal consistent. By doing this, the study is able to focus in on the pumping mechanism of the helical groove seal without substantially changing the energy dissipation. The mass flow rates from each simulation for a given inlet pressure are plotted and quadratic regression was used to calculate an optimal helix angle as a function of inlet pressure. This study also answers the question of whether is there a limit where circumferentially grooved, i.e. labyrinth, seals outperform helical groove seals for very high pressures. Results comparing the powerloss of helical groove seals versus labyrinth seals and the effect of helix angle on powerloss are also given.
8
Fang, Zhi, Zhigang Li, Jun Li, and Zhenping Feng. "Numerical Investigation on the Static and Rotordynamic Characteristics for Two Types of Novel Mixed Helical Groove Seals." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-16303.
Abstract:
Abstract Non-contracting annular seals, such as helical groove seals, are widely used between the impeller stages in the liquid turbomachinery to reduce the fluid leakage and stabilize the rotor-bearing system. However, previous literature has expounded that the helical groove seals possess the poor sealing property at low rotational speed condition and face the rotor instability problem inducing by negative stiffness and damping, which is undesirable for liquid turbomachinery. In this paper, to obtain the high sealing performance and the reliable rotordynamic capability for full operational conditions of the machine, two novel mixed helical groove seals, which possess a hole-pattern/pocket-damper stator matching with a helically-grooved rotor, were designed and assessed for a multiple-stage high-pressure centrifugal liquid pump. In order to assess the static and rotordynamic characteristics of these two types of mixed helical groove seals, a three-dimensional (3D) steady CFD-based method with the multiple reference frame theory was used to predict the seal leakage and drag power loss. Moreover, a proposed 3D transient CFD-based perturbation method, based on the multi-frequency one-dimensional stator whirling model, the multiple reference frame theory and a mesh deformation technique, was utilized for the predictions of seal rotordynamic characteristics. The accuracy of the numerical methods was demonstrated based on the experiment data of leakage and rotordynamic forces coefficients of published helical groove seals and hole-pattern seal. The leakage and rotordynamic forces coefficients of these two mixed helical groove seals were presented at five rotational speeds (0.5 krpm, 2.0 krpm, 4.0 krpm, 6.0 krpm, 8.0 kpm) with large pressure drop of 25MPa, and compared with three types of conventional helical groove seal (helical grooves on rotor, stator or both), and two types of damper seals (hole-pattern seal, pocket damper seal with smooth rotor). Numerical results show that the mixed groove seals possess generally better sealing capacity than the conventional helical groove seals, especially at low rotational speed conditions. The circumferentially-isolated cavities (hole or pocket) on the stator enhance the “pumping effect” of the helical grooves for mixed helical groove seals, what is more, the helical grooves also strengthen the dissipation of kinetic energy in the isolated cavities, thus the mixed helical groove seal offers less leakage. Although the mixed helical groove seals possess a slightly larger drag power loss, it is acceptable in consideration of reduced leakage for the high-power turbomachinery. The present novel mixed helical groove seals have pronounced stability advantages over the conventional helical groove seal, due to the obvious large positive stiffness and increased damping. The mixed helical groove seal with the hole-pattern stator and the helically-grooved rotor (HPS/GR) possesses the lowest leakage and the largest effective damping, especially for the high rotational speeds. From the viewpoint of sealing capacity and rotor stability, the novel mixed groove seals are better seal concepts for liquid turbomachinery.
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Mawet, Dimitri, Pierre Riaud, Charles Hanot, Denis Vandormael, Jérôme Loicq, Jacques Baudrand, Jean Surdej, and Serge Habraken. "The annular groove phase mask coronagraph: an achromatic optical vortex." In Optical Engineering + Applications, edited by Daniel R. Coulter. SPIE, 2007. http://dx.doi.org/10.1117/12.758406.
10
Mawet, Dimitri, Pierre Riaud, Olivier Absil, Jacques Baudrand, and Jean Surdej. "The four quadrant-ZOG and annular groove phase mask coronagraphs." In Optics & Photonics 2005, edited by Daniel R. Coulter. SPIE, 2005. http://dx.doi.org/10.1117/12.640363.
Reports on the topic "Annular groove":
1
Bettin, Scott. Oak Grove Fork Habitat Improvement Project, 1988 Annual Report. Office of Scientific and Technical Information (OSTI), April 1989. http://dx.doi.org/10.2172/901443.
2
Berger, Matthew. Sharp-tailed Grouse Restoration; Colville Tribes Restore Habitat for Sharp-tailed Grouse, Annual Report 2001-2002. Office of Scientific and Technical Information (OSTI), January 2003. http://dx.doi.org/10.2172/963046.
3
Whitney, Richard. Sharp-tailed Grouse Restoration; Colville Tribes Restore Habitat for Sharp-tailed Grouse, Annual Report 2002-2003. Office of Scientific and Technical Information (OSTI), January 2004. http://dx.doi.org/10.2172/963066.
4
Williams, Cameron. Channel Islands National Park: Terrestrial vegetation monitoring annual report - 2020. National Park Service, August 2023. http://dx.doi.org/10.36967/2299696.
Abstract:
This report presents the data collected in 2020 as part of the long-term terrestrial vegetation monitoring program at Channel Islands National Park. The purpose of this monitoring program is to document long-term trends in the park’s vegetation communities. Data are collected from 30-m-long transects using a point-line intercept method. In the past, each transect was sampled annually. However, beginning in 2012 the program began adding randomly located transects to improve the representativeness of the sampling, and transitioned to a rotating panel design. Now only a core subset of the transects are surveyed annually. Non-core transects are assigned to one of four panels, each of which is surveyed once every four years. Coronavirus disease (COVID-19) caused a global pandemic that prevented field data collection from most of the transects scheduled for 2020. As a result, just 29 of the 127 transects scheduled were visited, distributed as follows: Santa Barbara Island (n = 18), Santa Cruz Island (n = 11). The small size of this 2020 dataset offers limited comparisons to previous years. The program also planned to install 19 new transects on Santa Rosa and San Miguel islands to complete the probabilistic component of the study design (Tiszler et al. 2016a), but the safety response to COVID-19 did not permit these installations. Key 2020 results and interpretation: For the transects visited at both islands in 2020, a long-term decline in mean absolute cover, measured as the mean number of taxa intersecting each point along a transect, was apparent. Annual rainfall correlated positively with mean absolute cover of vegetation. Six vegetation communities were visited at Santa Barbara Island compared to nine at Santa Cruz Island, despite the smaller number of transects surveyed at the latter. Mean absolute cover at both islands together averaged 87%, with native plants covering 44% and non-natives covering 39%. Among vegetation communities, mean absolute cover ranged from a high of 137% in a Lyonothamnus grove to a low of 32% in a riparian community where few plants were encountered along one transect. Mean absolute cover was higher at Santa Cruz Island (105%) than Santa Barbara Island (77%), and mean absolute native cover followed the same pattern (57% vs 36%). For both islands combined, mean richness per transect was 11 taxa. Compared to Santa Barbara Island, Santa Cruz Island supported higher overall mean species richness (14 vs 9 taxa) and higher species evenness (0.70 vs 0.55). Santa Cruz Island’s higher absolute cover, higher native species cover, higher species richness, and higher species evenness indicate that its vegetation is in better overall condition compared to Santa Barbara Island, and that the rate of recovery after overgrazing is faster at Santa Cruz Island than Santa Barbara Island.
5
Hailiang, Zhang. PR-469-173823-R02 In-Line Inspection and Evaluation of Pinholes in Oil and Gas Pipelines - Phase II. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), September 2020. http://dx.doi.org/10.55274/r0011780.
Abstract:
Pinhole leaks have been reported as a significant cause of oil and gas pipeline failures in recent years. From 2010 to 2015, at least 131 significant incidents involving oil and gas pipelines in the United States (101 and 30, respectively) were attributed to pinhole leaks. The 9th European Gas Pipeline Incident Data Group Report states that as of 2013, the five-year moving average failure frequency for pinholes was equal to an approximate annual rate of 0.105 failures per 1,000 kilometers of pipeline. Pinholes may result from normal pipeline corrosion during routine operations, such as micro-biologically induced corrosion, or can be created by third-party activities, such as illegal tapping. These small leaks have become a major risk for many pipeline companies. Pinhole leaks are more likely to lead to serious consequences than larger leaks because they are difficult to discover through normal monitoring and patrolling. An undetected pinhole leak can lead to significant soil and groundwater pollution over time. The research objective of this phase is to improve the results based on the research of phase one. The major work of this phase are following. In response to the problems found in the pull test of phase one, a number of defects with different sizes have been designed, including pinhole, pitting and grooves, were added to further subdivide the detection boundary conditions. The NDT verification tool for pinhole defects was compared and selected, and the appropriate ultrasonic scanning system was selected as the NDT method for internal pinhole verification. According to the actual ILI report, two pinholes and three pittings were selected for dig verification, and the results were comprehensively compared and analyzed with the pull test.
6
Chambers, Jeanne C., David A. Pyke, Jeremy D. Maestas, Mike Pellant, Chad S. Boyd, Steven B. Campbell, Shawn Espinosa, Douglas W. Havlina, Kenneth E. Mayer, and Amarina Wuenschel. Using resistance and resilience concepts to reduce impacts of invasive annual grasses and altered fire regimes on the sagebrush ecosystem and greater sage-grouse: A strategic multi-scale approach. Ft. Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 2014. http://dx.doi.org/10.2737/rmrs-gtr-326.
7
Swanson, David. Tree investigations in the Noatak National Preserve, Alaska, 2011?2022: Old-growth and new forests. National Park Service, 2023. http://dx.doi.org/10.36967/2301700.
Abstract:
Tree rings in the Noatak National Preserve provide information about the growth of trees at the cold limit of tree survival in northwestern North America. The present study was based on cores and other tree measurements (tree basal area, height, and number per unit area) of white spruce (Picea glauca) and balsam poplar (Populus balsamifera) trees taken from 39 permanent monitoring plots (34 with coreable trees) at three locations in the Preserve. The tree rings widths were measured and then normalized using a 50-year smoothing spline to remove the effects of growth variations through the life cycles of the trees. Old-growth white spruce forests, which here include numerous trees over 200 years old and some that are more than 300 years old, form open stands on well-drained slopes. Stands of younger trees that became established in the 1900s are present near elevational tree-line, and in small groves on tussock tundra. These younger stands are interpreted primarily as the result of forest expansion due to climate warming, though re-establishment of trees after wildfire is also possible in the tussock tundra. On river floodplains and terraces, stands of both white spruce and balsam poplar were also initiated in the 1900s, but here the youth of the trees is probably due to colonization of new areas exposed by river channel migration. Both the old-growth and younger forests showed continuing growth (as expressed by an increase in stand basal area) between our initial visit in 2011 and re-visit in 2021 or 2022, with the greatest increases occurring on floodplains. Tree rings showed much year-to-year variation in width, but the effect of individual cold summers was surprisingly weak. Some of the major global climate perturbations due to volcanic eruptions were visible in the tree ring record, but the resulting ring growth was generally no worse than other bad growth years within a few decades of the volcanic event. Tree ring width was statistically correlated more closely with the average warmth of several preceding growing seasons (as expressed by the annual sum of thaw degree-days) than with the current year?s or the previous year?s warmth alone. This is probably due to the cumulative effect of several years? warmth (or cold) on the conditions in the tree rooting zone, on the amount of foliage available for photosynthesis, and the level of stored reserves in the tree.
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Sagebrush Biome, a framework for conservation action, 2021-2025. Washington, D.C.: Working Lands for Wildlife, Natural Resources Conservation Service, U.S. Department of Agriculture, 2021. http://dx.doi.org/10.32747/2021.8078216.nrcs.
Abstract:
The sagebrush biome is the largest habitat type in North America, spanning 175 million acres in 13 western states. The USDA Natural Resources Conservation Service’s (NRCS) Working Lands for Wildlife (WLFW) team developed a science-based framework to provide the common vision and coordination necessary to address resource concerns and ecosystem threats across boundaries in the sagebrush biome. The framework helps guide and target Farm Bill conservation actions spanning multiple states and focal species from 2021-25. Threats addressed by this framework include: 1) Exotic annual grass invasion; 2) Land use conversion (cropland conversion/subdivision); 3) Woodland expansion (conifer); 4) Riparian and wet meadow degradation. The framework uses a core area approach to build on past conservation efforts in addressing threats impacting sagebrush rangelands accomplished through the Sage Grouse Initiative. A combination of conservation practices, easements, and proper livestock grazing management are used to conserve and restore the landscape. This WLFW Sagebrush Biome framework for western rangeland shares the vision of achieving "Wildlife Conservation Through Sustainable Ranching," to benefit people, wildlife, and rural communities.