To see the other types of publications on this topic, follow the link: Leaf seal.
Journal articles on the topic 'Leaf seal'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Leaf seal.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Jahn, Ingo HJ. "Design approach for maximising contacting filament seal performance retention." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 5 (June 27, 2014): 926–42. http://dx.doi.org/10.1177/0954406214541433.
Full textAbstract:
Good sealing is a key requirement for modern efficient turbomachinery such as steam and gas turbines. A class of seals that promise better performance, compared to conventional labyrinth seals, are contacting filament seals such as brush, leaf, or finger seal. When new, these filament seals offer better performance; however, if poorly designed they wear excessively, resulting in leakages higher than a comparable labyrinth seal. This paper outlines a design methodology for selecting ideal contacting filament seal properties for a given operating cycle or set of operating cycles. Following this approach ensures the seal performs well, the seal retains its performance, and performance is retained if the operating cycle is altered. In the approach, the seals are described by four generic properties (stiffness, blow-down, cross-coupling, and build clearance), which are then used for a performance evaluation based on a number of test cycles. Once the ideal seal properties for a given operating cycle have been identified, a seal to match these can be designed. The approach is evaluated with a generic gas turbine cycle and recommendations for ideal contacting filament seal properties for this cycle are made.
2
ZHANG, Hongtao. "Comparative Analysis of Seal Structure and Aerodynamic Characteristics of Labyrinth and Leaf Seals." Journal of Mechanical Engineering 48, no. 22 (2012): 148. http://dx.doi.org/10.3901/jme.2012.22.148.
Full text
3
Fei, Yuan. "Analysis of the structure of door bottom drop sealing device." E3S Web of Conferences 236 (2021): 02027. http://dx.doi.org/10.1051/e3sconf/202123602027.
Full textAbstract:
-Drop Seals Is A Kind Of Hardware That Can Solve The Tightness Of The Door Bottom. This article will briefly introduce the common structural features of this hardware and analyze its impact on the sound insulation of the door leaf according to the experiment. Based on the comparative analysis of 5 sets of data, the experiment proved the effectiveness of the drop seals for the door bottom seal.
4
Langston, Lee S. "PALS - An Auspicious New Gas Turbine Seal." Mechanical Engineering 138, no. 03 (March 1, 2016): 54–55. http://dx.doi.org/10.1115/1.2016-mar-5.
Full textAbstract:
This article highlights various aspects of a new gas turbine shaft seal called the pressure activated leaf seal (PALS). The paper in detail discusses the architecture and working of a gas turbine seal. PALS is designed to use changing pressure drop forces across the seal to eliminate rub. The seal elements stay clear of the rotor seal surface during start-up and shutdown transients, and subsequently close to a small, non-contacting, steady-state running clearance. During start-up or shutdown, when the axial pressure difference across PALS is small, the leaves are in a relaxed open position, providing a general clearance gap for possible rotor seal surface eccentricities. At operating speeds, the resulting axial pressure difference causes the leaf element to elastically deflect and close, reaching the design clearance when they contact the support member. The test results show that the PALS concept provides for a potentially viable, robust, low leakage seal for gas turbine applications.
5
ZHANG, Hongtao. "Simulation Investigation on Application of Leaf Seal in Turbine Stage." Journal of Mechanical Engineering 50, no. 12 (2014): 177. http://dx.doi.org/10.3901/jme.2014.12.177.
Full text
6
Milovanovic, Bebina, and Angelina Raickovic-Savic. "Seal boxes from the Viminacium site." Starinar, no. 63 (2013): 219–36. http://dx.doi.org/10.2298/sta1363219m.
Full textAbstract:
Bronze seal boxes that had the function of holding the wax seal on the Viminacium site - Upper Moesia (Stari Kostolac, Serbia), mainly from the area of the necropolis (ten were found in the graves and ten at the cemetery between the graves). Six are from buildings that had a storage function, five are from public facilities - an amphitheatre, and only one find is from the military fort of the legion VII Claudia, which was stationed in Viminacium in the second half of the 1st century. Thirty-two seal boxes have been processed: nine whole, six with fragmented upper and lower parts, seven bases and ten covers. Seal boxes consist of two parts: the cover and the base. The cover is decorated with figural images, concentric rings and especially with applied ornaments. Some of the motifs are filled with enamel. The base always has three to five circular perforations at the bottom, the side walls are a height of 4 to 5 mm with two opposed notches or slots which are thought to have facilitated the tying of the seal box to a package or a document. The lock mechanism is operated using the hinges principle. Some specimens have a circular extension on the cover with a thorn on the bottom. This fits the hollow in the base, through which passes a thorn for the additional fixing of the cover. Based on shape and decoration, seal boxes were classified into five types: I - elliptical or oval shaped with a figural representation on the cover derived in relief; II/1 - leaf or heart-shaped with a special, riveted ornament; II/2 - leaf or heart-shaped with enamel on the cover; III/1 - circular showing a form in relief; III/2 - circular with cast concentric rings, with no enamel; III/3 - circular with concentric rings with enamel on the cover; IV - diamond shaped with enamel on the cover and V - square with enamel on the cover. The seal boxes dominate chronologically from the first half of the 2nd and throughout the 3rd century.
7
Dlhý, Dušan, and Katarína Minarovičová. "Door Bottom Joint Design and its Influence on Sound Transmission of the Door." Advanced Materials Research 899 (February 2014): 487–90. http://dx.doi.org/10.4028/www.scientific.net/amr.899.487.
Full textAbstract:
The higher the acoustical quality of the door leaf the greater the influence of the bottom gap on the resultant sound insulation of the door. If the design of the door bottom joint and the seal is not correct, any construction of the door leaf in order to increase sound insulation can be ineffective. The greatest influence on sound transmission of the door has the gap with the greatest width a door bottom joint. Modern ways of the sealing of the doorsill gap are able to provide required sound insulation of the door.
8
Floden, Aaron Jennings. "A new Solomon’s Seal (Polygonatum: Asparagaceae) from northern Thailand." Phytotaxa 236, no. 3 (December 1, 2015): 279. http://dx.doi.org/10.11646/phytotaxa.236.3.9.
Full textAbstract:
Polygonatum Miller (1754, without pagination) (Asparagaceae) is a relatively large genus containing approximately 60 taxa (Chen & Tamura 2000). The majority of species are eastern Asian (Jeffrey 1980, Chen & Tamura 2000). Phyllotaxy, cytology, and filament morphology have been recognized as important in delimiting species (Suomalainen 1947, Tamura 1990, 1991, 1993). Specimens of an anomalous Polygonatum collected by J.F. Maxwell from northern Thailand, Doi Inthanon have a general affinity to P. punctatum Royle ex Kunth (1850: 142) and have been reported as that species (Tamura 1993, Maxwell 1998), but differ in their emaculate white and longitudinally ridged perigone. Cultivated material from the same locality (BSWJ6599, Figs. 1–2) provides clear observation of the differences that are not as apparent on pressed specimens. It differs in several morphological features from P. punctatum: stem characters; phyllotaxy; leaf shape; inflorescence type and position; perigone color; and filament size, orientation, and morphology. The combined morphological differences and non-contiguous distributions of P. costatum in comparison to P. punctatum support its recognition as a new species, thus far documented only from the highest elevation in northern Thailand.
9
Santana, José Raniere Ferreira de, Renato Paiva, Ana Valéria de Souza, and Lenaldo Muniz de Oliveira. "Effect of different culture tube caps and concentrations of activated charcoal and sucrose on in vitro growth and budding induction of Annona glabra L." Ciência e Agrotecnologia 35, no. 5 (October 2011): 916–23. http://dx.doi.org/10.1590/s1413-70542011000500008.
Full textAbstract:
The present work evaluated the effects of different types of culture flask seals and varying concentrations of sucrose and activated charcoal on the in vitro induction and growth of buds of Annona glabra L.; an edible fruit-producing species popularly known as "araticum". Nodal segments obtained from A. glabra plants maintained in green houses were surface sterilized and inoculated into a WPM culture medium solidified with 7 g L-1 of agar and supplemented with sucrose (0.00; 29.21; 58.63 and 116.84 mM), activated charcoal (0.0 and 2.0 g L-1), and 250 mg L-1 benomyl. In addition to the varying concentrations of sucrose and activated charcoal, we evaluated the efficiency of two types of test tube seals: PVC film, and cotton plugs. All possible combinations of caps and nutrient media were tested with 4 repetitions with 5 tubes each, evaluating the number of buds, the percentage of explant responses, the number of expanded leaves per bud, the length of the largest leaves, leaf abscission, and the length and dry weight of the buds. The type of seal influenced organogenesis in nodal segments of A. glabra, and no bud induction was observed in the absence of sucrose. The largest number of expanded leaves were obtained when 58.42 mM of sucrose was used in tubes sealed with cotton plugs, and leaf abscission was halved in the presence of activated charcoal. The greatest bud length and dry weight were obtained in tubes sealed with cotton plugs and in the presence of activated charcoal.
10
Hüberli, D., K. L. Ivors, A. Smith, J. G. Tse, and M. Garbelotto. "First Report of Foliar Infection of Maianthemum racemosum by Phytophthora ramorum." Plant Disease 89, no. 2 (February 2005): 204. http://dx.doi.org/10.1094/pd-89-0204c.
Full textAbstract:
In May 2003, Phytophthora ramorum S. Werres & A.W.A.M. de Cock was isolated from the leaf tips of a single plant of false Solomon's seal (Maianthemum racemosum (L.) Link, formely known as Smilacina racemosa (L.) Desf.), a native, herbaceous perennial of the Liliaceae family, at the Jack London State Park in Sonoma County, California. Affected leaves had cream-to-brown lesions on the tips that were delimited by a yellow chlorotic zone. Lesions on the stems were not observed. The isolate (American Type Culture Collection [ATCC], Manassas, VA, MYA-3280; Centraal Bureau voor Schimmelcultures, Baarn, the Netherlands, CBS 114391) was typical of P. ramorum with large chlamydospores and caduceus, semipapillate sporangia, and the sequence (GenBank Accession No. AY526570) of the internal transcribed spacer region of the rDNA matched those published previously (4). The site, from which wood rose (Rosa gymnocarpa) was recently identified as a host, is a mixed forest containing confirmed P. ramorum-infected coast redwood (Sequoia sempervirens), California bay laurel (Umbellularia californica), and tanoak (Lithocarpus densiflora) trees (2,3). Two leaves per asymptomatic, pesticide free, potted plant of false Solomon's seal were inoculated with zoospores of the P. ramorum isolate obtained from infected false Solomon's seal (1). Five plants were inoculated in trial 1, and the following day, three plants were inoculated in trial 2. A control leaf of each plant was dipped in sterile deionized water. Plants were enclosed in plastic bags, misted regularly with sterile distilled water, and maintained at 16 to 21°C in the greenhouse. In both trials, plants did not have lesions on the leaves after 16 days and were reinoculated on separate days for each trial with higher concentrations of zoospores (1 × 105 [trial 1] and 2 × 105 [trial 2] zoospores/ml). Cream-colored lesions, similar to those observed in the field, were evident 1 week after the second inoculation and stopped progressing in both trials by 17 days. Lesions starting from the leaf tips averaged 13 mm (range 8 to 24 mm) long, and P. ramorum was reisolated on Phytophthora-selective agar medium modified with 25 mg of pentachloronitrobenzene from 44% (trial 1) and 83% (trial 2) of all lesions (4). Control leaves had no lesions, and P. ramorum was not reisolated. Sporangia were not observed on any leaves when examined with the dissecting microscope. The fact that lesions developed only after a second inoculation with higher concentrations of zoospores, and these lesions stopped progressing after 17 days, suggests that false Solomon's seal is much less susceptible than other hosts such as western starflower (Trientalis latifolia) (1) and wood rose (2). To our knowledge, this is the first report of a plant from the Liliaceae as a natural host for P. ramorum, although Smilax aspersa was identified as being susceptible in artificial inoculations of detached leaves (E. Moralejo and L. Hernández, personal communication). False Solomon's seal is popular in the horticultural industry. References: (1) D. Hüberli et al. Plant Dis. 87:599, 2003. (2) D. Hüberli et al. Plant Dis. 88:430, 2004. (3) P. E. Maloney et al. Plant Dis. 86:1274, 2002. (4) D. M. Rizzo et al. Plant Dis. 86:205, 2002.
11
Musin, A. "Small lead seals from Drochiczyn and small lead seals of “Drochiczyn type”: new light on the research on medieval “seal tags” in East-Central Europe." Archaeological News 31 (2021): 290–318. http://dx.doi.org/10.31600/1817-6976-2021-31-290-318.
Full textAbstract:
The article argues the commercial and fiscal nature of medieval small lead seals. For the first time, seal tags of the Piast dynasty are attested. Their symbols correlated with Polish Hohlpfennigs. The concentration of Rus’ and Polish seals on the border may indicate its dual jurisdiction. The practice of European small lead seals is regarded as transfers of the Byzantine tradition.
12
Gao, Xun, Ling Su, Guiquan Jiang, Jiuyin Pang, and Lin Lin. "Dimensional stability of lotus leaf-like nanostructure superhydrophobic bamboo by modification using xylan." BioResources 15, no. 2 (March 26, 2020): 3443–57. http://dx.doi.org/10.15376/biores.15.2.3443-3457.
Full textAbstract:
Xylan extracted from corncobs was used to modify bamboo and to improve its dimensional stability. A lotus leaf-like surface was prepared on the modified bamboo using a fresh lotus leaf and polydimethylsiloxane (PDMS) as the template and seal via soft lithography. The dimensional stability of bamboo was tested via anti-shrinkage efficiency (ASE), moisture excluding efficiency (MEE), weight percent gain (WPG), and its superhydrophobic property. The microstructures of lotus-like bamboo surface were analyzed via water contact angle (WCA), scanning electron microscopy, and atomic force microscopy (AFM). The study found that with increasing mass fraction of xylan content, the anti-swelling property and WPG of modified bamboo increased accordingly. When the mass fraction of xylan was 10%, its WPG was the largest (2.21%), and xylan had a better compatibilization effect on bamboo. The dimensional stability of bamboo was improved to a certain extent by xylan. Moreover, the anisotropy and superhydrophobicity of the lotus leaf-like bamboo treated by xylan were noticeably improved after modification, such that the WCA of the transverse, radial, and tangential sections were 157.5º, 145.5º, and 137.5º, respectively. This research lays a foundation for studies of dimensional stability of bamboo and the mechanism of modification to achieve hydrophobic properties.
13
Zailani, Muhammad, Retno Astuti Kuswardani, and Ellen L. Panggabean. "Growth Response and Crop Production (Brassica Juncea L.) Against Watering Time Interval at Various Hydroponics Media." Budapest International Research in Exact Sciences (BirEx) Journal 1, no. 1 (January 9, 2019): 9–22. http://dx.doi.org/10.33258/birex.v1i1.131.
Full textAbstract:
This study aims to determine the Response Growth and Production of Crops (Brassica juncea L.) Against Watering Time Interval In Various Hydroponics Media. The research was conducted at the experimental gardens of Faculty of Agriculture, Faculty of Agriculture, University of Medan Area, located on No. Pond Street. 1 Medan Estate. This research was conducted from October 2013 until December 2013. The design used was RAL Factorial, with 2 replications, 10 combinations. The first factor of the hydroponic planting medium is: M1: Frying Roots, M2: Coconut Coir Powder, M3: Fryer Seal, M4: Rokwool, and M5: Sawdust, the second factor is the time interval: I1: 3 hours a day I2: 5 hours a day, starting from 08:00 a.m to 06:00 p.m. The result of this research indicates that the treatment of watering liquid fertilizer with different time interval does not show a real effect on the growth of mustard plants, Media treatment used on hydroponic systems have an influence very evident on the parameters of plant height, leaf number, leaf area, production weight and significant effect on leaf level parameters, influential planting medium and have the best number is M3 (fuel husk). Interaction interval of watering time on various hydroponic media did not have a significant effect on observed parameters, namely: plant height, leaf number, wet weight, and weight of production, while the leaf color parameter had significant effect on leaf width.
14
Childs, D., and F. Garcia. "Test Results for Sawtooth-Pattern Damper Seals: Leakage and Rotordynamic Coefficients." Journal of Tribology 109, no. 1 (January 1, 1987): 124–28. http://dx.doi.org/10.1115/1.3261303.
Full textAbstract:
Test results consisting of direct and transverse force coefficients are presented for eleven, sawtooth-pattern, damper-seal configurations. The designation “damper” seal refers to a seal which uses a deliberately roughened stator and smooth rotor, as suggested by von Pragenau [1], to increase the net seal damping force. The designation “sawtooth-pattern” refers to a stator-roughness pattern whose cross section normal to the axis of the seal resembles saw teeth with the teeth direction opposing fluid motion in the direction of shaft rotation. The sawtooth pattern yields axial grooves in the stator which are interrupted by spacer elements which act as flow constrictions or “dams.” Sawtooth-pattern seals had more damping than smooth seals but less than the round-hole-pattern seals tested previously. Stiffness of sawtooth and round-hole-pattern seals were comparable. Leakage of maximum-damping configurations was greater for sawtooth-pattern than for round-hole-pattern seals; both types of seals leaked substantially less than did smooth seals. If damping is sacrificed, sawtooth-pattern seals can be designed to leak less than round-hole-pattern seals.
15
Laos, Hector E., John M. Vance, and Steven E. Buchanan. "Hybrid Brush Pocket Damper Seals for Turbomachinery." Journal of Engineering for Gas Turbines and Power 122, no. 2 (January 3, 2000): 330–36. http://dx.doi.org/10.1115/1.483211.
Full textAbstract:
Pocket damper seals perform a dual function: both sealing the pressurized gas around a rotating shaft and providing large amounts of vibration damping. The annular cavity between the labyrinth seal teeth is subdivided into separate annular cavities around the circumference of the rotor by partitioning walls. Also, the upstream and downstream teeth have different radial clearances to the rotor. These seals have been shown to provide a remarkable amount of direct damping to attenuate vibration in turbomachinery, but they generally leak more than conventional labyrinth seals if both seals have the same minimum clearance. Conversely, brush seals allow less than half the leakage of labyrinth seals, but published test results show no significant amount of damping. They are considered to be a primary choice for the seals in new aircraft engine designs because of their low leakage. This paper will describe a recently invented hybrid brush/pocket damper seal that combines high damping with low leakage. Previous brush seal results were studied and calculations were made to select a brush seal to combine with the pocket damper design. The result is a hybrid seal with high damping and low leakage. A special design feature can also allow active vibration control as a bonus benefit. A computer code written for the original pocket damper seal was modified to include the brush element at the exit blade. Results from the computer code indicate that the hybrid seal can have less leakage than a six bladed (or 6 knives) labyrinth seal along with orders of magnitude more damping. Experimental evaluations of the damping and leakage performance of the hybrid seal are being conducted by the authors. The experimental work reported here tested the damping capability of the new hybrid brush seal by exciting the seal journal through an impedance head. A conventional six-bladed labyrinth seal of the same working dimensions was also tested. The brush hybrid pocket damper seal is found to leak less than the labyrinth seal while producing two to three times more damping than the original pocket damper seal (orders of magnitude more than the conventional labyrinth). [S0742-4795(00)01102-9]
16
Lee, Jae Chun, Sung Park, Jun Suh Yu, Jong Ho Lee, Joo Sun Kim, and Hae Won Lee. "Sealing Behavior of Visco-Elastic Composite Seals for SOFC Applications." Key Engineering Materials 317-318 (August 2006): 921–0. http://dx.doi.org/10.4028/www.scientific.net/kem.317-318.921.
Full textAbstract:
Porous composites containing ceramic fiber have been developed for the fabrication of SOFC seals. They were fabricated using glass powder and alumino-silicate chopped fibers. Effect of mixing ratios of ceramic fiber and glass on the leak rates and strength of the composite seals was investigated. In addition, seal performance of commercial glasses was compared with that of SiO2-BaO-B2O3 glass synthesized in this work. The leak rate of the composite seals containing 55 vol% glass was seven times higher than the one containing 75 vol% glass. The flexural strength of the composite seals was reduced to one fourth of the initial value as the porosity increased from 1 to 29%. The incorporation of alumino-silicate chopped fibers into a sealing glass degraded room temperature strength and increased leak rates due to increase in porosity with increasing fiber content. The viscosity of glass at the seal test temperature is presumed to affect the leak rate of the glass seal.
17
Chou, Yeong-Shyung, and Jeffry W. Stevenson. "Novel silver/mica multilayer compressive seals for solid-oxide fuel cells: The effect of thermal cycling and material degradation on leak behavior." Journal of Materials Research 18, no. 9 (September 2003): 2243–50. http://dx.doi.org/10.1557/jmr.2003.0313.
Full textAbstract:
A novel Ag/mica compressive seal was thermally cycled between 100 °C and 800 °C in air to evaluate its stability. The novel Ag/mica compressive seal was composed of a naturally cleaved Muscovite mica sheet and two thin silver layers, and was reported in a previous study to have very low leak rates at 800 °C. In the present study, we examined the thermal cycle stability of the Ag/mica-based compressive seals pressed between mating couples with large and small mismatch in thermal expansion. For comparison, thermal cycling also was conducted on plain mica as well as plain silver only. In addition, the results were compared with published data of a similar mica seal using glass instead of Ag as the interlayers. For mating materials of large mismatch in thermal expansion coefficient (CTE; Inconel/alumina), the Ag/mica seal showed lower leak rates than the plain mica. For mating materials of small mismatch in CTE (SS430/alumina), the leak rates were similar for both the Ag/mica and the plain mica seal. Scanning electron microscopy was used to characterize the microstructure of the mica after thermal cycling. Microcracks, fragmentation, and wear-particle formation were observed on the mica and were correlated to the leak behavior. Overall, the novel Ag/mica seals present good thermal cycle stability for solid-oxide fuel cells, although the leak rates were greater than the corresponding mica seals with glass interlayers.
18
Gu, Li Zhi, and Z. Zhang. "A Biomimetic Approach to the Design of the Composite Bottle Cap and Deformation Analyses." Journal of Biomimetics, Biomaterials and Tissue Engineering 2 (May 2009): 59–72. http://dx.doi.org/10.4028/www.scientific.net/jbbte.2.59.
Full textAbstract:
On the combination analog of the mussel ripple and leaf embrace, designed a new composite bottle cap consisting of the outer body, the inner lining washer, and the resin embrace, for multi-function, especially for better seal and ready open. According to the structural feature and the functional requirements of the cap, two fundamental components, the lining washer and the outer body, were abstracted into a plate and a cylinder with thin wall, respectively. Under the pressing force the elastic and plastic deformations of both were studied with Tresca’s yielding rule and the limitation of the plastic deformation was presented when the two components were assembled into a unit. For the production of this kind of bottle cap, the maximum value of the allowance press and the maximum pressing velocity were also provided.
19
Mathieu, Barry, and Abhijit Dasgupta. "A Fractional-Factorial Numerical Technique for Stress Analysis of Glass-To-Metal Lead Seals." Journal of Electronic Packaging 116, no. 2 (June 1, 1994): 98–104. http://dx.doi.org/10.1115/1.2905512.
Full textAbstract:
Fracture of glass seals in metallic hermetic electronic packaging is a significant failure mode because it may lead to moisture ingress and also to loss of load carrying capacity of the glass seal. Seal glasses are intrinsically brittle and their fracture is governed by the stresses generated. This study investigates stresses in lead seals caused by handling, testing, mechanical vibration, and thermal excursions. Loads considered are axial tension, bending, and twisting of the lead. More general loading can be handled by superposition of these results. Factorial techniques, commonly used in multi-variable Design of Experiments (DoE), are used in conjunction with finite element parametric simulations, to formulate closed-form regression models which relate the maximum principal stress within the glass seal to the type of loading and geometry. The accuracy of the proposed closed-form equations are verified through analysis of residuals. The analysis reveals the sensitivity of the magnitude of the seal stress to design variables such as the materials and geometry of the seal, lead, and package. Manufacturing-induced problems such as defects and flaws are not considered. An additional purpose for presenting this study is to illustrate the use of design of experiment methods for developing closed-form models and design guidelines from simulation studies, in a multi-variable problem.
20
Yoshimoto, S., Y. Yoshida, and K. Yagi. "The Seal System in Aerostatic Journal Bearings for High Vacuum Chambers." Journal of Tribology 126, no. 2 (April 1, 2004): 310–15. http://dx.doi.org/10.1115/1.1611498.
Full textAbstract:
This paper investigates the performance of a seal system for an aerostatic journal bearing used in a high vacuum chamber. The seal system consists of axially spaced viscous seals and annular exhaust grooves that are located between the viscous seals. Each exhaust groove is coupled to a separate vacuum pump in order to achieve a vacuum chamber pressure of less than 10−3 Pa. The vacuum chamber pressure is affected by design parameters such as the number of viscous seal stages, seal length, seal gap, and exhaust tube conductance. The influence of these design parameters on the pressure distribution across seal regions and the vacuum chamber pressure are discussed theoretically. It is subsequently shown that an aerostatic journal bearing with three-stage seal system installed can obtain a reduction in the vacuum chamber pressure almost to the ultimate pressure of a vacuum pump, providing there is no leak or outgassing from materials.
21
Gransberg, Douglas D. "Chip Seal Program Excellence in the United States." Transportation Research Record: Journal of the Transportation Research Board 1933, no. 1 (January 2005): 72–82. http://dx.doi.org/10.1177/0361198105193300109.
Full textAbstract:
A survey of U.S. public highway and road agencies that use chip seals as a part of their roadway maintenance program was developed and conducted to identify best practices in chip seal design and construction. A total of 72 individual responses from 42 U.S. states and 12 U.S. cities and counties were received; of those, nine respondents reported that they were getting excellent results from their chip seal programs. Those responses were grouped together and analyzed by the case study method to identify trends that lead to consistently excellent chip seal results. The study found that the successful chip seal programs had much in common. They use chip seals as a preventive maintenance tool, applying them to roads before distress levels were classified as moderate. They require their contractors to use the latest technology, and they exploit advances in material science such as the use of modified binders. And most of them use chip seals on both high- and low-volume roads.
22
Castellini, M. A., and D. P. Costa. "Relationships between plasma ketones and fasting duration in neonatal elephant seals." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 259, no. 5 (November 1, 1990): R1086—R1089. http://dx.doi.org/10.1152/ajpregu.1990.259.5.r1086.
Full textAbstract:
Long-duration fasting in mammals can ultimately lead to stage three terminal starvation, which is characterized by depleted fat stores, a metabolic shift away from fat metabolism toward lean tissue catabolism, and a sharp decline in circulating levels of plasma fatty acids and ketone bodies. However, this biochemical shift has never been observed outside of the laboratory in a naturally fasting, nonhibernating mammal. In the current study, plasma levels of the ketone body D-beta-hydroxybutyrate (beta-HBA) were assayed in 10 Northern elephant seal pups during suckling and the postweaning fast and in 12 fasting adult seals. Plasma beta-HBA concentration in the pups was minimal during suckling (0.09 +/- 0.06 mM; n = 10) and began to increase immediately after weaning. The concentration rose until about 55 days into the fast (1.34 +/- 0.36 mM; n = 10) and then declined sharply. Within 10 days of this deflection point, the seal pups left for sea. By contrast, adult elephant seals showed consistently low levels of beta-HBA after several months of fasting (0.06 +/- 0.07 mM; n = 12). The data suggest that the duration of fasting in elephant seal pups may be determined, in part, by biochemical shifts that occur near the end of the fast and that the regulation of ketone concentration is different in fasting neonatal and adult elephant seals.
23
YU, YUNDAN, HONGLIANG GE, GUOYING WEI, LI JIANG, and DONG ZHANG. "2024 ALUMINUM OXIDE FILMS PREPARED BY THE INNOVATIVE AND ENVIRONMENT-FRIENDLY OXIDATION TECHNOLOGY." Surface Review and Letters 27, no. 12 (August 26, 2020): 2050020. http://dx.doi.org/10.1142/s0218625x20500201.
Full textAbstract:
A kind of environment-friendly anodic oxidation technology was used to oxidize 2024 aluminum alloys from mixed acid solutions to effectively improve the anticorrosion and mechanical performances. The influences of anode oxidation method on surface morphology, microstructure, composition, electrochemistry parameter, anticorrosion property were studied. Aluminum alloy oxidation is actually a dynamic equilibrium process of the formation and dissolution of oxide film which is composed of porous and non-porous layer. With the treatment of anodic oxidation, [Formula: see text]-Al2O3 and [Formula: see text]-Al2O3 structures were obtained on the surface of aluminum alloys, which contributed directly to the increase of anticorrosion performance. The potassium dichromate solution was used to seal the surface of oxide films to further improve the anticorrosion property. The oxide films sealed with potassium dichromate were covered with leaf-like structures resulting in larger corrosion resistance that attributed directly to the decrease of corrosion current.
24
Kömmling, Anja, Matthias Jaunich, Payam Pourmand, Dietmar Wolff, and Mikael Hedenqvist. "Analysis of O-Ring Seal Failure under Static Conditions and Determination of End-of-Lifetime Criterion." Polymers 11, no. 8 (July 29, 2019): 1251. http://dx.doi.org/10.3390/polym11081251.
Full textAbstract:
Determining a suitable and reliable end-of-lifetime criterion for O-ring seals is an important issue for long-term seal applications. Therefore, seal failure of ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) O-rings aged in the compressed state at 125 °C and at 150 °C for up to 1.5 years was analyzed and investigated under static conditions, using both non-lubricated and lubricated seals. Changes of the material properties were analyzed with dynamic-mechanical analysis and permeability experiments. Indenter modulus measurements were used to investigate DLO effects. It became clear that O-rings can remain leak-tight under static conditions even when material properties have already degraded considerably, especially when adhesion effects are encountered. As a feasible and reliable end-of-lifetime criterion for O-ring seals under static conditions should include a safety margin for slight dimensional changes, a modified leakage test involving a small and rapid partial decompression of the seal was introduced that enabled determining a more realistic but still conservative end-of-lifetime criterion for an EPDM seal.
25
Rhode, D. L., and R. I. Hibbs. "Clearance Effects on Corresponding Annular and Labyrinth Seal Flow Leakage Characteristics." Journal of Tribology 115, no. 4 (October 1, 1993): 699–704. http://dx.doi.org/10.1115/1.2921696.
Full textAbstract:
A previous Navier-Stokes finite difference computer code is extended in order to compute seal leakage directly from given upstream and downstream reservoir pressures. The numerical results are in excellent agreement with previous measurements, the discrepancy being less than eight percent. Annular seals are found to leak approximately twenty percent more than corresponding labyrinths over the entire range of realistic clearance. A rather unexpected finding is that a dramatic increase of swirl velocity occurs near the discharge of small-clearance annular seals, which does not arise in corresponding labyrinth seals. The results, which are used to explain this finding, show that a large density drop occurs near the small-clearance annular seal exit, which provides the swirl velocity increase in accordance with angular momentum conservation.
26
Mikkelsen, Bjarni. "A note on the harbour seal (Phoca vitulina) in the Faroe Islands." NAMMCO Scientific Publications 8 (September 1, 2010): 143. http://dx.doi.org/10.7557/3.2681.
Full textAbstract:
The harbour seal was exterminated as a breeding species in the Faroe Islands in the mid-19th Century. Historical sources document that the harbour seal used to be a common inhabitant of the sheltered fjords where breeding occurred. It was reported to be more common than the grey seal, the other pinniped specie resident around the Faroes. But the number of harbour seals seemingly decreased as human settlements and other anthropogenic activities increased. Seal hunting was apparently already introduced by the Norse that arrived on the islands in the 7th century, a hunt that finally lead to the extermination of the harbour seal. For the last 40 years the harbour seal has only been positively identified twice in the Faroe Islands, in 2001 and 2005.
27
Laflı, Ergün, and Werner Seibt. "Seven Byzantine lead seals from the museum of Ödemiş in western Anatolia." Byzantine and Modern Greek Studies 44, no. 1 (February 19, 2020): 21–39. http://dx.doi.org/10.1017/byz.2019.22.
Full textAbstract:
This short essay presents seven Byzantine lead seals, all of which originate from the local museum in Ödemiş in the province of Izmir in western Turkey. Almost all of them came as acquisition to Ödemiş by local antique dealers. All the pieces have been treated and interpreted here sigillographically for the first time. This small collection of seals is important regarding the administration of the theme of Thrakesion, especially about the offices of the seal owners, and the society of Cayster valley during the Byzantine period.
28
He, Wentao, Shaoping Wang, Chao Zhang, Xi Wang, and Di Liu. "Lubrication and Wear Characteristics of Mechanical Face Seals under Random Vibration Loading." Materials 13, no. 6 (March 12, 2020): 1285. http://dx.doi.org/10.3390/ma13061285.
Full textAbstract:
The service life of mechanical face seals is related to the lubrication and wear characteristics. The stable analytical methods are commonly used, but they cannot address effects of random vibration loading, which, according to experimental studies, are important factors for lubrication and wear of mechanical face seals used in air and space vehicles. Hence, a dynamic model for mechanical face seals is proposed, with a focus on the effects of random vibration loading. The mechanical face seal in the axial direction is described as a mass-spring-damping system. Spectrum analysis specified for random vibration is then performed numerically to obtain the response power spectral density (PSD) of the mechanical face seal and calculate the root mean square (RMS) values under random vibration conditions. A lumped parameter model is then developed to examine how dynamic parameters such as stiffness and damping affect the lubrication regimes of mechanical face seals. Based on the dynamic model and Archard wear equation, a numerical wear simulation method is proposed. The results elucidated that the increase of input acceleration PSDs, the decrease of axial damping, and the increase of axial stiffness lead to the probability of the mechanical face seal operating under full film lubrication regime increase and finally the decrease of wear. This research provides a guideline for improving the adaptability of mechanical face seals under random vibration environments.
29
Guo, An Nan, Xiao Jing Wang, Shen Gang, and Deng Feng Jiang. "Numerical Analysis of Annular Seal with Different Distribution of Surface Texture." Key Engineering Materials 642 (April 2015): 66–71. http://dx.doi.org/10.4028/www.scientific.net/kem.642.66.
Full textAbstract:
Surface texturing has been shown to reduce friction and increase the film thickness in various tribological applications (hydrodynamic bearings, mechanical seals, and cylinder-liner contacts). Studies have reported that surface-texture can reduce the resistance of sliding friction pair, increase the oil film thickness, increase the bearing’s capacity. Surface texture structure’s design and layout are very important, unfavorable design may lead to be counterproductive. In this paper, in combination with the 650mm seal structure, we are using the main design of groove type to seal the inner surface texture, so as to study the geometry structure and distribution's influence on seal property.
30
LeSage, Laurent. "THE EGGS AND LARVAE OF PACHYBRACHIS PECCANS AND P. BIVITTATUS, WITH A KEY TO THE KNOWN IMMATURE STAGES OF THE NEARCTIC GENERA OF CRYPTOCEPHALINAE (COLEOPTERA: CHRYSOMELIDAE)." Canadian Entomologist 117, no. 2 (February 1985): 203–20. http://dx.doi.org/10.4039/ent117203-2.
Full textAbstract:
AbstractThe egg and larval instars of Pachybrachis peccans Suffrian and P. bivittatus Say are described and illustrated. Adults of both species appear in late May, feed on willow leaves, mate and oviposit in June–July. The larvae, unable to climb the host plants, feed in the leaf litter of dead leaves of willow; they reach the second-last or last instar by the end of the fall; then they seal their case and overwinter. Pupation occurs the following spring, probably in early May.Larval instars can be distinguished as follows: first instar with egg bursters on meso- and metathorax, with typical head chaetotaxy consisting of flattened-papillate setae and 1 pair of very long simple setae, and tibiae with 2 pairs of spiniform setae; older instars without egg bursters, and showing differences in size, in head and pronotal chaetotaxy, and in the number of spiniform setae on the tibiae.In the larvae, the premental sclerites of the head seem to be present throughout the Campsomata, a group with case-bearing larvae and not only in the Lamprosomatinae as previously reported.
31
Lee, Jae Chun, Hyuk Chon Kwon, Young Pil Kwon, Ju Hyeon Lee, and Sung Park. "Sealing Properties of Ceramic Fiber Composites for SOFC Application." Solid State Phenomena 124-126 (June 2007): 803–6. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.803.
Full textAbstract:
For the sealing of solid oxide fuel cells (SOFCs), mid-term (~1,000 h) sealing performance was examined using composite seals prepared with mixtures of a glass and alumino-silicate ceramic fiber. Leak rate could be reduced to < ~0.04 sccm/cm when using a composite seal with 60 vol% glass. Viscosity of the glass at the seal operating temperature of 650 was 2.0×108 dPa·s (log η = 8.3) as estimated by beam-bending method, and found to be suitable for sealing operation.
32
Lu, Bin, Xiaojian Ma, Caiguang Wu, Haijun Xuan, and Weirong Hong. "The Wear of Seal Fins during High-Speed Rub between Labyrinth Seal Fins and Honeycomb Stators at Different Incursion Rates." Materials 14, no. 4 (February 19, 2021): 979. http://dx.doi.org/10.3390/ma14040979.
Full textAbstract:
Labyrinth seals as a noncontact sealing technology are widely used in aero-engine. To improve the efficiency of the aero-engine, the clearance between the rotor and stator must be as small as possible. However, the change of the clearance between the rotor and stator because of thermal expansion, vibration, mechanical loading may lead to undesirable high-speed rub, which will lead to the cracking of the seal fins. This paper focuses on the wear of the seal fin after the rub and presents the rubbing tests between seal fins and the metal honeycomb under rubbing speed of 380 m/s and incursion rates between 20 and 180 μm/s, with an incursion depth of 1500 μm and a temperature of 350 °C. The rubbing force and temperature were recorded, and the seal fins were checked by SEM and EDS. The results show that the wear mechanism of seal fins changed from oxidation wear and adhesive wear to delamination wear and then to metal wear with the increasing incursion rate. The axial cracks appeared on the worn surface of the seal fins due to the cracking of tribo-layers under periodic thermomechanical stress. The wear mechanism of the seal fin also has a great influence on the rubbing force and temperature.
33
Ivanisevic, Vujadin, and Bojana Krsmanovic. "New Byzantine seals from Morava (Margum) and Branicevo." Starinar, no. 68 (2018): 111–24. http://dx.doi.org/10.2298/sta1868111i.
Full textAbstract:
The authors present new finds of Byzantine lead seals at Morava (Margum), Branicevo and the broader area around them. The seals from Morava and Branicevo were unearthed in the course of archaeological excavations, which make these finds particularly important. Significant among them is the seal from Morava, which belonged to Symeon (?), magister and logothete of the dromos, from the end of the tenth century, which indicates the presence of Byzantine officials in Morava and the establishment of Byzantine authority along the north-western Danubian border following the fall of the Bulgarian empire in 971. Three new seals from Branicevo complement the list of Byzantine officials in connection with the events on the Danubian border in the eleventh and twelfth centuries. The seals found in the broader area of Brani~evo should also be added to this list. Of particular significance among them is the seal of Georgios Palaiologos Doukas Komnenos, megas hetaireiarches, a well known historical figure involved in events in Hungary, Serbia and on the Danubian border in the 1160s.
34
Nikas, G. K. "Analytical study of the extrusion of rectangular elastomeric seals for linear hydraulic actuators." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 217, no. 5 (May 1, 2003): 365–73. http://dx.doi.org/10.1243/135065003322445287.
Full textAbstract:
Rectangular elastomeric seals used on reciprocating piston rods in high-pressure hydraulic actuators often suffer from extrusion damage at the low-pressure side of the actuators. The extrusion takes place at the narrow clearance between the rod and the actuator, where the seal develops a ‘nip’ under conditions of high sealed pressure and/or high friction with the rod, which is amplified in the absence of a back-up ring. This form of strain can lead to permanent damage of the seal and impair the sealing performance of the system. This paper deals with the modelling of this kind of seal extrusion. Algebraic equations were developed to describe the shape and contact pressure of the extruded part of the seal with the rod. A study is presented about the effects of various operating parameters on the extent of seal extrusion in order to minimize the risks of damage. It was found that only the use of a back-up ring can adequately cancel the seal extrusion mechanism.
35
Cherry, John. "The Cloth Seal: A Mark of Quality, Identification, or Taxation?" Medieval Globe 4, no. 1 (2018): 167–92. http://dx.doi.org/10.17302/tmg.4-1.7.
Full textAbstract:
This survey explores the origins of the lead cloth seal and its use in the primary production process of cloth making, secondary processes such as dyeing, and widespread application in the taxation and the regulation of trade. It concentrates especially on the discovery, study, and historiography of cloth seals in England and France, and explores how the study of such seals provides evidence for manufacturing and commerce in the medieval and post-medieval worlds.
36
Kuhn, C. E., R. R. Ream, J. T. Sterling, J. R. Thomason, and R. G. Towell. "Spatial segregation and the influence of habitat on the foraging behavior of northern fur seals (Callorhinus ursinus)." Canadian Journal of Zoology 92, no. 10 (October 2014): 861–73. http://dx.doi.org/10.1139/cjz-2014-0087.
Full textAbstract:
Central place foraging by colonial breeders can lead to depleted prey resources around breeding areas. Segregation of foraging areas both within and between large colonies may act as a mechanism to reduce competition for prey resulting in increased foraging success. We reassessed horizontal (spatial) foraging habitat segregation for northern fur seals (Callorhinus ursinus (L., 1758)) within and between colonies on the Pribilof Islands, Alaska (St. Paul and St. George islands), after the population declined by approximately 40%. Additionally, we examined vertical habitat segregation, where foraging ranges overlapped, and describe the influence of different foraging habitats on northern fur seal dive behavior. Spatial habitat segregation in northern fur seal foraging areas occurred between islands but was variable within islands, which is similar to the pattern previously described. There was no evidence for vertical habitat segregation when fur seals from different rookeries on St. George Island used the same foraging area. Additionally, fur seals from St. Paul Island rookeries that foraged in similar habitats showed fewer differences in dive behavior, indicating that foraging habitat plays a significant role in shaping dive behavior. The use of multiple foraging strategies within the Pribilof Island fur seal population could indicate that a complex management and conservation strategy may be necessary to stop the continuing decline of this population.
37
Kanev, Nikolay. "Byzantine Lead Seal of Constantine, Notarios and Abydikos from Bulgaria." Vestnik Volgogradskogo gosudarstvennogo universiteta. Serija 4. Istorija. Regionovedenie. Mezhdunarodnye otnoshenija, no. 6 (January 2020): 90–94. http://dx.doi.org/10.15688/jvolsu4.2019.6.7.
Full textAbstract:
Introduction. The paper deals with a byzantine lead seal of Constantine, notarios and abydikos, which originated from the vicinity of the medieval fortress of Rusokastro, southeastern Bulgaria. Methods. A part of byzantine lead seals are a primary source of information regarding both the commercial and economic activity in the Byzantine Empire and the administrative structures and mechanisms for its control and management, in particular for the period of the 8th – 9 th centuries. Therefore, the appearance of any such new scrambling monument is of great importance and the information derived from it should be carefully analyzed and appropriately taken into account in any reconstruction of the picture of the socio-economic life of the Empire and its contacts with its neighbors, including the medieval Bulgaria. Analysis. The seal dates from the second half of the 8th – the first half of the 9th cc. A cross-shaped invocative monogram is depicted on its obverse, while there is an inscription in four lines placed in a partly preserved circle on the reverse. The whole text of the monogram and the legend is as follows: “+ Κύριε βοήθει τῷ σῷ δούλω Κωνσταντίνω νοταρίου καὶ ἀβυδηκοῦ +”. The article also focuses on retrieving possible information from the Byzantine lead seal published in it. Results. The Byzantine lead seal published here is a material proof related to the picture of the commercial and economic life in the area of the Byzantine Empire near the medieval Bulgarian state and its administration by the Byzantine provincial authorities. Finding it in the territory that for the most of this period was a part of the First Bulgarian Empire suggests that Constantine’s seal is undoubtedly a testimony of the nature of peacetime contacts between Byzantium and Bulgaria at that time.
38
Mikkelsen, Lonnie, Line Hermannsen, Kristian Beedholm, Peter Teglberg Madsen, and Jakob Tougaard. "Simulated seal scarer sounds scare porpoises, but not seals: species-specific responses to 12 kHz deterrence sounds." Royal Society Open Science 4, no. 7 (July 2017): 170286. http://dx.doi.org/10.1098/rsos.170286.
Full textAbstract:
Acoustic harassment devices (AHD) or ‘seal scarers’ are used extensively, not only to deter seals from fisheries, but also as mitigation tools to deter marine mammals from potentially harmful sound sources, such as offshore pile driving. To test the effectiveness of AHDs, we conducted two studies with similar experimental set-ups on two key species: harbour porpoises and harbour seals. We exposed animals to 500 ms tone bursts at 12 kHz simulating that of an AHD (Lofitech), but with reduced output levels (source peak-to-peak level of 165 dB re 1 µPa). Animals were localized with a theodolite before, during and after sound exposures. In total, 12 sound exposures were conducted to porpoises and 13 exposures to seals. Porpoises were found to exhibit avoidance reactions out to ranges of 525 m from the sound source. Contrary to this, seal observations increased during sound exposure within 100 m of the loudspeaker. We thereby demonstrate that porpoises and seals respond very differently to AHD sounds. This has important implications for application of AHDs in multi-species habitats, as sound levels required to deter less sensitive species (seals) can lead to excessive and unwanted large deterrence ranges on more sensitive species (porpoises).
39
Liao, Chuanjun, Xibao Xu, Hongrong Fang, Hongrui Wang, and Man Man. "A leakage model of metallic static seals based on micromorphology characteristics of turning flange surface." Industrial Lubrication and Tribology 67, no. 6 (September 14, 2015): 572–81. http://dx.doi.org/10.1108/ilt-04-2015-0049.
Full textAbstract:
Purpose – The purpose of this paper is to develop a leakage model of metallic static seals, which can be used to accurately predict the leakage rate and study the corresponding seal characteristics. The metallic static seal is effectively applied to severe rugged environments where conventional seals cannot meet the needs. More research efforts for deepening the understanding of its seal characteristics are important for its effective and safe applications, of which the study about its leak is one key component. Design/methodology/approach – In the microscopic observations of the turning surface that is general in the processing of flange surfaces, it is found that the spiral morphology is dominant, which had been also obtained by other researches. There are two potential leakage paths for the flange surface of spiral morphology, one is the radial direction perpendicular to the spiral ridges and the other is the circumferential direction along the spiral groove. Based on the microgeometry characteristics of spiral morphology, the micromorphology of turning flange surface is simplified for the calculation of leakage rate, and the simplified methods of the radial and circumferential leakage paths are presented separately. The topography of flange surface studied in this paper is actually measured, and the Abbott bearing surface curve is adopted to represent the micro-profiles parameters. The radial and circumferential leakage models are further developed based on the assumption of laminar flow of the viscous compressible gas. Findings – The experiments used to verify the leakage models were carried out, and the experimental values are well agreed with the calculated values. As the contact pressure increases, the change rules of both radial and circumferential leakage rates are obtained and the obvious transition from radial leak to circumferential leak can be found. Using the proposed leakage models, the effects of the key micro-profiles parameters on the leakage rates are studied, and some specific conclusions are given simultaneously, which are favorable for the theoretical study and practical application of the metallic static seal. Practical implications – By the interpretations of the micromorphology characteristics of turning flange surface, the leakage mechanism of the metallic static seal is further made clear. The proposed leakage model reveals the relationships between the key micro-profiles parameters and some sealing performances about the leakage and can predict the leakage rates of the metallic static seal used in various working conditions. Originality/value – For the metallic static seal, the simplification of the radial leakage path and the radial leakage model are put forward for the first time, so the total leakage model can be systematically reported based on the micromorphology characteristics of turning flange surface. The effects of the key micro-profiles parameters on the seal behaviors including of the leak rate, critical contact pressure and transition from radial leak to circumferential leak etc are also clarified firstly.
40
Wickens, P. A., P. A. Shelton, J. H. M. David, J. G. Field, W. H. Oosthuizen, J.-P. Roux, and A. M. Starfield. "A Fur Seal Simulation Model to Explore Alternative Management Strategies." Canadian Journal of Fisheries and Aquatic Sciences 49, no. 7 (July 1, 1992): 1396–405. http://dx.doi.org/10.1139/f92-155.
Full textAbstract:
A simulation model is formulated for the South African fur seal (Arctocephalus pusillus pusillus) to evaluate the appropriate management action when culling to reduce population growth rate, culling to decrease fish consumption by seals, or harvesting to maximise numbers of seals removed. There is disturbance associated with bull sealing which increases pup mortality and reduces pregnancy rates, but this is not well quantified. Disturbance can be included or excluded from model runs. To reduce population growth, cow removal is most effective, but the population sex ratio becomes severely altered and this may be undesirable ecologically. Reduction of fish consumption is best achieved either by removing cows, with the same caveat regarding sex ratio, or by removing bulls and including disturbance effects. However, the acceptability of a reduction achieved by humans disrupting seals is questionable, and the continued removal of bulls may eventually lead to further decreases in pregnancy rate. To maximise a harvest, the relative commercial value of different seal products is considered, and bull removal, excluding disturbance effects, followed by removal of pups achieves this aim most effectively.
41
Cao, Yuanguo, and Xudong Dai. "Modeling for performance degradation induced by wear of a hydraulic actuator of a hydraulic excavator." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 3 (May 15, 2014): 556–65. http://dx.doi.org/10.1177/0954406214535926.
Full textAbstract:
As an index of maintaining low fuel consumption, the digging force of an excavator is affected fully by the performance of the hydraulic actuators including boom cylinder, stick cylinder, and bucket cylinder. The seals are used widely in a fluid power system to prevent fluid leakage. However, wear induces changes in the diameter of the seal's cross-section area, having an effect on the sealing capability of seals. This article proposes a model for performance degradation induced by wear of a hydraulic actuator of an excavator. The model in this article describes the physical process of performance degradation of a hydraulic actuator by analyzing piston response when wear occurs. The model includes a dynamic model of a hydraulic actuator, a model of squeezing stress and deformation of a compressed elastomeric O-ring seal, a wear model of a seal, and a leak rate model. These models can be used for deducing the laws of performance degradation of a hydraulic actuator of an excavator and for predicting the useful life of a key component such as the seal. Finally, based on the established model, simulation results of a hydraulic actuator’s response are provided.
42
To̸nder, K. "Finely Striated Lip-Seal Surfaces: Part 1—General Effects." Journal of Tribology 115, no. 4 (October 1, 1993): 620–24. http://dx.doi.org/10.1115/1.2921685.
Full textAbstract:
The work presented previously by To̸nder and Salant (1992) is extended and generalized. In that work it was shown that the fine, axially oriented striations found on some lip-seals, under certain conditions, could lead to the total suppression of leakage through a fully lubricated seal. In the present work the behavior of the lubricant annulus is studied, as are the conditions required for leakage suppression. If the latter are met, it is shown that when a certain parameter—here called the seal number—is increased, the lubricant annulus width will shrink. This will lead to a reduction of the friction force. It is further shown that the striated roughness will also generate a radial force or load capacity. This effect does not involve local cavitation.
43
Kwanka, K. "Improving the Stability of Labyrinth Gas Seals." Journal of Engineering for Gas Turbines and Power 123, no. 2 (March 1, 1997): 383–87. http://dx.doi.org/10.1115/1.1359772.
Full textAbstract:
The flow through labyrinth seals of turbomachinery generates forces which can cause self-excited vibrations of the rotor above the stability limit. The stability limit is reached at a specific rotating speed or power. The continuous growth of power density and rotating speed necessitates an exact prediction of the stability limit of turbomachinery. Usually the seal forces are described with dynamic coefficients. A new, easy-to-handle identification procedure uses the stability behavior of a flexible rotor to determine the dynamic coefficients. Systematic measurements with a great number of labyrinth seal geometries lead to reasonable results and demonstrate the accuracy and sensitivity of the procedure. A comparison of the various methods used to minimize the excitation indicates which seal is more stable and will thus improve the dynamic behavior of the rotor.
44
Elizabeth and Mark Forrest. "Impressed in Metal: the Seals of a Devon Tax Collector." Antiquaries Journal 85 (September 2005): 366–73. http://dx.doi.org/10.1017/s0003581500074436.
Full textAbstract:
With the exception of papal bullae and royal golden seals, metal seals were very rare in northern Europe in the Middle Ages and early modern period. This paper explores a rare example of the use of lead as a medium into which to impress a seal, something that is not only of considerable interest in the context of medieval sigillography, but which provides an insight into the concerns and motives of an individual who in other circumstances would have remained an anonymous member of the Elizabethan gentry and county bureaucracy.
45
Ciupak, Anna, Bożena Gładyszewska, Władysław Michałek, and Katarzyna Rubinowska. "Mechanical properties of Polygonatum multiflorum leaves after treatment with growth stimulants." Canadian Journal of Plant Science 99, no. 3 (June 1, 2019): 303–11. http://dx.doi.org/10.1139/cjps-2018-0120.
Full textAbstract:
The mechanical properties of leaves are important in many aspects of plant science. Because of their delicate structure, leaves are sensitive to different, potentially harmful, environmental factors. The mechanical properties of leaves are important factors affecting leaf quality, longevity, susceptibility to damage, and decomposition. Two growth stimulants were applied to investigate selected mechanical properties of Solomon’s seal Variegatum [Polygonatum multiflorum (L.) All.] leaves grown under field cultivation and in an unheated polytunnel. The mechanical properties of leaves were assessed by measuring Young’s modulus. The agents used in the treatment were Actisil Hydro Plus at a concentration of 0.4% in the first series and Pentakeep V at a concentration of 0.04% in the second series. Foliar treatment with the stimulants was conducted six times at weekly intervals. The control plots were sprayed with distilled water. The research was carried out between 2012 and 2014. In comparison to the test series, the respective effects of Actisil Hydro Plus and Pentakeep V on the change in Young’s modulus was more notable in plant leaves obtained from the tunnel than those from field cultivation. Specifically, growth stimulants had more impact on the stiffness of leaves obtained from plants grown in the tunnel. Generally, plant leaves from field cultivation were stiffer than those from the tunnel.
46
Kong, Xiaozhi, Gaowen Liu, Yuxin Liu, Zhao Lei, and Longxi Zheng. "Performance evaluation of the inter-stage labyrinth seal for different tooth positions in an axial compressor." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 6 (November 6, 2017): 579–92. http://dx.doi.org/10.1177/0957650917739532.
Full textAbstract:
Labyrinth seals are normally used to control the leakage flow in the compressor stator well. The upstream and downstream rotor-stator cavities of the labyrinth seal can cause complex reverse leakage flows. Remarkable temperature increases and high swirl velocities are observed in this region. In addition, another characteristic of inter-stage labyrinth seal is that large expansions of rotor and stator may easily lead to severely rubbing between the teeth and shrouds, which can shorten the lifetime of the compressor obviously. Experiments were conducted at a rotating compressor inter-stage seal test facility. Different labyrinth rings were tested to compare the performances of inter-stage labyrinth seals with different tooth positions. Leakage flow rates, windage heating and swirl ratios in the outlet cavity were measured at different rotating speeds and pressure ratios. In order to get the working tip clearance accurately, the set up tip clearance was measured with plug gauges, while the radial displacements of rotating disc and stationary casing were measured separately with two high precision laser distance sensors. Numerical simulations were carried out to present the important flow physics responsible for the effects of different tooth positions. In this article, performances of different cases for single, double and triple teeth were investigated and the experimental data provide a new way for the design of inter-stage seals. This method can reduce the leakage flow and avoid severely rubbing at the same time by changing axial positions of teeth in the stator well. When teeth are placed downstream of the model and the tooth pitch is larger, the inter-stage seal would have better sealing performance. For triple teeth cases, N = 3-Case1 has the lowest discharge coefficients, 15% less than that of N = 3-Baseline.
47
Wang, Qiang, Ya-Ping Hu, and Hong-Hu Ji. "Leakage, heat transfer and thermal deformation analysis method for contacting finger seals based on coupled porous media and real structure models." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 10 (January 14, 2020): 2077–93. http://dx.doi.org/10.1177/0954406219900219.
Full textAbstract:
Finger seal is a type of compliant seal configuration that has superior sealing performance compared with conventional labyrinth seals and brush seals. However, complex working conditions lead to leakage, thermal gradient and deformation, which can be more serious for a contacting finger seal due to frictional heating. In this paper, a leakage and thermal performance analysis method coupled with porous media and a real structure model was developed to numerically simulate the leakage, heat transfer and thermal deformation characteristics of a contacting finger seal. The method innovatively established a porous media fluid dynamics and heat transfer model and modified the frictional heating model by introducing the concept of a friction work conversion ratio. Then, the thermal deformation of the fingers was calculated on the basis of pressure and temperature results by using the thermal-stress module of ANSYS Workbench. The results show that the leakage analysis porous media model has good calculation accuracy and most of the fluid leaks through the finger foot, while the pressure drops mainly in this field. The highest finger temperature occurs at the downstream side of the contact surface between the finger foot and the rotor. The largest thermal deformation of each laminate occurs at the finger foot toe and increases slightly along the flow direction. Additionally, the largest relative circumferential thermal deformation can reduce the gap between the fingers by approximately 5%, which is beneficial for reducing leakage. It is suggested to increase the seal inner diameter at the finger foot toe but decrease it at the finger foot heel during the design process to decrease wear and leakage.
48
Gerondeau, Maureen, Christophe Barbraud, Vincent Ridoux, and Cécile Vincent. "Abundance estimate and seasonal patterns of grey seal (Halichoerus grypus) occurrence in Brittany, France, as assessed by photo-identification and capture–mark–recapture." Journal of the Marine Biological Association of the United Kingdom 87, no. 1 (February 2007): 365–72. http://dx.doi.org/10.1017/s0025315407054586.
Full textAbstract:
It has been suggested that the large grey seal colonies around the British Isles form local populations within a metapopulation, and that seal movements outside the breeding season lead to considerable overlap between individual home ranges. Individual behaviour and population dynamics of small peripheral colonies may also play a role in the metapopulation. We studied the French grey seal colony of the Molène archipelago, at the southern-most limit of the species' range. We analysed photo-identification data with capture–mark–recapture techniques in order to estimate the total seasonal abundance of grey seals in the archipelago and to quantify the seasonal rates of occurrence or movements of male and female seals. We found that between 58 (95% confidence interval: 48–71) and 98 (95% CI: 75–175) individuals hauled out in the archipelago during the summers of 1999 and 2000. The use of multistate models allowed the assessment of seasonal site fidelity and indicated that it varied between key periods of the annual cycle, particularly for females. Males showed a constant fidelity rate of 56% from one season to another. Hence, even though they showed high inter-annual site fidelity, they did not seem to have a preferred season for using the archipelago. On the contrary, female grey seals showed the highest site fidelity between moult and summer (around 80%), and the lowest fidelity between summer and the breeding period (34–43%). Thus, females seem to use the Molène archipelago preferentially in summer and leave the site before the breeding season, which explains the very low local pup production. Philopatry may explain this pre-breeding emigration, and we suggest that most grey seals observed in the Molène archipelago were born and breed in other local breeding populations, probably the south-western British Isles.
49
Webb, P. M., D. E. Crocker, S. B. Blackwell, D. P. Costa, and B. J. Boeuf. "Effects of buoyancy on the diving behavior of northern elephant seals." Journal of Experimental Biology 201, no. 16 (August 15, 1998): 2349–58. http://dx.doi.org/10.1242/jeb.201.16.2349.
Full textAbstract:
Marine mammals experience radical seasonal changes in body composition, which would be expected to affect their buoyancy in the water. The aim of this study was to examine the relationship between such changes in buoyancy and diving behavior in northern elephant seals Mirounga angustirostris. This was achieved by modifying the buoyancy of 13 juvenile elephant seals translocated from Año Nuevo State Reserve, CA, USA, and released at various sites in Monterey Bay, CA, USA. The buoyancy of each seal was calculated and was increased or decreased using syntactic foam or lead weights, and their diving behavior was recorded as they returned to Año Nuevo. The seals were divided into three groups: increased buoyancy (B+), reduced buoyancy (B-) and control seals (Bc). Mean descent rates were 0.77+/-0.3 ms-1 for the B+ seals, 0.82+/-0.2 ms-1 for the control seals and 0.87+/-0.3 ms-1 for the B- seals, and were significantly different. Mean ascent rates for the three treatments were 0.82+/-0.3 ms-1 for the B+ seals, 0.86+/-0.3 ms-1 for the control seals and 0.82+/-0.3 ms-1 for the B- seals. All the B+ seals ascended faster than they descended, while four of the five B- seals descended faster than they ascended. There was a significant negative correlation between buoyancy and descent rate, with less buoyant seals descending faster than more buoyant seals. There was, however, no correlation between ascent rate and buoyancy. This suggests that seals may use negative buoyancy to drift passively during descent, but that all seals may swim continuously during ascent. There was a significant correlation between buoyancy and the drift descent rate of C-type drift dives, including upwards drift in the most buoyant seal. Buoyancy was not correlated with diving depth, trip duration, dive duration or surface-interval duration. This study demonstrates that buoyancy plays a significant role in shaping diving behavior in northern elephant seals and that elephant seals may adjust their behavior to suit their buoyancy, rather than adjusting their buoyancy to suit a dive. This study also validated the truncated cones method of calculating body composition in this species by comparing it with body composition determined using tritium dilution.
50
Cardona, Sebastian, Lesli Wood, Lorena Moscardelli, and Dallas Dunlap. "Cannibalization and sealing of deepwater reservoirs by mass-transport complexes — The Jubilee field, Gulf of Mexico." Interpretation 8, no. 4 (November 1, 2020): SV17—SV30. http://dx.doi.org/10.1190/int-2019-0274.1.
Full textAbstract:
Mass-transport complexes (MTCs) are important stratigraphic elements in many deepwater basins. In hydrocarbon exploration, MTCs have traditionally been identified as seals although they can also act as migration pathways or cannibalize and compartmentalize adjacent reservoirs. Although the ever-improving resolution of seismic data has enhanced the knowledge about these deposits (e.g., geometry, distribution), at present the potential of MTCs to act as top and/or lateral seals is difficult to predict predrilling and few case studies are publicly available. The key objective here is to present examples of seismically resolvable characteristics of two MTCs in the Jubilee gas field, offshore Gulf of Mexico: one of the MTCs cannibalized part of the reservoir, and the other acted as the top seal. The Jubilee field is an area where the ability of MTCs to act as a top seal has been proven — the field produced approximately 205 billion cubic feet of natural gas until abandonment in 2016. When evaluating the sealing potential of MTCs, seismic interpretation can offer a powerful technique to identify indicators of hydrocarbon leakage. Additionally, mass flows that form MTCs can be highly erosive and cannibalize underlying reservoir deposits, which increase reservoir heterogeneity that can lead to compartmentalization. Our results indicate that the seal MTC in the Jubilee field is a detached MTC and that the translational morphodomain overlies the gas accumulation. Consequently, when predicting the seal potential of MTCs from seismic data, it is important to determine (1) the type of MTC (i.e., attached versus detached), (2) the specific MTC morphodomain overlying the hydrocarbon accumulation/prospect (i.e., the headwall, translational, or toe morphodomains), and (3) the presence of seismic indicators of fluid migration pathways (e.g., gas chimneys, pockmarks, etc.). These results shed some light on the present challenges of predicting the seal potential of MTCs in frontier basins around the world.