Ability Of Seal Research Articles

Control and analysis of floating ability of aeronautical cylindrical spiral groove gas seal based on F-K model

The slip flow phenomenon caused by the gas floating seal in ultra-thin gas films and high-altitude rarefied gas environments occurs frequently. This study represents the first attempt to calculate the gas film floating force by considering the coupling relationship among the slip flow effect, the surface micro-grooves, and the eccentricity using a high-precision eight-node finite difference method based on the linearized Boltzmann equation for a spiral-grooved cylindrical gas seal. Furthermore, the influence of slip flow on the operational and groove parameters of the spiral-grooved cylindrical gas seal is investigated and discussed. Results show that the velocity gradient of the lubrication gas is reduced and the effect of the fluid hydrodynamic pressure is weakened because of slip flow, particularly in high-speed, low-pressure, and high-eccentricity fields. However, increases in groove depth, number, and length improve the gas film floating force, which strengthens the slip flow response in the grooves. Therefore, the slip flow reduces the gas film floating force, but when the groove depth exceeds 32 μm and the groove length is greater than 45 mm, the slip flow may become negligible. The results presented here provide a theoretical basis to broaden the application scope of dynamic seals in the aerospace field.

Experimental Study on Divergent Magnetic Fluid Seal with Small Clearance and Double Magnetic Source

In order to solve the problem of poor sealing performance of rotating machinery under the condition of small clearance, a new type of divergent magnetic fluid seal device with small clearance and double magnetic source is designed in this paper. The effect of magnetic fluid injection, tooth number and sealing clearance on the sealing pressure resistance of dual magnetic source divergence were studied and compared with the experimental value of ordinary magnetic fluid seal. The experiment results show that the pressure resistance ability of divergent magnetic fluid seal is at least 3 times that of ordinary magnetic fluid seal, which verifies the correctness of divergent magnetic seal with small clearance and double magnetic source pressure resistance theory, and has important theoretical guiding significance for solving the problem of poor magnetic fluid seal performance under small clearance.

Design and Experimental Study on Divergent Magnetic Fluid Seal with Large Clearance and Dual Magnetic Sources

In order to solve the leakage problem of rotating machinery under the condition of large clearance, a new type of divergent magnetic fluid sealing device with secondary magnetic source was designed. The magnetic field distribution in the clearance of the magnetic fluid seal was simulated by the finite element method of magnetic field, and the theoretical value of the sealing pressure resistance was calculated according to the pressure resistance theory of the divergent magnetic fluid seal. The influences of the volume of magnetic fluid injection, the number of teeth, the clearance, and the eccentricity of the rotating shaft on the pressure resistance abilities of divergent magnetic fluid seal were studied by experimental method and compared with the pressure resistance experimental value of ordinary magnetic fluid seal. The results showed that when the injection volume of magnetic fluid is more than 3 ml, the sealing pressure resistance ability of the magnetic fluid does increase greatly and tends to be stable gradually. The saturated magnetic fluid injection volume of divergent magnetic fluid seal with large clearance is 3 ml. With the increase of radial teeth, the pressure resistance ability of magnetic fluid seal first increases and then decreases. With the increase of axial teeth, the pressure resistance ability of magnetic fluid seal also increases. With the increase of radial clearance, the pressure resistance value of magnetic fluid seal first increases and then decreases. With the increase of axial clearance, the pressure resistance value of magnetic fluid seal decreases. The pressure resistance ability of divergent magnetic fluid seal is significantly higher than that of ordinary magnetic fluid seal.

Динамика формирования дифференцировочного следового условного рефлекса на звуковые раздражители определенной продолжительности у серого тюленя Halichoerus grypus Fabricius, 1791 методами оперантного обуславливания.

In the course of the study, a 15-year-old female gray seal was trained to press a button after displaying an audio signal for 5 seconds and ignore similar audio signals of longer or shorter duration. The conducted research has demonstrated the ability of the experimental seal to reliably differentiate sound signals with a difference in sound duration of 3 seconds. Changes in the reaction time and behavior of the seal during the demonstration of sound stimuli with distinguishable and indistinguishable time ranges are described.

ИССЛЕДОВАНИЕ ГЕРМЕТИЗИРУЮЩЕЙ СПОСОБНОСТИ КОМБИНИРОВАННОГО МАГНИТОЖИДКОСТНОГО УПЛОТНЕНИЯ ПОДШИПНИКОВЫХ УЗЛОВ

The purpose of the research is to increase the efficiency of hermetic ability of bearing assemblies by using com-bined ferrofluidic sealed. The research objective is theoretic justification of the maximum concentration of ferro-magnetic particles in fluid, investigation of hermatic ability of a combined ferrofluidic seal under conditions of tem-perature changing and speed of a shaft rotation of packing bearing assembly. The study of hermetic ability of lip and ferro-fluidic sealed was carried out on a test bench, allowing to determine the packing ability of seals both in static and dynamic mode. On the basis of theoretical data, formulas were determined to find the maximum concen-tration of hard and magnetic phases in a ferrofluid, and its composition based on a polyethylsiloxane liquid PES-5 with a 40 kA/m saturation magnetization and a 1.2 Pas dynamic viscosity coefficient was developed. A mixture of magnetite with powdered iron was used as the ferromagnetic phase. Oleic acid was used as a surfactant. Studies to determine hermetic capacity have shown a higher efficiency of the combined ferrofluidic seal compared to the lip one. During static test within the temperature range between 20 to 600C, the critical pressure difference of the com-bined seal was 
 4-16% higher than that of the lip seal. Temperature increase of the bearing assembly from 20 to 1200C causes a decrease in critical pressure difference of up to 50%. This is due to a decrease in the sedimentative stability of the magnetic fluid as a result of an increase in temperature. Studies show that the combined ferrofluidic seal has a higher hermetic tightness at the starting torque than the standard lip seal. In contrast to the lip seal (which tends to lose its tightness at the starting torque), no leakage of pressure fluid from the sealed unit was observed of the com-bined ferrofluidic one with a pressure drop of 0.094 MPa. The results obtained allow reasonably select the concen-tration of magnetic particles in the ferrofluid, and also prove the prospects of replacing standard lip seals with com-bined ferrofluidic ones.

The sealing properties of magnetorheological fluids under quasi-static tensile

In order to study the influences of sealing gap on the seal of magnetorheological fluids (MRF), the quasi-static tensile tests along the direction of magnetic field have been carried out by using a commercial plate-plate rheometer. Based on the experimental results, the relationships among the height of sealing gap, magnetic field intensity, particle concentration and the sealing properties of MRF are discussed. The analysis results show that the sealing performances of MRF will deteriorate with the increase of sealing gap, especially when the MRF is exposed to a strong magnetic field. This is probably due to the fact that the material properties of MRF become more similar to the solid with the rise of magnetic field, which makes the sealing layer more brittle and prone to leakage. The tensile process in low magnetic field can be divided into the forming of seal region, stable seal, leak and balanced-pressure four stages, in which the stable seal stage shows that the MRF has certain self-healing ability of seal. Furthermore, both the initial compressive strength and the sealing stability of MRF can be significantly improved by increasing the volume fraction of MRF. Finally, a theoretical model for calculating the burst pressure of MRF seal is proposed according to the theory of magnetic dipole. The description of the relationship between various influencing factors and the sealing characteristics of MRF by this model is consistent with the experimental results, which indicates that the model has favorable instructing value in the practical engineering application.

Influence of gravity on the anti-pressure ability of magnetic fluid seal

Influence of gravity on the anti-pressure ability of magnetic fluid seal

Effect of axial play on the sealing ability of the radial single-lip seal in an abrasive environment

The results of research focused on the specifics of frictional interaction between contacting surfaces of radial seal working in the environment with high abrasive content have been presented. The effect of the abrasive penetration through sealing during its axial play on the shaft, called the pumping effect, which results in the wear of the sealed friction joint parts and leads to the premature failure, has been found.

水素ガスシール性に及ぼす PEEK 系樹脂の接触面形状の影響

水素ガスシール性に及ぼす PEEK 系樹脂の接触面形状の影響

Brightness discrimination in the South African fur seal (Arctocephalus pusillus)

Underwater, the contrast between object and background is much larger reduced with increasing distance between object and observer than in air. For marine predators, such as pinnipeds, it would therefore be advantageous to possess a high sensitivity for brightness differences, since this would increase the distance at which prey can be detected visually. Few studies have examined the brightness discrimination thresholds of pinnipeds. Two studies with phocid seals have confirmed low brightness discrimination thresholds in pinnipeds whereas the threshold obtained for the South African fur seal seems to be twice as high as that of the phocids. However, the experiments with the South African fur seal have been conducted under inadequate conditions which likely resulted in an underestimation of the brightness discrimination ability of this species. The study at hand reinvestigated the brightness discrimination threshold of the South African fur seal under well controlled conditions. In a two alternative forced choice task, one fur seal was trained to indicate the position of the brighter of two gray discs presented on a black background on a monitor. The thresholds were determined for 11 standard intensities each tested against 8 lower comparison intensities. It was found that the fur seal was able to perceive brightness differences of 8-10%, which is better than the phocid species tested so far. For low standard intensities, however, the threshold increased which could to be due to a relative slow dark adaptation rate of the fur seal. The results are discussed in terms of the relevance of visual information for pinnipeds during foraging dives and are directly compared to the results obtained for the harbor seal which has been tested under the same conditions as the fur seal in a previous study.

Influence of apical taper on the quality of thermoplasticized root fillings assessed by micro-computed tomography

The objective of this study is to study the influence of final canal taper on the sealing ability of Real Seal 1 by using micro-computed tomography (micro-CT). Fifty-four single-rooted teeth were instrumented to apical size of 40 taper 4, 6, and 8. The teeth were divided into three groups. All teeth were filled with Real Seal 1 (RS1; SybronEndo, Orange, CA, USA). Roots were then scanned with mico-CT, and volume measurements of voids in the apical third and in sections at 1, 3, and 5mm from the apex were calculated in the obturated roots using specialized CT software. Measurements were analyzed statistically by using ANOVA followed by Bonferroni multiple comparison correction. Data analysis showed that 0.08% and 0.06% apical tapered RS1 obturations provided better results than 0.04% tapered samples. The present study showed that none of the root canals filled teeth were gap free. Mean percentages of voids were significantly higher with Real Seal 1 taper 0.04% (P = 0.05).There was no significant difference with 0.06 and 0.08 final taper. For Real Seal 1 technique 0.06 and 0.08 tapered preparations seem to be more optimal. At 1mm, final taper 0.08 showed less voids and gaps than the two other final tapers. In our daily practice, enlarging the apical third (last 3mm) of root canals to an 8% taper is necessary to achieve a better sealing ability and thus long-term success for our root canal obturations.

Effect of calcium hydroxide dressing on the long-term sealing ability of two different endodontic sealers: An in vitro study

The aim of this in vitro study was to evaluate the long-term sealing ability of Real Seal system and Endofill after calcium hydroxide (CH) dressing, by using a fluid filtration model. Four randomized groups of single-rooted teeth (N=110) were prepared using a crown-down technique to a size 50 file. Two groups (1 and 2) received CH dressing before filling. Roots were filled with gutta-percha and Endofill (groups 2 and 4) or Resilon and Real Seal (groups 1 and 3). Leakage was measured by using the fluid filtration method after 90 days and determined as microL/min.10 psi. Statistical analysis by Kruskal-Wallis and Mann-Whitney tests indicated that CH dressing groups showed higher leakage values than those where CH was not used (P=.001). It may be concluded that the use of CH as an intracanal dressing material affected the sealing ability of both Real Seal and Endofill sealers.

Sealing ability of Hybrid Root SEAL (MetaSEAL) in conjunction with different obturation techniques

The objective of this study was to evaluate the apical sealing ability of Hybrid Root SEAL (MetaSEAL) in conjunction with different obturation techniques. Sixty-eight extracted human mandibular straight single-rooted teeth with mature apices were prepared using a step-back technique and divided into 4 experimental groups (n = 15). An additional 8 teeth were prepared for controls (3 for positive, 3 for negative control, and 2 more for calculating 100% leakage). The experimental groups were obturated with Hybrid Root SEAL (MetaSEAL) using cold lateral condensation, vertical condensation, Thermafil, and Ultrafil techniques. Fluid movement along the filled canals was measured using a fluid filtration method. Measurements were made at 2-minute intervals for 8 minutes. The data were calculated as microL/min and statistically analyzed using 1-way ANOVA and Duncan Test. Cold lateral and vertical condensation had significantly less fluid movement than the Thermafil and Ultrafil groups. Thermafil group had the highest fluid movement values when compared with the other groups (P < .01). Hybrid Root SEAL (MetaSEAL) had less fluid movement with cold lateral and vertical condensation techniques when compared with Thermafil and Ultrafil techniques.

Electrochemical Deposition of Fluoridated Calcium Phosphate Thin Film on Titanium Substrates

Percutaneous type of orthopedic and dental implants requires not only a good adhesion with bone, but also the ability to form good attachment and seal with connective tissues and skins. Currently, the skin-seal of such implants still remains as a problem to be resolved. Electrochemical processing was used to modify the surface of titanium implants in order to improve the ability of anti-bacteria infection and skin seal around the implants by synthesizing a fluoridated calcium phosphate thin film on titanium substrate. The surface of titanium was cathodically treated in an electrochemical cell. A thin film of about 80 nm thickness was deposited on the titanium surface by controlling the treatment parameters. The dense and gel-like film was composed of calcium phosphate and fluorine ions. Fluorine ion has the anti-bacteria property and could help to improve the skin seal around the percutaneous device. The electrochemical method of fluoridated calcium phosphate thin film synthesis will provide an alternative method for surface treatment of orthopedic and dental implants.

An in-vitro evaluation of sealing ability of real seal using fluid filtration.

The aim of this study was to compare the sealing ability of Real Seal (RS) and Gutta-percha (GP). Forty nine extracted human maxillary central incisors were used. The coronal part of each tooth was removed, the root canal was prepared using the crown down technique and apical enlargement to rotary file # 40. The specimens were randomly divided in to 3 groups of 15 each and two control groups of 2 each. Group 1, was obturated with RS and group 2 and 3 were obturated with GP and AH26 sealer by lateral condensation technique. In group 1 and 3 the smear layer was removed by 5mL of 5.25% NaOCl and 3mL of 17% EDTA. Leakage of the obturated roots was measured using the fluid filtration technique. This method was done at 2 min intervals for 8 min. data were analyzed using ANOVA and Tukey tests. Statistical analysis indicated significant differences between groups 2 with 1 and 3. The most leakage value was observed in the group 2. Root canal filling with RS or GP in combination with smear layer removal showed better sealing. Therefore the smear layer has more effect one apical leakage than the obturation system.

Predictive value of the user seal check in determining half-face respirator fit

SummaryGuidelines issued by the Centers for Disease Control and Prevention and the World Health Organization state that healthcare workers should wear N95 masks or higher-level protection during all contact with suspected cases of severe acute respiratory syndrome. Before use, the manufacturer recommends performing a user seal check to ensure that the mask is fitted correctly. This study aimed to test the ability of the user seal check to detect poorly fitting masks. This study is a retrospective review of a mask-fitting programme carried out in the intensive care unit of the Prince of Wales Hospital in Hong Kong. In this programme, all staff were tested with two types of N95 mask and one type of N100 mask. The results of the documented user seal check were then compared with the formal fit-test results from a PortaCount. Using a PortaCount reading of 100 as the criterion for a correctly fitted mask, the user seal check wrongly indicated that the mask fitted on 18–31% of occasions, and wrongly indicated that it did not fit on 21–40% of occasions. These data indicate that the user seal check should not be used as a surrogate fit test. Its usefulness as a pre-use test must also be questioned.

Improving the Anti-seizure Ability of SiC Seal in Water with RIE Texturing

The demand for higher pressure and higher speed of sealing systems is currently increasing due to stricter standards for permissible emissions. Silicon carbide (SiC) is thought to be a promising material for sealing systems operating in water, since the combination of SiC and water is both environmentally friendly and energy saving. The purpose of this study is to improve the anti-seizure ability of SiC seals working in water by means of surface texturing. The texture pattern of micro-pits evenly distributed in a square array is formed on one of the contact surfaces by reactive ion etching (RIE). Experiments which simulate the working condition of mechanical seals were carried out to evaluate the effect of micro-pits on the critical seizure load. It is found that micro-pit texturing is an effective way to stabilize friction, to reduce the friction coefficient, and to expand the low-friction range (μ < 0.05) of SiC seals working in water.

Internet Seals of Approval: Effects on Online Privacy Policies and Consumer Perceptions

The use of Internet seal of approval programs has been touted as an alternative to potential legislation concerning consumer‐related online privacy practices. Questions have been raised, however, regarding the effectiveness of such programs with respect to maintaining privacy standards and aiding online consumers. The authors examine these issues in a series of three studies, the first of which is an exploratory application of Federal Trade Commission privacy standards to various online privacy policies in an effort to determine the ability of seal of approval program participation to act as a valid cue to a firm's stated privacy practices. The second and third studies are experiments designed to ascertain how online firm participation in Internet seal of approval programs affects consumers. Implications for consumer policy are discussed.

An in vitro comparison of thermoplasticised gutta‐percha obturation techniques with cold lateral condensation

This study compared the apical sealing ability, obturation time and extrusion of gutta-percha and sealer when root canals were obturated using either cold lateral condensation or one of the three methods using thermoplasticised gutta-percha (Alpha Seal, Thermafil or JS Quick Fill) in vitro. One hundred and thirty-one root canals from 78 extracted human teeth were used; 116 canals were divided into five groups so that they were balanced with respect to prepared canal anatomy, and the remaining 15 canals were used as positive and negative controls. The canals in the first four groups were prepared with hand files using the step-down technique to a standard apical size and flare. The last group was prepared using engine-driven rotary nickel-titanium files (McSpadden) to a similar apical size and flare. One of the four obturating techniques was used to fill the canals in each of the first four groups. The fifth group was obturated using the Alpha Seal technique. The roots were immersed in india ink, demineralised and rendered transparent to assess the extent of maximum lincar dye penetration. The Alpha Seal groups had the highest number of specimens without any leakage. There was a significant difference in the proportions of specimens that did not leak when the Alpha Seal (P < 0.01) and cold lateral condensation groups (P < 0.05) were compared with JS Quick Fill. Cold lateral condensation had a higher proportion of specimens with leakage in canals with curvature greater than 20 degrees than in canals with curvatures less than 20 degrees (P < 0.05). The curvature of canals had no effect on the sealing ability of the other techniques. The method of canal preparation had no effect on the sealing ability of Alpha Seal. Alpha Seal, Thermafil and JS Quick Fill were significantly quicker to perform than cold lateral condensation.

Early Spring Feeding Habits of Bearded Seals (&lt;i&gt;Erignathus Barbatus&lt;/i&gt;) in the Central Bering Sea, 1981

The diet of bearded seals, Erignathus barbatus , near St. Matthew Island, Bering Sea, was studied during the early spring of 1981. Eighty-six percent of the 78 seals' stomachs examined contained fish. Other prey taxon groups, in decreasing order of their percentages of occurrence, were crabs (73%), clams (55%), snails (47%), amphipods (32%), shrimp (18%), mysids (13%), marine worms (13%) and cephalopods (4%). The most frequently occurring prey species were capelin, Mallotus villosus, (82%); codfishes, Gadidae (64%); narrow snow crab, Chionoecetes opilio (63%); eelpouts, Lycodes spp. (56%); longsnout prickleback, Lumpenella longirostris (49%); nutshell clams, Nuculana sp. (42%); and moon snails, Polinices sp. (27%). Seventy-seven percent of the seals examined had consumed prey from three or more different taxon groups. We identified seven food items not previously reported as prey of the bearded seal in the Bering Sea. No differences were detected between the diets of males and females and between adults and juveniles, indicating no apparent segregation of foraging by sex or age. Bearded seals in the St. Matthew Island region of the Bering Sea forage in a manner similar to their conspecifics in other areas where fish constitute a major portion of their diet. Prey selection is probably dependent on availability, and diet may be highly diversified even within a relatively small area during a short period of time. Variety in prey consumption exemplified the ability of the bearded seal to forage in the seasonally changing habitat associated with the advance and retreat of the ice front. Key words: bearded seal, Erignathus barbatus , diet, demersal and pelagic fish, benthic invertebrates, prey species diversity