Aerial surveys were conducted in 1999 and 2000 to estimate the densities of ringed (Phoca hispida) and bearded (Erignathus barbatus) seals in the eastern Chukchi Sea. Survey lines were focused mainly on the coastal zone within 37 km of the shoreline, with additional lines flown 148–185 km offshore to assess how densities of seals changed as a function of distance from shore. Satellite-linked ti...

The seals are the important component of the aircraft engine to prevent leakage of gas or oil. Because the contact and friction problems have a great influence on the performance of the seals, the concept and theory of tribology is already widely applied in research and design processes of advanced seals. This report selected three kinds of representative seals which are co...

an r-module m is called epi-retractable if every submodule of mr is a homomorphic image of m. it is shown that if r is a right perfect ring, then every projective slightly compressible module mr is epi-retractable. if r is a noetherian ring, then every epi-retractable right r-module has direct sum of uniform submodules. if endomorphism ring of a module mr is von-neumann regular, then m is semi-...

A spring-energized seal, whose PTFE plastic shell has excellent self-lubrication and a low temperature stability, is used widely in liquid fuel valves’ rotating end-face seals. However, practical application, larger effect on not only the physical tribological properties of materials, but also leakage performance rings. Thus, high sealing test seal that applies to an engine was carried out. In ...

In view of the problems encountered in previous hydraulic 6-DOF parallel mechanism projects, flexible modes appear that actual natural frequencies x and y degrees freedom are lower than those obtained through calculation. The phenomenon above not only decreases dynamic response characteristics mechanism, but also leads to doubts about performance mechanism. real reason for is solved this paper....

In this study, electronic door seals (E-seals) are tested on shipping containers that traveled through ports, over borders, and on roadways. The findings show that using RFID devices increases supply chain efficiency and improves the security of containerized cargo movements, particularly when E-seals replace common mechanical seals. Before the benefits of E-seals can be realized, several barri...

Balance piston seals are subjected to large pressure differential and can generate large forces directly impacting the stability of centrifugal compressors. The most common designs are textured seals such as honeycomb, hole-pattern seals, and pocketed seals including pocket damper seals (PDS) and fully partition damper seals (FPDS), shown in Fig. 1. The dynamic performance of textured seals hav...

‎‎we exhibit an explicit construction for the second cohomology group‎ ‎$h^2(l‎, ‎a)$ for a lie ring $l$ and a trivial $l$-module $a$‎. ‎we show how the elements of $h^2(l‎, ‎a)$ correspond one-to-one to the‎ ‎equivalence classes of central extensions of $l$ by $a$‎, ‎where $a$‎ ‎now is considered as an abelian lie ring‎. ‎for a finite lie‎ ‎ring $l$ we also show that $h^2(l‎, ‎c^*) cong m(l)$‎...

Antibodies to Toxoplasma gondii were determined in serum samples from 47 grey seals (Halichoerus grypus) and 56 harbor seals (Phoca vitulina vitulina) from the Atlantic coasts of United Kingdom and France. Antibodies to T. gondii assayed by the modified agglutination test (MAT) were found in 14 (13.6%; IC(95%): 7.0-20.2) of 103 seals tested, with titres of 1:25 in 13 seals and 1:50 in 1 seal. S...