We have previously evaluated asbestos exposure associated with various maintenance procedures on light aircraft. The purpose of this study was to evaluate asbestos exposure during engine maintenance on light aircraft....We have previously evaluated asbestos exposure associated with various maintenance procedures on light aircraft. The purpose of this study was to evaluate asbestos exposure during engine maintenance on light aircraft. This test was designed to evaluate the potential for asbestos exposure to mechanics and others who remove asbestos-containing engine gaskets from reciprocating style aircraft engines. Utilized in this test was an air cooled, horizontally opposed, aviation gasoline burning engine, assembled during 1986 and operated intermittently up into 2015, having accumulated 1680 hours run time. Nearly 75% of the asbestos-containing gaskets installed during 1986 were still in place at the time of testing. Chrysotile asbestos contents of such gaskets ranged from 55% to 60% by area, for those of sheet style and 5% by area, for the spiral wound metal/asbestos style. Despite the levels of effort required to effect gasket removals, the professional aircraft mechanic was not exposed to airborne asbestos fibers at the lower limits of sampling and analytical detection achieved;all of which were substantially less than the current Occupational Safety and Health Administration Permissible Exposure Limits for asbestos. The results of this testing indicate an absence of gasket related asbestos exposure risk to mechanics who work with light aircraft engines, including those having asbestos-containing gaskets. These results are consistent with the findings of Mlyarek and Van Orden who studied the asbestos exposure risk occasioned during overhaul of larger radial style reciprocating aircraft engines [1].展开更多
The reliability of industrial installation requires minimum leakage of pressurized sealed joints during operation. At the design stage, the leakage behavior of the gasket must be one of the most important parameter in...The reliability of industrial installation requires minimum leakage of pressurized sealed joints during operation. At the design stage, the leakage behavior of the gasket must be one of the most important parameter in the gasket selection. The objective of the work presented in this paper is to develop an analytical leak rate prediction methodology used in gasketed joints. A pseudo analytical-experimental innovative approach was used to estimate the characteristics of the porous structure for the purpose of predicting accurate leak rate through gaskets with different fluids under conditions similar to those of operation. The analytical model assumes the flow to be continuum but employs a slip boundary condition on the leak path wall to determine the porosity parameters of the gasket. The analytical model results are validated and confronted against experimental data which were conducted under various conditions of fluid media, pressure, gasket stress and temperature. Two experimental test rigs fully automate that accurately reproduces the real leakage behavior of the gasketed joint have been developed to analyze the mechanical and thermal effects on the gasket flow regime. The gas leaks were measured with multi-gas mass spectrometers while liquid leaks were measure using a sophisticated detection system based on the pressure rise method.展开更多
In this paper, we firstly define a decreasing sequence {Pn(S)} by the generation of the Sierpinski gasket where each Pn(S) can be obtained in finite steps. Then we prove that the Hausdorff measure Hs(S) of the Sierpin...In this paper, we firstly define a decreasing sequence {Pn(S)} by the generation of the Sierpinski gasket where each Pn(S) can be obtained in finite steps. Then we prove that the Hausdorff measure Hs(S) of the Sierpinski gasket S can be approximated by {Pn(S)} with Pn(S)/(l + l/2n-3)s≤Hs(S)≤ Pn(S). An algorithm is presented to get Pn(S) for n ≤5. As an application, we obtain the best lower bound of Hs(S) till now: Hs(S)≥0.5631.展开更多
A series of cranial nerve decompression gaskets were prepared with fibers of different fineness and high crimp which were obtained in knit-de-knit texturing process by using different specification general polyethylen...A series of cranial nerve decompression gaskets were prepared with fibers of different fineness and high crimp which were obtained in knit-de-knit texturing process by using different specification general polyethylene terepthalate( PET) multifilament bought from market. The physical properties of the gasket were evaluated comprehensively and biocompatibility was analyzed with MTT assay.展开更多
We study in this paper the path properties of the Brownian motion and super-Brownian motion on the fractal structure-the Sierpinski gasket. At first some results about the limiting behaviour of its increments are obta...We study in this paper the path properties of the Brownian motion and super-Brownian motion on the fractal structure-the Sierpinski gasket. At first some results about the limiting behaviour of its increments are obtained and a kind of law of iterated logarithm is proved. Then A Lower bound of the spreading speed of its corresponding super-Brownian motion is obtained.展开更多
Let {X(t),t greater than or equal to 0} be Brownian motion on the Sierpinski gasket, E is a compact subset of [0,+infinity). In this paper, we determine when X(E) has k-multiple points and when not. We also obtain the...Let {X(t),t greater than or equal to 0} be Brownian motion on the Sierpinski gasket, E is a compact subset of [0,+infinity). In this paper, we determine when X(E) has k-multiple points and when not. We also obtain the exact Hausdorff dimension of k-multiple times.展开更多
In this paper, using spectral decimation, we prove that the "hot spots" conjecture holds on a class of homogeneous hierarchical gaskets introduced by Hambly,i.e., every eigenfunction of the second-smallest e...In this paper, using spectral decimation, we prove that the "hot spots" conjecture holds on a class of homogeneous hierarchical gaskets introduced by Hambly,i.e., every eigenfunction of the second-smallest eigenvalue of the Neumann Laplacian(introduced by Kigami) attains its maximum and minimum on the boundary.展开更多
On a homogeneous hierarchical gasket we give a linear extension method to compute the energy measures of harmonic functions with respect to the standard energy.
This paper is focused on finite element simulation of cylinder head gaskets.Finite element codes support several methodologies,each of which has its own strengths and weaknesses.One of the key points lies in the influ...This paper is focused on finite element simulation of cylinder head gaskets.Finite element codes support several methodologies,each of which has its own strengths and weaknesses.One of the key points lies in the influence of the gasket geometry on its final behaviour.Such a contribution can come from the detailed modelling of the gasket or by defining a global non-linear behaviour in which material and geometry non-linearities are summarised.Two approaches were used to simulate the gasket behaviour.The first one consists in using a 2D approach,which allows to model through-thickness non-linear behaviour of gasket.The second one consists in using conventional 3D finite element modelling.The numerical methods have been discussed and compared in relation to the accordance with experimental data,amount of information supplied and computational time required.Finally,a parametric study shows how some geometric parameters influence the compressive load and the elastic recovery of a single-layer steel gasket.展开更多
Taking the combustor composite structure of a high-strength diesel engine as the main research object,dedicated tests have been conducted to verify the accuracy of three distinct cylinder gasket pressure simulation mo...Taking the combustor composite structure of a high-strength diesel engine as the main research object,dedicated tests have been conducted to verify the accuracy of three distinct cylinder gasket pressure simulation models.Using the measured cylinder gasket compression rebound curve,a gasket unit has been designed and manufactured.For this unit,the influence of the bolt pretension,cylinder body and cylinder head material on gasket sealing pressure has been investigated systematically in conditions of thermo-mechanical coupling.The results show that the bolt pretension force is one of the most important factors affecting the cylinder gasket sealing pressure.The change of the body material has little effect on this pressure.The cylinder gasket seal pressure decreases progressively with the reduction of the elastic module of the cylinder head material.展开更多
文摘We have previously evaluated asbestos exposure associated with various maintenance procedures on light aircraft. The purpose of this study was to evaluate asbestos exposure during engine maintenance on light aircraft. This test was designed to evaluate the potential for asbestos exposure to mechanics and others who remove asbestos-containing engine gaskets from reciprocating style aircraft engines. Utilized in this test was an air cooled, horizontally opposed, aviation gasoline burning engine, assembled during 1986 and operated intermittently up into 2015, having accumulated 1680 hours run time. Nearly 75% of the asbestos-containing gaskets installed during 1986 were still in place at the time of testing. Chrysotile asbestos contents of such gaskets ranged from 55% to 60% by area, for those of sheet style and 5% by area, for the spiral wound metal/asbestos style. Despite the levels of effort required to effect gasket removals, the professional aircraft mechanic was not exposed to airborne asbestos fibers at the lower limits of sampling and analytical detection achieved;all of which were substantially less than the current Occupational Safety and Health Administration Permissible Exposure Limits for asbestos. The results of this testing indicate an absence of gasket related asbestos exposure risk to mechanics who work with light aircraft engines, including those having asbestos-containing gaskets. These results are consistent with the findings of Mlyarek and Van Orden who studied the asbestos exposure risk occasioned during overhaul of larger radial style reciprocating aircraft engines [1].
文摘The reliability of industrial installation requires minimum leakage of pressurized sealed joints during operation. At the design stage, the leakage behavior of the gasket must be one of the most important parameter in the gasket selection. The objective of the work presented in this paper is to develop an analytical leak rate prediction methodology used in gasketed joints. A pseudo analytical-experimental innovative approach was used to estimate the characteristics of the porous structure for the purpose of predicting accurate leak rate through gaskets with different fluids under conditions similar to those of operation. The analytical model assumes the flow to be continuum but employs a slip boundary condition on the leak path wall to determine the porosity parameters of the gasket. The analytical model results are validated and confronted against experimental data which were conducted under various conditions of fluid media, pressure, gasket stress and temperature. Two experimental test rigs fully automate that accurately reproduces the real leakage behavior of the gasketed joint have been developed to analyze the mechanical and thermal effects on the gasket flow regime. The gas leaks were measured with multi-gas mass spectrometers while liquid leaks were measure using a sophisticated detection system based on the pressure rise method.
文摘In this paper, we firstly define a decreasing sequence {Pn(S)} by the generation of the Sierpinski gasket where each Pn(S) can be obtained in finite steps. Then we prove that the Hausdorff measure Hs(S) of the Sierpinski gasket S can be approximated by {Pn(S)} with Pn(S)/(l + l/2n-3)s≤Hs(S)≤ Pn(S). An algorithm is presented to get Pn(S) for n ≤5. As an application, we obtain the best lower bound of Hs(S) till now: Hs(S)≥0.5631.
文摘A series of cranial nerve decompression gaskets were prepared with fibers of different fineness and high crimp which were obtained in knit-de-knit texturing process by using different specification general polyethylene terepthalate( PET) multifilament bought from market. The physical properties of the gasket were evaluated comprehensively and biocompatibility was analyzed with MTT assay.
文摘We study in this paper the path properties of the Brownian motion and super-Brownian motion on the fractal structure-the Sierpinski gasket. At first some results about the limiting behaviour of its increments are obtained and a kind of law of iterated logarithm is proved. Then A Lower bound of the spreading speed of its corresponding super-Brownian motion is obtained.
文摘Let {X(t),t greater than or equal to 0} be Brownian motion on the Sierpinski gasket, E is a compact subset of [0,+infinity). In this paper, we determine when X(E) has k-multiple points and when not. We also obtain the exact Hausdorff dimension of k-multiple times.
基金supported in part by NSFC grants Nos.11271327, 11771391
文摘In this paper, using spectral decimation, we prove that the "hot spots" conjecture holds on a class of homogeneous hierarchical gaskets introduced by Hambly,i.e., every eigenfunction of the second-smallest eigenvalue of the Neumann Laplacian(introduced by Kigami) attains its maximum and minimum on the boundary.
基金supported by the National Natural Science Foundation of China (No. 11201232)333 Project of Jiangsu Province
文摘On a homogeneous hierarchical gasket we give a linear extension method to compute the energy measures of harmonic functions with respect to the standard energy.
文摘This paper is focused on finite element simulation of cylinder head gaskets.Finite element codes support several methodologies,each of which has its own strengths and weaknesses.One of the key points lies in the influence of the gasket geometry on its final behaviour.Such a contribution can come from the detailed modelling of the gasket or by defining a global non-linear behaviour in which material and geometry non-linearities are summarised.Two approaches were used to simulate the gasket behaviour.The first one consists in using a 2D approach,which allows to model through-thickness non-linear behaviour of gasket.The second one consists in using conventional 3D finite element modelling.The numerical methods have been discussed and compared in relation to the accordance with experimental data,amount of information supplied and computational time required.Finally,a parametric study shows how some geometric parameters influence the compressive load and the elastic recovery of a single-layer steel gasket.
基金the Medium and Heavy Duty High Power-Density Clean Energy Power of National 863 Project。
文摘Taking the combustor composite structure of a high-strength diesel engine as the main research object,dedicated tests have been conducted to verify the accuracy of three distinct cylinder gasket pressure simulation models.Using the measured cylinder gasket compression rebound curve,a gasket unit has been designed and manufactured.For this unit,the influence of the bolt pretension,cylinder body and cylinder head material on gasket sealing pressure has been investigated systematically in conditions of thermo-mechanical coupling.The results show that the bolt pretension force is one of the most important factors affecting the cylinder gasket sealing pressure.The change of the body material has little effect on this pressure.The cylinder gasket seal pressure decreases progressively with the reduction of the elastic module of the cylinder head material.
