Transmission of elastic waves through a micro gap between two solids with consideration of frictional contact is investigated. By using the Fourier analysis technique and the corrective solution method, the nonlinear ...Transmission of elastic waves through a micro gap between two solids with consideration of frictional contact is investigated. By using the Fourier analysis technique and the corrective solution method, the nonlinear boundary problem is reduced to a set of algebraic equations. Numerical results exhibit the locations and extents of separation, slip, and stick zones, the interface tractions, and the energy partition. The effects of gap width, frictional coefficients, and the incident angle on the wave transmission are discussed in detail. The results show that higher harmonics are generated due to the local contact/slip at the interface.展开更多
Arc pressure is the key influencing factor to forming of molten pool. Countering the characteristic of tungsten inert gas arc welding with micro gap for tantalum sheet, according to the fundament of arc physics, a dis...Arc pressure is the key influencing factor to forming of molten pool. Countering the characteristic of tungsten inert gas arc welding with micro gap for tantalum sheet, according to the fundament of arc physics, a distribution model of arc pressure and forming mechanism of molten pool with micro butt gap are proposed, and the influences of arc pressure on forming of molten pool are discussed. Experimental researches for the dynamic formation process of weld molten pool by using high-speed vidicon camera show that when butt gap is appropriate, that is from 0. 1 to 0. 15 mm, molten metals formed on two workpiece uplift and grow up first, then are fused and form uniform molten pool finally.展开更多
A pilot-scale experiment of 20t/h for the treatment of ship＇s ballast water is reported in this paper. When the concentration of the dissolved OH. was 0.68 mg/L during the experiment, the rate of destroying bacteria,...A pilot-scale experiment of 20t/h for the treatment of ship＇s ballast water is reported in this paper. When the concentration of the dissolved OH. was 0.68 mg/L during the experiment, the rate of destroying bacteria, mono-algae, protozoan reached 100% within 2.67 s. The effect of hydroxyl radicals on biochemical processes was also studied. The attenuation rate of photosynthesis pigment was 100%. And the main reason for the cells＇ death was the strong destruction of the monose, amylose, protein, DNA and RNA in the cells. As an advanced oxidation method, the procedure can destroy invasive marine species when a ship is in the process of discharging its ballast water.展开更多
To understand the discharge characteristics under a gap of micrometers,the breakdown voltage and current–voltage curve are measured experimentally in a needle-to-plate electrode at a microscale gap of 3–50 μm in ai...To understand the discharge characteristics under a gap of micrometers,the breakdown voltage and current–voltage curve are measured experimentally in a needle-to-plate electrode at a microscale gap of 3–50 μm in air.The effect of the needle radius and the gas pressure on the discharge characteristics are tested.The results show that when the gap is larger than 10 μm,the relation between the breakdown voltage and the gap looks like the Paschen curve;while below 10 μm,the breakdown voltage is nearly constant in the range of the tested gap.However,at the same gap distance,the breakdown voltage is still affected by the pressure and shows a trend similar to Paschen＇s law.The current–voltage characteristic in all the gaps is similar and follows the trend of a typical Townsend-to-glow discharge.A simple model is used to explain the non-normality of breakdown in the micro-gaps.The Townsend mechanism is suggested to control the breakdown process in this configuration before the gap reduces much smaller in air.展开更多
With the physical method of micro-gap gas discharge, OH. radicals were produced by the ionization of O2 in air and H2O in the gaseous state, in order to explore more effective method totreat the ship＇s ballast water....With the physical method of micro-gap gas discharge, OH. radicals were produced by the ionization of O2 in air and H2O in the gaseous state, in order to explore more effective method totreat the ship＇s ballast water. The surface morphology of Al2O3 dielectric layer was analysed using Atomic Force Microscopy （AFM）, where the size of Al2O3 particles was in the range of 2 μm to 5 μm. At the same time, the biochemical effect of hydroxyl radicals on the introduced organisms and the quality of ship＇s ballast water were studied. The results indicate that the main reasons of cell death are lipid peroxide and damage of the antioxidant enzyme system in Catalase （CAT）, Peroxidase （POD） and Superoxide dismutase （SOD）. In addition, the quality of the ballast water was greatly improved.展开更多
OBJECTIVE To investigate the effect of gap junctions on the anti-tumor function induced by mi R-34a in glioma U87 cells.METHODS 1.Transfection(miR-34a mimics were transfected into glioma cells to upregulate their expr...OBJECTIVE To investigate the effect of gap junctions on the anti-tumor function induced by mi R-34a in glioma U87 cells.METHODS 1.Transfection(miR-34a mimics were transfected into glioma cells to upregulate their expression);2.Co-culture assay(U87cells were transfected with mi R-34a co-cultured with U87 cells that was transfected PCMV-eG FP plasmid);3.Flow cytometry analysis(select the e GFP labed U87 cells);4.RNA isolation and real-time PCR;5.CCK-8 assay;6.Western blotting.RESULTS Mi R-34a mimics transfered between the U87 cells.Parachute assay showed that GJ inhibition(CBX and 18-α-GA)can decrease mi R-34a expression than co-culture group.RA and galanglin enhanced mi R-34a expression than co-culture group.Mi R-34a relative expression reduced after co-culture,while gap junctions composed of Cx43 were down-regulated by sh RNA.Transfected with mi R-34a mimics reduced the survival of U87 cells in a dose-dependent manner.To more specifically establish the role of GJIC in mi R-34a induced growth inhibition of U87 cells,si RNA was used to knockdown the expression of Cx43,the dominant connexin expressed in U87 cells.CCK-8 assay showed that siR NAs have no effect on cell growth,but they could aggravate the growth inhibition of miR-34a to U87 cels.CONCLUSION Gap junctions enhance the antiproliferative effect of miR NA-34a in glioma cells.展开更多
Based on the phenomena that the deformation gap was observed before the great Tangshang earthquake, this paper discusses the strain gap according to test and theory. The (strain) patterns were recorded photographicall...Based on the phenomena that the deformation gap was observed before the great Tangshang earthquake, this paper discusses the strain gap according to test and theory. The (strain) patterns were recorded photographically by real-time holographic interferometry and shadow optical method of caustics, as soon as the loading process started. In the meantime, the AE (acoustic emission) signals were recorded by a micro crack information storage-analysis sys-tem. According to damage theory and location of micro fracture, we have studied the stain gap and gained: a) It is necessary that strain gap appears under the condition of linear elasticity theory, and its situation is relatively stable, corresponding to stress concentration. b) Micro fractures, which appear initially at area of high stress, occur rarely at the strain gap, and their locations are finally in the zone between the stress concentration area and the strain gap, which indicate the clusters or groups. However, the major macro fracture (final rupture) started from the shadow areas, and then grew quickly towards the strain gaps, which resulted in failure of sample.展开更多
The objective of this work research is to investigate the potential of using metallic powder mixed with electrical discharge machining (EDM) dielectric when machining hard electrically conductive materials. Nowadays, ...The objective of this work research is to investigate the potential of using metallic powder mixed with electrical discharge machining (EDM) dielectric when machining hard electrically conductive materials. Nowadays, the development of industries requires hard materials for various applications. Machining the hard materials using the traditional processes lead to tool break and poor machined product. Even<span style="font-family:Verdana;"> when</span><span style="font-family:Verdana;"> the conventional EDM can machine hard material as long as it </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> electrically conductive materials, the machined parts still present drawbacks. Metallic powder mixed with EDM dielectric (PMEDM) was hypothesized to improve the machined part. The presence of metallic powder ensures uniform distribution of spark and the electrical density of the spark decreases which reduces craters, cracks and voids on machined surface. The transfer and deposit of alloying elements during powder mixed electrical discharge machining improve the machined surface properties particularly micro-hardness and fatigue. Discharge current (IP), gap voltage (GapV), ON-time (ON) and aluminum powder are selected as machined variable parameters and the output responses are fatigue performance, micro-hardness and surface topography. The workpiece material selected </span><span style="font-family:Verdana;">is </span><span style="font-family:Verdana;">molybdenum high speed steel. Micro-hardness was determined using micro-hardness tester device. The fatigue performance was determined using empirical equation. Analysis of material transfer was done using energy dispersive spectroscopy (EDS) attached to FESEM. EDS analysis involves the generation of an X-ray spectrum from the entire scan area of the SEM. The use of PMEDM improve</span><span style="font-family:Verdana;">d</span><span style="font-family:Verdana;"> the fatigue, the micro-harness and the machined surface morphology as the above-mentioned parameters increased.</span>展开更多
基金Project supported by the National Natural Science Foundation of China(No.10772022)
文摘Transmission of elastic waves through a micro gap between two solids with consideration of frictional contact is investigated. By using the Fourier analysis technique and the corrective solution method, the nonlinear boundary problem is reduced to a set of algebraic equations. Numerical results exhibit the locations and extents of separation, slip, and stick zones, the interface tractions, and the energy partition. The effects of gap width, frictional coefficients, and the incident angle on the wave transmission are discussed in detail. The results show that higher harmonics are generated due to the local contact/slip at the interface.
文摘Arc pressure is the key influencing factor to forming of molten pool. Countering the characteristic of tungsten inert gas arc welding with micro gap for tantalum sheet, according to the fundament of arc physics, a distribution model of arc pressure and forming mechanism of molten pool with micro butt gap are proposed, and the influences of arc pressure on forming of molten pool are discussed. Experimental researches for the dynamic formation process of weld molten pool by using high-speed vidicon camera show that when butt gap is appropriate, that is from 0. 1 to 0. 15 mm, molten metals formed on two workpiece uplift and grow up first, then are fused and form uniform molten pool finally.
基金The project supported by Key Project of National Foundation Research under the Ministry of Science and Technology of China(2002CCC00900) General Project of the National Natural Science Foundation of China (No. 60371035) and Project under the SocialDevelopment Program of Dalian City (2004B3SF181)
文摘A pilot-scale experiment of 20t/h for the treatment of ship＇s ballast water is reported in this paper. When the concentration of the dissolved OH. was 0.68 mg/L during the experiment, the rate of destroying bacteria, mono-algae, protozoan reached 100% within 2.67 s. The effect of hydroxyl radicals on biochemical processes was also studied. The attenuation rate of photosynthesis pigment was 100%. And the main reason for the cells＇ death was the strong destruction of the monose, amylose, protein, DNA and RNA in the cells. As an advanced oxidation method, the procedure can destroy invasive marine species when a ship is in the process of discharging its ballast water.
基金supported by National Natural Science Foundation of China(11475019)the Electrostatic Research Foundation of Liu Shanghe Academicians and Experts Workstation,Beijing Orient Institute of Measurement and Test(BOIMTLSHJD20161002)
文摘To understand the discharge characteristics under a gap of micrometers,the breakdown voltage and current–voltage curve are measured experimentally in a needle-to-plate electrode at a microscale gap of 3–50 μm in air.The effect of the needle radius and the gas pressure on the discharge characteristics are tested.The results show that when the gap is larger than 10 μm,the relation between the breakdown voltage and the gap looks like the Paschen curve;while below 10 μm,the breakdown voltage is nearly constant in the range of the tested gap.However,at the same gap distance,the breakdown voltage is still affected by the pressure and shows a trend similar to Paschen＇s law.The current–voltage characteristic in all the gaps is similar and follows the trend of a typical Townsend-to-glow discharge.A simple model is used to explain the non-normality of breakdown in the micro-gaps.The Townsend mechanism is suggested to control the breakdown process in this configuration before the gap reduces much smaller in air.
基金supported by the Key Project of National Support Plan from Science and Technology Ministry of China （2006BAC11B06） the Key Project of International Cooperation from the Ministry of Science and Technology of China （2005DFA20800）+1 种基金the Support Plan of National New Century Excellent Youth of China （NCET-04-0286, -05-0398） the Project of National Natural Science Foundation of China （No. 60371035）
文摘With the physical method of micro-gap gas discharge, OH. radicals were produced by the ionization of O2 in air and H2O in the gaseous state, in order to explore more effective method totreat the ship＇s ballast water. The surface morphology of Al2O3 dielectric layer was analysed using Atomic Force Microscopy （AFM）, where the size of Al2O3 particles was in the range of 2 μm to 5 μm. At the same time, the biochemical effect of hydroxyl radicals on the introduced organisms and the quality of ship＇s ballast water were studied. The results indicate that the main reasons of cell death are lipid peroxide and damage of the antioxidant enzyme system in Catalase （CAT）, Peroxidase （POD） and Superoxide dismutase （SOD）. In addition, the quality of the ballast water was greatly improved.
基金The project supported by National Natural Science Foundation of China(81473234)
文摘OBJECTIVE To investigate the effect of gap junctions on the anti-tumor function induced by mi R-34a in glioma U87 cells.METHODS 1.Transfection(miR-34a mimics were transfected into glioma cells to upregulate their expression);2.Co-culture assay(U87cells were transfected with mi R-34a co-cultured with U87 cells that was transfected PCMV-eG FP plasmid);3.Flow cytometry analysis(select the e GFP labed U87 cells);4.RNA isolation and real-time PCR;5.CCK-8 assay;6.Western blotting.RESULTS Mi R-34a mimics transfered between the U87 cells.Parachute assay showed that GJ inhibition(CBX and 18-α-GA)can decrease mi R-34a expression than co-culture group.RA and galanglin enhanced mi R-34a expression than co-culture group.Mi R-34a relative expression reduced after co-culture,while gap junctions composed of Cx43 were down-regulated by sh RNA.Transfected with mi R-34a mimics reduced the survival of U87 cells in a dose-dependent manner.To more specifically establish the role of GJIC in mi R-34a induced growth inhibition of U87 cells,si RNA was used to knockdown the expression of Cx43,the dominant connexin expressed in U87 cells.CCK-8 assay showed that siR NAs have no effect on cell growth,but they could aggravate the growth inhibition of miR-34a to U87 cels.CONCLUSION Gap junctions enhance the antiproliferative effect of miR NA-34a in glioma cells.
基金The Dual Project of China Seismological Bureau (9691309020301) the Specialized Funds for National Key Basic Study (G1998040704) the project for the MOST under contract (2001BA601B02) and Youth Funds for applied basic study of the Science and Technolo
文摘Based on the phenomena that the deformation gap was observed before the great Tangshang earthquake, this paper discusses the strain gap according to test and theory. The (strain) patterns were recorded photographically by real-time holographic interferometry and shadow optical method of caustics, as soon as the loading process started. In the meantime, the AE (acoustic emission) signals were recorded by a micro crack information storage-analysis sys-tem. According to damage theory and location of micro fracture, we have studied the stain gap and gained: a) It is necessary that strain gap appears under the condition of linear elasticity theory, and its situation is relatively stable, corresponding to stress concentration. b) Micro fractures, which appear initially at area of high stress, occur rarely at the strain gap, and their locations are finally in the zone between the stress concentration area and the strain gap, which indicate the clusters or groups. However, the major macro fracture (final rupture) started from the shadow areas, and then grew quickly towards the strain gaps, which resulted in failure of sample.
文摘The objective of this work research is to investigate the potential of using metallic powder mixed with electrical discharge machining (EDM) dielectric when machining hard electrically conductive materials. Nowadays, the development of industries requires hard materials for various applications. Machining the hard materials using the traditional processes lead to tool break and poor machined product. Even<span style="font-family:Verdana;"> when</span><span style="font-family:Verdana;"> the conventional EDM can machine hard material as long as it </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> electrically conductive materials, the machined parts still present drawbacks. Metallic powder mixed with EDM dielectric (PMEDM) was hypothesized to improve the machined part. The presence of metallic powder ensures uniform distribution of spark and the electrical density of the spark decreases which reduces craters, cracks and voids on machined surface. The transfer and deposit of alloying elements during powder mixed electrical discharge machining improve the machined surface properties particularly micro-hardness and fatigue. Discharge current (IP), gap voltage (GapV), ON-time (ON) and aluminum powder are selected as machined variable parameters and the output responses are fatigue performance, micro-hardness and surface topography. The workpiece material selected </span><span style="font-family:Verdana;">is </span><span style="font-family:Verdana;">molybdenum high speed steel. Micro-hardness was determined using micro-hardness tester device. The fatigue performance was determined using empirical equation. Analysis of material transfer was done using energy dispersive spectroscopy (EDS) attached to FESEM. EDS analysis involves the generation of an X-ray spectrum from the entire scan area of the SEM. The use of PMEDM improve</span><span style="font-family:Verdana;">d</span><span style="font-family:Verdana;"> the fatigue, the micro-harness and the machined surface morphology as the above-mentioned parameters increased.</span>
