The relationship between observed early teeth wearing in cattle and the existence of large areas where excess nuoride in underground water prevails in Argentina, but has never been studied. Average values of bone fluo...The relationship between observed early teeth wearing in cattle and the existence of large areas where excess nuoride in underground water prevails in Argentina, but has never been studied. Average values of bone fluoride exceeding 5000 ppm and well water containing up to 10.5 ppm of this element were found in a farm (ETWF) where early teeth wearing is observed, while in a control farm (NETWF), those values were 1480 ppm and 3.0 ppm respectively. Urine samples from animals from the ETWF contained almost 4 times more fluoride than those from the latter.Forage in both farms contained about the same levels of fluoride (15 to 25 ppm). None of the farms was exPosed to industrial, volcanic, or geothermal activity. Lactating and adult animals were transferred from one farm to the other. After 30 months, adult animals from the NETWF showed no damage in teeth, while adults from the ETWF continued a rapid teeth wearing. Young animals from the NETWF developed severely damaged permanent teeth, while young animals from the ETWF developed normal teeth. We concluded that the problem exists in the ETWF and being a standard farm, the condition could be extrapolated to other areas展开更多
Several criteria for barrel lifetime were summarized and discussed. Based on large amount of test data,the advantages and disadvantages of the criteria were analyzed and the requirements for the easy and practical cri...Several criteria for barrel lifetime were summarized and discussed. Based on large amount of test data,the advantages and disadvantages of the criteria were analyzed and the requirements for the easy and practical criterion were put forward. Then,a new criterion based on the radical wear at the start points of the barrel lands was proposed. The close interrelationship between the radical wear and interior ballistic characteristics was illuminated theoretically and experimentally. The research results show the great value of this criterion to solve the problem of barrel lifetime.展开更多
The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination. Polycrystalline diamond （PCD） tools with different grain s...The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination. Polycrystalline diamond （PCD） tools with different grain sizes and geometries, and carbide tools with and without coatings were used in the experiments. Milling forces, milling temperatures, tool lifetimes, tool wear, and machined surface integrities were investigated. The PCD tool required a primary cutting force 15 % smaller than that of the carbide tool, while the uncoated carbide tool required a primary cutting force 10% higher than that of the TiA1N-eoated tool. A cutting force of 300 N per millimeter of the cutting edge （300 N/mm） was measured. This caused excessive tool chipping. The cutting temperature of the PCD tool was 20%-30% lower than that of the carbide tool, while that of the TiA1N-coated tool was 12% lower than that of the uncoated carbide tool. The cutting temperatures produced when using water-based cooling and minimal quantity lubrication （MQL） were reduced by 100 ~C and 200 ~C, compared with those recorded with dry cutting, respectively. In general, the PCD tool lifetimes were 2--3 times longer than the carbide tool lifetimes. The roughness Ra of the machined surface was less than 0.6μm, and the depth of the machined surface hardened layer was in the range of 0.15-0.25 mm for all of the PCD tools before a flank wear land of 0.2 mm was reached. The PCD tool with a 0.8 mm tool nose radius, 0% rake angle, 10% flank angle, and grain size of （30＋2） μm exhibited the best cutting performance. For this specific tool, a lifetime of 16 rain can be expected.展开更多
文摘The relationship between observed early teeth wearing in cattle and the existence of large areas where excess nuoride in underground water prevails in Argentina, but has never been studied. Average values of bone fluoride exceeding 5000 ppm and well water containing up to 10.5 ppm of this element were found in a farm (ETWF) where early teeth wearing is observed, while in a control farm (NETWF), those values were 1480 ppm and 3.0 ppm respectively. Urine samples from animals from the ETWF contained almost 4 times more fluoride than those from the latter.Forage in both farms contained about the same levels of fluoride (15 to 25 ppm). None of the farms was exPosed to industrial, volcanic, or geothermal activity. Lactating and adult animals were transferred from one farm to the other. After 30 months, adult animals from the NETWF showed no damage in teeth, while adults from the ETWF continued a rapid teeth wearing. Young animals from the NETWF developed severely damaged permanent teeth, while young animals from the ETWF developed normal teeth. We concluded that the problem exists in the ETWF and being a standard farm, the condition could be extrapolated to other areas
文摘Several criteria for barrel lifetime were summarized and discussed. Based on large amount of test data,the advantages and disadvantages of the criteria were analyzed and the requirements for the easy and practical criterion were put forward. Then,a new criterion based on the radical wear at the start points of the barrel lands was proposed. The close interrelationship between the radical wear and interior ballistic characteristics was illuminated theoretically and experimentally. The research results show the great value of this criterion to solve the problem of barrel lifetime.
基金supported by the National Natural Science Foundation of China(No.51275227)the Funding of Jiangsu Innovation Program for Graduate Education(No.CXLX11_0175)the Shanghai Aerospace Science and Technology Innovation Fund(No.SAST201326)
文摘The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination. Polycrystalline diamond （PCD） tools with different grain sizes and geometries, and carbide tools with and without coatings were used in the experiments. Milling forces, milling temperatures, tool lifetimes, tool wear, and machined surface integrities were investigated. The PCD tool required a primary cutting force 15 % smaller than that of the carbide tool, while the uncoated carbide tool required a primary cutting force 10% higher than that of the TiA1N-eoated tool. A cutting force of 300 N per millimeter of the cutting edge （300 N/mm） was measured. This caused excessive tool chipping. The cutting temperature of the PCD tool was 20%-30% lower than that of the carbide tool, while that of the TiA1N-coated tool was 12% lower than that of the uncoated carbide tool. The cutting temperatures produced when using water-based cooling and minimal quantity lubrication （MQL） were reduced by 100 ~C and 200 ~C, compared with those recorded with dry cutting, respectively. In general, the PCD tool lifetimes were 2--3 times longer than the carbide tool lifetimes. The roughness Ra of the machined surface was less than 0.6μm, and the depth of the machined surface hardened layer was in the range of 0.15-0.25 mm for all of the PCD tools before a flank wear land of 0.2 mm was reached. The PCD tool with a 0.8 mm tool nose radius, 0% rake angle, 10% flank angle, and grain size of （30＋2） μm exhibited the best cutting performance. For this specific tool, a lifetime of 16 rain can be expected.
