研究表明,中酸性岩浆岩(包括 SiO_2>56%的中酸性火山岩和侵入岩)的 Sr 和 Yb 是两个非常有意义的地球化学指标,如果大致按照 Sr=400×10^(-6)和 Yb=2×10^(-6)为标志,可以划分出4类花岗岩,即:高 Sr 低 Yb(Sr>400×10^...研究表明,中酸性岩浆岩(包括 SiO_2>56%的中酸性火山岩和侵入岩)的 Sr 和 Yb 是两个非常有意义的地球化学指标,如果大致按照 Sr=400×10^(-6)和 Yb=2×10^(-6)为标志,可以划分出4类花岗岩,即:高 Sr 低 Yb(Sr>400×10^(-6),Yb<2×10^(-6))、低 Sr 低 Yb(Sr<400×10^(-6),Yb<2×10^(-6))、低 Sr 高 Yb(Sr<400×10^(-6),Yb>2×10^(-6))和高 Sr 高 Yb(Sr>400×10^(-6),Yb>2×10^(-6))型花岗岩。其中,从低 Sr 高 Yb 型中还可以分出非常低 Sr 高 Yb(Sr<100×10^(-6),Yb>2×10^(-6))的一类。因此,按照 Sr 和 Yb 含量的不同,可以将花岗岩分为5类,文中着重探讨了这5类花岗岩形成的源区深度问题,指出按照残留相组成和花岗岩地球化学特征,可以将花岗岩形成的压力分为3或4个级别:即:(1)高压下与石榴石平衡的花岗岩具有高 Sr 低Yb 的特征;(2)在中等或较高压力、麻粒岩相(由斜长石+石榴石+角闪石+辉石组成)条件下,花岗岩具低 Sr 低 Yb 或高 Sr 高 Yb 的特点(取决于原岩成分);(3)低压下,残留相有斜长石无石榴石(角闪岩相),花岗岩为低 Sr 高 Yb 类型的;(4)与蛇绿岩有关的在洋壳剖面浅部由辉长岩部分熔融形成的 M 型花岗岩,具有非常低 Sr 高 Yb 的特点,形成深度约2～5km,可能是非常低压条件下形成的。研究表明,淡色花岗岩大多分布在低 Sr 低 Yb 区,部分正长岩和钾玄岩分布在高 Sr 高 Yb 区。藏南淡色花岗岩可能形成的压力较高。文中探讨了岩浆与深度的关系,得出了一些初步的认识,指出需要进一步研究的问题。为了得到经得起考验的结论,还需要更多资料的积累,更多理论的探讨和更多实验的佐证。展开更多
The three-dimensional unsteady turbulent flow in axial-flow pumps was simulated based on Navier-Stoke solver embedded with k - ε RNG turbulence model and SIMPLEC algorithm. Numerical results show that the unsteady pr...The three-dimensional unsteady turbulent flow in axial-flow pumps was simulated based on Navier-Stoke solver embedded with k - ε RNG turbulence model and SIMPLEC algorithm. Numerical results show that the unsteady prediction results are more accurate than the steady results, and the maximal error of unsteady prediction is only 4.54%. The time-domain spectrums show that the static pressure fluctuation curves at the inlet and outlet of the rotor and the outlet of the stator are periodic, and all have four peaks and four valleys. The pressure fluctuation amplitude increases from the hub to the tip at the inlet and outlet of the rotor, but decreases at the outlet of the stator. The pressure fluctuation amplitude is the greatest at the inlet of the rotor, and the average amplitude decreases sharply from the inlet to the outlet. The frequency spectrums obtained by Fast Fourier Transform （FFT） show that the dominant frequency is approximately equal to the blade passing frequency. The static pressure on the pressure side of hydrofoil on different stream surfaces remains almost consistent, and increases gradually from the blade inlet to the exit on the suction side at different time steps. The axial velocity distribution is periodic and is affected by the stator blade number at the rotor exit. The experimental results show that the flow is almost axial and the pre-rotation is very small at the rotor inlet under the conditions of 0.8 QN -1.2 QN Due to the clearance leakage, the pressure, circulation and meridional velocity at the rotor outlet all decrease near the hub leakage and tip clearance regions.展开更多
Dynamic properties of rocks are important in a variety of rock mechanics and rock engineering problems. Due to the transient nature of the loading, dynamic tests of rock materials are very different from and much more...Dynamic properties of rocks are important in a variety of rock mechanics and rock engineering problems. Due to the transient nature of the loading, dynamic tests of rock materials are very different from and much more challenging than their static counterparts. Dynamic tests are usually conducted using the split Hopkinson bar or Kolsl^j bar systems, which include both split Hopkinson pressure bar （SHPB） and split Hopkinson tension bar （SHTB） systems. Significant progress has been made on the quantification of various rock dynamic properties, owing to the advances in the experimental techniques of SHPB system. This review aims to fully describe and critically assess the detailed procedures and principles of tech- niques for dynamic rock tests using split Hopkinson bars. The history and principles of SHPB are outlined, followed by the key loading techniques that are useful for dynamic rock tests with SHPB （i.e. pulse shaping, momentum-trap and multi-axial loading techniques）. Various measurement techniques for rock tests in SHPB （i.e. X-ray micro computed tomography （CT）, laser gap gauge （LGG）, digital image corre- lation （DIC）, Moir~ method, caustics method, photoelastic coating method, dynamic infrared thermog- raphy） are then discussed. As the main objective of the review, various dynamic measurement techniques for rocks using SHPB are described, including dynamic rock strength measurements （i.e. dynamic compression, tension, bending and shear tests）, dynamic fracture measurements （i.e. dynamic imitation and propagation fracture toughness, dynamic fracture energy and fracture velocity）, and dy- namic techniques for studying the influences of temperature and pore water.展开更多
Acute pancreatitis is an inflammatory disease of the pancreas.The etiology and pathogenesis of acute pancreatitis have been intensively investigated for centuries worldwide.Many causes of acute pancreatitis have been ...Acute pancreatitis is an inflammatory disease of the pancreas.The etiology and pathogenesis of acute pancreatitis have been intensively investigated for centuries worldwide.Many causes of acute pancreatitis have been discovered,but the pathogenetic theories are controversial.The most common cause of acute pancreatitis is gallstone impacting the distal common bile-pancreatic duct.The majority ofinvestigators accept that the main factors for acute billiary pancreatitis are pancreatic hyperstimulation and bile-pancreatic duct obstruction which increase pancreatic duct pressure and active trypsin reflux.Acute pancreatitis occurs when intracellular protective mechanisms to prevent trypsinogen activation or reduce trypsin activity are overwhelmed.However,little is known about the other acute pancreatitis.We hypothesize that acute biliary pancreatitis and other causes of acute pancreatitis possess a common pathogenesis.Pancreatic hyperstimulation and pancreatic duct obstruction increase pancreatic duct pressure,active trypsin reflux,and subsequent unregulated activation of trypsin within pancreatic acinar cells.Enzyme activation within the pancreas leads to auto-digestion of the gland and local inflammation.Once the hypothesis is confirmed,traditional therapeutic strategies against acute pancreatitis may be improved.Decompression of pancreatic duct pressure should be advocated in the treatment of acute pancreatitits which may greatly improve its outcome.展开更多
文摘研究表明,中酸性岩浆岩(包括 SiO_2>56%的中酸性火山岩和侵入岩)的 Sr 和 Yb 是两个非常有意义的地球化学指标,如果大致按照 Sr=400×10^(-6)和 Yb=2×10^(-6)为标志,可以划分出4类花岗岩,即:高 Sr 低 Yb(Sr>400×10^(-6),Yb<2×10^(-6))、低 Sr 低 Yb(Sr<400×10^(-6),Yb<2×10^(-6))、低 Sr 高 Yb(Sr<400×10^(-6),Yb>2×10^(-6))和高 Sr 高 Yb(Sr>400×10^(-6),Yb>2×10^(-6))型花岗岩。其中,从低 Sr 高 Yb 型中还可以分出非常低 Sr 高 Yb(Sr<100×10^(-6),Yb>2×10^(-6))的一类。因此,按照 Sr 和 Yb 含量的不同,可以将花岗岩分为5类,文中着重探讨了这5类花岗岩形成的源区深度问题,指出按照残留相组成和花岗岩地球化学特征,可以将花岗岩形成的压力分为3或4个级别:即:(1)高压下与石榴石平衡的花岗岩具有高 Sr 低Yb 的特征;(2)在中等或较高压力、麻粒岩相(由斜长石+石榴石+角闪石+辉石组成)条件下,花岗岩具低 Sr 低 Yb 或高 Sr 高 Yb 的特点(取决于原岩成分);(3)低压下,残留相有斜长石无石榴石(角闪岩相),花岗岩为低 Sr 高 Yb 类型的;(4)与蛇绿岩有关的在洋壳剖面浅部由辉长岩部分熔融形成的 M 型花岗岩,具有非常低 Sr 高 Yb 的特点,形成深度约2～5km,可能是非常低压条件下形成的。研究表明,淡色花岗岩大多分布在低 Sr 低 Yb 区,部分正长岩和钾玄岩分布在高 Sr 高 Yb 区。藏南淡色花岗岩可能形成的压力较高。文中探讨了岩浆与深度的关系,得出了一些初步的认识,指出需要进一步研究的问题。为了得到经得起考验的结论,还需要更多资料的积累,更多理论的探讨和更多实验的佐证。
基金Project supported by the National High Technology Research and Development Program of China (863 Program,Grant No.2007AA05Z207)the Graduate Student Innovation Foundation of Jiangsu Province (Grant No.CX08B_064Z)the National Science and Technology Support Program (Grant No.2008BAF34B15)
文摘The three-dimensional unsteady turbulent flow in axial-flow pumps was simulated based on Navier-Stoke solver embedded with k - ε RNG turbulence model and SIMPLEC algorithm. Numerical results show that the unsteady prediction results are more accurate than the steady results, and the maximal error of unsteady prediction is only 4.54%. The time-domain spectrums show that the static pressure fluctuation curves at the inlet and outlet of the rotor and the outlet of the stator are periodic, and all have four peaks and four valleys. The pressure fluctuation amplitude increases from the hub to the tip at the inlet and outlet of the rotor, but decreases at the outlet of the stator. The pressure fluctuation amplitude is the greatest at the inlet of the rotor, and the average amplitude decreases sharply from the inlet to the outlet. The frequency spectrums obtained by Fast Fourier Transform （FFT） show that the dominant frequency is approximately equal to the blade passing frequency. The static pressure on the pressure side of hydrofoil on different stream surfaces remains almost consistent, and increases gradually from the blade inlet to the exit on the suction side at different time steps. The axial velocity distribution is periodic and is affected by the stator blade number at the rotor exit. The experimental results show that the flow is almost axial and the pre-rotation is very small at the rotor inlet under the conditions of 0.8 QN -1.2 QN Due to the clearance leakage, the pressure, circulation and meridional velocity at the rotor outlet all decrease near the hub leakage and tip clearance regions.
文摘Dynamic properties of rocks are important in a variety of rock mechanics and rock engineering problems. Due to the transient nature of the loading, dynamic tests of rock materials are very different from and much more challenging than their static counterparts. Dynamic tests are usually conducted using the split Hopkinson bar or Kolsl^j bar systems, which include both split Hopkinson pressure bar （SHPB） and split Hopkinson tension bar （SHTB） systems. Significant progress has been made on the quantification of various rock dynamic properties, owing to the advances in the experimental techniques of SHPB system. This review aims to fully describe and critically assess the detailed procedures and principles of tech- niques for dynamic rock tests using split Hopkinson bars. The history and principles of SHPB are outlined, followed by the key loading techniques that are useful for dynamic rock tests with SHPB （i.e. pulse shaping, momentum-trap and multi-axial loading techniques）. Various measurement techniques for rock tests in SHPB （i.e. X-ray micro computed tomography （CT）, laser gap gauge （LGG）, digital image corre- lation （DIC）, Moir~ method, caustics method, photoelastic coating method, dynamic infrared thermog- raphy） are then discussed. As the main objective of the review, various dynamic measurement techniques for rocks using SHPB are described, including dynamic rock strength measurements （i.e. dynamic compression, tension, bending and shear tests）, dynamic fracture measurements （i.e. dynamic imitation and propagation fracture toughness, dynamic fracture energy and fracture velocity）, and dy- namic techniques for studying the influences of temperature and pore water.
文摘Acute pancreatitis is an inflammatory disease of the pancreas.The etiology and pathogenesis of acute pancreatitis have been intensively investigated for centuries worldwide.Many causes of acute pancreatitis have been discovered,but the pathogenetic theories are controversial.The most common cause of acute pancreatitis is gallstone impacting the distal common bile-pancreatic duct.The majority ofinvestigators accept that the main factors for acute billiary pancreatitis are pancreatic hyperstimulation and bile-pancreatic duct obstruction which increase pancreatic duct pressure and active trypsin reflux.Acute pancreatitis occurs when intracellular protective mechanisms to prevent trypsinogen activation or reduce trypsin activity are overwhelmed.However,little is known about the other acute pancreatitis.We hypothesize that acute biliary pancreatitis and other causes of acute pancreatitis possess a common pathogenesis.Pancreatic hyperstimulation and pancreatic duct obstruction increase pancreatic duct pressure,active trypsin reflux,and subsequent unregulated activation of trypsin within pancreatic acinar cells.Enzyme activation within the pancreas leads to auto-digestion of the gland and local inflammation.Once the hypothesis is confirmed,traditional therapeutic strategies against acute pancreatitis may be improved.Decompression of pancreatic duct pressure should be advocated in the treatment of acute pancreatitits which may greatly improve its outcome.
