镶齿钻头中齿的过盈对其连接可靠性的影响

钻井实践表明,镶齿钻头的缺点是齿从牙轮上脱落,故往往不得不提前起钻,使钻头得不到充分的使用。脱齿或要发生在外圈齿上,因为外圈齿上的速度和动载大大高于其他各圆齿。对脱齿的原因研究文献不多。实际钻井上发现的脱齿都是由于没有按照技术规定将齿压入齿轮体内。例如,常常不能保证所要求的过盈,使其连接强度降低。为消除这一点,必须采用选配方法。     

A hybrid model of the CO2 geochemical cycle and its application to large impact events

A hybrid model of the carbonate-silicate geochemical cycle is presented which is capable of calculating the partitioning of carbon dioxide between the atmosphere, ocean, and sedimentary rocks. The ocean is subdivided into a shallow, mixed layer, which remains in equilibrium with the atmosphere, and a massive, deep layer which does not. Gradients in dissolved carbon content are established between the mixed layer and the deep ocean as a consequence of downward fluxes of fecal matter and of dead planktonic organisms. The dissolved carbon content and alkalinity of the ocean as a whole are controlled by weathering and metamorphism of sedimentary rocks. Equilibrium solutions are derived for the preindustrial atmosphere/ocean system and for a system that may be similar to that existing during the Late Cretaceous Period. The model is then used to determine how the modern and ancient marine biospheres might be affected by an oceanic impact of a large asteroid or comet. Such an event could perturb the carbon cycle in several different ways. Global darkening caused by stratospheric dust veil could destroy most of the existing phytoplankton in a period of several weeks to several months. At the same time, dissolution of atmospheric NOx compounds synthesized during the impact would lower the pH of ocean surface waters and release CO2 into the atmosphere. Both effects might be enhanced by an influx of CO2 released from upwelling of deep ocean water near the hot impact site, from oxidation of dead organic matter, and from the comet itself. The net result could be to raise surface temperatures by several degrees and to make the surface ocean uninhabitable by calcareous organisms for as much as 20 yrs (the time scale for mixing with deep ocean). It appears unlikely, however, that an impact could create a "Strangelove ocean," in which surface waters remained corrosive to calcium carbonate for thousands or tens of thousands of years. Thus, disruption of the carbon cycle by an impact event cannot by itself explain the scarcity of calcium carbonate in sediments found within the first few centimeters above the K/T boundary.     

Noncontact measurement of vibration using airborne ultrasound

A noncontact ultrasonic method for measuring the surface normal vibration of objects was studied. The instrument consists of a pair of 420 kHz ultrasonic air transducers. One is used to emit ultrasounds toward the moving surface, and the other receives the ultrasound reflected from the object under test. Two effects induce a phase modulation on the received signal. The first effect results from the variation of the round trip time interval tau required for the wavefront to go from the emitter to the moving surface and back to the receiver. This is the Doppler effect directly proportional to the surface displacement. The second effect results from the nonlinear parametric interactions of the ultrasonic beams (forward and backward) with the low frequency sound field emitted in the air by the vibrating surface. This latter phenomenon, which is a volume effect, is proportional to the velocity of the vibrating surface and increases with the distance between the transducers and the surface under test. The relative contribution of the Doppler and parametric effects are evaluated, and both have to be taken into account for ultrasonic interferometry in air.     

在研究浮选过程时的矿粉比表面积的测定

在研究浮选过程时的矿粉比表面积的测定在浮选过程中,所要利用的是矿石组成成分表面性质的差别,因而,在实践中所显示出各矿床的矿物多种多样的浮选行为是与其实际表面性质有关。因此,像表面积的大小、表面性质和状态这些因素,都应按它们对样品可浮性的影响分别研究。为此,在研究矿物与药剂的相互作用时,必须由相对值(从单位重量表示的)的研究改为绝对值(从单位表面积表示的)的分析。这个问题的迫切性还在增长,因为现代所采用的较     

关于六电极系套管井电法测井的效果分析

在已经提出的套管井电测井的众多方法中。有一种考虑套管壁厚度的方法，具有一定的意义(文献1)。     

Ultrafast vibrations of gold nanorings

We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We elucidate the corresponding mode shapes and find that the substrate plays an important role in determining the mode damping. This study demonstrates the need for a plasmonic nano-optics approach to understand the optical excitation and detection mechanisms for the vibrations of plasmonic nanostructures.