缘板错移量对封严泄漏特性影响的试验研究

为了获得一种羽状静止封严件的周向绕流泄漏特性,在缘板错移量为0、0.1 mm、0.2 mm及0.3 mm,压比范围1.1~3.5的工况下,研究不同缘板错移量对缘板插片结构封严特性的影响,并通过试验得出不同错移量时压比与泄漏量以及不同压比时错移量与泄漏量的关系曲线。结果表明,随着错移量增大,不同压比下的流量以及换算流量均呈现先增大后减小的趋势,较小的错移量使得羽状封严片与一侧封严槽之间空隙增大,使得气体更容易泄漏;随着压比增大,不同错移量下的流量均增大,且增长趋势几乎相同,而不同错移量下的换算流量均呈现先增大,到临界压比2.0~2.5左右后,呈现出不变的趋势;错移量较大时,错位的封严槽将封严片卡住,使得两者更贴紧,泄漏量反而变小。

合理运用猜想 科学发展思维

思维是数学的灵魂。在教学中,以情境猜想为前提,激起学生思维火花;以"错缘"猜想为手段,训练学生思维的逻辑性与缜密性;以探究猜想为策略,拓展学生思维的灵活性。总之,合理地运用猜想,能有利于科学发展学生的思维。

错过的兄弟缘

秦和我在大学时同系．上合堂的时候偶尔会坐在一块，聊上几句关于天气的废话。我爱游山玩水，他爱学习打工，我们根本没有交集．

A MODIFIED EDGE-ORIENTED SPATIAL INTERPOLATION ALGORITHM FOR CONSECUTIVE BLOCKS ERROR CONCEALMENT

This paper proposes a low-complexity spatial-domain Error Concealment (EC) algorithm for recovering consecutive blocks error in still images or Intra-coded (I) frames of video sequences. The proposed algorithm works with the following steps. Firstly the Sobel operator is performed on the top and bottom adjacent pixels to detect the most likely edge direction of current block area. After that one-Dimensional (1D) matching is used on the available block boundaries. Displacement between edge direction candidate and most likely edge direction is taken into consideration as an important factor to improve stability of 1D boundary matching. Then the corrupted pixels are recovered by linear weighting interpolation along the estimated edge direction. Finally the interpolated values are merged to get last recovered picture. Simulation results demonstrate that the proposed algorithms obtain good subjective quality and higher Peak Signal-to-Noise Ratio (PSNR) than the methods in literatures for most images.

Characteristics of Wind Erosion and Deposition in Oasis-desert Ecotone in Southern Margin of Tarim Basin,China

The oasis-desert ecotone is a fragile ecological zone that is affected both by oasis and desert conditions. To understand the impact of the differences in wind power, and the influence of wind erosion and deposition on the ecotone, meteorological data and con- temporaneous wind erosion and deposition data were collected on the southern margin of Tarim Basin with serious sand-blown hazards. The wind velocity, average wind velocity, sand drift potential （DP）, resultant sand drift potential （RDP）, and sand transportation rate decrease significantly and successively across four landscape types with increasing vegetation coverage （VC）. Flat surfaces and areas of shifting sandy ground experience intense wind erosion with fast movement of mobile sand dunes; semi-fixed sand areas experience ex- tensive wind deposition but only slight wind erosion; and fixed sand areas experience only slight wind erosion and deposition. Volume of wind erosion on bare newly reclaimed farmland is up to 6.96 times that of bare shifting sandy ground. Wind erosion volume per unit area and VC follow an exponential function relationship in natural conditions, while wind deposition volume per unit area does not conform to any functions which has close relationship with vary topography and arrangement patterns of vegetation besides for VC. The results indicate that the volume of wind erosion has a close correlation with VC, and different types and distribution patterns of topog- raphy and vegetation also profoundly influence the wind deposition volume in the field, and underground water tables in different land- scape types control the plant community distribution. Keywords： wind erosion; wind deposition; oasis-desert ecotone; vegetation coverage （VC）; topography; Cele County

Pressure Tolerant Power Electronics： IGBT Gate Driver for Operation in High Pressure Hydrostatic Environment

Abstract： This paper presents results from an on-going research project on pressure tolerant power electronics at SINTEF Energy Research, Norway. The driving force for this research is to enable power electronic components to operate in pressurized dielectric environment. The intended application is the converters for operation down to 3,000 meters ocean depth, primarily for subsea oil and gas processing. The paper focuses on the needed modifications to a general purpose gate driver for IGBT （insulated gate bipolar transistors） that will give pressure tolerance. Adaptations and modifications of the individual driver components are presented.The results from preliminary testing are promising, which shows that the considered adaptations give feasible solutions.

Dextral strike-slip of Sanguankou-Niushoushan fault zone and extension of arc tectonic belt in the northeastern margin of the Tibet Plateau

The kinematic characteristics of the Sanguankou-Niushoushan fault（SGK-NSSF） are of great significance to the understanding of the extension of the arc tectonic belt in the northeastern margin of the Tibet Plateau. Using field surveys and various data collection methods, including large-scale geological mapping, measurement of typical topographies, and dating of sedimentary strata, it was determined that the SGK-NSSF exhibits obvious dextral strike-slip characteristics and thus is not a sinistral strike-slip fault, as believed by previous researchers. The results of this study show that the geological boundaries for the Paleozoic, Mesozoic, and Cenozoic eras were all dextrally dislocated by the fault, with the faulted displacements being similar. The maximum strike-slip displacement of the fault, after elimination of topographic effects, was found to be 961±6 m. The Sanguankou fault at the northern section exhibits obvious characteristics of more recent activities, with a series of small gullies having undergone synchronized dextral writhing after traversing the fault. The average horizontal slip rate of the fault since the late Quaternary was determined to be approximately 0.35 mm/a. The pre-existing fold structures formed during the late Pliocene were dislocated by the fault and became ex situ, indicating that dextral strike-slip of the fault could not have occurred prior to the late Pliocene. The maximum displacements and average slip rates were used to estimate the onset time of the dextral strike-slip activities of the fault as being after 2.7 Ma. In this study, the understanding of previous researchers concerning the extension in the northeastern margin of the Tibet Plateau was combined with analyses of the successive relationships between fold deformations and fault activities. This led to the finding that the extension in the northeastern margin of the Tibet Plateau reached the vicinity of the SGK-NSSF during the late Pliocene（~2.7 Ma）, causing regional uplift and fold deformations of the strata there. During the early Quaternary, the northeastern compression of the Tibet Plateau and the counterclockwise rotation of the Ordos block collectively resulted in the dextral strike-slip activities of the SGK-NSSF. This then formed the foremost margin of the arc tectonic belt extension in the northeastern margin of the Tibet Plateau.

Rise and Fall:Deciphering Urban Sites and their Environment in Overlapping Agrarian/Pastoral Regions——Based on Examination of the Border Fortified Camps along the Yansui Section of the Great Wall during the Ming Dynasty

The area along the Grear Wall in northern Shaanxi between the Loess Plateau and the Ordos Desert is one of the major agrarian-pastoral regions of northwest China. Historically, the land was fought over by the nomadic and the agrarian peoples of the region. The Yansui section of the Ming Great Wall and thirty-nine fortified encampments along it were built during fighting between the Mongols and the Han people. As all of them were located along communication lines vital to economic development, they played an important role in politics, the economy and transport over three hundred years of Ming and Qing rule. However, they fell into disuse in the late Qing and the Republican period and are now in ruins. The main reason underlying their decline was that the sites had been chosen for their defensive value, so the subsequent northern expansion of China’s borders and structural changes in the border economy hastened their decline. Thus the rise and fall of these fortified towns at the intersection of the agrarian and the pastoral regions was closely related to imperial political and military activity and was in line with ethnic and tribal movements and migrations and the evolution of civilizations. In sum, the reasons behind the demise of these fortified towns and camps were highly complex and usually involved multiple factors.