共查询到18条相似文献,搜索用时 46 毫秒
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我队施工的矿区,第四系复盖层厚,泥浆砂侵严重,钻进砂层时,泥浆含砂量高达7%以上,严重破坏泥浆性能,必须采取机械除砂方法,来控制泥浆比重和含砂量。我队原自行加工的除砂器因结构不合理,除砂效果差,不能满足生产需要。为了选择较合 相似文献
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无锡探矿机械总厂研制的GXY1型立轴式轻便工程钻机,开孔直径150mm,终孔直径75mm,钻进深度可达150m。该机具有油压给进机构,采用球卡式夹持结构,可实现不停车倒杆。立轴最大给进压力20kN,最大起拔力25kN,最大扭矩1.2kNm,适合于温州... 相似文献
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针对传统的单动双管取心器存在的内外管同心度差、轴承容易损坏、没有滤浆沉砂装置、双管间隙容易堵塞、取心效率低等问题,研制出DJ型单动双管取心器。该取心器主要由滤浆沉砂装置、密封单动装置、内管(半合管)调节组件和卡心装置组成,具有同心度高、密封性好、滤液及水路设计合理、取心管长度大、可减少钻进回次、提高取心效率等特点。现场应用表明:该取心器取心效果好,使用寿命是传统取心器的2倍以上。 相似文献
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Randhir Singh P. K. Pal C. M. Kishtawal P. C. Joshi 《Journal of Earth System Science》2005,114(4):427-436
The initialization scheme designed to improve the representation of a tropical cyclone in the initial condition is tested
during Orissa super cyclone (1999) over Bay of Bengal using the fifth-generation Pennsylvania State University — National
Center for Atmospheric Research (Penn State — NCAR) Mesoscale Model (MM5). A series of numerical experiments are conducted
to generate initial vortices by assimilating the bogus wind information into MM5. Wind speed and location of the tropical
cyclone obtained from best track data are used to define maximum wind speed, and centre of the storm respectively, in the
initial vortex. The initialization scheme produced an initial vortex that was well adapted to the forecast model and was much
more realistic in size and intensity than the storm structure obtained from the NCEP analysis. Using this scheme, the 24-h,
48-h, and 72-h forecast errors for this case was 63, 58, and 46 km, respectively, compared with 120, 335, and 550 km for the
non-vortex initialized case starting from the NCEP global analysis. When bogus vortices are introduced into initial conditions,
the significant improvements in the storm intensity predictions are also seen.
The impact of the vortex size on the structure of the initial vortex is also evaluated. We found that when the radius of maximum
wind (RMW) of the specified vortex is smaller than that of which can be resolved by the model, the specified vortex is not
well adapted by the model. In contrast, when the vortex is sufficiently large for it to be resolved on horizontal grid, but
not so large to be unrealistic, more accurate storm structure is obtained. 相似文献
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Sensitivity experiments are conducted for three cases of cyclones for investigating the impact of different vortex initialization
schemes on the structure and track prediction of the cyclone using India Meteorological Department’s Limited Area Model. The
surface wind and pressure profiles generated using Holland and Rankine initialization schemes differ from each other. These
different generated profiles are compared with the actual data and the root mean square error (RMSE) was calculated between
them. In case of the Holland vortex, ‘b’ is found to be equal to 1.5 and 2.0 respectively for two cases of very severe cyclonic storms in the Arabian Sea, namely
6–10 June 1998 and 16–20 May 1999 and 2.25 for the severe cyclonic storm in the Bay of Bengal. The ‘α’ parameter in Rankine’s
scheme was found to be 0.5 for two cases and 0.4 for the third system. This shows that cyclones differ even if they attain
the same intensity. The values of these parameters i.e. ‘b’ and ‘α’ are used for generating the synthetic wind data for individual cyclones and the same is used in the data assimilation
system. The analysis and forecast generated for the above cases using the Holland scheme show that the simulated structure
has characteristics closer to the actual storm; however, the Rankine scheme shows a weaker circulation. The mean track error
for three cases in the Holland scheme is 93, 149, 257 and 307 km in 12-, 24-, 36- and 48-h forecast. The mean track errors
for the Rankine scheme are 152, 274, 345 and 327 km, respectively, for the same period. 相似文献
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Sensitivity of tropical cyclone intensification to boundary layer and convective processes 总被引:1,自引:1,他引:1
This study examines the role of the parameterization of convection, planetary boundary layer (PBL) and explicit moisture processes
on tropical cyclone intensification. A high-resolution mesoscale model, National Center for Atmospheric Research (NCAR) model MM5,
with two interactive nested domains at resolutions 90 km and 30 km was used to simulate the Orissa Super cyclone, the most
intense Indian cyclone of the past century. The initial fields and time-varying boundary variables and sea surface temperatures
were taken from the National Centers for Environmental Prediction (NCEP) (FNL) one-degree data set. Three categories of sensitivity
experiments were conducted to examine the various schemes of PBL, convection and explicit moisture processes. The results
show that the PBL processes play crucial roles in determining the intensity of the cyclone and that the scheme of Mellor-Yamada
(MY) produces the strongest cyclone. The combination of the parameterization schemes of MY for planetary boundary layer, Kain-Fritsch2
for convection and Mixed-Phase for explicit moisture produced the best simulation in terms of intensity and track. The simulated
cyclone produced a minimum sea level pressure of 930 hPa and a maximum wind of 65 m s−1 as well as all of the characteristics of a mature tropical cyclone with an eye and eye-wall along with a warm core structure.
The model-simulated precipitation intensity and distribution were in good agreement with the observations. The ensemble mean
of all 12 experiments produced reasonable intensity and the best track. 相似文献
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利用多种资料对黑龙江省两次由江淮气旋和蒙古气旋合并引发的暴雪过程的水汽、热动力条件和中尺度特征进行了对比分析。结果表明:(1)两次暴雪过程都发生在北支槽和短波槽合并、北支槽北部有冷涡的背景下,850 hPa上低涡合并促使江淮气旋和蒙古气旋合并;气旋合并后,低空急流为降雪提供了充足水汽,强暖平流使气旋爆发性发展,导致降雪加强。(2)两次降雪过程都表现出逗点云系的合并发展,"1211 "暴雪过程中高层形成涡旋偏西,700 hPa低涡东部偏南风引导气旋北上西折,低空急流和地形共同作用使暖湿空气强烈辐合上升,产生对流云,暴雪发生在A类逗点云系的头部,降雪强度大,范围广;"1412"暴雪过程高空槽低涡位置偏东,700 hPa低涡东部西南风始终引导气旋向东北方向移动,近地面层具有冷垫,暴雪主要发生在B类气旋逗点云系头部西侧中低云团中,降雪范围和强度较"1211"过程小。(3)低层(0.3 km)冷空气侵入和中高层(5.5 km)转为偏北风对判断降雪开始和结束有很好的表征意义。(4)冷涡前部强高压脊使冷涡移动缓慢,从而延长了降水的持续时间,气旋移动路径与高压脊伸展方向密切相关。 相似文献
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地下水污染监测网的设计包括取样点在空间上的采样位置和时间上的取样频率这两方面的确定,其目的是为了准确刻画污染羽在含水层中随时间的变化状况。介绍了一种新的基于Delaunay三角形剖分方法用于地下水污染监测网在空间上的去冗余设计。同时,针对Delaunay方法没有考虑含水层参数变化和不能新增必要监测点的缺陷,提出了改进措施。改进的Delaunay方法可以直接与污染物的运移模型耦合,通过获取的含水层参数能够比较好地检验监测网在空间上的去冗余设计效果。实例研究表明,该方法在保证监测精度的基础上,能够找到最优的空间取样位置点,同时与改进前相比,利用该方法得到的地下水污染监测网能更加客观地反映污染物在含水层中的空间分布特征。 相似文献
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Vulnerability from storm surges and cyclone wind fields on the coast of Andhra Pradesh,India 总被引:2,自引:0,他引:2
The results presented here are from a study conducted for the government of the state of Andhra Pradesh (GOAP) in India, as
part of a World Bank project on cyclone mitigation. A set of detailed maps were prepared depicting the Physical Vulnerability
(PV), specifically storm surge inundation zones are shown for frequent occurrence, 50-year return period, likely scenario
for global warming and extreme global warming. Similarly vulnerable areas from strong wind field from tropical cyclones (TCS)
are also presented for the same four parameters. Vulnerability zones are presented from a social point of view also based
upon certain socio-economic parameters that were included in determining the overall vulnerability of each Mandal in a coastal
district (a Mandal represents a group of villages and towns) include: population, senior citizens, women, children under different
age groups, type of housing, income level, cyclone shelters, hospitals and medical centres, schools and caste based population.
The study is about scenarios that could happen if global warming and the predicted intensification of TCS actually occur as
predicted by some numerical models. 相似文献
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Most tropical cyclones have very few observations in their vicinity. Hence either they go undetected in standard analyses
or are analyzed very poorly, with ill defined centres and locations. Such initial errors obviously have major impact on the
forecast of cyclone tracks using numerical models. One way of overcoming the above difficulty is to remove the weak initial
vortex and replace it with a synthetic vortex (with the correct size, intensity and location) in the initial analysis. The
objective of this study is to investigate the impact of introducing NCAR–AFWA synthetic vortex scheme in the regional model
MM5 on the simulation of a tropical cyclone formed over the Arabian Sea during November 2003. Two sets of numerical experiments
are conducted in this study. While the first set utilizes the NCEP reanalysis as the initial and lateral boundary conditions,
the second set utilizes the NCAR–AFWA synthetic vortex scheme. The results of the two sets of MM5 simulations are compared
with one another as well as with the observations and the NCEP reanalysis. It is found that inclusion of the synthetic vortex
has resulted in improvements in the simulation of wind asymmetries, warm temperature anomalies, stronger vertical velocity
fields and consequently in the overall structure of the tropical cyclone. The time series of the minimum sea level pressure
and maximum wind speed reveal that the model simulations are closer to observations when synthetic vortex was introduced in
the model. The central minimum pressure reduces by 17 hPa while the maximum wind speed associated with the tropical cyclone
enhances by 17 m s −1 with the introduction of the synthetic vortex. While the lowest central pressure estimated from the satellite image is 988 hPa,
the corresponding value in the synthetic vortex simulated cyclone is 993 hPa. Improvements in the overall structure and initial
location of the center of the system have contributed to considerable reduction in the vector track prediction errors ie.
642 km in 24 h, 788 km in 48 h and 1145 km in 72 h. Further, simulation with the synthetic vortex shows realistic spatial
distribution of the precipitation associated with the tropical cyclone. 相似文献