任意色阶区间精细选区创建方法初探

在通道中利用“阂值”命令创建选择X-255。在通道混合中创建任意色阶区间选择X1～X2。利用通道混合“减去”模式中“缩放”“补偿值”实现深度自由选择。     

Influence of diversion angle on water and sediment flow into diversion channel

Accumulation of the sediment in the stream of the diversion channels adversely affects its operational systems. Diversion channels are often constructed perpendicular to the main river. In this study, the water flow and sediment transport in the diversion channel with different angles were investigated in an attempt to maximize water discharge and minimize sediment discharge. A physical model with movable bed was used to simulate water and sediment flow with five diversion angles (θ) between (30°–90°). Moreover, three bed width ratios (B_r) (the relation between diversion to main channel bed width) between 30% and 50% and five total discharges between (7.25 L/s to 12.25 L/s) were considered for each case of (θ). The results showed, up to 10%, increasing in proportion discharge ratios for 30 and 45 diversion angles compared with 90° diversion angle. The results also showed that the lowest diversion sediment concentration was provided by the (θ) of 30°. Across all scenarios, the average proportion concentration reduction was 64%, compared with 90° diversion angle. Closer observation of the diversion system mechanism confirmed that decreased (θ) result in decreased sediment concentrations in the diversion channels. In conclusion, the diversion channel water and sediment discharge could be effectively managed by changing the (θ) to 30° or 45° instead of 90°.     

湖平面升降对浅水三角洲前缘砂体形态的影响

三角洲平原上的分流河道通过填积和湖面的频繁波动向湖泊中心方向长距离推进,在浅水三角洲前缘的浅水区发育很有特色的水下分流河道,且在湖面频繁波动过程中,河流、波浪和沿岸流的冲刷作用对沉积物分布起到再改造作用,导致了以水下分流河道砂体为主的三角洲前缘砂体不同程度的席状化。随着气候变得潮湿,湖面相对稳定,季节性、周期性湖面波动的频率、幅度减小,水动力对三角洲前缘砂体的改造和席状化强度减弱。     

Further assessment of flood‐ and drought‐dominated regimes in south‐eastern Australia

Kirkup et al. (1998) [Australian Geographer 29, pp. 241–55] criticise our theory of alternating flood regimes and question its application to river management. A brief but critical appraisal of their work shows many errors and misrepresentations. When these are corrected, their challenge is found deficient.     

MAXIMUM INFORMATION ENTROPY THEORY OF EFFLUENT BAND IN OPEN CHANNEL UNIFORM FLOW

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THE THEORETICAL STUDY ON THE LAWS OF DRAG REDUCTION BY AERATION IN OPEN CHANNEL 1

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汉江某区段堤防隐患探测的物探方法

运用探地雷达,电磁法,直流充电法以及自然电场法,查明了汉江某区段堤防中涌水通道的确切位置,渗水的范围,并根据物探异常的推断解释结果,提出了相应的治理方案。     

磁暴二倍法预报唐山7.8级地震

磁暴二倍法预报地震的依据是,应变能在运移过程中导致地壳膨胀和压缩形成一个周期,在时间上呈有二倍关系．唐山７．８级地震是我国７０年代最大地震,用磁暴二倍法推出有４组磁暴能对应这次地震．每组磁暴前后都发生了地震,由于这些地震释放的剩余能量在聚积过程中,地壳发生膨胀和压缩,地磁场就受到影响形成了磁暴．因此磁暴与地震能量变化有相关性．可见,磁暴二倍法可以预报地震．     

我国首座卫星信道数字化地震台网落成

文章较为详细地介绍了我国第一座卫星信道数字化地震观测台网各配套仪器的性能,使用环境及整套系统的运行情况和目前在地震观测中所起的作用。作者展望了该系统的发展前景及其对我国地震观测事业的影响。     

Hydrodynamic effect of the regulation project of Yangtze River deepwater channel downstream of Nanjing

A two-dimensional flow numerical model of the tidal reaches, which total length is more than 700 km, is established from Datong to the Yangtze River estuary. The tidal levels, velocities, diversion ratios and dynamic axes before and after the separate regulation of each reach and combined regulation of all reaches are obtained. The comparative analysis shows that the regulation project of a separate reach basically has no impact on velocity distributions and variations of diversion ratios of upper and lower reaches, the variations of dynamic axes are only within the local scope of the project. The regulation project of a separate reach also has less impact on the water level in the lower adjacent reaches, but will make the water levels in the upper reaches rise. After the implementation of the regulation projects for all reaches, the rise of water level in the upstream reaches will have a cumulative impact.