声音

“更加自觉地投入到‘地质找矿改革发展大讨论’当中去。把思想认识上和体制机制上存在的问题梳理出来,把功夫下在寻找应对之策上。”     

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<正>"目前房地产市场呈现出量跌价滞的态势,再过一个季度左右房地产市场可能会面临全面调整,房价会有所下降,但下降到什么程度不好说。"     

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“‘前门’要开得大大的。尽可能帮助地方政府,支持地方经济发展,同时要把‘后门’堵得严严的,一旦有违法违规情况,一定要查处,一定要整改,绝不手软。”     

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“你要有信心尽快投产,大陆现在出台的措施已经够硬,而且还有预备措施,根本不用担心。” ——3月17日,国土资源部部长、党组书记、国家土地总督察徐绍史在湘潭九华工业园考察台资企业时如是说。     

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从第四季度开始,全国地产市场的变化较大。划拨用地的数量和速度可能双双上升,土地出让市场走势难以预料,土地财政状况可能出现转机。将导致地方政府土地出让预期目标下降。     

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“根据各方面信息看,2009年地质灾害防治形势仍然十分严峻,防治任务仍然十分艰巨。责任十分重大。……更应该提醒大家要注意的是,地质灾害防治是一项长期的艰巨任务,要在看到它的复杂性、艰巨性的同时,更要重视它的长期性,从而使我们各级各个方面在做好地灾防治工作的同时,既要研究解决好新问题,更要重视解决好影响长期防灾的突出问题和基础性的一些困难问题。”     

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“中国将立足国内,加大地质找矿力度;坚持开放,扩大矿业国际合作。各国矿业界应把握时机,促进国际矿业稳定繁荣和世界经济复苏发展。”     

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＂18亿亩耕地红线万万动不得。＂ ——日前,全国政协常委、中国工程院院士袁隆平在接受《解放日报》记者采访时说到粮食安全问题,他直言＂这是一场输不起的战争＂。     

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“我们的管理职能要从微观走向宏观。从重审批走向重监管,从项目的实施走向制度的设计。国土资源部门要变‘大家围着我们转’为‘我们围着大家转’,把权力和责任真正放下去,把服务和监管切实抓起来,不与市场争权,不与企业争利,充分发挥市场在资源配置中的基础性作用,促进经济发展方式的转变。”     

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＂中国人着急,但改革不能急＂国家发改委城市和小城镇中心主任李铁近日接受媒体采访时表示：中国城镇化体制改革是势在必行的,根据发展情况进一步推进,不可能一年之内全部解决。中国人着急,对城市需求改善要求着急。但是改革不能着急,要放长眼光。     

草鱼网围养殖区声波的研究

对网围养殖区内草鱼的活动声波进行了采集与分析,并将采集的声波进行了回放。结果表明,草鱼网围养殖区声波频率范围为0~3.2 kHz,整个频段内没有宽带波峰。在草鱼饥饿、食饵和饱食的不同状态下养殖区内的水声特性有一定的差异。研究表明在网围养殖区通过声波回放能对草鱼起到诱集作用,在投饵回放、投饵不回放及不投饵回放声波的情况下,草鱼的响应时间分别为2.55、3.504、.80 min,存在显著差异。回放持续性声波和间隔性声波在响应时间上不存在显著差异。     

Sound propagation in two-axis underwater channel based on beam-displacement ray-mode theory

Sound propagation in a deep ocean two-axis underwater channel is often complex and difficult to simulate between surface channel and sound fixing and ranging (SOFAR) channel. The beam-displacement ray-mode (BDRM) theory is a normal mode method for propagation modeling in horizontally stratified shallow water. An improved method for computing the upper boundary reflection coefficient in the BDRM is proposed and applied to calculate the acoustic fields of a two-axis underwater channel. Transmission losses in the two-axis underwater channel are calculated in the new BDRM. The corresponding results are in good agreement with those from the Kraken code, and furthermore the computed speed of the new BDRM excels the other methods.     

Influence of Environmental Conditions on the Sound Velocity Ratio of Seafloor Surficial Sediment

In this work, we investigated the influences of salinity, temperature, and hydrostatic pressure on the acoustics of seafloor surficial sediment by theoretically and experimentally analyzing the sound velocity ratio of the seafloor sediment to the bottom seawater in typical environmental conditions. Temperature-and pressure-controlled experiments were conducted to examine the characteristics of the sound velocity ratio, the results of which agree with the theoretical analysis using the effective density fluid model. Of the three environmental factors considered, the sound velocity ratio was found to be sensitive to temperature and pressure but not to salinity, with the sound velocity ratio decreasing with temperature and hydrostatic pressure. With respect to surficial sediments, pore water plays a key role in the sound velocity ratio of sediment influenced by different environmental factors. The sound velocities of different types of sediments(sandy, silty, and clayey) change similarly with temperature, but change slightly differently with hydrostatic pressure. The influence of environmental factors on the sound velocity ratio of seafloor sediment is independent of the detection frequency. The results show that the sound velocity ratio can change up to 0.0008 per ℃ when the temperature ranges from 2℃ to 25℃ and up to 0.00064 MPa-1 when the seawater depth pressure ranges from 0 MPa to 40 MPa.     

南海西北部海区声速垂向及断面分布特征

根据南海西北部海区2012年2月实测的CTD资料计算出该海域的声速,给出了声速的垂向分布的几种类型和断面的分布状况以及它们的一些重要特征.并根据浅海声速跃层标准(ΔC/ΔH≥0.5/S),讨论了本海域声速跃层的分布状况.     

声速误差对圆走航水下控制点定位影响分析

针对圆走航定位声速剖面测量不准确引起水下控制点坐标解算存在偏差的问题,首先介绍了声速不确定性对测距误差的影响,并将声速测距误差分成背景声速剖面误差、随机误差、测距误差长周期项和测距误差短周期项,再通过分析坐标改正数方程得到不同声速测距误差项对控制点坐标定位的影响。最后,设计2组仿真实验对该理论进行验证,实验结果与理论推导的结论一致。     

Sound speed profiles in high spatiotemporal resolution using multigrid three-dimensional variational method: a coastal experiment off northern Shandong Peninsula

It is essential to acquire sound speed profiles (SSPs) in high-precision spatiotemporal resolution for undersea acoustic activities. However, conventional observation methods cannot obtain high-resolution SSPs. Besides, SSPs are complex and changeable in time and space, especially in coastal areas. We proposed a new space-time multigrid three-dimensional variational method with weak constraint term (referred to as STC-MG3DVar) to construct high-precision spatiotemporal resolution SSPs in coastal areas, in which sound velocity is defined as the analytical variable, and the Chen-Millero sound velocity empirical formula is introduced as a weak constraint term into the cost function of the STC-MG3DVar. The spatiotemporal correlation of sound velocity observations is taken into account in the STC-MG3DVar method, and the multi-scale information of sound velocity observations from long waves to short waves can be successively extracted. The weak constraint term can optimize sound velocity by the physical relationship between sound velocity and temperature-salinity to obtain more reasonable and accurate SSPs. To verify the accuracy of the STC-MG3DVar, SSPs observations and CTD observations (temperature observations, salinity observations) are obtained from field experiments in the northern coastal area of the Shandong Peninsula. The average root mean square error (RMSE) of the STC-MG3DVar-constructed SSPs is 0.132 m/s, and the STC-MG3DVar method can improve the SSPs construction accuracy over the space-time multigrid 3DVar without weak constraint term (ST-MG3DVar) by 10.14% and over the spatial multigrid 3DVar with weak constraint term (SC-MG3DVar) by 44.19%. With the advantage of the constraint term and the spatiotemporal correlation information, the proposed STC-MG3DVar method works better than the ST-MG3DVar and the SC-MG3DVar in constructing high-precision spatiotemporal resolution SSPs.