气象服务需求的理论研究

气象服务需求是气象经济学中亟待深入研究的问题。从经济学的需求意义上,立足于气象服务实践,提出气象服务需求主体与需求客体,进而把需求主体划分为政府和企业,把需求客体划分为公共产品和服务商品。并在此基础上,重点剖析制约公共气象服务产品的需求因素和制约气象商品的需求因素     

Numerical analysis of the forces exerted on offshore structures by ship waves

Ship-generated waves can contribute to the fatigue of offshore structures. This paper presents a numerical model for evaluating the forces exerted on a nearby fixed structure by ship-generated waves. The ship waves were modeled using Michell's thin-ship theory (Wigley waves), and the forces were computed using a boundary element method in the time domain. The simulation was validated by comparing its results with those of frequency-domain methods reported in the literature. It was then applied to calculate the forces exerted on a hemisphere by ship waves varying with the ship's speed, dimensions and distance from the hemisphere to the ship's path. Our results indicate that the ship waves have enormous effects on offshore structures and are not neglectable.     

小波多尺度分析在煤厚探测中的应用

根据声波反射法探测顶煤厚度中存在的问题,提出了将小波多尺度分析应用到实际煤厚探测信号分析中的信号处理方法。结果表明:小波多尺度分析大大改善了煤层顶板弱反射波的识别能力,提高了煤厚探测的精度。      

2002～2003年南极中山站地区风要素变化特征

利用2002年1月至2003年12月南极中山站24个月的天气观测记录和天气形势图,对中山站地区的风要素特征进行了天气学分析研究,本文较详细地分析了该地区的风向,风速的分布特征以及风向与风速相互间的变化规律,确定了不同季节的盛行风向,初步探讨了风要素变化与大气环流的关系。所得结论对了解该地区的天气变化特点,提高天气预报的准确率以及对中山站发展设计规划的制定都有重要的参考价值。     

Coupled Responses of Sewol, Twin Barges and Slings During Salvage

Korean Sewol is successfully lifted up with the strand jack system based on twin barges. During the salvage operation, two barges and Sewol encounter offshore environmental conditions of wave, current and wind. It is inevitable that the relative motions among the three bodies are coupled with the sling tensions, which may cause big dynamic loads for the lifting system. During the project engineering phase and the site operation, it is necessary to build up a simulation model that can precisely generate the coupled responses in order to define a suitable weather window and monitor risks for the salvage operation. A special method for calculating multibody coupled responses is introduced into Sewol salvage project. Each body’s hydrodynamic force and moment in multibody configuration is calculated in the way that one body is treated as freely moving in space, while other bodies are set as fixed globally. The hydrodynamic force and moment are then applied into a numerical simulation model with some calibration coefficients being inserted. These coefficients are calibrated with the model test results. The simulation model built up this way can predict coupled responses with the similar accuracy as the model test and full scale measurement, and particularly generate multibody shielding effects. Site measured responses and the responses only resulted from from the simulation keep project management simultaneously to judge risks of each salvage stage, which are important for success of Sewol salvage.     

Interannual variability of SST,SLA and wind waves in the Hawaii area and their responses to ENSO

Time series of sea surface temperature (SST),wind speed and significant wave height (SWH) from meteorologicalbuoys of the National Data Buoy Center (NDBC) are useful for studying the interannual variability and trend of these quantities at the buoy areas.The measurements from 4 buoys (B51001,B51002,B51003 and B51004) in the Hawaii area are used to study theresponses of the quantities to EI Nino and Southern Oscillation (ENSO).Long-term averages of these data reflect precise seasonaland climatological characteristics of SST,wind speed and SWH around the Hawaii area.Buoy observations from B51001 suggest asignificant warming trend which is,however,not very clear from the other three buoys.Compared with the variability of SST andSWH,the wind speeds from the buoy observations show an increasing trend.The impacts of El Nifio on SST and wind waves arealso shown.Sea level data observed by altimeter during October 1992 to September 2006 are analyzed to investigate the variabilityof sea level in the Hawaii area.The results also show an increasing trend in sea level anomaly (SLA).The low-passed SLA in theHawaii area is consistent with the inverse phase of the low-passed Sol (Southern Oscillation Index).Compared with the low-passedSOl and PDO (Pacific Decadal Oscillation),the low-passed PNA (Pacific-North America Index) has a better correlation with thelow-passed SLA in the Hawaii area.     

Seabed erosion and deposition related to the typhoon activity of the past millennium on the southeast coast of China

Catastrophic events often interrupt long-term Earth surface processes. In coastal areas, although millennial-scale trends of climatic and sea-level changes determine the trajectory of sedimentary landform evolution, storm and/or tsunami activity can cause abrupt changes in depositional conditions that may alter the long-term sedimentary processes. Here, we report a sedimentary hiatus that is widely observed from the late Holocene sedimentary sequence at the seabed along the southeast China coast. This hiatus was discovered by close temporal sedimentary and radiocarbon dating analyses of a seabed sedimentary sequence in the mouth area of the Pearl River estuary. The results suggest that a couple of metres in the middle to late Holocene sediment at the seabed were eroded by a catastrophic event happening c. 1000–800 cal. Years BP. In theory, a mega-tsunami generated from the Manila Trench could have caused such erosion at the seabed, but there is a lack of direct geological and historical evidence to support such a hypothesis. Much more likely, a super-typhoon struck the coast and caused the erosion. This hypothesis is strongly supported by the region's historical and geological records, which suggest a period characteristic of intense typhoons ranging from the Medieval Warm Period to the climate transition phase (c. 1000–600 cal. Years BP). During the subsequent Little Ice Age, deposition of sandy sediment continued, suggesting frequent but weaker typhoon activity. Over the past two centuries the deposition of sandy sediment and gravels began, implying the beginning of a phase of intensifying typhoon conditions, possibly a result of the recent warming climate. © 2020 John Wiley & Sons, Ltd.     

Analysis of attenuation and dispersion of propagating wave due to the coexistence of three fluid phases in the pore volume

In exploration geophysics, the efforts to extract subsurface information from wave characteristics exceedingly depend on the construction of suitable rock physics model. Analysis of different rock physics models reveals that the strength and magnitude of attenuation and dispersion of propagating wave exceedingly depend on wave-induced fluid flow at multiple scales. In current work, a comprehensive analysis of wave attenuation and velocity dispersion is carried out at broad frequency range. Our methodology is based on Biot's poroelastic relations, by which variations in wave characteristics associated with wave-induced fluid flow due to the coexistence of three fluid phases in the pore volume is estimated. In contrast to the results of previous research, our results indicate the occurrence of two-time pore pressure relaxation phenomenon at the interface between fluids of disparate nature, that is, different bulk modulus, viscosity and density. Also, the obtained results are compatible with numerical results for the same 1D model which are accounted using Biot's poroelastic and quasi-static equation in frequency domain. Moreover, the effects of change in saturation of three-phase fluids were also computed which is the key task for geophysicist. The outcomes of our research reveal that pore pressure relaxation phenomenon significantly depends on the saturation of distinct fluids and the order of saturating fluids. It is also concluded that the change in the saturation of three-phase fluid significantly influences the characteristics of the seismic wave. The analysis of obtained results indicates that our proposed approach is a useful tool for quantification, identification and discrimination of different fluid phases. Moreover, our proposed approach improves the accuracy to predict dispersive behaviour of propagating wave at sub-seismic and seismic frequencies.     

三氧二氮席夫碱冠醚DTDC合成的研究

设计了三条路线合成了席夫碱冠醚２,３：１０,１１－二苯并－１,１２,１５－三氧杂－５,８－二氧－２,３：４,５：８,９：１０,１１－十七环四烯（ＤＴＤＣ）,并通过红外、紫外、伏安法等手段对产品的性状进行了表征。结果表明,设计的路线都是可行的,且具有简便、产物纯度高等优点。