Estimation of wind speed and wave height during cyclones     

V. Sanil Kumar  S. Mandal  K. Ashok Kumar 《Ocean Engineering》2003,30(17):2239-2253

Wave and wind characteristics based on the cyclones, in the vicinity of the Nagapattinam coastline (east coast of India) were estimated. In all, 11 cyclones have crossed near the study region during 1960–1996. For the four severe cyclones, the isobaric charts were collected at three hourly intervals from the India Meteorological Department. The storm variables such as central pressure, radius of maximum wind, speed of forward motion and direction of storm movement were extracted and the method based on standard Hydromet pressure profile, were used for the hindcast of storm wind fields. For all the cyclones the maximum significant wave height within the storm and its associated spectral peak period was estimated using the Young’s model considering the moving wind field and the results are compared with the hurricane wave prediction techniques provided in the shore protection manual published by the US Army Corps of Engineers in 1984. The study shows that the estimated wind speed and the data reported by ships were comparable. Empirical expressions relating wind speed, wave height and wave period to storm parameters were derived. The design wave height for different return periods was obtained by fitting a two-parameter Weibull distribution to the estimated significant wave heights. The design wave height was 9.39 m for 1 in 100 year return period for a direct hit of cyclone.  相似文献   

2019年甘肃张掖5.0级、夏河5.7级地震前地磁低点位移时空分布特征     

裴东洋  戴勇  王磊  格根 《地震地磁观测与研究》2021,43(1):68-75

2019年甘肃张掖5.0级、夏河5.7级地震前中国大陆均有明显的“地磁低点位移”现象出现,2次地震震中均位于低点位移线出现明显转折的区域。通过对2次低点位移异常日中国大陆地磁台站低点时间进行梯度法分析,研究了2次中强地震震中位置与低点时间高梯度带分布间的关系。研究结果表明：①在2次低点位移异常日都同步出现了地磁垂直分量低点时间高梯度带分布;②2次中强地震震中位置均位于低点位移线出现明显转折处和低点时间高梯度带1.0 h/（°）等值线附近;③利用低点时间梯度法对低点位移异常进行分析有利于改进原有异常识别方法,较少虚报率。  相似文献   

Cyclic testing of a single bay reinforced concrete frames with various types of masonry infill     

Jurko Zovkic  Vladimir Sigmund  Ivica Guljas 《地震工程与结构动力学》2013,42(8):1131-1149

In this paper, a contribution of various types of masonry infill to the behaviour of reinforced concrete frames under lateral loads is presented. As a part of the bigger project, ten one‐bay, one‐storey reinforced concrete frames were designed according to the EC8, built in a scale 1:2.5, infilled with masonry and tested under constant vertical and cyclic lateral load. The masonry wall had various strength properties, namely, high strength hollow clay brick blocks, medium strength hollow clay brick blocks and low strength lightweight autoclaved aerated concrete blocks. There were no additional shear connectors between the masonry and frame. The results showed that the composite ‘framed wall’ structure had much higher stiffness, damping and initial strength than the bare frame structure. Masonry infill filled in the load capacity gap from very low (0.05%) to drifts when the frame took over (0.75%). The structures behaved as linear monolithic elements to drifts of 0.1%, reached the maximum lateral capacities at drift of 0.3%, maintained it to drifts of 0.75% and after that their behaviour depended on the frame. Masonry infill had severe damage at drift levels of about 0.75% but contributed to the overall system resistance to drifts of about 1%. At that drift level, the frame had only minor damage and was tested to drifts of about 2% without any loss of capacity. Improvement of the ‘infill provisions’ in the codes could be sought by taking into account the contribution of a common masonry that reduces expected damages by lowering the drift levels. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Classical and New Procedures of Whole Rock Dissolution for Trace Element Determination by ICP‐MS     

Aloísio J. B. Cotta  Jacinta Enzweiler 《Geostandards and Geoanalytical Research》2012,36(1):27-50

Sample digestion is a critical stage in the process of chemical analysis of geological materials by ICP‐MS. We present a new HF/HNO₃ procedure to dissolve silicate rock samples using a high pressure asher system. The formation of insoluble AlF₃ was the major obstacle in achieving full recoveries. This was overcome by setting an appropriate digestion temperature and adding Mg to the samples before digestion. Sodium peroxide sintering was also investigated and the inclusion of a heating step to the alkaline sinter solution improved the recoveries of thirteen elements other than the lanthanides. The results of these procedures were compared with data sets generated by common acid decomposition techniques. Forty‐one trace elements were determined using an ICP‐QMS equipped with a collision cell. Under optimum conditions of gas flow and kinetic energy discrimination, polyatomic interferences were eliminated or attenuated. The measurement bias obtained for eight reference materials (BCR‐2, BHVO‐2, BIR‐1, BRP‐1, OU‐6, GSP‐2, GSR‐1 and RGM‐1) and intermediate precision (RSD) were generally better than ± 5%. The expanded measurement uncertainties estimated for two certified reference materials were mostly between 7 and 15%. New data sets for the reference materials are provided, including constituents with previously unavailable values and also for the USGS candidate reference material G‐3.  相似文献   

A Proposal for the Publication of Geochemical Data in the Scientific Literature     

Philip J. Potts 《Geostandards and Geoanalytical Research》2012,36(3):225-230

A proposal is set out for the information and details that should accompany the publication of geochemical data in the research literature. This proposal is based on the principle that sufficient detail must be included both to allow independent replication of the results and for reviewers to confirm that data are fit‐for‐purpose in supporting the way in which they have been interpreted. In particular, it is recommended that all analytical measurements should be accompanied by an estimate of uncertainty that includes both field sampling and laboratory contributions together with a statement that summarises the way published data conform to the principles of traceability.  相似文献   

An Air‐Cooled,High‐Yield,Compact and Inexpensive Teflon Still for High‐Purity Reagents     

Kunchithapadam Gopalan 《Geostandards and Geoanalytical Research》2012,36(4):399-405

Mattinson’s (1972) well‐known simple design of a sub‐boiling still for the preparation of ultra high‐purity reagents consists of two Teflon bottles connected at right angles with one acting as the feed bottle and heated on its upper surface by infrared radiation and the other kept in a cold water bath serving both as the condenser and receiver. Connection of the two bottles in a vertical configuration and replacement of radiative surface heating with conductive bulk heating result in an equally simple and inexpensive still but with a smaller footprint, much larger yield and higher energy efficiency using only ambient air cooling. It can be easily configured for tandem distillation, supply of continuously purified reagent and fractional distillation. Ease and very low cost of fabrication of this still may be of particular interest to many geochemical laboratories requiring up to 500 ml of mineral acids and other common reagents per day.  相似文献   

‘ Global Change ’ Impact of Inter-Annual Variation in Water Discharge as a Driving Factor to Dredging and Spoil Disposal in the River Rhine System and of Turbidity in the Wadden Sea     

V. N. de Jong  D. J. de Jong 《Estuarine, Coastal and Shelf Science》2002,55(6):969

Between 1970 to 2000, the annual mean suspended matter (SPM) concentrations in the Vlie and Marsdiep tidal inlets of the Wadden Sea varied over five times. The present paper examines the possible relationship between SPM in the Wadden Sea and changing river Rhine discharges and dredging operations. The major short-term variations in annual mean SPM in part of the Wadden Sea appears to be a non-linear, exponential, function of river Rhine discharge and dredge spoil disposal (110 km to over 200 km from the area in front of the Dutch coast near the river Rhine outlet). Correlation coefficients (with SPM as the fixed and dredge disposal as the independent variable) ranged from R=0·8 (deep tidal inlet of Marsdiep) to R=0·2 (shallow inner area of Vlie) and weakened mainly as a function of distance to the disposal site. The best correlation with river discharge was for Marsdiep tidal inlet (r=0·45), indicating the superior effect of dredge disposal over river discharge-related processes. Taking the estimated regression equation as an explorative model, indicates that, without any disposal of dredge spoil, the expected SPM concentration levels in the tidal inlets of the Wadden Sea will be <15 g m⁻³ (comparable to the 1950s). The overall mean (and the highest mean) annual concentrations for the investigation period reached 42 (90) g m⁻³ at Marsdiep and 35 (75) g m⁻³ at Vlie. Assuming a 10% (220 m⁻³ s⁻¹) increase in river Rhine discharge over the next 50 years, and unchanged dredging policy and other circumstances, SPM concentrations would increase 5–15% for Marsdiep and Vlie. Compared with the calculated (12·4 g m⁻³ SPM in Marsdiep and 14·8 g m⁻³ SPM in Vlie) and measured (15 g m⁻³ SPM in Marsdiep) background SPM concentrations, the expected overall mean increase since 1950 is at least 250% of background. The natural variation in river Rhine discharge will cause further inter-annual variation. Changes in SPM concentrations, due to expected changes in wind climate, combined with river discharge are estimated to increase SPM concentrations 20% above the present situation. The possible implications of changes in land use in combination with further increasing river discharge, changed wind fields and increased temperature are discussed. An important management conclusion is that increasing mean river discharge will significantly increase the need for dredging and spoil disposal, and result in further elevated SPM concentrations in the Dutch coastal zone and the Wadden Sea. The presented relationships offer possibilities for developing new management strategies in relation to dredging and its effects.  相似文献   

Imaging of V_p, V_s, and Poisson’s ratio anomalies beneath Kyushu, southwest Japan: Implications for volcanism and forearc mantle wedge serpentinization     

Mohamed K. Salah  Tetsuzo Seno 《Journal of Asian Earth Sciences》2008,31(4-6):404-428

We determine detailed 3-D V_p and V_s structures of the crust and uppermost mantle beneath the Kyushu Island, southwest Japan, using a large number of arrival times from local earthquakes. From the obtained V_p and V_s models, we further calculate Poisson&#x2019;s ratio images beneath the study area. By using this large data set, we successfully image the 3-D seismic velocity and Poisson&#x2019;s ratio structures beneath Kyushu down to a depth of 150 km with a more reliable spatial resolution than previous studies. Our results show very clear low V_p and low V_s anomalies in the crust and uppermost mantle beneath the northern volcanoes, such as Abu, Kujyu and Unzen. Low-velocity anomalies are seen in the mantle beneath most other volcanoes. In contrast, there are no significant low-velocity anomalies in the crust or in the upper mantle between Aso and Kirishima. The subducting Philippine Sea slab is imaged generally as a high-velocity anomaly down to a depth of 150 km with some patches of normal to low seismic wave velocities. The Poisson&#x2019;s ratio is almost normal beneath most volcanoes. The crustal seismicity is distributed in both the high- and low-velocity zones, but most distinctly in the low Poisson&#x2019;s ratio zone. A high Poisson&#x2019;s ratio region is found in the forearc crustal wedge above the slab in the junction area with Shikoku and Honshu; this high Poisson&#x2019;s ratio could be caused by fluid-filled cracks induced by dehydration from the Philippine Sea slab. The Poisson&#x2019;s ratio is normal to low in the forearc mantle in middle-south Kyushu. This is consistent with the absence of low-frequency tremors, and may indicate that dehydration from the subducting crust is not vigorous in this region.  相似文献   

The Weichselian Late-glacial in southwestern Europe (Iberian Peninsula,Pyrenees, Massif Central,northern Apennines)     

J. -L. de Beaulieu  V. Andrieu  P. Ponel  M. Reille  J. J. Lowe 《第四纪科学杂志》1994,9(2):101-107

This paper presents a summary of Late-glacial environmental changes in southwestern Europe (lberian Peninsula, Pyrenees, Massif Central and the northern Apennines). The emphasis is on palaeoclimatic interpretations inferred from key sites in the region from which the most detailed records are available and which have been radiocarbon dated. The earliest evidence for climatic improvement following the end of the last glacial stage is dated to ca. 15 ka BP and is found at a few sites only. By 13 ka BP, a more widespread and marked climatic improvement is evident, although it is difficult to be precise in the timing and magnitude of the event. There are significant variations in detail between the Late-glacial records, but evidence for a significant cooling correlated with the Younger Dryas event is widespread throughout the region. Just two sites in the region provide evidence for an earlier, less emphatic phase of climatic cooling, which is tentatively equated with the ‘Older Dryas’ of continental northern Europe. Dry conditions appear to have predominated throughout the region in the later part of the Younger Dryas and the early Holocene.  相似文献   

3-D Non-linear Travel-time Tomography: Imaging High Contrast Velocity Anomalies   总被引：1，自引：0，他引：1  

Chao-ying?BaiEmail author  Stewart?Greenhalgh 《Pure and Applied Geophysics》2005,162(11):2029-2049

In this paper we present an approach for 3-D travel-time tomography, which works well in reconstructing high contrast velocity anomalies in both location and strength. It uses a revised ‘irregular&#x2019; approach to the shortest-path method as the ray tracer and a damped minimum norm, and constrained least-squares CG approach as the inversion solver. In ray tracing, the advantages of the revised ‘irregular&#x2019; over the ‘regular&#x2019; approach are that the secondary nodes introduced on the cell surfaces significantly improve accuracy of computed travel times, without dramatically increasing the total number of cells and nodes; the tri-linear velocity function defined across the cell guarantees accurate ray tracing in a high velocity contrast medium; and the capacity to calculate a relatively large 3-D model, due to the fast run speed (at least one order of magnitude over the ‘regular&#x2019; approach) and less number of total nodes. The introduction of ‘soft&#x2019; and ‘hard&#x2019; bounds into the inversion process changes the conditioning and makes the solution meaningful in a physical sense. Thus the artifacts caused by noise and high velocity contrasts are substantially suppressed and the image quality is considerably improved, making the solution realistic with noisy or inconsistent travel-time data. Several numerical tests indicate that we can obtain good quality images even for high velocity contrast anomalies (say more than 20%) in the target region. This means the inversion algorithm is an efficient and effective procedure. Meanwhile, the inversion procedure is not very sensitive to the quality of the travel-time data, which is promising for practical usage.  相似文献