Theoretical study of cross-valley wind circulation     

Professor Dr. Wen Tang 《Meteorology and Atmospheric Physics》1976,25(1):1-18

Summary An analytical model is developed to investigate the interaction between the large scale prevailing air flow and the thermally induced slope wind circulation. The Boussinesq approximation is assumed. The lower order successive approximation solutions are obtained in spectral representation for both typical daytime and night time cases. The results have produced interesting circulation features often observed in mountainous terrain.

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Theoretische Untersuchung der ein Tal überquerenden Windzirkulation

Zusammenfassung Es wird ein analytisches Modell zur Untersuchung der Wechselwirkung zwischen einer großräu mig vorherrschenden ein Tal überführenden Luftströmung und der thermisch ausgelösten Hangwindzirkulation entwickelt. Dabei wird die Approximation nach Boussinesq angewendet. Für typische Verhältnisse bei Tag und bei Nacht werden Näherungslösungen niedrigerer Ordnung in spektraler Darstellung erhalten. Die Ergebnisse haben interessante Zirkulationsformen aufgezeigt, die oft im gebirgigen Gelände beobachtet werden.

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With 8 Figures  相似文献   

Biogene,klastische und evaporitische Sedimentation in einem mesothermen monomiktischen ufernahen See (Golf von Aqaba)     

Professor Dr. Wolfgang E. Krumbein  Yehuda Cohen M.Sc. 《International Journal of Earth Sciences》1974,63(3):1035-1065

The genesis and development of a monomictic, mesothermal lake and its sediments is demonstrated by the analysis of sediment cores from different parts of the lake and from different stages of development. The compounds which build up the sediments, consist of irregular large particles from the surrounding crystalline rocks, of fine grained silt sediments from catastrophic flud deposits, of evaporitic series, and algae mats. The thickness of the different layers and their distribution in various parts of the lake; the different compounds, absolute age determinations, the carbonate layers and algae mats allow the definition of different stages of development of the lake. Causes and influences of an unusual type of monomixis with summer turnover are discussed and related to the sedimentary environment. Annual fluctuations in physical and biological limnology lead to the development of annual cycles in mat development and evaporites, which are reflected in the varved sediments. Inorganic sedimentation of terrestrial sediments, evaporites and organic matter accumulation are in shifting equilibrium which can be analysed by changes in the sediment types. Within the zone of biologic decay of algae via photosynthetic and other sulfur bacteria and heterotrophic bacteria, biogenic aragonite, Mg-Calcite and sulfides are precipitated. The autigenic dolomite occuring within the algae mats could not be attributed to biological precipitation so far. The lake started out as a lagoon approximately 4500 years B.P. Algae mat development was initiated after the lagoon was separated from the open sea (2400 B.P.). The central parts of the lake subsided at a time between 1900 and 1600 B.P. At this time the algae mat deposition, which until then took place in the whole lake, was restricted to the remaining shallow parts. Years of extremely high precipitation and catastrophic floods are represented by silt layers in the western parts of the lake, while coarser terrestrial sediments are intercalated in the algae mats of the eastern parts. Oöids, carbonate laminae, oncoliths and other types of carbonate particles within the algae mats are defined as biogenic by SEM analyses and laboratory experiments.  相似文献   

STEREOSCOPIC VISION APPLIED TO PHOTOGRAMMETRY     

Professor  W. D. Wright 《The Photogrammetric Record》1954,1(3):29-49

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Importance Sampling Method in V-Space   总被引：3，自引：0，他引：3  

Jin Weiliang Professor 《中国海洋工程》1997,(2)

Based on the observation of importance sampling and second order information about the fail-ure surface of a structure,an importance sampling region is defined in V-space which is obtained by ro-tating a U-space at the point of maximum likelihood.The sampling region is a hyper-ellipsoid that con-sists of the sampling ellipse on each plane of main curvature in V-space.Thus,the sampling probabilitydensity function can be constructed by the sampling region center and ellipsoid axes.Several exampleshave shown the efficiency and generality of this method.  相似文献   

Book review: Seismic Waves in Laterally Inhomogeneous Media, Vols I and II     

Professor  B. L. N. KENNETT 《Geophysical Journal International》1997,130(2):547-547

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IGU Working Group on Mountain Geology     

Secretary Peter W. Höllermann Professor Dr. 《GeoJournal》1981,5(4):397-397

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IGU Working Group on Resource Management in Drylands     

Professor Dr. H. G. Mensching 《GeoJournal》1982,6(4):393-394

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Prediction of wave pressures on smooth impermeable seawalls     

S. Neelamani  H. Schüttrumpf  M. Muttray  H. Oumeraci 《Ocean Engineering》1999,26(8):137

Simple prediction methods are proposed to estimate the wave induced pressures on smooth impermeable seawalls. Based on the physics of the wave structure interaction, the sloped seawall is divided into a total of five zones (zones 1, 2 and 3 during run-up (corresponding pressures are called as positive pressures) and zones 4 and 5 during run-down (corresponding pressures are called negative pressures)) (Fig. 1). Zone 1 (0<z<d−H_i/2), where the wave pressure is governed by the partial reflection and phase shift; Zone 2 (d−H_i/2<z<d), where the effect of wave breaking and turbulence is significant; Zone 3 (d<z<Run-up height), where the pressure is induced by the run-up water; Zone 4 (Run-down<z<d), where the wave pressure is caused by the run-down effect and Zone 5 (0<z<d-Run down), where the negative wave pressures are due to partial reflection and phase shift effects. Here d is the water depth at the toe of the seawall, H_i is the incident wave height and z is the vertical elevation with toe of the seawall as origin and z is positive upward. For wave pressure prediction in zones 1 and 5, the empirical formula proposed by Ahrens et al. (1993) to estimate the wave reflection and Sutherland and Donoghue's recommendations (1998) for the estimation of phase shift of the waves caused by the sloped structures are used. Multiple regression analysis is carried out on the measured pressure data and empirical formulas are proposed for zones 2, 3 and 4. The recommendations of Van der Meer and Breteler (1990) and Schüttrumpf et al. (1994) for the prediction of wave run-down are used for pressure prediction at zone 4. Comparison of the proposed prediction formulas with the experimental results reveal that the prediction methods are good enough for practical purposes. The present study also shows a strong relation between wave reflection, wave run-up, wave run-down and phase shift of waves on wave pressures on the seawalls.  相似文献   

The Behaviour of LNG Carrier Moored to a Jetty Exposed to Waves,Swell,Unsteady Wind and Current     

J. E. W. WICHERS 《中国海洋工程》1999,(1)

—Most terminals for tankers are piers and sea islands,while other types include single pointmoorings and multiple-buoy moorings.The LNG and LPG carrier moored to the jetty is a very commonterminal for transfer of gas in open seas.It is important to estimate the motions and line tensions of theLNG carrier when it moors to a jetty in metocean environment.Normally,the motions of the LNG carrierwould be restricted by the loading arm,which is connected to LNG carrier＇s manifold.An example of125,000m~3 LNG carrier moored to a jetty exposed to a set of environment conditions is given.Amathematical model which is based on the equations of motion in the time domain is used to the analysisof LNG moored to an offshore jetty exposed to waves,swell,wind and current.By means of a time do-main computer program TERMSIM computations are carried out to determine and optimize the lay-outand/or orientation of the jetty and mooring gear in terms of forces in mooring lines and fenders and theenvelope of motions of the loadi  相似文献   

Computation of Design Load and Motion for Floating Structures Navigating in Waves   总被引：1，自引：0，他引：1  

WANG Yanying  ZHU Renchuan  MIAO Jie Professor  School of Naval Architecture  Marine Engineering  Dalian University of Technology 《中国海洋工程》1999,(1)

—Analytical and numerical investigation is made of the source potential for floating structurewith forward speed in waves.A particular form is selected for numerical applications,where the double in-tegral of the Green function is transformed into the single one and the oscillation characteristics forintegrands in the specific computation domain are treated numerically.A comparison of calculated exam-p1es with published data is given and it shows that the numerical simulation is satisfactory and the accura-cy is adequate to engineering application.  相似文献