Ice Induced Low Temperature Fatigue Crack Propagation in Offshore Structural Steel A131     

DUAN Menglan  GAO Zhaojie  LIU Chuntu Senior Engineer  China Classification Society  Beijing  China. Research Professor 《中国海洋工程》1998,(3)

To investigate the low temperature fatigue crack propagation behavior of offshore structuralsteel A131 under random ice loading,three ice failure modes that are commonly present in the Bohai Gulfare simulated according to the vibration stress responses induced by real ice loading.The test data are pro-cessed by a universal software FCPUSL developed on the basis of the theory of fatigue crack propagationand statistics.The fundamental parameter controlling the fatigue crack propagation induced by randomice loading is determined to be the amplitude root mean square stress intensity factor K_(arm).The test resultsare presented on the crack propagation diagram where the crack growth rate da/dN is described as thefunction of K_(arm).It is evident that the ice failure modes have great influence on the fatigue crack propaga-tion behavior of the steel in ice-induced vibration.However,some of the experimental phenomena and testresults are hard to be physically explained at present.The work in this paper is an init  相似文献   

A Whitecap Coverage Model Based on the Surface Slope For Criterion of Wave Breaking   总被引：3，自引：2，他引：1  

Xu Delun  Yu Dingyong  Lu Hongmin Professor  Physical Oceanography Laboratory  Ocean University of Qindao  Qingdao Associate Professor  Engineering School  Ocean University of Qindao  Qingdao Senior Engineer  Physical Oceanography Laboratory  Ocean University of Qingdao  Qingdao 《中国海洋工程》1998,(1)

Using the limit surface slope as a criterion of wave breaking,a simple model for estimatingthe spatial fraction of breaking surface of sea at an instant,which is regarded as the whitecap coverge inthis paper,is analytically derived from the probability density of surface slope based on Gaussianstatistics.The resulting fraction is found depending on the fourth moment of wave spectum,m_4,as well asthe critical threshold of surface slope.By expressing the fourth moment in terms of the Neumannspectrum,a formula linking the fraction and wind speed for fully developed sea states is obtianed.Anotherformula relating the fraction to both wind speed and fetch(or duration)is achieved by expressing m_4 interms of the Krylov spectrum and applying the empirical relationships used in the SMB ocean wave pre-dicting technique.A comparison between these results and the field data of whitecap coverage collected byMonahan and O＇Muircheartuigh shows an encouraging agreement.  相似文献   

Assessing “Urban Karst” Effects from Groundwater–Storm Sewer System Interaction in a Till Aquitard     

Martin G. Shepley  Nick Schmidt  Matt J. Senior  Stephen R. H. Worthington  Ron B. Scheckenberger 《Ground water》2020,58(2):269-277

Storm sewer systems and their associated utility trenches may strongly influence the effects of urbanization on a groundwater system. This study was undertaken to identify the causes of district-wide basement infiltration in an aquitard system. It comprised widespread continuous monitoring of utility trench wells and dye tracing from storm sewer system exfiltration tests. The results indicate that a major effect of urbanization on shallow groundwater is related to storm sewer system exfiltration, which is marked by a characteristic pattern of head variations in the aquitard unrelated to distributed surface infiltration. The aquitard constrains flow from storm sewer system exfiltration to the utility trench, creating an urban flow path for groundwater discharge. Temporary buildup of water levels in the utility trench drives relatively high-velocity flow through the permeable sewer bedding material of the utility trench to a separate foundation drainage collector system, ultimately causing a severe “urban karst” effect that produces system surcharging and widespread basement water infiltration. The main conditions causing the “urban karst” are the large hydraulic conductivity ratio between the utility trench material and the aquitard, and the shallow depth and low gradient of the storm sewer system imposed by a very flat drainage basin.  相似文献   

A late-Glacial diatom and pigment history of Little Lake,New Brunswick with particular reference to the younger Dryas climatic oscillation     

David J. Rawlence  A. Senior 《Journal of Paleolimnology》1988,1(3):163-177

Diatom and pigment data are presented from a 6.39 m core from Little Lake, New Brunswick. From its inception to ca. 11.5k y.B.P., the lake was dominated by benthic alkaliphilic diatoms, predominantly Fragilaria spp, which are believed to have grown in the moat of a lake with extended periods of ice cover. Ice free summers apparently prevailed for up to 500 years (ca. 11.5–11k y.B.P.), during which time planktonic species — Cyclotella bodanica Eulenst. and C. stelligera Cl. & Grun. appeared for the first time. From ca. 11.–10k y.B.P. the lake was dominated by Fragilaria pinnata Ehr.v. pinnata, F. construens v. venter (Ehr.) Grun. and F. construens (Ehr.) Grun. The reappearance of these species, coincident with distinct changes in sediments, organic matter, pollen types and influx rates, is believed to represent the influence of the younger Dryas climatic cooling. Little Lake appears to have reverted to a period of only partial summer melting. The ca. 10k y.B.P. warming is marked by a Navicula/Cymbella/Cyclotella community, representing growth of both littoral and planktonic communities. Navicula was subsequently replaced by Eunotia and Tabellaria, and finally by a Pinnularia/Stauroneis/Eunotia community, in which Fragilaria pinnata v. pinnata and F. construens v. venter increase again. These two recent phases represent increasing growth of a littoral community, and some increase in littoral alkaliphilous elements. Trends in organic matter and pigment values are consistent with a gradual increase in biomass, particularly from ca. 10k y.B.P. Diatom growth is indicative of increasing littoral and benthic growth with time, but there is no indication that Little Lake was ever eutrophic.  相似文献   

A proposed method of defining deeply weathered rock units based on regional geological mapping in southwest Queensland     

B. R. Senior  J. A. Mabbutt 《Australian Journal of Earth Sciences》2013,60(5-6):237-254

A practical system of defining deeply weathered rock horizons is proposed, using the concept of a profile, defined as the vertical extent of a weathered rock sequence from the initiating land surface or originating surface down to unweathered parent rock. Advantages inherent in this system lie in the strict stratigraphic approach, its applicability to field mapping, and its broad accordance with accepted principles and concepts of the Australian Code of Stratigraphic Nomenclature. Establishment of a reference (type) section for each profile, with formal registration by a central authority, together with validation through publication, are recommended. Profile names, which carry some genetic implications, are distinguished from lithostrati‐graphic units through the use of distinctive map symbols and inclusion of the word profile within profile names. Three weathered rock units (Morney profile, Canaway profile and Curalle silcrete profile), and one altered rock unit (Haddon silcrete) which is believed to be a product of subsurface silicification, are formally defined. Parent rocks of these profiles (Winton and Eyre Formations) are described to demonstrate the nature of weathering and substantiate the recognition of a particular profile. Combinations of parent rock and weathered profile relationships are given to explain regional continuity of these profiles throughout southwest Queensland.  相似文献   

Assessing underwater noise levels during pile-driving at an offshore windfarm and its potential effects on marine mammals     

Helen Bailey  Bridget Senior  Jan Rusin  Paul M. Thompson 《Marine pollution bulletin》2010,60(6):888-897

Marine renewable developments have raised concerns over impacts of underwater noise on marine species, particularly from pile-driving for wind turbines. Environmental assessments typically use generic sound propagation models, but empirical tests of these models are lacking. In 2006, two 5 MW wind turbines were installed off NE Scotland. The turbines were in deep (>40 m) water, 25 km from the Moray Firth Special Area of Conservation (SAC), potentially affecting a protected population of bottlenose dolphins. We measured pile-driving noise at distances of 0.1 (maximum broadband peak to peak sound level 205 dB re 1 μPa) to 80 km (no longer distinguishable above background noise). These sound levels were related to noise exposure criteria for marine mammals to assess possible effects. For bottlenose dolphins, auditory injury would only have occurred within 100 m of the pile-driving and behavioural disturbance, defined as modifications in behaviour, could have occurred up to 50 km away.  相似文献   

The flotation of gersdorffite in sulphide nickel systems — A single mineral study     

G.D. Senior  L.K. Smith  E. Silvester  W.J. Bruckard   《International Journal of Mineral Processing》2009,93(2):165-171

The flotation response of gersdorffite has been determined in a series of batch flotation tests in which a sulphide sample containing about 76% gersdorffite was floated from mixtures with quartz.Using xanthate as collector, the arsenide floated strongly at pH 9, irrespective of whether lime, sodium hydroxide or sodium carbonate was used as pH modifier. When the pH was raised further to 10 or more using lime, the flotability decreased sharply.Changing the pulp potential at pH 9 also strongly affected the flotation response. Above about − 230 mV SHE, the mineral floated strongly, but below this potential it was essentially non-flotable. As far as it was tested (up to + 400 mV SHE), no upper limiting potential was found.Adding cyanide to the grinding mill brought about only a weak depressant effect on subsequent gersdorffite flotation at both pH 9 and 10. However, adding the same amount of cyanide to the flotation cell produced a strong depressant effect at the same pH values. At both pH 9 and pH 10, a threshold cyanide addition existed below which gersdorffite floated strongly, and above which it did not. For the conditions used in this study, this addition equates to about 100 g/t at pH 9 and about 80 g/t at pH 10. A hypothesis for the depression effect is presented which is consistent with both the available flotation data and a series of diagnostic analyses of grinding and flotation pulps completed during the test work.  相似文献   

An assessment of measures of storminess: simulated changes in northern hemisphere winter due to increasing C02     

R. E. Carnell  C. A. Senior  J. F. B. Mitchell 《Climate Dynamics》1996,12(7):475-496

A range of diagnostics from two GCM simulations, one of the present-day climate and one of the last glacial maximum (LGM) is used to gain insight into their different temperature structures and eddy dynamics. There are large local increases in baroclinicity at the LGM, especially in the Atlantic storm track, with large accompanying increases in the low level transient eddy heat flux. However, the differences in the zonal mean are much smaller, and the increases in both baroclinicity and heat flux are confined to low levels. Supplementary experiments with baroclinic wave lifecycles confirm the marked contrast between local and zonal mean behaviour, but do not adequately explain the differences between the zonal mean climates. The total flux of energy across latitude circles in the Northern Hemisphere does not change much during DJF, although its transient component is actually reduced at the LGM (during JJA the transient component is increased). Calculations of total linear eddy diffusivity reveal that changes in the time mean stationary waves are chiefly responsible for the seasonal range of this quantity at the LGM, while they only account for half the seasonal range at the present-day.  相似文献   

The second Hadley Centre coupled ocean-atmosphere GCM: model description, spinup and validation   总被引：2，自引：0，他引：2  

T. C. Johns  R. E. Carnell  J. F. Crossley  J. M. Gregory  J. F. B. Mitchell  C. A. Senior  S. F. B. Tett  R. A. Wood 《Climate Dynamics》1997,13(2):103-134

  相似文献   

RENOVATION IN HANDUN IRRIGATION DISTRICT AND ITS EFFECT     

WAN Zhaohui  Professor  China Institute of Water Resources & Hydropower Research  P.QBox Beijing  China GAO Jianen  Senior Engineer  North-West Hydro-technical Science ReSearch Institute  Yangling  Shaangxi  China ZHANG Anmin Director 《国际泥沙研究》1997,(3)

LIRRIGAnONALONGTHELOWERYELLOW~RYellowairisoneOfthemainwaterresourcesinNOrthChina.Sincetheames70diVersionslthees,28siphonsand30PUmpingstationshavebeenbuiltalongtheLowerYellowRad.Thetotaldischargingcapacityis3363m3lsacthetotalirrigationareaisnearlytwOInillinnh~s.Intheeighties,asanaVerage,Il.lxloom3ofwaterwasdiVertalfromtheYellowairannually.In198915.4-cio'm3ofwatCfwasdiVerted.AstheYdlowforerisaheavilysediment-ladenone,sedimentisdiVertedsimultalleouslywhenwaterisdiverted.Inthe…  相似文献