A simple relationship for crenulate-shaped bay in static equilibrium     

Zhi-Qian Wang  Soon-Keat Tan  Nian-Sheng Cheng  Keng-Wee Goh 《Coastal Engineering》2008

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The oxidation states of copper and iron in mineral sulfides, and the oxides formed on initial exposure of chalcopyrite and bornite to air     

Siew Wei Goh  Robert N. Lamb  Damian Moran 《Geochimica et cosmochimica acta》2006,70(9):2210-2228

Metal L_2,3, sulfur K and oxygen K near-edge X-ray absorption fine structure (NEXAFS) spectra for chalcopyrite, bornite, chalcocite, covellite, pyrrhotite and pyrite have been determined from single-piece natural mineral specimens in order to assess claims that chalcopyrite should be regarded as Cu^IIFe^IIS₂ rather than Cu^IFe^IIIS₂, and that copper oxide species are the principal initial oxidation products on chalcopyrite and bornite exposed to air. Spectra were obtained using both fluorescence and electron yields to obtain information representative of the bulk as well as the surface. Where appropriate, NEXAFS spectra have been interpreted by comparison with the densities of unfilled states and simulated spectra derived from ab initio calculations using primarily the FEFF8 code and to a lesser extent WIEN2k. Metal 2p and S 2p photoelectron spectra excited by monochromatised Al K_α X-rays were determined for each of the surfaces characterised by NEXAFS spectroscopy. The X-ray excited Cu LMM Auger spectrum was also determined for each copper-containing sulfide. FEFF8 calculations were able to simulate the experimental NEXAFS spectra quite well in most cases. For covellite and chalcocite, it was found that FEFF8 did not provide a good simulation of the Cu L₃-edge spectra, but WIEN2k simulations were in close agreement with the experimental spectra. Largely on the basis of these simulations, it was concluded that there was no convincing evidence for chalcopyrite to be represented as Cu^IIFe^IIS₂, and no strong argument for some of the Cu in either bornite or covellite to be regarded as Cu(II). The ab initio calculations for chalcopyrite and bornite indicated that the density of Cu d-states immediately above the Fermi level was sufficient to account for the Cu L₃-edge absorption spectrum, however these incompletely filled Cu d-states should not be interpreted as indicating some Cu(II) in the sulfide structure. It was also concluded that the X-ray absorption spectra were quite consistent with the initial oxidation products on chalcopyrite and bornite surfaces being iron oxide species, and inconsistent with the concomitant formation of copper-oxygen species.  相似文献   

The distribution of the 9 cm radio emission over the solar disk during the sunspot minimum     

J. Roosen  T. Goh 《Solar physics》1967,1(2):242-253

The brightness distribution of the quiet sun on 9.1 cm wavelength is determined from the Stanford pencil-beam radioheliograms for three periods in the recent solar activity minimum, centred at July 15 and September 15, 1964 and at April 5, 1965. The brightness maxima near the limbs are not symmetric with respect to the central meridian, but are situated at 76 °E and 66 °W longitude, respectively. On the disk, the brightness temperature is likewise distributed asymmetrically, but the direction of this asymmetry changes as the new cycle starts. The asymmetries are tentatively explained by assuming the presence of inhomogeneous streamers in the solar atmosphere, which are tilted by the solar rotation. The eastward shift of the limb maxima with respect to the optical disk is confirmed by the 21 cm-heliograms obtained at Fleurs near Sydney, Australia.  相似文献   

Environmental impact of economic development in peninsular malaysia: a review     

Goh Kim Chuan 《Applied geography (Sevenoaks, England)》1982,2(1):3-16

Malaysia's rapid economic development in the two decades since independence has brought benefits to the nation as a whole. However, it has also produced problems in relation to the natural resources and the environment, particularly in Peninsular Malaysia. The urgency with which economic, social and political objectives have to be achieved through development has greatly taxed the nation's natural resources, such as land, forests and water, whilst the discharge of wastes of various kinds has resulted in the degradation of rivers, the seas and air. Serious pollution problems have surfaced in various forms and these have prompted the government to formulate policy guidelines on the environment vis-á-vis development. This paper reviews the different kinds of problems relating to resource exploitation and environmental deterioration and their implications with particular reference to Peninsular Malaysia.  相似文献   

Updating Soil Parameters Using Spreadsheet Method for Predicting Wall Deflections in Braced Excavations     

Wengang Zhang  Anthony T. C. Goh  Yanmei Zhang 《Geotechnical and Geological Engineering》2015,33(6):1489-1498

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Assessment of apparent earth pressure for braced excavations in anisotropic clay     

Zhang  Runhong  Goh  Anthony Teck Chee  Li  Yongqin  Hong  Li  Zhang  Wengang 《Acta Geotechnica》2021,16(5):1615-1626

Acta Geotechnica - The evaluation of strut forces is critical to ensure the system stability of braced excavation in urban areas. The most common empirical approach to determine the forces in the...  相似文献   

Modern analogues and the early history of microbial life     

Brendan P. Burns  Roberto Anitori  Philip Butterworth  Ruth Henneberger  Falicia Goh  Michelle A. Allen  Raquel Ibaez-Peral  Peter L. Bergquist  Malcolm R. Walter  Brett A. Neilan 《Precambrian Research》2009,173(1-4):10

Revealing the geological history of microbial life is very challenging. Microbes rarely are preserved with morphological fidelity, and even when they are, morphology is a poor guide to phylogeny and metabolism. Biological studies of environments considered analogous to those of paleobiological interest on the ancient Earth can inform interpretations and suggest new approaches. This paper reviews recent advances in our understanding of the biological diversity of two environments relevant to Archean paleobiology: those of extreme acidity and temperature (the Mt. Hood and White Island volcanoes), and high salinity (living stromatolites in Shark Bay). The combination of traditional microbial isolation with the use of modern molecular techniques has revealed that the microbial communities in these environments are much more diverse than originally thought. Through the extraction of whole microbial community DNA, enzymatic amplification of evolutionarily conserved genes, and cloning and sequencing of these genes, more specific and informed inferences concerning functional complexity in these extreme environments have now been made. Studies of the modern stromatolites have demonstrated that they have a very diverse range of micoorganisms, and contrary to previous interpretations, cyanobacteria are not the most abundant microbes present. In addition, many of the microorganisms are unique with no known close relatives, and these microorganisms may also possess novel physiologies vital to the integrity and persistence of stromatolites through space and time. Microbes in the volcanoes studied are present ubiquitously and include geochemically significant sulfur- and iron-cycling taxa. The findings from the studies reviewed here suggest that the Archean biota may have been functionally diverse and much more complex than has yet been revealed. The importance of studying modern analogues is stressed in that the biogeochemical processes occurring in these communities leave morphological, mineralogical, lipid and isotopic signals that could be sought in the rock record.  相似文献   

Interaction of cuprite with dialkyl dithiophosphates     

Alan N. Buckley  Siew Wei Goh  William M. Skinner  Ronald Woods  Liang-Jen Fan 《International Journal of Mineral Processing》2009,93(2):155-164

The interaction of freshly abraded surfaces of cuprite, Cu₂O, with neutral or mildly alkaline aqueous solutions of diethyl or di-n-butyl dithiophosphate (DTP) has been investigated by means of conventional and synchrotron X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. It was confirmed that DTP adsorbs readily on Cu atoms in the surface layer of the mineral treated with solutions of the collector at pH values near 7 and 9 in the presence of air, and renders the surface hydrophobic. When cuprite is treated with relatively high concentrations of DTP for sufficiently long periods, collector can also be adsorbed as CuDTP, but the coverage does not exceed a thin layer of CuDTP on the adsorbed DTP monolayer, unlike the situation with Cu metal or chalcocite where a thick multilayer can be formed.  相似文献   

Development and assessment of GPS virtual reference stations for RTK positioning   总被引：6，自引：2，他引：4  

G.R. Hu  H.S. Khoo  P.C. Goh  C.L. Law 《Journal of Geodesy》2003,77(5-6):292-302

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Differences in Ecosystem Dynamics between the Northern and Southern Parts of the Japan Sea: Analyses with Two Ecosystem Models     

Goh?OnitsukaEmail author  Tetsuo?Yanagi 《Journal of Oceanography》2005,61(3):415-433

Differences in ecosystem dynamics between the northern and southern parts of the Japan Sea have been investigated with two nitrogen based ecosystem models forced by climatological mixed layer depth and euphotic layer depth. Models having 4 and 9 compartments with the same biochemical parameters were applied to the northern and southern parts. The spring bloom in the southern part is earlier and smaller than that in the northern part according to both models, which is supported by satellite ocean color images. The difference of the timing is related to the variation of mixed layer depth, and the magnitude of blooming is also related to the concentrations of surface nutrient and herbivorous zooplankton in early spring. The simulated seasonal variations of ecosystem characteristics (standing stock of each compartment, primary production and the ratio of export flux of organic particles to the primary production) are not significantly different between two models. The ratio of export flux of organic particles to the primary production are about 36% and 23% in the northern and southern parts according to the 4-compartment model, while the values are 31% and 18% by 9-compartment model. These results suggest that the biological pump in the northern part is more active than that in the southern part of the Japan Sea. Sensitivity analyses have been carried out to examine the differences of the response to the models.  相似文献