Reconstruction of modern climate and environmental changes in east Asia using inland natural climate archives can provide valuable insights on decadal–multidecadal climate and environmental patterns that are probably related to both natural and anthropogenic forcing. Here we investigated an 89‐cm‐long sediment core (TH1) from Tian Lake, southeastern China, for sedimentological, physical and geochemical parameters in order to understand climate and environmental changes for the latest two centuries. 137Cs‐ and 210Pb‐based age models show that the fine sand–coarse silt‐dominated core contains ~170 years (c. AD 1842–2011) of continuous sedimentation. Sediments with fine sands, low MS values, high water content, high TOC content and a high C:N ratio from c. AD 1842 to 1897 suggest intense hydrological conditions and strong runoff in the catchment, probably because of a humid climate. From AD 1897 to 1990, sediments with very fine sand and coarse silt, high MS values, low water content and unchanged TOC and C:N ratios indicate normal hydrological conditions and in‐lake algae‐derived organic matter. During this interval, the chemical weathering indicators show stronger weathering conditions compared with sediments deposited during AD 1842–1897, supporting the dominance of weathered surface soil input in the earlier interval and physical erosion dominance in the later period, respectively. Since AD 1990, the continuous decrease of geochemical proxies suggests human‐interacted Earth surface processes in the catchment of Tian Lake. A PCA revealed four dominant geochemical controlling factors – detrital input, trophic status, grain size and early diagenesis –, accounting for 26, 20, 18 and 16% of total variance, respectively. This study for the first time provides lacustrine geochemical evidence for the most recent two centuries of climate and environmental changes in coastal southeastern China, a region that is currently undergoing an inversion of critical zone, i.e. an overturning of its soil profile, owing to swift modernization. 相似文献
The high-temperature enthalpies of liquid and glassy CaAl2Si2O8 were measured by drop calorimetry using a diphenyl ether drop calorimeter. These data are combined with published values of the high-temperature enthalpy of crystalline anorthite and the enthalpy of vitrification of anorthite to obtain the enthalpy of fusion of anorthite. Analysis of the data yields the following preferred values (enthalpy in kcal/mol, uncertainty limits correspond to two standard deviations):enthalpy of vitrification at 985 K,
vHv985=18.6±0.6; enthalpy of the liquid at 1,830 K, H1830l300g
=130.4±1.2; enthalpy of the glass at 985 K, H985g
-H300g
=46.7±0.4; enthalpy of crystalline anorthite between 985 and 1,830 K, H1830c
-H985c
=69.9±1.4; calculated enthalpy of fusion of anorthite at 1,830 K,
fH1830= 32.4±2.1.The average heat capacity of supercooled liquid CaAl2Si2O8 between the glass transition (Tg 1,086 K) and the melting point (Tf7=1,830 K) is 102 ± 2 cal/mol/K. The large difference between the enthalpy of fusion and the enthalpy of vitrification for the minerals anorthite and diopside is emphasized. The practice of assuming
fH vH should be discontinued for silicate compounds for which TfTg. 相似文献
Enzyme induced carbonate precipitation (EICP) is an emerging soil improvement method using free urease enzyme for urea hydrolysis. This method has advantages over the commonly used microbially induced carbonate precipitation (MICP) process as it does not involve issues related to bio-safety. However, in terms of efficiency of calcium carbonate production, EICP is considered lower than that of MICP. In this paper, a high efficiency EICP method is proposed. The key of this new method is to adopt a one-phase injection of low pH solution strategy. In this so-called one-phase-low-pH method, EICP solution consisting of a mixture of urease solution of pH?=?6.5, urea and calcium chloride is injected into soil. The test results have shown that the one-phase-low-pH method can improve significantly the calcium conversion efficiency and the uniformity of calcium carbonate distribution in the sand samples as compared with the conventional two-phase EICP method. Furthermore, the unconfined compressive strength of sand treated using the one-phase-low-pH method is much higher than that using the two-phase method and the one-phase-low-pH method is also simpler and more efficient as it involves less number of injections.
Zusammenfassung
a) Es werden die Ergebnisse eines Messverfahrens besprochen, dessen Aufgabe die überprüfung des Injektionserfolges ist. -b) Das Verfahren wurde an verschiedenen Baustellen bei sehr verschiedenen Bodenverhältnissen eingesetzt. Die Ergebnisse werden mitgeteilt. Es war in vielen Fällen möglich, die durch elektrische Messungen begründete Vorhersage mit den mechanisch gewonnenen Befunden zu vergleichen. Auch diese Ergebnisse werden mitgeteilt. -c) Im Zuge dieser Untersuchungen wurde die elektrische Mischtheorie experimentell untersucht und ein geoelektrisches Verfahren zur Bestimmung desK-Wertes entwickelt. -d) Die richtige Verbindung der elektrischen und mechanischen Messverfahren ermöglicht ein weit genaueres Studium des Injektionsvorganges und eine viel richtigere Beurteilung des Injektionserfolges als die bisher übliche blosse Wasserverpressung.
Summary The results of a geoelectrical method of measurement for controlling cement injections are discussed. This method was practised already at several building-sites e. g. at building-sites in the bare and rocky Alpine region (Carso) of Yugoslavia. By means of this geoelectrical method the volumetric distribution of the injection mass can be controlled and therefore also the quantity discharged from the injection volume. In many cases the results obtained by geoelectrical measurements were later mechanically controlled. These results show the usefulness of this method. By means of this geoelectrical method more precise results may be obtained than by water pressure which method was used exclusively before. In this paper the fundamentals of this method and the geoelectrical mixture theory are discussed. Then the results obtained at the building-sites of Kaprun (Austria) and of Lokvarka and Cetina (Yugoslavia) are compared.
Nach Referaten auf der Vierten Allgem. Tagung derSocietà Italiana di Geofisica e Meteorologia in Genova (5.–8. April 1956).Der Verfasser dankt allen, die ihm bei der Durchführung der Untersuchungen geholfen haben und insbesondere seinen Mitarbeitern. Besonderen Dank spricht er den Herren der Tauernkraftwerke A. G. und Geofizika in Zagreb aus. 相似文献
Based on the discrete form of the main governing equation derived, a single wave as the main motion of the instability analysis
was found. This solution gives the whole process from the initial stage to the nonlinear equilibrium state.
Next we examined the instability of the main motion above-mentioned in the initial stage and showed the instability properties
of a developing process.
Contribution No. 987 from the Institute of Oceanology, Academia Sinica. 相似文献
Unit hydrographs (UHs), along with design rainfalls, are frequently used to determine the discharge hydrograph for design
and evaluation of hydraulic structures. Due to the presence of various uncertainties in its derivation, the resulting UH is
inevitably subject to uncertainty. Consequently, the performance of hydraulic structures under the design storm condition
is uncertain. This paper integrates the linearly constrained Monte-Carlo simulation with the UH theory and routing techniques
to evaluate the reliability of hydraulic structures. The linear constraint is considered because the water volume of each
generated design direct runoff hydrograph should be equal to that of the design effective rainfall hyetograph or the water
volume of each generated UH must be equal to one inch (or cm) over the watershed. For illustration, the proposed methodology
is applied to evaluate the overtopping risk of a hypothetical flood detention reservoir downstream of Tong-Tou watershed in
Taiwan. 相似文献