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1.
The presence of underground voids has an adverse influence on the performance of shallow foundations. In this study, the bearing capacity and failure mechanism of footings placed on cohesive-frictional soils with voids are evaluated using discontinuity layout optimization. By introducing a reduction coefficient, a set of design charts that can be directly applied to the classical bearing capacity formulation is presented. The results indicate that the undrained bearing capacity with voids is sensitive to soil weight and cohesion, as both the bearing capacity and stability issues exist in the problem. The failure mechanism is directly related to a variety of soil properties, the locations of single voids, and the horizontal distance between two voids. The presence of voids has a more dominant effect on c–φ soils compared to that on undrained soil. An interpretation of the critical and adverse locations for single-void and dual-void cases with various soil strengths is presented.  相似文献   

2.
We have analyzed light curves from the MOST satellite for the two active dwarfs ? Eri and κ Cet. Our maps of the stellar surface-temperature inhomogeneities were obtained with no a priori assumptions about the shape, configuration, and number of spots. We find variations of the surface-temperature inhomogeneities with time, also on time scales about equal to their rotation periods. We consider a model of a spotted star with two types of surface inhomogeneities—spots and related plage fields—and demonstrate that the best agreement between the theoretical and observed light curves is achieved for small ratios of the plage-field area to the area of cool spots. This conclusion indicates that long-term brightness variations of stars younger than the Sun are mainly due to variable spots on their surfaces, while the contribution from plage fields becomes more significant for older stars.  相似文献   

3.
The thermoelastic parameters of the CAS phase (CaAl4Si2O11) were examined by in situ high-pressure (up to 23.7 GPa) and high-temperature (up to 2,100 K) synchrotron X-ray diffraction, using a Kawai-type multi-anvil press. P–V data at room temperature fitted to a third-order Birch–Murnaghan equation of state (BM EOS) yielded: V 0,300 = 324.2 ± 0.2 Å3 and K 0,300 = 164 ± 6 GPa for K′ 0,300 = 6.2 ± 0.8. With K′ 0,300 fixed to 4.0, we obtained: V 0,300 = 324.0 ± 0.1 Å3 and K 0,300 = 180 ± 1 GPa. Fitting our P–V–T data with a modified high-temperature BM EOS, we obtained: V 0,300 = 324.2 ± 0.1 Å3, K 0,300 = 171 ± 5 GPa, K′ 0,300 = 5.1 ± 0.6 (?K 0,T /?T) P  = ?0.023 ± 0.006 GPa K?1, and α0,T  = 3.09 ± 0.25 × 10?5 K?1. Using the equation of state parameters of the CAS phase determined in the present study, we calculated a density profile of a hypothetical continental crust that would contain ~10 vol% of CaAl4Si2O11. Because of the higher density compared with the coexisting minerals, the CAS phase is expected to be a plunging agent for continental crust subducted in the transition zone. On the other hand, because of the lower density compared with lower mantle minerals, the CAS phase is expected to remain buoyant in the lowermost part of the transition zone.  相似文献   

4.
Bearing capacity of foundations is often determined for saturated state of the soil, regarding its simple and conservative results. This assumption, however, results in very uneconomic and overconservative design for a wide range of climates in the world. In this paper, plasticity equations were employed and extended for unsaturated soils to establish a theoretical approach to investigate the bearing capacity of unsaturated soils. It is achieved by combining the concept of effective stress and plasticity equations in terms of effective stress in unsaturated soils. The advantage of Bishop’s (4) effective stress concept was employed to simplify the equations. The equations were then transformed onto the zero extension lines directions to generalize this method for both associative and non-associative problems by which both stress and velocity field can be determined for unsaturated soils. A computer code was also developed to solve the relatively complex plasticity equations for a wide range of soil friction angles and matric suctions to compute the corresponding bearing capacity factor, N γ , for strip foundations with smooth and rough base. This factor seems to be one of the major contributors in the bearing capacity of shallow foundations. The results have been presented in design charts and theoretical equations.  相似文献   

5.
The staged high-pressure annealing of natural cubic diamonds with numerous melt microinclusions from the Internatsional’naya kimberlite pipe was studied experimentally. The results mainly show that the carbonate phases, the daughter phases in partially crystallized microinclusions in diamonds, may undergo phase transformations under the mantle P–T conditions. Most likely, partial melting and further dissolution of dolomite in the carbonate–silicate melt (homogenization of inclusions) occur in inclusions. The experimental data on the staged high-pressure annealing of diamonds with melt microinclusions allow us to estimate the temperature of their homogenization as 1400–1500°C. Thus, cubic diamonds from the Internatsional’naya pipe could have been formed under quite high temperatures corresponding to the lithosphere/asthenosphere boundary. However, it should be noted that the effect of selective capture of inclusions with partial loss of volatiles in relation to the composition of the crystallization medium is not excluded during the growth. This may increase the temperature of their homogenization significantly between 1400 and 1500°C.  相似文献   

6.
Observations of sunspot umbrae in the HeII λ304 Å and HeI λ10830 Å lines are analyzed and compared. Spectral observations in the HeI λ10830 line obtained on the Large Non-Eclipse Solar Coronograph of the Sayan Solar Observatory are used, together with HeII λ304 data obtained with the SOHO/EIT and CORONAS-f spacecraft. The contrast in the HeII λ304 line was chosen as an indicator of the UV flux. The dependences of the contrast in the HeII λ304 line and the parameters of the HeI λ10830 IR triplet on the sunspot area are obtained. The sunspot areas were determined using white-light images. A division of the dependences of the parameters of the HeI λ10830 and HeII λ304 lines on the sunspot area into two branches can be distinguished for leading and trailing sunspots. Possible origins of this behavior of the line parameters are discussed.  相似文献   

7.
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8.
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9.
The emergence of antibiotics residues in pharmaceutical industrial wastewater has been a significant environment problem. However, current methods of treating antibiotic-polluted wastewater are inefficient, of high cost and time-consuming. In this study, highly effective enzymatic Fe3O4 magnetic nanoparticles were developed, which is extremely simple and can degrade antibiotics in a fast manner at a low cost. β-Lactamase, a representative enzyme for β-lactam antibiotic degradation, was covalently immobilized on the surface of magnetic nanoparticles modified with amino groups by a simple cross-linking process. The immobilized β-lactamase displayed a wider pH and temperature range for penicillin G degradation than the free enzyme. Meanwhile, the thermostability and storage stability of the immobilized β-lactamase were improved. Fifty milligrams magnetic nanoparticles immobilized with β-lactamase can thoroughly degrade 100 mL penicillin G (5–50 mg L?1) within 5 min. Even if the β-lactamase immobilized on the nanoparticles was reused 35 times in the 5 mg L?1 penicillin G solution, it still kept more than 95% degradation efficiency. These suggest that magnetic nanoparticles immobilized with β-lactamase have a sufficient capacity for degrading antibiotics in wastewater and will serve as a practical and economical solution to antibiotic pollution in pharmaceutical industrial wastewater treatment.  相似文献   

10.
The Belomorian Mobile Belt (BMB) in northern Karelia mostly consists of gently sloping shear zones, whose gneisses and migmatized amphibolites and blastomylonites are typically thinly banded, with their banding consistently dipping north- and northeastward. These gently sloping shear zones were not affected by folding after they were produced and are not cut by Paleoproterozoic metabasite dikes. Intrusive metabasites in the gently sloping shear zones make up relatively small (usually <5 m) equant or elongate bodies and occur as fragments of larger bodies. These fragments are often concentrated in stripes. Metabasites in the gently sloping shear zone are sometimes also found as lenses and tabular bodies of relatively small thickness, which are conformable with the foliation of the host rocks. The gently sloping shear zones cut across older domains of more complicated structure, which suggests that these zones are gently sloping ductile shear zones. Along these zones, the nappes were thrust south- and southwestward, and this process was the last in the origin of major structural features of BMB when the Paleoproterozoic Lapland–Kola orogen was formed. Practically identical age values were obtained for the gently sloping shear zone in the two widely separated Engonozero and Chupa segments of BMB: 1879 ± 21 Ma (40Ar/39Ar amphibole age of amphibolite whose protolith was mafic rock) and 1857 ± 13 Ma (Sm–Nd mineral isochron age of garnet amphibolites after gabbronorite). The P–T metamorphic parameters in these gently sloping shear zones are remarkably different from the metamorphic parameters outside these zones: the pressure is 3–4 kbar lower and the temperature is 60–100°C lower. Thrusting-related decompression triggered the transition from the older high-pressure episode of Paleoproterozoic metamorphism to a younger syn-thrusting higher temperature metamorphic episode. The peak metamorphic parameters corresponding to the boundary between the amphibolite and granulite facies were reached only in the central portions of the shear zones: T= 680–760°C, P = 8.0–11.9 kbar. In areas of the most intense migmatization, temperature estimates in the central portions of the shear are as high as 810–830°C. The marginal portions of the shear zones were formed at lower temperatures of 610–630°C. The temperature heterogeneous and rock heating in the gently sloping shear zones may have resulted from flows of high-temperature metamorphic fluid that were focused to the central portions of the zones.  相似文献   

11.
The volcano–clastic sequence of Trompia Valley, which caps the Tre Valli Bresciane Variscan basement (TVB), comprises the Dosso dei Galli Conglomerate (DGC), the oldest deposit containing up to metre-sized metamorphic pebbles. This Lower Permian formation of the Trompia Basin was fed by the erosion products of the Variscan chain. We used microstructural and mineral chemical data on metamorphic pebbles of the DGC to infer a quantitative tectono-thermal evolution of the eroded pre-Permian basement and to compare them with those of TVB and the surrounding Southalpine basement units (tectono-metamorphic units = TMUs). Metapelitic and metaintrusive pebbles record a polyphase metamorphism with two metamorphic re-equilibrations: the first under epidote amphibolite facies (M1, ) and the second under greenschist facies (M2) conditions. Rock types and metamorphic data largely match those of TVB basement unit. The structural and metamorphic records in the pebbles are pre-Permian, and the conglomerate matrix is non-metamorphic. The DGC deposition age (283 ± 1–280.5 ± 2 Ma) constrains the minimal exhumation age of its basement source. The lack of staurolite bearing assemblages in metamorphic pebbles suggests that the DGC basement source was already exhumed to shallow structural levels (greenschist facies conditions) before the thermal equilibration consequent upon continental crust thickening induced by the Variscan collision.  相似文献   

12.
The results of the investigations of the transformation of impurity defects in natural diamonds of various habits at the stage of high-temperature annealing at P = 6 GPa and T = 2200°C are presented. The studies conducted allowed us to ascertain that the transformations of Aand B-defects in diamonds of octahedral and cubic habits follow general regularities. This fact shows that most of the diamonds of cubic habit with low degree of aggregation of nitrogen centers were not really annealed over a long-term interval. Unlike octahedral diamonds, those of cubic habit are characterized by a pronounced increase in the peak of H-containing defects (3107 cm–1) after annealing.  相似文献   

13.
We examined relationships between freshwater inflow and population abundance and distribution of two size classes (15–50 mm Standard Length and 51–100 mm SL) of spotted seatrout (Cynoscion nebulosus) and red drum (Sciaenops ocellatus) over our 13-year study covering shallow waters of Tampa Bay and several adjacent rivers. Juveniles of seatrout were relatively abundant most years and broadly distributed primarily in the bay. Freshwater inflow was positively related to spatial distribution and abundance of smaller juveniles of seatrout, yet it was unrelated to the larger size class. Red drum juveniles were less abundant and narrowly distributed primarily within the rivers. Lower portions of the Alafia, Little Manatee, and Manatee Rivers—a combined area comprising only 2 % of the study area—contained 40–96 % of the annual population. Freshwater inflow was positively related to population distribution and abundance of larger red drum suggesting that reductions in inflow can reduce both habitat area and populations. Inflow was related to abundance but not distribution of the smaller red drum suggesting that inflow may increase habitat quality but perhaps not quantity at this earlier growth stage. Comparing spatial and population dynamics of multiple species can help prioritize them for conservation and management issues, such as freshwater inflow regulation. Reductions in inflow reduce populations and spatial distribution of at least one juvenile life stage of these two fishery species. Due to their narrow spatial distribution in the rivers, juveniles of red drum appear to be particularly vulnerable to modification of the riverine environment.  相似文献   

14.
Experimental study of gabbro–norite eclogitization and melting at P = 4 GPa has made it possible to reveal the effective influence of fluid and temperature on the phase relationships. The melt composition varies from andesite–dacite in “dry conditions” to phonolite and carbonate in the presence of a fluid. The Grt-containing melting curve is replaced by the Cpx-containing liquidus as the temperature changes or a fluid is added. Hence, the possible presence of “garnetitite” and “clinopyroxenite” in the upper mantle was proved experimentally. The ultimate pressure of the spinel facies at the depth of the eclogite upper mantle is controlled by the stability of Cht ≤ 4 GPa. The revealed similarity of the spectra of REE-adakite, tonalite–trondhjemite–granodiorite (TTG), and melts formed under the partial melting of eclogitized gabbro–norite does not contradict the existing ideas of the eclogite source of the TTG rocks. Wide variations in the interphase microelement distribution factors D (Grt, Cpx)/L are indicative of effective fractionation of the microelements in the course of eclogite melting and differentiation.  相似文献   

15.
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16.
The aim of this study is to investigate the effects of conventional deficit irrigation strategy on yield components and water use efficiency in the red pepper. The field study was performed in Çumra, a town in the province of Konya in the years of 2012 and 2013. The irrigation treatments were applied as follows: (i) full irrigation regime (100% of water requirement for plant, I100) and (ii) two conventional deficit irrigations regime at the rate of 80% (I80) and 60% (I60) of I100 at 5-day intervals. The irrigation water was used based on soil water content measurement through the gravimetric method where evaporation was measured by a class A pan cup simultaneously. The maximum marketable yields were obtained in the treatment of I100 with 22.0 and 24.0 t ha?1 for the years of 2012 and 2013, respectively. The seasonal crop water requirement was calculated as 454, 591, and 726 mm for 2012 and as 498, 652, and 806 mm for 2013, respectively. The values of crop yield response factors (ky) at I80 and I60 were found as 1.03 and 1.37 in 2012 and 0.66 and 1.54 in 2013, respectively. The highest levels of water use efficiency (WUE) and irrigation water use efficiency (IWUE) were determined for the treatment of 20% deficit during the period of study. The complete irrigation levels (FC) were calculated through 0.87 times the pan A evaporation. The results reveal that full irrigation strategy is the best choice to obtain maximum yield or net return while 20% deficit irrigation is a viable solution for water poor environments.  相似文献   

17.
A dramatic increase in prevalence of the recently discovered bopyrid isopod parasite, Orthione griffenis, likely introduced in the 1980s from Asia to the Pacific coast of North America, coincided with the 2002 collapse of a population of its burrowing mud shrimp host, Upogebia pugettensis, in Willapa Bay, Washington that had been stable since monitoring began in 1988. An examination of whether O. griffenis infections were sufficient to cause this decline and other recently noted U. pugettensis population collapses in Pacific Coast estuaries was conducted. O. griffenis prevalence was the highest in large reproductive-sized female shrimp and caused an estimated average 68% loss of U. pugettensis reproduction in Yaquina Bay, Oregon over a 5-year period. O. griffenis prevalence fluctuated from year to year, but trends were similar in all estuaries sampled. Uninfected shrimp transplanted back into locations from which they had disappeared acquired the parasite, suggesting that O. griffenis is extremely effective at finding its host even in estuaries with very low host density. Since both U. pugettensis and O. griffenis have pelagic larval stages, their population dynamics are also influenced by coastal nearshore oceanography and estuarine recruitment success. Coastwide lack of estuarine recruitment appears to coincide with declines in density of a co-occurring thalassinid shrimp, Neotrypaea californiensis, but cannot alone explain U. pugettensis population collapses. Although patterns observed to date could be explained by the presence of either a native or introduced parasitic castrator, assumptions of a resilient co-evolved host–parasite relationship do not apply for introduced species, so continued efforts to follow the spatial extent and consequences of the O. griffenis–U. pugettensis host–parasite relationship are warranted.  相似文献   

18.
Garnet-bearing metapelites and amphibolites are exposed in the south and middle parts of the Zanhuang complex, which is located in the central segment of the nearly NS-striking Trans-North China Orogen. These rocks preserve three metamorphic mineral assemblages forming at the prograde, peak and post-peak decompression stages. The prograde metamorphic stage (M1) is represented by mineral inclusions within garnet porphyroblasts, the peak metamorphic stage (M2) is represented by garnet rims and matrix minerals, whereas the retrograde stage (M3) is represented by amphibole + plagioclase symplectite rimming garnet porphyroblasts in the amphibolites and biotite + plagioclase symplectite rimming garnet porphyroblasts in the metapelites. All garnet porphyroblasts in the metapelites preserve prograde chemical zoning except for the ubiquitous, quite narrow zones from the underwent post-peak decompression. It has been determined through thermobarometric computation that the metamorphic conditions are 650–710°C at 8.2−9.2 kbar for the M1 (inclusion) assemblages, >810°C at >12.5 kbar for the metamorphic peak M2 (matrix) assemblages, and 660–680°C at 4.4–4.5 kbar for the retrograde M3 (symplectite) assemblages. These rocks are thus determined to have undergone metamorphism with clockwise P–T paths involving nearly isothermal decompression (ITD) segments, which is inferred to be related to the amalgamation of the Eastern and Western Blocks to form the coherent basement of the North China Craton along the Trans-North China Orogen in the late Paleoproterozoic (1.88–1.85 Ga).  相似文献   

19.
The low-angle dip schistosity zones of the Belomorian mobile belt of northern Karelia are zones of plastic flow of thrust origin. They were formed from 1.85 to 1.90 Ga: 1879 ± 21 Ma according to 40Ar/39Ar for amphibole from amphibolites and 1857 ± 13 Ma according to the Sm–Nd isochron in amphibolites. The P–T parameters of rock metamorphism in low-angle dip schistosity zones correspond to the boundary of amphibolite and granulite facies of metamorphism: T = 640–765°C, rarely rising to 826°C; P = 8.0–11.7 kbar. The hypothesis of the two-stage Paleoproterozoic metamorphism of rocks of the Belomorian mobile belt was introduced.  相似文献   

20.
Joint burial places of mollusks and Pleuromeia plants allow specification of a period of stratigraphic occurrence of this genus in the west of the Republic of Kazakhstan within the Gorny Mangyshlak. Two places of occurrences of pleuromeias were found in marine Triassic rocks: one in the Karadzhatyk Formation of the northern slope of the Karatauchik Range close to the Dolnapa well, where the fossils of Pleuromeia sternbergii (Münster) Corda plants are associated with ammonoid shells, and the other one in the Karaduan Formation of the southern slope of Mt. Karashek, where this plant was found along with bivalves and gastropods. The mollusk fauna from both occurrences indicates that the Mangyshlak pleuromeias occurred from the late Olenekian Substage to Anisian Stage.  相似文献   

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