A coupling of mixed and continuous Galerkin finite element methods for poroelasticity I: the continuous in time case

In this paper, we formulate a finite element procedure for approximating the coupled fluid and mechanics in Biot’s consolidation model of poroelasticity. Here, we approximate the pressure by a mixed finite element method and the displacements by a Galerkin method. Theoretical convergence error estimates are derived in a continuous in-time setting for a strictly positive constrained specific storage coefficient. Of particular interest is the case when the lowest-order Raviart–Thomas approximating space or cell-centered finite differences are used in the mixed formulation, and continuous piecewise linear approximations are used for displacements. This approach appears to be the one most frequently applied to existing reservoir engineering simulators.     

Devonian ichnofossils from the Farakah Muth section of the Pin Valley,Spiti Himalaya

The Muth Formation is one of the most characteristic marker horizon traced throughout the northwestern Himalaya. The present studies were carried out in the Farakah Muth (Pin Valley) section of Spiti Basin. The formation uniformly consists of quartzarenite with a high textural and compositional maturity. The development of carbonate beds in the upper part of the Muth Formation separates it conformably from the overlying Lipak Formation. A variety of traces were observed throughout the succession, includes: Metaichna, Planolites, Skolithos, vertical and horizontal burrows. The presence of ichnofossils in the Muth Formation of the Farakah section indicates subtidal settings having soft sandy substrate, whereas, the gradual maturity of the quartz grains from base to top indicates deposition under high energy condition.     

Ammonium Silicate Stability Relations

A method has been developed to control ammonium fugacity, \(f_{{\text{NH}}_{3}}\), at elevated temperatures and pressures. The method uses an internal nitrogen buffer, the assemblage Cr + CrN, in conjunction with a traditional external hydrogen buffer. In this manner, all gas fugacities in the system N-O-H can be calculated.The Cr + CrN buffer has been applied to study equilibria between buddingtonite (ammonium feldspar), ammonium muscovite, sillimanite, and quartz at a constant gas pressure of 2,000 bars. Two of the five relevant reactions were measured experimentally; from these data, it is possible to calculate isothermal sections at 500, 600, and 700° C.Below 600° C, ammonium muscovite is stable even at extremely low levels of \(f_{{\text{NH}}_{3}}\), while buddingtonite requires \(f_{{\text{NH}}_{3}}\;\geqq\;10^4\) bars. Release of NH₃ during progressive metamorphism can be achieved by three processes: thermal decomposition, dehydration, and cation exchange. Within the crust, \(f_{{\text{NH}}_{3}}\) predominates over \(f_{{\text{N}}_{2}}\) by several orders of magnitude; but on the surface, nitrogen released as NH₃ by metamorphism will be oxidized to N₂. Biological materials provide important intermediate storage for nitrogen compounds during the nitrogen cycle.     

The assessment of landslide susceptibility mapping using random forest and decision tree methods in the Three Gorges Reservoir area,China

Landslide susceptibility mapping is an indispensable prerequisite for landslide prevention and reduction. At present, research into landslide susceptibility mapping has begun to combine machine learning with remote sensing and geographic information system (GIS) techniques. The random forest model is a new integrated classification method, but its application to landslide susceptibility mapping remains limited. Landslides represent a serious threat to the lives and property of people living in the Zigui–Badong area in the Three Gorges region of China, as well as to the operation of the Three Gorges Reservoir. However, the geological structure of this region is complex, involving steep mountains and deep valleys. The purpose of the current study is to produce a landslide susceptibility map of the Zigui–Badong area using a random forest model, multisource data, GIS, and remote sensing data. In total, 300 pre-existing landslide locations were obtained from a landslide inventory map. These landslides were identified using visual interpretation of high-resolution remote sensing images, topographic and geologic data, and extensive field surveys. The occurrence of landslides is closely related to a series of environmental parameters. Topographic, geologic, Landsat-8 image, raining data, and seismic data were used as the primary data sources to extract the geo-environmental factors influencing landslides. Thirty-four layers of causative factors were prepared as predictor variables, which can mainly be categorized as topographic, geological, hydrological, land cover, and environmental trigger parameters. The random forest method is an ensemble classification technique that extends diversity among the classification trees by resampling the data with replacement and randomly changing the predictive variable sets during the different tree induction processes. A random forest model was adopted to calculate the quantitative relationships between the landslide-conditioning factors and the landslide inventory map and then generate a landslide susceptibility map. The analytical results were compared with known landslide locations in terms of area under the receiver operating characteristic curve. The random forest model has an area ratio of 86.10%. In contrast to the random forest (whole factors, WF), random forest (12 major factors, 12F), decision tree (WF), decision tree (12F), the final result shows that random forest (12F) has a higher prediction accuracy. Meanwhile, the random forest models have higher prediction accuracy than the decision tree model. Subsequently, the landslide susceptibility map was classified into five classes (very low, low, moderate, high, and very high). The results demonstrate that the random forest model achieved a reasonable accuracy in landslide susceptibility mapping. The landslide hazard zone information will be useful for general development planning and landslide risk management.     

The effects of water stress on yield performance of drip-irrigated pepper (<Emphasis Type="Italic">Capsicum annum</Emphasis> L. cv<Emphasis Type="Italic">. Capya</Emphasis> var. <Emphasis Type="Italic">Yalova yağlık</Emphasis> 28) in the Central Anatolian region of Turkey

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.     

Bristen granite: a highly differentiated,fluorite-bearing A-type granite from the Aar massif,Central Alps,Switzerland

Bristen granite is a body of fine-grained leucogranite occurring in the Gotthard rail base tunnel in the Central Alps. During construction of the tunnel, Bristen granite (Brgr) has been drilled along a 600 m long section. The aplite-granite belongs to the suite of Variscan granitoid intrusions of the Aar massif and contains a variety of accessory minerals typical of highly differentiated granites. Rock forming fluorite, partly enriched in yttrium (Y) and rare earth elements (REE), is intergrown with the late Y- and REE-bearing carbonate mineral synchysite. The granite contains a variety of Ti- and Y-REE-niobates, thorite, and zircon. Compared with the calc-alkaline central Aar granite (cAgr), Bristen granite is strongly depleted in Ti, P, Mg, Sr, and Ba and shows a remarkable enrichment in incompatible elements such as Rb, Th, U, Nb, Y, HREE and F. Bristen granite is the most evolved granitoid rock of the Aar massif. The composition of Brgr is typical of post-collisional reduced (ferroan) A-type granites. The Brgr melt formed in the lower crust and crystallized from a highly differentiated melt at the cotectic point in the quartz-feldspar system close to 100 MPa and 700 °C. The Brgr intruded as a small isolated stock pre-Variscan gneisses with sharply discordant contacts. The primary igneous host of Nb, Ta, Y, U, Th and REE is biotite in addition to minor amounts of allanite, and zircon. The presence of Y-REE-fluorite, synchysite, parisite and Y- and Ti-niobates and other REE-minerals can be related to reaction of igneous biotite and primary fluorite with hydrothermal fluids. The reaction is associated with alpine metamorphism, because Y-bearing fluorite and synchysite have been reported from Alpine fissures. The transformation of primary biotite to chlorite and muscovite released the heavy metal oxides under lower greenschist facies conditions that formed the Alpine diagnostic mineral stilpnomelane at about 300 °C.     

Solar-, monsoon- and Kuroshio-influenced thermocline depth and sea surface salinity in the southern Okinawa Trough during the past 17,300 years

Factors influencing millennial-scale variability in the thermocline depth (vertical mixing) and sea surface salinity (SSS) of the southern Okinawa Trough (OT) during the past 17,300 years were investigated based on foraminifer oxygen isotope records of the surface dweller Globigerinoides ruber sensu stricto and the thermocline dweller Pulleniatina obliquiloculata in the AMS ¹⁴C dated OKT-3 core. The thermocline depth is influenced by surface thermal buoyancy (heat) flux, in turn controlled by the annual mean insolation at 30°N and the strength of the East Asian winter monsoon (EAWM). Strong insolation and weak EAWM tend to increase buoyancy gain (decrease buoyancy loss), corresponding to shallow thermocline depths, and vice versa. Regional SSS is influenced by the global ice volume, the Kuroshio Current (KC), and vertical mixing. A deep thermocline coincides with a high SSS because strong vertical mixing brings more, saltier subsurface KC water to the surface, and vice versa. Local SSS (excluding the global ice volume effect) became lower in the northern OT than in the southern OT after ~9.2 ka, implying that Changjiang diluted water had stronger influence in the northern sector. SSS show no major changes during the Bølling/Allerød and Younger Dryas events, probably because the KC disturbed the North Atlantic signals. This argues against earlier interpretations of sea surface temperature records of this core. Wavelet and spectral analyses of the Δδ¹⁸O_P-G (δ¹⁸O of P. obliquiloculata minus G. ruber s.s.) and δ¹⁸O_local records display 1,540-, 1,480-, 1,050-, 860-, 640-, and 630-year periods. These are consistent with published evidence of a pervasive periodicity of 1,500 years in global climate as well as EAWM and KC signatures, and a fundamental solar periodicity of 1,000 years and intermediary derived periodicity of 700 years.     

2008年春季中国南方冰雪冻害林木折损分析

An abrupt ice and snow storm disaster which occurred in the spring of 2008 se-verely destroyed forests over a surprisingly large portion of southern China.A transect crossing Jinggang Mountain-Jitai Basin-Yushan Mountain-Wuyi Mountain was selected as the study area.The authors integrated field data collected in two field surveys to analyze the impacts of the disturbance on forests.The following results were obtained.(1) The extent of damage to plantations along the transect decreased in the order of slash pine > masson pine > mixed plantation > Chinese fir.Slash pine is an introduced species from southern America which is characterized by fast growth,low wood quality and rich oleoresin,and showed a damage rate of 61.3% of samples,of which 70.4% cannot recover naturally.Masson pine is the native pioneer species of forests with harder wood,and 52.5% were damaged due to turpentine,of which 60.9% cannot recovery naturally.Chinese fir is a local tree species and samples showed a rate of 46% and a relative rate of 32.5%,lower than the mixed plantation.(2) From west to east along the transect,we can see that evergreen broad-leaved forest of the western transect on Jinggang Mountain showed the lightest damage extent,and a Cryp-tomeria plantation at an altitude of 700 m was severely destroyed while Chinese fir showed light damage below 700 m and relatively severe damage above 900 m.Masson pine and slash pine in the central transect in Jitai Basin were damaged severely due to turpentine ac-tivities,and closed natural secondary deciduous broad-leaved forest was damaged severely due to high ice and snow accumulation on intertwined shrubs.Masson pine aerial-seeding plantations below 400 m along the eastern transect in Xingguo and Ningdu counties were nearly undamaged for small tree sizes,and Chinese fir at 500-900 m altitude showed a lighter damage extent.However,masson pine which was distributed above 400 m and planted in the 1960s,was severely damaged due to turpentine.     

Wetland Loss Patterns and Inundation-Productivity Relationships Prognosticate Widespread Salt Marsh Loss for Southern New England

Tidal salt marsh is a key defense against, yet is especially vulnerable to, the effects of accelerated sea level rise. To determine whether salt marshes in southern New England will be stable given increasing inundation over the coming decades, we examined current loss patterns, inundation-productivity feedbacks, and sustaining processes. A multi-decadal analysis of salt marsh aerial extent using historic imagery and maps revealed that salt marsh vegetation loss is both widespread and accelerating, with vegetation loss rates over the past four decades summing to 17.3 %. Landward retreat of the marsh edge, widening and headward expansion of tidal channel networks, loss of marsh islands, and the development and enlargement of interior depressions found on the marsh platform contributed to vegetation loss. Inundation due to sea level rise is strongly suggested as a primary driver: vegetation loss rates were significantly negatively correlated with marsh elevation (r ²?=?0.96; p?=?0.0038), with marshes situated below mean high water (MHW) experiencing greater declines than marshes sitting well above MHW. Growth experiments with Spartina alterniflora, the Atlantic salt marsh ecosystem dominant, across a range of elevations and inundation regimes further established that greater inundation decreases belowground biomass production of S. alterniflora and, thus, negatively impacts organic matter accumulation. These results suggest that southern New England salt marshes are already experiencing deterioration and fragmentation in response to sea level rise and may not be stable as tidal flooding increases in the future.