Death valley regional ground-water flow model calibration using optimal parameter estimation methods and geoscientific information systems

A regional-scale, steady-state, saturated-zone ground-water flow model was constructed to evaluate potential regional ground-water flow in the vicinity of Yucca Mountain, Nevada. The model was limited to three layers in an effort to evaluate the characteristics governing large-scale subsurface flow. Geoscientific information systems (GSIS) were used to characterize the complex surface and subsurface hydrogeologic conditions of the area, and this characterization was used to construct likely conceptual models of the flow system. Subsurface properties in this system vary dramatically, producing high contrasts and abrupt contacts. This characteristic, combined with the large scale of the model, make zonation the logical choice for representing the hydraulic-conductivity distribution. Different conceptual models were evaluated using sensitivity analysis and were tested by using nonlinear regression to determine parameter values that are optimal, in that they provide the best match between the measured and simulated heads and flows. The different conceptual models were judged based both on the fit achieved to measured heads and spring flows, and the plausibility of the optimal parameter values. One of the conceptual models considered appears to represent the system most realistically. Any apparent model error is probably caused by the coarse vertical and horizontal discretization.     

Improved energy estimates for interior penalty, constrained and discontinuous Galerkin methods for elliptic problems. Part I

Three Galerkin methods using discontinuous approximation spaces are introduced to solve elliptic problems. The underlying bilinear form for all three methods is the same and is nonsymmetric. In one case, a penalty is added to the form and in another, a constraint on jumps on each face of the triangulation. All three methods are locally conservative and the third one is not restricted. Optimal a priori hp error estimates are derived for all three procedures.     

Four cultures: the evolution of a parsimonious model

Cultural theory works with a parsimonious model of four cultural types, each emanating from a specific form of organisation. The four types are identified as attitudes and values that justify the organisation. The hierarchical type, with its ranked levels and symmetrical branchings, depends on the adoption of hierarchical values and the expression of matching judgements. Likewise for the enclavist culture, the individualist culture and that of the isolates. There is no assumption of fixity, on the contrary, the four types are represented in any community, and social life is in permanent tension and flux. This article gives a summary of the early history of the theory. This revised version was published online in August 2006 with corrections to the Cover Date.     

Pesticides in Sediments From Queensland Irrigation Channels and Drains

Pesticide concentration in sediment from irrigation areas can provide information required to assess exposure and fate of these chemicals in freshwater ecosystems and their likely impacts to the marine environment. In this study, 103 sediment samples collected from irrigation channels and drains in 11 agricultural areas of Queensland were analysed for a series of past and presently used pesticides including various organochlorines, synthetic pyrethroids, benzoyl ureas, triazines and organophosphates. The most often detected compounds were endosulphans (, β and/or endosulphan sulphate) which were detectable in 78 of the 103 samples and levels ranged from below the limit of quantification (0.1 ng g⁻¹ dw) up to 840 ng g⁻¹ dw. DDT and its metabolites were the second most often detected pesticide investigated (74 of the 103 samples) with concentrations up to 240 ng g⁻¹ dw of ∑DDTs. Mean ∑endosulphan and ∑DDT concentrations were 1–2 orders of magnitude higher in sediments from the irrigation areas which are dominated by cotton cultivation compared to those which are dominated by sugarcane cultivation. In contrast to these insecticides, the herbicides diuron, atrazine and ametryn were the compounds which were most often detected in sediments from irrigation drains in sugarcane areas with maximum concentrations in areas of 120, 70 and 130 ng g⁻¹ dw, respectively. In particular during flood events, when light is limiting, transport of these photosynthesis inhibiting herbicides from the sugarcane cultivation areas to the marine environment may result in additional stress of marine plants.     

Potential impact of sea level rise on coastal surges in southeast Louisiana

Potential impacts of 0.5 and 1.0 m of relative sea level rise (RSLR) on hurricane surge and waves in southeast Louisiana are investigated using the numerical storm surge model ADCIRC and the nearshore spectral wave model STWAVE. The models were applied for six hypothetic hurricanes that produce approximately 100 yr water levels in southeastern Louisiana. In areas of maximum surge, the impact of RSLR on surge was generally linear (equal to the RSLR). In wetland or wetland-fronted areas of moderate peak surges (2-3 m), the surge levels were increased by as much as 1-3 m (in addition to the RSLR). The surge increase is as much as double and triple the RSLR over broad areas and as much as five times the RSLR in isolated areas. Waves increase significantly in shallow areas due to the combined increases in water depth due to RSLR and surge increases. Maximum increases in wave height for the modeled storms were 1-1.5 m. Surge propagation over broad, shallow, wetland areas is highly sensitive to RSLR. Wave heights also generally increased for all RSLR cases. These increases were significant (0.5-1.5 m for 1 m RSLR), but less dramatic than the surge increases.     

On optimization algorithms for the reservoir oil well placement problem

Determining optimal locations and operation parameters for wells in oil and gas reservoirs has a potentially high economic impact. Finding these optima depends on a complex combination of geological, petrophysical, flow regimen, and economical parameters that are hard to grasp intuitively. On the other hand, automatic approaches have in the past been hampered by the overwhelming computational cost of running thousands of potential cases using reservoir simulators, given that each of these runs can take on the order of hours. Therefore, the key issue to such automatic optimization is the development of algorithms that find good solutions with a minimum number of function evaluations. In this work, we compare and analyze the efficiency, effectiveness, and reliability of several optimization algorithms for the well placement problem. In particular, we consider the simultaneous perturbation stochastic approximation (SPSA), finite difference gradient (FDG), and very fast simulated annealing (VFSA) algorithms. None of these algorithms guarantees to find the optimal solution, but we show that both SPSA and VFSA are very efficient in finding nearly optimal solutions with a high probability. We illustrate this with a set of numerical experiments based on real data for single and multiple well placement problems.     

下-中奥陶统之交陆架周期性缺氧：来自美国犹他州的遗迹沉积学证据?

美国犹他州中西部、北美下-中奥陶统之交重要剖面上的遗迹沉积学证据表明，在奥陶纪生物爆发的重要时期─早、中奥陶世之交和重要生态领域─陆架区，存在持续3.4 Ma、周期性的陆架缺氧事件。主要的遗迹沉积学证据包括：低的遗迹化石分异度，非常浅的生物扰动层厚度和潜穴深度（小于4 cm, 现代陆架区大于20 cm），稀少的居住滤食迹，遗迹化石和遗迹组构的分布与风暴事件层密切相关；细小的Chondrites 阶层占据较浅或最浅的生态阶层 （中生代以来，细小的Chondrites 阶层总是占据最深的生态阶层）；地层序列具轨道旋回地层结构，并且富含呈黄铁矿假象的褐铁矿结核。早古生代较低的大气氧水平，快速和高幅度的奥陶纪耗氧生物大辐射，早、中奥陶世之交陆架区快速和高幅度的海进和温暖的陆架环境可能是导致早、中奥陶世之交陆架环境周期性缺氧的主要原因。轨道旋回地层的研究表明，这次周期性缺氧事件始于473.27 Ma, 结束于 469.87 Ma，持续时间约3.4 Ma，如果早、中奥陶世之交的同位素年龄值为473.0 Ma。早、中奥陶世之交陆架环境周期性缺氧事件的发现，给正确认识奥陶纪生物辐射、古生代演化生物群起源环境和显生宙生物集群绝灭与缺氧关系增添了新资料。     

Geomorphological and seismostratigraphic evidence for multidirectional polyphase glaciation of the northern Celtic Sea

High-resolution seismic and bathymetric data offshore southeast Ireland and LIDaR data in County Waterford are presented that partially overlap previous studies. The observed Quaternary stratigraphic succession offshore southeast Ireland (between Dungarvan and Kilmore Quay) records a sequence of depositional and erosional events that supports regional glacial models derived from nearby coastal sediment stratigraphies and landforms. A regionally widespread, acoustically massive facies interpreted as the ‘Irish Sea Till’ infills an uneven, channelized bedrock surface overlying irregular mounds and deposits in bedrock lows that are probably earlier Pleistocene diamicts. The till is truncated and overlain by a thin, stratified facies, suggesting the development of a regional palaeolake following ice recession of the Irish Sea Ice Stream. A north–south oriented seabed ridge to the north is interpreted as an esker, representing southward flowing subglacial drainage associated with a restricted ice sheet advance of the Irish Ice Sheet onto the Celtic Sea shelf. Onshore topographic data reveal streamlined bedforms that corroborate a southerly advance of ice onto the shelf across County Waterford. The combined evidence supports previous palaeoglaciological models. Significantly, for the first time, this study defines a southern limit for a Late Midlandian Irish Ice Sheet advance onto the Celtic Sea shelf. © 2020 John Wiley & Sons, Ltd.