A fine-granularity scheduling algorithm for parallel XDraw viewshed analysis

Viewshed analysis is widely used in many terrain applications such as siting problem, path planning problem, and etc. But viewshed computation is very time-consuming, in particular for applications with large-scale terrain data. Parallel computing as a mainstream technique with the tremendous potential has been introduced to enhance the computation performance of viewshed analysis. This paper presents a revised parallel viewshed computation approach based on the existing serial XDraw algorithm in a distributed parallel computing environment. A layered data-dependent model for processing data dependency in the XDraw algorithm is built to explore scheduling strategy so that a fine-granularity scheduling strategy on the process-level and thread-level parallel computing model can be accepted to improve the efficiency of the viewshed computation. And a parallel computing algorithm, XDraw-L, is designed and implemented taken into account this scheduling strategy. The experimental results demonstrate a distinct improvement of computation performance of the XDraw-L algorithm in this paper compared with the coarse-partition algorithm, like XDraw-E which is presented by Song et al. (Earth Sci Inf 10(5):511–523, 2016), and XDraw-B that is the basic algorithm of serial XDraw. Our fine-granularity scheduling algorithm can greatly improve the scheduling performance of the grid cells between the layers within a triangle region.     

Stability study on the northern batter of MBC Open Pit using Plaxis 3D

Cracks appeared on the northern batter at Maddingley Brown Coal Open Pit Mine, Victoria, Australia, on 8 November 2013 and a 2-day rainfall event happened 5 days later. This study models the stability of the northern batter considering the effect of the rainfall event and an emergency buttress using finite element method (FEM) encoded in Plaxis 3D. It is found that the batter tended to lead to block sliding after overburden removal. The observed vertical crack would be a combined action of the overburden removal and groundwater flow. The simulated location of cracks agrees well with the actual location, and the simulated heave of the coal seam is in good agreement with the experience in Victoria brown coal open pit mining. The rainfall accelerated the development of the cracks. With the construction of the emergency buttress, the batter became stable that is in good agreement with the monitored data.     

Analysis of radial movement of an unconfined leaky aquifer due to well pumping and injection

Radial movement of an unconfined leaky aquifer was studied with respect to hydraulic forces that are induced by well recharge and discharge. New analytic solutions in the velocity and displacement fields were found and applied to describe transient movement in an unconfined leaky aquifer. Linear momentum and mass balance of saturated porous sediments, the Darcy-Gersevanov law, and the analytic solution of hydraulic drawdown for unsteady flow within the unconfined leaky aquifer were introduced to find the new solutions. Analytic results indicate that the nonlinear relation between the initial hydraulic head (h₀) and the well function has an insignificant effect on the aquifer transient movement when the drawdown s<0.02h ₀. When the well function is simplified with different assumptions and pumping conditions, the new solutions correspondingly reduce to cases that are similar to the Hantush-Jacob, Muskat, and Theis transient movement of a confined leaky aquifer. It was found that large leakance is important in slowing radial movement and reducing aquifer deformation. Flow velocity in the aquifer is more responsive to leakance than to cumulative displacement within the aquifer. The zones and boundary with tensile stress can be located using the same approach applied to a confined aquifer for risk assessment of earth fissuring.

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Résumé Le mouvement radial dans un aquifère semi-perméable libre a été étudié en considérant les forces hydrauliques induites par la recharge et le prélèvement au niveau d’un puits. De nouvelles solutions analytiques des champs de vitesse et de déplacement ont été trouvées et appliquées pour décrire le mouvement transitoire dans un aquifère semi-perméable libre. Pour trouver les nouvelles solutions, le moment linéaire et le bilan de masse dans les sédiments poreux saturés, la loi de Darcy-Gersevanov, et la solution analytique du rabattement hydraulique pour un écoulement transitoire dans un aquifère semi-perméable libre sont pris en compte. Les résultats analytiques montrent que la relation non-linéaire entre le potentiel hydraulique initial (h₀) et la fonction de puits a un effet insignifiant sur le mouvement transitoire de l’aquifère quand le rabattements s <0.02h₀. Si la fonction de puits est simplifiée en tenant compte de différentes hypothèses et conditions de pompage, les nouvelles solutions se réduisent en conséquence à des cas similaires au mouvement transitoire dans un aquifère semi-perméable captif selon Hantush-Jacob, Muskat, et Theis. Il s’est avéré qu’une drainance élevée est importante pour le ralentissement du mouvement radial et la réduction de la déformation de l’aquifère. La vitesse d’écoulement dans l’aquifère est plus sensible à la drainance qu’au déplacement cumulé dans l’aquifère. Les zones et la frontière présentant des contraintes de traction peuvent être localisées en utilisant la même approche appliquée à un aquifère captif pour l’évaluation des risques de fissuration du sol.

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Resumen Se ha estudiado el movimiento radial en un acuífero no confinado con fuga en relación a las fuerzas hidráulicas que son inducidas por la descarga y recarga del pozo. Se encontraron nuevas soluciones analíticas en los campos de desplazamiento y velocidad, las cuales se aplicaron para describir el movimiento transitorio en un acuífero no confinado con fuga. Se han introducido cálculos de balance de masa y momentum lineal de los sedimentos porosos saturados, la Ley Darcy-Gersevanov, y la solución analítica de descenso hidráulico para flujo sin régimen permanente dentro del acuífero no confinado con goteo para encontrar las nuevas soluciones. Los resultados analíticos indican que la relación no lineal entre la presión hidráulica inicial (h₀) y la función del pozo tiene efecto insignificante en el movimiento transitorio del acuífero cuando el descenso s < 0.02h₀. Cuando se simplifica la función del pozo en base a diferentes supuestos y condiciones de bombeo se reducen las nuevas soluciones a casos que son similares a el movimiento transitorio Hantush-Jacob, Muskat, y Theis de un acuífero confinado con goteo. Se encontró que las fugas grandes son importantes en la disminución del movimiento radial y en la reducción de la deformación del acuífero. La velocidad de flujo en el acuífero responde más a las fugas que al desplazamiento acumulativo dentro del acuífero. Pueden localizarse zonas y límites con esfuerzos tensionales usando el mismo enfoque aplicado a acuíferos confinados para evaluación de riesgo de generación de fracturas en el terreno.

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Spatial and Temporal Variations in <Emphasis Type="Italic">Pyrodinium bahamense</Emphasis> Cyst Concentrations in the Sediments of Bioluminescent Mangrove Lagoon,St. Croix,USVI

Mangrove Lagoon, located on the island of St. Croix, US Virgin Islands (USVI), is one of few actively bioluminescent lagoons in a location experiencing significant anthropogenic impacts. The bioluminescence is due to an abundance of the dinoflagellate Pyrodinium bahamense in the water column. We recovered surface sediments and sediment cores from Mangrove Lagoon to analyze the spatial distribution and temporal variability of P. bahamense cysts in this system. Surface sediment P. bahamense cyst concentrations ranged from 0 to 466 cysts g^?1 dry sediment, with higher abundances associated with elevated surface water nutrient concentrations and a mixed terrestrial–marine organic matter source regime. In combination with available bioassay data, we hypothesize that phytoplankton utilize nutrients rapidly and subsequent decay of organic matter makes nutrients available for dinoflagellates at the sediment–water interface in the eastern and northern quadrants of the lagoon. However, the nutrients are rapidly exhausted during counterclockwise lagoon circulation resulting in the decline of primary productivity and dinoflagellate abundance in the western quadrants. Downcore profiles suggest that P. bahamense blooms have been occurring for decades, declining in recent years. No cysts were present in sediments predating dredging activities of the 1960s that created Mangrove Lagoon. Recent reductions in cyst abundance may be the result of limited primary productivity caused by restricted water exchange with Salt River Bay due to shallowing of a sill at the mouth of the lagoon. This research highlights the need for more comprehensive geochemical and fossil analyses to better understand long-term ecological variability and inform conservation efforts of these unique habitats.     

In situ investigation into fracture and subsidence of overburden strata for solid backfill mining

Controlling the subsidence of overburden strata is the main objective for backfill mining technology. In order to understand the controlling effect of filling body, a detection scheme with three direction boreholes was designed in the tailgate of T₃290 mining face in Tangshan Coal Mine to monitor the fracture developing process of overburden strata. In addition, a few displacement and stress sensors used for monitoring the roof subsidence and filling body stress were arranged behind the longwall face to monitor and record the force and deformation of gangue. The field investigation shows that the solid backfill mining technology can effectively reduce the fracture of overburden strata, i.e., the fracture height and the damage degree. The subsidence of overburden strata is mainly caused by the subsidence of roof which is divided into four stages: roof subsidence stage of mining face, rapid subsidence stage of gob roof, relatively stable stage, and long-term rheological stage. The gauge plays an essential role in slowing down the subsidence in each stage of the overburden subsidence, especially the relatively stable stage.     

直脉蝎蛉科(昆虫纲长翅目) 3个异物同名和 1个种的修正

1996 年,张海春发表《新疆准噶尔盆地中生代直脉科(昆虫纲)昆虫化石》一文[古生物学报,35(4)：442-494],共有5个新种和5个老种,其中1个老种定为Mesopanorpa obscura(Martynov, 1927),包含3 个标本：① NIGP126378(92-T-22/K1),② NIGP126377(58SK15/K3),③ NIGP126376(92-T-22/K3)。另1个标本NIGP126379(93-HE-2K1,2)定为Protorthophlebia latipennis Tillyard, 1933。笔者在研究长翅目化石的过程中,发现张的4个标本系异物同名,前3 个标本即：① NIGP126378号标本勉强修订为1个近似种P. (Protorthophlebia) aff. obscura (Martynov,1925) Martynov,1927;② NIGP126377号标本修订为新名种Protorthophlebia(Protorthophlebia) badouwanica nom. nov.;③ NIGP126376号标本, 由于这个标本脉序结构与副蝎蛉科 Parachoristidae Tillyard, 1937的脉序特征相同,已被修订为另一个属、种Junggarochorista tuzigouensis Hong, 2009[13],已转移归入该科。④另1个标本NIGP126379号标本被修订为新名种 P.(Protorthophlebia) karamayiensis nom. nov.。上述被修订后的新名属、种在本文中作了必要的重新描述。修订的标本,都根据张海春论文中原标本照片显示的脉纹特征和文字描述。所修订学名的原标本均按原文的记录保存在中国科学院南京地质古生物研究所。     

A rational method for development of limit state for liquefaction evaluation based on shear wave velocity measurements

This papers presents a new approach for developing a limit state for liquefaction evaluation based on field performance data. As an example to illustrate the new approach, a database that consists of, among many other features, in situ shear wave velocity measurements and field observations of liquefaction/non‐liquefaction in historic earthquakes is analysed. This database is first used to train a neural network to classify liquefaction/non‐liquefaction based on soil resistance parameters and load parameters. The successfully trained and tested neural network is then used to establish a limit state, a multiple dimension boundary that separates ‘zone’ of liquefaction from ‘zone’ of non‐liquefaction. The limit state yields cyclic resistance ratio for a given set of soil resistance parameters. Examination of all cases in the database show that the developed limit state has a high degree of accuracy in predicting the occurrence of liquefaction/non‐liquefaction. The developed neural network model can accurately predict the cyclic resistance ratio of soils. Copyright © 2000 John Wiley & Sons, Ltd.     

Assessment of the Pacific decadal oscillation’s contribution to the occurrence of local torrential rainfall in north China

On 21–22 July 2012, torrential rains hit North China, with the daily precipitation record at Beijing station reaching 160.6 mm; this event is named the Beijing 7–21 case. This paper assesses the likelihood of the occurrence of local torrential rains, such as the Beijing 7–21 case, from the perspective of climate variability. In particular, the influence of the Pacific Decadal Oscillation (PDO) is assessed. There were five extreme events, with daily precipitation records equal to or larger than 160.6 mm, at Beijing station during the period 1951–2012; all of these events happened during negative phases of the PDO. The present analysis indicates that precipitation events more extreme than the Beijing 7–21 case should happen more than once per decade during negative phases of the PDO, but only about once every four decades during positive PDO phases. The negative phase of the PDO is found to be associated with a much greater probability of daily records of southerly winds in North China during summer. Strong southerly summer monsoons are deemed favorable for increasing the occurrence of local extreme rainfall over North China.     

Testing for quantized redshifts. I. The project

A project intended to examine the long-standing claims that extragalactic redshifts are periodic or quantized was initiated some years ago at the Royal Observatory, Edinburgh. The approach taken is outlined, and the main conclusions to date are summarized. The existence of a galactocentric redshift quantization is confirmed at a high confidence level.