共查询到20条相似文献，搜索用时 31 毫秒
1.
In November 2017, Bali's ‘great volcano’, Gunung Agung, erupted for the first time since 1963—leading to the evacuation of nearly 150 000 people from a preliminary danger zone within a radius of 9–12 km from the summit. Since the phreatic onset of the eruption on 21 November, intermittent magmatic (Vulcanian) explosions continued to threaten local residents and disrupt air traffic to and from Indonesia's favourite tourist destination. Whereas the opening of the eruption seems to have been less energetic than the opening of the 1963 events, as of January 2018, the volcanic Alert Level for Agung remains at the highest level. Indeed, it remains unclear at this point what course the eruption will take and how long it will last, and the possibility remains that the eruption may turn more energetic in the months to come. 相似文献
2.
Kirstin K. Holsman David A. Armstrong David A. Beauchamp Jennifer L. Ruesink 《Estuaries and Coasts》2003,26(4):1155-1173
Complex intertidal habitats characteristic of northeastern Pacific coastal estuaries provide critical nursery environments for young-of-the-year Dungeness crab,Cancer magister, yet their role in supporting subsequent year classes remains unclear. SubadultC. magister (40–130 mm; 1+ and >1+ year classes), which reach densities as high as 4,300 crabs ha?1 in subtidal channels during low tides, migrate during flood tides from subtidal refuges into intertidal habitats to forage. As with other brachyuran species that undertake extensive tidally-driven migrations, intertidal foraging may contribute significantly to the energy budget of subadultC. magister. In order to explore the energetic incentive for intertidal migrations by subadult crabs, we developed an ontogenetically-based bioenergetics model for crabs within Willapa Bay, Washington. The model showed that energetic demand varied spatially across the bay, with the highest average energetic demand of a population of subadult crabs (2.13×106 kJ ha?1) occurring in a habitat stratum termed lower side channel (LSC) and characterized by relatively little subtidal area and extensive intertidal flats. Comparison of model results with subtidal prey production revealed that the latter could not satisfy subadultC. magister energetic demands, especially in LSC where modeled crab predation depleted subtidal prey biomass within 17 simulation days. We estimate that 1 ha of subtidal crabs from LSC would minimally require an additional 1.6 ha of intertidal area to satisfy energetic demands without depleting prey biomass. Our model results support the assertion thatC. magister make regular migrations to forage on productive intertidal flats, and suggest that intertidal foraging may contribute significantly to the diet of subadult crabs in coastal estuaries. 相似文献
3.
4.
Jeffrey M Dick 《Geochemical transactions》2008,9(1):10
Background
Proteins of various compositions are required by organisms inhabiting different environments. The energetic demands for protein formation are a function of the compositions of proteins as well as geochemical variables including temperature, pressure, oxygen fugacity and pH. The purpose of this study was to explore the dependence of metastable equilibrium states of protein systems on changes in the geochemical variables. 相似文献5.
Several coastal zones are facing shoreline retreat problems, losing territory due to energetic sea actions, negative sediment transport balances and climate change phenomena. To deal with this problem, efficient tools are necessary to help decision-makers choose the right procedures to follow. These tools should assess, estimate and project scenarios of coastal evolution in a medium-to-long-term perspective. To perform reliable projections, as many variables as possible should be analysed, and the impact of each of these variables on the shoreline evolution should be understood. This study aimed to analyse three climate change phenomena that are considered the most important in a Portuguese west coast stretch (at Aveiro region). The considered phenomena are the wave height increasing due to storms, the wave direction changes and the sea level rise. A shoreline evolution numerical model, long-term configuration, developed to support coastal zone planning and management in relation to erosion problems was applied. This work defined a methodology for classification of risk areas, considering the uncertainty associated with different wave climate sequences on simulations. As a result, different risk maps according to considered climate change effects were obtained, defining areas of high, medium and low risk of territory loss due to erosion. A generalized erosion tendency and shoreline retreat were observed, particularly in the downdrift side of groins. The sea water level rise showed lower impacts in the shoreline evolution than wave direction changes, or wave height increasing, which presents the highest impact. 相似文献
6.
On the basis of the diffusion approach, statistical analysis of seismicity is carried out in order to reveal the peculiarities characteristic of random walk processes. In accordance with the hypothesis on connectivity of earthquakes and energetic criterion, the expansion of the seismic process into a set of sequences is made; each sequence is a Brownian process with specific spatial, temporal, and energetic scales. The statistical distributions of sequences by the number of links, total energies, distances, time, and flight velocities between events are built. 相似文献
7.
Mohammed Taaouati Driss Nachite Javier Benavente Abdelmounim Elmrini 《Environmental Earth Sciences》2011,64(5):1225-1236
The morphodynamic behavior of a mesotidal sandy beach was monitored during both calm and energetic conditions. Two years of
seasonal surveys were carried out on Charf el Akab, a gently sloped beach in the North Atlantic coast of Morocco. The method
of survey consisted of a 3D study of the beach morphological changes and provided 2 cm vertical accuracy. During the surveyed
period, Charf el Akab beach underwent very energetic wave conditions, and the breaking wave height was of H
b ≥ 1.5 m. The beach is characterized by a nonpermanent swash bar and composed of well-sorted medium sand. The application
of environmental parameters revealed a dissipative state with very low beach gradient which did not vary significantly over
the studied period. Morphological changes consist of beach erosion and bar decay under high-energy waves, whereas the intertidal
bar re-established and the beach recorded an accentuated accretion due to relatively fair weather conditions. The beach volume
reveals a seasonal behavior; the sand accumulated during summer is dramatically removed during winter season. The range in
beach sand volume from the most accreted to the most eroded conditions observed is about −5,493 m3. The average sand volume flux between surveys reaches −1 and 0.4 m2/day during peak erosion and accretion periods. The relationships between the wave forcing and the sand volume adjustments
were examined. The sand volume change was found to be highly correlated (0.91) with the wave energy flux. The highest correspondence
(0.95) was found between the sand flux rate and the wave energy flux. The wave forcing is expected to be the main factor governing
beach morphodynamics at Charf el Akab site. 相似文献
8.
《International Geology Review》2012,54(10):1219-1228
This article examines a report in the 27th chapter of the Gospel of Matthew in the New Testament that an earthquake was felt in Jerusalem on the day of the crucifixion of Jesus of Nazareth. We have tabulated a varved chronology from a core from Ein Gedi on the western shore of the Dead Sea between deformed sediments due to a widespread earthquake in 31 BC and deformed sediments due to an early first-century earthquake. The early first-century seismic event has been tentatively assigned a date of 31 AD with an accuracy of ±5 years. Plausible candidates include the earthquake reported in the Gospel of Matthew, an earthquake that occurred sometime before or after the crucifixion and was in effect ‘borrowed’ by the author of the Gospel of Matthew, and a local earthquake between 26 and 36 AD that was sufficiently energetic to deform the sediments at Ein Gedi but not energetic enough to produce a still extant and extra-biblical historical record. If the last possibility is true, this would mean that the report of an earthquake in the Gospel of Matthew is a type of allegory. 相似文献
9.
A common facies observed in deep‐water slope and especially basin‐floor rocks of the Neoproterozoic Windermere Supergroup (British Columbia, Canada) is structureless, coarse‐tail graded, medium‐grained to coarse‐grained sandstone with from 30% to >50% mud matrix content (i.e. matrix‐rich). Bed contacts are commonly sharp, flat and loaded. Matrix‐rich sandstone beds typically form laterally continuous units that are up to several metres thick and several tens to hundreds of metres wide, and commonly adjacent to units of comparatively matrix‐poor, scour‐based sandstone beds with large tabular mudstone and sandstone clasts. Matrix‐rich units are common in proximal basin‐floor (Upper Kaza Group) deposits, but occur also in more distal basin‐floor (Middle Kaza Group) and slope (Isaac Formation) deposits. Regardless of stratigraphic setting, matrix‐rich units typically are directly and abruptly overlain by architectural elements comprising matrix‐poor coarse sandstone (i.e. channels and splays). Despite a number of similarities with previously described matrix‐rich beds in the literature, for example slurry beds, linked debrites and co‐genetic turbidites, a number of important differences exist, including the stratal make‐up of individual beds (for example, the lack of a clean sandstone turbidite base) and their stratigraphic occurrence (present throughout base of slope and basin‐floor strata, but most common in proximal lobe deposits) and accordingly suggest a different mode of emplacement. The matrix‐rich, poorly sorted nature of the beds and the abundance and size of tabular clasts in laterally equivalent sandstones imply intense upstream scouring, most probably related to significant erosion by an energetic plane‐wall jet or within a submerged hydraulic jump. Rapid energy loss coupled with rapid charging of the flow with fine‐grained sediment probably changed the rheology of the flow and promoted deposition along the margins of the jet. Moreover, these distinctive matrix‐rich strata are interpreted to represent the energetic initiation of the local sedimentary system, most probably caused by a local upflow avulsion. 相似文献
10.
岩溶裂隙介质可视为双重孔隙度介质。根据水流连续性原理、质量守衡和达西定律,建立了裂隙-岩溶承压含水层非稳定流双重介质数学模型,采用有限体积法对其求解,并以深圳龙岗区为例对模型进行验证。结果表明,计算模型与实际水文地质条件比较接近,计算水位与实测水位相吻合。 相似文献
11.
M. M. Katsova L. L. Kitchatinov D. Moss K. Oláh D. D. Sokoloff 《Astronomy Reports》2018,62(8):513-519
The Kepler mission has identified huge flares on various stars, including some solar-type stars. These events are substantially more energetic than solar flares, and are referred to as superflares. Even a low probability of such a superflare occurring on the Sun would be a menace to modern society. A flare comparable in energy to that of superflares was observed on September 24 and 25, 1989 on the binary HK Lac. Unlike the Kepler stars, observations of differential rotation are available for HK Lac. This differential rotation appears to be anti-solar. In the case of anti-solar differential rotation, dynamo models can producemagnetic-activity waves with dipolare symmetry, as well as quasi-stationary magnetic configurations with quadrupolar symmetry. The magnetic energy of such stationary configurations is usually about two orders of magnitude higher than the energy associated with activity waves. We believe that this mechanism could provide sufficient energy to produce superflares on late-type stars. Some simple models in support of this idea are presented. 相似文献
12.
地球物理勘探中的含油气储层通常被认为是一种典型的双相介质,这种介质模型能更精确的描述含气性储层的特征,开展双相介质波场传播特性的研究具有十分重要意义。研究以Biot理论为基础,从双相介质中的纵波方程出发,导出求解双相各向同性介质中纵波方程的高阶差分格式,在此基础上实现双相各向同性介质中纵波方程的高阶有限差分法正演模拟,数值模拟结果表明:这种算法能在少量增加计算量的前提下大大提高精度,同时波场模拟结果与理论相吻合,波场快照快慢纵波的波场反映出不同速度、相位相反等特征差异,对将该理论应用于实际有重要的指导意义。 相似文献
13.
Doklady Earth Sciences - An increase in the flux of energetic particles under thunderstorm clouds is a result of the multiplication and acceleration of particles of secondary cosmic rays in the... 相似文献
14.
在波浪水槽实验的基础上,对海啸波作用下的床沙组成变化规律开展研究。实验采用1/10~1/20的组合坡度,选取N波作为入射波。实验对波高进行采集,对波浪的上爬、回落和水跃过程进行拍摄记录,对每个波作用后的地形进行测量,并对初始和最终的床面顶层泥沙进行采样筛分。实验结果表明,N波作用下泥沙在离岸区水跃发生区域堆积,淤积沙坝泥沙粒径呈粗化趋势。同时采用规则波和非规则波进行对比,波浪作用后形成岸滩也为沙坝剖面,淤积沙坝泥沙粒径呈细化趋势,结果均遵循Çelikoğlu提出的泥沙运动的基本规律,细颗粒泥沙会在强烈的紊动作用下从床面中被筛选出来,并被搬运到低紊动地区,此过程造成了剧烈紊动区泥沙的粗化。 相似文献
15.
顺层岩质滑坡是最常见的斜坡灾害,研究其渐进破坏过程、建立预报判据对于防灾减灾具有重要意义.以秭归杉树槽滑坡为例,在野外调查和室内岩石试验的基础上,利用JRC-JCS模型及GSI法估算得出滑坡基本力学参数;通过FLAC3D模拟滑坡渐进破坏过程,分析顺层岩质滑坡变形破坏的发展规律;基于能量守恒和虚功原理,提出了顺层岩质滑坡迈入加速变形的能量学判据.研究表明:杉树槽滑坡由后缘向前渐进破坏,后缘变形累积的总位移值不断增大,前缘切层段的锁固作用使变形迅速降低,当临近破坏时,前缘位移由前向后发展,滑面快速贯通;滑体沿滑动方向应变曲线可近似表示为"S"型曲线,随渐进破坏该曲线向坡下发展;以滑体动能增量大于0作为滑坡迈入加速变形的能量学判据,其结果符合滑坡地质演化观点,与FLAC3D模拟结果吻合. 相似文献
16.
混合润湿孔隙介质普遍存在, 使得多相流体渗流过程十分复杂, 但对其研究和认识至今仍很肤浅, 是油气运移成藏、剩余油气分布等方面研究中必须解决的关键难题。本文通过对饱和水的混合润湿模型进行油自吸实验, 观察不同混合润湿程度条件下油自吸运移过程, 分析认识混合润湿孔隙介质中多相渗流的机理。实验结果表明, 在混合润湿孔隙介质中油是否能够自发地运移与介质中亲油颗粒的比例关系密切, 但并非简单的单调变化关系。研究认为, 亲油颗粒与亲水颗粒随机分布, 导致多种与喉道配位颗粒的亲油-亲水关系, 当亲油颗粒比例占优才表现为亲油喉道。机理上, 混合润湿孔隙介质中油自吸运移的发生与否及程度取决于亲油喉道在空间上的连通程度, 后者与孔隙介质中亲油颗粒比例相当。仅有当孔隙介质中亲油颗粒足够多, 且组成的亲油喉道能够相互接触形成连续亲油通道时, 油才能够通过自吸运移进入多孔介质。 相似文献
17.
正交各向异性介质中地震记录的有限差分数值模拟 总被引：9，自引：3，他引：6
本文首先介绍了正交各向异性介质弹性波动方程的建立过程,然后讨论了高阶有限差分算法的实现原理、算法的稳定性和收敛性以及吸收边界条件的选取,并对正交各向异性介质作了正演模拟。通过波场快照、共炮点地震记录和ＶＳＰ模拟记录等正演分析,结果表明该算法在模拟各向异性介质中弹性波的传播是有效的 相似文献
18.
通过采用单和管、双管法所做的4组不同条件下旋喷桩试验,对其结果进行分析,认为高压喷射范围取决于液流动能。设法降低管路中能量损耗和喷嘴对液流的阻力,合理配置水泥浆液,对提高液流的动能、增大旋喷桩桩径有着重要的作用。 相似文献
19.
R. C. Reedy 《Journal of Earth System Science》1998,107(4):433-440
Modern solar energetic particles (SEPs) have been studied for about 50 years by satellites and groundbased observations. These
measurements indicate much about the nature of SEPs but cover too short a period to quantify the probabilities of very large
solar particle events. Many SEPs have high enough energies to make nuclides in material in which they interact. Radionuclides
measured in lunar samples have been used to extend the record about SEPs back several million years. Some new measurements
of modern SEPs during the last solar cycle and new results for nuclides made by SEPs in lunar samples are presented and their
implications discussed. Both the modern and ancient records need to be improved, and methods to get a better understanding
of solar energetic particles discussed. The fluxes of SEPs during the last million years show an increasing trend when averaged
over shorter radionuclide half-lives. 相似文献