共查询到20条相似文献，搜索用时 31 毫秒
1.
Andreas F. Hofmann Karline Soetaert Jack J. Middelburg Filip J. R. Meysman 《Aquatic Geochemistry》2010,16(4):507-546
AquaEnv
is an integrated software package for aquatic chemical model generation focused on ocean acidification and antropogenic CO2 uptake. However, the package is not restricted to the carbon cycle or the oceans: it calculates, converts, and visualizes
information necessary to describe pH, related CO2 air–water exchange, as well as aquatic acid–base chemistry in general for marine, estuarine or freshwater systems. Due to
the fact that it includes the relevant acid–base systems, it can also be applied to pore water systems and anoxic waters.
AquaEnv
is implemented in the open source programming language
R
, which allows for a flexible and versatile application:
AquaEnv
’s functionality can be used stand-alone as well as seamlessly integrated into reactive-transport models in the
R
modelling environment. Additionally,
AquaEnv
provides a routine to simulate and investigate titrations of water samples with a strong acid or base, as well as a routine
that allows for a determination of total alkalinity and total carbonate values from recorded titration curves using non-linear
curve-fitting. 相似文献
2.
Evolution of sedimentary systems at large temporal and spatial scales cannot be scaled down to laboratory dimensions by conventional hydraulic Froude scaling. Therefore, many researchers question the validity of experiments aiming to simulate this evolution. Yet, it has been shown that laboratory experiments yield stratigraphic responses to allocyclic forcing that are remarkably similar to those in real‐world prototypes, hinting at scale independency with strong dependence on boundary conditions but weak dependence on the actual sediment transport dynamics. This paper addresses the dilemma by contrasting sediment transport rules that apply in the laboratory with those that apply in real‐world geological systems. It is demonstrated that the generation of two‐dimensional stratigraphy in a flume can be simulated numerically by the non‐linear diffusion equation. Sediment transport theory is used to demonstrate that only suspension‐dominated meandering rivers should be simulated with linear diffusion. With increasing grain‐size (coarse sand to gravel) and shallowness of river systems, the prediction of long‐term transport must be simulated by non‐linear, slope‐dependent diffusion to allow for increasing transport rates and thus change in stratigraphic style. To point out these differences in stratigraphic style, three stages in infill of accommodation have been defined here: (i) a start‐up stage, when the system is prograding to base level (e.g. the shelf edge) with no sediment flux beyond the base‐level point; (ii) a fill‐up stage, when the system is further aggrading while progressively more sediment is bypassing base level with the progression of the infill; and (iii) a keep‐up stage, when more than 90% of the input is bypassing the base level and less than 10% is used for filling the accommodation. By plotting the rate of change in flux for various degrees of non‐linearity (varying the exponent in the diffusion equation) it was found that the error between model and real‐world prototype is largest for the suspension‐dominated prototypes, although never more than 30% and only at the beginning of the fill‐up stage. The error reduces to only 10% for the non‐linear sandy‐gravelly and gravelly systems. These results are very encouraging and open up ways to calibrate numerical models of sedimentary system evolution by such experiments. 相似文献
3.
M. T. Holroyd 《Mathematical Geosciences》1983,15(1):229-230
During the past 15 years earth science survey data compilation has gradually changed from a manual process to one almost entirely computer automated. Computer methods were at first an optional means for improvement of the speed and efficiency of certain phases of the work. They eventually became mandatory as in-flight digital acquisition devices were introduced and rates of data acquisition increased to the point where manual methods became totally inadequate. As a consequence of the phased replacement of manual systems with digital ones, and the pressing need to avoid interruptions to the work, the resulting software is highly specialized. Software systems are incompatible between different organizations compiling the same kind of data and even between systems for different kinds of data within one organization. The result is wastage of manpower in maintaining, learning to use, and improving the great variety of existing systems, and wastage of man and computer time in converting data to a form compatible with the peculiarities of each particular system. Comparative analysis of highly specialized compilation systems form several different earth science disciplines reveals that processes do exist at the fundamental level which are generally applicable to a range of disciplines. Hence a generalized compilation system capable of eradicating the problems inherent in multiple specialized systems is at least conceptually feasible. The most serious obstacle to its realization however, is the diversity of data content and structure among the various disciplines. To surmount this obstacle, a system with a great degree of physical and logical independence of data from software will be necessary. Existing methods of achieving such independence within data base management systems are found to be largely inapplicable to earth science survey compilation, the principle reasons being the very large quantities of data involved and significant differences between the data retrieval requirements of compilation systems and data base management systems. It is found that, although the data contents and structures vary greatly between the various compilation systems examined, a general abstract model can be constructed which adequately represents all of them and which incorporates the means for achievement of data independence. The logical data structures of current data base management systems are based variously on relational calculus, set theory, and graph theory. The compilation data structure model is based on simple algebra with the addition of some components of vector algebra. It is further found that simple algebraic manipulation of the model expressions faith-fully simulates the actual data manipulation processes which are applied by the various compilation systems. Furthermore, unlike the logical models of the data base management systems, the logical structure of the compilation data model also represents the actual physical structure exhibited by the data in its most common, sequential form. 相似文献
4.
P. K. Sharma Manoj Khandelwal T. N. Singh 《International Journal of Earth Sciences》2011,100(1):189-195
The main objective of this study was to establish statistical relationship between Schmidt hammer rebound numbers with impact
strength index (ISI), slake durability index (SDI) and P-wave velocity. These are important properties to characterize a rock
mass and are being widely used in geological and geotechnical engineering. Due to its importance, Schmidt hammer rebound number
is considered as one of the most important property for the determination of other properties, like ISI, SDI and P-wave velocity.
Determination of these properties in the laboratory is time consuming and tedious as well as requiring expertise, whereas
Schmidt hammer rebound number can be easily obtained on site which in addition is non-destructive. So, in this study, an attempt
has been made to determine these index properties in the laboratory and each index property was correlated with Schmidt hammer
rebound values. Empirical equations have been developed to predict ISI, SDI and P-wave velocity using rebound values. It was
found that Schmidt hammer rebound number shows linear relation with ISI and SDI, whereas exponential relation with P-wave
velocity. To check the sensitivity of empirical relations, Student’s t test was done to verify the correlation between rebound values and other rock index properties. 相似文献
5.
A conceptual investigation of the ontological commensurability of spatial data infrastructures among different cultures 总被引：1，自引：0，他引：1
David J. Saab 《Earth Science Informatics》2009,2(4):283-297
Humans think and communicate in very flexible and schematic ways, and a Spatial Data Infrastructure (SDI) for the Amazon and
associated information system ontologies should reflect this flexibility and the adaptive nature of human cognition in order
to achieve semantic interoperability. In this paper I offer a conceptual investigation of SDI and explore the nature of cultural
schemas as expressions of indigenous ontologies and the challenges of semantic interoperability across cultures. Cultural
schemas are, in essence, our ontologies, but they are markedly different than classical formal ontologies. They shape our
ontological commitments to what exists in the world as well as the ways in which we approach and engage the world. And while
they help structure our understanding of the world in which we are embedded, they are associative and flexible. They help
to focus our attention to particular details of our experiences and give them salience, yet they cannot be simply reduced
to a series of extracted features. They allow us to make meaning of the contextualized, cultural experience in which we are
always immersed. An SDI is a shared social-technological-informational structure that, if it is to be useful and successful
for sustainability in the Amazon, must incorporate and use indigenous cultural schemas. Indigenous communities must have the
ability to contribute to the collection of geospatial data and their contributions recognized as legitimate forms of knowledge.
In order for the SDI to work, it must recognize the larger cultural landscape to which cultural schemas can connect to the
ready-to-hand elements of salient cultural experiences. 相似文献
6.
Unidata’s Common Data Model mapping to the ISO 19123 Data Model 总被引：1，自引：1，他引：0
Access to real-time distributed Earth and Space Science (ESS) information is essential for enabling critical Decision Support
Systems (DSS). Thus, data model interoperability between the ESS and DSS communities is a decisive achievement for enabling
cyber-infrastructure which aims to serve important societal benefit areas. The ESS community is characterized by a certain
heterogeneity, as far as data models are concerned. Recent spatial data infrastructures implement international standards
for the data model in order to achieve interoperability and extensibility. This paper presents well-accepted ESS data models,
introducing a unified data model called the Common Data Model (CDM). CDM mapping into the corresponding elements of the international
standard coverage data model of ISO 19123 is presented and discussed at the abstract level. The mapping of CDM scientific
data types to the ISO coverage model is a first step toward interoperability of data systems. This mapping will provide the
abstract framework that can be used to unify subsequent efforts to define appropriate conventions along with explicit agreed-upon
encoding forms for each data type. As a valuable case in point, the content mapping rules for CDM grid data are discussed
addressing a significant example.
相似文献
| Lorenzo BigagliEmail: URL: www.imaa.cnr.it |
7.
岩石类材料峰后本构关系研究进展 总被引：5，自引：0，他引：5
由于岩石、混凝土等材料的复杂性，使其峰后本构理论的研究非常困难。国内外许多学者依据多种力学理论建立了各种各样的本构模型。本文在讨论岩石力学本构模型发展理论的基础上，概要介绍了已有的各类本构模型并进行了简单评述，最后指出了其发展趋势。 相似文献
8.
Philip Howell 《Geoforum》1994,25(4)
This paper seeks to trace and re-evaluate the convergence between political geography and contemporary political theory regarding the normative ascendancy of the local, contingent, concrete and particular over universal, abstract and general theories of justice. The search for universal norms has been roundly critiqued, principally by postmodern, communitarian and feminist authors, and in part this has paved the way for a recovery of content and context that appeals to political geographers. It is argued, however, that the wholesale rush to what is called here a persistent localism—in the form of the promotion of the claims of particular communities, partial and situated knowledges, the politics of difference—is premature. The dangers and inconsistencies of the latter may be avoided it is claimed by reiterating the minimal universalism contained in Habermas's theory of the public sphere. The theory is discussed and illustrated, compared to more aggressive proponents of universal standards of justice, and argued to be both normatively defensible and potentially geographically sensitive. The paper concludes that the aspiration to universality may be maintained within political geography. 相似文献
9.
裂隙岩体溶质运移模型研究 总被引：7，自引：0，他引：7
核废料的地下深部贮存、垃圾填埋造成的污水下渗、海水入侵、输油管道老化引起渗漏等诸多应用领域的发展,要求从机理、试验和模型等方面发展裂隙岩体溶质运移理论。基于裂隙岩体系统溶质运移的多尺度概念模型,分析了目前描述裂隙岩体系统中溶质运移各种数学模型的适用性和优缺点,为选取合理的数学模型求解具体的问题提供了参考依据。最后提出了需要进一步研究的问题。 相似文献
10.
Janaina Bezzerra Silva Mariana A. Giannotti Ana Paula C. Larocca José Alberto Quintanilha 《GeoJournal》2017,82(2):293-310
Spatial data have been used for the environmental monitoring of the consequences of accidents that involve the transportation of hazardous chemical products. This spatial data infrastructure (SDI), which was created for the sharing and use of spatial data, is limited by the absence of policies to support its establishment. The main objective of this study was to explore the use of social network analysis (SNA) as a tool to identify spatial data sharing between organizations involved in the management of accidents related to road transport of hazardous materials (RTHM). In addition, to discuss the existing policies and institutional agreements, and to initiate a conceptual SDI framework for RTHM sector. In this context, the institutions that are involved with RTHM were identified and information concerning their interest in the use and sharing of spatial data via a SDI was collected through interviews and consolidated. The interviews were at 39 institutions with representative employees. The interview data were tabulated and entered into the UCINET software (2000 version) to calculate metrics of centrality. From the SNA, the flow of data among the participating institutions was identified through the visual representation of the spatial data sharing and use networks. Subsequently, the existing institutional agreements for spatial data sharing were analyzed and discussed. The compiled results enabled the proposal of a conceptual SDI framework to support the management of disasters involving RTHM, based on the application of SNA theory, and the development of a methodology that supports the analysis of interactions among the various actors of an SDI. The purpose is to facilitate the formulation of policies for the sharing of spatial data for decision-making and preventive disaster management. The results indicate that the 39 institutions share spatial data, but this sharing is not always predetermined by formal agreements. Furthermore, there is a strong demand, by the institutions involved in the management of RTHM accidents, regarding legal mechanisms governing the sharing of data for the purpose of producing maps that help to describe actions of preparedness, prevention, management and immediate relief involving RTHM incidents. Finally, it was possible to propose a conceptual framework with data that is considered essential for creating an SDI for RTHM. 相似文献
11.
The present experimental investigations study the effect of layering over rigid base on the dynamic behavior of foundation under vertical mode of vibration. Model block vibration tests were conducted on a rigid surface footing resting on different layered soil systems underlain by rigid base. The rigid base was used to simulate the presence of bedrock. The tests were carried out in a pit of size 2.0?m?×?2.0?m?×?1.9?m (deep) using a concrete footing of size 0.4?m?×?0.4?m?×?0.1?m. A rotating mass type mechanical oscillator was used for inducing vibration in vertical direction. Different layered soil systems were prepared within the total depth of 1,200?mm over the rigid base. Locally available gravel and fly ash were used to form different layered soil systems. In total, 132 nos. model block vibration tests in vertical mode were conducted for different layering and loading combinations. The experimentally obtained results are also compared with the results obtained from the analysis by mass-spring-dashpot and equivalent half-space theory. 相似文献
12.
The design of earthquake-resistant structures depends greatly on the soil–foundation–structure interaction. This interaction is more complex in the presence of liquefiable soils. Pile and rigid inclusion systems represent a useful practice to support structures in the presence of liquefiable soils in seismic zones. Both systems increase the bearing capacity of soil and allow reducing the settlements in the structure. Numerical models with a 3-storey reinforced concrete frame founded on inclusions systems (soil–inclusion–platform–structure) and pile systems (soil–pile–structure) were analyzed. Finite difference numerical models were developed using Flac 3D. Two different soil profiles were considered. A simple constitutive model for liquefaction analysis that relates the volumetric strain increment to the cyclic shear strain amplitude was utilized to represent the behavior of the sand, and the linear elastic perfectly plastic constitutive model with a Mohr–Coulomb failure criterion was used to represent the behavior of the earth platform. Two earthquakes were used to study the influence of the different frequency of excitation in the systems. The results were presented in terms of maximum shear forces distribution in the superstructure and spectrum response of each system. The efforts and displacements in the rigid elements (piles or rigid inclusions) were compared for the different systems. The bending and buckling failure modes of the pile were examined. The results show that the pile system, the soil profile and the frequency of excitation have a great influence on the magnitude and location of efforts and displacements in the rigid elements.
相似文献13.
The determination of the compaction parameters such as optimum water content (wopt) and maximum dry unit weight (γdmax) requires great efforts by applying the compaction testing procedure which is also time consuming and needs significant amount of work. Therefore, it seems more reasonable to use the indirect methods for estimating the compaction parameters. In recent years, the artificial neural network (ANN) modelling has gained an increasing interest and is also acquiring more popularity in geotechnical engineering applications. This study deals with the estimation of the compaction parameters for fine‐grained soils based on compaction energy using ANN with the feed‐forward back‐propagation algorithm. In this study, the data including the results of the consistency tests, standard and modified Proctor tests, are collected from the literature and used in the analyses. The optimum structure of a network is determined for each ANN models. The analyses showed that the ANN models give quite reliable estimations in comparison with regression methods, thus they can be used as a reliable tool for the prediction of wopt and γdmax. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
14.
Jan Košler Jiří Sláma Elena Belousova Fernando Corfu George E. Gehrels Axel Gerdes Matthew S. A. Horstwood Keith N. Sircombe Paul J. Sylvester Massimo Tiepolo Martin J. Whitehouse Jon D. Woodhead 《Geostandards and Geoanalytical Research》2013,37(3):243-259
Inter‐laboratory comparison of laser ablation ICP‐MS and SIMS U‐Pb dating of synthetic detrital zircon samples provides an insight into the state‐of‐the art of sedimentary provenance studies. Here, we report results obtained from ten laboratories that routinely perform this type of work. The achieved level of bias was mostly within ± 2% relative to the ID‐TIMS U‐Pb ages of zircons in the detrital sample, and the variation is likely to be attributed to variable Pb/U elemental fractionation due to zircon matrix differences between the samples and the reference materials used for standardisation. It has been determined that ~ 5% age difference between adjacent age peaks is currently at the limit of what can be routinely resolved by the in situ dating of detrital zircon samples. Precision of individual zircon age determination mostly reflects the data reduction and procedures of measurement uncertainty propagation, and it is largely independent of the instrumentation, analytical technique and reference samples used for standardisation. All laboratories showed a bias towards selection of larger zircon grains for analysis. The experiment confirms the previously published estimates of the minimum number of grains that have to be analysed in order to detect minor zircon age populations in detrital samples. 相似文献
15.
16.
典型地物波谱知识库建库与波谱服务的若干问题 总被引：15，自引：1，他引：14
地物波谱知识库的建立旨在满足应用需求。为达到数据的共享,波谱知识库应对遥感实验测量的波谱数据和相关信息如观测规范、实验环境有清楚的说明,即要有完备的元数据让用户知道波谱知识库中是什么样的数据。为弥补地面测量数据与用户需要数据的时间空间尺度差异,用于外延观测数据的遥感物理模型必不可少;这要求收集分析遥感物理模型,评价其适用条件并创建模型元数据,使用户了解在其工作条件下有何适用的模型,模型的依据是什么;同时波谱库使用遥感物理解析模型和计算机模拟模型完成植被参数的时间扩展和沿叶片-冠层-像元 3个层次的观测尺度空间扩展,从而产生像元尺度可见光到热红外波段的参考波谱。为实现因特网上的波谱知识共享,需要研究如何组织波谱数据和模型,让用户方便地远程检索实测的典型地物波谱数据,并可以实时获取由遥感物理模型外延的波谱数据。从上述 3个方面归纳了波谱库建设和服务需要解决的 6个问题。 相似文献
17.
The energy flux vector is familiar to geophysical fluid dynamics, but only in the abstract. Equations for computing the energy balance and the energy flux vector (S) for a quasigeostrophic numerical ocean model are provided in both analytic and finite difference form. The multilayer model includes wind, lateral and bottom friction, and bathymetry. The finite difference approximation to the analytic energy balance is consistent with the finite difference approximation to the quasigeostrophic potential vorticity equation. An application of the algorithms to a simple steady ocean gyre illustrates their use. This choice of the flux vector (from an infinity of possibilities) has several advantages: it is computationally convenient; it is capable of field measurement; it has nice mathematical properties in the limit of small amplitude motion; and it facilitates intuition about the dynamics. 相似文献
18.
卵砾石层大断面斜井井筒支护方法现场试验研究 总被引：1，自引：0，他引：1
我国缺少在巨厚卵砾石层中采用普通施工方法掘进煤矿斜井井筒的成熟支护经验。结合伊犁一矿材料斜井和回风斜井的施工过程,设计了现场支护试验方案,对不含水和含水卵砾石层大断面斜井井筒的多种支护方法进行了试验。研究结果表明,含水与不含水卵砾石层斜井井筒相比,其支架变形量和支护难度显著变大;架棚临时支护结合钢筋混凝土永久井壁支护是不含水卵砾石层大断面斜井井筒有效的支护方法;含水卵砾石层地压显现明显,采用超前支护、架棚临时支护和钢筋混凝土永久井壁支护相结合的方法可以实现围岩稳定。由试验推断,库仑和太沙基土压力理论用于计算卵砾石层围岩压力误差显著。 相似文献
19.
Groundwater in unconfined aquifers of limited saturated thickness can be a valuable resource but frequently it is not developed because conventional boreholes are unsuitable. However, successful exploitation of shallow unconfined aquifers has been achieved using either a line of wellpoints or horizontal wells extending for more than 100 m. The flow processes by which wellpoints and horizontal wells collect water from unconfined aquifers are explored by developing conceptual and computational models. Several representative examples are considered and it is found that similar discharges occur if the wellpoints are closely spaced. The sensitivity of the yield to physical dimensions of the wells and aquifers is explored; the impact of alternative aquifer parameters is also examined. Results from these computational models are used to identify the causes of air entry into wellpoint systems; the prevention of air entry into horizontal wells is also considered. This evaluation demonstrates that wellpoint systems and horizontal wells can efficiently abstract water from unconfined aquifers of limited saturated thickness provided that precautions are taken to prevent air entry. 相似文献
20.
矿物原料基地建设技术经济评价初论 总被引：1，自引：1，他引：0
对矿物原料基地建设评价的基本理论、内容体系,指标体系和评价工作的突出特点－项目群评价进行了初步分析,提出了矿物原料基地建设技术经济评价的基本框架。 相似文献