Steven B. Kraines

Wind-wave driven circulation on the coral reef at Bora Bay, Miyako Island

Abstract Current records from three surveys at Bora Bay, Miyako Island, all showed strong unidirectional flows. Ocean water entered the lagoon over the shallower western half of the reef flat and exited the lagoon through a channel on the eastern side. Fourier transform of one of the survey data sets showed that this unidirectional flow is modulated on a cycle with a period half as long as the dominant M2 tidal cycle. The prominent features of the observed time-series current profiles were well reproduced using a numerical simulation that includes a depth dependent formulation of the wind-wave forced cross-reef water flow. The water residence times of the lagoon varied from 1.5 h to 3.7 h when calculated directly from the modeled current field, and from 2.0 h to 9.3 h when calculated as the time required for modeled particles to exit the lagoon. These residence times are surprisingly short and may help to explain how this reef supports high net organic production. Furthermore, the short particle residence times show the importance of analyzing currents on time scales smaller than the dominant tidal cycle to understand the fate of organic material produced in coral reefs.

Rapid water exchange between the lagoon and the open ocean at Majuro Atoll due to wind, waves, and tide

Current measurements and conductivity-temperature-depth surveys of the lagoon and ocean at Majuro Atoll, the Republic of the Marshall Islands, were made from January 10 to 24, 1997. A vertically integrated tidal current model reproduced qualitatively well tidal ellipses calculated from the observed current measurements by Fourier transform. A three-dimensional, robust diagnostic residual current model explained the major features observed in the current measurements averaged over the dominant tidal cycles. We used the diagnostic model to examine the effects of wind stress, radiation stress, density gradients, and tidal stress on the exchange of water between the lagoon and the ocean. Wind effectively mixes the lagoon water in approximately 2 weeks. Tidal flushing appears to be restricted to a small area near the main channels connecting the lagoon to the ocean. Cross-reef-flat currents induced by radiation stress and flowing to the deep channels in the center of the northern boundary form the dominant mechanism for exchange between the lagoon and the open ocean, causing water to exchange completely with the ocean in about 15 days. Computer-generated particles tracked through the lagoon showed that radiation stress is also the main forcing mechanism for particle export from the lagoon. However, the coupling of tidal exchange through the Calalin Channel and wind-stress-induced mixing in the lagoon could also provide a significant export mechanism, particularly for particles originating uniformly inside the lagoon.

Internet-Based Integrated Environmental Assessment Using Ontologies to Share Computational Models

Summary New advances in Internet technologies and computer modeling provide opportunities for collaborative systems to support research and development in the field of industrial ecology. In particular, new information technologies such as semantic search engines based on ontologies could help researchers to link fragments of knowledge generated at research centers from around the world. Using a storyline of four imaginary researchers who hope to find collaborators in order to develop their research findings, we illustrate two levels of a four-level architecture for an Internet-based knowledge integration and collaboration environment for integrated environmental assessment. The foundation of the proposed architecture is a belief that computational models are an effective medium for conveying expert knowledge of various phenomena. Drawing from this premise, the first level of the architecture stands on a base of computational models that in some way represent the expert knowledge of the model builder. At the second level, we provide markup and interface definition tools to describe the type of knowledge contained in each model, together with the types of information services that can be provided. The results of research at these two levels of an Internet-based knowledge integration environment for integrated environmental assessment in industrial ecology are presented in this article. Our work on the third level of model searching and matching and the fourth level of parametric model integration and solving will be presented in subsequent articles.

EKOSS: a knowledge-user centered approach to knowledge sharing, discovery, and integration on the semantic web

The scientific enterprise depends on the effective transfer of knowledge from creator to user. Recently the rate of scientific knowledge production is overwhelming the ability for researchers to process it. Semantic web technologies may help to handle this vast amount of scientific knowledge. However, automatic computerized techniques that extract semantics from natural language text for use in matching with the requests of knowledge seekers achieve only mediocre results. Clearly, semantic descriptions of expert knowledge that are constructed by the knowledge creators themselves will be more accurate. We report an approach and software implementation of a knowledge sharing platform based on semantic web technologies, called EKOSS for expert knowledge ontology-based semantic search, that helps knowledge creators construct semantic descriptions of their knowledge. The EKOSS system enables knowledge creators to construct computer-interpretable semantically rich statements describing their knowledge with minimal effort and without any knowledge of semantic web technologies.

Seasonal variations in the exchange of water and water-borne particles at Majuro Atoll, the Republic of the Marshall Islands

Abstract To clarify the mechanisms controlling the exchange of water and water-borne materials between the lagoon at Majuro Atoll and the open ocean, we examine flow fields generated using a robust diagnostic three-dimensional numerical simulation. The simulation is forced by data from CTD profiles, wind vectors, observed wave heights, and calculated tidal current stresses. Observed data from April 1998, November 1998, January 1999, and June 1999 were used. Exchange between the lagoon and the ocean was estimated in two ways: from the volumetric flow across the atoll boundaries, and by using a Lagrangian particle-tracking model to calculate export times for particles originating in the lagoon. Modeled water exchange rates were controlled by radiation stress. However, comparison of the spatial distribution of flushed and non-flushed areas with density profiles and simulated flow fields indicate that particle export patterns are strongly influenced by density gradients in the lagoon and between the lagoon and the ocean.

An Integrated Computational Infrastructure for a Virtual Tokyo Concepts and Examples

Summary The evaluation of tradeoffs between technologies and policies for mitigation of environmental problems requires a systematic investigation of effects over the entire region under consideration. When attempting to model such large complex systems, issues such as usability, maintenance, and computing efficiency often become major modeling barriers. In this work a software prototype for integrating the services of computational models over the Internet, called DOME (distributed object-based modeling environment) is used to facilitate the construction of virtual Tokyo—a simulation platform for evaluating holistically the tradeoffs between various technologies for reducing the emissions of greenhouse gases. In making steps toward this ultimate goal, two models have been developed that use data defining spatial land-use distributions and the flows of goods expressed as an input-output table to provide information on the spatial and temporal characteristics of an urban region. Integrated, these models form a preliminary virtual Tokyo model when applied to Tokyo-specific databases. Given this platform, process models are applied to examine the effectiveness of using photovoltaic (PV) modules on the demand side to reduce conventional electric power generation and, thereby, also reduce carbon dioxide emissions. The results of introducing PV modules on the rooftops of buildings in Tokyo under various installation conditions are presented as a working example of the prototype. For full deployment on usable rooftop space, PV power generation could reduce carbon dioxide emissions from electric power generation by more than 12%. Future work will use the same methods as presented in this paper to examine cost, a critical determinant in the actual feasibility of PV module installation.

Environmental Input-Output Models for Life-Cycle Analysis

The Leontief input-output model has beenapplied for macro environmental analysis since1970, and life cycle analysis has been used inindustrial design over the last decade. Thispaper presents two extended environmentalinput-output models for life cycle analysis inpollutant abatement and towards resourcerecycling. It is demonstrated that thesuggested models are systematic tools that canbe used for integrated environmental analysisand planning.

Urban sustainability technology evaluation in a distributed object-based modeling environment

A sustainability technology evaluation platform has been prototyped for simulating integrated technology systems within a specific urban regional context. “Sustainability technologies” refer to available and potentially available technologies that may help to decrease human pressures on the environment or natural resources while providing a desired standard of living. The platform is based on an Internet-based infrastructure for integrating distributed models, called DOME (distributed object-based modeling environment) that has been developed to provide a simulation environment in which large systems, such as an urban region, can be modeled. The infrastructure can support flexible and transparent integration of independently developed computational tools from a wide range of fields such as geographic information systems, input–output analysis, life cycle analysis, and technology process modeling. The tools are linked in a decentralized ad-hoc manner so that an integrated simulation can be developed as understanding of the system grows. Tools are available to observe and understand the emerging structure of the system simulation, and to evaluate and optimize the system based upon its behavior. The urban sustainability technology evaluation platform is built from three basic types of computational elements linked through DOME. These are elements that provide information defining the urban region, elements that simulate behavior of technologies to be evaluated, and elements that integrate and analyze the region-specific effects of the technologies. As an example of the first type, a GIS (geographic information system)-based land use object has been developed to provide information needed to drive simulation models for a wide variety of urban technologies. Examples of the second type include technology simulation models of photovoltaic solar cell modules (PV modules). An object that provides a generalized life-cycle assessment by calculating both the direct and indirect effects of a given technology on total production levels and total pollution emissions in a region using Leontief Input–Output analysis represents the third type of computational element. All of the objects support Internet-enabled GUIs (graphic user interfaces) through the DOME infrastructure, allowing users to transparently connect to, interact with, and utilize object functionality or data. A system model is constructed from these elements to study the economic cost and effect on emissions of CO2 associated with installing PV modules on the rooftops of buildings in Tokyo, Japan. The development of this technology evaluation simulation illustrates the use of the three types of objects and how, by using the DOME infrastructure, they may be linked to form system models to evaluate sustainability technologies.

A System for Ontology-Based Sharing of Expert Knowledge in Sustainability Science

Work towards creation of a knowledge sharing system for sustainability science through the application of semantic data modeling is described. An ontology grounded in description logics was developed based on the ISO 15926 data model to describe three types of sustainability science conceptualizations: situational knowledge, analytic methods, and scenario frameworks. Semantic statements were then created using this ontology to describe expert knowledge expressed in research proposals and papers related to sustainability science and in scenarios for achieving sustainable societies. Semantic matching based on logic and rule-based inference was used to quantify the conceptual overlap of semantic statements, which shows the semantic similarity of topics studied by different researchers in sustainability science, similarities that might be unknown to the researchers themselves.

A Random Network Generator with Finely Tunable Clustering Coefficient for Small-World Social Networks

Many social networks share two generic distinct features: power law distributions of degrees and a high clustering. In some cases, it is difficult to obtain the structure information of real networks. Network generators provide a way to generate test networks for simulation. We present a random network generator to generate test networks with prescribed power law distributions of degrees and a finely tunable average clustering coefficient. The generator is composed of three steps. First, the degree sequences are generated following the given degree power law exponents. Second, the generator constructs a test network with these degree sequences. Third, the test network is modified to meet the prescribed average clustering coefficient as closely as possible. Experiments show the impact of the clustering coefficient on network connectivity using this generator. The comparison with existing random network generators is presented.