Grid System

This paper describes the dynamic behaviour of a doubly-fed induction machine, operating with wind turbine. The rotor circuit of the machine consists only of a generator-side converter working under abnormal condition at stator side (fault condition and voltage drop take place in transmission lines of the grid system). The induction machine model is based on the stationary reference frame and the control-unit model is based on the line-voltage oriented reference frame. The generator-side controller provides good decoupling between active and reactive power. A powerful MATLAB/SIMULINK was used for the simulation of the wind energy conversion system of a 4 kW wind generator. The simulation results of the generator side converter show that the speed, torque and the ϕ sin (power factor) can be regulated independently to match the reference signals. The effects of assumed abnormal condition in the grid system are discussed with regard to stator current and rotor current of the induction m...

In Grid systems, users may require assurance for completing their jobs on shared resources. Such guarantees can only be provided by reserving resources in advance. In this paper, we introduce an elastic reservation model, where users can query about a resource availability on a given time interval. They can also provide a reservation duration time and/or number of compute nodes needed as soft constraints to the query. Next, we provide an adapted version of an on-line strip packing algorithm, that takes into a consideration of resource utilization when processing reservation requests. We evaluate our algorithm with a real workload trace and show that the proposed algorithm manages a higher resource utilization and number of acceptance compared to an ad-hoc rigid approach.

The recently published Iraqi earthquake data file over the period 1905-1984 is used to derive a local lo-M s formula. This is then combined with a local intensity attenuation relationship to compile the observed I o (MM) zoning map for Iraq. Earthquake risk is calculated using the log N (M,) relation for selected design magnitudes and periods and is mapped as the (%) probability of occurrence using a 0.5 deg latitude/longitude grid system. It is observed that the intensity zones and contour distributions are highly influenced by the presence of large magnitude shocks while risk maps reveal the Tauros seismogenic zone as having a greater risk of occurrence than the Zagros zone. The compiled zoning maps are intended for the use of local practising engineers for earthquake-resistant design procedures that are currently being adopted in the country.

Distributed generation (DG) inclusion within the grid system potentially introduces problems related to control, protection, harmonics, and network transients. This paper analyses one of the key issues: protection of the network, by ascertaining the impact of rotary DG inclusion on existing protection system of SWER (single wire earth return) lines and the DG sensitivity during faults. The analysis is carried out by estimating fault-sensitivity for the worst-case situation, determining the DG impact on the existing protection scheme, and comparing the network situation with and without DG during the fault. A model of arc voltage is used to represent a fault on a SWER scheme. The size of DG is selected based on the SWER capacity and SWER load. The study is conducted on an example SWER system by considering the SWER lines with and without DG and faults on the SWER backbone and laterals, and simulation results are reported. In every case studied, the fault current from the DG significantly exceeded the DG rating and the DG would have tripped. Thus the system reverts to the case with no DG. Even if DG did not trip, the fault current from the source would be largely independent of the DG, and thus the original feeder protection would continue to provide the same quality of performance. Hence, net sensitivity and existing protection system will not be adversely affected by DG inclusion in SWER lines. #

Mass culture of benthic macroalgae under rough offshore conditions in the North Sea requires rigid culture support systems that cannot only withstand rough weather conditions but can also be effectively handled while at the same time retain the cultured species. Various carrier constructions and different mooring systems were tested. Laminaria saccharina grew on all of these carriers with initially high (up to 14.5% per day) and later decreasing length increments. Longlines, ladder and grid systems had certain disadvantages and these are discussed. The study results led to a new ring carrier (patent pending), first used in 1994/1995, which was gradually improved until 2002. This system now emerges as being superior, since it resists not only rough weather conditions (2 m s −1 current velocity, 6 m wave height) but also permits ease of handling when compared to other constructions. The ring allows various operational modes and can be equipped with culture lines that can be collected offshore or transported to shore facilities for harvesting. The modular nature of the tested ring system lends itself for future use in integrated aquaculture systems located in or attached to offshore wind farms.

The 3D finite-element gun and collector modeling code, MICHELLE, has been under development at SAIC in collaboration with industrial partners and national laboratories (ref. 1). This development program has been designed to address the shortcomings of current beam optics simulation and modeling tools for vacuum electron devices. The program specifically targets problem classes including gridded-guns, sheet-beam guns, multi-beam devices, and anisotropic collectors, with a focus on improved physics models. The code includes both structured and unstructured grid systems for meshing flexibility. Advances have been made in the areas of accurate particle tracking through the mesh and beam emission methods, including new models for thermionic, temperature-limited, Child's law and secondary emission.

This study proposes an effective numerical model based on the Computational Fluid Dynamics (CFD) approach to obtain the flow structure around a passenger car with wing type rear spoiler. The topology of the test vehicle and grid system is constructed by a commercial package, ICEM/CFD. FLUENT is the CFD solver employed in this study. After numerical iterations are completed, the aerodynamic data and detailed complicated flow structure are visualized using commercial packages, Field View and Tecplot. The wind effect on the aerodynamic behavior of a passenger car with and without a rear spoiler and endplate is numerically investigated in the present study. It is found that the installation of a spoiler with an appropriate angle of attack can reduce the aerodynamic lift coefficient. Furthermore, the installation of an endplate can reduce the noise behind the car. It is clear that the vertical stability of a passenger car and its noise elimination can be improved. Finally, the aerodynamics and aero-acoustics of the most suitable design of spoiler is introduced and analyzed.

The international introduction of electric vehicles (EVs) will see a change in private passenger car usage, operation and management. There are many stakeholders, but currently it appears that the automotive industry is focused on EV manufacture, governments and policy makers have highlighted the potential environmental and job creation opportunities while the electricity sector is preparing for an additional electrical load on the grid system. If the deployment of EVs is to be successful the introduction of international EV standards, universal charging hardware infrastructure, associated universal peripherals and user-friendly software on public and private property is necessary. The focus of this paper is to establish the state-of-the-art in EV charging infrastructure, which includes a review of existing and proposed international standards, best practice and guidelines under consideration or recommendation.

A domain-specific software architecture (DSSA) represents an effective, generalized, reusable solution to constructing software systems within a given application domain. In this paper, we revisit the widely cited DSSA for the domain of grid computing. We have studied systems in this domain over the past five years. During this time, we have repeatedly observed that, while individual grid systems are widely used and deemed successful, the grid DSSA is actually underspecified to the point where providing a precise answer regarding what makes a software system a grid system is nearly impossible. Moreover, every one of the existing purported grid technologies actually violates the published grid DSSA. In response to this, based on an analysis of the source code, documentation, and usage of eighteen of the most pervasive grid technologies, we have significantly refined the original grid DSSA. We demonstrate that this DSSA much more closely matches the grid technologies studied. Our refinements allow us to more definitively identify a software system as a grid technology, and distinguish it from software libraries, middleware, and frameworks.

... pp. 208-213. [10] C. Marnay, F. Rubio, A. Sadsiqui. 2001. Shape of the microgrid. ... IEEE Trans Power Electron. 22(2): 613-625. [17] JA Pecas Lopes, Moreira CL, AG Madureira. 2006. Defining control strategies for microgrids islanded operation. IEEE Trans Power System. ...

Purpose Radiation doses have been monitored for a long time, as we are aware that radiation can produce biological effects. However, there is a limited amount of information available on patient dose from cervical spine examinations. In addition, the techniques used are variable between radiographic departments and even radiographers within one department. The difference in technique of particular concern is the use of radiographic grids. While it reduces scatter and improve image quality, the use of a grid demands increased exposure factors and dose to obtain the same optical density on the film. Method This study investigated the range of doses for lateral cervical spine examinations in the Hunter and Sydney metropolitan regions of New South Wales, Australia. Radiation doses were calculated from X-ray tube output measurements and patient exposure parameters. Results Differences in dose for 116 patients (53 non-grid, 63 grid) examined on 13 X-ray units were analysed. The study calculated the mean entrance surface dose for the non-grid system (228 lGy) to be significantly lower at the 95% significance level than the mean entrance surface dose for the grid techniques (505 lGy). However, the use of a grid for computed radiography systems did not produce any differences in dose with the use or non-use of a grid, while there was a three-fold increase for film-screen systems. Conclusion The increased level of dose and the inherent air-gap nature of the lateral cervical spine examination raises severe doubt on the use of anti-scatter grids and the recommendation is that they should not be used.

Wind power generation differs from conventional thermal generation due to the stochastic nature of wind. Thus wind power forecasting plays a key role in dealing with the challenges of balancing supply and demand in any electricity system, given the uncertainty associated with the wind farm power output. Accurate wind power forecasting reduces the need for additional balancing energy and reserve power to integrate wind power. Wind power forecasting tools enable better dispatch, scheduling and unit commitment of thermal generators, hydro plant and energy storage plant and more competitive market trading as wind power ramps up and down on the grid. This paper presents an in-depth review of the current methods and advances in wind power forecasting and prediction. Firstly, numerical wind prediction methods from global to local scales, ensemble forecasting, upscaling and downscaling processes are discussed. Next the statistical and machine learning approach methods are detailed. Then the techniques used for benchmarking and uncertainty analysis of forecasts are overviewed, and the performance of various approaches over different forecast time horizons is examined. Finally, current research activities, challenges and potential future developments are appraised.

Grid technology is increasingly being looked upon as a natural extension of the internet for engaging in complex data processing tasks over resources which are distributed across the world. Architects and developers employing grid systems must take into consideration security implications. Dynamic generation of virtual organizations leads to a synergistic picture which has to address security requirements never encountered before. Globus toolkit has devised a framework for making secure use of grid resource components which has been proved to be a feasible solution by a number of academic and scientific organizations. This paper is an attempt to identify and discern mechanisms proposed by Globus security model with certain test scenarios [1] .

An unsteady Reynolds-averaged Navier-Stokes method is developed to compute motions and the resulting flow and wave fields around surface ships. Although the formulation and RANS code are generalized for six-degree-of-freedom motions, the method is demonstrated here for the viscous phenomenon of roll decay motion for a surface combatant. The method is based on an extension of CFDSHIP-IOWA (a general-purpose code for computational ship hydrodynamics) to predict ship motions with larger amplitude and non-slender geometry, in comparison to traditional linearized methods. The flow solver uses higher-order upwind discretization, PISO method for pressure-velocity coupling, a blended k-x/k-e two-equation turbulence model, free surface tracking approach, and structured multi-block grid systems. As an initial step, unsteady simulations of a modern surface combatant with predicted roll decay and prescribed sinusoidal roll motion are performed. Roll decay motion is simulated by releasing the model from an initial roll angular displacement and by computing the resulting roll motion. Verification of the time history of the roll motion is performed using iteration, grid, and time step studies and numerical uncertainties are shown to be less than 1%. Validation is performed by comparison with available experimental data with the predictions validated at 1.7% and 1.5% for the uncorrected and corrected solutions, respectively. For simulations with prescribed motions, the periodic response of the boundary layer to the rolling motion is described and quantified using a Fourier analysis. A spring-mass-damper system is used to compare the current non-linear predictions to traditional linear strip theory results. The method is shown to accurately predict the natural rolling frequency and roll decay rate at multiple ship speeds both without and with bilge keels, which demonstrates the ability to assess seakeeping characteristics for practical geometries.

The energy demand around the world increases; the need for a renewable energy source that will not harm the environment has been increased i. e. Wind power is one of them. There are many loads (such as remote villages, islands, ships etc) that are away from the main grid. They require stand-alone generator system (which can provide constant nominal voltage and frequency) to provide for their local electrification. Wind power can be used in off-grid systems, also called stand-alone systems, not connected to an electric distribution system or grid.

Problem statement: The purpose of this study is to design a renewable energy hydrogen based power system to provide electricity to a coastal residential area in east coast area (Kuala Terengganu) of Malaysia. Approach: The selected case study represents a power demand of 20 kWh day −1 . The autonomous system used in this study is diesel generator, wind and photovoltaic hybrid system. The power system was redesigned and optimized as hydrogen-based autonomous power systems in order to meet the existing user's power demand at a minimum cost of energy. Wind speed and solar radiations data obtained from Malaysian Meteorological Department have been used in the simulation process through optimization software, Hybrid Optimization Model for Electric Renewables (HOMER). Results: Three systems that were considered in this study area are stand alone PV-wind-diesel, stand alone PV-wind-hydrogen and grid connected PV-wind-hydrogen energy system. The proposed systems then were compared regarding on their operational characteristics and cost values. The comparisons prove that grid connected PV-wind-hydrogen energy system had the lowest total net present cost and cost of energy, $53,197 and $0.57/kWh, respectively that makes it the most cost effective system and followed by PV-wind-diesel and stand alone PV-wind-hydrogen system. Conclusion/Recommendations: It can be concluded that the hydrogen-based system can become a favorable system without aid from the grid system and bring advantage in technical and economic point of view and also suitable to be applied in the coastal residential application as energy carrier if only the current cost of wind turbine, PV arrays and hydrogen system technology have been reduced to its minimum rate.

Grid computing has been the subject of many large national and international IT projects. However, not all goals of these projects have been achieved. In particular, the number of users lags behind the initial forecasts laid out by proponents of grid technologies. This underachievement may have led to claims that the grid concept as a whole is on its way to being replaced by Cloud computing and various X-as-a-Service approaches. In this paper, we try to analyze the current situation and to identify promising directions for future grid development. Although there are shortcomings in current grid systems, we are convinced that the concept as a whole remains valid and can benefit from new developments, including Cloud computing. Furthermore, we strongly believe that some future applications will require the grid approach and that, as a result, further research is required in order to turn this concept into reliable, efficient and user-friendly computing platforms.

The force acting on a current carrying body, which is induced by magnetic fields gained more interest due to new applications. These magnetic techniques are used for decades to accelerate or move objects, for instance for catheter navigation in the human body, metal forming or for fast opening of electrical circuit breakers. Due to the increase in short circuit power in most grid systems, and thereby larger prospective currents, conventional AC and DC switches lose interest. This has led to an increased interest in faster and hybrid switching techniques. For this reason a novel electro-mechanical set-up has been developed, which accelerates a movable electrical contact extremely fast by using the combination of Lenz law and the Lorentz force. This contribution describes the mixed domain simulation environment and the validation of the set-up, which consist of a linear electro-magnetic drive and a mechanical damper system. The prototype used for validation is capable to generate a maximum driving force of approximately 200 kN, which accelerates the movable contact of 2.7 kg to 18 m s À1 . Initial simulations have been compared with the measurements and the results are in good agreement. This tool can be used to develop generic hybrid circuit breakers, reduces the risk for switchgear manufacturers and speed up the introduction of hybrid switch systems, which is urgently needed due to the ever increase of short circuit power in grid systems and the introduction of DC grid systems.

Users of Grid systems often need to attach Quality of Service (QoS) information such as time or performance constraints to guarantee timely execution of their application. Grid resources have varying quality and reliability and can easily be swamped by competing applications. If this coincides with the users execution their results may be delayed. In support of this we propose a Service Level Agreement (SLA) management system including resource reservation and run-time adaptation. Our system has the capability of predicting the execution time of an SLA bound application before and during runtime. A historical usage record for auditing and prediction of future execution times is also described. Through experimental analysis we show our solution is capable of predicting with some accuracy the execution time of SLA bound applications before and during runtime. Mechanisms for automated monitoring and violation capture are presented showing how performance and time constraints can be validated. Adaptation through migration is proved useful in reducing the execution time of our application when the CPU load available to that application is reduced.

The international introduction of electric vehicles (EVs) will see a change in private passenger car usage, operation and management. There are many stakeholders, but currently it appears that the automotive industry is focused on EV manufacture, governments and policy makers have highlighted the potential environmental and job creation opportunities while the electricity sector is preparing for an additional electrical load on the grid system. If the deployment of EVs is to be successful the introduction of international EV standards, universal charging hardware infrastructure, associated universal peripherals and user-friendly software on public and private property is necessary. The focus of this paper is to establish the state-of-the-art in EV charging infrastructure, which includes a review of existing and proposed international standards, best practice and guidelines under consideration or recommendation.

This paper deals with the modeling and analysis of dynamic model of Solid Oxide Fuel Cell (SOFC) system in response to the grid connection using PSCAD/EMTDC simulation software. Fuel cells are known for their reliability, power quality, eco-friendly nature and fuel efficiency. Its promising technology and extremely significant in the near future. A voltage source inverter controller is developed for conversion of SOFC generation into ac grid system. The designed controller is also implemented to analyzed the output response of the developed fuel cell that can be used in distributed generation applications.

The higher-than-ever gas prices and soaring living expenses are driving people back to city centers in search of reduced travel costs and greater proximity to services. This calls for an immediate need to revive our downtowns to make them attractive and increase their efficiency toward accommodating a variety of transportation modes, motorized and non-motorized. As a principal measure to this

In this study the flora of Hacikadin valley (Keçiören, Ankara) has been investigated. The study area i s in Irano- Turanian phytogeographic region and also in A4 square according the grid system applied for Turkish Fl ora by Davis. The results of 14 excursions between 2006 and 2008, and herbarium and literature investigations showed that this area covers 63 families

The growth of the generation of electrical energy and the increased interconnection of networks lead to higher fault current levels. The short circuit current will impose high dynamical and thermal stresses on electrical equipments. All equipments have to have a short circuit rating capable of withstanding this level.

TOUGHREACT is a powerful simulator for multiphase fluid, heat, and chemical transport, but has a steep learning curve and the creation of the input files is time intensive, particularly for heterogeneous and complex geometries such as those in mining rock pile formations. TOUGHER is an application developed by the acid rock drainage research group of the Department of Chemical Engineering at the University of Utah in order to develop TOUGHREACT models rapidly for two-dimensional problems and to be able to visualize the simulation results in an intuitive way. It also reduces errors when creating complex layered 2D models and makes debugging easier. The software is currently limited to 2D rectangular grids with constant spatial sizes. The application is written in C++ and can be used on any computer with a Windows or Linux operating system. This paper will describe the overall structure of the application and give some examples of how it interfaces with the TOUGHREACT program. In particular, it will be shown how the application can generate a grid system for a rock pile containing several distinct geological layers, how the properties of each layer are set, and how the input sections (ELEM and CONNE) for TOUGHREACT are generated automatically. In addition, visualizing the flow and chemical output files generated by TOUGHREACT for a particular rock pile will be demonstrated. This includes transient vector as well as transient scalar data. At the end of the paper, two case studies, one with a simplified geometry and another with more complex layered rock geometry, will be presented.

Complex applications are describing using workflows. Execution of these workflows in Grid environments require optimized assignment of tasks on available resources according with different constrains. This paper presents a decentralized scheduling algorithm based on genetic algorithms for the problem of DAG scheduling. The genetic algorithm presents a powerful method for optimization and could consider multiple criteria in optimization process. Also, we describe in this paper the integration platform for the proposed algorithm in Grid systems. We make a comparative evaluation with other existing DAG scheduling solution: Cluster ready Children First, Earliest Time First, Highest Level First with Estimated Times, Improved Critical Path with Descendant Prediction) and Hybrid Remapper. We carry out our experiments using a simulation tool with various scheduling scenarios and with heterogeneous input tasks and computation resources. We present several experimental results that offer a support for near-optimal algorithm selection.

Wind power generation differs from conventional thermal generation due to the stochastic nature of wind. Thus wind power forecasting plays a key role in dealing with the challenges of balancing supply and demand in any electricity system, given the uncertainty associated with the wind farm power output. Accurate wind power forecasting reduces the need for additional balancing energy and reserve power to integrate wind power. Wind power forecasting tools enable better dispatch, scheduling and unit commitment of thermal generators, hydro plant and energy storage plant and more competitive market trading as wind power ramps up and down on the grid. This paper presents an in-depth review of the current methods and advances in wind power forecasting and prediction. Firstly, numerical wind prediction methods from global to local scales, ensemble forecasting, upscaling and downscaling processes are discussed. Next the statistical and machine learning approach methods are detailed. Then the techniques used for benchmarking and uncertainty analysis of forecasts are overviewed, and the performance of various approaches over different forecast time horizons is examined. Finally, current research activities, challenges and potential future developments are appraised.

Nowadays, Grid has become a leading technology in distributed computing. Grid poses a seamless sharing of heterogeneous computational resources belonging to different domains and conducts efficient collaborations between Grid users. The core Grid functionality defines computational services which allocate computational resources and execute applications submitted by Grid users. The vast models of collaborations and openness of Grid system require a secure, scalable, flexible and expressive authorization model to protect these computational services and Grid resources. Most of the existing authorization models for Grid have granularity to manage access to service invocations while behavioral monitoring of applications executed by these services remains a responsibility of a resource provider. The resource provider executes an application under a local account, and acknowledges all permissions granted to this account to the application. Such approach poses serious security threats to breach system functionality since applications submitted by users could be malicious. We propose a flexible and expressive policy-driven credential-based authorization system to protect Grid computational services against a malicious behavior of applications submitted for the execution. We split an authorization process into two levels: a coarse-grained level that manages access to a computational service; and a fine-grained level that monitors the behavior of applications executed by the computational service. Our framework guarantees that users authorized on a coarse-grained level behave as expected on the fine-grained level. Credentials obtained on the coarse-grained level reflect on fine-grained access decisions. The framework defines trust negotiations on coarse-grained level to overcome scalability problem, and preserves privacy of credentials and security policies of, both, Grid users and providers. Our authorization system was implemented to control access to the Globus Computational GRAM service. A comprehensive performance evaluation shows the practical scope of the proposed system.

This paper identifies challenges in managing resources in a Grid computing environment and proposes computational economy as a metaphor for effective management of resources and application scheduling. It identifies distributed resource management challenges and requirements of economy-based Grid systems, and discusses various representative economy-based systems, both historical and emerging, for cooperative and competitive trading of resources such as CPU cycles, storage, and network bandwidth. It presents an extensible, service-oriented Grid architecture driven by Grid economy and an approach for its realization by leveraging various existing Grid technologies. It also presents commodity and auction models for resource allocation. The use of commodity economy model for resource management and application scheduling in both computational and data grids is also presented.

Renewable energy portfolio standards have created a large increase in the amount of renewable electricity production, and one technology that has benefited greatly from these standards is wind power. The uncertainty inherent in wind electricity production dictates that additional amounts of conventional generation resources be kept in reserve, should wind electricity output suddenly dip. The introduction of plug-in hybrid electric vehicles into the transportation fleet presents an possible solution to this problem through the concept of vehicle-to-grid power. The ability of vehicle-to-grid power systems to help solve the variability and uncertainty issuess in systems with large amounts of wind power capacity is examined through a multiparadigm simulation model. The problem is examined from the perspectives of three different stakeholders: policy makers, the electricity system operator and plug-in hybrid electric vehicle owners. Additionally, a preliminary economic analysis of the technology is performed, and a comparison made with generation technologies that perform similar functions.

Tuff buildings are a significant part of the Mediterranean area and are to be preserved from a structural viewpoint especially in seismic areas. Over the past few decades, the interest in strengthening of historical tuff masonry structures has led to developing specific and noninvasive architectural and engineering strategies. In the present paper, a comprehensive experimental program on tuff masonry panels is presented; the results are intended as a contribution to the knowledge of in-plane behavior of tuff masonry strengthened with composite materials. Particularly, a cement based matrix-coated alkali resistant glass grid system ͑CMG͒ was used to strengthen tuff masonry walls; different CMG layouts were selected, and overall performances were compared with those of as-built ones. The characterization of base materials was carried out first, followed by uniaxial tests of masonry and shear tests on triplets. Finally, tuff masonry panels were subjected to diagonal compression loading under displacement control in order to measure their in-plane deformation and strength properties, including the postpeak softening regime in view of seismic applications.

Distributed generation (DG) inclusion within the grid system potentially introduces problems related to control, protection, harmonics, and network transients. This paper analyses one of the key issues: protection of the network, by ascertaining the impact of rotary DG inclusion on existing protection system of SWER (single wire earth return) lines and the DG sensitivity during faults. The analysis is carried out by estimating fault-sensitivity for the worst-case situation, determining the DG impact on the existing protection scheme, and comparing the network situation with and without DG during the fault. A model of arc voltage is used to represent a fault on a SWER scheme. The size of DG is selected based on the SWER capacity and SWER load. The study is conducted on an example SWER system by considering the SWER lines with and without DG and faults on the SWER backbone and laterals, and simulation results are reported. In every case studied, the fault current from the DG significantly exceeded the DG rating and the DG would have tripped. Thus the system reverts to the case with no DG. Even if DG did not trip, the fault current from the source would be largely independent of the DG, and thus the original feeder protection would continue to provide the same quality of performance. Hence, net sensitivity and existing protection system will not be adversely affected by DG inclusion in SWER lines. #

Effect of curvature ratios on the heat transfer and flow developments in the horizontal spirally coiled tubes are investigated. The spirally coiled tube is fabricated by bending a 8.00 mm diameter straight copper tube into a spiral-coil of five turns. The spirally coiled tube with three different curvature ratios of 0.02, 0.04, 0.05 under constant wall temperature are tested. Cold water entering the innermost turn flows along the spiral tube and flows out at the outermost turn. The turbulent flow and heat transfer developments are simulated by using the k-e standard turbulence model. A finite volume method with an unstructured nonuniform grid system is employed for solving the model. The simulated results are validated by comparing with the present experiment. The predicted results for the convective heat transfer and flow characteristics are reasonable agreement with the experiments. The centrifugal force has significant effect on the enhancements of heat transfer and pressure drop. In addition, due to this force, the heat transfer and pressure drop obtained from the spirally coiled tube are higher than those from the straight tube.

The Legion Grid Portal is an interface to a grid system. Users interact with the portal, and hence a grid through an intuitive interface from which they can view files, submit and monitor runs, and view accounting information. The architecture of the portal is designed to accommodate multiple diverse grid infrastructures, legacy systems and application-specific interfaces. The current implementation of the Legion Grid Portal is with familiar web technologies over the Legion grid infrastructure. The portal can be extended in a number of directionsadditional support for grid administrators, greater number of application-specific interfaces, interoperability between grid infrastructures, and interfaces for programming support. The portal has been in operation since February 2000 on npacinet, a worldwide grid managed by Legion on NPACI resources.

A new generator portfolio planning model is described that is capable of quantifying the carbon emissions associated with systems that include very high penetrations of variable renewables. The model combines a deterministic renewable portfolio planning module with a Monte Carlo simulation of system operation that determines the expected least-cost dispatch from each technology, the necessary reserve capacity, and the expected carbon emissions at each hour. Each system is designed to meet a maximum loss of load expectation requirement of 1 day in 10 years. The present study includes wind, centralized solar thermal, and rooftop photovoltaics, as well as hydroelectric, geothermal, and natural gas plants. The portfolios produced by the model take advantage of the aggregation of variable generators at multiple geographically disperse sites and the incorporation of meteorological and load forecasts. Results are presented from a model run of the continuous two-year period, 2005e2006 in the California ISO operating area. A low-carbon portfolio is produced for this system that is capable of achieving an 80% reduction in electric power sector carbon emissions from 2005 levels and supplying over 99% of the annual delivered load with non-carbon sources. A portfolio is also built for a projected 2050 system, which is capable of providing 96% of the delivered electricity from non-carbon sources, despite a projected doubling of the 2005 system peak load. The results suggest that further reductions in carbon emissions may be achieved with emerging technologies that can reliably provide large capacities without necessarily providing positive net annual energy generation. These technologies may include demand response, vehicle-to-grid systems, and large-scale energy storage.

Modern Grid systems use web services to interact with remote and distributed subsystem components to achieve an effective and common connection. Next generation Grid solutions will include instruments and sensors as part of the Grid, in addition to computational units (CE) and disk storage (SE). The Instrument Element (IE) is a new component that provides access to these remotely distributed pieces of hardware. The IE can organize generic devices in a "Grid of Instruments", providing a set of facilities to allow interaction between sensors and the existing classical grid infrastructure. In this paper, we describe the architecture of an Instrument Element system and present a collection of applications that successfully integrate and utilize this framework.

The effects of tropical forest structure and species composition on species diversity were studied using the data of 279 biodiversity inventory plots, in the forest reserves of the East Usambara Mountains (EUM) in the northeastern part of Tanzania, among the 25 global``hot spots'' for biodiversity conservation. A standard method of vegetation plot sampling was used, based on a 450 m grid system constructed throughout the forest on transect lines. A plot of 50 m  20 m was sampled in each grid square and all trees with a diameter at breast height (dbh) (!10 cm) were measured and identi®ed. The results revealed that the tree species richness and abundance in the EUM were comparable to the reported maximum richness and abundance in the Neotropics and in Southeast Asia. No signi®cant difference in species numbers between intact mature natural forest and former logged or former ®red forest or former cultivated area was observed, but size inequality in species richness and stem density in the intact mature forest was signi®cantly less than that in disturbed forests. This implied that biodiversity of intact mature forest was more stable and frequent human disturbances would threaten the stability of biodiversity. The number of species and stems decreased from the smallest trees to emergent trees, while the occurrence rate of species (species number/stem) increased with tree size. Signi®cant negative relationship between relative species richness (species number/1000 stems) and tree densities in all tested size classes suggested a global negative power-law in the relationship between them. The results of the present study, in summary, revealed that species diversity in Tanzanian tropical forests was signi®cantly in¯uenced by structure and composition of forests. #