WorldWideScience

Sample records for risk natural flow

  1. Analysis of regional natural flow for evaluation of flood risk according to RCP climate change scenarios

    Science.gov (United States)

    Lee, J. Y.; Chae, B. S.; Wi, S.; KIm, T. W.

    2017-12-01

    Various climate change scenarios expect the rainfall in South Korea to increase by 3-10% in the future. The future increased rainfall has significant effect on the frequency of flood in future as well. This study analyzed the probability of future flood to investigate the stability of existing and new installed hydraulic structures and the possibility of increasing flood damage in mid-sized watersheds in South Korea. To achieve this goal, we first clarified the relationship between flood quantiles acquired from the flood-frequency analysis (FFA) and design rainfall-runoff analysis (DRRA) in gauged watersheds. Then, after synthetically generating the regional natural flow data according to RCP climate change scenarios, we developed mathematical formulas to estimate future flood quantiles based on the regression between DRRA and FFA incorporated with regional natural flows in unguaged watersheds. Finally, we developed a flood risk map to investigate the change of flood risk in terms of the return period for the past, present, and future. The results identified that the future flood quantiles and risks would increase in accordance with the RCP climate change scenarios. Because the regional flood risk was identified to increase in future comparing with the present status, comprehensive flood control will be needed to cope with extreme floods in future.

  2. Flow of wet natural pozzolana

    Energy Technology Data Exchange (ETDEWEB)

    Medici, M E; Benegas, O A; Aguirre, F; Baudino, M R [Departamento de Mineria, Universidad Nacional de San Luis, 5700 San Luis (Argentina); Unac, R O; Vidales, A M [INFAP-CONICET, Departamento de Fisica, Universidad Nacional de San Luis, 5700 San Luis (Argentina); Ippolito, I, E-mail: avidales@unsl.edu.a [GMP, CONICET y Facultad de Ingenieria, Universidad de Buenos Aires, 1063 Buenos Aires (Argentina)

    2009-05-01

    We present experimental results on the flow and stability conditions for natural pozzolana, a natural volcanic sand widely used in concrete production. We measured different angles involved in equilibrium conditions for sand piles and relate them to the flux parameters necessary to produce a silo evacuation. We vary some of the geometrical parameters in the silo to inspect the different flux responses of the system. Results are showed as a function of humidity present in the system. In this way, we related critical angles with flux conditions through a silo under different geometric setups and different humidity degrees, thus setting up a basic phase diagram for flux.

  3. Natural Flow Air Cooled Photovoltaics

    Science.gov (United States)

    Tanagnostopoulos, Y.; Themelis, P.

    2010-01-01

    Our experimental study aims to investigate the improvement in the electrical performance of a photovoltaic installation on buildings through cooling of the photovoltaic panels with natural air flow. Our experimental study aims to investigate the improvement in the electrical performance of a photovoltaic installation on buildings through cooling of the photovoltaic panels with natural air flow. We performed experiments using a prototype based on three silicon photovoltaic modules placed in series to simulate a typical sloping building roof with photovoltaic installation. In this system the air flows through a channel on the rear side of PV panels. The potential for increasing the heat exchange from the photovoltaic panel to the circulating air by the addition of a thin metal sheet (TMS) in the middle of air channel or metal fins (FIN) along the air duct was examined. The operation of the device was studied with the air duct closed tightly to avoid air circulation (CLOSED) and the air duct open (REF), with the thin metal sheet (TMS) and with metal fins (FIN). In each case the experiments were performed under sunlight and the operating parameters of the experimental device determining the electrical and thermal performance of the system were observed and recorded during a whole day and for several days. We collected the data and form PV panels from the comparative diagrams of the experimental results regarding the temperature of solar cells, the electrical efficiency of the installation, the temperature of the back wall of the air duct and the temperature difference in the entrance and exit of the air duct. The comparative results from the measurements determine the improvement in electrical performance of the photovoltaic cells because of the reduction of their temperature, which is achieved by the naturally circulating air.

  4. Risk assessment future cash flows

    OpenAIRE

    Chachina H. G.

    2012-01-01

    This article is about risk assessment in planning future cash flows. Discount rate in DCF-model must include four factors: risk cash flow, inflation, value of investments, turnover assets. This has an influence net present value cash flow and make his incomparable.

  5. Energy, entropy, and the flow of nature

    CERN Document Server

    Sherman, Thomas F

    2018-01-01

    A fresh and unified exploration of the laws that govern natural change, examining the historical roots and meaning of the concepts of energy and entropy. All natural processes--mechanical, thermal, chemical, electrical, and biological--are viewed as a flow across free energy gradients that interact with one another.

  6. Flow chemistry syntheses of natural products.

    Science.gov (United States)

    Pastre, Julio C; Browne, Duncan L; Ley, Steven V

    2013-12-07

    The development and application of continuous flow chemistry methods for synthesis is a rapidly growing area of research. In particular, natural products provide demanding challenges to this developing technology. This review highlights successes in the area with an emphasis on new opportunities and technological advances.

  7. Prediction of flow instability during natural convection

    International Nuclear Information System (INIS)

    Farhadi, Kazem

    2005-01-01

    The occurrence of flow excursion instability during passive heat removal for Tehran Research Reactor (TRR) has been analyzed at low-pressure and low-mass rate of flow conditions without boiling taking place. Pressure drop-flow rate characteristics in the general case are determined upon a developed code for this purpose. The code takes into account variations of different pressure drop components caused by different powers as well as different core inlet temperatures. The analysis revealed the fact that the instability can actually occur in the natural convection mode for a range of powers per fuel plates at a predetermined inlet temperature with fixed geometry of the core. Low mass rate of flow and high sub-cooling are the two important conditions for the occurrence of static instability in the TRR. The calculated results are compared with the existing data in the literature. (author)

  8. Burnout heat flux in natural flow boiling

    International Nuclear Information System (INIS)

    Helal, M.M.; Darwish, M.A.; Mahmoud, S.I.

    1978-01-01

    Twenty runs of experiments were conducted to determine the critical heat flux for natural flow boiling with water flowing upwards through annuli of centrally heated stainless steel tube. The test section has concentric heated tube of 14mm diameter and heated lengthes of 15 and 25 cm. The outside surface of the annulus was formed by various glass tubes of 17.25, 20 and 25.9mm diameter. System pressure is atmospheric. Inlet subcooling varied from 18 to 5 0 C. Obtained critical heat flux varied from 24.46 to 62.9 watts/cm 2 . A number of parameters having dominant influence on the critical heat flux and hydrodynamic instability (flow and pressure oscillations) preceeding the burnout have been studied. These parameters are mass flow rate, mass velocity, throttling, channel geometry (diameters ratio, length to diameter ratio, and test section length), and inlet subcooling. Flow regimes before and at the moments of burnout were observed, discussed, and compared with the existing physical model of burnout

  9. Flow and transport in the natural environment

    Science.gov (United States)

    Steffen, W. L.

    An international symposium on flow and transport in the natural environment was held in early September in Canberra. The meeting, sponsored by the Australian Academy o f Science and hosted by the Division of Environmental Mechanics to mark the official opening of Stage 2 of its laboratory, attracted over 100 scientists representing 10 countries.The symposium, organized around flow and transport processes in soil, plants, and the lower layers of the atmosphere, identified and discussed areas where significant advances have taken place over the past 20 years. In addition, it pointed to gaps and weaknesses in present-day understanding. A quarter of the meeting was devoted to closely related transport processes arising in industrial applications.

  10. Modeling of information flows in natural gas storage facility

    Science.gov (United States)

    Ranjbari, Leyla; Bahar, Arifah; Aziz, Zainal Abdul

    2013-09-01

    The paper considers the natural-gas storage valuation based on the information-based pricing framework of Brody-Hughston-Macrina (BHM). As opposed to many studies which the associated filtration is considered pre-specified, this work tries to construct the filtration in terms of the information provided to the market. The value of the storage is given by the sum of the discounted expectations of the cash flows under risk-neutral measure, conditional to the constructed filtration with the Brownian bridge noise term. In order to model the flow of information about the cash flows, we assume the existence of a fixed pricing kernel with liquid, homogenous and incomplete market without arbitrage.

  11. Place attachment and natural environmental risk

    DEFF Research Database (Denmark)

    Bonaiuto, Marino; Alves, Susana; De Dominicis, Stefano

    2016-01-01

    Little is known about place attachment affecting natural environmental risk perception and coping. A systematic search of social science databases revealed 31 works (1996–2016) directly addressing place attachment in relation to different types of natural hazard risks (e.g., seismic, volcanic, etc.......). Across different contexts, the research shows: (a) positive and/or negative relationships between place attachment and natural environmental risk perception; (b) positive and/or negative relationships between place attachment and risk coping; and (c) mediating and moderating relationships. In particular......, results show that: (a) highly attached individuals perceive natural environmental risks but underestimate their potential effects; (b) highly attached individuals are unwilling to relocate when facing natural environmental risks and more likely to return to risky areas after a natural environmental...

  12. Naturalness, value systems and perception of risk

    International Nuclear Information System (INIS)

    Drottz Sjoberg, B.M.

    1998-01-01

    Full text of publication follows: what is natural? And what is Nature? Are perceptions of Nature and naturalness related to perceptions of risk? This paper focuses on these aspects based on results from a Swedish representative sample (N=731), where subjects indicated e.g. the degree of naturalness of various phenomena, their views of nature, and personal life values, as well as perceptions of risk in specified contexts. The results showed a tendency to perceive as natural the phenomenon which is positively valued, i.e. what is natural is also good or desirable. Further, there were weak correlations between perceived naturalness and indicators of technological optimism, possibly indicating that persons with a more generous view of what is natural also more easily might accept change and outcomes due to human intelligence and activity. The construct of 'tampering with nature' has previously been shown to be one good predictor of perceived risk. The respondents also rated their agreement with items aimed to reflect the four 'views of nature' as suggested by Cultural Theory, i.e. nature as robust, capricious, tolerant and fragile. Nature was foremost perceived as fragile, but the main result clearly revealed that peoples' views of nature were complex and most often involved several of the suggested categories. The discussion focuses on the possible implications on environmental concern and risk perception given that Nature would develop into an undesirable type of locality. (author)

  13. History of natural flows--Kansas River

    Science.gov (United States)

    Leeson, Elwood R.

    1958-01-01

    confluence of the Smoky Hill and Republican Rivers, From that point the river flows eastward about 175 miles to Kansas City where it empties into the Missouri River. The basic history of its natural flow can be depicted in general by the records from three gaging stations. The one at Bonner Springs, about 21 miles upstream from the mouth, may be considered as representing the total outflow from the basin; the one at Ogden, about 8 miles downstream from the confluence of the Smoky Hill and Republican Rivers, may be considered as representing the combined contribution of those streams to the Kansas River flow; and the one at Topeka, being only about 16 river miles nearer to Ogden than to Bonner Springs, may be considered as representing flows at the mid-point along the river.

  14. Forecasting risks of natural gas consumption in Slovenia

    Energy Technology Data Exchange (ETDEWEB)

    Potocnik, Primoz; Govekar, Edvard; Grabec, Igor [Laboratory of Synergetics, Ljubljana (Slovenia). Faculty of Mechanical Engineering; Thaler, Marko; Poredos, Alojz [Laboratory for Refrigeration, Ljubljana (Slovenia). Faculty of Mechanical Engineering

    2007-08-15

    Efficient operation of modern energy distribution systems often requires forecasting future energy demand. This paper proposes a strategy to estimate forecasting risk. The objective of the proposed method is to improve knowledge about expected forecasting risk and to estimate the expected cash flow in advance, based on the risk model. The strategy combines an energy demand forecasting model, an economic incentive model and a risk model. Basic guidelines are given for the construction of a forecasting model that combines past energy consumption data, weather data and weather forecast. The forecasting model is required to estimate expected forecasting errors that are the basis for forecasting risk estimation. The risk estimation strategy also requires an economic incentive model that describes the influence of forecasting accuracy on the energy distribution systems' cash flow. The economic model defines the critical forecasting error levels that most strongly influence cash flow. Based on the forecasting model and the economic model, the development of a risk model is proposed. The risk model is associated with critical forecasting error levels in the context of various influential parameters such as seasonal data, month, day of the week and temperature. The risk model is applicable to estimating the daily forecasting risk based on the influential parameters. The proposed approach is illustrated by a case study of a Slovenian natural gas distribution company. (author)

  15. Forecasting risks of natural gas consumption in Slovenia

    International Nuclear Information System (INIS)

    Potocnik, Primoz; Thaler, Marko; Govekar, Edvard; Grabec, Igor; Poredos, Alojz

    2007-01-01

    Efficient operation of modern energy distribution systems often requires forecasting future energy demand. This paper proposes a strategy to estimate forecasting risk. The objective of the proposed method is to improve knowledge about expected forecasting risk and to estimate the expected cash flow in advance, based on the risk model. The strategy combines an energy demand forecasting model, an economic incentive model and a risk model. Basic guidelines are given for the construction of a forecasting model that combines past energy consumption data, weather data and weather forecast. The forecasting model is required to estimate expected forecasting errors that are the basis for forecasting risk estimation. The risk estimation strategy also requires an economic incentive model that describes the influence of forecasting accuracy on the energy distribution systems' cash flow. The economic model defines the critical forecasting error levels that most strongly influence cash flow. Based on the forecasting model and the economic model, the development of a risk model is proposed. The risk model is associated with critical forecasting error levels in the context of various influential parameters such as seasonal data, month, day of the week and temperature. The risk model is applicable to estimating the daily forecasting risk based on the influential parameters. The proposed approach is illustrated by a case study of a Slovenian natural gas distribution company

  16. Natural convection flow between moving boundaries | Chepkwony ...

    African Journals Online (AJOL)

    The two-point boundary value problem governing the flow is characterized by a non-dimensional parameter K. It is solved numerically using shooting method and the Newton-Raphson method to locate the missing initial conditions. The numerical results reveal that no solution exists beyond a critical value of K and that dual ...

  17. PARAMETRIC INSURANCE COVER FOR NATURAL CATASTROPHE RISKS

    Directory of Open Access Journals (Sweden)

    Serghei Margulescu

    2013-11-01

    Full Text Available With economic losses of over USD 370 bn caused by 325 catastrophic events, 2011 ranks as the worst ever year in terms of costs to society due to natural catastrophes and man-made disasters. Inthe same time, 2011 is the second most expensive year in the history for the insurance industry, with insured losses from catastrophic events amounting to USD 116 bn. Both the high level of damages and insured losses, as well as the unprecedented gap between the two values, made insurers and reinsurers worldwide to understand that some risks had so far been underestimated and they have to be better integrated in the catastrophes modelling.On the other hand, governments have to protect themselves against the financial impact of natural catastrophes and new forms of cooperation between the public and private sectors can help countries finance disaster risks. Viewed in a country’s wider risk management context, the purchase of parametric insurance cover, which transfers natural catastrophe risk to the private sector using an index- based trigger, is a necessary shift towards a pre-emptive risk management strategy. This kind of approach can be pursued by central governments or at the level of provincial or municipal governments, and a number of case studies included in the publication “Closing the financial gap” by Swiss Re (2011 illustrates how new forms of parametric insurance can help countries finance disaster risks.

  18. Natural-technological risk assessment and management

    Science.gov (United States)

    Burova, Valentina; Frolova, Nina

    2016-04-01

    EM-DAT statistical data on human impact and economic damages in the 1st semester 2015 are the highest since 2011: 41% of disasters were floods, responsible for 39% of economic damage and 7% of events were earthquakes responsible for 59% of total death toll. This suggests that disaster risk assessment and management still need to be improved and stay the principle issue in national and international related programs. The paper investigates the risk assessment and management practice in the Russian Federation at different levels. The method is proposed to identify the territories characterized by integrated natural-technological hazard. The maps of the Russian Federation zoning according to the integrated natural-technological hazard level are presented, as well as the procedure of updating the integrated hazard level taking into account the activity of separate processes. Special attention is paid to data bases on past natural and technological processes consequences, which are used for verification of current hazard estimation. The examples of natural-technological risk zoning for the country and some regions territory are presented. Different output risk indexes: both social and economic, are estimated taking into account requirements of end-users. In order to increase the safety of population of the Russian Federation the trans-boundaries hazards are also taken into account.

  19. Experimental study of natural circulation flow instability in rectangular channels

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Tao; Qi, Shi; Song, Mingqiang [North China Electric Power Univ., Beijing (China). School of Nuclear Science and Engineering; Passive Nuclear Safety Technology, Beijing (China). Beijing Key Lab.; Xiao, Zejun [Nuclear, Reactor Thermal Hydraulics Technology, Chengdu (China). CNNC Key Lab.

    2017-05-15

    Experiments of natural circulation flow instability were conducted in rectangular channels with 5 mm and 10 mm wide gaps. Results for different heating powers were obtained. The results showed that the flow will tend to be instable with the growing of heating power. The oscillation period of pressure D-value and volume flow are the same, but their phase positions are opposite. They both can be described by trigonometric functions. The existence of edge position and secondary flow will strengthen the disturbance of fluid flow in rectangle channels, which contributes to heat transfer. The disturbance of bubble and fluid will be strengthened, especially in the saturated boiling section, which make it possible for the mixing flow. The results also showed that the resistance in 5 mm channel is bigger than that in 10 mm channel, it is less likely to form stable natural circulation in the subcooled region.

  20. Radiation energy devaluation in diffusion combusting flows of natural gas

    International Nuclear Information System (INIS)

    Makhanlall, Deodat; Munda, Josiah L.; Jiang, Peixue

    2013-01-01

    Abstract: CFD (Computational fluid dynamics) is used to evaluate the thermodynamic second-law effects of thermal radiation in turbulent diffusion natural gas flames. Radiative heat transfer processes in gas and at solid walls are identified as important causes of energy devaluation in the combusting flows. The thermodynamic role of thermal radiation cannot be neglected when compared to that of heat conduction and convection, mass diffusion, chemical reactions, and viscous dissipation. An energy devaluation number is also defined, with which the optimum fuel–air equivalence for combusting flows can be determined. The optimum fuel–air equivalence ratio for a natural gas flame is determined to be 0.7. The CFD model is validated against experimental measurements. - Highlights: • Thermodynamic effects of thermal radiation in combusting flows analyzed. • General equation for second-law analyses of combusting flows extended. • Optimum fuel–air equivalence ratio determined for natural gas flame

  1. Natural stream flow-rates measurements by tracer techniques

    International Nuclear Information System (INIS)

    Cuellar Mansilla, J.

    1982-01-01

    This paper presents the study of the precision obtained measuring the natural stream flow rates by tracer techniques, especially when the system presents a great slope and a bed constituted by large and extended particle size. The experiences were realized in laboratory pilot channels with flow-rates between 15 and 130 [1/s]; and in natural streams with flow-rates from 1 to 25 m 3 /s. Tracer used were In-133m and Br-82 for laboratory and field measurements respectively. In both cases the tracer was injected as a pulse and its dilution measured collecting samples in the measured section, at constant flow-rates, of 5[1] in laboratory experiences and 60[1] of water in field experiences. Precisions obtained at a 95% confidence level were about 2% for laboratory and 3% for field. (I.V.)

  2. Rotating thermal flows in natural and industrial processes

    CERN Document Server

    Lappa, Marcello

    2012-01-01

    Rotating Thermal Flows in Natural and Industrial Processes provides the reader with a systematic description of the different types of thermal convection and flow instabilities in rotating systems, as present in materials, crystal growth, thermal engineering, meteorology, oceanography, geophysics and astrophysics. It expressly shows how the isomorphism between small and large scale phenomena becomes beneficial to the definition and ensuing development of an integrated comprehensive framework.  This allows the reader to understand and assimilate the underlying, quintessential mechanisms withou

  3. Supercritical water natural circulation flow stability experiment research

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Dongliang; Zhou, Tao; Li, Bing [North China Electric Power Univ., Beijing (China). School of Nuclear Science and Engineering; North China Electric Power Univ., Beijing (China). Inst. of Nuclear Thermalhydraulic Safety and Standardization; North China Electric Power Univ., Beijing (China). Beijing Key Lab. of Passive Safety Technology for Nuclear Energy; Huang, Yanping [Nuclear Power Institute of China, Chengdu (China). Science and Technology on Reactor System Design Technology Lab.

    2017-12-15

    The Thermal hydraulic characteristics of supercritical water natural circulation plays an important role in the safety of the Generation-IV supercritical water-cooled reactors. Hence it is crucial to conduct the natural circulation heat transfer experiment of supercritical water. The heat transfer characteristics have been studied under different system pressures in the natural circulation systems. Results show that the fluctuations in the subcritical flow rate (for natural circulation) is relatively small, as compared to the supercritical flow rate. By increasing the heating power, it is observed that the amplitude (and time period) of the fluctuation tends to become larger for the natural circulation of supercritical water. This tends to show the presence of flow instability in the supercritical water. It is possible to observe the flow instability phenomenon when the system pressure is suddenly reduced from the supercritical pressure state to the subcritical state. At the test outlet section, the temperature is prone to increase suddenly, whereas the blocking effect may be observed in the inlet section of the experiment.

  4. Comparative Assessment Of Natural Gas Accident Risks

    International Nuclear Information System (INIS)

    Burgherr, P.; Hirschberg, S.

    2005-01-01

    The study utilizes a hierarchical approach including (1) comparative analyses of different energy chains, (2) specific evaluations for the natural gas chain, and (3) a detailed overview of the German situation, based on an extensive data set provided by Deutsche Vereinigung des Gas- und Wasserfaches (DVGW). According to SVGW-expertise DVGW-data can be regarded as fully representative for Swiss conditions due to very similar technologies, management, regulations and safety culture, but has a substantially stronger statistical basis because the German gas grid is about 30 times larger compared to Switzerland. Specifically, the following tasks were carried out by PSI to accomplish the objectives of this project: (1) Consolidation of existing ENSAD data, (2) identification and evaluation of additional sources, (3) comparative assessment of accident risks, and (4) detailed evaluations of specific issues and technical aspects for severe and smaller accidents in the natural gas chain that are relevant under Swiss conditions. (author)

  5. Risk and FDI flows to developing countries

    Directory of Open Access Journals (Sweden)

    Jay van Wyk

    2011-08-01

    Full Text Available The explanatory power of institutional and macroeconomic variables for FDI stock accumulation in developing countries is investigated. Hypotheses are tested by means of pooled least squares regressions. The impact of institutional variables on FDI flows produced mixed results: levels of economic freedom facilitate inward FDI; political risk dampens investment. Some macroeconomic variables displayed significant explanatory power: market size (as measured by per capita income in the base year and absolute growth of GDP positively impacts FDI inflows.  Other key macroeconomic variables, such as lower current account balance, appreciation of host country’s currency, and lower inflation rate stimulate FDI inflows.

  6. Time-Dependent Natural Convection Couette Flow of Heat ...

    African Journals Online (AJOL)

    Time-Dependent Natural Convection Couette Flow of Heat Generating/Absorbing Fluid between Vertical Parallel Plates Filled With Porous Material. ... The numerical simulation conducted for some saturated liquids reveled that at t ≥ Pr the steady and unsteady state velocities (as well as the temperature of the fluid) ...

  7. Computational Optimization of a Natural Laminar Flow Experimental Wing Glove

    Science.gov (United States)

    Hartshom, Fletcher

    2012-01-01

    Computational optimization of a natural laminar flow experimental wing glove that is mounted on a business jet is presented and discussed. The process of designing a laminar flow wing glove starts with creating a two-dimensional optimized airfoil and then lofting it into a three-dimensional wing glove section. The airfoil design process does not consider the three dimensional flow effects such as cross flow due wing sweep as well as engine and body interference. Therefore, once an initial glove geometry is created from the airfoil, the three dimensional wing glove has to be optimized to ensure that the desired extent of laminar flow is maintained over the entire glove. TRANAIR, a non-linear full potential solver with a coupled boundary layer code was used as the main tool in the design and optimization process of the three-dimensional glove shape. The optimization process uses the Class-Shape-Transformation method to perturb the geometry with geometric constraints that allow for a 2-in clearance from the main wing. The three-dimensional glove shape was optimized with the objective of having a spanwise uniform pressure distribution that matches the optimized two-dimensional pressure distribution as closely as possible. Results show that with the appropriate inputs, the optimizer is able to match the two dimensional pressure distributions practically across the entire span of the wing glove. This allows for the experiment to have a much higher probability of having a large extent of natural laminar flow in flight.

  8. Flight tests of a supersonic natural laminar flow airfoil

    International Nuclear Information System (INIS)

    Frederick, M A; Banks, D W; Garzon, G A; Matisheck, J R

    2015-01-01

    A flight test campaign of a supersonic natural laminar flow airfoil has been recently completed. The test surface was an 80 inch (203 cm) chord and 40 inch (102 cm) span article mounted on the centerline store location of an F-15B airplane. The test article was designed with a leading edge sweep of effectively 0° to minimize boundary layer crossflow. The test article surface was coated with an insulating material to avoid significant heat transfer to and from the test article structure to maintain a quasi-adiabatic wall. An aircraft-mounted infrared camera system was used to determine boundary layer transition and the extent of laminar flow. The tests were flown up to Mach 2.0 and chord Reynolds numbers in excess of 30 million. The objectives of the tests were to determine the extent of laminar flow at high Reynolds numbers and to determine the sensitivity of the flow to disturbances. Both discrete (trip dots) and 2D disturbances (forward-facing steps) were tested. A series of oblique shocks, of yet unknown origin, appeared on the surface, which generated sufficient crossflow to affect transition. Despite the unwanted crossflow, the airfoil performed well. The results indicate that the sensitivity of the flow to the disturbances, which can translate into manufacturing tolerances, was similar to that of subsonic natural laminar flow wings. (paper)

  9. Study of turbulent natural-circulation flow and low-Prandtl-number forced-convection flow

    International Nuclear Information System (INIS)

    Chung, K.S.; Thompson, D.H.

    1980-01-01

    Calculational methods and results are discussed for the coupled energy and momentum equations of turbulent natural circulation flow and low Prandtl number forced convection flow. The objective of this paper is to develop a calculational method for the study of the thermal-hydraulic behavior of coolant flowing in a liquid metal fast breeder reactor channel under natural circulation conditions. The two-equation turbulence model is used to evaluate the turbulent momentum transport property. Because the analogy between momentum transfer and heat transfer does not generally hold for low Prandtl number fluid and natural circulation flow conditions, the turbulent thermal conductivity is calculated independently using equations similar to the two-equation turbulence model. The numerical technique used in the calculation is the finite element method

  10. The role of new technologies in risks from natural hazards

    International Nuclear Information System (INIS)

    Gardner, J.S.

    1982-01-01

    The author places some prior natural hazards research into the context of risk from new technologies to show that some beneficial technologies increase the risk from natural hazards. He examines the role of new technologies in risks from natural hazards in a historical perspective, using examples from research on mountain hazards

  11. Integration of expert knowledge and uncertainty in natural risk assessment

    Science.gov (United States)

    Baruffini, Mirko; Jaboyedoff, Michel

    2010-05-01

    Natural hazards occurring in alpine regions during the last decades have clearly shown that interruptions of the Swiss railway power supply and closures of the Gotthard highway due to those events have increased the awareness of infrastructure vulnerability also in Switzerland and illustrate the potential impacts of failures on the performance of infrastructure systems. This asks for a high level of surveillance and preservation along the transalpine lines. Traditional simulation models are only partially capable to predict complex systems behaviours and the subsequently designed and implemented protection strategies are not able to mitigate the full spectrum of risk consequences. They are costly, and maximal protection is most probably not economically feasible. In addition, the quantitative risk assessment approaches such as fault tree analysis, event tree analysis and equivalent annual fatality analysis rely heavily on statistical information. Collecting sufficient data to base a statistical probability of risk is costly and, in many situations, such data does not exist; thus, expert knowledge and experience or engineering judgment can be exploited to estimate risk qualitatively. In order to overcome the statistics lack we used models based on expert's knowledge in order to qualitatively predict based on linguistic appreciation that are more expressive and natural in risk assessment. Fuzzy reasoning (FR) can be used providing a mechanism of computing with words (Zadeh, 1965) for modelling qualitative human thought processes in analyzing complex systems and decisions. Uncertainty in predicting the risk levels arises from such situations because no fully-formalized knowledge are available. Another possibility is to use probability based on triangular probability density function (T-PDF) that can be used to follow the same flow-chart as FR. We implemented the Swiss natural hazard recommendations FR and probability using T-PDF in order to obtain hazard zoning and

  12. RISKS AND CONTRADICTORY OF INTERNATIONAL CAPITAL FLOWS IN BANKING

    Directory of Open Access Journals (Sweden)

    V. Shevchenko

    2014-03-01

    Full Text Available The content of the international capital flows are studied, its contradictor influence on global and national processes. Some theoretical approaches on contradictory impact of capital flows. The major risks of international capital flows in banking sector are determined including financial, currency, assets value decrease, credit rating etc. The capital flows reversal flows are explained. The modern changes of international capital flows to banking sector of Ukraine are discovered.

  13. Management of Combined Natural Risks - A New Approach: Keynote Address

    Science.gov (United States)

    Hanisch, Jörg

    A new attempt is made to illustrate and to quantify the relationships of individual natural hazards, their combinations and the human vulnerability to natural hazards. During many catastrophic events, combinations of different natural events aggravate their occurrence substantially. Earthquakes are frequently associated with heavy landsliding (El Salvador 2001) and heavy rainstorms are able to trigger fast running debris flows and not only floods (like during the Mitch disaster in Central America in 1998). That signifies that natural hazard maps should show the combinations of different hazards and their genetic relationships. To put into effect this, first, the individual hazards have to be assessed and presented in hazard zones (0 to 3). Then these hazards zones will be overlain using GIS techniques. In this way, e.g., an earthquake-prone area which coincides with an area susceptible to landslides (ranking 0 to 3 as well) can show hazard concentrations of up to a value of 6, simply adding the individual hazard zones. To get the result of the corresponding risk zones, the vulnerability maps of human settlements and infra-structure have to be overlain on the maps of these combinations of natural hazards.

  14. Heat Transfer and Fluid Flow in Naturally Ventilated Greenhouses

    Directory of Open Access Journals (Sweden)

    M. Elashmawy

    2017-08-01

    Full Text Available In this paper, heat transfer and fluid flow in naturally ventilated greenhouses are studied numerically for tow configuration according to the number and positions of the opening. The equations governing the phenomenon are developed using the stream function-vorticity formalism and solved using the finite volume method. The aim of the study is to investigate how buoyancy forces influence airflow and temperature patterns inside the greenhouse. Rayleigh number is the main parameter which changes from 103 to 106 and Prandtl number is fixed at Pr=0.71. Results are reported in terms of stream function, isotherms and average Nusselt number. It is found that the flow structure is sensitive to the value of Rayleigh number and the number of openings. Also, that using asymmetric opening positions improve the natural ventilation and facilitate the occurrence of buoyancy induced upward cross-airflow inside the greenhouse.

  15. Prediction of Mass Flow Rate in Supersonic Natural Gas Processing

    Directory of Open Access Journals (Sweden)

    Wen Chuang

    2015-11-01

    Full Text Available The mass flow rate of natural gas through the supersonic separator was numerically calculated by various cubic equations of state. The numerical results show that the compressibility factor and specific heat ratio for ideal gas law diverge remarkably from real gas models at a high inlet pressure. Simultaneously, the deviation of mass flow calculated by the ideal and real gas models reaches over 10 %. The difference increases with the lower of the inlet temperature regardless of the inlet pressure. A higher back pressure results in an earlier location of the shock wave. The pressure ratio of 0.72 is the first threshold to get the separator work normally. The second threshold is 0.95, in which case the whole flow is subsonic and cannot reach the choked state. The shock position moves upstream with the real gas model compared to the ideal gas law in the cyclonic separation section.

  16. Electrification of particulates in industrial and natural multiphase flows

    CERN Document Server

    Gu, Zhaolin

    2017-01-01

    This book introduces comprehensive fundamentals, numerical simulations and experimental methods of electrification of particulates entrained multiphase flows. The electrifications of two particulate forms, liquid droplets and solid particles, are firstly described together. Liquid droplets can be charged under preset or associated electric fields, while solid particles can be charged through contact. Different charging ways in gas (liquid)-liquid or gas-solid multiphase flows are summarized, including ones that are beneficial to industrial processes, such as electrostatic precipitation, electrostatic spraying, and electrostatic separation, etc., ones harmful for shipping and powder industry, and ones occurring in natural phenomenon, such as wind-blown sand and thunderstorm. This book offers theoretical references to the control and utilization of the charging or charged particulates in multiphase flows as well.

  17. Nonlinear Multiplicative Schwarz Preconditioning in Natural Convection Cavity Flow

    KAUST Repository

    Liu, Lulu; Zhang, Wei; Keyes, David E.

    2017-01-01

    A natural convection cavity flow problem is solved using nonlinear multiplicative Schwarz preconditioners, as a Gauss-Seidel-like variant of additive Schwarz preconditioned inexact Newton (ASPIN). The nonlinear preconditioning extends the domain of convergence of Newton’s method to high Rayleigh numbers. Convergence performance varies widely with respect to different groupings of the fields of this multicomponent problem, and with respect to different orderings of the groupings.

  18. Natural Regulation of Energy Flow in a Green Quantum Photocell

    OpenAIRE

    Arp, Trevor B.; Barlas, Yafis; Aji, Vivek; Gabor, Nathaniel M.

    2015-01-01

    Manipulating the flow of energy in nanoscale and molecular photonic devices is of both fundamental interest and central importance for applications in light harvesting optoelectronics. Under erratic solar irradiance conditions, unregulated power fluctuations in a light harvesting photocell lead to inefficient energy storage in conventional solar cells and potentially fatal oxidative damage in photosynthesis. Here, we show that regulation against these fluctuations arises naturally within a tw...

  19. Experimental control of natural perturbations in channel flow

    OpenAIRE

    Juillet , Fabien; Mckeon , J.; Schmid , Peter J.

    2014-01-01

    International audience; A combined approach using system identification and feed-forward control design has been applied to experimental laminar channel flow in an effort to reduce the naturally occurring disturbance level. A simple blowing/suction strategy was capable of reducing the standard deviation of the measured sensor signal by 45 %, which markedly exceeds previously obtained results under comparable conditions. A comparable reduction could be verified over a significant streamwise ex...

  20. Nonlinear Multiplicative Schwarz Preconditioning in Natural Convection Cavity Flow

    KAUST Repository

    Liu, Lulu

    2017-03-17

    A natural convection cavity flow problem is solved using nonlinear multiplicative Schwarz preconditioners, as a Gauss-Seidel-like variant of additive Schwarz preconditioned inexact Newton (ASPIN). The nonlinear preconditioning extends the domain of convergence of Newton’s method to high Rayleigh numbers. Convergence performance varies widely with respect to different groupings of the fields of this multicomponent problem, and with respect to different orderings of the groupings.

  1. Disaster Risks Reduction for Extreme Natural Hazards

    Science.gov (United States)

    Plag, H.; Jules-Plag, S.

    2013-12-01

    Mega disasters associated with extreme natural hazards have the potential to escalate the global sustainability crisis and put us close to the boundaries of the safe operating space for humanity. Floods and droughts are major threats that potentially could reach planetary extent, particularly through secondary economic and social impacts. Earthquakes and tsunamis frequently cause disasters that eventually could exceed the immediate coping capacity of the global economy, particularly since we have built mega cities in hazardous areas that are now ready to be harvested by natural hazards. Unfortunately, the more we learn to cope with the relatively frequent hazards (50 to 100 years events), the less we are worried about the low-probability, high-impact events (a few hundred and more years events). As a consequence, threats from the 500 years flood, drought, volcano eruption are not appropriately accounted for in disaster risk reduction (DRR) discussions. Extreme geohazards have occurred regularly throughout the past, but mostly did not cause major disasters because exposure of human assets to hazards was much lower in the past. The most extreme events that occurred during the last 2,000 years would today cause unparalleled damage on a global scale and could worsen the sustainability crisis. Simulation of these extreme hazards under present conditions can help to assess the disaster risk. Recent extreme earthquakes have illustrated the destruction they can inflict, both directly and indirectly through tsunamis. Large volcano eruptions have the potential to impact climate, anthropogenic infrastructure and resource supplies on global scale. During the last 2,000 years several large volcano eruptions occurred, which under today's conditions are associated with extreme disaster risk. The comparison of earthquakes and volcano eruptions indicates that large volcano eruptions are the low-probability geohazards with potentially the highest impact on our civilization

  2. Natural Length Scales Shape Liquid Phase Continuity in Unsaturated Flows

    Science.gov (United States)

    Assouline, S.; Lehmann, P. G.; Or, D.

    2015-12-01

    Unsaturated flows supporting soil evaporation and internal drainage play an important role in various hydrologic and climatic processes manifested at a wide range of scales. We study inherent natural length scales that govern these flow processes and constrain the spatial range of their representation by continuum models. These inherent length scales reflect interactions between intrinsic porous medium properties that affect liquid phase continuity, and the interplay among forces that drive and resist unsaturated flow. We have defined an intrinsic length scale for hydraulic continuity based on pore size distribution that controls soil evaporation dynamics (i.e., stage 1 to stage 2 transition). This simple metric may be used to delineate upper bounds for regional evaporative losses or the depth of soil-atmosphere interactions (in the absence of plants). A similar length scale governs the dynamics of internal redistribution towards attainment of field capacity, again through its effect on hydraulic continuity in the draining porous medium. The study provides a framework for guiding numerical and mathematical models for capillary flows across different scales considering the necessary conditions for coexistence of stationarity (REV), hydraulic continuity and intrinsic capillary gradients.

  3. Modeling the natural convective flow of micropolar nanofluids

    KAUST Repository

    Bourantas, Georgios

    2014-01-01

    A micropolar model for nanofluidic suspensions is proposed in order to investigate theoretically the natural convection of nanofluids. The microrotation of the nanoparticles seems to play a significant role into flow regime and in that manner it possibly can interpret the controversial experimental data and theoretical numerical results over the natural convection of nanofluids. Natural convection of a nanofluid in a square cavity is studied and computations are performed for Rayleigh number values up to 106, for a range of solid volume fractions (0 ≤ φ ≤ 0.2) and, different types of nanoparticles (Cu, Ag, Al2O3 and TiO 2). The theoretical results show that the microrotation of the nanoparticles in suspension in general decreases overall heat transfer from the heated wall and should not therefore be neglected when computing heat and fluid flow of micropolar fluids, as nanofluids. The validity of the proposed model is depicted by comparing the numerical results obtained with available experimental and theoretical data. © 2013 Elsevier Ltd. All rights reserved.

  4. Natural Regulation of Energy Flow in a Green Quantum Photocell.

    Science.gov (United States)

    Arp, Trevor B; Barlas, Yafis; Aji, Vivek; Gabor, Nathaniel M

    2016-12-14

    Manipulating the flow of energy in nanoscale and molecular photonic devices is of both fundamental interest and central importance for applications in light energy harvesting optoelectronics. Under erratic solar irradiance conditions, unregulated power fluctuations in a light-harvesting photocell lead to inefficient energy storage in conventional solar cells and potentially fatal oxidative damage in photosynthesis. Here, we compare the theoretical minimum energy fluctuations in nanoscale quantum heat engine photocells that incorporate one or two photon-absorbing channels and show that fluctuations are naturally suppressed in the two-channel photocell. This intrinsic suppression acts as a passive regulation mechanism that enables the efficient conversion of varying incident solar power into a steady output for absorption over a broad range of the solar spectrum on Earth. Remarkably, absorption in the green portion of the spectrum provides no inherent regulatory benefit, indicating that green light should be rejected in a photocell whose primary role is the regulation of energy flow.

  5. Does Operational Risk Disclosure Quality Increase Operating Cash Flows?

    Directory of Open Access Journals (Sweden)

    Haitham Nobanee

    2017-12-01

    Full Text Available This study aims to measure the degree of operational risk disclosure and examine its impact on operating cash flow of banks listed on the UAE Abu Dhabi Stock Exchange (ADX and Dubai Financial Market (DFM during the period 2003-2016. The authors conducted content analysis of the annual reports to measure the degree of operational risk disclosure. In addition, they used dynamic panel data regressions to analyze the impact of operational risk disclosure on the operating cash flow generated by the banks. The results show a low degree of operational risk disclosure for all UAE banks, both Islamic and conventional. In addition, the results show no association between the levels of disclosure of operational risk and cash flow for all banks, conventional and Islamic. Operational risk disclosure of Islamic banks has not been examined by any prior researchers. In addition, this paper examines the potential impact of operational risk disclosure on the operating cash flow generated by the banks.

  6. Natural radiation, radioactive waste and chemical risk determinants

    International Nuclear Information System (INIS)

    Christensen, T.; Mustonen, R.; Edhwall, H.; Hansen, H.; Soerensen, A.; Stranden, E.

    1990-01-01

    Doses from natural radiation to the population in the Nordic countries are summarized, and man-made modifications of the natural radiation environment are discussed. An account is given for the radiological concequences of energy concervation by reduced ventilation. Risks from possible future releases of radioactivity from final depositories of spent nuclear fuel are compared to the risks from present natural radioactivity in the environment. The possibilities for comparison between chemical and radiological risks are discussed. 104 refs., 36 figs., 47 tabs

  7. Building a Practical Natural Laminar Flow Design Capability

    Science.gov (United States)

    Campbell, Richard L.; Lynde, Michelle N.

    2017-01-01

    A preliminary natural laminar flow (NLF) design method that has been developed and applied to supersonic and transonic wings with moderate-to-high leading-edge sweeps at flight Reynolds numbers is further extended and evaluated in this paper. The modular design approach uses a knowledge-based design module linked with different flow solvers and boundary layer stability analysis methods to provide a multifidelity capability for NLF analysis and design. An assessment of the effects of different options for stability analysis is included using pressures and geometry from an NLF wing designed for the Common Research Model (CRM). Several extensions to the design module are described, including multiple new approaches to design for controlling attachment line contamination and transition. Finally, a modification to the NLF design algorithm that allows independent control of Tollmien-Schlichting (TS) and cross flow (CF) modes is proposed. A preliminary evaluation of the TS-only option applied to the design of an NLF nacelle for the CRM is performed that includes the use of a low-fidelity stability analysis directly in the design module.

  8. Experimental observations of natural circulation flow in the NSTF

    Energy Technology Data Exchange (ETDEWEB)

    Lisowski, Darius D., E-mail: dlisowski@anl.gov; Kraus, Adam R.; Bucknor, Matthew D.; Hu, Rui; Farmer, Mitch T.

    2016-09-15

    A 1/2 scale test facility has been constructed at Argonne National Laboratory to study the heat removal performance and natural circulation flow patterns in a Reactor Cavity Cooling System (RCCS). Our test facility, the Natural convection Shutdown heat removal Test Facility (NSTF), supports the broader goal of developing an inherently safe and fully passive ex-vessel decay heat removal for advanced reactor designs. The project, initiated in 2010 to support the Advanced Reactor Technologies (ART), Small Modular Reactor (SMR), and Next Generation Nuclear Plant (NGNP) programs, has been conducting experimental operations since early 2014. The following paper provides a summary of some primary design features of the 26-m tall test facility along with a description of the data acquisition suite that guides our experimental practices. Specifics of the distributed fiber optic temperature measurements will be discussed, which introduces an unparalleled level of data density that has never before been implemented in a large scale natural circulation test facility. Results from our test series will then be presented, which provide insight into the thermal hydraulic behavior at steady-state and transient conditions for varying heat flux levels and exhaust chimney configuration states.

  9. High-Fidelity Aerodynamic Shape Optimization for Natural Laminar Flow

    Science.gov (United States)

    Rashad, Ramy

    To ensure the long-term sustainability of aviation, serious effort is underway to mitigate the escalating economic, environmental, and social concerns of the industry. Significant improvement to the energy efficiency of air transportation is required through the research and development of advanced and unconventional airframe and engine technologies. In the quest to reduce airframe drag, this thesis is concerned with the development and demonstration of an effective design tool for improving the aerodynamic efficiency of subsonic and transonic airfoils. The objective is to advance the state-of-the-art in high-fidelity aerodynamic shape optimization by incorporating and exploiting the phenomenon of laminar-turbulent transition in an efficient manner. A framework for the design and optimization of Natural Laminar Flow (NLF) airfoils is developed and demonstrated with transition prediction capable of accounting for the effects of Reynolds number, freestream turbulence intensity, Mach number, and pressure gradients. First, a two-dimensional Reynolds-averaged Navier-Stokes (RANS) flow solver has been extended to incorporate an iterative laminar-turbulent transition prediction methodology. The natural transition locations due to Tollmien-Schlichting instabilities are predicted using the simplified eN envelope method of Drela and Giles or, alternatively, the compressible form of the Arnal-Habiballah-Delcourt criterion. The boundary-layer properties are obtained directly from the Navier-Stokes flow solution, and the transition to turbulent flow is modeled using an intermittency function in conjunction with the Spalart-Allmaras turbulence model. The RANS solver is subsequently employed in a gradient-based sequential quadratic programming shape optimization framework. The laminar-turbulent transition criteria are tightly coupled into the objective and gradient evaluations. The gradients are obtained using a new augmented discrete-adjoint formulation for non-local transition

  10. Natural phenomena risk assessment at Rocky Flats Plant

    International Nuclear Information System (INIS)

    Foppe, T.L.

    1985-01-01

    A realistic approach is currently being used at the Rocky Flats Plant to assess the risks of natural phenomena events. The methodology addresses frequency of occurrence estimates, damage stress on the facility and vital equipment, material-at-risk, release fractions and source terms, leakpath, dispersion and dosimetric models, risk curves, and an uncertainty analysis. 28 references, 1 figure

  11. Groundwater flow through a natural fracture. Flow experiments and numerical modelling

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, Erik [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept of Geology

    1997-09-01

    Groundwater flow and transport play an important role not only for groundwater exploration but also in environmental engineering problems. This report considers how the hydraulic properties of fractures in crystalline rock depend on the fracture aperture geometry. Different numerical models are discussed and a FDM computer code for two- and three- dimensional flow-modelling has been developed. Different relations between the cells in the model are tested and compared with results in the literature. A laboratory experimental work has been done to carry out flow experiments and aperture measurements on the same specimen of a natural fracture. The drilled core sample had fractures parallel to the core axis and was placed inside a biaxial cell during the experiments. The water pressure gradient and the compression stress were varied during the experiments and also a tracer test was done. After the flow experiments, the aperture distribution for a certain compression was measured by injecting an epoxy resin into the fracture. The thickness of the resin layer was then studied in saw cut sections of the sample. The results from the experiments were used to validate numerical and analytical models, based on aperture distribution, for flow and transport simulations. In the disturbed zone around a drift both water and air are present in the fractures. The gas will go to the most wide part of the fracture because the capillarity and the conductivity decrease. The dependence of the effective conductivity on the variance of the conductivity and the effect of extinction of highly conductive cells has also been studied. A discussion of how gas in fractures around a drift can cause a skin effect is modelled and an example is given of what a saturation depending on the magnitude of the flow causes. 25 refs, 17 tabs, 43 figs.

  12. Groundwater flow through a natural fracture. Flow experiments and numerical modelling

    International Nuclear Information System (INIS)

    Larsson, Erik

    1997-09-01

    Groundwater flow and transport play an important role not only for groundwater exploration but also in environmental engineering problems. This report considers how the hydraulic properties of fractures in crystalline rock depend on the fracture aperture geometry. Different numerical models are discussed and a FDM computer code for two- and three- dimensional flow-modelling has been developed. Different relations between the cells in the model are tested and compared with results in the literature. A laboratory experimental work has been done to carry out flow experiments and aperture measurements on the same specimen of a natural fracture. The drilled core sample had fractures parallel to the core axis and was placed inside a biaxial cell during the experiments. The water pressure gradient and the compression stress were varied during the experiments and also a tracer test was done. After the flow experiments, the aperture distribution for a certain compression was measured by injecting an epoxy resin into the fracture. The thickness of the resin layer was then studied in saw cut sections of the sample. The results from the experiments were used to validate numerical and analytical models, based on aperture distribution, for flow and transport simulations. In the disturbed zone around a drift both water and air are present in the fractures. The gas will go to the most wide part of the fracture because the capillarity and the conductivity decrease. The dependence of the effective conductivity on the variance of the conductivity and the effect of extinction of highly conductive cells has also been studied. A discussion of how gas in fractures around a drift can cause a skin effect is modelled and an example is given of what a saturation depending on the magnitude of the flow causes

  13. Natural risks assessment and management (project of monograph)

    International Nuclear Information System (INIS)

    Ragozin, A.L.

    1998-01-01

    Full text of publication follows: large-scale theoretic and practical works on the issue of natural risk assessment and management started in Russia in the end of the 80's. By now there has been made a considerable progress, which allowed for the preparation of a collective monograph on the subject mentioned in the title of this abstract. It is supposed to be published in 1999 in order to become a Russian contribution to the International Decade of Natural Disasters Reduction. The monograph included 6 chapters with the following titles: 1. Methodological foundations of natural risk analysis and assessment. 2. Investigating and forecasting natural hazards for the purpose of risk assessment. 3. Assessment of economic, social and ecological damage from natural hazards. 4, Theory of natural risk assessment. 5. Examples of natural risk assessment and mapping. 6. Natural risk management. In the report there is described the content of the monograph and unsolved questions are discussed. Executive editor offers all international experts to cooperate in the compilation of this monograph, which is to be completed by the end of 1998, especially of chapter 5 and 6. (author)

  14. REVIEW: Towards a risk register for natural capital.

    Science.gov (United States)

    Mace, Georgina M; Hails, Rosemary S; Cryle, Philip; Harlow, Julian; Clarke, Stewart J

    2015-06-01

    Natural capital is essential for goods and services on which people depend. Yet pressures on the environment mean that natural capital assets are continuing to decline and degrade, putting such benefits at risk. Systematic monitoring of natural assets is a major challenge that could be both unaffordable and unmanageable without a way to focus efforts. Here we introduce a simple approach, based on the commonly used management tool of a risk register, to highlight natural assets whose condition places benefits at risk.We undertake a preliminary assessment using a risk register for natural capital assets in the UK based solely on existing information. The status and trends of natural capital assets are assessed using asset-benefit relationships for ten kinds of benefits (food, fibre (timber), energy, aesthetics, freshwater (quality), recreation, clean air, wildlife, hazard protection and equable climate) across eight broad habitat types in the UK based on three dimensions of natural capital within each of the habitat types (quality, quantity and spatial configuration). We estimate the status and trends of benefits relative to societal targets using existing regulatory limits and policy commitments, and allocate scores of high, medium or low risk to asset-benefit relationships that are both subject to management and of concern.The risk register approach reveals substantial gaps in knowledge about asset-benefit relationships which limit the scope and rigour of the assessment (especially for marine and urban habitats). Nevertheless, we find strong indications that certain assets (in freshwater, mountain, moors and heathland habitats) are at high risk in relation to their ability to sustain certain benefits (especially freshwater, wildlife and climate regulation). Synthesis and applications . With directed data gathering, especially to monitor trends, improve metrics related to asset-benefit relationships, and improve understanding of nonlinearities and thresholds, the

  15. Evolution of natural risk: research framework and perspectives

    Science.gov (United States)

    Hufschmidt, G.; Crozier, M.; Glade, T.

    2005-05-01

    This study presents a conceptual framework for addressing temporal variation in natural risk. Numerous former natural risk analyses and investigations have demonstrated that time and related changes have a crucial influence on risk. For natural hazards, time becomes a factor for a number of reasons. Using the example of landslides to illustrate this point, it is shown that: 1. landslide history is important in determining probability of occurrence, 2. the significance of catchment variables in explaining landslide susceptibility is dependent on the time scale chosen, 3. the observer's perception of the geosystem's state changes with different time spans, and 4. the system's sensitivity varies with time. Natural hazards are not isolated events but complex features that are connected with the social system. Similarly, elements at risk and their vulnerability are highly dynamic through time, an aspect that is not sufficiently acknowledged in research. Since natural risk is an amalgam of hazard and vulnerability, its temporal behaviour has to be considered as well. Identifying these changes and their underlying processes contributes to a better understanding of natural risk today and in the future. However, no dynamic models for natural risks are currently available. Dynamic behaviour of factors affecting risk is likely to create increasing connectivity and complexity. This demands a broad approach to natural risk, since the concept of risk encapsulates aspects of many disciplines and has suffered from single-discipline approaches in the past. In New Zealand, dramatic environmental and social change has occurred in a relatively short period of time, graphically demonstrating the temporal variability of the geosystem and the social system. To understand these changes and subsequent interactions between both systems, a holistic perspective is needed. This contribution reviews available frameworks, demonstrates the need for further concepts, and gives research

  16. Flow Visualization of Forced and Natural Convection in Internal Cavities

    International Nuclear Information System (INIS)

    Crepeau, John; Mcllroy, Hugh M. Jr.; McEligot, Donald M.; Condie, Keith G.; McCreery, Glenn; Clarsean, Randy; Brodkey, Robert S.; Guezennec, Yann G.

    2002-01-01

    The report describes innovative flow visualization techniques, fluid mechanics measurements and computational models of flows in a spent nuclear fuel canister. The flow visualization methods used a fluid that reacted with a metal plate to show how a local reaction affects the surrounding flow. A matched index of refraction facility was used to take mean flow and turbulence measurements within a generic spent nuclear fuel canister. Computational models were also made of the flow in the canister. It was determined that the flow field in the canister was very complex, and modifications may need to be made to ensure that the spent fuel elements are completely passivated

  17. Flow Visualization of Forced and Natural Convection in Internal Cavities

    Energy Technology Data Exchange (ETDEWEB)

    John Crepeau; Hugh M. Mcllroy,Jr.; Donald M. McEligot; Keith G. Condie; Glenn McCreery; Randy Clarsean; Robert S. Brodkey; Yann G. Guezennec

    2002-01-31

    The report descries innovative flow visualization techniques, fluid mechanics measurements and computational models of flows in a spent nuclear fuel canister. The flow visualization methods used a fluid that reacted with a metal plate to show how a local reaction affects the surrounding flow. A matched index of refraction facility was used to take mean flow and turbulence measurements within a generic spent nuclear fuel canister. Computational models were also made of the flow in the canister. It was determined that the flow field in the canister was very complex, and modifications may need to be made to ensure that the spent fuel elements are completely passivated.

  18. Study on reverse flow characteristics under natural circulation in inverted U-tube steam generator

    International Nuclear Information System (INIS)

    Duan Jun; Zhou Tao; Zhang Lei; Hong Dexun; Liu Ping

    2013-01-01

    Natural circulation is important for application in the nuclear power industry. Aiming at the steam generator of AP1000 pressurized water reactor loop, the mathematical model was established to analysis the reverse flow of single-phase water in the inverted U-tubes of a steam generator in a natural circulation system. The length distribution and the mass flow rates in both tubes with normal and reverse flow were determined respectively. The research results show that the reverse flow may result in sharp decrease of gravity pressure head, circulation mass flow rate and heat release rate of natural circulation. It has adverse influence on natural circulation. (authors)

  19. Spectrally-consistent regularization modeling of turbulent natural convection flows

    International Nuclear Information System (INIS)

    Trias, F Xavier; Gorobets, Andrey; Oliva, Assensi; Verstappen, Roel

    2012-01-01

    The incompressible Navier-Stokes equations constitute an excellent mathematical modelization of turbulence. Unfortunately, attempts at performing direct simulations are limited to relatively low-Reynolds numbers because of the almost numberless small scales produced by the non-linear convective term. Alternatively, a dynamically less complex formulation is proposed here. Namely, regularizations of the Navier-Stokes equations that preserve the symmetry and conservation properties exactly. To do so, both convective and diffusive terms are altered in the same vein. In this way, the convective production of small scales is effectively restrained whereas the modified diffusive term introduces a hyperviscosity effect and consequently enhances the destruction of small scales. In practice, the only additional ingredient is a self-adjoint linear filter whose local filter length is determined from the requirement that vortex-stretching must stop at the smallest grid scale. In the present work, the performance of the above-mentioned recent improvements is assessed through application to turbulent natural convection flows by means of comparison with DNS reference data.

  20. Optimal natural resources management under uncertainty with catastrophic risk

    Energy Technology Data Exchange (ETDEWEB)

    Motoh, Tsujimura [Graduate School of Economics, Kyoto University, Yoshida-honmochi, Sakyo-ku, Kyoto 606-8501 (Japan)

    2004-05-01

    We examine an optimal natural resources management problem under uncertainty with catastrophic risk and investigate the optimal rate of use of a natural resource. For this purpose, we use stochastic control theory. We assume that, until a catastrophic event occurs, the stock of the natural resource is governed by a stochastic differential equation. We describe the catastrophic phenomenon as a Poisson process. From this analysis, we show the optimal rate of use of the natural resource in explicit form. Furthermore, we present comparative static results for the optimal rate of use of the natural resource.

  1. Optimal natural resources management under uncertainty with catastrophic risk

    International Nuclear Information System (INIS)

    Motoh, Tsujimura

    2004-01-01

    We examine an optimal natural resources management problem under uncertainty with catastrophic risk and investigate the optimal rate of use of a natural resource. For this purpose, we use stochastic control theory. We assume that, until a catastrophic event occurs, the stock of the natural resource is governed by a stochastic differential equation. We describe the catastrophic phenomenon as a Poisson process. From this analysis, we show the optimal rate of use of the natural resource in explicit form. Furthermore, we present comparative static results for the optimal rate of use of the natural resource

  2. Flow restriction of multicontrolled natural gas; Restritor de fluxo de gas natural microcontrolado

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, Lauro C.; Reis, Antonio M.; Maldonado, Waldemar; Suzuqui, Moises [Universidade para o Desenvolvimento do Estado e da Regiao do Pantanal (UNIDERP), Campo Grande, MS (Brazil). Nucleo de Energia, Automacao e Controle; Scucuglia, Jose W.; Cortez, Marco A.A. [Universidade para o Desenvolvimento do Estado e da Regiao do Pantanal (UNIDERP), Campo Grande, MS (Brazil). Curso de Engenharia Eletrica; Teixeira, Marcelo C.M. [UNESP, Ilha Solteira, SP (Brazil). Faculdade de Engenharia Eletrica; Carrasco, Benjamim N. [PETROBRAS, Rio de Janeiro, RJ (Brazil)

    2004-07-01

    One of the specific cases of control in the operation of natural gas distribution is of the automatic restriction of the outflow due the violations of standards of draining of the natural gas in the ducts. With the objective to get a device of low cost, with national technology and high technological value aggregate, developed an electronic, microcontrolled, programmable device, and of low cost, that will function connected the sensors and valves of flow control, of form to monitor in real time the outflow of draining of the natural gas in the respective ducts and to restrict of automatic form the outflow, that necessary or always convenient. The developed hardware was conceived using micro controllers of high performance with capacity of reading of sensors of pressure, temperature and measurers of outflow. Had to a serial communication and the storage in memory of mass with 264 capacity of Kbytes is possible the pertinent visualization of graphs and reports to the behavior of the outflow and performance of the system. An internal RTC - Real Clock Teams, added to the hardware a clock and a calendar for acquisition of data in the schedule defined, as well as the possibility of unloading of the data through the telephonic line, using one embedded modem. (author)

  3. Effects of risk communication on natural hazards on real estate owners' risk perception and risk behaviour

    Science.gov (United States)

    Buchecker, M.; Maidl, E.

    2012-04-01

    In the last decade, in most of the European countries risk maps on natural hazards have been elaborated but there is so far little experience how to efficiently communicate these maps to the public. Recently, the public authorities of Zurich informed the owners of buildings located within the hazard zone on urban flood risks The owners received official letters containing information on potential danger, the probability of flood events, constructional safety measures, and guidelines for appropriate actions in case of an immediate flood. In the cover letter they were also encouraged to achieve more detailed information about the particular risks for their building using an online accessible risk map within a geographic information system (GIS). This risk communication campaign was based on the expectation that informing citizens increases their risk awareness and that citizens aware of risks are more likely to undertake actions to protect themselves and their property. There is, however, little empirical evidence that these expected outcomes can be achieved by written forms of risk communication. With this project we aim to find out to which degree a campaign of written risk communication can shape land owners risk perception and risk behaviour, and which other factors (e.g. trust in authorities, risk, risk zone category of the building) contributed to these outcomes... In collaboration with public authorities we conducted a survey among 1500 owners of buildings in the hazard zones in Zurich (50 % in blue zone, 50 % in yellow and yellow-white zone), that is 14% of all persons who were addressed by the authorities of the city. The standardized questionnaire comprises in particular items measuring respondents' evaluation of the virtual and physical information material, the time they spent for studying the information material, the dimensions of their risk perception, their acceptability of risks and their preparedness to implement constructional and other safety

  4. Sovereign Risk and Natural Disasters in Emerging Markets

    NARCIS (Netherlands)

    Klomp, Jeroen

    2015-01-01

    In this article, we explore the effect of large-scale natural disasters on sovereign default risk. We use a heterogeneous dynamic panel model including a set of more than 380 large-scale natural disasters for about forty emerging market countries in the period 1999-2010. After testing for the

  5. A generalised correlation for the steady state flow in single-phase natural circulation loops

    International Nuclear Information System (INIS)

    Vijayan, P.K.; Bade, M.H.; Saha, D.; Sinha, R.K.; Venkat Raj, V.

    2000-08-01

    To establish the heat transport capability of natural circulation loops, it is essential to know the flow rate. A generalized correlation for steady state flow valid for uniform and non-uniform diameter loops has been theoretically derived

  6. Building a Natural Disaster Risk Index for Supply Chain Operations

    OpenAIRE

    Kun Liao; Ozden Bayazit; Fang Wang

    2014-01-01

    Risk for an organization is associated with uncertainties in all areas of its operations. As firms move toward global sourcing, supply chain risk increases dramatically, which is linked to lower financial performance and market value. One major type of supply chain risk is disruptions caused by natural or man-made disasters. In this paper, major factors causing supply chain disruptions are identified based on resource dependency theory and contingency theory. As a result of the study, a compr...

  7. Natural convection heat transfer between vertical channel with flow resistance at the lower end

    International Nuclear Information System (INIS)

    Iwamoto, S.; Nishimura, S.; Ishihara, I.

    2003-01-01

    For natural convection in the geometrically complicated channel, the convection flow is suppressed by flow resistance due to such channel itself and the lopsided flow may take place. This could result in serious influences on the heat transfer in the channel. In order to investigate fundamentally the natural convection flow and heat transfer in such the channel, the vertical channel in which wall was heated with uniform heat flux and the flow resistance was given by small clearance between the lower end of channel and a wide horizontal floor. Flow pattern was observed by illuminating smoke filled in the channel and heat transfer rate was measured. (author)

  8. Flow visualization of bubble behavior under two-phase natural circulation flow conditions using high speed digital camera

    Energy Technology Data Exchange (ETDEWEB)

    Lemos, Wanderley F.; Su, Jian, E-mail: wlemos@con.ufrj.br, E-mail: sujian@lasme.coppe.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Faccini, Jose L.H., E-mail: faccini@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. de Termo-Hidraulica Experimental

    2013-07-01

    The The present work aims at identifying flow patterns and measuring interfacial parameters in two-phase natural circulation by using visualization technique with high-speed digital camera. The experiments were conducted in the Natural Circulation Circuit (CCN), installed at Nuclear Engineering Institute/CNEN. The thermo-hydraulic circuit comprises heater, heat exchanger, expansion tank, the pressure relief valve and pipes to interconnect the components. A glass tube is installed at the midpoint of the riser connected to the heater outlet. The natural circulation circuit is complemented by acquisition system of values of temperatures, flow and graphic interface. The instrumentation has thermocouples, volumetric flow meter, rotameter and high-speed digital camera. The experimental study is performed through analysis of information from measurements of temperatures at strategic points along the hydraulic circuit, besides natural circulation flow rates. The comparisons between analytical and experimental values are validated by viewing, recording and processing of the images for the flows patterns. Variables involved in the process of identification of flow regimes, dimensionless parameters, the phase velocity of the flow, initial boiling point, the phenomenon of 'flashing' pre-slug flow type were obtained experimentally. (author)

  9. Flow visualization of bubble behavior under two-phase natural circulation flow conditions using high speed digital camera

    International Nuclear Information System (INIS)

    Lemos, Wanderley F.; Su, Jian; Faccini, Jose L.H.

    2013-01-01

    The The present work aims at identifying flow patterns and measuring interfacial parameters in two-phase natural circulation by using visualization technique with high-speed digital camera. The experiments were conducted in the Natural Circulation Circuit (CCN), installed at Nuclear Engineering Institute/CNEN. The thermo-hydraulic circuit comprises heater, heat exchanger, expansion tank, the pressure relief valve and pipes to interconnect the components. A glass tube is installed at the midpoint of the riser connected to the heater outlet. The natural circulation circuit is complemented by acquisition system of values of temperatures, flow and graphic interface. The instrumentation has thermocouples, volumetric flow meter, rotameter and high-speed digital camera. The experimental study is performed through analysis of information from measurements of temperatures at strategic points along the hydraulic circuit, besides natural circulation flow rates. The comparisons between analytical and experimental values are validated by viewing, recording and processing of the images for the flows patterns. Variables involved in the process of identification of flow regimes, dimensionless parameters, the phase velocity of the flow, initial boiling point, the phenomenon of 'flashing' pre-slug flow type were obtained experimentally. (author)

  10. Modeling flow in naturally fractured reservoirs : effect of fracture aperture distribution on dominant sub-network for flow

    NARCIS (Netherlands)

    Gong, J.; Rossen, W.R.

    2017-01-01

    Fracture network connectivity and aperture (or conductivity) distribution are two crucial features controlling flow behavior of naturally fractured reservoirs. The effect of connectivity on flow properties is well documented. In this paper, however, we focus here on the influence of fracture

  11. Analysis of reverse flow in inverted U-tubes of steam generator under natural circulation condition

    International Nuclear Information System (INIS)

    Yang Ruichang; Liu Ruolei; Liu Jinggong; Qin Shiwei

    2008-01-01

    In this paper, we report on the analysis of reverse flow in inverted U-tubes of a steam generator under natural circulation condition. The mechanism of reverse flow in inverted U-tubes of the steam generator with natural circulation is graphically analyzed by using the full-range characteristic curve of parallel U-tubes. The mathematical model and numerical calculation method for analyzing the reverse flow in inverted U-tubes of the steam generator with natural circulation have been developed. The reverse flow in an inverted U-tube steam generator of a simulated pressurized water reactor with natural circulation in analyzed. Through the calculation, the mass flow rates of normal and reverse flows in individual U-tubes are obtained. The predicted sharp drop of the fluid temperature in the inlet plenum of the steam generator due to reverse flow agrees very well with the experimental data. This indicates that the developed mathematical model and solution method can be used to correctly predict the reverse flow in the inverted U-tubes of the steam generator with natural circulation. The obtained results also show that in the analysis of natural circulation flow in the primary circuit, the reverse flow in the inverted U-tubes of the steam generator must be taken into account. (author)

  12. Static Behaviour of Natural Gas and its Flow in Pipes

    OpenAIRE

    Ohirhian, Peter

    2010-01-01

    1. 2. A general differential equation that governs static behavior of any fluid and its flow in horizontal, uphill and downhill pipes has been developed. classical fourth order Runge-Kutta numerical method is programmed in Fortran 77, to test the equation and results are accurate. The program shows that a length ncrement as large as 10,000 ft can be used in the Runge-Kutta method of solution to differential equation during uphill gas flow and up to 5700ft for downhill gas flow The Runge-Kutta...

  13. Measurement and Modelling of Air Flow Rate in a Naturally Ventilated Double Skin Facade

    DEFF Research Database (Denmark)

    Heiselberg, Per; Kalyanova, Olena; Jensen, Rasmus Lund

    2008-01-01

    Air flow rate in a naturally ventilated double skin façade (DSF) is extremely difficult to measure due to the stochastic nature of wind, and as a consequence non-uniform and dynamic flow conditions. This paper describes the results of two different methods to measure the air flow in a full...... by the thermal simulation program, BSim, based on measured weather boundary conditions are compared to the measured air temperature, temperature gradient and mass flow rate in the DSF cavity. The results show that it is possible to predict the temperature distribution and airflow in the DSF although some......-scale outdoor test facility with a naturally ventilated double skin façade. Although both methods are difficult to use under such dynamic air flow conditions, they show reasonable agreement and can be used for experimental validation of numerical models of natural ventilation air flow in DSF. Simulations...

  14. Modeling the natural convective flow of micropolar nanofluids

    KAUST Repository

    Bourantas, Georgios; Loukopoulos, Vassilios C.

    2014-01-01

    transfer from the heated wall and should not therefore be neglected when computing heat and fluid flow of micropolar fluids, as nanofluids. The validity of the proposed model is depicted by comparing the numerical results obtained with available

  15. Role of a naturally varying flow regime in Everglades restoration

    Science.gov (United States)

    Harvey, Judson; Wetzel, Paul R.; Lodge, Thomas E.; Engel, Victor C.; Ross, Michael S.

    2017-01-01

    The Everglades is a low-gradient floodplain predominantly on organic soil that undergoes seasonally pulsing sheetflow through a network of deepwater sloughs separated by slightly higher elevation ridges. The seasonally pulsing flow permitted the coexistence of ridge and slough vegetation, including the persistence of productive, well-connected sloughs that seasonally concentrated prey and supported wading bird nesting success. Here we review factors contributing to the origin and to degradation of the ridge and slough ecosystem in an attempt to answer “How much flow is needed to restore functionality”? A key restoration objective is to increase sheetflow lost during the past century to reestablish interactions between flow, water depth, vegetation production and decomposition, and transport of flocculent organic sediment that build and maintain ridge and slough distinctions. Our review finds broad agreement that perturbations of water level depth and its fluctuations were primary in the degradation of landscape functions, with critical contributions from perturbed water quality, and flow velocity and direction. Whereas water levels are expected to be improved on average across a range of restoration scenarios that replace between 79 and 91% of predrainage flows, the diminished microtopography substantially decreases the probability of timely improvements in some areas whereas others that retain microtopographic differences are poised for restoration benefits. New advances in predicting restoration outcomes are coming from biophysical modeling of ridge–slough dynamics, system-wide measurements of landscape functionality, and large-scale flow restoration experiments, including active management techniques to kick-start slough regeneration.

  16. The Mutable Nature of Risk and Acceptability: A Hybrid Risk Governance Framework.

    Science.gov (United States)

    Wong, Catherine Mei Ling

    2015-11-01

    This article focuses on the fluid nature of risk problems and the challenges it presents to establishing acceptability in risk governance. It introduces an actor-network theory (ANT) perspective as a way to deal with the mutable nature of risk controversies and the configuration of stakeholders. To translate this into a practicable framework, the article proposes a hybrid risk governance framework that combines ANT with integrative risk governance, deliberative democracy, and responsive regulation. This addresses a number of the limitations in existing risk governance models, including: (1) the lack of more substantive public participation throughout the lifecycle of a project; (2) hijacking of deliberative forums by particular groups; and (3) the treatment of risk problems and their associated stakeholders as immutable entities. The framework constitutes a five-stage process of co-selection, co-design, co-planning, and co-regulation to facilitate the co-production of collective interests and knowledge, build capacities, and strengthen accountability in the process. The aims of this article are twofold: conceptually, it introduces a framework of risk governance that accounts for the mutable nature of risk problems and configuration of stakeholders. In practice, this article offers risk managers and practitioners of risk governance a set of procedures with which to operationalize this conceptual approach to risk and stakeholder engagement. © 2015 Society for Risk Analysis.

  17. Conceptual geoinformation model of natural hazards risk assessment

    Science.gov (United States)

    Kulygin, Valerii

    2016-04-01

    Natural hazards are the major threat to safe interactions between nature and society. The assessment of the natural hazards impacts and their consequences is important in spatial planning and resource management. Today there is a challenge to advance our understanding of how socio-economical and climate changes will affect the frequency and magnitude of hydro-meteorological hazards and associated risks. However, the impacts from different types of natural hazards on various marine and coastal economic activities are not of the same type. In this study, the conceptual geomodel of risk assessment is presented to highlight the differentiation by the type of economic activities in extreme events risk assessment. The marine and coastal ecosystems are considered as the objects of management, on the one hand, and as the place of natural hazards' origin, on the other hand. One of the key elements in describing of such systems is the spatial characterization of their components. Assessment of ecosystem state is based on ecosystem indicators (indexes). They are used to identify the changes in time. The scenario approach is utilized to account for the spatio-temporal dynamics and uncertainty factors. Two types of scenarios are considered: scenarios of using ecosystem services by economic activities and scenarios of extreme events and related hazards. The reported study was funded by RFBR, according to the research project No. 16-35-60043 mol_a_dk.

  18. Numerical Simulation of Natural Gas Flow in Anisotropic Shale Reservoirs

    KAUST Repository

    Negara, Ardiansyah

    2015-11-09

    Shale gas resources have received great attention in the last decade due to the decline of the conventional gas resources. Unlike conventional gas reservoirs, the gas flow in shale formations involves complex processes with many mechanisms such as Knudsen diffusion, slip flow (Klinkenberg effect), gas adsorption and desorption, strong rock-fluid interaction, etc. Shale formations are characterized by the tiny porosity and extremely low-permeability such that the Darcy equation may no longer be valid. Therefore, the Darcy equation needs to be revised through the permeability factor by introducing the apparent permeability. With respect to the rock formations, several studies have shown the existence of anisotropy in shale reservoirs, which is an essential feature that has been established as a consequence of the different geological processes over long period of time. Anisotropy of hydraulic properties of subsurface rock formations plays a significant role in dictating the direction of fluid flow. The direction of fluid flow is not only dependent on the direction of pressure gradient, but it also depends on the principal directions of anisotropy. Therefore, it is very important to take into consideration anisotropy when modeling gas flow in shale reservoirs. In this work, the gas flow mechanisms as mentioned earlier together with anisotropy are incorporated into the dual-porosity dual-permeability model through the full-tensor apparent permeability. We employ the multipoint flux approximation (MPFA) method to handle the full-tensor apparent permeability. We combine MPFA method with the experimenting pressure field approach, i.e., a newly developed technique that enables us to solve the global problem by breaking it into a multitude of local problems. This approach generates a set of predefined pressure fields in the solution domain in such a way that the undetermined coefficients are calculated from these pressure fields. In other words, the matrix of coefficients

  19. Numerical Simulation of Natural Gas Flow in Anisotropic Shale Reservoirs

    KAUST Repository

    Negara, Ardiansyah; Salama, Amgad; Sun, Shuyu; Elgassier, Mokhtar; Wu, Yu-Shu

    2015-01-01

    Shale gas resources have received great attention in the last decade due to the decline of the conventional gas resources. Unlike conventional gas reservoirs, the gas flow in shale formations involves complex processes with many mechanisms such as Knudsen diffusion, slip flow (Klinkenberg effect), gas adsorption and desorption, strong rock-fluid interaction, etc. Shale formations are characterized by the tiny porosity and extremely low-permeability such that the Darcy equation may no longer be valid. Therefore, the Darcy equation needs to be revised through the permeability factor by introducing the apparent permeability. With respect to the rock formations, several studies have shown the existence of anisotropy in shale reservoirs, which is an essential feature that has been established as a consequence of the different geological processes over long period of time. Anisotropy of hydraulic properties of subsurface rock formations plays a significant role in dictating the direction of fluid flow. The direction of fluid flow is not only dependent on the direction of pressure gradient, but it also depends on the principal directions of anisotropy. Therefore, it is very important to take into consideration anisotropy when modeling gas flow in shale reservoirs. In this work, the gas flow mechanisms as mentioned earlier together with anisotropy are incorporated into the dual-porosity dual-permeability model through the full-tensor apparent permeability. We employ the multipoint flux approximation (MPFA) method to handle the full-tensor apparent permeability. We combine MPFA method with the experimenting pressure field approach, i.e., a newly developed technique that enables us to solve the global problem by breaking it into a multitude of local problems. This approach generates a set of predefined pressure fields in the solution domain in such a way that the undetermined coefficients are calculated from these pressure fields. In other words, the matrix of coefficients

  20. The PREVIEW Global Risk Data Platform: a geoportal to serve and share global data on risk to natural hazards

    Directory of Open Access Journals (Sweden)

    G. Giuliani

    2011-01-01

    Full Text Available With growing world population and concentration in urban and coastal areas, the exposure to natural hazards is increasing and results in higher risk of human and economic losses. Improving the identification of areas, population and assets potentially exposed to natural hazards is essential to reduce the consequences of such events. Disaster risk is a function of hazard, exposure and vulnerability. Modelling risk at the global level requires accessing and processing a large number of data, from numerous collaborating centres.

    These data need to be easily updated, and there is a need for centralizing access to this information as well as simplifying its use for non GIS specialists. The Hyogo Framework for Action provides the mandate for data sharing, so that governments and international development agencies can take appropriate decision for disaster risk reduction.

    Timely access and easy integration of geospatial data are essential to support efforts in Disaster Risk Reduction. However various issues in data availability, accessibility and integration limit the use of such data. In consequence, a framework that facilitate sharing and exchange of geospatial data on natural hazards should improve decision-making process. The PREVIEW Global Risk Data Platform is a highly interactive web-based GIS portal supported by a Spatial Data Infrastructure that offers free and interoperable access to more than 60 global data sets on nine types of natural hazards (tropical cyclones and related storm surges, drought, earthquakes, biomass fires, floods, landslides, tsunamis and volcanic eruptions and related exposure and risk. This application portrays an easy-to-use online interactive mapping interface so that users can easily work with it and seamlessly integrate data in their own data flow using fully compliant OGC Web Services (OWS.

  1. The PREVIEW Global Risk Data Platform: a geoportal to serve and share global data on risk to natural hazards

    Science.gov (United States)

    Giuliani, G.; Peduzzi, P.

    2011-01-01

    With growing world population and concentration in urban and coastal areas, the exposure to natural hazards is increasing and results in higher risk of human and economic losses. Improving the identification of areas, population and assets potentially exposed to natural hazards is essential to reduce the consequences of such events. Disaster risk is a function of hazard, exposure and vulnerability. Modelling risk at the global level requires accessing and processing a large number of data, from numerous collaborating centres. These data need to be easily updated, and there is a need for centralizing access to this information as well as simplifying its use for non GIS specialists. The Hyogo Framework for Action provides the mandate for data sharing, so that governments and international development agencies can take appropriate decision for disaster risk reduction. Timely access and easy integration of geospatial data are essential to support efforts in Disaster Risk Reduction. However various issues in data availability, accessibility and integration limit the use of such data. In consequence, a framework that facilitate sharing and exchange of geospatial data on natural hazards should improve decision-making process. The PREVIEW Global Risk Data Platform is a highly interactive web-based GIS portal supported by a Spatial Data Infrastructure that offers free and interoperable access to more than 60 global data sets on nine types of natural hazards (tropical cyclones and related storm surges, drought, earthquakes, biomass fires, floods, landslides, tsunamis and volcanic eruptions) and related exposure and risk. This application portrays an easy-to-use online interactive mapping interface so that users can easily work with it and seamlessly integrate data in their own data flow using fully compliant OGC Web Services (OWS).

  2. The case study of climate change : the nature of risk and the risk of nature

    Energy Technology Data Exchange (ETDEWEB)

    Good, J. [Cornell Univ., Ithaca, NY (United States). Dept. of Communication

    2000-06-01

    The science of climate change is complex, large-scale and uncertain. The challenges of communicating the risks of climate change were described with particular emphasis on working with communities to explain climate change with its complex, scientific and social realities. The greenhouse effect is a feature of the earth in which a carbon dioxide blanket absorbs the sun's heat as it radiates off the earth. The paper stated that the greenhouse effect is arguably the best accepted theory in climatology, but the question is whether the huge increase in carbon dioxide that the industrial revolution has brought forth has increased the efficiency of this blanket and set the earth on a warming trend. The ultimate question is whether the earth is warming in response to human activity. It could be claimed that apart from the risk of nuclear war, the risk of climate change is the largest scale risk facing today's society. Climate change pits the burning of fossil fuels against the climate and as a modern day risk, climate change is far removed from the historic roots of environmental risks. The paper argued, that in a world based on burning fossil fuels and where those who are involved with the supply of fossil fuels hold tremendous influence, it is difficult to accept that the burning might have to stop. This paper explored how and what people currently learn about the environment and climate change through the media. A three-step communication strategy based in the United States was then proposed. The first step is aimed at journalists with focus on improved accuracy of climate change information. The second step focuses on urban centres and has as its guiding concepts self-efficacy, reasoned action and the importance of reaching people in diverse communities. The final step is aimed at political leaders, beginning with municipalities, and relies on campaigns for alternative energy.

  3. The NOKO/TOPFLOW facility for natural convection flow

    International Nuclear Information System (INIS)

    Hicken, E.F.; Jaegers, H.; Schaffrath, A.; Weiss, F.-P.

    2002-01-01

    For the study of the effectiveness of passive safety systems a high pressure (up to 7 MPa) and high power (up to 4 MW) test facility - named NOKO - has been constructed and operated at the Forschungszentrum Juelich. From 1996-1998 this facility was used for a project within the 4th FP of the EU 'European BWR R and D Cluster for Innovative Passive Safety Systems'. An overview and selected results are given for the tests with two bundles of the emergency condenser, with the building and plate condenser, with 4 different passive initiators, with a passive flooding system and with decay heat removal tests during shutdown. It has been decided to decrease substantially the safety research at the Forschungszentrum Juelich; to maintain the experimental competence for two-phase flow the NOKO facility will be transferred to the Forschungszentrum Rossendorf by the end of the year 2000 up to the beginning of the year 2001. The facility will be named TOPFLOW; the main objectives of future tests will be oriented towards more generic research: investigation of steady state and transient two-phase flow phenomena especially transient two-phase flow patterns, the development of two-phase flow instrumentation, the generation of a data basis for Computational Fluid Dynamic (CFD)-Code validation and testing of heat exchangers and safety systems. An overview will be given about the modifications and improvements related to the test facility and the planned tests. (author)

  4. Measurement of Air Flow Rate in a Naturally Ventilated Double Skin Facade

    DEFF Research Database (Denmark)

    Kalyanova, Olena; Jensen, Rasmus Lund; Heiselberg, Per

    2007-01-01

    Air flow rate in a naturally ventilated space is extremely difficult to measure due to the stochastic nature of wind, and as a consequence non-uniform and dynamic flow conditions. This paper describes three different methods to measure the air flow in a full-scale outdoor test facility...... with a naturally ventilated double skin façade. In the first method, the air flow in the cavity is estimated on the basis of six measured velocity profiles. The second method is represented by constant injection of tracer gas and in the third method a measured relation in the laboratory is used to estimate...... the flow rate on the basis of continues measurement of the pressure difference between the surface pressure at the opening and inside pressure of the double skin façade. Although all three measurement methods are difficult to use under such dynamic air flow conditions, two of them show reasonable agreement...

  5. Calculation of reverse flow in inverted U-Tubes of steam generator during natural circulation

    International Nuclear Information System (INIS)

    Yang Ruichang; Liu Jinggong; Liu Ruolei; Qin Shiwei; Huang Yanping

    2010-01-01

    The mechanism of reverse flow in inverted U-tubes of steam generators of pressurized water reactors during natural circulation is analyzed by using the full range characteristic curve of parallel U-tubes. A lumped-distributed model to calculate the reverse flow occurred in inverted U-tubes of real steam generators with a large number of U-tubes during natural circulation is developed. The model has the advantages of quick calculation and high accuracy for the analysis of reverse flow in inverted U-tubes of real steam generators with natural circulation. This model has been used to calculate the normal and reverse flows occurred in inverted U-tubes of a steam generator with natural circulation. The comparison of calculated results indicates a well agreement with that predicted by the model in which normal or reverse flow in each individual U-tube is analyzed, which verifies the reliability of the model developed in this paper. (authors)

  6. U.S. natural gas pipeline flow and demand trends

    International Nuclear Information System (INIS)

    Carson, M.M.

    1992-01-01

    It is no surprise that regional natural gas supply and demand patterns in North America are constantly changing. A consensus of forecasters agree that the natural gas resource base is larger than envisaged in the early 1980s due to advances in exploration and production technology. In addition, on the demand side more gas will be burned by US power generators to meet growth in electricity. Gas consumption is up in the commercial sector, and natural gas is correctly seen as environmentally protective. But how much more natural gas does the US need? This paper reports that new pipeline projects are springing up all over the nation --- 43 to be exact, with most of them connecting gas deliverability out of basins west of the Mississippi to new markets along the Atlantic and Pacific coasts

  7. Post Analysis of Two Phase Natural Circulation Mass Flow Rate for CE-PECS

    Energy Technology Data Exchange (ETDEWEB)

    Park, R. J.; Ha, K. S.; Rhee, B. W.; Kim, H. Y. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    The coolant in the inclined channel absorbs the decay heat and sensible heat transferred from the corium through the structure of the core catcher body and flows up to the pool as a two phase mixture. On the other hand, some of the pool water will flow into the inlet of the downcomer piping, and will flow into the inclined cooling channel of the core catcher by gravity. The engineered cooling channel is designed to provide effective long-term cooling and stabilization of the corium mixture in the core catcher body while facilitating steam venting. To maintain the integrity of the ex-vessel core catcher, however, it is required that the coolant be circulated at a rate along the inclined cooling channel sufficient to avoid CHF (Critical Heat Flux) on the heating surface of the cooling channel. In this study, post simulations of two phase natural circulation in the CEPECS have been performed to evaluate two phase flow characteristics and the natural circulation mass flow rate in the flow channel using the RELAP5/MOD3 computer code. Post simulations of two phase natural circulation in the CE-PECS have been conducted to evaluate two phase flow characteristics and the natural circulation mass flow rate in the flow channel using the RELAP5/MOD3 computer code. The RELAP5/MOD3 results have shown that the water circulation mass flow rate is approximately 8.7 kg/s in the base case.

  8. Post Analysis of Two Phase Natural Circulation Mass Flow Rate for CE-PECS

    International Nuclear Information System (INIS)

    Park, R. J.; Ha, K. S.; Rhee, B. W.; Kim, H. Y.

    2015-01-01

    The coolant in the inclined channel absorbs the decay heat and sensible heat transferred from the corium through the structure of the core catcher body and flows up to the pool as a two phase mixture. On the other hand, some of the pool water will flow into the inlet of the downcomer piping, and will flow into the inclined cooling channel of the core catcher by gravity. The engineered cooling channel is designed to provide effective long-term cooling and stabilization of the corium mixture in the core catcher body while facilitating steam venting. To maintain the integrity of the ex-vessel core catcher, however, it is required that the coolant be circulated at a rate along the inclined cooling channel sufficient to avoid CHF (Critical Heat Flux) on the heating surface of the cooling channel. In this study, post simulations of two phase natural circulation in the CEPECS have been performed to evaluate two phase flow characteristics and the natural circulation mass flow rate in the flow channel using the RELAP5/MOD3 computer code. Post simulations of two phase natural circulation in the CE-PECS have been conducted to evaluate two phase flow characteristics and the natural circulation mass flow rate in the flow channel using the RELAP5/MOD3 computer code. The RELAP5/MOD3 results have shown that the water circulation mass flow rate is approximately 8.7 kg/s in the base case

  9. Risk Assessment and Risk Governance of Liquefied Natural Gas Development in Gladstone, Australia.

    Science.gov (United States)

    van der Vegt, R G

    2018-02-26

    This article is a retrospective analysis of liquefied natural gas development (LNG) in Gladstone, Australia by using the structure of the risk governance framework developed by the International Risk Governance Council (IRGC). Since 2010 the port of Gladstone has undergone extensive expansion to facilitate the increasing coal export as well as the new development of three recently completed LNG facilities. Significant environmental and socio-economic impacts and concerns have occurred as a result of these developments. The overall aim of the article, therefore, is to identify the risk governance deficits that arose and to formulate processes capable of improving similar decision-making problems in the future. The structure of the IRGC framework is followed because it represents a broad analytical approach for considering risk assessment and risk governance in Gladstone in ways that include, but also go beyond, the risk approach of the ISO 31000:2009 standard that was employed at the time. The IRGC risk framework is argued to be a consistent and comprehensive risk governance framework that integrates scientific, economic, social, and cultural aspects and advocates the notion of inclusive risk governance through stakeholder communication and involvement. Key aspects related to risk preassessment, risk appraisal, risk tolerability and acceptability, risk management, and stakeholder communication and involvement are considered. The results indicate that the risk governance deficits include aspects related to (i) the risk matrix methodology, (ii) reflecting uncertainties, (iii) cumulative risks, (iv) the regulatory process, and (v) stakeholder communication and involvement. © 2018 Society for Risk Analysis.

  10. Afghanistan Multi-Risk Assessment to Natural Hazards

    Science.gov (United States)

    Diermanse, Ferdinand; Daniell, James; Pollino, Maurizio; Glover, James; Bouwer, Laurens; de Bel, Mark; Schaefer, Andreas; Puglisi, Claudio; Winsemius, Hessel; Burzel, Andreas; Ammann, Walter; Aliparast, Mojtaba; Jongman, Brenden; Ranghieri, Federica; Fallesen, Ditte

    2017-04-01

    The geographical location of Afghanistan and years of environmental degradation in the country make Afghanistan highly prone to intense and recurring natural hazards such as flooding, earthquakes, snow avalanches, landslides, and droughts. These occur in addition to man-made disasters resulting in the frequent loss of live, livelihoods, and property. Since 1980, disasters caused by natural hazards have affected 9 million people and caused over 20,000 fatalities in Afghanistan. The creation, understanding and accessibility of hazard, exposure, vulnerability and risk information is key for effective management of disaster risk. This is especially true in Afghanistan, where reconstruction after recent natural disasters and military conflicts is on-going and will continue over the coming years. So far, there has been limited disaster risk information produced in Afghanistan, and information that does exist typically lacks standard methodology and does not have uniform geo-spatial coverage. There are currently no available risk assessment studies that cover all major natural hazards in Afghanistan, which can be used to assess the costs and benefits of different resilient reconstruction and disaster risk reduction strategies. As a result, the Government of Afghanistan has limited information regarding current and future disaster risk and the effectiveness of policy options on which to base their reconstruction and risk reduction decisions. To better understand natural hazard and disaster risk, the World Bank and Global Facility for Disaster Reduction and Recovery (GFDRR) are supporting the development of new fluvial flood, flash flood, drought, landslide, avalanche and seismic risk information in Afghanistan, as well as a first-order analysis of the costs and benefits of resilient reconstruction and risk reduction strategies undertaken by the authors. The hazard component is the combination of probability and magnitude of natural hazards. Hazard analyses were carried out

  11. Quantitative Microbial Risk Assessment for in Natural and Processed Cheeses

    Directory of Open Access Journals (Sweden)

    Heeyoung Lee

    2016-08-01

    Full Text Available This study evaluated the risk of Clostridium perfringens (C. perfringens foodborne illness from natural and processed cheeses. Microbial risk assessment in this study was conducted according to four steps: hazard identification, hazard characterization, exposure assessment, and risk characterization. The hazard identification of C. perfringens on cheese was identified through literature, and dose response models were utilized for hazard characterization of the pathogen. For exposure assessment, the prevalence of C. perfringens, storage temperatures, storage time, and annual amounts of cheese consumption were surveyed. Eventually, a simulation model was developed using the collected data and the simulation result was used to estimate the probability of C. perfringens foodborne illness by cheese consumption with @RISK. C. perfringens was determined to be low risk on cheese based on hazard identification, and the exponential model (r = 1.82×10−11 was deemed appropriate for hazard characterization. Annual amounts of natural and processed cheese consumption were 12.40±19.43 g and 19.46±14.39 g, respectively. Since the contamination levels of C. perfringens on natural (0.30 Log CFU/g and processed cheeses (0.45 Log CFU/g were below the detection limit, the initial contamination levels of natural and processed cheeses were estimated by beta distribution (α1 = 1, α2 = 91; α1 = 1, α2 = 309×uniform distribution (a = 0, b = 2; a = 0, b = 2.8 to be −2.35 and −2.73 Log CFU/g, respectively. Moreover, no growth of C. perfringens was observed for exposure assessment to simulated conditions of distribution and storage. These data were used for risk characterization by a simulation model, and the mean values of the probability of C. perfringens foodborne illness by cheese consumption per person per day for natural and processed cheeses were 9.57×10−14 and 3.58×10−14, respectively. These results indicate that probability of C. perfringens

  12. Shuttle Gaseous Hydrogen Venting Risk from Flow Control Valve Failure

    Science.gov (United States)

    Drummond, J. Philip; Baurle, Robert A.; Gafney, Richard L.; Norris, Andrew T.; Pellett, Gerald L.; Rock, Kenneth E.

    2009-01-01

    This paper describes a series of studies to assess the potential risk associated with the failure of one of three gaseous hydrogen flow control valves in the orbiter's main propulsion system during the launch of Shuttle Endeavour (STS-126) in November 2008. The studies focused on critical issues associated with the possibility of combustion resulting from release of gaseous hydrogen from the external tank into the atmosphere during assent. The Shuttle Program currently assumes hydrogen venting from the external tank will result in a critical failure. The current effort was conducted to increase understanding of the risk associated with venting hydrogen given the flow control valve failure scenarios being considered in the Integrated In-Flight Anomaly Investigation being conducted by NASA.

  13. Self-organizing maps applied to two-phase flow on natural circulation loop study

    International Nuclear Information System (INIS)

    Castro, Leonardo Ferreira

    2016-01-01

    Two-phase flow of liquid and gas is found in many closed circuits using natural circulation for cooling purposes. Natural circulation phenomenon is important on recent nuclear power plant projects for decay heat removal. The Natural Circulation Facility (Circuito de Circulacao Natural CCN) installed at Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN, is an experimental circuit designed to provide thermal hydraulic data related to single and two-phase flow under natural circulation conditions. This periodic flow oscillation behavior can be observed thoroughly in this facility due its glass-made tubes transparency. The heat transfer estimation has been improved based on models that require precise prediction of pattern transitions of flow. This work presents experiments realized at CCN to visualize natural circulation cycles in order to classify two-phase flow patterns associated with phase transients and static instabilities of flow. Images are compared and clustered using Kohonen Self-organizing Maps (SOM's) applied on different digital image features. The Full Frame Discret Cosine Transform (FFDCT) coefficients were used as input for the classification task, enabling good results. FFDCT prototypes obtained can be associated to each flow pattern, enabling a better comprehension of each observed instability. A systematic test methodology was used to verify classifier robustness.

  14. Classification of natural circulation two-phase flow patterns using fuzzy inference on image analysis

    International Nuclear Information System (INIS)

    Mesquita, R.N. de; Masotti, P.H.F.; Penha, R.M.L.; Andrade, D.A.; Sabundjian, G.; Torres, W.M.

    2012-01-01

    Highlights: ► A fuzzy classification system for two-phase flow instability patterns is developed. ► Flow patterns are classified based on images of natural circulation experiments. ► Fuzzy inference is optimized to use single grayscale profiles as input. - Abstract: Two-phase flow on natural circulation phenomenon has been an important theme on recent studies related to nuclear reactor designs. The accuracy of heat transfer estimation has been improved with new models that require precise prediction of pattern transitions of flow. In this work, visualization of natural circulation cycles is used to study two-phase flow patterns associated with phase transients and static instabilities of flow. A Fuzzy Flow-type Classification System (FFCS) was developed to classify these patterns based only on image extracted features. Image acquisition and temperature measurements were simultaneously done. Experiments in natural circulation facility were adjusted to generate a series of characteristic two-phase flow instability periodic cycles. The facility is composed of a loop of glass tubes, a heat source using electrical heaters, a cold source using a helicoidal heat exchanger, a visualization section and thermocouples positioned over different loop sections. The instability cyclic period is estimated based on temperature measurements associated with the detection of a flow transition image pattern. FFCS shows good results provided that adequate image acquisition parameters and pre-processing adjustments are used.

  15. Cutting risk, boosting cash flow and developing marginal fields

    International Nuclear Information System (INIS)

    Baustad, T.; Courtin, G.; Davies, T.; Kenison, R.; Turnbull, J.; Gray, B.; Jalali, Y.; Remondet, J.C.; Hjelmsmark, L.; Oldfield, T.; Romano, C.; Saier, R.; Rannestad, G.

    1996-01-01

    To minimize financial risk and accelerate return on investment, oil companies are using low-cost, reusable production systems. The scope of these development options is illustrated by looking at three offshore case studies that range from extended well test to marginal field development. In each case, production systems technology has been deployed to provide superior data, early oil or both, thus reducing economic uncertainty and delivering accelerated cash flow. 10 figs., 23 refs

  16. Natural convection in a porous medium: External flows

    International Nuclear Information System (INIS)

    Cheng, P.

    1985-01-01

    Early theoretical work on heat transfer in porous media focussed its attention on the onset of natural convection and cellular convection in rectangular enclosures with heating from below. Recently, increased attention has been directed to the study of natural convection in a porous medium external to heated surfaces and bodies. Boundary layer approximations were introduced, and similarly solutions have been obtained for steady natural convection boundary layers adjacent to a heated flat plate, a horizontal cylinder and a sphere as well as other two-dimensional and axisymmetric bodies of arbitrary shape. Higher order boundary layer theories have been carried out to assess the accuracy of the boundary layer approximation. The effects of entrainments at the edge of the boundary layer, the inclination angle of the heated inclined plate, and the upstream geometry on the heat transfer characteristics have been investigated based on the method of matched asymptotic expansions. The conditions for the onset of vortex instability in porous layers heated from below were determined based on linear stability analyses. The effects of no-slip boundary conditions, non-Darcy and thermal dispersion, which were neglected in all of the previous theoretical investigations, have recently been re-examined. Experimental investigations on natural convection about a vertical and inclined heated plate, a horizontal cylinder, as well as plume rise from a horizontal line source of heat have been conducted. All of this work is reviewed in this paper

  17. Hydrological classification of natural flow regimes to support environmental flow assessments in intensively regulated Mediterranean rivers, Segura River Basin (Spain).

    Science.gov (United States)

    Belmar, Oscar; Velasco, Josefa; Martinez-Capel, Francisco

    2011-05-01

    Hydrological classification constitutes the first step of a new holistic framework for developing regional environmental flow criteria: the "Ecological Limits of Hydrologic Alteration (ELOHA)". The aim of this study was to develop a classification for 390 stream sections of the Segura River Basin based on 73 hydrological indices that characterize their natural flow regimes. The hydrological indices were calculated with 25 years of natural monthly flows (1980/81-2005/06) derived from a rainfall-runoff model developed by the Spanish Ministry of Environment and Public Works. These indices included, at a monthly or annual basis, measures of duration of droughts and central tendency and dispersion of flow magnitude (average, low and high flow conditions). Principal Component Analysis (PCA) indicated high redundancy among most hydrological indices, as well as two gradients: flow magnitude for mainstream rivers and temporal variability for tributary streams. A classification with eight flow-regime classes was chosen as the most easily interpretable in the Segura River Basin, which was supported by ANOSIM analyses. These classes can be simplified in 4 broader groups, with different seasonal discharge pattern: large rivers, perennial stable streams, perennial seasonal streams and intermittent and ephemeral streams. They showed a high degree of spatial cohesion, following a gradient associated with climatic aridity from NW to SE, and were well defined in terms of the fundamental variables in Mediterranean streams: magnitude and temporal variability of flows. Therefore, this classification is a fundamental tool to support water management and planning in the Segura River Basin. Future research will allow us to study the flow alteration-ecological response relationship for each river type, and set the basis to design scientifically credible environmental flows following the ELOHA framework.

  18. Vertebral Artery Diameter and Flow: Nature or Nurture.

    Science.gov (United States)

    Tarnoki, Adam Domonkos; Fejer, Bence; Tarnoki, David Laszlo; Littvay, Levente; Lucatelli, Pierleone; Cirelli, Carlo; Fanelli, Fabrizio; Sacconi, Beatrice; Fagnani, Corrado; Medda, Emanuela; Farina, Filippo; Meneghetti, Giorgio; Horvath, Tamas; Pucci, Giacomo; Schillaci, Giuseppe; Stazi, Maria Antonietta; Baracchini, Claudio

    2017-09-01

    In contrast with the carotid arteries, the vertebral arteries (VAs) show considerable variation in length, caliber, and vessel course. This study investigated whether the variation in diameter and flow characteristics of the VAs might be inherited. A total of 172 Italian twins from Padua, Perugia, and Terni (54 monozygotic, 32 dizygotic) recruited from the Italian Twin Registry underwent B-mode and pulsed-wave Doppler ultrasound assessment of their VAs. VA diameters, peak systolic velocity (PSV) and end diastolic velocity (EDV) were assessed at the level of a horizontal V2 segment. Univariate quantitative genetic modeling was performed. Fourteen percent of the sample had VA hypoplasia. Within pair correlation in monozygotic twins was higher than in dizygotics (.552 vs. .229) for VA diameter. Age- and sex-adjusted genetic effect, under the most parsimonious model, accounted for 54.7% (95% CI: 42.2-69.1%) of the variance of VA diameter, and unshared environmental effect for 45.3% (95% CI: 30.9-57.8%). No heritability was found for the PSV of VA, but shared (34.1%; 95% CI: 16.7-53.7%) and unshared (65.9%; 95% CI: 45.9-83.1%) environmental factors determined the variance. EDV of VA is moderately genetically influenced (42.4%; 95% CI: 16.1-64.9%) and also determined by the unshared environment (57.6%; 95% CI: 34.7-83.7%). The diameter of the VAs is moderately genetically determined. Different factors influence the PSV and EDV of VAs, which may highlight the complex hemodynamic background of VA flow and help to understand the vertebral flow anomalies found by ultrasound. Copyright © 2017 by the American Society of Neuroimaging.

  19. An experimental study on two-phase flow pattern in low pressure natural circulation system

    International Nuclear Information System (INIS)

    Wu Shaorong; Han Bing; Zhou Lei; Zhang Youjie; Jiang Shengyao; Wu Xinxin

    1991-10-01

    An experimental study on two-phase flow pattern in the riser of low pressure natural circulation system was performed. The local differential pressure signal was analysed for flow pattern. It is considered that Sr f·d/v can be used to distinguish different flow patterns and it has clear and definite physical meaning. Flow patterns at different inlet temperature with different system pressures (1.5 MPa, 0.24 MPa and 0.1 MPa) are described. It is considered that the flow pattern is only bubble flow without flow pattern change during the period of low quality density-wave instability at 1.5 MPa. There is no density-wave oscillation in the system, when flow pattern is in bubble-intermittent transition area. The effect of flash vaporization on stability at low pressure is discussed

  20. Theoretical analysis of effect of ocean condition on natural circulation flow

    International Nuclear Information System (INIS)

    Gong Houjun; Yang Xingtuan; Jiang Shengyao; Liu Zhiyong

    2010-01-01

    According to the simulation loop of Integrated natural circulation reactor,the mathematical model of natural circulation in non-inertial reference system is established, and the influence mechanism of ocean condition upon natural circulation is analyzed. Software is programmed to investigate the behaviors in the cases of rolling without heating power, static state with different power and rolling with heating power, and calculation results show that: the inertia force added by rolling causes the periodical fluctuating of the flow rate of channels, but it is not the direct reason of core flow fluctuation. The heave changes the driving head, and causes the same flow rate fluctuation of all channels. Inclining makes the core flow rate decrease, but the change of flow rate of different channels is different.(authors)

  1. Debris Flow Risk Management Framework and Risk Analysis in Taiwan, A Preliminary Study

    Science.gov (United States)

    Tsao, Ting-Chi; Hsu, Wen-Ko; Chiou, Lin-Bin; Cheng, Chin-Tung; Lo, Wen-Chun; Chen, Chen-Yu; Lai, Cheng-Nong; Ju, Jiun-Ping

    2010-05-01

    Taiwan is located on a seismically active mountain belt between the Philippine Sea plate and Eurasian plate. After 1999's Chi-Chi earthquake (Mw=7.6), landslide and debris flow occurred frequently. In Aug. 2009, Typhoon Morakot struck Taiwan and numerous landslides and debris flow events, some with tremendous fatalities, were observed. With limited resources, authorities should establish a disaster management system to cope with slope disaster risks more effectively. Since 2006, Taiwan's authority in charge of debris flow management, the Soil and Water Conservation Bureau (SWCB), completed the basic investigation and data collection of 1,503 potential debris flow creeks around Taiwan. During 2008 and 2009, a debris flow quantitative risk analysis (QRA) framework, based on landslide risk management framework of Australia, was proposed and conducted on 106 creeks of the 30 villages with debris flow hazard history. Information and value of several types of elements at risk (bridge, road, building and crop) were gathered and integrated into a GIS layer, with the vulnerability model of each elements at risk applied. Through studying the historical hazard events of the 30 villages, numerical simulations of debris flow hazards with different magnitudes (5, 10, 25, 50, 100 and 200 years return period) were conducted, the economic losses and fatalities of each scenario were calculated for each creek. When taking annual exceeding probability into account, the annual total risk of each creek was calculated, and the results displayed on a debris flow risk map. The number of fatalities and frequency were calculated, and the F-N curves of 106 creeks were provided. For F-N curves, the individual risk to life per year of 1.0E-04 and slope of 1, which matched with international standards, were considered to be an acceptable risk. Applying the results of the 106 creeks onto the F-N curve, they were divided into 3 categories: Unacceptable, ALARP (As Low As Reasonable Practicable) and

  2. Estimation of natural historical flows for the Manitowish River near Manitowish Waters, Wisconsin

    Science.gov (United States)

    Juckem, Paul F.; Reneau, Paul C.; Robertson, Dale M.

    2012-01-01

    The Wisconsin Department of Natural Resources is charged with oversight of dam operations throughout Wisconsin and is considering modifications to the operating orders for the Rest Lake Dam in Vilas County, Wisconsin. State law requires that the operation orders be tied to natural low flows at the dam. Because the presence of the dam confounds measurement of natural flows, the U.S. Geological Survey, in cooperation with the Wisconsin Department of Natural Resources, installed streamflow-gaging stations and developed two statistical methods to improve estimates of natural flows at the Rest Lake Dam. Two independent methods were used to estimate daily natural flow for the Manitowish River approximately 1 mile downstream of the Rest Lake Dam. The first method was an adjusted drainage-area ratio method, which used a regression analysis that related measured water yield (flow divided by watershed area) from short-term (2009–11) gaging stations upstream of the Manitowish Chain of Lakes to the water yield from two nearby long-term gaging stations in order to extend the flow record (1991–2011). In this approach, the computed flows into the Chain of Lakes at the upstream gaging stations were multiplied by a coefficient to account for the monthly hydrologic contributions (precipitation, evaporation, groundwater, and runoff) associated with the additional watershed area between the upstream gaging stations and the dam at the outlet of the Chain of Lakes (Rest Lake Dam). The second method used to estimate daily natural flow at the Rest Lake Dam was a water-budget approach, which used lake stage and dam outflow data provided by the dam operator. A water-budget model was constructed and then calibrated with an automated parameter-estimation program by matching simulated flow-duration statistics with measured flow-duration statistics at the upstream gaging stations. After calibration of the water-budget model, the model was used to compute natural flow at the dam from 1973 to

  3. Zero Flow Global Ischemia-Induced Injuries in Rat Heart Are Attenuated by Natural Honey

    OpenAIRE

    Najafi, Moslem; Zahednezhad, Fahimeh; Samadzadeh, Mehrban; Vaez, Haleh

    2012-01-01

    Purpose: In the present study, effects of preischemic administration of natural honey on cardiac arrhythmias and myocardial infarction size during zero flow global ischemia were investigated in isolated rat heart. Methods: The isolated hearts were subjected to 30 min zero flow global ischemia followed by 120 min reperfusion then perfused by a modified drug free Krebs-Henseleit solution throughout the experiment (control) or the solution containing 0.25, 0.5, 1 and 2% of natural honey...

  4. Assessing natural hazard risk using images and data

    Science.gov (United States)

    Mccullough, H. L.; Dunbar, P. K.; Varner, J. D.; Mungov, G.

    2012-12-01

    Photographs and other visual media provide valuable pre- and post-event data for natural hazard assessment. Scientific research, mitigation, and forecasting rely on visual data for risk analysis, inundation mapping and historic records. Instrumental data only reveal a portion of the whole story; photographs explicitly illustrate the physical and societal impacts from the event. Visual data is rapidly increasing as the availability of portable high resolution cameras and video recorders becomes more attainable. Incorporating these data into archives ensures a more complete historical account of events. Integrating natural hazards data, such as tsunami, earthquake and volcanic eruption events, socio-economic information, and tsunami deposits and runups along with images and photographs enhances event comprehension. Global historic databases at NOAA's National Geophysical Data Center (NGDC) consolidate these data, providing the user with easy access to a network of information. NGDC's Natural Hazards Image Database (ngdc.noaa.gov/hazardimages) was recently improved to provide a more efficient and dynamic user interface. It uses the Google Maps API and Keyhole Markup Language (KML) to provide geographic context to the images and events. Descriptive tags, or keywords, have been applied to each image, enabling easier navigation and discovery. In addition, the Natural Hazards Map Viewer (maps.ngdc.noaa.gov/viewers/hazards) provides the ability to search and browse data layers on a Mercator-projection globe with a variety of map backgrounds. This combination of features creates a simple and effective way to enhance our understanding of hazard events and risks using imagery.

  5. Grid dependency of wall heat transfer for simulation of natural convection flow problems

    NARCIS (Netherlands)

    Loomans, M.G.L.C.; Seppänen, O.; Säteri, J.

    2007-01-01

    In the indoor environment natural convection is a well known air flow phenomenon. In numerical simulations applying the CFD technique it is also known as a flow problem that is difficult to solve. Alternatives are available to overcome the limitations of the default approach (standard k-e model with

  6. Analysis of the Conditions for the Inception of Natural Pulsing Flow in Cocurrent Packed Columns

    Czech Academy of Sciences Publication Activity Database

    Akramov, T. A.; Stavárek, Petr; Jiřičný, Vladimír; Staněk, Vladimír

    2008-01-01

    Roč. 47, č. 19 (2008), s. 7424-7432 ISSN 0888-5885 R&D Projects: GA MPO FT-TA/039 Institutional research plan: CEZ:AV0Z40720504 Keywords : natural pulsing flow * cocurrent flow * packed columns Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.895, year: 2008

  7. Self-organizing maps applied to two-phase flow on natural circulation loop studies

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Leonardo F.; Cunha, Kelly de P.; Andrade, Delvonei A.; Sabundjian, Gaiane; Torres, Walmir M.; Macedo, Luiz A.; Rocha, Marcelo da S.; Masotti, Paulo H.F.; Mesquita, Roberto N. de, E-mail: rnavarro@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Two-phase flow of liquid and gas is found in many closed circuits using natural circulation for cooling purposes. Natural circulation phenomenon is important on recent nuclear power plant projects for heat removal on 'loss of pump power' or 'plant shutdown' accidents. The accuracy of heat transfer estimation has been improved based on models that require precise prediction of pattern transitions of flow. Self-Organizing Maps are trained to digital images acquired on natural circulation flow instabilities. This technique will allow the selection of the more important characteristics associated with each flow pattern, enabling a better comprehension of each observed instability. This periodic flow oscillation behavior can be observed thoroughly in this facility due its glass-made tubes transparency. The Natural Circulation Facility (Circuito de Circulacao Natural - CCN) installed at Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN, is an experimental circuit designed to provide thermal hydraulic data related to one and two phase flow under natural circulation conditions. (author)

  8. Assessing the risk posed by natural hazards to infrastructures

    Science.gov (United States)

    Eidsvig, Unni Marie K.; Kristensen, Krister; Vidar Vangelsten, Bjørn

    2017-03-01

    This paper proposes a model for assessing the risk posed by natural hazards to infrastructures, with a focus on the indirect losses and loss of stability for the population relying on the infrastructure. The model prescribes a three-level analysis with increasing level of detail, moving from qualitative to quantitative analysis. The focus is on a methodology for semi-quantitative analyses to be performed at the second level. The purpose of this type of analysis is to perform a screening of the scenarios of natural hazards threatening the infrastructures, identifying the most critical scenarios and investigating the need for further analyses (third level). The proposed semi-quantitative methodology considers the frequency of the natural hazard, different aspects of vulnerability, including the physical vulnerability of the infrastructure itself, and the societal dependency on the infrastructure. An indicator-based approach is applied, ranking the indicators on a relative scale according to pre-defined ranking criteria. The proposed indicators, which characterise conditions that influence the probability of an infrastructure malfunctioning caused by a natural event, are defined as (1) robustness and buffer capacity, (2) level of protection, (3) quality/level of maintenance and renewal, (4) adaptability and quality of operational procedures and (5) transparency/complexity/degree of coupling. Further indicators describe conditions influencing the socio-economic consequences of the infrastructure malfunctioning, such as (1) redundancy and/or substitution, (2) cascading effects and dependencies, (3) preparedness and (4) early warning, emergency response and measures. The aggregated risk estimate is a combination of the semi-quantitative vulnerability indicators, as well as quantitative estimates of the frequency of the natural hazard, the potential duration of the infrastructure malfunctioning (e.g. depending on the required restoration effort) and the number of users of

  9. Electro-Magnetic Flow Control to Enable Natural Laminar Flow Wings

    Data.gov (United States)

    National Aeronautics and Space Administration — This research team has developed a solid-state electromagnetic device that, when embedded along the leading edge of an aircraft wing, can disrupt laminar air flow on...

  10. Risk reduction by combining nature values with flood protection?

    Directory of Open Access Journals (Sweden)

    Van Loon-Steensma Jantsje M.

    2016-01-01

    Full Text Available In the Netherlands, the concept of a multifunctional dike has already often been implemented, and has been identified as a promising climate adaptation measure. In a multifunctional dike, functions like urban development, transport infrastructure, recreation, agriculture or nature are deliberately combined with its primary flood protection function. This means that the design must be based on the requirements and life span of all different functions, while in a monofunctional dike only the flood protection function is considered. By accommodating other functions, a multifunctional dike may easier fit into, or even contribute to the quality of the landscape. Moreover, these other functions may help in financing the flood protection works, but governance is more complicated. To avoid costly adjustments forthcoming from changed safety standards, incorporation of multiple functions can require a more “robust” flood defence than a monofunctional flood defence. A robust flood defence can withstand more extreme situations than required by the present safety standards, and has a substantially lower flooding probability. Therefore, a multifunctional dike may be attractive in view of the uncertainties regarding the effects of climate change and a changing world. Moreover, it will result in reduced flood risk. As part of the Dutch Delta programme, several explorative studies on multifunctional dikes were initiated. Most studies focused on urban areas, but also in the rural area interest emerged for multifunctional dikes, e.g. for the integration of salt marshes into the flood defences. Marshes provide valuable habitat for vegetation and invertebrate species, and are important for wading birds. Furthermore, under condition of abundant sediment availability they can keep pace with sea level rise. Explorative modelling results indicate that vegetated forelands affect wave heights, even under extreme conditions. However, the inclusion of a vegetated

  11. Predicting Free Flow Speed and Crash Risk of Bicycle Traffic Flow Using Artificial Neural Network Models

    Directory of Open Access Journals (Sweden)

    Cheng Xu

    2015-01-01

    Full Text Available Free flow speed is a fundamental measure of traffic performance and has been found to affect the severity of crash risk. However, the previous studies lack analysis and modelling of impact factors on bicycles’ free flow speed. The main focus of this study is to develop multilayer back propagation artificial neural network (BPANN models for the prediction of free flow speed and crash risk on the separated bicycle path. Four different models with considering different combinations of input variables (e.g., path width, traffic condition, bicycle type, and cyclists’ characteristics were developed. 459 field data samples were collected from eleven bicycle paths in Hangzhou, China, and 70% of total samples were used for training, 15% for validation, and 15% for testing. The results show that considering the input variables of bicycle types and characteristics of cyclists will effectively improve the accuracy of the prediction models. Meanwhile, the parameters of bicycle types have more significant effect on predicting free flow speed of bicycle compared to those of cyclists’ characteristics. The findings could contribute for evaluation, planning, and management of bicycle safety.

  12. Risk management of a fund for natural disasters

    Science.gov (United States)

    Flores, C.

    2003-04-01

    Mexico is a country which has to deal with several natural disaster risks: earthquakes, droughts, volcanic eruptions, floods, slides, wild fires, extreme temperatures, etc. In order to reduce the country's vulnerability to the impact of these natural disasters and to support rapid recovery when they occur, the government established in 1996 Mexico's Fund for Natural Disasters (FONDEN). Since its creation, its resources have been insufficient to meet all government obligations. The aim of this project is the development of a dynamic strategy to optimise the management of a fund for natural disasters starting from the example of FONDEN. The problem of budgetary planning is being considered for the modelling. We control the level of the fund's cash (R_t)0money borrowed at time t. For the initial model, we assume that the deterministic payments for risk transfer and debt are made at t=0. We determine c>0 at t=0 and then we try to pull at every moment the process to this objective. Multifractal models in geophysics are physically based stochastic models. A multiplicative cascade model fitted to a data set can be used for generation of synthetic sequences that resemble the original data in terms of its scaling properties. Since recent years, uncertainty concepts based on multifractal fields are being applied to the development of techniques to calculate marginal and conditional probabilities of an extreme rainfall event in a determined zone. As initial point to the development of the model, a multifractal model for extreme rainfall events will be used as part of the input for the stochastic control model. A theme for further research is linking more warning systems to the model. Keywords: risk management, stochastic control, multifractal measures, multiplicative cascades, heavy rainfall events.

  13. Natural rubber latex: determination and interpretation of flow curves

    Directory of Open Access Journals (Sweden)

    Harrison Lourenço Corrêa

    2015-08-01

    Full Text Available AbstractAs consumers become more demanding, the importance grows of guaranteeing the quality of products. The employment of reliable testing techniques that assure the origin and characteristics of the inputs used by industry is a key factor in this respect. In the rubber processing industry, the most commonly used characterization tests include determination of the total solids and dry rubber content, mechanical stability, odor, color and presence of volatile compounds, among others. For the most part, these tests are sufficient for the latex transformation industry. However, in situations where there is a need to know the behavior of latex in reaction to the mechanical forces of machines (mixers, pumps, etc., other tests must be used. Rheological tests to determine viscoelastic data by means of plotting flow curves combined with the application of theoretical models can provide important details for characterization of different types of latex. This article presents the protocol employed by the Rheology and Image Laboratory of Rio de Janeiro State University (UERJ for the rheological study of Brazilian latex. The samples analyzed came from the state of São Paulo.

  14. Integrated Risk Assessment to Natural Hazards in Motozintla, Chiapas, Mexico

    Science.gov (United States)

    Novelo-Casanova, D. A.

    2012-12-01

    An integrated risk assessment includes the analysis of all components of individual constituents of risk such as baseline study, hazard identification and categorization, hazard exposure, and vulnerability. Vulnerability refers to the inability of people, organizations, and societies to withstand adverse impacts from multiple stressors to which they are exposed. These impacts are due to characteristics inherent in social interactions, institutions, and systems of cultural values. Thus, social vulnerability is a pre-existing condition that affects a society's ability to prepare for and recover from a disruptive event. Risk is the probability of a loss, and this loss depends on three elements: hazard, exposure, and vulnerability. Thus, risk is the estimated impact that a hazard event would have on people, services, facilities, structures and assets in a community. In this work we assess the risk to natural hazards in the community of Motozintla located in southern Mexico in the state of Chiapas (15.37N, 92.25W) with a population of about 20 000 habitants. Due to its geographical and geological location, this community is continuously exposed to many different natural hazards (earthquakes, landslides, volcanic eruptions, and floods). To determine the level of exposure of the community to natural hazards, we developed integrated studies and analysis of seismic microzonation, landslide and flood susceptibility as well as volcanic impact using standard methodologies. Social vulnerability was quantified from data obtained from local families interviews. Five variables were considered: household structure quality and design, availability of basic public services, family economic conditions, existing family plans for disaster preparedness, and risk perception.The number of families surveyed was determined considering a sample statistically significant. The families that were interviewed were selected using the simple random sampling technique with replacement. With these

  15. Industrial Accidents Triggered by Natural Hazards: an Emerging Risk Issue

    Science.gov (United States)

    Renni, Elisabetta; Krausmann, Elisabeth; Basco, Anna; Salzano, Ernesto; Cozzani, Valerio

    2010-05-01

    Natural disasters such as earthquakes, tsunamis, flooding or hurricanes have recently and dramatically hit several countries worldwide. Both direct and indirect consequences involved the population, causing on the one hand a high number of fatalities and on the other hand so relevant economical losses that the national gross product may be affected for many years. Loss of critical industrial infrastructures (electricity generation and distribution, gas pipelines, oil refineries, etc.) also occurred, causing further indirect damage to the population. In several cases, accident scenarios with large releases of hazardous materials were triggered by these natural events, causing so-called "Natech events", in which the overall damage resulted from the simultaneous consequences of the natural event and of the release of hazardous substances. Toxic releases, large fires and explosions, as well as possible long-term environmental pollution, economical losses, and overloading of emergency systems were recognised by post-event studies as the main issues of these Natech scenarios. In recent years the increasing frequency and severity of some natural hazards due to climate change has slowly increased the awareness of Natech risk as an emerging risk among the stakeholders. Indeed, the iNTeg-Risk project, co-funded by the European Commission within the 7th Framework Program specifically addresses these scenarios among new technological issues on public safety. The present study, in part carried out within the iNTeg-Risk project, was aimed at the analysis and further development of methods and tools for the assessment and mitigation of Natech accidents. Available tools and knowledge gaps in the assessment of Natech scenarios were highlighted. The analysis mainly addressed the potential impact of flood, lightning and earthquake events on industrial installations where hazardous substances are present. Preliminary screening methodologies and more detailed methods based on

  16. Analytical evaluation of two-phase natural circulation flow characteristics under external reactor vessel cooling

    International Nuclear Information System (INIS)

    Park, Jong Woon

    2009-01-01

    This work proposes an analytical method of evaluating the effects of design and operating parameters on the low-pressure two-phase natural circulation flow through the annular shaped gap at the reactor vessel exterior surface heated by corium (molten core) relocated to the reactor vessel lower plenum after loss of coolant accidents. A natural circulation flow velocity equation derived from steady-state mass, momentum, and energy conservation equations for homogeneous two-phase flow is numerically solved for the core melting conditions of the APR1400 reactor. The solution is compared with existing experiments which measured natural circulation flow through the annular gap slice model. Two kinds of parameters are considered for this analytical method. One is the thermal-hydraulic conditions such as thermal power of corium, pressure and inlet subcooling. The others are those for the thermal insulation system design for the purpose of providing natural circulation flow path outside the reactor vessel: inlet flow area, annular gap clearance and system resistance. A computer program NCIRC is developed for the numerical solution of the implicit flow velocity equation.

  17. An experimental study on the flow instabilities and critical heat flux under natural circulation

    International Nuclear Information System (INIS)

    Kim, Yun II; Chang, Soon Heung

    2004-01-01

    This study has been carried out to investigate the hydrodynamic stabilities and Critical Heat Flux (CHF) characteristics for the natural and forced circulation. A low pressure experimental loop was constructed, and experiments under various conditions have been performed. In the experiments of the natural circulation, flow oscillations has been observed and the average mass flux under flow oscillation have been measured. Several parameters such as heat flux, the inlet temperature of test section, friction valve opening and riser length have been varied in order to investigate their effects on the flow stability of the natural circulation system. And the CHF data from low flow experiments, namely the natural and forced circulation, have been compared with each other to identify the effects of the flow instabilities on the CHF for the natural circulation mode. The test conditions for the CHF experiments were a low flow of less than 70 kg/m 2 s of water in a vertical round tube with diameter of 0.008 m at near atmospheric pressure. (author)

  18. Efficient network-matrix architecture for general flow transport inspired by natural pinnate leaves.

    Science.gov (United States)

    Hu, Liguo; Zhou, Han; Zhu, Hanxing; Fan, Tongxiang; Zhang, Di

    2014-11-14

    Networks embedded in three dimensional matrices are beneficial to deliver physical flows to the matrices. Leaf architectures, pervasive natural network-matrix architectures, endow leaves with high transpiration rates and low water pressure drops, providing inspiration for efficient network-matrix architectures. In this study, the network-matrix model for general flow transport inspired by natural pinnate leaves is investigated analytically. The results indicate that the optimal network structure inspired by natural pinnate leaves can greatly reduce the maximum potential drop and the total potential drop caused by the flow through the network while maximizing the total flow rate through the matrix. These results can be used to design efficient networks in network-matrix architectures for a variety of practical applications, such as tissue engineering, cell culture, photovoltaic devices and heat transfer.

  19. Natural Disasters and Safety Risks at Nuclear Power Stations

    Science.gov (United States)

    Tutnova, T.

    2012-04-01

    In the aftermath of Fukushima natural-technological disaster the global opinion on nuclear energy divided even deeper. While Germany, Italy and the USA are currently reevaluating their previous plans on nuclear growth, many states are committed to expand nuclear energy output. In China and France, where the industry is widely supported by policymakers, there is little talk about abandoning further development of nuclear energy. Moreover, China displays the most remarkable pace of nuclear development in the world: it is responsible for 40% of worldwide reactors under construction, and aims at least to quadruple its nuclear capacity by 2020. In these states the consequences of Fukushima natural-technological accident will probably result in safety checks and advancement of new reactor technologies. Thus, China is buying newer reactor design from the USA which relies on "passive safety systems". It means that emergency power generators, crucial for reactor cooling in case of an accident, won't depend on electricity, so that tsunami won't disable them like it happened in the case of Fukushima. Nuclear energy managed to draw lessons from previous nuclear accidents where technological and human factors played crucial role. But the Fukushima lesson shows that the natural hazards, nevertheless, were undervalued. Though the ongoing technological advancements make it possible to increase the safety of nuclear power plants with consideration of natural risks, it is not just a question of technology improvement. A necessary action that must be taken is the reevaluation of the character and sources of the potential hazards which natural disasters can bring to nuclear industry. One of the examples is a devastating impact of more than one natural disaster happening at the same time. This subject, in fact, was not taken into account before, while it must be a significant point in planning sites for new nuclear power plants. Another important lesson unveiled is that world nuclear

  20. Natural disturbance reduces disease risk in endangered rainforest frog populations.

    Science.gov (United States)

    Roznik, Elizabeth A; Sapsford, Sarah J; Pike, David A; Schwarzkopf, Lin; Alford, Ross A

    2015-08-21

    Natural disturbances can drive disease dynamics in animal populations by altering the microclimates experienced by hosts and their pathogens. Many pathogens are highly sensitive to temperature and moisture, and therefore small changes in habitat structure can alter the microclimate in ways that increase or decrease infection prevalence and intensity in host populations. Here we show that a reduction of rainforest canopy cover caused by a severe tropical cyclone decreased the risk of endangered rainforest frogs (Litoria rheocola) becoming infected by a fungal pathogen (Batrachochytrium dendrobatidis). Reductions in canopy cover increased the temperatures and rates of evaporative water loss in frog microhabitats, which reduced B. dendrobatidis infection risk in frogs by an average of 11-28% in cyclone-damaged areas, relative to unaffected areas. Natural disturbances to the rainforest canopy can therefore provide an immediate benefit to frogs by altering the microclimate in ways that reduce infection risk. This could increase host survival and reduce the probability of epidemic disease outbreaks. For amphibian populations under immediate threat from this pathogen, targeted manipulation of canopy cover could increase the availability of warmer, drier microclimates and therefore tip the balance from host extinction to coexistence.

  1. Analysis of Two Phase Natural Circulation Flow in the Cooling Channel of the PECS

    Energy Technology Data Exchange (ETDEWEB)

    Park, R. J; Ha, K. S; Rhee, B. W; Kim, H. Y [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    Decay heat and sensible heat of the relocated and spread corium are removed by the natural circulation flow at the bottom and side wall of the core catcher and the top water cooling of the corium. The coolant in the inclined channel absorbs the decay heat and sensible heat transferred from the corium through the structure of the core catcher body and flows up to the pool as a two phase mixture. On the other hand, some of the pool water will flow into the inlet of the downcomer piping, and will flow into the inclined cooling channel of the core catcher by gravity. As shown in Fig. 1, the engineered cooling channel is designed to provide effective long-term cooling and stabilization of the corium mixture in the core catcher body while facilitating steam venting in the PECS. To maintain the integrity of the ex-vessel core catcher, however, it is necessary that the coolant be sufficiently circulated along the inclined cooling channel to avoid CHF (Critical Heat Flux) on the heating surface of the cooling channel. For this reason, a verification experiment on the cooling capability of the EU-APR1400 core catcher has been performed in the CE (Cooling Experiment)-PECS facility at KAERI. Preliminary simulations of two-phase natural circulation in the CE-PECS were performed to predict two-phase flow characteristics and to determine the natural circulation mass flow rate in the flow channel. In this study, simulations of two-phase natural circulation in a real core catcher of the PECS have been performed to determine the natural circulation mass flow rate in the flow channel using the RELAP5/MOD3 computer code.

  2. The 5 key questions coping with risks due to natural hazards, answered by a case study

    Science.gov (United States)

    Hardegger, P.; Sausgruber, J. T.; Schiegg, H. O.

    2009-04-01

    Based on Maslow's hierarchy of needs, human endeavours concern primarily existential needs, consequently, to be safeguarded against both natural as well as man made threads. The subsequent needs are to realize chances in a variety of fields, as economics and many others. Independently, the 5 crucial questions are the same as for coping with risks due to natural hazards specifically. These 5 key questions are I) What is the impact in function of space and time ? II) What protection measures comply with the general opinion and how much do they mitigate the threat? III) How can the loss be adequately quantified and monetized ? IV) What budget for prevention and reserves for restoration and compensation are to be planned ? V) Which mix of measures and allocation of resources is sustainable, thus, optimal ? The 5 answers, exemplified by a case study, concerning the sustainable management of risk due to the debris flows by the Enterbach / Inzing / Tirol / Austria, are as follows : I) The impact, created by both the propagation of flooding and sedimentation, has been forecasted by modeling (numerical simulation) the 30, 50, 100, 150, 300 and 1000 year debris flow. The input was specified by detailed studies in meteorology, precipitation and runoff, in geology, hydrogeology, geomorphology and slope stability, in hydraulics, sediment transport and debris flow, in forestry, agriculture and development of communal settlement and infrastructure. All investigations were performed according to the method of ETAlp (Erosion and Transport in Alpine systems). ETAlp has been developed in order to achieve a sustainable development in alpine areas and has been evaluated by the research project "nab", within the context of the EU-Interreg IIIb projects. II) The risk mitigation measures of concern are in hydraulics at the one hand and in forestry at the other hand. Such risk management is evaluated according to sustainability, which means economic, ecologic and social, in short, "triple

  3. An experimental study on the flow instabilities and critical heat flux under natural circulation

    International Nuclear Information System (INIS)

    Kim, Yun Il

    1993-02-01

    This study has been carried out to investigate the hydrodynamic stabilities of natural circulation and to analyze Critical Heat Flux (CHF) characteristics for the natural and forced circulation. A low pressure experimental loop was constructed, and experiments under various conditions have been performed. In the experiments of the natural circulation, flow oscillations and the average mass flux have been observed. Several parameters such as heat flux, the inlet temperature of test section, friction valve opening and riser length have been varied in order to investigate their effects on the flow stability of the natural circulation system. The results show that the flow instability has strongly dependent on geometric conditions and operating parameters, the inlet temperature and the heat flux of test section. It was found that unstable region for the heat flux and the inlet temperature exists between the single-phase stable region of low heat and low inlet temperature and the two-phase stable region of very high heat flux and high inlet temperature. The CHF data from the natural and forced circulation experiments have been compared each other to identify the effects of the flow instabilities on the CHF for the natural circulation mode. The test conditions were low flow less than 70 kg/m 2 s of water in vertical round tube with diameter of 0.008m at near atmospheric pressure. In this study, no difference in CHF values is observed between natural and fored circulation. Since low flow usually has the oscillation characteristic of relatively low amplitude and high frequency, the effect of the flow instabilities on the CHF seems to be negligible

  4. Global Natural Disaster Risk Hotspots: Transition to a Regional Approach

    Science.gov (United States)

    Lerner-Lam, A.; Chen, R.; Dilley, M.

    2005-12-01

    The "Hotspots Project" is a collaborative study of the global distribution and occurrence of multiple natural hazards and the associated exposures of populations and their economic output. In this study we assess the global risks of two disaster-related outcomes: mortality and economic losses. We estimate risk levels by combining hazard exposure with historical vulnerability for two indicators of elements at risk-gridded population and Gross Domestic Product (GDP) per unit area - for six major natural hazards: earthquakes, volcanoes, landslides, floods, drought, and cyclones. By calculating relative risks for each grid cell rather than for countries as a whole, we are able to estimate risk levels at sub-national scales. These can then be used to estimate aggregate relative multiple hazard risk at regional and national scales. Mortality-related risks are assessed on a 2.5' x 2.5' latitude-longitude grid of global population (GPW Version 3). Economic risks are assessed at the same resolution for gridded GDP per unit area, using World Bank estimates of GDP based on purchasing power parity. Global hazard data were compiled from multiple sources. The project collaborated directly with UNDP and UNEP, the International Research Institute for Climate Prediction (IRI) at Columbia, and the Norwegian Geotechnical Institute (NGI) in the creation of data sets for several hazards for which global data sets did not previously exist. Drought, flood and volcano hazards are characterized in terms of event frequency, storms by frequency and severity, earthquakes by frequency and ground acceleration exceedance probability, and landslides by an index derived from probability of occurrence. The global analysis undertaken in this project is clearly limited by issues of scale as well as by the availability and quality of data. For some hazards, there exist only 15- to 25-year global records with relatively crude spatial information. Data on historical disaster losses, and particularly on

  5. Risk premium in the UK natural gas forward market

    International Nuclear Information System (INIS)

    Hobaek Haff, Ingrid; Lindqvist, Ola; Loeland, Anders

    2008-01-01

    This report investigates the UK natural gas market, and tests whether it is a fair-game efficient forward market, using forward contracts ranging from one to five months time to delivery. The forward and spot price series are separately non-stationary, but cointegrated. Furthermore, the forward prices are biased predictors of both the future spot and the 1-month-ahead forward price. The risk premium on the forward prices is positive, as opposed to the US gas market, where the risk premium was found to be negative in similar work. Moreover, the analysis reveals that the storage model is an incomplete model for the relationship between the spot and forward prices. However, storage has a clear effect on this relationship, an effect that appears to be non-linear. (author)

  6. Drought Risk Assessment based on Natural and Social Factors

    Science.gov (United States)

    Huang, Jing; Wang, Huimin; Han, Dawei

    2015-04-01

    In many parts of the world, drought hazard is becoming more frequent and severe due to climate change and human activities. It is crucial to monitor and assess drought conditions, especially for decision making support in agriculture sector. The vegetation index (VI) decreases, and the land surface temperature (LST) increases when the vegetation is under drought stress. Therefore both of these remotely sensed indices are widely used in drought monitoring and assessment. Temperature-Vegetation Dryness Index (TVDI) is obtained by establishing the feature space of the normalized difference vegetation index (NDVI) and LST, which reflects agriculture dry situation by inverting soil moisture. However, these indices only concern the natural hazard-causing factors. Our society is a complex large-scale system with various natural and social elements. The drought risk is the joint consequence of hazard-causing factors and hazard-affected bodies. For example, as the population increases, the exposure of the hazard-affected bodies also tends to increase. The high GDP enhances the response ability of government, and the irrigation and water conservancy reduces the vulnerability. Such characteristics of hazard-affected bodies should be coupled with natural factors. In this study, the 16-day moderate-resolution imaging spectroradiometer (MODIS) NDVI and LST data are combined to establish NDVI-Ts space according to different land use types in Yunnan Province, China. And then, TVDIs are calculated through dry and wet edges modeled as a linear fit to data for each land cover type. Next, the efforts are turned to establish an integrated drought assessment index of social factors and TVDI through ascertaining attribute weight based on rough sets theory. Thus, the new CDI (comprehensive drought index) recorded during spring of 2010 and the spatial variations in drought are analyzed and compared with TVDI dataset. Moreover, actual drought risk situation in the study area is given to

  7. Climate change, natural disasters, and the risk of violent conflict

    Energy Technology Data Exchange (ETDEWEB)

    Slettebak, Rune Thorkildsen

    2012-07-01

    This PhD project aims to assess the relation between natural disasters triggered by extreme weather events and the risk of violent conflict. The focus on these natural disasters stems from expectations that climate change will increase the frequency and severity of extreme weather events, combined with frequent suggestions that climate change in general and natural disasters in particular can be expected to trigger more violent conflicts. A number of conflict types, ranging from riots to civil war, are tested. Case studies have found examples where environmental factors have contributed to triggering conflict. However, without systematic assessments, we do not know whether these cases are exceptions or parts of a common pattern. Learning more about this is a prime aim of this thesis. As the effects of climate change are still mainly in the future, I turn to the past for learning more about these connections. Although future relations may differ from those in the past, learning from history is considered the best way of increasing our basis of knowledge on what to expect from the future. The thesis tests two opposing theoretical traditions against each other. On one side is the environmental security literature, which holds that environmentally induced adversity is likely to increase the risk of violent conflict. The other, relatively unknown tradition, called disaster sociology, expects adversity to stimulate altruistic behavior and replace past ascribed identities with new 'communities of sufferers' in the disaster aftermath. In a violent conflict setting, this argument is read as that disasters should reduce conflict risk. Four analyses have been conducted. The first has a global coverage, two focus on India and the last one on Indonesia. The first analysis aims to uncover general trends, while the three others use cases where environmentally driven violence is considered particularly likely, and disaggregated analytical designs that should be well

  8. Multi-attribute risk assessment for risk ranking of natural gas pipelines

    International Nuclear Information System (INIS)

    Brito, A.J.; Almeida, A.T. de

    2009-01-01

    The paper presents a decision model for risk assessment and for risk ranking of sections of natural gas pipelines based on multi-attribute utility theory. Pipeline hazard scenarios are surveyed and the reasons for a risk assessment model based on a multi-attribute approach are presented. Three dimensions of impact and the need to translate decision-makers' preferences into risk management decisions are highlighted. The model approaches these factors by using a multi-attribute utility function, in order to produce multi-dimensional risk measurements. By using decision analysis concepts, this model quantitatively incorporates the decision-maker's preferences and behavior regarding risk within clear and consistent risk measurements. In order to support the prioritizing of critical sections of pipeline in natural gas companies, this multi-attribute model also allows sections of pipeline to be ranked into a risk hierarchy. A numerical application based on a real case study was undertaken so that the effectiveness of the decision model could be verified

  9. Simulation and scaling for natural convection flow in a cavity with isothermal boundaries

    International Nuclear Information System (INIS)

    Jiracheewanun, S.; Armfield, S.W.; McBain, G.D.; Behnia, M.

    2005-01-01

    A numerical study of the transient two-dimensional natural convection flow within a differentially heated square cavity with iso-flux side walls and adiabatic top and bottom boundaries is presented. The governing equations are discretized using a non-staggered mesh and solved using a non-iterative fractional-step pressure correction method which provides second-order accuracy in both time and space. Results are obtained with the iso-flux boundary condition for Ra = 5.8 x 10 9 and Pr = 7.5. The results show that the transient flow features obtained for the iso-flux cavity are similar to the flow features for the isothermal case. However, the fully developed flow features of the iso-flux cavity are very different from the isothermal case. The scalings for the fully developed iso-flux boundary condition flow have been found to be different to those of the isothermal boundary condition flow. (authors)

  10. Vortex flow and motion of notices in nature and technical science. Wirbelstroemung in Natur und Technik

    Energy Technology Data Exchange (ETDEWEB)

    Lugt, H.J.

    1979-01-01

    First the publication gives a historical overview on classical mechanics and the theories of vortices. Then the paper offers an intelligible introduction in the motion of vortices comprising the following topics: Properties of vortices, vorticity, detachment, instability and turbulence, fluid flow in a rotating system, changes of density in ocean and atmosphere, cyclones. The paper contains no mathematical applications but computer graphics and experiments are described.

  11. Non-linear time series analysis on flow instability of natural circulation under rolling motion condition

    International Nuclear Information System (INIS)

    Zhang, Wenchao; Tan, Sichao; Gao, Puzhen; Wang, Zhanwei; Zhang, Liansheng; Zhang, Hong

    2014-01-01

    Highlights: • Natural circulation flow instabilities in rolling motion are studied. • The method of non-linear time series analysis is used. • Non-linear evolution characteristic of flow instability is analyzed. • Irregular complex flow oscillations are chaotic oscillations. • The effect of rolling parameter on the threshold of chaotic oscillation is studied. - Abstract: Non-linear characteristics of natural circulation flow instabilities under rolling motion conditions were studied by the method of non-linear time series analysis. Experimental flow time series of different dimensionless power and rolling parameters were analyzed based on phase space reconstruction theory. Attractors which were reconstructed in phase space and the geometric invariants, including correlation dimension, Kolmogorov entropy and largest Lyapunov exponent, were determined. Non-linear characteristics of natural circulation flow instabilities under rolling motion conditions was studied based on the results of the geometric invariant analysis. The results indicated that the values of the geometric invariants first increase and then decrease as dimensionless power increases which indicated the non-linear characteristics of the system first enhance and then weaken. The irregular complex flow oscillation is typical chaotic oscillation because the value of geometric invariants is at maximum. The threshold of chaotic oscillation becomes larger as the rolling frequency or rolling amplitude becomes big. The main influencing factors that influence the non-linear characteristics of the natural circulation system under rolling motion are thermal driving force, flow resistance and the additional forces caused by rolling motion. The non-linear characteristics of the natural circulation system under rolling motion changes caused by the change of the feedback and coupling degree among these influencing factors when the dimensionless power or rolling parameters changes

  12. Prediction of flow recirculation in a blanket assembly under worst-case natural-convection conditions

    International Nuclear Information System (INIS)

    Khan, E.U.; Rector, D.R.

    1982-01-01

    Reactor fuel and blanket assemblies within a Liquid Metal Fast Breeder Reactor (LMFBR) can be subjected to severe radial heat flux gradients. At low-flow conditions, with power-to-flow ratios of nearly the same magnitude as design conditions, buoyancy forces cause flow redistribution to the side of a bundle with the higher heat generation rate. Recirculation of fluid within a rod bundle can occur during a natural convection transient because of the combined effect of flow coastdown and buoyancy-induced redistribution. An important concern is whether recirculation leads to high coolant temperatures. For this reason, the COBRA-WC code was developed with the capability of modeling recirculating flows. Experiments have been conducted in a 2 x 6 rod bundle for flow and power transients to study recirculation in the mixed-convection (forced cooled) and natural-convection regimes. The data base developed was used to validate the recirculation module in the COBRA-WC code. COBRA-WC code calculations were made to predict flow and temperature distributions in a typical LMFBR blanket assembly for the worst-case, natural-circulation transient

  13. Numerical simulation of shell-side heat transfer and flow of natural circulation heat exchanger

    International Nuclear Information System (INIS)

    Xue Ruojun; Deng Chengcheng; Li Chaojun; Wang Mingyuan

    2012-01-01

    In order to analyze the influence on the heat transfer and flow characteristics of the heat exchanger model of different solving models and structures, a variety of transformation to the model equivalent for the heat exchanger was studied. In this paper, Fluent software was used to simulate the temperature-field and flow-field of the equivalent model, and investigate its heat-transferring and flow characteristics. Through comparative analysis of the distribution of temperature-field and flow-field for different models, the heat-transferring process and natural convection situation of heat exchanger were deeply understood. The results show that the temperature difference between the inside and outside of the natural circulation heat exchanger tubes is larger and the flow is more complex, so the turbulence model is the more reasonable choice. Asymmetry of tubes position makes the flow and heat transfer of the fluid on both sides to be dissymmetrical and makes the fluid interaction, and increases the role of natural convection. The complex structure of heat exchanger makes the flow and heat transfer of the fluid on both sides to be irregular to some extent when straight tubes into C-bent are transformed, and all these make the turbulence intensity increase and improve the effect of heat transfer. (authors)

  14. Natural circulation in single-phase and two-phase flow

    International Nuclear Information System (INIS)

    Cheung, F.B.; El-Genk, M.S.

    1989-01-01

    Natural circulation usually arises in a closed loop between a heat source and a heat sink were the fluid motion is driven by density difference. It may also occur in enclosures or cavities where the flow is induced primarily by temperature or concentration gradients within the fluid. The subject has recently received special attention by the heat transfer and nuclear reactor safety communities because of it importance to the areas of energy extraction, decay, heat removal in nuclear reactors, solar and geothermal heating, and cooling of electronic equipment. Although many new results and physical insights have been gained of the various natural circulation phenomena, a number of critical issues remain unresolved. These include, for example, transition from laminar to turbulent flow, buoyancy-induced turbulent flow modeling, change of flow regimes, flow field visualization, variable property effects, and flow instability. This symposium volume contains papers presented in the Natural Circulation in Single-Phase and Two-Phase Flow session at the 1989 Winter Annual Meeting of ASME, by authors from different countries including the United States, Japan, Canada, and Brazil. The papers deal with experimental and theoretical studies as well as state-of-the-art reviews, covering a broad spectrum of topics in natural circulation including: variable-conductance thermosyphons, microelectronic chip cooling, natural circulation in anisotropic porous media and in cavities, heat transfer in flat plat solar collectors, shutdown heat removal in fast reactors, cooling of light-water and heavy-water reactors. The breadth of papers contained in this volume clearly reflect the importance of the current interest in natural circulation as a means for passive cooling and heating

  15. Study on natural circulation flow under reactor cavity flooding condition in advanced PWRs

    International Nuclear Information System (INIS)

    Tao Jun; Yang Jiang; Cao Jianhua; Lu Xianghui; Guo Dingqing

    2015-01-01

    Cavity flooding is an important severe accident management measure for the in-vessel retention of a degraded core by external reactor vessel cooling in advanced PWRs. A code simulation study on the natural circulation flow in the gap between the reactor vessel wall and insulation material under cavity flooding condition is performed by using a detailed mechanistic thermal-hydraulic code package RELAP 5. By simulating of an experiment carried out for studying the natural circulation flow for APR1400 shows that the code is applicable for analyzing the circulation flow under this condition. The analysis results show that heat removal capacity of the natural circulation flow in AP1000 is sufficient to prevent thermal failure of the reactor vessel under bounding heat load. Several conclusions can be drawn from the sensitivity analysis. Larger coolant inlet area induced larger natural circulation flow rate. The outlet should be large enough and should not be submerged by the cavity water to vent the steam-water mixture. In the implementation of cavity flooding, the flooding water level should be high enough to provide sufficient natural circulation driven force. (authors)

  16. Design of a naturalized flow regime—An example from the Lower Missouri River, USA

    Science.gov (United States)

    Jacobson, Robert B.; Galat, David L.

    2008-01-01

     group of river managers, stakeholders, and scientists met during summer 2005 to design a more naturalized flow regime for the Lower Missouri River (LMOR). The objective was to comply with requirements under the U.S. Endangered Species Act to support reproduction and survival of threatened and endangered species, with emphasis on the endangered pallid sturgeon (Scaphirhynchus albus), while minimizing negative effects to existing social and economic benefits of prevailing river management. Specific hydrograph requirements for pallid sturgeon reproduction are unknown, hence much of the design process was based on features of the natural flow regime. Environmental flow components (EFCs) extracted from the reference natural flow regime were used to design and assess performance of alternative flow regimes.The design process incorporated a primary stage in which conceptual hydrographs were developed and assessed for their general ecological and social-economic performance. The second stage accounted for hydroclimatic variation by coding the conceptual hydrographs into reservoir release rules, adding constraints for downstream flooding and low-storage precludes, and running the rules through 100 years of hydroclimatic simulation. The output flow regimes were then evaluated for presumed ecological benefits based on how closely they resembled EFCs in the reference natural flow regime. Flow regimes also were assessed for social-economic cost indicators, including days of flooding of low-lying agricultural land, days over flood stage, and storage levels in system reservoirs.Our experience with flow-regime design on the LMOR underscored the lack of confidence the stakeholders place in the value of the natural flow regime as a measure of ecosystem benefit in the absence of fundamental scientific documentation. Stakeholders desired proof of ecological benefits commensurate with the certainty of economic losses. We also gained insight into the processes of integrating science

  17. Influence of land-use dynamics on natural hazard risk

    Science.gov (United States)

    Piazza, Giacomo; Thaler, Thomas; Fuchs, Sven

    2016-04-01

    In the recent past the magnitude and frequency of natural hazard events has increased notably worldwide, along with global GDP. A higher number of elements are exposed to natural events, therefore the risk is higher. Both estimated losses and understanding about natural hazards have increased during the past decades, which is contradictory as we may logically think. Risk is increasing, due to climate change and societal change: more severe hazards are happening due to changing climatic patterns and conditions, while society is concentrating assets and people in punctual places leading to a higher exposure. Increasing surface of settled area and the concentration of highly valuable assets (e.g. technology) in exposed areas lead to higher probability of losses. Human use of land resources, namely landuse, is the product of human needs and biophysical characteristics of the land. Landuse involves arrangements, activities and inputs people undertake in a certain land cover type to produce, change or maintain it. These changes are due to many reasons, or driving factors: socio-economical, environmental, accessibility to land, land-tenure, etc. The change of those factors may cause many effects and impacts, at various levels and at different time spans. The relation between driving factors and impacts is not straight. It is although a complex interrelation that turns around two central questions: (1) what drives landuse changes and why and (2) what are the impacts on the environment and on the human society of these changes, regarding to natural hazards. The aim of this paper is to analyse the spatio-temporal environmental changes referring to exposure as well as to test the possibilities and limitations of the land use change model Dyna-CLUEs in a mountain region taking parts of the Republic of Austria as an example, and simulating the future landuse dynamics until 2030. We selected an area composed by eighteen municipalities in the Ill-Walgau in the Austrian federal

  18. Perception of Lava Flow Hazards and Risk at Mauna Loa and Hualalai Volcanoes, Kona, Hawaii

    Science.gov (United States)

    Gregg, C. E.; Houghton, B. F.; Johnston, D. M.; Paton, D.; Swanson, D. A.

    2001-12-01

    The island of Hawaii is composed of five sub-aerially exposed volcanoes, three of which have been active since 1801 (Kilauea, Mauna Loa, Hualalai). Hawaii has the fastest population growth in the state and the local economy in the Kona districts (i.e., western portion of the island) is driven by tourism. Kona is directly vulnerable to future lava flows from Mauna Loa and Hualalai volcanoes, as well as indirectly from the effects of lava flows elsewhere that may sever the few roads that connect Kona to other vital areas on the island. A number of factors such as steep slopes, high volume eruptions, and high effusion rates, combine to mean that lava flows from Hualalai and Mauna Loa can be fast-moving and hence unusually hazardous. The proximity of lifelines and structures to potential eruptive sources exacerbates societies' risk to future lava flows. Approximately \\$2.3 billion has been invested on the flanks of Mauna Loa since its last eruption in 1984 (Trusdell 1995). An equivalent figure has not yet been determined for Hualalai, but an international airport, several large resort complexes, and Kailua-Kona, the second largest town on the island, are down-slope and within 15km of potential eruptive Hualalai vents. Public and perhaps official understanding of specific lava flow hazards and the perceptions of risk from renewed volcanism at each volcano are proportional to the time lapsed since the most recent eruption that impacted Kona, rather than a quantitative assessment of risk that takes into account recent growth patterns. Lava flows from Mauna Loa and Hualalai last directly impacted upon Kona during the notorious 1950 and circa 1801 eruptions, respectively. Various non-profit organizations; local, state and federal government entities; and academic institutions have disseminated natural hazard information in Kona but despite the intuitive appeal that increased hazard understanding and risk perception results in increased hazard adjustment adoption, this

  19. Chances and risks in the sale of natural gas

    International Nuclear Information System (INIS)

    Spaeth, F.

    1995-01-01

    'Natural gas is number one among the growth industries of the energy sector' proclaim today's augurs. What with growth rates of 20% in western and more than 100% in eastern Germany, the gas supply companies could really look ahead in confidence. However, the situation does not merit unrestrained euphoria. For one thing, predictions should quite generally be viewed with a good measure of healthy scepticism, or, as Prof. Dr. Dieter Schmitt, energy economist from Essen, recently put it in a nutshell: 'Prognoses are no prophecies. Only prophets are really able to tell the future'. The other point is that natural gas will only be able to carry its past success on into the future if it can fulfill the consumer's expectations regarding security of supply, environment and climate friendly utilisation, possibilities to save energy, and, most important of all, competitivity. The last point, in particular, is beset with many imponderabilities on which gas supply companies have little influence. Therefore, despite the favourable forecasts, the chances and risks involved in the sale of natural gas must be assessed judiciously. (orig.) [de

  20. Natural Disasters, Corpses and the Risk of Infectious Diseases

    Directory of Open Access Journals (Sweden)

    JM Conly

    2005-01-01

    Full Text Available The recent occurrence of the category 4 Hurricane Katrina devastated the United States? Gulf Coast. The hurricane caused widespread destruction and flooding, and left hundreds of thousands of people homeless. The mounting death toll was reported at almost 300 deaths as of September 8, 2005 (1,2. The unfolding events and high death toll have left an unusual situation in which there are many decomposing corpses either lying on the streets or floating in the flood waters. The presence of these corpses in open settings, such as in public places and in the water that has inundated much of the city of New Orleans, naturally raises concerns about the occurrence of infectious disease epidemics (3. In the aftermath of large natural disasters, instinctive uncertainties arise among workers and the general population with respect to the appropriate handling and disposal of dead bodies and human remains. Given the recent occurrence of Hurricane Katrina as a large natural disaster and the unprecedented setting of the numerous corpses requiring disposal, it was considered timely to review the infectious disease risks associated with the handling of dead bodies.

  1. Reliability and effectiveness of early warning systems for natural hazards: Concept and application to debris flow warning

    International Nuclear Information System (INIS)

    Sättele, Martina; Bründl, Michael; Straub, Daniel

    2015-01-01

    Early Warning Systems (EWS) are increasingly applied to mitigate the risks posed by natural hazards. To compare the effect of EWS with alternative risk reduction measures and to optimize their design and operation, their reliability and effectiveness must be quantified. In the present contribution, a framework approach to the evaluation of threshold-based EWS for natural hazards is presented. The system reliability is classically represented by the Probability of Detection (POD) and Probability of False Alarms (PFA). We demonstrate how the EWS effectiveness, which is a measure of risk reduction, can be formulated as a function of POD and PFA. To model the EWS and compute the reliability, we develop a framework based on Bayesian Networks, which is further extended to a decision graph, facilitating the optimization of the warning system. In a case study, the framework is applied to the assessment of an existing debris flow EWS. The application demonstrates the potential of the framework for identifying the important factors influencing the effectiveness of the EWS and determining optimal warning strategies and system configurations. - Highlights: • Warning systems are increasingly applied measures to reduce natural hazard risks. • Bayesian Networks (BN) are powerful tools to quantify warning system's reliability. • The effectiveness is defined to assess the optimality of warning systems. • By extending BNs to decision graphs, the optimal warning strategy is identified. • Sensors positioning significantly influence the effectiveness of warning systems

  2. Operator splitting method for simulation of dynamic flows in natural gas pipeline networks

    Science.gov (United States)

    Dyachenko, Sergey A.; Zlotnik, Anatoly; Korotkevich, Alexander O.; Chertkov, Michael

    2017-12-01

    We develop an operator splitting method to simulate flows of isothermal compressible natural gas over transmission pipelines. The method solves a system of nonlinear hyperbolic partial differential equations (PDEs) of hydrodynamic type for mass flow and pressure on a metric graph, where turbulent losses of momentum are modeled by phenomenological Darcy-Weisbach friction. Mass flow balance is maintained through the boundary conditions at the network nodes, where natural gas is injected or withdrawn from the system. Gas flow through the network is controlled by compressors boosting pressure at the inlet of the adjoint pipe. Our operator splitting numerical scheme is unconditionally stable and it is second order accurate in space and time. The scheme is explicit, and it is formulated to work with general networks with loops. We test the scheme over range of regimes and network configurations, also comparing its performance with performance of two other state of the art implicit schemes.

  3. Natural hazards knowledge and risk perception of Wujie indigenous community in Taiwan

    Science.gov (United States)

    Roder, Giulia; Ruljigaljig, Tjuku; Lin, Ching-Weei; Tarolli, Paolo

    2015-04-01

    The purpose of this work is to investigate the natural hazard knowledge and risk perception of Wujie indigenous community, located in Fazhi Village in the Central Mountain Range of Taiwan. Taiwan has encountered many different types of natural hazards (e.g. landslides and debris flows) that have increased sharply in the last century. Because of that, they are one of the most critical issues for the government and for the people living in mountainous areas. These areas are mainly populated by indigenous people that have experienced economic competition and military conflict with a series of colonizing periods causing a progressive loss of their original cultural identity. The motivation of selecting the case study of Wujie community is because (i) it has suffered, more than others, generations of devastating colonial oppression by foreign governments; (ii) the consequences of hydroelectric projects that moved a lot of water and sediment to the valley and modified the path of the river through the years; (iii) the documented landslides and debris flows occurred in the region during the last decades. Two questions appear spontaneously: How indigenous people are nowadays living with natural hazards? Have land use change or any other human footprint affected their knowledge and perception on natural hazards? This research, the first carried out in Taiwan involving an indigenous community, can offer a unique opportunity to answer these questions. The investigation utilized a variety of participatory methods conducted at the household and community level by the use of 65 face-to-face interviews. Results revealed that residents felt a higher worry about landslide and flood risks, and a slight preparedness to face them. This discrepancy may derive from an unsatisfactory level of communication and information, and the most considerable differences were found between the evaluations of individual subjects as opposed to overall communities. Results revealed also the complexity

  4. An experimental investigation of natural circulated air flow in the passive containment cooling system

    International Nuclear Information System (INIS)

    Ryu, S.H.; Oh, S.M.; Park, G.C.

    2004-01-01

    The objective of this study is to investigate the effects of air inlet position and external conditions on the natural circulated air flow rate in a passive containment cooling system of the advanced passive reactor. Experiments have been performed with 1/36 scaled segment type passive containment test facility. The air velocities and temperatures are measured through the air flow path. Also, the experimental results are compared with numerical calculations and show good agreement. (author)

  5. Characteristics of Buoyant Flow from Open Windows in Naturally Ventilated Rooms

    DEFF Research Database (Denmark)

    Nielsen, Peter V.; Dam, Henrik; Sørensen, Lars C.

    An important element in the natural ventilation design procedure is the flow-pressure characteristics of a window with a -given opening area. The flow in the room is another important element that is often ignored in the design phase due to lack of relevant information on the air movement....... This paper shows the outcome of experiments with the room air distribution. The results show that the velocity distribution in the occupied zone can be described by a semiempirical model....

  6. Risks in global natural gas markets: Investment, hedging and trade

    International Nuclear Information System (INIS)

    Egging, Ruud; Holz, Franziska

    2016-01-01

    Recent supply security concerns in Europe have revived interest into the natural gas market. We investigate infrastructure investment and trade in an imperfect market structure for various possible risks for both supply and demand. We focus on three possible scenarios in a stochastic global gas market model: (i) transit of Russian gas via Ukraine that may be disrupted from 2020 on; (ii) natural gas intensity of electricity generation in OECD countries that may lead to higher or lower natural gas demand after 2025; and (iii) availability of shale gas around the globe after 2030. We illustrate how the timing of investments is affected by inter-temporal hedging behavior of market agents, such as when LNG capacity provides ex-ante flexibility or an ex-post fallback option if domestic or nearby pipeline supply sources are low. Moreover, we find that investment in LNG capacities is more determined by demand side pull – due to higher needs in electric power generation – than by supply side push, e.g. higher shale gas supplies needing an outlet. We focus on Europe, North America, and China that are the world's most important gas consuming and supplying regions. - Highlights: •We use the stochastic variant of the multi-period Global Gas Model. •We investigate the effects of uncertainty in Russian exports, demand, and shale gas. •We find that LNG is preferred as hedging option in anticipation of uncertain events. •Pipelines may be chosen as recourse decision after uncertain events realized. •China will dominate the global natural gas market regardless the scenario.

  7. Systematic analysis of natural hazards along infrastructure networks using a GIS-tool for risk assessment

    Science.gov (United States)

    Baruffini, Mirko

    2010-05-01

    Due to the topographical conditions in Switzerland, the highways and the railway lines are frequently exposed to natural hazards as rockfalls, debris flows, landslides, avalanches and others. With the rising incidence of those natural hazards, protection measures become an important political issue. However, they are costly, and maximal protection is most probably not economically feasible. Furthermore risks are distributed in space and time. Consequently, important decision problems to the public sector decision makers are derived. This asks for a high level of surveillance and preservation along the transalpine lines. Efficient protection alternatives can be obtained consequently considering the concept of integral risk management. Risk analysis, as the central part of risk management, has become gradually a generally accepted approach for the assessment of current and future scenarios (Loat & Zimmermann 2004). The procedure aims at risk reduction which can be reached by conventional mitigation on one hand and the implementation of land-use planning on the other hand: a combination of active and passive mitigation measures is applied to prevent damage to buildings, people and infrastructures. With a Geographical Information System adapted to run with a tool developed to manage Risk analysis it is possible to survey the data in time and space, obtaining an important system for managing natural risks. As a framework, we adopt the Swiss system for risk analysis of gravitational natural hazards (BUWAL 1999). It offers a complete framework for the analysis and assessment of risks due to natural hazards, ranging from hazard assessment for gravitational natural hazards, such as landslides, collapses, rockfalls, floodings, debris flows and avalanches, to vulnerability assessment and risk analysis, and the integration into land use planning at the cantonal and municipality level. The scheme is limited to the direct consequences of natural hazards. Thus, we develop a

  8. Effectiveness of horizontal air flow fans supporting natural ventilation in a Mediterranean multi-span greenhouse

    OpenAIRE

    López, Alejandro; Valera, Diego Luis; Molina-Aiz, Francisco Domingo; Peña, Araceli

    2013-01-01

    Natural ventilation is the most important method of climate control in Mediterranean greenhouses. In this study, the microclimate and air flow inside a Mediterranean greenhouse were evaluated by means of sonic anemometry. Experiments were carried out in conditions of moderate wind (≈ 4.0 m s-1), and at low wind speed (≈ 1.8 m s-1) the natural ventilation of the greenhouse was supplemented by two horizontal air flow fans. The greenhouse is equipped with a single roof vent opening t...

  9. Synthesis of Natural and Unnatural Cyclooligomeric Depsipeptides Enabled by Flow Chemistry.

    Science.gov (United States)

    Lücke, Daniel; Dalton, Toryn; Ley, Steven V; Wilson, Zoe E

    2016-03-14

    Flow chemistry has been successfully integrated into the synthesis of a series of cyclooligomeric depsipeptides of three different ring sizes including the natural products beauvericin (1 a), bassianolide (2 b) and enniatin C (1 b). A reliable flow chemistry protocol was established for the coupling and macrocyclisation to form challenging N-methylated amides. This flexible approach has allowed the rapid synthesis of both natural and unnatural depsipeptides in high yields, enabling further exploration of their promising biological activity. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  10. Mathematical Model and Program for the Sizing of Counter-flow Natural Draft Wet Cooling Towers

    Directory of Open Access Journals (Sweden)

    Victor-Eduard Cenușă

    2017-08-01

    Full Text Available Assuring the necessary temperature and mass flow rate of the cooling water to the condenser represents an essential condition for the efficient operation of a steam power plant. The paper presents equations which describe the physical phenomena and the mathematical model for the design of counter-flow natural draft wet cooling towers. Following is given the flow-chart of the associated computer program. A case study is made to show the results of the computer program and emphasize the interdependence between the main design parameters.

  11. Effect of swirling device on flow behavior in a supersonic separator for natural gas dehydration

    DEFF Research Database (Denmark)

    Wen, Chuang; Li, Anqi; Walther, Jens Honore

    2016-01-01

    is designed for an annular supersonic separator. The supersonic swirling separation flow of natural gas is calculated using the Reynolds Stress model. The results show that the viscous heating and strong swirling flow cause the adverse pressure in the annular channel, which may negatively affect......The supersonic separator is a revolutionary device to remove the condensable components from gas mixtures. One of the key issues for this novel technology is the complex supersonic swirling flow that is not well understood. A swirling device composed of an ellipsoid and several helical blades...

  12. Climate and weather risk in natural resource models

    Science.gov (United States)

    Merrill, Nathaniel Henry

    This work, consisting of three manuscripts, addresses natural resource management under risk due to variation in climate and weather. In three distinct but theoretically related applications, I quantify the role of natural resources in stabilizing economic outcomes. In Manuscript 1, we address policy designed to effect the risk of cyanobacteria blooms in a drinking water reservoir through watershed wide policy. Combining a hydrologic and economic model for a watershed in Rhode Island, we solve for the efficient allocation of best management practices (BMPs) on livestock pastures to meet a monthly risk-based as well as mean-based water quality objective. In order to solve for the efficient allocations of nutrient control effort, we optimize a probabilistically constrained integer-programming problem representing the choices made on each farm and the resultant conditions that support cyanobacteria blooms. In doing so, we employ a genetic algorithm (GA). We hypothesize that management based on controlling the upper tail of the probability distribution of phosphorus loading implies different efficient management actions as compared to controlling mean loading. We find a shift to more intense effort on fewer acres when a probabilistic objective is specified with cost savings of meeting risk levels of up to 25% over mean loading based policies. Additionally, we illustrate the relative cost effectiveness of various policies designed to meet this risk-based objective. Rainfall and the subsequent overland runoff is the source of transportation of nutrients to a receiving water body, with larger amounts of phosphorus moving in more intense rainfall events. We highlight the importance of this transportation mechanism by comparing policies under climate change scenarios, where the intensity of rainfall is projected to increase and the time series process of rainfall to change. In Manuscript 2, we introduce a new economic groundwater model that incorporates the gradual shift

  13. Risk Due to Radiological Terror Attacks With Natural Radionuclides

    Science.gov (United States)

    Friedrich, Steinhäusler; Stan, Rydell; Lyudmila, Zaitseva

    2008-08-01

    The naturally occurring radionuclides radium (Ra-226) and polonium (Po-210) have the potential to be used for criminal acts. Analysis of international incident data contained in the Database on Nuclear Smuggling, Theft and Orphan Radiation Sources (CSTO), operated at the University of Salzburg, shows that several acts of murder and terrorism with natural radionuclides have already been carried out in Europe and Russia. Five different modes of attack (T) are possible: (1) Covert irradiation of an individual in order to deliver a high individual dose; (2) Covert irradiation of a group of persons delivering a large collective dose; (3) Contamination of food or drink; (4) Generation of radioactive aerosols or solutions; (5) Combination of Ra-226 with conventional explosives (Dirty Bomb). This paper assesses the risk (R) of such criminal acts in terms of: (a) Probability of terrorist motivation deploying a certain attack mode T; (b) Probability of success by the terrorists for the selected attack mode T; (c) Primary damage consequence (C) to the attacked target (activity, dose); (d) Secondary damage consequence (C') to the attacked target (psychological and socio-economic effects); (e) Probability that the consequences (C, C') cannot be brought under control, resulting in a failure to manage successfully the emergency situation due to logistical and/or technical deficits in implementing adequate countermeasures. Extensive computer modelling is used to determine the potential impact of such a criminal attack on directly affected victims and on the environment.

  14. Risk Due to Radiological Terror Attacks With Natural Radionuclides

    International Nuclear Information System (INIS)

    Friedrich, Steinhaeusler; Lyudmila, Zaitseva; Stan, Rydell

    2008-01-01

    The naturally occurring radionuclides radium (Ra-226) and polonium (Po-210) have the potential to be used for criminal acts. Analysis of international incident data contained in the Database on Nuclear Smuggling, Theft and Orphan Radiation Sources (CSTO), operated at the University of Salzburg, shows that several acts of murder and terrorism with natural radionuclides have already been carried out in Europe and Russia. Five different modes of attack (T) are possible: (1) Covert irradiation of an individual in order to deliver a high individual dose; (2) Covert irradiation of a group of persons delivering a large collective dose; (3) Contamination of food or drink; (4) Generation of radioactive aerosols or solutions; (5) Combination of Ra-226 with conventional explosives (Dirty Bomb).This paper assesses the risk (R) of such criminal acts in terms of: (a) Probability of terrorist motivation deploying a certain attack mode T; (b) Probability of success by the terrorists for the selected attack mode T; (c) Primary damage consequence (C) to the attacked target (activity, dose); (d) Secondary damage consequence (C') to the attacked target (psychological and socio-economic effects); (e) Probability that the consequences (C, C') cannot be brought under control, resulting in a failure to manage successfully the emergency situation due to logistical and/or technical deficits in implementing adequate countermeasures. Extensive computer modelling is used to determine the potential impact of such a criminal attack on directly affected victims and on the environment

  15. Experimental study of flow instability and CHF in a natural circulation system with subcooled boiling

    International Nuclear Information System (INIS)

    Yang, R.C.; Shi, D.Q.; Lu, Z.Q.; Zheng, R.C.; Wang, Y.

    1996-01-01

    Experimental study has been performed to investigate flow instability and critical heat flux (CHF) in a natural circulation system with subcooled boiling. In the experiments three kinds of heated sections were used. Freon-12 was used as the working medium. The experiments show which one of the two phenomena, flow instability and CHF condition, may first occur in the system depends on not only the heat input power to the heated section and the parameters of the working medium, but also the construction of the heated section. The occurrence of the flow instability mainly depends on the total heat input power to the heated section and the CHF condition is mainly caused by the local heat flux of the heated section. In the experiments two kinds of flow instability, flow instability with high frequency and flow instability with low frequency, were found. But they all belong to density wave instability. The influence of the parameters of the working medium on the onset of the flow instability and CHF condition in the system were investigated. The stability boundaries were determined through the experiments. By means of dimensional analysis of integral equations, a common correlation describing the threshold condition of onset of the flow instability was obtained

  16. Effect of inlet and outlet flow conditions on natural gas parameters in supersonic separation process.

    Directory of Open Access Journals (Sweden)

    Yan Yang

    Full Text Available A supersonic separator has been introduced to remove water vapour from natural gas. The mechanisms of the upstream and downstream influences are not well understood for various flow conditions from the wellhead and the back pipelines. We used a computational model to investigate the effect of the inlet and outlet flow conditions on the supersonic separation process. We found that the shock wave was sensitive to the inlet or back pressure compared to the inlet temperature. The shock position shifted forward with a higher inlet or back pressure. It indicated that an increasing inlet pressure declined the pressure recovery capacity. Furthermore, the shock wave moved out of the diffuser when the ratio of the back pressure to the inlet one was greater than 0.75, in which the state of the low pressure and temperature was destroyed, resulting in the re-evaporation of the condensed liquids. Natural gas would be the subsonic flows in the whole supersonic separator, if the mass flow rate was less than the design value, and it could not reach the low pressure and temperature for the condensation and separation of the water vapor. These results suggested a guidance mechanism for natural gas supersonic separation in various flow conditions.

  17. Coping strategies, stress and risk perception in a natural and industrial catastrophe risk situation

    International Nuclear Information System (INIS)

    Lopez Vasquez, E.

    1998-01-01

    People are exposed to different environmental risks, their manifestations harm people according to the magnitude, intensity and the number of people concerned. This subject is very ample, therefore we consider only two kinds of risks: the natural risks (especially earthquakes) that have always threatened humanity, and the industrial risks that characterise our modern society. We are interested in risk perception, stress and coping strategies in these two kinds of extreme situations. We concentrate our study on two Mexican events: an industrial explosion accident in 1984 and 1985 (big earthquake, both devastated big urban zones. The consequences were enormous at all levels: personal, psychological, social, political and economical. Facing risk situations people can have stress reactions when a sign of danger appears. According to Jean RIVOLIER (1994), these situations must not be confounded with banal events of everyday life. Stress in those cases is not the stress we confront everyday, so people have to apply other strategies to face she stress and the incidents of the kind of extreme situations. To tackle our subject we are going to review some concepts used in our study: stress, coping strategies and risk perception. (author)

  18. A RELAP5 study to identify flow regime in natural circulation phenomenon

    Energy Technology Data Exchange (ETDEWEB)

    Sabundjian, Gaiane; Torres, Walmir M.; Macedo, Luiz A.; Mesquita, Roberto N.; Andrade, Delvonei A.; Umbehaun, Pedro E.; Conti, Thadeu N.; Masotti, Paulo H.F.; Belchior Junior, Antonio; Angelo, Gabriel, E-mail: gdjian@ipen.b, E-mail: umbehaun@ipen.b, E-mail: wmtorres@ipen.b, E-mail: tnconti@ipen.b, E-mail: rnavarro@ipen.b, E-mail: lamacedo@ipen.b, E-mail: pmasotti@ipen.b, E-mail: abelchior@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    There has been a crescent interest in the scientific community in the study of natural circulation phenomenon. New generation of compact nuclear reactors uses the natural circulation of the fluid as a system of cooling and of residual heat removal in case of accident or shutdown. The objective of this paper is to compare the flow patterns of experimental data and numerical simulation for the natural circulation phenomenon in two-phase flow regime. An experimental circuit built with glass tubes is used for the experiments. Thus, it allows the thermal hydraulic phenomena visualization. There is an electric heater as the heat source, a heat exchanger as the heat sink and an expansion tank to accommodate fluid density excursions. The circuit instrumentation consists of thermocouples and pressure meters to better keep track of the flow and heat transfer phenomena. Data acquisition is performed through a computer interface developed with LABVIEW. The characteristic of the regime is identified using photography techniques. Numerical modeling and simulation is done with the thermal hydraulic code RELAP5, which is widely used for this purpose. This numerical simulation is capable to reproduce some of the flow regimes which are present in the circuit for the natural circulation phenomenon. Comparison between experimental and numerical simulation is presented in this work. (author)

  19. Two-phase flow patterns recognition and parameters estimation through natural circulation test loop image analysis

    Energy Technology Data Exchange (ETDEWEB)

    Mesquita, R.N.; Libardi, R.M.P.; Masotti, P.H.F.; Sabundjian, G.; Andrade, D.A.; Umbehaun, P.E.; Torres, W.M.; Conti, T.N.; Macedo, L.A. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Nuclear Engineering Center], e-mail: rnavarro@ipen.br

    2009-07-01

    Visualization of natural circulation test loop cycles is used to study two-phase flow patterns associated with phase transients and static instabilities of flow. Experimental studies on natural circulation flow were originally related to accidents and transient simulations relative to nuclear reactor systems with light water refrigeration. In this regime, fluid circulation is mainly caused by a driving force ('thermal head') which arises from density differences due to temperature gradient. Natural circulation phenomenon has been important to provide residual heat removal in cases of 'loss of pump power' or plant shutdown in nuclear power plant accidents. The new generation of compact nuclear reactors includes natural circulation of their refrigerant fluid as a security mechanism in their projects. Two-phase flow patterns have been studied for many decades, and the related instabilities have been object of special attention recently. Experimental facility is an all glass-made cylindrical tubes loop which contains about twelve demineralized water liters, a heat source by an electrical resistor immersion heater controlled by a Variac, and a helicoidal heat exchanger working as cold source. Data is obtained through thermo-pairs distributed over the loop and CCD cameras. Artificial intelligence based algorithms are used to improve (bubble) border detection and patterns recognition, in order to estimate and characterize, phase transitions patterns and correlate them with the periodic static instability (chugging) cycle observed in this circuit. Most of initial results show good agreement with previous numerical studies in this same facility. (author)

  20. Reverse primary-side flow in steam generators during natural circulation cooling

    International Nuclear Information System (INIS)

    Stumpf, H.; Motley, F.; Schultz, R.; Chapman, J.; Kukita, Y.

    1987-01-01

    A TRAC model of the Large Scale Test Facility with a 3-tube steam-generator model was used to analyze natural-circulation test ST-NC-02. For the steady state at 100% primary mass inventory, TRAC was in excellent agreement with the natural-circulation flow rate, the temperature distribution in the steam-generator tubes, and the temperature drop from the hot leg to the steam-generator inlet plenum. TRAC also predicted reverse flow in the long tubes. At reduced primary mass inventories, TRAC predicted the three natural-circulation flow regimes: single phase, two phase, and reflux condensation. TRAC did not predict the cyclic fill-and-dump phenomenon seen briefly in the test. TRAC overpredicted the two-phase natural-circulation flow rate. Since the core is well cooled at this time, the result is conservative. An important result of the analysis is that TRAC was able to predict the core dryout and heatup at approximately the same primary mass inventory as in the test. 4 refs., 8 figs., 2 tabs

  1. Experimental study on convective heat transfer of water flow in a heated tube under natural circulation

    International Nuclear Information System (INIS)

    Yang Ruichang; Liu Ruolei; Zhong Yong; Liu Tao

    2006-01-01

    This paper reports on an experimental study on transitional heat transfer of water flow in a heated vertical tube under natural circulation conditions. In the experiments the local and average heat transfer coefficients were obtained. The experimental data were compared with the predictions by a forced flow correlation available in the literature. The comparisons show that the Nusselt number value in the fully developed region is about 30% lower than the predictions by the forced flow correlation due to flow laminarization in the layer induced by co-current bulk natural circulation and free convection. By using the Rayleigh number Ra to represent the influence of free convection on heat transfer, the empirical correlations for the calculation of local and average heat transfer behavior in the tube at natural circulation have been developed. The empirical correlations are in good agreement with the experimental data. Based on the experimental results, the effect of the thermal entry-length behavior on heat transfer design in the tube under natural circulation was evaluated

  2. Two-phase flow patterns recognition and parameters estimation through natural circulation test loop image analysis

    International Nuclear Information System (INIS)

    Mesquita, R.N.; Libardi, R.M.P.; Masotti, P.H.F.; Sabundjian, G.; Andrade, D.A.; Umbehaun, P.E.; Torres, W.M.; Conti, T.N.; Macedo, L.A.

    2009-01-01

    Visualization of natural circulation test loop cycles is used to study two-phase flow patterns associated with phase transients and static instabilities of flow. Experimental studies on natural circulation flow were originally related to accidents and transient simulations relative to nuclear reactor systems with light water refrigeration. In this regime, fluid circulation is mainly caused by a driving force ('thermal head') which arises from density differences due to temperature gradient. Natural circulation phenomenon has been important to provide residual heat removal in cases of 'loss of pump power' or plant shutdown in nuclear power plant accidents. The new generation of compact nuclear reactors includes natural circulation of their refrigerant fluid as a security mechanism in their projects. Two-phase flow patterns have been studied for many decades, and the related instabilities have been object of special attention recently. Experimental facility is an all glass-made cylindrical tubes loop which contains about twelve demineralized water liters, a heat source by an electrical resistor immersion heater controlled by a Variac, and a helicoidal heat exchanger working as cold source. Data is obtained through thermo-pairs distributed over the loop and CCD cameras. Artificial intelligence based algorithms are used to improve (bubble) border detection and patterns recognition, in order to estimate and characterize, phase transitions patterns and correlate them with the periodic static instability (chugging) cycle observed in this circuit. Most of initial results show good agreement with previous numerical studies in this same facility. (author)

  3. Economic impacts of natural gas flow disruptions between Russia and the EU

    NARCIS (Netherlands)

    Bouwmeester, Maaike; Oosterhaven, Jan

    2016-01-01

    In this paper we use a non-linear programming approach to predict the wider interregional and interindustry impacts of natural gas flow disruptions. In the short run, economic actors attempt to continue their business-as-usual and follow established trade patters as closely as possible. In the model

  4. Buoyancy and Pressure Driven Flow of Hot Gases in Vertical Shafts with Natural and Forced Ventilation

    Science.gov (United States)

    Tamm, Gunnar; Jaluria, Yogesh

    2003-11-01

    An experimental investigation has been carried out on the buoyancy and pressure induced flow of hot gases in vertical shafts, in order to simulate the propagation of combustion products in elevator shafts due to fire in multilevel buildings. Various geometrical configurations are studied, with regard to natural and forced ventilation imposed at the top or bottom of the vertical shaft. The aspect ratio is taken at a fixed value of 6 and the inflow conditions for the hot gases, at a vent near the bottom, are varied in terms of the Reynolds and Grashof numbers. Temperature measurements within the shaft allow a detailed study of the steady state thermal fields, from which optimal means for smoke alleviation in high-rise building fires may be developed. Flow visualization is also used to study the flow characteristics. The results obtained indicate a wall plume as the primary transport mechanism. Flow recirculation dominates at high Grashof number flows, while increased Reynolds numbers gives rise to greater mixing in the shaft. The development and stability of the flow and its effect on the spread of smoke and hot gases are assessed for the different shaft configurations and inlet conditions. It is found that the fastest smoke removal and lowest shaft temperatures occur for a configuration with natural ventilation at the top and forced ventilation up from the shaft bottom. It is also shown that forced ventilation can be used to arrest smoke spread, as well as to dilute the effects of the fire.

  5. Reduced-order modellin for high-pressure transient flow of hydrogen-natural gas mixture

    Science.gov (United States)

    Agaie, Baba G.; Khan, Ilyas; Alshomrani, Ali Saleh; Alqahtani, Aisha M.

    2017-05-01

    In this paper the transient flow of hydrogen compressed-natural gas (HCNG) mixture which is also referred to as hydrogen-natural gas mixture in a pipeline is numerically computed using the reduced-order modelling technique. The study on transient conditions is important because the pipeline flows are normally in the unsteady state due to the sudden opening and closure of control valves, but most of the existing studies only analyse the flow in the steady-state conditions. The mathematical model consists in a set of non-linear conservation forms of partial differential equations. The objective of this paper is to improve the accuracy in the prediction of the HCNG transient flow parameters using the Reduced-Order Modelling (ROM). The ROM technique has been successfully used in single-gas and aerodynamic flow problems, the gas mixture has not been done using the ROM. The study is based on the velocity change created by the operation of the valves upstream and downstream the pipeline. Results on the flow characteristics, namely the pressure, density, celerity and mass flux are based on variations of the mixing ratio and valve reaction and actuation time; the ROM computational time cost advantage are also presented.

  6. Roads at risk: traffic detours from debris flows in southern Norway

    Science.gov (United States)

    Meyer, N. K.; Schwanghart, W.; Korup, O.; Nadim, F.

    2015-05-01

    Globalisation and interregional exchange of people, goods, and services has boosted the importance of and reliance on all kinds of transport networks. The linear structure of road networks is especially sensitive to natural hazards. In southern Norway, steep topography and extreme weather events promote frequent traffic disruption caused by debris flows. Topographic susceptibility and trigger frequency maps serve as input into a hazard appraisal at the scale of first-order catchments to quantify the impact of debris flows on the road network in terms of a failure likelihood of each link connecting two network vertices, e.g. road junctions. We compute total additional traffic loads as a function of traffic volume and excess distance, i.e. the extra length of an alternative path connecting two previously disrupted network vertices using a shortest-path algorithm. Our risk metric of link failure is the total additional annual traffic load, expressed as vehicle kilometres, because of debris-flow-related road closures. We present two scenarios demonstrating the impact of debris flows on the road network and quantify the associated path-failure likelihood between major cities in southern Norway. The scenarios indicate that major routes crossing the central and north-western part of the study area are associated with high link-failure risk. Yet options for detours on major routes are manifold and incur only little additional costs provided that drivers are sufficiently well informed about road closures. Our risk estimates may be of importance to road network managers and transport companies relying on speedy delivery of services and goods.

  7. Parametric study of natural circulation flow in molten salt fuel in molten salt reactor

    Energy Technology Data Exchange (ETDEWEB)

    Pauzi, Anas Muhamad, E-mail: Anas@uniten.edu.my [Centre of Nuclear Energy, Universiti Tenaga Nasional (UNITEN), Jalan IKRAM-UNITEN, 43000 Kajang, Selangor (Malaysia); Cioncolini, Andrea; Iacovides, Hector [School of Mechanical, Aerospace, and Civil Engineering (MACE), University of Manchester, Oxford Road, M13 9PL Manchester (United Kingdom)

    2015-04-29

    The Molten Salt Reactor (MSR) is one of the most promising system proposed by Generation IV Forum (GIF) for future nuclear reactor systems. Advantages of the MSR are significantly larger compared to other reactor system, and is mainly achieved from its liquid nature of fuel and coolant. Further improvement to this system, which is a natural circulating molten fuel salt inside its tube in the reactor core is proposed, to achieve advantages of reducing and simplifying the MSR design proposed by GIF. Thermal hydraulic analysis on the proposed system was completed using a commercial computation fluid dynamics (CFD) software called FLUENT by ANSYS Inc. An understanding on theory behind this unique natural circulation flow inside the tube caused by fission heat generated in molten fuel salt and tube cooling was briefly introduced. Currently, no commercial CFD software could perfectly simulate natural circulation flow, hence, modeling this flow problem in FLUENT is introduced and analyzed to obtain best simulation results. Results obtained demonstrate the existence of periodical transient nature of flow problem, hence improvements in tube design is proposed based on the analysis on temperature and velocity profile. Results show that the proposed system could operate at up to 750MW core power, given that turbulence are enhanced throughout flow region, and precise molten fuel salt physical properties could be defined. At the request of the authors and the Proceedings Editor the name of the co-author Andrea Cioncolini was corrected from Andrea Coincolini. The same name correction was made in the Acknowledgement section on page 030004-10 and in reference number 4. The updated article was published on 11 May 2015.

  8. Experimental study of the transition from forced to natural circulation in EBR-II at low power and flow

    International Nuclear Information System (INIS)

    Gillette, J.L.; Singer, R.M.; Tokar, J.V.; Sullivan, J.E.

    1979-01-01

    A series of tests have been conducted in EBR-II which studied the dynamics of the transition from forced to natural circulation flow in a liquid-metal-cooled fast breeder reactor (LMFBR). Each test was initiated by abruptly tripping an electromagnetic pump which supplies 5 to 6% of the normal full operational primary flow rate. The ensuing flow coast-down reached a minimum value after which the flow increased as natural circulation was established. The effects of secondary system flow through the intermediate heat exchanger and reactor decay power level on the minimum in-core flow rates and maximum in-core temperatures were examined

  9. A stratified percolation model for saturated and unsaturated flow through natural fractures

    International Nuclear Information System (INIS)

    Pyrak-Nolte, L.J.

    1990-01-01

    The geometry of the asperities of contact between the two surfaces of a fracture and of the adjacent void spaces determines fluid flow through a fracture and the mechanical deformation across a fracture. Heuristically we have developed a stratified continuum percolation model to describe this geometry based on a fractal construction that includes scale invariance and correlation of void apertures. Deformation under stress is analyzed using conservation of rock volume to correct for asperity interpenetration. Single phase flow is analyzed using a critical path along which the principal resistance is a result of laminar flow across the critical neck in this path. Results show that flow decreases with apparent aperture raised to a variable power greater than cubic, as is observed in flow experiments on natural fractures. For two phases, flow of the non-wetting phase is likewise governed by the critical neck along the critical path of largest aperture but flow of the wetting phase is governed by tortuosity. 17 refs., 10 figs

  10. Energy Efficient Thermal Management for Natural Gas Engine Aftertreatment via Active Flow Control

    Energy Technology Data Exchange (ETDEWEB)

    David K. Irick; Ke Nguyen; Vitacheslav Naoumov; Doug Ferguson

    2006-04-01

    The project is focused on the development of an energy efficient aftertreatment system capable of reducing NOx and methane by 90% from lean-burn natural gas engines by applying active exhaust flow control. Compared to conventional passive flow-through reactors, the proposed scheme cuts supplemental energy by 50%-70%. The system consists of a Lean NOx Trap (LNT) system and an oxidation catalyst. Through alternating flow control, a major amount of engine exhaust flows through a large portion of the LNT system in the absorption mode, while a small amount of exhaust goes through a small portion of the LNT system in the regeneration or desulfurization mode. By periodically reversing the exhaust gas flow through the oxidation catalyst, a higher temperature profile is maintained in the catalyst bed resulting in greater efficiency of the oxidation catalyst at lower exhaust temperatures. The project involves conceptual design, theoretical analysis, computer simulation, prototype fabrication, and empirical studies. This report details the progress during the first twelve months of the project. The primary activities have been to develop the bench flow reactor system, develop the computer simulation and modeling of the reverse-flow oxidation catalyst, install the engine into the test cell, and begin design of the LNT system.

  11. Air flow distribution in and around a single-sided naturally ventilated room

    Energy Technology Data Exchange (ETDEWEB)

    Eftekhari, M.M.; Marjanovic, L.D.; Pinnock, D.J. [Loughborough University (United Kingdom). Dept. of Civil and Building Engineering

    2002-03-01

    The objective of this research is to compare calculated and measured air flow distributions inside a test room which is naturally ventilated. The test room is situated in a relatively sheltered location and to visualise the resultant local wind pattern around the room for all prevailing wind directions, wind tunnel trials were carried out. Both the wind tunnel and full-scale measurements show that the wind direction at the test cell was generally restricted to either a westerly or an easterly direction. To investigate air flow inside the room, the air pressures and velocities across the openings together with indoor air temperature and velocity at four locations and six different levels are measured. The experimental results demonstrate that for both winter and summer the air was entering the test room at bottom and leaving at the top louvre. Separate air flow and thermal modelling programs are used to predict the spatial distribution of the air flow and thermal comfort. The air flow distribution was predicted using a network air flow program. The predicted flow showed similar trends and the simulation results were in agreement with the measured data. An explicit finite-difference thermal modeling simulation package was used to predict the thermal comfort indices.(author)

  12. Spatial Modeling of Risk in Natural Resource Management

    Directory of Open Access Journals (Sweden)

    Peter Jones

    2002-01-01

    Full Text Available Making decisions in natural resource management involves an understanding of the risk and uncertainty of the outcomes, such as crop failure or cattle starvation, and of the normal spread of the expected production. Hedging against poor outcomes often means lack of investment and slow adoption of new methods. At the household level, production instability can have serious effects on income and food security. At the national level, it can have social and economic impacts that may affect all sectors of society. Crop models such as CERES-Maize are excellent tools for assessing weather-related production variability. WATBAL is a water balance model that can provide robust estimates of the potential growing days for a pasture. These models require large quantities of daily weather data that are rarely available. MarkSim is an application for generating synthetic daily weather files by estimating the third-order Markov model parameters from interpolated climate surfaces. The models can then be run for each distinct point on the map. This paper examines the growth of maize and pasture in dryland agriculture in southern Africa. Weather simulators produce independent estimates for each point on the map; however, we know that a spatial coherence of weather exists. We investigated a method of incorporating spatial coherence into MarkSim and show that it increases the variance of production. This means that all of the farmers in a coherent area share poor yields, with important consequences for food security, markets, transport, and shared grazing lands. The long-term aspects of risk are associated with global climate change. We used the results of a Global Circulation Model to extrapolate to the year 2055. We found that low maize yields would become more likely in the marginal areas, whereas they may actually increase in some areas. The same trend was found with pasture growth. We outline areas where further work is required before these tools and methods

  13. Natural hazards on alluvial fans: the debris flow and flash flood disaster of December 1999, Vargas state, Venezuela

    Science.gov (United States)

    Larsen, Matthew C.; Wieczorek, Gerald F.; Eaton, L.S.; Torres-Sierra, Heriberto; Sylva, Walter F.

    2001-01-01

    Large populations live on or near alluvial fans in locations such as Los Angeles, California, Salt Lake City, Utah, Denver, Colorado, and lesser known areas such as Sarno, Italy, and Vargas, Venezuela. Debris flows and flash floods occur episodically in these alluvial fan environments, and place many communities at high risk during intense and prolonged rainfall. In December 1999, rainstorms induced thousands of landslides along the Cordillera de la Costa, Vargas, Venezuela. Rainfall accumulation of 293 mm during the first 2 weeks of December was followed by an additional 911 mm of rainfall on December 14 through 16. Debris flows and floods inundated coastal communities resulting in a catastrophic death toll of as many as 30,000 people. Flash floods and debris flows caused severe property destruction on alluvial fans at the mouths of the coastal mountain drainage network. In time scales spanning thousands of years, the alluvial fans along this Caribbean coastline are dynamic zones of high geomorphic activity. Because most of the coastal zone in Vargas consists of steep mountain fronts that rise abruptly from the Caribbean Sea, the alluvial fans provide practically the only flat areas upon which to build. Rebuilding and reoccupation of these areas requires careful determination of hazard zones to avoid future loss of life and property. KEY TERMS: Debris flows, flash floods, alluvial fans, natural hazards, landslides, Venezuela

  14. Study of core flow distribution for small modular natural circulation lead or lead-alloy cooled fast reactors

    International Nuclear Information System (INIS)

    Chen, Zhao; Zhao, Pengcheng; Zhou, Guangming; Chen, Hongli

    2014-01-01

    Highlights: • A core flow distribution calculation code for natural circulation LFRs was developed. • The comparison study between the channel method and the CFD method was conducted. • The core flow distribution analysis and optimization design for a 10MW natural circulation LFR was conducted. - Abstract: Small modular natural circulation lead or lead-alloy cooled fast reactor (LFR) is a potential candidate for LFR development. It has many attractive advantages such as reduced capital costs and inherent safety. The core flow distribution calculation is an important issue for nuclear reactor design, which will provide important input parameters to thermal-hydraulic analysis and safety analysis. The core flow distribution calculation of a natural circulation LFR is different from that of a forced circulation reactor. In a forced circulation reactor, the core flow distribution can be controlled and adjusted by the pump power and the flow distributor, while in a natural circulation reactor, the core flow distribution is automatically adjusted according to the relationship between the local power and the local resistance feature. In this paper, a non-uniform heated parallel channel flow distribution calculation code was developed and the comparison study between the channel method and the CFD method was carried out to assess the exactness of the developed code. The core flow distribution analysis and optimization design for a 10MW natural circulation LFR was conducted using the developed code. A core flow distribution optimization design scheme for a 10MW natural circulation LFR was proposed according to the optimization analysis results

  15. Influences of buoyancy and thermal boundary conditions on heat transfer with naturally-induced flow

    International Nuclear Information System (INIS)

    Jackson, J.D.; Li, J.

    2002-01-01

    A fundamental study is reported of heat transfer from a vertical heated tube to air which is induced naturally upwards through it by the action of buoyancy. Measurements of local heat transfer coefficient were made using a specially designed computer-controlled power supply and measurement system for conditions of uniform wall temperature and uniform wall heat flux. The effectiveness of heat transfer proved to be much lower than for conditions of forced convection. It was found that the results could be correlated satisfactorily when presented in terms of dimensionless parameters similar to those used for free convection heat transfer from vertical surfaces provided that the heat transfer coefficients were evaluated using local fluid bulk temperature calculated utilising the measured values of flow rate induced through the system. Additional experiments were performed' with pumped flow. These covered the entire mixed convection region. It was found that the data for naturally-induced flow mapped onto the pumped flow data when presented in terms of Nusselt number ratio (mixed to forced) and buoyancy parameter. Computational simulations of the experiments were performed using an advanced computer code which incorporated a buoyancy-influenced, variable property, developing wall shear flow formulation and a low Reynolds number k-ε turbulence model. These reproduced observed behaviour quite well. (author)

  16. Study of transient and permanent flow in the event of natural convection in a confined environment

    International Nuclear Information System (INIS)

    Tenchine, Denis.

    1978-01-01

    This report deals with natural convection in a confined environment, in connection with the studies on the safety of nuclear reactors of the sodium cooled breeder type (possibilities of removing the residual power of the fuel by natural convection in the liquid sodium). These natural convection exchanges develop in a confined environment between various sodium volumes separated by metallic structures. The study covered a cavity heated by the roof or by the bottom and cooled laterally. The results are compared with those achieved along heating plates, vertical or horizontal, in an infinite medium and the effect of the thermal limit conditions are highlighted by comparison with the case of bottom heated and roof cooled cavities. Placed in a bidimensional geometry situation, with water as fluid, this leads to tackling the problems of similitude between water and sodium flows. A digital code has been developed in plane bidimensional geometry with a laminar and permanent flow. A description is given of the 'BIDIM' experimental rig as well as the measuring and display devices. A permanent flow study of the two previously mentioned configurations produces references for the analysis of transient flows, particularly in the case of the heating bottom (field of medium temperatures and medium exchange coefficient). The turbulence intensity and frequency distribution determinations of the temperature changes are given. Then the determinations of the temperature changes are given. Then the determinations in transient flow are dealt with in the case of the heating bottom. The cavity being initially cold, a power rise is initiated in the heating plates and the establishment and growth of natural convection and the change in the field of medium temperatures and exchange coefficient are studied [fr

  17. Risk and size estimation of debris flow caused by storm rainfall in mountain regions

    Institute of Scientific and Technical Information of China (English)

    CHENG; Genwei

    2003-01-01

    Debris flow is a common disaster in mountain regions. The valley slope, storm rainfall and amassed sand-rock materials in a watershed may influence the types of debris flow. The bursting of debris flow is not a pure random event. Field investigations show the periodicity of its burst, but no directive evidence has been found yet. A risk definition of debris flow is proposed here based upon the accumulation and the starting conditions of loose material in channel. According to this definition, the risk of debris flow is of quasi-periodicity. A formula of risk estimation is derived. Analysis of relative factors reveals the relationship between frequency and size of debris flow. For a debris flow creek, the longer the time interval between two occurrences of debris flows is, the bigger the bursting event will be.

  18. Prediction about chaotic times series of natural circulation flow under rolling motion

    International Nuclear Information System (INIS)

    Yuan Can; Cai Qi; Guo Li; Yan Feng

    2014-01-01

    The paper have proposed a chaotic time series prediction model, which combined phase space reconstruction with support vector machines. The model has been used to predict the coolant volume flow, in which a synchronous parameter optimization method was brought up based on particle swarm optimization algorithm, since the numerical value selection of related parameter was a key factor for the prediction precision. The average relative error of prediction values and actual observation values was l,5% and relative precision was 0.9879. The result indicated that the model could apply for the natural circulation coolant volume flow prediction under rolling motion condition with high accuracy and robustness. (authors)

  19. Flow injection spectrophotometric determination of low concentrations of orthosphate in natural waters employing ion exchange resin

    International Nuclear Information System (INIS)

    Pessenda, L.C.R.

    1981-01-01

    A simple and fast method for the determination of low concentrations of orthophosphate in natural waters is described. Ion exchange is incorporated into a flow injection system by usina a resin column in the sample loop of a proportion injector. Effects of sample aspiration rate, sampling time, eluting agent concentration, pumping rate of the sample carrier stream and interfaces, were investigated both using 32 PO 3- 4 or 31 PO 3- 4 with columns coupled to a gerger-muller detector and incorporated in a flow system with molybdenum blue colorinetry. (M.A.C.) [pt

  20. Two-phase flow stability structure in a natural circulation system

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Zhiwei [Nuclear Engineering Laboratory Zurich (Switzerland)

    1995-09-01

    The present study reports a numerical analysis of two-phase flow stability structures in a natural circulation system with two parallel, heated channels. The numerical model is derived, based on the Galerkin moving nodal method. This analysis is related to some design options applicable to integral heating reactors with a slightly-boiling operation mode, and is also of general interest to similar facilities. The options include: (1) Symmetric heating and throttling; (2) Asymmetric heating and symmetric throttling; (3) Asymmetric heating and throttling. The oscillation modes for these variants are discussed. Comparisons with the data from the INET two-phase flow stability experiment have qualitatively validated the present analysis.

  1. Velocity Fields Measurement of Natural Circulation Flow inside a Pool Using PIV Technique

    International Nuclear Information System (INIS)

    Kim, Seok; Kim, Dong Eok; Youn, Young Jung; Euh, Dong Jin; Song, Chul Hwa

    2012-01-01

    Thermal stratification is encountered in large pool of water increasingly being used as heat sink in new generation of advanced reactors. These large pools at near atmospheric pressure provide a heat sink for heat removal from the reactor or steam generator, and the containment by natural circulation as well as a source of water for core cooling. For examples, the PAFS (passive auxiliary feedwater system) is one of the advanced safety features adopted in the APR+ (Advanced Power Reactor Plus), which is intended to completely replace the conventional active auxiliary feedwater system. The PAFS cools down the steam generator secondary side and eventually removes the decay heat from the reactor core by adopting a natural convection mechanism. In a pool, the heat transfer from the PCHX (passive condensation heat exchanger) contributed to increase the pool temperature up to the saturation condition and induce the natural circulation flow of the PCCT (passive condensate cooling tank) pool water. When a heat rod is placed horizontally in a pool of water, the fluid adjacent to the heat rod gets heated up. In the process, its density reduces and by virtue of the buoyancy force, the fluid in this region moves up. After reaching the top free surface, the heated water moves towards the other side wall of the pool along the free surface. Since this heated water is cooling, it goes downward along the wall at the other side wall. Above heater rod, a natural circulation flow is formed. However, there is no flow below heater rod until pool water temperature increases to saturation temperature. In this study, velocity measurement was conducted to reveal a natural circulation flow structure in a small pool using PIV (particle image velocimetry) measurement technique

  2. Unified fluid flow model for pressure transient analysis in naturally fractured media

    International Nuclear Information System (INIS)

    Babak, Petro; Azaiez, Jalel

    2015-01-01

    Naturally fractured reservoirs present special challenges for flow modeling with regards to their internal geometrical structure. The shape and distribution of matrix porous blocks and the geometry of fractures play key roles in the formulation of transient interporosity flow models. Although these models have been formulated for several typical geometries of the fracture networks, they appeared to be very dissimilar for different shapes of matrix blocks, and their analysis presents many technical challenges. The aim of this paper is to derive and analyze a unified approach to transient interporosity flow models for slightly compressible fluids that can be used for any matrix geometry and fracture network. A unified fractional differential transient interporosity flow model is derived using asymptotic analysis for singularly perturbed problems with small parameters arising from the assumption of a much smaller permeability of the matrix blocks compared to that of the fractures. This methodology allowed us to unify existing transient interporosity flow models formulated for different shapes of matrix blocks including bounded matrix blocks, unbounded matrix cylinders with any orthogonal crossection, and matrix slabs. The model is formulated using a fractional order diffusion equation for fluid pressure that involves Caputo derivative of order 1/2 with respect to time. Analysis of the unified fractional derivative model revealed that the surface area-to-volume ratio is the key parameter in the description of the flow through naturally fractured media. Expressions of this parameter are presented for matrix blocks of the same geometrical shape as well as combinations of different shapes with constant and random sizes. Numerical comparisons between the predictions of the unified model and those obtained from existing transient interporosity ones for matrix blocks in the form of slabs, spheres and cylinders are presented for linear, radial and spherical flow types for

  3. Dynamic behaviour of high-pressure natural-gas flow in pipelines

    International Nuclear Information System (INIS)

    Gato, L.M.C.; Henriques, J.C.C.

    2005-01-01

    The aim of the present study is the numerical modelling of the dynamic behaviour of high-pressure natural-gas flow in pipelines. The numerical simulation was performed by solving the conservation equations, for one-dimensional compressible flow, using the Runge-Kutta discontinuous Galerkin method, with third-order approximation in space and time. The boundary conditions were imposed using a new weak formulation based on the characteristic variables. The occurrence of pressure oscillations in natural-gas pipelines was studied as a result of the compression wave originated by the rapid closure of downstream shut-off valves. The effect of the partial reflection of pressure waves was also analyzed in the transition between pipes of different cross-sectional areas

  4. Discrete-Roughness-Element-Enhanced Swept-Wing Natural Laminar Flow at High Reynolds Numbers

    Science.gov (United States)

    Malik, Mujeeb; Liao, Wei; Li, Fei; Choudhari, Meelan

    2015-01-01

    Nonlinear parabolized stability equations and secondary-instability analyses are used to provide a computational assessment of the potential use of the discrete-roughness-element technology for extending swept-wing natural laminar flow at chord Reynolds numbers relevant to transport aircraft. Computations performed for the boundary layer on a natural-laminar-flow airfoil with a leading-edge sweep angle of 34.6 deg, freestream Mach number of 0.75, and chord Reynolds numbers of 17 × 10(exp 6), 24 × 10(exp 6), and 30 × 10(exp 6) suggest that discrete roughness elements could delay laminar-turbulent transition by about 20% when transition is caused by stationary crossflow disturbances. Computations show that the introduction of small-wavelength stationary crossflow disturbances (i.e., discrete roughness element) also suppresses the growth of most amplified traveling crossflow disturbances.

  5. Analysis of natural convection heat transfer and flows in internally heated stratified liquid pools

    International Nuclear Information System (INIS)

    Gubaidullin, A.A. Jr.; Dinh, T.N.; Sehgal, B.R.

    1999-01-01

    In this paper, natural convection flows and heat transfer in a liquid pool, with two superposed immiscible fluid layers, are analyzed. The objective of the study is to examine the effect of interfacial hydrodynamics and to develop a method which enables energy splitting to be evaluated in a stratified liquid pool. The thermal convection, with and without an internal heat source, in a rectangular cavity with different pairs of fluids was numerically simulated by a CFD code FLOW-3D. It was found that the code performs very well for prediction of heat transfer coefficients for different conditions. The hydrodynamic coupling between immiscible layers was found to have minor, if any, impact on the natural convection heat transfer for the conditions examined. Calculated results were used to develop, and validate, a new correlation for energy splitting and for heat transfer in stratified liquid pools

  6. Dynamic behaviour of high-pressure natural-gas flow in pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Gato, L.M.C. [Department of Mechanical Engineering, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)]. E-mail: lgato@mail.ist.utl.pt; Henriques, J.C.C. [Department of Mechanical Engineering, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)]. E-mail: jcch@mail.ist.utl.pt

    2005-10-01

    The aim of the present study is the numerical modelling of the dynamic behaviour of high-pressure natural-gas flow in pipelines. The numerical simulation was performed by solving the conservation equations, for one-dimensional compressible flow, using the Runge-Kutta discontinuous Galerkin method, with third-order approximation in space and time. The boundary conditions were imposed using a new weak formulation based on the characteristic variables. The occurrence of pressure oscillations in natural-gas pipelines was studied as a result of the compression wave originated by the rapid closure of downstream shut-off valves. The effect of the partial reflection of pressure waves was also analyzed in the transition between pipes of different cross-sectional areas.

  7. DRE-Enhanced Swept-Wing Natural Laminar Flow at High Reynolds Numbers

    Science.gov (United States)

    Malik, Mujeeb; Liao, Wei; Li, Fe; Choudhari, Meelan

    2013-01-01

    Nonlinear parabolized stability equations and secondary instability analyses are used to provide a computational assessment of the potential use of the discrete roughness elements (DRE) technology for extending swept-wing natural laminar flow at chord Reynolds numbers relevant to transport aircraft. Computations performed for the boundary layer on a natural laminar flow airfoil with a leading-edge sweep angle of 34.6deg, free-stream Mach number of 0.75 and chord Reynolds numbers of 17 x 10(exp 6), 24 x 10(exp 6) and 30 x 10(exp 6) suggest that DRE could delay laminar-turbulent transition by about 20% when transition is caused by stationary crossflow disturbances. Computations show that the introduction of small wavelength stationary crossflow disturbances (i.e., DRE) also suppresses the growth of most amplified traveling crossflow disturbances.

  8. Dynamic Optimal Energy Flow in the Integrated Natural Gas and Electrical Power Systems

    DEFF Research Database (Denmark)

    Fang, Jiakun; Zeng, Qing; Ai, Xiaomeng

    2018-01-01

    . Simulation on the test case illustrates the success of the modelling and the beneficial roles of the power-to-gas are analyzed. The proposed model can be used in the decision support for both planning and operation of the coordinated natural gas and electrical power systems.......This work focuses on the optimal operation of the integrated gas and electrical power system with bi-directional energy conversion. Considering the different response times of the gas and power systems, the transient gas flow and steady- state power flow are combined to formulate the dynamic...... optimal energy flow in the integrated gas and power systems. With proper assumptions and simplifications, the problem is transformed into a single stage linear programming. And only a single stage linear programming is needed to obtain the optimal operation strategy for both gas and power systems...

  9. Cash Flow and Discount Rate Risk in Up and Down Markets: What is actually priced?

    NARCIS (Netherlands)

    Botshekan, M.; Kraeussl, R.G.W.; Lucas, A.

    2012-01-01

    We test whether asymmetric preferences for losses versus gains affect the prices of cash flow versus discount rate risk. We construct a return decomposition distinguishing cash flow and discount rate betas in up and down markets. Using U.S. data, we find that downside cash flow and discount rate

  10. Computational Fluid Dynamics Modeling to Improve Natural Flow Rate and Sweet Pepper Productivity in Greenhouse

    OpenAIRE

    W. Limtrakarn; P. Boonmongkol; A. Chompupoung; K. Rungprateepthaworn; J. Kruenate; P. Dechaumphai

    2012-01-01

    Natural flow rate and sweet peppers productivity in tropical greenhouse are improved by CFD simulation is the main objective of this research work. Most of the greenhouse types today are in the arch shape. To develop an improved greenhouse structure for the region, the arch type was built and used as the control model. Mae Sar Mai agriculture research station under the royal project foundation was selected as the field test site. Temperature sensors with data logger were installed to monitor ...

  11. The Fractional Step Method Applied to Simulations of Natural Convective Flows

    Science.gov (United States)

    Westra, Douglas G.; Heinrich, Juan C.; Saxon, Jeff (Technical Monitor)

    2002-01-01

    This paper describes research done to apply the Fractional Step Method to finite-element simulations of natural convective flows in pure liquids, permeable media, and in a directionally solidified metal alloy casting. The Fractional Step Method has been applied commonly to high Reynold's number flow simulations, but is less common for low Reynold's number flows, such as natural convection in liquids and in permeable media. The Fractional Step Method offers increased speed and reduced memory requirements by allowing non-coupled solution of the pressure and the velocity components. The Fractional Step Method has particular benefits for predicting flows in a directionally solidified alloy, since other methods presently employed are not very efficient. Previously, the most suitable method for predicting flows in a directionally solidified binary alloy was the penalty method. The penalty method requires direct matrix solvers, due to the penalty term. The Fractional Step Method allows iterative solution of the finite element stiffness matrices, thereby allowing more efficient solution of the matrices. The Fractional Step Method also lends itself to parallel processing, since the velocity component stiffness matrices can be built and solved independently of each other. The finite-element simulations of a directionally solidified casting are used to predict macrosegregation in directionally solidified castings. In particular, the finite-element simulations predict the existence of 'channels' within the processing mushy zone and subsequently 'freckles' within the fully processed solid, which are known to result from macrosegregation, or what is often referred to as thermo-solutal convection. These freckles cause material property non-uniformities in directionally solidified castings; therefore many of these castings are scrapped. The phenomenon of natural convection in an alloy under-going directional solidification, or thermo-solutal convection, will be explained. The

  12. Tacking Flood Risk from Watersheds using a Natural Flood Risk Management Toolkit

    Science.gov (United States)

    Reaney, S. M.; Pearson, C.; Barber, N.; Fraser, A.

    2017-12-01

    In the UK, flood risk management is moving beyond solely mitigating at the point of impact in towns and key infrastructure to tackle problem at source through a range of landscape based intervention measures. This natural flood risk management (NFM) approach has been trailed within a range of catchments in the UK and is moving towards being adopted as a key part of flood risk management. The approach offers advantages including lower cost and co-benefits for water quality and habitat creation. However, for an agency or group wishing to implement NFM within a catchment, there are two key questions that need to be addressed: Where in the catchment to place the measures? And how many measures are needed to be effective? With this toolkit, these questions are assessed with a two-stage workflow. First, SCIMAP-Flood gives a risk based mapping of likely locations that contribute to the flood peak. This tool uses information on land cover, hydrological connectivity, flood generating rainfall patterns and hydrological travel time distributions to impacted communities. The presented example applies the tool to the River Eden catchment, UK, with 5m grid resolution and hence provide sub-field scale information at the landscape extent. SCIMAP-Flood identifies sub-catchments where physically based catchment hydrological simulation models can be applied to test different NFM based mitigation measures. In this example, the CRUM3 catchment hydrological model has been applied within an uncertainty framework to consider the effectiveness of soil compaction reduction and large woody debris dams within a sub-catchment. It was found that large scale soil aeration to reduce soil compaction levels throughout the catchment is probably the most useful natural flood management measure for this catchment. NFM has potential for wide-spread application and these tools help to ensure that the measures are correctly designed and the scheme performance can be quantitatively assessed and predicted.

  13. Instrumental record of debris flow initiation during natural rainfall: Implications for modeling slope stability

    Science.gov (United States)

    Montgomery, D.R.; Schmidt, K.M.; Dietrich, W.E.; McKean, J.

    2009-01-01

    The middle of a hillslope hollow in the Oregon Coast Range failed and mobilized as a debris flow during heavy rainfall in November 1996. Automated pressure transducers recorded high spatial variability of pore water pressure within the area that mobilized as a debris flow, which initiated where local upward flow from bedrock developed into overlying colluvium. Postfailure observations of the bedrock surface exposed in the debris flow scar reveal a strong spatial correspondence between elevated piezometric response and water discharging from bedrock fractures. Measurements of apparent root cohesion on the basal (Cb) and lateral (Cl) scarp demonstrate substantial local variability, with areally weighted values of Cb = 0.1 and Cl = 4.6 kPa. Using measured soil properties and basal root strength, the widely used infinite slope model, employed assuming slope parallel groundwater flow, provides a poor prediction of hydrologie conditions at failure. In contrast, a model including lateral root strength (but neglecting lateral frictional strength) gave a predicted critical value of relative soil saturation that fell within the range defined by the arithmetic and geometric mean values at the time of failure. The 3-D slope stability model CLARA-W, used with locally observed pore water pressure, predicted small areas with lower factors of safety within the overall slide mass at sites consistent with field observations of where the failure initiated. This highly variable and localized nature of small areas of high pore pressure that can trigger slope failure means, however, that substantial uncertainty appears inevitable for estimating hydrologie conditions within incipient debris flows under natural conditions. Copyright 2009 by the American Geophysical Union.

  14. Effect of ship motions and flow stability in a small marine reactor driven by natural circulation

    International Nuclear Information System (INIS)

    Yoritsune, Tsutomu; Ishida, Toshihisa

    2001-12-01

    By using a small reactor as a power source for investigations and developments under sea, widely expanded activity is expectable. In this case, as for a nuclear reactor, small-size and lightweightness, and simplification of a system are needed with the safety. In JAERI, very small reactors for submersible research vessel (Deep-sea Reactor DRX and submersible Compact Reactor SCR) have been designed on the basis of needs investigation of sea research. Although the reactor is a PWR type, self-pressurization and natural circulation system are adopted in a primary system for small size and lightweightness. The fluid flow condition of the reactor core outlet is designed to be the two-phase with a low quality. Although the flow of a primary system is the two-phase flow with a low quality, the density wave oscillation may occur according to operating conditions. Moreover, since there are ship motions of heaving (the vertical direction acceleration) etc., when a submersible research vessel navigates on the sea surface, the circulation flow of the primary system is directly influenced by this external force. In order to maintain stable operations of the reactor, it is necessary to clarify effects of the flow stability characteristic of the primary coolant system and the external force. Until now, as for the flow stability of a nuclear reactor itself, many research reports have been published including the nuclear-coupled thermal oscillation of BWRs such as LaSalle-2, WNP-2 etc. As for the effect of external force, it is reported that the acceleration change based on a seismic wave affects the reactor core flow and the reactor power in a BWR. On the other hand, also in a PWR, since adoption of natural circulation cooling is considered for a generation 4 reactor, it is thought that the margin of the reactor core flow stability becomes an important parameter in the design. The reactor coolant flow mentioned in this report is the two-phase natural circulation flow coupled with

  15. "Near-term" Natural Catastrophe Risk Management and Risk Hedging in a Changing Climate

    Science.gov (United States)

    Michel, Gero; Tiampo, Kristy

    2014-05-01

    Competing with analytics - Can the insurance market take advantage of seasonal or "near-term" forecasting and temporal changes in risk? Natural perils (re)insurance has been based on models following climatology i.e. the long-term "historical" average. This is opposed to considering the "near-term" and forecasting hazard and risk for the seasons or years to come. Variability and short-term changes in risk are deemed abundant for almost all perils. In addition to hydrometeorological perils whose changes are vastly discussed, earthquake activity might also change over various time-scales affected by earlier local (or even global) events, regional changes in the distribution of stresses and strains and more. Only recently has insurance risk modeling of (stochastic) hurricane-years or extratropical-storm-years started considering our ability to forecast climate variability herewith taking advantage of apparent correlations between climate indicators and the activity of storm events. Once some of these "near-term measures" were in the market, rating agencies and regulators swiftly adopted these concepts demanding companies to deploy a selection of more conservative "time-dependent" models. This was despite the fact that the ultimate effect of some of these measures on insurance risk was not well understood. Apparent short-term success over the last years in near-term seasonal hurricane forecasting was brought to a halt in 2013 when these models failed to forecast the exceptional shortage of hurricanes herewith contradicting an active-year forecast. The focus of earthquake forecasting has in addition been mostly on high rather than low temporal and regional activity despite the fact that avoiding losses does not by itself create a product. This presentation sheds light on new risk management concepts for over-regional and global (re)insurance portfolios that take advantage of forecasting changes in risk. The presentation focuses on the "upside" and on new opportunities

  16. Assessing natural hazards in forestry for risk management: a review

    Science.gov (United States)

    Marc Hanewinkel; Susan Hummel; Axel Albrecht

    2011-01-01

    We address the problem of how to integrate risk assessment into forest management and therefore provide a comprehensive review of recent and past literature on risk analysis and modeling and, moreover, an evaluation and summary on these papers. We provide a general scheme on how to integrate concepts of risk into forest management decisions. After an overview of the...

  17. Laboratory studies of groundwater degassing in replicas of natural fractured rock for linear flow geometry

    International Nuclear Information System (INIS)

    Geller, J.T.

    1998-02-01

    Laboratory experiments to simulate two-phase (gas and water) flow in fractured rock evolving from groundwater degassing were conducted in transparent replicas of natural rock fractures. These experiments extend the work by Geller et al. (1995) and Jarsjo and Geller (1996) that tests the hypothesis that groundwater degassing caused observed flow reductions in the Stripa Simulated Drift Experiment (SDE). Understanding degassing effects over a range of gas contents is needed due to the uncertainty in the gas contents of the water at the SDE. The main objectives of this study were to: (1) measure the effect of groundwater degassing on liquid flow rates for lower gas contents than the values used in Geller for linear flow geometry in the same fracture replicas of Geller; (2) provide a data set to develop a predictive model of two-phase flow in fractures for conditions of groundwater degassing; and (3) improve the certainty of experimental gas contents (this effort included modifications to the experimental system used by Geller et al. and separate gas-water equilibration tests). The Stripa site is being considered for a high-level radioactive waste repository

  18. From cat's eyes to disjoint multicellular natural convection flow in tall tilted cavities

    Energy Technology Data Exchange (ETDEWEB)

    Nicolas, Alfredo, E-mail: anc@xanum.uam.mx [Depto. Matematicas, 3er Piso Ed. AT-Diego Bricio, UAM-I, 09340 Mexico D.F. (Mexico); Baez, Elsa [Depto. Matematicas Aplicadas y Sistemas, UAM-C, 01120 Mexico D.F. (Mexico); Bermudez, Blanca [Facultad de C. de la Computacion, BUAP, 72570 Puebla, Pue. (Mexico)

    2011-07-11

    Numerical results of two-dimensional natural convection problems, in air-filled tall cavities, are reported to study the change of the cat's eyes flow as some parameters vary, the aspect ratio A and the angle of inclination φ of the cavity, with the Rayleigh number Ra mostly fixed; explicitly, the range of the variation is given by 12≤A≤20 and 0{sup o}≤φ≤270{sup o}; about Ra=1.1x10{sup 4}. A novelty contribution of this work is the transition from the cat's eyes changes, as A varies, to a disjoint multicellular flow, as φ varies. These flows may be modeled by the unsteady Boussinesq approximation in stream function and vorticity variables which is solved with a fixed point iterative process applied to the nonlinear elliptic system that results after time discretization. The validation of the results relies on mesh size and time-step independence studies. -- Highlights: → Fixed point iterative method for solving symmetric linear elliptic problems. → Robust method to study effects as aspect ratio and angle of inclination vary. → Interest on the dynamics and evolution of the fluid flow and on heat transfer. → Study of transition from cat's eyes instability to a disjoint multicellular flow.

  19. Assessing Ecological Flow Needs and Risks for Springs and Baseflow Streams With Growth and Climate Change

    Science.gov (United States)

    Springer, A. E.; Stevens, L. E.

    2008-12-01

    Ecological flow needs assessments are beginning to become an important part of regulated river management, but are more challenging for unregulated rivers. Water needs for ecosystems are greater than just consumptive use by riparian and aquatic vegetation and include the magnitude, frequency, duration and timing of flows and the depth and annual fluctuations of groundwater levels of baseflow supported streams. An ecological flow needs assessment was adapted and applied to an unregulated, baseflow dependent river in the arid to semi-arid Southwestern U.S. A separate process was developed to determine groundwater sources potentially at risk from climate, land management, or groundwater use changes in a large regional groundwater basin in the same semi-arid region. In 2007 and 2008, workshops with ecological, cultural, and physical experts from agencies, universities, tribes, and other organizations were convened. Flow-ecology response functions were developed with either conceptual or actual information for a baseflow dependent river, and scoring systems were developed to assign values to categories of risks to groundwater sources in a large groundwater basin. A reduction of baseflow to the river was predicted to lead to a decline in cottonwood and willow tree abundance, decreases in riparian forest diversity, and increases in non-native tree species, such as tamarisk. These types of forest vegetation changes would likely cause reductions or loss of some bird species. Loss of riffle habitat through declines in groundwater discharge and the associated river levels would likely lead to declines in native fish and amphibian species. A research agenda was developed to develop techniques to monitor, assess and hopefully better manage the aquifers supporting the baseflow dependent river to prevent potential threshold responses of the ecosystems. The scoring system for categories of risk was applied to four systems (aquifers, springs, standing water bodies, and streams) in

  20. Integrated risk management in a commercial market-maker bank using the 'cash flow at risk' approach

    OpenAIRE

    Voloshyn, Ihor; Voloshyn, Mykyta

    2013-01-01

    In this article, on the basis of the "cash flow at risk" approach, the system of the integrated (credit, market, operational and liquidity risks) risk management in a market-maker commercial bank is developed. This system guarantees reaching profitability, liquidity and coverage of banking risks and thus allows the fullest protection of the interests of depositors, creditors and shareholders of the bank providing its sustainable development.

  1. Risk assessment of natural disasters in the course of selection of nuclear waste disposal

    International Nuclear Information System (INIS)

    Wu Weicheng; Ai Guigen

    1995-01-01

    Natural disasters are calamities which bring about enormous damage to human beings and their accommodations and equipment. Based on the research of disaster risk and example study of volcanism, we tried to carry out the risk assessment of natural disasters which potentially occur in the candidate area of nuclear waste disposal by three steps of analyses, defining the most frequent occurring area of disasters, determining the parameters of risk assessment and dividing the most dangerous site and risk grades

  2. Transient behavior of natural circulation for boiling two-phase flow, 2

    International Nuclear Information System (INIS)

    Aritomi, Masanori; Chiang, Jing-Hsien; Mori, Michitugu.

    1991-01-01

    In this set of experiments, natural circulation in boiling two-phase flow has been investigated for power transients, simulating the start-up process in a natural circulation BWR. This was done in order to understand the underlying mechanism of thermo-hydraulic instability which may appear during a start-up. In this paper, geysering is dealt with especially and the driving mechanism is clarified by investigating the stability related to effects of inlet velocity, subcooling, temperature in an outlet plenum and non-heated length between heated section and the outlet plenum. Furthermore, by considering these results and the operational experience in the Dodewaard reactor, recommendations on how the thermo-hydraulic instabilities can be prevented from occurring are proposed concerning a reactor configuration and start-up procedure for natural circulation BWRs. (author)

  3. Experimental Study on Pressure Drop and Flow Dispersion in Packed Bed of Natural Zeolite

    Directory of Open Access Journals (Sweden)

    Ruya Petric Marc

    2018-01-01

    Full Text Available The use of conventional correlation for pressure drop and dispersion coefficient calculation may result in inaccurate values for zeolite packed bed as the correlations are generally developed for regularly shaped and uniformly sized particles. To support the research on the application of modified natural zeolite as tar cracking catalyst, the research on the hydrodynamic behaviour of zeolite packed bed has been conducted. Experiments were carried out using a glass column with diameter of 37.8 mm. Natural zeolite with particle size of about 2.91 to 6.4 mm was applied as packing material in the column, and the bed height was varied at 9, 19 and 29 cm. Air was used as the fluid that flows through the bed and nitrogen was used as a tracer for residence time distribution determination. Air flow rates were in the range of 20 to 100 mL/s which correspond to the laminar-transitional flow regime. The pressure drops through the bed were in the range of 1.7 to 95.6 Pa, depending on the air flow rate and bed height. From these values, the parameters in the Ergun equation were estimated, taking into account the contribution by wall effect when the ratio of column to particle diameter is low. The viscous and inertial term constants in the Ergun equation calculated ranges from 179 to 199 and 1.41 to 1.47 respectively while the particle sphericity ranges from 0.56 to 0.59. The reactor Peclet number were determined to range from 5.2 to 5.5, which indicated significant deviation from a plug flow condition.

  4. Effectiveness of horizontal air flow fans supporting natural ventilation in a Mediterranean multi-span greenhouse

    Directory of Open Access Journals (Sweden)

    Alejandro López

    2013-08-01

    Full Text Available Natural ventilation is the most important method of climate control in Mediterranean greenhouses. In this study, the microclimate and air flow inside a Mediterranean greenhouse were evaluated by means of sonic anemometry. Experiments were carried out in conditions of moderate wind (≈ 4.0 m s-1, and at low wind speed (≈ 1.8 m s-1 the natural ventilation of the greenhouse was supplemented by two horizontal air flow fans. The greenhouse is equipped with a single roof vent opening to the windward side and two side vents, the windward one being blocked by another greenhouse close to it, while the leeward one is free of obstacles. When no fans are used, air enters through the roof vent and exits through both side vents, thus flowing contrary to the thermal effect which causes hot air to rise and impairing the natural ventilation of the greenhouse. Using fans inside the greenhouse helps the air to circulate and mix, giving rise to a more homogeneous inside temperature and increasing the average value of normalized air velocity by 365 %. These fans also increase the average values of kinetic turbulence energy inside the greenhouse by 550 % compared to conditions of natural ventilation. As the fans are placed 4 m away from the side vents, their effect on the entrance of outside air is insufficient and they do not help to reduce the inside temperature on hot days with little wind. It is therefore recommended to place the fans closer to the side vents to allow an additional increase of the air exchange rate of greenhouses.

  5. Economic impacts of natural gas flow disruptions between Russia and the EU

    International Nuclear Information System (INIS)

    Bouwmeester, Maaike C.; Oosterhaven, J.

    2017-01-01

    In this paper we use a non-linear programming approach to predict the wider interregional and interindustry impacts of natural gas flow disruptions. In the short run, economic actors attempt to continue their business-as-usual and follow established trade patters as closely as possible. In the model this is modelled by minimizing the information gain between the original pattern of economic transactions and the situation in which natural gas flows are disrupted. We analyze four scenarios that simulate Russian export stops of natural gas by means of a model calibrated on an international input-output table with six sectors and six regions. The simulations show that at the lower levels of aggregation considerable effects are found. At the aggregate level of the whole economy, however, the impacts of the four scenarios are negligible for Europe and only a little less so for Russia itself. Interestingly, the effects on the size of the economy, as measured by its GDP, are predominantly positive for the various European regions, but negative for Russia. The effects on the welfare of the populations involved, however, as measured by the size of domestic final demand, have an opposite sign; with predominantly negligible but negative effects for European regions, and very small positive effects for the Russian population. - Highlights: • First application of new model for wider economic impacts of disasters and trade boycotts. • Russian natural gas export stops would have considerable impacts on international gas flows. • Wider economic impacts on the EU are negligible. Those on Russia only a little larger. • Impacts on GDP are positive for the EU and negative for Russia. • Impacts on welfare (domestic final demand) have an opposite sign.

  6. Estimating the Natural Flow Regime of Rivers With Long-Standing Development: The Northern Branch of the Rio Grande

    Science.gov (United States)

    Blythe, Todd L.; Schmidt, John C.

    2018-02-01

    An estimate of a river's natural flow regime is useful for water resource planning and ecosystem rehabilitation by providing insight into the predisturbance form and function of a river. The natural flow regime of most rivers has been perturbed by development during the 20th century and in some cases, before stream gaging began. The temporal resolution of natural flows estimated using traditional methods is typically not sufficient to evaluate cues that drive native ecosystem function. Additionally, these traditional methods are watershed specific and require large amounts of data to produce accurate results. We present a mass balance method that estimates natural flows at daily time step resolution for the northern branch of the Rio Grande, upstream from the Rio Conchos, that relies only on easily obtained streamflow data. Using an analytical change point method, we identified periods of the measured flow regime during the 20th century for comparison with the estimated natural flows. Our results highlight the significant deviation from natural conditions that occurred during the 20th century. The total annual flow of the northern branch is 95% lower than it would be in the absence of human use. The current 2 year flood has decreased by more than 60%, is shorter in duration, and peaks later in the year. When compared to unregulated flows estimated using traditional mass balance accounting methods, our approach provides similar results.

  7. Parameters, which effect the mass flow in the PRHRS under a natural convection condition

    International Nuclear Information System (INIS)

    Chung, Y. J.; Lee, G. H.; Kim, H. C.; Kim, K. K.; Zee, S. Q.

    2004-01-01

    Small and medium sized integral type reactors for the diverse utilization of nuclear energy are getting much attention from the international nuclear community. They diversify the peaceful uses of nuclear energy in the areas of seawater desalination, district heating, industrial heat-generation process and ship propulsion. The SMART (System integrated Modular Advanced ReacTor) is a small modular integral type pressurized water reactor, which was developed for the dual purposes application of seawater desalination and small-scaled power generation in KOREA. The reactor is designed for a forced convection core cooling during start-up and normal operating conditions and for a natural circulation core cooling during accidental conditions. The main safety objective of the SMART is to increase the degree of inherent safety features by advanced designs such as a passive residual heat removal system (PRHRS). The passive residual heat removal system removes the core decay heat and sensible heat by a natural circulation in the case of emergency conditions. This study focuses on the flow behavior in the passive residual heat removal system of the integral reactor. The system necessitates a hydraulic head to achieve the required natural circulation flow rate, which in turn, may cause a larger two-phase pressure drop and flow oscillation. Also, it is of interest to investigate the complex effects of the boiling and condensation in such low frequency thermo-hydraulic oscillations. Thermal hydraulic analysis for the passive residual heat removal system has been carried out by means of the MARS code for a full range of reactor operating conditions. The MARS code has been developed at the Korea Atomic Energy Research Institute by consolidating and restructuring the RELAP5/MOD3.2 and COBRA-TF which has the capabilities of analyzing the one-dimensional or three-dimensional best estimated thermal-hydraulic system and the fuel responses of the light water reactor transients. A selected

  8. Applying the Land Use Portfolio Model with Hazus to analyse risk from natural hazard events

    Science.gov (United States)

    Dinitz, Laura B.; Taketa, Richard A.

    2013-01-01

    This paper describes and demonstrates the integration of two geospatial decision-support systems for natural-hazard risk assessment and management. Hazus is a risk-assessment tool developed by the Federal Emergency Management Agency to identify risks and estimate the severity of risk from natural hazards. The Land Use Portfolio Model (LUPM) is a risk-management tool developed by the U.S. Geological Survey to evaluate plans or actions intended to reduce risk from natural hazards. We analysed three mitigation policies for one earthquake scenario in the San Francisco Bay area to demonstrate the added value of using Hazus and the LUPM together. The demonstration showed that Hazus loss estimates can be input to the LUPM to obtain estimates of losses avoided through mitigation, rates of return on mitigation investment, and measures of uncertainty. Together, they offer a more comprehensive approach to help with decisions for reducing risk from natural hazards.

  9. Unsteady single-phase natural circulation flow mixing prediction using CATHARE three-dimensional capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Salah, Anis Bousbia; Vlassenbroeck, Jacques [Bel V - Subsidiary of the Belgian Federal Agency for Nuclear Contro, Brussels (Belize)

    2017-04-15

    Coolant mixing under natural circulation flow regime constitutes a key parameter that may play a role in the course of an accidental transient in a nuclear pressurized water reactor. This issue has motivated some experimental investigations carried out within the OECD/NEA PKL projects. The aim was to assess the coolant mixing phenomenon in the reactor pressure vessel downcomer and the core lower plenum under several asymmetric steady and unsteady flow conditions, and to provide experimental data for code validations. Former studies addressed the mixing phenomenon using, on the one hand, one-dimensional computational approaches with cross flows that are not fully validated under transient conditions and, on the other hand, expensive computational fluid dynamic tools that are not always justified for large-scale macroscopic phenomena. In the current framework, an unsteady coolant mixing experiment carried out in the Rossendorf coolant mixing test facility is simulated using the three-dimensional porous media capabilities of the thermal–hydraulic system CATHARE code. The current study allows highlighting the current capabilities of these codes and their suitability for reproducing the main phenomena occurring during asymmetric transient natural circulation mixing conditions.

  10. An experimental study of two-phase natural circulation in an adiabatic flow loop

    International Nuclear Information System (INIS)

    Tan, M.J.; Lambert, G.A.; Ishii, Mamoru.

    1988-01-01

    An experimental investigation was conducted to study the two-phase flow aspect of the phenomena of interruption and resumption of natural circulation, two-phase flow patterns and pattern transitions in the hot legs of B and W light water reactor systems. The test facility was a scaled adiabatic loop designed in accordance with the scaling criteria developed by Kocamustafaogullari and Ishii. The diameter and the height of the hot leg were 10 cm and 5.5 m, respectively; the working fluid pair was nitrogen-water. The effects of the thermal center in the steam generators, friction loss in the cold leg, and configuration of the inlet to the hot leg on the flow conditions in the hot leg were investigated by varying the water level in a gas separator, controlling the size of opening of a friction loss control valve, and using two inlet geometries. Methods for estimating the distribution parameter and the average drift velocity are proposed so that they may be used in the application of one-dimensional drift-flux model to the analysis of the interruption and resumption of natural circulation in a similar geometry. 7 refs., 17 figs., 4 tabs

  11. Study of flow instabilities in double-channel natural circulation boiling systems

    International Nuclear Information System (INIS)

    Durga Prasad, Gonella V.; Pandey, Manmohan; Pradhan, Santosh K.; Gupta, Satish K.

    2008-01-01

    Natural circulation boiling systems consisting of parallel channels can undergo different types of oscillations (in-phase or out-of-phase) depending on the geometric parameters and operating conditions. Disturbances in one channel affect the flow in other channels, which triggers thermal-hydraulic oscillations. In the present work, the modes of oscillation under different operating conditions and channel-to-channel interaction during power fluctuations and on-power refueling in a double-channel natural circulation boiling system are investigated. The system is modeled using a lumped parameter mathematical model and RELAP5/MOD3.4. Parametric studies are carried out for an equal-power double-channel system, at different operating conditions, with both the models, and the results are compared. Instabilities, non-linear oscillations, and effects of recirculation loop dynamics and geometric parameters on the mode of oscillations, are studied using the lumped model. The two channels oscillate out-of-phase in Type-I region, but in Type-II region, both the modes of oscillation are observed under different conditions. Channel-to-channel interaction and on-power refueling studies are carried out using the RELAP model. At high powers, disturbances in one channel significantly affect the stability of the other channel. During on-power refueling, a near-stagnation condition or low-velocity reverse flow can occur, the possibility of reverse flow being higher at lower pressures

  12. Nature and extent of lava-flow aquifers beneath Pahute Mesa, Nevada Test Site

    Energy Technology Data Exchange (ETDEWEB)

    Prothro, L.B.; Drellack, S.L. Jr.

    1997-09-01

    Work is currently underway within the Underground Test Area subproject of the US Department of Energy/Nevada Operations Office Environmental Restoration Program to develop corrective action plans in support of the overall corrective action strategy for the Nevada Test Site as established in the Federal Facility Agreement and Consent Order (FFACO, 1996). A closure plan is currently being developed for Pahute Mesa, which has been identified in the FFACO as consisting of the Western and Central Pahute Mesa Corrective Action Units. Part of this effort requires that hydrogeologic data be compiled for inclusion in a regional model that will be used to predict a contaminant boundary for these Corrective Action Units. Hydrogeologic maps have been prepared for use in the model to define the nature and extent of aquifers and confining units that might influence the flow of contaminated groundwater from underground nuclear tests conducted at Pahute Mesa. Much of the groundwater flow beneath Pahute Mesa occurs within lava-flow aquifers. An understanding of the distribution and hydraulic character of these important hydrogeologic units is necessary to accurately model groundwater flow beneath Pahute Mesa. This report summarizes the results of a study by Bechtel Nevada geologists to better define the hydrogeology of lava-flow aquifers at Pahute Mesa. The purpose of this study was twofold: (1) aid in the development of the hydrostratigraphic framework for Pahute Mesa, and (2) provide information on the distribution and hydraulic character of lava-flow aquifers beneath Pahute Mesa for more accurate computer modeling of the Western and Central Pahute Mesa Corrective Action Units.

  13. Benchmarking computational fluid dynamics models of lava flow simulation for hazard assessment, forecasting, and risk management

    Science.gov (United States)

    Dietterich, Hannah; Lev, Einat; Chen, Jiangzhi; Richardson, Jacob A.; Cashman, Katharine V.

    2017-01-01

    Numerical simulations of lava flow emplacement are valuable for assessing lava flow hazards, forecasting active flows, designing flow mitigation measures, interpreting past eruptions, and understanding the controls on lava flow behavior. Existing lava flow models vary in simplifying assumptions, physics, dimensionality, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess existing models and guide the development of new codes, we conduct a benchmarking study of computational fluid dynamics (CFD) models for lava flow emplacement, including VolcFlow, OpenFOAM, FLOW-3D, COMSOL, and MOLASSES. We model viscous, cooling, and solidifying flows over horizontal planes, sloping surfaces, and into topographic obstacles. We compare model results to physical observations made during well-controlled analogue and molten basalt experiments, and to analytical theory when available. Overall, the models accurately simulate viscous flow with some variability in flow thickness where flows intersect obstacles. OpenFOAM, COMSOL, and FLOW-3D can each reproduce experimental measurements of cooling viscous flows, and OpenFOAM and FLOW-3D simulations with temperature-dependent rheology match results from molten basalt experiments. We assess the goodness-of-fit of the simulation results and the computational cost. Our results guide the selection of numerical simulation codes for different applications, including inferring emplacement conditions of past lava flows, modeling the temporal evolution of ongoing flows during eruption, and probabilistic assessment of lava flow hazard prior to eruption. Finally, we outline potential experiments and desired key observational data from future flows that would extend existing benchmarking data sets.

  14. A Risk-Based Ecohydrological Approach to Assessing Environmental Flow Regimes

    Science.gov (United States)

    Mcgregor, Glenn B.; Marshall, Jonathan C.; Lobegeiger, Jaye S.; Holloway, Dean; Menke, Norbert; Coysh, Julie

    2018-03-01

    For several decades there has been recognition that water resource development alters river flow regimes and impacts ecosystem values. Determining strategies to protect or restore flow regimes to achieve ecological outcomes is a focus of water policy and legislation in many parts of the world. However, consideration of existing environmental flow assessment approaches for application in Queensland identified deficiencies precluding their adoption. Firstly, in managing flows and using ecosystem condition as an indicator of effectiveness, many approaches ignore the fact that river ecosystems are subjected to threatening processes other than flow regime alteration. Secondly, many focus on providing flows for responses without considering how often they are necessary to sustain ecological values in the long-term. Finally, few consider requirements at spatial-scales relevant to the desired outcomes, with frequent focus on individual places rather than the regions supporting sustainability. Consequently, we developed a risk-based ecohydrological approach that identifies ecosystem values linked to desired ecological outcomes, is sensitive to flow alteration and uses indicators of broader ecosystem requirements. Monitoring and research is undertaken to quantify flow-dependencies and ecological modelling is used to quantify flow-related ecological responses over an historical flow period. The relative risk from different flow management scenarios can be evaluated at relevant spatial-scales. This overcomes the deficiencies identified above and provides a robust and useful foundation upon which to build the information needed to support water planning decisions. Application of the risk assessment approach is illustrated here by two case studies.

  15. A review of investigations on flow instabilities in natural circulation boiling loops

    International Nuclear Information System (INIS)

    Gonella V Durga Prasad; Manmohan Pandey; Manjeet S Kalra

    2005-01-01

    Full text of publication follows: Steam generation systems are subjected to flow instabilities due to parametric fluctuations, inlet conditions etc., which may result in mechanical vibrations of components (called flow induced vibrations) and system control problems. Analysis of these instabilities in natural circulation boiling loops is very important for the safety of nuclear reactors and other boiling systems. This paper presents the state of the art in this area by reviewing over 100 contributions made in the past 30 years. A large number of experimental and numerical investigations have been conducted to study and understand the conditions for inception of flow instabilities, parametric effects of instabilities, and the system behavior under such conditions. Work done on instabilities due to channel thermal-hydraulics as well as neutronics-thermohydraulics coupling has been reviewed. Different methods of analysis used by researchers and results obtained by them have been discussed. Various numerical techniques adopted and computer codes developed have also been discussed. The knowledge obtained from the investigations made in the past three decades has been summarized to present the state of the art of the understanding of flow instabilities. (authors)

  16. Removal of natural organic matter and arsenic from water by electrocoagulation/flotation continuous flow reactor.

    Science.gov (United States)

    Mohora, Emilijan; Rončević, Srdjan; Dalmacija, Božo; Agbaba, Jasmina; Watson, Malcolm; Karlović, Elvira; Dalmacija, Milena

    2012-10-15

    The performance of the laboratory scale electrocoagulation/flotation (ECF) reactor in removing high concentrations of natural organic matter (NOM) and arsenic from groundwater was analyzed in this study. An ECF reactor with bipolar plate aluminum electrodes was operated in the horizontal continuous flow mode. Electrochemical and flow variables were optimized to examine ECF reactor contaminants removal efficiency. The optimum conditions for the process were identified as groundwater initial pH 5, flow rate=4.3 l/h, inter electrode distance=2.8 cm, current density=5.78 mA/cm(2), A/V ratio=0.248 cm(-1). The NOM removal according to UV(254) absorbance and dissolved organic matter (DOC) reached highest values of 77% and 71% respectively, relative to the raw groundwater. Arsenic removal was 85% (6.2 μg As/l) relative to raw groundwater, satisfying the drinking water standards. The specific reactor electrical energy consumption was 17.5 kWh/kg Al. The specific aluminum electrode consumption was 66 g Al/m(3). According to the obtained results, ECF in horizontal continuous flow mode is an energy efficient process to remove NOM and arsenic from groundwater. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Self-organized natural roads for predicting traffic flow: a sensitivity study

    International Nuclear Information System (INIS)

    Jiang, Bin; Zhao, Sijian; Yin, Junjun

    2008-01-01

    In this paper, we extended road-based topological analysis to both nationwide and urban road networks, and concentrated on a sensitivity study with respect to the formation of self-organized natural roads based on the Gestalt principle of good continuity. Both annual average daily traffic (AADT) and global positioning system (GPS) data were used to correlate with a series of ranking metrics including five centrality-based metrics and two PageRank metrics. It was found that there exists a tipping point from segment-based to road-based network topology in terms of correlation between ranking metrics and their traffic. To our great surprise, (1) this correlation is significantly improved if a selfish rather than utopian strategy is adopted in forming the self-organized natural roads, and (2) point-based metrics assigned by summation into individual roads tend to have a much better correlation with traffic flow than line-based metrics. These counter-intuitive surprising findings constitute emergent properties of self-organized natural roads, which are intelligent enough for predicting traffic flow, thus shedding substantial light on the understanding of road networks and their traffic from the perspective of complex networks

  18. Concept of CFD model of natural draft wet-cooling tower flow

    Directory of Open Access Journals (Sweden)

    Hyhlík T.

    2014-03-01

    Full Text Available The article deals with the development of CFD model of natural draft wet-cooling tower flow. The physical phenomena taking place within a natural draft wet cooling tower are described by the system of conservation law equations along with additional equations. The heat and mass transfer in the counterflow wet-cooling tower fill are described by model [1] which is based on the system of ordinary differential equations. Utilization of model [1] of the fill allows us to apply commonly measured fill characteristics as shown by [2].The boundary value problem resulting from the fill model is solved separately. The system of conservation law equations is interlinked with the system of ordinary differential equations describing the phenomena occurring in the counterflow wet-cooling tower fill via heat and mass sources and via boundary conditions. The concept of numerical solution is presented for the quasi one dimensional model of natural draft wet-cooling tower flow. The simulation results are shown.

  19. Risk management technique for liquefied natural gas facilities

    Science.gov (United States)

    Fedor, O. H.; Parsons, W. N.

    1975-01-01

    Checklists have been compiled for planning, design, construction, startup and debugging, and operation of liquefied natural gas facilities. Lists include references to pertinent safety regulations. Methods described are applicable to handling of other hazardous materials.

  20. Experimental study of natural two-phase flow circulation using a visualization technique

    International Nuclear Information System (INIS)

    Vinhas, Pedro A.M.; Su, Jian

    2013-01-01

    This paper presents an experimental study of natural two-phase flow in a circuit that simulates, on a smaller scale, a typical residual heat removal system of passive reactors APWR (Advanced Pressurized Water Reactor). The circuit was formed by a heater, a heat exchanger and piping. The experimental study was the application of a visualization technique, using a high speed camera, for measuring the size and speed of vapor bubbles generated in the heater with different power heating. The camera was positioned in the central region of the pipe connecting the heater to the heat exchanger, where there is a clear passage. The flow of images were processed and analyzed using commercial software that allowed the determination of the length and velocity of the bubbles. The results were then compared with correlations available in literature

  1. Reversing flow catalytic converter for a natural gas/diesel dual fuel engine

    Energy Technology Data Exchange (ETDEWEB)

    Liu, E.; Checkel, M.D. [Alberta Univ., Edmonton, AB (Canada). Dept. of Mechanical Engineering; Hayes, R.E. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical and Materials Engineering; Alberta Univ., Edmonton, AB (Canada). Dept. of Mechanical Engineering; Zheng, M.; Mirosh, E. [Alternative Fuel Systems Inc., Calgary, AB (Canada)

    2001-07-01

    An experimental and modelling study was performed for a reverse flow catalytic converter attached to a natural gas/diesel dual fuel engine. The catalytic converter had a segmented ceramic monolith honeycomb substrate and a catalytic washcoat containing a predominantly palladium catalyst. A one-dimensional single channel model was used to simulate the operation of the converter. The kinetics of the CO and methane oxidation followed first-order behaviour. The activation energy for the oxidation of methane showed a change with temperature, dropping from a value of 129 to 35 kJ/mol at a temperature of 874 K. The reverse flow converter was able to achieve high reactor temperature under conditions of low inlet gas temperature, provided that the initial reactor temperature was sufficiently high. (author)

  2. Daily variation in natural disaster casualties: information flows, safety, and opportunity costs in tornado versus hurricane strikes.

    Science.gov (United States)

    Zahran, Sammy; Tavani, Daniele; Weiler, Stephan

    2013-07-01

    Casualties from natural disasters may depend on the day of the week they strike. With data from the Spatial Hazard Events and Losses Database for the United States (SHELDUS), daily variation in hurricane and tornado casualties from 5,043 tornado and 2,455 hurricane time/place events is analyzed. Hurricane forecasts provide at-risk populations with considerable lead time. Such lead time allows strategic behavior in choosing protective measures under hurricane threat; opportunity costs in terms of lost income are higher during weekdays than during weekends. On the other hand, the lead time provided by tornadoes is near zero; hence tornados generate no opportunity costs. Tornado casualties are related to risk information flows, which are higher during workdays than during leisure periods, and are related to sheltering-in-place opportunities, which are better in permanent buildings like businesses and schools. Consistent with theoretical expectations, random effects negative binomial regression results indicate that tornado events occurring on the workdays of Monday through Thursday are significantly less lethal than tornados that occur on weekends. In direct contrast, and also consistent with theory, the expected count of hurricane casualties increases significantly with weekday occurrences. The policy implications of observed daily variation in tornado and hurricane events are considered. © 2012 Society for Risk Analysis.

  3. Credit risk in liberalised power and natural gas markets

    International Nuclear Information System (INIS)

    Lapson, E.; Hunter, Richard

    1999-01-01

    This chapter examines the relationship of market structure and price volatility to credit risk, and discusses credit risk and energy market structures, credit risk in bilateral contracts, market evolution, and the effect of liberalising power markets on credit quality considering the power liberalising in Europe, the pace of change, and the new risks and opportunities. The market structure in Europe is addressed, and the EU Directive 96/92/EC, structural requirements, access for new generation capacity, and transmission costs are considered. Details of the liberalisation in the UK electricity market, the German market, and the Nord Pool are given, and the best credit practices in bilateral markets, and the quantifying of expected credit loss are described. Panels highlighting the need to know your counterparty in evaluating and negotiating bilateral contracts, and lessons learnt from the June 1998 US power price spike are presented

  4. [Climate change risk of nature reserve and its assessment: A case study of Dalinuoer National Nature Reserve in Inner Mongolia Autonomous Region].

    Science.gov (United States)

    Zhao, Wei; Shen, Wei Shou; Liu, Hai Yue

    2016-12-01

    According to the theoretical framework of addressing climate change based on risk mana-gement and the challenge to nature reserve management under climate change, climate change risk of nature reserve was analyzed and defined. Focus on birds and water habitat, grassland habitat, forest habitat, wetland habitat in Dalinuoer Nature Reserve, risk assessment method of nature reserve under climate change was formulated, climate change risks to Dalinuoer Nature Reserve and its habitats were assessed and predicted. The results showed that, during the period from 1997 to 2010, there was significant volatility in dynamic changes of climate change risks to Dalinuoer Nature Reserve and waterbody, grassland, forest, wetland in the region, Dalinuoer Nature Reserve and its habitats were in status of risk in 1999, 2001, 2005 and 2008, wetland habitat was also in status of risk in 2002 and 2004. Under scenario A, B and C, climate change risks to Dalinuoer Nature Reserve and waterbody, grassland, forest, wetland in the region would be more serious in 2020 and 2030, compared with the 2010 level. Climate change risks to different habitats were different significantly, with most serious climate change risk to wetland habitat due to its sensitivity to climate change and rich bird resources. The effect of climate change on nature reserve and related risk would be aggravated by excess utilization of water resource and grassland resource. As climate change risks had appeared in Dalinuoer Nature Reserve, risk management associated with climate change could greatly help to maintain and enhance biodiversity protection function of nature reserves.

  5. Zero Flow Global Ischemia-Induced Injuries in Rat Heart Are Attenuated by Natural Honey

    Directory of Open Access Journals (Sweden)

    Moslem Najafi

    2012-06-01

    Full Text Available Purpose: In the present study, effects of preischemic administration of natural honey on cardiac arrhythmias and myocardial infarction size during zero flow global ischemia were investigated in isolated rat heart. Methods:The isolated hearts were subjected to 30 min zero flow global ischemia followed by 120 min reperfusion then perfused by a modified drug free Krebs-Henseleit solution throughout the experiment (control or the solution containing 0.25, 0.5, 1 and 2% of natural honey for 15 min before induction of global ischemia (treated groups, respectively. Cardiac arrhythmias were determined based on the Lambeth conventions and the infarct size was measured by computerized planimetry. Results: Myocardial infarction size was 55.8±7.8% in the control group, while preischemic perfusion of honey (0.25, 0.5, 1 and 2% reduced it to 39.3±11, 30.6±5.5 (P<0.01, 17.9±5.6 (P<0.001 and 8.7±1.1% (P<0.001, respectively. A direct linear correlation between honey concentrations and infarction size reduction was observed (R2=0.9948. In addition, total number of ventricular ectopic beats were significantly decreased by all used concentrations of honey (P<0.05 during reperfusion time. Honey (0.25, 0.5 and 1 % also lowered incidence of irreversible ventricular fibrillation (P<0.05. Moreover, number and duration of ventricular tachycardia were reduced in all honey treated groups. Conclusion: Preischemic administration of natural honey before zero flow global ischemia can protect isolated rat heart against ischemia/reperfusion injuries as reduction of infarction size and arrhythmias. Maybe, antioxidant and free radical scavenging activities of honey, reduction of necrotized tissue and providing energy sources may involve in these cardioprotective effects of honey.

  6. Zero Flow Global Ischemia-Induced Injuries in Rat Heart Are Attenuated by Natural Honey

    Science.gov (United States)

    Najafi, Moslem; Zahednezhad, Fahimeh; Samadzadeh, Mehrban; Vaez, Haleh

    2012-01-01

    Purpose: In the present study, effects of preischemic administration of natural honey on cardiac arrhythmias and myocardial infarction size during zero flow global ischemia were investigated in isolated rat heart. Methods: The isolated hearts were subjected to 30 min zero flow global ischemia followed by 120 min reperfusion then perfused by a modified drug free Krebs-Henseleit solution throughout the experiment (control) or the solution containing 0.25, 0.5, 1 and 2% of natural honey for 15 min before induction of global ischemia (treated groups), respectively. Cardiac arrhythmias were determined based on the Lambeth conventions and the infarct size was measured by computerized planimetry. Results: Myocardial infarction size was 55.8±7.8% in the control group, while preischemic perfusion of honey (0.25, 0.5, 1 and 2%) reduced it to 39.3±11, 30.6±5.5 (Phoney concentrations and infarction size reduction was observed (R2=0.9948). In addition, total number of ventricular ectopic beats were significantly decreased by all used concentrations of honey (PHoney (0.25, 0.5 and 1 %) also lowered incidence of irreversible ventricular fibrillation (Phoney treated groups. Conclusion: Preischemic administration of natural honey before zero flow global ischemia can protect isolated rat heart against ischemia/reperfusion injuries as reduction of infarction size and arrhythmias. Maybe, antioxidant and free radical scavenging activities of honey, reduction of necrotized tissue and providing energy sources may involve in these cardioprotective effects of honey. PMID:24312788

  7. Fish Distribution in Far Western Queensland, Australia: The Importance of Habitat, Connectivity and Natural Flows

    Directory of Open Access Journals (Sweden)

    Adam Kerezsy

    2014-06-01

    Full Text Available The endorheic Lake Eyre Basin drains 1.2 million square kilometres of arid central Australia, yet provides habitat for only 30 species of freshwater fish due to the scarcity of water and extreme climate. The majority are hardy riverine species that are adapted to the unpredictable flow regimes, and capable of massive population booms following heavy rainfall and the restoration of connectivity between isolated waterholes. The remainder are endemic specialists from isolated springs with very restricted ranges, and many are listed under relevant state and national endangered species legislation and also by the International Union for Conservation of Nature (IUCN. For these spring communities, which are sustained by water from the Great Artesian Basin, survival is contingent on suitable habitat persisting alongside extractive mining, agriculture and the imposition of alien species. For the riverine species, which frequently undertake long migrations into ephemeral systems, preservation of the natural flow regime is paramount, as this reinstates riverine connectivity. In this study, fish were sampled from the Bulloo River in the east to the Mulligan River in the west, along a temporal timeframe and using a standard set of sampling gears. Fish presence was influenced by factors such as natural catchment divides, sampling time, ephemerality and the occurrence of connection flows and flooding. Despite the comparatively low diversity of species, the aquatic systems of this isolated region remain in good ecological condition, and as such they offer excellent opportunities to investigate the ecology of arid water systems. However, the presence of both endangered species (in the springs and invasive and translocated species more widely indicates that active protection and management of this unique area is essential to maintain biodiversity and ecosystem integrity.

  8. The effect of natural disturbances on the risk from hydrogeomorphic hazards under climate change

    Science.gov (United States)

    Scheidl, Christian; Thaler, Thomas; Seidl, Rupert; Rammer, Werner; Kohl, Bernhard; Markart, Gerhard

    2017-04-01

    Recent storm events in Austria show once more how floods, sediment transport processes and debris flows constitute a major threat in alpine regions with a high density of population and an increasing spatial development. As protection forests have a major control function on runoff and erosion, they directly affect the risk from such hydrogeomorphic processes. However, research on future climate conditions, with an expected increase of the global average surface temperature of 3-5°C by 2100, compared to the first decade of the 20th century, raises a number of open questions for a sustainable and improved hazard management in mountain forests. For Europe, for instance, a climate-induced increase in forest disturbances like wildfire, wind, and insect's outbreaks is highly likely for the coming decades. Especially in protection forests, future scenarios of such climate induced natural disturbances and their impact on the protective effect remain an unresolved issue. Combining methods from forestry, hydrology and geotechnical engineering our project uses an integral approach to simulate possible effects of natural disturbances on hydrogeomorphic hazards in the perspective of future protection forest developments. With the individual-based forest landscape and disturbance model (iLand) we conduct an ensemble of forest landscape simulations, assessing the impact of future changes in natural disturbance regimes in four selected torrential catchments. These catchments are situated in two different forest growth areas. Drainage rate simulations are based on the conceptual hydrological model (ZEMOKOST), whereas simulations of the effect of forest disturbances on hillslope erosion processes are conducted by the Distributed Hydrology Soil Vegetation Model (DHSVM). Beside process based simulations, we also emphasis to identify the risk perception and adaptive capacity to mitigate a probable loss of protection functions in forests. For this reason, a postal survey among

  9. The affect heuristic, mortality salience, and risk: domain-specific effects of a natural disaster on risk-benefit perception.

    Science.gov (United States)

    Västfjäll, Daniel; Peters, Ellen; Slovic, Paul

    2014-12-01

    We examine how affect and accessible thoughts following a major natural disaster influence everyday risk perception. A survey was conducted in the months following the 2004 south Asian Tsunami in a representative sample of the Swedish population (N = 733). Respondents rated their experienced affect as well as the perceived risk and benefits of various everyday decision domains. Affect influenced risk and benefit perception in a way that could be predicted from both the affect-congruency and affect heuristic literatures (increased risk perception and stronger risk-benefit correlations). However, in some decision domains, self-regulation goals primed by the natural disaster predicted risk and benefit ratings. Together, these results show that affect, accessible thoughts and motivational states influence perceptions of risks and benefits. © 2014 Scandinavian Psychological Associations and John Wiley & Sons Ltd.

  10. Java project on periodontal diseases. The natural development of periodontitis: risk factors, risk predictors and risk determinants : risk factors, risk predictors and risk determinants

    NARCIS (Netherlands)

    Van der Velden, U.; Abbas, F.; Armand, S.; Loos, B. G.; Timmerman, M. F.; Van der Weijden, G. A.; Van Winkelhoff, A. J.; Winkel, E. G.

    Objective: To identify risk factors, risk predictors and risk determinants for onset and progression of periodontitis. Material and Methods: For this longitudinal, prospective study all subjects in the age range 15-25 years living in a village of approximately 2000 inhabitants at a tea estate on

  11. Unsteady natural convection flow past an accelerated vertical plate in a thermally stratified fluid

    Directory of Open Access Journals (Sweden)

    Deka Rudra Kt.

    2009-01-01

    Full Text Available An exact solution to one-dimensional unsteady natural convection flow past an infinite vertical accelerated plate, immersed in a viscous thermally stratified fluid is investigated. Pressure work term and the vertical temperature advection are considered in the thermodynamic energy equation. The dimensionless governing equations are solved by Laplace Transform techniques for the Prandtl number unity. The velocity and temperature profiles as well as the skin-friction and the rate of heat transfer are presented graphically and discussed the effects of the Grashof number Gr, stratification parameter S at various times t.

  12. Low-pressure dynamics of a natural-circulation two-phase flow loop

    International Nuclear Information System (INIS)

    Manera, A.; Kruijf, W.J.M. de; Hartmann, H.; Mudde, R.F.; Hagen, T.H.J.J. van der

    2001-01-01

    Flashing induced oscillations in a natural circulation loop are studied as function of heating power and inlet subcooling in symmetrical and asymmetrical power conditions. To unveil the effects of power/velocity asymmetries on the two-phase flow stability at low power and low pressure conditions different signals at several locations in the loop are recorded. In particular a Laser Doppler Anemometry set-up is used to measure the velocity simultaneously in two parallel channels and a wire-mesh sensor is used to measure the 2D void fraction distribution in a section of the ascendant part of the loop. (orig.)

  13. Gas-liquid two-phase flows in double inlet cyclones for natural gas separation

    DEFF Research Database (Denmark)

    Yang, Yan; Wang, Shuli; Wen, Chuang

    2017-01-01

    The gas-liquid two-phase flow within a double inlet cyclone for natural gasseparation was numerically simulated using the discrete phase model. The numericalapproach was validated with the experimental data, and the comparison resultsagreed well with each other. The simulation results showed...... that the strong swirlingflow produced a high centrifugal force to remove the particles from the gas mixture.The larger particles moved downward on the internal surface and were removeddue to the outer vortex near the wall. Most of the tiny particles went into the innervortex zones and escaped from the up...

  14. Rheological analysis of fine-grained natural debris-flow material

    Science.gov (United States)

    Major, Jon J.; Pierson, Thomas C.; ,

    1990-01-01

    Experiments were conducted on large samples of fine-grained material (???2mm) from a natural debris flow using a wide-gap concentric-cylinder viscometer. The rheological behavior of this material is compatible with a Bingham model at shear rates in excess of 5 sec. At lesser shear rates, rheological behavior of the material deviates from the Bingham model, and when sand concentration of the slurry exceeds 20 percent by volume, particle interaction between sand grains dominates the mechanical behavior. Yield strength and plastic viscosity are extremely sensitive to sediment concentration.

  15. Testing the impact on natural risks' awareness of visual communication through an exhibition

    Science.gov (United States)

    Charrière, Marie; Bogaard, Thom; Junier, Sandra; Malet, Jean-Philippe; Mostert, Erik

    2014-05-01

    The need to communicate about natural disasters in order to improve the awareness of communities at risk is not a matter for debate anymore. However, communication can be implemented using different media and tools, and their effectiveness may be difficult to grasp. Current research on the topic is usually focused on assessing whether communication practices meet users' needs, whereas impact assessment is mostly left out. It can be explained by difficulties arising from (1) the definition of the impact to measure, i.e. awareness, and the appropriate indicators to measure it and its variations, and (2) the implementation of a research design that allows assessing these impacts without bias. This research aims at both developing a methodology to measure risk awareness and to use it for testing the effectiveness of visual communication. The testing was conducted in the Ubaye Valley in France, an alpine area affected by multiple hazards, from December 2013 to mid-February 2014. The setting consisted of an exhibition in the public library of the main town, Barcelonnette. The main natural hazards of the study case (i.e. landslides, avalanches, flooding, debris flows and earthquakes), as well as structural and non-structural measures were presented to the general public using local examples of hazards events and mitigation. Various visualization tools were used: videos, Google earth map, interactive timeline, objects, mock-ups, technical devices as well as posters with pictures, drawings and graphs. In order to assess the effects of the exhibition on risk awareness, several groups of children and adults were submitted to a research design, consisting of 1) a pre-test, 2) the visit of the exhibition and 3) a post-test similar to the pre-test. Close-ended questions addressed the awareness indicators according to the literature, i.e. worry level, previous experiences with natural hazards events, exposure to awareness raising, ability to mitigate/respond/prepare, attitude to

  16. Metrological evaluation of petroleum, his derivatives, natural gas and alcohol flow computers; Avaliacao metrologica de computadores de vazao de petroleo, seus derivados, gas natural e alcool

    Energy Technology Data Exchange (ETDEWEB)

    Orlando, A.F.; Callegario, E. [Pontificia Univ. Catolica do Rio de Janeiro (PUC/Rio), RJ (Brazil)], Emails: afo@puc-rio.br, callegario@puc-rio.br; Ferreira, A.; Pinheiro, J.A.; Oliveira, T.B.V. [PETROBRAS, Rio de Janeiro, RJ (Brazil)], Emails: andref@petrobras.com.br, jose.pinheiro@petrobras.com.br, thiagovidal@petrobras.com.br

    2009-07-01

    This work presents results of petroleum flow computers, his derivatives, natural gas and alcohol, used on fiscal measurements, appropriation and custodial transfer system. It is intended that the used proceed give subsides for the model approval and verify initially the flow computers, besides the periodic verification of installed flow computers. The test procedures are focused at the algorithm deviations, at the A/D (analog - digital) and D/D (digital-digital)conversion deviations, simulating static pressure transmitters, pressure differential, temperature, specific mass, BSW (Basic Sediment and Waste), and at the pulse counting deviations of the flow computer. The presented methodology is based on specific document for certification and initial verification of flow computers for the WELMEC (European Cooperation in Legal Metrology), and improved to attend the measurement requirements in Brazil. The test show various no conformities among the performance of tested flow computers compared with allowed values by the developed procedure.

  17. Natural convective flow of a magneto-micropolar fluid along a vertical plate

    Directory of Open Access Journals (Sweden)

    M. Ferdows

    2018-03-01

    Full Text Available This paper presents a numerical study of natural convective flow of an electrically conducting viscous micropolar fluid past a vertical plate. Internal heat generation (IHG versus without IHG in the medium are discussed in the context of corresponding similarity solutions. Results are presented in terms of velocity, angular velocity, temperature, skin friction in tabular forms, local wall-coupled stress, and Nusselt number. Computations have been accomplished by parametrizing the micropolar, micro-rotation, magnetic field, suction parameters, and the Prandtl number. Several critical issues are addressed at the end of the paper with reference to a previous study by El-Hakiem. The study is relevant to high-temperature electromagnetic materials fabrication systems. Keywords: Natural convection, Thermal boundary layer, Micropolar fluid, Similarity transformation, Internal heat generation

  18. Wind dependence on the flow rate in a natural draught cooling tower

    International Nuclear Information System (INIS)

    Baer, E.; Ernst, G.; Wurz, D.

    1981-01-01

    The efficiency of a natural draught cooling tower depends, among other things, on the effect of the wind on the flow in the tower stack. Determinations were made on a natural draught wet cooling tower 100 metres high, for the purpose of studying this effects. As characteristic quantity, a typical height was determined, the values of which were worked out from the results of the measurements. The efficiency of the stack is affected the most in the case of average wind velocities (when the velocity of the wind is about equal to the mean velocity of the plume). This effect diminishes when the velocity of the wind increases. In the case of average wind velocities, the direction of the wind has an effect, owing to the neighbouring buildings; for slightly greater wind velocities, no effect could be found [fr

  19. Understanding the nature of nuclear power plant risk

    International Nuclear Information System (INIS)

    Denning, R. S.

    2012-01-01

    This paper describes the evolution of understanding of severe accident consequences from the non-mechanistic assumptions of WASH-740 to WASH-1400, NUREG-1150, SOARCA and today in the interpretation of the consequences of the accident at Fukushima. As opposed to the general perception, the radiological human health consequences to members of the Japanese public from the Fukushima accident will be small despite meltdowns at three reactors and loss of containment integrity. In contrast, the radiation-related societal impacts present a substantial additional economic burden on top of the monumental task of economic recovery from the nonnuclear aspects of the earthquake and tsunami damage. The Fukushima accident provides additional evidence that we have mis-characterized the risk of nuclear power plant accidents to ourselves and to the public. The human health risks are extremely small even to people living next door to a nuclear power plant. The principal risk associated with a nuclear power plant accident involves societal impacts: relocation of people, loss of land use, loss of contaminated products, decontamination costs and the need for replacement power. Although two of the three probabilistic safety goals of the NRC address societal risk, the associated quantitative health objectives in reality only address individual human health risk. This paper describes the types of analysis that would address compliance with the societal goals. (authors)

  20. Predicting the natural flow regime: Models for assessing hydrological alteration in streams

    Science.gov (United States)

    Carlisle, D.M.; Falcone, J.; Wolock, D.M.; Meador, M.R.; Norris, R.H.

    2009-01-01

    Understanding the extent to which natural streamflow characteristics have been altered is an important consideration for ecological assessments of streams. Assessing hydrologic condition requires that we quantify the attributes of the flow regime that would be expected in the absence of anthropogenic modifications. The objective of this study was to evaluate whether selected streamflow characteristics could be predicted at regional and national scales using geospatial data. Long-term, gaged river basins distributed throughout the contiguous US that had streamflow characteristics representing least disturbed or near pristine conditions were identified. Thirteen metrics of the magnitude, frequency, duration, timing and rate of change of streamflow were calculated using a 20-50 year period of record for each site. We used random forests (RF), a robust statistical modelling approach, to develop models that predicted the value for each streamflow metric using natural watershed characteristics. We compared the performance (i.e. bias and precision) of national- and regional-scale predictive models to that of models based on landscape classifications, including major river basins, ecoregions and hydrologic landscape regions (HLR). For all hydrologic metrics, landscape stratification models produced estimates that were less biased and more precise than a null model that accounted for no natural variability. Predictive models at the national and regional scale performed equally well, and substantially improved predictions of all hydrologic metrics relative to landscape stratification models. Prediction error rates ranged from 15 to 40%, but were 25% for most metrics. We selected three gaged, non-reference sites to illustrate how predictive models could be used to assess hydrologic condition. These examples show how the models accurately estimate predisturbance conditions and are sensitive to changes in streamflow variability associated with long-term land-use change. We also

  1. Some risks related to the short-term trading of natural gas

    International Nuclear Information System (INIS)

    Ahmed El Hachemi Mazighi

    2004-01-01

    Traditionally guided by long-term contracts, the international natural gas trade is experiencing new methods of operating, based on the short term and more flexibility. Today, indeed, the existence of uncommitted quantities of natural gas, combined with gas price discrepancies among different regions of the world, gives room for the expansion of the spot-trading of gas. The main objective of this paper is to discuss three fundamental risks related to the short-term trading of natural gas: volume risk, price risk and infrastructure risk. The defenders Of globalisation argue that the transition from the long-term to the short-term trading of natural gas is mainly a question of access to gas reserves, decreasing costs of gas liquefaction, the building of liquefied natural gas (LNG) fleets and regasification facilities and third-party access to the infrastructure. This process needs to be as short as possible, so that the risks related to the transition process will disappear rapidly. On the other hand, the detractors of globalisation put the emphasis on the complexity of the gas value chain and on the fact that eliminating long- term contracts increases the risks inherent to the international natural gas business. In this paper, we try to untangle and assess the risks related to the short-term trading of natural gas. Our main conclusions are: the short-term trading of gas is far from riskless; volume risk requires stock-building in both consuming and producing countries. (author)

  2. Management of natural hazard risk in Cartago, Costa Rica

    NARCIS (Netherlands)

    Montoya, L.; Masser, Ian

    Cities are particularly vulnerable to natural disasters due to the concentration of population,buildi ngs and infrastructure. With urbanisation on the rise,parti cularly in developing countries, the incorporation of disaster management is high on urban agendas as the losses from a single event can

  3. Risk-taking in disorders of natural and drug rewards

    DEFF Research Database (Denmark)

    Voon, Valerie; Morris, Laurel S; Irvine, Michael A

    2015-01-01

    greater risk-taking, similar to substance-use disorders. Methamphetamine-dependent subjects had greater nonlinearity of probability weighting along with impaired subjective discrimination of probability and reward magnitude. Ex-smokers also had lower risk-taking to rewards compared with non......-smokers. In the anticipation of losses, obesity without binge eating had a similar pattern to other substance-use disorders. Obese subjects with binge eating also have impaired discrimination of subjective value similar to that of the methamphetamine-dependent subjects. Nonlinearity of probability weighting was associated...

  4. Natural hazard risk perception of Italian population: case studies along national territory.

    Science.gov (United States)

    Gravina, Teresita; Tupputi Schinosa, Francesca De Luca; Zuddas, Isabella; Preto, Mattia; Marengo, Angelo; Esposito, Alessandro; Figliozzi, Emanuele; Rapinatore, Matteo

    2015-04-01

    Risk perception is judgment that people make about the characteristics and severity of risks, in last few years risk perception studies focused on provide cognitive elements to communication experts responsible in order to design citizenship information and awareness appropriate strategies. Several authors in order to determine natural hazards risk (Seismic, landslides, cyclones, flood, Volcanic) perception used questionnaires as tool for providing reliable quantitative data and permitting comparison the results with those of similar surveys. In Italy, risk perception studies based on surveys, were also carried out in order to investigate on national importance Natural risk, in particular on Somma-Vesuvio and Phlegrean Fields volcanic Risks, but lacked risk perception studies on local situation distributed on whole national territory. National importance natural hazard were frequently reported by national mass media and there were debate about emergencies civil protection plans, otherwise could be difficult to obtain information on bonded and regional nature natural hazard which were diffuses along National territory. In fact, Italian peninsula was a younger geological area subjected to endogenous phenomena (volcanoes, earthquake) and exogenous phenomena which determine land evolution and natural hazard (landslide, coastal erosion, hydrogeological instability, sinkhole) for population. For this reason we decided to investigate on natural risks perception in different Italian place were natural hazard were taken place but not reported from mass media, as were only local relevant or historical event. We carried out surveys in different Italian place interested by different types of natural Hazard (landslide, coastal erosion, hydrogeological instability, sinkhole, volcanic phenomena and earthquake) and compared results, in order to understand population perception level, awareness and civil protection exercises preparation. Our findings support that risks

  5. Comparative Risk Assessment to Inform Adaptation Priorities for the Natural Environment: Observations from the First UK Climate Change Risk Assessment

    Directory of Open Access Journals (Sweden)

    Iain Brown

    2015-11-01

    Full Text Available Risk assessment can potentially provide an objective framework to synthesise and prioritise climate change risks to inform adaptation policy. However, there are significant challenges in the application of comparative risk assessment procedures to climate change, particularly for the natural environment. These challenges are evaluated with particular reference to the first statutory Climate Change Risk Assessment (CCRA and evidence review procedures used to guide policy for the UK government. More progress was achieved on risk identification, screening and prioritisation compared to risk quantification. This was due to the inherent complexity and interdependence of ecological risks and their interaction with socio-economic drivers as well as a climate change. Robust strategies to manage risk were identified as those that coordinate organisational resources to enhance ecosystem resilience, and to accommodate inevitable change, rather than to meet specific species or habitats targets. The assessment also highlighted subjective and contextual components of risk appraisal including ethical issues regarding the level of human intervention in the natural environment and the proposed outcomes of any intervention. This suggests that goals for risk assessment need to be more clearly explicated and assumptions on tolerable risk declared as a primer for further dialogue on expectations for managed outcomes. Ecosystem-based adaptation may mean that traditional habitats and species conservation goals and existing regulatory frameworks no longer provide the best guide for long-term risk management thereby challenging the viability of some existing practices.

  6. Essays on risk management of natural resources in developing countries

    DEFF Research Database (Denmark)

    Salazar Espinoza, César Antonio

    choice is sensitive to past weather shocks, and reallocation seems temporary. This is consistent with a self-insurance approach and buffer stock arguments. The third chapter employs rural household data of rice producers from Vietnam to examine the risk effect of pesticide use. Results reveal that higher...

  7. Risk Management of the Natural Gas Consumption using Genetic Algorithms

    Czech Academy of Sciences Publication Activity Database

    Pelikán, Emil; Šimůnek, Milan

    2005-01-01

    Roč. 15, - (2005), s. 425-436 ISSN 1210-0552 R&D Projects: GA AV ČR 1ET400300513 Institutional research plan: CEZ:AV0Z10300504 Keywords : forecasting * risk-management * energy consumption Subject RIV: BB - Applied Statistics, Operational Research

  8. Longevity Risk and Natural Hedge Potential in Portfolios Of Life Insurance Products : The Effect of Investment Risk

    NARCIS (Netherlands)

    Stevens, R.S.P.; De Waegenaere, A.M.B.; Melenberg, B.

    2011-01-01

    Payments of life insurance products depend on the uncertain future evolution of survival probabilities. This uncertainty is referred to as longevity risk. Existing literature shows that the effect of longevity risk on single life annuities can be substantial, and that there exists a (natural) hedge

  9. An Experimental Study of Natural Circulation in a Loop with Parallel Flow Test Sections

    International Nuclear Information System (INIS)

    Mathisen, R.P.; Eklind, O.

    1965-10-01

    The dynamic behaviour of a natural circulation loop parallel round duct channels has been studied. The test sections were both electrically heated and the power distribution was uniform along the 4300 mm heated length of the 20 mm dia. channels. The inter channel interference and the threshold of flow instability were obtained by using a dynamically calibrated flowmeter in each channel. The pressure was 50 bars and the sub-cooling 6 deg C. The main parameters varied, were the flow restrictions in the one-phase and two-phase sections. The instability data were correlated to the resistance coefficients due to these restrictions. Theoretical calculations for parallel channels in natural circulation have been compared with the experimental results. For the conditions determined by the above mentioned magnitudes, the steady-state computations are in excellent agreement with experiment. The transients are also nearly similar, except for the resonance frequency which for the theoretical case is higher by an amount between 0.3 and 0.5 c.p.s

  10. Development of Modified Incompressible Ideal Gas Model for Natural Draft Cooling Tower Flow Simulation

    Science.gov (United States)

    Hyhlík, Tomáš

    2018-06-01

    The article deals with the development of incompressible ideal gas like model, which can be used as a part of mathematical model describing natural draft wet-cooling tower flow, heat and mass transfer. It is shown, based on the results of a complex mathematical model of natural draft wet-cooling tower flow, that behaviour of pressure, temperature and density is very similar to the case of hydrostatics of moist air, where heat and mass transfer in the fill zone must be taken into account. The behaviour inside the cooling tower is documented using density, pressure and temperature distributions. The proposed equation for the density is based on the same idea like the incompressible ideal gas model, which is only dependent on temperature, specific humidity and in this case on elevation. It is shown that normalized density difference of the density based on proposed model and density based on the nonsimplified model is in the order of 10-4. The classical incompressible ideal gas model, Boussinesq model and generalised Boussinesq model are also tested. These models show deviation in percentages.

  11. Development of Modified Incompressible Ideal Gas Model for Natural Draft Cooling Tower Flow Simulation

    Directory of Open Access Journals (Sweden)

    Hyhlík Tomáš

    2018-01-01

    Full Text Available The article deals with the development of incompressible ideal gas like model, which can be used as a part of mathematical model describing natural draft wet-cooling tower flow, heat and mass transfer. It is shown, based on the results of a complex mathematical model of natural draft wet-cooling tower flow, that behaviour of pressure, temperature and density is very similar to the case of hydrostatics of moist air, where heat and mass transfer in the fill zone must be taken into account. The behaviour inside the cooling tower is documented using density, pressure and temperature distributions. The proposed equation for the density is based on the same idea like the incompressible ideal gas model, which is only dependent on temperature, specific humidity and in this case on elevation. It is shown that normalized density difference of the density based on proposed model and density based on the nonsimplified model is in the order of 10-4. The classical incompressible ideal gas model, Boussinesq model and generalised Boussinesq model are also tested. These models show deviation in percentages.

  12. Ventilation and internal structure effects on naturally induced flows in a static aircraft wing

    International Nuclear Information System (INIS)

    Moore, Daithi; Newport, David; Egan, Vanessa; Lacarac, Vesna

    2012-01-01

    The ventilation performance within an aircraft wing leading edge is investigated for a number of enclosure and ventilation configurations. The natural convection regime present is found to be highly sensitive to enclosure conditions, particularly the introduction of a partition. The presence of a partition reduced the overall heat exhausted from the cavity by up to 60%. The optimum ventilation strategy is also changed from a forward biased vent orientation (found for the unpartitioned case), to one where both the rear and front vents within the enclosure had the same open area. Cylinder plume effects dominate within the enclosure and were the main driver of the convective regime, with steady-state enclosure conditions highly dependent upon cylinder placement and plume orientation. An externally heated enclosure with internal heat source, combined with ventilation and an internal structure produced a complex natural convection regime which is sensitive to enclosure conditions. Hence an adequate knowledge of such conditions is necessary in order to fully appreciate the convective regime. - Highlights: → Optimum ventilation strategy changed between unpartitioned and partitioned cases. → Flow path and plume orientation are important to consider when analysing ventilation. → Bleed duct placement significantly alters flow path and temperature distribution. → Enclosure partitioning reduced heat exhaustion by 60%.

  13. An Experimental Study of Natural Circulation in a Loop with Parallel Flow Test Sections

    Energy Technology Data Exchange (ETDEWEB)

    Mathisen, R P; Eklind, O

    1965-10-15

    The dynamic behaviour of a natural circulation loop parallel round duct channels has been studied. The test sections were both electrically heated and the power distribution was uniform along the 4300 mm heated length of the 20 mm dia. channels. The inter channel interference and the threshold of flow instability were obtained by using a dynamically calibrated flowmeter in each channel. The pressure was 50 bars and the sub-cooling 6 deg C. The main parameters varied, were the flow restrictions in the one-phase and two-phase sections. The instability data were correlated to the resistance coefficients due to these restrictions. Theoretical calculations for parallel channels in natural circulation have been compared with the experimental results. For the conditions determined by the above mentioned magnitudes, the steady-state computations are in excellent agreement with experiment. The transients are also nearly similar, except for the resonance frequency which for the theoretical case is higher by an amount between 0.3 and 0.5 c.p.s.

  14. Towards a comprehensive assessment and framework for low and high flow water risks

    Science.gov (United States)

    Motschmann, Alina; Huggel, Christian; Drenkhan, Fabian; León, Christian

    2017-04-01

    Driven by international organizations such as the Intergovernmental Panel on Climate Change (IPCC) the past years have seen a move from a vulnerability concept of climate change impacts towards a risk framework. Risk is now conceived at the intersection of climate-driven hazard and socioeconomic-driven vulnerability and exposure. The concept of risk so far has been mainly adopted for sudden-onset events. However, for slow-onset and cumulative climate change impacts such as changing water resources there is missing clarity and experience how to apply a risk framework. Research has hardly dealt with the challenge of how to integrate both low and high flow risks in a common framework. Comprehensive analyses of risks related to water resources considering climate change within multi-dimensional drivers across different scales are complex and often missing in climate-sensitive mountain regions where data scarcity and inconsistencies represent important limitations. Here we review existing vulnerability and risk assessments of low and high flow water conditions and identify critical conceptual and practical gaps. Based on this, we develop an integrated framework for low and high flow water risks which is applicable to both past and future conditions. The framework explicitly considers a water balance model simulating both water supply and demand on a daily basis. We test and apply this new framework in the highly glacierized Santa River catchment (SRC, Cordillera Blanca, Peru), representative for many developing mountain regions with both low and high flow water risks and poor data availability. In fact, in the SRC, both low and high flow hazards, such as droughts and floods, play a central role especially for agricultural, hydropower, domestic and mining use. During the dry season (austral winter) people are increasingly affected by water scarcity due to shrinking glaciers supplying melt water. On the other hand during the wet season (austral summer) high flow water

  15. Determination of Nitrite and Nitrate in Natural Waters Using Flow Injection with Spectrophotometric Detection

    International Nuclear Information System (INIS)

    Yaqoob, M.; Nabi, A.

    2013-01-01

    A simple and sensitive flow injection spectrophotometric method is reported for the room temperature determination of nitrite and nitrate based on the Griess reaction and a copperised cadmium column for reduction of nitrate. Calibration graphs were linear over the range 2 - 1000 micro g N L /sup -1/ (R2 = 0.9997 and 0.9999, n = 9) with a limit of detection (3 s.d.) of 1.0 micro g N L and relative standard deviations (n = 10) of 0.9 and 1.2% for 50 micro g N L nitrite and nitrate respectively. The sample throughput was 50 h. The effect of reagent concentrations, physical parameters (flow rate, sample volume, reaction coil and copperised cadmium column length) and the potential interferences are reported. The effect of salinity on the blank and on the determination of nitrite and nitrate are also presented. The method was applied to natural waters (rainwater, freshwater and estuarine water) and the results for nitrite + nitrate (140 - 7310 micro g N L/sup -1/) were not significantly different (95% confidence interval) from results obtained using a segmented flow analyser reference method with spectrophotometric detection. (author)

  16. Computational Fluid Dynamics Modeling to Improve Natural Flow Rate and Sweet Pepper Productivity in Greenhouse

    Directory of Open Access Journals (Sweden)

    W. Limtrakarn

    2012-01-01

    Full Text Available Natural flow rate and sweet peppers productivity in tropical greenhouse are improved by CFD simulation is the main objective of this research work. Most of the greenhouse types today are in the arch shape. To develop an improved greenhouse structure for the region, the arch type was built and used as the control model. Mae Sar Mai agriculture research station under the royal project foundation was selected as the field test site. Temperature sensors with data logger were installed to monitor variation of temperature inside the greenhouse. The measured temperature data were used as the boundary conditions for the CFD analysis. A new greenhouse model with two-step roof shape was designed and the air flow behavior was simulated by using CFD. Regarding CFD results the air flow rate of the new model is about 39% higher than that of old model. The maximum temperature of the new model is lower than that of the old one. The sweet paper growths in both greenhouse models were measured and compared. Results show that the new model obtains 4°C lower maximum temperature in day time, 97% in number and 90% in weight higher the first grade pepper productivity than the old one.

  17. Cross section of equity returns and assets’ fundamental cash-flow risk

    NARCIS (Netherlands)

    Galsband, V.

    2010-01-01

    The decomposition of consumption beta into a component driven by assets' cash-flow news and one related to assets' discount-rate news reveals that macroeconomic risks embodied in cash flows largely account for the cross-sectional dynamics of average stock returns. Empirically, we find that

  18. Natural and anthropogeneous radiation in the Erzgebirge: Risk factor radon

    International Nuclear Information System (INIS)

    Jacobi, W.

    1992-01-01

    The geological formations in the saxoinian-thuringian low mountain range contain rocks with a relatively high share of uranium ( 238 U) and its follow-up product radium ( 226 Ra). Independent of mining this results in increased radiation levels to which the local population has always been exposed. Natural radiation levels may, of course, vary strongly from one location to the next and therefore human exposure varies accordingly. (orig.) [de

  19. Colloid and radionuclide retention mechanisms in fractured rock under near-natural flow conditions

    International Nuclear Information System (INIS)

    Delos, A.; Schaefer, T.; Geckeis, H.; Guimera, J.; Carrera, J.; Fanghaenel, T.

    2005-01-01

    Full text of publication follows: Experiments in fractured host rock (Grimsel Test Site, GTS, Switzerland) revealed that the colloid relevance for actinide migration is high due to the specific geochemical groundwater conditions [1]. However, even under such conditions it is found that retention of colloids and colloid-borne actinides becomes significant under near-natural groundwater flow rates (1-10 m/a) [2]. Underlying mechanisms of colloid and radionuclide retention are not well understood up to now. The present study co-funded by the NoE ACTINET-6 focuses on (i) the kinetics of actinide-colloid interactions and (ii) the relevance of matrix diffusion as a competition process to other retention mechanisms which affect the actinides behavior in fractured rock systems such as the Grimsel granodiorite. Colloid migration is studied with well defined model colloids as e.g. fluorescence dyed carboxylated polystyrene particles, and natural colloids extracted from bentonite (FEBEX) and from fracture filling material (GTS). In order to study the influence of matrix porosity on actinides migration, those experiments are performed in columns of well defined geometry filled with microporous unmodified silica spheres, porous ceramic material and natural fracture filling material from the GTS. The behaviour of actinides (Pu(IV) and Am(III)) sorbed onto bentonite colloids is investigated in column and batch experiments. All experiments are performed under anoxic conditions. Colloid characterization methods used in this study include the combination of photon correlation spectroscopy (PCS), laser-induced breakdown detection (LIBD), fluorimetry and field flow fractionation (FFF). Experimental results and their application to the parametrisation of reactive colloid transport models are discussed. [1] Geckeis H, Schaefer T, Hauser W, Rabung T, Missana T, Degueldre C, Moeri A, Eikenberg J, Fierz T, Alexander WR (2004) Results of the Colloid and Radionuclide Retention experiment

  20. Crop to wild gene flow: Does more sophisticated research provide better risk assessment?

    International Nuclear Information System (INIS)

    Jong, Tom J. de; Rong, Jun

    2013-01-01

    Highlights: ► Genes can sometimes flow from genetically modified crops to wild plants. ► The probability can be predicted from seed production of hybrids and backcrosses. ► Nevertheless predictions about introgression remain uncertain. ► One should be reluctant to ask too much detail in Environmental Risk Assessment. ► Instead possible harm should have a more central place. -- Abstract: Research into introgression, the permanent incorporation of alleles of one species into another, is flourishing and gives new insights into evolution and speciation. The possible transfer of transgenes from crop species to wild relatives is of major concern for regulators. Applicants that want to introduce a genetically modified (GM) crop on the European market need to indicate the likelihood of introgression and its anticipated effects in an Environmental Risk Analysis (ERA). The European Food Safety Association (EFSA) and competent authorities of different countries evaluate the ERA. Predicting which crop alleles will or will not be permanently incorporated into wild populations requires, apart from information on seed production of hybrids, information on how these crop alleles are associated with fitness. Advances in genetics open new avenues to address this question in more detail. We argue, however, that, even with the best techniques, predicting introgression from crop to wild species will always have a considerable margin of uncertainty. One must therefore be prudent to demand more detailed research for the ERA, especially since the possible harm of transgenes in natural populations remains so poorly defined by regulators

  1. Removal of natural organic matter and arsenic from water by electrocoagulation/flotation continuous flow reactor

    International Nuclear Information System (INIS)

    Mohora, Emilijan; Rončević, Srdjan; Dalmacija, Božo; Agbaba, Jasmina; Watson, Malcolm; Karlović, Elvira; Dalmacija, Milena

    2012-01-01

    Highlights: ► A continuous electrocoagulation/flotation reactor was designed built and operated. ► Highest NOM removal according to UV 254 was 77% relative to raw groundwater. ► Highest NOM removal accordance to DOC was 71%, relative to raw groundwater. ► Highest As removal archived was 85% (6.2 μg/l), relative to raw groundwater. ► Specific reactor energy and electrode consumption was 1.7 kWh/m 3 and 66 g Al/m 3 . - Abstract: The performance of the laboratory scale electrocoagulation/flotation (ECF) reactor in removing high concentrations of natural organic matter (NOM) and arsenic from groundwater was analyzed in this study. An ECF reactor with bipolar plate aluminum electrodes was operated in the horizontal continuous flow mode. Electrochemical and flow variables were optimized to examine ECF reactor contaminants removal efficiency. The optimum conditions for the process were identified as groundwater initial pH 5, flow rate = 4.3 l/h, inter electrode distance = 2.8 cm, current density = 5.78 mA/cm 2 , A/V ratio = 0.248 cm −1 . The NOM removal according to UV 254 absorbance and dissolved organic matter (DOC) reached highest values of 77% and 71% respectively, relative to the raw groundwater. Arsenic removal was 85% (6.2 μg As/l) relative to raw groundwater, satisfying the drinking water standards. The specific reactor electrical energy consumption was 17.5 kWh/kg Al. The specific aluminum electrode consumption was 66 g Al/m 3 . According to the obtained results, ECF in horizontal continuous flow mode is an energy efficient process to remove NOM and arsenic from groundwater.

  2. Removal of natural organic matter and arsenic from water by electrocoagulation/flotation continuous flow reactor

    Energy Technology Data Exchange (ETDEWEB)

    Mohora, Emilijan, E-mail: emohora@ifc.org [University of Novi Sad Faculty of Sciences, Department of Chemistry, Biochemistry and Environmental Protection, Trg D. Obradovica 3, 21000 Novi Sad (Serbia); Roncevic, Srdjan; Dalmacija, Bozo; Agbaba, Jasmina; Watson, Malcolm; Karlovic, Elvira; Dalmacija, Milena [University of Novi Sad Faculty of Sciences, Department of Chemistry, Biochemistry and Environmental Protection, Trg D. Obradovica 3, 21000 Novi Sad (Serbia)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer A continuous electrocoagulation/flotation reactor was designed built and operated. Black-Right-Pointing-Pointer Highest NOM removal according to UV{sub 254} was 77% relative to raw groundwater. Black-Right-Pointing-Pointer Highest NOM removal accordance to DOC was 71%, relative to raw groundwater. Black-Right-Pointing-Pointer Highest As removal archived was 85% (6.2 {mu}g/l), relative to raw groundwater. Black-Right-Pointing-Pointer Specific reactor energy and electrode consumption was 1.7 kWh/m{sup 3} and 66 g Al/m{sup 3}. - Abstract: The performance of the laboratory scale electrocoagulation/flotation (ECF) reactor in removing high concentrations of natural organic matter (NOM) and arsenic from groundwater was analyzed in this study. An ECF reactor with bipolar plate aluminum electrodes was operated in the horizontal continuous flow mode. Electrochemical and flow variables were optimized to examine ECF reactor contaminants removal efficiency. The optimum conditions for the process were identified as groundwater initial pH 5, flow rate = 4.3 l/h, inter electrode distance = 2.8 cm, current density = 5.78 mA/cm{sup 2}, A/V ratio = 0.248 cm{sup -1}. The NOM removal according to UV{sub 254} absorbance and dissolved organic matter (DOC) reached highest values of 77% and 71% respectively, relative to the raw groundwater. Arsenic removal was 85% (6.2 {mu}g As/l) relative to raw groundwater, satisfying the drinking water standards. The specific reactor electrical energy consumption was 17.5 kWh/kg Al. The specific aluminum electrode consumption was 66 g Al/m{sup 3}. According to the obtained results, ECF in horizontal continuous flow mode is an energy efficient process to remove NOM and arsenic from groundwater.

  3. Boron dilution transients during natural circulation flow in PWR-Experiments and CFD simulations

    Energy Technology Data Exchange (ETDEWEB)

    Hoehne, Thomas [Forschungszentrum Dresden-Rossendorf (FZD)-Institute of Safety Research, P.O. Box 510119, D-01314 Dresden (Germany)], E-mail: T.Hoehne@fzd.de; Kliem, Soeren; Rohde, Ulrich; Weiss, Frank-Peter [Forschungszentrum Dresden-Rossendorf (FZD)-Institute of Safety Research, P.O. Box 510119, D-01314 Dresden (Germany)

    2008-08-15

    Coolant mixing in the cold leg, downcomer and the lower plenum of pressurized water reactors is an important phenomenon mitigating the reactivity insertion into the core. Therefore, mixing of the de-borated slugs with the ambient coolant in the reactor pressure vessel was investigated at the four loops 1:5 scaled Rossendorf coolant mixing model (ROCOM) mixing test facility. In particular thermal hydraulics analyses have shown, that weakly borated condensate can accumulate in the pump loop seal of those loops, which do not receive a safety injection. After refilling of the primary circuit, natural circulation in the stagnant loops can re-establish simultaneously and the de-borated slugs are shifted towards the reactor pressure vessel (RPV). In the ROCOM experiments, the length of the flow ramp and the initial density difference between the slugs and the ambient coolant was varied. From the test matrix experiments with 0 resp. 2% density difference between the de-borated slugs and the ambient coolant were used to validate the CFD software ANSYS CFX. To model the effects of turbulence on the mean flow a higher order Reynolds stress turbulence model was employed and a mesh consisting of 6.4 million hybrid elements was utilized. Only the experiments and CFD calculations with modeled density differences show stratification in the downcomer. Depending on the degree of density differences the less dense slugs flow around the core barrel at the top of the downcomer. At the opposite side, the lower borated coolant is entrained by the colder safety injection water and transported to the core. The validation proves that ANSYS CFX is able to simulate appropriately the flow field and mixing effects of coolant with different densities.

  4. Computational simulation of flow and heat transfer in single-phase natural circulation loops

    International Nuclear Information System (INIS)

    Pinheiro, Larissa Cunha

    2017-01-01

    Passive decay heat removal systems based on natural circulation are essential assets for the new Gen III+ nuclear power reactors and nuclear spent fuel pools. The aim of the present work is to study both laminar and turbulent flow and heat transfer in single-phase natural circulation systems through computational fluid dynamics simulations. The working fluid is considered to be incompressible with constant properties. In the way, the Boussinesq Natural Convection Hypothesis was applied. The model chosen for the turbulence closure problem was the k -- εThe commercial computational fluid dynamics code ANSYS CFX 15.0 was used to obtain the numerical solution of the governing equations. Two single-phase natural circulation circuits were studied, a 2D toroidal loop and a 3D rectangular loop, both with the same boundary conditions of: prescribed heat flux at the heater and fixed wall temperature at the cooler. The validation and verification was performed with the numerical data provided by DESRAYAUD et al. [1] and the experimental data provided by MISALE et al. [2] and KUMAR et al. [3]. An excellent agreement between the Reynolds number (Re) and the modified Grashof number (Gr_m), independently of Prandtl Pr number was observed. However, the convergence interval was observed to be variable with Pr, thus indicating that Pr is a stability governing parameter for natural circulation. Multiple steady states was obtained for Pr = 0,7. Finally, the effect of inclination was studied for the 3D circuit, both in-plane and out-of-plane inclinations were verified for the steady state laminar regime. As a conclusion, the Re for the out-of-plane inclination was in perfect agreement with the correlation found for the zero inclination system, while for the in-plane inclined system the results differ from that of the corresponding vertical loop. (author)

  5. Risks to offshore installations in Europe due to natural hazards

    Science.gov (United States)

    Necci, Amos; Krausmann, Elisabeth

    2017-04-01

    Natural hazards, such as storms, earthquakes, or lightning are a major threat to industry. In particular, chemical plants, storage facilities, pipelines, and offshore oil and gas facilities are vulnerable to natural events which can cause hazardous materials releases and thereby endanger workers, the population and the environment. These technological accidents are commonly referred to as Natech accidents. Recent events have increased concerns about safety in the offshore oil and gas sector, and the need for improving knowledge on the matter has become evident. With those premises, we analyzed accidents, near misses and accident precursors at offshore facilities in Europe caused by natural events using both a statistical and a qualitative approach. For this purpose, we screened the World Offshore Accident Database (WOAD) to identify all incidents that featured natural events as causes or aggravating factors. A dataset of 1,085 global Natech events was built for the statistical analysis. Among those, a subset composed of 303 European records was selected. The results of the analysis showed that offshore Natech events in Europe are frequent; they resulted, however, in low consequences. The main threat to offshore facilities resulted from bad weather, such as strong winds and heavy seas. Storms can put intense loads on the structural parts of offshore installations, eventually exceeding design resistance specifications. Several incidents triggered by lightning strikes and earthquakes were also recorded. Substantial differences in terms of vulnerability, damage modality and consequences emerged between fixed and floating offshore structures. The main damage mode for floating structures was the failure of station keeping systems due to the rupture of mooring or anchors, mainly caused by adverse meteorological conditions. Most of the incidents at fixed offshore structures in Europe involved falling loads for both metal jacket and concrete base platforms due to storms. In

  6. THE SOCIAL PERCEPTION OF NATURAL HAZARDS RISK: PORTUGAL AND TUVALU

    OpenAIRE

    Rodrigo Rudge Ramos Ribeiro; Celeste Oliveira Alves Coelho

    2012-01-01

    Los efectos del cambio climático y del nivel del mar deben causar graves problemas para los habitantes de algunas pequeñas islas como Tuvalu en el futuro. Como resultado de una combinación de procesos naturales y acción antropogénica, el cambio del nivel del mar genera un impacto diferente. Esta investigación aborda la percepción del riesgo natural y del cambio climático en Portugal y Tuvalu. La percepción de algunos riesgos naturales, como la subida del nivel del mar, puede ser distinta para...

  7. A numerical study on the influence of slope and curvature on smoke flow in special section tunnel with natural ventilation

    Science.gov (United States)

    Wang, Wenzhou; Zhou, Xianping; Liu, Zhigang; Liu, Ya; Liu, Wanfu; Hong, Li

    2017-09-01

    In this study, a special section tunnel model was established by using FDS (Fire Dynamics Simulator). The influences of lope and curvature on smoke flow under natural ventilation have been studied. The results showed that under the condition of natural ventilation, the slope has some influences on the smoke flow in special section tunnel. The smoke spreading speed is accelerated along the upstream direction and decrease along the downstream direction due to buoyancy effect of slope. The steeper the tunnel, the more obvious the buoyancy effect. The curvature has little effect on the flow of flue gas.

  8. Experimental Observations of Natural Circulation Flow in the NSTF at Steady-State Conditions

    International Nuclear Information System (INIS)

    Lisowski, Darius D.; Farmer, Mitch T.

    2014-01-01

    A ½ scale test facility has been constructed at Argonne National Laboratory (ANL) to study the heat removal performance and natural circulation flow patterns in a Reactor Cavity Cooling System (RCCS). Our test facility, the Natural convection Shutdown heat removal Test Facility (NSTF), supports the broader goal of developing an inherently safe and fully passive ex-vessel decay heat removal for advanced reactor designs. The project, initiated in 2010 to support the Advanced Reactor Concepts (ARC), Small Modular Reactor (SMR), and Next Generation Nuclear Plant (NGNP) programs, has been conducting experimental operations since early 2014. The following paper provides a summary of some primary design features of the 26-m tall test facility along with a description of the data acquisition suite that guides our experimental practices. Specifics of the distributed fiber optic temperature measurements will be discussed, which introduces an unparalleled level of data density that has never before been implemented in a large scale natural circulation test facility. Results from our first test series will then be presented, which provide insight into the thermal hydraulic behavior at steady-state conditions for varying heat flux levels and exhaust chimney configuration states. (author)

  9. Probabilistic disaggregation of a spatial portfolio of exposure for natural hazard risk assessment

    DEFF Research Database (Denmark)

    Custer, Rocco; Nishijima, Kazuyoshi

    2018-01-01

    In natural hazard risk assessment situations are encountered where information on the portfolio of exposure is only available in a spatially aggregated form, hindering a precise risk assessment. Recourse might be found in the spatial disaggregation of the portfolio of exposure to the resolution...... of a portfolio of buildings in two communes in Switzerland and the results are compared to sample observations. The relevance of probabilistic disaggregation uncertainty in natural hazard risk assessment is illustrated with the example of a simple flood risk assessment....

  10. Development of a risk monitoring system for nuclear power plants based on GO-FLOW methodology

    International Nuclear Information System (INIS)

    Yang, Jun; Yang, Ming; Yoshikawa, Hidekazu; Yang, Fangqing

    2014-01-01

    Highlights: • A method for developing Living PSA is proposed. • Living PSA is easy to update with online modification to system model file. • A risk monitoring system is designed and developed using the GO-FLOW. • The risk monitoring system is useful for plant daily operation risk management. - Abstract: The paper presents a risk monitoring system developed based on GO-FLOW methodology which is a success-oriented system reliability modeling technique for phased mission as well as time-dependent problems analysis. The risk monitoring system is designed to receive information on plant configuration changes either from equipment failures, operator interventions, or maintenance activities, then update the Living PSA model with online modification to the system GO-FLOW model file which contains all the functional modes of equipment represented by a proposed generalized GO-FLOW modeling structure, and display risk values graphically. The risk monitoring system can be used to assist safety engineers and plant operators in their maintenance management and daily operation risk management at NPPs

  11. Development of a risk monitoring system for nuclear power plants based on GO-FLOW methodology

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jun, E-mail: youngjun51@hotmail.com [College of Nuclear Science and Technology, Harbin Engineering University, No. 145 Nantong Street, Nangang District, Harbin 150001 (China); Yang, Ming, E-mail: yangming@hrbeu.edu.cn [College of Nuclear Science and Technology, Harbin Engineering University, No. 145 Nantong Street, Nangang District, Harbin 150001 (China); Yoshikawa, Hidekazu, E-mail: yosikawa@kib.biglobe.ne.jp [Symbio Community Forum, Kyoto (Japan); Yang, Fangqing, E-mail: yfq613@163.com [China Nuclear Power Technology Research Institute, 518000 (China)

    2014-10-15

    Highlights: • A method for developing Living PSA is proposed. • Living PSA is easy to update with online modification to system model file. • A risk monitoring system is designed and developed using the GO-FLOW. • The risk monitoring system is useful for plant daily operation risk management. - Abstract: The paper presents a risk monitoring system developed based on GO-FLOW methodology which is a success-oriented system reliability modeling technique for phased mission as well as time-dependent problems analysis. The risk monitoring system is designed to receive information on plant configuration changes either from equipment failures, operator interventions, or maintenance activities, then update the Living PSA model with online modification to the system GO-FLOW model file which contains all the functional modes of equipment represented by a proposed generalized GO-FLOW modeling structure, and display risk values graphically. The risk monitoring system can be used to assist safety engineers and plant operators in their maintenance management and daily operation risk management at NPPs.

  12. Integration of risk matrix and event tree analysis: a natural stone ...

    Indian Academy of Sciences (India)

    M Kemal Özfirat

    2017-09-27

    Sep 27, 2017 ... Different types of accidents may occur in natural stone facilities during movement, dimensioning, cutting ... are numerous risk analysis methods such as preliminary ..... machine type and maintenance (MM) event, block control.

  13. A study of natural circulation cooling using a flow visualization rig

    International Nuclear Information System (INIS)

    Bowman, W.C.; Ferch, R.L.; Omar, A.M.

    1985-01-01

    A flow visualization rig has been built at Monserco Limited to provide visual insight into the thermalhydraulic phenomena which occur during single phase and two phase thermosyphoning in a figure-of-eight heat transport loop. Tests performed with the rig have provided design information for the scaling and instrumentation of a high pressure rig being investigated for simulating CANDU reactor conditions during natural circulation cooling. A videotape was produced, for viewing at this presentation, to show important thermalhydraulic features of the thermosyphoning process. The rig is a standard figure-of-eight loop with two steam generators and three heated channels per pass. An elevated surge tank open to atmosphere was used for pressure control. Two variable speed pumps provided forced circulation for warming up the rig, and for establishing the desired initial conditions for testing. Test rig power could be varied between 0 and 15 kW

  14. Molecular orbital evaluation of charge flow dynamics in natural pigments based photosensitizers.

    Science.gov (United States)

    Heera, Thekinneydath Rajan; Cindrella, Louis

    2010-03-01

    The relationship between structure and photo electrochemical property of ten natural pigments from plants, insects and microbes has been analyzed using density functional theory (DFT) at the B3LYP/6-31G(d) level. The essential parameters for their photoelectrochemical behaviour such as ground state geometries, electronic transition energies and oxidation potentials are computed. The attachment tendency of the anchoring groups, expressed as the deprotonation order, is determined by calculating the proton affinities at different sites of the molecules. A thorough analysis of the charge flow dynamics in the molecular orbitals (HOMO and LUMO) of these molecules has been carried out and presented to emphasize the role of these orbitals in effective charge separation, the important feature of photosensitizers for DSSC. This study highlights that the flexible spatial orientation provided by the bridging aliphatic unsaturation favours the oscillator strength and the hydroxyl anchor group attached to the ring of delocalized pi electron cloud acts as the effective anchor.

  15. Actin retrograde flow controls natural killer cell response by regulating the conformation state of SHP-1.

    Science.gov (United States)

    Matalon, Omri; Ben-Shmuel, Aviad; Kivelevitz, Jessica; Sabag, Batel; Fried, Sophia; Joseph, Noah; Noy, Elad; Biber, Guy; Barda-Saad, Mira

    2018-03-01

    Natural killer (NK) cells are a powerful weapon against viral infections and tumor growth. Although the actin-myosin (actomyosin) cytoskeleton is crucial for a variety of cellular processes, the role of mechanotransduction, the conversion of actomyosin mechanical forces into signaling cascades, was never explored in NK cells. Here, we demonstrate that actomyosin retrograde flow (ARF) controls the immune response of primary human NK cells through a novel interaction between β-actin and the SH2-domain-containing protein tyrosine phosphatase-1 (SHP-1), converting its conformation state, and thereby regulating NK cell cytotoxicity. Our results identify ARF as a master regulator of the NK cell immune response. Since actin dynamics occur in multiple cellular processes, this mechanism might also regulate the activity of SHP-1 in additional cellular systems. © 2018 The Authors.

  16. Attoclock reveals natural coordinates of the laser-induced tunnelling current flow in atoms

    DEFF Research Database (Denmark)

    Pfeiffer, Adrian N.; Cirelli, Claudio; Smolarski, Mathias

    2012-01-01

    the attoclock technique4 to obtain experimental information about the electron tunnelling geometry (the natural coordinates of the tunnelling current flow) and exit point. We confirm vanishing tunnelling delay time, show the importance of the inclusion of Stark shifts5, 6 and report on multi-electron effects......In the research area of strong-laser-field interactions and attosecond science1, tunnelling of an electron through the barrier formed by the electric field of the laser and the atomic potential is typically assumed to be the initial key process that triggers subsequent dynamics1, 2, 3. Here we use...... clearly identified by comparing results in argon and helium atoms. Our combined theory and experiment allows us to single out the geometry of the inherently one-dimensional tunnelling problem, through an asymptotic separation of the full three-dimensional problem. Our findings have implications for laser...

  17. Detailed evaluation of the natural circulation mass flow rate of water propelled by using an air injection

    International Nuclear Information System (INIS)

    Park, Rae-Joon; Ha, Kwang-Soon; Kim, Jae-Cheol; Hong, Seong-Wan; Kim, Sang-Baik

    2008-01-01

    One-dimensional (1D) air-water two-phase natural circulation flow in the thermohydraulic evaluation of reactor cooling mechanism by external self-induced flow - one-dimensional' (THERMES-1D) experiment has been verified and evaluated by using the RELAP5/MOD3 computer code. Experimental results on the 1D natural circulation mass flow rate of water propelled by using an air injection have been evaluated in detail. The RELAP5 results have shown that an increase in the air injection rate to 50% of the total heat flux leads to an increase in the water circulation mass flow rate. However, an increase in the air injection rate from 50 to 100% does not affect the water circulation mass flow rate, because of the inlet area condition. As the height increases in the air injection part, the void fraction increases. However, the void fraction in the upper part of the air injector maintains a constant value. An increase in the air injection mass flow rate leads to an increase in the local void fraction, but it has no influence on the local pressure. An increase in the coolant inlet area leads to an increase in the water circulation mass flow rate. However, the water outlet area does not have an influence on the water circulation mass flow rate. As the coolant outlet moves to a lower position, the water circulation mass flow rate decreases. (author)

  18. Modeling Flow in Naturally Fractured Reservoirs : Effect of Fracture Aperture Distribution on Critical Sub-Network for Flow

    NARCIS (Netherlands)

    Gong, J.; Rossen, W.R.

    2014-01-01

    Fracture network connectivity and aperture (or conductivity) distribution are two crucial features controlling the flow behavior of fractured formations. The effect of connectivity on flow properties is well documented. We focus here on the influence of fracture aperture distribution. We model a

  19. Effects of T-type Channel on Natural Convection Flows in Airflow-Path of Concrete Storage Cask

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Gyeong Uk; Kim, Hyoung Jin; Cho, Chun Hyung [KORAD, Daejeon (Korea, Republic of)

    2016-05-15

    The natural convection flows occurring in airflow-path are not simple due to complex flow-path configurations such as horizontal ducts, bent tube and annular flow-path. In addition, 16 T type channels acting as the shroud are attached vertically and 16 channel supporting the canister are attached horizontally on the inner surface of over-pack. The existence and nonexistence of T type channels have influences on the flow fields in airflow- path. The concrete storage cask has to satisfy the requirements to secure the thermal integrity under the normal, off-normal, and accident conditions. The present work is aiming at investigating the effects of T type channels on the flows in airflow-path under the normal conditions using the FLUENT 16.1 code. In order to focus on the flows in airflow-path, fuel regions in the canister are regarded as a single cylinder with heat sources and other components are fully modeled. This study investigated the flow fields in airflow-path of concrete storage cask, numerically. It was found that excepting for the fuel regions, maximum temperatures on other components were evaluated below allowable values. The location of maximum velocities depended on support channels, T type channels and flow area. The flows through air inlets developed along annular flow- path with forming the hot plumes. According to the existence and nonexistence of T type channel, the plume behavior showed the different flow patterns.

  20. Radiated chemical reaction impacts on natural convective MHD mass transfer flow induced by a vertical cone

    Science.gov (United States)

    Sambath, P.; Pullepu, Bapuji; Hussain, T.; Ali Shehzad, Sabir

    2018-03-01

    The consequence of thermal radiation in laminar natural convective hydromagnetic flow of viscous incompressible fluid past a vertical cone with mass transfer under the influence of chemical reaction with heat source/sink is presented here. The surface of the cone is focused to a variable wall temperature (VWT) and wall concentration (VWC). The fluid considered here is a gray absorbing and emitting, but non-scattering medium. The boundary layer dimensionless equations governing the flow are solved by an implicit finite-difference scheme of Crank-Nicolson which has speedy convergence and stable. This method converts the dimensionless equations into a system of tri-diagonal equations and which are then solved by using well known Thomas algorithm. Numerical solutions are obtained for momentum, temperature, concentration, local and average shear stress, heat and mass transfer rates for various values of parameters Pr, Sc, λ, Δ, Rd are established with graphical representations. We observed that the liquid velocity decreased for higher values of Prandtl and Schmidt numbers. The temperature is boost up for decreasing values of Schimdt and Prandtl numbers. The enhancement in radiative parameter gives more heat to liquid due to which temperature is enhanced significantly.

  1. Energy efficiency enhancement of natural rubber smoking process by flow improvement using a CFD technique

    International Nuclear Information System (INIS)

    Tekasakul, Perapong; Promtong, Machimontorn

    2008-01-01

    A non-uniform flow and large temperature variation in a natural rubber smoking-room cause an inefficient use of energy. Flow uniformity and temperature variation can be improved by using a computational fluid dynamics (CFD) simulation. The effects of the size, position and number of gas supply ducts and ventilating lids which were at the inlets and the outlets of the smoking-room were investigated. The optimal rubber smoking-room of size 2.6 m x 6.2 m x 3.6 m contains 154 50 mm-diameter hot gas supply ducts, and four 0.25 x 0.25 m and four 0.25 x 0.20 m ventilating lids. The velocity distribution of this model in the rubber-hanging area was rather uniform. The average monitoring temperature of 54 positions was 62.1 deg. C. This model could reduce the temperature variation by a factor of three from the original room model, i.e., from 15 to 5.5 deg. C. In a further study, the heat input of an appropriate room model was finely adjusted to obtain a suitable temperature (60 deg. C) for the smoking process. It was found that an appropriate heat supply at this temperature is 11 kW. At this rate, the temperature variation is 5.3 deg. C. This improved model should help the rubber smoking cooperatives to achieve at least a 31.25% saving in energy

  2. Energy efficiency enhancement of natural rubber smoking process by flow improvement using a CFD technique

    Energy Technology Data Exchange (ETDEWEB)

    Tekasakul, Perapong [Energy Technology Research Center and Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90112 (Thailand)], E-mail: perapong.t@psu.ac.th; Promtong, Machimontorn [Division of Mechanical Engineering, School of Engineering and Resources, Walailak University, Nakhon Si Thammarat 80160 (Thailand)

    2008-09-15

    A non-uniform flow and large temperature variation in a natural rubber smoking-room cause an inefficient use of energy. Flow uniformity and temperature variation can be improved by using a computational fluid dynamics (CFD) simulation. The effects of the size, position and number of gas supply ducts and ventilating lids which were at the inlets and the outlets of the smoking-room were investigated. The optimal rubber smoking-room of size 2.6 m x 6.2 m x 3.6 m contains 154 50 mm-diameter hot gas supply ducts, and four 0.25 x 0.25 m and four 0.25 x 0.20 m ventilating lids. The velocity distribution of this model in the rubber-hanging area was rather uniform. The average monitoring temperature of 54 positions was 62.1 deg. C. This model could reduce the temperature variation by a factor of three from the original room model, i.e., from 15 to 5.5 deg. C. In a further study, the heat input of an appropriate room model was finely adjusted to obtain a suitable temperature (60 deg. C) for the smoking process. It was found that an appropriate heat supply at this temperature is 11 kW. At this rate, the temperature variation is 5.3 deg. C. This improved model should help the rubber smoking cooperatives to achieve at least a 31.25% saving in energy.

  3. Experimental investigation of a solar dryer with natural convective heat flow

    Energy Technology Data Exchange (ETDEWEB)

    Gbaha, P.; Yobouet Andoh, H.; Kouassi Saraka, J. [Laboratoire d' Energies d' Energies Nouvelles et Renouvelables, Institut National Polytechnique Felix Houphoeuet-Boigny, B.P. 1526 Yamoussoukro (Ivory Coast); Kamenan Koua, B.; Toure, S. [Laboratoire d' Energie Solaire, Universite de Cocody, 22 B.P.: 582, Abidjan 22 (Ivory Coast)

    2007-09-15

    A direct type natural convection solar dryer is designed. It is constructed in local materials (wood, blades of glass, metals) then tested experimentally in foodstuffs drying (cassava, bananas, mango). It is about an experimental approach which consists in analyzing the behavior of the dryer. The study relates mainly kinetics and establishment of drying heat balances. The influence of significant parameters governing heat and mass transfers, such as solar incident radiation, drying air mass flow and effectiveness, is analyzed in order to evaluate its thermal performances. Experimental data can be represented by empirical correlations of the form M(t)=M{sub i}exp(-kt) for representation of drying process. The resolution of these drying equations makes-possible to predict total drying time of each product. Moreover, this drying process allows to reduce the moisture content of cassava and sweet banana approximately to 80% in 19 and 22 h, respectively to reach the safety threshold value of 13%. This value permits the conservation of these products about one year without deterioration. The determination of parameters, like ambient temperature, drying chamber temperature, drying air mass flow and incident heat fluxes, allow to predict the drying effectiveness for modeling and refining the dimensioning of the elaborate prototype. (author)

  4. Some risks related to the short-term trading of natural gas

    International Nuclear Information System (INIS)

    Mazighi, Ahmed El Hachemi

    2004-01-01

    Traditionally guided by long-term contracts, the international natural gas trade is experiencing new methods of operating, based on the short term and more flexibility. Today, indeed, the existence of uncommitted quantities of natural gas, combined with gas price discrepancies among different regions of the world, gives room for the expansion of the spot-trading of gas. The main objective of this paper is to discuss three fundamental risks related to the short-term trading of natural gas: volume risk, price risk and infrastructure risk. The defenders of globalisation argue that the transition from the long-term to the short-term trading of natural gas is mainly a question of access to gas reserves, decreasing costs of gas liquefaction, the building of liquefied natural gas (LNG) fleets and regasification facilities and third-party access to the infrastructure. This process needs to be as short as possible, so that the risks related to the transition process will disappear rapidly. On the other hand, the detractors of globalisation put the emphasis on the complexity of the gas value chain and on the fact that eliminating long-term contracts increases the risks inherent to the international natural gas business. In this paper, we try to untangle and assess the risks related to the short-term trading of natural gas. Our main conclusions are: the short-term trading of gas is far from riskless; volume risk requires stock-building in both consuming and producing countries; price risk, through the high volatility for gas, induces an increase in options prices; there is no evidence to suggest that money-lenders' appetite for financing gas infrastructure projects will continue in a short-term trading system. This would be a threat to consumers' security of supply. (Author)

  5. THE SOCIAL PERCEPTION OF NATURAL HAZARDS RISK: PORTUGAL AND TUVALU

    Directory of Open Access Journals (Sweden)

    Rodrigo Rudge Ramos Ribeiro

    2012-01-01

    Full Text Available Los efectos del cambio climático y del nivel del mar deben causar graves problemas para los habitantes de algunas pequeñas islas como Tuvalu en el futuro. Como resultado de una combinación de procesos naturales y acción antropogénica, el cambio del nivel del mar genera un impacto diferente. Esta investigación aborda la percepción del riesgo natural y del cambio climático en Portugal y Tuvalu. La percepción de algunos riesgos naturales, como la subida del nivel del mar, puede ser distinta para cada sitio. La percepción de los cambios climáticos en Tuvalu es poco conocida por la comunidad académica de la Universidad de Aveiro, y creen que los impactos del aumento del nivel del mar para Portugal y Tuvalu no son los mismos. La distancia geográfica tiene una influencia en la percepción del riesgo, a mayor distancia se le da una menor atención.

  6. The Role of Knowledge in the prevention of natural hazards and related risks.

    Directory of Open Access Journals (Sweden)

    Enrico Miccadei

    2014-02-01

    Full Text Available Human activities, especially over the last two centuries, have had a huge impact on the environment and the landscape. Mankind is able to control and induce landscape changes but is subject to natural processes and hazards due to severe and extreme events (particularly earthquakes but also landslides and flooding and related risks. Risks are the result of hazards, exposed elements and vulnerability and they are consequently not only an expression of the natural environment, but also related to human interaction with nature. Risks need to be addressed regularly by means of a high level of knowledge in order to provide most up­to­date information for any decision which needs to be taken by any party involved. A high level of knowledge concerning natural hazards and related risks stems from the geological and geomorphological history and from the historical records of the natural processes and grows with multi­scale, multi­temporal and multidisciplinary studies and investigations, which include land management, economic and social issues. A strong effort has to be made in this way to improve risk assessment and the enforcement of existing laws and ­ if necessary ­ new laws, really stem from recent disasters. This will help to achieve improved and effective land management, based on an interdisciplinary approach in which expert geologists and land managers will play a role, because of the importance of natural processes in inducing risks.

  7. Radon risk and natural radioactivity of Ziar Basin territory

    International Nuclear Information System (INIS)

    Urminska, J.; Khun, M.; Jurkovic, L.

    1999-01-01

    Radon is one of the most important detection elements for assessing the environmental conditions, e.g.in conurbations. The radon radiation waters, and rocks on the Ziar Basin territory [Central Slovakia] was fully studied. Potential risk areas can be found in the vicinity of tectonic faults (verified and supposed). An excess of over 11% of the radon limit concentration was detected in the environment of some buildings. But in terms of high radioactivity Basin region, the dominant position is kept by the rhyolites, rhyodacites and their pyroclastic rocks. Higher values for the 222 Rn volume activity were identified for the samples of waters in rhyolite and granodiorite bodies situated in the tectonic lines of the NE - SW direction. During its transfer through living material the ionizing radiation causes ionization and produces changes in its structure and composition at the same time. This results along with heavy metals in cell death, damage to genetic material, and an increase in the incidence of malignant tumors of the digestation system and lymph-nodes, leukaemia and cancer of the lung. Since 1990, the localities under investigation have shown a higher sickness rate (congenital evolution defects, tumor diseases) when compared to the all-Slovak average

  8. Press freedom, oil exports, and risk for natural disasters: a challenge for climato-economic theory?

    Science.gov (United States)

    Arantes, Joana; Grace, Randolph C; Kemp, Simon

    2013-10-01

    Does the interaction between climactic demands, monetary resources, and freedom suggest a more general relationship between the environmental challenges that human societies face and their resources to meet those challenges? Using data on press freedom (Van de Vliert 2011a), we found no evidence of a similar interaction with natural resources (as measured by oil exports) or risk for natural disasters.

  9. A regional-scale ecological risk framework for environmental flow evaluations

    Science.gov (United States)

    O'Brien, Gordon C.; Dickens, Chris; Hines, Eleanor; Wepener, Victor; Stassen, Retha; Quayle, Leo; Fouchy, Kelly; MacKenzie, James; Graham, P. Mark; Landis, Wayne G.

    2018-02-01

    Environmental flow (E-flow) frameworks advocate holistic, regional-scale, probabilistic E-flow assessments that consider flow and non-flow drivers of change in a socio-ecological context as best practice. Regional-scale ecological risk assessments of multiple stressors to social and ecological endpoints, which address ecosystem dynamism, have been undertaken internationally at different spatial scales using the relative-risk model since the mid-1990s. With the recent incorporation of Bayesian belief networks into the relative-risk model, a robust regional-scale ecological risk assessment approach is available that can contribute to achieving the best practice recommendations of E-flow frameworks. PROBFLO is a holistic E-flow assessment method that incorporates the relative-risk model and Bayesian belief networks (BN-RRM) into a transparent probabilistic modelling tool that addresses uncertainty explicitly. PROBFLO has been developed to evaluate the socio-ecological consequences of historical, current and future water resource use scenarios and generate E-flow requirements on regional spatial scales. The approach has been implemented in two regional-scale case studies in Africa where its flexibility and functionality has been demonstrated. In both case studies the evidence-based outcomes facilitated informed environmental management decision making, with trade-off considerations in the context of social and ecological aspirations. This paper presents the PROBFLO approach as applied to the Senqu River catchment in Lesotho and further developments and application in the Mara River catchment in Kenya and Tanzania. The 10 BN-RRM procedural steps incorporated in PROBFLO are demonstrated with examples from both case studies. PROBFLO can contribute to the adaptive management of water resources and contribute to the allocation of resources for sustainable use of resources and address protection requirements.

  10. Reverse flow injection spectrophotometric determination of thiram and nabam fungicides in natural water samples

    International Nuclear Information System (INIS)

    Asghar, M.; Yaqoob, M.; Nabi, A.

    2014-01-01

    A reverse flow injection (rFI) spectrophotometric method is reported for determination of thiram and nabam fungicides in natural water samples. The method is based on the reduction of iron(III) in the presence of thiram/nabam in acidic medium at 60 degree C and formation of iron(II)-ferricyanide complex was measured at 790 nm. The limits of detection (3s blank) were 0.01 and 0.05 micro g mL1 for thiram and nabam respectively with a sample throughput of 60 h1. Calibration graphs were linear over the range of 0.02 - 8.0 micro g mL1 (R2 = 0.9999, n = 8) and 0.1 - 30 micro g mL1 (R2 = 0.9982, n = 10) for thiram and nabam with relative standard deviations (RSDs; n = 3) in the range of 0.8 - 1.6% respectively. Experimental parameters and potential interferences were examined. Thiram and nabam were determined in natural water samples using solid-phase extraction (SPE) procedure and recoveries were in the range of 93+-3 - 105+-2% and 87+-4 - 102+-3% respectively. The results obtained were not significantly different compared with a HPLC method. (author)

  11. Assessment of MELCOR condensation models with the presence of noncondensable gas in natural convection flow regime

    International Nuclear Information System (INIS)

    Yoon, Dhongik S; Jo, HangJin; Corradini, Michael L

    2017-01-01

    Condensation of steam vapor is an important mode of energy removal from the reactor containment. The presence of noncondensable gas complicates the process and makes it difficult to model. MELCOR, one of the more widely used system codes for containment analyses, uses the heat and mass transfer analogy to model condensation heat transfer. To investigate previously reported nodalization-dependence in natural convection flow regime, MELCOR condensation model as well as other models are studied. The nodalization-dependence issue is resolved by using physical length from the actual geometry rather than node size of each control volume as the characteristic length scale for MELCOR containment analyses. At the transition to turbulent natural convection regime, the McAdams correlation for convective heat transfer produces a better prediction compared to the original MELCOR model. The McAdams correlation is implemented in MELCOR and the prediction is validated against a set of experiments on a scaled AP600 containment. The MELCOR with our implemented model produces improved predictions. For steam molar fractions in the gas mixture greater than about 0.58, the predictions are within the uncertainty margin of the measurements. The simulation results still underestimate the heat transfer from the gas-steam mixture, implying that conservative predictions are provided.

  12. Natural Disaster Risk and Engagement in the Arctic

    Science.gov (United States)

    Eichelberger, J. C.

    2015-12-01

    The Arctic is beset with natural hazards no less than other regions of Earth, but there are some special aspects that require attention. The presence of ice leads to spring river flooding and dynamics of coastal erosion not present in warmer climates. Vast boreal forests are subject to wildfires that are huge pollution events and a positive feedback to climate change through production of CO2, other gases, and black carbon. Darkness and extreme cold that prevail for a significant portion of the year is a challenge to disaster response. Special societal aspects of the Arctic produce vulnerabilities on two scales. One is the development of infrastructure in support of growing extractive industries and Arctic shipping. Reliance on such facilities, which often lack redundancy, and on long supply lines for food and fuel from the south impedes resilience. In 1964, Alaska lost much of its infrastructure to the 9.2 magnitude earthquake and subsequent tsunamis. Today, Alaska has greater dependency on external supplies and less internal redundancy. Planning that affects vulnerability of infrastructure is often done by corporations and regulated by government agencies based outside the Arctic. The work of scientists who understood Alaska, both within and outside government, provided information to energy corporations persuading them to include expensive design measures into the Trans Alaska Pipeline for crossing an active fault and preventing thawing of permafrost. This is a success story that should not be forgotten. At the other end of the size scale are isolated off-grid and off-road remote communities with fragile power, water, and sanitation facilities. A disaster there can pose an immediate threat to health and even life. Long-term evacuation and the cost a reconstruction may mean that the community is never re-established. Where such communities are centers of indigneous culture, the culture is threatened. With the goal of identifying best practices with these

  13. DEVELOPMENT OF A LOW COST INFERENTIAL NATURAL GAS ENERGY FLOW RATE PROTOTYPE RETROFIT MODULE

    Energy Technology Data Exchange (ETDEWEB)

    E. Kelner; D. George; T. Morrow; T. Owen; M. Nored; R. Burkey; A. Minachi

    2005-05-01

    In 1998, Southwest Research Institute began a multi-year project to develop a working prototype instrument module for natural gas energy measurement. The module will be used to retrofit a natural gas custody transfer flow meter for energy measurement, at a cost an order of magnitude lower than a gas chromatograph. Development and evaluation of the prototype energy meter in 2002-2003 included: (1) refinement of the algorithm used to infer properties of the natural gas stream, such as heating value; (2) evaluation of potential sensing technologies for nitrogen content, improvements in carbon dioxide measurements, and improvements in ultrasonic measurement technology and signal processing for improved speed of sound measurements; (3) design, fabrication and testing of a new prototype energy meter module incorporating these algorithm and sensor refinements; and (4) laboratory and field performance tests of the original and modified energy meter modules. Field tests of the original energy meter module have provided results in close agreement with an onsite gas chromatograph. The original algorithm has also been tested at a field site as a stand-alone application using measurements from in situ instruments, and has demonstrated its usefulness as a diagnostic tool. The algorithm has been revised to use measurement technologies existing in the module to measure the gas stream at multiple states and infer nitrogen content. The instrumentation module has also been modified to incorporate recent improvements in CO{sub 2} and sound speed sensing technology. Laboratory testing of the upgraded module has identified additional testing needed to attain the target accuracy in sound speed measurements and heating value.

  14. Health risk assessment linked with purified biogas injection in a natural gas distribution system

    International Nuclear Information System (INIS)

    Leroux, Carole; Modelon, Hugues; Rousselle, Christophe; Zdanevitch, Isabelle; Evanno, Sebastien

    2009-06-01

    This document provides for the opinion of the French Agency for Environmental and Occupational Health and Safety (Afsset) expressed after the collective expertise carried out for the evaluation of the health risk linked with biogas injection in the natural gas distribution system. Following the recommendations issued by the Afsset, works have been started in order to collect the sludge-derived biogas and to analyse its composition. These data will be used to assess accidental risks (resulting from biogas valorisation, pipeline transport, industrial and domestic energy valorisation) as well as health risks for users (resulting from the injection in the natural gas distribution system)

  15. Evaluations of two-phase natural circulation flow induced in the reactor vessel annular gap under ERVC conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Kwang Soon, E-mail: tomo@kaeri.re.kr [Korea Atomic Energy Research Institute, 1045 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Cheung, Fan-Bill [The Pennsylvania State University, University Park, PA 16802 (United States); Park, Rae Joon; Kim, Sang Baik [Korea Atomic Energy Research Institute, 1045 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer Two-phase natural circulation flow induced in insulation gap was investigated. Black-Right-Pointing-Pointer Half-scaled non-heating experiments were performed to evaluate flow behavior. Black-Right-Pointing-Pointer The loop-integrated momentum equation was formulated and solved asymptotically. Black-Right-Pointing-Pointer First-order approximate solution was obtained and agreed with experimental data. - Abstract: The process of two-phase natural circulation flow induced in the annular gap between the reactor vessel and the insulation under external reactor vessel cooling conditions was investigated experimentally and analytically in this study. HERMES-HALF experiments were performed to observe and quantify the induced two-phase natural circulation flow in the annular gap. A half-scaled non-heating experimental facility was designed by utilizing the results of a scaling analysis to simulate the APR1400 reactor and its insulation system. The behavior of the boiling-induced two-phase natural circulation flow in the annular gap was observed, and the liquid mass flow rates driven by the natural circulation loop and the void fraction distribution were measured. Direct flow visualization revealed that choking would occur under certain flow conditions in the minimum gap region near the shear keys. Specifically, large recirculation flows were observed in the minimum gap region for large air injection rates and small outlet areas. Under such conditions, the injected air could not pass through the minimum gap region, resulting in the occurrence of choking near the minimum gap with a periodical air back flow being generated. Therefore, a design modification of the minimum gap region needs to be done to facilitate steam venting and to prevent choking from occurring. To complement the HERMES-HALF experimental effort, an analytical study of the dependence of the induced natural circulation mass flow rate on the inlet area and the

  16. Assessing climate change risks to the natural environment to facilitate cross-sectoral adaptation policy.

    Science.gov (United States)

    Brown, Iain

    2018-06-13

    Climate change policy requires prioritization of adaptation actions across many diverse issues. The policy agenda for the natural environment includes not only biodiversity, soils and water, but also associated human benefits through agriculture, forestry, water resources, hazard alleviation, climate regulation and amenity value. To address this broad agenda, the use of comparative risk assessment is investigated with reference to statutory requirements of the UK Climate Change Risk Assessment. Risk prioritization was defined by current adaptation progress relative to risk magnitude and implementation lead times. Use of an ecosystem approach provided insights into risk interactions, but challenges remain in quantifying ecosystem services. For all risks, indirect effects and potential systemic risks were identified from land-use change, responding to both climate and socio-economic drivers, and causing increased competition for land and water resources. Adaptation strategies enhancing natural ecosystem resilience can buffer risks and sustain ecosystem services but require improved cross-sectoral coordination and recognition of dynamic change. To facilitate this, risk assessments need to be reflexive and explicitly assess decision outcomes contingent on their riskiness and adaptability, including required levels of human intervention, influence of uncertainty and ethical dimensions. More national-scale information is also required on adaptation occurring in practice and its efficacy in moderating risks.This article is part of the theme issue 'Advances in risk assessment for climate change adaptation policy'. © 2018 The Author(s).

  17. Assessing climate change risks to the natural environment to facilitate cross-sectoral adaptation policy

    Science.gov (United States)

    Brown, Iain

    2018-06-01

    Climate change policy requires prioritization of adaptation actions across many diverse issues. The policy agenda for the natural environment includes not only biodiversity, soils and water, but also associated human benefits through agriculture, forestry, water resources, hazard alleviation, climate regulation and amenity value. To address this broad agenda, the use of comparative risk assessment is investigated with reference to statutory requirements of the UK Climate Change Risk Assessment. Risk prioritization was defined by current adaptation progress relative to risk magnitude and implementation lead times. Use of an ecosystem approach provided insights into risk interactions, but challenges remain in quantifying ecosystem services. For all risks, indirect effects and potential systemic risks were identified from land-use change, responding to both climate and socio-economic drivers, and causing increased competition for land and water resources. Adaptation strategies enhancing natural ecosystem resilience can buffer risks and sustain ecosystem services but require improved cross-sectoral coordination and recognition of dynamic change. To facilitate this, risk assessments need to be reflexive and explicitly assess decision outcomes contingent on their riskiness and adaptability, including required levels of human intervention, influence of uncertainty and ethical dimensions. More national-scale information is also required on adaptation occurring in practice and its efficacy in moderating risks. This article is part of the theme issue `Advances in risk assessment for climate change adaptation policy'.

  18. Experimental and modelling study of reverse flow catalytic converters for natural gas/diesel dual fuel engine pollution control

    Energy Technology Data Exchange (ETDEWEB)

    Liu, B.

    2000-07-01

    There is renewed interest in the development of natural gas vehicles in response to the challenge to reduce urban air pollution and consumption of petroleum. The natural gas/diesel dual fuel engine is one way to apply natural gas to the conventional diesel engine. Dual fuel engines operating on natural gas and diesel emit less nitrogen oxides, and less carbon soot to the air compared to conventional diesel engines. The problem is that at light loads, fuel efficiency is reduced and emissions of hydrocarbons and carbon monoxide are increased. This thesis focused on control methods for emissions of hydrocarbons and carbon monoxide in the dual fuel engine at light loads. This was done by developing a reverse flow catalytic converter to complement dual fuel engine exhaust characteristics. Experimental measurements and numerical simulations of reverse flow catalytic converters were conducted. Reverse flow creates a high reactor temperature even when the engine is run at low exhaust temperature levels at light loads. The increase in reactor temperature from reverse flow could be 2 or 3 times higher than the adiabatic temperature increase, which is based on the reactor inlet temperature and concentration. This temperature makes it possible for greater than 90 per cent of the hydrocarbon and carbon monoxide to be converted with a palladium based catalyst. Reverse flow appears to be better than conventional unidirectional flow to deal with natural gas/diesel dual fuel engine pollution at light loads. Reverse flow could also maintain reactor temperature at over 800 K and hydrocarbon conversion at about 80 per cent during testing. The newly presented model simulates reactor performance with reasonable accuracy. Both carbon monoxide and methane oxidation over the palladium catalyst in excess oxygen and water were described using first order kinetics.

  19. Comparative assessment of severe accident risks in the coal, oil and natural gas chains

    International Nuclear Information System (INIS)

    Burgherr, Peter; Eckle, Petrissa; Hirschberg, Stefan

    2012-01-01

    This study compared severe accident risks of fossil energy chains (coal, oil and natural gas), based on the historical experience contained in the comprehensive database ENSAD. Considered risk indicators focused on human health impacts, i.e., fatality rates and maximum consequences were calculated for a broad range of country groups. Generally, expected fatality rates were lowest for natural gas, intermediate for oil and highest for coal. Concerning maximum consequences of a single accident, natural gas also performed best, followed by coal, whereas accidents in the oil chain can claim significantly more fatalities. In general, OECD and EU 27 ranked top, while non-OECD countries and China in the case of coal were worst. The consideration of numerous additional country groups enabled a more detailed differentiation within the main bounding groups. Furthermore, differences among country groups are distinctly decreasing from coal to oil and natural gas, both for fatality rates and maximum consequences. The use of import adjusted-fatality rates indicates that fatality risks in supply countries are an essential aspect to understand how specific risk reduction strategies may affect other components of energy security, and thus tradeoffs and compromises are necessary. Finally, the proposed fatality risk score for fossil chains (FRS F ) allows a comparison of the combined accident risk for the considered fossil energy chains across individual countries, which can be visualized using risk mapping.

  20. THE LIQUID NITROGEN SYSTEM FOR CHAMBER A; A CHANGE FROM ORIGINAL FORCED FLOW DESIGN TO A NATURAL FLOW (THERMO SIPHON) SYSTEM

    International Nuclear Information System (INIS)

    Homan, J.; Montz, M.; Ganni, V.; Sidi-Yekhlef, A.; Knudsen, P.; Creel, J.; Arenius, D.; Garcia, S.

    2010-01-01

    NASA at the Johnson Space Center (JSC) in Houston is presently working toward modifying the original forced flow liquid nitrogen cooling system for the thermal shield in the space simulation chamber-A in Building 32 to work as a natural flow (thermo siphon) system. Chamber A is 19.8 m (65 ft) in diameter and 35.66 m (117 ft) high. The LN 2 shroud environment within the chamber is approximately 17.4 m (57 ft) in diameter and 28 m (92 ft) high. The new thermo siphon system will improve the reliability, stability of the system. Also it will reduce the operating temperature and the liquid nitrogen use to operate the system. This paper will present the requirements for the various operating modes. System level thermodynamic comparisons of the existing system to the various options studied and the final option selected will be outlined. A thermal and hydraulic analysis to validate the selected option for the conversion of the current forced flow to natural flow design will be discussed. The proposed modifications to existing system to convert to natural circulation (thermo siphon) system and the design features to help improve the operations, and maintenance of the system will be presented.

  1. Investigation on the heat transfer characteristics during flow boiling of liquefied natural gas in a vertical micro-fin tube

    Science.gov (United States)

    Xu, Bin; Shi, Yumei; Chen, Dongsheng

    2014-03-01

    This paper presents an experimental investigation on the heat transfer characteristics of liquefied natural gas flow boiling in a vertical micro-fin tube. The effect of heat flux, mass flux and inlet pressure on the flow boiling heat transfer coefficients was analyzed. The Kim, Koyama, and two kinds of Wellsandt correlations with different Ftp coefficients were used to predict the flow boiling heat transfer coefficients. The predicted results showed that the Koyama correlation was the most accurate over the range of experimental conditions.

  2. Natural-Scale Lava Flow Experiments on Video: Variations with Temperature, Slope, and Effusion Rate

    Science.gov (United States)

    Karson, J. A.; Wysocki, R.; Edwards, B. R.; Lev, E.

    2013-12-01

    Investigations of active basaltic lava flows and analog materials show that flow dynamics and final flow morphology are strongly determined by the rapidly evolving rheology of the lava crust which constrains the downslope advance of the lava flow. The non-dimensional factor Ψ (ratio of the time scale of crust formation to advective heat loss) provides a useful means of comparing different flows. The key parameters that control Ψ include the melt viscosity, temperature, effusion rate, and slope. Experimental lava flows, up to several meters long created in the Syracuse University Lava Project permit these variables to be investigated independently and in combination in volume-limited flows (Pele), that provide additional information on lava crust development. New, continuous flow (cooling-limited) experiments show downslope variations under constant flow conditions.

  3. Computational Analysis of Natural Ventilation Flows in Geodesic Dome Building in Hot Climates

    Directory of Open Access Journals (Sweden)

    Zohreh Soleimani

    2016-08-01

    Full Text Available For centuries, dome roofs were used in traditional houses in hot regions such as the Middle East and Mediterranean basin due to its thermal advantages, structural benefits and availability of construction materials. This article presents the computational modelling of the wind- and buoyancy-induced ventilation in a geodesic dome building in a hot climate. The airflow and temperature distributions and ventilation flow rates were predicted using Computational Fluid Dynamics (CFD. The three-dimensional Reynolds-Averaged Navier-Stokes (RANS equations were solved using the CFD tool ANSYS FLUENT15. The standard k-epsilon was used as turbulence model. The modelling was verified using grid sensitivity and flux balance analysis. In order to validate the modelling method used in the current study, additional simulation of a similar domed-roof building was conducted for comparison. For wind-induced ventilation, the dome building was modelled with upper roof vents. For buoyancy-induced ventilation, the geometry was modelled with roof vents and also with two windows open in the lower level. The results showed that using the upper roof openings as a natural ventilation strategy during winter periods is advantageous and could reduce the indoor temperature and also introduce fresh air. The results also revealed that natural ventilation using roof vents cannot satisfy thermal requirements during hot summer periods and complementary cooling solutions should be considered. The analysis showed that buoyancy-induced ventilation model can still generate air movement inside the building during periods with no or very low wind.

  4. Estimating Risk of Natural Gas Portfolios by Using GARCH-EVT-Copula Model.

    Science.gov (United States)

    Tang, Jiechen; Zhou, Chao; Yuan, Xinyu; Sriboonchitta, Songsak

    2015-01-01

    This paper concentrates on estimating the risk of Title Transfer Facility (TTF) Hub natural gas portfolios by using the GARCH-EVT-copula model. We first use the univariate ARMA-GARCH model to model each natural gas return series. Second, the extreme value distribution (EVT) is fitted to the tails of the residuals to model marginal residual distributions. Third, multivariate Gaussian copula and Student t-copula are employed to describe the natural gas portfolio risk dependence structure. Finally, we simulate N portfolios and estimate value at risk (VaR) and conditional value at risk (CVaR). Our empirical results show that, for an equally weighted portfolio of five natural gases, the VaR and CVaR values obtained from the Student t-copula are larger than those obtained from the Gaussian copula. Moreover, when minimizing the portfolio risk, the optimal natural gas portfolio weights are found to be similar across the multivariate Gaussian copula and Student t-copula and different confidence levels.

  5. Estimating Risk of Natural Gas Portfolios by Using GARCH-EVT-Copula Model

    Directory of Open Access Journals (Sweden)

    Jiechen Tang

    2015-01-01

    Full Text Available This paper concentrates on estimating the risk of Title Transfer Facility (TTF Hub natural gas portfolios by using the GARCH-EVT-copula model. We first use the univariate ARMA-GARCH model to model each natural gas return series. Second, the extreme value distribution (EVT is fitted to the tails of the residuals to model marginal residual distributions. Third, multivariate Gaussian copula and Student t-copula are employed to describe the natural gas portfolio risk dependence structure. Finally, we simulate N portfolios and estimate value at risk (VaR and conditional value at risk (CVaR. Our empirical results show that, for an equally weighted portfolio of five natural gases, the VaR and CVaR values obtained from the Student t-copula are larger than those obtained from the Gaussian copula. Moreover, when minimizing the portfolio risk, the optimal natural gas portfolio weights are found to be similar across the multivariate Gaussian copula and Student t-copula and different confidence levels.

  6. Rethink potential risks of toxic emissions from natural gas and oil mining.

    Science.gov (United States)

    Meng, Qingmin

    2018-09-01

    Studies have showed the increasing environmental and public health risks of toxic emissions from natural gas and oil mining, which have become even worse as fracking is becoming a dominant approach in current natural gas extraction. However, governments and communities often overlook the serious air pollutants from oil and gas mining, which are often quantified lower than the significant levels of adverse health effects. Therefore, we are facing a challenging dilemma: how could we clearly understand the potential risks of air toxics from natural gas and oil mining. This short study aims at the design and application of simple and robust methods to enhance and improve current understanding of the becoming worse toxic air emissions from natural gas and oil mining as fracking is becoming the major approach. Two simple ratios, the min-to-national-average and the max-to-national-average, are designed and applied to each type of air pollutants in a natural gas and oil mining region. The two ratios directly indicate how significantly high a type of air pollutant could be due to natural gas and oil mining by comparing it to the national average records, although it may not reach the significant risks of adverse health effects according to current risk screening methods. The min-to-national-average and the max-to-national-average ratios can be used as a direct and powerful method to describe the significance of air pollution by comparing it to the national average. The two ratios are easy to use for governments, stakeholders, and the public to pay enough attention on the air pollutants from natural gas and oil mining. The two ratios can also be thematically mapped at sampled sites for spatial monitoring, but spatial mitigation and analysis of environmental and health risks need other measurements of environmental and demographic characteristics across a natural gas and oil mining area. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Natural streamflow simulation for two largest river basins in Poland: a baseline for identification of flow alterations

    Science.gov (United States)

    Piniewski, Mikołaj

    2016-05-01

    The objective of this study was to apply a previously developed large-scale and high-resolution SWAT model of the Vistula and the Odra basins, calibrated with the focus of natural flow simulation, in order to assess the impact of three different dam reservoirs on streamflow using the Indicators of Hydrologic Alteration (IHA). A tailored spatial calibration approach was designed, in which calibration was focused on a large set of relatively small non-nested sub-catchments with semi-natural flow regime. These were classified into calibration clusters based on the flow statistics similarity. After performing calibration and validation that gave overall positive results, the calibrated parameter values were transferred to the remaining part of the basins using an approach based on hydrological similarity of donor and target catchments. The calibrated model was applied in three case studies with the purpose of assessing the effect of dam reservoirs (Włocławek, Siemianówka and Czorsztyn Reservoirs) on streamflow alteration. Both the assessment based on gauged streamflow (Before-After design) and the one based on simulated natural streamflow showed large alterations in selected flow statistics related to magnitude, duration, high and low flow pulses and rate of change. Some benefits of using a large-scale and high-resolution hydrological model for the assessment of streamflow alteration include: (1) providing an alternative or complementary approach to the classical Before-After designs, (2) isolating the climate variability effect from the dam (or any other source of alteration) effect, (3) providing a practical tool that can be applied at a range of spatial scales over large area such as a country, in a uniform way. Thus, presented approach can be applied for designing more natural flow regimes, which is crucial for river and floodplain ecosystem restoration in the context of the European Union's policy on environmental flows.

  8. Natural streamflow simulation for two largest river basins in Poland: a baseline for identification of flow alterations

    Directory of Open Access Journals (Sweden)

    M. Piniewski

    2016-05-01

    Full Text Available The objective of this study was to apply a previously developed large-scale and high-resolution SWAT model of the Vistula and the Odra basins, calibrated with the focus of natural flow simulation, in order to assess the impact of three different dam reservoirs on streamflow using the Indicators of Hydrologic Alteration (IHA. A tailored spatial calibration approach was designed, in which calibration was focused on a large set of relatively small non-nested sub-catchments with semi-natural flow regime. These were classified into calibration clusters based on the flow statistics similarity. After performing calibration and validation that gave overall positive results, the calibrated parameter values were transferred to the remaining part of the basins using an approach based on hydrological similarity of donor and target catchments. The calibrated model was applied in three case studies with the purpose of assessing the effect of dam reservoirs (Włocławek, Siemianówka and Czorsztyn Reservoirs on streamflow alteration. Both the assessment based on gauged streamflow (Before-After design and the one based on simulated natural streamflow showed large alterations in selected flow statistics related to magnitude, duration, high and low flow pulses and rate of change. Some benefits of using a large-scale and high-resolution hydrological model for the assessment of streamflow alteration include: (1 providing an alternative or complementary approach to the classical Before-After designs, (2 isolating the climate variability effect from the dam (or any other source of alteration effect, (3 providing a practical tool that can be applied at a range of spatial scales over large area such as a country, in a uniform way. Thus, presented approach can be applied for designing more natural flow regimes, which is crucial for river and floodplain ecosystem restoration in the context of the European Union's policy on environmental flows.

  9. Flow injection spectrophotometry using natural reagent from Morinda citrifolia root for determination of aluminium in tea.

    Science.gov (United States)

    Tontrong, Sopa; Khonyoung, Supada; Jakmunee, Jaroon

    2012-05-01

    A flow injection (FI) spectrophotometric method with using natural reagent extracted from Morinda citrifolia root has been developed for determination of aluminium. The extract contained anthraquinone compounds which could react with Al(3+) to form reddish complexes which had maximum absorption wavelength at 499.0nm. The extract could be used as a reagent in FI system without further purification to obtain pure compound. A sensitive method for determination of aluminium in concentration range of 0.1-1.0mgL(-1), with detection limit of 0.05mgL(-1) was achieved. Relative standard deviations of 1.2% and 1.7% were obtained for the determination of 0.1 and 0.6mgL(-1) Al(3+) (n=11). Sample throughput of 35h(-1) was achieved with the consumption of 3mL each of carrier and reagent solutions per injection. The developed method was successfully applied to tea samples, validated by the FAAS standard method. The method is simple, fast, economical and could be classified as a greener analytical method. Copyright © 2011 Elsevier Ltd. All rights reserved.

  10. Natural Convection Flow of Fractional Nanofluids Over an Isothermal Vertical Plate with Thermal Radiation

    Directory of Open Access Journals (Sweden)

    Constantin Fetecau

    2017-03-01

    Full Text Available The studies of classical nanofluids are restricted to models described by partial differential equations of integer order, and the memory effects are ignored. Fractional nanofluids, modeled by differential equations with Caputo time derivatives, are able to describe the influence of memory on the nanofluid behavior. In the present paper, heat and mass transfer characteristics of two water-based fractional nanofluids, containing nanoparticles of CuO and Ag, over an infinite vertical plate with a uniform temperature and thermal radiation, are analytically and graphically studied. Closed form solutions are determined for the dimensionless temperature and velocity fields, and the corresponding Nusselt number and skin friction coefficient. These solutions, presented in equivalent forms in terms of the Wright function or its fractional derivatives, have also been reduced to the known solutions of ordinary nanofluids. The influence of the fractional parameter on the temperature, velocity, Nusselt number, and skin friction coefficient, is graphically underlined and discussed. The enhancement of heat transfer in the natural convection flows is lower for fractional nanofluids, in comparison to ordinary nanofluids. In both cases, the fluid temperature increases for increasing values of the nanoparticle volume fraction.

  11. Rapid solar-thermal dissociation of natural gas in an aerosol flow reactor

    International Nuclear Information System (INIS)

    Dahl, Jaimee K.; Buechler, Karen J.; Finley, Ryan; Stanislaus, Timothy; Weimer, Alan W.; Lewandowski, Allan; Bingham, Carl; Smeets, Alexander; Schneider, Adrian

    2004-01-01

    A solar-thermal aerosol flow reactor process is being developed to dissociate natural gas (NG) to hy drogen (H 2 ) and carbon black at high rates. Concentrated sunlight approaching 10 kW heats a 9.4 cm long x2.4 cm diameter graphite reaction tube to temperatures ∼2000 K using a 74% theoretically efficient secondary concentrator. Pure methane feed has been dissociated to 70% for residence times less than 0.1 s. The resulting carbon black is 20-40 nm in size, amorphous, and pure. A 5 million (M) kg/yr carbon black/1.67 M kg/yr H 2 plant is considered for process scale-up. The total permanent investment (TPI) of this plant is $12.7 M. A 15% IRR after tax is achieved when the carbon black is sold for $0.66/kg and the H 2 for $13.80/GJ. This plant could supply 0.06% of the world carbon black market. For this scenario, the solar-thermal process avoids 277 MJ fossil fuel and 13.9 kg-equivalent CO 2 /kg H 2 produced as compared to conventional steam-methane reforming and furnace black processing

  12. CFD model of air movement in ventilated facade: comparison between natural and forced air flow

    Energy Technology Data Exchange (ETDEWEB)

    Mora Perez, Miguel; Lopez Patino, Gonzalo; Lopez Jimenez, P. Amparo [Hydraulic and Environmental Engineering Department, Universitat Politècnica de Valencia (Spain)

    2013-07-01

    This study describes computational fluid dynamics (CFD) modeling of ventilated facade. Ventilated facades are normal facade but it has an extra channel between the concrete wall and the (double skin) facade. Several studies found in the literature are carried out with CFD simulations about the behavior of the thermodynamic phenomena of the double skin facades systems. These studies conclude that the presence of the air gap in the ventilated facade affects the temperature in the building skin, causing a cooling effect, at least in low-rise buildings. One of the most important factors affecting the thermal effects of ventilated facades is the wind velocity. In this contribution, a CFD analysis applied on two different velocity assumptions for air movement in the air gap of a ventilated facade is presented. A comparison is proposed considering natural wind induced velocity with forced fan induced velocity in the gap. Finally, comparing temperatures in the building skin, the differences between both solutions are described determining that, related to the considered boundary conditions, there is a maximum height in which the thermal effect of the induced flow is significantly observed.

  13. Modelling and simulation of a natural convection flow in a saturated porous cavity

    International Nuclear Information System (INIS)

    Costa, M.L.M.; Sampaio, R.; Gama, R.M.S. da.

    1991-09-01

    The natural convection flow in a two-dimensional fluid-saturated porous cavity is modelled by means of a Theory of Mixtures viewpoint in which fluid and porous medium are regarded as continuous constituents of a binary mixture, coexisting superposed. A local description, that allows distinct temperature profiles for both fluid and solid constituents is obtained. The model, simplified by the Boussinesq approximation, is simulated with the help of the Control Volumes Method. The effect of some usual parameters like Rayleigh, Darcy and Prandtl numbers and of a new dimensionless number, relating coefficients associated to the heat exchange between fluid and solid constituents (due to its temperature difference) and coefficients of heat conduction for each constituent, is considered. Stream lines for the fluid constituent and isotherms for both fluid and solid constituents are presented for some cases. Qualitative agreement with results using the classical approach (Darcy's law and additional terms to account for boundary and inertia effects, used as momentum equation) was obtained. (author)

  14. Perception of Natural Hazards and Risk among University of Washington Students

    Science.gov (United States)

    Herr, K.; Brand, B.; Hamlin, N.; Ou, J.; Thomas, B.; Tudor, E.

    2012-12-01

    Familiarity with a given population's perception of natural hazards and the threats they present is vital for the development of effective education prior to and emergency management response after a natural event. While much work has been done in other active tectonic regions, perception of natural hazards and risk among Pacific Northwest (PNW) residents is poorly constrained. The objective of this work is to assess the current perception of earthquake and volcanic hazards and risk in the PNW, and to better understand the factors which drive the public's behavior concerning preparedness and response. We developed a survey to assess the knowledge of natural hazards common to the region, their perception of risk concerning these hazards, and their level of preparedness should a natural hazard occur. The survey was distributed to University of Washington students and employees via an internet link as part of a class project in 'Living with Volcanoes' (ESS 106) in March of 2012, which returned more than 900 responses. The UW student population was chosen as our first "population" to assess because of their uniqueness as a large, semi-transient population (typical residence of less than 5 years). Only 50% of participants correctly reported their proximity to an active volcano, indicating either lack of knowledge of active volcanoes in the region or poor spatial awareness. When asked which area were most at risk to lahars, respondents indicated that all areas close to the hazard source, including topographically elevated regions, were at a higher risk than more distal and low-lying localities that are also at high risk, indicating a lack of knowledge concerning the topographic dependency of this hazard. Participants perceived themselves to be able to cope better with an earthquake than a volcanic event. This perception may be due to lack of knowledge of volcanic hazards and their extent or due to a false sense of security concerning earthquakes fostered by regular

  15. Comparison study on qualitative and quantitative risk assessment methods for urban natural gas pipeline network.

    Science.gov (United States)

    Han, Z Y; Weng, W G

    2011-05-15

    In this paper, a qualitative and a quantitative risk assessment methods for urban natural gas pipeline network are proposed. The qualitative method is comprised of an index system, which includes a causation index, an inherent risk index, a consequence index and their corresponding weights. The quantitative method consists of a probability assessment, a consequences analysis and a risk evaluation. The outcome of the qualitative method is a qualitative risk value, and for quantitative method the outcomes are individual risk and social risk. In comparison with previous research, the qualitative method proposed in this paper is particularly suitable for urban natural gas pipeline network, and the quantitative method takes different consequences of accidents into consideration, such as toxic gas diffusion, jet flame, fire ball combustion and UVCE. Two sample urban natural gas pipeline networks are used to demonstrate these two methods. It is indicated that both of the two methods can be applied to practical application, and the choice of the methods depends on the actual basic data of the gas pipelines and the precision requirements of risk assessment. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

  16. Nature and characteristics of pulsing flow in trickle-bed reactors

    NARCIS (Netherlands)

    Boelhouwer, J.G.; Piepers, H.W.; Drinkenburg, A.A.H.

    2002-01-01

    Pulsing flow is well known for its advantages in terms of an increase in mass and heat transfer rates, complete catalyst wetting and a decrease in axial dispersion compared to trickle flow. The operation of a trickle-bed reactor in the pulsing flow regime is favorable in terms of a capacity increase

  17. Verification procedures of ultrasonic flow meters for natural gas applications; Procedimento de verificacao de medidores ultra-sonicos para gas natural

    Energy Technology Data Exchange (ETDEWEB)

    Lourenco, Tulio C. [TRANSPETRO, Rio de Janeiro, RJ (Brazil)

    2009-12-19

    In recent years, the use of ultrasonic flow meters for natural gas applications has grown significantly, especially after the issuance of AGA Report 9 and AGA Report 10. The reasons this technology has stood out from the others, such as orifice-plates or turbines, are: accuracy, wide range ability, it is bi-directional, robustness, low maintenance and, mainly, integrated diagnostic parameters, such as sound velocity, signal quality and profile velocity analysis. TRANSPETRO currently operates 56 ultrasonic natural gas flow-meter systems. For operational control applications, 90% of the meters are ultrasonic, of which 85% are provided with internal diagnostic tools through the manufacturer's software. Within this perspective, it is essential and unquestionable that there are procedures and routines for ultrasonic flow-meter verification and analysis, in order to monitor their performance and integrity, in addition to the early identification of potential problems. This paper discusses the practical application of several tools and diagnostic parameters inherent in ultrasonic flow meters in periodical verifications using TRANSPETRO's procedure. (author)

  18. Selective grazing by adults and larvae of the zebra mussel (Dreissena polymorpha): application of flow cytometry to natural seston

    NARCIS (Netherlands)

    Pires, L.M.D.; Jonker, R.M.; Van Donk, E.; Laanbroek, H.J.

    2004-01-01

    1. Selective grazing of adults and larvae of the zebra mussel (Dreissena polymorpha) on phytoplankton and detritus from both laboratory cultures and natural seston was quantified using flow cytometry. 2. Mean clearance rate of adult zebra mussels was higher on a mixture of the green alga Scenedesmus

  19. Selective grazing by adults and larvae of the zebra mussel (Dreissena polymorpha): application of flow cytometry to natural seston

    NARCIS (Netherlands)

    Dionisio Pires, L.M.; Jonker, R.R.; Donk, E.van; Laanbroek, H.J.

    2004-01-01

    1. Selective grazing of adults and larvae of the zebra mussel (Dreissena polymorpha) on phytoplankton and detritus from both laboratory cultures and natural seston was quantified using flow cytometry. 2. Mean clearance rate of adult zebra mussels was higher on a mixture of the green

  20. Consequences of preferential flow in cracking clay soils for contamination-risk of shallow aquifers

    NARCIS (Netherlands)

    Oostindie, K.; Bronswijk, J.J.B.

    1995-01-01

    A method is presented to asses the contamination risk of aquifers covered with cracking clay soils, with special emphasis on preferential flow through shrinkage cracks. A water extraction area was divided into units with homogeneous soil types and hydrological conditions. For each unit, a

  1. Debris flows risk analysis and direct loss estimation: the case study of Valtellina di Tirano, Italy

    Czech Academy of Sciences Publication Activity Database

    Blahůt, Jan; Glade, T.; Sterlacchini, S.

    2014-01-01

    Roč. 11, č. 2 (2014), s. 288-307 ISSN 1672-6316 Institutional support: RVO:67985891 Keywords : Debris flows * Risk analysis * Economic losses * Central Alps * Italy Subject RIV: DE - Earth Magnetism, Geodesy, Geography OBOR OECD: Physical geography Impact factor: 0.963, year: 2014

  2. Estimating the Risk of River Flow under Climate Change in the Tsengwen River Basin

    Directory of Open Access Journals (Sweden)

    Hsiao-Ping Wei

    2016-03-01

    Full Text Available This study evaluated the overflow risk of the Tsengwen River under a climate change scenario by using bias-corrected dynamic downscaled data as inputs for a SOBEK model (Deltares, the Netherlands. The results showed that the simulated river flow rate at Yufeng Bridge (upstream, Erxi Bridge (midstream, and XinZong (1 (downstream stations are at risk of exceeding the management plan’s flow rate for three projection periods (1979–2003, 2015–2039, 2075–2099. After validation with the geomorphic and hydrological data collected in this study, the frequency at which the flow rate exceeded the design flood was 2 in 88 events in the base period (1979–2003, 6 in 82 events in the near future (2015–2039, and 10 in 81 events at the end of the century (2075–2099.

  3. Health risk assessment based on injection of upgraded biogas in natural gas grid

    International Nuclear Information System (INIS)

    Leroux, C.; Modelon, H.; Rousselle, C.; Zdanevitch, I.; Evanno, S.

    2010-01-01

    This document presents the opinion of the French Agency for Environmental and Occupational Health Safety (AFSSET). Results are based on a collective expertise conducted to assess health risks associated with the injection of biogas in the natural gas grid. The complete assessment is published and available on the web site of the Agency; only the major results are presented in this document. Following recommendations issued by AFSSET in 2008, a new study has been initiated to collect and analyze data on the composition of biogas from sewage sludge. The French National Institute for Industrial Environment and Risks (INERIS) is in charge of this project. The data will be used to assess the accidental risks (resulting from the upgrading of biogas, transport by pipeline and utilization for energy purposes) and health risks for users (resulting from the injection in the natural gas grid). (authors)

  4. The General Urban Plan of Casimcea territorial administrative unit, map of natural and anthropogenic risks

    Directory of Open Access Journals (Sweden)

    Sorin BĂNICĂ

    2013-08-01

    Full Text Available The General Urban Plan represents the legal ground for any development action proposed. After endorsement and approval as required by law, GUP is act of authority of local government for the area in which it applies. The aim is to establish priorities regulations applied in land use planning and construction of structures. In terms of geographical location, the administrative territory of Casimcea, Tulcea county, falls in the central Northwest Plateau Casimcei. This is the second unit of the Central Dobrogea Plateau. Geographical location in southeastern Romania, climatic and relief conditions and anthropogenic pressure, expose the village administrative territorial unit Casimcea, permanent susceptibility to produce natural and antropogenical risks. In this context, we identified the following categories of natural and anthropogenic risks: i natural risk phenomena (earthquakes, strong winds, heavy rains, floods caused by overflowing or precipitation, erosion of river banks and torrents, gravitational processes, rain droplet erosion and surface soil erosion; and ii anthropogenic risk phenomena (overgrazing, chemicals use in agriculture, road transport infrastructure and electricity, wind turbines for electricity production, waste deposits, agro-zootechnical complexs, and human cemeteries. Extending their surface was materialized by creating a map of natural and anthropogenic risk on Casimcea territorial administrative unit, explaining the share of potentially affected areas as territorial balance

  5. Natural hazard management high education: laboratory of hydrologic and hydraulic risk management and applied geomorphology

    Science.gov (United States)

    Giosa, L.; Margiotta, M. R.; Sdao, F.; Sole, A.; Albano, R.; Cappa, G.; Giammatteo, C.; Pagliuca, R.; Piccolo, G.; Statuto, D.

    2009-04-01

    The Environmental Engineering Faculty of University of Basilicata have higher-level course for students in the field of natural hazard. The curriculum provides expertise in the field of prediction, prevention and management of earthquake risk, hydrologic-hydraulic risk, and geomorphological risk. These skills will contribute to the training of specialists, as well as having a thorough knowledge of the genesis and the phenomenology of natural risks, know how to interpret, evaluate and monitor the dynamic of environment and of territory. In addition to basic training in the fields of mathematics and physics, the course of study provides specific lessons relating to seismic and structural dynamics of land, environmental and computational hydraulics, hydrology and applied hydrogeology. In particular in this course there are organized two connected examination arguments: Laboratory of hydrologic and hydraulic risk management and Applied geomorphology. These course foresee the development and resolution of natural hazard problems through the study of a real natural disaster. In the last year, the work project has regarded the collapse of two decantation basins of fluorspar, extracted from some mines in Stava Valley, 19 July 1985, northern Italy. During the development of the course, data and event information has been collected, a guided tour to the places of the disaster has been organized, and finally the application of mathematical models to simulate the disaster and analysis of the results has been carried out. The student work has been presented in a public workshop.

  6. Laboratory experiments on heat-drive two-phase flows in natural and artificial rock fractures

    International Nuclear Information System (INIS)

    Kneafsey, Timothy J.; Pruess, Karsten

    1998-01-01

    Water flow in partially saturated fractures under thermal drive may lead to fast flow along preferential localized pathways and heat pipe conditions. At the potential high-level nuclear waste repository at Yucca Mountain, water flowing in fast pathways may ultimately contact waste packages and transport radionuclides to the accessible environment. Sixteen experiments were conducted to visualize heat-driven liquid flow in fracture models that included (1) assemblies of roughened glass plates, (2) epoxy replicas of rock fractures, and (3) a fractured specimen of Topopah Spring tuff. Continuous rivulet flow was observed for high liquid flow rates, intermittent rivulet flow and drop flow for intermediate flow rates, and film flow for lower flow rates and wide apertures. Heat pipe conditions (vapor-liquid counterflow with phase change) were identified in five of the seven experiments in which spatially resolved thermal monitoring was performed but not when vapor-liquid counterflow was hindered by very narrow apertures and when an inadequate working fluid volume was used

  7. Estimation of roughness lengths and flow separation over compound bedforms in a natural-tidal inlet

    DEFF Research Database (Denmark)

    Lefebvre, Alice; Ernstsen, Verner Brandbyge; Winter, Christian

    2013-01-01

    was found to underestimate the length of the flow separation zone of the primary bedforms. A better estimation of the presence and shape of the flow separation zone over complex bedforms in a tidal environment still needs to be determined; in particular the relationship between flow separation zone......The hydraulic effect of asymmetric compound bedforms on tidal currents was assessed from field measurements of flow velocity in the Knudedyb tidal inlet, Denmark. Large asymmetric bedforms with smaller superimposed ones are a common feature of sandy shallow water environments and are known to act...... as hydraulic roughness elements in dependence with flow direction. The presence of a flow separation zone on the bedform lee was estimated through analysis of the measured velocity directions and the calculation of the flow separation line. The Law of the Wall was used to calculate roughness lengths and shear...

  8. Arenal-type pyroclastic flows: A probabilistic event tree risk analysis

    Science.gov (United States)

    Meloy, Anthony F.

    2006-09-01

    A quantitative hazard-specific scenario-modelling risk analysis is performed at Arenal volcano, Costa Rica for the newly recognised Arenal-type pyroclastic flow (ATPF) phenomenon using an event tree framework. These flows are generated by the sudden depressurisation and fragmentation of an active basaltic andesite lava pool as a result of a partial collapse of the crater wall. The deposits of this type of flow include angular blocks and juvenile clasts, which are rarely found in other types of pyroclastic flow. An event tree analysis (ETA) is a useful tool and framework in which to analyse and graphically present the probabilities of the occurrence of many possible events in a complex system. Four event trees are created in the analysis, three of which are extended to investigate the varying individual risk faced by three generic representatives of the surrounding community: a resident, a worker, and a tourist. The raw numerical risk estimates determined by the ETA are converted into a set of linguistic expressions (i.e. VERY HIGH, HIGH, MODERATE etc.) using an established risk classification scale. Three individually tailored semi-quantitative risk maps are then created from a set of risk conversion tables to show how the risk varies for each individual in different areas around the volcano. In some cases, by relocating from the north to the south, the level of risk can be reduced by up to three classes. While the individual risk maps may be broadly applicable, and therefore of interest to the general community, the risk maps and associated probability values generated in the ETA are intended to be used by trained professionals and government agencies to evaluate the risk and effectively manage the long-term development of infrastructure and habitation. With the addition of fresh monitoring data, the combination of both long- and short-term event trees would provide a comprehensive and consistent method of risk analysis (both during and pre-crisis), and as such

  9. Risk predicting of macropore flow using pedotransfer functions, textural maps and modeling

    DEFF Research Database (Denmark)

    Iversen, Bo Vangsø; Børgesen, Christen Duus; Lægdsmand, Mette

    2011-01-01

    of this study were first to develop pedotransfer functions (PTFs) predicting near-saturated [k(−1)] and saturated (Ks) hydraulic conductivity using simple soil parameters as predictors and second to use this information and a newly developed rasterbased soil property map of Denmark to identify risk areas...... modeling were used to construct a new map dividing Denmark into risk categories for macropore flow. This map can be combined with other tools to identify areas where there is a high risk of contaminants leaching out of the root zone....

  10. The Natural Convection Heat Transfer inside Vertical Pipe: Characteristic of Pipe Flow according to the Boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    Ohk, Seung Min; Chung, Bum Jin [Kyunghee University, Yongin (Korea, Republic of)

    2016-05-15

    The Passive Cooling System (PCS) driven by natural forces drew research attention since Fukushima nuclear power plant accident. This study investigated the natural convection heat transfer inside of vertical pipe with emphasis on the phenomena regarding the boundary layer interaction. Numerical calculations were carried out using FLUENT 6.3. Experiments were performed for the parts of the cases to explore the accuracy of calculation. Based on the analogy, heat transfer experiment is replaced by mass transfer experiment using sulfuric acid copper sulfate (CuSO{sub 4}. H{sub 2}SO{sub 4}) electroplating system. The natural convection heat transfer inside a vertical pipe is studied experimentally and numerically. Experiments were carried out using sulfuric acid-copper sulfate (H{sub 2}SO{sub 4}-CuSO{sub 4}) based on the analogy concept between heat and mass transfer system. Numerical analysis was carried out using FLUENT 6.3. It is concluded that the boundary layer interaction along the flow passage influences the heat transfer, which is affected by the length, diameter, and Prandtl number. For the large diameter and high Prandtl number cases, where the thermal boundary layers do not interfered along the pipe, the heat transfer agreed with vertical flat plate for laminar and turbulent natural convection correlation within 8%. When the flow becomes steady state, the forced convective flow appears in the bottom of the vertical pipe and natural convection flow appears near the exit. It is different behavior from the flow on the parallel vertical flat plates. Nevertheless, the heat transfer was not different greatly compared with those of vertical plate.

  11. Using Modelica to investigate the dynamic behaviour of the German national standard for high pressure natural gas flow metering

    International Nuclear Information System (INIS)

    Von der Heyde, M; Schmitz, G; Mickan, B

    2016-01-01

    This paper presents a computational model written in Modelica for the high pressure piston prover (HPPP) used as the national primary standard for high pressure natural gas flow metering in Germany. With a piston prover the gas flow rate is determined by measuring the time a piston needs to displace a certain volume of gas in a cylinder. Fluctuating piston velocity during measurement can be a significant source of uncertainty if not considered in an appropriate way. The model was built to investigate measures for the reduction of this uncertainty. Validation shows a good compliance of the piston velocity in the model with measured data for certain volume flow rates. Reduction of the piston weight, variation of the start valve switching time and integration of a flow straightener were found to reduce the piston velocity fluctuations in the model significantly. The fast and cost effective generation of those results shows the strength of the used modelling approach. (paper)

  12. Analytical study of flow instability behaviour in a boiling two-phase natural circulation loop under low quality conditions

    International Nuclear Information System (INIS)

    Nayak, A.K.; Kumar, N.; Vijayan, P.K.; Saha, D.; Sinha, R.K.

    2002-01-01

    Analytical investigations have been carried out to study the flow instability behaviour in a boiling two-phase natural circulation loop under low quality conditions. For this purpose, the computer code TINFLO-S has been developed. The code solves the conservation equations of mass, momentum and energy and equation of state for homogeneous equilibrium twophase flow using linear analytical technique. The results of the code have been validated with the experimental data of the loop for both the steady state and stability. The study reveals that the stability behaviour of low quality flow oscillations is different from that of the high quality flow oscillations. The instability reduces with increase in power and throttling at the inlet of the heater. The instability first increases and then reduces with increase in pressure at any subcooling. The effects of diameter of riser pipe, heater and the height of the riser on this instability are also investigated. (orig.) [de

  13. Impacts of natural events and processes on groundwater flow conditions: a case study in the Horonobe Area, Hokkaido, Northern Japan

    International Nuclear Information System (INIS)

    Niizato, T.; Yasue, K.I.; Kurikami, H.

    2009-01-01

    In order to assess the long-term stability of the geological environments for over several hundred thousand years, it is important to consider the influence of natural events and processes, such as uplift, subsidence, denudation and climate change, on the geological environments, especially in an active region such as Japan. This study presents a conceptual model related to the future natural events and processes which have potential impacts on the groundwater flow conditions in the Horonobe area, Hokkaido, northern Japan on the basis of the neo-tectonics, palaeogeography, palaeo-climate, historical development of landform, and present state of groundwater flow conditions. We conclude that it is important to consider interactions among natural events and processes on the describing of the best-possible approximation of the time-variation of geological environment. (authors)

  14. THE IMPACT OF NATURAL RISKS ON AGRICULTURAL DEVELOPMENT OF THE REPUBLIC OF MOLDOVA

    Directory of Open Access Journals (Sweden)

    Elena NIREAN

    2013-01-01

    Full Text Available Climate, topography and soil are natural conditions of basic agricultural yields. In general, Moldova has favorable climatic conditions and relief. Soils in the North have a high degree of fertility, while the central and southern regions are of average fertility. At the same time natural calamities such as droughts, late spring frosts, hail and floods have a destructive impact on crops. Climate instability is one of the main causes of unstable yields and is an inherent risk for agriculture of the country. More than that, most of the plots lose their natural fertility and require rehabilitation.

  15. ATLAS “RUSSIAN ARCTIC IN XXI CENTURY: NATURAL CHALLENGES AND RISKS OF DEVELOPMENT”

    Directory of Open Access Journals (Sweden)

    N. A. Alekseevskiy

    2013-01-01

    Full Text Available  The huge investigation of Arctic region of Russia was performed by team of researchers from Faculty of Geography of Lomonosov Moscow State University. This investigation resulted in creation of atlas “Russian Arctic in XXI century: natural challenges and risks of development”. In the first place this atlas was made for pupils and school teachers, letting them study modern features of natural environment and socio-economical processes. Atlas contains 7 sections, including both natural and socio-economical maps.

  16. Globe of Natural Hazard - A new assessment tool for risk managers

    Science.gov (United States)

    Siebert, A. C.

    2009-04-01

    A large number of tropical cyclones and the earthquake in Sichuan made 2008 one of the most devastating years on record. Throughout the world, more than 220,000 people died as a result of natural catastrophes this year. Overall losses totaled some US 200bn (2007: US 82bn). Insured losses in 2008 rose to US 45bn, about 50% higher than in the previous year. Mainly driven by high losses from weather-related natural catastrophes, 2008 was - on the basis of figures adjusted for inflation - even the third most expensive year on record for the insurance industry, exceeded only by the hurricane year of 2005 and by 1995, the year of the Kobe earthquake. Munich Re, a worldwide operating reinsurance company, is a world leader in terms of investigating risks from natural hazards of all kinds. 2008 has again shown the insurance industry how important it is to analyse risks like natural hazards and climate change in all their facets and to manage the insurance business accordingly. An excellent example of the wealth of knowledge Munich Re has developed in natural hazard assessment is the DVD "Globe of Natural Hazards". It combines the geoscientific data and findings Munich Re has accumulated over a period of 35 years. First devised as a wall-map in 1978, the product has established itself as a standard work for the identification, exposure assessment and risk management of natural hazards. Over 80,000 copies of the CD-ROM version of 2000 have been provided to clients - a mark achieved by no other service product in Munich Re's history. Since the beginning of 2009, the fully updated fourth-generation version has been available. The bilingual DVD (German and English) shows natural hazards and climate effects at a glance: the global maps are presented on a 3D globe, underlaid with satellite images. The hazard complexes of hail, tornado and winter storms have been completely revised and flood incorporated as a new hazard. Users can intuitively home in on and enlarge any location on

  17. Pollen flow of wheat under natural conditions in the Huanghuai River Wheat Region, China

    Science.gov (United States)

    Sun, Ai-Qing; Zhang, Chun-Qing; Wu, Cheng-Lai; Gao, Qing-Rong

    2015-01-01

    abstract The transgenic pollen spread is the main pathway of transgenic plant gene flow. The maximum distance of pollen dispersal (horizontal), the spatial dynamics of pollen movement (vertical), and the patterns of pollen dispersal are important considerations in biosafety assessments of genetically modified crops. To evaluate wheat (Triticum aestivum) pollen dispersal, we measured the pollen suspension velocity and analyzed pollen dispersal patterns under natural conditions in the Huanghuai River wheat-growing region in 2009. The pollen suspension velocity was 0.3–0.4 m/s. The highest pollen densities were detected in the north, northwest, and south of the pollen source. Pollen was dispersed over distances greater than 245 m in the northwest and northeast directions. At the pollen source center, pollen density decreased with increasing vertical height. In the north of the pollen source, the pollen density from 65 m to 225 m showed a wave-mode decrease with increasing height. The horizontal transport of pollen over longer distances fitted polynomial equations. In the north, the pollen density was highest at 45 m from the pollen source, and decreased with increasing distance. In the northwest, the pollen density showed a double-peak trend. In the northeast, pollen density was highest from 45 m to 125 m from the source. Wind speeds greater than the pollen suspension velocity and the duration of continuous gusts were the main factors affecting pollen dispersal. This information will be useful for determining the spatial isolation distances for hybrid seed production and for the commercial production of transgenic wheat. PMID:25658025

  18. Climate change will increase the naturalization risk from garden plants in Europe.

    Science.gov (United States)

    Dullinger, Iwona; Wessely, Johannes; Bossdorf, Oliver; Dawson, Wayne; Essl, Franz; Gattringer, Andreas; Klonner, Günther; Kreft, Holger; Kuttner, Michael; Moser, Dietmar; Pergl, Jan; Pyšek, Petr; Thuiller, Wilfried; van Kleunen, Mark; Weigelt, Patrick; Winter, Marten; Dullinger, Stefan; Beaumont, Linda

    2017-01-01

    Plant invasions often follow initial introduction with a considerable delay. The current non-native flora of a region may hence contain species that are not yet naturalized but may become so in the future, especially if climate change lifts limitations on species spread. In Europe, non-native garden plants represent a huge pool of potential future invaders. Here, we evaluate the naturalization risk from this species pool and how it may change under a warmer climate. Europe. We selected all species naturalized anywhere in the world but not yet in Europe from the set of non-native European garden plants. For this subset of 783 species, we used species distribution models to assess their potential European ranges under different scenarios of climate change. Moreover, we defined geographical hotspots of naturalization risk from those species by combining projections of climatic suitability with maps of the area available for ornamental plant cultivation. Under current climate, 165 species would already find suitable conditions in > 5% of Europe. Although climate change substantially increases the potential range of many species, there are also some that are predicted to lose climatically suitable area under a changing climate, particularly species native to boreal and Mediterranean biomes. Overall, hotspots of naturalization risk defined by climatic suitability alone, or by a combination of climatic suitability and appropriate land cover, are projected to increase by up to 102% or 64%, respectively. Our results suggest that the risk of naturalization of European garden plants will increase with warming climate, and thus it is very likely that the risk of negative impacts from invasion by these plants will also grow. It is therefore crucial to increase awareness of the possibility of biological invasions among horticulturalists, particularly in the face of a warming climate.

  19. Natural gas for electric power generation: Strategic issues, risks and opportunities

    International Nuclear Information System (INIS)

    Linderman, C.

    1992-01-01

    Natural gas is again being regarded as a significant fuel for electric power generation. It was once a predominant fuel for utilities in gas-producing areas, but natural gas consumption declined greatly after the 1973 oil shock because of reduced electricity demand and increased coal and nuclear generation. Moreover, wellhead price and other forms of regulation produced gas shortages in the 1970s. The resurgence of natural gas in future resource plans stems from its inherent ideal fuel characteristics: short lead time; low capital costs; small increments of modular capacity; delivered close to load centers; environmentally benign, preferable to oil and coal; and potential for high thermal efficiency in gas turbines. Natural gas, if available and attractively priced, is an ideal fuel for electric power generation. No other fuel shares these attractive characteristics, and utilities, facing higher than expected load growth, are relying on an increasing proportion of gas-fired combustion turbines, combined cycle plants, and cogeneration to meet a growing, yet uncertain, future demand for electricity. Despite these desirable operating characteristics, the varied past and uncertain future of natural gas markets raise legitimate concerns about the riskiness of current utility natural gas strategies. This report, which summarizes the major findings from research efforts, is intended to help utility decision-makers understand the full range of risks they face with natural gas electric power generation and to identify actions they can take to mitigate those risks

  20. Risk-targeted safety distance of reinforced concrete buildings from natural-gas transmission pipelines

    International Nuclear Information System (INIS)

    Russo, Paola; Parisi, Fulvio

    2016-01-01

    Natural-gas pipeline accidents mostly result in major damage even to buildings located far away. Therefore, proper safety distances should be observed in land use planning to ensure target safety levels for both existing and new buildings. In this paper, a quantitative risk assessment procedure is presented for the estimation of the annual probability of direct structural damage to reinforced concrete buildings associated with high-pressure natural-gas pipeline explosions. The procedure is based on Monte Carlo simulation and takes into account physical features of blast generation and propagation, as well as damage to reinforced concrete columns. The natural-gas jet release process and the flammable cloud size are estimated through SLAB one-dimensional integral model incorporating a release rate model. The explosion effects are evaluated by a Multi-Energy Method. Damage to reinforced concrete columns is predicted by means of pressure–impulse diagrams. The conditional probability of damage was estimated at multiple pressure–impulse levels, allowing blast fragility surfaces to be derived at different performance limit states. Finally, blast risk was evaluated and allowed the estimation of minimum pipeline-to-building safety distances for risk-informed urban planning. The probabilistic procedure presented herein may be used for performance-based design/assessment of buildings and to define the path of new natural-gas pipeline networks. - Highlights: • The safety of buildings against blast loads due to pipeline accidents is assessed. • A probabilistic risk assessment procedure is presented for natural-gas pipelines. • The annual risk of collapse of reinforced concrete building columns is evaluated. • Monte Carlo simulation was carried out considering both pipeline and column features. • A risk-targeted safety distance is proposed for blast strength class 9.

  1. Flow visualization on a natural circulation inter-wrapper flow. Experimental and numerical results under a geometric condition of button type spacer pads

    Energy Technology Data Exchange (ETDEWEB)

    Yasuda, A.; Miyakoshi, H.; Hayashi, K.; Nishimura, M.; Kamide, H.; Hishida, K. [Japan Nuclear Cycle Development Inst., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1999-04-01

    Investigations on the inter-wrapper flow (IWF) in a liquid metal cooled fast breeder reactor core have been carried out. The IWF is a natural circulation flow between wrapper tubes in the core barrel where cold fluid is coming from a direct heat exchanger (DHX) in the upper plenum. It was shown by the sodium experiment using 7-subassembly core model that the IWF can cool the subassemblies. To clarify thermal-hydraulic characteristics of the IWF in the core, the water experiment was performed using the flow visualization technique. The test rig for IWF (TRIF) has the core simulating the fuel subassemblies and radial reflectors. The subassemblies are constructed featuring transparent heater to enable both Joule heating and flow visualization. The transparent heater was made of glass with thin conductor film coating of tin oxide, and the glass heater was embedded on the wall of modeled wrapper tube made of acrylic plexiglass. In the present experiment, influences of peripheral geometric parameters such as flow holes of core formers on the thermal-hydraulic field were investigated with the button type spacer pads of the wrapper tube. Through the water tests, flow patterns of the IWF were revealed and velocity fields were quantitatively measured with a particle image velocimetry (PIV). Also, no substantial influence of peripheral geometry was found on the temperature field of the IWF, as far as the button type spacer pad was applied. Numerical simulation was applied to the experimental analysis of IWF by using multidimensional code with porous body model. The numerical results reproduced the flow patterns within TRIF and agreed well to experimental temperature distributions, showing capability of predicting IWF with porous body model. (author)

  2. Risk Governance of Multiple Natural Hazards: Centralized versus Decentralized Approach in Europe

    Science.gov (United States)

    Komendantova, Nadejda; Scolobig, Anna; Vinchon, Charlotte

    2014-05-01

    The multi-risk approach is a relatively new field and its definition includes the need to consider multiple hazards and vulnerabilities in their interdependency (Selva, 2013) and the current multi-hazards disasters, such as the 2011 Tohoku earthquake, tsunami and nuclear catastrophe, showed the need for a multi-risk approach in hazard mitigation and management. Our knowledge about multi-risk assessment, including studies from different scientific disciplines and developed assessment tools, is constantly growing (White et al., 2001). However, the link between scientific knowledge, its implementation and the results in terms of improved governance and decision-making have gained significantly less attention (IRGC, 2005; Kappes et al., 2012), even though the interest to risk governance, in general, has increased significantly during the last years (Verweiy and Thompson, 2006). Therefore, the key research question is how risk assessment is implemented and what is the potential for the implementation of a multi-risk approach in different governance systems across Europe. More precisely, how do the characteristics of risk governance, such as the degree of centralization versus decentralization, influence the implementation of a multi-risk approach. The methodology of this research includes comparative case study analysis of top-down and bottom-up interactions in governance in the city of Naples, (Italy), where the institutional landscape is marked by significant autonomy of Italian regions in decision-making processes for assessing the majority of natural risks, excluding volcanic, and in Guadeloupe, French West Indies, an overseas department of France, where the decision-making process is marked by greater centralization in decision making associated with a well established state governance within regions, delegated to the prefect and decentralised services of central ministries. The research design included documentary analysis and extensive empirical work involving

  3. The Impact of Public Guarantees on Bank Risk Taking : Evidence from a Natural Experiment

    NARCIS (Netherlands)

    Gropp, R.; Grundl, C.; Guttler, A.

    2010-01-01

    In 2001, government guarantees for savings banks in Germany were removed following a law suit. We use this natural experiment to examine the effect of government guarantees on bank risk taking, using a large data set of matched bank/borrower information. The results suggest that banks whose

  4. Food supply chain disruption due to natural disaster: Entities, risks and strategies for resilience

    Science.gov (United States)

    The resilience of food supply chain (FSC) to disruptions has not kept pace with the extended, globalized and complex network of modern food chain. This chapter presents a holistic view of the FSC, interactions among its components, risks and vulnerabilities of disruption in the context of natural d...

  5. Reducing the Risk of Posttraumatic Stress Disorder in Children Following Natural Disasters

    Science.gov (United States)

    Mohay, Heather; Forbes, Nicole

    2009-01-01

    A significant number of children suffer long-term psychological disturbance following exposure to a natural disaster. Evidence suggests that a dose-response relationship exists, so that children and adolescents who experience the most intense or extensive exposure to the risk factors for posttraumatic stress disorder (PTSD) are likely to develop…

  6. Natural Products for the Prevention and Alleviation of Risk Factors for Diabetes: Chromium and Cinnamon

    Science.gov (United States)

    Natural products are widespread for the alleviation and prevention of the risk factors of the metabolic syndrome and diabetes. We have shown that glucose, insulin, cholesterol, and hemoglobin A1c levels are all improved in people with type 2 diabetes following chromium supplementation in a double-b...

  7. Age at natural menopause and risk of type 2 diabetes : A prospective cohort study

    NARCIS (Netherlands)

    T. Muka (Taulant); E. Asllanaj (Eralda); N. Avazverdi (Naim); L. Jaspers (Loes); N. Stringa (Najada); J. Milic (Jelena); S. Ligthart (Symen); M.K. Ikram (Kamran); J.S.E. Laven (Joop); M. Kavousi (Maryam); A. Dehghan (Abbas); O.H. Franco (Oscar)

    2017-01-01

    markdownabstract__Aims/hypothesis__ In this study, we aimed to examine the association between age at natural menopause and risk of type 2 diabetes, and to assess whether this association is independent of potential mediators. __Methods__ We included 3639 postmenopausal women from the

  8. Pricing, hedging and risk management : practical tips for natural gas buyers and sellers

    International Nuclear Information System (INIS)

    Shields, D.

    1998-01-01

    Risk analysis and techniques to manage risk as it pertains to the natural gas industry were discussed. Portfolio allocations for long-term, short-term fixed price and variable price contracts were described. Options were defined as a market instrument offering the benefits of a fixed price purchase or sale without the obligation of incurring financial or opportunity losses if the market goes against the option buyer. Options should be used as a defence strategy to protect portfolios from price risk in times of uncertainty and to take advantage of current floating market conditions without making a full price commitment. Options can also be used as an offensive strategy to make a directional play on the market or on volatility. Options selling was regarded as a much higher risk than options buying. The variables that affect options premiums were: (1) volatility, (2) time to expiration, (3) underlying price versus strike price, and (4) flexibility. Williams Energy's new world class energy trading floor in Tulsa, Oklahoma was also described. Williams is the largest-volume transporter of natural gas in the U.S. with more than 27,000 miles of pipelines. Williams pipelines transport 16 per cent of all the natural gas used in the U.S. and the company is one of the nation's largest natural gas gatherers and processors. tabs., figs

  9. Social and economic factors of the natural risk increasing: estimation of the Russian regions

    Directory of Open Access Journals (Sweden)

    E. Petrova

    2004-01-01

    Full Text Available This study is an attempt to assess quantitatively social and economic factors that determine vulnerability of Russian regions to natural risk, to trace the space differences of the considered factors, and to group the regions by their similarity. In order to indicate the regional differences in social and economic development, equipment condition, dangerous substances accumulation, and social trouble four the most suitable parameters were estimated, including the per capita production of Gross Regional Product (GRP, capital consumption, volume of total toxic waste, and crime rate. Increase of the first parameter causes vulnerability reducing, the increase of the last three causes its increasing. Using multidimensional cluster analysis five types of regions were found for Russia according to similarity of the considered parameters. These types are characterized with higher value of a single (rarely two chosen parameter, which seems to be sufficient enough to affect natural risks increasing in these regions in near future. Only few regions belonging to the fifth type proved to have rather high value of GRP and relatively low values of the other parameters. The negative correlation was found between a number of natural disasters (ND and the per capita GRP in case when some parameters reached anomalously high value. The distinctions between regions by prevailing different parameters, which result in natural risk increasing, help risk management to find directions where to focus on.

  10. Prototype of a web - based participative decision support platform in natural hazards and risk management

    NARCIS (Netherlands)

    Aye, Z.C.; Jaboyedoff, M.; Derron, M.H.; van Westen, C.J.

    2015-01-01

    This paper presents the current state and development of a prototype web-GIS (Geographic Information System) decision support platform intended for application in natural hazards and risk management, mainly for floods and landslides. This web platform uses open-source geospatial software and

  11. Natural convection flow and heat transfer between a fluid layer and a porous layer inside a rectangular enclosure

    International Nuclear Information System (INIS)

    Beckermann, C.; Ramadhyani, S.; Viskanta, R.

    1986-01-01

    A numerical and experimental study is performed to analyze the steady-state natural convection fluid flow and heat transfer in a vertical rectangular enclosure that is partially filled with a vertical layer of a fluid-saturated porous medium. The flow in the porous layer is modeled utilizing the Brinkman-Forchheimer-extended Darcy equations. The numerical model is verified by conducting a number of experiments with spherical glass beads as the porous medium and water and glycerin as the fluids in rectangular test-cells. The agreement between the flow visualization results and temperature measurements and the numerical model is, in general, good. It is found that the amount of fluid penetrating from the fluid region into the porous layer depends strongly on the Darcy (Da) and Rayleigh (Ra) numbers. For a relatively low product of Ra x Da, the flow takes place primarily in the fluid layer, and heat transfer in the porous layer is by conduction only. On the other hand, fluid penetrating into a relatively highly permeable porous layer has a significant impact on the natural convection flow patterns in the entire enclosure

  12. [Responses of sap flow to natural rainfall and continuous drought of tree species growing on bedrock outcrops].

    Science.gov (United States)

    Zhang, Hui Ling; Ding, Ya Li; Chen, Hong Song; Wang, Ke Lin; Nie, Yun Peng

    2018-04-01

    This study focused on bedrock outcrops, a very common habitat in karst region of southwest China. To reveal the responses of plant transpiration to natural rainfall and continuous drought, two tree species typical to this habitat, Radermachera sinica and Triadica rotundifolia, were selected as test materials. A rainout shelter was used to simulate continuous drought. The sap flow dynamics were monitored using the method of Granier's thermal dissipation probe (TDP). Our results showed that sap flow density increased to different degrees after rain in different stages of the growing season. Sap flow density of the deciduous species T. rotundifolia was always higher than that of the semi-deciduous species R. sinica. After two months without rainfall input, both species exhibited no obvious decrease in sap flow density, indicating that rainfall was not the dominant source for their water uptake, at least in the short-term. Based on the regression relationships between sap flow density and meteorological factors before and after rainfall, as well as at different stages of continuous drought, we found that the dynamics of meteorological factors contributed little to plant transpiration. The basic transpiration characteristics of both species were not changed in the circumstance of natural rainfall and short-term continuous drought, which would be closely related to the special water storage environments of bedrock outcrops and the reliance on deep water sources by tree species.

  13. Infrastructure Systems Interdependencies and Risk Informed Decision Making (RIDM: Impact Scenario Analysis of Infrastructure Risks Induced by Natural, Technological and Intentional Hazards

    Directory of Open Access Journals (Sweden)

    Rudolph Frederick Stapelberg

    2008-10-01

    Full Text Available This paper reviews current research into infrastructure systems interdependencies with regard to safesty risks induced by natural, technological and intentional hazards. The paper further considers risk informed decision-making.

  14. Hydrodynamic Instability and Dynamic Burnout in Natural Circulation Two-Phase Flow. An Experimental and Theoretical Study

    Energy Technology Data Exchange (ETDEWEB)

    Becker, Kurt M; Jahnberg, S; Haga, I; Hansson, P T; Mathisen, R P

    1964-09-15

    A theoretical model for predicting the threshold of instability for two phase flow in a natural circulation loop is presented. The model calculates the flow transient caused by a step disturbance of the heat input, and is based upon the conservation laws of mass, momentum and energy in one dimensional form. Empirical correlations are used in the model for estimating the void fractions and the two-phase flow pressure drops. The equations are solved numerically in a finite difference approximation coded for a digital computer. An experimental study of the hydrodynamic instability and dynamic burnout in two-phase flow has been performed in a natural circulation loop in the pressure range from 10 to 70 atg. The test sections were round ducts of 20, 30 and 36 mm inner diameter and 4890 mm heated length. The experimental results showed that within the ranges tested, the stability of the flow increases with increasing pressure and increasing throttling before the test section, but decreases with increasing Inlet subcooling and increasing throttling after the test section. Comparing the natural circulation burnout steam qualities with corresponding forced circulation data shoved that the former data were low by a factor up to 2.5. However, by applying inlet throttling of the flow the burnout values approached and finally coincided with the forced circulation data. The present experimental results as well as data available from other sources have been compared with the stability thresholds obtained with the theoretical model. The comparisons included circular, annular and rod cluster geometries, and the agreement between the experimental and theoretical stability limits was good. Finally the application of the experimental and theoretical results on the assessment of boiling heavy water reactor design is discussed.

  15. Hydrodynamic Instability and Dynamic Burnout in Natural Circulation Two-Phase Flow. An Experimental and Theoretical Study

    International Nuclear Information System (INIS)

    Becker, Kurt M.; Jahnberg, S.; Haga, I.; Hansson, P.T.; Mathisen, R.P.

    1964-09-01

    A theoretical model for predicting the threshold of instability for two phase flow in a natural circulation loop is presented. The model calculates the flow transient caused by a step disturbance of the heat input, and is based upon the conservation laws of mass, momentum and energy in one dimensional form. Empirical correlations are used in the model for estimating the void fractions and the two-phase flow pressure drops. The equations are solved numerically in a finite difference approximation coded for a digital computer. An experimental study of the hydrodynamic instability and dynamic burnout in two-phase flow has been performed in a natural circulation loop in the pressure range from 10 to 70 atg. The test sections were round ducts of 20, 30 and 36 mm inner diameter and 4890 mm heated length. The experimental results showed that within the ranges tested, the stability of the flow increases with increasing pressure and increasing throttling before the test section, but decreases with increasing Inlet subcooling and increasing throttling after the test section. Comparing the natural circulation burnout steam qualities with corresponding forced circulation data shoved that the former data were low by a factor up to 2.5. However, by applying inlet throttling of the flow the burnout values approached and finally coincided with the forced circulation data. The present experimental results as well as data available from other sources have been compared with the stability thresholds obtained with the theoretical model. The comparisons included circular, annular and rod cluster geometries, and the agreement between the experimental and theoretical stability limits was good. Finally the application of the experimental and theoretical results on the assessment of boiling heavy water reactor design is discussed

  16. Flood Risk Mapping Using Flow Energy Equation and Geographic Information System

    Directory of Open Access Journals (Sweden)

    pourya Javan

    2013-09-01

    Full Text Available Flooding and its damages are not only found uplift water level in a region. In other words, the depth and speed parameters together have determining the level of flood risk at each point. This subject is visible in flooded plain with low height and high speed of 2 meters per second, which damages are extensive. According to the criteria of having both velocity and flow depth in the governing equation to the flows energy, this equation seems appropriate to analysis in this study. Various methods have been proposed for increase accuracy in flood zoning with different return periods and risks associated with it in land border of river. For example, some of these methods are considered factors such as analysis of past flooding in the area affected by floods, hydrological factors and consideration of hydraulic elements affecting in flood zoning (such as flow velocity. This paper investigates the effect of flood zoning by the energy flow in the areas affected by floods. Also risk due to flood based on energy flow in each section of the river is compared by the proposed graphs of hazard interval and other done flood zoning in this field. In this study, the FORDO river has been selected as the case study. This river is part of the rivers located in the city of QOM KAHAK. The characteristics of river in upstream and downstream are mountain, young and stable and adult, respectively. Also this river in different seasons is exposed the flood damage. The proposed method in this study can be improving recognition accuracy of flood risk in areas affected by flood. Also, this method facilitate the identify parts of the river bed, that is affected by severe flooding, for decision making to improve rivers organizing.

  17. Standardization of natural phenomena risk assessment methodology at the Savannah River Plant

    International Nuclear Information System (INIS)

    Huang, J.C.; Hsu, Y.S.

    1985-01-01

    Safety analyses at the Savannah River Plant (SRP) normally require consideration of the risks of incidents caused by natural events such as high-velocity straight winds, tornadic winds, and earthquakes. The probabilities for these events to occur at SRP had been studied independently by several investigators, but the results of their studies were never systematically evaluated. As part of the endeavor to standardize our environmental risk assessment methodology, these independent studies have been thoroughly reviewed and critiqued, and appropriate probability models for these natural events have been selected. The selected probability models for natural phenomena, high-velocity straight winds and tornadic winds in particular, are in agreement with those being used at other DOE sites, and have been adopted as a guide for all safety studies conducted for SRP operations and facilities. 7 references, 3 figures

  18. Risk perception and access to environmental information in four areas in Italy affected by natural or anthropogenic pollution.

    Science.gov (United States)

    Coi, A; Minichilli, F; Bustaffa, E; Carone, S; Santoro, M; Bianchi, F; Cori, L

    2016-10-01

    A human biomonitoring (HBM) survey in four areas affected by natural or anthropogenic arsenic pollution was conducted in Italy within the framework of the SEpiAs project. A questionnaire, including the exploration of risk perception (RP) regarding environmental hazards and access to and trust in information, was administered to 282 subjects stratified by area, gender and age. The survey was designed to investigate how populations living in polluted areas could adopt prevention-oriented habits, fostered by the awareness of existing risks and, in addition, how increased knowledge of RP and information flows could support researchers in identifying recommendations, and presenting and disseminating HBM results. This study characterizes the four areas in terms of RP and access to and trust in environmental information, and provides insights into the influence of RP and environmental information on food consumption. For the data analysis, a combined random forest (RF) and logistic regression approach was carried out. RF was applied to the variables derived from the questionnaire in order to identify the most important in terms of the aims defined. Associations were then tested using Fisher's exact test and assessed with logistic regression in order to adjust for confounders. Results showed that the perception of and personal exposure to atmospheric and water pollution, hazardous industries and waste, hazardous material transportation and waste was higher in geographical areas characterized by anthropogenic pollution. Citizens living in industrial areas appeared to be aware of environmental risks and had more confidence in environmental non-governmental organizations (NGOs) than in public authorities. In addition, they reported an insufficient circulation of information. Concerning the influence of RP and environmental information on food consumption, a high perception of personal exposure to atmospheric pollution and hazardous industries was associated with a lower

  19. Evaluation method for core thermohydraulics during natural circulation in fast reactors numerical predictions of inter-wrapper flow

    International Nuclear Information System (INIS)

    Kamide, H.; Kimura, N.; Miyakoshi, H.; Nagasawa, K.

    2001-01-01

    Decay heat removal using natural circulation is one of the important functions for the safety of fast reactors. As a decay heat removal system, direct reactor auxiliary cooling system has been selected in current designs of fast reactors. In this design, dumped heat exchanger provides cold sodium and it covers the reactor core outlet. The cold sodium can penetrate into the gap region between the subassemblies. This gap flow is referred as inter-wrapper flow (IWF). A numerical estimation method for such natural circulation phenomena in a reactor core has been developed, which models each subassembly as a rectangular duct with gap region between the subassemblies and also the upper plenum in a reactor vessel. This numerical simulation method was verified based on experimental data of a sodium test using 7- subassembly core model and also a water test which simulates IWF using the 1/12 sector model of a reactor core. We applied the estimation method to the natural circulation in a 600 MW class fast reactor. The temperature in the core strongly depended on IWF, flow redistribution in the core, and inter-subassembly heat transfer. It is desired for prediction methods on the natural circulation to simulate these phenomena. (author)

  20. MHD heat and mass diffusion flow by natural convection past a surface embedded in a porous medium

    Directory of Open Access Journals (Sweden)

    Chaudhary R.C.

    2009-01-01

    Full Text Available This paper presents an analytical study of the transient hydromagnetic natural convection flow past a vertical plate embedded in a porous medium, taking account of the presence of mass diffusion and fluctuating temperature about time at the plate. The governing equations are solved in closed form by the Laplace-transform technique. The results are obtained for temperature, velocity, penetration distance, Nusselt number and skin-friction. The effects of various parameters are discussed on the flow variables and presented by graphs.

  1. No Man is an Island: Social Distance, Network Flow, and Other-Regarding Behaviors in a Natural Field Experiment

    Directory of Open Access Journals (Sweden)

    XIAOYE LI

    2012-01-01

    Full Text Available A natural field experiment is designed to explore the impacts of social distanceand network flow on other-regarding behaviors. A greater degree ofcommunication between the voluntary organization and volunteers was found toreduce their social distance and thereby improve volunteering commitment. Theimprovement was even more notable if the party initiating communication was thevoluntary organization. Two other practical means of lessening social distancewere for volunteers to learn more about other volunteers, and for informationtobe dispersed throughout the organization more rapidly. Additionally, this studyshows a reversed “U-shaped” relationship between network flow and volunteeringcommitment.

  2. On the computations analyzing natural optic flow : Quantitative model analysis of the blowfly motion vision pathway

    NARCIS (Netherlands)

    Lindemann, J.P.; Kern, R.; Hateren, J.H. van; Ritter, H.; Egelhaaf, M.

    2005-01-01

    For many animals, including humans, the optic flow generated on the eyes during locomotion is an important source of information about self-motion and the structure of the environment. The blowfly has been used frequently as a model system for experimental analysis of optic flow processing at the

  3. Flow visualization of forced and natural convection in internal cavities. 1998 annual progress report

    International Nuclear Information System (INIS)

    Brodkey, R.S.; Clarksean, R.; Crepeau, J.C.; Guezennec, Y.G.; McEligot, D.M.

    1998-01-01

    'The objective of this research program is to understand the fluid physics when corroded spent nuclear fuel (SNF) elements are passivated by injecting treatment gases into a storage canister. By developing a reliable predictive technique for the energy, mass, and momentum transfer in the presence of surface reactions, transfer and storage systems can be efficiently and safely designed. The objective will be reached by using innovative flow visualization techniques and experimental measurements of the flow field to support computational models. This report summarizes work completed after eight months of a three-year, collaborative project. A generic idealization of a combined drying and passivation approach has been defined, which represents a section of a vertical canister with baskets of SNF elements. This simulation includes flow phenomena that occur in canisters for high- and/or low-enrichment fuels. A steady flow of the passivation fluid is introduced at the bottom of the canister via a central tube from the top. Fluid flows through an array of holes in the perforated basket support plate then around the simulated elements and out the top. Dimensions and flow rates for the idealized situation correspond to those for typical drying canisters. Approximate calculations have identified the ranges of values of flow parameters needed to determine the flow regimes occurring in practice.'

  4. The implementation of local wisdom in reducing natural disaster risk: a case study from West Sumatera

    Science.gov (United States)

    Zulfadrim, Z.; Toyoda, Y.; Kanegae, H.

    2018-01-01

    The purpose of this paper is to introduce some local wisdoms in West Sumatra and propose their challenges that modern values have degraded its knowledge. In a contemporary context, traditional stories (written and oral stories) still relevant to be used and internalized in disaster risk reduction. Traditional knowledge or local wisdom is a system of knowledge derived from long experienced process in the past, adopted and handed over to next generation through evolutionary process. Indigenous or traditional knowledge can be practiced in understanding the nature of natural disaster, to propose the best action in mitigation, to respond in emergency phase, and to suggest more option for recovery process based on previous experience. The paper based on four weeks field research in west Sumatra which is known with their natural hazards due to its geographical location. In the beginning, this paper discusses the nature of local wisdom and how it can be matched in disaster management, then continues to the specific case how the traditional stories in West Sumatera can be internalized and integrated with contemporary disaster risk reduction. This paper proves that local wisdom can be useful as an effective instrument to deal with natural disaster or natural hazard.

  5. Toward the Validation of Depth-Averaged Three Dimensional, Rans Steady-State Simulations of Fluvial Flows at Natural Scale

    Science.gov (United States)

    Mateo Villanueva, P. A.; Hradisky, M.

    2010-12-01

    Simulations of fluvial flows are strongly influenced by geometric complexity and overall uncertainty on measured flow variables, including those assumed to be well known boundary conditions. Often, 2D steady-state models are used for computational simulations of flows at the scale of natural rivers. Such models have been successfully incorporated in iRIC (formerly MD_SWMS), one of the widely used quasi-3D CFD solvers to perform studies of environmental flows. iRIC aids in estimating such quantities as surface roughness and shear stress, which, in turn, can be used to estimate sediment transport. However, the computational results are inherently limited in accuracy because of restricting the computations to 2D, or quasi-3D, space, which can affect the values of these predictions. In the present work we perform computer-based simulations of fluvial flows using OpenFOAM, a free, open source fully 3D CFD software package, and compare our results to predictions obtained from iRIC. First, we study the suitability of OpenFOAM as the main CFD solver to analyze fluvial flows and validate our results for two well documented rectangular channel configurations: the first case consists of a large aspect-ratio channel (ratio of depth over width 0.017, ratio of depth over length 0.0019) with a rectangular obstacle mounted at the bottom wall; the second case involves a large aspect-ratio channel (ratio of depth over width 0.1, ratio of depth over length 0.0025) with cubic obstacles mounted at the lower wall (one obstacle) and upper wall (two obstacles). Secondly, we apply our model to simulation or river at natural scale and compare our results to the output obtained from iRIC to quantify the differences in velocity profiles and other flow parameters when comparable solution techniques are used. Steady-state, RANS k-epsilon models are employed for all simulations.

  6. A HYPOTHESIS: COULD PORTABLE NATURAL GRASS BE A RISK FACTOR FOR KNEE INJURIES?

    Directory of Open Access Journals (Sweden)

    John Orchard

    2008-03-01

    Full Text Available Previous study has shown a likely link between increased shoe- surface traction and risk of knee Anterior Cruciate Ligament (ACL injury. Portable natural grass systems are being used more often in sport, but no study to date has investigated their relative safety. By their nature, they must have high resistance to falling apart and therefore newly laid systems may be at risk of creating excessive shoe-surface traction. This study describes two clusters of knee injuries (particularly non-contact ACL injuries, each occurring to players of one professional football team at single venue, using portable grass, in a short space of time. The first series included two ACL injuries, one posterolateral complex disruption and one lateral ligament tear occurring in two rugby league games on a portable bermudagrass surface in Brisbane, Australia. The second series included four non-contact ACL injuries over a period of ten weeks in professional soccer games on a portable Kentucky bluegrass/perennial ryegrass surface in Barcelona, Spain. Possible intrinsic risk factors are discussed but there was no common risk shared by the players. Although no measures of traction were made at the Brisbane venue, average rotational traction was measured towards the end of the injury cluster at Camp Nou, Barcelona, to be 48 Nm. Chance undoubtedly had a part to play in these clusters, but the only obvious common risk factor was play on a portable natural grass surface soon after it was laid. Further study is required to determine whether portable natural grass systems may exhibit high shoe-surface traction soon after being laid and whether this could be a risk factor for knee injury

  7. An investigation of transient nature of the cavitating flow in injector nozzles

    International Nuclear Information System (INIS)

    He, Zhixia; Zhong, Wenjun; Wang, Qian; Jiang, Zhaochen; Fu, Yanan

    2013-01-01

    In diesel engines, the cavitating flow in nozzles greatly affects the fuel atomization characteristics and then the subsequent combustion and exhaust emissions. In this paper, with the needle lift curve on the basis of injection rate experimental data, a moving mesh generation strategy was applied for 3D simulation of the nozzle cavitating flow. Based on the third-generation synchrotrons of Shanghai Synchrotron Radiation facility (SSRF), a high-precision three-dimension structure of testing nozzle with detailed internal geometry information was obtained using X-ray radiography for a more accurate simulation. A flow visualization experiment system with a transparent scaled-up vertical multi-hole injector nozzle tip was setup. The experimental data was obtained to make a comparison to validate the calculated results and good qualitative agreement was shown between them. Afterward, the effects of needle movement on development of the cavitating flow and flow characteristics parameters were investigated. Finally, the influence of fuel temperature on development of the cavitating flow was also studied. Research of the flow characteristics for the diesel and biodiesel revealed that the flow characteristics of the biodiesel with a temperature rise of between 50 K and 60 K in injector nozzles will be similar to those of the diesel fuel. -- Highlights: ► The detailed geometry information was obtained using X-ray radiography. ► A visualization experiment system was setup for validating the numerical models. ► The detailed cavitating flow in nozzles can be gotten with a moving mesh. ► The flow characteristics between the diesel and biodiesel fuel are investigated

  8. Risk Analysis on Leakage Failure of Natural Gas Pipelines by Fuzzy Bayesian Network with a Bow-Tie Model

    OpenAIRE

    Shan, Xian; Liu, Kang; Sun, Pei-Liang

    2017-01-01

    Pipeline is the major mode of natural gas transportation. Leakage of natural gas pipelines may cause explosions and fires, resulting in casualties, environmental damage, and material loss. Efficient risk analysis is of great significance for preventing and mitigating such potential accidents. The objective of this study is to present a practical risk assessment method based on Bow-tie model and Bayesian network for risk analysis of natural gas pipeline leakage. Firstly, identify the potential...

  9. A meta-analysis of risk factors for depression in adults and children after natural disasters.

    Science.gov (United States)

    Tang, Bihan; Liu, Xu; Liu, Yuan; Xue, Chen; Zhang, Lulu

    2014-06-19

    A number of studies have shown a range of negative psychological symptoms (e.g. depression) after exposure to natural disasters. The aim of this study was to determine risk factors for depression in both children and adults who have survived natural disasters. Four electronic databases (PubMed, Embase, Web of Science, and PsychInfo) were used to search for observational studies (case-control, cross-sectional, and cohort studies) about depression following natural disasters. The literature search, study selection, and data extraction were conducted independently by two authors. Thirty-one articles were included in the study, of which twenty included adult participants and eleven included child participants. Summary estimates were obtained using random-effects models. Subgroup analysis, sensitivity analysis, and publication bias tests were performed on the data. The prevalence of depression after natural disasters ranged from 5.8% to 54.0% in adults and from 7.5% to 44.8% in children. We found a number of risk factors for depression after exposure to natural disasters. For adults, the significant predictors were being female ;not married;holding religious beliefs; having poor education; prior trauma; experiencing fear, injury, or bereavement during the disaster; or losing employment or property, suffering house damage as a result of the disaster. For children, the significant predictors were prior trauma; being trapped during the disaster; experiencing injury, fear, or bereavement during the disaster; witnessing injury/death during the disaster; or having poor social support. The current analysis provides evidence of risk factors for depression in survivors of natural disasters. Further research is necessary to design interventions to improve the mental health of survivors of natural disasters.

  10. Experimental study of natural two-phase flow circulation using a visualization technique; Estudo experimental da circulacao natural bifasica utilizando uma tecnica de visualizacao

    Energy Technology Data Exchange (ETDEWEB)

    Vinhas, Pedro A.M., E-mail: Pedro_mvinhas@poli.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Nuclear; Faccini, Jose L.H., E-mail: faccini@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Su, Jian, E-mail: sujian@lasme.coppe.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear

    2013-07-01

    This paper presents an experimental study of natural two-phase flow in a circuit that simulates, on a smaller scale, a typical residual heat removal system of passive reactors APWR (Advanced Pressurized Water Reactor). The circuit was formed by a heater, a heat exchanger and piping. The experimental study was the application of a visualization technique, using a high speed camera, for measuring the size and speed of vapor bubbles generated in the heater with different power heating. The camera was positioned in the central region of the pipe connecting the heater to the heat exchanger, where there is a clear passage. The flow of images were processed and analyzed using commercial software that allowed the determination of the length and velocity of the bubbles. The results were then compared with correlations available in literature.

  11. Natural disaster risk analysis for critical infrastructure systems: An approach based on statistical learning theory

    International Nuclear Information System (INIS)

    Guikema, Seth D.

    2009-01-01

    Probabilistic risk analysis has historically been developed for situations in which measured data about the overall reliability of a system are limited and expert knowledge is the best source of information available. There continue to be a number of important problem areas characterized by a lack of hard data. However, in other important problem areas the emergence of information technology has transformed the situation from one characterized by little data to one characterized by data overabundance. Natural disaster risk assessments for events impacting large-scale, critical infrastructure systems such as electric power distribution systems, transportation systems, water supply systems, and natural gas supply systems are important examples of problems characterized by data overabundance. There are often substantial amounts of information collected and archived about the behavior of these systems over time. Yet it can be difficult to effectively utilize these large data sets for risk assessment. Using this information for estimating the probability or consequences of system failure requires a different approach and analysis paradigm than risk analysis for data-poor systems does. Statistical learning theory, a diverse set of methods designed to draw inferences from large, complex data sets, can provide a basis for risk analysis for data-rich systems. This paper provides an overview of statistical learning theory methods and discusses their potential for greater use in risk analysis

  12. A method of quantitative risk assessment for transmission pipeline carrying natural gas

    International Nuclear Information System (INIS)

    Jo, Young-Do; Ahn, Bum Jong

    2005-01-01

    Regulatory authorities in many countries are moving away from prescriptive approaches for keeping natural gas pipelines safe. As an alternative, risk management based on a quantitative assessment is being considered to improve the level of safety. This paper focuses on the development of a simplified method for the quantitative risk assessment for natural gas pipelines and introduces parameters of fatal length and cumulative fatal length. The fatal length is defined as the integrated fatality along the pipeline associated with hypothetical accidents. The cumulative fatal length is defined as the section of pipeline in which an accident leads to N or more fatalities. These parameters can be estimated easily by using the information of pipeline geometry and population density of a Geographic Information Systems (GIS). To demonstrate the proposed method, individual and societal risks for a sample pipeline have been estimated from the historical data of European Gas Pipeline Incident Data Group and BG Transco. With currently acceptable criteria taken into account for individual risk, the minimum proximity of the pipeline to occupied buildings is approximately proportional to the square root of the operating pressure of the pipeline. The proposed method of quantitative risk assessment may be useful for risk management during the planning and building stages of a new pipeline, and modification of a buried pipeline

  13. Burst Speed of Wild Fishes under High-Velocity Flow Conditions Using Stamina Tunnel with Natural Guidance System in River

    Science.gov (United States)

    Izumi, Mattashi; Yamamoto, Yasuyuki; Yataya, Kenichi; Kamiyama, Kohhei

    Swimming experiments were conducted on wild fishes in a natural guidance system stamina tunnel (cylindrical pipe) installed in a fishway of a local river under high-velocity flow conditions (tunnel flow velocity : 211 to 279 cm·s-1). In this study, the swimming characteristics of fishes were observed. The results show that (1) the swimming speeds of Tribolodon hakonensis (Japanese dace), Phoxinus lagowshi steindachneri (Japanese fat-minnow), Plecoglossus altivelis (Ayu), and Zacco platypus (Pale chub) were in proportion to their body length under identical water flow velocity conditions; (2) the maximum burst speed of Japanese dace and Japanese fat-minnow (measuring 4 to 6 cm in length) was 262 to 319 cm·s-1 under high flow velocity conditions (225 to 230 cm·s-1), while the maximum burst speed of Ayu and Pale chub (measuring 5 cm to 12 cm in length) was 308 to 355 cm·s-1 under high flow velocity conditions (264 to 273 cm·s-1) ; (3) the 50cm-maximum swimming speed of swimming fishes was 1.07 times faster than the pipe-swimming speed; (4) the faster the flow velocity, the shorter the swimming distance became.

  14. A systematic review of the risks factors associated with the onset and natural progression of hydrocephalus.

    Science.gov (United States)

    Walsh, Stephanie; Donnan, Jennifer; Morrissey, Andrea; Sikora, Lindsey; Bowen, Sonya; Collins, Kayla; MacDonald, Don

    2017-07-01

    The purpose of this study was to systematically assess and synthesize the world literature on risk factors for the onset and natural progression of hydrocephalus, thereby providing a basis for policy makers to identify appropriate risk management measures to mitigate the burden of disease in Canada. Evidence for risk factors was limited for both onset and progression. Two meta-analyses that examined a risk factor for onset met the inclusion criteria. One found a significant protective effect of prenatal vitamins among case control studies, but not cohort/randomized controlled trials (RCTs). The second found maternal obesity to be a significant risk factor for congenital hydrocephalus. Significant risk factors among 25 observational studies included: biological (multiple births, maternal parity, common cold with fever, maternal thyroid disease, family history, preterm birth, hypertension, ischemic heart disease, ischemic ECG changes, higher cerebrospinal fluid protein concentration following vestibular schwannoma); lifestyle (maternal obesity, high-density lipoprotein (HDL) cholesterol, maternal diabetes, maternal age), healthcare-related (caesarean section, interhospital transfer, drainage duration following subarachnoid hemorrhage, proximity to midline for craniectomy following traumatic brain injury); pharmaceutical (prenatal exposure to: tribenoside, metronidazole, anesthesia, opioids); and environmental (altitude, paternal occupation). Three studies reported on genetic risk factors: no significant associations were found. There are major gaps in the literature with respect to risk factors for the natural progression of hydrocephalus. Only two observational studies were included and three factors reported. Many risk factors for the onset of hydrocephalus have been studied; for most, evidence remains limited or inconclusive. More work is needed to confirm any causal associations and better inform policy. Copyright © 2016. Published by Elsevier B.V.

  15. A Hypothesis: Could Portable Natural Grass be a Risk Factor for Knee Injuries?

    Science.gov (United States)

    Orchard, John; Rodas, Gil; Til, Lluis; ArdevÒl, Jordi; Chivers, Ian

    2008-01-01

    Previous study has shown a likely link between increased shoe- surface traction and risk of knee Anterior Cruciate Ligament (ACL) injury. Portable natural grass systems are being used more often in sport, but no study to date has investigated their relative safety. By their nature, they must have high resistance to falling apart and therefore newly laid systems may be at risk of creating excessive shoe-surface traction. This study describes two clusters of knee injuries (particularly non-contact ACL injuries), each occurring to players of one professional football team at single venue, using portable grass, in a short space of time. The first series included two ACL injuries, one posterolateral complex disruption and one lateral ligament tear occurring in two rugby league games on a portable bermudagrass surface in Brisbane, Australia. The second series included four non-contact ACL injuries over a period of ten weeks in professional soccer games on a portable Kentucky bluegrass/perennial ryegrass surface in Barcelona, Spain. Possible intrinsic risk factors are discussed but there was no common risk shared by the players. Although no measures of traction were made at the Brisbane venue, average rotational traction was measured towards the end of the injury cluster at Camp Nou, Barcelona, to be 48 Nm. Chance undoubtedly had a part to play in these clusters, but the only obvious common risk factor was play on a portable natural grass surface soon after it was laid. Further study is required to determine whether portable natural grass systems may exhibit high shoe-surface traction soon after being laid and whether this could be a risk factor for knee injury. Key pointsExcessive shoe-surface traction is a hypothesised risk factor for knee ligament injuries, including anterior cruciate ligament injuries.Portable natural grass systems (by their nature in order to prevent grass rolls or squares from falling apart) will tend to exhibit high resistance to tearing when first

  16. Post-Mastectomy and Phantom Breast Pain: Risk Factors, Natural History, and Impact on Quality of Life

    National Research Council Canada - National Science Library

    Dworkin, Robert

    2003-01-01

    .... The primary aims of this research were to identify risk factors for these chronic pain syndromes following surgical procedures for breast cancer, characterize their natural history, and examine...

  17. Interactive effects of vascular risk burden and advanced age on cerebral blood flow

    Directory of Open Access Journals (Sweden)

    Katherine eBangen

    2014-07-01

    Full Text Available Vascular risk factors and cerebral blood flow (CBF reduction have been linked to increased risk of cognitive impairment and Alzheimer’s disease (AD; however the possible moderating effects of age and vascular risk burden on CBF in late life remain understudied. We examined the relationships among elevated vascular risk burden, age, CBF, and cognition. Seventy-one non-demented older adults completed an arterial spin labeling MR scan, neuropsychological assessment, and medical history interview. Relationships among vascular risk burden, age, and CBF were examined in a priori regions of interest (ROIs previously implicated in aging and AD. Interaction effects indicated that, among older adults with elevated vascular risk burden (i.e., multiple vascular risk factors, advancing age was significantly associated with reduced cortical CBF whereas there was no such relationship for those with low vascular risk burden (i.e., no or one vascular risk factor. This pattern was observed in cortical ROIs including medial temporal (hippocampus, parahippocampal gyrus, uncus, inferior parietal (supramarginal gyrus, inferior parietal lobule, angular gyrus, and frontal (anterior cingulate, middle frontal gyrus, medial frontal gyrus cortices. Furthermore, among those with elevated vascular risk, reduced CBF was associated with poorer cognitive performance. Such findings suggest that older adults with elevated vascular risk burden may be particularly vulnerable to cognitive change as a function of CBF reductions. Findings support the use of CBF as a potential biomarker in preclinical AD and suggest that vascular risk burden and regionally-specific CBF changes may contribute to differential age-related cognitive declines.

  18. Risk and contributing factors of ecosystem shifts over naturally vegetated land under climate change in China.

    Science.gov (United States)

    Yin, Yuanyuan; Tang, Qiuhong; Wang, Lixin; Liu, Xingcai

    2016-02-12

    Identifying the areas at risk of ecosystem transformation and the main contributing factors to the risk is essential to assist ecological adaptation to climate change. We assessed the risk of ecosystem shifts in China using the projections of four global gridded vegetation models (GGVMs) and an aggregate metric. The results show that half of naturally vegetated land surface could be under moderate or severe risk at the end of the 21(st) century under the middle and high emission scenarios. The areas with high risk are the Tibetan Plateau region and an area extended northeastward from the Tibetan Plateau to northeast China. With the three major factors considered, the change in carbon stocks is the main contributing factor to the high risk of ecosystem shifts. The change in carbon fluxes is another important contributing factor under the high emission scenario. The change in water fluxes is a less dominant factor except for the Tibetan Plateau region under the high emission scenario. Although there is considerable uncertainty in the risk assessment, the geographic patterns of the risk are generally consistent across different scenarios. The results could help develop regional strategies for ecosystem conservation to cope with climate change.

  19. Ecological risk assessment and natural resource management on the Outer Continental Shelf

    International Nuclear Information System (INIS)

    Goeke, G.; Roscigno, P.F.

    1993-01-01

    Since 1988 beginning with the Drilling Impact Assessment Task Force, Minerals Management Service (MMS) has used formal risk analysis methodologies in the Gulf of Mexico to determine the potential impact of gas and oil activities son natural resources. In the process, a list of assumptions, critical for the assessment of potential impacts, was generated. These assumptions were incorporated into a scenario where several levels of certainty described the hazards in terms of expected frequency of effects and the seriousness of the consequences. A risk matrix was generated from these assumptions and was used to generate a risk assessment for the various impact-producing factors on ecological endpoints. Recommendations for risk management were also provided so that decision-makers were given insight into acceptable/unacceptable levels of risk. This process insured that those issues with the highest potential impact were given the highest priority in terms of resources. One of the most important aspect so f the development of a risk assessment was determining the frequency of effects of the impact-producing factors. A paucity of data concerning the effects of impact-producing factors on estuarine and marine ecosystems remains the primary limiting factor in the development of ecological risk assessments. Presented here is a broad outline of the risk assessment methodology using chemosynthetic communities found in the Gulf of Mexico as an example

  20. Implications of using on-farm flood flow capture to recharge groundwater and mitigate flood risks along the Kings River, CA.

    Science.gov (United States)

    Bachand, Philip A M; Roy, Sujoy B; Choperena, Joe; Cameron, Don; Horwath, William R

    2014-12-02

    The agriculturally productive San Joaquin Valley faces two severe hydrologic issues: persistent groundwater overdraft and flooding risks. Capturing flood flows for groundwater recharge could help address both of these issues, yet flood flow frequency, duration, and magnitude vary greatly as upstream reservoir releases are affected by snowpack, precipitation type, reservoir volume, and flood risks. This variability makes dedicated, engineered recharge approaches expensive. Our work evaluates leveraging private farmlands in the Kings River Basin to capture flood flows for direct and in lieu recharge, calculates on-farm infiltration rates, assesses logistics, and considers potential water quality issues. The Natural Resources Conservation Service (NRCS) soil series suggested that a cementing layer would hinder recharge. The standard practice of deep ripping fractured the layer, resulting in infiltration rates averaging 2.5 in d(-1) (6 cm d(-1)) throughout the farm. Based on these rates 10 acres are needed to infiltrate 1 cfs (100 m(3) h(-1)) of flood flows. Our conceptual model predicts that salinity and nitrate pulses flush initially to the groundwater but that groundwater quality improves in the long term due to pristine flood flows low in salts or nitrate. Flood flow capture, when integrated with irrigation, is more cost-effective than groundwater pumping.

  1. The effect of sildenafil citrate (Viagra) on cerebral blood flow in patients with cerebrovascular risk factors.

    Science.gov (United States)

    Lorberboym, M; Mena, I; Wainstein, J; Boaz, M; Lampl, Y

    2010-06-01

    Sildenafil citrate is widely used for erectile dysfunction. The present study examined the short-term effects of sildenafil administration in individuals with cerebrovascular risk factors, including patients with a history of stroke. Twenty-five consecutive male patients with erectile dysfunction and vascular risk factors were included in the study. A perfusion brain SPECT study was performed at baseline and 1 h after the oral administration of sildenafil. Associations between any of the risk factors and the perfusion scores were not detected, with the exception of stroke. Stroke patients showed significantly more areas with diminished perfusion after sildenafil administration compared to baseline. In patients with diabetes or hypertension, a dose of 50 mg sildenafil does not appear to produce detrimental effects on cerebral blood flow. However, patients with a history of stroke may be at increased risk of hemodynamic impairment after the use of sildenafil.

  2. The low-power low-pressure flow resonance in a natural circulation cooled boiling water reactor

    Energy Technology Data Exchange (ETDEWEB)

    Hagen, T.H.J.J. van der; Stekelenburg, A.J.C. [Delft Univ. of Technology (Netherlands)

    1995-09-01

    The last few years the possibility of flow resonances during the start-up phase of natural circulation cooled BWRs has been put forward by several authors. The present paper reports on actual oscillations observed at the Dodewaard reactor, the world`s only operating BWR cooled by natural circulation. In addition, results of a parameter study performed by means of a simple theoretical model are presented. The influence of relevant parameters on the resonance characteristics, being the decay ratio and the resonance frequency, is investigated and explained.

  3. Risk Exposure and Net Flow in Investment Funds: Do Shareholders Monitor Asset Allocation?

    Directory of Open Access Journals (Sweden)

    Rafael Felipe Schiozer

    2014-03-01

    Full Text Available This study investigates the impact of asset allocation on the net flow of fixed income funds in the Brazilian market, by exploiting the exogenous variation in the risk perception of bank liabilities (CDs caused by the financial turmoil that followed Lehman Brothers’ demise in September 2008. The central hypothesis is that the exposure to assets negatively affected by the crisis impacts negatively the fund’s net flow. We find that, for mutual funds, the larger proportion of assets negatively affected by the crisis the larger the net outflow of resources, indicating that shareholders monitor asset allocation and exert disciplining power on fund managers by withdrawing their resources. In exclusive (fundos exclusivos, i.e., funds with a single shareholder, for which the shareholder is presumed to exert more influence on asset reallocation, we find no significant relationship between the exposure to assets negatively affected by the crisis and net flows.

  4. Modeling the Link between Left Ventricular Flow and Thromboembolic Risk Using Lagrangian Coherent Structures

    Directory of Open Access Journals (Sweden)

    Karen May-Newman

    2016-11-01

    Full Text Available A thrombus is a blood clot that forms on a surface, and can grow and detach, presenting a high risk for stroke and pulmonary embolism. This risk increases with blood-contacting medical devices, due to the immunological response to foreign surfaces and altered flow patterns that activate the blood and promote thromboembolism (TE. Abnormal blood transport, including vortex behavior and regional stasis, can be assessed from Lagrangian Coherent Structures (LCS. LCS are flow structures that bound transport within a flow field and divide the flow into regions with maximally attracting/repelling surfaces that maximize local shear. LCS can be identified from finite time Lyapunov exponent (FTLE fields, which are computed from velocity field data. In this study, the goal was to use FTLE analysis to evaluate LCS in the left ventricle (LV using velocity data obtained from flow visualization of a mock circulatory loop. A model of dilated cardiomyopathy (DCM was used to investigate the effect of left ventricular assist device (LVAD support on diastolic filling and transport in the LV. A small thrombus in the left ventricular outflow tract was also considered using data from a corresponding LV model. The DCM LV exhibited a direct flow of 0.8 L/cardiac cycle, which was tripled during LVAD support Delayed ejection flow was doubled, further illustrating the impact of LVAD support on blood transport. An examination of the attracting LCS ridges during diastolic filling showed that the increase is due primarily to augmentation of A wave inflow, which is associated with increased vortex circulation, kinetic energy and Forward FTLE. The introduction of a small thrombus in the left ventricular outflow tract (LVOT of the LV had a minimal effect on diastolic inflow, but obstructed systolic outflow leading to decreased transport compared with the unobstructed LVOT geometry. Localized FTLE in the LVOT increased dramatically with the small thrombus model, which reflects

  5. COUNTRY RISK EVALUATION IMPACT ON FDI FLOW. MEDIUM RUN EVIDENCE FROM ROMANIA

    Directory of Open Access Journals (Sweden)

    EMILIA UNGUREANU

    2014-10-01

    Full Text Available During the last two decades, Romanian economy suffered numerous changes, with direct impact in the socio-economic and political life. This affected also the investment environment, the degree of attractiveness for investors and the flow of FDIs. As the economic system has a global dimension, the need of evaluating different countries from a risk perspective (that will serve as starting point for investor’s decision has increased the role of rating agencies, especially in the economic crisis context. Therefore, by applying two econometric models, we will determine in which degree the risk rating (using the Euromoney index is influencing the FDI flow in Romania, having as evidence the period 1996-2012.

  6. Toward Design Guidelines for Stream Restoration Structures: Measuring and Modeling Unsteady Turbulent Flows in Natural Streams with Complex Hydraulic Structures

    Science.gov (United States)

    Lightbody, A.; Sotiropoulos, F.; Kang, S.; Diplas, P.

    2009-12-01

    Despite their widespread application to prevent lateral river migration, stabilize banks, and promote aquatic habitat, shallow transverse flow training structures such as rock vanes and stream barbs lack quantitative design guidelines. Due to the lack of fundamental knowledge about the interaction of the flow field with the sediment bed, existing engineering standards are typically based on various subjective criteria or on cross-sectionally-averaged shear stresses rather than local values. Here, we examine the performance and stability of in-stream structures within a field-scale single-threaded sand-bed meandering stream channel in the newly developed Outdoor StreamLab (OSL) at the St. Anthony Falls Laboratory (SAFL). Before and after the installation of a rock vane along the outer bank of the middle meander bend, high-resolution topography data were obtained for the entire 50-m-long reach at 1-cm spatial scale in the horizontal and sub-millimeter spatial scale in the vertical. In addition, detailed measurements of flow and turbulence were obtained using acoustic Doppler velocimetry at twelve cross-sections focused on the vicinity of the structure. Measurements were repeated at a range of extreme events, including in-bank flows with an approximate flow rate of 44 L/s (1.4 cfs) and bankfull floods with an approximate flow rate of 280 L/s (10 cfs). Under both flow rates, the structure reduced near-bank shear stresses and resulted in both a deeper thalweg and near-bank aggradation. The resulting comprehensive dataset has been used to validate a large eddy simulation carried out by SAFL’s computational fluid dynamics model, the Virtual StreamLab (VSL). This versatile computational framework is able to efficiently simulate 3D unsteady turbulent flows in natural streams with complex in-stream structures and as a result holds promise for the development of much-needed quantitative design guidelines.

  7. Does natural disaster influence people's risk preference and trust? An experiment from cyclone prone coast of Bangladesh

    DEFF Research Database (Denmark)

    Ahsan, Dewan

    2014-01-01

    Natural catastrophic events may have enormous negative effects on economic growth. People affected by the disaster might be risk averse because of anxiety about the future uncertainty of economic returns. The purpose of this empirical study is to highlight the effect of natural disasters...... (specifically coastal cyclonic storm surges) on individuals' risk preference and level of trust. This study also aims to disentangle risk propensity from trust. It reveals that natural disasters can significantly reduce people's risk-taking attitudes, whereas the catastrophic events have no influence...... on trusting behavior. The study suggests that risk attitudes are significantly negatively correlated with trust....

  8. Buying natural gas in the spot market: risks related to the natural gas industry globalization; Aquisicao de gas natural em bases 'spot': riscos associados a globalizacao da industria do gas natural

    Energy Technology Data Exchange (ETDEWEB)

    Mathias, Melissa Cristina [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Szklo, Alexandre Salem [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE). Programa de Planejamento Energetico

    2008-07-01

    The growth of the international natural gas trade during the last decade resulted in the expectation that this product would be traded as a commodity. This expectation created a boom in the investments related to the commercialization of natural gas between borders, especially in the distinct segments of the chain of liquefied natural gas (LNG). Different agents launched themselves into liquefaction and regasification enterprises, and the ordering of ships also showed significant growth. Despite that, the natural gas market still cannot be considered global, and international gas transactions are primarily done within regional markets. This article investigates the challenges posed to the constitution of a global natural gas market. These challenges represent risks to the commercialization of this product in spot bases, for the agents that launch themselves into projects to export or import LNG to be commercialized through short term contracts in the international market for this product. (author)

  9. The Nature and Assessment of Systemic Risk in Terms of Liquidity of the Banking System

    Directory of Open Access Journals (Sweden)

    Lavreniuk Vladyslav V.

    2016-11-01

    Full Text Available The aim of the article is to determine the nature of systemic risk as a threat to the financial stability of the banking system and develop analytical tools to assess its impact on the banking system in terms of its liquidity. To solve the tasks assigned, there used general scientific and specific methods, such as: logical and dialectical method, mathematical and graphical one. Based on the generalization, analysis and comparison of different interpretations, there clarified the concept of «systemic risk» as a risk generated by financial institutions or individual sectors through the implementation of the mechanism of risk transmission, achieving significant scale of distribution and adversely affecting the stability of the financial system and the real sector of economy. There identified key aspects of systemic risk: a systemic risk is not a sum of all individual risks of financial institutions; b spreads through the channels of interconnectedness between financial institutions; c is a result of accumulated structural imbalances; d affects the stability of the financial/banking system, public confidence and the real sector of economy. Analytical tools for estimation of the bank’s contribution to the systemic liquidity risk on the basis of which it is determined that the first place in terms of the effect on the aggregate systemic risk of liquidity of the Ukrainian banking system is occupied by banks of Group I, the second place — by Privatbank, the third, fourth, fifth places — by banks in Group II — Oschadbank, Ukreximbank. It is found that it is systemically important state-owned banks that have a significant impact on systemic liquidity risk. It is determined that the probability of default of a leading systemically important bank could result in considerable cumulative losses for the entire banking system and real economy. The prospects of further research are the development of tools for systemic risk assessment with respect to

  10. Mathematical Model of Two Phase Flow in Natural Draft Wet-Cooling Tower Including Flue Gas Injection

    Directory of Open Access Journals (Sweden)

    Hyhlík Tomáš

    2016-01-01

    Full Text Available The previously developed model of natural draft wet-cooling tower flow, heat and mass transfer is extended to be able to take into account the flow of supersaturated moist air. The two phase flow model is based on void fraction of gas phase which is included in the governing equations. Homogeneous equilibrium model, where the two phases are well mixed and have the same velocity, is used. The effect of flue gas injection is included into the developed mathematical model by using source terms in governing equations and by using momentum flux coefficient and kinetic energy flux coefficient. Heat and mass transfer in the fill zone is described by the system of ordinary differential equations, where the mass transfer is represented by measured fill Merkel number and heat transfer is calculated using prescribed Lewis factor.

  11. EU Enlargement: Migration flows from Central and Eastern Europe into the Nordic countries - exploiting a natural experiment

    DEFF Research Database (Denmark)

    Pytlikova, Mariola; Pedersen, Peder J.

    We look at migration flows from 8 Central and Eastern European Countries (CEECs) to 5 Nordic countries over the years 1985 - 2005 and we can exploit a natural experiment that arose from the fact that while Sweden opened its labour market from the day one of the 2004 EU enlargement, the other Nordic...... countries chose a transition period in relation to the "new" EU members. We employ a differences-in-differences estimator in our analysis. The results show that the estimated effect of the opening of Swedish labour market in 2004 on migration is insignificantly different from zero. Further, we...... are interested in the overall effect of the "EU entry" on migration. Therefore we look at migration flows from CEECs during the first round EU enlargement towards CEECs in 2004 and compare them with migration flows from Bulgaria and Romania. We again used a DD estimator in our analysis. The estimated effect...

  12. Optimisation of the flow path in a conceptual pool type reactor under natural circulation with lead coolant

    International Nuclear Information System (INIS)

    Thiele, R.; Anglart, H.

    2014-01-01

    This contribution investigates the effects of a bypass flow blocking bottom plate and the influence of the heat transfer between the hot and cold leg in a small pool type reactor cooled through natural convection with lead coolant. The computations are carried out using 3D computational fluid dynamics, where small-detail parts, such as the core and heat exchangers are modeled using a porous media approach. The introduction of full conjugate heat transfer shows that the heat transfer between the hot and cold leg can deteriorate flow in the cold leg and lead to recirculation zones. These zones become even more pronounced with the introduction of a bottom plate, which on the other hand also increases the flow through the core and lowers the maximum temperature in the core by approximately 150 K. Based on the results, redesign suggestions for the bottom plate and the internal wall are made. (author)

  13. Assessing global exposure and vulnerability towards natural hazards: the Disaster Risk Index

    Directory of Open Access Journals (Sweden)

    P. Peduzzi

    2009-07-01

    Full Text Available This paper presents a model of factors influencing levels of human losses from natural hazards at the global scale, for the period 1980–2000. This model was designed for the United Nations Development Programme as a building stone of the Disaster Risk Index (DRI, which aims at monitoring the evolution of risk. Assessing what countries are most at risk requires considering various types of hazards, such as droughts, floods, cyclones and earthquakes. Before assessing risk, these four hazards were modelled using GIS and overlaid with a model of population distribution in order to extract human exposure. Human vulnerability was measured by crossing exposure with selected socio-economic parameters. The model evaluates to what extent observed past losses are related to population exposure and vulnerability. Results reveal that human vulnerability is mostly linked with country development level and environmental quality. A classification of countries is provided, as well as recommendations on data improvement for future use of the model.

  14. Analyses in support of risk-informed natural gas vehicle maintenance facility codes and standards :

    Energy Technology Data Exchange (ETDEWEB)

    Ekoto, Isaac W.; Blaylock, Myra L.; LaFleur, Angela Christine; LaChance, Jeffrey L.; Horne, Douglas B.

    2014-03-01

    Safety standards development for maintenance facilities of liquid and compressed gas fueled large-scale vehicles is required to ensure proper facility design and operation envelopes. Standard development organizations are utilizing risk-informed concepts to develop natural gas vehicle (NGV) codes and standards so that maintenance facilities meet acceptable risk levels. The present report summarizes Phase I work for existing NGV repair facility code requirements and highlights inconsistencies that need quantitative analysis into their effectiveness. A Hazardous and Operability study was performed to identify key scenarios of interest. Finally, scenario analyses were performed using detailed simulations and modeling to estimate the overpressure hazards from HAZOP defined scenarios. The results from Phase I will be used to identify significant risk contributors at NGV maintenance facilities, and are expected to form the basis for follow-on quantitative risk analysis work to address specific code requirements and identify effective accident prevention and mitigation strategies.

  15. A novel tool for user-friendly estimation of natural, diagnostic and professional radiation risk: Radio-Risk software

    International Nuclear Information System (INIS)

    Carpeggiani, Clara; Paterni, Marco; Caramella, Davide; Vano, Eliseo; Semelka, Richard C.; Picano, Eugenio

    2012-01-01

    Background: Awareness of radiological risk is low among doctors and patients. An educational/decision tool that considers each patient’ s cumulative lifetime radiation exposure would facilitate provider–patient communication. Aim: The purpose of this work was to develop user-friendly software for simple estimation and communication of radiological risk to patients and doctors as a part of the SUIT-Heart (Stop Useless Imaging Testing in Heart disease) Project of the Tuscany Region. Methods: We developed a novel software program (PC-platform, Windows OS fully downloadable at (http://suit-heart.ifc.cnr.it)) considering reference dose estimates from American Heart Association Radiological Imaging 2009 guidelines and UK Royal College of Radiology 2007 guidelines. Cancer age and gender-weighted risk were derived from Biological Effects of Ionising Radiation VII Committee, 2006. Results: With simple input functions (demographics, age, gender) the user selects from a predetermined menu variables relating to natural (e.g., airplane flights and geo-tracked background exposure), professional (e.g., cath lab workers) and medical (e.g., CT, cardiac scintigraphy, coronary stenting) sources. The program provides a simple numeric (cumulative effective dose in milliSievert, mSv, and equivalent number of chest X-rays) and graphic (cumulative temporal trends of exposure, cancer cases out of 100 exposed persons) display. Conclusions: A simple software program allows straightforward estimation of cumulative dose (in multiples of chest X-rays) and risk (in extra % lifetime cancer risk), with simple numbers quantifying lifetime extra cancer risk. Pictorial display of radiation risk may be valuable for increasing radiological awareness in cardiologists.

  16. A novel tool for user-friendly estimation of natural, diagnostic and professional radiation risk: Radio-Risk software

    Energy Technology Data Exchange (ETDEWEB)

    Carpeggiani, Clara; Paterni, Marco [CNR, Institute of Clinical Physiology (Italy); Caramella, Davide [Radiology Department, Pisa University, Pisa (Italy); Vano, Eliseo [San Carlos Hospital, Radiology Department, Complutense University, Madrid (Spain); Semelka, Richard C. [University of North Carolina, Chapel Hill, NC (United States); Picano, Eugenio, E-mail: picano@ifc.cnr.it [CNR, Institute of Clinical Physiology (Italy)

    2012-11-15

    Background: Awareness of radiological risk is low among doctors and patients. An educational/decision tool that considers each patient' s cumulative lifetime radiation exposure would facilitate provider-patient communication. Aim: The purpose of this work was to develop user-friendly software for simple estimation and communication of radiological risk to patients and doctors as a part of the SUIT-Heart (Stop Useless Imaging Testing in Heart disease) Project of the Tuscany Region. Methods: We developed a novel software program (PC-platform, Windows OS fully downloadable at (http://suit-heart.ifc.cnr.it)) considering reference dose estimates from American Heart Association Radiological Imaging 2009 guidelines and UK Royal College of Radiology 2007 guidelines. Cancer age and gender-weighted risk were derived from Biological Effects of Ionising Radiation VII Committee, 2006. Results: With simple input functions (demographics, age, gender) the user selects from a predetermined menu variables relating to natural (e.g., airplane flights and geo-tracked background exposure), professional (e.g., cath lab workers) and medical (e.g., CT, cardiac scintigraphy, coronary stenting) sources. The program provides a simple numeric (cumulative effective dose in milliSievert, mSv, and equivalent number of chest X-rays) and graphic (cumulative temporal trends of exposure, cancer cases out of 100 exposed persons) display. Conclusions: A simple software program allows straightforward estimation of cumulative dose (in multiples of chest X-rays) and risk (in extra % lifetime cancer risk), with simple numbers quantifying lifetime extra cancer risk. Pictorial display of radiation risk may be valuable for increasing radiological awareness in cardiologists.

  17. Nature of the observed oscillatory flows in shelf waters of the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Shenoi, S.S.C.; Antony, M.K.; Sundar, D.

    of internal waves with frequencies close to semidiurnal period (internal tide) controlling the flow structure. The temperature records at these levels together with the B.T. time series data collected in the vicinity of mooring site supported the presence...

  18. Development of a new solvent-free flow efficiency coating for natural gas pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Fogg, Graham A.; Morse, Jennifer [Bredero Shaw, Houston, TX (United States)

    2005-07-01

    Pipeline design engineers have traditionally considered external anti-corrosion coatings for the protection of gas transmission pipelines, with less consideration given to the benefits of internal flow efficiency coatings. This paper reviews the benefits of using a traditional solvent-based flow efficiency coating, and the relationship between the internal surface roughness of a pipe, the pressure drop across the pipeline, and the maximum flow rate of gas through the pipeline. To improve upon existing solvent-based flow efficiency coatings, a research program was undertaken to develop a solvent-free coating. The stages in the development of this coating are discussed, resulting in the plant application of the coating and final qualification to API RP 5L2. (author)

  19. Nature of turbulent transport across sheared zonal flows: insights from gyrokinetic simulations

    International Nuclear Information System (INIS)

    Sanchez, R; Newman, D E; Leboeuf, J-N; Decyk, V K

    2011-01-01

    The traditional view regarding the reduction of turbulence-induced transport across a stable sheared flow invokes a reduction of the characteristic length scale in the direction perpendicular to the flow as a result of the shearing and stretching of eddies caused by the differential pull exerted in the direction of the flow. A reduced effective transport coefficient then suffices to capture the reduction, that can then be readily incorporated into a transport model. However, recent evidence from gyrokinetic simulations of the toroidal ion-temperature-gradient mode suggests that the dynamics of turbulent transport across sheared flows changes in a more fundamental manner, and that the use of reduced effective transport coefficients fails to capture the full dynamics that may exhibit both subdiffusion and non-Gaussian statistics. In this contribution, after briefly reviewing these results, we propose some candidates for the physical mechanisms responsible for endowing transport with such non-diffusive characteristics, backing these proposals with new numerical gyrokinetic data.

  20. Experimental study of gas–liquid two-phase flow through packed bed under natural circulation conditions

    International Nuclear Information System (INIS)

    Chen, Shao-Wen; Miwa, Shuichiro; Griffiths, Matt

    2016-01-01

    Dry-out phenomena in packed beds or porous media may cause a significant digression of cooling/reaction performance in heat transfer/chemical reactor systems. One of the phenomena responsible for the dry-out in packed beds is known as the counter-current flow limitation (CCFL). In order to investigate the CCFL phenomena induced by gas–liquid two-phase flow in packed beds inside a pool, a natural circulation packed bed test facility was designed and constructed. A total of 27 experimental conditions covering various packing media sizes (sphere diameters: 3.0, 6.4 and 9.5 mm), packed bed heights (15, 35 and 50 cm) and water level heights (1.0, 1.5 and 2.0 m) were tested to examine the CCFL criteria with adiabatic air–water two-phase flow under natural circulation conditions. Both CCFL and flow reversal phenomena were observed, and the experimental data including instantaneous and time-averaged void fraction, differential pressure and superficial gas–liquid velocities were collected. The CCFL criteria were determined when periodical oscillations of void fraction and differential pressure appear. In addition, the Wallis correlation for CCFL was utilized for data analysis, and the Wallis coefficient, C, was determined experimentally from the packed bed CCFL tests. Compared to the existing data-sets in literature, the higher C values obtained in the present experiment suggest a possibly higher dry-out heat flux for natural circulation debris systems, which may be due to the water supply from both top and bottom surfaces of the packed beds. Considering the effects of bed height and hydraulic diameter of the packing media, a newly developed model for the Wallis coefficient, C, under natural circulation CCFL is presented. The present model can predict the experimental data with an averaged absolute error of ±7.9%. (author)

  1. A structured elicitation method to identify key direct risk factors for the management of natural resources

    Directory of Open Access Journals (Sweden)

    Michael Smith

    2015-11-01

    Full Text Available The high level of uncertainty inherent in natural resource management requires planners to apply comprehensive risk analyses, often in situations where there are few resources. In this paper, we demonstrate a broadly applicable, novel and structured elicitation approach to identify important direct risk factors. This new approach combines expert calibration and fuzzy based mathematics to capture and aggregate subjective expert estimates of the likelihood that a set of direct risk factors will cause management failure. A specific case study is used to demonstrate the approach; however, the described methods are widely applicable in risk analysis. For the case study, the management target was to retain all species that characterise a set of natural biological elements. The analysis was bounded by the spatial distribution of the biological elements under consideration and a 20-year time frame. Fourteen biological elements were expected to be at risk. Eleven important direct risk factors were identified that related to surrounding land use practices, climate change, problem species (e.g., feral predators, fire and hydrological change. In terms of their overall influence, the two most important risk factors were salinisation and a lack of water which together pose a considerable threat to the survival of nine biological elements. The described approach successfully overcame two concerns arising from previous risk analysis work: (1 the lack of an intuitive, yet comprehensive scoring method enabling the detection and clarification of expert agreement and associated levels of uncertainty; and (2 the ease with which results can be interpreted and communicated while preserving a rich level of detail essential for informed decision making.

  2. Curvilinear immersed-boundary method for simulating unsteady flows in shallow natural streams with arbitrarily complex obstacles

    Science.gov (United States)

    Kang, Seokkoo; Borazjani, Iman; Sotiropoulos, Fotis

    2008-11-01

    Unsteady 3D simulations of flows in natural streams is a challenging task due to the complexity of the bathymetry, the shallowness of the flow, and the presence of multiple nature- and man-made obstacles. This work is motivated by the need to develop a powerful numerical method for simulating such flows using coherent-structure-resolving turbulence models. We employ the curvilinear immersed boundary method of Ge and Sotiropoulos (Journal of Computational Physics, 2007) and address the critical issue of numerical efficiency in large aspect ratio computational domains and grids such as those encountered in long and shallow open channels. We show that the matrix-free Newton-Krylov method for solving the momentum equations coupled with an algebraic multigrid method with incomplete LU preconditioner for solving the Poisson equation yield a robust and efficient procedure for obtaining time-accurate solutions in such problems. We demonstrate the potential of the numerical approach by carrying out a direct numerical simulation of flow in a long and shallow meandering stream with multiple hydraulic structures.

  3. Nature of convection-stabilized dc arcs in dual-flow nozzle geometry

    International Nuclear Information System (INIS)

    Serbetci, I.; Nagamatsu, H.T.

    1990-01-01

    In this paper, an experimental investigation of the steady-state low-current air arcs in a dual-flow nozzle system is presented. First, the cold flow with no arc as determined for various nozzle geometries, i.e., two- and three-dimensional and orifice nozzles, and nozzle pressure ratios. Supersonic flow separation and oblique and detached shock waves were observed in the flow field. Using a finite-element computer program, the Mach number contours were determined in the flow field for various nozzle-gap spacings and pressure ratios. In addition, the dc arc voltage and current measurements were made for an electrode gap spacing of ∼ 5.5 cm and current levels of I ∼ 25, 50, and 100 A for the three nozzle geometries. The arc voltage and arc power increased rapidly as the flow speed increased from zero to sonic velocity at the nozzle throat. The shock waves in the converging-diverging nozzles resulted in a decrease in the overall resistance by about 15 percent

  4. Coupling model and solving approach for performance evaluation of natural draft counter-flow wet cooling towers

    Directory of Open Access Journals (Sweden)

    Wang Wei

    2016-01-01

    Full Text Available When searching for the optimum condenser cooling water flow in a thermal power plant with natural draft cooling towers, it is essential to evaluate the outlet water temperature of cooling towers when the cooling water flow and inlet water temperature change. However, the air outlet temperature and tower draft or inlet air velocity are strongly coupled for natural draft cooling towers. Traditional methods, such as trial and error method, graphic method and iterative methods are not simple and efficient enough to be used for plant practice. In this paper, we combine Merkel equation with draft equation, and develop the coupled description for performance evaluation of natural draft cooling towers. This model contains two inputs: the cooling water flow, the inlet cooling water temperature and two outputs: the outlet water temperature, the inlet air velocity, equivalent to tower draft. In this model, we furthermore put forward a soft-sensing algorithm to calculate the total drag coefficient instead of empirical correlations. Finally, we design an iterative approach to solve this coupling model, and illustrate three cases to prove that the coupling model and solving approach proposed in our paper are effective for cooling tower performance evaluation.

  5. Differential Dynamic Evolutionary Model of Emergency Financial Service Supply Chain in Natural Disaster Risk Management

    Directory of Open Access Journals (Sweden)

    Shujian Ma

    2016-01-01

    Full Text Available A government-market-public partnership (GMPP could be a feasible arrangement for providing insurance coverage for natural disaster. Firstly, we put forward GMPP management mode. Secondly, the emergency financial service supply chain for natural disaster risk is built from the view of supply chain. Finally, the objective of this paper is to obtain insights into the cooperative and competitive relationship in GMPP system. We establish the cooperative and competitive differential dynamic evolutionary models and prove the existence of equilibrium solutions in order to solve the coordination problems. In conclusion, the equilibrium solutions can be achieved among the insurers, the operating governments, and the public.

  6. Two-Phase Flow Simulations In a Natural Rock Fracture using the VOF Method

    International Nuclear Information System (INIS)

    Crandall, Dustin; Ahmadi, Goodarz; Smith, Duane H.; Bromhal, Grant

    2010-01-01

    Standard models of two-phase flow in porous media have been shown to exhibit several shortcomings that might be partially overcome with a recently developed model based on thermodynamic principles (Hassanizadeh and Gray, 1990). This alternative two-phase flow model contains a set of new and non-standard parameters, including specific interfacial area. By incorporating interfacial area production, destruction, and propagation into functional relationships that describe the capillary pressure and saturation, a more physical model has been developed. Niessner and Hassanizadeh (2008) have examined this model numerically and have shown that the model captures saturation hysteresis with drainage/imbibition cycles. Several static experimental studies have been performed to examine the validity of this new thermodynamically based approach; these allow the determination of static parameters of the model. To date, no experimental studies have obtained information about the dynamic parameters required for the model. A new experimental porous flow cell has been constructed using stereolithography to study two-phase flow phenomena (Crandall et al. 2008). A novel image analysis tool was developed for an examination of the evolution of flow patterns during displacement experiments (Crandall et al. 2009). This analysis tool enables the direct quantification of interfacial area between fluids by matching known geometrical properties of the constructed flow cell with locations identified as interfaces from images of flowing fluids. Numerous images were obtained from two-phase experiments within the flow cell. The dynamic evolution of the fluid distribution and the fluid-fluid interface locations were determined by analyzing these images. In this paper, we give a brief introduction to the thermodynamically based two-phase flow model, review the properties of the stereolithography flow cell, and show how the image analysis procedure has been used to obtain dynamic parameters for the

  7. Generation risk assessment in volatile conditions with wind, hydro, and natural gas units

    International Nuclear Information System (INIS)

    Sahin, Cem; Shahidehpour, Mohammad; Erkmen, Ismet

    2012-01-01

    Highlights: ► Stochastic price-based unit commitment (PBUC) for a generation company (GENCO). ► Water inflow, wind, and NG interruption uncertainties are considered. ► Diversification of assets and bilateral contracts enhance payoff and decrease financial risk. ► The utilization of NG in the risk-neutral GENCO case increases as the wind uncertainty increases. ► NG utilization is lowered by the algorithm to decrease in risk-considered case. -- Abstract: This paper studies a generating company (GENCO)’s midterm (a few months to a year) scheduling payoffs and risks in volatile operating conditions. The proposed algorithm considers the integration of intermittent wind units into a GENCO’s generation assets and coordinates the GENCO’s hourly wind generation schedule with that of natural gas (NG) units (with volatile gas prices) and hydro units (with water inflow forecast) for maximizing the GENCO’s payoff. The proposed midterm GENCO model applies market price forecasts to the risk-constrained stochastic price-based unit commitment (PBUC) for calculating the GENCO’s risk in energy and ancillary services markets. The proposed PBUC minimizes the cost of (a) NG contracts, storage, startup and shutdown, (b) startup and shutdown of cascaded hydro units, and (c) penalty for defaulting on the scheduled power delivery. Simulation results show that the diversification of generating assets including bilateral contracts (BCs) could enhance the GENCO’s midterm planning by increasing the expected payoff and decreasing the financial risk.

  8. Military Ecological Risk Assessment Framework (MERAF) for Assessment of Risks of Military Training and Testing to Natural Resources

    Energy Technology Data Exchange (ETDEWEB)

    Suter II, G.W.

    2003-06-18

    The objective of this research is to provide the DoD with a framework based on a systematic, risk-based approach to assess impacts for management of natural resources in an ecosystem context. This risk assessment framework is consistent with, but extends beyond, the EPA's ecological risk assessment framework, and specifically addresses DoD activities and management needs. MERAF is intended to be consistent with existing procedures for environmental assessment and planning with DoD testing and training. The intention is to supplement these procedures rather than creating new procedural requirements. MERAF is suitable for use for training and testing area assessment and management. It does not include human health risks nor does it address specific permitting or compliance requirements, although it may be useful in some of these cases. Use of MERAF fits into the National Environmental Policy Act (NEPA) process by providing a consistent and rigorous way of organizing and conducting the technical analysis for Environmental Impact Statements (EISs) (Sigal 1993; Carpenter 1995; Canter and Sadler 1997). It neither conflicts with, nor replaces, procedural requirements within the NEPA process or document management processes already in place within DoD.

  9. Production of Natural Gas and Fluid Flow in Tight Sand Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Maria Cecilia Bravo

    2006-06-30

    This document reports progress of this research effort in identifying relationships and defining dependencies between macroscopic reservoir parameters strongly affected by microscopic flow dynamics and production well performance in tight gas sand reservoirs. These dependencies are investigated by identifying the main transport mechanisms at the pore scale that should affect fluids flow at the reservoir scale. A critical review of commercial reservoir simulators, used to predict tight sand gas reservoir, revealed that many are poor when used to model fluid flow through tight reservoirs. Conventional simulators ignore altogether or model incorrectly certain phenomena such as, Knudsen diffusion, electro-kinetic effects, ordinary diffusion mechanisms and water vaporization. We studied the effect of Knudsen's number in Klinkenberg's equation and evaluated the effect of different flow regimes on Klinkenberg's parameter b. We developed a model capable of explaining the pressure dependence of this parameter that has been experimentally observed, but not explained in the conventional formalisms. We demonstrated the relevance of this, so far ignored effect, in tight sands reservoir modeling. A 2-D numerical simulator based on equations that capture the above mentioned phenomena was developed. Dynamic implications of new equations are comprehensively discussed in our work and their relative contribution to the flow rate is evaluated. We performed several simulation sensitivity studies that evidenced that, in general terms, our formalism should be implemented in order to get more reliable tight sands gas reservoirs' predictions.

  10. Using flow cytometry for counting natural planktonic bacteria and understanding the structure of planktonic bacterial communities

    Directory of Open Access Journals (Sweden)

    Josep M. Gasol

    2000-06-01

    Full Text Available Flow cytometry is rapidly becoming a routine methodology in aquatic microbial ecology. The combination of simple to use bench-top flow cytometers and highly fluorescent nucleic acid stains allows fast and easy determination of microbe abundance in the plankton of lakes and oceans. The different dyes and protocols used to stain and count planktonic bacteria as well as the equipment in use are reviewed, with special attention to some of the problems encountered in daily routine practice such as fixation, staining and absolute counting. One of the main advantages of flow cytometry over epifluorescence microscopy is the ability to obtain cell-specific measurements in large numbers of cells with limited effort. We discuss how this characteristic has been used for differentiating photosynthetic from non-photosynthetic prokaryotes, for measuring bacterial cell size and nucleic acid content, and for estimating the relative activity and physiological state of each cell. We also describe how some of the flow cytometrically obtained data can be used to characterize the role of microbes on carbon cycling in the aquatic environment and we prospect the likely avenues of progress in the study of planktonic prokaryotes through the use of flow cytometry.

  11. Observations of Scour and Transport at Coastal Structures from the 2011 Tohoku Tsunami - Implications for Flow in Natural Terrain

    Science.gov (United States)

    Petroff, C. M.

    2011-12-01

    Before the March 11, 2011 Tohoku tsunami, many communities along the Japan coast had shore protection barriers, some designed specifically to provide protection from tsunamis and others for typhoon and storm surge protection. A vast number of these structures were overtopped, damaged or destroyed by the high inundation and currents generated in the tsunami. Observations are presented about scour features at man-made coastal structures in the Tohoku region as well as the hydraulic transport of debris from these structures. Along with providing lessons for structure design and maintenance, these observations have implications for hydraulic transport in natural terrain, not only at hard points such as rock outcrops but also at other features such as river mouths, barrier islands and coastal dunes. As an example, Photo 1 shows the overtopping flow at the seawall at Noda, in the Iwate prefecture. From the point of view of hydraulics the type of flow seen in the photo is more like that at an in-line weir or spillway than the wave conditions for which the structure was designed. On the lee or downstream side of such structures, the flow is supercritical resulting in a supercritical to subcritical transition near the landward toe of the seawall. High flow velocities along with increased pore pressure and overturning flow create very deep scour in these locations Such as the zone clearly seen in Photo 2 behind the seawall at the Sendai airport. It is anticipated that similar hydraulic conditions would occur for flow over a high coastal dune ridge where the ridge would act as a flow control point and locally high velocities on the landward side of the ridge would result in high erosion and scour. Other examples are given.

  12. Natural disasters and the challenge of extreme events: risk management from an insurance perspective

    Science.gov (United States)

    Smolka, Anselm

    2006-08-01

    Loss statistics for natural disasters demonstrate, also after correction for inflation, a dramatic increase of the loss burden since 1950. This increase is driven by a concentration of population and values in urban areas, the development of highly exposed coastal and valley regions, the complexity of modern societies and technologies and probably, also by the beginning consequences of global warming. This process will continue unless remedial action will be taken. Managing the risk from natural disasters starts with identification of the hazards. The next step is the evaluation of the risk, where risk is a function of hazard, exposed values or human lives and the vulnerability of the exposed objects. Probabilistic computer models have been developed for the proper assessment of risks since the late 1980s. The final steps are controlling and financing future losses. Natural disaster insurance plays a key role in this context, but also private parties and governments have to share a part of the risk. A main responsibility of governments is to formulate regulations for building construction and land use. The insurance sector and the state have to act together in order to create incentives for building and business owners to take loss prevention measures. A further challenge for the insurance sector is to transfer a portion of the risk to the capital markets, and to serve better the needs of the poor. Catastrophe bonds and microinsurance are the answer to such challenges. The mechanisms described above have been developed to cope with well-known disasters like earthquakes, windstorms and floods. They can be applied, in principle, also to less well investigated and less frequent extreme disasters: submarine slides, great volcanic eruptions, meteorite impacts and tsunamis which may arise from all these hazards. But there is an urgent need to improve the state of knowledge on these more exotic hazards in order to reduce the high uncertainty in actual risk evaluation to

  13. Flow characteristics of natural circulation in a lead-bismuth eutectic loop

    Institute of Scientific and Technical Information of China (English)

    Chen-Chong Yue; Liu-Li Chen; Ke-Feng Lyu; Yang Li; Sheng Gao; Yue-Jing Liu; Qun-Ying Huang

    2017-01-01

    Lead and lead-alloys are proposed in future advanced nuclear system as coolant and spallation target.To test the natural circulation and gas-lift and obtain thermal-hydraulics data for computational fluid dynamics (CFD) and system code validation,a lead-bismuth eutectic rectangular loop,the KYLIN-Ⅱ Thermal Hydraulic natural circulation test loop,has been designed and constructed by the FDS team.In this paper,theoretical analysis on natural circulation thermal-hydraulic performance is described and the steady-state natural circulation experiment is performed.The results indicated that the natural circulation capability depends on the loop resistance and the temperature and center height differences between the hot and cold legs.The theoretical analysis results agree well with,while the CFD deviate from,the experimental results.

  14. Probabilistic disaggregation model with application to natural hazard risk assessment of portfolios

    OpenAIRE

    Custer, Rocco; Nishijima, Kazuyoshi

    2012-01-01

    In natural hazard risk assessment, a resolution mismatch between hazard data and aggregated exposure data is often observed. A possible solution to this issue is the disaggregation of exposure data to match the spatial resolution of hazard data. Disaggregation models available in literature are usually deterministic and make use of auxiliary indicator, such as land cover, to spatially distribute exposures. As the dependence between auxiliary indicator and disaggregated number of exposures is ...

  15. Relationship between age at natural menopause and risk of heart failure.

    Science.gov (United States)

    Rahman, Iffat; Åkesson, Agneta; Wolk, Alicja

    2015-01-01

    We investigated whether younger age at natural menopause confers a risk of heart failure. We also examined a possible modifying effect of tobacco smoking. This study used the population-based Swedish Mammography Cohort; 22,256 postmenopausal women with information on age at natural menopause were followed from 1997 through 2011. First event of heart failure was ascertained through the Swedish National Patient Register and the Cause of Death Register. Cox proportional hazards regression analyses were conducted to estimate multivariable-adjusted hazard ratios (HRs) and 95% CIs. During a mean follow-up of 13 years, we ascertained 2,532 first events of heart failure hospitalizations and deaths. The mean age at menopause was 51 years. Early natural menopause (40-45 y), compared with menopause at ages 50 to 54 years, was significantly associated with heart failure (HR, 1.40; 95% CI, 1.19 to 1.64). In analyses stratified by smoking status, similar HRs were observed for this age group among never smokers (HR, 1.33; 95% CI, 1.06 to 1.66) and ever smokers (HR, 1.39; 95% CI, 1.09 to 1.78). Among ever smokers, increased incidence (HR, 1.25; 95% CI, 1.06 to 1.47) of heart failure could be detected even among those who entered menopause at ages 46 to 49 years. We found a significant interaction between age at natural menopause and smoking (P = 0.019). This study indicates that women who experience early natural menopause are at increased risk for developing heart failure and that smoking can modify the association by increasing the risk even among women who enter menopause around ages 46 to 49 years.

  16. Hydromagnetic natural convection flow between vertical parallel plates with time-periodic boundary conditions

    International Nuclear Information System (INIS)

    Adesanya, S.O.; Oluwadare, E.O.; Falade, J.A.; Makinde, O.D.

    2015-01-01

    In this paper, the free convective flow of magnetohydrodynamic fluid through a channel with time periodic boundary condition is investigated by taking the effects of Joule dissipation into consideration. Based on simplifying assumptions, the coupled governing equations are reduced to a set of nonlinear boundary valued problem. Approximate solutions are obtained by using semi-analytical Adomian decomposition method. The effect of pertinent parameters on the fluid velocity, temperature distribution, Nusselt number and skin friction are presented graphically and discussed. The result of the computation shows that an increase in the magnetic field intensity has significant influence on the fluid flow. - Highlights: • The influence of magnetic field on the free convective fluid flow is considered. • The coupled equations are solved by using Adomian decomposition method. • The Adomian series solution agreed with previously obtained result. • Magnetic field decreases the velocity maximum but enhances temperature field

  17. Treatment of natural rubber processing wastewater using a combination system of a two-stage up-flow anaerobic sludge blanket and down-flow hanging sponge system.

    Science.gov (United States)

    Tanikawa, D; Syutsubo, K; Hatamoto, M; Fukuda, M; Takahashi, M; Choeisai, P K; Yamaguchi, T

    2016-01-01

    A pilot-scale experiment of natural rubber processing wastewater treatment was conducted using a combination system consisting of a two-stage up-flow anaerobic sludge blanket (UASB) and a down-flow hanging sponge (DHS) reactor for more than 10 months. The system achieved a chemical oxygen demand (COD) removal efficiency of 95.7% ± 1.3% at an organic loading rate of 0.8 kg COD/(m(3).d). Bacterial activity measurement of retained sludge from the UASB showed that sulfate-reducing bacteria (SRB), especially hydrogen-utilizing SRB, possessed high activity compared with methane-producing bacteria (MPB). Conversely, the acetate-utilizing activity of MPB was superior to SRB in the second stage of the reactor. The two-stage UASB-DHS system can reduce power consumption by 95% and excess sludge by 98%. In addition, it is possible to prevent emissions of greenhouse gases (GHG), such as methane, using this system. Furthermore, recovered methane from the two-stage UASB can completely cover the electricity needs for the operation of the two-stage UASB-DHS system, accounting for approximately 15% of the electricity used in the natural rubber manufacturing process.

  18. Myocardial infarction in the conscious dog: three dimensional mapping of infarct, collateral flow and region at risk

    International Nuclear Information System (INIS)

    Jugdutt, B.I.; Hutchins, G.M.; Bulkley, B.H.; Becker, L.C.

    1979-01-01

    Myocardial infarcts were examined in dogs to determine the spatial distribution of infarction in the region at risk and the relation between infarction and collateral blood flow. Permanent occlusion of the left circumflex (LC) coronary artery at a constant site was made in 27 conscious dogs that were sacrificed 2 days later. The anatomic region at risk was defined by postmortem coronary arteriography as the volume of the occluded LC coronary bed. The masses of the left ventricle (LV), infarct (I) and risk region (R) were calculated from planimetered areas of weighted bread-loaf sections of LV. Infarct size was directly related to the mass of the risk region (I = 0.53 R - 9.87; r = 0.97; p < 0.001). There was no infarction when R was less than about 20 g or 20% of the LV. The infarcts were mainly subendocardial and tapered from base to apex of the LV; 34% of the risk region became infarcted at the base compared with 22% at the apex. In all dogs, a significant rim of noninfarcted myocardium was identified at lateral aspects of the risk region, even at the endocardial surface. Using 9-μ radioactive microspheres, initial postocclusion flow at the margin of the infarct, but well within the risk region, was higher than at the center, and outer flows were higher than inner flows. Postocclusion flow was even higher in the noninfarcted rim within the risk region, but was still significantly less than flow to normal, nonrisk areas. Collateral flows throughout the risk region increased during the first hour after occlusion, and were even higher at 2 days.Epicardially and laterally within the anatomic risk region there is a substantial amount of tissue that does not infarct despite initally reduced blood flow

  19. A rapid detection method using flow cytometry to monitor the risk of Legionella in bath water.

    Science.gov (United States)

    Taguri, Toshitsugu; Oda, Yasunori; Sugiyama, Kanji; Nishikawa, Toru; Endo, Takuro; Izumiyama, Shinji; Yamazaki, Masayuki; Kura, Fumiaki

    2011-07-01

    Legionella species are the causative agents of human legionellosis, and bathing facilities have been identified as the sources of infection in several outbreaks in Japan. Researchers in Japan have recently reported evidence of significant associations between bacterial counts and the occurrence of Legionella in bathing facilities and in a hot tub model. A convenient and quantitative bacterial enumeration method is therefore required as an indicator of Legionella contamination or disinfection to replace existing methods such as time-consuming Legionella culture and expensive Legionella-DNA amplification. In this study, we developed a rapid detection method (RDM) to monitor the risk of Legionella using an automated microbial analyzing device based on flow cytometry techniques to measure the total number of bacteria in water samples within two minutes, by detecting typical patterns of scattered light and fluorescence. We first compared the results of our RDM with plate counting results for five filtered hot spring water samples spiked with three species of bacteria, including Legionella. Inactivation of these samples by chlorine was also assessed by the RDM, a live/dead bacterial fluorescence assay and plate counting. Using the RDM, the lower limit of quantitative bacterial counts in the spiked samples was determined as 3.0×10(3)(3.48log)counts mL(-1). We then used a laboratory model of a hot tub and found that the RDM could monitor the growth curve of naturally occurring heterotrophic bacteria with 1 and 2 days' delayed growth of amoeba and Legionella, respectively, and could also determine the killing curve of these bacteria by chlorination. Finally, samples with ≥3.48 or bacterial counts mL(-1) were tested using the RDM from 149 different hot tubs, and were found to be significantly associated with the positive or negative detection of Legionella with 95% sensitivity and 84% specificity. These findings indicated that the RDM can be used for Legionella control at

  20. Risk analysis procedure for post-wildfire natural hazards in British Columbia

    Science.gov (United States)

    Jordan, Peter

    2010-05-01

    Following a severe wildfire season in 2003, and several subsequent damaging debris flow and flood events, the British Columbia Forest Service developed a procedure for analysing risks to public safety and infrastructure from such events. At the same time, the Forest Service undertook a research program to determine the extent of post-wildfire hazards, and examine the hydrologic and geomorphic processes contributing to the hazards. The risk analysis procedure follows the Canadian Standards Association decision-making framework for risk management (which in turn is based on international standards). This has several steps: identification of risk, risk analysis and estimation, evaluation of risk tolerability, developing control or mitigation strategies, and acting on these strategies. The Forest Service procedure deals only with the first two steps. The results are passed on to authorities such as the Provincial Emergency Program and local government, who are responsible for evaluating risks, warning residents, and applying mitigation strategies if appropriate. The objective of the procedure is to identify and analyse risks to public safety and infrastructure. The procedure is loosely based on the BAER (burned area emergency response) program in the USA, with some important differences. Our procedure focuses on identifying risks and warning affected parties, not on mitigation activities such as broadcast erosion control measures. Partly this is due to limited staff and financial resources. Also, our procedure is not multi-agency, but is limited to wildfires on provincial forest land; in British Columbia about 95% of forest land is in the publicly-owned provincial forest. Each fire season, wildfires are screened by size and proximity to values at risk such as populated areas. For selected fires, when the fire is largely contained, the procedure begins with an aerial reconnaissance of the fire, and photography with a hand-held camera, which can be used to make a

  1. Computational simulation of flow and heat transfer in single-phase natural circulation loops; Simulacao computacional de escoamento e transferencia de calor em circuitos de circulacao natural monofasica

    Energy Technology Data Exchange (ETDEWEB)

    Pinheiro, Larissa Cunha

    2017-07-01

    Passive decay heat removal systems based on natural circulation are essential assets for the new Gen III+ nuclear power reactors and nuclear spent fuel pools. The aim of the present work is to study both laminar and turbulent flow and heat transfer in single-phase natural circulation systems through computational fluid dynamics simulations. The working fluid is considered to be incompressible with constant properties. In the way, the Boussinesq Natural Convection Hypothesis was applied. The model chosen for the turbulence closure problem was the k -- εThe commercial computational fluid dynamics code ANSYS CFX 15.0 was used to obtain the numerical solution of the governing equations. Two single-phase natural circulation circuits were studied, a 2D toroidal loop and a 3D rectangular loop, both with the same boundary conditions of: prescribed heat flux at the heater and fixed wall temperature at the cooler. The validation and verification was performed with the numerical data provided by DESRAYAUD et al. [1] and the experimental data provided by MISALE et al. [2] and KUMAR et al. [3]. An excellent agreement between the Reynolds number (Re) and the modified Grashof number (Gr{sub m}), independently of Prandtl Pr number was observed. However, the convergence interval was observed to be variable with Pr, thus indicating that Pr is a stability governing parameter for natural circulation. Multiple steady states was obtained for Pr = 0,7. Finally, the effect of inclination was studied for the 3D circuit, both in-plane and out-of-plane inclinations were verified for the steady state laminar regime. As a conclusion, the Re for the out-of-plane inclination was in perfect agreement with the correlation found for the zero inclination system, while for the in-plane inclined system the results differ from that of the corresponding vertical loop. (author)

  2. Policy issues arising from the judgmental nature of risk-based decision making

    International Nuclear Information System (INIS)

    Mcquaid, J.

    1998-01-01

    The regulation of risks is pervaded by the need to exercise judgement. The scientific basis for characterising risk problems and judging the effectiveness of possible controls is often uncertain, lacking information and understanding of the processes involved. However, the risk management measures adopted will not be determined by science alone, but must reflect sociological, economic, ethical and political considerations. These in turn are in themselves judgmental, informed to a greater or lesser extent by empirical evidence and influenced by the prevailing climate of public opinion. The overall process provides a rich source of confusion for the public as to the status of the eventual policy decision, with important implications for the manner in which the process of communication is managed. The important role of judgement, as distinct from formal analysis, at every stage needs to be reflected in risk communication. The engagement of those who bear the risks, and of other interested parties in the exercise of judgement must be tailored to nature of the judgement and to the decision to be made. Appropriate procedures need to be adopted to enable that engagement. Although the issue has come into particular prominence in recent years, it is not a new phenomenon. The presentation will describe the arrangements that have been developed in the UK over the past 25 years, and will be illustrated by some specific examples of risk decision making on issues of high public concern. (author)

  3. Perceived risks of produced water management and naturally occurring radioactive material content in North Dakota.

    Science.gov (United States)

    Torres, Luisa; Yadav, Om Prakash; Khan, Eakalak

    2017-07-01

    Unconventional oil and gas development using hydraulic fracturing has caused conflict and controversy across the globe including the U.S. where some States banned the practice. Nevertheless, North Dakota (ND) has supported the practice because the State perceives the risks to be acceptable and because it has brought growth and opportunities to small communities. However, social acceptance of new technology is based on a number of factors and not contingent on economic benefits. To date, no research has been conducted to understand public risk perception of hazards associated with produced water from hydraulic fracturing in ND. This study focuses on understanding the risk perception of select ND stakeholder groups regarding produced water management and naturally occurring radioactive material. The software Qualtrics was used to create an online survey, collect data, and perform statistical analysis. The most important variables that seem to influence risk perception are the images and thoughts associated with produced water, level of knowledge about produced water handling and content, and knowing how to proceed in case of a spill of produced water. Overall, social risk perception could be in alignment with actual technical risk if availability of objective information is improved. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Three-dimensional dose-response models of competing risks and natural life span

    International Nuclear Information System (INIS)

    Raabe, O.G.

    1987-01-01

    Three-dimensional dose-rate/time/response surfaces for chronic exposure to carcinogens, toxicants, and ionizing radiation dramatically clarify the separate and interactive roles of competing risks. The three dimensions are average dose rate, exposure time, and risk. An illustration with computer graphics shows the contributions with the passage of time of the competing risks of death from radiation pneumonitis/fibrosis, lung cancer, and natural aging consequent to the inhalation of plutonium-239 dioxide by beagles. These relationships are further evaluated by mathematical stripping with three-dimensional illustrations that graphically show the resultant separate contribution of each fatal effect. Radiation pneumonitis predominates at high dose rates and lung cancer at intermediate dose rates. Low dose rates result in spontaneous deaths from natural aging, yielding a type of practical threshold for lung cancer induction. Risk assessment is benefited by the insights that become apparent with these three-dimensional models. The improved conceptualization afforded by them contributes to the planning and evaluation of epidemiological analyses and experimental studies involving chronic exposure to toxicants

  5. Integrating natural and social science perspectives on plant disease risk, management and policy formulation

    Science.gov (United States)

    Mills, Peter; Dehnen-Schmutz, Katharina; Ilbery, Brian; Jeger, Mike; Jones, Glyn; Little, Ruth; MacLeod, Alan; Parker, Steve; Pautasso, Marco; Pietravalle, Stephane; Maye, Damian

    2011-01-01

    Plant diseases threaten both food security and the botanical diversity of natural ecosystems. Substantial research effort is focused on pathogen detection and control, with detailed risk management available for many plant diseases. Risk can be assessed using analytical techniques that account for disease pressure both spatially and temporally. We suggest that such technical assessments of disease risk may not provide an adequate guide to the strategies undertaken by growers and government to manage plant disease. Instead, risk-management strategies need to account more fully for intuitive and normative responses that act to balance conflicting interests between stakeholder organizations concerned with plant diseases within the managed and natural environments. Modes of effective engagement between policy makers and stakeholders are explored in the paper, together with an assessment of such engagement in two case studies of contemporary non-indigenous diseases in one food and in one non-food sector. Finally, a model is proposed for greater integration of stakeholders in policy decisions. PMID:21624923

  6. Risk analysis on heavy metal contamination in sediments of rivers flowing into Nansi Lake.

    Science.gov (United States)

    Cao, Qingqing; Song, Ying; Zhang, Yiran; Wang, Renqing; Liu, Jian

    2017-12-01

    In order to understand the risk of heavy metals in sediments of the rivers flowing into Nansi Lake, 36 surface sediments were sampled from six rivers and seven heavy metals (Cr, Cu, Ni, Zn, As, Pb, and Cd) were determined. Potential ecological risk index (RI) of the six rivers showed significant differences: Xinxue River, Jiehe River, and Guangfu River were at medium potential risk, whereas the risk of Chengguo River was the lowest. Jiehe River, Xuesha River, and Jiangji River were meeting the medium potential risk at river mouths. Geo-accumulation index (I geo ) of the seven heavy metals revealed that the contamination of Cu and Cd was more serious than most other metals in the studied areas, whereas Cr in most sites of our study was not polluted. Moreover, correlation cluster analysis demonstrated that the contamination of Cu, Ni, and Zn in six rivers was mainly caused by local emissions, whereas that of As, Pb, and Cd might come from the external inputs in different forms. Consequently, the contamination of Cu and Cd and the potential risk in Xinxue River, Jiehe River, and Guangfu River as well as the local emissions should be given more attention to safeguard the water quality of Nansi Lake and the East Route Project of South to North Water Transfer.

  7. RAPID-N: Assessing and mapping the risk of natural-hazard impact at industrial installations

    Science.gov (United States)

    Girgin, Serkan; Krausmann, Elisabeth

    2015-04-01

    Natural hazard-triggered technological accidents (so-called Natech accidents) at hazardous installations can have major consequences due to the potential for release of hazardous materials, fires and explosions. Effective Natech risk reduction requires the identification of areas where this risk is high. However, recent studies have shown that there are hardly any methodologies and tools that would allow authorities to identify these areas. To work towards closing this gap, the European Commission's Joint Research Centre has developed the rapid Natech risk assessment and mapping framework RAPID-N. The tool, which is implemented in an online web-based environment, is unique in that it contains all functionalities required for running a full Natech risk analysis simulation (natural hazards severity estimation, equipment damage probability and severity calculation, modeling of the consequences of loss of containment scenarios) and for visualizing its results. The output of RAPID-N are risk summary reports and interactive risk maps which can be used for decision making. Currently, the tool focuses on Natech risk due to earthquakes at industrial installations. However, it will be extended to also analyse and map Natech risk due to floods in the near future. RAPID-N is available at http://rapidn.jrc.ec.europa.eu. This presentation will discuss the results of case-study calculations performed for selected flammable and toxic substances to test the capabilities of RAPID-N both for single- and multi-site earthquake Natech risk assessment. For this purpose, an Istanbul earthquake scenario provided by the Turkish government was used. The results of the exercise show that RAPID-N is a valuable decision-support tool that assesses the Natech risk and maps the consequence end-point distances. These end-point distances are currently defined by 7 kPa overpressure for Vapour Cloud Explosions, 2nd degree burns for pool fire (which is equivalent to a heat radiation of 5 kW/m2 for 40s

  8. Measurement of natural radionuclides in Malaysian bottled mineral water and consequent health risk estimation

    Energy Technology Data Exchange (ETDEWEB)

    Priharti, W.; Samat, S. B.; Yasir, M. S. [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia)

    2015-09-25

    The radionuclides of {sup 226}Ra, {sup 232}Th and {sup 40}K were measured in ten mineral water samples, of which from the radioactivity obtained, the ingestion doses for infants, children and adults were calculated and the cancer risk for the adult was estimated. Results showed that the calculated ingestion doses for the three age categories are much lower than the average worldwide ingestion exposure of 0.29 mSv/y and the estimated cancer risk is much lower than the cancer risk of 8.40 × 10{sup −3} (estimated from the total natural radiation dose of 2.40 mSv/y). The present study concludes that the bottled mineral water produced in Malaysia is safe for daily human consumption.

  9. The Atlas of Natural Hazards and Risks of Austria: first results for fluvial and pluvial floods

    Science.gov (United States)

    Mergili, Martin; Tader, Andreas; Glade, Thomas; Neuhold, Clemens; Stiefelmeyer, Heinz

    2015-04-01

    Incoherent societal adaptation to natural processes results in significant losses every year. A better knowledge of the spatial and temporal distribution of hazards and risks, and of particular hot spots in a given region or period, is essential for reducing adverse impacts. Commonly, different hazard and risk estimations are performed within individual approaches based on tailor-made concepts. This works well as long as specific cases are considered. The advantage of such a procedure is that each individual hazard and risk is addressed in the best possible manner. The drawback, however, consists in the fact that the results differ significantly in terms of quality and accuracy and therefore cannot be compared. Hence, there is a need to develop a strategy and concept which uses similar data sources of equivalent quality in order to adequately analyze the different natural hazards and risks at broader scales. The present study is aiming to develop such a platform. The project Risk:ATlas focuses on the design of an atlas visualizing the most relevant natural hazards and, in particular, possible consequences for the entire territory of Austria. Available as a web-based tool and as a printed atlas, it is seen as a key tool to improve the basis for risk reduction, risk adaptation and risk transfer. The atlas is founded on those data sets available for the entire territory of Austria at a consistent resolution and quality. A 1 m resolution DEM and the official cadastre and building register represent the core, further data sets are employed according to the requirements for each natural hazard and risk. In this contribution, the methodology and the preliminary results for fluvial and pluvial floods and their consequences to buildings for three selected test areas in different types of landscapes (rural, urban and mountainous) are presented. Flooding depths expected for annualities of 30, 100 and 300 are derived from existing data sets for fluvial floods and are computed

  10. Measurement of natural radionuclides in Malaysian bottled mineral water and consequent health risk estimation

    Science.gov (United States)

    Priharti, W.; Samat, S. B.; Yasir, M. S.

    2015-09-01

    The radionuclides of 226Ra, 232Th and 40K were measured in ten mineral water samples, of which from the radioactivity obtained, the ingestion doses for infants, children and adults were calculated and the cancer risk for the adult was estimated. Results showed that the calculated ingestion doses for the three age categories are much lower than the average worldwide ingestion exposure of 0.29 mSv/y and the estimated cancer risk is much lower than the cancer risk of 8.40 × 10-3 (estimated from the total natural radiation dose of 2.40 mSv/y). The present study concludes that the bottled mineral water produced in Malaysia is safe for daily human consumption.

  11. Communicating with the public about the risks of naturally occurring asbestos

    Directory of Open Access Journals (Sweden)

    Claire Hooker

    2017-12-01

    Full Text Available Objectives: To explore the application of evidence based risk communication to community messaging about naturally occurring asbestos (NOA. Type of program or service: Risk communication education about NOA. Methods: We apply principles and determinants of risk communication to the topic of NOA. Results: We emphasise the importance of erring on the side of transparency and trust, even when officials may be concerned about inadvertently heightening needless public concern. We offer a range of practical suggestions for how to lower public concern and outrage relating to the issue of NOA when it arises in local contexts. Lessons learnt: Public concern and outrage can be reduced by favouring early and frequent communication, awareness and use of the ‘rule of threes’ in media communication, open acknowledgement of uncertainty, prioritising response to community concern above narrow myth-busting strategies, and supporting community action.

  12. A prototype web-GIS application for risk analysis of natural hazards in Switzerland

    Science.gov (United States)

    Aye, Zar Chi; Nicolet, Pierrick; Jaboyedoff, Michel; Derron, Marc-Henri; Gerber, Christian; Lévy, Sebastien

    2016-04-01

    Following changes in the system of Swiss subsidy in January 2008, the Swiss cantons and the Federal Office for the Environment (FOEN) were forced to prioritize different natural hazard protection projects based on their cost-effectiveness, as a response to limited financial resources (Bründl et al., 2009). For this purpose, applications such as EconoMe (OFEV, 2016) and Valdorisk (DGE, 2016) were developed for risk evaluation and prioritization of mitigation projects. These tools serve as a useful decision-making instrument to the community of practitioners and responsible authorities for natural hazard risk management in Switzerland. However, there are several aspects which could be improved, in particular, the integration and visualization of spatial information interactively through a web-GIS interface for better risk planning and evaluation. Therefore, in this study, we aim to develop an interactive web-GIS application based on the risk concepts applied in Switzerland. The purpose of this tool is to provide a rapid evaluation of risk before and after protection measures, and to test the efficiency of measures by using a simplified cost-benefit analysis within the context of different protection projects. This application allows to integrate different layers which are necessary to calculate risk, in particular, hazard intensity (vector) maps for different scenarios (such as 30, 100 and 300 years of return periods based on Swiss guidelines), exposed objects (such as buildings) and vulnerability information of these objects. Based on provided information and additional parameters, risk is calculated automatically and results are visualized within the web-GIS interface of the application. The users can modify these input information and parameters to create different risk scenarios. Based on the resultant risk scenarios, the users can propose and visualize (preliminary) risk reduction measures before realizing the actual design and dimensions of such protective

  13. Shared Freight Transportation and Energy Commodities Phase One: Coal, Crude Petroleum, & Natural Gas Flows

    Energy Technology Data Exchange (ETDEWEB)

    Chin, Shih-Miao [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hwang, Ho-Ling [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Davidson, Diane [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-07-01

    The Freight Analysis Framework (FAF) integrates data from a variety of sources to create a comprehensive picture of nationwide freight movements among states and major metropolitan areas for all modes of transportation. It provides a national picture of current freight flows to, from, and within the United States, assigns selected flows to the transportation network, and projects freight flow patterns into the future. The latest release of FAF is known as FAF4 with a base year of 2012. The FAF4 origin-destination-commodity-mode (ODCM) matrix is provided at national, state, major metropolitan areas, and major gateways with significant freight activities (e.g., El Paso, Texas). The U.S. Department of Energy (DOE) is interested in using FAF4 database for its strategic planning and policy analysis, particularly in association with the transportation of energy commodities. However, the geographic specification that DOE requires is a county-level ODCM matrix. Unfortunately, the geographic regions in the FAF4 database were not available at the DOE desired detail. Due to this limitation, DOE tasked Oak Ridge National Laboratory (ORNL) to assist in generating estimates of county-level flows for selected energy commodities by mode of transportation.

  14. Air flow distribution in and around a single-sided naturally ventilated room

    OpenAIRE

    Marjanovic-Halburd, Ljiljana; Eftekhari, M. M.; Pinnock, D. J.

    2003-01-01

    This paper reports on the initial findings of the EPSRC project on rule-based control in naturally ventilated buildings which led to Marjanovic's PhD thesis, supervised by Eftekhari. Marjanovic is the second author.

  15. Earth sciences, GIS and geomatics for natural hazards assessment and risks mitigation: a civil protection perspective

    Science.gov (United States)

    Perotti, Luigi; Conte, Riccardo; Lanfranco, Massimo; Perrone, Gianluigi; Giardino, Marco; Ratto, Sara

    2010-05-01

    Geo-information and remote sensing are proper tools to enhance functional strategies for increasing awareness on natural hazards and risks and for supporting research and operational activities devoted to disaster reduction. An improved Earth Sciences knowledge coupled with Geomatics advanced technologies has been developed by the joint research group and applied by the ITHACA (Information Technology for Humanitarian Assistance, Cooperation and Action) centre, within its partnership with the UN World Food Programme (WFP) with the goal of reducing human, social, economic and environmental losses due to natural hazards and related disasters. By cooperating with local and regional authorities (Municipalities, Centro Funzionale of the Aosta Valley, Civil Protection Agency of Regione Piemonte), data on natural hazards and risks have been collected, compared to national and global data, then interpreted for helping communities and civil protection agencies of sensitive mountain regions to make strategic choices and decisions to better mitigation and adaption measures. To enhance the application of GIS and Remote-sensing technologies for geothematic mapping of geological and geomorphological risks of mountain territories of Europe and Developing Countries, research activities led to the collection and evaluation of data from scientific literature and historical technical archives, for the definition of predisposing/triggering factors and evolutionary processes of natural instability phenomena (landslides, floods, storms, …) and for the design and implementation of early-warning and early-impact systems. Geodatabases, Remote Sensing and Mobile-GIS applications were developed to perform analysis of : 1) large climate-related disaster (Hurricane Mitch, Central America), by the application of remote sensing techniques, either for early warning or mitigation measures at the national and international scale; 2) distribution of slope instabilities at the regional scale (Aosta

  16. The effects of preferential flow and soil texture on risk assessments of a NORM waste disposal site

    International Nuclear Information System (INIS)

    Pontedeiro, E.M.; Genuchten, M.Th. van; Cotta, R.M.; Simunek, J.

    2010-01-01

    This paper investigates the environmental fate of radionuclide decay chains (specially the 238 U and 232 Th series) being released from a conventional mining installation processing ore containing natural occurring radioactive materials (NORMs). Contaminated waste at the site is being disposed off in an industrial landfill on top of a base of earth material to ensure integrity of the deposit over relatively long geologic times (thousands of years). Brazilian regulations, like those of many other countries, require a performance assessment of the disposal facility using a leaching and off-site transport scenario. We used for this purpose the HYDRUS-1D software package to predict long-term radionuclide transport vertically through both the landfill and the underlying unsaturated zone, and then laterally in groundwater. We assumed that a downgradient well intercepting groundwater was the only source of water for a resident farmer, and that all contaminated water from the well was somehow used in the biosphere. The risk assessment was carried out for both a best-case scenario assuming equilibrium transport in a fine-textured (clay) subsurface, and a worst-case scenario involving preferential flow through a more coarse-textured subsurface. Results show that preferential flow and soil texture both can have a major effect on the results, depending upon the specific radionuclide involved.

  17. Systems-level analysis of risk genes reveals the modular nature of schizophrenia.

    Science.gov (United States)

    Liu, Jiewei; Li, Ming; Luo, Xiong-Jian; Su, Bing

    2018-05-19

    Schizophrenia (SCZ) is a complex mental disorder with high heritability. Genetic studies (especially recent genome-wide association studies) have identified many risk genes for schizophrenia. However, the physical interactions among the proteins encoded by schizophrenia risk genes remain elusive and it is not known whether the identified risk genes converge on common molecular networks or pathways. Here we systematically investigated the network characteristics of schizophrenia risk genes using the high-confidence protein-protein interactions (PPI) from the human interactome. We found that schizophrenia risk genes encode a densely interconnected PPI network (P = 4.15 × 10 -31 ). Compared with the background genes, the schizophrenia risk genes in the interactome have significantly higher degree (P = 5.39 × 10 -11 ), closeness centrality (P = 7.56 × 10 -11 ), betweeness centrality (P = 1.29 × 10 -11 ), clustering coefficient (P = 2.22 × 10 -2 ), and shorter average shortest path length (P = 7.56 × 10 -11 ). Based on the densely interconnected PPI network, we identified 48 hub genes and 4 modules formed by highly interconnected schizophrenia genes. We showed that the proteins encoded by schizophrenia hub genes have significantly more direct physical interactions. Gene ontology (GO) analysis revealed that cell adhesion, cell cycle, immune system response, and GABR-receptor complex categories were enriched in the modules formed by highly interconnected schizophrenia risk genes. Our study reveals that schizophrenia risk genes encode a densely interconnected molecular network and demonstrates the modular nature of schizophrenia. Copyright © 2018 Elsevier B.V. All rights reserved.

  18. Environmental assessment for the natural fluctuation of water level in Par Pond and reduced water flow in Steel Creek below L-Lake at the Savannah River Site

    International Nuclear Information System (INIS)

    1995-08-01

    The Savannah River Operations Office Strategic Plan directs Savannah River Site (SRS) to find ways to reduce operating costs, and to determine what site infrastructure must be maintained and what infrastructure is surplus. Because of the mission change, L-Lake, Par Pond, and the river water system are no longer needed to support current missions and therefore provide an opportunity for operating cost reduction. If SRS determines that L-Lake, Par Pond, and the river water system are no longer needed to support future missions and are considered surplus, appropriate NEPA documentation will be prepared. The purpose of the proposed action in this Environmental Assessment is to begin an examination of the need for the Site's river water system by (1) developing data needed to evaluate the potential environmental impacts of further reducing or eliminating the flow demands from the Site's river water system and; (2) evaluating the potential of reducing operating costs by allowing the water level in Par Pond to fluctuate naturally through reduced pumping. This action also includes reducing the current flow rates from L-Lake to Steel Creek to natural stream flows while maintaining full pool. The recently approved Par Pond CERCLA Interim Action Proposed Plan (IAPP) committed to evaluate in a NEPA document the environmental consequences of this proposed action. This document evaluated the remediation of human health and ecological risks associated with the three year drawdown of Par Pond. Should any of the parameters sampled in the reservoir and streams (e.g., water quality, biota, etc.) exceed established threshold levels during the implementation of the proposed action, water would again be pumped into the reservoir to minimize any impacts by bringing the water level back to an appropriate level about 58.2 m (195 ft)

  19. Environmental assessment for the natural fluctuation of water level in Par Pond and reduced water flow in Steel Creek below L-Lake at the Savannah River Site

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-08-01

    The Savannah River Operations Office Strategic Plan directs Savannah River Site (SRS) to find ways to reduce operating costs, and to determine what site infrastructure must be maintained and what infrastructure is surplus. Because of the mission change, L-Lake, Par Pond, and the river water system are no longer needed to support current missions and therefore provide an opportunity for operating cost reduction. If SRS determines that L-Lake, Par Pond, and the river water system are no longer needed to support future missions and are considered surplus, appropriate NEPA documentation will be prepared. The purpose of the proposed action in this Environmental Assessment is to begin an examination of the need for the Site`s river water system by (1) developing data needed to evaluate the potential environmental impacts of further reducing or eliminating the flow demands from the Site`s river water system and; (2) evaluating the potential of reducing operating costs by allowing the water level in Par Pond to fluctuate naturally through reduced pumping. This action also includes reducing the current flow rates from L-Lake to Steel Creek to natural stream flows while maintaining full pool. The recently approved Par Pond CERCLA Interim Action Proposed Plan (IAPP) committed to evaluate in a NEPA document the environmental consequences of this proposed action. This document evaluated the remediation of human health and ecological risks associated with the three year drawdown of Par Pond. Should any of the parameters sampled in the reservoir and streams (e.g., water quality, biota, etc.) exceed established threshold levels during the implementation of the proposed action, water would again be pumped into the reservoir to minimize any impacts by bringing the water level back to an appropriate level about 58.2 m (195 ft).

  20. Development of TPNCIRC code for Evaluation of Two-Phase Natural Circulation Flow Performance under External Reactor Vessel Cooling Conditions

    International Nuclear Information System (INIS)

    Choi, A-Reum; Song, Hyuk-Jin; Park, Jong-Woon

    2015-01-01

    During a severe accident, corium is relocated to the lower head of the nuclear reactor pressure vessel (RPV). Design concept of retaining the corium inside a nuclear reactor pressure vessel (RPV) through external cooling under hypothetical core melting accidents is called external reactor vessel cooling (ERVC). In this respect, validated two-phase natural circulation flow (TPNC) model is necessary to determine the adequacy of the ERVC design and operating conditions such as inlet area, form losses, gap distance, riser length and coolant conditions. The most important model generally characterizing the TPNC are void fraction and two-phase friction factors. Typical experimental and analytical studies to be referred to on two-phase circulation flow characteristics are those by Reyes, Gartia et al. based on Vijayan et al., Nayak et al. and Dubey et al. In the present paper, two-phase natural circulation (TPNC) flow characteristics under external reactor vessel cooling (ERVC) conditions are studied using two existing TPNC flow models of Reyes and Gartia et al. incorporating more improved void fraction and two-phase friction models. These models and correlations are integrated into a computer program, TPNCIRC, which can handle candidate ERVC design parameters, such as inlet, riser and downcomer flow lengths and areas, gap size between reactor vessel and surrounding insulations, minor loss factors and operating parameters of decay power, pressure and subcooling. Accuracy of the TPNCIRC program is investigated with respect to the flow rate and void fractions for existing measured data from a general experiment and ULPU specifically designed for the AP1000 in-vessel retention. Also, the effect of some important design parameters are examined for the experimental and plant conditions. Using the flow models and correlations are integrated into a computer program, TPNCIRC, a number of correlations have been examined. This seems coming from the differences of void fractions

  1. Experimental and numerical study on single-phase flow characteristics of natural circulation system with heated narrow rectangular channel under rolling motion condition

    International Nuclear Information System (INIS)

    Yu, Shengzhi; Wang, Jianjun; Yan, Ming; Yan, Changqi; Cao, Xiaxin

    2017-01-01

    Highlights: • The phasic difference between flow rate and frictional pressure drop is negligible. • Effect mechanism of rolling motion on flow behaviors of NC is interpreted. • The startup model is proposed and verified. • Steady-state correlations are feasible to predict transient resistance. • The in-house code can simulate instantaneous flow behaviors of NC correctly. - Abstract: Effects of rolling motion on flow characteristics in a natural circulation system were investigated experimentally and numerically. The numerical results from validated code were mainly used to provide detailed information for the discussion and analysis of experimental results. The results indicate that under rolling motion condition, the phasic difference between flow rate and frictional pressure drop of narrow rectangular channel is negligible. Angular acceleration is the eigenvalue for the effects of rolling motion on flow rate under single-phase natural circulation condition. When angular acceleration is approximately equal, even though either the angle or the period of rolling motion is different, peak, trough and time-averaged values of flow rate are approximately equal. Under rolling motion and single-phase natural circulation conditions, the phenomenon that dimensionless time-averaged mass flow rate is smaller than that under steady state condition is controlled by the nonlinear relationship between mass flow rate and the resistance of loop. The factor also causes the result that the absolute difference of dimensionless flow rate between peak and steady state is smaller than that between trough and steady state. The startup model which is proposed in present paper can be used to predict the flow characteristics of single-phase natural circulation system at startup stage of rolling motion favorably. The self-developed code can simulate instantaneous flow characteristics of single-phase natural circulation system under rolling motion and steady state conditions

  2. Social and economic factors of the natural risk growth: estimation of the Russian regions

    Science.gov (United States)

    Petrova, E.

    2003-04-01

    Òhe vulnerability of the population and economy territorial complexes (PETC) to the influence of unfavorable and dangerous natural processes and events is determined not only by the physical parameters of natural hazards in the given region, but also by economic and social peculiarities of the PETC by itself. It depends on economy type, on PETC’s age, structure and dimensions as well as on degree of its participation in the territorial division of labor. PETC would be more vulnerable to the natural hazards impact if its population density, concentration of the industrial capacities (especially of the objects that additionally create the potential danger of the man-caused catastrophes such as nuclear-power stations, chemical enterprises, oil refineries and so on), concentration of transport and other means of communication, the technological complexity, the originality of the objects included in it as well as the originality of PETC by itself would be higher. The PETC with the unfavorable socio-political and ecological situation and underdeveloped management structures are more vulnerable. The estimation of regions by PETC vulnerability degree to the natural hazards were marked out on a base of data about the actual distribution of the natural hazards in Russia and analysis of the economic indices of the Russian Federation subjects. Among the economic indexes the per capita production of Gross Regional Product (GRP), population density, road density, the degree of appraisal depreciation of the fixed assets, the land cultivation degree of the territory, forest share and so on were taken into account. As the analysis showed, the economic and social factors of the natural risk growth are active in the majority of the regions of the Russian Federation. Such a situation demands the increased attention of state and local authorities to this problem for lowering the economic and social constituents of the growth of natural hazards.

  3. DECSERVIS-2: A tool for natural decay series mass flow simulation

    International Nuclear Information System (INIS)

    Azzam, Saad; Suksi, Juhani; Ammann, Michael

    2009-01-01

    After the publication of 'DECSERVIS: a tool for radioactive decay series visualisation' we have further developed our DECSERVIS software. With the new tool DECSERVIS-2 one can simulate radioactive decay chains in open systems, i.e. when the concentrations of nuclides change also due to mass flows. Decay chains can be simulated under continuous and successive nuclide mass flow events into and out from the system and in freely determined time intervals. Simulation output for the entire decay chain (nuclide activity, mass, number of nuclides, nuclide ratios) can be presented as a function of time with various graphical presentations such as solid curve and column diagrams or animation. In this paper we introduce DECSERVIS-2 and demonstrate its use with simulation examples. DECSERVIS-2 is easy to use and has been designed with an eye on the demands of teaching.

  4. Experimental study on two-phase flow natural circulation in a core catcher cooling channel for EU-APR1400 using air-water system

    Energy Technology Data Exchange (ETDEWEB)

    Song, Ki Won [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Korea Atomic Energy Research Institute, Daejeon 34057 (Korea, Republic of); Nguyen, Thanh Hung [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47906 (United States); Ha, Kwang Soon; Kim, Hwan Yeol; Song, Jinho [Korea Atomic Energy Research Institute, Daejeon 34057 (Korea, Republic of); Park, Hyun Sun [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Revankar, Shripad T., E-mail: shripad@postech.ac.kr [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); School of Nuclear Engineering, Purdue University, West Lafayette, IN 47906 (United States); Kim, Moo Hwan [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Korea Institute of Nuclear Safety, Daejeon 305-338 (Korea, Republic of)

    2017-05-15

    Highlights: • Two-phase flow regimes and transition behavior were observed in the coolant channel. • Test were conducted for natural circulation with air-water. • Data were obtained on flow regime, void fraction, flow rates and re-wetting time. • The data were related to a cooling capability of core catcher system. - Abstract: Ex-vessel core catcher cooling system driven by natural circulation is designed using a full scaled air-water system. A transparent half symmetric section of a core catcher coolant channel of a pressurized water reactor was designed with instrumentations for local void fraction measurement and flow visualization. Two designs of air-water top separator water tanks are studied including one with modified ‘super-step’ design which prevents gas entrainment into down-comer. In the experiment air flow rates are set corresponding to steam generation rate for given corium decay power. Measurements of natural circulation flow rate, spatial local void fraction distribution and re-wetting time near the top wall are carried out for various air flow rates which simulate boiling-induced vapor generation. Since heat transfer and critical heat flux are strongly dependent on the water mass flow rate and development of two-phase flow on the heated wall, knowledge of two-phase flow characteristics in the coolant channel is essential. Results on flow visualization showing two phase flow structure specifically near the high void accumulation regions, local void profiles, rewetting time, and natural circulation flow rate are presented for various air flow rates that simulate corium power levels. The data are useful in assessing the cooling capability of and safety of the core catcher system.

  5. Water velocity and the nature of critical flow in large rapids on the Colorado River, Utah

    Science.gov (United States)

    Magirl, Christopher S.; Gartner, Jeffrey W.; Smart, Graeme M.; Webb, Robert H.

    2009-01-01

    Rapids are an integral part of bedrock‐controlled rivers, influencing aquatic ecology, geomorphology, and recreational value. Flow measurements in rapids and high‐gradient rivers are uncommon because of technical difficulties associated with positioning and operating sufficiently robust instruments. In the current study, detailed velocity, water surface, and bathymetric data were collected within rapids on the Colorado River in eastern Utah. With the water surface survey, it was found that shoreline‐based water surface surveys may misrepresent the water surface slope along the centerline of a rapid. Flow velocities were measured with an ADCP and an electronic pitot‐static tube. Integrating multiple measurements, the ADCP returned velocity data from the entire water column, even in sections of high water velocity. The maximum mean velocity measured with the ADCP was 3.7 m/s. The pitot‐static tube, while capable of only point measurements, quantified velocity 0.39 m below the surface. The maximum mean velocity measured with the pitot tube was 5.2 m/s, with instantaneous velocities up to 6.5 m/s. Analysis of the data showed that flow was subcritical throughout all measured rapids with a maximum measured Froude number of 0.7 in the largest measured rapids. Froude numbers were highest at the entrance of a given rapid, then decreased below the first breaking waves. In the absence of detailed bathymetric and velocity data, the Froude number in the fastest‐flowing section of a rapid was estimated from near‐surface velocity and depth soundings alone.

  6. Water pollution risk associated with natural gas extraction from the Marcellus Shale.

    Science.gov (United States)

    Rozell, Daniel J; Reaven, Sheldon J

    2012-08-01

    In recent years, shale gas formations have become economically viable through the use of horizontal drilling and hydraulic fracturing. These techniques carry potential environmental risk due to their high water use and substantial risk for water pollution. Using probability bounds analysis, we assessed the likelihood of water contamination from natural gas extraction in the Marcellus Shale. Probability bounds analysis is well suited when data are sparse and parameters highly uncertain. The study model identified five pathways of water contamination: transportation spills, well casing leaks, leaks through fractured rock, drilling site discharge, and wastewater disposal. Probability boxes were generated for each pathway. The potential contamination risk and epistemic uncertainty associated with hydraulic fracturing wastewater disposal was several orders of magnitude larger than the other pathways. Even in a best-case scenario, it was very likely that an individual well would release at least 200 m³ of contaminated fluids. Because the total number of wells in the Marcellus Shale region could range into the tens of thousands, this substantial potential risk suggested that additional steps be taken to reduce the potential for contaminated fluid leaks. To reduce the considerable epistemic uncertainty, more data should be collected on the ability of industrial and municipal wastewater treatment facilities to remove contaminants from used hydraulic fracturing fluid. © 2012 Society for Risk Analysis.

  7. Natural convection enhancement by a discrete vibrating plate and a cross-flow opening: a numerical investigation

    Science.gov (United States)

    Florio, L. A.; Harnoy, A.

    2011-06-01

    In this study, a unique combination of a vibrating plate and a cross-flow passage is proposed as a means of enhancing natural convection cooling. The enhancement potential was estimated based on numerical studies involving a representative model which includes a short, transversely oscillating plate, placed over a transverse cross-flow opening in a uniformly heated vertical channel wall dividing two adjacent vertical channels. The resulting velocity and temperature fields are analyzed, with the focus on the local thermal effects near the opening. The simulation indicates up to a 50% enhancement in the local heat transfer coefficient for vibrating plate amplitudes of at least 30% of the mean clearance space and frequencies of over 82 rad/s.

  8. Gas hydrates and clathrates. Flow assurance, environmental and economic perspectives and the Nigerian liquefied natural gas project

    International Nuclear Information System (INIS)

    Gbaruko, B.C.; Igwe, J.C.; Nwokeoma, R.C.; Gbaruko, P.N.

    2007-01-01

    Gas hydrates are nonstoichiometric crystalline compounds that belong to the inclusion group known as clathrates. They occur when water molecules attach themselves together through hydrogen bonding and form cavities which can be occupied by a single gas or volatile liquid molecule. Gas hydrates, asphaltenes and waxes are three major threats to flow assurance that must be well assessed by design team uptime. Gas hydrates are also looked upon as a future energy source and as a potential climate hazard. The purpose of this review is to show the chemistry and mechanism of gas hydrate formation, the problems they pose, especially to flow assurance, their system implications, their environmental and economic perspectives with respect to their prospects as storage and transport alternative to the liquefied natural gas technology. (author)

  9. Quasi One-Dimensional Model of Natural Draft Wet-Cooling Tower Flow, Heat and Mass Transfer

    Directory of Open Access Journals (Sweden)

    Hyhlík Tomáš

    2015-01-01

    Full Text Available The article deals with the development of CFD (Computational Fluid Dynamics model of natural draft wet-cooling tower flow, heat and mass transfer. The moist air flow is described by the system of conservation laws along with additional equations. Moist air is assumed to be homogeneous mixture of dry air and water vapour. Liquid phase in the fill zone is described by the system of ordinary differential equations. Boundary value problem for the system of conservation laws is discretized in space using Kurganov-Tadmor central scheme and in time using strong stability preserving Runge-Kutta scheme. Initial value problems in the fill zone is solved by using standard fourth order Runge-Kutta scheme. The interaction between liquid water and moist air is done by source terms in governing equations.

  10. Thermomyces lanuginosus lipase-catalyzed synthesis of natural flavor esters in a continuous flow microreactor.

    Science.gov (United States)

    Gumel, Ahmad Mohammed; Annuar, M S M

    2016-06-01

    Enzymatic catalysis is considered to be among the most environmental friendly processes for the synthesis of fine chemicals. In this study, lipase from Thermomyces lanuginosus (Lecitase Ultra™) was used to catalyze the synthesis of flavor esters, i.e., methyl butanoate and methyl benzoate by esterification of the acids with methanol in a microfluidic system. Maximum reaction rates of 195 and 115 mM min -1 corresponding to catalytic efficiencies (k cat /K M ) of 0.30 and 0.24 min -1  mM -1 as well as yield conversion of 54 and 41 % were observed in methyl butanoate and methyl benzoate synthesis, respectively. Catalytic turnover (k cat ) was higher for methyl butanoate synthesis. Rate of synthesis and yield decreased with increasing flow rates. For both esters, increase in microfluidic flow rate resulted in increased advective transport over molecular diffusion and reaction rate, thus lower conversion. In microfluidic synthesis using T. lanuginosus lipase, the following reaction conditions were 40 °C, flow rate 0.1 mL min -1 , and 123 U g -1 enzyme loading found to be the optimum operating limits. The work demonstrated the application of enzyme(s) in a microreactor system for the synthesis of industrially important esters.

  11. Implications of deregulation in natural gas industry on utility risks and returns

    Science.gov (United States)

    Addepalli, Rajendra P.

    This thesis examines the changes in risk and required return on capital for local distribution utility companies in the increasingly competitive natural gas industry. The deregulation in the industry impacts the LDCs in several ways. First, with the introduction of competition consumers have been given choices among suppliers besides the traditional monopoly, the local utility, for purchasing their natural gas supply needs. Second, with the introduction of competition, some of the interstate pipelines were stuck with 'Take Or Pay' contracts and other costs that resulted in 'stranded costs', which have been passed on to customers of the pipeline including the LDCs. Third, the new obligation for the LDCs to purchase gas from the market, as opposed to buying it from pipelines and passing on the costs to its customers, brought opportunities and risks as well. Finally, with the introduction of competition, in some states LDCs have been allowed to enter into unregulated ventures to increase their profits. In the thesis we first develop a multifactor model (MFM) to explain historical common stock returns of individual utilities and of utility portfolios. We use 'rolling regression' analysis to analyze how different variables explain the variation in stock returns over time. Second, we conduct event studies to analyze the events in the deregulation process that had significant impacts on the LDC returns. Finally we assess the changes in risk and required return on capital for the LDCs over a 15 year time frame, covering the deregulation period. We employ four aspects in the examination of risk and return profile of the utilities: measuring (a) changes in required return on common equity and Weighted Average Cost of Capital, (b) changes in risk premium (WACC less an interest rate proxy), (c) changes in utility bond ratings, and (d) changes in dividend payments, new debt and equity issuances. We perform regression analysis to explain the changes in the required WACC using

  12. A framework for profiling the characteristics of risk governance in diverse European natural hazard contexts

    Science.gov (United States)

    Walker, G.; Tweed, F.

    2012-04-01

    Risks are always managed within a broader context of relationships between governments, citizens, civil society and private business; these relationships shift and evolve over time with changing political currents and economic conditions. In Europe over the past 20 years or so, there has been a move away from government towards a broader practice of 'governance', a shift that is as relevant to the handling of natural hazards as it is to other societal concerns such as housing, economic regeneration or transport. Key characteristics of this change include the emergence of multi-level governance processes and the 'hollowing out' of the nation state; moves away from the exercise of centralised authority towards the involvement and collaboration of a multiplicity of actors specific to each policy area; the creation of new forms of authority and control; and changing distributions of responsibilities between the state and other actors. However, the extent to which these shifts have taken place across the full diversity of European national contexts and can be observed specifically in relation to the governance of natural hazards is open to analysis and debate. In this paper, we propose a framework for profiling risk governance approaches in relation to key characteristics identified in both the general governance literature and in more specific work on risk governance. This framework can be flexibly applied in relation to a specific hazard and national/regional context and enables qualitative profiling across a spectrum of nine governance characteristics. Past trends and likely future changes can also be represented. We discuss the formulation of this framework as well as illustrating how it can be used in a process of discussion and debate about risk governance issues. We provide examples of the ways in which the profiling approach can enable comparison between risk governance contexts and approaches, and how it can be used in a variety of potential settings.

  13. Coupled deformation and fluid-flow behavior of a natural fracture in the CSM in situ test block

    International Nuclear Information System (INIS)

    Gertsch, L.S.

    1989-01-01

    The primary goal was the evaluation of an in situ block test as a data source for modeling the coupled flow and mechanical behavior of natural rock fractures. The experiments were conducted with the Colorado School of Mines in situ test block, an 8 m 3 (280 ft 3 ) gneiss cube which has been the focus of several previous studies. A single continuous fracture within the block was surrounded with instruments to measure stresses, deformations, and gas conductivity. The setup was subjected to combinations of normal and shear stress by pressurizing the block sides differentially with hydraulic flatjacks. The induced fracture deformation, as measured by two separate sensor systems, did not correlate closely with the fracture conductivity changes or with each other. The test fracture is more complicated physically than two parallel rock faces. Many joints which were not detected by mapping intersect the test fracture and strongly influence its behavior. These invisible joints create sub-blocks which react complexly to changes in applied load. The flow tests reflected the aggregate sub-block dislocations in the flow path. The deformation readings, however, were the movements of discrete points sparsely located among the sub-blocks. High-confidence extrapolation of block test results to large volumes, such as required for nuclear waste repository design, is not feasible currently. Present instrumentation does not sample rock mass behavior in situ at the proper scales. More basically, however, a fundamental gap exists between the nature of jointed rock and our conception of it. Therefore, the near-field rock mass must be discounted as an easily controllable barrier to groundwater flow, until radically different approaches to rock mass testing and modeling are developed

  14. U.S. Natural Gas Storage Risk-Based Ranking Methodology and Results

    Energy Technology Data Exchange (ETDEWEB)

    Folga, Steve [Argonne National Lab. (ANL), Argonne, IL (United States); Portante, Edgar [Argonne National Lab. (ANL), Argonne, IL (United States); Shamsuddin, Shabbir [Argonne National Lab. (ANL), Argonne, IL (United States); Tompkins, Angeli [Argonne National Lab. (ANL), Argonne, IL (United States); Talaber, Leah [Argonne National Lab. (ANL), Argonne, IL (United States); McLamore, Mike [Argonne National Lab. (ANL), Argonne, IL (United States); Kavicky, Jim [Argonne National Lab. (ANL), Argonne, IL (United States); Conzelmann, Guenter [Argonne National Lab. (ANL), Argonne, IL (United States); Levin, Todd [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-10-01

    This report summarizes the methodology and models developed to assess the risk to energy delivery from the potential loss of underground gas storage (UGS) facilities located within the United States. The U.S. has a total of 418 existing storage fields, of which 390 are currently active. The models estimate the impacts of a disruption of each of the active UGS facilities on their owners/operators, including (1) local distribution companies (LDCs), (2) directly connected transporting pipelines and thus on the customers in downstream States, and (3) third-party entities and thus on contracted customers expecting the gas shipment. Impacts are measured across all natural gas customer classes. For the electric sector, impacts are quantified in terms of natural gas-fired electric generation capacity potentially affected from the loss of a UGS facility. For the purpose of calculating the overall supply risk, the overall consequence of the disruption of an UGS facility across all customer classes is expressed in terms of the number of expected equivalent residential customer outages per year, which combines the unit business interruption cost per customer class and the estimated number of affected natural gas customers with estimated probabilities of UGS disruptions. All models and analyses are based on publicly available data. The report presents a set of findings and recommendations in terms of data, further analyses, regulatory requirements and standards, and needs to improve gas/electric industry coordination for electric reliability.

  15. Some aspects of risks and natural hazards in the rainfall variability space of Rwanda.

    Science.gov (United States)

    Nduwayezu, Emmanuel; Derron, Marc-Henri; Jaboyedoff, Michel; Penna, Ivanna; Kanevski, Mikhaïl

    2014-05-01

    Rwanda is facing challenges related to its dispersed population and their density. Risk assessment for natural disasters is becoming important in order to reduce the extent and damages of natural disasters. Rwanda is a country with a diversity of landscapes. Its mountains and marshes have been considered as a water reserve, a forest and grazing reserve by the population (currently around 11 million). Due to geologic and climate conditions, the country is subject of different natural processes, in particular hydrological events (flooding and also landslides), but also earthquakes and volcanism, which the communities have to live with in the western part. In the last years, population expansion for land by clearing of forests and draining marshes, seems to be acting as an aggravating factor. Therefore, a risk assessment for rainfall related hazards requires a deep understanding of the precipitation patterns. Based on satellite image interpretation, historical reports of events, and the analysis of rainfalls variability mapping and probabilistic analyses of events, the aim of this case study is to produce an overview and a preliminary assessment of the hazards scenario in Rwanda.

  16. Quantifying the value of investing in distributed natural gas and renewable electricity systems as complements: Applications of discounted cash flow and real options analysis with stochastic inputs

    International Nuclear Information System (INIS)

    Pless, Jacquelyn; Arent, Douglas J.; Logan, Jeffrey; Cochran, Jaquelin; Zinaman, Owen

    2016-01-01

    One energy policy objective in the United States is to promote the adoption of technologies that provide consumers with stable, secure, and clean energy. Recent work provides anecdotal evidence of natural gas (NG) and renewable electricity (RE) synergies in the power sector, however few studies quantify the value of investing in NG and RE systems together as complements. This paper uses discounted cash flow analysis and real options analysis to value hybrid NG-RE systems in distributed applications, focusing on residential and commercial projects assumed to be located in the states of New York and Texas. Technology performance and operational risk profiles are modeled at the hourly level to capture variable RE output and NG prices are modeled stochastically as geometric Ornstein-Uhlenbeck (OU) stochastic processes to capture NG price uncertainty. The findings consistently suggest that NG-RE hybrid distributed systems are more favorable investments in the applications studied relative to their single-technology alternatives when incentives for renewables are available. In some cases, NG-only systems are the favorable investments. Understanding the value of investing in NG-RE hybrid systems provides insights into one avenue towards reducing greenhouse gas emissions, given the important role of NG and RE in the power sector. - Highlights: • Natural gas and renewable electricity can be viewed as complements. • We model hybrid natural gas and renewable electricity systems at the hourly level. • We incorporate variable renewable power output and uncertain natural gas prices. • Hybrid natural gas and renewable electricity systems can be valuable investments.

  17. Communicating with children and adolescents about the risk of natural disasters.

    Science.gov (United States)

    Midtbust, Liv Gunvor Hove; Dyregrov, Atle; Djup, Heidi Wittrup

    2018-01-01

    A vast number of people annually are affected by natural disasters. Children are at risk of losing their lives and suffer mentally or physically after such events. The fostering of resilience and preparedness ahead of disasters can reduce untoward effects of disastrous events. Risk communication and disaster education are considered important aspects of disaster preparedness, but little is known about whether such strategies influence children's behaviour when natural disasters occur or how they cope in the aftermath. This paper presents and discusses various strategies that promote preparedness activities to save lives. To a minor extent, it also includes strategies that can promote coping in the aftermath. Strategies such as informational campaigns, educational activities, psychoeducation and parental guidance are addressed. The literature to date indicates that schools are a suitable arena for risk communication, and that adolescents themselves should be involved and engaged in the communication strategies. However, the relationship between knowledge of preparedness strategies and the resulting preparedness actions is largely unknown. It is unknown whether changes in awareness and attitudes have resulted in actual behaviour change. It is advocated that preparedness activities and parental involvement should supplement information-based strategies.

  18. Communicating Science to Officials and People at Risk During a Slow-Motion Lava Flow Crisis

    Science.gov (United States)

    Neal, C. A.; Babb, J.; Brantley, S.; Kauahikaua, J. P.

    2015-12-01

    From June 2014 through March 2015, Kīlauea Volcano's Púu ´Ō´ō vent on the East Rift Zone produced a tube-fed pāhoehoe lava flow -the "June 27th flow" - that extended 20 km downslope. Within 2 months of onset, flow trajectory towards populated areas in the Puna District caused much concern. The USGS Hawaiian Volcano Observatory (HVO) issued a news release of increased hazard on August 22 and began participating in public meetings organized by Hawai`i County Mayor and Civil Defense two days later. On September 4, HVO upgraded the volcano alert level to WARNING based on an increased potential for lava to reach homes and infrastructure. Ultimately, direct impacts were modest: lava destroyed one unoccupied home and one utility pole, crossed a rural roadway, and partially inundated a waste transfer station, a cemetery, and agricultural land. Anticipation that lava could reach Pāhoa Village and cross the only major access highway, however, caused significant disruption. HVO scientists employed numerous methods to communicate science and hazard information to officials and the at-risk public: daily (or more frequent) written updates of the lava activity, flow front locations and advance rates; frequent updates of web-hosted maps and images; use of the 'lines of steepest descent' method to indicate likely lava flow paths; consistent participation in well-attended community meetings; bi-weekly briefings to County, State, and Federal officials; correspondence with the public via email and recorded phone messages; participation in press conferences and congressional briefings; and weekly newspaper articles (Volcano Watch). Communication lessons both learned and reinforced include: (1) direct, frequent interaction between scientists and officials and at-risk public builds critical trust and understanding; (2) images, maps, and presentations must be tailored to audience needs; (3) many people are unfamiliar with maps (oblique aerial photographs were more effective); (4

  19. Self-organizing maps applied to two-phase flow on natural circulation loop study; Aplicacao de mapas auto-organizaveis na classificacao de padroes de escoamento bifasico

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Leonardo Ferreira

    2016-11-01

    Two-phase flow of liquid and gas is found in many closed circuits using natural circulation for cooling purposes. Natural circulation phenomenon is important on recent nuclear power plant projects for decay heat removal. The Natural Circulation Facility (Circuito de Circulacao Natural CCN) installed at Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN, is an experimental circuit designed to provide thermal hydraulic data related to single and two-phase flow under natural circulation conditions. This periodic flow oscillation behavior can be observed thoroughly in this facility due its glass-made tubes transparency. The heat transfer estimation has been improved based on models that require precise prediction of pattern transitions of flow. This work presents experiments realized at CCN to visualize natural circulation cycles in order to classify two-phase flow patterns associated with phase transients and static instabilities of flow. Images are compared and clustered using Kohonen Self-organizing Maps (SOM's) applied on different digital image features. The Full Frame Discret Cosine Transform (FFDCT) coefficients were used as input for the classification task, enabling good results. FFDCT prototypes obtained can be associated to each flow pattern, enabling a better comprehension of each observed instability. A systematic test methodology was used to verify classifier robustness.

  20. Inlet throttling effect on the boiling two-phase flow stability in a natural circulation loop with a chimney

    International Nuclear Information System (INIS)

    Furuya, M.; Inada, F.; Yasuo, A.

    2001-01-01

    Experiments have been conducted to investigate an effect of inlet restriction on the thermal-hydraulic stability. A Test facility used in this study was designed and constructed to have non-dimensional values that are nearly equal to those of natural circulation BWR. Experimental results showed that driving force of the natural circulation at the stability boundary was described as a function of heat flux and inlet subcooling independent of inlet restriction. In order to extend experimental database regarding thermal-hydraulic stability to different inlet restriction, numerical analysis was carried out based on the homogeneous flow model. Stability maps in reference to the core inlet subcooling and heat flux were presented for various inlet restrictions using the above-mentioned function. Instability region during the inlet subcooling shifted to the higher inlet subcooling with increasing inlet restriction and became larger with increasing heat flux. (orig.)

  1. Natural convective magneto-nanofluid flow and radiative heat transfer past a moving vertical plate

    Directory of Open Access Journals (Sweden)

    S. Das

    2015-03-01

    Full Text Available An investigation of the hydromagnetic boundary layer flow past a moving vertical plate in nanofluids in the presence of a uniform transverse magnetic field and thermal radiation has been carried out. Three different types of water-based nanofluids containing copper, aluminum oxide and titanium dioxide are taken into consideration. The governing equations are solved using Laplace transform technique and the solutions are presented in closed form. The numerical values of nanofluid temperature, velocity, the rate of heat transfer and the shear stress at the plate are presented graphically for several values of the pertinent parameters. The present study finds applications in engineering devices.

  2. Investigations on hydrodynamic stability of two phase flow in a low pressure natural circulation system

    Energy Technology Data Exchange (ETDEWEB)

    Shaorong, Wu; Dazhong, Wang; Meisheng, Yao; Jinhai, Bo; Yunxian, Tong; Shengyao, Jiang; Bing, Han [Institute of Nuclear Energy and Technology, Tsingua Univ., Beijing (China)

    1997-09-01

    Appropriately scaled ``Loop Stability`` tests and ``Channel Stability`` tests were performed with single heated channel system and two parallel channel system separately at the Institute of Nuclear Energy Technology (INET) of the Tsinghua University in China. A broad range of several operational parameters such as heating power, system pressure, test inlet subcooling and resistance coefficient were investigated. It was found that under certain geometric conditions and operating parameters a self-sustaining, low frequency, even amplitude mass flow oscillation may be excited at very low steam qualities and subcooling conditions. Stability maps under different conditions have been provided to assist the design of the NHR. (author). 6 refs, 15 figs.

  3. Sele coastal plain flood risk due to wave storm and river flow interaction

    Science.gov (United States)

    Benassai, Guido; Aucelli, Pietro; Di Paola, Gianluigi; Della Morte, Renata; Cozzolino, Luca; Rizzo, Angela

    2016-04-01

    Wind waves, elevated water levels and river discharge can cause flooding in low-lying coastal areas, where the water level is the interaction between wave storm elevated water levels and river flow interaction. The factors driving the potential flood risk include weather conditions, river water stage and storm surge. These data are required to obtain inputs to run the hydrological model used to evaluate the water surface level during ordinary and extreme events regarding both the fluvial overflow and storm surge at the river mouth. In this paper we studied the interaction between the sea level variation and the river hydraulics in order to assess the location of the river floods in the Sele coastal plain. The wave data were acquired from the wave buoy of Ponza, while the water level data needed to assess the sea level variation were recorded by the tide gauge of Salerno. The water stages, river discharges and rating curves for Sele river were provided by Italian Hydrographic Service (Servizio Idrografico e Mareografico Nazionale, SIMN).We used the dataset of Albanella station (40°29'34.30"N, 15°00'44.30"E), located around 7 km from the river mouth. The extreme river discharges were evaluated through the Weibull equation, which were associated with their return period (TR). The steady state river water levels were evaluated through HEC-RAS 4.0 model, developed by Hydrologic Engineering Center (HEC) of the United States Army Corps of Engineers Hydrologic Engineering Center (USACE,2006). It is a well-known 1D model that computes water surface elevation (WSE) and velocity at discrete cross-sections by solving continuity, energy and flow resistance (e.g., Manning) equation. Data requirements for HEC-RAS include topographic information in the form of a series of cross-sections, friction parameter in the form of Manning's n values across each cross-section, and flow data including flow rates, flow change locations, and boundary conditions. For a steady state sub

  4. Visualization of Two Phase Natural Convection Flow in a Vertical Pipe using the Sulfuric Acid - Copper Sulfate Electroplating System

    Energy Technology Data Exchange (ETDEWEB)

    Ohk, Seung-Min; Chae, Myeong-Seon; Chung, Bum-Jin [Kyung Hee Univ., Yongin (Korea, Republic of)

    2014-10-15

    The passive containment cooling system (PCCS) driven by natural forces convection gain draws research interests after Fukushima NPP accident. The PCCS was classified into three categories: Containment pressure suppression, Containment passive heat removal/pressure suppression systems and Passive containment spray. Among the types of containment passive heat removal/pressure suppression systems, the system composed of an internal heat exchanger and an external coolant tank is considered. In a severe accident condition, the heat from the containment atmosphere is transferred to the outer surface of the heat exchanger by the convection and condensation of the mixture of steam and gases. On the other hand, the heat is transferred to external pool by single phase or two phase natural convection inside of heat exchanger pipes. The study aimed at investigating the influence of the diameter (D) and height (H) of the heat exchanger pipes on the single phase and two phase natural convection heat transfer. As the initial stage of the study, the two phase natural convection flow inside a vertical pipe is visualized. In order to achieve the aim with ample test rig, a sulfuric acid - cooper sulfate electroplating system was employed based on the analogy between heat and mass transfer. The reduction of hydrogen ion at the cathode surface at high potential was used to simulate the boiling phenomena. This study tried to visualize the boiling heat transfer inside a vertical pipe using a cupric acid-copper sulfate (H{sub 2}SO{sub 4}-CuSO{sub 4}) electroplating system. This seems to be successful so far. However further study has to be done to compare the result with real two phase flow situation. The surface tension and surface characteristics are to be tuned to simulate the real situation.

  5. Probabilistic disaggregation model with application to natural hazard risk assessment of portfolios

    DEFF Research Database (Denmark)

    Custer, Rocco; Nishijima, Kazuyoshi

    In natural hazard risk assessment, a resolution mismatch between hazard data and aggregated exposure data is often observed. A possible solution to this issue is the disaggregation of exposure data to match the spatial resolution of hazard data. Disaggregation models available in literature...... disaggregation model that considers the uncertainty in the disaggregation, taking basis in the scaled Dirichlet distribution. The proposed probabilistic disaggregation model is applied to a portfolio of residential buildings in the Canton Bern, Switzerland, subject to flood risk. Thereby, the model is verified...... are usually deterministic and make use of auxiliary indicator, such as land cover, to spatially distribute exposures. As the dependence between auxiliary indicator and disaggregated number of exposures is generally imperfect, uncertainty arises in disaggregation. This paper therefore proposes a probabilistic...

  6. Epistemic uncertainties and natural hazard risk assessment - Part 1: A review of the issues

    Science.gov (United States)

    Beven, K. J.; Aspinall, W. P.; Bates, P. D.; Borgomeo, E.; Goda, K.; Hall, J. W.; Page, T.; Phillips, J. C.; Rougier, J. T.; Simpson, M.; Stephenson, D. B.; Smith, P. J.; Wagener, T.; Watson, M.

    2015-12-01

    Uncertainties in natural hazard risk assessment are generally dominated by the sources arising from lack of knowledge or understanding of the processes involved. There is a lack of knowledge about frequencies, process representations, parameters, present and future boundary conditions, consequences and impacts, and the meaning of observations in evaluating simulation models. These are the epistemic uncertainties that can be difficult to constrain, especially in terms of event or scenario probabilities, even as elicited probabilities rationalized on the basis of expert judgements. This paper reviews the issues raised by trying to quantify the effects of epistemic uncertainties. Such scientific uncertainties might have significant influence on decisions that are made for risk management, so it is important to communicate the meaning of an uncertainty estimate and to provide an audit trail of the assumptions on which it is based. Some suggestions for good practice in doing so are made.

  7. Benchmarking Discount Rate in Natural Resource Damage Assessment with Risk Aversion.

    Science.gov (United States)

    Wu, Desheng; Chen, Shuzhen

    2017-08-01

    Benchmarking a credible discount rate is of crucial importance in natural resource damage assessment (NRDA) and restoration evaluation. This article integrates a holistic framework of NRDA with prevailing low discount rate theory, and proposes a discount rate benchmarking decision support system based on service-specific risk aversion. The proposed approach has the flexibility of choosing appropriate discount rates for gauging long-term services, as opposed to decisions based simply on duration. It improves injury identification in NRDA since potential damages and side-effects to ecosystem services are revealed within the service-specific framework. A real embankment case study demonstrates valid implementation of the method. © 2017 Society for Risk Analysis.

  8. Preparing our Workforce: Discussing Traditional and Non-Traditional Geoscience Careers - Natural hazard risk

    Science.gov (United States)

    Castaldi, A.

    2013-12-01

    Many young people interested in science think that their only professional opportunities lie within academia or in some government sponsored project. The private sector is often dismissed as not providing the opportunities to a natural scientist or at least an opportunity where they can make a difference. The threat of natural disasters and in the rise of economic losses caused by these disasters as well as the potential problems brought about by climate change have opened up a number of opportunities for the natural scientist. The insurance industry and reinsurance industry is one industry looking for natural scientists and structural engineers. The insurance industry's largest singular threat comes from the risks caused by geological or atmospheric hazards. Over the last decade more and more scientists have used their seismological, hydrological, or weather related knowledge to develop new tools and technology to identify and estimate the economic and social impact due to these natural events. The insurance and reinsurance industry were one of the first industries to call attention to the risk posed by climate change. Our goal is to reduce losses and the cost to insure these losses. Our work starts with the hazard. Hazard identification is one of the best methods for reducing loss nevertheless not all areas of the world have t