Study of storm surge due to Typhoon Linda (1997) in the Gulf of Thailand using a three dimensional ocean model

Numerical integrations using the three dimensional ocean model based on the princeton ocean model (POM) were applied for the study of both sea level elevation and ocean circulation patterns forced by the wind fields during typhoons that moved over the Gulf of Thailand (GoT). The simulation concerned a case of Typhoon Linda which occurred during November 1-4, 1997. Typhoon Linda was one of the worst storms that passed the Gulf of Thailand and hit the southern coastal provinces of Thailand on November 3, 1997. It caused flooding and a strong wind covering large areas of agriculture and fisheries, which destroyed households, utilities and even human lives. The model is the time-dependent, primitive equation, Cartesian coordinates in a horizontal and sigma coordinate in the vertical. The model grid has 37 × 97 orthogonal curvilinear grid points in the horizontal, with variable spacing from 2 km near the head of the GoT to 55 km at the eastern boundary, with 10 sigma levels in the vertical conforming to a realistic bottom topography. Open boundary conditions are determined by using radiation conditions, and the sea surface elevation is prescribed from the archiving, validation and interpretation of satellite oceanographic data (AVISO). The initial condition is determined from the spin up phase of the first model run, which was executed by using wind stress calculated from climatological monthly mean wind, restoring-type surface heat and salt and climatological monthly mean freshwater flux. The model was run in spin up phase until an ocean model reached an equilibrium state under the applied force. A spatially variable wind field taken from the European Centre for Medium-Range Weather Forecasts (ECMWF) is used to compute the wind stress directly from the velocity fluctuations. Comparison of tendency between the sea surface elevations from model and the observed significant wave heights of moored buoys in the Gulf of Thailand under Seawatch project is investigated. The model predicts the sea level elevation up to 68.5 cm at the Cha-Am area located in the north of where the typhoon strands to the shore. Results of sea level elevation show that there is an area of peak set-up in the upper gulf, particularly in the western coast, and the effects of the storm surge are small at the lower gulf. During the entire period of this study, the surge in the gulf was induced by the northeasterly wind blowing over it.     

The fresh-salt water interface in a semi-pervious aquifer

The paper determines the location of the steady state interface between fresh and saltwater in a plane coastal aquifer. The lower boundary is totally impervious while the upper one is impervious below land and semi-pervious below the sea allowing an outflow through this part of the upper boundary. The model equations reduce to two boundary value problems, one valid in x < 0 and the other in x > 0 here x is measured along the aquifer with the origin at the coast. In each region unknown boundaries have to be determined as part of the solution using boundary and continuity conditions. Two cases are presented using the Dupuit approximation. One where the solution can be written down in terms of elementary functions and the other in which we have to use a phase space analysis.     

A higher accuracy predictor-corrector method for the simulation of sea pollution

A predictor-corrector scheme developed for the integration of the equations describing the evolution of interactive pollutants in a shallow sea, has been improved by introducing a compact differencing of the spatial derivatives. The higher-order scheme is shown to be far less sensitive to nonlinear instability and to need no stabilizing numerical diffusion. It allows a very good representation of the diffusive processes in cases where the advection terms are strongly dominant.     

A 3D hydrodynamic numerical model of the Río de la Plata and Montevideo’s coastal zone

The 3D hydrodynamic numerical model MOHID was applied in the Río de la Plata and Montevideo coastal zone in order to represent the main dynamics and to study its complex circulation pattern. The hydrodynamic model was calibrated and validated considering the following main forces: fresh water flow, astronomical and meteorological tides in the oceanic boundary, and wind acting on the water surface. A series of water levels measured at six coastal stations and vertical profiles of current velocity measured at four different locations in the estuarine zone of the Río de la Plata were used for calibrating and validating the hydrodynamic model. The calibration process was carried out in two steps. First the astronomical waves propagation was calibrated comparing harmonic constants of observed and computed sea surface elevation data. Next, both the astronomical and meteorological wave propagation was calibrated. Direct comparison of scatter plot and root-mean square errors of model results and field data were used when evaluating the calibration quality. The calibrated model shows good agreement with the measured water surface level in the entire domain with mean error values being minor than 20% of the measured data and correlation factors higher than 0.74. Also, the intensity and velocity direction observed in the currents data are well represented by the model in both bottom and surface levels with errors similar to 30% of the currents data components. Using the 3D calibrated model the bottom and surface residual circulation for a four month period of time was analyzed.     

Modelling the impact of wind stress and river discharge on Danshuei River plume

A three-dimensional, time-dependent, baroclinic, hydrodynamic and salinity model, UnTRIM, was performed and applied to the Danshuei River estuarine system and adjacent coastal sea in northern Taiwan. The model forcing functions consist of tidal elevations along the open boundaries and freshwater inflows from the main stream and major tributaries in the Danshuei River estuarine system. The bottom friction coefficient was adjusted to achieve model calibration and verification in model simulations of barotropic and baroclinic flows. The turbulent diffusivities were ascertained through comparison of simulated salinity time series with observations. The model simulation results are in qualitative agreement with the available field data.     

Insolvent corporate groups with cross guarantees: A forensic-LP Case study in liquidation

In many countries a significant method of corporate-group capital raising is cross-guarantee financing, where each company within a guarantee group guarantees the performance of the others. However, implementing cross-guarantee claims in liquidations has proved difficult and they have usually been set aside. This paper investigates the administrator's settlement of a large Australian guarantee-group insolvency, after a seven year administration period. Desirable properties of cross-guarantee settlements are analysed and modelled as a linear programme, based on equity principles under English law or in other jurisdictions with a common law tradition. The LP solution for the case study gives an alternative notional settlement. A post-optimality analysis provides evidence of the liquidation principles of the administrator's settlement and demonstrates inter alia that the nature of creditor protection given by cross guarantees may be unexpected, particularly if all companies are held severally responsible for the group deficiency.     

Modeling civil violence in Afghanistan: Ethnic geography,control, and collaboration

We develop a computational model to explore how ethnic geography shapes the distribution of violence in civil war. We seed the model with disaggregated data on ethnic settlement patterns in Afghanistan and calibrate the model parameters to fit empirically observed locations of violence against civilians. Our simulation suggests that (i) political actors are more likely to attack civilians in heterogeneous areas where members of one ethnic group are exposed to members of a rival group; (ii) violence directed at civilians occurs with greater frequency in locations where one political actor exercises hegemonic but incomplete territorial control (relative to areas of complete or mixed control); and (iii) geographically concentrated ethnic minorities face a higher risk of violence. © 2012 Wiley Periodicals, Inc. Complexity, 2012     

Using Simulation in Capacity Planning

This paper describes a case study concerning the application of simulation to manufacturing capacity planning. Visual interactive models were developed and used to investigate the manufacturing strategy for a particular organization. However, there are several practical difficulties which may arise in using these techniques to support managerial decisions. One of these concerns the meaning of the term ‘manufacturing capacity’. This problem was overcome by using a visual interactive version of an established procedure to complement the use of a simulation model.     

Improving the computational efficiency in a global formulation (GLIDE) for interactive multiobjective optimization

In this paper, we present a new general formulation for multiobjective optimization that can accommodate several interactive methods of different types (regarding various types of preference information required from the decision maker). This formulation provides a comfortable implementation framework for a general interactive system and allows the decision maker to conveniently apply several interactive methods in one solution process. In other words, the decision maker can at each iteration of the solution process choose how to give preference information to direct the interactive solution process, and the formulation enables changing the type of preferences, that is, the method used, whenever desired. The first general formulation, GLIDE, included eight interactive methods utilizing four types of preferences. Here we present an improved version where we pay special attention to the computational efficiency (especially significant for large and complex problems), by eliminating some constraints and parameters of the original formulation. To be more specific, we propose two new formulations, depending on whether the multiobjective optimization problem to be considered is differentiable or not. Some computational tests are reported showing improvements in all cases. The generality of the new improved formulations is supported by the fact that they can accommodate six interactive methods more, that is, a total of fourteen interactive methods, just by adjusting parameter values.     

Simulation and the Micro

Simulation is established as a proven and effective aid to decision-making in business and industry, providing a means of investigation where to experiment on the `real world' would be costly or disruptive. This paper first traces the pioneering developments carried out in simulation by a B.S.C. O.R. team, in particular in:

• - simulation packages, making model construction sounder and easier,
• - the use of visual displays to communicate model behaviour as a simulation run progresses,
• - interactive simulation (`gaming'), involving operational personnel, such as line management and planners, in the simulation process.

The paper goes on to describe how the advent of the microprocessor, in desk-top computers and colour graphics, has enabled more power and flexibility to be brought to these areas. It also discusses the further benefits arising from the use of micros in simulation and identifies for comparison the benefits of using a mainframe or mini-computer. The paper also describes how the early development areas have culminated in the FORSSIGHT computer-aided decision-making package.     

Controlling the precision of estimated means in interactive simulation

The computing power of modern workstations has made it possible to simulate many queueing systems interactively. Recent development in simulation software has mainly concentrated on interactive facilities. Unfortunately the precision of estimates has widely been overlooked in interactive simulation. In this paper we propose a method for controlling the precision of estimated means during an interactive simulation run. Since in a typical situation of interactive simulation the user is simultaneously interested in several means, we consider both the simultaneous precision and individual precisions of the estimated means. The method is based on the existing methods for estimating standard errors and on the Bonferroni inequality. The Bonferroni inequality is used to obtain a lower bound for the simultaneous precision.     

基于贪婪算法的水上漂移目标救助物资协同调度方法

受复杂水文、气象等条件影响,水上遇险目标在等待外部救援的过程中可能发生漂移,其漂移的速度与方向将直接影响到水上救助物资调度方案的制订。针对水上事故及其救援的特殊性,在对水上遇险目标漂移路径进行预测的基础上,构建了满足运力、时间限制及应急救助物资需求,包括水上遇险目标周边船舶、岸基救助基地及其附近陆地应急物资储备点共同参与的水陆两阶段多层级协同调度模型,并运用贪婪算法对其进行求解,最后通过算例对模型和算法的有效性进行验证。     

Using soft OR principles for collaborative simulation: a case study in the Dutch airline industry

Collaborative simulation is a method to handle problem situations that are technologically and socially complex. It combines discrete event simulation with methods, techniques and tools designed to help groups progress with their problems. Discrete event simulation and group support both appear to have clear promises in embedding soft OR principles, yet also contain limitations. Furthermore, simulation and group support appear to be complementary, balancing each other's limitations. Therefore, the combination of group support and discrete event simulation seems to be a fruitful vehicle for the application of soft OR principles. Through experiences in a case study at the cargo department of a major airline, we examine how collaborative simulation can be applied in practice as problem structuring method. We conclude that collaborative simulation has definite potential as a soft OR technique, but further research is required to speed up different steps of simulation to fully use simulation in interactive decision making sessions with multiple stakeholders.     

A Longitudinal Analysis of an Out‐of‐School Science Experience

A phenomenological approach was used to investigate the longitudinal recollections of participants of an out‐of‐school science program. The experience was a field trip to the Shenandoah National Park (USA) conducted in the fall of 2004. The science topic was geologic history and features related to the Shenandoah Valley. Two major themes relating to the participants' long term recollection of the out‐of‐school science field trip were identified after the interview data was analyzed. First, recollections were highly influenced by actions taken by the students, and, second, program content / subject matter were retained by all of the students to varying degrees. The interactive experiences that aided in memory retrieval from this study closely relates to the interactive experiences associated with memory and learning theory associated with the psychological domain. This linkage and its impact on how students learn in out‐of‐school science experiences are discussed.     

A comprehensive general simulation of small twin screw displacement hull boats with validation

A comprehensive general simulation of small twin screw displacement hull boats is developed as a tool to estimate ship and actuator responses in support of developing and tuning of control systems. The general form of this model allows many small displacement hull vessels to be rapidly simulated by specifying a set of 17 vessel parameters. The response of the vessel in the surge, sway and yaw degrees of motion are estimated from parametric equations and data compiled from literature and, when not found in literature, inferred from sea trials. Model validation and tuning of the coefficients not found in literature is accomplished using manoeuvring and response data obtained in a series of sea trials. The parametric model proved to be accurate and, when compared with the sea trial data, model estimates have rms errors over the vessel operational range of 0.09 m/s and 0.02 m/s for surge velocity when moving in a straight line in forward and reverse, respectively. For rotating on a fixed point, the simulation overestimates the rotational velocity by 7.6% and has an rms error of 0.27°/s. Open loop circle tests show that with both propellers rotating at 580 rpm, the simulated vessel has a minimum turning radius of 24.4 m and can complete a circle in 44 s, which is 18% smaller and 8% faster than during sea trials. Simulated rotation with the engines in opposite gears at similar RPMs of 500 result in a complete revolution in 68 s, 3 s faster than during sea trials.     

Combating eutrophication in coastal areas at risk for oil spills

In this study we evaluate the profitability of nutrient abatement measures in eutrophied coastal areas exposed to a risk of frequent oil spills. The case studied is the Gulf of Finland, which forms part of the Baltic Sea. We present a dynamic model that integrates land loads of nitrogen and phosphorus, cost of nutrient abatement measures in agriculture, nutrient dynamics in the sea basins adjoining the Finnish coast, exogenous risk of oil spills, and recreational value of the sea, which faces environmental damage of uncertain magnitude and duration. Monte Carlo simulation is applied to evaluate the profitability of nutrient abatement measures carried out unilaterally by Finland or as a joint effort by Estonia, Finland and Russia. We demonstrate that a high exogenous risk of oil damage may render investments in nutrient abatement economically infeasible. On the other hand, several components of the model entail uncertainties owing to the scarcity of data and our limited understanding of the relationship between the ecological processes involved and the values people place on natural resources. For example, the uncertainties related to the curvature of the value function outweigh the uncertainties connected with the oil spills and their potential consequences.     

MODELING THE EFFECT OF SEA SURFACE TEMPERATURE ON SEA TURTLE NESTING ACTIVITIES BY INVESTIGATING SEASONAL TRENDS

ABSTRACT. In the present study, a series of models have been developed in order to investigate the effect of sea water temperature upon the nesting activities of marine turtles. Autoregressive integrated moving average (ARIMA) models, ARIMA models with transfer functions and regression models were developed for forecasting variations in the breeding activity of loggerheads, nesting at the island of Zakynthos, West Greece. Identification and development of the models was determined by the use of several statistical criteria. Weekly data series of sea turtles emerging attempts and number of nests laid were analyzed and compared with sea surface temperature (SST) data series. Our results indicate that whether SST data were included in the ARIMA models with transfer functions and the regression models that developed to describe both emergence data and number of nests, tended to improve fitting and forecasting accuracy. Data series of the number of nests laid was further correlated with observation of emergence data. Adding the effect of previous and current year nesting attempts and including SST data resulted to higher forecasting accuracy and fitting performance.     

Computer-Assisted Statistics Education at Delft University of Technology

Abstract

At Delft University of Technology many students experience difficulties in mastering basic concepts of probability and statistics. In the past few years the lectures have undergone a radical change—the lecture notes now contain modern data analysis techniques, like kernel density estimation, simulation, and bootstrapping. In the TWI-Stat project, a computer-aided instruction course was developed to help students become more familiar with modern statistical analysis. The course presents itself as a dynamic, interactive, personal book. Highly interactive analysis tools are available. The software will be available for MS-Windows.     

The NATO strategic commanders' assessment of requirements for strategic sea and airlift

With the end of the Cold War and the adoption of a new NATO strategic concept, NATO nations now emphasize the use of mobile, flexible, and multinational military forces to be deployed for a myriad of crisis response operations outside the normal NATO treaty area. One critical shortfall for a number of NATO members has been the ready availability of strategic sea and airlift assets. Most NATO nations rely on the civilian transport market to provide dry cargo vessels and wide-body cargo aircraft. The two NATO strategic commands, Supreme Headquarters Allied Powers Europe (SHAPE) and Headquarter Supreme Allied Command Atlantic (SACLANT), have been assessing the requirements for sea and airlift and have proposed to nations a variety of measures to improve their movement and transport capability. SACLANT staff has been developing the operations research methods to assist in this assessment. The current paper conveys the methodology and the mathematical programming model used in this analysis, using ship, aircraft, and port availability constraints. Furthermore, the paper presents a framework of the modeling and simulation capability of the NATO commands and agencies in the movement and transportation area. Additionally, the paper provides an example of the use of simulation models in follow-up activities such as high-level seminars in which national military force planners and movement and transport staff participate. During these events, participants are provided with the results from a number of transportation simulation models, in an attempt to steer the decision making process in NATO.