Using the Ecopath with Ecosim Modeling Approach to Understand the Effects of Watershed-based Management Actions in Coastal Ecosystems

Resource managers are often tasked with identifying and assessing the potential impacts of management actions on the biotic communities under their care. When the management activities directly influence a single species of interest, managers can turn to a variety of models to aid in their understanding of potential changes to that population. However, as ecosystem-based management becomes more widely accepted, managers will have to understand how proposed actions will impact entire biotic communities, through both direct and indirect mechanisms. Thus, there is a need for ecosystem models that account for both trophic and non-trophic interactions, and that can be relatively easily used to assess a variety of management scenarios. We reviewed the available literature regarding incorporation of eutrophication and other anthropogenic impacts into Ecopath with Ecosim (EwE), one of the more widely used trophic ecosystem modeling frameworks. We found that a number of mechanisms of varying complexity have been used to include these stressors in models, providing managers with a suite of options that can be used to complement their existing management options as they seek to understand the impacts of human interactions on the natural environment.     

Effect of bed vicinity on vortex shedding and force coefficients of fluid flow on an offshore pipeline

The effect of rigid bed proximity on flow parameters and hydrodynamic loads in offshore pipelines exposed to turbulent flow is investigated numerically. The Galerkin finite volume method is employed to solve the unsteady incompressible 2D Navier–Stokes equations. The large eddy simulation turbulence model is solved using the artificial compressibility method and dual time-stepping approach. The proposed algorithm is developed for a wide range of turbulent flows with Reynolds numbers of 9500 to 1.5×10⁴. Evaluation of the developed numerical model shows that the proposed technique is capable of properly predicting hydrodynamic forces and simulating the flow pattern. The obtained results show that the lift and drag coefficients are strongly affected by the gap ratio. The mean drag coefficient slightly increases as the gap ratio increases, although the mean lift coefficient rapidly decreases. The vortex shedding suppression happen at the gap ratio of less than 0.2.     

Marine Protected Areas in the Canadian Pacific: Do They Fulfill Network Criteria?

As a signatory to the Convention on Biological Diversity, Canada has committed to establishing a network of marine protected areas (MPAs) that effectively conserves at least 10% of coastal and marine areas by 2020. Research shows that the most effective MPAs are large, well enforced, no-take, and designed as part of a network. Canada's Pacific MPAs, designated site-by-site, cover approximately 3% of Canadian Pacific waters. We investigated how these MPAs could effectively contribute to Canada's national network by analyzing the implementation of management intent through the application of fisheries closures and conducting a preliminary assessment of their size and spacing relative to scientific guidelines. Fisheries closures outside of MPAs were similarly assessed. Results showed that 90% of existing MPAs were intended to exclude commercial fishing, yet only 2.5% fully or partially met this goal, therefore management intent was not achieved. Further, existing MPAs were small, 75% less than 10 km² in size, but were reasonably spaced, from one to 50 km apart. While a suite of fisheries closures may be better suited to effectively contribute to a network than MPAs without fisheries closures, they would require permanent designations and management plans to meet network inclusion criteria.     

Stability Analysis of the Human Controlled Vehicle Moving Along a Curved Path

A method to study handling characteristics of a vehicle moving along a curved path is presented. A simple bicycle model and a feedback controller with proportional gain are used to simulate the vehicle and the driver. The lateral stability of the vehicle/driver system is analyzed by using the root locus method and numerical integration in the time domain. The effect of the curvature on the system stability is discussed in detail. A new suggestion is made for the look ahead distance to calculate the preview lateral error of the vehicle with respect to the center of the road. Interesting results are shown for some important parameters such as the gain factor, the vehicle speed and the curvature of the path. Possible extensions of the method to more general cases and other applications are discussed.     

Development of a probabilistic model to optimize disseminated real‐time bus arrival information for pre‐trip passengers

In the advent of Advanced Traveler Information Systems (ATIS), the total wait time of passengers for buses may be reduced by disseminating real‐time bus arrival times for the next or series of buses to pre‐trip passengers through various media (e.g., internet, mobile phones, and personal digital assistants). A probabilistic model is desirable and developed in this study, while realistic distributions of bus and passenger arrivals are considered. The disseminated bus arrival time is optimized by minimizing the total wait time incurred by pre‐trip passengers, and its impact to the total wait time under both late and early bus arrival conditions is studied. Relations between the optimal disseminated bus arrival time and major model parameters, such as the mean and standard deviation of arrival times for buses and pre‐trip passengers, are investigated. Analytical results are presented based on Normal and Lognormal distributions of bus arrivals and Gumbel distribution of pre‐trip passenger arrivals at a designated stop. The developed methodology can be practically applied to any arrival distributions of buses and passengers.     

Optimizing the transportation of international container cargoes in Korea

This paper considers a multimodal transportation problem, which is the problem of determining the transportation flow, i.e. volume of container cargoes, and the transportation mode in each trade route, for the objective of minimizing the sum of shipping and inland transportation costs. The problem takes account of two restrictions: maximum cargo volumes capacitated at each seaport and maximum number of vehicles available at each transportation mode. To solve optimally the problem, this paper employs a mixed integer programming, which is an operations research technique. A case study is performed on the container cargo data in Korea and we draw several implications to improve efficiency in the transportation of international trade cargoes in Korea.     

Automatic FE modeler using stiffener-based mesh generation algorithm for ship structural analysis

Shipbuilding industries have started to employ 3D CAD systems to integrate all design and production processes by achieving seamless data transfer and data sharing. The emerging 3D CAD system brings a considerable change in FE analysis field. The availability of 3D geometry increased the recognition of the need for developing automatic FE modeling system consequently.

However, general automatic mesh algorithms developed by academic research field have a limitation. The difficulty in satisfying lots of line constraints and the absence of proper idealization of 3D geometry entities defined in CAD system hinders directly employing the general mesh algorithms.

In this research, an automatic FE modeling system has been developed for cargo hold FE modeling and whole ship FE modeling. The basic concept of the algorithm is to decompose surfaces using stiffener lines into subregions and generate mesh using a rule established based on FE modeling practice of ship structure. Since the decomposed subregions take simple polygon, they can be easily transformed into elements by decomposing the polygon according to the rule defined considering the shape of the polygon and mesh seed on its perimeter. The algorithm is also designed to treat appropriate geometry idealizations for bracket-type surface and stiffener connections. The idealization process is also completely customized based on FE modeling practice. The validity of the developed system is verified through illustrative examples.     

Wheel Slip Control in Traction Control System for Vehicle Stability

Traction control systems are used to prevent wheel slippage and to maximize traction forces. This paper proposes a new scheme to enhance vehicle lateral stability with a traction control system during cornering and lane changes. This scheme controls wheel slip during cornering by varying the slip ratio as a function of the slip angle. It assumes that a traction control system with the engine throttle angle is used. The scheme is dynamically simulated with a model of front-wheel-driven passenger vehicles. Simulation results show that the proposed scheme is robust and superior to a conventional one, which is based upon fixed slip ratios, during cornering and lane changes.     

Improving the Performance of Loop-Sensor-Based Traffic-Information System by (M+PLL) Circuit

Conventionally a phase-shift detection method (PSDM) and a frequency-shift detection method (FSDM) have been used in loop detectors. The PSDM has a fast response time and is very effective in detecting vehicles traveling at normal speeds. However, it is well known that the detection results are erroneous for vehicles traveling at low speeds in heavy traffic conditions. On the other hand, the FSDM greatly improves the detector performance for heavy traffic conditions. However, this method is not effective in fast and normal traffic conditions. Thus, in order to collect accurate traffic data for all traffic conditions, this paper proposes combining two methods using the digital OR logic. In the developed circuit, a phase-locked loop (PLL) circuit is used for measuring the phase change. This paper also develops a new loop detector instrumentation method using the so-called M circuit for detecting frequency change. The developed method has been tested for various traffic conditions. Experimental results show that the new combined M and PLL detection method greatly improves the accuracy in all traffic conditions, reducing the error rate in measuring traffic flow by more than 83%, when compared to the PSDM.     

The estimation of wave elevation and wave disturbance caused by the wave orbital motion of a fully submerged hydrofoil craft

The current control system of a fully submerged hydrofoil craft has manual input of fore-foil depth and control mode selection to improve the performance of the control system. However, the manual input needs skillful human operation and observation of waves the encountered to work well over a wide range of waves. In order to use information about the waves encountered in the control system, we considered the estimation of wave elevation and wave disturbance which was caused by the orbital motion of the waves in irregular waves. First, we investigated the wave disturbance by a fully submerged hydrofoil craft, in a state-space model of wave disturbance, and in hydrofoil craft motion, etc. We than considered estimations of the wave elevation and wave disturbance using a shaping filter, a Kalman filter, an autoregressive (AR) model, etc. Finally, we confirmed through simulations that the estimation results and estimation error of wave elevation and wave disturbance were valid.