Active response control of an offshore structure under wave loads using a modified probabilistic neural network

Offshore structures are subjected to wave, wind, and earthquake loads. The failure of offshore structures can cause sea pollution as well as loss of property and life. Therefore, the safety of such structures is an important issue. The reduction of the dynamic response of an offshore structure subjected to wind-generated random ocean waves is another critical problem with regard to the serviceability, fatigue life, and safety of the structure. In this article, the responses of offshore structures under random ocean waves are controlled using a modified probabilistic neural network (MPNN). As a more advanced method, it uses the global probability density function (PDF) produced by summing the heterogeneous local PDFs automatically determined from the individual standard deviation of each variable. The state vectors in a state-space model of a structure and the resulting control forces made by a linear quadratic regulator algorithm were used to generate the training patterns for the MPNN and a conventional multilayer perceptron (MLP). The results were compared with those produced by back-propagation based on the MLP. The proposed MPNN method shows good results not only in controlling the responses but also in terms of the computation time.     

A two‐leveled multi‐objective symbiotic evolutionary algorithm for the hub and spoke location problem

We consider a hub and spoke location problem (HSLP) with multiple scenarios. The HSLP consists of four subproblems: hub location, spoke location, spoke allocation, and customer allocation Under multiple scenarios, we aim to provide a set of well‐distributed solutions, close to the true Pareto optimal solutions, for decision makers. We present a novel multi‐objective symbiotic evolutionary algorithm to solve the HSLP under multiple scenarios. The algorithm is modeled as a two‐leveled structure, which we call the two‐leveled multi‐objective symbiotic evolutionary algorithm (TMSEA). In TMSEA, two main processes imitating symbiotic evolution and endosymbiotic evolution are introduced to promote the diversity and convergence of solutions. The evolutionary components suitable for each sub‐problem are defined. TMSEA is tested on a variety of test‐bed problems and compared with existing multi‐objective evolutionary algorithms. The experimental results show that TMSEA is promising in solution convergence and diversity.     

Conceptual design of high-speed semi-low-floor bogie for train-tram

Train-tram railway vehicles implement the connection between urban tramlines and the surrounding railway network. Train-tram railway vehicles, which use existing infrastructure, can help to avoid large investments in new railways or tramlines and make interchanges between city center and surrounding cities unnecessary. However, present train-tram rail vehicle cannot carry out the integration of operating by means of high speed in intercity railways with operating on small radius of curvature in inner city tramlines. This paper aims to develop a new model for solid wheelsets train-tram railway vehicles, which will not only pass the curve of 25mR radius of curvature traveling on inner city tramlines with the speed of 18 km/h, but also can travel on straight railway with 200 km/h high speed between intercity. In this paper, a new train-tram model, including five car-body and five motor bogies with ten traction motors, is addressed. Expect as a real rail vehicle testing, this study prefer virtual simulation, which is an effective way to show the rail vehicle performance, such as ride stability, ride comfort and ride safety, by means of evaluating the dynamic characteristics of rail vehicle. Moreover, Design of Experiment (DOE) method is used to optimize solid wheelsets bogie system on improving passenger comfort, safety and stability of train-tram. Parameters of components of bogie system are tuned to minimize the derailment coefficient and the ride comfort index. The results shows that the best comfort index for passenger and minimum derailment coefficient are found. The results also show that this optimized new train-tram model is reliable and practical enough to be applied on real rail vehicle design.     

Schedule construction under precedence constraints in flexray in-vehicle networks

As embedded time-triggered applications have widely replaced mechanical systems in modern automobiles, holistic scheduling of tasks and messages of such applications on in-vehicle networks has become a critical issue. For offering QoS (Quality of Service) guarantees, the holistic schedule must satisfy numerous constraints such as protocol specifications, delay constraints and precedence constraints between tasks schedules and messages transmissions. Existing approaches to this problem search through a vast design space of all possible joint task and message schedules. This leads to a high complexity and limits the scalability of such approaches for scheduling the large scale systems. To cope with this problem, we propose an approach that divides the holistic scheduling problem to two sub-problems: the sub-problem of message scheduling and the sub-problem of task scheduling, while precedence relations and end-to-end information passing between task instances and messages are preserved and the end-to-end deadlines are guaranteed. This helps to reduce the workload on the problem solvers and improves efficiency and scalability. In the first sub-problem, our approach optimizes scheduling the set of messages and allocates time windows for scheduling each task with respect to precedence constraints, end-to-end deadlines and FlexRay protocol specifications. The length of each time window helps to preserve the respective tasks schedulability and to provide flexibility for both task and message scheduling. The objective is defined with respect to extensibility issues. In the second sub-problem, our approach optimizes schedule of the set of tasks with respect to their allocated time windows and timing constraints. The objective is defined with respect to latency issues. We optimize the solution to each sub-problem using Mixed Integer Linear Programming optimization framework. Performance evaluations show that, compared with existing holistic scheduling approaches, our approach is more scalable and obtains better solutions in a reasonable amount of time.     

Travelers' preferences for in-vehicle information systems: An exploratory analysis

A sample of travelers' preferences toward in-vehicle traffic information systems was undertaken and appropriate statistical models were estimated. Specifically, ordered logit and regression analyses were conducted to quantify travelers' ratings of the importance of in-vehicle system attributes, and the distance ahead that they prefer to be notified of various types of information provided by in-vehicle systems. Model estimation results show that travelers' socio-economics, habitual travel patterns, commute congestion levels and attitudes toward in-vehicle technologies are significant determinants of travelers' importance ratings and the preferred distance ahead of in-vehicle system information. These model results provide important information for both marketing and design of in-vehicle information systems.     

Characteristics of VIV in multi-degree-of-freedom tensioned beams using a numerical method

The object of this study is to analyze the characteristics of vortex-induced vibration of a slender marine structure with the numerical method. Applying a dynamic analysis method for a slender marine structure based on the 3D finite difference method, we carried out case studies for a tensioned beam model at a constant flow speed. The hydrodynamic forces, in the direction of inline and cross-flow, created by vortex shedding are simultaneously considered based on Morison equation. The frequency of force in the inline direction corresponding to the unstable zone is evaluated. An eigenvalue analysis for different flow speeds of a tensioned beam considering the effect of the tension increase due to the inline and cross-flow drag forces is performed. We found that a revision of the eigenvalue should be considered if the tension along a riser or beam is significantly affected by an environmental or functional load. From a trajectory on the XY plane it was shown that the riser did not move in an exact 8 shape for all flow conditions due to the phase angle difference between inline and cross-flow displacement. It is believed that the phase angles between inline and cross-flow displacements in high modes are different among the nodes.     

Development of early warning index in Korean shipping industry by using signal approach

ABSTRACT

The study aims to investigate and prevent shipping companies’ insolvency that can be derived from depressed market sentiment in the shipping industry. For this purpose, the paper focuses on developing an early warning index. The main factors that contribute to the change in the shipping industry are derived. Sixty independent variables were accounted in the development of early warning index, some of which are shipping, shipbuilding, and finance. Suggestions drew from the result of early warning index are described as below. Firstly, the results of a signal approach towards independent variables showed lowest the signal error value in newbuilding price of containership, bunker price, Commodity Research Bureau (CRB) commodity index, and order book of bulkship. These indicators have proven to be a high level of variation factor during shipping markets’ crisis. Secondly, the early warning index confirmed that it preceded by 6 months compared to probability of default. Thirdly, in order to validate the accuracy of the early warning index, the adequacy of the model was tested using a mean square error and time lag correlations. As a result of the verification, value proved to be at a high level of compliance at 0.097.     

基于边界元和爆震分析韩国天安舰水下爆炸事件(英文)

On March 26,2010 an underwater explosion(UWE)led to the sinking of the ROKS Cheonan.The official Multinational Civilian-Military Joint Investigation Group(MCMJIG)report concluded that the cause of the underwater explosion was a 250 kg net explosive weight(NEW)detonation at a depth of 6 9 m from a DPRK"CHT-02D"torpedo.Kim and Gitterman(2012a)determined the NEW and seismic magnitude as 136 kg at a depth of approximately 8m and 2.04,respectively using basic hydrodynamics based on theoretical and experimental methods as well as spectral analysis and seismic methods.The purpose of this study was to clarify the cause of the UWE via more detailed methods using bubble dynamics and simulation of propellers as well as forensic seismology.Regarding the observed bubble pulse period of 0.990 s,0.976 s and 1.030 s were found in case of a 136NEW at a detonation depth of 8 m using the boundary element method(BEM)and 3D bubble shape simulations derived for a 136kg NEW detonation at a depth of 8 m approximately 5 m portside from the hull centerline.Here we show through analytical equations,models and 3D bubble shape simulations that the most probable cause of this underwater explosion was a 136 kg NEW detonation at a depth of 8m attributable to a ROK littoral"land control"mine(LCM).     

Properties of roadway particles from interaction between the tire and road pavement

A large fraction of urban PM₁₀ concentrations is due to non-exhaust traffic emissions, including road dust, particles from tire/road interface, and brake lining particles. Although potential health and environmental impacts associated with tire wear debris have increased, few environmentally and biologically relevant studies of actual tire wear debris have been conducted. Tire wear particles (TWP) are released from the tire tread as a result of the interaction between the tire and the pavement. Roadway particles (RP), meanwhile, are particles on roads composed of a mixture of elements from tires, pavement, fuels, brakes, environmental dust, and the atmosphere. The main objective of the present study is to identify the contribution of tires to the generation of RP and to assess the potential environmental and health impacts of this contribution. First, a mobile measurement system was constructed and used to measure the RP on asphalt roads according to vehicle speed. The equipment of the mobile system provides PM₁₀ concentration by DustTrak DRX, and mass and number size distribution of fine and ultrafine particles by a fast mobility particle sizer (FMPS) and an aerosol particle sizer (APS). The dependence of RP mass and particle number concentration on vehicle speed was observed. It was also found that many particles were generated by rapid deceleration of the vehicle.     

Robust design optimization of the dynamic responses of a tracked vehicle system

This paper presents the robust design optimization of the dynamic responses of a heavy military tracked vehicle system. The tracked vehicle model addressed in this study has 954 degrees of freedom and consists of 189 bodies in total: 37 bodies for the chassis, such as sprockets, road wheels, road arms, etc.; 76 track link bodies for each track subsystem; 36 revolute joints; and 152 bushing elements. The design objectives were to minimize the maximum vertical acceleration of the hull and its variance while satisfying the wheel travel constraints for torsion bars and the hydro-pneumatic suspension units within ±1σ ranges. To avoid the difficulty of the design sensitivity analysis and to overcome the numerical noise, a progressive meta-model technique was employed in the optimization process. First, space-filling methods were used to determine the minimum number of sample points. Second, the simultaneous kriging method was used to construct the initial meta-models, and the augmented Lagrange multiplier (ALM) method was then used to solve the robust design problems of the meta-models. Third, the new design results were added to the analysis results for the initial sample points, and the meta-models were updated automatically. Next, the optimizer resolved the robust design problems of the updated meta-models. These processes were repeated until the convergence tolerances were satisfied. The robust design optimization of the tracked vehicle system, with 11 random design variables, was solved in only 26 analyses, including 12 analyses for the initial meta-models and 14 analyses added during the iterative optimization process.