Evaluation of a brake assistance system (BAS) using an injury severity prediction model for pedestrians

Through the years, traffic engineers and researchers have developed a variety of countermeasures to enhance pedestrian safety. Pedestrian-vehicle collisions are regarded as the most serious type of accident since they incur high fatality rates. A fundamental concept in developing effective countermeasures is to analyze pedestrian-vehicle collisions scientifically, which can identify the causes of accidents and accident severity. The objective of this study was to investigate the pedestrian safety benefit of the brake assistance system (BAS) and a functional requirement associated with BAS, namely the time needed to safely detect a pedestrian ahead. An injury severity prediction model for pedestrians was developed to systematically evaluate the BAS in this study. Ordered multinomial logistic regression analysis was used to establish a statistical model capable of predicting pedestrian injury severity. In addition to vehicle characteristics, collision speed and pedestrian characteristics were used as independent predictor variables. The outcomes of this study would be useful in directing the development of safety policies and technologies associated with pedestrian safety.     

Theoretical,Simulation and Experimental Analysis of Microfluidic Droplet Generation and Recovering Process with Applications in Frying Oil Assessments

The research on microfluidic droplet size prediction has been extensive and fruitful, while the droplet deforming process has been seldom studied. In this paper, a frying-oil-assessing microfluidic device was designed to study the droplet deforming and recovering processes, which were dominated by channel geometry, flow rates, sheath flow viscosity and interfacial tension of the two phases. Theoretical expressions of the deforming process and its extreme value were obtained for the first time, supported by simulation and experiments. Theoretical, simulation and experimental results indicated that the steady-state droplet length could be a useful parameter for frying oil assessment.     

Dynamic response analysis of a multi-column tension-leg-type floating wind turbine under combined wind and wave loading

Floating wind turbines (FWTs) are subjected to combined aerodynamic and hydrodynamic loads varying both in time and amplitude. In this study, a multi-column tension-leg-type FWT (i.e., WindStar TLP system) is investigated for its global performance under normal operating conditions and when parked. The selected variables are analysed using a fully coupled aero-hydro-servo-elastic time domain simulation tool FAST. Three different loading scenarios (wind only, wave only and both combined) are examined to identify the dominant load influencing each response. The key response variables are obtained and compared with those for an NREL 5MW baseline wind turbine installed on land. The results should aid the detailed design of the WindStar TLP system.     

A stochastic concession model for infrastructure projects under build-operate-transfer schemes

Concession period is a key factor in the arrangement of a build-operate-transfer (BOT) contract. This paper proposes a stochastic concession period model for infrastructure projects under a BOT scheme, which takes into account the impact of risks and the risk attitudes of the private investor and the government. A hypothetical case is simulated by using the Monte Carlo simulation method to illustrate the proposed model. The results indicate that even for a project with the same estimations, the concession interval can be different and depends a lot on the risk attitudes of the private investor and the government. The proposed model provides a more reasonable concession interval based on which a specific concession period can be obtained through negotiation between the two parties.     

Drive control system design for stability and maneuverability of a 6WD/6WS vehicle

This paper describes a drive controller designed to improve the lateral vehicle stability and maneuverability of a 6-wheel drive / 6-wheel steering (6WD/6WS) vehicle. The drive controller consists of upper and lower level controllers. The upper level controller is based on sliding control theory and determines both front and middle steering angle, additional net yaw moment, and longitudinal net force according to the reference velocity and steering angle of a manual drive, remotely controlled, autonomous controller. The lower level controller takes the desired longitudinal net force, yaw moment, and tire force information as inputs and determines the additional front steering angle and distributed longitudinal tire force on each wheel. This controller is based on optimal distribution control and takes into consideration the friction circle related to the vertical tire force and friction coefficient acting on the road and tire. Distributed longitudinal/lateral tire forces are determined as proportion to the size of the friction circle according to changes in driving conditions. The response of the 6WD/6WS vehicle implemented with this drive controller has been evaluated via computer simulations conducted using the Matlab/Simulink dynamic model. Computer simulations of an open loop under turning conditions and a closed-loop driver model subjected to double lane change have been conducted to demonstrate the improved performance of the proposed drive controller over that of a conventional DYC.     

Breakup modeling of a liquid jet in cross flow

We propose a novel breakup model to simulate the catastrophic breakup regime in a supersonic cross flow. A developed model has been extended from an existing Kelvin-Helmholtz/Rayleigh-Taylor (K-H/R-T) hybrid model. A new mass reduction rate equation, which has critical effects on overall spray structure, is successfully adopted, and the breakup length, which is an important parameter in existing model, is replaced by the breakup initiation time. Measured data from the supersonic wind tunnel with a dimension of 762×152×127 mm was employed to validate the newly developed breakup model. A nonaerated injector with an orifice diameter of 0.5 mm is used to inject water into a supersonic flow prescribed by the momentum flux ratio of the liquid jet to free stream air, q ₀ . The conservation-element and solution-element (CE/SE) method, a novel numerical framework for the general conservation law, is applied to simulate the supersonic compressible flow. The spray penetration height and average droplet size along with a spray penetration axis are quantitatively compared with data. The shock train flow structures induced by the presence of a liquid jet are further discussed.     

船体表面矩形块优化敷设设计(英文)

Rectangular tiles can be laid on a ship’s hull for protection, but the sides of the tiles must be adjusted so adjacent tiles will conform to the curvature of the hull. A method for laying tiles along a reference line was proposed, and an allowable range of displacement for the four vertices of the tile was determined. Deformations of each tile on a specific reference line were then obtained. It was found that the least deformation was required when the tiles were laid parallel to a line with the least curvature. After calculating the mean curvature on the surface, the surface was divided into three layout areas. A set of discrete points following the least deformation of the principal curvatures was obtained. A NURBS interpolation curve was then plotted as the reference line for laying tiles. The optimum size of the tiles was obtained, given the allowable maximum deformation condition. This minimized the number of bolts and the amount of stuffing. A typical aft hull section was selected and divided into three layout areas based on the distribution of curvature. The optimum sizes of rectangular tiles were obtained for every layout area and they were then laid on the surface. In this way the layout of the rectangular tiles could be plotted.     

Characteristic analysis of underwater acoustic scattering echoes in the wavelet transform domain

Underwater acoustic scattering echoes have time–space structures and are aliasing in time and frequency domains. Different series of echoes properties are not identified when incident angle is unknown. This article investigates variations in target echoes of monostatic sonar to address this problem. The mother wavelet with similar structures has been proposed on the basis of preprocessing signal waveform using matched filter, and the theoretical expressions between delay factor and incident angle are derived in the wavelet domain. Analysis of simulation data and experimental results in free-field pool show that this method can effectively separate geometrical scattering components of target echoes. The time delay estimation obtained from geometrical echoes at a single angle is consistent with target geometrical features, which provides a basis for object recognition without angle information. The findings provide valuable insights for analyzing elastic scattering echoes in actual ocean environment.     

Resistance analysis of a semi-SWATH design concept in shallow water

Resistance analysis is an important analytical method used to evaluate the hydrodynamic performance of High Speed Craft (HSC). Analysis of multihull resistance in shallow water is essential to the performance evaluation of any type of HSC. Ships operating in shallow water experience increases in resistance because of changes in pressure distribution and wave pattern. In this paper, the shallow water performance of an HSC design concept, the semi-Small Waterplane Area Twin Hull (semi-SWATH) form, is studied. The hull is installed with fin stabilizers to reduce dynamic motion effects, and the resistance components of the hull, hull trim condition, and maximum wave amplitude around the hull are determined via calm water resistance tests in shallow water. These criteria are important in analyzing semi-SWATH resistance in shallow water and its relation to flow around hull. The fore fin angle is fixed to zero degrees, while the aft fin angle is varied to 0°, 5°, 10°, and 15°. For each configuration, investigations are conducted with depth Froude numbers (Fr _H ) ranging from 0.65 to 1.2, and the resistance tests are performed in shallow water at the towing tank of UTM. Analysis results indicate that the resistance, wave pattern, and trim of the semi-SWATH hull form are affected by the fin angle. The resistance is amplified whereas the trim and sinkage are reduced as the fin angle increases. Increases in fin angle contribute to seakeeping and stability but affect the hull resistance of HSCs.