Wave propagation in head on bonnet impact: Material and design issues

Head on bonnet impact is becoming more and more important in automotive design as regulations on pedestrian safety become more demanding. Despite the relatively low amount of energy involved, these impacts are truly dynamic phenomena as the event duration is comparable with the traveling time of the different wavefronts generated by the impact. In this paper, we show that we can build up a simplified model for the impact based on wave propagation analysis. Using this model, we can analyze head acceleration on existing bonnets or predict it on new ones. Head acceleration in a bonnet impact can thus be estimated over the whole area of the bonnet with a few minutes of CPU.     

A new hybrid terrain coverage method for underwater robotic exploration

It is well known that it is difficult to explore underwater terrains using an autonomous underwater vehicle due to the varieties and complexities of underwater terrain elements. Since conventional underwater terrain coverage techniques are usually based on the assumption that the underwater surface is planar, they generate an unnecessary exploration path especially on steep sloped surfaces of ocean basins. This paper proposes a new type of coverage technique, the hybrid terrain coverage framework (HTCF), which considers various surface conditions in three-dimensional environments and generates an efficient exploration path for all environments. The HTCF incorporates a planar terrain coverage algorithm, a spiral path terrain coverage algorithm, and a hybrid decision module to recognize and select the most suitable technique depending on the sloped surface variations. Simulation results show that the proposed HTCF is more efficient than the conventional terrain coverage algorithm in terms of the energy consumption of the underwater vehicle.     

Review of Secure Communication Approaches for In-Vehicle Network

In the connected vehicles, connecting interfaces bring threats to the vehicles and they can be hacked to impact the vehicles and drivers. Compared with traditional vehicles, connected vehicles require more information transfer. Sensor signals and critical data must be protected to ensure the cyber security of connected vehicles. The communications among ECUs, sensors, and gateways are connected by in-vehicle networks. This paper discussed the state-of-art techniques about secure communication for in-vehicle networks. First, the related concepts in automotive secure communication have been provided. Then we have compared and contrasted existing approaches for secure communication. We have analyzed the advantages/disadvantages of MAC and digital signatures for message authentication and compared the performance and limitations of different cryptographic algorithms. Firewall and intrusion detection system are introduced to protect the networks. The constraints and features of different intrusion detection approaches are presented. After that, the technical requirements for cryptographic mechanism and intrusion detection policy are concluded. Based on the review of current researches, the future development directions of the automotive network security have been discussed. The purpose of this paper is to review current techniques on automotive secure communication and suggest suitable secure approaches to implement on the in-vehicle networks.     

Systematic budget allocation for transportation construction projects: a case in Taiwan

It has always been a daunting task for any government to allocate the budgets for public infrastructure effectively so as to maximize the benefits of the limited resources. The most important contribution this paper makes is to conduct an empirical study of the budget allocations of the six region-based road system construction plans in northern Taiwan using the transportation budget allocation model devised in this paper. After reviewing the results, the experts consulted while preparing this paper believe that these results are both objective and able to meet the actual requirements. The competent authority also believes that they are better than those obtained using their original approach. In particular, the construction of this model takes into consideration the highest-level supervisors. To a certain degree, it caters for the practices in budget allocation so that the managers are able to assume the authority corresponding to their responsibility concerning management efficiency and final outcomes.     

Experimental study on a model azimuthing podded propulsor in ice

The objective of this study was to investigate the performance of a model azimuthing podded propulsor in ice-covered water. Model tests were carried out with two different depths of cut into the ice (15 and 35 mm), two different ice conditions (presawn and pack ice conditions), and four different azimuthing angles. The depth of cut is the maximum penetration depth of the propeller blade into the ice block. The 0.3-m-diameter model propeller was operated in a continuous ice milling condition. Ice loads were measured by several sensors which were installed in various positions on the model. Six one-axis pancake-style load cells on the top of the model measured the global loads and two six-component dynamometers were installed on the shaft to measure the shaft loads. One six-component dynamometer was attached to the one of the propeller blades inside the hub to measure the blade loads. The pod unit and propeller performance in ice are presented. Ice-related loads, which were obtained when the blade was inside the ice block, are introduced and discussed. During the propeller–ice interaction, a blade can experience the path generated by the previous blade, which is called the shadowing effect. The effects of shadowing, depth of cut, azimuthing angle, and advance coefficient on propulsor performance are presented and discussed.     

Investigation of ship waves in a narrow channel

This paper presents a discussion of the characteristics of ship waves in a narrow channel restricted by vertical walls, based on observed data and the results computed by a 2-D model. In the numerical model, the propagation of waves generated by a moving ship is simulated by solving 2-D depth-integrated Boussinesq equations. To get the boundary conditions at the location of the ship, the slender-ship approximation is employed. A field observation was carried out at a straight length of navigation channel. The ships targeted in the observations are two kinds of waterbuses with lengths of 28 and 24 m. The relative depth Froude number for the river current, an appropriate parameter for assessing the influence of the current on ship wave characteristics in a navigation channel, ranged from 0.47 to 0.76. The observed maximum wave height varied between 0.13 and 1.26 m. The maximum wave height of the wave train is sharply increased when the relative depth Froude number exceeds 0.6. The results computed by the present model agree fairly well with the observed data.     

Trip generation of vulnerable populations in three Canadian cities: a spatial ordered probit approach

This paper provides an analysis of trip generation of three vulnerable groups: single-parent families, low income households, and the elderly. It compares the mobility of these groups to that of the general population in three Canadian urban areas of Hamilton, Montreal and Toronto, based on data from large-sample metropolitan transport surveys. An ordered probit model with spatially expanded coefficients is used for the analysis. Spatial expansion shows that there are spatial mobility trends for elderly populations and low-income populations even after socio-economic attributes are accounted for. Such spatial differences are not generally found for single parent families. This novel spatial analysis provides clues as to where vulnerable populations may experience greater degrees of social exclusion. It provides information to help prioritize transportation infrastructure projects or other social programs to take into account the needs of vulnerable populations with the lowest levels of mobility.     

基于SPH方法的波浪对水平板冲击的数值模拟(英文)

A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely used in the free-surface hydrodynamic flows with good accuracy. The improvement includes the employment of a corrective function for enhancement of angular momentum conservation in a particle-based calculation and a new estimation method to predict the pressure on the horizontal deck. The simulation results show a good agreement with the experiment. The present numerical model can be used to study wave impact load on the horizontal deck.     

Strong bottom–up effects on phytoplankton community caused by a rainfall during spring and summer in Sagami Bay,Japan

To assess the consequences of bottom-up effects on phytoplankton community composition during the rainy season, phytoplankton levels and environmental factors were monitored daily from 12 April to 22 July 2003 in Sagami Bay, Japan. The relevant environmental factors were analyzed using cross-correlation analyses. Based on time-series analysis, low surface salinity conditions lasting 0 or 2 days after heavy rainfalls resulted in significant nutrient loading, such as dissolved inorganic nitrogen (DIN), into the coastal area. Also, Chlorophyll-a (Chl-a) concentration frequently increased 2 and 6 days after rainfall. Based on the high total Chl-a concentration, the time was divided into three periods, from 1 to 11 May (Period A), 26 May to 9 June (Period B) and 30 June to 22 July (Period C). The phytoplankton assemblages during Period A were dominated by two dinoflagellates, Ceratium furca and Ceratium fusus. Prior to these species blooming, the heterotrophic dinoflagellate Noctiluca scintillans was dominant. During Period B, the phytoplankton communities were dominated primarily by the diatoms Rhizosolenia delicatula, Hemiaulus sinensis and Navicula spp. Finally, Cerataulina dentata, Rhizosolenia spp., Lauderia borealis and Neodelphineis pelagica were dominant during Period C. After increases in phytoplankton abundance, available nitrogen (N) and phosphorous (P) were consumed and exhausted, which were considered a potential cause of the shift in the dominant organisms from large diatoms to pico- and nano-plankton in the low Chl-a environment. In particular, silicate (Si) was not a major limiting factor for phytoplankton production, since the Si:DIN and Si:P ratios clearly demonstrated that there were no any potential stoichiometric Si limitations, and almost all silicate concentrations were > 2.0 µM during this study. Our results reveal that nutrient sources supplied by river discharge are a main cue for strong bottom–up effects on algal bloom succession during the early summer season in Sagami Bay.     

An investigation of the performance of an electronic in-line pump system for diesel engines

WIT Electronic Fuel System Co., Ltd. has developed a new fuel injector, the Electronic In-line Pump （EIP） system, designed to meet China＇s diesel engine emission and fuel economy regulations. It can be used on marine diesel engines and commercial vehicle engines through different EIP systems. A numerical model of the EIP system was built in the AMESim environment for the purpose of creating a design tool for engine application and system optimization. The model was used to predict key injection characteristics under different operating conditions, such as injection pressure, injection rate, and injection duration. To validate these predictions, experimental tests were conducted under the conditions that were modeled. The results were quite encouraging and in agreement with model predictions. Additional experiments were conducted to study the injection characteristics of the EIP system. These results show that injection pressure and injection quantity are insensitive to injection timing variations, this is due to the design of the constant velocity cam profile. Finally, injection quantity and pressure vs. pulse width at different cam speeds are presented, an important injection characteristic for EIP system calibration.