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891.
J.F. Guan Hai Yang S.C. Wirasinghe 《Transportation Research Part B: Methodological》2006,40(10):885-902
Passenger transportation in most large cities relies on an efficient mass transit system, whose line configuration has direct impacts on the system operating cost, passenger travel time and line transfers. Unfortunately, the interplay between transit line configuration and passenger line assignment has been largely ignored in the literature. This paper presents a model for simultaneous optimization of transit line configuration and passenger line assignment in a general network. The model is formulated as a linear binary integer program and can be solved by the standard branch and bound method. The model is illustrated with a couple of minimum spanning tree networks and a simplified version of the general Hong Kong mass transit railway network. 相似文献
892.
A model for assessing the effects of dynamic travel time information via variable message signs 总被引:2,自引:0,他引:2
In view of the serious traffic congestion during peak hours in most metropolitan areas around the world and recent improvement
of information technology, there is a growing aspiration to alleviate road congestion by applications of electronic information
and communication technology. Providing drivers with dynamic travel time information such as estimated journey times on major
routes should help drivers to select better routes and guide them to utilise existing expressway network. This can be regarded
as one possible strategy for effective traffic management. This paper aims to investigate the effects and benefits of providing
dynamic travel time information to drivers via variable message signs at the expressway network. In order to assess the effects
of the dynamic driver information system with making use of the variable message signs, a time-dependent traffic assignment
model is proposed. A numerical example is used to illustrate the effects of the dynamic travel time information via variable
message signs.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
893.
894.
E-R模型特殊超类/子类结构转换方法研究 总被引:1,自引:0,他引:1
分析了该系统的概念结构中出现的特殊超类/子类结构,即:超类实体对不同的子类实体具有不同的主码,其主属性仅仅是所有子类实体共同的主属性,各子类实体拥有各自特定的主属性. 相似文献
895.
A. S. Koraim 《Journal of Marine Science and Technology》2011,16(3):331-342
The performance of a slotted breakwater consisting of one row of vertical slots was investigated theoretically and experimentally
under normal regular waves. A simple theoretical model based on an eigenfunction was developed. The wave transmission, reflection,
energy loss, and hydrodynamic force exerted on the breakwater were calculated for different values of the wave and structure
parameters. The validity of the theoretical model was examined by comparing its results with theoretical and experimental
results obtained from different studies. It was found that the transmission coefficient decreases with increasing dimensionless
wavenumber (kh), increasing wave steepness (H
i/L), and decreasing breakwater porosity (ε). The reflection coefficient showed the opposite trend to the transmission coefficient. Also, about 20–50% of incident wave
energy was lost due to the effect of the breakwater. In addition, the proposed theoretical model can be used for predicting
the performance of slotted breakwaters and the hydrodynamic forces exerted on these structures using the friction coefficient
f = 1.5. 相似文献
896.
Long-term variability of the biogeochemical properties during the formation of central waters in the Eastern North Atlantic were analyzed between 42–47°N and 10–20°W from the dataset gathered during the Galicia VII (GVII) and C. Darwin 58/59 (CD58/59) cruises. These cruises that showed important changes in the thermohaline properties and the nutrient abundance of the upper layers were carried out under contrasting conditions of the North Atlantic Oscillation (NAO) index. The different climate forcing led a meridional shift of the transition zone between the formation regions of subpolar and subtropical Eastern North Atlantic Central Water (ENACWp and ENACWt, respectively). This displacement conditioned the presence of each ENACW in the study region and so the thermohaline and biogeochemical properties. The effect of the observed variability at decadal scale on the air–sea CO2 gradient (ΔfCO2) and exchange (FCO2) was analyzed using 1D model approach throughout 11 weekly-steps that simulated the development of a spring bloom during the shoaling of the mixed layer. The outputs of the model showed an intensification of the ocean CO2 uptake due to higher biological CO2 drawdown, during positive NAO conditions and its weakening under negative NAO influence. 相似文献
897.
898.
[Objective]To simplify the ship modeling process and improve modeling efficiency, this paper proposes a method for rapidly implementing hull model creation based on hull line drawing.[Methods]Using the CATIA platform, this method adopts the component application architecture (CAA) development tool for secondary development. First, by reading the geometry elements and label information of the hull lines in a drawing, the transformation of the offset points from 2D to 3D is realized. On this basis, the creation of the hull lines, stern and bow is completed, and a 3D wireframe model obtained. Finally, the hull 3D modeling is completed in conjunction with the CATIA native surface creation command. The stability and reliability verification of the developed type value extraction and bow generation program is then carried out via application analysis.[Results]The results show that the compiled program can realize the automatic creation of offset points, transverse lines, waterlines, profile lines and other boundary lines except the top line of the wall, and the centerline and tangent lines created by the bow generator are easily modified and simple for users to operate. [Conclusions]The verification results show that the method of a creating hull model using "Generative Shape Design" and "Drafting" with the hull line drawing as the data input is stable, reliable and able to realize rapid hull modeling, giving it certain practical value. © The Author(s) 2022. 相似文献
899.
Virginia R. Ferritto 《WMU Journal of Maritime Affairs》2016,15(2):353-380
Presenteeism research has only recently extended from a construct capturing lost productivity due to attending work despite health issues to a construct representing students’ perceived academic performance. Aligning with presenteeism’s prevalent research paradigm, the pioneering studies used health-related issues to measure presenteeism. In contrast, this study used the Presenteeism and Perceived Academic Performance (PPAP) Scale, which the researcher developed for this study. The PPAP Scale comprises aspects of student behavior that support academic performance. This study filled gaps in the literature by investigating presenteeism as a concept associated with students’ perceived academic performance, measured with the PPAP Scale, and factors specific to maritime education. The factors investigated were self-identified by the study respondents, in sufficient numbers to support statistical analysis, as favorably (i.e., cruise and license/maritime instruction) or negatively (i.e., mandatory regimental activity, taps, morning or afternoon formations, and watch) impacting their academic performance. This study found no statistical evidence to suggest the level of presenteeism, measured with the PPAP Scale, among the study’s sample of license students is associated with factors perceived to favorably or negatively impact academic performance. Additional insight can be gained from license student participants’ responses to the study’s open-ended questions (e.g., a perceived imbalance between time available to allocate to their academics and time needed to fulfill regimental responsibilities). 相似文献
900.
This paper aims to evaluate the influence of policies, attitudes and perceptions when incentivizing alternative fuel vehicles. The impact of possible policies such as gasoline taxes increases, purchase price subsidies, tax exemptions, and increases in fuel recharging station availability for alternative fuelled vehicles is evaluated using hybrid choice models. The models also allow assessing the sensitivity of latent variables (i.e., attitudes and perceptions) in the car purchase behaviour. The models are estimated using data from a stated choice survey collected in five Colombian cities. The latent variables are obtained from the rating of statements related to the transport system, environmental concern, vehicle preferences, and technology. The modelling approach includes regression between latent variables. Results show that environmental concern and the support for green transport policies have a positive influence on the intention to purchase alternative fuel vehicles. Meanwhile, people who reveal to be car-dependent prefer to buy standard fuelled vehicles. The analysis among cities shows similar trends in individual behaviour, although there are differences in attribute sensitivities. The policy scenario analysis revealed high sensitivity to capital cost and the need for extensive investments in refuelling stations for alternative fuel vehicles to become attractive. Nevertheless, all policies should not only be directed at infrastructure and vehicles but also be focused on user awareness and acceptance of the alternative fuel vehicles. The analysis suggests that in an environmentally conscious market, people prefer alternative fuels. However, if the transport policies support private transport, the market shares of alternative fuel vehicles will decrease. 相似文献