Experimental Study of the Tunnels with Natural Ventilation for Various Parameters of Ventilation Openings北大核心CSCD

In order to compare the ventilation efficiency and air speed of the tunnel for different parameters of ventilation openings, the acrylic board is used to build a 1:15 tunnel model and carry out the proportional model test. Four working conditions are set up to compare the ventilation in the tunnel under different ventilation openings in terms of number, length and height. The experimental results show that the air velocity distribution and ventilation efficiency change significantly under different ventilation openings in terms of number, length and height. Based on the test results, the best setting pattern of the ventilation opening is proposed in this paper. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Adaptation Pathways in Coastal Case Studies: Lessons Learned and Future Directions

Climate change adaptation presents a difficult challenge for coastal towns around the world, forcing local governments to plan for sea level rise in a contentious decision-making space. The concept of “adaptation pathways,” a diagnostic and analytical tool to assist in adaptive planning and decision-making, is gaining traction as a way of framing and informing climate adaptation. It provides decisionmakers a way to acknowledge the inter-temporal complexities and uncertainties associated with the novel dynamics of climate change and a mechanism to manage these challenges in the local context. In 2012, the Australian Government funded an 18-month program to provide decisionmakers in the coastal zone an opportunity to test the utility of the adaptation pathways concept for coastal climate adaptation. Using a selection of completed projects as case studies, we performed a document analysis to better understand the learnings from the projects. The main themes surrounded: (1) the utility of the adaptation pathway framework in developing options, (2) decision-making rationale and criteria, and (3) stakeholder participation in pathway development. A project participant survey was developed to further understand these themes. Our analysis reveals that “adaptation pathways” was generally framed narrowly and conservatively to emphasize extant economic, administrative and legal considerations over community, participatory, or exploratory ones. Although some case study projects were able to reach a point in the pathway discussion to actively involve stakeholders in their decision-making process, many case studies continued to build technical data as a method for defending policies and actions. These results indicate that coastal adaptation can take-up adaptation pathways as a useful concept for decision-making and planning; however, many councils may still require assistance in stakeholder communication processes in order to develop sociallyacceptable plans that take into account the full range of values affecting local coastal environments.     

The human talent and its role in ISM Code effectiveness and competitiveness in the shipping industry

The present study empirically evaluates the role of human talent in the effective implementation of quality management systems in the shipping industry context. Specifically, we analyze the relationships among top management commitment to quality, ISM (International Safety Management) Code effectiveness and competitiveness as well as we assess the influence of talent in these associations. We test our research hypotheses using a sample of 199 shipping companies located in Greece. The findings show that ISM Code effectiveness acts as a mediator between top management commitment and shipping company competitiveness, while the different talent philosophies were found to moderate this relationship.     

Minimal-revenue congestion pricing Part II: An efficient algorithm for the general case

The second of a two-part series, this paper derives an efficient solution to the minimal-revenue tolls problem. As introduced in Part I, this problem can be defined as follows: Assuming each trip uses only a path whose generalized cost is smallest, find a set of arc tolls that simultaneously minimizes both average travel time and out-of-pocket cost. As a point of departure, this paper first re-solves the single-origin problem of Part I, modeling it as a linear program. Then with a change of variable, it transforms the LP's dual into a simple longest-path problem on an acyclic network. The multiple-origin problem – where one toll for each arc applies to all origins – solves analogously. In this case, however, the dual becomes an elementary linear multi-commodity max-cost flow problem with an easy bundling constraint and infinite arc capacities. After a minor reformulation that simplifies the model's input to better accommodate output from common traffic assignment software, a solution algorithm is exemplified with a numerical example.     

Fatigue life prediction of welded stiffened 350WT steel plates

The propagation of fatigue cracks under constant amplitude cyclic loading was studied in welded stiffened steel plates. The residual stresses in the stiffened plates were measured using the neutron diffraction strain-scanning technique. A finite element model of the stiffened plate was constructed to simulate the residual stresses by an uncoupled thermal and thermo-mechanical analysis. Both the finite element model and the neutron diffraction measurements indicated that in general the residual stresses were tensile near the welded stiffeners and compressive between the stiffeners and ahead of the starter notch tip. Fatigue testing indicated that the fatigue crack growth rates of the stiffened plates were in general lower than that of a corresponding unstiffened plate, especially near the notch tip where compressive residual stresses existed. Both the finite element method and Green's function predicted the fatigue crack growth rates with reasonable accuracy.     

The economic impact of the ATA/Southwest Airlines code-share agreement

This paper examines the economic impact of the code-sharing agreement between ATA and Southwest Airlines, the first time Southwest has chosen to enter markets via a code-share alliance rather than direct entry. We examine the impact of complementary code-sharing on incumbent airline's fares and passenger volumes and also the overall impact on consumer welfare in Denver airline markets. Empirical results show that air fares decreased and passenger volumes increased for incumbent carriers operating on code-shared routes. Further, we find evidence that this code-sharing arrangement increased both consumer and producer surplus. Thus, the well-known “Southwest Effect” is observed not only when Southwest enters a route directly, but also when it enters a route via a code-share agreement with another airline.     

Experimental study of an electro-mechanical CVT ratio controller

This paper introduces an electro-mechanical, dual acting pulley, continuously variable transmission (EMDAPCVT) and presents its real time ratio controller using a proportional-derivative-plus-conditional-integral (PDPCI) controller. The ratio controller system is developed based on primary (input) and secondary (output) pulley position controllers. Each position controller has two PID parameters, releasing and clamping, which are determined experimentally using a relay feedback method. A PC-based ratio controller system is implemented using Matlab/Simulink® software and a Keithley DAS-1602 data acquisition system card. The experimental results show that the PDPCI controller system can control the CVT ratio adequately.     

The intelligent use of finite element methods

The structural analysis based on application of numerical methods used in the solution of complex structural problems, when applied correctly, is a powerful tool leading to rational structural design of ships. This paper discusses the practicalities of its application and indicates that in order to achieve the stated objective, the following are essential pre-requisites: a) full understanding of the problem; b) ability to solve the problem using currently available methods; and c) ability to interpret the results of the analysis correctly. Whilst there is still a lot of discussion on whether the structural analysis represents a structural design or a structural verification tool, the view expressed in this paper is that the structural analysis should mainly be used in the latter context. This means that a sound engineering solution ought to be established in the first phase of the analysis and used as a basis. The final results will then only be used to perfect the structural detail and modify the areas where rapid stress gradients occur. Any other approach would invariably require repetitive, time consuming and costly iterations which under normal circumstances may prove to be counter-productive. This paper presents a few examples of practical application, the methodology of achieving the solution and the way of interpreting the results.     

Optimal Linear Active Suspensions with Integral Constraint

This paper considers the application of linear optimal control to the design of an active automobile suspension system. By inclusion of an integral constraint in the performance index it is possible to achieve zero steady state axle to body response to both static body forces and ramp road inputs. Full state feedback is achieved by reconstructing the state variables from easily measured quantities.