Experimental investigation of rain-wind-induced vibration of cables in cable-stayed bridges and its mitigation

Rain-wind-induced vibration of cables in cable-stayed bridges is presently a worldwide problem of great concern. Because it is sensitively influenced by many parameters, this peculiar phenomenon is difficult to be replicated in laboratory conditions; its mechanism has not been well explained yet. In this paper, the phenomenon of rain-wind-induced vibration of a cable model is successfully reproduced under actual rain conditions in a wind tunnel. The effects of several main factors, including the inclination angle, frequency and damping of the cable as well as the wind yaw angle, etc. on the characteristics of rain-wind-induced vibration are investigated in detail in the test. The countermeasures of double-spiral wires and dampers for the mitigation of the vibration are also experimentally studied. The results show that the size and twine direction and the pitch of the spiral wires twined on the surface of cables have great effects on the mitigation efficiency of rain-wind-induced vibration of cables.     

On Abstraction in Scenarios

Scenarios are ways of representing knowledge. They may take many forms, from films of real events through acted scenes to documented procedures. These forms differ in many ways, including how vivid or abstract they are, how accessible they are as specifications, and how effective they are in helping to elicit requirements. Scenarios, especially as Use Cases, are in use or proposed for many aspects of systems engineering. Understanding of the different forms scenarios may take, and then of the costs and benefits of applying these forms in practice, may be valuable.     

Psychological factors influencing laypersons’ acceptance of climate engineering,climate change mitigation and business as usual scenarios

In the past two decades, research on so-called climate engineering approaches has increased. These technologies are considered to be potential substitutes for mitigation strategies in combating climate change. The ongoing process of layperson acceptance and resultant opinion formation can be expected to play a crucial role in future public debate about field experiments or the actual deployment of climate engineering.In July 2017, we assessed public reactions from the German population in a representative online survey. Participants were given a brief text informing them about climate change and one of four different scenarios in a between-subject design (N = 678). Two of the scenarios described the use of climate engineering technologies - stratospheric aerosol injection (SAI) and bio-energy with carbon capture and storage (BECCS) - one of them covered conventional mitigation strategies and the fourth group was given an outline of the business-as-usual (BAU) approach.The mitigation scenario (willingness for individual behaviour changes) showed the highest acceptance rate (M = 74.23), which was significantly higher than acceptance of the other scenarios (p < .001). Acceptance of BECCS (M = 53.15) was higher than acceptance of SAI (M = 46.25, p = .043) and BAU (M = 42.94; p = .006). We undertook a relative-importance analysis to investigate the influence of multiple predictor variables on acceptance formation for each scenario; the variance thus explained ranged from 80.3% to 86.8%. The results point up the influence of perceived risks, subjective norms and affective responses on the acceptance of climate engineering technologies. By contrast, person-specific and relatively stable variables, such as environmental attitudes and wishful thinking, are particularly relevant in the evaluation of the mitigation scenario.     

A Representational Framework for Scenarios of System Use

Scenarios are becoming widely used in three areas of system development: software engineering, human–computer interaction (HCI), and organisational process design. There are many reasons to use scenarios during system design. The one usually advanced in support of the practice is to aid the processes of validating the developers’ understanding of the customers’ or users’ work practices, organisational goals and structures, and system requirements. All three areas identified above deal with these processes, and not surprisingly this has given rise to a profusion of scenario-based practices and representations. Yet there has been little analysis of why scenarios should be useful, let alone whether they are. Only by having such a framework for understanding what scenarios are, and what they are for, can we begin to evaluate different scenario approaches in specific development contexts. This paper is a contribution toward such a framework. We lay out a space of representational possibilities for scenarios and enumerate a set of values or criteria that are important for different uses of scenarios. We then summarise several salient representations drawn from the software engineering, HCI, and organisational process design communities to clarify how these representational choices contribute to or detract from the goals of the respective practices. Finally, we discuss how scenario representations from one area of design may be useful in others, and we discuss the relationship between these representations and other significant early-design and requirements engineering practices.     

Scenario-Based Analysis of COTS Acquisition Impacts

When an enterprise considers the acquisition of a COTS (commercial off-the-shelf) system, the procurement process typically includes consideration of technical criteria such as feature sets and ease of integration with other systems. However, any selected COTS system will also have an impact on how the enterprise runs – how the work of the enterprise gets done and ultimately how the services of the enterprise are delivered to its customers. This paper presents a method for determining these enterprise-level impacts. A notion of enterprise-level impacts is delineated, and a scenario-based technique is presented for uncovering and assessing these impacts. The method is informal and lightweight – it does not require extensive modelling, formal rigour, or management of artefacts. Some insights, experience and lessons are reported. Some comparisons are made with past experience using a more formal, heavyweight method and tool.     

Security Concerns in IPv6 and Transition Networks

ABSTRACT

This whitepaper introduces the concept of a transitional network, defines what it is, how it is used and why a transitional network is necessary. A brief history of IPv6 is given followed by a review of the known vulnerabilities associated with the IPv6 protocol. Popular transition strategies are explored in greater detail around issues of cost, implementation and security vulnerabilities. Mitigation techniques and counter-measures are reviewed against known exploits for each of the transition mechanisms. The last section offers an in depth investigation into the IPv6 mobility protocol, Network Address Translation - Protocol Translation (NAT-PT) and tunneling options.     

Scenario relaxation algorithm for finite scenario-based min–max regret and min–max relative regret robust optimization

Most practical decision-making problems are compounded in difficulty by the degree of uncertainty and ambiguity surrounding the key model parameters. Decision makers may be confronted with problems in which no sufficient historical information is available to make estimates of the probability distributions for uncertain parameter values. In these situations, decision makers are not able to search for the long-term decision setting with the best long-run average performance. Instead, decision makers are searching for the robust long-term decision setting that performs relatively well across all possible realizations of uncertainty without attempting to assign an assumed probability distribution to any ambiguous parameter. In this paper, we propose an iterative algorithm for solving min–max regret and min–max relative regret robust optimization problems for two-stage decision-making under uncertainty (ambiguity) where the structure of the first-stage problem is a mixed integer (binary) linear programming model and the structure of the second-stage problem is a linear programming model. The algorithm guarantees termination at an optimal robust solution, if one exists. A number of applications of the proposed algorithm are demonstrated. All results illustrate good performance of the proposed algorithm.     

VRML虚拟场景跳转及三维造型交互

VRML构造复杂三维场景时,通常需要多个场景的组合。如何实现三维空间场景跳转和三维造型的动态效果十分关键？结合实例讨论并给出利用Anchor组节点实现多场景跳转的方法,在动态三维造型的基础上利用传感器Sensor节点,实现复杂的交互功能：     

Generating generic response signals for scenario calculation of management effects on carbon sequestration in agriculture: approximation of main effects using CENTURY

In this study, a well bounded and validated biogeochemical model, CENTURY, is used to mimic behaviour of soil carbon under different agricultural management regimes in Australian conditions to provide simple soil carbon response signals for use in a multi-criteria, spatial framework for analysis of management effects on carbon storage. The study is concerned with relative change in soil carbon resulting from change in management, and not concerned with absolute values either of change or final stock. Simulations were run for a range of starting soil carbon levels, soil physical properties, and climate sites using two carbon pool allocations within the model. A simplified set of agricultural land management options was used consisting of warm season native grassland, warm/cool season mixed native grassland, improved pasture, continuous wheat, conservation tillage, and long and short cereal rotations with lucerne. There were large differences in simulation results between crop and pasture systems and management types within systems. Within management types, starting soil carbon levels had the major influence on simulation outcomes. The derived carbon response signals for agricultural management practices, summarised over soils and climate, tended to underestimate losses under cropping and overestimate gains from perennial grassland when compared to field data. The value of these signals in a scenario analysis is discussed.