增加调节参数代替联动坐标加工特种回转面刀具

提出了通过增加安装调节参数来代替部分数控联动坐标,加工特种回转面刀具的方法,该方法减少了对机床的要求,又改善了加工条件和齿槽形状,只要用 3坐标联动的机床或数控装置便可加工出原本需5坐标甚至6坐标数控才能加工的刀具。     

自由衰减模型试验的横摇阻尼评估方法研究(英文)

The methodology to obtain the non-linear roll damping from decay tests is very old. It has been proposed by Froude in the 19th century and used from then on. Behind it there is a quadratic model [θ│θ│] for the damping and a subsequent equivalent linearization. Probably all model basin in the world follows this approach to assess the damping from a decay test. This is well documented and so is the methods to get the p1-p2 coefficients. This is very general in the sense that in principle,it could be applied t...     

在面内压力作用下点腐蚀低碳钢板的非线性有限元分析(英文)

无论是军船还是民船,船体及主要结构构件表面的点腐蚀对于船舶结构强度和安全性都有较大的破坏作用.文中采用系列非线性有限元计算研究了点腐蚀对于低碳钢板极限抗压强度的影响,模型中计及板初始缺陷的影响,详细讨论了板和点腐蚀物理、几何特性的变化对于板极限承载能力的作用.研究发现在众多影响因素中(例如点腐蚀的直径和深度、板的柔度系数等),点腐蚀密集度指标DOP对于板的极限承载能力有主要和直接的影响.此外,在腐蚀环境恶劣的情况下,厚低碳钢板的使用不一定如预期的那样能延长其使用期限.     

Analysis of Clogging Mechanism and Filter-cake Structure of Slurry Containing Coarse-particle Materials in Sandy Strata北大核心CSCD

The problem of filter-cake formation in highly permeable strata is urgently to be solved for slurry shield tunnelling. Adding coarse-particle materials in slurry is an effective method to solve the problem. A selfdesigned test device of slurry invasion and filter-cake formation in strata was adopted, and one kind of lightweight sand was selected as coarse particle materials. By changing the particle sizes of light-weight sand particles, the filtrate mass and the time of filter-cake formation under the condition of different additive contents and pressures were measured. And the influence of particle size of coarse-particle materials on filter-cake formation characteristics was analyzed. A triangular constriction calculation method was proposed, which can be used to quickly determine the influence range of coarse-particle materials on the pore size variation of the strata. The test results show that: (1) the addition of coarse-particle materials can significantly reduce the inter-particle pore size and effectively improve the clogging effectiveness under the condition of this tested strata. (2) The particle size of coarse-particle materials has a great influence on filter-cake formation characteristics. The coarse-particle material with smaller particle size has a better clogging effect, and its filter-cake formation characteristics are more stable. The coarse-particle material with larger particle size has a higher volatility in its filter-cake formation characteristics. (3) Coarse-particle materials with different particle sizes result in different final filter-cake structures. When the coarse-particle materials possess a larger particle size, a mixed filtercake structure is formed, and when the particle size is small, a double-layer filter-cake structure is formed. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Research on a Calculation Method for the Damage Evaluation of the Existing Urban Tunnel Lining Structure北大核心CSCD

The operation safety of the public transport is seriously threaten by the occurrence of defects and damages in existing urban tunnels, which affects the quality of traffic, and will shorten the service life of urban tunnels. Therefore, it is of great significance to evaluate the damages of the tunnel lining structure quickly and accurately. The damage evaluation methods of the existing urban tunnel lining structure are investigated and analyzed in this paper, and a combination method of the macroscopic evaluation of the existing damaged urban tunnel and the damage mechanism of the lining structural material is proposed. Among them, the assessment method specified in the national criterion is selected to evaluate the damages of the lining structure for the macroscopic evaluation, and the classification of tunnel health levels is optimized. Meanwhile, the damage modulus based on the elastic modulus is selected, and the concept of elastic modulus reduction rate is introduced for the mechanism of damage. Furthermore, the assumed function relationship between the health level and the damage degree of existing urban tunnels is proposed and established, which provides a new idea for structural damage assessment of existing urban tunnels. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Study of Controlling Measures for Existing Railway Deformation Caused by Metro Shield Tunnel Under-passing Construction北大核心CSCD

Based on the background of the first phase project of the R3 line of Jinan Rail Transit, and in view of the metro shield tunnel passing under the existing railway bridge and subgrade, this paper uses Abaqus to establish a numerical model to simulate the deformation of the existing bridge and subgrade of the Jiaoji railway line under the two conditions of non-active reinforcement and reinforcement. The results show that under the condition of no reinforcement, the maximum settlement of the top bridge on the pier is -5.88 mm, and the maximum settlement difference is 5.16 mm, which exceed the deformation control requirements of the 5 mm regarding the bridge pier of the railway with ballast track. The maximum lateral displacement and longitudinal displacement of the pier are 0.28 mm and -3.01 mm, respectively. After the reinforcement measures of the bored piles are adopted, the maximum settlement of the top bridge on the pier is -1.71 mm, and the maximum settlement difference is 1.16 mm, which fully meet the bridge pier deformation control standard. The maximum lateral displacement and longitudinal maximum displacement are -0.245 mm and -2.83 mm, respectively, which meet the requirements of the control standard. The vertical settlement of the railway subgrade is relatively small. The maximum settlement values under the two working conditions are -12.31 mm and -11.97 mm, respectively, which meet the subgrade settlement control requirement of 20 mm. It is proved that the reinforcement effect of the bored pile is good, and the reinforcement scheme is safe and feasible. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Across the waves: a bibliometric analysis of container shipping research since the 1960s

The paper investigates collaborative and semantic patterns that emerged between 1967 and 2013 about the theme of container shipping based on a corpus of 294 articles published in scholarly journals within the fields of transportation, supply chain, economics, geography, regional planning and development, and operations research. An analysis based on the co-occurrence of title words allows identifying dominant sub-themes and their evolution. Main results point to the gradual diversification of container shipping research, from the dominance of economics towards a more trans-disciplinary set of approaches which integrate port-related activities and multimodal networks. Yet, disciplinary specialization remains strong up to nowadays so that container shipping research remains rather fragmented. While co-authorships have increased over time, they remain polarized by few, weakly connected research battalions. Our study suggests that research on container shipping would benefit from more frequent contacts between such communities to foster in-depth cross-disciplinary studies and fundamental cooperation.     

Effective Public Participation is Fundamental for Marine Conservation—Lessons from a Large-Scale MPA

The Representative Areas Program (RAP) was, at the time, the most comprehensive process of community involvement and participatory planning for any environmental issue in Australia. The RAP was a key component of the widely acclaimed rezoning of the Great Barrier Reef Marine Park, and although completed in 2003, many lessons learned are still relevant today. This paper provides an analysis of the comprehensive public participation program that significantly influenced the final planning outcome. It provides insights into a fundamental component of effective marine planning, assessing what worked well and what did not in terms of public engagement. Some aspects of the public participation program were innovative, and some were more effective than others. The outcome was one-third of the Marine Park was declared as highly protected no-take zones in 2004, with the remainder of the park also zoned to provide lower levels of protection. The methods used to engage the public and the 25 lessons discussed in this paper should be of interest for practitioners, policy makers and academics elsewhere aiming for “good practice” approaches to achieve environmental conservation.     

Inviting travelers to the smorgasbord of sustainable urban transport: evidence from a MaaS field trial

A Mobility-as-a-Service (MaaS) concept, UbiGo, was implemented in Gothenburg, Sweden, and used for a 6-month period by 195 individuals in 83 households. Four participant subgroups were identified: Car shedders, Car accessors, Simplifiers, and Economizers. A qualitative analysis revealed that the subgroups had different reasons to join the service and different expectations of the change that would occur on the basis of the altered preconditions offered by the service. Previous car users reduced their use of private car and increased their use of public transport and active modes. Participants who did not have access to a privately-owned car but thought they needed one discovered that they managed well without. Other participants were reinforced in their existing behaviors but in ways they did not envisage, depending on which goals they had at the outset of the trial. Overall, the participants were also satisfied with the service, as well as with stated changes and non-changes, even if this in some cases meant more planning. Based on the empirical findings it could be argued that a service approach, such as UbiGo, has the potential to reduce the need for private car ownership, and enable people to change their mode choices and travel patterns. The potential relies however on a number of specific features of the service of which flexibility and a need- rather than a mode-based approach are key features.     

Revisiting port pricing; a proposal for seven port pricing principles

A review of seven large landlord port authorities around the world reveals a notable diversity of pricing structures. While port authorities increasingly act as commercial undertakings, port pricing often seems to be not driven by commercial considerations. In this paper, we argue that ports can be regarded as “business ecosystems” with multiple users. This provides a valuable perspective on pricing and raises the question of whether ports can be regarded as two-sided markets. We argue this is not the case. The business ecosystem perspective provides a basis for deducing seven pricing principles for port authorities that are detailed in the paper and illustrated with cases these principles. These pricing principles are broadly follow a direct user pays approach; capture value from “non-core” tenants; price aggressively for activities with a high strategic value; differentiate pricing based on price elasticity and connectivity improvements; maximize revenue from long-term lease agreements, price port dues competitively; critically consider differentiation of charges based on environmental performance; and finally use incentives to align interests of terminal operators and shipping lines. We conclude that the ecosystem perspective is central to the understanding of pricing decisions of port authorities and that various pricing issues deserve more attention.