释能降压技术在野三关隧道中的应用

在溶腔处理中,宜万铁路首次采用释能降压施工技术,成功降低溶腔水位,对施工安全风险进行科学研究,确保施工安全。     

我国新能源汽车零部件发展必须解决7大问题

在政府主导下的新能源汽车发展热潮中，我国新能源汽车零部件受整车带动，技术水平得到一定提升，市场规模得以扩大，产业化取得一定进展。文章指出，我国新能源汽车总体上与国际先进水平仍有一定差距，特别是在关键材料和零部件的配套能力方面、关键技术的研发水平以及整车的性能等方面有待于进一步提高。为使新能源汽车零部件得到又好又快发展，必须着手解决7大问题。政府应加大支持力度，调动各方面积极性，在最短的时间内实现我国新能源汽车的跨越式发展。     

我国重型汽车车桥历史、现状及发展趋势

简要介绍我国重型汽车车桥的发展历史和现状,主要制造商及其产品,技术发展水平,对比国外先进车桥技术,分析和总结我国重型汽车车桥的发展趋势及发展对策。     

基于MR阻尼器的船用隔离器系统试验研究

随着船舶技术的发展，现代船舶对船用隔离器系统提出了越来越高的要求，即船用隔离器系统应同时具备低频减振和高频抗冲击的能力，这是传统的船用减振器系统所无法做到的．为了解决此问题，本文提出了一种新的船用隔离器系统，该系统由钢丝绳弹簧和磁流变阻尼器相并联组成．文中对该船用隔离器系统的减振和抗冲击性能进行了模型试验研究。减振试验的激振力频率为1-15Hz，力幅为2．94．11．76kN；冲击试验的最大冲击输入加速度为20g，脉宽为10ms，减振试验和冲击试验均采用MTS液压加载系统来进行．试验结果表明，该船用隔离器系统具有较好的减振效果，使用了MR阻尼器后系统得共振峰值被明显的削弱；在冲击试验中，冲击响应的衰减速度随着MR阻尼器的阻尼增加而明显加快，但是MR阻尼器再冲击瞬间的出力特性明显与低频振动情况下不同，MR阻尼器的出力表现为受控制电流强度影响不大．     

Influence of slip boundary on flow separation and drag of flow past bluff body at high Reynolds numbers北大核心CSCD

［Objectives］Flow separation increases the drag and noise of underwater vehicles, and influences the controllability of their control surfaces. Therefore, the influence of slip caused by superhydrophobic surfaces on drag reduction and flow separation is studied. ［Methods］A partial slip boundary condition is developed, and the flow around a circular cylinder and foil with a slip boundary at high Reynolds numbers are numerically simulated. ［Results］The results show that the when the slip length increases, the flow around the cylinder goes through three stages: the turbulent Kármán vortex street, laminar Kármán vortex street and non-separation Stokes flow. The drag coefficient increases first and then decreases, and the vortex shedding frequency increases. For flow around a foil, the separation position moves downstream until the separation region disappears when the slip length increases, and the drag coefficient decreases while the lift coefficient increases. ［Conclusions］The results of this study show that for flow past bluff body at high Reynolds number, the slip boundary can control flow separation and reduce drag effectively, providing technical support for the application of superhydrophobic surfaces for the flow control of underwater vehicle appendages. © 2022 Journal of Clinical Hepatology. All rights reserved.     

Driving cycles that reproduce driving patterns,energy consumptions and tailpipe emissions

This study presents the Energy Based Micro-trip (EBMT) method, which is a new method to construct driving cycles that represent local driving patterns and reproduce the real energy consumption and tailpipe emissions from vehicles in a given region. It uses data of specific energy consumption, speed, and percentage of idling time as criteria of acceptable representativeness. To study the performance of the EBMT, we used a database of speed, fuel consumption, and tailpipe emissions (CO₂, CO, and NO_x), which was obtained monitoring at 1 Hz, the operation of 15 heavy-duty vehicles when they operated within different traffic conditions, during eight months. The speed vs. time data contained in this database defined the local driving pattern, which was described by 19 characteristic parameters (CPs). Using this database, we ran the EBMT and described the resulting driving cycle by 19 characteristics parameters (CPs*). The relative differences between CPs and CPs* quantified how close the obtained driving cycle represented the driving pattern. To observe tendencies of our results, we repeated the process 1000 times and reported the average relative difference (ARD) and the interquartile range (IQR) of those differences for each CP.. We repeated the process for the case of a traditional Micro-trip method and compared to previous results. The driving cycles constructed by the EBMT method showed the lowest values of ARDs and IQRs, meaning that it produces driving cycles with the highest representativeness of the driving patterns, and the best reproduction of energy consumption, and tailpipe emissions.     

Atmospheric dispersion modeling near a roadway under calm meteorological conditions

Atmospheric pollutant dispersion near sources is typically simulated by Gaussian models because of their efficient compromise between reasonable accuracy and manageable computational time. However, the standard Gaussian dispersion formula applies downwind of a source under advective conditions with a well-defined wind direction and cannot calculate air pollutant concentrations under calm conditions with fluctuating wind direction and/or upwind of the emission source. Attempts have been made to address atmospheric dispersion under such conditions. This work evaluates the performance of standard and modified Gaussian plume models using measurements of NO₂, PM₁₀, PM_2.5, five inorganic ions and seven metals conducted near a freeway in Grenoble, France, during 11–27 September 2011. The formulation for calm conditions significantly improves model performance. However, it appears that atmospheric dispersion due to vehicle-induced turbulence is still underestimated. Furthermore, model performance is poor for particulate species unless road dust resuspension by traffic is explicitly taken into account.     

Does emission control area policy reduce sulfur dioxides concentration in Shanghai?

As an important measure to abate ship-source air emissions, the establishment of Emission Control Area (ECA) has been adopted not only at international level, but also at national and regional level. However, there exists a research gap of employing econometric models to enrich the ECA policy evaluation research by testing the effectiveness of an ECA policy based on the empirical data. This paper focuses on the effectiveness of the ECA policy in shanghai port by adopting regression discontinuity (RD) approach. The RD design is considered as a wonderful substitution for the randomized control trial, which usually serves as a conventional and effective tool to address endogeneity. The causal effect of the ECA policy on the SO₂ concentration reduction can be detected by the RD approach. According to the estimated results, there is a discontinuity around the ECA policy cutoff point, and it is indicated that the SO₂ concentration in Shanghai decreased by at least 0.229 μg/m³ daily on average due to the implementation of the ECA policy. The positive role that the ECA policy plays in reducing SO₂ concentration in Shanghai is well demonstrated. This paper also puts forward an agenda for the future studies in the domain of the ECA policy evaluation.     

Onboard tuning of vessel seakeeping model parameters and sea state characteristics

It is essential for a safe and cost-efficient marine operation to improve the knowledge about the real-time onboard vessel conditions. This paper proposes a novel algorithm for simultaneous tuning of important vessel seakeeping model parameters and sea state characteristics based on onboard vessel motion measurements and available wave data. The proposed algorithm is fundamentally based on the unscented transformation and inspired by the scaled unscented Kalman filter, which is very computationally efficient for large dimensional and nonlinear problems. The algorithm is demonstrated by case studies based on numerical simulations, considering realistic sensor noises and wave data uncertainties. Both long-crested and short-crested wave conditions are considered in the case studies. The system state of the proposed tuning framework consists of a vessel state vector and a sea state vector. The tuning results reasonably approach the true values of the considered uncertain vessel parameters and sea state characteristics, with reduced uncertainties. The quantification of the system state uncertainties helps to close a critical gap towards achieving reliability-based marine operations.     

基于生产降本提效的船舶焊缝设计优化

为降低生产成本及提高施工效率,结合现有生产工艺的特点,通过研究入级船级社规范对焊缝设计的要求,考虑焊缝设计的经济性及可操作性,建立有效的焊缝设计优化工作机制,在详细设计阶段和生产设计阶段实现焊缝设计优化。优化的焊缝设计可充分利用现有资源,减少额外的生产投入,降低生产综合成本。将降低施焊难度及推广自动焊的设计理念融入焊缝设计中,在提高焊接效率的同时,产品焊缝的焊接质量特别是外观成形质量可得到保证,减少焊缝的补焊及打磨工作,提高产品的整体生产效率。