盾构法施工单机核算管理模式的应用

近年来盾构机越来越多地应用于各种隧道工程中,其中地铁应用的数量最多,约占80%。现代盾构已演变成为一种高度智能化的大型工程机械装备,对其控制的好坏将直接影响到整个工程的施工成本和企业的经营效益,而通过单机核算降低机械成本是降低施工成本、提高企业效益的有效手段,因此推行盾构法施工单机核算显得尤为重要。文章结合地铁2222标施工项目,重点介绍了盾构法单机核算管理模式及其在施工中的应用。     

A hedonic test of the effects of the Alternative Motor Fuels Act

Under the Alternative Motor Fuels Act (AMFA), vehicles that run on ethanol, methanol, or natural gas get extra credits in the calculation of Corporate Average Fuel Economy (CAFE). This paper uses hedonic techniques to examine the effect of production of alternative-fuel vehicles (AFVs) on the implicit price of fuel economy. This study finds that, after AFVs came to market, the marginal value of fuel economy from companies producing them decreased. This finding suggests that manufacturers who produced AFVs were willing to offer a lower price for fuel economy, because automakers had an additional way to achieve fuel economy standards beyond improving the fuel efficiency of conventional cars. These findings bolster the argument that a major role of the AMFA credit for AFVs is to allow automakers to increase their production of fuel-inefficient vehicles.     

Key technologies of ship remote control system in inland waterways under ship-shore cooperation conditions北大核心CSCD

［Objective ］ To meet the requirements of remotely controlling ship in curved, narrow and crowded inland waterways, this paper proposes an approach that consists of CNN-based algorithms and knowledge based models under ship-shore cooperation conditions. ［Method］On the basis of analyzing the characteristics of ship-shore cooperation, the proposed approach realizes autonomous perception of the environment with visual simulation at the core and navigation decision-making control based on deep reinforcement learning, and finally constructs an artificial intelligence system composed of image deep learning processing, navigation situation cognition, route steady-state control and other functions. Remote control and short-time autonomous navigation of operating ships are realized under inland waterway conditions, and remote control of container ships and ferries is carried out. ［Results］The proposed approach is capable of replacing manual work by remote orders or independent decision-making, as well as realizing independent obstacle avoidance, with a consistent deviation of less than 20 meters. ［Conclusions］The developed prototype system carries out the remote control operation demonstration of the above ship types in such waterways as the Changhu Canal Shenzhou line and the Yangtze River, proving that a complete set of algorithms with a CNN and reinforcement learning at the core can independently extract key navigation information, construct obstacle avoidance and control awareness, and lay the foundation for inland river intelligent navigation systems. © 2022 Journal of Clinical Hepatology. All rights reserved.     

Hybrid process of fabricating high-quality micro wine-glass fused silica resonators

A new hybrid method, which combines improved glass-blown technology with wet etching, is reported to fabricate micro wine-glass resonators with high-quality fused silica. The optimum placement is compared to achieve the resonators with good shell shape. The typical shell diameter is about 4mm and its thickness covers from dozens to hundreds of micrometers. The etching rates in corrosion solutions with different ratios and at different thicknesses of hemispherical shells are studied. We also conclude how to precisely control the thickness. The corrosion solutions with different ratios of HF solution to NH₄F solution make the spherical shells rougher in different degrees. The best roughness is 0.581 nm in the 1: 8 ratio corrosion solution while the original roughness is 0.537 nm. This fact shows that the resonator remains atomically smooth surface. Based on the glassblowing spherical fused silica structure, the thickness of the resonator is effectively controlled by buffered oxide etch (BOE) technology according to the measured etching rate. The measured resonant frequency of the hemispherical shell at ambient pressure and room temperature is 1.75 kHz of rocking mode which is close to the simulated frequency. Using such a low-cost hybrid approach, we can fabricate high-quality microscale resonators in batch.     

两种跨平台航迹精度测评方法研究

跨平台航迹精度测评对多平台协同使用传感器航迹数据具有指导意义,论文介绍了相对于本平台距离/方位的测评方法(方法一)和空间距离精度的测评方法(方法二),从非线性坐标变换的角度分析了本平台位置对测评结果的影响,其中方法一的计算结果在两平台位置相差不大的情况下主要受被探测目标相对于这两个平台的方位角度差影响,方法二的计算结果则不受本平台位置的影响,因而后者更有意义。     

港口供电系统改进

目前港口供电系统存在体积大、结构设置不合理和不适应环境等问题,经研究提出了减小体积、优化系统配置、提高箱变安全性和环境适应性等相应对策,在研究的基础上设计了一种新型箱式变电站,解决了目前港口供电系统存在的不足.     

Simulation of mixed gas formation for a spray-wall complex guided LPG direct injection engine

To obtain an ultralean air-fuel ratio and to reduce engine-out NOX and HC emissions induced by the richer mixture near the spark plug, a spray and wall complex guided combustion system has been developed by utilizing the fuel characteristics of LPG. The new combustion system configuration is optimized by using a commercial CFD code, FIRE V2013, and the reliability of the system has been experimentally demonstrated by Plane Laser-Induced Fluorescence (PLIF). The mixture formation in the new combustion system under part load (2,000 rpm) is numerically simulated. With an injection timing of 40°CA BTDC, the LPG spray which is injected from two upper holes, reaches the ignition point, and the other part of the LPG spray which is injected from the bottom hole, is directed to the ignition point through the vertical vortices at the same time. At the ignition timing of about 20°CA BTDC, the two-part mixtures have been shown to form a stable and richer stratified mixture around the ignition point, and the maximum global air-fuel ratio reaches to 60: 1.     

Modelling,simulation and applications of longitudinal train dynamics

ABSTRACT

Significant developments in longitudinal train simulation and an overview of the approaches to train models and modelling vehicle force inputs are firstly presented. The most important modelling task, that of the wagon connection, consisting of energy absorption devices such as draft gears and buffers, draw gear stiffness, coupler slack and structural stiffness is then presented. Detailed attention is given to the modelling approaches for friction wedge damped and polymer draft gears. A significant issue in longitudinal train dynamics is the modelling and calculation of the input forces – the co-dimensional problem. The need to push traction performances higher has led to research and improvement in the accuracy of traction modelling which is discussed. A co-simulation method that combines longitudinal train simulation, locomotive traction control and locomotive vehicle dynamics is presented. The modelling of other forces, braking propulsion resistance, curve drag and grade forces are also discussed. As extensions to conventional longitudinal train dynamics, lateral forces and coupler impacts are examined in regards to interaction with wagon lateral and vertical dynamics. Various applications of longitudinal train dynamics are then presented. As an alternative to the tradition single wagon mass approach to longitudinal train dynamics, an example incorporating fully detailed wagon dynamics is presented for a crash analysis problem. Further applications of starting traction, air braking, distributed power, energy analysis and tippler operation are also presented.     

The Kalker book of tables for non-Hertzian contact of wheel and rail

A new regularisation of non-elliptical contact patches has been introduced, which enables building the look-up table called by us the Kalker book of tables for non-Hertzian contact (KBTNH), which is a fast creep force generator that can be used by multibody dynamics system simulation programs. The non-elliptical contact patch is regularised by a simple double-elliptical contact region (SDEC). The SDEC region is especially suitable for regularisation of contact patches obtained with approximate non-Hertzian methods for solving the normal contact problem of wheel and rail. The new regularisation is suitable for wheels and rails with any profiles, including worn profiles.

The paper describes the new procedure of regularisation of the non-elliptical contact patch, the structure of the Kalker book of tables, and parameterisation of the independent variables of the tables and creep forces.

A moderate volume Kalker book of tables for SDEC region suitable for simulation of modern running gears has been computed in co-simulation of Matlab and program CONTACT.

To access the creep forces of the Kalker book of tables, the linear interpolation has been applied.

The creep forces obtained from KBTNH have been compared to those obtained by program CONTACT and FASTSIM algorithm. FASTSIM has been applied on both the contact ellipse and the SDEC contact patch. The comparison shows that KBTNH is in good agreement with CONTACT for a wide range of creepage condition and shapes of the contact patch, whereas the use of FASTSIM on the elliptical patch and SDEC may lead to significant deviations from the reference CONTACT solutions.

The computational cost of calling creep forces from KBTNH has been estimated by comparing CPU time of FASTSIM and KBTNH. The KBTNH is 7.8–51 times faster than FASTSIM working on 36–256 discretisation elements, respectively.

In the example of application, the KBTNH has been applied for curving simulations and results compared with those obtained with the creep force generator employing the elliptical regularisation. The results significantly differ, especially in predicted creepages, because the elliptical regularisation neglects generation of the longitudinal creep force by spin creepage.     

小型直喷式柴油机燃用生物质能燃料的性能研究

文章主要研究了生物质能混合燃料在柴油机上的应用,通过在一台小型直喷式柴油机上进行不同组分柴油-生物柴油-乙醇混合燃料的燃烧、油耗和排放性能对比试验,分析了乙醇含量的改变对混合燃料的发动机燃烧压力、滞燃期、放热规律、比油耗和排放的影响．