中国城市公共交通运营财税可持续框架体系研究

在国家"公交优先"发展战略背景下,系统分析了中国大部分城市所采取的公交执行票价远低于成本票价的低票价政策,指出这种政策使得公交票价的制定与成本脱钩且长期不变,导致城市公交企业运营成本急剧攀升、企业经营难以为继、城市公共财政补贴不可持续、低票价对于客流吸引力逐渐减弱等一系列问题,进而引发公共交通服务质量难以有效提升。为构建可持续的城市公共交通运营财税机制,从城市公共交通三个利益主体即乘客、企业、政府对于公共交通的相关诉求出发,系统性研究了公共交通服务质量、成本、票价、财政补贴间的相互关系,在此基础上研究构建了以服务质量为导向的成本、补贴、票价联动的框架体系,以便为我国城市公共交通运营财税的可持续发展提供支持。     

Instantaneous 2-D visualization of spray combustion and flame luminosity of GTL and GTL-biodiesel fuel blend under quiescent ambient conditions

An experimental study has been performed on spray combustion and two-dimensional soot concentration in diesel (ULSD), GTL and GTL-biodiesel fuel jets under high-pressure, high-temperature quiescent conditions. Instantaneous images of the fuel jets were obtained with a high-speed camera. It was confirmed that by blending GTL with 20% rapeseed biodiesel, certain fuel properties such as kinematic viscosity, density, surface tension, volatility, lower heating value and others may be designed and improved to be more like those of conventional diesel fuel but with considerable decrease in the amount of sulfur, PAH, cold filter plugging point, etc. The results showed that the spray tip penetration increased and the spray cone angle decreased when 20% biodiesel fuel was added to GTL fuel. Autoignition of the GTL-biodiesel blend occurred slightly earlier than that of diesel fuel. Experiments under high-pressure, high-temperature conditions showed that higher injection pressure induced a lower soot formation rate. The integrated flame luminosity, which serves as an indicator of soot concentration in the fuel jet, was slightly higher for the GTL-biodiesel blend than for pure GTL fuel due to the slightly higher sulfur content of pure biodiesel fuel.     

Simplified Technique for Predicting Offshore Pipeline Expansion

In this study, we propose a method for estimating the amount of expansion that occurs in subsea pipelines, which could be applied in the design of robust structures that transport oil and gas from offshore wells. We begin with a literature review and general discussion of existing estimation methods and terminologies with respect to subsea pipelines. Due to the effects of high pressure and high temperature, the production of fluid from offshore wells is typically caused by physical deformation of subsea structures, e.g., expansion and contraction during the transportation process. In severe cases, vertical and lateral buckling occurs, which causes a significant negative impact on structural safety, and which is related to on-bottom stability, free-span, structural collapse, and many other factors. In addition, these factors may affect the production rate with respect to flow assurance, wax, and hydration, to name a few. In this study, we developed a simple and efficient method for generating a reliable pipe expansion design in the early stage, which can lead to savings in both cost and computation time. As such, in this paper, we propose an applicable diagram, which we call the standard dimensionless ratio (SDR) versus virtual anchor length (L_A) diagram, that utilizes an efficient procedure for estimating subsea pipeline expansion based on applied reliable scenarios. With this user guideline, offshore pipeline structural designers can reliably determine the amount of subsea pipeline expansion and the obtained results will also be useful for the installation, design, and maintenance of the subsea pipeline.     

用于预报离岸管线膨胀的简化技术（英文）

In this study, we propose a method for estimating the amount of expansion that occurs in subsea pipelines, which could be applied in the design of robust structures that transport oil and gas from offshore wells. We begin with a literature review and general discussion of existing estimation methods and terminologies with respect to subsea pipelines. Due to the effects of high pressure and high temperature, the production of fluid from offshore wells is typically caused by physical deformation of subsea structures, e.g., expansion and contraction during the transportation process. In severe cases, vertical and lateral buckling occurs,which causes a significant negative impact on structural safety, and which is related to on-bottom stability, free-span, structural collapse, and many other factors. In addition, these factors may affect the production rate with respect to flow assurance, wax, and hydration, to name a few. In this study, we developed a simple and efficient method for generating a reliable pipe expansion design in the early stage, which can lead to savings in both cost and computation time. As such, in this paper, we propose an applicable diagram, which we call the standard dimensionless ratio(SDR) versus virtual anchor length(LA) diagram, that utilizes an efficient procedure for estimating subsea pipeline expansion based on applied reliable scenarios. With this user guideline,offshore pipeline structural designers can reliably determine the amount of subsea pipeline expansion and the obtained results will also be useful for the installation, design, and maintenance of the subsea pipeline.     

Regional Cooperation in the Post-South China Sea Arbitration Era: Potential Mechanism and Cooperative Areas

Although the South China arbitration has been settled recently, the final settlement of the South China Sea disputes remains in a political stalemate, at least for the near future. This article proposes a regional mechanism that could form the basis for further cooperation in the South China Sea. This mechanism is informed by political theory, facts on the grounds, and lessons learned from cooperative practices in other regions. As a way to work toward a resolution to the South China Sea's sovereignty disputes, and to improve on current cooperative practices, the objective of this mechanism is to involve all parties in the region and thus cover the entire South China Sea, including the disputed areas. Based on incentives for claimants, the level of political sensitivity, the advantage of involving all claimants and disputed areas, and past practices that have facilitated Taiwan's participation, it is the conclusion of this analysis that the conservation and management of marine living resources is the most promising area of cooperation. In addition, the practice in Western and Central Pacific Fisheries Commission is recommended as an appropriate model to be applied mutatis mutandis in the South China Sea.     

Flexible Overlap Technology for the Lining Trolley of Single-track Railway Tunnels北大核心CSCD

Falling-off of rock piece at tunnel arch and invert heave are the main potential safety problems affecting normal operation of the railway tunnel. The reasons causing falling-off of rock piece include squeezing by lining trol⁃ ley at construction joint, concrete cutting by cantilever end of water stop at construction joint, construction cold joint at arch, concrete quality deficiency and so on. To eliminate the falling-off of rock piece at tunnel arch caused by rig⁃ id overlap, modification of lining trolley and the flexible overlap technique combining tray with rubber gasket were adopted during the construction of Nuwashan tunnel on China-Laos railway, and the potential quality problem due to rigid overlap at construction joint of tunnel lining were effectively solved. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Distribution Laws of Earth Pressure Acting on a Shield Tunnel Based on Measured Data北大核心CSCD

The earth pressure acting on a shield tunnel is intrinsically related to synchronous grouting, the position of the shield machines, the rigidity of the segment and stratum, etc. Existing theoretical formulas and empirical methods couldn′t exactly reflect the actual state of the segment of a shield tunnel during construction due to the com⁃plexities mentioned above. Based on earth pressure data measured at 52 monitoring sections in 35 tunnels, the distri⁃bution laws and influential factors are analyzed. The results show that: 1) the earth pressure scope is 0 to 400 kPa for over 90% of the total samples, but is recommended to be 0.3 to 0.4 MPa for the empirical grouting pressure; 2)the earth pressure on the segment and the buried depth approximately have an exponential relationship, with the dif⁃ference between the max. earth pressure and the stable earth pressure decreasing with an increase of the buried depth; 3) the lateral pressure coefficient range is 0.5 to 2.3, which is partially out of the scope of recommended values(0.5 to 1.0) of surrounding rock of grade Ⅵ, so it is not appropriate to follow the recommended values in the specifi⁃cation; 4) the relationship of the earth pressure and the segment/soil stiffness ratio presents a quadratic function, and the most reasonable value for the stiffness ratio of the segment/soil is 1.0; and 5) there are four typical stages of the spatial distribution of earth pressure on a segment in clay stratum—the erection stage, the grouting influence stage,the consolidation contraction stage and the recovery stage, with the distribution of the circumferential earth pressure being asymmetrical. The distribution curves of the earth and water pressure in sand and soil layers are classified as a“weak decay pulse fluctuation”and“double hump,”respectively. After stabilizing, the circumferential earth pressure is notably in a symmetrical distribution, and the water pressure exhibits a light bulb shaped distribution (large at the lower part and small at the upper part). These conclusions provide a reference for studying the mechanism of earth pressure functions and perfecting the design of segments for shield tunnelling. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Application of BIM Technology in the Construction Management of a Metro Station北大核心CSCD

For the restricted construction site of a Beijing metro station surrounded by many important buildings and characterized by complex staggered underground pipelines, many construction difficulties and a high level of re-quired management, settlement monitoring is necessary for the sake of construction safety. A 3D model of the metro,a model of the specially shaped structure and models of many details of the metro were established using the BIM technique, allowing for: creation of a 3D presentation, extraction of construction quantities, construction conse-quence optimization, guidance of construction endeavors, simulation of the construction process, 4D dynamic con-struction management and 4D dynamic settlement monitoring. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Axial Response of a Compression Pile to Nearby Excavation北大核心CSCD

One of the major concern in the excavation in soft soil areas is the effect of soil movement on adjacent pile foundations. In this paper, three-dimensional finite element models are established to study the axial response of the adjacent pile foundations close to an excavation in soft soil. The results show that, due to the nearby excavation, the axial bearing capacity of a single pile under compression decreases about 13.6%, and considerable additional settlements of a single pile subjected to the working compression load are generated. Therefore, the characteristics of load transfer mechanism between pile shaft and around soil, as well as the tip soil reaction are investigated extensively, which demonstrates that, as expected, the nearby excavation leads to a reduction of ultimate soil friction resistance. Furtherly, the widely employed load transfer method for pile foundation is modified to consider the effects of nearby excavation, which can be employed to predict the axial response of an axially loaded pile foundation beside an excavation. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Effect of WO<Subscript>3</Subscript> nanoparticle loading on the microstructural,mechanical and corrosion resistance of Zn matrix/TiO<Subscript>2</Subscript>-WO<Subscript>3</Subscript> nanocomposite coatings for marine application

In this study, for marine application purposes, we evaluated the effect of process parameter and particle loading on the microstructure, mechanical reinforcement and corrosion resistance properties of a Zn-TiO₂-WO₃ nanocomposite produced via electrodeposition. We characterized the morphological properties of the composite coatings with a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive Spectrometer (EDS). We carried out mechanical examination using a Dura Scan hardness tester and a CERT UMT-2 multi-functional tribological tester. We evaluated the corrosion properties by linear polarization in 3.5% NaCl. The results show that the coatings exhibited good stability and the quantitative particle loading greatly enhanced the structural and morphological properties, hardness behavior and corrosion resistance of the coatings. We observed the precipitation of this alloy on steel is greatly influenced by the composite characteristics.