Hyperbola-Logistic模型预测列车引起的地面振动     

陈功奇  高广运  蒋建平 《岩土力学》2013,34(Z1):313-317

振动波在土介质中传播包含呈幂函数关系的几何衰减和呈指数函数关系的阻尼衰减两方面,针对振动波衰减的两种性质,提出Hyperbola-Logistic组合模型来描述振动波沿地表的传播。实例分析表明,Hyperbola-Logistic组合模型既可以用来预测地面位移、速度、加速度及振级的衰减,又可以预测高架桥段、路堤段及地下列车引起的地面振动。Hyperbola-Logistic组合模型具有较高的拟合精度,相关系数R均在0.95以上,决定系数R2均在0.90以上,它对振动衰减的拟合是可信的。通过对比,文中模型无论数值大小还是分布趋势,都能更好地预测列车引起的地面振动。  相似文献   

Tubeworm-associated communities at hydrothermal vents on the Juan de Fuca Ridge,northeast Pacific     

《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(5):611-629

Hydrothermal vent communities on a mid-ocean ridge crest can be separated by large distances on separate segments. Heat sources, vent character, fluid chemistry and current patterns may differ markedly. This study examines whether vent community characteristics on three of the four southern segments of the Juan de Fuca Ridge are significantly different. Taxonomic composition and relative abundance of the fauna over 1 mm in size associated with vestimentiferan tubeworm bushes are examined from fifty-one collections. Among nearly 350,000 specimens, 37 taxa are recognized, most to species level. Another 14 taxa are meiofaunal in size classification. Species richness and selected diversity indicators are highest on Axial Volcano while animal density within the bushes does not differ significantly. Cluster analysis does not group collections by location, year of collection or vent temperature; collection substratum—basalt or sulphide—may influence clustering. The architecture of the tubes of tubeworm bushes appears to affect the numbers of species present and the resultant clusters. The tightly interwoven, knotted Ridgeia piscesae tubes found on Axial host twice as many species as tubeworm bushes with a less complex structure. Four species dominate most of the collections: two gastropods (Lepetodrilus fucensis and Depressigyra globulus) and two polychaetes (Paralvinella pandorae and Amphisamytha galapagensis). Other vent species are low in abundance (<1% relative abundance) and patchy in distribution. Four collections with no visible flow had markedly different assemblages representing a transition state from vent assemblages to normal deep-sea fauna. There are differences in community structure among the segments, but the causes for these differences are unclear. Higher diversity on Axial Volcano may be supported by a greater time of sustained venting, a larger venting area, water circulation contained within the caldera, or flow conditions that sponsor growth of more complex habitat.  相似文献   

利用WAVEWATCH和SWAN嵌套计算珠江口附近海域的风浪场^*   总被引：3，自引：0，他引：3       下载免费PDF全文

张洪生  辜俊波  王海龙  王乐铭 《热带海洋学报》2013,32(1):8-17

基于CCMP(Cross Calibrated Multi-platform)卫星遥感海面风场数据,通过将WAVEWATCH和SWAN (Simulating WAves Nearshore)模型嵌套的方法,数值模拟了珠江口附近海域的风浪场。将总计10个月的数值模拟的有效波高、波周期和波向分别与相应的观测值进行了定量比较。结果说明,有效波高的平均绝对误差为15.4cm,分散系数SI为0.240,相关系数为0.925;波周期的平均绝对误差为1.9s,分散系数SI为0.433,相关系数为0.636;波向的平均绝对误差为23.9°。计算的波高和波向与观测结果的变化趋势相吻合。由于第三代海浪模式本身的缺陷,导致所计算的波周期偏小。总体说来,本文所采用的数值模式能较好地模拟珠江口附近海域的风浪场。另外,还设计了6个算例以探讨采用不同的计算方法和风场对计算结果精度的影响。结果表明使用本文的数值方法和高精度的CCMP风场确实可以提高计算结果的精度。  相似文献   

海洋微生物在船舶用结构钢表面附着成膜过程及其腐蚀研究   总被引：1，自引：0，他引：1  

董耀华  贺中意  郭娜  刘涛  董丽华 《海洋学研究》2015,33(1):39-44

通过紫外分光光度计测定了海洋微生物需钠弧菌 Vibrio natriegens 的生长曲线,通过扫描电镜和原子力显微镜观测了该细菌在船舶用结构钢(DH32)钢样表面成膜过程及试样腐蚀形貌,探讨了生物膜的形成过程及其对材料表面腐蚀的影响。结果表明,生物膜的形成过程与微生物生命活动关系密切。根据对比暴露在菌液和无菌培养基中的试样表面形貌,发现细菌的附着及成膜过程的不均匀性,改变了DH32钢样表面的物理和化学状态。细菌附着区与周围形成的氧浓差电池,以及细菌新陈代谢主要产物对金属离子的络合,共同促进了试样局部腐蚀加速。  相似文献   

Experimental and numerical investigations on hydrodynamic and aerodynamic characteristics of the tunnel of planing trimaran     

《Applied Ocean Research》2017

The planing trimaran possesses distinctive hybrid hydrodynamic and aerodynamic performance due to the presence of tunnel. The research described in this paper was carried out based on the observation of wave characteristics of a planing trimaran model in towing tests, in which the resistance drops as soon as the wave surface separates from tunnel roof. In order to gain a deeper insight into the relationship between wave flow and forces in tunnel region, a comprehensive series of viscous CFD simulations considering free-surface and 2-DOF motion of the hull (heave and pitch) have been performed for the tested model at the volume based Froude numbers ranging from 3.16 to 5.87. The calculated results were validated by comparison with experimental data and showed good agreement. Numerical results of wave contours, longitudinal wave cuts and lifting force distributions at the calculated speeds were presented for the analysis of ventilation process in tunnel region and the corresponding variation of tunnel forces. It is found that, for the speeds higher than Froude number of 4.52, the aerodynamic forces provide major tunnel lift and mainly act on the straight section of the tunnel. And, therefore, numerical simulations of two modified models have also been performed for the analysis of influence of straight section length on the hydrodynamic and aerodynamic performance of planing trimaran.  相似文献   

System-based investigation on 4-DOF ship maneuvering with hydrodynamic derivatives determined by RANS simulation of captive model tests     

《Applied Ocean Research》2017

For the non-negligible roll-coupling effect on ship maneuvering motion, a system-based method is used to investigate 4-DOF ship maneuvering motion in calm water for the ONR tumblehome model. A 4-DOF MMG model is employed to describe ship maneuvering motion including surge, sway, roll, and yaw. Simulations of circular motion test, static drift and heel tests are performed by solving the Reynolds-averaged Navier-Stokes (RANS) equations, after a convergence study quantifying the necessary grid spacing and time step to resolve the flow field adequately. The local flow field is analyzed for the selected cases, and the global hydrodynamic forces acting on the ship model are compared with the available experiment data. Hydrodynamic derivatives relating to sway velocity, yaw rate, and heel angle are computed from the computed force/moment data using least square method, showing good agreement with those obtained from EFD data overall. In order to investigate further the validity of these derivatives, turning circle and zigzag tests are simulated by using the 4-DOF MMG model with these derivatives. The trajectories and the time histories of the kinematic variables show satisfactory agreement with the data of free-running model tests, indicating that the system-based method coupled with CFD simulation has promising capability to predict the 4-DOF ship maneuvering motion for the unconventional vessel.  相似文献   

Safety and CO2 emissions: Implications of using organic fluids in a ship’s waste heat recovery system     

《Marine Policy》2017

This paper considers the practical application of exhaust gas waste heat recovery from the main engines of merchant ships. A water-based Rankine Cycle is used as a baseline and this is compared with five organic Rankine cycle systems using benzene, heptane, hexamethyldisiloxane, toluene and R245fa. The thermodynamic model of the waste heat recovery system is described. This is then applied in a case study utilising an Aframax tanker. The case study allows the comparison of the different waste heat recovery systems in more realistic scenarios. The efficiency of the different systems is compared as well as their potential to reduce CO₂ emissions, ship impact, and economic viability are also discussed. The paper closes with consideration of the safety and regulatory issues associated with the use of organic fluids in the marine environment.  相似文献   

The development of ship registration policy in China: Response to flags of convenience     

《Marine Policy》2017

In order to expand registered fleet tonnage and strengthen ship management, China began to introduce a special tax-free ship registration (STFSR) policy in July 2007. However, more than eight years following its implementation, the policy ended in complete failure at the end of 2015. This paper comprehensively evaluates the main content and implementation process of the Chinese STFSR policy, analyzes the effects of the policy, and summarizes the concrete reasons for the policy's failure and lessons to be learnt. A new governance framework is being designed and future directions are being developed to explore how the government can implement a successful ship registry policy. This research is intended to provide new ideas and information to the Chinese shipping industry's policymakers and stakeholders in order to handle the “flagging out” problem, thereby mitigating the current adverse situation of ship flagging overseas while strengthening the management of ship operation.  相似文献   

Chinese women seafarers: A case study of the women cadets in Shanghai     

《Marine Policy》2017

In the maritime sector, seafaring has been predominantly a male industry. The industry had developed its own culture which denied or precluded women's participation. This paper draws on the data and analysis of the Gender, Empowerment and Multi-cultural Crew (GEM) Project, an international study aiming to examine seafarers’ welfare, focusing on gender issues arising from a multi-cultural crew environment in three countries: China, Nigeria and the UK. The main research findings, which relate to China, are reported under the headings of motivation, training, employment opportunities and barriers, and career prospects for women. The paper concludes with a discussion on an important new state policy concerning gender equality in university recruitment and with recommendations to move things forward.  相似文献   

A new mixing technique for solidifier and dredged fill in coastal area     

Wenhui Shi  Sanjay Nimbalkar  Wenbai Liu 《Marine Georesources & Geotechnology》2017,35(1):52-61

One of the major drawbacks of the conventional method of land reclamation, which involves mixing cement with the dredged soils at the disposal site, is the high cost associated with its manufacturing and transportation. In this study, a new solidified dredged fill (SDF) technique and a new additive are proposed and their practical applications are discussed. Unlike the conventional approach, the dredged marine soils were mixed with the solidifiers using a newly designed mixing technique prior to its transport to site, which would significantly reduce the cost of site machinery and effectively reclaim land with adequate engineering properties necessary for the construction of infrastructure. To evaluate the performance of the reclaimed land using the proposed technique, a series of laboratory and field tests (namely, static and dynamic cone penetration tests, and plate load tests) were conducted on grounds filled with and without solidified dredged marine soils, respectively. The results showed that the engineering behavior of the reclaimed land with dredged marine soils using SDF technique had significantly improved. The SDF technique combined with the newly designed mixing system improved the performance of ground and has thus proved to be both cost-effective and safe.  相似文献