旋挖钻机回油系统及补油系统的分析和应用

旋挖钻机的回油系统及补油系统在整车液压系统中具有重要作用,是影响整车液压油液的通畅循环和各执行元件的平稳起停的重要因素,进而影响着整车运动部件的和谐运转。因此,合理科学的设计回油系统及补油系统是旋挖钻机技术提升的重点。通过对液压油冷却系统中回油系统及补油系统管路的设计方式、存在的问题、改进措施及改进前后性能比较的详细阐述,进一步综合分析了回油及补油系统之间的相互作用。     

广义帕雷托分布在波浪极值推算中的应用

以CCMP风场(1988年1月~2010年12月)为驱动,本文采用第三代海浪数值模式SWAN对中国海海区进行风浪场的数值模拟,并利用浮标资料对驱动风场和计算有效波高进行验证。根据模拟的结果分别采用广义帕雷托分布(GPD)和常用的广义极值分布(GEV)拟合累积频率曲线并进行效果检验,进而分析和比较2种分布的优缺点,并运用广义帕雷托分布(GPD)模型进行重现期波要素的推算,分析GPD模型的应用前景。     

Numerical simulation of wave field in the South China Sea using WAVEWATCH III

Wave fi elds of the South China Sea(SCS) from 1976 to 2005 were simulated using WAVEWATCH III by inputting high-resolution reanalysis wind fi eld datasets assimilated from several meteorological data sources. Comparisons of wave heights between WAVEWATCH III and TOPEX/Poseidon altimeter and buoy data show a good agreement. Our results show seasonal variation of wave direction as follows: 1. During the summer monsoon(April–September), waves from south occur from April through September in the southern SCS region, which prevail taking about 40% of the time; 2. During the winter monsoon(December–March), waves from northeast prevail throughout the SCS for 56% of the period; 3. The dominant wave direction in SCS is NE. The seasonal variation of wave height H s in SCS shows that in spring, H s ≥1 m in the central SCS region and is less than 1 m in other areas. In summer, H s is higher than in spring. During September–November, infl uenced by tropical cyclones, H s is mostly higher than 1 m. East of Hainan Island, H s 2 m. In winter, H s reaches its maximum value infl uenced by the north-east monsoon, and heights over 2 m are found over a large part of SCS. Finally, we calculated the extreme wave parameters in SCS and found that the extreme wind speed and wave height for the 100-year return period for SCS peaked at 45 m/s and 19 m, respectively, SE of Hainan Island and decreased from north to south.     

乌苏里拟鲿的不可逆点、窒息点及其对5种常见渔药的敏感性研究

通过实验生态学方法,研究了乌苏里拟鲿(Pseudobagrus ussuriensis)的初次摄食率、不可逆点、窒息点以及对5种常见渔药的敏感性.结果表明:水温22～23℃条件下,乌苏里拟鲿第7日龄初次摄食率达到最高值100%,仔鱼不可逆点(PNR)发生在孵化后第13天;窒息点与水温呈正相关性性(R=0.9093,P<...     

穿山半岛北侧近岸"回流"现象的二维数值模拟

通过对穿山半岛北部海域定点潮流观测及表层海流漂流迹线跟踪资料的分析,螺头水道南侧的流场可分为3个流区:即主槽的主流区、靠近岸线的回流区及岬角之间的次生回流区,各流区的流场呈现不同特点.基于实测资料,采用正交曲线网格建立了二维潮流数值模型,对研究区的"回流"现象和"次生回流"现象进行了模拟,模拟结果显示:研究区流场模拟计...     

多维距离对流动人口回流意愿的影响及群体异质性

人口回流正成为中国人口流动的重要趋势,并将深刻影响中西部及沿海地区的发展前景。本文从地理学的“距离”视角切入,在传统人口迁移理论的基础上,将两个非经济因素的距离维度,即制度距离和文化距离引入人口回流研究,构建了多维距离影响流动人口回流意愿的理论框架,并运用全国层面的流动人口调查数据进行实证分析。结果发现：与理论预测一致,流入地与户籍地间的多维距离对流动人口的回流意愿具有显著的影响。经济距离抑制了流动人口的回流,而地理距离、制度距离和文化距离均对人口回流产生促进作用。在考虑了解释变量可能存在的测量误差后,这一发现依然稳健。此外,多维距离对回流意愿的影响因流动人口个体及所在城市特征的差异而不同。个体异质性方面,随着流动人口年龄的增长和文化水平的提高,经济距离对回流意愿的影响不断增强,而地理距离的影响则逐渐减弱。城市异质性方面,随着城市人口规模的增加,制度距离对回流意愿的促进作用不断减弱;城市经济水平的提高则弱化了地理距离对回流意愿的正向效应。     

ON THE FUTURE PROSPECTS OF METEOR DETECTIONS (INVITED REVIEW)

The successful application of modern observing techniques for Leonid storm observations show that meteor (shower) detections will have a bright future if the field will pursue difficult but important questions. How to forecast a satellite threatening meteor storm? What happens to the organic matter in meteors and can this be an important source of prebiotic molecules? What range of variations in composition and morphology exists among cometary grains and what does this tell us about the origin of the solar system? What long-period comets approach Earth orbit and can meteoroid streams provide early warning for giant impacts? What are the sources of interstellar and interplanetary grains? Just to mention a few. To answer these questions will need new technologies and facilities, some of which are being developed for other use. This may include NASA’s Stratospheric Observatory For Infrared and sub-millimeter Astronomy (SOFIA). In addition, big-science space missions can drive the field if meteor detections are an integral part. Special events, such as meteor outbursts and the “artificial meteor” from the reentry of sample return capsules from interplanetary space, can mobilize observing and theoretical efforts. These and other future opportunities are briefly discussed.     

Estimation of extreme marine hydrodynamic variables in western Laizhou Bay

Laizhou Bay and its adjacent waters are of great importance to China's marine oil and gas development. It is therefore crucial to estimate return-period values of marine environmental variables in this region to ensure the safety and success of maritime engineering and maritime exploration. In this study, we used numerical simulations to estimate extreme wave height, sea current velocity and sea-level height in western Laizhou Bay. The results show that the sea-level rise starts at the mouth of the bay, increases toward west/southwest, and reaches its maximum in the deepest basin of the bay. The 100-year return-period values of sea level rise can reach 3.4–4.0 m in the western bay. The elevation of the western part of the Qingdong Oil Field would remain above the sea surface during extreme low sea level, while the rest of the oil field would be 1.6–2.4 m below the sea surface. The return-period value of wave height is strongly affected by water depth; in fact, its spatial distribution is similar to the isobath's. The 100-year return-period values of effective wave height can be 6 m or higher in the central bay and be more than 1 m in the shallow water near shore. The 100-year return-period values of current velocity is about 1.2–1.8 m s-1 in the Qingdong Oil Field. These results provide scientific basis for ensuring construction safety and reducing construction cost.     

Poroelastic two‐phase material modeling: theoretical formulation and embedded finite element method implementation

This paper presents the formulation of FEMs for the numerical modeling of a poroelastic two‐phase (aggregates/mixture phase) solid. The displacement and pressure fields are decomposed, following the Enhanced Assumed Strain (EAS) method, into a regular part and an enhanced part. This leads to discontinuous strain and pressure gradient fields allowing to capture the jump in mechanical and hydrical properties passing through the interface between the aggregates and the mixture phase. All these enhanced fields are treated in the context of the embedded FEM through a local enhancement of the finite element interpolations as these jumps appear. The local character of these interpolations leads after a static condensation of the enhanced fields to a problem exhibiting the same structure as common poroelastic finite element models but incorporating now the mechanical and hydrical properties of a two‐phase solid. Copyright © 2015 John Wiley & Sons, Ltd.     

Recharge sources and hydrogeological effects of irrigation and an influent river identified by stable isotopes in the Motril‐Salobreña aquifer (Southern Spain)

Measurement of the stable isotopes oxygen‐18 and deuterium in water is an important tool to characterize aquifer recharge sources. In the driest areas of the Mediterranean, this application is of special interest due to the scarcity of water and the resulting common incidence of human influence on natural hydrological systems. The Motril‐Salobreña detrital aquifer (southern Spain) is a clear example of such an impact as inhabitants have designed irrigation systems and a dam was recently built across the course of the Guadalfeo River, which feeds the aquifer. The sampling of (river or ground) water has allowed the determination of stable isotope contents (oxygen‐18 and deuterium), both temporally and spatially, and the relative importance of the main recharge sources in certain sectors. In addition, we were able to infer seasonal trends and to improve existing knowledge of the main flow paths and the position of a seasonal groundwater divide. Data analysis shows evaporation plays a minor role (despite the high temperatures in the zone), scarce rainwater influence, and the overwhelming contribution of recharge from the Guadalfeo River and from the carbonate aquifer (Escalate aquifer) in contact with the Motril‐Salobreña aquifer. Irrigation return flow during the summer months comprises the main recharge due to the significant volumes of water that infiltrate. The construction of the dam will almost certainly entail great changes in the current dynamics of the hydrogeology of the Motril‐Salobreña aquifer; therefore, knowledge of its behaviour is crucial in order to carry out sustainable use of its groundwater resources. Copyright © 2011 John Wiley & Sons, Ltd.