Diurnal variation in relative photosynthetic performance of marestail (Hippuris vulgaris Linn.) Across a water temperature gradient using PAM fluorometry in Jiuzhaigou National Nature Reserve, Sichuan Province, China

This paper reports the first photosynthetic study of marestail in Jiuzhaigou. In this work, we used PAM fluorometry to examine photosynthetic rates of submerged and emerged marestail in three lakes. Three lakes were studied across a gradient of water temperature, with low water temperature conditions in Grass Lake and Arrow Bamboo Lake, and higher water temperature in Five Colored Lake. In the field, electron transport rates (ETR_max) were measured as rapid light curves (RLCs) by in situ yield measurements. Submerged and emerged marestail showed higher photosynthetic activity in Five Colored Lake compared to the other lakes, a response consistent with the adaptation of marestail in Five Colored Lake to high water temperature. The optimal temperature for photosynthesis of submerged marestail in Jiuzhaigou was about 12 °C. Nonphotochemical quenching (NPQ) of submerged and emerged marestail increased with increasing water temperature. Maximum quantum yield (F _v/F _m) of submerged marestail in Five Colored Lake showed full recovery at 1700 h due to higher NPQ. Further, the chlorophyll a for submerged marestail was the highest in Grass Lake and the lowest in Five Colored Lake. These results indicate that in different lakes the function of these aquatic plants is associated with a diversity of place-dependent environmental conditions, especially water temperature that leads to pronounced differences in the plant’s ecophysiological reactions.     

Characteristics of sand damages and dynamic environment along the Tuotuohe section of the Qinghai-Tibet Railway

Sand damages along the Qinghai-Tibet Railway occur frequently and have spread rapidly since it was completely opened to traffic in 2006. The goal of this study was to understand the effects of sand damages on the railway via meteorological data and in situ observation of wind-blown sand. We selected the Tuotuohe section of this railway as a typical research object, and we systematically investigated its characteristics of sand damages, drift potential, sand-driving wind rose, and their time variation. The direction of sand-drifting wind clearly varies with the season. In winter, the predominant wind blows from the west and lasts for three months, while in summer the frequency of northeasterly wind begins to increase and multi-directional winds also occurs in July. The drift potential in this area is 705.81 VU, which makes this a high-energy wind environment according to Fryberger’s definition. The directional variability (RDP/DP) is 0.84 and the resultant drift potential is 590.42 VU with a resultant direction of 89.1°.     

Robust coordinated motion control of an underwater vehicle-manipulator system with minimizing restoring moments

For autonomous manipulation in water, an underwater vehicle-manipulator system (UVMS) should be able to generate trajectori9es for the vehicle and manipulators and track the planned trajectories accurately. In this paper, for trajectory generation, we suggest a performance index for redundancy resolution. This index is designed to minimize the restoring moments of the UVMS during manipulation, and it is optimized without impeding the performance of a given task. As a result, the restoring moments of the UVMS are decreased, and control efforts are also reduced. For tracking control of the UVMS, a nonlinear H_∞ optimal control with disturbance observer is proposed. This control is robust against parameter uncertainties, external disturbances, and actuator nonlinearities. Numerical simulations are presented to demonstrate the performance of the proposed coordinated motion control of the UVMS. The results show that control inputs for tracking are reduced, and the UVMS can successfully track generated trajectories.     

单桩复合地基静载荷试验系统的设计与应用研究

复合地基是通过褥垫层的调整作用,充分发挥桩间土的承载作用,使桩土共同承担荷载的地基。基于复合地基的实际工况,设计了一种单桩复合地基静载荷试验系统,既体现了褥垫层的调整作用,又可测得复合地基中桩体、桩问土、复合地基的荷载与其相应的沉降,同时可得出复合地基受力过程中桩土荷载分配过程与桩土应力比,提示了复合地基工作机理。通过工程实例测试,探讨了复合地基的工作机制,为复合地基的科研、设计与检测提供了依据。     

Evidence for significant clockwise rotations of the Korean Peninsula during Cretaceous

In an effort to evaluate the Cretaceous magnetostratigraphy for the Korean Peninsula and to establish the tectonic coherence of its various elements, we collected paleomagnetic data from 121 samples from 20 sites within the Chilgok Formation (108.3–109.9 Ma) in the Gyeongsang Basin. Together with previously published data, we evaluate the results from a total of 163 sites in the basin.We combine our age model with results from recent stratigraphic, paleomagnetic and radiometric geochemical studies. In this study, we found that two distinct declination shifts decrease with younging direction, indicating two clockwise rotational events of the Korean Peninsula with respect to the Eurasia continent. The earlier event took place during 130–100 Ma (Phase I, newly termed “Goguryeo Disturbance”) and a later one during 80–50 Ma (Phase III, belonging to “Bulguksa Orogeny”). The mean rotation rate in the interval from 115.2 to 103.8 Ma (Phase I) is about 0.74°/Ma, while the rate from 90.9 to 79.8 Ma (Phase II) is 0.19°/Ma. Based on paleolatitude change during Phase I, we infer that the Korean Peninsula (eastern part of the Sino-Korea Block) migrated southward about 300 km after the complete amalgamation of the Sino-Korea Block into the Eurasian continent resulting in N–S compression within the Korean peninsula and Manchuria. Large-scale strike-slip faults (e.g., Tan-Lu Fault, Okcheon Boundary Fault) were probably rejuvenated in the Sino-Korea Block during Phase I.     

Chemical and Strontium Isotopic Compositions of the Hanjiang Basin Rivers in China: Anthropogenic Impacts and Chemical Weathering

The Hanjiang River, the largest tributaries of the Changjiang (Yangtze) River, is the water source area of the Middle Route of China’s South-to-North Water Transfer Project. The chemical and strontium isotopic compositions of the river waters are determined with the main purpose of understanding the contribution of chemical weathering processes and anthropogenic inputs on river solutes, as well as the associated CO₂ consumption in the carbonate-dominated basin. The major ion compositions of the Hanjiang River waters are characterized by the dominance of Ca²⁺ and HCO₃ ⁻, followed by Mg²⁺ and SO₄ ²⁻. The increase in TDS and major anions (Cl⁻, NO₃ ⁻, and SO₄ ²⁻) concentrations from upstream to downstream is ascribed to both extensive influences from agriculture and domestic activities over the Hanjiang basin. The chemical and Sr isotopic analyses indicate that three major weathering sources (dolomite, limestone, and silicates) contribute to the total dissolved loads. The contributions of the different end-members to the dissolved load are calculated with the mass balance approach. The calculated results show that the dissolved load is dominated by carbonates weathering, the contribution of which accounts for about 79.4% for the Hanjiang River. The silicate weathering and anthropogenic contributions are approximately 12.3 and 6.87%, respectively. The total TDS fluxes from chemical weathering calculated for the water source area (the upper Hanjiang basin) and the whole Hanjiang basin are approximately 3.8 × 10⁶ and 6.1 × 10⁶ ton/year, respectively. The total chemical weathering (carbonate and silicate) rate for the Hanjiang basin is approximately 38.5 ton/km²/year or 18.6 mm/k year, which is higher than global mean values. The fluxes of CO₂ consumption by carbonate and silicate weathering are estimated to be 56.4 × 10⁹ and 12.9 × 10⁹ mol/year, respectively.     

徐沛煤田晚古生代成煤环境与聚煤规律研究

根据已有研究成果及大量钻孔资料,运用沉积学、煤田地质学的基本理论和方法,分析了徐沛煤田晚古生代的成煤环境,并总结了其聚煤规律及控制因素。结果表明,石炭—二叠纪聚煤作用主要发生在海岸带的堡岛体系和过渡相中,由海岸带向两侧,聚煤条件逐渐变差;堡岛体系泥炭坪形成的煤层厚度小,结构单一;三角洲体系分流间湾泥炭坪和泛滥平原泥炭沼泽形成的煤层厚度大;煤层在垂向上由薄至厚,结构由简单至复杂,稳定性逐渐变差;平面上,自北而南含煤层数逐渐增多,含煤层位逐渐抬高,条带状富煤带有向南迁移趋势。     

Characteristics of winter mass balance of Glacier No.1 at the headwaters of the Urumqi River,Tianshan Mountains

This study analyzes the response of glacier to climate change during the past 49 years in Urumqi River source region, the Tianshan Mountains of China. The temporal and spatial variations of winter mass balance (bn-w) at different time scales were analyzed to identify their response to climate change during 1988–2006 (The observation of winter mass balance observation began in 1988) on the Glacier No.1 at the headwaters of the Urumqi River, Tianshan Mountains, China. The winter accumulation shows a significantly decreasing trend. The results show that the cumulative values on Glacier No.1 is 2,202 mm water equivalent during 1988–2006 and the mean values is 116 mm a⁻¹. Furthermore, the trend analysis of the winter mass balance indicates a rapid decrease since 1990, and the mean mass balance is only 79 mm a⁻¹ during 1997–2006. Winter mass balance correlates well negatively with the total evaporation from September to April (r = −0.68, α = 0.01), and positively with the total precipitation from September to April (r = 0.74, α = 0.01). However, winter mass balance shows a weak correlation with mean minimum air temperature during September to April (r = −0.35), and runoff on September (r = −0.13).     

Relocation effects of dredged marine sediments on mercury geochemistry: Venice lagoon,Italy

Understanding the biogeochemical process of Hg is critical in the overall evaluation of the ecological impacts resulting from the reuse of Hg-contaminated dredged sediment. Sediment banks (V1 and V2) were constructed with freshly dredged sediments from a navigational channel in Venice Lagoon, Italy, with the goal of clarifying potential differences in the biogeochemistry of Hg between the reused dredged sediments and those from surrounding sites (SS1 and S2). Toward this purpose, Hg and monomethylmercury (MMHg) concentrations, and Hg methylation rates (MMRs) in the surface 2.5 cm sediments were monitored, along with ammonium, iron, sulfate and sulfide concentrations in the pore waters of banks and surrounding sites from November 2005 to February 2007. Pore water analyses indicate that the bank sediments are characterized by lower levels of sulfate and iron, and by higher levels of ammonium and sulfide compared to the surrounding sediments. With respect to Hg speciation, the fractions of MMHg in total Hg (%MMHg/Hg) and the MMRs were significantly lower in the bank V1 compared to those in the reference site SS1, whereas the %MMHg/Hg and the MMRs were similar between V2 and S2. A negative correlation is found between the logarithm of the particle-water partition coefficient of Hg and the MMR, indicating that the reduced MMRs in V1 are caused by the limited concentrations of dissolved Hg. Organic matter appears to play a key role in the control of MMR via the control of Hg solubility.     

基于DTU的加速度强振动记录终端的设计

设计基于DTU的强振记录终端,采用SOC系列C8051F015型单片机对MEMS加速度计的输出信号进行A/D转换,监测待测体所经受的强振加速度值,并通过DTU内嵌的GPRS无线网络通讯方式将数据发送到远程数据中心.该系统具有体积小,安装与操作方便,免维护等特性.