基于“水-基”形成的道路工程建设工期的拟定研究

道路的行车空间形成于道路环境。从生命离不开水、有水就有可能有生命的角度讲,服务于社会生活、社会行为的道路工程建设,也是源起于水-基、回归于水-基的生活行为建设。道路工程建设工期就必须满足道路的行车空间和工程的水-基环境建设的需要。

Exploration of Water and Soil Conservation's Function in Construction of Eco-environment

Eco-environment lays foundation for human existence and development, and social and economy evolvement. Therefore, it is a fundamental principle to pro- tact and construct eco-environment and achieve sustainable development. With ur- ban development, and destruction on natural environment, however, the issue of water and soil losses has become a serious problem, affecting people＇s life and production. The research, therefore, explored the role of water and soil conservation in ecological civilization construction, including bomprehensive treatment of water storage and sand reduction, improving agricultural structure and advancing rural econ- omy, relieving the conflict between supply and demand of water resources, improv- ing eco-environment in mountainous regions and accelerating eco-construction.

Short Baseline Positioning with an Improved Time Reversal Technique in a Multi-path Channel

The existence of a multi-path channel under the water greatly decreases the accuracy of the short baseline positioning system.In this paper,the application of a time reversal mirror to the short baseline positioning system was investigated.The time reversal mirror technique allowed the acoustic signal to better focus in an unknown environment,which effectively reduced the expansion of multi-path acoustic signals as well as improved the signal focusing.The signal-to-noise ratio（SNR） of the time reversal operator greatly increased and could be obtained by ensonifying the water.The technique was less affected by the environment and therefore more applicable to a complex shallow water environment.Numerical simulations and pool experiments were used to demonstrate the efficiency of this technique.

Sacrificial Anode Stability and Polarization Potential Variation in a Ternary Al-xZn-xMg Alloy in a Seawater-Marine Environment

In this paper, the effects of zinc （Zn） and magnesium （Mg） addition on the performance of an aluminum-based sacrificial anode in seawater were investigated using a potential measurement method. Anodic efficiency, protection efficiency, and polarized potential were the parameters used. The percentages of Zn and Mg in the anodes were varied from 2% to 8% Zn and 1% to 4% Mg. The alloys produced were tested as sacrificial anodes for the protection of mild steel in seawater at room temperature. Current efficiency as high as 88.36% was obtained in alloys containing 6% Zn and 1% Mg. The polarization potentials obtained for the coupled （steel/Al-based alloys） are as given in the Pourbaix diagrams, with steel lying within the immunity region/cathodic region and the sacrificial anodes within the anodic region. The protection offered by the sacrificial anodes to the steel after the 7th and 8th week was measured and protection efficiency values as high as 99.66% and 99.47% were achieved for the A1-6%Zn-l%Mg cast anode. The microstructures of the cast anodes comprise of intermetallic structures of hexagonal Mg3Zn2 and body-centered cubic A12Mg3Zn3. These are probably responsible for the breakdown of the passive alumina film, thus enhancing the anode efficiency.

Main properties of ultra-high performance fiber reinforced cement composites under couple effect of load and environment

This study aims to reveal the mechanism that how the content of steel fibers and strength grades affect the macro performance of the ultra-high performance fiber reinforced cementitious composite （UHPFRCC） and to study the UHPFRCC durability under the combined effect of loads and environments. Three types of high and ultra-high performance fiber reinforced cement composites with different strength grades （100, 150, 200 MPa） and different steel fiber volume fractions （0%, 1%, 2%, 3%） are prepared. The main properties of mechanical performance and short-term durability are studied. A preloading frame is designed to apply a four- point load external flexural stress with a stress selection ratio of 0.5 for UHPFRCC150 specimens. The results show that the growth in strength grade with a proper content of steel fiber greatly increases the strength and toughness of the HPFRCC and the UHPFRCC while decreasing the dry-shrinkage ratio. For the loaded specimens, the existence of steel fiber can reduce the negative influence of tensile stress on the Cl- penetration resistance of the UHPFRCC in addition to improving its ability to resist the freeze-thaw damage.

Water Effect on Amine-Modification of Adsorbents for Separation of CO_2/N_2

The adsorption of CO2can be enhanced through loading amines on adsorbents,therefore,the separation of CO2from other gases is promoted.Water plays an important role in this process.Water increases both the adsorption amount of CO2and the separation coefficient with N2for all amines loaded.However,the effect of loading trialkylamines is not remarkable in the absence of water.The effect of loading dialkylamine does not depend on water,but the adsorbent cannot be regenerated at ambient temperature.In comparison,an adsorbent loading trialkylamine can be regenerated at ambient temperature even in the presence of water with fairly good stability.

Practice and adaptable conditions classification of aquifer-protective mining in longwall coalface for shallow seam with thin bedrock

A set of adaptable conditions classification of aquifer-protective mining in the Iongwall coalface for shallow coal seams with thin bedrock was put forward to deal with the conflict between water protection and high efficiency for the mining field in west China. This classification was suitable for shallow coal seams with different thickness and was beneficial to the local environmental protection. Using the 3-Universal Distinct Element Code （3DEC） numerical software, the height of the fractured zones for shallow coal seams with thin bedrock was calculated and analyzed, and its predicting formula was achieved. Meanwhile, according to the lithology and the weathering degree of the shallow coal seam the thickness of the protective layer was determined as 10 m and the overlying water body of loose water-bearing sand for shallow coal seams with thin bedrock was divided into three types, namely, weak, medium and strong. Based on these, the necessary bedrock thickness of the Iongwall coalface for shallow coal seams with thin bedrock was confined according to the different mining height and water yield nature of the overlying loose water-bearing sand. Combined with the present mining status, a set of new methods of adaptable conditions classification of aquifer-protective mining technology in the Iongwall coalface for shallow coal seams with thin bedrock was put forward.

Genotypic and environmental variation in cadmium, chromium, arsenic, nickel, and lead concentrations in rice grains

Genotypic and environmental variation in Cd, Cr, As, Ni and Pb concentrations of grains, and the relationships between these heavy metals and Fe, Zn were investigated using 9 rice genotypes grown in 6 locations for two successive years. Significant genotypic variation was detected in the five heavy metal concentrations in grains, indicating the possibility to reduce the concentration of these heavy metals in grains through breeding approach. The environmental effect varied with metal, with Pb and Ni having greater variation than the other three metals. There was significant genotype-environment (location) interaction of the concentrations of all five heavy metals in grains, suggesting the importance of cultivar choice in producing rice with low heavy metal concentrations in grains for a given location. Correlation analysis showed that Cd and As, Cr and Ni, and As and Pb con-centrations in rice grains were closely associated, and that Ni concentration in grains was negatively correlated with Zn concen-tration.

Application of Equilibrium Partitioning Approach to the Derivation of Sediment Quality Guidelines for Metals in Dianchi Lake

For the past 20 years, numerous studies have been carried out on the application of equilibrium partitioning approach （EqPA） for the derivation of sediment quality guidelines （SQGs）. However, for metals, few Equilibrium-partitioning- based numerical SQGs have been developed or are currently available because of the confounding factors mediating the bioavailability of metals. A study was conducted at Dianchi Lake, which is a heavily eutrophicated lake on the Yunnan- Guizhou Plateau, China with the focus on the measurement of partitioning coefficient （Kp） and SQGs derivation and normalization to acid volatile sulfide （AVS）, fine material, and organic carbon. Using new normalization methods, SQGs were formulated for seven metals including copper, zinc, lead, cadmium, chromium, mercury, and arsenic in Dianchi Lake. In Dianchi Lake sediments, the fine material contributed 25.4%-36.0% to the SQG values, with the largest contribution to the SQG value of mercury; AVS contributed 2.9%-75.0% to the SQG values, with the largest contribution to the SQG value of cadmium. This indicated that the fine material and the AVS were the most important controlling factors to the bioavailability of mercury and caximium, respectively. The contribution of total organic carbon （TOC） to the SQG values of copper and leaxi was 3.8% and 7.1%, respectively, indicating that at relatively lower concentrations, the contribution of TOC was not significant. In addition to normalization methods, appropriate procedures for the application of EqPA including sample collection, storage, and analysis are also essential to improve the reliability of SQGs. The normalized Dianchi Lake SQGs were higher than most of the empirically based SQGs developed in North America, but lower than Hong Kong interim SQGs except for cadmium and arsenic. The differences could be attributed to the approaches used for derivation of SQGs and the water quality criteria adopted and the differences in the physical and chemical characteristics of the sediments.

Genotypic variations in nitrogen use efficiency of rice cultivars at various levels of nitrogen under subtropical environment

Insufficient N supply is an important constraint to productivity of lowland rice. Studies on N nutrition of rice cultivars with different durations representing the north western part of Indo-Gangetic Plains are scanty. A field experiment was conducted during kharif seasons of 2006 and 2007 at PAU, Ludhiana to assess the differences in grain yield and N utilization of three popular rice cultivars at varying N doses. Significant differences among genotypes were observed in grain yield, N uptake, N use efficiency and N utilization efficiency. The cultivar PAU-201 was found to be superior among all the tested genotypes. Total N uptake and grain N uptake was highest in cultivar PAU-201 followed by cultivars PR-115 and PR-113. On an average, the response to applied N for grain yield was observed upto 90 kg N ha1. Grain yield increased significantly up to 90 kg N hal in cultivars PR-115 and PAU-201 and up to 120 kg N ha1 in PR-113. Apparent recovery efficiency （ARE） and Partial factor productivity （PFPN） of N was significantly reduced at higher level of N （150 kg N hal）. It was concluded that N uptake is predominant factor in grain yield formation and cultivars differ in NUE suggesting that it may be possible to develop cultivars that are efficient at low nutrient level or are capable of using N more efficiently when applied as fertilizer.

The consequences of genomic architecture on ecological speciation in postglacial fishes

The quest for the origin of species has entered the genomics era. Despite decades of evidence confirming the role of the environment in ecological speciation, an understanding of the genomics of ecological speciation is still in its infancy. In this review, we explore the role of genomic architecture in ecological speciation in postglacial fishes. Growing evidence for the num- ber, location, effect size, and interactions among the genes underlying population persistence, adaptive trait divergence, and re- productive isolation in these fishes reinforces the importance of considering genomic architecture in studies of ecological speci- ation. Additionally, these populations likely adapt to new freshwater environments by selection on standing genetic variation, as de novo mutations are unlikely under such recent divergence times. We hypothesize that modular genomic architectures in post- glacial fish taxa may be associated with the probability of population persistence. Empirical studies have confirmed the genic na- ture of ecological speciation, implicating surprisingly extensive linkage disequilibrium across the genome. An understanding of these genomic mosaics and how they contribute to reproductive barriers remains unclear, but migration rates and the strength of selection at these loci is predicted to influence the likelihood of population divergence. Altogether, understanding the role of ge- nomic architecture is an important component of speciation research and postglacial fishes continue to provide excellent organ- isms to test these questions, both from the perspective of variation in architectures among taxa, and with respect to the distinct environments they have colonized. However, more empirical tests of ecological speciation predictions are needed [Current Zoo- logy 59 （1）： 53-71, 2013].