Mineral Resource Potential of Tajikistan: As an Important Component of Sustainable Development of the Silk Road Economic Belt

<正>The presence of rich natural resources and their rational use is the basis of dynamic and sustainable development of the state and society in general.The most effective integrated use of natural resources,which include mineral resources,predetermines the development of productive forces,the development of new areas,and the deployment of new industries,solves the problems of employment and contributes to economic growth of the     

南海海槽西部俯冲带日向滩地区俯冲九州—帕劳洋脊的成像

为了研究九州—帕劳洋脊(KPR)俯冲部分与同震破裂扩展、地震活动性和浅部甚低频地震的关系,对南海海槽西部俯冲带日向滩地区进行了三维地震层析成像。结合岸上和近海记录的主动源和被动源地震数据,成像了从该海槽轴附近到海岸地区的深部板块。我们的结果表明,俯冲的九州—帕劳洋脊为西北—东南向的低速带,向下扩展到约30km的深度。在这个深度,我们认为俯冲的九州—帕劳洋脊与板块分离,成为上覆大陆板块的底座。由于过去大地震的同震滑动地区没有延伸到俯冲的九州—帕劳洋脊,我们认为九州—帕劳洋脊可能阻碍了破裂的扩展。俯冲的九州—帕劳洋脊的内部在很宽的深度上分布有活跃的板内地震活动。浅部甚低频地震在俯冲的九州—帕劳洋脊上部连续发生,而在俯冲的九州—帕劳洋脊的东北部却是间歇地出现。因此,俯冲的九州—帕劳洋脊看来是这个地区同震破裂扩展和地震现象的一个重要因素。     

Seismic performance and global ductility of RC frames rehabilitated with retrofitted joints by CFRP laminates

This paper presents a new FRP retrofi tting scheme to strengthen local beam-column joints in reinforced concrete(RC) frames.The new retrofi tting scheme was proposed following a preliminary study of four different existing retrofi tting schemes.A numerical simulation was conducted to evaluate the effectiveness of FRP-strengthened reinforced concrete frames by bridging behavior of local joints to the whole structure.Local confi nement effects due to varying retrofi tting schemes in the joints were simulated in the frame model.The seismic behavior factor was used to evaluate the seismic performance of the strengthened RC frames.The results demonstrated that the new proposed retrofi tting scheme was robust and promising,and fi nite element analysis appropriately captured the strength and global ductility of the frame due to upgrading of the local joints.     

日本超低频地磁场测量及关于1998年Iwateken Nairiku Hokubu地震的近期研究成果

过去对Spitak,Loma Prieta和Guam地震的研究表明,大地震发生之前都会有相应的磁场异常。为了确认这一事实并详细研究超低频（ULF）现象,日本建立了一个超低频磁力仪的监测网络,开展了包括小型台阵在内的网络观测工作。文中同时介绍了在Matsukawa台站观测到的与Iwateken Nairiku Hokubu地震（震级M6．1级,发生在1998年9月3日,震源深度为10km）相关的地磁资料。分析了4．5年的资料,并对获得的结果进行了讨论。在地震前两个星期,水平和垂直分量之间的谱密度比的（极化）变化表现出异常情况。这是在相当长的数据分析中发现的一次独特的变化,它暗示了这种异常变化可能是大地震孕育期间的一个信号。     

亚马逊上空的烟雨云

人们观测到亚马逊森林大火的浓烟减小了云滴的大小,使降水产生延迟。因为清洁云在云底以上1．5km处就可以产生降水,而被污染的云中这个高度要抬升到5km以上．在火成云中就要到7km以上了。云中低层被抑止的降雨和气溶胶沉降使得水份和烟尘向高层输送,高层的云就像能卸下很多污染物的‘烟’。在抬高了的降雨启动高度上,由于相变触发的上升气流导致强的雷雨、大雹以及其他类似的云体突破云顶进入平流层,在平流层沉降的污染物和水汽的辐射效应对气候系统有深刻的影响。大气中激发的风暴在更高层释放出潜热,这就从本质上影响了区域和全球的环流系统。这些过程共同影响了水份循环、大气中污染物的分布以及大气环流的动力学特征。     

LONGITUDINAL DISPERSION IN SEDIMENT-LADEN OPEN CHANNEL FLOWS

Laboratory experiments on longitudinal dispersion in clear-water and sediment-laden open channel flows are reported. Data from these experiments and those available from previous studies indicate that the suspended sediment present in the flow affects the longitudinal dispersion process. The observed velocity distributions over the depth of sediment-laden flows indicate that the velocity deviates from the mean velocity more in sediment-laden flows than in clear-water flows. The velocity distributions over the cross section and secondary flow in the channel are also expected to be altereddue to the presence of suspended sediments in the flow. For these reasons, more dispersion is found in sediment-laden flows than in corresponding clear-water flows. A predictor for the dispersion coefficient in sediment-laden flows is proposed.     

Improved prediction of clay soil expansion using machine learning algorithms and meta-heuristic dichotomous ensemble classifiers

Soil swelling-related disaster is considered as one of the most devastating geo-hazards in modern history.Hence,proper determination of a soil’s ability to expand is very vital for achieving a secure and safe ground for infrastructures.Accordingly,this study has provided a novel and intelligent approach that enables an improved estimation of swelling by using kernelised machines(Bayesian linear regression(BLR)&bayes point machine(BPM)support vector machine(SVM)and deep-support vector machine(D-SVM));(multiple linear regressor(REG),logistic regressor(LR)and artificial neural network(ANN)),tree-based algorithms such as decision forest(RDF)&boosted trees(BDT).Also,and for the first time,meta-heuristic classifiers incorporating the techniques of voting(VE)and stacking(SE)were utilised.Different independent scenarios of explanatory features’combination that influence soil behaviour in swelling were investigated.Preliminary results indicated BLR as possessing the highest amount of deviation from the predictor variable(the actual swell-strain).REG and BLR performed slightly better than ANN while the meta-heuristic learners(VE and SE)produced the best overall performance(greatest R2 value of 0.94 and RMSE of 0.06%exhibited by VE).CEC,plasticity index and moisture content were the features considered to have the highest level of importance.Kernelized binary classifiers(SVM,D-SVM and BPM)gave better accuracy(average accuracy and recall rate of 0.93 and 0.60)compared to ANN,LR and RDF.Sensitivity-driven diagnostic test indicated that the meta-heuristic models’best performance occurred when ML training was conducted using k-fold validation technique.Finally,it is recommended that the concepts developed herein be deployed during the preliminary phases of a geotechnical or geological site characterisation by using the best performing meta-heuristic models via their background coding resource.     

Irrigation effects in the northern lake states: Wisconsin central sands revisited

Irrigated agriculture has expanded greatly in the water-rich U.S. northern lake states during the past half century. Source water there is usually obtained from glacial aquifers strongly connected to surface waters, so irrigation has a potential to locally decrease base flows in streams and water levels in aquifers, lakes, and wetlands. During the nascent phase of the irrigation expansion, water availability was explored in works of some fame in the Wisconsin central sands by Weeks et al. (1965) on the Little Plover River and Weeks and Stangland (1971) on "headwater area" streams and lakes. Four decades later, and after irrigation has grown to a dominant landscape presence, we revisited irrigation effects on central sands hydrology. Irrigation effects have been substantial, on average decreasing base flows by a third or more in many stream headwaters and diminishing water levels by more than a meter in places. This explains why some surface waters have become flow and stage impaired, sometimes to the point of drying, with attendant losses of aquatic ecosystems. Irrigation exerts its effects by increasing evapotranspiration by an estimated 45 to 142 mm/year compared with pre-irrigated land cover. We conclude that irrigation water availability in the northern lake states and other regions with strong groundwater-surface water connections is tied to concerns for surface water health, requiring a focus on managing the upper few meters of aquifers on which surface waters depend rather than the depletability of an aquifer.     

Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater

Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in the bioavailability of naturally occurring DOC might contribute to these observations. This hypothesis was examined by comparing nine different biochemical indicators of DOC bioavailability in groundwater sampled from these two systems. Concentrations of DOC, total hydrolysable neutral sugars (THNS), total hydrolysable amino acids (THAA), mole% glycine of THAA, initial bacterial cell counts, bacterial growth rates, and carbon dioxide production/consumption were greater in SC samples relative to CA samples. In contrast, the mole% glucose of THNS and the aromaticity (SUVA(254)) of DOC was greater in CA samples. Each of these indicator parameters were observed to change with depth in the SC system in a manner consistent with active biodegradation. These results are uniformly consistent with the hypothesis that the bioavailability of DOC is greater in SC relative to CA groundwater samples. This, in turn, suggests that the presence/absence of a hyperbolic DO-DOC relationship may be a qualitative indicator of relative DOC bioavailability in groundwater systems.     

Photochemical degradation of phenanthrene as a function of natural water variables modeling freshwater to marine environments

Photolysis rates of phenanthrene as a function of ionic strength (salinity), oxygen levels and humic acid concentrations were measured in aqueous solution over the range of conditions found in fresh to marine waters. Photolysis followed first order kinetics, with an estimated photodegradation half-life in sunlight in pure water of 10.3±0.7h, in the mid-range of published results. Photolysis rate constants decreased by a factor of 5 in solutions with humic acid concentrations from 0 to 10 mg C L(-1). This decrease could be modeled entirely based on competitive light absorption effects due to the added humics. No significant ionic strength or oxygen effects were observed, consistent with a direct photolysis mechanism. In the absence of significant solution medium effects, the photodegradation lifetime of phenanthrene will depend only on solar fluxes (i.e. temporal and seasonal changes in sunlight) and not vary with a freshwater to marine environment.