GENERATION AND ACCUMULATION OF QUATERNARY SHALLOW GAS IN EASTERN QAIDAM BASIN, NW CHINA

This study presents an overview on the geological setting and geochemical characteristics of Pleistocene shallow gas accumulations in eastern Qaidam Basin, NW China. Five largest gas accumulations discovered in this region have a combined enclosure area of about 87 km2 and {7.9} trillion cubic feet (tcf) of proven plus controlled gas reserves. The dominance of methane ({>99.9%}) and the {δ{}{13}C} and δD values of methane ({-68.51‰} to {-65.00‰} and {-227.55‰} to {-221.94‰}, respectively) suggest that these gases are biogenic, derived from the degradation of sedimentary organic matter by methanogens under relatively low temperatures (<75℃). A sufficient supply and adequate preservation of organic matter in the Pleistocene sediments is made possible by the lake basin’s high altitude (2600-3000 m), high water salinity (>15%) and strong stratification. The deposition and extensive lateral occurrence of shore and shallow lake sands/silts in beach sand sheets and small sand bars provided excellent reservoirs for the biogenic gas generated from adjacent rocks. Effective but dynamic gas seals were provided by such factors as intermittent vertical variations in the sediment lithologies, hydraulic trapping due to mudstone water saturation, the hydrocarbon gradient created as a result of gas generation from potential caprocks, and the presence of a regional caprock consisting of 400-800-m-thick mudstones and evaporites. It appears that the most favorable traps for large gas accumulations occur on structural slopes near the major gas kitchen, and the prolific gas pools are often those large gentle anticlines with little faulting complication.

Assessment of Groundwater Source of Piedmont Plain Area of China Northwest Arid Region Based On Numerical Modeling

After the middle of 1960s,along with the appearance and extensive utilization of computer featured in large capacity and rapid speed,numerical method(mainly include finite difference method and finite

Research on nonlinear characteristics of strata collapse because of the multi-frequency mining

Based on the complexity of mine stratum and coupling of the multi-frequency for the damage of mine stratum,using the method of on-site inspection and mathematical statistics,the regulation and nonlinear characteristics of strata collapse in mine stratum's multi-frequency mining were put forward and systemically studied.Study result shows that the influence of multi-frequency mining in mine stratum has the feature of multi-frequency incontinuity,multi-characteristic and multi-type nonlinear collapse,strata collapse activa- tion turned worse,presenting an accumulation effect of multi-frequency mining for the strata damage.With the example of multi-frequency mining in the mine,the real characte- ristics of strata collapse by multi-frequency mining and nonlinear characteristics of accu- mulative response damage were analyzed.Research achievements about the surface re- cover and controlling of strata collapse by the multi-frequency mining have instruction meaning.

Research of Mining STATCOM Based on Hybrid Multilevel H-bridge Inverter

The paper presents a new STATCOM system based on H-bridge inverter. It can be used in mine power network. It has been commonly verified for the positive effects of SVG on the reactive power compensation and voltage fluctuation suppression. This paper focuses on a generalized structure of multilevel power converter where individual voltage sources are not necessarily the same. The cascade H-bridge consists of two cells, high-voltage cell and low-voltage cell. The high-voltage cell is responsible for voltage lifting, while the low-voltage cell is responsible for PWM modulation. If two cells are cascaded with DC voltages in a ratio of 2:1, the single-phase output voltage can reach 7 levels. Increasing voltage levels of output waveform can bring up AC current quality, optimize harmonic spectrum and enhance converter efficiency. The hybrid multilevel is characterized by per-phase series connection of a high-voltage H-bridge converter and a low-voltage H-bridge converter. Due to the different capacitor voltage, it is a key problem as to how to maintain the capacitor’s voltage at a reference level. Independent DC source can effectively ensure the DC voltage. Through the reactive power compensation technology, the three-phase voltage and current can remain at the same phase.

Effects of Coal Rank and High Organic Sulfur on the Structure and Optical Properties of Coal-based Graphene Quantum Dots

Coal-based graphene quantum dots(GQDs) were successfully produced via a one-step chemical synthesis from six different coal ranks, from which two superhigh organic sulfur(SHOS) coals were selected as natural S-doped carbon sources for the preparation of S-doped GQDs. The effects of coal properties on coal-based GQDs were analyzed by means of high-resolution transmission electron microscopy(HRTEM), X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, X-ray photoelectron spectroscopy(XPS), ultraviolet-visible(UV-Vis) absorption spectroscopy, and fluorescence emission spectra. It was shown that all coal samples can be used to prepare GQDs, which emit bluegreen and blue fluorescence under ultraviolet light. Anthracite-based GQDs have a hexagonal crystal structure without defects, the largest size, and densely arranged carbon rings in their lamellae; the highrank bituminous coal-based GQDs are relatively reduced in size, with their hexagonal crystal structure being only faintly visible; the low-rank bituminous coal-based GQDs are the smallest, with sparse lattice fringes and visible internal defects. As the metamorphism of raw coals increases, the yield decreases and the fluorescence quantum yield(QY) initially increases and then decreases. Additionally, the surface of GQDs that were prepared using high-rank SHOS coal(high-rank bituminous coal) preserves rich sulfur content even after strong oxidation, which effectively adjusts the bandgap and improves the fluorescence QY. Thus, high-rank bituminous coal with SHOS content can be used as a natural S-doped carbon source to prepare S-doped GQDs, extending the clean utilization of low-grade coal.

An Efficient and Stable Ionic Liquid System for Synthesis of Ethylene Glycol via Hydrolysis of Ethylene Carbonate

An ionic liquid system of [Bmim]X/[Bmim]OH(X Cl,BF4,and PF6,) was developed for the hydroly-sis of ethylene carbonate to ethylene glycol. The important parameters,such as the variety of ionic liquids,molar ratio of [Bmim]X to [Bmim]OH,amount of ionic liquid,molar ratio of water to ethylene carbonate,reaction tem-perature,pressure and reaction time,were investigated systematically. Excellent yield(>93%) and high selectivity(99.5%) of ethylene glycol were achieved. Under the optimum reaction conditions,the ionic liquid system could be reused at least five times and the selectivity of ethylene glycol remained higher than 99.5%.

Full-field mapping of internal strain distribution in red sandstone specimen under compression using digital volumetric speckle photography and X-ray computed tomography

It is always desirable to know the interior deformation pattern when a rock is subjected to mechanical load.Few experimental techniques exist that can represent fullfi eld three-dimensional(3D)strain distribution inside a rock specimen.And yet it is crucial that this information is available for fully understanding the failure mechanism of rocks or other geomaterials.In this study,by using the newly developed digital volumetric speckle photography(DVSP)technique in conjunction with X-ray computed tomography(CT)and taking advantage of natural 3D speckles formed inside the rock due to material impurities and voids,we can probe the interior of a rock to map its deformation pattern under load and shed light on its failure mechanism.We apply this technique to the analysis of a red sandstone specimen under increasing uniaxial compressive load applied incrementally.The fullfi eld 3D displacement fi elds are obtained in the specimen as a function of the load,from which both the volumetric and the deviatoric strain fi elds are calculated.Strain localization zones which lead to the eventual failure of the rock are identi fi ed.The results indicate that both shear and tension are contributing factors to the failure mechanism.

Global sensitivity analysis of the AquaCrop model for winter wheat under different water treatments based on the extended Fourier amplitude sensitivity test

Sensitivity analysis(SA) is an effective tool for studying crop models;it is an important link in model localization and plays an important role in crop model calibration and application.The objectives were to(i) determine influential and non-influential parameters with respect to above ground biomass(AGB),canopy cover(CC),and grain yield of winter wheat in the Beijing area based on the Aqua Crop model under different water treatments(rainfall,normal irrigation,and over-irrigation);and(ii) generate an Aqua Crop model that can be used in the Beijing area by setting non-influential parameters to fixed values and adjusting influential parameters according to the SA results.In this study,field experiments were conducted during the 2012–2013,2013–2014,and 2014–2015 winter wheat growing seasons at the National Precision Agriculture Demonstration Research Base in Beijing,China.The extended Fourier amplitude sensitivity test(EFAST) method was used to perform SA of the Aqua Crop model using 42 crop parameters,in order to verify the SA results,data from the 2013–2014 growing season were used to calibrate the Aqua Crop model,and data from 2012–2013 and 2014–2015 growing seasons were validated.For AGB and yield of winter wheat,the total order sensitivity analysis had more sensitive parameters than the first order sensitivity analysis.For the AGB time-series,parameter sensitivity was changed under different water treatments;in comparison with the non-stressful conditions(normal irrigation and over-irrigation),there were more sensitive parameters under water stress(rainfall),while root development parameters were more sensitive.For CC with time-series and yield,there were more sensitive parameters under water stress than under no water stress.Two parameters sets were selected to calibrate the Aqua Crop model,one group of parameters were under water stress,and the others were under no water stress,there were two more sensitive parameters(growing degree-days(GDD) from sowing to the maximum rooting depth(root) and the maximum effective rooting depth(rtx)) under water stress than under no water stress.The results showed that there was higher accuracy under water stress than under no water stress.This study provides guidelines for Aqua Cropmodel calibration and application in Beijing,China,as well providing guidance to simplify the AquaC rop model and improve its precision,especially when many parameters are used.

Advanced oxidation technology for H_2S odor gas using non-thermal plasma

Non-thermal plasma technology is a new type of odor treatment processing.We deal with H_2Sfrom waste gas emission using non-thermal plasma generated by dielectric barrier discharge.On the basis of two criteria,removal efficiency and absolute removal amount,we deeply investigate the changes in electrical parameters and process parameters,and the reaction process of the influence of ozone on H_2S gas removal.The experimental results show that H_2S removal efficiency is proportional to the voltage,frequency,power,residence time and energy efficiency,while it is inversely proportional to the initial concentration of H_2S gas,and ozone concentration.This study lays the foundations of non-thermal plasma technology for further commercial application.

Water-conducting Characteristics and Micro-dynamic Self-adjusting Behavior of Polyacrylamide/Montinorillonite Coating

A water-conducting polyacrylamide/montmorillonite coating was prepared by solutionblending.The coating was coated on fiber and then composited with polymer to form a composite film material that used for water saving and tree planting in arid and desert regions.The coating's water-conducting characteristics and dynamic self-adjusting behavior were investigated by Fourier transform infrared(FTIR)spectroscopy,thermal analysis(TG-DTA),and environmental scanning electron microscopy(ESEM).The results showed that the coating's water-conducting rate increased but water-retention capacity weakened with increasing montmorillonite content.The water-loss rate was positively related to temperature and negatively related to soil moisture.Water potential greatly influenced the water-conducting rate of the coating during its water conduction process.When the coating was at a low water potential,the montmorillonite particles interconnected and water was conducted quickly via montmorillonite layers,whereas when the coating was at a high potential,the montmorillonite particles disconnected and water was conducted slowly via the swelled polyacrylamide net structure.The rate can be regulated by changing the proportion of polyacrylamide and montmorillonite to guarantee a reasonable water supply for trees and make trees easier to survive.Thus,the survival rate of trees can be increased and the use of water resources can be significantly reduced.

Improved Method and Application of EMD Endpoint Continuation Processing for Blasting Vibration Signals

In order to deal with the non-stationary characteristics of blasting vibration signals and the end issue in the empirical mode decomposition(EMD), an improved endpoint continuation method is proposed. First, the linear continuation method of extreme points is used to determine the extremum of the signal endpoint fast. Secondly, the extreme points of transition section outside the signal ends are obtained by a mirror continuation method of extreme points, and then the envelope and continuation curve of the transition section of the signal are constructed. Lastly, the sinusoid of the stationary section outside the signal is constructed to achieve the continuation curve from the transition section to the stationary section. Based on the "singular extreme points" phenomenon of blasting vibration signal, the negative maxima and positive minimum are eliminated, then the maximum and minimum are guaranteed to appear at intervals. Thus,the number of iterations is reduced and the instability of EMD decomposition is improved. The calculation formula of amplitude, cycle and initial phase are given for the transition section and stationary section outside the signal. The endpoint processing effect of the simulated signal and the measured blasting vibration signal show that the improved endpoint continuation method can suppress the signal endpoint effect well.

Research on hydraulic slotting technology controlling coal-gas outbursts

Measured to control serious coal-gas outburst in coal seam were analyzed by theory and experimented in test site.A new technique to distress the coal-bed and drain methane,called hydraulic slotting,was described in detail,and the mechanism of hydrau- lic slotting was put forward and analyzed.The characteristic parameter of hydraulic slotting was given in Jiaozuo mining area and the characteristic of validity,adaptability and secu- rity was evaluated.The results show that the stress surrounding the strata and the gas in coal seam is released efficiently and thoroughly while new techniques are taken,as slot- ting at heading face by high pressure large diameter jet.The resistance to coal and gas outbursts is increased dramatically once the area of slotting is increased to a certain size. In the process of driving 2 000 m tunnel by hydraulic slotting excavation,coal and gas outburst never occurre.The technique could be used to prevent and control potential coal-gas outburst in the proceeding of tunnel driving,and the speed tunneling could be as high as more than 2 times.