一类Block型李代数的2-局部导子

对一类Block型李代数的2-局部导子进行研究,证明了这类Block型李代数的2-局部导子都是导子.

Cause analysis and solutions of water blocking damage in cracked/non-cracked tight sandstone gas reservoirs

After hydraulic fracturing treatment,a reduction in permeability caused by the invasion of fracturing fluids is an inevitable problem,which is called water blocking damage.Therefore,it is important to mitigate and eliminate water blocking damage to improve the flow capacities of formation fluids and flowback rates of the fracturing fluid.However,the steady-state core flow method cannot quickly and accurately evaluate the effects of chemical agents in enhancing the fluid flow capacities in tight reservoirs.This paper introduces a time-saving and accurate method,pressure transmission test(PTT),which can quickly and quantitatively evaluate the liquid flow capacities and gas-drive flowback rates of a new nanoemulsion.Furthermore,scanning electron microscopy(SEM)was used to analyze the damage mechanism of different fluids and the adsorption of chemical agents on the rock surface.Parallel core flow experiments were used to evaluate the effects of the nanoemulsion on enhancing flowback rates in heterogeneous tight reservoirs.Experimental results show that the water blocking damage mechanisms differ in matrices and fractures.The main channels for gas channeling are fractures in cracked cores and pores in non-cracked cores.Cracked cores suffer less damage from water blocking than non-cracked cores,but have a lower potential to reduce water saturation.The PTT and SEM results show that the permeability reduction in tight sandstones caused by invasion of external fluids can be list as guar gum fracturing fluid>slickwater>brine.Parallel core flow experiments show that for low-permeability heterogenous s andstone reservoirs with a certain permeability ratio,the nanoemulsion can not only reduce reverse gas channeling degree,but also increase the flowback rate of the fracturing fluid.The nanoemulsion system provides a new solution to mitigate and eliminate water blocking damage caused by fracturing fluids in tight sandstone gas reservoirs.

Temperature-Triggered Hardware Trojan Based Algebraic Fault Analysis of SKINNY-64-64 Lightweight Block Cipher

SKINNY-64-64 is a lightweight block cipher with a 64-bit block length and key length,and it is mainly used on the Internet of Things(IoT).Currently,faults can be injected into cryptographic devices by attackers in a variety of ways,but it is still difficult to achieve a precisely located fault attacks at a low cost,whereas a Hardware Trojan(HT)can realize this.Temperature,as a physical quantity incidental to the operation of a cryptographic device,is easily overlooked.In this paper,a temperature-triggered HT(THT)is designed,which,when activated,causes a specific bit of the intermediate state of the SKINNY-64-64 to be flipped.Further,in this paper,a THT-based algebraic fault analysis(THT-AFA)method is proposed.To demonstrate the effectiveness of the method,experiments on algebraic fault analysis(AFA)and THT-AFA have been carried out on SKINNY-64-64.In the THT-AFA for SKINNY-64-64,it is only required to activate the THT 3 times to obtain the master key with a 100%success rate,and the average time for the attack is 64.57 s.However,when performing AFA on this cipher,we provide a relation-ship between the number of different faults and the residual entropy of the key.In comparison,our proposed THT-AFA method has better performance in terms of attack efficiency.To the best of our knowledge,this is the first HT attack on SKINNY-64-64.

基于水-岩相互作用的富水断层破碎带隧道突涌灾害演化特征

为研究开挖卸荷和水力荷载耦合作用下富水断层破碎带隧道突涌灾害演化特征,以沈白高铁西谷隧道工程为依托,考虑不同富水破碎带构造形式及地下水赋存特征,开展隧道突涌灾害演化过程研究。基于水-岩相互作用原理,建立三维离散元粘合块体-裂隙流耦合模型,明确不同地质构造特征下的隧道突涌灾害模式,分析破碎岩体裂隙扩展和地下水渗流的时空演化规律。研究结果有:引入黏合块体模型和裂隙流组合模型,建立了富水断层破碎带水岩相互作用力学模型,再现了富水破碎带隧道突涌灾害演化过程。不同富水破碎带构造形式引起的突涌灾变模式差异显著,且具有不同的触发条件和表现形式。断层破碎带倾角为45°时,破碎岩体沿掌子面下部溜塌涌入隧道,倾角为90°时,围岩向掌子面挤出,倾角为-45°时,表现为拱顶围岩垮塌。富水破碎带突涌灾害程度随着水头增大而加剧,其中倾角为-45°时,突涌灾害程度受水头高度的影响最显著,倾角为90°时,水头高度影响相对较弱,但突涌灾害程度最严重。

基于ASPP-SCBAM-DenseUnet的高分遥感影像水体提取研究

针对遥感影像水体提取研究存在细小水体和水体边缘等细节信息关注不足的情况,以及水体连通性较差的问题,文章提出基于改进的空洞空间金字塔池化和随机双注意力机制的密集连接U型网络(ASPP-SCBAM-DenseUnet)。文章首先利用Dense Block块组成Unet的编码器和解码器部分,并引入SCBAM注意力机制,减少噪声干扰,提高水体边界分割的准确性;其次,添加ASPP_SCBAM模块,设置不同的空洞率、扩大感受野,结合小型水体的浅层和深层特征,补偿采样过程造成的特征损失;最后,通过结合Dice系数和像素级二元交叉熵的联合损失函数来训练网络,有效地处理因小水体造成的不平衡数据集,这样不仅确保了分割的精度,还能够产生更加平滑和连续的分割边界,从而防止模型出现过拟合或者过度细化的现象。实验结果表明,ASPP-SCBAM-DenseUnet网络模型提取水体的像素准确率、召回率和F1分数分别为94.19%、94.29%和95.15%,加权交并比和均交并比分别为89.02%、88.63%,明显优于Unet、Linknet等语义分割网络,同时,减少了水体误分类和遗漏,优化了水体边缘细节,提高了对细小水体的识别和水体连通性。

基于GAT-BILSTM-Res的水质预测模型

针对水质数据在时间维度的依赖关系以及水质监测站点在空间维度的依赖关系,基于海河流域天津段实际监测的历史水质数据,设计了有效提取时空特征的方法,提出一种融合图注意力网络(GAT)、双向长短期记忆网络(Bi-LSTM)以及残差块(ResBlock)的时空水质预测模型(GAT-BILSTM-Res).该模型首先通过GAT捕获水质监测站点之间的拓扑关系,建立空间相关性模型;同时通过Bi-LSTM捕捉水质监测数据的动态变化,并对时间相关性进行建模;然后将时空特征融合,输入残差块;最后使用全连接层对预测结果进行输出.实验结果表明,相较于基线模型,该模型能够实现6.6%~25.2%的性能提升.

基于均值-方差相交的定价因子研究——兼论GMM中估计Block-Bootstrap模拟的区组选择

根据最优投资组合理论,本文证明可以采用均值-方差相交的方法确定模拟资产组合作为因素模型的定价因子。为了得到稳健的实证结论,文中对GMM估计的Wald统计量进行了Block-Bootstrap模拟,同时研究了模拟过程中区组(Block)长度的选择问题。实证结果表明,本文构造的大、中、小三个规模组合可以作为中国股市的定价因子;当区组长度选定时,GMM-Wald统计量的Block-Bootstrap模拟不会随着模拟次数的变化发生显著变化,但当区组长度超过10时,它与其它区组长度对应的模拟结果会有显著差异。

Pore network modeling of water block in low permeability reservoirs

A pore network model was used in this paper to investigate the factors, in particular, throat radius, wettability and initial water saturation, causing water block in low permeability reservoirs. A new term - ＇relative permeability number＇ （RPN） was firstly defined, and then used to describe the degree of water block. Imbibition process simulations show that the RPN drops in accordance with the extension of the averaged pore throat radius from 0.05 to 1.5 μm, and yet once beyond that point of 1.5 μm, the RPN reaches a higher value, indicating the existence of a critical pore throat radius where water block is the maximum. When the wettability of the samples changes from water-wet to weakly water-wet, weakly gas-wet, or gas（oil）-wet, the gas RPN increases consistently, but this consistency is disturbed by the RPN dropping for weakly water-wet samples for water saturations less than 0.4, which means weakly waterwet media are more easily water blocked than water-wet systems. In the situation where the initial water saturation exceeds 0.05, water block escalates along with an increase in initial water saturation.

Mechanisms of shale hydration and water block removal

Shale samples of Silurian Longmaxi Formation in the Changning area of the Sichuan Basin, SW China, were selected to carry out scanning electron microscopy, CT imaging, high-pressure mercury injection, low-temperature nitrogen adsorption and imbibition experiments to compare the hydration characteristics of montmorillonite and illite, analyze the main factors affecting the water block removal of shale, and reveal the mechanisms of pore structure evolution during shale hydration. The hydration characteristics of shale are closely related to the composition of clay minerals, the shale with high illite content is not susceptible to hydration and thus has limited room for pore structure improvement;the shale with high montmorillonite is susceptible to hydration expansion and thus has higher potential of pore structure improvement by stimulation;the shale with high illite content has stronger imbibition in the initial stage, but insufficient diffusion ability, and thus is likely to have water block;the shale with high montmorillonite content has weaker imbibition in the initial stage but better water diffusion, so water blocking in this kind of shale can be removed to some degree;the shale reservoir has an optimal hydration time, when it is best in physical properties, but hydration time too long would cause damage to the reservoir, and the shale with high illite content has a shorter optimal hydration time;inorganic cations can inhibit the hydration of clay minerals and have stronger inhibition to illite expansion, especially K^(+);for the reservoir with high content of montmorillonite, the cation content of fracturing fluid can be lowered to promote the shale hydration;fracturing fluid with high K^(+) content can be injected into reservoirs with high illite content to suppress hydration.

Three-dimensional hydrodynamic model of Xiamen waters

A semi-implicit and Eulerian - Lagrangian finite difference method for three-dimensionalshallow flow has been extended to a more complete system of equations incorporating second-moment turbulence closure model and transport equations of salinity and temperature. The simulation for flooding and drying of mudflats has been improved. The model is applied to Xiamen waters. Based on extensive survey data, water level elevation, temperature and salinity field along the eastern open boundary and at the Jiulong River inlets and runoffs are analyzed, specified and calibrated. The computed results show good agreement with the measured data, reproduce flooding, emergence of large and complex mudflat region.

Research on Hydraulic Block Scenarios in the Land Conservation Zone of the Headwaters Area of Jinshu Bay

[Objective] The aim was to study the hydraulic block scenarios in the water source land conservation zone in Jinshu Bay so as to ensure the water quality in the water sources in Jinshu Bay.[Method] By dint of one dimension water amount and water quality mode in the river net in Taihu,the water flow movement characteristics and pollutants transportation rules in the water sources areas in Jinshu Bay under five kinds of hydraulic block scenarios were compared and discussed.[Result] After demolishing the temporary soil dam in the water source conservation zone in Jinshu Bay,water amount and pollutants increased and water quality deteriorated.It was necessary to take certain hydraulic power to block and control the pollutants in the preservation area;after demolishing the dam,there was less water amount and pollutants.The water quality improved significantly.The hydraulic block facility in the preservation area and its surroundings were all releasing and not introducing;the one along the mouth of the river of Mentianji Gang,Jinshugang and Longtanggang were introducing and not releasing,which only restricted poor-quality water in Beijing-Hangzhou Canal and Huguang Canal flowing into the conservation zone.The water into the conservation zone was all from Gonghu.The water mobility within the conservation zone was good.The regional water quality improved to the largest scale.[Conclusion] Judging from the water flow movement characteristics and pollutants transportation rules in Jinshu Bay,the fifth proposal was more appropriate.

The diffusive fluxes of inorganic nitrogen across the intertidal sediment-water interface of the Changjiang Estuary in China

Ammonium and nitrate concentrations were analyzed in near-bottom water and pore water collected from ten stations of the intertidal flat of the Changjiang Estuary during April, July, November and February. The magnitudes of the benthic exchange fluxes were determined on the basis of concentration gradients of ammonium and nitrate at the near-bottom water and interstitial water interface in combination with calculations of a modified Fick＇ s first law. Ammonium fluxes varied from - 5.05 to 1.43 μg/（ cm^2·d） and were greatly regulated by the production of ammonium in surface sediments, while nitrate fluxes ranged from - 0. 38 to 1.36 μg/ （ cm^2·d） and were dominated by nitrate concentrations in the tidal water. It was found that ammonium was mainly released from sediments into water columns at most of stations whereas nitrate was mostly diffused from overlying waters to intertidal sediments. In total, 823.75 t/a ammonium-N was passed from intertidal sediments to water while about 521.90 t/a nitrate-N was removed from overlying waters to intertidal sediments. This suggests that intertidal sediments had the significant influence on modulating inorganic nitrogen in the tidal water.

Using irrigation intervals to optimize water-use efficiency and maize yield in Xinjiang,northwest China

Worldwide, scarce water resources and substantial food demands require efficient water use and high yield.This study investigated whether irrigation frequency can be used to adjust soil moisture to increase grain yield and water use efficiency(WUE) of high-yield maize under conditions of mulching and drip irrigation.A field experiment was conducted using three irrigation intervals in 2016: 6, 9, and 12 days(labeled D6, D9, and D12) and five irrigation intervals in 2017: 3, 6, 9, 12, and 15 days(D3, D6, D9, D12, and D15).In Xinjiang, an optimal irrigation quota is 540 mm for high-yield maize.The D3, D6, D9, D12, and D15 irrigation intervals gave grain yields of 19.7, 19.1–21.0, 18.8–20.0, 18.2–19.2, and 17.2 Mg ha^-1 and a WUE of 2.48, 2.53–2.80, 2.47–2.63, 2.34–2.45, and 2.08 kg m-3, respectively.Treatment D6 led to the highest soil water storage, but evapotranspiration and soil-water evaporation were lower than other treatments.These results show that irrigation interval D6 can help maintain a favorable soil-moisture environment in the upper-60-cm soil layer, reduce soilwater evaporation and evapotranspiration, and produce the highest yield and WUE.In this arid region and in other regions with similar soil and climate conditions, a similar irrigation interval would thus be beneficial for adjusting soil moisture to increase maize yield and WUE under conditions of mulching and drip irrigation.

Development and Performance Evaluation of Self-Generating Enhanced Foam Water Plugging System

For the waterflooding of late development on an offshore oilfield has become worse, and some wells group has entered into high water cut-off period, water plugging work becomes particularly important. Due to the limited construction of offshore oilfield, space water supply difficulties, and stability of plugging agent, self-generating enhanced foam has been designed as the aimed block plugging system. The formula is determined as: 23.25% of NH4Cl + 30% of NaNO2 + 0.1% of catalyst + 0.6% of COSL-3 foaming agent + 0.25% of HS-type HPAM foam stabilizer. Measurement point of pipe with permeability of 0.5 μm2 and 2 μm2 has been used in the plugging and EOR experiments. The experiments show that this system has the selective plugging effect for the heterogeneous formation, especially for middle and posterior part of high permeability formation, and the recovery rate of low permeability pipe is enhanced up to 32.15%.

Layer regrouping for water-flooded commingled reservoirs at a high water-cut stage

Layer regrouping is to divide all the layers into several sets of production series according to the physical properties and recovery percent of layers at high water-cut stage, which is an important technique to improve oil recovery for high water-cut multilayered reservoirs. Dif- ferent regroup scenarios may lead to different production performances. Based on unstable oil-water flow theory, a multilayer commingled reservoir simulator is established by modifying the production split method. Taking into account the differences of layer properties, including per- meability, oil viscosity, and remaining oil saturation, the pseudo flow resistance contrast is proposed to serve as a characteristic index of layer regrouping for high water-cut multilayered reservoirs. The production indices of multi- layered reservoirs with different pseudo flow resistances are predicted with the established model in which the data are taken from the Shengtuo Oilfield. Simulation results show that the pseudo flow resistance contrast should be less than 4 when the layer regrouping is implemented. The K-means clustering method, which is based on the objec- tive function, is used to automatically carry out the layer regrouping process according to pseudo flow resistances. The research result is applied to the IV-VI sand groups of the second member of the Shahejie Formation in the Shengtuo Oilfield, a favorable development performance is obtained, and the oil recovery is enhanced by 6.08 %.

The Coupling Coordination Evolution Research of Economy - Ecology - Society System in Xinjiang：Based on the Interaction Perspective of Water Resources

Under the water resources perspective,coupling coordination of economy-ecology-society system in Xinjiang was taken as the research object. By building the coupling evaluation index system of the water resources-economy-ecology-society system,quantitative evaluation and analysis of the coupling coordination of the water resources-economy-ecology-society system from 2001 to 2014 were conducted. The results showed that benefit indexes of economic system and social system grew rapidly,while benefit indexes of water resources system and ecosystem fluctuated smoothly from 2001 to 2014; coupling state of the whole system was at rival stage,and coupling coordination was reluctant coordination type,and the coupling index was slightly higher than the coupling coordination index. Moreover,it showed that the more the coupling systems,the lower indices of coupling and the coupling coordination.

Water blocking effect caused by the use of hydraulic methods for permeability enhancement in coal seams and methods for its removal

To research techniques for removing the water blocking effect caused by hydraulic applications in coal seams,the use of surfactants is proposed,based on the mechanics of the water blocking effect.Centrifugal experiments were used to validate the effects of using surfactants;the results show that after dealing with vacuum saturation with water,the volume of micropores decreases,which results in a larger average pore size,and the volume of transitional pores,mesopores,macropores and total pores increases.Based on the distribution of pore size,the operation mode of ‘‘water infusion after gas extraction,then continuing gas extraction" is recommended to improve the volume of coal mine gas drainage.When the reflectance of vitrinite in coal samples is less than 1,using the surfactants Fast T,1631,APG,BS can mitigate the damage caused by the water blocking effect.But when the reflectance of vitrinite is larger than 1.4,the damage caused by the water blocking effect can be increased.When the surfactant CMC is used in hydraulic applications,the capillary forces of coal samples are almost negative,which means the capillary force is in the same direction as the gas extraction.The direction of capillary forces benefits the gas flow.So,using CMC can play an active role in removing the water blocking effect.Centrifugal experiments confirm that using CMC can effectively remove the water blocking effect,which has a beneficial effect on improving the gas drainage volume.

Extreme Cold Events in North America and Eurasia in November-December 2022: A Potential Vorticity Gradient Perspective

From 17 November to 27 December 2022, extremely cold snowstorms frequently swept across North America and Eurasia. Diagnostic analysis reveals that these extreme cold events were closely related to the establishment of blocking circulations. Alaska Blocking(AB) and subsequent Ural Blocking(UB) episodes are linked to the phase transition of the North Atlantic Oscillation(NAO) and represent the main atmospheric regimes in the Northern Hemisphere. The downstream dispersion and propagation of Rossby wave packets from Alaska to East Asia provide a large-scale connection between AB and UB episodes. Based on the nonlinear multi-scale interaction(NMI) model, we found that the meridional potential vorticity gradient(PVy) in November and December of 2022 was anomalously weak in the mid-high latitudes from North America to Eurasia and provided a favorable background for the prolonged maintenance of UB and AB events and the generation of associated severe extreme snowstorms. However, the difference in the UB in terms of its persistence,location, and strength between November and December is related to the positive(negative) NAO in November(December). During the La Ni?a winter of 2022, the UB and AB events are related to the downward propagation of stratospheric anomalies, in addition to contributions by La Ni?a and low Arctic sea ice concentrations as they pertain to reducing PVyin mid-latitudes.

GREY CLASSIFICATION FOR EVALUATING THE STABILITY OF DANGEROUS ROCK-BLOCK MASSES

This paper introduces a grey classifica- tion method forevaluating the stability of dangerous rock- block masses according tothe Grey System Theory. This method is applied to the stability ofthe V~# dangerous rock- block masses of Qingjiang water conservancyproject, and better results are abtained. The method which isadvanced in the article is very single and practical, and it can meetall kinds of project's demands.