New technological partition for “three zones” spontaneous coal combustion in goaf

On detailed analysis basis of spontaneous coal combustion for the three zones in mine goaf,we use O2 and CO concentrations to divide the three zones of the coal combustion.Through our experiment,we selected a typical working face and focused on the changes in gas concentrations.In order to overcome establishment limitations of actual layout location and underground conditions in a mine goaf,we based our observations on the three zones,combined them with numerical simulation,described the distribution and the changes in O2 and CO concentrations during the coal spontaneous combustion in the goaf,which provided us with an understanding of the distribution of coal spontaneous combustion in the three zones in the form of maps.Essentially,our study summarizes the changes of O2and CO concentrations in the entire goaf and shows them to be in agreement with our observations at the scene.The study shows that it is feasible to divide the three zones,given our comprehensive targets of O2,CO and our numerical simulation.This method avoids the limitation of dividing the three zones with a single target and the likely errors of observations at the scene.In addition,the method offers a basis for optimizing measures of fre-fghting with important and practical effects.

Research on ＂three zone＂ classification of spontaneous combustion and its numerical simulation in gob of mines under the sea

According to the classification standard of spontaneous combustion ＂three zone＂ in gob and the analysis of aerodynamics and energy equation of relax loose coal body, the paper used the method of computer simulation analysis to get the air distribution. The paper also determined the three zone area of H2103 fully mechanized caving face in Beizao Mine.

Fractal characterization of sediment particle-size distribution in the water-level fluctuation zone of the Three Gorges Reservoir, China

The combined effect of periodic water impoundment and seasonal natural flood events has created a 30 m high water-level fluctuation zone(WLFZ) around the Three Gorges Reservoir(TGR), China, forming a unique eco-landscape. Siltation, eutrophication, enrichment of heavy metals, and methane emissions in the WLFZ have been widely associated with sediment and soil particles generated from the upstream catchment or upland slopes. However, little attention has been paid to the complexity of sediment particle-size distributions in the WLFZ. In the present study, core samples(from a 345 cm thick sediment core from the base of the WLFZ), slope transect surface samples(across/up a WLFZ slope), and along-river/longitudinal surface samples(from the reservoir reaches) were collected. Laser granulometry and a volume-based fractal model were used to reveal the characteristics of sediment particle-size distributions. Results indicate that the alternation of coarse and fine particles in the sedimentary core profile is represented as a fluctuation of low and high values of fractal dimension(D), ranging from 2.59 to 2.77. On the WLFZ slope transect, surface sediment particles coarsen with increasing elevation, sand content increases from 3.3% to 78.5%, and D decreases from 2.76 to 2.53. Longitudinally, surface sediments demonstrate a downstream-fining trend, and D increases gradually downstream. D is significantly positively correlated with the fine particle content. We conclude that D is a useful measure for evaluating sediment particle-size distribution.

Spatial-Temporal Evolution Characteristics and Driving Factors of Agricultural Space in Jianghan Plain from the Perspective of “Three-Zone Space”

Studying the agricultural spatial distribution characteristics of Jianghan Plain from 2000 to 2018 and its spatial-temporal transformation with ecological space and urban space is of great significance for optimizing the spatial structure of the country, enhancing the supply capacity of agricultural products, and ensuring food security. The research results show that during the period from 2000 to 2018, the agricultural spatial concentration in the area along the “Xiaogan-Jingzhou” link was relatively high, and the areas with large declines were mainly distributed in the flat areas between the Yangtze River and Han River;the space is continuously reduced by the occupation of ecological space and urban space, and ecological space and urban space have been improved respectively;agricultural space has been transformed into ecological space, and the largest urban space has been transformed. Ecological space has been transformed into agricultural space and urban space. Less urban space has been transformed into agricultural space and ecological space.

Protection and Ecological Restoration of Water Level Fluctuation Zone in the Three Gorges Reservoir

Water level fluctuation zone(hereinafter referred to as "WLFZ") is a transitional ecosystem between terrestrial ecosystem and aquatic ecosystem,and also a key area to control its neighboring terrestrial and aquatic ecosystem. After the Three Gorges Reservoir was put into use,ecological environment of its WLFZ has aroused wide concern from domestic and foreign experts. On the basis of introducing characteristics of WLFZ of the Three Gorges Reservoir,current ecological environment and main problems of this area were analyzed,plant selection and configuration was elaborated as well as the implementation effect of many WLFZ protection and ecological restoration modes. In view of the actual conditions,pertinent suggestions were proposed for WLFZ of the Three Gorges Reservoir,namely classified protection and ecological restoration,enhancing monitoring and assessment of current situation and change tendency,carrying out technical researches and demonstration of WLFZ wetland ecological restoration.

区域视角下跨境电商产业集聚效率研究——基于超效率SBM-Malmquist模型分析

跨境电商在国际贸易转型发展中起着至关重要的作用,而长三角、京津冀、珠三角区域作为中国跨境电商头部经济区在外贸中表现十分活跃。因此为进一步了解跨境电商产业集聚状况,本文选取2016—2021年长三角、京津冀、珠三角三大经济区面板数据,运用超效率SBM-Malmquist模型从静态和动态两个维度对三大经济区跨境电商集聚效率进行评价。结果显示,跨境电商集聚效率整体表现为珠三角>长三角>京津冀,而纯技术效率和规模效率是拉开差异的主要原因。应该着力推动跨境电商集群均衡发展,加强三大经济区内特色品牌和优势资源互通、技术扩散和知识溢出,强化区域间协同合作。

Malaria Transmission Potential in the Three Gorges Reservoir of the Yangtze River, China

Objective To define and evaluate the malaria transmission potential in the Yangtze River, following construction of the Three Gorges Reservoir. Methods Six villages, namely, Kaixian, Fengjie, Wanzhou, Fuling, Yubei, and Zigui were selected for investigating the malaria transmission potential in the reservoir. Transmission potential was estimated by mathematical modeling and evaluation of the local malaria situation. Factors that influenced the transmission potential were analyzed using Poisson regression analysis in combination with Grey Systematic Theory （based on evaluation by the Delphi method）. Results Indirect fluorescent antibody data and the incidence of malaria in the local population were consistent with the malaria transmission potential calculated for the area. Multivariate Poisson regression analysis showed a statistically significant association between the riparian zone and the man‐biting rate. Conclusion The risk of a malaria epidemic can be forecasted using the malaria transmission potential parameters investigated here which was closely correlated with the riparian zone.

Karst subzone division in vertical cycle zone and its significance

Vertical cycle karst zone has been studied for more than 100 years, however karst subzones in the zone have never been divided and affected depth of CO2 from rainwater in the zone has never been studied. On the basis of field observation, survey and chemical analysis, the difference of karst processes indicated by CaCO3 and pH values in fine and loose sedimentary strata as well as limestone strata, and the vertical cycle zone ascertained by predecessors can be divided into three subzones, that is, the upper first subzone, characterized by unsaturated water solution and strong dissolution processes, the middle second subzone, characterized by supersaturated water solution and precipitation, and the lower third subzone, characterized by unstable water solution and weak dissolution or weak precipitation. The three subzones can indicate the vertical CO2 cycle. In fine and loose sediment strata, the bottom of the first subzone is the lower boundary strongly influenced by CO2 from rainwater, soil and air; all CO2 from rainwater, soil and air is almost exhausted in the second subzone. In the early developmental period of karst process in limestone strata, karst funnels and vertical caves do not form, vertical seeping of rainwater and soil water is very slow, and CO2 from soil, rainwater and air almost can reach the third subzone, but in the middle and late developmental periods, karst funnels and vertical caves occur, CO2 from soil, rainwater and air can reach deep seasonal change zone and horizontal cycle zone and quicken development of karst morphology. Deep karst morphology near groundwater level under vertical cycle zone develops better in the middle and late periods of karst process.

Deep Seismogenic Environment in the Southern Section of the Longmenshan Fault Zone on the Eastern Margin of the Tibetan Plateau and Lushan M_s 7.0 Earthquake

The 2,026 earthquake events registered by the Sichuan regional digital seismic network and mobile seismic array after the April 20th, 2013 Lushan earthquake and 28,188 pieces of data were selected to determine direct P waves arrival times. We applied the tomographic method to inverse the characteristics of the velocity structure for the three-dimensional （3D） P wave in the mid-upper crust of the seismic source region of the Lushan earthquake. The imaging results were combined with the apparent magnetization inversion and magnetotelluric （MT） sounding retest data to comprehensively study the causes of the deep seismogenic environment in the southern section of the Longmenshan fault zone and explore the formation of the Lushan earthquake. Research has shown that there are obvious differences in velocity structure and magnetic distribution between the southern and northern sections of the Longmenshan fault zone. The epicenter of the Lushan earthquake is located near the boundary of the high and low-velocity anomalies and favorable for a high-velocity section. Moreover, at the epicenter of the Lushan earthquake located on the magnetic dome boundary of Ya＇an, the development of high velocity and magnetic solid medium favors the accumulation and release of strain energy. Low- velocity anomalies are distributed underneath the are of seismogenic origin, The inversion results of the MT retest data after the April 20th Lushan earthquake also indicate that there a high-conductor anomaly occurs under the area of seismogenic origin of the Lushan earthquake, Therefore, we speculated that the presence of a high-conductivity anomaly and low-velocity anomaly underneath the seismogenic body of the Lushan earthquake could be related to the existence of fluids. The role of fluids caused the weakening of the seismogenic layer inside the mid-upper crust and resulted in a seismogenic fault that was prone to rupture and pIayed a triggering role in the Lushan earthquake.

基于变分模态分解的采空区“三带”微震信号能量衰减规律

为探明微震信号能量在采空区“三带”结构中的衰减规律,拟开展采空区覆岩相似模型试验,采集人工激发微震波经由采空区结构传播的微震信号,通过变分模态分解(variational mode decomposition,VMD)处理微震信号,获取各频率下模态分量。针对采空区微震信号在VMD下各模态分量中心频率与能量之间的关系展开分析。根据中心频率法确定微震信号最佳模态数量,并计算微震信号欠分解状态、最佳分解状态、过分解状态下各分量能量;对各震源下信号最佳分解状态时各模态分量能量与中心频率分布关系进行拟合,分析在“三带”结构中,微震信号不同传播状态下各结构层对信号能量影响作用。研究结果表明:(1)在VMD过程中,人工激发震动信号有效模态数量在6~11范围内,微震信号能量随模态数量变化明显。(2)采用幂函数可实现对微震信号模态能量与频率关系的拟合,且拟合状态良好(决定系数大于0.9),其中低频模态分量包含能量占信号总能量近50%;采用高斯函数可以拟合震源各分量能量在频域上的分布表现,拟合状态较好,且表现出高斯单峰特征。(3)微震信号穿越采空区“三带”结构,微震信号能量随震源位置与传感器距离增加而减小,同时信号能量随震源位置到达传感器穿越岩层数量增加而减小,信号能量在经由垮落带时,能量变化明显,相较于裂隙带和弯曲下沉带,垮落带对信号能量衰减作用明显。

Subprime Mortgage Crisis and the Exchange Rate Channel: Evidence from Six Countries of the Zone Euro-Med

This article proposes to assess the impact of the subprime mortgage crisis on the exchange rate channel in 6 countries of the Euro-Med zone. To do this, our analysis is based on three evaluation methods that allow us to conclude that the exchange rate channel is better evaluated by the non-linear approach of the countries studied. Thus, the depreciation of the exchange rate adopted by the countries of the Med zone did worse macroeconomic stability and economic convergence.

浅埋深综放工作面采空区“三带”分布研究

为研究浅埋深综放工作面采空区“三带”分布规律,在串草圪旦煤矿6101综放工作面采空区埋设束管,对采空区“三带”进行了现场实测。实测结果表明:由于煤层埋深浅、地表起伏大、进风侧存在地表漏风,进风侧采空区“三带”明显滞后于回风侧,进回风两侧氧化带宽度分别为87.8 m和61.4 m。利用FLUENT软件对实测条件下该工作面采空区“三带”进行了数值模拟,模拟结果和现场实测结果基本一致。同时模拟了不漏风条件下该工作面采空区“三带”分布,此时采空区散热带、氧化带范围大幅度减小,进风侧采空区氧化带稍大,而工作面中部和回风侧“三带”分布基本一致。

《“三下”开采规范》中安全煤(岩)柱留设问题探讨

针对《建筑物、水体、铁路及主要井巷煤柱留设与压煤开采规范》中安全煤(岩)柱设计以及水压对顶板突水控制作用等问题进行探讨。首先分析了规范的附表4-3表头文字,指出保护层厚度的有关规定仅适用于松散含水层(含地表水体),至于基岩含水层下采煤应如何确定保护层厚度则未明确;进而以泥岩与黏性土层均具有阻水功能为桥梁,推导出基岩含水层下采煤可参照“松散层下黏性土层累计厚度大于采厚”条件执行,遵照“就高不就低原则”,基岩含水层下保护层厚度统一取采厚的4倍为宜;既然规范适用条件为单层采厚不大于3.0 m,则附表4-3中“松散层厚度小于采厚”的规定难以理解,建议删除。其次,基于“保护”一词的科学内涵对“保护层”重新定义,即导水裂缝带顶界面到含水层底界面之间的隔水岩层均具有“保护”功能,应统称为保护层H_(b);进而提出了保护系数B_(s)概念,即保护层厚度与单层采厚的比值;松散含水层下保护系数分区阈值(B_(i)=2、3、4、5、6、7),基岩含层下保护系数分区阈值B_(i)=4,据此对顶板水害风险进行等级划分:突水区(B_(s)≤0)、危险区(0<B_(s)<B_(i))、安全区(B_(s)≥B_(i))。此外,借鉴底板突水系数概念,将单位厚度保护层承受的水头压力称为保护层承压系数(T=P/H_(b)),通过对3种煤水结构条件下承压系数的分析,得出第4系松散含水层、非煤系基岩含水层下采煤可以不考虑水压,煤系基岩含水层下采煤随着开采深度增加、水压随之增大而带来突(涌)水风险。最后,分析了底板含水层顶部存在被泥质物充填隔水带时,《“三下”开采规范》给出的底板防水安全煤(岩)柱表达式(h_(a)≥h_(1)+h_(2)+h_(4))与附图相矛盾,正确的表达式应为h_(a)≥h_(1)+h_(2)-h_(4)。

多物理场耦合下采空区煤自燃三带数值模拟研究

采空区煤自燃三带分布范围的确定对自燃火灾防治至关重要。以平煤五矿己_(16-17)-23260工作面为例,综合运用试验分析、现场观测及数值模拟等方法,对综采面采空区自燃三带的分布范围进行了深入探究。结果表明:己_(16-17)煤层煤温为θ时的实际放热强度为q(θ)=4.8337 e^(0.0467θ);基于COMSOL的采空区自燃三带温度场、渗流场和应力场(Thermal Hydrological Mechanical,THM)多场耦合模拟结果与现场实测结果相互对比,得出进风巷与回风巷氧化带的最大宽度分别为48 m和31 m,相对误差为0.04和0.02,氧化带中的温度峰值分别为78.36℃和68.15℃,划分出的自燃三带范围基本一致;采空区x-y截面氧化带呈弧形分布,y-z截面氧化带呈抛物线分布;工作面三带范围随着工作面风速和倾向长度的增大呈现逐步扩大的趋势,而且逐步向采空区内部延伸。

Assessment of Sub-Endometrial Junction Zone by 3-Dimensional Transvaginal Ultrasound in Unexplained Recurrent Implantation Failure and Its Effect on ICSI Outcomes

BACKGROUND: Sub-endometrial junction zone (JZ) plays an important role in most of reproductive functions. OBJECTIVE: To find out the effect of the sub-endometrial JZ thickness assessment by 3-D trans-vaginal ultrasound (TVUS) on intracytoplasmic sperm injection (ICSI) outcomes in patients with unexplained recurrent implantation failure (RIF). SETTING: ART Unit of Obstetrics and Gynecology Department, Faculty of Medicine, South Valley University, Qena, Egypt. DURATION: From April 2016 to October 2018. STUDY DESIGN: A prospective observational study. METHDS: Fifty couples with history of unexplained RIF in previous ICSI cycles and prepared for another ICSI cycle (group I) and fifty couples with unexplained infertility prepared for ICSI for the first time (group II) had been included in this study. At time of ovum pick up, 3-DTVUS was done for all cases in both groups for assessment of sub endometrial junction zone thickness and correlated with ICSI outcome. RESULTS: There were statistically significant differences between group I and group II in JZ thickness in the 3 uterine regions (fundus, anterior and posterior walls) with p 0.001, but there were mildly statistically significant differences between both groups in chemical and clinical pregnancy rates with p < 0.01. CONCLUSIONS: The thickness of JZ in patients with history of unexplained RIF was higher than those with unexplained infertility scheduled for ICSI. The JZ thickness was inversely correlated with increased embryo implantation rates in ICSI procedures, the thinner the JZ thickness was associated with higher pregnancy rates (both chemical and clinical pregnancy rates).

A Study of the Crustal Stability in the Yangtze Three Gorges Area

The Three Gorges Dam on the Yangtze River is situated on the intact rock mass composed of diorite granite at the southern termination of the Huangling block which, as a sub plate with a double layer structure (crystalline basement and sedimentary cover) in the Chinese inland, keeps a constant but slow uplift as a whole since its formation in the Indoncisia movement. Tectonic deformation within the block is not significant, with the exception of a slight southeastward tilt. The block is confined by many active structures, of which the sub longitudinal Yuanan and Xiannvshan ( Mount Fairy ) deep fault zones are the main strongly seismogenic zones. The Yuan’an fault zone represents a regional boundary among West Henan, West Hubei and West Hunan mountainous regions as well as the Nanyang, Jianghan and Dongting Lake basins, with a total length of more than 1,000 km. Two M 6 5 earthquakes (in Changde and Nanyang) occurred in the fault zone in historic time and the distance between the two epicenters is about 500 km. The Mount Fairy fault zone extends northward along the Xiangxi River and ends at the Qingfeng fault. It runs a total length of more than 220 km. southward across Yuyang Pass and then its trace is unknown. The fault zone has a tectonic condition for occurrences of M 6.0 earthquakes. The possible seismic risk for the dam may come from these two strong seismogenic zones. Thus the seismic intensity to influence the dam is estimated to be Ⅵ～Ⅶ and the horizontal peak acceleration to be 0 1～0 15 g.

不同通风方式下“110工法”采空区自燃“三带”数值模拟研究

为探究不同通风方式下“110工法”采空区自燃“三带”分布特征,以顾北矿1532(1)工作面“两进一回”通风方式为工程背景,基于风流控制方程、浓度组分方程和能量方程等,利用Fluent数值模拟方法建立煤自然发火多物理场耦合数值模型、工作面实时动态推进模型,模拟了3种通风方式下“110工法”采空区自燃“三带”分布特征。结果表明:随着工作面不断推进,在通风方式1(机巷侧和沿空留巷进风,回风巷回风)和通风方式2(机巷侧和回风巷进风,沿空留巷回风)条件下,采空区氧化自燃带均匀分布在运输巷侧、工作面中部和留巷侧,其氧气体积分数分布形状相差不大,采空区温度首先升高,开采约50 d后,最高温度出现在运输巷侧深部,且该位置温度不随工作面继续推进而升高;在通风方式3(沿空留巷和回风巷进风,机巷侧回风)条件下,采空区留巷侧氧化自燃带变宽2~4倍,工作面中部和运输巷侧明显变窄,采空区运输巷侧氧气体积分数较低,留巷侧氧气体积分数较高,漏风量明显增大。采空区高温位置主要出现在1532(1)工作面始采线留巷侧,且当工作面开采50 d后,此处采空区温度最高。综上所述并结合现场实际情况,对氧化自燃带宽度及位置进行分析,最终确定通风方式3更有利于防止煤自燃的发生,对矿井煤自燃的预防提供了理论指导。

基于FME的国土空间规划“三区三线”成果数据质检设计

科学划定“三区三线”是现在国土空间规划编制中的一项基础性工作和关键任务。为确保“三区三线”划定成果数据质量,本文基于FME设计了“三区三线”划定的成果数据质检方案,对甘肃省各县区“三区三线”划定的成果数据进行了质量检查。该质检方案有效地提高了数据质检的效率,保障了“三区三线”成果数据质量,对其他空间数据质量检查具有借鉴意义。

基于COMSOL采空区自燃“三带”数值模拟研究

为深入研究梁宝寺煤矿35003工作面采空区“三带”的分布规律,根据工作面实际情况,构建采空区物理模型,设置合理的边界与初始条件,并运用COMSOL多物理场模拟软件对采空区的风流速度场、氧浓度场及压力场展开数值仿真。通过迭代比较仿真结果与实测数据,校准了仿真参变量,以确保仿真结果与实测数据相契合,进而获得最终的氧浓度场和速度场,准确界定出采空区“三带”的具体范围。同时,针对风速分别为1.04m/s,0.54m/s的条件,模拟了采空区流场的变化。研究结果表明:风流速度对采空区内不同带的宽度和分布具有显著影响,风流速度的增加会使散热带及自燃带相应拓宽,同时窒息带向远离工作面的方向扩展;反之,散热带及自燃带相应收缩,而窒息带则向工作面靠拢。通过随时调整自燃“三带”的风速等控制措施,可以有效减少自燃风险,保障生产过程的顺利进行。