Application of 3D-computed tomography angiography technology in large meningioma resection

Objective:To discuss the role of 3D-computed tomography angiography(3D-CTA) technology in reducing injuries of large meningioma surgery.Methods:3D-CTA preoperative examinations were done in 473 patients with large meningioma(simulated group).The images were analyzed by 30 post-processing workstation.By observing the major intracranial blood vessels,venous sinus,and the compression and invasion pattern in the nerve region,assessing risk level of the surgery,simulating the surgical procedures,the surgical removal plan,surgical routes and tumor blood-supplying artery embolisation plan were performed.Two hundred and fifty seven large meningioma patients who didn’t underwent 3D-CTA preoperative examination served as control group.The incidence of postoperative complications,intraoperative blood transfusion and the operation time were compared between these two groups.Results:Compared with the control group,the Simpson’s grade 1 and 11 resection rate was 80.3%(380/473),similar with that of the control(81.3%,209/257).The incidence of postoperative complications in 3D-CTA simulated group was 37.0%which was significantly lower than that(48.2%) of the control(P【0.01). The intraoperative blood supply for simulated group and the control was(523.4±208.1) mL and (592.0±263.3) mL,respectively,with significant difference between two groups(P【0.01).And the operation time[(314.8±106.3)]min was significantly lower in simulated group than that in the control[(358.4±147.9) min](P【0.01).Conclusions:Application of 3D-CTA imaging technology in risk level assessment before large-scaled meningioma resection could assist in the rational planning of tumor resectin,surgical routes,and is helpful in reducing injuries and complications and enhancing the prognosis of the patients.

Pressure from surrounding rock of three shallow tunnels with large section and small spacing

With the increasing traffic demand, the closely built three or more tunnels with large section play a significant role in the tunnel construction. However, the interaction among tunnels has important influences on the security and economy of tunnel engineering, and the calculation of pressure from the surrounding rock during the excavation is one of the problems that need to be solved urgently. Based on the practical engineering of three tunnels, the load model of three tunnels was proposed in consideration of the interaction and excavation sequence between tunnels. In comparison with the load model of single tunnel, the construction mechanical characteristics of the three tunnels were analyzed. The results show that the rock pressure of three tunnels calculated by the current tunnel design code is not reliable, and the interaction force increases with the spacing between tunnels.

Similar simulation study on the deformation and failure of surrounding rock of a large section chamber group under dynamic loading

Large and super-large section chamber groups in coal mines are frequently affected by dynamic loads resulting from production activities such as roadway driving and blasting.The stability of the surrounding rock is poor,and it is difficult to control.In this paper,a similar simulation test was used to study the deformation and evolution laws of the surrounding rock of a triangle-shaped chamber group under different dynamic loads.The results showed that under dynamic loading,the vertical stress of the surrounding rock of the chamber group increased in an oscillatory form.The maximum stress concentration coefficient reached 4.09.The damage degree of the roof was greater than that of the two sides.The deformation of the roof was approximately 1.2 times that of the two sides.For the chamber closer to the power source,the stress oscillation amplitude of the surrounding rock was larger,and the failure was more serious.The force of the anchorage structure showed a phased increasing characteristic;additionally,the force of the anchorage structure on the adjacent side of the chambers was greater than that on the other side.This study reveals the deformation and failure evolution laws of the surrounding rock of large section chamber groups under dynamic loading.

Key technologies and equipment for a fully mechanized top-coal caving operation with a large mining height at ultra-thick coal seams

Thick and ultra-thick coal seams are main coal seams for high production rate and high efficiency in Chinese coal mines, which accounts for 44 % of the total minable coal reserve. A fully mechanized top-coal caving mining method is a main underground coal extraction method for ultra-thick coal seams. The coal extraction technologies for coal seams less than 14 m thick were extensively used in China. However, for coal seams with thickness greater than 14 m, there have been no reported cases in the world for underground mechanical extraction with safe performance, high efficiency and high coal recovery ratio. To deal with this case, China Coal Technology ＆ Engineering Group, Datong Coal Mine Group, and other 15 organizations in China launched a fundamental and big project to develop coal mining technologies and equipment for coal seams with thicknesses greater than 14 m. After the completion of the project, a coal extraction method was developed for top-coal caving with a large mining height, as well as a ground control theory for ultra-thick coal seams. In addition, the mining technology for top-coal caving with a large mining height, the ground support technology for roadway in coal seams with a large cross-section, and the prevention and control technology for gas and fire hazards were developed and applied. Furthermore, a hydraulic support with a mining height of 5.2 m, a shearer with high reliability, and auxiliary equipment were developed and manufactured. Practical implication on the technologies and equipment developed was successfully completed at the No. 8105 coal face in the Tashan coal mine, Datong, China. The major achievements of the project are summarized as follows： 1. A top-coal caving method for ultra-thick coal seams is proposed with a cutting height of 5 m and a top-coal caving height of 15 m. A structural mechanical model of overlying strata called cantilever beam-articulated rock beam is established. Based on the model, the load resistance of the hydraulic support with a large mining height for top-coal caving method is determined. With the analysis, the movement characteristics of the top coal and above strata are evaluated during top-coal caving operation at the coal face with a large mining height. Furthermore, there is successful development of comprehensive technologies for preventing and controlling spalling of the coal wall, and the top-coal caving technology with high efficiency and high recovery at the top-coal caving face with a large mining height. This means that the technologies developed have overcome the difficulties in strata control, top-coal caving with high efficiency and high coal recovery, and enabled to achieve a production rate of more than 10 Mtpa at a single top-coal caving face with a large mining height in ultra-thick coal seams; 2. A hydraulic support with 5.2 m supporting height and anti-rockburst capacity, a shearer with high reliability, a scraper conveyor with a large power at the back of face, and a large load and long distance headgate belt conveyor have been successfully developed for a top-coal caving face with large mining height. The study has developed the key technologies for improving the reliability of equipment at the coal face and has overcome the challenges in equipping the top-coal caving face with a large mining height in ultra-thick coal seams; 3. The deformation characteristics of a large cross-section roadway in ultra-thick coal seams are discovered. Based on the findings above, a series of bolt materials with a high yielding strength of 500-830 MPa and a high extension ratio, and cable bolt material with a 1 × 19 structure, large tonnage and high extension ratio are developed. In addition, in order to achieve a safe roadway and a fast face advance, installation equipment for high pre-tension bolt is developed to solve the problems with the support of roadway in coal seams for top-coal caving operation with a large mining height; 4. The characteristics of gas distribution and uneven emission at top-coal caving face with large mining height in ultra-thick coal seams are evaluated. With the application of the technologies of gas drainage in the roof, the difficulties in gas control for high intensive top-coal caving mining operations, known as ＂low gas content, high gas emission＂, are solved. In addition, large flow-rate underground mobile equipment for making nitrogen are developed to solve the problems with fire prevention and safe mining at a top-coal caving face with large mining height and production rate of more than 10 Mtpa. A case study to apply the developed technologies has been conducted at the No. 8105 face, the Tashan coal mine in Datong, China. The case study demonstrates that the three units of equipment, i.e., the support, shearer and scraper conveyor, are rationally equipped. Average equipment usage at the coal face is 92.1%. The coal recovery ratio at the coal face is up to 88.9 %. In 2011, the coal production at the No. 8105 face reached 10.849 Mtpa, exceeding the target of 10 Mtpa for a topcoal caving operation with large mining height performed by Chinese-made mining equipment. The technologies and equipment developed provide a way for extracting ultra-thick coal seams. Currently, the technologies and equipment are used in 13 mining areas in China including Datong, Pingshuo, Shendong and Xinjiang. With the exploitation of coal resources in Western China, there is great potential for the application of the technologies and equipment developed.

Large Eddy Simulations of Flow Instabilities in a Stirred Tank Gen-erated by a Rushton Turbine

The aim of this work is to investigate the flow instabilities in a baffled, stirred tank generated by a single Rushton turbine by means of large eddy simulation （LES）. The sliding mesh method was used for the coupling between the rotating and the stationary frame of references. The calculations were carried out on the ＂Shengcao-21C＂ supercomputer using a computational fluid dynamics （CFD） code CFX5. The flow fields predicted by the LES simulation and the simulation using standard κ-ε model were compared to the results from particle image velocimetry （PIV） measurements. It is shown that the CFD simulations using the LES approach and the standard κ-ε model agree well with the PIV measurements. Fluctuations of the radial and axial velocity are predicted at different frequencies by the LES simulation. Velocity fluctuations of high frequencies are seen in the impeller region, while low frequencies velocity fluctuations are observed in the bulk flow. A low frequency velocity fluctuation with a nondimensional frequency of 0.027Hz is predicted by the LES simulation, which agrees with experimental investigations in the literature. Flow circulation patterns predicted by the LES simulation are asymmetric, stochastic and complex, spanning a large portion of the tanks and varying with time, while circulation patterns calculated by the simulation using the standard κ-ε model are symmetric. The results of the present work give better understanding to the flow instabilities in the mechanically agitated tank. However, further analysis of the LES calculated velocity series by means of fast Fourier transform （FFT） and/or spectra analysis are recommended in future work in order to gain more knowledge of the complicated flow phenomena.

High prestress truss cable support principle and its application in large cross section coal roadway

With the enlarge of cross section of roadway, the radius of plastic area and broken area increase, and the tensile stress and shear stress distributing in roof coal-rock layers relevantly increase, which induce support effect not obvious for ordinary bolt（cable）. While bounding point and support structure of the truss cable is in vertex angle of roadway, and supplies coal-rock layers in bounding area with the horizontal and vertical pressure, so it settles the support problems in large cross section coal roadway. From the point of view of mechanics, gave emphasis on the invalid mechanics of ordinary bolt （cable） in large cross section coal roadway and supported mechanics of prestress truss cable. The author successfully used this technique in Wuyang Mine, and had the huge economic efficiency and the social benefit.

Formation conditions and exploration direction of large natural gas reservoirs in the oil-prone Bohai Bay Basin, East China

The Bohai Bay Basin is a typical oil-prone basin, in which natural gas geological reserves have a small proportion. In this basin, the gas source rock is largely medium-deep lake mudstone with oil-prone type Ⅱ2-Ⅱ1 kerogens, and natural gas preservation conditions are poor due to active late tectonic movements. The formation conditions of large natural gas fields in the Bohai Bay Basin have been elusive. Based on the exploration results of Bohai Bay Basin and comparison with large gas fields in China and abroad, the formation conditions of conventional large-scale natural gas reservoirs in the Bohai Bay Basin were examined from accumulation dynamics, structure and sedimentation. The results show that the formation conditions of conventional large natural gas reservoirs in Bohai Bay Basin mainly include one core element and two key elements. The core factor is the strong sealing of Paleogene "quilt-like" overpressure mudstone. The two key factors include the rapid maturation and high-intensity gas generation of source rock in the late stage and large scale reservoir. On this basis, large-scale nature gas accumulation models in the Bohai Bay Basin have been worked out, including regional overpressure mudstone enriching model, local overpressure mudstone depleting model, sand-rich sedimentary subsag depleting model and late strongly-developed fault depleting model. It is found that Bozhong sag, northern Liaozhong sag and Banqiao sag have favorable conditions for the formation of large-scale natural gas reservoirs, and are worth exploring. The study results have important guidance for exploration of large scale natural gas reservoirs in the Bohai Bay Basin.

Intelligent optimization of the structure of the large section highway tunnel based on improved immune genetic algorithm

As in the building of deep buried long tunnels,there are complicated conditions such as great deformation,high stress,multi-variables,high non-linearity and so on,the algorithm for structure optimization and its application in tunnel engineering are still in the starting stage. Along with the rapid development of highways across the country,it has become a very urgent task to be tackled to carry out the optimization design of the structure of the section of the tunnel to lessen excavation workload and to reinforce the support. Artificial intelligence demonstrates an extremely strong capability of identifying,expressing and disposing such kind of multiple variables and complicated non-linear relations. In this paper,a comprehensive consideration of the strategy of the selection and updating of the concentration and adaptability of the immune algorithm is made to replace the selection mode in the original genetic algorithm which depends simply on the adaptability value. Such an algorithm has the advantages of both the immune algorithm and the genetic algorithm,thus serving the purpose of not only enhancing the individual adaptability but maintaining the individual diversity as well. By use of the identifying function of the antigen memory,the global search capability of the immune genetic algorithm is raised,thereby avoiding the occurrence of the premature phenomenon. By optimizing the structure of the section of the Huayuan tunnel,the current excavation area and support design are adjusted. A conclusion with applicable value is arrived at. At a higher computational speed and a higher efficiency,the current method is verified to have advantages in the optimization computation of the tunnel project. This also suggests that the application of the immune genetic algorithm has a practical significance to the stability assessment and informationization design of the wall rock of the tunnel.

Large deflections of non-prismatic nonlinearly elastic cantilever beams subjected to non-uniform continuous load and a concentrated load at the free end

This work studies large deflections of slen- der, non-prismatic cantilever beams subjected to a combined loading which consists of a non-uniformly distributed con- tinuous load and a concentrated load at the free end of the beam. The material of the cantilever is assumed to be non- linearly elastic. Different nonlinear relations between stress and strain in tensile and compressive domain are considered. The accuracy of numerical solutions is evaluated by com- paring them with results from previous studies and with a laboratory experiment.

Stability Analysis of Large Section Rocky Tunnel Support Structure

In order to study the stress characteristics of the initial support and secondary lining of the large section tunnel and to solve the problem of secondary lining cracking during operation. Taking the large section tunnel in Zihong village, Qi County as the research object, a numerical simulation method was used to establish a finite element model of the large section tunnel. So as to simulate and analyze the stress characteristics of the support structure of this tunnel. Through the simulation of the initial support and second lining of this large section tunnel in terms of displacement, stress, plastic zone damage and anchor shaft force, the results show that as the excavation progresses, the stress and displacement on the surface of the newly excavated tunnel profile is faster, especially at the side walls and arch footings, the stress and displacement values are slightly larger than other characteristic points, but the final values are stable and converge, and are basically consistent with the field monitoring results, which indicates that this support system is basically in stable state. Therefore, during the tunnel excavation and support process, special attention should be paid to the stability of the sidewalls and footings, and the results of this study will be of great practical significance for tunnel construction and maintenance.

Investigation on some key problems of large power AC-DC-AC converter

China is an important country in iron and steel industry.Power electronics converters are widely used.For the cold rolling mills of high speed,AC-DC-AC converters should be used.In the paper,the design and the control system of the large power three-level AC - DC - AC converter with IGCTs is investigated,and a back-to-back large power three-level AC - DC - AC converter with IGCTs has been got. With a series experiments,the performance of the converter is examined.The experiment result indicates the converter reaches the design requirement and it shows excellent performance.The converter system has been put into use safely.It is estimated that the AC - DC - AC converter system will be used in the drive systems for rolling mills in the near future.

North slope transition zone of Songnan-Baodao sag in Qiongdongnan Basin and its control on medium and large gas fields,South China Sea

Based on analysis of newly collected 3D seismic and drilled well data,the geological structure and fault system of Baodao sag have been systematically examined to figure out characteristics of the transition fault terrace belt and its control on the formation of natural gas reservoirs.The research results show that the Baodao sag has the northern fault terrace belt,central depression belt and southern slope belt developed,among them,the northern fault terrace belt consists of multiple transition fault terrace belts such as Baodao B,A and C from west to east which control the source rocks,traps,reservoirs,oil and gas migration and hydrocarbon enrichment in the Baodao sag.The activity of the main fault of the transition belt in the sedimentary period of Yacheng Formation in the Early Oligocene controlled the hydrocarbon generation kitchen and hydrocarbon generation potential.From west to east,getting closer to the provenance,the transition belt increased in activity strength,thickness of source rock and scale of delta,and had multiple hydrocarbon generation depressions developed.The main fault had local compression under the background of tension and torsion,giving rise to composite traps under the background of large nose structure,and the Baodao A and Baodao C traps to the east are larger than Baodao B trap.Multiple fault terraces controlled the material source input from the uplift area to form large delta sand bodies,and the synthetic transition belt of the west and middle sections and the gentle slope of the east section of the F12 fault in the Baodao A transition belt controlled the input of two major material sources,giving rise to a number of delta lobes in the west and east branches.The large structural ridge formed under the control of the main fault close to the hydrocarbon generation center allows efficient migration and accumulation of oil and gas.The combination mode and active time of the main faults matched well with the natural gas charging period,resulting in the hydrocarbon gas enrichment.Baodao A transition belt is adjacent to Baodao 27,25 and 21 lows,where large braided river delta deposits supplied by Shenhu uplift provenance develop,and it is characterized by large structural ridges allowing high efficient hydrocarbon accumulation,parallel combination of main faults and early cessation of faulting activity,so it is a favorable area for hydrocarbon gas accumulation.Thick high-quality gas reservoirs have been revealed through drilling,leading to the discovery of the first large-scale gas field in Baodo 21-1 of Baodao sag.This discovery also confirms that the north transition zone of Songnan-Baodao sag has good reservoir forming conditions,and the transition fault terrace belt has great exploration potential eastward.

Decentralized Stabilization of Large-scale Uncertain Systems with State-Delays——LMIs Approach

This paper deals with the problem of decentralized robustcontrol for a class of interconnected uncertain systemswith state delays.The parameter uncertainties are un-known but norm-bounded.A new sufficient condition isobtained for each subsystem and overall system to be sta-bilizable via linear memoryless state feedback robust de-centralized controllers.The results depend on the size of the delays and are given in terms of linear matrix ine-qualities,so they are less conservative than those of delay-independent.Moreover,matching condition is not a necessary condition.Finally,an example is presented to illustrative the effectiveness of the proposed method.

Utilization Survey of Livestock Manure Resources in Large-scale Farms of Yangzhou

Based on surveying the conditions of large -scale farms and commercial manure in the each county of Yangzhou city, the situations and problems for utilization of livestock manure resources were grasped. After an analysis of the potential value of livestock manure, the suggestion and strategy for utilization of livestock manure resources were proposed based on the actual conditions in Yangzhou city.

Dynamic evolution in mechanical characteristics of complex supporting structures during large section tunnel construction

The shallow tunnelling method(STM)often uses temporary supports to divide large section tunnels into several closed or semiclosed sections so as to share the upper load.The complex support system composed of primary and temporary supports can ensure safety during tunnel construction.Based on the large section tunnel of Beijing Subway Line 12,the mechanical characteristics of support system by the double-side-drift method(DSDM)during excavation and demolition were analyzed through numerical simulation and monitoring.The study showed that the middle cave excavation was the most critical stage of the DSDM,during which the load on the supporting structure increased significantly.The temporary vertical support bore most of the new load during middle cave excavation.During the demolition stage,the load was redistributed,which caused arch settlement and section convergence.The removal of the temporary vertical support exerted the greatest impact in this process.The lateral temporary inverted arch changed from axial compression to axial tension after the middle and lower caves were excavated.Based on the mechanical characteristics of the support system,some engineering suggestions were proposed for large section tunnel construction.These research results can provide reference for the design and construction of similar large section tunnels.

工艺孔对大截面部分包覆钢-混凝土组合梁受弯性能影响的试验研究

为了研究工艺孔对大截面部分包覆钢-混凝土组合梁(大截面PEC梁)受弯性能的影响,对5根不同构造的大截面PEC梁进行了静力试验,研究了两点加载下主次梁腹板开洞方式对大截面PEC梁试件受弯性能、延性、破坏模式等的影响规律。结果表明:静力荷载作用下,各个试件均表现出良好的延性,腹部开孔对试件承载力和截面刚度有一定的削弱作用。型钢主钢件的应变与混凝土的应变沿截面高度方向均大致呈线性变化,符合平截面假定。按《部分包覆钢-混凝土组合结构技术规程》(T/CECS 719—2020)计算得到的开工艺孔的大截面PEC梁抗弯承载力与试验值误差较小,受尺寸效应影响不大,所采用计算公式安全可靠。

面间煤柱与顺槽“掘-充-留”一体化科学问题与技术

我国将煤炭作为兜底保障能源的局面短期内无法改变,仍将长时间面临煤炭资源保护与煤基固废利用率低的难题。通过创新采掘方法,同时实现提高煤炭资源回采率、规模化处置煤基固废,为煤炭行业绿色可持续发展提供了新途径。在深入调研煤炭资源开采技术发展现状的基础上,提出了煤矿“掘-充-留”掘进新工法。从大断面巷道快速掘进、连续高效充填和巷道安全留设3个方面,通过理论分析、数值模拟等手段,系统论述了“掘-充-留”工法的科学问题和关键技术,研究结果表明:①针对大断面巷道快速掘进、掘进工作面围岩稳定性控制等工程难题,凝练了煤岩特性与掘进机截割参数匹配机制、覆岩载荷空间传递机制与围岩变形机理、锚杆/索-顶板相互作用关系及支护机制3个科学难题,构建了以掘进区地质环境超前实时感知、落-装-运煤多工序智能协同作业、钻锚支架随掘随支围岩时效控制和大断面巷道防漏风及通风优化为核心的技术体系;②从大断面巷道承载体系及时构建及其承载性能调控两个方面凝练了连续高效充填的科学问题,包括充填体-煤层-锚杆/索协同承载机制、多元固废基充填材料水化固结机制,明晰充填体物理力学特性时空演化规律,建立了充填空间安全高效搭建、充填材料工作性能调控、充填材料流动-固结感知为核心的连续高效充填关键技术体系,相关理论与技术的突破可以为充填材料的原材料优选及配比设计、添加剂开发/选型及工作性能调控、掘进速率及充填步距优化设计、充填体固结监测等提供基础理论依据;③基于巷道安全留设及全生命周期内围岩易断裂、易片帮和易损伤等关键难题,阐述了巷道围岩应力场时空分布特征、巷道变形与损伤演化机制、巷道围岩工程质量监测与稳定性调控理论3个科学问题,形成了以巷道围岩稳定性智能预警、巷道围岩变形控制为核心的关键技术体系。开展煤矿“掘-充-留”工法的科学研究与工程示范,实现固废规模化处置-面间煤柱高效回收-顺槽快速掘进的协同,可以推动煤炭行业绿色低碳转型发展。

Crack elongation and its width of large depth reinforced concrete beams

In order to meet the requirement of structural inspection,the crack spacing and crack width at various heights in the tensile zone of six large depth reinforced concrete beams were measured under several loading levels of serviceability state.The effects of the depth of normal section beams on the crack spacing and crack width were analyzed,and the modified model is proposed for calculating the average crack spacing by thinking about the depth of normal section,the reinforcement arrangement and the effective reinforcement ratio.The relationships of crack widths at any position in the tensile zone and at the reinforcement level on the side surface of beam were studied.By theoretical and statistical analysis,a method is proposed to calculate the ratios of crack widths between any position and the reinforcement level on the side surface of large depth reinforced concrete beams.