一种改进的引入修正矩阵的波束赋行算法

提出了一种改进的引入修正矩阵的波束赋行算法。改进的算法在原有的多波束赋行算法(GOB算法)的基础上,通过引入修正矩阵,纠正业务波束在扇区边缘的指向偏差。理论分析和仿真结果表明改进的算法相比原算法提高了业务波束在扇区边缘的指向准确度,对系统性能有一定的提升。

6阵元智能天线赋形方法性能测试研究

本文研究蜂窝小区6阵元智能天线在不同场景下的天线赋形增益,及不同智能天线赋形算法的性能。实验测试结果表明,对于6阵元智能天线,采用赋形比不采用赋形方式能得到3～5dB的增益,采用特征分解赋性算法(EBB)比固定波束赋形算法(GOB)增益高1～3dB左右。

Domino instability effect of surrounding rock-coal pillars in a room-and-pillar gob

To discuss the domino instability effect and large area roof falling and roof accidents of surrounding rockcoal pillars in a room-and-pillar gob,the equilibrium equation for a roof-coal pillar-floor system with the influence of mining floor was developed based on the engineering conditions of the surrounding rock in a room-and-pillar gob in the 3^(-2)coal seam of Tanggonggou mine.The conditions of system instability and the relationship between system stability and system stiffness were analyzed from an energetic point of view.Numerical simulation using the discrete element software UDEC was also carried out to simulate conditions causing the domino effect on surrounding rock-coal pillars in a 3^(-2)room-and-pillar gob.The results show that:if we want the system to destabilize,the collective energy in roof-and-floor must be larger than that in the coal pillar.When the stiffness of the coal pillars and the roof-and-floor are both greater than zero,the system is stable.When the stiffness of the coal pillars is negative but the summed stiffness of the coal pillars and roof-and-floor is larger than or equal to zero,the system is statically destroyed.When the sum of the coal pillars and the roof-floor stiffness is negative,the system suffers from severe damages.For equal advance distances of the coal mining face,the wider coal pillars can reduce the probability of domino type instability.Conversely,the smaller width pillars can increase the instability probability.Domino type instability of surrounding rock-coal pillars is predicted to be unlikely when the width of coal pillars is not less than 8 m.

静52-H1Z分支水平井钻井液技术

静52-H1Z井是位于大民屯凹陷静安堡潜山静52块的一口20分支水平井。该井二开井眼尺寸大且长(2813m),需要解决大斜度、大井眼的携岩、井壁稳定、润滑和油气层保护问题,通过应用固相含量低、具有良好的触变性、流动性、悬屑和携岩性能的复合膜钻井液,并配合使用替代柴油的的新型润滑剂LH-Ⅸ、屏蔽暂堵技术、超低渗透降滤失剂及相关的工艺技术解决了上述问题。该井三开水平段有20个分支,水平位移超过2000m,需要解决水平段、分支井段的钻井液携岩、润滑问题以及套管磨损问题和油气层保护问题,通过应用GOB携岩技术、具有很高动塑比的PWG新型无固相钻井液及相关的工艺技术很好地解决了上述问题,形成了一套完整的潜山储层鱼骨多分支水平井钻井液工艺技术。应用结果表明,复合膜钻井液、PGW新型无固相钻井液在深水平井中具有很好的应用效果。

Criterion of local energy release rate of gob instability in deep mines considering unloading stress path

The stress path characteristics of surrounding rock in the formation of gob were analyzed and the unloading was solved. Taking Chengchao Iron Mine as the engineering background, the model for analyzing the instability of deep gob was established based on the mechanism of stress relief in deep mining.The energy evolution law was analyzed by introducing the local energy release rate index(LERR), and the energy criterion of the instability of surrounding rock was established based on the cusp catastrophe theory. The results show that the evolution equation of the local energy release of the surrounding rock is a quartic function with one unknown and the release rate increases gradually during the mining process.The calculation results show that the gob is stable. The LERR per unit volume of the bottom structure is relatively smaller which means that the stability is better. The LERR distribution showed that there was main energy release in the horizontal direction and energy concentration in the vertical direction which meets the characteristics of deep mining. In summary, this model could effectively calculate the stability of surrounding rock in the formation of gob. The LERR could reflect the dynamic process of energy release,transfer and dissipation and that provided an important reference for the study of the stability of deep mined out area.

Analysis of global and local stress changes in a longwall gateroad

A numerical-model-based approach was recently developed for estimating the changes in both the horizontal and vertical loading conditions induced by an approaching longwall face.In this approach, a systematic procedure is used to estimate the model's inputs.Shearing along the bedding planes is modeled with ubiquitous joint elements and interface elements.Coal is modeled with a newly developed coal mass model.The response of the gob is calibrated with back analysis of subsidence data and the results of previously published laboratory tests on rock fragments.The model results were verified with the subsidence and stress data recently collected from a longwall mine in the eastern United States.

Unanticipated multiple seam stresses from pillar systems behaving as pseudo gob–case histories

Underground coal mining in the U.S. is conducted in numerous regions where previous workings exist above and/or below an actively mined seam. Miners know that overlying or underlying fully extracted coal areas, also known as gob regions, can result in abutment stresses that affect the active mining. If there was no full extraction, and the past mining consists entirely of intact pillars, the stresses on the active seam are usually minimal. However, experience has shown that in some situations there has been sufficient yielding in overlying or underlying pillar systems to cause stress transfer to the adjoining larger pillars or barriers, which in turn, transfer significant stresses onto the workings of the active seam. In other words, the overlying or underlying pillar system behaves as a ‘‘pseudo gob." The presence of a pseudo gob is often unexpected, and the consequences can be severe. This paper presents several case histories, summarized briefly below, that illustrate pseudo gob phenomenon:(1) pillar rib degradation at a West Virginia mine at 335 m depth that contributed to a rib roll fatality,(2) pillar rib deterioration at a Western Kentucky mine at 175 m depth that required pillar size adjustment and installation of supplemental bolting,(3) roof deterioration at an eastern Kentucky mine at 400 m depth that stopped mine advance and required redirecting the section development,(4) coal burst on development at an eastern Kentucky mine at 520 m depth that had no nearby pillar recovery, and(5) coal burst on development at a West Virginia mine at the relatively shallow depth of 335 m that also had no nearby pillar recovery. The paper provides guidance so that when an operation encounters a potential pseudo gob stress interaction the hazard can be mitigated based on an understanding of the mechanism encountered.

Synergistic instability of coal pillar and roof system and filling method based on plate model

The security challenges from room and pillar gobs include land subsidence, spontaneous combustion of coal pillars and mine flood caused by gob water. To explore the instability mechanism of room and pillar gob, we established a mechanical model of elastic plate on elastic foundation in which pillars and hard roofs were considered as continuous Winkler foundations and elastic plates, respectively. The synergetic instability of pillar and roof system was analyzed based on plate bending theory and catastrophe theory. In addition, mechanical conditions and math criterion of roof failure and overall instability of coal pillar and roof system were given. Through analyzing both advantages and disadvantages of some technologies such as induced caving, filling, gob sealing and isolation, we presented a new filling method named box-filling, in view of box foundation theory, to control the disasters of ground collapse, water inrush and mine fire. In a gob's treatment project in Ordos, safety assessment and filling design of a room and pillar gob have been done by the mechanical model. The results show that the gob will collapse when the pillars' average yield band is wider than 0.93 m, and box-filling can control land collapse, mine flood and mine fire economically and efficiently. So it is worth to study further and popularize.

Optimization of gob ventilation boreholes design in longwall mining

Gob ventilation boreholes(GVBs)are widely used for degasification in U.S.longwall coal mines.Depending on geological conditions,30–50%of methane can be recovered from longwall gob using GVBs.A NIOSH funded research at the Colorado School of Mines confirmed that GVBs can efficiently reduce methane at the face.However,GVBs can also draw some fresh air from the face and create explosive gas zones(EGZs).Explosive gas mixtures may be formed in gob areas due to the increased ingress of oxygen from GVBs.It is critical to identify the locations for GVBs for maximizing extraction of methane and minimizing hazards of explosion.This study analyzes the effect of operating parameters and design of GVB on methane extraction,EGZs formation,and face and tailgate methane concentrations.Methane extraction,formation of EGZs,and concentration of methane in working areas are significantly impacted by various factors.These factors include the distance of work face and tailgate from GVBs,diameter of GVBs,vacuum pressure of wellhead,GVB distance from the roof of the coal seam,and number of operating GVBs in a panel.Computational fluid dynamics(CFD)evaluations suggest optimal design and operating parameters of GVBs that can contribute to maximum benefits with minimum risks.

Temperature field simulation of gob influenced by atmospheric pressure

The current temperature field model of mine gob does not take the boundary conditions of the atmospheric pressure into account, while the actual atmospheric pressure is influenced by weather, so as to produce differences between ventilation negative pressure of the working face and the negative pressure of gas drainage in gob, thus interfering the calculated results of gob temperature field. According to the characteristics of the actual air flow and temperature change in gob, a two-dimensional temperature field model of the gob was built, and the relational model between the air pressure of intake and outlet of the gob and the atmospheric pressure was established, which was introduced into the boundary conditions of temperature field to conduct calculation. By means of analysis on the simulation example, and comparison with the traditional model, the results indicate that atmospheric pressure change had notable impact on the distribution of gob temperature field. The laboratory test system of gob temperature field was constructed, and the relative error between simulated and measured value was no greater than 9.6%, which verified the effectiveness of the proposed model. This work offers theoretical basis for accurate calculation of temperature and prediction of ignition source in mine gob, and has important implications on preventing spontaneous combustion of coal.

一种支持多业务承载的广义光突发汇聚机制

引入广义光突发汇聚(GOBA)概念对传统光突发交换(OBS)进行扩展,形成新的广义OBS(GOBS)网络。针对GOBS的多业务承载目标,提出了一种支持多业务承载的GOBA机制,采用将业务最小时延要求作为汇聚时间的汇聚方式,将多种用户数据业务汇聚到不同粒度的广义数据突发(GDB)中。仿真结果表明,在GOBS环境下,与MSMAP(max burst-size max assembly period)机制相比,GOBA能够在满足较高数据成功接收率的基础上显著地减小约10%的总体数据超时率,同时降低约15%的突发碰撞率,并提高约20%信道利用率。

Iterative Selection of GOB Poles in the Context of System Modeling

This paper is concerned with the problem of system identification using expansions on generalized orthonormal bases(GOB). Three algorithms are proposed to optimize the poles of such a basis. The first two algorithms determine a GOB with optimal real poles while the third one determines a GOB with optimal real and complex poles. These algorithms are based on the estimation of the dominant mode associated with a residual signal obtained by iteratively filtering the output of the process to be modelled. These algorithms are iterative and based on the quadratic error between the linear process output and the GOB based model output. They present the advantage to be very simple to implement. No numerical optimization technique is needed, and in consequence there is no problem of local minima as is the case for other algorithms in the literature. The convergence of the proposed algorithms is proved by demonstrating that the modeling quadratic error between the process output and the GOB based model is decreasing at each iteration of the algorithm. The performance of the proposed pole selection algorithms are based on the quadratic error criteria and illustrated by means of simulation results.