水体与混凝土防爆墙消波减爆作用对比研究

为掌握水体防爆墙消波减爆作用特性,应用量纲分析法建立了防爆墙试验模型尺度律;依据尺度律设计防范汽车炸弹爆炸破坏的水体防爆墙及对比的混凝土防爆墙试验模型;通过数值模拟和实爆试验,验证试验模型尺度律的可适用性,研究水体防爆墙与混凝土防爆墙的消波减爆作用。研究结果表明。所建立的防爆墙模型尺度律具有一定的可适用性;水体防爆墙及混凝土防爆墙的消波减爆作用显著,两种防爆墙对爆炸冲击波峰值压力的衰减程度均可以达到70%以上;水体防爆墙对爆炸冲击波峰值压力的衰减作用稍强于混凝土防爆墙。

水幕减爆防护技术数值仿真

高能炸药爆轰爆炸在极短的时间内产生强烈的冲击波,对周边的结构造成严重的破坏,并导致附近人员的伤亡.水幕减爆作为一种新颖的防护技术,通过在装药或者需要保护结构的外面布置水袋,利用水的加热、压缩和蒸发转移爆炸产生的能量,改变爆炸冲击波的传播方式,减弱爆炸冲击波的影响.建立安全可靠、稳定有效的水幕减爆装置需要大量的参数分析,从而进行优化设计.数值实验仿真提供了研究水幕减爆成本低廉并且没有任何危险的可行方式.传统的网格方法模拟水幕减爆问题存在很多困难.该文应用无网格粒子方法SPH对不同状况下的水幕减爆问题进行了一系列研究,得到一些初步的研究结果,对水幕减爆防护装置的设计和布置具有一定的指导意义.

密闭空间内三种防爆隔墙的减爆吸能效应分析

通过墙体的变形来耗散爆炸能量,可以有效地减轻爆炸冲击波对目标的破坏作用。采用一维应力波理论分析比较钢板夹泡沫铝、钢板夹聚氨脂和钢板夹混凝土三种防爆隔墙的减爆吸能效应,并运用ANSYS/LS-DYNA有限元程序对三种墙体在爆炸冲击波作用下的减爆吸能效应进行数值模拟。研究结果表明:钢板夹泡沫铝的防护效应最好,钢板夹混凝土次之,钢板夹聚氨酯最差。防护效应随着测点到防爆隔墙距离的增加而增大。防爆隔墙的减爆性能不仅与防爆隔墙的变形程度有关,还与防爆隔墙的自身强度有关。

钢板-聚氨酯复合墙体的减爆吸能效应分析

墙体自身变形吸收和耗散爆炸能量，可以有效地减轻爆炸冲击波对目标的破坏作用。采用一维应力波理论分析、比较钢板-聚氨酯和钢板-混凝土复合墙体的减爆吸能效应，并运用ANSYS／LS-DYNA有限元程序对2种复合墙体在爆炸冲击波作用下的减爆吸能性能进行数值模拟。研究结果表明：钢板．聚氨酯复合墙体比钢板．混凝土复合墙体具有更好的减爆吸能效果，主要原因是聚氨酯材料允许墙体产生明显的大变形，耗散了大部分爆炸能量。

空中水下爆炸条件下泡沫铝夹芯板的消波吸能效应

为研究泡沫铝夹芯板在空中与水下爆炸条件下的消波吸能效应,建立空中与水下爆炸冲击有限宽泡沫铝夹芯板的全耦合模型,从爆炸冲击波的反射、透射、绕射及汇聚过程入手,对比分析爆炸冲击波在空气和水中的传播与衰减规律,探讨泡沫铝厚度对夹芯板消波效应的影响。结果表明,泡沫铝夹芯板对空中及水下爆炸均有较好的消波吸能效果;受冲击波绕射及板后汇聚影响,空气和水2种介质中的抗爆设防应以近距离为主;为增强消波效果及芯层的吸能效果,应优先选择芯层较厚的泡沫铝夹芯板。

一种提高管片隧道衬砌结构抗内爆炸性能的工程措施研究

地铁等城市隧道是恐怖爆炸袭击的主要目标之一。盾构管片隧道由不同类型的预制混凝土管片通过接头处的紧固螺栓拼装而成的。由于接头的存在,与整体式衬砌结构相比,其整体刚度和承载水平比较弱,变形和破坏机理与整体式衬砌结构不同。考虑内爆炸的恐怖袭击条件,目前关于管片隧道衬砌结构抗内爆炸的研究成果很少。从分析全尺寸管片内爆炸试验结果入手,分析了内爆炸荷载作用下管片衬砌结构变形和破坏规律,梳理出控制衬砌结构破坏的关键因素和关键位置,提出一种在接头螺栓处添加柔性垫圈来降低与螺栓接触区域管片的破坏程度的方法,以期达到优化衬砌结构抗内爆炸性能的目的。最后采用数值模拟方法,对所提出了抗爆减爆工程措施进行了分析研究。结果表明,该方法可以有效减小管环在接头处的局部破坏,提高管片衬砌的抗内爆炸性能。

沈阳市五区小学生龋病情况调查分析

目的获得目标人群龋病患病和龋齿治疗的相关数据,为适宜措施的实施提供依据。方法样本来自沈阳市口腔医院及口腔预防专业单位每年定期口腔健康检查的沈阳市市内五区小学学生,按照WHO口腔健康调查基本方法第3版为诊断标准进行龋病调查,对龋齿进行早期充填。累计调查10年,对学生龋病患病情况及每年新发龋病治疗充填情况进行统计学分析。结果学生龋病发病率逐年下降;新发龋齿的在校充填率逐年下降,各年度组间新龋充填率差异均有统计学意义(P<0.0001)。结论沈阳市学校口腔卫生保健措施对学生患龋率的逐年下降起促进作用;口腔医疗技术的发展使就医者的选择性拓宽,学生新发龋齿的在校充填率相应下降。

Weak solution for a fourth-order nonlinear wave equation

The existence and the nonexistence,the uniqueness and the energy decay estimate of solution for the fourth-order nonlinear wave equation utt＋αΔ2 u-bΔut-βΔu＋ut｜ut｜^r＋g（u）=0 in Ω×（0,∞） are studied with the boundary condition u=（u）/（υ）=0 onΩ and the initial condition u（x,0）=u0（x）,ut（x,0）=u1（x,0） in bounded domain ΩR^n ,n≥1.The energy decay rate of the global solution is estimated by the multiplier method.The blow-up result of the solution in finite time is established by the ideal of a potential well theory,and the existence of the solution is gotten by the Galekin approximation method.

Exponential decay law of acoustic emission and microseismic activities caused by disturbances associated with multilevel loading and mining blast

To investigate decay law of acoustic emission and microseismic activities caused by disturbances associated with multilevel loading and mining blast,a new exponential decay(ED)law was proposed.The results show that the micro-fracture activity decay law after multistage stress loading and blasting disturbance conforms to the ED model,in which the sum of A and n represents the number of initial micro-fracture events,and n represents the level of background micro-fracture events.The ED model can describe the number of initial micro-fracture events with a deviation less than 10%.The ED model outperforms the traditional aftershock models in describing the micro-fracture event decay law in the three cases considered.The ED model can provide a reference for selecting the blasting interval in mines,which is of great significance to maintain the stability of the surrounding rock and ensure safe production in metal mines.

The test research on partial relieving pressure for the entry in the deep mine under high stress and friable surrounding rock

Based on the geological condition of Zhangxiaolou deep mine in Xuzhou mining area, under 986 m in depth, 20.6-31.6 MPa in maximum horizontal principal stress, and friable and fractured surrounding rock, test researches on partial relieving pressure were completed for the entry with U-steel arched yielding support. The relieving pressure parameters, technology process and results of springing blasting by boreholes and excavating pockets in the two sides of entry were introduced. It is demonstrated that springing will not be shaped under the condition of single borehole arrangement after exploded, the arrangement by a group, it will make borehole bottom form springing in 0.6-0.8 m in diameter, that convergence of two sides and roof to floor have some increments by using springing blasting for reliving pressure. This kind of method for reliving pressure is not suitable to use in the deep mine, and that the convergence of two sides obviously declined by excavating pocket in two sides, it can be still used in the entry with metal support, while maintenance of entry in deep mines is difficult, and can not be supported by bolt or bolt with wire mesh.

Forecast correct model of overpressure attenuation during gas explosion in excavation roadway

Through analyzing experimental data of gas explosions in excavation roadwaysand the forecast models of the literature, Found that there is no direct proportional linearcorrelation between overpressure and the square root of the accumulated volume of gas,the square root of the propagation distance multiplicative inverse.Also, attenuation speedof the forecast model calculation is faster than that of experimental data.Based on theoriginal forecast models and experimental data, deduced the relation of factors by introducinga correlation coefficient with concrete volume and distance, which had been verifiedby the roadway experiment data.The results show that it is closer to the roadway experimentaldata and the overpressure amount increases first then decreases with thepropagation distance.

由上市公司商誉减值爆雷带来的会计思考

截至2018年底,上市公司商誉余额为1.31万亿元,分布在2,048家上市公司,共有885家上市公司计提了商誉减值损失,合计金额为1,667.64亿元。上市公司年底巨额商誉减值集中计提,愈发成为引发证券市场黑天鹅事件的重要因素之一。本文将从现行企业会计准则对商誉的相关规定出发,从商誉形成的源头,即企业并购行为过程中的风险防范提出建议,供有关人员参考。

Mechanism of energy limit equilibrium of rock burst in coal mine

With the increase of mining depth,the effect of rock burst on coal mining is becoming more and more obvious and the rock burst mechanism becomes more and more complicated.Scholars from many countries had put forward different mechanisms,but no one gave a reasonable explanation to the mechanism of rock burst.In this paper,based on the energy theories,we studied the energy limit equilibrium（ELE） of coal mine rock burst The coal seam with rock burst is divided into energy limit equilibrium zone（ELEZ）（A） and elastic zone（B）;we also determined the position where the rock burst occurs,including the roof and floor of coal seams;in addition,we derived the limit width of ELEZ and the mathematic relationship between the limit width and occurrence mechanism of rock burst：the energy difference function（EDF）,w（x） = w_j - w_p,because first-order derivative w＇（x）,is less than 0.So EDF is a monotonically decreasing function.The graph of the energy difference function was also determined, through which we analysed the occurrence mechanism of rock burst.

Blasting technologies of vibration damping in subway tunnel passing under upper buildings closely

Reducing the blasting vibration is important for blasting excavation in subway tunnel construction.Taking the 3rd bid section of Line 3 of Qingdao subway project as an example,the distance between tunnel vault and ground is 5 ~ 8 m.In order to insure the safety of the upper buildings,technologies of parallel cut with large diameter empty hole,one-time initiation and delay by parts,and multiple shallow holes were adopted in the project.The results showed that the maximum value of vertical vibration was limited in the criterion allowance,and the upper buildings were not damaged.Besides,problems were solved that the number of nonel detonator was difficult to meet the requirements of excavating a large cross-section tunnel by blasting,multiple cross-section could’t be initiated simultaneously,and construction efficiency was low,which ensure the construction safety and schedule.

A Blast Shock Isolation System with MRFD and Its Semi-Active Control Analysis

To effectively reduce the damage to people and devices in civil defense engineering subjected to blast shock, a blast shock isolation system with magnetorheological fluid dampers (MRFD) is proposed. MRFD can provide continuously adjustable Coulomb friction and has many advantages for semi-active control. Numerical simulation of this isolation system is finished using Matlab simulink toolbox. General semi-active control algorithms are consided based on instantaneous optimal active control algorithm. And the results indicate that the shock isolation system can work efficiently, decreasing about 93% of the peak acceleration of the isolation floor.

A modified method of coracoid transposition for the treatment of complete dislocation of acromioclavicular joint

Objective: To report a new method of coracoid transposition for the treatment of complete dislocation of acromioclavicular joint and to evaluate its efficacy. Methods: We modified Dewar’s surgical method as follows: (1) Two small incisions, a transversal incision on the acromioclavicular joint and a longitudinal incision on the coracoid, were made instead of a conventional large arc incision from the acromion to coracoid. (2) The foreign body in the acromioclavicular joint was cleared out. The chondral surface at the lateral segment of clavicle was resected to form a pseudarthrosis and meanwhile the residual joint capsule and ligaments were repaired. (3) The coracoid was moved to the anteroinferior edge of the clavicle instead of the anterior margin and (4) the coracoid was moved to the lateral border of the clavicle instead of the superior border of the coracoclavicular ligament. Results: The follow up duration in 30 patients of the series was from 6 to 72 months (mean 41 months). Functional assessment was carried out by the criteria delineated previously by Karkson, in which Grade A was in 24 cases, Grade B in 4cases, and C in 2. Conclusions: This modified technique, having less postoperative complications and less injuries to tissues and according well with the requirement of biomechanics, can achieve a stable reduction of acromioclavicular joint with a good functional and cosmetic result and therefore is preferable to use clinically on a large scale.

Energy Decaying and Blow-Up of Solution for a Kirchhoff Equation with Strong Damping

The initial boundary value problem for a Kirchhoff equation with Lipschitz type continuous coefficient is studied on bounded domain.Under some conditions,the energy decaying and blow-up of solution are discussed.By refining method,the exponent decay estimates of the energy function and the estimates of the life span of blow-up solutions are given.

Complete L5 burst fracture treated by 270-degree decompression and reconstruction using titanium mesh cage via a single posterior vertebrectomy

Complete burst fractures of the L5 is relatively uncommon.How to accomplish a rigid internal fixation as well as preserve motor function is an enormous challenge.We report such a case treated via a single posterior vertebrectomy with 270-degree decompression and reconstruction using titanium mesh cage.The disc between L5/S1 was preserved by placing the titanium mesh cage on the inferior endplate of the L5.We hope this method can offer a possible solution for other surgeons when they meet a similar fracture pattern.