底板切槽卸压控鼓技术在高应力软岩巷道中的应用

随着冲击地压防治措施的落实执行,巷道及硐室层位更多考虑布置于煤层底板或顶板中。受深部高应力显现及底板软岩特性等影响,巷道形变特别是底鼓尤为突出,通过在巷道底板施工切槽,将高应力转移到巷道基角和底板深部围岩,为巷道底板围岩变形提供补偿空间,使应力升高区向围岩深部转移,用切槽的形变量代替了巷道底板变形量,塑性区范围逐步扩大,应力变化区域平稳,应力集中现象减弱,从而防止高水平应力场下严重底鼓的发生达到卸压控鼓的目的;同时,采取疏、排、堵等控水措施减少因水理因素造成的巷道底鼓现象。

振动排痰仪联合控压鼓肺对颅脑手术患者肺部感染的预防

目的:观察在颅脑手术患者中振动排痰仪联合控压鼓肺对其肺部感染的预防效果。方法:选取某医院收治的80例颅脑手术患者作为研究对象,随机分为对照组和观察组,各40例,对照组使用控压鼓肺,观察组使用振动排痰仪联合控压鼓肺,对比两组术后动脉血气指标改善结果、肺部感染发生率以及排痰效果。结果:观察组患者术后1天和1周的PaCO_(2)、PaO_(2)、SaO_(2)及排痰效果均优于对照组,差异均有统计学意义(P<0.05);观察组患者的感染率低于对照组,差异有统计学意义(P<0.05)。结论:对颅脑手术患者使用振动排痰仪结合控压鼓肺,能够有效地控制患者肺部感染发生率,促进患者的呼吸道痰液排出,控制低氧血症,改善肺通气功能,达到良好的预防效果。

可控鼓泡式正压呼吸支持装置在婴幼儿疾病中的应用

目的观察可控鼓泡式正压呼吸支持装置对需要呼吸支持患儿的临床治疗效果。方法对我院PICU、NICU及C ICU中行无创呼吸支持的113例患儿进行临床疗效观察。将所有患儿随机分为两组,其中治疗组(53例)在常规治疗基础上给予可控鼓泡式正压呼吸支持装置-鼻塞式气道持续正压通气(NCPAP)呼吸支持,对照组(60例)在常规治疗基础上给予德国STEPHAN CPAP-A呼吸机NCPAP呼吸支持,动态监测两组患儿治疗前、治疗后1、2、8、12 h的动脉血气,并对两组患儿插管机械通气发生率进行比较。结果治疗后两组患儿血气指标比较差异无统计学意义(P>0.05),插管机械通气发生率比较差异无统计学意义(P>0.05)。结论可控鼓泡式正压呼吸支持装置对需要初步呼吸支持的患儿临床治疗效果良好,能达到同类机器的治疗效果,且结构简单,操作方便,价格低廉,适合在基层医院中推广使用。

TRANSONIC DRAG REDUCTION ON SUPERCRITICAL WING SECTION USING SHOCK CONTROL BUMPS

Two-dimensional and three-dimensional shock control contour bumps are designed for a supercritical wing section with the aim of transonic wave drag reduction. The supercritical airfoil （NASA SC （02）-0714） is selected considering the fact that most modern jet transport aircrafts that operate in the transonic flow regime （cruise at transonic speeds） employ supercritical airfoil sections. Here it is to be noted that a decrease in the transonic wave drag without loss in lift would result in an increased lift to drag ratio, which is a key range parameter that can potentially increase both the range and endurance of the aircraft. The major geometric bump parameters such as length, height and span are altered for both the two-dimensional and three-dimensional bumps in order to obtain the optimum location and shape of the bump. Once an optimum standalone three-dimensional bump is acquired, an array of bumps is manually placed spanwise of an unswept supercritical wing and analyzed under fully turbulent flow conditions. Different configurations are tested with varying three-dimensional bump spacing in order to determine the contribution of bump spacing on overall performance. The results show a 14% drag reduction and a consequent 16% lift to drag ratio rise at the design Mach number for the optimum arrangement of bumps along the wing span.

Control technology for floor heave of Jurassic soft rock in the Erdos Basin of China: A case study

The deformation of soft rock roadway caused by floor heave is a major challenge for coal mines in China western mining areas. To achieve security and stability of soft rock roadway, this work considered the headgate at panel 11505 of the Yushujing Coal Mine as background. First, based on the limit equilibrium method and slip line field theory,a model of floor heave was established, the mechanism of floor heave control was analyzed, and an optimized support method was proposed. Then, the displacement, stress and failure zones around the surrounding rock with the original and optimized support were studied by FLAC. Finally, the serviceability of the support method was verified by field application. The results showed that the main deformation form of soft rock roadway is floor heave, and 0.5 m is relatively reasonable thicknesses of the inverted arch. The extrusion failure zone and shear failure zone were mainly affected by tensile and shear failure, respectively. The modification of floor and the effective support are key points. The failure zone was consistent between numerical simulation and theoretical calculation. The maximum convergences of floor heave determined by numerical simulation and field measurement were 220 mm and 240 mm, respectively, which were reduced by 55% and 60% compared with the original support, and the convergence between sidewalls decreased considerably. The optimized support method controls the floor heave well.

Deformation control of asymmetric floor heave in a deep rock roadway:A case study

In order to control asymmetric floor heave in deep rock roadways and deformation around the surrounding rock mass after excavation, in this paper we discuss the failure mechanism and coupling control countermeasures using the finite difference method （FLAC^3D） combined with comparative analysis and typical engineering application at Xingcun coal mine, It is indicated by the analysis that the simple symmetric support systems used in the past led to destruction of the deep rock roadway from the key zone and resulted in the deformation of asymmetric floor heave in the roadway. Suitable rein- forced support countermeasures are proposed to reduce the deformation of the floor heave and the potential risk during mining. The application shows that the present support technology can he used to better environmental conditions. The countermeasures of asymmetric coupling support can not only effectively reduce the discrepancy deformation at the key area of the surrounding rock mass, hut also effectively control floor heave, which helps realize the integration of support and maintain the stability of the deep rock roadways at Xingcun coal mine.

Numerical simulation of grooving method for floor heave control in soft rock roadway

Grooving method can restrain the deformation and destruction of surrounding rock by transferring the maximum stress to deep rock,bringing about the effective control for floor heave in soft rock roadway. Based on this important effect,and to discuss the relationship between cutting parameters and pressurerelief effect,this paper carried out a numerical simulation of grooving along bottom slab and two sides of gateway with finite difference software FLAC^（2D）.The results show that the control effect on floor heave in soft rock tunnel can be improved by selecting appropriate cutting parameters.Appropriately increasing the crevice depth in the middle of the floor can improve the stress state of bottom slab by stress transfer. So the floor heave can be more effectively controlled.To lengthen the crevice in the corners of roadway can simultaneously transfer the maximum stresses of bottom slab and two sides to deep rock,and promote the pressure-relief effect.Extending the crevice length and crevice width on both sides within a certain range can decrease the stress concentration in the corners of roadway,and reduce the deformation of two sides.The cutting position beneficial to restrain the floor heave is close to the bottom slab.

Experimental and Analytical Analysis of Perforated Plate Aerodynamics

Perforated walls and transpiration flow play an important role in aerodynamics due to an increasing interest in application of flow control by means of blowing and/or suction. An experimental study was carried out which has led to the determination of a transpiration flow characteristics in the form of a simple formula that is very useful in modelling such flows. In connection to this relation a method of 'aerodynamic porosity' determination has been proposed which is much more reliable than geometric description of the porosity. A theoretical analysis of the flow through a perforation hole was also carried out. The flow was considered as compressible and viscous. The gasdynamic analysis led us to a very similar result to the relation obtained from the experiment. The adequacy of the theoretical result is discussed in respect to the experiment.