Application of pressure relief and permeability increased by slotting a coal seam with a rotary type cutter working across rock layers

Pressure relief to increase permeability significantly improves gas extraction efficiency from coal seams. In this paper we report results from simulations using FLAC^3D code to analyze changes in coal displacement and stress after special drill slots were formed. We investigated the mechanism of pressure relief and permeability increase in a high-gas and low-permeability coal seam through the modeling of gas flow. This allows the development of the technology. Slotting across rock layers in the coal seam with a rotary type cutter was then applied in the field. The results show that pressure relief and permeability increases from slotting the coal seam can increase the transport and the fracture of the coal. This expands the range of pressure relief from the drilling and increases the exposed area of the seam. The total quantity of gas extracted from slotted bore holes was three times that seen with ordinary drilling. The concentration of gas extracted from the slotted drills was from two to three times that seen using ordinary drills. The gas flow was stable at 80%. Improved permeability and more efficient gas extraction are the result of the slotting. The roadway development rate is increased by 30–50% after gas drainage. This technology diminishes the lag between longwall production and roadway development and effectively prevents coal and gas outburst, which offers the prospect of broad application.     

多层大跨度桁框结构体系及优化设计

多层大跨度桁框结构主要由桁架梁和框架柱组成,在我国尚属新型结构体系,为探讨桁框结构合理的经济尺寸和用钢量,进而对结构初步设计提出优化建议;文章针对不同建筑尺寸、不同荷载情况,设计了21个桁框结构模型试件,并进行了用钢量分析,重点探讨了结构用钢量与楼面活载、开间、跨度、跨数、层数的关系。结果表明：多层桁框结构的单位面积用钢量与多层框架结构基本相同,跨度、楼面荷载对用钢量的影响最显著。分析发现桁框结构的经济跨度为18m左右,经济开间为6—10m,跨数不宜少于2跨。     

SQLite系统构架及虚拟机分析

就目前广泛使用的轻量级数据库SQLite的构架进行分析,特别是对其中的虚拟数据库引擎(VDBE)做了原理性的剖析,并结合实例,展示了SQLite的应用及SQLite内部VDBE指令程序的运行方式。     

温度变化对钾离子跨膜通道蛋白传输能力的影响

为了研究温度变化对生物膜跨膜传输能力的影响,本文以钾离子跨膜通道蛋白为研究对象,利用Gromacs分子生物学模拟软件包和Gromos96(53a6)分子力场,通过分子动力模拟技术和伞状采样方法详细研究了300K和275K两个温度条件下钾离子跨膜通道蛋白对单个钾离子的传输机理和Potentials of Means Force自由能在整个传输过程中的变化曲线。分析伞状采样的计算结果表明,温度的下降对钾离子跨膜通道蛋白的传输能力具有较大影响,300K时,钾离子在跨膜通道蛋白中的传输过程是热力学自发过程;然而,当温度下降到275K后,跨膜通道蛋白前沿空腔对钾离子的捕捉能力明显下降,选择性位点的能垒和传输通道的自由能普遍上升,导致跨膜通道蛋白出口的自由能高于其入口的自由能,最终使钾离子跨膜通道蛋白对钾离子传输方向发生逆转。同时该结果还可以对冷害发生的机理和防治给予重要的启示:说明温度下降后,果蔬体内物质传输能力的下降和停滞是造成冷害发生的一个主要原因。     

塑料瓶贴标用乳液胶的研究

本文分析了塑料瓶的表面结构特性及其对贴标胶的要求，简介乳液胶的合成过程，讨论了聚会温度、搅拌速度、增粘剂和改性剂对贴标胶的影响。     

Photocatalytic properties of the SBA-15 mesoporous silica molecular sieve modified with titanium

We describe three methods of post-synthesis modification of the SBA-15 mesoporous molecular sieve with titanium: impregnation with Ti(OEt)₄ in an ethanolic solution, grafting with titanocene dichloride, and modification with colloidal titania. The products were characterized using X-ray diffraction (XRD) and N₂ adsorption as well as Fourier-transform infrared and ²⁹Si NMR spectroscopies. All three methods yield materials containing 1.4--4.7 wt.% titanium and with high surface areas. The absorbance at 960 cm⁻¹ in SBA-15 modified with colloidal titania and SBA-15 grafted with titanocene indicates the formation of Ti–O bonds. All products showed significant activity towards the degradation of p-chlorophenol. UV-vis absorption spectra of SBA-15 samples modified with titanium indicate that the variation in the photocatalytic activity is governed by isolated titanium sites.     

Synthesis of Ti2SnC from Ti/Sn/TiC powder mixtures by pressureless sintering technique

Ti/Sn/TiC powder mixtures were first employed to synthesize Ti₂SnC powder by pressureless sintering in the temperature range of 950–1250 °C at vacuum atmosphere. Ti₂SnC began to form at 950 °C, its content increased with increasing temperature. High purity of Ti₂SnC was obtained by sintering the mixtures with deficient Sn and TiC at 1200 °C for 15 min. A reaction mechanism was proposed to explain the formation of Ti₂SnC. The Ti₂SnC powder was characterized by scan electron microscopy (SEM) and X-ray diffraction (XRD). Using the above mixtures and process, the Ti₂SnC ceramic powder can be obtained on a larger scale.     

神经网络在蒸养粉煤灰砖抗压强度预测中的应用

首先简要阐述蒸养粉煤灰砖的生产流程,然后通过建立BP神经网络模型来预测粉煤灰砖的抗压强度值,仿真结果表明此模型用于强度预测是可行的。     

基于通用USB接口的软件加密狗设计

USB接口已逐渐成为计算机上最常用的接口之一,基于USB接口的软件加密狗相对于并口或串口的软件加密狗将具有更强的通用性。同时,由于USB接口的热插拔特性,用户使用时更加便捷。本文主要讨论了基于单片机扩展USB接口设计软件加密狗的方法,给出了硬件原理图并介绍了固件程序、设备驱动、RC5加密算法的编制过程。     

入侵检测技术研究

论文介绍了入侵检测技术的概念,分类和通用入侵检测框架,详细分析了各种入侵检测技术。并对入侵检测技术的未来发展方向进行了探讨。