巷道快速掘进技术在贵州省煤与瓦斯突出煤层中的探讨与应用

巷道快速掘进技术是一项系统工程。为了实现矿井高产高效,必须以巷道快速掘进技术为前提和保障。本文以贵州省为例,探讨了巷道快速掘进技术的研究现状及影响因素。针对贵州某矿突出综合检测指标经常超限、掘进速度慢等问题,采用了高压水射流割缝与瓦斯抽放边抽边掘相结合技术。研究表明:该项技术能有效削弱煤层突出危险性,大幅度提高瓦斯抽放量且巷道掘进速度提高了2~3倍。同时根据贵州省的本土情况,提出了针对性地建议和措施,能为巷道快速掘进技术的推广与应用提供一定的指导。     

长距离隧道的通风选型问题浅析

笔者以新建兰渝铁路六标段花石隧道为例,对该隧道的应有的通风设计,结合现有通风方式的弊端和改进,进行浅要的比较分析,在此基础上对同类型隧道的通风选型进行总结。     

我国乡村生态旅游发展中的政府行为研究

乡村生态旅游作为一种新的旅游业态,在乡村旅游中注重生态环境与产业的可持续发展,对农民增收与农村环境保护有重要的促进作用。但目前国内大部分地区对于乡村生态旅游,从概念上到操作上仍然是十分模糊的,这在很大程度上限制了政府对旅游项目有效管理。文章研究认为,乡村生态旅游具有一定公共物品属性,完全依靠市场调节是远远不够的,在不同地区和不同阶段都需要政府介入,但政府行为应当结合具体阶段特征采取适宜策略。政府应通过乡村旅游试点项目的实施,对其有效性、效率、影响和可持续性进行科学的监测和评价;将能力建设同具体的项目操作有机地结合起来,促进乡村生态旅游项目实施效果和效率的提高;应尽量减少行政干预,通过经济宏观调控,强化规划引领、市场监管和公共服务提供。总之,在乡村生态旅游发展中,政府应该有所为有所不为,扮演好主导、扶持与服务的角色。     

隧道工程岩爆地段施工技术措施

本文简要介绍岩爆产生的原因,岩爆分类及特征。通过怀玉山隧道岩爆段的工程实例的分析,得出该隧道所遇岩爆类型为弹射型岩爆。根据弹射岩爆的特点结合施工经验,制定相关技术措施,安全、有效、顺利完成岩爆段的施工。     

Tick Size and Financial Reporting Quality in Small-Cap Firms: Evidence from a Natural Experiment

Using a natural experiment (the SEC's 2016 Tick Size Pilot Program), we investigate the effects of an increase in tick size on financial reporting quality. The tick size pilot program reduces algorithmic trading (AT) and increases fundamental investors’ information acquisition and trading activities. This in turn increases the scrutiny of managers’ financial reporting choices and reduces their incentives to engage in misreporting. Using a difference-in-differences research design, we find a significant decrease in the magnitude of discretionary accruals, a significant reduction in the likelihood of just meeting or beating analysts’ forecasts, and a marginally significant decrease in restatements for the treated firms in the pilot program. Furthermore, we find that the change in financial reporting quality is concentrated in treated firms experiencing decreases in AT and increases in information acquisition activities. We also find that the mispricing of accruals is significantly lower for treated firms. Taken together, our results suggest that an increase in tick size has a causal effect on firms’ financial reporting quality.     

自进式锚杆在隧道超前支护中的应用

隧道极其破碎兼涌水段围岩施工一直是影响隧道施工安全及进度的重要因素之一,自进式锚杆代替超前小导管,是保证隧道施工安全及进度的方法之一,本文详细阐述了自进式锚杆施工工艺,为今后隧道破碎围岩及涌水围岩段施工提供了经验。     

大跨度公路隧道穿越断层破碎带施工技术

结合工程实例,通过对穿越F19(鸡笼山断裂)、F20(源潭断裂)的莲花山2#隧道施工实践的归纳,借助超前地质预报手段,根据围岩情况及时调整施工方案,取得良好效果,通过该段施工更加深了对地下工程特别是特殊地质的认识。     

浅谈营盘山隧道岩溶处理

本文主要通过对营盘山大型溶洞施工组织顺序上的调整和对施工工艺工法顺序的处理方法调整及选择方面介绍,希望对类似的溶洞处理的施工有一定借鉴意义。     

一种带辅助译码比特的Polar码译码方法

在传统的Polar码译码的基础上，引入辅助译码比特，构造了一个辅助的Polar码字以提高译码性能。辅助比特由信道选择辅助窗口内的信息位决定。接收端如译码失败，将进行二次译码尝试。译码方案分两阶段进行：基于相同结构的扩展生成矩阵，将辅助译码比特译出；结合译出的辅助比特，对原码字进行译码，提高译码成功率。仿真结果显示，使用所提方法进行译码，其译码性能明显优于普通串行抵消译码方法；与两种传统的自动重传请求方案相比，能分别获得1 dB和1.9 dB的性能增益。     

Linking of sample data to small areas

We consider methods for estimating the means of survey variables in domains of a finite population, where sample sizes are too small to obtain reliable direct estimates. We construct generalized compositions from the direct and traditional design-based synthetic estimators and propose the methodology for evaluating their coefficients. This methodology measures similarities among sample elements and estimates of the domain means. We propose the compositions for two cases of auxiliary information: domain-level characteristics are available; true means of auxiliary variables are available for the estimation domains, and unit-level auxiliary vectors are known for the sample elements. In the simulation study, we show where the generalized compositions improve the traditional synthetic and composite estimators.