Mechanisms of support failure and prevention measures under double-layer room mining gobs——A case study: Shigetai coal mine

In the practice of mining shallow buried ultra-close seams,support failure tends to occur during the process of longwall undermining beneath two layers of room mining goaf(TLRMG).In this paper,the factors causing support failure are summarized into geology and mining technology.Combining column lithology and composite beam theory,the key stratum of the rock strata is determined.A finite element numerical simulation is used to analyze the overlying load distribution rule of the main roof for different plane positions of the upper and lower room mining pillars.The tributary area theory(TAT)is adopted to analyze the vertical load distribution of each pillar,and dynamic models of coal pillar instability and main roof fracture are established.Through key block instability analysis,two critical moments are established,of which critical moment A has the greater dynamic load strength.Great economic losses and safety hazards are created by the dynamic load of the fracturing of the main roof.To reduce these negative effects,a method of pulling out supports is developed and two alternative measures for support failure prevention are proposed:reinforcing stope supports in conjunction with reducing mining height,or drilling ground holes to pre-split the main roof.Based on a comprehensive consideration of economic factors and the two categories of support failure causes,the method of reinforcing stope supports while reducing mining height was selected for use on the mining site.

Effect of Supportive Measures Guidelines on Nurses’ Practices during Labor

Objectives: To investigate the effect of supportive measures guidelines on nurses’ practices during labor. Methods: A quasi-experimental design (an interventional pre and post-test study). Setting: The study was conducted at obstetric wards and intrapartum units at Nasser Institute Hospital. Sample: All nurses provide guided direct care, there were 40 nurses included in the study. Tools: Three tools were used to collect data named self-administered questionnaire sheet, labor supportive measures’ observational checklists, and nurses’ satisfaction sheet. Results: There was a highly significant improvement in total knowledge and total practical skills among the studied sample pre-intervention compared to immediate post and follow-up intervention (p ≤ 0.01). Additionally, 95% of the studied sample was satisfied with the advanced knowledge included in the guidelines. Conclusion: The supportive measures guidelines had an efficient improving nurses’ knowledge and practices post-intervention. Also, the majority of the studied sample was satisfied with the implemented guidelines. Recommendations: Implementation of labor supportive measure guidelines in different childbirth units to improve nurses’ practice. Further research is required to investigate parturient woman’s satisfaction with the childbirth process after implementing labor supportive measures and the effect of labor supportive measures on childbirth process outcome.

“To measure is to know”: how advances in image analysis are supporting neural repair strategies

Neuronal regeneration in the peripheral nervous system arises via a synergistic interplay of neurotrophic factors,integrins,cytoskeletal proteins,mechanical cues,cytokines,stem cells,glial cells and astrocytes.

10 Finance Measures Constituted by the Party's Central Committee to Support Enterprise Reform

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Experimental study of a technique for load measurement of powered supports

Despite the increasing popularity of mechanized coal mining, there are no convenient and accurate means available to measure the loads of powered supports. The measurement of such loads is important for monitoring mine pressure and ensuring production safety. The load-carrying features of a powered support were used to develop a method for load measurement using the mag-netoelastic principle. A cross bridge-type magnetoelastic stress sensor was designed for the support structures to measure the different parts of the supports. Tests on single-body hydraulic cylinders and simulated linkages showed that an approximately linear relationship between the values of the sensor output signal and the loads borne by the hydraulic cylinders or linkages. The results were used to analyze the load-carrying measurements of powered supports with the cross bridge-type magnetoelastic stress sensor.

Some Results for Exact Support Recovery of Block Joint Sparse Matrix via Block Multiple Measurement Vectors Algorithm

Block multiple measurement vectors (BMMV) is a reconstruction algorithm that can be used to recover the support of block K-joint sparse matrix X from Y = ΨX + V. In this paper, we propose a sufficient condition for accurate support recovery of the block K-joint sparse matrix via the BMMV algorithm in the noisy case. Furthermore, we show the optimality of the condition we proposed in the absence of noise when the problem reduces to single measurement vector case.

Evaluation of preventive,supportive and awareness building measures among international students in China in response to COVID-19:a structural equation modeling approach

Background:Education institutions promptly implemented a set of steps to prevent the spread of COVID-19 among international Chinese students,such as restrictive physical exercise,mask wear,daily health reporting,etc.Success of such behavioral change campaigns largely depends on awareness building,satisfaction and trust on the authorities.The purpose of this current study is to assess the preventive,supportive and awareness-building steps taken during the COVID-19 pandemic for international students in China,that will be useful for planning such a behavioral change campaign in the potential pandemic situation in other parts of the world.Methods:We conducted an online-based e-questionnaire survey among 467 international students in China through WeChat.The data collection duration was from February 20,2020 to March 10,2020 and we focused on their level of awareness,satisfaction,and trust in authorities regarding pandemic measures.Simple bivariate statistics was used to describe the background characteristics of the respondents along with adoption of the partial least squares-structural equation modeling(PLS-SEM)as the final model to demonstrate the relationship between the variables.Results:In our study,the leading group of the respondents were within 31 to 35 years’age group(39.82%),male(61.88%),living single(58.24%)and doctoral level students(39.8%).The preventive and supportive measures taken by students and/or provided by the respective institution or authorities were positively related to students’satisfaction and had an acceptable strength(β=0.611,t=9.679,p<0.001).The trust gained in authorities also showed an acceptable strength(β=0.381,t=5.653,p<0.001)with a positive direction.Again,the personnel awareness building related to both students’satisfaction(β=0.295,t=2.719,p<0.001)and trust gain(β=0.131,t=1.986,p<0.05)in authorities had a positive and acceptable intensity.Therefore,our study clearly demonstrates the great impact of preventive and supportive measures in the development of students’satisfaction(R2=0.507 indicating moderate relationship).The satisfied students possessed a strong influence which eventually helped in building sufficient trust on their institutions(R2=0.797 indicating above substantial relationship).Conclusions:The worldwide student group is one of the most affected and vulnerable communities in this situation.So,there is a profound ground of research on how different states or authorities handle such situation.In this study,we have depicted the types and magnitude of care taken by Chinese government and educational institutions towards international students to relieve the panic of pandemic situation.Further research and such initiatives should be taken in to consideration for future emerging conditions.

Prototype Engineering Test Platform of ITER Magnet Gravity Support

ITER magnet gravity support （GS） has been redesigned as a structure of pre- assembled nmlti-flexible plates instead of the original welded structure. In the past several years, engineering tests of the new structure have been proposed. A prototype engineering test plat- form is being developed. In order to apply the loads/load combinations onto the test mock-up, seven hydraulic bolt tensioners in three directions have been applied to simulate various loads （forces and moments）, through which the deformation of bolts, flexible plates and clamp blocks, the stress distribution in the flexible plates, the friction between the contact surface, etc. can be monitored/tested. The measurement and control system includes seven sets of synchronization controller, a 16-channel strain gauge, 25 sets of displacement sensors, etc. Principles of EDC220 digital controller and development of multi-channel control software are also demonstrated.

Confidence support vector domain description

To accelerate the training of support vector domain description （SVDD）, confidence support vector domain description （CSVDD） is proposed based on the observation that the description boundary is determined by a small subset of training data called support vectors. Namely, the number of training samples in the userdefined sphere is calculated and taken as the confidence measure, according to which the training samples are ranked in ascending order. Those former ranked ones are selected as the boundary targets for the SVDD training. Simulations on UCI data demonstrate the effectiveness and superiority of CSVDD： the number of training targets and the training time are reduced without any loss of accuracy.

Roadway failure and support in a coal seam underlying a previously mined coal seam

The influence of an upper,mined coal seam on the stability of rock surrounding a roadway in a lower coal seam is examined.The technical problems of roadway control are discussed based on the geological conditions existing in the Liyazhuang Mine No.2 coal seam.The stress distribution and floor failure in the lower works after mining the upper coal is studied through numerical simulations.The failure mechanism of the roof and walls of a roadway located in the lower coal seam is described.The predicted deformation and failure of the roadway for different distances between the two coal seams are used to design two ways of supporting the lower structure.One is a combined support consisting of anchors with a joist steel tent and a combined anchor truss.A field test of the design was performed to good effect.The results have significance for the design of supports for roadways located in similar conditions.

ON THE WEIGHTED OCCUPATION TIME AND SUPPORT OF SUPER-BROWNIAN MOTION CONDITIONED ON NON-EXTINCTION

This paper investigates the property of super-Brownian motion conditioned on non-extinction. The authors obtain a representation of Laplace functional for the weighted occupation time of this class of processes. By this, they get a result about the distribution of the support of it.

Non-Intrusive Objective Speech Quality Measurement Based on Fuzzy GMM and SVR for Narrowband Speech

Based on fuzzy Gaussian mixture model （FGMM） and support vector regression （SVR）,an improved version of non-intrusive objective measurement for assessing quality of output speech without inputting clean speech is proposed for narrowband speech.Its perceptual linear predictive （PLP） features extracted from clean speech and clustered by FGMM are used as an artificial reference model.Input speech is separated into three classes,for each a consistency parameter between each feature pair from test speech signals and its counterpart in the pre-trained FGMM reference model is calculated and mapped to an objective speech quality score using SVR method.The correlation degree between subjective mean opinion score （MOS） and objective MOS is analyzed.Experimental results show that the proposed method offers an effective technique and can give better performances than the ITU-T P.563 method under most of the test conditions for narrowband speech.

A Fast Small-Sample Modeling Method for Precision Inertial Systems Fault Prediction and Quantitative Anomaly Measurement

Inertial system platforms are a kind of important precision devices,which have the characteristics of difficult acquisition for state data and small sample scale.Focusing on the model optimization for data-driven fault state prediction and quantitative degreemeasurement,a fast small-sample supersphere one-class SVMmodelingmethod using support vectors pre-selection is systematically studied in this paper.By theorem-proving the irrelevance between themodel’s learning result and the non-support vectors(NSVs),the distribution characters of the support vectors are analyzed.On this basis,a modeling method with selected samples having specific geometry character fromthe training sets is also proposed.The method can remarkably eliminate theNSVs and improve the algorithm’s efficiency.The experimental results testify that the scale of training samples and the modeling time consumption both give a sharply decrease using the support vectors pre-selection method.The experimental results on inertial devices also show good fault prediction capability and effectiveness of quantitative anomaly measurement.

Using Non-Additive Measure for Optimization-Based Nonlinear Classification

Over the past few decades, numerous optimization-based methods have been proposed for solving the classification problem in data mining. Classic optimization-based methods do not consider attribute interactions toward classification. Thus, a novel learning machine is needed to provide a better understanding on the nature of classification when the interaction among contributions from various attributes cannot be ignored. The interactions can be described by a non-additive measure while the Choquet integral can serve as the mathematical tool to aggregate the values of attributes and the corresponding values of a non-additive measure. As a main part of this research, a new nonlinear classification method with non-additive measures is proposed. Experimental results show that applying non-additive measures on the classic optimization-based models improves the classification robustness and accuracy compared with some popular classification methods. In addition, motivated by well-known Support Vector Machine approach, we transform the primal optimization-based nonlinear classification model with the signed non-additive measure into its dual form by applying Lagrangian optimization theory and Wolfes dual programming theory. As a result, 2n – 1 parameters of the signed non-additive measure can now be approximated with m (number of records) Lagrangian multipliers by applying necessary conditions of the primal classification problem to be optimal. This method of parameter approximation is a breakthrough for solving a non-additive measure practically when there are relatively small number of training cases available (mn-1). Furthermore, the kernel-based learning method engages the nonlinear classifiers to achieve better classification accuracy. The research produces practically deliverable nonlinear models with the non-additive measure for classification problem in data mining when interactions among attributes are considered.

Combined soft measurement on key indicator parameters of new competitive advantages for China’s export

The estimation of the difference between the new competitive advantages of China’s export and the world’s trading powers have been the key measurement problems in China-related studies.In this work,a comprehensive evaluation index system for new export competitive advantages is developed,a soft-sensing model for China’s new export competitive advantages based on the fuzzy entropy weight analytic hierarchy process is established,and the soft-sensing values of key indexes are derived.The obtained evaluation values of the main measurement index are used as the input variable of the fuzzy least squares support vector machine,and a soft-sensing model of the key index parameters of the new export competitive advantages of China based on the combined soft-sensing model of the fuzzy least squares support vector machine is established.The soft-sensing results of the new export competitive advantage index of China show that the soft measurement model developed herein is of high precision compared with other models,and the technical and brand competitiveness indicators of export products have more significant contributions to the new competitive advantages of China’s export,while the service competitiveness indicator of export products has the least contribution to new competitive advantages of China’s export.

复杂地质条件下多级高边坡组合支护方案与稳定性预测研究

以镇赫高速陈贝屯至煤灰堡段为例,根据工程地质、边坡等级和边坡特性等因素对边坡不同剖面采用衡重式挡墙、俯斜式挡墙、桩+锚索、锚杆+面板等支护形式。从病害原因分析和处治手段出发,研究了多级高边坡支护的质量保证措施。基于LightGBM算法建立边坡稳定性预测模型,验证模型精确性后给出预测模型的特征相对重要性结果和预测结果。结果表明:建立预测模型可较好地预测边坡稳定性;影响边坡稳定性最关键的因素为中土体粘聚力,其次为边坡角β,孔隙压力比和土体重度对边坡稳定性影响不大;镇赫高速K2+051~K2+340段边坡稳定概率为0.9,失稳概率为0.1。本项目运营经验表明,组合支护方案及质量保障措施有效提高了项目施工质量、减少了返工现象,保证了项目的经济效益。

蚀变岩隧洞围岩变形破坏发生机制及支护措施适应性研究

地下工程开挖施工过程中,由蚀变岩引发的工程问题愈发突出。为此,以新疆某隧洞工程为依托,基于现场调查和室内试验成果,研究了蚀变岩洞段开挖过程中出现的围岩变形破坏问题,揭示了围岩变形破坏发生机制,并通过建立敞开式TBM开挖隧洞围岩变形和支护受力安全评价方法,分析了不同类型支护措施对蚀变岩洞段围岩稳定性的控制效果。结果表明,围岩强度低、胶结程度较弱和构造发育是蚀变岩洞段出现塌方、围岩大变形等问题的主要原因,地下水和开挖扰动等也是重要影响因素;钢拱架和锚杆等措施可有效限制围岩出露护盾后的变形,而通过施加超前加固措施,可限制围岩在护盾区间内的变形,降低TBM掘进过程中发生卡机的风险。

支架固定馆藏人物俑文物振动台试验研究

为研究博物馆最常用的支架固定措施固定馆藏人物俑文物的抗震有效性,开展了两类典型体型易损、材质易损人物俑文物复制品‐支架固定措施抗震系统足尺振动台试验研究。获得了人物俑在不同工况下的地震响应及人物俑与支架间的相互作用,探讨人物俑关键体型参数、金属支架卡固位置、支架尺寸、固定措施与人物俑间安装缝隙对该类文物运动状态的影响,评估了支架固定措施的抗震有效性并提出了合理建议,为兼顾安全性及最小干预原则的支架固定人物俑文物的优化设计提供必要依据。研究结果表明:浮放人物俑均发生倾覆,具有极大震损风险;采用支架固定后可有效降低人物俑的摇摆响应,随着人物俑复制品的质心高度与底座宽度比值增加以及其质量增大,较小尺寸支架发生明显塑性变形甚至根部断裂,导致人物俑倾覆并损坏;随着支架尺寸的增加,其对文物固定效果的提高作用有限,基于文物保护最小干预原则,综合考虑文物的抗震安全及艺术展示效果,优化支架尺寸;支架固定人物俑肩部时,人物俑摇摆响应得到一定控制,但随着支架固定位置的提高,人物俑滑移响应愈加明显;当支架与人物俑相互作用时,人物俑表面出现明显损伤,在两者缝隙填充硅胶垫,人物俑的摇摆响应和滑移响应分别降低近40%和50%,支架根部应变下降近40%,人物俑与支架接触处应变下降近60%,有效提高了支架固定措施的抗震有效性。

软土地层三线小角度叠交盾构隧道施工影响规律及位移控制

天津地铁6号线入出段线盾构隧道上穿既有隧道,通过现场实测和数值模拟对既有隧道结构变形规律、变形影响因素、不同变形控制措施的效果进行了研究。结果表明:盾构上穿过程中既有隧道竖向位移整体呈现出隆起-沉降-隆起的变化规律;刀盘距叠交部位断面距离L=2.0D(D为隧道直径)时,叠交部位断面轴力达到最大值,L=0~2.0D时,叠交部位断面弯矩逐渐由L≤0时的横8字形转变为L≥2.0D时的三叶草形;新建隧道与既有隧道的叠交角度在15°~60°、竖向净距小于1.0D时,既有隧道竖向位移受新建隧道影响较大,实际工程中应使叠交角度大于60°,竖向净距大于1.0D;设置支撑台车后,支撑台车影响范围约为2倍台车长度,在影响范围内横断面位移得到控制,但随着支撑台车离开,原来位置处对位移的控制效果逐渐消失;与不注浆相比,深孔注浆加固后既有隧道竖向位移最大值和水平位移最大值分别减小了67.4%、76.0%。