指向学习升级:课堂学习场景的重构

我们需要重构学生课堂学习的场景,改变传统的学习方式,形成知识沉淀的完整链路:“营火”让学生在“中心化”课堂中得到启蒙;“水源”创设与同伴交流的时空;“洞穴”为学生创建自主体验与消化沉思的机会;最后让学生登上“山顶”,学以致用,从而实现学习的升级。

Coal seam methane distribution and its significance in Pingdingshan mining area

A study aimed at the coal seam group E and F in Pingdingshan mining area has been completed. This study is on the relationship of the coal seam methane reserve to coal thickness, coal rank, coal seam depth, surrounding rock and geological structure and other factors. The study indicates that different geological factor plays different role in controlling the law of coal seam methane reserve. The coal seam methane rich area, which was formed because of various factors and comprehensive effect, is the coal and methane outburst prone area, and also the key area for coal bed methane recovery. Among all factors, coal seam depth and geological structure is more important factor in affecting coal seam methane content in Pingdingshan mining area.

Splitting and Restoration of Kondo Peak in a Deformed Molecule Quantum Dot Coupled to Ferromagnetic Electrodes

We adopt the nonequilibrium Green＇s function method to theoretically study the Kondo effect in a deformed molecule, which is treated as an electron-phonon interaction （EPI） system. The self-energy for phonon part is calculated in the standard many-body diagrammatic expansion up to the second order in EPI strength. We find that the multiple phonon-assisted Kondo satellites arise besides the usual Kondo resonance. In the antiparallel magnetic configuration the splitting of main Kondo peak and phonon-assisted satellites only happen for asymmetrical dot-lead couplings, but it is free from the symmetry for the parallel magnetic configuration. The EPI strength and vibrational frequency can enhance the spin splitting of both main Kondo and satellites. It is shown that the suppressed zero-bias Kondo resonance can be restored by applying an external magnetic field, whose magnitude is dependent on the phononic effect remarkably. Although the asymmetry in tunnel coupling has no contribution to the restoration of spin splitting of Kondo peak, it can shrink the external field needed to switch tunneling magnetoresistance ratio between large negative dip and large positive peak.

STUDY ON THE FRACTURE AND WEIGHTING OF MAIN ROOF UNDER COMPLICATED CONDITIONS IN LONGWALL MINING

To clarify and control the collapse and weighting of main roof in longwall mining is one of the important research problems in ground control. Based on the results of physical model experiment and field measurement, the behaviour of main roof above trapezoidal goaf or with fault is studied in this paper. The fracture and weighting of main roof above trapezoidal goaf are different from those above rectangular goaf. It depends on the mechanical relation between main roof blocks whether the plate blocks of main roof on both sides of fault simultaneously break and collapse.

Prediction of the maximum water inflow in Pingdingshan No.8 mine based on grey system theory

In order to prevent and control the water inflow of mines, this paper built a new initial GM（1, 1） model to torecast the maximum water inflow according to the principle of new information. The effect of the new initial GM（1, 1） model is not ideal by the concrete example. Then according to the principle of making the sum of the squares of the difference between the calculated sequences and the original sequences, an optimized GM（1, I） model was established. The result shows that this method is a new prediction method which can predict the maximum water inflow accurately. It not only conforms to the guide- line of prevention primarily, but also provides reference standards to managers on making prevention measures.

NONLINEAR ANALYSES OF VOID DIFFUSION MODEL AND ITS APPLICATION TO SUBSIDENCE PREDICTION

The void diffusion model for mining-effected strata can be analyzed by means of a nonlinear finite element method. This paper presents the fundamental principles of the analyses. The key to the analyses is the determination of roof subsidence and the nonlinear relationship between diffusion coefficient and subsidence. This paper discusses these problems and determines the coefficient for Pingdingshan mining district, with which several profiles are predicted. It is found that the predicted profiles are coincident with the corresponding field profiles.

RATIONAL CHOICE OF TECHNICAL REFORM SCHEMES OF MINE NO.1,PINGDINGSHAN MINING BUREAU

Seven schemes for the developing extension, four schemes for the mining of the whole field and five schemes for the parameter are put forward in this paper to rational choice of technical reform schemes of Mine No.1. Pingdingshan Mining Bureau.On the basis of conventional technical analysis, an optimum economy-mathmetical model of the developing preparatory schemes is worked out and a synthetic optimum is carried out.

APPLICATION OF THE ROOF DISTURBANCE TO MONITORING AND PREDICTING THE GROUND PRESSURE

Based on study of the influence of main roof fracture on ground pressure, this paper considered the immediate roof as a semi-infinite long beam on a Winkler elastic foundation. In the model the coal seam is the foundation and the pressure caused by mian roof deflection is the load. Having solved the model and analyzed relevant factors,the authors indicate that the disturbance caused by the breakage of the mian roof can be observed in both gates of longwall face and explain why it can be. The paper points out that the applicability of the method to obtain the disturbance information by measuring the loads on supports is wider than that by measuring the roof convergence rate. The results are useful for monitoring and predicting ground pressure.

Geological division of gas in the Pingdingshan mine area based on its tectonic dynamics characteristics

In this paper,we used tectonic dynamics theories to study the tectonic evolution characteristics of the Pingdingshan mine area,and analyzed the impact of tectonic progressive control on gas occurrence.The study results are as follows:the Pingdingshan mine area has been mainly controlled by multiple squeezing and shearing actions of the Qinling orogenic belt since early and middle Yanshan,forming the tectonic control characteristics of master control in two directions,namely NWW trending and NNE trending;the NWW trending structure is dominated by squeezing and shearing,while the NNE trending structure is dominated by tension.Progressively controlled by the structure,the gas occurrence presents partition and zonation,i.e.compared with the western structure,the eastern NWW-NW trending structure of the mine area is more highly developed,resulting in the mine area gas occurrence distribution characteristics are distinct in the east while indistinct in the west.Based on this,the mine area can be divided into the following two geological dynamic areas:the western half of mine area,namely the Guodishan fault control area,where the NW-SE trending synchronous tension action suffered by the northeast side(footwall) is relatively strong,and compared with the southwest side(hanging wall),its coal and gas outburst seriousness is weak;and the eastern half of mine area,namely the NWW-NW thrust nappe fracture fold control area,which is a serious area of coal and gas outburst,in particular the axial area of the Likou syncline is the intersection compound and combination position of the NW and NE trending structures,a tectonic concentrated area,and the gas pressure and content here are the largest.

Analysis of roof and pillar failure associated with weak floor at a limestone mine

A limestone mine in Ohio has had instability problems that have led to massive roof falls extending to the surface. This study focuses on the role that weak, moisture-sensitive floor has in the instability issues.Previous NIOSH research related to this subject did not include analysis for weak floor or weak bands and recommended that when such issues arise they should be investigated further using a more advanced analysis. Therefore, to further investigate the observed instability occurring on a large scale at the Ohio mine, FLAC3 D numerical models were employed to demonstrate the effect that a weak floor has on roof and pillar stability. This case study will provide important information to limestone mine operators regarding the impact of weak floor causing the potential for roof collapse, pillar failure, and subsequent subsidence of the ground surface.

A CUSP CATASTROPHE, PRECURSORS PATTERN AND EVOLUTION PROCESS OF ROCKBUST OF COAL PILLAR UNDER A HARD ROCK SUBJECT TO ELASTIC SUPPORT

The rockburst of the poal pillar under a thick hard roof stratum is modelled as the instability failure problem of coal pillars under strata subject to elastic support. The instability mechanism of rockburst is studied by applying cusp catastrophic theory. The effects of the stiffness ratio of the system and loads imposed on the system on the rockburst are explicated.The factors affecting rockbursts are discussed. Based on them, the evolution process, the forewarning regularity arid forewarning sings of rockbursts are studied. It is indicated that the subsidence velocity of roof stratum, which increases quickly and tends to infinity, is the forewarning measurable signs of the rockbursts of coal pillar.

THEORY AND TECHNOLOGY FOR HARD ROOF CONTROL OF LONGWALL FACE IN CHINESE COLLIERIES

This paper introduced systematically the present situation of the research on theory and technology for hard roof control of coal face in Chinese collieries.

Research on evolution of mining pressure field and fracture field and gas emission features

The relation between mining pressure field-fracture field and gas emission of working face is analyzed, and the concept that there is a stress point （or strain point） among permeability of coal is presented. It is believed that the mutation of coal permeability caused by the sudden loading or unloading of working face roof as periodic weighting occurs is the main reason that a lot of gas pour into the working face. Based on the above concept, the relation is established among abutment pressure during periodie weighting, permeability of coal seam and gas emission, and relation graph is drawn. Then the loading and unloading features of coal at the moment of fracture and non-fracture of main roof are revealed. And finally it is presented that the process of sudden loading or unloading as periodic weighting occurs plays an important role in rupture propagation of coal, analytical movement of gas and gas emission.

Numerical simulation on the risk of roof water inrush in Wuyang Coal Mine

Water-inrush in mine is one of the mine disasters caused by mining.In order to assess the risk of roof water-inrush in Wuyang Coal Mine based on the geological material of the coal mine,we built numerical models for the roof fracture and seepage development rule by using RFPA2D and COMSOL respectively,to analyze the changes in fracture zone,stress,water pressure and seepage vector with the advancement of working face,and compared the results with the field investigated data.The numerical simulation results indicate that:(1) with the advancement of the working faces,the stress relief range and fracture zone in the overlying strata increased rapidly up to about 90 m,and then tended to remain constant,reaching a final height of about 95 m which agrees with the field investigation;(2) the seepage flow constantly increased with a larger flow volume both in the front and rear area,where the stress concentration are the most serious.

Lower Triassic Smithian-Spathian Boundary at West Pingdingshan Section in Chaohu,Anhui Province

The West Pingdingshan Section in Chaohu, Anhui Province, has been extensively studied in recent years and become one of the classic Lower Triassic sequences well-clarified in multiple stratigraphies. Also it is an important section that defines the Smithian-Spathian (S-S) boundary within the Olenekian Stage. The S-S boundary strata at the section are restudied in high-resolution conodont biostratigraphy and carbon isotopes. The refined S-S boundary defined by the FAD of conodont Neospathodus pingdingshanensis is at 30 cm above the base of Bed 52, corresponding to a rapid diversification of conodonts. A sharp positive shift of δ13Ccarb curve co-occurs at the S-S boundary and it can be used as a key reference to define the boundary. The defined S-S boundary position and carbon isotopes curve can be well correlated globally.

The vertical structure and seasonal changes of atmosphere ozone and temperature at Zhongshan Station over East Antarctica

The vertical structure of the atmospheric ozone and temperature as well as the seasonal variations is presented by using ozone sounding data at Zhongshan Station over East Antarctica from February, 2008 to February, 2009. The results show that the heights of thermal tropopause and ozone tropopause are mostly the same with yearly mean 7.9 and 7.4 km separately above the station. There is obvious seasonal variation in the pressure and temperature of the tropopause, manifested by the clear one-wave pattern with an opposite phase. As the turning point of the tropopause temperature is visible in autumn and faint in spring and winter, the tropopause height can be better confirmed by utilization of the changes of ozone. Seasonal variation of the tropospheric ozone of vertical distribution is not clear, relative to stratosphere. In the spring, ozone in the low level of stratosphere lost seriously. The minimum partial ozone in 14 km was 1.57 MPa only and the maximum partial ozone occurred in the up level stratosphere. In the rest of the season the ozone increases with height rising in the low level of stratosphere. The evidence shows that ozone lost in spring is closely related with low temperature of polar night and the process of PSC photochemical destruction ozone in the stratosphere. From the vertical characteristics and seasonal variation of ozone and temperature, it is meaningful to understand formation and development of Antarctic ozone deletion.