Study of electromagnetic characteristics of stress distribution and sudden changes in the mining of gob-surrounded coal face

The incidence of dynamic coal or rock disasters is closely related to the distribution of stress in the surrounding rock. Our experiments show that electromagnetic radiation （EMR） signals are related to the state of stress of a coal body. The higher the stress, the more intense the deformation and fractures of a coal body and the stronger the EMR signals. EMR signals reflect the degrees of concentrated stress of a coal body and danger of a rock burst. We selected EMR intensity as the test index of the No.237 gob-surrounded coal face in the Nanshan coal mine. We tested the EMR characteristics of the stress distribution on the strike, on the incline and in the interior of the coal body. The EMR rule of rock bursts, caused by sudden changes in stress, is analyzed. Our research shows that EMR technology can be not only used to test qualitatively the stress distribution of the surrounding rock, but also to predict a possible occurrence of rock burst. Based on this, effective distress measures are used to eliminate or at least weaken the incidence of rock bursts. We hooe that safetv in coalmines will be enhanced.

Research on the sudden changes and the controlling factors of deep coal mining conditions

It was illustrated that the mining conditions inducing disasters changed with depth both in regularity of gradual and sudden change.The sudden change depth for different disaster conditions are different and controlled by different factors.The high temperature and its change with depth are mainly controlled by strata structures and rock heat conductiv- ity property,the high rock stress and dynamical engineering disasters and their change with depth are mainly controlled by tectonic conditions,roof strata rock property and deep rock mechanical property,coal mine water disasters and their change with depth are mainly con- trolled by rock mechanical property of coal seam floor and regional groundwater circulation conditions,gas disaster conditions and their change with depth are mainly controlled by buried conditions of coal seam and opening conditions of geological structures.It is men- tioned that the key point for the control of deep coal mining disaster is to clearly understand the sudden change depth of different factors causing disasters.

Effects of sudden change in wind loads on running performance of trains on a highway-railway one-story bridge in crosswinds

To investigate the effects of sudden change in wind loads on the running performance of trains on the bridge in crosswinds,a highway-railway one-story bridge was taken as the research object.Aerodynamic coefficients of the train and the bridge were measured in a series of train-bridge system segment models through wind tunnel tests when two trains passed each other on the bridge and when a train entered and left the wind barrier section of the bridge.Based on the improved SIMPACK and ANSYS rigid-flexible coupling simulation method,a wind-double train-track-bridge system coupled vibration model was established.The dynamic responses of the train were analyzed under the effects of sudden change in wind loads caused by two trains passing each other and a train entering and leaving the wind barrier section of the bridge.The results show that the effects of sudden wind load change caused by the trains passing each other had less effects on the running safety of the leeward-side train than the wind shielding effect caused by the windward-side train in the wind speed range of 10−25 m/s.With the decrease in the porosity of wind barriers,the effects of the sudden wind load change played an increasingly important role in the running safety and comfort of the train.With the increase in wind speed,the lateral response of the train increased obviously because of the effects of sudden wind load change,which affects both the lateral running stability and the comfort of the train.

Super Typhoon Hinnamnor(2022)with a Record-Breaking Lifespan over the Western North Pacific

Super Typhoon Hinnamnor(2022)was a rare and unique western North Pacific typhoon,and throughout its lifespan,it exhibited all of the major features that pose current challenges in typhoon research.Specifically,during different stages of its lifespan,it experienced a sudden change of track,underwent rapid intensification,interacted and merged with another vortex,expanded in size,underwent rapid weakening,produced a strong cold wake,exhibited eyewall replacement,and underwent extratropical transition.Therefore,a timely identification and review of these features of Hinnamnor(2022),as reported in this article,will help update and enrich the case sets for each of these scientific issues and provide a background for more in-depth mechanistic studies of typhoon track,intensity,and structural changes in the future.We also believe that Hinnamnor(2022)can serve as an excellent benchmark to quickly evaluate the overall performance of different numerical models in predicting typhoon’s track,intensity,and structural changes.

Spatial-temporal Evolution and Driving Force of Cultivated Land Quality in Henan Province

The purpose of this study was to find out the spatial-temporal rules and driving force of cultivated land quality in Henan Province in the last ten years. Agricultural land grading factor evaluation was used to evaluate the cultivated land quality of 2002 and 2012 in Henan Province, and to research the change laws. Method of correlation coefficient was employed to select the driving forces affecting cultivated land quality evolution. The results indicated that the cultivated land quality in Henan Province increased slightly in the last ten years in general, and in spatial there were unchanged regions, increased regions and decreased regions. The cultivated land quality in spatial presented the trend of good becoming better, bad becoming worse, which should be highly valued in cultivated land quality protection and management. Land development and consolidation projects had significant contributions to increasing the cultivated land quality. Driving forces between the sudden change regions and gradual change regions were significantly different. The paper concluded that the research on the spatial-temporal evolution and driving force of cultivated land quality based on cultivated land quality evolution had important academic significance and practical value.

Changing Characteristics of Temperature in Longnan City in Recent 54 Years

Based on the observation data of temperature in Chengxian meteorological station（ the climate representative station of Longnan City,Gansu Province） during 1961-2014,the annual,seasonal and monthly changes of temperature were analyzed,and the abrupt changes in relevant variables were tested using the cumulative anomaly method. The results showed that annual average temperature in Chengxian County increased by 0. 138 ℃/10 a in the past 54 years. There was an obvious sudden change in annual average temperature around 1996. The annual average temperature showed a downward trend before 1996 and an upward trend after 1996. Average temperature in spring,summer,autumn and winter increased by 0. 113,0. 028,0. 157 and 0. 259 ℃/10 a respectively. The fluctuation of average temperature in spring and winter was the largest,followed by summer,while the fluctuation was the smallest in autumn. There were certain differences between various seasons in terms of the years with sudden changes in average temperature,which was not consistent with the years with the sudden changes in annual average temperature. The changing rate of monthly average temperature was the largest in February（ up to 0. 412 ℃/10 a）,followed by March,April and November,but it was the smallest in May（ only 0. 005 ℃/10 a）. The maximum of monthly average temperature appeared mostly in the 21 stcentury,while the minimum appeared in the 20 thcentury.

Abnormal Phenomena Recorded by Several Earthquake Precursor Observation Instruments Before the M_s 8.0 Wenchuan,Sichuan Earthquake

The paper introduces the anomalies observed by digital tiltmeter, cross-fault deformation meter, 4-component borehole strainmeter and geothermometer before May 12, 2008, Ms8.0 Wenchuan earthquake, Sichuan. The digital tiltmeter installed in the epicentral region in Shifang County recorded the tilt anomalies 15 days before the earthquake with variation amplitude of 3.7 times larger than the annual deviation of 2007. The cross-fault deformation meter installed at Zimakua station on the Xianshuihe-Anninghe fault zone detected displacement anomaly occurring since 2006 with the variation amplitude exceeding the cumulative value of the last ten years. Five borehole strainmeter stations in the Chongqing section of Three Gorges Reservoir area observed unconventional strain changes occurring in the period from May 1 through 12, 2008. Among them, the strainmeter at Wanzhou station recorded the great compression strain rate on the EW component at 14：00 o＇clock of May 10, and the anomaly amplitude was so large that the instrument output exceeded its dynamic range, corresponding to a level of -10^4 nanostrains. The geothermometers installed in Xi＇an, Chongqing and Xichang recorded the sudden temperature changes from November 2007 to January 2008 with the variation amplitudes several times larger than the ordinary deviation. The above phenomena and the criteria for distinguishing the anomalies from background fluctuations are discussed in this paper.

Aerodynamic characteristics of a high-speed train crossing the wake of a bridge tower from moving model experiments

In a strong crosswind,the wake of a bridge tower will lead to an abrupt change of the aerodynamic forces acting on a vehicle passing through it,which may result in problems related to the transportation safety.This study investigates the transient aerodynamic characteristics of a high-speed train moving in a truss girder bridge and passing by a bridge tower in a wind tunnel.The scaled ratio of the train,bridge,and tower are 1:30.Effects of various parameters such as the incoming wind speed,train speed,and yaw angle on the aerodynamic performance of the train were considered.Then the sudden change mechanism of aerodynamic loads on the train when it crosses over the tower was further discussed.The results show that the bridge tower has an apparent shielding effect on the train passing through it,with the influencing width being larger than the width of the tower.The train speed is the main factor affecting the influencing width of aerodynamic coefficients,and the mutation amplitude is mainly related to the yaw angle obtained by changing the incoming wind speed or train speed.The vehicle movement introduces an asymmetry of loading on the train in the process of approaching and leaving the wake of the bridge tower,which should not be neglected.

A multi-functional dynamic state estimator for error validation:measurement and parameter errors and sudden load changes

We propose a new and efficient algorithm to detect, identify, and correct measurement errors and branch parameter errors of power systems. A dynamic state estimation algorithm is used based on the Kalman filter theory. The proposed algorithm also successfully detects and identifies sudden load changes in power systems. The method uses three normalized vectors to process errors at each sampling time: normalized measurement residual, normalized Lagrange multiplier, and normalized innovation vector. An IEEE 14-bus test system was used to verify and demonstrate the effectiveness of the proposed method. Numerical results are presented and discussed to show the accuracy of the method.

Analysis on the Variation Characteristics of Temperature in Wengyuan from 1961 to 2018

Based on the monthly average temperature data from Wengyuan national meteorological observation station in Guangdong Province from 1961 to 2018, statistical methods were used for the trend analysis, mutation detection and wavelet analysis of annual average temperature and seasonal average temperature from 1961 to 2018. The results show that the annual, summer, autumn and winter average temperature in Wengyuan all showed a warming trend from 1961 to 2018, among which winter average temperature contributed the most to the increase of annual average temperature, and the increasing trend of average temperature in spring did not pass the significance test. The annual, summer, autumn and winter average temperature in Wengyuan changed significantly in 1994, 1981, 1996 and 1990, respectively. Wavelet analysis shows that the annual average temperature in Wengyuan had periodic oscillations on the time scales of 12-13, 24-25 and 6 years.

An Overview： The Sudden Change of the Chinese Economy and Macroeconomic Policy Choices

With the rapid growth of the Chinese economy, some new phenomena appeared before mid--2008： these included excess liquidity of the banking system, increasing inflation pressure, huge increase of foreign exchange reserves, growing pressure of RMB revaluation, high price of real estate, consistent growth of equity price, rising reserves requirements ratio, large pressure of raising the RMB interest rate. /~er that, due to the international financial crisis, the external demand on China has decreased and the goal of the Chinese macro economy was directed to ensure economic growth. Proactive fiscal policy and moderately loose monetary policy were adopted by the Chinese government. It was a tough task to maintain steady growth of the macro economy under the impact of the global financial crisis. In 2009, stimulated by the macroeconomic policy, the Chinese economy showed a V-shape rebound. The paper mainly explores the sudden economic change due to the global financial crisis, and the situation of the Chinese economy in these two different phases. Finally the paper puts forward the corresponding policy suggestions.

THE INTERACTION BETWEEN EDDY FLUX AND ZONAL AVERAGED FLOW IN“JUNE SUDDEN CHANGE”

In this paper,Eliassen-Palm theory and associated diagnostic method are used to discuss the dynamical mechanism of the interaction between eddy flux and zonal averaged flow in the sudden change of the general circulation in the Northern Hemisphere in early summer of 1982,which indicates that the northward jump of subtropic jet stream is closely related to the enhanced transport of mid-latitude eddy energy to the subtropic tro- popause.However,the direction of the transport is conditioned by the structure of zonal averaged flow.It is evident that the adjustment of zonal averaged flow responses quickly to the eddy transport during this episode. As regard to the suddenness of the change of circulation,the critical role is played by the eddy forcing,

CLIMATIC ABRUPT CHANGE IN THE NORTHERN HEMISPHERE FOR 1920s AND 1950s

In recent years,a large number of papers on the climatic sudden change have been presented.From the viewpoint of climatic sudden change,two methods of studying climatic sudden change are applied in this paper.The Northern Hemi- sphere land temperature(NHLT)during 1851—1984,China temperature(CT)during 1873—1990 and the Northern Hemisphere sea-level pressure(NHSLP)at each grid point during 1899—1987 are analyzed by the moving T-test.The results show that there exist two climatic sudden changes in the 1920s and the 1950s during the past 100 years,and then features of circulation for the two sudden changes are discussed by the NHSLP data.