scholarly journals A Supporting Design Method When Longwall FaceStrides across and Passes through a Roadway

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Weidong Pan ◽  
Xinyuan Li ◽  
YiWei Li ◽  
Xiaobin Li ◽  
Qing Qiao ◽  
...  
Keyword(s):  
Stress Condition ◽  
Underground Mining ◽  
Design Method ◽  
Elastic Model ◽  
Mechanical Behaviours ◽  
Normal Production ◽  
Maximum Subsidence ◽  
Seam Mining ◽  
Rock Strata ◽  
Good Agreement

In coal underground mining, situation of longwall face striding across (SAR) or passing through roadway (PTR) is very common, especially in an inclined coal seam mining. A roadway supporting design method, consisting of a model using to determine the minimal rock strata thickness and a segmental supporting scheme, is developed. In addition, to represent the mechanical behaviour of the caved material authentically, an elastic model was developed. The results showed that the elastic model has a good agreement with the caved material mechanical behaviours at a relatively lower stress condition. By using a FDEM method, a real case in Xutuan coal mine is studied. Compared with the process without backfill, the z-displacement of cross-cut roof decreased shapely after backfilling, with a maximum z-displacement, decreases from 0.76 m to 0.13 m and from 0.39 m to 0.064 m in PTR and SAR section, respectively. Therefore, the possibility of fall of ground (FOG) and crushing accidents can be reduced effectively with backfilling material of wood cribs. And the maximum subsidence (SAR section side) of face floor is 0.16 m, which is small enough to ensure normal production. The results of this study are likely to be useful as a reference for the safe and efficient mining of coal resources under similar conditions.

scholarly journals A novel approach of determining the parameters of Asadi profiling function for predictiong ground subsidence due to inclied coal seam mining at Quang Ninh coal basin

2020 ◽  
Vol 61 (2) ◽  
pp. 86-95
Author(s):  
Long Quoc Nguyen ◽  
Keyword(s):  
Underground Mining ◽  
Mean Absolute Error ◽  
Absolute Error ◽  
Ground Subsidence ◽  
Coal Basin ◽  
Novel Approach ◽  
Maximum Subsidence ◽  
Seam Mining ◽  
Subsidence Monitoring ◽  
Quang Ninh

In this paper, we proposed a novel approach for estimating preliminary values of parameters of the Asadi profiling function (APF), then the least-squares principle was used with these preliminary values and ground subsidence monitoring data at the Thong Nhat underground mine to determine to the final parameters of the APF. This function was employed to predict ground subsidence at the Mong Duong mine where there are geological and rock geomachenial conditions well as seams’ inclination similar to those of Thong Nhat mine. The results show that the Rood Mean Square Error (RMSE) and Mean Absolute Error (MAE) equal to 0.081 m and 0.055 m or 9.9% and 6.7% of maximum subsidence, respectively, and a correlation coefficient of 0.973. These results prove that the APF with calculated parameters can be used to predict ground subsidence due to underground mining in the areas that have the similar conditions to Thong Nhat mine.

scholarly journals A balanced-to-balanced directional coupler based on branch-slotline coupled structure

Frequenz ◽  
2020 ◽  
Vol 74 (11-12) ◽  
pp. 427-433
Author(s):  
Yaxin Liu ◽  
Feng Wei ◽  
Xiaowei Shi ◽  
Cao Zeng
Keyword(s):  
Directional Coupler ◽  
Return Loss ◽  
Design Method ◽  
Differential Mode ◽  
Arbitrary Power ◽  
Measurement Results ◽  
Transition Structures ◽  
Coupled Structures ◽  
Better Than ◽  
Good Agreement

AbstractIn this paper, a balanced-to-balanced (BTB) branch-slotline directional coupler (DC) is firstly presented, which can realize an arbitrary power division ratios (PDRs). The coupler is composed by microstrip-to-slotline (MS) transition structures and branch-slotline coupled structures. The single-ended to balanced-ended conversion is simplified and easy to implemented by the MS transition structures, which intrinsically leads to the differential-mode (DM) transmission and common-mode (CM) suppression. Moreover, the different PDRs which are controlled by the widths of branch-slotlines can be achieved. In order to verify the feasibility of the proposed design method, two prototype circuits of the proposed coupler with different PDRs are fabricated and measured. The return loss and the isolation of two designs are all better than 10 dB. Moreover, the CM suppressions are greater than 35 dB. A good agreement between the simulation and measurement results is observed.

scholarly journals Mechanism and Prevention and Control of Mine Earthquake in Thick and Hard Rock Strata considering the Horizontal Stress Evolution of Stope

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Ming Zhang ◽  
Xuelong Hu ◽  
Hongtao Huang ◽  
Guangyao Chen ◽  
Shan Gao ◽  
...  
Keyword(s):  
Hard Rock ◽  
Design Method ◽  
Horizontal Stress ◽  
Prevention Measures ◽  
Stress Concentrations ◽  
Estimation Model ◽  
Working Face ◽  
Mining Design ◽  
And Control ◽  
Rock Strata

This study investigated the mechanism, prevention measures, and control methods for earthquake disasters typically occurring in mines with thick and hard rock strata. A mine stope with large faults and thick hard rock strata in Hebei Province was taken as the background study object. Then, theoretical analysis and numerical simulation methods were adopted in conjunction with field monitoring to explore how horizontal stress evolves in the thick and hard hanging roofs of such mines, potentially leading to mining earthquakes. Then, based on the obtained results, a mining design method was proposed to reduce the horizontal stress levels of earthquake mitigation. The results showed that, under the control of large faults, semiopen and semiclosed stopes with thick hard rock strata are formed, which cause influentially pressurized and depressurized zones during the evolution of the overburden movements and horizontal stress. It was determined that the stress concentrations mainly originated from the release and transfer of horizontal stress during the rock fractures and movements in the roof areas, which were calculated using a theoretical estimation model. The horizontal stress concentrations formed “counter torques” at both ends of the thick and hard strata, which prevented the support ending due to tensile failures. As a result, the limit spans were increased. This study proposed a mining strategy of using narrow working faces, strip mining processes, and reasonable mining speeds, which could effectively reduce horizontal stress concentrations and consequently prevent and control mining earthquakes. This study’s research results were successfully applied to the mining practices in working face 16103.

A Filtering Power Divider with Tunable Center Frequency and Wide Stopband

Frequenz ◽  
2019 ◽  
Vol 73 (9-10) ◽  
pp. 301-306
Author(s):  
Xuehan Hu ◽  
Feng Wei ◽  
Jiawen Hao ◽  
Xiaowei Shi
Keyword(s):  
Design Method ◽  
Power Divider ◽  
Center Frequency ◽  
Electrical Length ◽  
Transmission Zeros ◽  
Quarter Wavelength ◽  
Varactor Diodes ◽  
Measurement Results ◽  
Band Pass ◽  
Good Agreement

AbstractIn this paper, a tunable power divider (PD) with a good band-pass filtering response using quarter-wavelength stepped impedance resonators (SIRs) is presented. By appropriately adjusting the impedance and electrical length ratio of SIR, the proposed structure can achieve wide stopband performance. Meanwhile, four varactor diodes are loaded to the external resonators to achieve electrical reconfiguration. In addition, a pair of transmission zeros (TZs) can be generated by applying source and load coupling on each side of the passband, which can effectively improve passband selectivity and out-of-band rejection. In order to verify the feasibility of the proposed design method, a prototype circuit of the proposed filtering power divider (FPD) with tunable center frequency is simulated, fabricated and measured. A good agreement between the simulation and measurement results is observed.

scholarly journals Comparison between Duncan and Chang’s EB Model and the Generalized Plasticity Model in the Analysis of a High Earth-Rockfill Dam

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Weixin Dong ◽  
Liming Hu ◽  
Yu Zhen Yu ◽  
He Lv
Keyword(s):  
Constitutive Models ◽  
Elastic Model ◽  
Plasticity Model ◽  
Rockfill Dam ◽  
Generalized Plasticity ◽  
Rockfill Materials ◽  
Confining Pressures ◽  
Mechanical Behaviours ◽  
Nonlinear Elastic ◽  
Relationship Of

Nonlinear elastic model and elastoplastic model are two main kinds of constitutive models of soil, which are widely used in the numerical analyses of soil structure. In this study, Duncan and Chang's EB model and the generalized plasticity model proposed by Pastor, Zienkiewicz, and Chan was discussed and applied to describe the stress-strain relationship of rockfill materials. The two models were validated using the results of triaxial shear tests under different confining pressures. The comparisons between the fittings of models and test data showed that the modified generalized plasticity model is capable of simulating the mechanical behaviours of rockfill materials. The modified generalized plasticity model was implemented into a finite element code to carry out static analyses of a high earth-rockfill dam in China. Nonlinear elastic analyses were also performed with Duncan and Chang's EB model in the same program framework. The comparisons of FEM results andin situmonitoring data showed that the modified PZ-III model can give a better description of deformation of the earth-rockfill dam than Duncan and Chang’s EB model.

A Reinforcement Design Method Based on Analysis of Large Openings in Cylindrical Pressure Vessels

1996 ◽  
Vol 118 (4) ◽  
pp. 502-506 ◽  
Author(s):  
M. D. Xue ◽  
K. C. Hwang ◽  
W. Lu¨ ◽  
W. Chen
Keyword(s):  
Fourier Series ◽  
Present Method ◽  
Fourier Coefficients ◽  
Design Method ◽  
Large Diameter ◽  
Pressure Vessels ◽  
Diameter Ratio ◽  
Cylindrical Coordinates ◽  
Reinforcement Design ◽  
Good Agreement

The analytical solution is given for two orthogonally intersecting cylindrical shells with large diameter ratio d/D subjected to internal pressure. The modified Morley equation is used for the shell with cutout and the Love equation for the tube with nonplanar end. The continuity conditions of forces and displacements at the intersection are expressed in 3-D cylindrical coordinates (ρ, θ, z), and are expanded in Fourier series of θ. The Fourier coefficients are obtained by numerical quadrature. The present results are in good agreement with those obtained by tests and by FEM for ρ0 = d/D ≤ 0.8. The typical curves of SCF versus t/T and d/DT and reinforcement coefficients g, h versus D/T0 for each ρ0 are given on the present method.

Design method of a two-phase annular nozzle in cryogenic liquid expander

2019 ◽  
Vol 233 (6) ◽  
pp. 762-772
Author(s):  
Hongyang Li ◽  
Wen Li ◽  
Xuehui Zhang ◽  
Yangli Zhu ◽  
Zhitao Zuo ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Design Method ◽  
Cryogenic Liquid ◽  
Annular Nozzle ◽  
Critical Component ◽  
Two Phase ◽  
Step Process ◽  
Second Stage ◽  
Nonequilibrium Effects ◽  
Good Agreement

The two-phase annular nozzle is a critical component of liquid expanders. It matches the outlet of the first stage and the inlet of the second stage. A design method of two-phase annular nozzle involving a two-step process is proposed. Nonequilibrium effects are introduced by the area factor during the second process. The flashing in two-phase annular nozzle is simulated through the cavitation method and validated by the experimental results of Brookhaven National Laboratory’s nozzle and Hord’s hydrofoil. A forward flashing two-phase annular nozzle and a backward flashing two-phase nozzle are designed with different centerline angle distributions where they show a good agreement with the design. Forward flashing two-phase annular nozzle exhibits high curvature and nonuniformity. Backward flashing two-phase nozzle exhibits lower nonuniformity and a slightly higher boundary layer ratio, which shows a better performance in terms of the nonequilibrium effects.

Analysis of the Thermo-Mechanical Behaviour of Steel-to-Timber Connections in Bending

2014 ◽  
Vol 5 (2) ◽  
pp. 97-112 ◽  
Author(s):  
Dhionis Dhima ◽  
Maxime Audebert ◽  
Abdelhamid Bouchaïr
Keyword(s):  
Mechanical Behaviour ◽  
Yield Criterion ◽  
Element Model ◽  
Fire Tests ◽  
Fire Exposure ◽  
Mechanical Behaviours ◽  
Timber Connections ◽  
The Hill ◽  
Temperature Time ◽  
Good Agreement

Two different configurations of steel-to-timber connections are tested in bending in normal conditions and under ISO-fire exposure. To observe the influence of clearances in the connection area on the fire resistance of the connections, two specimens were previously tested under cyclic loadings. These tests consist in the application of loading-unloading cycles by controlled displacements. The experimental results of connections tested in cold and under ISO-fire conditions are analyzed and commented. These results are then used to validate a finite element model. This model allows to simulate numerically the evolution of the temperatures inside the connections as well as their mechanical and thermo-mechanical behaviours. The thermal modelling is validated on the basis of the temperature-time evolutions measured during fire tests. The nonlinear modelling of the mechanical behaviour of timber is done using the Hill yield criterion in combination with the Tsaï-Wu failure criterion. The thermo-mechanical modelling allows obtaining fire resistances of the tested connections in good agreement with the experimental ones.

scholarly journals Achievement of Various Widebands: A Design of Wide-Slot Antennas Using Shape Blending

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Aiting Wu ◽  
Zhonghai Zhang ◽  
Boran Guan ◽  
Liang Peng
Keyword(s):  
Geometric Structure ◽  
Design Method ◽  
Antenna Design ◽  
Impedance Bandwidth ◽  
Slot Antennas ◽  
Regular Trend ◽  
Shape Blending ◽  
New Process ◽  
Convenient Model ◽  
Good Agreement

When designing printed wide-slot antennas, the shape or profile of the tuning stub is a key geometric structure that affects the impedance bandwidth of the antenna. This article introduces a new process for designing tuning stub shapes, which are the blended results of a diamond and a circle. By using different geometry shapes, the design could generate a series of bandwidths with a regular trend. Detailed investigations and analysis were conducted on some key geometry parameters to explore their impact on the impedance bandwidth of the antenna. To certify the new design method, several prototypes were simulated, developed, and measured. The experimental and simulated results showed good agreement with each other. The results indicate that by properly selecting various blended shapes, a BW range from 80.1 to 117.3% for a VSWR of less than 2 could be obtained, which provides a convenient model for a wideband antenna design.

DESIGN AND FABRICATION OF HIGH-PERFORMANCE INFRARED HOLLOW FIBER FOR MEDICAL LASER POWER DELIVERY

2009 ◽  
Vol 02 (01) ◽  
pp. 101-106 ◽  
Author(s):  
YI-WEI SHI ◽  
XIAO-SONG ZHU ◽  
KE-RONG SUI ◽  
XIAO-LI TANG
Keyword(s):  
Hollow Fiber ◽  
High Performance ◽  
Dielectric Film ◽  
Design Method ◽  
Power Delivery ◽  
Material Dispersion ◽  
Medical Laser ◽  
Beam Transmission ◽  
Improved Design ◽  
Good Agreement

We proposed a method to evaluate the material dispersion of the dielectric film in dielectric-coated silver hollow fiber. By taking into consideration the derived material dispersion, the wavelengths of the loss peaks and valleys in the loss spectra of the hollow fiber can be predicted more accurately. Then, we fabricated the dielectric-coated silver hollow fiber according to the parameters obtained by using the improved design method. The measured data showed good agreement with the calculated results. The loss for medical laser of Er :YAG and CO 2 was less than 0.3 dB/m. The loss for green or red pilot beams was around 5 dB/m, which is sufficiently low for the purpose of pilot beam transmission. The derived material dispersion plays an important role in the design and fabrication of the hollow fiber for multiwavelength delivery.

Sign in / Sign up

Export Citation Format

Share Document