scholarly journals Determination of technological parameters of rock freezing systems based on the condition of maintaining design thickness of ice wall

2021 ◽  
Vol 6 (3) ◽  
pp. 192-202
Author(s):  
M. A. Semin ◽  
A. V. Bogomyagkov ◽  
L. Y. Levin
Keyword(s):  
Theoretical Analysis ◽  
Wall Thickness ◽  
Operation Mode ◽  
Emergency Operation ◽  
Normal Operation ◽  
Thermal Calculation ◽  
Clay Layer ◽  
Technological Parameters ◽  
Under Construction ◽  
Thermotechnical Calculation

Artificial freezing ensures the formation of a temporary ice wall around the shaft under construction, which prevents groundwater penetration into the shaft and increases the strength of rocks around the unsupported walls of the shaft until the permanent support is erected. The purpose of the study is to carry out thermotechnical calculation of ice wall with subsequent theoretical analysis of changing ice wall thickness with shifting to the passive freezing stage. The idea of the study is to determine these technological parameters based on the condition of maintaining the design ice wall thickness at the stage of passive freezing. The methodology and results of thermotechnical calculation of ice wall for the clay layer as applied to the case of the shafts under construction of a potash mine in the Republic of Belarus are presented. The thermal calculation of the ice wall was carried out numerically in the ANSYS software package using the finite element method. The findings of the numerical multiparameter modeling allowed theoretical analysis of ice wall thickness decrease with shifting to the passive freezing stage with higher brine temperature. The decrease in ice wall thickness was studied both during normal operation of the freezing station and at emergency operation mode caused by the failure of one of the freezing columns. Special attention in the analysis was paid to studying the influence of the duration of the active freezing stage and the distance between the columns on the decrease in the ice wall thickness. When analyzing changes in ice wall thickness at different distances between the freezing columns, it was found that the most common column spacing in the range from 1.1 to 1.3 m requires observing restrictions on the duration of active freezing to prevent a critical decrease in ice wall thickness during the passive freezing stage or decreasing the distance between the freezing columns. In this case, preservation of positive dynamics of ice wall thickness growth is ensured. For the clay layer considered in the study and the distance between the columns from 1.1 to 1.3 m, the minimum time of active freezing is also about 4.3 months. As a result of the analysis, the technological parameters of the freezing system (duration of the active freezing stage and the distance between the freezing columns) were determined, at which the ice wall thickness at the passive freezing stage did not become lower than the minimum permissible values calculated based on the strength and creep conditions.

scholarly journals Theoretical analysis of frozen wall dynamics during transition to ice holding stage

2020 ◽  
Vol 243 ◽  
pp. 319
Author(s):  
Mikhail Semin ◽  
Lev Levin ◽  
Aleksandr Bogomyagkov
Keyword(s):  
Rock Mass ◽  
Pore Water ◽  
Wall Thickness ◽  
Operation Mode ◽  
Emergency Operation ◽  
Freezing Temperature ◽  
Normal Operation ◽  
Emergency Situations ◽  
Frozen Wall ◽  
Potash Mine

Series of calculations for the artificial freezing of the rock mass during construction of mineshafts for the conditions of a potash mine in development was carried out. Numerical solution was obtained through the finite element method using ANSYS software package. Numerical dependencies of frozen wall thickness on time in the ice growing stage and ice holding stage are obtained for two layers of the rock mass with different thermophysical properties. External and internal ice wall boundaries were calculated in two ways: by the actual freezing temperature of pore water and by the temperature of –8 °С, at which laboratory measurements of frozen rocks' strength were carried out. Normal operation mode of the freezing station, as well as the emergency mode, associated with the failure of one of the freezing columns, are considered. Dependence of a decrease in frozen wall thickness in the ice holding stage on the duration of the ice growing stage was studied. It was determined that in emergency operation mode of the freezing system, frozen wall thickness by the –8 °C isotherm can decrease by more than 1.5 m. In this case frozen wall thickness by the isotherm of actual freezing of water almost always maintains positive dynamics. It is shown that when analyzing frozen wall thickness using the isotherm of actual freezing of pore water, it is not possible to assess the danger of emergency situations associated with the failure of freezing columns.

Emergency Control of Vehicle Platoons: Control of Following-Law Vehicles

1976 ◽  
Vol 98 (3) ◽  
pp. 239-244 ◽  
Author(s):  
R. J. Rouse ◽  
L. L. Hoberock
Keyword(s):  
Emergency Operation ◽  
Dynamical Analysis ◽  
Normal Operation ◽  
Target Velocity ◽  
Longitudinal Control ◽  
Emergency Control ◽  
Vehicle System ◽  
Design Speed ◽  
Vehicle Platoons

This work presents a dynamical analysis of platooned following-law vehicles under longitudinal control proposed in [1]. It is shown that controller gains selected for normal operation give inadequate performance in emergency operation. Dangerous spacing in platoons moving at lower than design speed and delayed target velocity update effects are investigated. Stability of the vehicle system in emergency operation is related to controller gains, and simulations for various emergency contingencies are presented.

scholarly journals Study on Impedance Characteristics of Aircraft Cables

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Weilin Li ◽  
Wenjie Liu ◽  
Xiaobin Zhang ◽  
Zhaohui Gao ◽  
Meng Xie ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Power System ◽  
Electric Power ◽  
Electrical Equipment ◽  
Electric Power System ◽  
Normal Operation ◽  
Variable Frequency ◽  
Forming Mechanism ◽  
Changing Trends ◽  
Impedance Characteristics

Voltage decrease and power loss in distribution lines of aircraft electric power system are harmful to the normal operation of electrical equipment and may even threaten the safety of aircraft. This study investigates how the gap distance (the distance between aircraft cables and aircraft skin) and voltage frequency (variable frequency power supply will be adopted for next generation aircraft) will affect the impedance of aircraft cables. To be more precise, the forming mechanism of cable resistance and inductance is illustrated in detail and their changing trends with frequency and gap distance are analyzed with the help of electromagnetic theoretical analysis. An aircraft cable simulation model is built with Maxwell 2D and the simulation results are consistent with the conclusions drawn from the theoretical analysis. The changing trends of the four core parameters of interest are analyzed: resistance, inductance, reactance, and impedance. The research results can be used as reference for the applications in Variable Speed Variable Frequency (VSVF) aircraft electric power system.

scholarly journals Bilevel Optimal Dispatch Strategy for a Multi-Energy System of Industrial Parks by Considering Integrated Demand Response

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1942 ◽  
Author(s):  
Yuehao Zhao ◽  
Ke Peng ◽  
Bingyin Xu ◽  
Huimin Li ◽  
Yuquan Liu ◽  
...  
Keyword(s):  
Demand Response ◽  
Operation Mode ◽  
Energy Operator ◽  
Energy System ◽  
Optimal Operation ◽  
Normal Operation ◽  
Heavy Load ◽  
Optimal Dispatch ◽  
Industrial Parks ◽  
Upper Level

To combat energy shortage, the multi-energy system has gained increasing interest in contemporary society. In order to fully utilize adjustable multi-energy resources on the demand side and reduce interactive compensation, this paper presents an integrated demand response (IDR) model in consideration of conventional load-shedding and novel resource-shifting, due to the fact that participants in IDR can use more abundant resources to reduce the consumption of energy. In the proposed IDR, cooling, heating, electricity, gas and so forth are considered, which takes the connection between compensation and load reductions into consideration. Furthermore, a bilevel optimal dispatch strategy is proposed to decrease the difficulty in coordinated control and interaction between lower-level factories and upper-level multi-energy operators in industrial parks. In this strategy, resources in both multi-energy operator and user sides are optimally controlled and scheduled to maximize the benefits under peak shifting constraint. In the normal operation mode, this strategy can maximize the benefits to users and multi-energy operators. Particularly in heavy load conditions, compared to the conventional electricity demand response, there are more types of adjustable resources, more flexibility, and lower interactive compensations in IDR. The results indicate that optimal operation for factories and multi-energy operators can be achieved under peak shifting constraint and the overall peak power value in industrial park is reduced.

scholarly journals On Stability of Open-Loop Operation without Rotor Information for Brushless DC Motors

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Zhong Wu ◽  
Haotun Lyu ◽  
Yongli Shi ◽  
Di Shi
Keyword(s):  
Theoretical Analysis ◽  
Operation Mode ◽  
Open Loop ◽  
Control Mode ◽  
Open Loop Control ◽  
Brushless Dc Motors ◽  
Loop Control ◽  
Rotor Position ◽  
Brushless Dc ◽  
Dc Motors

Open-loop operation mode is often used to control the Brushless DC Motors (BLDCMs) without rotor position sensors when the back electromotive force (EMF) is too weak due to the very low rotor velocity. The rotor position information is not necessary in this mode and the stator windings are supplied with voltages under a certain ratio of the amplitude to the frequency. However, the rotor synchronization will be destroyed once if the commutation instant is inappropriate. In order to improve the reliability of the open-loop operation mode, a dynamic equation is established to represent the synchronization error between the rotor and the stator. Thereafter, the stability of the open-loop control mode is analyzed by using Lyapunov indirect method. Theoretical analysis indicates that the open-loop control mode is asymptotically stable only when the commutation instant of the stator current lags behind the ideal one suitably. Finally, theoretical analysis is verified through the experimental results of a certain BLDCM.

Feedback Control to Prevent Damage by Rotor Rubbing After an Impact Load

2009 ◽  
Author(s):  
Lucas Ginzinger ◽  
Benjamin Heckmann ◽  
Heinz Ulbrich
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Control Strategy ◽  
Impact Load ◽  
Operation Mode ◽  
Rotor System ◽  
Contact Forces ◽  
Normal Operation ◽  
Control Force ◽  
Auxiliary Bearing

A new approach to control a rubbing rotor by applying an active auxiliary bearing has been developed. The control force is applied indirectly using the auxiliary bearing, only in case of rotor rubbing. The auxiliary bearing is actuated using two unidirectional actuators. A three-phase control strategy has been developed which stabilizes the rotor system in case of an impact load and effectively avoids “backward whirling” which is very destructive. As soon as the load ceased the auxiliary bearing is separated from the rotor again and normal operation mode is continued. During the normal operation state, the feedback control does not interfere with the rotor system at all. A test rig has been developed to experimentally verify the control system. Various experiments show the success of the control strategy. In case of rubbing, the contact forces are reduced up to 95 percent. At the same time, the rotor deflection is decreased too. The activation and deactivation of the control system is operated fully automatically. A simulation framework for an elastic rotor including the non-smooth nonlinear dynamics of contacts is presented, which has been used to develop the feedback controller.

scholarly journals Modelling of magnetostriction of transformer magnetic core for vibration analysis

Open Physics ◽  
2017 ◽  
Vol 15 (1) ◽  
pp. 803-808
Author(s):  
Janis Marks ◽  
Sandra Vitolina
Keyword(s):  
Power Transformer ◽  
Operation Mode ◽  
Magnetic Core ◽  
Power Transformers ◽  
Normal Operation ◽  
Elastic Deformations ◽  
Properties Of Materials ◽  
Transformer Core ◽  
Normal Operation Mode

Abstract Magnetostriction is a phenomenon occurring in transformer core in normal operation mode. Yet in time, it can cause the delamination of magnetic core resulting in higher level of vibrations that are measured on the surface of transformer tank during diagnostic tests. The aim of this paper is to create a model for evaluating elastic deformations in magnetic core that can be used for power transformers with intensive vibrations in order to eliminate magnetostriction as a their cause. Description of the developed model in Matlab and COMSOL software is provided including restrictions concerning geometry and properties of materials, and the results of performed research on magnetic core anisotropy are provided. As a case study modelling of magnetostriction for 5-legged 200 MVA power transformer with the rated voltage of 13.8/137kV is conducted, based on which comparative analysis of vibration levels and elastic deformations is performed.

scholarly journals Modeling the user’s choice in the constraints of the cold start of the recommender system.

2019 ◽  
Vol 1 (92) ◽  
pp. 14-19
Author(s):  
V.O. Leshchynskyi ◽  
I.O. Leshchynska
Keyword(s):  
Recommender System ◽  
Consumer Choice ◽  
Input Data ◽  
Operation Mode ◽  
Cold Start ◽  
Normal Operation ◽  
Time Interval ◽  
Problem Structuring ◽  
Object A ◽  
Object Selection

The problem of supporting user choice in recommender systems is considered, taking into accountthe limitations that arise when solving a cold start problem. Structuring of this problem was carried out and suchaspects of a cold start were highlighted as the emergence of a new user, the emergence of a new consumer interest object, a change in the user selection context, a change in consumer interests over time. A system-oriented model of object selection in the normal operation mode of the recommender system was proposed, as well as a model-oriented model of object selection under cold start conditions. Restrictions in the proposed models are presented in the form of predicates on variables that characterize the properties of consumers and objects of theirinterest, as well as the context of consumer choice. The advantage of the proposed models is the ability to limit the input data, so that they correspond to the most significant laws of consumer choice in this context at a given time interval, which allows us to simplify the construction of recommendations for new consumers and new objects. An approach to building recommendations in the context of cold start restrictions is proposed. The approach assumes the formation of constraints based on the intellectual analysis of the input data of the recommender system, as well as the further use of these constraints in constructing recommendations in cold start conditions.

scholarly journals Assessments of land subsidence along Rizhao-Lankao High-speed Railway at Heze, China between 2015 and 2019 with Sentinel-1 data

2020 ◽  
Author(s):  
Chuanguang Zhu ◽  
Wenhao Wu ◽  
Mahdi Motagh ◽  
Liya Zhang ◽  
Zongli Jiang ◽  
...  
Keyword(s):  
Land Subsidence ◽  
High Speed ◽  
Underground Mining ◽  
Ground Deformation ◽  
Ground Subsidence ◽  
Normal Operation ◽  
Monthly Precipitation ◽  
High Speed Railway ◽  
Subsidence Area ◽  
Under Construction

Abstract. The Heze section of Rizhao-Lankao High-speed Railway (RLHR-HZ) has been under construction since 2018 and will be operative by the end of 2021. However, there is a concern that land subsidence in Heze region may affect the normal operation of RLHR-HZ. In this study, we investigate the contemporary ground deformation in the region between 2015 and 2019 by using more than 350 C-band interferograms constructed from two tracks of Sentine-1 data over the region. The Small Baselines Subset (SBAS) technique is adopted to compile the time series displacement. We find that the RLHR-HZ runs through two main subsidence areas: One is located east of Heze region with rates ranging from −4 cm/yr to −1 cm/yr, and another one is located in the coal field with rates ranging from −8 cm/yr to −2 cm/yr. A total length of 35 km of RLSR-HZ are affected by the two subsidence basins. Considering the previous investigation and the monthly precipitation, we infer that the subsidence bowl east of Heze region is due to massive extraction of deep groundwater. Close inspections of the relative locations between the second subsidence area and the underground mining reveals that the subsidence there is probably caused by the groundwater outflow and fault instability due to mining, rather than being directly caused by mining. The InSAR-derived ground subsidence implies that it's necessary to continue monitoring the ground deformation along RLSR-HZ.

Numerical Assessment of Hydraulic Performances of Main Coolant Pump for Integral Reactor Smart

2002 ◽  
Author(s):  
Min-Hwan Kim ◽  
Jong-In Kim ◽  
Jin-Seok Park
Keyword(s):  
Flow Rate ◽  
Operation Mode ◽  
Reactor Core ◽  
Normal Operation ◽  
Reverse Direction ◽  
Performance Curve ◽  
Coolant Pump ◽  
Axial Pump ◽  
General Capacity ◽  
Typical Type

The performance prediction of SMART MCP was performed using a computational fluid dynamics code. A general capacity-head performance curve of MCP was obtained and it showed the typical type axial pump performance curve. When four MCPs operate in parallel and one of them stops while the others continue to operate, SMART is designed to operate with reduced power. A procedure for predicting the performance of this SMART operation mode was developed and verified with available experimental data. An analysis based on the developed procedure was performed for two cases; the impeller of stopped MCP is assumed to be fixed or free to rotate in the reverse direction. According to the results, 73% flow rate of normal operation enters the reactor core in the case of a fixed impeller. In the case of a free impeller, the flow rate entering the reactor core is 63.3%.

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