228 results about "Coupling problem" patented technology

A Signal Conditioning Filter (SCF) and a Signal Integrity Unit (SIU) address the coupled problem of equalization and noise filtering in order to improve signal fidelity for decoding. Specifically, a received signal can be filtered in a manner to optimize the signal fidelity even in the presence of both significant (large magnitudes of) ISI and noise. The present invention can provide an adaptive method that continuously monitors a signal fidelity measure. Monitoring the fidelity of a multilevel signal can be performed by external means such as by the SIU. A received signal y(t) can be “conditioned” by application of a filter with an electronically adjustable impulse response g(t). A resulting output z(t) can then be interrogated to characterize the quality of the conditioned signal. This fidelity measure q(t) can be used to adjust the filter response to maximize the fidelity measure of the conditioned signal.

The invention relates to the technical field of PMSMs, solves a coupling problem during online identification of multiple parameters of a surface-mounted type PMSM, and achieves online decoupling identification of PMSM inductance, stator resistance and rotor flux linkage. Accordingly, the technical scheme adopted by the invention is that an online decoupling identification method of multiple parameters of the PMSM comprises the steps as follows: 1) identifying and coupling analysis of parameters of the PMSM; 2) a decoupling identification strategy, wherein voltage deviation before and after D shaft current injection is used for increasing the order of a motor mathematical equation, so that the decoupling identification of multiple parameters of the surface-mounted type PMSM inductance, the stator resistance and the rotor flux linkage are achieved; 3) neural network identifier design, wherein according to a parameter online identification problem of the PMSM, online identification is performed on motor parameters by adopting a self-adaptive neural network structure and a weight convergence algorithm based on a least mean square algorithm. The method is mainly applied to the design and manufacture of the PMSM.

The invention discloses a digital controlled lathe thermal error measuring compensation system and method. The system comprises an eddy current displacement sensor, a platinum resistor temperature sensor, a laser interferometer, a displacement collecting and processing module, a thermal error compensation module and a PC. The platinum resistor temperature sensor measures the temperature of a lathe body heat sensitive point, the eddy current displacement sensor measures heat deformation of a spindle, the laser interferometer measures the locating error of a feeding system, and the spindle and a feeding shaft system are subjected to real-time thermal error comprehensive modeling. The thermal error compensation module compensates for axial heat expansion and radial heat inclination of a spindle workpiece in real time according to the temperature of the heat sensitive point and the coordinate value of a tool. The coupling problem of the digital controlled lathe spindle and the feeding shaft thermal error is solved, the thermal error can be compensated for in real time, and the machining precision of a digital controlled lathe is improved.

The invention provides a pedestrian re-recognition method and device based on deep learning. The pedestrian re-recognition method comprises the steps of acquiring a target pedestrian image and a reference pedestrian image from a first video stream and a second video stream respectively, wherein the first video stream and the second video stream are videos shot by cameras with different angles in a preset region; by using a pre-trained deep learning network model, extracting an image feature of the target pedestrian image to act as a first image feature, and extracting an image feature of the reference pedestrian image to act as a second image feature; calculating the feature similarity of the first image feature and the second image feature; if the feature similarity conforms to a preset requirement, determining a target pedestrian in the target pedestrian image and a reference pedestrian in the reference pedestrian image are the same pedestrian. Implicit features of the target pedestrian image and the reference pedestrian image are learnt respectively by adopting a deep learning technology, a coupling problem existing in paired pedestrian images adopted by a traditional pedestrian re-recognition method is overcome, and the flexibility is good.

The invention discloses a motor vehicle exhaust smoke video identification system. The motor vehicle exhaust smoke video identification system comprises a video acquisition unit, a video data processing unit and a data center unit, wherein the video acquisition unit comprises an industrial network camera, the video data processing unit comprises an industrial control computer, and the industrial control computer comprises a vehicle tracking and processing module, a license plate identification and processing module, a vehicle speed measuring module and a vehicle exhaust monitoring module. The motor vehicle exhaust smoke video identification system has properties of simple structure, good robustness and no linkage equipment and has no equipment linkage coupling problem. Multi-lane monitoring, excessive vehicle discharge monitoring and license plate recording can be accomplished at one step, position recording is intelligible, and video recording is more persuasive. According to the motor vehicle exhaust smoke video identification system, the industrial network camera and the industrial control computer are only needed to realize processing on the lanes such as vehicle exhaust monitoring, license plate identification, smoke detection, vehicle velocity measurement, cost for equipment and mounting is greatly saved, and smoke detection efficiency is improved.

The invention relates to a method for analyzing grid-connected inverter system stability by a modified generalized impedance method. The method for analyzing the grid-connected inverter system stability includes establishing a small-signal model of an inverter under polar coordinates according to a grid-connected inverter system, and then establishing a generalized admittance interface model of the inverter and a generalized admittance interface model of a power grid; using the generalized admittance interface models to obtain modified generalized impedance of the inverter and the power grid; acquiring modified generalized impedance criteria from a ratio of the modified generalized impedance of the inverter to the modified generalized impedance of the power grid so as to be used for system stability analysis. The method for analyzing the grid-connected inverter system stability can be used for grid-connected inverter stability analysis with voltage feed-forward filtering reckoned in, is capable of better solving the coupling problem as compared with a general impedance method and can be used for accurately analyzing stability of large-scale grid-connected problems.

The invention provides a plug-in implement method based on a micro network visual platform. Plug-ins are loaded through a plug-in management class. The plug-in loading mode comprises simple loading of a plurality of plug-ins, simple loading of a plug-in, loading of plug-ins under walking contents, loading of static library plug-ins and loading of plug-ins through configuration files. Each plug-in comprises functions of information, an order, an event and an interface. Through the functions, interface interaction of menus, toolbars and the like, and functional call among components are achieved. Life cycles of the components can be maintained through an intelligent indicator, and robustness, safety and uniqueness of data can be ensured. The function of the loading of the static library plug-ins is provided, when software is published, only one main program file is needed, a plurality of static library modules are arranged in the interior, thus, not only are the advantages that the plug-ins can be reusable played, but also the number of program files can be reduced, the plug-ins are enabled to provide cross-platform support, and reusability of the program can be improved. The method is suitable for solving the coupling problem between the micro network visual platform and each plug-in of different sub systems.

The invention discloses a speed-tension coordination control method for jigger fabrics; the method mainly uses a fuzzy control system to compare the sampling speed of a photoelectric coder with the set speed, and compare the tension-detection value of a tension detection device with the set tension, so as to timely adjust the control rules according to the dynamic changes of the errors to subsectionally and alternately control the speed and the tension to respectively obtain a coiling frequency fA and an unwinding frequency fB needed in maintaining the equal linear velocity constant tension of dyeing fabrics; a coiling electromotor and an unwinding electromotor are respectively controlled by a coiling transducer working in speed mode and an unwinding transducer working in torque conversion mode. The method solves the coupling problem between the speed and the tension of the jigger fabrics and makes more accurate speed-tension coordination control of the double-input / double-output, coupled and time-varying non-linear system of jiggers, so as to reduce dyeing color difference caused by instable speed and tension and improve the dyeing quality of fabrics.

The invention discloses an effective method for accurately detecting multiple targets by an automobile blind zone monitoring radar. Aiming at the distance speed coupling problem of frequency modulated continuous wave (FMCW) signals with single frequency modulation slope, the invention provides FMCW radar emitting signals with variable frequency modulation slope for accurately detecting real targets on the basis of variable-period FMCW signals. Aiming at the measurement precision limitation problem during fast fourier transform (FFT) difference frequency signal analysis, different distances and speed errors are obtained by time domain taking and frequency domain interpolating methods according to different target distances. When targets are in a remote distance, rough distance and speed information is obtained only through FFT analysis; and for targets in middle distance and short distance, traffic accidents can more easily occur, so the time domain taking and frequency domain interpolating methods are used for measuring more precise distance and speed. The effective method can be used for the multi-target detection of the automobile blind zone monitoring radar in the road traffic safety field.

The invention discloses a rotational coordinate transformation based current decoupling control method for a three-phase grid-connected inverter. With regard to a grid-connected inverter with an LCL (Inductor Capacitor Inductor) filter, an inversion three-phase output current signal and a grid-side three-phase current signal are transformed into two groups of orthogonal current signals in a synchronous rotation coordinate system through adopting coordinate transformation, the two groups of orthogonal current signals are subjected to the calculation of weighted average to be used as an inverter current controlled feedback signal and an inverter current controlled decoupling signal under a rotational coordinate system, the feedback signal is compared with a control given signal to obtain anerror signal, and the obtained error signal is subjected to proportional-integral regulation and then is subjected to a combined operation with the decoupling signal to obtain a pulse duty-ratio signal for controlling a three-phase inverter switch to operate under the rotational coordinate system, so that output current waveform and amplitude control of the grid-connected inverter can be realized. Through adopting the method disclosed by the invention, the signal coupling problem existing in three-phase current control of the LCL filter three-phase grid-connected inverter can be effectively solved, the capacity of independently controlling each phase of output current is enhanced, and the favorable output current waveform of a grid-connected system can be achieved.

The invention provides an active disturbance rejection control method for cluster spacecraft electromagnetic traction, complexity of a cluster spacecraft system and model uncertainty are fully considered, an electromagnetic force / torque model and a relative motion dynamics equation are established, so that the active disturbance rejection control method formed by a most speed tracking differentiator, a non-linear extension observer and a non-linear feedback control law has good working performance, a coupled problem of a dynamic model is effectively solved, high precise electromagnetic traction control can be realized, and the effectiveness and the Lyapunov asymptotic stability of the method are verified; compared with the control performance of a finite time control method, the control method has better rapidity, vibration resistance ability and disturbance rejection, and the control method is simple in design and has engineering realizability.

The invention provides a flying wing unmanned aerial vehicle maneuvering flight control method based on multi-mode control. The method comprises step 1, dynamic analysis is carried out on a pluralityof typical maneuvering actions, and a plurality of maneuvering sub-modes are extracted from the dynamic analysis; step 2, autostability design is firstly conducted for a longitudinal channel, a transverse channel and a course channel of a flying wing unmanned aerial vehicle, and then a controller of each maneuvering sub-mode is designed; step 3, different maneuvering actions are realized through combination of different maneuvering sub-modes, namely switching of maneuvering sub-mode controllers; and step 4, aimed at the coupling problem of maneuvering, the feedforward decoupling compensation design is combined with the maneuvering sub-mode controller. Compared with an advanced control method which only stays at the theoretical research stage at present, the RSLQR and the PID control methodadopted by the method all have practical engineering application bases which are already verified in the actual unmanned aerial vehicle flying process, so that the safety of the flying wing unmannedaerial vehicle during maneuvering flight can be guaranteed.

The invention discloses an integrated control method used for a semi-strapdown guided missile. The method includes the following steps that firstly, missile guider stable tracking and missile body posture control integrated mathematical models are established and include a missile body posture kinematic model, a frame kinematic model, an angle tracking system model and an integrated mathematical model; secondly, an integrated controller configuration is designed; and thirdly, controller design based on non-linear dynamic inverse is conducted. According to the integrated models, the integrated control configuration based on an inner ring and an outer ring is designed, the coupling problem between control loops is solved, the conservative property of design of a control system is reduced, and the comprehensive performance of the system is improved.

The invention provides a bushing modeling method. The method includes: dividing parts of a bushing 3D (three-dimensional) model predefined, into finite element grids; determining material attributes of the finite element grids of the parts of the bushing 3D model, with the material attributes referring to density, Poisson's ratio and elastic modulus of materials of each part of the bushing; according to order, computing mode and load-step of output modality of a flexible body of the predefined bushing, computing the finite element grids to obtain frequencies and vibration modes of all orders of modality of the flexible body and also an animation file of the flexible body; converting the animation file of the flexible body into a modal neutral file, and importing the modal neutral file into motion simulation software of the flexible body, and establishing a bushing flexible body model. The bushing flexible body model acquired by the bushing modeling method can reflect isotropic stiffness coupling problems of the bushing, a bushing stiffness curve can be acquired with no need for testing, precision of the bushing flexible body model is improved, and testing time is saved.

The invention discloses an array substrate, a driving method thereof, a display panel and a display device. By changing the layout way of data lines on the periphery of an open area, the data lines located on the periphery of the open area are divided into first data lines and second data lines, the layout way of the first data lines are changed into an L-shaped layout way, namely the first data lines are divided into first portions extending in the second direction and second portions extending in the first direction, meanwhile for avoiding the phenomenon that the second portions of the firstdata lines are mutually crossed with the second data lines to cause signal interference, the second data lines extending in the second direction are stopped at the second portions to form certain separation distances with the second portions, and accordingly the problem of mutual crosstalk of data signals is avoided. By adopting the layout way of the data lines on the periphery of the open area,it can be avoided that signal lines having smaller intervals are arranged at the frame of the open area. Therefore, more severe coupling problems produced in the charging process can be decreased, andthe color cast problem under the condition of heavy load pictures can be avoided.

The invention relates to a five-degree-of-freedom hybrid excitation bearingless switched reluctance motor which is composed of a 12 / 14 bearingless switched reluctance motor, a first permanent magnet, a radial bearing, a second permanent magnet, an axial bearing and a rotating shaft. The permanent magnets provides a bias magnetic field required for generating suspension force for the 12 / 14 bearingless switched reluctance motor, the radial bearing and the axial bearing through the effect of a magnetic conductive plate so that excessive coils used for generating bias magnetic axis can be omitted, the loss is low and the system structure is compact; and the coupling problem between the torque winding and the suspension force winding of the bearingless switched reluctance motor can be solved so that decoupling control of the torque and the suspension force can be realized on the motor body, and stable suspension of the bearingless switched reluctance motor rotor can be facilitated by the characteristic that the suspension force is not influenced by the rotor position angle.

The invention relates to a driving circuit unit, a driving circuit and a display device, which can be applied to an AMOLED display, a TFT-LCD, etc. The driving circuit unit in the present applicationcan meet the requirements of multi-type scanning signals of the AMOLED pixel circuits and the driving circuit unit can meet the requirements of multi-type scanning signals of the AMOLED pixel circuits, By adopting a separate input structure, a separate double bootstrap node is formed, which solves the charge coupling problem between different bootstrap nodes caused by clock feed-through effect, restrains the voltage drop of the bootstrap node caused by the leakage of the thin film transistor, and makes the pulse shape of the output scanning signal more complete and symmetrical, and shortens the rise and fall time. By introducing a feedback transistor, the low-level sustain node can still maintain a high level when the threshold voltage of the transistor is negative, and the scanning signalat the output terminal can be maintained at a corresponding low level. The driving method of the present application can improve the electrical performance of the AMOLED pixel circuit, so that the stability and uniformity of the AMOLED display are better.

Provided are a multi-ground shielding semiconductor package including analog and digital circuit blocks and capable of preventing a coupling problem between the analog and digital circuit blocks caused by high frequency noise. A method of fabricating the multi-ground shielding semiconductor package, and a method of preventing noise in the multi-ground shielding semiconductor package are also provided. The multi-ground shielding semiconductor package includes at least one semiconductor chip; and a circuit board on which the semiconductor chip is mounted and on which a plurality of circuit blocks are formed, wherein a conductive ground shielding is formed between the circuit blocks and separately from grounds of the circuit blocks to prevent noise between the circuit blocks.

The invention relates to a design method for stiffness matching and diameter of vehicle suspension stabilizer bars and belongs to the technical field of vehicle suspensions, aiming to fill a gap of the reliable optimal design method for diameter of the stabilizer bars due to limitation of radial deformation analytic analysis and inter-coupling of the stabilizer bars and rubber bushings. The design method is characterized by including the steps of firstly, performing matching design on stiffness of angle of roll of a front suspension stabilizer bar system and a rear suspension stabilizer bar system according to vehicle parameters and roll models; secondly, building an optimal design mathematical model of the stabilizer bar diameter d according to the matching design value of stiffness of the angle of roll, the radial stiffness coefficient Kx of the rubber bushings and the deformation coefficient expression Gw of ends of the stabilizer bars so as to obtain the accurate and reliable optimal design value of the stabilizer bar diameter d by means of a Matlab program. By the design method, design level and performance of the suspensions and the stabilizer bars can be improved, riding comfort and safety of vehicles can be improved, and meanwhile, design speed for product development can be increased and cost for design and test can be reduced.

The invention discloses a CubeSat satellite platform based on a mobile phone. The CubeSat satellite platform comprises the smartphone, an interface switching module and an external module, wherein the external module comprises one or more of an attitude control module, a communication module, a maneuvering module and an extendable loading module, the smartphone is used for performing interaction with the attitude control module, the communication module, the maneuvering module and / or the extendable loading module respectively through the interface switching module to complete satellite platform tasks, the attitude control module is used for achieving attitude control of a CubeSat, the a CubeSat is used for achieving information interaction between the CubeSat and a ground station or other spacecrafts, the maneuvering module is used for controlling the CubeSat to operate in a set orbit, and the extendable loading module is used for extending load and / or adding corresponding functional units so as to achieve extendibility of the satellite platform under the control of the smartphone. The coupling problem of satellite design, tasks and progress is effectively solved, the period of study and development is short, and expansibility and reconfigurability are high.

The invention discloses a predictive control system and a method for reducing the common-mode voltage of a three-level VIENNA rectifier system, which are used for solving the problems of high common-mode voltage of the three-level VIENNA rectifier system in a wind power generation system, zero-crossing point distortion of an AC side current and unbalance of a DC side neutral point voltage. The algorithm limits the common-mode voltage of the system to a very low range. The coupling problem of current zero-crossing distortion and DC neutral-point voltage imbalance control is solved. By classifying the space voltage vectors, the computational complexity is greatly reduced. The algorithm does not need current inner loop controller and PWM modulation module, and avoids the design of complex controller and the selection of complex parameters. The system and method have characteristics of simpleness, directness and effectiveness, which makes the algorithm has high application value.

The invention relates to a novel broadband coaxial waveguide orthomode coupler based on a turnstile structure. The novel broadband coaxial waveguide orthomode coupler comprises the turnstile structure, two power synthesizers or distributors or two impedance transformers, wherein the turnstile structure comprises a coaxial waveguide, an impedance matching structure and a coupling rectangular waveguide; each of the power synthesizers or distributors comprises a bent waveguide and a three-port cavity structure; and the impedance transformers are fifth-order rectangular waveguide step gradual-changing structures. According to the novel broadband coaxial waveguide orthomode coupler, the orthogonalp polar signal coupling problem in a coaxial feed waveguide in a multi-frequency satellite communication antenna system, and the broadband working characteristic problem of the coaxial waveguide orthomode coupler are solved, and the orthogonal signal coupling function requirements within dual receiving and sending frequency bands of a Ku-frequency-band satellite communication feed source antenna can be satisfied.

The invention relates to an imitated gecko sole capable of self-sensing and self-adapting to a contact force with an initiative sticking / desorbing function and belongs to the field of robot technology application. The imitated gecko sole comprises a shank beam (1), a one-dimensional sensor (2), a wire-pull steering engine bracket (3), a rotating support frame (4), a wire-pull steering engine (5), a rotating flange (6), a two-dimensional force sensor (7), a bulb (8), a fetlock cover, a spring, a toe slice base and a sticking material. The imitated gecko sole can initiatively drive a plurality of toes and can realize an initiative sticking function and an initiative desorbing function; the one-dimensional sensor and the two-dimensional force sensor along different directions are combined and are moved and decoupled together with an initiative sticking and desorbing mechanism, so that the coupling problem of motion and force sensing can be avoided; the fetlock at three degrees of freedom constrained by eight resetting springs is added, so that the space surface has self-adaptive ability.

The invention discloses an implementation method for building an intermediate service platform between a telephone line terminal and a service system application server based on a network B / S architecture. The method employing the structure with the unified line integrated with the service platform on the basis of the network B / S architecture is convenient to update and release, and can quickly adapt to integration with new service platforms, and reduces the cost and risk. Moreover, by utilizing the web service technology, the service platform achieves the interaction between the telephone line (client terminal) and the service system (server), thereby better solving problem of tightly coupling the telephone line and the service system, and greatly improving the efficiency of promotion and integration of new service systems.

An improved method and apparatus for altering the effective electrical length of trace on a circuit board. In the present invention small tabs of etch are routed perpendicular to the trace in the unused areas between adjacent traces. In an embodiment of the invention, a method of tuning the delay characteristics of a transmission line is implemented by inserting compensation tabs into the unused area between the segments of adjacent straight traces or a serpentine run. Utilizing the method and apparatus of the present invention, it is possible to achieve significantly greater electrical length for an electrical trace without introducing coupling problems or utilizing large amounts of space on a circuit board.

The invention relates to a contactor contact system on-load multi-physical-field coupling simulating and optimization design system which comprises an electric arc calculating module, an electromagnetic field-dynamics-acoustics solving module, an electromagnetic field-temperature field solving module, a multi-stage design module and a graphical user interface module. The simulating and optimization design system of an overall-process three-dimensional virtual prototype considering the on-load suction process, suction holding process and the separation process of a contact system is provided, and the on-load troubles in a contact system on a contactor simulating technology in the current industry and the multi-field coupling problems on contactor design are solved.

The invention provides a method for simulating a wind-wave coupling load value of a lower structure of a large-span bridge, which solves the multiple coupling problems of interaction of the environment and the structure from the three aspects of coupling of the wind and the wave, coupling of the wind and the structure and coupling of the wave and the structure in a simulation process. The method comprises the following steps of firstly, implementing synchronous coupling simulation in time domains of two random processes of the wind and the wave through coupling of a pulse wind speed spectrum and a wave frequency spectrum; secondly, implementing coupling simulation of the wind and the structure through the pulse wind speed spectrum of the peripheral wind field of a Reynolds stress tensor correction structure; lastly, implementing coupling simulation of the wave and the structure through an MacCamy-Fuchs diffraction theory. The method comprehensively applies a computational fluid dynamics (CFD) method, a fast Fourier transform (FFT) method, a proper orthogonal decomposition (POD) method and a frequency interpolation method, and the method has the advantages of high computational efficiency, simple simulation process and clear physical significance and can be popularized to simulation of the wind-wave coupling load value of the other ocean-like structures.

The invention discloses a method for analyzing the coupling problem of static geometric nonlinearity and material nonlinearity of a plane frame structure based on a rigid body criterion, aiming at solving the problems that the prior method needs to adopt a complex element stiffness matrix, the number of divided elements is large, and the calculation efficiency and precision are insufficient. The method comprises the following steps: step 1, establishing a concentrated plastic hinge spring planar beam element model; 2, establishing an element stiffness matrix corresponding to the model satisfying the rigid body criterion; 3, establish an incremental iterative process for sol that equation based on the updated Lagrangian scheme and the rigid body criterion; Step 4, iteratively solving the incremental equation to obtain the load-displacement curve and the limit load in the loading process of the structure. The invention has the advantages of being applicable to the coupling problem of geometrical non-linearity and material non-linearity of plane frame structure, simple geometrical stiffness matrix form, linear stiffness matrix, less element division, high calculation efficiency and precision, and is suitable for engineering application.

The invention provides a forecasting method for vehicle body structure-acoustic coupling based on a smoothed finite element boundary element method. The method comprises the following steps: generating a vehicle body structure-acoustic grid model; utilizing the smoothed finite element method to perform smooth processing on the stress field in a shell unit; adopting a mixed integral method to perform separate integral of shearing items subjected to shearing strain in the shell under a natural coordinate system; building a smooth Galerkin weak form of a vehicle body shell structure kinetic equation, and obtaining a dynamic equation after the weak form is subjected to discrete processing; creating an acoustic realistic model by using the boundary element method; according to the continuous displacement and pressure of the coupling interface, obtaining a structure-acoustic coupled smoothed finite element boundary element model; performing simulation forecasting by utilizing the coupled model. When the method is used for solving the vehicle body structure-acoustic coupling problem, relatively good calculation effect can be obtained, and the band frequency width can be analyzed more effectively. Moreover, the method has relatively low quality requirements on the model to reduce the pretreatment time, and has a wide engineering application prospect.

The invention discloses a test method for coal matrix deformation mechanical parameters. A coal sample test piece is placed into a closed clamping chamber body, a gas injection cavity and a gas outlet cavity are formed in two ends of a coal sample respectively, helium is guided into the gas injection cavity, the helium is firstly seeped into a coal fracture and then start to diffuse into a coal matrix, relations of a pressure value and a strain value as well as log time are drawn into graphs respectively, and a strain value and a fracture pore pressure value at the end of seepage and a strain value at the end of diffusion are obtained according to the graphs; finally, the coal matrix volume modulus in the seepage stage and the pore pressure variation in the matrix in the diffusion stage are calculated. A test method for deformation parameters of coal in all directions under the triaxial stress state condition is provided aiming at the high adsorption characteristic of coal-seam gas and considering the effect of pore pressure to a coal pore structure in the flowing process of gas and the effect of coal matrix deformation to permeability, and a new research means is provided for in-depth study of a coal-gas coupling problem.