Pub Date : 2011-10-13DOI: 10.1109/CCA.2011.6044413
Vincent Denoel, E. Detournay
We address the problem of computing the deformed configuration of a drillstring, constrained to deform inside a curved borehole. This problem is encountered in applications such as torque-and-drag and directional drilling. In contrast to the traditional Lagrangian approach, the deformed drillstring is described by means of the distance from the borehole axis, in terms of the curvilinear coordinate defined along the borehole. This model is further implemented within a segmentation algorithm — where the borehole and the drillstring are divided into segments limited by contacts, which interestingly transforms the problem into a sequence of analogous auxiliary problems. This Eulerian view of the drillstring flow into the borehole resolves in one stroke a series of issues that afflict the classical Lagrangian approach: (i) the contact detection is reduced to checking whether a threshold on the distance function is violated, (ii) isoperimetric conditions are transformed into regular boundary conditions, instead of being treated as external integral constraints, (iii) the method yields a well-conditioned set of equations that does not degenerate with decreasing flexural rigidity of the drillstring and/or decreasing clearance between the drillstring and the borehole. Theoretical developments related to this Eulerian formulation of the drillstring are presented, along with an example illustrating the advantages of this approach.
{"title":"Eulerian formulation of a drillstring constrained inside a curved borehole","authors":"Vincent Denoel, E. Detournay","doi":"10.1109/CCA.2011.6044413","DOIUrl":"https://doi.org/10.1109/CCA.2011.6044413","url":null,"abstract":"We address the problem of computing the deformed configuration of a drillstring, constrained to deform inside a curved borehole. This problem is encountered in applications such as torque-and-drag and directional drilling. In contrast to the traditional Lagrangian approach, the deformed drillstring is described by means of the distance from the borehole axis, in terms of the curvilinear coordinate defined along the borehole. This model is further implemented within a segmentation algorithm — where the borehole and the drillstring are divided into segments limited by contacts, which interestingly transforms the problem into a sequence of analogous auxiliary problems. This Eulerian view of the drillstring flow into the borehole resolves in one stroke a series of issues that afflict the classical Lagrangian approach: (i) the contact detection is reduced to checking whether a threshold on the distance function is violated, (ii) isoperimetric conditions are transformed into regular boundary conditions, instead of being treated as external integral constraints, (iii) the method yields a well-conditioned set of equations that does not degenerate with decreasing flexural rigidity of the drillstring and/or decreasing clearance between the drillstring and the borehole. Theoretical developments related to this Eulerian formulation of the drillstring are presented, along with an example illustrating the advantages of this approach.","PeriodicalId":208713,"journal":{"name":"2011 IEEE International Conference on Control Applications (CCA)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129552716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-13DOI: 10.1109/CCA.2011.6044421
Q. Zheng, Kiran K. Chedella, Weifeng Xu, Liying Wu
In this paper a novel control strategy, the reduced-order active disturbance rejection control (RADRC) with reduced-order extended state observer (RESO) is applied for induction motor control. In the RADRC framework, the disturbance and unmodeled dynamics associated with induction motors are treated as an additional state variable, which is then estimated and compensated for in real time. This reduces a normally complex, time-varying, nonlinear, and uncertain dynamic process to an approximately linear, time-invariant, cascade integral form, where a simple proportional plus derivative controller suffices. Simulation results demonstrate excellent tracking, disturbance rejection, and robustness performance of the RADRC in the absence of an accurate mathematical model of the induction motor.
{"title":"Reduced-order active disturbance rejection control for induction motors","authors":"Q. Zheng, Kiran K. Chedella, Weifeng Xu, Liying Wu","doi":"10.1109/CCA.2011.6044421","DOIUrl":"https://doi.org/10.1109/CCA.2011.6044421","url":null,"abstract":"In this paper a novel control strategy, the reduced-order active disturbance rejection control (RADRC) with reduced-order extended state observer (RESO) is applied for induction motor control. In the RADRC framework, the disturbance and unmodeled dynamics associated with induction motors are treated as an additional state variable, which is then estimated and compensated for in real time. This reduces a normally complex, time-varying, nonlinear, and uncertain dynamic process to an approximately linear, time-invariant, cascade integral form, where a simple proportional plus derivative controller suffices. Simulation results demonstrate excellent tracking, disturbance rejection, and robustness performance of the RADRC in the absence of an accurate mathematical model of the induction motor.","PeriodicalId":208713,"journal":{"name":"2011 IEEE International Conference on Control Applications (CCA)","volume":"468 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122811777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-13DOI: 10.1109/CCA.2011.6044486
Balaje T. Thumati, Miles A. Feinstein, J. Fonda, Alfred Turnbull, Fay J. Weaver, Mark E. Calkins, S. Jagannathan
In this paper, a model based fault detection and isolation (FDI) scheme with online fault learning capabilities is proposed for HVAC systems. An observer comprising of an online approximator in discrete-time (OLAD) and a robust term is used for detection. A fault is detected if the generated detection residual, which is defined as the error between the observer outputs and HVAC system states, exceeds an apriori chosen threshold. The OLAD term in the FD observer learns the fault dynamics online while the robust term guarantees asymptotic estimation of the system states. Subsequent to detection, a fault isolation observer, which comprises of the model of fault functions and another robust term, is initiated to identify the root cause. A fault is identified if the isolation residual converges to zero, where the residual is obtained by comparing outputs of the isolation observer and the system. Additionally, we consider different fault scenarios in the system such as single or simultaneous multiple faults. Analytical results for the FDI scheme guarantee the robustness and stability of the proposed scheme. Finally, a simulation example is used to demonstrate the proposed FDI scheme.
{"title":"An online model-based fault diagnosis scheme for HVAC systems","authors":"Balaje T. Thumati, Miles A. Feinstein, J. Fonda, Alfred Turnbull, Fay J. Weaver, Mark E. Calkins, S. Jagannathan","doi":"10.1109/CCA.2011.6044486","DOIUrl":"https://doi.org/10.1109/CCA.2011.6044486","url":null,"abstract":"In this paper, a model based fault detection and isolation (FDI) scheme with online fault learning capabilities is proposed for HVAC systems. An observer comprising of an online approximator in discrete-time (OLAD) and a robust term is used for detection. A fault is detected if the generated detection residual, which is defined as the error between the observer outputs and HVAC system states, exceeds an apriori chosen threshold. The OLAD term in the FD observer learns the fault dynamics online while the robust term guarantees asymptotic estimation of the system states. Subsequent to detection, a fault isolation observer, which comprises of the model of fault functions and another robust term, is initiated to identify the root cause. A fault is identified if the isolation residual converges to zero, where the residual is obtained by comparing outputs of the isolation observer and the system. Additionally, we consider different fault scenarios in the system such as single or simultaneous multiple faults. Analytical results for the FDI scheme guarantee the robustness and stability of the proposed scheme. Finally, a simulation example is used to demonstrate the proposed FDI scheme.","PeriodicalId":208713,"journal":{"name":"2011 IEEE International Conference on Control Applications (CCA)","volume":"44 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120900280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-13DOI: 10.1109/CCA.2011.6044465
Yun-Yao Lee, R. Wu, S. T. Xu
The non-contact type application on the permanent magnet and linear Hall-effect sensor gauging rotary system is introduced in this paper. For such a contactless case, there is no wear. This provides a longer life span in association, and in particular, high reliability to achieve continuous use. The main component of the angular position estimation system is the linear Hall-effect sensor. The angle gauge depends on the Hall voltage at the rotation of the magnetic induction. The advantage of the system is its reliable operation in special environmental conditions, such as high vibration, humidity, or dust. Higher accuracy and precision will be achieved, as shown by the experimental results, and it can be widely used in the angular measurement field.
{"title":"Applications of linear Hall-effect sensors on angular measurement","authors":"Yun-Yao Lee, R. Wu, S. T. Xu","doi":"10.1109/CCA.2011.6044465","DOIUrl":"https://doi.org/10.1109/CCA.2011.6044465","url":null,"abstract":"The non-contact type application on the permanent magnet and linear Hall-effect sensor gauging rotary system is introduced in this paper. For such a contactless case, there is no wear. This provides a longer life span in association, and in particular, high reliability to achieve continuous use. The main component of the angular position estimation system is the linear Hall-effect sensor. The angle gauge depends on the Hall voltage at the rotation of the magnetic induction. The advantage of the system is its reliable operation in special environmental conditions, such as high vibration, humidity, or dust. Higher accuracy and precision will be achieved, as shown by the experimental results, and it can be widely used in the angular measurement field.","PeriodicalId":208713,"journal":{"name":"2011 IEEE International Conference on Control Applications (CCA)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115200825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-13DOI: 10.1109/CCA.2011.6044501
Y. Mitrishkin, A. Efremov, S. M. Zenkov, I. S. Sushin, V. Dokuka, R. Khayrutdinov
The paper is devoted to a hardware-in-the-loop simulation stage in the whole cycle of tokamak plasma control system design starting from practical needs and challenges and ending up in applications of developed control systems deployed in real world plants to achieve desirable objectives. Control problems of tokamak plasmas are described. The hardware-in-the-loop test case simulation is implemented into the Test Bed which consists of target PCs for modeling MIMO plant and controller on real-time operating system xPC Target from MathWorks and a workstation (Host PC) with MATLAB/Simulink development environment. This environment allows to automatically generate and compile plant and controller codes with Real-Time Workshop and to upload compiled programs to the target PCs. The raw Ethernet is used to connect the target PCs to each other. Two plasma shape and current MIMO H∞ control systems were designed and simulated on the Test Bed specifically for tokamaks T-15MD and ITER on linear plasma models obtained from nonlinear plasma physics DINA code on plasma current flat-top phase. The real time hardware-in-the-loop simulation results are presented for both tokamaks when minor disruptions occur.
{"title":"Hardware-in-the-loop simulation as a stage of plasma control system model-based design in tokamaks: A test case","authors":"Y. Mitrishkin, A. Efremov, S. M. Zenkov, I. S. Sushin, V. Dokuka, R. Khayrutdinov","doi":"10.1109/CCA.2011.6044501","DOIUrl":"https://doi.org/10.1109/CCA.2011.6044501","url":null,"abstract":"The paper is devoted to a hardware-in-the-loop simulation stage in the whole cycle of tokamak plasma control system design starting from practical needs and challenges and ending up in applications of developed control systems deployed in real world plants to achieve desirable objectives. Control problems of tokamak plasmas are described. The hardware-in-the-loop test case simulation is implemented into the Test Bed which consists of target PCs for modeling MIMO plant and controller on real-time operating system xPC Target from MathWorks and a workstation (Host PC) with MATLAB/Simulink development environment. This environment allows to automatically generate and compile plant and controller codes with Real-Time Workshop and to upload compiled programs to the target PCs. The raw Ethernet is used to connect the target PCs to each other. Two plasma shape and current MIMO H∞ control systems were designed and simulated on the Test Bed specifically for tokamaks T-15MD and ITER on linear plasma models obtained from nonlinear plasma physics DINA code on plasma current flat-top phase. The real time hardware-in-the-loop simulation results are presented for both tokamaks when minor disruptions occur.","PeriodicalId":208713,"journal":{"name":"2011 IEEE International Conference on Control Applications (CCA)","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115320227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-13DOI: 10.1109/CCA.2011.6044505
B. Besselink, N. Wouw, H. Nijmeijer
The mechanisms leading to torsional vibrations in drilling systems are considered in this paper. Thereto, a drill string model of the axial and torsional dynamics is proposed, where coupling is provided by a rate-independent bit-rock interaction law. Analysis of this model shows that the fast axial dynamics exhibit an axial stick-slip limit cycle. This generates an apparent velocity-weakening effect in the torque-on-bit, explaining the onset of torsional vibrations. Based on this analysis, a strategy for control design aiming at the suppression of torsional vibrations is presented.
{"title":"Model-based analysis and control of axial and torsional stick-slip oscillations in drilling systems","authors":"B. Besselink, N. Wouw, H. Nijmeijer","doi":"10.1109/CCA.2011.6044505","DOIUrl":"https://doi.org/10.1109/CCA.2011.6044505","url":null,"abstract":"The mechanisms leading to torsional vibrations in drilling systems are considered in this paper. Thereto, a drill string model of the axial and torsional dynamics is proposed, where coupling is provided by a rate-independent bit-rock interaction law. Analysis of this model shows that the fast axial dynamics exhibit an axial stick-slip limit cycle. This generates an apparent velocity-weakening effect in the torque-on-bit, explaining the onset of torsional vibrations. Based on this analysis, a strategy for control design aiming at the suppression of torsional vibrations is presented.","PeriodicalId":208713,"journal":{"name":"2011 IEEE International Conference on Control Applications (CCA)","volume":"49 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132312384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-13DOI: 10.1109/CCA.2011.6044375
Alan Mutka, Z. Kovačić
This paper presents the method of solving kinematics of a flipper-track robot. A general kinematics framework based on the screw theory is introduced for the leg-wheel robots. Focusing on the contact point between a flipper and the ground surface, the flipper-track robot kinematics is presented with the equivalent hybrid leg-wheel robot kinematics. For a studied four flipper-track robot, several robot control modes and corresponding kinematics solutions are identified. The algorithm for robot posture and tracking control is presented respecting robot's mechanical constraints. The kinematics and robot posture control were tested by simulation on a virtual robot in the MATLAB-ODE simulation environment.
{"title":"A leg-wheel robot-based approach to the solution of flipper-track robot kinematics","authors":"Alan Mutka, Z. Kovačić","doi":"10.1109/CCA.2011.6044375","DOIUrl":"https://doi.org/10.1109/CCA.2011.6044375","url":null,"abstract":"This paper presents the method of solving kinematics of a flipper-track robot. A general kinematics framework based on the screw theory is introduced for the leg-wheel robots. Focusing on the contact point between a flipper and the ground surface, the flipper-track robot kinematics is presented with the equivalent hybrid leg-wheel robot kinematics. For a studied four flipper-track robot, several robot control modes and corresponding kinematics solutions are identified. The algorithm for robot posture and tracking control is presented respecting robot's mechanical constraints. The kinematics and robot posture control were tested by simulation on a virtual robot in the MATLAB-ODE simulation environment.","PeriodicalId":208713,"journal":{"name":"2011 IEEE International Conference on Control Applications (CCA)","volume":"120 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125432737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-13DOI: 10.1109/CCA.2011.6044410
M. Kögel, R. Findeisen
We present an algorithm based on the fast gradient method and augmented Lagrange multipliers for model predictive control of linear, discrete-time, time-invariant, systems with constraints. In particular, the algorithm solves the underlying quadratic program in the so-called condensed form and takes advantage of the problem structure. At the end, we illustrate the performance of the algorithm, which is competitive with tailored interior-point methods, by an example.
{"title":"Fast predictive control of linear, time-invariant systems using an algorithm based on the fast gradient method and augmented Lagrange multipliers","authors":"M. Kögel, R. Findeisen","doi":"10.1109/CCA.2011.6044410","DOIUrl":"https://doi.org/10.1109/CCA.2011.6044410","url":null,"abstract":"We present an algorithm based on the fast gradient method and augmented Lagrange multipliers for model predictive control of linear, discrete-time, time-invariant, systems with constraints. In particular, the algorithm solves the underlying quadratic program in the so-called condensed form and takes advantage of the problem structure. At the end, we illustrate the performance of the algorithm, which is competitive with tailored interior-point methods, by an example.","PeriodicalId":208713,"journal":{"name":"2011 IEEE International Conference on Control Applications (CCA)","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115906548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-13DOI: 10.1109/CCA.2011.6044430
T. Emami, J. Watkins, Tae-bong Lee
In this paper, a unified approach is introduced for finding the stability boundary and the number of unstable poles in the integral derivative (ID) plane for continuous-time or discrete-time PID controllers. The ID plane is particularly important because in this plane it is easier than in the PI or PD planes to determine the entire stability region. These problems can be solved by finding all achievable PID controllers that stabilize the closed-loop polynomial of a single-input single-output (SISO) linear time invariant (LTI) system. This method is used to predict the number of unstable poles of the closed-loop system in any region of the parameter space of a PID controller. The delta operator is used to describe the controllers because it provides not only numerical properties superior to the discrete-time shift operator, but also converges to the continuous-time case as the sampling period approaches zero. A key advantage of this approach is that the stability boundary can be found when only the frequency response and not the parameters of the plant transfer function are known. A unified approach allows us to use the same procedure for finding the continuous-time or discrete-time stability region and the number of unstable poles of the closed-loop system.
{"title":"Determination of all stabilizing analog and digital PID controllers","authors":"T. Emami, J. Watkins, Tae-bong Lee","doi":"10.1109/CCA.2011.6044430","DOIUrl":"https://doi.org/10.1109/CCA.2011.6044430","url":null,"abstract":"In this paper, a unified approach is introduced for finding the stability boundary and the number of unstable poles in the integral derivative (ID) plane for continuous-time or discrete-time PID controllers. The ID plane is particularly important because in this plane it is easier than in the PI or PD planes to determine the entire stability region. These problems can be solved by finding all achievable PID controllers that stabilize the closed-loop polynomial of a single-input single-output (SISO) linear time invariant (LTI) system. This method is used to predict the number of unstable poles of the closed-loop system in any region of the parameter space of a PID controller. The delta operator is used to describe the controllers because it provides not only numerical properties superior to the discrete-time shift operator, but also converges to the continuous-time case as the sampling period approaches zero. A key advantage of this approach is that the stability boundary can be found when only the frequency response and not the parameters of the plant transfer function are known. A unified approach allows us to use the same procedure for finding the continuous-time or discrete-time stability region and the number of unstable poles of the closed-loop system.","PeriodicalId":208713,"journal":{"name":"2011 IEEE International Conference on Control Applications (CCA)","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117337721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-13DOI: 10.1109/CCA.2011.6044441
M. Gholami, V. Cocquempot, H. Schiøler, Thomas Bak
A passive fault tolerant controller (PFTC) based on state feedbac is proposed for discrete-time piecewise affine (PWA) systems. The controller is tolerant against actuator faults and is able to track the reference signal while the control inputs are bounded. The PFTC problem is transformed into feasibility of a set of linear matrix inequalities (LMIs). The method is applied on a large-scale live-stock ventilation model.
{"title":"Passive fault tolerant control of piecewise affine systems with reference tracking and input constraints","authors":"M. Gholami, V. Cocquempot, H. Schiøler, Thomas Bak","doi":"10.1109/CCA.2011.6044441","DOIUrl":"https://doi.org/10.1109/CCA.2011.6044441","url":null,"abstract":"A passive fault tolerant controller (PFTC) based on state feedbac is proposed for discrete-time piecewise affine (PWA) systems. The controller is tolerant against actuator faults and is able to track the reference signal while the control inputs are bounded. The PFTC problem is transformed into feasibility of a set of linear matrix inequalities (LMIs). The method is applied on a large-scale live-stock ventilation model.","PeriodicalId":208713,"journal":{"name":"2011 IEEE International Conference on Control Applications (CCA)","volume":"120 12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115484028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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